Impedance Modeling and Stability Analysis of DFIG-Based Wind Energy Conversion System Considering Frequency Coupling

Impedance-based stability analysis is an effective method for addressing a new type of SSO accidents that have occurred in recent years, especially those caused by the control interaction between a DFIG and the power grid. However, the existing impedance modeling of DFIGs is mostly focused on a single converter, such as the GSC or RSC, and the influence between the RSC and GSC, as well as the frequency coupling effect inside the converter are usually overlooked, reducing the accuracy of DFIG stability analysis. Hence, the entire impedance is proposed in this paper for the DFIG-based WECS, taking coupling factors into account (e.g., DC bus voltage dynamics, asymmetric current regulation in the dq frame, and PLL). Numerical calculations and HIL simulations on RT-Lab were used to validate the proposed model. The results indicate that the entire impedance model with frequency coupling is more accurate, and it is capable of accurately predicting the system’s possible resonance points

The amplification profiles of <i>Aphelenchoides besseyi</i> isolates; (A) <i>Abe GH5-1</i> gene, (B) <i>Abe GH45-2</i> and (C) <i>Abe GH45-3</i>.

<p>(A) An <i>Abe GH5-1</i> gene product of 1688 bp was amplified exclusively from the Fm, Fsx and Fgk isolates. Both <i>Abe GH45-2</i> (B) and <i>Abe GH45-3</i> (C) primers could amplify a major band from all five <i>Aphelenchoides besseyi</i> isolates.</p

The protein and genomic DNA sequences of <i>Abe GH5-1</i>.

<p>The Abe GH5-1 protein contains a SCP-like domain at the N-terminus and a GH5 cellulase domain at the C-terminus, as well as five introns were found in the <i>Abe GH5-1</i> gene.</p

A maximum likelihood phylogeny of nematode GH5 proteins. Orthologues of nematodes are represented using brown branches, and those of other species are shown as grey branches labeled with either green (bacteria) or blue (non-nematode eukaryotes) arcs.

<p>Nematodes included in GH5_1 are <i>Pristionchus pacificus</i> (clade V). The phylogeny was computed using FastTree (as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158663#sec002" target="_blank">Materials and Methods</a>), and a high bootstrap support values of 0.91 reveals that GH5 orthologues of nematodes can be clearly distinguished from those of other eukaryotes and bacteria. For more details, please see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158663#pone.0158663.s005" target="_blank">S5 Fig</a>.</p

The symptoms on the bird’s-nest fern leaves 21 days after inoculated with different host-origin <i>Aphelenchoides besseyi</i> isolates.

<p>The bird’s-nest fern leaves inoculated with the (A) Fm, (B) Fsx and (C) Fgk isolates showed typical dark-brown patches. No symptoms were observed on bird’s-nest fern leaves inoculated with the rice-origin (D) Rl and (E) Rdg isolates. Leaves treated with <i>Alternaria citr</i>i hyphal suspensions were used as (F) controls. The scale bars represent 10 cm.</p

Identification of the <i>Abe GH5-1</i> gene by Southern blotting.

<p>Genomic DNA isolated from the five <i>Aphelenchoides besseyi</i> isolates were digested with <i>Hinf I</i>, and it was hybridized with an AbeFm-GH5-specific DNA probe.</p

Localization of the <i>Abe GH5-1</i> gene transcript in the <i>Aphelenchoides besseyi</i> by <i>in situ</i> hybridization with digoxigenin-labelled antisense (A and B) or sense probes (C).

<p>The scale bars represent 20 μm. O: ovary, V: vulva, S: spicule and T: testis.</p

Glycoside Hydrolase (GH) 45 and 5 Candidate Cellulases in <i>Aphelenchoides besseyi</i> Isolated from Bird’s-Nest Fern

<div><p>Five <i>Aphelenchoides besseyi</i> isolates collected from bird’s-nest ferns or rice possess different parasitic capacities in bird’s-nest fern. Two different glycoside hydrolase (GH) 45 genes were identified in the fern isolates, and only one was found in the rice isolates. A <i>Abe GH5-1</i> gene containing an SCP-like family domain was found only in the fern isolates. <i>Abe GH5-1</i> gene has five introns suggesting a eukaryotic origin. A maximum likelihood phylogeny revealed that Abe GH5-1 is part of the nematode monophyletic group that can be clearly distinguished from those of other eukaryotic and bacterial GH5 sequences with high bootstrap support values. The fern <i>A</i>. <i>besseyi</i> isolates were the first parasitic plant nematode found to possess both GH5 and GH45 genes. Surveying the genome of the five <i>A</i>. <i>besseyi</i> isolates by Southern blotting using an 834 bp probe targeting the GH5 domain suggests the presence of at least two copies in the fern-origin isolates but none in the rice-origin isolates. The <i>in situ</i> hybridization shows that the <i>Abe GH5-1</i> gene is expressed in the nematode ovary and testis. Our study provides insights into the diversity of GH in isolates of plant parasitic nematodes of different host origins.</p></div

The gene structures of three GH45 genes in <i>Aphelenchoides besseyi</i>.

<p>The introns not to exist in the <i>Abe GH45-1</i> and presence in the <i>Abe GH45-2</i> and <i>Abe GH45-3</i> genes. Two introns, 163 bp and 142 bp, were found in the <i>Abe GH45-2</i> and a 46-bp sized intron was found in the <i>Abe GH45-3</i> gene.</p