Design Of Vehicle Charger Based On PWM Rectifier

As given timetables for the ban on fuel vehicles were given by countries,electric vehicles have increasingly become the focus of research and application.AC-DC transformation was the key technology of electric vehicle charger.The harmonics generated by traditional rectifier devices or technology led to a lot of wasted electrical energy,and it was in low utilization rate.On the contrary,PWM rectifier could solve such problems well.In this paper,a three-phase three level PWM rectifier was used as the core of the components,and the design of vehicle charger system was completed.First,the topology and working principle of the diode clamped rectifier were analyzed.The mathematical model was given through static coordinate transformation and rotation coordinate transformation.Considering the coupling of current in two coordinates in the d-q coordinate system,in order to simplify the calculation method,the feedforward decoupling measures were used to decouple them.Secondly,the SPWM modulation strategy was studied.By analyzing the characteristics that DSP chip could be generated by only a set of upper triangular waves,an improved SPWM modulation method of three-phase three level rectifier was proposed.This method was not only equivalent to the previous SPWM modulation method,but also because only one triangle wave was used in it,so it was more easily implemented in DSP.The mathematical model of the symmetric regular sampling method was derived,and the conclusion that the pulse duration of SPWM wave was determined by the three quantities of the carrier period of the triangular wave carrier,the amplitude of the modulation and the ratio of the carrier.Then,the PI parameters of the voltage outer loop and the inner loop were designed.On this basis,a simulation model of current decoupling and double closed loop control strategy was built by using Matlab.The simulation results verified the correctness of the improved SPWM modulation method and the adopted control strategy,and drew other conclusions.Finally,a vehicle charger system with an input voltage of 380 V ±10%,a frequency of 50 HZ,and a rated power of 10 KW was designed.The design of the main circuit of the rectifier was completed.The hardware and software design of the control system was completed based on the TMS320F2812 DSP chip.