Wind power's ability to deliver grid services

Background

Wind power has good opportunities to promote the transition towards a sustainable energy system by contributing to all the grid services that SVK needs, to ensure a robust electricity system with security of supply. Future wind power needs to support the electricity grid when needed. Wind power's ability and incentives to provide system services are related to its economics. With new regulations, which the Swedish TSO Svenska kraftnät (SVK) introduced in 2025, it is even more important to produce in accordance to the bids that have been set. Otherwise, there is a risk of high imbalance costs.

Purpose

The purpose of this project is to:

• increase wind power's contribution to the various ancillary services that SVK procures.
• demonstrate the potential and costs for a wind farm to provide support services
• demonstrate how different turbines in the farm can and should interact to deliver a stable and predictable combination of electricity production and ancillary services.

Wind power reserve

To provide sustainable flexibility, similar to base load production, some form of power curtailment is required. However, the compensation for support services must exceed the value of the energy spilled. A crucial quantity is “Available power” and “Reserve power”. The latter forms the basis for compensation from SVK when the power is curtailed or turned off. These quantities can be calculated in different ways. A first idea could be to use the anemometer on the nacelle roof to measure wind speed and based on that calculate the available power. However, this signal contains several systematic errors, especially during operation. The project has developed and validated an algorithm for how “Available power” can be calculated more accurately, see document “Calculation and analysis of available power signal” below.

Tests and validations on Chalmers’ research turbine

Within the project, several tests and validations have been carried out on Chalmers research turbine in Sweden. It is a turbine with a diameter of 17 meters and approximately 30 kW of power. It has been curtailed during operation to create a “Reserve power”. The turbine has then been controlled to follow a synthetic grid frequency, where the frequency has been changed both stepwise and in sine waves. The turbine has also been connected to the actual grid frequency and counteracted actual deviations from 50 Hz. See more about these exciting experiments in the document “Results from Björkö field tests” below.

Loads and noise

Other important aspects are loads, lifetime and noise related to the delivery of ancillary services to the grid. When wind power deliberately limits its power and leaves the maximum Cp, it can be implemented in different ways, which has consequences for loads on different systems and noise. One can increase or decrease the Tip Speed ​​Ratio (TSR, dimensionless speed) and thereby reduce Cp by moving vertically in the graph below. Another way is to stay at a constant TSR and reduce power by pitching. These two extremes can also be combined arbitrarily.

The project has analyzed how a wind farm can be curtailed in three different ways and how it affects the turbine loads, see document “Wind Farm Service dispatching” below. There is certainly more to explore. 

Further analyses, simulations and tests have been carried out to see, at turbine level, how loads and noise are affected by two different power curtailment methods “Constant TSR” vs “Variable TSR” operation. More information in below presentation “Structural loads and noise”.

The project has analyzed how a wind farm can be curtailed in three different ways and how it affects the turbine loads, see document “Wind Farm Service dispatching” below. There is certainly more to explore. 

Further analyses, simulations and tests have been carried out to see, at turbine level, how loads and noise are affected by two different power curtailment methods “Constant TSR” vs “Variable TSR” operation. More information in below presentation “Structural loads and noise”.