A power decoupling control method for an isolated single‐phase AC‐to‐DC converter based on a high‐frequency cycloconverter

This paper proposes a new power decoupling method for a high‐frequency cycloconverter which converts the single‐phase line‐frequency ac input to the high‐frequency ac output directly. The cycloconverter consists of two half‐bridge inverters, two input filter capacitors, and a series‐resonant circuit. The proposed power decoupling method stores the input power ripple at double the line frequency in the filter capacitors. Therefore, the proposed method achieves a unity power factor in ac input and a constant current amplitude in the high‐frequency output without any additional switching device or energy storage element. This paper theoretically discusses the principle and operating performance of the proposed power decoupling method, and the viability is confirmed by using an experimental isolated ac‐to‐dc converter based on the high‐frequency cycloconverter. As a result, the proposed power decoupling method effectively improved the displacement power factor in the line current to more than 0.99 and reduced the output voltage ripple to 4% without any electrolytic capacitor.     

Synthesis of barium hexaferrite for magnetic recording media using the KCl flux system

Individual and fine crystals of barium hexaferrite were prepared by a modified flux method using the KCI flux system. Co²⁺-Ti⁴⁺-substituted barium hexaferrite with a homogeneous composition was synthesized at 950° C for 5 h or at 1000° C for 1 h from a mixture of BaCO₃, Fe₂O₃, CoO and TiO₂ with 30 wt% KCI added. Laboratory-prepared fine Fe₂O₃, was preferred because it gave ferrite particles with diameters of 0.2 to 0.4m. Magnetic properties were controlled by the Co-Ti content in hexaferrite crystals. Coercive force and Curie temperature decreased with the degree of Co-Ti substitution with saturation magnetization held at high value. The present process, from which individual and fine barium hexaferrite crystals can be prepared by using the KCI flux system, is recommended as a means of mass-production of ferrite powders with controlled magnetic properties for use in magnetic recording media.     

Area day-ahead photovoltaic power prediction by just-in-time modeling with meso-scale ensemble prediction system

Photovoltaics (PV) output prediction, which is indispensable for power system operation, can affects demand and supply adjustment adversely when large prediction error occurs. Thus, the reduction of large error as well as average error is required in PV power prediction. In 2019, the operation of the Meso-scale Ensemble Prediction System (MEPS) of numerical weather prediction started from the JapanMeteorological Agency, and the amount of forecasting information would be potentially useful for the improvement of PV power prediction. However, very few studies on inputting multiple meteorological elements of the MEPS have been reported. In this paper, we newly develop the prediction model for an area day-ahead PV power output composed of Just-In-Time Modeling (JIT Modeling) with multiple elements of theMEPS. The developed method achieves precise forecasts with low computational load by both selecting meteorological elements valid for improving prediction accuracy and adequately devising the structure of JIT Modeling. Some numerical examples demonstrating the effectiveness of the developed method are also presented. In particular, the proposed method reduces large error significantly.     

Real-time supply-demand schedule update and operation for generators and battery energy storage system based on forecasted and actual photovoltaic power outputs

The photovoltaic (PV) power output might be frequently curtailed to maintain electricity supply-demand balance in future power systems. In our previous study, we proposed a new method for updating the battery energy storage system (BESS) charge/discharge and the generator unit commitment (UC) schedules based on the forecasted and actual PV power outputs. The forecast dataset was updated every 3 h (eight times a day). Although the simulation results showed that the proposed method could reduce the supply-demand imbalances, it was not clear whether the forecasted or actual values made contributions. Therefore, in this study, we propose and evaluate a real-time scheduling and operation method using the forecasted and actual PV power outputs assuming that the forecasted dataset is updated only once a day. Numerical simulations of supply-demand operations are conducted on the power system model of the Kanto area of Japan for one year. The results show that the previous study method has a slight advantage over proposed method in terms of curtailed PV energy and operational cost of thermal generators reduction, but the difference is very small, indicating that the contribution of the actual PV power outputs is greater than that of the forecasted PV power outputs.     

Intercalation on Transition Metal Trichalcogenides via a Quasi-Amorphous Phase with 1D Order

Intercalation into 1D transition metal trichalcogenides (TMTs) in which fibers are bonded by a weak van der Waals force can be expected to create various intercalation compounds and develop unique physical properties according to the combination of the host materials and guest ions. However, structural changes via intercalation into 1D TMTs are not as simple as those in 2D transition metal dichalcogenides (TMDs) and are still not understood comprehensively. ZrTe₃: a typical compound with a 1D trigonal prismatic structure, belongs to TMTs. Herein, through the Ag introduction to ZrTe₃ via solid-state intercalation, a novel crystal phase with a 1D octahedral structure and a quasi-amorphous (QA) phase during the structural transition are discovered; the QA phase is a novel state of matter in which long-range order is lost while retaining 1D order. Based on the Ag concentration, the transport properties are flexibly modulated from superconductivity to semiconductivity. Density functional theory calculations indicate the attraction between Ag ions and the pair diffusion due to their attraction. Furthermore, judging the attraction or repulsion between guest ions predicts whether to induce a QA phase or simple lattice expansion like the intercalation into 2D TMDs.     

The Effect of Environmental Temperature on Distribution of Unit Chains of Rice Amylopectin

The effects of environmental temperature during the early development of seeds on the structural characteristics of the endosperm starch were investigated using near‐isogenic lines of rice plants (Taichung 65, waxy), grown under temperature controlled conditions. High performance gel permeation chromatography (HPLC) demonstrated that Pseudomonas isoamylase‐debranched amylopectins of rice plants grown at lower temperature (25°C) contain increased amounts of short chains and decreased amounts of long chains as compared with amylopectins obtained from rice plants grown at higher temperature (30°C). By high performance anion exchange chromatography with pulsed amperometric detection (HPAEC‐PAD) of isoamylase‐debranched amylopectins it was detected that the amount of unit chains with degree of polymerization (DP) 6 and 11‐13, in the amylopectin of rice plants grown at lower temperature (25°C) had significantly increased and the amount of unit chains with DP 8, 22‐24 and 29 had significantly decreased, as compared with the amylopectin of rice plants grown at higher temperature (30°C). It was confirmed that the environmental temperature between 5 and 10 d after pollination strongly influenced the structure characteristics of the endosperm starch of rice plants.     

Copper‐Catalyzed Aromatic Trifluoromethylation via Group Transfer from Fluoral Derivatives

Starting from a readily available fluoral derivative, catalytic aromatic trifluoromethylation has been successfully achieved. A small amount of copper(I) iodide‐phenanthroline complex catalyzed the cross‐coupling reactions of aryl/heteroaryl iodides with the O‐silylated hemiaminal of fluoral (trifluoroacetaldehyde) to provide trifluoromethylated arenes in moderate to high yields.