Research On Modulation And Double Loop Predictive Control Of SWISS Rectifier

As a new energy vehicle,electric vehicle(EV)has great advantages in energy conversion efficiency,environmental protection and alleviating dependence on oil,and is becoming the mainstream direction of the future development of new energy vehicles in China.However,compared with the world-class electric vehicles,domestic electric vehicles are not mature in technology and facilities,especially in the process of research and development,production and use of charging devices.As a new type of three-phase PFC rectifier which can be used in electric vehicle charging device,SWISS rectifier has the advantages of smaller switching loss,lower current harmonic distortion rate and unit power factor operation,so it has high research significance and practical application value.First of all,by analyzing the switch state and circuit conduction loop relationship of the SWISS rectifier in different working sectors,the equivalent buck converter is processed,and then the equivalent buck mathematical model of the SWISS rectifier is deduced,which lays a solid foundation for the research of the modulation strategy and double loop predictive control strategy in this paper.Secondly,aiming at the unbalanced condition of three-phase power supply voltage,the switch mismatch problem of the space vector pulse width modulation(SVPWM)strategy of the SWISS rectifier is analyzed.Based on the traditional modulation strategy of the SWISS rectifier,the sector identification method and duty cycle calculation formula are improved,Under the condition of weak unbalanced voltage amplitude,the SWISS rectifier can still maintain the power factor above 0.95 and the current harmonic distortion rate below 5%.Finally,according to the model predictive control(MPC)theory and the discrete mathematical model of the SWISS rectifier,the control rates of the outer voltage loop and the inner current loop of the dual loop predictive controller are derived,and the closed-loop stability of the control system is analyzed.Aiming at the problems of large steady-state error and ripple of the output voltage of the SWISS rectifier under the double loop predictive control,a voltage error prediction model based on the recurrent neural network(RNN)is constructed,and the feedback correction term is introduced into the voltage outer loop control of the double loop predictive controller,The improved double loop predictive controller not only realizes fast and error free tracking of output voltage,but also effectively improves the ability of anti load interference.