微网保护分析

对微网特性以及影响保护的因素进行了分析,提出了微网的保护机制并进行了仿真。微网系统内部的保护须考虑逆变式电源的限流作用和微网双向潮流特性,还须综合考虑通信的应用,保护在不同运行方式下的适应性,与控制方式的协调性以及动作时间的合理设置等问题。在对这些因素进行分析的基础上,提出了微网的保护机制:对于线路故障,采用纵联保护;对于负荷故障,采用各相电流矢量和作为故障判据。研究中利用下垂控制原理在PSCAD中搭建了微网的模型,并对微网孤岛运行模式下各种负荷故障情况进行了仿真,仿真结果表明了所提负荷故障保护方法在孤岛运行方式下的有效性。

Analysis of microgrid protection

Based on the analysis of microgrid characteristics and factors that affect protection, a protection scheme is proposed and simulated. Microgrid protection should take into account the current limitation of inverter-based DGs and the bidirectional powerflow in the grid. Utilization of communication, adaption of protection in different operating modes, coordination with the control system and fault clearing time should also be considered. Based on the analysis of the above factors, a protection scheme is proposed. As for the line fault, pilot protection is used in the protection; as for the load fault, the vector sum of each phase current is adopted as the fault criterion. A microgrid model is established using droop control with a PSCAD software, and different load faults in the islanded microgrid are simulated, and the result shows that the proposed load-fault protection is valid in an islanded operating mode.