Large-signal simulation model of single-phase power electronic transformer

Abstract

The invention relates to the field of power system transformer simulation, in particular to a large-signal simulation model of a single-phase power electronic transformer, aiming at improving the simulation speed. The simulation model of the invention comprises an equivalent large signal model of a cascaded H-bridge converter and an equivalent large signal model of a dual active bridge converter.The cascaded H-bridge converter equivalent large signal model is composed of a cascaded H-bridge converter module, a first controlled voltage source H1, a first controlled current source S1 and a support capacitor C1. The cascaded H-bridge converter module includes four input signals and four output terminals. The equivalent large signal model of double active bridge converters is composed of double active bridge converter modules, an equivalent resistor Req, an equivalent inductor Leq, an output capacitor C2, a second controlled voltage source H2 and a second controlled current source S2. Thedual active bridge converter module consists of four input signals and four output terminals. The model can accelerate the simulation speed of the single-phase power electronic transformer when the single-phase power electronic transformer is disturbed by large signals such as load switching or fault.

Description

technical field [0001] The invention relates to the field of power system transformer simulation, in particular to a large-signal simulation model of a single-phase power electronic transformer. Background technique [0002] In order to meet the application requirements of the medium and high voltage distribution network in the smart grid in the future, research on various types of power electronic transformers (Power Electronic Transformer, PET) has been carried out at home and abroad. In addition to the voltage level conversion and electrical isolation functions of traditional transformers, PET can also realize functions such as bidirectional flow of power flow, power quality control, and automatic protection of devices. Considering the withstand voltage level of power semiconductor devices, PET currently used in medium and high voltage distribution networks is generally composed of multiple power modules cascaded, and each power module includes an H-bridge converter and a...

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Problems solved by technology

For the equivalent large-signal model of the cascaded H-bridge converter, the existing schemes are generally based on the principle of power balance, ignoring the power loss in the converter, using the equivalent model of the gyrator, and the AC input side and the DC output side of the converter are equivalent to two The control signal of the controlled current source on the output side comes from the output of the capacitor voltage single closed-loop control system. The simulation speed of this model is fast, but it cannot simulate the double closed-loop control system in the physical simulation model; for dual active Bridge converters generally include LC resonant type and non-resonant type. In LC resonant dual active bridge converters, when the switching frequency of the power semiconductor is the same as the frequency of the LC resonant circuit in the converter, the output duty ratio of 50% can be used. The open-loop control method of wave voltage is used for power transmission. This control method is relatively simple. When the equivalent large-signal model of this type of dual active converter is established by using a gyrator, it often needs to go through complicated computer programming to obtain the affected model in the gyrator model. The control signal of the control current source

In addition to the gyrator model, existing solutions can also use discrete domain models and large signal models based on modern control theory. The simulation accuracy is high, but the model is relatively complex, and the analytical form of the system in the time domain cannot be obtained.

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