适用于弱互联电网的光伏逆变器LVRT控制策略研究

目前,光伏装机在电网中占比越来越高,并网光伏逆变器也有严格的低电压穿越要求。现行低电压穿越标准要求逆变器在低电压穿越期间按照曲线给予电网足够的无功电流支撑,但是没有对期间的有功电流响应做出明确要求。弱互联区域电网稳定不仅和无功电流相关,也在很大程度上和有功电流相关,同时低电压穿越期间有功缺额对频率也有较大影响。文章分析了电网电压不平衡时锁相环控制方法,并提出了一种基于解耦双同步坐标系锁相环的低电压穿越期间有功电流无功电流协调控制策略,搭建了基于F28335+CPLD的硬件控制平台,并最终在硬件在环仿真平台中验证了控制策略的有效性。

Research on LVRT control strategy of photovoltaic inverter for weak interconnection grid

At present,the proportion of photovoltaic installed in the grid is higher and higher,and grid connected photovoltaic inverter also has strict low-voltage ride through requirements.In the current low voltage ride through standard,the inverter is required to provide enough reactive current support to the grid according to the curve during the low voltage ride through period,but there is no clear requirement for the active current response during the low voltage ride through period.The voltage of weakly interconnected regional power grid is not only related to reactive current,but also to active current to a large extent.At the same time,the active power shortage during the low-voltage period also has a great impact on the frequency.This paper analyzes the phase-locked loop control method when the power grid voltage is unbalanced,and proposes a coordinated control strategy of active current and reactive current during the low voltage ride through based on the phase-locked loop in the decoupled double synchronous coordinate system.The hardware control platform based on F28335+CPLD is built,and finally the validity of the control strategy is verified in hardware-in-the-loop simulation platform.