Feedback linearization control of photovoltaic inverter with LCL filter

This paper presents a method to design a control system for grid-connected Photovoltaic (PV) inverter which has a LCL-type filter to suppress the output current total harmonic distortion (THD). The conventional approach to design the control system is in synchronous reference domain, which transforms the ac variables into dc quantities and thus, possibility of applying the simple PI controller. However, in a LCL-type filter, the coupling terms are complicated due to the filter capacitance and inductance, and have not been formulated so far. It has been found that the major limitations of real and reactive power are the coupling terms. In this paper, the PV inverter adopts conventional double loops control strategy, inner inductance current control loop and outer DC link voltage control loop. An accurate linear model of three phase PV inverter is derived using feedback linearization method. The linearization system has successfully decoupled the real and reactive current loops and achieves desirable performance. A 250-kW three phase full bridge grid-connected inverter is presented to confirm the analytical results. Simulation results, using MATLAB/SIMULINK, presented for this strategy confirm the effectiveness of the control scheme.