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Square-Wave Voltage Injection Based PMSM Sensorless Control Considering Time Delay at Low Switching Frequency

This article proposes a global delay compensation method to improve the sensorless control performance of square-wave voltage injection (SWVI) over low switching frequency applications. The cost function with delay information is preliminarily constructed by simple calculation of high-frequency (HF) αβ-axes current and estimated position; second, the cost function is minimized by the gradient descent method, so as to estimate the delay time and corresponding compensation angle. The compensation angle that estimated delay time multiplies rotor speed is used for reducing the lag angle in the estimated position, thus improves the current control performance. At the same time, the inverse of the cosine signal is proposed to substitute the conventional differential current demodulation of SWVI. In addition, the compensation angle is used to offset the phase shift in the cosine signal, thus suppressing the amplitude error of HF response current caused by time delay. Hence, the SWVI method with the proposed delay compensation has good position estimation performance. Finally, a 1.5 kW interior permanent magnet synchronous motor test bench is adopted to demonstrate the effectiveness of the proposed method