Research Of Vector Control System And Optimal Efficiency

By measuring the stator current vector and using coordinate transformation theory to convert three-phase AC current into the DC component in rotating coordinate system, then according to the principle of field oriented theory, the vector control theory control the two current components respectively to achieve the purposes of the induction motor speed control. Actually, the vector control decouples the flux and torque components, and designs regulator for both independently. So the properties are similar with the DC motor speed control. Vector control system can regulate the velocity in a wide range and has a good dynamic performance. In the thesis, a vector control inverter based on DSP and the efficiency optimization of vector control were studied.Firstly, the establishment of the model of induction motor and the fundamental principles of vector control were introduced. A simulation model of the vector control system was established in Matlab/Simulink to verify the correctness and stability of the system. In the aspect of hardware, using DSP as the controller and IPM as the inverter, a velocity modulation system was designed. The structure of the system, power circuit, current detection circuit, the voltage detection circuit, power supply module and the protection circuit were briefly introduced. On the software side, velocity modulation system was programmed with C language. The main program and main sub-module were briefly introduced such as PI regulator module, SVPWM module, the current, speed and flux detection module.Secondly, the development and research of the motor's loss optimal control was presented. Considered that the efficiency of vector controlled induction motor is low when operation at light load, a mathematical model of the asynchronous motor including the iron losses was deduced and on the basis of the model a vector control system was established in Matlab/Simulink. Then the loss mode control and the search control were compared via a lot of simulation base on the vector control system we established. Finally, based on much previous experience, a hybrid control strategy based on the fuzzy search combined with loss model was proposed. At the steady-state light-load condition, the initial value of the optimal flux was obtained by the loss model of motor, and a fuzzy search in a certain range around the initial flux value was applied to determine the practical optimal flux. The simulation results show that the proposed control strategy was effective.Finally, the directions to be improved were pointed out.