基于电网电压前馈补偿的光伏并网逆变器零电压穿越控制

Zero Voltage Ride-through Control Strategy of Photovoltaic Grid-connected Inverter Based on Compensation for Phase of Feed-forward Grid Voltage

根据相关国家标准要求,大型光伏并网逆变器需具备零电压穿越(ZVRT)能力以防止其发生低压自动脱网,从而影响电力系统正常稳定运行。在分析光伏并网逆变器ZVRT标准的基础上,详细讨论了逆变器实现ZVRT的各项关键技术,包括电网电压正负序分离及锁相、逆变器有功和无功电流控制、电网电压不平衡时系统控制等。在此基础上,进一步提出向系统电流环引入电网电压前馈分量相位超前补偿环节,以改善逆变器故障穿越瞬间并网电流过冲现象。最后,利用RTDS和一台500 k W样机的实验结果验证了所述光伏并网逆变器ZVRT控制策略的正确性和有效性。

According to the national standard, the high power photovoltaic gird-connected inverter should have the zero voltage ride through （ZVRT） ability of avoiding automatic off-grid phenomenon under the condition of low voltage, which will affect the stable operation of power system. Based on an analysis of the standard about ZVRT of photovoltaic grid-connected inverter, some key technologies including the separation of positive from negative sequence of grid voltage, phase-lock loop （PLL）, the control strategy of active/reactive current, the control strategy of inverter under the condition of unbalanced grid voltage, etc are discussed. In addition, the leading phase compensation for the feed-forward component of grid voltage is proposed and introduced into the current loop of control system to limit the current overshoot during the transients of ZVRT. The effectiveness of the proposed ZVRT control strategy is verified by simulation on RTDS and experimental results of a 500 kW prototype.