Control method and system of IGCT converter valve

Abstract

The invention relates to a control method and system of an IGCT converter valve, and belongs to the technical field of high-voltage direct-current power transmission. According to the method, when it is detected that the voltage of a single valve which is controlled to be not conducted in advance in the IGCT converter valve is reduced and the current of the single valve is increased, if the current of the single valve is smaller than the current corresponding to the maximum turn-off capacity of the single valve, a valve control system is controlled to send a turn-off signal used for cutting off the current of the single valve to the single valve. According to the invention, the single valve can be controlled to be switched off under the condition of commutation failure, so that the conditions of voltage drop of an alternating current power grid and even collapse of the power grid caused by commutation failure are avoided, the risk of commutation failure is reduced, and the stability and reliability of a power transmission system are improved.

Description

Technical Field

[0001] The invention relates to a control method and system for an IGCT converter valve, belonging to the technical field of high-voltage direct current transmission. Background Art

[0002] Most high-voltage direct current (HVDC) transmission systems mainly use line commutated converters (LCCs). LCCs can achieve large-capacity power transmission to meet the needs of long-distance and large-scale power transmission. They also have the advantages of low loss, rapid response, high reliability and economy.

[0003] The commonly used switching device in the LCC converter valve is the thyristor, which is a semi-controlled device that can only control its conduction but not its shutdown. In the LCC commutation process, commutation is achieved by controlling the conduction angle of the thyristor, thereby controlling the magnitude of the DC output voltage. Specifically, when the LCC converter valve is working, it will use the AC network for natural commutation. The direction of the DC current is immutable and the control freedom is low. Due to the use of thyristors, the LCC converter valve depends on the voltage and phase of the AC grid during the commutation process. When the receiving grid is weak or when transmitting power through long line cables, the inverter is prone to commutation failure, which may cause the AC grid voltage to drop, and even cause the grid to collapse in severe cases.

[0004] In order to deal with commutation failure, the Chinese invention patent with application publication number CN115425865A discloses a technical solution of an IGCT commutation valve section structure and a commutation valve with the function of suppressing commutation failure. The technical solution is based on the use of integrated gate commutation thyristors. The integrated gate commutation thyristors are fully controlled devices. They take into account the advantages of thyristor valves and insulated gate bipolar transistor valves, can effectively suppress inverter commutation failure, and can also reduce equipment costs and improve reliability. It is of great significance for the construction of new power grids and research on power systems. However, the occurrence of commutation failure is often closely related to complex power grid environments and changeable operating conditions. Therefore, even if IGCT commutation valves are used, the risk of commutation failure is still high. Summary of the invention

[0005] The purpose of the present invention is to provide a control method and system for an IGCT commutation valve, so as to solve the problem that the risk of commutation failure is still relatively high in the current method of using an IGCT commutation valve to deal with commutation failure.

[0006] In order to solve the above-mentioned technical problems, the present invention provides a control method for an IGCT converter valve, the method comprising: when it is detected that the voltage of a single valve that is pre-controlled to be non-conductive in the IGCT converter valve decreases and the current increases, if the current of the single valve is less than the current corresponding to the maximum shut-off capacity of the single valve, the valve control system sends a shut-off signal to the single valve for cutting off the current of the single valve.

[0007] Furthermore, the method of controlling the valve control system to send the shutoff signal to the single valve includes: sending a shutoff enable signal for controlling the valve control system to send the shutoff signal to the single valve to the valve control system through an upper control device.

[0008] Furthermore, the method of sending a shutdown signal to the single valve for cutting off the current of the single valve includes: continuously sending a shutdown signal to the single valve for cutting off the current of the single valve within a set time until a shutdown success signal fed back by the IGCT of the single valve is received.

[0009] Furthermore, it also includes: when the trigger control signal received by the valve control system for controlling the opening of the IGCT is invalid and the shutdown enable signal is not received, the valve control system sends a status query signal for detecting the status of the single valve to the IGCT of each single valve of the IGCT converter valve; the single valve IGCT that receives the status query signal sends a driving status signal to the valve control system, which contains information on the operating status of the driving unit of the IGCT of the single valve and the operating status of the IGCT.

[0010] Furthermore, the set time is greater than the duration of the shutdown enable signal.

[0011] Furthermore, the state query signal is a coded modulation signal; and the driving state signal is a coded modulation signal.

[0012] Furthermore, the driving unit operation state includes: a driving unit power failure state, a driving body function failure state and a driving unit normal operation state.

[0013] Furthermore, the IGCT operating state includes: a short circuit fault state, a cathode overvoltage fault state, a cathode undervoltage fault state and an IGCT normal operating state.

[0014] Beneficial effects: The present invention provides a new control method for IGCT converter valves. When the method detects that the voltage of a single valve that is pre-controlled to be non-conductive decreases and the current increases, it indicates that the single valve is conductive (the single valve is triggered by mistake or is not normally closed after being triggered to be conductive before), that is, the single valve fails to change phase; if the current of the single valve is less than the current corresponding to the maximum shutoff capacity of the single valve, the valve control system is controlled to send a shutoff signal for cutting off the current of the valve to the single valve, so that the current of the single valve is cut off, the single valve is successfully shut down, and the phase change is completed. The present invention can control the single valve to shut down in the case of phase change failure, avoiding the voltage drop of the AC power grid caused by the phase change failure, and even causing the collapse of the power grid, reducing the risk of phase change failure, and improving the stability and reliability of the power transmission system.

[0015] The present invention also provides a control system for an IGCT converter valve, comprising a processor, wherein the processor is used to execute a computer program to implement the steps of the above-mentioned IGCT converter valve control method.

[0016] The control system of the IGCT converter valve can achieve the same beneficial effects as the control method of the IGCT converter valve described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a flow chart of a control method for an IGCT converter valve in an embodiment of the control method for an IGCT converter valve of the present invention;

[0018] Figure 2 It is a timing diagram of the triggering control of the IGCT converter valve in the embodiment of the control method of the IGCT converter valve of the present invention. DETAILED DESCRIPTION

[0019] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0020] IGCT converter valve control method embodiment

[0021] This embodiment provides a technical solution for a control method of an IGCT converter valve, the method comprising: when it is detected that the voltage of a single valve that is pre-controlled to be non-conductive in the IGCT converter valve decreases and the current increases, if the current of the single valve is less than the current corresponding to the maximum shutoff capacity of the single valve, the valve control system (also referred to as the valve control device) sends a shutoff signal for cutting off the current of the single valve to the single valve. The present invention can control the single valve to shut down in the case of commutation failure, thereby avoiding the voltage drop of the AC power grid caused by the commutation failure, and even causing the power grid to collapse, reducing the risk of commutation failure, and improving the stability and reliability of the power transmission system.

[0022] The flow chart of the control method of the IGCT converter valve is as follows: Figure 1As shown, the control method of the IGCT converter valve is specifically described below:

[0023] The method includes: when it is detected that the voltage of a single valve that is pre-controlled to be non-conductive in the IGCT converter valve decreases and the current increases (i.e., commutation fails), if the current of the single valve is less than the current corresponding to the maximum shutoff capacity of the single valve, the valve control system is controlled to send a shutoff signal (also called shutoff) to the single valve for cutting off the current of the single valve. In this embodiment, the current corresponding to the maximum shutoff capacity of the single valve is 5kA.

[0024] Among them, the method of controlling the valve control system to send the shutoff signal to the single valve includes: sending a shutoff enable signal for controlling the valve control system to send the shutoff signal to the single valve through the upper control device. The method of sending a shutoff signal for cutting off the current of the single valve to the single valve includes: continuously sending a shutoff signal for cutting off the current of the single valve to the single valve within a set time until receiving a shutoff success signal fed back by the IGCT of the single valve. Since the single valve of the converter valve is falsely triggered at this time, the current is large, considering the characteristics of the single valve IGCT shutting off large current (that is, the current of the single valve is reduced from 90% of the current corresponding to the maximum shutoff capacity of the single valve to 10%, which takes 40 to 50us), in this embodiment, the duration of the shutoff enable signal for controlling the valve control system to send the shutoff signal to the single valve is set to 100us; considering a certain shutoff delay, the set time is greater than the duration of the shutoff enable signal, and in this embodiment, the set time is 150us. When the trigger control signal received by the valve control system for controlling the opening of the IGCT is invalid and no shutdown enable signal is received, the valve control system sends a status query signal for detecting the status of the single valve to the IGCT of each single valve of the IGCT converter valve; the IGCT of the single valve that receives the status query signal sends a driving status signal to the valve control system, which contains information on the operating status of the driving unit of the IGCT of the single valve and the operating status of the IGCT.

[0025] Among them, the status query signal is a coded modulation signal; the adjustment frequency is 1MHz, a total of 8 bits, and the encoding is 10100101. The drive status signal is a coded modulation signal, the adjustment frequency is 1MHz, and the information frame consists of 3 parts, divided into a frame header, data, and a frame tail. Among them, the frame header part occupies two bits, encoded as "11"; the frame tail also occupies two bits, which are 1 bit of XOR check and 1 bit of XOR check negation; and the data part includes 4 bits of drive operation related status (also called drive unit operation status) and 4 bits of IGCT operation related status, among which the drive unit operation status includes: drive unit power supply fault status, drive body function fault status and drive unit normal operation status. The IGCT operation status includes: short circuit fault status, cathode overvoltage fault status, cathode undervoltage fault status and IGCT normal operation status.

[0026] The specific encoding information of the data part including the driving unit operating status and the IGCT operating status is shown in the following Table 1:

[0027] Table 1

[0028]

[0029] Specifically, the control process of the IGCT converter valve also includes the conduction and active shutdown stages of triggering the single-valve IGCT. The IGCT converter valve trigger control timing diagram is shown in FIG. Figure 2 As shown in the figure, the specific control process in the three stages of triggering single-valve IGCT conduction, active shutdown, and status query is as follows:

[0030] First, when the valve control device detects the trigger control signal sent by the upper control device, it enters the first stage (triggering the conduction stage of the single-valve IGCT), and then directly sends a trigger instruction to the IGCT of the single valve at the rising edge of the signal to control the IGCT to open. In the effective interval of the trigger control signal, when the forward voltage of the IGCT exceeds 50V, the IGCT driver sends a forward voltage establishment signal to the valve control device. After the valve control device detects the forward voltage feedback signal (forward voltage establishment signal), it reissues the trigger instruction to the IGCT (the pulse width is the same as the normal trigger instruction, 10us). In this embodiment, the two supplementary pulses must be 100us apart, and there is no limit on the number of supplementary pulses within the effective interval of the trigger control signal. The IGCT drive unit monitors the voltage status at both ends of the IGCT in real time. When the voltage rises rapidly to the protection action trigger level, the IGCT is forced to open. At this time, the IGCT drive unit sends a protection action feedback signal (protection action signal) to the valve control device.

[0031] When the valve control device receives the IGCT current zero-crossing signal during the period when the trigger control signal is invalid, it enters the second stage (triggering the single-valve IGCT active shutdown stage, active shutdown belongs to the shutdown control under natural conditions), and sends a shutdown command to the IGCT. In the T1 monitoring interval after sending the shutdown command, the valve control device does not receive the IGCT shutdown success report signal (also called the shutdown success signal), then it is judged that the IGCT active shutdown fails. In the T1 monitoring interval, monitor whether the valve control device receives the shutdown success report signal. The setting of the T1 monitoring interval needs to refer to the characteristics of the IGCT shutting down small current (because it is monitoring whether the valve control device can receive the shutdown success signal when the current is at zero crossing and the IGCT is actively shut down, so the current is small); in this embodiment, T1 is set to 50us.

[0032] The valve control system enters the status query stage (the third stage) when the trigger control signal received for controlling the opening of the IGCT is invalid and the shutdown enable signal is not received. In this embodiment, the valve control device sends a status query instruction to the IGCT 6ms after the falling edge of the trigger control signal if the shutdown enable signal is not received. After receiving the instruction, the IGCT sends a status coding signal to the valve control device based on the driving status signal containing information on the operating status of the driving unit of the IGCT of the single valve and the operating status of the IGCT.

[0033] Among them, the trigger, shutdown command, forward voltage establishment signal, current zero crossing signal, shutdown success signal and protection action signal use pulse signals, and the information is represented by pulse width modulation. In this embodiment, the trigger command pulse width is 5us, the shutdown command pulse width is 8us, the forward voltage establishment signal pulse width is 5us, the current zero crossing signal pulse width is 10us, the protection action signal pulse width is 20us, and the shutdown success signal pulse width is 30us.

[0034] IGCT converter valve control system embodiment

[0035] This embodiment provides a technical solution for a control system of an IGCT converter valve. The system includes a processor, and the processor is used to execute a computer program to implement the steps of a control method of the IGCT converter valve.

[0036] Since the specific implementation process and principle of the control system of the IGCT converter valve in this embodiment have been described in detail in the embodiment of the control method of the IGCT converter valve, they will not be repeated here.

Claims

1. A control method for an IGCT converter valve, characterized in that: include: When it is detected that the voltage of a single valve in the IGCT converter valve that is pre-controlled to be non-conductive decreases and the current increases, if the current of the single valve is less than the current corresponding to the maximum shut-off capacity of the single valve, the valve control system sends a shut-off signal to the single valve to cut off the current of the single valve.

2. The control method of the IGCT converter valve according to claim 1, characterized in that: The manner of controlling the valve control system to send the shutoff signal to the single valve includes: sending a shutoff enable signal for controlling the valve control system to send the shutoff signal to the single valve to the valve control system through an upper control device.

3. The control method of the IGCT converter valve according to claim 2, characterized in that: The method of sending a shutdown signal to the single valve for cutting off the current of the single valve includes: continuously sending a shutdown signal to the single valve for cutting off the current of the single valve within a set time until a shutdown success signal fed back by the IGCT of the single valve is received.

4. The control method of the IGCT converter valve according to claim 2, characterized in that: Also includes: When the trigger control signal received by the valve control system for controlling the opening of the IGCT is invalid and no shutdown enable signal is received, the valve control system sends a status query signal for detecting the status of the single valve to the IGCT of each single valve of the IGCT converter valve; the IGCT of the single valve that receives the status query signal sends a driving status signal to the valve control system, which contains information on the operating status of the driving unit of the IGCT of the single valve and the operating status of the IGCT.

5. The control method of the IGCT converter valve according to claim 3, characterized in that: The set time is greater than the duration of the shutdown enable signal.

6. The control method of the IGCT converter valve according to claim 4, characterized in that: The state query signal is a coded modulation signal; the driving state signal is a coded modulation signal.

7. The control method of the IGCT converter valve according to claim 4, characterized in that: The operating status of the drive unit includes: a drive unit power failure status, a drive body function failure status, and a drive unit normal operation status.

8. The control method of the IGCT converter valve according to claim 4, characterized in that: The IGCT operating states include: short circuit fault state, cathode overvoltage fault state, cathode undervoltage fault state and IGCT normal operating state.

9. A control system for an IGCT converter valve, comprising a processor, characterized in that: The processor is used to execute a computer program to implement the steps of the IGCT converter valve control method according to any one of claims 1 to 8.

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