Single-phase grid-connected voltage source converter for LCL filter with grid-current feedback

LCL filters are extensively integrated with single-phase grid-tied voltage source converters due to their higher ripple attenuation capability. LCL filters lead to system instability due to the resonance of the filter. Limited range of resonance frequency and bandwidth ensures the stability of the system by proper design of the current controller and filter. This paper presents the modeling, design and control of a single-phase grid-connected VSC, including an LCL filter, with reactive power injecting capability. A simple PI controller in the unbalanced synchronous reference frame is designed with the Extended Symmetrical Optimum method for the grid current feedback control loop. The q-axis current control is used to inject the reactive power. The system is modeled and simulated in MATLAB/Simulink® and results are verified with an experimental setup of 1.5 kVA VSC.