Power System Reliability Considerations in Energy Planning

We discuss how to incorporate reliability considerations into power system expansion planning problem. Power system reliability indexes can be broadly categorized as probabilistic and deterministic. Increasingly, the probabilistic criteria have received more attention from the utilities since these can more effectively deal with the uncertainty in system parameters. We propose a stochastic programming framework to effectively incorporate random uncertainties in generation, transmission line capacity and system load for the expansion problem. Favourable system reliability and cost trade off is achieved by the optimal solution. The problem is formulated as a two-stage recourse model where random uncertainties in area generation, transmission lines, and area loads are considered. Power system network is modelled using DC flow analysis. Reliability index used in this problem is the expected cost of load loss as it incorporates duration and magnitude of load loss. Due to exponentially large number of system states (scenarios) in large power systems, we apply sample-average approximation (SAA) concept to make the problem computationally tractable. The method is implemented on the 24-bus IEEE reliability test system.