Local Reactive Power Support for Grids with Large Share of Decentralised Generation Capacity

For future grids it is foreseen that a large share of decentralised generation capacity will exist at the distribution level. As decentralised generation depends on variable power sources like air flow (wind turbines), solar irradiation (PV-cells) and space heating equipment (temperature switched micro CHP), power generation may change dramatically from minute to minute. As these power sources in general are devised to supply only real power, reactive power still has to be delivered by the HV- and MVgrid parts. In this future situation, HV-grid parts may temporarily deliver a relatively low amount of real power to their MVgrid parts whilst the reactive power need in these parts remains the same. To adapt to this situation in a flexible way, a significant part of the central generation capacity temporarily may have to be committed to delivering reactive power mainly. As delivering mainly reactive power is not an economically viable way of operating central generation capacity and HV grids, a solution is sought by generating reactive power at the decentralised generators. The problem addressed in this paper is how to generate the optimum amount of reactive power at all times for a group of decentralised generators equipped with power converters in one and the same local MV-grid.