Research On Fuel Cell Serial-parallel Hybrid Power Supply System And Energy Management Strategy

Proton Exchange Membrane Fuel Cell(PEMFC)is a new type of power generation device that directly converts hydrogen energy into electrical energy.The reaction process only generates water and heat.It has the advantages of high efficiency,no pollution,and high reliability.It is widely used in new energy vehicles,distributed power generation and other fields,and has great application prospects.Aiming at the problems of low output voltage,soft output characteristics and no overload during PEMFC power generation,this paper studies the series-parallel hybrid topology to improve the flexibility of PEMFC power generation system,and designs an active network boost converter with charge pump to increase the output vlotage of PEMFC.The power following control strategy is proposed to ensure the stable operation of the hybrid power supply system.Firstly,because the efficiency advantage of the traditional series and parallel hybrid topology is affected by the load power distribution,a high-efficiency series-parallel hybrid topology is proposed to improve the flexibility of the PEMFC power generation system.The pulse load with non-regenerative is used to compare the three topological efficiency,the results show that the efficiency of the series-parallel topology does not depend on the load power distribution,and the efficiency advantage is obvious.Secondly,in order to solve the problem of low output voltage of PEMFC,an active network boost converter with a charge pump is proposed to reduce voltage stress on switch and output diode while increasing voltage gain.The working principle of the converter when the parameters are consistent and inconsistent are analyzed.The advantages of the converter are reflected from several aspects such as voltage gain and voltage stress of the switching.The principle prototype is made for experimental verification.The experimental results confirm the correctness of the theoretical analysis.Then,a power following control strategy is proposed on the series-parallel topology.This strategy determines the operating state of the system and allocates the output power of the power source according to the load demand power and the state of the power source.A simplified PEMFC model and a battery Thevenin equivalent circuit model are established,and the SOC of the battery is estimated by combining the time-of-hour integration and the open-circuit voltage method;Based on the high-frequency network equivalent principle,dynamic models of converters and systems in different states are established,and corresponding closed-loop regulators are designed;A simulation model of a hybrid power supply system is built in Simulink.The simulation results show that the power following control strategy has good stability and rapidity.Finally,an experimental prototype of the hybrid power supply system is set up,the hardware circuit design of the system and the software design based on TMS320F28335 are completed.The experimental results verify the effectiveness of the power following control strategy on the series-parallel hybrid power supply system.