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This paper proposes a measurement-based voltage stability assessment method considering VAR limits of generators. Traditional measurement-based methods for monitoring a load bus or a load area often simplify the external system as a simple constant electromotive force (e.m.f.) behind a Thevenin impedance, which may give inaccurate voltage stability margin when some external generator reaches its VAR limit. In this paper, a novel method is proposed to consider the VAR limits of generators by deriving a relationship between the variations of their e.m.f. and the load, which can be identified and tracked in real time. Thus, a more accurate voltage stability margin is derived by an analytical expression under variations of both generator terminal voltages and loads. The proposed method is compared with a typical Thevenin method and demonstrated on a two-area system and the IEEE 39-bus power system.

This study proposes an online measurement-based method for n−1 voltage stability assessment on a load area by means of an equivalent system of N + 1 buses introduced by Hu et al. to represent N boundary buses of the load area and the external system. This method utilises real-time synchro-phasor measurements on N boundary buses and online state estimation on the load area to analyse n−1 sensitivities for equivalent transfer admittances and power flows by means of a modified line outage distribution factor in order to estimate the voltage stability margin of power transfer to each boundary bus under an anticipated n−1 condition. The method is demonstrated on the Northeast Power Coordinating Council 48-machine, 140-bus power system.

In this paper, we study a prosumer’s energy trading behavior in a proposed local energy market (LEM). The prosumer will try to make the best use of its available energy resources, such as its PV panel and battery, with the self-learning capability to make a smart operation strategy. By adapting a deep reinforcement learning (DRL) technique and a rainflow battery aging mechanism, it can be taken as a contribution that the proposed intelligent and economical decision-making framework will facilitate more customers while encouraging active participation in the localized energy ecosystem. Meanwhile, more energy business models can be strategically redesigned on top of it.

This paper proposes a measurement-based voltage stability monitoring method for a load area fed by N tie lines. Compared to a traditional Thevenin equivalent based method, the new method adopts an N $+1$ buses equivalent system so as to model and monitor individual tie lines. For each tie line, the method solves the power transfer limit against voltage instability analytically as a function of all parameters of that equivalent, which are online identified from real-time synchronized measurements on boundary buses of the load area. Thus, this new method can directly calculate the real-time power transfer limit on each tie line. The method is first compared with a Thevenin equivalent based method using a 4-bus test system and then demonstrated by case studies on the Northeast Power Coordinating Council (NPCC) 48-machine, 140-bus power system.

This paper proposes an online steady-state voltage stability assessment scheme to evaluate the proximity to voltage collapse at each bus of a load area. Using a non-iterative holomorphic embedding method (HEM) with a proposed physical germ solution, an accurate loading limit at each load bus can be calculated based on online state estimation on the entire load area and a measurement-based equivalent for the external system. The HEM employs a power series to calculate an accurate Power-Voltage (P-V) curve at each load bus and accordingly evaluates the voltage stability margin considering load variations in the next period. An adaptive two-stage Pade approximants method is proposed to improve the convergence of the power series for accurate determination of the nose point on the P-V curve with moderate computational burden. The proposed method is illustrated in detail on a 4-bus test system and then demonstrated on a load area of the Northeast Power Coordinating Council (NPCC) 48-geneartor, 140-bus power system., Comment: Revised and Submitted to IEEE Transaction on Power Systems

This article introduces a measurement-based voltage stability monitoring method for a load area fed by N tie lines. Compared to a traditional Thevenin equivalent (TE)-based method, the new method adopts an N + 1 buses equivalent system so as to model and monitor individual tie lines. For each tie line, the method solves the power transfer limit against voltage instability analytically as a function of all parameters of that equivalent, which are identified online from real-time synchronized measurements on boundary buses of the load area. Thus, this new method can directly calculate the real-time power transfer limit on each tie line. The method is first compared with a TE-based method using a four-bus test system and then demonstrated by case studies on the Northeast Power Coordinating Council's 48-machine, 140-bus power system.

A new cobalt(II) coordination polymer with 2,4′-biphenyl- dicarboxylate acid (H2bpdc) and 1,4-bis(4-pyridylmethy) piperazine (bpp) has been prepared by hydrothermal synthesis and characterized by single-crystal X-ray diffraction, IR, and EA. Complex [Co(bpdc)2(bpp)1.5(H2O)]n(1), is triclinic, space group P-1with a = 12.0253(8), b = 12.4854(8), c = 13.1509(8) A, α = 102.1117(8), β = 111.7334(8)°, γ = 91.1778(8), V = 1782.8(2) A3, Z = 2, Mr = 716.67, Dc = 1.335 g/cm3, F(000) = 748, and μ = 0.53 cm−1. The final refinement gave R = 0.0587 and wR = 0.1630 for 6,411 reflections with I > 2σ(I). X-ray diffraction analysis reveals that the title complex [Co(bpdc)2(bpp)1.5(H2O)]n (1) displays shows a three-fold diamond topological net. Furthermore, the luminescent property of complex 1 is investigated.

Two new Ni(II) coordination polymers, {[Ni(ipa)(bib)]·3H2O}n (1) and {[Ni(bdc) (bib)]·H2O}n(2)(H2ipa = 5-hydroxyisophthalic acid, H2bdc = 2,4’-biphenyl-dicarboxylate acid and bib = 1,4-bis(imidazol-1-yl)benzene), have been synthesized and characterized by IR, elemental analysis, and single-crystal X-ray diffraction. Complex 1 shows two-dimensional layer structure and complex 2 exhibits three-dimensional pcu topology.

Two new Mn(II) coordination polymers, {[Mn(5-CH3-ip)(bib)]·2H2O}n (1) and [Mn (5-CH3- ip)(bib)0.5]n (2) (5-CH3-ip = 5-Methyl-1,3-benzenedicarboxylic acid bib = 1,4-bis(imidazol-1-yl) benzene), have been synthesized and characterized by elemental analysis, IR, and X-ray diffraction. Complex 1 shows a 2D layer structure. Complex 2 is a 3D structure (3,7)-connected topology with a Schafli symbol of (620.8).(63). The topology has been well controlled by pH value.

A new 3D coordination polymer {[Zn(3,4-PDC)(bib)0.5]· (H2O)}n (1) [3,4’-PDC = 3,4-pyridinedicarboxylic acid and bib = 1,4-bis(2-methyl-imidazol-1-yl)butane] was prepared by hydrothermal synthesis and characterized by single-crystal X-ray diffraction, FTIR spectra, and element analysis. Complex 1 shows a 3D (3, 4)-connected dmc topological net. Furthermore, the solid-state photoluminescence property of title compound is investigated at room temperature.

The 3D coordination polymer {[Cd(dpa)(bpe)]·2H2O}n (1)[H2dpa = 2,4′-biphenyl dicarboxylic acid and bpe = 1,2-bis(4-pyridyl)ethane] was prepared by hydrothermal synthesis and characterized by single X-ray diffraction, FTIR spectra and element analysis. The title complex 1 exhibits an unusual three-dimensional framework with (6,6)-connected (32.42.52.68.8) (34.44.54.63) topology. Furthermore, the solid-state photoluminescence property of 1 is investigated at room temperature.

The authors studied the synthesis of calcium carbonate (CaCO3) in hexamethylenetetramine (HMT) aqueous solution using diethyl carbonate as CO2 supplier. Scanning electron microscopy and X-ray powder diffractometry were used to characterize the products. The results showed that calcite crystals with rough surface were formed in solution, while calcite polyhedrons and “flowers” were formed at the air/solution interface. The FTIR results indicated a strong interaction between HMT molecules and Ca2+ ions. The possible formation mechanism of the CaCO3 crystals obtained in the solution and at the interface was discussed, which could be explained by mesocrystal assembly.

This paper describes a new method for estimating the power transfer limits on tie lines of a load area represented using a three-bus equivalent recently proposed. This new method uses companion matrix eigenvalues to solve a sextic equation about the maximum active power transfer against voltage instability and is able to handle more general load increase scenarios. The proposed method is compared with a previously proposed partial derivative calculation based method using an artificial three-bus system to demonstrate its better accuracy and is also tested on the Northeast Power Coordinating Council 140-bus power system for calculating the power transfer limits of three tie lines of the Connecticut Load Center.

A measurement-based voltage stability assessment and closed-loop control strategy is proposed and demonstrated on the Center for Ultra-Wide-Area Resilient Electric Energy Transmission Networks (CURENT) Hardware Test Bed (HTB) system, a power electronic converter-based research and experiment platform. This new strategy is based on an N+1 buses equivalent proposed recently by Ref. [1] for calculating real-time voltage stability margins on individual tie lines of a load area. Two voltage stability scenarios are designed and implemented on the HTB system that emulates a three-area power system integrating conventional generation, wind generation, and multi-terminal HVDC transmission. The tests validate the effectiveness of real-time monitoring and closed-loop control against voltage instability initiated from one tie line of the load area.

Four new copper(II) complexes [Cu(HL)(im)](ClO4)2 (1), [Cu(HL)(py)](ClO4)2 (2), [Cu2(HL)2(bpy)2](ClO4)4·H2O (3), and [Cu2(HL)2(bpy)](ClO4)4·H2O (4) (im = imidazole; py = pyridine; bpy = 4,4′-bipyridine) were synthesized by reactions of tripodal ligandN1-(2-aminoethyl)-N1-(1H-imidazol-4-ylmethyl)-ethane-1,2-diamine(HL) and Cu(ClO4)2·6H2O with different nitrogen-containing aromatic ligands. It was found that the size of the N-containing aromatic ligand, and the ratio of the ligand and metal ion, have great influence on the formation and structure of the complexes.

In this paper, crystal growth of calcium carbonate (CaCO3) in the presence of biomolecules of lotus root was investigated. Scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray powder diffractometry were used to characterize the products. The results indicate that calcite spherical particles were constructed from small rhombohedral subunits. Similar CaCO3 crystals were also gained when crystal growth of CaCO3 in aqueous solution containing extracts of lotus root was performed, suggesting that the soluble biomolecules of lotus root play a crucial role in directing the formation of hierarchical calcite spherical particles. The possible formation mechanism of the CaCO3 crystals by using lotus root is also discussed, which can be interpreted by particle-aggregation based non-classical crystallization laws. The biomolecules of lotus root might induce and control the nucleation and growth of calcium carbonate crystals. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The optical properties of 2 mixing types of CdS‐CdSe nanoparticles (i.e., coprecipitated CdS‐CdSe nanoparticles, CdS‐coated CdSe (CdSe/CdS)) were studied. Results indicated that the co‐precipitated nanoparticles kept the similar optical properties of both CdS and CdSe's, while the CdS/CdSe core‐shell structure showed totally different optical properties from the simple components. We paid special attention to the core/shell structure, as the core‐shell structure showed a better passivating effect. Therefore, the XRD and TEM were tested on the core‐shell structure. XRD results showed that the diffraction patterns of core‐shell structure were roughly the same as their simple components. And the TEM indicated the core‐shell structure had a uniform dispersion in the solution.

A system wide disturbance event usually triggers inter-area oscillations at the system. Understanding the nature of those oscillations is important for taking necessary early mitigation actions. This work presents a novel scheme for analyzing inter-area oscillations by identification of the centers of oscillation (CoO) using two methods based on wide-area measurement data: one method directly calculate CoOs for transmission lines with synchrophasors on both ends and the other estimate CoOs based on contour visualization about frequency deviations extrapolated for the entire map. CoOs serve as pivots between oscillating parts under disturbances and hence indicate the grid interfaces involved in oscillation, so this scheme can provide the operator recommendations on where mitigation actions may be taken to prevent instability. The proposed scheme is tested using simulated synchrophasor data on a WECC 179-bus test system.

This paper utilizes an adaptive three-bus power system equivalent for measurement-based voltage stability analysis. With that equivalent identified online, a measurement-based approach is developed to estimate real-time voltage stability margin for a load-rich area supported by remote generation via multiple tie lines. Compared with traditional Thevenin equivalent based approach, this new approach is able to provide more accurate voltage stability margin for each individual tie line. This approach is validated on a three-bus system and the IEEE 39-bus system.

This paper proposes a new approach using phasor measurement units (PMUs) to estimate real-time voltage stability margin for a load area supported by multiple tie lines. For the monitored tie lines, it can provide accurate real and reactive power transfer margins. Compared to a traditional Thevenin equivalent-based approach, the new approach is more tolerant of fluctuations in the phase angles of the external system and the power factors of tie-line flows. A two-bus power system and the IEEE 39-bus system are used to test this new approach and compare it with the traditional approach.

In the title complex, (C12H10FN2)2[Ni(C4N2S2)2], the anion lies on an inversion center with the NiII ion coordinated by four S atoms in a slightly distorted square-planar environment. In the unique cation, the dihedral angle between the benzene and pyridine rings is 7.1 (2) Å.