| Summary: | 碩士 === 國立交通大學 === 電控工程研究所 === 105 === The purpose of this thesis is to not only develop the digital controller in application to a three-phase PM synchronous motor dirver with small dc-link capacitor for high power factor but also analysis its performance. For the motor drive system fed by single-phase ac source, large DC-link capacitor is uesd to be adopted for voltage regulation between diode rectifier and 3-phase inverter. In this thesis, the capacitance is reduced to less than 1% of the capacitance in the conventional drives. The traditional electrolytic capacitor can be replaced by smaller film capacitor which has much higher reliability. Even though no switch or large reactor is installed in proposed adjustable-speed PMSM drive, superior power factor still can be achieved. However, since small DC-link capacitance leads to severe fluctuation of DC-link voltage, the control capability of motor deteriorates naturally. DC-link voltage compensation and voltage decoupling control are applied to improve the performance of current regulation. Thus, with less consideration of power factor, adjustable speed control can also be operated without large torque ripple under the condition of small dc-link capacitor. However, for higher power factor, the desired inverter power and corresponding power factor with different operating speed are derived with consideration of input voltage and capacitance. Then, input current is power factor corrected by modification of the motor current reference. Modified current may result in above 100% torque ripple. Therefore, centrifugal load with large inertia is the more appropriate application in the proposed system due to stronger capability to supress speed ripple. The control structure based on FOC consists of inner current loop and outer speed loop. Experiment verification The proposed digital control structure is implemented on STM32F3 micro-controller with floating-point unit and then verifies the results of experiment. The experimental performance of power factor, torque ripple and efficiency with different capacitance is evaluated and analyzed.
|
|---|
