Research Projects
Security of Multi-Area Power Systems
Introduction
Ensuring the security of electricity delivery is one of the key objectives of power system planning and operation. The security criterion currently used is the N-1 criterion, which dictates that the system shall be able to withstand the unexpected outage of any single component, with the N-k extension, which accounts for selected simultaneous failures. In single area systems, where a single transmission system operator (TSO) is responsible, the N-1 criterion exhibits imperfections. In multi-area systems, such as the ENTSO-E (formerly UCTE) system, the N-1 criterion does not provide a security definition. In multi-area systems each operator determines, using limited knowledge of their surroundings, the security of their own system but there is no superior entity which considers the security of the whole system. This approach was suitable when cross-border flows of energy, and thus the influences of one system on others, were negligible, but with increasing trading this is no longer necessarily the case. It is possible that an outage in one system is well-handled in that particular system, but causes devastating problems in neighboring systems. In the last decade, this effect has been a contributor in many of the large disturbances resulting in blackouts both in Europe and in North America.
The goal of this project is to define security in multi-area system, determine how the responsibility and the costs for maintaining security shall be shared, and how cross-border transmission capacity might be allocated while taking into account such security considerations.
Project Goals
Defining security for multi-area system is a very challenging problem. The difficulty is compounded when it must be decided how responsibility and costs shall be shared among the participants. This project intends to address some of the topics associated with this question. Specific targets are given be the following questions:
• Are the current practices for network operation adequate from a security perspective?
• Can system vulnerability be decreased while simultaneously maintaining transmission capacity for trading?
• Does the N-1 criterion need to be complemented, or even replaced, for multi-area operation?
The project goals are given by the desire to answer the questions above.
• Required extensions of the current single area security criteria to account for deficiencies.
• Definition of a security criteria for multi-area systems
• Determining how responsibility for security is to be shared between the participants in multi area systems.
• Determining how the costs for maintaining security are to be shared between the participants in multi area systems.
In addition to the question of system security in multi-area systems a targeted question is also the trading of control reserves in such systems. Current practices dictate that each area is responsible for providing and keeping sufficient reserves for its own needs (secondary and tertiary control reserves), as well as a proportional amount of the demand of neighboring system (primary frequency control reserves). In order to target the most economical allocation and provision of such control reserves by allowing inter-system trading, the principles governing inter-area trading and capacity allocation must be investigate in more depth. The need to reformulate such guidelines should however not be taken for granted, although it may occur.
Bibliography
Wehenkel, L., Glavic, M., & Ernst, D. (2006). On multi-area security assessment of large interconnected power systems. Second Carnegie Mellon Conference in Electric Power Systems.
Zima, M., & Ernst, D. (2005). On multi-area control in electric power systems. 15th Power System Computation Conference. 22-26 August, Liege, Belgium.
Partnership: swisselectric research, EPF Lausanne
