Study On Power Management Strategy For Miniature Fuel Cell-Battery Hybrid System

As a newly arisen energy source, fuel cell has broad application prospects because of its high efficiency and cleanness. The hybrid power source, which consists of miniature fuel cell and auxiliary power and is used to power mobile electronic equipments, is a research focus in recent years. The research on power management strategy for miniature fuel cell is studied in this thesis.By taking the miniature Direct Methanol Fuel Cell (DMFC) / lithium ion battery hybrid power sources as the research object, the power management strategy is studied through analyzing passive management,half-passive management and active management. Through method of voltage limiting power, the power matching between DMFC and lithium ion battery is analyzed under charging and mix-discharging modes.For the DMFC/lithium ion battery hybrid power source managed by passive strategy, the current direction and power distribution in hybrid power source are determined during the process of system design based on the charging characteristic of lithium ion battery and method of voltage limiting power. The management system for hybrid power source is established with MSP430 single-chip microcomputer as the controller, which keeps the hybrid power source running through current and voltage collection. The power matching is verified by using serials of square wave simulation loads connected to the hybrid power source. Results show that the current direction and power distribution are consistent with that of analysis.For the DMFC/lithium ion battery hybrid power source managed by half-passive strategy, a switch control link is adopted between main and auxiliary battery to reduce energy flow in hybrid power sources and improve efficiency. The DMFC hybrid power source powering mobile phone is established with MSP430 single-chip microcomputer as the controller. Meanwhile, the working parameters is displayed by LCD module and sent to computer through RS232 serial port. The power matching is verified by using serials of square wave simulation loads connected to the hybrid power source.For the DMFC/lithium ion battery hybrid power source managed by active strategy, an active control circuit is designed with MSP430 single-chip microcomputer,DC/DC converter and digital potentiometer. The control strategy is designed to realize active power matching control for hybrid power sources. The feasibility of active control strategy is verified by using constant simulation loads and varying simulation loads.