Performing grid test to validate simulation models and converter-driven stability phenomena

The amount of converter connected production continues to increase in the Finnish power system. Most of the new production is wind power which is concentrating on the 400 km long area in the western coast of Finland. This area currently has more than 5 GW of wind power and very little load or synchronous generators, creating issues with converter-driven stability. The studies on converter-driven stability and the required mitigation methods and actions are mostly based on the wide area electromagnetic transient (EMT) simulation studies. To verify and improve the accuracy of these models, Fingrid planned a real-life grid test where converter-driven instability was planned to be evoked intentionally by reducing the network strength in a limited area in the western coast. In the grid test the converter-driven instability was successfully evoked in a controlled manner. The voltage oscillations measured during the test match relatively closely with the oscillations observed in the simulation models. This confirmed the capability of the simulation models to replicate the response of the converters in a realistic manner, and the data received from the test results could be used to further enhance the accuracy of the simulation models.