适用于直流电网的LCL谐振式模块化多电平DC/DC变换器

LCL-Based Resonant Modular Multilevel DC/DC Converter for DC Grids

针对直流电网中不同电压等级线路的直流互联需求,结合隔离型模块化多电平DC/DC变换器和绝缘栅双极型晶体管(insulated gate bipolar transistor,IGBT)直串型LCL-DC/DC变换器的拓扑优点,提出了一种LCL谐振式模块化多电平DC/DC变换器拓扑。首先,介绍了该变换器电气拓扑,并分析了其工作原理,包括运行方式、功率传递机理等;其次,从功率传递和谐波抑制等角度提出了该变换器中LCL谐振网络的参数设计方法;然后,提出了适应于该变换器的控制保护策略,保证在不同功率传递下实现两侧模块化多电平换流器(modular multilevel converter,MMC)的零无功传输以及直流故障电流的迅速抑制;最后,在Matlab/Simulink中对所提拓扑及其控制保护策略进行了仿真验证。结果表明:根据LCL设计方法得到的电气参数能够满足装置的控制需求,所提控制策略在潮流反转、输入电压突变等工况下具有较好的静态和动态性能,且保护策略能够抑制直流侧的短路故障电流。

To fulfill requirement of connecting transmission lines at different voltages in DC grids, a modular multilevel DC/DC（MMC DC/DC） converter based on LCL tank is proposed. This converter combines merits of isolated MMC DC/DC and IGBT-direct-serial-based LCL-DC/DC converters. The converter topology is described and its working principle analyzed. Following that, determination of the LCL tank parameters in the converter is proposed on basis of power transfer and harmonics mitigation. Control and protection strategies applicable to the converter are brought up to transfer power with zero reactive power flowing from one side of MMC to another and to limit DC fault currents. This topology and the control and protection strategies are verified with Matlab/Simulink. Results show that the proposed control strategy makes the converter exhibit good static and dynamic performance under different operation conditions. Fault current can also be limited with the protection strategy.