A power disturbance observer-based sliding mode frequency controller for grid-forming converters

Grid-forming converters (GFMs) can enable power electronics to mimic the inertia response of synchronous generators (SGs), which can enhance the frequency stability of the ac grids with high penetration of renewable energy sources (RESs). However, GFMs potentially induce oscillations during frequency support because of the similar external dynamics with SGs. In this paper, a power disturbance observer-based sliding mode frequency controller (PDOSMFC) is proposed to facilitate flexible frequency support and enhance system damping through GFMs. By leveraging the intrinsic ability of GFMs to respond to power disturbances in ac grids autonomously, we designed a power disturbance observer to estimate the internal state variables and the external power disturbance using only the local measurements from GFMs. With the estimates of disturbance and states, a modified super-twisting sliding mode control is employed to compensate for the power disturbance to achieve accurate and flexible frequency support. The proposed PDOSMFC is validated via two test systems in a PowerFactory-MATLAB co-simulation environment. The simulation results verified the external power disturbance estimation performance and the frequency support performance. • The proposed model is developed to ensure the observable and controllable. • The disturbance observer can estimate the power disturbance by only the local measurements. • The proposed power compensation command block can achieve the flexible frequency regulation mode. • Both tracking and damping enhancement are achieved by the super-twisting sliding mode controller.