A New Resonant Modular Multilevel Step-Down DC–DC Converter with Inherent-Balancing

Abstract

Modular multilevel converters (MMCs) have become increasingly interesting in dc-dc applications, as there is a growing demand for dc-dc converters in high voltage applications. Power electronics transformers (PETs) are commonly used for high step-down ratio dc-dc power conversion, with high power rating and efficiency achieved.However, this arrangement requires a large number of high isolation voltage transformers and a complicated balancing control scheme. To provide a simple solution with inherent voltage balancing, this paper presents a new resonant MMC topology for dc-dc conversion. The proposed converter achieves high voltage step-down ratio depending on the number of sub-modules. The converter also exhibits simplicity and scalability with no necessary requirement of high voltage isolation transformers. By using phase-shift control, a much higher converter operating frequency is achieved compared to the switching frequency. Resonant conversion is achieved between the series inductor and sub-module capacitors. The operation principle and theoretical analysis are presented in this paper, which have been verified by experimental results based on a bench scale prototype.

The Modular Multilevel Converter for High Step-Up Ratio DC–DC Conversion

“…In medium and high voltage applications, modular multilevel converters (MMCs) used for dc-dc conversion are emerging technologies [9], [23]. These converters are based on conventional MMCs [24]- [29].…”

The new family of high step ratio modular multilevel DC-DC converters

“…This converter achieves galvanic isolation between input and output. However, this converter with single diode rectifier results in higher current stress and has no advantage compared to its variation with full bridge rectifier in [10] (see Fig. 2 (d)).…”

“…Modular multilevel converters (MMCs) used for dc-dc conversion in medium and high voltage applications are emerging technologies [1], [10]. These converters based on conventional MMCs [11]- [15] require a complicated balancing control scheme to maintain the voltage levels.…”

Reliability Analysis of MMCs Considering Submodule Designs with Individual or Series-Operated IGBTs

“…arrangement of power electronic switches, with a floating submodule capacitor. Since the concept of MMC was proposed by R. Marquardt in 2001 [3], various topologies based upon the modular multilevel concept have been developed for high voltage applications for both dc-ac conversion [4], [5] and dc-dc conversion [6]. In the HVDC transmission application, researchers have mainly focused their efforts on improving the performance of MMCs, including topology optimization [7], modulation [8], voltage balancing [9] and power loss evaluation [10].…”