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Once modular multilevel converter (MMC) dc-side short-circuit fault occurs, the conventional fault ride-through (FRT) strategy indeed eliminates dc fault current quickly with the utilization of full-bridge submodules. Thereupon, ac-side active power declines sharply. However, instantaneous high power outage will cause ac-grid power and frequency oscillation and voltage instability, especially in MMC-based high-voltage direct-current transmission system. In order to solve this problem, a novel FRT strategy based on capacitor energy storage (CES) inside MMC (FRT-CES) is proposed, which can accomplish the clearance of dc fault current, ac-side grid support, and stable operation of MMC simultaneously. Through theoretical analysis and mathematical derivation, the prerequisite of CES utilization and universal design of improving ac-side transient characteristics are proposed and quantified. Based on the quantified results, the potential capability of MMC inner CES can be excavated to attenuate the transient change of ac-side active power after dc fault. Also, the proposed universal design is applicable to other MMCs with different capacity ratings. Finally, the threat of dc fault and its negative impact propagating into ac grid are both suppressed. Simulation and experimental results are provided to demonstrate the validity of the proposed FRT-CES strategy.

In modular multilevel converter (MMC)-based high-voltage direct current transmission system, hundreds of submodules (SMs) with large SM capacitance in each arm result in expensive cost and bulky volume. In full-bridge submodules (FBSMs)-based MMC (FB-MMC), a novel capacitor voltage ripple suppression method based on three available variables manipulation is proposed to reduce SM capacitance requirement. In the interaction of these available variables, the dominant fundamental-frequency and second-order harmonic fluctuations of SM capacitor voltage can be eliminated under different power factors. Under the proposed method, three-to-five times frequency fluctuation components will be reduced as much as possible. By establishing capacitor voltage fluctuation model, the concrete mathematical expressions of the three desired available variables under different power factors can be derived, which are easily implemented to suppress capacitor voltage ripple. Compared with normal operation, SM capacitor voltage ripple can be reduced by 80% with the proposed method when the power factor of 0.9–1 is considered. In other words, SM capacitance requirement can be reduced by 80% under the same constraint of capacitor voltage ripple. Therefore, the cost and volume of SM capacitors can be significantly reduced. Simulation results confirm the feasibility and validity of the proposed method.

The porous and biomimetic cobalt silicate@diatomite (Co

Mature pod color (PC) and pod size (PS) served as important characteristics are used in the soybean breeding programs. However, manual phenotyping of such complex traits is time-consuming, laborious, and expensive for breeders. Here, we collected pod images from two different populations, namely, a soybean association panel (SAP) consisting of 187 accessions and an inter-specific recombinant inbred line (RIL) population containing 284 RILs. An image-based phenotyping method was developed and used to extract the pod color- and size-related parameters from images. Genome-wide association study (GWAS) and linkage mapping were performed to decipher the genetic control of pod color- and size-related traits across 2 successive years. Both populations exhibited wide phenotypic variations and continuous distribution in pod color- and size-related traits, indicating quantitative polygenic inheritance of these traits. GWAS and linkage mapping approaches identified the two major quantitative trait loci (QTL) underlying the pod color parameters, i.e., qPC3 and qPC19, located to chromosomes 3 and 19, respectively, and 12 stable QTLs for pod size-related traits across nine chromosomes. Several genes residing within the genomic region of stable QTL were identified as potential candidates underlying these pod-related traits based on the gene annotation and expression profiling data. Our results provide the useful information for fine-mapping/map-based cloning of QTL and marker-assisted selection of elite varieties with desirable pod traits. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11032-021-01223-2.

phytochrome B (phyB) acts as the red light photoreceptor and negatively regulates the growth-promoting factor PHYTOCHROME INTERACTING 4 (PIF4) through a direct physical interaction, which in turn changes the expression of a large number of genes. phyB-PIF4 module regulates a variety of biological and developmental processes in plants. In this study, we demonstrate that B-BOX PROTEIN 11 (BBX11) physically interacts with both phyB and PIF4. BBX11 negatively regulates PIF4 accumulation as well as its biochemical activity, consequently leading to the repression of PIF4-controlled genes' expression and promotion of photomorphogenesis in the prolonged red light. This study reveals a regulatory mechanism that mediates red light signal transduction and sheds a light on phyB-PIF4 module in promoting red light-dependent photomorphognenesis.The online version contains supplementary material available at 10.1007/s42994-021-00037-2.

Phospholipases A (PLAs) in plants play a crucial role in growth and development, as well as in response to biotic/abiotic stresses. To-date, there has not been any well documented, systematic analysis and comprehensive study of PLAs multigene family in soybean. Therefore, we conducted genome-wide characterization of PLAs in soybean (GmPLAs). Moreover, two paralog genes, GmpPLA-IIe & GmpPLA-IIζ, were knock-out by CRISPR/Cas9 (Clustered regular interspaced short palindromic repeat/CRISPR-associated protein9) technology to study their modulating role in soybean response to multiple abiotic stresses. A total 112 GmPLAs were identified in soybean genome comprising 78 PLA1, 29 patatin-like PLAs and 5 secretory sPLA2. Tandem and segmental duplication events accounted for expansion of PLAs in soybean genome. Some of the mutant lines exhibited superior performance under flooding and drought conditions. Also, the knock-out of the two paralog genes individually or simultaneously disturbed the root's response to a phosphorus-deficient environment relative to the wild type. All the mutants performed better under iron deficient condition compared to the wild type. Our study suggests that PLAs in soybean have diverse physiological and regulatory roles in abiotic stress response and tolerance. The mutants would be useful genetic materials to unravel molecular mechanism underlying soybean response to multiple abiotic stress conditions.

Seed-weight is one of the most important traits determining soybean yield. Hence, it is prerequisite to have detailed understanding of the genetic basis regulating seed-weight for the development of improved cultivars. In this regard, the present study used high-density interspecific linkage map of NJIR4P recombinant inbred population evaluated in four different environments to detect stable Quantitative trait loci (QTLs) as well as mine candidate genes for 100-seed weight. In total, 19 QTLs distributed on 12 chromosomes were identified in all individual environments plus combined environment, out of which seven were novel and eight are stable identified in more than one environment. However, all the novel QTLs were minor (R2 < 10%). The remaining 12 QTLs detected in this study were co-localized with the earlier reported QTLs with narrow genomic regions, and out of these only 2 QTLs were major (R2 > 10%) viz., qSW-17-1 and qSW-17-4. Beneficial alleles of all identified QTLs were derived from cultivated soybean parent (Nannong493-1). Based on Protein ANalysis THrough Evolutionary Relationships, gene annotation information, and literature search, 29 genes within 5 stable QTLs were predicted to be possible candidate genes that might regulate seed-weight/size in soybean. However, it needs further validation to confirm their role in seed development. In conclusion, the present study provides better understanding of trait genetics and candidate gene information through the use high-density inter-specific bin map, and also revealed considerable scope for genetic improvement of 100-seed weight in soybean using marker-assisted breeding.

This paper proposes a novel fault ride-through strategy based on modular multilevel converter (MMC) inner capacitor energy storage (FRT -CES) to cope with dc short-circuit fault. The previous studies normally focus on the dc-side dynamic process during riding through the dc fault, but ac-side characteristics are less considered. Once dc fault occurs, a sudden large ac power loss may lead to frequency oscillation and voltage instability for ac grid system, especially in the high voltage large power occasion. With the adoption of FRT -CES, MMC inner stored energy is utilized to improve dynamic regulation of MMC ac-side power. Whatever level dc voltage drops to due to different faults, FRT-CES can regulate MMC ac-side power smoothly on its own and makes MMC transmit active power to ac grid as much as possible. Simulation results under different conditions of dc voltage sag are provided to demonstrate the validity of the proposed FRT-CES in three-phase hybrid MMC.

Phase-locked loops (PLLs) are very important in power and energy areas. Many PLLs have been proposed in recent literatures, and all these methods are to design a robust filter and let them be as a preprocessing tool before the synchronous reference frame PLL (SRF-PLL) input. Among these PLLs, a interesting PLL is Least-Error Squares (LES) Filter-Based PLL (LES-PLL), which is composed of a LES filter and a SRF-PLL. This paper does several works about LES filter-based PLL. First, through analyzing LES filter, a conclusion is that the LES filter can eliminate arbitrary harmonic series by appropriately configured, which is not proposed before. Secondly, a cascaded LES (CLES) filter is proposed to deal with the issue that the high complexity of LES filter when it is used to eliminate too much harmonics. Finally, based on CLES filter, CLES-PLL is proposed. And a realization of frequency adaptability of CLES-PLL is presented, which has low computational advantage compared with other method. To verify the effectiveness and robust performance of proposed CLES-PLL, experiments are carried out.

In this paper, we consider the compound binomial risk model with the time-correlated claims. It is assumed that every main claim will produce a by-claim but the occurrence of the by-claim may be delayed. We obtain the recursive formula of the joint distribution of the surplus immediately prior to ruin and deficit at ruin. Furthermore, the ruin probability is given by means of ruin probability and the deficit at ruin of the classical compound binomial risk model. Finally, we derive an upper bound for the ruin probability.