A method, device and storage medium for suppressing overvoltage of SLCC converter valve

Abstract

The present invention discloses a method, device and storage medium for suppressing overvoltage of SLCC converter valves, the method comprising: obtaining a first extreme working condition by traversing overvoltage fault scenarios through simulation, and optimizing the bridge arm reactor parameters according to the first extreme working condition to obtain a first scheme for suppressing overvoltage; when the first scheme cannot effectively suppress overvoltage, simulation is performed based on the first extreme working condition and the optimized bridge arm reactor parameters, and the valve-controlled unbalanced protection action constant is optimized to obtain a second scheme for further suppressing overvoltage; when the second scheme cannot effectively suppress overvoltage, simulation is performed based on the optimized bridge arm reactor parameters and the valve-controlled unbalanced protection action constant to obtain a second extreme working condition; based on the second extreme working condition, combined with engineering requirements, the converter valve assembly is optimized until a scheme that can effectively suppress overvoltage is obtained. The present invention realizes effective suppression of overvoltage of SLCC converter valves through the joint design of primary and secondary systems.

Description

Technical Field

[0001] The present invention relates to the field of direct current transmission technology, and in particular to a method, device and storage medium for suppressing overvoltage of a SLCC converter valve. Background Art

[0002] With the maturity of renewable energy power generation technology, the installed capacity of renewable energy is growing rapidly, and the demand for long-distance transmission of renewable energy is increasing. Due to the weak system support capacity of renewable energy units, conventional DC transmission technology is difficult to adapt. However, SLCC (Self-Commutated Converter) has received extensive attention and application in recent years due to its advantages. SLCC is a converter composed of LCC (Line Commutated Converter) and SVG (Static VarGenerator) configured on the valve side of the transformer. It can compensate for reactive power consumption and harmonic current during the operation of LCC. The system does not need to be additionally configured with AC filters / shunt capacitors, which can effectively solve problems such as AC low voltage ride-through and receiving end commutation failure. Compared with flexible DC transmission, it occupies a smaller area and has stronger economy. However, the SLCC system has not yet been put into engineering application in the UHV DC transmission scenario, and the overvoltage problem of its SVG submodule needs to be solved.

[0003] Similar to flexible direct current transmission, the converter valve is the basic control unit of SVG. The main form of direct current transmission is to effectively transmit electric energy by controlling the on and off of the converter valve. The overvoltage / overcurrent carrying capacity of the converter valve under transient conditions is limited by the device specifications and the existing technical level. When the overvoltage borne by the IGBT submodule is higher than its carrying capacity, the submodule will be broken down. In existing direct current transmission projects, more attention has been paid to the analysis and suppression methods of flexible direct current overvoltage. However, as a new type of converter, the overvoltage problem of the converter valve submodule in the SVG of the SLCC system has not received sufficient attention. In addition, due to the different topological forms, the SLCC cannot directly draw on the relevant conclusions of the existing flexible direct current overvoltage problem.

[0004] Therefore, a method for suppressing overvoltage of SLCC converter valve is urgently needed. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a SLCC converter valve overvoltage suppression method, device and storage medium. Through the joint design of the primary system and the secondary system, the overvoltage of the SLCC converter valve is effectively suppressed, and the reliability and safety of the SLCC DC transmission system are improved.

[0006] An embodiment of the present invention provides a method for suppressing overvoltage of a SLCC converter valve, comprising:

[0007] Based on the SLCC DC transmission system simulation model, the fault scenarios of overvoltage of the SLCC converter valve submodule are simulated and traversed to obtain the first extreme working condition; according to the change of the voltage across the bridge arm reactor in the converter valve under the first extreme working condition, the bridge arm reactor parameters are optimized to obtain the first solution; it is determined whether the first solution meets the preset conditions, and if so, the first solution is determined to be an overvoltage suppression solution; wherein the preset condition is that the converter valve submodule voltage meets the equipment tolerance requirement;

[0008] If the first scheme does not meet the preset conditions, simulation is performed according to the first extreme working condition and the bridge arm reactor parameters to optimize the valve-controlled unbalanced protection action constant to obtain a second scheme; it is determined whether the second scheme meets the preset conditions, and if so, the second scheme is determined to be an overvoltage suppression scheme;

[0009] If the second scheme does not meet the preset conditions, the overvoltage fault scenario of the SLCC converter valve submodule is simulated and traversed according to the bridge arm reactor parameters and the valve-controlled unbalanced protection action constant to obtain the second extreme operating condition; based on the second extreme operating condition and in combination with the preset engineering requirements, the converter valve assembly is optimized until an overvoltage suppression scheme that meets the preset conditions is obtained.

[0010] As an improvement of the above solution, the SLCC converter valve submodule overvoltage fault scenario includes: internal fault and external fault of the static VAR generator;

[0011] The internal faults include but are not limited to: one or more of: a neutral point grounding fault, a single-phase grounding fault between the bridge arm reactor and the valve, a two-phase grounding fault, and a three-phase grounding fault;

[0012] The external faults include, but are not limited to: one or more of: system short circuit fault, bus fault, load sudden change fault, lightning fault and circuit breaker fault.

[0013] As an improvement of the above solution, the optimizing the bridge arm reactor parameters according to the change of the voltage across the bridge arm reactor in the converter valve under the first extreme working condition includes:

[0014] Analyze the overvoltage condition and fault path of the converter valve submodule under the first extreme working condition to obtain the valve side voltage before and after the fault and the valve side voltage of the bridge arm reactor of the static VAR generator;

[0015] For an internal fault of the static VAR generator, the maximum voltage across the bridge arm reactor before and after the fault is calculated based on the difference between the valve side voltage before the fault and the valve side voltage of the bridge arm reactor of the static VAR generator after the fault; for an external fault of the static VAR generator, the maximum voltage across the bridge arm reactor before and after the fault is calculated based on the difference between the valve side voltage of the bridge arm reactor of the static VAR generator before the fault and the valve side voltage after the fault;

[0016] The maximum current rise rate that the system can tolerate is obtained, and the optimized bridge arm reactor parameters are calculated according to the ratio of the maximum voltage across the bridge arm reactor before and after the fault to the maximum current rise rate.

[0017] As an improvement of the above solution, the simulation is performed according to the first extreme working condition and the bridge arm reactor parameters to optimize the valve-controlled unbalanced protection action setting value, including:

[0018] Based on the bridge arm reactor parameters, a simulation analysis is performed on the first extreme working condition to obtain an overvoltage condition of the converter valve submodule under the first extreme working condition;

[0019] Obtain the overcurrent condition of the static VAR generator;

[0020] According to the overvoltage condition of the converter valve submodule and the overcurrent condition of the static VAR generator, the valve-controlled unbalanced protection action constant is optimized with the goal of suppressing the converter valve overvoltage while ensuring no false operation during normal operation.

[0021] As an improvement of the above solution, the converter valve assembly is optimized, including: one or more of increasing the number of submodules, increasing the capacitance value of the submodules, and adding a lightning arrester.

[0022] As an improvement of the above solution, if the converter valve assembly is optimized to increase the number of submodules, the converter valve assembly is optimized until an overvoltage suppression solution that meets the preset conditions is obtained, including:

[0023] On the basis of the second solution, the number of submodules is gradually increased and the overvoltage condition of the converter valve is verified until the preset conditions are met, thereby obtaining an overvoltage suppression solution.

[0024] As an improvement of the above solution, if the converter valve assembly is optimized to increase the submodule capacitance value, the converter valve assembly is optimized until an overvoltage suppression solution that meets the preset conditions is obtained, including:

[0025] On the basis of the second scheme, the submodule capacitance value is gradually increased and the overvoltage condition of the converter valve is checked until the preset condition is met, thereby obtaining an overvoltage suppression scheme.

[0026] As an improvement of the above solution, if the converter valve assembly is optimized by adding a lightning arrester, the converter valve assembly is optimized until an overvoltage suppression scheme that meets the preset conditions is obtained, including:

[0027] On the basis of the second scheme, the arrester parameters are configured according to the current converter valve overvoltage situation, the converter valve overvoltage situation after the arrester is added is simulated and verified, and the arrester parameters are iteratively modified according to the simulation results until the preset conditions are met, thereby obtaining an overvoltage suppression scheme;

[0028] The arrester parameters include: protection level, rated voltage, coordination current, normal operating voltage and arrester energy.

[0029] The embodiment of the present invention further provides an SLCC converter valve overvoltage suppression device, comprising:

[0030] The bridge arm reactor optimization module is used to simulate and traverse the fault scenario of overvoltage of the SLCC converter valve submodule based on the SLCC DC transmission system simulation model to obtain the first extreme working condition; according to the change of the voltage across the bridge arm reactor in the converter valve under the first extreme working condition, the bridge arm reactor parameters are optimized to obtain the first solution; it is determined whether the first solution meets the preset conditions, and if so, the first solution is determined to be an overvoltage suppression solution; wherein the preset condition is that the converter valve submodule voltage meets the equipment tolerance requirement;

[0031] A secondary system optimization module, for, if the first scheme does not meet the preset conditions, simulating according to the first extreme working condition and the bridge arm reactor parameters, optimizing the valve-controlled unbalanced protection action constant, and obtaining a second scheme; judging whether the second scheme meets the preset conditions, and if so, determining that the second scheme is an overvoltage suppression scheme;

[0032] The converter valve assembly optimization module is used to simulate and traverse the overvoltage fault scenario of the SLCC converter valve submodule according to the bridge arm inductor parameters and the valve-controlled unbalanced protection action constant to obtain a second extreme operating condition if the second scheme does not meet the preset conditions; based on the second extreme operating condition, combined with preset engineering requirements, the converter valve assembly is optimized until an overvoltage suppression scheme that meets the preset conditions is obtained.

[0033] An embodiment of the present invention further provides a computer-readable storage medium, which stores a computer program. When the computer program is running, the device where the computer-readable storage medium is located is controlled to execute any one of the above-mentioned SLCC converter valve overvoltage suppression methods.

[0034] Compared with the prior art, the SLCC converter valve overvoltage suppression method, device and storage medium provided by the embodiments of the present invention have the following beneficial effects:

[0035] By optimizing the arm reactor parameters according to the extreme working conditions, the first scheme for suppressing overvoltage is obtained; simulation is performed based on the first extreme working condition and the optimized arm reactor parameters, and the valve-controlled unbalanced protection action constant is optimized to obtain the second scheme for further suppressing overvoltage; re-simulation is performed based on the optimized arm reactor parameters and the valve-controlled unbalanced protection action constant to obtain the extreme working conditions, and the converter valve components are optimized in combination with engineering requirements until a scheme that can effectively suppress overvoltage is obtained, which solves the overvoltage problem of the converter valve submodule in the UHV SLCC DC transmission system and is conducive to improving the reliability and economy of the SLCC UHV DC transmission system;

[0036] By combining the characteristics of the SLCC system, the protection that affects the overvoltage of the converter valve is defined as valve-controlled unbalance protection for the first time, which narrows the focus of the protection strategy and action setting value and improves the analysis and suppression efficiency of the converter valve overvoltage.

[0037] For the first time, it was proposed to effectively suppress overvoltage in the converter valve submodule of the SLCC ultra-high voltage direct current transmission system through the joint design of the primary system (bridge arm reactor parameters, number of submodules, submodule capacitance, valve arrester) and the secondary system (valve-controlled unbalanced protection), thus realizing the system joint optimization of SLCC. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a flow chart of a method for suppressing overvoltage of a SLCC converter valve provided by an embodiment of the present invention;

[0039] Figure 2 is a schematic diagram of the internal fault location of an SVG provided by an embodiment of the present invention;

[0040] Figure 3 is an overvoltage waveform diagram of the overvoltage suppression front submodule provided by an embodiment of the present invention;

[0041] Figure 4 It is a structural schematic diagram of an SLCC converter valve overvoltage suppression device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] In view of the overvoltage problem of the SVG converter valve submodule in the UHV SLCC direct current transmission system, an embodiment of the present invention provides a SLCC converter valve overvoltage suppression method. The SLCC converter valve overvoltage suppression method includes:

[0044] Based on the SLCC DC transmission system simulation model, the fault scenarios of overvoltage of the SLCC converter valve submodule are simulated and traversed to obtain the first extreme working condition; according to the change of the voltage across the bridge arm reactor in the converter valve under the first extreme working condition, the bridge arm reactor parameters are optimized to obtain the first solution; it is determined whether the first solution meets the preset conditions, and if so, the first solution is determined to be an overvoltage suppression solution; wherein the preset condition is that the converter valve submodule voltage meets the equipment tolerance requirement;

[0045] If the first scheme does not meet the preset conditions, simulation is performed according to the first extreme working condition and the bridge arm reactor parameters to optimize the valve-controlled unbalanced protection action constant to obtain a second scheme; it is determined whether the second scheme meets the preset conditions, and if so, the second scheme is determined to be an overvoltage suppression scheme;

[0046] If the second scheme does not meet the preset conditions, the overvoltage fault scenario of the SLCC converter valve submodule is simulated and traversed according to the bridge arm reactor parameters and the valve-controlled unbalanced protection action constant to obtain the second extreme operating condition; based on the second extreme operating condition and in combination with the preset engineering requirements, the converter valve assembly is optimized until an overvoltage suppression scheme that meets the preset conditions is obtained.

[0047] For details, please refer to Figure 1 , Figure 1 It is a flow chart of a method for suppressing overvoltage of an SLCC converter valve provided in an embodiment of the present invention.

[0048] Firstly, based on the initial parameters, a simulation model of the SLCC DC transmission system is built, the fault type and operating conditions are set, all fault scenarios that may cause overvoltage in the converter valve submodule are traversed, and extreme operating conditions are obtained.

[0049] As one of the optional embodiments, the SLCC converter valve submodule overvoltage fault scenario includes: internal fault and external fault of the static VAR generator;

[0050] The internal faults include but are not limited to: one or more of: a neutral point grounding fault, a single-phase grounding fault between the bridge arm reactor and the valve, a two-phase grounding fault, and a three-phase grounding fault;

[0051] The external faults include, but are not limited to: one or more of: system short circuit fault, bus fault, load sudden change fault, lightning fault and circuit breaker fault.

[0052] Specifically, for the outside of SVG, it is necessary to cover the faults that may cause a large fluctuation in the valve-side voltage of the converter transformer, including but not limited to system short circuit faults, busbar faults, load sudden change faults, lightning faults and circuit breaker faults, which are subject to the system analysis results. For the inside of SVG, it is necessary to include neutral point grounding faults, single-phase grounding, two-phase grounding and three-phase grounding faults between the bridge arm reactor and the converter valve, and the fault locations are as follows: Figure 2 shown.

[0053] Furthermore, the overvoltage conditions and fault paths of the submodules under extreme working conditions are analyzed, and the parameters of the bridge arm reactors are designed and optimized according to the voltage drop amplitude under extreme conditions.

[0054] As one of the optional embodiments, the optimizing the bridge arm reactor parameters according to the change of the voltage across the bridge arm reactor in the converter valve under the first extreme working condition includes:

[0055] Analyze the overvoltage condition and fault path of the converter valve submodule under the first extreme working condition to obtain the valve side voltage before and after the fault and the valve side voltage of the bridge arm reactor of the static VAR generator;

[0056] For an internal fault of the static VAR generator, the maximum voltage across the bridge arm reactor before and after the fault is calculated based on the difference between the valve side voltage before the fault and the valve side voltage of the bridge arm reactor of the static VAR generator after the fault; for an external fault of the static VAR generator, the maximum voltage across the bridge arm reactor before and after the fault is calculated based on the difference between the valve side voltage of the bridge arm reactor of the static VAR generator before the fault and the valve side voltage after the fault;

[0057] The maximum current rise rate that the system can tolerate is obtained, and the optimized bridge arm reactor parameters are calculated according to the ratio of the maximum voltage across the bridge arm reactor before and after the fault to the maximum current rise rate.

[0058] Among them, the valve-side voltage is the voltage at the input or output end of the converter valve, that is, the port voltage of the valve during power transmission or conversion; the valve-side voltage of the static VAR generator (SVG) bridge arm reactor is the voltage at the connection between the SVG internal bridge arm reactor and the converter valve.

[0059] Specifically, let the valve side voltage before the fault be U v0 , the valve side voltage of the SVG bridge arm reactor is U LV0 ; The valve side voltage after the fault is U vF , the valve side voltage of the SVG bridge arm reactor is U LVF .

[0060] For the internal fault of SVG, the maximum voltage across the bridge arm reactor before and after the fault can be approximately considered as dU=U v0 -ULVF ; For SVG external fault, the voltage across the bridge arm reactor is approximately considered to be dU=U LV0 -U vF ;

[0061] Then, the maximum current rise rate di that the system can tolerate is calculated based on the protection action delay. max / dt, substitute it into the formula: dU=L d max / dt, the arm reactor parameter L that can suppress the overvoltage of the converter valve is calculated, and the first solution is obtained.

[0062] Furthermore, it is determined whether the converter valve submodule voltage corresponding to the first solution is less than the equipment tolerance capability. If so, the first solution is output to achieve effective suppression of overvoltage of the faulty submodule in the converter station.

[0063] Furthermore, when the first solution cannot meet the overvoltage suppression requirements, the overvoltage situation of the submodule under extreme working conditions is simulated and analyzed based on the optimized parameters of the bridge arm reactor, and the valve-controlled unbalanced protection action constant is optimized in combination with the SVG overcurrent situation to obtain the second solution.

[0064] As one of the optional embodiments, the simulation is performed according to the first extreme working condition and the bridge arm reactor parameters to optimize the valve-controlled unbalanced protection action setting value, including:

[0065] Based on the bridge arm reactor parameters, a simulation analysis is performed on the first extreme working condition to obtain an overvoltage condition of the converter valve submodule under the first extreme working condition;

[0066] Obtain the overcurrent condition of the static VAR generator;

[0067] According to the overvoltage condition of the converter valve submodule and the overcurrent condition of the static VAR generator, the valve-controlled unbalanced protection action constant is optimized with the goal of suppressing the converter valve overvoltage while ensuring no false operation during normal operation.

[0068] Specifically, based on the extreme operating conditions and arm reactor parameters obtained in the above steps, the critical operating conditions are re-simulated and calculated. When there is still overvoltage in the converter valve, the overvoltage in the converter valve is further suppressed by modifying the valve-controlled unbalanced protection action setting. The valve-controlled unbalanced protection action setting should be designed based on engineering experience and combined with the overvoltage and overcurrent simulation results to achieve effective suppression of overvoltage and overcurrent while ensuring no false operation under normal operation.

[0069] Furthermore, according to the optimized valve-controlled unbalanced protection action setting and the bridge arm reactor parameters, a second scheme for suppressing the overvoltage of the converter valve is obtained. Accordingly, it is determined whether the converter valve submodule voltage corresponding to the second scheme is less than the equipment tolerance capacity. If so, the second scheme is output to achieve effective suppression of the overvoltage of the faulty submodule in the converter station.

[0070] Furthermore, when the second scheme cannot meet the overvoltage suppression requirements, that is, when the optimized valve-controlled unbalanced protection action constant still cannot completely suppress the overvoltage before the converter valve is locked, it is necessary to optimize the primary equipment parameter design again on the basis of the above design scheme, specifically to optimize the converter valve assembly.

[0071] As one of the optional embodiments, the optimization of the converter valve assembly includes: one or more of increasing the number of submodules, increasing the capacitance value of the submodules, and adding a lightning arrester.

[0072] Specifically, based on the optimized parameters of the bridge arm reactor and the action setting of the valve-controlled unbalanced protection, the faults in the SLCC converter station are simulated again to obtain extreme operating conditions. Based on the analysis results of the extreme operating conditions and comprehensive consideration of engineering requirements such as cost and land occupation, a comprehensive design scheme is proposed by increasing the number of sub-modules, improving the capacitance of the sub-modules, and adding valve arresters to effectively suppress the overvoltage of the faulty sub-modules in the converter station.

[0073] As one of the optional embodiments, if the converter valve assembly is optimized to increase the number of submodules, the converter valve assembly is optimized until an overvoltage suppression scheme that meets the preset conditions is obtained, including:

[0074] On the basis of the second solution, the number of submodules is gradually increased and the overvoltage condition of the converter valve is verified until the preset conditions are met, thereby obtaining an overvoltage suppression solution.

[0075] As one of the optional embodiments, if the converter valve assembly is optimized to increase the submodule capacitance value, the converter valve assembly optimization is performed until an overvoltage suppression scheme that meets the preset conditions is obtained, including:

[0076] On the basis of the second scheme, the submodule capacitance value is gradually increased and the overvoltage condition of the converter valve is checked until the preset condition is met, thereby obtaining an overvoltage suppression scheme.

[0077] As one of the optional embodiments, if the converter valve assembly is optimized to add a lightning arrester, the converter valve assembly is optimized until an overvoltage suppression scheme that meets the preset conditions is obtained, including:

[0078] On the basis of the second scheme, the arrester parameters are configured according to the current converter valve overvoltage situation, the converter valve overvoltage situation after the arrester is added is simulated and verified, and the arrester parameters are iteratively modified according to the simulation results until the preset conditions are met, thereby obtaining an overvoltage suppression scheme;

[0079] The arrester parameters include: protection level, rated voltage, coordination current, normal operating voltage and arrester energy.

[0080] Specifically, the parameters of the arrester are configured according to the preliminary converter valve overvoltage situation. After setting the preliminary parameters, the arrester suppression effect is verified through simulation operation to obtain or adjust the key parameters of the arrester, such as protection level, rated voltage, normal operating voltage, and arrester energy tolerance. Then, according to the simulation results, the parameters of the arrester are optimized and iteratively adjusted until the requirements for suppressing the converter valve overvoltage are met. At this time, the number of arrester columns (the number of series connections) and the UI characteristics of the arrester are determined according to the parameter configuration of the arrester to ensure that it can work stably under different current conditions.

[0081] Furthermore, according to the feasibility of the project, the optimal solution is selected from increasing the number of submodules, increasing the submodule capacitance and adding valve arresters, and a comprehensive design scheme that can effectively suppress the overvoltage of faulty submodules in the converter station is obtained. This scheme combines the primary system (bridge arm reactor parameters, number of submodules, submodule capacitance, valve arrester) and the secondary system (valve-controlled unbalanced protection) to achieve the system joint optimization of SLCC.

[0082] In a specific example, a UHV DC transmission project with a voltage level of ±800kV, a transmission power of 8GW, and a SLCC at the sending end is used as an example, and the SVG capacity is 550MVA. In this system, 4.5kV, 3kA-level IGBT devices are used, the submodule rated voltage is 2.4kV, the submodule capacitance is 18mF, and the number of submodules is 83. According to the capacity of the converter valve equipment, the overvoltage before the submodule is locked cannot exceed 4.1kV.

[0083] First, the simulation traverses the faults in the SLCC converter station to obtain the extreme faults and operating conditions of the overvoltage before the SVG converter valve is locked. According to preliminary simulation research, when a grounding fault occurs at the neutral point of the SVG, a large freewheeling overvoltage will be generated. The overvoltage of the submodule before locking can reach 4.61kV, which exceeds the tolerance of the equipment. The voltage waveform of the submodule is as follows: Figure 3 As shown, the corresponding curve of Usmc is the submodule voltage when a ground fault occurs at the neutral point of SVG.

[0084] Secondly, analyze the overvoltage and fault path of the submodule under extreme working conditions. When a ground fault occurs at the neutral point of SVG, Uv0 The maximum value is 800kV, U LVF The voltage is 0kV, the action value of the valve-controlled overcurrent protection is 4.8kA, the action delay is 150μs, and the device withstand current is 6kA. That is, when the current rise rate of the converter valve is less than 8A / μs, the valve-controlled overcurrent protection can be activated in time. max / dt=8A / μs. In order to make the SVG converter valve fault current rise rate less than di max / dt, substitute it into dU=L d max / dt, L should be no less than 10mH, and is taken as 15mH.

[0085] Then, based on the above parameters, the overvoltage situation of the submodule under extreme working conditions was simulated and analyzed again. Based on engineering experience and combined with the overvoltage and overcurrent simulation results, the valve-controlled unbalanced protection action constant was set to 1kA.

[0086] Furthermore, based on the optimized parameters of the bridge arm reactors and the action settings of the valve-controlled unbalanced protection, the faults in the SLCC converter station were simulated again, and the extreme operating conditions did not change.

[0087] Finally, based on the analysis results, in order to control the engineering cost and valve hall space and improve the utilization rate of submodules, the overvoltage of faulty submodules in the converter station is effectively suppressed by adding valve arresters. The valve arrester scheme obtained after iteration is: the normal working voltage is 200kV, the charge rate is 0.8, 20 columns are connected in parallel, the residual voltage is 314kV, and the matching current is 4kA. At this time, the maximum overvoltage of the converter valve submodule is 4.04kV, and the energy is 2.2MJ, which meets the equipment tolerance requirements. The SLCC converter valve overvoltage suppression scheme including bridge arm reactor parameters, submodule number, submodule capacitance, valve arrester and valve-controlled unbalanced protection action setting is obtained.

[0088] The embodiment of the present invention optimizes the bridge arm reactor parameters according to the extreme working conditions to obtain a first solution for suppressing overvoltage; performs simulation based on the first extreme working condition and the optimized bridge arm reactor parameters, optimizes the valve-controlled unbalanced protection action constant, and obtains a second solution for further suppressing overvoltage; performs simulation again based on the optimized bridge arm reactor parameters and the valve-controlled unbalanced protection action constant, obtains the extreme working conditions, and optimizes the converter valve assembly in combination with engineering requirements until a solution that can effectively suppress overvoltage is obtained, thereby solving the overvoltage problem of the converter valve submodule in the ultra-high voltage SLCC DC transmission system, and is conducive to improving the reliability and economy of the SLCC ultra-high voltage DC transmission system. By combining the characteristics of the SLCC system, the protection that affects the converter valve overvoltage is clearly defined as valve-controlled unbalanced protection for the first time, narrowing the scope of attention of the protection strategy and the action constant, and improving the analysis and suppression efficiency of the converter valve overvoltage. For the first time, it was proposed to effectively suppress overvoltage in the converter valve submodule of the SLCC ultra-high voltage direct current transmission system through the joint design of the primary system (bridge arm reactor parameters, number of submodules, submodule capacitance, valve arrester) and the secondary system (valve-controlled unbalanced protection), thus realizing the system joint optimization of SLCC.

[0089] Correspondingly, the present invention also provides an SLCC converter valve overvoltage suppression device, which can implement all the processes of the SLCC converter valve overvoltage suppression method in the above embodiment.

[0090] See also Figure 4 , Figure 4 1 is a schematic diagram of the structure of an SLCC converter valve overvoltage suppression device provided by an embodiment of the present invention. The SLCC converter valve overvoltage suppression device comprises:

[0091] The bridge arm reactor optimization module 401 is used to simulate and traverse the fault scenario of overvoltage of the SLCC converter valve submodule based on the SLCC DC transmission system simulation model to obtain a first extreme working condition; optimize the bridge arm reactor parameters according to the change of the voltage across the bridge arm reactor in the converter valve under the first extreme working condition to obtain a first solution; determine whether the first solution meets the preset conditions, and if so, determine that the first solution is an overvoltage suppression solution; wherein the preset condition is that the converter valve submodule voltage meets the equipment tolerance requirement;

[0092] The secondary system optimization module 402 is used for, if the first scheme does not meet the preset conditions, simulating according to the first extreme working condition and the bridge arm reactor parameters, optimizing the valve-controlled unbalanced protection action constant, and obtaining a second scheme; judging whether the second scheme meets the preset conditions, and if so, determining that the second scheme is an overvoltage suppression scheme;

[0093] The converter valve assembly optimization module 403 is used to simulate and traverse the overvoltage fault scenario of the SLCC converter valve submodule according to the bridge arm inductor parameters and the valve-controlled unbalanced protection action constant to obtain a second extreme operating condition if the second scheme does not meet the preset conditions; based on the second extreme operating condition, combined with the preset engineering requirements, the converter valve assembly is optimized until an overvoltage suppression scheme that meets the preset conditions is obtained.

[0094] Preferably, the SLCC converter valve submodule overvoltage fault scenario includes: internal fault and external fault of the static VAR generator;

[0095] The internal faults include but are not limited to: one or more of: a neutral point grounding fault, a single-phase grounding fault between the bridge arm reactor and the valve, a two-phase grounding fault, and a three-phase grounding fault;

[0096] The external faults include, but are not limited to: one or more of: system short circuit fault, bus fault, load sudden change fault, lightning fault and circuit breaker fault.

[0097] Preferably, the optimizing the parameters of the bridge arm reactor according to the change of the voltage across the bridge arm reactor in the converter valve under the first extreme working condition includes:

[0098] Analyze the overvoltage condition and fault path of the converter valve submodule under the first extreme working condition to obtain the valve side voltage before and after the fault and the valve side voltage of the bridge arm reactor of the static VAR generator;

[0099] For an internal fault of the static VAR generator, the maximum voltage across the bridge arm reactor before and after the fault is calculated based on the difference between the valve side voltage before the fault and the valve side voltage of the bridge arm reactor of the static VAR generator after the fault; for an external fault of the static VAR generator, the maximum voltage across the bridge arm reactor before and after the fault is calculated based on the difference between the valve side voltage of the bridge arm reactor of the static VAR generator before the fault and the valve side voltage after the fault;

[0100] The maximum current rise rate that the system can tolerate is obtained, and the optimized bridge arm reactor parameters are calculated according to the ratio of the maximum voltage across the bridge arm reactor before and after the fault to the maximum current rise rate.

[0101] Preferably, the simulation is performed according to the first extreme working condition and the bridge arm reactor parameters to optimize the valve-controlled unbalanced protection action setting value, including:

[0102] Based on the bridge arm reactor parameters, a simulation analysis is performed on the first extreme working condition to obtain an overvoltage condition of the converter valve submodule under the first extreme working condition;

[0103] Obtain the overcurrent condition of the static VAR generator;

[0104] According to the overvoltage condition of the converter valve submodule and the overcurrent condition of the static VAR generator, the valve-controlled unbalanced protection action constant is optimized with the goal of suppressing the converter valve overvoltage while ensuring no false operation during normal operation.

[0105] Preferably, the converter valve assembly optimization includes: one or more of increasing the number of submodules, increasing the capacitance value of the submodules and adding a lightning arrester.

[0106] Preferably, if the converter valve assembly is optimized to increase the number of submodules, the optimization of the converter valve assembly is performed until an overvoltage suppression scheme that meets the preset conditions is obtained, including:

[0107] On the basis of the second solution, the number of submodules is gradually increased and the overvoltage condition of the converter valve is verified until the preset conditions are met, thereby obtaining an overvoltage suppression solution.

[0108] Preferably, if the converter valve assembly is optimized to increase the submodule capacitance value, the converter valve assembly optimization is performed until an overvoltage suppression scheme that meets the preset conditions is obtained, including:

[0109] On the basis of the second scheme, the submodule capacitance value is gradually increased and the overvoltage condition of the converter valve is checked until the preset condition is met, thereby obtaining an overvoltage suppression scheme.

[0110] Preferably, if the converter valve assembly is optimized by adding a lightning arrester, the optimization of the converter valve assembly is performed until an overvoltage suppression scheme that meets the preset conditions is obtained, including:

[0111] On the basis of the second scheme, the arrester parameters are configured according to the current converter valve overvoltage situation, the converter valve overvoltage situation after the arrester is added is simulated and verified, and the arrester parameters are iteratively modified according to the simulation results until the preset conditions are met, thereby obtaining an overvoltage suppression scheme;

[0112] The arrester parameters include: protection level, rated voltage, coordination current, normal operating voltage and arrester energy.

[0113] In the specific implementation, the working principle, control process and technical effect achieved by the SLCC converter valve overvoltage suppression device provided in the embodiment of the present invention are the same as those of the SLCC converter valve overvoltage suppression method in the above embodiment, and will not be repeated here.

[0114] An embodiment of the present invention further provides a computer-readable storage medium, which includes a stored computer program, wherein when the computer program is running, the device where the computer-readable storage medium is located is controlled to execute the SLCC converter valve overvoltage suppression method described in any of the above embodiments.

[0115] The embodiment of the present invention provides a method, device and storage medium for suppressing overvoltage of SLCC converter valves, and its beneficial effects are: by optimizing the bridge arm reactor parameters according to extreme working conditions, a first scheme for suppressing overvoltage is obtained; based on the first extreme working condition and the optimized bridge arm reactor parameters, simulation is performed to optimize the valve-controlled unbalanced protection action constant, and a second scheme for further suppressing overvoltage is obtained; based on the optimized bridge arm reactor parameters and the valve-controlled unbalanced protection action constant, simulation is performed again to obtain extreme working conditions, and in combination with engineering requirements, the converter valve components are optimized until a scheme that can effectively suppress overvoltage is obtained, which solves the overvoltage problem of the converter valve submodule in the ultra-high voltage SLCC direct current transmission system, and is conducive to improving the reliability and economy of the SLCC ultra-high voltage direct current transmission system. By combining the characteristics of the SLCC system, the protection that affects the overvoltage of the converter valve is clearly defined as valve-controlled unbalanced protection for the first time, narrowing the scope of attention of the protection strategy and the action constant, and improving the analysis and suppression efficiency of the converter valve overvoltage. For the first time, it was proposed to effectively suppress overvoltage in the converter valve submodule of the SLCC ultra-high voltage direct current transmission system through the joint design of the primary system (bridge arm reactor parameters, number of submodules, submodule capacitance, valve arrester) and the secondary system (valve-controlled unbalanced protection), thus realizing the system joint optimization of SLCC.

[0116] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for suppressing overvoltage of a SLCC converter valve, characterized in that: include: Based on the self-commutated converter SLCC DC transmission system simulation model, the fault scenario of overvoltage of SLCC converter valve submodule is simulated and the first extreme working condition is obtained; According to the change of the voltage across the bridge arm reactor in the converter valve under the first extreme working condition, the bridge arm reactor parameters are optimized to obtain a first solution; judging whether the first solution meets the preset conditions, and if so, determining that the first solution is an overvoltage suppression solution; wherein the preset condition is that the converter valve submodule voltage meets the equipment tolerance requirement; If the first scheme does not meet the preset conditions, simulation is performed according to the first extreme working condition and the bridge arm reactor parameters to optimize the valve-controlled unbalanced protection action constant to obtain a second scheme; it is determined whether the second scheme meets the preset conditions, and if so, the second scheme is determined to be an overvoltage suppression scheme; If the second scheme does not meet the preset conditions, the overvoltage fault scenario of the SLCC converter valve submodule is simulated and traversed according to the bridge arm reactor parameters and the valve-controlled unbalanced protection action constant to obtain the second extreme operating condition; based on the second extreme operating condition and in combination with the preset engineering requirements, the converter valve assembly is optimized until an overvoltage suppression scheme that meets the preset conditions is obtained.

2. The SLCC converter valve overvoltage suppression method according to claim 1, characterized in that: The SLCC converter valve submodule overvoltage fault scenario includes: internal fault and external fault of the static VAR generator; The internal faults include but are not limited to: one or more of: a neutral point grounding fault, a single-phase grounding fault between the bridge arm reactor and the valve, a two-phase grounding fault, and a three-phase grounding fault; The external faults include, but are not limited to: one or more of: system short circuit fault, bus fault, load sudden change fault, lightning fault and circuit breaker fault.

3. The SLCC converter valve overvoltage suppression method according to claim 1, characterized in that: The optimizing the parameters of the bridge arm reactor according to the change of the voltage across the bridge arm reactor in the converter valve under the first extreme working condition includes: Analyze the overvoltage condition and fault path of the converter valve submodule under the first extreme working condition to obtain the valve side voltage before and after the fault and the valve side voltage of the bridge arm reactor of the static VAR generator; For an internal fault of the static VAR generator, the maximum voltage across the bridge arm reactor before and after the fault is calculated based on the difference between the valve side voltage before the fault and the valve side voltage of the bridge arm reactor of the static VAR generator after the fault; for an external fault of the static VAR generator, the maximum voltage across the bridge arm reactor before and after the fault is calculated based on the difference between the valve side voltage of the bridge arm reactor of the static VAR generator before the fault and the valve side voltage after the fault; The maximum current rise rate that the system can tolerate is obtained, and the optimized bridge arm reactor parameters are calculated according to the ratio of the maximum voltage across the bridge arm reactor before and after the fault to the maximum current rise rate.

4. The SLCC converter valve overvoltage suppression method according to claim 1, characterized in that: The simulating according to the first extreme working condition and the bridge arm reactor parameters to optimize the valve-controlled unbalanced protection action setting value includes: Based on the bridge arm reactor parameters, a simulation analysis is performed on the first extreme working condition to obtain an overvoltage condition of the converter valve submodule under the first extreme working condition; Obtain the overcurrent condition of the static VAR generator; According to the overvoltage condition of the converter valve submodule and the overcurrent condition of the static VAR generator, the valve-controlled unbalanced protection action constant is optimized with the goal of suppressing the converter valve overvoltage while ensuring no false operation during normal operation.

5. The SLCC converter valve overvoltage suppression method according to claim 1, characterized in that: The converter valve assembly optimization includes: one or more of increasing the number of submodules, increasing the capacitance value of the submodules, and adding lightning arresters.

6. The SLCC converter valve overvoltage suppression method according to claim 5, characterized in that: If the converter valve assembly is optimized to increase the number of submodules, the converter valve assembly is optimized until an overvoltage suppression scheme that meets the preset conditions is obtained, including: On the basis of the second solution, the number of submodules is gradually increased and the overvoltage condition of the converter valve is verified until the preset conditions are met, thereby obtaining an overvoltage suppression solution.

7. The SLCC converter valve overvoltage suppression method according to claim 5, characterized in that: If the converter valve assembly is optimized to increase the submodule capacitance value, the converter valve assembly is optimized until an overvoltage suppression scheme that meets the preset conditions is obtained, including: On the basis of the second scheme, the submodule capacitance value is gradually increased and the overvoltage condition of the converter valve is checked until the preset condition is met, thereby obtaining an overvoltage suppression scheme.

8. The SLCC converter valve overvoltage suppression method according to claim 5, characterized in that: If the converter valve assembly is optimized by adding a lightning arrester, the converter valve assembly is optimized until an overvoltage suppression scheme that meets the preset conditions is obtained, including: On the basis of the second scheme, the arrester parameters are configured according to the current converter valve overvoltage situation, the converter valve overvoltage situation after the arrester is added is simulated and verified, and the arrester parameters are iteratively modified according to the simulation results until the preset conditions are met, thereby obtaining an overvoltage suppression scheme; The arrester parameters include: protection level, rated voltage, coordination current, normal operating voltage and arrester energy.

9. An SLCC converter valve overvoltage suppression device, characterized in that: include: The bridge arm reactor optimization module is used to simulate and traverse the overvoltage fault scenario of the SLCC converter valve submodule based on the self-commutated converter SLCC DC transmission system simulation model to obtain the first extreme working condition; According to the change of the voltage across the bridge arm reactor in the converter valve under the first extreme working condition, the bridge arm reactor parameters are optimized to obtain a first solution; judging whether the first solution meets the preset conditions, and if so, determining that the first solution is an overvoltage suppression solution; wherein the preset condition is that the converter valve submodule voltage meets the equipment tolerance requirement; A secondary system optimization module, for, if the first scheme does not meet the preset conditions, simulating according to the first extreme working condition and the bridge arm reactor parameters, optimizing the valve-controlled unbalanced protection action constant, and obtaining a second scheme; judging whether the second scheme meets the preset conditions, and if so, determining that the second scheme is an overvoltage suppression scheme; The converter valve assembly optimization module is used to simulate and traverse the overvoltage fault scenario of the SLCC converter valve submodule according to the bridge arm inductor parameters and the valve-controlled unbalanced protection action constant to obtain a second extreme operating condition if the second scheme does not meet the preset conditions; based on the second extreme operating condition, combined with preset engineering requirements, the converter valve assembly is optimized until an overvoltage suppression scheme that meets the preset conditions is obtained.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, wherein when the device where the computer-readable storage medium is located executes the computer program, the SLCC converter valve overvoltage suppression method according to any one of claims 1 to 8 is implemented.

Images