Nos publications scientifiques
Study of Turn-to-Turn Electrical Breakdown for Superconducting Fault Current Limiter Applications
The rational insulation design of a resistive superconducting fault current limiter (r-SCFCL) requires data gathered from experimental setups representative of the final apparatus. Therefore, an experimental study was performed to characterize the electrical breakdown (BD) of liquid nitrogen (LN2) in the peculiar conditions of a quenching superconducting device.
Arc appearance and cathode spot distribution in a long gap high-current vacuum arc controlled by an external axial magnetic field
An experimental study of a high-current vacuum arc (VA) generated between two static CuCr25 contacts spaced 20 or 30 mm apart was conducted to characterize the arc appearance and the cathode spot (CS) distribution.
Packaging of 10 kV SiC MOSFETs: Trade-Off Between Electrical and Thermal Performances
SiC transistors can achieve blocking voltages of 10kV and more. This makes them especially attractive for energy transmission and distribution. Although SiC devices can in theory operate at high temperature (more than 200°C), the on-state resistance of SiC MOSFETs exhibits a strong dependency on the junction temperature. As a consequence, it is shown that these transistors must actually operate at a relatively low junction temperature (less than 100°C) to increase conversion efficiency and prevent thermal runaway. This requirement for high-performance cooling systems has consequences on the packaging technology: the corresponding power modules must both offer a high voltage insulation and a low thermal resistance. In particular, there is a trade-off in the thickness of the ceramic substrate located between the SiC devices and the cooling system. We propose a new substrate structure, with raised features, which improves the voltage strength of a substrate without increasing its thickness. This structure is demonstrated experimentally.
Assessment methodology and performance indicators for HVDC grid protection strategies
A methodology to assess HVDC grid protection strategies using reliability and speed indicators derived from Monte Carlo simulations.
Energy Control of Modular Multilevel Converters in MTDC Grids for Wind Power Integration
The role of Modular Multilevel Converters (MMCs) in HVDC grid greatly differs depending on whether it is an offshore or an onshore station. From the common point in their control schemes, an unexploited ability of the MMC—the controllability of the internally stored energy—is identified in both offshore and onshore applications. The virtual capacitor control, previously proposed by the authors, makes use of this degree of freedom to provide energy contribution to the DC grid. The impact of this control is demonstrated by time-domain simulations of a five-terminal HVDC grid.
HVDC protection criteria for transient stability of AC systems with embedded HVDC links
The objective of this study is to propose a methodology for the transient stability assessment of a simple but representative AC grid in case of DC fault. After validation of the methodology, some HVDC link protection criteria are defined in terms of the Critical Time to Return to Operation. These criteria will be helpful for the design of HVDC protection systems or for the sizing of future HVDC links in order to respect the constraints of the existing protection strategies.
Electrical properties of epoxy systems based on ionic liquids
In accordance with their interesting properties, ionic liquids (ILs) have attracted in the recent years a great interest in the material field. Recently, few authors have demonstrated the reactivity of ionic liquids towards epoxy in order to form new epoxy-based networks...
Design considerations for the 2- phase cooling system of a 5 MW MVDC converter
This presentation will provide an update on our current project: designing a cooler for a high power (5 MW) MVDC converter for offshore wind turbines applications. A number of constraints are imposed, mainly related to a limited volume, environmental, safety and health regulations, and of course cooling performance. Indeed, as we presented last year (ATW 2017), the silicon carbide power semiconductors used in this converter should operate at a junction temperature lower than 100 °C for better efficiency.
AC Grid Forming by Coordinated Control of Offshore Wind Farm connected to Diode Rectifier based HVDC Link-Review and Assessment of Solutions
This paper reviews a few of the major control solutions for AC grid forming and operation of DR-HVDC based OWFs. Then these solutions are compared based on their approach in solving the major challenges involved.
Analysis of the Lower Limit of Allowable Energy in Modular Multilevel Converters
In this paper, a thorough analysis of the converter arm behavior is presented, which gives an analytic expression of the lower limit of the energy as a function of the converter operating point and the connected grid conditions. The relation between the lower energy limit and the operating power is analyzed by using the practical MMC specifications of an HVDC application. An experimental test of a small-scale MMC mock-up demonstrates the validity of the theoretical analysis.
