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PSSEModeler

The PSSEModeler provides the interface between WEC-Grid and Siemens PSS®E software.
It implements commercial-grade power system analysis with industry-standard modeling capabilities and comprehensive licensing management.

Responsibilities

  • PSS®E Integration

    • Initialize PSS®E Python API and manage licensing requirements
    • Load power system cases (.sav and .raw formats)
    • Execute Newton–Raphson power flow solutions with convergence checking

  • WEC Farm Implementation

    • Create new buses for WEC connections in PSS®E model
    • Add WEC generators with time-varying power output profiles
    • Build transmission lines connecting WEC farms to existing grid

  • Grid State Management

    • Extract comprehensive grid data using PSS®E API calls
    • Convert PSS®E data formats to standardized GridState schema
    • Capture bus voltages, generator outputs, line flows, and load consumption

Key Features

Commercial Power System Analysis

  • Industry Standard — Proven algorithms used by utilities worldwide
  • Professional Modeling — Detailed generator, load, and transmission line parameters
  • Advanced Solvers — Robust Newton–Raphson with validated convergence properties
  • Comprehensive Analysis — Voltage stability, thermal limits, reactive power management

WEC-Specific Adaptations

  • Generator Reactive Limits — Removes Q limits to align with PyPSA modeling assumptions
  • Dynamic Updates — Per-snapshot generator power updates from WEC-Sim time series
  • Grid Connection Modeling — Automatic creation of collection buses and transmission lines

PSS®E API Integration

Initialization Sequence

psseinit() → case()/read() → sysmva() → fnsl() → solved()

Core API Calls

  • Power Flow Solution

    • fnsl() — Full Newton–Raphson power flow solution
    • solved() — Convergence status check (0 = converged)
    • iterat() — Iteration count from last solution attempt

  • Data Extraction

    • abuschar(), abusint(), abusreal() — Bus names, numbers, voltages [pu/deg/kV]
    • amachint(), amachreal() — Generator locations, power output [MW/MVAr]
    • aloadint(), aloadcplx() — Load locations, power consumption [MW/MVAr]
    • abrnchar(), abrnint(), abrnreal() — Line IDs, connections, loading [%]

  • Grid Modification

    • bus_data_4() — Add new buses for WEC connections
    • plant_data_4() — Add plant records to buses
    • branch_data_3() — Create transmission lines between buses

Technical Specifications

System Requirements

  • PSS®E Software: Version 35.3 or later with valid commercial license
  • Python Integration: PSS®E Python API (psspy, psse35, redirect)
  • File Formats: .sav (saved cases) and .raw (raw data)
  • Operating System: Windows (PSS®E is Windows-only)

Data Schema Compliance

All PSS®E data is converted to WEC-Grid’s standardized format:

  • Units: Per-unit on system MVA base; angles in degrees; line loading in %
  • Naming: Sequential IDs with descriptive names (Bus_1, Gen_1, …)
  • Time-Series: Consistent timestamps and component indexing across snapshots
  • Cross-Platform: Identical schemas enable direct comparison with PyPSA results

Error Handling and Troubleshooting

Common PSS®E Error Codes

  • ierr = 1 — Invalid OPTIONS value or parameter out of range
  • ierr = 3 — Island without swing bus (check generator/bus types)
  • ierr = 4 — Bus type inconsistencies (verify load/generator connections)

License Issues

  • Ensure the PSS®E license server is accessible
  • Verify Python API modules are on PYTHONPATH (or use pssepath.add_pssepath())
  • Check PSS®E version compatibility with your Python version