ATC-Based System Reduction for Planning Power Systems With Correlated Wind and Loads

Simulations of production costs, flows, and prices are crucial inputs to generation and transmission planning studies. To calculate average system performance for many alternatives over long time periods, it is necessary to simulate large numbers of hourly combinations of renewable production and loads across large regions. As this is usually impractical for full network representations of such systems, aggregation of buses and lines is desirable. We propose an improved aggregation method for creating multi-area representations of power systems that yields more accurate estimates of the quantities required by planners. The method is based on partitioning the original large system into smaller areas and making a reduced equivalent for each area. The partitioning is based on available transfer capability (ATC) between each pair of network buses. Because ATC depends on net load conditions, separate partitions are defined for subsets of similar load and wind conditions, significantly enhancing the accuracy of optimal power flow solutions. We test the method on the IEEE 118-bus test system and the Polish 3120-bus system considering 150 load/wind scenarios, comparing the results to those of admittance-based partitioning methods. Accuracy is improved with only a negligible increase in simulation time.