Active Disturbance Rejection Control Based Single Current Feedback Resonance Damping Strategy for LCL-Type Grid-Connected Inverter

The LCL-type grid-connected inverter (GCI) is widely adopted between distributed generation (DG) and power grid to realize DC/AC power conversion. However, the underdamped LCL filter will cause a resonance phenomenon near the control stability boundary, which may lead to instability of the GCI system. The traditional passive damping method will cause power loss, while the active damping method may have the need for additional sensors or be sensitive to parameter changes. In this article, a control scheme based on active disturbance rejection control (ADRC) is proposed for the LCL-type GCI, and the systematic parameter design method is presented through root locus analysis. With the proposed strategy, only the grid-injected current is sensed to achieve the objectives of grid-injected current direct control and robust resonance damping for the LCL-type GCI. In the design process, the influence of digital control delay and grid impedance uncertainty on system stability is explicitly analyzed in detail. Through this, the GCI can work stably over a wide range of the typical inductive-resistive grid impedance. In addition, it is found that the proposed strategy also has good adaptability to the filter parameter perturbation. Simulation and experimental results validate the theoretical analysis in this paper.