Electromagnetic System Optimization (ESO)

  • Background and research motivation

Principle of the wireless power transfer

Example of a wireless charging for smart phones

Wireless power transfer (WPT) means that the electric power is transferred from the power supplier (transmitter) to the device (receiver) by using the electromagnetic induction. Due to the convenience and safety, the WPT technologies have been widely applied to many applications such as electric vehicles, smart phones, AUVs, and so on.

In the single transmitter-single receiver systems, the resonant condition and electric performance can be calculated analytically. However, in the multiple-receiver systems, it is challenging to derive their explicit mathematical solutions because the receiver coils are coupled one another (i.e., higher system complexity). To enhance the performance of multi-receiver WPT systems, the break-through technologies are demanded.

  • Research overview

To solve the challenges of the multi-receiver WPT systems, we have two different approaches: optimal resonant condition and optimal load. In principle, the electric performance (e.g., transfer efficiency) can be adjusted by changing input voltage, capacitor, and loads in the WPT systems. Therefore, if the optimal resonant condition and/or optimal load can be determined, we can enhance the performance of the multi-receiver WPT systems and operate them in a more efficient and stable way.

  • Area 1: Determination of optimal resonant condition

In the single transmitter and single receiver WPT systems, the resonant condition can be easily determined by removing the reactance between capacitor and coil. However, in the multi-receiver WPT systems, the above LC compensation scheme cannot guarantee the performance. We proposed a novel scheme of determining the optimal resonant condition for multi-receiver WPT systems which can maximize the performance (e.g., transfer efficiency) while satisfying the given conditions (e.g., rate power) for reliable operation. Here, cross-coupling which occurs between the receivers are fully considered to reflect the system characteristic and behavior.

  • Area 2: Determination of optimal load condition

To supply the power in the load, the rectifier and dc/dc converter are used. From the viewpoint of the input resistance, when the dc/dc converter adjusts the output power or voltage, it is equivalent to change the loads which can affect the performance of the WPT systems. Although numerous studies have used simple power electronics for single WPT systems, a new technique is required for multi-receiver WPT systems. Based on optimization, we proposed a novel method that determines the optimal loads for multi-receiver WPT systems to maximize the efficiency while satisfy the rated power required.