Today, urgent action to address climate change is driving a transition in energy generation and consumption patterns. Renewable energy sources (RES) are central to the transition. However, with an increasing share of RES and decommissioning of conventional synchronous generating units, the nature of the power system changes, leading to reduced system inertia and increased sensitivity to frequency disturbances. In this context, hybrid power plants (HPPs) are increasingly recognized as a key contributor to supporting the future power systems. HPPs integrate multiple RES, often in combination with an energy storage solution, behind a single point of connection to the grid. The coordinated control of the plants within the HPP enables new opportunities for providing frequency support.

This paper investigates the frequency support capability of a grid-integrated, utility-scale HPP comprising a wind power plant, solar power plant, and a battery energy storage system (BESS). The study focuses on the provision of ancillary frequency services, specifically frequency containment reserve and fast frequency reserve as defined by the market in DK2. The HPP is modeled in MATLAB/Simulink and integrated into a modified IEEE 9-bus system, which is slightly modified to capture the desired characteristics of weak grid conditions. The grid frequency response during a frequency disturbance is analyzed with the modified IEEE 9-bus system and with one generator replaced by the HPP model.

The results show that under weak grid conditions, the modified IEEE 9-bus system with only conventional generators provides more effective frequency support than the HPP with grid following control. To address this limitation of the HPP, a grid forming (GFM) control strategy is applied to the BESS within the HPP. The results demonstrate that GFM control in the BESS significantly improved the HPP’s capability to support the grid frequency under weak grid conditions. The work leading to these findings was conducted as part of a Master’s thesis at the Technical University of Denmark.