An Improved Control Strategy for Bidirectional Wireless Power Transfer in Grid-to-Vehicle and Vehicle-to-Home Applications Using a Fuzzy Logic Controller

Abstract: The progress in the charging strategies for electric vehicles is expected to have significant impacts on the electric grid in the near future. Electric vehicle battery chargers are designed to facilitate bidirectional power transfer in accordance with the vehicle-to-grid concept, thereby providing essential services to both the distribution grid and the domestic grid of the vehicle owner. Wireless power transfer battery chargers present a safer and more user-friendly option for individuals who may lack confidence in handling technological devices. Bidirectional wireless power transfer chargers that support vehicle-to-grid services represent a natural progression of the previously mentioned concepts. This paper addresses the development of a control strategy for such a battery charger, concentrating on the requirements of the power conversion stages necessary for the operation of a charger designed for vehicle-to-home functionality. Initially, the division of the control strategy into two distinct levels is discussed, followed by an introduction to the interaction between the algorithms at the internal and external levels. In the implementation of the control algorithms, the decision was made to design the controllers with simplicity in mind. This approach allowed for the adoption of well-established techniques within the scientific community for their design, while also minimizing the computational resources required for their execution. Despite the straightforward nature of the controllers, the introduction and management of interactions among the various algorithms resulted in the formulation of a comprehensive control strategy that simultaneously adheres to the voltage and current limits imposed by the grid and the battery, while also preventing the maximum operating conditions of the static converters that comprise the system from being exceeded. The algorithms and their corresponding controllers are developed sequentially in the continuous time domain, utilizing techniques grounded in the analysis of Bode diagrams of the transfer functions integral to the system's operation. In the design of the controllers, the implications of their subsequent effects are also taken into account.