DC/DC Converters for Multiterminal HVDC Systems: Based on Modular Multilevel Converter

The increase in the energy demand has resulted in searching for new energy sources. Due to the increased prices of fossil fuels and the environmental issues, renewable energy sources has become popular in Europe. Renewable energy generation such as wind, solar and wave has point-to-point connections with the main grid. In order to minimize the...

A Computational Intelligence Approach to Voltage and Power Control in HV-MTDC Grids

An ever increasing interest in renewable energy sources (RES) in order to reduce global carbon emissions and alleviate problems posed by climate changes has lead to dramatic increase particularly in offshore wind energy projects. Several different projects are currently being executed and so many are being planned for the future. The location of...

Review of Current Control Strategies in Modular Multilevel Converter

Analysis of Negative Sequence Current Control for MMC HVDC Transmission Systems

High Voltage Direct Current (HVDC) transmission system technology has recently attracted a lot of attention within the power system community. Modular Multilevel Converter (MMC) HVDC is the state of the art HVDC transmission technology, which contains hundreds and even thousands of submodules. It is the modularity, scalability and efficiency...

DC/DC Converters in Multi-terminal HVDC System for Integrating Offshore Wind Farms

The development of far-offshore wind farms and other large-scale renewable energy sources, together with the increasing needs for long distance power transmission is resulting in more HVDC systems being integrated into the traditional AC power network. Due to the capability for operation in isolated AC grids, VSCs are becoming the preferred...

Partial Discharge Recognition of Defects in Gas Insulated Systems under DC Voltage

The thesis consists of 7 chapters. The first chapter will explain the background, motivations and the general overview of the thesis. Chapter 2 is a literature review describing the physics behind the creation of PDs. The conditions necessary for the occurrence of PDs are covered in addition to an analysis of the different types of PD in GIS...

Partial Discharge Analysis in HVDC Gas Insulated Substations

Nowadays, Gas Insulated Substations (GIS) are vital nodes of the Transmission Network due to their compact dimensions permitted by the use of SF6 as insulating medium and the high reliability guaranteed. Nonetheless, the strictly requirements of safety in operation and continuous power supply catalyse the attention to improve the reliability and...

Investigation of space charge injection, conduction and trapping mechanisms in polymeric HVDC mini-cables

Polymeric insulation materials have not been used in HVDC cable systems until recently. The main cause of this being the tendency of polymers to deplete accumulated charge very slowly. Research into the dynamics of space charge trapping, injection and conduction in polymers can reveal important information from which new materials can be...

Online diagnostics in Smart Grids: An approach to the future power grid.

In this study the term smart grid is specified toward online diagnostics. It is investigated which online diagnostics techniques fit well within smart grids and whether existing technologies can be used in a smarter way. Smart grids and online diagnostics Since 2005, the term smart grids is widely used in literature. To assess what smart grid...

Modeling and investigation of the NorNed HVDC link with RTDS

VSC-HVDC based Network Reinforcement

The recent development in semiconductor and control equipment has made HVDC transmission based on voltage-source converter (VSC-HVDC) feasible. VSC-HVDC has numerous advantages such as a controllable short-circuit current contribution, the rapid and independent control of active and reactive power, and good power quality. With these advantages...