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Hybrid Sensorless Control 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 full speed range has recently been demonstrated. However, at high-speed, current waveforms become distorted due to extension of the zero voltage vectors. This paper presents a hybrid position and speed estimation technique which uses current derivatives at the first active-voltage vector during each PWM switching period (the Modified Fundamental PWM Excitation – FPE-method) for enhancing the performance of a Sliding Mode Observer at low and very low speeds. This paper presents the theory and experimental evaluation of the proposed sensorless method for IPMSM over wide speed range from zero to rated speed. The experimental results have shown a significant improvement of speed and position estimation accuracy at low speeds and a significant enhancement of the current waveform over the full speed range, compared to conventional FPE methods, which utilizes current derivatives at two active-voltage vectors and two zero-voltage vectors during each PWM cycle for sensorless control.