Reactive voltage control method for compensating three-roll transformer non-SVG grid-connected point

Abstract

The invention relates to a reactive voltage control method for compensating a non-SVG grid-connected point of a three-roll transformer, and the method comprises the steps: connecting an SVG to a low-voltage side of the three-roll transformer, collecting voltage and current signals of a medium-voltage side of the three-roll transformer, and obtaining a medium-voltage side voltage feedback signal of a voltage control mode of the medium-voltage side of the SVG and a medium-voltage side load reactive instruction of a reactive compensation mode of a high-voltage side of the SVG; voltage and current signals of the low-voltage side of the three-roll transformer are collected and used for obtaining low-voltage side reactive power, including SVG output reactive power and load reactive power, in an SVG high-voltage side reactive power compensation mode; closed-loop control over the medium-voltage side voltage of the three-roll transformer and high-voltage side reactive compensation without signal acquisition are achieved through control over the SVG on the low-voltage side of the three-roll transformer. The method has the advantages that by controlling the low-voltage side SVG to output reactive power, closed-loop control over the three-roll transformer medium-voltage side voltage of the non-grid-connected point of the SVG is achieved, the SVG voltage compensation target point is expanded, the compensation position is more flexible, and high-voltage side reactive power compensation can be achieved under the condition that the high-voltage side voltage and current cannot be collected.

Description

Technical Field

[0001] The invention relates to the technical field of static VAR generator control, and in particular to a reactive voltage control method for compensating a three-winding transformer non-SVG grid-connected point. Background Art

[0002] With the increasing number of high-voltage grid-connected devices such as wind turbines, photovoltaics, and energy storage equipment and the diversity of loads, the reactive power loss of power transmission lines, the reactive power and voltage of assessment points are difficult to meet the standards. High-voltage cascade static VAR generators (SVGs) have been widely used in new energy stations, steel mills, and long-distance power transmission to compensate for reactive power and voltage drops and reactive power support during transient processes.

[0003] In some special occasions, such as when the main transformer has a three-winding transformer topology structure and the voltage and current on the high-voltage side of the three-winding transformer cannot be collected, it is required to compensate the medium-voltage side voltage and the high-voltage side reactive power. The control mode of the general standard SVG is difficult to complete. Therefore, based on the functions of the standard SVG, we explore and develop diversified compensation modes to make SVG cover a wider range in the field of reactive power compensation. Summary of the invention

[0004] The purpose of the present invention is to provide a reactive voltage control method for compensating a three-winding transformer non-SVG grid-connected point. To complete the control of the voltage outside the SVG grid-connected point, the voltage signal on the medium voltage side is collected, and the medium voltage side voltage is controlled by the low voltage side SVG through the three-winding transformer; when the PT and CT signals on the high voltage side cannot be collected, the reactive power on the high voltage side is compensated, and the reactive power compensation on the high voltage side without signal collection is completed by collecting the voltage and current on the medium voltage side and the low voltage side and the SVG current, and considering the reactive power caused by the load rate of the high voltage side to the medium voltage and the low voltage side respectively.

[0005] To achieve the above purpose, the present invention is completed by the following technical solutions:

[0006] A reactive voltage control method for compensating a non-SVG grid-connected point of a three-winding transformer, wherein the loads are located at the medium-voltage side and the low-voltage side of the three-winding transformer respectively, and the SVG is connected to the low-voltage side of the three-winding transformer. The voltage and current signals of the medium-voltage side of the three-winding transformer are collected to obtain the medium-voltage side voltage feedback signal of the SVG medium-voltage side voltage control mode and the medium-voltage side load reactive power instruction of the SVG high-voltage side reactive power compensation mode. The voltage and current signals of the low-voltage side of the three-winding transformer are collected to obtain the reactive power of the low-voltage side in the SVG high-voltage side reactive power compensation mode, including the SVG output reactive power and the load reactive power.

[0007] By controlling the SVG on the low-voltage side of the three-winding transformer, closed-loop control of the medium-voltage side voltage of the three-winding transformer and reactive power compensation on the high-voltage side without signal collection are completed respectively.

[0008] The control of the SVG on the low voltage side of the three-winding transformer can complete the closed-loop control of the voltage on the medium voltage side of the three-winding transformer. The contents are as follows:

[0009] When SVG operates in the medium voltage side voltage control mode, the medium voltage side target voltage is taken as the given value and the medium voltage side actual collected voltage U is taken as the given value. 110fdb is the feedback value, which is used as the voltage outer loop for PI closed-loop control to obtain the SVG reactive current inner loop instruction, which is used to complete the closed-loop regulation of the medium voltage side voltage through the low voltage side SVG. 110fdb The calculation is as follows: Collect the voltage U on the medium voltage side of the three-winding transformer 110a , U 110b , U 110c , U obtained by three-phase voltage dq transformation d , U q , the medium voltage side grid voltage amplitude U is calculated 110fdb , the formula is as follows:

[0010]

[0011] The control of the SVG on the low-voltage side of the three-winding transformer can complete reactive power compensation on the high-voltage side without sampling the voltage and current on the high-voltage side. The contents are as follows:

[0012] 1) Collect the current I on the medium voltage side of the three-winding transformer 110a ,I 110b ,I 110c , and the medium voltage side voltage U 110a , U 110b , U 110c The formula for calculating the reactive power instruction of the medium voltage side load of the three-winding transformer in the reactive power compensation mode of SVG is as follows:

[0013] Q Load110 =Q 110 =U 110d *I 110q -U 110q *I 110d ②

[0014] At the same time, the active power on the medium voltage side of the three-winding transformer is calculated as follows:

[0015] P 110 =U 110d *I 110d +U 110q *I 110q ③

[0016] 2) Calculate the load rate Load_Rate of the high voltage side of the three-winding transformer to the medium voltage side HM and the reactive power Q caused by it HM , the formula is as follows:

[0017]

[0018] Among them, U 110d , U 110q ,I 110d ,I 110q is the components of the three-phase voltage and current on the medium voltage side of the three-winding transformer in the dq coordinate system, P 110 , Q 110 Indicates the active power and reactive power of the medium voltage side of the three-winding transformer, Sn 110 Indicates the rated capacity of the medium voltage side of the three-winding transformer, Z HM % is the short-circuit impedance percentage of the high voltage side to the medium voltage side.

[0019] The voltage and current signals of the low-voltage side of the three-winding transformer are collected to obtain the reactive power on the low-voltage side. The contents are as follows:

[0020] 1) Collect the low voltage side voltage U 35a , U 35b , U 35c , calculate the low voltage side grid voltage amplitude U 35fdb , used to calculate the reactive power of SVG, the formula is as follows:

[0021]

[0022] U 35d , U 35q is the component of the low voltage three-phase voltage in the dq coordinate system;

[0023] 2) Collect low-voltage side grid current I 35a ,I 35b ,I 35c And SVG Hall current I Svga ,I Svgb ,I Svgc , and the low voltage side voltage U 35a , U 35b , U 35c Calculate the reactive power QLoad on the low voltage side 35 and SVG reactive power Q Svg , the formula is as follows:

[0024] QLoad 35 =Q 35 =U 35d *I 35q -U 35q *I 35d ⑦

[0025] Calculate the active power on the low-voltage side of the three-winding transformer using the following formula:

[0026] P 35 =U 35d *I 35d +U 35q*I 35q ⑧

[0027] To calculate the reactive power of SVG, the formula is as follows:

[0028] Q Svg =U 35fdb *I SvgQ ⑨

[0029] Among them I 35d ,I 35q ,I SvgD ,I SvgQ are the components of the low voltage three-phase grid current and the SVG current in the dq coordinate system;

[0030] 3) Calculate the load rate of the high voltage side to the low voltage side and the reactive power caused by it Load_Rate HL , Q HL The formula is as follows:

[0031]

[0032] The reactive power compensation of the low-voltage side SVG to the high-voltage side grid: the reactive power Q Load110 The low voltage side SVG outputs reactive power Q Load35 , and load reactive power Q HM Add together the reactive power caused by the load rate of the high voltage side to the medium voltage side and the reactive power Q caused by the load rate of the high voltage side to the low voltage side HL , get the total reactive power on the high voltage side, minus the reactive power Q output by SVG Svg , get the load reactive power instruction of SVG in the reactive power compensation mode on the high-voltage side, complete the reactive power compensation of SVG on the low-voltage side to the high-voltage side grid, and the total reactive power instruction of SVG Q SvgRef The calculation formula is as follows:

[0033] Q SvgRef =Q Load110 +Q Load35 +Q HM +Q HL -Q Svg

[0034] The high-voltage side of the three-winding transformer is connected to the high-voltage power grid. There is no PT or CT signal collection. The voltage and current signals on the medium and low-voltage sides are collected through current and voltage sensors. The current and voltage sensors use announcement number CN217879401U, and the patent name is a current and voltage sensor and a basic circuit for self-power supply. Other models can also be used.

[0035] A computer device comprises: at least one processor, and a memory in communication with the at least one processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor executes any method for controlling reactive voltage of a non-SVG grid-connected point for compensating three-winding transformers as claimed in any one of claims 1 to 6.

[0036] A computer-readable storage medium storing computer instructions for causing the computer to execute any of the reactive voltage control methods for compensating a three-winding transformer non-SVG grid-connected point in claims 1-6.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. To control the voltage outside the SVG grid connection point, the voltage signal on the medium voltage side is collected, and the medium voltage side voltage is controlled by the low voltage side SVG through three coils; when the PT and CT signals on the high voltage side cannot be collected, the reactive power on the high voltage side must be compensated. By collecting the voltage and current on the medium voltage side and the low voltage side and the SVG current, and considering the reactive power caused by the load rate of the high voltage side on the medium voltage and low voltage sides, the reactive power compensation on the high voltage side without signal collection is completed;

[0039] 2. By controlling the reactive power output of the SVG on the low-voltage side, the closed-loop control of the voltage on the medium-voltage side of the three-winding transformer at the non-grid-connected point of the SVG is completed, the target point of SVG voltage compensation is expanded, and the compensation position is more flexible;

[0040] 3. By collecting the voltage and current on the low-voltage side of the three-winding transformer and calculating the reactive power caused by the load rate on the medium and low-voltage sides, reactive power compensation on the high-voltage side can be completed even when the voltage and current on the high-voltage side cannot be collected;

[0041] 4. The signal sampling of this system is not limited to the target position. At the scene where the target control signal cannot be collected, the compensation amount of the target position is converted by collecting voltage and current signals at other positions, and the strategic control of the target with or without signal collection outside the SVG grid connection point is completed. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a three-volume topological diagram of the high, medium and low voltage sides.

[0043] Figure 2 It is a system structure where the low voltage side SVG controls the voltage on the medium voltage side.

[0044] Figure 3 The low voltage side SVG compensates the high voltage side reactive power system structure

[0045] Figure 4 This is the structural diagram of the SVG control system, power cabinet, and charging cabinet. DETAILED DESCRIPTION

[0046] The present invention is described in detail below in conjunction with the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0047] The following examples are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples. The methods used in the following examples are conventional methods unless otherwise specified.

[0048] [Example 1]

[0049] The load is located on the medium voltage side and low voltage side of the three-winding transformer, and the SVG is located on the low voltage side of the three-winding transformer. Figure 1 When the assessment target is the medium voltage side voltage, the medium voltage side target voltage is taken as the given value and the actual collected voltage U 110fdb U is the feedback value, which is used as the voltage outer loop for PI closed-loop control to obtain the SVG reactive current inner loop instruction, which is used to complete the closed-loop regulation of the medium voltage side voltage through the low voltage side SVG. 110fdb The calculation is as follows: Collect the voltage U on the medium voltage side of the three-winding transformer 110a , U 110b , U 110c , U obtained by three-phase voltage dq transformation d , U q , the medium voltage side grid voltage amplitude U is calculated 110fdb , the formula is as follows:

[0050]

[0051] The control of the SVG on the low voltage side of the three-winding transformer is used to complete the closed-loop control of the voltage on the medium voltage side of the three-winding transformer. When the SVG operates in the medium voltage side voltage control mode, see Figure 2 , taking the 110kV side voltage as the given target and the 110kV side actual collected voltage U 110fdb As the feedback value, closed-loop control is performed to obtain the SVG reactive current command, and the closed-loop regulation of the low-voltage side SVG on the medium-voltage side voltage is completed; in this process, since the voltage at the SVG grid connection point is not controlled, the short-circuit impedance of the medium-voltage side to the low-voltage side must be considered. Therefore, the cascade number and insulation of the high-voltage cascade SVG must be sufficient, so as to ensure that the SVG can output enough low-voltage side voltage to offset the voltage drop of the medium-voltage side winding of the transformer to the low-voltage side winding, so as to achieve the purpose of controlling the medium-voltage side voltage, and prevent the voltage on the low-voltage side from rising too high when there is no load or light load on the low-voltage side, thereby preventing the SVG modulation wave from saturating due to excessive voltage rise on the low-voltage side.

[0052] [Example 2]

[0053] The load is located on the medium voltage side and low voltage side of the three-winding transformer, and the SVG is located on the low voltage side of the three-winding transformer. Figure 1, when the assessment target is the reactive power on the high voltage side; by collecting the voltage and current on the medium voltage side and the low voltage side, the load reactive power and the SVG output reactive power are calculated, and the reactive power caused by the load rate of the high voltage side to the medium voltage and low voltage sides is considered, all reactive power is added up and the SVG output reactive power is subtracted, and the reactive power instruction of the SVG on the low voltage side to compensate the high voltage side can be obtained. The scheme is as follows:

[0054] The high-voltage side of the three-roll transformer is 220kV, connected to the high-voltage power grid, without PT and CT signal collection, the medium-voltage side is 110kV, and the low-voltage side is 35kV, both with PT and CT signal collection. The loads are located on the medium-voltage side and low-voltage side of the three-roll transformer, and the high-voltage cascade SVG is located on the low-voltage side of the three-roll transformer. The voltage and current signals on the medium-voltage side of the three-roll transformer are collected to obtain the reactive power instructions of the medium-voltage side load when the SVG runs in the reactive power compensation mode on the high-voltage side. The voltage and current signals on the low-voltage side of the three-roll transformer are collected to obtain the reactive power on the low-voltage side when the SVG runs in the reactive power compensation mode on the high-voltage side, including the SVG output reactive power and the load reactive power. The voltage and current signals are collected through current and voltage sensors (the current and voltage sensors are adopted with the announcement number CN217879401U, and the patent name is a current and voltage sensor and a basic circuit for self-collection of electricity).

[0055] 1) Collect the current I on the medium voltage side of the three-winding transformer 110a ,I 110b ,I 110c , and the medium voltage side voltage U 110a , U 110b , U 110c The formula for calculating the reactive power instruction of the medium voltage side load of the three-winding transformer in the reactive power compensation mode of SVG is as follows:

[0056] Q Load110 =Q 110 =U 110d *I 110q -U 110q *I 110d ②

[0057] At the same time, the active power on the medium voltage side of the three-winding transformer is calculated as follows:

[0058] P 110 =U 110d *I 110d +U 110q *I 110q ③

[0059] 2) Calculate the load rate Load_Rate of the high voltage side of the three-winding transformer to the medium voltage side HM and the reactive power Q caused by it HM , the formula is as follows:

[0060]

[0061] Among them, U 110d , U 110q ,I 110d ,I 110q is the components of the three-phase voltage and current on the medium voltage side of the three-winding transformer in the dq coordinate system, P 110 , Q 110 Indicates the active power and reactive power of the medium voltage side of the three-winding transformer, Sn 110 Indicates the rated capacity of the medium voltage side of the three-winding transformer, Z HM % is the short-circuit impedance percentage of the high voltage side to the medium voltage side.

[0062] The voltage and current signals of the low-voltage side of the three-winding transformer are collected to obtain the reactive power on the low-voltage side. The contents are as follows:

[0063] 1) Collect the low voltage side voltage U 35a , U 35b , U 35c , calculate the low voltage side grid voltage amplitude U 35fdb , used to calculate the reactive power of SVG, the formula is as follows:

[0064]

[0065] U 35d , U 35q is the component of the low voltage three-phase voltage in the dq coordinate system.

[0066] 2) Collect low-voltage side grid current I 35a ,I 35b ,I 35c And SVG Hall current I Svga ,I Svgb ,I Svgc , and the low voltage side voltage U 35a , U 35b , U 35c Calculate the reactive power QLoad on the low voltage side 35 and SVG reactive power Q Svg , the formula is as follows:

[0067] QLoad 35 =Q 35 =U 35d *I 35q -U 35q *I 35d ⑦

[0068] Calculate the active power on the low-voltage side of the three-winding transformer using the following formula:

[0069] P 35 =U 35d *I 35d +U 35q *I 35q⑧

[0070] To calculate the reactive power of SVG, the formula is as follows:

[0071] Q Svg =U 35fdb *I SvgQ ⑨

[0072] Among them I 35d ,I 35q ,I SvgD ,I SvgQ are the components of the low voltage three-phase grid current and the SVG current in the dq coordinate system.

[0073] 3) Calculate the load rate of the high voltage side to the low voltage side and the reactive power caused by it Load_Rate HL , Q HL The formula is as follows:

[0074]

[0075] The three-winding medium voltage load reactive power Q Load110 The low voltage side SVG outputs reactive power Q Load35 , and load reactive power Q HM Add together the reactive power caused by the load rate of the high voltage side to the medium voltage side and the reactive power Q caused by the load rate of the high voltage side to the low voltage side HL , get the total reactive power on the high voltage side, minus the reactive power Q output by SVG Svg , get the load reactive power instruction of SVG in the reactive power compensation mode on the high-voltage side, complete the reactive power compensation of SVG on the low-voltage side to the high-voltage side grid, and the total reactive power instruction of SVG Q SvgRef The calculation formula is as follows:

[0076] Q SvgRef =Q Load110 +Q Load35 +Q HM +Q HL -Q Svg

[0077] When SVG operates in high voltage side reactive power compensation mode, see Figure 3 First, calculate the reactive power of the medium voltage side load and the reactive power of the low voltage side. Since the sampling point of the low voltage side is at the low voltage side bus outlet, the reactive power of the low voltage side is actually the sum of the reactive power of the SVG and the reactive power of the load. Add the reactive power caused by the load rate of the medium voltage side and the reactive power caused by the load rate of the low voltage side to get the total reactive power of the high voltage side. Subtract the reactive power of the SVG output to get the SVG load reactive command Q SvgRef :

[0078] Computer equipment for reactive voltage control method of compensating three-winding transformer non-SVG grid-connected point, see Figure 4, mainly including single-board controller, host computer, power supply unit, PT adapter board, CT adapter board, digital input board, digital output board. The single-board controller centrally completes the functions of CPU board, analog board, digital board and PWM board. The single-board controller and control system adopt the announcement number CN217848961U, and the patent name is a SVG multi-machine parallel control device based on single-board controller. Other models can also be used; SVG is composed of control cabinet, power cabinet and charging cabinet. The PT adapter board, CT adapter board and digital input board in the control cabinet transmit analog data and digital data to the single-board controller. The host computer sends commands and parameters to the single-board controller through the standard Modbus communication protocol. The single-board controller is the control core. The DSP executes the SVG main control algorithm, and the FPGA performs carrier modulation, sorting algorithm and unit data. Processing, the waveform and data are transmitted to the host computer through the network port and Modbus communication protocol, so as to monitor the SVG operation status in real time; the power cabinet is mainly composed of three-phase power units, and the H-bridge series topology is adopted between the power units. Each phase power unit and the single-board controller and the power units are connected by a single single-phase optical fiber loop back to complete the series communication; the charging cabinet mainly includes charging resistors, bypass contactors / circuit breakers, SVG connection reactors, etc.; SVG sends a high-voltage closing instruction through the digital output board under the premise that the cooling system is started, the grid voltage signal is normal, and the power module is normal. After the high-voltage closing, the unit capacitor is pre-charged through the charging resistor. When the unit voltage meets the minimum limit value, the charging resistor is bypassed; after the SVG is ready, the SVG can be set to run at different compensation target points and compensation strategies through the host computer parameters.

[0079] The present invention aims to control the voltage outside the SVG grid-connected point, and the medium-voltage side voltage is controlled by the low-voltage side SVG through three-winding transformers by collecting the medium-voltage side voltage signal; when the high-voltage side PT and CT signals cannot be collected, the high-voltage side reactive power is compensated, and the reactive power compensation of the high-voltage side without signal collection is completed by collecting the medium-voltage side and low-voltage side voltage, current and SVG current, and considering the reactive power caused by the load rate of the high-voltage side to the medium-voltage and low-voltage sides respectively; by controlling the low-voltage side SVG to output reactive power, the closed-loop control of the medium-voltage side voltage of the three-winding transformer at the SVG non-grid-connected point is completed, the SVG voltage compensation target point is expanded, and the compensation position is more flexible; by collecting the low-voltage side voltage and current of the three-winding transformer and calculating the reactive power caused by the load rate of the medium and low voltage sides, the high-voltage side reactive power compensation can be completed even when the high-voltage side voltage and current cannot be collected; the signal sampling of the system is not limited to the target position. At the site where the control target signal cannot be collected, the compensation amount of the target position is converted by collecting the voltage and current signals of other positions, and the strategy control of the target with and without signal collection outside the SVG grid-connected point is completed.

Claims

1. A method for controlling reactive voltage of a non-SVG grid-connected point for compensating three-winding transformers, characterized in that: The loads are located on the medium-voltage side and low-voltage side of the three-winding transformers respectively. The SVG is connected to the low-voltage side of the three-winding transformers to collect voltage and current signals on the medium-voltage side of the three-winding transformers, which are used to obtain the medium-voltage side voltage feedback signal of the SVG medium-voltage side voltage control mode and the medium-voltage side load reactive power instruction of the SVG high-voltage side reactive power compensation mode. The voltage and current signals on the low-voltage side of the three-winding transformers are collected to obtain the reactive power of the medium- and low-voltage side of the SVG high-voltage side reactive power compensation mode, including the SVG output reactive power and the load reactive power. By controlling the SVG on the low-voltage side of the three-winding transformer, closed-loop control of the medium-voltage side voltage of the three-winding transformer and reactive power compensation on the high-voltage side without signal collection are completed respectively.

2. A reactive voltage control method for compensating a three-winding transformer non-SVG grid-connected point according to claim 1, characterized in that: The control of the SVG on the low voltage side of the three-winding transformer is used to complete the closed-loop control of the voltage on the medium voltage side of the three-winding transformer, and the contents are as follows: When SVG operates in the medium voltage side voltage control mode, the medium voltage side target voltage is taken as the given value and the medium voltage side actual collected voltage U is taken as the given value. 110fdb is the feedback value, which is used as the voltage outer loop for PI closed-loop control to obtain the SVG reactive current inner loop instruction, which is used to complete the closed-loop regulation of the medium voltage side voltage through the low voltage side SVG. 110fdb The calculation is as follows: Collect the voltage U on the medium voltage side of the three-winding transformer 110a , U 110b , U 110c , U obtained by three-phase voltage dq transformation d , U q , the medium voltage side grid voltage amplitude U is calculated 110fdb , the formula is as follows:

3. The reactive voltage control method for compensating a three-winding transformer non-SVG grid-connected point according to claim 1 is characterized in that: The control of the SVG on the low-voltage side of the three-winding transformer is used to complete reactive power compensation on the high-voltage side without sampling the voltage and current on the high-voltage side. The content is as follows: 1) Collect the current I on the medium voltage side of the three-winding transformer 110a ,I 110b ,I 110c , and the medium voltage side voltage U 110a , U 110b , U 110c The formula for calculating the reactive power instruction of the medium voltage side load of the three-winding transformer in the reactive power compensation mode of SVG is as follows: Q Load110 =Q 110 =U 110d *I 110q -U 110q *I 110d ② Simultaneously calculate the active power of the medium voltage side of the three transformers, the formula is as follows: P 110 =U 110d *AND 110d +U 110q *AND 110q ③ 2) Calculate the load rate Load_Rate of the high voltage side of the three-winding transformer to the medium voltage side HM and the reactive power Q caused by it HM , the formula is as follows: Among them, U 110d , U 110q ,I 110d ,I 110q is the components of the three-phase voltage and current on the medium voltage side of the three-winding transformer in the dq coordinate system, P 110 , Q 110 Indicates the active power and reactive power of the medium voltage side of the three-winding transformer, Sn 110 Indicates the rated capacity of the medium voltage side of the three-winding transformer, Z HM % is the short-circuit impedance percentage of the high voltage side to the medium voltage side.

4. The reactive voltage control method for compensating a three-winding transformer non-SVG grid-connected point according to claim 1 is characterized in that: The voltage and current signals of the low-voltage side of the three-winding transformer are collected to obtain the reactive power of the low-voltage side, and the content is as follows: 1) Collect the low voltage side voltage U 35a , U 35b , U 35c , calculate the low voltage side grid voltage amplitude U 35fdb , used to calculate the reactive power of SVG, the formula is as follows: U 35d , U 35q is the component of the low voltage three-phase voltage in the dq coordinate system; 2) Collect low-voltage side grid current I 35a ,I 35b ,I 35c And SVG Hall current I Svga ,I Svgb ,I Svgc , and the low voltage side voltage U 35a , U 35b , U 35c Calculate the reactive power QLoad on the low voltage side 35 and SVG reactive power Q Svg , the formula is as follows: QLoad 35 =Q 35 =U 35d *I 35q -U 35q *I 35d ⑦ Calculate the active power on the low-voltage side of the three-winding transformer. The formula is as follows: P 35 =U 35d *I 35d +U 35q *I 35q ⑧Calculate the reactive power of SVG, the formula is as follows: Q Svg =U 35fdb *I SvgQ ⑨Among them I 35d ,I 35q ,I SvgD ,I SvgQ are the components of the low voltage three-phase grid current and the SVG current in the dq coordinate system; 3) Calculate the load rate of the high voltage side to the low voltage side and the reactive power caused by it Load_Rate HL , Q HL The formula is as follows:

5. The reactive voltage control method for compensating a three-winding transformer non-SVG grid-connected point according to claim 1 is characterized in that: The reactive power compensation of the low-voltage side SVG to the high-voltage side grid: the reactive power Q Load110 The low voltage side SVG outputs reactive power Q Load35 , and load reactive power Q HM Add together the reactive power caused by the load rate of the high voltage side to the medium voltage side and the reactive power Q caused by the load rate of the high voltage side to the low voltage side HL , get the total reactive power on the high voltage side, minus the reactive power Q output by SVG Svg , get the load reactive power instruction of SVG in the reactive power compensation mode on the high-voltage side, complete the reactive power compensation of SVG on the low-voltage side to the high-voltage side grid, and the total reactive power instruction of SVG Q SvgRef The calculation formula is as follows:

6. The reactive voltage control method for compensating a three-winding transformer non-SVG grid-connected point according to claim 1 is characterized in that: The high-voltage side of the three-winding transformer is connected to the high-voltage power grid. There is no PT or CT signal collection. The voltage and current signals on the medium and low voltage sides are collected through current and voltage sensors.

7. A computer device, characterized in that: include: At least one processor, and a memory in communication with the at least one processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor executes the reactive voltage control method for compensating a non-SVG grid-connected point of a three-winding transformer as described in any one of claims 1-6.

8. A computer-readable storage medium, characterized in that The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the reactive voltage control method for compensating a non-SVG grid-connected point with three-winding transformers as described in any one of claims 1-6.

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