Multi-SIN Based Real-Time Impedance Estimation for Self-Commissioning Controller and Active Damping in an LCL-Grid-Tied VSI

This paper introduces a novel method for self-commissioning controllers and active damping in LCL grid-tied three phase Voltage Source Inverters (VSIs). The proposed impedance estimation method is designed with the goal of minimizing invasiveness on the grid and ultimately optimizing the result. To obtain the values of resistance and inductance, a cyclical algorithm is performed. The estimated values are then fed into the self-commissioning Proportional-Integral (PI) controller, in which the gains are calculated based on the current estimated values of the grid resistance and inductance, and into the self-commissioning active damping system, in which the resonance frequency is calculated using the estimated grid inductance and used to change the operating frequency of the active damping. The experimental results are obtained using Hardware-in-The-Loop (HIL) and actual hardware. The experimental results validate the proposed estimation along with its functioning with the self-commissioning control system and active damping. The contributions of the present paper are a presentation of active impedance estimation, a control design that adapts PI gains based on current grid impedance estimates, and an improved Active Damping method using second order Butterworth filters to enhance stability and noise mitigation.