可隔离直流故障的直流电网用DC/DC变换器拓扑

直流电网作为光伏和风电等新能源汇集的重要手段,近些年获得了快速发展。DC/DC变换器作为直流电网中电压变换和隔离直流侧故障的关键设备也日益受到关注。提出了一种适用于直流电网的可隔离直流故障的新型DC/DC变换器拓扑,该拓扑基于半桥模块化多电平换流器型DC/DC变换器,增加故障转移支路,发生直流故障时更易切断故障电流,同时提出了其故障隔离策略。对比该拓扑与半桥式DC/DC变换器的技术性和经济性差异发现,当DC/DC变换器出口侧连接有多个换流站时,提出的DC/DC变换器方案不仅可以更快地切除故障线路,还减少了故障隔离对于直流断路器的依赖。在PSCAD/EMTDC中,针对两个直流电网的典型场景,进行了直流双极短路故障仿真。仿真结果表明,所提出的拓扑具备直流故障穿越能力,非常适用于大规模直流电网系统。

DC/DC Converter Topology with DC Fault Isolation Capability Applicable for DC Grid

Due to the effective integration of large scale photovoltaic and wind power, multi-terminal DC grid gets extensive attention in recent years. Fast and reliable DC transformation and DC fault detection are key techniques in DC grid. A novel DC/DC converter topology with DC fault isolation capability, which is developed from the traditional half-bridge modular multilevel converter(MMC)based DC/DC converter, is proposed. It has additional fault current transfer branch to make the fault current interruption easier, also the corresponding control strategy is proposed. Compared to the traditional topology, when the new topology is connected to more than one DC terminals, the new approach is more efficient in terms of both economy and technology by minimizing the requirements for DC circuit breaker. In the PSCAD/EMTDC based validation, two DC grid scenarios are simulated with DC-side pole to pole short-circuit fault. Simulation results validate the effectiveness of the proposed DC/DC topology, showing that it is suitable for large scale DC grid.