Abstract
To quickly and accurately estimate the parameters of the fundamental positive- and negative-sequence under the unbalanced and distorted grid voltage, a synchronization method is presented in this paper. The proposed method is based on both a harmonic decoupling network consisting of multiple dual second-order generalized integrators (MDSOGIs) and an improved frequency locked loop (IFLL), so it is called the MDSOGI-IFLL. Due to the IFLL, the system has the feature that the dynamic performance of estimating the fundamental frequency is independent of the variation of both the fundamental positive- and negative-sequence voltage. In this paper, a first-order linear frequency adaption model is established for the design of the IFLL. Finally, the good performance of the proposed MDSOGI-IFLL is validated by the simulation and experiment.
Highlights
The grid voltage parameters, such as frequency, phase angle, and amplitude, are important information for ensuring the stable operation of grid-connected inverters [1,2]
In 2002, a positive sequence filter is designed by Yuan et al to detect the fundamental positive sequence from the unbalanced and distorted grid voltage [8]
A new synchronization technique based on the multiple dual second-order generalized integrators (MDSOGIs)-improved frequency locked loop (IFLL) is proposed for three-phase grid-connected inverter under unbalanced and distorted grid conditions in this paper
Summary
The grid voltage parameters, such as frequency, phase angle, and amplitude, are important information for ensuring the stable operation of grid-connected inverters [1,2]. In 2002, a positive sequence filter is designed by Yuan et al to detect the fundamental positive sequence from the unbalanced and distorted grid voltage [8]. Several synchronization methods, such as the software. Unlike the way of reducing the bandwidth, the scheme is based on a cross-feedback network consisting of multiple dual second-order generalized integrators It can accurately extract the fundamental positive- and negative-sequence while maintaining a satisfactory dynamic response speed even when the low-order harmonics are relatively large. A new synchronization technique based on the MDSOGI-IFLL is proposed for three-phase grid-connected inverter under unbalanced and distorted grid conditions in this paper.
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