Observer-based Control for Grid-connected LCL-filtered Inverter with Only Grid Current Feedback

This paper presents an observer-based control scheme for a grid-connected LCL-filtered inverter with only grid-side current feedback. The proposed control scheme is composed of a state feedback regulator and an augmented state observer. The augmented state observer is used to estimate the inverter states which are then employed to construct the regulator. In addition to inverter states, the observer also estimates the grid voltages which are utilized to remove the effects of abnormal grid voltage and system parameter variations, as well as to synchronize the inverter with the grid. As a result of using the observer, only grid-side current sensors are required to control the inverter system even under unbalanced and distorted grid voltages. The effectiveness of the suggested control approach is verified through numerical results.