Hiroaki Tsutsui

Bio: Hiroaki Tsutsui is an academic researcher from Tokyo Institute of Technology. The author has contributed to research in topics: Electromagnetic coil & Tokamak. The author has an hindex of 16, co-authored 94 publications receiving 890 citations.

Wind farms linked by SMES systems

Abstract: The objective of this paper is to introduce the concept of wind farms linked by SMES systems. In this work, the SMES system is applied to a wind farm that is interconnected with a grid through a back-to-back DC link for the variable speed operation of the wind turbines. This system enables the output power leveling of the wind farm depending on the power demand and can reduce the capacity of the converter system by selecting an optimal discharge/charge rate of the SMES. By using the stored energy of the SMES, this system can also compensate the inertia of the blades so that the wind turbine speed can be rapidly controlled depending on the wind condition. This paper describes the design condition of the SMES for the output power leveling of the wind farm and discusses the SMES configuration for a 100-MW class wind farm.

High performance tokamak experiments with a ferritic steel wall on JFT-2M

Abstract: Compatibility between the plasma and low activation ferritic steel, which is a candidate material for fusion demonstration reactors, has been investigated step by step in the JFT-2M tokamak. We have entered the third stage of the Advanced Material Tokamak EXperiment (AMTEX), where the inside of the vacuum vessel wall is completely covered with ferritic steel plates ferritic inside wall (FIW). The effects of a FIW on the plasma production, impurity release, the operation region, and H-mode characteristics have been investigated. No negative effect has been observed up to now. A high normalized beta plasma of βN ~ 3, having both an internal transport barrier and a steady H-mode edge was obtained. A remarkable reduction in ripple trapped loss from 0.26 MW m−2 (without ferritic steel) to less than 0.01 MW m−2 was demonstrated by the optimization of the thickness profile of FIW. A code to calculate fast ion losses, taking into account the full three-dimensional magnetic structure was developed, and values obtained using the code showed good agreement with experimental results. Thus, encouraging results are obtained for the use of this material in the demo-reactor.

Flexible Power Interconnection With SMES

Abstract: Electric power networks are usually interconnected with each other through a back-to-back direct-current (DC) link to increase reliability of electric power networks and to improve system operations. The objective of this work is to discuss the concept of a superconducting magnetic energy storage (SMES) incorporated into a back-to-back interconnection. In this case, the back-to-back system is used as a power conditioning system for the SMES coils. Since the AC/DC converter can be designed independently of the frequency of the power system, a two-way switch is connected to the AC side of each converter. This two-way switch can select the interconnected power system. By using the two-way switches, this system can increase the availability factor of the back-to-back interconnection during the SMES operations and also enables the flexible power interchange between interconnected power networks with an optimal time interval for the power demand of each interconnected power network. This work discusses the design considerations of the back-to-back interconnection with the SMES that enables the replacement of a pumped hydro storage. In this case, the SMES system is composed of a number of superconducting coils in order to decrease the risk of the superconducting coil constructions by the effect of mass production. In this work, the SMES coils are optimized from the required mass of the structure and the leakage magnetic field

Effects of ELM mitigation coils on energetic particle confinement in ITER steady-state operation

Abstract: The effects of edge-localized mode (ELM) mitigation coils (ELM coils) on the loss of NBI-produced fast ions and fusion-produced alpha particles are investigated using an orbit following Monte Carlo code. The ELM mitigation coil field (EMC field) may cause a significant loss of fast ions produced by NBI on the order of 16.0–17.0% for a 9 MA steady-state ITER scenario. A significant transit-particle loss occurs in the case of the toroidal mode number n = 4 in which magnetic surfaces are ergodic near the plasma periphery. When the number of ELM coils in each toroidal row is nine, the main toroidal mode n = 4 is accompanied by a complementary mode nc = 5. Concerning the resonance of fast-ion trajectories, the anti-resonant surfaces of n = 4 are very close to the resonant surfaces of nc = 5 and vice versa. Since the effect of resonance on fast-ion trajectories dominates that of anti-resonance, a synergy effect of the main and complementary modes effectively enlarges the resonant regions. In a single n-mode EMC field, the resonant and anti-resonant regions are well separated. The peak heat load due to the loss of NB-produced fast ions near the upper ELM coils is as high as 1.0–1.5 MW m−2, which exceeds the allowable level in ITER. Rotation of the EMC field is essential for ITER to alleviate the local peak heat load. Most loss particles hit the inner side of the torus of the dome in the ITER divertor. The loss of alpha particles is also increased by the effect of the EMC field. The loss is still acceptably low at less than 1.0%.

Optimization of SMES coil by using virial theorem

Abstract: The coil for the superconducting magnetic energy storage (SMES) is optimized by use of the virial theorem with stored energy and stress. In this work, we show the theoretical limit of stored energy with the maximum stress. To achieve the ideal limit, we propose the toroidal coil with helical winding. It is a hybrid coil of a toroidal field (TF) coil and a solenoidal coil helically wound on a torus. The winding is modulated in such a way that the toroidal field is created in the torus whereas the poloidal field is only out of the torus. In this case, the electromagnetic force is represented by the difference in the poloidal and the toroidal magnetic pressure. The virial theorem in the magnet is the relation of the magnetic energy and the averaged stress, and shows that the best coil to store the magnetic energy under the weakest averaged stress requires equal averaged principal stresses in all directions, which determines the ratio of the poloidal and toroidal current of our toroidal coil. The coil increases the magnetic energy to 4 times the conventional TF coil with the same maximum stress.

Power-Electronic Systems for the Grid Integration of Renewable Energy Sources: A Survey

Abstract: The use of distributed energy resources is increasingly being pursued as a supplement and an alternative to large conventional central power stations. The specification of a power-electronic interface is subject to requirements related not only to the renewable energy source itself but also to its effects on the power-system operation, especially where the intermittent energy source constitutes a significant part of the total system capacity. In this paper, new trends in power electronics for the integration of wind and photovoltaic (PV) power generators are presented. A review of the appropriate storage-system technology used for the integration of intermittent renewable energy sources is also introduced. Discussions about common and future trends in renewable energy systems based on reliability and maturity of each technology are presented

A review of energy storage technologies for wind power applications

Abstract: Due to the stochastic nature of wind, electric power generated by wind turbines is highly erratic and may affect both the power quality and the planning of power systems. Energy Storage Systems (ESSs) may play an important role in wind power applications by controlling wind power plant output and providing ancillary services to the power system and therefore, enabling an increased penetration of wind power in the system. This article deals with the review of several energy storage technologies for wind power applications. The main objectives of the article are the introduction of the operating principles, as well as the presentation of the main characteristics of energy storage technologies suitable for stationary applications, and the definition and discussion of potential ESS applications in wind power, according to an extensive literature review.