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Generally, there exist voltage differences between the voltage commands and the output voltages of the three-phase pulse-width modulated (PWM) voltage-source inverter (VSI), which are caused by the intended dead-time to prevent the armshort of a leg and the nonlinearities of switching devices. These voltage differences (or voltage distortion) affect the current distortion, torque pulsations, and degradation of control performances. To overcome these drawbacks, a simple and low-cost observation and compensation method of the voltage distortion is proposed. The proposed method is employing model reference adaptive system (MRAS) techniques and does not require any additional hardware circuits such as voltage sensors. The voltage distortions caused by the nonlinearities of the switching devices are estimated by a voltage distortion observer which is based on the electrical model of the PMSM. And the estimated voltage distortions are fed-forward to compensate the voltage commands. In comparison with the previous existing methods, the proposed method has a simple structure and good performances. Also, it can be implemented without any extra devices such as voltage sensors and the computing effort is very small. The execution of the algorithm can be easily embedded in the existing systems without major modification. To show the effectiveness of the proposed method, the experiments are carried out for the digitally controlled PMSM drive system. The experimental results verify the validity of the proposed method and show that the proposed method gives good performance and practical value.

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