Design And Implementation Of Distributed PV-Battery System Power Controller

This paper proposes a new type of distributed PV-battery system.The proposed system has good applicability in the application of solar powered UAVs and airships,which have high requirements on energy utilization and reliability,and the surface illumination distribution of which is uneven.Moreover,it overcomes the disadvantages of centralized or common distributed PV-battery systems,such as poor stability,low capacity utilization and low specific power of mass.Through the research on the structure and control strategy of the proposed system,the full utilization of photovoltaic power and energy balance of batteries under arbitrary lighting conditions are realized.Therefore,while ensuring UAV's long-term stable operation,the equipment capacity of the power system can be fully utilized.The main work includes the following four aspects:(1)The theoretical design of the new distributed photovoltaic-battery system structure and operation mode is carried out.The new distributed system consists of a series of PV-battery modules that connected in series and parallel.Each module can be divided into a photovoltaic control unit and a power output unit according to functions.Through the cooperation between modules and the overall power scheduling,the system can run efficiently and stably to meet the needs of special occasions.Then,the grouping method of the PV cell in the system and the influence of the bypass diodes on the system are explained based on the analysis of the PV output characteristics.Thereby ensuring the rational use of PV capacity and maximizing the overall performance of the system.(2)The control algorithms involved in the PV control unit in the system are analyzed,including maximum power point tracking,command power point tracking of PV and battery full charge protection strategy.Through the cooperation of these control strategies,the PV control unit can ensure the safe operation of the battery while maximizing the utilization of PV power.(3)The control algorithms involved in the power-output control unit in the system are analyzed.The U-I droop control is used to realize the power allocation between the strings;within the string,a control strategy that can proportionally allocate the power of each input channel is proposed.The power output unit cooperates with the PV control unit can make the proposed system to meet the load requirements while balancing the battery.So that it can operate efficiently,stably,and safely.(4)The hardware of the PV controller and output controller were designed.The parameters calculation and control circuit design of the two controllers are respectively made to meet the requirements of controlling electric power,sampling,protection,driving,communication and control.