Design and Performance Evaluation of a Three Phase AC Power Source with Virtual Impedance for Validation of Grid Connected Components

The paper reports design and performance evaluation of a three-phase AC power source which is mainly used for the development, validation and testing of grid connected converter system and components. The main objective of the designed AC power source is the controllability of the output (grid) voltage amplitude and frequency, harmonic components as well as of the grid impedance characteristic. The small signal bandwidth of the proposed system is specified up to 2 kHz. To fulfill this requirement at very low output noise voltage levels, the target switching frequency has to be in the region of 200 kHz. For achieving acceptable efficiency 1200V silicon carbide (SiC) MOSFETs are used. The paper presents a comparison of estimated and measured semiconductor losses for discrete as well as module packaging and discusses the implementation of the gate driver stage, of the DC link and of the EMI output filter.