Modular Stacked Multiport Wireless Energy Interconnection System With Virtual AC Bus and Its Power Flow Control Strategy

This article proposes a modular stacked multiport wireless energy interconnection (WEI) system with a virtual ac bus for multisource and multiload wireless power transfer (WPT) applications, which has the following advantages. 1) It can serve as an interface for WPT among multiple sources and loads. 2) Bipolar coils are adopted to eliminate the undesired cross-coupling among multiple coils, which simplifies the complexity of system modeling and power flow control. 3) The relay coil with constant current characteristics is introduced as a virtual ac bus, from which the derived multicoil structure provides the bidirectional channel for power transfer between any two ports. 4) System applicability and scalability are greatly enhanced due to the modularization of coils, power converters, and compensation circuits. For power flow control, the hybrid phase-shifted control method matched with the WEI system is applied, in which the power flow direction is determined by the external phase-shifted angles between ports, whereas the power values are regulated by the internal phase-shifted angles. Furthermore, the peak value of the current of the virtual ac bus, as an intermediate control variable, is controlled to be constant; thus, distributed control can be further realized. Finally, a four-port experimental prototype was built and experiments were carried out under different operating conditions. The efficiency curves and loss distribution, as well as the tolerance analysis of coil misalignments, are given. From the experimental results, the effectiveness of the proposed system architecture and its power flow control strategy is verified.