Ultra-high Efficiency Solar Inverter in Compact Size Enabled by SiC MOSFET

The global penetration of solar power is increasing rapidly. SiC MOSFET, a breakthrough technology in power electronics, enables the introduction of compact and ultra-high efficiency solar inverters into the increasingly competitive renewable market.

Article | Spring 2021

Due to the significant growth of solar power driven by environmental concerns, the penetration of solar inverter for grid connection of solar plant is increasing accordingly. The main objective of the solar inverter is to provide a stable power flow between the solar panel and the grid while maximizing the power generation. In a utility-scale solar plant, a considerable amount of additional power can be generated by improving the efficiency of the installed solar inverters. As the market expands rapidly, increasingly high performance is demanded of solar inverters. Therefore, the trend of solar inverters is moving towards higher efficiency with higher power density requirements, and the competition is continuously increasing.

Semiconductor switching devices are the key technology to determine the performance of the solar inverter, and Si IGBT has been a major driving force so far. In order to push the performance boundaries of state-of-the-art technology, the recent advance of SiC MOSFET technology is being applied to solar inverters. Compared to Si IGBT, SiC MOSFET features lower switching losses, lower conduction losses, and operability at higher temperature. With higher switching frequency operation enabled by SiC device technology, the higher power can be processed within the given size of the solar inverter by reducing filter requirements while improving the system efficiency.

Professor Ki-Bum Park from The Cho Chun Shik Graduate School of Green Transportation at KAIST has been working on a compact and ultrahigh efficiency solar inverter enabled by SiC MOSFET. To maximize the benefit from SiC MOSFET, a system-level multi-objective hardware optimization methodology for solar inverters has been developed. It is based on multi-domain modeling considering the coupling between the core technologies such as circuit topology, semiconductor, cooling, magnetics, and filters. The developed optimization procedure explores the performance limitation of the existing solutions and provides us with optimal combination of core technologies in terms of efficiency and power density. In addition, it guides the research of the core technology in the right direction, which enables the solar inverter with 99% efficiency in compact size.