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Krishna K.C.

Sep 2024 – May 2026 · University of Maine

Real-Time Microgrid & Hardware-in-the-Loop

OPAL-RT / RT-LAB · Raspberry Pi + OP8666 DSP · System Identification

A real-time microgrid model integrating photovoltaic, wind, inverter-based and conventional generation, run in closed loop with embedded hardware to study dynamic response and identify inverter dynamics.

Hardware-in-the-loop schematic. Inside a real-time simulator running OPAL-RT and RT-LAB, photovoltaic, wind, inverter-based and conventional generation share a common bus that feeds a load. Measurement signals flow from the simulator down to embedded hardware — a Raspberry Pi and an OP8666 DSP microcontroller — and control signals flow back up, closing the loop between the real controllers and the simulated microgrid.

Illustrative diagram — not a client or employer drawing.

◆Explore the system

OPAL-RT with RT-LAB runs the microgrid as a real-time plant. PV, wind, inverter-based and conventional generation share a common bus with the loads.

The model was developed to evaluate voltage, frequency and dynamic response under changing generation and loading conditions.

01Project overview

As part of graduate research at the University of Maine, a real-time microgrid model was built and validated using OPAL-RT and RT-LAB. The model integrated photovoltaic, wind, inverter-based and conventional generation resources on a common electrical bus.

The work connected embedded hardware to the real-time simulator so that controllers ran in closed loop against the simulated grid, allowing dynamic behavior to be studied under changing generation and loading conditions.

02Engineering problem

Inverter-dominated microgrids behave differently from conventional grids: their dynamics depend heavily on power-electronic controls rather than large rotating machines.

Studying that behavior safely and repeatably requires a real-time environment where controllers interact with an accurate model of the grid before any hardware is exposed to real power.

03Responsibilities

  • Built and validated the real-time microgrid model in OPAL-RT / RT-LAB.
  • Integrated photovoltaic, wind, inverter-based and conventional generation resources into the model.
  • Interfaced a Raspberry Pi and an OP8666 DSP microcontroller for closed-loop hardware-in-the-loop operation.
  • Developed and evaluated probing-signal and ARX-based identification methods to estimate dynamic transfer functions from inverter input-output measurements.

04System architecture

  • Generation sources (PV, wind, inverter-based and conventional) feed a common microgrid bus that also serves the loads.
  • The plant runs in real time on OPAL-RT under RT-LAB; measurement signals leave the simulator and control signals return to it, closing the loop.
  • A Raspberry Pi and an OP8666 DSP sit in that loop as the embedded controller / interface layer, exchanging input-output signals with the simulated grid.

05Engineering methodology

  • The model was developed to evaluate voltage, frequency and dynamic response under changing generation and loading.
  • Probing signals were injected at inverter inputs, and the resulting input-output measurements were used to fit ARX (AutoRegressive with eXogenous input) models.
  • The identified transfer functions describe how an inverter responds dynamically, which supports analysis and control design.

06Tools & platforms

  • OPAL-RT
  • RT-LAB
  • Raspberry Pi
  • OP8666 DSP
  • MATLAB
  • Simulink

07Validation approach

  • The real-time model was validated as part of building it, and its outputs were used to evaluate voltage, frequency and dynamic response.
  • System-identification results were assessed by comparing model-predicted behavior against the measured inverter input-output data.

08Engineering considerations

  • Real-time execution imposes a fixed computation budget per time step, so model fidelity is balanced against real-time performance.
  • Hardware-in-the-loop keeps real controllers in the loop while avoiding the risk of testing directly on energized equipment.

09Outcomes

  • A validated real-time microgrid model with multiple generation types running in closed loop with embedded hardware.
  • Probing-signal and ARX-based methods that estimate inverter dynamic transfer functions from measured data.
  • Findings from the broader effort are reflected in an accepted publication on real-time-simulation-based inverter control (see Research).

10Skills demonstrated

  • Real-time simulation
  • Hardware-in-the-loop
  • System identification
  • Power electronics
  • Control systems
  • Embedded interfacing
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