The New Vacuum Solar Telescope (NVST) is a 1 meter vacuum solar telescope that aims to observe the fine structures on the Sun. The main tasks of NVST are high resolution imaging and spectral observations, including the measurements of solar magnetic field.NVST is the primary ground-based facility of Chinese solar community in this solar cycle. It is located by the Fuxian Lake of southwest China, where the seeing is good enough to perform high resolution observations. In this paper, we first introduce the general conditions of Fuxian Solar Observatory and the primary science cases of NVST. Then, the basic structures of this telescope and instruments are described in detail. Finally, some typical high resolution data of solar photosphere and chromosphere are also shown.

With increasing penetration of the renewable energy, the grid-tied PWM inverters need to take corresponding responsibilities for the security and stability of future grid, behaving like conventional rotational synchronous generator (RSG). Therefore, recognizing the inherent relationship and intrinsic differences between inverters and RSGs is essential for such target. By modeling the typical electromechanical transient of grid-tied PWM inverters, this paper first proves that PWM inverters and RSGs are similar in physical mechanism and equivalent in mathematical model, and the concept of static synchronous generator (SSG) is thereby developed. Furthermore, the comprehensive comparison between RSG and SSG is carried out in detail, and their inherent relation is built. Based on these findings, the rationality and feasibility of migrating the concepts, tools, and methods of RSG stability analysis to investigate the dynamic behaviors and stability issues of SSG is therefore confirmed. Taking stability issues as an example, the criteria of small signal and transient stability of a typical grid-tied PWM inverter is put forward to demonstrate the significance of the developed SSG model (including synchronizing coefficient, damping coefficient, inertia constant, and power-angle curve), providing clear physical interpretation on the dynamic characteristics and stability issues. The developed SSG model promotes grid-friendly integration of renewable energy to future grid and stimulates interdisciplinary research between power electronics and power system.

No abstract

No abstract

No abstract

Solid‐state nuclear magnetic resonance (ssNMR) has received extensive attention in characterizing alkali‐ion battery materials because it is highly sensitive for probing the local environment and dynamic information of atoms/ions. However, precise spectral assignment cannot be carried out by conventional DFT for high‐rate battery materials at room temperature. Herein, combining DFT calculation of paramagnetic shift and deep potential molecular dynamics (DPMD) simulation to achieve the converged Na+ distribution at hundreds of nanoseconds, we obtain the statistically averaged paramagnetic shift, which is in excellent agreement with ssNMR measurements. Two 23Na shifts induced by different stacking sequences of transition metal layers are revealed in the fast chemically exchanged NMR spectra of P2‐type Na2/3(Mg1/3Mn2/3)O2 for the first time. This DPMD simulation auxiliary protocol can be beneficial to a wide range of ssNMR analysis in fast chemically exchanged material systems.

A novel strategy for selecting additives is adopted and a bifunctional additive is investigated for H2O/HF-scavenging and enhanced cell performance.

This paper proposes a novel three-phase PLL algorithm, which focuses on the reforming of the primary signals before grid synchronization rather than improving the phase estimation methodologies. The unbalanced signals are reformed to balanced ones without damage to the phase angle, through which the negative sequence of the grid voltages is removed. This eliminates the estimation errors of conventional synchronous reference frame PLL (SRF-PLL) and enhances its response speed with a higher bandwidth. The reforming process is supposed to be carried out at every zero-crossing point of the three-phase voltages and choose one phase as reference to balance the other two. Coefficients for the signal reforming are calculated at one zero-crossing point and updated until the next comes. In implementation, a certain phase is chosen as the reference all along and the reforming process will be suspended when it just crosses the zero line. This PLL algorithm has a fast and precise character to reform the three-phase grid voltages and is flexible for application. Under heavily distorted grid conditions, it can still perform effectively even with multiple zero-crossings. Comprehensive experimental results from a digital signal processor based laboratory prototype are provided to validate the performance of this PLL algorithm.