Dispatch of reactive power compensators in transmission grids

Abstract

The phase-out of conventional power plants reduces the reactive power reserve from synchronous generators in transmission grids. Operational concepts need to be adapted to integrate reactive power compensators such as STATCOMs into voltage control schemes. This paper presents a novel two-stage optimization method for determining reactive power schedules, distinguishing manual and automatized control variables. The first stage optimizes the reactive power dispatch iteratively for the considered period using successive linear programming based on continuous variables due to relaxed integrality conditions. Afterwards, an embedded genetic algorithm re-discretizes integer variables. The second stage determines pareto-optimal reactive power schedules based on grid losses and switching frequency. Therefore, points of time are modeled as nodes and loss energies between two time-coupled points of time are modeled as arcs in a directed acyclic graph. The investigated scenario indicates that a high number of switching actions for passive compensators, such as shunt capacitors or reactors, is not necessary. Furthermore, it becomes apparent that the automated control of flexible devices like STATCOMs enables a reduction of active power losses.