Fuzzy logic controlled power balancing for low voltage ride-through capability enhancement of large-scale grid-connected PV plants

摘要

This paper proposes an advanced control methodology to enhance the low-voltage ride-through (LVRT) capability of a large-scale two-stage grid-connected photovoltaic (PV) plants. The inverter of the three-phase grid-connected PV system should insert the reactive power according to the LVRT regulations without exceeding the maximum current rating during the grid fault. Both active and reactive power control schemes are incorporated according to the recent grid code. Since a PV system is nonlinear in nature, a fuzzy logic controller (FLC) has been implemented for the active power insertion considering the severity of grid voltage dip. The effectiveness of the proposed methodology in improving the LVRT of the grid-connected PV system is verified by applying both balanced and unbalanced faults in the network. The proposed method is able to protect the DC-link overvoltage, and is capable of suppressing the transient overcurrent and inserting the reactive current. Also, the proposed method is better than the conventional control strategy during the event of grid fault without incurring the extra device.