Our scientific publications
Development of a protection strategy for future DC networks based on low-speed DC circuit breakers
This paper presents a novel protection scheme based on converter breaker; its key element, namely a low-speed mechanical DC breaker, is located at each DC converter output.
Assessment methodology and performance indicators for HVDC grid protection strategies
This paper presents an assessment methodology of protection strategies for meshed grids. It also proposes the computation of two performance indicators to evaluate protection strategies through a reliability and speed perspective. The Monte Carlo method is used to calculate the two indicators proposed. These two indexes can be used as criteria for comparison between protection strategies. Due to the increasing debate around the protection for HVDC grids, three proposals of protection of HVDC grids were chosen as application cases.
Protection strategy for MTDC grids using SFCLS at converter station output
This study proposes a non-selective protection strategy for multi-terminal high voltage direct current grids based on resistive-type superconducting fault current limiters (SFCLs). Located at the output of AC/DC converters, the SFCL limits the current contribution from the AC grid in case of DC fault. With this approach, the fault clearing time constraint is relieved allowing the use of mechanical DC circuit breakers for fault current interruption. Furthermore, the breaking capability and energy dissipation requirements of the breaker are greatly reduced. To achieve a fast restoration of the DC grid, a redundant SFCL is introduced in parallel to those in operation, bypassing them when the fault is effectively suppressed. In addition, primary and back-up protection schemes are described and tested using a three-terminal bipolar HVDC grid based on half-bridge modular multilevel converters and cable transmission. Simulations are implemented in EMTP-RV® to analyse and discuss performances of the proposed fault clearing strategy.
Evaluation of HVDC cable impedance and admittance matrices by finite element method
In this work, a 2D Finite Element Method (FEM) is used to calculate the frequency dependent impedance and admittance matrices of underground and submarine cables. A harmonic magnetodynamic formulation is used to calculate the series impedances, and for the calculation of the parallel admittance an electrodynamic formulation is applied.
Robustness study of 1700 V 45 mΩ SiC MOSFETs
The threshold voltage instability is a main reliability issue of Silicon Carbide MOSFET transistors. It is a critical parameter when it comes to give a failure in time rate for industrial power applications. In this context, a static ageing test based on JEDEC standard is proposed and the resulting gate oxide degradation is studied and discussed in this paper.
Technical and economic analysis of the R-type SFCL […] in HVDC grids
Mainly used in AC grids, resistive type superconducting fault current limiters may be still more interesting for DC systems due to their capability to reduce high short circuit currents appearing in case of DC cable fault. This limiter reduces the breaking capability, speed, and energy requirements of the required DC circuit breaker allowing the implementation of electro mechanical breakers for fault current interruption. These breakers have lower breaking capability, on load losses, and investment costs in comparison with hybrid circuit breakers based on power electronics. This paper presents a technical and economic analysis of a superconducting fault current limiter used in a radial three terminal high voltage DC grid to protect a cable link. Based on simulation studies using an electro magnetic transient program, an effective system protection will be demonstrated with special attention to the continuity of power flow through healthy parts of the grid.
