Coordinated reactive power control to ensure fairness in active distribution grids

This paper deals with the influence of a large share of dispersed generation (DG) in the medium-voltage distribution networks. Distribution networks traditionally operate in a way that they don´t predict the influence of DG and the voltage drop is assumed to be increasing with the distance from the substation. A large share of DG can cause that at the local level the voltage upper limits are reached. This problem can be solved in many ways. In the paper a coordinated voltage control is presented which on the basis of time dependent power factor of DG determines the amount of reactive power they have to produce. Development of the control is based on the fact that in the near future the new technologies will allow bidirectional data flow in real time. This will allow more active participation of the users in the network. With reactive power dispatching the voltages can be correlated and furthermore losses can be minimized. The paper deals with the fact that DG will have to produce different amounts of reactive power. That is why the options of fair contribution of reactive power are investigated. Different solutions were evaluated by means of computer simulations. The simulated network was a part of medium-voltage distribution system in Slovenia. The network was modified by increasing the number of DG as their growth is very fast in Slovenia.