Modeling of the Inverter Current Distortion in the Double-sided LCC Compensation for Inductive Power Transfer Systems

Abstract

The double-sided LCC (DLCC) compensation has been widely used in inductive power transfer (IPT) systems because it has a load-independent current source output directly proportional to the coils’ coupling, which makes it inherently safe against misalignment. The input current of the DLCC typically has high harmonic distortion due to the low-pass filter characteristic of the input LC components. Consequently, predicting the inverter’s turn-off current through circuit modeling using the first-harmonic approximation (FHA) would result in a significant estimation error. However, an accurate computation is essential to determine whether the inverter’s zero-voltage switching (ZVS) turn-on is achieved. This paper defines an analytical model that effectively predicts the inverter turn-off current point for any operating condition, i.e., when the diode rectifier operates in continuous and discontinuous conduction modes. It has been found that the inverter turn-off current depends on the loading condition. Therefore, the proposed method is based on modeling the equivalent load as the rectifier together with the battery. Experimental verification has been conducted using two IPT systems with nominal power levels of 3.7 kW and 7.7 kW.