A design method for distributed battery storage capacity has been developed for evaluating battery storage advantage on demand-supply imbalance control in distribution systems with which large-scale home photovoltaic powers connected. The proposed method is based on a linear storage capacity minimization model with design basis demand load and photovoltaic output time series subjective to battery management constraints. The design method has been experimentally applied to a sample distribution system with substation storage and terminal area storage. From the numerical results, the developed method successfully clarifies the charge-discharge control and stored power variation, satisfies peak cut requirement, and pinpoints the minimum distributed storage capacity.
Photovoltaic (PV) systems are rapidly gaining acceptance as some of the best alternative energy sources. Usually the power output of PV system fluctuates depending on weather conditions. In order to control the fluctuating power output for PV system, it requires control method of energy storage system. This paper proposes an optimization approach to determine the operational planning of power output for PV system with battery energy storage system (BESS). This approach aims to obtain more benefit for electrical power selling and to smooth the fluctuating power output for PV system. The optimization method applies genetic algorithm (GA) considering PV power output forecast error. The forecast error is based on our previous works with the insolation forecasting at one day ahead by using weather reported data, fuzzy theory and neural network(NN). The validity of the proposed method is confirmed by the computer simulations.
This paper describes a wind power forecasting method and its confidence interval estimation. Recently, flat control of wind power generators by various batteries is required. For the flat control, accurate wind power forecasts and their error confidence intervals are needed. In this paper, wind speed forecasts are calculated by regression models using GPV (Grid Point Vale) weather forecasts. The forecasts are adjusted by the fuzzy inference using the latest errors. The wind power forecasts are translated from the wind speed forecasts using two power-curves. The power-curves are selected or combined by fuzzy inference depending on wind direction. The error confidence interval models are generated for each forecasting target time. Each confidence interval is combined by the other fuzzy inference. The proposed methods are applied to actual wind power generators, and found that forecasting errors are better than the conventional methods. The almost all of forecasts can be within error confidence intervals estimated by the proposed method. The results show the effectiveness of the proposed methods.
A penetration of renewable energy sources such as photovoltaic, wind power etc to prevent global warming is become increasing highly. However, a random unpredictable wind power output may cause frequency fluctuation on isolated hybrid wind-diesel power system. This paper proposes design of coordinated control of governor, pitch and battery to stabilize frequency fluctuation in isolated wind-diesel power system. A well coordinated control between governor, pitch and battery controller are able to improve a performance and also minimize an interaction between the controllers. The structure of the proposed controllers are the first-order PI controller. They are simple and easy to implement in power system utilities. The robustness of the proposed PI controllers are guaranteed by applying an inverse additive perturbation to represent possible unstructured uncertainties in the power system such as variation of system parameters, generating and loading conditions etc. The proposed PI control parameters are optimized and achieved by a genetic algorithm (GA). Simulation studies have been done to show the control effect and robustness of the proposed PI controller in isolated hybrid wind-diesel power system against various disturbances and system uncertainties.
Mutual smoothing effect of renewable energy (RE) is quite important because amount and cost of countermeasure for maintaining soundness of power system highly depend on evaluation of the effect. In spite of the importance, there is no established method to evaluate the effect yet. The paper presents a method for presuming total output fluctuation of highly penetrated RE from few measured data considering the effect. By analyzing measured data, existing photovoltaic (PV) output fluctuation is revealed to be coherent at slower swing period and random at faster. To represent the PV's output fluctuation tendencies, “Transfer Hypothesis” is introduced. “Constant transfer swing period hypothesis” and “-20dB/dec slope hypothesis” are supplementary introduced. Those hypotheses are verified by direct and indirect methods using the measured data. Only 3 sites' data are able to presume total fluctuation of 15 sites successfully. Relationship of distance and transfer swing period of every 2 sites out of the 15 sites agrees to those hypotheses. Finally, the paper shows total fluctuation presumption of highly penetrated PV in Hokuriku region using proposed methods.
A microgrid (MG) is one of the measures for enhancing the high penetration of renewable energy (RE)-based distributed generators (DGs). If a number of MGs are controlled to maintain the predetermined electricity demand including RE-based DGs as negative demand, they would contribute to supply-demand balancing of whole electric power system. For constructing a MG economically, the capacity optimization of controllable DGs against RE-based DGs is essential. By using a numerical simulation model developed based on a demonstrative study on a MG using PAFC and NaS battery as controllable DGs and photovoltaic power generation system (PVS) as a RE-based DG, this study discusses the influence of forecast accuracy of PVS output on the capacity optimization. Three forecast cases with different accuracy are compared. The main results are as follows. Even with no forecast error during every 30 min. as the ideal forecast method, the required capacity of NaS battery reaches about 40% of PVS capacity for mitigating the instantaneous forecast error within 30 min. The required capacity to compensate for the forecast error is doubled with the actual forecast method. The influence of forecast error can be reduced by adjusting the scheduled power output of controllable DGs according to the weather forecast. Besides, the required capacity can be reduced significantly if the error of balancing control in a MG is acceptable for a few percentages of periods, because the total periods of large forecast error is not so often.
This paper presents the evaluation on the impact of an extensive introduction of photovoltaic (PV) system and stationary battery technology into optimal power generation mix in Kanto and Kinki region. The introduction of solar PV system is expected to be extensively deployed in Japanese household sector and utility company in order to address the concerns of energy security and climate change. Considering this expected large-scale deployment of PV system in electric power system, it is necessary to investigate the optimal power generation mix which is technologically capable of controlling and accommodating the intermittent output-power fluctuation inherently derived from PV system. On these backgrounds, we develop both solar photovoltaic power generation model and optimal power generation mix model, including stationary battery technology, which are able to explicitly analyze the impact of PV output fluctuation in detailed resolution of time interval like 10 minutes at consecutive 365 days. Simulation results reveal that PV introduction does not necessarily increase battery technology due to the cost competitiveness of thermal power plants in load following requirement caused by PV system. Additionally, on the basis of sensitivity analysis on PV system cost, dramatic cost reduction proves to be indispensable enough for PV to supply a bulk of electricity similarly as thermal and nuclear power plant.
A photovoltaic power generation system (PVS) is one of the promising measures to develop a low carbon society. Because of the unstable power output characteristics, a robust forecast method must be employed for realizing the high penetration of PVS into an electric power system. Considering the difference in power output patterns among PVSs dispersed in the service area of electric power system, the forecast error would vary among locations, resulting in the reduced forecast error of the ensemble average power output of high penetration PVS. In this paper, by using the multi-point data of insolation observed in Chubu area during four months, we evaluated the forecast error of the ensemble average insolation of 11 districts, and compared it with the forecast error of individual district. As the results, the number of periods with the forecast error larger than the average insolation during four months is reduced by 16 hours for the ensemble average insolation compared with the average value of individual forecast. The largest forecast error during four months is also reduced to 0.45 kWh/m2 for the ensemble average insolation from 0.68 kWh/m2 on average of 11 districts.
Smoothing effect of photovoltaic (PV) generation is quite important because amount and cost of countermeasure for maintaining soundness of power system highly depends on assessment of the effect. In order to estimate the PV generation accurately, it is important to take into account of PV sites' distribution. In this paper, we propose a method for estimating the total output of PV considering reduction of smoothing effect caused by uneven distribution of PV sites, using some measured data. In the thought experiment, we made some ideal model representing uneven distribution. The model is extended to apply realistic distribution of Hokuriku region. Finally, total PV output fluctuations in Hokuriku region are estimated both even and uneven distribution cases.
Penetrating the Photovoltaic Power Generation System (PV) on an enormous scale over a next decade has some crucial problems which affect on, for example, power grid stabilization and operation including existing power stations for electric power utilities. It would be therefore important for future operation to estimate power output generated by PV in advance. We focus on interpolation using observed solar irradiation (SI) and brightness of pixel on a satellite visible image for estimating SI even in non-observed point. Our results by single regression analysis between observed SI and brightness on a satellite image as cloudiness show that a shift of highest determination coefficient on each hour would represent solar movement and this higher determination coefficient would indicate a position which SI and cloud would cross. Finally assessment of error in this interpolation shows enough accuracy at least in daytime period, which is important for electricity utilities.
Transmission characteristics of multi-hop wireless LAN (IEEE 802.11g) are degraded according to the number of hops due to the nature of multiple access control. To decrease the number of hops in the multi-hop network, a connecting node selection method according to the depth of hop is evaluated. To prevent packet congestion due to the flooding packet using the L3 routing method, L2 routing method using only data link layer information such as received power is also evaluated. The maximum number of hops, which indicates the minimum throughput and maximum response time in the multi-hop network, is effectively decreased even under the condition of high repeater-node density by using the number of hops together with the received power as the metrics, in comparison with the conventional metric of received power only.
Standing from a chair is an important task of daily living for physically handicapped people. In a rehabilitation center, a health care professional is planning motion based on the experience and knowledge so that a patient may stand up with few loads. Therefore, there is a problem that the plan is different occasionally as each health care professional. In this paper, a generation method of motion trajectory to stand from a seated position with few loads by using Genetic Algorithm (GA) was proposed. The human body was expressed as three-rigid-link model. In the model, the ankle, the knee, and the waist were set to the joint. Moreover, Electromyography (EMG) generated from the muscle to drive each joint was measured, and the model between each joint torque and EMG was constructed with the ARX model. The motion trajectory to stand from the seated position was generated by using GA with the evaluation function based on the constructed ARX model. The generated motion trajectory was evaluated by the experimental work with eight healthy subjects. As a result, the effect of the proposed method was objectively verified by subject's EMG. In addition, subjective effect of the proposed method was verified by analysis of variance about subject's impression.
A mobile feeding assistive robotic arm for people with physical disabilities of the extremities has been developed in this paper. This system is composed of a robotic arm, microcontroller, and its interface. The main unit of the robotic arm can be contained in a laptop computer's briefcase. Its weight is 5kg, including two 12-V lead acid rechargeable batteries. This robotic arm can be also mounted on a wheelchair. To verify performance of the mobile robotic arm system, drinking tea task was experimentally performed by two able-bodied subjects as well as three persons suffering from muscular dystrophy. From the experimental results, it was clear that they could smoothly carry out the drinking task, and that the robotic arm could firmly grasp a commercially available 500-ml plastic bottle. The eating task was also performed by the two able-bodied subjects. The experimental results showed that they could eat porridge by using a spoon without any difficulty.
This paper introduces a multi-hopped wireless sensor network for remote bridge health monitoring, including system architecture, transmission protocol, data acquiring and processing. This system based on detecting the three-dimension vibration or acceleration data of the bridge, which data is caused by external impacts such as a car or a truck. Comparing with traditional monitoring systems, this bridge health monitoring system has advantages in human-free, long-life, and real-time responses. Additionally, to compare data of a damaged bridge and a healthy one, an experiment of making artificial damage to a bridge is carried out with consent of related departments. Moreover, this system can be applied in any form of bridges. In the future, it is even expected to be applied in other kind of buildings more than bridges.
This paper proposes a design method of dynamic quantizers for MIMO networked control systems. It is well known that feedback type dynamic quantizers are effective for quantization of the data series in the meaning of noise shaping. The dynamic quantizers include a set of a dynamic filter and a static quantizer. When it is required to use the quantizer under the network communication, the data size of signal should be minimized appropriately by the quantizers. The authors have proposed a design method of the dynamic quantizers for SISO systems based on the communication rate constraint. In this paper, the design method is extended to MIMO systems. By this extension, we can handle the communication rate constraint for a kind of concentrated systems. In the setting of the quantizer for MIMO system, bit assignment is important matter for appropriate design of information flow. The effectiveness of proposed design method is shown by numerical examples.
Two experimental studies have been conducted in order to propose practice indexes for the improvement of the embouchure of French horn players, two experimental studies have been conducted. In both studies, the same task was performed by advanced and amateur French horn players. The first study investigated the activity, while performing the above-mentioned task, of the 5 facial muscles (levator labii superioris, zygomaticus major, depressor anguli oris, depressor labii inferioris, and risorius muscles) on the right side of the face by surface electromyography, and the facial movement on the left side of the face by attaching two markers above each muscle and using two high-speed cameras simultaneously. The results of the study showed that it is possible for the four markers around the lower lip to practice indexes. The second study evaluated whether the above-mentioned markers are appropriate as practice indexes using a 3-D tracking system and questionnaires. The results showed that both the advanced and the amateur players assessed that the markers were suitable as practice indexes for improving the embouchure. This set of approaches could be useful for selecting practice indexes and developing scientific practice methods not only for the French horn but also for other instruments and other fields.
Histogram equalization (HE) is a simple and effective method for contrast enhancement as it can automatically define the gray-levels transformation function based on the distribution of gray-levels included in the image. HE fails to produce satisfactory results for a broad variety of low-contrast images because the HE does not use a spatial feature included in the input image. This paper proposes a novel contrast enhancement method using not only the conventional histogram but also the differential gray-levels histogram of the input image. The differential gray-levels histogram contains edge information of the input image. Edge information is one of the important spatial features of the image. We can extract the regions where are wanted to be emphasized by using both the conventional histogram and the differential gray-levels histogram. The input histogram is modified by the histogram of the extracted regions. The gray-levels transformation function is derived by the modified histogram.
The flow of freshwater into the sea, termed as submarine groundwater discharge, is a key factor for understanding the hydrological cycle in both the sea and land regions. The numerous positions from which freshwater gushes out or its quantity impedes the understanding of its properties. In our previous study, we have detected groundwater discharge points arising due to the difference in freshwater and seawater by using the multispectral Landsat ETM+ signals with 30m spatial resolution. The details of seawater surface information regarding the submarine groundwater discharge haven't been obtained yet. Therefore, this paper analyzes features in water properties around the groundwater discharge points by using the ALOS AVNIR-2 outputs, providing 10m spatial resolution. That is, classified maps obtained by the k-means clustering are compared with the measurements in the ground survey, the geologic map, and the estimation map of the relative salinity. Our experimental results obtained by the AVNIR-2 are in considerable agreement with the realities in the study area.
In order to execute multiple policies in policy-based automation system safely and efficiently, we propose and develop the concurrency control mechanism for policy-based automation system. This mechanism analyzes the logical structure of the target application system to identify the IT resources affected by the policy action, and locks the resources to prevent multiple policies' conflicts. Additionally, the efficient preemptive scheduling scheme for the multiple policy executions is also developed.
The purpose of this paper is to propose a new index for the seismic damage estimation of service lines. The proposed index is evaluated based on the tension of each service line due to an earthquake event. Because the tension is evaluated based on not only the seismic intensity, but also the dynamic property of the major components of the distribution equipment including the pole, line, transformer, and service line, the proposed index enables us to quantitatively differentiate the seismic damage level of every distribution pole. On the basis of the seismic damage record caused by the 2007 Niigata-Ken Chuetsu-Oki earthquake, the estimate accuracy of the proposed index is compared to those with existing damage indices. As a result, it was clarified that the proposed index is more appropriate than existing indices for the equipment damage estimation.
Recently, digital documents in companies increase rapidly and are required to be ensured. Pop-up of business information according to PC usage situation can achieve this goal. Two functions are required to it: One is to correctly discriminate pop-up conditions from contents of business-use application, and the other is to select suppression keywords from incorrect pop-up documents. The suppression keywords should improve true negative rate without drop of recall. Based on observation of typical phrases and increase of frequencies for characteristic phrases in contents of business-use applications, we select suppression keywords according to their frequency in positive and negative cases and their occurrence in feedback document. Our evaluation using three kinds of business information shows that the proposed method can achieve both high true negative rate and high recall, and to correctly discriminate pop-up conditions.
Power-law distributions have been found in natural and social phenomena (known as ‘power-law’). City population studies have shown that the power-law holds for relations between city sizes and their ranks. Here population distributions of Okinawa islands are examined using census data from 1955 to 2005. Obtained results reveal that sizes of islands populations provide power-law distributions. Furthermore, power-law distributions are observed in sizes of population shifts for a range of periods from five years to 50 years. The spatio-temporal structure may shed light on self-organizing mechanisms underlying power-law distributions.
There is a roundrobin method that simply distributes communication load to multiple communication ports. However, because high-performance interconnections process several frames at a time, the discontinuous frames in each port cause frequent out of order processes. The proposed N-roundrobin method, that decreases out of order, improves communication bandwidth.