统一潮流控制器的平滑启动和停运策略

Smooth Start and Stop Strategies for Unified Power Flow Controllers

统一潮流控制器(UPFC)包含串联和并联两个部分,其并联部分与静止同步补偿器(STATCOM)类似,目前已有成熟的策略实现其启动和停运,但对于串联部分,尚缺乏对实现其平稳接入和退出交流系统的有效策略研究。文中对UPFC的结构和运行原理进行分析,通过并联部分对串联侧换流器进行部分充电,再通过串联侧换流器的主动充电策略将其充电至额定状态,以减小其解锁时对换流器的冲击;另一方面,通过串联侧换流器控制线路电流在串联变压器绕组和串联变压器旁路开关之间的平稳转移,使串联变压器旁路开关在零电流断开和闭合,以及使串联侧换流器在零功率闭锁,从而实现UPFC的平滑启动和停运。基于PSCAD的仿真结果表明,该策略可以使UPFC的启动和停运过程对交流系统基本无影响。

Unified power flow controller(UPFC)consists of two parts the series part and parallel part.The parallel part is similar to a static synchronous compensator(STATCOM),and there have been mature strategies for achieving its start and stop.But for the series parts,there is no effective strategy for accessing and exiting the AC grid.The series converter is charged through the parallel part firstly,and then charged to rated condition by the active charging strategy to reduce the impact of deblocking.In addition,by controlling the line current transfer between the series transformer winding and the series transformer bypass switch,the bypass switch of the series transformer can open and close at zero current,while the series converter is able to block at zero power so as to realize smooth start and stop of UPFC.The simulation results based on PSCAD show that this strategy is capable of making UPFC to start and stop without disturbance to the AC grid.