# How SPS Software software works: a conceptual overview 🧠

**URL:** <https://community.opal-rt.com/t/how-sps-software-software-works-a-conceptual-overview/48>\
**Category:** Q&A\
**Tags:** sps-software\
**Created:** [February 25, 2026, 1:50am UTC](https://community.opal-rt.com/t/how-sps-software-software-works-a-conceptual-overview/48 "2026-02-25T01:50:23Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![MariaZanutto](https://avatars.discourse-cdn.com/v4/letter/m/43a26b/32.png) [@MariaZanutto](https://community.opal-rt.com/u/MariaZanutto)\
**Post date:** [February 25, 2026, 1:50am UTC](https://community.opal-rt.com/t/how-sps-software-software-works-a-conceptual-overview/48/1 "2026-02-25T01:50:23Z")

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Every time you start a simulation, SPS Software calls a special initialization mechanism before any simulation steps are taken. This process computes the state-space model of your electric circuit and builds the equivalent system that can be simulated by the Simulink engine.

Here is a conceptual overview of what happens under the hood and some important limitations to keep in mind.

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### ⚙ The Initialization Process (Step-by-Step)

**1. Topology Evaluation**  
SPS Software sorts all the blocks in your model, retrieves their parameters, and evaluates the network topology. The blocks are separated into **linear** and **nonlinear** blocks. Each electrical node is automatically assigned a node number.

**2. State-Space Computation**  
Once the topology is mapped, the state-space model (A, B, C, D matrices) of the _linear_ part of the circuit is computed. All steady-state calculations and initializations are performed at this stage.

- **Discrete Simulation:** If you have chosen to discretize your circuit (highly recommended for speed), the discrete state-space model is computed from the continuous one.
- **Phasor Solution:** If using the phasor method, the state-space model is replaced with the complex transfer matrix `H(jω)` relating inputs and outputs (voltage and current phasors) at the specified frequency.

**3. Simulink Model Construction**  
SPS Software builds the Simulink model of your circuit and stores it inside the **`powergui`** block located at the top level of your model.

- It uses an S-Function block to model the linear part of the circuit, as well as the switches and power electronic devices.
- Predefined Simulink models are used to simulate nonlinear elements.
- The nonlinear models are connected in a feedback loop between the voltage outputs and current inputs of the linear model.

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### 🛠 Simulation & Analysis Tools

Once initialization is complete, the simulation starts. During and after the simulation, you can:

- Observe waveforms on standard scopes.
- Access the **Linear System Analyzer** via the `powergui` block to obtain transfer functions.
- Perform an **FFT analysis** on recorded signals to obtain their frequency spectrum.
- Perform a **Load Flow** with circuits involving three-phase machinery to initialize the machine models in steady state (avoiding long mechanical transients).
- Visualize **impedance curves** over a specified frequency range.

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### ⚠ Important Limitations of Nonlinear Models

Because nonlinear models in SPS Software are simulated as **current sources** , there are a few strict electrical rules you must follow to avoid errors:

- **No series inductors / No open terminals:** Nonlinear models cannot be connected in series with inductors, and their terminals cannot be left open.
- **The “Inductive Source” Error:** If you feed a machine through an inductive source, SPS Software will prompt an error. _Fix:_ You can avoid this by connecting large resistances in parallel with the source inductances or across the machine terminals.
- **Snubber Circuits:** A series RC snubber circuit is included in the models of the _Breaker_ block and power electronics blocks.
  - If you keep them in service, you won’t encounter issues.
  - To change to a single resistance: set `Cs = inf`.
  - To change to a single capacitor: set `Rs = 0`.
  - **To eliminate the snubber entirely:** specify `Rs = inf` or `Cs = 0`.

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**Author:** ![louis](https://avatars.discourse-cdn.com/v4/letter/l/ecb155/32.png) [@louis](https://community.opal-rt.com/u/louis)\
**Post date:** [July 23, 2026, 1:49pm UTC](https://community.opal-rt.com/t/how-sps-software-software-works-a-conceptual-overview/48/2 "2026-07-23T13:49:26Z")

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Thanks Maria,  
It’s so interesting and important to know what’s going on behind the scenes !