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Wind power needs balance and transmission capacity

The increase in wind power production is putting the power system to the test. In the future, the grid will need solutions to ensure stability and more transmission line connections.

Finland has approximately 1,400 wind turbines with a combined output of just under 5,700 megawatts.

Fingrid expects this capacity to quadruple over the next decade. Wind power will then account for as much as 90 per cent of Finland´s energy production at times.

Anni Mikkonen, CEO of the Finnish Wind Power Association, points out the other significance of wind power:

“Our wind power market is among the most exciting in Europe at the moment. Wind power is the industry that attracts the largest investments to Finland every year. No other form of electricity production can be built in Finland as quickly and cost-effectively as wind power.”

Mikkonen points out that wind power also boosts the vitality of many small communities.

“Every year, wind power attracts more money in investments to Finland than any other industry,” says Anni Mikkonen, CEO of the Finnish Wind Power Association.

From synchronous machines to frequency converters

As wind power accounts for an increasingly large share of energy production, new solutions are required to ensure the functionality of the power system. The method for connecting wind power to the grid differs in a technical sense from the method for conventional power plants.

In hydro and thermal power plants, a turbine rotates a generator at the same pace as the grid frequency. If the frequency or voltage of the grid changes, a synchronous machine naturally resists such changes.

Wind turbines, however, are connected to the grid via frequency converters.

At traditional power plants, the connection is a physical one. At wind power plants, it is a question of programming.

“At traditional power plants, the connection is a physical one. However, at wind power plants, it is a question of programming based on power electronics,” says Antti Harjula, Head of Power System Engineering Unit at Fingrid.

Power converters follow the grid

The wind power construction boom is displacing the synchronous machines at conventional power plants from the electricity network. However, power converters only follow the grid – as they are programmed to react – and do not stabilise the network as synchronous machines do.

“Power converters lock into the grid frequency and supply power accordingly,” Harjula explains.

“The challenges include the interactions between power converters. Production based on power electronics also required more accurate modelling and analysis to ensure the stable operation of the power system.”

As power converters do not support the power system like synchronous machines do, power system stability may be degraded. As a result, also transmission system protection and the quality of electricity may suffer. In addition, the power system will become more difficult to manage.

Solutions from the market, wind turbines and the grid

Harjula lists three categories of solutions for boosting grid stability: solutions purchased from the market, implemented into wind power plants, and built into the grid.

Solutions can be implemented locally, regionally or even at the pan-Nordic level.

Transmission system operators around the world research opportunities together with customers and equipment manufacturers.

In the future, Fingrid may buy production from power plants to support the grid rather than to produce energy.

In the future, Fingrid may buy production from power plants to support the grid rather than to produce energy. An example of market-based solution is the Fast Frequency Reserve (FFR), which is activated in low-inertia situations.

Fingrid will set new requirements for production facilities connecting to the grid in due course. For example, power converters should be capable of creating voltage and maintaining the frequency without an external reference.

Commercial solutions are already available for grid energy storage facilities based on power converters that are grid forming. However, solutions integrated into power plants are still in the development stage, and standards are lacking.

The third category covers devices integrated into the power system. Fingrid can for example install synchronous machines in the grid that work without an energy source.                  

“Fingrid is responsible for ensuring the overall functionality of the power system in Finland. In time, we will find the most cost-efficient solutions,” Harjula says. 

In any case, solutions must provide predictability and technical reliability.  

Strengthening the main grid on the west coast

Our wind power production has strong regional concentrations.

As much as three-quarters of wind power production, at present and in the near future, is in the regions of Ostrobothnia. This part of Finland will host a wind power cluster to rival the output of the Olkiluoto and Loviisa nuclear power plants.

“By the end of 2025, the area between Pori and Oulu will contain about 5,000 megawatts of wind power production. In addition, thousands more megawatts of production are planned on land and at sea,” says Petri Parviainen, Customer Manager at Fingrid.

More transmission line connections are needed on the west coast.

Although Fingrid has renewed and strengthened the main grid on the west coast, the transmission capacity is already being pushed to its limits due to the growth in onshore wind power, especially during maintenance and faults. So more transmission line connections are needed in the area.

Fingrid is preparing and conducting environmental impact assessments on a new 400-kilovolt transmission line connection from Kristinestad to Tampere and two similar transmission line connections from Kalajoki to Central Finland. The connections will be completed in 2027 and 2028.

“The new transmission lines will significantly increase the electricity transmission capacity in the region and facilitate the connection of new wind power production to the power system. However, the timetable for building these connections could slow the execution of some wind power projects,” Parviainen mentions.

Synchronous compensator to be installed in Kalajoki

Increasing the transmission capacity of the main grid is an important project, but the west coast also needs solutions that can be implemented more quickly.

Fingrid ordered a synchronous compensator – a large synchronous machine – for installation at the Jylkkä substation in Kalajoki. The synchronous compensator will balance the grid without an energy source.

“According to the plans, we will commission the synchronous compensator in 2025. This will make it possible to connect some new wind power to the grid along the Kokkola–Raahe axis,” says Parviainen.

Fingrid also intends to deploy Dynamic Line Rating technology on the west coast to provide more accurate data on the possibilities for loads and capacity in the transmission grid in different weather conditions. The technology will provide room for manoeuvre in grid operations.

Reserve terms and conditions amended following pilot project

At the moment, wind power producers only participate in the mFRR in Finland – in other words, in the balancing energy market.

Based on lessons learned in other countries, wind power could also be used to provide automatic reserve products: the automatic Frequency Restoration Reserve (aFRR), the Frequency Containment Reserve for Disturbances (FCR-D), the Frequency Containment Reserve for Normal Operation (FCR-N), and the Fast Frequency Reserve (FFR).

In 2023, Fingrid will arrange a pilot project on the participation of wind power in the reserve market for automatic products.

The aim of the pilot project is to address issues such as the interpretation of the reserve terms, prequalification tests for specific reserve products, or sending control signals to wind farms. Fingrid will use the lessons learned to develop its reserve terms and conditions.

Fingrid’s pilot partners are Enefit Green, Centrica Energy Trading and Prime Capital AG.

Wind power fully enters the reserve market

Reserves balance fluctuations in electricity consumption and production. Wind power is also needed in the reserve market.

Market parties should match their electricity production for sale and their electricity purchases for consumption as well in advance as possible. If market parties succeed in this, Fingrid will have less work to maintain a momentary balance between consumption and production in the power system.

Fingrid maintains the momentary balance using reserve products purchased in the reserve market. Producers and consumers bear the costs of purchasing and activating reserves.

The rapid increase in wind power production in Finland is leading to occasional shortages of reserves for reducing production – known as down-regulation reserves. Wind power also needs to be fully integrated into the reserve market to ensure the effective, market-based management of the power balance in the future.

So far, wind power producers have had little involvement in the reserve market in relation to their capacity.

New earning opportunities

In early 2023, Fingrid began purchasing down-regulation capacity in the balancing capacity market to ensure sufficient down-regulation resources.

Alongside the balancing energy market, there is now a capacity market where balancing service providers receive compensation for offers they make the previous day to submit balancing bids. This represents a new earning opportunity for wind power producers.

One wind power producer participating in the reserve market is EPV Energy Oy, which wholly owns EPV Tuulivoima Oy. EPV Tuulivoima’s current production capacity of approximately 500 megawatts will increase by one-fifth when three new wind farms are commissioned.

“We have begun offering wind power in the balancing capacity market,” says Mika Luoto, Operations Center Manager.

“As EPV Energy operates on the Mankala principle, meaning that we produce and purchase energy for our shareholders on a cost basis and do not seek to make a profit, we do not have any long-term customer contracts preventing us from participating in the reserve market.”

Luoto says that forecasting production volumes is one of the main challenges of participating in the reserve market.


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