多有源桥型电力电子变压器简化电磁暂态等效模型

Simplified Electromagnetic Transient Equivalent Model of Multi-active-bridge-based Power Electronic Transformer

电力电子变压器是柔性直流配电网的关键设备,其高频特征导致仿真步长小,在多有源桥等场合下其详细电磁暂态仿真效率依然较低,需要进行提速。文中提出了一种级联H桥型多有源桥电力电子变压器简化电磁暂态等效模型,分析了多有源桥的结构特征。对于级联H桥慢变电路,采用开关函数模型划分电路状态;对于多有源桥快变电路,以广义状态空间平均法为基础,实现傅里叶分解并保留关键次谐波特征的等效。此外,提出了不同级联方式下端口电气值处理方法,在保留精度的前提下提升仿真加速比。在PSCAD/EMTDC中实现了输入串联输出并联型多有源桥电力电子变压器的详细模型和简化等效模型建模。仿真结果表明,与详细模型相比,简化电磁暂态等效模型具有相似的精度和更高的效率。

The power electronic transformer(PET)is one of the key devices in the flexible DC distribution system.Due to the small simulation step size caused by high-frequency characteristics of PET,the detailed electromagnetic transient(EMT)simulation of PET is extremely time-consuming,especially for the multi-active-bridge(MAB)based PET.Hence the simulation speed needs to be accelerated.This paper proposes a simplified EMT equivalent model of the cascaded H-bridge(CHB)type MABbased PET.The structural characteristics of MAB are analyzed.For the CHB slow-change circuit,the switching function model is adopted to divide the circuit states.Based on the generalized state-space average method,for the fast-changing circuit of MAB,the equivalent that the Fourier decomposition method is used and the harmonic characteristics of key orders are kept is achieved.The processing methods of port electrical variables in different cascading modes are proposed to improve the simulation acceleration ratio while preserving accuracy.The detailed model and the simplified equivalent model of input-series output-parallel type MABbased PET are built in PSCAD/EMTDC.The simulation results show that the simplified EMT equivalent model has similar accuracy and higher efficiency compared with the detailed model.