A Hybrid Sensorless Controller of an Interior Permanent Magnet Synchronous Machine Using Current Derivative Measurements and a Sliding Mode Observer

The ability of current-derivative based speed and position estimation of IPMSMs over a full speed range has recently been demonstrated. However, at high-speeds, the modulation index becomes limited because the extension of the zero-voltage vectors and current waveforms become distorted. This article proposes a hybrid position and speed estimation technique which uses current derivatives at the first active-voltage vector during each pulsewidth modulation (PWM) switching period for enhancing the performance of a sliding mode observer at low and very low speeds. This article presents the theoretical analysis and experimental evaluation of the proposed sensorless method for an IPMSM over a full speed range from zero to rated speed. The experimental results have shown a significant improvement in speed and position estimation accuracy at low speeds and a considerable reduction of the current distortion over the full speed range, compared to the existing fundamental PWM excitation sensorless control methods.