Grid Voltage Estimation and Feedback Linearization based Control of a Three phase Grid Connected Inverter under Unbalanced Grid Conditions with LCL Filter

Voltage sensing in a three phase grid connected inverter is expensive and introduces vulnerability in the presence of faulty components. A feedback linearization based current control strategy independent of grid voltage sensor information is presented in this paper. Initially the current controller is tuned with the assumption of known grid voltage. Next, an internal model based grid voltage estimation technique is proposed to estimate the grid voltage by using the error of the grid current and known filter parameters. The estimated grid voltage from the proposed technique was utilized in feedback linearization based current control to achieve successful current control. The proposed method has been verified via computer simulations based on MATLAB R/Simulink R and PLECS R and the efficacy of the system was checked with various case studies.