Modern power systems are rapidly replacing synchronous machines with converter-based renewable generation. While grid-forming (GFM) converters are expected to support voltage and frequency stability, their potential contribution to power quality (PQ) in distribution networks remains insufficiently understood. Weak grids, low X/R ratios, voltage unbalance, and harmonic distortion create challenging operating conditions where conventional approaches may struggle. GRID-GAP investigates how GFM converters behave under realistic PQ disturbances and whether they can actively support voltage quality while maintaining stable operation. The project combines shared expertise, benchmark test cases, and multi-laboratory testing methodologies to assess the capabilities and limitations of GFM converters in future active distribution networks.
Objectives
The project combines benchmark-system development, real-time simulation, and hardware-in-the-loop (HIL) testing to evaluate GFM converter performance under distribution-grid PQ disturbances. Shared datasets and harmonised test procedures are used to reproduce voltage unbalance, harmonic distortion, and weak-grid conditions in a comparable manner across participating laboratories. Different PQ-oriented GFM control approaches are assessed under both grid-connected and islanded operation, enabling reproducible multi-laboratory validation and comparison of converter behaviour.
Description
The increasing penetration of inverter-based renewable energy resources is transforming the dynamic behaviour of modern power systems. As synchronous machines are progressively displaced, essential characteristics such as inertia, voltage stiffness, and natural damping are reduced. In this context, GFM converters have emerged as a key technology for future converter-dominated grids due to their capability to actively establish voltage and frequency.
Beyond stability support, future distribution networks require advanced solutions to address growing PQ challenges. Unbalanced loads, converter-interfaced generation, and nonlinear devices can lead to voltage unbalance and harmonic distortion, particularly in weak distribution systems with high feeder impedances and low X/R ratios. Traditionally, these problems have been mitigated using dedicated active filters or power-quality conditioners. However, GFM converters may also provide these functionalities directly through advanced control strategies.
GRID-GAP investigates the capability of GFM converters to operate robustly under realistic PQ disturbances while contributing to voltage-quality improvement. Rather than proposing a single control method, the project focuses on collaborative assessment through benchmark systems, harmonised testing methodologies, and shared experimental platforms. Particular attention is given to the interaction between GFM converters and the surrounding grid impedance, as well as to their behaviour under grid-connected and islanded operation.
Process
- Collection of representative PQ disturbance datasets from field and laboratory environments
- Development of benchmark test cases for voltage unbalance and harmonic distortion scenarios
- Reproduction of disturbances using real-time simulation and HIL platforms
- Multi-laboratory testing of PQ-oriented GFM control approaches under different grid conditions
- Consolidation of results into technical recommendations, guidance material and dissemination activities
Planned publications
- Technical guidance report on PQ-oriented GFM converter assessment
- Benchmark test-case documentation for multi-laboratory validation
- Possible journal publication related to GFM converters and power quality in distribution networks
- Dissemination through ISGAN-SIRFN workshops, presentations, and professional media
Contacts
Dr. Alfredo Velázquez
Zurich University of Applied Sciences (ZHAW)
Email
Dr. Artjoms Obusevs
Zurich University of Applied Sciences (ZHAW)
Email
