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The conventional grid-connected photovoltaic (PV) inverter is controlled by a dual-loop control strategy in synchronous reference frame, and the controllers are designed for steady-state operating point based on the small signal model by neglecting the high-order and coupling terms. However, in an LCL filter, the coupling terms are complicated due to the dq transformation which will affect the dynamic performance. In this paper, an innovative simplified feedback linearization (SFL) control strategy is proposed for the PV inverter with the LCL filter, which offers satisfactory performance, particularly, in decoupling the control system, improving the dynamic performance, and enhancing the adaptability. Furthermore, the SFL controllers are simpler than the high-order tracking controllers used in conventional feedback linearization control. The detailed simplification process and accurate transfer functions for SFL control strategy have been presented, and the performance comparisons between the proposed SFL control strategy and the classical dual-loop method are carried out to show the characteristics of the proposed control algorithm. Finally, a laboratory prototype of a 150-kW PV inverter with the LCL filter has been implemented to test the feasibility and effectiveness of the proposed strategy. The proposed SFL control strategy can also be applied to a higher order system or other power converters.
Date of Publication: June 2013