System stability
Ancillary services from flexible production provides support when required
In the past few years, the share of weather-dependent power sources, such as wind and solar power, has increased. This development increases the risk of imbalances occurring in the electricity system – which can result in electricity shortages or serious disruptions in the electricity grid. It could be said that the more weather-dependent power we utilize, the more important it is that we also have access to hydro and nuclear power, which, jointly with our various ancillary services, can also balance and stabilize the system when required.
Disturbance reserve – a quick starter that kicks in when the frequency falls
The disturbance reserve is an ancillary service procured by Svenska kraftnät, which is Sweden’s system operator. The disturbance reserve consists of electricity generation resources that can be rapidly activated to restore balance to the system. At present, the disturbance reserve primarily comprises gas turbines that produce electricity and which can be fully operational in a couple of minutes in the event of a frequency drop. Uniper is a contributor of this reserve.
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Frequency control enables a power plant to be ramped up or down
In the event of a deviation in frequency, it is paramount to stabilize the frequency quickly. To achieve this, various methods of frequency control are utilized as an ancillary service. The frequency can be regulated both automatically and manually. Automatic frequency controls are featured in many hydropower plants. The equipment that is linked to a power plant turbine cab automatically increase or decrease electricity generation based on the prevailing frequency.
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System inertia – kinetic energy that buys time while imbalances are corrected
A third vital ancillary service that is required to quickly offset frequency deviations is system inertia – a kinetic energy that can only be provided by the turbines and generators of major power plants. As the power plant stops driving the generator, the turbines continue to spin for a while, due to kinetic energy. This allows for the power plant to continue generating electricity for a little longer. Simplifying it somewhat, it could be said that system inertia buys time that can be used to regulate the frequency. The heavier the generator and turbine, the longer it continues to spin. The more rotational energy we have in our electricity system, the easier it is to maintain the frequency and thereby stabilize the electricity system. Hydro and nuclear power provide considerable amounts of system inertia, while weather-dependent power sources such as wind and solar power lack this characteristic.
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Power reserve – when insufficient electricity is generated
A fourth support for the electricity system is the power reserve, which has a somewhat longer planning horizon. The power reserve is used temporarily when our electricity consumption is deemed to exceed the electricity being generated. The power reserve is usually used on very cold winter days, when our demand for electricity is particularly high. Uniper’s Karlshamnsverket power station is part of Svenska kraftnät’s power reserve during the winter season. The power plant can be started up quickly and produce electricity on short notice when needed. It only takes two hours for Karlshamnsverket to go from standby to production.
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We ensure that the electricity system remains stable
As part of the global Uniper Group, we are a major electricity and power producer for Swedish base industry and a guarantor of stable and reliable electricity generation. We have power plants throughout the country for fossil-free hydro and nuclear power, as well as the Nordic region’s greatest peak power and reserve power. Uniper’s electricity is used to ensure that our society and industries function, regardless of the weather and time of year. In terms of hydropower, we are the third-largest producer in Sweden. Our 74 wholly and jointly owned hydropower plants, distributed from Lycksele in the North to Kristianstad in the South, account for approximately 12% of Sweden’s total hydropower production. The Uniper Group is a co-owner of all three of Sweden’s active nuclear power plants.
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