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In this letter, a systematic static voltage stability index for evaluating system loading status in distribution networks is deduced from complex power flow models. The proposed index facilitates impact analysis on the integration of inverter-based distributed generators under different control modes, which may affect the static voltage stability. The case study, including various scenarios, is performed to validate the accuracy of the theoretical results.

In this letter, a phase reformulation-based sliding framework is proposed for microgrid to adequately decouple control interacts cross the quadrature axes. This is implemented by formulating another virtual coordinate that rotates with the synchronism frequency, while the original coordinate rotates with the reference frequency. The deviation during transients between coordinates is thus to be eventually mitigated by the intersected controller. The case study in PSCAD/EMTDC shows that, with the sliding framework, frequency and voltage fluctuations can be dramatically reduced.

Due to inappropriate control strategy and analytic technique, large penetration of converter-based renewable energy sources to the grid has threaten the network fault level to an extremely low level. Aiming at these issues, this paper firstly elaborates on a weak grid solution for inverter control and its corresponding impedance model in positive and negative-sequence domain. For system wise, the critical point for inverter-grid voltage stability and thus minimum short circuit ratio (SCR) that the inverter can remain small-signal stable are presented using comprehensive controller and system impedance model. The viability of the proposed control strategy and analytic method is validated by both numerical and simulation results.

In this study, Ag3PO4@holmium phosphate (HP) composite photocatalysts were first prepared by silver-ammonia-solution-assisted solution co-deposition. During co-deposition, Ag3PO4 particles were encapsulated by a flocculent amorphous substance layer of HP, affording a Ag3PO4@HP core–shell heterojunction structure with a Ho/Ag molar ratio of 0.05/2.95. The core–shell structure significantly improved the photocatalytic activity of Ag3PO4. In addition, the photocatalytic mechanism of Ag3PO4@HP was discussed.

Distributed controllers for voltage and frequency, based on consensus power sharing algorithm, are proposed in this paper. Event-triggered mechanism is adopted as cybernetics in the communication network. Convergence of real and reactive power dissipation and stability for inter-event instants are also held with Lyapunov function. A benchmarking multimicrogrid cluster (MMC) has been built in PSCAD/EMTDC software to validate that, compared to traditionally periodical sampling scheme, the proposed control strategy can dramatically alleviate communication burdens without sacrificing microgrid performances in proportional power sharing, controller convergence and interval stability.

This paper proposes a novel control strategy for the smooth transition between grid-attached and islanded mode of microgrid. The proposed control strategy is based on a proportional resonant current controller to regulate inverter current, without requiring any islanding detection algorithm or switching between different controllers. Equal power sharing is achieved as well by droop control using reference current, while restoration algorithm is applied when frequency deviates. With the proposed control strategy, the microgrid has a satisfactory performance in different operating modes and transition process. Moreover, the power is equally shared among all DGs in all conditions. Simulations are presented to validate the proposed control strategy.

The development of a polar-view Kirkpatrick-Baez microscope, fielded in the upper polar zone of the Shenguang-III laser fusion facility, is presented. With this microscope, the resolving power of polar-direction X-ray imaging diagnostics is improved, to the 3 ~5 μm scale. The microscope is designed for implosion asymmetry studies, with response energy points at 1.2 keV, 3.5 keV, and 8 keV. A biperiodic multilayer scheme is adopted to accommodate multiple implosion stages. We present the overall optical system design, target aiming scheme, characteristic composite imaging diagnostic experiments and initial results. The inertial-driven quasi-one-dimensional spherical implosions were observed from orthogonal directions with a convergence ratio of ~14.4. Fine features of the stagnating hot spot core are also resolved.

In order to counter drug-related crimes effectively, and to safeguard homeland security as well as public safety, it is important to inspect drugs, explosives and other contraband quickly and accurately from the express mail system, luggage, vehicles and other objects. In this paper, we discuss X-ray backscatter inspection system based on a novel lobster-eye X-ray objective, which is an effective inspection technology for drugs, explosives and other contraband inspection. Low atomic number materials, such as drugs and explosives, leads to strong Compton scattering after irradiated by X-ray, which is much stronger than high atomic number material, such as common metals, etc. By detecting the intensity of scattering signals, it is possible to distinguish between organics and inorganics. The lobster-eye X-ray optical system imitates the reflective eyes of lobsters, which field of view can be made as large as desired and it is practical to achieve spatial resolution of several millimeters for finite distance detection. A novel lobster-eye X-ray objective is designed based on modifying Schmidt geometry by using multi-lens structure, so as to reduce the difference of resolution between the horizontal and vertical directions. The demonstration experiments of X-ray backscattering imaging were carried out. A suitcase, a wooden box and a tire with several typical samples hidden in them were imaged by the X-ray backscattering inspection system based on a lobster-eye X-ray objective. The results show that this X-ray backscattering inspection system can get a resolution of less than five millimeters under the FOV of more than two hundred millimeters with ~0.5 meter object distance, which can still be improved.