Case Study of Non-Isolated MMC DC-DC Converter in HVDC Grids

2021-08-11T16:54:28+02:00June 7th, 2019|Electronique de puissance & convertisseurs, Publications|

This article presents the topology for non-isolated MMC-based DC-DC converter. The initial design study illustrates that such DC/DC converter will have overall semiconductor count comparable to a MMC AC-DC (used with HVDC transmission) converter of similar rating. A full controller schematic is presented and operating principles are discussed.

New challenges for High Voltage transmission

2023-01-31T13:35:57+01:00May 15th, 2019|Appareillage électrique haute tension, Publications|

In able to fully integrate renewable energies and to stop to use fossil energy and nuclear power, there is a need to evolve the current electric grid in a new one called the supergrid. This new grid will be based on a mix of High Voltage AlternativeCurent (HVAC) and High voltage Direct Current (HVDC) junctions highly meshed with Gas Insulation Substation (GIS) as nodes. While HVAC GIS technologies are well mastered, HVDC ones are still at the beginning. One weakness of the equipment being dielectric insulators, industries may have to conceive new dielectric formulations or improved ones. This paper presents a list of properties and values to target for future dielectrics formulation. At the end, it highlights as well, the importance of health and environnement and how their consideration have to be at the same level of attention than the final properties of the dielectrics.

Power electronic traction transformers in 25 kV / 50 Hz systems: Optimisation of DC/DC Isolated Converters with 3.3 kV SiC MOSFETs

2021-08-11T16:54:55+02:00May 9th, 2019|Electronique de puissance & convertisseurs, Publications|

In AC electric trains, power electronic traction transformers (PETT) are multilevel single phase AC/DC converters connected to the AC medium voltage overhead line. For indirect topologies, DC/DC isolated converters are key elements of PETTs. This paper shows a method to design such DC/DC converters, and several variants are considered. Finally, the comparison results, in the case of a 25 kV / 50 Hz power supply and 3.3 kV SiC MOSFETs, show that the variant with a resonant AC link, with only one controlled bridge and a switching frequency lower than the resonant frequency, offers the best efficiency at rated power for a given volume.

A New Energy Management Control of Modular Multilevel Converters for Coping with Voltage Stress on Sub-Modules

2023-01-31T13:26:55+01:00April 24th, 2019|Appareillage électrique haute tension, Publications|

This paper investigates the impact of the operating condition on the SM voltage ripples. In particular, it is revealed that under the classical control scheme where the Modular Multilevel Converter internal energy varies naturally with the DC grid voltage, the traditional sizing approach based on the analytical expression of instantaneous SM voltage may fail to respect the SM voltage constraint. To tackle this problem, this paper presents a solution by incorporating the advantages of the explicit energy management and the developed analytical expressions of the SM voltage ripple, which achieves a better utilization of the converter asset.

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