Self-adaptable reactive power-voltage controller for virtual synchronous generators

With a higher and higher penetration of renewable energy in the grid, the principle of the virtual synchronous generator (VSG) is proposed as an attractive solution to controlling the grid-connected inverters. In common, active power-frequency and reactive power-voltage controllers play major roles in VSG control system. However, the line impedance and local loads are the critical case effecting on the control result of the two controllers. Compared with reactive power-voltage controller, active power-frequency controller is more easier to product the load sharing among the VSGs accurately. This paper presents a self-adaptable reactive power-voltage controller to deal with the sharing problem of reactive power in the parallel VSGs system, using the reactive power difference to adjust reactive power-voltage control coefficient. Then, a linearised small-signal model is established for stability analysis of the reactive power-voltage control coefficient to the parallel VSGs system. Finally, an experiment of two parallel VSGs system based on the self-adaptable reactive power-voltage controllers is performed, with different line impedance. Results obtained from the experiment verify the effectiveness of the proposed self-adaptable reactive power-voltage controllers in the parallel VSGs system