Performance Analysis of SRF PLL Type-3 with Dynamic Feed Forward Frequency Estimator for Abnormal Grid Conditions

Abstract

A phase-locked loop (PLL) is a closed-loop feedback control device that synchronizes its output signal with an input signal both in frequency and in time. This paper presents a robust method for tracking against adverse conditions of the fundamental sequence component of utility voltage. The proposed phase-locked loop (PLL) is a hybrid configuration of the phase-locked loop type-3 (SRF type-3) synchronous reference frame coupled with a feed-forward frequency estimator using a selective harmonic filtering technique. An SRF type -2 based PLL has a secondary closed path. Under the ramp frequency transition, it has a steady-state step and a frequency error. In the proposed PLL, the constant gain loop filter is used to eliminate the phase and frequency error. Feed-forward operation with selective harmonic pre-filtering allows fast-tracking with a low tracking error of the reference signal. From the results it is evident that the proposed PLL achieves a high bandwidth and quick dynamic response without endangering the stability and filtering capability. The proposed system has been tested through MATLAB® Simulink platform under abnormal conditions.