Proportional integral — Resonant and dual loop current control structure comparison for grid connected converters in the rotating frame

Over the past few years, due the increasing penetration of renewable energy, there has been a steady rise in the harmonic content in grid voltages. In such circumstances, a proportional integral (PI) based current control in the synchronous reference rotating frame (dq) for a grid connected voltage source converter may not be adequate to suppress the harmonic components and to precisely follow the fundamental frequency component with zero steady state error. Several current control structures have been proposed, with proportional integral - resonant controller (PI-RES) based structure being one of the most popular. In this paper, the PI-RES has been compared to the recently introduced dual loop current control structure. Both these current control structures have been compared in terms of their tracking, filtering and disturbance rejection capability. Robustness of both these structures has also been analyzed under a grid impedance variation. Simulation and experimental results have been provided to validate the analysis presented.