• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.810-819
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• 2016

Uncoordinated charging of large-scale electric vehicles (EVs) will have a negative impact on the secure and economic operation of the power system, especially at the distribution level. Given that the charging load of EVs can be controlled to some extent, research on the optimal charging control of EVs has been extensively carried out. In this paper, two possible smart charging scenarios in China are studied: centralized optimal charging operated by an aggregator and decentralized optimal charging managed by individual users. Under the assumption that the aggregators and individual users only concern the economic benefits, new load peaks will arise under time of use (TOU) pricing which is extensively employed in China. To solve this problem, a simple incentive mechanism is proposed for centralized optimal charging while a rolling-update pricing scheme is devised for decentralized optimal charging. The original optimal charging models are modified to account for the developed schemes. Simulated tests corroborate the efficacy of optimal scheduling for charging EVs in various scenarios.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.298-299
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• 2011

The impacts of EV charging demands on power system such as increased peak demands may be developed by means of modeling a stochastic distribution of charging and a demand dispatch calculation. Optimization processes are proposed to determine optimal demand distribution portions so that charging costs and demands can be managed optimally. There are two optimization methods which have different effects on the outcome. These focus either on the Electric vehicle customer side (cost optimization) or the System Operator side (Load-weighted optimization).

• Journal of the Korean Society for Railway
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• v.8 no.3
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• pp.235-243
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• 2005

Following the rail reform in 2004, rail industry in Korea has separated into two parts: one is the infrastructure manager and the other is train operator. Amongst many aspects, track access charging system is one of the imminent aspects to be studied closely to make the rail reform successful. In this study, track access charging systems of European countries are closely investigated and compared one another and lessons learnt from their experiences are derived. Finally, policy directions regarding the track access charging system to be adopted in Korea are suggested.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.213-214
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• 2001

This paper describes a power supply for a rapid pulse power charging system designed for charging a $0.35{\mu}F$ capacitor to 20kV in approximately 3ms. The power supply should be capable of recharging the load capacitor maximum 300 times within one second. This power supply is based on a series resonant 3-phase inverter followed by the step-up transformers. The experiments have been carried out at different repetition rates and charging voltages.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.12
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• pp.1866-1872
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• 2017

This paper presents the design of in-wheel type Switched Reluctance Motor (SRM) which can be used as both traction motor and power pickup device in a wireless charging system of electric vehicles. The SRM acts as a traction drive in driving mode and a power receiver in charging mode to avoid any additional weights. Double stator axial field SRM is used due to its structure that can be mounted inside the wheel. The charging circuit is integrated with the asymmetric converter and phase windings of SRM, reducing the cost and size of the system. Magnetic resonance is implemented to increase the efficiency. Simulations done in Maxwell and Simplorer verify the effectiveness of the proposed system.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.451-458
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• 2017

An Electric Vehicle (EV) is operated with the electric energy of a battery in place of conventional fossil fuels. Thus, a suitable charging infrastructure must be provided to expand the use of electric vehicles. Because the battery of an EV must be charged to operate the EV, expanding the number of EVs will have a significant influence on the power supply and demand. Therefore, to maintain the balance of power supply and demand, it is important to be able to predict the numbers of charging EVs and monitor the events that occur in the distribution system. In this paper, we predict the hourly charging rate of electric vehicles using transformation matrix, which can describe all behaviors such as resting, charging, and driving of the EVs. Simulation with transformation matrix in a specific region provides statistical results using the Monte-Carlo Method.

• Journal of Hydrogen and New Energy
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• v.28 no.3
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• pp.273-278
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• 2017

In this paper, a fuel cell battery charger system, which is capable of bi-directional power transmission without built in battery, has been designed and fabricated. Performance and states of the notebook battery in bi-directional power transmission using the manufactured system have been tested. Before initializing the fuel cell charging system for 1 minute, the system received 10 W of electric power from notebook battery. Then the fuel cell charging system has been normal charging to notebook battery by 50 W. As a result of the experiment, the state of the notebook battery discharged less than 5% at the initial charging time, but then it has been charged. This results proves bi-directional power transmission in notebook computers increase the availability of fuel cell chargers.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.10
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• pp.990-998
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• 2004

Dynamic behavior of an ammonia-water absorption system was investigated numerically. Thermal-hydraulic model for a single-effect 3 RT chiller was developed by applying transient conservation equations of total mass, $NH_3$ mass, energy and momentum to each component. Transient variations of system properties and transport variables were analysed during start-up operation. Numerical analyses were performed to quantify the effects of bulk concentration and charging ratio on the system performance in terms of cooling capacity, coefficient of performance, and time constant of system. For an absorption chiller considered in the present study, optimum charging ratio and bulk concentration were to found to exist, which resulted in the maximum cooling capacity and COP. The time constant increased as the charging ratio increased, but decreased with the increase of bulk concentration.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.102-107
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• 2021

In this paper, the measurements of received power was shown and compared in two developed 5.8GHz 25W wireless charging systems. One is the system using commercial transmission antenna, and the other is the system using transmission antenna combined with metamaterial. The system combined with metamaterial shows higher received power due to negative reflective index of metamaterial. In addition, a comparative analysis of the systems shows that the transmission efficiency in the systems can decrease the real gain of transmission antenna due to higher side robe of beam pattern. The side robe beams of transmitting antenna interferes transmitted beam with the reflected beams from the bottom region due to the side robes. The failure problems of the RF wireless charging systems are discussed and proposed in order to charge mobile devices through the RF wireless charging system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.632-639
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• 2018

Recently, a policy has been enforced to supply Plug-in Electric Vehicles (PEVs) but this may require reinforcement of the power system depending on its clustering because PEVs are charged directly from power systems. On the other hand, as the reinforcement of power system is limited by time and budget, it is important to supply the charging demand of PEVs efficiently using the existing power systems to increase the diffusion of PEVs. This paper establishes a charging schedule for Plug-in Electric Vehicles (PEVs) considering the power system constraints. For this, the required amount and time of the charging demand for an individual PEV was modeled to integrate into power systems based on the driving pattern and charging tariff of PEV. Furthermore, the charging schedule of PEVs was established to meet the power system constraints by calculating the operating conditions of the power systems with PEVs.