Hybrid commutation converter valve topology system and control method thereof

Abstract

The invention relates to the technical field of high-voltage direct-current power transmission, in particular to a hybrid commutation converter valve topology system and a control method thereof.The system comprises power modules of converter valve bodies and a power module control unit, and the two ends of each power module are connected with phase change energy absorption resistors in parallel; the phase change energy absorption resistor is used for being in a high resistance state when the converter valve is normal, the protection voltage level of the phase change energy absorption resistor is higher than the voltage at the two ends of a power module in the converter valve in the normal state, and the phase change energy absorption resistor is used for absorbing energy generated on the power module when the converter valve has a non-communication fault and is not broken down. When the absorption energy value reaches a phase change absorption energy threshold value, a low-resistance state is presented, so that current flowing through the phase change energy absorption resistor is increased, the phase change energy absorption resistor is fused and withdrawn, device damage caused by the fact that voltages at the two ends of the power module are maintained at an overhigh level for a long time is effectively avoided, protection is provided for the power module, and the service life of the power module is prolonged. And the operation reliability of the hybrid commutation converter valve is improved.

Description

Technical Field

[0001] This invention relates to the field of high voltage direct current transmission technology, specifically to a hybrid commutation converter valve topology system and its control method. Background Technology

[0002] In recent years, hybrid commutator (HCC) technology based on integrated gate commutator thyristors (IGCTs) with controllable turn-off capability has received increasing attention. This technology fundamentally enhances the commutation capability and fault response capability of the system by introducing power modules with self-turn-off capability into the traditional LCC commutator topology.

[0003] Existing research results indicate that HCC topologies exhibit good characteristics in real-time simulation, fault recovery, and control strategy optimization. For example, Chinese invention application CN120280982A discloses a control optimization method to improve the fault ride-through capability of hybrid commutated converters, thereby enhancing the HCC's ability to withstand commutation failures. This application demonstrates that both domestic and international efforts are focused on topology modifications to the inverter side of LCC-HVDC converters. However, during HCC operation, if an IGCT fails to turn off properly due to certain faults when active turn-off is required, the current energy that should flow through that IGCT must be shared by other IGCTs. This IGCT turn-off failure causes overvoltage problems for other series-connected IGCTs. Existing HCCs exhibit poor performance in IGCT voltage overshoot protection and IGCT fault tolerance, resulting in low reliability during long-term operation. Summary of the Invention

[0004] The purpose of this invention is to provide a hybrid commutator valve topology system and its control method to solve the problem that the existing hybrid commutator valves have poor protection capabilities against IGCT voltage overshoot.

[0005] To address the aforementioned technical problems, this invention provides a hybrid commutation valve topology system, comprising a power module and a power module control unit for the commutation valve body. Each power module has a phase-change energy-absorbing resistor connected in parallel across its terminals. When a fault alarm in the commutation valve is not a communication fault and the commutation valve is not broken down, the phase-change energy-absorbing resistor absorbs the energy generated on the power module during the fault. When the absorbed energy value reaches the phase-change energy absorption threshold, it exhibits a low-resistance state, increasing the current flowing through the phase-change energy-absorbing resistor, causing the phase-change energy-absorbing resistor to melt and disconnect. When the hybrid commutation valve needs to actively shut off the fault current, the phase-change energy-absorbing resistor absorbs the energy generated on the power module during the shutdown current, ensuring that the absorbed energy value is less than the phase-change resistor's energy absorption threshold; that is, the phase-change resistor does not undergo a phase change during the current shutdown process.

[0006] Furthermore, it also includes a high-voltage BOD protection circuit and a low-voltage BOD protection circuit. After the phase change energy absorption resistor blows and stops operating, the high-voltage BOD protection circuit is activated first, and the low-voltage BOD protection circuit is activated when the number of BOD actions reaches a set threshold, so as to realize overvoltage protection for the converter valve power module.

[0007] Furthermore, the phase change energy-absorbing resistor includes a current-limiting resistor, a phase change resistor, and a fuse connected in series. Under normal conditions, the phase change resistor exhibits a high resistance state. Under fault conditions, the phase change resistor is used to absorb the energy generated when the power module fails, and undergoes a phase change when the absorbed energy reaches the phase change energy absorption threshold, exhibiting a low resistance state. The fuse is used to blow when the phase change resistor transforms into a low resistance state and the current rises to a certain value, causing the phase change energy-absorbing resistor to stop operating. The current-limiting resistor is used to limit the current flowing through the phase change energy-absorbing resistor when the phase change resistor undergoes a phase change and the fuse does not blow and the resistor is removed.

[0008] Furthermore, the power module control unit adopts redundant communication. When a power module control unit is unable to communicate with the power module or valve control system, communication with the power module or valve control system is achieved through other power module control units.

[0009] Furthermore, the redundant communication adopts cross-redundant communication. Each power module control unit is equipped with a trigger redundancy fiber optic interface and a return check redundancy fiber optic interface. Each power module control unit is paired with the adjacent power module control unit. The trigger redundancy fiber optic interface on each power module control unit is connected to the trigger redundancy fiber optic interface of the power module control unit in the same group. The return check redundancy fiber optic interface on each power module control unit is connected to the corresponding return check redundancy fiber optic interface on the adjacent power module control unit.

[0010] A control method for a hybrid commutator valve topology system includes: Phase change energy absorption resistors are connected in parallel across the power module. When the fault alarm of the converter valve is not a communication fault and the converter valve is not broken down, the phase change energy-absorbing resistor is used to absorb the energy generated on the power module during the fault. When the absorbed energy value reaches the phase change energy absorption threshold, it presents a low resistance state, which increases the current flowing through the phase change energy-absorbing resistor, and the phase change energy-absorbing resistor melts and exits. When the hybrid commutation converter valve needs to actively shut off the fault current, the phase change energy-absorbing resistor is used to absorb the energy generated on the power module when the current is shut off. The absorbed energy value is less than the phase change resistor energy absorption threshold, that is, the phase change resistor does not undergo phase change during the current shutdown process.

[0011] Furthermore, the method also includes first activating the high-voltage BOD protection circuit when the phase change resistor blows out, and then activating the low-voltage BOD protection circuit when the number of BOD operations reaches a set threshold, so as to achieve overvoltage protection for the converter valve power module.

[0012] Furthermore, the phase change energy-absorbing resistor includes a current-limiting resistor, a phase change resistor, and a fuse connected in series. Under normal conditions, the phase change resistor exhibits a high resistance state. Under fault conditions, the phase change resistor absorbs the energy generated when the power module fails, and when the absorbed energy reaches the phase change energy absorption threshold, a phase change occurs, exhibiting a low resistance state. The fuse blows when the phase change resistor transitions to a low resistance state and the current rises to a certain value, causing the phase change energy-absorbing resistor to stop operating. The current-limiting resistor limits the current flowing through the phase change energy-absorbing resistor when the phase change resistor undergoes a phase change and the fuse has not blown.

[0013] Furthermore, the power module control unit adopts redundant communication. When a power module control unit cannot communicate with the power module or valve control system, communication with the power module or valve control system is achieved through other power module control units.

[0014] Furthermore, the redundant communication adopts cross-redundant communication. Each power module control unit is equipped with a trigger redundancy fiber optic interface and a return check redundancy fiber optic interface. Each power module control unit is paired with the adjacent power module control unit. The trigger redundancy fiber optic interface on each power module control unit is connected to the trigger redundancy fiber optic interface of the power module control unit in the same group. The return check redundancy fiber optic interface on each power module control unit is connected to the corresponding return check redundancy fiber optic interface on the adjacent power module control unit.

[0015] The beneficial effects of this invention are as follows: As an improved invention, this invention includes a phase-change energy-absorbing resistor connected in parallel across both ends of each power unit. This phase-change energy-absorbing resistor is in a high-resistance state when the converter valve is operating normally. When the converter valve experiences a fault that is not a communication fault and is not broken down, the phase-change energy-absorbing resistor is used to absorb the energy generated on the power module to avoid excessive voltage on the power module (i.e., IGCT) causing a breakdown fault. This effectively prevents the voltage across the power module components from being maintained at an excessively high level for a long time, thus preventing device damage and providing protection for the power module. This improves the reliability of the hybrid commutation converter valve operation. Attached Figure Description

[0016] Figure 1 Flowchart of the control method for a hybrid commutator valve topology system; Figure 2 Topology diagram of a two-stage IGCT for a hybrid phase-commutation valve; Figure 3 This is a structural diagram of a phase change energy-absorbing resistor; Figure 4 This is a schematic diagram of cross-redundant communication at the IGCT board level. Figure 5 This is a schematic diagram of 14 consecutive levels of IGCT board-level cross-redundancy communication. Detailed Implementation

[0017] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0018] This invention effectively prevents the voltage across the power module from being maintained at an excessively high level for a long time, which could damage the device, by setting a phase-change energy-absorbing resistor in parallel on the power module.

[0019] Hybrid commutator valve topology implementation In existing technologies, hybrid commutation converter valve topologies include multiple power modules, phase-change energy-absorbing resistor circuits, and damping voltage equalization circuits. The phase-change energy-absorbing resistor circuits and damping voltage equalization circuits are connected in parallel with the power modules to protect the power module control unit. The power modules are controlled by the power module control unit and connected to the valve control system to send feedback signals to the valve control system or receive trigger signals from the valve control system. The following explanation uses IGCT devices as power modules. If a converter valve malfunctions, the voltage across the IGCT devices will continuously rise. To prevent the voltage across the power modules from remaining excessively high for an extended period, phase-change energy-absorbing resistors are connected in parallel across each IGCT device. The HCC circuit with the phase-change energy-absorbing resistors is as follows: Figure 2 As shown, each IGCT device is connected in parallel with a corresponding phase change energy-absorbing resistor. For example, IGCT1 is connected in parallel with phase change energy-absorbing resistor Rd1, IGCT2 is connected in parallel with phase change energy-absorbing resistor Rd2, and PCR1 and PCR2 are the phase change energy-absorbing resistor circuits of IGCT1 and IGCT2, respectively.

[0020] Specifically, such as Figure 3As shown, the phase change energy-absorbing resistor includes a fuse, a phase change resistor, and a current-limiting resistor connected in series. The fuse quickly melts after the phase change resistor undergoes a phase change, forming an insulation gap with a withstand voltage greater than 10 kV, ensuring the phase change resistor can be taken out of operation without pressure release, thus avoiding the risk of the phase change energy-absorbing resistor exploding due to overvoltage. The current-limiting resistor has a stable resistance value and is mainly used to limit the current flowing through the phase change energy-absorbing resistor when the phase change resistor undergoes a phase change and the fuse has not melted. The phase change resistor absorbs energy generated during power module failures and undergoes a phase change when the absorbed energy reaches the phase change absorption energy threshold, changing from a high-resistance state to a low-resistance state. This reduces the overall resistance of the phase change energy-absorbing resistor, increasing the current flowing through it, and thus causing the fuse to melt quickly. As one embodiment, the phase change resistor is a vanadium oxide-based phase change resistor with a valve plate, formed by mixing and pressing vanadium oxide and zinc oxide in a certain proportion. The current-limiting resistor can be a nickel-chromium alloy resistor.

[0021] The phase-change energy-absorbing resistor is used to maintain a high resistance state when the converter valve is operating normally. Its protection voltage level is higher than the voltage across the power module in the converter valve under normal conditions, but lower than the high-voltage BOD protection setting of the device. When the fault alarm of the converter valve is not a communication fault and the converter valve is not broken down, the phase-change energy-absorbing resistor is used to absorb the energy generated on the power module during the fault. When the absorbed energy value reaches the phase-change energy absorption threshold, it presents a low resistance state, which increases the current flowing through the phase-change energy-absorbing resistor, causing the phase-change energy-absorbing resistor to melt and exit. When the HCC actively shuts off the fault current, the phase-change energy-absorbing resistor is used to absorb the energy generated on the power module when the current is shut off. This absorbable energy value is less than the phase-change resistor energy absorption threshold, that is, the phase-change resistor does not undergo a phase change during the current shutdown process.

[0022] When the converter valve is functioning normally, such as Figure 3As shown, the voltage (U4) across the IGCT device is normal, and the phase-change resistor is in a high-impedance state (R1). At this time, the protection level (U3) of the phase-change energy-absorbing resistor is higher than the voltage (U4) across the IGCT device. The phase-change energy-absorbing resistor is mainly used for auxiliary voltage equalization. When the IGCT device alarms, and the alarm is not caused by a communication failure (such as a failure of the integrated control unit triggering and protection triggering functions of the converter valve) and the IGCT device is not broken down, the IGCT control unit (also called the IGCT integrated control unit) fails or the external communication fails completely. The IGCT device loses its normal control function. At this time, the voltage of the IGCT device continuously reaches the protection level value (U3) of the phase-change energy-absorbing resistor in each triggering cycle. The phase-change energy-absorbing resistor begins to continuously absorb the energy generated by the fault. During this stage, the phase-change resistor has not yet undergone a phase change, and its resistance value remains at a high level, enabling the HCC converter valve system to maintain stable operation. As the fault continues, the phase change energy absorption resistor continuously absorbs energy. When the energy it absorbs exceeds the design threshold (E), the phase change resistor in the phase change energy absorption resistor undergoes a phase change and transforms into a low impedance state (R2). The current flowing through the phase change energy absorption resistor increases significantly until the fuse blows and the phase change resistor is taken out of operation.

[0023] To ensure the safe and stable operation of the IGCT devices and HCC converter valves after the phase-change resistors are decommissioned, this invention also configures high-voltage BOD protection circuits and low-voltage BOD protection circuits within the IGCT integrated control unit, both implemented through hardware circuitry. The high-voltage BOD protection circuit has a trigger voltage of 7.6kV±100V, and the low-voltage BOD protection circuit has a trigger voltage of 2kV±100V. Initially, the IGCT control unit operates with the high-voltage BOD protection circuit. This invention is designed to automatically switch to the low-voltage BOD overvoltage protection circuit when the high-voltage BOD activation count of the IGCT devices reaches 50 consecutive times. After the low-voltage BOD overvoltage protection circuit is activated, it reduces the BOD protection trigger voltage from 7.6 kV to 2 kV. This process is irreversible; the IGCT integrated control unit must be powered on again to switch the circuit back to the high-voltage BOD protection circuit. This effectively prevents malfunctioning IGCT devices from being continuously powered on by the high-voltage BOD protection trigger voltage, which could lead to excessive voltage stress and damage, thereby improving the overall reliability of the HCC converter valve system.

[0024] As one embodiment, the present invention sets R1 > 1MΩ, R2 < 100Ω, U1 to 7.6kV ± 100V, U2 to 2kV ± 100V, U3 to 6.8kV, and E to 1.2MJ.

[0025] Once the bus voltage returns to normal, the system sequentially resets the protection devices: the phase-change energy-absorbing resistor returns to a low-resistance state, the bypass thyristor turns off, and the protection threshold switches back to its initial state. The entire switching logic adaptively adjusts the protection level as the fault evolves, thereby providing stable overvoltage protection.

[0026] In existing hybrid converters, a single IGCT control unit is typically used to control, trigger, and check the status of an IGCT device. If the IGCT control unit fails to generate or transmit trigger and check commands, the valve control device will be unable to control the IGCT device's operation.

[0027] To improve the reliability of control between IGCT devices and valve control systems, this invention adds a feature such as... between the IGCT control units corresponding to two adjacent IGCT devices on the IGCT board. Figure 5 The cross-redundant communication channel shown allows the IGCT device to communicate with the valve control system through cross-redundant communication when the IGCT control unit of a certain IGCT device cannot transmit trigger commands and return test commands normally with the valve control system, but the trigger and return test functions of the board on which the IGCT device is located can still operate normally. This means that the IGCT device can communicate with the valve control system by utilizing the IGCT control units of adjacent IGCT devices.

[0028] Specifically, such as Figure 4 As shown, this invention adds trigger redundancy fiber optic interfaces (C11, C12) and check redundancy fiber optic interfaces (H11, H12) to the IGCT control unit, pairing adjacent IGCT devices. The trigger redundancy fiber optic interfaces of two adjacent IGCT control units are connected accordingly (i.e., C11 connects to C21, C12 connects to C22), and the check redundancy fiber optic interfaces are connected accordingly (H11 connects to H21, H12 connects to H22), forming a cross-redundant communication system. During normal operation of the IGCT control unit, the communication link of the IGCT device is: IGCT device - IGCT control unit - CF / HJ conductive fiber - valve control system. When a communication failure occurs between the IGCT control unit and the valve control system, the auxiliary communication path of the IGCT device is: IGCT device - check redundancy fiber optic interface of the corresponding IGCT control unit - adjacent IGCT control unit (i.e., cross-redundant IGCT control unit) - CF / HJ conductive fiber - valve control system.

[0029] When adjacent IGCT devices, IGCT control units, and transmission optical fibers (triggering and feedback) are functioning normally, the two systems operate independently. Each IGCT device receives trigger commands from the valve control system and monitors its own feedback signal via its corresponding IGCT control unit. If a communication anomaly is detected in an IGCT device (such as loss of trigger or feedback signal), the integrated control unit of the IGCT device automatically switches the corresponding IGCT device to the auxiliary communication path.

[0030] Since communication failures are relatively easy to resolve and occur frequently, during the control process, when an IGCT device experiences a fault alarm, its communication path is first switched to the corresponding auxiliary communication path. Once the cross-redundant communication system is operational, if the IGCT device's fault alarm is cleared, it indicates that the original communication link of the IGCT device has failed. In this case, because the cross-redundant communication system can continue to ensure the safe and stable operation of the IGCT device, the equipment can operate normally without shutdown; only the faulty communication fiber needs to be replaced or repaired during subsequent power outage maintenance. If the IGCT device's fault alarm is not cleared after the cross-redundant communication system is operational, it is necessary to determine whether the IGCT device itself has experienced a breakdown fault. If a breakdown fault occurs, the valve control system will further determine whether the number of faulty IGCT devices in the HCC has reached the redundancy threshold. If the number of faulty devices reaches the redundancy threshold, a temporary power outage must be requested immediately for fault repair; if the redundancy threshold is not reached, operation can continue temporarily until maintenance is scheduled for further fault handling. For example, taking a single valve module with 12 IGCT devices as an example, it can tolerate a maximum of 2 failed devices. If only one IGCT device in the single valve is damaged, the single valve can continue to operate normally. However, if three IGCT devices in the single valve are damaged, it is necessary to immediately shut down the power for repair.

[0031] As one embodiment, depending on actual usage requirements, cross-redundant communication channels can be established between any adjacent IGCT control units. In this way, the IGCT control units at both ends have only one adjacent IGCT control unit, while other IGCT control units have two adjacent IGCT control units. When other IGCT control units experience communication failures, any one of the adjacent IGCT control units can be used to trigger control and perform backtesting sampling on the IGCT device.

[0032] The improved hybrid commutator valve topology described above can optimize the system as a whole from multiple levels, including communication and overvoltage protection, thereby improving system stability and fault self-healing capabilities. The actual operation of this hybrid commutator valve topology system follows the following workflow: Figure 1 As shown: 1) First, when the IGCT device issues a fault alarm, the IGCT device is switched to communicate with the valve control system via the IGCT control unit connected through the cross-redundant communication channel.

[0033] 2) After the IGCT device switches to communicate with the valve control system via the cross-redundant communication channel, determine whether the fault alarm has been cleared. If the fault alarm is cleared, it indicates that a communication failure has occurred between the IGCT control unit corresponding to the IGCT device and the valve control system, and it needs to be repaired during subsequent maintenance. If the fault alarm is not cleared, it indicates that the fault is not a communication fault, and in this case, it is necessary to determine whether the IGCT device has experienced a breakdown fault.

[0034] If the IGCT device experiences a breakdown fault, it is determined whether the number of broken IGCT devices has reached the set redundancy threshold. If the redundancy threshold is reached, a temporary power outage is required for fault repair. If the redundancy threshold is not reached, the backup IGCT device set in the converter valve is activated to maintain the operation of the converter valve. If no breakdown fault occurs, it is determined that the communication function of the IGCT device board in the converter valve is faulty.

[0035] 3) When the fault alarm of the IGCT device in the converter valve is not a communication fault and the IGCT is not broken down, the system uses the phase change energy absorption resistor to continuously absorb the fault energy, provide continuous overvoltage protection for the IGCT device, and melts when the absorbed energy value reaches the threshold.

[0036] When a fault first occurs, the phase-change resistor in the phase-change energy-absorbing resistor is in a high-resistance state. In the initial stage of the IGCT device board communication function failure, the phase-change energy-absorbing resistor continuously absorbs the energy generated by the fault on the IGCT device. At this time, the phase-change resistor has not yet undergone a phase change, and the overall resistance value of the phase-change energy-absorbing resistor is high, allowing the HCC converter valve system to maintain stable operation. As the fault duration continues to increase, the phase-change resistor in the phase-change energy-absorbing resistor continues to absorb energy. When the energy absorbed by the phase-change resistor reaches the design threshold, the phase-change resistor undergoes a phase change, transforming into a low-resistance state. The resistance value of the phase-change energy-absorbing resistor will decrease significantly, leading to an increase in the current flowing through the phase-change energy-absorbing resistor. Under the action of the large current, the fuse blows, and the phase-change energy-absorbing resistor stops working.

[0037] 4) When the phase change energy absorption resistor blows, the IGCT device continues to conduct through the BOD function of the integrated control unit of the IGCT device.

[0038] Specifically, when the periodic triggering and reporting function of the IGCT device board fails and the phase change energy absorption resistor (MOV) has blown and stopped working, the IGCT device can be kept on by controlling the BOD function of the IGCT device integrated control unit. To further ensure the safe and stable operation of the IGCT device and the HCC converter valve, this invention sets that when the cumulative number of BOD actions of the IGCT device reaches a set threshold, the overvoltage protection circuit will automatically switch, reducing the BOD protection trigger voltage from 7.6 kV to 2 kV. This effectively prevents the voltage across the IGCT device from remaining at an excessively high level for a long time, thus avoiding device damage and improving the overall reliability of the HCC converter valve system. As an example, the threshold for the number of BOD actions is set to 50 times in this invention.

[0039] Implementation of the control method for a hybrid commutator valve topology system This invention proposes a control method for a hybrid commutator valve topology system, comprising: Phase change energy absorption resistors are connected in parallel across the power module. When the fault alarm of the converter valve is not a communication fault and the converter valve is not broken down, the phase change energy absorption resistor is used to absorb the energy generated on the power module when the fault occurs. When the energy absorption value reaches the energy absorption threshold, the phase change energy absorption resistor presents a low resistance state, the current flowing through the phase change energy absorption resistor increases, and the phase change energy absorption resistor melts and is removed.

[0040] This method is based on hardware improvements to the hybrid commutator valve topology system. The hardware improvements mainly involve two aspects. Firstly, to prevent the voltage across the power module from remaining at an excessively high level for extended periods, phase-change energy-absorbing resistors are connected in parallel across each IGCT device. The HCC circuit with these phase-change energy-absorbing resistors is shown below. Figure 2 As shown, a corresponding deformation-absorbing resistor (such as Rd1 on IGCT1 and Rd2 on IGCT2) is connected in parallel with each IGCT device. To improve the reliability of the control between the IGCT devices and the valve control system, a resistor such as Rd1 on IGCT1 and Rd2 on IGCT2 is added between the IGCT control units corresponding to two adjacent IGCT devices on the IGCT board. Figure 5 The cross-redundant communication channel shown allows the IGCT device to communicate with the valve control system through cross-redundant communication when the IGCT control unit of a certain IGCT device cannot transmit trigger commands and return test commands normally with the valve control system, but the trigger and return test functions of the board on which the IGCT device is located can still operate normally. This means that the IGCT device can communicate with the valve control system by utilizing the IGCT control units of adjacent IGCT devices.

[0041] Its workflow is as follows: 1) First, when the IGCT device issues a fault alarm, the IGCT device is switched to communicate with the valve control system via the IGCT control unit connected through the cross-redundant communication channel.

[0042] 2) After the IGCT device switches to communicate with the valve control system via the cross-redundant communication channel, determine whether the fault alarm has been cleared. If the fault alarm is cleared, it indicates that a communication failure has occurred between the IGCT control unit corresponding to the IGCT device and the valve control system, and it needs to be repaired during subsequent maintenance. If the fault alarm is not cleared, it indicates that the fault is not a communication fault, and in this case, it is necessary to determine whether the IGCT device has experienced a breakdown fault.

[0043] If the IGCT device experiences a breakdown fault, it is determined whether the number of broken IGCT devices has reached the set redundancy threshold. If the redundancy threshold is reached, a temporary power outage is required for fault repair. If the redundancy threshold is not reached, the backup IGCT device set in the converter valve is activated to maintain the operation of the converter valve. If no breakdown fault occurs, it is determined that the communication function of the IGCT device board in the converter valve is faulty.

[0044] 3) When the fault alarm of the IGCT device in the converter valve is not a communication fault and the IGCT is not broken down, the system uses the phase change energy absorption resistor to continuously absorb the fault energy, provide continuous overvoltage protection for the IGCT device, and melts when the absorbed energy value reaches the threshold.

[0045] When a fault first occurs, the phase-change resistor in the phase-change energy-absorbing resistor is in a high-resistance state. In the initial stage of the IGCT device board communication function failure, the phase-change energy-absorbing resistor continuously absorbs the energy generated by the fault on the IGCT device. At this time, the phase-change resistor has not yet undergone a phase change, and the overall resistance value of the phase-change energy-absorbing resistor is high, allowing the HCC converter valve system to maintain stable operation. As the fault duration continues to increase, the phase-change resistor in the phase-change energy-absorbing resistor continues to absorb energy. When the energy absorbed by the phase-change resistor reaches the design threshold, the phase-change resistor undergoes a phase change, transforming into a low-resistance state. The resistance value of the phase-change energy-absorbing resistor will decrease significantly, leading to an increase in the current flowing through the phase-change energy-absorbing resistor. Under the action of the large current, the fuse blows, and the phase-change energy-absorbing resistor stops working.

[0046] 4) When the phase change energy absorption resistor blows, the IGCT device continues to conduct through the BOD function of the integrated control unit of the IGCT device.

[0047] Specifically, when the periodic triggering and reporting function of the IGCT device board fails and the phase change energy absorption resistor (MOV) has blown and stopped working, the IGCT device can be kept on by controlling the BOD function of the IGCT device integrated control unit. To further ensure the safe and stable operation of the IGCT device and the HCC converter valve, this invention sets that when the cumulative number of BOD actions of the IGCT device reaches a set threshold, the overvoltage protection circuit will automatically switch, reducing the BOD protection trigger voltage from 7.6 kV to 2 kV. This effectively prevents the voltage across the IGCT device from remaining at an excessively high level for a long time, thus avoiding device damage and improving the overall reliability of the HCC converter valve system. As an example, the threshold for the number of BOD actions is set to 50 times in this invention.

Claims

1. A hybrid commutation converter valve topology system, comprising a power module for the converter valve body and a power module control unit, characterized in that, Each power module has a phase-change energy-absorbing resistor connected in parallel across its two ends. When the fault alarm of the converter valve is not a communication fault and the converter valve is not broken down, the phase-change energy-absorbing resistor is used to absorb the energy generated on the power module during the fault. When the absorbed energy value reaches the phase-change energy absorption threshold, it presents a low-resistance state, which increases the current flowing through the phase-change energy-absorbing resistor, causing the phase-change energy-absorbing resistor to melt and exit. When the hybrid commutation converter valve needs to actively shut off the fault current, the phase-change energy-absorbing resistor is used to absorb the energy generated on the power module when the current is shut off. This absorbs the energy value less than the phase-change resistor energy absorption threshold, that is, the phase-change resistor does not undergo a phase change during the current shutdown process.

2. The hybrid commutation converter valve topology system according to claim 1, characterized in that, It also includes a high-voltage BOD protection circuit and a low-voltage BOD protection circuit. After the phase change energy absorption resistor blows and stops operating, the high-voltage BOD protection circuit is activated first, and the low-voltage BOD protection circuit is activated when the number of BOD actions reaches a set threshold, so as to realize overvoltage protection for the converter valve power module.

3. The hybrid commutation converter valve topology system according to claim 1, characterized in that, The phase change energy-absorbing resistor includes a current-limiting resistor, a phase change resistor, and a fuse connected in series. Under normal conditions, the phase change resistor exhibits a high resistance state. Under fault conditions, the phase change resistor is used to absorb the energy generated when the power module fails, and undergoes a phase change when the absorbed energy reaches the phase change energy absorption threshold, exhibiting a low resistance state. The fuse is used to blow when the phase change resistor transforms into a low resistance state and the current rises to a certain value, causing the phase change energy-absorbing resistor to stop operating. The current-limiting resistor is used to limit the current flowing through the phase change energy-absorbing resistor when the phase change resistor undergoes a phase change and the fuse does not blow and the resistor is removed.

4. The hybrid commutation valve topology system according to claim 1, characterized in that, The power module control unit adopts redundant communication. When a power module control unit cannot communicate with the power module or valve control system, it communicates with the power module or valve control system through other power module control units.

5. The hybrid commutation converter valve topology system according to claim 4, characterized in that, The redundant communication adopts cross-redundancy communication. Each power module control unit is equipped with a trigger redundancy fiber optic interface and a return check redundancy fiber optic interface. Each power module control unit is paired with the adjacent power module control unit. The trigger redundancy fiber optic interface on each power module control unit is connected to the trigger redundancy fiber optic interface of the power module control unit in the same group. The return check redundancy fiber optic interface on each power module control unit is connected to the corresponding return check redundancy fiber optic interface on the adjacent power module control unit.

6. A control method for a hybrid commutator valve topology system, characterized in that, include: Phase change energy absorption resistors are connected in parallel across the power module. When the fault alarm of the converter valve is not a communication fault and the converter valve is not broken down, the phase change energy-absorbing resistor is used to absorb the energy generated on the power module during the fault. When the absorbed energy value reaches the phase change energy absorption threshold, it presents a low resistance state, which increases the current flowing through the phase change energy-absorbing resistor, and the phase change energy-absorbing resistor melts and exits. When the hybrid commutation converter valve needs to actively shut off the fault current, the phase change energy-absorbing resistor is used to absorb the energy generated on the power module when the current is shut off. The absorbed energy value is less than the phase change resistor energy absorption threshold, that is, the phase change resistor does not undergo phase change during the current shutdown process.

7. The control method for the hybrid commutator valve topology system according to claim 6, characterized in that, The method also includes first activating the high-voltage BOD protection circuit when the phase change resistor blows out, and then activating the low-voltage BOD protection circuit when the number of BOD actions reaches a set threshold, so as to achieve overvoltage protection for the converter valve power module.

8. The control method for the hybrid commutator valve topology system according to claim 6, characterized in that, The phase change energy-absorbing resistor includes a current-limiting resistor, a phase change resistor, and a fuse connected in series. Under normal conditions, the phase change resistor exhibits a high resistance state. Under fault conditions, the phase change resistor absorbs the energy generated when the power module fails. When the absorbed energy reaches the phase change energy absorption threshold, a phase change occurs, and the phase change resistor exhibits a low resistance state. The fuse blows when the phase change resistor transitions to a low resistance state and the current rises to a certain value, causing the phase change energy-absorbing resistor to stop operating. The current-limiting resistor limits the current flowing through the phase change energy-absorbing resistor when the phase change resistor undergoes a phase change and the fuse has not blown.

9. The control method for the hybrid commutator valve topology system according to claim 6, characterized in that, The power module control unit adopts redundant communication. When a power module control unit cannot communicate with the power module or valve control system, communication with the power module or valve control system is achieved through other power module control units.

10. The control method for the hybrid commutator valve topology system according to claim 9, characterized in that, The redundant communication adopts cross-redundancy communication. Each power module control unit is equipped with a trigger redundancy fiber optic interface and a return check redundancy fiber optic interface. Each power module control unit is paired with the adjacent power module control unit. The trigger redundancy fiber optic interface on each power module control unit is connected to the trigger redundancy fiber optic interface of the power module control unit in the same group. The return check redundancy fiber optic interface on each power module control unit is connected to the corresponding return check redundancy fiber optic interface on the adjacent power module control unit.

Images