Framework for comparing power system reliability criteria Evelyn Heylen Prof. Geert Deconinck Prof. Dirk Van Hertem Durham Risk and Reliability modelling for Energy Systems day November 12 th, 2014

2 Introduction Current situation in power system reliability management Deterministic N-1 criterion with various shortcomings Major evolutions in the power system Increasing uncertainties Probabilistic reliability management Take into account probabilities Could tackle shortcomings of N-1 Many academic references Not fully used in practice  Amongst others due to lack of quantified benefits Framework for Comparing power system reliability criteria

3 Outline Framework for comparing power system reliability criteria o Overview o General schematic of the implementation o Implementation of deterministic reliability management module o Assumptions o Comparison of deterministic criteria Conclusion

4 Outline Framework for comparing power system reliability criteria o Overview o General schematic of the implementation o Implementation of deterministic reliability management module o Assumptions o Comparison of deterministic criteria Conclusion

5 Framework for comparing reliability criteria Objectives of the framework: 1.Quantification of performance of various power system reliability criteria and their management 2.Comparison of performance 3.Identifying alternative reliability criteria

6 General schematic

N-1 criterion: ‘System should be able to withstand at all times the loss of any one of its main elements (lines, transformers, generators, etc.) without significant degradation of service quality.’ 2. State enumeration: Run power flow Check for operational limit violations 4. Reliability actions Corrective actions Preventive actions 4 Deterministic reliability management module 3. Decision = balance reliability and cost

8 Reliability management modules Reliability assessment methods Analytical contingency enumeration Event tree/fault tree analysis Random sampling (Monte Carlo) Markov analysis Reliability criteria N-kOptimization Limits on reliability indicators Optimization and limits on reliability indicators Reliability control Preventive/corrective control Asset management System development

9 Reliability management modules Reliability assessment methods Analytical contingency enumeration Event tree/fault tree analysis Random sampling (Monte Carlo) Markov analysis Reliability criteria N-k (i.e. N-0 and N-1)Optimization Limits on reliability indicators Optimization and limits on reliability indicators Reliability control Preventive/corrective control Asset management System development

10 General schematic

11 Framework for comparing reliability criteria

12 Data generation Unit commitment model Monte Carlo Data modules Matlab m-file Events and triggers Input reliability assessment

13 Test Setup (I) Reliability criterion e.g. N-1, N-0  Extended problem formulation using islanded systems Reliability control e.g. preventive, corrective  Interlinking constraints between islanded systems PF = Power flow SW = Social welfare OPF = Optimal power flow

14 Test setup (II) Objective function  Minimal cost for society == maximal social welfare Probabilistic approach in large system  State selection PF = Power flow SW = Social welfare OPF = Optimal power flow

15 PF = Power flow SW = Social welfare OPF = Optimal power flow Simulation Optimization, e.g. SCOPF, OPF  Economic dispatch of generators satisfying operational limits, reliability criterion and control constraints

16 TSO actions Short term: Preventive and corrective actions Medium term: asset management & operational planning Long term: system development PF = Power flow SW = Social welfare OPF = Optimal power flow

17 Reliability assessment Check performance of reliability criterion and reliability control using PF and OPF for: All contingency cases Contingency cases of truncated state space Specific scenarios (i.e. events)

18 Events Evaluate performance of reliability management for specific cases Time series including results of events due to: o Natural hazard o Operational conditions o Human behaviour Which can lead to: o Discrepancy between generation and load o Generator/branch outage at particular moment in time o Failure caused by several simultaneous faults (failure of cable or power line in same trace etc.) o …

19 Economic evaluation Based on market model Social welfare evaluation Total cost evaluation  Could be substituted by more complex evaluation techniques

20 Comparison of reliability criteria Methodology for comparing reliability criteria Appropriate metric for comparing reliability criteria

21 Assumptions No generator ramp rates or minimal on/off times Knowledge of Value of Lost Load at every node Linear cost curves  constant marginal costs of different units Corrective actions o Generation redispatch o Load shedding Constant failure and repair rates  exponential distribution Aggregated branch models No failure of corrective actions Reliability assessment considers only branch outages No forecasts errors included (wind, load…)  No stochastic, multi-stage optimization Single TSO, Single area DC power flow

22 Comparison: Results Three node test system Comparison of o N-0 corrective o N-1 preventive o N-1 corrective Varying value of lost load (VoLL) Performance of reliability criteria and their management dependent on VoLL

23 Outline Framework for comparing power system reliability criteria o Overview o General schematic of the implementation o Implementation of deterministic reliability management module o Assumptions o Comparison of deterministic criteria Conclusion

24 Conclusion Comparing power system reliability criteria is important Framework for comparing power system reliability criteria and reliability management o Objectives of the framework: 1.Quantification of performance of various reliability criteria and their management 2.Comparison of the performance 3.Identifying alternative reliability criteria o Quite complex, even with many assumptions included Preliminary result: Performance of reliability criteria and their management dependent on VoLL

Thank you! Questions? The work of Evelyn Heylen is funded by: Research in the framework of the Garpur project