基于附加电流指令的抑制多馈入直流系统相继换相失败渐进恢复策略

Incremental Recovery Strategy Based on Additional Current Order to Suppress the Successive Commutation Failure of Multi-infeed DC System

多馈入直流系统结构复杂,各直流系统间相互耦合,一回直流系统换相失败故障可能导致邻近直流系统相继换相失败,造成区域性失电的重大事故。为有效抑制多馈入直流系统相继换相失败,实现各直流系统的有序恢复,提出了一种基于附加电流指令的渐进恢复策略。该策略将各直流换流母线电压有效值与额定值的差额作为系统无功裕度的衡量指标,并计算相应的附加电流指令。考虑到多馈入直流系统各直流系统强度不同,结合多馈入短路比对各直流系统的附加电流指令进行权重分配。最后通过与低压限流环节叠加得到整流侧电流给定值,实现多馈入直流系统的渐进恢复。在PSCAD/EMTDC上搭建测试系统,仿真结果验证了所提策略的有效性。

The structure of multi-infeed DC(MIDC) system is complex, and there is coupling between DC systems. The commutation failure(CF) of one DC system may leads to the successive CF of the adjacent DC system, resulting in a serious regional power loss. In order to effectively suppress the successive CF of MIDC system and realize the orderly recovery, an incremental recovery strategy based on additional current order is proposed in this paper. In this strategy, the voltage of the converter bus is used as a criterion of reactive power margin, and the corresponding additional current order is calculated according to an appropriate scale factor. Considering the different intensity of the DC systems, the multi-infeed short circuit ratio(MISCR) is utilized to calculate the scale factor. Finally, by the superposition of voltage dependent current order limiter(VDCOL) and the additional current order, the current setting value at rectifier side is obtained to realize the incremental recovery. The test system is built in PSCAD/EMTDC, and the simulation results verify the validation of the proposed strategy.