Research On Vehicle-mounted Charging Power Supply For Electric Vehicles

The problem of energy shortage and environmental deterioration have promoted the rapid development of the global electric vehicle industry.Pure electric vehicles use batteries as their power storage energy source,which provides electric energy to the motor through the battery to drive the motor for running,thereby promoting the car to run.Therefore,research on energy storage battery charging technology is one of the key technologies to promote the promotion of new energy electric vehicles.Based on the existing domestic and foreign literatures on topology circuit structure and control method,The control strategy and topology of the on-board charging power supply for new energy electric vehicles were optimized.Aiming at the problem that traditional AC/DC uncontrollable rectifier circuits emit a large number of harmonics and reactive power,affecting the power quality of the grid system and reducing the battery charging efficiency and service life,this paper uses a three-phase voltage-based PWM rectifier bridge topology as the front-end circuit of vehicle charging power supply.Firstly,the working principle,mathematical model,observability and controllability of three-phase voltage-type PWM rectifier bridge topology are analyzed in detail.A V~2based current feedforward direct power improved control method is adopted.Through theoretical analysis,this improved method uses voltage square as the outer loop of the direct power control,reduces the starting current of the rectifier circuit,and introduces the load current feed forward,reduces the voltage tracking output error,and at the same time,improves the dynamic performance of the circuit.The simulation of the front-end rectifier topology circuit in MATLAB software shows that the three-phase voltage-type PWM rectifying bridge topology not only makes the network-side current sinusoidal,unit power factor operation,and output voltage stable under the improved direct power control strategy.Compared with the direct power control,the THD is lower and the system tracking performance is better,which is in line with the charging requirements of the back-end circuit of the electric vehicle-mounted charging power supply.At the same time,the rear end of the vehicle-mounted charging power supply of the electric vehicle adopts a DC/DC conversion circuit.By comparing and analyzing the advantages and disadvantages of various resonant DC/DC conversion circuit topologies,as a back-end converter topology,a symmetric control full-bridge resonant PWM converter(FB-RPWM)is adopted.The working mode of the full-bridge resonant PWM soft-switching converter is analyzed in detail.The steady-state characteristics of the converter are analyzed to make the voltage transfer ratio of the converter irrelevant to the load,switching frequency and duty cycle,presenting DC-DC transformer characteristics.Then the soft switching operating conditions are analyzed,the converter can realize the zero-voltage turn-on switching of the circuit switch tube and zero-current turn-off switching of the transformer secondary side output diode.The primary side of the FB-RPWM converter's transformer uses a DC blocking capacitor,so that the DC offset of the magnetizing inductor current is 0,which reduces the transformer losses and further improves the efficiency of the back converter.Symmetrical control simulation is performed in PSIM software.The simulation results verify the correctness of the proposed topology theory.Finally,the prototype of the experimental vehicle was built for the rear-end FB-RPWM converter of the electric vehicle-mounted vehicle charging power supply proposed in this paper.The experimental results show that the topology of FB-RPWM converter is controlled by symmetric control strategy,which achieves better resonance effect and realizes the soft-switching function of the back-end DC/DC conversion circuit,which verifies the correctness of the theory.