Optimization Of Resonant Inductance In LLC Resonant Converters For Charging Piles

The resonant inductor is the key components, which plays a decisive role in achieving the soft-switching. Mostly single air-gap structure is used for the magnetic circuit structure of the traditional resonant inductor, and when the resonant inductor is working, the problems of local overheating and high temperature rise appear. It does not only affects the normal operation, but also shortens its lifespan and reduces the overall efficiency. For the problems of the car battery pile with a single air-gap resonant inductor, the resonant inductor with three air-gap magnetic core is proposed.The resonant inductor of the car battery pile with high-power LLC resonant converter is modeled. The circuit topology and the working process of the converter are analyzed in this paper. For the core structure and material of resonant inductor, this article makes a comparison and analysis and chooses the core material which is suitable for the resonant inductor of the car battery pile with LLC resonant converter,and three air-gap magnetic core of resonant inductor is presented. With the method of magnetic and thermal field modeling, this paper presents a structure of resonant inductor based on the finite element theory on high power LLC resonant converter. The finite element analysis software ANSYS is respectively used to establish the three-dimensional(3D) mathematic model of a single air-gap and three air-gap resonant inductor.The magnetic and thermal coupling simulation of three-dimensional mathematical model of resonant inductor is made. Based on a single air-gap resonant inductor and three air-gap resonant inductor modeling and simulation, the magnetic induction intensity vector diagram of single air-gap resonant inductor and three air-gap resonant inductor is respectively obtained, and induction intensity distribution cloud of magnetic core is also gained; Through electromagnetic field and temperature field coupling simulation, temperature distribution cloud of the single air-gap and three air-gap resonant inductor is obtained; In the view of theory, the influence of air-gap on the temperature rise and loss of resonant inductor is analyzed, and the reason of local temperature of a single air-gap is also given; By further simulation of three air-gap resonant inductor, the temperature gradient vector diagram of different air-gap location is obtained, and by adjusting the air-gap position and repeated simulation, the optimal placement of three air gap curve is given, so the best of the three air-gap in the resonant inductor core is obtained.The project of three air-gap resonant inductor is validity by electromagnetic field and temperature field coupling simulation and experimental analysis, and successfully applied to the car battery pile.