柔性直流配电系统负荷波动对系统过电压及过电流影响研究

柔性直流配电系统因其诸多优势而成为未来智能电网的重要发展趋势,而系统故障中的过电压和过电流分析及其及防护方法研究是其关键技术之一。由于柔性直流配电系统所接入的负荷具有波动性和间歇性等特性,故针对±10 kV两端柔性直流配系统开展了负荷波动对系统过电压及过电流影响研究。分析了故障下电压和电流的产生机理、影响因素以及负荷波动对电压和电流影响情况,并提出了后续研究中负荷的等效建模方法。首先根据两端柔性直流配电系统拓扑结构,在PSCAD/EMTDC电磁暂态仿真程序中建立其仿真模型。其次,根据系统接口设备拓扑结构,理论分析接口设备出口发生单极接地故障和双极短路故障下电压和电流的产生机理、影响因素以及负荷波动对电压和电流影响情况。最后,仿真验证接口设备出口发生单极接地故障和双极短路故障下负荷不同波动方式对电压和电流的影响,并提出负荷的等效建模方法。

Study on the influence of load fluctuation on overvoltage and overcurrent of a VSC-DC distribution system

The VSC-DC distribution system has become an important trend for development of the smart grid because of its advantages. Analysis of overvoltage and overcurrent in typical faults and their protection methods is a key aspect. Because the loads connected to the VSC-DC distribution system have characteristics of fluctuation and intermittence, this paper studies the influence of load fluctuation on overvoltage and overcurrent of a ±10 kV two-terminal VSC-DC distribution system. The generation mechanism and influencing factors of overvoltage and overcurrent under fault and the influence of load fluctuation on overvoltage and overcurrent are analyzed, and the equivalent modeling method of loads for subsequent research is proposed. First, according to the topology of a two-terminal VSC-DC distribution system, a simulation model is established in PSCAD/EMTDC. Secondly, according to the topological structure of the plug-in devices, the generation mechanism and influencing factors of overvoltage and overcurrent under pole-to-ground fault and pole-to-pole fault at the line side of the plug-in devices, as well as the influence of load fluctuation on over-voltage and overcurrent are analyzed theoretically. Finally, the influence of different load fluctuation modes on overvoltage and overcurrent under pole-to-ground fault and pole-to-pole fault at the line side of the plug-in devices is verified by simulation, and an equivalent load modeling method is proposed. This work is supported by National Natural Science Foundation of China (No. 51807068).