In the future energy system, hydrogen as an energy carrier will play a role of increasing importance. Electrical energy can be converted into hydrogen locally by electrolysers and stored for a relatively long period. Then, the hydrogen can be used by final consumers like the transportation system or industries, as conceptually illustrated in Fig. 1. The flexibility of electrolysers offers promising possibilities for electrical grid support by the provision of ancillary services. Currently, a pilot power-to-gas facility with a 1-MW electrolyser is installed in the northern part of the Netherlands. A larger electrolysis plant of 300 MW may be installed in this area later. The feasibility of this large-scale plant, its impact on the stability of the electrical transmission network and the possibilities for ancillary services provision are currently being investigated in the project TSO2020 .
Fig. 1: Conceptual illustration of TSO2020 (figure adapted from ).
TSO2020 (Electric “Transmission and Storage Options” for 2020) consists of several activities, including a Cost-Benefit Analysis (CBA), the pilot 1-MW electrolyser, an analysis of the scale-up to mass production and a study on the impact on power system stability including the possibilities for ancillary services provision. This last activity is divided into several tasks:
- Development of an electrolyser model for real-time simulation
- Development of the network model for real-time simulation
- Analysis of the impact of electrolysers on power system stability
- Hardware-in-the-Loop (HIL) tests of the electrolyser rectifier and controller
- Investigation of the possibilities of ancillary services provision by electrolysers
- Development of control schemes for ancillary services provision
The stability analyses of this activity will be performed in real time on the Real-Time Digital Simulator (RTDS). As models of large (>1 MW) electrolysers have not been described in literature yet, electrical models of the 1-MW and 300-MW electrolysers have been developed specifically for this project in RSCAD, to be simulated on the RTDS. These models also include the controls required for ancillary services provision. The performance of the electrolyser models are validated against data from existing literature and against field measurements of the 1-MW pilot electrolyser in the Netherlands. The transmission network of the northern Netherlands has been modelled in RSCAD as well and includes the 700-MW HVDC NorNed connection (to Norway), the 700-MW HVDC COBRAcable (to Denmark),
the 600-MW GEMINI offshore wind farm and several conventional generators.
To investigate the possibilities of ancillary services provision by electrolysers, the current regulations of the Dutch and European market have been reviewed, thereby concentrating on frequency balancing, voltage control and congestion management. Based on this review, it is expected that electrolysers have the largest potential in providing frequency support, especially in the short term by participating in Frequency Containment Reserve (FCR). Under certain conditions, electrolysers could also participate in Automatic Frequency Restoration Reserve (aFRR) and voltage control.
Several simulations have been performed, in which the response of the power system to a selection of possible contingencies was studied. These contingencies include the disconnection of generators, wind farms and submarine interconnections, and some shortcircuit faults. These initial simulations show that the frequency response of the system improves if part of the FCR is provided by electrolysers instead of conventional generators.
Future work includes the validation of the electrolyser model against field measurements. Also, further simulations will be performed, considering also voltage and frequency support by electrolysers operating at lower (than rated) capacities. The provision of ancillary services will be investigated further and control schemes for this purpose will be developed. General recommendations for the provision of ancillary services will then be given.
B. Tuinema, P. Ayivor, V. Garcia Suarez, M. Adabi, L. Liu, J. Rueda Torres, P. Palensky, M. van der Meijden, CIGRE Symposium Aalborg 2019, Session 15, paper 034, June 4 - 7, 2019
KEYWORDS: Ancillary Services, Electrolyser, Power System Stability, Real-Time Simulation