Convex Optimization of Wireless Power Transfer Systems With Multiple Transmitters

Abstract

Wireless power transfer systems with multiple transmitters promise advantages of higher transfer efficiencies and focusing effects over single-transmitter systems. From the standard formulation, straightforward maximization of the power transfer efficiency is not trivial. By reformulating the problem, a convex optimization problem emerges, which can be solved efficiently. Further, using Lagrangian duality theory, analytical results are found for the achievable maximum power transfer efficiency and all parameters involved. With these closed-form results, planar and coaxial wireless power transfer setups are investigated.Index Terms-Convex optimization, maximum transfer efficiency, multiple transmitters, wireless power transfer.

Comparison of magnetic field exposure for SISO and MISO wireless power transfer systems

“…As shown in [2], the process of optimizing these parameters leads to closed-form expressions, whereby the optimal receiver load resistance R L , the receiver reactance x r , as well as the transmitter currents i t,n can be obtained from the impedance matrix Z of the WPT system, directly.…”

“…As a result, wireless power transfer (WPT) systems have been widely studied both theoretically and experimentally. It has been demonstrated that multiple-input single-output (MISO) systems feature advantages compared to single-input single-output (SISO) systems, most importantly higher power transfer efficiency [1], [2]. This paper explores further advantages associated with such MISO WPT systems, particularly in terms of operating magnetic field strengths and exposure levels.…”

kQ-product formula for multiple-transmitter inductive power transfer system

“…Compared to one transmitter, multiple transmitters have more degree of freedom of the input current distribution and, therefore, provide the possibilities of efficiency enhancement as well as energy focusing toward target receiver. Maximum efficiency of multiple-transmitter system has been analyzed using linear programing or convex optimization [6,7,8]. However, these analyses give little physical insights into the system behavior, e.g., the relation between efficiency of the whole system and those of individual transmitter-receiver links.…”

Theoretical limits of rectifying efficiency for low-power wireless power transfer

“…Although substantial studies have been conducted on the performance limits of near‐field WPT, those of far‐field and low‐power rectennas are still critically lacking. For example, earlier studies have attempted to establish the theoretical limits of near‐field conversion efficiency by solving the associated convex programming problems . In addition, such maximum achievable efficiency of near‐field WPT has also been analyzed by using two‐port parameters and deriving a closed‐form analytic solution for the optimal load or performing numerical search for the optimal load under the transmitter‐diversity scheme .…”