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Isomura, Yoshinori,Yamamoto, Kichiro,Morimoto, Shigeo,Maetani, Tatsuo,Watanabe, Akihiko,Nakano, Keisaku Journal of International Conference on Electrical 2014 Journal of international Conference on Electrical Vol.3 No.3
The voltage source PWM inverter generally used to drive the air conditioning (A/C) fans has been posing a large issue that the bearings in air conditioning fan motors are highly possible to be corroded electrically. Potential difference called shaft voltage is generated between inner and outer rings of the bearings due to inverter switching. The shaft voltage causes bearing lubricant breakdown dielectrically. As a result, bearing current is caused. This current causes the bearing corrosion. In previous work, we demonstrated that the shaft voltage can be reduced by using an insulator inserted between the outer and inner cores of the rotor in an air conditioning fan motor without grounding. This paper proposes the other countermeasure for reducing the shaft voltage in fan motors. The countermeasure which adds a capacitor between the brackets and the stator core is effective even for fan motors with non-insulated rotor. The effectiveness is confirmed by both simulated and experimental results.
Yoshida, Yoshiaki,Fujiwara, Koji,Ishihara, Yoshiyuki,Suzuki, Hirokazu Journal of International Conference on Electrical 2014 Journal of international Conference on Electrical Vol.3 No.3
When large penetration of the distributed generators (DGs) such as photovoltaic (PV) systems is growing up in grid system, it is important to quickly prevent islanding caused by power system fault to ensure electrical safety. We propose a novel active method for islanding prevention by harmonic injection synchronized with the exciting current harmonics of the pole transformer to avoid mutual interference between active signals. We confirm the validity of the proposed method by performing the basic tests of islanding by using a current source superimposed the harmonic active signal. Further, we carry out the simulation using PSCAD/EMTDC, and verify the fast islanding detection.
Robust and Efficient 3D Model of an Electromagnetic Induction (EMI) Sensor
Antoun, Chafic Abu,Perriard, Yves Journal of International Conference on Electrical 2014 Journal of international Conference on Electrical Vol.3 No.3
Eddy current induction is used in a wide range of electronic devices, for example in detection sensors. Due to the advances in computer hardware and software, the need for 3D computation and system comprehension is a requirement to develop and optimize such devices nowadays. Pure theoretical models are mostly limited to special cases. On the other hand, the classical use of commercial Finite Element (FE) electromagnetic 3D models is not computationally efficient and lacks modeling flexibility or robustness. The proposed approach focuses on: (1) implementing theoretical formulations in 3D (FE) model of a detection device as well as (2) an automatic Volumetric Estimation Method (VEM) developed to selectively model the target finite elements. Due to these two approaches, this model is suitable for parametric studies and optimization of the number, location, shape, and size of PCB receivers in order to get the desired target discrimination information preserving high accuracy with tenfold reduction in computation time compared to commercial FE software.
A Turnout without Movable Parts for Magnetically Levitated Vehicles with Hybrid Magnets
Kakinoki, Toshio,Yamaguchi, Hitoshi,Yoshinaga, Naoya,Mukai, Eiichi,Nishi, Hiroyuki Journal of International Conference on Electrical 2014 Journal of international Conference on Electrical Vol.3 No.3
This paper describes a turnout without movable parts for magnetically levitated vehicles with hybrid magnets, which have been studied by the authors in place of streetcars. Their low construction cost and low maintenance is key to their practical use. Magnetic levitation systems using forces of attraction can generate guidance force automatically, but the damping force against lateral motion is negligible. However, the lateral damping characteristic was improved by using divided iron type magnets and rails. Using this turnout without movable parts will facilitate smooth direction switching.
Fekari, Seyyed Amir,Iranaq, Ali Reza Marami,Sabahi, Mehran Journal of International Conference on Electrical 2014 Journal of international Conference on Electrical Vol.3 No.3
In this paper, a new switching pattern is presented for multilevel inverters. With changing off-angel of each switch, the on time interval of all switches will approximately be equal and then the lifetime of inverter will increase, also using this method can reduce electrical stress on switches in higher levels of inverter. Switching angels as for desired modulation index are calculated using genetic algorithm whereas selective harmonics are controlled within the allowable range. The computed angels are simulated in Matlab/Simulink for respective circuits to validate the results.
Improvement of Responsivity of Unified Power Flow Controller in Digital Control System
Hamasaki, Shin-ichi,Miyazaki, Shinya,Takaki, Tsuyoshi,Tsuji, Mineo Journal of International Conference on Electrical 2014 Journal of international Conference on Electrical Vol.3 No.3
The Unified Power Flow Controller (UPFC) can flexibly manage power flow and maintain line voltage. The UPFC consists of two inverters in parallel side and series side. In parallel side, the reactive power can be compensated to improve the power factor. In series side, the voltage drop can be compensated to maintain proper line voltage. It is necessary for the operation in both sides to output the current and the voltage quickly and accurately. As the method for the UPFC control, the deadbeat control with state observer is applied. The deadbeat control is able to realize a quick response of the current and voltage control for only a sampling period compared with the general PI control. A principle and simulation results are presented in this paper.
An Improved Global Maximum Power Point Tracking Scheme under Partial Shading Conditions
Kim, Rae-Young,Kim, Jun-Ho Journal of International Conference on Electrical 2013 Journal of international Conference on Electrical Vol.2 No.1
A photovoltaic array exhibits several local and single global maximum power points under partial shading conditions. To track the global maximum power point precisely, a novel global maximum power point tracking scheme is proposed in this paper. In the proposed scheme, robustness of the tracking performance has been improved by enhancing searching profile. In addition, the paper addresses the tracking failure condition, and provides the experimental verification with several simulation and experimental results.
Ishikura, Keisuke,Inaba, Hiromi,Kishine, Keiji,Nakai, Mitsuki,Ito, Takuma Journal of International Conference on Electrical 2014 Journal of international Conference on Electrical Vol.3 No.3
A large capacity power conversion system constructed by using two or more existing power converters has a lot of flexibility in how the power converters are used. However, at the same time, it has a problem of cross current flows between power converters. The cross current must be suppressed by controlling the system while miniaturizing the combination reactor. This paper focuses on two current control methods of a power conversion system constructed by using two power converters connected in parallel supplying the same power. In order to elucidate the control performance of cross current, each control method which are aimed at controlling cross current and not directly controlling it are examined in simulations.
Parallel Multiple Electric Power Conversion System Constructed by Connecting Three Power Converters
Nakai, Mitsuki,Inaba, Hiromi,Kishine, Keiji,Ishikura, Keisuke Journal of International Conference on Electrical 2014 Journal of international Conference on Electrical Vol.3 No.3
The electric power conversion system constructed by connecting two or more power converters in parallel is an advantageous method for making to large capacity and standardization. In this paper, the control method of cross current when three power converters are operated is examined, and it reexamined a preferable system construction method.
Single-Phase Virtual Synchronous Generator for Distributed Energy Resources Integration
Zeng, Zheng,Cheng, Chong,Tang, Shengqing,Yang, Huan,Zhao, Rongxiang Journal of International Conference on Electrical 2014 Journal of international Conference on Electrical Vol.3 No.3
Virtual synchronous generator (VSG) in single-phase to interface distributed renewable energy resources is investigated in this paper. Mathematical models and numerical analysis are utilized to illustrate the features of the VSG. Enhanced control strategy is presented to ensure the performance of the VSG. Besides, a second order generalized integer (SOGI) is employed to calculate the instantaneous output power of the VSG in virtual ${\alpha}{\beta}$ frame. By the means of a phase-locked loop based scheme, the VSG can seamlessly transform between islanded and grid-tied modes, which can meet the requirements of micro-grid. At last, the validation and the proposed approach are verified by the simulated results using PSCAD/EMTDC.