| Recently, as the crisis of the fossil energy and the environment pollution getting worse, the Electric Vehicle(EV) as a kind of green transportation enters explosive development. The induction motor is widely used in the area of EV. However the Direct Torque Control(DTC) and the Rotor Filed Oriented Control(RFOC) are often applied in the control strategy of induction motor. Both of these two control strategies have shortcoming. DTC has a big torque ripple and variable switching frequency. RFOC needs decoupling and depends heavily on the motor parameter. For the disadvantage of these two control strategies, a novel control strategy of induction motor with stator flux orientation is given in this thesis, which comes from the analysis of the mathematical model of induction motor. Meanwhile, Quasi-Proportional-Resonant(QPR) is introduced into the control system, which overcomes the deficiency of the PI and could realize no static error adjustment tracking the AC signal in the stationary coordinate system. The main research contents of this thesis are listed as follows.(1) Induction motor is considered as the control target and studied form the space vector control theory perspective. The principle of the Voltage Source Inverter(VSI) controlled in Pulse Width Modulation(PWM) is analyzed. Several kinds of PWM control technology are described in the thesis, besides the properties of them are summarized.(2) The block diagram of the RFOC is given and its advantages and disadvantages are summarized. The DTC system under different sampling frequency were simulated and the property of DTC can be summarized from the simulation results. The Space Vector Pulse Width Modulation(SVPWM) is introduced and the vector switching time is derived. Besides, DTC based on SVPWM is described and a root-locus analysis method using for turning the flux and torque controller is given, which turns out to be true by simulating.(3) The property of the QPR controller is analyzed and the parameter choosing method of it is given. The Second Order Generalized Integrator(SOGI) is analyzed. Meanwhile, theoretical derivation of the Double Second Order Generalized Integrator Frequency Lock Loop(DSOGI_FLL) based on SOGI is given. It is been used in locking the synchronous frequency of induction motor. Otherwise, a novel flux observer based on DSOGI_FLL is deduced and it is be used in observing the stator flux. Based on all above analysis, a novel QPR control of Induction motor based on stator flux orientated is given in this thesis, which is simulated inMATLAB/Simulink.(4) The hardware of EV controller is designed and the DSP experiment program is written. The control strategy given in this thesis is applied in the experiment. The feasibility of the control strategy given in this thesis is verified by MATLAB/Simulink. Besides, the experiment results show that the motor under the strategy given in this thesis can maintain a fast dynamic response characteristics as well as a little torque ripple, but also a little harmonic in stator current. |
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