A Novel Buck–Boost AC–AC Converter With Both Inverting and Noninverting Operations and Without Commutation Problem (original) (raw)

This paper proposes a new type of ac-ac converter which can operate as traditional non-inverting buck and boost converters, and inverting buck-boost converter as well. The proposed converter uses six unidirectional current flowing and bidirectional voltage blocking switches, implemented by six reverse blocking IGBTs or series MOSFET-diode pairs, two input and output filter capacitors, and one inductor. It has no shoot-through problem of voltage source (or capacitor) even when all switches are turned-on and therefore; PWM dead times are not needed resulting in high quality waveforms, and solves the commutation problem without using bulky and lossy RC snubbers or dedicated soft-commutation strategies. It has smaller switching losses because; only two switches out of six are switched at high frequency during each half cycle of input voltage, and it can use power MOSFETs as body diode never conducts, making it immune from MOSFET failure risk which otherwise may occur due to poor reverse recovery problem of body diode. The non-inverting buck-boost mode of proposed converter can be used in applications with both step-up and step-down demand, while the inverting buck-boost mode can also be used in its application as DVR. Detailed analysis of the proposed converter is given, and experimental results are also provided.