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XFLEX Hydro technology models’ documentation

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To evaluate the performance of different hydroelectric technologies and solutions under development in the XFLEX HYDRO demonstrators, detailed engineering studies were performed. This involved 1D time domain simulations to quantify the magnitude of the flexibility products and to characterise the corresponding dynamic response over time. Such evaluation is important to validate the performance of the different technological solutions applied in each demonstrator with respect to the technical specification of the flexibility products under evaluation. These simulation results were condensed in the Ancillary Service Matrix (ASM) using a scoring system of the different demonstrations and technologies with respect to the envisioned ancillary services.

Regarding the progressive integration of the hydropower technologies in the Electric Power System (EPS), it is necessary to identify and consolidate proper simulation models to evaluate the resulting impact on the system dynamic performance. Hence, within the basket of flexibility products addressed in the ASM, those related to active power balancing (automatic frequency regulation reserve) and power-frequency regulation (synthetic inertia, fast frequency response and frequency containment reserve) were selected for this purpose.

With respect to fixed speed Hydro Power Plants (HPP), the proposed models were selected among those widely available in the literature and existing also in different EPS simulation packages, namely among the HYGOV, IEEEG3 and PIDGOV models. Regarding variable speed HPP (or any type of technology relying on a power electronic interface for grid connection), proposed models resort to an approximation of the physical component’s dynamic response by simpler transfer functions with the corresponding limits. Such a modelling approach is intended to properly reflect the physical components interaction with the grid without exhaustively representing all the physical phenomena taking place.

As a main outcome of this work, HPP reduced order dynamic models capable of representing the provision of the flexibility services under different conditions were identified and validated, within the scope of the project demonstrators. The identification and consolidation of these models follows a grey box approach: the model architecture/block diagram representing the main dynamics of the unit power response is assumed a priori; then, the set of parameters and limits for each model were identified resorting to an advanced algorithm to best fit the proposed model response to the 1D time domain simulation of the different demonstrators and associated technologies. The model parametrisation fitting to 1D time domain simulations may require different sets of parameters for best reproducing the dynamic response associated to different services.

The obtained results, which are summarised next, demonstrate the ability of the proposed models to properly represent the main dynamics of the studied HPP and associated technologies with respect to specific grid services. The following list summarises the information regarding the set of models developed for each demonstrator with the technologies assumed to be implemented/tested for the provision of the selected ancillary services.


FFR provision

FCR and aFRR provision


SI provision

FFR provision


FCR and aFRR provision

  • Fixed speed model with and without SPPS and with and without HSC – Click for model


FFR provision

FCR and aFRR provision


FFR provision

FCR and aFRR provision


FFR provision

FCR provision (N/A for aFRR)


SI: Synthetic Inertia

FCR: Frequency Containment Reserve

FSFC: Full-size Frequency Converter

SPPS: Smart power plant supervisor

N/A: Not applicable

FFR: Fast Frequency Response

aFRR: automatic Frequency Restoration Reserve

DFIM: Douby Fed Induction Machine

HSC: Hydraulic short-circuit

N/C: No capability to comply with service requirements