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Power flow ​

NumaSim can solve the steady-state power flow of your electrical circuit alongside the time-domain simulation. Use it to size a network, check bus voltages under load, or validate a PSS®E case before streaming it into a transient run.

A power-flow case is a set of buses joined by branches, with generators and loads attached. Each bus is one of three types — a slack bus that sets the reference voltage and angle, a PV bus that holds a scheduled voltage, or a PQ bus that draws fixed real and reactive power:

A small power-flow case. The slack bus sets the reference voltage and angle, the PV (generator) bus holds its scheduled voltage, and the PQ (load) bus draws fixed real and reactive power. The branches carry the resulting flows.

When to use it ​

A time-domain simulation answers "what is the voltage at this node right now?". A power-flow solve answers "what is the steady-state voltage at every bus, given the loads and generation specified?". They complement each other:

  • Run power flow first to verify your network is feasible.
  • Then run a transient simulation to see how it responds to a disturbance.

Solving a power flow ​

  1. Build (or import) an electrical circuit with buses, branches, generators, and loads.
  2. Open the Power Flow dialog from the toolbar.
  3. Pick the solver (Newton-Raphson is the default; Gauss-Seidel and fast-decoupled are available).
  4. Click Solve. The dialog reports per-bus voltage magnitude and angle, slack bus power, and any convergence issues.

Under the hood, the default Newton-Raphson solver is iterative: it starts from an initial guess, computes how far each bus is from its scheduled power (the mismatch), solves a linearized update from the Jacobian, applies it, and repeats until the mismatch is within tolerance.

The iterative power-flow solve. Each pass computes the bus power mismatch, solves a linear update JΔx=ΔS from the Jacobian, and applies it; the loop ends when the mismatch is within tolerance.

Visualizing the result on the canvas ​

When a power-flow solution is loaded, every bus and branch on the canvas can display an overlay (voltage magnitude / angle, line MW / MVAR flow). Toggle the overlay from the dialog's footer.

Importing PSS®E cases ​

If you already have a network in PSS®E .raw format, use File > Import PSS/E. The importer reads the raw file and lays out an equivalent circuit on the canvas.