Implementation of proportional-integral (PI) controllers in synchronous reference frame (SRF) is a wellestablished current control solution for electric drives. It is a general and effective method in digital control as long as the ratio of Sampling to Fundamental (S2F) frequency ratio, rS2F, remains sufficiently large. When the aforesaid condition is violated, such as operations in high-speed or high-power drives, the performance of the closed-loop system becomes incrementally poor or even unstable. This is due to the cross-coupling of the signal flow between d and q axes, which is introduced by the SRF. In this article, an accurate model of current dynamics which captures the computational delay and PWM characteristics in discrete time domain is developed. This motivates the investigation of eliminating cross-coupling effects in PMSM drive systems. A new current control structure in the discrete time domain is proposed targeting full compensation of cross-coupling effects of SRF whilst improving dynamic stiffness at low S2F ratios. The matching simulation and experimental results carried out on a 5-kW high speed drive corroborate the theoretical analysis.

Dihydroflavonol 4-reductase (DFR) is a key enzyme in the flavonoid biosynthetic pathway and is essential for the formation of plants’ color. In this study, 26 BnDFR genes were identified using 6 Arabidopsis DFR genes as reference. The physicochemical properties, subcellular localization, and conserved structure of BnDFR proteins were analyzed; the evolutionary relationship, collinearity analysis, and expression characteristics of BnDFR genes were studied; and the correlation between the expression level of BnDFR genes and anthocyanin content in rape petals were analyzed. The results showed that the 26 BnDFRs were located in chloroplasts, cytoplasm, nuclei, and mitochondria, distributed on 17 chromosomes, and divided into 4 groups; members of the same group have a similar function, which may be related to the environmental response elements and plant hormone response elements. Intraspecific collinearity analysis showed 51 pairs of collinear genes, and interspecific collinearity analysis showed 30 pairs of collinear genes. Analysis of the expression levels of BnDFRs and anthocyanin content in different color rape petals showed that BnDFR6 and BnDFR26 might play an important role in the synthesis of anthocyanins in rape petals. This provides theoretical guidance for further analysis of the anthocyanin anabolism mechanism involved in the DFR gene in Brassica napus.

Synchronous reluctance (Syn-Rel) machines with embedded permanent magnets (PMs) are research hotspots in variable speed motor drives due to their robust rotor structure and wide constant power speed range (CPSR). In this paper, the potential of PM-assisted Syn-Rel machine to be next generation heavy duty traction motor solution has been investigated, with special attention put on one key geometric parameter, i.e., airgap length. Careful machine design and optimization has been conducted based on geometric parametrization including airgap length variation, for 15000rpm peak speed and 350kW peak power output. In low speed operations, the influence of airgap length on different torque components has been analyzed in detail based on the frozen permeability method. In field weakening region, the variation trend of several key parameters such as output power, torque ripple, and power losses have been investigated along with airgap length. It is found that with high electric and magnetic loading, reducing the electromagnetic airgap length is not always beneficial. There exists a suitable airgap length value to comprehensively balance torque/power density, cooling capability, efficiency and reliability. Numerical FEA and experimental tests of the prototype are combined to verify the conclusions.

In high performance drive systems, wide bandwidth and reference tracking accuracy of current control loop are fundamental requirements. The conventional PI controller provides robustness against the machine parameter mismatching and zero steady-state error, but its dynamic performance degrades at high-speed due to the bandwidth limitation. In this paper, a new control structure of discrete PI controller with a deadbeat response is proposed, which combines the advantage of conventional PI controller with deadbeat characteristic. The proposed controller shows a decoupled tracking performance of up to 15% of the switching frequency, while also providing an extra control freedom of the disturbance rejection, which effectively improves the system stability. Experiments show a reduction of oscillation by 30% compared to the conventional PI and the validity and applicability of the proposed control method for high-speed applications with low sampling to fundamental frequency ratios.

Rapeseed is an important oil crop in China. Low winter temperatures (LT) often limit plant growth and cause seed yield losses in rapeseed. Although exogenous application of 5-aminolevulinic acid (ALA) has been shown to enhance plant tolerance to various abiotic stressors, its physiological mechanisms for improving cold tolerance in rapeseed are not yet fully understood. In this study we investigated the physiological responses to exogenous ALA using the chilling-tolerant cultivar Zayou15 (ZY15) and the chilling-sensitive cultivar Huiyou 49 (HY49) under low-temperature stress. The results showed that low-[A1] temperature stress caused a considerable decrease the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), as well as in the contents of endogenous hormones GA, IAA, and CTK. These resulted in the accumulation of reactive oxygen species, with both the content of H2O2 and O2- showing considerable increases, as well as in membrane lipid peroxidation with considerable increases in both malondialdehyde content (MDA) and relative electrical conductivity (REC). Moreover, the contents of chlorophyll（Chl）b, Chl a/Chl b, transpiration rate (Tr), net photosynthesis (Pn), stomatal conductance (Gs), and intercellular CO2 concentration (Ci) were considerably decreased by low-temperature stress, resulting in remarkable growth inhibition (with the aboveground fresh weight significantly decreased). Although, 20 mgL-1 exogenous ALA significantly reduced O2-, H2O2, and MDA content, and REC in both cultivars; it did not increase POD, SOD, CAT, or ascorbic acid peroxidase (APX) under short-term low-temperature stress (12–48 h). However, ALA substantially increased the activities of GA, Pn, Tr, Gs and Ci, resulting in a considerable increase in aboveground fresh weight. Post-treatment spraying of rapeseed plants with 5 mL of 20 mg·L-1 ALA was more effective than pre-treatment spraying. Both cultivars sprayed with ALA post-treatment showed greater reduction in MDA content. The optimum ALA dosage and concentration were 5 mL and 20 mg·L-1, respectively, leading to considerable decrease in MDA, and REC content and increase in Chl content in leaves. In conclusion, our results demonstrate that exogenous application of ALA is an appropriate strategy for rapeseed to resist winter low-temperature stress.