Detailed requirements and constraints for the control of flexibility

Seppo Hänninen, Anastasios Kyritsis, Ibrahim Abdulhadi, Roman Schwalbe , Thomas Strasser, Michael Kosmecki, Bogdan Sobczak , Robert Rink, Bartosz Kedra, Maclej Wilk, Robert Jankowski , Mattia Marinelli, Junjie Hu, Jef Verbeeck, Artjoms Obushevs, Antonio Guagliardi, Marita Blank, Sebastian Lehnhoff, Christoph Mayer, Evangelos RikosFidalgo Jose Nuno, Abdullah Nadar, Kari Mäki , Corentin Evens

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    Abstract

    This Electra internal report includes the work of Task T6.1 describing the nature, availability and
    contribution of flexibility resources. This task also models the interactions across control
    boundaries and identifies sources of control conflicts, giving also an overview of experiences from
    the ELECTRA partners regarding the realization of controllers in demonstration and field test
    projects. The work was carried out during the period from May to December 2014.
    The different type of flexibility resources, their characteristics, affecting market mechanisms and
    potential for aggregation were researched using a survey among project partners. The parameters
    used to characterise flexibility include the amount of power modulation, the duration, the rate of
    change, the response time, the location, the availability, the controllability, etc. Views were also
    received how these parameters will develop until 2030 and what are the general trends for
    development of amount and controllability of this resource types. The parameters characterising
    different energy resources provide the technical requirements for their applicability to flexible
    operation of the grid and their suitability for frequency and voltage control now and in the future.
    Regarding the flexibility of electricity generation, gas turbines and other heat motors as
    reciprocating engines can be started quickest. The speed of power change is clearly the highest for
    heat motors and their minimum power is low. Also steam and combined heat and power plants
    can be utilised in the relatively quick increasing of the electricity generation. Slower power changes
    are possible also with the nuclear power but they cannot be carried out continuously. The
    regulation characteristics of hydro power are superb in comparison to the other electricity
    generation methods. Besides the sun power, wind power is increasing most quickly in the world in
    the coming years. The modern wind power plants are able to active and reactive power control.
    Storage systems can contribute to the frequency and voltage control mechanisms. Charging and
    discharging of the storage system at the right moments (response within milli-seconds to seconds)
    can help to preserve the balance between consumption and generation. Storages can also provide
    secondary and tertiary frequency control. Static compensation devices maintain desired voltage
    level by feeding the grid with necessary reactive power. FACTS devices and cross-border
    connections based on HVDC converter schemes can play an important role in frequency and
    voltage support. Demand response, including industrial loads and household devices and electric
    vehicles, will have great influence in flexible operation of the grid.
    This report describes appropriate models that characterize the interactions across control
    boundaries under normal and emergency situations, introducing suitable data rates and models of
    use by real-time control functions. In the future power system scheme, TSOs will be able to control
    significantly smaller part of the generation compared to the traditional centralized configuration,
    and thus they will not be able any more to compensate large deviations in the power balance.
    Moreover, increased electricity loads and sources such as EVs and residential PV systems, will
    influence the balance between day-ahead production and consumption schedule and will leave
    energy markets with higher and less predictable need for balancing power. The actors involved in
    the future grid control are balance responsible Party (BRP), cell system operator (CSO), cell
    operational information system (COIS), distribution system operator (DSO). Their respective roles
    are described and these actors play roles both to technical and market operations. Considering the
    web of cells concept developed in this project, the generation units will be smaller and in many
    cases these will be renewable resources which are less suitable for frequency control [1]. For that
    reason a more important role for participation at the demand side will be expected for voltage and
    frequency control in the future. The report describes “model based interfaces”, where the flexibility
    user and the flexibility contributor agree on a simplified model which describes the actual behaviour
    and constraints of the flexibility resource. Main outcomes of the work are the definition of controller conflict from a flexible power system perspective, a review of state of the art in power system control conflict and an outline of the methodology for identifying these conflicts during system operation and their impact on system stability. The report summaries the main findings from the literature and from project participant’s experience in terms of scenarios or examples of controller interactions resulting in conflict. A measure of controller conflict is presented for each example. This can be used as an indicator of the impact of controller conflict on system stability. Suggestions for resolving controller conflict are
    also presented. The report describes the methodology proposed to construct such a dynamic
    model for the purposes of extracting conflicting interactions of interest from the point of view
    frequency and voltage stability. From the voltage stability perspective there are many factors which
    may significantly influence the environment for voltage stability. It seems quite certain, that
    possible conflicts affecting voltage stability may occur mainly due to lack of proper coordination
    among players in the system voltage control and reactive power reserves management which are
    TSOs, DSOs, Generators and Aggregators. Generally the scenery foreseen for frequency, voltage
    and reactive power control in 2030+ is much more complicated than it is presently.
    An overview of experiences from the ELECTRA partners regarding the realization of controllers in
    demonstration and field test projects are also provided. It summarizes best practices and lessons
    learned which will provide valuable inputs for the implementation of control concepts and their
    testing and validation. The main requirements for controllers are reliability, fault tolerance and
    robustness.
    Original languageEnglish
    Number of pages118
    Publication statusPublished - 2015

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