Research On Photovoltaic Energy Storage Generation System And Its Energy Management Strategy

With the rapid development of photovoltaic power generation at home and abroad,it has become an important part of the power grid.The combination of photovoltaic power generation and energy storage system is the development trend of photovoltaic power generation,which effectively alleviates the problem of photovoltaic power fluctuation,reduces the impact on the grid,and reduces the photovoltaic energy abandonment rate.Through the analysis of the development direction of photovoltaic technology,the research significance and background of the subject are put forward.In this paper,the software and hardware of photovoltaic energy storage power generation system are designed.Based on the hardware platform,photovoltaic MPPT control,grid-connected control,charge and discharge control and energy hierarchical management are studied.The main work of this paper is as follows:(1)The hardware structure of 3KW photovoltaic energy storage power generation system is designed based on DC bus structure.The "Boost + Full Bridge" photovoltaic grid-connected system and the "Push-Pull + Phase-Shift Full Bridge" charging and discharging system are designed.The magnetic components and power devices of each power circuit are designed and selected.The simulation results show that the designed hardware circuit meets the system operation requirements.(2)The control algorithm of each functional module of photovoltaic energy storage power generation system is studied.In the former Boost maximum power tracking device,the disturbance observation method of fuzzy control is used to realize MPPT tracking with variable step size.The simulation results show that the control algorithm has good tracking accuracy,fast dynamic response,and the system can be stabilized within 0.3 seconds when the photovoltaic power fluctuates.In the latter full-bridge circuit grid-connected process,the control method of "voltage PI outer loop + current PR inner loop" is adopted.The simulation results show that the grid-connected harmonics can be reduced to 3.37%.When the battery is working,the voltage and current in the charging and discharging process are controlled,and the improved four-stage charging algorithm is realized by double closed-loop control.(3)The energy management strategy of photovoltaic energy storage system is studied.Based on the bus voltage grading method,the operation modes and energy flow directions of the system are analyzed,and the control methods in the process of off-grid and grid-connected switching are analyzed.In order to realize the monitoring and management of photovoltaic energy storage and power generation system,local monitoring of the whole photovoltaic energy storage and power generation system and Ali cloud monitoring are realized based on WiFi232 module.The experimental results show that the monitoring platform can achieve the predetermined functions stably and reliably.(4)On the basis of self-developed prototype,a test platform was established to verify the auxiliary power supply,signal conditioning circuit,maximum power tracking,charging and discharging system,and to test the mode switching of the system.The experimental results show that the designed system has good performance: the maximum power point tracking efficiency of the former Boost circuit can reach 99.89%,and it can achieve multi-peak tracking function;the latter full-bridge circuit carries out off-grid and rectifier tests,the output of off-grid is stable,the dynamic response speed is fast,the grid-connected harmonics under rated power is as low as 3.86%,and the power factor is as high as 98.84%;In the process of switching,there is no obvious voltage and current spike impact,and the fast and smooth transition of working mode is realized.