A Hidden Block in a Grid Connected Active Front End System: Modelling, Control and Stability Analysis

An LCL filter utilized in an active front end (AFE) converter can generate significant resonance, which can affect quality and stability of the system. Thus, a proper active or passive damping technique and/or a suitable controller is required to be designed for the converter. The duty cycle constraint-though inevitable in practical inverter systems-is often ignored in most of the existing literature. The effects of measurement noise on filter control system performance must be considered and evaluated under different conditions. Finally, almost all inverter control systems are implemented digitally using microcontrollers. Consequently, the effects of sampling on control system stability and performance should be evaluated as well. Thus, this paper presents stability analysis of an AFE converter-based filter design with a complete practical system configuration, including saturation and sampling blocks and measurement noises. Mathematical analysis and simulations have been carried out to validate the proposed method.