Real-time simulation and controller-hardware-in-the-loop (CHiL) testing of power system stabilizers (PSS) on low-cost microcontrollers with Modelica and eFMI.

Repository archived on Zenodo — DOI: 10.5281/zenodo.20583549

Top left & bottom right: Modelica Model & derived eFMI STM32 firmware in Dymola & STM32CubeIDE; Bottom down & top right: MiL simulation of CHiL setup & actual measurements in Diligent WaveForms.

This repository is the open-source companion to the paper "Real-time Simulation and CHiL Testing of Power System Stabilizers on Microcontrollers with Modelica and eFMI", accepted at the American Modelica & FMI Conference 2026 (a pre-print is available on ResearchGate). It provides an end-to-end, traceable workbench that takes a power system stabilizer (PSS) — a damping controller — and the power plant it regulates from physics-based Modelica models all the way to production code running on ARM Cortex-M microcontrollers, validated at every step.

Warning

Microsoft Windows users should clone into a short root path. Generated artefacts have deeply nested file paths; cloning under a long location will hit the MAX_PATH limit and cause build failures.

Warning

This is a large repository. It ships generated, reproducibility artifacts — the eFMUs, and SiL/MiL/CHiL simulation results — so the models and the evidence for the paper's claims travel together.

Tip

If you only want to read and run the models, clone a shallow snapshot via:

git clone --depth 1 --recurse-submodules --shallow-submodules \
  https://github.com/ALSETLab/efmi-pss-use-case.git C:/dev/efmi-pss-use-case

---

Overview

Modern grids increasingly suffer from poorly damped oscillations (e.g., the 2025 Iberian grid incident), which demand controllers that can be re-tuned and re-deployed throughout their lifecycle. Today, the path from a control design to a hardware test is slow and error-prone: offline tools like PSS/E or PSCAD cannot run in real time, forcing manual re-implementation and breaking traceability between design and deployment.

This project demonstrates an automated alternative built on the Modelica language and the eFMI (FMI for embedded systems) standards. Using the eFMI tooling of Dymola, both the controller (the PSS) and the plant (a synchronous generator with its excitation control system, interconnected to a grid) are synthesized into MISRA C:2023 and SEI CERT C Coding Standard compliant, safety-critical and hard-real time suited, embedded code, deployable onto low-cost STM32 boards. The result is validated through a full suite of Model-in-the-Loop (MiL), Software-in-the-Loop (SiL), and Controller-Hardware-in-the-Loop (CHiL) experiments, providing an open, traceable, and inexpensive alternative to proprietary real-time platforms.

The workflow is realized through a new Modelica library, OpenIPSL_CHIL, which extends the Open-Instance Power System Library (OpenIPSL) for embedded real-time applications.

Tooling and workflow

The following diagram sketches the general model based software engineering (MBSE) workflow:

flowchart LR
  A["Modelica models<br/>OpenIPSL_CHIL<br/>plant + PSS controller"] --> B["eFMI synthesis<br/>Dymola eFMI tooling<br/>MISRA C:2023 / SEI CERT C code"]
  B --> C["MiL and SiL experiments<br/>verify vs. offline simulation"]
  C --> D["STM32 integration<br/>STM32CubeMX and STM32CubeIDE"]
  D --> E["Deploy to NUCLEO boards<br/>H723ZG = plant<br/>L476RG = controller"]
  E --> F["CHiL experiments<br/>control and real-time validation"]

Loading

Repository structure

Path	Contents
models	The OpenIPSL_CHIL Modelica library — the heart of the project (see below); and a git submodule for the OpenIPSL library. ./models/start-Dymola.bat is a one-click Windows script that launches Dymola, preconfigures its working directory and loads all required Modelica libraries -- like OpenIPSL and OpenIPSL_CHIL -- and the generated artifacts like eFMUs, eFMU SiL-stubs, eFMU production code based source code FMUs, etc.
firmware/	STM32CubeIDE and STM32CubeMX projects for developing the STM32 microcontroller firmware for PSS and plant based on generated eFMI production codes.
measurements/	Digilent WaveForms capture projects and recorded data of CHiL experiments; includes predefined setups to conduct the measurements required for the paper figures using the Analog Discovery 3 oscilloscope (i.e., to reproduce the CHiL experiments like computation time analyses).
postprocessing/	MATLAB scripts for analyses of MiL, SiL and CHiL experiments, for example, analyses of PSS redesign simulations, CHiL-setup simulations, and actual CHiL measurements.
documentation/	Accompanying documentation of used hardware and tooling, the pin-configuration of the CHiL setup, etc.

The OpenIPSL_CHIL library

OpenIPSL_CHIL (OpenIPSL for CHiL: Extensions of OpenIPSL for embedded real-time applications) is organized into:

• Components: OpenIPSL components modified for embedded deployment, alongside new components stemming from additional embeeded domain requirements. The PSS sub-package holds the controller variants, their building blocks, and the eFMU generation configurations; Auxiliary and Machines encapsulate modified variants of OpenIPSL transmission line, fault, and machine models that required adaptations to be suited for the embedded, hard real-time domain; Tests provides unit tests for component models, including continuous, clocked, and eFMU PSS variants.
• Generator: Variants of the generator unit (machine + excitation control system) for the successive stages of control design, redesign, and embedded integration.
• Network: Variants of the grid without the generator unit, used to assemble simulation and eFMU export models.
• RTS: Plant models targeted at real-time simulation (HiL and CHiL), including their eFMU generation configurations.
• Examples: Whole system experiments with closed-loop PSS controller and plant for offline simulations from continuous, toward sampled system and eventually expected final CHiL setup behavior (MiL and SiL).

Requirements

Software

• Dymola 2026x Refresh 1 with Dymola Source Code Generation License: Required for eFMI code generation (GALEC code of Algorithm Code container and derived C11 code of Production Code container). For requirement details, please consult the documentation of DymolaEmbedded.UsersGuide.Requirements of the DymolaEmbedded library shipped with Dymola.
• Java 21: Required by Dymola's eFMI tooling. For the paper we used the portable (i.e., zip, not MSI installer) Eclipse Temurin JDK 21.0.11+10 unpacked in its default installation directory (C:\Program Files\Java\jdk-21.0.11+10 in Windows).
• STM32CubeMX 6.17.0 and STM32CubeIDE 2.1.0: Required for pin and timer configuration, generation of STM32 hardware abstraction layer (HAL) integration code, firmware development and final flashing on SMT32 boards.
• Digilent WaveForms 3.25.1 (if the Analog Discovery 3 oscilloscope is used, cf. hardware below): Required to visualize and store measurements of the CHiL experiments.
• MATLAB: Required to postprocess experiment results.

Optional for production code analyses based on the strict configuration profiles provided by Dymola (cf. DymolaEmbedded.EmbeddedConfiguration.ProductionCode.check_codes()):

• Cppcheck Premium 26.3.0: To check MISRA C:2023 and SEI CERT C Coding Standard compliance, and for general bugs, undefined behavior and dangerous coding constructs.
• Python 3.14 and Pygments: Required by Cppcheck Premium for HTML reports. Python needs to be in its default installation directory (e.g., C:\Users\<<your user name>>\AppData\Local\Programs\Python\Python314 in Windows).
• clang-tidy (Clang Tools 19.1.5): To check general code quality.

Hardware (for CHiL experiments)

• NUCLEO-H723ZG: Runs the plant model.
• NUCLEO-L476RG: Runs the controller (PSS).
• Breadboard and patch wires: To interconnect the analog I/O of the two boards.
• A data-recording instrument: To capture the closed-loop signals during the CHiL experiments. We suggest the Analog Discovery 3 used in the paper, but any oscilloscope or data-acquisition device with comparable bandwidth and resolution works.

Getting started

The following step-wise workflow generates all involved artefacts for the paper's controller and plant setup from scratch, accompanied by respective MiL, SiL, and CHiL experiments.

Note

The repository already ships with generated eFMUs, eFMU SiL-stubs, SiL experiments, and eFMU production code based source code FMUs; all under ./models/working-directory. Likwise, the respository already provides generated STM32 HAL integration code for the board configurations; all under ./firmware/.

Warning

If artifacts are (re)generated, the existing ones are overwritten! If anything goes wrong, you can always discard your local changes; if you do not intend to commit new versions, just build on a local git branch.

Note

Steps 1-5 can be skipped if one just wants to conduct the CHiL experiments with the models as they are. But compilation and flashing of binaries with SMT32CubeIDE as described from step 6 is still required since binaries are not shipped with the repository.

1. Clone repository with submodules

OpenIPSL is linked as a submodule, so clone recursively (or use a lighter shallow clone as explained in the tip at the beginning):

git clone --recurse-submodules https://github.com/ALSETLab/efmi-pss-use-case.git

If you already cloned without --recurse-submodules, run:

git submodule update --init --recursive

2. Load models in Dymola

Option A — automated launcher (recommended): Just double-click ./models/start-Dymola.bat.

Option B — manual:

1. Start Dymola.
2. Set Dymola's working directory to ./models/working-directory.
3. Load the OpenIPSL library from ./models/OpenIPSL-submodule/OpenIPSL/.
4. Load the OpenIPSL_CHIL library from ./models/OpenIPSL_CHIL/.
5. Load eFMU SiL-stubs by executing .DymolaEmbedded_menu.load_all("OpenIPSL_CHIL") (can also be done via: Tools ribbon -> eFMI® button -> Load eFMU Co-simulation Stubs... -> select the library as package_name using the selection dialog opened via the directory-tree button).

3. Generate eFMUs in Dymola

Note

This step can be skipped if only interested in offline design and MiL experiments.

The eFMU generation configurations live next to the models they target — for example, the configuration for the controller is OpenIPSL_CHIL.Components.PSS.eFMUs.PSSTypeIISimpleHPF and for the plant it is OpenIPSL_CHIL.RTS.CHIL.eFMUs.Grid4CHIL. To build a configuration's eFMU from scratch, just call its build() function with update=false and build_binary_stub=true.

4. Conduct Mil and SiL experiments in Dymola

TODO

5. Generate STM32 HAL integration code in STM32CubeMX

TODO

6. Load embedded code projects in STM32CubeIDE

TODO

7. Compile and flash binary code in STM32CubeIDE

TODO

8. Conduct CHiL experiments in WaveForms

The signal path of the CHiL experimental setup of the paper is (C is the controller board, P the plant board):

1. Wire the boards and Analog Discovery 3 as shown in the picture above (signal path).
2. Flash the controller firmware in ./firmware/PSSTypeIISimpleHPF_L476RG/Release/PSSTypeIISimpleHPF_L476RG.elf on the NUCLEO-L476RG.
3. Flash the plant firmware in ./firmware/Grid4CHIL_H723ZG/Release/Grid4CHIL_H723ZG.elf on the NUCLEO-H723ZG.
4. Reset both boards via the reset button.
5. Conduct measurements in Diligent WaveForms using the capture projects in ./measurements/*. Remember that sustained fault injection via the B1 button will cause the plant to destabilize beyond recovery; if that happens, plant and controller need to be reset via their B2 buttons. Likewise, with the PSS controller disengaged the plant cannot compensate injected faults (the B1 button disengages/enagages the controller). See the paper for details.
6. Analyze captured results using the MATLAB scripts in ./postprocessing/*.

Original authors and how to cite

Originally developed by ALSETLab, Rensselaer Polytechnic Institute, in collaboration with Dassault Systèmes by Luigi Vanfretti, Christoff Bürger, Joseph Pizzimenti, Kyle R. Wilt, and Hao Chang, and released under the 3-Clause BSD License with Copyright © 2025–2026, ALSETLab and Dassault Systèmes.

If you use these models or the workflow, please cite our original paper (DOI: 10.13140/RG.2.2.32454.84808; ResearchGate link):

L. Vanfretti, C. Bürger, J. Pizzimenti, K. R. Wilt, and H. Chang, "Real-time Simulation and CHiL Testing of Power System Stabilizers on Microcontrollers with Modelica and eFMI," American Modelica & FMI Conference, 2026.

@inproceedings{Vanfretti2026_eFMI_PSS,
  author    = {Vanfretti, Luigi and B{\"u}rger, Christoff and Pizzimenti, Joseph and Wilt, Kyle R. and Chang, Hao},
  title     = {Real-time Simulation and {CHiL} Testing of Power System Stabilizers on Microcontrollers with {Modelica} and {eFMI}},
  booktitle = {American Modelica \& FMI Conference},
  year      = {2026},
  note      = {Accepted, but not published yet -- add pages and DOI once published.}
}

You can also cite this repository directly via its Zenodo DOI: 10.5281/zenodo.20583549.