Tests for integration of decentralized, renewable energy sources in the grid

Balancing demand and supply of electricity from/to grid

To maintain the balance in large electricity grids and ensure the security of the supply of electricity in the future, Transmission System Operators (TSOs) have to integrate the increasing influx of decentralized power from renewable energy sources like wind turbines and “solar-PV” fields into the so-called “Frequency Containment Reserve” (FCR) control. Frequency Containment Reserve is (a part of) a electricity production capacity that is reserved for increasing or reducing its energy output depending on possible frequency deviations in the grid. If the grid frequency decreases, the output of a “FCR unit” (in fact of all allocated FCR units) has to increase, in order to reduce the imbalance in the grid, and the other way around. In the past FCR was supplied only by large power plants. As their share in the total supply to the grid is expected to decrease further at the expense of the vast growing number of – in general low capacity and often intermittently operating – renewable power sources, it becomes more and more important to introduce a form of FCR also for this class of resources.

Pilot project FCR aggregation

TenneT (TSO for the Netherlands and part of Germany) has carried out a pilot project in 2017-2018 allowing aggregations of multiple decentralized sources to offer FCR to the TSO. As such type of (‘pool’) FCR was new the bidders had to prequalify that they were able to aggregate a pool of distributed, small energy sources to behave as one virtual unit with a minimum (FCR) capacity of 1 MW. The aggregation (control and information) systems of the bidders were audited by a third party.

Frequency response tests on the level of individual assets in the pool

Part of the audits were the frequency response tests of at least one representative member of each type of energy source on a predefined set of disturbances in frequency. In this framework CerTa Veritas has carried out frequency response tests of a cluster of 3 wind turbines, 2 biogas engines, a battery energy storage system (Tesla Power wall) and 2 types of electrical vehicle (EV) chargers.

The tests were carried out with a high speed power analyzer. The results gave our client a good impression of the frequency response performance and possible limitations. The project provides an important contribution to the further integration of renewables, energy storage systems and EV-charge infrastructure into the grid.