Modelling and Optimal Design of a Multifunctional Single-Stage Buck-Boost Differential Inverter

In this paper, a single-stage buck-boost differential inverter is optimally designed for applications with varying input DC voltage (e.g., photovoltaics and fuel cell systems). The designed inverter has multiple functionalities, including power decoupling and AC output filtering, and it can operate with a wide DC voltage range without adding extra power conversion stages or filters. Hence, it is naturally compact and highly efficient. To fully exploit its benefits, the proposed inverter operating principle and mathematical model were first developed to form the foundation of an optimal design. The criteria for selecting the inverter's key components have been presented. This ensures that the developed inverter meets the aforementioned functional requirements without being overly sized. A digital design procedure based on artificial neural networks is followed for further multiple objective optimization, targeting high efficiency, high power density and low cost. A 1.8kW prototype of the inverter was fabricated through the digital design. The inverter's operating functionality with varying DC voltage, power decoupling, and filtering was demonstrated by both simulation studies and experimental tests on the prototype. The accuracy of the optimal design was also validated.