Three-level hierarchical microgrid control—model development and laboratory implementation

Problem and Research Question

Islanded microgrids require coordinated control across multiple time scales: fast local regulation to stabilize voltage and frequency after disturbances, slower secondary control to restore nominal values, and tertiary control to optimize economic dispatch. Most published architectures treat these levels separately and validate them only in simulation. The central question: can a unified three-level hierarchical control architecture for microgrids be developed and validated on physical hardware, not merely in simulation?

Simulation-only validation cannot capture communication delays, equipment constraints, timing requirements, or real-world controller interactions. Hardware-in-the-loop (HIL) testing bridges the gap between pure simulation and full physical deployment.

Method

This paper developed a three-level hierarchical control architecture for islanded microgrids:

• Primary control — local droop-based voltage and frequency regulation at the inverter level, acting on millisecond timescales to stabilize the system immediately after disturbances.
• Secondary control — centralized restoration of voltage and frequency to nominal values, compensating for the steady-state deviations introduced by primary droop control.
• Tertiary control — economic dispatch and power flow optimization, managing energy distribution among sources and storage over longer time horizons.

The architecture was implemented and tested on a hardware-in-the-loop (HIL) laboratory platform, connecting real controllers to a real-time simulated microgrid. This setup captures control timing, communication delays, and equipment constraints that pure simulation cannot represent.

Personal Contribution

Frederik Banis was a co-author. He contributed to the laboratory implementation and experimental validation, working on the integration of control layers and the HIL testing setup. The first author (Mateo Beus, University of Zagreb) led the model development and overall architecture design. Niels Kjølstad Poulsen (DTU) and Hrvoje Pandžić (University of Zagreb) provided supervision.

Validation and Key Results

• The three-level control architecture was successfully implemented and tested on a HIL platform, demonstrating coordinated operation across all control levels.
• The laboratory validation confirmed that the hierarchical scheme maintains stable frequency and voltage under load changes and source switching, beyond what simulation-only validation could guarantee.
• The HIL setup revealed practical timing and communication constraints that informed the control design — constraints that would not have surfaced in pure simulation.

The method was published in Electric Power Systems Research (2020), a peer-reviewed journal.

Related Outputs

• PhD thesis: Efficient Operation of Energy Grids, DTU, 2020. DOI: 10.11581/DTU.00000334
• Related work: Load Frequency Control in Microgrids using target adjusted MPC, IET RPG, 2019. DOI: 10.1049/iet-rpg.2019.0487

Collaborators and Institutions

• DTU Compute, Technical University of Denmark — Niels Kjølstad Poulsen (supervisor)
• University of Zagreb — Mateo Beus (first author), Hrvoje Pandžić (supervisor)

Status and Next Steps

Status: Published (2020). This project distinguishes simulation from physical implementation — the HIL validation is the key contribution beyond pure modeling.

Transfer to current research: The closed-loop experimentation architecture — measure, infer, decide, act, with physical validation — is the same pillar that now drives human-supervised autonomous bioassay platforms. The shift is from energy hardware to biomedical hardware, but the closed-loop validation methodology is shared.

See the related project page for the broader research context and the Methods page for the closed-loop experimentation pillar.