Study On Direct Torque Control Of PMSM Used For Electric Vehicle

Because of its advantages of zero-emission and high efficiency, electric vehicles are considered to be a important direction to ease the energy shortage and improve environmental pollution by all developed countries, while the motor and drive are one of the key technologies of electric vehicles. Abandon the thinking of decoupling in vector control, direct torque control implement stator flux orientation, which avoid complex vector control coordinate transformation. The estimating of stator flux relates only to the stator resistance, reduced dependence on motor parameters. Besides permanent magnet synchronous motor with its advantage of high power density,high efficiency, small size, low inertia, fast response and wide speed range, etc, it has important theoretical and practical value to study permanent magnet synchronous motor of Direct Torque Control drive technology for the development of electric vehicles.However, there is a big flux and torque ripple in the conventional direct torque control.To solve this problem, based on the analysis of basic principle of direct torque control (DTC), the thesis build a DTC model of permanent magnet synchronous motor in Matlab/Simulink environment and compare the controlled table which was added in zero vector and without zero vector in DTC. The simulation results show that adding zero vector in DTC can make ripple torque reduced and switching frequency of power electronics switch reduced.There is a disadvantage of the switching frequency which is not fixed in the model permanent magnet synchronous motor DTC, so this thesis establishe a permanent magnet motor of space vector PWM (SVPWM) control model and compare the simulation results of DTC and SVPWM models. This thesis combine the method of DTC and SVPWM, which not only can fix switching frequency of power electronics,but also can reduce the ripple torque.