Advanced control and analysis of energy conversion systems for electric vehicles

Abstract

By utilizing the electric motor as the propulsion system, the electric vehicle (EV) establishes a new bridge between renewable energies and our daily life, which meanwhile has to face with a brand new technical issue, namely the energy management and conversion. Then, the performance of energy conversion systems has become a new evaluation criteria for EVs. Accordingly, this study works on the analysis and control of the EV energy conversion system, including the secure charging system via wireless power transmission (WPT), advanced driving control via electric propulsion system, and bidirectional power interface via electromagnetic interference (EMI) mitigation technique.

First, this study proposes a novel energy encryption algorithm for WPT systems. In the presented scheme, the energy can be encrypted by chaotically regulating the frequency of the power source based on the unpredictable security key. The authorized receptor can effectively receive the energy by simultaneously adjusting the circuit to decoding the encrypted energy based on the acquired security key, while the unauthorized receptor cannot obtain the energy without knowledge of the security key. In this study, both simulation and experimental results are provided to verify the feasibility of the proposed secure WPT system.

Subsequently, this study proposes a new dynamic model of EV powering steering systems, by synthetically taking into account characteristics of the electric propulsion motor, driver’s operation, and uncertain disturbances caused by irregularities of the road surface. By using various nonlinear analysis methods, the unstable chaotic behaviors can be revealed in the power steering system, especially when the vehicle turns a concern at a high speed. Additionally, a new control algorithm is designed and implemented to stabilize the EV power steering system, and corresponding validity is also mathematically proved in this study.

Thirdly, an integrated driving control system is designed based on the aforementioned dynamic analysis, which is used to enhance the stability and maneuverability performances of four-in-wheel independently-driven (4WID) EVs. By adopting the supervisor-actuator structure, the proposed driving control scheme not only effectively improves the performance of tracking reference paths, but also optimally distribute the desired yaw moment to each in-wheel motor. In this study, the mathematical proof and the simulation are both conducted to demonstrate the feasibility of the proposed integrated driving control strategy.

Lastly, this study also works on the EMI issue caused by switch-mode energy conversion devices for EVs. In this section, a new pulse-width-modulation (PWM) method is designed by utilizing the random-like sequence, aiming to suppress the conducted peaky EMI over the whole power spectrum, thereby ensuring the working performance for electronic instruments in EVs. For demonstrating the effectiveness of the proposed soft-chaoizing scheme, this study takes two exemplifications such as the electric propulsion drive system and the bidirectional power interface for vehicle-to-grid (V2G) systems.