Optimization method and system of direct current converter station based on network construction type SVG (Static Var Generator)

Abstract

The invention discloses a method and a system for optimizing a direct current converter station based on network construction type SVGs, and relates to the technical field of direct current transmission. N groups of network construction type SVGs are connected to the alternating current side of the direct current converter station; the network-forming SVG comprises a transformer, a starting resistor and a three-bridge-arm SVG valve which are connected in sequence; each bridge arm of the three-bridge-arm SVG valve comprises a plurality of full-bridge sub-modules; and according to a reactive compensation demand, a harmonic filtering demand and a charging limitation demand of a converter valve in the direct current converter station, calculating the group number of the network-forming SVG and parameters of an SVG valve, a transformer and a starting resistor in the network-forming SVG, and setting the network-forming SVG in the direct current converter station through the parameters. By adopting the embodiment of the invention, the network-forming SVG can be reasonably configured in the direct current converter station, reactive compensation and harmonic filtering functions of the converter station are realized, the SVG capability is fully exerted to provide rapid reactive support for an alternating current system to help fault recovery, the stability of a direct current power transmission system accessing an alternating current power grid is improved, and the support superiority of the system is exerted.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current transmission, and in particular to an optimization method and system for a direct current converter station based on a grid-type SVG. Background Art

[0002] DC transmission technology is a key technology for building a new power system and has broad application prospects in long-distance, large-capacity energy transmission. Many DC transmission projects have been built or are under construction at home and abroad, most of which use current source converters.

[0003] In the context of AC systems with an increasing proportion of renewable energy, the system's synchronous stability resources have been greatly reduced. Traditional LCC (line-commutated converter) valves consume a large amount of reactive power during operation, so reactive power compensation devices of corresponding capacity need to be configured. On the other hand, LCC valves generate a large amount of harmonics during operation, which cannot flow into the AC power grid to cause harmonic pollution, so corresponding harmonic filtering devices need to be configured.

[0004] Traditional LCC direct current transmission technology has at least the following technical problems: in the context of an AC system with an increasing proportion of renewable energy, the system's synchronous stability resources have been greatly reduced. LCC direct current transmission technology lacks the ability to provide reactive power support to the system during fault recovery, resulting in slow power and voltage recovery under system faults. When the fault is restored, the reactive power of the filter group cannot be adjusted immediately, which can easily cause transient overvoltage problems at the sending end. Summary of the invention

[0005] The technical problem to be solved by the present invention is how to improve the reactive power compensation capability of conventional DC converter stations. An optimization method and system for a DC converter station based on a meshed SVG are provided, which can meet the reactive power compensation requirements of converter valves and the requirements for filtering harmonics of converter valves, and can give full play to the advantages of meshed SVG in supporting rapid fault recovery of the system, thereby improving the operating stability of conventional DC converter stations and giving full play to the supporting superiority of the system.

[0006] In order to solve the above technical problems, an embodiment of the present invention provides an optimization method of a DC converter station based on a meshed SVG, comprising:

[0007] Connecting N groups of meshed SVG to the AC side of the DC converter station; the meshed SVG includes a transformer, a starting resistor and a three-bridge arm SVG valve connected in sequence; each bridge arm of the three-bridge arm SVG valve includes a number of full-bridge sub-modules;

[0008] Obtaining reactive power compensation requirements, harmonic filtering requirements, and charging restriction requirements of converter valves in the DC converter station as system requirements;

[0009] Obtaining parameters of the three-bridge-arm SVG valve according to the reactive power compensation demand and the wiring mode of the three-bridge-arm SVG valve;

[0010] Determine whether the additional reactive power providing capability and harmonic distortion rate of the DC converter station meet the system requirements, and obtain the number of groups of the network-forming SVG according to the determination result;

[0011] Calculating transformer parameters of the transformer according to the reactive power compensation demand and the three-bridge-arm SVG valve parameters;

[0012] According to the charging restriction requirement, obtaining a starting resistance parameter of the starting resistor;

[0013] The meshing type SVG in the DC converter station is set according to the number of groups of the meshing type SVG, the SVG valve parameters, the transformer parameters and the starting resistance parameters.

[0014] As an improvement of the above solution, the three-bridge-arm SVG valve parameters are obtained according to the reactive power compensation demand and the wiring mode of the three-bridge-arm SVG valve, including:

[0015] According to the reactive power compensation demand, the reactive power capacity demand of the converter valve is obtained;

[0016] According to the wiring mode of the three-bridge-arm SVG valve, a bridge-arm voltage is obtained;

[0017] Obtaining a bridge arm current according to the reactive capacity requirement and the bridge arm voltage;

[0018] The three-bridge-arm SVG valve parameters are obtained according to the bridge-arm voltage and the bridge-arm current.

[0019] As an improvement of the above solution, obtaining the bridge arm current according to the reactive capacity requirement and the bridge arm voltage includes:

[0020] According to the bridge arm voltage, a bridge arm fundamental wave voltage is obtained;

[0021] Calculating a bridge arm fundamental wave current according to the reactive capacity requirement and the bridge arm fundamental wave voltage;

[0022] Obtaining harmonic current filtering times of the DC converter station;

[0023] Calculating the bridge arm harmonic current according to the harmonic current filtering times and the bridge arm fundamental current;

[0024] The bridge arm current is obtained by performing root mean square or absolute value addition processing on the bridge arm fundamental wave current and the bridge arm harmonic current.

[0025] As an improvement of the above solution, the three-bridge-arm SVG valve parameters are obtained according to the bridge-arm voltage and the bridge-arm current, including:

[0026] According to the bridge arm voltage, selecting the average voltage of the full-bridge submodule;

[0027] Calculating the number of submodules of the full-bridge submodule of each bridge arm in the three-bridge-arm SVG valve according to the average voltage and a preset redundancy ratio;

[0028] According to the number of submodules and the bridge arm current, the three-bridge arm SVG valve parameters are obtained.

[0029] As an improvement of the above solution, the method of judging whether the additional reactive power providing capability and harmonic distortion rate of the DC converter station meet the system requirements and obtaining the number of groups of the meshed SVG according to the judgment result includes:

[0030] Calculate the additional reactive power providing capacity and harmonic distortion rate of the DC converter station under the condition of N-1 groups of the grid-type SVG;

[0031] When the additional reactive power providing capacity and harmonic distortion rate do not meet the system requirements, a group of meshing type SVG is added or the valve parameters of the three-bridge arm SVG are adjusted until the system requirements are met;

[0032] When the additional reactive power providing capability and the harmonic distortion rate meet the system requirements, the number of groups of the meshed SVG is obtained.

[0033] As an improvement of the above solution, the transformer parameters of the transformer are calculated according to the reactive power compensation demand and the three-bridge arm SVG valve parameters, including:

[0034] According to the preset DC grid-side voltage and transformer ratio, the SVG valve voltage level is obtained;

[0035] According to the valve parameters of the three-arm SVG, the single-group capacity of the single-group grid-forming SVG and the dynamic maximum reactive power support capacity of the grid-forming SVG are obtained;

[0036] Obtaining a transformer rated capacity according to the SVG valve voltage level and the single group capacity;

[0037] Obtaining the overload capacity of the transformer according to the dynamic maximum reactive power support capacity;

[0038] Determining the leakage reactance parameter of the transformer according to the dynamic reactive support response speed requirement in the reactive compensation requirement;

[0039] The transformer parameters of the transformer are obtained according to the rated capacity of the transformer, the overload capacity and the leakage reactance parameter.

[0040] As an improvement of the above solution, obtaining the starting resistance parameter of the starting resistor according to the charging restriction requirement includes:

[0041] Obtaining a charging current limit and a charging time limit from the charging limit requirement;

[0042] A starting resistance parameter of the starting resistor is obtained according to the charging current limit and the charging time limit.

[0043] As an improvement of the above solution, the bridge arms of the three-bridge-arm SVG valve are connected via a connecting reactor, and the optimization method of the DC converter station based on the grid-type SVG further includes:

[0044] Calculating the terminal voltage of the connection reactor according to the bridge arm current;

[0045] Determining the reactor parameters of the connection reactor according to the terminal voltage;

[0046] The grid-type SVG in the DC converter station is set according to the reactor parameters.

[0047] As an improvement of the above solution, the bridge arms of the three-bridge-arm SVG valve are connected by connecting reactors and bushings, and the optimization method of the DC converter station based on the grid-type SVG further includes:

[0048] Calculating the terminal voltage of the connection reactor according to the bridge arm current;

[0049] Calculating the voltage of the connection reactor and the bushing to ground according to the terminal voltage;

[0050] According to the bridge arm current, obtaining the current level of the connection reactor and the bushing;

[0051] Determining the reactor parameters of the connection reactor and the bushing parameters of the bushing according to the voltage to ground and the current level;

[0052] The grid-type SVG in the DC converter station is set according to the reactor parameters and the bushing parameters.

[0053] The embodiment of the present invention further provides an optimization system for a DC converter station based on a meshed SVG, comprising:

[0054] A meshing SVG connection module is used to connect N groups of meshing SVGs to the AC side of a DC converter station; the meshing SVG includes a transformer, a starting resistor and a three-bridge arm SVG valve connected in sequence; each bridge arm of the three-bridge arm SVG valve includes a number of full-bridge sub-modules;

[0055] A system demand acquisition module, used to acquire reactive power compensation demand, harmonic filtering demand, and charging restriction demand of the converter valve in the DC converter station as system demand;

[0056] A three-bridge-arm SVG valve parameter calculation module, used to obtain the three-bridge-arm SVG valve parameters according to the reactive power compensation demand and the wiring mode of the three-bridge-arm SVG valve;

[0057] A mesh-type SVG group number calculation module is used to determine whether the additional reactive power providing capability and harmonic distortion rate of the DC converter station meet the system requirements, and obtain the number of mesh-type SVG groups according to the determination result;

[0058] A transformer parameter calculation module, used to calculate the transformer parameters of the transformer according to the reactive power compensation demand and the three-bridge arm SVG valve parameters;

[0059] A starting resistance parameter calculation module, used for obtaining a starting resistance parameter of the starting resistance according to the charging restriction requirement;

[0060] The improved setting module of the DC converter station is used to set the grid-type SVG in the DC converter station according to the number of groups of the grid-type SVG, the SVG valve parameters, the transformer parameters and the starting resistance parameters.

[0061] Compared with the prior art, the present invention discloses an optimization method and system for a DC converter station based on a meshed SVG, wherein N groups of meshed SVG are connected to the AC side of the DC converter station; the meshed SVG includes a transformer, a starting resistor and a three-arm SVG valve connected in sequence; each bridge arm of the three-arm SVG valve includes a number of full-bridge sub-modules; the reactive compensation demand, harmonic filtering demand and charging restriction demand of the converter valve in the DC converter station are obtained as system requirements; the three-arm SVG valve parameters are obtained according to the reactive compensation demand and the wiring mode of the three-arm SVG valve; it is judged whether the additional reactive power providing capacity and harmonic distortion rate of the DC converter station meet the system requirements, and the number of meshed SVG groups is obtained according to the judgment result; the transformer parameters of the transformer are calculated according to the reactive compensation demand and the three-arm SVG valve parameters; the starting resistor parameters of the starting resistor are obtained according to the charging restriction requirement; the meshed SVG in the DC converter station is set according to the number of meshed SVG groups, the SVG valve parameters, the transformer parameters and the starting resistor parameters. By adopting the embodiments of the present invention, the meshing type SVG can be reasonably configured in the DC converter station to realize the reactive power compensation and harmonic filtering functions of the converter station. At the same time, the SVG capability can be fully utilized to provide fast reactive power support to the AC system to help fault recovery, thereby improving the stability of the DC transmission system connected to the AC power grid and giving full play to the superiority of system support. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a schematic flow chart of the steps of an optimization method of a DC converter station based on a meshed SVG provided in an embodiment of the present invention;

[0063] Figure 2 is a system topology diagram of a DC converter station obtained by using the optimization method of a DC converter station based on a meshed SVG provided in an embodiment of the present invention;

[0064] Figure 3 1 is a schematic structural diagram of a full-bridge submodule of a three-bridge-arm SVG valve provided in an embodiment of the present invention;

[0065] Figure 4 It is a structural schematic diagram of an optimization system for a DC converter station based on a meshed SVG provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0066] 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.

[0067] In the description of the specification and claims, it is to be understood that the terms first, second, etc. in the specification and claims are only used for the purpose of describing the same technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated, nor necessarily describing the order or time sequence. The terms are interchangeable where appropriate. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0068] The existing LCC DC transmission uses AC filters and parallel capacitor groups, which have at least the following problems: in the context of AC systems with an increasing proportion of new energy, the system's synchronous stability resources have been greatly reduced, and LCC DC transmission technology lacks the ability to provide reactive power support to the system during fault recovery, resulting in slow power and voltage recovery under system faults; the reactive power of the filter group cannot be adjusted immediately when the fault is restored, which can easily cause transient overvoltage problems at the sending end; faults can easily cause multiple DC commutation failures at the receiving end; and it occupies a larger area than flexible DC transmission technology.

[0069] Based on the above considerations, an embodiment of the present invention provides an optimization method for a DC converter station based on a meshed SVG. By improving the conventional DC converter station with a meshed SVG, the reactive compensation requirements of the converter valve and the requirements for filtering the harmonics of the converter valve can be met, and the advantages of the meshed SVG in supporting the rapid fault recovery of the system can be fully utilized, the operating stability of the conventional DC converter station can be improved, and the support superiority of the system can be brought into play.

[0070] See also Figure 1 In this embodiment, the optimization method of the DC converter station based on the grid-type SVG is specifically performed through steps S1 to S7:

[0071] S1. Connect N groups of meshed SVG to the AC side of a DC converter station; the meshed SVG includes a transformer, a starting resistor and a three-bridge-arm SVG valve connected in sequence; each bridge arm of the three-bridge-arm SVG valve includes a number of full-bridge sub-modules.

[0072] In the embodiment of the present invention, a meshed SVG is used to replace a conventional AC filter. It has both reactive power output capability to meet the reactive power compensation requirements of the converter valve and harmonic filtering capability to meet the requirements of filtering harmonics of the converter valve. In addition, it can quickly recover reactive power when a fault is locked and does not cause overvoltage problems in the AC system. It can provide reactive power support to the system during fault recovery and help the fault to recover quickly.

[0073] S2. Obtain reactive power compensation demand, harmonic filtering demand, and charging restriction demand of the converter valve in the DC converter station as system demand.

[0074] It should be noted that, in the embodiment of the present invention, the reactive compensation demand includes reactive capacity demand and dynamic reactive support response speed demand; the harmonic filtering demand includes harmonic distortion rate demand; and the charging limitation demand includes charging current limitation and charging time limitation.

[0075] S3. Obtaining parameters of the three-bridge-arm SVG valve according to the reactive power compensation demand and the wiring mode of the three-bridge-arm SVG valve.

[0076] It should be noted that the connection modes of the three-bridge-arm SVG valve include star connection and delta connection.

[0077] S4. Determine whether the additional reactive power providing capability and harmonic distortion rate of the DC converter station meet the system requirements, and obtain the number of groups of the meshed SVG according to the determination result.

[0078] S5. Calculate transformer parameters of the transformer according to the reactive power compensation demand and the three-bridge-arm SVG valve parameters.

[0079] S6. Obtaining a starting resistance parameter of the starting resistor according to the charging restriction requirement.

[0080] S7. According to the number of groups of the meshing type SVG, the SVG valve parameters, the transformer parameters and the starting resistance parameters, the meshing type SVG in the DC converter station is set.

[0081] In the above scheme, the grid-forming SVG can be reasonably configured in the DC converter station to realize the reactive power compensation and harmonic filtering functions of the converter station. At the same time, the SVG capability can be fully utilized to provide fast reactive power support to the AC system to help fault recovery, improve the stability of the DC transmission system connected to the AC power grid, and give full play to the superiority of system support.

[0082] In some embodiments, the system topology diagram of the DC converter station obtained by the optimization method of the DC converter station based on the meshed SVG is as follows: Figure 2 As shown. Figure 2 Two connection modes of the three-bridge-arm SVG valve are shown in FIG.

[0083] More preferably, see Figure 3 The full-bridge submodule includes a DC capacitor C1, a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a bypass switch K1, a resistor R1, and a transition thyristor T1:

[0084] One end of the full-bridge submodule is electrically connected to one end of the bypass switch K1, the cathode of the turning thyristor T1, the first end of the first switch S1, and the second end of the second switch S2; the other end of the full-bridge submodule is electrically connected to the other end of the bypass switch K1, the anode of the turning thyristor T1, the first end of the third switch S3, and the second end of the fourth switch S4; the second end of the first switch S1 is electrically connected to the second end of the third switch S3, one end of the DC capacitor C1, and one end of the resistor R1; the first end of the second switch S2 is electrically connected to the first end of the fourth switch S4, the other end of the DC capacitor C1, and the other end of the resistor R1;

[0085] One end of the full-bridge submodule is electrically connected to the other end of the previous full-bridge submodule or the connecting inductor; the other end of the full-bridge submodule is electrically connected to one end of the next full-bridge submodule or the connecting inductor.

[0086] As a preferred implementation, step S3, according to the reactive power compensation demand and the wiring mode of the three-bridge-arm SVG valve, obtains the three-bridge-arm SVG valve parameters, which is specifically performed through steps S31-S34:

[0087] S31. Obtaining a reactive capacity requirement of the converter valve according to the reactive compensation requirement.

[0088] S32. Obtaining a bridge arm voltage according to a wiring method of the three-bridge arm SVG valve.

[0089] Exemplarily, according to the wiring mode of the three-bridge-arm SVG valve, the line voltage of the three-bridge-arm SVG valve can be obtained, and further the bridge-arm voltage can be obtained.

[0090] S33. Obtain a bridge arm current according to the reactive capacity requirement and the bridge arm voltage.

[0091] S34. Obtain three-bridge-arm SVG valve parameters according to the bridge-arm voltage and the bridge-arm current.

[0092] Further, preferably, step S33 includes:

[0093] According to the bridge arm voltage, a bridge arm fundamental wave voltage is obtained;

[0094] Calculating a bridge arm fundamental wave current according to the reactive capacity requirement and the bridge arm fundamental wave voltage;

[0095] Obtaining harmonic current filtering times of the DC converter station;

[0096] Calculating the bridge arm harmonic current according to the harmonic current filtering times and the bridge arm fundamental current;

[0097] The bridge arm current is obtained by performing root mean square or absolute value addition processing on the bridge arm fundamental wave current and the bridge arm harmonic current.

[0098] For example, by I p =I1+I h or Calculate the bridge arm current; where I1 is the bridge arm fundamental current, I h is the harmonic current of the bridge arm.

[0099] Preferably, step S34 includes:

[0100] According to the bridge arm voltage, selecting the average voltage of the full-bridge submodule;

[0101] Calculating the number of submodules of the full-bridge submodule of each bridge arm in the three-bridge-arm SVG valve according to the average voltage and a preset redundancy ratio;

[0102] According to the number of submodules and the bridge arm current, the three-bridge arm SVG valve parameters are obtained.

[0103] As a preferred implementation, step S4, judging whether the additional reactive power providing capability and harmonic distortion rate of the DC converter station meet the system requirements, and obtaining the number of groups of the network-type SVG according to the judgment result, comprises:

[0104] Calculate the additional reactive power providing capacity and harmonic distortion rate of the DC converter station under the condition of N-1 groups of the grid-type SVG;

[0105] When the additional reactive power providing capacity and harmonic distortion rate do not meet the system requirements, a group of meshing type SVG is added or the valve parameters of the three-bridge arm SVG are adjusted until the system requirements are met;

[0106] When the additional reactive power providing capability and the harmonic distortion rate meet the system requirements, the number of groups of the meshed SVG is obtained.

[0107] It should be noted that N is the initial number of groups of the mesh-type SVG, N≥1, and the specific value of N does not affect the beneficial effects of the embodiment of the present invention. In the embodiment of the present invention, in subsequent calculations, if it is found that the number of groups of the current mesh-type SVG cannot meet the system requirements, that is, the reactive power compensation and harmonic wave filtering functions cannot be achieved, the number of groups of the mesh-type SVG can be adjusted.

[0108] In some embodiments, while calculating the number of groups of the meshing type SVG, the voltage level of the meshing type SVG may also be adjusted, and the goal of the adjustment is to meet the system requirements.

[0109] As a preferred implementation, step S5, calculating the transformer parameters of the transformer according to the reactive power compensation demand and the three-bridge arm SVG valve parameters, includes:

[0110] According to the preset DC grid-side voltage and transformer ratio, the SVG valve voltage level is obtained;

[0111] According to the valve parameters of the three-arm SVG, the single-group capacity of the single-group grid-forming SVG and the dynamic maximum reactive power support capacity of the grid-forming SVG are obtained;

[0112] Obtaining a transformer rated capacity according to the SVG valve voltage level and the single group capacity;

[0113] Obtaining the overload capacity of the transformer according to the dynamic maximum reactive power support capacity;

[0114] Determining the leakage reactance parameter of the transformer according to the dynamic reactive support response speed requirement in the reactive compensation requirement;

[0115] The transformer parameters of the transformer are obtained according to the rated capacity of the transformer, the overload capacity and the leakage reactance parameter.

[0116] In the embodiment of the present invention, the transformer parameters include transformer rated capacity, overload capacity and leakage reactance parameters. In practical applications, other parameters need to be set for the transformer in the DC converter valve. The embodiment of the present invention shows the setting method of several main parameters.

[0117] As a preferred implementation, step S6, obtaining a starting resistance parameter of the starting resistor according to the charging restriction requirement, includes:

[0118] Obtaining a charging current limit and a charging time limit from the charging limit requirement;

[0119] A starting resistance parameter of the starting resistor is obtained according to the charging current limit and the charging time limit.

[0120] In the above scheme, the starting time can be determined by charging current limitation and charging time limitation, and the starting resistance parameter can be calculated. In practical applications, the starting resistance parameter can enable the grid-forming SVG of the DC converter station to start and provide reactive power compensation and harmonic wave filtering for the branch converter station.

[0121] In some preferred embodiments, the bridge arms of the three-bridge-arm SVG valve are connected via a connecting reactor, and the optimization method of the DC converter station based on the grid-type SVG further includes:

[0122] Calculating the terminal voltage of the connection reactor according to the bridge arm current;

[0123] Determining the reactor parameters of the connection reactor according to the terminal voltage;

[0124] The grid-type SVG in the DC converter station is set according to the reactor parameters.

[0125] In the above solution, the bridge arms of the three-bridge-arm SVG valve are connected only by connecting the reactors. When configuring the DC converter station, it is necessary to configure the connection reactor parameters.

[0126] In some other preferred embodiments, the bridge arms of the three-bridge-arm SVG valve are connected via connecting reactors and bushings, and the optimization method of the DC converter station based on the grid-type SVG further includes:

[0127] Calculating the terminal voltage of the connection reactor according to the bridge arm current;

[0128] Calculating the voltage of the connection reactor and the bushing to ground according to the terminal voltage;

[0129] According to the bridge arm current, obtaining the current level of the connection reactor and the bushing;

[0130] Determining the reactor parameters of the connection reactor and the bushing parameters of the bushing according to the voltage to ground and the current level;

[0131] The grid-type SVG in the DC converter station is set according to the reactor parameters and the bushing parameters.

[0132] In the above scheme, the bridge arms of the three-bridge-arm SVG valve are connected by connecting reactors and bushings. When configuring the DC converter station, it is necessary to configure the connection reactor parameters and bushing parameters.

[0133] The optimization method of a DC converter station based on a meshed SVG provided in an embodiment of the present invention can meet the requirements of reactive power compensation of converter valves and filtering harmonics of converter valves, give full play to the advantages of meshed SVG in supporting rapid fault recovery of the system, improve the operating stability of conventional DC converter stations, and give full play to the support superiority of the system.

[0134] The embodiment of the present invention provides an optimization system for a DC converter station based on a meshed SVG. Figure 4 The optimization system of the DC converter station based on the grid-type SVG includes a grid-type SVG connection module 11, a system demand acquisition module 12, a three-bridge arm SVG valve parameter calculation module 13, a grid-type SVG group number calculation module 14, a transformer parameter calculation module 15, a starting resistance parameter calculation module 16 and a DC converter station improvement setting module 17, wherein:

[0135] A meshed SVG connection module 11 is used to connect N groups of meshed SVGs to the AC side of a DC converter station; the meshed SVG includes a transformer, a starting resistor and a three-bridge arm SVG valve connected in sequence; each bridge arm of the three-bridge arm SVG valve includes a number of full-bridge sub-modules;

[0136] A system demand acquisition module 12 is used to acquire reactive power compensation demand, harmonic filtering demand, and charging restriction demand of the converter valve in the DC converter station as system demand;

[0137] A three-bridge-arm SVG valve parameter calculation module 13, used to obtain the three-bridge-arm SVG valve parameters according to the reactive power compensation demand and the wiring mode of the three-bridge-arm SVG valve;

[0138] A mesh-type SVG group number calculation module 14 is used to determine whether the additional reactive power providing capability and harmonic distortion rate of the DC converter station meet the system requirements, and obtain the number of mesh-type SVG groups according to the determination result;

[0139] A transformer parameter calculation module 15, configured to calculate the transformer parameters of the transformer according to the reactive power compensation requirement and the three-bridge arm SVG valve parameters;

[0140] A starting resistance parameter calculation module 16, used to obtain a starting resistance parameter of the starting resistance according to the charging restriction requirement;

[0141] The DC converter station improvement setting module 17 is used to set the grid-type SVG in the DC converter station according to the number of groups of the grid-type SVG, the SVG valve parameters, the transformer parameters and the starting resistance parameters.

[0142] As a preferred implementation, the three-bridge-arm SVG valve parameter calculation module includes:

[0143] A reactive capacity demand acquisition unit, configured to obtain the reactive capacity demand of the converter valve according to the reactive compensation demand;

[0144] A bridge arm voltage calculation unit, used for obtaining a bridge arm voltage according to a wiring mode of the three-bridge arm SVG valve;

[0145] A bridge arm current calculation unit, used for obtaining a bridge arm current according to the reactive capacity requirement and the bridge arm voltage;

[0146] The three-bridge-arm SVG valve parameter calculation unit is used to obtain the three-bridge-arm SVG valve parameters according to the bridge-arm voltage and the bridge-arm current.

[0147] Further, preferably, the bridge arm current calculation unit is specifically used for:

[0148] According to the bridge arm voltage, a bridge arm fundamental wave voltage is obtained;

[0149] Calculating a bridge arm fundamental wave current according to the reactive capacity requirement and the bridge arm fundamental wave voltage;

[0150] Obtaining harmonic current filtering times of the DC converter station;

[0151] Calculating the bridge arm harmonic current according to the harmonic current filtering times and the bridge arm fundamental current;

[0152] The bridge arm current is obtained by performing root mean square or absolute value addition processing on the bridge arm fundamental wave current and the bridge arm harmonic current.

[0153] Preferably, the three-bridge-arm SVG valve parameter calculation unit is specifically used for:

[0154] According to the bridge arm voltage, selecting the average voltage of the full-bridge submodule;

[0155] Calculating the number of submodules of the full-bridge submodule of each bridge arm in the three-bridge-arm SVG valve according to the average voltage and a preset redundancy ratio;

[0156] According to the number of submodules and the bridge arm current, the three-bridge arm SVG valve parameters are obtained.

[0157] As a preferred implementation, the mesh-type SVG group number calculation module includes:

[0158] A system capacity calculation unit, used for calculating the additional reactive power providing capacity and harmonic distortion rate of the DC converter station under the condition of N-1 groups of the grid-type SVG;

[0159] A system demand evaluation unit, configured to add a group of meshing type SVG or adjust the valve parameters of the three-bridge arm SVG when the additional reactive power providing capability and harmonic distortion rate do not meet the system demand, until the system demand is met;

[0160] The meshing type SVG adjustment unit is used to obtain the number of groups of the meshing type SVG when the additional reactive power provision capability and the harmonic distortion rate meet the system requirements.

[0161] As a preferred implementation, the transformer parameter calculation module includes:

[0162] The SVG valve voltage level calculation unit is used to obtain the SVG valve voltage level according to the preset DC grid side voltage and the transformer ratio;

[0163] The capacity and reactive support calculation unit is used to obtain the single group capacity of the single group grid-forming SVG and the dynamic maximum reactive support capacity of the grid-forming SVG according to the three-bridge arm SVG valve parameters;

[0164] A rated capacity calculation unit, used for obtaining the rated capacity of the transformer according to the SVG valve voltage level and the single group capacity;

[0165] An overload capacity calculation unit, used to obtain the overload capacity of the transformer according to the dynamic maximum reactive power support capacity;

[0166] A leakage reactance parameter calculation unit, used to determine the leakage reactance parameter of the transformer according to the dynamic reactive power support response speed requirement in the reactive power compensation requirement;

[0167] A transformer parameter generating unit is used to obtain the transformer parameters of the transformer according to the rated capacity of the transformer, the overload capacity and the leakage reactance parameter.

[0168] As a preferred implementation, the starting resistance parameter calculation module includes:

[0169] a limit extraction unit, configured to obtain a charging current limit and a charging time limit from the charging limit requirement;

[0170] A starting resistance parameter calculation unit is used to obtain a starting resistance parameter of the starting resistance according to the charging current limit and the charging time limit.

[0171] As a preferred implementation, the bridge arms of the three-bridge-arm SVG valve are connected via connecting reactors and bushings, and the optimization system of the DC converter station based on the grid-type SVG further includes:

[0172] A terminal voltage calculation module, used for calculating the terminal voltage of the connection reactor according to the bridge arm current;

[0173] A reactor parameter calculation module, used to determine the reactor parameters of the connected reactor according to the terminal voltage;

[0174] The first DC converter station setting submodule is used to set the grid-type SVG in the DC converter station according to the reactor parameters.

[0175] As another preferred implementation, the bridge arms of the three-bridge-arm SVG valve are connected via connecting reactors and bushings, and the optimization system of the DC converter station based on the grid-type SVG further includes:

[0176] A terminal voltage calculation module, used for calculating the terminal voltage of the connection reactor according to the bridge arm current;

[0177] A voltage-to-ground calculation module, used for calculating the voltage-to-ground of the connection reactor and the bushing according to the terminal voltage;

[0178] A current level calculation module, used for obtaining the current level of the connection reactor and the bushing according to the bridge arm current;

[0179] a parameter generating unit, configured to determine a reactor parameter of the connection reactor and a bushing parameter of the bushing according to the voltage to ground and the current level;

[0180] The second DC converter station setting submodule is used to set the grid-type SVG in the DC converter station according to the reactor parameters and the bushing parameters.

[0181] An optimization system for a DC converter station based on a meshed SVG provided by an embodiment of the present invention can meet the requirements for reactive power compensation of converter valves and filtering harmonics of converter valves, and can give full play to the advantages of the meshed SVG in supporting rapid fault recovery of the system, thereby improving the operating stability of conventional DC converter stations and giving full play to the support superiority of the system.

[0182] A person skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0183] 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 optimizing a DC converter station based on a grid-type SVG, characterized in that: include: Connecting N groups of meshed SVG to the AC side of the DC converter station; the meshed SVG includes a transformer, a starting resistor and a three-bridge arm SVG valve connected in sequence; each bridge arm of the three-bridge arm SVG valve includes a number of full-bridge sub-modules; Obtaining reactive power compensation requirements, harmonic filtering requirements, and charging restriction requirements of converter valves in the DC converter station as system requirements; Obtaining parameters of the three-bridge-arm SVG valve according to the reactive power compensation demand and the wiring mode of the three-bridge-arm SVG valve; Determine whether the additional reactive power providing capability and harmonic distortion rate of the DC converter station meet the system requirements, and obtain the number of groups of the network-forming SVG according to the determination result; Calculating transformer parameters of the transformer according to the reactive power compensation demand and the three-bridge-arm SVG valve parameters; According to the charging restriction requirement, obtaining a starting resistance parameter of the starting resistor; The meshing type SVG in the DC converter station is set according to the number of groups of the meshing type SVG, the SVG valve parameters, the transformer parameters and the starting resistance parameters.

2. The optimization method of a DC converter station based on a meshed SVG according to claim 1, characterized in that: The obtaining of the three-bridge-arm SVG valve parameters according to the reactive power compensation requirement and the wiring mode of the three-bridge-arm SVG valve includes: According to the reactive power compensation demand, the reactive power capacity demand of the converter valve is obtained; According to the wiring mode of the three-bridge-arm SVG valve, a bridge-arm voltage is obtained; Obtaining a bridge arm current according to the reactive capacity requirement and the bridge arm voltage; The three-bridge-arm SVG valve parameters are obtained according to the bridge-arm voltage and the bridge-arm current.

3. The optimization method of a DC converter station based on a meshed SVG according to claim 2, characterized in that: The obtaining the bridge arm current according to the reactive capacity requirement and the bridge arm voltage comprises: According to the bridge arm voltage, a bridge arm fundamental wave voltage is obtained; Calculating a bridge arm fundamental wave current according to the reactive capacity requirement and the bridge arm fundamental wave voltage; Obtaining harmonic current filtering times of the DC converter station; Calculating the bridge arm harmonic current according to the harmonic current filtering times and the bridge arm fundamental current; The bridge arm current is obtained by performing root mean square or absolute value addition processing on the bridge arm fundamental wave current and the bridge arm harmonic current.

4. The optimization method of a DC converter station based on a meshed SVG according to claim 2, characterized in that: The obtaining of the three-bridge-arm SVG valve parameters according to the bridge-arm voltage and the bridge-arm current includes: According to the bridge arm voltage, selecting the average voltage of the full-bridge submodule; Calculating the number of submodules of the full-bridge submodule of each bridge arm in the three-bridge-arm SVG valve according to the average voltage and a preset redundancy ratio; According to the number of submodules and the bridge arm current, the three-bridge arm SVG valve parameters are obtained.

5. The optimization method of a DC converter station based on a meshed SVG according to claim 1, characterized in that: The step of judging whether the additional reactive power providing capability and harmonic distortion rate of the DC converter station meet the system requirements and obtaining the number of groups of the network-forming SVG according to the judging result includes: Calculate the additional reactive power providing capacity and harmonic distortion rate of the DC converter station under the condition of N-1 groups of the grid-type SVG; When the additional reactive power providing capacity and harmonic distortion rate do not meet the system requirements, a group of meshing type SVG is added or the valve parameters of the three-bridge arm SVG are adjusted until the system requirements are met; When the additional reactive power providing capability and the harmonic distortion rate meet the system requirements, the number of groups of the meshed SVG is obtained.

6. The optimization method of a DC converter station based on a meshed SVG according to claim 1, characterized in that: The step of calculating the transformer parameters of the transformer according to the reactive power compensation requirement and the three-bridge arm SVG valve parameters includes: According to the preset DC grid-side voltage and transformer ratio, the SVG valve voltage level is obtained; According to the valve parameters of the three-arm SVG, the single-group capacity of the single-group grid-forming SVG and the dynamic maximum reactive power support capacity of the grid-forming SVG are obtained; Obtaining a transformer rated capacity according to the SVG valve voltage level and the single group capacity; Obtaining the overload capacity of the transformer according to the dynamic maximum reactive power support capacity; Determining the leakage reactance parameter of the transformer according to the dynamic reactive support response speed requirement in the reactive compensation requirement; The transformer parameters of the transformer are obtained according to the rated capacity of the transformer, the overload capacity and the leakage reactance parameter.

7. The optimization method of a DC converter station based on a meshed SVG according to claim 1, characterized in that: The obtaining, according to the charging restriction requirement, a starting resistance parameter of the starting resistance includes: Obtaining a charging current limit and a charging time limit from the charging limit requirement; A starting resistance parameter of the starting resistor is obtained according to the charging current limit and the charging time limit.

8. The optimization method of a DC converter station based on a meshed SVG according to claim 2, characterized in that: The bridge arms of the three-bridge-arm SVG valve are connected via connecting reactors, and the optimization method of the DC converter station based on the grid-type SVG further includes: Calculating the terminal voltage of the connection reactor according to the bridge arm current; Determining the reactor parameters of the connection reactor according to the terminal voltage; The grid-type SVG in the DC converter station is set according to the reactor parameters.

9. The optimization method of a DC converter station based on a meshed SVG according to claim 2, characterized in that: The bridge arms of the three-bridge-arm SVG valve are connected via connecting reactors and bushings, and the optimization method of the DC converter station based on the grid-type SVG further includes: Calculating the terminal voltage of the connection reactor according to the bridge arm current; Calculating the voltage of the connection reactor and the bushing to ground according to the terminal voltage; According to the bridge arm current, obtaining the current level of the connection reactor and the bushing; Determining the reactor parameters of the connection reactor and the bushing parameters of the bushing according to the voltage to ground and the current level; The grid-type SVG in the DC converter station is set according to the reactor parameters and the bushing parameters.

10. An optimization system for a DC converter station based on a grid-type SVG, characterized in that: include: A meshing SVG connection module is used to connect N groups of meshing SVGs to the AC side of a DC converter station; the meshing SVG includes a transformer, a starting resistor and a three-bridge arm SVG valve connected in sequence; each bridge arm of the three-bridge arm SVG valve includes a number of full-bridge sub-modules; A system demand acquisition module, used to acquire reactive power compensation demand, harmonic filtering demand, and charging restriction demand of the converter valve in the DC converter station as system demand; A three-bridge-arm SVG valve parameter calculation module, used to obtain the three-bridge-arm SVG valve parameters according to the reactive power compensation demand and the wiring mode of the three-bridge-arm SVG valve; A mesh-type SVG group number calculation module is used to determine whether the additional reactive power providing capability and harmonic distortion rate of the DC converter station meet the system requirements, and obtain the number of mesh-type SVG groups according to the determination result; A transformer parameter calculation module, used to calculate the transformer parameters of the transformer according to the reactive power compensation demand and the three-bridge arm SVG valve parameters; A starting resistance parameter calculation module, used for obtaining a starting resistance parameter of the starting resistance according to the charging restriction requirement; The improved setting module of the DC converter station is used to set the grid-type SVG in the DC converter station according to the number of groups of the grid-type SVG, the SVG valve parameters, the transformer parameters and the starting resistance parameters.

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