Effects of inertia distribution on regional frequency heterogeneity

Heterogeneous inertia distribution can result in large regional frequency deviations and inter-area oscillations that exceed protection limits configured based on system-wide averaged performance. This paper examines how the spatial distribution of inertia affects frequency heterogeneity. Along with varying inertia distribution, variations in generator turbine-governor control and network topology are studied to make the results more generalisable across wide-ranging operating conditions. An investigation into the effects of different fast frequency response (FFR) schemes on frequency heterogeneity is also presented. The frequency heterogeneity is quantified by calculating cosine similarity between regional frequency trajectories. The key results are obtained using a two-area model and verified using a mixed AC/DC power system. A key finding is that the localness of regional frequency is independent of the inertia of a specific area, nor of the total system inertia. The inertia ratio, described as the ratio of the disturbance area inertia to that of the non-disturbance area, is shown to have a strong correlation with frequency heterogeneity. This correlation is shown to be very robust to changes in generator dynamics and network topology. Providing derivative FFR within the disturbance area always demonstrates benefits regarding frequency heterogeneity inhibition, whereas droop scheme typicallyintroduces deterioration in frequency heterogeneity

Fully Conjugated Phthalocyanine Copper Metal-Organic Frameworks for Sodium-Iodine Batteries with Long-Time-Cycling Durability

Rechargeable sodium-iodine (Na-I-2) batteries are attracting growing attention for grid-scale energy storage due to their abundant resources, low cost, environmental friendliness, high theoretical capacity (211 mAh g(-1)), and excellent electrochemical reversibility. Nevertheless, the practical application of Na-I-2 batteries is severely hindered by their poor cycle stability owing to the serious dissolution of polyiodide in the electrolyte during charge/discharge processes. Herein, the atomic modulation of metal-bis(dihydroxy) species in a fully conjugated phthalocyanine copper metal-organic framework (MOF) for suppression of polyiodide dissolution toward long-time cycling Na-I-2 batteries is demonstrated. The Fe-2[(2,3,9,10,16,17,23,24-octahydroxy phthalocyaninato)Cu] MOF composited with I-2 (Fe-2-O-8-PcCu/I-2) serves as a cathode for a Na-I-2 battery exhibiting a stable specific capacity of 150 mAh g(-1) after 3200 cycles and outperforming the state-of-the-art cathodes for Na-I-2 batteries. Operando spectroelectrochemical and electrochemical kinetics analyses together with density functional theory calculations reveal that the square planar iron-bis(dihydroxy) (Fe-O-4) species in Fe-2-O-8-PcCu are responsible for the binding of polyiodide to restrain its dissolution into electrolyte. Besides the monovalent Na-I-2 batteries in organic electrolytes, the Fe-2-O-8-PcCu/I-2 cathode also operates stably in other metal-I-2 batteries like aqueous multivalent Zn-I-2 batteries. Thus, this work offers a new strategy for designing stable cathode materials toward high-performance metal-iodine batteries

Selective Excited-State Dynamics in a Unique Set of Rationally Designed Ni Porphyrins

In this work, we report the design and photophysical properties of a unique class of Ni porphyrins, in which the tert-butyl benzene substituents at the meso positions of the macrocycle were tethered by ethers with alkyl linkers. This not only results in the permanently locked ruf distortion of the macrocycle but also enables the engineering of the degree of distortion through varying the length of alkyl linkers, which addressed the complication of uncertainty in the specific structural distortions that has long plagued the porphyrin photophysical community. Using advanced time-resolved optical and X-ray absorption spectroscopy, we observed tunability in the excited-state relaxation pathway depending on the degree of distortion and characterized the associated transient intermediate structure. These findings provide a new avenue to afford accessibility to a wide range of excited-state properties in nonplanar porphyrins

Effects of Droop Based Fast Frequency Response on Rotor Angle Stability During System Wide Active Power Deficits

The effects of fast frequency response (FFR) on rotor angle stability have predominately been established by examining the oscillatory behavior of synchronous generators (SGs). What remains largely unexamined, however, is the effect that FFR has on the angle separation and power transfer between SGs. This paper systematically examines the evolution of the angle separation and power transfer between SGs during FFR provision in the context of frequency containment events. Droop based FFR schemes, which are popular and effective in practical systems, are analyzed. This research investigates how the location of the initiating system wide active power deficit, the location of resources providing FFR, and the delays associated with FFR provision all impact rotor angle stability. The key results are obtained using a modified IEEE 39-bus system and further verified using a reduced-order dynamic Great Britain system model. The results show that the angle separation and power transfer between SGs decrease when power deficits occur in areas with extensive generation sources which, conversely, implies that angle stability deteriorates if power deficits occur near load centers. A key finding is that providing the FFR at locations closest to the source of the initial power deficit does not always enhance angle stability, and sometimes has a significant adverse effect. The effect that FFR delays have on rotor angle stability is explained, highlighting the necessity to carefully consider and design FFR provision timing, particularly in areas with diminishing levels of inertia

Development of a Near Ground Remote Sensing System

Unmanned Aerial Vehicles (UAVs) have shown great potential in agriculture and are increasingly being developed for agricultural use. There are still a lot of experiments that need to be done to improve their performance and explore new uses, but experiments using UAVs are limited by many conditions like weather and location and the time it takes to prepare for a flight. To promote UAV remote sensing, a near ground remote sensing platform was developed. This platform consists of three major parts: (1) mechanical structures like a horizontal rail, vertical cylinder, and three axes gimbal; (2) power supply and control parts; (3) onboard application components. This platform covers five degrees of freedom (DOFs): horizontal, vertical, pitch, roll, yaw. A stm32 ARM single chip was used as the controller of the whole platform and another stm32 MCU was used to stabilize the gimbal. The gimbal stabilizer communicates with the main controller via a CAN bus. A multispectral camera was mounted on the gimbal. Software written in C++ language was developed as the graphical user interface. Operating parameters were set via this software and the working status was displayed in this software. To test how well the system works, a laser distance meter was used to measure the slide rail’s repeat accuracy. A 3-axis vibration analyzer was used to test the system stability. Test results show that the horizontal repeat accuracy was less than 2 mm; vertical repeat accuracy was less than 1 mm; vibration was less than 2 g and remained at an acceptable level. This system has high accuracy and stability and can therefore be used for various near ground remote sensing studies

Galactomannan in Bronchoalveolar Lavage Fluid for Diagnosis of Invasive Pulmonary Aspergillosis with Nonneutropenic Patients

Background. We evaluated the utility of galactomannan (GM) in bronchoalveolar lavage fluid (BALF) for the diagnosis of invasive pulmonary aspergillosis (IPA) in nonneutropenic patients. Methods. A total of 183 patients were included in the final analysis. Bronchoscopies and the detection of GM in BALF were all performed on them. Results. Ten cases of IPA were diagnosed. ROC data demonstrated that, for diagnosing IPA, an optimal cutoff value for GM in BALF of 0.76 yielded a sensitivity of 100.0% and a specificity of 76.2%. Symptoms and radiological findings had no significant difference between proven or probable IPA group and non-IPA group. In our case-control analysis, although nine patients with false-positive results received treatment with Piperacillin/tazobactam, there was no significant difference between case and control group. Conclusions. BALF GM detection is a valuable adjunctive diagnostic tool. Our retrospective study suggests that the optimal value of GM detection in BALF is 0.76 in nonneutropenic patients

Fine-Tuning of Electronic Structure of Cobalt(II) Ion in Nonplanar Porphyrins and Tracking of a Cross-Hybrid Stage: Implications for the Distortion of Natural Tetrapyrrole Macrocycles

The core size of the porphyrin macrocycles was closely related to their stability of the different electron structure in the central metal ion. Cobalt­(II) ions can undergo a conversion in electron configurations upon N₄ core contraction of 0.05 Å in nonplanar porphyrins, and these ions still maintain low spin forms after and before conversion. The structural fine-tuning can induce the appearance of a cross-hybrid stage [d­(_{<i>x</i>²−<i>y</i>}^₂)­sp² ↔ d­(_<i>z</i>²)­sp²] based on quadrilateral coordination of the planar core. The results indicate that the configuration conversion plays a key role in electron transfer in redox catalysis involving cobalt complexes. The electronic properties of six monostrapped cobalt­(II) porphyrins were investigated by spectral, paramagnetic, and electrochemical methods. The macrocyclic deformations and size parameters of Co-containing model compounds were directly obtained from their crystal structures