Comparative Assessment of Multi-Port MMCs for High-Power Applications

Yuan Li,Gregory J Kish

doi:10.1109/access.2022.3152536

Abstract

Multi-port converters can interconnect different dc and ac systems while reducing semiconductor requirements and losses by eliminating redundant power conversion stages. Modular multilevel converter (MMC)-based multiport systems are well suited for application in mixed ac-dc grids containing high-voltage dc (HVDC) and medium-voltage dc (MVDC) systems. This paper conducts a detailed comparative assessment of multi-port dc-dc-ac MMCs for high power applications. Four representative topologies are chosen for study due to their contrasting internal power processing characteristics. Three different network scenarios are investigated that include HVDC and MVDC applications, covering several different power flow cases. The multi-port MMCs are compared in terms of losses, semiconductor effort, internal energy storage and magnetics requirements. The results are extensively discussed and general conclusions are summarized.

Highlights

The growing global trend of integrating renewable energy resources such as wind turbines and photovoltaics into the legacy ac grid is giving rise to mixed ac/dc power systems
Mixed ac-dc power systems can utilize multi-port converters to control power flows between the different dc and ac grids, e.g., to inject power extracted from offshore wind turbines to the onshore ac load centres [5]
This paper performs a detailed comparative assessment of multi-port dc-dc-ac Modular multilevel converter (MMC) for high power applications, where two different dc systems are interconnected with an external ac grid

Summary

INTRODUCTION

The growing global trend of integrating renewable energy resources such as wind turbines and photovoltaics into the legacy ac grid is giving rise to mixed ac/dc power systems. This paper performs a detailed comparative assessment of multi-port dc-dc-ac MMCs for high power applications, where two different dc systems are interconnected with an external ac grid. Such systems can be adopted for largescale integration of renewable power generations into HVDC transmission or local ac/dc distribution systems with different dc and ac voltage levels. Comparing (8) with (6) confirms the power processed by the MP-AT transformer converter-side windings can be reduced relative to the MP-F2F, depending on Gv and the port power flows. This is because the MP-AT employs single-stage dc-dc conversion due to its partial power processing structure

POWER PROCESSING CHARACTERISTICS OF TOPOLOGIES WITH MULTITASKING TRANSFORMERS

CURRENT STRESSES AND SEMICONDUCTOR

SUBMODULE CAPACITIVE STORED ENERGY

EXEMPLAR SIMULATION RESULTS

CONCLUSION