Southern Company Interconnection Module Package

Stage 1: Cluster Request Window and Customer Engagement Window

• Support you in preparing a valid Interconnection Request under LGIP Section 3.4.2 for the annual Cluster Request Window, including the Generating Facility technical data and models entered in SCT's online application tool (ICON for Cluster Study requests).
• Develop site-specific plant models in the three formats SCT requires for IBRs: a PSS/E standard library (generic) model, a PSS/E user-defined model (UDM) and a PSCAD model, each as a standalone package at Continuous, Rated MW Output, per SCT's Model Submittal Requirements for Transmission Connected IBRs.
• Build all three plant models with one aggregated unit and one aggregated unit transformer per identical IBR design, an equivalent collector system derived from your cable data, explicit main power transformers and shunt devices on the medium-voltage collector bus, and the station service load, flexible AC transmission system (FACTS) devices, plant controller and interconnection tie line that apply.
• Coordinate with inverter, turbine and power plant controller manufacturers to obtain models, original equipment manufacturer (OEM) attestations that the IBR unit and plant controller models represent the planned equipment, and type test or hardware-in-the-loop (HIL) test results that validate the IBR unit model.
• Check the PSS/E models against SCT's PSS/E requirements (PSS/E version 35, no library models the North American Electric Reliability Corporation (NERC) lists as unacceptable, bus numbers above 1000, table-driven UDMs, quarter-cycle minimum time step) and the PSCAD model against SCT's PSCAD requirements (actual control code where possible, transformer core saturation, negative sequence current injection, snapshot and multiple run support, no required time step below 10 microseconds and no required specific time step).
• Perform the model performance attestation in Section 4 of SCT's Model Submittal Requirements (the MQA): run the required tests in a single-machine-infinite bus system on all three models (Initialization, Balanced Fault Ride-Through, Small Voltage Disturbance, Small Frequency Disturbance, High- and Low-Voltage Ride-Through, High- and Low-Frequency Ride-Through and Short Circuit Ratio tests) and on the PSCAD model alone (Unbalanced Fault and Phase Angle Change tests), plus the supplemental tests SCT recommends.
• Benchmark the PSS/E standard library, PSS/E UDM and PSCAD responses by overlaying them on the same axes, tune the models toward alignment, and explain any remaining discrepancies as the attestation requires.
• Prepare the Model Performance Attestation Report in SCT's Appendix A template and the completed Model Checklist; for a hybrid plant, report each resource type operating in parallel.
• For a synchronous Generating Facility, prepare the generator, excitation system, governor and power system stabilizer model data that Attachment A to Appendix 1 of the LGIP requests.
• Review the application package against the deficiencies SCT reports most often (technical data that does not match the single-line diagram, missing or inaccurate models, documentation, attestation report or checklist) before you submit, since no updates are accepted after the Cluster Request Window closes.
• Prepare technical material for the Scoping Meeting in the Customer Engagement Window and update the models for any modification LGIP Section 4.4.1 permits before you execute the Cluster Study Agreement.

Stage 2: Cluster Study, Cluster Restudy and Interconnection Facilities Study

• Review the Cluster Study Report (power flow, grounding review, reactive power, stability and short circuit analyses) and any Cluster Restudy Report for your request, and support you at the Cluster Study Report Meeting.
• Assess plant-side mitigation, such as control tuning or reactive device changes, for issues the study assigns to your request, and prepare the updated models and attestation results that a modification request under LGIP Section 4.4 must carry.
• Prepare the revised steady-state modeling data, single-line diagram inputs and dynamic modeling data for a technological advancement request under LGIP Section 4.4.6 when you change equipment before executing the Interconnection Facilities Study Agreement.
• Respond to SCT data requests and model deficiency findings, and prepare the technical data due with the executed Interconnection Facilities Study Agreement.
• Carry the weighted short circuit ratio (WSCR) and X/R (reactance to resistance) ratio at the Point of Interconnection (POI) from the interconnection study report into all later attestation tests, as SCT requires.

Stage 3: GIA Execution, Commencement of Work and Pre-Sync Activities

• Prepare the non-confidential Generating Facility modeling data SCT requests after GIA execution, including the three-phase dynamic model and electric storage resource data, or confirm that the study models have not changed.
• Develop the as-planned site-specific models (power flow, positive sequence, electromagnetic transient (EMT) and short circuit) reflecting the proposed equipment, control configuration and parameters, and protection settings, with verifying documentation.
• Rerun the MQA on the as-planned models and update the Model Performance Attestation Report and Model Checklist.
• Support you through SCT's Model Quality Check, Performance Evaluation and Detailed EMT Analysis: prepare responses to review comments, propose and model solutions to identified deficiencies for your decision, and prepare the updated models that reflect the chosen solution for you to submit.
• Develop the as-built (pre-synchronization) models from the as-built equipment, control configuration and parameters, protection settings and plant controller settings, with supporting documentation such as nameplate photos, inverter settings snapshots and plant controller screenshots.

Stage 4: Trial Operation and Performance Validation Testing

• Update the as-built models after commissioning when parameters change before Trial Operation Phase 2 (performance validation testing) begins.
• Develop the final as-left models, including any changes made during performance validation testing, with documentation showing that the as-left equipment and parameters match the models.
• Support your reactive power capability test on SCT's test template and the voltage step and capacitor bank test documentation.
• Compare the as-left model response with the measured voltage and frequency step test response before submittal, and correct model-to-field mismatches.
• For a synchronous Generating Facility, prepare the excitation system, speed governing system and power system stabilizer dynamic model data due before the Commercial Operation Date (COD), and support the power system stabilizer and frequency/speed step test documentation.
• Support the root-cause investigation of deficiencies SCT finds during performance validation with simulations and model updates, toward SCT's approval of readiness for Commercial Operation.

Stage 5: Post-Commissioning

• Update the models and the MQA report when you change equipment, inverter or plant controller firmware, control settings or protection settings, and prepare the documentation for SCT's evaluation of the change.
• Update the dynamic, power flow and PSCAD models when you add energy storage or grid charging at an existing Generating Facility.
• Support model verification and validation under NERC MOD-026-2, including EMT models benchmarked against positive sequence models, following the dynamic modeling requirements Southern Company Services issues as Planning Coordinator and Transmission Planner under MOD-026-2 Requirement R1.
• Analyze measurement data SCT requests for event analysis, performance verification and model validation, and update the models where the measurements show the dynamics data should change.