级联H桥型电力电子变压器的闭锁状态等效建模方法

Research on Equivalent Modeling Method of Cascaded H-bridge Based PET Under Blocking State

电力电子变压器(power electronic transformer,PET)是未来交直流混合配电网的关键设备,对其进行多工况高效仿真的一个关键难点为闭锁等效建模。该文提出一种适用于级联H桥型PET(cascaded H-bridge based PET,CHB-PET)闭锁状态的等效建模方法。首先,以一个实际算例说明闭锁状态的电路特征;其次,经过合理简化后,推导部分闭锁和完全闭锁状态下的戴维南-诺顿等效参数;然后,分析闭锁等效模型的3种实施方式,提出一种与非闭锁模型共用状态变量存储单元的集成方法;最后,在PSCAD/EMTDC软件中搭建典型的10kV/3kV三相CHB-PET系统,并进行启动、电压暂降及直流故障闭锁工况仿真。结果表明,与详细模型相比,所提闭锁等效模型具有足够的仿真精度。

Power Electronic Transformer(PET) is the key equipment of future AC/DC hybrid power distribution network. One of the key difficulties for efficient simulation of PET’s multiple working conditions is equivalent modelling under blocking state. This paper put forward an equivalent modeling method suitable for the blocking state of cascaded H-bridge based PET(CHB-PET). First, a practical example was used to explain the circuit characteristics of the blocking state. After the simplification, the Thévenin-Norton equivalent parameters in the partially blocking and totally blocking states were derived. Then, three implementation methods of the blocking equivalent model were analyzed, and an integrated method of sharing the state variable storage unit with the non-blocked model is proposed. A typical 10 kV/3 kV three-phase CHB-PET system was built in PSCAD/EMTDC, and the blocking conditions during startup process, AC voltage sag, and DC fault were simulated. The results show that compared with the detailed model, the blocking methods proposed in this paper have sufficient simulation accuracy. The work in this paper can also provide a reference for the blocking modeling of other modular converters containing multi-stage power transformation.