多端口分布式光伏接入直流配电系统整体故障穿越协调控制

Integrated fault ride through control for multi-port DC distribution system with distributed photovoltaic generation

因新能源渗透率高,多端口光伏分布式接入直流配电系统在并网换流器交流送出线路发生故障时应具备故障穿越的能力。然而,并网换流器与光伏直流变压器的容量、控制方式不同,即使两者在故障穿越期间可以相互高速通信协调,但是由于不同换流设备功率调节响应存在差异,直流母线电压容易发生较大波动,进而导致整个系统脱网。为此,提出了基于光伏端口电压调节的变功率控制方式,对直流配电系统有功功率进行动态补偿,可使直流母线电压快速恢复至额定运行点,解决交流故障导致的直流母线电压大范围波动问题,并给出了调节系数的整定与电压触发阈值的选取方式,从而实现可靠的故障穿越。PSCAD仿真结果表明,与传统控制策略相比,所提方法在不同故障程度、系统在交流故障前运行在不同有功功率的情况下,光伏电站均能有效且快速调节有功功率,避免了直流配电系统中换流器闭锁,保障了并网换流器故障穿越的实现。

Due to the high penetration of renewable energy,multi-port DC distribution system with distributed photovoltaic generation should have the ability of fault ride through when the AC lines of the grid connected converter fail.However,the grid connected converter and photovoltaic DC transformer are different in capacity and control mode.Even if they can communicate and coordinate with each other at high speed during fault ride through period,due to the difference of power regulation response of different converters,the DC bus voltage is prone to large fluctuation,and then cause the whole system trip-off from grid.Therefore,a variable power control method based on the regulation of photovolatic array port voltage is proposed,which can dynamically compensate the active power of the DC distribution system.The DC bus voltage can be quickly recovered to the rated operating point,and the wide-range fluctuation of DC bus voltage caused by AC fault is solved.The setting principle of adjustment coefficient and the selection of voltage threshold are given to realize reliable fault ride through.Results of PSCAD simulation show that compared with the traditional control strategy,the proposed method can effectively and quickly adjust the active power of photovolatic station under different fault levels and different active power before AC fault occurs,thus avoiding converter blocking in DC distribution system and ensuring the realization of fault ride through of the grid connected converter.