| As the shortage of energy and the aggravation of environment pollution, specialattention has been paid to renewable energy sources. The road of sustainabledevelopment is the trend of globalization. World countries are scrambling to develophybrid and pure electric vehicles, photovoltaic, wind power and other new energyapplications in order to minimize the dependence of on non-renewable resources suchas oil. These power equipments need energy storage devices. Lithium battery for itshigh terminal voltage, low self-discharge rate, the energy volume ratio and no memoryeffect, excellent performance has been widely applied, but in the process of use, theseries lithium batteries because of the energy state inconsistency in single cells causedamage to single cells. So the battery pack requires the balance of energy to keep thesame battery energy state and extend the life of the battery pack. At present，domesticand foreign scholars have done some research on the equalization for series-connectedlithium battery string. However, in the field of equalization circuit and control algorithm,there are still some problems, such as structure complicated, balancing speed andaccuracy poor, low efficiency and so on. In response to this situation, this paperproposes a novel improved Cuk two-way nondissipative equalization circuit and afuzzy-PI controller to carry through lithium battery pack energy equalization control,this paper uses the battery voltage to represent battery’s state of charge, so energyequalization control in this text means equalization voltage control. The main work ofthis paper is as follows.①An improved Cuk two-way nondissipative equalization circuit is proposed,which eliminates the problems of structure complicated and poor portability in theprevious circuits. Then this paper establishes lithium battery pack charge and dischargedistributed energy control system, studies the energy transfer pathways and theexchange process and analyzes the mathematical model in detail by circuit structure.②In response to the improved Cuk two-way nondissipative equalization circuit,this paper studies the fuzzy control algorithm widely used in lithium battery packenergy equalization management. According to lithium battery pack system models, thispaper improves fuzzy control algorithm, which is PI controller is added into fuzzycontroller to form fuzzy-PI compound controller. This controller eliminates theproblems of control accuracy poor, voltage oscillation, and solves energy distributed control algorithm problem.③According to the proposed two-way nondissipative equalization circuitstructure and new controller, this paper designs system experimental hardware prototype,including system voltage, current, temperature sampling, energy balance, the MOSFETtransformer-isolated drive control, charge and discharge control, man-machine interfaceand power supply circuits. After the proper debugging of the functional modules, thehardware prototype can meet the follow-up experimental validation.④After comparing several equalization circuit experimental results, this paperverifies, compares and analyzes both fuzzy and fuzzy-PI control algorithm byexperiments, and gives the experimental results. The proposed equalization circuitstructure and fuzzy control algorithm are more effective. And then fuzzy-PI compoundcontroller is used in the new hardware prototype, solving energy equalization controlproblems for series-connected lithium battery string in charge and discharge process.In response to the problems on the equalization for series-connected lithium batterystring at present, this paper studies and compares existing equalization circuit structuresand control algorithm, illustrates their shortcomings and proposes a novel equalizationcircuit structure and fuzzy-PI compound controller in battery pack energy equalizationmanagement. System experimental hardware prototype is designed. Finally, the resultsof simulation and experiment show that the novel improved Cuk two-waynondissipative equalization circuit and fuzzy-PI control algorithm proposed in thispaper used in combination can effectively solve the problem of lithium battery packenergy nondissipative equalization management. The system achieves the anticipatedfunctions and meets application requirements. |
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