In the context of increasing diffusion of renewable energy sources and simultaneous decommissioning of conventional power plants, stability of the main electric grid parameters (frequency and voltage) could be challenged due to the reduction of rotating masses connected to the grid. Increasing the panel of resources which can offer frequency and voltage regulation services can be one of the actions to address this issue. In the framework of the Horizon 2020 OSMOSE project Work Package 5 two wind power plants (one integrating a storage system), located in Basilicata, were involved in a live experimentation aimed at characterizing the capability of wind generators in providing voltage regulation to the grid. This paper traces the main phases of the experimentation, from technical requirements to implementations and testing while offering a complete overview of test results.