Research Of Photovoltaic Energy-storage Converter And Its Battery Management System

The addition of energy storage is the inevitable trend of distributed photovoltaic power generation at present,which can restrain the power fluctuation and grid oscillation in the PV power generation system,improve the power quality of the power grid,shave Peak and fill valley and control the abandonment rate,so that the PV power generation system can be further improved.The Photovoltaic Energy-storage Converter was taken as research object in this paper,focusing on the PV efficient new MPPT algorithm,efficient battery charge and discharge topology and a reasonable battery management system,studying the hardware system and software algorithms in depth.Firstly,the key technologies’ research status of Photovoltaic Energy-storage Converter was analyzed.Then,based on the theoretical analysis and simulation,the hardware system was designed,and the system control strategy was developed.Finally,the Photovoltaic Energy-storage experimental platform was set up and a series of verification experiments were carried out.The main work of the paper are as follows:(1)The overall hardware solution of Photovoltaic Energy-storage Converter was determined.According to the requirements of the system’s technical parameters,the hardware system scheme of “MPPT staggered parallel BOOST+push-pull discharge + full-bridge phase-shift charge” was selected,and the corresponding simulation model was established for analysis;the hardware parameters and key hardware circuits of the system were analyzed and designed in detail.(2)The MPPT algorithm based on fuzzy control was studied.Aiming at the research of high efficient MPPT algorithm,a new MPPT algorithm combined with perturbation observation method and fuzzy controller was designed and verified by simultaion.The results showed that the fuzzy MPPT algorithm has higher tracking accuracy and tracking speed,and the dynamic response is faster.(3)The charge control strategy suited for photovoltaic systems was proposed.The existing problems of the traditional charging algorithm in the photovoltaic power generation system were analyzed,a new battery charge control strategy was proposed,which combined the MPPT and the improved four-stage charging algorithm toensure that the charging is not affected by the fluctuation of the photovoltaic power.In addition,the control strategy of matintaining the BUS stable during charging was analyzed.After the charging was completed,the battery equalization was performed using the equalization strategy based on the cell voltage method.(4)The performance test and charge and discharge experiments of Photovoltaic Energy-storage converter were carried out.A 3.2KW Photovoltaic Energy-storage Converter was developed and the experiment platform was set up,and the basic performance of each circuit were tested.The MPPT experiment was conducted,MPPT tracking error and tracking efficiency were tested.Battery charge and discharge performance was tested,voltage and current waveforms during charge and discharge were analyzed,feasibility of charge and discharge algorithm was verified.Battery equalization performance was tested,and the feasibility of equalization algorithm was verified.The experimental results showed that the hardware system of the 3.2KW photovoltaic energy storage converter can work normally and its performance was good,which showed that the design of various hardware parameters was reasonable and reliable.The MPPT racking efficiency was up to 99.921%,the MPPT algorithm was efficient and feasible.The battery discharge efficiency could reach 93.43%.The charging process was in accordance with the design stage-charging algorithm,the voltage regulation accuracy and steady current accuracy were in line with the charging requirements.The busbars remain stable during the switching of battery charge and discharge.the battery equalization worked well.