This study proposes a rotor position estimating method by detecting the stator currents under each pulse-width modulation switching state for an interior permanent magnet synchronous motor drive system. The proposed sensorless motor drive system can be applied in an air conditioner without injecting any high-frequency sinusoidal or cosine voltage signal. The operating speed range can be effectively extended because the maximum available voltage is increased when compared to the high-frequency sinusoidal or cosine voltage injection method. The detailed analysis is discussed here. A digital signal processor, TMS-320-F-2812, is used to execute the rotor position estimator and controller. Several experimental results are included to evaluate the theoretical analysis. The experimental results show that the proposed sensorless method can provide satisfactory performance for a closed-loop interior permanent magnet synchronous motor drive system applied in an air conditioner.

This study proposes implementation of a predictive controller for a sensorless synchronous reluctance drive system. First, high-frequency voltage is injected in the α-axis. Then by measuring the α-β axis high-frequency currents, the rotor position of the SynRM can be estimated. After that, a predictive speed controller is implemented to improve transient responses, load disturbance responses, and tracking responses. To demonstrate its viability, a proposed 560 W sensorless drive system is implemented by using a TMS-320F-28335 DSP made by Texas Instruments and some circuits. Experimental results clearly indicate that the proposed high-frequency α-axis voltage injection method with a predictive speed-loop controller offers superior responses including faster transient responses, better load disturbance responses, and better tracking responses than a high-frequency d-q axis voltage injection method with a PI speed-loop controller.

This study proposes a new control method for a dual-motor drive system to share its output torque and extend its operating speed range. When the drive system is operated below the rated speed, the dual motors are operated in parallel to share the total output torque. By using the proposed parallel dual-motor, the efficiency of the whole drive system can be effectively increased. On the other hand, when the drive system is operated beyond the rated speed, one motor is operated at a standstill and its stator inductances are used as three-phase boost inductances. In addition, an interleave control algorithm is used for the boost converter to reduce the input current ripples. The other motor is used as a driving motor fed by the boost converter. As a result, an extended speed, reaching twice the rated speed range with a near constant torque, is obtained. Several experimental results are included to evaluate the theoretical analysis. This study proposes a new control method for the dual-motor drive system, which can be applied to the electric drive systems in the industrial applications.

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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