An Improved Observer-Based State Feedback Controller for Grid-Tied Inverters with LCL filters

LCL-filters are typically employed in renewable energy systems between voltage source inverters and the power grid for their high harmonic attenuation capability. However, because of the LCL-filter resonance, the control design of such systems is very challenging particularly under parameter uncertainties and grid disturbances. This work aims at developing a new solution based on linear matrix inequality (LMI) for robust observer-based current control of grid-tied inverters with LCL-filters. The application of the state observer will eliminate the need of additional sensor for active damping. Moreover, a sufficient stability condition is proposed in terms of LMIs based on the Lyapunov theory, which guarantee effective suppression of the LCL-filter resonance under parameter uncertainties with a predefined grid disturbance attenuation level. The general formulation of the control design leads to an LMI optimization problem that can be easily solved using LMI solvers. The obtained results illustrate the performance and robustness of the proposed control method under parameters uncertainties and grid disturbances.