Germany has about 65 GW of installed capacity of which about 20 GW is contributed by wind power and balance is through Coal, Gas, Solar, Biomass and Hydro. Variability of wind power as always been a concern to the grid operators and Germany has successfully handled grid integration of wind through various approaches. The major initiative taken by Germany to handle such a large capacity was that they ensured balancing of power in order to absorb the fluctuations of wind power.
The transmission network in Germany is predominantly at 380KV level and there are four grid operators to handle the overall transmission system. Apart from transmission operators there are about 70 regional grid operators which operate at voltage level of 220KV, 110KV, and 20KV. The regional grid operators do not buy or sale powers rather they provide the wheeling facility for the electricity. German grid operators have very high capability of forecasting the electricity demand as well as generation and accordingly the balancing reserves are planned to fill the buffer. While the system has about 20GW of wind power there is large variation in wind power generation on regional basis which can go up to 1GW of variability.
The grid operators are very well equipped with forecasting the generation as well as demand and there are special electricity trading products available in real time so that the projected fluctuations can be deviated through price sensitive electricity trading products. This products include intraday trading and wind reserve which are applicable for two hour ahead production.
In some areas at some times the wind power is more than the grid capability and wind farms are subjected to shut down and stop producing electricity which effects up to 10% of their revenues of wind power generators. German law provides compensation to wind power generators for not absorbing the electricity during such events. There are additional initiatives to absorb such high wind power, this initiatives include the construction of energy storage facilities in the form of MW class battery storage systems, 300 MW pump hydro systems as well as compressed air storage systems.
Apart from these initiatives Germany has also started adopting demand side management and load shifting options to handle the variability of the grid. Germany is also trying to implement the joint operation of various decentralized plants to handle the variability of wind power. For example wind power plants are being integrated with CHP, PV and Micro hydro as a joint operation plant which is controlled in combination from one central point. The country is also adopted smart grid solutions which include uses of plug in hybrid electrical vehicles, installing energy management systems in buildings advanced metering technologies and better communication system.
The systems of the four German interconnected companies with parts of Denmark, Luxembourg and Austria together form the German control bloc. The load frequency controller for the German control unit is located in Brauweiler (Amprion GmbH, Transmission System Operation). It controls the exchange of electrical energy vis-à-vis the UCTE system, including the CENTREL system (Poland, Slovakia, Czech Republic, Hungary). Within the German control bloc, each interconnected company controls the import/export with the neighboring systems for his own control zone. The surplus wind energy can fed to other zones through this interconnected German bloc.
While India is also facing the grid integration issues for wind power and there is need to learn from German experience and adopt the solutions in the form of better scheduling and forecasting, investment in balancing reserves, upgrading the transmission line for congestion management and use of storage facilities the integration of southern grid with NEW grid will also help in evacuating power from wind farms located in southern there is a need to introduce various demand side management (DSM measures) and innovative electricity trading to take benefit of real time demand variations. There is no single formula for grid integration, but it is need to take technical, policy and market mechanisms to handle large scale wind power in the Indian electricity system.
Image source: Fraunhofer , energytransistion.de