Ervin Spahic

Wind Energy Storages - Possibilities

The volatility of wind power can cause large problems for power systems operation. To remedy the disadvantages of wind power generation different storage technologies can be applied. In this paper technical and economical analysis of possible wind energy storages has been made. According to technical parameters the applicable technologies have been selected. Afterwards, for selected storages economical analyses which take into account different scenarios of investment and electricity prices have been made. Obtained results suggested compressed air energy storages, batteries and pump hydro storages as very good solutions for wind energy storage. Due to lack of suitable places in Germany a pump hydro storage solution is less feasible.

Offshore wind farms - VSC-based HVDC connection

Due to significantly higher and more constant wind speeds and the shortage of suitable sites for wind turbines on the land, offshore wind farms are becoming very attractive. The connection of the large offshore wind farms is possible with HVAC, classical HVDC and voltage source converter (VSC- based) HVDC technology. In this paper their main features will be given. From the economical and technical viewpoint, the type of connection depends on the size of the wind farm and on the distance to the connection point of the system. As very promising technology, especially from the technical viewpoint, the focus of this paper will be put on the VSC-based HVDC technology. Its main technical features as well as its model will be detailed. At the end, obtained simulation results for different faults and disturbances for one offshore wind farm connected with VSC-based HVDC technology will be presented.

Reliability model of large offshore wind farms

For investors of wind farms projects, it is indispensable to get reliable prognosis of the expected energy produced per year, taking into account technical failures and the stochastic characteristic of the wind. This applies especially for offshore wind farms with higher installation costs and difficult maintenance conditions. The repair of components located on sea may take many days or even weeks because of limited access caused by bad weather conditions. Additionally, transmission system operators which are providing the point of common coupling (PCC) have to know the impact of the wind farm on the reliability of the grid. In this paper a model for the probabilistic reliability calculation of the offshore wind farms as a whole and as a part of the entire system has been introduced.

Power fluctuation from a large wind farm

The planed increase of the offshore wind farm is significant and, therefore, their influence on the power systems. In this paper the influence of several factors such as wind farm size, wind pattern, wind speed and wind direction which impact the wind farm power output have been analysed. Different sizes of wind farms have been modelled and their effects on power output have been presented. Different wind patterns and different wind speeds have been considered. Also, the impact of wind directions has been analysed. The relation of different wind directions, i.e. wind rose and the power output has been investigated. The obtained results show a high dependence of the power output on the size and position of the wind farm as well as on the wind pattern. With the increase of the wind farm size the power output fluctuations from the whole wind farm reduce significantly

Impact of the VSC HVDC Connection of Large Offshore Wind Farms on Power System Stability and Control

The impact of the wind power on the power system stability and control is already notable. With the increase of their power (single offshore wind farms will reach over 1000 MW) their impact will increase too. In this paper the use of voltage source converter HVDC transmission technology for the connection of the large offshore wind farms to the power system will be presented. The modelling of VSC HVDC and its control parameters and loops has been detailed. The impact of such connection on the power system stability and control has been analysed on a test power system.

Optimal location of series FACTS devices to control line overloads in power systems with high wind feeding

The planned offshore wind farms in Germany are basically located in North region. For wind integration in Germany, establishing new transmission lines and employing new technologies have become unavoidable. Establishing new transmission lines is very costly and difficult regarding enviromental condition. One of the solutions is the utilization of Flexible AC Transmission Systems (FACTS). This paper discusses a method for determining the placement of series compensation to control line overload in power systems with wind power penetration. By a sensitivity based method critical lines can be identified quickly and accurately, to obtain desired wind feeding into the system. Thyristor Controlled Series Compensator (TCSC) is applied for system stabilization as a typical FACTS devices. This method is applied to realistic scenarios in a test system, which simulates reduced 380 kV network of Germany. Simulation results showed that the proposed method is effective and can enhance the transfer capability margin of existing power systems.