Performance assessment of single and dual loops discrete PR controllers with LCL filter for inverter-based distributed generation

Due to the rapid growth of the electric energy demands, the necessity of involvement of distributed generation (DG) to overcome this demand became a must. When distributed generation renewable energy sources are coupled to the grid through a DC-AC inverter, the injected currents to the grid should be characterized by high quality and low distortion. Many factors play an important role to produce high quality output beginning with the order of the passive filter used, type of controller used and last but not least the presence of distortions in the grid. This paper demonstrates the evaluation of performance, in normal and abnormal grid conditions, between single and dual loop control for the three phase inverter tied to the grid through a LCL passive filter and controlled with discrete proportional resonant (PR) controller, taking into account how filter parameters, control gains and sampling frequency would affect the dynamics of the system as well as its stability in order to perform adequate tuning. The concluded assumptions were simulated & verified through Matlab/Simulink.