一种计及交流谐波扰动的混合微电网直流保护方案

A DC Protection Scheme for Hybrid Microgrid Considering AC Harmonic Disturbances

混合微电网交流侧故障产生的谐波扰动可通过换流器传递至直流侧,影响直流系统的稳定运行,尤其对于直流分布式电源,其控制系统的快速调节特性会快速响应谐波扰动,使输出功率剧烈波动。因此,在为混合微电网直流侧设计保护时应当充分考虑交流谐波扰动的影响。首先分析交流故障产生的谐波扰动对混合微电网直流系统的影响,之后从动作时序角度出发,提出一种混合微电网直流保护方案,通过选择合适的故障参量及延时因子保证系统的选择性,有效地避免谐波扰动对保护的影响。最后,在PSCAD/EMTDC仿真平台搭建混合微电网交流故障等值模型,验证了保护方案的有效性。

The harmonic disturbances generated by the AC side of hybrid microgrid can be transmitted to the DC side through the inverter, which affects the stable operation of the DC system, especially for the DC distributed power supply. The fast adjustment characteristic of the control system will respond quickly to the harmonic disturbance, which makes the output power fluctuate violently.Therefore,AC harmonic disturbance on the DC distribution network protection should be fully considered in DC protection. The influence of harmonic disturbance caused by the typical AC fault on the hybrid microgrid is analyzed in detail. After that, a DC protection scheme from the perspective of action timing is proposed. By choosing the appropriate fault parameters and delay factors, the selectivity of the system is ensured and the influence of harmonic disturbance on DC protection is avoided effectively. Finally, the AC fault equivalent model of hybrid microgrid is set up on PSCAD/EMTDC simulation platform to verify the effectiveness of protection scheme.