Study On Some Issues For Vector Control Technology Of Induction Motor

Vector control is an advanced theory, which is based on motor unification principle, energy conversion and vector coordinate transformation theory. It has many advantages such as novelty, practicability and practicality. Stator current can be decomposed into two components that one is named excitation current component and the other is named torque current component under synchronous circular coordinate system based on rotor field orientation. Then the magnetic field and torque can be separately controlled by controlling the two current components like separately excited DC motor.First, this paper introduces the correlative information of variable frequeney speed regulating, describes the theory of vector control principle in detail, analyzes and elaborates the mathematieal model establishlnent of the asynehronous motor, and through Matlab/simulink modeling and simulation for vector control system.Second, this paper describes the fundamental principles the voltage space vector pulse width modulation (SVPWM), the inverters based on SVPWM technique have many good qualitics, such as less pulsating torque, higher use of DC bus voltage, less switching loss. So it is applicable for the high-performance motor control system. This research from the reduction of switching frequency and voltage modulation in these two areas applies a number of improvement strategies, to make a better system performance. In the problem of reduction of switching frequency, we analyze form the zero-vector insertion and five-segment type SVPWM and seven-segment type SVPWM, the experimental waveforms indicate the feasibility of the methods. In the problem of voltage over-modulation, use dual-mode and single mode, and in different mode gives the simulation results and analysis. Then apply space vector pulse width modulation to vector control, establish vector control system based on SVPWM, and through Matlab/simulink modeling and simulation for vector control based on SVPWM, the simulation results are obtained. Comparing simulation results, illustrate the superiority of the latter.Finally, based on the theory described earlier, use digital signal processor as microprocessors to build a vector control system. The SVPWM vector control experiment is conducted on experiment platform, which realizes the AC variable speed and validates the effectiveness and the feasibility of the proposed technique. In the end, we sum up the insufficiency of the whole system and predict the direction of vector control as well.