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Enable Ancillary Services bY Renewable Energy Sources

Periodic Reporting for period 3 - EASY-RES (Enable Ancillary Services bY Renewable Energy Sources)

Reporting period: 2020-05-01 to 2021-12-31

EASY-RES provides a solution for the operation of the future electrical power grids with very large share (even 100%) of Renewable Energy Sources (RES).
To achieve this, firstly, EASY-RES enabled the Distributed RES (DRES) to offer Ancillary Services (AS) that are vital for the stable operation of the power grids. Note that these AS are currently offered mainly by large rotating machines (Synchronous Generators) driven by power plants that mostly use either fossil fuels or nuclear reactors. Secondly, EASY-RES developed new methods for the aggregation of the AS which could be provided even by DRES of small size connected in the distribution grids. In this way large or small active distribution networks (ADN) can be considered as Dynamic Virtual Power Plants that can contribute significantly to the power grid stability.
EASY-RES focused on the DRES that are connected to the power grid via power-electronic converters, like the PV, wind generators and battery energy storage systems. We developed and tested a new type of converter which includes a fast energy storage system and is controlled by newly developed algorithms. We named this new converter as Unified Virtual Synchronous Generator (UVSG), because it enables a DRES to provide, in a unified and fully controllable way, the following AS from a single physical device:
1. True inertial response with adaptable inertia time constant (02. Operate as Frequency Containment Reserve with adaptable droops and frequency deadband for both under- and overfrequency events.
3. Power Smoothing (ramp-rate limitation) of the injected active power
4. Controllable contribution of currents for fault-clearing in distribution networks
5. Reactive power support for voltage regulation in distribution grids
6. Operation as active harmonic filter for voltage harmonic mitigation

A Distribution System Operator (DSO) or an Aggregator can enable/disable or adjust remotely the amount of each of these AS for each DRES, creating in this way a fully adjustable portfolio of aggregated AS at distribution grid level. The EASY-RES solution enables the aggregation of those AS in a way that respects the technical constraints set by the DSO.
EASY-RES has also developed and tested tools that now enable the Transmission System Operators (TSO) to consider and exploit the new dynamic capabilities of small DRES connected in distribution grids. We designed and tested an innovative Information and Communication infrastructure that can support the control and accounting of all the above AS and facilitate the close cooperation between Aggregator(s)-DSOs-TSOs.
We have demonstrated (up to TRL5) that, by applying the EASY-RES solution, the power grids can host very large amounts of RES and allow the safe decommission of equal amounts of conventional, fuel driven power plants. This is feasible due to the following EASY-RES results:

• The inertia of the system can be kept in the current levels or even increase because the RES with UVSGs can offer similar or increased true inertia with respect to the inertia currently offered by the conventional generators that will be displaced.
• The RES with UVSGs can operate equally well as reserve units to tackle frequency stability issues. Actually, the conventional reserves can be replaced by RES in a 1-to-1 analogy.
• The RES with UVSGs are more “grid-friendly” because the inherent RES volatility can be reduced. EASY-RES has shown that the active power ramp-rate can be limited to 30% at DRES level and 10%/min at ADN level (the percentages refer to the respective nominal power).
• The protection coordination in ADN can be maintained with the legacy protection means even with 100% DRES penetration. This means that additional relevant investments in the distribution grids can be avoided.
• The power quality (voltage harmonic pollution) in ADN can be improved or maintained at today's levels despite the increasing DRES penetration.
• with the developed methods for voltage regulation within the ADN, the DRES hosting capacity can increase (with respect to the currently employed voltage regulation methods) by 10-45% in low voltage grids and 1-56% in medium voltage grids
• The DRES with UVSGs can provide all the aforementioned ancillary services in a unified and controllable way with an additional investment cost that is of the order of 7-10% of the current DRES investment cost.

Furthermore, EASY-RES developed new business models for each of the aforementioned AS and for relevant stakeholders such as: DRES owners, Aggregators, DSO, TSO, and Balancing Service Providers.

It is noted that the current grid codes and market regulatory frameworks pose some limits in the deployment of the EASY-RES solution. This happens because, those codes and frameworks, were established with the state-of-the-art of past years. For this reason, EASY-RES identified these obstacles and suggested modifications in both the codes and in the electricity markets framework.

EASY-RES made significant steps beyond the relevant scientific state of the art. This is testified by the 19 papers in scientific journals and the 18 presentations in scientific conferences (all of them peer reviewed) that were published in open-access form and are based on the work and results within EASY-RES.

The work we did in the frame of EASY-RES resulted in 16 Key Exploitable Results (KER) that range from hardware prototypes (UVSG) to algorithms and methodologies implemented in open access software tools. More details on the KERs can be found in
CIGRE scaled-down MV grid in the lab of University of Seville
DRES Functionalities in EASY-RES concept