Research On Three-phase Voltage Source PWM Rectifier And Its Control Strategy

As a key device for energy flowing from the grid to the load,rectifiers are used in the power electronics industry widely.Traditional diode rectifiers and thyristor phase-controlled rectifiers have disadvantages such as low power factor,high Grid-side current harmonic content,and large output voltage ripple,which reduces power supply reliability and power safety seriously.With the advancement of power electronics technology,the PWM rectifier has achieved development rapidly.Because of its advantages such as high power factor,low current harmonic content,adjustable DC-side output voltage,and bidirectional flow of energy,it is used in electrical transmission,new Energy generation and other fields widely.The thesis takes three-phase voltage source PWM rectifier as the main research object,and makes in-depth research on its working principle,control strategy and parameter design.The main contents include:The basic working principle of the three-phase voltage source PWM rectifier is analyzed.Based on its main topology and the Kirchhoff voltage and current law,mathematical models of the PWM rectifier in different coordinate systems are established.Aiming at the problem that the PWM rectifier adopts the voltage-current double-closed-loop control strategy,a large inrush current is generated during its startup process.A pre-charge-slow giving hybrid control inrush current suppression strategy is proposed to make the DC-side reference voltage transition to a given value smoothly,which achieve low current stress to start the PWM rectifier.Finally,the feasibility of this hybrid control strategy is verified by MATLAB/Simulink simulation model.Based on the traditional predictive control strategy,a fixed-frequency predictive control strategy is designed in combination with the space voltage vector modulation method.Combining the model predictive control with the space voltage vector modulation strategy,the traditional predictive control strategy has solved the problems of unfixed switching frequency and difficult filter design fundamentally.Finally,the advantages and disadvantages of traditional predictive control and improved fixed-frequency predictive control are compared and analyzed by MATLAB/Simulink simulation model.The reversible operation control strategy of the three-phase voltage source PWM rectifier is studied.According to the theory of predictive control,using the relationship between the DC-side output voltage and the reference voltage of the PWM rectifier,a voltage-current double closed-loop control strategy based on model predictive control is proposed to realize the four-quadrant operation of the PWM rectifier.Finally,the feasibility of this control strategy is verified by MATLAB/Simulink simulation model.A three-phase voltage source PWM rectifier hardware experimental platform is set up,and its main circuit and control circuit core are introduced.Finally,based on the experimental platform,the control strategy proposed in this paper is experimentally verified.