Single-Stage Three-Phase Buck-Boost DC/AC Converter Design, Analysis, and Validation

Three-phase DC/AC power converters enable several applications including photovoltaic systems, electric traction inverters, uninterruptible power supplies, and utility systems. The classical three-phase voltage source inverter (VSI) topology only operates in voltage step-down or buck mode of operation. Increasing number of applications including transformer-less photovoltaic systems, battery cells, fuel cells, and traction motors require a wide range of input and output voltage range. Therefore, a DC/AC power converter topology capable of voltage buck and boost operation will enable wider operating range resulting in efficient and higher performance system designs. This thesis presents a single-stage bidirectional power flow DC/AC inverter topology capable of buck and boost mode of operation with a minimum switch count and a carrier-based sine-pulse-width modulation approach. Furthermore, due to the presence of intermediate but small reactive elements sized to filter switching frequency, the output voltages and currents are non-switched non-pulsating waveforms thus improving output harmonic performance and reducing over-voltages due to long motor cables. The proposed topology is examined through analytical, simulated, and experimental results.