Simulation modeling method of modular multilevel converter

Abstract

The invention provides a simulation modeling method of a modular multilevel converter, which comprises the following steps of: performing simulation modeling on a core power device of one of six bridge arms through a digital model by adopting a mode of 1: 1 with engineering practice, the core power device comprises an IGBT (Insulated Gate Bipolar Translator), an anti-parallel diode and a parallel capacitor; carrying out equivalent simulation modeling on the other five bridge arms in the six bridge arms; the upper and lower positions of the abc three phases of the bridge arm which is modeled in the simulation modeling mode are changed through setting according to simulation analysis requirements. According to the invention, the problem that the simulation efficiency and the internal fault simulation requirement of the current modular multilevel converter cannot be considered at the same time is solved.

Description

Technical Field

[0001] The invention relates to the technical field of simulation modeling, and in particular to a simulation modeling method for a modular multi-level converter. Background Art

[0002] Since the 1990s, due to the objective fact that power sources and loads are distributed inversely, my country has vigorously promoted the application of high-voltage direct current transmission technology to meet the sustainable development of the national economy and the growing needs of the people for a better life. As one of the emerging technology routes, flexible direct current (VSC-HVDC) has become a new hotspot in the development and engineering application of high-voltage direct current transmission technology in recent years with its own technical advantages.

[0003] The modular multilevel converter (MMC) was formally proposed at the beginning of this century. It fundamentally solves the problem that the manufacturing process level of fully controlled power semiconductor devices cannot meet the requirements of two-level bridge topology for high-voltage and large-capacity scenarios. With the emergence of MMC, flexible DC has ushered in a peak period of technological development and engineering application in the field of high voltage and large capacity in the past 10 years. At present, MMC has become the first choice for flexible DC transmission project construction worldwide, and has been further extended to the field of medium and low voltage DC distribution technology.

[0004] At the same time, compared with the two-level bridge topology, the biggest disadvantage of MMC lies in its economic performance, which is specifically manifested in the huge number of its power components - sub-modules. The number of fully controlled power semiconductor devices required is twice or more than that of the two-level bridge topology, and there are tens of thousands of high-voltage and large-capacity flexible DC converter valve sub-modules, which not only greatly increases the cost of engineering construction and operation and maintenance, but also causes the practical problem that the efficiency and internal fault simulation requirements cannot be taken into account during MMC simulation. If each MMC sub-module is accurately modeled, a large amount of simulation resources will be consumed and the efficiency will be low; if the entire MMC is equivalently modeled, it will be impossible to carry out simulation analysis for the internal faults of the MMC itself.

[0005] Therefore, it is necessary to study the simulation modeling method of modular multilevel converters to provide a practical means to balance the simulation efficiency of MMC and the internal fault simulation requirements, and to ensure the safe and stable operation of flexible DC transmission projects and even power grids. Summary of the invention

[0006] The object of the present invention is to provide a simulation modeling method for a modular multilevel converter, so as to solve the problem that the simulation efficiency of the modular multilevel converter and the internal fault simulation requirements cannot be taken into account at the same time.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] A simulation modeling method for a modular multilevel converter, wherein the abc three-phase of the modular multilevel converter has a total of six bridge arms.

[0009] The core power device of one of the six bridge arms is simulated and modeled by a digital model in a 1:1 manner with the actual engineering practice, wherein the core power device includes an IGBT, an anti-parallel diode, and a parallel capacitor;

[0010] Perform equivalent simulation modeling on the other five bridge arms among the six bridge arms;

[0011] The bridge arm modeled by the simulation modeling method is configured to change the upper and lower positions of the abc three-phases to which the bridge arm belongs according to the simulation analysis requirements.

[0012] Furthermore, the core power device of one of the six bridge arms is simulated and modeled by a digital model in a 1:1 manner with the actual engineering practice, specifically including:

[0013] According to the electrical structure of MMC, the basic components in the bridge arm are decomposed into IGBT, anti-parallel diode and parallel capacitor. The corresponding simulation modules provided by the simulation software are selected and electrically connected to form a sub-module. Then, multiple sub-modules are electrically connected to form a bridge arm with MMC. Then, multiple sub-modules are packaged into one package module, and multiple package modules are used to realize the simulation of a bridge arm of MMC. Finally, according to the simulation object, the corresponding electrical parameters are set to complete the simulation modeling.

[0014] Furthermore, performing equivalent simulation modeling on the other five bridge arms among the six bridge arms specifically includes: respectively realizing simulation modeling through equivalent digital models of the bridge arms provided by the simulation system.

[0015] Furthermore, the simulation system adopts simulation software RTDS, RTLAB or PSCAD.

[0016] Furthermore, the above-mentioned changing the upper and lower positions of the abc three-phases to which the bridge arm belongs by setting includes: the bridge arm to be simulated and modeled is changed by modifying the circuit wiring of the simulation model according to the internal fault simulation requirements of the modular multilevel converter.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The simulation modeling method of the modular multilevel converter proposed in the present invention can greatly improve the simulation efficiency while ensuring the simulation effect of the modular multilevel converter, and can realize the simulation analysis of the internal faults of the modular multilevel converter body, and adjust the electrical structure of the constructed simulation model by setting according to the different locations of the fault points. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of simulation modeling of a modular multi-level converter provided by the present invention.

[0020] Figure 2 A schematic diagram of simulation modeling of a modular multilevel converter packaging module provided by the present invention.

[0021] Figure 3 A schematic diagram of simulation modeling of a modular multilevel converter submodule provided by the present invention.

[0022] Figure 4 A schematic diagram for comparing the existing full equivalent simulation modeling and the equivalent + simulation modeling of the present invention;

[0023] Figure 5 It is a schematic diagram comparing the simulation effects of the existing full equivalent simulation modeling and the equivalent + simulation modeling of the present invention. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention.

[0025] See also Figure 1-3 The embodiment of the present invention provides a simulation modeling method for a modular multilevel converter, wherein the modular multilevel converter has a total of six bridge arms, the abc three-phase upper and lower arms, and the method includes:

[0026] Step 1: simulate and model the core power device of one of the six bridge arms through a digital model in a 1:1 manner with the actual engineering practice, wherein the core power device includes an IGBT, an anti-parallel diode, and a parallel capacitor.

[0027] Specifically, according to the electrical structure of MMC, the basic component unit of the bridge arm, the sub-module, is decomposed into IGBT, anti-parallel diode, and shunt capacitor. The corresponding simulation module provided by the simulation software is selected and electrically connected to form a sub-module. Then, multiple sub-modules are electrically connected to form a bridge arm with MMC. That is, each sub-module is modeled using the simulation model of the core power device (IGBT, anti-parallel diode, shunt capacitor). Figure 3 As shown in FIG. 1 , the modeling effect of 20 sub-modules is shown; then the 20 sub-modules are packaged into one package module, and multiple package modules are used to realize the simulation of one bridge arm of MMC, as shown in FIG. Figure 2 As shown; the final accurate simulation model of one bridge arm of the MMC is Figure 1 Finally, according to the simulation object, set the corresponding electrical parameters to complete the simulation modeling.

[0028] To ensure the readability and modifiability of the simulation model, when there are a large number of modular multilevel converter sub-modules, a packaging module is set to batch modify the modular multilevel converter sub-module parameters and to modify the modular multilevel converter sub-module structure and parameters in a targeted manner.

[0029] The bridge arm that is accurately simulated and modeled can be set to change its electrical position in the modular multilevel converter, i.e., the upper bridge arm of phase a or the lower bridge arm of phase b, according to the needs of simulation analysis. According to the needs of the internal fault simulation of the modular multilevel converter (the fault may occur in any bridge arm), the position of the bridge arm that is accurately simulated and modeled can be changed by modifying the circuit wiring of the simulation model. That is, according to the cause of the fault, when we know which submodule of which bridge arm has a fault, we can first set the accurately simulated bridge arm to the position of the faulty bridge arm by modifying the electrical wiring of the simulation model, and then select the simulation model corresponding to the faulty submodule and set the fault according to the cause of the fault to achieve the simulation of the fault.

[0030] The current common MMC simulation method uses an equivalent modeling method, which cannot achieve the simulation of MMC internal faults because MMC is an equivalent module. The present invention provides an accurately simulated MMC bridge arm. In actual engineering, any internal fault of any bridge arm of MMC can be targeted by the present invention to achieve internal fault simulation.

[0031] Step 2: Perform equivalent simulation modeling on the other five bridge arms among the six bridge arms;

[0032] Specifically, equivalent simulation modeling is performed on the other five bridge arms except the bridge arm with accurate simulation modeling, that is, simulation modeling is respectively realized by using the equivalent digital model of the bridge arm provided by the simulation system. At present, mainstream simulation software such as RTDS, RTLAB, PSCAD, etc. provide equivalent simulation modules for modular multilevel converters. The present invention uses the bridge arm equivalent simulation module of the existing modular multilevel converter to complete the modeling and simulation of the other five bridge arms except the bridge arm with accurate simulation modeling.

[0033] The bridge arm modeled by the simulation modeling method is set to change the upper and lower positions of the abc three-phases to which the bridge arm belongs according to the simulation analysis needs.

[0034] Taking a typical flexible DC transmission project as an example, in order to verify the simulation effect of the present invention, two simulation models are constructed, such as Figure 4 shown.

[0035] Through the simulation results, the red one is the full equivalent modeling simulation result, and the purple one is the equivalent + accurate modeling simulation result of the embodiment of the present invention. Figure 5 As shown in the figure, the simulation results of the two are basically the same, and the latter is faster.

[0036] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A simulation modeling method for a modular multilevel converter, wherein the abc three-phase modular multilevel converter has a total of six bridge arms, characterized in that: The core power device of one of the six bridge arms is simulated and modeled by a digital model in a 1:1 manner with the actual engineering practice, wherein the core power device includes an IGBT, an anti-parallel diode, and a parallel capacitor; Perform equivalent simulation modeling on the other five bridge arms among the six bridge arms; The bridge arm modeled by the simulation modeling method is configured to change the upper and lower positions of the abc three-phases to which the bridge arm belongs according to the simulation analysis requirements.

2. The simulation modeling method of a modular multilevel converter according to claim 1, characterized in that: The core power device of one of the six bridge arms is simulated and modeled by a digital model in a 1:1 manner with the actual engineering practice, specifically including: According to the electrical structure of MMC, the basic components in the bridge arm are decomposed into IGBT, anti-parallel diode and parallel capacitor. The corresponding simulation modules provided by the simulation software are selected and electrically connected to form a sub-module. Then, multiple sub-modules are electrically connected to form a bridge arm with MMC. Then, multiple sub-modules are packaged into one package module, and multiple package modules are used to realize the simulation of a bridge arm of MMC. Finally, according to the simulation object, the corresponding electrical parameters are set to complete the simulation modeling.

3. The simulation modeling method of a modular multilevel converter according to claim 1, characterized in that: The performing equivalent simulation modeling on the other five bridge arms among the six bridge arms specifically includes: respectively performing simulation modeling through equivalent digital models of the bridge arms provided by the simulation system.

4. The simulation modeling method of a modular multilevel converter according to claim 1, characterized in that: The simulation system adopts simulation software RTDS, RTLAB or PSCAD.

5. The simulation modeling method of a modular multilevel converter according to claim 1, characterized in that: The method of changing the upper and lower positions of the abc three-phases to which the bridge arm belongs by setting includes: the bridge arm being simulated and modeled is changed by modifying the circuit wiring of the simulation model according to the internal fault simulation requirements of the modular multi-level converter body, so as to change the position of the bridge arm being simulated and modeled.

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