An Efficient FPGA Implementation of a Quadrature Signal-Generation Subsystem in SRF PLLs in Single-Phase PFCs

Abstract

Synchronization with the utility voltage is naturally carried out by a diode bridge stage in single phase active rectifiers, while an active synchronization is included in the control algorithms applied to modern bridgeless topologies. Sensorless line current rebuilding algorithms also need synchronization with the line voltage to compensate at least for part of the current estimation error. The PLL circuits employed in single phase AC-DC converters are reviewed and a new digital PLL algorithm, based on the synchronous reference frame, is proposed. It is implemented in a Field Programmable Gate Array (FPGA) to utilize the parallelism and superior time resolution. Considering a restricted frequency variation of the line voltage around the central frequency, the orthogonal signal is obtained by a discrete differential operator designed to ensure unity gain at the central frequency. Its performance, including the memory and computational cost, versus previously consolidated algorithms implemented in the same device is analyzed. Simulations and experimental results prove its suitable behavior in steady-state at different line frequencies and under line voltage and frequency transients.

Power Quality Enhancement in Residential Smart Grids Through Power Factor Correction Stages

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Frequency Estimation for Grid-connected Converters under Time-varying Harmonics and Inter-harmonics

“…Although the SRF scheme was originally designed for threephase systems, several authors have directed the principle to single-phase cases [26], [27]. For this, the single phase system is considered as a balanced three-phase system, where the αcomponent (from the Clarke's transform) is represented by the single-phase voltage of the network, while the β-component (or quadrature companion signal -QCG) is synthesized using several approaches [28], [29]. Thus, these two quadrature signals are equivalent to a "virtual" or an "emulated" three-phase system, in a fixed-frame representation to which the same ideas developed for three-phase SRF-PLLs can be directly applied [15].…”

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“…Thus, the performance of the system is compromised. In addition, the synchronous reference frame (SRF) [12], pulsewidth modulation technique [13], extended Kalman filter [14] etc. are generally used for control of grid connected converter for synchronisation of the grid.…”