A switched-capacitorless energy-encrypted transmitter for roadway-charging electric vehicles

Abstract

Due to cleanliness, convenience and high efficiency, wireless power transfer (WPT) technology has been extensively and deeply investigated. In recent years, energy encryption has drawn researchers' attention to satisfy practical requirements of security and reliability in the theme of intelligent transportation and smart city. Especially for roadway-charging electric vehicles (EVs), the use of energy encryption can guarantee the transmitted energy being effectively harvested by the authorized receptors instead of being secretly stolen by the unauthorized ones. Recently, a chaotic encryption strategy based on switched capacitor arrays has been proposed to realize energy security in WPT systems [1, 2]. However, because of the need of discretely adjusting the resonant capacitance and hence the operating frequency, this encryption scheme suffers from the drawbacks of limited energy-transferred channels, high voltage stress across switches and relatively low flexibility. In addition, a generic encryption model based on certificate-less cryptography has been developed to improve the energy security performance for WPT systems [3], but its computational complexity and time involved seriously restrain from dynamically encrypting the operating frequency. Meanwhile, a traditional series-to-series (SS) topology with fixed values of resonant inductance and capacitance has been identified to exhibit a selective characteristic for multiple loads when operating at the selected receptor's resonant frequency [4]. This mechanism can be newly extended to derive an energy-encrypted transmitter without using a switched-capacitor array for multiple energy receptors such as roadway-charging EVs. Consequently, in this paper, a switched-capacitorless energy-encrypted transmitter is proposed for roadway-charging EVs. Moreover, a two-dimension chaotic frequency-and-duration encryption (FDE) algorithm is proposed to improve the security performance while maintaining relatively high efficiency.