| As an effective means of alleviating the energy crisis and improving the environment, Electric Vehicles (EVs) have drawn attention from governments, car manufacturers and energy companies, and been gradually popularized and applied worldwide. Compared with the traditional conductive charging mode, wireless charging for EVs, based on the wireless power transmission technology, has many advantages such as making charging more convenient by setting program to charge automatically without man management after parking, and more secure as settling the issues of wire aging and leakage without mechanical friction and exposed cables. It can not only interact with the grid, more efficiently to suppress the fluctuations of the output of renewable energy and reduce the impact on the power grid, but also improve the mileage of EVs with the smaller capacity and size of battery. This technology is in favor of the development and popularization of EVs. However, with the popularity of EVs in the future, the large-scale access of EVs to the grid will have the significant effect on the entire grid. Coordinated control of EVs charging and discharging is the inevitable trend of the development of smart grid.In the EVs wireless charging system, how to design the appropriate compensation topology according to various types of vehicles and how to make this system more stabilized and efficient by introducing the optimized control technology remain the important problems to be solved. Meanwhile, for the significant temporal and spatial distribution characteristics of EVs charging load, how to make more accurate load calculation and more effective coordination control of EVs charging and discharging are the main issues to reduce the impact of large-scale EVs on power grid so as to better promote the development and popularization of EVs.Firstly, this dissertation gives a description of the basic principle of wireless charging technology for EVs, a comparative analysis of its four main implementations, as well as a review of the research status and application progress at home and abroad of EVs wireless charging technology and the impacts of EVs; Next, compared with the plug-in charging model, the ability and advantages of interacting with power grid of the EVs based on wireless charging model are analyzed and investigated. Then, several key issues are studied, such as topology design, optimal control of wireless charging system, optimal design of parking system, EVs charging load forecasting and optimal control of EVs battery swap station. Finally, a test platform is built for EVs wireless charging and related experimental studies are carried out. Based on the idea of hierarchical partition, a four-layer V2G system has been designed, which consists of distribution network scheduling management system, subarea scheduling management system, charge/discharge area management system and vehicle-mounted intelligent terminal.Some achievements have been made in this dissertation and the main innovative contributions are as follows.1. Aiming at the problem of the resonant compensation capacitances of transmitting coil varied with load except SS topology, a phase controlled inductor circuit is proposed and applied to SP topology in experiment. By detecting real-time voltage and current of receiving coil and adjusting the triggering angle to make the impedance angle of receiving coil equal to zero, the dynamic tuning control can be achieved to optimize system with maximum power transfer. The presented measures can guarantee the flexible applications of all topologies in the field of EVs wireless charging.2. To solve the problem of transmission performance degradation caused by the misalignment between transmitting coil and receiving coil when EVs parking, a novel design method of wireless charging parking is proposed to optimize the transmission performance by moving or rotating the transmitting coil to seek the local maxima of coupling point within its activity range. This technology could provide some technical support for the practical application of EVs wireless charging system.3. Based on the real-time SOC, the single EV charging power model for wireless charging has been set up. Furthermore, considering electricity price, development of wireless charging technology and coordinated control of charging and discharging, four scenarios have been established to analyze the influence of large-scale EVs on the grid.4. Concerning the problem of optimal control on EVs battery swap station, a SFLA-based optimal control strategy and its realization have been proposed. The minimum variance of the local load profile including the charging load generated by EVs battery swap station is set as the optimization objective, and the nonlinear optimization models have been established for the charge mode and the bidirectional-power mode. According to the two modes, the frog positions have been variously defined to solve the proposed mathematical models to minimize the variance with a better control effect. |
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