Grid current low‐order harmonics suppression of the three‐phase grid converter with an LCL filter under the distorted grid voltage

This article presents an extended backstepping control method to reduce the grid‐side current harmonics caused by grid voltage distortion. A dynamic model considering the grid voltage as an external disturbance is derived in the stationary reference frame. The extended back‐stepping design procedure based on pole displacement guarantees that the system is stable without damping. The proposed method has a general low‐order harmonics suppression instead of selective harmonics elimination. Zero steady‐state error can be obtained tracking the grid currents. Stability, as well as good transient and steady‐state performance are verified through numerical simulation. A comparison with the state‐of‐the‐art proportional resonant control with active damping is also conducted. The results show that a good low‐order harmonics reduction in the grid current is achieved by the proposed control method.