A Delay Compensation Method to Improve the Current Control Performance of the LCL-Type Grid-Connected Inverter

Abstract

Capacitive current feedback active damping is widely used in the LCL-type grid-connected inverter, which can effectively suppress the resonance peak of the system. However, the control delay in digital control system can change the characteristic of capacitive current feedback active damping and make the positive and negative boundary frequency of equivalent resistance is fs/6, which affects the stability of the grid-connected inverter and the robustness to grid impedance. At the same time, the control delay would introduce phase lag and limit the bandwidth of the control loop. Therefore, a delay compensation method considering both active damping characteristics and loop bandwidth is proposed, which can expand the boundary frequency to 0.43fs and greatly improve the robustness and dynamic performance of the system. Moreover, the sampling method is synchronous sampling, which strong switching-noise immunity. Simulation results verify the validity of the proposed method.