Renewables at >50% in European grids

E-distribuzione intends to demonstrate that the technologies that will be developed or improved within the EU-SysFlex project allow a distribution system operator to acquire total autonomy in the control of distributed resources connected to its own network.

Currently, the distribution networks in Italy are characterized by a high penetration of distributed generation. In 2017, about 31.3 GW of plants were connected to distribution networks which represents 26.7% of the gross national capacity. This can cause voltage violations and congestions. In addition, decentralization of the power system requires an improvement in the observability and the participation of distributed energy resources (DERs) in the provision of ancillary services.

For this purpose, an advanced solution for managing flexibilities connected to the distribution network is going to be developed in the portion of the grid involved in the demo of the EU-SysFlex project. It will also improve the coordination with the transmission system operator (TSO). This is important in situations where, due to the increasing share of renewable energy sources (RES) and to the corresponding decrease in conventional generation capacity, there is a scarcity of resources in the transmission network for providing ancillary services.

In this context, it is important to emphasize that in Italy the division of roles is as follows:

  • Transmission system operator is responsible for:
    • Activities of dispatching, transmission, balancing of the whole electrical system;
    • Dispatching of resources directly connected to the transmission grid and, through aggregators, of resources connected to distribution networks;
  • Distribution system operators are responsible for:
    • Medium-voltage (MV) and low-voltage (LV) grid operation and metering. They can control the voltage profile through On-Load-Tap-Changer (OLTC), capacitor banks and any other devices owned by themselves. DERs cannot be managed by the distribution system operators (DSOs) in terms of active and reactive power flow (although directly connected to the DSOs grid).

Still according to the Italian regulatory framework, DERs cannot exchange services with DSOs. The only two allowed controls are related functions that can be activated in local mode just as required by the Italian standard rules for connection and operation of DERs.

It means that the Italian regulatory scenario does not offer to the DSOs the opportunity to operate directly on DERs in a “standardized” way but only on an experimental basis. In 2017 in fact, in order to match EU guidelines, the Authority launched a pilot project (“Delibera 300/2017”) to allow DERs to participate to the ancillary services market after a pre-validation carried out by the involved DSOs.

Other experiences about the direct control of distributed resources, this time by the DSOs, were tested in other pilot projects like Grid4EU (its demo is the basis for the development of the EU-SysFlex demo).

In these cases and for EU-SysFlex, too, in addition to the Central System and to the Remote Terminal Units, DERs can receive modulation requests from the DSO by an Interface for Energy Regulation (a field device, IRE). The weak aspect of these experimentations is the fact that IREs can be installed on DERs premises only under a voluntary agreement between producer and DSO.

E-distribuzione, as a DSO, intends to demonstrate that the technologies that will be developed or improved within the EU-SysFlex project allow the DSO to acquire total autonomy in the control of distributed resources connected to its own network.

More in detail, the innovation of the Italian demonstrator consists of including RES, storage and (Static Synchronous Compensator) in the congestion management, balancing and voltage regulation of both transmission and distribution networks.

From a technical point of view, the most important and innovative elements of the project concern:

  • The installation of a STATCOM (in the primary substation of the demo) that will be used for voltage support by reactive power regulation;
  • The development of a function of aggregated reactive power capability calculation that allows the DSO to determine the reactive power that can be provided by local resources to TSO;
  • The improvement of the existing optimization algorithm in order to obtain a desired exchange of active and reactive power at the primary substation (high/mid-voltage substation) level, while optimizing the overall network state;
  • The improvement of data exchange between DSO and TSO for a better coordination and observability for the TSO of the aggregated flexibility at the primary substation interface.

Due to the inability of the DSO to operate directly on DERs, within the Italian EU-SysFlex Demonstrator, all the available resources will be involved in the field test of voltage regulation services. Moreover, the integration of RES and storage for congestion management and frequency control in the transmission grid will be at least simulated.

The voltage regulation will be tested by interfacing RES and DSO resources (storage, STATCOM and OLTC) with the existing remote control infrastructure.

 

Environment and scope of the Italian Demo

 

The forecasting tool, combined with the network state estimation and the function for the calculation of reactive power capability, will demonstrate that the DSO can provide to the TSO reliable information on the amount of powerthat can be supplied by local resources. The improved observability of the distributed resources will also support the network state estimation contributing to a better management of the network. In addition, the results will demonstrate the capability of the DSO to support the TSO requests in both simulated and real field tests.

The demonstration will not only allow to evaluate the effectiveness of the adopted solutions, but also to build expertise exploitable to improve network operation and to upgrade the SCADA system in order to be ready for the potential new functionalities requested by the regulator.

Eventually, by considering that the STATCOM is a new device in E-distribuzione infrastructure, the project represents an opportunity to demonstrate that its action is effective in managing reactive power capability. In particular its operation will provide the following benefits:

  • Limitation of reactive power flow at the primary substation;
  • Meeting TSO requests at TSO/DSO interface;
  • Supporting voltage control;
  • Power factor compensation.

Considering that the increasing availability of distributed flexible resources is encouraging the evolution of national regulations and that Italian authority, TSO and DSOs are working to implement, by 2020, the following two documents:

  • Commission regulation (EU) 2017/1485 establishing a Guideline on electricity transmission system operation (SOGL)
  • KORRR (Key Organizational Requirements, Roles and Responsibilities)

the results of the Italian demonstrator will contribute to the discussion about the opportunity of opening to a direct interaction between DSOs and distributed resources.

Written by:

E-distribuzione SPA is a Distribution System Operator (DSO) and a subsidiary of the ENEL Group, Italy’s largest power company and Europe’s second listed utility by installed capacity. With about 32 million consumers and more than 1,100,000 km lines, E-distribuzione is the second largest DSO in Europe. As well as providing power distribution services to its household and business consumers, the company runs RD&D activities with the aim to constantly improve supply services to consumers and facilitate new advanced services to the customers in the framework of smart grids developments. Solutions for the integration of renewable energy sources as well as the active participation of customers in the management of the electricity network have been investigated and tested by the company under different national and European projects.

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Disclaimer: blog entries reflect individual views of the author(s) that may not reflect official positions or communication of the project / project consortium.

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