Mastering power grid dynamics

With renewables and decentralized power generation, power grids are becoming increasingly more dynamic, requiring faster operator responses and more dynamic controls for grid stability. Now a joint effort between industry, researchers and grid operators like Germany’s 50Hertz have created a new dynamic control center.

 

by Mortiz Gathmann

Few know better than Gunter Scheibner what challenges face our grids as coal and nuclear power generation are being phased out in favor of a massive transition to renewables. Scheibner is Head of Systems Management for the transmission grid operator 50Hertz, one of the four companies operating Germany’s high-voltage grid.

 

With an electrical circuit length running up to 10,200 kilometers – longer than the distance from Berlin to Rio de Janeiro – 50Hertz is responsible for the operation, maintenance and planning of the high-voltage grid in eastern Germany and greater Hamburg. And there’s a remarkably high penetration of renewables flowing into their grid area: more than 40 percent of Germany’s installed wind power capacity. The onshore and offshore installed wind capacity in 2017 was around 18,600 megawatts and continues to rise. But strong fluctuations inherent to the generation of electricity by wind turbines mean that the amount of generated electricity rarely corresponds to the demand. In 2015, to cover demand and ensure the stability of the grid, 50Hertz had to spend a whopping €354 million for the purchase of electricity on so-called “redispatch” costs and the regulation of renewables to control grid bottlenecks and ensure stability. One reason for this is that new capacities for renewable energy are constantly being built up in the north while the electricity they’re generating is needed in the south, and there aren’t enough transmission lines.

With our current grid we have to transport significantly more electricity than was planned for in the past.
Gunter Scheibner, Head of Systems Management, 50Hertz

Grid operators under pressure

“The pressure is immense because the previously planned network expansion is far from what’s needed,” says Scheibner, “and we’re still lagging behind.” The delay in expansion comes from the approval process for high-voltage lines, which takes around ten years. Take the example of a 115-kilometer, 380-kilovolt line from the Uckermark to Berlin, suggests Scheibner, already delayed now by six years because of nature conservation concerns.

 

The challenge: “As a result with our current grid we have to transport significantly more electricity than was planned for in the past,” he explains. “Grid operation today still follows the 100-year-old rule of loading only 70 percent of the grid and maintaining the other 30 percent as a reserve for incidents. But if that 30 percent is permanently reduced by an increasing overload, new technologies are needed,” says Scheibner.

50Hertz and the other three transmission system operators (TSOs) are placing great hopes in the “DynaGrid Center,” which was presented in September as part of a research project at the Technical University of Ilmenau. And this is what it could look like: A model of the German power transmission grid is projected onto the wall in front of the computer tables. Phasor measurement units (PMUs) transmit the magnitude and phase angle of current and voltage every 20 milliseconds. These monitoring programs, already available in today’s control centers, allow the operator in the control room to see load changes in real time, making critical situations visible that can arise during an overload early on. The dynamic control center adds intelligent assistance systems or dynamic controls that advise the operator in selecting suitable countermeasures. In extreme situations, the assistance systems can initiate the necessary countermeasures much faster than humans.

Increasing resilience

The model is the result of three years research by the universities of Ilmenau, Magdeburg and Bochum, several Fraunhofer Institutes and the four German TSOs. Spearheading the project was Siemens: “The dynamic control center increases the resilience, stability and safety of the grid,” says Professor Rainer Krebs, project leader of the “DynaGridCenter” and Head of System Protection Operation and Control Department in the Energy Management Division at Siemens. “The control center’s task is to make oscillations in the system visible and to function as a passive and active assistance system,” says Krebs.

 

Control centers are already managing power grids all over the world. But because in many countries the share of large-scale power plants in the electricity mix is declining and renewable energies or decentralized power generators are taking their place, electricity feed-in is becoming more volatile and compartmentalized. For example, in order to keep the voltage in the grid stable, the operator in front of the control center screens must keep an overview and act with foresight to prevent – in the worst case – a blackout of the system. The same need for overview and action applies to grid frequency. In short, a dynamic network requires a dynamic control center. Krebs compares the new system with an active lane-keeping system in an automobile: On the one hand, assistance systems enable the system to automatically regulate certain tasks, while on the other, it helps the operator to recognize obstacles or faults early on in order to avoid them.

Mastering costs and complications

The four German transmission system operators 50Hertz, Tennet, Amprion and TransnetBW were associated partners of the project. And their interest in a solution to the challenges arising from changes in the electricity mix is high. The four operators had to raise a total of €1.4 billion last year in “redispatch” costs. A dynamic control room would drastically reduce this. “We can optimize control centers so that the right power plants are started up and shut down. We need these assistance systems tomorrow rather than the day after,” Gunter Scheibner is convinced. For his company, the greatest challenge for the future is to master even the most complicated situations and recognize problems in the grid before they become significant.

The dynamic control center increases the resilience, stability and safety of the grid.
Professor Rainer Krebs, head of the “DynaGridCenter” project, Siemens Energy Management

Mastering costs and complications

The four German transmission system operators 50Hertz, Tennet, Amprion and TransnetBW were associated partners of the project. And their interest in a solution to the challenges arising from changes in the electricity mix is high. The four operators had to raise a total of €1.4 billion last year in “redispatch” costs. A dynamic control room would drastically reduce this. “We can optimize control centers so that the right power plants are started up and shut down. We need these assistance systems tomorrow rather than the day after,” Gunter Scheibner is convinced. For his company, the greatest challenge for the future is to master even the most complicated situations and recognize problems in the grid before they become significant.

 

50Hertz has already purchased the grid management system Spectrum Power from Siemens, which links power systems of any size into an easily and centrally controlled grid. The success of the current research project has reinforced their decision: “It’s been possible to use a commercially available control system and initiate new solutions, create new models that come very close to the behavior of a real network,” says Scheibner. At the same time research is continuing: DynaGrid is now being followed by another project called InnoSys2030, in which the TSOs will bear the main responsibility. The dynamic control center, which was previously only located at the university, will be run parallel to an actual control center on the real system – and from there it’s only a step away from implementation.

2019-01-19

Moritz Gathmann works as a freelance journalist in Berlin.

Picture credits: Olaf Tiedje

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