Kawasaki Technology Co.

Akashi, Japan

Kawasaki Technology Co.

Akashi, Japan
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Hirase Y.,Kawasaki Technology Co. | Noro O.,Kawasaki Technology Co. | Katsura S.,Kawasaki Technology Co. | Abe K.,Kawasaki Technology Co. | And 3 more authors.
IEEJ Transactions on Industry Applications | Year: 2017

In Japan, commercial grid for ordinary residential houses consists of a single-phase three-wire system. In general, unbalanced load power is supplied by the commercial grid. Recently, there have been an increasing number of houses equipped with the emergency power units in preparation for possible power outages. However, because most of the conventional power inverters in these units cannot supply unbalanced power, home appliances must be reconnected to dedicated outlets when they are used in the grid-disconnected operation. To solve such an inconvenient situation, we propose a method that enables the uninterruptible power supply between the grid-connected and grid-disconnected operations for single-phase three-wire systems. This control method is mounted on the power inverters and is called the virtual synchronous generator (VSG) control. The method is developed expanding the previous method for a single-phase two-wire system. © 2017 The Institute of Electrical Engineers of Japan.


Hirase Y.,Kawasaki Technology Co. | Abe K.,Kawasaki Technology Co. | Sugimoto K.,Kawasaki Heavy Industries | Sakimoto K.,Kawasaki Heavy Industries | And 2 more authors.
Applied Energy | Year: 2017

To achieve a more sustainable supply of electricity, consumers are expected to rely increasingly on combinations of various types of power generators. Among them, distributed generators (DGs) utilizing renewable energy sources (RESs) are a promising solution. However, introducing renewable energy based DGs into microgrids (MGs) can reduce the inertia of the whole power system, and hence, the system frequency and the voltage can be fluctuated. Furthermore, unnecessary interference occurs as the number of synchronous machines increases. To address these issues, it is desirable to develop a noble inverter control method for DGs, and to gain an intuitive understanding of the dynamic characteristics of MG power systems. In this paper, the impacts of frequency/voltage deviations in MGs are mathematically investigated using algebraic-type virtual synchronous generator (VSG). The algebraic-type VSG with a minimal number of parameters has an ability to suppress the system frequency and voltage deviations. The proposed control approach presents a suitable solution for penetration of more and more renewable energy into the existing power grids. The results of the analysis were verified via simulations and experiments. © 2017 Elsevier Ltd.


Hirase Y.,Kawasaki Technology Co. | Abe K.,Kawasaki Technology Co. | Sugimoto K.,Kawasaki Heavy Industries | Shindo Y.,Kawasaki Heavy Industries
IEEJ Transactions on Power and Energy | Year: 2012

This paper presents the experimental results of a grid connected inverter. The control of the inverter is based on the virtual synchronous generator model of algebraic type. In case of using the virtual synchronous generator model of algebraic type, there is no evidence for the satisfactory operation with unbalanced load and nonlinear load, because the generator model are constructed under the assumption that the load is linear and balanced. By choosing the feedback control loop gain appropriately, the satisfactory operation is achieved even if the unbalanced and nonlinear load is connected. Experimental results show that the power controls, active and reactive, are achieved preferably in grid connecting mode. Smooth transitions are also achieved from connecting mode to the island mode. The inverter can operate satisfactorily when the unbalanced load is connected. Harmonic analysis is done when a three-phase full-wave rectifier is connected as a nonlinear load. The harmonic current is supplied by the inverter and its output LC filter. It is shown that the harmonic current is supplied mainly by the inverter and that the voltage waveform is practically acceptable. © 2012 The Institute of Electrical Engineers of Japan.


Yamanaka T.,Okayama University | Maeto K.,Okayama University | Maeto K.,Geothermal Engineering Co. | Akashi H.,Okayama University | And 17 more authors.
Journal of Volcanology and Geothermal Research | Year: 2013

Active hydrothermal venting from shallow seafloor (200-m depth) with talc chimneys has been discovered at the Wakamiko Crater floor in the Aira Caldera, southern Kyushu, Japan. The major chemical composition of the fluids suggests that the fluids are supplied from a single reservoir. The fluid is characterized by a low chloride concentration, low δD value, and a high δ18O value, suggesting that the endmember hydrothermal fluid is a mixture of seawater and andesitic water and possibly contribution of meteoric water and/or phase separation. Such noticeable magmatic input may be supported by high helium isotopic ratio (6.77 RA) of fumarolic gas discharging from the crater. Silica and alkaline geothermometers indicate that the fluid-rock interaction in the reservoir occurs in the temperature range of 230 to 250°C. The high alkalinity and high ammonium and dissolved organic matter concentrations in the fluid indicate interaction of the fluid with organic matter in sedimentary layers. At least three hydrothermal vents have been observed in the crater. Two of these have similar cone-shaped chimneys. The chimneys have a unique mineralogy and consist dominantly of talc (kerolite and hydrated talc) with lesser amounts of carbonate (dolomite and magnesite), anhydrite, amorphous silica, and stibnite. The precipitation temperature estimated from δ18O values of talc was almost consistent with the observed fluid temperature. Geochemical modeling calculations also support the formation of talc and carbonate upon mixing of the endmember hydrothermal fluid with seawater and suggest that the talc chimneys are currently growing from venting fluid. © 2013 Elsevier B.V.


Hirase Y.,Kawasaki Technology Co. | Abe K.,Kawasaki Technology Co. | Noro O.,Kawasaki Technology Co. | Sugimoto K.,Kawasaki Heavy Industries | Sakimoto K.,Kawasaki Heavy Industries
2016 IEEE 17th Workshop on Control and Modeling for Power Electronics, COMPEL 2016 | Year: 2016

Because of the increasing use of renewable energy technology, distributed power sources and greatly varying loads can be critical factors in power system destabilization. This problem has hampered the adoption of renewable energy; thus, researchers have studied various control method types that enable an inverter to be operated as a synchronous generator (SG). Some of these methods, referred to as Virtual Synchronous Generators (VSGs), are designed to provide virtual inertia. Using VSG technology, we can decrease the introduction of fossil fuel-based power, which allows a variety of energy sources to be combined. In this study, we derived and analyzed the frequency system dynamics of microgrids, and show that a VSG expressed as a first-order equation can stabilize the frequency of a grid without causing resonance among the generators and loads. Furthermore, we derived excitation system dynamics, and observed that a VSG applying constant impedance can reduce the voltage fluctuations in the system. The results were verified in laboratory experiments and through a simulation using EMTP-RV. The simulation test results, which were generated using data acquired from an actual photovoltaic facility, indicated that the VSG could effectively suppress system deviations caused by sudden weather change. © 2016 IEEE.


Nagae N.,Kawasaki Technology Co.
Nihon Kikai Gakkai Ronbunshu, C Hen/Transactions of the Japan Society of Mechanical Engineers, Part C | Year: 2013

The predictive accuracy for the dynamic behaviour of a rotor under conditions of high-speed spinning depends on the accuracy of the numerical model of the rotor, the dynamic characteristics of the bearings and/or the seals, and the external force. In order to improve the accuracy of the numerical model, we propose a method to identify all characteristic matrices in the vibration equation of a rotor based on the information on rigid and elastic properties which can be obtained by a vibration test without spinning. The rotor is assumed to be composed of a shaft which can be modeled as beam elements and rigid discs. The proposed method can be applied for model reduction in which the reduced number of beam elements is feasible to calculate the dynamic behaviour of the rotor. © 2013 The Japan Society of Mechanical Engineers.


Hirase Y.,Kawasaki Technology Co. | Abe K.,Kawasaki Technology Co. | Sugimoto K.,Kawasaki Heavy Industries | Shindo Y.,Kawasaki Heavy Industries
Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi) | Year: 2013

Summary This paper presents experimental results on a grid-connected inverter. The control of the inverter is based on a virtual synchronous generator model of algebraic type. When using the virtual synchronous generator model of algebraic type, there is no evidence for satisfactory operation with unbalanced load and nonlinear load, because the generator models are constructed under the assumption that the load is linear and balanced. By choosing the feedback control loop gain appropriately, satisfactory operation is achieved even if an unbalanced and nonlinear load is connected. Experimental results show that the power controls, active and reactive, are achieved preferably in grid-connecting mode. Smooth transitions are also achieved from the connected mode to the island mode. The inverter can operate satisfactorily when the unbalanced load is connected. Harmonic analysis is performed with a three-phase full-wave rectifier connected as a nonlinear load. The harmonic current is supplied by the inverter and its output LC filter. It is shown that the harmonic current is supplied mainly by the inverter and that the voltage waveform is acceptable for practical use. © 2013 Wiley Periodicals, Inc.


Shindo Y.,Kawasaki Heavy Industries | Noro O.,Kawasaki Technology Co.
IEEJ Transactions on Fundamentals and Materials | Year: 2014

Simulation models of magnetic sheets are proposed. The partial fraction decomposition for trigonometric functions is used to obtain the models in the form of Foster I and II realizations, while the formulas for Bessel functions are used to obtain the models in the form of Cauer I. It is shown that the convergence speed of Cauer realization is much faster than that of Foster's. It implies that the circuit behaviors with wide frequency range can be evaluated by using small number of circuits components. Cauer II realization is obtained by transforming impedance functions given by Cauer I. It is shown that the flux behaviors in the magnetic sheets can be properly estimated by Cauer II models. Simulation models for magnetic wires are also presented by the methods mentioned above. The proposed method is applied to the analysis of inverter surge voltage. The results show that the proposed method is adequate for practical use. © 2014 The Institute of Electrical Engineers of Japan.


Hirase Y.,Kawasaki Technology Co. | Noro O.,Kawasaki Technology Co. | Sugimoto K.,Kawasaki Heavy Industries | Sakimoto K.,Kawasaki Heavy Industries | And 2 more authors.
IECON 2015 - 41st Annual Conference of the IEEE Industrial Electronics Society | Year: 2015

When a greatly varying load is connected to a weak system, stability of the system becomes a problem. In these days, because the use of renewable energy is accelerating, not only the loads but also the distributed power sources can be critical factors in destabilizing the system. The virtual synchronous generator (VSG) control allows a static inverter to behave similar to a synchronous generator (SG). Using this VSG technology, we can decrease the introduction ratio of SGs with fossil fuels, and thus, we can combine various types of power sources. At the same time, if the combination of governor and rotor inertia is represented in a first-order lag element, the VSG can suppress the frequency fluctuations in microgrids. In this paper, we present a design guideline of a VSG. The simulation results by EMTP-RV confirmed that the parallel-connected VSG can suppress the frequency fluctuation. In addition, the results were almost consistent with the experimental test results. © 2015 IEEE.


Hirase Y.,Kawasaki Technology Co. | Noro O.,Kawasaki Technology Co. | Yoshimura E.,Kawasaki Technology Co. | Nakagawa H.,Kawasaki Technology Co. | And 2 more authors.
2014 International Power Electronics Conference, IPEC-Hiroshima - ECCE Asia 2014 | Year: 2014

We have proposed the Virtual Synchronous Generator control (VSG control) and have tested it using the demonstration equipment [1]. By using the VSG control, three-phase inverters of current control type are able to run both in grid-connecting operation and in grid-disconnecting operation. Furthermore, in order to control a single-phase inverter like a three-phase inverter using the VSG control, we have applied the technique called 'Double Decoupled Synchronous Reference Frame'(DDSRF). In this paper, we will show you the simulation results and experimental results of the single-phase inverter using the VSG control with DDSRF. © 2014 IEEE.

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