Quasi-Transformer Mode Control of Interlinking Converter for Multivoltage Levels DC Grids

In this article, the concept of quasi-transformer (Quasi-T) mode control is proposed for dc–dc interlinking converter. In multivoltage level dc systems, the interlinking converter serves for voltage conversion and mutual power support. The traditional operating modes for converters can be classified into constant voltage, current, power, or a mix of them. In the duality of dc–dc converter in dc grid, the ac transformers in the traditional ac grid maintain the proportional relationship between the input and output voltage. By combining constant voltage mode with equivalent transformer mode, system stability can be enhanced through the design of compensator and weight coefficients. The small-signal model of the interlinking converter with Quasi-T mode control is first established, and the control design method is analyzed according to the passivity-based stability criterion. The Quasi-T mode control design ensures steady-state voltage regulation and improves the dynamic response of the dc system. The steady-state operation, control design process, and influencing factors are comparatively evaluated through numerical simulations and experimental results, in verification of the enhanced system stability.

I. Introduction

Multivoltage levels dc distribution power system (DPS) receives increasing interest as the effective solution for various industrial applications, including renewable energy integration [1], marine power systems [2], electric vehicle charging infrastructure [3], etc. The system efficiency, reliability, and flexible power regulation can be significantly improved with multivoltage levels dc systems [4], [5]. Despite those advantages, the stability of multivoltage levels dc network remains a severe challenge [6].