电动汽车电场谐振无线充电理论与技术研究

Aimed at the application of wireless charging for electric vehicles, the project proposes using electric field resonance to achieve efficient mid-long range high-power wireless power transfer. Related theories and technologies will be studied in depth. The complex coupling and stray capacitors among the vehicle chassis, the ground, and the coupling plates are taken into consideration. By incorporating those capacitors into the compensation network system, a wireless power transfer method using electric field resonance, which is a dual circuit of the four coil magnetic field resonance, is proposed. The key factors of achieving high efficient electric field coupling wireless power transfer are analyzed. A multi-objective optimization model considering the reactive power in coupling capacitors and compensation network, the voltage between the plates, will be established. A general optimization algorithm for the parameters of the compensation circuit will be proposed. The effects on power transfer characteristics and device soft-switching when vehicle position shift will be studied. By establishing the switching process model considering high order harmonics, accurate analysis of the soft switching will be conducted. A 3kW wireless charging prototype will be built and setup on an actual vehicle to verify the theoretical and simulation results. The research results may significantly reduce the weight and cost of the sending and receiving pads. It will be an important supplement and perfection of the existing wireless power transfer theoretical system.

针对电动汽车无线充电的应用特点，提出使用电场谐振方式实现中远距离大功率高效无线电能传输，对相关理论和技术进行深入研究。考虑车辆和大地同耦合极板所形成的复杂耦合及杂散电容结构，并将相关电容纳入补偿网络体系，形成和四线圈磁共振方式对偶的基于电场谐振的无线电能传输方式。分析实现高效电场耦合无线电能传输的关键因素，建立基于耦合电容无功、补偿网络无功、极板间电压等多优化目标的模型，提出补偿网络参数的优化方法。研究车辆位置偏移对功率传输特性及器件软开关的影响，建立考虑高次谐波的开关过程模型，对软开关过程进行精确分析。搭建3kW无线充电样机并装置在实际车辆上，对理论和仿真研究结论进行验证。项目的研究成果，可大幅降低电动汽车无线充电设备发射接收盘的重量和成本，将对现有无线能量传输理论体系形成重大补充和完善。

电场谐振方式的电动汽车无线充电系统，可使用轻薄的耦合极板，降低耦合极板的成本，且不存在对车体和金属异物的加热效应，是一种潜在的无线充电技术方式。本项目主要研究内容有：考虑屏蔽后发射接收耦合电容极板的设计与分析，基于电场谐振方式的补偿网络参数的优化设计，碳化硅和氮化镓功率器件的高频驱动技术，电力电子变换器的软开关检测与调谐。经过三年的研究，在以上几个方面均取得了较好的成果，找到了一套补偿网络参数优化设计方法，实现了补偿网络无功最小，并提出了一套将屏蔽和高压补偿电容集成的耦合机构设计方法，掌握了碳化硅和氮化镓功率器件的高频驱动技术，提出了一种低成本的软开关状态精确检测方法。所提出的软开关检测方法，可在500kHz频率下判断无线电能传输系统的软开关状态，并以此进行调谐，实验验证系统效率比固定500kHz固定频率提高3.1%。提出的参数补偿优化方法，从理论上求出了使得补偿系统无功最小的补偿网络参数，同之前论文中的结构相比系统效率从91.6%提高到93.2%。项目研究中有关软开关的成果，可广泛应用于高频电力电子变换器提高频率和功率密度。而补偿网络最优参数的相关研究成果，有望成为电容式无线电能传输谐振补偿网络的设计准则。