How ETAP user-defined dynamic models help evaluate renewable energy integration in a 250 MW peak-load islanded power system

We benefited greatly from the different dynamic models provided in ETAP, both built-in and in the UDM version. For UDMs, we could run all the studies, and wherever we were stuck, user support was always there to guide us through and help us out.
By Ankit Jotwani, Electrical Engineer at Energynautics GmbH

This comprehensive case study explores the evolving landscape of electrical power generation. The shift from fuel-based dominance to the anticipated prominence of renewable energy sources serves as a focal point. This study supports a national initiative to increase the renewable penetration of an islanded power system with a 250 MW peak load. The goal was to determine how much renewable energy the system could integrate by 2028, while maintaining system stability and complying with safety and security requirements. To achieve this, Energynautics used ETAP UDM (User-Defined Dynamic Models) to build detailed component-level representations of converters, controllers, synchronous machines, and storage systems. These models enabled precise simulation of transient stability, frequency behaviour, fault responses, converter interactions, and grid-forming / grid-following dynamics. The outcome is a verified, high-fidelity digital model capable of accurately predicting system dynamics and helping planners define expansion strategies for future renewable integration.

Energynautics is a German-based consulting company for the integration of renewable energy and electromobility into power grids. The company conducts research and consulting projects for grid operators, non-governmental organizations, regulators, public clients, wind and solar manufacturers, renewable energy project developers, investors and other clients. The projects focus on issues related to the integration of renewables into electrical grids; the range of systems studied extends from individual generators or consumers to small island grids and distribution networks to interconnected systems across regions. Major projects in recent years include the development of grid codes for wind and solar power generation and a series of renewable energy integration studies for grid operators in Europe, North and Central America, the Caribbean, and Asia.

Location: Darmstadt, Germany

Year: 2023

To build a model evaluating renewable grid expansion

Challenges

  • Evaluate renewable integration potential up to 2028 for different penetration scenarios in the chosen region.
  • Model the entire electrical system—generation, controls, grid-forming converters, protection, and network behaviour—using ETAP.
  • Convert HOMER sizing results into a detailed ETAP model by creating accurate load and generation profiles.
  • Integrate vendor-provided dynamic models of GFL and GFM inverters, modifying them as needed for simulations.
  • Assess system stability for renewable scenarios up to 250 MW, including inertia reduction, fast frequency response, and voltage control.
  • Validate frequency dynamics for multiple generation mixes, battery operations, and fault events.

Which solutions did they choose?

Selected applications

  • ETAP Digital Twin modelling for complete grid representation.
  • Graphical Dynamic Model Software to create User-Defined Dynamic Models (UDMs).
  • Multidimensional ETAP Database for managing network data, loads, generation profiles, and contingencies.
  • SQLite Database + Python scripts to automate model transfers from HOMER to ETAP.
  • ETAP Time-Domain Stability for frequency, voltage, and fault studies.

Why do they use ETAP?

Main customer benefits

ETAP enabled the engineering team to create a reliable benchmark model of the islanded grid, integrating all renewable sources and validating operational behaviour under multiple what-if scenarios. The UDM environment was crucial for representing converter dynamics beyond what built-in models allow.

1. End-to-end digital model creation

Complete network modelling was carried out using ETAP’s Digital Twin capabilities, allowing engineers to evaluate the complete system from steady-state to dynamic performance.

2. HOMER-to-ETAP model integration

Data from HOMER was imported using the ETAP SQLite database structure and Python scripting, eliminating manual entry and ensuring consistency in model creation.

3. Accurate modelling of converters and plant controllers

  • UDM models were built for PV systems, wind turbines, converters, GFM/GFL controllers, and BESS controls.
  • Built-in ETAP models were combined with UDMs to represent realistic behaviour under different events.

4. Scenario analysis for 2023–2028

Engineers evaluated renewable penetration up to 40% in 2023, 80% in 2024, 110% in 2025, and up to fully renewable scenarios by 2028, analysing:
  • frequency nadir and RoCoF
  • stability margins
  • inertia contribution
  • battery dispatch
  • plant controller actions
  • converter response to faults and contingencies

5. What-If and Dynamic Event Simulations

Using ETAP’s What-If engine, the team simulated:
  • loss of major generating units
  • short-circuit events
  • battery state-of-charge impacts
  • transitions between GFL and GFM modes
  • multi-scenario system recovery behaviour

6. Efficient revisions

UDMs were adjusted throughout the project to incorporate additional vendor model details, and ETAP’s graphical tools made each revision fast and traceable.


What do they think about ETAP?

Customer perspectives

The ETAP UDM models allow us to adapt the dynamic behaviour of the plant. They let us use the internal vendor logic and tune it when required. The built-in models are also helpful for grid-forming machines. With all these models, it was possible to run the entire project and perform dynamic simulations efficiently.
— Ayad Ahmad, Electrical Engineer, Energynautics GmbH

For the most accurate analysis, the different GFL and GFM inverter models - each representing a vendor design - were adapted and integrated into ETAP’s UDM environment. This flexibility was essential.
— Ayad Ahmad, Energynautics GmbH



Videos

Assessment of Renewable Energy Integration in a 250 MW Peak Load Islanded Power System Using ETAP UDM Models

This comprehensive study, initiated in 2019 and spanning evaluations from 2020 to 2023, examines the evolving landscape of power generation, focusing on the transition from fuel-based dominance to anticipated renewable energy prominence by 2030, employing worst-case operational scenarios to assess system resilience and efficiency, supported by ETAP's robust multi-dimensional database structure and dynamic model integration, with upcoming insights into model behavior and tool utility aimed at enhancing understanding and preparation for future power generation challenges and opportunities.


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