CN102684208B - Wide-area reactive optimal running method for power distribution network - Google Patents

Abstract

A wide-area reactive power optimization operation method for a distribution network belongs to the technical field of reactive power compensation for power system distribution networks. The present invention uses a computer to input the basic data of the distribution network and its reactive power compensation devices through a program, then calculates the compensation range and priority level of each reactive power compensation device, and then according to the compensation range and priority of each reactive power compensation device The real-time measurement information of the root node of the distribution network and each compensation point calculates the switching capacity of each reactive power compensation device, and controls the switching of each capacitor bank. The invention fully considers the overall voltage and reactive power operation status of the distribution network, greatly improves the utilization rate of the compensation equipment, reduces the power loss and voltage loss of the distribution network, improves the voltage quality of the distribution network, and ensures that the electrical equipment It operates under rated conditions and has the characteristics of significant social and economic benefits. The invention can be widely applied to the optimal operation and control of the voltage and reactive power of the distribution network of the electric power system.

Description

Wide-area reactive power optimization operation method for distribution network

technical field

The invention belongs to the technical field of reactive power compensation of power system distribution network, and in particular relates to an optimal operation method of reactive power compensation of power system distribution network.

Background technique

The distribution network is an important link directly related to the power system and users. It covers a large area and has a large number of equipment. It is an important part of the power system. Improving the voltage quality of the distribution network and reducing the operating loss of the distribution network are of great significance for improving the quality of power supply and ensuring the high-quality economic operation of the power system. Reactive power compensation is one of the effective measures to improve the voltage quality of distribution network and reduce the operation loss of distribution network.

The reactive power optimization operation of the transmission network is usually based on the power flow equation of the power system, and the optimization method is used to calculate the optimal reactive power compensation capacity. This method requires complete power system power flow information. At present, the degree of automation of the distribution network in my country is not high, and it is difficult to obtain real-time status information of the distribution network. Therefore, this method is not suitable for the reactive power optimization operation of the distribution network.

The reactive power compensation of the current distribution network is based on the provisions of Article 8 of the "Technical Principles for Reactive Power Compensation Configuration of the Power System of the State Grid Corporation" of the Q/GDW "State Grid Corporation Enterprise Standard" issued in 2008: the reactive power compensation of the distribution network Power compensation is mainly based on centralized compensation on the low-voltage side of the distribution network transformer; the capacitor group of the distribution transformer is equipped with a control device that uses voltage as a constraint and performs group automatic switching according to reactive power (reactive current). The switching method of the current reactive power compensation device in the distribution network is at the installation point of each reactive power compensation device (that is, the low-voltage side of the distribution transformer), according to the principle of reactive power local balance, according to the balance of the reactive power load of the distribution transformer To meet the voltage requirements of the installation point of the reactive power compensation device, the switching capacity of the compensation capacitor bank is automatically controlled. The main disadvantage of the current switching method of reactive power compensation devices in the distribution network is that it can only automatically switch the compensation capacity of the compensation capacitor according to the reactive power load balance of each distribution transformer, and only realize the partial area of each distribution transformer and the following power grid. The reactive power balance of the distribution network cannot control the switching of reactive power compensation capacity from the overall situation of the reactive power load of the distribution network. Since the variation rules of distribution transformer loads (including reactive loads) in the distribution network are not the same, the current method of switching reactive power compensation devices in the distribution network does not fully utilize the compensation capacitors, and it is difficult to ensure the overall no-power load of the distribution network. Power balance, thus affecting the high-quality economic operation of the distribution network.

Contents of the invention

The purpose of the present invention is to provide a wide-area reactive power optimization operation method for the distribution network in view of the deficiencies of the current reactive power compensation control method for the distribution network. The voltage and reactive power operation status of the distribution network can automatically calculate the switching capacity of each reactive power compensation device and control the switching of each reactive power compensation device, which can effectively improve the utilization rate of the compensation equipment and the voltage quality of the distribution network, and reduce the Distribution network operating loss.

The technical solution for realizing the object of the present invention is: a wide-area reactive power optimization method for distribution network, using a computer, through a program, first input the basic data of the distribution network and its reactive power compensation devices; then calculate the reactive power of each reactive power compensation device Compensation range and its priority level; then according to the compensation range of each reactive power compensation device and the real-time measurement information of the root node of the distribution network and each compensation point, calculate the switching capacity of each reactive power compensation device, and control each capacitor group to perform correct switching. The concrete steps of described method are as follows:

(1) Input basic data

First, the basic data of the distribution network, the basic data of each reactive power compensation device, the historical switching data of each reactive power compensation device, and the measurement data of the root node of the distribution network and each reactive power compensation point are input. Among them, the basic data of the distribution network includes the basic data of each node, that is, the node number, the voltage level of the node, the upper limit of the node voltage, and the lower limit line of the _node ; , reactance ( X _l ), susceptance ( B _l ), rated voltage ( U _Bl ); the basic data of each distribution transformer, that is, the load number of the distribution transformer, the node numbers on both sides, the resistance R _T ), the reactance X _T ), conductance ( G _m ), susceptance ( B _m ), transformation ratio ( k _T ), rated capacity ( S _NT ), rated voltage of high voltage side ( U _Bl1 ), rated voltage of low voltage side U _Bl2 ). The basic data of each reactive power compensation device includes the node number where the compensation capacitor bank is located, the compensation capacity of a single group ( Q _ref ), the number of groups ( n ), the total compensation capacity ( Q _c ), the maximum compensation capacity ( Q _max ), and the minimum compensation capacity ₍ Qmin ). The historical switching data of each reactive power compensation device includes the capacity data before and after switching of the capacitors of each reactive power compensation device at the previous moment, the voltage data of the root node of the distribution network and each reactive power compensation point, the root node of the distribution network and each reactive power compensation point. The measurement data of the power compensation point includes the measured voltage ( U ), active power ( P ) and reactive power ( Q ) at the current moment.

Calculate the control priority level and control range of each reactive power supply

After (1) is completed, according to the connection relationship of each node of the distribution network, the breadth-first search algorithm is used to determine the control priority level of each reactive power source (including the root node of the distribution network and each reactive power compensation device). The process is as follows:

For the root node and reactive power compensation device in the distribution network, start from the root node, and mark the root node as level 0, and the reactive power compensation device adjacent to level 0 without definite level is the first level. The reactive power compensation devices adjacent to the first level without a certain level are the second level, and so on, use the breadth first to search the nodes where the reactive power compensation devices are located until all the reactive power compensation devices are searched, and the last reactive power compensation device will be searched. The device is marked as class m . Level m is the highest control priority of the reactive power supply, and level 0 represents the root node of the distribution network.

The equivalent loss of the kth load caused by the reactive power flow of reactive power point i :

                                                                                    (1)

(1)

In the formula: L _ki is the network equivalent loss generated by the reactive power flow of reactive power point i _for the kth load; S _k is the capacity of the distribution transformer where the kth load is located; Rki is the connection of the kth load The sum of the resistance of all branches (including lines and transformer branches) of the node where it is located and the reactive power point i .

If the kth load is connected to the reactive power point with the smallest equivalent loss, the distribution transformer where the kth load is located will belong to the control range of the reactive power point. Calculate the equivalent loss corresponding to all loads and reactive power sources until all loads are connected to the corresponding reactive power points.

(3) Calculate the switching capacity ratio of each reactive power compensation device

After step (2) is completed, calculate the switching capacity ratio of each reactive power source except the root node of the distribution network, that is, each reactive power compensation device.

The switching capacity ratio of the jth reactive power compensation device

                                                                              (2)

(2)

In the formula: α _j is the switching capacity ratio of the jth reactive power compensation device; T is the set of distribution transformers in the entire distribution network; S _t is the capacity of the tth distribution transformer; T _j is the jth reactive power A collection of distribution transformers within the control range of the compensation device; S _tj is the capacity of the t _jth distribution transformer.

According to the calculation result of step (2), combine the control range of each reactive power compensation device to calculate the switching capacity ratio of each compensation device.

Calculation of voltage and reactive sensitivity matrix

After the completion of (3), calculate the voltage reactive power sensitivity matrix between the voltage monitoring point and the reactive power compensation point.

Firstly, the voltage monitoring point is determined as the root node of the distribution network and the node where the reactive power compensation device is located.

Then determine the voltage reactive power sensitivity matrix S _UQ between the voltage monitoring point and the reactive power compensation point:

                                   (3)

(3)

In the formula: SUQ is a ( m +1)× m -dimensional matrix; d U _{i /} d Q _Cj is the voltage reactive power sensitivity between reactive power compensation device j reactive power compensation capacity and voltage monitoring point i .

Then calculate the value of each element _in SUQ , the calculation formula is:

                                                                (4)

(4)

In the formula: d U _i /d Q _Cj is the voltage reactive power sensitivity between the reactive power compensation capacity of reactive power compensation device j and voltage monitoring point i ; Δ Q _Cj is the variation of compensation capacity of compensation node j ; Δ U _i is The change of voltage at voltage monitoring point i after the compensation capacity changes (the sensitivity is calculated from the voltage history data of the voltage monitoring point and the historical switching data of each compensation device, specifically, the voltage amplitude of the voltage monitoring point at two moments before and after capacitor switching value change and capacitor capacity change).

After the value of each element _in SUQ is obtained, SUQ _is formed according to formula (3).

Calculate the switching capacity of each reactive power compensation device

After the completion of (4), first calculate the total reactive power load Q _L of the distribution network, and the calculation formula is:

                                                        (5)

(5)

是第j个无功补偿装置上一时刻电容器补偿容量，写成向量形式则为

。 In the formula, Q _L is the total reactive power load of the distribution network; Q ₁ is the reactive power measurement value of the root node of the distribution network at the current moment;

is the capacitor compensation capacity of the jth reactive power compensation device at the last moment, written in vector form as

.

Then, according to the switching capacity ratio of each low-voltage reactive power compensation device, calculate the reactive power demand within the control range of each reactive power compensation device. The formula for calculating the reactive power demand within the control range of the jth reactive power compensation device is:

                                                               (6)

(6)

In the formula, Q′ _Cj-Need is the reactive power demand within the control range of the j -th reactive power compensation device; α _j is the switching capacity ratio of the j- th reactive power compensation device; Q _L is the total reactive power load of the distribution network.

When the compensation capacity of the jth reactive power compensation device is surplus, and the compensation capacity of the reactive power compensation devices near the reactive power compensation device is insufficient, the remaining compensation capacity shall be compensated and controlled preferentially to control the reactive power compensation device with a higher priority level than itself The reactive power demand within the range, and then compensate the reactive power demand within the control range of the reactive power compensation device whose priority level is lower than itself.

Recalculate the reactive power demand of the reactive power compensation device, the calculation formula is:

                                                     (7)

(7)

或

                    (8)

or

(8)

In the formula, Q _{Cj-Need is} the reactive power demand within the control range of the jth reactive power compensation device after recalculation; α _j is the switching capacity ratio of the jth reactive power compensation device; Q _L is the reactive power of the distribution network The total load; ΔQ _j-Need is the reactive capacity of the jth reactive power compensation device supporting nearby reactive power compensation devices.

Then, considering the constraint conditions, the switching capacity of each reactive power compensation device is calculated. Taking the minimum sum of the difference between the actual switching capacity of each reactive power compensation device capacitor and the reactive power demand of the load within the control range as the objective function, the upper and lower limits of the voltage monitoring node voltage, the compensation amount limit of the reactive power compensation node, and the reactive power compensation node The transformer capacity limit is a constraint condition, and the wide-area reactive power optimization model of the distribution network can be expressed as follows:

    j=1，2，…，m                         (9) Objective function:

j = 1, 2, ..., m (9)

Restrictions:

                                          (10) Voltage qualification constraints:

(10)

Output constraint of reactive power compensation device: (11)

                         (12) Reactive power compensation point distribution transformer capacity constraint:

(12)

；Q _Cj-Need 为第j个无功补偿装置的无功需求；U为各电压监测点的电压向量，U=[U ₀, U _1,…,U _i,…,U _m ]^T，U _max 、U _min 分别表示电压监测点的电压幅值上下限向量；Q _max 、Q _min 分别表示各无功补偿装置容量上下限向量；P _j 表示第j个无功补偿装置所在负荷的有功功率，Q _j 表示第j个无功补偿装置所在负荷的有功功率，S _NTj 表示第j个变压器容量上限。 In the formula: Q _Cj represents the reactive power compensation capacity of the capacitor of the jth reactive power compensation node. When the compensation device uses a capacitor bank as the reactive power supply, Q _Cj is a discrete quantity, written in vector form as

; Q _Cj-Need is the reactive power demand of the jth reactive power compensation device; U is the voltage vector of each voltage monitoring point, U= [ U ₀ , U _1, …, U _{i ,} …, U _m ] ^T ， U _max and U _min respectively represent the upper and lower limit vectors of the voltage amplitude at the voltage monitoring point; Q _max and Q _min represent the upper and lower limit vectors of the capacity of each reactive power compensation device respectively; P _j represents the active power of the load where the jth reactive power compensation device is located, Q _j represents the active power of the load where the j -th reactive power compensation device is located, and S _NTj represents the upper limit of the j -th transformer capacity.

In formula (10), the formula for calculating the voltage vector U of each voltage monitoring point at the next moment after capacitor switching is

(13)

是无功补偿装置上一时刻补偿容量向量。 In the formula: U= [ U ₀ , U _{1 ,} …, U _{i ,} …, U _m ] ^T ; U ⁰ is the voltage vector of each voltage monitoring point at the current moment; S _UQ is the relationship between the voltage monitoring point and the reactive power compensation point The voltage reactive power sensitivity matrix between; Q _C is the capacitor compensation capacity vector of the reactive power compensation device;

is the compensation capacity vector of the reactive power compensation device at the last moment.

。 Use the enumeration method to solve formulas (9)~(12) to obtain Q _C , that is, to obtain the vector of switching capacity of each compensation device

.

( 6) Output the switching capacity of each reactive power compensation device

After the step (5) is completed, first output the vector ΔQ _C of the switching capacity of the reactive power compensation device obtained in the step (5), which is the switching amount of the capacitance of each reactive power compensation device. Then switch the capacitors of each reactive power compensation device separately, and record the capacitor compensation capacity and the voltage amplitude change of the voltage monitoring point before and after switching, which are used as the input data at the next moment.

After the present invention adopts above-mentioned technical scheme, mainly have following effect:

1. Compared with the low-voltage reactive power compensation of the distribution network under the local control mode, the method of the present invention makes the reactive power of the distribution network balanced according to the compensation area of the reactive power compensation device, and fully considers the overall voltage of the distribution network. Power operation status, thereby reducing the flow of reactive power in the distribution network, reducing the loss of the distribution network, which has significant economic benefits, and makes full use of high-quality secondary energy, which plays a role in energy saving and emission reduction, and contributes to the construction of saving energy. society is important.

2. Compared with the low-voltage reactive power compensation of the distribution network under the local control mode, the method of the present invention enables the reactive power of the distribution network to be balanced according to the compensation area of the reactive power compensation device, and reduces the distance between the root node of the distribution network and the load node. The voltage loss between them improves the voltage quality of the distribution network and ensures the normal operation of electrical equipment under rated conditions, which has significant social and economic benefits.

3. Compared with the low-voltage reactive power compensation of the distribution network under the local control mode, the method of the present invention adopts the operation mode of switching the reactive power compensation device according to the compensation area, which overcomes the shortcomings of insufficient use of the compensation capacitor in the existing method , which greatly improves the utilization rate of the compensation equipment and further improves the economic benefits of the distribution network.

The invention can be widely applied to the optimal operation and control of the voltage and reactive power of the distribution network of the electric power system. the

Description of drawings

Fig. 1 is a program flow diagram of the inventive method;

Fig. 2 is a system wiring diagram of the distribution network of the embodiment.

In the figure: 1-390 is the node number of the distribution network. Node 1 is the first node of the distribution network and the root node of the distribution network. Reactive power compensation is set at nodes 54, 178, 238 and 334 device.

Detailed ways

The present invention will be further described below in combination with specific embodiments.

Example

As shown in Figures 1 and 2, the specific steps of a wide-area reactive power optimization operation method for a certain 10kV distribution network are as follows:

(1) Enter basic data

First input the basic data of a 10kV distribution network shown in Figure 2 (including the basic data of each node, that is, the node number, the voltage level of the node, the upper limit of the node voltage, the lower limit of the node line; the basic data of each line, that is, the beginning and end of the line Node number, resistance R _l , reactance X _l , susceptance B _l , rated voltage U _Bl ; the basic data of each distribution transformer, that is, the load number of the distribution transformer, the node numbers on both sides, resistance R _T , reactance X _T , conductance G _m , susceptance B _m , transformation ratio k _T , rated capacity S _NT , rated voltage U _Bl1 on the high voltage side, rated voltage U _Bl2 on the low voltage side). The basic data of each reactive power compensation device is: single group capacity Q _ref =0.015MVar, number of groups n =7, total capacity Q _c =0.105MVar, maximum compensation capacity Q _max =0.105MVar, minimum compensation capacity Q _min =0. The historical switching data of each reactive power compensation device is shown in Table 1~Table 4.

Table 1 Historical switching data of No. 1 compensation device (where the node number is 54)

Table 2 Historical switching data of No. 2 compensation device (where the node number is 178)

Table 3 Historical switching data of No. 3 compensation device (where the node number is 238)

Table 4 Historical switching data of No. 4 compensation device (the node number is 334)

The measured data of the distribution network root node and each reactive power compensation point at the current moment are shown in Table 5.

Table 5 The measured data at the current moment of the distribution network root node and each reactive power compensation point

(2) Calculate the control priority level and control range of each reactive power supply

After the completion of (1), according to the connection relationship between the distribution network lines and the transformers, starting from the root node (that is, the No. 1 node, the first node) to use the wide-area priority to search for each reactive power point, the search results are shown in Table 6 .

Table 6 Search results of each reactive power priority level

 

Calculate the equivalent loss of each load when the reactive power is provided by each reactive power compensation device by formula (1). Table 7 shows the equivalent loss of each reactive power source corresponding to the No. 1 load.

Table 7 The reactive power equivalent loss corresponding to the No. 1 load

From Table 7, it can be seen that the No. 1 load should be connected to the 0th-level reactive power supply (root node of the distribution network), and the distribution transformer where the No. 1 load is located should belong to the control range of the 0-level reactive power supply. By analogy, determine the distribution transformers within the control range of each reactive power supply, as shown in Table 8.

Table 8 Control range of each reactive power supply

(3) Calculate the switching capacity ratio of each reactive power compensation device

After (2) is completed, according to Table 8, the control range of the first-stage reactive power supply is the 13th to 31st loads, and the switching capacity ratio of the compensation device is

In the same way, the switching capacity ratios of the remaining compensation devices are calculated, as shown in Table 9.

Table 9 The switching capacity ratio of each compensation device

Then, A =[26.41%,26.48%,18.12%,15.80%] ^T .

(4) Calculation of voltage and reactive power sensitivity matrix

After the completion of (3), in this embodiment, the voltage monitoring point is the root node of the distribution network and the node where the reactive power compensation device is located, that is, nodes No. 1, 54, 178, 238 and 334.

It can be obtained from Table 1 that when Δ Q _C1 =0.015, each voltage monitoring point ΔU =[0,0.00098,0.00019,0.00019,0.00019] ^T . Therefore, the sensitivity between the voltage at the voltage monitoring point and the compensation capacity of the No. 1 reactive power compensation device is

d U /d Q _C1 =[0,0.06546,0.01286,0.01289,0.01292] ^T

Similarly, to calculate the sensitivity between the voltage at the voltage monitoring point and the compensation capacity of other reactive power compensation devices, we get:

(5) Calculate the switching capacity of each reactive power compensation device

After step (4) is completed, the total reactive power load Q _L of the distribution network is calculated, and the calculation formula is

To calculate the reactive power demand of the load within the control range of the No. 1 reactive power compensation point, the calculation formula is:

The reactive power requirements of other reactive power compensation devices can be deduced by analogy, and the calculation results are shown in Table 10.

Table 10 Reactive power demand within the control range of each compensation device

From the calculation results of reactive power demand, in addition to compensating the reactive power demand in the area controlled by itself, the No. 3 reactive power compensation device has a remaining capacity of 0.045Mvar, while the No. 4 reactive power compensation device can compensate The reactive power demand of the No. 2 reactive power compensation device is not enough to compensate the reactive power demand in the area controlled by itself. Therefore, No. 3 reactive power compensation device should support part of the reactive power of No. 2 reactive power compensation device, namely:

The reactive power demand within the control range of each reactive power compensation device after correction is shown in Table 11.

Table 11 Reactive power demand within the control range of each compensation device after correction

Considering the voltage constraints and distribution transformer capacity constraints, the optimization model is formed according to formulas (9)~(12), and the optimization problem is solved by enumeration method, and the compensation capacity Q _C of each reactive power compensation device is obtained =[0.105,0.105,0.105, 0.090] ^T . Taking the compensation capacity as an example, calculate whether the voltage value of the voltage monitoring point after capacitor switching and the apparent power of the distribution transformer meet the requirements.

To calculate the capacitor input capacity ΔQ _C of the reactive power compensation device, the calculation formula is:

Calculate the voltage vector U of each voltage monitoring point at the next moment after the capacitor is put into operation, and the calculation formula is:

=

=

=

None of them exceeded the voltage range stipulated in the relevant national guidelines.

Calculate the corresponding apparent power of the distribution transformer after the capacitor of the No. 1 reactive power compensation device is put into operation, and the calculation formula is:

The rated capacity of the distribution transformer is 0.315, and the apparent power of the distribution transformer does not exceed the limit of the distribution transformer capacity after the capacitor is put into operation. In the same way, the apparent power of the distribution transformer where the remaining reactive power compensation devices are located can be calculated, see Table 12.

Table 12 The apparent power of the distribution transformer where each reactive power compensation device is located

It can be seen from Table 12 that the apparent power of the distribution transformer after the capacitor is put into operation does not exceed the limit of the distribution transformer capacity.

Therefore, the compensation capacity Q _C =[0.105,0.105,0.105,0.090] ^T of each reactive power compensation device requires input capacity ΔQ _C =[0.090,0.090,0.090,0.075] ^T .

(6) Output the switching capacity of each reactive power compensation device

After the step (5) is completed, output the switching capacity ΔQ _C of the switching capacity of the reactive power compensation device obtained by the solution, which is the switching amount of the capacitance of each reactive power compensation device.

Each reactive power compensation device should be switched separately when switching capacitors, and the capacitor compensation capacity and voltage monitoring point voltage before and after switching should be recorded as the input data at the next moment.

Experimental effect

After the reactive power compensation device adopting the wide-area control method of this embodiment is put into operation, capacitor switching is performed according to the compensation area. Compared with the current local control reactive power compensation method, the equipment utilization ratio of each reactive power compensation device is shown in Table 13. Show.

Table 13 Utilization of reactive power compensation equipment under different control modes

It is known from Table 13 that after the wide-area control mode is adopted for each reactive power compensation device, the equipment utilization rate of each reactive power compensation device is significantly improved.

After using the method of the present invention to carry out wide-area control on the reactive power compensation device, the calculation results of the voltage and reactive power status of the line on a certain day are shown in Table 14.

Table 14 Line operation results after compensation

It can be seen from Table 14 that after adopting the wide-area control method of the present invention, the voltage quality of the distribution network is obviously improved, and the line loss rate is obviously reduced.

Claims (1)

1. A distribution network wide-area reactive power optimization operation mode, utilizes computer, through program, calculates the switching capacity of each reactive power compensation device and controls the normal switching of each capacitor bank, it is characterized in that the concrete steps of described method as follows: (1) Input basic data First, the basic data of the distribution network, the basic data of each reactive power compensation device, the historical switching data of each reactive power compensation device, and the measurement data of the root node of the distribution network and each reactive power compensation point are input. The basic data includes the basic data of each node, that is, the node number, the voltage level of the node, the upper limit of the node voltage, and the lower limit line of the node; the basic data of each line, that is, the first and last node numbers, resistance, reactance, susceptance, and rated voltage of each The basic data of the distribution transformer, that is, the load number of the distribution transformer, the node number on both sides, resistance, reactance, conductance, susceptance, transformation ratio, rated capacity, rated voltage on the high-voltage side, rated voltage on the low-voltage side, and reactive power The basic data of the compensation device includes the node number of the compensation capacitor bank, the compensation capacity of a single group, the number of groups, the total compensation capacity, the maximum compensation capacity, and the minimum compensation capacity. The capacity data of the compensation device capacitor before and after switching and the voltage data of the distribution network root node and each reactive power compensation point, the measurement data of the distribution network root node and each reactive power compensation point include the current measured voltage, active power, reactive power; (2) Calculate the control priority level and control range of each reactive power supply After step (1) is completed, according to the connection relationship of each node of the distribution network, the breadth-first search algorithm is used to determine the control priority levels of each reactive power source, including the root node of the distribution network and each reactive power compensation device. The process is as follows : For the root node and reactive power compensation device in the distribution network, start from the root node, and mark the root node as level 0, and the reactive power compensation device adjacent to level 0 without definite level is the first level. The reactive power compensation devices adjacent to the first level without a certain level are the second level, and so on, use the breadth first to search the nodes where the reactive power compensation devices are located until all the reactive power compensation devices are searched, and the last reactive power compensation device will be searched. The device is marked as the mth level, the m level is the highest control priority of the reactive power supply, and the 0th level represents the root node of the distribution network; Define the equivalent loss of the kth load generated by the reactive power flow of reactive power point i :

(1) In the formula: L _ki is the network equivalent loss generated by the reactive power flow of reactive power point i _for the kth load; S _k is the capacity of the distribution transformer where the kth load is located; Rki is the connection of the kth load All branches between the node where it is located and reactive power point i , including the sum of line and transformer branch resistances; Connect the kth load to the reactive power point with the smallest equivalent loss, then the distribution transformer where the kth load is located will belong to the control range of the reactive power point, and calculate the equivalent loss corresponding to all loads and reactive power sources until All loads are connected to corresponding reactive power points; (3) Calculate the switching capacity ratio of each reactive power compensation device After step (2) is completed, calculate the switching capacity ratio of each reactive power source except the root node of the distribution network, that is, each reactive power compensation device; First define the switching capacity ratio of the jth reactive power compensation device (2) In the formula: α _j is the switching capacity ratio of the jth reactive power compensation device; T is the set of distribution transformers in the entire distribution network; S _t is the capacity of the tth distribution transformer; T _j is the jth reactive power The set of distribution transformers within the control range of the compensation device, S _tj is the capacity of the t _jth distribution transformer; According to the calculation result of step (2), the switching capacity ratio of each compensation device is calculated in combination with the control range of each reactive power compensation device; (4) Calculate the voltage reactive power sensitivity matrix After step (3) is completed, calculate the voltage reactive power sensitivity matrix between the voltage monitoring point and the reactive power compensation point; First determine the voltage monitoring point as the root node of the distribution network and the node where the reactive power compensation device is located; Then determine the voltage reactive power sensitivity matrix S _UQ between the voltage monitoring point and the reactive power compensation point:

(3) In the formula: SUQ is a ( m +1)× m -dimensional matrix; d U _i /d Q _Cj is _the voltage reactive power sensitivity between the reactive power compensation device j reactive power compensation capacity and the voltage monitoring point i ; Then calculate the value of each element _in SUQ , the calculation formula is:

(4) In the formula: d U _i /d Q _Cj is the voltage reactive power sensitivity between the reactive power compensation capacity of reactive power compensation device j and voltage monitoring point i ; Δ Q _Cj is the variation of compensation capacity of compensation node j ; Δ U _i is Change amount of voltage at voltage monitoring point i after compensation capacity change; After obtaining the value of each element _in SUQ , form SUQ according to formula (3) _; (5) Calculate the switching capacity of each reactive power compensation device After step (4) is completed, first calculate the total reactive power load Q _L of the distribution network, and the calculation formula is:

(5) In the formula: Q _L is the total reactive power load of the distribution network; Q ₁ is the reactive power measurement value of the root node of the distribution network at the current moment;

is the capacitor compensation capacity of the jth reactive power compensation device at the last moment, written in vector form as

; Then, according to the switching capacity ratio of each low-voltage reactive power compensation device, calculate the reactive power demand within the control range of each reactive power compensation device. The formula for calculating the reactive power demand within the control range of the jth reactive power compensation device is:

(6) In the formula: Q′ _Cj-Need is the reactive power demand within the control range of the jth reactive power compensation device; α _j is the switching capacity ratio of the jth reactive power compensation device; Q _L is the total reactive power load of the distribution network; When the compensation capacity of the jth reactive power compensation device is surplus, and the compensation capacity of the reactive power compensation devices near the reactive power compensation device is insufficient, the remaining compensation capacity shall be compensated and controlled preferentially to control the reactive power compensation device with a higher priority level than itself The reactive power demand within the range, and then compensate the reactive power demand within the control range of the reactive power compensation device whose control priority is lower than itself; Recalculate the reactive power demand of the reactive power compensation device, the calculation formula is:

(7)

or

(8) In the formula: Q _Cj-Need is the reactive power demand within the control range of the jth reactive power compensation device after recalculation; α _j is the switching capacity ratio of the jth reactive power compensation device; Q _L is the reactive power of the distribution network The total load; Δ Q _j-Need is the reactive capacity of the jth reactive power compensation device supporting nearby reactive power compensation devices; Then consider the constraint conditions, calculate the switching capacity of each reactive power compensation device, take the minimum sum of the difference between the actual switching capacity of each reactive power compensation device capacitor and the reactive power demand of the load within the control range as the objective function, and use the voltage monitoring node The upper and lower limits of voltage, the limit of compensation amount of reactive power compensation node, and the limit of transformer capacity of reactive power compensation node are constrained conditions. The wide-area reactive power optimization model of distribution network can be expressed as follows: Objective function:

j = 1, 2, ..., m (9) Restrictions: Voltage qualification constraints: (10) Output constraint of reactive power compensation device:

(11) Reactive power compensation point distribution transformer capacity constraint:

(12) In the formula: Q _Cj represents the reactive power compensation capacity of the capacitor of the jth reactive power compensation node. When the compensation device uses a capacitor bank as the reactive power supply, Q _Cj is a discrete quantity, written in vector form as

; Q _Cj-Need is the reactive power demand of the jth reactive power compensation device; U is the voltage vector of each voltage monitoring point, U= [ U ₀ , U _1, …, U _{i ,} …, U _m ] ^T ， U _max and U _min respectively represent the upper and lower limit vectors of the voltage amplitude at the voltage monitoring point; Q _max and Q _min represent the upper and lower limit vectors of the capacity of each reactive power compensation device respectively; P _j represents the active power of the load where the jth reactive power compensation device is located, Q _j represents the reactive power of the load where the j- th reactive power compensation device is located, and S _NTj represents the upper limit of the j -th transformer capacity; In formula (10), the formula for calculating the voltage vector U of each voltage monitoring point at the next moment after capacitor switching is

(13) In the formula: U= [ U ₀ , U _{1 ,} …, U _{i ,} …, U _m ] ^T ; U ⁰ is the voltage vector of each voltage monitoring point at the current moment; S _UQ is the distance between the voltage monitoring point and the reactive power compensation point The voltage reactive power sensitivity matrix; Q _C is the capacitor compensation capacity vector of the reactive power compensation device;

is the compensation capacity vector of the reactive power compensation device at the previous moment; When the scale is not large, use the enumeration method to solve the problems of formulas (9)~(12) to obtain Q _C , that is, to obtain the switching capacity vector of each compensation device

; ( 6) Output the switching capacity of each reactive power compensation device After step (5) is completed, firstly output the obtained reactive power compensation device switching capacity vector ΔQ _C , which is the switching amount of the capacitance of each reactive power compensation device; then switch the capacitors of each reactive power compensation device separately, And record the capacitor compensation capacity before and after switching and the amplitude change voltage of the voltage monitoring point as the input data at the next moment.

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