A Generic Robust Model-Based Estimator for Active Damping of Single-Phase GridTied Inverters

Abstract

This paper presents the design and analysis of a signal estimator with improved robustness applied in the active damping (AD) of a single-phase grid-tied inverter with LCL low-pass filter. The proposed estimator is based on the mathematical model of the LCL filter, with resistors in series with the converter-side inductor and capacitor for improving robustness. The implementation method is also capable of estimate multiple filter signals. The control strategy presented uses a virtual resistor based AD, that suppresses the resonance ensuring stability and robustness, helping comply with power quality standards, such as IEEE 1547 and IEC 61727. The signal necessary for achieving the AD is obtained through the estimator, dismissing the use of additional sensors. The current control structure uses grid-side current feedback with proportional-resonant controller and harmonic compensation. The system is designed by the root locus approach to achieve stability despite grid parameter variance. The estimator and overall system is analyzed through mathematical modeling, computational simulation and experimental setup. The results show that the estimator presented is capable of providing the necessary AD feedback signal, even with grid inductance variation.

Keywords

• Control
• Current Estimator
• Grid-connected inverters
• Power quality
• renewable energy
• stability