基于干扰观测器的MMC-PET交直流混合微电网并网/离网切换控制策略

Grid-connected/off-grid Switching Control Strategy of MMC-PET AC/DC Hybrid Microgrid Based on Disturbance Observer

针对模块化多电平换流器(modular multilevel converter,MMC)-电力电子变压器(power electronic transformers,PET)交直流混合微网在并网和离网两种模式下开关切换过程中存在瞬态过流和过压问题,从而影响输电质量并增加设备损耗,为此提出了一种基于扰动观测器(disturbance observer,DO)的并/离网切换控制策略。在该策略中,通过采用DO观测器对并离网切换引起的突变电流跟踪,并将实际电流与理论电流的差值作为等效干扰量,再将其输入到电流内环控制器进行补偿,从而可实现对突变电流的抑制。最后在Matlab/Simulink软件上搭建了MMC-PET交直流混合微网系统,并在并网-离网、离网-并网的两种切换工况下,通过把加入DO观测器与未加入DO观测器两种情况进行仿真对比,验证了所提的切换控制策略的有效性和可行性。

A grid-connected/off-grid switching control strategy based on disturbance observer(DO)is proposed to address the transient overcurrent and overvoltage during switching process of grid-connected mode and off-grid mode of AC/DC hybrid microgrids based on modular multilevel converters(MMC)and power electronic transformers(PET),which affect transmission quality and increase equipment losses.In this strategy,a DO observer is used to track the sudden change in current caused by grid-connected/off-grid switching,the difference between the actual current and the theoretical current is used as the equivalent interference quantity,and it is then input into the current inner loop controller for compensation,thereby achieving suppression of the sudden current change.Finally,an MMC-PET AC/DC hybrid microgrid system is built on Matlab/Simulink software,and the effectiveness and feasibility of the switching control strategy proposed in this paper are verified by simulating and comparing the scenarios in the presence and absence of a DO observer during two switching of grid-connected mode and off-grid mode.