Performance comparison of phase looked loop algorithms applied to micro-inverters for distributed photovoltaic generation

The paper deals with the experimental comparison of different phase locked loop (PLL) algorithms for single phase, grid tied, photovoltaic generation systems; in particular, this work analyzes the effects of abnormal grid conditions on the output current and power control loops of a 250W micro-inverter unit, highlighting pros and cons of each PLL algorithm. The effectiveness of such algorithms has been evaluated by means of experimental tests analyzing the micro inverter operations when the grid voltage is affected by sags, dips, frequency variations and harmonic distortion. Harmonics rejection and dynamic response of the control algorithm in these operating conditions has been highlighted. In addition the computational burden required by each algorithm has been evaluated.