特高压MMC环流抑制策略

Circulating Current Suppression Strategy of Ultra-high Voltage MMC

我国目前已经开始规划±800kV特高压柔性直流输电系统,这种高压大容量换流器相间环流造成的损耗成为不可忽视的问题。为了抑制桥臂环流,提出了一种通过控制桥臂电感压降进而抑制环流的方法。该方法直接应用于阀基控制器,根据环流的流向增减子模块的投切个数,进而将环流抑制在限定范围以内,降低换流器损耗。搭建了PSCAD仿真系统以及9电平10kW实验样机,对所提环流抑制策略进行验证,证明了该策略可以有效抑制换流器的相间环流。

At present,China has begun to plan±800kV ultra-high voltage flexible direct current transmission system.The losses caused by the inter-phase circulation of high voltage and large capacity converters can not be ignored.In order to suppress the circulating current of each arm,a method of suppressing the circulating current by controlling the inductance voltage drop is proposed.This method is directly applied to the valve-based controller,which increases or decreases the number of switching sub-modules according to the flow direction of the circulating current,and then suppresses the circulating current within a limited range to reduce the converter loss.A PSCAD simulation system and a 9-level 10kW experimental prototype are built to verify the proposed circulating current suppression strategy,which proves that the strategy can effectively suppress the inter-phase circulating current of the converter.