Extensive assessment of virtual synchronous generators in intentional island mode

Virtual Synchronous Generators (VSGs) are considered one of the most effective cutting-edge technologies for seamlessly integrating Renewable Energy Systems (RESs) into power grids. While various VSG control schemes have been proposed and analysed for different technical aspects, not many experimental demonstrations have been published about VSGs operating in Intentional Island Mode (IIM). Inversely, the IIM has become increasingly attractive, nowadays, to energize those remote areas of the world where entire districts are served by a small number of RESs operating off-grid. In this scenario, the main objective of this paper is to present an extensive performance assessment of the VSG operating in IIM. Different working conditions are considered, with special focus on: black start capability, grid-connected-to-IIM transition, grid reconnection, feeding of non-linear and asymmetric local loads, load sharing between multiple VSGs operating in parallel. In order to achieve this objective, an improved structure of VSG is implemented on 8kVA three-phase converters and significant experimental results are presented. Algorithms for black start capability and grid synchronization are illustrated in detail as well. Meaningful information is provided for engineers involved in activity of designing and testing islanded VSGs.