Design And Implementation Of Low-Voltage Photovoltaic System Integrated With Battery Energy Storage

The photovoltaic(PV)power generation systems are susceptible to external meteorological conditions.In field applications,PV systems are usually combined with battery energy storage systems to form integrated power generation systems,and suppress output power fluctuation.In low power application scenarios,power converter topology optimization and fine energy management are effective methods to improve the overall efficiency of the power conversion system.Aiming at efficiency improvement,this study proposes a series partial power converter(SPPC),which is suitable for sources and loads with near voltage levels.Also,a lithium-ion battery management system(BMS)regulating the state of charge(SOC)is studied.According to the power and voltage levels of PV sources and target battery packs,a continuous current and boost SPPC topology based on Cuk converter is constructed.The operation modes of the converter are analyzed,and component parameters are calculated.Based on the average model of Cuk converter,time and frequency domain characteristics of the Cuk and the SPPC are analyzed using LTspice software.The incremental conductance algorithm of PV maximum power point tracking(MPPT)for SPPC is studied,and the control system is simulated in PSIM software.A control system realized by dsPIC33FJ06GS101 and ATmega328p is designed.The main circuit,signal detection and conditioning circuit,driving circuit and charge state management circuit based on bq34z100-G1 are designed.The efficiency verification test of SPPC in laboratory environment is completed,with outdoor start-up test,photovoltaic full cover test and steady-state operation test under different power levels.The results show that the SPPC can achieve 95%-98%converter efficiency with the 87W-242W power range.The incremental conductance method based on SPPC can realize dynamic MPPT under constant illumination and changing meteorological conditions.The BMS transmits battery charge status information to the main controller through I2C,which can realize the system operation management based on battery status.