Research On Bidirectional Converter And Multi-Mode Control Strategy Applied To Battery Charge-Discharge System

Battery power supply system has been widely used in power supply for the long-pulse magnetic field,uninterruptible power supply,energy storage system and other fields because of its advantages of voltage stability,large output current and flexible configuration.Bidirectional converter,as the key technology in the application of battery power supply,is the core unit in the process of battery charging and discharging,battery test&research and maintenance.Its performance is directly related to the reliability of battery bank power supply systems,the charging performance,energy utilization rate and power quality of grid-side.With the increasing capacity of battery bank power supply,the research on bi-directional converter with large capacity,multi-function,modular-scalability,digital intelligence and high efficiency has great practical significance.In this paper,aiming at the development of battery charge-discharge devices,a charge-discharge converter,with high power factor and wide range of output voltage,is taken as the research object.The coordinated control of cascade system is studied.A three-level digital control scheme is proposed,which is composed of upper computer,median computer and lower machine,with ARM+DSP+FPGA as the core.A chargedischarge device with the characteristics of energy-saving,high efficiency,access to multiple batteries,flexible configuration of batteries and independent control of each module has been developed.The stability,digitalization and intelligentization of the device are improved,which lays a foundation for the large-scale application of the charging and discharging device.The working principle of two-stage bi-directional converter under different operation modes are respectively analyzed.The small-signal dynamic models in corresponding with each mode are established.The double-closed-loop controller of the current in ac side employing svpwm strategy based on feed-forward decoupling algorithm and feedback of bus voltage and the control strategies of DC/DC converter in each mode are proposed.The design method and digital realization of the corresponding compensation controller in each mode are given in detail.In the realization of this subject,according to the two-stage topology and its technical specifications,the parameters of main circuit such as power module are calculated,and the design of hardware control circuits,including multi-processor control circuit,driving circuit,data acquisition circuit,data interaction and so on,are introduced.The digital control program was presented according to the design requirements of the control system in this thesis.The Simulink simulation model and experimental platform of the battery charging and discharging converter are built,and the steady-state performance and dynamic performance of the converter under different working modes are simulated and verified experimentally,and the simulation and experimental results indicate that the converter has good electrical performance,with the characteristics of sinusoidal current,high power factor and stable bus voltage.The proposed converter can realize the bidirectional flow of energy and various charging-discharging functions of the battery,and validate the feasibility of multi-processor,multi-stage control structure and the effectiveness of the proposed control algorithms.