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

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.