Input Reactive Power Control of Bidirectional WPT to Improve System Efficiency

Misalignment can significantly affect the mutual inductance of a wireless power transfer (WPT) system, thereby impacting the system's power transfer capabilities and efficiency. Traditionally, to achieve optimal efficiency with constant output power under misalignment, individual closed-loop feedback control needs to be used on both the transmitter and receiver sides. The receiver side phase shift (
$\beta$
) is controlled to maintain the constant output power, and the transmitter side phase shift (
$\alpha$
) is controlled to achieve zero power factor angle (ZPA) for optimal efficiency. The ZPA condition is achieved by making the input reactive power (
$Q_{in}$
) equal to zero. However, this necessitates additional high-bandwidth sensing circuitry, thereby increasing system complexity. Moreover, it also introduces the cross-coupling issue due to formation of multi input multi output (MIMO) system. This paper proposes a simple, decoupled, and fast response control approach for mitigating the impact of misalignment and load variation by employing a single receiver-side PI controller. A closed form analytical relationship between
$\alpha$
and
$\beta$
has been established in this paper to maintain optimal efficiency while regulating output power under misalignment conditions. The proposed method obtains
$\beta$
from the receiver side controller and
$\alpha$
from the derived relation. The proposed control method is validated using an experimental setup of a 1 kW bidirectional wireless power transfer (BWPT) system. The simulation and experimental results of the BWPT system under various loading and misalignment conditions are presented.