Current source inverter-based photovoltaic system with enhanced active filtering functionalities

This study proposes a three-phase photovoltaic (PV) inverter, with active power filtering capability that allows for maximum power point tracking (MPPT) and a nearly unitary power factor (PF) in the connection to the low voltage grid. A single-stage current source inverter, with an inductive DC link, connects the PV array to the three-phase grid for reduced cost and improved performances, and the MPPT algorithm controls directly the power of the PV array. On the basis of the power balance of the whole system, the grid current references are generated in a grid-synchronised dq frame allowing for the mitigation of low-frequency current harmonics introduced by a non-linear load connected at the point of common coupling, without the need for additional measurements. Active damping is used to minimise filter losses and reduce the high-frequency harmonics that result from the semiconductors switching. Simulation and experimental results are presented in unloaded and loaded situations, and with varying irradiance, to confirm the active filtering, PF regulation and MPPT operate correctly.