Grid-Connected Photovoltaic Power Plant without Phase Angle Synchronization Able to Address Fault Ride-Through Capability

This paper discusses the control of large-scale grid-connected photovoltaic power plants (GCPPPs) operating under unbalanced grid voltage sags. The positive and negative sequences of the output currents are controlled to achieve different targets: injecting constant power (i) to the grid, or (ii) to the ac side of the converter, i.e., including the filter and the grid. Traditionally, synchronization with the grid voltages is required, which is usually performed by a phase-locked-loop (PLL) technique. In this paper, the proposed control technique does not require any grid voltage synchronization. An arbitrary angle is used instead with the only requirement of having a frequency equal or close to the grid frequency. The fault-ride-through capability of the GCPPP during unbalanced voltage sags is addressed by proposing a current limiter. Simulation and experimental results verify the performance of the proposed GCPPP.