Efficient operating concepts for electrical grids
The middle and high voltage grids face considerable challenges as a result of the feed-in of large volumes of renewable energy. In order to secure the efficient operation of the existing power grids and limit the need for their expansion, this WindNODE workstream on the one hand systematically considers the transmission and distribution grids and on the other hand develops new technical components and procedures for efficient operation.
The real-time lab of TU Berlin (SENSE) focuses on comprehensive system optimisation of the trans-mission system with an interface to the distribution system and develops a demonstrator for innovative and future-oriented system operation methods. This makes it possible to carry out a functional test of the smart grid technology and scale its effect on the entire WindNODE area for 2020-2050. At the Barnstädt site to the south-west of Halle, we are therefore constructing a combined system of wind power and storage units that can contribute to the efficient integration of wind power into the distribution system. This combination of real operational data and practical experience allows us to improve the grid model of the real-time lab.
BTU Cottbus-Senftenberg (EVH) is working on the further development of the control system for the already existing smart grid at the university’s main campus in Cottbus. That is why we are testing innovative forecast tools, analysis systems and interface enhancements to improve the integration of smart grid applications. Distribution system operators supply us with information to categorise the renewable feed-in, which we process together with the real time control system data and publish and also use for scientific research on residual loads, feed-in behaviour and generation forecasts. We process the data using big data management methods to practically validate operating strategies within a smart grid environment, deduce contributions for the smart grid of the future and develop a load profile for ‘administration and other office use’.
The growing share of decentralised generating units in the grids continues to push large-scale thermal power plants out of the electricity market. However, in addition to the generation of electricity, they are also used to provide a large number of ancillary services, in particular for frequency and voltage control. In the future, we therefore need to make greater use of high-performing grid nodes or distribution grid areas to provide control and compensation measures. By means of demonstrators, WEMAG Netz is studying how renewable energy installations can supply reactive power in the future. This especially requires adjustments to the control technology, remote technology and telecommunication links. We take specific measures for active control of reactive power to render adjustment potentials of decentralised generating units useful for grid operation.
Due to the development of the grid, underground cables have to be designed to withstand a high volatile current load. The existing approaches for the calculation of temperatures are nevertheless based on almost constant loads; as a result, the transfer potential of a route is often estimated incorrectly for electricity from renewable sources. That is why TU Berlin (Site Studies & Soil Protection) is developing the CableEarth cable monitoring method to calculate conductor temperatures and validating it based on experimentation. In addition, we are conducting detailed studies in the physical laboratory on the water and heat transport of soil and substrates. The results enable real time monitoring of the cable temperature for efficient operational management and optimal use of the transfer capacity of grids as well as an assessment with regard to ecological factors.
We can only maintain secure and stable grid operations in the energy system of the future if the renewable energy installations also achieve the production capacity of conventional power stations with regard to grid and system support. In this project, the Rostock university is therefore conducting operational optimisation analyses and designing models to simulate the control system of the electricity generation system. In the process, we study stability limits for various operating and expansion scenarios for renewable energy in the 50Hertz control area. Using the intended research method, it will be possible to make detailed assertions on the load flow tolerance, voltage profile tolerance, frequency control by rotating masses as well as the primary and secondary control capability in times of high feed-in of renewables.
In order to plan grid development at the distribution level, we have to know the load factor of secondary substations. However, the measuring methods that are currently used will not be conclusive enough for the future energy system. At the same time, insights about the decentralised feed-in of energy from renewable sources is becoming increasingly important for us, as local energy flows can arise at the medium and low-voltage level that are no longer visible for measurement in the substations. That is why we need to equip the secondary substations with a new measuring system. In this project, Stromnetz Berlin is developing an online measuring system as a mature system operator standard that takes into account all technical and operational requirements.