A sensorless Kalman filter-based active damping technique for grid-tied VSI with LCL filter

Employing the LCL passive filter in inverter-based distributed generation to ensure high quality power delivery comes at the expense of poor performance due to the resonance phenomenon. Literature elucidated several active approaches to mitigate this phenomenon. This paper proposes a sensorless active damping technique that is able to restrain the resonant current component through the estimation of the filter capacitor current using the Kalman filter. The Kalman filter is able to improve the quality of the estimated variables in noisy environments accompanied with measurements and model uncertainties. The effect of LCL filter parameter mismatch on the performance of the Kalman filter is assessed. Stability and convergence analyses are also conducted. An effective tuning method for the grid current controller employing a proportional-resonant controller is adopted. Experimental evaluations were conducted to validate the proposed control strategy.