CN118473013B - Low voltage distribution network voltage over-limit suppression method and device based on control input optimization - Google Patents

Abstract

The invention belongs to the technical field of new energy grid connection of an electric power system, and discloses a low-voltage distribution network voltage out-of-limit suppression method and device based on control input optimization; the low-voltage distribution network voltage out-of-limit inhibition method comprises the following steps: constructing and obtaining a node voltage out-of-limit model, and constructing and obtaining a voltage out-of-limit inhibition scheme of the cooperation of distributed energy storage and distributed power generation; based on the voltage out-of-limit inhibition scheme, performing sensitivity analysis on the control input signal, and calculating to obtain a comprehensive influence coefficient index; based on the comprehensive influence coefficient index, a two-stage control input signal optimizing method comprising active control set screening and redundant control signal screening is adopted, and an optimal control input signal is obtained through screening; and performing low-voltage distribution network voltage out-of-limit suppression based on the optimal control input signal. The technical scheme of the invention can effectively solve the problem that the low-voltage distribution network voltage out-of-limit caused by distributed energy is difficult to effectively inhibit in the prior art.

Description

Low voltage distribution network voltage over-limit suppression method and device based on control input optimization

Technical Field

The present invention belongs to the technical field of new energy grid connection in power systems, and in particular relates to a method and device for suppressing voltage over-limit in a low-voltage distribution network based on optimal control input.

Background Art

The penetration of distributed energy into low-voltage distribution networks (explanatory, low-voltage distribution networks refer to distribution networks with voltage levels of 1kV and below in power systems) has brought many challenges to the operation of the distribution network itself; among them, the more prominent problem is the voltage over-limit problem. Specifically, due to the randomness and volatility of distributed generation (DG), the incorporation of multiple DG units into the distribution network will lead to overvoltage or undervoltage problems; further explanatory, when the power generation of the distribution network feeder exceeds its load consumption, there will be a reverse flow of power (reverse power flow), resulting in node overvoltage. In addition, DG-based voltage regulation measures will conflict with other traditional voltage regulation devices (for example, such as on-load tap changers, voltage regulators and capacitor banks), which may cause coordination problems between protection devices and even cause equipment tripping risks. In addition, with the complexity of the distribution network structure, the problem of voltage over-limit in the distribution network caused by distributed energy has become more prominent.

In order to solve the problem of voltage over-limit in distribution network caused by distributed energy, the existing traditional method is to achieve the redistribution of distribution network flow through equipment upgrade and network structure optimization; the above-mentioned existing traditional solutions have greatly increased the demand for medium-term investment. In addition, since the control system in the low-voltage distribution network involves a very wide range and there may be multiple voltage over-limit nodes in the distribution network, it is difficult to identify the most effective control signal for the over-limit node among many control inputs, and it is impossible to achieve effective voltage over-limit suppression.

Summary of the invention

The purpose of the present invention is to provide a method and device for suppressing over-limit voltage in a low-voltage distribution network based on control input optimization, so as to solve one or more of the above-mentioned technical problems. The technical solution provided by the present invention can effectively suppress over-limit voltage by screening and selecting control input signals, and can avoid conflicts with other control schemes, effectively solving the problem in the prior art that over-limit voltage in a low-voltage distribution network caused by distributed energy is difficult to effectively suppress.

In order to achieve the above object, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a method for suppressing voltage over-limit in a low-voltage distribution network based on control input optimization, comprising the following steps:

According to the target low-voltage distribution network system, a node voltage over-limit model is constructed; wherein the target low-voltage distribution network system includes a distributed power generation system and a distributed energy storage system;

Based on the node voltage over-limit model, a voltage over-limit suppression scheme for coordinated distributed energy storage and distributed generation is constructed;

Based on the voltage over-limit suppression scheme, a sensitivity analysis of the control input signal is performed to obtain the influence of the control input signal on the voltage of all bus nodes in the low-voltage distribution network; based on the influence of the control input signal on the voltage of all bus nodes in the low-voltage distribution network, a comprehensive influence coefficient index is calculated;

Based on the comprehensive influence coefficient index, a two-stage control input signal selection method including effective control set screening and redundant control signal screening is adopted to screen and obtain the optimal control input signal;

Based on the optimal control input signal, voltage over-limit suppression of the low-voltage distribution network is performed.

A further improvement of the present invention is that the voltage over-limit suppression scheme includes:

Based on the charge and discharge droop coefficient, droop control is used to determine the power exchange between the distributed energy storage system and the low-voltage distribution network for the bus node with abnormal voltage to ensure the voltage balance of the bus node.

A further improvement of the present invention is that, based on the voltage over-limit suppression scheme, a sensitivity analysis of the control input signal is performed to obtain the influence of the control input signal on the voltages of all bus nodes in the low-voltage distribution network; based on the influence of the control input signal on the voltages of all bus nodes in the low-voltage distribution network, the step of calculating and obtaining a comprehensive influence coefficient index comprises:

Based on the voltage over-limit suppression scheme, a sensitivity matrix of bus node voltage to bus output power is constructed;

Based on the sensitivity matrix, the bus node voltage amplitude change caused by the bus output power change is calculated; based on the bus node voltage sensitivity matrix to the bus output power, the bus node voltage sensitivity to the control input signal is obtained;

Based on the bus node voltage amplitude change caused by bus output power change and the bus voltage sensitivity to the control input signal, a bus node voltage coupling model of the target low-voltage distribution network system is constructed and a generalized electrical distance model is defined.

Based on the generalized electrical distance model and the control input signal cost, the comprehensive impact coefficient index is calculated;

Among them, the calculation expression of the comprehensive influence coefficient is:

;

In the formula, represents the comprehensive impact coefficient; Represents the total number of nodes with over-limit voltage, 1≤ ≤ ; represents the normalized generalized electrical distance; Indicates that at the node The unit cost corresponding to applying the control input signal at .

A further improvement of the present invention is that, in the step of constructing a bus node voltage coupling model for a target low-voltage distribution network system and defining a generalized electrical distance model based on the bus node voltage amplitude change caused by the bus output power change and the sensitivity of the i -th bus voltage to the control input signal,

The functional expression of the bus node voltage coupling model is:

;

_{Where αim} is the distance between node i and node The attenuation amplitude of direct voltage change; Respectively represent node i and node The voltage amplitude change;

The normalized expression of generalized electrical distance is:

;

_{Where, Dix} represents the normalized generalized electrical distance; represents the generalized electrical distance between the control input signal applied at node x and the target node i in the low-voltage distribution network;

;

In the formula, represents the attenuation amplitude of the control input signal applied at node x to node i ; represents the attenuation amplitude of the control input signal applied at node i to node x ; represents the logarithmic function;

in,

In the formula, represents the voltage amplitude of node i ; represents the voltage amplitude of node x ; represents the reactive power injected into node x by the distributed energy storage system and distributed generation system; represents the applied reactive power control input signal at node x ; represents the applied active power control input signal at node x .

A further improvement of the present invention is that, based on the comprehensive influence coefficient index, a two-stage control input signal selection method including effective control set screening and redundant control signal screening is adopted, and the step of screening and obtaining the optimal control input signal includes:

Based on the comprehensive influence coefficient index, an effective control set whose control effect meets the preset requirements is selected from the control set composed of all control input signals;

Redundant control signals are screened out based on the effective control set to obtain an optimal control input signal; wherein, during the redundant control signal screening process, if the bus node voltage is still greater than a threshold after the selected control input signal is screened out from the effective control set, the selected control input signal is screened out.

A further improvement of the present invention is that in the step of constructing a node voltage over-limit model according to the target low-voltage distribution network system,

The target low-voltage distribution network system is a feeder of a low-voltage distribution network system containing photovoltaics and storage, including a distributed energy storage system, a photovoltaic panel, a local load, a first bus, a second bus, a transformer and a power grid; wherein the first bus is connected to the distributed energy storage system, the photovoltaic panel and the local load; a feeder resistance and a feeder reactance are connected in series between the first bus and the second bus; and the transformer is connected in series between the second bus and the power grid;

The expression of the node voltage over-limit model is:

In the formula, represents the voltage amplitude at the first bus; represents the voltage amplitude at the second bus; R and X represent the _feeder resistance and feeder reactance respectively; Pn represents the net actual active power injected into the first bus _by photovoltaic and load; Qn represents the load reactive power at the first bus.

A further improvement of the present invention is that in the voltage over-limit suppression scheme,

The calculation expression of the power exchanged between the distributed energy storage system and the low-voltage distribution network system is:

In the formula, Represents the power exchanged between the distributed energy storage system and the low-voltage distribution network system; and are the droop coefficients in charge and discharge modes, respectively; represents the node voltage of the ith bus, V _thrc and V _thrd are the upper and lower limits of the bus voltage for energy storage startup voltage regulation control respectively;

;

;

Where, V _nom is the rated voltage at the first busbar; and are the maximum photovoltaic power generation and the maximum load demand, respectively;

in,

Power capacity required for distributed energy storage systems for,

;

In the formula, and They represent the upper and lower limits of the node voltage of the i -th bus respectively.

In a second aspect of the present invention, there is provided a low voltage distribution network voltage over-limit suppression device based on control input optimization, comprising:

A first construction module is used to construct and obtain a node voltage over-limit model according to a target low-voltage distribution network system; wherein the target low-voltage distribution network system includes a distributed power generation system and a distributed energy storage system;

A second construction module is used to construct a voltage over-limit suppression scheme for coordinated distributed energy storage and distributed generation based on the node voltage over-limit model;

An index calculation module is used to perform a sensitivity analysis of the control input signal based on the voltage over-limit suppression scheme to obtain the influence of the control input signal on the voltage of all bus nodes in the low-voltage distribution network; based on the influence of the control input signal on the voltage of all bus nodes in the low-voltage distribution network, calculate and obtain a comprehensive influence coefficient index;

An optimization module is used to select and obtain the optimal control input signal based on the comprehensive influence coefficient index by adopting a two-stage control input signal selection method including effective control set screening and redundant control signal screening;

The voltage over-limit suppression module is used to suppress the voltage over-limit of the low-voltage distribution network based on the optimal control input signal.

According to a third aspect of the present invention, there is provided an electronic device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method for suppressing voltage over-limit in a low-voltage distribution network based on control input optimization as described in any one of the first aspect of the present invention is implemented.

According to a fourth aspect of the present invention, a non-transitory computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, a method for suppressing voltage over-limit in a low-voltage distribution network based on control input optimization as described in any one of the first aspect of the present invention is implemented.

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

In the technical solution provided by the present invention, firstly, a node voltage over-limit model of the target low-voltage distribution network system is constructed. This step is the basis of the technical solution of the embodiment of the present invention. Through precise modeling, the actual situation of the node voltage over-limit in the low-voltage distribution network system can be accurately reflected, which provides a solid foundation for the subsequent analysis and design of the suppression scheme; in addition, on the basis of establishing the node voltage over-limit model, a targeted voltage over-limit suppression scheme is further designed. This scheme is closely matched with the model and can ensure effective intervention and control of the voltage over-limit problem; further, a control input sensitivity analysis is carried out, and a comprehensive influence coefficient index is obtained. Through the sensitivity analysis, the technical solution of the present invention can evaluate the influence of different control inputs on the voltage over-limit suppression effect, and then derive the key index of the comprehensive influence coefficient. This index provides an important reference basis for the subsequent control signal selection; finally, a two-stage control input selection algorithm including effective control set screening and redundant control signal screening is adopted. The algorithm first screens out the effective control set, and then further screens out the redundant control signal, and finally realizes the selection of the optimal control signal. This algorithm greatly improves the control efficiency and accuracy. In summary, the embodiments of the present invention propose a practical solution to the problem that it is difficult to effectively suppress over-limit voltage in the low-voltage distribution network after distributed energy is connected. Through the implementation of the technical solution, it is possible to effectively suppress over-limit voltage while avoiding conflicts with other control schemes. This feature makes the present invention highly feasible and practical in practical applications.

In the embodiment of the present invention, a calculation scheme for the comprehensive influence coefficient index is specifically provided, so as to select the control signal with the lowest cost and the best effect, thereby suppressing the over-limit voltage with the minimum operating cost.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below; obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

1 is a schematic flow chart of a method for suppressing voltage over-limit in a low-voltage distribution network based on optimal control input in an embodiment of the present invention;

2 is a schematic diagram of a simplified feeder of a low-voltage distribution network system including a photovoltaic-storage system in an embodiment of the present invention;

3 is a schematic diagram of an equivalent circuit of a feeder of a solar-storage low-voltage distribution network system in FIG2 in an embodiment of the present invention;

FIG4 is a schematic diagram of feeder voltage rise under different powers in an embodiment of the present invention;

5 is a schematic diagram of feeder voltage drops at different powers in an embodiment of the present invention;

FIG6 is a schematic diagram of a process for screening effective control sets according to an embodiment of the present invention;

7 is a schematic diagram of a process for screening out redundant control signals in an embodiment of the present invention;

8 is a schematic diagram of a low-voltage distribution network voltage over-limit suppression system based on control input optimization in an embodiment of the present invention;

The explanation of the reference numerals in the figure is as follows:

1. Distributed energy storage system; 2. Photovoltaic panels; 3. Local load; 4. First busbar; 5. Second busbar; 6. Transformer; 7. Power grid.

DETAILED DESCRIPTION

In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

Referring to FIG. 1 , in an embodiment of the present invention, a method for suppressing voltage over-limit in a low-voltage distribution network based on optimal control input is provided, which specifically includes the following steps:

Step 1: construct and obtain a node voltage over-limit model according to a target low-voltage distribution network system; wherein the target low-voltage distribution network system includes a distributed power generation system and a distributed energy storage system; further illustratively, the distributed power generation system is a new energy power generation system, and the new energy power generation system can be photovoltaic power generation or wind power generation, etc.;

Step 2: Based on the node voltage over-limit model, a voltage over-limit suppression scheme for coordinated distributed energy storage and distributed generation is constructed;

Step 3: Based on the voltage over-limit suppression scheme, a sensitivity analysis of the control input signal is performed to obtain the influence of the control input signal on the voltage of all bus nodes in the low-voltage distribution network; based on the influence of the control input signal on the voltage of all bus nodes in the low-voltage distribution network, a comprehensive influence coefficient index is calculated;

Step 4: Based on the comprehensive influence coefficient index, a two-stage control input signal selection method including effective control set screening and redundant control signal screening is adopted to screen and obtain the optimal control input signal;

Step 5, based on the optimal control input signal, voltage over-limit suppression is performed; further illustratively, the output power obtained by the optimal control input signal is injected into the bus node, so as to achieve optimal voltage over-limit suppression.

In the technical solution provided by the embodiment of the present invention, a node voltage over-limit model of the target low-voltage distribution network system is constructed, and a voltage over-limit suppression scheme is constructed to match it; then, based on the voltage over-limit suppression scheme, a control input sensitivity analysis is performed, and a comprehensive influence coefficient index is obtained; finally, based on the comprehensive influence coefficient index, a two-stage control input optimization algorithm including effective control set screening and redundant control signal screening is adopted to realize the selection of the optimal control signal; the present invention can achieve effective suppression of over-limit voltage, avoid conflicts with other control schemes, and effectively solve the problem that the distribution network voltage over-limit caused by distributed energy is difficult to effectively suppress.

In one embodiment of the present invention, the voltage over-limit suppression scheme for the coordinated distributed energy storage and distributed generation constructed in step 2 is to use droop control on the voltage-abnormal bus node to determine the power exchange between the distributed energy storage system and the low-voltage distribution network based on the charge and discharge droop coefficient to ensure the voltage balance of the bus node.

In one embodiment of the present invention, in step 3, based on the voltage over-limit suppression scheme, a sensitivity analysis of the control input signal is performed to obtain the influence of the control input signal on the voltage of all bus nodes in the low-voltage distribution network; based on the influence of the control input signal on the voltage of all bus nodes in the low-voltage distribution network, the step of calculating and obtaining the comprehensive influence coefficient index includes:

Step 3.1), based on the voltage over-limit suppression scheme, establish a sensitivity matrix of bus node voltage to bus output power;

Step 3.2), based on the sensitivity matrix, calculate the bus node voltage amplitude change caused by the bus output power change; based on the bus node voltage to bus output power sensitivity matrix, obtain the bus node voltage to the control input signal sensitivity;

Step 3.3), based on the bus node voltage amplitude change caused by the bus output power change and the bus voltage sensitivity to the control input signal, a bus node voltage coupling model of the target low-voltage distribution network system is constructed and a generalized electrical distance model is defined;

Step 3.4), based on the generalized electrical distance model and the control input signal cost, calculate and obtain the comprehensive impact coefficient index;

Among them, the calculation expression of the comprehensive influence coefficient is:

;

In the formula, represents the comprehensive impact coefficient; Represents the total number of nodes with over-limit voltage, 1≤ ≤ ; represents the normalized generalized electrical distance; represents the unit cost corresponding to applying the control input signal at node x .

In one embodiment of the present invention, step 3.3) specifically includes:

Step 3.3.1), the bus node voltage coupling model is established, and the function is expressed as:

;

_{Where αim} is the distance between node i and node The attenuation amplitude of the direct voltage change; the value of α _ix is between 0 and 1; Respectively represent node i and node The voltage amplitude change;

in,

During reactive power control, ;

Other controls, ;

During active control, ;

In the formula, represents the attenuation amplitude of the control input signal applied at bus node x to node i ; represents the voltage amplitude of node i ; represents the voltage amplitude of node x ; represents the reactive power injected into node x by the distributed energy storage system and distributed generation system; represents the applied reactive power control input signal at node x ; represents the applied active power control input signal at node x ;

Step 3.3.2), based on the bus node voltage coupling model, the generalized electrical distance between the control input signal of node x and any node in the low-voltage distribution network is obtained. The function is expressed as follows:

;

In the formula, represents the attenuation amplitude of the control input signal applied at node x to node i ; represents the attenuation amplitude of the control input signal applied at node i to node x ; represents the logarithmic function; represents the generalized electrical distance between the control input signal applied at node x and the target node i in the low-voltage distribution network system;

Step 3.3.3), based on the generalized electrical distance in step 3.3.2), define the normalized electrical distance, the function is expressed as follows,

;

_{Where Dix} represents the normalized generalized electrical distance; N represents the total number of nodes with over-limit voltage.

In one embodiment of the present invention, in step 4, based on the comprehensive influence coefficient index, a two-stage control input signal selection method including effective control set screening and redundant control signal screening is adopted, and the step of screening to obtain the optimal control input signal specifically includes:

Step 4.1), based on the comprehensive influence coefficient index, select the effective control set whose control effect meets the preset requirements from the control set composed of all control input signals;

Step 4.2), performing redundant control signal screening processing on the effective control set obtained in step 4.1), and obtaining the optimal control input signal; wherein, during the redundant control signal screening processing, if a control input signal is screened out from the effective control set, and the node voltage is still greater than the threshold, then the control input signal is an invalid control signal, and the control input signal can be screened out.

In the preferred scheme of the embodiment of the present invention, through the sensitivity analysis between the voltage of the low-voltage distribution network feeder bus node and the control input signal, and taking into full consideration multiple operating conditions (especially cost) constraints, the control input signals that are effective in suppressing over-limit voltages at multiple locations are sorted, so as to select the control input signal with the lowest cost and the best effect, thereby suppressing the over-limit voltage with the lowest operating cost, avoiding conflicts with other control schemes, and effectively solving the voltage over-limit problem of the low-voltage distribution network system caused by distributed energy.

Referring to FIG. 2 to FIG. 7 , in a specific embodiment of the present invention, a method for suppressing voltage over-limit of a low-voltage distribution network based on optimal control input is provided, comprising the following steps:

Step 1: construct a node voltage over-limit model, including:

The target low-voltage distribution network system is specifically a low-voltage distribution network system taking photovoltaic storage into consideration, including a distributed energy storage system 1, photovoltaic panels 2, a local load 3, a first bus 4, a second bus 5, a transformer 6 and a power grid 7; wherein the distributed energy storage system 1 is used to suppress the bus node voltage exceeding the limit; the photovoltaic panels 2 are used to convert light energy into electrical energy and provide power for the local load 3.

Specifically, as shown in Figures 2 and 3, Figure 2 shows a simplified feeder of a low-voltage distribution network system containing photovoltaics and storage, and Figure 3 shows the equivalent circuit of the feeder in Figure 2; in Figure 2, the first bus 4 is composed of a distributed energy storage system, photovoltaic panels and local loads. The impact of energy storage on the system is not considered for the time being. The net power injection of photovoltaics and the load connected to the first bus 4 are regarded as a current source. When the injection current flowing through the bus n is I _n , the voltage deviation on the feeder It is expressed as,

; (1)

Where, Z is the feeder impedance between the first busbar and the medium voltage distribution transformer or the low voltage distribution transformer; “-” is the conjugate operator symbol;

In formula (1), The calculation expression of is:

; (2)

In the formula, represents the voltage at the first busbar, _; Sn represents the complex power at the first bus; represents the net actual active power injected _by photovoltaic and load into the first bus; Qn represents the reactive power of load at the first bus; Indicates the imaginary part operation symbol; " " represents the conjugation operator symbol;

; (3)

Wherein, R and X represent the feeder resistance and feeder reactance respectively _; ΔVd and _ΔVq represent the direct-axis and quadrature -axis components of the feeder voltage deviation respectively; Pn represents the net actual active power injected by the photovoltaic and load into the first bus _; Qn represents the load reactive power at the first bus; j _represents the imaginary part operation symbol; “||” represents the modulus symbol.

According to formula (3), the second bus voltage The calculation expression of the amplitude of _G is,

(4)

In formula (4), since Δ V _q is much smaller than ,therefore It can be approximately written as,

(5)

In addition, according to formula (3), Δ V _d can be approximately treated as:

(6)

Finally, according to equations (5) and (6), we establish The expression of

(7)

In the formula, represents the voltage amplitude at the first bus; represents the voltage amplitude at the second bus; R and X represent the _feeder resistance and feeder reactance respectively; Pn represents the net actual active power injected into the first bus _by photovoltaic and load; Qn represents the load reactive power at the first bus.

Further explanation, since the R / X of the low voltage distribution network is usually higher, the first bus voltage amplitude It is mainly related to Pn . Assume that the reactive _power Qn of the load at the first bus in equation (7) _is a constant, and photovoltaic power generation does not use reactive power control; at this time, if Pn is positive, _the voltage on the feeder will increase; otherwise, the feeder voltage will decrease along the feeder.

Please refer to Figures 4 and 5, which show the voltage curves on the feeder; Figures 4 and 5 are the voltage rise curve during the peak period of photovoltaic power generation and the voltage drop curve during the peak period of load, respectively; depending on the direction of the power flow, the voltage on the feeder may increase or decrease, thereby causing a voltage over-limit problem.

Step 2: construct a voltage over-limit suppression solution, including:

Considering the role of distributed energy storage system, the energy storage capacity is configured first; in order to effectively regulate the bus node voltage containing photovoltaic feeders, the power capacity required by the energy storage system is,

(8)

In the formula, and Respectively represent the upper and lower limits of the node voltage; V _thrc and V _thrd are the upper and lower limits of the bus voltage for energy storage startup voltage regulation control; and are the droop coefficients in charge and discharge modes, respectively;

, ; (9)

Where, V _nom is the rated voltage at the first busbar; and are the maximum photovoltaic power generation and the maximum load demand respectively.

Then, according to formula (9), for specific voltage abnormal nodes, droop control is used to determine the power exchange between the distributed energy storage system and the low-voltage distribution network system to ensure the voltage balance of the node at the first bus. The charging and discharging power of each distributed energy storage system is,

(10)

In the formula, Represents the power exchanged between the distributed energy storage system and the low-voltage distribution network system; represents the node voltage of the i -th bus, V _thrc and V _thrd are the upper and lower limits of the bus voltage for energy storage startup voltage regulation control respectively;

Step 3: Based on the voltage over-limit suppression scheme, perform control input sensitivity analysis to obtain comprehensive impact coefficient indicators, including:

Under certain conditions, the voltage amplitude of the i -th bus can be obtained when the control input signal changes slightly. For distributed generation and distributed energy storage systems, according to equations (7) and (10), the sensitivity of the bus node voltage to the bus output power can be obtained through the Jacobian inverse matrix, i.e., P ^-1 , as shown in the following equation:

, (11)

Where Δ P and Δ Q are the change vectors of active and reactive power injected into the node respectively; and Δ V are the change vectors of node voltage phase angle and amplitude respectively; and are the sensitivity vectors of the node voltage phase angle to the injected active and reactive power, respectively; and are the sensitivity vectors of node voltage amplitude to the injected active and reactive power, respectively.

Assume that the low-voltage distribution network contains n nodes, and a distributed generation and distributed energy storage system is at the xth node; at this time, the voltage amplitude change on the bus node caused by the output power change is,

(12)

Where, i is the node number;

According to formula (12), for the i -th node, (13)

In formula (13), The term is related to the change in active power injected by distributed generation and distributed energy storage systems. Its size depends on the type of unit and its operation mode, and it only has an indirect impact on the bus node voltage. The term can be directly used to control the bus node voltage. The term can be used to analyze the sensitivity of the bus node voltage to the reactive power output of the distributed generation and distributed energy storage system at the xth node. When the reactive power output of the distributed generation and distributed energy storage system is not enough for voltage correction, the output active power can also be used for voltage control. Therefore, in equation (13) It can be used to obtain the sensitivity of the node voltage at the i -th bus to the active power output of the distributed generation and distributed energy storage system at the x -th bus.

In order to obtain the sensitivity of the node voltage at the ith bus to the existing control input signal, the power flow equation of the power grid at a specific working point is established and expressed as:

(14)

Where H and L represent the reactive and active power equations injected at all PQ nodes, respectively; V is the bus voltage; u and u' are the reactive control and active control input vectors, respectively.

According to formula (14), the partial differential equation of the power grid flow is obtained and expressed as:

(15)

According to formula (15), the sensitivity of bus voltage to control input variable u _j can be obtained, which is expressed as:

(16)

Where [ H _V ] ^-1 and [ L _V ] ^-1 are the inverse matrices of the Jacobian matrix; and are known vectors, which respectively represent how the injected active and reactive power changes with the control input signal and The amount of change changes.

According to formula (16), the node voltage change caused by the change of the control input signal can be obtained, which is expressed as:

(17)

Assuming that the voltage control device is connected to the xth node, according to equation (17), the bus node voltage change caused by the change in its control input signal is:

(18)

Where, i is the node number;

According to formula (18), for the i -th node, (19)

According to equation (19), the sensitivity of the bus voltage at the i -th node to the control input signal (voltage regulator or capacitor bank) is: .

In order to further quantify the impact of the same control signal on different node voltages, the concept of electrical distance is used to measure the impact of the control signal on the node voltage, as shown below:

(20)

_{Where αim} is the distance between node i and node The attenuation amplitude of the direct voltage change; the value of α _ix is between 0 and 1; Respectively represent node i and node The voltage amplitude change.

In equation (20), the elements of the voltage sensitivity vector in equation (12) or equation (18) are divided by or , we can get the attenuation amplitude of the control signal from node x to node i , expressed as,

In the formula, represents the attenuation amplitude of the control input signal applied at bus node x to node i ; represents the voltage amplitude of node i ; represents the voltage amplitude of node x ; represents the reactive power injected into node x by the distributed energy storage system and distributed generation system; represents the applied reactive power control input signal at node x ; represents the applied active power control input signal at node x .

Then, the generalized electrical distance between any control input of node x and any node in the distribution network is defined as,

(twenty two)

In the formula, represents the attenuation amplitude of the control input signal applied at bus node x to node i ; represents the attenuation amplitude of the control input signal applied at bus node i to node x ; represents the logarithmic function; Represents the generalized electrical distance between the control input signal applied at node x and the target node i within the low-voltage distribution network system.

According to formula (22), after normalization, we can get:

(twenty three)

_{Where Dix} represents the normalized generalized electrical distance.

Considering the cost of applying the control signal, assuming that the unit cost corresponding to applying the x -th control signal input is C _x , according to formula (23), and for the control input signal u _x , we get:

(twenty four)

In the formula, represents the comprehensive impact coefficient; Represents the total number of nodes with over-limit voltage, 1≤ ≤ ; represents the normalized generalized electrical distance; It represents the unit cost corresponding to applying the control input signal on the x -th bus.

Step 4, based on the comprehensive influence coefficient index, adopting a two-stage control input signal optimization method including effective control set screening and redundant control signal screening to screen and obtain the optimal control input signal, including:

First, according to formula (24), the signal set with the best control effect is screened out; in order to estimate the influence of any control input signal on the over-limit voltage, in each iteration of the screening process, It will grow in steps of its sensitivity to the control input, expressed as,

(25)

in, is the vector of all over-limit voltages, , and They respectively represent the yth reactive power control input signal and active power control input signal applied.

Please refer to FIG. 6 , which shows the effective control set screening process, and multiple iterations are performed according to equation (25) until all the over-limit voltages are within the normal range; wherein N _c is the total number of all available control input signals, and y represents the control input signal indicator.

Then, in order to further refine or optimize the obtained control input signal set, it is necessary to evaluate the control input signals in the effective control set obtained by equation (25) and filter out unnecessary control input signals. First, the influence of eliminating a certain control input signal on the final voltage (set as v = [ v ₁ , v ₂ ,..., v _N ]) is estimated, and then the sensitivity value of a certain control input signal to a certain control input signal is subtracted from the obtained voltage variable, that is,

(26)

In the embodiment of the present invention, the redundant control input signal screening process is shown in FIG. 7. The new node voltage obtained according to equation (26) is the screened control input signal The new node voltage after the control input signal from After being screened out, if the node voltage is still greater than its threshold value Vmin _, the control input signal is considered to be an invalid control input signal and can be screened out. Finally, the updated control input signal set is obtained. When the redundancy screening of the original effective control set is completed and the simplified set is obtained, further redundancy screening can be performed to achieve a better screening effect. and The control input signal set and Number of internal control input signals.

The following are device embodiments of the present invention, which can be used to implement the method embodiments of the present invention. For details not disclosed in the device embodiments, please refer to the method embodiments of the present invention.

Please refer to FIG8 . In an embodiment of the present invention, a low-voltage distribution network voltage over-limit suppression device based on control input optimization is provided, comprising:

A first construction module is used to construct and obtain a node voltage over-limit model according to a target low-voltage distribution network system; wherein the target low-voltage distribution network system includes a distributed power generation system and a distributed energy storage system;

A second construction module is used to construct a voltage over-limit suppression scheme for coordinated distributed energy storage and distributed generation based on the node voltage over-limit model;

An index calculation module is used to perform a sensitivity analysis of the control input signal based on the voltage over-limit suppression scheme to obtain the influence of the control input signal on the voltage of all bus nodes in the low-voltage distribution network; based on the influence of the control input signal on the voltage of all bus nodes in the low-voltage distribution network, calculate and obtain a comprehensive influence coefficient index;

An optimization module is used to select and obtain the optimal control input signal based on the comprehensive influence coefficient index by adopting a two-stage control input signal selection method including effective control set screening and redundant control signal screening;

The voltage over-limit suppression module is used to suppress the voltage over-limit of the low-voltage distribution network based on the optimal control input signal.

In one embodiment of the present invention, a computer device is provided, the computer device comprising a processor and a memory, the memory being used to store a computer program, the computer program comprising program instructions, and the processor being used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or may be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions in a computer storage medium to implement a corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used to perform the operation of a low-voltage distribution network voltage over-limit suppression method based on control input optimization.

In one embodiment of the present invention, a storage medium is provided, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It is understandable that the computer-readable storage medium here can include both built-in storage media in the computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM (Random Access Memory) memory, or a non-volatile memory (non-volatile memory), such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the method for suppressing voltage over-limit of a low-voltage distribution network based on the optimization of control input in the above embodiment.

Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application 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, optical storage, etc.) containing computer-usable program codes.

The present application is described with reference to the flowcharts and/or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and/or box in the flowchart and/or block diagram, as well as the combination of the processes and/or boxes 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 generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate a device for implementing the functions specified in one process or multiple processes in the flowchart and/or one box or multiple 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 operate 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 it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims (7)

1. A method for suppressing voltage over-limit in a low-voltage distribution network based on optimal control input, characterized in that it comprises the following steps: According to the target low-voltage distribution network system, a node voltage over-limit model is constructed; wherein the target low-voltage distribution network system includes a distributed power generation system and a distributed energy storage system; Based on the node voltage over-limit model, a voltage over-limit suppression scheme for coordinated distributed energy storage and distributed generation is constructed; Based on the voltage over-limit suppression scheme, a sensitivity analysis of the control input signal is performed to obtain the influence of the control input signal on the voltage of all bus nodes in the low-voltage distribution network; based on the influence of the control input signal on the voltage of all bus nodes in the low-voltage distribution network, a comprehensive influence coefficient index is calculated; Based on the comprehensive influence coefficient index, a two-stage control input signal selection method including effective control set screening and redundant control signal screening is adopted to screen and obtain the optimal control input signal; Based on the optimal control input signal, voltage over-limit suppression is performed on the low-voltage distribution network; in, The voltage over-limit suppression scheme includes: based on the droop coefficients in the charging and discharging modes, using droop control on the voltage abnormal bus node to determine the power exchange between the distributed energy storage system and the low-voltage distribution network to ensure the voltage balance of the bus node; The step of performing sensitivity analysis of the control input signal based on the voltage over-limit suppression scheme to obtain the influence of the control input signal on the voltages of all bus nodes in the low-voltage distribution network; and calculating and obtaining the comprehensive influence coefficient index based on the influence of the control input signal on the voltages of all bus nodes in the low-voltage distribution network comprises: Based on the voltage over-limit suppression scheme, a sensitivity matrix of bus node voltage to bus output power is constructed; Based on the sensitivity matrix, the bus node voltage amplitude change caused by the bus output power change is calculated; based on the bus node voltage sensitivity matrix to the bus output power, the bus node voltage sensitivity to the control input signal is obtained; Based on the bus node voltage amplitude change caused by bus output power change and the bus node voltage sensitivity to the control input signal, a bus node voltage coupling model of the target low-voltage distribution network system is constructed and a generalized electrical distance model is defined. Based on the generalized electrical distance model and the control input signal cost, the comprehensive impact coefficient index is calculated; Among them, the calculation expression of the comprehensive influence coefficient is: ; In the formula, represents the comprehensive impact coefficient; Represents the total number of nodes with over-limit voltage, 1≤ ≤ ; represents the normalized generalized electrical distance; Indicates that at the node The unit cost corresponding to the control input signal applied at In the step of constructing a bus node voltage coupling model for a target low-voltage distribution network system and defining a generalized electrical distance model based on the bus node voltage amplitude change caused by the bus output power change and the bus node voltage sensitivity to the control input signal, The functional expression of the bus node voltage coupling model is: ; _{Where αim} is the distance between node i and node The attenuation amplitude of direct voltage change; Respectively represent node i and node The voltage amplitude change; The normalized expression of generalized electrical distance is: ; _{Where, Dix} represents the normalized generalized electrical distance; represents the generalized electrical distance between the control input signal applied at node x and the target node i in the low-voltage distribution network; ; In the formula, represents the attenuation amplitude of the control input signal applied at node x to node i ; represents the attenuation amplitude of the control input signal applied at node i to node x ; represents the logarithmic function; in, In the formula, represents the voltage amplitude of node i ; represents the voltage amplitude of node x ; represents the reactive power injected into node x by the distributed energy storage system and distributed generation system; represents the applied reactive power control input signal at node x ; represents the applied active power control input signal at node x . 2. A method for suppressing voltage over-limit in a low-voltage distribution network based on control input optimization according to claim 1, characterized in that the step of selecting the optimal control input signal based on the comprehensive influence coefficient index and using a two-stage control input signal optimization method including effective control set screening and redundant control signal screening comprises: Based on the comprehensive influence coefficient index, an effective control set whose control effect meets the preset requirements is selected from the control set composed of all control input signals; Redundant control signals are screened out based on the effective control set to obtain an optimal control input signal; wherein, during the redundant control signal screening process, if the bus node voltage is still greater than a threshold after the selected control input signal is screened out from the effective control set, the selected control input signal is screened out. 3. A method for suppressing voltage over-limit in a low-voltage distribution network based on control input optimization according to claim 1, characterized in that, in the step of constructing a node voltage over-limit model according to a target low-voltage distribution network system, The target low-voltage distribution network system is a feeder of a photovoltaic-storage low-voltage distribution network system, comprising a distributed energy storage system (1), a photovoltaic panel (2), a local load (3), a first bus (4), a second bus (5), a transformer (6) and a power grid (7); wherein the first bus (4) is connected to the distributed energy storage system (1), the photovoltaic panel (2) and the local load (3); a feeder resistance and a feeder reactance are connected in series between the first bus (4) and the second bus (5); and the transformer (6) is connected in series between the second bus (5) and the power grid (7); The expression of the node voltage over-limit model is: In the formula, represents the voltage amplitude at the first bus; represents the voltage amplitude at the second bus; R and X represent the _feeder resistance and feeder reactance respectively; Pn represents the net actual active power injected into the first bus _by photovoltaic and load; Qn represents the load reactive power at the first bus. 4. A method for suppressing voltage over-limit in a low-voltage distribution network based on optimal control input according to claim 3, characterized in that, in the voltage over-limit suppression scheme, The calculation expression of the power exchanged between the distributed energy storage system and the low-voltage distribution network system is: In the formula, Represents the power exchanged between the distributed energy storage system and the low-voltage distribution network system; and are the droop coefficients in charge and discharge modes, respectively; represents the node voltage of the ith bus, V _thrc and V _thrd are the upper and lower limits of the bus voltage for energy storage startup voltage regulation control respectively; ; ; Where, V _nom is the rated voltage at the first busbar; and are the maximum photovoltaic power generation and the maximum load demand, respectively; in, Power capacity required for distributed energy storage systems for, ; In the formula, and They represent the upper and lower limits of the node voltage of the i -th bus respectively. 5. A low voltage distribution network voltage over-limit suppression device based on control input optimization, characterized in that it includes: A first construction module is used to construct and obtain a node voltage over-limit model according to a target low-voltage distribution network system; wherein the target low-voltage distribution network system includes a distributed power generation system and a distributed energy storage system; A second construction module is used to construct a voltage over-limit suppression scheme for coordinated distributed energy storage and distributed generation based on the node voltage over-limit model; An index calculation module is used to perform a sensitivity analysis of the control input signal based on the voltage over-limit suppression scheme to obtain the influence of the control input signal on the voltage of all bus nodes in the low-voltage distribution network; based on the influence of the control input signal on the voltage of all bus nodes in the low-voltage distribution network, calculate and obtain a comprehensive influence coefficient index; An optimization module is used to select and obtain the optimal control input signal based on the comprehensive influence coefficient index by adopting a two-stage control input signal selection method including effective control set screening and redundant control signal screening; A voltage over-limit suppression module, used for suppressing voltage over-limit of a low-voltage distribution network based on the optimal control input signal; in, The voltage over-limit suppression scheme includes: based on the droop coefficients in the charging and discharging modes, using droop control on the voltage abnormal bus node to determine the power exchange between the distributed energy storage system and the low-voltage distribution network to ensure the voltage balance of the bus node; The step of performing sensitivity analysis of the control input signal based on the voltage over-limit suppression scheme to obtain the influence of the control input signal on the voltages of all bus nodes in the low-voltage distribution network; and calculating and obtaining the comprehensive influence coefficient index based on the influence of the control input signal on the voltages of all bus nodes in the low-voltage distribution network comprises: Based on the voltage over-limit suppression scheme, a sensitivity matrix of bus node voltage to bus output power is constructed; Based on the sensitivity matrix, the bus node voltage amplitude change caused by the bus output power change is calculated; based on the bus node voltage sensitivity matrix to the bus output power, the bus node voltage sensitivity to the control input signal is obtained; Based on the bus node voltage amplitude change caused by bus output power change and the bus node voltage sensitivity to the control input signal, a bus node voltage coupling model of the target low-voltage distribution network system is constructed and a generalized electrical distance model is defined. Based on the generalized electrical distance model and the control input signal cost, the comprehensive impact coefficient index is calculated; Among them, the calculation expression of the comprehensive influence coefficient is: ; In the formula, represents the comprehensive impact coefficient; Represents the total number of nodes with over-limit voltage, 1≤ ≤ ; represents the normalized generalized electrical distance; Indicates that at the node The unit cost corresponding to the control input signal applied at In the step of constructing a bus node voltage coupling model for a target low-voltage distribution network system and defining a generalized electrical distance model based on the bus node voltage amplitude change caused by the bus output power change and the bus node voltage sensitivity to the control input signal, The functional expression of the bus node voltage coupling model is: ; _{Where αim} is the distance between node i and node The attenuation amplitude of direct voltage change; Respectively represent node i and node The voltage amplitude change; The normalized expression of generalized electrical distance is: ; _{Where, Dix} represents the normalized generalized electrical distance; represents the generalized electrical distance between the control input signal applied at node x and the target node i in the low-voltage distribution network; ; In the formula, represents the attenuation amplitude of the control input signal applied at node x to node i ; represents the attenuation amplitude of the control input signal applied at node i to node x ; represents the logarithmic function; in, In the formula, represents the voltage amplitude of node i ; represents the voltage amplitude of node x ; represents the reactive power injected into node x by the distributed energy storage system and distributed generation system; represents the applied reactive power control input signal at node x ; represents the applied active power control input signal at node x . 6. An electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method for suppressing voltage over-limit in a low-voltage distribution network based on control input optimization as described in any one of claims 1 to 4 is implemented. 7. A non-transitory computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the method for suppressing voltage over-limit in a low-voltage distribution network based on control input optimization as described in any one of claims 1 to 4 is implemented.