Study On Improving Power Factor Of AC Motor Control System

The conventional rectifiers produce harmonic problem in power system,eliminating harmonic pollution and improving power factor are the quite important task in the field of power electronics. In Three-phase asynchronism motor AC/DC/AC control system, adopting conventional rectifiers as former AC/DC conversion device, harmonic problem of the input current is so severity that affects the improving of power factor. For the sake of eliminating harmonic pollution, improving power factor,and realizing high power factor, energy bidirectional flowing, stabile and regulable direct current voltage output ,this paper adopts three-phase voltage-style PWM rectifier as former AC/DC conversion device. Three-phase PWM voltage source rectifiers (VSR) can provide constant direct current voltage and get low harmonic distortion of input current. It also has line power feedback capability.This paper mainly introduces three-phase VSR, including its principle,the topology, the mathematical model, the control strategies, and its hardware. The mathematical model of VSR is the essential means to investigate the VSR. Low frequency models and high frequency models are set up in ABC coordinate,αβcoordinate, and dq coordinate, respectively. Low frequency models is suitable for system design, high frequency models is suitable for emulation. Method of three-phase PWM voltage source rectifiers includes indirect current control and direct current control, and their principles are introduced in this paper. Base on the performance comparing of indirect current control and direct current control,this paper focuses on the space vector control strategy,and set up its emulational models. The simulation is done with Simulink in MATLAB and the results verified the correction of controlling solution.Based on the emulational models,this paper designs and realizes the three-phase VSR hardware system,The design includes a DSP microcontroller ,source, signal collections and conversion , drive circuit and protect circuit of IPM, simultaneously, this paper also introduces the parameters design of LC. The experimental conclusion verified the simulation and the design.