Wind energy is forecasted to supply about 28% of global electricity generation by 2050. In terms of installed power capacity this corresponds to about 6.3 TW which is more than six times the total wind installed capacity in 2023. Different regions and nations around the globe have ambitious targets to use wind power to fuel supply their loads while movie away from fossil-based generators. To achieve such targets, wind turbines (WTs) are being deployed in large amounts both onshore and offshore. All these turbines must go through testing and verification of the grid connection requirements before being connected to the grid. WT manufacturers and the wind project developers would like this process to take as little time as possible to ensure quick delivery times and lower overall project costs.

Traditionally, such tests were only conducted on full-scale prototypes of the product connected to the grid in the field. These tests may extend over longer durations due to the availability of suitable test equipment and conditions suitable for the tests. Such long waiting periods cause long delays and additional expenses for the manufacturers and the project developers who want to limit the overall costs of the product and the projects. Additionally, as the turbines grow larger, the testing process faces additional challenges in terms of the capabilities of the test equipment. On the other hand, as wind energy takes more prominent share of the generators, it is demanded by regulators to take responsibility to help keep the grid stable by supporting the grid voltage and frequency. One of the upcoming requirements for both offshore and onshore wind farms is “Grid-forming” capabilities which mandates the WTs to imitate the synchronous machines to maintain grid voltage and provide inertia from the rotating mass in case of frequency events. Apart from these core functions, a grid forming WT might also need to demonstrate capability for services requiring island operation and black-start activities.

Capabilities required by grid-forming regulations would not only be complex for operation but also pose a stiff challenge in their verification. For example, the inertial support to the grid by utilizing the energy reserve in rotating mass of the turbine may need to be verified. Some of the regulations might need the demonstration of island operations or verify the grid-forming operation after the disconnection of the last synchronous generator. To address these challenges, there is a growing need for novel methodologies and processes to support field measurement-based verification in providing verification of such advanced capabilities which are otherwise not feasible to be tested on field. Several Hardware-in-Loop (HiL) methods and test-benches are developed to speed up the testing and verification process of WTs. This paper presents co-simulation style Controller Hardware-in-Loop (CHiL) tests to verify the grid-forming of a WT.

The aerodynamic and mechanical systems of the WT are simulated using Bladed® software from DNV while the wind turbine Permanent Magnet Synchronous Generator (PMSG), the converter power stage, and the electrical network are modelled and simulated on a real-time simulator. The Wind turbine and the PMSG are controlled using a wind turbine controller and a converter controller respectively which are integrated in the testbed. This testbed has two distinct advantages: Co-simulation enables study and verification of interaction of mechanical and electrical domains of a grid-forming WT during events in scenarios where electrical and mechanical dynamics are strongly coupled together such as faults other disturbances in grid voltage and frequency thus helping to verify the use of instantaneous energy reserves of the WT rotating mass. It also allows the integration of OEM models of the turbine as well as actual controller replicas for the turbine and converter control.