LVRT Operation Enhancement of Single-Stage Photovoltaic Power Plants: An Analytical Approach

The impact of grid-connected PV power plants (GCPPP) operation on the grid entails mandatory provision and conformable execution of futuristic grid-codes (GC) by GCPPP stakeholders. While standard GC-compliant reactive power injection occurs in the advent of voltage drops at the point of common coupling (PCC), weather-dependent active power delivery should also coincide. Hence, it is essential to derive the PV inverter current reference set-points meticulously and confine its current range. This paper proposes a novel control strategy for realization of enhanced LVRT operation in three-phase single-stage GCPPPs. The control scheme encompasses the following features: (a) PCC negative-sequence current reference set-points determination from its positive-sequence counterpart; as well as the analytical determination of PCC voltage sequence components, (b) GC-compliant reactive power injection, without causing second-order harmonic oscillations in the delivered active power to the grid during asymmetrical PCC faults, (c) utilization of a current limiter for immaculate regulation of the PV array output power. Simulation results reflect on the developed control scheme's effectiveness in significantly improving GCPPP LVRT operation for a wide range of operating conditions.