Active-Load-Decoupling Based Online Mutual Inductance Estimation for Bidirectional Inductive Wireless Power Transfer Systems

Mutual inductance greatly impacts the performance of bidirectional inductive wireless power transfer (BD-WPT) systems, yet it is usually unknown due to the uncertain position of the coils or some environmental variations. To acquire the mutual inductance online, this article proposes an online mutual inductance estimation method. This method constructs a virtual circuit and uses coordinate transformation to decouple the active load on the secondary of the system equivalently. Based on this active load decoupling idea, the estimation model of the mutual inductance is simplified in the time domain, and the primary-side online fast estimation of mutual inductance is implemented by only sampling the primary ac current. Verifications are provided by the experimental results of the prototype BD-WPT system. Compared with the existing methods for BD-WPT systems, the proposed method is load-information-free, and it achieves online mutual inductance estimation rapidly and accurately. And no communication, additional switches, or auxiliary circuits are required.