Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

De pollutie van het elektrische net door harmonischen kreeg de laatste jaren meer en meer aandacht vanuit de industrie. Ook tijdens onze studies werd aan dit fenomeen veel aandacht geschonken. Door de toename van het aantal niet-lineaire lasten wekt dit probleem steeds meer de aandacht op. In hoofdstuk 1 wordt het probleem van harmonischen gesitueerd in het concept van de netvervuiling. Maar wat zijn nu eigenlijk harmonischen? Dit wordt uitgelegd in hoofdstuk 2. Er zijn twee mogelijke oorzaken van deze harmonische vervuiling. Enerzijds zorgen niet-lineaire lasten voor een vervuiling door de niet-sinusvormige stroom die ze trekken. Deze stroom zal over de netimpedantie een niet-sinusvormige spanning plaatsen die op de 'zuivere' spanning komt te staan. Deze vervuilde spanning zal dan op zijn beurt een harmonische stroom veroorzaken in alle gebruikers. De mate van vervuiling door de niet-lineaire lasten wordt bepaald door de grootte van de netimpedantie. Anderzijds kan de distorsie bij he

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Managing the security of a power system poses a big challenge for the Transmission System Operators (TSOs) in the present days due to large amount of renewable energy source integration into the system. Congestion is now a frequent issue in a meshed power system like that in Europe, due to increased market competition after decentralization and high integration of renewables. This demands the existing transmission infrastructure to be expanded, but serious limitations are posed mainly due to the enquote{not in my backyard} attitude. Another major aspect of congestion management is the incurred cost to the TSOs for generation re-dispatch in the decentralized environment. Hence, TSOs are forced to find other means of managing congestion, keeping the costly actions as their last means. Moreover, the existing grid has to be operated more flexibly in order to integrate more renewables, thereby diverting flows to non-congested areas in the system. Traditional N-1 principle for guaranteeing security of the power system will no longer be sufficient in the future due to enormous renewable integration into the system, as the cumulative forecast error can be significantly large. This, in turn, leads to serious challenges for the system operators to plan the operation of their systems day-ahead for real-time operation. Risk-based methods need to be developed in such a case in order to circumvent the limitation of the current approach of system security in the presence of increased renewables. Power flow controlling devices (PFCS) have gained increasing attention among the TSOs in Europe. Many of these devices are installed and operated mainly to limit loop flows and manage transit flows through their systems. These devices are also used to manage critical contingencies in the system, but their operation mainly lies on the operator expertise. These devices also have a critical impact on the neighboring interconnected system, as these devices can create congestion and endanger system security of the neighboring grids if not controlled in a coordinated manner. This thesis proposes algorithms to manage security and handle contingencies in the system with the help of already installed PFCs in a coordinated manner. It is also shown that operating the grid flexibly by these devices indeed helps integrating more renewables and handling more uncertainties in the system. A novel risk-based methodology is also developed in this thesis with which the system operators can learn the optimal operation point in their day-ahead operational planning, making maximum use of the system with a given confidence that the uncertainties present in the system due to renewables do not cause system overloads. It is also shown that the confidence can be significantly increased by a coordinated control of the PFCs.

Theses

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Europe aims to reach net-zero greenhouse gas emissions by 2050. Offshore wind energy is a cornerstone in reaching this goal: the EU targets an installed capacity of 300GW of offshore wind by 2050. Integrating such large amounts of offshore wind in to the current energy system will have a massive impact on the existing electricity grid. Traditionally the offshore grid has had a strong national focus: wind farms were connected to a single national onshore grid, while connections between countries relied on using separate cables. In the future this could change by building hybrid interconnectors. Using a hybrid interconnector design, electrical connections to multiple countries are possible. These connections are multifunctional: capacity is allocated to transport power from the wind farm to shore or for electricity trade between countries. Previous studies have shown that hybrid interconnector projects have the potential to increase welfare in Europe. However, there are many stakeholders involved in such projects. A hybrid interconnector will only be realized if all individual stakeholders have clear incentives to integrate their assets in a hybrid solution. Therefore this thesis will determine the optimal hybrid interconnector dimensions for all stakeholders involved. This work aims to evaluate if it is possible to dimension a hybrid interconnector so that all parties have the necessary incentives. We build a model of the Western-European electricity grid and use it to answer these questions based on a case study of a hybrid interconnector between Belgium and Great Britain. The case study results showed that the hybrid interconnector could be more beneficial than building a separate point-to-point interconnector and a radially connected windfarm. However, the optimal dimensions of the hybrid interconnector for different stakeholders are conflicting. We investigate the solution-space where all stakeholders are guaranteed to increase their benefit while the total welfare increase in Europe is more significant than by building separate offshore assets. There exists a large domain for which the project dimensions fulfil these criteria. However, the supra-national optimum that maximizes the welfare of the entire system cannot be reached using this approach.

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

For the large-scale integration of renewable energy sources into the power system, transmission corridors with power ratings and lengths greatly exceeding those in the existing power system will be needed. To realize these corridors, Voltage Source Converter High Voltage Direct Current (VSC HVDC) offers several advantages over the currently widely used ac technology. The use of VSC HVDC in a large-scale meshed grid can provide the major reinforcements to the power system needed for the integration of massive amounts of renewable energy sources.Selective protection against dc side faults is essential to safely and reliably operate meshed HVDC grids. Since required operating times for HVDC grid protection are ten to hundred times faster than existing ac protection, HVDC grid protection algorithms are fundamentally different from those used in ac systems. Furthermore, the limited number of HVDC grid protection algorithms reported in the recent literature were only tested in specific small-scale test systems. For a generally applicable and reliable HVDC grid protection, a more fundamental approach towards the development of protection algorithms is needed.This work provides the necessary concepts to develop communication-less protection algorithms for meshed HVDC grids. A detailed overview of dc fault phenomena is provided and fault clearing strategies proposed in the literature are discussed and classified. The fault current contribution of the half-bridge modular multilevel converter is characterized and a reduced converter model for dc fault studies, is proposed. Guidelines for the design of fault detection methods, based on fundamental traveling wave theory, are provided. Furthermore, signal processing requirements for protection algorithms, in particular required sampling frequency and digital filtering, are investigated. Finally, fast and selective HVDC grid protection algorithms for primary and backup protection are developed. These algorithms are tailored for selective fault clearing in VSC HVDC cable grids with inductive cable termination.