A phase-locked loop (PLL) is a closed-loop feedback control device that synchronizes its output signal with an input signal in both frequency and 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. A 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 enables 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.
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This paper describes a shunt active power filter for compensating harmonic currents and reactive power. The shunt active power filter (SAPF) was implemented with a phase pulse modulated current control voltage source inverter. The proposed system is based on PLL synchronization with reduced fuzzy logic controller (RD-FLC). These control techniques for SAPF prove that source current is sinusoidal even when load is nonlinear. The CC-VSI inverter switching is done according to gating pulse obtained from the hysteresis controller using RD-FLC controller. The proposed system is investigated using simulation results. The effectiveness of the controller is observedin the form of total harmonic distortion, reactive power compensation and settling time of dc link voltage under non linearload condition. This technology reduced the rules of fuzzy logic controller from 49 to 37.
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