Multilevel Voltage-Source-Converter Topologies for Industrial Medium-Voltage Drives

This paper presents a technology review of voltage-source-converter topologies for industrial medium-voltage drives. In this highly active area, different converter topologies and circuits have found their application in the market. This paper covers the high-power voltage-source inverter and the most used multilevel-inverter topologies, including the neutral-point-clamped, cascaded H-bridge, and flying-capacitor converters. This paper presents the operating principle of each topology and a review of the most relevant modulation methods, focused mainly on those used by industry. In addition, the latest advances and future trends of the technology are discussed. It is concluded that the topology and modulation-method selection are closely related to each particular application, leaving a space on the market for all the different solutions, depending on their unique features and limitations like power or voltage level, dynamic performance, reliability, costs, and other technical specifications.

I. Introduction

The field of high-power drives has been one of the most active areas in research and development of power electronics in the last decades. Several industrial processes have increased their power-level needs, driven mainly by economy of scale (production levels and efficiency), triggering the development of new power semiconductors, converter topologies, and control methods. The development of high-power converters and medium-voltage (MV) drives started in the mid-1980s when 4500-V gate-turn-off (GTO) thyristors became commercially available [1]. The GTO was the standard for the MV drive until the advent of high-power insulated-gate bipolar transistors (IGBTs) and gate-commutated thyristors (GCTs) in the late 1990s [2], [3]. These switching devices are now extensively used in high-power drives due to their superior switching characteristics, reduced power losses, ease of gate control, and snubberless operation.