Composite switch for switching reactive compensation capacitor bank and control method thereof

Abstract

The invention discloses a composite switch for reactive compensation capacitor bank switching and a control method thereof, and relates to the technical field of capacitor switching, and the method comprises the steps: detecting the capacity and switching data of each branch in a back-to-back capacitor bank through a reactive compensation controller, and determining a group capacitor to be subjected to switching operation according to a preset switching control condition; the reactive compensation controller determines the switching time sequence of each phase of each group capacitor according to the confirmed input / output operation instruction to be executed and the reference voltage of each group capacitor; and calculating the reactive state and the switching state of the switched power system through the reactive compensation controller. Compared with a conventional switching control method, the automatic phase selection switching control method has the advantages that closing inrush current and overvoltage are lower, the accuracy of phase control switching of the capacitor bank can be improved, high-frequency inrush current and pre-breakdown arcing phenomena can be reduced, meanwhile, the probability of rebreakdown can be reduced, and the service life of the capacitor bank can be prolonged. And the performance of the composite switch switched capacitor bank is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitor switching, in particular to a composite switch for switching a reactive compensation capacitor group and a control method thereof. Background Art

[0002] Shunt capacitor banks are often used for reactive power compensation to improve grid voltage quality, increase the utilization of transmission and transformation equipment, and ensure grid safety and stability. The inrush current and overvoltage generated during the switching of capacitor banks can damage equipment.

[0003] When switching capacitor banks, especially back-to-back banks, vacuum switches generate high-frequency inrush currents. The resulting pre-breakdown arc can cause localized ablation and even welding. This inrush current also generates overvoltage across the capacitor bank, posing a risk of breakdown and damage. Reducing the inrush current and overvoltage generated during the switching of back-to-back banks has become a pressing challenge in the development of switches for switching reactive power compensation capacitor banks.

[0004] With the advancement of power electronics technology, research has leveraged the rapid current interruption and impact-free switching characteristics of high-power thyristors (SCRs), combining thyristor valves with mechanical switches, to develop solid-state composite switches for 10kV reactive power compensation systems. However, because the triggering of the SCR valve assembly requires strict monitoring of the system voltage zero crossing and the di / dt triggering time, the control strategy still faces significant challenges and requires further improvement.

[0005] The currently widely used medium-voltage compound switch solution, which uses thyristor valves as the basic structural unit, requires precise trigger control signals to achieve better switching effects. However, this also presents problems such as high control technology requirements and high costs. In the medium-voltage field, the structure and characteristics of compound switches below 35kV need to be changed to meet higher voltage levels and control accuracy requirements. The compound switch technology solution combining power diodes with mechanical switches can overcome the problems of mechanical switches' inability to accurately select phases and the problems of triggering and controlling semi-controlled devices. However, it still requires the development of more comprehensive strategies and methods for the switching control of three-phase back-to-back capacitor banks to improve their overall closing and breaking performance.

[0006] Therefore, in order to solve the above problems, it is necessary to design an analysis method and system that is suitable for the failure of the water-solar-storage-grid source system. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to solve the deficiencies in the prior art and to design a control method for a composite switch for switching a reactive compensation capacitor group. The method comprises detecting the capacity and switching data of each branch in a back-to-back capacitor group by a reactive compensation controller, and determining the capacitor group to be switched according to the switching control conditions preset by the reactive compensation controller; determining the switching timing of each phase of the capacitor group to be switched according to the confirmed switching / initiating operation instructions and reference voltage of each capacitor group; calculating the reactive state and switching state of the power system after switching is completed by the reactive compensation controller, and waiting for the next operation instruction after confirmation, thereby realizing automatic phase selection and switching control of the composite switch for the capacitor group.

[0008] Compared with the conventional "three-phase synchronous closing / opening" or "three-phase asynchronous, single composite switch main break and shunt break different phases", it has lower closing inrush current and overvoltage, can improve the accuracy of phase-controlled switching of capacitor groups, reduce high-frequency inrush current and pre-breakdown arcing caused by pre-breakdown dispersion, and at the same time reduce the probability of re-breakdown, thereby improving the performance of composite switch switching capacitor groups; in addition, the method of the present invention can, on the one hand, utilize the forward conduction and reverse cut-off characteristics of high-voltage diodes under sinusoidal voltage in the process of composite switch switching back-to-back capacitor groups, realize automatic phase selection operation at zero crossing, and reduce the influence of pre-breakdown on phase selection accuracy; on the other hand, during the operation process, by determining the control timing of the three-phase switching switch of the small group capacitor, further improve the performance of the composite switch closing and disconnecting capacitor groups, reduce high-frequency inrush current and transient overvoltage, improve the performance of the composite switch, and provide a technical basis for switching capacitors of reactive power compensation group in power systems.

[0009] The solution adopted by the present invention to solve the technical problem is:

[0010] A composite switch for switching reactive compensation capacitor banks.

[0011] It is characterized in that

[0012] The composite switch is a structure in which a shunt break is connected in parallel with a high-voltage diode and then connected in series with a main break.

[0013] In the normal state, the anode of the high-voltage diode is close to the system side and the cathode is close to the neutral point. In the reverse setting, the anode is close to the neutral point and the cathode is close to the system side.

[0014] When the compound switch is closed / opened:

[0015] The main breaker is always closed / opened ahead of the target phase, with a lead time of no more than 1 / 4 system cycle; the shunt breaker is always closed / opened behind the target phase, with a lead / lag time of no more than 1 / 4 system cycle, so that the main breaker and shunt breaker can be closed / opened in the positive and negative half-waves of the sinusoidal voltage / current respectively.

[0016] A control method for a composite switch used for switching a reactive compensation capacitor bank.

[0017] The following steps are involved:

[0018] Step 101: Detecting the capacity and switching data of each branch in the back-to-back capacitor bank through the reactive power compensation controller, and determining the capacitor bank to be switched based on the switching control conditions preset by the reactive power compensation controller;

[0019] Step 102: The reactive power compensation controller determines the switching timing of each phase of the capacitor group to be switched based on the input / output operation instructions and reference voltage that have been confirmed for each capacitor group.

[0020] Step 103: Calculate the reactive power state and switching state of the power system after switching is completed through the reactive power compensation controller, and wait for the next operation instruction after confirmation.

[0021] As a preferred embodiment of the present invention,

[0022] The switching timings of each phase determined in step 102 include a first switching timing setting, a second switching timing setting, and a third switching timing setting.

[0023] The first switching timing setting: Assuming that the A-phase voltage of the capacitor group to be switched is the reference voltage, the C-phase of the capacitor group to be switched is selected as the first closing phase, and the corresponding reference voltage A0 is closed after 1 / 6 of the system cycle. The B-phase of the capacitor group to be switched is the second closing phase. The high-voltage diode of the B-phase of the capacitor group to be switched is set in reverse, and is closed after A01 / 4 of the system cycle. The A-phase of the capacitor group to be switched is the last closing phase, and is closed after A01 / 2 of the system cycle.

[0024] The second switching sequence setting: take the phase A current of the capacitor group to be switched as the reference signal, cut off the phase at the zero point of the phase A current of the capacitor group to be switched, and after a delay of 1 / 4 system cycle, cut off the phases B and C of the capacitor group to be switched at the same time;

[0025] The third switching sequence setting: the leading target phase does not exceed 1 / 4 of the system cycle to operate the main breaker, and the lagging target phase does not exceed 1 / 4 of the system cycle to operate the shunt breaker;

[0026] When the group of capacitors that should be switched on needs to be put into operation, the switching timing of each phase should meet the switching timing of each phase set in the first switching timing setting. When the group of capacitors that should be switched off needs to be withdrawn, the switching timing of each phase should meet the switching timing of each phase set in the second switching timing setting. When the composite switch of a phase of the group of capacitors that should be switched on is closed / opened, the switching timing of each phase should meet the switching timing of each phase set in the third switching timing setting.

[0027] As a preferred embodiment of the present invention,

[0028] When the reactive compensation controller detects the switching data of each branch in the back-to-back capacitor group in step 101, the group capacitor switching data at least includes the current switching state, historical switching frequency and historical switching duration of the branch.

[0029] As a preferred embodiment of the present invention,

[0030] The switching timing of each phase determined in step 102 includes the minimum synchronous delay of each phase opening and closing and the delay between the target switching phase and the reference voltage / current zero point.

[0031] As a preferred embodiment of the present invention,

[0032] The switching control conditions preset by the reactive power compensation controller in step 101 include:

[0033] When the power system currently has inductive or capacitive reactive power and the power factor is less than the specified value, the reactive power compensation controller follows the cyclic switching principle, that is, the capacitor group that is switched on first should be switched off first;

[0034] The current reactive power type of the above power system is detected by the reactive power compensation controller.

[0035] As a preferred embodiment of the present invention,

[0036] In step 102, when the reactive compensation controller determines the switching sequence of each phase of the capacitor group to be switched, the first phase to be switched should avoid the reference phase.

[0037] As a preferred embodiment of the present invention,

[0038] Also includes:

[0039] When there is only a single-phase reactive power compensation system consisting of a single capacitor group or a back-to-back capacitor group, the action sequence of the main disconnect and shunt disconnect of the composite switch for branch switching should meet the switching sequence set in the third switching sequence setting.

[0040] As a preferred embodiment of the present invention,

[0041] The minimum synchronization delay Tdk should meet the following requirements:

[0042] ,

[0043] Where, T dk is the minimum synchronization delay of phase k, f represents the grid frequency, T Z1 Represents the time from the closing command to the synchronous reference zero point, T clk Represents the break closing time, T c1 is the microprocessor calculation time, mod is the remainder calculation, n is the minimum integer to ensure Td1>0, t k is the k-phase complementary delay, T obk It is the time between the best closing phase of the first conjunction and the zero point of the reference phase closest to the front of the time axis.

[0044] Beneficial effects:

[0045] 1. The present invention can realize automatic phase selection and switching control of the composite switch for capacitor banks. Compared with the conventional "three-phase synchronous closing / opening" or "three-phase asynchronous closing / opening, with the main and shunt ruptures of a single composite switch operating in different phases", it has lower closing inrush current and overvoltage. It can improve the accuracy of phase-controlled switching of capacitor banks, reduce high-frequency inrush current and pre-breakdown arcing caused by pre-breakdown dispersion, and reduce the probability of restrike, thereby improving the performance of composite switch switching of capacitor banks.

[0046] 2. A control method for a composite switch for switching a reactive compensation capacitor group using the method of the present invention can, on the one hand, utilize the forward conduction and reverse cutoff characteristics of the high-voltage diode under a sinusoidal voltage to realize automatic phase selection operation at the zero point during switching back-to-back capacitor groups by the composite switch, thereby reducing the influence of pre-breakdown on the phase selection accuracy; on the other hand, during operation, by determining the control timing of the three-phase switching switch of the small group capacitor, the performance of the composite switch in closing and disconnecting the capacitor group is further improved, high-frequency inrush current and transient overvoltage are reduced, the performance of the composite switch is improved, and a technical basis is provided for switching capacitors of reactive compensation groups in power systems.

[0047] 3. The composite switch proposed in the present invention has better breaking performance than the traditional mechanical switch, and by setting the high-voltage diode with the characteristic of automatically switching the closing and opening states at the zero point, it can avoid the uncertainty of the actual time of inputting / exiting the capacitor group caused by pre-breakdown; compared with other thyristor valves, IGBTs and other devices as basic structural units, the composite switch can eliminate the trigger control link, making control more convenient and easy and reducing losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1This is a flow chart of a control method of a certain embodiment of a control method of a composite switch for switching a reactive compensation capacitor bank proposed by the present invention;

[0049] Figure 2 This is a flow chart of a control method of a certain embodiment of a control method of a composite switch for switching a reactive compensation capacitor bank proposed by the present invention;

[0050] Figure 3 This is the electrical topology diagram of the composite switch for switching reactive compensation capacitor banks proposed by the present invention;

[0051] Figure 4 This is the electrical topology diagram of the composite switch for switching reactive compensation capacitor banks proposed by the present invention;

[0052] Figure 5 This is a timing diagram of the three-phase coupling operation of the composite switch in the control method of the composite switch for switching a reactive compensation capacitor bank proposed by the present invention;

[0053] Figure 6 This is a timing diagram of the three-phase coupling operation of the composite switch in the control method of the composite switch for switching the reactive compensation capacitor group proposed by the present invention.

[0054] Description of reference numerals;

[0055] 1. Main fracture,

[0056] 2. Shunt fracture,

[0057] 3. High voltage diode. DETAILED DESCRIPTION

[0058] The specific implementation of the present invention is described below with reference to the accompanying drawings and embodiments:

[0059] It should be noted that the structures, colors, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions under which the present invention can be implemented. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in the present invention without affecting the efficacy and purpose that can be achieved by the present invention.

[0060] In the present invention, unless otherwise clearly stipulated and limited, the terms "install", "set", "connect", "fix", "screw" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to the specific circumstances.

[0061] The drawings in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology, and are not intended to limit the conditions under which the present invention can be implemented. Any structural modifications, changes in proportional relationships, or adjustments in size should still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and objectives that can be achieved by the present invention.

[0062] like Figure 3-Figure 4 As shown in the electrical topology diagram of the composite switch suitable for switching reactive compensation capacitor groups, the composite switch for switching reactive compensation capacitor groups proposed by the present invention has a structure in which a shunt break 2 is connected in parallel with a high-voltage diode 3 and then in series with a main break 1.

[0063] Main breaker 1 is primarily responsible for carrying steady-state current, while shunt breaker 2 is connected in parallel with high-voltage diode 3 and then in series with the main circuit. This prevents the risk of contact welding caused by reverse current and improves the reliability of the switch under impact loads.

[0064] Using high-voltage diodes 3 instead of other devices such as thyristors and IGBTs as basic structural units makes it unnecessary for the reactive power compensation control system to issue control signals of power electronic devices, thus simplifying the transmission control process.

[0065] In a normal state, the anode of the high-voltage diode 3 is close to the system side and the cathode is close to the neutral point. When the voltage on the system side is higher than the neutral point voltage, the diode is turned on and the current flows from the system side to the neutral point. When the reverse setting is on, the anode is close to the neutral point and the cathode is close to the system side. When the voltage on the system side is lower than the neutral point, the diode is turned off to block the reverse current.

[0066] When the switch is closed to charge the capacitor bank, the system voltage rises above the neutral point, and the diode conducts in the forward direction. Due to the nonlinear characteristics of the diode, the inrush current at the moment of closing the switch is limited, preventing capacitor plate breakdown or switch contact erosion.

[0067] After the capacitor bank is fully charged, if the system voltage fluctuates and the neutral point potential rises above the system side, the diode can reversely cut off, thereby preventing the capacitor bank from discharging in the opposite direction through the switch. This protects the switch contacts from damage caused by reverse surge current and avoids frequent charging and discharging of the capacitor bank, thereby extending the service life of the capacitor bank.

[0068] When the above-mentioned compound switch is closed / opened: the main breaker 1 is always closed / opened ahead of the target phase, wherein the amount of advance / lag does not exceed 1 / 4 system cycle; the shunt breaker 2 is always closed / opened behind the target phase, wherein the amount of advance / lag does not exceed 1 / 4 system cycle, so as to realize the main breaker 1 and the shunt breaker 2 closing / opening at the positive and negative half-waves of the sinusoidal voltage / current respectively.

[0069] The specific lead and lag values ​​should be determined based on actual control requirements. The lead value of the main port and the lag value of the shunt port of a composite switch are not fixed values ​​but must be dynamically matched based on load characteristics, system voltage levels, and protection accuracy requirements. Specific calculations and analysis require a combination of simulation modeling and on-site debugging. Only by measuring the voltage and current waveforms at the port outputs with an oscilloscope can the optimal timing parameter combination be optimized.

[0070] As shown in Figure 1, the present invention proposes a control method for a composite switch for switching a reactive compensation capacitor bank, comprising the following steps:

[0071] Step 101: Detecting the capacity and switching data of each branch in the back-to-back capacitor bank through the reactive power compensation controller, and determining the capacitor bank to be switched based on the switching control conditions preset by the reactive power compensation controller;

[0072] Step 102: The reactive power compensation controller determines the switching timing of each phase of the capacitor group to be switched based on the input / output operation instructions and reference voltage that have been confirmed for each capacitor group.

[0073] Step 103: Calculate the reactive power state and switching state of the power system after switching is completed through the reactive power compensation controller, and wait for the next operation instruction after confirmation.

[0074] In another embodiment, the switching sequences of each phase determined in step 102 include a first switching sequence setting, a second switching sequence setting, and a third switching sequence setting, and corresponding operations are performed according to the required switching on and off and the closing / opening of the composite switch.

[0075] First switching sequence setting:

[0076] Assume that the phase A voltage of the small group capacitor that should be switched is the reference voltage, select the phase C of the small group capacitor that should be switched as the first closing phase, and the corresponding reference voltage A0 is closed after 1 / 6 system cycle. The phase B of the small group capacitor that should be switched is the second closing phase. The high-voltage diode 3 of the phase B of the small group capacitor that should be switched is set in reverse and is closed after A01 / 4 system cycle. The phase A of the small group capacitor that should be switched is the last closing phase and is closed after A01 / 2 system cycle.

[0077] Second switching sequence setting:

[0078] Taking the phase A current of the capacitor group that should be switched as the reference signal, the phase is cut off at the zero point of the phase A current of the capacitor group that should be switched, and after a delay of 1 / 4 system cycle, the phases B and C of the capacitor group that should be switched are cut off at the same time.

[0079] The third switching sequence setting:

[0080] If the leading target phase does not exceed 1 / 4 of the system cycle, the main breaker 1 will be operated; if the lagging target phase does not exceed 1 / 4 of the system cycle, the shunt breaker 2 will be operated.

[0081] The target phase is the action phase determined for each phase in the first switching sequence setting and the second switching sequence setting. This target phase is the actual time when this phase is put into operation during actual operation. The time when the main breaker 1 and shunt breaker 2 of each phase actuates is before or after the target phase of this phase.

[0082] like Figure 2 As shown, when the small group of capacitors that should be switched on needs to be put into operation, the switching timing of each phase should meet the switching timing of each phase set in the first switching timing setting; when the small group of capacitors that should be switched on needs to be withdrawn, the switching timing of each phase should meet the switching timing of each phase set in the second switching timing setting; when a phase composite switch of the small group of capacitors that should be switched on is closed / opened, the switching timing of each phase should meet the switching timing of each phase set in the third switching timing setting.

[0083] In another embodiment, when the reactive compensation controller detects the switching data of each branch in the back-to-back capacitor group in step 101, the group capacitor switching data at least includes the current switching state, historical switching frequency and historical switching duration of the branch.

[0084] In addition, based on actual on-site conditions or the need to set switching sequences, group capacitor switching data can also include switching reason records, operating environment data, and equipment health status data, such as capacitor temperature rise, insulation resistance, and other parameters.

[0085] In another embodiment, the phase switching sequence determined in step 102 includes the minimum synchronization delay for each phase opening and closing, and the delay between the target switching phase and the reference voltage / current zero point. Precisely controlling the switching sequence parameters for each phase can significantly improve the switching safety of power equipment and the operational stability of the power grid, which has important engineering significance in reactive power compensation scenarios in distribution networks.

[0086] In another embodiment, the switching control conditions preset by the reactive power compensation controller in step 101 include:

[0087] 1. The power system currently has inductive reactive power or capacitive reactive power and the power factor is less than the specified value. The reactive power types such as inductive reactive power or capacitive reactive power currently involved in the power system are detected by the reactive power compensation controller.

[0088] 2. The reactive power compensation controller follows the cyclic switching principle. The cyclic switching principle means that the controller switches on and off each group of capacitors in turn according to a preset order. When switching on, priority is given to the group that has not been put into operation or has the shortest operation time. When switching off, priority is given to the group that has been in operation for the longest time. In this way, the switching times and operating time of each group of capacitors are balanced, which can not only avoid excessive wear of a certain group of equipment due to frequent operation and extend the overall service life, but also ensure the orderliness and stability of reactive power compensation. At the same time, it can also cooperate with functions such as switching delay to prevent repeated operations in a short period of time. It is suitable for reactive power compensation scenarios with multiple groups of capacitors and the need to balance the use of equipment. In short, it follows the principle of first switching on and first switching off, and last switching on and last switching off. The capacitor group that is put into operation first should be cut off first.

[0089] In another embodiment, Figure 5-Figure 6 As shown, in step 102, when the reactive power compensation controller determines the switching sequence for each phase of the capacitor group to be switched, the first phase to be switched on should avoid the reference phase. This can optimize the electrical parameters at the switching moment while avoiding equipment damage and excessive inrush current caused by phase overlap or voltage surge at the closing moment.

[0090] Taking phase A as the reference voltage as an example, when the small group capacitor is put into operation, phase C is selected as the first closing phase, phase B as the second closing phase, and phase A as the last closing phase to reduce the impact of reference phase voltage fluctuations; when other phases are selected as reference phases, the closing and opening order of each phase should be changed.

[0091] In another embodiment, the various switching sequences described above are applicable to three-phase capacitor bank reactive power compensation. A single-phase reactive power compensation system consisting of only a single capacitor bank or a back-to-back capacitor bank can also satisfy the aforementioned switching control method for the composite switch. Specifically, the operating sequence for the main breaker 1 and shunt breaker 2 of the composite switch used for branch switching should satisfy the following requirement: when a phase composite switch is closed / opened, the main breaker 1 actuates no more than 1 / 4 of the target phase cycle ahead of the target phase, and the shunt breaker 2 actuates no more than 1 / 4 of the target phase cycle behind the target phase.

[0092] That is, when there is only a single-phase reactive compensation system consisting of a single capacitor group or a back-to-back capacitor group, the action sequence of the main break 1 and the shunt break 2 of the branch switching composite switch should meet the switching sequence set in the third switching sequence setting.

[0093] In another embodiment, the minimum synchronization delay T dk Should meet the following requirements:

[0094] ,

[0095] Where, T dk is the minimum synchronization delay of phase k, f represents the grid frequency, T Z1 Represents the time from the closing command to the synchronous reference zero point, T clk Represents the break closing time, T c1 is the microprocessor calculation time, mod is the remainder calculation, and n is the time to ensure T d1 The smallest integer > 0, t k is the k-phase complementary delay, T obk It is the time between the best closing phase of the first conjunction and the zero point of the reference phase closest to the front of the time axis.

[0096] Through the minimum synchronization delay T dk When determining the main break 1 and shunt break 2 of each phase compound switch, the delay that should be waited for when issuing the close / open operation instruction in the controller can compensate for the delay and reduce the error in the phase selection and closing zero crossing time caused by the delay.

[0097] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0098] Many other changes and modifications can be made without departing from the spirit and scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments, and the scope of the present invention is defined by the appended claims.

Claims

1. A composite switch for switching reactive compensation capacitor banks. It is characterized by: The composite switch is a structure in which a shunt break is connected in parallel with a high-voltage diode and then connected in series with a main break. In the normal state, the anode of the high-voltage diode is close to the system side and the cathode is close to the neutral point. In the reverse setting, the anode is close to the neutral point and the cathode is close to the system side. When the compound switch is closed / opened: The main breaker is always closed / opened ahead of the target phase, with a lead time of no more than 1 / 4 system cycle; the shunt breaker is always closed / opened behind the target phase, with a lead / lag time of no more than 1 / 4 system cycle, so that the main breaker and shunt breaker can be closed / opened in the positive and negative half-waves of the sinusoidal voltage / current respectively.

2. A control method for a composite switch for switching a reactive compensation capacitor bank, comprising: It is characterized by: The following steps are involved: Step 101: Detecting the capacity and switching data of each branch in the back-to-back capacitor bank through the reactive power compensation controller, and determining the capacitor bank to be switched based on the switching control conditions preset by the reactive power compensation controller; Step 102: The reactive power compensation controller determines the switching timing of each phase of the capacitor group to be switched based on the input / output operation instructions and reference voltage that have been confirmed for each capacitor group. Step 103: Calculate the reactive power state and switching state of the power system after switching is completed through the reactive power compensation controller, and wait for the next operation instruction after confirmation.

3. The control method of the composite switch for switching a reactive compensation capacitor bank according to claim 2, It is characterized by: The switching timings of each phase determined in step 102 include a first switching timing setting, a second switching timing setting, and a third switching timing setting. The first switching timing setting: Assuming that the A-phase voltage of the capacitor group to be switched is the reference voltage, the C-phase of the capacitor group to be switched is selected as the first closing phase, and the corresponding reference voltage A0 is closed after 1 / 6 of the system cycle. The B-phase of the capacitor group to be switched is the second closing phase. The high-voltage diode of the B-phase of the capacitor group to be switched is set in reverse, and is closed after A01 / 4 of the system cycle. The A-phase of the capacitor group to be switched is the last closing phase, and is closed after A01 / 2 of the system cycle. The second switching sequence setting: take the phase A current of the capacitor group to be switched as the reference signal, cut off the phase at the zero point of the phase A current of the capacitor group to be switched, and after a delay of 1 / 4 system cycle, cut off the phases B and C of the capacitor group to be switched at the same time; The third switching sequence setting: the leading target phase does not exceed 1 / 4 of the system cycle to operate the main breaker, and the lagging target phase does not exceed 1 / 4 of the system cycle to operate the shunt breaker; When the group of capacitors that should be switched on needs to be put into operation, the switching timing of each phase should meet the switching timing of each phase set in the first switching timing setting. When the group of capacitors that should be switched off needs to be withdrawn, the switching timing of each phase should meet the switching timing of each phase set in the second switching timing setting. When the composite switch of a phase of the group of capacitors that should be switched on is closed / opened, the switching timing of each phase should meet the switching timing of each phase set in the third switching timing setting.

4. The control method of the composite switch for switching a reactive compensation capacitor bank according to claim 2, It is characterized by: When the reactive compensation controller detects the switching data of each branch in the back-to-back capacitor group in step 101, the group capacitor switching data at least includes the current switching state, historical switching frequency and historical switching duration of the branch.

5. The control method of the composite switch for switching a reactive compensation capacitor bank according to claim 2, It is characterized by: The switching timing of each phase determined in step 102 includes the minimum synchronous delay of each phase opening and closing and the delay between the target switching phase and the reference voltage / current zero point.

6. The control method of the composite switch for switching a reactive compensation capacitor bank according to claim 2, It is characterized by: The switching control conditions preset by the reactive power compensation controller in step 101 include: When the power system currently has inductive or capacitive reactive power and the power factor is less than the specified value, the reactive power compensation controller follows the cyclic switching principle, that is, the capacitor group that is switched on first should be switched off first; The current reactive power type of the above power system is detected by the reactive power compensation controller.

7. The control method of the composite switch for switching a reactive compensation capacitor bank according to claim 2, It is characterized by: In step 102, when the reactive compensation controller determines the switching sequence of each phase of the capacitor group to be switched, the first phase to be switched should avoid the reference phase.

8. The control method of the composite switch for switching a reactive compensation capacitor bank according to claim 3, It is characterized by: Also includes: When there is only a single-phase reactive power compensation system consisting of a single capacitor group or a back-to-back capacitor group, the action sequence of the main break and shunt break of the composite switch used for branch switching should meet the switching sequence set in the third switching sequence setting.

9. The control method of the composite switch for switching a reactive compensation capacitor bank according to claim 5, It is characterized by: The minimum synchronization delay T dk Should meet the following requirements: ， Where, T dk is the minimum synchronization delay of phase k, f represents the grid frequency, T Z1 Represents the time from the closing command to the synchronous reference zero point, T clk Represents the break closing time, T c1 is the microprocessor calculation time, mod is the remainder calculation, and n is the time to ensure T d1 The smallest integer > 0, t k is the k-phase complementary delay, T obk It is the time between the best closing phase of the first conjunction and the zero point of the reference phase closest to the front of the time axis.

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