The Design Of Photovoltaic Charging And Discharging Controller For Storage Battery

Because of the energy crisis, Photovoltaic(PV) power is more and more important for people, and it has become one of the mainstream new energy .But PV cells is a kind of nonlinear sources, so a whole of PV power system must be contained a charging-discharging controller except photovoltaic cells, storage battery and load. The controller is the core of the PV system, it can control the charging/discharging current and voltage.In the past, most of papers about PV controller were based on achieving some functions, however, the control performance of PV controller had been ignored. The actual state of PV controller may be not satisfactory. Therefore, this paper is based on the control system characteristics, analyzes and establishes the charging system mathematical model. Then, designs charging circuit by engineering design method of continuous system. Thereby ensure the reliability and performance of the controller. After that, designs some functions about PV system.In this topic, The characteristics of PV charging/discharging system has first been analyzed. Then the mathematical model of current loop circuit and voltage loop charging system has been established. After that according to the engineering design methods of continuous system, the transfer functions of current regulator and voltage regulator have been figure out. The result has been verified by MATLAB simulation, that is in keeping with optimal second-order system. In addition, the perturbation influence of photovoltaic cell has been analyzed. And then some solutions have been put forward.The hardware structure of PV charging/discharging controller has also been deeply discussed in this paper. The main components selection and parameter setting have been finished. The sep-down DC/DC-BUCK circuit, the MOSFET drive circuit, PWM modulator circuit, voltage and current feedback circuit, current and voltage regulator circuit have been designed.This paper adopts PIC16F877A to manage the working state of the system, the paper also elaborates on the whole design frame of the software and the design thinking the main software's functions. The functions of battery overcharge protection, battery overdischarge protection, automatic adjustment of a given state of charge, photocontrol load on/off and setting of main charge parameters have been completed.