A Single Feedback Current Control Design Technique for LCL Grid-Connected Inverters Based on Pole Allocation in the Frequency Domain

This paper proposes a polynomial-based pole-placement technique for designing high-order current controllers of LCL grid-connected inverters. The technique relies on a feedback scheme composed of a tracking block and a damping block controller, which assure that all the poles of the system's closed-loop transfer function (CLTF) are on the left-hand side of the complex plane, without needing observers for internal states. Hence, it only requires the measurement of the injected current, unlike more conventional approaches that also demand assessment of the current or capacitor voltage for actively damping the system's response. Moreover, the proposed design procedure minimizes the number of CLTF zeros, which cannot be determined beforehand. Besides, it can cope with the delay usually added to the system due to the digital realization of the controllers. This delay introduces new CTLP poles that can impair the system's dynamics. The results show that the proposed design technique provides stability robustness and suitable dynamic response for a broad range of the grid parameter variation.