Converter valve overpressure protection method, converter valve overpressure protection device and converter valve system

Abstract

The invention provides an overvoltage protection method of a converter valve, an overvoltage protection device of the converter valve and a converter valve system. The method comprises the steps of obtaining an anode voltage of an IGCT device in the converter valve; determining whether the IGCT device loses pulses or not according to the magnitude and the duration time of the anode voltage of the IGCT device; if the IGCT device loses the pulse, reducing the initial overvoltage protection voltage of the IGCT device to the target overvoltage protection voltage, keeping the initial overvoltage protection voltage for a first preset time length, and controlling the IGCT device to be started under the condition that a preset condition is met in the first preset time length, so as to avoid a fault of the lightning arrester; the preset condition is that the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage. According to the method, the pulse loss judgment of the IGCT device can be completed through the abnormal through-current / abnormal voltage, and after the pulse loss is judged, the forward overvoltage protection threshold of the IGCT with the abnormal opening is switched to be the secondary overvoltage protection threshold, so that the through-current of the lightning arrester can be avoided.

Description

Technical Field

[0001] This application relates to the field of high voltage direct current transmission technology, and more specifically, to an overvoltage protection method for a converter valve, an overvoltage protection device for a converter valve, and a converter valve system. Background Technology

[0002] In the field of high-voltage direct current (HVDC) transmission, the core of the hybrid commutation converter valve is the IGCT device. During operation, the converter valve must be able to withstand a certain overvoltage, because excessively high voltage surges can easily cause the power electronic devices to break down, thereby seriously endangering the stable operation of the converter valve. Therefore, in actual operation, it is essential to equip the power electronic components with a corresponding overvoltage protection system, such as device-level parallel surge arresters (MOVs) and drive-level overvoltage protection (BOD).

[0003] Because of the inherent characteristics of IGCTs, they cannot achieve active voltage equalization through driving. Therefore, to ensure consistent voltage equalization during IGCT operation, a parallel MOV (Multi-Active Device) scheme can be used, typically with an MOV connected in parallel to each IGCT stage. However, the fewer devices protected by the MOV, the more susceptible the MOV is to the adverse effects of direct current overheating caused by IGCT turn-on failure. Current technology generally uses a solution where a fuse is connected in series with the MOV to allow it to be melted and disconnected in case of overheating. However, this solution is passive disconnection, and the MOV cannot be reused after cooling down, presenting economic problems. Summary of the Invention

[0004] The main objective of this application is to provide an overpressure protection method, an overpressure protection device, and a converter valve system for converter valves, so as to at least solve the problem that existing converter valves will damage the surge arresters connected in parallel with the IGCT after the IGCT fails to start, thus leading to low system reliability.

[0005] To achieve the above objectives, according to one aspect of this application, an overvoltage protection method for a converter valve is provided, comprising: acquiring the anode voltage of an IGCT device in the converter valve; determining whether the IGCT device has lost a pulse based on the magnitude and duration of the anode voltage of the IGCT device; in the case of the IGCT device losing a pulse, reducing the initial overvoltage protection voltage of the IGCT device to a target overvoltage protection voltage and maintaining it for a first preset duration, and controlling the IGCT device to open if a preset condition is met within the first preset duration, so as to avoid a surge arrester failure, wherein the preset condition is that the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage, wherein the target overvoltage protection voltage is the overvoltage protection voltage of the IGCT device to avoid a surge arrester failure, and the surge arrester is connected in parallel with the IGCT device.

[0006] Optionally, determining whether the IGCT device has lost a pulse based on the magnitude and duration of the anode voltage of the IGCT device includes: determining a target overvoltage protection voltage and a second preset duration, wherein the second preset duration is the shortest duration for which the anode voltage of the IGCT device is higher than the target overvoltage protection voltage after the IGCT device loses a pulse; determining whether the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage; if the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage, determining whether the duration for which the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage exceeds the second preset duration; and if the duration for which the anode voltage of the IGCT device exceeds the second preset duration, determining that the IGCT device has lost a pulse.

[0007] Optionally, before determining whether the IGCT device has lost a pulse based on the magnitude and duration of the anode voltage of the IGCT device, the method further includes: determining the minimum operating current of the converter valve, and determining the minimum current-carrying residual voltage of the surge arrester based on the minimum operating current, wherein the minimum current-carrying residual voltage corresponds to the minimum operating current; determining the PCOV of the IGCT device, wherein the PCOV is the peak value of the continuous operating voltage of the IGCT device including commutation overshoot; and determining the target overvoltage protection voltage based on the minimum current-carrying residual voltage of the surge arrester and the PCOV of the IGCT device, wherein the target overvoltage protection voltage is greater than or equal to the PCOV of the IGCT device and less than or equal to the minimum current-carrying residual voltage of the surge arrester.

[0008] Optionally, the converter valve includes a surge arrester connected in parallel with the IGCT device. Determining a second preset duration includes: acquiring the active turn-off commutation duration of the IGCT device, the duration required for the surge arrester to absorb rated energy, the bridge arm current conduction duration of the converter valve, and the shortest duration of the AC voltage of the converter valve. The active turn-off commutation duration of the IGCT device is the time required for the IGCT device to transition from an on-state to an off-state. The duration required for the surge arrester to absorb rated energy is the duration required for the surge arrester to absorb rated energy under maximum current. The shortest duration of the AC voltage of the converter valve... The duration is the shortest time it takes for the AC voltage of the converter valve to rise to the target overvoltage protection voltage and remain stable. The second preset duration is determined based on the active turn-off commutation duration of the IGCT device, the duration required for the surge arrester to absorb rated energy, the conduction duration of the bridge arm current of the converter valve, and the shortest duration of the anode voltage of the IGCT device. The second preset duration is longer than the active turn-off commutation duration of the IGCT device, longer than the shortest duration of the anode voltage of the IGCT device, shorter than the duration required for the surge arrester to absorb rated energy, and shorter than the conduction duration of the bridge arm current of the converter valve.

[0009] Optionally, obtaining the active turn-off commutation duration of the IGCT device includes: obtaining the commutation inductance of the commutator valve, the DC current of the commutator valve, and the voltage of a single arm of the commutator valve; determining a first calculated value as a first preset multiple of the product of the square of the DC current of the commutator valve and the commutation inductance of the commutator valve; determining a second calculated value as the product of the DC current of the commutator valve and the voltage of a single arm of the commutator valve; and determining the ratio of the first calculated value to the second calculated value as the active turn-off commutation duration of the IGCT device.

[0010] Optionally, obtaining the time required for the surge arrester to absorb rated energy includes: obtaining the rated energy of the surge arrester, the maximum turn-off current of the IGCT device, and the residual voltage of the surge arrester under the maximum turn-off current of the IGCT device; determining the product of the maximum turn-off current of the IGCT device and the residual voltage of the surge arrester under the maximum turn-off current of the IGCT device as a third calculated value; and determining the ratio of the rated energy of the surge arrester to the third calculated value as the time required for the surge arrester to absorb rated energy.

[0011] Optionally, the converter valve includes a multi-stage IGCT assembly, the IGCT assembly including the IGCT device. Obtaining the shortest duration of the AC voltage of the converter valve includes: obtaining the number of series stages of the IGCT assembly in the converter valve, the rated AC valve voltage of the converter valve, the AC grid angular velocity of the converter valve, and the load shedding coefficient of the converter valve, wherein the rated AC valve voltage is the highest AC voltage during fault-free operation of the converter valve; determining the product of the number of series stages of the IGCT assembly in the converter valve and the target overvoltage protection voltage as a fourth calculated value, and determining the load shedding coefficient of the converter valve and the rated AC valve voltage of the converter valve as a fifth calculated value; determining the ratio of the fourth calculated value and the fifth calculated value as a sixth calculated value; and determining the absolute value of the ratio of the inverse cosine function of the sixth calculated value to the AC grid angular velocity of the converter valve as the shortest duration of the AC voltage of the converter valve.

[0012] Optionally, the converter valve includes a surge arrester connected in parallel with the IGCT device, and the first preset duration is longer than the heat dissipation time of the surge arrester.

[0013] Optionally, in the event that the IGCT device loses a pulse, the redundancy level of the converter valve is reduced by one.

[0014] According to another aspect of this application, an overpressure protection device for a converter valve is provided, comprising: a controller, configured to execute at least one of the overpressure protection methods for the converter valve described above; a voltage detection circuit, electrically connected to the controller, configured to acquire the anode voltage of an IGCT device in the converter valve; and a gate pulse amplifier circuit, wherein the input terminal of the gate pulse amplifier circuit is electrically connected to the controller, and the output terminal of the gate pulse amplifier circuit is configured to be electrically connected to the gate of the IGCT device, wherein the gate pulse amplifier circuit is configured to amplify and output a gate control signal of the IGCT device sent by the controller to the gate of the IGCT device when the anode voltage of the IGCT device is greater than a target overpressure protection voltage, so as to control the IGCT device to turn on.

[0015] According to another aspect of this application, a converter valve system is provided, comprising: a converter valve including at least one stage IGCT assembly, the IGCT assembly including IGCT devices and surge arresters connected in parallel; and an overvoltage protection device for the converter valve.

[0016] Applying the technical solution of this application, the overvoltage protection method for the converter valve first obtains the anode voltage of the IGCT device in the converter valve; then, based on the magnitude and duration of the anode voltage of the IGCT device, it is determined whether the IGCT device has lost a pulse; finally, in the case of pulse loss of the IGCT device, the initial overvoltage protection voltage of the IGCT device is reduced to the target overvoltage protection voltage and maintained for a first preset duration. Within the first preset duration, if a preset condition is met, the IGCT device is controlled to open to prevent arrester failure. The preset condition is that the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage. Since the arrester will directly conduct current after pulse loss, although the IGCT can monitor the anode voltage through drive, due to the voltage limiting effect of the arrester, although it will not cause the positive overvoltage protection threshold to activate, it may cause the arrester to blow. Therefore, pulse loss can be determined by identifying such abnormal current flow and / or abnormal voltage. After pulse loss is determined, the forward overvoltage protection threshold of the abnormally activated IGCT is switched to the secondary overvoltage protection threshold, which can prevent the surge arrester from flowing through. This solves the problem that the existing converter valve will damage the surge arrester connected in parallel with the IGCT after the IGCT fails to activate, thus leading to low system reliability. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0018] Figure 1 A schematic flowchart of an overpressure protection method for a converter valve according to an embodiment of this application is shown.

[0019] Figures 2(a)-2(d) show a schematic diagram comparing the surge arrester current under different overvoltages according to an embodiment of this application;

[0020] Figure 3 A schematic flowchart of another overpressure protection method for a converter valve according to an embodiment of this application is shown;

[0021] Figure 4 A schematic diagram of an overpressure protection device for a converter valve according to an embodiment of this application is shown.

[0022] Figure 5 A schematic diagram of the structure of a hybrid commutation valve provided according to an embodiment of this application is shown.

[0023] The above figures include the following reference numerals:

[0024] 10. Controller; 20. Voltage detection circuit; 30. Gate pulse amplifier circuit; 40. IGCT device. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0027] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0028] For ease of description, the following explains some of the nouns or terms used in the embodiments of this application:

[0029] Integrated Gate-Commutated Thyristor (IGCT): An IGCT is a power electronic device that combines the high power handling capability of a thyristor with the fast gate-controlled turn-off characteristics of an insulated-gate bipolar transistor (IGBT), making it suitable for high-voltage, high-power power conversion systems.

[0030] Peak value of the continuous operating voltage (PCOV), including commutation overshoot, is an important parameter for determining the reference voltage of the DC surge arrester in the converter station.

[0031] As described in the background section, due to the inherent characteristics of IGCTs, they cannot achieve active voltage equalization through driving. Therefore, to ensure consistent voltage equalization during IGCT operation, a scheme of parallel MOVs connecting device units can be adopted. The scheme of parallel MOVs connecting each IGCT stage provides the best voltage equalization effect. However, the fewer devices protected by the MOVs, the more susceptible the MOVs are to the adverse effects of direct current flow overheating caused by IGCT turn-on failure. Currently, there are solutions that use series fuses to allow the MOVs to be melted and disconnected in case of overheating. However, such solutions are passive disconnections, and the MOVs cannot be reused after cooling down due to overheating, posing an economic problem. To address the problem that existing converter valves damage the surge arresters connected in parallel with the IGCT after IGCT turn-on failure, leading to low system reliability, embodiments of this application provide an overvoltage protection method, an overvoltage protection device, and a converter valve system for a converter valve.

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0033] This embodiment provides an overpressure protection method for a converter valve. Figure 1 This is a flowchart of an overpressure protection method for a converter valve according to an embodiment of this application. Figure 1 As shown, the method includes the following steps:

[0034] Step S101: Obtain the anode voltage of the IGCT device in the converter valve;

[0035] Specifically, the anode voltage is first obtained by monitoring the anode voltage of the device through a voltage sensor or internal circuitry, which is used to reflect whether the IGCT device has lost pulses.

[0036] Step S102: Determine whether the IGCT device has lost a pulse based on the magnitude and duration of the anode voltage of the IGCT device.

[0037] Specifically, under normal operating conditions, the IGCT should only turn on upon receiving a trigger pulse. If the voltage across the IGCT abnormally increases and remains elevated for a certain period (exceeding the set threshold and duration), it may be because the IGCT has not turned on as expected, i.e., pulse loss has occurred. By comparing the voltage with the preset threshold and duration, it is possible to effectively detect whether the IGCT is in an abnormal state, i.e., whether it has lost the trigger pulse, which helps to identify potential fault sources in a timely manner.

[0038] Step S103: In the event that the IGCT device loses its pulse, the initial overvoltage protection voltage of the IGCT device is reduced to the target overvoltage protection voltage and maintained for a first preset duration. If a preset condition is met within the first preset duration, the IGCT device is controlled to turn on to prevent the surge arrester from malfunctioning. The preset condition is that the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage. The target overvoltage protection voltage is the overvoltage protection voltage of the IGCT device to prevent the surge arrester from malfunctioning. The surge arrester and the IGCT device are connected in parallel.

[0039] Specifically, once the IGCT pulse loss is confirmed, the system automatically adjusts the IGCT's overvoltage protection threshold, lowering it from a high initial threshold to a lower target threshold. This is because when the IGCT is not conducting properly, the MOV connected to it may experience higher voltage, leading to overheating or even damage. By lowering the overvoltage protection threshold, the IGCT can be triggered even with a slight increase in abnormal voltage, thus preventing the MOV from experiencing excessive voltage and reducing the risk of MOV damage. The initial preset duration ensures that the IGCT remains in a more sensitive protection state during the fault period until the fault is cleared or further processing is performed.

[0040] If the adjusted overvoltage protection threshold is still insufficient to prevent the voltage across the IGCT from continuing to rise and reaching or exceeding the target overvoltage protection voltage, the system will forcibly open the IGCT, allowing current to flow through the IGCT instead of just through the MOV, thereby protecting the MOV from damage. By forcibly opening the IGCT, even under abnormal conditions, an alternative path is provided to release excess voltage energy, preventing the MOV from overheating and blowing. This step is essentially an emergency protection measure, ensuring that the system can react quickly to overvoltage threats and protect critical components.

[0041] For IGCT devices to operate normally, overvoltage protection schemes need to be configured at both the hardware and software levels. Hardware overvoltage protection mainly relies on BOD devices and parallel voltage limiting circuits; software overvoltage protection primarily relies on overvoltage protection triggering. Currently, HCC converter valves are mainly equipped with these two types of overvoltage protection.

[0042] However, currently, the MOV is directly connected in parallel across both sides of the IGCT, making it susceptible to cascading failures due to IGCT malfunctions. In the event of a signal transmission line fault or IGCT pulse loss, the IGCT will be unable to receive a switching signal. At this time, the MOV will directly carry the bridge arm current during the bridge arm conduction period, continuously absorbing energy and generating heat, eventually leading to MOV damage. For a scheme where each stage of the device has a parallel MOV, such failures are unavoidable. Therefore, to prevent abnormal damage to the MOV, other over-energy protection schemes need to be implemented. Therefore, we consider configuring an MOV monitoring strategy directly on the IGCT driver board to prevent MOV damage.

[0043] Figures 2(a)-(d) are schematic diagrams comparing the surge arrester current under different overvoltage conditions. As shown in Figures 2(a)-(d), Figure 2(a) is the circuit diagram of the IGCT when it is actively turned off, Figure 2(c) is the current diagram of the surge arrester branch when the IGCT is actively turned off, Figure 2(b) is the circuit diagram of the IGCT when the turn-on pulse is lost, and Figure 2(d) is the current diagram of the surge arrester branch when the IGCT turn-on pulse is lost. As shown in Figures 2(a)-(d), since the MOV will directly carry current after the pulse is lost, the device has a large anode voltage. Although the IGCT can monitor the anode voltage through the drive, due to the voltage limiting effect of the MOV, although it will not cause BOD to activate, it may cause the MOV to blow. Therefore, pulse loss judgment can be completed by identifying such abnormal current / abnormal voltage. After judging that the pulse is lost, the forward overvoltage protection threshold (BOD) of the IGCT with abnormal turn-on is switched to the secondary overvoltage protection threshold (SBOD) to avoid MOV current carrying.

[0044] The above embodiments allow protection to be untriggered under normal operating conditions, while permitting protection thresholds to be reached under extreme AC overvoltage and commutation enhancement conditions, with the driver itself shielding against secondary overvoltage protection malfunctions. Furthermore, upon detecting a secondary overvoltage signal, the driver should quickly switch the BOD threshold to trigger immediate protection, thus preventing continuous current flow through the MOV.

[0045] The overvoltage protection method for the converter valve described in this application first obtains the anode voltage of the IGCT device in the converter valve; then, based on the magnitude and duration of the anode voltage of the IGCT device, it determines whether the IGCT device has lost a pulse; finally, in the case of pulse loss, the initial overvoltage protection voltage of the IGCT device is reduced to the target overvoltage protection voltage and maintained for a first preset duration. If a preset condition is met within the first preset duration, the IGCT device is controlled to open to prevent arrester failure. The preset condition is that the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage. Since the arrester will directly conduct current after pulse loss, although the IGCT can monitor the anode voltage through drive, due to the arrester's voltage limiting effect, it may not cause the positive overvoltage protection threshold to activate, but it may lead to arrester fuse protection. Therefore, pulse loss can be determined by identifying such abnormal current / abnormal voltage. After pulse loss is determined, the forward overvoltage protection threshold of the abnormally activated IGCT is switched to the secondary overvoltage protection threshold, which can prevent the surge arrester from carrying current. This solves the problem that the existing converter valve will damage the surge arrester connected in parallel with the IGCT after the IGCT fails to activate, thus leading to low system reliability.

[0046] The process of determining whether the IGCT device has lost a pulse, based on the magnitude and duration of the anode voltage of the IGCT device, includes the following steps:

[0047] Step S201: Determine the target overvoltage protection voltage and the second preset duration. The second preset duration is the shortest duration during which the anode voltage is higher than the target overvoltage protection voltage after the IGCT device loses its pulse.

[0048] Step S202: Determine whether the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage (Uref).

[0049] Step S203: When the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage, determine whether the duration for which the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage exceeds the second preset duration (Tref).

[0050] Step S204: If the duration of the anode voltage of the IGCT device exceeds the second preset duration, it is determined that the IGCT device has lost a pulse.

[0051] Specifically, the target overvoltage protection voltage (Uref) and the second preset duration (Tref) are key parameters for determining whether an IGCT device has lost a pulse. The target overvoltage protection voltage is typically set slightly higher than the normal operating voltage, but lower than the voltage level that could damage the device or MOV (metal-oxide-semiconductor). The second preset duration is the time reference used to distinguish between normal voltage fluctuations and abnormal voltage rises. If the IGCT anode voltage is greater than or equal to the preset voltage value Uref, this may mean that the IGCT has failed to conduct as expected, or that an abnormal overvoltage has occurred in the circuit. Simply exceeding the set value is not enough to confirm that the IGCT has lost a pulse; it is also necessary to verify whether this overvoltage state has lasted for a certain period of time (i.e., beyond Tref). This is because, under certain normal operating conditions (such as voltage spikes), the IGCT may also experience brief overvoltages, but this does not indicate a device failure. If the IGCT anode voltage is greater than or equal to Uref, and this state lasts for the time Tref, then this likely means that the IGCT has not received or correctly responded to the trigger pulse, or that there is another type of fault in the circuit causing the persistent overvoltage. This confirmation step enables the system to accurately identify instances of IGCT pulse loss, thereby triggering subsequent protection actions, such as adjusting the overvoltage protection threshold or taking other emergency measures.

[0052] The above steps provide a dynamic assessment of the IGCT device's operating status, enabling immediate identification of potential anomalies, particularly pulse loss. Precisely set Uref and Tref effectively prevent protection malfunctions caused by brief voltage fluctuations, while ensuring timely response in the event of a fault, protecting the IGCT and its associated MOVs from damage, thereby improving the stability and reliability of the entire converter valve system. In this way, the system can not only monitor the health status of the IGCT device in real time but also take measures in the early stages of a fault, preventing escalation and greater losses. This refined control strategy is particularly important for applications with extremely high reliability requirements, such as high-voltage direct current transmission systems, as it significantly improves the system's adaptive protection capabilities and fault recovery speed without sacrificing normal operating performance.

[0053] Before determining whether the IGCT device has lost a pulse based on the magnitude and duration of the anode voltage of the IGCT device, the method further includes the following steps:

[0054] Step S301: Determine the minimum operating current of the converter valve and determine the minimum residual voltage of the surge arrester based on the minimum operating current. The minimum residual voltage corresponds to the minimum operating current.

[0055] Step S302: Determine the PCOV of the IGCT device. The PCOV is the peak value of the continuous operating voltage of the IGCT device including commutation overshoot. The PCOV is the maximum peak value of the voltage that the IGCT device can withstand during continuous operation for a preset time.

[0056] Step S303: Determine the target overvoltage protection voltage based on the minimum residual current voltage of the surge arrester and the PCOV of the IGCT device, wherein the target overvoltage protection voltage is greater than or equal to the PCOV of the IGCT device and less than or equal to the minimum residual current voltage of the surge arrester.

[0057] Specifically, the target overvoltage protection voltage Uref should not exceed the minimum residual voltage of the MOV. To avoid the impact on system operation caused by erroneous secondary overvoltage protection signals, the target overvoltage protection voltage should be higher than the system PCOV (i.e., the peak value of the continuous operating voltage including commutation overshoot). For example, if the minimum operating current of the system is 500A, the corresponding MOV residual voltage is approximately 4.3kV. To avoid the impact on system operation caused by erroneous secondary overvoltage protection signals, the target overvoltage protection voltage Uref should be designed to be higher than the PCOV of a single-stage device, calculated as Uref > PCOV / N (PCOV is a system parameter, meaning the peak value of the continuous operating voltage including commutation overshoot, and N is the number of series stages in the system without redundancy). For example, if the PCOV is 293kV and the number of series stages of a single valve is 80, then the PCOV of a single-stage device is approximately 3.66kV. Therefore, we can set 3.66kV ≤ target overvoltage protection voltage Uref ≤ 4.3kV, and thus the threshold Uref can be set to 3.7kV.

[0058] PCOV (peak value of the continuous operating voltage) refers to the highest continuous voltage that electrical equipment (such as converter valves) may encounter during normal operation of a power system, including all commutation processes. PCOV incorporates the effects of commutation overshoot and is a key indicator for assessing the voltage level faced by electrical equipment under continuous operating conditions.

[0059] Converter stations encounter various voltage conditions during operation, including normal DC voltage, overshoot voltage during commutation, and other potential transient voltage events. As crucial devices protecting converter valves from overvoltage damage, surge arresters must be designed and configured to match the power ductility control (PCOV) to ensure effective protection under all operating conditions. Specifically, the PCOV directly determines the surge arrester's reference voltage, which is its initial operating voltage during normal operation. The reference voltage needs to be set higher than the system's maximum continuous voltage level during normal operation, but not too high, to avoid affecting the surge arrester's response speed and energy absorption capacity.

[0060] Surge arresters (usually referring to valve arresters) are used to protect circuits from overvoltage surges. Their minimum current-carrying residual voltage (MPC) refers to the voltage across the arrester when it carries the minimum operating current of the circuit. This voltage value marks the starting point for the arrester to begin conducting significantly to dissipate excess voltage energy. By understanding the arrester's MPC under the minimum operating current condition of the converter valve, an upper limit can be set to ensure that the IGCT's overvoltage protection threshold does not exceed this range, preventing the arrester from being frequently activated under normal operating conditions, thus affecting its lifespan and circuit efficiency. PCOV refers to the maximum transient voltage that may occur when the IGCT is suddenly turned off after being turned on. This is a critical parameter used to assess the voltage surge capability that the IGCT can withstand. Defining the IGCT's PCOV helps set a lower limit for overvoltage protection, ensuring that the IGCT receives sufficient protection under all possible sudden conditions, preventing overvoltage breakdown and ensuring the safe operation of the equipment.

[0061] Ideally, the target overvoltage protection voltage Uref should be between the PCOV of a single-stage IGCT and the minimum residual voltage of the surge arrester. This ensures that overvoltage protection intervenes promptly when the IGCT fails but before the surge arrester activates, while preventing false triggering of protection during normal operation or minor voltage fluctuations. By precisely matching the characteristics of the surge arrester and IGCT, the target overvoltage protection voltage ensures effective protection of the IGCT while avoiding over-activation of the surge arrester, thus making the entire protection system more efficient and energy-saving. Furthermore, this setting enhances the system's robustness, providing stable protection over a wider voltage range without easily triggering unnecessary protection actions.

[0062] The aforementioned converter valve includes a surge arrester, which is connected in parallel with the aforementioned IGCT device (the specific structure is shown in Figures 2(a) and 2(b)). Determining the second preset duration includes the following steps:

[0063] Step S401: Obtain the active turn-off commutation time of the IGCT device, the time required for the surge arrester to absorb rated energy, the conduction time of the bridge arm current of the converter valve, and the shortest duration of the AC voltage of the converter valve. The active turn-off commutation time of the IGCT device is the time required for the IGCT device to switch from the on state to the off state. The time required for the surge arrester to absorb rated energy is the time required for the surge arrester to absorb rated energy under maximum current. The shortest duration of the AC voltage of the converter valve is the shortest duration for the AC voltage of the converter valve to rise to the target overvoltage protection voltage and remain stable.

[0064] Step S402: Based on the active turn-off commutation time of the IGCT device, the time required for the surge arrester to absorb rated energy, the conduction time of the bridge arm current of the converter valve, and the shortest duration of the anode voltage of the IGCT device, the second preset time is determined, wherein the second preset time is greater than the active turn-off commutation time of the IGCT device, greater than the shortest duration of the anode voltage of the IGCT device, less than the time required for the surge arrester to absorb rated energy, and less than the conduction time of the bridge arm current of the converter valve.

[0065] To prevent long-term current flow in the MOV, Tref must first be lower than the on-time of the bridge arm current, Ton. The on-time of the bridge arm current is as follows: .

[0066] Specifically, by collecting information at these critical time points, a comprehensive assessment of the dynamic conditions in the IGCT operating environment can be achieved. This ensures that the Tref setting can accommodate various possible operating scenarios, preventing false protection triggering during normal commutation or voltage fluctuations, while also ensuring timely response when a fault actually occurs. Through this setting logic, the Tref can effectively distinguish between temporary voltage fluctuations and genuine device faults. It ensures that the protection system can quickly and accurately identify abnormal states of the IGCT, adjust the overvoltage protection threshold in a timely manner, protect the MOV from damage, and avoid unnecessary protection actions that could impact system operation. This Tref setting improves the accuracy and reliability of overvoltage protection, contributing to the stable operation of the converter valve and extending the service life of related components.

[0067] The process of determining the second preset duration Tref ensures that the overvoltage protection mechanism can accurately assess the health status of the IGCT, thereby taking effective protective measures before a fault damages the circuit. This method avoids frequent false triggers caused by oversensitivity in the protection system, and also avoids the problem of failing to protect the circuit in time due to slow response. Through careful design of Tref, the system's operating efficiency and economy can be maximized while ensuring equipment safety.

[0068] The process of obtaining the active shutdown commutation time of the aforementioned IGCT device includes the following steps:

[0069] Step S40111: Obtain the commutation inductance of the converter valve, the DC current of the converter valve, and the voltage of a single bridge arm of the converter valve.

[0070] Step S40112: The first preset multiple of the product of the square of the DC current of the converter valve and the commutation inductance of the converter valve is determined as the first calculated value.

[0071] Step S40113: The product of the DC current of the converter valve and the voltage of a single bridge arm of the converter valve is determined as the second calculated value.

[0072] Step S40114: The ratio of the first calculated value to the second calculated value is determined as the active turn-off commutation time of the IGCT device.

[0073] To avoid overvoltage misidentification during active shutdown, the second preset duration Tref must be longer than the commutation time during active commutation when the IGCT's maximum turn-off current is reached under a three-phase ground fault on the AC side. For example, the maximum single active shutdown current Imax of the IGCT device is 10kA, and the leakage inductance L of the commutator transformer is 13.37mH. Under active commutation, the valve arrester and MOV simultaneously bear the commutation energy, with the valve arrester bearing the majority of the commutation energy. Therefore, the bridge arm current under active shutdown needs to be estimated based on the current shunting between the valve arrester and MOV. In the current case, the current shunting ratio after the valve arrester and N-level MOV are connected in series is approximately 7:3. When actively shutting off 10kA, the commutation voltage U1 provided by the bridge arm arresters (valve arrester and MOV) is approximately 387kV. The estimated single commutation time is approximately: Therefore, Tref > 690μs. Where L is the commutation inductance of the converter valve, I1 is the DC current of the converter valve, and U is the voltage of a single bridge arm of the converter valve. The first preset multiple is 2.

[0074] Specifically, by accurately calculating the commutation duration, normal commutation processes can be avoided from being misjudged as faults, reducing the possibility of false triggering of overvoltage protection and thus improving the overall performance and reliability of the protection mechanism. Once the lost pulse of the IGCT is accurately identified, the overvoltage protection threshold can be adjusted in a timely manner to prevent the MOV from being subjected to excessive voltage energy, reducing the probability of MOV damage, extending its service life, and lowering maintenance costs. Reasonable commutation duration calculation helps to balance the triggering timing of overvoltage protection, avoiding both overly conservative approaches that lead to protection delays and overly aggressive approaches that lead to frequent false trips, ensuring that the system has good self-protection capabilities while operating efficiently. By obtaining the active shutdown commutation duration of the IGCT device and using it as part of the overvoltage protection triggering logic, the effectiveness of the IGCT device-level overvoltage protection scheme can be significantly improved. This not only protects the IGCT and its related components (such as the MOV) from overvoltage damage but also optimizes the overall operational stability of the system, reducing operational risks and maintenance costs.

[0075] The time required to obtain the rated energy absorbed by the aforementioned surge arrester includes the following steps:

[0076] Step S40121: Obtain the rated energy of the surge arrester, the maximum turn-off current of the IGCT device, and the residual voltage of the surge arrester under the maximum turn-off current of the IGCT device.

[0077] Step S40122: The product of the maximum turn-off current of the IGCT device and the residual voltage of the surge arrester under the maximum turn-off current of the IGCT device is determined as the third calculated value.

[0078] Step S40123: The ratio of the rated energy of the surge arrester to the third calculated value is determined as the time required for the surge arrester to absorb the rated energy.

[0079] In the case of pulse loss in the aforementioned IGCT device, the time required for the surge arrester to absorb rated energy is actually the time required for the surge arrester to absorb rated energy under the direct-through bridge arm current condition.

[0080] To avoid long-term current flow in the MOV, Tref must first be lower than the on-time Ton of the bridge arm current, and secondly, it must be lower than the time required for the MOV to absorb rated energy under the maximum turn-off current of the IGCT.

[0081] Time required for an MOV to absorb rated energy at the maximum turn-off current of an IGCT: .

[0082] For example: The rated energy of an MOV is 80kJ, and its residual voltage at a current of 10kA is 5.4kV. Therefore, it can be calculated that: Where 80kJ is the rated energy of the surge arrester, U is the residual voltage of the IGCT device under the maximum turn-off current, and I is the maximum turn-off current of the IGCT device. Therefore, Tref < 1.48ms.

[0083] Specifically, by calculating the time required for a surge arrester to absorb its rated energy, it can be determined within what time frame the arrester can effectively protect the circuit from overvoltage damage. This provides crucial data for designing overvoltage protection strategies, ensuring the timeliness and effectiveness of protection measures. In overvoltage protection strategies, determining this duration helps set the trigger threshold for overvoltage protection. If the voltage of the IGCT device exceeds the threshold for longer than the time required for the surge arrester to absorb its rated energy, the system should immediately take measures, such as switching to secondary overvoltage protection, to prevent damage to the surge arrester due to energy exceeding limits, while simultaneously protecting the entire converter valve system. As a critical protective component in the converter valve system, the accurate calculation of the surge arrester's operating time helps ensure the stability and reliability of the entire system. In applications such as high-voltage direct current transmission, avoiding surge arrester overload is crucial for preventing system-level failures. The time required for the surge arrester to absorb rated energy, calculated through the above steps, can help system designers and maintenance personnel to more accurately understand and set the triggering conditions for overvoltage protection. This ensures that critical components such as the IGCT are effectively prevented from being damaged by overvoltage without harming the surge arrester, thereby maintaining the operational stability and safety of the converter valve system.

[0084] The aforementioned converter valve includes a multi-stage IGCT assembly, which in turn includes the aforementioned IGCT device. Obtaining the shortest duration of the AC voltage of the converter valve includes the following steps:

[0085] Step S40131: Obtain the number of IGCT components in series in the converter valve, the AC valve rated voltage of the converter valve, the AC grid angular velocity of the converter valve, and the load shedding coefficient of the converter valve. The AC valve rated voltage is the highest AC voltage of the converter valve when it is operating without faults.

[0086] Step S40132: The product of the number of IGCT components in the converter valve and the target overvoltage protection voltage is determined as the fourth calculated value, and the load shedding coefficient of the converter valve and the AC valve rated voltage of the converter valve are determined as the fifth calculated value.

[0087] Step S40133: The ratio of the fourth calculated value and the fifth calculated value is determined as the sixth calculated value;

[0088] Step S40134: The absolute value of the ratio of the inverse cosine function of the sixth calculated value to the AC grid angular velocity of the converter valve is determined as the shortest duration of the AC voltage of the converter valve.

[0089] To avoid false overvoltage identification under a load shedding factor of n, Tref should be at least greater than the duration during which the valve voltage is higher than the SBOD value Uref when the system is operating at a 90° transient operating condition (where the valve voltage is highest) during AC load shedding. Where n is the AC load shedding factor. Let N be the shortest duration of the AC voltage of the converter valve under n times the load shedding, where N is the number of IGCT components in the converter valve connected in series. The target overvoltage protection voltage, The AC valve rated voltage of the converter valve. This refers to the AC grid angular velocity of the converter valve. Taking a load shedding factor of 1.3 as an example: Therefore, Tref > 741.7μs.

[0090] Considering the above conditions, to ensure that no misjudgment occurs, Tref can be selected from 1 to 1.2 ms.

[0091] Specifically, by accurately calculating the shortest duration of AC voltage, system designers can more precisely set the overvoltage protection trigger threshold, avoiding false triggering of protection under brief voltage fluctuations or load shedding conditions. This enhances the system's self-regulation capability and stability in the face of grid fluctuations. The calculation result of the shortest duration provides an important time reference for the overvoltage protection mechanism, helping to distinguish between normal voltage fluctuations and abnormal voltage conditions requiring intervention. This ensures that the protection strategy can respond to potential threats in a timely manner while avoiding unnecessary interference, improving the targeting and efficiency of protection. By avoiding unnecessary overvoltage protection triggers, the number of maintenance operations caused by false triggers is reduced, lowering maintenance costs. Simultaneously, this also reduces downtime caused by maintenance, improving the overall availability and economic benefits of the system. In conclusion, calculating the shortest duration of AC voltage not only helps in designing smarter and faster-responding overvoltage protection strategies but also has significant positive effects on improving the operating efficiency of converter valve systems, reducing maintenance costs, and extending device lifespan.

[0092] The aforementioned converter valve includes a surge arrester, which is connected in parallel with the aforementioned IGCT device, and the aforementioned first preset duration is longer than the heat dissipation time of the surge arrester.

[0093] If the IGCT experiences prolonged pulse loss, and overvoltage duration is relied upon for judgment in each cycle, the MOV will absorb energy continuously for multiple cycles. Although the IGCT can be activated after identification, continuous energy accumulation in the MOV will lead to MOV failure. Therefore, to prevent the MOV from absorbing energy for the duration of Tref in each bridge arm conduction cycle when the device loses fiber, prolonged operation will also cause the MOV to melt and fail. The pulse loss signal needs to be maintained for a period of time. During this time, repeated overvoltage duration judgment is unnecessary, and the MOV can be adequately cooled. Therefore, the pulse loss signal extension duration should be greater than the MOV's cooling time.

[0094] Specifically, surge arresters generate heat when absorbing overvoltage. If the overvoltage duration exceeds their heat dissipation time, the surge arrester may overheat due to insufficient heat dissipation, ultimately leading to performance degradation or even damage. By setting a first preset duration longer than the surge arrester's heat dissipation time, the system can ensure that protective measures are taken before the surge arrester overheats, such as switching the IGCT to secondary overvoltage protection mode, thereby avoiding the risk of the surge arrester overheating due to continuous absorption of excessive energy. As a crucial protective component in the converter valve, the surge arrester's proper operation is essential for maintaining the overall reliability of the system. Through the above settings, even in the event of IGCT device failure or abnormal overvoltage, the surge arrester can obtain sufficient "rest" time, ensuring that it is still in optimal condition when it needs to function again, reducing the possibility of system failure due to surge arrester malfunction. The surge arrester's heat dissipation time is closely related to its durability and service life. By controlling the first preset duration, the workload of the surge arrester under extreme operating conditions is reduced, thereby helping to extend the surge arrester's service life and indirectly ensuring the long-term stable operation of the IGCT device. Preventing frequent overheating and damage to surge arresters reduces the frequency of system maintenance and repairs, lowering the costs associated with replacing or overhauling surge arresters during long-term operation. Simultaneously, this also optimizes system design and component selection, reducing overall maintenance costs by improving component efficiency and system operational economy.

[0095] The method further includes: in the event that the IGCT device loses a pulse, determining that the redundancy level of the converter valve is reduced by one.

[0096] Specifically, in the event of a lost pulse from an IGCT (Integrated Gate Commutated Thyristor) device, reducing the redundancy level of the converter valve by one is crucial to ensuring the safety and reliability of the converter valve system. The change in redundancy level directly reflects the actual number of usable IGCT devices. When a device loses a pulse and malfunctions, the system automatically adjusts the redundancy level; reducing it by one indicates that the system has detected this change, which is essential for monitoring the system's health. A reduction in redundancy levels signifies a decrease in system redundancy, triggering a series of protective measures and early warning strategies. For example, the system may automatically adjust its operating mode to a more conservative state, or increase the use of other protective components, such as enabling an additional MOV (Metal Oxide Varistor) or activating secondary overvoltage protection, to compensate for the missing device function and prevent further fault propagation. After the redundancy level change, the control system can reschedule resources and adjust current and voltage distribution according to the new redundancy status, ensuring the safe and stable operation of the remaining IGCT devices while preventing the entire converter valve from failing due to a single device failure.

[0097] To enable those skilled in the art to more clearly understand the technical solution of this application, the implementation process of the overvoltage protection method for the converter valve of this application will be described in detail below in conjunction with specific embodiments.

[0098] This embodiment relates to a specific overvoltage protection method for a converter valve. As Figure 3 shown, it includes the following steps:

[0099] Step S1: First, detect the anode voltage through the anode voltage. If the voltage exceeds the set value Uref, start calculating the overvoltage duration, and end the timing when the anode voltage is lower than Uref.

[0100] Step S2: If the overvoltage duration exceeds the set value Tref, it is determined that the device has lost pulses. Extend this pulse loss signal to ensure that the IGCT device is in the secondary overvoltage protection mode (SBOD = Uref) within a certain period; if the device has not lost pulses, the overvoltage protection mode still uses the BOD threshold.

[0101] Step S3: The overvoltage trigger signal is given through the gate pulse amplification signal. Among them, it is necessary to design Uref (overvoltage measurement threshold, secondary overvoltage protection level SBOD), the pulse loss duration criterion Tref, and the pulse loss extension duration Th.

[0102] Among them, Figure 3 The Chinese translation of Monostable is usually "monostable circuit" or simply "monostable" for short. This is an electronic circuit that can be stable in one state and will briefly switch to another state when triggered, and then automatically return to the original stable state. Monostable circuits are often used for functions such as generating timing pulses and delaying switches. In the context of the patent description, it is used to extend or adjust the duration of the overvoltage protection signal to ensure that the IGCT device can be protected in a timely and appropriate manner.

[0103] In the above-mentioned embodiment, when the converter valve is operating normally, it can ensure that the device does not undergo overvoltage breakdown, prevent device damage caused by external overvoltage and thus loss of redundancy; when a fiber optic dropout fault occurs, it can ensure that the device is stably triggered, a non-periodic turn-on occurs after the first recognition of the fault (MOV commutes the IGCT, with relatively large stress), and it will then work stably in the continuous secondary overvoltage protection state, avoiding MOV fusing and disconnection. There is no need to make excessive improvements to hardware devices and communication lines, mainly relying on drive logic detection; the monitoring of different IGCTs is independent of each other and will not be affected by other devices. And conventional overvoltage protection in the past could only achieve device protection and could not take into account the protection reliability under faults of auxiliary components such as MOV, making MOV rely only on fusing for fault removal, resulting in low utilization rate of components. The above-mentioned embodiment can achieve multi-level protection functions under device faults.

[0104] In some embodiments, the dynamically adaptive redundancy management system aims to automatically adjust the redundancy configuration of converter valves through real-time monitoring and cloud computing or edge computing technologies to cope with unforeseen operating conditions. The key to this system is its ability to intelligently adjust the redundancy levels of IGCT devices based on current operating status and changes in the external environment, ensuring that the system maintains optimal stability and efficiency under all circumstances.

[0105] Specifically, the steps include the following:

[0106] Real-time monitoring of the operating parameters of the IGCT device, including at least the anode voltage and ambient temperature of the IGCT device;

[0107] The operating parameters of the above-mentioned IGCT device are analyzed using a deep learning algorithm to predict the risk level of the above-mentioned IGCT device and obtain the prediction results. The deep learning algorithm is a machine learning model or a deep network model.

[0108] The redundancy level of the IGCT device is automatically adjusted based on the above prediction results. Specifically, when the prediction results indicate that the ambient temperature of the IGCT device reaches a preset high temperature threshold or the load reaches a preset high load threshold, the number of IGCT devices is increased to improve the redundancy level. When the prediction results indicate that the ambient temperature of the IGCT device decreases to a preset low temperature threshold or the load decreases to a preset low load threshold, the number of IGCT devices is reduced to decrease the redundancy level.

[0109] The system collects real-time data on the operating status of IGCT devices, ambient temperature, and load changes through a sensor network. This data is then sent to the cloud or edge computing devices for processing. Utilizing advanced data analysis algorithms, such as machine learning or deep neural networks, the system can analyze this data to predict potential failure risks of IGCT devices and the stability of system operation. Based on the data analysis results, the system can automatically adjust the redundancy levels. For example, under high-temperature or high-load conditions, the system can increase the redundancy levels to ensure sufficient backup devices to cope with potential failures; while under milder operating conditions, the redundancy levels can be appropriately reduced to improve system efficiency and economy. The system adopts a hybrid computing architecture, leveraging the powerful processing capabilities of cloud computing for complex data analysis and long-term prediction, while edge computing is responsible for real-time data processing and rapid response, ensuring that redundancy configuration adjustments are both accurate and timely.

[0110] In other embodiments, composite cooling materials with high thermal conductivity and low coefficient of thermal expansion can be developed, such as graphene-reinforced thermal pads or carbon nanotube-based heat dissipation films. These materials can effectively conduct heat generated by the device, improving the efficiency of the cooling system. For example, a cooling structure for an IGCT device includes a microchannel cooling assembly that integrates multiple tiny cooling channels, each in contact with both the IGCT and MOV devices. The geometry of these tiny cooling channels includes one of the following: linear, spiral, or mesh-like distribution. The cooling structure is communicatively connected to a controller, which acquires the temperatures of the IGCT and MOV devices in real time. The controller adjusts the operating power of the cooling structure in real time based on the temperatures of the IGCT and MOV devices. Specifically, when the temperature of the IGCT device is greater than a first temperature threshold and / or the temperature of the MOV device is greater than a second temperature threshold, the controller increases the operating power of the cooling structure. When the temperature of the IGCT device is less than or equal to the first temperature threshold and the temperature of the MOV device is less than or equal to the second temperature threshold, the controller keeps the operating power of the cooling structure constant.

[0111] When designing cooling systems for IGCT and MOV devices, microchannel cooling technology is employed, which integrates tiny cooling channels inside or around the device. These microchannels accelerate heat transfer and reduce the distance between the heat source and the cooling medium, thereby improving cooling speed and efficiency. Combined with temperature sensors and intelligent control algorithms, the system can dynamically adjust the cooling strategy based on the device's real-time temperature. For example, under high loads, the cooling system's workload is automatically increased, while under low loads, the cooling intensity can be appropriately reduced to save energy.

[0112] Another embodiment of this application also provides an overpressure protection device for a converter valve, such as... Figure 4 As shown, the circuit includes: a controller 10, used to execute at least one of the above-described overvoltage protection methods for the converter valve; a voltage detection circuit 20, electrically connected to the controller, used to acquire the anode voltage of the IGCT device 40 in the converter valve; and a gate pulse amplifier circuit 30, the input of which is electrically connected to the controller 10, and the output of which is electrically connected to the gate of the IGCT device 40. The gate pulse amplifier circuit 30 is used to amplify and output the gate control signal of the IGCT device 40 sent by the controller 10 to the gate of the IGCT device 40 when the anode voltage of the IGCT device 40 is greater than the target overvoltage protection voltage, so as to control the IGCT device 40 to turn on.

[0113] In the overvoltage protection device described in this application, the voltage detection circuit can monitor the anode voltage of the IGCT device in real time. Once the anode voltage is detected to be greater than or equal to the preset target overvoltage protection voltage, a signal is immediately sent to the controller. The system can respond to overvoltage events instantly, preventing damage to the IGCT device due to continuous overvoltage, thus enhancing the system's safety and the reliability of the IGCT device. After receiving the information from the voltage detection circuit, the controller can process and make decisions based on the preset overvoltage protection method. When protection is confirmed, it activates the gate pulse amplifier circuit to enhance the strength of the gate control signal, ensuring that the IGCT device can be accurately controlled to turn on or off. This precise control method helps avoid the failure of protection measures due to weak signals or interference. The gate pulse amplifier circuit amplifies and outputs a control signal when the IGCT anode voltage is higher than the target overvoltage protection voltage, which directly controls the on-state of the IGCT device. In this way, the circuit can quickly reduce the voltage borne by the IGCT device, preventing overvoltage breakdown and thus reducing the probability of the entire converter valve system facing overvoltage risks.

[0114] Another embodiment of this application also provides a converter valve system, including: a converter valve, including at least one IGCT assembly, the IGCT assembly including IGCT devices and surge arresters connected in parallel; and an overvoltage protection device for the converter valve.

[0115] As shown in Figure 2(a) or Figure 2(b), this is the structure of an IGCT component, in which the surge arrester is an MOV.

[0116] Specifically, such as Figure 5 As shown, the aforementioned converter valve is a hybrid commutation converter valve. Each bridge arm consists of multiple IGCT modules and saturated reactors connected in series, and each bridge arm is connected in parallel with a valve surge arrester. The valve surge arrester can also be connected in series with a fuse. Each IGCT module consists of an RC buffer circuit, a static voltage equalization resistor Rd, and a component voltage equalization MOV (MOV for short). The above overvoltage protection method is designed for single-stage IGCT pulse loss conditions. Under normal operating conditions, all IGCTs in the bridge arm should be turned on and off simultaneously. However, if a single-stage IGCT triggering fault or communication failure occurs, the single-stage IGCT may fail to turn on. In this case, the MOV of the faulty IGCT will directly pass through the bridge arm current. Long-term energy accumulation will damage the MOV, affecting the safety of the converter valve.

[0117] The converter valve system described in this application, through real-time monitoring and precise control of the anode voltage, can quickly take protective measures when the device is at risk of overvoltage, thus preventing damage to the IGCT device. This directly enhances the stability and durability of the IGCT component in the converter valve. Since the surge arrester is connected in parallel with the IGCT device, the converter valve indirectly protects the surge arrester by monitoring and controlling the voltage of the IGCT device, preventing it from absorbing high energy for extended periods due to abnormal conditions of the IGCT device (such as pulse loss), thereby reducing the risk of overheating and damage to the surge arrester and extending its service life. The overvoltage protection of the converter valve no longer relies solely on hardware measures (such as surge arresters and MOVs), but incorporates software logic judgment and control, forming a multi-layered protection system combining software and hardware. This comprehensive protection strategy significantly improves the overall operational reliability of the converter valve in applications such as high-voltage direct current transmission. This method helps reduce the failure rate of IGCT devices and surge arresters, reduces the high costs incurred due to frequent replacement of damaged devices, and also reduces maintenance workload, indirectly improving the economic efficiency of the converter valve system. By optimizing the operating conditions of IGCT devices and surge arresters, the aforementioned converter valve significantly enhances the stability and reliability of the converter valve system, reduces downtime due to failures, and improves economy and maintainability.

[0118] It is obvious to those skilled in the art that the modules or steps of the present invention described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. They can be implemented using computer-executable program code, and thus can be stored in a storage device for execution by a computing device. In some cases, the steps shown or described can be performed in a different order than those described herein, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, the present invention is not limited to any particular combination of hardware and software.

[0119] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0120] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0121] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0122] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0123] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0124] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0125] Computer-readable media include both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0126] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0127] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0128] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0129] 1) The overvoltage protection method for the converter valve described in this application first detects the anode voltage of the IGCT device in the converter valve; then, based on the magnitude and duration of the anode voltage of the IGCT device, it is determined whether the IGCT device has lost a pulse; finally, in the case of pulse loss of the IGCT device, the initial overvoltage protection voltage of the IGCT device is reduced to the target overvoltage protection voltage and maintained for a first preset duration. Within the first preset duration, if a preset condition is met, the IGCT device is controlled to open to prevent the surge arrester from malfunctioning. The preset condition is that the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage. Since the surge arrester will directly conduct current after the pulse is lost, although the IGCT can monitor the anode voltage through drive, due to the voltage limiting effect of the surge arrester, although it will not cause the positive overvoltage protection threshold to activate, it may cause the surge arrester to blow. Therefore, pulse loss can be determined by identifying such abnormal current / abnormal voltage. After pulse loss is determined, the forward overvoltage protection threshold of the abnormally activated IGCT is switched to the secondary overvoltage protection threshold, which can prevent the surge arrester from carrying current. This solves the problem that the existing converter valve will damage the surge arrester connected in parallel with the IGCT after the IGCT fails to activate, resulting in low system reliability.

[0130] 2) In the overvoltage protection device described in this application, the voltage detection circuit can monitor the anode voltage of the IGCT device in real time. Once the anode voltage is detected to be greater than or equal to the preset target overvoltage protection voltage, a signal is immediately sent to the controller. The system can respond to overvoltage events instantly, preventing damage to the IGCT device due to continuous overvoltage, thus enhancing the system's safety and the reliability of the IGCT device. After receiving the information from the voltage detection circuit, the controller can process and make decisions based on the preset overvoltage protection method. When protection is confirmed, it activates the gate pulse amplifier circuit to enhance the strength of the gate control signal, ensuring that the IGCT device can be accurately controlled to open or close. This precise control method helps avoid the failure of protection measures due to weak signals or interference. The gate pulse amplifier circuit amplifies and outputs a control signal when the IGCT anode voltage is higher than the target overvoltage protection voltage, which directly controls the opening state of the IGCT device. In this way, the circuit can quickly reduce the voltage borne by the IGCT device, preventing overvoltage breakdown and thus reducing the probability of the entire converter valve system facing overvoltage risks.

[0131] 3) The converter valve system described in this application, through real-time monitoring and precise control of the anode voltage, can quickly take protective measures when the device is at risk of overvoltage, avoiding damage to the IGCT device. This directly enhances the stability and durability of the IGCT component in the converter valve. Since the surge arrester is connected in parallel with the IGCT device, the converter valve indirectly protects the surge arrester by monitoring and controlling the voltage of the IGCT device, avoiding prolonged high-energy absorption caused by abnormal conditions of the IGCT device (such as pulse loss), thereby reducing the risk of overheating and damage to the surge arrester and extending its service life. The overvoltage protection of the converter valve no longer relies solely on hardware measures (such as surge arresters and MOVs), but incorporates software logic judgment and control, forming a multi-layered protection system combining software and hardware. This comprehensive protection strategy significantly improves the overall operational reliability of the converter valve in applications such as high-voltage direct current transmission. This method helps reduce the damage rate of IGCT devices and surge arresters, reduces the high costs incurred due to frequent replacement of damaged devices, and also reduces maintenance workload, indirectly improving the economic efficiency of the converter valve system. By optimizing the operating conditions of IGCT devices and surge arresters, the aforementioned converter valve significantly enhances the stability and reliability of the converter valve system, reduces downtime due to failures, and improves economy and maintainability.

[0132] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An overpressure protection method for a converter valve, characterized in that, include: Obtain the anode voltage of the IGCT device in the converter valve; Based on the magnitude and duration of the anode voltage of the IGCT device, determine whether the IGCT device has lost a pulse; In the event of a pulse loss in the IGCT device, the initial overvoltage protection voltage of the IGCT device is reduced to a target overvoltage protection voltage and maintained for a first preset duration. If a preset condition is met within the first preset duration, the IGCT device is controlled to turn on to prevent the surge arrester from malfunctioning. The preset condition is that the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage, wherein the target overvoltage protection voltage is the overvoltage protection voltage of the IGCT device to prevent the surge arrester from malfunctioning, and the surge arrester is connected in parallel with the IGCT device.

2. The method according to claim 1, characterized in that, Determining whether the IGCT device has lost a pulse based on the magnitude and duration of the anode voltage of the IGCT device includes: A second preset duration is determined, which is the shortest duration during which the anode voltage is higher than the target overvoltage protection voltage after the IGCT device loses a pulse; Determine whether the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage; If the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage, determine whether the duration for which the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage exceeds the second preset duration; If the duration of the anode voltage of the IGCT device exceeds the second preset duration, it is determined that the IGCT device has lost a pulse.

3. The method according to claim 1, characterized in that, Before determining whether the IGCT device has lost a pulse based on the magnitude and duration of the anode voltage of the IGCT device, the method further includes: Determine the minimum operating current of the converter valve, and determine the minimum residual voltage of the surge arrester based on the minimum operating current, wherein the minimum residual voltage corresponds to the minimum operating current; Determine the PCOV of the IGCT device, where PCOV is the peak value of the continuous operating voltage of the IGCT device including commutation overshoot; The target overvoltage protection voltage is determined based on the minimum residual current voltage of the surge arrester and the PCOV of the IGCT device; wherein the target overvoltage protection voltage is greater than or equal to the PCOV of the IGCT device and less than or equal to the minimum residual current voltage of the surge arrester.

4. The method according to claim 2, characterized in that, The converter valve includes a surge arrester, which is connected in parallel with the IGCT device; Determine the second preset duration, including: The active turn-off commutation time of the IGCT device, the time required for the surge arrester to absorb rated energy, the conduction time of the bridge arm current of the converter valve, and the shortest duration of the AC voltage of the converter valve are obtained. The active turn-off commutation time of the IGCT device is the time required for the IGCT device to switch from the on state to the off state. The time required for the surge arrester to absorb rated energy is the time required for the surge arrester to absorb rated energy using the maximum current. The shortest duration of the AC voltage of the converter valve is the shortest duration for the AC voltage of the converter valve to rise to the target overvoltage protection voltage and remain stable. The second preset duration is determined based on the active turn-off commutation duration of the IGCT device, the duration required for the surge arrester to absorb rated energy, the conduction duration of the bridge arm current of the converter valve, and the shortest duration of the anode voltage of the IGCT device; wherein the second preset duration is greater than the active turn-off commutation duration of the IGCT device, greater than the shortest duration of the anode voltage of the IGCT device, less than the duration required for the surge arrester to absorb rated energy, and less than the conduction duration of the bridge arm current of the converter valve.

5. The method according to claim 4, characterized in that, The active shutdown commutation time of the IGCT device is obtained, including: Obtain the commutation inductance of the converter valve, the DC current of the converter valve, and the voltage of a single bridge arm of the converter valve; The first calculated value is determined by a first preset multiple of the product of the square of the DC current of the converter valve and the commutation inductance of the converter valve. The product of the DC current of the converter valve and the voltage of a single bridge arm of the converter valve is determined as the second calculated value; The ratio of the first calculated value to the second calculated value is determined as the active shutdown commutation time of the IGCT device.

6. The method according to claim 4, characterized in that, The time required to obtain the rated energy absorbed by the surge arrester includes: The rated energy of the surge arrester, the maximum turn-off current of the IGCT device, and the residual voltage of the surge arrester under the maximum turn-off current of the IGCT device are obtained. The product of the maximum turn-off current of the IGCT device and the residual voltage of the surge arrester under the maximum turn-off current of the IGCT device is determined as the third calculated value. The ratio of the rated energy of the surge arrester to the third calculated value is determined as the time required for the surge arrester to absorb the rated energy.

7. The method according to claim 4, characterized in that, The converter valve includes a multi-stage IGCT assembly, the IGCT assembly including the IGCT device, and the method for obtaining the shortest duration of the AC voltage of the converter valve includes: The number of IGCT components in the converter valve, the AC valve rated voltage of the converter valve, the AC grid angular velocity of the converter valve, and the load shedding coefficient of the converter valve are obtained. The AC valve rated voltage is the highest AC voltage of the converter valve when it is operating without faults. The product of the number of IGCT components in the converter valve and the target overvoltage protection voltage is determined as the fourth calculated value, and the load shedding coefficient of the converter valve and the AC valve rated voltage of the converter valve are determined as the fifth calculated value. The ratio of the fourth calculated value to the fifth calculated value is determined as the sixth calculated value; The absolute value of the ratio of the inverse cosine function of the sixth calculated value to the AC grid angular velocity of the converter valve is determined as the shortest duration of the AC voltage of the converter valve.

8. The method according to claim 1, characterized in that, The converter valve includes a surge arrester, which is connected in parallel with the IGCT device, and the first preset duration is greater than the heat dissipation time of the surge arrester.

9. The method according to claim 1, characterized in that, The method further includes: In the event that the IGCT device loses a pulse, the redundancy level of the converter valve is reduced by one.

10. An overpressure protection device for a converter valve, characterized in that, include: A controller, at least for performing the overpressure protection method for the converter valve according to any one of claims 1 to 9; A voltage detection circuit, electrically connected to the controller, is used to acquire the anode voltage of the IGCT device in the converter valve; A gate pulse amplifier circuit is provided, wherein the input terminal of the gate pulse amplifier circuit is electrically connected to the controller, and the output terminal of the gate pulse amplifier circuit is electrically connected to the gate of the IGCT device. The gate pulse amplifier circuit is used to amplify the gate control signal of the IGCT device sent by the controller and output it to the gate of the IGCT device when the anode voltage of the IGCT device is greater than the target overvoltage protection voltage, so as to control the IGCT device to turn on.

11. A converter valve system, characterized in that, include: A converter valve, including at least one stage of IGCT assembly, the IGCT assembly including IGCT devices and surge arresters connected in parallel; The overpressure protection device for the converter valve as described in claim 10.

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