Smooth Switching Between Two Different Control Methods Based on Kalman Filter for Grid-Connected Inverter

The stable and efficient operation of the grid-connected inverter (GCI) is facing severe challenges under the large short-circuit ratio (SCR) fluctuations. In order to ensure the operation quality of the GCI, the dual-mode control was proposed to select the current source mode (CSM) or voltage source mode (VSM) according to the SCR. However, due to the different principles of the dual-mode, when the GCI directly switches from the CSM to the VSM, the grid-injected current and the PCC voltage will have large oscillations. In this paper, a smooth switching dual-mode control method is proposed by using a Kalman Filter observer to suppress the oscillations during mode switching process. The proposed method has been fully verified through simulations and experiments.