Design of High-order vector control strategy for grid-connected PV systems with LCL filters

This paper proposes a vector control strategy for grid-connected PV systems with LCL filters. The proposed control strategy is inherently capable of attenuating the resonance phenomenon of such systems. This is an advantage over the existing methods, which require additional damping techniques. Renewable energy sources such as solar energy make increasing contributions to electric utility networks. A theoretical analysis, modeling, controlling and a simulation of a grid connected photovoltaic system using output LCL filters are described in detail. Those sources are commonly coupled to the grid through a pulse width modulation inverter and filter. Moreover, the proposed vector control strategy is able to fully decouple the direct (d) and quadrature (q) components of the current in a rotating reference frame. It utilizes the multi-input multi-output (MIMO) nonparametric model of the system along with a high-order linearly parameterized MIMO controller to form an open-loop transfer function matrix. Minimizing the second norm of the error between the open-loop transfer function matrix and a desired one, the coefficients of the controller are optimally determined. The performance of the proposed vector controller is evaluated both by means of time domain simulation studies in MATLAB/Simulink.