Siemens Energy, Inc. Power Technology Issue 111 A New Way to Work in the ERCOT Market Joseph M. Smith Senior Staff Business Development Specialist joseph_smith@siemens.com In recent months The Electric Reliability Council of Texas (ERCOT) has changed the way it provides models to the marketing community within the region. Previously ERCOT provided a bi-weekly model of the transmission system to marketers in a standard PSS E format. These models were used throughout the ERCOT region as a starting point for estimated operational conditions for the upcoming days and weeks. The marketing community relied on the accuracy of the models to conduct hedging predictions and to benchmark the ability to move power in the region and ensure that their customers electricity needs were met. These same models are now being distributed in the Common Information Model (CIM) format, from the ERCOT network model management system (NMMS). These new models represent an equipment level detail configuration of transmission equipment and represent the ERCOT operational model. With this change come new challenges for marketers in the ERCOT region. They may ask: 1. Can I interpret the new model? 2. Can I study the system with a CIM model? 3. Can I use this with the processes that I have in place? 4. Can I convert this model to a format I am used to? 5. Can I leverage this new model to improve my business? 6. Is there a way for me to read, process and convert this format to meet my business needs? The answer to each of these is YES! Siemens PTI provides a unique stand-alone solution that is capable of managing, viewing, studying, manipulating and converting the ERCOT CIM format operational model. The solution is PSS ODMS, a fully CIM-compatible model, management and analysis program that is able to read, store and manipulate the ERCOT model in a full CIM format. PSS ODMS provides flexible options for your business, including the ability to utilize the ERCOT CIM model for studies within the PSS ODMS environment. This also includes the ability to incrementally update the model when new representations are received from ERCOT, run power flow and contingency analysis and convert the model to a repeatable bus branch PSS E RAW format case. The following use case describes the dataflow from ERCOT into PSS ODMS and provides for model updates and conversion. Model Assembly The model assembly workflow is a one-time setup process to prepare the system to be deployed in the production environment.
PSS ODMS Application User Interface (menu commands, hierarchical, spreadsheet, and one-line diagram editors, etc.) Populate initial CIM model ERCOT System Model CIM/XML Model CIM Database Bus Mapping Table (csv) Reference Cases (PSS E RAW) Add redacted data (load, generation, voltages, ratings, etc.) Populate/update bus numbers and names Figure 1 - Model Assembly Data Flow This process involves the following steps: 1. The ERCOT-produced CIM/XML model is imported into the PSS ODMS CIM database using the standard Import CIM/XML Model function. The model is then validated using PSS ODMS features for visualization, detailed association and attribute checking. These include the Validate Model function, the automatic one-line diagram generation capability for graphical visualization, and the CIMedit hierarchical interface for detailed association and attribute checking. More advanced validation involves building an operational base case from the database model using the Build Case feature. 2. The Create Topology function is used to create TopologicalNodes in the PSS ODMS database, based on the default switching configuration in the operational base case. These TopologicalNodes will act as placeholders to persistently store the bus mapping information. 3. The Export Bus Mapping Table function is used to export a CSV file containing a record for each BusbarSection/ConnectivityNode in the model with corresponding columns for the Bus Number and Bus Name. This file is then edited (either manually or via some basic scripting) to include the desired bus numbers and names (corresponding to the dynamics data). The edited file is then re-imported into the PSS ODMS database using the Import Bus Mapping Table function. Page 2
Figure 2 - Example Bus Mapping Table 4. The CIMedit and/or Network spreadsheet interface is used to populate the PSS E equipment identifiers in the model as needed. Figure 3 - CIMedit View Page 3
5. An operational base case is again built from the PSS ODMS database and exported to PSS E RAW format to validate the finalized bus and equipment identifier mapping. 6. Season enumerations are configured as desired using the CIMedit interface. These will act as reference placeholders for schedule data. Figure 4 - Season Enumeration Screen 7. The Import PSS E Schedule command is used to import load, generation, voltages, etc. into the PSS ODMS database from a reference PSS E case in RAW format. This is repeated with different profile cases as needed for each Season. After importing the schedule data, the Load Schedule Data function is used to load the data corresponding to each selected Season into the current study case, which is then solved, exported to PSS E and validated externally. 8. Similar to the above step, the Import PSS E Ratings command is used to import Season-associated line and transformer ratings into the PSS ODMS database from multiple reference PSS E cases in RAW format. 9. Substation one-line diagrams and/or system overview diagrams are automatically generated within PSS ODMS. The initial default layout of each diagram may be manually adjusted as needed and saved for future visualization purposes. PSS ODMS will intelligently synchronize any previously saved diagram with the network model as changes are introduced. One-line diagram displays can be especially useful for power flow results visualization and validation prior to exporting a given case for further planning study. Page 4
Figure 5 - Example PSS ODMS Substation Diagram Upon completing these steps, PSS ODMS is now ready for production deployment. Once the initial model is in place, model updates from ERCOT are handled easily with the PSS ODMS incremental CIM update functionality described below. Model Update Note: any of the Model Assembly steps above, except for the very first step (importing the initial CIM/XML model), may be repeated as needed to facilitate the model update process. The model update workflow process is ongoing and repeated periodically as needed. When network model changes (such as new substations and/or equipment) are introduced into the ERCOT model, these changes need to be propagated into the PSS ODMS CIM database model for consistency. This process is largely automated by the Compare Models feature of PSS ODMS, which extracts Incremental CIM/XML model data based on an automated comparison of the current CIM database model and the user-selected CIM/XML file (in this case, the new ERCOT CIM/XML model). The incremental CIM file is then incorporated into the existing PSS ODMS CIM database, completing the update of the model. According to our current understanding, this process is expected to occur approximately every two weeks, but may be executed as often as needed. Page 5
ERCOT model (updated biweekly) Updated CIM/ XML model PSS ODMS (Compare Models Feature) Incremental CIM/XML Import/update CIM Database Figure 6 - Model Update Data Flow This process involves the following steps: 1. An updated CIM/XML model is acquired from ERCOT. 2. The Compare Models feature of PSS ODMS is used to create an Incremental CIM/XML file by extracting the differences between the current CIM database model and the new ERCOT CIM/XML model. 3. By selecting the appropriate option, the resulting Incremental CIM/XML file is automatically imported into the CIM database. 4. Changes are validated by building and solving an operational base case. The PSS ODMS CIM database model should be updated as often as needed using the process described above. Note: This process assumes that all RDF IDs in the ERCOT-produced CIM/XML file are globally unique and persistent. Study Case Creation The study case creation workflow represents the ultimate objective of the solution. This is a repeated process which is initiated by a PSS ODMS user to produce an up-to-date operational snapshot planning study case in PSS E format. This procedure involves building a case from the CIM database model, initializing the case with Season-associated schedule and ratings data, solving power flow and exporting the case to a PSS E RAW file. Page 6
3. Solve power flow PSS ODMS Application 4. Export PSS E RAW 1. Build case 2. Initialize case from seasonal schedule data CIM Database Figure 7 - Study Case Creation Data Flow This process involves the following steps: 1. The case is built using the appropriate command in PSS ODMS. 2. When prompted after the initial case build, the user selects the Season for which to initialize the case from the seasonal schedule data stored in the CIM database model. 3. The user invokes the Solve Power Flow command and validates the solution results. 4. The user invokes the Export Case command to export the solved case to PSS E RAW format. At this point, the operational node-breaker case is converted to planning bus-branch format. Since the complete bus and equipment mappings have already been established during the initial Model Assembly process, it is now handled automatically by the software during each study case creation process. This ensures that the bus and equipment identifiers in the exported PSS E RAW file are consistent from one study case creation process to the next. This solution provides marketing clients a new way to manage the models, create needed study scenarios and evaluate opportunities and congestion in the ERCOT market. These tools and methodologies leverage ERCOT practices and available information to provide marketing firms the best models for hedging their business opportunities and capitalizing on the changing system conditions in ERCOT. Siemens PTI has actively deployed this solution within the ERCOT market. The ERCOT model management system is also a Siemens solution. Page 7