Comprehensive Analysis of 1st Harmonic Approximation for Multiple Active Bridge Converters

Abstract

Multiple Active Bridge (MAB) converters are gaining popularity due to the rise of multi-source and multi-load systems, such as those found in ships, aircraft, and hybrid energy storage systems, as well as recent advancements in multi-source Electric Vehicle (EV) chargers. Numerous researchers have explored different control techniques to enable independent power flow across each port and ensure fast dynamics. However, many of these methods assume that power flows at the switching frequency, often omitting a detailed analysis of this assumption. This paper presents a comprehensive analysis of the First Harmonic Approximation (FHA), evaluating its validity, operational limits, and inherent errors. Specifically, the study examines the FHA of power and currents through the MAB transformer to define its applicable operating range. The analysis begins with an ideal case before relaxing the assumptions to account for real-world conditions. The study is validated through simulations of a four-port MAB converter and experimental testing of a three-port MAB converter using two different modulation techniques: phase-shift modulation and dq-frame control.