Community Research and Development Information Service - CORDIS

FP7

INCREASE Report Summary

Project ID: 608998
Funded under: FP7-ENERGY
Country: Belgium

Final Report Summary - INCREASE (INCREASING THE PENETRATION OF RENEWABLE ENERGY SOURCES IN THE DISTRIBUTION GRID BY DEVELOPING CONTROL STRATEGIES AND USING ANCILLARY SERVICES)

Executive Summary:
The significant rise in distributed renewable energy sources has placed an enormous burden on the secure operation of the electrical grid. The massive increase of the intermittent distributed renewable energy sources (DRES) in low (LV) and medium (MV) voltage networks has led to a bidirectional power flow, which raises the urgent need for new operational and control strategies in order to maintain the ability of the system operator to provide the consumers a reliable supply of electricity at an acceptable power quality level and cost.

Technically, INCREASE has focused on how to manage renewable energy sources in LV and MV networks, to provide ancillary services (towards distribution system operators (DSO), but also transmissions system operators (TSOs)), in particular voltage control and the provision of reserve. A simulation platform has been developed enabling an efficient development of the INCREASE solutions. It also proved to be an efficient tool for the DSO to study the impact new solutions have on the congestion challenges related to the penetration of renewables as well as to investigate the influence of DRES on their distribution network.
Starting from the technical solutions, INCREASE studied the regulatory framework, grid code structure and ancillary market mechanisms, and proposed adjustments to facilitate successful provisioning of ancillary services that are necessary for the operation of the electricity grid, including flexible market products.

INCREASE proposes a three level approach for maximizing the integration of renewables. The first level only uses local parameters (voltage at the point of connection, exchanged power) for the control. This is a fast control that mitigates the voltage unbalance (at the LV network) and uses P-V droops to achieve soft curtailment to solve the overvoltage problem. The first level control ensures the reliability and stability of the system. The second level control results in an optimal system and aims to minimise the loss of renewable energy as well as ensuring a fair distribution of the possible curtailed energy. This second level control is achieved by a multi-agent aggregator concept and consists of fair power sharing, the coordination of on-load tap changer (OLTC) control and PV inverters to solve (current and voltage) congestion. In order for the DSO to evolve from congestion manager to capacity manager, a service layer is developed. This service layer is the third level in the INCREASE approach. It solves a multi-objective optimisation problem by combining and extending optimisation strategies and results in flexible energy products to provide ancillary services with them. The DSO always needs to have control over the grid in order to prevent that the demand response (DR) and DRES schedules worsen the supply security. For this purpose, a Traffic Light System (TLS) is used that gives the DSOs the ultimate control over the DR unit schedules.
The use of INCREASE solutions result in a more efficient exploitation of the current grid capacity, thus facilitating higher DRES penetration at reduced cost. Because of the more efficient use of the existing infrastructure, grid tariffs could decrease, potentially resulting in a lower cost for the consumers.

The INCREASE solutions are validated (i) by simulation, (ii), by lab tests, as well as (iii) in four field trials in the real-life operational distribution network of Energienetze Steiermark in Austria, of Eandis in Belgium, of Elektro Gorenjska in Slovenia, and of Liander in the Netherlands. Different parts of the INCREASE solutions were successfully tested in the different field trials. The results from the field trials enabled us to prove the successful functioning of the developed solutions. Even more, due to the successful validation and the positive experience during the field trials, EG decided to continue using the developed OLTC control algorithm after the end of the project, since it proved to be better than the classical ones.

Project Context and Objectives:
The significant rise in distributed renewable energy sources (DRES) has placed an enormous burden on the secure operation of the electrical grid, impacting both the transmission system operators (TSOs) and distribution system operators (DSOs). The majority of these units are connected in the distribution network on medium and low voltage levels (MV and LV) which have been traditionally operated as radial networks with the flow of energy typically coming from the transmission network side towards the distribution network-connected loads. The massive increase of the intermittent DRES in LV and MV networks has led to a bidirectional power flow (i.e., also originating in the DSO networks). This raises the urgent need for new operational and control strategies including protection algorithms in order to maintain the ability of the system to provide the consumers (i.e. loads) with reliable supply of electricity of an acceptable power quality level. This will clearly impact the operation of the energy market, in terms of business/market models and regulation.
In addition to the energy-based electricity markets, on a technical level ancillary services (AS) are needed for the secure operation of the power system. Ancillary services are grid support services required by the transmission or distribution system operator to maintain the integrity and stability of the transmission or distribution system as well as the power quality. These services typically include regulation of frequency, active power reserves, voltage and reactive power control, black start capability and islanding.
INCREASE enables DRES and loads (i.e., consumers) to go beyond just exchanging power with the grid, and also provide ancillary services. INCREASE investigates the regulatory framework, grid code structure and ancillary market mechanisms, and proposes adjustments to facilitate successful provisioning of ancillary services that are necessary for the operation of the electricity grid. Technically, INCREASE focuses on how to manage renewable energy sources in medium and low voltage networks, to provide ancillary services (towards DSO, but also TSOs), in particular voltage control and the provision of reserve.
This is achieved by means of smart control strategies on two timescales: fast and slow control. The distribution network must be kept stable in the event of disturbances by using a fast control strategy that uses local parameters (e.g. voltage, available power) as input. On this short timescale, communication with remote entities is avoided as to maximize the reliability of the system. The slow control, which typically uses communication, helps the system to reach an optimal state. In this project both aforementioned control strategies have been developed and combined such that a stable and reliable distribution network operation is obtained.
At the low voltage (LV) network, the penetration of DRES is currently limited by emerging voltage unbalance that is caused by the high number of the (mainly) single-phase connected DRES. Moreover, the DSO does not always know the DRES’s locations nor the phase they are connected to which complicates the problem and prohibits a centralized solution. A solution to this problem is to add smart control strategies to the inverters of every single DRES. INCREASE has developed a control strategy for three-phase grid-connected inverters that mitigates voltage unbalance by distributing the active power between the phases. INCREASE’s control strategy will enable local voltage control. The focus is on quasi-steady state phenomena such as voltage unbalance mitigation, under/over voltages. Decreasing the voltage unbalance will result in an improved voltage profile allowing a higher penetration of individual RES in the low voltage network.
Due to physical natures (the ratio of reactance over resistance is low), voltage problems and current congestion are strongly interrelated in distribution grids. INCREASE solves possible current congestion in the distribution feeder by exposing the feeder’s current measurement to the grid-connected inverters that subsequently can use this signal as input for their local controller. Thus, the congestion problems at LV level have been tackled by developing a multi-agent system to coordinate the distributed DRES’s inverters: such a distributed solution is a very viable one to address the complex problem caused by the high number of connections in the low-voltage network. Congestions at the medium voltage (MV) level can also be relieved by the multi-agent system proposed for LV networks. In the MV-network, the proposed smart control strategies use ICT innovations and can be based on real-time line-rating, advanced forecasting techniques and demand-side management. These advanced techniques allow for increasing the penetration of distributed renewables with only limited grid investments (or avoid them altogether).
The solutions developed in INCREASE – i.e., (i) three-phase four-wire grid-connected inverters, (ii) their control strategy and (iii) the multi-agent coordination system –enable the DSO to evolve from a congestion manager to capacity manager. This results in a more efficient exploitation of the current power grid capacity, thus facilitating higher DRES penetration at reduced investment cost. Because of the more efficient use of the existing infrastructure, grid tariffs could decrease, thus potentially resulting in a lower cost for the consumers.
To carefully design, analyse and optimise the proposed solutions, INCREASE has developed supporting simulation tools. This enables the DSOs to perform careful investigations on the integrated smart distribution network, first of all in a simulated environment. To this end, INCREASE has developed an integrated simulation platform, incorporating not only the power system characteristics, but also the information and communication technology (ICT) infrastructure, e.g., supporting the multi-agent system. Indeed, current state-of-the-art in large-scale analysis of the functionalities of the multi-agent control system as envisioned by INCREASE, such as dynamic load flow, system stability, voltage control and congestion management, is still a very preliminary phase. Thus, the INCREASE simulation framework is especially targeted to the analysis of those multi-agent systems.
The INCREASE simulation platform enables the validation of the proposed control strategies and provides the DSOs with a tool they can use to investigate the influence of DRES on their distribution network. Apart from thorough simulation, the INCREASE solutions has been also validated (i) by lab tests using experimental infrastructure of Lemcko - Ghent University, as well as (ii) using the results in four field trials in the real-life operational distribution network of Energienetze Steiermark in Austria, of Elektro Gorenjska in Slovenia, of Eandis in Belgium and of Liander in the Netherlands.
In addition to the energy-based electricity markets, ancillary services (AS) are needed on a technical level for the secure operation of the power system. Ancillary services are grid support services required by the transmission or distribution system operator to maintain the integrity and stability of the transmission or distribution system as well as the power quality. These services typically include regulation of frequency, active power reserves, voltage and reactive power control, black start capability and islanding. On the distribution network, AS include voltage and reactive power control, network impedance control, phase symmetry balancing, generation flexibility provision and capability to handle fault currents.
INCREASE enables DRES and loads (i.e., consumers) to go beyond just exchanging power with the grid, and also provide ancillary services. INCREASE has investigated the regulatory framework; grid code structure and ancillary market mechanisms; and proposed adjustments to facilitate successful provisioning of ancillary services that are necessary for the operation of the electricity grid, including flexible market products. Technically, INCREASE focuses on how to connect renewable energy sources in medium and low voltage networks, to provide ancillary services (towards DSO, but also TSOs), in particular voltage control and the provision of reserve.
INCREASE has the following scientific objectives:
(1) the development of a 3-phase grid inverter with functionality that enables ancillary services from DSOs.
(2) distributed control algorithms for global optimisation of the distribution grid,
(3) a complete ICT solution communicating with the inverters from 1 and implementing the algorithms from 2, and incorporating the required decision support systems for planning, procurement and exchange of ancillary services
(4) simulation and analysis tools that enable grid operators to accurately assess the impact of 1-3,
(5) extensive validation of 1-3 in both lab environments and real-life grids, and
(6) definition and analysis of the regulatory context and market models to support/exploit the technical innovations of 1-3.
We discuss each of these major objectives in detail below.
• Objective 1: Development of 3-phase inverters for renewable generation units with variable set-point, including their local control. The latter uses both local parameters (e.g. voltage and available power measured at the inverter itself) and parameters supplied externally (e.g., measurement values of current in the distribution feeder connecting also other DRES) The local control is targeting voltage unbalance mitigation, over/under voltage control and grid support in case of disturbances and faults. This control strategy thus enables an intelligent control of the voltage profile and improves the reliability of distribution grid in times of disturbances and grid faults. To realize optimisation at the scale of the whole distribution feeder (and ultimately enabling DSOs to provide ancillary services to TSOs through the joint control of, e.g., multiple inverters), the set-points of multiple such inverter controllers need to be coordinated. This is to be realized by the distributed control system discussed next.
• Objective 2: Development of a multi-service/objective distributed control system which provides a global optimisation for the whole distribution grid. This distributed control system comprises a high number of loads, and tackles the following problems on the scale of a complete DSO network: (i) over/under voltage, (ii) congestion, (iii) phase unbalance at the LV level, (iv) provision balancing (tertiary control) to the TSO. INCREASE realizes this through a multi agent control strategy, in combination with the inverter’s local control (see objective 1). The multi-agent system furthermore incorporates advanced techniques such as real-time line rating (to maximally exploit real-time available power line capacity), demand-side management (to adapt loads, i.e., both industrial consumers and households, to e.g., fluctuating wind energy) and forecasting techniques (to accurately predict e.g., local wind energy production at the level of MV feeders).
• Objective 3: Develop and implement the ICT system architecture to realize the aforementioned control strategies in an operational DSO network. Note that this is broader than just the mere input/output control signals. INCREASE proposes a complete Ancillary Services Management System (ASMS). This ASMS provides the following functions:
o Load and production forecasting
o Optimal planning of local controller settings.
o Optimal planning of regional controller settings.
o Optimal planning and operation of provision for balancing energy to TSO.
o Optimal planning and operation of DSM.
This ASMS is thus integrated in a trading and settlement system, i.e., the overall ICT system for ancillary services trading, scheduling, settlement and DSM. In defining and analysing the system performance, a crucial part will encompass the communication system. Such analysis is performed using the simulation toolset discussed next.
• Objective 4: Development of a simulation toolset to thoroughly analyse the INCREASE control strategies. This toolset is offered to DSOs to enable them to do case specific assessments of the potential of INCREASE’s innovations in their particular network. Thus, we model the components as discussed in objectives 1-3. This encompasses simulation tools that allow to jointly(!) analyse the performance of the various system constituents, i.e., (i) the electrical power grid, (ii) the multi-agent coordination algorithms and (iii) the communication network. As such, INCREASE will propose solutions to enable detailed analysis of distribution networks with high penetration of DRES penetration (for which we will develop dynamic models suitable for MV/LV network analysis).
• Objective 5: Lab-scale and real-life validation of distributed control offering ancillary services. The technical innovations as explained in objectives 1-4 are not only validated by means of the simulation platform (see objective 4), but also (i) by lab tests in experimental grid infrastructure of Lemcko, Ghent University, and (ii) in four field trials in the real-life distribution network of Energienetze Steiermark in Austria, of Elektro Gorenjska in Slovenia, of Eandis in Belgium and of Liander in the Netherlands.
• Objective 6: Design of market and regulatory framework for share of responsibility, cost and benefits Investigation of the provision and remuneration aspects of distribution-level AS, in light of ENTSO-E priority issue of “which AS should be mandatory, payable or provided via AS market?”, using a common definition of ancillary services in the Transmission system and also in the Distribution system. Following this, national and EU regulatory setup are investigated, comprising the TSO and DSO grid codes, regulations and directives and action plans. Finally, market designs are investigated and their adaptation proposed that allow DRES operator to act as a provider of Ancillary Services. They are adapted to the market conditions to take into account the balancing needs and the needs for ancillary services brought about by RES.

Project Results:
For this part, we refer to the attached document with file name: finalreport_INCREASE_part3.pdf
Potential Impact:
For this part, we refer to the attached document with file name: finalreport_INCREASE_part4.pdf
List of Websites:
http://www.project-increase.eu

Related information

Documents and Publications

Contact

Saskia Vanden Broeck
Tel.: +32 9 264 3124
E-mail
Record Number: 199795 / Last updated on: 2017-06-20
Follow us on: RSS Facebook Twitter YouTube Managed by the EU Publications Office Top