Low-Voltage Ride-Through Capability of Cascaded H-Bridge Multilevel Converters for Large-Scale Photovoltaic Power Plants

Abstract

Multilevel cascade H-bridge (CHB) converters are increasingly applied for large-scale grid-connected photovoltaic power plants (GCPVPPs) because of their improved quality of output voltage waveforms, high efficiency due to the elimination of the line frequency transformer and modular structure. On the other hand, due to the high penetration of the installed distributed generation units in the power system, low-voltage ride-through (LVRT) capability and injection of reactive power during voltage sags are becoming necessary for large-scale GCPVPPs. This paper studies the LVRT capability of the grid-connected CHB inverter of a GCPVPP during various voltage sag conditions. Active/reactive power injection to the grid is also considered according to grid codes. The performance of the grid-connected seven-level CHB with LVRT capability is investigated on a 10-MVA GCPVPP, connected to the 6.6 kV medium-voltage grid simulation model during various voltage sag conditions.