Coordinate Transformation-Based Nonlinear Power Decoupling Control for Differential Buck Grid-Tied Inverter

Nonlinear time-varying systems complicate the analysis and controller design compared to nonlinear time-invariant systems. Single-phase differential grid-tied inverter is a classic nonlinear time-varying system. In this article, an input-output linearization (IOL) based coordinate transformation and a nonlinear power decoupling control scheme are proposed for the single-phase differential grid-tied inverter. Because of the transformation, the nonlinear periodic time-varying system is transformed into a nonlinear time-invariant one. Based on the nonlinear time-invariant model, a nonlinear power decoupling control scheme based on the idea similar to back-stepping control is designed, which realizes good grid current control and power decoupling. Furthermore, the small-signal stability of the inverter is proved by eigenvalue analysis method in the linear time-invariant (LTI) framework. Experiment results validate the effectiveness of the proposed control strategy and stability analysis.