Netondersteunende diensten met HVDC-systemen

This thesis investigates the role of High Voltage Direct Current (HVDC) systems in enabling ancillary services provision and assesses the impact of their use for reserve procurement and exchange on overall reserve procurement and system operation costs. The Transmission System Operator (TSO) is entrusted with the responsibility of transmitting electrical energy from generation sources to regional and local distribution system operators, and ensuring secure power system operation within its control area. To achieve this, the TSO relies on ancillary services, i.e., technical support services that maintain reliable and secure system operation under both normal (steady-state) and contingency conditions. These services are procured from a variety of market participants, including conventional generators, storage providers, and increasingly from renewable energy resources. In the EU, the liberalisation of the electricity sector and the creation of the Internal Electricity Market (IEM) through the first, second, and third energy packages have enabled TSOs to procure these ancillary services beyond their control area and national borders. This cross-border access facilitates the optimal use of resources and infrastructure for secure and cost-efficient power system operation. Increased competition among service providers reduces procurement costs, which are ultimately passed on to consumers, thereby enhancing overall social welfare and the efficiency of the power system. The growing share of renewable generation has significantly reduced the availability of conventional resources for ancillary services. Consequently, cross-border access to ancillary resources and the integration of emerging technologies are becoming crucial for secure and efficient power system operation. Asynchronous HVDC systems enable TSOs to access resources from other countries and markets in different synchronous areas. In particular, VSC-based HVDC systems can directly provide ancillary services, such as reactive power support. It is therefore essential to study the role of HVDC systems in delivering and facilitating the exchange of ancillary services in power systems. This dissertation contributes to the fundamental understanding of ancillary service requirements for European TSOs, focusing on how HVDC system capacity and capabilities can support their procurement. Ancillary service products differ in their technical and market requirements, such as full activation time, minimum bid size, and restrictions on allowed cross-border procurement volume. These differences necessitate specialised optimisation modules tailored to each product. In addition, power system characteristics, such as temporary overloading of transmission lines must be incorporated into these modules when modelling ancillary service procurement. To address these challenges, the thesis develops a set of optimisation modules for analysing the optimal use of HVDC systems in ancillary service procurement, both for individual products and for the co-procurement of frequency control services across multiple countries. The results demonstrate the benefits of reserve sharing and highlight the role of HVDC as an enabler of cross-border reserve exchange, thereby enhancing social welfare and operational efficiency. In addition, the thesis highlights the potential of HVDC systems to support emerging ancillary services such as inertia provision. The findings also demonstrate the trade-offs involved in allocating HVDC system capacity between energy exchange and ancillary services, particularly in scenarios with a high share of RES. Based on these findings, the thesis concludes with practical recommendations for the effective integration of HVDC systems into ancillary service markets, outlining regulatory, technical and market requirements for future power systems.