Decouple control strategy of three-phase grid-connected inverter with LCL filter

Compared with the traditional single L filter, LCL filter can suppress the switching ripple current and ripple voltage effectively and reduce harmonic pollution to the grid, however, the increase of the system order also brought difficulties to system control. The LCL filter model in dq frame is complex and couple seriously, to break down those problems, a decouple control strategy with Linear Extended State Observer(LESO) is presented. Through the reasonable design of LESO, the original system can be decoupled meanwhile the performance of the system can be also considerable improved. Compared with the conventional decoupling method such as feed forward decoupling, not only saves the cost of the sensors but also have better effect. Simulation and experiments indicate that the proposed control strategy solves coupling problems more effectively compared with the conventional control strategy. It effectively improve the quality of grid-side current which can be considered as a powerful robust tool for renewable power integration.