DC Component Suppression for Grid-Connected Photovoltaic Inverters Based on Kalman Filter

Aiming at the problem of DC components injection to the grid caused by the quasi-Z-source PV grid-connected inverter without an isolation transformer, a DC current suppression strategy based on the Kalman filter is proposed, which only needs to sample the grid-connected current and requires no more other sensors. Firstly, the causes of the DC component adopted by the traditional control strategy are analyzed. Then, the proposed method for eliminating the DC bias of the grid-connected current using a Kalman filter is designed and estimated accurately. Finally, the proposed control strategy is verified by simulation. The simulations show that the proposed strategy can effectively reduce the DC component of the grid-connected current and suppress it to less than 0.1% of the rated current.