Performance analysis of robust second order adaptive filters for power quality improvement in a polluted grid

Synchronization of the power electronics system with the grid system in phase and frequency is the most important concept of distributed power generation system. The synchronization speed and precision of the signals depend on the technical implementation of the phase-looked loop (PLL) system. This technology decides the quality of grid utility power to be delivered and consumed. The disturbance rejection capability of the (PLL)s can be improved by implementing different filtering techniques. Synchronous reference frame phase locked loop (SRF-PLL) is the most commonly used synchronisation technique because of its simple operation good dynamic response. The conventional (SRF-PLL) controller with high bandwidth is preferable in case of balanced and undistorted grid voltage signals, however fails to work properly in case of distorted and polluted grid conditions. So the estimated signals can have a substantial amount of unnecessary ripple. The detection system bandwidth can be reduced to attenuate the effect of harmonics on the output in case of balanced but polluted grid voltage with higher order harmonics of reasonable amplitude. In this paper a robust second order adaptive filters (SOAF) is used to extract the harmonic components existing in a balanced and polluted harmonic grid signal. This filter tracks properly even if the fundamental harmonic frequency as well as the magnitude of the grid voltage abruptly varies.