Grid-connected three-input PV/FC/Battery power system with active power filter capability

This paper develops a grid connected hybrid PV/FC/Battery power system proposed by authors. This system integrates photovoltaic (PV) array, fuel cell (FC) stack and battery as input power sources in a unified structure by means of a new three-input DC-DC boost converter which supplies a grid-connected inverter. In this structure, each switching cycle of the proposed boost converter is divided into five switching periods in comparison with the conventional structure. These switching periods introduce five different duty ratios for the proposed boost converter. Because the summation of these duty ratios should be equaled to one in the prior paper, achieving a high level output voltage at the DC-link is not possible. Therefore, this paper tries to presents some modifications in order to cancel this limitation of the duty ratios and control them independently. Consequently, a high level output voltage is achieved in addition to tracking the maximum power of the PV source, setting the power of FC source, and charging or discharging the battery. Utilizing a unified structure and improving the control strategy of the proposed three-input DC-DC converter facilitate power management of the input sources in order to supply a grid-connected residential load. All the system possible power operation modes are defined and managed by the power management control scheme. The proposed system is also able to compensate both reactive and harmonic current components drawn by nonlinear loads as active filter functionality.