The important agronomic traits, such as grain type, plant height, and panicle composition, are closely related to rice yield, and their gene inheritance is complex. Chromosome segment substitution lines (CSSLs) are useful materials for studying these complex traits. An excellent CSSL, Z746, containing seven substitution segments and with an average substitution length of 3.99 Mb, was identified from Nipponbare as a recipient and 'Xihui 18' as a donor parent. There were significant differences in plant height, panicle composition and grain size between Z746 and Nipponbare. Furthermore, a total of 36 quantitative trait loci (QTL) were detected on chromosomes 2, 3, 4, 6, and 11 in the secondary F 2 population constructed by hybridization between Nipponbare and Z746. Five of them may be alleles of the cloned genes, such as qPH3-1, and eight can be detected by multiple times, indicating that these were genetically stable major QTLs. The grain length in Z746 was mainly controlled by four QTLs 作 物 学 报 第 47 卷 (qGL3, qGL4, qGL2, and qGL6), and the phenotypic variation of qGL3 and qGL4 for grain length was 60.28% and 27.47%, respectively. Plant height was controlled by five QTLs, panicle length by four QTLs, grain number per panicle by two QTLs, and the 1000-grain weight by two QTLs. Eight single segment substitution lines (SSSLs) were developed in F 3 population by molecular marker-assisted selection (MAS), and relevant QTLs verification was conducted in F 4 . Finally, 24 QTLs were detected by 8 SSSLs and the repeat detection rate was 66.7%, indicating that these QTLs were genetically stable. These results provide a good foundation for further research on genetic mechanisms of the target QTLs and molecular design breeding.

This paper focuses on the power grid oscillation of grid-side converter (GSC) in doubly-fed induction generator (DFIG) caused by grid sub-synchronous oscillation (SSO), and designs a measure to improve the output power quality of GSC. Firstly, the influence mechanism of multipath disturbance of GSC under SSO is sorted out, and the disturbance factors and action modes are clarified. Secondly, the influence of SSO on the output estimation of phase-locked loop (PLL) in the control strategy and power calculation process is analyzed. Furthermore, the mathematical model of GSC output power considering the influence of PLL is established. At the same time, the key factors of SSO for GSC power oscillation suppression strategy are determined by analyzing the oscillation suppression effect of quasi-resonant controller when SSO amplitude, frequency and phase change. Based on the above theoretical analysis and research, the resonant controller is used to eliminate the estimation error of the PLL; at the same time, an adaptive algorithm is designed according to the mechanism analysis of SSO characteristic changes to improve the fixed resonant frequency of the quasi-resonant controller, and a DFIG-GSC sub-synchronous power oscillation suppression strategy based on the adaptive quasi-resonant controller is proposed, thus eliminating the influence of SSO on the multipath disturbance of GSC and improving the power quality of its output. Finally, the effectiveness of the proposed suppression strategy is verified by simulation and experimental results.INDEX TERMS Power quality, doubly-fed induction generator (DFIG), grid side converter (GSC), phase locked loop (PLL), sub-synchronous oscillation frequency change, adaptive quasi-resonant controller.

With the increasing utilization of electronic equipment in the power system, sub-synchronous oscillation (SSO) has occurred many times and caused off-grid accidents because of power oscillation. SSO has become one of the main problems that restrict the development of new energy. In this paper, power oscillation in grid-side converters (GSCs) in doubly-fed induction generators (DFIGs) under SSO is studied. Firstly, the influence mechanism of SSO on GSC multipath disturbance is studied. Secondly, the problem of coupling oscillation caused by PLL output errors after coordinate transformation is studied, and the mathematical model of GSC output power considering SSO multipath disturbance is established. By analyzing the oscillation suppression ability of the quasi-resonant controller under variable SSO states, the key influencing factors of SSO for GSC power oscillation suppression strategies are determined. Furthermore, based on the above theoretical analysis and research, an improved PLL is designed to eliminate the influence of its output errors on the disturbance of GSC. At the same time, a DFIG-GSC power oscillation suppression strategy using an adaptive quasi-resonant controller is designed to eliminate the influence of SSO on the multi-path disturbance of GSC. Finally, the effectiveness of the proposed suppression strategy is verified using simulation and experimental results.

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In this paper, we establish a framework for the construction of Moran set driven by dynamics. Under this framework, we study the Hausdorff dimension of the generalized intrinsic level set with respect to the given ergodic measure in a class of non-uniformly hyperbolic interval maps with finitely many branches.