System Identification of the LCL Filter Parameters in Grid-Tied Voltage Source Inverters

A method is presented to estimate the parameters of inductive-capacitive-inductive (LCL) filters in grid-tied voltage source inverter (VSI) systems. The estimation approach involves specific filtering schemes to overcome the presence of time-derivative quantities in the dynamic model of LCL filters and also to remove the disturbing effects of the grid source voltage and its harmonics on the estimation process. The inverter current is measured while the pulse width modulation (PWM) reference signals available through the VSI controller outputs are combined with measurements of the DC link voltage to quantify the inverter voltage for the estimation process. Simulation and experimental results for a grid-tied VSI are provided to demonstrate the effectiveness of the algorithm.