Comparative Evaluation and Simulation of Current Control Methods of LLC Converters in EV Battery Chargers

The aim of this paper is to provide guidelines for a feasibility study on the most suitable current control of a high efficiency resonant LLC converter used in battery chargers for electric vehicles. This paper analyzes and compares three current control methods of a full bridge LLC resonant converter. After a brief analysis of the operation and of the requirements of the current control in a resonant LLC converter, three generally used current control methods are introduced. The converter analysis is based on the first harmonic approximation in order to simplify the system model. The dynamic performances are evaluated by several simulations based on an actual application. The full bridge LLC resonant converter is designed for an actual 3.3 kW on-board battery charger for electric vehicles. Finally, advantages and drawbacks of the different current control methods are explained to allow a critical evaluation for an accurate LLC resonant converter control design.