A control strategy for smooth power tracking of a grid-connected virtual synchronous generator based on linear active disturbance rejection control

Abstract

The power quality of new energy resources has received tremendous attention recently. The control approach for the inverter, an interface between the new energy resources, and the infinite bus system is of vital importance. For the virtual synchronous generator (VSG), one of the research hotspots in the inverter control field, there are some challenges remaining to be dealt with. First is the contradiction between the rapid response and overshoot of active power output if VSG is connected to the grid. Secondly, the active power is deeply influenced by the fluctuation of gird frequency and this may bring power oscillation to VSG in weak grids. In this article, an active power controller for power tracking of grid-connected VSG is designed based on linear active disturbance rejection control (LADRC) by compensating for the lumped disturbance in a feedforward fashion. The parameters of the controller are analyzed and tuned in the frequency domain to acquire a desirable control performance. Moreover, the robustness of the control system is also considered. Simulation results show that the designed control system can transmit active power to the grid in a timely manner with no overshoot, as demanded. Additionally, it can output active power steadily according to the power reference without using a phase-locked loop (PLL) when the grid frequency has different features of fluctuation. In addition, the simulation results demonstrate that the improved VSG has strong robustness to the model parameter perturbation and mismatch.