Research And Implementation Of Single Phase AC-DC-DC Bi-directional Power Supply Based On DSP

In recent years,the development of electric vehicles,solar power generation and other new energy industry,the use of the battery is also more and more high demand,battery charging and discharging technology has become a hot research field of power electronics.Both charging and discharging of the battery involves the energy conversion between the power grid and the load,so the bi-directional ac-dc-dc converter technology is the key technology to charge and discharge the battery,which can be used in emergency power supply,battery chemical composition capacity,battery pack charge and discharge cycle test,BMS detection,inverter and so on.Bidirectional charge-discharge equipment,compared with the traditional unidirectional equipment,realizes voltage grid-connection and energy feedback,and saves energy when the battery is discharged.Lithium battery charging and discharging equipment will develop towards high efficiency,high frequency and miniaturization.This paper studies the power factor correction technology and high-precision constant-current technology of battery charging and discharging system.The main contents are as follows:(1)The multistage single-phase ac-dc-dc bidirectional power supply studied in this paper is divided into three levels.The preamble bidirectional ac-dc converter realizes PFC function,rectifies 220.00 V AC into 400.00 V bus voltage,improves power factor and reduces harmonic.The intermediate isolated bi-directional dc-dc converter transforms the bus voltage and power to DC 12.00 V and realizes electrical isolation to separate the back stage from the front stage of the power grid and protect the equipment.The post-stage non-isolated bi-directional dc-dc converter transforms the DC voltage from 12.00 V to 5.00 V to achieve high-precision current and thus charge the lithium battery.On the contrary,the discharge process of lithium battery is a boost process.This paper focuses on the study of the system's front-stage bi-directional ac-dc converter and its back-stage non-isolated bi-directional dc-dc converter.(2)The system framework applied to battery charging and discharging equipment is studied,and the topology of single-phase bi-directional ac-dc-dc converter is selected.(3)The topological structure of the front-stage single-phase full-bridge main circuit is studied,the working mode of the full-bridge circuit is analyzed in detail,and the realization of bidirectional energy flow based on SPWM driving mode is studied.In order to realize the power factor correction technology,the control strategy was compared and analyzed,and the voltage current double closed-loop PI control algorithm based on the average current method was studied to achieve stable voltage output.The topological structure of the back-stage half-bridge synchronous rectifier circuit is studied,and the principle of its bidirectional energy flow is analyzed.In order to achieve high-precision constant current output,two-stage LC filter circuit is adopted.The main inductance and capacitance are calculated from the technical parameters.(4)The double-loop control of voltage and current based on the average current method is analyzed,and the full-bridge circuit of the front stage is simulated with PSIM simulation software.The measured input current THD=3.18% and the circuit PF=0.9946 are realized,and the power factor correction and output voltage are also relatively constant.(5)To the level of half bridge circuit control strategy is studied,using voltage loop current inner ring double closed loop control strategy,implementation of the battery charge and discharge,the single stage LC filter circuit and two stage LC filter using PSIM simulation software simulation analysis respectively,it is concluded that two stage LC filter circuit has the very good effect of constant current,output current error in 50 mA.(6)Making a dsp-based prototype,using TI's C2000 series fixed-point TMS320F28035 and floating point TMS320F28335 as the core controller,respectively designed a set of 5.00 KW bi-directional ac-dc converter and a set of 300.00 w nonisolated bi-directional dc-dc converter.The design of related hardware is given,including the selection of MCU,the selection of switch tube,the design of auxiliary power supply and the design of some signal sampling circuits.(7)The development process of relevant software and the analysis of actual hardware test results are introduced.It is concluded that PF=0.993 at full power of the front circuit,input current THD=6.7%,and constant current accuracy of the rear circuit is 0.05%.