The Minimum MVAR Generation as an Effective Criterion for the Reactive Power Dispatching

Abstract The aim of the reactive power optimization is to improve as much as possible the quality of the service. The main efficiency figures taken into account are the minimum losses in the transmissio system, the warranty of a determined voltage level for the consumers and the maximum reactive margin in the generating units. The latter is also an effective criterion for operating in order to cope with some contingencies in the power system. Therefore, the proposed procedure determines the minimum total MVAR generation, while observing the voltage constraints and guaranteeing that all the units operate in the feasible region delimited by the capability charts. Further constraints can be introduced in order to take into account the effects of possible regional voltage regulators. This involves the requirement of the same value in p.u. for the reactive power generation of all control units belonging to the same area. From a mathematical point of view we minimize the sum of the absolute values of the reactive powers generated with linearized constraints on the dependent variables. A linear programming model allows the application of our procedure to a large-size network with about 100 control units. The computational tests performed on the Italian network show some diminution in transmission losses with regard to the day time operation while useless reactive power loops are avoided at night.