A modeling method for improving the speed of electromagnetic transient simulation in flexible substations

Abstract

The invention relates to a modeling method for improving the electromagnetic transient simulation speed of a flexible substation, comprising the following steps: (1) Equivalent of the MMC sub-module of the flexible substation: the IGBT of the upper and lower bridge arms in the sub-module is equivalent to Two controlled resistors R that can switch between high and low resistance values ​​according to the turn-on signal 1 , R 2 , according to the implicit trapezoidal integration method, the sub-module capacitance is equivalent to the constant resistance R c with a controlled voltage source V CEQ in series form, and the constant resistor R c and a controlled voltage source V CEQ There are circuit interfaces at both ends of the series branch for connecting to the four-winding intermediate frequency isolated DC / DC converter on the low voltage side. (2) The equivalent of a four-winding IF isolated DC / DC converter in a flexible substation.

Description

technical field [0001] The invention belongs to the field of modeling and simulation of multi-port power electronic power conversion devices. Aiming at the problem of low simulation efficiency of detailed switch models of flexible substations, a modeling method for improving the speed of electromagnetic transient simulation of flexible substations is proposed. Background technique [0002] The flexible substation is composed of a modular multilevel converter (MMC) and a four-winding intermediate frequency isolated DC / DC converter, and is highly integrated with multiple ports such as medium voltage DC, medium voltage AC, and low voltage DC. Advanced power electronic equipment can be flexibly connected to energy storage and distributed new energy [1] . attached figure 1 The structure of the flexible substation is shown, which has multiple ports, which can be flexibly connected to power sources such as energy storage and distributed new energy, and can also be connected to DC...

AI Technical Summary

Problems solved by technology

[0003] The core of the flexible substation adopts a modular multilevel converter (MMC) and a four-winding intermediate frequency isolated DC / DC converter. Among the existing MMC simulation models, the detailed switch model based on the IGBT switch tube model is very detailed. , all the simulation details of the flexible substation can be considered, but the detailed switch model needs to consider the switching process of each switching device when performing simulation calculations. When simulating a flexible substation with large-scale sub-modules, the simulation efficiency is greatly reduced[2][3 ][4]

And with the continuous development of flexible DC transmission to higher transmission power and voltage levels, the number of sub-modules and four-winding intermediate frequency isolation DC / DC converter modules required by MMC is also increasing, which seriously reduces the model's operation simulation. Therefore, it is particularly important to develop a speed-up simulation model suitable for electromagnetic transient simulation of flexible substations

[0004] In order to improve the simulation efficiency, most of the current MMC simulations use the Thevenin equivalent model based on the equivalent of the entire bridge arm [5][6] , and due to the high equivalence of this type of model, the external interface of the sub-module is not reserved, and the influence of the external circuit of the sub-module capacitor on the capacitor voltage is ignored, which cannot meet the needs of current flexible substations and many other practical projects.

At the same time, the specially designed four-winding transformer in the flexible substation adopts a three-phase common capacitance structure, which can offset the fluctuation power of the fundamental frequency and double frequency between phases in the transformer core, reduce the power fluctuation on the sub-module capacitance, and thus greatly reduce the The sub-module capacitance of three-phase MMC, but in the current fast simulation field, there is no relevant simulation technology that considers the simulation modeling of this technology

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