Design and Implementation of a Single Grid- Current Feedback Active Damping Strategy for LCL-Filtered Grid-Connected Inverters

Abstract

This paper investigates a design method for regulating the injected current of renewable energy systems
connected to the power grid through single- or three-phase voltage source inverters equipped with LCL filters.
Inspired by the structure of passive damping schemes, a virtual resistance concept based on single grid-current
feedback is adopted to achieve active damping without requiring additional sensors, thereby reducing system
cost. Closed-loop analysis reveals that the proposed control strategy is equivalent to a conventional dual-loop
control with capacitor-current feedback. However, such equivalence can only be achieved through an accurate
second derivative approximation. To address the noise sensitivity associated of the derivative operation
connection of a pure second derivative and a second-order low-pass filter is proposed. A proportional-resonant
controller is employed to track the AC reference current, and a straightforward design procedure for determining
the active damping controller parameters is introduced. To evaluate the performance of the proposed control
method, the system is experimentally tested on a laboratory setup under distorted grid voltage. The obtained
results confirm the effectiveness of the selected active damping approach.