Chengbin Ma

A Cascaded Boost–Buck Converter for High-Efficiency Wireless Power Transfer Systems

Wireless power transfer (WPT) has attracted an ever increasing interest from both industry and academics over the past few years. Its applications vary from small power devices such as mobile phones and tablets to high power electric vehicles and from small transfer distance of centimeters to large distance of tens of centimeters. In order to achieve a high-efficiency WPT system, each circuit should function at a high efficiency along with the proper impedance matching techniques to minimize the power reflection due to the impedance mismatch. This paper proposes an analysis on the system efficiency to determine the optimal impedance requirement for coils, rectifier, and dc-dc converter. A novel cascaded boost-buck dc-dc converter is designed to provide the optimal impedance matching in WPT system for various loads including resistive load, ultracapacitors, and batteries. The proposed 13.56-MHz WPT system can achieve a total system efficiency over 70% in experiment.

Analysis and Tracking of Optimal Load in Wireless Power Transfer Systems

All the wireless power transfer (WPT) systems share a similar configuration including a power source, a coupling system, a rectifying circuit, a power regulating, and charging management circuit and a load. For such a system, both a circuit- and a system-level analyses are important to derive requirements for a high overall system efficiency. Besides, unavoidable uncertainties in a real WPT system require a feedback mechanism to improve the robustness of the performance. Based on the above basic considerations, this paper first provides a detailed analysis on the efficiency of a WPT system at both circuit and system levels. Under a specific mutual inductance between the emitting and receiving coils, an optimal load resistance is shown to exist for a maximum overall system efficiency. Then, a perturbation-and-observation-based tracking system is developed through additional hardware such as a cascaded boost-buck dc-dc converter, an efficiency sensing system, and a controller. Finally, a 13.56-MHz WPT system is demonstrated experimentally to validate the efficiency analysis and the tracking of the optimal load resistances. At a power level of 40 W, the overall efficiency from the power source to the final load is maintained about 70% under various load resistances and relative positions of coils.

Fractional-order control: Theory and applications in motion control [Past and present]

The concept of fractional-order control (FOC) means controlled systems and/or controllers are described by fractional-order differential equations. Expanding derivatives and integrals to fractional orders is by no means new and actually has a firm and long-standing theoretical foundation. The paper discusses the three main advantages for introducing fractional-order calculus to control control engineering.

NONLINEAR DYNAMICS OF DUFFING SYSTEM WITH FRACTIONAL ORDER DAMPING

In this paper, nonlinear dynamics of Duffing system with fractional order damping is investigated. The four order Runge-Kutta method and ten order CFE-Euler methods are introduced to simulate the fractional order Duffing equations. The effect of taking fractional order on the system dynamics is investigated using phase diagrams, bifurcation diagrams and Poincare map. The bifurcation diagram is also used to exam the effects of excitation amplitude and frequency on Duffing system with fractional order damping. The analysis results show that the fractional order damped Duffing system exhibits period motion, chaos, period motion, chaos, period motion in turn when the fractional order changes from 0.1 to 2.0. A period doubling route to chaos is clearly observed.Copyright

Utility Function-Based Real-Time Control of A Battery Ultracapacitor Hybrid Energy System

This paper discusses a utility function-based control of a battery-ultracapacitor (UC) hybrid energy system. The example system employs the battery semiactive topology. In order to represent different performance and requirements of the battery and UC packs, the two packs are modeled as two independent but related agents using the NetLogo environment. Utility functions are designed to describe the respective preferences of battery and UC packs. Then, the control problem is converted to a multiobjective optimization problem solved by using the Karush-Kuhn-Tucker (KKT) conditions. The weights in the objective functions are chosen based on the location of the knee point in the Pareto set. Both the simulation and experimental results show the utility function-based control provides a comparable performance with the ideal average load demand (ALD)-based control, while the exact preknowledge of the future load demand is not required. The utility function-based control is fast enough to be directly implemented in real time. The discussion in this paper gives a starting point and initial results for dealing with more complex hybrid energy systems.

Polynomial-Method-Based Design of Low-Order Controllers for Two-Mass Systems

In this paper, low-order integral-proportional (IP), modified IP (m-IP), and modified integral-proportional-derivative (m-IPD) controllers are designed for the speed control of a two-mass system based on a normalized model and polynomial method. In order to have sufficient damping, the parameters of the controllers are determined through characteristic-ratio assignment under the principle that all the characteristic ratios should be larger than two. It is found that for an inertia ratio smaller than one-third, an IP controller can effectively suppress the vibrations with proper damping, while for a relatively larger inertia ratio, an m-IP controller (i.e., IP controller with an additional low-pass filter) is effective. m-IPD control is theoretically effective for a large inertia ratio. However, the necessity of a negative derivative gain leads to a very poor robustness. Both simulation and experimental results verified the effectiveness of the designed IP and m-IP controllers when the inertia ratio is relatively small. For the m-IPD controller, its poor robustness is demonstrated by introducing a large gear backlash in experiments, while the IP and m-IP controllers show promising results of a much better robustness against the gear backlash nonlinearity.

Parameter Design for a 6.78-MHz Wireless Power Transfer System Based on Analytical Derivation of Class E Current-Driven Rectifier

Magnetic resonance coupling working at megahertz (MHz) is widely considered as a promising technology for the mid-range transfer of a medium amount of power. It is known that the soft-switching-based Class E rectifiers are suitable for high-frequency rectification, and thus potentially improve the overall efficiency of MHz wireless power transfer (WPT) systems. This paper reports new results on optimized parameter design of a MHz WPT system based on the analytical derivation of a Class E current-driven rectifier. The input impedance of the Class E rectifier is accurately derived, for the first time, considering the on-resistance of the diode and the equivalent series resistance of the filter inductor. This derived input impedance is then used to develop and guide design procedures that determine the optimal parameters of the rectifier, coupling coils, and a Class E PA in an example 6.78-MHz WPT system. Furthermore, the efficiencies of these three components and the overall WPT system are also analytically derived for design and evaluation purposes. In the final experiments, the analytical results are found to well match the experimental results. With loosely coupled coils (mutual inductance coefficient

An Adaptive Fuzzy Logic-Based Energy Management Strategy on Battery/Ultracapacitor Hybrid Electric Vehicles

k

Compensation of Cross Coupling in Multiple-Receiver Wireless Power Transfer Systems

=0.1327), the experimental 6.78-MHz WPT system can achieve 84% efficiency at a power level of 20 Watts.

A 13.56 MHz wireless power transfer system without impedance matching networks

One of the key issues for the development of electric vehicles (EVs) is the requirement of a supervisory energy management strategy, especially for those with hybrid energy storage systems. An adaptive fuzzy logic-based energy management strategy (AFEMS) is proposed in this paper to determine the power split between the battery pack and the ultracapacitor (UC) pack. A fuzzy logic controller is used due to the complex real-time control issue. Furthermore, it does not need the knowledge of the driving cycle ahead of time. The underlying principles of this adaptive fuzzy logic controller are to maximize the system efficiency, to minimize the battery current variation, and to minimize UC state of charge (SOC) difference. NetLogo is used to assess the performance of the proposed method. Compared with other three energy management strategies, the simulation and experimental results show that the proposed AFEMS promises a better comprehensive control performance in terms of the system efficiency, the battery current variation, and differences in the UC SOC, for both congested city driving and highway driving situations.