In Japan, grid outages are becoming increasingly frequent. Photovoltaic (PV) power generation and storage batteries can be introduced to office buildings to continue operations during grid outages. However, such energy sources can only supply a limited amount of energy during a grid outage. Therefore, the rationalization of energy management is required in office buildings to reduce the costs incurred by companies during a disaster. In this study, we propose a method to rationalize the energy management of office buildings during grid outages caused by disasters. Accordingly, we realize the rationalization of energy by considering the priority of work in the office for each employee. The priority of work in the office enables to develop energy management that considers the value of each use of electricity. We evaluated the proposed method by comparing the minimized costs and the optimal equipment capacity for the cases considering the priority of work in the office and without it. The distribution of the minimized costs and the optimized capacities were estimated using a Monte Carlo simulation to consider the uncertainty of disaster occurrence.

With the developments in power electronics equipment, the electromagnetic environment has become severe for electronic equipment. In the smart facility field, the stable operation of electronic devices is indispensable, and noise countermeasures must to be improved. To suppress intrusive noise from cables, shielded cables are used in many cases. However, electromagnetic induction cannot be suppressed when the shield is grounded at one end, and when grounding both ends of the shield, current flows through the shield creating intrusive noise in the cable. That is, even if a shielded cable is used, a sufficient effect cannot be obtained. Therefore, as a countermeasure, this study prototypes and evaluates cables that combine double shielded cables with magnetic cores. Evaluations conducted using the copper pipe method, triaxial method, and impulse test confirm that the shielded performance improved by 10 to 30dB compared with the conventional shielded cable.

Mixed integer linear programming (MILP) and particle swarm optimization (PSO) are applied to create operational plans for microgrid systems composed of photovoltaic, battery, and co-generation systems. In this study, yearly operation plans are created using either MILP or PSO method with different optimization characteristics to minimize the operational cost, and evaluates the practicality of each method in terms of calculation accuracy and calculation time. Furthermore, a novel hybridized method is developed using the two calculation methods, and its usefulness is evaluated.

To optimally conduct capital investment and energy management for buildings with storage batteries and photovoltaic (PV) generation, it is essential to accurately predict the electricity demand not only on weekdays but also on holidays and event days. However, predicting the building power demand on holidays and event days is difficult because facility operations and the number of occupants in a building are different from weekdays. In this paper, we propose a method to estimate unusual power demand by considering the power demand structure of existing buildings. The proposed method is an application of disaggregation techniques based on linear regression. First, a power demand structure model is developed by calculating the facility status demand contribution and number of occupants from weekday operational data. Second, the daily power demand is estimated with high accuracy by applying hypothetical operational scenarios, such as holidays, to the model. Experimental data from real offices confirm that the proposed method could estimate the power demand during weekends and vacation periods when the attendance rate is reduced by half.

This paper proposes anomaly detection for hydroelectric generating units by Fast Robust Random Cut Forest with a fast feature selection method by considering characteristics of operating data and Random Cut Trees. Hydroelectric generating units are renewable electric generating sources for electricity supply. Therefore, it is crucial to accurately detect anomalies of hydroelectric generating units. Moreover, effective features for anomaly detection should be selected to reduce operation costs of anomaly detection services. The proposed anomaly detection method can detect anomalies approximately thirty times faster than the conventional Robust Random Cut Forest with an accuracy comparative to that of the conventional method. The proposed feature selection method can select effective features almost fifty times faster than the conventional feature selection method.

Static electricity is used in numerous practical applications, such as copy machines and dust collectors. When a person gets up from a chair or walks in a room using an air conditioner, the person's body becomes charged. When a charged body approaches or moves away from the metal case of an electronic device, the electronic device suffurs a malfunction or failure due to the electrostatically induced voltage. The electrostatically induced voltage of a charged body moving away from a metal case is higher than the voltage induced when the charged body approaches the metal case. We conducted an experimental study on the electrostatically induced voltage generated in two ungrounded metal cases when a charged body moves away from the metal cases. The results showed that electrostatically induced voltages of 0.4 to 0.5 times was generated in the two ungrounded metal cases against the voltage of the charged body when each electrostatic induction electrode with a spark gap and each electromagnetic wave sensor is used of a noncontact electrostatic measuring device. We believe that these results will aid in the prevention of malfunction or failure of electronic devices.

Recently, with the rapid increase in electric power supply, ground faults such as electric shocks and fires frequently occur. Hence, leakage protection has become increasingly important. Meanwhile, with the development of power electronic technology, distortions in power systems owing to power supply switching have increased considerably. In this paper, we present the leakage current caused by ground capacitance when the system voltage includes harmonics, and a large error is noted in the measurement results of the ground fault detection method Ior, which is currently mainstream.

This paper focuses on the propeller's rotational speed measurement by WLAN sensing using the channel state information (CSI) that indicates the multipath propagation characteristic between transmitting and receiving antennas. To measure the rotation speed by the measurement device via light and reflecting label with contactless, the distance from the target object has to be short, and such devices are not ideal for long-distance measurements from the target object. We propose a rotational speed estimation algorithm using CSI comprising time, frequency, and space domain information in MIMO-OFDM transmission to overcome this problem. The proposed algorithm transforms the time series data for each subcarrier into the normalized amplitude spectrum. After that, the rotational speed is estimated using the sum of the normalized amplitude spectrum in all subcarriers. The experimental results reveal that the proposed algorithm achieves high accuracy at a distance of 5 m from the propeller fabricated with an acrylic material and a blade length of 15cm. Moreover, if the propeller is fabricated with an aluminum, the proposed algorithm achieves high accuracy at a distance of 5 m even if the blade length is short, 5cm.

In recent years, the global movement toward decarbonization has accelerated, and renewable energy has attracted increasing attention. Among the various systems adopted for renewable power generation, photovoltaic (PV) power generation systems are becoming widespread as they have no moving or rotating parts and are easy to install. However, PV power generation modules generally emit noise during power generation and suffer from radio wave interference with the amplitude modulated radio band (531kHz to 1602kHz). In our previous study we confirmed radiation noise suppression with the installation of a noise suppression wire with a closed loop of copper wire in a 15-W-class PV module. In this study, we aim to clarify the noise suppression effect produced by a noise suppression wire installed on a 250-W-class PV module with a larger power generation capability than that in our previous study and a different internal structure of the PV module. Our results suggest that the proposed noise suppression method is effective for 250-W-class PV modules as well.

In this paper, we propose a novel method to improve the circuit simulation accuracy of insulated-gate bipolar transistor (IGBT) power devices under a short-circuit state. To determine the IGBT junction temperature, the transient thermal resistance of an IGBT device on the order of micro seconds is estimated by transient thermal simulations. The saturation current without self-heating effects is estimated based on a short-circuit test and the transient thermal resistance. The IGBT SPICE parameter is extracted from the saturation current characteristics during the short-circuit state. The coupled electrical-thermal simulations with the SPICE model and thermal resistance model are applied to several short-circuit evaluations with different parasitic impedance and gate driving condition, and the results are consistent with the measured current and voltage waveforms.

Various PWM modulation schemes have been proposed for three-phase voltage source inverters with different representation methods. This paper proposes a novel representation method for various modulation schemes in a unified manner by introducing a variable called the zero-voltage vector ratio. This paper also shows that the proposed method can represent three conventional modulation schemes.

Our research focuses on energy electronics including high efficiency switching converters for DC power supply systems, battery management system for recycling used EV batteries, and solar power generation systems for mobilities.