AbstractThe increasing penetration of distributed generation (DG) in the electricity grid will result in a reduction of the number of connected conventional power plants, which are nowadays responsible for control of the electricity network frequency. Currently DG units do not contribute to frequency control. With increasing penetration of DG it will become necessary, however, that they also contribute to frequency control. A significant part of the DG units are connected to the grid by a power electronic converter. It is possible to implement additional control in this converter to let the DG unit contribute to frequency control. In this paper it is investigated how these controllers can be implemented and it is analysed how large the contribution of several types of DG units can be. Copyright © 2006 John Wiley & Sons, Ltd.