Genetic variation and recombination analysis of the GP5 (GP5a) gene of PRRSV-2 strains in China from 1996 to 2022

Porcine reproductive and respiratory syndrome virus (PRRSV) has been prevalent in China for more than 25 years and remains one of the most significant pathogens threatening the pig industry. The high rate of mutation and frequent recombination of PRRSV have exacerbated its prevalence, particularly with the emergence of highly pathogenic PRRSV (HP-PRRSV) has significantly increased the pathogenicity of PRRSV, posing a serious threat to the development of Chinese pig farming. To monitor the genetic variation of PRRSV-2 in China, the GP5 sequences of 517 PRRSV-2 strains from 1996 to 2022 were analyzed and phylogenetic trees were constructed. Furthermore, a total of 60 PRRSV strains, originating from various lineages, were carefully chosen for nucleotide and amino acid homologies analysis. The results showed that the nucleotide homologies of the PRRSV GP5 gene ranged from 81.4 to 100.0%, and the amino acid homologies ranged from 78.1 to 100.0%. Similarly, the PRRSV GP5a gene showed 78.0 ~ 100.0% nucleotide homologies and 70.2 ~ 100.0% amino acid homologies. Amino acid sequence comparisons of GP5 and GP5a showed that some mutations, such as substitutions, deletions, and insertions, were found in several amino acid sites in GP5, these mutations were primarily found in the signal peptide region, two highly variable regions (HVRs), and near two T-cell antigenic sites, while the mutation sites of GP5a were mainly concentrated in the transmembrane and intramembrane regions. Phylogenetic analysis showed that the prevalent PRRSV-2 strains in China were divided into lineages 1, 3, 5, and 8. Among these, strains from lineage 8 and lineage 1 are currently the main prevalent strains, lineage 5 and lineage 8 have a closer genetic distance. Recombination analysis revealed that one recombination event occurred in 517 PRRSV-2 strains, this event involved recombination between lineage 8 and lineage 1. In conclusion, this analysis enhances our understanding of the prevalence and genetic variation of PRRSV-2 in China. These findings provide significant insights for the development of effective prevention and control strategies for PRRS and serve as a foundation for future research in this field

Interleaved High Step-Up Current Sharing Converter with Coupled Inductors

An interleaved high-step-up current sharing DC–DC converter with coupled inductors is proposed in this paper. The operation principle and property of this converter are analyzed. The ripple of the input current in the proposed converter is decreased significantly by using the two-phase parallel interleaved input. The voltage gain is extended and the switch voltage stress is reduced by the coupled inductors. The leakage inductance of the coupled inductors reduces the reverse-recovery problem of the output diode, resulting in the reduction of reverse-recovery losses. As there are two interleaved phases in the proposed converter, the third winding of each coupled inductor is embedded in another phase. With this design, when the leakage inductance or duty cycle is asymmetrical, the current sharing performance is still positive. Consequently, the new topology is very suitable for applications to occasions with low voltage input and high voltage output, such as the fuel cell power system. Finally, the performance of this topological circuit is verified by a prototype with 500 W output

Improved Modulation Strategy Based on Minimum Energy Storage Principle for Electrolytic-Capacitor-Less Six-Switch Converter

An improved modulation strategy based on minimum energy storage for DC-link capacitance reduction in a six-switch AC-AC converter is proposed. The proposed modulation strategy enables the energy on the capacitor to accumulate and release twice each in a complete switching cycle, achieving the effect of “fast charging and discharging”. Meanwhile, the inversion and rectification are modulated synchronously. Hence, there is minimum energy stored in the DC-link capacitor. Then, the time average modeling analysis is presented to take insight analysis. When there is the same voltage ripples constraint on the DC side for the conventional and improved modulation strategies, the six-switch converter under the improved modulation strategy has the much less capacitance value of the storage capacitor and even realizes non-electrolytic capacitance. Therefore, improving the system efficiency, power density, and output waveform quality and extending the system life can be achieved. The operation principle and modulation strategy are discussed in detail. Finally, the simulation model and experimental prototype are built to verify effectiveness of the topology and correctness of the proposed six-switch AC-AC converter modulation strategy

High-Performance Bridge Modular Switched-Capacitor Converter With Small Component Requirement Based on Output Impedance Analysis for Low Loss

In this paper, a novel multilevel bridge modular switched-capacitor converter is proposed for the application in high voltage gain. Compared with the conventional switched-capacitor converters, it utilizes fewer components (switching device and capacitor) to obtain the same voltage conversion, as well as some advantages including low total power device rating, output capacitor requirement, and low output voltage ripple. In order to illustrate its superiority, an output impedance analysis method is developed, which can comprehensively evaluate a two-phase switched-capacitor converter's steady-state performance by judging its output impedance. The simple formulation developed not only permits optimization of the capacitor sizes to meet several constraints such as a total capacitance or total energy storage limit, but also permits optimization of the switch sizes subject to constraints on total switch conductance or total switch volt-ampere products. Consequently, the output impedance under the optimizations has contributed to the comparison of the latest switched-capacitor converters. As a result, the performance (based on conduction loss) of the proposed converter is proved to be optimum in fast-switching-limit impedance and does well in slow-switching-limit output impedance as well. Simulation and experimental results have validated the principle and properties of this converter and the analysis method

Multilevel DC-DC power conversion system with multiple bridge modular switched-capacitor converter

Conference Name:28th Annual IEEE Applied Power Electronics Conference and Exposition, APEC 2013. Conference Address: Long Beach, CA, United states. Time:March 17, 2013 - March 21, 2013.Power Sources Manufacturers Association; IEEE Industry Applications Society; IEEE Power Electronics SocietyMultilevel converters have been demonstrated to have many advantages such as low harmonic, low voltage stress, and high power capability. A multilevel DC-DC power conversion system with multiple bridge modular switched-capacitor converters (BMSCC) is proposed in this paper, with this conversion system, the output voltage can be changed almost continuously without any magnetic component, where the very high temperature operation is possible. Compared with other existing switched-capacitor converters, low semiconductor VA rating, low device requirement is available. Compared with other traditional step-up converters based on output impedance analysis method, the proposed converter brings about a higher efficiency advantage. Experimental results are provided to confirm the analysis and control concept. ? 2013 IEEE

Novel Quasi-Resonant Bridge Modular Switched-Capacitor Converter With Enhanced Efficiency and Reduced Output Voltage Ripple

A novel quasi-resonant bridge modular switched-capacitor converter (BMSCC) is proposed in the paper. The main merit is that its resonant circuit has high stability and simplicity, resulting from the employment of the stray inductance distributed in the circuit as a collective resonant inductor. Accordingly, the current spike during switching operation is removed due to zero-current- switching (ZCS) realization. Another distinct merit is that the proposed converter features symmetric construction. With this kind of construction, the voltage ripple of charge/pump capacitors can be cancelled out with each other and then output voltage ripple will be largely reduced. Thus, it is unnecessary to use a bulky capacitor to reduce output voltage ripple. Compared with conventional SCCs, at the same conversion ratio, the BMSCC with symmetric construction requires fewer switches and capacitors with lower voltage stress, so as to cut the size and cost and promote the power destiny further. It is also noteworthy that the symmetric construction character assures that the two symmetric parts can work independently under a simplified control strategy. In addition, the modular configuration contributes to convenient voltage extension conveniently. The simulation and experimental results of a 100 W prototype with a voltage conversion ratio of eight validate the principle and features of this topology

A novel quasi-resonant bridge modular switched-capacitor converter with enhanced efficiency and reduced output voltage ripple

A novel quasi-resonant bridge modular switchedcapacitor converter (BMSCC) is proposed in the paper. The main merit is that its resonant circuit has high stability and simplicity, resulting from the employment of the stray inductance distributed in the circuit as a collective resonant inductor. Accordingly, the current spike during switching operation is removed due to zerocurrent- switching (ZCS) realization. Another distinct merit is that the proposed converter features symmetric construction.With this kind of construction, the voltage ripple of charge/pump capacitors can be cancelled out with each other and then output voltage ripple will be largely reduced. Thus, it is unnecessary to use a bulky capacitor to reduce output voltage ripple. Compared with conventional SCCs, at the same conversion ratio, the BMSCC with symmetric construction requires fewer switches and capacitors with lower voltage stress, so as to cut the size and cost and promote the power destiny further. It is also noteworthy that the symmetric construction character assures that the two symmetric parts can work independently under a simplified control strategy. In addition, the modular configuration contributes to convenient voltage extension conveniently. The simulation and experimental results of a 100Wprototype with a voltage conversion ratio of eight validate the principle and features of this topology. ? 1986-2012 IEEE