Method and system for determining bus voltage variation when switching on and off shunt capacitors in substations

Abstract

The present invention belongs to the field of transformer substations, and provides a method and system for determining the bus voltage change amount when a parallel capacitor is switched on and off in a transformer substation. The method includes identifying the external equivalent circuit parameters of the high-voltage side bus and the bus side load parameters; judging whether a single transformer is in operation based on the identified parameters; when a single transformer is in operation, the high-voltage bus load equivalent impedance before the parallel capacitor is switched on and off is calculated according to the equivalent circuit, and then the voltage change amount of each bus after the parallel capacitor is switched on and off is obtained according to the relationship between the load equivalent impedance, current change and voltage change; when a non-single transformer is in operation, the impedance parameters after the transformation are calculated according to the Y / Δ transformation of the equivalent circuit, an admittance matrix is ​​formed, the load after the parallel capacitor is switched on and off is calculated, and finally the voltage change amount of each bus after the parallel capacitor is switched on and off is obtained according to the power flow calculation equation.

Description

Technical Field

[0001] The invention belongs to the field of transformer substations, and in particular relates to a method and a system for determining a bus voltage variation when a parallel capacitor is switched on and off in a transformer substation. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] As a hub site, it is very important for 500kV substation to accurately estimate and calculate the change in voltage amplitude of each busbar after the parallel capacitor is switched on and off in order to realize automatic voltage control. For on-site control of the substation, the sensitivity of the control measures must be determined first. For real-time control, the most ideal way is to calculate the sensitivity online based on on-site measurement data and then implement control. If the online calculation is accurate enough, the significance for real-time control is not only to maintain good voltage quality, but also to optimize and coordinate various reactive compensation equipment and prevent voltage instability. The inventors found that the previous sensitivity calculation was basically based on the typical flow data of the entire network, ignoring the differences in load models and operating modes, and the accuracy was insufficient. Summary of the invention

[0004] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a method and system for determining the voltage change of the busbar when the shunt capacitor of the substation is switched on and off, which can calculate the voltage change of the busbar when the shunt capacitor of the substation is switched on and off.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A first aspect of the present invention provides a method for determining a bus voltage change amount when a shunt capacitor is switched on and off in a substation, comprising:

[0007] Identify the external equivalent circuit parameters of the high-voltage side bus and the bus side load parameters;

[0008] Determine whether a single transformer is operating based on the identified parameters;

[0009] When a single transformer is in operation, the equivalent impedance of the high-voltage bus load before the parallel capacitor is switched on and off is calculated based on the equivalent circuit, and then the voltage change of each bus after the parallel capacitor is switched on and off is obtained based on the relationship between the load equivalent impedance, current change and voltage change.

[0010] When more than one transformer is in operation, the impedance parameters after transformation are calculated according to the Y / Δ transformation of the equivalent circuit to form an admittance matrix, and the load after the parallel capacitor is switched on / off is calculated. Finally, the voltage change of each bus after the parallel capacitor is switched on / off is obtained according to the power flow calculation equation.

[0011] A second aspect of the present invention provides a system for determining a bus voltage variation amount when a shunt capacitor is switched on and off in a transformer substation, comprising:

[0012] A parameter identification module, which is used to identify the external equivalent circuit parameters of the high-voltage side bus and the bus side load parameters;

[0013] A single transformer operation judgment module, which is used to judge whether a single transformer is operating based on the identified parameters;

[0014] The bus voltage variation calculation module is used to:

[0015] When a single transformer is in operation, the equivalent impedance of the high-voltage bus load before the parallel capacitor is switched on and off is calculated based on the equivalent circuit, and then the voltage change of each bus after the parallel capacitor is switched on and off is obtained based on the relationship between the load equivalent impedance, current change and voltage change.

[0016] When more than one transformer is in operation, the impedance parameters after transformation are calculated according to the Y / Δ transformation of the equivalent circuit to form an admittance matrix, and the load after the parallel capacitor is switched on / off is calculated. Finally, the voltage change of each bus after the parallel capacitor is switched on / off is obtained according to the power flow calculation equation.

[0017] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the method for determining the bus voltage change amount when a parallel capacitor is switched on and off in a substation as described above.

[0018] The fourth aspect of the present invention provides 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 steps in the method for determining the bus voltage change amount when switching on and off parallel capacitors in a substation as described above are implemented.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention adopts the technical means of converting the external Thevenin equivalent of the substation and the equivalent circuit of the transformer in the station to obtain the application effect of accurately calculating the bus voltage change of each voltage level after the low-voltage bus parallel capacitor is switched on and off, providing an accurate quantitative calculation theoretical basis for the voltage regulation and reactive power optimization control of the substation.

[0021] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0023] Figure 1 It is a 500kV substation equivalent circuit of an embodiment of the present invention;

[0024] Figure 2 It is the equivalent circuit of a 500kV substation after Y-Δ transformation according to an embodiment of the present invention;

[0025] Figure 3 is a structural diagram of a three-winding transformer parallel operation system according to an embodiment of the present invention;

[0026] Figure 4 It is an equivalent circuit of a 35kV side switching capacitor of a 500kV substation three-winding transformer according to an embodiment of the present invention;

[0027] Figure 5 It is a flow chart of a method for determining a bus voltage change amount when switching on and off a shunt capacitor in a substation according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0029] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0031] Embodiment 1

[0032] Reference Figure 5 This embodiment provides a method for determining the bus voltage change amount when a shunt capacitor is switched on and off in a substation, which specifically includes the following steps:

[0033] Step 1: Identify the external equivalent circuit parameters of the high-voltage side bus and the bus side load parameters.

[0034] In some specific implementations, the process of identifying the external equivalent circuit parameters of the high-voltage side bus is: identifying the Thevenin equivalent voltage source and impedance parameters by measuring voltage and current values.

[0035] In other embodiments, in order to improve the accuracy of identification, the external equivalent circuit parameters of the high-voltage side bus are optimized and identified by the least squares method.

[0036] In one or more embodiments, the relevant parameters of the dynamic equivalent model are identified using the invariance of injected power flow and the dynamic equivalent theory.

[0037] In other embodiments, Kalman filtering may also be used to identify random signal characteristics, construct a measurement state equation, and identify bus side load parameters.

[0038] A typical 500kV substation usually has two three-winding transformers running in parallel. Its equivalent circuit is as follows: Figure 1 As shown. Bus1 is a 500kV bus, Bus2 is a 220kV bus, and Bus31 and Bus32 are 35kV buses respectively. Their voltages are U1, U2, U31 and U32 respectively. The Thevenin equivalent is performed outside the high-voltage bus, represented by an ideal voltage source E and impedance Zeq. The loads of Bus2, Bus31 and Bus32 can all be obtained based on the sum of the measured bus voltage and the current of the transformer winding. Among them, Zt11, Zt21, Zt31, Zt12, Zt22, and Zt32 are the equivalent impedances of the windings of the first and second transformers respectively. The currents flowing through them are I11, I21, I31, I12, I22, and I32 respectively. Assume that the parallel capacitor on Bus31 is put into use, and its capacitance value is C, which is equivalent to injecting reactive power U 31p 2 ωC, angular frequency ω=2πf, f=50Hz. 31p The voltage of Bus31 after parallel connection. To solve the change in the voltage amplitude of each bus, after Y-Δ transformation, the equivalent circuit is as follows Figure 2 As shown in the figure, Z b12 is the impedance from Bus1 to Bus2, Z b131 is the impedance from Bus1 to Bus31, Z b132 is the impedance from Bus1 to Bus32, Z b231 is the impedance from Bus2 to Bus31, Z b232 is the impedance from Bus2 to Bus32.

[0039] Assume that each bus load is a voltage amplitude related model, that is, P2(U2)+jQ2(U2), P 31 (U 31 )+jQ 31 (U 31) and P 32 (U 32 )+jQ 32 (U 32 ). This problem is transformed into the power flow calculation after reducing the reactive load. The voltage amplitudes of each bus before the capacitor is put into operation are recorded as U1, U2, U3 and U4, and the voltage amplitudes of each bus after the capacitor is put into operation are recorded as U 1p , U 2p , U 3p and U 4p , the phase angle is θ 1p ,θ 2p ,θ 3p and θ 4p The voltage of the balancing node Slack Bus is the reference, its amplitude is the value after the measurement of the equal value U5 = E, and the phase angle is 0. The node admittance matrix of the system is Ybus, Figure 2 The node numbers in the equivalent circuit are: Slack bus is node 1, Bus1 is node 2, Bus2 is node 3, Bus31 is node 4, and Bus32 is node 5. The values ​​of the matrix elements are as follows:

[0040]

[0041] Y 25 =0

[0042] Y 34 =0, Y 35 =0

[0043] Y 45 =0

[0044] Y 52 =0, Y 53 =0, Y 54 =0,

[0045] Among them, Y ij is the admittance between nodes i and j, and its real part is G ij , the imaginary part is B ij .

[0046] Let Y ij =G ij +B ij (i=1,2,3,4,5; j=1,2,3,4,5)

[0047] The load model on Bus2, Bus31 and Bus32 can be estimated from the measured values. After the capacitors are put into use, the load of each node is P2(U 2p )+jQ2(U2p ), P 31 (U 3p )+j[Q 31 (U 3p )-U 3p 2 ωC] and P 32 (U 4p )+jQ 32 (U 4p ), then the power equation of each node is as follows:

[0048] Bus1 active and reactive equations:

[0049]

[0050]

[0051] Bus2 active and reactive power equations:

[0052]

[0053]

[0054] Bus31 active and reactive power equations:

[0055]

[0056]

[0057] Bus32 active and reactive power equations:

[0058]

[0059]

[0060] where θ ij =θ i -θ j .

[0061] According to the power equation and power flow calculation process, the voltage of each node before and after the capacitor is put into operation can be calculated.

[0062] To verify the accuracy of the calculation method, we first use MatLab's Simulink to build a system with two three-winding transformers running in parallel. Figure 3 shown.

[0063] The parameters of the simulation system are as follows:

[0064] E = 500 kV, phase 0; Zeq = 2 + j5.2088 Ω; P2 = 60 MW, Q2 = 30 MVar;

[0065] The rated voltages of the three windings of the transformer are 500kV, 220kV and 35kV respectively. The impedance of each winding is 0.002+j0.08 per unit. The parallel capacitance on the 35kV side is 1 microfarad. The 220kV bus load model is a constant impedance. After the capacitor is put into use, the voltage changes of each bus are calculated by equivalent value and the changes obtained by simulation are shown in Table 1. (The unit of voltage change is V):

[0066] Table 1 The changes of each bus voltage and the changes obtained by simulation

[0067]

[0068] For the external equivalent value on the 500kV side:

[0069] (1) Thevenin equivalence.

[0070] For the equivalent value of the outer part of the high-voltage bus, the simplest method is to identify its Thevenin equivalent voltage source and impedance parameters by measuring the voltage and current values. Because the current Ieq flowing through Zeq is the sum of the currents of the two transformer windings, it can be obtained by measurement. Add the measured Bus1 bus voltage U1, so for any time k, there should be EI eqk Zeq=U 1k Therefore, a more appropriate data window before switching can be selected. The simplest algorithm is to have two sets of sampling data, E=Er+jEi, Zeq=R TH +jX TH ,U1=u+jw,I1=g+jh,then:

[0071]

[0072] According to equation (1), two important parameters E and Zeq of the external Thevenin equivalent circuit of the high-voltage bus can be solved.

[0073] A more accurate method is to take n sets of sampled data and use the least squares method to optimize and identify E and Zeq. The cost is a large amount of calculation.

[0074] (2) Dynamic equivalence. The relevant parameters of the dynamic equivalence model are identified using the invariance of the injected power flow and the dynamic equivalence theory. In this scenario, the frequency correlation can be ignored and the correlation of the voltage amplitude can be focused on.

[0075] For the load model parameter identification on the 220kV side:

[0076] A more accurate method is to take enough sample data to identify the load model parameters on the 220kV side. However, due to the steady-state control conditions, the load model has little effect on the operation near the rated voltage. In the simulation results, if the constant power model is used for calculation, the results are shown in Table 2.

[0077] Table 2 Comparison of calculation results and simulation results of different load models

[0078]

[0079]

[0080] The results shown in Table 2 show that the error caused by the influence of the load model is small, which meets the actual engineering needs. In addition, the use of the constant power load model greatly reduces the difficulty of program development for device implementation, which can shorten the R&D cycle.

[0081] The fluctuation of measurement caused by random fluctuation of load is an important problem in actual operation. It can be simply handled by multi-point averaging and setting fluctuation threshold value. If it is handled accurately, Kalman filtering can be used to identify the characteristics of random signals and construct the measurement state equation.

[0082] Step 2: Determine whether a single transformer is operating based on the identified parameters.

[0083] Step 3: When a single transformer is in operation, the high-voltage bus load equivalent impedance before the parallel capacitor is switched on and off is calculated based on the equivalent circuit, and then the voltage change of each bus after the parallel capacitor is switched on and off is obtained based on the relationship between the load equivalent impedance, current change and voltage change;

[0084] When more than one transformer is in operation, the impedance parameters after transformation are calculated according to the Y / Δ transformation of the equivalent circuit to form an admittance matrix, and the load after the parallel capacitor is switched on / off is calculated. Finally, the voltage change of each bus after the parallel capacitor is switched on / off is obtained according to the power flow calculation equation.

[0085] Processing when running on a single machine:

[0086] When a transformer in a substation is under maintenance or fails, the system operation is converted to single-unit operation mode. The specific processing methods are as follows.

[0087] For a three-winding transformer in a 500kV substation, the equivalent circuit for switching capacitors on the 35kV side can be Figure 4 In the figure, U1, U2 and U3 are the voltages of Bus1, Bus2 and Bus3 respectively, Zt1, Zt2, Zt3 are the impedances of the three windings of the transformer respectively, and I1, I2 and I3 are the currents of the three windings of the transformer respectively. E and Zeq are the Thevenin equivalent potential and equivalent impedance on the 500kV side.

[0088] Identification of external equivalent circuit parameters of high-voltage busbar (calculation of E and Zeq):

[0089] According to equation (1), two important parameters E and Zeq of the external Thevenin equivalent circuit of the high-voltage bus can be solved.

[0090] Quantitative analysis of the impact of switching capacitors (or reactors) on bus voltages:

[0091] Assume that the load equivalent impedance of Bus2 before the parallel capacitor is connected is (or ), Bus3 load equivalent impedance (or ), (Bus2 and Bus3 bus voltages can be measured, and transformer winding currents I1, I2 and I3 can also be measured)

[0092] After connecting capacitors in parallel, Where Zc is the impedance of the parallel capacitor.

[0093] Before connecting capacitors in parallel, the current

[0094] In the formula (Z t2 +Z2) / / (Z t3 +Z3) refers to the impedance (Z t2 +Z2) and impedance (Z t3 +Z3) in parallel.

[0095] After the capacitor is connected in parallel, the current

[0096] Therefore, the voltage changes of each bus are:

[0097] Bus1,ΔU1=(I eq -I' eq )·Z eq

[0098] Bus2, before switching

[0099] After cutting

[0100] The voltage change is:

[0101]

[0102] Similarly, the bus voltage change ΔU3 of Bus 3 can be deduced.

[0103] The influence of different load types on the quantitative analysis of the voltage change of switching parallel capacitors:

[0104] When the load connected to Bus2 is a constant impedance load, the above derivation has no approximation or assumption, and its quantitative results are accurate. After building an equivalent circuit with MatLab, the simulation results are completely consistent with the theoretical derivation results. When the load type is other types, especially when voltage changes affect the load size, the above derivation will have a certain error. The specific analysis is as follows:

[0105] Assume that the load type of Bus2 and Bus3 is ZIP, which is a combination of constant power, constant impedance and constant current loads. The expression is:

[0106]

[0107]

[0108] Assume that the changes in the Bus2 and Bus3 bus voltages caused by capacitor switching are ΔU2 and ΔU3 (to be determined). After switching, the Bus2 and Bus3 bus loads become:

[0109]

[0110]

[0111] The relevant parameters P in equations (2)-(5) are con2 , P con3 , Q con2 , Q con3 , a2, b2, a3, b3, α2, β2, α3 and β3 can all be estimated using the least squares method.

[0112] Therefore, after switching on, the equivalent load impedance of Bus2 is The equivalent load impedance of Bus3 is (Before switching, assume that the equivalent load impedances of Bus2 and Bus3 are and can be calculated based on the measured value). According to the previous derivation,

[0113] Before connecting capacitors in parallel,

[0114] After connecting capacitors in parallel,

[0115] Therefore, the voltage changes of each bus are:

[0116] Bus1 ΔU1=(I eq -I' eq )·Z eq (8)

[0117] Bus2,

[0118] Before switching

[0119] After cutting

[0120] The voltage change is:

[0121]

[0122]

[0123] Bus 3,

[0124] Before switching

[0125] After cutting

[0126] The voltage change ΔU3 is:

[0127] Substituting equations (6) and (7) into equations (8)-(10), we can obtain three equations containing only three unknowns ΔU1, ΔU2 and ΔU3.

[0128] This method is applicable to various load types. As long as the load type expression is accurate, this method does not have any assumptions or approximations, and the results are accurate.

[0129] Simulation results:

[0130] Using Simulink in Matlab, first build Figure 1 The equivalent circuit is Figure 2 shown.

[0131] Figure 2 :MatLab simulation equivalent circuit diagram

[0132] in

[0133] E = 110e3;

[0134] Zeq = 0.0500 + 0.3142i;

[0135] Z t1 =6.2+158.02i;

[0136] Zt2=8.41+91.0119i;

[0137] Zt3=3.3-3.9992i;

[0138] Zc=-4.0833e+003i;

[0139] The loads connected to Bus2 and Bus3 are directly connected to the simulation circuit using equal impedance.

[0140] Z2=4.2+47.1239i;

[0141] Z3=0.01-4.0833e+003i;

[0142] Table 3 Comparison of theoretical calculation results and actual simulation results 1

[0143] Theoretical calculation results: Actual simulation results: <![CDATA[ΔU1=1.9681]]> <![CDATA[ΔU1=1.9681]]> <![CDATA[ΔU2=334.3803]]> <![CDATA[ΔU2=334.3748]]> <![CDATA[ΔU3=931.6181]]> <![CDATA[ΔU3=931.6026]]>

[0144] The results show that the theoretical calculations are consistent with the simulation results.

[0145] In order to be closer to engineering practice, a three-winding transformer is directly used in the simulation circuit, and the load type is constant impedance. The relevant parameters of the simulation circuit are as follows:

[0146] Table 4 Simulation circuit related parameters

[0147] Rated voltage(V) Winding resistance (per unit value) Winding inductance (per unit value) Winding 1 1.21e+005 0.00425 0.153 Winding 2 3.85e+005 0.00575 0.094001 Winding 3 11000 0.00225 -0.0059999

[0148] The load impedance connected to Bus2 and Bus3 is:

[0149] Z2x=4.2+47.1239i;

[0150] Z3x=0.01-4.0833e+003i;

[0151] The Zc connected to Bus3 is:

[0152] Zcx = -4.0833e+003i;

[0153] According to the transformer parameters, it is converted into the equivalent circuit impedance on the high voltage side:

[0154] Z t1 =6.2224+224.01i;

[0155] Zt2=8.4186e+000+137.63i;

[0156] Zt3=3.2942-8.7845i;

[0157] Z2=Z2x*(121 / 38.5) 2

[0158] Z3=Z3x*(121 / 11) 2

[0159] Zc=Zcx*(121 / 11) 2

[0160] E = 98.796e3;

[0161] The comparison between theoretical calculation results and simulation results is shown in the table below.

[0162] Table 5 Comparison of theoretical calculation results and actual simulation results 2

[0163]

[0164]

[0165] The results show that the theoretical calculations and simulation results are still consistent.

[0166] Embodiment 2

[0167] This embodiment provides a system for determining bus voltage variation when switching on and off shunt capacitors in a substation, which includes the following modules:

[0168] A parameter identification module, which is used to identify the external equivalent circuit parameters of the high-voltage side bus and the bus side load parameters;

[0169] A single transformer operation judgment module, which is used to judge whether a single transformer is operating based on the identified parameters;

[0170] The bus voltage variation calculation module is used to:

[0171] When a single transformer is in operation, the equivalent impedance of the high-voltage bus load before the parallel capacitor is switched on and off is calculated based on the equivalent circuit, and then the voltage change of each bus after the parallel capacitor is switched on and off is obtained based on the relationship between the load equivalent impedance, current change and voltage change.

[0172] When more than one transformer is in operation, the impedance parameters after transformation are calculated according to the Y / Δ transformation of the equivalent circuit to form an admittance matrix, and the load after the parallel capacitor is switched on / off is calculated. Finally, the voltage change of each bus after the parallel capacitor is switched on / off is obtained according to the power flow calculation equation.

[0173] It should be noted here that each module in this embodiment corresponds to each step in Example 1 one by one, and the specific implementation process is the same, which will not be repeated here.

[0174] Embodiment 3

[0175] This embodiment provides a computer-readable storage medium having a computer program stored thereon. When the program is executed by a processor, the steps in the method for determining the change in bus voltage when switching on and off a shunt capacitor in a substation as described above are implemented.

[0176] Embodiment 4

[0177] This embodiment provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps in the method for determining the bus voltage change amount when switching on and off a parallel capacitor in a substation as described above are implemented.

[0178] The present invention is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems) and computer program products of the embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram and the combination of the processes and / or blocks in the flowchart and / or block diagram can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0179] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for determining the bus voltage change when a shunt capacitor is switched on and off in a substation, characterized in that: include: Identify the external equivalent circuit parameters of the high-voltage side bus and the bus side load parameters; Determine whether a single transformer is operating based on the identified parameters; When a single transformer is in operation, the equivalent impedance of the high-voltage bus load before the parallel capacitor is switched on and off is calculated based on the equivalent circuit, and then the voltage change of each bus after the parallel capacitor is switched on and off is obtained based on the relationship between the load equivalent impedance, current change and voltage change. Among them, the relationship between load equivalent impedance, current change and voltage change is: ； ； ； , and They are the changes in the Bus1, Bus2 and Bus3 bus voltages caused by capacitor switching; is the Thevenin equivalent impedance; , , are the impedances of the three windings of the transformer respectively; is the equivalent load impedance of Bus2 after switching on; is the equivalent load impedance of Bus3 after switching on; is the equivalent load impedance of Bus2 before switching; is the equivalent load impedance of Bus3 before switching; is the voltage of Bus2 before switching; is the voltage of Bus3 before switching; when the transformer is not in single operation, according to the Y / Transform, calculate the transformed impedance parameters, form an admittance matrix, calculate the load after the parallel capacitor is switched on / off, and finally obtain the voltage change of each bus after the parallel capacitor is switched on / off according to the power flow calculation equation.

2. The method for determining the bus voltage variation when switching on and off a shunt capacitor in a substation according to claim 1, characterized in that: The identification process of the external equivalent circuit parameters of the high-voltage side bus is: the Thevenin equivalent voltage source and impedance parameters are identified by measuring voltage and current values.

3. The method for determining the bus voltage variation when switching on and off a shunt capacitor in a substation according to claim 1, characterized in that: The external equivalent circuit parameters of the high-voltage side bus are optimized and identified by the least squares method.

4. The method for determining the bus voltage variation when switching on and off a shunt capacitor in a substation according to claim 1, characterized in that: The relevant parameters of the dynamic equivalent model are identified using the invariance of injected power flow and the dynamic equivalent theory.

5. The method for determining the bus voltage variation when switching on and off a shunt capacitor in a substation according to claim 1, characterized in that: Kalman filtering is used to identify the characteristics of random signals, construct the measurement state equation, and identify the bus side load parameters.

6. A system for determining bus voltage variation when switching on and off shunt capacitors in a substation, characterized in that: include: A parameter identification module, which is used to identify the external equivalent circuit parameters of the high-voltage side bus and the bus side load parameters; A single transformer operation judgment module, which is used to judge whether a single transformer is operating based on the identified parameters; The bus voltage variation calculation module is used to: When a single transformer is in operation, the equivalent impedance of the high-voltage bus load before the parallel capacitor is switched on and off is calculated based on the equivalent circuit, and then the voltage change of each bus after the parallel capacitor is switched on and off is obtained based on the relationship between the load equivalent impedance, current change and voltage change. Among them, the relationship between load equivalent impedance, current change and voltage change is: ； ； ； , and They are the changes in the Bus1, Bus2 and Bus3 bus voltages caused by capacitor switching; is the Thevenin equivalent impedance; , , are the impedances of the three windings of the transformer respectively; is the equivalent load impedance of Bus2 after switching on; is the equivalent load impedance of Bus3 after switching on; is the equivalent load impedance of Bus2 before switching; is the equivalent load impedance of Bus3 before switching; is the voltage of Bus2 before switching; is the voltage of Bus3 before switching; When the transformer is not in single operation, according to the Y / Transform, calculate the transformed impedance parameters, form an admittance matrix, calculate the load after the parallel capacitor is switched on / off, and finally obtain the voltage change of each bus after the parallel capacitor is switched on / off according to the power flow calculation equation.

7. The system for determining bus voltage variation when switching on and off a shunt capacitor in a substation according to claim 6, characterized in that: In the parameter identification module, the identification process of the external equivalent circuit parameters of the high-voltage side bus is: the Thevenin equivalent voltage source and impedance parameters are identified by measuring voltage and current values.

8. The system for determining bus voltage variation when switching on and off a shunt capacitor in a substation according to claim 6, characterized in that: In the parameter identification module, the external equivalent circuit parameters of the high-voltage side bus are optimized and identified by the least squares method.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps in the method for determining the bus voltage change amount when switching on and off a shunt capacitor in a substation as described in any one of claims 1 to 5 are implemented.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps in the method for determining the bus voltage change amount of switching on and off a shunt capacitor in a substation according to any one of claims 1 to 5 are implemented.

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