级联H桥型电力电子变压器平均值模型

Average-value model of cascaded H-bridge type power electronic transformer

针对电力电子变压器仿真效率较低和死区效应越来越显著的问题,基于级联H桥型双有源桥结构电力电子变压器,提出一种考虑死区效应的平均值模型。首先,计及寄生参数将双有源桥单元简化为一阶RL电路,分析各个死区工况下电压电流特性,求解电流的平均化解析表达式,通过等效电流源代替全桥及高频变压器实现对双有源桥单元的平均值建模。其次,基于状态空间平均法,通过占空比将H桥整流单元各工况整合为一个统一的模型,进而使用受控源代替H桥整流单元与交流电网、双有源桥的接口电路。最后,建立输入侧串联输出侧并联型的级联H桥型电力电子变压器平均值模型并给出计算流程。在PSCAD/EMTDC仿真软件上分别搭建电力电子变压器详细模型与平均值模型,仿真结果表明所提出的模型具有较高的精度和运行效率。

In order to solve the problems of low simulation efficiency and the growing influence of deadtime effect of power electronic transformer(PET),an average-value model considering dead-time effect is proposed for cascaded H-bridge(CHB)type PET with dual active bridge(DAB)structure.Firstly,considering parasitic parameters,the DAB unit is simplified to a first-order RL circuit.After analyzing the voltage and current characteristics under each dead-time condition,the average analytical expression of current is derived.By applying equivalent current source to replace full-bridge and high-frequency transformer,the average-value modeling of DAB unit is realized.Secondly,based on state space average method,each working condition of H-bridge rectifier unit is integrated into a unified model through duty ratio.Then equiva⁃lent sources are used to substitute for the interface circuit between H-bridge rectification unit and AC grid or DAB.Finally,the average-value model of input series output parallel(ISOP)type CHB-PET is de⁃rived,and the calculation flow is given.The detailed model and average-value model of PET are built on PSCAD/EMTDC,and the simulative results show that the proposed model has high accuracy and opera⁃tion efficiency.