A Reduced-Switch-Count Family of Soft-Switched High-Frequency Inductive AC-Link Converters

This article introduces a new family of partial-resonance high-frequency ac-link converters with a reduced number of switches, which contributes to enhanced reliability and reduced size. The proposed family of converters can be configured to interface various number of single-/multiport dc and/or single-/multiphase ac systems of sources and loads through a partial-resonance parallel LC link. The LC link is composed of a small inductor and a very small ac capacitor without the use of bulky and short life-cycle electrolytic capacitors. The high-frequency ac link is responsible for transferring power between different ports of the system entirely or partially as well as realizing zero voltage switching for all the power switches/diodes over the full load range, which results in minimized stress over the switches as well as low electromagnetic interference (EMI). This class of converters, which only employs two-quadrant switches, is inherently bidirectional with voltage step-up/step-down capability. It allows variable frequencies and power factors between the input and output terminals in one stage of power conversion. The proposed converters can function in buck-boost, buck, and/or boost modes of operation to step up and/or step down the input voltage. Functioning in buck or boost modes of operation can significantly reduce the link peak current and voltage, contributing to reduced power loss, size of components, voltage/current stress of power switches/diodes, and EMI. Furthermore, the proposed converters are robust against the open-circuit/short-circuit problems of input, output, and link inductors/capacitors, which place emphasis on improved reliability of the system. They are also capable of minimizing poor recovery issues and related losses of the body diodes of switches by using external fast recovery diodes in series with the main switching devices. In view of these features, this class of converters is expected to exhibit improved reliability, efficiency, power density, functionality, and flexibility compared to most existing power converters. A current modulation approach is also developed for each function to regulate the input and output currents on a switching cycle-by-cycle basis. A detailed performance analysis to investigate the challenges of each function in terms of frequency, power factor, and voltage amplitude is presented. The effectiveness of the proposed configurations along with the modulation schemes is verified theoretically using simulation software and experimentally via a low-power laboratory prototype at different operating conditions.