A bidirectional buck-cascaded buck-boost PV inverter with active power filtering

Recently, many high-efficiency buck-boost typed inverters for the photovoltaic (PV) grid-connection applications have been proposed. However, the PV grid-connection inverters are in idle state at nighttime or low insolation. Based on green energy demand, the presented work proposes a high-efficiency bidirectional buck-cascaded buck-boost (BuCBB) inverter. It is developed via the connection of a bidirectional BuCBB converter and an H-bridge unfolding circuit with line-commutated. At nighttime, the proposed inverter can function as an active power filter (APF) for compensating reactive power and suppressing current harmonic distortions. The proposed circuit can work functionally as either a step-down or step-up inverter, resulting in low dc-bus voltage. Electrolytic capacitors with lower voltage-rating can be adopted for improving system life-time and reducing costs. A laboratory prototype with 110 Vrms/60 Hz utility-line voltage is implemented accordingly to verify the feasibility of the proposed inverter.