Multilevel Multichannel Interleaved AC-DC Converter for High Current Applications

In this paper an analysis and implementation of a voltage source multi-level multi-channel interleaved ac/dc converter structure is presented. The primary application is on grid-tie converters to interface renewable energy sources, energy storage devices and VAR Compensators. The multilevel structure ensures reaching higher voltage levels and the parallel interleaved approach allows for reaching higher currents and higher effective carrier frequency. Significant reduction on the size and weight of the passive components, such as the ac interface reactor and the grid side ac filter can be attained, as well as reduction of the ripple and RMS value of the dc bus capacitor's current. The converter structure has a modular architecture where each converter sub-module will be able to switch at switching frequencies that would comfortably ensure low total switching losses and increased effective carrier frequency. The reduction of the input inductance will also contribute to reduction on copper losses and therefore higher converter efficiency. The reduction on dc bus capacitor's current will result in lower heat dissipation, thereby extending its lifetime. The paper presents an example with three 3-Level interleaved channels where the control of the circulating currents among the sub-channels is attained by the addition of a closed-loop zero-component controller to the traditional d-q synchronous reference frame. Simulations and experimental results for a down-scale prototype 230 V/15 kVA are presented and discussed.