Feed-forward DC-bus control loop applied to a single-phase grid-connected PV system operating with PSO-based MPPT technique and active power-line conditioning

摘要

This study deals with a double-stage single-phase grid-connected photovoltaic (PV) system operating with an additional feed-forward control loop (FFCL). Owing to the PV array being constantly subjected to abrupt solar irradiance change, the DC-bus voltage varies and can interfere in adequate PV system operation. Therefore, an FFCL is proposed to improve the DC-bus voltage dynamic response, and reduce the settling time and overshoot. The FFCL acts on the generation of the inverter current reference, such that the dynamic behaviour of the current injected into the grid is also improved. Furthermore, the PV system performance is affected by problems associated with mismatching phenomena such as partial shading. This problem can be overcome using the maximum power point tracking (MPPT) technique based on particle swarm optimisation (PSO). The PSO-based MPPT is compared with the conventional perturb-and-observe MPPT technique, in order to highlight its effectiveness. In this study, the PV system also performs active power-line conditioning. Thereby, whereas the step-up DC-DC converter carries out the MPPT, the proper inverter current reference is computed to inject active power into the grid, as well as perform power-line conditioning. The performance and effectiveness of the PV system are evaluated through extensive experimental tests.