• Ocean Systems Engineering
• /
• v.3 no.3
• /
• pp.203-217
• /
• 2013

A PTO (power-take-off) mechanism by using relative heave motions between a floating buoy and its inner mass (magnet or amateur) is suggested. The inner power take-off system is characterized by a mass with linear stiffness and damping. A vertical truncated cylinder is selected as a buoy and a special station-keeping system is proposed to minimize pitch motions while not affecting heave motions. By numerical examples, it is seen that the maximum power can actually be obtained at the optimal spring and damper condition, as predicted by the developed WEC(wave energy converter) theory. Then, based on the developed theory, several design strategies are proposed to further enhance the maximum PTO, which includes the intentional mismatching among heave natural frequency of the buoy, natural frequency of the inner dynamic system, and peak frequency of input wave spectrum. By using the intentional mismatching strategy, the generated power is actually increased and the required damping value is significantly reduced, which is a big advantage in designing the proposed WEC with practical inner LEG (linear electric generator) system.

• Proceedings of the KIPE Conference
• /
• 2000.07a
• /
• pp.535-538
• /
• 2000

There are several electricity applied sterilizers such as sterilizer with high frequency sterilizer with ozone sterilizer with high voltage and so on Those sterilizers feature "because there is no chemical process there is no secondly environmental pollution" At the power conversion part ZVS and ZCS methods have been used that it results in reduced switching loss miniaturized size and lightened weight, Besides the current in the device is smaller than that of existing method. Thus it is expected that the cost of sterilization process when quality of the device is measured by power consumption will be reduced.e reduced.

• Proceedings of the KIPE Conference
• /
• 1999.07a
• /
• pp.535-539
• /
• 1999

This paper presents the 2nd excitation control of the wound-rotor induction motor with Fly-wheel. In the wound-rotor induction motor, the primary power is controlled by AC excitation which used the secondary power conversion. Based on theory, this paper describes the dynamic response analysis of the wound-rotor induction motor with Fly-wheel and Simulation using MATLAB is performed to verify the proposed control method.

• Proceedings of the IEEK Conference
• /
• 2001.06e
• /
• pp.237-240
• /
• 2001

There are several electricity applied sterilizers such as sterilizer with high frequency, sterilizer with ozone, sterilizer with high voltage, and so on. Those sterilizers feature “because there is no chemical process, there is no secondly environmental pollution” At the power conversion part, AVS and ZCS methods have been used that it results in reduced switching loss, miniaturized size, and lightened weight. Besides, the current in the device is smaller than that of existing method. Thus, it is expected that the cost of sterilization process, when quality of the device is measured by power consumption, will be reduced.

• Journal of Power Electronics
• /
• v.19 no.1
• /
• pp.179-189
• /
• 2019

Four-quadrant converters (4QCs) are widely used as AC-DC power conversion interfaces in many areas. A control delay commonly exists in the digital implementation process of 4QCs, especially for high power 4QCs with a low switching frequency. This usually results in alternating current distortion, increased current harmonic content and system instability. In this paper, the control delay is divided into a computation delay and a PWM delay. The impact of the control delay on the performance of a 4QC is briefly analyzed. To obtain a fundamental value of AC current that is as accurately as possible, a specific sampling method considering the PWM pattern is introduced. Then a current predictive control based on a modified z-transform is proposed, which is effective in reducing the control delay and easy in terms of digital implementation. In addition, it does not depend on object models and parameters. The feasibility and effectiveness of the proposed predictive current control method is verified by simulation and experimental results.

• Journal of Astronomy and Space Sciences
• /
• v.36 no.2
• /
• pp.69-74
• /
• 2019

Spacecraft requires sufficient power in orbit to perform its mission. So as to comply with system requirements, the sufficient power should be made by a solar cell array by photovoltaic power conversion. A life time of space program depends on its mission considering parts reliability and parts grade. Based on the mission life time, power equipment might be designed to meet specifications. In outer space, solar cell array might generate the dc power by photovoltaic conversion effects and GaInP/GaAs/Ge solar cells are used in this study. Space programs that require more than five years should select parts for high reliability applications. Therefore, reliability analysis for high reliability applications should be performed to check its fulfilment of the requirements. This program should also require more five years for its mission and we performed its analysis using parts count method (PCM) for its reliability. Finally, we performed reliability analysis and obtained quantitative figures found out 99.9%. In this study, we presented the reliability analysis of the 300 W GaInP/GaAs/Ge solar cell array.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.6
• /
• pp.1280-1285
• /
• 2011

Recently, due to the use of fossil fuels for electric power production, carbon emissions increased excessively. Thereby, in order to replace fossil fuels, many studies about fossil fuels such as solar and fuel cell energy source are progressing. Fuel cell system has high energy conversion efficiency. Also, fuel cell system is environmentally friendly system because the carbon emission is almost not occur. Therefore, the fuel cell system is considered as the core technology of in the fields of the future energy and environmental. Fuel cell system has an effect on distribution power system because another power source of other than large power plants. So, fuel cell system can be degradation reason of power quality in the power system. In this paper, we constructed the system for an assessment on harmonics effect. The system is composed with power source, harmonics generation and linear load, fuel cell system. we also performed assessment on harmonics effect in customer and the distributed power system during grid connection of residential fuel cell system. An assessment cases are divided into three. A Case 1 is state that residential load and fuel system are connected to grid, Case 2 is state that residential load and harmonics load are connected to grid, and Case 3 is state that all loads are connected to grid. As a output of fuel cell system is increase, analysis results based on assessment system showed that power quality became more aggravation as effect of harmonics.

• Journal of Electrical Engineering and Technology
• /
• v.9 no.6
• /
• pp.2004-2012
• /
• 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.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.12 no.2
• /
• pp.1-6
• /
• 2016

Several efforts to replace the use of existing fossil energy resources have already been made around the world. As a result, a new industry of renewable energy has been created, and efficient energy distribution and storage has been promoted intensively. Among the newly explored renewable energy sources, the most widely used one is solar energy generation, which has a high market potential. An energy storage system (ESS) is a system as required. In this paper, the design and implementation of an ESS for the efficient use of power in stand-alone street lights is presented. In current ESS applied to stand-alone street lights, either 12V~24V DC (from solar power) or 110V~220V AC (from commercial power) is used to recharge power in systems with lithium batteries. In this study, an ESS that can support both solar power and commercial power was designed and implemented; it can also perform emergency recharge of portable devices from solar powered street lights. This system can maximize the scalability of ESSes using lithium batteries with efficient energy conversion, with the advantage of being an eco-friendly technology. In a ripple effect, it can also be applied to smart grids, electric vehicles, and new, renewable storage markets where energy storage technology is required.

• Journal of Power Electronics
• /
• v.9 no.4
• /
• pp.643-653
• /
• 2009

Voltage-controlled voltage source inverter (VCVSI) based distributed generation systems (DGS) using renewable energy sources (RES) is becoming increasingly popular as grid support systems in both remote isolated grids as well as end of rural distribution lines. In VCVSI based DGS for load voltage stabilization, the power angle between the VCVSI output voltage and the grid is an important design parameter because it affects not only the power flow and the power factor of the grid but also the capacity of the grid, the sizing of the decoupling inductor and the VCVSI. In this paper, the steady state modeling and analysis in terms of power flow and power demand of the each component in the system at the different values of maximum power angle is presented. System design considerations are examined for various load and grid conditions. Experimental results conducted on a I KVA VCVSI based DGS prove the analysis and simulation results.