Research On Three-phase Converter For Battery Charging

With the rapid development of new energy systems,the application of batteries is becoming more and more extensive as an important energy storage link.The bulky traditional charger not only charges slowly,but also causes irreversible damage to the battery,which seriously affects the service life of the battery.Therefore,it is of great significance to study high-efficiency,small-sized and intelligent charging switching power supply modules.For the 48 V battery pack,this paper designs a charging power supply with a maximum output current of 100 A and an output voltage range of 35V-62 V under the condition of three-phase three-wire power grid.The power supply adopts a two-stage structure.The former stage uses the VIENNA circuit as the topology and uses VIENNA as the three-level structure circuit.The voltage stress of the switch tube is half of the output voltage,which is suitable for high-voltage output occasions.The latter stage uses two-way half-bridge LLC circuit cascade as the main circuit topology.The LLC circuit can realize ZVS without adding auxiliary network,which can greatly improve the working frequency of the switches and reduce the volume of the power supply.Both stages use TMS320F28035 as the control chip to realize digital control,and the isolated optical coupler is used for signal transmission.After a detailed analysis of the working principle of the VIENNA circuit and the LLC circuit,the parameter design and device selection of the main circuit are carried out,and the control scheme of the charging power supply is determined.The VIENNA circuit uses SPWM modulation to achieve unity power factor correction of the circuit.The algorithm is simple and easy to program.The LLC circuit uses a hybrid control strategy of PFM+PWM to broaden the gain range of the LLC circuit.The simulation of VIENNA circuit and LLC circuit was carried out by using MATLAB and PSIM simulation software to verify the validity of parameter design and control strategy.Finally,an experimental prototype of three-phase 380V±20% input and 35~62V/100 A output was fabricated and tested.Test results show that the input side of the circuit canachieve power factor correction,when the load is more than half,PF>0.94,the THD of the current is <5%,the latter stage LLC circuit can realize a wide range output of 35V-62 V,and the switch tube can realize ZVS soft switch in the whole range.