Securely integrating wind farm clusters in the grid

Project state
Graphical representation of IMOWEN’s overall system concept
IMOWEN’s overall system concept: Interaction of the WCMS, forecasts and the subordinate wind farm control method.
Source: Fraunhofer IWES

The IMOWEN project is concerned with intelligently integrating a large number of wind farms within the voltage and reactive power control concept for a 110-kV distribution grid area. Here, several wind farms no more than 80 kilometres apart are being grouped together to form a wind farm cluster in terms of the grid operation. Fraunhofer IWES’s Wind Farm Cluster Management System (WCMS) is being further developed so that it can record and analyse complex grid structures consisting of a large number of cities, large wind farms, other renewable energy sources and conventional power plants, etc, and then, by using adapted modern optimisation methods, derive appropriate target values for the wind farms.

The project participants led by project manager David Sebastian Stock are developing a new concept for providing effective voltage and reactive power control for the 110-kV distribution grid. It partly comprises the superordinate optimisation of the WCMS. In addition, the researchers also want to develop methods that will enable winds to be forecast more accurately in a timeframe from 15 minutes to three hours.
A further aspect of the project is a subordinate wind farm control system that investigates, for example, interactions within a cluster. The aim is to automatically adapt the reactive power fed into the grid by the wind farms so that the wind energy can help balance the reactive power requirement of entire grid regions.

Challenge in the current grid operation: Maintaining the reactive power balance between the transfer nodes for the transmission and 110-kV distribution grids.
Challenge in the current grid operation: Maintaining the reactive power balance between the transfer nodes for the transmission and 110-kV distribution grids. Source: Fraunhofer IWES

In previous practice, wind turbines have worked with a fixed active-reactive power ratio, the so-called cosφ power factor. This means that the voltage can be adjusted directly at the wind farms. However, this practice reaches it limits when there are many infeeds, as occur in large wind farm clusters. If the cosφ power factor were used here, the wind turbines would in total feed too much reactive power into the grid. This could then under certain circumstances be no longer maintained in the prescribed ranges. The wind farm cluster management system being developed is aimed at maintaining the limits while simultaneously remaining within the prescribed voltage limits.

Project schedule

During the initial phases of the project, the researchers will use software to model the grid region being investigated. The resulting model will then be used to develop and test the new optimisation methods. As a first milestone, the researchers want to link the grid model developed with optimisation approaches designed for this purpose. In addition, the project partners are investigating interactions between the voltage regulation systems. For this purpose they want to create a design model in which they can identify and analyse interactions and develop measures for a fluctuation-free cluster operation.

Project duration

08/2014 – 08/2017


David Sebastian Stock
Project coordinator
Fraunhofer-Institut für Windenergie und Energiesystemtechnik (IWES)
Königstor 59
34119 Kassel, Germany

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