Research On Battery Charging And Discharging Technology In Independent Photovoltaic System

Energy shortage and environmental pollution is becoming increasingly serious,vigorously develop clean and renewable energy to replace the traditional fossil energy imminent,inexhaustible solar energy as a clean energy gradually by the attention of the countries all over the world,the photovoltaic industry in the country vigorously support and subsidies is gradually moving towards maturity. But compared with traditional solar energy, although widely distributed,no pollution,but also by the light intensity,temperature,weather, altitude,geographical and other factors limit.And the battery has a limited number of charge and discharge,short life in energy storage system.Storage costs,especially in the stand-alone PV system to account for a large proportion. How to improve the photovoltaic efficiency and reduce the cost of electricity has become the study of photovoltaic power generation system needs attention.So it is particularly important for solar cell maximum power point tracking(MPPT) control and appropriate battery charge and discharge control in photovoltaic system.First,the paper discusses in the independent PV systems maximum power point tracking(MPPT) control and battery charge and discharge control principle,and maximum power point tracking(MPPT) control circuit and a battery charge and discharge control circuit and control method has been described.Combined the maximum power point tracking(MPPT) and a three-stage charging as a method of controlling the system,in the control process takes into account the battery overshoot,less filling,gassing and other issues in order to extend battery life and reduce system cost.This approach not only makes full use of light resources,improve the efficiency of power generation systems,but also protects the battery;reducing gassing in the battery generated during charging and discharging,and prolong battery life.Building the simulation model of the system in the simulation software MATLAB /Simulink,solar cells and batteries and other components parameters to experimental platform as the basis,the simulation results show that the control method can effectively control the normal operation of photovoltaic power generation systems, and issued maximum power depending on the circumstances,consistent with the theoretical analysis.Secondly,in the experimental platform designed hardware and software programs.The control circuit used digital signal processor(Digital Signal Processing) TMS320F2812 DSP as the core element of the whole experiment,to design and welded the signal detection circuit,a buffer circuit,a driving circuit,a conditioning circuit and circuit isolation amplifier control circuit.Software design is implemented in CCS3.3 software development platform,each control function is written into a separate subroutine. The main program to complete initialization of each module register,and the interrupt program is completed portions of specific control work needed to call a subroutine,the program continues through commissioning,operation,program can be used to obtain the experimental control.Through continuous debugging and running of the program,the program can be used for the control of the experiment.Finally,in the experiment,the parameters of the control circuit are continuously improved,and the control parameters of the program are adjusted continuously,until the control task of the photovoltaic power generation system is completed,and the experimental results are obtained. The results show that the solar cell can achieve maximum power point tracking(MPPT) control in the case of external conditions change;In considering the battery overcharge,insufficient charging,condensate gas and other issues of the case,through the three stage charging control method,system can maintain constant DC bus voltage;Only when the battery is in full charge,and the photovoltaic system has the remaining power,will make the solar battery out of the maximum power point tracking(MPPT) control state, into the constant power output state.Experimental control works well,it has once again proven the combining power point tracking(MPPT) and three-stage charging method control feasibility.