Research On Control Strategy Of PWM Rectifier

In the modern industrial field,a large number of applications of electrical devices generates lots of harmonics,which may pollute grid,affect the quality of power,and reduce the power factor.With the increasing requirement of clear power in the whole society,PWM based converting technology has been taken more and more seriously.This phenomenon can be found in the related studies in the field of power conversion and transmission.Compared with the traditional converters,PWM rectifier has many advantages,such as,it has the stable output voltage,the sine-shaped input current.Besides,the power factor of PWM converter can be regulated between-1 to 1.Thus,the power electronics industry is more concerned with the study of PWM rectifiers than the traditional converter.Most conventional power conversion strategies apply diode based rectification and phase-controlled based rectification.These two rectification methods have the own defects.For example,although the energy regulation with these two methods can be realized,the harmonics cannot be eliminated obviously.Moreover,compared with the PWM rectification based method,the traditional converting method has the low DC voltage utilization efficiency during the power conversion,the larger power loss and tends to the extra heat,these demerits reduce the remaining life of the electronic device.Different from the traditional converting methods,PWM rectifier has an ability to realize the dual-direction energy flowing between the AC side and the DC side.This property makes the PWM rectifier can run in the AC / DC state,and also can work in the AC / DC state.This paper focuses on the control method for the voltage source based PWM rectifier,and first introduces the related working principle and the existing control strategy,the main content shows as follows,First,this paper presents the research object,the basics of PWM rectifier,the working states,and constructs the mathematical model of PWM rectifier.Second,according to the mathematical model of three-phase PWM rectifier,this paper concludes and compares the typical current based control strategies,from the controlling principle,critical parameters,advantages,and disadvantages.After that,this paper proposes a fixed frequency hysteresis control algorithm with fixed frequency and double hysteresis loops.This control strategy restrains the high harmonics through the switch state of the inner hysteresis loop and keeps the current response speed with the outer loop of voltage.At last,on the basis of the proposed control strategy,this paper sets up the experimental platform and verifies the proposed fixed frequency hysteresis control strategy.