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Red phosphorus has attracted more attention as a promising sodium storage material due to its ultra-high theoretical capacity and suitable sodiation potential. However, the low intrinsic electrical conductivity and large volume change of pristine red phosphorus lead to high polarization and fast capacity fading during cycling. Herein, surface synergistic protections on red phosphorus composite are successfully proposed by conductive poly(3,4-ethylenedioxythiophene) (PEDOT) coating and electrolyte strategy. Nanoscale red phosphorus is confined in porous carbon skeleton and the outside is packaged by PEDOT coating via in-situ polymerization. Porous carbon provides rich pathways for rapid Na+ diffusion and empty spaces accommodate the volume expansion of red phosphorus, PEDOT coating isolates the direct contact between electrolyte and active materials to form a stable solid electrolyte interphase. In addition, the reformulated electrolyte with 3 wt% SbF3 additives can stabilize the electrode surface and thus enhance the electrochemical performance, especially cycling stability and rate capability (433 mA·h·g−1 at high current density of 10 A/g).

In power electronics and power systems, the dual-phase-locked loop (DPLL) is a well-accepted approach to maintain zero steady-state errors when subjecting to a frequency ramp input. This distinctive characteristic of the DPLL may make it as a promising candidate for speed estimation in speed-sensorless drive systems. Considering this issue, a DPLL-based speed estimation scheme for linear induction motor speed-sensorless drive systems is presented in this article to achieve accurate speed estimation. The basics of the DPLL and the direct application of the DPLL scheme are provided. However, in practice, the direct application of the DPLL scheme may degrade the performance of the entire system, which includes the nonidealities in the secondary electromotive force (EMF) signals, such as harmonics and parameter variations. Accordingly, the prefilter and the amplitude normalization scheme are employed to mitigate the effect of nonidealities. Meanwhile, the small-signal model of the proposed DPLL scheme is presented, enabling the analysis of the dynamic performance and the comparison of the synchronous reference frame phase locked-loop scheme. In addition, a parameter tuning guideline of the proposed DPLL scheme is detailed by using the derived small signal model. The performance of the proposed DPLL scheme is investigated by experimental tests.

Meteorological factors have been confirmed to affect the COVID-19 transmission, but current studied conclusions varied greatly. The underlying causes of the variance remain unclear. Here, we proposed two scientific questions: (1) whether meteorological factors have a consistent influence on virus transmission after combining all the data from the studies; (2) whether the impact of meteorological factors on the COVID-19 transmission can be influenced by season, geospatial scale and latitude. We employed a meta-analysis to address these two questions using results from 2813 published articles. Our results showed that, the influence of meteorological factors on the newly-confirmed COVID-19 cases varied greatly among existing studies, and no consistent conclusion can be drawn. After grouping outbreak time into cold and warm seasons, we found daily maximum and daily minimum temperatures have significant positive influences on the newly-confirmed COVID-19 cases in cold season, while significant negative influences in warm season. After dividing the scope of the outbreak into national and urban scales, relative humidity significantly inhibited the COVID-19 transmission at the national scale, but no effect on the urban scale. The negative impact of relative humidity, and the positive impacts of maximum temperatures and wind speed on the newly-confirmed COVID-19 cases increased with latitude. The relationship of maximum and minimum temperatures with the newly-confirmed COVID-19 cases were more susceptible to season, while relative humidity's relationship was more affected by latitude and geospatial scale. Our results suggested that relationship between meteorological factors and the COVID-19 transmission can be affected by season, geospatial scale and latitude. A rise in temperature would promote virus transmission in cold seasons. We suggested that the formulation and implementation of epidemic prevention and control should mainly refer to studies at the urban scale. The control measures should be developed according to local meteorological properties for individual city.

This article proposes a review of the modeling approaches for floating offshore wind turbines (FOWTs) for nonlinear control design. The aerodynamic, hydrodynamic and mooring line dynamic modules for the FOWT have been reviewed to provide an overview of several modeling approaches with their respective features. Next, three control-oriented models from the literature are revisited by presenting their methodological approaches to modeling and identification. These three models cover the three most popular types of FOWTs. Then, the performances of these models are validated with the open fatigue, aerodynamics, structures, and turbulence (OpenFAST) code, and their performances are evaluated according to several criteria. Finally, one of the three models is used to illustrate a nonlinear second-order sliding mode control based on the twisting algorithm to optimize the performance of the FOWT in terms of energy extraction and reduction in the platform pitch oscillation.

This paper presents a speed estimation scheme by combining a second-order sliding-mode observer (SMO) with the model reference adaptive system (MRAS) in the sensorless-vector-controlled linear induction motor (LIM) drives for medium-low speed maglev applications. A state space-vector model of the LIM considering the dynamic end effects is rearranged in order to be represented by the form of the super-twisting algorithm (STA). Then, an STA-SMO-based stator current observer of the LIM with Popov's hyperstability theory is designed, which is used to replace the reference model of the MRAS-based scheme. Correspondingly, the actual stator current model is regarded as the adaptive model of the MRAS for speed estimation. Meanwhile, because the variation of stator resistance associated with stator temperature may lead to a large estimated error and even system instability, a parallel stator resistance on-line identification scheme is adopted in the proposed speed estimation scheme to reduce the speed error and improve the stability of the sensorless control system. Compared to the speed estimation schemes based on the Luerberger observer with MRAS and the single-manifold SMO, the proposed speed estimation scheme exhibits better estimated performance. The effectiveness and feasibility of the proposed speed estimation scheme have been verified by simulation and hardware-in-the-loop tests.

International audience; This paper proposes a novel Hermite neural network-based second-order sliding-mode (HNN-SOSM) control strategy for the synchronous reluctance motor (SynRM) drive system. The proposed HNN-SOSM control strategy is a nonlinear vector control strategy consisting of the speed control loop and the current control loop. The speed control loop adopts a composite speed controller, which is composed of three components: 1) a standard super-twisting algorithm-based SOSM (STA-SOSM) controller for achieving the rotor angular speed tracking control, 2) a HNN-based disturbance estimator (HNN-DE) for compensating the lumped disturbance, which is composed of external disturbances and parametric uncertainties, and 3) an error compensator for compensating the approximation error of the HNN-DE. The learning laws for the HNN-DE and the error compensator are derived by the Lyapunov synthesis approach. In the current control loop, considering the magnetic saturation effect, two composite current controllers, each of which comprises two standard STA-SOSM controllers, are designed to make direct and quadrature axes stator current components in the rotor reference frame track their references, respectively. Comparative hardware-in-the-loop (HIL) tests between the proposed HNN-SOSM control strategy and the conventional STA-SOSM control strategy for the SynRM drive system are performed. The results of the HIL tests validate the feasibility and the superiority of the proposed HNN-SOSM control strategy.

The dc-link oscillation is a typical phenomenon happening in the metro traction drive system (MTDS) due to the negative input impedance associated with the constant power load, which is considered as a thorny problem that needs to be resolved well. This paper proposes an active damping stabilization scheme based on inverter power regulation that can effectively eliminate the dc-link oscillation of the MTDS. The proposed stabilization scheme is mainly composed of two parts: 1) the generation of damping power; and 2) the inverter power control loop. The damping power, linked to the deviation of the dc-link voltage through the gain units, is fed back to the vector-controlled induction motor drive system to establish the inverter power control loop. From this control loop, the added q -axis current is obtained, which is regarded as the stabilization term. The additional stabilization term is combined with the q -axis current command of the induction motor for achieving the improvements of the drive performance and the system stability. The effectiveness of the proposed active damping stabilization scheme is verified by simulation and hardware-in-the-loop tests.

This study proposes a speed estimation scheme for the sensorless-vector-controlled linear induction motor (LIM) drives for medium-low-speed maglev applications, which is composed of two parts: (i) a sliding mode model reference adaptive system observer for speed estimation; and (ii) a parallel secondary resistance online identification for achieving the improvements of the proposed speed estimation scheme performance. The sliding mode observer (SMO) is established on the basis of the state space-vector model of the LIM considering the dynamic end effect. Based on SMO, both speed and secondary resistance estimation algorithms are obtained by utilising Popov's hyperstability theory. Moreover, the Lyapunov stability theory is adopted for the stability analysis of the proposed speed estimation scheme. The effectiveness of the proposed speed estimation algorithm has been verified and compared with the performance of the conventional speed estimation scheme based on single-manifold SMO by the simulation and hardware-in-the-loop tests.

This paper presents a model-based open-circuit fault diagnosis approach for single-phase three-level neutral-point-clamped (3LNPC) converters in electric railway application. The diagnosis algorithm, which only requires the signals existing in the control system, not only detects open-circuit faults but also identifies the faulty device among the transistors and clamping diodes. The mixed logical dynamic (MLD) model of the converter is built to estimate the grid current. The residual generated from the measured current subtracting the estimated one is analyzed under different open-circuit faults. According to the characteristics of the residual changing rate, the proposed approach allows fault localization. The proposed method is effective both in traction and regenerative braking operation and has fast diagnosis speed. Hardware-in-the-loop (HIL) experiments are carried out to verify the effectiveness of the proposed fault diagnosis algorithm.

In this study, a direct torque control (DTC) strategy based on a novel switching table for induction motor drives fed by the eight-switch three-phase inverter (ESTPI), which is the post-fault reconfigured topology for the three-level neutral-point-clamped inverter with the open-circuit fault occurring in a leg, is proposed to reduce the torque ripple and suppress the dc-link capacitor voltages offset. The influence of each basic voltage vector provided by the ESTPI on the stator flux, the electromagnetic torque and the dc-link capacitor voltages is analysed in detail, and the causes of the torque ripple and the capacitor voltages offset are also revealed. To suppress the dc-link capacitor voltages offset, a hysteresis comparator is added to regulate the dc-link capacitor voltages. Based on that, an optimised switching table to achieve not only torque ripple reduction but also dc-link capacitor voltages offset suppression is proposed. The feasibility and the effectiveness of the proposed DTC strategy are verified by simulations and experimental results.

Vascular endothelial cell growth factor (VEGF)-C promotes tumorigenesis by allowing lymph node metastasis and lymphangiogenesis, among other actions. RNA interference (RNAi) is a novel technique for suppressing target gene expression and may increase the effectiveness of cancer treatments. The present study assessed the influence of VEGF-C RNAi on the apoptosis and proliferation of mouse breast cancer cells in vitro and in vivo. A total of three pairs of small interfering RNA (siRNA) targeting mouse VEGF-C were designed and synthesized prior to transfection into 4T1 cells via a liposomal approach. Reverse transcription polymerase chain reaction, western blot analysis, a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, Hoechst 33258 staining and flow cytometry were performed in vitro to analyze VEGF-C expression, cleaved caspase-3 protein expression and 4T1 cell proliferation and apoptosis. Experiments were also conducted in vivo on BALB/c mice with breast cancer. Tumor weight and volume were measured and the number of apoptotic cells in tumor tissues was assessed by a TUNEL assay. Immunohistochemical assays and an enzyme-linked immunosorbent assay were used to measure the expression of VEGF-C in tumor tissues. The results demonstrated that the three pairs of siRNA, particularly siV2, significantly reduced VEGF-C mRNA and protein levels in 4T1 cells. siV2 was deemed to be the most efficient siRNA and therefore was selected to be used in subsequent experiments. Furthermore, in vitro studies indicated that VEGF-C RNAi significantly decreased cell growth, induced apoptosis and upregulated the expression of cleaved caspase-3 protein. Tumor weight and volume in breast cancer in vivo models was reduced by the intratumoral injection of siV2. Antitumor efficacy was associated with decreased VEGF-C expression and increased induction of apoptosis. The present study therefore indicated that VEGF-C RNAi inhibited mouse breast cancer growth in vitro and in vivo and that it may be a novel targeted therapy for breast cancer.

The relationship between common-mode voltages (CMVs) and switching states in the post-fault reconfigured topology of the three-level neutral-point-clamped inverter with open-circuit fault in a leg, which is named eight-switch three-phase inverter (ESTPI), is revealed, and based on that, two modified space vector pulse-width modulation (M-SVPWM) algorithms for the CMV reduction in the ESTPI are proposed. The maximum CMV of the ESTPI with two proposed M-SVPWM algorithms is only half of that with two conventional SVPWM algorithms. Experimental results have shown the effectiveness of two proposed M-SVPWM algorithms.

A model predictive current control scheme with dc-link capacitor voltages fluctuation suppression for the four-switch three-phase rectifier (FSTPR) in balanced grids is presented. The proposed control scheme is a type of the finite-control-set model predictive control scheme and is based on the discrete-time model of the system. From this model, the values of input currents and dc-link capacitor voltages are predicted for all switching states of the FSTPR. On the basis of a predefined cost function, the switching state, which minimises the errors between input currents and their references as well as the difference between two dc-link capacitor voltages at the next sampling instant, is selected. Simulation results are presented to confirm the effectiveness of the proposed control scheme.

Based on analysing the load currents, a current sensor fault diagnosis method for three-phase voltage source inverters in high-speed railway electrical traction drive system is presented. Then, a fault-tolerant algorithm is applied to reconstruct the three-phase currents. This fault diagnosis and tolerant control approach is an extension of the normalised average currents method, which requires no additional hardware and permits much more robust diagnostics. Experimental results confirm the effectiveness and accuracy of the proposed algorithm. It is shown that such diagnosis method can locate the faulty sensor, identify the fault modes, and recover the drive system in a fundamental period which is important to avoid catastrophic consequences.

On the basis of sampling theory, an online open-switch fault diagnosis and location method for single-phase pulse-width modulation rectifiers applied in electric railway traction is presented. First, on the basis of analysing the features of the post-fault line current under instantaneous current control strategy at low switching frequency, two specific pulse sequences for sampling line current are generated via the modulation. Then, the DC component of the sampled signal, which is easy to use for diagnostic decision, is obtained through filters. Experimental results are presented to illustrate the validity of the proposed scheme.

Four-switch three-phase inverters (FSTPIs) are post-fault reconfigured topologies for a two-level inverter with failure of a power switch or a leg, and space vector pulse-width modulation (SVPWM) strategies have been used to control FSTPIs. However, different faulty legs correspond to different topologies of FSTPIs which are controlled by different SVPWM strategies; therefore, three SVPWM strategies need to be prepared for three FSTPIs, respectively, which takes up lots of memory space in the controller and increases the complexity of the control strategy. To overcome these disadvantages, a general SVPWM strategy that can be used to control three FSTPIs is proposed. Experimental results have shown the validity and feasibility of the proposed strategy.

Space-vector pulse-width modulation (SVPWM) and carrier-based PWM (CBPWM) of eight-switch three-phase inverters (ESTPIs) which are the post-fault reconfigured topologies for the three-level neutral-point-clamped inverter with an open-circuit fault in a leg are introduced. On the basis of the PWM regular sampling method, the modulating functions of CBPWM which are equivalent to SVPWM of ESTPIs are derived, therefore the relationship between SVPWM and CBPWM of ESTPIs is revealed. The validity of the theoretical analysis is verified by experimental results.