变功率跟踪轨迹的光伏并网低电压穿越策略

提出了一种新型的变功率跟踪轨迹的低电压穿越控制策略。通过电压跌落幅度的前馈控制对功率跟踪轨迹进行调节,实时改变光伏电池端电压,进而快速有效地控制光伏电池功率的输出,实现逆变器两侧功率的平衡;通过与并网逆变器的协同控制,保证逆变器并网输出电流在不越限的前提下,为电网提供尽可能多的有功功率和无功功率,最大限度地支持电网电压的恢复,实现了光伏并网系统的零电压穿越。通过在不同光照强度和温度条件下对多种场景的仿真模拟,验证了所提控制策略的有效性。与传统控制策略相比,采用该策略不需要添加额外的设备,不仅实现了系统的安全、稳定运行,而且降低了光伏发电系统的成本,更具实用性。

LVRT strategy of grid-connected photovoltaic system with variable power point tracking

A control strategy of LVRT(Low-Voltage Ride-Through) is presented for the two-stage three-phase PV(PhotoVoltaic) system with VPPT(Variable Power Point Tracking),which adopts the feed-forward control of voltage dip depth to regulate the power tracking trajectory for changing the voltage of PV cell to effectively control its power output for balancing the power between two sides of inverter, and applies the coordinated control with the grid-connecting inverter to supply as much active and reactive powers as possible to grid for fully supporting the grid voltage recovery to realize the ZVRT(Zero-Voltage Ride-Through) of grid-connected PV system without any limit violation of grid-connecting current. Multi-scenario simulation for different illumination intensities and site temperatures proves the effectiveness of the proposed strategy. Compared with traditional strategies, the practical strategy proposed, without any additional equipment, realizes the safe and stable system operation and reduces the system cost.