| PWM rectifier is the first choice for AC-DC application because of its simple structure,strong reliability and double-flowenergy.At the same time,due to such advantages as high grid side power factor and low current harmonics,it has been widely applied in new energy power generation,railway traction power supply system and other fields.This paper studies the related problems of single-phase voltage source PWM rectifier.Because of some alternating current time-varying physical quantities in single-phase PWM rectifier,the control system can’t be designed in an effective way.By building the mathematical model of two-phase rotating coordinate system(d-q axis system)with grid voltage orientation as the basis,a control strategy of outer current and inner voltage is designed.The grid voltage’s rich harmonics has seriously affected the detection precision of the voltage phase.Therefore,a discrete extraction method of grid-side voltage fundamental component is proposed.What’s more,the virtual component of grid-side current can not be sampled directly,soa digital detection method without PLL is put forward.On the basis of theoretical research,MATLAB / SIMULINK is used to perform software simulation of the rectifier.In the SIMULINK simulation environment of MATLAB,the topology of the rectifier,the control model based on grid voltage orientation,the discrete model of the second-order resonant filter,and the discrete detection model of the virtual orthogonal component of the grid current are built toperform stimulation under the steady-state condition,dynamic working condition,as well as the conditions of sudden load increase,sudden load decrease,and half-load.At the same time,under the conditions where the second-order resonant filter is introduced and the second-order resonant filter is not introduced,comparison with simulated experiments is carried out to verify the inhibitory effect of the voltage fundamental component extraction methodon grid voltage harmonics.The experiment platform is built,the design principle of main body of hardware circuit,the parameter design process of main circuit and the framework process of corresponding software design are put forward.Both simulation and experimental results show that under different loads,the output voltage of single-phase PWM rectifier can follow the precision of the given value,and the dynamic performance is good.And the grid-side current and electromotive force keep running at the unit power factor.Therefore,the feasibility and correctness of the proposed detection method of virtual current,extraction method and control strategy of voltage fundamental component are proved. |
