Multiple Harmonics Analysis for Variable Frequency Variable Duty-Cycle Controlled Inductive Power Transfer Systems

Abstract

Variable Frequency Variable Duty-Cycle (VFVDC) control is widely used in Inductive Power Transfer (IPT) systems to control the amount of power that is transferred. This control scheme is also adopted in Qi, one of the world’s most well-known wireless charging standards. Conventionally, analysis of IPT systems is based on First Harmonics Approximation (FHA), which only considers the fundamental harmonic signals. This could be inaccurate for variable frequency variable duty-cycle controlled IPT systems because VFVDC inherently produces more harmonics, especially the second harmonic. In this paper a new analytical technique called Multiple Harmonics Analysis (MHA) is developed to analyze IPT systems operating at variable frequency and variable duty-cycle mode. The MHA technique can predict behaviors of harmonics and give insights into IPT systems. It is also shown that MHA is more accurate than FHA by both calculation and measurements.