A Buck-Boost AC-AC Converter Topology Eliminating Commutation Problem with Multiple Mode of Operations

AC - AC power conversions were traditionally done by using thyristor power controllers, phase angle control or by integral cycle control, but had low PF and other disadvantages. Variable voltage, variable frequency high power conversions are nowadays use DC link and Matrix converters, with higher efficiency and better regulation. But in situations where only voltage regulation is required and the circuit need to be simple and less complicated, directed PWM AC-AC converters are more preferred, due to reduced size and components. This project presents the design and simulation of 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. This 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.