I. Talavera

Optimized regulation of dispersed generation units for minimization of reactive power consumption

Because of the increasing share of renewable energies violations of the statuary voltage limits occur more and more often in the German distribution grids. Therefore, distribution system operators take advantage of reactive power support by dispersed generation units for voltage regulation. Commonly, only one standard cosφ(P)-profile is implemented as a control-method for all units to decrease voltage rises. This profile is independent of network characteristics and the point of common coupling. However, additional reactive power consumption causes additional reactive power unbalances in the networks which have to be compensated by the overlaid transmission grid. This becomes more difficult in times of a decreasing number of large conventional power plants. In order to reduce the additional reactive power demand caused by the improvement of statuary voltage stability this paper describes two methods to calculate optimized cosφ(P)-profiles for reactive power support. Beside the reduction of reactive power demand the optimized control-methods have also the positive effect of lower power losses in the distribution grids.

Vertical reactive power flexibility through distributed energy resources for a reactive energy management

The transition of the power grid with fewer reactive power sources demands new solutions to locally compensate reactive power in order to reduce transmission losses in the extra high voltage grid. The capability of high voltage clusters to meet these requirements is evaluated in this paper taking different approaches into account. The feasible contribution of distributed energy resources to provide reactive power is analyzed for two high voltage clusters, which are based on real network data. The load flow is carried out for every hour of a year. Two different reactive power characteristics are introduced and analyzed towards their possible reactive power flexibility. Current German guidelines limit the possible reactive power of the distributed energy resources, while they have a bigger potential as shown with the second characteristic. Furthermore, an economic comparison with mechanically switched capacitors is performed. A specific reactive power exchange boundary is chosen to achieve comparable situations. The costs calculation considers investment, operating and maintenance costs. Each network cluster has its own economic solution. In general, the costs of reactive power supply from distributed energy resources rises with the period of use. Nevertheless, it is shown that distributed energy resources could fulfill an economical competitive reactive power management.