A Coupled-Inductor Based Common-Ground Buck-Boost Inverter With Three-Level Input and Output

This research proposes a new coupled-inductor-based buck-boost inverter with phase-shifted pulse-width modulation (PWM). The proposed inverter consists of three dual-buck phase legs with coupled-inductors, a small energy-storing and snubber capacitor, and input/output LC filters. It provides three-level input and output voltages (across LC filters) for each half-cycle, increasing the voltage levels of the input and output inductors with smaller voltage steps. Moreover, phase-shifted PWM is employed to exploit the PWM dead- and overlap-times, effectively doubling the frequency across the input/output filters compared to the actual switching frequency. As a result, input and output filtering requirements are significantly reduced with smaller current ripples in both the input DC source and the output load. The key features of the proposed topology include continuous input and output currents with low ripple, a common-ground point between the input and output, a constant common-mode voltage, and reactive power support. Since the MOSFET body diodes are not utilized in the proposed inverter, the adverse effects of poor reverse recovery are avoided. The detailed comparative evaluations verify the reduction of input/output ripples and inductor requirement in the proposed inverter. Finally, experimental results from a 400 W, 110Vrmslaboratory prototype are presented for a DC input voltage range of 100–200 V.