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Explore the challenges and solutions for accurate grid modeling and data exchange in the context of power system operations and planning, emphasizing the need for consistent, up-to-date network models across interconnected systems.
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A Family of CIM EMS Exchange Standards based on CIM/XML (61970-552)- Static Network Model Exchange (61970-452)- Dynamic Model Exchange?- Schematic Layout Exchange (61970-453)- Solved State Exchange (61970-456)- EMS Static Model Update (proposed)- - Contingency Definition?- … Jay Britton jay.britton@areva-td.com
The Basic Model Exchange Business Problem • The members of an interconnection share a mutual necessity to achieve: • Accurate assessment of grid reliability. • Appropriate, timely response to insecure conditions. • A pre-requisite to the above are: • Accurate, up-to-date network models. • Consistent network models (at each responsible site). • In an interconnection, this requires: • Exchange of models. • Exchange of solved analytical results. • 2008 NERC Real-Time Best Practices Report: • “Although defining the elements represented in internal network models is relatively straightforward, the task force finds that defining the elements to be represented in external models is much more complex.” • “Issue #5: External Modeling and Data Exchange Practices Should be Improved by Explicit Reference to the Definition of the Wide-Area-View Boundary. A consistent, uniform set of modeling and data exchange practices, procedures, and standards are needed to support creation and maintenance of accurate external models…” • These requirements apply in operations and planning contexts.
There is high-level consensus about the right approach. • Basic Modeling: • Each TSO is the authority for data about its own territory. • Each TSO exports its internal model to its neighbors and/or regional authority, and keeps it up to date. • Regional authorities assemble internal regional models from member TSO internal models. • All parties assemble external models from the internal models of other sites. • Analysis: • Responsibility is usually distributed among cooperating sites. • Solution exchange is required, depending on the problem. • Exchanged solutions should be based on consistent underlying models. • These goals apply to both operations and planning. • Operations focus is on as-built and near future changes. • If operations and planning share the same as-built base model, then the planning focus is on exchange of plans.
Contributing Use Cases • Exchange of network models. • EMS A and B are neighbors in an interconnection and therefore each needs to represent the other as part of its external model. • Requires exchange of internal models. • Scope is limited to network data and measurement placements. • Exchange of schematics with models is desirable. • Common Modeling Source between planning and operations. • One modeling application for the enterprise. • An EMS requires a model that covers any point in time. • Other targets require data for a specific “case”. • Exchange of solved cases. Several variations… • Real-time exchange among different applications. • Real-time cases to study or planning. • Exchange of study or planning cases between different tools. • Import of study cases to EMS. • ENTSO-E DACF. • Study cases are generated for the next day by each TSO representing the expected state of their internal network.
A Generic Model Exchange Business Process(ENTSO-E, ERCOT, WECC, …)
Preview – We are working toward defining model partitioning into non-overlapping XML submodels that satisfy all of the use cases.
The initial CIM model exchange (61970-452) standard focused only on transfer of complete models: CIM Exchange (full, partial, incremental update) CIM import / export CIM import / export System B Import Model System A Import Model a Proprietary / Home grown Extract / Merge Tools Proprietary / Home grown Extract / Merge Tools b A Internal Model B’s Model of A System A Local Vendor Model System B Local Vendor Model A’s model of B B Internal Model System B EMS System A EMS
A More Desirable Process Site A makes a change: • A changes its ModelAuthoritySet using its CIM modeller. • A imports the change into its EMS. • A exports the change to B. • B receives the change (full or incremental), updating A’s ModelAuthoritySet within its CIM modeller. • B renames any new elements and repeats any reduction of A’s ModelAuthoritySet. • B imports the new model into its EMS.
Merge/Extract with Model Authority Sets • Each object is in one and only one set. • Simple labeling technique for assigning responsibility. • Associations connect some objects that are in different sets. • Currently directional from n to 1 (“foreign key” convention) – under discussion. • Regional Sets: • No associations with other regional sets. • External associations to boundary sets only. • Boundary Sets: • External associations from regional sets. • External associations with other boundary sets. • A regional set may be referentially validated independent of other regional sets. • Modeling processes can proceed independently in each region. • Goal: • Maximize independence. • Design boundary sets to achieve: • Minimum data • Infrequent change
Hierarchical Process Definition for an Interconnection • Bottom level. • No significant differences. • Export changes as the model authority. • Import externals from the full interconnection model. • Upper level: • Manages boundary sets. • Creates the full interconnection model. • Model quality evaluation. • Study state estimation. • Derives operational model in the same manner as lower levels. • Different reduction criteria. • Design extends to any number of hierarchical levels.
Consolidating Planning with Operations • Full interconnection model is the common source for all models. • Interconnection planning shown on diagram. • No procedural difference required to support analytical functions running at any level for any purpose. • Planning adds other requirements. • New information modeling in CIM. • Accommodate bus-oriented apps. • Add short circuit, dynamics, etc. • Incremental model standard expands to model plans. • CIM modeling applications need to have a temporal axis. • 2007 EPRI “CIM for Planning” project. • Goal is eliminate duplication of modeling.
Evolving Support for Analytical Processes • The original 61970-452 standard exchanged EMS models. • Did not deal with planning (‘bus-branch’ models). • Did not support power flow solution exchange (or any other type of analytical result). • Several recent efforts defined other needed support. • 2007 EPRI ‘CIM for Planning’ • 2008-2010 ENTSO-E Day Ahead Congestion Analysis • 2008-2009 EPRI ‘CIM for Dynamics’ • Recent IEC WG13 Accomplishments • 61970-452 now supports planning models in addition to operations. • Draft 61970-456 defines solved power system state exchange. • Operations and planning share the same standard. • ENTSO-E DACF supported. • Draft 61970-454 defines display layout exchange. • Update of 61970-552 includes header specifications. • Current WG13 Agenda • Unify distribution and transmission network modeling. • Object registry specification 61970-453.
Current Modularity • 61970-452 Static Model. • Equipment Profile. • Identifies equipment and describes basic characteristics. • Describes electrical connectivity that would be input to topology processing. (Optional for planning.) • Describes input to functions that derive parameters for a specific point in time. (Optional for planning.) • Dynamics Profile. • Describes dynamic characteristics. • 61970-456 Solved Power System State • Topology Profile. • The result of topology processing. i.e. Description of how equipment connects into buses and how buses makeup connected systems. • Analogs Profile. • The set of SCADA values for analog measurements for a particular point in time. • Status Profile. • The state of switches – input to topology processing. • State Variables Profile. • This is the set of state variables used in the mathematical formulation that the algorithms work with. • Used to represent starting conditions or ending conditions of analysis. • 61970-454 Display Layouts • The position of objects within a schematic or geographic presentation.
61970-453 Display Layout Exchange • Purpose: • To exchange schematic display layouts accompanying model or solution exchanges. • Corresponds to the part of display maintenance work that normally goes with model maintenance. • Defines graphic objects used in the sender’s displays: • Usually linked to a model object, but can also be background. • One or more location coordinates. (Optional glue points.) • Graphic style reference. • Does not define Interpretation of graphic style references. • Usage • Sender describes diagram. • Senders disclose the way their system uses graphic styles. • Object placements describe sender’s diagram as is. • Receiver must decide how to render the diagram in its system. • Create interpretation of sender’s styles. • Receivers are not expected to duplicate functionality. • Receivers may break apart complex styles or combine simpler styles. • Receiver provides the graphic style interpretation models for their display management software. • Result: • Layouts and names of things should be familiar. • Exact replication graphically is likely only when sender and receiver applications are the same. • Exact replication functionally is likely only when sender and receiver applications are the same.
