Challenges for a reduced inertia power system due to the large-scale integration of renewable energy

This paper reports on the status of technology development under a national project launched in 2019 to address the problem of decreased system inertia associated with the large-scale integration of renewable energy.The project comprises two parts:the development of a system inertia observation technology using a continuous monitoring system to observe inertia and development of an inverter equipped with a function to provide virtual inertia as a countermeasure device.Utilizing both these efforts,the project aims to facilitate the introduction of renewable energy in the future with minimum restrictions.It was confirmed that the trend of inertia observed with the developed method was generally the same as that of the total inertia of synchronous machines observed by an electric utility.The effectiveness of the countermeasure device in reducing the frequency swing during a disturbance was confirmed through evaluation tests.

功率波动引起电压波动最小化的风力发电系统无功功率最优控制

本文提出了一种新的控制方案,最大限度地减少风力发电系统输出功率产生的电网电压波动。这种控制方案可以使风力发电系统抑制不同的电网条件下电压波动。使用这种控制策略的风力发电系统通过计算其输出功率的波动和电网电压波动之间的相关性来在线估计阻抗比R/X。通过输出最佳的无功功率,其值等于阻抗比与发电功率相乘,可有效地抑制电压波动。通过抑制电压波动,使其低于电网规范中所规定的可接受水平,可以提高接入给定电网的风力发电系统容量。仿真及与电网模拟器相连的小功率实验结果验证了所提出的控制方案。

Experimental antithrombotic effect of potatoes harvested in the autumn

Prevention of arterial thrombotic diseases has a high priority in developed countries. While an inappropriate diet is known to enhance the risk for acute thrombotic events, a regular diet with proven antithrombotic effects might be beneficial in the prevention of such diseases. The present study is part of a series of investigations aimed to assess the possible antithrombotic activity of various fruits and vegetables. Previously we demonstrated antithrombotic effect of specific potato varieties harvested in the spring. The present study aimed to test seven varieties of potatoes, which were harvested in the autumn. The in vitro Global Thrombosis Test (GTT) was used for selection, which was then followed by the He-Ne laser-induced in vivo thrombosis test in mice treated with potato filtrates orally. We have shown that all seven potato varieties showed some antithrombotic effect and the heat-resistant effect of four varieties was highly significant. Our present findings add further components to a diet containing fruits and vegetables with antithrombotic effect.

Usefulness of the SNR Using the Subtraction Method and Image Visibility Using the Howlett Chart Method in X-Ray Fluoroscopic System

X-ray fluoroscopy has been used not only for diagnoses but also for treatment, as in interventional radiology. The aim of this study is to assess the usefulness of the signal-to-noise ratio (SNR) using the subtraction method, which is used in the quality assurance/quality control (QA/QC) of magnetic resonance imaging (MRI) equipment, and image visibility using the Howlett chart method in the fluoroscopic examination. The fluoroscopy unit has a detector with an image intensifier and a color liquid crystal display. A 2620 dosimeter and an ionization chamber were selected for the dose measurement. Fluoroscopic images for visual and physical evaluations were collected as dynamic data. The skin surface absorbed dose rates for each tube current were measured using a dosimeter. The SNR using the subtraction method and image visibility using the Howlett chart method were examined. The results from both indicate that as the SNR improves, visual evaluation increases, but the rate of increase gradually saturates. Therefore, physical and visual evaluations are possible with the SNR using the subtraction method and the image visibility using the Howlett chart method.

Thermal physiological response to local heating and cooling during sleep

For a healthy and productive life, good steep is essential, which has prompted studies on how comfortable sleep can be achieved. Understanding the relationship between thermal environment and physiological responses such as skin and core temperatures, and psychological responses such as thermal and sleep sensations is necessary to identify the most suitable thermal environment for steep. As an energy-saving and practical method of creating the most appropriate thermal environment for sleep, local heating or cooling is sometimes used, which takes into consideration the differences in local thermal responses. We performed this study to identify the most effective thermal environment for inducing comfortable sleep by identifying the physiological responses during sleep on the basis of sleep experiments conducted under local body heating or cooling conditions. We also used a human thermal model, which can be applied for predicting physiological responses. In the experiments, the feet of the subject were the primary area to be heated or cooled, which was achieved by installing a flexible duct with an outlet placed close to the subject＇s feet and inlet connected to an air conditioner. Differences in the fluctuation of body temperature and sleep stage depended on the airflow direction from the duct to the feet. When air was blown downward towards the feet, body temperature decreased and the subject was able to sleep well. Measured skin and core temperatures were calculated using an improved 27-node human thermal model that was originally developed for use in subjects who are not in steep. Although skin

Development of a Mobile Sensing Unit and Its Prototype Implementation

This paper represents a design and development of a mobile sensing unit as well as its prototype implementation for railway track monitoring. The unit consists of an ultra-small personal computer (PC), a global positioning system (GPS) receiver, an accelerometer and an ADC (Analog/Digital Converter) so that the unit can trace the route while capturing an acceleration response of a passenger vehicle. The unit enables more frequent and qualitative data acquisition compared with traditional and the state of the practice railway track inspection equipments. Locating disorder is the key of our unit, which has a reasonable accuracy of positioning with GPS data, existing facilities landmarks, and car acceleration responses. The proposed unit is a promising device for efficient properties management of railway agencies. The prototype implementation shows a result that car acceleration responses are related with the track displacements in low frequencies. The results also imply that sensor settlement on a vehicle floor, not axes or bogies, is effective for capturing track vertical displacements.