A method and system for optimizing a DC converter station based on a networked SVG

Abstract

The application discloses a kind of based on network type SVG's direct current converter station optimization method and system, it is related to direct current transmission technical field, by connecting N groups network type SVG in the AC measurement of direct current converter station;Network type SVG includes transformer, starting resistance and three bridge arms SVG valve connected in turn;Every bridge arm of the three bridge arms SVG valve includes several full-bridge sub-modules;Again according to the reactive power compensation demand, harmonic filter demand and charging limit demand of converter valve in direct current converter station, the number of groups of network type SVG and the parameters of SVG valve, transformer and starting resistance in network type SVG are calculated, and the network type SVG in the direct current converter station is set by the above parameters.The embodiment of the application can reasonably configure network type SVG in direct current converter station, realize converter station reactive power compensation and harmonic filter function, simultaneously give full play to SVG capacity to provide quick reactive power support to AC system to help fault recovery, improve the stability of direct current transmission system access AC power grid, play system support superiority.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of direct current transmission, in particular to a method and system for optimizing a direct current converter station based on network-forming SVG. BACKGROUND

[0002] Direct current transmission technology is a key technology for building a new power system and has a broad application prospect in long-distance and large-capacity power transmission. Many direct current 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 an AC system with a continuously increasing proportion of new energy, the synchronous stability resources of the system are greatly reduced. The traditional LCC (line-commutated converter) converter valve consumes a large amount of reactive power during operation, so a corresponding capacity of reactive power compensation device needs to be configured. On the other hand, the LCC converter valve generates a large amount of harmonics during operation, which cannot flow into the AC power grid to cause harmonic pollution, so a corresponding harmonic filter device needs to be configured.

[0004] The traditional LCC direct current transmission technology at least has the following technical problems: in the context of an AC system with a continuously increasing proportion of new energy, the synchronous stability resources of the system are greatly reduced, the 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 fault; the filter group reactive power cannot be adjusted immediately during fault recovery, which is easy to cause transient overvoltage problem at the sending end. SUMMARY

[0005] The technical problem to be solved by the present application is how to improve the reactive power compensation capability of a conventional direct current converter station. The present application provides a method and system for optimizing a direct current converter station based on network-forming SVG, which can meet the requirements of reactive power compensation and harmonic filtering of the converter valve, fully utilize the advantages of network-forming SVG in supporting system fast fault recovery, and improve the operation stability of the conventional direct current converter station and the superiority of system support.

[0006] To solve the above technical problems, the present application provides a method for optimizing a direct current converter station based on network-forming SVG, comprising:

[0007] N groups of network-forming SVGs are connected to the AC side of the direct current converter station; the network-forming SVG comprises a transformer, a starting resistor and a three-bridge SVG valve connected in sequence; each bridge arm of the three-bridge SVG valve comprises a plurality of full-bridge sub-modules;

[0008] Obtain the reactive power compensation demand, harmonic filtering demand and charging restriction demand of the converter valve in the direct current converter station as system demand;

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

[0010] judging whether the additional reactive power providing capability and the harmonic distortion rate of the DC converter station meet system requirements, and obtaining the group number of the grid-forming SVG according to a judgment result;

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

[0012] obtaining starting resistance parameters of the starting resistance according to the charging restriction demand;

[0013] setting the grid-forming SVG in the DC converter station according to the group number of the grid-forming SVG, the SVG valve parameters, the transformer parameters and the starting resistance parameters.

[0014] As an improvement of the above scheme, 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, and the method comprises the following steps:

[0015] obtaining a reactive power capacity demand of the converter valve according to the reactive power compensation demand;

[0016] obtaining a bridge-arm voltage according to the wiring mode of the three-bridge-arm SVG valve;

[0017] obtaining a bridge-arm current according to the reactive power capacity demand and the bridge-arm voltage;

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

[0019] As an improvement of the above scheme, the bridge-arm current is obtained according to the reactive power capacity demand and the bridge-arm voltage, and the method comprises the following steps:

[0020] obtaining a bridge-arm fundamental voltage according to the bridge-arm voltage;

[0021] obtaining a bridge-arm fundamental current by calculation according to the reactive power capacity demand and the bridge-arm fundamental voltage;

[0022] obtaining a harmonic current filtering frequency of the DC converter station;

[0023] obtaining a bridge-arm harmonic current according to the harmonic current filtering frequency and the bridge-arm fundamental current;

[0024] obtaining a bridge-arm current by performing root mean square or absolute value addition processing on the bridge-arm fundamental current and the bridge-arm harmonic current.

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

[0026] The average voltage of the full-bridge sub-module is selected according to the bridge arm voltage;

[0027] The number of sub-modules of the full-bridge sub-module in each bridge arm of the three-bridge SVG valve is calculated according to the average voltage and a preset redundancy ratio;

[0028] The three-bridge SVG valve parameters are obtained according to the number of sub-modules and the bridge arm current.

[0029] As an improvement of the above scheme, the number of groups of the grid-connected SVG is obtained according to the judgment result of whether the additional reactive power supply capability and the harmonic distortion rate of the DC converter station meet the system requirement, and the judgment comprises:

[0030] The additional reactive power supply capability and the harmonic distortion rate of the DC converter station under the condition of N-1 groups of the grid-connected SVG are calculated;

[0031] When the additional reactive power supply capability and the harmonic distortion rate do not meet the system requirement, one group of the grid-connected SVG is added or the three-bridge SVG valve parameters are adjusted until the system requirement is met;

[0032] When the additional reactive power supply capability and the harmonic distortion rate meet the system requirement, the number of groups of the grid-connected SVG is obtained.

[0033] As an improvement of the above scheme, the transformer parameters of the transformer are calculated according to the reactive power compensation requirement and the three-bridge SVG valve parameters, and the calculation comprises:

[0034] The SVG valve voltage grade is obtained according to a preset DC grid side voltage and a transformer ratio;

[0035] The single-group capacity of a single group of the grid-connected SVG and the dynamic maximum reactive power support capability of the grid-connected SVG are obtained according to the three-bridge SVG valve parameters;

[0036] The transformer rated capacity is obtained according to the SVG valve voltage grade and the single-group capacity;

[0037] The overload capability of the transformer is obtained according to the dynamic maximum reactive power support capability;

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

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

[0040] As an improvement of the above scheme, the starting resistance parameter of the starting resistance is obtained according to the charging limit requirement, comprising:

[0041] The charging current limit and the charging time limit are obtained from the charging limit requirement;

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

[0043] As an improvement of the above scheme, the three-bridge SVG valve is connected between each bridge arm through a connecting reactor, and the optimization method of the DC converter station based on the network SVG further comprises:

[0044] The terminal voltage of the connecting reactor is calculated according to the bridge arm current;

[0045] The reactor parameter of the connecting reactor is determined according to the terminal voltage;

[0046] The network SVG in the DC converter station is set according to the reactor parameter.

[0047] As an improvement of the above scheme, the three-bridge SVG valve is connected between each bridge arm through a connecting reactor and a bushing, and the optimization method of the DC converter station based on the network SVG further comprises:

[0048] The terminal voltage of the connecting reactor is calculated according to the bridge arm current;

[0049] The ground voltage of the connecting reactor and the bushing is calculated according to the terminal voltage;

[0050] The current level of the connecting reactor and the bushing is obtained according to the bridge arm current;

[0051] The reactor parameter of the connecting reactor and the bushing parameter of the bushing are determined according to the ground voltage and the current level;

[0052] The network SVG in the DC converter station is set according to the reactor parameter and the bushing parameter.

[0053] The embodiment of the application further provides an optimization system of a DC converter station based on a network SVG, comprising:

[0054] A network SVG connection module is configured to connect N groups of network SVGs in an AC measurement of a DC converter station; the network SVG comprises a transformer, a starting resistance and a three-bridge SVG valve connected in sequence; each bridge arm of the three-bridge SVG valve comprises a plurality of full-bridge sub-modules;

[0055] A system requirement acquisition module is configured to acquire reactive power compensation requirements, harmonic filtering requirements, and charging limit requirements of the converter valve in the DC converter station as system requirements.

[0056] A three-bridge SVG valve parameter calculation module is configured to obtain three-bridge SVG valve parameters according to the reactive power compensation requirements and a wiring mode of the three-bridge SVG valve.

[0057] A network-configuration SVG group number calculation module is configured to determine whether the additional reactive power providing capability and the harmonic distortion rate of the DC converter station meet system requirements, and obtain a group number of the network-configuration SVG according to a determination result.

[0058] A transformer parameter calculation module is configured to calculate transformer parameters of the transformer according to the reactive power compensation requirements and the three-bridge SVG valve parameters.

[0059] A starting resistor parameter calculation module is configured to obtain starting resistor parameters of the starting resistor according to the charging limit requirements.

[0060] A DC converter station improvement setting module is configured to set the network-configuration SVG in the DC converter station according to the group number of the network-configuration SVG, the SVG valve parameters, the transformer parameters, and the starting resistor parameters.

[0061] Compared with the prior art, the disclosed method and system for optimizing a DC converter station based on a network-configuration SVG, by connecting N groups of network-configuration SVGs in the AC system of the DC converter station, the network-configuration SVGs include a transformer, a starting resistor, and a three-bridge SVG valve connected in sequence, each bridge arm of the three-bridge SVG valve includes a plurality of full-bridge sub-modules, the reactive power compensation requirements, the harmonic filtering requirements, and the charging limit requirements of the converter valve in the DC converter station are acquired as system requirements, three-bridge SVG valve parameters are obtained according to the reactive power compensation requirements and a wiring mode of the three-bridge SVG valve, it is determined whether the additional reactive power providing capability and the harmonic distortion rate of the DC converter station meet system requirements, and a group number of the network-configuration SVG is obtained according to a determination result, transformer parameters of the transformer are calculated according to the reactive power compensation requirements and the three-bridge SVG valve parameters, starting resistor parameters of the starting resistor are obtained according to the charging limit requirements, and the network-configuration SVG in the DC converter station is set according to the group number of the network-configuration SVG, the SVG valve parameters, the transformer parameters, and the starting resistor parameters. By using the embodiment of the present application, the network-configuration SVG can be reasonably configured in the DC converter station, the reactive power compensation and harmonic filtering functions of the converter station are realized, the SVG capability is fully utilized to provide fast reactive power support to the AC system to help fault recovery, and the stability of the DC power transmission system in accessing the AC power grid and the superiority of system support are improved. BRIEF DESCRIPTION OF DRAWINGS

[0062] Figure 1 is a step flow schematic diagram of an optimization method of a DC converter station based on a network construction type SVG provided by an embodiment of the present application;

[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 network construction type SVG provided by the present application;

[0064] Figure 3 is a structural schematic diagram of a full-bridge sub-module of a three-bridge-arm SVG valve provided by an embodiment of the present application;

[0065] Figure 4 is a structural schematic diagram of an optimization system of a DC converter station based on a network construction type SVG provided by an embodiment of the present application. DETAILED DESCRIPTION

[0066] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0067] In the description and claims of the specification, it is to be understood that the terms first, second, etc. are used only for the purpose of description and are not to be construed as indicating or implying relative importance or an indicated number of features. They are also not necessarily used to describe a sequence or an order, unless otherwise explicitly indicated. Where appropriate, terms are interchangeable. Thus, features described with "first" and "second" can explicitly or implicitly include at least one of the features.

[0068] The existing LCC DC power transmission adopts an AC filter and a parallel capacitor bank, which at least has the following problems: in the background of an increasing proportion of new energy in an AC system, the synchronous stability resources of the system are greatly reduced, the LCC DC power 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 fault; the filter bank reactive power cannot be immediately adjusted during fault recovery, which is easy to cause transient overvoltage problems at the sending end; the fault is easy to cause multi-loop DC commutation failure at the receiving end; compared with the flexible DC power transmission technology, the occupation area is larger.

[0069] Based on the above thinking, the embodiment of the present application provides an optimization method of a DC converter station based on a network-forming SVG. The network-forming SVG is used to improve the conventional DC converter station, so that the reactive power compensation requirement of the converter valve and the requirement of filtering the harmonic of the converter valve can be met, the advantages of the network-forming SVG in supporting the rapid fault recovery of the system can be fully played, and the operation stability of the conventional DC converter station is improved, and the superiority of the system in support is played.

[0070] Please refer to Figure 1 In the embodiment, the optimization method of the DC converter station based on the network-forming SVG is specifically executed through steps S1 to S7.

[0071] S1, connecting N groups of network-forming SVGs at an AC side of the DC converter station; the network-forming SVG comprises a transformer, a starting resistor and a three-bridge SVG valve connected in sequence; each bridge arm of the three-bridge SVG valve comprises a plurality of full-bridge sub-modules.

[0072] In the embodiment of the present application, the network-forming SVG is used to replace the conventional AC filter, which has the ability of reactive power output to meet the requirement of reactive power compensation of the converter valve, and has the function of harmonic filtering to meet the requirement of filtering the harmonic of the converter valve. In addition, the reactive power can be quickly recovered during fault blocking, and the problem of overvoltage of the AC system is not caused. During the fault recovery period, the system is provided with reactive power support to help the rapid recovery of the fault.

[0073] S2, obtaining the requirement of reactive power compensation, the requirement of harmonic filtering and the requirement of charging limitation of the converter valve in the DC converter station as system requirements.

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

[0075] S3, obtaining the parameters of the three-bridge SVG valve according to the requirement of reactive power compensation and the connection mode of the three-bridge SVG valve.

[0076] It should be noted that the connection mode of the three-bridge SVG valve includes star connection and angle connection.

[0077] S4, judging whether the additional reactive power providing capacity and the harmonic distortion rate of the DC converter station meet the system requirements, and obtaining the number of network-forming SVGs according to the judgment result.

[0078] S5, calculating the transformer parameters of the transformer according to the requirement of reactive power compensation and the parameters of the three-bridge SVG valve.

[0079] S6, obtaining the starting resistor parameters of the starting resistor according to the requirement of charging limitation.

[0080] S7, setting the network-forming SVG in the DC converter station according to the number of the network-forming SVGs, the SVG valve parameters, the transformer parameters and the starting resistance parameters.

[0081] In the above scheme, the network-forming SVG can be reasonably configured in the DC converter station, the reactive power compensation and harmonic filtering functions of the converter station are realized, the SVG capacity is fully utilized to provide fast reactive power support to the AC system to help fault recovery, and the stability of the DC power transmission system connected to the AC power grid and the superiority of system support are improved.

[0082] In some embodiments, the system topology of the DC converter station obtained by the optimization method of the network-forming SVG is as shown in Figure 2 Two connection modes of the three-bridge-arm SVG valve are shown in Figure 2

[0083] More preferably, referring to Figure 3 , the full-bridge sub-module 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 turning thyristor T1.

[0084] One end of the full-bridge sub-module 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 sub-module 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 sub-module is electrically connected to the other end of the previous full-bridge sub-module or connected to the electric reactor. The other end of the full-bridge sub-module is electrically connected to one end of the next full-bridge sub-module or connected to the electric reactor.

[0086] As a preferred embodiment, step S3 obtains 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, which is specifically performed by steps S31-S34.

[0087] S31, obtaining the reactive power capacity demand of the converter valve according to the reactive power compensation demand.

[0088] S32, obtaining the bridge-arm voltage according to the wiring mode of the three-bridge-arm SVG valve.

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

[0090] S33, obtaining bridge-arm current according to the reactive power demand and the bridge-arm voltage.

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

[0092] Further, preferably, step S33 comprises:

[0093] obtaining bridge-arm fundamental voltage according to the bridge-arm voltage;

[0094] calculating bridge-arm fundamental current according to the reactive power demand and the bridge-arm fundamental voltage;

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

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

[0097] obtaining bridge-arm current by performing root mean square or absolute value addition processing on the bridge-arm fundamental current and the bridge-arm harmonic current.

[0098] Exemplarily, bridge-arm current is calculated by I p = I1+ I h or ; wherein, I1 is bridge-arm fundamental current, and I h is bridge-arm harmonic current.

[0099] Preferably, step S34 comprises:

[0100] selecting average voltage of the full-bridge sub-module according to the bridge-arm voltage;

[0101] calculating sub-module number of the full-bridge sub-module of each bridge arm in the three-bridge-arm SVG valve according to the average voltage and preset redundancy ratio;

[0102] obtaining three-bridge-arm SVG valve parameters according to the sub-module number and the bridge-arm current.

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

[0104] calculating the additional reactive power providing capability and the harmonic distortion rate of the DC converter station under the condition of N-1 groups of the network-forming SVG;

[0105] When the additional reactive power supply capability and the harmonic distortion rate do not meet the system requirement, a set of grid-forming SVGs or the three-bridge SVG valve parameters are adjusted until the system requirement is met;

[0106] When the additional reactive power supply capability and the harmonic distortion rate meet the system requirement, the number of sets of the grid-forming SVGs is obtained.

[0107] It should be noted that N is the initial number of sets of the grid-forming SVGs, N≥1, and the specific value of N does not affect the beneficial effects of the embodiments of the present application. In the embodiments of the present application, if it is found that the number of sets of the grid-forming SVGs cannot meet the system requirement, that is, the reactive power compensation and harmonic filtering functions cannot be achieved, the number of sets of the grid-forming SVGs can be adjusted.

[0108] In some embodiments, the voltage level of the grid-forming SVGs can also be adjusted while the number of sets of the grid-forming SVGs is calculated, and the target of the adjustment is to meet the system requirement.

[0109] As a preferred implementation, step S5, according to the reactive power compensation requirement and the three-bridge SVG valve parameters, calculates the transformer parameters of the transformer, including:

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

[0111] According to the three-bridge SVG valve parameters, the single set capacity of a single set of grid-forming SVGs and the dynamic maximum reactive power support capability of the grid-forming SVGs are obtained;

[0112] According to the SVG valve voltage level and the single set capacity, the transformer rated capacity is obtained;

[0113] According to the dynamic maximum reactive power support capability, the overload capacity of the transformer is obtained;

[0114] According to the dynamic reactive power support response speed requirement in the reactive power compensation requirement, the leakage reactance parameter of the transformer is determined;

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

[0116] In the embodiments of the present application, the transformer parameters include the transformer rated capacity, the overload capacity and the leakage reactance parameter, and in actual application, other parameters also need to be set for the transformer in the DC converter valve, and the present application embodiment shows the setting method of the main parameters.

[0117] As a preferred implementation, the step S6 comprises:

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

[0119] obtaining the starting resistance parameter of the starting resistance according to the charging current limit and the charging time limit.

[0120] In the above scheme, the starting time can be determined through the charging current limit and the charging time limit, and the starting resistance parameter is calculated. In actual application, the starting resistance parameter can enable the network-type SVG of the DC converter station to start, and provide reactive power compensation and harmonic filtering for the branch converter station.

[0121] In some preferred embodiments, the three-bridge-arm SVG valve is connected between the bridge arms through a connecting reactor, and the optimization method of the DC converter station based on the network-type SVG further comprises:

[0122] calculating an end voltage of the connecting reactor according to the bridge arm current;

[0123] determining a reactor parameter of the connecting reactor according to the end voltage;

[0124] setting the network-type SVG in the DC converter station according to the reactor parameter.

[0125] In the above scheme, the three-bridge-arm SVG valve is connected between the bridge arms through the connecting reactor, and the connecting reactor parameter needs to be configured when the DC converter station is configured.

[0126] In other preferred embodiments, the three-bridge-arm SVG valve is connected between the bridge arms through the connecting reactor and a bushing, and the optimization method of the DC converter station based on the network-type SVG further comprises:

[0127] calculating an end voltage of the connecting reactor according to the bridge arm current;

[0128] calculating a ground voltage of the connecting reactor and the bushing according to the end voltage;

[0129] obtaining a current level of the connecting reactor and the bushing according to the bridge arm current;

[0130] determining a reactor parameter of the connecting reactor and a bushing parameter of the bushing according to the ground voltage and the current level;

[0131] setting the network-type SVG in the DC converter station according to the reactor parameter and the bushing parameter.

[0132] In the above scheme, the connection between each bridge arm of the three-bridge-arm SVG valve is connected through the connection reactor and the bushing, and when the DC converter station is configured, the connection reactor parameters and the bushing parameters need to be configured.

[0133] The optimization method of the DC converter station based on the network-forming SVG provided by the embodiment of the present application can meet the requirements of reactive power compensation and harmonic filtering of the converter valve, can fully exert the advantages of the network-forming SVG in supporting system rapid fault recovery, and can improve the operation stability of the conventional DC converter station and exert the superiority of system support.

[0134] The embodiment of the present application provides an optimization system of a DC converter station based on a network-forming SVG, please refer to Figure 4 The optimization system of the DC converter station based on the network-forming SVG comprises a network-forming SVG connection module 11, a system demand acquisition module 12, a three-bridge-arm SVG valve parameter calculation module 13, a network-forming 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] The network-forming SVG connection module 11 is used for connecting N groups of network-forming SVGs in the AC measurement of the DC converter station; the network-forming SVG comprises a transformer, a starting resistance and a three-bridge-arm SVG valve connected in sequence; each bridge arm of the three-bridge-arm SVG valve comprises a plurality of full-bridge sub-modules;

[0136] The system demand acquisition module 12 is used for acquiring the reactive power compensation demand, the harmonic filtering demand and the charging limitation demand of the converter valve in the DC converter station as system demands;

[0137] The three-bridge-arm SVG valve parameter calculation module 13 is used for obtaining 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] The network-forming SVG group number calculation module 14 is used for judging whether the additional reactive power providing capability and the harmonic distortion rate of the DC converter station meet the system requirements, and obtaining the group number of the network-forming SVG according to the judgment result;

[0139] The transformer parameter calculation module 15 is used for calculating the transformer parameters of the transformer according to the reactive power compensation demand and the three-bridge-arm SVG valve parameters;

[0140] The starting resistance parameter calculation module 16 is used for obtaining the starting resistance parameters of the starting resistance according to the charging limitation demand;

[0141] The direct current converter station improvement setting module 17 is configured to set the grid-forming SVG in the direct current converter station according to the number of groups of the grid-forming 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 comprises:

[0143] The reactive power capacity requirement obtaining unit is configured to obtain the reactive power capacity requirement of the converter valve according to the reactive power compensation requirement.

[0144] The bridge-arm voltage calculation unit is configured to obtain the bridge-arm voltage according to the wiring mode of the three-bridge-arm SVG valve.

[0145] The bridge-arm current calculation unit is configured to obtain the bridge-arm current according to the reactive power capacity requirement and the bridge-arm voltage.

[0146] The three-bridge-arm SVG valve parameter calculation unit is configured 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 configured to:

[0148] obtain the bridge-arm fundamental voltage according to the bridge-arm voltage;

[0149] obtain the bridge-arm fundamental current by calculation according to the reactive power capacity requirement and the bridge-arm fundamental voltage;

[0150] obtain the harmonic current filtering frequency of the direct current converter station;

[0151] obtain the bridge-arm harmonic current according to the harmonic current filtering frequency and the bridge-arm fundamental current;

[0152] obtain the bridge-arm current by root mean square or absolute value addition processing on the bridge-arm fundamental current and the bridge-arm harmonic current.

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

[0154] select the average voltage of the full-bridge sub-module according to the bridge-arm voltage;

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

[0156] obtain the three-bridge-arm SVG valve parameters according to the sub-module number and the bridge-arm current.

[0157] As a preferred implementation, the grid-forming SVG group number calculation module comprises:

[0158] a system capacity calculation unit, configured to calculate an additional reactive power providing capacity and a harmonic distortion rate of the DC converter station under the condition of N-1 groups of the network-forming SVG;

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

[0160] a network-forming SVG adjustment unit, configured to obtain the number of groups of the network-forming SVG when the additional reactive power providing capacity and the harmonic distortion rate meet the system demand.

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

[0162] an SVG valve voltage level calculation unit, configured to obtain an SVG valve voltage level according to a preset DC network side voltage and a transformer ratio;

[0163] a capacity and reactive power support calculation unit, configured to obtain a single-group capacity of a single group of the network-forming SVG and a dynamic maximum reactive power support capacity of the network-forming SVG according to the three-bridge-arm SVG valve parameters;

[0164] a rated capacity calculation unit, configured to obtain a transformer rated capacity according to the SVG valve voltage level and the single-group capacity;

[0165] an overload capacity calculation unit, configured to obtain a transformer overload capacity according to the dynamic maximum reactive power support capacity;

[0166] a leakage reactance parameter calculation unit, configured to determine a transformer leakage reactance parameter according to a dynamic reactive power support response speed demand in the reactive power compensation demand;

[0167] a transformer parameter generation unit, configured to obtain a transformer parameter of the transformer according to the transformer rated capacity, the overload capacity and the leakage reactance parameter.

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

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

[0170] a starting resistance parameter calculation unit, configured to obtain a starting resistance parameter of the starting resistance according to the charging current limitation and the charging time limitation.

[0171] As a preferred embodiment, the three-bridge SVG valve is connected through a connecting reactor and a bushing between each bridge arm, and the optimization system of the DC converter station based on the network-type SVG further comprises:

[0172] an end voltage calculation module configured to calculate an end voltage of the connecting reactor according to the bridge arm current;

[0173] a reactor parameter calculation module configured to determine a reactor parameter of the connecting reactor according to the end voltage;

[0174] a first DC converter station setting sub-module configured to set the network-type SVG in the DC converter station according to the reactor parameter.

[0175] As another preferred embodiment, the three-bridge SVG valve is connected through a connecting reactor and a bushing between each bridge arm, and the optimization system of the DC converter station based on the network-type SVG further comprises:

[0176] an end voltage calculation module configured to calculate an end voltage of the connecting reactor according to the bridge arm current;

[0177] a ground voltage calculation module configured to calculate a ground voltage of the connecting reactor and the bushing according to the end voltage;

[0178] a current level calculation module configured to obtain a current level of the connecting reactor and the bushing according to the bridge arm current;

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

[0180] a second DC converter station setting sub-module configured to set the network-type SVG in the DC converter station according to the reactor parameter and the bushing parameter.

[0181] The optimization system of the DC converter station based on the network-type SVG can meet the requirements of reactive power compensation and harmonic filtering of the converter valve, can fully exert the advantages of the network-type SVG in supporting system fast fault recovery, and can improve the operation stability of the conventional DC converter station and exert the support superiority of the system.

[0182] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by a computer program instructing relevant hardware, and the program can be stored in a computer readable storage medium. When the program is executed, the program can include the processes of the above-mentioned embodiment methods. The storage medium can be a magnetic disc, an optical disc, a read-only memory (ROM), a random access memory (RAM), or the like.

[0183] The above is the preferred embodiment of the present application. It should be pointed out that, for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which are also considered within the scope of protection of the present application.

Claims

1. A method for optimizing a DC converter station based on a network-forming SVG, characterized in that, The application relates to a method for setting a network-type SVG in a DC converter station. The network-type SVG comprises a transformer, a starting resistor and a three-bridge SVG valve connected in sequence; each bridge arm of the three-bridge SVG valve comprises a plurality of full-bridge sub-modules; Obtain reactive power compensation demand, harmonic filtering demand and charging restriction demand of a converter valve in the DC converter station as system demand; According to the reactive power compensation demand and the wiring mode of the three-bridge SVG valve, obtain three-bridge SVG valve parameters; Determine whether the additional reactive power supply capability and the harmonic distortion rate of the DC converter station meet system requirements, and obtain the number of groups of the network-type SVG according to the determination result; According to the reactive power compensation demand and the three-bridge SVG valve parameters, calculate transformer parameters of the transformer; According to the charging restriction demand, obtain starting resistor parameters of the starting resistor; According to the number of groups of the network-type SVG, the SVG valve parameters, the transformer parameters and the starting resistor parameters, set the network-type SVG in the DC converter station.

2. The method of claim 1, wherein the method is based on a network configuration type SVG of a DC converter station. According to the reactive power compensation demand and the wiring mode of the three-bridge SVG valve, obtain three-bridge SVG valve parameters, which comprises: According to the reactive power compensation demand, obtain reactive power capacity demand of the converter valve; According to the wiring mode of the three-bridge SVG valve, obtain bridge arm voltage; According to the reactive power capacity demand and the bridge arm voltage, obtain bridge arm current; According to the bridge arm voltage and the bridge arm current, obtain three-bridge SVG valve parameters.

3. The method of claim 2, wherein the method comprises: According to the reactive power capacity demand and the bridge arm voltage, obtain bridge arm current, which comprises: According to the bridge arm voltage, obtain bridge arm fundamental wave voltage; According to the reactive power capacity demand and the bridge arm fundamental wave voltage, calculate bridge arm fundamental wave current; Obtain harmonic current filtering times of the DC converter station; According to the harmonic current filtering times and the bridge arm fundamental wave current, calculate bridge arm harmonic current; Obtain bridge arm current 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 method of claim 2, wherein the method is characterized by: According to the bridge arm voltage and the bridge arm current, obtain three-bridge SVG valve parameters, which comprises: According to the bridge arm voltage, select average voltage of the full-bridge sub-modules; According to the average voltage and a preset redundancy ratio, calculate the number of sub-modules of the full-bridge sub-modules in each bridge arm of the three-bridge SVG valve; According to the number of sub-modules and the bridge arm current, obtain three-bridge SVG valve parameters.

5. The method of claim 1, wherein the method is based on a network configuration type SVG of a DC converter station. Determine whether the additional reactive power supply capability and the harmonic distortion rate of the DC converter station meet system requirements, and obtain the number of groups of the network-type SVG according to the determination result, which comprises: Calculate the additional reactive power supply capability and the harmonic distortion rate of the DC converter station under the condition of N-1 groups of the network-type SVG; When the additional reactive power supply capability and the harmonic distortion rate do not meet the system demand, then one group of the network-type SVG is added or the three-bridge SVG valve parameters are adjusted until the system demand is met; When the additional reactive power supply capability and the harmonic distortion rate meet the system demand, obtain the number of groups of the network-type SVG.

6. The method of claim 1, wherein the method is based on a network configuration type SVG of a DC converter station. The transformer parameter of the transformer is calculated according to the reactive power compensation demand and the three-bridge SVG valve parameter, and the transformer parameter includes: According to the preset DC network side voltage and transformer ratio, the SVG valve voltage grade is obtained; According to the three-bridge SVG valve parameter, the single group capacity of the single group network type SVG and the dynamic maximum reactive power support ability of the network type SVG are obtained; According to the SVG valve voltage grade and the single group capacity, the transformer rated capacity is obtained; According to the dynamic maximum reactive power support ability, the overload capacity of the transformer is obtained; According to the dynamic reactive power support response speed demand in the reactive power compensation demand, the leakage reactance parameter of the transformer is determined; According to the transformer rated capacity, the overload capacity and the leakage reactance parameter, the transformer parameter of the transformer is obtained.

7. The method of claim 1, wherein the method is based on a network configuration type SVG of a DC converter station. The starting resistance parameter of the starting resistance is obtained according to the charging limit demand, and the starting resistance parameter includes: The charging current limit and the charging time limit are obtained from the charging limit demand; According to the charging current limit and the charging time limit, the starting resistance parameter of the starting resistance is obtained.

8. The optimization method for a DC converter station based on a grid-type SVG as described in claim 2, characterized in that, The connection reactors are connected between the bridge arms of the three-bridge SVG valve, and the optimization method of the DC converter station based on the network type SVG further includes: According to the bridge arm current, the terminal voltage of the connection reactor is calculated; According to the terminal voltage, the reactor parameter of the connection reactor is determined; According to the reactor parameter, the network type SVG in the DC converter station is set.

9. The method of claim 2, wherein the method is based on a network configuration type SVG of a DC converter station, and the method comprises the steps of: The connection reactors and the bushings are connected between the bridge arms of the three-bridge SVG valve, and the optimization method of the DC converter station based on the network type SVG further includes: ​ According to the bridge arm current, the terminal voltage of the connection reactor is calculated; According to the terminal voltage, the ground voltage of the connection reactor and the bushing is calculated; According to the bridge arm current, the current level of the connection reactor and the bushing is obtained; According to the ground voltage and the current level, the reactor parameter of the connection reactor and the bushing parameter of the bushing are determined; According to the reactor parameter and the bushing parameter, the network type SVG in the DC converter station is set.

10. An optimization system for a DC converter station based on a networked SVG, characterized in that, It includes: The network type SVG connection module is used for connecting N groups of network type SVG in the AC measurement of the DC converter station; the network type SVG includes a transformer, a starting resistance and a three-bridge SVG valve connected in sequence; each bridge arm of the three-bridge SVG valve includes a plurality of full-bridge sub-modules; The system demand acquisition module is used for acquiring the reactive power compensation demand, the harmonic filtering demand and the charging limit demand of the converter valve in the DC converter station as system demands; The three-bridge SVG valve parameter calculation module is used for obtaining the three-bridge SVG valve parameter according to the reactive power compensation demand and the wiring mode of the three-bridge SVG valve; The network type SVG group number calculation module is used for judging whether the additional reactive power providing ability and the harmonic distortion rate of the DC converter station meet the system requirements, and obtaining the group number of the network type SVG according to the judgment result. The transformer parameter calculation module is configured to calculate transformer parameters of the transformer according to the reactive power compensation demand and the three-bridge-arm SVG valve parameters. The starting resistor parameter calculation module is configured to obtain starting resistor parameters of the starting resistor according to the charging limitation demand. The DC converter station improvement setting module is configured to set the grid-forming SVG in the DC converter station according to the number of groups of the grid-forming SVG, the SVG valve parameters, the transformer parameters and the starting resistor parameters.

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