Capacitor Current Feedback Active Damping with Generalized Integrator-Based Differentiator for LCL-type Inverters

Abstract

Capacitor Current Feedback Active Damping (CCFAD) is widely adopted in the industry because it can effectively achieve resonant damping of LCL filters by simply adding a current sensor. However, due to digital control delays, conventional proportional CCFAD exhibits virtual negative resistance in frequency ranges higher than one-sixth of the sampling frequency (fs/6). This virtual negative resistance introduces open-loop Right-Half Plane (RHP) poles, making the inverter system easily unstable under varying grid inductance conditions. Therefore, the Virtual Positive Resistance Region (VPRR) must be extended to construct a robust inverter system. This paper proposes a simple and effective method for extending VPRR through capacitor current feedback with a Generalized Integrator (GI)-based differentiator. © 2024 IEEE.