Research On Output Performance And Parameters Optimization Of Magnetic Coupler For EVs’ Wireless Power Supply

With the popularity of electric vehicles, the EVs’ charging issue emerges. At present, EVs utilize the plug-in approach to get charged, it has various disadvantages including electric leakage, complexity of operating. What’s more, inherent issues of EVs, such as limited mile range and high cost are the main obstructions that make EVs’ development and promotion more difficult. Inductively coupled power transfer(IPT) technology achieves power transfer from grid to EVs’ wirelessly, so the various issues with EVs charging can be solved. In addition to wireless charging, On-road EVs can also be supplied with energy which will add mile range to EVs and reduce the battery size.High power, high efficiency, middle to long distance and highly stable magnetic coupler are the foundation and key point of EVs’ wireless power supply. It can be classified into two types according to EVs running states, Static charging when EVs are static and dynamic power supply when EVs are running. This paper puts emphasis on the structure, efficiency and parameter optimization of magnetic coupler and the validity of theoretical analysis and research methods is verified in practical physical system. The works related to this paper are as follows:① Research on magnetic coupler structure for EVs’ wireless power supply.EVs wireless power supplying needs magnetic coupler to be highly efficient, has good space properties and high power density, the research is based on the three factors. Firstly, high power, high efficiency and high receiving degree of freedom magnetic coupler was designed for the static EVs wireless charging. In the EVs wireless power supplying system, position randomness of the receiving coil is relatively large and can be easily disturbed, so it is important to solve the problem of receiving coil’s insufficient degree of freedom. In addition, there exists two common problems: receiving voltage drop when EVs are running and low coupling efficiency due to high AC impedance of the rails. From the point of the structure of transmitting rail, we put emphasis on the rail structure design approach under cascading supplying mode.② Electrical parameter modeling of magnetic coupler.The electrical parameter model of magnetic coupler should indicate its relationship with efficiency. As coupling model can represent the power transfer process between magnetic couplers, the study investigates the couple model and analyzes magnetic coupler’s influences on the efficiency and frequency properties of the IPT system, through that, the design strategy of electric parameter can be obtained.③ Research of NLP modeling and parameters optimization method in magnetic coupler.Based on the electric parameter model, the function between coupling mechanism structure parameter(mainly coil turns, size) and system frequency was studied, and from this the Non-Linear Programming(NLP) model can be obtained. Multi-objective constraints exist in the NLP model because many variables and constraints are involved in magnetic coupler parameter optimization. Therefore cross entropy algorithm was introduced to handle the optimization problem. Based on the cutting edge thoughts of Pareto, traditional CE algorithm was modified to a more advanced CE algorithm based on Pareto optimum. In addition, Hypercube hypercube sampling was utilized to carry out the population initialization and through adaptive penalty function method, constraint handling is obtained. Ordering rule of the algorithm was changed to enhance MOP processing capacity of the cross entropy algorithm and ensure overall importance of the parameter optimization.The main innovative points of this paper are as follows:① Aiming at the problem of performance evaluation and parameters design for magnetic coupler, a method based on fuzzy comprehensive evaluation is proposed, which contain with the analysis for characteristics of power and efficiency, space and power density. The model of power efficiency characheristic and structure parameter is derived, the problem of blindness and limitation when designing magnetic coupler parameters is solved.② Aiming at the problem of improving the space characteristic for EVs’ wireless power supply,a cross type and a DLDD type coil is proposed based on the distribution of magnetic field, the problems of lacking voltage when switching rail and lacking charging area when EVs’ is wireless charging are derived.③ An improved cross entropy algorithm based on Pareto optimum was proposed according to the Non-Linear Programming(NLP) model with multi-objective constraints in the magnetic coupler the global search capacity of the cross entropy algorithm was increased and multi-objective parameter optimization problem of magnetic coupler was solved.