Study On The Combined System Of The Photovoltaic Generation And Energy Storage Based On The Lead-Acid Battery

With the rapid development of the microgrid,it is an inevitable development trend in the future that the distributed energy storage units are used in the microgrid to regulate the energy and realize the interaction with the microgrid.The combined system of the photovoltaic(PV)generation and energy storage based on the lead-acid battery and its related control strategies are studied in this paper.The combined system consists of a PV array and its converter,charging and discharging circuit of the lead-acid battery,etc..The PV array provides the energy for the load,and the excess or insufficient energy is dynamically adjusted by the battery charge and discharge.The core of the energy management system is that the inverter and bi-directional DC-DC converter are controlled to work in the appropriate mode in the light of the operating state of the PV array and battery and the relationship between the DC bus voltage and real-time charging or discharging power,therefore,the PV array and the battery work in coordination to ensure the efficient and stable operation of the power supply system and has the rapid dynamic response.First of all,the charging and discharging characteristics of the lead-acid battery are analyzed by combining the mathematical model,and the charging and discharging control strategies are made by the demand function.Secondly,the bi-directional DC-DC converter and its working principle are analyzed in detail,the similarity and difference between independent PWM control mode and complementary PWM control mode are compared,mathematical models of the bi-directional DC-DC converter in Buck mode and in Boost mode are established respectively,on the basis,the driving mode of three interleaved DC-DC conveters,and the causes of unbalanced current in the driving mode are analyzed in detail,the corresponding interleaved parallel current sharing control strategy is formulated.In the case of parallel connection of multiple bi-directional DC-DC converters,two working modes of charging and discharging are analyzed,and the corresponding charging and discharging control strategy is studied.The circuit model is built in PSIM simulation software,and the feasibility of these control algorithms is verified.Then,considering the actual changes in the external environment,the working mode of the combined system is analyzed.According to these conditions,the corresponding energy coordination control strategy is discussed,and the circuit model is built in PSIM simulation software.Finally,the system software and hardware implementation scheme are designed,and the main circuit parameters such as the inductance,capacitance and switching device are designed according to the rated capacity of the system.The experimental platform is built based on Infineon XE164 FN microcontroller,control algorithm program is compiled,and the rationality and feasibility of the control strategy are proved by the experimental results.