A Novel Sliding Mode Control Strategy for VSG-Based Inverters with Disturbance Estimation

Abstract

The interface inverter control system based on virtual synchronous generator (VSG) technology, has been widely used in new power systems due to its ability to provide system inertia. To enhance the robustness of the VSG-based inverter control system against uncertain disturbances, this paper proposes a novel sliding mode control (SMC) strategy consisting of two control layers for VSG-based inverters based on disturbance estimation. Firstly, the VSG-based outer loop control layer is established to mitigate the transient instability during pre-synchronization process, which consists of an active frequency control loop with a phase angle regulator and a reactive voltage control loop with an amplitude regulator. Secondly, an SMC-based inner loop control layer is designed to replace the traditional voltage and current dual loop control for robustness improvement, where the uncertain disturbance can be estimated and fed back to the controlled system for disturbance suppression. Moreover, both of the eigenvalue method based small signal stability and the Lyapunov functional based large signal stability are analysed for different control layers, and the comparative simulations are conducted between the proposed strategy and traditional pre-synchronization control as well as voltage current dual loop control, in scenarios of grid-connected voltage fluctuation and islanded load power variation. The dSPACE based prototype physical experiment further validates the effectiveness of the sliding mode control strategy for VSG-based inverters with disturbance estimation.