Guideline to Series-Series Compensation Design and Bifurcation Mitigation in Multi-Modular IPT Systems

The compensation and high-efficiency operation of the multimodular inductive power transfer (IPT) systems has been a challenge because of the inter- and cross-coupling between modular charging pads. This article analyzes the series–series (S–S) compensation and the associated bifurcation problem in multimodular IPT systems based on closed-form analytical modeling of the coupled circuits. From the analytical results, an improved compensation tuning method for multimodular systems is demonstrated. This improved compensation addresses the intercoupling between coils on the same side, in addition to the self-inductance of the charging pad. As a result, the system’s efficiency improves while also saving an extra capacitor compared with other circuit-based decoupling methods. In addition, a design guideline based on the sum of the coupling coefficients including cross-coupling is derived to avoid bifurcation. The phase angle of the input impedance is studied under various scenarios, demonstrating the validity of the proposed design guideline. Experimental results on a downscaled prototype show that the improved compensation method enhances efficiency by more than 2% compared with scenarios where intercoupling is not compensated, and verification of the proposed bifurcation mitigation guideline.