孤岛微电网中虚拟机差异化故障穿越方法

Differentiated Fault Ride-Through Method for Synchronverter in Islanded Microgrid

孤岛条件下,多虚拟机组成的微电网在暂态过程中存在严重的过流及稳定性问题。分析了虚拟机冲击电流的数学模型,提出了快速限流控制和虚拟阻抗限流控制两种限流方法。在此基础上,考虑微电网的安全性与稳定性,提出了孤岛微电网中虚拟机差异化故障穿越控制策略。该策略对故障程度严重的近端虚拟机,采用快速电流控制抑制冲击电流同时合理分配功率;对于故障程度较浅的远端虚拟机,采用虚拟阻抗控制限制短路电流同时为微电网提供频率支撑。基于PSCAD/EMTDC的仿真结果验证了控制策略的有效性。

In islanding mode, microgrids composed of multiple synchronverters suffer from serious overcurrent and stability problems during transient process. A mathematical model of inrush current of synchronverter is established. Two current limiting methods, fast current restraining control and virtual impedance current limiting control, are proposed to eliminate fault current. Then, differentiated fault ride-through control strategy is put forward for security and stability of the microgrid considered. In the proposed strategy, fast current restraining control is used to suppress inrush current and distribute the power reasonably. Virtual impedance current limiting control is used to limit short circuit current and provide frequency support for the microgrid. Simulation results based on PSCAD/EMTDC verify effectiveness of the proposed control strategy.