Volume and efficiency optimization of an industrial flying capacitor GaN multilevel inverter

Abstract:
Three phase grid connected inverters are widely used in industrial applications. These inverters often suffer from bulky passive components as current inductors or filter components. A possible approach to reduce these passive components is the use of a multilevel topology. It benefits of a more sinusoidal output voltage and requires only small filter components. The flying capacitor multilevel topology is seen as a promising topology due to a small required capacitance and an increased output switching frequency up to several megahertz. The aim of this paper is to find an optimal flying capacitor design for a standard three phase inverter (40 ARMS, 400 VAC, 24 kw). For this purpose, the minimal design constrains for a flying capacitor industrial GaN multilevel inverter are investigated. This includes the flying capacitors, the power inductors, the EMI filter and the loss calculation. Based on these formulas a Monte Carlo optimization is used to highlight the pareto front. An appropriate design on the pareto front obtains an efficiency of nearly 99.4 % and a theoretical volume of four liters. In comparison to comprehensive actual standard industrial two-level inverters this is a volume reduction of factor ten.