• Journal of Navigation and Port Research
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• v.36 no.1
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• pp.35-41
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• 2012

In this paper, we analyze the current submarine cooling system and study control algorithms for cooling system. Cooling system are installed in the submarine propulsion motor to protect the motor from high-temperature by iron loss and copper loss. The cooling system control the sea water and fresh water pump RPM to keep the motor temperature stable by external environment and motor RPM holding time. The cooling system simulation program is made for checking the cooling performance, and simulation is performed with various control strategy. The results with proposed cooling algorithm is shown to improve the thermal stability and efficiency of cooling system.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.1
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• pp.195-201
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• 2010

In this paper, a cooling system of high-power propulsion motor with Energy Saving System(ESS) is described. Normally, the cooling system for ship consists of fresh water pump, sea water pump, 3-way valve and cooler. In the cooling system, F.W(Fresh Water) and S.W(Sea Water) pump is operated on rated rpm, and the 3-way valve is controlled for preventing over-cooling. So, the consumption power of pump's motor is changed according to a sea water temperature. In the proposed cooling system, F.W. pump and S.W pump is controlled by inverter, and it is can be reduced the consumption power. Also, it is proved with simulation.

• The Korean Journal of Applied Statistics
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• v.30 no.6
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• pp.827-849
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• 2017

Self-sufficiency (SS), which is often used in the social welfare policy of the American welfare system, is an important concept in the field of social welfare and has been studied so much. Among such studies there are also studies on how the employment hope scale and the perceived employment barrier scale, which the psychological SS (PSS) consists of, affect the economic SS (ESS) for low-income job seekers in the United States. These studies are generally conducted using survey data, which are mainly analyzed by structural equation model (SEM) in the field of social science field. In the survey data, the number of measurement variables is generally large and there is a correlation between variables. In such cases, Principal Component Analysis (PCA) can be used. The purpose of this study is to compare the results of SEM and PCA on the survey data mainly dealt with in the social science field. We compare the performance of the two analyzing methods through a small simulation study. We also analyze a real survey data of the ESS and the PSS by using these two methods and compare the results.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.179-184
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• 2019

In many countries, such as developing countries where electricity is scarce, small wind turbines in the form of Off Grid are an effective solution to solve power supply problems. In some countries, the expansion of power systems and the decline of electricity-intensive areas have led to the use of small wind power in urban road lighting, mobile communications base stations, aquaculture and seawater desalination. With this change, the size of the small wind power industry is expected to have greater potential than large-scale wind power. In the case of small wind power generators, the generator is controlled at a variable speed, and the voltage and current generated by the generator have many harmonic components. To solve this problem, the AC to DC converter to be studied in this paper is a three-phase step-up type converter with a single switch. The inductor current is controlled in discontinuous mode, and has a characteristic of having a unit power factor by eliminating the harmonic of the input current. The proposed converter is composed of LCL filter and three phase rectification boost converter at the input stage and a single phase full bridge for grid connection. It is a control system with energy storage system(ESS) that the system stabilization can be pursued against the electric power.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.77-86
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• 2020

Power quality problems caused by feeder voltage drop and extension construction cost problems can occur with the increasing utilization rates of the existing fixed-type EV (electric vehicle) charger. Moreover, EV users might not be able to access the EV charger due to a lack of EV charging facilities. Therefore, this paper proposes an MPSD (movable power supply device) for EVs to overcome user inconvenience caused by the insufficient number of chargers and extension cost issues. The proposed MPSD was mainly composed of a PV (photovoltaic) system, ESS (energy storage system), EV charging system, and monitoring and control system. Furthermore, there are three operation modes available to enhance the flexibility of the MPSD application, depending on the situation. This paper also presents an economical evaluation modeling using the present worth method to consider the cost and benefit elements. The simulation results based on proposed modeling showed that MPSD is more economical than the existing EV charger. Moreover, its profit can be increased significantly depending on the distance to the installation point.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.786-794
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• 2015

In this paper, a new power control strategy for the bipolar-type low voltage direct current (LVDC) distribution system is being proposed. The dc distribution system is considered as an innovative system according to the increase of dc loads and dc output type distribution energy resources (DERs) such as photovoltaic (PV) systems and energy storage systems (ESS). Since the dc distribution system has many advantages such as feasible connection of DERs, reduction of conversion losses between dc output sources and loads, no reactive power issues, it is very suitable solution for new type buildings and residences interfaced with DERs and ESSs. In the bipolar-type, if it has each grid-interfaced converter, both sides (upper, lower-side) can be operated individually or collectively. A complementary power control strategy using two ESSs in both sides for effective and reliable operation is proposed in this paper. Detailed power control methods of the host controller and local controllers are described. To verify the performances of the proposed control strategy, simulation analysis using PSCAD/EMTDC is being performed where the results show that the proposed strategy provides efficient operations and can be applied to the bipolar-type dc distribution system.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.674-690
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• 2021

This study proposes a hybrid marine power system combining dual-fuel generators, a fuel cell, and Vanadium Redox Flow Batteries (VRFB). Rigorous verification and validation of the dynamic modelling and integration of the system are conducted. A case study for the application of the hybrid propulsion system to a passenger ship is conducted to examine its time-variant behaviour. A comprehensive model of the reversible and irreversible capacity degradation of the VRFB stack unit is proposed and validated. The capacity retention of the VRFB stack is simulated by being integrated within the hybrid propulsion system. Reversible degradation of the VRFB stack is precisely predicted and rehabilitated based on the predefined operational schedule, while the irreversible portion is retained until the affected components are replaced. Consequently, the advantages of the VRFB system as an on-board ESS are demonstrated through the application of a hybrid propulsion system for liner shipping with fixed routes.

• Journal of the Korean Society of Systems Engineering
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• v.20 no.spc1
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• pp.97-107
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• 2024

Efforts to respond to climate change are being made in various ways around the world, and in the energy field, continuous research and pilot projects are underway through new and renewable energy, efficient power grid management, and power grid services. Systems are in place to realize these efforts, and the systems created allow for better effectiveness. When implementing a system, systems engineering methodology helps design a more systematic system and can provide verification accuracy and uniformity through intuitive connectivity. In this paper, the original requirements of the power grid stabilization system and the architecture of the system's essential constraints are constructed as a conceptual model and the boundaries and flows between components are defined. By utilizing distributed resources such as EV(Electric Vehicle) and ESS(Energy Storage System) in the power service platform system, we plan to design and build a next-generation power service system that can participate in the power stabilization market and implement a system necessary to respond to climate change in the future.

• Journal of the Korean earth science society
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• v.37 no.5
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• pp.309-322
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• 2016

This paper presents an analytical framework of Conceptual Understandings of Earth Systems (CUES) that shows a relationship between disciplinary knowledge of Earth systems and the specific thinking skills required to understand that knowledge. This framework is developed through an extensive literature review of students' and teachers' understandings of earth systems concepts and systems thinking in earth science context. This study first presents the categories of disciplinary knowledge of Earth systems, Earth System Knowledge (ESK). This study then illustrates a relationship between categories of ESK and the ontological categories (Matter, Process, Systems) that has been used to study students' conceptual understandings of Earth systems. Finally, this study presents the CUES framework to show the relationship between disciplinary knowledge and thinking skills. The implications of using this framework for curriculum development, assessment, and teacher education and ESS research are discussed.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.455-456
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• 2016

최근 신재생 에너지원을 이용한 분산전원에 대한 연구가 활발하게 진행되고 있다. 본 논문에서는 신재생 에너지원과 에너지 저장장치로 이루어진 마이크로 그리드에서 안정적인 운전전략을 제안한다. 신재생 에너지원은 기상에 따라 출력이 달라지기 때문에 부하에 안정적인 전력을 공급하기 위해 에너지 저장장치를 사용한다. 에너지 저장장치의 안정적인 운전을 위해 SOC를 고려하여 제어한다. 배터리 충전/방전 시 외부조건에 의해 각 배터리 셀마다 충전량이 달라져 에너지 저장장치가 충분히 전력을 공급해주지 못하는 경우가 발생한다. 그러므로 각 셀마다 SOC를 측정하여 운전함으로써 부하에 안정적인 전력을 공급하는 제어전략은 제안한다. 제안된 마이크로 그리드 운전 제어 전략은 PSiM 시뮬레이션으로 검증하였다.