Research On Finite Control Set Model Predictive Current Control Strategy Of VIENNA Rectifier

VIENNA rectifier is a three-level PWM rectifier with high power factor,low harmonic and controllable output voltage.It can not only guarantee active power transmission to DC link but also avoid injecting reactive power and harmonics into the grid.It has received extensive attention of scholars and enterprises at home and abroad.How to control the VIENNA rectifier is of great significance for improving its performance.Model predictive control with its no PWM modulation,no control parameters setting and optimization of multiple targets at the same time has got a lot of applications in the field of power electronics in recent years.This thesis extends finite control set model predictive control strategy(FCS-MPC)to VIENNA rectifier in order to improve the performance of system.The thesis studies the FCS-MPC strategy that is suitable for VIENNA rectifier,builds switch state table based on three-level voltage space vector,gives cost function by performance requirements,founds the FCS-MPC system on the basis of mathematical model in static two-phase coordinate of VIENNA rectifier.The shortcomings of traditional FCS-MPC have been given:more times of vector selection,longer program execution time,too much calculation.In view of the traditional strategy and its disadvantages,this thesis puts forward a simplified FCS-MPC control strategy of VIENNA rectifier with a fast vector selection method based on sector division.This thesis analyzes how to reduce the times of vector selection and the calculation time of the program by means of the simplified strategy.Aiming at the neutral-point voltage balance problem of the VIENNA rectifier,combining with the feature that FCS-MPC can handle multiple optimization goal flexibly,the thesis adds neutral-point voltage optimization goal to the cost function.Then the control strategy selects the switch state that minimizes the cost function through constrain with a weighting factor,then uses the chosen switch state to control VIENNA rectifier and regulates the neutral-point voltage balance.An experimental prototype with TMS320F2812DSP as control core of VIENNA rectifier is built,the hardware and software design of is finished.Hardware include system input and output filter,driver circuit,sampling control circuit,over-voltage and over-current protection circuit.The software include main program and interrupt service routines.Experiments of voltage oriented-current decoupling control and simplified FCS-MPC are completed on the prototype.By the comparison of experimental results,the steady-state performance of simplified FCS-MPCC and the conventional strategy is the same on the whole.For the dynamic performance,especially dynamic response speed of current control on the basis of simplified FCS-MPCC is significantly faster than that of conventional control strategy,the simplified control strategy improves the dynamic performance of system.