Multi-transmitter Wireless Power Transfer Systems Research Articles

Self-Decoupled and Integrated Coils for Modular Multitransmitter Wireless Power Transfer Systems

The use of multiple transmitters (Txs) has been an attractive solution for enabling free-positioning wireless power transfer (WPT) in a large area. One of the key challenges in such multi-Tx WPT systems is the cross-coupling between Tx coils. This letter proposes a compact self-decoupled Tx coil solution for multi-Tx WPT systems. The measured cross-coupling between Tx coils has been reduced by 95% compared with conventional coil designs. In addition, an integration method for a compensation inductor with the main Tx coil is proposed. Therefore, the coil design proposed in this letter facilitates creation of fully modular and scalable Tx coils for multi-Tx WPT systems. The proposed designs are experimentally verified in a laboratory prototype.

Machine Learning Assisted Characteristics Prediction for Wireless Power Transfer Systems

One of the main challenges in wireless power transfer (WPT) devices is performance degradation when the receiver’s position and characteristics vary. Therefore, the load resistance and receiver position must be monitored to ensure proper optimization of power transfer. This study proposes a machine learning (ML) assisted method that estimates the power delivered to the receiver by only using measurements at the transmitter side. Based on the delivered power estimation, we also propose a method to identify if the system efficiency is too low, so that the transmitter should be turned off. This activation control method can be useful in multi-transmitter WPT systems. In addition, we propose an ML method to estimate the load resistance and the coupling coefficient. Using the proposed method, the characteristics of an inductor-capacitor-capacitor (LCC)-Series tuned WPT system are successfully predicted only using the measured root-mean-square and the harmonic contents of the input current. The proposed approach is experimentally validated using a laboratory prototype.

Efficiency Improvement of Wireless Power Transfer Based on Multitransmitter System

Multitransmitter wireless power transfer system gets more and more applications as it can maintain high efficiency in a large space range. This article focuses on modeling the multitransmitter system, and proposes an impedance matching method to improve efficiency under lateral-misalignment conditions. The theoretical analysis shows that the maximum transfer efficiency can be achieved as long as the equivalent input impedance of the transmitters is regulated to be the same under misalignment condition. Hence, a double closed-loop control strategy is proposed to realize maximum efficiency point tracking, where the primary control loop adjusts the input impedance of the transmitters through pulsewidth modulation, while the second control loop maintains constant output power by a dc–dc converter. A 500-W prototype is built to validate the feasibility of the proposed method. The efficiency is always higher than 90% with an improvement of up to 20.3% compared to that without such a method when the lateral misalignment increases from 0 to 10 cm (0%–41% of maximum coil size).

Expandable N-Legged Converter to Drive Closely Spaced Multitransmitter Wireless Power Transfer Systems for Dynamic Charging

Expandable and flexible wireless power transfer (WPT) systems have been in demand in numerous industry applications, especially for dynamic chargers in electric vehicles. Those systems, however, bring about certain technical issues such as modulation technique and topology of the transmitter side, and transferred power profile of the transmitters. In this article, a new converter topology to drive closely spaced segmented dynamic wireless power transfer (DWPT) systems is proposed. The proposed converter can be expanded to cater for different number of transmitters, and it can provide a uniform transferred power profile throughout the path of transmitter coils, known as track. Furthermore, this article focuses on analyzing the operation of the converter and the effect of closely spaced transmitters over its operation. To show the effectiveness of the proposed topology and its modulation technique, the converter is simulated and experimentally tested using a laboratory prototype. The results are compared and analyzed, and their close agreement shows the validity of the proposed technique.

Layout Optimization of the Receiver Coils for Multitransmitter Wireless Power Transfer Systems

This paper presents a novel method which is proposed to determine the optimal receiver coils when the transmitter coils are predetermined for multitransmitter wireless power transfer system, using the gradient-based optimization algorithm. The fixed grid-based coil representation, which is newly introduced, allows for effective changes in the coil layout during the optimization through assigning appropriate values for the reference coil turn and relative coil turns, which are set as design variables in the proposed method. The magnetic field strength, induced voltage, and coil mass are mathematically derived in order to obtain their analytical sensitivities with respect to the design variables. As an application example, a wireless portable charger with multiple transmitter coils is selected in order to minimize the mass of the receiver coils, while satisfying the induced voltage and magnetic field strength constraints. The optimized coil layouts are then experimentally validated, which demonstrates the feasibility and potential of the proposed method.