Voltage control in distribution networks with distributed generation

One of the goals of the European energy policy is to reach the ''20-20-20'' targets which by 2020 foresee a 20 % increase in energy efficiency, a 20 % reduction in CO2 gas emissions and a 20 % increase in power production from renewable energy sources. As a result there will probably be a substantial increase in the share of renewable (and dispersed) energy sources in final consumption and accelerated investment in renewable energy sources and their integration into the electric power system. The nominal power of distributed generation (DG) is relatively small and it is not concentrated in just one part of the network but throughout it. Due to their limited power, DG sources are connected to the distribution network. Their production depends on a number of factors and is difficult to predict. Inclusion of a large share of DG in the distribution network was not planned when the network was designed. As DG affects network operation, some difficulties may be expected. One of the first ones is most likely to be violation of the set limits because of the changes in network voltage. The paper is structured as follows. First, changes taking place in power network due to DG connection are described. To follow are a description of the impact of DG on the network voltage states and analytical determination of its impact on the voltage. Possible voltage control strategies with DG are shown by means of network simulations. The paper end by comparing losses incurred in different voltage-control regimes.