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The voltage-source grid-supporting inverters (GSIs) are important to establish and support the frequency and voltage of a microgrid (MG) in both islanded and grid-connected modes. Traditionally, a cascaded control strategy that includes an external droop-based control loop and an inner proportional-integral (PI) based voltage and current control loop is adopted to control a GSI, which shows barely inertia and limited control performance. In this paper, a novel cascaded control strategy is proposed for a GSI. In the external loop, a VSG-based control strategy is adopted to increase the frequency stability of the MG, and a novel synchronization control method that does not use a complex PLL unit is proposed to satisfy the plug-and-play requirements of a GSI. In the inner voltage and current control loop, the paper proposes an SMC-based vector control strategy which uses the fixed switching frequency and inherits the robustness and fast response speed of the SMC control. Both simulation and experiments demonstrate the effectiveness and improved performance of the proposed control strategy.

This paper proposes a novel distributed event-triggered secondary control method to overcome the drawbacks of primary control for DC microgrids. With event-triggered distributed communication, the proposed control method can achieve system-wide control of parallel operating DGs with two main control objectives: a) estimate the average bus voltage and regulate it at the nominal value; b) achieve accurate current sharing among the DGs in proportion to their power output ratings. Furthermore, the proposed control strategy can be implemented in a distributed way that sharing the required tasks between the DGs. Thus, it shows the advantages of flexible and scalable. Furthermore, this paper also proposes a simple event-triggered condition that does not need extra state estimator. Thus, limited communication among neighbors is required only when the event-triggered condition is satisfied, which significantly reduce communication burden in the cyber layer.

With the increasing integration of PV generation in AC microgrids, it is challenging to keep the stability of system frequency due to the intermittent and stochastic nature of PVs. Thus, in order to reduce the investment and maintenance costs of storage systems, the electric utility has shown increasing interest in calling on PVs to provide frequency regulation services. In this paper, a novel sliding mode control (SMC) based adaptive power point tracking (APPT) control strategy is proposed to provide bi-directional primary frequency regulation (BPFR) of an AC microgrid. In this strategy, in order to restrain the variation of frequency, the sliding mode surface is adaptively regulated to provide an adaptive power reserve. Thus, the PVs will have a power headroom to regulate the frequency both up and down through releasing the reserved power or increasing the reserves of the PV systems. Furthermore, the sliding mode surface is adaptively regulated only based on the locally measured frequency of the microgrid without the requirements of communication, detailed PV model, irradiance sensors as well as MPP estimators. Thus, the proposed control strategy shows the advantages of easy to implement and reduces the investment and maintenance costs of installing storage systems or irradiance sensors.

Direct‐drive permanent magnet synchronous generators (DDPMSGs) are gaining more and more attention in the field of wind power because of the advantages of simple structure, high efficiency and high reliability. However, due to the extremely low rotational speed, large volume and heavy weight of DDPMSGs, it poses serious challenges for transportation and installation, which limits its application. Therefore, a DDPMSG with novel toroidal windings (NTW) is proposed to improve power density in this paper. Unlike regular windings, each coil of the NTWs is wound onto the stator yoke in the same direction. The special configuration enables the generator to have higher winding coefficient, so that the DDPMSG with NTWs (NTW‐DDPMSG) can achieve higher power density than traditional fractional slot concentrated windings (FCW). The proposed topology and operating principles are described in detail. To verify the merits of the proposed NTW‐DDPMSG, the electromagnetic parameters of two external rotor surface‐mounted DDPMSGs equipped with NTW and FCW respectively are designed. The characteristics of air‐gap magnetic field, no‐load electromotive force, output power, loss and efficiency are analysed on the conditions of different loads and speeds. Comparison results show that the proposed NTW‐DDPMSG has higher power density than FCW‐DDPMSG.

With the increasing integration of renewable and sustainable energy in microgrids, the prediction errors of these energy resources may degrade the economic efficiency of a microgrid because there is a time-scale gap between the large time-scale economic dispatch and the small time-scale frequency restoration control. In this paper, a distributed event-triggered secondary control method is proposed to deal with the economic dispatch and frequency restoration control for droop-controlled AC microgrids. The proposed control strategy can ensure economic dispatch and frequency restoration control at the same time, which reduces the operation cost of AC microgrids by bridging the time-scale gap between them. Furthermore, a simple event-triggered condition is designed to implement the proposed event-triggered secondary control, which only requires the communication between the neighboring agents when a significant change of state in the microgrid occurs, which is easy to implement and can reduce the communication burden.

Marsdenia tenacissima injection (MTE), a traditional Chinese medical injection extracted from the rattan of Marsdenia tenacissima (Roxb.) Moon, has been approved for clinical use in China as an adjuvant therapeutic agent in multiple cancers, including esophageal cancer, gastric cancer, lung cancer, and liver cancer. However, the activity and mechanism of MTE on prostate cancer (PCa) remain to be defined.To investigate the activity and the underlying mechanism of MTE in the treatment of PCa.The component characterization of MTE was analyzed by HPLC-CAD-QTOF-MS/MS technology. Cell Counting Kit-8 (CCK-8) assay was used to assess PCa cell proliferation. Colony formation assay was applied to detect the clonogenic ability of the cells. MetaboAnalyst5.0 database was employed to analyze the altered metabolites of PC3 cells treated with MTE obtained by UPLC-QTOF-MS/MS. Combined with metabolomics analysis and network pharmacology, we predicted the potential targets, which further were verified by Western Blot, RT-qPCR, and Immunohistochemistry assays. Finally, SeeSAR software was applied to predict the potential active components of MTE against PCa.A total of 21 components in MTE were confirmed by HPLC-CAD-QTOF-MS/MS analysis. MTE inhibited the proliferation and colony formation of PCa cells. A total of 20 metabolites closely related to glycerophospholipid metabolism, glycolysis/gluconeogenesis, and tricarboxylic acid (TCA) cycle were significantly changed in PC3 cells treated with MTE. The network pharmacology analysis revealed that MTE suppressed the growth of PC3 cells might by regulating the ErbB2-GSK3β-HIF1α signaling axis. Furthermore, we also confirmed that stimulation of MTE significantly inhibited the phosphorylation of ErbB2 at Tyr877 and the activities of its downstream signal transducers (GSK3β and HIF1α) in PCa, as well as the mRNA levels of critical factors (IDH2, LDHA, and HIF1A) in the tricarboxylic acid (TCA) cycle. Molecular docking further suggested that Tenacissimoside E, cryptochlorogenic acid, and scopoletin might be the active ingredients of MTE for PCa treatment.This study proposed that MTE exerts a potential anti-tumor effect in PCa through inhibiting ErbB2-GSK3β-HIF1α signaling axis, which may be related to the TCA cycle.

Owing to its many benefits, including a high power density, high accuracy, and smooth feeding, the permanent magnet linear synchronous motor (PMLSM) is widely used in many industrial applications. However, the power-angle curve of the PMLSM has an obvious left deviation phenomenon, which affects the performance of the PMLSM. Hence, in this study, the basic reasons and critical conditions for the deviation are investigated. First, the cause of the deviation is analysed, and a finite-element model is established to verify the analytical results. Then, using an analytical method, the critical condition of the power-angle deviation for a PMLSM is determined. Finally, a prototype of a PMLSM is manufactured, and the simulated and experimental results are compared to verify the conclusion. The good comparison results validate the conclusion of this study. This research on the power-angle characteristics of the PMLSM will provide a significant reference for the design research and precise control of PMLSMs.

Developing marine resources (such as abundant wind energy and wave energy) is an inspiring way to ease the global fossil energy crisis. In this paper, a wind-wave combined energy conversion (WWCEC) system based on a linear-rotary generator is introduced. The corresponding novel double-stator linear-rotary permanent magnet generator (DSLRPMG) is presented, and its multi-objective optimization of key structural parameters is finished based on TOPSIS decision making to enhancing no-load back-electromotive force (BEMF), decreasing the cogging torque, detent force and total harmonic distortion (THD) of BEMF. The specific optimization process is given, including the sensitivity analysis of different structure variables and the weight coefficients determination of different optimization objects. The optimized and performances are exhibited through finite element calculation finally, which prove that the multi-objective optimization of the DSLRPMG is achieved, and the decision-making results are reasonable.

Tubular permanent magnet linear generator (TPMLGs) is widely used in direct drive wave energy conversion system (DD-WECs) due to their simple structure, friendly maintenance and high efficiency. Unfortunately, the power density of this type of generator is relatively small due to their low operation speed. To improve the power density, a TPMLG with 120° phase belt toroidal windings (120°-TPMLG) is proposed in this paper. Firstly, the structure of the 120°-TPMLG is introduced, and its operation principle is analyzed by describing the variation of the magnetic field generated by the permanent magnet. Furthermore, to investigate the performances and the unique advantages of the 120°-TPMLG, a traditional toroidal windings tubular permanent magnet linear generator (T-TPMLG) is compared with the generator based on the similar dimensions. Finally, the unstable AC electricity generated by the generators is rectified, which can transform the AC electricity to the stable DC electricity for supping the equipment. The results indicate that the proposed 120°-TPMLG has superiority in detent force, power density and generation efficiency than the T-TPMLG.

Ocean-going vessels frequently experience severe weather conditions. Occasionally, the actual environmental loads are much larger than design values, resulting in deviations from design conditions that may cause serious structural damage. A structural digital twin can enhance predictability and reliability of marine structures, and thus provide vessel operators, owners, and stakeholders with a more accurate overview of a vessel’s condition. It can also help reduce lifecycle costs through proposing rational and optimal inspection, maintenance, repair programs, and assist on maximizing service life and mission availability. This paper uses a benchmark vessel to investigate structural behaviors of the vessel through dynamic loading approach. The correlation between structure members and critical responses are established, and high stress concentration areas have been identified. Subsequently, this paper develops a conceptual digital twin architecture. The proposed digital twin predicts responses of the entire structure to measured or predicted environmental conditions with a hybrid model combining numerical simulations with measurements. While the traditional structural monitoring system focuses on the health condition of typical hot spots, the proposed digital twin may improve structural health awareness of the entire hull structure based on a limited number of sensors.

A tubular permanent-magnet linear generator is suitable for direct drive wave energy conversion owing to its simple structure, easy maintenance and high efficiency. In this study, a novel Gramme winding tubular permanent-magnet linear generator (GW) is designed to increase power density. First, the structure of the Gramme winding and concentrated winding tubular permanent-magnet linear generator is introduced and the operation principle of the generator is analysed. Second, the initial parameters of GW are determined based on the similar overall dimensions to those of the concentrated winding tubular permanent-magnet linear generator. Third, the air gap flux density, external characteristics, voltage regulation, output power, and loss of the two generators are compared. Finally, the DC load capacities of the two generators are compared based on a three-phase full-control bridge rectifying circuit. The results show that the GW has a higher power density than the latter.

Building integrated photovoltaic (BIPV) is one of the most efficient ways to utilize renewable energy in buildings. However, the stochastic characteristic of PV power generation and load challenges the optimal dispatch of the BIPV. This paper proposes an optimal scheduling strategy of BIPV microgrid considering virtual energy storage (VES), which intends to further improve the operating economy of a BIPV microgrid. Firstly, existing research findings and gaps in this research area were analyzed. Then, the mathematical model of each unit in the system was created, meanwhile, the air conditioner-based VES (ACVES) model and electric water heater-based VES (EWHVES) model are built by exploiting the heat/cold storage capability of building and the electric water heater, respectively. Next, the optimal scheduling model considering the VES is designed. Finally, the optimal scheduling model is solved by CPLEX to obtain the optimal scheduling strategy that reduces the operating cost of the system. Simulation results demonstrate that the proposed strategy can reduce the operating cost of the system. Furthermore, the VES shows the potential to replace the battery energy storage system.

Obtaining appropriate parameters of photovoltaic models based on measured current-voltage data is crucial for the evaluation, control, and optimization of photovoltaic systems. Although many techniques have been developed to solve this problem, it is still challenging to identify the model parameters accurately and reliably. To improve parameters identification of different photovoltaic models, a multiple learning backtracking search algorithm (MLBSA) is proposed in this paper. In MLBSA, some individuals learn from the current population information and historical population information simultaneously, which aims to maintain population diversity and enhance the exploration ability. While other individuals learn from the best individual of current population to improve the convergence speed and thus enhance the exploitation ability. In addition, an elite strategy based on chaotic local search is developed to further refine the quality of current population. The proposed MLBSA is employed to solve the parameters identification problems of different photovoltaic models, i.e., single diode, double diode, and photovoltaic module. Comprehensive experimental results and analyses demonstrate that MLBSA outperforms other state-of-the-art algorithms in terms of accuracy, reliability, and computational efficiency.

The wave runup caused by a vertical cylinder surging in regular waves is studied both experimentally and numerically. The so-called DualSPHysics Smoothed Particle Hydrodynamics (SPH) code is used for the 3-D numerical modelling. A wide range of cylinder sizes and wave conditions is investigated with results comparing favourably between the experimental and SPH model under both fixed and forced-surge conditions. The experimental and SPH results are further used to predict the maximum runup amplification, in particular the ratio of the runup caused by the surging cylinder to that of the fixed, over the phase difference between the incident wave and surge motion. This maximum runup ratio has been analysed for its dependence on factors such as wave steepness, wave scattering and surge amplitude. An empirical equation is proposed for predicting the maximum runup ratio from known incident wave and surge conditions. Comparison with results from linear solvers suggests that the linear solvers under-predict the full nonlinear runup by a factor of 1.3–1.5.

The six-phase direct-drive (DD) permanent magnet synchronous motor (PMSM) has the advantages of low voltage, high power, low speed and high torque, and has a good prospect in electric vehicles, ship propulsion, aerospace and other fields. In this paper, a six-phase DDPMSM with novel toroidal winding (NTW) is proposed. Each coil of the NTWs is wound onto the stator yoke in the same direction, which is different from traditional overlapping windings. The topology of the proposed motor is introduced, and its operation principle is analyzed by describing the variation of the magnetic field produced by the six- phase NTWs versus time. Furthermore, based on the same power grade and effective volume, two six-phase PMSM with different windings are designed. The magnetic field distribution, back-EMF, cogging torque, torque, and loss characteristics are studied in detail. The results show that compared with the traditional six-phase permanent magnet synchronous motor the proposed six-phase DDPMSM with NTWs has the characteristics of low speed and high torque that are desirable for direct-drive systems.

To review the advances in double-bundle anterior cruciate ligament (ACL) reconstruction in adolescents at home and abroad.Recent literature about double-bundle ACL reconstruction in adolescents at home and abroad was extensively consulted, and the relationship between bone canal and epiphyseal plate, clinical verification of surgical safety, and clinical effectiveness of double-bundle ACL reconstruction in adolescents were summarized and analyzed.Double-bundle ACL reconstruction has certain advantages in clinical stability and re-rupture rate when compared with single-bundle ACL reconstruction in adolescents, and there is no significant difference in safety between them.Double-bundle ACL reconstruction in adolescents can achieve lower re-rupture rate and better stability when compared with single-bundle reconstruction. However, the sample size of clinical research is too small, and the follow-up time is too short, so the effectiveness needs to be continuously observed.了解国内外青少年前交叉韧带（anterior cruciate ligament，ACL）双束重建的研究进展。.广泛查阅近年国内外与青少年 ACL 双束重建相关文献，对与青少年 ACL 双束重建相关的骨道与骺板关系、手术安全性临床验证和临床效果进行总结分析。.青少年 ACL 双束重建与单束重建相比，安全性无区别，但对于控制术后膝关节稳定性有一定优势且再断裂率更低。.青少年 ACL 双束重建术后再断裂率低、稳定性好，但目前临床研究观察的样本量太小、随访时间短，其疗效有待持续观察。.

This paper focuses on the cogging torque minimization of novel direct-drive PMSM with toroidal windings (NTWDDPMSM). First, the motor structure is described and its parameters are reported. And the influence of cogging torque on the rated torque is analyzed. Second, the method of different combinations of polar arc coefficients (PAC) is introduced. After that, the cogging torque expression is derived. Then, the finite-element models of NTWDDPMSM with different combinations of PAC are established. The cogging torque and rated torque are calculated and compared. Besides, the static and dynamic performances of motors with different permanent magnets are studied, such as no-load back electromotive force (EMF), air-gap flux density and efficiency. Finally, it is confirmed that the cogging torque of NTWDDPMSM can be effectively minimized using different combinations of PAC. Moreover, the rated output torque is also improved.

The pole arc coefficient of permanent magnets directly affects the performance of permanent magnet synchronous generators. This paper takes a new type of toroidal winding permanent magnet generator as the research object. The effects of different pole arc coefficients on the performance of the generator were investigated. In this paper, no-load induced electromotive force of the generator with different pole arc coefficient was analyzed. The pole arc coefficient of the generator is optimized. The load characteristics of the generator were also analyzed. Finally, the optimal pole arc coefficient of the novel toroidal-winding permanent magnet generator is obtained.

A two-degree-of-freedom direct-drive induction motor (2DoFDDIM), whose solid rotor is coated with a copper layer, is capable of linear, rotary, and helical motions and has widespread applications. For solid-rotor motors, the calculation and analysis of rotor total eddy current loss (TECL) are crucial in studying the factors causing such a loss and possible loss reduction methods. In this study, a new nonlinear analytical method considering the saturation of the rotor core is proposed to solve the fundamental magnetic field. The new method divides the time period into segments. The magnetic field distribution at any time is obtained using Maxwell equations. The eddy current losses in the copper layer and rotor core caused by the fundamental magnetic field are calculated. The surface eddy current losses in the copper layer and rotor core caused by harmonics are calculated using a 2D analytical method. TECL is determined by the sum of eddy current and surface eddy current losses. Coefficients are utilized to consider eddy, saturation, and end-region effects when calculating the rotor core TECL. The new method is verified using 3D FEM, and the results show the proposed method has higher accuracy than the original method. The errors of the rotor core and copper layer TECLs are less than 6 % and 7.3 % , respectively.

Fuel supply systems have a great impact on output characteristics and lifetime of the hydrogen/oxygen fuel cell. On the basis of the fuel supply systems of the fuel cell, this study has studied the models of hydrogen supply system and oxygen supply system. Moreover, the fuzzy self-adaptive proportional–integral–derivative (PID) controllers for hydrogen supply system are designed according to the characteristics of hydrogen and oxygen supply systems. The simulation results show that fuzzy self-adaptive PID control method can achieve better performance for supply system.

To deal with the issues caused by the high integration of renewable resources, the parallel operation of the converters is generally required to improve the system stability and reliability. To support the parallel operation of buck-boost DC/DC converters, they are generally regulated by a cascaded control strategy, which includes droop control loop, and nested proportional-integral (PI) based voltage and current control loops. However, it can provide barely inertia support and needs precise system model to reach the desired performance. In order to overcome these drawbacks, this paper proposes a novel cascaded control strategy for parallel operation of buck-boost DC/DC converters. The proposed cascaded control strategy involves a voltage synchronization loop, a virtual inertia control (VIC) loop, and two nested NTSMC based voltage and current control loops. The voltage synchronization controller can enable the plug and play requirements by synchronizing the output voltage of the converter with the voltage at the point of common coupling (PCC) before connecting a DC/DC converter to the DC microgrid. The VIC can improve the inertia of the converter-interfaced DGs. The nested-loop NTSMC based voltage and current controller can improve the robustness of converter system. Hardware experiments demonstrate the improved performance of the proposed control strategy.