适用于MMC型直流变压器的直流故障主动限流控制方法

Active Current Limiting Control Method for DC Fault of MMC Based DC Transformer

为满足模块化多电平换流器(MMC)型直流变压器对直流故障电流快速限制的要求,有必要对其主动限流控制方法进行研究。文中通过对双极短路故障机理的详细分析和故障电流的建模,得到了考虑上升阶段交流馈入量后的桥臂电流,以及短路电流峰值和峰值时间的表达式,然后给出了可以通过降低在故障发生后每相子模块投入数量来限制故障电流的结论。基于此结论,设计了一种新型主动限流控制方法。该方法通过产生附加直流偏置和交流增益,进而调整桥臂电压的直流分量和交流分量,再经调制环节达到限流目的。最后通过仿真验证了所提出方法的有效性和优越性。

In order to meet the requirements of fast current limiting of DC fault for modular multilevel converter（MMC）based DC transformer,the research of active current limiting control is necessary.By a detailed analysis of DC pole-to-pole fault mechanism and modeling of the fault current,the expressions of arm currents considering the feed at rising stage,the peak current and the peak time of short-circuit current are derived,then the conclusion that the fault current can be limited by reducing the number of submodules to switch on at each phase after DC fault is obtained.According to this conclusion,a novel active current limiting control method is proposed.By producing additional DC offset and AC gain,the DC component and AC component of the bridge-arm voltage are adjusted to achieve the purpose of current limiting through the modulation process.Finally,the simulation results verify the effectiveness and superiority of the proposed method.