交流谐波干扰的直流配电网故障保护方案

A Fault Protection Scheme for Direct Current Distribution Network Considering the Alternating Current Harmonic Disturbances

直流配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,使得输出功率剧烈波动。因此,在为直流配电网设计保护时应当充分考虑交流谐波扰动对直流配电网的影响。为此,首先深入分析了典型交流接地故障产生的谐波扰动对直流配电网的影响,给出分布式电源典型控制策略下控制系统内环参考电流的计算方法。其次在PSCAD/EMTDC软件仿真平台搭建直流配电网交流故障等值模型,验证了理论分析。最后,从动作时序角度出发,提出一种适用于直流配电网的故障保护方案,通过选择合适的故障参量以及延时因子,保证系统的选择性,有效地避免谐波扰动的影响。

The harmonic disturbances generated by the Alternating Current（AC） side of a Di rect Current（DC） distribution network 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 dis turbance, which makes the output power fluctuate violently. Therefore, in the design of DC distri bution network protection, the AC harmonic disturbance on the DC distribution network protection should be fully considered. In this paper, the influence of the harmonic disturbance caused by the typical AC ground fault on the DC distribution network is analyzed in detail, and the calculation method of the internal reference current of the control system under the typical control strategy of distributed power supply is given. Moreover, the AC fault equivalent model of the DC distribution network is set up on the PSCAD/EMTDC simulation platform to verify the above theoretical analy sis. Finally, from the perspective of action timing, a fault protection scheme for the DC distribution network is proposed. By choosing the appropriate fault parameters and delay factors, the selectivity of the system is ensured, and the influence of harmonic disturbance is avoided effectively.