Slip Frequency Controlled Type of Sensorless Vector Control of Induction Motor Using Flux Observer

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The speed sensorless vector control has attracted the attention because of high performance speed control of an induction motor comparing with the constant V/f control. In this research, new flux observer based sensorless vector control systems are proposed and implemented by using DSP controlled IGBT inverter. In order to realize excellent steady-state and transient performances for various operating conditions, the design of controller is studied and an accurate voltage control of PWM inverter is developed.Principal results obtained by this work are as follows ;1. Experimental system : The digital signal processor (TMS320C30) is used for the implementation of the control system. Two kinds of softwares have been developed. One is an observer based sensorless vector control program written in the DSP assembly language and the other is a monitoring program written in C language. By compensating the voltage drop and dead time of IGBT,an accurate voltage control of PWM inverter was developed.2. Computed and experimental results : The experimental results of proposed method show good agreement with the computed ones concerning with the steady state and transient condition. Therefore, the system design which is based on the proposed analytical model is attained.3. Stability improvement : We proposed a sensorless method in which the leakage inductance was omitted in the voltage computation. As the result, our method is more stable than the conventional one.4. Parameter identification : By adding an altanative component in the magnetizing current, both the stator resistance and the rotor one were identified. By using this method, the robustness will be improved satisfactory.5. Another sensorless vector control : A sensorless vector control using q-axis flux with stator resistance identification was proposed and tested experimentally. And a sensorless vector control using a reactive power was proposed too. In this method, the stator resistance is not necessary.