Communicationless Phase Cooperative Control of Inductive Power Transfer Using Asymmetrical Modulations

The dual-side control (DSC) of inductive power transfer (IPT) generally requires communication between the system sides to coordinate the local controllers. For the reduction of component count and operation in challenging environments, such as underwater, communicationless DSC is beneficial. This article investigates if and how asymmetric modulations, known for their improved performance in IPT, can be applied to phase cooperative communicationless DSC. A per side separate steady-state model is derived, and the selection criteria for modulation schemes to be suitable for phase cooperative control are determined. The crucial importance of bijective or unique phase behavior in modulations for this control scheme is identified and demonstrated. In comparison with phase modulation, it is shown that the asymmetric voltage cancelation of full-bridges is not reliably applicable to phase cooperative DSC, but the asymmetrical modulation of half-bridges is. Therefore, a phase cooperative half-bridge DSC system as a simplified low-complexity DSC scheme is further investigated, and the load step regulation boundary is derived. Analysis is verified in experiment and simulation, demonstrating zero-voltage-switching behavior, dynamic load step regulation, the impact of harmonics on magnetics losses for high coupling, and the impact of variable voltage ratio.