Pole-to-ground fault protection strategy for HVDC grids under symmetrical monopolar configuration

2019-06-24T13:54:30+00:00June 25th, 2019|Publications, Supergrid Architecture & Systems|

This paper proposes a novel pole-to-ground fault protection strategy for HVDC grids under symmetrical monopolar configuration employing low-speed DC breakers and pole rebalancing reactor (PRR) located at AC side to manage the rebalancing of the pole voltages. The first part of the paper is dedicated to the detailed description of the primary and backup protection sequences. In the second part, the proposed concept is validated through EMT simulations performed on a 4-terminal HVDC grid.

Effect of the Surge Arrester Configuration in MMC-HVDC Systems under DC and Converter Fault Conditions

2019-06-18T08:58:58+00:00June 18th, 2019|Publications, Supergrid Architecture & Systems|

Different surge arrester configurations are studied for a modular multilevel converter (MMC) in a symmetrical monopole configuration. Each configuration is analyzed under fault conditions including DC side faults and faults inside the converter station. The configurations considered are compared in terms of overvoltages, current levels and energy dissipation. It is found that the selection of the surge arrester parameters does not only depend on the overvoltage levels of the equipment, but also on the surge arrester configuration considered. The action of the surge arresters could result in higher longitudinal withstand voltage requirements of the arm reactors. Furthermore, special attention shall also be given to the possible low inductance loops created by the conduction of the arresters during a transient event.

SuperGrid Institute’s participation in PROMOTioN’s Work Package 9

2019-05-22T14:23:46+00:00May 22nd, 2019|Supergrid Architecture & Systems|

SuperGrid Institute is proud to have been an active participant in the PROMOTioN project since 2016. This project is part of the European Union’s Horizon 2020 program and is made up of several work packages (WP) that share a common aim: developing meshed HVDC offshore grids that are both cost effective and reliable, through technological innovation. SuperGrid Institute is an active member of several Work Packages, including WP9 whose objective is to develop fault clearing strategies using Hardware-in-the-Loop (HIL) real-time simulation (RTS).

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

2019-04-24T11:17:05+00:00April 24th, 2019|Publications, Supergrid Architecture & Systems|

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.

Overview of DC–DC Converters Dedicated to HVdc Grids

2019-04-17T10:20:39+00:00February 19th, 2019|Power Electronics & Converters, Publications, Supergrid Architecture & Systems|

This paper presents an overview of the dc–dc power converters dedicated to HVdc proposing a classification based on their structure. Two large families are established: those which provide galvanic isolation, and those which do not. Several subfamilies are also proposed. An overview of the main HVdc applications that can be targeted with each family is also presented, highlighting the main converter requirements for each application case.

PhD Amjad MOUHAIDALI “Contribution to the modelling of HVDC cables for electromagnetic transient simulations”

2019-02-13T11:02:37+00:00February 13th, 2019|Phd, Supergrid Architecture & Systems|

The integration of new technologies in the electric grids made them more and more complex, and most likely future growth of power grids will be based more on underground cables than overhead lines. One problem here, is that the mathematical model for electromagnetic simulation of power cables still has some shortcomings regarding stability, accuracy and passivity. In this thesis, we evaluate the cable parameters using analytical and numerical methods.

FMEA of a non-selective fault-clearing strategy for HVDC grids

2019-04-17T10:24:03+00:00February 7th, 2019|Publications, Supergrid Architecture & Systems|

The Failure Mode Effect Analysis (FMEA) is a technique used to investigate failures in a process or component and to identify the resultant effects of these failures on system operations. In this paper it is explained how the FMEA can be used to define and assess the impact of the failure modes (FM) of a protection strategy for High Voltage Direct Current (HVDC) grids.

Virtual Capacitor Control for Stability Improvement of HVDC System Comprising DC Reactors

2019-04-17T10:17:08+00:00February 7th, 2019|Publications, Supergrid Architecture & Systems|

This paper first analyzes the underlying instability issue attributed to the DC reactor by using a simplified converter station model, which reveals that the DC-link capacitor can compensate for the detrimental effect of the DC reactor and increase the stability margin. This capacitor, however, is usually avoided and distributed over the capacitors in sub-modules in the state-of-the-art Modular Multilevel Converters (MMCs).