Wireless Power Transfer Control Research Articles

Control of Wireless Power Transfer

Control of Wireless Power Transfer

Robust Control of Wireless Power Transfer Despite Load and Data Communications Uncertainties

This article focuses on the robust control of wireless power transfer (WPT) systems, to work satisfactorily around the desired resonant frequency in the presence of load and data communications uncertainties. The proposed robust control system is based on the quantitative feedback theory (QFT), consisting of a feedback compensator and a prefilter, which are designed by shaping the system's frequency responses, to satisfy the design constraints defined in terms of stability, tracking, and other desired requirements. A feature of QFT is to provide the designer with interactive graphical tools for the design and tuning of the feedback compensator and prefilter. Without loss of generality, this article elaborates the design of the QFT-based robust control for a WPT system with a full-bridge inverter and series-series capacitor-based compensation circuits and uncertain direct-current (dc) load. The data communications uncertainties are also addressed in the design. The effectiveness of the proposed QFT-based robust control methodology is evaluated through simulations and practical experiments and compared with H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> and Skogestad internal model control (SIMC) design methods. Since QFT is a model-based approach, this article also elaborates on small-signal transfer function modeling of WPT systems.

Frequency-Modulated Phase Shift Keying Communication for MEPT Control of Wireless Power Transfer

The closed-loop control of wireless power transfer (WPT) systems requires a communication link between the power transmitter and the power receiver for dual-side cooperation. Near-field communication techniques that utilize the power link are preferred for this purpose due to high reliability and security. In this letter, we propose a frequency-modulated phase shift keying (FMPSK) communication technique for the closed-loop maximum efficiency point tracking (MEPT) control of WPT. The technique uses very shallow phase modulation depth to minimize the disturbance on power flow and reduce the efficiency drop caused by the PSK. Meanwhile, it ensures the signal accuracy and precision by multiple methods and precise frequency modulation and demodulation. In experiment, we obtained 82%-85% system efficiency with a 25-125 W load over a distance equal to the coil diameter, and 93% efficiency over a distance equal to the coil radius. The efficiency drop caused by FMPSK was less than 1%. The dynamic processes of voltage regulation and MEPT took only about 1 ms and 10 ms, respectively.

Dual-Side Phase-Shift Control of Wireless Power Transfer Implemented on Primary Side Based on Driving Windings

The isolated feature between primary and secondary sides in wireless power transfer requires dual-side communication, phase synchronization, and two controllers on both sides. The phase difference between dual-side ac voltages can be changed for output regulation or bidirectional power flow. Zero crossing detection of the secondary ac voltage or current is normally conducted for frequency locking and phase synchronization. However, it is inaccurate at light-load conditions for high-power applications due to a large sensing scale and much noise; also, it can generate undesired results with discontinuous or distorted waveforms having more than two zero crossing points in one cycle. To solve these issues, this letter proposes a dual-side phase-shift implementation method using driving windings to regulate the dual-side phase difference conducted only on the primary side. By controlling the phase difference between the primary-side power and driving windings, the phase difference between the dual-side power windings can be regulated. In this way, the dual-side regulation is independent from power transfer to get rid of the issues of the conventional phase synchronization method, and bidirectional power flow can be more easily realized.

Path planning and energy flow control of wireless power transfer for sensor nodes in wireless sensor networks

Path planning and energy flow control of wireless power transfer for sensor nodes in wireless sensor networks

Control of wireless power transfer to a bioelectronic device by harmonic feedback

We demonstrate control of wireless power transfer to an implanted bioelectronic device using harmonic feedback from the backscattered field. The feedback mechanism relies only on inherent nonlinearities in the receiver circuit and can provide a direct measurement of the extracted power without any modification of the device. We use the method to control an implanted light-emitting diode while varying the coupling between the source and receiver.

Decoupled control of wireless power transfer: Eliminating the interdependence of load resistance and coupling to achieve a simple control framework with fast response times

Wireless power transfer (WPT) is an exciting technology that attempts to transfer energy via loosely coupled inductors. This paper suggests an automated system in which load side impedance matching is utilized to regulate power to a variable load. Such a scheme requires proper selection of topology and component values so that reactance is not a function of load resistance or coupling. Since the maximum power point (MPP) and maximum efficiency point (MEP) do not arise at the same load resistance, careful selection of resistance must be made so efficiency is maximized while target power is maintained. The result is a system that is quick, accurate, simple, robust, and operates without the need of a backward communications link.

Primary-Side Power Flow Control of Wireless Power Transfer for Electric Vehicle Charging

Various noncontacting methods of plug-in electric vehicle charging are either under development or now deployed as aftermarket options in the light-duty automotive market. Wireless power transfer (WPT) is now the accepted term for wireless charging and is used synonymously for inductive power transfer and magnetic resonance coupling. WPT technology is in its infancy; standardization is lacking, especially on interoperability, center frequency selection, magnetic fringe field suppression, and the methods employed for power flow regulation. This paper proposes a new analysis concept for power flow in WPT in which the primary provides frequency selection and the tuned secondary, with its resemblance to a power transmission network having a reactive power voltage control, is analyzed as a transmission network. Analysis is supported with experimental data taken from Oak Ridge National Laboratory's WPT apparatus. This paper also provides an experimental evidence for frequency selection, fringe field assessment, and the need for low-latency communications in the feedback path.