Stability of synchronous reference frame-phase locked loop for grid-connected inverter

In this paper, synchronization of a voltage source inverter (VSI) to the grid is presented.VSI can control both active and reactive power which depends on the modulation index, LCL filter and the control method used. In order to avoid resonance effect, to reduce harmonic current, and to improve the stability of the current control loop, a passive damping resistor is introduced in the basic LCL filter. A synchronous reference frame-phase locked loop is used to synchronize the grid and VSI. Design of a 3-phase Y-connected LCL-damping resistor filter and two PI current controller along with control strategy of grid connected inverter is presented. Proposed schematic is simulated in MATLAB/SIMULINK 2010 and simulation results are provided.