Resilienz Alex J + (composing)
2023-04-01 publication

System resilience: A network of swarms

In the future, power from many thousands of wind turbines and millions of solar installations is to drive all the applications in our everyday life. However, the all-electric society will only work if generators, consumers and storage operators work in close concert. Such a complex, decentralized system presents both an opportunity and a risk with regard to network resilience.

By Eva Augsten


VDE dialog - the technology magazine

Ten years ago, Jochen Homann presented the technical thriller Blackout. The head of the Federal Network Agency at that time praised the realism with which author Marc Elsberg depicted how all aspects of infrastructure depend on the power grid. Gas stations would not be able to sell gas without electric pumps, and heating systems would no longer keep our homes warm. Making readers understand the vulnerability of the system that supplies our power – and the merits of keeping a flashlight, a couple of cans of food and a warm blanket handy – was a challenge ten years ago.

However, several once-in-a-century droughts, coupled with cooling problems at power plants, a catastrophic mud flow, a pandemic, a war in Europe and a resulting energy crisis, have all changed our perception of related risks. Since the fall of 2022, the number of online searches for the terms “blackout” and “power failure” has been higher than ever before. With the Federal Network Agency now pointing out that you can’t simply charge millions of EVs after work without a central control system, alarm bells have begun to ring: Can our power system really supply an all-electric society?

The flooding disaster in the Ahr valley in 2021 also destroyed a number of power lines. In order to protect them better against such extreme events in the future, some of the lines were restored at a higher altitude, running through a vineyard.


Status quo: protecting central components

A blackout of the magnitude described in Elsberg’s novel has never occurred, but there have been relatively large power failures. After an extra-high-voltage line over the River Ems was deactivated in 2006, an overload in another line led to a cascading power failure that affected 1.5 million people. According to the Federal Network Agency, various types of malfunctions it views as falling under the “purview of the grid operator” were the cause of more than half of the power failures in 2021, as well. About one third of such failures are caused by the “involvement of third parties” – such as the power failure that lasted a day and a half in Berlin-Köpenick in 2019, when an excavator damaged both of the 110-kV lines supplying the district. “Atmospheric phenomena”, such as the ice-covered power lines that pulled down masts in the Münster region in 2005, accounted for about 10 percent of the power failures in 2021. Meanwhile, the recent flood catastrophe in the Ahr Valley – where huge mud flows destroyed not only houses, but also power lines and transformers – was a rare example of “force majeure”, which causes just 3 percent of power failures. Cyber attacks like those in Blackout are a constant factor, but according to the Federal Network Agency, none of them has caused a power failure in Germany so far.

Decentralized units stabilize the overall grid

Even though most disruptions are much shorter and affect fewer people than the cases mentioned above, they do all have one thing in common as a rule: They are due to the failure of a few central components. The tried-and-tested countermeasures are physical backups and redundancy. In its report on the Münster region’s power failure, the Federal Network Agency recommended that standards should be adapted to the more frequent occurrence of extreme weather situations. That is already happening in locations where new infrastructure is being created, confirms VDE FNN managing director Heike Kerber: “During the restoration work in the Ahr Valley, lines were routed through the vineyards instead of through the valley in some cases. Some of the transformer stations are now also at a higher elevation.” However, power failures can never be ruled out completely. “Infinite security is infinitely expensive,” Kerber offers in summary. Switching from several hundred major power plants to many thousands of wind turbines and millions of solar installations will change the basic foundation of our power supply. Models show that millions of solar storage units, wall boxes and heat pumps may present an opportunity in terms of grid resilience. One scenario examined by the think tank Agora Energiewende anticipates that in Germany, the output of household storage units and car batteries capable of feeding power back into the grid will exceed the pump-storage output by as early as the end of the 2020s. “It's highly likely that we could have prevented power failures like the one caused by overloaded lines in the Ems region in 2006 if the transmission network operators had been able to activate such systems in an aggregated way,” declares Christian Hachmann. He specializes in the planning and operation of transmission networks at the Fraunhofer Institute for Energy Economics and Energy System Technology (IEE).

Flutkatastrophe im Ahrtal 2021: Nepomukbrücke

Destroyed Nepomuk Bridge in the municipality of Rech in the Ahr valley several months after the flooding disaster


To enable these decentralized units to truly stabilize the grid, wall boxes, heat pumps and smart control systems all have to work together like a swarm of bees instead of merely optimizing individual consumption and using the grid as a buffer, as in the past.

The basis for this could be a traffic-light concept like the one designed by VDE FNN. This system differentiates between the preventive use of flexibility in the yellow phase (long- and medium-term prognosis) and curative emergency measures in the red phase (short-term prognosis).

A field test conducted by the flexQgrid project in the Black Forest village of Freiamt has just demonstrated how such an approach can work in practice. The participants included the Karlsruhe Research Center for Information Technology (FZI) and the distribution network operator Netze BW. The 40 participating households controlled their photovoltaic systems, heat pumps and wall boxes in coordination with a “network traffic light”. If the light was green, these prosumer components could operate without any restrictions. During midday feed peaks or after working hours, when many people typically charge their EV, the light would switch to yellow. Then a quota would specify the maximum amount of power that could be drawn from the grid or fed back into it. If a sudden deviation occurred or a grid component failed, however, the traffic light would switch to red. In that case, an automated network controller would intervene and throttle the generators or consumers as required.

Personal preferences in energy management can result in disruptions

However, this swarm-like behavior can also lead to risks. The scientific academies acatech, Leopoldina and the Union of the German Academies of Sciences and Humanities examined this possibility in the joint project Energy Systems of the Future (ESYS). As both consumers and generators vary their energy management depending on the market and weather situation and their users’ personal preferences, patterns may emerge that lead to “new, complex disruption sequences”. The ESYS project found that such sequences are scarcely foreseeable and can only be stopped with rapid, automated software updates.

It is presumably likely that hackers will try to provoke such malfunctions. New major consumers such as wall boxes and heat pumps are just one of the possible targets. While the smart meters that control these consumers nowadays resemble impenetrable fortress gates, new back doors are opening up in households all the time. And we haven’t even gotten to the point where millions of refrigerators and washing machines connect to the Internet of Things via local routers! SBA Research, an Austrian research center in IT security, demonstrated back in 2017 that a bot network attack could manipulate the performance of a large number of computers enough to disrupt the power grid.

The System Resilience Roadmap

With the System Resilience Roadmap, the federal government aims to prepare itself as effectively as possible for the new world of energy

Achieving greenhouse-gas neutrality by 2045 is the overall goal, and making sure that 80 percent of the country's electricity is green is the milestone for 2030.

At present, about half of the electricity in Germany comes from renewable energies. A pan-European electricity system that supplies hundreds of millions of people, with the wind and sun as the most important energy sources, is new technical territory. Anyone who wants to explore such unknown terrain safely would be well-advised to at least bring a map.

With the System Resilience Roadmap, the federal government aims to prepare itself as effectively as possible for the new world of energy. An advisory board comprising the most important stakeholders – including VDE ETG, VDE FNN and DKE – is to help take as many aspects as possible into account in good time.

To ensure a resilient electricity system, it's necessary to not only consider risks such as severe storms and cyber attacks, but to rethink everyday tasks, as well. How can the oscillating weights of major power plants be replaced? How can even small units take on grid-forming characteristics? The advisory board is responsible for answering these and other questions. Its explicit aim is to consider resilient grid operation; issues relating to the energy market are being discussed in other forums. The kickoff meeting of the System Resilience Advisory Board took place in October 2022. The roadmap is due to be complete by the late summer in 2023.

The more elements are involved, the harder it becomes to hack the whole system

IT security is a game of cat and mouse, and will remain so in digital power networks. The Oldenburg-based IT institute OFFIS has been running corresponding simulations in its laboratories. Sebastian Lehnhoff, Professor for Energy Informatics at OFFIS and a member of the ESYS project, assumes that the vision of a robust system attackers can't even begin to penetrate will no longer be viable in the long term. “This is particularly critical because attackers multiply their efforts as soon as they get a foot in the door,” he says. The most spectacular IT attack on a power grid that the world has seen so far occurred in Ukraine in 2015, when phishing mails with infected Windows files acted as that foot. But even in a case like this, Prof. Lehnhoff believes a blackout is hardly inevitable. “Nobody can hack an entire system at the same time. That means we need to design our networks so they can still be controlled by the part that’s not corrupted,” he explains. For instance, if an attacker were to capture a control room, smart network nodes could potentially take over and bring the system back to normal.

In the event of a blackout in the future – that is, when an actual power plant fails – it should be possible to rebuild the network with decentralized generating systems. In Pfinztal near Karlsruhe, Fraunhofer ICT is combining wind energy, photovoltaics and a battery on the DC side to form a microgrid. “This new combination of wind, PV and battery systems will be able to start up in a blackout and supply the entire campus in island mode,” says Peter Hussinger from the project's developer, Baywa r.e. In normal operation, direct-current coupling reduces conversion loss and thus provides more green electricity for both Fraunhofer and grid feed-in. A research project under the auspices of the International Energy Agency is also using six examples from Europe and North America to examine how decentralized generators can be optimized for both climate protection and resilience. Nowadays, a simple emergency power socket is even provided on many PV inverters for private residences. It’s rare for a household to have a backup power supply for its entire grid, but even this is becoming more common.

Netz der Zukunft als Schwarm

In the network of the future, many energy producers, consumers and storage devices will work together in a swarm – with all the advantages and disadvantages this brings.

| studio + Circle + (composing)

With the rollout of smart meters, the hardware for a networked all-electric society is being introduced in many thousands of households, and it will soon be millions. While bees seem quite comfortable with the idea, however, most people are not yet aware that the plan is for them to become an active part of an integral system. “We have to learn to communicate better on this topic. This debate needs to be featured on talk shows, and the advantages of flexibility have to be explained simply and comprehensively,” declares Alexander Nollau, head of the energy department at the DKE, which he also represents on the German federal government's advisory board on system stability (see box, p. 23).

To encourage electricity customers to take part, they need to be able to see the added value in market- and grid-oriented behavior. This type of incentive is already coming into view: Providers such as Tibber and awattar are now offering dynamic electricity prices, which are due to become standard by the middle of the decade. Automotive corporations and wall box and heat pump manufacturers are also itching to win new customers with lucrative marketing that promises flexibility.

In principle, this is in the interest of grid operators, as well. “The aim is to control electricity flows via the market whenever possible,” emphasizes Heike Kerber, who also sits on the system stability advisory board, representing VDE FNN. However, she says, it’s also necessary to prepare for situations where that simply does not work. “For instance, if lots of wind energy pushes down the electricity price and many customers want to charge their electric vehicles at the same time, that could also cause shortages in the distribution network. Grid operators then need to be able to intervene and throttle the power supplied to flexible consumers down to a guaranteed minimum.” Those providing the flexibility agree with this arrangement – in principle.

But would such throttling be permitted regularly, or only in an emergency? Would these rules apply automatically to all flexible consumers, or is participation voluntary? How would this flexibility be rewarded? It will take some time before these matters are settled. To make sure the smart meter rollout doesn’t end up taking even longer, it needs to be agile: The devices will be installed, and the rules on grid management will be provided later via a software update. We just can't spend another 10 years on this endeavor – because an all-electric society without clear rules is definitely not a good idea.

Eva Augsten is a freelance journalist in Hamburg, Germany, who specializes in renewable energy.