Distributed Photovoltaic Power Generation System Based On Supercapacitor Hybrid Energy Storage

The development of distributed photovoltaic power generation is an advantageous way to achieve carbon peak,carbon neutralization and target in China,and it is also the trend of new energy development.In view of the randomness and intermittentity of photovoltaic power generation,a hybrid energy storage method based on supercapacitor is applied to distributed photovoltaic power generation system.By using the charging and discharging characteristics of supercapacitor and batteries,the high and low frequency voltage pulsations on the bus side of photovoltaic DC are suppressed,which is helpful to improve the stability of distributed photovoltaic grid-connected system.The main research contents are as follows:First,the overall structure of distributed photovoltaic power generation system is constructed,and the influence of each part on the power stability of DC bus side is analyzed.By analyzing the working principle and modeling of each part,the changes of irradiance,temperature and DC load will affect the stability of DC bus side power.Secondly,the working characteristics of the accumulator and the supercapacitor are analyzed.The accumulator can effectively handle the average voltage pulsation in the distributed grid-connected photovoltaic power generation system,and the supercapacitor can effectively handle the instantaneous voltage pulsation.Therefore,a method to suppress DC bus voltage pulsation by combining supercapacitor with accumulator is presented.Then,the supercapacitor-inductor-accumulator hybrid storage structure is proposed by analyzing the advantages and disadvantages of several common hybrid storage modes.The hybrid energy storage structure is composed of batteries connected in parallel by inductors and super capacitors.The inductors and super capacitors can form a high frequency filter,which not only suppresses the high and low frequency voltage pulsation of DC bus,but also filters out the high frequency harmonics flowing to the batteries,improves the life and operation efficiency of the batteries.The structure is small in size and low in cost,and is suitable for distributed photovoltaic power generation systems.Finally,the hardware circuit of distributed photovoltaic power generation system based on supercapacitor hybrid energy storage is designed.It mainly includes main circuit,control circuit,sampling circuit,over-voltage and over-current protection circuit,drive circuit and so on.The main circuit is composed of Boost conversion circuit,SCBI hybrid energy storage circuit and grid-connected inverter circuit.The results show that the voltage pulsation of dc side is less than 7%,the battery output current is stable,the inverter side outputs smooth sine wave voltage,and the grid-connected current THD is 1.81%.Experimental results show that the proposed hybrid energy storage circuit can effectively suppress the high and low frequency fluctuation of photovoltaic DC bus voltage,and the power quality is good and meets the requirements of grid connection.Fig.[74] Table [2] Reference [81]...