交直流配电网交流侧非对称故障情况下直流侧电压波动特性分析与控制

直流配电网以其高效消纳直流电能的优势,成为未来分布式电源并网的重要方式。但是交流配电网发生非对称故障会引起与其互联的直流配电网电压波动,从而危害直流配电系统的正常运行。为此,首先,分析了交流配电网发生单相接地故障情况下有功功率和直流电压波动的特性,推导给出了滤波电感上瞬时有功功率的表达式,并指出了滤波电感上的瞬时有功功率是导致直流电压波动的重要原因。其次,提出了一种改进锁相环对正序电压的相位进行跟踪,所提方法仅对传统锁相环的补偿器进行重新设计,原理清晰,易于实现。最后,在PSCAD/EMTDC中搭建了典型的双端交直流配电系统仿真模型,验证了理论分析正确性及所提控制方法的有效性。

Analysis and Control of DC Side Voltage Fluctuation Characteristics under Unbalanced Fault of AC Side in AC/DC Distribution Network

DC distribution network, with its advantage of efficient absorption of direct current energy, will become an important way of connecting the future distributed generators. However, the unbalanced faults of the AC distribution networks will cause the voltage fluctuation of the DC distribution networks, which will harm the normal operation of the DC distribution system. To tackle the problem aforementioned, this paper firstly analyzes the characteristics of active power and DC voltage fluctuations in the case of single-phase-to-ground fault in AC distribution network, especially deduces the expression of instantaneous active power of filter inductance, and points out that the instantaneous active power of filter inductance is the important cause of DC voltage fluctuation. Secondly, an improved phase lock loop (PLL) is proposed to track the phase of positive-sequence voltage. The proposed method only redesigns the compensator of the traditional PLL, which is clear in principle and easy to implement. Finally, a simulation model of typical two-terminal AC-DC distribution system is built in PSCAD/EMTDC to verify the correctness of the theoretical analysis and the effectiveness of the proposed control method.