Design of the Power Grid Model core

The Power Grid Model at its core is a header-only C++ interface library, wrapped by a dynamic/shared C API library. The core itself is an engine called the MainModel that provides the C++ interface and contains the logic for the various aspects that play a role in power grid calculations. The MainModel itself can be decomposed into an API part, a dispatch part, the grid model and the actual calculation logic.

Calculation logic and data flow

The logic involved in power grid calculations in turn can be divided in a number of separate modules. Coincidentally, those phases also translate to fields of expertise, which enables a reasonably clean architecture.

Logic/control module	Description	Expertise
I/O	Constructing, updating, and outputting components in the power grid	Software Engineering
Electrical parameter construction	Constructing electrical parameters from the power grid components	Electrical Engineering
General topology construction	Constructing the overall topological layout of the grid, including open connections and disabled components	Topology
Topology reduction	Splitting the general topological layout into a multi-scale topological representation by merging links on nodes	Topology
Mathematical topology construction	Constructing a graph representation of the reduced topology for efficient matrix solving	Topology
\(Y_{\text{bus}}\) construction	Constructing the \(Y_{\text{bus}}\) from the electrical parameters and the mathematical topology	Electrical Engineering
Solver construction/Grid extraction	Translation from \(Y_{\text{bus}}\) to a solvable system of equations and from the solution back to physical values	Physics
Math solving	Abstract solution to the macro-scale system of equations	Mathematics
Topological node solving	Abstract solution to the micro-scale structure using the macro-scale solution	Mathematics

Note

Software Engineering obviously also plays a role in the general design, but that general design does not involve the logic/control flow and therefore is not listed in this table.

The data flow can be visualized as such:

        graph TD
    ComponentInput(Input/Update data) -->|Input| Components[Power Grid Components]

    Params[Electrical parameters]
    Components -->|Electrical parameter construction| Params
    Components -->|Static topology construction| GeneralTopo["General Topology (including disabled components)"]

    GeneralTopo -->|Topology reduction| ReducedTopo["Reduced Topology (split into topological nodes and substructures)"]

    ReducedTopo -->|Mathematical topology construction| MathTopo[Mathematical topology]

    MathTopo -->|Ybus construction| Ybus(Ybus)
    Params --> Ybus

    Ybus -->|Solver construction| Equations(Solvable system of equations)
    Equations -->|Math solving| Solution(Mathematical solution)

    Solution -->|Grid extraction| MacroGridResult(Macro-grid result)
    Ybus --> MacroGridResult

    MacroGridResult -->|Optional optimization| Params

    MacroGridResult -->|Topological node solving| FullGridResult("Full grid result")
    ReducedTopo --> FullGridResult

    FullGridResult -->|Component extraction| ComponentsOutput(Components result)
    Components --> ComponentsOutput

    ComponentsOutput -->|Output| Output(Output data)
    

Detailed Power Grid Model core design

The sheer size and complexity of the Power Grid Model core implementation makes it hard to generate an up-to-date and comprehensive graph of its design. For a full overview of the core, it is recommended to build and access the Power Grid Model core documentation by following the steps in the build guide.