Three-phase buck-boost Y-inverter with wide DC input voltage range

Abstract

Driven by the needs of the continuously growing fuel-cell industry, a promising three-phase inverter topology, the Y-inverter, is proposed, which comprises three identical buck-boost DC/DC converter modules connected to a common star point. Each module constitutes a phase-leg and can be operated in similar fashion to conventional DC/DC converters, independent of the remaining two phases. Therefore, a straightforward and simple operation is possible. In addition, the Y-inverter allows for continuous output AC voltage waveforms, eliminating the need of additional AC-side filtering. Due to the buck-boost nature of each phase leg, the AC voltages can be higher or lower than the DC input voltage. This is an essential feature for fuel-cell applications, which suffer from a wide DC input voltage range. This paper details the operating principle of the Y-inverter, outlines the control system design and verifies its functionality by means of simulation results. The Y-inverter performance in terms of efficiency η and power density ρ is briefly analyzed by means of a multi-objective optimization and a converter design is selected which is compared to a benchmark system realized with a conventional inverter solution.