Online phase current and voltage offset calibration using inverter voltage distortion

Precise current and voltage sensing is crucial for accurate control of power electronic systems. Due to parasitic effects such as the temperature dependency of analog circuit components, the measured currents and voltages are subject to sensor offset drift. This can cause significant degradation of the control performance and even instability for example in speed-transducer-less drive systems. It is of major importance that sensor offsets are considered in the control algorithm to avoid offset integration. Additionally, they are often re-calibrated during system start. Existing online calibration methods usually use an error feedback in the control algorithm which is often influenced by other parameter errors. In this paper, a new online sensor offset calibration method is proposed, that is completely decoupled from the control algorithm. Current and voltage sensors are calibrated for each phase independently by detection of the current dependent voltage distortion caused by the dead time and the semiconductor voltage drop. The paper includes a detailed description of the algorithm and experimental verification.