Closed loop scalar control of induction machine

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Dr. Stumpf Péter Pál
Department of Automation and Applied Informatics

Induction motors are the workhorse of the industry. These machines consume over 50% of the industrial electric energy. In order to use these motors effectively, we need to apply proper controller. The aim of my final project is to implement a scalar speed control for an asynchronous motor. However, the vector controlled-drives has much better dynamic behaviours, the scalar speed control is also popular due to its simplicity. The essence of the scalar speed control is that controlling the frequency and the amplitude of the stator voltage, we are able to adjust the speed of the motor. In order to produce constant stator flux, the ratio of the frequency and the amplitude of the stator voltage is kept constant.

In my final project, I describe the measurement and the calculation of the motor parameters. After the motor parameters are known, different motor models are implemented into MATLAB Simulink. During the simulations the behaviour of the dq- and Kloss-model is examined. The built-in MATLAB model is a more detailed motor model, but the advantage of the Kloss model’s simplicity that it requires less computation, which leads to less computation time.

PI controller is used to realize the closed loop scalar speed control. In order to get proper results, the parameters of the model need to be determined carefully. Furthermore, the switching operation of the three-phase inverter is also taken into consideration.

Last but not least, measurements has been carried out in the laboratory. For the test, prototype PCB has been produced, which contains the input and output ports of the microcontroller and an amplifier circuit.


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