Customer application 27 August 2020
The Digital Energy Transition with High-Tech Controllers

The expansion of renewable energies can only succeed if the fluctuating supplies from solar and wind arrays are compensated by flexible electrical consumers and batteries. Digital technology can help to solve this problem: Intelligent systems convert the analog electrical network into a communicative smart grid and pave the way for linking virtual power plants, generators and consumers.

There are troubles ahead for wind energy. Although wind turbines are supposed to provide the lion’s share of the electrical supply in the long term, the federal government wants to put the brakes on new construction in northern Germany to a significant degree. Since 2017, Bremen, Hamburg, Schleswig-Holstein, Mecklenburg-Western Pomerania and the northern parts of Lower Saxony have only been permitted a maximum new wind output of 902 megawatts – this is not even 60 % of the output that is currently available. This is because the electrical lines in the stormy coastal regions have reached their capacity limits. Wind turbines are increasingly switched off as part of so-called supply management, because the large amounts of green energy could damage network stability.

The Energy Transition Goes Digital – Here’s How WAGO Supports You:

WAGO’s controllers ensure secure communication and control.
The new VHReady communication standard facilitates the interplay of decentralized systems.
Data encryption and specially secured connections defend against unauthorized access.

Stored Energy Counteracts Network Fluctuations

The difficult question is how to take the breaks off the energy transition. New electrical lines are supposed to transport the wind power from the coast of the North Sea to the south; however, the network expansion has been held up because laying the ground cables has taken longer than planned. Another challenge is gaining control over the weather-dependent, fluctuating green energy production. Solar arrays and wind farms already provide one-third of the electricity required in Germany – a proportion which is supposed to increase to 100 percent by 2050. According to experts, technical adaptations and new business models for marketing renewable energy are desperately needed. “We are relying on a type of generation that fluctuates, is decentralized and distributed and involves small producers This leads to new requirements on the infrastructure, the electrical grid, the control and the flexibility that used to be available in controllable power plants,” says Tobias Kurth from Energy Brainpool, energy marketing experts from Berlin.

The industry faces a mammoth task: It must develop solutions that retain stability in the electrical grid at a frequency of 50 Hz, even with increasing renewable energy production. Possibilities include batter storage units, as they can quickly accommodate excess current and discharge it again as needed. If they were installed, for example, at the base of large wind farms, then the stored energy could be used as balancing power to compensate for short-term fluctuations in the electrical grid. This would also avoid forced switch-off of wind turbines. The combination of batteries with photovoltaics is also logical. If solar batteries are coupled to charging stations, then EV charging stations can operate around the clock, providing solar energy to electric vehicles, or the batteries could also be used in the residential sector as storage systems. These could increase personal consumption and simultaneously cap the midday peaks from solar production that endanger the electrical grid.

The digitization of the energy transition is the prerequisite for managing a decentralized energy market.

Tobias Kurth, Energy Brainpool

Heat and Fuel from Electricity

Power-to-heat and power-to-gas systems offer additional options for flexibility. They convert green energy into heat, using electric boilers, or into hydrogen and then methane through electrolysis. The heat can be supplied to a local district heating network; the gas can be stored for longer periods in the existing natural gas network that supplies residential areas, power plants and fuel stations. Thus, power-to-heat and power-to-gas both reduce the load on the electrical grid and also incorporate the heating and mobility sectors, which have previously played a subordinate role in the energy transition. “We could use northern Germany as a gigantic test lab for sector linkages. A few possibilities include: gas or heat generation using excess wind energy, local subsidy programs for heat pumps or e-vehicles and test routes for electric trucks or buses using overhead lines. This would also enable the quick expansion of the wind energy sector,” says Volker Quaschning, Professor in renewable energy technologies at the University of Applied Sciences Berlin.

However, the development of options for flexibility, such as batteries, is not the only challenge. Batteries must also be networked with the decentralized generators and consumers. The energy originates in a system built from thousands of producers, dominated by solar arrays and wind turbines, and flows in many combinations in several directions; it is comparable to data on the Internet. Therefore, intelligent, digital systems are necessary to measure the complex energy flows and to control and monitor the production systems according to the network situation. In addition, the systems must enable absolutely secure communication between the production level and the control technology; hacker attacks on power plants and the electrical grid are common and can endanger the supply network. “The digitization of the energy transition is the prerequisite for managing a decentralized energy market,” says Kurth.

Virtual Power Plants Relieve the Electrical Grid

The good news: according to the study, “Germany’s Energy Suppliers are Going Digital”, conducted by the consulting firm pwc, more than two-thirds of the energy production companies consider decentralized energy solutions highly relevant and view digitization as a lever for increasing their process efficiency. Digitization potential arises along the entire energy added-value chain. Flexible electricity pricing, which follows the availability of renewable energy, is an approach that is especially appealing to commercial and industrial consumers: When solar arrays and wind turbines produce a lot of energy, suppliers offer electricity at reduced prices. This encourages consumers to adjust their use to the fluctuating generation. This is merely a first step: “Increasing numbers of households produce their own electricity with small CHPs and solar modules. They are no longer just consumers, but have become prosumers, who both consume and provide excess power to the grid,” says Kurth.

If these households were networked together, they could balance supply and demand among themselves. Virtual power plants are a move in the same direction. They combine decentralized producers, like biogas, solar arrays, wind turbines, CHPs, heat pumps, emergency generators and batteries, with intelligent control technology to form a flexibly controllable group. Network operators supply balancing energy from registered suppliers to compensate for fluctuations in the higher-level transmission networks. Some companies are already using virtual power plants to offer this service. Trianel, a municipal utility cooperative, bundles generating and storage technologies into a balancing pool with more than 700 megawatts of total output. In practice, the biogas systems, storage facilities etc. in the Trianel power plant are operated as usual. If the network operator calls for balancing power, then an algorithm in the control system selects the suitable systems and controls them from the control center. The advantage of the Trianel power plant is that it is composed of 400 individual systems and thus offers a high level of flexibility. It can thus cushion short-term fluctuations quite well.

Easily Managing Complex Energy Flows

Intelligent local network stations (iLNS) can also play an important role in digitization of the network. Earlier transformers were passive elements that stepped down the electrical voltage from the medium-voltage network to the lower voltage used by the local supply network using a fixed ratio. An iLNS, in contrast, records various measurement kinds of data in the medium-voltage network and offers the option of reading these values out remotely. This allows the network operators to adjust the voltage levels at any time. For example, if, on a sunny day, a lot of solar power is supplied, which increases the voltage, an iLNS can quickly compensate for this. This increases the accommodation capacity of the network and prevents bottlenecks, which can ultimately put the brakes on the expansion of renewables. WAGO’s developments help promote the digitization of the energy supply. In order to convert conventional local network stations into intelligent ones, it is essential to synchronize the primary and secondary components in a reliable way that conforms to standards.

In conjunction with their project partners, WAGO has already created a corresponding system and completely equipped it with automation technology. The station uses a PFC200 XTR Controller for the medium voltage, a PFC200 Controller for low voltage, an e!DISPLAY panel for visualizing the measurement and control data directly at the LNS and completely automated connection technology. The WAGO Controllers, which are freely programmable via CODESYS, collect all data from the substation’s various systems via digital and analog signals (e.g., via Modbus RTU). These controllers then translate the data into supplier-required communication protocols (IEC 60870-5-101/-104 or IEC 61850) and transmit the data to the control center via data lines. In the opposite direction, the control center can access the substation’s systems, such as the medium-voltage control cabinet, protective devices or measurement systems from different manufacturers, using the WAGO Controllers.

Protected from Hackers

The WAGO Controllers protect the data flow against unauthorized access by encrypting the data using TLS1.2 and also by transmitting the data via specially secured connections, like IPsec or OpenVPN in accordance with the BDEW White Paper. WAGO’s technology provides secure communication and control for virtual power plants as well. The generators and consumers combined into this type of power plant speak different languages and can thus barely communicate. The new open-source communication standard VHPready (Virtual Heat and Power Ready) can change this. It functions like a translator so that control centers and distributed systems understand one another. Instead of a system-specific set of variables, as was previously used, VHPready communicates via predefined profiles using uniform data point systems. In addition to communication, domain-specific specifications, e.g., concerning behavior and reaction times, are also defined. This provides the ability to control systems using timetables. Thus, the power plant control center can transmit control parameters for a time period of 24 hours. Without digitization, the energy transition will not succeed – intelligent control systems are thus becoming the key technology on the energy market.

Text: Heiko Tautor, WAGO

Photo: Manfred H. Vogel | vor-ort-foto.de, iStockphoto.com