A robust back-stepping stabilization scheme for virtual synchronous generators in weak grids

This paper presents a new control scheme for virtual synchronous generators connected to weak grids. The proposed approach consists of two major parts. The first part holds a cooperative linear and nonlinear controller in order to emulate the synchronous generator behavior such that by preparing virtual inertia, power and frequency oscillations get damped. The second part deals with a control scheme for voltage and current inner loops. Both control schemes are based on the back-stepping method, while in the latter sliding mode controllers in the dq reference frame are also used. The controller system design is such that in addition to tracking reference commands, it is robust to system model uncertainties and disturbances. In the process of controller design the system stability is also considered. The desired performance of the proposed control scheme for a virtual synchronous generator connected to weak grids in the presence of disturbances and uncertainties in model parameters is demonstrated through simulation results.