Research On Wireless Charging System Of Electric Vehicle Based On Magnetic Resonance

With the exhaustion of energy and the serious environmental problems, saving energy and reducing waste emissions are getting more and more attention. Reducing energy consumption in the field of transportation is an important part of environmental protection. Under this background, electric cars are getting extensive attention because of its low energy consumption and low pollution. At present, the electric vehicle charging problem has become one of the main factors restricting its promotion. Cable charging method has many problems, such as wear and tear, producing electric spark, unsafe and so on. Wireless charging mode can provide electrical energy flexibly and it has no electrical connection, can effectively solve the defect of cable charging. This charging mode can promote the application of electric vehicle.This paper developes a wireless charging system for electric vehicles. The system is based on the principle of magnetic resonance coupling, in the middle of the transmission distance, can realize high efficiency and high electric power transmission. The balance coil metal detection technology is applied to the wireless charging system, solving the safety problem of metal mixing in the field of magnetic field. The electrical energy transfer efficiency can be effectively improved.Firstly, the principle of magnetically-coupled resonant wireless power transmission is studied by using the mutual inductance coupling theory. The transmission properties of two kinds of structures are compared, which are series-series resonance(PSSS) and series-parallel resonance(PSSP). This paper establishes the magnetic field simulation model and electric field simulation model, analyses the influence of main parameters on the output power and transmission efficiency, including load resistance, coupling coefficient and frequency. The system chooses series-series resonant (PSSS) compensation structure.Then based on the Ansoft electromagnetic simulation, the system adopts asymmetric flat magnetic core structure, to enhance the strength of the magnetic field and improve the robust performance of the system. Combined with metal detection technology based on balance coil, a modified balance coil structure is proposed. The function module of metal detection is developed. The paper designs control circuit with STM32F103 as core and completes the design of hardware circuit, including rectifier circuit, DC-DC circuit, high frequency inverter circuit, high-frequency rectifier circuit, drive circuit, sampling and protection circuit. Information transmission via Bluetooth wireless communication technology, to realize the closed-loop control. The system uses three-stage charging method, and complete the writing and debugging of the software program.Finally, the charging performance of the system is verified by experiments. Experiments show:in the vertical distance 200mm, the horizontal displacement in the range of 100mm, the system can achieve the maximum charging power of 2kW and the highest power transmission efficiency can reach 86.7%.