State Key Laboratory of Advanced Electromagnetic Engineering and Technology

Natural wood-based materials are directly utilized to construct ultra-thick all-wood-structured supercapacitors with ultra-high capacitance and energy density.

Sulfur-doped disordered carbon exhibits high capacity and excellent cyclability as an anode for sodium ion batteries.

This paper focuses on the optimal operation of the integrated gas and electrical power system with bidirectional energy conversion. Considering the different response times of the gas and power systems, the transient gas flow and steady-state power flow are combined to formulate the dynamic optimal energy flow in the integrated gas and power systems. With proper assumptions and simplifications, the problem is transformed into a single-stage linear programming to obtain the optimal operation strategy for both gas and power systems. Simulation on the test case illustrates the success of the modeling and the beneficial roles of the power-to-gas are analyzed. The proposed model can be used in the decision support for both planning and operation of the coordinated natural gas and electrical power systems.

In this paper, an LLC resonant converter design methodology for battery charging applications is proposed aiming at achieving high efficiency. Compared with traditional resistive or constant power load applications, the battery voltage and current are nonlinear and vary with the charging profiles, making the optimal design of battery charger more difficult and complicated. Based on the characteristics of the battery charging profiles, a new time-weighted average efficiency (TWAE) index is proposed, which represents the average weight of conversion efficiency during battery charging period. Converter's losses are calculated based on the standard loss models using the current and voltage information derived from the LLC steady-state model, which is solved utilizing the numerical non-linear programming techniques. In addition, the TWAE is achieved serving as the objective function to optimize the converter parameters. To reduce the search space and speed up the search algorithm, a variable-step exhaustive search algorithm is applied considering the constraints of operation and variable range. Finally, a 3 kW prototype LLC converter, which converts 220 VAC from the grid to a wide output voltage range from 60 to 100 V is built and a TWAE of 94.74% and a peak efficiency of 95.19% are achieved, validating the effectiveness of the presented method.

Magnetic manipulation is very promising for the motion control of micro- and nano-objects, which has wide applications in the mixing, trapping, colloidal assembly and object transport, and the recent progress in these areas is reviewed in this work.

S-doped carbon nanofibers derived from bacterial cellulose with interlinked networks and pores were facilely prepared in a sustainable approach. This product presents a high Na-ion storage capacity and excellent rate performances.

An additive-free and free-standing GPE with excellent Li⁺ mobility and polysulfide localization is prepared <italic>via</italic> a facile route.

Selenium-doped sulfurized polyacrylonitrile delivers superior rate and cycle performance in room temperature sodium-sulfur batteries.

Na₃V₂(PO₄)₃/C, as a high-performance cathode material for sodium ion batteries, was synthesized <italic>via</italic> a facile agarose-assisted solid-phase method.

Modular multilevel converters (MMCs) become popular in high-voltage dc transmission systems; however, their applications in medium-voltage (MV) motor drives are still limited due to the technical challenge of low-frequency voltage fluctuation. This paper proposes a new solution to address this problem. Full-bridge submodules (SMs) are used in the place of half-bridge SMs in the MMC to significantly reduce the low-frequency pulsating power in the SM capacitors in startup or low-speed motor drives. Furthermore, quasi-resonant controllers are adopted to acquire improved tracking performance for injected circulating current. Simulation and experimental results are presented and have proved the validity of the proposed method. Comparisons of efficiency and cost between the conventional and the proposed solutions further demonstrate the potential of proposed method for MV drive applications.

A Na-rich cathode is developed by grafting the electron-withdrawing -SO3Na group on polyaniline chains. Due to the immobile doping and effective activation of the sulfonate group, this polymer demonstrates a high capacity (133 mA h g(-1)) and excellent cyclability through a cation-exchange reaction, offering a low cost and sustainable cathode for SIBs.

Benefiting from the unique structure of ultrafine NiS_x nanospheres uniformly wrapped in the <italic>in situ</italic> S-doped rGO matrix, the NiS_x–rGOS electrode delivers a high reversible capacity of 516 mA h g⁻¹ at 0.2 A g⁻¹ and a remarkable rate performance of 414 mA h g⁻¹ at 4 A g⁻¹, offering a low cost and high performance anode material for Na-ion batteries.

In this work, a co-culture system with liver cancer cell line HepG2 and normal cell line L02 is used to investigate the selective effect on cancer and normal cells by plasma activated medium (PAM), which is closer to the real environment where cancer cells develop. Besides, the co-culture system is a better model to study the selective effect than the widely used separate culture systems, where the cancer cell line and normal cell line are cultured independently. By using the co-culture system, it is found that there is an optimum dose of PAM to induce significant cancer cell apoptosis while keeping minimum damage to normal cells.

A closed-form analytical model is developed to build the special rules for vernier permanent magnet (VPM) machines comparison. Based on the finite element analysis (FEA), comparisons of some key parameters including power factor are made among three novel VPM topologies, i.e., Halbach, dual-stator (DS), and DS spoke-array (DSSA) structures. The results from both the analytical model and FEA model demonstrate that the DSSA VPM machine exhibits highest power factor, viz., ~0.91, highest torque density and fewest magnet usage.

This paper presents an accurate method to extract parameters of induction motor (IM) from finite element field solutions. A 2-D non-linear time-harmonic application of IM is used in the simulation. And to separate the leakage reactances, the frozen permeability method is used in the static magnetic field simulation for the slot leakage flux calculation. Then, the slot leakage reactance and the harmonic reactance can be determined separately with the consideration of skin effect and the saturation. A defect of modeling the rotation of rotor in time-harmonic field is pointed out in this paper. Finally, the determination of reactances as a function of speed variation is concerned. An application example is provided to confirm the accuracy of the presented method.

Cation doping in Li₇PS₆ to stabilize the HT argyrodite phase with high ionic conductivity and good compatibility with Li metal.

A high-performance Faraday-effect polarimeter-interferometer system has been developed for the J-TEXT tokamak. This system has time response up to 1 μs, phase resolution < 0.1° and minimum spatial resolution ∼15 mm. High resolution permits investigation of fast equilibrium dynamics as well as magnetic and density perturbations associated with intrinsic Magneto-Hydro-Dynamic (MHD) instabilities and external coil-induced Resonant Magnetic Perturbations (RMP). The 3-wave technique, in which the line-integrated Faraday angle and electron density are measured simultaneously by three laser beams with specific polarizations and frequency offsets, is used. In order to achieve optimum resolution, three frequency-stabilized HCOOH lasers (694 GHz, >35 mW per cavity) and sensitive Planar Schottky Diode mixers are used, providing stable intermediate-frequency signals (0.5-3 MHz) with S/N > 50. The collinear R- and L-wave probe beams, which propagate through the plasma poloidal cross section (a = 0.25-0.27 m) vertically, are expanded using parabolic mirrors to cover the entire plasma column. Sources of systematic errors, e.g., stemming from mechanical vibration, beam non-collinearity, and beam polarization distortion are individually examined and minimized to ensure measurement accuracy. Simultaneous density and Faraday measurements have been successfully achieved for 14 chords. Based on measurements, temporal evolution of safety factor profile, current density profile, and electron density profile are resolved. Core magnetic and density perturbations associated with MHD tearing instabilities are clearly detected. Effects of non-axisymmetric 3D RMP in ohmically heated plasmas are directly observed by polarimetry for the first time.

Up to now, all studies on the dynamics behavior of non-equilibrium plasma plumes were focussed on noble gas plasma plumes. It was found out that they are electrically driven rather than gas flow dependent. Our study on the dynamics of a non-equilibrium N2 plasma plume reveals that the propagation velocity of the N2 plasma plume is several orders magnitude lower than those previously reported and further studies show that it is close to the gas flow velocity. The gas flow has a significant effect on the length of the plasma plume, and the results provide some fundamental knowledge about atmospheric pressure plasma jets.

Benefiting from the fast charge-transfer kinetics and robust structure, the nano-embedded microstructured FeS₂@C demonstrates significantly improved Na-storage performance in NaPF₆/DME.

In order to meet the grid code of distributed generation, a control strategy for low voltage ride through(LVRT) of inverter interfaced distributed generation(IIDG) is proposed. Based on it, the dynamic responses of inverter controller and fault current characteristics of IIDG are studied under conditions of symmetric fault and asymmetric fault. Besides, the calculation model of the fault current of IIDG is established. Moreover, the fault analysis method for the distribution network with penetration of IIDGs is analyzed. Digital simulation results validate the correctness of the theoretical analysis results. The research results are helpful to improve the LVRT capability of IIDG and study the fault characteristics of the power grid with IIDGs. The research results can also provide reference for principle study and performance evaluation of the relaying protection which is applicable for the power gird with penetration of IIDGs.