• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.2004-2012
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• 2014

Energy storage devices are necessary to obtain stable utilization of renewable energy sources. When black-out occurs, distributed renewable power sources with energy storage devices can operate under standalone mode as uninterruptable power supply. This paper proposes a dynamic response analysis with small-signal modeling for the standalone operation of a photovoltaic power generation system that includes a bidirectional charger/discharger with a battery. Furthermore, it proposes a DC-link voltage controller design of the entire power conditioning system, using the storage current under standalone operation. The purpose of this controller is to guarantee the stable operation of the renewable source and the storage subsystem, with the power conversion of a very efficient bypass-type PCS. This paper presents the operating principle and design guidelines of the proposed scheme, along with performance analysis and simulation. Finally, a hardware prototype of 1-kW power conditioning system with an energy storage device is implemented, for experimental verification of the proposed converter system.

• 태양에너지
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• 제9권1호
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• pp.30-35
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• 1989

This paper dealt with an experiments on temperature vairation in the heat storage zone due to change of vertical location (height) of sink diffuser and flow extraction in small saltless solar pond ($0.5{\times}0.5{\times}1.0M$), and the honeycomb device for this experimental purpose consisted of one-tired, sealed, and air filled by honeycomb panels. As results of experiments, 1) The storage zone was formed under lower region below the honeycomb device. 2) The higher vertical location of sink diffuser was placed, the more mixing phenomenon increased in the pond at steady flow extraction. 3) The more flow extraction increased, the more mixing phenomenon decreased at constant heat exchanger and variable flow extraction.

• Journal of Electrical Engineering and Technology
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• 제6권4호
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• pp.447-458
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• 2011

In this paper, a novel flywheel energy storage device, called the flexible power conditioner, which integrates both the characteristics of the flywheel energy storage and the doubly-fed induction machine, is proposed to improve power system stability. A prototype is developed and its principle, composition, and design are described in detail. The control system is investigated and the operating characteristics are analyzed. The test results based on the prototype are presented and evaluated. The test results illustrate that the prototype meets the design requirement on power regulation and starting, and provides a cost-effective and effective means to improve power system stability.

• 전력전자학회논문지
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• 제17권2호
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• pp.114-120
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• 2012

Recently, integrated electric propulsion system has been vigorously adopted into naval vessels. To enhance effectiveness and efficiency of power management in these propulsion systems, this paper investigates necessity of energy storage devices and their operation strategies. By introducing the energy storage devices, engine can operate at higher efficiency point and accordingly costs for fuel and maintenance are significantly reduced. In addition, transient performance can also be improved with support of the devices and it leads to stable operation of shipboard power bus. To validate the proposal of this paper, computer simulation has been conducted with real load data of existing electric propulsion system.

• 한국정밀공학회지
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• 제17권12호
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• pp.151-156
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• 2000

A vibration in a high-speed machine may lead to machinery malfunction and even catastrophic failure. So solving the vibration problem is a fundamental requirement for the stability of the high-speed machine. The flywheel energy storage system using superconducting magnetic bearings is a device to store electrical energy as rotational kinetic energy by motor and to convert it to electrical by generator when necessary. The high-speed rotating flywheel has large amplitude at a critical speed. And it has an unstable behavior by the electric torque at the first stage of the energy generation. In this paper, the stability analysis is performed with an analytical model and equations of motion-which is considered the effect of the electric torque-to identify the stable driving condition and the dynamic behavior.

• 전력전자학회논문지
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• 제21권4호
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• pp.335-342
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• 2016

This paper proposes an energy storage-assisted, series-connected module-integrated power conversion system that integrates a photovoltaic power conditioner and a charge balancing circuit. In conventional methods, a photovoltaic power conditioner and a cell-balancing circuit are needed for photovoltaic systems with energy storage devices, but they cause a complex configuration and high cost. Moreover, an imbalanced output voltage of the module-integrated converter for PV panels can be a result of partial shading. Partial shading can lead to the fault condition of the boost converter in shaded modules and high voltage stresses on the devices in other modules. To overcome these problems, a bidirectional buck-boost converter with an integrated magnetic device operating for a charge-balancing circuit is proposed. The proposed circuit has multiple secondary rectifiers with inductors sharing a single magnetic core, which works as an inductor for the main bidirectional charger/discharger of the energy storage. The secondary rectifiers operate as a cell-balancing circuit for both energy storage and the series-connected multiple outputs of the module-integrated converter. The operating principle of the cell-balancing power conversion circuit and the power stage design are presented and validated by PSIM simulation for analysis. A hardware prototype with equivalent photovoltaic modules is implemented for verification. The results verify that the modularized photovoltaic power conversion system in the output series with an energy storage successfully works with the proposed low-cost bidirectional buck-boost converter comprising a single magnetic device.

• 정보처리학회논문지A
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• 제16A권5호
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• pp.357-368
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• 2009

플래시 메모리와 하드디스크의 저장 공간 제약을 문제를 극복하기 위한 방법으로 모바일 IP 스토리지가 제안되었다. 모바일 IP 스토리지는 무선 IP 네트워크를 통하여 모바일 장치에 거의 무제한적인 저장 공간을 제공한다. 하지만, 모바일 IP 스토리지를 이용한 멀티미디어 컨텐츠 스트리밍 시 무선랜 장치의 지속적인 전력소모로 인해 모바일 장치의 배터리 수명이 급격히 감소하는 문제가 발생한다. 본 논문에서는 모바일 IP 스토리지를 통하여 멀티미디어 컨텐츠를 실행할 시에 무선랜 장치의 전력을 효율적으로 제어할 수 있는 기법을 제안한다. 제안된 기법은 선반입 버퍼 입출력 모듈, 무선랜 장치 전력제어 모듈, 선반입 버퍼 재구성 모듈로 구성되어 있다. 또한, 제안된 기법은 멀티미디어 컨텐츠의 품질에 적응적으로 선반입 버퍼의 크기를 자동적으로 결정하고 멀티미디어 컨텐츠가 실행되는 동안 On-Off 동작을 기반으로 무선랜 장치 전력 상태를 동적으로 제어한다. 제안된 기법의 성능을 임베디드 리눅스 2.6.11, 인텔 iSCSI 참조코드, 무선랜 장치를 이용하는 PXA270기반 모바일 장치 상에서 평가한다. 다양한 실험을 통하여 제안된 기법이 전력제어를 하지 않을 때에 비해 QVGA급 멀티미디어 컨텐츠 실행 시 무선랜 카드의 에너지 소모를 최대 8.5배 정도 감소시킴을 보인다.

• 전기학회논문지
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• 제62권7호
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• pp.1045-1052
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• 2013

In this study we deal with design procedures for the flywheel energy storage system that has the capacity to store the regenerative energy produced from the railway vehicles. The flywheel energy storage system (FESS) stores the regenerative electrical energy into the high speed rotational flywheel, by conversion the electrical energy into the mechanical rotational energy. Thus the FESS is composed of the energy conversion components, such as the motor and generator, mechanical support components, such as the rotational rotor, the magnetic bearings to support the rotor, and the digital controller to control the air gap between the rotor and the magnetic bearings. In this paper the design procedures for the rotor operating at the rigid mode and the magnetic bearings to support the rotational rotor without contact are presented.

• 한국초전도ㆍ저온공학회논문지
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• 제1권1호
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• pp.22-27
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• 1999

Recently, small-sized superconducting magnetic storage($\mu$SMES) coils become commercially as an energy storage device for a power conditioner. In design and fabrication of the $\mu$SMES coils, to determine optimum current capacity of the superconducting(SC) conductors is one of the important things. We thus investigated the effect of conductor's current capacity, current density, and stability on the coil's maximum stored energy density in consideration of AC losses and switching device's capacities in a power converter. The results show that the smaller current capacity of the SC conductors is preferred for the $\mu$SMES coils but can increase their induced voltage excessively.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권11호
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• pp.572-576
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• 2003

For quite a long time various researches and developments of superconducting magnetic energy storage(SMES) device have been done for enhancement of power qualify control of sensitive electric load. This paper describes the design. fabrication and experimental results for the 3MJ SMES magnet made by using the design code of a SMES device that we developed. A computer code was developed to find the parameters of the SMES magnet which has minimum amount of superconductor for the same stored energy, and the 3MJ SMES magnet was designed based upon that. And the 3MJ SMES magnet designed based upon those. In addition, 3MJ SMES magnet was made based on several research results which were ramp up to 1㎄ without quench.