Research On Low-power Modular Three-phase VIENNA Rectified Power Supply

Grid-connected rectifiers are widely used in all walks of life.To improve the power factor of grid connected rectifier and reduce its harmonic pollution to the grid has become one of the key issues of grid connected rectifier research.As a three-level grid-connected rectifier,VIENNA rectifier has been widely regarded in engineering applications because of its high power factor,few switching devices,no through-threatening hazards and low switching stress.This thesis will study the topology of VIENNA rectifier,modulation and control methods,simulation and prototype production.Firstly,the working principle of Vienna rectifier and its mathematical model in abc natural coordinate system,?? two-phase static coordinate system and dq rotation coordinate system are analyzed.Secondly,the simplified control method of three-level to two-level SVPWM of VIENNA rectifier is studied.In this method,three-level voltage vector is transformed into two-level voltage vector plane by coordinate transformation,so that two-level SVPWM method can be used for calculation,which greatly reduces the amount of calculation.Then the pulse waveforms of the current voltage vector in different intervals are analyzed and summarized,and the obtained rules can be used for simulation model control and utility program writing.On the basis of theoretical analysis,this thesis focuses on the control strategy of VIENNA rectifier.Firstly,the phase-locked loop control in a single synchronous coordinate system is analyzed.Secondly,the voltage and current double closed loop PI control is studied.The current inner loop also needs to be decoupled.Then the influence of each voltage vector on the midpoint potential is analyzed,and the redundant positive and negative short vectors are used to balance the midpoint potential.After that,a soft start is added for closed-loop control,and a three-stage starting method is adopted to avoid current shock at the instant of starting.In the follow-up,the problem of zero-crossing distortion of VIENNA rectifier during SVPWM modulation is also studied,and a solution is given.Finally,the quasi-proportional resonance control is introduced for the shortcoming of the current inner loop when using PI control,and the sliding mode control is introduced for the problem of the slow response speed of the voltage outer loop.According to the above theoretical analysis,this thesis simulates the VIENNA rectifier and its control strategy,and gives the simulation results,proving that the analysis method and parameter design meet the expected requirements.In addition,this thesis also gives a complete calculation process of the parameters of the experimental prototype,and designs specific hardware circuits such as the driving circuit,voltage and current sampling and conditioning circuit,compiles the control software,and gives a detailed control flow chart.