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Engine

The Engine is the orchestration layer of WEC-Grid. It coordinates grid modelers (PSS®E / PyPSA), WEC-Sim runs, time management, persistence to the SQLite database, and plotting. This page explains how the Engine works conceptually and then embeds the API reference via mkdocstrings, which is generated from your docstrings.

Responsibilities

  • Configuration & Setup
  • Select and initialize power‑system backends (PSS®E, PyPSA)
  • Connect to / initialize the WEC-Grid SQLite database (WECGridDB)
  • Set the simulation timeline (WECGridTime)
  • Model Management
  • Load a grid case (IEEE test systems or custom .RAW)
  • Apply one or more WEC farms at target buses; resolve device metadata from the DB
  • Simulation Orchestration
  • For each snapshot: update generator/load setpoints, ask each backend to solve power flow, collect snapshots into a standardized GridState
  • Optionally persist results to the DB and trigger comparisons/plots
  • Visualization
  • Provide a single plotting surface (WECGridPlot) that works across modelers

Functionality

  1. Create an engine and (optionally) set the database path
  2. Case: set the case file the modelers will load
  3. Load: initialize one or more power‑system modelers (PSS®E/PyPSA)
  4. Apply WEC: attach a WEC farm to a bus (pull cached WEC-Sim results or trigger runs via WECSimRunner)
  5. Simulate: run the time‑series (quasi‑steady‑state) loop; collect GridState snapshots
  6. Persist / Plot: save results to DB; generate time‑series, comparisons, and SLDs

Key Concepts

  • PowerSystemModeler (ABC)
    An abstract interface implemented by PSSEModeler and PyPSAModeler. The Engine only calls the standard methods (e.g., init_api(), add_wec_farm(), solve_powerflow(), take_snapshot()), which keeps user experience consistent across backends.

  • GridState
    A standardized container for results. It defines consistent DataFrame schemas for bus, gen, line, and load snapshots, plus wide‑format time‑series dictionaries (*_t). This enables cross‑backend comparisons and unified plotting.

  • WECFarm / WECDevice
    A farm aggregates one or more WEC devices. The farm‑to‑grid mapping is one generator per farm (not per device). Device‑level time‑series are downsampled to the grid resolution and aggregated.

  • WECGridDB
    Encapsulates all DB operations (initialize schema, save simulations, query WEC-Sim runs, etc.). The Engine delegates all persistence here.

  • WECGridTime
    Stores start/end/resolution, and exposes update() to adjust the simulation window.

  • WECGridPlot
    Unified plotting API for per‑bus, per‑generator, and backend‑comparison plots.