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Research On Dynamic Equalization Of Supercapacitors Bank Applied In Electric Bus

Posted on:2008-01-27Degree:DoctorType:Dissertation
Country:ChinaCandidate:Z G KongFull Text:PDF
GTID:1102360245996577Subject:Motor and electrical appliances
Abstract/Summary:PDF Full Text Request
Energy is an essential element factor for human survival. The energy storage technology, close to human life, develops with new industry technology, new material and new fabrication technology. And one of its latest achievements is supercapacitor (SC), for which commercialization products with a relative low capacitance have been widely used in different fields. Traction SC appears to have incomparable advantage and promising application prospect in space power supply, electric vehicle, electromagnetism launch, and so on. Better use and protection of super capacitor is the key for the development of energy storage technology. So it needs to grasp the SC external characteristics exactly and build an electrical model with definite physical significance. On the other side, series connected SC bank is needed to meet the load power and voltage rank for the unit voltage is low. But the energy stored will not be completely used for the non-uniformity of cells'characteristics, which results in the increase of energy storage equipment cost. Guarantee of work uniformity of each unit in series to improve energy storage use factor is difficult for application of SCs. And traction SC can provide an acceptable solution in some specific occasions with its high power density and long cycle life. The correlation research is a beneficial discussion, also has certain foresightedness and some impetus function regarding SC promotion.In this paper, traction SC is regarded as"black box", whose external characteristics are obtained through experiment to establish characteristic described model. Coupled with its practical application, the SC's external characteristics are researched in different process, such as charge and discharge with constant current, with constant power, with constant voltage but limited current, and discharge with constant resistance process, circulation charge and discharge process, et al. Experimental phenomena above can be explained perfectly by characteristic described model based on comprehensive analysis. Also the relationships between model parameters and operation voltages and currents are studied. Based on reasonable simplified analysis, model parameters are obtained through characteristic operation interval and special experimental method. Simulation results verified the rationality of characteristics described model.Modeling and analysis method for equalization structure based on the directed graph is advanced. Existing equalization circuit is analyzed through completeness and the weight conception of directed graph. It is indicated that there is isomorphic graph in both switch/relay equalization technology and transformers equalization technology with multiple output windings. And that's the same to high speed switch capacitor network equalization technology and distributed DC-DC transducer equalization technology, and it is not the superior structure because its longest trace has a big weight. Diagrammatic representation of the perfect equalization structure for equalization circuit is proposed, and graph of derivation structure based on distributed converters is analyzed. It is pointed out that some structures have ideal equalization graph in the view of energy transfer, and this is a new research direction. As SC's characteristics are considered, a new equalization structure based on buck-boost converter and ?UK converter are proposed. Furthermore, it is analyzed with graph theory and simulated. A design method for equalization structure of reasonable group, dichotomy group and reasonable assembled group are also described, which could improve efficiency of the equalization technology application in ultra long series SC group, which was simulated.Dynamic equalization technology (DET) is proposed to improve stored energy use efficiency. Firstly, embarked from the balanced technique origin, general questions about DET are analyzed. It is revealed that the purpose of DET is to fully use limited energy storage with safely operation, Secondly, coupled with DET distinctiveness of SC, state pre-estimation based control algorithm is advanced to meet the demand of dynamic performance, and also design method for its hardware and software is proposed. Equalization circuit and SC are regarded as a body, and dynamic equalization is realized with fuzzy control. The feasibility of DET and rationality of design method are confirmed by simulation and experiment results.An acceptable and compromise solution for city transportation are shown with traction SC as the only on-board emery storage equipment on electric bus. Firstly, large voltage variation range and low voltage rand of SC are consider, several bidirectional power converters are comparative studied. As a result, a solution to satisfy vehicle operation using half bridge and gearbox is given. Furthermore, a passive snubber soft switch converter is designed. Experimental results show that it has satisfactory efficiency and reliability. Secondly, a method to optimize vehicle performance by means of variable step tracing is proposed. Vehicle performance experiments show that the short and medium transportation can be satisfied by electric bus with SC as the only on-board energy storage apparatus, and the vehicle has high efficiency under frequently start-stop and accelerate- decelerate operation condition.
Keywords/Search Tags:Traction supercapacitor, Characteristics described model, Dynamic equalization, Directed graph, Electric bus
PDF Full Text Request
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