Operational planning for distribution system with windmills

The implementation of wind turbines in Egypt has increased significantly during the last decade. Wind turbines are normally connected directly to the utility grid. The power production from a wind turbine depends on the wind condition. Favorable wind conditions are often found in thin populated areas, where the grid may be "weak". With an increasing number of wind turbines in such areas, it becomes more difficult to maintain an acceptable voltage quality. Problems such as under-voltages and over-voltages are well known. The over-voltages, which occur in case of low loads and high wind production, must be avoided due to the risk of damage to appliances of the customers. Using traditional load flow analysis, it is not possible to achieve a realistic impression of where and. when the over-voltage occur in a distribution system over a whole year. These analysis are normally based on some selected combinations of consumer loads and wind power productions. An investigation of the voltage condition is possible if the variations of both loads and productions are taken into account. This paper describes a method of determining the voltage conditions in a distribution system calculated over a year. The consumer loads and wind power productions are assumed as normal distributed within a year. The probability of undervoltage and over-voltage within a year is calculated, considering that the phase to neutral voltage at the consumers should be within the range based on the Egyptian Standard for voltage quality as given by IEC.