Reliable Cooperative Charging Protocol For Supercapacitors Charging Systems

As energy storage devices,supercapacitors have the superiorities of fast charging speed,long service life,high energy efficiency and environmental.Therefore,supercapacitors are extremely important in green transportation system.For example,supercapacitors are widely used in catenary-free trams,because they can solve the problems of a short charging time and a high charging current.The main challenge of supercapacitors while being used in catenaryfree trams is the high-power-charging load.The charging current of supercapacitors is too high that a single-module charging system can hardly satisfy.A distributed charging protocol is a promising method to handle with the problem.The distributed charging protocol is a kind of multi-module low-power charging protocol,it adds information interaction among charging modules to reduce current imbalance which may cause circulation in circuit.The limitation of the distributed charging protocol is that it highly relies on the accuracy of data and the reliability of all the charging modules.However,the vulnerabilities of hardware and software may cause fault data or output error,which are inevitable.In this case,the charging system under the distributed charging protocol becomes unreliable.In this thesis,we design reliable charging protocols basing on the distributed charging protocol to solve the problems of fault data and output error.In addition,we prove the reliability of the protocols by analysis,simu-lation and experiment.Our major contributions are summarized as follows:· We summarize the development of catenary-free trams and supercapacitors,introduce the research status of charging methods and control strategies.The research status of security in charging system is also expounded.And we analyze the shortcoming of the existing works,put forward the significance and innovation of this paper.· The causes and effects of fault data in cooperative charging system are analyzed first.Then,we propose a cooperative charging protocol with a date screening mechanism.We show the protocol can guarantee the reliability of the charging system from fault data by analysis and simulation.We build an experimental platform of charging system and take experiments to verify feasibility of the protocol.· We introduce the causes and effects of output error in cooperative charging system.We design a cooperative charging strategy with charging demand being input on all charging modules.Stability of the charging system under the strategy is proof by Layapunov stability criterion.Both simulations and experiments are conducted to verify the reliability of the strategy.· Fault data and output error are both unreliable data.To guarantee the reliability of charging system with any unreliable data,we propose a reliable cooperative charging protocol.We also prove the feasibility of the protocol by analysis,simulations and experiments.Finally,we make a summary and give a prospect.