Increasing DG Capacity of Existing Networks through Reactive Power Control and Curtailment

Renewable energy sources (RES), especially wind turbines, have become more important during the last years. An increasing number of distributed generation (DG) units are connected to weak medium voltage distribution networks in rural areas where they have a large influence on the voltage and the line losses. Voltage rise is in this case often a limiting factor for the maximum amount of DG capacity. Already current wind turbines with a capacity of 2 MW can often not easily be connected to existing 10 kV feeders. To increase the DG capacity of existing networks without reinforcement DG units can be controlled. This paper proposes abandoning unity power factor used today and letting the converters used as network interface of many new wind turbine generators absorb reactive power to reduce the voltage level. Since reactive power has great influence on losses in the network the use of reactive power is limited. Line losses due to the transfer of reactive power are taken into account in this study. Furthermore the use of curtailment is analysed. Simulations of voltage change and line losses when using reactive power control by the connected wind turbines and curtailment in a simple test system are presented. Without reinforcement of the network it was possible to increase the DG capacity from 2;7MW to more than 4MW in the test network without violating voltage limits. Line losses increase but to a reasonable extent and lost energy due to curtailment is insignificant

Managing legitimacy in hybrid governance

Session 4: Public Managemen

Interactive research - an attempt to analyse two change programmes

"This article describes and discusses an interactive research approach, and illustrates this approach by presenting two examples of national change projects. Our aim in presenting these two examples is to demonstrate how interactive research can be conducted in close co-operation with those concerned, within the framework of a critical and reflective community. The two cases presented serve to illustrate how an interactive research approach can support the development and dissemination of project experience, but also how the interactive approach can act as a means of generating theoretical knowledge in order to identify and understand more of the mechanisms involved in sustainable work environment and health work." (author's abstract