Reactive power support with feedforward control for low voltage ride through operation in grid-connected photovoltaic inverters

Fluctuation of the grid voltage often has adverse effects on the grid-connected photovoltaic (PV) system, e.g., a grid fault that causes a significant drop in grid voltage can even take the PV system off the grid, severely threatening grid safety operation.To address this problem, this paper proposes a control strategy for grid-connected PV inverters with low voltage ride through (LVRT) capability.Grid voltage feed-forward control is introduced in the current inner loop to suppress the effects of small voltage fluctuations.When the grid voltage drops, the grid voltage feed-forward control can calculate a new reactive current reference value based on the drop depth and deliver reactive power to the grid through the grid-connected PV inverter to support grid voltage recovery.Moreover, this strategy limits the inverter overcurrent and thus prevents the PV system from operating off grid.The effectiveness of the proposed method is compared with the current-limiting method.The results show that the proposed strategy in this paper has better LVRT capability and supports the voltage recovery to 90% of the rated voltage within 1 s, which fully demonstrates its feasibility.