An MMC based IPT System with Integrated Magnetics and ZVS Operations

Abstract

This article proposes a novel high-frequency modular multilevel converter (MMC) for an inductive power transfer (IPT) system. MMCs have many benefits, such as larger modulation depth, more degrees of control, and lower device stresses in comparison to traditional full-bridge converters. However, MMCs are traditionally used for low-frequency applications. Their high-frequency operation differs significantly and has not been reported yet. This article focuses on the 85-kHz operation of an MMC driving the primary compensation circuit of an IPT system. The high-frequency operation of the MMC allowed the proposed design to integrate the dc arm inductors with the primary compensation network of an IPT system, lowering the component count. A digitized modulation scheme is used to regulate the output power while maintaining zero-voltage switching under the range of operating conditions considered. To validate the proposed MMC-based IPT system, an SAE J2954 WPT2/Z2 compliant prototype is built and tested, which achieves up to 93% efficiency when transferring 7.7 kW with a 220% variation in coupling factor and a varying output battery voltage between 280 and 420 V.