A contactor control system for APF

Abstract

The present invention relates to a contactor control system of an APF, including a large contactor for controlling the APF grid connection, a small contactor for precharging the APF DC side capacitor, and a contactor control module for controlling the large and small contactors; the contactor control module includes a comprehensive processing module and a large and small contactor control module and an internal unit; wherein, when the system determines that there is no fault, the comprehensive processing module controls the large contactor to open; otherwise, it cannot be opened; when the large contactor is energized, the system cannot be restarted; the small contactor is opened; the DC side voltage detection unit is running, and when the DC side voltage reaches a preset value, the large contactor is opened. The technical solution provided by the present invention can simultaneously have multiple functions such as DC side voltage detection, convenient for reasonable control of large and small contactors, can receive and process instructions issued by users through the screen, can process processing results from the protection module, and can issue power on and off instructions from the board.

Description

Technical Field

[0001] The invention belongs to the technical field of active power filter control and relates to a contactor control system of an APF. Background Art

[0002] Active power filter (APF) is a new type of power electronic device used to dynamically suppress harmonics and compensate reactive power. The coordinated control and monitoring in APF is based on the APF system, which can complete the functions of harmonic extraction and reactive power calculation, three-phase grid phase locking, grid-side current closed-loop control, APF compensation current reference tracking control, system protection logic control, high-speed optical fiber communication and user interactive display;

[0003] The functions that the APF system needs to have include: controlling the power on / off and fault elimination commands sent by the receiving screen, processing protection events, DC side voltage detection, processing results from the protection module, and controlling multiple contactors. The known APF system cannot realize the above functions at the same time, and there is no good logical control sequence when realizing the above functions. It only corresponds to a single functional module, and the control effect on the contactor is poor.

[0004] It is relatively difficult to set up the control logic of the functions of the contactor control system in the existing APF system. When setting up the APF control over the contactor, how to balance the control logic of various functions of the contactor is a problem to be solved. Therefore, the inventors have made improvements to the technical defects existing in the prior art and are committed to making up for the problems of poor control effect and unclear control logic of the APF control system in the prior art. Summary of the invention

[0005] The present invention provides a contactor control system applied to APF, which has the functions of DC side voltage detection, convenient for reasonable control of large and small contactors, capable of receiving and processing instructions issued by users through a screen, capable of processing processing results from a protection module and issuing power on / off instructions from a board, and at the same time has clear control logic of the contactor and more stable control effect.

[0006] The specific technical solution is as follows:

[0007] A contactor control system for an APF, the APF comprising an APF system, a large contactor for controlling the APF to be connected to the grid, and a small contactor for precharging a capacitor on a DC side of the APF, the APF further comprising a contactor control system, the contactor control system being used to control a contactor control module of the large and small contactors;

[0008] The contactor control module includes a comprehensive processing module for processing system power on / off, large contactor switch and small contactor switch, and the comprehensive processing module includes a global reset unit with a low level effective, a first fault elimination unit with a high level effective, a contactor signal unit for receiving an on or off signal sent by the screen, a restart unit for receiving a protection module signal, a closing instruction unit for controlling the large contactor, an opening unit for indicating the contactor opening process, and a power-on unit for outputting a power-on instruction;

[0009] Among them, when the APF system determines that there is no fault, the comprehensive processing module controls the large contactor to open; when the system determines that a fault event occurs, the comprehensive processing module prevents the APF large contactor from opening; when the comprehensive processing module configures the large contactor to be closed, the APF system cannot be restarted;

[0010] The contactor control module also includes a large and small contactor control module, the input end of the large and small contactor control module includes a switch unit, a DC side voltage detection unit, a reset unit and a large contactor feedback unit; the output end of the large and small contactor control module includes a power-on fault coding unit, a slave board instruction unit and a power-on process display unit;

[0011] Among them, when the switch unit is at a high level, the APF system starts and the small contactor is turned on; the DC side voltage detection unit runs, and when the DC side voltage reaches a preset value, the large contactor is turned on; the slave board instruction unit sends a slave board start instruction to turn on the slave board and the clock.

[0012] The technical solution of the present invention has the following beneficial effects compared with the prior art:

[0013] The APF parallel connection system (contactor control system) of the present invention can simultaneously have multiple functions such as DC side voltage detection, convenient for reasonable control of large and small contactors, receiving and processing instructions issued by users through the screen, processing results from the protection module, and issuing switch commands from the board, etc., with diverse functions. Through the comprehensive processing module and the large and small contactor control module, the control logic of the contactor can be clearly controlled, and the control effect is more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The overall structural block diagram of the APF system of the parallel connection system of the present invention;

[0015] Figure 2 A control flow chart of a contactor control module of the parallel connection system of the present invention;

[0016] Figure 3 A schematic diagram of an FPGA implementation of a contactor control module of the parallel connection system of the present invention;

[0017] Figure 4 It is a principle diagram of the comprehensive processing module of the parallel connection system of the present invention;

[0018] Figure 5 It is a schematic diagram of the large and small contactor control module of the parallel connection system of the present invention;

[0019] Figure 6 It is a schematic diagram of a DC side voltage detection module of the parallel connection system of the present invention;

[0020] Figure 7 It is a principle diagram of the instruction processing module of the parallel connection system of the present invention;

[0021] Figure 8 It is a schematic diagram of the second instruction processing module of the parallel connection system of the present invention;

[0022] Fig. 9 It is a schematic diagram of a protection result processing module of the parallel connection system of the present invention;

[0023] Fig.10 It is a schematic diagram of a PWM instruction issuing module of a slave board of the parallel connection system of the present invention;

[0024] Fig.11 It is a schematic diagram of a slave board PWM instruction buffer module of the parallel connection system of the present invention;

[0025] Fig.12 The schematic diagram of the clock module of the parallel connection system of the present invention is shown in FIG. DETAILED DESCRIPTION

[0026] The contactor control system of an APF of the present invention is further described in detail below in conjunction with the accompanying drawings and the following embodiments.

[0027] APF usually refers to the entire APF equipment / machine; APF system usually refers to the APF software part except the contactor control system, sometimes referred to as the system for short.

[0028] Combination Figure 1 As shown, the contactor in the figure is a large contactor for controlling the APF grid connection, and the small contactor is not shown, but various types of small contactors used to pre-charge the APF DC side capacitor are within the selection range of the present invention, and the present invention does not specifically limit the positions of the large contactor and the small contactor.

[0029] Combination Figure 1-Figure 5 As shown, some embodiments of the present invention disclose a contactor control system of an APF.

[0030] The contactor control module in the embodiment performs the following functions:

[0031] (1) DC side voltage detection;

[0032] (2) Reasonable control of large and small contactors;

[0033] (3) Receive and process instructions sent by users through the screen;

[0034] (4) Processing the processing results from the protection module;

[0035] (5) Processing emergency stop button feedback;

[0036] (6) Issue the power on / off command to the slave board;

[0037] The APF includes a large contactor for controlling the APF grid connection, a small contactor for precharging the APF DC side capacitor, and a contactor control module for controlling the large and small contactors; the contactor control module includes a comprehensive processing module for processing the system on / off and the large and small contactor switches, and the comprehensive processing module includes a low-level effective global reset unit, a high-level effective first fault elimination unit, a contactor signal unit for receiving the on or off signal from the screen, a restart unit for receiving a protection module signal, a closing command unit for controlling the large contactor, a starting unit for indicating the contactor opening process, and a starting unit for outputting a starting command; wherein, when the system determines that there is no fault, the comprehensive processing module controls the large contactor to open; When the system determines that a fault event occurs, the comprehensive processing module prevents the system and the large contactor from being turned on; when the large contactor is energized, the system cannot be restarted; the contactor control module also includes large and small contactor control modules, and the large and small contactor control modules include a switch unit for signal input, a DC side voltage detection unit, a reset unit and a large contactor feedback unit; the large and small contactor control modules also include a power-on fault coding unit for signal output, a slave board instruction unit and a power-on process display unit; wherein, when the switch unit is at a high level, the control system starts and the small contactor is turned on; when the DC side voltage detection unit is running, and the DC side voltage reaches a preset value, the large contactor is turned on; the slave board instruction unit sends a slave board start instruction to turn on the slave board and the clock.

[0038] In some FPGA-based embodiments of the present invention, the contactor control module is implemented based on FPGA, and the FPGA includes a contactor control module, a FIFO, and a control module corresponding to the FIFO to complete the function implementation of the contactor.

[0039] Further integration Figure 6As shown, in some embodiments, the contactor control module also includes a DC side voltage detection module for contactor control and harmonic current benchmark slow-start; the DC side voltage detection has two functions, one is for contactor control, and the other is for harmonic current benchmark slow-start. The DC side voltage detection module includes a global reset signal unit, a DC side voltage input unit, and a second fault elimination unit for receiving the fault elimination signal below the screen, and also includes a controller signal output unit and a harmonic current output unit; the global reset signal unit is used to receive the reset signal input by the system, and is set to be valid at a low level, the DC side voltage input unit is used to receive the input DC side voltage signal of the three-phase APF; the second fault elimination unit is valid at a high level; the controller signal output unit is used to output a high-level valid flag signal for contactor control, and the harmonic current output unit is used to output a high-level valid flag signal for harmonic current benchmark slow-start.

[0040] Combination Figure 6 As shown in Table 1 below, the unit definition of the DC side voltage detection module is shown.

[0041] Table 1 Unit definition of DC side voltage detection module

[0042]

[0043] The DC side voltage detection module detects the three-phase DC voltage in real time. When the three-phase DC side voltage is detected to be greater than 250V for 1s, DC_Voltage_Ready is set high. When any phase DC side voltage is detected to be lower than 250V for 1s, DC_Voltage_ Ready is set low. When the three-phase DC side voltage is detected to be greater than 390V for 1s, PR _Ready is set high. When any phase DC side voltage is detected to be lower than 200V for 1s, PR _ Ready is set low. When RSTn_all is low or Prot_Reset is high, DC_Voltage_Ready and PR _Ready are set low, and the DC side voltage detection starts again.

[0044] Furthermore, the DC side voltage detection module detects the three-phase DC voltage in real time. When it is continuously detected that the three-phase DC side voltage is greater than the standard setting value, the controller signal output unit is set to high, otherwise it is set to low when it is less than the standard setting value; when it is continuously detected that the three-phase DC side voltage is greater than the high setting value (second setting value), the harmonic current output unit is set to high, and when it is lower than the low setting value, the harmonic current output unit is set to low; when the global reset signal unit is at a low level or the second fault elimination unit is at a high level, the controller signal output unit and the harmonic current output unit are both at a low level, and the DC side voltage detection is restarted.

[0045] In certain embodiments, further combined Figure 7As shown, the contactor control module also includes a command processing module for processing the commands issued by the input end in real time. The command processing module processes the commands issued by the user in real time, including three types of signals: power on, power off and standby; the signal input unit of the command processing module includes an input command notification unit, a specific command unit and a protection event display unit; the signal output unit of the command processing module includes a power on / off command output unit and a harmonic current reference control unit; after the command notification unit receives the input signal, the specific command unit determines the type of command issued, and then pulls up the power on / off command output unit; wherein, the output value of the harmonic current reference control unit can be changed, the power on / off command output unit is a notification signal, and its high level width is the global clock, and the encoding format of the specific command unit is consistent with the encoding of the screen communication;

[0046] Combination Figure 7 As shown in Table 2 below, the unit definition of the instruction processing module.

[0047] Table 2 Unit definition of instruction processing module

[0048]

[0049] When R_Cmd is pulled high, the module detects R_Cmd_Dt[15..0], determines the type of instruction issued by the screen, and then pulls up the corresponding Cmd_St or Cmd_Close, or changes the value of Sl_Ref_Cmd[8..0]. Note that R_Cmd, Cmd_St and Cmd_Close are notification signals, and their high-level width is a global clock, that is, 1 / 50Ms.

[0050] The encoding format of R_Cmd_Dt[15..0] is consistent with the encoding of screen communication. The upper eight bits indicate the module to which the instruction applies, and the lower eight bits indicate the specific instruction. The following table 3 shows the command format.

[0051] Table 3 Command format

[0052]

[0053] Sl_Ref_Cmd[8..0] is the harmonic reference sent from the control board to the slave board. When the user wants a slave board module (slave board) to be in grid-connected standby state, that is, only PFC grid-connected, no harmonic compensation or harmonic emission, the lowest bit of this signal will be set low. When a slave board module (slave board) is expected to work normally, this bit will be set high. The high eight bits of this signal indicate the module to which the signal acts, and the module code is consistent with the screen communication code.

[0054] The AND2 module in the command processing module performs the logic AND of the Under_Way signal and Cmd_St. If the motherboard is processing a protection event, the power-on signal sent by the screen will be ineffective. The purpose of doing so is to ensure the integrity of the protection event processing and the integrity of the power-on and power-off logic.

[0055] Furthermore, the harmonic current reference control unit is used to control the harmonic reference of the slave board sent from the main board; when the input end needs to put any module in the grid-connected standby state, no harmonic compensation or harmonic emission, the lowest position of the harmonic current reference control unit is a low level; when the input end needs to put any module in the operating state, the harmonic current reference control unit is a high level;

[0056] In some embodiments, a second instruction processing module is also provided, such as Figure 8 As shown in Table 4. The second instruction processing module includes a second instruction notification unit, a second specific instruction unit, a second protection event processing unit, a second shutdown instruction output unit, and a second fault elimination instruction unit; the protection event processing unit is used to identify whether a protection event is being processed, if so, it is a high level; Sys_Prot_Un_Way[8..0] is used to identify whether a protection event is currently being processed, if so, Under_Way is always at a high level. The high eight bits of Sys_Prot_Un_Way[8..0] identify the specific APF station number, and the lowest bit identifies whether a protection event is currently being processed.

[0057] Table 4 Definition of the second instruction processing module signals

[0058]

[0059] Further integration Fig. 9 As shown in Table 5, in some embodiments, the contactor control module also includes a protection result processing module, the function of the protection processing module is to shut down or close the contactor according to the processing result of the protection module, and the protection result processing module controls the large contactor based on the processing result of the protection module; the input signal unit of the protection result processing module includes a protection event processing result notification unit and a specific protection event processing result unit; the output signal unit of the protection result processing module includes a large contactor control unit; the large contactor control unit can issue a large AC contactor shutdown instruction caused by a restartable protection event, a large AC contactor shutdown instruction caused by a non-restartable protection event, and a system restart instruction caused by a restartable protection event.

[0060] Table 5 Signal definition of protection result processing module

[0061]

[0062] In some embodiments, further in combination with Table 6, the protection event processing result notification unit detects the notification signal in real time, and when it is at a high level, it indicates that there is a new retention processing result; the specific protection event processing result unit is used to store the specific processing result, and generate a specific switch contactor command according to the processing result; the specific protection event processing result unit encodes the protection event. The module detects the protection event processing result notification signal in real time. Once it is pulled high, it means that a new retention processing result has arrived. The specific protection event processing result stores the specific processing result. The module generates a specific switch contactor command based on the processing result, and is combined with the input terminal indicating the specific protection event processing result shown in the following table.

[0063] Table 6 Protection processing result coding

[0064]

[0065] Further in combination with what is shown in Table 7, in some embodiments, the contactor control module further includes a harmonic current reference slow-start enabling module, which includes a global reset unit effective at a low level, a power-on command issuing slave board unit, a large contactor feedback unit, a shutdown instruction unit, a three-phase DC side voltage value determination unit, and a harmonic current reference enabling signal output unit. The harmonic current reference slow-start enabling module is used to determine the slow-start time and generate an enabling signal;

[0066] Among them, the conditions for determining the slow-start time of the reference current are:

[0067] (1) The power-on command is sent to the slave board, that is, after the large contactor is closed;

[0068] (2) The large contactor is closed;

[0069] (3) The three-phase DC side voltages are all greater than the high setting value;

[0070] When the above three conditions are met at the same time, the output terminal of the harmonic current reference slow-start enabling module is set to a high level, and the harmonic current reference starts to slow-start; otherwise, it is set to a low level.

[0071] Table 7 Definition of input and output signals of harmonic current reference slow start enable module

[0072]

[0073] Further integration Fig.10As shown in Table 8, in some embodiments, the contactor control module also includes a slave board PWM switch instruction issuing module, which is used to implement the PWM switch instruction of the slave board; after the large contactor is energized, the slave board PWM switch instruction issuing module issues an opening instruction to the slave board; when the large contactor needs to be closed, the slave board PWM switch instruction issuing module issues a closing instruction to the slave board, thereby closing the large contactor.

[0074] Table 8 Definition of module signal sent from board PWM instruction

[0075]

[0076] In certain embodiments, in combination Fig.11 As shown in Table 9, the contactor control module also includes a FIFO buffer module. All instructions to be sent from the contactor control module to the slave board are first stored in the FIFO buffer module, and then sent to the slave board one by one. The purpose of the FIFO buffer module is to consider when multiple machines are connected in parallel. When multiple machines are connected in parallel, multiple contactor control modules are provided, and several slave board instructions will be sent at the same time, and data will be buffered through the buffer module;

[0077] Among them, the instructions output by FIFO are first written to a FIFO module in the system protection module, and then the output of the module is directly sent to the slave control board. The protection module sends the slave board PWM command signal, and the control system collects all the instructions to be sent and then sends them in sequence.

[0078] At the same time, the instructions output by this FIFO are not immediately sent to the slave control board through the optical fiber, but are first written to a FIFO module in the system protection module. Finally, the output of this module is directly sent to the slave control board. Since the protection module will also send the slave board PWM command signal, the control system needs to collect all the instructions to be sent, and then send them in sequence to ensure reliability. When the FIFO in this module writes to the FIFO in the protection module, it is necessary to first determine whether there is a protection event being processed (determine whether the request signal of the protection event is high level) to avoid conflicts with the instructions sent in the protection module (avoid writing FIFO at the same time).

[0079] Table 9 Command buffer module signal definition

[0080]

[0081] In some embodiments, each module is provided with a corresponding clock module. Fig.12 As shown in Table 10

[0082] The main function of the system clock module is to generate the global clock of the entire system. In addition, there is a power-on global configuration parameter initialization module (Power_Up_Parameter_Upd). When the power is just turned on, after a delay of 1s, the initialization data of the RAM storing the configuration data is first read out, the configuration parameters are updated, and then a delay of 1s is made before enabling the protection module. This module generates 3 system clocks.

[0083] Table 10 Global clock of system clock module

[0084]

[0085] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. All other implementations obtained by those skilled in the art based on the implementations in the present invention without creative work are within the scope of protection of the present invention. Without departing from the concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by those of ordinary skill in the art should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A contactor control system for an APF, the APF comprising an APF system, a large contactor for controlling the APF to be connected to the grid, and a small contactor for precharging the APF DC side capacitor, characterized in that: The APF further includes a contactor control system, wherein the contactor control system includes a contactor control module for controlling the large contactor and the small contactor, and the contactor control module is implemented based on FPGA; The contactor control module includes a comprehensive processing module for controlling the APF to start or shut down, the large contactor to start or shut down, and the small contactor to start or shut down. The comprehensive processing module includes a first low-level effective global reset unit, a high-level effective first obstacle elimination unit, a contactor signal unit for receiving an on or off signal sent by the screen, a restart unit for receiving a protection module signal, a closing instruction unit for controlling the large contactor to shut down, an opening unit for identifying the opening state of the large contactor and the small contactor, and a power-on unit for outputting a power-on instruction; Among them, when the APF system determines that there is no fault, the comprehensive processing module controls the large contactor to open; when the APF system determines that a fault event occurs, the comprehensive processing module prevents the APF system and the large contactor from being opened; when the comprehensive processing module configures the large contactor to be closed, the APF system cannot be restarted; The contactor control module also includes a large and small contactor control module, which includes a switch unit for signal input, a DC side voltage detection unit, a reset unit and a first large contactor feedback unit; the large and small contactor control module also includes a power-on fault coding unit for signal output, a slave board instruction unit and a power-on process display unit; Among them, when the switch unit receives a high-level signal, the APF system starts and the small contactor is turned on; the DC side voltage detection unit runs, and when the DC side voltage reaches a preset value, the large contactor is turned on; the slave board instruction unit sends a slave board start instruction to turn on the slave board and the clock.

2. The contactor control system of APF according to claim 1, characterized in that: The contactor control module also includes a DC side voltage detection module for contactor control and harmonic current reference slow start; The DC side voltage detection module includes a global reset signal unit, a DC side voltage input unit, a second fault elimination unit for receiving a fault elimination signal sent by the screen, and also includes a controller signal output unit and a harmonic current output unit; The global reset signal unit is used to receive the reset signal output by the APF system and input to the global reset signal unit, and is set to be effective at a low level. The DC side voltage input unit is used to receive the input three-phase DC side voltage; the second fault elimination unit is effective at a high level; The controller signal output unit is used to output a high-level valid flag signal for contactor control, and the harmonic current output unit is used to output a high-level valid flag signal for harmonic current reference slow start.

3. The contactor control system of APF according to claim 2, characterized in that: The DC side voltage detection module detects the three-phase DC side voltage in real time. When the three-phase DC side voltage is continuously detected to be greater than the standard setting value, the controller signal output unit is set to high, otherwise it is set to low when it is less than the standard setting value; when the three-phase DC side voltage is continuously detected to be greater than the high setting value, the harmonic current output unit is set to high, and when it is lower than the low setting value, the harmonic current output unit is set to low; When the global reset signal unit inputs a low-level signal or the second fault elimination unit inputs a high-level signal, the controller signal output unit and the harmonic current output unit both output low-level signals and restart detecting the three-phase DC side voltage.

4. The contactor control system of APF according to claim 1, characterized in that: The contactor control module also includes an instruction processing module for real-time processing of instructions issued by the control mainboard; The signal input unit of the instruction processing module includes an input instruction notification unit, a specific instruction unit and a protection event display unit; the signal output unit of the instruction processing module includes a power on / off instruction output unit and a harmonic current reference control unit; After the input instruction notification unit receives the input signal, the specific instruction unit determines the type of instruction to be issued, and then pulls up the power on / off instruction output unit; Among them, the output value of the harmonic current reference control unit can be changed, the power on / off command output unit is a notification signal, the width of its high level is the global clock, and the encoding format of the specific instruction unit is consistent with the encoding of the screen communication.

5. The contactor control system of APF according to claim 4, characterized in that: The harmonic current reference control unit outputs a harmonic current reference control signal sent from the control main board to the slave board; When the control mainboard needs to put any slave board module in the grid-connected standby state, no harmonic compensation or harmonic emission, the lowest position of the harmonic current reference control unit is a low level; when the control mainboard needs to put any slave board module in the operating state, the harmonic current reference control unit outputs a high level signal; The contactor control module also includes a second instruction processing module, which includes a second instruction notification unit, a second specific instruction unit, a second protection event processing unit, a second shutdown instruction output unit, and a second fault elimination instruction unit; the second protection event processing unit is used to identify whether there is a protection event being processed, and if so, it is a high level.

6. The contactor control system of APF according to claim 1, characterized in that: The contactor control module further comprises a protection result processing module, and the protection result processing module controls the large contactor based on the processing result of the protection module; The input signal unit of the protection result processing module includes a protection event processing result notification unit and a specific protection event processing result unit; the output signal unit of the protection result processing module includes a large contactor control unit; The large contactor control unit issues a large contactor closing instruction caused by a restartable protection event, a large contactor closing instruction caused by a non-restartable protection event, and an APF system restart instruction caused by a restartable protection event.

7. The contactor control system of the APF according to claim 6, characterized in that: The protection event processing result notification unit detects the notification signal in real time, and when the notification signal is at a high level, it indicates that there is a new protection event processing result; the specific protection event processing result unit is used to store the specific processing result and generate a specific switch contactor command according to the processing result; the specific protection event processing result unit encodes the protection event.

8. The contactor control system of APF according to claim 1, characterized in that: The contactor control module also includes a harmonic current reference slow-start enabling module, which includes a second low-level effective global reset unit, a power-on command issuing slave board unit, a second large contactor feedback unit, a shutdown instruction unit, a three-phase DC side voltage value determination unit, and a harmonic current reference enabling signal output unit. The harmonic current reference slow-start enabling module is used to determine the slow-start time and generate an enabling signal; Among them, the conditions for determining the slow-start time of the reference current are: 1) The power-on command is sent to the slave board, that is, after the large contactor is closed; 2) The large contactor is closed; 3) The three-phase DC side voltages are all greater than the high setting value; When the above three conditions are met at the same time, the output terminal of the harmonic current reference slow-start enabling module is set to a high level, and the harmonic current reference starts to slow-start; otherwise, it is set to a low level.

9. The contactor control system of APF according to claim 1, characterized in that: The contactor control module also includes a slave board PWM switch instruction issuing module, and the slave board PWM switch instruction issuing module is used to issue a slave board PWM wave opening instruction or a slave board PWM wave closing instruction; After the large contactor is energized, the slave board PWM switch instruction issuing module issues a PWM wave opening instruction to the slave board; when the large contactor needs to be closed, the slave board PWM switch instruction issuing module issues a PWM wave closing instruction to the slave board, thereby closing the large contactor.

10. The contactor control system of APF according to claim 9, characterized in that: The contactor control module also includes a FIFO buffer module. All instructions to be sent from the contactor control module to the slave board are first stored in the FIFO buffer module and then sent to the slave board one by one.

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