• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.4
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• pp.278-287
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• 2009

Plug-in hybrid electric vehicle (PHEV) with capability of being recharged from the power-grid will reduce oil consumption. Also, the PHEV will affect the utility operations by adding additional electricity demand for charging. In this research, the power-grid impact by demand of PHEV charging is presented and the optimal charging control strategy for utility operators is proposed with simulated data. The penetration of PHEV is assumed to be 50% in the circumstances of Korean passenger car market and Korean power-grid market limitedly. To obtain smooth load shape and utilize the surplus electricity in power-grid at midnight and dawn, the peak of charging demand should be controlled to be located before 4:00 a.m., and the time slot which can supply the electricity power to PHEV should be allowed between 1:00 a.m.$\sim$7:00 a.m.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.742-751
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• 2018

Electric vehicles (EV) are emerging as the future transportation vehicle reflecting their potential safe environmental advantages. Vehicle to Grid (V2G) system describes the hybrid system in which the EV can communicate with the utility grid and the energy flows with insignificant effect between the utility grid and the EV. The paper presents an optimal power control and energy management strategy for Plug-In Electric Vehicle (PEV) charging stations using Wind-PV-FC-Battery renewable energy sources. The energy management optimization is structured and solved using Multi-Objective Particle Swarm Optimization (MOPSO) to determine and distribute at each time step the charging power among all accessible vehicles. The Model-Based Predictive (MPC) control strategy is used to plan PEV charging energy to increase the utilization of the wind, the FC and solar energy, decrease power taken from the power grid, and fulfil the charging power requirement of all vehicles. Desired features for EV battery chargers such as the near unity power factor with negligible harmonics for the ac source, well-regulated charging current for the battery, maximum output power, high efficiency, and high reliability are fully confirmed by the proposed solution.

• Journal of Communications and Networks
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• v.14 no.6
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• pp.672-681
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• 2012

A potential breakthrough of the electrification of the vehicle fleet will incur a steep rise in the load on the electrical power grid. To avoid huge grid investments, coordinated charging of those vehicles is a must. In this paper, we assess algorithms to schedule charging of plug-in (hybrid) electric vehicles as to minimize the additional peak load they might cause. We first introduce two approaches, one based on a classical optimization approach using quadratic programming, and a second one, market based coordination, which is a multi-agent system that uses bidding on a virtual market to reach an equilibrium price that matches demand and supply. We benchmark these two methods against each other, as well as to a baseline scenario of uncontrolled charging. Our simulation results covering a residential area with 63 households show that controlled charging reduces peak load, load variability, and deviations from the nominal grid voltage.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.4
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• pp.395-402
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• 2016

When the operation of battery is converted at charging and discharging system based on a DC micro grid, the voltage is fluctuated. And excessive voltage fluctuation could cause damage or failure of charging and discharging equipment. Therefore, in this paper, we studied the operating schedule of the charging and discharging system based on the DC micro grid and a design point of the capacitor which was able to reduce the voltage fluctuation. A result of computer simulation showed that when a fluctuation-reducing capacitor which had an initial value of 600V/35mF was applied at the charging and discharging system based on a DC micro grid which was operated with three charging battery sets and five discharging battery sets, voltage fluctuation by charging and discharging operation was reduced by about 63.3%. Furthermore, voltage fluctuation which occurred when initial network voltage was stabilized was reduced by about 73%.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.1
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• pp.10-17
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• 2014

The Jeju Special Self-Government Provincial Government has made the plan penetrating gradually electric vehicles(EVs) in the Jeju Special Self-Government Province(Jejudo). However the effects of EVs penetration on the electrical grid of the Jejudo is not reported. In this paper the yearly electric energy consumed by the EVs was calculated and the effects of the EV penetration on the peak power of the grid were analyzed in the Jejudo for the future 10 years, and we hope that our study results will help the governors realize the EVs penetration plan in the Jejudo. The calculation results show that the rate of the electric energy used by the EVs will become to 2.9% at its maximum at the 2017 year when the penetration rate of EVs in passenger cars becomes 10%, and the rate of the electric energy consumed by the EVs will become to 9.4% at its maximum at the 2020 year when the penetration rate of EVs in passenger cars becomes 30%. The concepts of smart-charging capacity and 100%-valley-filling charging capacity of the grid were defined and calculated for the Jeju Grid, and the grid was analyzed to have the sufficient EV charging capacity until the 2022 year.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.3
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• pp.315-319
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• 2020

The modern transportation and mobility sector is expected to encounter high penetration of Electric Vehicles (EVs) because EVs contribute to reducing the harmful emissions from fossil fuel-powered vehicles. With the prospective growth of EVs, sufficient and convenient facilities for fast charging are crucial toward satisfying the EVs' quick charging demand during their trip. Therefore, the Fast Electric Vehicle Charging Stations (FECS) will be a similar role to gas stations. In this paper, we study a charging scheduling problem for the FECS with solar photovoltaic (PV) and an Energy Storage System (ESS). We formulate an optimization problem that minimizes the operational costs of FECS. There are two cost and one revenue terms that are buying cost from main grid power, ESS degradation cost, and revenue from the charging fee of the EVs. Simulation results show that the proposed scheduling algorithm reduces the daily operational cost by effectively using solar PV and ESS.

• Journal of Technology Innovation
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• v.23 no.3
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• pp.137-167
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• 2015

Based on the stakeholder theory, this paper analyzes a clash of standards in Korea's Electric Vehicle(EV) market, particularly between an EV charging standard and a smart grid communication standard in 2012~2013. For charging, EV is connected with the electric power grid and simultaneously exchanges data regarding the charging status. When EV is connected with the power grid, a clash between two standards may arise. It actually happened when BMW entered into the Korean EV market with the DC Combo charging system. In that course, the frequency interference occurred between the EV data communication technology adopted by BMW and the AMI(Advanced Metering Infrastructure) for the smart grid system in Korea. Standardization of Korea's EV charging systems was required to solve this problem. However, it had been delayed due to the confrontation between various stakeholders involved in the process of standardization. It lasted until the DC combo was accepted as one of the Korea EV charging standards(KSAE SAE 1772-2040, 2014.1) by KSAE(The Korea Society of Automotive Engineers) in January 2014. This is an interesting case in the age of convergence. As it deals with the standard competition not among EV standards, but a clash between the EV industry and the smart grid, i.e. electric power industry, it addresses the necessity to consider standardization processes between different industries. This study draws on the stakeholder theory to analyse the dynamics of the standard clash between EV charging systems and the smart grid system, which is a unique example of standard clash between different industries. We expect such clashes to increase in the age of convergence.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.547-554
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• 2016

Analyze the customer daily load patterns, be used to determine the optimal charging and discharging schedule which can minimize the electrical charges through the battery energy storage system(BESS) installed in consumers is an object of this paper. BESS, which analyzes the load characteristics of customer and reduce the peak load, is essential for optimal charging and discharging scheduling to save electricity charges. This thesis proposes optimal charging and discharging scheduling method, using particle swarm optimization (PSO) and penalty function method, of BESS for reducing energy charge. Since PSO is a global optimization algorithm, best charging and discharging scheduling can be found effectively. In addition, penalty function method was combined with PSO in order to handle many constraint conditions. After analysing the load patterns of target BESS, PSO based on penalty function method was applied to get optimal charging and discharging schedule.

• Analytical Science and Technology
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• v.14 no.6
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• pp.486-493
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• 2001

The effect of SIMS analysis conditions such as mesh grid, offset voltage and ion species on the in-depth profile for bismuth titanate thin film was examined in terms of charging effect and detection limit. The results shows that the use of offset voltage -40 V reduces the charging effect and the detection limit. The employment of mesh grid in sample preparation leads to the reduction of the charging effect in small amount, but deteriorate the detection limit. Utilization of primary $O^-$ ion for SIMS analysis of bismuth titanate thin film showed almost the same effect as using offset voltage -40 V. However, it takes approximately triple acquisition time than using $O_2{^+}$ ion due to the poor beam current of the source in the experiment.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.222-227
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• 2015

This paper presents the optimal energy generation systems for economical EVs(Electric Vehicles) charging stations located in an island area. The system includes grid electricity, diesel generator and renewable energy sources of wind turbines and PV(Photovoltaic) panels. The independent generation system is designed with data resources such as annual average wind speed, solar radiation and the grid electricity price by calculating system cost under different structures. This sensitive analysis on the varying data resources allows for the configuration of the most economical generation system for charging stations by comparing initial capital, operating cost, NPC(Net Present Cost) and COE(Cost of Energy). Depending on the increase of the grid cost, the NPC variation of the most economical system which includes renewable energy generations and grid electricity can be smaller than those of other generation systems.