Active voltage ripple compensation in PV Systems for domestic uses

Photo Voltaic (PV) generators today find application in the domestic field, where the decentralized power conversion concept has proven to be more advantageous than the conventional string architecture. According to the decentralized power conversion concept, PV modules are connected to a single phase AC grid through a two stage converter composed of a DC/DC converter and an inverter. The DC/DC converter accomplishes the Maximum Power Point Tracking (MPPT) and boosts the voltage. It must also include a suitable capacitor bank to solve the unbalance between the DC power generated by the modules and the AC power drawn by the grid. Such a power unbalance in fact generates a voltage ripple that negatively affects the MPPT, forcing the system to work only around its optimal operating point. On the other hand, electrolytic capacitors are highly disliked in PV systems for reliability reasons. Therefore, active current ripple reduction techniques have been proposed in the past, exploiting active filters that increase the complexity and the cost of the system. An alternative approach is proposed in this paper where an active filter is integrated into a Double Interleaved Boost Converter, without introducing extra power devices. According to the proposed approach the size of the electrolytic capacitor bank can be largely reduced, thus improving the reliability and the efficiency of PV systems.