Sub-module Converters Research Articles

Modular‐multilevel converter topologies and applications – a review

Recently developed modular-multilevel converter (M-MC) has a major attention in the industry and research works which is moving into feasible technology for many medium and high-power applications. M-MCs have been improved by existing power conversion technology in several aspects, including efficiency, modular structure, power quality, transformerless operational capability, fault tolerant and redundancy operations having a low expense, standard components utilisation, high availability, excellent quality of output wave forms. However, as several challenges combined with M-MC topologies, include reduced voltage stress, compact size, and substantially lower semiconductor losses. These attributes the lower operating cost for high-power applications such as distribution systems and high-voltage direct current (HVDC) transmission systems. The main contribution of this study is to bring the scrutiny of M-MC applications and different circuit topologies. These M-MC configurations consist of converter structures with sub-module converters and M-MC family members. In such a way, the M-MC applications are generalised and it results the size and cost halved, reduced conduction and switching losses and increases system reliabilities. Moreover, in each application of M-MC, drawbacks, and advantages have been discussed in detail. This review presents the latest performance of M-MC with respect to the mentioned research areas and new applications.

A Static Ground Power Unit Based on the Improved Hybrid Active Neutral-Point-Clamped Converter

This paper proposes a new configuration for static ground power unit (GPU) based on the novel 25-level hybrid active neutral-point-clamped (HANPC) converter. The superiority of the proposed converter, as compared with conventional and other suggested multilevel converters, is significant decreasing the number of switches and minimizing the number of flying capacitors (FC) in converter. This improvement is possible by using suggested low-voltage submodule converter to the ANPC converter and proposed modulation method. This results in reduction of the size and cost of converter and makes it more feasible and reliable. Applying the active voltage balancing method for FC in the proposed HANPC converter guaranties fast charging and voltage-level regulation of FC without using balance booster circuit. Improving output voltage spectrum leads to inductance reduction of output L–C filter which enhances static GPU performance. The simulation and experimental results verify the validity and feasibility of the proposed converter.