Design Of Three-phase Voltage Source PWM Rectifier With High Power Factor

With the improvement of the semiconductor power switch’s capability,especially thefull-controlled power switch，the power electronic devices can not only be performed highpower density and high efficiency，but also have high power degree.It is well known,the uncontrolled rectifier used diodes and Phase-controlled rectifier arevery mature and easy controlled and cheap,but they contain lots of current harmonics andreactive power,which can pollute the grid.The PWM rectifier,which used the full-controlled switchs and the PWM (Pulse WidthModulation)technology,can archive unity power factor and low harmoniccontent,and its inputcurrent is almost sinusoidal,even can regulate its reactive power flexibility.Power factor is one of the PWM rectifier’s output characteristics.PWM rectifier not onlycan make its dc output voltage steady,but also can make its power factor be1(when thepower factor is1,the PWM rectifier is on unity power factor rectified;when the power factoris-1,the PWM rectifier is on unity power factor inverter.),which means the electric power canbe conducted in two direction.The PWM rectifier with high power factor can reduce thepollution to the grid fundamentally.The main research of this paper is high power factor controlled strategy of the PWMrectifier,which is based on the three-phase Voltage Source half-bridge circuit.The three-phase Voltage Source half-bridge PWM rectifier is a strongnonlinear,time-varying and variable-coupling system.In order to archive a performantoutput,The three-phase Voltage Source half-bridge PWM rectifier employed the voltagecontrol loop and current control loop strategy.The voltage control loop can control andstabilize the PWM rectifier’s dc output voltage.The current control loop can let the PWMrectifier have unity power factor.For the purpose of more easily to control the currentloop,usually we can change the three-phase current’s coordinate,which become direct variablefrom alternating variable.Even so,there arestill have variable-coupling situation.For that, we can employed the feedforward decoupling strategy of the PI controller(proportionalintegral controller),which make the control system have no static error adjustment.Becausethe current which is changed coordinate is represented of the active power and the reactivepower,and if we want the PWM rectifier have performant dynamic performance and staticperformance,the key is the design of the current controll loop.The application of OptimalControl Theory can help us find a time optimal control strategy of the current control loop,andbuild the control equations of current control loop.In this paper, the research background and worth of PWM rectifier were introduced onthe beginning.And then, the commonly used topology of the PWM rectifierwere summed andcompared.Because the three-phase Voltage Source half-bridge PWM rectifier is mainly usedcircuit of this paper,its operating principle is analyzed in details,and then build itsmathematical model.And then introduce the control strategy of the PWM rectifier,and timeoptimal control strategy of the current control loop,and introduce how SVPWM (Space VectorPulse Width Modulation) calculate the on-off signal.The simulation model of the three-phase Voltage Source half-bridge PWM rectifier wasbuilded in PSIM.And the writer run the simulation to testify the control strategy.The experiment model of the three-phase Voltage Source half-bridge PWM rectifier wasbuilded.And the writer do some experiment to testify the simulation model and its controlstrategy.