access icon free Minimum resonant capacitor design of high-power LLC resonant converter for comprehensive efficiency improvement in battery charging application

© The Institution of Engineering and Technology
Received 14/09/2017, Accepted 15/05/2018, Revised 03/04/2018, Published 16/05/2018

Here, a minimum resonant capacitor design approach is proposed for the insulated-gate bipolar transistor (IGBT)-based high-power LLC resonant converter to improve its comprehensive efficiency in the electric vehicle (EV) battery charging application. The mathematical model of LLC resonant converter is established by using the first harmonic approximation (FHA) method. Then, the switching losses of IGBT-based high-power LLC resonant converter are analysed. Also, the relationship between predominant turn-off losses and turn-off current of power device IGBT is derived. To improve the comprehensive efficiency, the minimum resonant capacitor is proposed to reduce the turn-off losses, avoiding complex control or auxiliary circuit. Finally, the proposed approach is verified by a 2 kW LLC resonant converter prototype with 690 V DC input voltage and 75–150 V DC output voltage. Experimental results show the comprehensive efficiency of the prototype is up to 93.7%.

Inspec keywords: secondary cells; insulated gate bipolar transistors; switching convertors; resonant power convertors; power capacitors; electric vehicle charging; bipolar transistor circuits; battery powered vehicles; approximation theory

Other keywords: minimum resonant capacitor design approach; voltage 690.0 V; IGBT-based high-power LLC resonant converter; FHA method; LLC resonant converter prototype; insulated-gate bipolar transistor-based high-power LLC resonant converter; switching losses; voltage 75.0 V to 150.0 V; first harmonic approximation method; power 2.0 kW; EV battery charging application; comprehensive efficiency improvement; electric vehicle battery charging application; power device IGBT

Subjects: Secondary cells; Interpolation and function approximation (numerical analysis); Other power apparatus and electric machines; Automobile electronics and electrics; Power convertors and power supplies to apparatus

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