Sensorless PMSM Drive with DC-link Current Measurement

The paper proposes a motion-sensorless control method for permanent magnet synchronous motor drives when only the DC-link current is measured instead of the motor phase currents. A two-phase pulse-width modulation method is used, allowing the DC-link current to be sampled twice in a switching period at uniform intervals during active voltage vectors. A method is proposed for obtaining the current feedback for vector control, and an adaptive observer is used for estimating the rotor speed and position. The estimation is augmented with a high- frequency signal injection method at low speeds; a modified high- frequency excitation voltage is proposed for better performance. The proposed method enables stable operation of the permanent magnet synchronous motor drive in a wide speed range and under various loads. The effectiveness of the proposed method is demonstrated both by simulations and laboratory experiments.