Stable smart grids in spite of renewables

Smart grids signify the transition from a centrally controlled mains power supply to a smart, decentralised alternative. Better stability in the grid is among the most significant aspects in the roll-out of smart grids.

Incorporating regenerative sources of energy into the electricity grid presents power companies with a huge challenge. It is no longer the case that only a few large power stations need to be coordinated, as it was previously. Instead, there is now a multitude of energy sources and storage facilities. Furthermore, the actual amount of energy generated from volatile sources such as solar or wind is hard to predict or even influence. This is making it more and more difficult to keep the generation and consumption of electricity in balance. All while maintaining a stable grid. To avoid blackouts and bottlenecks, supply and demand need to be optimally coordinated. A smart grid assumes responsibility for this task.

Energy plus data with smart grids

The term “smart grid” refers to a smart electricity grid that not only transports energy, but also data. The information exchange among all participants enables electricity generation, storage, and consumption to be more effectively coordinated. Smart meters are a crucial part of any smart grid. These record electricity consumption in real time and communicate this figure to the power companies or electricity providers. Yet smart meters are also capable of receiving data – such as the current electricity tariff – as well as transmitting it.

In this way, household appliances can be automatically switched on when there is a surplus of energy in the grid. And electricity is particularly cheap. One such appliance might be a suitably prepared washing machine. Another possibility is a heat pump that fine-tunes the buffer tank temperature. Or that of the underfloor heating to raise it just a little when the tariff is especially low. Enabling the cheap energy to be stored indirectly.

All kinds of technologies are used for transmitting the information in question. 5G is particularly suitable for real-time management and automation of the smart grid. Low-power wireless networks are a low-cost alternative to mobile communications in cases where a low bandwidth suffices and a high latency is acceptable, as with the simple reading of measurement data from smart meters. Broadband infrastructure where data is transmitted through power lines promises high availability and an easy rollout.

Forecasting energy demand

The information and measurements made available through the smart grid can be used by power companies to control and monitor systems – and to predict their variable energy demand. Yet the biggest problem in this context is the sheer amount of data and time required to analyse the information.

That is why Arizona Public Service is putting its faith in Artificial Intelligence (AI). The power company ranks third in the USA in terms of capacity from solar power. The company combines its smart-meter data with weather and demographic data from third-party suppliers to predict energy demand. A software tool developed by Innowatts is put to good use here. The platform is connected to over 43 million smart meters worldwide and uses AI to analyse over five billion data points every hour.

“More than ever, electricity suppliers and grid operators find themselves in need of data insights to make informed decisions that best serve their customers, today and tomorrow,” explains David Boundy, Innowatts’ Chief Product and Technology Officer and General Manager Europe. “By summer 2021, the UK alone is expected to have over 25 million smart meters producing billions of bits of data an hour. However, to date, much of this data has remained untapped.”

Digitalisation minimises malfunctions

Enel is a shining example of how digitalisation boosts operational efficiency and can improve service quality for a power company. In just ten years, Enel has reduced the system average interruption duration index (SAIDI – an indicator of the grid quality) by 65 per cent and currently spends almost a third of its investment budget on digital technology.

(Source: IEA)

Tightly controlled energy flows with smart grids

Alongside smart-grid technologies, power electronics are a key technology when it comes to sustainable energy generation, distribution, and use. Without them, it will be difficult to integrate renewable energies, as explained by Professor Joachim Böcker, Head of Power Electronics and Electrical Drives in the University of Paderborn’s Department of Electrical Engineering and Information Technology. “There is no single form of electrical energy. In actual fact, every consumer requires a slightly different, tailored supply of electricity,” Böcker states.

“This concerns both the level of the voltage and the question of whether to use AC or DC voltage. There is even variety in terms of the electricity generated by energy providers. Photovoltaic facilities supply DC voltage, while wind turbines supply AC voltage, albeit sadly not at the frequency that matches the AC electricity grid. On the other hand, 50 Hz high-voltage grids predominate for energy transmission and distribution. Then there are also more and more high-voltage DC transmission scenarios, such as connecting offshore wind turbines or joining up the German and Norwegian electricity grids using undersea cables.”

It also allows the energy flow to be precisely controlled, laying essential foundations for smart energy systems. Professor Böcker is conducting research into converters that enable stand-alone grids to be started up independently of the mains electricity grid through the use of virtual synchronous machines. In conventional power stations, synchronous machines (rotating electrical machines) are used to create immediately available power reserves, such as in the event of an abrupt generation outage or a sudden increase in consumer load. This behaviour can be simulated using power electronics, enabling the voltage in the grid to be built up again in the event of a power failure. This crucially contributes to making the sustainable power grids of the future reliable and stable.


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