Fault ride through enhancement of large-scale solar plants using distributed converters

Abstract

The grid-connected photovoltaic plants (GCPVPs) encounter various types of anomalies during fault occurrence in the main grid. During a fault occurrence on the grid side, the voltage of the point of common coupling (PCC) drops, causing the DC connection voltage to become too high for power balancing. This high DC voltage may damage the inverter and DC link equipment, which necessitates a reliable control scheme with low voltage passage requirements. These requirements, which obligate the GCPVP to remain connected to the main grid during abnormal conditions are generally known as low voltage ride-through (LVRT). Herein, a developed LVRT method in the control approach that injects maximum rated current during a sag is proposed to rectify the shortcomings in single and multi-inverter grid topologies. The proposed approach utilizes a current limiter combined with a DC braking chopper to guarantee the GCPVP's continuous participation in the power supply. Different scenarios including low and high power generations as well as two-phase and three-phase severe faults to the ground are considered. The results show that the proposed approach not only improves the performance in the single-inverter system but also remedies the defects aggravated in the case of a GCPVP with several inverters.