Integration and control of wind farms in the Danish electricity system

 

The Danish power system starts to face problems when integrating thousands megawatts of wind power, which is produced in a stochastic behaviour due to natural wind fluctuations. The rapid power fluctuations from the large-scale wind farms introduce several challenges to reliable operation and contribute to deviations in the planned power generation which may lead to power system control problems. Therefore, detailed analysis of long-term stability simulation is required to investigate the impact of wind power on transmission systems. The main challenge problem is the power system performance with focus on power and frequency control, and power system stability under the dynamic behaviour of the wind power sources. In order to analyze the effects resulting from the structural changes in power generation and transmission by the penetration of wind energy, a generic model for a dynamic power system simulation is needed. The project focuses on the active power balance with regard to the system stability and to examine the ability of the secondary control of the power plants to reduce the affect caused by the power fluctuations from the large-scale wind farms on the power system.

 

In this project, the generic models of an Automatic Generation Control (AGC) system, wind farm, conventional power plant and Combined Heat and Power (CHP) unit, together with a coordinated generation control for long-term stability analysis should be implemented and developed. A generic model with a similarity to the Danish power grid including the connections with neighbour countries will be set up and the active power balance should be taken into account. An aggregated wind farm model employing different technology concepts should be developed. The CHP plant model will be implemented and analysed whether the power control should be changed with regard to taking part in the reserve. In the centralized thermal power plant models, secondary control and thermal dynamics of the boilers must be included with the overall control of the network to get a stability analysis. The total generic model will be used to evaluate the active power balance, power system stability at different control strategies in the wind-farms and at different loads and production situations. Control strategies for the wind turbines in the wind-farms with regard to power and frequency control and the system stability should be analyzed. The operation and control of the power system for the different control strategies should be analysed both at normal conditions and during very fluctuating power production from the wind farms. The power system analysis will focus on the power control from wind turbines in relation to the secondary control on the power plants and the connections with neighbour countries. The identification of technical problems, which might set up a limit for the wind turbine power penetration on the transmission level, should be examined.

 

The main result obtained so far is the generic models of the Danish power system, an AGC system, wind farm, conventional power plant and Combined Heat and Power (CHP) unit for long-term stability analysis. This project focuses on power balance and system stability with regard to power and frequency control. Therefore the Danish power system model has been simplified with connected power generating units and loads. The model consists of both eastern and western part of Denmark. The connections to neighbour countries and the overall control will be included in the model. Based on this generic model, analysis of the active power balance and long-term stability in power system is to be done. This project is made jointly between the Institute of Energy Technology; Aalborg University, DONG Energy (Elsam Engineering), Risoe National Laboratory and the follow group with members from Energinet.dk and funded by the 2004-PSO-programme.