Evelyn Heylen

Framework for Evaluating and Comparing Performance of Power System Reliability Criteria

Evolutions in the power system challenge the manner in which power system reliability is managed. In particular, currently used reliability criteria, typically the deterministic N-1 criterion, are increasingly inadequate. Moving to an alternative approach is difficult as quantifying benefits is hard in a multifaceted environment and system operators are reluctant to move away from the easy and transparent existing criterion. This paper presents a generic framework to evaluate and compare socio-economic and reliability performance of power system reliability criteria, focussing on the short term decision making process of transmission system operators (TSO). The framework can also be used to tune the parameters of reliability criteria. Short term operational planning and real time operation TSO decision making processes are simulated considering various reliability criteria. The framework is applied to a 5 node test system and the 24 node IEEE reliability test system, showing that the applied probabilistic reliability criterion outperforms deterministic N-0 and N-1 approaches in those systems in terms of expected reliability and socio-economic indicator values. The effect is larger in the bigger system with more operational flexibility.

Impact of value of lost load on performance of reliability criteria and reliability management

Evaluating the performance of various power system reliability criteria and their management is important in order to obtain a cost effective reliability level of the power system. However, the performance of reliability criteria depends on several parameters, of which one is value of lost load (VoLL). Value of lost load is typically difficult and complex to model, which hampers making a general conclusion about the most appropriate reliability criterion. This paper gives a methodology to assess the impact of VoLL on the performance of reliability criteria and their management. The assessment is made for a 5 node test system, based on the Roy Billinton reliability test system, using 4 different reliability criteria, i.e. 2 probabilistic and 2 deterministic approaches. The focus is on operational planning and real time operation.

Impact of increased uncertainty in power systems on performance of short term reliability management

Power system states are not accurately known ahead of real time and are subject to natural variability, which leads to uncertainty in the system. Sources of uncertainty are amongst others load, renewable energy sources and contingencies. An aggregate measure for systems uncertainty is determined in order to have a single quantified value of the uncertainty level in the system. This allows to compare performance of power system reliability management according to various reliability criteria at different uncertainty levels in a transparent manner. A case study for a 5 node test system illustrates the use of the aggregate uncertainty measure and the impact of different uncertainty levels on short term reliability management of transmission system operators according to three reliability criteria. Results of the case study illustrate that probabilistic reliability management can lead to significant improvements in performance in terms of total system cost and curtailment of non-flexible load compared to reliability management based on deterministic N-0 and N-1 criteria, especially at high uncertainty levels in heavily loaded system conditions.