A buck-boost converter based multi-input DC-DC/AC converter
The buck-boost inverter can be easily used to construct a multi-input converter due to its inherent symmetrical and extendable differential structure. This paper proposed a multi-input converter derived from the buck-boost inverter to interface different input sources. When two pure DC voltages are chosen as the references for the two output capacitor voltages, the proposed converter will operate in DC-DC mode. When two dc-biased sinusoidal voltages with 180° phase shift are chosen as the references, the proposed converter will operate in DC-AC mode. Compared to the boost inverter based multi-input converters, an advantage is that the output voltages of the capacitors are not limited to be larger than the input voltages. A control strategy based on the average model of the circuit is proposed for the proposed converter. Single current control loops are designed for the buck-boost converters that used for interfacing the input sources and controlling the input power. Voltage-current double control loops are designed for the buck-boost converters that used for forming the buck-boost inverter and interfacing the energy storage system. The proposed control strategy can deal well with the varying operating points and the disturbances of the input voltage and load conditions. Simulation results are worked out to verify the effectiveness and validity of the proposed converter and its control strategy.