| Summary: | 碩士 === 國立成功大學 === 工程科學系碩博士班 === 93 === The traditional indirect field-oriented control (FOC) needs nonlinear coordinate transformation and that will increase the computation time. To improve the above drawback, the decoupled direct control (DDC) for the induction motor drive is developed in this thesis. The decoupled direct control is based on a decoupled matrix, which is used to directly control torque and rotor flux to generate voltage command and make the estimated torque and rotor flux track to their command quickly. The method has some advantages: 1) Because of directly controlling the rotor flux and torque without coordinate transformation, the computational time can be decreased largely. 2) There is not any controller in current loop so the transient response of the torque and rotor flux can be improved.
Next, using the space voltage vector theorem to develop a digitalized pulse width modulation (PWM) algorithm for voltage source inverter. The frequency control unit uses the principle of non-zero-voltage vectors to control the output voltage frequency of the voltage-source inverter and the voltage control unit uses the principle of zero-voltage vectors to control the output voltage magnitude of the voltage-source inverter. To reduce torque pulsation and switching loss, the algorithm proposes an adaptable table so that the low stator currents harmonic can be obtained by adjusting content of the adaptable table. Combining decoupled direct control scheme and digitalized PWM algorithm, a high-performance induction motor drive can be achieved.
The proposed control scheme is implemented by using a 32-bit TMS320F2812 digital signal processor and motor driver circuit. Simulation and experiment results demonstrate the proposed control scheme is superior to the traditional FOC scheme and has good performance.
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