分布式光伏逆变器并网侧短路暂态特性分析

Analysis on Transient Characteristics of the Distributed Photovoltaic Inverter in the Grid Side Short-circuit

随着光伏发电的成本降低,越来越多的户用光伏发电系统分散接入配电网,给电网的运行管理带来了一定的风险。文中从分布式光伏并网逆变器的电路拓扑和控制策略出发,对逆变器在不同开关模态下的短路故障的暂态特征进行了分析,研究了不同导通逻辑下短路电流的变化趋势,并对逆变器在不同输出功率、跌落深度和跌落相位角等工况条件下进行了短路试验。试验结果表明,逆变器网侧短路时由于电感两端的磁势失衡,会引起电感电流的瞬时上升,在经过逆变器固有的惯性延迟后,内部的控制环路通过对开关管占空比的调节能够抑制电流的上升,最后由逆变器本体保护动作封锁驱动,不会引起越级跳闸事故。

Photovoltaic（PV） generation is widely accepted as an alternative energy for its gradually reducing cost. The increasing number of PV stations integrated into distribution grid brings a challenge to the grid operation. In this paper, based on the control strategy and the circuit topology of PV inverter, electromagnetic transient characteristic of the PV inverter short-circuit was studied theoretically. The short current changing trend under different switching states was studied. Besides,three short current experiments have been done under different output power, voltage drop depth and voltage angel. The experimental results show that the inverter inner closed loop controls can inhibit rush current. Moreover, the inverter self-protection action would block driving signal so as the bypassing trip accident wouldn＇t be caused.