Research For Unity Power Factor Rectifier Based On Voltage Space-vector Pulse-width Modulation

It needs plentiful rectifying power supply in industrial field. And people has realized that the rectifying system with lower power factor can bring harmonic pollution and induce the electric net problem since the modern power electronics technology has uninterrupted development. So, improved the power factor has been the develop tendency of the rectifying system, and unity power factor rectifier is becoming the research focus for domestic and overseas scholars.The higher power factor realization needs to apply the pulse-width modulated (PWM) technology. The thesis starts with the control principle of three-phase PWM rectifier, analyzes and compares the several maturely researched control methods for PWM, and finds out the common problem which is urgently solved is that the switching frequency is conflicted with its losses. The foreign scholars have presented one PWM technology based on voltage space-vector (SVPWM) which can solve this common problem in a certain extent. The SVPWM scheme has the merits of the larger linear range of fundamental voltages, easily digital realization and can fulfil higher power factor. Based on the research of conventional SVPWM control scheme, the thesis has presented a novel simply control algorithm for SVPWM scheme.In order to theoretically testify the feasibility of the simple algorithm, the thesis makes a concrete analysis of working modes under rectifying operation and of the algorithmic calculation. At the same time, from the concrete analysis, the rectifying system applied the simple algorithm can make the power bi-directional flow. The novel control scheme adopts the two-phase modulation and it makes smaller switching losses compared with the quasi-optimal modulated method of conventional SVPWM scheme. Aimed at the requirement of the control scheme, several important parameters are analyzed and calculated, such as inductance of AC side, voltage of DC side, proportional and integral parameters of PI controller.To farther testify the correctness and feasibility of the scheme, the control scheme is simulated using the dynamic simulated tool SIMULINK of MATLAB5.3 software and thedynamic performance is analyzed. And the full digital rectifying control system is composed which the TMS320F240 digital signal processor (DSP) is its core and is applied experimental test.From the simulated result is accord with the experimental result, we can find the conclusion that the novel scheme is reliably able to fulfil the three-phase rectifier with higher power factor which can operate both rectifying and regenerating mode. Moreover, its control algorithm is easy and the range of DC utilizing efficiency is large.