• Smart Structures and Systems
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• 제19권6호
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• pp.615-624
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• 2017

This paper experimentally investigates the feasibility of harvesting vibration energy from whistles using piezoelectric materials. The end goal of this research is to generate sufficient power from the whistle to power a small radio transmitter to relay a basic signal - for example, a distress call. First, the paper discusses the current literature in energy harvesting from acoustic resonance. Next, the concept of an active whistle is presented. Next, results from energy harvesting experiments conducted on conventional and ultrasonic whistles undergoing human-actuation and actuation by a pressure-regulated air supply are presented. The maximum power density of the conventional whistle actuated by a human at 100 dB sound pressure level is $98.1{\mu}W/cm^3$.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(1)
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• pp.330-334
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• 2004

A new SEPIC-Flyback converter is proposed. The proposed converter is the integration of SEPIC and Flyback converter. Not only SEPIC output but also Flyback output could be fully regulated by constant frequency PWM control. Merged SEPIC and Flyback topology can share the transformer and power MOSFET. When the switch turns on, one topology operates via capacitive energy transfer. The other topology acts as inductive energy transfer while the switch is off. So, it can increase power density per one cycle. The experimental result is presented and verified.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 추계학술대회 논문집
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• pp.145-146
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• 2012

Recently the problem of the fouling organisms, especially Sn-compounds is expanded to environmental problems from the chemical reaction with imposex and secondary contamination. One of the existing antifouling system, antifouling paints, is regulated from 2012, July because of seriousness about toxic substances such as TBT, mercury, copper and so on. TBT is known that causes a variety of biological inhibition in various chemicals even a very small amount of concentration. So it has been developed to replace it. In this paper, we try to develope a new system with the environmental background and the research of the adhesion characteristics of fouling organisms using a low current, high frequency high voltage pulse power, not toxic compounds.

• 제어로봇시스템학회논문지
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• 제18권4호
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• pp.371-374
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• 2012

DC/DC switching power converters produce DC output voltages from different stable DC input sources regulated by a bi-polar transistor. The converters can be used in regenerative braking of DC motors to return energy back in the supply, resulting in energy savings for the systems containing frequent stops. The voltage mode DC/DC converter is composed of a PWM (Pulse Width Modulation) controller, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), an inductor, and capacitors, etc. PWM is applied to control and regulate the total output voltage. It is shown that the output of DC/DC converter depends on the variation of threshold voltage at MOSFET and the variation of pulse width. In the PWM operation, the missing pulses, the changes in pulse width, and a change in the period of the output waveform are studied by SPICE (Simulation Program with Integrated Circuit Emphasis) and experiments.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.515-518
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• 2002

A synchronous generator is equipped with an automatic voltage regulator(AVR), which is responsible for keeping the output voltage constant under normal operating conditions at various levels. The output voltage of Synchronous Generator is regulated constantly by field voltage control in excitation system. High frequency PWM converter (Buck converter) type excitation system for synchronous generator that can sustain prefer output voltage level even at the fault condition happened. The proper operation of the proposed excitation system was verified through the simulations and the experiments.

• STI Policy Review
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• 제4권1호
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• pp.119-134
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• 2013

The Fukushima nuclear incident of 2011 served as an external shock that prompted Japan to reform its nuclear energy sector. The collusive relationship between the regulators within the Japanese government and the regulated power industry, as well as the lack of institutional independence of the regulatory agency, had derailed Japanese efforts to reform the sector for decades. The Fukushima crisis exposed these deeply-entrenched flaws in the system, causing public distrust and anger toward the government and the nuclear power sector. This paper discusses the institutional reform measures the Japanese government introduced in the wake of the Fukushima crisis to recover public confidence and revamp the sector to prevent future disasters. The paper also discusses the challenges the Japanese government faces on its road to a successful implementation of nuclear sector reforms.

• Journal of Power Electronics
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• 제16권1호
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• pp.93-101
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• 2016

A new four-primary-switch diode clamped soft switching three-level DC-DC converter (TLDC) with full zero-voltage switching (ZVS) load range and TL secondary voltage waveform is proposed. The operation principle and characteristics of the presented converter are discussed, and experimental results are consistent with theoretical predictions. The improvements of the proposed converter include a simple and compact primary structure, TL secondary rectified voltage waveform, wide load range ZVS for all primary switches, and full output-regulated range with soft switching operation. The proposed converter also has some disadvantages. The VA rating of the transformer is slightly larger than that of conventional TLDCs in variable input and constant output mode. The conduction loss of the primary coil is slightly higher because an air gap is inserted into the magnetic cores of the transformer. Finally, the secondary circuit is slightly complex.

• Journal of Electrical Engineering and Technology
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• 제7권2호
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• pp.273-280
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• 2012

Most variable speed wind turbines have pitch control mechanisms and one of their objectives is to protect turbines when the wind speed is too high. By adjusting pitch angles of wind turbine, the inlet power and the torque developed by the turbine are regulated. In this paper, the difference between the real wind speed and its rated value is regarded as a disturbance, and a component called disturbance observer (DOB) is added to the pre-designed control loop. The additional DOB based controller estimates the disturbance and generates a compensating signal to suppress the effect of disturbance on the system. As a result, the stability and the performance of the closed loop system guaranteed by an outer-loop controller (designed for a nominal system without taking into account of disturbances) are approximately recovered in the steady state. Simulation results are presented to verify the performance of the proposed control scheme.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 전력전자학술대회 논문집
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• pp.146-147
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• 2014

This paper presents an operation of the modular multilevel converter-high voltage direct current (MMC-HVDC) system as a Statcom to support the grid voltage. The advantage of the MMC-HVDC system is that it can control the active and reactive powers independently. The proposed control scheme will be designed by combining this performance and the control method of the Statcom. The grid voltage is regulated by the control of the reactive power, meanwhile the active power is controlled according to its applications. The simulation results based on the PSCAD/EMTDC simulation program will evaluate the effectiveness of the control scheme.

• 항공우주시스템공학회지
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• 제14권6호
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• pp.74-78
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• 2020

The cooler driver electronics (CDE) for maintaining a low temperature of a satellite payload IR sensor has a compressor with a pulsation current load when in operation. This pulsation current creates a large voltage fluctuation and may negatively affect both the load and regulated bus stability. Thus, a CDE power conditioning system has a battery for use as a buffer that is connected in front of the CDE load line. In this system, a battery charger limiter circuit is required to protect from an over-charge of the battery and power to the load. In this study, an optimal design and parameter selection were developed and simulated.