Surge protection method and apparatus for fully controlled valve in controllable line-commutated converter, computer device, computer readable storage medium and computer program product

Abstract

The present disclosure relates to the technical field of high-voltage direct-current power transmission, and provides a surge protection method and apparatus for a fully controlled valve in a controllable line-commuted converter, a computer device, a computer readable storage medium and a computer program product. The method comprises: monitoring a terminal voltage of a fully controlled valve in real time; when a wave turn-off voltage per cycle of a primary IGBT valve exceeds an operating voltage of a surge arrester, subtracting 1 from an available action count of the surge arrester of the primary IGBT valve, and when a wave turn-off voltage per cycle of a secondary IGBT valve exceeds an operating voltage of a surge arrester, subtracting 1 from an available action count of the surge arrester of the secondary IGBT valve; when the available action count of the surge arrester of the primary IGBT valve is less than a second preset count, or when the available action count of the surge arrester of the secondary IGBT valve is less than the second preset count, controlling a converter to return to a power grid line-commutation operation mode; and when the available action count of the surge arrester of the primary IGBT valve is greater than a third preset count, or when the available count of the surge arrester of the secondary IGBT valve is greater than the third preset count, controlling the converter to enter a controllable line-commutation operation mode.

Description

A controllable phase-commutating converter full-control valve lightning protection method and device, computer equipment, computer-readable storage medium, and computer program product

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The embodiments of the present disclosure are based on Chinese patent application number 202410115378.X, application date January 26, 2024, and application name “A method and device for lightning protection of a full-controlled valve of a controllable phase-commutating converter”, and claim the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby introduced into the present disclosure as a reference. Technical Field

[0003] The present disclosure relates to, but is not limited to, the field of high-voltage direct current transmission technology, and specifically to a method and device for lightning protection of a controllable commutation converter with a full-control valve, computer equipment, a computer-readable storage medium, and a computer program product. Background Art

[0004] High-voltage direct current (HVDC) transmission technology based on line commutated converters (LCC-HVDC) boasts the advantages of large transmission capacity, long distances, high efficiency, low losses, and a small footprint, and has been widely adopted worldwide. Due to the semi-controlled nature of the thyristor, the fundamental component, when the AC voltage at the receiving-end converter station of an LCC-HVDC system distorts or drops due to AC system faults or other reasons, the thyristors cannot reliably shut down, resulting in commutation failure in the converter. This is also a unique failure mode of conventional LCC converters. To address this commutation failure issue, a new controllable line-commutated converter (CLCC) topology with controllable shutdown capability has been developed. This topology utilizes a mix of fully controlled insulated-gate bipolar transistors (IGBTs) and semi-controlled thyristors, using IGBTs to assist in reliable thyristor recovery and shutdown, achieving controlled commutation between bridge arms.

[0005] When there are no AC faults in the system, the converter valves operate according to the normal alternating control sequence. The operating voltage of the fully controlled valves in the main and auxiliary branches is lower than the arrester's operating voltage, and the current flowing through the arrester is leakage current, which does not absorb energy. However, if the sub-valves open or close abnormally or the valve control system malfunctions, the IGBTs may shut off the high current and transfer it to the arrester branch, causing them to periodically or continuously absorb energy. Eventually, the energy absorbed reaches its upper limit, causing damage, which in turn affects the normal operation of the converter valves.

[0006] When an AC fault occurs in the system, the controllable commutation valves operate in a forced commutation control sequence. Under this sequence, the fully controlled valves of the controllable commutation valves actively shut off high currents, allowing the parallel surge arresters to flow high currents, building up voltage and facilitating commutation between the main and auxiliary branches, or between the bridge arms. The surge arresters absorb energy during this process, but do not exceed their tolerances. Abnormal opening and closing of sub-valves or valve control system failures can cause the surge arresters to absorb energy beyond their capacity, potentially damaging them and affecting the normal operation of the valves. Summary of the Invention

[0007] The technical problem to be solved by the present disclosure is to overcome the defect in the prior art that abnormal situations such as abnormal opening and closing of the sub-valve or failure of the valve control system lead to abnormal energy absorption of the lightning arrester, which is damaged when the energy limit is reached, thereby affecting the normal operation of the converter valve, thereby providing a controllable phase-changing converter full-control valve lightning protection method and device, computer equipment, computer-readable storage medium, and computer program product.

[0008] To achieve the above objectives, the present disclosure provides the following technical solutions:

[0009] In the first aspect, the embodiment of the present disclosure provides a controllable phase-changing converter full-control valve lightning protection method, each bridge arm of the converter is composed of a main branch and an auxiliary branch connected in parallel, the main branch is composed of a main thyristor valve and a main IGBT valve in series, the auxiliary branch is composed of an auxiliary IGBT valve and an auxiliary thyristor valve in series, the main IGBT valve and the auxiliary IGBT valve are both connected in parallel with a lightning arrester, and the controllable phase-changing converter full-control valve lightning protection method includes: real-time monitoring of the full-control valve terminal voltage, when the cycle turn-off voltage of the main IGBT valve exceeds the arrester action voltage, the number of available actions of the main IGBT valve lightning arrester is reduced by 1, and when the cycle turn-off voltage of the auxiliary IGBT valve exceeds the arrester action voltage , the number of available actions of the lightning arrester of the auxiliary IGBT valve is reduced by 1; the number of available actions of the lightning arrester is increased by a first preset number every first preset time; when the number of available actions of the lightning arrester of the main IGBT valve is less than the second preset number, the converter is controlled to return to the grid commutation operation mode; or, when the number of available actions of the lightning arrester of the auxiliary IGBT valve is less than the second preset number, the converter is controlled to return to the grid commutation operation mode; when the number of available actions of the lightning arrester of the main IGBT valve is greater than the third preset number, the converter is controlled to enter the controllable commutation operation mode; when the available number of times the lightning arrester of the auxiliary IGBT valve is greater than the third preset number, the converter is controlled to enter the controllable commutation operation mode.

[0010] In some embodiments, the first preset time and the first preset number of times should satisfy the following relationship: M=W / Ws, N≤M,

[0011] Among them, W is the design rated energy of the lightning arrester; Ws is the maximum energy that the lightning arrester can absorb normally in a single time; N is the initial value of the number of available actions set by the lightning arrester; a is the first preset time; b is the first preset number of times; H is the time it takes for the lightning arrester to absorb full energy again after absorbing full energy once.

[0012] In some embodiments, when the converter operates in a controllable commutation mode, the controllable commutation converter full-control valve lightning protection method also includes: real-time monitoring of the terminal voltage of the main IGBT valve; when the terminal voltage of the main IGBT valve continuously exceeds the first voltage reference value for a third preset time, it is determined that the lightning arrester of the main IGBT valve is overvoltage; and actively triggering the conduction of the main IGBT valve.

[0013] In some embodiments, the controllable commutation converter full-control valve lightning protection method also includes: within a period of time, when the terminal voltage of the main IGBT valve is higher than the second voltage reference value for a cumulative number of times reaching a fourth preset number, it is determined that the converter operation is abnormal, and the converter is controlled to permanently return to the grid commutation mode.

[0014] In some embodiments, when the converter operates in a controllable commutation mode, the controllable commutation converter full-control valve lightning protection method also includes: real-time monitoring of the terminal voltage of the auxiliary IGBT valve; when the terminal voltage of the auxiliary IGBT valve continuously exceeds the third voltage reference value for a fourth preset time, determining that the lightning arrester of the auxiliary IGBT valve is overvoltage; and actively triggering the conduction of the auxiliary IGBT valve.

[0015] In some embodiments, the controllable commutation converter full-control valve lightning protection method also includes: within a period of time, when the terminal voltage of the auxiliary IGBT valve is higher than the fourth voltage reference value for a cumulative number of times reaching a fourth preset number, it is determined that the converter operation is abnormal, and the converter is controlled to permanently return to the grid commutation mode.

[0016] In the second aspect, the embodiment of the present disclosure provides a controllable phase-changing converter full-control valve lightning protection device. Based on the method of the first aspect and any embodiment thereof, the controllable phase-changing converter full-control valve lightning protection device includes: a monitoring part, configured to monitor the full-control valve terminal voltage in real time, when the cycle shutdown voltage of the main IGBT valve exceeds the arrester action voltage, the number of available actions of the main IGBT valve lightning arrester is reduced by 1, and when the cycle shutdown voltage of the auxiliary IGBT valve exceeds the arrester action voltage, the number of available actions of the auxiliary IGBT valve lightning arrester is reduced by 1; every first preset time, the number of available actions of the lightning arrester increases by a first value. preset number of times; the first switching part is configured to control the converter to return to the grid commutation operation mode when the number of available actions of the lightning arrester of the main IGBT valve is less than the second preset number of times; or, when the number of available actions of the lightning arrester of the auxiliary IGBT valve is less than the second preset number of times, control the converter to return to the grid commutation operation mode; the second switching part is configured to control the converter to enter the controllable commutation operation mode when the number of available actions of the lightning arrester of the main IGBT valve is greater than the third preset number of times; when the available number of times the lightning arrester of the auxiliary IGBT valve is greater than the third preset number, control the converter to enter the controllable commutation operation mode.

[0017] In some embodiments, the controllable phase-commutating converter full-control valve lightning protection device also includes: a first single-cycle continuous overvoltage protection part, configured to monitor the terminal voltage of the main IGBT valve in real time; when the terminal voltage of the main IGBT valve continuously exceeds the first voltage reference value for a third preset time, it is determined that the lightning arrester of the main IGBT valve is overvoltage; and the main IGBT valve is actively triggered to be turned on; a second single-cycle continuous overvoltage protection part, configured to monitor the terminal voltage of the auxiliary IGBT valve in real time; when the terminal voltage of the auxiliary IGBT valve continuously exceeds the third voltage reference value for a fourth preset time, it is determined that the lightning arrester of the auxiliary IGBT valve is overvoltage; and the auxiliary IGBT valve is actively triggered to be turned on.

[0018] In some embodiments, the controllable commutation converter full-control valve lightning protection device also includes: a first multi-cycle continuous overvoltage protection part, configured to, within a period of time, when the terminal voltage of the main IGBT valve is higher than the second voltage reference value for a cumulative number of times reaching a fourth preset number, determine that the converter operation is abnormal, and control the converter to permanently exit the grid commutation mode; a second multi-cycle continuous overvoltage protection part, configured to, within a period of time, when the terminal voltage of the auxiliary IGBT valve is higher than the fourth voltage reference value for a cumulative number of times reaching a fourth preset number, determine that the converter operation is abnormal, and control the converter to permanently exit the grid commutation mode.

[0019] In a third aspect, an embodiment of the present disclosure provides a computer device comprising: at least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the controllable phase-commutated converter full-control valve lightning protection method of the first aspect of the embodiment of the present disclosure and any embodiment thereof.

[0020] In a fourth aspect, an embodiment of the present disclosure provides a computer-readable storage medium, which stores computer instructions, and the computer instructions are used to enable a computer to execute the controllable phase-commutated converter full-control valve lightning protection method of the first aspect of the embodiment of the present disclosure and any optional implementation manner thereof.

[0021] In the fifth aspect, an embodiment of the present disclosure provides a computer program product, which includes a computer program or instructions. When the computer program or instructions are run on a computer device, the computer device executes the controllable phase-commutated converter full-control valve lightning protection method of the first aspect of the embodiment of the present disclosure and any implementation method thereof. Beneficial effects:

[0022] The present disclosure aims at a controllable phase-changing converter valve that can resist phase-changing failure, and proposes a controllable phase-changing converter full-control valve arrester protection strategy. Corresponding to different working conditions or different operating sequences, according to the operating characteristics of the full-control sub-valve under different fault conditions of the full-control valve, by limiting the cumulative number of overvoltages or duration, different protection actions are taken to protect the full-control sub-valve arrester from damage, thereby improving the operating reliability of the converter valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific embodiments of the present disclosure or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] FIG1 is a schematic diagram of the structure of a controllable commutation converter provided by an embodiment of the present disclosure;

[0025] FIG2 is a flow chart of a method for protecting a controllable commutation converter with a fully controlled valve arrester according to an embodiment of the present disclosure;

[0026] FIG3 is a schematic diagram of the composition structure of a computer device provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0027] The technical solutions of the present disclosure are described clearly and completely below in conjunction with the accompanying drawings. Obviously, the embodiments described are only a portion of the embodiments of the present disclosure, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present disclosure without creative effort are within the scope of protection of the present disclosure.

[0028] In addition, the technical features involved in different embodiments of the present disclosure described below can be combined with each other as long as they do not conflict with each other.

[0029] An embodiment of the present disclosure provides a fully controlled valve lightning protection method for a controllable commutation converter. As shown in FIG1 , each bridge arm of the controllable commutation converter is composed of a main branch and an auxiliary branch in parallel. The main branch is composed of a main thyristor valve V11 and a main IGBT valve V12 in series. The auxiliary branch is composed of an auxiliary IGBT valve V13 and an auxiliary thyristor valve V14 in series. Both the main IGBT valve and the auxiliary IGBT valve are connected in parallel with a lightning arrester.

[0030] There are two operating modes for controllable commutation converters, namely line commutation mode (LCC) and controlled commutation mode (CLCC), as follows:

[0031] LCC operation mode: The full-control valve (V12) of the main branch of the controllable commutation converter bridge arm is locked, and the bypass thyristor valve in parallel with it is put into operation. It is triggered and turned on at the same time as the main branch thyristor, and the auxiliary branch is locked. The main branch of each bridge arm operates in the conventional LCC commutation valve mode, and the grid is commutated.

[0032] CLCC operation mode: The main branch IGBT valve and auxiliary branch of the controllable commutation converter bridge arm are put into operation, the main branch IGBT valve and bypass thyristor valve are locked, and the switch timing of each branch is divided into two situations according to whether an AC fault occurs:

[0033] (1) Normal alternating operation: When no AC fault is detected, the V12 sub-valve shut-off time is when the bridge arm current drops to a set lower reference value, and the auxiliary branch shut-off time is determined by the V12 shut-off time delay;

[0034] (2) Forced commutation operation: After an AC fault is detected, the V12 sub-valve is closed at the start of commutation, that is, when the CP signal of the other bridge arm participating in the commutation is issued. During the AC fault, the V12 closing time and the auxiliary branch V14 opening and V13 closing time are overall moved forward, and the delay time relative to the V12 closing time remains unchanged.

[0035] The disclosed embodiments are mainly divided into two categories for the protection strategies of fully controlled valve arresters. One is for the abnormal situation that the arrester absorbs energy normally in a single cycle but lasts for too long, and the other is mainly for the abnormal situation that the arrester absorbs energy abnormally in a single cycle and causes an over-limit. The valve control needs to have the function of monitoring the voltage at the fully controlled valve end. As shown in Figure 2, for the abnormal situation that the arrester absorbs energy normally in a single cycle but lasts for too long, the lightning protection method includes:

[0036] Step S11: Real-time monitoring of the voltage at the full-control valve end. When the cycle turn-off voltage of the main IGBT valve exceeds the arrester action voltage, the number of available actions of the arrester of the main IGBT valve is reduced by 1. When the cycle turn-off voltage of the auxiliary IGBT valve exceeds the arrester action voltage, the number of available actions of the arrester of the auxiliary IGBT valve is reduced by 1. Every first preset time, the number of available actions of the arrester increases by a first preset number of times.

[0037] Step S12: When the number of available actions of the lightning arrester of the main IGBT valve is less than the second preset number, the converter is controlled to return to the grid commutation operation mode; or, when the number of available actions of the lightning arrester of the auxiliary IGBT valve is less than the second preset number, the converter is controlled to return to the grid commutation operation mode.

[0038] Step S13: When the available action times of the lightning arrester of the main IGBT valve are greater than the third preset times, the converter is controlled to enter the controllable commutation operation mode; when the available action times of the lightning arrester of the auxiliary IGBT valve are greater than the third preset times, the converter is controlled to enter the controllable commutation operation mode.

[0039] Specifically, it is known that the design rated energy of the lightning arrester is W. After the lightning arrester absorbs full energy once, the time from the next full energy absorption is H. This time can ensure that the lightning arrester can fully dissipate heat after absorbing the first full energy. Assume that when the converter valve operates in the controllable phase-changing operation sequence, the maximum energy that the fully controlled valve lightning arrester can normally absorb in a single time is Ws. Set the number of available actions x for the lightning arrester, with an initial value of N, and the following relationship: M=W / Ws (1) N≤M (2)

[0040] Note: Taking appropriate margin into account, N is an integer less than or equal to M.

[0041] During operation, the valve control dynamically adjusts the available times x of the arrester. The valve control monitors the voltage at the full control valve end in real time. When the cycle shutoff voltage exceeds the action voltage U MOV, the available number of actions is reduced by 1. When the available number x≤4, the converter returns to LCC operation until the available number x≥5 is met and then re-enters CLCC mode operation. The valve control automatically increases the available number by b times (the first preset number) every unit time a (the first preset time). However, the available number shall not exceed the upper limit N. The following relationship is established:

[0042] Taking the fully controlled valve arrester of the main and auxiliary branches of an operating project as an example, the protection strategy of the available number of operations of the fully controlled valve arrester is explained.

[0043] For the main branch full-control valve arrester, the selected V12 sub-valve arrester absorbs full energy once and can absorb full energy again after a time interval of 4 hours. The nominal energy of the arrester is 456kJ. When the converter valve operates in the controllable phase-changing operation sequence, the full-control valve arrester can normally absorb a maximum energy of about 3.5kJ in a single time. The initial value is designed to be 120 times, which is the upper limit. During operation, the valve control dynamically adjusts the available times and monitors the V12 sub-valve terminal voltage in real time. The V12 sub-valve shut-off voltage exceeds the arrester action voltage U MOV12 , the available number of actions is reduced by 1. When the available number is ≤ 4, it returns to LCC operation until the available number ≥ 5 conditions are met and then re-enters CLCC mode operation. The valve control automatically increases the available number by 5 every 10 minutes, but the available number shall not exceed the upper limit.

[0044] Similarly, for the auxiliary branch full-control valve arrester, the time interval for the selected arrester to absorb full energy once and then absorb full energy again is 4 hours. The nominal energy of the arrester is 6MJ. When the converter valve operates in the controllable phase-changing operation sequence, the maximum energy absorbed by the full-control valve arrester in a single normal operation is about 300kJ. The initial value is designed to be 20 times, which is the upper limit. During operation, the valve control dynamically adjusts the available times and monitors the V13 sub-valve terminal voltage in real time. The V13 sub-valve shut-off voltage exceeds the arrester action voltage U MOV13 , the available number of actions is reduced by 1. When the available number is ≤ 4, it returns to LCC operation until the available number is ≥ 5 and then re-enters CLCC mode operation. The valve control automatically increases the available number by 2 every 30 minutes, but the available number shall not exceed the upper limit.

[0045] The disclosed embodiments provide two protection strategies for the abnormal situation of over-limit caused by abnormal single-cycle energy absorption of the arrester: a single-cycle continuous overvoltage protection strategy and a multi-cycle continuous overvoltage protection strategy. The specific strategies are as follows:

[0046] When the converter operates in the controllable commutation mode, the single-cycle continuous overvoltage protection strategy for the main IGBT valve includes: (1) real-time monitoring of the terminal voltage of the main IGBT valve; (2) when the terminal voltage of the main IGBT valve continuously exceeds the first voltage reference value for the third preset time, it is determined that the lightning arrester of the main IGBT valve is overvoltage; (3) actively triggering the conduction of the main IGBT valve.

[0047] When the converter operates in the controllable commutation mode, the single-cycle continuous overvoltage protection strategy for the auxiliary IGBT valve includes: (1) real-time monitoring of the terminal voltage of the auxiliary IGBT valve; (2) when the terminal voltage of the auxiliary IGBT valve continuously exceeds the third voltage reference value for the fourth preset time, it is determined that the lightning arrester of the auxiliary IGBT valve is overvoltage; (3) actively triggering the conduction of the auxiliary IGBT valve.

[0048] Specifically, the converter valve operates in CLCC mode, the valve control receives an AC fault signal, and the converter enters forced commutation operation sequence. There is a fault condition that keeps the current in the full-control valve arrester branch, and the full-control sub-valve is continuously over-voltage. When the current flowing through the arrester is high, the arrester absorbs energy rapidly and may quickly reach its energy absorption upper limit within a cycle. In order to avoid damage, the valve control is required to make judgments by real-time monitoring of the voltage at the full-control sub-valve end and protectively trigger the full-control sub-valve IGBT.

[0049] When the valve control monitors that the voltage at the full-control valve terminal is higher than the voltage reference value Urefs for a period of Ts, the valve control determines that the full-control valve arrester is overvoltage and actively triggers the full-control valve IGBT to turn on. Ts_down≤Ts≤Ts_up (4) Urefs_down≤Urefs≤Urefs_up (5)

[0050] Among them, Ts_down is the continuous operation time of the lightning arrester during normal forced commutation operation; Ts_up is the operation time when the lightning arrester absorbs the energy to the upper limit under abnormal conditions; Urefs_down is the lightning arrester operation voltage, and Urefs_up is the peak voltage of normal forced commutation operation.

[0051] When the converter operates in the controllable commutation mode, the multi-cycle continuous overvoltage protection strategy for the main IGBT valve includes: when the terminal voltage of the main IGBT valve is higher than the second voltage reference value for the cumulative number of times reaching a fourth preset number, the converter is determined to be operating abnormally, and the converter is controlled to permanently return to the grid commutation mode.

[0052] When the converter operates in the controllable commutation mode, the multi-cycle continuous overvoltage protection strategy for the auxiliary IGBT valve includes: within a period of time, when the terminal voltage of the auxiliary IGBT valve is higher than the fourth voltage reference value for the cumulative number of times reaching a fourth preset number, the converter is determined to be operating abnormally, and the converter is controlled to permanently return to the grid commutation mode.

[0053] Specifically, the converter valve operates in a controllable commutation mode, the valve control does not receive an AC fault signal, the converter operates in a normal alternating operation sequence, and the V12 sub-valve generally does not frequently overvoltage. If the measuring device or control system fails, the voltage at the full-control valve end increases and is significantly higher than the voltage during normal operation, and may even cause the lightning arrester to absorb energy periodically, which may reach its energy limit. In order to avoid damage to the lightning arrester due to continuous energy absorption under this abnormal operating condition, the valve control is required to make a judgment by real-time monitoring of the voltage at the full-control sub-valve end and permanently return to the grid commutation mode.

[0054] When the valve control monitors that the voltage at the full control valve end is higher than the voltage reference value Urefm for D times in the Tm time period, the valve control determines that the operation is abnormal and permanently returns to the LCC mode. Urefm_down≤Urefm≤Urefm_up (6)

[0055] Where Urefm_down is the peak terminal voltage during normal operation, and Urefm_up is the arrester operating voltage. In the case of non-AC faults, the values ​​of Tm and D are primarily determined based on the failure rate of the valve control system in different projects.

[0056] Taking the fully controlled valve arrester of the main and auxiliary branches of an operating project as an example, the abnormal situation of over-limit caused by abnormal single-cycle energy absorption of the arrester is explained.

[0057] 1. Main branch full control valve arrester protection strategy

[0058] The terminal voltage peak of the V12 sub-valve is about 15kV during normal operation, and about 27kV during normal forced commutation operation. The arrester action voltage is 20.9kV, and the nominal energy is 456kJ. It is known that the maximum duration of the voltage of the V12 sub-valve arrester exceeding 24kV under normal forced commutation operation is 123μs. Considering the most serious fault condition, when the system fault current is the largest, the current cannot be transferred from the main branch to the auxiliary branch. The V12 sub-valve arrester will absorb about 400kJ of energy within 8.5ms. Considering an appropriate energy margin, the following relationship is obtained: 0.123ms≤Ts≤8.5ms (7) 20.9kV≤Urefs≤27kV (8) 15kV≤Urefm≤20.9kV (9)

[0059] Considering appropriate energy margin, the single-cycle continuous overvoltage reference value Urefs of the V12 sub-valve is set to 24kV, and the duration Ts is set to 2ms. When the valve control determines that the V12 sub-valve meets the protection condition, the IGBT is actively triggered to turn on.

[0060] The converter valve is in controllable commutation mode and operates in normal alternating operation sequence. Due to a failure in the measuring device or control system, the valve control may determine that the V12 sub-valve has an abnormal multi-cycle continuous overvoltage. In the absence of an AC fault signal, the valve control monitors that the V12 sub-valve has overvoltage 10 times within 5 seconds (the voltage reference value Urefm is 20.9kV), and the converter valve permanently returns to LCC mode.

[0061] 2. Auxiliary branch full control valve arrester protection strategy

[0062] The terminal voltage peak of the V13 sub-valve is about 25kV during normal operation, and about 279kV during normal forced commutation operation. The arrester action voltage is 212kV, and the nominal energy is 6500kJ. It is known that the maximum duration of the voltage of the V13 sub-valve arrester exceeding 240kV under normal forced commutation operation is 1550μs. Considering the most serious fault condition, when the system fault current is the largest and cannot be switched to the next bridge arm, the V13 sub-valve arrester will absorb about 3000kJ of energy within 5ms, and the following relationship exists. 1.55ms≤Ts≤5ms (10) 212kV≤Urefs≤279kV (11) 25kV≤Urefm≤212kV (12)

[0063] Considering appropriate energy margin, the single-cycle continuous overvoltage reference value Urefs of the V13 sub-valve is set to 240kV, and the duration Ts is set to 3.5ms. When the valve control determines that the V13 sub-valve meets the protection condition, the IGBT is actively triggered to turn on.

[0064] The converter valve is in controllable commutation mode and operates in normal alternating operation sequence. Due to a failure in the measuring device or control system, the valve control may determine that the V13 sub-valve has an abnormal multi-cycle continuous overvoltage. In the absence of an AC fault signal, the valve control monitors that the V13 sub-valve has overvoltage 10 times within 5 seconds (the voltage reference value Urefm is 150kV), and the converter permanently returns to LCC mode.

[0065] The present disclosure provides a fully controlled valve lightning protection device for a controllable commutation converter. Based on the method of the above embodiment and any implementation method thereof, the fully controlled valve lightning protection device for a controllable commutation converter includes:

[0066] The monitoring part is configured to monitor the voltage at the full-control valve end in real time. When the cycle shutdown voltage of the main IGBT valve exceeds the arrester action voltage, the number of available actions of the main IGBT valve's arrester is reduced by 1. When the cycle shutdown voltage of the auxiliary IGBT valve exceeds the arrester action voltage, the number of available actions of the auxiliary IGBT valve's arrester is reduced by 1. Every first preset time, the number of available actions of the arrester increases by a first preset number. This module executes the method described in the above embodiment and will not be repeated here.

[0067] The first switching part is configured to control the converter to return to the grid commutation operation mode when the number of available actions of the lightning arrester of the main IGBT valve is less than the second preset number; or, when the number of available actions of the lightning arrester of the auxiliary IGBT valve is less than the second preset number, control the converter to return to the grid commutation operation mode; this module executes the method described in the above embodiments and will not be repeated here.

[0068] The second switching part is configured to control the converter to enter a controllable commutation operation mode when the number of available actions of the lightning arrester of the main IGBT valve is greater than a third preset number; when the number of available actions of the lightning arrester of the auxiliary IGBT valve is greater than a third preset number, control the converter to enter a controllable commutation operation mode; this module executes the method described in the above embodiment and will not be repeated here.

[0069] In some embodiments, the controllable phase-commutated converter full-control valve lightning protection device further includes:

[0070] The first single-cycle continuous overvoltage protection part is configured to monitor the terminal voltage of the main IGBT valve in real time; when the terminal voltage of the main IGBT valve continuously exceeds the first voltage reference value for the third preset time, it is determined that the lightning arrester of the main IGBT valve is overvoltage; and the main IGBT valve is actively triggered to be turned on; this module executes the method described in the above embodiment and will not be repeated here.

[0071] The second single-cycle continuous overvoltage protection part is configured to monitor the terminal voltage of the auxiliary IGBT valve in real time; when the terminal voltage of the auxiliary IGBT valve continuously exceeds the third voltage reference value for the fourth preset time, it is determined that the lightning arrester of the auxiliary IGBT valve is overvoltage; and the auxiliary IGBT valve is actively triggered to be turned on; this module executes the method described in the above embodiment and will not be repeated here.

[0072] In some embodiments, the controllable phase-commutated converter full-control valve lightning protection device further includes:

[0073] The first multi-cycle continuous overvoltage protection part is configured to determine that the converter operation is abnormal and control the converter to permanently return to the grid commutation mode when the cumulative number of times the terminal voltage of the main IGBT valve is higher than the second voltage reference value reaches a fourth preset number within a period of time; this module executes the method described in the above embodiment and will not be repeated here.

[0074] The second multi-cycle continuous overvoltage protection part is configured to determine that the converter operation is abnormal and control the converter to permanently return to the grid commutation mode when the cumulative number of times the terminal voltage of the auxiliary IGBT valve is higher than the fourth voltage reference value reaches a fourth preset number within a period of time; this module executes the method described in the above embodiment and will not be repeated here.

[0075] In the embodiments of the present disclosure and other embodiments, "part" can be part of a circuit, part of a processor, part of a program or software, etc., and of course it can also be a unit, a module, or a non-modular one.

[0076] An embodiment of the present disclosure provides a computer device, as shown in FIG3 , comprising: at least one processor 401, such as a CPU (Central Processing Unit), at least one communication interface 403, a memory 404, and at least one communication bus 402. The communication bus 402 is used to implement connection and communication between these components. The communication interface 403 may include a display screen and a keyboard, and the optional communication interface 403 may also include a standard wired interface or a wireless interface. The memory 404 may be a high-speed RAM memory (Ramdom Access Memory) or a non-volatile memory, such as at least one disk storage. The memory 404 may optionally be at least one storage device located away from the aforementioned processor 401. The processor 401 may execute the controllable commutation converter full-control valve lightning protection method of the above embodiment and any optional implementation thereof. The memory 404 stores a set of program codes, and the processor 401 calls the program codes stored in the memory 404 to execute the controllable commutation converter full-control valve lightning protection method of the above embodiment and any optional implementation manner thereof.

[0077] Communication bus 402 may be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus. Communication bus 402 may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, FIG3 shows only one line, but this does not mean that there is only one bus or only one type of bus.

[0078] Among them, the memory 404 may include a volatile memory (English: volatile memory), such as a random-access memory (English: random-access memory, abbreviated: RAM); the memory may also include a non-volatile memory (English: non-volatile memory), such as a flash memory (English: flash memory), a hard disk drive (English: hard disk drive, abbreviated: HDD) or a solid-state drive (English: solid-state drive, abbreviated: SSD); the memory 404 may also include a combination of the above types of memory.

[0079] The processor 401 may be a central processing unit (CPU), a network processor (NP), or a combination of a CPU and a NP.

[0080] The processor 401 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The PLD may be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a generic array logic (GAL), or any combination thereof.

[0081] Optionally, the memory 404 is further configured to store program instructions. The processor 401 may call the program instructions to implement the controllable commutation converter full-control valve lightning protection method in the above embodiment and any optional implementation manner thereof as described in the present application.

[0082] The present disclosure also provides a computer-readable storage medium having computer-executable instructions stored thereon, which can execute the controllable phase-commutated converter full-control valve lightning protection method of the above embodiment and any optional implementation thereof. The storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), a random access memory (RAM), a flash memory, a hard disk drive (HDD), or a solid-state drive (SSD); the storage medium can also include a combination of the above types of memory.

[0083] The embodiments of the present disclosure also provide a computer program product, which includes a computer program or instructions. When the computer program or instructions are run on a computer device, the computer device is enabled to execute the controllable phase-commutated converter full-control valve lightning protection method of the first aspect of the embodiments of the present disclosure and any implementation method thereof.

[0084] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications derived therefrom remain within the scope of protection of the present disclosure. Industrial Applicability

[0085] The embodiments of the present disclosure provide a method and apparatus for lightning protection of a fully controlled valve of a controllable commutation converter, a computer device, a computer-readable storage medium, and a computer program product, wherein the method includes: real-time monitoring of the voltage at the fully controlled valve terminal; when the cycle turn-off voltage of the main IGBT valve exceeds the arrester action voltage, the number of available actions of the arrester of the main IGBT valve is reduced by 1, and the number of available actions of the arrester is increased by a first preset number every first preset time; when the cycle turn-off voltage of the auxiliary IGBT valve exceeds the arrester action voltage, the number of available actions of the arrester of the auxiliary IGBT valve is reduced by 1; when the number of available actions of the arrester of the main IGBT valve is less than a second preset number, or when the number of available actions of the arrester of the auxiliary IGBT valve is less than the second preset number, controlling the converter to return to the grid commutation operation mode; when the number of available actions of the arrester of the main IGBT valve is greater than a third preset number, or when the number of available actions of the arrester of the auxiliary IGBT valve is greater than the third preset number, controlling the converter to enter the controllable commutation operation mode. The above scheme adopts different protection actions to protect the fully controlled sub-valve arrester from damage, thereby improving the operational reliability of the converter valve.

Claims

1. A lightning protection method for a fully controlled valve of a controllable commutation converter, each bridge arm of the converter is composed of a main branch and an auxiliary branch connected in parallel, and the main branch includes: The main thyristor valve and the main IGBT valve, the auxiliary branch includes: an auxiliary IGBT valve and an auxiliary thyristor valve, and lightning arresters are connected in parallel to both the main IGBT valve and the auxiliary IGBT valve. The method for lightning protection of the fully controlled valves of the controllable commutation converter includes: Monitor the voltage at the fully controlled valve terminals in real time. When the turn-off voltage per cycle of the main IGBT valve exceeds the operating voltage of the lightning arrester, the available operating times of the lightning arrester of the main IGBT valve are reduced by 1. When the turn-off voltage per cycle of the auxiliary IGBT valve exceeds the operating voltage of the lightning arrester, the available operating times of the lightning arrester of the auxiliary IGBT valve are reduced by 1; every first preset time, the available operating times of the lightning arrester are increased by the first preset number of times; When the available operating times of the lightning arrester of the main IGBT valve are less than the second preset number of times, control the converter to return to the line-commutated operation mode; or, when the available operating times of the lightning arrester of the auxiliary IGBT valve are less than the second preset number of times, control the converter to return to the line-commutated operation mode; When the available operating times of the lightning arrester of the main IGBT valve are greater than the third preset number of times, control the converter to enter the controllable commutation operation mode; when the available operating times of the lightning arrester of the auxiliary IGBT valve are greater than the third preset number of times, control the converter to enter the controllable commutation operation mode.

2. The controllable commutation converter full-control valve lightning protection method according to claim 1, wherein, The first preset time and the first preset number of times should satisfy the following relational expression: M = W / Ws, N ≤ M, Wherein, W is the rated energy designed for the lightning arrester; Ws is the maximum energy normally absorbed by the lightning arrester in a single time; N is the initial value of the available operating times set for the lightning arrester; a is the first preset time; b is the first preset number of times; H is the time duration from when the lightning arrester absorbs a full energy once to when it absorbs a full energy again next time.

3. The controllable commutation converter full-control valve lightning protection method according to claim 1 or 2, wherein When the converter is operating in the controllable commutation mode, the method for lightning protection of the fully controlled valves of the controllable commutation converter further includes: Monitor the voltage at the terminals of the main IGBT valve in real time; When the voltage at the terminals of the main IGBT valve continuously exceeds the first voltage reference value for the third preset time, it is determined that the lightning arrester of the main IGBT valve is overvoltage; Actively trigger and conduct the main IGBT valve.

4. The all-controlled valve lightning protection method for a controllable commutation converter according to claim 3, wherein, The method for lightning protection of the fully controlled valves of the controllable commutation converter further includes: Within a period of time, when the cumulative number of times that the voltage at the terminals of the main IGBT valve is higher than the second voltage reference value reaches the fourth preset number of times, it is determined that the converter is operating abnormally, and control the converter to permanently retreat to the line-commutated mode.

5. The controllable commutation converter full-control valve lightning protection method according to claim 1 or 2, wherein, When the converter is operating in the controllable commutation mode, the method for lightning protection of the fully controlled valves of the controllable commutation converter further includes: Monitor the voltage at the terminals of the auxiliary IGBT valve in real time; When the voltage at the terminals of the auxiliary IGBT valve continuously exceeds the third voltage reference value for the fourth preset time, it is determined that the lightning arrester of the auxiliary IGBT valve is overvoltage; Actively trigger and conduct the auxiliary IGBT valve.

6. The controllable commutation converter full-control valve lightning protection method according to claim 5, wherein, The method for lightning protection of the fully controlled valves of the controllable commutation converter further includes: Within a period of time, when the cumulative number of times that the voltage at the terminals of the auxiliary IGBT valve is higher than the fourth voltage reference value reaches the fourth preset number of times, it is determined that the converter is operating abnormally, and control the converter to permanently retreat to the line-commutated mode.

7. A lightning protection device for a fully controlled valve of a controllable phase-shifting converter, based on the lightning protection method for the fully controlled valve of the controllable phase-shifting converter according to any one of claims 1-6, the lightning protection device for the fully controlled valve of the controllable phase-shifting converter comprising: A monitoring part, configured to monitor the voltage at the fully controlled valve end in real time. When the turn-off voltage per cycle of the main IGBT valve exceeds the lightning arrester operating voltage, the available operation times of the lightning arrester of the main IGBT valve are reduced by 1. When the turn-off voltage per cycle of the auxiliary IGBT valve exceeds the lightning arrester operating voltage, the available operation times of the lightning arrester of the auxiliary IGBT valve are reduced by 1; Every first preset time, the available operation times of the lightning arrester are increased by the first preset number of times; A first switching part, configured to control the converter to return to the line-commutated operation mode when the available operation times of the lightning arrester of the main IGBT valve are less than the second preset number of times; or, when the available operation times of the lightning arrester of the auxiliary IGBT valve are less than the second preset number of times, control the converter to return to the line-commutated operation mode; A second switching part, configured to control the converter to enter the controllable phase-shifting operation mode when the available operation times of the lightning arrester of the main IGBT valve are greater than the third preset number of times; when the available operation times of the lightning arrester of the auxiliary IGBT valve are greater than the third preset number of times, control the converter to enter the controllable phase-shifting operation mode.

8. The lightning protection device for the fully controlled valve of the controllable phase-shifting converter according to claim 7, the lightning protection device for the fully controlled valve of the controllable phase-shifting converter further comprising: A first single-cycle continuous overvoltage protection part, configured to monitor the voltage at the end of the main IGBT valve in real time; When the voltage at the end of the main IGBT valve continuously exceeds the first voltage reference value for the third preset time, it is determined that the lightning arrester of the main IGBT valve is overvoltage; actively trigger and conduct the main IGBT valve; A second single-cycle continuous overvoltage protection part, configured to monitor the voltage at the end of the auxiliary IGBT valve in real time; when the voltage at the end of the auxiliary IGBT valve continuously exceeds the third voltage reference value for the fourth preset time, it is determined that the lightning arrester of the auxiliary IGBT valve is overvoltage; actively trigger and conduct the auxiliary IGBT valve.

9. The lightning protection device for the fully controlled valve of the controllable phase-shifting converter according to claim 8, the lightning protection device for the fully controlled valve of the controllable phase-shifting converter further comprising: A first multi-cycle continuous overvoltage protection part, configured to determine that the converter is operating abnormally and control the converter to permanently return to the line-commutated mode when the cumulative number of times the voltage at the end of the main IGBT valve is higher than the second voltage reference value reaches the fourth preset number of times within a period of time; A second multi-cycle continuous overvoltage protection part, configured to determine that the converter is operating abnormally and control the converter to permanently return to the line-commutated mode when the cumulative number of times the voltage at the end of the auxiliary IGBT valve is higher than the fourth voltage reference value reaches the fourth preset number of times within a period of time.

10. A computer device, comprising: At least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to cause the at least one processor to execute the controllable commutation converter full-control valve lightning protection method according to any one of claims 1 to 6.

11. A computer-readable storage medium storing computer instructions for causing a computer to execute the controllable commutation converter full-control valve lightning protection method according to any one of claims 1 to 6.

12. A computer program product comprising a computer program or instructions, which, when running on a computer device, cause the computer device to execute the controllable commutation converter full-control valve lightning protection method according to any one of claims 1 to 6.

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