Multi-receiver Wireless Power Transfer Systems Research Articles

A Single-Transmitter Multi-Receiver Wireless Power Transfer System with High Coil Misalignment Tolerance and Variable Power Allocation Ratios

This article proposes a single-transmitter multi-receiver wireless power transfer (STMR-WPT) system, which uses a cross-overlapped bipolar coil as the transmitter and multiple square unipolar coils as the receivers. By using this structure, the magnetic field of the system can be adjusted to accommodate different coil misalignment conditions. In addition, the proposed system uses C-CLCs networks to achieve separate load power allocation. Thus, relay coils, complex multi-frequency transmission channels and multiple independent power supplies can be avoided. A mapping impedance-based circuit model was established to analyze the characteristics of the system, and then a single-frequency power allocation method was presented. Through this method, the STMR-WPT system can achieve load power allocation at any specified ratios under different mutual inductance and load impedance conditions. Finally, an experimental STMR-WPT system was built. The side lengths of the transmitter and receiver coils are 400 mm and 160 mm, respectively. The measurement results indicated that when the lateral or longitudinal coil misalignment varies within the range of 0~200 mm, the coupling coefficient decreases by a maximum of 6% compared to the initial value, and when the angular coil misalignment varies within the range of 0~90 degrees, the coupling coefficient decreases by a maximum of 22% compared to the initial value. In four different power allocation scenarios, the experimental STMR-WPT system successfully achieved the expected power allocation goals.

Importance of Functional Parameters on the Effective Operation of Resonant Multi-receiver Wireless Power Transfer System

Importance of Functional Parameters on the Effective Operation of Resonant Multi-receiver Wireless Power Transfer System

Design and Performance Analysis of a Repeater-Assisted Multireceiver Wireless Power Transfer System Operating at MHz Frequencies

Design and Performance Analysis of a Repeater-Assisted Multireceiver Wireless Power Transfer System Operating at MHz Frequencies

Maximum Efficiency Tracking for Multitransmitter Multireceiver Wireless Power Transfer System on the Submerged Buoy

The wireless power transfer (WPT) system is widely applied in the underwater environment. A multitransmitter multireceiver WPT system is proposed in this article for the application of the submerged buoy, and numbers of beacons can be charged at the same time to send more data. Both series and parallel connection structures of several coils are analyzed in detail. In order to increase the system efficiency at ultracapacitors charging process, a maximum efficiency tracking with a primary current controller and an optimal resistance controller is studied and designed. All mentioned above analyses are verified in a three-receiver WPT system prototype. When ultracapacitors are charged from 10 to 25 V, the system efficiency is achieved at almost 70.5%, and the charging voltage of all three receivers can be stabled.

Adaptive Decoupling Between Receivers of Multireceiver Wireless Power Transfer System Using Variable Switched Capacitor

Simultaneously charging multiple devices is a unique advantage of wireless power transfer (WPT). However, it is challenging to analyze and optimize the performance of a multireceiver (multi-Rx) WPT system due to the intricate coupling among coils. In this article, a method for adaptive decoupling between Rxs is proposed for electronic device charging, which can achieve independent regulation of each output in a multi-Rx WPT system. A simple feedback control avoids tedious system structure and position parameters’ measurement and calculation. With a fixed driving frequency, the number of Rx is not limited. It is analyzed that the quadrature phenomenon of the transmitter (Tx) and Rx currents can be used as a sign that the cross-coupling is fully compensated. A phase synchronization channel is established that shares power transfer coils. An microprogrammed control unit-(MCU) free feedback loop is constructed in Rx to control the variable switched capacitor and finally realize adaptive cross-coupling compensation. A two-load experimental prototype was built to verify the theoretical analysis. Compared with the system without adaptive decoupling between Rxs, the measured system efficiency and output power of the proposed system were improved by 69% and 14.3 times, respectively.

Dynamic analysis and multi-objective parameter optimization in multi-receiver wireless power transfer systems

Dynamic analysis and multi-objective parameter optimization in multi-receiver wireless power transfer systems

Design of a High-Power High-Efficiency Multi-Receiver Wireless Power Transfer System

This paper proposes a new control method to regulate the power flow into multiple receivers. This system consists of one transmitter controller and three receiver controllers. They work independently to decide the power distribution with their combined operation. The simulated and experimental models have been built, and the experimental results are in good agreement with the theoretical analysis results. The proposed method is robust, flexible, and generalizable, and can be employed under various wireless charging conditions.

A Multireceiver Wireless Power Transfer System Using Self-Oscillating Source Composed of Zero-Voltage Switching Full-Bridge Inverter

Nowadays, much effort focuses on research for the multireceiver wireless power transfer (WPT) system based on magnetic resonance. However, its output characteristics are significantly deteriorated by the variation of transfer spacing, loads, and cross-couplings, which exerts harmful effects on the performances of cascading bucks before loads if needed. Inspired by the work of a single-receiver WPT system based on the parity time symmetric model, in this article, the self-oscillating source is first applied to the multireceiver WPT system to tackle these drawbacks. Based on the coupled-mode theory, the proposed system's modeling is established and deduced to analyze its performance. The model analysis shows how the system can achieve zero-voltage switching simply via choosing the minimum dead time and leading time whose calculation method is provided. Meanwhile, a transmitting coil for a uniform magnetic field is designed to improve the free-positioning performance. The analysis is validated on a 36-W prototype, including the effects of the variation of transfer spacing, cross-couplings, and loads on the output characteristics, efficiency, and operating frequency. The proposed system is demonstrated to provide a much more robust power transfer than the conventional magnetic-resonant multireceiver WPT system, which helps extend the transfer distance and improve the system efficiency.

Opportunistic Waveform Scheduling for Wireless Power Transfer With Multiple Devices

In this paper, we study a waveform scheduling problem for a multi-receiver wireless power transfer (WPT) system considering time-varying channel conditions and minimum average output direct-current (DC) voltage requirement of each receiver. To this end, we formulate a stochastic optimization problem that aims at maximizing the average of the sum of output DC voltages of receivers while satisfying the minimum average output DC voltage requirements of all receivers, and by solving it, we develop a waveform scheduling algorithm. In the waveform scheduling algorithm, we need to solve a problem for maximizing the weighted-sum of output DC voltages of receivers, which is a non-convex optimization problem. To cope with this difficulty, we develop a low-complexity approximated algorithm with which the waveform for the multi-receiver WPT system is optimized to maximize the weighted sum of output DC voltages of receivers. Numerical results show that our waveform design algorithm provides the higher performance of the weighted-sum of the output DC voltages than the existing algorithms, and our opportunistic waveform scheduling provides good performance while well satisfying the minimum average output DC voltage requirement of each receiver.

Determination of the Optimal Resonant Condition for Multireceiver Wireless Power Transfer Systems Considering the Transfer Efficiency and Different Rated Powers With Altered Coupling Effects

Recently, there has been an ever-growing demand for multireceiver wireless power transfer (WPT) systems with a high power transfer efficiency. In this article, a novel optimization-based method is proposed to precisely determine the optimal resonant condition for multireceiver WPT systems in order to maximize the power transfer efficiency while satisfying all the rated power that can be differently required in each receiver module. The proposed method links the optimization module and the analysis module to iteratively update the design variables during optimization based on electric performance evaluated in the analysis module. After being verified with a “single-transmitter-to-a-single-receiver” WPT system which has a well-known resonance condition, the proposed method is applied to determine the optimal resonant condition for various “single-transmitter-to-multiple-receiver” WPT systems in both initial and disturbed configurations. The experimental validation demonstrates the performance and potential of the proposed method to compensate the coupling changes of multireceiver WPT systems.

On the Load-Independence of a Multi-Receiver Wireless Power Transfer System

Research and development of wireless power transfer (WPT) systems has attracted much attention in recent years for their potential widespread applications. One of the much desirable features of a WPT system is load-independence. In this letter, we propose the insertion of a simple T-type network into a multi-receiver WPT magnetically coupled resonant WPT system to achieve the load-independence. We then present theoretical analysis, simulation, and experimental verifications; as a result, they lay the foundation for further investigations, improvements, and implementations of realistic WPT systems.

Waveform Design for Fair Wireless Power Transfer With Multiple Energy Harvesting Devices

In this paper, we study the waveform design in the wireless power transfer (WPT) system with multiple receivers. In the multi-receiver WPT system, due to the severe power attenuation of RF signals according to the distance and the heterogeneity in the energy harvesting capability, there exists severe unfairness in energy harvesting among receivers at different distances from the transmitter and/or different energy harvesting capabilities. Hence, alleviating unfairness in energy harvesting among receivers is one of the critical challenges in the multi-receiver WPT system. To tackle this challenge in a systematic way, we consider the fairness in our waveform design applying the $\alpha $ -proportional fairness. With the analysis of the rectenna circuit, we derive the output dc voltage and power of the rectifier in closed forms. Thereby, we formulate an optimization problem to design the waveform for fair WPT. The problem is shown to be a non-convex optimization problem, which is hard to solve in general. However, with proper approximations, we convert it into a convex optimization problem that can be solved easily and obtain the waveform for fair WPT. Numerical results show that our designed waveform makes receivers harvest energy fairly and can control the degree of the fairness easily.

Omnidirectional Wireless Power Transfer System Based on Rotary Transmitting Coil for Household Appliances

An omnidirectional magnetically coupled resonant wireless power transfer (WPT) system based on rotary transmitting coil is presented. The proposed scheme can ease the variations of the transfer efficiency and output power caused by the deviation of transfer direction, and improve the unbalanced power distribution phenomenon between the receivers, which are still not fully achieved in current WPT systems. The modified coupled-mode model is built first to describe the non-rotary multi-receiver WPT system. The analysis indicates that the transfer efficiency and output power of the system can be expressed as functions of the deviation angle between the transmitting coil and receiving coil, which has a non-negligible influence on the system performances. Then, the modified high order coupled-mode model containing time-varying parameters about the deviation angle is derived for the proposed omnidirectional WPT system. Theoretical analysis and simulated results indicate that this system can transfer power to multiple receivers around the transmitter synchronously and evenly, which is very suitable for wireless charging for household appliances indoors. The scheme feasibility and theoretical analysis are verified by experimental results.