Research On Design And Control Strategy Of Dynamic Wireless Charging System For Electric Vehicles

With the rapid development of the global economy,it has brought about the increasingly depleted fossil energy and the continuous deterioration of the environment.Exploring the methods and technologies to solve energy and environmental problems has become one of the most popular research directions in the world today.Electric vehicles(EVs)have the characteristics of high energy efficiency and low polluting gas emissions,and have great advantages in energy saving and emission reduction and reducing human’s dependence on traditional fossil energy.In order to achieve the goal of carbon peak and carbon neutrality,the development of EVs is a strategic choice to promote green development and ensure energy security.At present,the development of EVs is limited by the imperfect construction of charging facilities and the current charging problems.The wired charging method mainly used in EVs has problems such as inflexible charging,poor user experience,anxiety about mileage,poor environmental adaptability,and bulky batteries.In addition,EVs are developing towards intelligence,connectivity and sharing.EVs with autonomous driving capabilities will become a research hotspot.In the future of autonomous EVs,wired charging can no longer meet the requirements of intelligence.Wireless charging technology for EVs based on the principle of magnetic coupling wireless power transfer(WPT)provides new ideas for solving the charging problem of EVs.In particular,the technology of dynamic wireless charging for EVs(EV-DWC),which is one of the frontier hotspots in this field,has received extensive attention.The EV-DWC technology can enables EVs to be charged during driving,and has the characteristics of no mileage anxiety,fewer or no batteries,and lower costs.The technology of EV-DWC has not been widely used,and the EV-DWC system design and charging control strategy are still in the preliminary research stage.The dynamic wireless charging technology of cluster EVs for large-scale EVs is also in urgent need of research.The cluster EV-DWC system involves system design and modeling,characteristic analysis,power fluctuation suppression,efficiency optimization and other issues that require in-depth research.For the cluster EV-DWC system based on long-track transmitting coils,it is necessary to design the number of EVs allowed by a single long-track transmitting coil and propose corresponding charging power and efficiency optimization control strategies.And the cluster EV-DWC system based on short-segmented transmitting coils has multiple transmitting coils energized at the same time,and the connection methods and driving modes of the transmitting coils are also diverse.Therefore,the design of the cluster EV-DWC system based on short-segmented transmitting coils is more complicated.It is also necessary to study the ground-end integrated circuit suitable for the short-segmented transmitting coil structure to reducing the construction cost.Moreover,there is uncertainty in the number of cluster EVs,which not only affects the design of system parameters,but also puts forward higher requirements for charging control and system efficiency optimization strategies.In response to the above problems,this dissertation focuses on the design and control strategy of dynamic wireless charging system for EVs.The main contents include:1)The EV-DWC system design and charging control strategy based on the DC/DC circuit at the vehicle-end.The circuit model of the EV-DWC system with one transmitting coil and one receiving coil is analyzed.Different resonance compensation topologies are compared and analyzed,and the resonance compensation topologies suitable for EV-DWC system are discussed.Based on the analysis of the EV-DWC system with LCC-S compensation topology and the DC/DC circuit at the vehicle-end,the power fluctuation suppression strategy based on Buck-Boost circuit on-line real-time adjustment of duty cycle is proposed.2)The EV-DWC system design and charging control strategy based on the controllable rectifier circuit at the vehicle-end.The circuit model of EV-DWC system with a structure of double-sided LCC compensation topology and containing controllable rectifier circuit at the vehicle-end is established.By analyzing the output characteristics of the system,the expressions of the key parameters of the system are derived.The constant current/voltage charging control strategy based on the phase shift control of the controllable rectifier circuit and the efficiency optimization strategy based on dynamic equivalent impedance matching are proposed,which also lays the foundation for the research of cluster EV-DWC system.3)The design and charging control strategy for cluster EV-DWC system based on long-track transmitting coils.Established the cluster EV-DWC system mathematical model based on the long-track transmitting coils,and analyzed the output characteristics of the system.Considering factors such as vehicle speed,power supply capacity,safe braking distance,and overall system efficiency,a method for designing the number of EVs allowed by one long-track transmitting coils is proposed.A charging power control strategy adapted to the driving speed of EVs based on the controllable rectifier circuit at the vehicle-end and the strategy for optimizing the system efficiency in a variable quantity EVs are also proposed.4)The design and charging control strategy for cluster EV-DWC system based on short-segmented transmitting coils.The basic structure of the cluster EV-DWC system with short-segmented transmitting coils is introduced,and the design method based on the integration of the ground-end circuit is proposed.The output characteristics of the cluster EV-DWC system with parallel-connected transmitting coils are analyzed,and mathematical expressions such as the optimal transfer efficiency and the optimal equivalent impedance are derived.Finally,the ground-end integrated circuit design method and control strategy,the charging power control and system efficiency optimization strategy are proposed for the parallel-connected transmitting coils of cluster EV-DWC system,which greatly reduce the hardware cost of the system.