Multi-alternating-current feed-out converter station simulation method and device, terminal equipment, storage medium and multi-alternating-current feed-out converter station

Abstract

The invention discloses a multi-alternating-current feed-out type converter station simulation method and device, terminal equipment, a storage medium and a multi-alternating-current feed-out type converter station. Determining the DC side voltage of the MMC in the multi-AC feed-out converter station, the number of half-bridge type sub-modules in the MMC, the bridge arm inductance of the MMC, the capacitance value of the half-bridge type sub-modules in the MMC, the number of full-bridge type sub-modules in the eACPFC and the capacitance value of the full-bridge type sub-modules according to the power flow parameters; and then, when the determined key parameters and the power flow parameters are input into preset simulation software, the generated simulation result can more accurately evaluate the performance of the multi-AC feed-out converter station system, and the initial investment and operation cost of the system are reduced.

Description

Technical Field

[0001] The present invention relates to the field of power systems, and in particular to a simulation method, device, terminal equipment, storage medium and a multi-AC feed-type converter station. Background Art

[0002] At present, multi-terminal flexible DC transmission projects often use the back-to-back modular multi-level converter (BTB-MMC) solution, where multiple lines are interconnected with high-voltage DC lines via full-power MMCs. Although the existing solution combines the advantages of flexible interconnection and DC transmission, it is costly and occupies a large area, which is not conducive to large-scale promotion and application.

[0003] In response to the above problems, some researchers have proposed a multi-AC feed-in converter station at the receiving end of the sea breeze flexible DC system. The multi-AC feed-in converter station at the receiving end of the sea breeze flexible DC system consists of an MMC and an AC power flow controller (embedded AC power flow controller, eACPFC) embedded in the MMC. The eACPFC can interconnect multiple AC lines and has the ability to independently decouple and control the active and reactive power of each line, thereby realizing the joint consumption of DC-transmitted sea wind power by multiple lines. By adjusting the DC component and interacting with the MMC DC circulation, the embedded eACPFC power balance can be achieved. Compared with the traditional BTB-MMC solution, the proposed multi-AC feed-in converter station at the receiving end of the sea breeze flexible DC system has the advantages of compactness, low cost, and easy expansion. When simulating the multi-AC-fed converter station system at the receiving end of the offshore wind flexible DC system, if there is a lack of reasonable main circuit parameters, there may be a large deviation between the simulation results and the actual operating conditions. This will not only make it impossible to accurately evaluate the dynamic and steady-state performance of the system, but may also mislead design decisions and increase the initial investment and operating costs of the system. Summary of the invention

[0004] The present invention provides a multi-AC feed type converter station simulation method, device, terminal equipment, storage medium and multi-AC feed type converter station. The simulation results generated by the multi-AC feed type converter station simulation method can more accurately evaluate the performance of the multi-AC feed type converter station system and reduce the initial investment and operating costs of the system.

[0005] An embodiment of the present invention provides a multi-AC feed-in converter station simulation method, comprising:

[0006] Get preset power flow parameters;

[0007] According to the power flow parameters, determining the DC side voltage of the MMC in the multi-AC feed-out converter station, the number of half-bridge submodules in the MMC, the bridge arm inductance of the MMC, and the capacitance value of the half-bridge submodule in the MMC;

[0008] According to the power flow parameters, determining the number of full-bridge submodules in the eACPFC and the capacitance value of the full-bridge submodules; wherein the eACPFC is embedded in the MMC;

[0009] The power flow parameters, the DC side voltage, the number of half-bridge sub-modules in the MMC, the bridge arm inductance, the capacitance value of the half-bridge sub-modules in the MMC, the number of full-bridge sub-modules in the eACPFC and the capacitance value of the full-bridge sub-modules are input into the preset simulation software to generate the simulation results of the multi-AC feed-out converter station.

[0010] Furthermore, the power flow parameters include: rated line voltage of the AC line, rated capacity of the feeder, effective value of the output voltage of the AC port, compensated DC common mode voltage, rated current of the DC side, preset working voltage of the switching device, grid angular frequency, preset maximum fluctuation rate of sub-module capacitor voltage, rated capacitor voltage of the full-bridge sub-module in eACPFC, MMC modulation index, preset equivalent reactance capacity interval, preset bridge arm current rise rate, double frequency current, phase voltage rated value, maximum DC common mode voltage, bridge arm fundamental frequency differential mode output voltage, AC line current value and DC circulating current of the full-bridge sub-module.

[0011] Further, the determining, according to the power flow parameters, the DC side voltage of the MMC in the multi-AC feed-out converter station, the number of half-bridge submodules in the MMC, the bridge arm inductance of the MMC, and the capacitance value of the half-bridge submodule in the MMC comprises:

[0012] Determining the DC side voltage of the MMC in the multi-AC feeder type converter station according to the effective value of the AC port output voltage and the compensated DC common mode voltage;

[0013] Determining the rated capacitance voltage of the MMC submodule according to the preset operating voltage of the switch device;

[0014] Determining the number of half-bridge submodules in the MMC according to the rated capacitance voltage of the MMC submodule and the DC side voltage of the MMC in the multi-AC feed-out converter station;

[0015] Determine the capacitance value of the half-bridge submodule in the MMC according to the rated capacity of the feeder, the grid angular frequency, the maximum fluctuation rate of the preset submodule capacitor voltage, the DC side voltage of the MMC in the multi-AC feeder converter station, the MMC modulation degree and the number of half-bridge submodules in the MMC;

[0016] The bridge arm inductance of the MMC is determined according to the preset equivalent reactance capacity interval, the bridge arm current rise rate, the DC side voltage of the MMC in the multi-AC feeder converter station, the grid angular frequency, the capacitance value of the half-bridge submodule in the MMC, the rated capacitance voltage of the MMC submodule, the double frequency current and the feeder rated capacity.

[0017] Further, the determining of the bridge arm inductance of the MMC according to the preset equivalent reactance capacity interval, the bridge arm current rise rate, the DC side voltage of the MMC in the multi-AC feeder converter station, the grid angular frequency, the capacitance value of the half-bridge submodule in the MMC, the rated capacitance voltage of the MMC submodule, the double frequency current and the feeder rated capacity includes:

[0018] Determining a first candidate interval of the bridge arm inductance in the MMC according to the preset equivalent reactance capacity interval;

[0019] Determine a first lower limit of the bridge arm inductance in the MMC according to the grid angular frequency, the capacitance value of the half-bridge submodule in the MMC, the rated capacitance voltage of the MMC submodule, the double frequency current, the rated capacity of the feeder, and the DC side voltage of the MMC in the multi-AC feeder converter station;

[0020] Determine a second lower limit value of the bridge arm inductance in the MMC according to the bridge arm current rising rate and the DC side voltage of the MMC in the multi-AC feeder type converter station;

[0021] The bridge arm inductance of the MMC is determined according to the first candidate interval, the first lower limit value, and the second lower limit value.

[0022] Further, the determining the number of full-bridge submodules in the eACPFC and the capacitance value of the full-bridge submodules according to the power flow parameter includes:

[0023] Determining the number of full-bridge submodules in the eACPFC according to the rated capacitance voltage of the MMC submodule, the phase voltage rating, and the maximum DC common mode voltage;

[0024] The capacitance value of the full-bridge submodule is determined according to the preset maximum fluctuation rate of the submodule capacitor voltage, the grid angular frequency, the number of full-bridge submodules in the eACPFC, the compensated DC common mode voltage, the rated capacitor voltage of the full-bridge submodule in the eACPFC, the bridge arm fundamental frequency differential mode output voltage, the AC line current value and the DC circulating current of the full-bridge submodule.

[0025] Furthermore, the multi-AC feed-out converter station simulation method further includes:

[0026] Determining a feeder rated current according to the rated line voltage and the feeder rated capacity;

[0027] Determining the operating current of the switching device according to the feeder rated current and the DC side rated current;

[0028] The model information of the switch device in the half-bridge submodule in the MMC is determined according to the operating current of the switch device and the preset operating voltage of the switch device.

[0029] An embodiment of the present invention further provides a multi-AC feed-in converter station simulation device, comprising: a data acquisition module, an MMC parameter determination module, an eACPFC parameter determination module and a simulation module;

[0030] The data acquisition module is used to obtain preset power flow parameters;

[0031] The MMC parameter determination module is used to determine the DC side voltage of the MMC in the multi-AC feed-out converter station, the number of half-bridge submodules in the MMC, the bridge arm inductance of the MMC, and the capacitance value of the half-bridge submodule in the MMC according to the power flow parameters;

[0032] The eACPFC parameter determination module is used to determine the number of full-bridge submodules in the eACPFC and the capacitance value of the full-bridge submodules according to the power flow parameters; wherein the eACPFC is embedded in the MMC;

[0033] The simulation module is used to input the power flow parameters, the DC side voltage, the number of half-bridge sub-modules in the MMC, the bridge arm inductance, the capacitance value of the half-bridge sub-modules in the MMC, the number of full-bridge sub-modules in the eACPFC and the capacitance value of the full-bridge sub-modules into a preset simulation software to generate a simulation result of the multi-AC feed-out converter station.

[0034] The present application also provides a terminal device, including:

[0035] one or more processors;

[0036] A memory, coupled to the processor, for storing one or more programs;

[0037] When the one or more programs are executed by the one or more processors, the one or more processors implement the multi-AC feed-in converter station simulation method as described in the above-mentioned embodiment of the invention.

[0038] The present application also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the multi-AC feed-in converter station simulation method as described in the above-mentioned embodiment of the invention is implemented.

[0039] An embodiment of the present invention further provides a multi-AC feed-out converter station, characterized in that it comprises: an MMC and an eACPFC embedded in the MMC;

[0040] The MMC is composed of three phase units connected in parallel, each of the phase units includes two bridge arms, and each of the bridge arms is composed of a plurality of half-bridge sub-modules connected in cascade;

[0041] The eACPFC comprises a plurality of eACPFC sub-units, each of which is composed of a plurality of full-bridge sub-modules;

[0042] Among them, the DC side voltage of the MMC in the multi-AC feeder converter station, the number of half-bridge sub-modules in the MMC, the bridge arm inductance of the MMC, the capacitance value of the half-bridge sub-module in the MMC, the number of full-bridge sub-modules in the eACPFC and the capacitance value of the full-bridge sub-module are determined according to the preset power flow parameters.

[0043] The following beneficial effects are achieved by implementing the present invention:

[0044] The present invention provides a simulation method, device, terminal equipment, storage medium and multi-AC feeder type converter station. The method obtains preset power flow parameters and determines the key parameters of the main circuit according to the power flow parameters, wherein the key parameters of the main circuit include the DC side voltage of the MMC in the multi-AC feeder type converter station, the number of half-bridge submodules in the MMC, the bridge arm inductance of the MMC and the capacitance value of the half-bridge submodule in the MMC, the number of full-bridge submodules in the eACPFC and the capacitance value of the full-bridge submodule; wherein the eACPFC is embedded in the MMC, thereby, when the key parameters of the main circuit and the preset power flow parameters are input into the preset simulation software, the generated simulation results can more accurately evaluate the performance of the multi-AC feeder type converter station system, thereby facilitating engineering design and reducing the initial investment and operating costs of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the implementation manner will be briefly introduced below. Obviously, the drawings described below are only some implementation manners of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0046] Figure 1 It is a flowchart of a multi-AC feed-in converter station simulation method provided in a certain embodiment of the present application;

[0047] Figure 2 It is a capacitor voltage waveform of some submodules of a multi-AC feed-out converter station MMC provided in a certain embodiment of the present application;

[0048] Figure 3 It is a capacitor voltage waveform of some submodules of a multi-AC feed-out converter station eACPFC provided in a certain embodiment of the present application;

[0049] Figure 4 It is a current waveform of line 1 connected to a multi-AC feed-out converter station provided in a certain embodiment of the present application;

[0050] Figure 5 It is the current waveform of line 2 connected to a multi-AC feed-out converter station provided in a certain embodiment of the present application;

[0051] Figure 6 It is the current waveform of line 3 connected to a multi-AC feed-out converter station provided in a certain embodiment of the present application;

[0052] Figure 7 The voltage and current waveforms of the DC lines connected to the multi-AC feeder type converter station provided in a certain embodiment of the present application;

[0053] Figure 8 It is the active power waveform of each line connected to the multi-AC feed-out converter station provided in a certain embodiment of the present application;

[0054] Fig. 9 It is the reactive power waveform of each line connected to the multi-AC feed-out converter station provided in a certain embodiment of the present application;

[0055] Fig.10 It is a schematic diagram of the topological structure of a multi-AC feed-out converter station provided in a certain embodiment of the present application;

[0056] Fig.11 It is a structural schematic diagram of a multi-AC feed-out converter station simulation device provided in a certain embodiment of the present application;

[0057] Fig.12 It is a structural diagram of a terminal device provided in a certain embodiment of the present application. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0060] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0061] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0062] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0063] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0064] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0065] See also Figure 1 , is a flow chart of a multi-AC feed-in converter station simulation method provided by an embodiment of the present invention, comprising:

[0066] S1. Obtain preset power flow parameters;

[0067] In a preferred embodiment, the power flow parameters include: the rated line voltage of the AC line, the rated capacity of the feeder, the effective value of the AC port output voltage, the compensated DC common mode voltage, the DC side rated current, the preset operating voltage of the switching device, the grid angular frequency, the preset sub-module capacitor voltage maximum fluctuation rate, the rated capacitor voltage of the full-bridge sub-module in the eACPFC, the MMC modulation index, the preset equivalent reactance capacity interval, the preset bridge arm current rise rate, the double frequency current, the phase voltage rated value, the maximum DC common mode voltage, the bridge arm fundamental frequency differential mode output voltage, the AC line current value and the DC circulating current of the full-bridge sub-module.

[0068] S2. Determine the DC side voltage of the MMC in the multi-AC feed-out converter station, the number of half-bridge submodules in the MMC, the bridge arm inductance of the MMC, and the capacitance value of the half-bridge submodule in the MMC according to the power flow parameters;

[0069] In a preferred embodiment, the determining, according to the power flow parameters, the DC side voltage of the MMC in the multi-AC feed-out converter station, the number of half-bridge submodules in the MMC, the bridge arm inductance of the MMC, and the capacitance value of the half-bridge submodule in the MMC comprises:

[0070] Determining the DC side voltage of the MMC in the multi-AC feeder type converter station according to the effective value of the AC port output voltage and the compensated DC common mode voltage;

[0071] Determining the rated capacitance voltage of the MMC submodule according to the preset operating voltage of the switch device;

[0072] Determining the number of half-bridge submodules in the MMC according to the rated capacitance voltage of the MMC submodule and the DC side voltage of the MMC in the multi-AC feed-out converter station;

[0073] Determine the capacitance value of the half-bridge submodule in the MMC according to the rated capacity of the feeder, the grid angular frequency, the maximum fluctuation rate of the preset submodule capacitor voltage, the DC side voltage of the MMC in the multi-AC feeder converter station, the MMC modulation degree and the number of half-bridge submodules in the MMC;

[0074] Determine the bridge arm inductance of the MMC according to the preset equivalent reactance capacity interval, the bridge arm current rise rate, the DC side voltage of the MMC in the multi-AC feeder converter station, the grid angular frequency, the capacitance value of the half-bridge submodule in the MMC, the rated capacitance voltage of the MMC submodule, the double frequency current and the feeder rated capacity;

[0075] Specifically, according to the actual application scenario requirements, select the rated line voltage V of the AC line line , feeder rated capacity S N_line , then the feeder rated current is recorded as I N ,MMC rated capacity S N Same as the feeder rated capacity, i.e. S N =S N_line .

[0076] Specifically, in order to ensure the required voltage of the MMC bridge arm output, it is first necessary to analyze the components of the MMC bridge arm voltage. The components of the upper and lower bridge arm voltages of the MMC can be expressed as

[0077]

[0078] In the formula, v p is the voltage modulation wave of the upper bridge arm of MMC; v n is the voltage modulation wave of the lower bridge arm of MMC; V dc is the DC side voltage of the MMC in the multi-AC feeder converter station; V diff is the effective value of the AC port output voltage; V c_dc To compensate for the DC common mode voltage, compensation is performed in the MMC bridge arm, thereby preventing the introduction of additional circulating current in the MMC.

[0079] It should be noted that the DC side voltage is the voltage of the DC line connected to the MMC part of the multi-AC feeder converter station;

[0080] To ensure that the MMC bridge arm can modulate the above voltage components, the DC side voltage of the MMC must meet

[0081]

[0082] Among them, V diff is the effective value of the AC port output voltage; V c_dcTo compensate for the DC common mode voltage.

[0083] Therefore, according to formula (3), according to the obtained AC port output voltage effective value V diff and compensated DC common mode voltage V c_dc , the DC side voltage of the MMC in the multi-AC feeder type converter station is calculated.

[0084] Schematically, the bridge arm of the MMC is a cascaded half-bridge structure. The number of half-bridge sub-modules in the MMC directly depends on the selection of the sub-module capacitor voltage and the DC side voltage. In order to ensure the reliability of the device, a certain margin is usually reserved when selecting the number of half-bridge sub-modules. When the selected half-bridge sub-module capacitor voltage value is too large, a switch device with a higher withstand voltage value is required, and the corresponding manufacturing cost will also increase sharply. The output voltage level of a small number of half-bridge sub-modules is low, and the harmonic characteristics are poor. If the selected half-bridge sub-module capacitor voltage value is too low, the manufacturing cost of the required switching device is greatly reduced, but too many half-bridge sub-modules make the control complex and the overall volume of the device larger. According to engineering experience, the operating voltage of the IGBT is generally suitable for 50% to 70% of its rated voltage. When the operating voltage is too high, the device loss will increase greatly, and when the operating voltage is too low, the device utilization rate is insufficient;

[0085] Specifically, when determining the preset operating voltage V corresponding to the selected switch device type IGBT Then, according to the preset working voltage V IGBT , determine the rated capacitance voltage of the MMC submodule, as shown in the following formula:

[0086] 0.5 V IGBT ≤V c ≤0.7·V IGBT ; (4)

[0087] Where V c is the rated capacitance voltage of the MMC submodule;

[0088] Then, according to the rated capacitance voltage of the MMC submodule and the DC side voltage of the MMC in the multi-AC feeder converter station, the number of half-bridge submodules in the MMC is determined, and the number N of half-bridge submodules in the MMC is determined by the following formula: MMC :

[0089]

[0090] Thus, the number of half-bridge submodules in the MMC is determined according to the determined rated capacitance voltage of the MMC submodule and the DC side voltage of the MMC in the multi-AC feeder converter station.

[0091] Schematically, the determination of the capacitance value of the half-bridge submodule in the MMC is mainly based on the suppression effect of the capacitor on the DC voltage ripple, and its capacitor voltage fluctuation is constrained within a specified range to limit the voltage stress of the device;

[0092] The bridge arm voltage of MMC is shown in formula (1), and the bridge arm current can be expressed as

[0093]

[0094] In the formula, I dc is the DC side current, i diff is the MMC differential mode AC output current, where the instantaneous expression of the AC component is

[0095]

[0096] Where V diff is the effective value of the AC port output voltage; δ diff is the AC port output voltage phase; I diff is the effective value of the AC port output current; ρ diff is the AC port output current phase. The MMC modulation index is

[0097]

[0098] Combining equations (1), (5) and (6), the current flowing into the MMC submodule capacitor can be expressed as

[0099]

[0100] Due to the power balance constraint, the DC component of the capacitor current of the half-bridge submodule is 0, and the capacitor voltage fluctuation of the half-bridge submodule can be expressed as

[0101]

[0102] The capacitor voltage fluctuation of the half-bridge submodule in the MMC includes the fundamental frequency component and the double frequency component, and their fluctuation rates can be expressed as

[0103]

[0104] From formula (10), it can be seen that when cosφ=0, the fundamental frequency fluctuation reaches the maximum value. Considering the fundamental frequency component and the double frequency component of the capacitor voltage fluctuation, the maximum fluctuation rate is set to ε, and the capacitance value of the half-bridge submodule of the MMC satisfies the following formula:

[0105]

[0106] Where N MMC is the number of half-bridge submodules in the MMC; SN is the rated capacity of the MMC; ω is the grid angular frequency; ε is the maximum fluctuation rate of the preset submodule capacitor voltage; V dc is the DC side voltage of the MMC in the multi-AC feeder converter station; m' is the MMC modulation index.

[0107] Specifically, the capacitance value of the half-bridge submodule in the MMC is determined according to the obtained MMC modulation degree, grid angular frequency, preset submodule capacitor voltage maximum fluctuation rate, the number of half-bridge submodules in the MMC, the DC side voltage of the MMC in the multi-AC feed-out converter station, and the MMC rated capacity;

[0108] Schematically, the bridge arm inductor acts as a link for power transmission between the MMC and the AC power grid, and plays a role in regulating power transmission and suppressing output current fluctuations. The bridge arm inductor constitutes a part of the internal circulating current loop of the MMC, and has a good suppression effect on the internal circulating current. The design of the bridge arm inductor is of great significance to the stable operation of the MMC part and the performance of the system. Therefore, the parameter design needs to be comprehensively considered from multiple aspects such as meeting the system power operation requirements, circulating current suppression and fault current suppression;

[0109] In a preferred embodiment, the determining of the bridge arm inductance of the MMC according to the preset equivalent reactance capacity interval, the bridge arm current rise rate, the DC side voltage of the MMC in the multi-AC feeder converter station, the grid angular frequency, the capacitance value of the half-bridge submodule in the MMC, the rated capacitance voltage of the MMC submodule, the double frequency current and the rated capacity of the feeder includes:

[0110] Determining a first candidate interval of the bridge arm inductance in the MMC according to the preset equivalent reactance capacity interval;

[0111] Determine a first lower limit of the bridge arm inductance in the MMC according to the grid angular frequency, the capacitance value of the half-bridge submodule in the MMC, the rated capacitance voltage of the MMC submodule, the double frequency current, the rated capacity of the feeder, and the DC side voltage of the MMC in the multi-AC feeder converter station;

[0112] Determine a second lower limit value of the bridge arm inductance in the MMC according to the bridge arm current rising rate and the DC side voltage of the MMC in the multi-AC feeder type converter station;

[0113] Determining the bridge arm inductance of the MMC according to the first to-be-selected interval, the first lower limit value, and the second lower limit value;

[0114] Specifically, first, the bridge arm inductance of the MMC should meet the system power operation requirements. It is known that the rated capacity of the MMC is S N Based on this capacity, the unit value of the equivalent reactance is

[0115]

[0116] In the formula, S LN is the per unit value of equivalent reactance capacity; S L is the equivalent reactance capacity; I N is the rated phase current effective value; U ON is the effective value of the MMC output phase voltage; I ON is the effective value of the MMC output phase current; X is the bridge arm reactance. The capacity of the equivalent reactance is related to the phase difference δ between the grid voltage and the MMC output voltage. In the steady state, δ is between 6 and 19. Therefore, the preset equivalent reactance capacity interval S LN (pu) takes 0.1 to 0.3;

[0117] Specifically, according to formula (12) and the preset equivalent reactance capacity interval, a first candidate interval of the bridge arm inductance in the MMC is obtained;

[0118] Secondly, the bridge arm inductance of the MMC should meet the requirements of circulating current suppression, mainly considering the suppression effect of the double frequency circulating current. In order to accurately calculate the size of the double frequency circulating current, the double frequency voltage fluctuation and the double frequency circulating current should be added to the bridge arm voltage and bridge arm current respectively, and the total energy of the upper and lower bridge arms should be recalculated. The calculated bridge arm energy is

[0119]

[0120] In the formula, I 2f is the double frequency current; θ 2f is the phase of the double frequency circulating current; U 2f In addition, considering the double frequency fluctuation of the capacitor voltage of the half-bridge submodule, it is assumed that the double frequency voltage fluctuation is evenly distributed to the 2N half-bridge submodules of each phase unit, then the energy stored in the phase unit is W c It is expressed as:

[0121]

[0122] The bridge arm energy generated by the double frequency circulating current should be equal to the energy stored in the phase capacitor, that is, the double frequency components in equations (13) and (14) should be equal, so

[0123]

[0124] The double frequency circulating current amplitude can be calculated from the formula, and the inductance value under the specified circulating current suppression effect can be obtained from it, as shown in the following formula:

[0125]

[0126] In the formula, I2f is the double frequency current; U 2f is the double frequency voltage; ω is the grid angular frequency; L is the MMC bridge arm inductance; S N is the rated capacity of MMC; C MMC is the capacitance value of the half-bridge submodule in the MMC; V c is the rated capacitance voltage of the MMC submodule; V dc is the DC side voltage of the MMC in the multi-AC feeder converter station;

[0127] Specifically, according to formula (16), the obtained grid angular frequency ω and double frequency current I 2f , and determine the MMC submodule rated capacitance voltage V c , the DC side voltage V of the MMC in the multi-AC feeder converter station dc 、Capacitance value C of half-bridge submodule in MMC MMC 、MMC rated capacity S N , determining a first lower limit value of the bridge arm inductance in the MMC;

[0128] In addition, the bridge arm inductance of the MMC should also be able to limit the surge current in the event of a system fault. Considering the most serious short-circuit fault of the positive and negative busbars on the DC side, the short-circuit current can form a loop through the same phase unit. Based on Kirchhoff's voltage theorem, the increase rate of the bridge arm current is

[0129]

[0130] In the case of limiting transient conditions, when the maximum rate of increase of the bridge arm current is α, the bridge arm inductance should satisfy

[0131]

[0132] Where α is the bridge arm current rising rate; V dc is the DC side voltage of the MMC in the multi-AC feeder converter station;

[0133] Therefore, according to formula (18), the bridge arm current rise rate and the DC side voltage of the MMC in the multi-AC feeder type converter station, the second lower limit value of the bridge arm inductance in the MMC is determined;

[0134] Based on the first candidate interval calculated by formula (12), the first lower limit value calculated by formula (16), and the second lower limit value calculated by formula (18), the bridge arm inductance L of the MMC is determined.

[0135] S3. Determine the number of full-bridge submodules in the eACPFC and the capacitance value of the full-bridge submodules according to the power flow parameters; wherein the eACPFC is embedded in the MMC;

[0136] In a preferred embodiment, determining the number of full-bridge submodules and the capacitance value of the full-bridge submodules in the eACPFC according to the power flow parameters includes:

[0137] Determining the number of full-bridge submodules in the eACPFC according to the rated capacitance voltage of the MMC submodule, the phase voltage rating, and the maximum DC common mode voltage;

[0138] Determine the capacitance value of the full-bridge submodule according to the preset maximum fluctuation rate of the submodule capacitor voltage, the grid angular frequency, the number of full-bridge submodules in the eACPFC, the compensated DC common mode voltage, the rated capacitance voltage of the full-bridge submodule in the eACPFC, the bridge arm fundamental frequency differential mode output voltage, the AC line current value and the DC circulating current of the full-bridge submodule;

[0139] Schematically, the submodule of eACPFC adopts a full-bridge structure. The number of full-bridge submodules in eACPFC directly depends on the selection of the full-bridge submodule capacitor voltage and the bridge arm output voltage amplitude. Since the bridge arm current rating of eACPFC is the same as the bridge arm current rating of MMC, the full-bridge submodule capacitor voltage of eACPFC is set to be the same as the half-bridge submodule capacitor voltage of MMC, which is V c * ;

[0140] It should be noted that the switch device parameters of eACPFC are the same as those of MMC, which ensures the consistency of the device. Next, the bridge arm output voltage amplitude is analyzed. The eACPFC bridge arm voltage contains the following components:

[0141]

[0142] In the formula, v cpk is the upper bridge arm output voltage of the kth cluster of eACPFC; v cnk is the output voltage of the lower bridge arm of the kth cluster of eACPFC; V c_dc To compensate for the DC common mode voltage; V ck_diff is the base frequency differential mode output voltage of the eACPFC bridge arm, is the equivalent series voltage between lines, and is used to adjust the power between lines.

[0143] Since eACPFC regulates the line power flow by controlling the differential mode output voltage, its regulation principle is similar to the regulation principle of the series part of the traditional UPFC. The AC component amplitude of the series voltage is selected to be 0.1 times the phase voltage amplitude, that is:

[0144]

[0145] Where V ck_diff_maxis the maximum differential mode output voltage of the eACPFC bridge arm, V phase is the phase voltage rating, all of which are effective values. Considering the typical application scenario constraints of multi-port flexible DC converters, the maximum DC common mode voltage injected into the eACPFC is V c_dc_max .

[0146] The number of eACPFC submodules satisfies the following formula:

[0147]

[0148] Specifically, since the capacitor voltage of the full-bridge submodule of eACPFC is V c * Same as the rated capacitor voltage of the MMC submodule, i.e. V c * =V c Thus, the number of full-bridge submodules in the eACPFC is determined by obtaining the phase voltage rated value, the maximum DC common mode voltage, the MMC submodule rated capacitor voltage, the phase voltage rated value and the maximum DC common mode voltage.

[0149] The determination of the capacitance value of the eACPFC full-bridge sub-module is mainly based on the capacitor's suppression effect on voltage ripple, and its capacitor voltage fluctuation is constrained within a specified range to limit the voltage stress of the device.

[0150] The bridge arm voltage of eACPFC is shown in formula (22), and the bridge arm current can be expressed as

[0151]

[0152] In the formula, i pk is the upper arm current of the kth cluster of eACPFC; i nk is the lower arm current of the kth cluster of eACPFC; I dc is the DC side current; n line is the number of AC lines connected to the eACPFC; i k is the current of the kth line, therefore, the instantaneous value expressions of the differential-mode output voltage and feeder current of the eACPFC bridge arm are:

[0153]

[0154] Where V ck_diff is the effective value of the base frequency differential mode output voltage of the eACPFC bridge arm; ck_diff is the base frequency differential mode output phase of the eACPFC bridge arm; I k is the effective value of the current in the kth line; ρ k is the phase of the kth line current.

[0155] Combining equations (19), (22) and (23), the current flowing into the capacitor of the eACPFC full-bridge submodule can be expressed as

[0156]

[0157] Due to the power balance constraint, the DC component of the full-bridge submodule capacitor current is 0. Taking the upper bridge arm of the kth cluster of eACPFC as an example, the full-bridge submodule capacitor voltage fluctuation can be expressed as:

[0158]

[0159] The full-bridge submodule capacitor voltage fluctuation contains fundamental frequency and double frequency components. When the following relationship is satisfied

[0160] δ ck_diff =ρ k ; (26)

[0161] The fundamental frequency fluctuation reaches the maximum value, which can be expressed as:

[0162]

[0163] Considering the superposition of the fundamental frequency fluctuation and the double frequency fluctuation amplitude, given the preset submodule capacitor voltage maximum fluctuation rate ε, the eACPFC submodule capacitor value satisfies

[0164]

[0165] Where V c_dc To compensate for the DC common mode voltage; I k is the AC line current value; V ck_diff is the bridge arm fundamental frequency differential mode output voltage; I ck is the DC circulating current of the full-bridge submodule; ω is the grid angular frequency; ε is the maximum fluctuation rate of the capacitor voltage of the preset submodule; N eMMC is the number of full-bridge submodules in eACPFC; V c_ref is the rated capacitor voltage of the full-bridge submodule in eACPFC.

[0166] Specifically, the capacitance value of the eACPFC submodule is determined based on the obtained compensated DC common-mode voltage, the bridge arm fundamental frequency differential-mode output voltage, the AC line current value, the DC circulating current of the full-bridge submodule, the grid angular frequency, the preset submodule capacitor voltage maximum fluctuation rate, and the determined number of full-bridge submodules in the eACPFC.

[0167] S4, inputting the power flow parameters, the DC side voltage, the number of half-bridge submodules in the MMC, the bridge arm inductance, the capacitance value of the half-bridge submodule in the MMC, the number of full-bridge submodules in the eACPFC and the capacitance value of the full-bridge submodule into a preset simulation software to generate a simulation result of the multi-AC feed-out converter station;

[0168] Specifically, for the determination of MMC parameters, the DC side voltage of the MMC in the multi-AC feeder converter station is selected as 500kV, the rated capacitance voltage of the MMC submodule is determined to be 2300V, the number of half-bridge submodules in the MMC is determined to be 220, and the capacitance value of the half-bridge submodule in the MMC is 20mF.

[0169] Then considering the system power operation requirements, since the preset equivalent reactance capacity interval is 0.1~0.3pu, considering that the design of the inductance needs to satisfy formula (16) when the double frequency circulating current is suppressed, when the fault current rise rate is not greater than 0.1kA / μs, the inductance value should be greater than 2.5mF, and the bridge arm inductance of the MMC is 7mH.

[0170] Similarly, for the design of some parameters of eACPFC, the first is the design of the number of eACPFC submodules. Since the bridge arm current rating of eACPFC is the same as the bridge arm current rating of MMC, the rated capacitor voltage of the eACPFC submodule is set to be the same as the rated capacitor voltage of the MMC submodule, which is 2300V. At this time, the switch device parameters of eACPFC are also the same as those of MMC, which ensures the consistency of the device and is conducive to early manufacturing and later maintenance. The number of full-bridge submodules in the eACPFC is 15. The design of the submodule capacitor takes into account the suppression of the base frequency, double frequency and triple frequency ripples by the capacitor voltage. When the ripple is suppressed within 10%, the capacitance value of the full-bridge submodule is designed to be 21mF.

[0171] Then, the simulation is performed. Figure 2 It is the capacitor voltage of the MMC half-bridge submodule, and its capacitor voltage fluctuation is about 8.66%, which meets the design requirements. Figure 3 is the capacitor voltage of the eACPFC full-bridge submodule, and its maximum capacitor voltage fluctuation is about 9.29%, which is less than the design value of 10%, so it also meets the requirements. In addition, the capacitor voltage fluctuations of the eACPFC full-bridge submodules connected to different feeders have significant differences, which is consistent with the theoretical analysis. Figures 4 to 6 They are the current waveforms of each AC line respectively. Figure 7 It is the voltage and current waveform of DC line. Figure 8 and Fig. 9The waveforms are respectively the active power waveform and reactive power waveform of each line. The voltage and current waveforms of each line meet the requirements. The simulation results show that this application can achieve efficient and stable operation of the device, and the effectiveness of the proposed design method is verified in the results.

[0172] In a preferred embodiment, the multi-AC feed-in converter station simulation method further includes:

[0173] Determining a feeder rated current according to the rated line voltage and the feeder rated capacity;

[0174] Determining the operating current of the switching device according to the feeder rated current and the DC side rated current;

[0175] Determining the model information of the switching device in the half-bridge submodule in the MMC according to the operating current of the switching device and the preset operating voltage of the switching device;

[0176] Specifically, the operating current of the switch device in the MMC is consistent with the bridge arm current, which mainly includes base frequency AC and DC, that is,

[0177]

[0178] In the formula, I dc is the DC side current; I N is the feeder rated current;

[0179] Therefore, the operating current of the switching device can be determined according to the feeder rated current and the DC side rated current, and a switching device that meets the requirements can be selected according to the operating current of the switching device and the preset operating voltage of the switching device.

[0180] See also Fig.10 , is a multi-AC feed-out type converter station provided by an embodiment of the present invention, comprising: an MMC and an eACPFC embedded in the MMC;

[0181] The MMC is composed of three phase units connected in parallel, each of the phase units includes two bridge arms, and each of the bridge arms is composed of a plurality of half-bridge submodules FBSM cascaded;

[0182] The eACPFC comprises a plurality of eACPFC sub-units, each of which is composed of a plurality of full-bridge sub-modules HBSM;

[0183] Among them, the DC side voltage of the MMC in the multi-AC feed-out converter station, the number of half-bridge submodules FBSM in the MMC, the bridge arm inductance of the MMC, the capacitance value of the half-bridge submodule FBSM in the MMC, the number of full-bridge submodules HBSM in the eACPFC and the capacitance value of the full-bridge submodule HBSM are determined according to the preset power flow parameters;

[0184] It should be noted that the specific calculation method of the DC side voltage of the MMC in the above-mentioned multi-AC feeder converter station, the number of half-bridge sub-modules FBSM in the MMC, the bridge arm inductance of the MMC, the capacitance value of the half-bridge sub-module FBSM in the MMC, the number of full-bridge sub-modules HBSM in the eACPFC and the capacitance value of the full-bridge sub-module HBSM is consistent with the calculation method mentioned in the above-mentioned method embodiment of the present invention, and will not be repeated here.

[0185] See also Fig.11 , is a multi-AC feed-in converter station simulation device provided by an embodiment of the present invention, comprising: a data acquisition module, an MMC parameter determination module, an eACPFC parameter determination module and a simulation module;

[0186] The data acquisition module is used to obtain preset power flow parameters;

[0187] The MMC parameter determination module is used to determine the DC side voltage of the MMC in the multi-AC feed-out converter station, the number of half-bridge submodules in the MMC, the bridge arm inductance of the MMC, and the capacitance value of the half-bridge submodule in the MMC according to the power flow parameters;

[0188] The eACPFC parameter determination module is used to determine the number of full-bridge submodules in the eACPFC and the capacitance value of the full-bridge submodules according to the power flow parameters; wherein the eACPFC is embedded in the MMC;

[0189] The simulation module is used to input the power flow parameters, the DC side voltage, the number of half-bridge sub-modules in the MMC, the bridge arm inductance, the capacitance value of the half-bridge sub-modules in the MMC, the number of full-bridge sub-modules in the eACPFC and the capacitance value of the full-bridge sub-modules into a preset simulation software to generate a simulation result of the multi-AC feed-out converter station.

[0190] See also Fig.12 , a certain embodiment of the present application further provides a terminal device, including:

[0191] one or more processors;

[0192] A memory, coupled to the processor, for storing one or more programs;

[0193] When the one or more programs are executed by the one or more processors, the one or more processors implement the multi-AC feed-in converter station simulation method as described above.

[0194] The processor is used to control the overall operation of the terminal device to complete all or part of the steps of the above-mentioned multi-AC feed-in converter station simulation method. The memory is used to store various types of data to support the operation of the terminal device, and these data may include, for example, instructions for any application or method used to operate on the terminal device, and data related to the application. The memory can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (Static Random Access Memory, referred to as SRAM), electrically erasable programmable read-only memory (Electrically Erasable Programmable Read-Only Memory, referred to as EEPROM), erasable programmable read-only memory (Erasable Programmable Read-Only Memory, referred to as EPROM), programmable read-only memory (Programmable Read-Only Memory, referred to as PROM), read-only memory (Read-Only Memory, referred to as ROM), magnetic memory, flash memory, disk or optical disk.

[0195] In an exemplary embodiment, the terminal device can be implemented by one or more application specific integrated circuits (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD), programmable logic devices (PLD), field programmable gate arrays (FPGA), controllers, microcontrollers, microprocessors or other electronic components to execute the multi-AC feed-type converter station simulation method as described in any of the above embodiments and achieve the same technical effect as the above method.

[0196] In another exemplary embodiment, a computer-readable storage medium including a computer program is also provided, and when the computer program is executed by a processor, the steps of the multi-AC feed type converter station simulation method as described in any of the above embodiments are implemented. For example, the computer-readable storage medium can be the above-mentioned memory including the computer program, and the above-mentioned computer program can be executed by the processor of the terminal device to complete the multi-AC feed type converter station simulation method as described in any of the above embodiments, and achieve the technical effect consistent with the above method.

[0197] 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 simulating a multi-AC feed-in converter station, characterized in that: include: Get preset power flow parameters; According to the power flow parameters, determining the DC side voltage of the MMC in the multi-AC feed-out converter station, the number of half-bridge submodules in the MMC, the bridge arm inductance of the MMC, and the capacitance value of the half-bridge submodule in the MMC; According to the power flow parameters, determining the number of full-bridge submodules in the eACPFC and the capacitance value of the full-bridge submodules; wherein the eACPFC is embedded in the MMC; The power flow parameters, the DC side voltage, the number of half-bridge sub-modules in the MMC, the bridge arm inductance, the capacitance value of the half-bridge sub-modules in the MMC, the number of full-bridge sub-modules in the eACPFC and the capacitance value of the full-bridge sub-modules are input into the preset simulation software to generate the simulation results of the multi-AC feed-out converter station.

2. The multi-AC feed-in converter station simulation method according to claim 1, characterized in that: The power flow parameters include: the rated line voltage of the AC line, the rated capacity of the feeder, the effective value of the output voltage of the AC port, the compensated DC common mode voltage, the rated current of the DC side, the preset working voltage of the switching device, the grid angular frequency, the preset maximum fluctuation rate of the sub-module capacitor voltage, the rated capacitor voltage of the full-bridge sub-module in the eACPFC, the MMC modulation degree, the preset equivalent reactance capacity interval, the preset bridge arm current rise rate, the double frequency current, the phase voltage rated value, the maximum DC common mode voltage, the bridge arm fundamental frequency differential mode output voltage, the AC line current value and the DC circulating current of the full-bridge sub-module.

3. The multi-AC feed-in converter station simulation method according to claim 2, characterized in that: The step of determining the DC side voltage of the MMC in the multi-AC feed-out converter station, the number of half-bridge submodules in the MMC, the bridge arm inductance of the MMC, and the capacitance value of the half-bridge submodule in the MMC according to the power flow parameters includes: Determining the DC side voltage of the MMC in the multi-AC feeder type converter station according to the effective value of the AC port output voltage and the compensated DC common mode voltage; Determining the rated capacitance voltage of the MMC submodule according to the preset operating voltage of the switch device; Determining the number of half-bridge submodules in the MMC according to the rated capacitance voltage of the MMC submodule and the DC side voltage of the MMC in the multi-AC feed-out converter station; Determine the capacitance value of the half-bridge submodule in the MMC according to the rated capacity of the feeder, the grid angular frequency, the maximum fluctuation rate of the preset submodule capacitor voltage, the DC side voltage of the MMC in the multi-AC feeder converter station, the MMC modulation degree and the number of half-bridge submodules in the MMC; The bridge arm inductance of the MMC is determined according to the preset equivalent reactance capacity interval, the bridge arm current rise rate, the DC side voltage of the MMC in the multi-AC feeder converter station, the grid angular frequency, the capacitance value of the half-bridge submodule in the MMC, the rated capacitance voltage of the MMC submodule, the double frequency current and the feeder rated capacity.

4. The multi-AC feed-in converter station simulation method according to claim 3, characterized in that: The determining of the bridge arm inductance of the MMC according to the preset equivalent reactance capacity interval, the bridge arm current rise rate, the DC side voltage of the MMC in the multi-AC feeder type converter station, the grid angular frequency, the capacitance value of the half-bridge submodule in the MMC, the rated capacitance voltage of the MMC submodule, the double frequency current and the feeder rated capacity includes: Determining a first candidate interval of the bridge arm inductance in the MMC according to the preset equivalent reactance capacity interval; Determine a first lower limit of the bridge arm inductance in the MMC according to the grid angular frequency, the capacitance value of the half-bridge submodule in the MMC, the rated capacitance voltage of the MMC submodule, the double frequency current, the rated capacity of the feeder, and the DC side voltage of the MMC in the multi-AC feeder converter station; Determine a second lower limit value of the bridge arm inductance in the MMC according to the bridge arm current rising rate and the DC side voltage of the MMC in the multi-AC feeder type converter station; The bridge arm inductance of the MMC is determined according to the first candidate interval, the first lower limit value, and the second lower limit value.

5. The multi-AC feed-in converter station simulation method according to claim 2, characterized in that: The determining, according to the power flow parameters, the number of full-bridge submodules in the eACPFC and the capacitance value of the full-bridge submodules includes: Determining the number of full-bridge submodules in the eACPFC according to the rated capacitor voltage of the MMC submodule, the phase voltage rating, and the maximum DC common mode voltage; The capacitance value of the full-bridge submodule is determined according to the preset maximum fluctuation rate of the submodule capacitor voltage, the grid angular frequency, the number of full-bridge submodules in the eACPFC, the compensated DC common mode voltage, the rated capacitor voltage of the full-bridge submodule in the eACPFC, the bridge arm fundamental frequency differential mode output voltage, the AC line current value and the DC circulating current of the full-bridge submodule.

6. The multi-AC feed-in converter station simulation method according to claim 3, characterized in that: Also includes: Determining a feeder rated current according to the rated line voltage and the feeder rated capacity; Determining the operating current of the switching device according to the feeder rated current and the DC side rated current; The model information of the switch device in the half-bridge submodule in the MMC is determined according to the operating current of the switch device and the preset operating voltage of the switch device.

7. A multi-AC feed-in converter station simulation device, characterized in that: include: Data acquisition module, MMC parameter determination module, eACPFC parameter determination module and simulation module; The data acquisition module is used to obtain preset power flow parameters; The MMC parameter determination module is used to determine the DC side voltage of the MMC in the multi-AC feed-out converter station, the number of half-bridge submodules in the MMC, the bridge arm inductance of the MMC, and the capacitance value of the half-bridge submodule in the MMC according to the power flow parameters; The eACPFC parameter determination module is used to determine the number of full-bridge submodules in the eACPFC and the capacitance value of the full-bridge submodules according to the power flow parameters; wherein the eACPFC is embedded in the MMC; The simulation module is used to input the power flow parameters, the DC side voltage, the number of half-bridge sub-modules in the MMC, the bridge arm inductance, the capacitance value of the half-bridge sub-modules in the MMC, the number of full-bridge sub-modules in the eACPFC and the capacitance value of the full-bridge sub-modules into a preset simulation software to generate a simulation result of the multi-AC feed-out converter station.

8. A terminal device, characterized in that: include: one or more processors; A memory, coupled to the processor, for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the multi-AC feed-type converter station simulation method as described in any one of claims 1-6.

9. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the multi-AC feed-in converter station simulation method according to any one of claims 1 to 6 is implemented.

10. A multi-AC feed-in converter station, characterized in that: include: An MMC and an eACPFC embedded in the MMC; The MMC is composed of three phase units connected in parallel, each of the phase units includes two bridge arms, and each of the bridge arms is composed of a plurality of half-bridge sub-modules connected in cascade; The eACPFC comprises a plurality of eACPFC sub-units, each of which is composed of a plurality of full-bridge sub-modules; Among them, the DC side voltage of the MMC in the multi-AC feeder converter station, the number of half-bridge sub-modules in the MMC, the bridge arm inductance of the MMC, the capacitance value of the half-bridge sub-module in the MMC, the number of full-bridge sub-modules in the eACPFC and the capacitance value of the full-bridge sub-module are determined according to the preset power flow parameters.

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