Method for overvoltage protection of a converter valve, overvoltage protection device for a converter valve and converter valve system

Abstract

The application provides a method for overvoltage protection of a converter valve, an overvoltage protection device of a converter valve and a converter valve system. The method comprises: obtaining an anode voltage of an IGCT device in the converter valve; determining whether the IGCT device loses a pulse according to the size and duration of the anode voltage of the IGCT device; if the IGCT device loses the pulse, reducing an initial overvoltage protection voltage of the IGCT device to a target overvoltage protection voltage and maintaining for a first preset time length, and controlling the IGCT device to be turned on under the condition that a preset condition is met within the first preset time length, so as to avoid failure of a lightning arrester, and the preset condition is that the anode voltage of the IGCT device is greater than or equal to the target overvoltage protection voltage. The method can complete the loss pulse judgment of the IGCT device through abnormal current flow / abnormal voltage, and after the pulse loss is judged, the forward overvoltage protection threshold of the IGCT which is abnormally turned on is switched to a secondary overvoltage protection threshold, so that the lightning arrester current flow can be avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-voltage direct current transmission, in particular to a method for overvoltage protection of a converter valve, an overvoltage protection device of a converter valve and a converter valve system. BACKGROUND

[0002] The core of the hybrid commutation converter valve in the field of high-voltage direct current transmission is the IGCT device. During the operation of the converter valve, it needs to have the ability to withstand a certain overvoltage, because a too high voltage impact is easy to cause the power electronic device to be broken down, thereby seriously endangering the stable operation state of the converter valve. Therefore, in the actual operation, it is necessary to match the corresponding overvoltage protection system for the power electronic element, such as the device-level parallel lightning arrester (hereinafter referred to as MOV) and the configuration of the drive-level overvoltage protection (BOD) and other measures.

[0003] Due to the characteristics of IGCT itself, it cannot rely on the drive to achieve the effect of active voltage equalization. Therefore, in order to ensure that IGCT can achieve the consistency of voltage equalization during operation, the device unit parallel MOV scheme can be used, and generally, MOV is connected in parallel for each level of IGCT. However, the fewer devices protected by MOV, the more likely it is that MOV will be adversely affected by the direct flow overheat phenomenon caused by the failure of IGCT to turn on. In the prior art, the scheme of connecting a fuse in series with the MOV is generally used to make the MOV be fused and cut off under the condition of overheating, but such a scheme is passive cutting, and the MOV cannot be used continuously after cooling down, which has economic problems. SUMMARY

[0004] The main purpose of the present application is to provide a method for overvoltage protection of a converter valve, an overvoltage protection device of a converter valve and a converter valve system, to at least solve the problem that the existing converter valve will damage the lightning arrester connected in parallel with the IGCT after the failure of the IGCT to turn on, thereby causing low system reliability.

[0005] In order to achieve the above object, according to one aspect of the present application, a method for overvoltage protection of a converter valve is provided, comprising: obtaining an anode voltage of an IGCT device in the converter valve; determining whether the IGCT device loses a pulse according to the size and duration of the anode voltage of the IGCT device; in the case that the IGCT device loses a pulse, lowering an initial overvoltage protection voltage of the IGCT device to a target overvoltage protection voltage and maintaining for a first preset time duration, and in the case that a preset condition is met within the first preset time duration, controlling the IGCT device to be turned on, so as to avoid failure of a surge arrester, the preset condition being 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 an overvoltage protection voltage of the IGCT device for avoiding failure of the surge arrester, and the surge arrester is connected in parallel with the IGCT device.

[0006] Optionally, the determining whether the IGCT device loses a pulse according to the size and duration of the anode voltage of the IGCT device comprises: determining a target overvoltage protection voltage and a second preset time duration, the second preset time duration being a shortest duration for which the anode voltage 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; in the case that 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 time duration; and in the case that the duration for which the anode voltage of the IGCT device exceeds the second preset time duration, determining that the IGCT device loses a pulse.

[0007] Optionally, before the determining whether the IGCT device loses a pulse according to the size and duration of the anode voltage of the IGCT device, the method further comprises: determining a minimum operating current of the converter valve, and determining a minimum residual voltage of the surge arrester according to the minimum operating current, the minimum residual voltage corresponding to the minimum operating current; determining a PCOV of the IGCT device, the PCOV being a peak value of a continuous operating voltage of the IGCT device containing a commutation overshoot; and determining the target overvoltage protection voltage according to the minimum 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 residual voltage of the surge arrester.

[0008] Optionally, the converter valve comprises a surge arrester connected in parallel with the IGCT device, and the second preset time length is determined by: obtaining a time length of active turn-off commutation of the IGCT device, a time length required for the surge arrester to absorb a rated energy, a time length of bridge arm current conduction of the converter valve, and a shortest time length of the AC voltage of the converter valve, the time length of active turn-off commutation of the IGCT device being a time required for the IGCT device to switch from a conduction state to an off state, the time length required for the surge arrester to absorb the rated energy being a time required for the surge arrester to absorb the rated energy under a maximum current, and the shortest time length of the AC voltage of the converter valve being a shortest time duration for which the AC voltage of the converter valve rises to the target overvoltage protection voltage and remains stable; and determining the second preset time length according to the time length of active turn-off commutation of the IGCT device, the time length required for the surge arrester to absorb the rated energy, the time length of bridge arm current conduction of the converter valve, and the shortest time length of the anode voltage of the IGCT device, wherein the second preset time length is greater than the time length of active turn-off commutation of the IGCT device, greater than the shortest time length of the anode voltage of the IGCT device, less than the time length required for the surge arrester to absorb the rated energy, and less than the time length of bridge arm current conduction of the converter valve.

[0009] Optionally, the time length of active turn-off commutation of the IGCT device is obtained by: obtaining a commutation inductance of the converter valve, a DC current of the converter valve, and a single bridge arm voltage of the converter valve; determining a first preset multiple of a product of a square of the DC current of the converter valve and the commutation inductance of the converter valve as a first calculation value; determining a product of the DC current of the converter valve and the single bridge arm voltage of the converter valve as a second calculation value; and determining a ratio of the first calculation value to the second calculation value as the time length of active turn-off commutation of the IGCT device.

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

[0011] Optionally, the converter valve comprises a multi-stage IGCT assembly, the IGCT assembly comprising the IGCT device, and the shortest duration of the AC voltage of the converter valve is obtained by: obtaining the number of series stages of the IGCT assembly 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 rejection factor of the converter valve, the AC valve rated voltage being the highest AC voltage when the converter valve is in fault-free operation; 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 calculation value, and determining the load rejection factor of the converter valve and the AC valve rated voltage of the converter valve as a fifth calculation value; determining the ratio of the fourth calculation value and the fifth calculation value as a sixth calculation value; and determining the absolute value of the ratio of the inverse cosine function of the sixth calculation value and 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 comprises a lightning arrester, the lightning arrester being connected in parallel with the IGCT device, and the first preset duration is greater than the heat dissipation time of the lightning arrester.

[0013] Optionally, in the case that the IGCT device loses a pulse, the number of redundant stages of the converter valve is determined to be one less.

[0014] According to another aspect of the present application, a kind of overvoltage protection device of converter valve is provided, comprising: controller, at least for executing any one described overvoltage protection method of converter valve;Voltage detection circuit, electrically connected with the controller, for obtaining the anode voltage of IGCT device in converter valve;Gate pulse amplification circuit, the input of the gate pulse amplification circuit is electrically connected with the controller, and the output of the gate pulse amplification circuit is used to be electrically connected with the gate of the IGCT device, and the gate pulse amplification circuit is used to amplify and output the gate control signal of the IGCT device sent by the controller to the gate of the IGCT device to control the IGCT device to open in the case that the anode voltage of the IGCT device is greater than target overvoltage protection voltage.

[0015] According to another aspect of the present application, a kind of converter valve system is provided, comprising: converter valve, comprising at least one level IGCT assembly, the IGCT assembly comprising parallelly connected IGCT device and lightning arrester;The overvoltage protection device of the described converter valve.

[0016] With the technical solution of the present application, the overvoltage protection method of the above-mentioned converter valve first acquires the anode voltage of the IGCT device in the converter valve; then determines whether the IGCT device loses the pulse according to the size and duration of the anode voltage of the IGCT device; and finally, in the case that the IGCT device loses the pulse, reduces the initial overvoltage protection voltage of the IGCT device to the target overvoltage protection voltage and maintains for a first preset time length, and controls the IGCT device to be turned on in the case that the preset condition is met within the first preset time length, so as to avoid the failure of the lightning arrester, and 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 direct flow of the lightning arrester will occur after the loss of the pulse, at this time, the device has a large anode voltage, and the IGCT can monitor the anode voltage through the driving, but due to the voltage limiting effect of the lightning arrester, although the positive overvoltage protection threshold will not act, the lightning arrester may be blown. Therefore, the loss of the pulse can be determined by identifying such abnormal flow and / or abnormal voltage, and after determining the loss of the pulse, the positive overvoltage protection threshold of the abnormal IGCT is switched to the secondary overvoltage protection threshold, so as to avoid the flow of the lightning arrester, and solve the problem that the existing converter valve will damage the lightning arrester connected in parallel with the IGCT after the IGCT fails to turn on, and thus the system reliability is low. BRIEF DESCRIPTION OF DRAWINGS

[0017] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their description serve the purpose of explaining the present application. The accompanying drawings do not constitute an inappropriate limitation on the present application. In the drawings:

[0018] Figure 1 A flowchart of an overvoltage protection method of a converter valve according to an embodiment of the present application is shown;

[0019] FIGS. 2(a)-2(d) show lightning arrester current contrast diagrams under different overvoltages according to an embodiment of the present application;

[0020] Figure 3 A flowchart of another overvoltage protection method of a converter valve according to an embodiment of the present application is shown;

[0021] Figure 4 A structural diagram of an overvoltage protection device of a converter valve according to an embodiment of the present application is shown;

[0022] Figure 5 A structural diagram of a hybrid commutation converter valve according to an embodiment of the present application is shown.

[0023] Among the above-mentioned drawings, the following reference signs are included:

[0024] 10, controller; 20, voltage detection circuit; 30, gate pulse amplification circuit; 40, IGCT device. DETAILED DESCRIPTION

[0025] It should be noted that the embodiments and features of the embodiments in the present application can be combined with each other without conflict. The technical solutions in the embodiments of the present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0026] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0027] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not necessarily limit to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0028] For the convenience of description, the following describes some nouns or terms related to the embodiments of the present application:

[0029] IGCT (Integrated Gate-commutated Thyristor) is a power electronic device that combines the high-power processing capability of thyristor and the fast gate control turn-off characteristics of IGBT (Insulated Gate Bipolar Transistor), and is suitable for high-voltage and high-power power conversion systems.

[0030] PCOV (peak value of the continuous operating voltage) is an important parameter for determining the reference voltage of the DC lightning arrester of the commutation 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 case that the IGCT device loses the pulse, the initial overvoltage protection voltage of the IGCT device is reduced to a target overvoltage protection voltage, and is maintained for a first preset time length, and in the case that a preset condition is met within the first preset time length, the IGCT device is controlled to be turned on, so as to avoid the failure of the lightning arrester, and 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 for avoiding the failure of the lightning arrester, and the lightning arrester is connected in parallel with the IGCT device.

[0039] Specifically, once it is confirmed that the IGCT loses the pulse, the system automatically adjusts the overvoltage protection threshold of the IGCT, which is reduced from a higher initial threshold to a lower target threshold. The reason for doing so is that when the IGCT does not conduct normally, the MOV connected in parallel with the IGCT may bear a higher voltage, leading to heating and even damage. By reducing the overvoltage protection threshold, the IGCT can be triggered when the abnormal voltage slightly rises, thereby avoiding the MOV from bearing an excessively high voltage and reducing the risk of damage to the MOV. The first preset time length is to ensure that during the failure, the IGCT can be in a more sensitive protection state until the failure is cleared or further processing is performed.

[0040] When the adjusted overvoltage protection threshold is still insufficient to prevent the voltage across the IGCT from continuing to rise to or beyond the target overvoltage protection voltage, the system forcibly controls the IGCT to be turned on, so that the current can pass through the IGCT instead of only passing through the MOV, thereby protecting the MOV from being damaged. By forcibly turning on the IGCT, even in abnormal situations, another path is provided for the circuit to release excess voltage energy, avoiding the risk of the MOV being blown due to overheating. This step is essentially an emergency protection measure, which ensures that the system can quickly respond when facing an overvoltage threat and protect critical components.

[0041] The overvoltage protection scheme of the IGCT device needs to be configured from the hardware and software levels. The hardware overvoltage protection mainly uses BOD devices and parallel voltage limiting circuits; the software overvoltage protection mainly uses overvoltage protection triggering. Currently, HCC converter valves mainly configure these two types of overvoltage protection.

[0042] But at present, MOV is directly connected in parallel with IGCT on both sides, which is easy to be affected by IGCT fault state and lead to chain failure. After the failure of signal transmission line or the loss of IGCT pulse, IGCT will not be able to obtain the switching signal, at this time MOV will pass through the bridge arm current during the bridge arm conduction, and the continuous energy absorption and heating will cause the damage of MOV. As for the scheme of parallel connection of MOV for each device, such failure cannot be avoided, therefore, in order to avoid the abnormal damage of MOV, other over-energy protection schemes need to be set for it. Therefore, the MOV monitoring strategy is considered to be directly configured to the IGCT drive board to avoid the damage of MOV.

[0043] FIGS. 2(a)-2(d) are a schematic diagram of arrester current under different overvoltages, as shown in FIGS. 2(a)-2(d), FIG. 2(a) is a circuit principle diagram when IGCT actively turns off, FIG. 2(c) is a current schematic diagram of arrester branch when IGCT actively turns off, FIG. 2(b) is a circuit principle diagram when IGCT opening pulse loss, and FIG. 2(d) is a current schematic diagram of arrester branch when IGCT opening pulse loss. As shown in FIGS. 2(a)-2(d), since MOV will directly pass through current after pulse loss, at this time, the device has a large anode voltage, IGCT can monitor the anode voltage through the drive, but due to the limiting pressure of MOV, although BOD will not act, MOV may be blown to protect. Therefore, the loss of pulse can be determined by identifying such abnormal current / abnormal voltage, and after determining the loss of pulse, the positive overvoltage protection threshold (BOD) of the IGCT with abnormal opening is switched to the secondary overvoltage protection threshold (SBOD), which can avoid the flow of MOV.

[0044] The above embodiment can make the protection not be triggered under normal operating conditions, and allow the protection threshold to be reached under extreme AC overvoltage conditions and commutation enhancement conditions, and the secondary overvoltage protection misoperation is avoided by shielding the drive itself. After the drive detects the secondary overvoltage signal, the BOD threshold should be switched as soon as possible to trigger it immediately, so as to avoid the continuous flow of MOV.

[0045] The overvoltage protection method of the above-mentioned converter valve of the present application first acquires the anode voltage of the IGCT device in the converter valve; then determines whether the IGCT device loses the pulse according to the size and duration of the anode voltage of the IGCT device; and finally, in the case where the IGCT device loses the pulse, reduces the initial overvoltage protection voltage of the IGCT device to the target overvoltage protection voltage and maintains for a first preset duration, and controls the IGCT device to be turned on in the case where the preset condition is met within the first preset duration, so as to avoid the failure of the lightning arrester, and 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 direct current flow of the lightning arrester will occur after the loss of the pulse, at this time, the device has a large anode voltage, and the IGCT can monitor the anode voltage through the drive, but due to the voltage limiting effect of the lightning arrester, although it will not cause the action of the forward overvoltage protection threshold, it may cause the fuse protection of the lightning arrester. Therefore, the loss of the pulse can be determined by identifying such abnormal current flow / abnormal voltage, and after determining the loss of the pulse, the forward overvoltage protection threshold of the IGCT which is abnormally turned on is switched to the secondary overvoltage protection threshold, so as to avoid the current flow of the lightning arrester, and solve the problem that the existing converter valve will damage the lightning arrester connected in parallel with the IGCT after the failure of the IGCT to turn on, and thus cause the low reliability of the system.

[0046] Wherein, determining whether the above-mentioned IGCT device loses the pulse according to the size and duration of the above-mentioned anode voltage of the IGCT device comprises the following steps:

[0047] Step S201, determining the target overvoltage protection voltage and the second preset duration, and the second preset duration is the shortest duration that the above-mentioned anode voltage is higher than the above-mentioned target overvoltage protection voltage after the above-mentioned IGCT device loses the pulse;

[0048] Step S202, determining whether the anode voltage of the above-mentioned IGCT device is greater than or equal to the above-mentioned target overvoltage protection voltage (Uref);

[0049] Step S203, in the case where the anode voltage of the above-mentioned IGCT device is greater than or equal to the above-mentioned target overvoltage protection voltage, determining whether the duration that the anode voltage of the above-mentioned IGCT device is greater than or equal to the above-mentioned target overvoltage protection voltage exceeds the above-mentioned second preset duration (Tref);

[0050] Step S204, in the case where the duration of the anode voltage of the above-mentioned IGCT device exceeds the above-mentioned second preset duration, determining that the above-mentioned IGCT device loses the pulse.

[0051] In particular, the target overvoltage protection voltage (Uref) and the second preset time length (Tref) are the key parameters for determining whether the IGCT device has lost the pulse. The target overvoltage protection voltage is usually set slightly higher than the normal operating voltage, but lower than the voltage level that can cause damage to the device or MOV (Metal Oxide Varistor). The second preset time length is a time reference for distinguishing between normal voltage fluctuations and abnormal voltage rises. If the IGCT anode voltage is greater than or equal to the pre-set voltage value Uref, it may mean that the IGCT fails to turn on as expected, or there is an abnormal overvoltage in the circuit. Just the voltage exceeding the set value is not enough to confirm that the IGCT has lost the pulse, it also needs to verify whether this overvoltage state has lasted for a certain time (i.e. exceeds Tref). This is because, under certain normal operating conditions (such as voltage spikes), the IGCT may also appear overvoltage for a short time, but this does not mean device failure. If the IGCT anode voltage is greater than or equal to Uref and this state lasts for Tref time, it is likely to mean that the IGCT has not received or properly responded to the trigger pulse, or there is other type of fault in the circuit causing continuous overvoltage. This confirmation step enables the system to accurately identify the situation where the IGCT has lost the pulse, thereby triggering subsequent protection actions such as adjusting the overvoltage protection threshold or taking other emergency measures.

[0052] The above steps provide dynamic evaluation of the operating state of the IGCT device, enabling identification of possible abnormalities, particularly loss of pulse, at the first time. By precisely setting Uref and Tref, it can effectively avoid protection misoperation due to temporary voltage fluctuations, while ensuring timely response when there is indeed a fault, protecting the IGCT and its associated MOV from being damaged, thereby improving the stability and reliability of the entire converter valve system. In this way, the system not only monitors the health status of the IGCT device in real time, but also takes measures at the early stage of failure to avoid escalation of the fault causing greater loss. This fine control strategy is particularly important for high-voltage direct current transmission systems and other applications with extremely high reliability requirements, as it can significantly improve the adaptive protection capability and fault recovery speed of the system without sacrificing normal operating performance.

[0053] Before determining whether the IGCT device has lost the pulse according to the size and duration of the anode voltage of the IGCT device, the method further comprises 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 according to the minimum operating current, the minimum residual voltage corresponding 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 containing commutation overshoot, PCOV is the maximum voltage peak value that the IGCT device can withstand for a predetermined time of continuous operation;

[0056] Step S303, determine the target overvoltage protection voltage according to the minimum residual voltage of the 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 voltage of the arrester.

[0057] Specifically, the target overvoltage protection voltage Uref needs to be no higher than the MOV minimum residual voltage and to avoid the impact on system operation caused by false secondary overvoltage protection signal, the target overvoltage protection voltage should be higher than the system PCOV (i.e. the peak value of the continuous operating voltage containing commutation overshoot). For example, the minimum operating current of the system is 500A, and the corresponding MOV residual voltage is about 4.3kV. To avoid the impact on system operation caused by false secondary overvoltage protection signal, the target overvoltage protection voltage Uref should be designed to be higher than the PCOV of the single-stage device, which is calculated as Uref>PCOV / N (PCOV is a system parameter, which means the peak value of the continuous operating voltage containing commutation overshoot, and N is the series number of the system without redundancy). For example: PCOV is 293kV, and the series number of the single valve is 80, so the PCOV of the single-stage device is about 3.66kV, therefore, the target overvoltage protection voltage Uref can be set as 3.66kV≤target overvoltage protection voltage Uref≤4.3kV, so the threshold Uref can be set as 3.7kV.

[0058] PCOV (peak value of the continuous operating voltage), i.e. the peak value of the continuous operating voltage, refers to the highest continuous voltage that the power system may encounter during normal operation, including all commutation processes. PCOV includes the influence of such commutation overshoot and is a key indicator for evaluating the voltage level faced by power equipment under continuous operation conditions.

[0059] Converter stations encounter various voltage situations during operation, including normal DC voltage, overshoot voltage during commutation, and other possible transient voltage events. As an important device for protecting the converter valve from overvoltage damage, the arrester must be designed and performed to match the PCOV to ensure effective protection under all operating conditions. Specifically, PCOV directly determines the reference voltage of the arrester, which is the initial operating voltage of the arrester during normal operation. The setting of the reference voltage needs to be higher than the maximum continuous voltage level of the system during normal operation, but cannot be too high to affect the response speed and energy absorption capacity of the arrester.

[0060] A surge arrester (typically referred to as a valve arrester) is used to protect electrical circuits from the impact of overvoltages. The minimum current residual voltage refers to the voltage that appears across the arrester when it is passing the minimum operating current of the circuit. This voltage value is the starting point for the arrester to begin conducting significantly to dissipate the excess voltage energy. By understanding the arrester residual voltage under the minimum operating current condition of the converter valve, an upper limit can be set to ensure that the overvoltage protection threshold of the IGCT does not exceed this range, preventing the arrester from being frequently activated under normal operating conditions, thus affecting its lifespan and the operating efficiency of the circuit. 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 for evaluating the voltage mutation capability that the IGCT can withstand. Clearly defining the PCOV of the IGCT helps set the lower limit of the overvoltage protection, ensuring that the IGCT is adequately protected under all possible transient states, preventing overvoltage breakdown of the device and ensuring safe operation of the equipment.

[0061] Ideally, the target overvoltage protection voltage Uref should be between the PCOV of the single-stage IGCT and the minimum current residual voltage of the arrester. This ensures that the overvoltage protection can intervene in time when the IGCT fails but does not reach the level of arrester activation, while avoiding false triggering of protection under normal operation or minor voltage fluctuations. By finely matching the characteristics of the arrester and the IGCT, the target overvoltage protection voltage can ensure effective protection of the IGCT while avoiding excessive activation of the arrester, making the entire protection system more efficient and energy-saving. In addition, this setting also enhances the robustness of the system, providing stable protection functions over a wider voltage range without easily triggering unnecessary protection actions.

[0062] Wherein, the above converter valve comprises an arrester, the above arrester is connected in parallel with the above IGCT device (the specific structure is shown in FIG. 2(a) and FIG. 2(b)), a second preset time length is determined, comprising the following steps:

[0063] Step S401, obtaining the active turn-off commutation time length of the IGCT device, the time length required for the arrester to absorb the rated energy, the bridge arm current conduction time length of the converter valve, and the shortest duration of the AC voltage of the converter valve. The active turn-off commutation time length of the IGCT device is the time required for the IGCT device to transition from the on state to the off state. The time length required for the arrester to absorb the rated energy is the time length required for the arrester to absorb the rated energy under 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;

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

[0065] Wherein, in order to avoid the long-term conduction of the MOV, Tref must be lower than the bridge arm current conduction time length Ton first, and the bridge arm current conduction time length: .

[0066] Specifically, by collecting the information of these key time lengths, the dynamic conditions in the IGCT operating environment can be comprehensively evaluated, ensuring that the setting of Tref can take into account various possible operating conditions, avoiding false triggering of protection during normal commutation or voltage fluctuations, while also ensuring timely response in the event of a real fault. Through such a setting logic, Tref can effectively distinguish between temporary voltage fluctuations and real device faults. It ensures that the protection system can quickly and accurately identify abnormal states of the IGCT, adjust the overvoltage protection threshold in time, protect the MOV from damage, while avoiding unnecessary protection actions affecting system operation. The Tref thus set improves the accuracy and reliability of overvoltage protection, helping to maintain the stable operation of the converter valve and prolong the service life of related components.

[0067] This process of determining the second preset time length Tref ensures that the overvoltage protection mechanism can accurately determine the health status of the IGCT, so that effective protective measures can be taken before the fault causes damage to the circuit. This method avoids the problem of frequent false triggering of the protection system due to excessive sensitivity, while also avoiding the problem of being unable to protect the circuit in time due to sluggishness. Through careful design of Tref, the safety of the equipment can be ensured while maximizing the efficiency and economy of the system.

[0068] Wherein, the active turn-off commutation time length of the IGCT device is obtained by the following steps:

[0069] Step S40111, obtaining the commutation inductance of the converter valve, the DC current of the converter valve, and the single bridge arm voltage of the converter valve;

[0070] Step S40112, determining 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 as the first calculation value;

[0071] Step S40113, determining the product of the DC current of the above-mentioned converter valve and the single bridge arm voltage of the above-mentioned converter valve as a second calculation value;

[0072] Step S40114, determining the ratio of the above-mentioned first calculation value and the above-mentioned second calculation value as the active turn-off commutation time length of the above-mentioned IGCT device.

[0073] To avoid overvoltage misrecognition of the active turn-off condition, the second preset time length Tref needs to be higher than the commutation time length of the active commutation of the maximum turn-off current of the IGCT under three-phase ground fault of the AC side. For example, the maximum current Imax of the single active turn-off of the IGCT device is 10 kA, and the converter leakage inductance L is 13.37 mH. Under the active commutation condition, the valve arrester and the MOV bear the commutation energy at the same time, and the valve arrester bears the main commutation energy. At this time, the bridge arm current under the active turn-off needs to be estimated according to the shunt of the valve arrester and the MOV. In the current case, the shunt ratio of the valve arrester and the N-level MOV in series is about 7:3. When the active turn-off is 10 kA, the commutation voltage U1 provided by the bridge arm arrester (valve arrester and MOV) is about 387 kV. It can be estimated that the single commutation time length is about: Therefore, Tref>690μs. Wherein, L is the commutation inductance of the converter valve, I1 is the DC current of the converter valve, and U is the single bridge arm voltage of the converter valve. The first preset multiple is 2.

[0074] Specifically, by accurately calculating the commutation time length, the normal commutation process can be avoided to be misjudged as a fault, the possibility of overvoltage protection mis-triggering is reduced, and the overall performance and reliability of the protection mechanism are improved. Once the IGCT loses the pulse is accurately identified, the overvoltage protection threshold can be adjusted in time to prevent the MOV from bearing excessive voltage energy, reduce the probability of MOV damage, prolong its service life, and reduce maintenance costs. Reasonable commutation time length calculation helps to balance the triggering time of overvoltage protection, neither too conservative leading to protection delay, nor too aggressive leading to frequent misoperation, ensuring that the system runs efficiently while having good self-protection ability. By obtaining the active turn-off commutation time length of the IGCT device and taking it as part of the overvoltage protection triggering logic, the efficiency of the IGCT device level overvoltage protection scheme can be significantly improved, not only protecting the IGCT and its related components (such as MOV) from overvoltage damage, but also optimizing the overall operation stability of the system, reducing the operation risk and maintenance cost.

[0075] Wherein, the time length required for the arrester to absorb the rated energy includes the following steps:

[0076] Step S40121, obtaining the rated energy of the above-mentioned arrester, the maximum turn-off current of the above-mentioned IGCT device, and the residual voltage of the above-mentioned arrester under the maximum turn-off current of the above-mentioned 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 at the maximum turn-off current of the IGCT device is determined as a third calculation value;

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

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

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

[0081] The time required for the MOV to absorb the rated energy under the maximum turn-off current of the IGCT: .

[0082] For example: the rated energy of the MOV is 80kJ, and the residual voltage under 10kA current is 5.4kV, so we can calculate: , wherein 80kJ is the rated energy of the surge arrester, U is the residual voltage under the maximum turn-off current of the IGCT device, and I is the maximum turn-off current of the IGCT device. Therefore, Tref<1.48ms.

[0083] Specifically, by calculating the time required for the surge arrester to absorb the rated energy, it can be determined that the surge arrester can effectively protect the circuit from overvoltage damage within a certain time. This provides key data for designing overvoltage protection strategies, ensuring the timeliness and effectiveness of protection measures. In the overvoltage protection strategy, the determination of this time helps to set the trigger threshold of the overvoltage protection. If the voltage of the IGCT device continues to exceed the threshold for a time longer than the time required for the surge arrester to absorb the rated energy, the system should immediately take measures such as switching to secondary overvoltage protection to avoid damage due to overload of the surge arrester, while protecting the entire converter valve system. The accurate calculation of the working time of the surge arrester as a key protection element in the converter valve system helps to ensure the stability and reliability of the entire system. In high-voltage direct current transmission and other applications, avoiding overload of the surge arrester is crucial to prevent system-level failures. The time required for the surge arrester to absorb the rated energy calculated by the above steps can help system designers and maintenance personnel better understand and set the trigger conditions for overvoltage protection, ensuring that key components such as IGCT are effectively protected from overvoltage damage without compromising the surge arrester, thereby maintaining the operational stability and safety of the converter valve system.

[0084] wherein the above converter valve comprises a plurality of IGCT assemblies, the IGCT assembly comprising the IGCT device, the shortest duration of the AC voltage of the converter valve comprises the following steps:

[0085] In step S40131, the number of series of the IGCT assembly 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 rejection factor of the converter valve are obtained, and the AC valve rated voltage is the highest AC voltage when the converter valve is in normal operation;

[0086] In step S40132, the product of the number of series of the IGCT assembly in the converter valve and the target overvoltage protection voltage is determined as a fourth calculation value, and the load rejection factor of the converter valve and the AC valve rated voltage of the converter valve are determined as a fifth calculation value;

[0087] In step S40133, the ratio of the fourth calculation value and the fifth calculation value is determined as a sixth calculation value;

[0088] In step S40134, the absolute value of the ratio of the inverse cosine function of the sixth calculation value and 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 overvoltage misidentification under n times load rejection factor, Tref should be at least greater than the duration when the valve voltage is higher than the SBOD value Uref when the AC load rejection occurs and the valve is just operating at 90° transient operating condition (the valve voltage is the highest in this condition): wherein n is the AC load rejection factor, the shortest duration of the AC voltage of the converter valve under n times load rejection, N is the number of series of the IGCT assembly in the converter valve, the target overvoltage protection voltage, the AC valve rated voltage of the converter valve, the AC grid angular velocity of the converter valve. Taking 1.3 times load rejection factor as an example: Therefore, Tref > 741.7 μs.

[0090] In summary, to ensure that misjudgment does not occur, Tref can be selected as 1-1.2 ms.

[0091] Specifically, by accurately calculating the minimum duration of the AC voltage, system designers can set the triggering threshold of the overvoltage protection more precisely, avoiding false triggering of the protection in the case of short-term voltage fluctuations or load shedding, thereby enhancing the self-regulation ability and stability of the system in the face of grid fluctuations. The calculation result of the minimum duration provides an important time reference for the overvoltage protection mechanism, helping to distinguish between normal voltage fluctuations and voltage abnormal situations that require intervention, ensuring 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 triggering, the number of maintenance times due to false triggering is reduced, and the maintenance cost is reduced. At the same time, this also reduces the downtime caused by maintenance, improving the overall availability and economic benefits of the system. In summary, calculating the minimum duration of the AC voltage not only helps to design a more intelligent and responsive overvoltage protection strategy, but also has a significant positive effect on improving the operating efficiency of the converter valve system, reducing maintenance costs, and prolonging the life of the device.

[0092] wherein the converter valve comprises a surge arrester, the surge arrester is connected in parallel with the IGCT device, and the first preset time duration is greater than a heat dissipation time of the surge arrester.

[0093] If the IGCT has a long-term pulse loss problem, the overvoltage duration is used to judge every cycle, and the MOV will absorb energy for multiple cycles. Although the IGCT can be turned on after recognition, the MOV also has continuous energy accumulation, which can cause MOV failure. Therefore, to prevent the device from falling off the fiber, the MOV absorbs energy for Tref duration every bridge arm conduction cycle, and the MOV will also be fused and fail after a long time of operation. The loss pulse signal needs to be maintained for a period of time, and during this time, the overvoltage duration does not need to be repeatedly judged, and the MOV can be fully cooled during this time. Therefore, the loss pulse signal extension duration should be greater than the MOV heat dissipation time.

[0094] Specifically, when absorbing overvoltage, the arrester generates heat. If the duration of overvoltage exceeds the heat dissipation time of the arrester, the arrester may overheat due to insufficient heat dissipation, eventually leading to performance degradation or even damage. By setting the first preset time period to be greater than the heat dissipation time of the arrester, the system can ensure that protective measures such as switching the IGCT to a secondary overvoltage protection mode are taken before the arrester overheats, thereby avoiding the risk of the arrester overheating due to continuous absorption of excessive energy. As an important protective component in the converter valve, the good operating state of the arrester is crucial to maintaining the overall reliability of the system. Through the above setting, even in the case of IGCT device failure or abnormal overvoltage, the arrester can obtain sufficient "rest" time, ensuring that it is still in the best state when it needs to function again, reducing the possibility of system failure due to arrester failure. The heat dissipation time of the arrester is closely related to its durability and service life. By controlling the first preset time period, the working burden of the arrester under extreme working conditions is reduced, thereby helping to prolong the service life of the arrester, and indirectly ensuring the long-term stable operation of the IGCT device. Avoiding frequent overheating and damage of the arrester reduces the frequency of system maintenance and repair, and reduces the cost of replacing or repairing the arrester during long-term operation. At the same time, this is also an optimization of system design and device selection, which improves the efficiency of device use and the economy of system operation, and reduces the overall maintenance cost.

[0095] In the above method, the method further comprises: in the case that the IGCT device loses a pulse, determining that the redundancy level of the converter valve is reduced by one.

[0096] Specifically, in the case that the IGCT (Integrated Gate Commutated Thyristor) device loses a pulse, determining that the redundancy level of the converter valve is reduced by one is to ensure the safety and reliability of the converter valve system. The change in redundancy level directly reflects the actual number of available IGCT devices. When a device loses a pulse and cannot work normally, the system automatically adjusts the redundancy level, and a decrease of one indicates that the system has detected this change, which is very important for monitoring the health of the system. The decrease in redundancy level means that the system redundancy decreases, which triggers a series of protection measures and warning strategies. For example, the system may automatically adjust the operating mode, enter a more conservative state, or increase the use of other protective components, such as enabling additional MOV (Metal Oxide Varistor) or starting secondary overvoltage protection, to compensate for the missing device function and avoid further spread of the fault. After the redundancy level changes, the control system can re-schedule resources according to the new redundancy state, adjust the distribution of current and voltage, and ensure that the remaining IGCT devices can operate safely and stably, while avoiding the failure of the entire converter valve due to a single device failure.

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

[0098] The present embodiment relates to a specific overvoltage protection method for a converter valve, as shown in the following steps: Figure 3

[0099] Step S1: First, the anode voltage is detected by the anode voltage, and if the voltage exceeds the set value Uref, the overvoltage duration is started to be calculated, and when the anode voltage is lower than Uref, the timing is ended.

[0100] Step S2: If the overvoltage duration exceeds the set value Tref, it is judged that the device loses the pulse, and the lost pulse signal is extended to ensure that the IGCT device is in the secondary overvoltage protection mode (SBOD=Uref) within a certain time; if the device does not lose the pulse, the overvoltage protection mode still uses the BOD threshold value.

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

[0102] Among them, Figure 3 The Chinese name of Monostable is usually "monostable circuit" or simply "monostable". It is an electronic circuit that can be stable in one state, and when triggered, it will switch to another state for a short time, and then automatically return to the original stable state. Monostable circuit is often used to generate timing pulses, delay switches, etc. In the context of 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 time and appropriately.

[0103] In the above embodiment, when the converter valve is running normally, it can ensure that the device does not overvoltage breakdown, prevent the device from being damaged by external overvoltage and then lose redundancy; when the fiber optic fault occurs, it can ensure that the device is triggered stably, and the first identification of the fault causes a non-periodic opening (MOV has a large stress on IGCT converter), and thereafter it works in a continuous secondary overvoltage protection state, avoiding causing the MOV to be blown off. No need to make too many hardware devices and communication line improvements, 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 the conventional overvoltage protection can only realize device protection, and cannot take into account the protection reliability under MOV and other auxiliary component faults, so that MOV can only rely on the fuse for fault removal, and the utilization rate of components is low. The above embodiment can realize the multi-level protection function under device failure. ​

[0104] In some embodiments, the dynamically adaptive redundancy management system aims to automatically adjust the redundancy configuration of the converter valve to cope with unforeseen operating conditions through real-time monitoring and cloud computing or edge computing technology. The key of this system is to intelligently adjust the redundancy level of IGCT devices according to the current operating state and changes in external environment, ensuring that the system maintains optimal stability and efficiency in any situation.

[0105] Specifically comprising the following steps:

[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] Using a deep learning algorithm to analyze the operating parameters of the IGCT device to predict the risk level of the IGCT device, obtaining a prediction result, and the deep learning algorithm is a machine learning model or a deep network model;

[0108] Based on the prediction result, automatically adjust the redundancy level of the IGCT device, wherein when the prediction result represents 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 increase the redundancy level, and when the prediction result represents 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 reduce the redundancy level.

[0109] That is, the system collects real-time data such as the working state of the IGCT device, the ambient temperature, and the load change through a sensor network, and these data are sent to the cloud or edge computing device for processing. Using advanced data analysis algorithms such as machine learning or deep neural networks, the system can analyze these data, predict the potential failure risk of the IGCT device and the stability of the system operation. Based on the data analysis results, the system can automatically adjust the redundancy level. For example, in high temperature or high load conditions, the system can increase the redundancy level to ensure that there are enough spare devices to cope with potential failures; while in relatively mild operating conditions, the redundancy level can be appropriately reduced to improve system efficiency and economy. The system uses a hybrid computing architecture, using the powerful processing power 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 the adjustment of the redundancy configuration is both accurate and timely.

[0110] In other embodiments, composite cooling materials with high thermal conductivity and low thermal expansion coefficient can be developed, such as graphene-reinforced thermal pads or carbon nanotube-based heat dissipation films, which can effectively conduct the heat generated by the device and improve the efficiency of the cooling system. For example, a cooling structure for IGCT devices includes a micro-channel cooling assembly that integrates multiple micro cooling channels in contact with IGCT devices and MOV devices. The geometry of the micro cooling channels includes one of the following: straight, spiral, and mesh distribution. The cooling structure is communicatively connected to a controller that obtains the temperature of the IGCT device and the temperature of the MOV device in real time. The controller adjusts the operating power of the cooling structure in real time based on the temperature of the IGCT device and the temperature of the MOV device. 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 controls the operating power of the cooling structure to remain unchanged.

[0111] That is, when designing the cooling system of IGCT and MOV devices, micro-channel cooling technology is used, that is, micro cooling channels are integrated inside or around the device. These micro channels can 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 according to the real-time temperature of the device. For example, when the load is high, the cooling system automatically increases the working strength, and when the load is low, the cooling strength can be appropriately reduced to save energy.

[0112] Another embodiment of the present application also provides an overvoltage protection device for a converter valve, as shown in Figure 4 The circuit includes a controller 10 for performing at least one of the above-mentioned overvoltage protection methods for a converter valve; a voltage detection circuit 20 electrically connected to the controller for obtaining the anode voltage of an IGCT device 40 in the converter valve; a gate pulse amplification circuit 30, the input end of the gate pulse amplification circuit 30 is electrically connected to the controller 10, the output end of the gate pulse amplification circuit 30 is electrically connected to the gate of the IGCT device 40, and the gate pulse amplification 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 to control the IGCT device 40 to turn on when the anode voltage of the IGCT device 40 is greater than the target overvoltage protection voltage.

[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 above commutation valve system of the present application can take protective measures quickly when the risk of overvoltage occurs in the device through real-time monitoring and accurate control of the anode voltage, avoiding damage to the IGCT device. This directly enhances the stability and durability of the IGCT components in the commutation valve. Since the arrester is connected in parallel with the IGCT device, the above commutation valve indirectly protects the arrester by monitoring and controlling the voltage of the IGCT device, avoiding long-term high-energy absorption of the arrester due to abnormal conditions of the IGCT device (such as pulse loss), thereby reducing the risk of overheating and damage of the arrester and prolonging its service life. The overvoltage protection of the commutation valve is no longer dependent on hardware measures (such as the arrester and MOV), but software logic judgment and control are added to form a multi-level protection system combining software and hardware. This comprehensive protection strategy significantly improves the overall operation reliability of the commutation valve in high-voltage direct current transmission and other applications. The method helps to reduce the damage rate of the IGCT device and the arrester, reduces the high cost caused by frequent replacement of damaged devices, and also reduces the maintenance workload, indirectly improving the economic benefit of the commutation valve system. The above commutation valve significantly enhances the stability and reliability of the commutation valve system by optimizing the working state of the IGCT device and the arrester, reduces the downtime, and improves the economy and maintainability.

[0118] Obviously, those skilled in the art should understand that the above-mentioned modules or steps of the present application can be realized by general computing devices, which can be concentrated on a single computing device or distributed on a network composed of multiple computing devices, and they can be realized by program codes executable by computing devices, so that they can be stored in storage devices and executed by computing devices, and in some cases, the steps shown or described can be executed in different order, or they can be made into individual integrated circuit modules, or multiple modules or steps can be made into a single integrated circuit module. Therefore, the present application is not limited to any specific combination of hardware and software.

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

[0120] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 one or more flow or blocks

[0121] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the function specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 one or more flow or blocks

[0122] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 one or more flow or blocks

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

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

[0125] Computer-readable media includes permanent and non-permanent, movable and non-movable media that can be implemented by any method or technology to store information. The information can be computer-readable instructions, data structures, program modules 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, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information accessible by a computing device. According to the definition herein, computer-readable media does not include transitory media such as modulated data signals and carriers.

[0126] The technical features of the above-described embodiments can be combined in any manner. In order to make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, but as long as the combinations of the technical features do not exist contradictions, it should be considered as the scope of the present disclosure.

[0127] It should also be noted that the terms "comprising", "including", or any other variant thereof are intended to cover non-exclusive inclusion, so that processes, methods, articles or devices including a series of elements not only include those elements, but also include other elements not explicitly listed, or inherent to such processes, methods, articles or devices. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0128] From the above description, it can be seen that the above-described embodiments of the present application achieve the following technical effects:

[0129] 1) The overvoltage protection method of the above-mentioned converter valve of the present application first detects the anode voltage of the IGCT device in the converter valve; then determines whether the IGCT device loses the pulse according to the size and duration of the anode voltage of the IGCT device; and finally, in the case of the IGCT device losing the pulse, reduces the initial overvoltage protection voltage of the IGCT device to the target overvoltage protection voltage and maintains for a first preset time length, and controls the IGCT device to open in the case of satisfying the preset condition within the first preset time length, so as to avoid the failure of the lightning arrester, and 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 direct flow of the lightning arrester will occur after the loss of the pulse, at this time, the device has a large anode voltage, and although the IGCT can monitor the anode voltage through the drive, due to the voltage limiting effect of the lightning arrester, although it will not cause the positive overvoltage protection threshold to act, it may cause the lightning arrester to fuse protection. Therefore, the loss of the pulse can be judged by identifying such abnormal flow / abnormal voltage, and after judging the loss of the pulse, the positive overvoltage protection threshold of the abnormal IGCT is switched to the secondary overvoltage protection threshold, which can avoid the flow of the lightning arrester, and solves the problem that the existing converter valve will damage the lightning arrester connected in parallel with the IGCT after the IGCT fails to open, resulting in low system reliability.

[0130] 2) In the above-mentioned overvoltage protection device of the present application, the voltage detection circuit can monitor the anode voltage of the IGCT device in real time, and once it detects that the anode voltage is greater than or equal to the preset target overvoltage protection voltage, it immediately sends a signal to the controller. The system can respond to the overvoltage event in time to avoid damage to the IGCT device due to sustained overvoltage, thereby enhancing the safety of the system and the reliability of the IGCT device. After receiving the information from the voltage detection circuit, the controller can process and decide the information according to the preset overvoltage protection method. When it confirms that protection is needed, it will activate the gate pulse amplification 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 to avoid the failure of protection measures due to weak signals or interference. The role of the gate pulse amplification circuit is to amplify and output the control signal when the anode voltage of the IGCT 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 that the IGCT device bears, preventing the device from being overvoltage breakdown, thereby reducing the probability of overvoltage risk faced by the entire converter valve system.

[0131] 3) The above-mentioned converter valve system of the present application can quickly take protective measures when the device is at risk of overvoltage, avoiding damage to the IGCT device through real-time monitoring and accurate control of the anode voltage. This directly enhances the stability and durability of the IGCT components in the converter valve. Since the arrester is connected in parallel with the IGCT device, the above-mentioned converter valve indirectly protects the arrester by monitoring and controlling the voltage of the IGCT device, avoiding long-term high-energy absorption of the arrester due to abnormal conditions of the IGCT device (such as pulse loss), thereby reducing the risk of overheating and damage to the arrester and prolonging its service life. The overvoltage protection of the converter valve is no longer dependent on hardware measures (such as arrester and MOV), but also includes software logic judgment and control, forming a multi-level protection system combining software and hardware. This comprehensive protection strategy significantly improves the overall operational reliability of the converter valve in high-voltage direct current transmission and other applications. This method helps to reduce the damage rate of IGCT devices and arresters, reduces the high cost of frequent replacement of damaged devices, and also reduces the maintenance workload, indirectly improving the economic benefits of the converter valve system. The above-mentioned converter valve significantly enhances the stability and reliability of the converter valve system by optimizing the working state of the IGCT device and the arrester, reduces the downtime due to faults, and improves the economy and maintainability.

[0132] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various changes and modifications to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present 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; 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 current 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 residual voltage of the surge arrester. 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. 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.

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 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.

4. The method according to claim 3, 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.

5. The method according to claim 3, 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.

6. The method according to claim 3, 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.

7. 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.

8. 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.

9. 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 8; 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.

10. A converter valve system, characterized in that, include: A converter valve includes at least one stage of an 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 9.

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