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Study of Multiplexed Inverters for Medium Voltage Drives

par Laurence Laffont - publié le

Vinicius KREMER’s thesis defense, intitled Study of Multiplexed Inverters for Medium Voltage Drives, will be taking place on July, 8th 2022 at 10:00 am in Grenoble – Schneider Electric.

The work thesis has been realised in group CS-LAPLACE in partnership with the company Schneider Electric - Grenoble.

Jury :

Mr Yves LEMBEYE, G2Elab - Université Grenoble Alpes, Rapporteur
Mr Philippe LE MOIGNE, L2EP - Centrale Lille, Rapporteur
Mrs Ilknur COLAK, Schneider Electric, Reviewer
Mr Timothé DELAFORGE, Berner Fachhochschule BFH, Reviewer
Mr Alain LACARNOY, Schneider Electric, guest, thesis co-supervizor
Mr Thierry MEYNARD, INPT - CNRS, LAPLACE, Thesis director

Abstract :

Electric motor-driven systems represent the largest total global electricity consumption worldwide with medium-voltage motors consuming around 10 percent of the world’s energy. On the other hand, the energy cost is increasing, and energy consumption must be reduced for economic and environmental reasons. Therefore, medium-voltage (MV) motors are a clear target for energy improvement ; not just to limit energy bills but also to comply with tightening regulations.
Nevertheless, today only a small amount of installed medium-voltage motors are controlled by variable speed drives, opening the door for introducing efficient adjustable speed drives in a wide range of industrial applications. This technology will help the industry around the world to save energy use without compromising performance or production efficiency. Therefore, the medium-voltage drive market is expected to grow significantly during the next decade.
This thesis introduces and studies a three-phase multilevel converter topology based on the multiplexed concept which is especially intended for medium-voltage drives. The main targets are four-quadrant 4.16 kV and 6.6 kV power drives.
Chapter I presents the context and the state of the art of the MV power drives : their applications, their potential to reduce the energy consumption in the industry, the market expectations, and a description of the aim of this study. The state of the art presents the classical and advanced multilevel topologies that have been implemented as standard products for MV industrial drives and the performance and cost limitation of the MV semiconductors used in these topologies.
Chapter II presents the multiplexed family of converters and proposes different structures that could meet the cost and performance requirements of this study by minimizing the number of MV semiconductors. Additionally, the proposed structures are compared in terms of semiconductors cost with two well-established solutions in the market.
Chapter III presents the working principle of this topology and two different modulations schemes that have been developed for the structures proposed previously. A carried-based modulation and a space vector modulation have been developed to reduce the switching efforts of the MV semiconductors. Moreover, the two modulation schemes have been compared in terms of waveform quality.
Finally, chapter IV presents the experimental results that validated some particular technical aspects of the multiplexed structure and some assumptions made during this work. Three different test benches (one being a complete inverter) have been used to validate the series connection of 1.7 kV and 4.5 kV IGBTs, to measure the switching energies of MV semiconductors under reduced voltage and measure the stray inductances of the inverter. These results have been used to estimate the efficiency of the proposed structure, study the distribution of semiconductors losses, and compare the performances of the two developed modulation schemes.

Keywords : Medium-voltage drives, multilevel topologies, multiplexed topology, space vector modulation, power semiconductors characterization, IGBTs series connection.Keywords : Medium-voltage drives, multilevel topologies, multiplexed topology, space vector modulation, power semiconductors characterization, IGBTs series connection.