含分布式光伏及储能变流器的微网故障特征与保护

在并网时，微网中所含的分布式电源可能包括恒功率控制的光伏变流器或电流下垂控制的储能变流器，其中传统电流下垂控制的储能变流器在电网电压跌落时所输出的较低的故障电流，以及可能会出现的功角失稳现象都为其故障保护带来了困难，而基于滞环控制的改进电流下垂控制可以使其在电网故障时保持功角稳定，同时具备低压穿越能力，给故障电流带来新的特征，有利于故障检测以及保护判据的配置。本文考虑变流器的低压穿越特性，分析了含分布式光伏及储能变流器的微网内部不同位置发生故障时的电流特征，利用正序电流故障分量与母线正序电压故障分量的相位差来判断故障方向，并提出基于EtherCAT工业以太网的集中式保护方案。最后，通过仿真与实验验证了所提方案的可行性。

Fault Characteristics and Protection of Micro-grid Containing Distributed Photovoltaic and Energy-storage Converters

When connected to the grid, the distributed generators contained in the microgrid may consist of either a constant power-controlled pho-tovoltaics (PV) converter or a current droop-controlled power conversion systems (PCS). The traditional current droop-controlled PCS outputs low fault current during grid voltage drops and may suffer from power angle destabilization, which both make its fault protection more difficult. Current droop control based on hysteresis loop control enables PCS to keep the work angle unchanged during grid faults and has low-voltage ride-through capability, bringing new characteristics to the fault current and facilitating fault detection and configuration of protection criteria. In this paper, the fault characteristics of microgrid system containing distributed PV and PCS are analyzed taking into account the low-voltage ride-through char-acteristics, the phase difference between the positive sequence current fault component and the positive sequence voltage fault component of the bus is used to determine the fault direction, and a centralized protection scheme based on EtherCAT is proposed.. Finally, the feasibility of the proposed scheme is verified by simulation and experiments.