Our grid structure has changed fundamentally in recent decades and will continue to do so. The energy transition is forcing us to consider a resource-saving power supply that guarantees the necessary quality and stability of the grid. Power generation used to be based on a simple AC voltage system with one-way power flows. Centralized power plants produced electricity that flowed to the load centers and then to consumers.
Today the situation is much more complex, with an irreversible trend toward decentralized energy systems.
Demand for grid quality and stability is on the rise
Present and future power grids need at least the same degree of availability and reliability as those of the past. Renewable energy sources, modern power electronics, and potential disruptive factors from electromobility are all affecting grid quality. At the same time, the demand for power quality (PQ) is continuing to grow due to the increasing complexity of processes and the increasing use of sensitive electronic devices. Typical problems like deviations in the supply voltage, harmonics, voltage dips, and transient disruptions can result in considerable damage. Massive disruptions in the power supply system can cause the grid frequency to substantially deviate from the target frequency (50 Hz). Stabilizing the target frequency after a few seconds is possible, but only if appropriate countermeasures are defined: for example, feeding positive balancing energy into undersupplied grid areas. In a number of ways, grid operators have to guarantee that these high demands are consistently met on all voltage levels. If stability can’t be restored immediately, larger or even comprehensive service disruptions are conceivable.
Storage technologies stabilize grids
Energy storage systems play a central role in this context because they can absorb electricity during power peaks and release it during voltage dips. As a result, both the power being transmitted and grid utilization remain constant. This ability to balance fluctuating power infeed is vital, and not just due to the use of renewables. Even more important is the fact that energy storage systems can make a significant contribution to overall grid stability, thanks to their characteristic strengths. Battery storage systems are especially beneficial. Unlike other storage technologies or power plants, they’re ready to operate at full load within milliseconds. In the event of deviations in the grid frequency, battery storage systems can supply balancing energy almost immediately, decentrally, and at a sufficient capacity – until the power plants are started up for primary control. Even short-term oscillations can be damped in a matter of seconds.
Battery storage proven in an emergency
Siemens’ battery storage system (Siestorage) is a modular solution that combines state-of-the-art power electronics for grid applications with high-capacity lithium-ion batteries. In addition to its storage function, the system can balance voltage fluctuations by compensating reactive power, thanks to the integrated inverter.
What this means in practical terms is being demonstrated in the northern Bavarian town of Wunsiedel. As part of a technology partnership, Siemens and the local energy provider SWW Wunsiedel GmbH have been testing out new options for a future-ready decentralized power supply since 2018. An 8.4 MW Siestorage storage system is also being deployed. The system’s special feature is its connection to a cloud-based monitoring system via MindSphere, the open IoT platform, which makes it possible to gather, evaluate, and compare huge quantities of data in real time.
This article was originally published in German.