Modeling and Control of a Single-Phase Grid-Connected Inverter with LCL Filter

The increasing penetration of renewable energy sources is pushing low-voltage electrical grids to become predominantly power electronic-based. Consequently, the design and operation of the related grid-connected converters must be achieved under proper manner, in order to maintain stability and support reliable operation of the entire power system. Thus, this work presents the modeling and control of a single-phase grid-connected multifunctional converter, which operates as a current-controlled voltage source inverter using an LCL-type output filter. An active damping approach is employed for attenuation of oscillations occurring from interactions between the grid and the inductances and capacitance of the LCL filter. Additionally, the voltage and current control loops of the inverter are addressed in this paper, along with the design of their respective controllers, considering that the grid impedance is unknown. Experimental results demonstrate stable operation of the inverter and show its satisfactory behavior under steady state conditions, proving its capability to offer ancillary services such as active filtering.