Measuring extremely low magnetic signals of diamagnetic materials such as water and ethanol with high sensitivity is important in various fields. Ethanol is widely used as a solvent in areas such as chemical industry and drug discovery; therefore, it is important to measure its concentration with high sensitivity. We have already reported a hybrid-type magnetometer using a high temperature superconductor superconducting quantum interference device (HTS-SQUID), which can measure and evaluate magnetic characteristics by vibrating and rotating a sample. However, the signal-to-noise ratio (SNR) of the system needs to be improved as magnetic signals from diamagnetism in water and ethanol are extremely low in magnitude. In this study, digital frequency filters were applied to the signals measured by the HTS-SQUID magnetometer with a rotating sample container in order to improve the SNR of the system, and then the magnetic properties of ethanol and water were studied. As a result, the SNR of the system improved about twice the level obtained by conventional signal processing method.
From growing interests in the environment issues, promotion of photovoltaic power generation (PV) is accelerated in the world. Meanwhile, rapid chargers (RCs) for popularized electric vehicles are being installed in urban areas. These two trends in distribution system might cause severer voltage fluctuation problems. On the other hand, a RC can provide the reactive power support, which is capable of voltage regulation. Based on this viewpoint, this paper proposes a new framework of voltage regulation, in which the reactive power compensation by RCs is actively utilized. The proposed voltage regulation method combines two different control functions with consideration for over-compensation avoidance. This paper ascertains the validity of proposed voltage regulation method through numerical simulations.
Recent growth of renewable energy (RE) generations with natural variability, would make the demand and supply regulation in a whole power system more difficult, and therefore, alternatives for demand and supply regulation resources would be required. The authors focus on co-generation system (CGS) owned by the consumers as one of regulation resources and have proposed a novel optimal operation strategy of CGSs to provide the demand and supply regulation. This paper discusses the optimal installation design including two configurations of CGS based on the economic viewpoints considering the energy supply cost and the financial incentive associated with the contribution for demand and supply regulation. The discussions are based on numerical case studies with the actual electrical and thermal demand profiles and equipment cost of CGS.
This paper describes a novel compact model for a SiC-MOSFET. The model is useful to achieve accurate simulation of output characteristics from a linear region to a saturation region, selecting both gate-source voltage and temperature as parameters. In order to construct the model systematically, attention is paid to a physics-based modeling procedure with channel mobility as an adjustable parameter. The model also features characterization and modeling of an internal drain-gate capacitor. The model shows fairly good agreement in the output characteristics and the dynamic behavior of both gate drive circuit and main power circuits between the experimental and simulated results. This successful validation indicates that this model offers a promising circuit-based simulation tool for designing whole power conversion systems using SiC-MOSFETs.
Recent growth of renewable energy (RE) generations with natural variability, such as photovoltaic generation and wind turbine generation, would make the demand and supply control in a whole power system more difficult, and therefore, alternatives for demand and supply regulation resources would be required. The authors focus on co-generation system (CGS) as one of regulation resources. In order to procure adequate volume of regulation capability, an aggregator coordinates a number of CGSs efficiently and flexibly considering the wide variety of electricity/thermal demands of CGS owners. This paper proposes a novel optimal operation strategy of CGS coordinated by the aggregator considering the energy balance and operation cost of individual CGS owner. This paper also demonstrates the availability of CGSs for regulation capability by numerical case studies in which the actual consumption profile is employed.
Because of a large number of facilities in distribution lines, the rationalization of power distribution equipment is an important issue. In recent years, photovoltaic power generation system (PV) has become increasingly interconnected, so the use of distributed power sources and storage battery to streamline facilities is also being studied. However, large capacity of the storage battery is required to reduce power flow in distribution lines using only the storage battery. Dynamic rating (DR), on the other hand, dynamically changes the current capacity of transmission lines and transformers according to weather conditions and other factors. In this study, the necessary capacity of the storage battery is evaluated by distribution lines according to DR. Furthermore, considering transitional characteristics of the wire temperature about current that it takes several minutes to change after varying current can increase the allowable current capacity in distribution lines based on DR. Since downsizing distribution lines to rationalize distribution facilities increases the impedance in distribution system, there is a problem that the voltage fluctuation becomes large. Therefore, this paper proposes a method for calculating the necessary capacity of storage battery according to DR considering transient temperature change and voltage fluctuations in the distribution system. Then, the necessary capacity of the storage battery is evaluated through numerical simulations based on actual annual data.
