Control Scheme for Wide-Bandgap Motor Inverters with an Observer-Based Active Damped Sine Wave Filter

Abstract:
This paper presents an effective method for the active damping of a two-stage sine wave LC output filter for wide-bandgap motor inverters avoiding any sensing of filter voltages/currents. The method is based on a linear observer model, which is used for estimating the filter capacitor currents required for implementing the active damping. The motor currents are controlled using a conventional PI-type controller with additional feedback based on the estimated filter capacitor currents. Using the proposed method, the inverter‘s standard output current sensing can be used also in case of active filter damping avoiding any additional measurement channels and dissipative losses, which appear in case of passive filter damping. The paper reports the operating principle and analyzes the stability region and robustness of the total system by simulations. Finally, the proposed scheme is tested by implementation of a laboratory inverter prototype based on GaNMOSFETs at a switching frequency of 100 kHz.