Flexibility evaluation and flexible comprehensive optimization in power systems

SUMMARY Smart grid puts forward new requirements in the planning, operation and management of power systems. Flexibility is one of the most important characters among the requirements. Traditional optimization analysis methods with single objective function and rigid constraints can hardly meet such requirements. This paper introduces the original concept of flexibility in industry process system analysis into power system analysis, analyzes their main differences and makes subdivision of power system flexibility into four kinds, namely property, constraint, load and structure flexibility. Rigid constraints in traditional analysis methods are transformed into flexible forms, and a power system flexibility evaluation method is proposed. Flexibility indices are defined and calculated to give intuitive measure of power system flexibility to grid dispatchers. Then, a flexible comprehensive optimization model in power system analysis is established. The result obtained is not an optimization for a single objective, but a comprehensive optimization considering system economy, safety and other objectives. Case study on IEEE 30-bus test system shows the validity of the methodology proposed. Copyright © 2011 John Wiley & Sons, Ltd.