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This study proposes a high-performance sensorless interior permanent-magnet synchronous motor control system using a high-frequency injection technique. A new estimation method that uses both the high-frequency d-axis current and q-axis current to estimate the rotor position is investigated. By using the proposed method, the hypothesis-synchronisation signal used in the conventional high-frequency injection method can be eliminated. A 1.25 kHz, 15 V, sinusoidal waveform voltage is injected into the d-axis synchronous frame of the motor and then the high-frequency d-axis and q-axis currents can be measured to determine the rotor position of the motor. In addition, a new compensation method is developed to reduce the estimation position error because of the mutual inductance and saturation effect of the motor. By using this new method, the estimated rotor-position error is within +2 electrical degrees. A digital signal processor, TMS-320-F2812, is used as the estimating and control centre. The experimental results show that the proposed method can be applied in both a sensorless speed control system and a sensorless position control system. The sensorless speed control system has fast response, good load disturbance response and good tracking response.

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