Research And Implementation Of Photovoltaic System Charge And Discharge Controller Based On MPPT Algorithm

Now energy shortage and environmental pollution have become the most important problems in the world.As an inexhaustible,clean and non-polluting renewable energy,solar energy has great development potential and application value.However,environmental factors such as temperature and solar illumination can seriously affect the output power and utilization ratio of photovoltaic cells.Therefore,it is of great significance to study the photovoltaic charge and discharge controller with maximum power point tracking function..On the basis of analyzing the output characteristics of photovoltaic cells,a simulation model of photovoltaic cells under uniform illumination was established with Isc,Uoc,Im and Uoc as parameters.Compared with the actual measurement curve,the error is 4.2%,which proves the effectiveness of the model.On this basis,the output characteristics of photovoltaic arrays under partial shadow environment were simulated and studied.According to the main function of the PV charge and discharge controller,the circuit design of each module is completed.It mainly includes MCU module,power circuit,voltage reference circuit,DC/DC circuit,MOSFET driving circuit,voltage and current sampling circuit and input filter circuit.High-performance Chip MC9S12XET256(The Freescale)is adopted as the microcontroller of the system,and the DC/DC circuit consists of four MOSFET full bridge circuits,high frequency transformer and output filter circuit.According to the output characteristics of PV cells,The study analyzes the working principles,advantages and disadvantages of common MPPT algorithm.An improved MPPT control algorithm based on the conductance increment method with the PID control is proposed for the uniform illumination condition.The advantages of the algorithm are verified by comparing the simulation with the conductance increment method and the PID control method in Matlab.In order to prevent the system from falling into the local maximum,a partial scan is proposed to obtain the global peak value in the shadow condition,and then the multiple peak MPPT algorithm based on the improved control method is further accurately tracked,and the simulation analysis is carried out in different environments.Simulation results in different environments show that this algorithm has good tracking performance in complex environments.Finally,The design and development of the system software is completed the on the CodeWarrior development platform by C language,mainly including A / D sampling program,battery charge and discharge control program with MPPT control algorithm,PWM program and fault display program and so on.This study creates the system test platform and verifies the photovoltaic charge and discharge controller.The result shows the power generation power of the charge and discharge controller of the PV system can be improved by 6.8W and the tracking speed is 170 ms,and the maximum power point of the photovoltaic cell is tracked.