Power-System Level Classification of Voltage-Source HVDC Converter Stations Based Upon DC Fault Handling Capabilities

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Modeling and Control of DC Grids (Modellering en controle van DC netten)

The European Union's energy policy strives for a competitive, sustainable and secure energy supply. One of the most obvious results of this policy is the ongoing strong increase of renewable energy sources in the energy supply. The transmission grid updates required to accommodate this envisaged massive amount of renewable energy sources in the transmission system go well beyond standard system reinforcements used in the past: in the coming decades, a North-Sea grid interconnecting various offshore wind farms is expected to be built. This grid can gradually evolve into a European overlay supergrid connecting the offshore wind resources with the demand centers on the continent. Also solar energy, concentrated in the south of Europe, will require similar solutions. Voltage Source Converter High Voltage Direct Current (VSC HVDC) is the most suitable technological candidate to build such a grid.One of the challenges to use this technology relates to the control of the DC voltage in case of DC system contingencies, such as a converter outage. This thesis deals with the modeling and control of VSC HVDC in a meshed DC grid and multi-terminal DC systems in general. Models are developed to address both the interactions with the AC system and the control of the DC system. The main contributions of the work include a detailed comparison of different DC voltage control strategies for multi-terminal DC systems, the development of detailed dynamic and steady-state models as well as an open-source Matlab-based power flow software program, MatACDC, which enables the study of the influence of the DC voltage control on the power flows in the AC and DC systems. Furthermore, the impact of a distributed DC voltage control on the AC system transient stability is investigated, as well as the influence of the DC system layout on the DC voltage control after a contingency.nrpages: 237status: publishe

Modeling and Control of DC grids - KBVE/SRBE Robert Sinave Award 2013

This paper discusses the background and main contributions of my PhD thesis entitled “modeling and control of DC grids”. The expected advent of multi-terminal HVDC systems and meshed DC grids poses major challenges to the control and operation of our power system. The article describes these challenges and explains how the work has contributed in the field of the development of steady-state and dynamic models to study the future power grid. Furthermore, the article describes new fundamental insights in system interactions that have been analyzed in the thesis.status: publishe

A Comprehensive Modeling Framework for Dynamic and Steady-State Analysis of Voltage Droop Control Strategies in HVDC Grids

This paper presents a comprehensive modeling framework to analyze and compare the performance of different voltage droop control characteristics in an HVDC grid. All models are fully derived mathematically, both for dynamic simulations and for steady-state power flow analysis. The main contribution lies in the development of a common modeling and control approach for the different droop-based control schemes that have been presented in the literature. The discussion includes power- and current-based droop control, either in their standard form or combined with a deadband, a constant voltage control or consisting of different slopes. Dynamic simulations show that, when applying a comparable underlying dynamic converter control framework, similar dynamic responses can be expected from the different droop control schemes, while the steady-state voltage deviations and power sharing after a contingency are different. A comparison with results from a full-detailed power flow implementation shows that these voltage deviations and power sharing can accurately be predicted by the derived steady-state power flow models, thereby avoiding the need for time-consuming dynamic simulations.status: publishe

MATACDC - an open source software tool for steady-state analysis and operation of HVDC grids

With the increased interest in HVDC grids and their steady-state interactions with existing AC systems, there is a growing need for the development of tools to study the power flows in these systems. In this paper, we present MATACDC, an open source software for the analysis of hybrid AC/DC systems. The tool is available for everyone to download and allows to study the power flows in complex hybrid AC/DC systems. Incorporation of different converter control strategies enables the study of their steady-state impact for different contingencies, such as line outages or converter outages. MATACDC has been fully integrated with the power flow routines of MATPOWER, the open source MATLAB toolbox for solving AC system power flow and optimal power flow problems. A case study of the CIGRE B4 DC grid test system shows that the tools can be used to analyse complex hybrid AC/DC systems.status: publishe