Research On Lithium Iron Phosphate Charging Device And Its Control Strategy

Nowadays the energy shortage and environmental pollution are two major problems restricting economic development of countries around the world. Lithium iron phosphate power electric vehicles with increasingly mature technology, not only uses a secondary energy as power, but also has the outstanding advantages of high security, energy saving and long life. In practice, simple charging method results in nearly bad performance and short life for ninety percent of batteries. Compared with the existing charging device, taking into account the advantages of small and medium-power current-source PWM rectifiers, this paper introduces a current-source PWM charging device structure, with directly current regulation, high stability, fast dynamic response and good battery characteristics protection.In this paper, the core power battery pack and charger for electric vehicles are researched. The first of all, characteristics of lithium iron phosphate battery and modeling are studied, then a model of the improved lithium iron phosphate battery is built in MATLAB/SIMULINK, and the corresponding confirmatory simulation analysis is conducted for the prototype battery pack made. Then rectifier topology based on the current-source PWM is proposed, and theoretical derivation and important elements are executed for the main circuit and control circuit. Then the existing current-source PWM based direct power control (DPC) is improve after the theoretical analysis, the inner loop control based on the original six intervals proposes control method divided twelve interval space vector according to the power effect, increasing the control precision and fast response speed, and is validated in MATLAB/SIMULINK simulation platform. On this basis, flux-oriented control system where current-source PWM without the grid voltage sensor is virtually directed is proposed, simplifiing the algorithm, improving system response speed and network performance when grid voltage is not ideal, and then making the simulation and validation in MATLAB/SIMULINK platform. Hardware system with FPGA+DSP as the core is designed, describing the control flow, and conducting the fast charging experiment on the lithium iron phosphate groups platform.