A grid-connected photovoltaic system with direct coupled power quality control

This paper presents a grid-connected photovoltaic (PV) system with direct coupled power quality controller (PQC), which uses an inner current control loop (polarized ramp time (PRT)) and outer feedback control loops to improve grid power quality and maximum power point tracking (MPPT) of PV arrays. To reduce the complexity, cost and number of power conversions, which results in higher efficiency, a single stage CCVSI is used. The system operation has been divided into two modes (sunny and night). In night mode, the current controlled inverter (CCVSI) operates to compensate the reactive power demanded by nonlinear or variation in loads. In sunny mode, the proposed system performs PQC to reduce harmonic current and improve power factor as well as MPPT to supply active power from the PV arrays simultaneously. It is shown that the proposed system improves the system utilization factor (SUF) to 100%, which is generally low for PV systems (20%). Mathematical modelling, computer simulations and experimental results for a 1kVA CCVSI are presented.