CN114123355B - Voltage control method and system under high photovoltaic penetration rate based on intelligent terminals in Taiwan area - Google Patents

Abstract

The invention provides a photovoltaic high-permeability lower voltage control method and system based on a platform area intelligent terminal, comprising the following steps: when node voltage exceeding occurs in the power distribution network, the intelligent terminal of the platform area calculates the voltage exceeding value of each node with voltage exceeding based on the electric data of each node reported by the intelligent ammeter, calculates the comprehensive voltage sensitivity of each node with distributed photovoltaic power supply during power adjustment, and respectively selects the node with the largest comprehensive voltage sensitivity in a distributed photovoltaic reactive power adjustment mode and an energy storage adjustment mode; on the basis of equivalent regulation, calculating the regulation cost of the corresponding node regulation mode, and selecting the regulation mode with the minimum regulation cost for power regulation; and after the node adjustable power with the minimum adjustment cost is used up, the comprehensive voltage sensitivity and the adjustment cost are recalculated until the voltage of each node is no longer out of limit. The invention can calculate the voltage sensitivity of the multipoint voltage when exceeding the limit, and accurately design the voltage control strategy by considering the adjustment cost.

Description

Voltage control method and system under high photovoltaic penetration based on intelligent terminal in the substation area

Technical Field

The present invention belongs to the technical field of power distribution operation and maintenance, and specifically relates to a voltage control method and system under high photovoltaic penetration based on intelligent terminals in an area.

Background Art

The penetration rate of distributed resources such as distributed power sources and distributed energy storage in the distribution network will be further improved. In the low-voltage distribution network, household distributed photovoltaic power generation connected to the roof has been used in many places, and the voltage over-limit problem is one of the important reasons affecting the consumption of photovoltaic power generation. In recent years, with the construction of digital distribution, software-defined intelligent terminals based on the substation area have been installed on the substation side, and the information of distributed power sources, smart meters, smart circuit breakers and other equipment has been connected to realize the centralized control of distributed power sources, providing a solution to the problem of voltage over-limit for distributed power sources. Based on the intelligent distribution network, the method of calculating the voltage sensitivity of the overvoltage node to the power change of the control node and determining the node voltage over-limit control measures has been widely studied by scholars.

However, the previous calculation of voltage sensitivity is not practical. On the one hand, many methods use the Newton-Raphson method to solve the derivative of power to voltage in the Jacobian matrix of the power flow equation to obtain voltage sensitivity. However, the Newton-Raphson method uses the node admittance matrix to calculate the power flow equation. The mutual admittance of non-adjacent nodes is zero, and the calculated derivative of power to voltage is zero, which cannot be used to calculate voltage sensitivity. On the other hand, single-point voltage sensitivity cannot solve the situation where multiple voltages exceed the limit at the same time. Since the voltage control strategy needs to be designed with reference to voltage sensitivity, the inaccuracy of voltage sensitivity calculation directly leads to the inaccuracy of the voltage control strategy. Therefore, it is necessary to improve the existing voltage control strategy.

Summary of the invention

In order to overcome the deficiencies of the above-mentioned prior art, the present invention proposes a voltage control method under high photovoltaic penetration based on a smart terminal in a substation, comprising:

When the voltage of a node in the distribution network exceeds the limit, the intelligent terminal in the substation calculates the voltage limit value of each node where the voltage exceeds the limit, and the comprehensive voltage sensitivity of each node containing distributed photovoltaic power sources during power adjustment based on the electrical data of each node in the distribution network reported by the smart meter;

Select the nodes with the largest comprehensive voltage sensitivity in different regulation modes of distributed photovoltaic power sources respectively, calculate the regulation cost of the corresponding node regulation mode on the basis of equivalent regulation, and select the regulation mode with the smallest regulation cost for power regulation;

When the adjustable power of the node with the minimum adjustment cost is used up, the comprehensive voltage sensitivity and adjustment cost of each available node containing distributed photovoltaic power sources are recalculated, and power adjustment is performed until the voltage of each node no longer exceeds the limit;

Among them, the nodes containing distributed photovoltaic power sources include energy storage device nodes and photovoltaic inverter nodes, the adjustment methods include active power adjustment of energy storage devices, active power adjustment of photovoltaic inverters and reactive power adjustment of photovoltaic inverters, and the adjustment costs include the adjustment costs of photovoltaic inverters and the adjustment costs of energy storage devices.

Preferably, the intelligent terminal in the substation area calculates the voltage over-limit value of each node in the distribution network where the voltage over-limit occurs based on the electrical data of each node in the distribution network reported by the smart meter, and calculates the comprehensive voltage sensitivity of each node containing distributed photovoltaic power sources during power regulation, including:

Based on the electrical data of each node in the distribution network reported by the smart meter, the intelligent terminal in the substation area uses the Newton-Raphson method to obtain the Jacobian matrix and calculates the voltage sensitivity of each node containing distributed photovoltaic power sources in the distribution network to each voltage-limited node.

The intelligent terminal in the substation calculates the voltage over-limit value of each node in the distribution network where the voltage over-limit occurs based on the electrical data of each node in the distribution network reported by the smart meter;

Based on the voltage sensitivity of the power regulation of the distributed photovoltaic power node in the distribution network to each voltage-over-limit node and the voltage-over-limit value of each node where the voltage over-limit occurs, the comprehensive voltage sensitivity of each distributed photovoltaic power node in the distribution network during power regulation is calculated;

The electrical data of each node of the distribution network reported by the smart meter includes the voltage of each node, the power of each node, the output of the distributed power source and the charge state data of the energy storage device.

Preferably, the comprehensive voltage sensitivity of each distributed photovoltaic power source node in the distribution network during power regulation is calculated as follows:

In the formula, is the comprehensive voltage sensitivity of node H in the distribution network containing distributed photovoltaic power generation during reactive power regulation, is the comprehensive voltage sensitivity of node H containing distributed photovoltaic power generation in the distribution network during active power regulation, m is the number of all voltage-exceeding nodes in the distribution network, _ΔVk is the voltage-exceeding value of the kth voltage-exceeding node in the distribution network, is the voltage sensitivity of the reactive power regulation of node H containing distributed photovoltaic power in the distribution network to the kth voltage-limited node, is the voltage sensitivity of the active power regulation of node H containing distributed photovoltaic power in the distribution network to the kth voltage-exceeding node;

Among them, the voltage over-limit value of the kth voltage over-limit node in the distribution network is calculated as follows:

ΔV _k = V _k - V _max

Where _Vk is the voltage value of the kth voltage-over-limit node in the distribution network, and _Vmax is the maximum voltage.

Preferably, the calculation of the voltage sensitivity of each distributed photovoltaic power source node power regulation in the distribution network to each voltage-overlimit node includes:

For each node containing a distributed photovoltaic power source in the distribution network, the voltage sensitivity of power regulation to each voltage-exceeding node is calculated when the node containing the distributed photovoltaic power source is an upstream node, a downstream node, and a node on a branch of the line where the node is located;

The upstream node of the voltage over-limit node is the line from the distribution transformer through the voltage over-limit node to the terminal node of the distribution network, excluding the voltage over-limit node, and the remaining nodes on the line between the distribution transformer and the voltage over-limit node;

The downstream nodes of the voltage-exceeding node are, excluding the voltage-exceeding node, the remaining nodes on the line between the voltage-exceeding node and the terminal node of the distribution network, including the terminal node of the distribution network.

Preferably, when the node containing the distributed photovoltaic power source is an upstream node of the voltage-exceeding node, the voltage sensitivity of the power regulation to each voltage-exceeding node is calculated as follows:

In the formula, In order to adjust the reactive power of the distributed photovoltaic power generation node A upstream of the voltage-limit node N in the distribution network, the voltage sensitivity of the voltage-limit node N is calculated. In order to adjust the voltage sensitivity of the voltage-over-limit node N when the active power of the distributed photovoltaic power node A upstream of the voltage-over-limit node N in the distribution network is adjusted, j is the adjacent node of node A, n is the number of nodes adjacent to node A, _Vj is the voltage of node j, G _Aj is the conductance between node A and node j, B _Aj is the susceptance between node A and node j, δ _Aj is the power angle between node A and node j, V _A is the voltage of node A, B _AA is the susceptance between node A and node A, i is the i-th node between node N and node A upstream of node N, V _i is the voltage of node i, and V _i-1 is the voltage of the previous upstream node of node i.

Preferably, when the node containing the distributed photovoltaic power source is a downstream node of the voltage-exceeding node, the voltage sensitivity of the power regulation to each voltage-exceeding node is calculated as follows:

In the formula, In order to adjust the reactive power of the distributed photovoltaic power generation node Y downstream of the voltage-limit node N in the distribution network, the voltage sensitivity of the voltage-limit node N is calculated. In order to adjust the voltage sensitivity of the voltage-over-limit node N in the distribution network when the downstream of the voltage-over-limit node N contains the active power of the distributed photovoltaic power node Y, V _N is the voltage of the node N, V _Y is the voltage of the node Y, is the partial derivative of the reactive power generated by the distributed photovoltaic power source at node Y with respect to the voltage, is the partial derivative of the active power generated by the distributed photovoltaic power source at node Y with respect to the voltage, l is the lth node between node N and node Y downstream of node N, X _l is the reactance between node l and the previous upstream node of node l, and R _l is the resistance between node l and the previous upstream node of node l.

Preferably, when the node containing the distributed photovoltaic power source is a node on a branch of a line where a voltage-exceeding node is located, the voltage sensitivity of the power regulation to each voltage-exceeding node is calculated as follows:

In the formula, In order to adjust the reactive power of the distributed photovoltaic power source node E on the branch of the line where the voltage-over-limit node N is located in the distribution network, the voltage sensitivity of the voltage-over-limit node N is determined. In order to adjust the active power of the distributed photovoltaic power supply node E on the branch of the line where the voltage-over-limit node N in the distribution network is located, the voltage sensitivity of the voltage-over-limit node N is determined. _VC is the voltage of the node C, _VE is the voltage of the node E, is the partial derivative of the reactive power generated by the distributed photovoltaic power source at node E with respect to the voltage, is the partial derivative of the active power generated by the distributed photovoltaic power source at node E with respect to the voltage, r is the r-th node from the starting node F to node E on the branch where node E is located, _Xr is the reactance between node r and the previous upstream node of node r, _Rr is the resistance between node r and the previous upstream node of node r, s is the s-th node from the connecting node C to the line including node N, the branch where node E is located and node N, _Vs is the voltage of node s, and Vs _-1 is the voltage of the node before node s in the direction from node C to node N.

Preferably, the regulation cost of the energy storage device is calculated as follows:

Where Cost ₀ is the cost of the energy storage device when regulating the active power of node T, ΔP is the change in the active power of the line where node T is located, U _N is the rated voltage of the line where node T is located, t is the tth node from the line origin to node T on the line where node T is located, P _t is the active power flowing into node t from the previous upstream node of node t, R _t is the resistance between node t and the previous upstream node of node t, and ΔP _ess is the active power absorbed by the energy storage device.

Preferably, the adjustment cost of the photovoltaic inverter includes:

The PV inverter maintains the active power unchanged, increasing the cost of the reactive power stage;

After reaching the capacity limit, the photovoltaic inverter adjusts the power factor angle, reducing the active power while increasing the cost of the reactive power stage;

After the power factor angle of the photovoltaic inverter reaches the limit, the cost of the active power and reactive power stages is reduced proportionally.

Preferably, the photovoltaic inverter maintains the active power unchanged and increases the cost of the reactive power stage, which is calculated as follows:

Where Cost ₁ is the cost of the PV inverter to maintain the active power unchanged and increase the reactive compensation stage, ΔQ is the reactive power change of the line where node T is located, U _N is the rated voltage of the line where node T is located, t is the tth node from the line origin to node T on the line where node T is located, Q _t is the reactive power flowing into node t from the previous upstream node of node t, and R _t is the resistance between node t and the previous upstream node of node t.

Preferably, after reaching the capacity limit, the photovoltaic inverter adjusts the power factor angle to reduce the active power while increasing the cost of the reactive power stage, which is calculated as follows:

Wherein, Cost ₂ is the cost of the photovoltaic inverter adjusting the power factor angle to reduce active power and increase reactive power after reaching the capacity limit, ΔP is the change in active power of the line where node T is located, U _N is the rated voltage of the line where node T is located, t is the tth node from the line origin to node T on the line where node T is located, P _t is the active power flowing into node t from the previous upstream node of node t, R _t is the resistance between node t and the previous upstream node of node t, ΔQ is the change in reactive power of the line where node T is located, and Q _t is the reactive power flowing into node t from the previous upstream node of node t.

Preferably, after the power factor angle of the photovoltaic inverter reaches the limit, the cost of the active power and reactive power stages is proportionally reduced, as calculated by the following formula:

Wherein, Cost ₃ is the cost of the photovoltaic inverter in the stage of proportionally reducing active power and reactive power after the power factor angle reaches the limit, ΔP is the change in active power of the line where node T is located, U _N is the rated voltage of the line where node T is located, t is the tth node from the line origin to node T on the line where node T is located, P _t is the active power flowing into node t from the previous upstream node of node t, R _t is the resistance between node t and the previous upstream node of node t, ΔQ is the change in reactive power of the line where node T is located, and Q _t is the reactive power flowing into node t from the previous upstream node of node t.

Preferably, the calculating of the adjustment cost of the corresponding node adjustment method on the basis of equivalent adjustment includes:

Based on the comprehensive voltage sensitivity, different regulation methods achieve the same voltage regulation effect by adjusting power, resulting in regulation costs.

Preferably, the substation intelligent terminal stores a distribution network topology model, which is used to calculate the voltage over-limit value of each node in the distribution network where the voltage over-limit occurs, the comprehensive voltage sensitivity of each node containing distributed photovoltaic power sources during power adjustment, and the power adjustment amount and adjustment cost required to adjust the voltage over-limit value of each node at the maximum comprehensive voltage sensitivity; and is used to store the photovoltaic inverter capacity, the maximum power factor angle of the photovoltaic inverter, the active adjustment margin of the photovoltaic inverter, the reactive adjustment margin of the photovoltaic inverter, the charge capacity limit of the energy storage device, the rated active power of the energy storage device, the active adjustment margin of the energy storage device and the voltage limit of each node.

Based on the same inventive concept, the present invention also provides a voltage control system under high photovoltaic penetration based on a smart terminal in a substation, including: a comprehensive voltage sensitivity module, a sorting module and a power regulation module;

The comprehensive voltage sensitivity module is used for calculating the voltage over-limit value of each node in the distribution network where the voltage over-limit occurs, and the comprehensive voltage sensitivity of each node containing distributed photovoltaic power sources during power adjustment based on the electrical data of each node in the distribution network reported by the smart meter when the node voltage over-limit occurs in the distribution network;

The sorting module is used to select the nodes with the largest comprehensive voltage sensitivity among the different regulation modes of the distributed photovoltaic power source, calculate the regulation cost of the corresponding node regulation mode on the basis of equivalent regulation, and select the regulation mode with the smallest regulation cost for power regulation;

The power regulation module is used to recalculate the comprehensive voltage sensitivity and regulation cost of each available node containing distributed photovoltaic power sources after the adjustable power of the node with the minimum regulation cost is used up, and perform power regulation until the voltage of each node no longer exceeds the limit;

Among them, the nodes containing distributed photovoltaic power sources include energy storage device nodes and photovoltaic inverter nodes, the adjustment methods include active power adjustment of energy storage devices, active power adjustment of photovoltaic inverters and reactive power adjustment of photovoltaic inverters, and the adjustment costs include the adjustment costs of photovoltaic inverters and the adjustment costs of energy storage devices.

Compared with the closest prior art, the present invention has the following beneficial effects:

The present invention provides a voltage control method and system under high photovoltaic penetration based on intelligent terminals in a substation, comprising: when a node voltage exceeds a limit in a distribution network, the intelligent terminal in the substation calculates the voltage over-limit value of each node in the distribution network where the voltage exceeds the limit, and the comprehensive voltage sensitivity of each node containing a distributed photovoltaic power source during power regulation based on the electrical data of each node in the distribution network reported by a smart meter; selects nodes with the largest comprehensive voltage sensitivity in different regulation modes of distributed photovoltaic power sources respectively, calculates the regulation cost of the corresponding node regulation mode on the basis of equivalent regulation, and selects the regulation mode with the smallest regulation cost for power regulation; when the adjustable power of the node with the smallest regulation cost is used up, recalculates the comprehensive voltage sensitivity and regulation cost of each available node containing a distributed photovoltaic power source, and performs power regulation until the voltage of each node no longer exceeds the limit; wherein, the node containing a distributed photovoltaic power source includes an energy storage device node and a photovoltaic inverter node, the regulation mode includes active regulation of the energy storage device, active regulation of the photovoltaic inverter, and reactive regulation of the photovoltaic inverter, and the regulation cost includes the regulation cost of the photovoltaic inverter and the regulation cost of the energy storage device. The present invention designs a more accurate voltage sensitivity calculation method, and proposes a comprehensive voltage sensitivity to describe the regulation capability of distributed photovoltaic resources, which solves the problem that the voltage sensitivity is not easy to calculate when the voltages at multiple points exceed the limit at the same time, and provides accurate data guidance for voltage adjustment under the power distribution Internet of Things; the present invention designs a voltage regulation method that takes cost into account, which can accurately control the voltage while minimizing the cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic flow chart of a voltage control method under high photovoltaic penetration based on a smart terminal in an area provided by the present invention;

FIG2 is a schematic diagram of a low-voltage distribution network according to an embodiment of a voltage control method under high photovoltaic penetration rate based on a smart terminal in an area provided by the present invention;

FIG3 is a diagram showing the relationship between reactive power and active power output by a photovoltaic inverter provided by the present invention;

FIG4 is a flow chart of a voltage regulation measure based on a smart terminal in a photovoltaic area under high penetration rate provided by the present invention;

FIG5 is a schematic diagram of the basic structure of a voltage control system under high photovoltaic penetration based on an intelligent terminal in an area provided by the present invention.

DETAILED DESCRIPTION

The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings.

Embodiment 1:

A schematic flow chart of a voltage control method under high photovoltaic penetration rate based on a smart terminal in a substation provided by the present invention is shown in FIG1 , and includes:

Step 1: When a node voltage exceeds the limit in the distribution network, the intelligent terminal in the substation calculates the voltage limit value of each node where the voltage exceeds the limit in the distribution network based on the electrical data of each node in the distribution network reported by the smart meter, and the comprehensive voltage sensitivity of each node containing distributed photovoltaic power during power regulation;

Step 2: Select the nodes with the largest comprehensive voltage sensitivity among the different regulation modes of distributed photovoltaic power sources respectively, calculate the regulation cost of the corresponding node regulation mode on the basis of equivalent regulation, and select the regulation mode with the smallest regulation cost for power regulation;

Step 3: When the adjustable power of the node with the minimum adjustment cost is used up, the comprehensive voltage sensitivity and adjustment cost of each available node containing distributed photovoltaic power sources are recalculated, and power adjustment is performed until the voltage of each node no longer exceeds the limit;

Among them, the nodes containing distributed photovoltaic power sources include energy storage device nodes and photovoltaic inverter nodes, the adjustment methods include active power adjustment of energy storage devices, active power adjustment of photovoltaic inverters and reactive power adjustment of photovoltaic inverters, and the adjustment costs include the adjustment costs of photovoltaic inverters and the adjustment costs of energy storage devices.

The purpose of the present invention is to design a practical voltage sensitivity calculation method based on the intelligent terminal of the substation, and secondly to propose a voltage control strategy that enables more photovoltaic power generation, less system loss and greater user benefits.

The present invention firstly calculates the voltage sensitivity of a single node using the chain rule, then proposes a comprehensive voltage sensitivity for multi-node voltage exceeding the limit and studies the calculation method, and then designs a voltage control method taking cost into account. While controlling the system voltage, it achieves greater photovoltaic power generation, smaller system loss and more user benefits.

Step 1 specifically includes:

Based on the electrical data of each node in the distribution network reported by the smart meter, the intelligent terminal in the substation uses the Newton-Raphson method to obtain the Jacobian matrix, and calculates the voltage sensitivity of each power regulation of each distributed photovoltaic power node in the distribution network to each voltage-exceeding node.

For each node containing a distributed photovoltaic power source in the distribution network, the voltage sensitivity of power regulation to each voltage-exceeding node is calculated when the node containing the distributed photovoltaic power source is an upstream node, a downstream node, and a node on a branch of the line where the node is located;

The upstream node of the voltage over-limit node is the line from the distribution transformer through the voltage over-limit node to the terminal node of the distribution network, excluding the voltage over-limit node, and the remaining nodes on the line between the distribution transformer and the voltage over-limit node;

The downstream nodes of the voltage-exceeding node are, excluding the voltage-exceeding node, the remaining nodes on the line between the voltage-exceeding node and the terminal node of the distribution network, including the terminal node of the distribution network.

The substation intelligent terminal stores a distribution network topology model, which is used to calculate the voltage over-limit value of each node in the distribution network where the voltage over-limit occurs, the comprehensive voltage sensitivity of each node containing distributed photovoltaic power sources during power adjustment, and the power adjustment amount and adjustment cost required to adjust the voltage over-limit value of each node under the maximum comprehensive voltage sensitivity; and is used to store the photovoltaic inverter capacity, the maximum power factor angle of the photovoltaic inverter, the active adjustment margin of the photovoltaic inverter, the reactive adjustment margin of the photovoltaic inverter, the charge capacity limit of the energy storage device, the rated active power of the energy storage device, the active adjustment margin of the energy storage device and the voltage limit of each node.

Since most low-voltage distribution networks adopt a closed-loop design and an open-loop power supply mode, their structure is radial. In this embodiment, a schematic diagram of a low-voltage distribution network is shown in FIG2 :

Among them, V _N is the voltage value of node N; R _N and X _N are the resistance and reactance values of the branch between node N-1 and node N; P _N and Q _N are the active and reactive power flowing from the upstream node to node N; _PLN and Q _LN are the active and reactive power of the load of node N; P _GN and Q _GN are the active and reactive power generated by node N connected to DG.

Taking node N connected to DG as the reference point, when the voltage of node N exceeds the limit, for the convenience of analysis, the nodes except node N are divided into three categories, namely upstream nodes (1, 2...N-1), downstream nodes (N+1...X) and other branch nodes (E, F, etc.). Taking the reactive power control of the upstream node as an example, the chain rule shows that the sensitivity of the reactive power control of node 2 to the voltage of node N can be expressed as:

1) The sensitivity of upstream node power adjustment to node N voltage is calculated as follows:

When the influence of the voltage transverse component is ignored, the voltage relationship between node i-1 upstream of node 2 and node i is:

V _i =V _i-1 -(P _i R _i +Q _i X _i )/V _i-1 (2)

Wherein, _Vi is the voltage of node i, Vi _-1 is the voltage of the upstream node before node i, _Pi is the active power flowing into node i from the upstream node of node i, _Qi is the reactive power flowing into node i from the upstream node of node i, _Ri is the resistance value between node i-1 and node i, and _Xi is the reactance value between node i-1 and node i.

Formula (2) can be transformed into:

When only the reactive power injected by node 2 changes and the power of other nodes is not adjusted, the power loss of the branch and line downstream of node 2 does not change much and can be ignored, that is, _Pi and _Qi of any node i downstream of node 2 can be considered constant. Derivatives of both sides of the equation with respect to _Vi yield:

When the Newton-Raphson method in polar coordinate form is used to solve the power flow equation, the Jacobian matrix gives the partial derivatives of the reactive power of the node itself and the adjacent nodes with respect to the voltage. Equations (5) and (6) are the partial derivatives of the reactive power generated by the distributed photovoltaic power source at node 2 with respect to the voltage at node 2:

G _2j and G ₁₂ represent the conductance between nodes 2 and j and between nodes 1 and 2, respectively. B _2j and B ₁₂ represent the susceptance between nodes 2 and j and between nodes 1 and 2, respectively. δ _2j and δ ₁₂ represent the power angle between nodes 2 and j and between nodes 1 and 2, respectively.

Therefore, the reactive power adjustment of the upstream node 2 and the voltage sensitivity of the node N can be calculated. Substituting equations (4) and (5) into equation (1), we can obtain:

Similarly, it can be calculated that the voltage sensitivity of node N is calculated by adjusting the active power of upstream node 2:

In formulas (7) and (8), In order to adjust the voltage sensitivity of the voltage-over-limit node N in the distribution network when the reactive power of the distributed photovoltaic power source node 2 is upstream of the voltage-over-limit node N, In order to adjust the voltage sensitivity of the voltage-overlimit node N in the distribution network when the upstream of the voltage-overlimit node N contains the active power of the distributed photovoltaic power node 2, j is the adjacent node of node 2, n is the number of nodes adjacent to node 2, _Vj is the voltage of node j, _G2j is the conductance between node 2 and node j, _B2j is the susceptance between node 2 and node j, _δ2j is the power angle between node 2 and node j, _V2 is the voltage of node 2, _B22 is the susceptance between node 2 and node 2, i is the i-th node between node N and node 2 upstream of node N, _Vi is the voltage of node i, and Vi _-1 is the voltage of the previous upstream node of node i.

2) The sensitivity of downstream node power adjustment to node N voltage is calculated as follows:

Taking the reactive power adjustment of node X as an example, the sensitivity of the downstream node power adjustment to the voltage of node N is calculated. The voltage relationship between the upstream node i and node i+1 of node X can be expressed as:

_Vi is the voltage of node i, Vi ₊₁ is the voltage of the downstream node after node i, Pi ₊₁ is the active power flowing into node i+1 from the upstream node of node i+1, _Qi is the reactive power flowing into node i+1 from the upstream node of node i+1, R _i+1 is the resistance value between node i and node i+1, and Xi ₊₁ is the reactance value between node i and node i+1.

Formula (9) can be transformed into:

In formula (10), the third term is much smaller than the first two terms and can be simplified as:

By adding equation (11) corresponding to node N and node X, we can get:

It can be seen that R _i+1 and Xi ₊₁ are constant values, the voltage value of node N depends on the value of node X and the power value flowing into each node from node N to node X. Since only the injected reactive power of node X is adjusted, the power change of the branch from node N to node X can be ignored, that is, _ΔPN = _ΔPN+1 = … = _ΔPN and _ΔQN = _ΔQN+1 = … = _ΔPN , and since the adjustment time interval is small, Pi ₊₁ is considered constant, that is, _ΔPN = _ΔPN+1 = … = _ΔPN = 0 and _ΔQN = _ΔQN+1 = … = _ΔPN = ₀ .

Therefore, taking the derivative on both sides of equation (12) we get:

Will Substituting into equation (13), we get the reactive power adjustment of downstream node X and the voltage sensitivity calculation formula of node N:

Similarly, the voltage sensitivity calculation formula of node N can be calculated by adjusting the active power of downstream node X:

In formulas (14) and (15), In order to adjust the reactive power of the distributed photovoltaic power generation node X downstream of the voltage-limit node N in the distribution network, the voltage sensitivity of the voltage-limit node N is calculated. In order to adjust the voltage sensitivity of the voltage-overlimit node N in the distribution network when the active power of the distributed photovoltaic power node X downstream of the voltage-overlimit node N is contained, V _N is the voltage of the node N, V _X is the voltage of the node X, i is the i-th node between the node N and the node X downstream of the node N, _Xi is the reactance between the node i and the previous upstream node of the node i, and _Ri is the resistance between the node i and the previous upstream node of the node i.

3) The sensitivity of the power adjustment of the remaining branch nodes to the voltage of node N is calculated as follows:

Taking the reactive power adjustment of node E as an example, firstly, the voltage sensitivity of the reactive power adjustment of node E to the upstream common connection node 3 is calculated, and then the voltage sensitivity of the voltage change of the common connection node 3 to the downstream node N is calculated;

The calculated sensitivity of node E reactive power adjustment to node N voltage is:

Similarly, calculate the sensitivity of node E active power adjustment to node N voltage:

In formulas (16) and (17), In order to adjust the reactive power of the distributed photovoltaic power source node E on the branch of the line where the voltage-over-limit node N is located in the distribution network, the voltage sensitivity of the voltage-over-limit node N is determined. In order to adjust the voltage sensitivity of the voltage-over-limit node N to the active power of the distributed photovoltaic power node E on the branch of the line where the voltage-over-limit node N is located in the distribution network, _V3 is the voltage of node 3, _VE is the voltage of node E, i is the i-th node from the branch starting node F to node E on the branch where node E is located, _Xi is the reactance between node i and the previous upstream node of node i, _Ri is the resistance between node i and the previous upstream node of node i, j is the j-th node connecting node 3 to node N on the line including node N, the branch where node E is located and node N, _Vj is the voltage of node j, and Vj _-1 is the voltage of the node before node j in the direction from node 3 to node N.

Based on the voltage sensitivity of the power regulation of the distributed photovoltaic power node in the distribution network to each voltage-over-limit node and the voltage-over-limit value of each node where the voltage over-limit occurs, the comprehensive voltage sensitivity of each distributed photovoltaic power node in the distribution network during power regulation is calculated;

The electrical data of each node of the distribution network reported by the smart meter includes the voltage of each node, the power of each node, the output of the distributed power source and the charge state data of the energy storage device.

When the voltages of multiple nodes exceed the limit, in order to make the adjustment measures proceed in an orderly manner and achieve the optimal adjustment measures, node power adjustment needs to consider the comprehensive impact on the voltage sensitivity of different nodes that exceed the limit. Therefore, this paper proposes a comprehensive voltage sensitivity calculation method based on the degree of exceeding the limit.

From the calculation of voltage sensitivity of the above single point, it can be known that any node power adjustment will adjust the voltage of all nodes. In order to optimize the adjustment measures, improve the adjustment efficiency and avoid overshoot, the voltage sensitivity of the node with larger over-limit voltage should account for a larger proportion in the comprehensive voltage sensitivity, that is, the sensitivity of each node in the comprehensive voltage sensitivity is distributed according to the over-limit ratio. Taking the node N and node X in Figure 2 exceeding the upper limit, and adjusting the reactive power of node 2 as an example, the comprehensive voltage sensitivity of adjusting the reactive power of node 2 is calculated.

From the above analysis, it can be seen that the voltage sensitivity of nodes N and X when adjusting the reactive power of node 2 is Calculate the voltage over-limit value ΔV:

ΔV _N =V _N -V _max (18)

ΔV _X =V _X -V _max (19)

In equations (18) and (19), ΔV _N and ΔV _X are the voltage over-limit values of the voltage over-limit nodes N and X in the distribution network, V _N and V _X are the voltage values of the voltage over-limit nodes N and X in the distribution network, and V _max is the maximum voltage.

The comprehensive voltage sensitivity when adjusting the reactive power and active power of node 2 can be expressed as:

In the formula, is the comprehensive voltage sensitivity of node 2 containing distributed photovoltaic power generation in the distribution network during reactive power regulation, is the comprehensive voltage sensitivity of node 2 containing distributed photovoltaic power generation in the distribution network during active power regulation, is the voltage sensitivity of reactive power regulation of node 2 containing distributed photovoltaic power in the distribution network to the voltage exceeding the limit node N, It is the voltage sensitivity of active power regulation of node 2 containing distributed photovoltaic power generation in the distribution network to the voltage exceeding the limit node X.

By analogy, when the voltages of nodes 1, 2, 3, etc. exceed the limit, the comprehensive voltage sensitivity when adjusting the reactive power of node A can be expressed as:

The calculation method of the regulation cost of the regulation method corresponding to the nodes with the same comprehensive voltage sensitivity in step 2 is as follows:

1) Adjustment cost calculation

The present invention mainly adopts photovoltaic inverter regulation and energy storage regulation arrangement regulation measures.

Energy storage device regulation cost:

The energy storage device absorbs active power to adjust the node voltage. During the adjustment, the active power on the line increases and the loss increases. Therefore, its adjustment cost is expressed as:

Cost ₀ =ΔP _loss -ΔP _ess (21)

In the formula, ΔP _loss represents the active power loss of the line, and ΔP _ess represents the active power absorbed by the energy storage device.

The calculation of ΔP _loss is based on:

Wherein, U _N is the rated voltage of the line where node i is located, _Pi is the active power flowing into node i from the previous upstream node of node i, _Qi is the reactive power flowing into node i from the previous upstream node of node i, _{and Ri} is the resistance between node i and the previous upstream node of node i.

When the active power of the line is adjusted, ignoring the influence of reactive power, the loss change can be expressed as:

Where ΔP is the change in active power of the line where node i is located.

The first term in the numerator is much larger than the second term, so the second term can be ignored, and the change of branch active power is ignored, that is, the ΔP of each line is the same. When node I adjusts the active power, the active power loss corresponding to different upstream nodes is superimposed, and the following is obtained:

Among them, the calculation of _Pi can be done by collecting smart meter data, ignoring line losses according to the network topology, and superimposing the active power of all meters downstream of node i. Therefore, the energy storage regulation cost can be expressed as:

Where Cost ₀ is the cost of the energy storage device when regulating the active power of node T, ΔP is the change in the active power of the line where node I is located, U _N is the rated voltage of the line where node I is located, i is the i-th node from the line origin to node I on the line where node I is located, _Pi is the active power flowing into node i from the previous upstream node of node i, _Ri is the resistance between node i and the previous upstream node of node i, and ΔP _ess is the active power absorbed by the energy storage device.

Photovoltaic inverter power conditioning cost:

Through research, we know that most photovoltaic inverters can achieve decoupling control of active power and reactive power, that is, they can compensate for reactive power while generating active power. As shown in Figure 3, the regulation cost can be divided into three stages:

The PV inverter maintains the active power unchanged, increasing the cost of the reactive power stage;

After reaching the capacity limit, the photovoltaic inverter adjusts the power factor angle, reducing the active power while increasing the cost of the reactive power stage;

After the power factor angle of the photovoltaic inverter reaches the limit, the cost of the active power and reactive power stages is reduced proportionally.

Stage 1: a-b, that is, when the active output exceeds the voltage limit at point a, the active output is maintained unchanged and reactive power compensation is increased. The cost calculation of this stage is:

Cost ₁ = ΔP _loss (26)

According to the above reasoning, when node I performs the first stage reactive power regulation of the inverter, its cost can be expressed as:

Where Cost ₁ is the cost of the PV inverter to maintain the active power unchanged and increase the reactive compensation stage, ΔQ is the change in reactive power of the line where node I is located, U _N is the rated voltage of the line where node I is located, i is the i-th node from the line origin to node I on the line where node I is located, _Qi is the reactive power flowing into node i from the previous upstream node of node i, and _Ri is the resistance between node i and the previous upstream node of node i.

Phase 2: b-c, that is, after the inverter reaches the capacity limit, the power factor angle is adjusted to reduce active power and increase reactive power. The cost calculation of this phase is:

Cost ₂ = ΔP _loss + ΔP (28)

Further sorting:

Wherein, Cost ₂ is the cost of the photovoltaic inverter adjusting the power factor angle to reduce active power and increase reactive power after reaching the capacity limit, ΔP is the change in active power of the line where node I is located, U _N is the rated voltage of the line where node I is located, i is the i-th node from the line origin to node I on the line where node I is located, _Pi is the active power flowing into node i from the previous upstream node of node i, _Ri is the resistance between node i and the previous upstream node of node i, ΔQ is the change in reactive power of the line where node I is located, _{and Qi} is the reactive power flowing into node i from the previous upstream node of node i.

Stage 3: After c, that is, when the power factor angle reaches the limit, active and reactive power are reduced proportionally. The cost of this stage is calculated as:

Cost ₃ = ΔP _loss + ΔP (30)

Further sorting:

Wherein, Cost ₃ is the cost of the photovoltaic inverter in the stage of proportionally reducing active power and reactive power after the power factor angle reaches the limit, ΔP is the change in active power of the line where node I is located, U _N is the rated voltage of the line where node I is located, i is the i-th node from the line origin to node I on the line where node I is located, _Pi is the active power flowing into node i from the previous upstream node of node i, _Ri is the resistance between node i and the previous upstream node of node i, ΔQ is the change in reactive power of the line where node I is located, _{and Qi} is the reactive power flowing into node i from the previous upstream node of node i.

2) Voltage control strategy

Based on the above research on comprehensive sensitivity, this embodiment adopts a point-by-point control method, that is, the active power regulation of energy storage nodes and the inverter regulation of photovoltaic nodes are sorted according to the comprehensive voltage sensitivity, respectively, and the minimum cost control method among the four control methods (three stages of active power regulation of energy storage nodes and inverter regulation of photovoltaic nodes) is adopted on the basis of equivalent regulation. After the adjustment measures of the nodes with the highest sensitivity and the lowest cost are exhausted, the comprehensive sensitivity of the remaining nodes is re-sorted, and adjustment is performed point by point again until the voltage of each node in the distribution network no longer exceeds the limit.

Since the second and third stages of the inverter both involve reduction in photovoltaic active power output, the second and third stage adjustments of the inverter can be collectively referred to as inverter active power adjustment, and the first stage adjustment of the inverter is referred to as inverter reactive power adjustment. Based on this, the cost-taking adjustment measures proposed in the embodiment can be divided into three stages:

Phase 1: If energy storage regulation and inverter reactive regulation have regulation margin and the regulation cost is less than inverter active regulation, energy storage regulation and inverter reactive regulation will be used (the word "and" here is because energy storage active regulation or photovoltaic inverter reactive regulation alone may not meet the requirements, so a combination of the two methods may be required).

The second stage: energy storage regulation and inverter reactive regulation have regulation margin, but their regulation cost is greater than or equal to inverter active regulation. At this time, if energy storage device regulation or inverter reactive regulation is performed, it is equivalent to photovoltaic power generating more active power for line loss, that is, the power grid company accepts photovoltaic power grid access, but this part of active power is used for line loss. Therefore, this paper proposes to perform inverter active regulation at this stage, and at the same time, the side equipment counts the regulation amount and regulation time, and compensates users in equal amounts, which reduces line loss, guarantees user benefits, and preserves adjustment measures;

The third stage: if there is no regulation margin for energy storage regulation and inverter reactive power regulation, the inverter active power regulation will be carried out, but no subsidy will be provided for reducing photovoltaic output in this stage.

This embodiment designs a practical calculation method for voltage sensitivity, and proposes a comprehensive voltage sensitivity to describe the distributed resource control capability, providing a calculation method for voltage adjustment under the power distribution Internet of Things;

A cost-effective voltage control method was also designed to achieve a balance between greater photovoltaic power generation, smaller system losses and greater user benefits while controlling the system voltage.

Embodiment 2:

A flow chart of a voltage regulation measure based on a smart terminal in a substation under high photovoltaic penetration provided by this embodiment is shown in FIG4 , and the specific steps include:

1) When photovoltaic and energy storage devices are connected to the substation, the photovoltaic inverter capacity S _pv.max , the maximum power factor angle δ _pv.max , the charge capacity limit of the energy storage device [S _ess.min , S _ess.max ], the rated active power P _ess.N , and the node voltage limit [V _min , V _max ] are collected in the model of the substation intelligent terminal, and the topology structure is updated at the same time, and the node admittance matrix and the node impedance matrix are calculated.

2) The smart meter reports node voltage, power, distributed power output (P _pv , Q _pv ), and energy storage device charge status information to the edge device every 5 minutes. Based on the collected information, the area smart terminal calculates the voltage sensitivity of the distributed resource node to the other nodes, the total power of downstream users of each node, and the maximum adjustable reactive power Q _pv.max of the first stage of the photovoltaic inverter. The calculation is as follows:

3) When the node voltage exceeds the limit, the smart meter will actively report and calculate the voltage value ΔV _i (i.e., the voltage exceeding the limit) that needs to be adjusted for each node. Since the voltage changes slowly, the voltage sensitivity calculated at the previous collection point can be used for calculation;

4) Calculate the comprehensive voltage sensitivity, find the nodes with the largest comprehensive voltage sensitivity in the currently available photovoltaic inverter reactive power regulation and energy storage device active power regulation, and calculate the reactive power and active power required to adjust ΔV _i under the comprehensive voltage sensitivity;

5) Determine whether the reactive power required for adjusting the reactive power of the inverter ΔV _i is less than the maximum adjustable reactive power Q _pv.max of the inverter reactive power adjustment, and whether the active power required for adjusting the active power of the energy storage device ΔV _i is less than the rated active power P _ess.N of the energy storage device;

6) If 5) is established, the reactive power adjustment cost of the inverter and the adjustment cost of the energy storage device are calculated, and the active power adjustment amount and adjustment cost of the inverter are calculated according to the maximum sensitivity, and the method with the lowest cost among the four methods is executed, and the operation is terminated;

If 5) is not true, then calculate ΔV _ess.N (voltage regulation amount of the energy storage device) and ΔV _pv.max (voltage regulation amount of the photovoltaic inverter) corresponding to P _ess.N and Q _pv.max , and make ΔV _i+1 =min(ΔV _ess.N , ΔV _pv.max ), and then calculate the adjustment amount and adjustment cost of the four adjustment methods according to the maximum comprehensive sensitivity when calculating the adjustment voltage ΔV _i+1 , and execute the one with the lowest cost;

7) Since the comprehensive voltage sensitivity will change after each cycle is executed, the adjustment method is selected and adjusted, so it is necessary to re-determine the currently available node with the largest comprehensive sensitivity, remove the nodes without adjustment capability, set ΔV _i = ΔV _i - ΔV _i+1 , i = i+1, and loop through steps 4) to 7).

Embodiment 3:

Based on the same inventive concept, the present invention also provides a voltage control system under high photovoltaic penetration based on a smart terminal in a substation, as shown in FIG5 , including: a comprehensive voltage sensitivity module, a sorting module and a power regulation module;

The comprehensive voltage sensitivity module is used for calculating the voltage over-limit value of each node in the distribution network where the voltage over-limit occurs, and the comprehensive voltage sensitivity of each node containing distributed photovoltaic power sources during power adjustment based on the electrical data of each node in the distribution network reported by the smart meter when the node voltage over-limit occurs in the distribution network;

The sorting module is used to select the nodes with the largest comprehensive voltage sensitivity among the different regulation modes of the distributed photovoltaic power source, calculate the regulation cost of the corresponding node regulation mode on the basis of equivalent regulation, and select the regulation mode with the smallest regulation cost for power regulation;

The power regulation module is used to recalculate the comprehensive voltage sensitivity and regulation cost of each available node containing distributed photovoltaic power sources after the adjustable power of the node with the minimum regulation cost is used up, and perform power regulation until the voltage of each node no longer exceeds the limit;

Among them, the nodes containing distributed photovoltaic power sources include energy storage device nodes and photovoltaic inverter nodes, the adjustment methods include active power adjustment of energy storage devices, active power adjustment of photovoltaic inverters and reactive power adjustment of photovoltaic inverters, and the adjustment costs include the adjustment costs of photovoltaic inverters and the adjustment costs of energy storage devices.

The integrated voltage sensitivity module is specifically used for:

Based on the electrical data of each node in the distribution network reported by the smart meter, the intelligent terminal in the substation area uses the Newton-Raphson method to obtain the Jacobian matrix and calculates the voltage sensitivity of each node containing distributed photovoltaic power sources in the distribution network to each voltage-limit node.

The intelligent terminal in the substation calculates the voltage over-limit value of each node in the distribution network where the voltage over-limit occurs based on the electrical data of each node in the distribution network reported by the smart meter;

Based on the voltage sensitivity of the power regulation of the distributed photovoltaic power node in the distribution network to each voltage-over-limit node and the voltage-over-limit value of each node where the voltage over-limit occurs, the comprehensive voltage sensitivity of each distributed photovoltaic power node in the distribution network during power regulation is calculated;

The electrical data of each node of the distribution network reported by the smart meter includes the voltage of each node, the power of each node, the output of the distributed power source and the charge state data of the energy storage device.

The comprehensive voltage sensitivity of each distributed photovoltaic power node in the distribution network during power regulation is calculated as follows:

In the formula, is the comprehensive voltage sensitivity of node H in the distribution network containing distributed photovoltaic power generation during reactive power regulation, is the comprehensive voltage sensitivity of node H containing distributed photovoltaic power generation in the distribution network during active power regulation, m is the number of all voltage-exceeding nodes in the distribution network, _ΔVk is the voltage-exceeding value of the kth voltage-exceeding node in the distribution network, is the voltage sensitivity of the reactive power regulation of node H containing distributed photovoltaic power in the distribution network to the kth voltage-limited node, is the voltage sensitivity of the active power regulation of node H containing distributed photovoltaic power in the distribution network to the kth voltage-exceeding node;

Among them, the voltage over-limit value of the kth voltage over-limit node in the distribution network is calculated as follows:

ΔV _k = V _k - V _max

Where _Vk is the voltage value of the kth voltage-over-limit node in the distribution network, and _Vmax is the maximum voltage.

The calculation of the voltage sensitivity of each distributed photovoltaic power source node power regulation in the distribution network to each voltage-limited node includes:

For each node containing a distributed photovoltaic power source in the distribution network, the voltage sensitivity of power regulation to each voltage-exceeding node is calculated when the node containing the distributed photovoltaic power source is an upstream node, a downstream node, and a node on a branch of the line where the node is located;

The upstream node of the voltage over-limit node is the line from the distribution transformer through the voltage over-limit node to the terminal node of the distribution network, excluding the voltage over-limit node, and the remaining nodes on the line between the distribution transformer and the voltage over-limit node;

The downstream nodes of the voltage-exceeding node are, excluding the voltage-exceeding node, the remaining nodes on the line between the voltage-exceeding node and the terminal node of the distribution network, including the terminal node of the distribution network.

When the node containing the distributed photovoltaic power source is the upstream node of the voltage-exceeding node, the voltage sensitivity of the power regulation to each voltage-exceeding node is calculated as follows:

In the formula, In order to adjust the reactive power of the distributed photovoltaic power generation node A upstream of the voltage-limit node N in the distribution network, the voltage sensitivity of the voltage-limit node N is calculated. In order to adjust the voltage sensitivity of the voltage-over-limit node N when the active power of the distributed photovoltaic power node A upstream of the voltage-over-limit node N in the distribution network is adjusted, j is the adjacent node of node A, n is the number of nodes adjacent to node A, _Vj is the voltage of node j, G _Aj is the conductance between node A and node j, B _Aj is the susceptance between node A and node j, δ _Aj is the power angle between node A and node j, V _A is the voltage of node A, B _AA is the susceptance between node A and node A, i is the i-th node between node N and node A upstream of node N, V _i is the voltage of node i, and V _i-1 is the voltage of the previous upstream node of node i.

When the node containing the distributed photovoltaic power source is a downstream node of the voltage-exceeding node, the voltage sensitivity of the power regulation to each voltage-exceeding node is calculated as follows:

In the formula, In order to adjust the reactive power of the distributed photovoltaic power generation node Y downstream of the voltage-limit node N in the distribution network, the voltage sensitivity of the voltage-limit node N is calculated. In order to adjust the voltage sensitivity of the voltage-over-limit node N in the distribution network when the downstream of the voltage-over-limit node N contains the active power of the distributed photovoltaic power node Y, V _N is the voltage of the node N, V _Y is the voltage of the node Y, is the partial derivative of the reactive power generated by the distributed photovoltaic power source at node Y with respect to the voltage, is the partial derivative of the active power generated by the distributed photovoltaic power source at node Y with respect to the voltage, l is the lth node between node N and node Y downstream of node N, X _l is the reactance between node l and the previous upstream node of node l, and R _l is the resistance between node l and the previous upstream node of node l.

When the node containing the distributed photovoltaic power source is a node on the branch of the line where the voltage-exceeding node is located, the voltage sensitivity of the power regulation to each voltage-exceeding node is calculated as follows:

In the formula, In order to adjust the reactive power of the distributed photovoltaic power source node E on the branch of the line where the voltage-over-limit node N is located in the distribution network, the voltage sensitivity of the voltage-over-limit node N is determined. In order to adjust the active power of the distributed photovoltaic power supply node E on the branch of the line where the voltage-over-limit node N in the distribution network is located, the voltage sensitivity of the voltage-over-limit node N is determined. _VC is the voltage of the node C, _VE is the voltage of the node E, is the partial derivative of the reactive power generated by the distributed photovoltaic power source at node E with respect to the voltage, is the partial derivative of the active power generated by the distributed photovoltaic power source at node E with respect to the voltage, r is the r-th node from the starting node F to node E on the branch where node E is located, _Xr is the reactance between node r and the previous upstream node of node r, _Rr is the resistance between node r and the previous upstream node of node r, s is the s-th node from the connecting node C to the line including node N, the branch where node E is located and node N, _Vs is the voltage of node s, and Vs _-1 is the voltage of the node before node s in the direction from node C to node N.

The regulation cost of the energy storage device is calculated as follows:

Where Cost ₀ is the cost of the energy storage device when regulating the active power of node T, ΔP is the change in the active power of the line where node T is located, U _N is the rated voltage of the line where node T is located, t is the tth node from the line origin to node T on the line where node T is located, P _t is the active power flowing into node t from the previous upstream node of node t, R _t is the resistance between node t and the previous upstream node of node t, and ΔP _ess is the active power absorbed by the energy storage device.

The regulation cost of the photovoltaic inverter includes:

The PV inverter maintains the active power unchanged, increasing the cost of the reactive power stage;

After reaching the capacity limit, the photovoltaic inverter adjusts the power factor angle, reducing the active power while increasing the cost of the reactive power stage;

After the power factor angle of the photovoltaic inverter reaches the limit, the cost of the active power and reactive power stages is reduced proportionally.

The photovoltaic inverter maintains the active power unchanged and increases the cost of the reactive power stage, which is calculated as follows:

Where Cost ₁ is the cost of the PV inverter to maintain the active power unchanged and increase the reactive compensation stage, ΔQ is the reactive power change of the line where node T is located, U _N is the rated voltage of the line where node T is located, t is the tth node from the line origin to node T on the line where node T is located, Q _t is the reactive power flowing into node t from the previous upstream node of node t, and R _t is the resistance between node t and the previous upstream node of node t.

After the photovoltaic inverter reaches the capacity limit, the power factor angle is adjusted to reduce the active power while increasing the reactive power stage cost, which is calculated as follows:

Wherein, Cost ₂ is the cost of the photovoltaic inverter adjusting the power factor angle to reduce active power and increase reactive power after reaching the capacity limit, ΔP is the change in active power of the line where node T is located, U _N is the rated voltage of the line where node T is located, t is the tth node from the line origin to node T on the line where node T is located, P _t is the active power flowing into node t from the previous upstream node of node t, R _t is the resistance between node t and the previous upstream node of node t, ΔQ is the change in reactive power of the line where node T is located, and Q _t is the reactive power flowing into node t from the previous upstream node of node t.

After the power factor angle of the photovoltaic inverter reaches the limit, the cost of the active power and reactive power stages is proportionally reduced, as calculated by the following formula:

Wherein, Cost ₃ is the cost of the photovoltaic inverter in the stage of proportionally reducing active power and reactive power after the power factor angle reaches the limit, ΔP is the change in active power of the line where node T is located, U _N is the rated voltage of the line where node T is located, t is the tth node from the line origin to node T on the line where node T is located, P _t is the active power flowing into node t from the previous upstream node of node t, R _t is the resistance between node t and the previous upstream node of node t, ΔQ is the change in reactive power of the line where node T is located, and Q _t is the reactive power flowing into node t from the previous upstream node of node t.

The calculation of the adjustment cost of the corresponding node adjustment method based on the equivalent adjustment includes:

Based on the comprehensive voltage sensitivity, different regulation methods achieve the same voltage regulation effect by adjusting power, resulting in regulation costs.

The substation intelligent terminal stores a distribution network topology model, which is used to calculate the voltage over-limit value of each node in the distribution network where the voltage over-limit occurs, the comprehensive voltage sensitivity of each node containing distributed photovoltaic power sources during power adjustment, and the power adjustment amount and adjustment cost required to adjust the voltage over-limit value of each node under the maximum comprehensive voltage sensitivity; and is used to store the photovoltaic inverter capacity, the maximum power factor angle of the photovoltaic inverter, the active adjustment margin of the photovoltaic inverter, the reactive adjustment margin of the photovoltaic inverter, the charge capacity limit of the energy storage device, the rated active power of the energy storage device, the active adjustment margin of the energy storage device and the voltage limit of each node.

Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

The present invention is described with reference to the flowchart and/or block diagram of the method, device (system), and computer program product according to the embodiment of the present invention. It should be understood that each process and/or box in the flowchart and/or block diagram, as well as the combination of the process and/or box in the flowchart and/or block diagram can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for implementing the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device that implements the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

These computer program instructions may also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit its protection scope. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that after reading the present invention, those skilled in the art can still make various changes, modifications or equivalent substitutions to the specific implementation methods of the invention, but these changes, modifications or equivalent substitutions are all within the protection scope of the pending claims of the invention.

Claims (9)

1. A method for controlling voltage under high photovoltaic penetration rate based on intelligent terminals in a metropolitan area, characterized by comprising: When the voltage of a node in the distribution network exceeds the limit, the intelligent terminal in the substation calculates the voltage limit value of each node where the voltage exceeds the limit, and the comprehensive voltage sensitivity of each node containing distributed photovoltaic power sources during power adjustment based on the electrical data of each node in the distribution network reported by the smart meter; Select the nodes with the largest comprehensive voltage sensitivity in different regulation modes of distributed photovoltaic power sources respectively, calculate the regulation cost of the corresponding node regulation mode on the basis of equivalent regulation, and select the regulation mode with the smallest regulation cost for power regulation; When the adjustable power of the node with the minimum adjustment cost is used up, the comprehensive voltage sensitivity and adjustment cost of each available node containing distributed photovoltaic power sources are recalculated, and power adjustment is performed until the voltage of each node no longer exceeds the limit; The nodes containing distributed photovoltaic power sources include energy storage device nodes and photovoltaic inverter nodes, the regulation methods include active regulation of energy storage devices, active regulation of photovoltaic inverters, and reactive regulation of photovoltaic inverters, and the regulation costs include the regulation costs of photovoltaic inverters and the regulation costs of energy storage devices; The intelligent terminal in the substation area calculates the voltage over-limit value of each node in the distribution network where the voltage over-limit occurs based on the electrical data of each node in the distribution network reported by the smart meter, and calculates the comprehensive voltage sensitivity of each node containing distributed photovoltaic power sources during power regulation, including: Based on the electrical data of each node in the distribution network reported by the smart meter, the intelligent terminal in the substation area uses the Newton-Raphson method to obtain the Jacobian matrix and calculates the voltage sensitivity of each node containing distributed photovoltaic power sources in the distribution network to each voltage-limited node. The intelligent terminal in the substation calculates the voltage over-limit value of each node in the distribution network where the voltage over-limit occurs based on the electrical data of each node in the distribution network reported by the smart meter; Based on the voltage sensitivity of the power regulation of the distributed photovoltaic power node in the distribution network to each voltage-over-limit node and the voltage-over-limit value of each node where the voltage over-limit occurs, the comprehensive voltage sensitivity of each distributed photovoltaic power node in the distribution network during power regulation is calculated; The electrical data of each node of the distribution network reported by the smart meter includes the voltage of each node, the power of each node, the output of the distributed power source and the charge state data of the energy storage device; The comprehensive voltage sensitivity of each distributed photovoltaic power node during power regulation is calculated as follows: In the formula, is the comprehensive voltage sensitivity of node H containing distributed photovoltaic power generation in the distribution network during reactive power regulation, is the comprehensive voltage sensitivity of node H containing distributed photovoltaic power generation in the distribution network during active power regulation, m is the number of all voltage-exceeding nodes in the distribution network, _ΔVk is the voltage-exceeding value of the kth voltage-exceeding node in the distribution network, is the voltage sensitivity of the reactive power regulation of node H containing distributed photovoltaic power in the distribution network to the kth voltage-limited node, is the voltage sensitivity of the active power regulation of node H containing distributed photovoltaic power in the distribution network to the kth voltage-exceeding node; Among them, the voltage over-limit value of the kth voltage over-limit node in the distribution network is calculated as follows: ΔV _k = V _k - V _max Where _Vk is the voltage value of the kth voltage-over-limit node in the distribution network, and _Vmax is the maximum voltage; The calculation of the voltage sensitivity of each distributed photovoltaic power source node power regulation in the distribution network to each voltage-limited node includes: For each node containing a distributed photovoltaic power source in the distribution network, the voltage sensitivity of power regulation to each voltage-exceeding node is calculated when the node containing the distributed photovoltaic power source is an upstream node, a downstream node, and a node on a branch of the line where the node is located; The upstream node of the voltage over-limit node is the line from the distribution transformer through the voltage over-limit node to the terminal node of the distribution network, excluding the voltage over-limit node, and the remaining nodes on the line between the distribution transformer and the voltage over-limit node; The downstream nodes of the voltage-exceeding node are, excluding the voltage-exceeding node, the remaining nodes on the line between the voltage-exceeding node and the terminal node of the distribution network, including the terminal node of the distribution network; When the node containing the distributed photovoltaic power source is the upstream node of the voltage-exceeding node, the voltage sensitivity of the power regulation to each voltage-exceeding node is calculated as follows: In the formula, In order to adjust the reactive power of the distributed photovoltaic power generation node A upstream of the voltage-over-limit node N in the distribution network, the voltage sensitivity of the voltage-over-limit node N is calculated. In order to adjust the voltage sensitivity of the voltage-over-limit node N when the active power of the distributed photovoltaic power node A upstream of the voltage-over-limit node N in the distribution network is contained, j is the adjacent node of node A, n is the number of nodes adjacent to node A, _Vj is the voltage of node j, G _Aj is the conductance between node A and node j, B _Aj is the susceptance between node A and node j, δ _Aj is the power angle between node A and node j, V _A is the voltage of node A, B _AA is the susceptance between node A and node A, i is the i-th node between node N and node A upstream of node N, V _i is the voltage of node i, and V _i-1 is the voltage of the previous upstream node of node i; When the node containing the distributed photovoltaic power source is a downstream node of the voltage-exceeding node, the voltage sensitivity of the power regulation to each voltage-exceeding node is calculated as follows: In the formula, In order to adjust the reactive power of the distributed photovoltaic power generation node Y downstream of the voltage-limit node N in the distribution network, the voltage sensitivity of the voltage-limit node N is calculated. In order to adjust the voltage sensitivity of the voltage-over-limit node N in the distribution network when the downstream of the voltage-over-limit node N contains the active power of the distributed photovoltaic power node Y, V _N is the voltage of the node N, V _Y is the voltage of the node Y, is the partial derivative of the reactive power generated by the distributed photovoltaic power source at node Y with respect to the voltage, is the partial derivative of the active power generated by the distributed photovoltaic power source at node Y with respect to the voltage, l is the lth node between node N and node Y downstream of node N, X _l is the reactance between node l and the previous upstream node of node l, and R _l is the resistance between node l and the previous upstream node of node l; When the node containing the distributed photovoltaic power source is a node on the branch of the line where the voltage-exceeding node is located, the voltage sensitivity of the power regulation to each voltage-exceeding node is calculated as follows: In the formula, In order to adjust the reactive power of the distributed photovoltaic power source node E on the branch of the line where the voltage-over-limit node N is located in the distribution network, the voltage sensitivity of the voltage-over-limit node N is determined. In order to adjust the active power of the distributed photovoltaic power supply node E on the branch of the line where the voltage-over-limit node N in the distribution network is located, the voltage sensitivity of the voltage-over-limit node N is determined. _VC is the voltage of the node C, _VE is the voltage of the node E, is the partial derivative of the reactive power generated by the distributed photovoltaic power source at node E with respect to the voltage, is the partial derivative of the active power generated by the distributed photovoltaic power source at node E with respect to the voltage, r is the r-th node from the starting node F to node E on the branch where node E is located, _Xr is the reactance between node r and the previous upstream node of node r, _Rr is the resistance between node r and the previous upstream node of node r, s is the s-th node from the connecting node C to the line including node N, the branch where node E is located and node N, _Vs is the voltage of node s, and Vs _-1 is the voltage of the node before node s in the direction from node C to node N. 2. The method according to claim 1, characterized in that the adjustment cost of the energy storage device is calculated as follows: Where Cost ₀ is the cost of the energy storage device when regulating the active power of node T, ΔP is the change in the active power of the line where node T is located, U _N is the rated voltage of the line where node T is located, t is the tth node from the line origin to node T on the line where node T is located, P _t is the active power flowing into node t from the previous upstream node of node t, R _t is the resistance between node t and the previous upstream node of node t, and ΔP _ess is the active power absorbed by the energy storage device. 3. The method according to claim 1, wherein the adjustment cost of the photovoltaic inverter comprises: The PV inverter maintains the active power unchanged, increasing the cost of the reactive power stage; After reaching the capacity limit, the photovoltaic inverter adjusts the power factor angle, reducing the active power while increasing the cost of the reactive power stage; After the power factor angle of the photovoltaic inverter reaches the limit, the cost of the active power and reactive power stages is reduced proportionally. 4. The method according to claim 3, characterized in that the photovoltaic inverter maintains the active power unchanged and increases the cost of the reactive power stage, which is calculated as follows: Where Cost ₁ is the cost of the PV inverter to maintain the active power unchanged and increase the reactive compensation stage, ΔQ is the reactive power change of the line where node T is located, U _N is the rated voltage of the line where node T is located, t is the tth node from the line origin to node T on the line where node T is located, Q _t is the reactive power flowing into node t from the previous upstream node of node t, and R _t is the resistance between node t and the previous upstream node of node t. 5. The method according to claim 3, characterized in that after the photovoltaic inverter reaches the capacity limit, the power factor angle is adjusted to reduce the active power while increasing the cost of the reactive power stage, which is calculated as follows: Wherein, Cost ₂ is the cost of the photovoltaic inverter adjusting the power factor angle to reduce active power and increase reactive power after reaching the capacity limit, ΔP is the change in active power of the line where node T is located, U _N is the rated voltage of the line where node T is located, t is the tth node from the line origin to node T on the line where node T is located, P _t is the active power flowing into node t from the previous upstream node of node t, R _t is the resistance between node t and the previous upstream node of node t, ΔQ is the change in reactive power of the line where node T is located, and Q _t is the reactive power flowing into node t from the previous upstream node of node t. 6. The method according to claim 3, characterized in that, after the power factor angle of the photovoltaic inverter reaches the limit, the cost of the active power and reactive power stages is proportionally reduced, calculated as follows: Wherein, Cost ₃ is the cost of the photovoltaic inverter in the stage of proportionally reducing active power and reactive power after the power factor angle reaches the limit, ΔP is the change in active power of the line where node T is located, U _N is the rated voltage of the line where node T is located, t is the tth node from the line origin to node T on the line where node T is located, P _t is the active power flowing into node t from the previous upstream node of node t, R _t is the resistance between node t and the previous upstream node of node t, ΔQ is the change in reactive power of the line where node T is located, and Q _t is the reactive power flowing into node t from the previous upstream node of node t. 7. The method according to claim 1, wherein the step of calculating the adjustment cost of the corresponding node adjustment method based on the equivalent adjustment comprises: Based on the comprehensive voltage sensitivity, different regulation methods achieve the same voltage regulation effect by adjusting power, resulting in regulation costs. 8. The method as claimed in claim 1 is characterized in that a distribution network topology model is stored in the substation intelligent terminal, which is used to calculate the voltage over-limit value of each node in the distribution network where the voltage over-limit occurs, the comprehensive voltage sensitivity of each node containing distributed photovoltaic power sources during power adjustment, and the power adjustment amount and adjustment cost required to adjust the voltage over-limit value of each node under the maximum comprehensive voltage sensitivity; and is used to store the photovoltaic inverter capacity, the maximum power factor angle of the photovoltaic inverter, the active adjustment margin of the photovoltaic inverter, the reactive adjustment margin of the photovoltaic inverter, the charge capacity limit of the energy storage device, the rated active power of the energy storage device, the active adjustment margin of the energy storage device and the voltage limit of each node. 9. A voltage control system under high photovoltaic penetration rate based on intelligent terminals in a substation, used to implement a voltage control method under high photovoltaic penetration rate based on intelligent terminals in a substation as described in any one of claims 1 to 8, characterized in that it comprises: a comprehensive voltage sensitivity module, a sorting module and a power regulation module; The comprehensive voltage sensitivity module is used for calculating the voltage over-limit value of each node in the distribution network where the voltage over-limit occurs, and the comprehensive voltage sensitivity of each node containing distributed photovoltaic power sources during power adjustment based on the electrical data of each node in the distribution network reported by the smart meter when the node voltage over-limit occurs in the distribution network; The sorting module is used to select the nodes with the largest comprehensive voltage sensitivity among the different regulation modes of the distributed photovoltaic power source, calculate the regulation cost of the corresponding node regulation mode on the basis of equivalent regulation, and select the regulation mode with the smallest regulation cost for power regulation; The power regulation module is used to recalculate the comprehensive voltage sensitivity and regulation cost of each available node containing distributed photovoltaic power sources after the adjustable power of the node with the minimum regulation cost is used up, and perform power regulation until the voltage of each node no longer exceeds the limit; The nodes containing distributed photovoltaic power sources include energy storage device nodes and photovoltaic inverter nodes, the regulation methods include active regulation of energy storage devices, active regulation of photovoltaic inverters, and reactive regulation of photovoltaic inverters, and the regulation costs include the regulation costs of photovoltaic inverters and the regulation costs of energy storage devices; The comprehensive voltage sensitivity of each node containing distributed photovoltaic power sources during power regulation is calculated as follows: In the formula, is the comprehensive voltage sensitivity of node H containing distributed photovoltaic power generation in the distribution network during reactive power regulation, is the comprehensive voltage sensitivity of node H containing distributed photovoltaic power generation in the distribution network during active power regulation, m is the number of all voltage-exceeding nodes in the distribution network, _ΔVk is the voltage-exceeding value of the kth voltage-exceeding node in the distribution network, is the voltage sensitivity of the reactive power regulation of node H containing distributed photovoltaic power in the distribution network to the kth voltage-limited node, is the voltage sensitivity of the active power regulation of node H containing distributed photovoltaic power in the distribution network to the kth voltage-exceeding node; Among them, the voltage over-limit value of the kth voltage over-limit node in the distribution network is calculated as follows: ΔV _k = V _k - V _max Where _Vk is the voltage value of the kth voltage-over-limit node in the distribution network, and _Vmax is the maximum voltage.