The presence of ostreid herpesvirus 1 (OsHV-1) and the percentage of viral DNA detected in Pacifi... more The presence of ostreid herpesvirus 1 (OsHV-1) and the percentage of viral DNA detected in Pacific oyster Crassostrea gigas adults were investigated monthly between May and November 2012 at three locations along the southern coast of Korea. Among 210 oysters examined by polymerase chain reaction (PCR) analysis, OsHV-1 DNA was detected in only one oyster collected in August. The low detection rate of OsHV-1 DNA was consistent with the lack of reported OsHV-1-associated disease in C. gigas cultured in Korea. The sequence of the present PCR product amplified with the C2/C6 primer pair was identical to that of OsHV-1 μVar except for one nucleotide, and the sequence amplified with Del36-37F2/Del36-37R showed a 605-bp deletion as in OsHV-1 μVar. Although these sequence data are insufficient to determine genotype, the results suggest that the herpesvirus detected was similar to OsHV-1 μVar. This is the first report on the presence of OsHV-1 in adult Pacific oysters cultured in Korea.
A current flowing through a distribution conductor produces induced voltage, which is harmful to ... more A current flowing through a distribution conductor produces induced voltage, which is harmful to a telecommunication line. Previous research on induced voltage has been focused on singlecircuit lines in the distribution system. However, the double-circuit lines, referred to as parallel distribution lines, are widely used in distribution systems because they have significant economic and environmental advantages over single-circuit lines. Therefore, a study on the induced voltage in double-circuit lines is needed. This paper presents a method of calculating the induced voltage in a parallel distribution system using four-terminal parameters and vector analysis. The calculation method is verified by the Electromagnetic Transient Program (EMTP) simulation.
Variations in solar irradiance and wind speed cause fluctuations in voltage of distribution netwo... more Variations in solar irradiance and wind speed cause fluctuations in voltage of distribution networks. Battery energy storage systems (BESSs) are usually installed in the distribution networks to mitigate the effects of these voltage fluctuations. The lifespan of a BESS-battery is affected by various factors such as the operating temperature, the level of depth of discharge and the magnitude of charging and discharging currents. In this paper, a new methodology is proposed in which the factors affecting the lifespan of the battery are modelled to find the optimal location and size of BESSs. The problem is formulated as a multi-objective optimization problem. The first objective function represents total energy losses of a distribution network, whereas the second objective function contains total investment cost associated with the installation of a BESS. Moreover, voltage regulation is carried out with the BESS. An IEEE 906 bus test feeder is used for the simulations, and both wind a...
The increasing penetration of electric vehicles (EVs) in the distribution grid has established th... more The increasing penetration of electric vehicles (EVs) in the distribution grid has established them as a prospective resource for ancillary services. These services require adequate control strategies for prompt and efficient operation. In this study, an energy management scheme (EMS) has been proposed to employ an off-board EV smart charger to support the grid during short-term variance of renewables and reactive load onset. The scheme operates by calculating power references for the charger instantaneously. The EMS incorporates a proportional power division methodology, proposed to allocate power references to the individual EVs connected to the charger DC-bus. This methodology considers the state-of-charge and battery sizes of the EVs, and it can aggregate energy from various types of EVs. The proposed scheme is compared with another power allocation method, and the entire EMS is tested under the scenarios of power mismatch and voltage sag/swell events. The results show that the proposed scheme achieves the goal of the aggregation of EVs at the charger level to support the grid. The EMS also fulfills the objectives of voltage regulation and four-quadrant operation of the smart charger.
The lifespan of a battery in battery energy storage systems (BESSs) is affected by various factor... more The lifespan of a battery in battery energy storage systems (BESSs) is affected by various factors such as the operating temperature of the battery, depth of discharge, and magnitudes of the charging/discharging currents supplied to or drawn from the battery. In this study, the optimal location and size of a BESS are found for voltage regulation in a distribution system while increasing the lifespan of the battery. Various factors that affect the lifespan of a battery are considered and modelled. The problem is formulated as a multi-objective optimisation problem with two-objective functions. The first objective function calculates the energy losses in the system, whereas the second objective function represents the total investment cost of the distributed generator (DG) and BESS installations. Wind and solar DGs with uncertainties in their output powers are also considered with the BESSs. An elitist non-dominated sorting genetic algorithm-II with a utopian point method is used to solve the optimisation problem. Furthermore, an IEEE 906 bus European low-voltage test feeder and eight test cases are considered for this study. The results show reduced losses and cost, improvement in the voltage profile, and extended lifespan of the batteries.
International Journal of Electrical Power & Energy Systems
The progression towards smarter grids, incorporating clean energy resources, has increased the in... more The progression towards smarter grids, incorporating clean energy resources, has increased the integration of distributed generators (DGs) into power distribution networks. The DGs often cause a rise in voltage at their points of common coupling. Ordinary voltage regulation devices such as on-load tap changers (OLTCs) are not capable of addressing these issues adequately without careful coordination with DGs. In this paper, a new supervisory control and data acquisition-based two-stage voltage control scheme for the coordination of an OLTC transformer, capacitor banks (CBs) and the DGs is presented. The proposed scheme sets forth a new criterion for the selection of tap positions of an OLTC. In the first stage, tap positions of the OLTC are changed optimally using the micro genetic algorithm, whereas in the second stage, a recursive genetic algorithm is run to minimise the power losses in order to find the optimal reactive powers for the distribution network. Stochastic modelling of wind speed and solar irradiance data is also performed. The scheme is verified by studying it under four different test cases. An OLTC, CBs, photovoltaic panels, wind power DGs and dispatchable DGs are installed in the distribution network, and an IEEE 37node test feeder is used for the verification of the proposed scheme. The simulation results show that the scheme achieves the objective of voltage regulation.
Energy storage systems (ESSs) are essential in future power systems because they can improve powe... more Energy storage systems (ESSs) are essential in future power systems because they can improve power usage efficiency. In this paper, a novel coordinated control algorithm is proposed for distributed battery ESSs (BESSs). The neighboring BESSs of a simulation system are grouped and controlled by a main control center. The main control center sends charging or discharging operation signals to each BESS. The primary objective of the proposed coordinated control scheme is to mitigate voltage and frequency deviations. In order to verify the proposed algorithm, the BESSs are connected to a distribution system of the Korea Electric Power Corporation. The results are compared with those obtained using uncoordinated control scheme with on-load tap changer considering aspects of power quality (voltage and frequency variation). The simulation results show that the voltage and frequency deviations are reduced with the proposed coordinated control algorithm.
Journal of Electrical Engineering and Technology, Mar 1, 2014
Due to increased concerns for rising oil prices and environmental problems, various solutions hav... more Due to increased concerns for rising oil prices and environmental problems, various solutions have been proposed for solving energy problems through tightening environmental regulations such as those regarding CO 2 reduction. Among them, Electrical Vehicles (EVs) are evaluated to be the most realistic and effective approach. Accordingly, research and development on EVs and charging infrastructures are mainly proceeding in developed countries. Since EVs operate using electric energy form a battery, they must be connected to the power system to charge the battery. If many EVs are connected during a short time, power quality problems can occur such as voltage sag, voltage unbalance and harmonics which are generated from power electronics devices. Therefore, when EVs are charged, it is necessary to analyze the effect of power quality on the distribution system, because EVs will gradually replace gasoline vehicles, and the number of EVs will be increased. In this paper, a battery for EVs and a PWM converter are modeled using an ElectroMagnetic Transient Program (EMTP). The voltage sag and unbalance are evaluated when EVs are connected to the distribution system of the Korea Electric Power Corporation (KEPCO). The simulation results are compared with IEEE standards.
Journal of Electrical Engineering and Technology, 2014
As environmentally friendly energy takes center stage, interests for Electric Vehicles/Plug in Hy... more As environmentally friendly energy takes center stage, interests for Electric Vehicles/Plug in Hybrid Electric Vehicles (EVs/PHEVs) are getting increase. With this trend, there is no doubt EVs will take large portion to penetrations of total cars. Therefore, accurate EV modeling is required. Battery is one of the main components with the power system view of aspect. Hence, in this paper, reviews and discussions of some types of batteries for EV are contained by considering energy density and weight of the batteries. In addition, simulations of Li-Ion battery are accomplished with various variables such as temperature, capacity fading and charge/discharge current. It is confirmed that temperature is the main factor of capacity fading. Validation of the modeled battery is also conducted by comparing it with commercialized battery.
It is well known that the Low-Voltage DC (LVDC) distribution system is a promising topology as a ... more It is well known that the Low-Voltage DC (LVDC) distribution system is a promising topology as a future smart distribution system due to its high efficiency and reliability. However, there are still some challenges in the construction and implementation of an LVDC system. For practical application of the LVDC system, therefore, it is necessary to perform any simulation in advance by considering various conditions that can occur in an LVDC system. In order to provide a foundation for analyzing a DC system, this paper presents an LVDC distribution system model including essential components such as power electronic devices, Distributed Energy Resource (DER), and Energy Storage System (ESS), which can be considered for implementation in an LVDC system using ElectroMagnetic Transient Program (EMTP) software. Moreover, an analysis of the characteristic in both the steady state and the transient state is conducted in an LVDC distribution system.
Journal of Electrical Engineering and Technology, Jul 1, 2015
This paper analyzes the effect of voltage sag on distribution systems due to the connection of El... more This paper analyzes the effect of voltage sag on distribution systems due to the connection of Electric Vehicles (EVs). In order to study the impact of the voltage sag on the power system, two scenarios have been selected in this paper. The distribution system and EVs are modeled using the Electro Magnetic Transients Program (EMTP). The numbers of EVs are predicted based on the number of vehicles in distribution system of Seoul. In addition, the number of EVs is set up using realtime traffic in Seoul to simulate Scenario I and II. The simulation results show that voltage sag can occur if the distribution system has more than 30% of the total number of vehicles.
The presence of ostreid herpesvirus 1 (OsHV-1) and the percentage of viral DNA detected in Pacifi... more The presence of ostreid herpesvirus 1 (OsHV-1) and the percentage of viral DNA detected in Pacific oyster Crassostrea gigas adults were investigated monthly between May and November 2012 at three locations along the southern coast of Korea. Among 210 oysters examined by polymerase chain reaction (PCR) analysis, OsHV-1 DNA was detected in only one oyster collected in August. The low detection rate of OsHV-1 DNA was consistent with the lack of reported OsHV-1-associated disease in C. gigas cultured in Korea. The sequence of the present PCR product amplified with the C2/C6 primer pair was identical to that of OsHV-1 μVar except for one nucleotide, and the sequence amplified with Del36-37F2/Del36-37R showed a 605-bp deletion as in OsHV-1 μVar. Although these sequence data are insufficient to determine genotype, the results suggest that the herpesvirus detected was similar to OsHV-1 μVar. This is the first report on the presence of OsHV-1 in adult Pacific oysters cultured in Korea.
A current flowing through a distribution conductor produces induced voltage, which is harmful to ... more A current flowing through a distribution conductor produces induced voltage, which is harmful to a telecommunication line. Previous research on induced voltage has been focused on singlecircuit lines in the distribution system. However, the double-circuit lines, referred to as parallel distribution lines, are widely used in distribution systems because they have significant economic and environmental advantages over single-circuit lines. Therefore, a study on the induced voltage in double-circuit lines is needed. This paper presents a method of calculating the induced voltage in a parallel distribution system using four-terminal parameters and vector analysis. The calculation method is verified by the Electromagnetic Transient Program (EMTP) simulation.
Variations in solar irradiance and wind speed cause fluctuations in voltage of distribution netwo... more Variations in solar irradiance and wind speed cause fluctuations in voltage of distribution networks. Battery energy storage systems (BESSs) are usually installed in the distribution networks to mitigate the effects of these voltage fluctuations. The lifespan of a BESS-battery is affected by various factors such as the operating temperature, the level of depth of discharge and the magnitude of charging and discharging currents. In this paper, a new methodology is proposed in which the factors affecting the lifespan of the battery are modelled to find the optimal location and size of BESSs. The problem is formulated as a multi-objective optimization problem. The first objective function represents total energy losses of a distribution network, whereas the second objective function contains total investment cost associated with the installation of a BESS. Moreover, voltage regulation is carried out with the BESS. An IEEE 906 bus test feeder is used for the simulations, and both wind a...
The increasing penetration of electric vehicles (EVs) in the distribution grid has established th... more The increasing penetration of electric vehicles (EVs) in the distribution grid has established them as a prospective resource for ancillary services. These services require adequate control strategies for prompt and efficient operation. In this study, an energy management scheme (EMS) has been proposed to employ an off-board EV smart charger to support the grid during short-term variance of renewables and reactive load onset. The scheme operates by calculating power references for the charger instantaneously. The EMS incorporates a proportional power division methodology, proposed to allocate power references to the individual EVs connected to the charger DC-bus. This methodology considers the state-of-charge and battery sizes of the EVs, and it can aggregate energy from various types of EVs. The proposed scheme is compared with another power allocation method, and the entire EMS is tested under the scenarios of power mismatch and voltage sag/swell events. The results show that the proposed scheme achieves the goal of the aggregation of EVs at the charger level to support the grid. The EMS also fulfills the objectives of voltage regulation and four-quadrant operation of the smart charger.
The lifespan of a battery in battery energy storage systems (BESSs) is affected by various factor... more The lifespan of a battery in battery energy storage systems (BESSs) is affected by various factors such as the operating temperature of the battery, depth of discharge, and magnitudes of the charging/discharging currents supplied to or drawn from the battery. In this study, the optimal location and size of a BESS are found for voltage regulation in a distribution system while increasing the lifespan of the battery. Various factors that affect the lifespan of a battery are considered and modelled. The problem is formulated as a multi-objective optimisation problem with two-objective functions. The first objective function calculates the energy losses in the system, whereas the second objective function represents the total investment cost of the distributed generator (DG) and BESS installations. Wind and solar DGs with uncertainties in their output powers are also considered with the BESSs. An elitist non-dominated sorting genetic algorithm-II with a utopian point method is used to solve the optimisation problem. Furthermore, an IEEE 906 bus European low-voltage test feeder and eight test cases are considered for this study. The results show reduced losses and cost, improvement in the voltage profile, and extended lifespan of the batteries.
International Journal of Electrical Power & Energy Systems
The progression towards smarter grids, incorporating clean energy resources, has increased the in... more The progression towards smarter grids, incorporating clean energy resources, has increased the integration of distributed generators (DGs) into power distribution networks. The DGs often cause a rise in voltage at their points of common coupling. Ordinary voltage regulation devices such as on-load tap changers (OLTCs) are not capable of addressing these issues adequately without careful coordination with DGs. In this paper, a new supervisory control and data acquisition-based two-stage voltage control scheme for the coordination of an OLTC transformer, capacitor banks (CBs) and the DGs is presented. The proposed scheme sets forth a new criterion for the selection of tap positions of an OLTC. In the first stage, tap positions of the OLTC are changed optimally using the micro genetic algorithm, whereas in the second stage, a recursive genetic algorithm is run to minimise the power losses in order to find the optimal reactive powers for the distribution network. Stochastic modelling of wind speed and solar irradiance data is also performed. The scheme is verified by studying it under four different test cases. An OLTC, CBs, photovoltaic panels, wind power DGs and dispatchable DGs are installed in the distribution network, and an IEEE 37node test feeder is used for the verification of the proposed scheme. The simulation results show that the scheme achieves the objective of voltage regulation.
Energy storage systems (ESSs) are essential in future power systems because they can improve powe... more Energy storage systems (ESSs) are essential in future power systems because they can improve power usage efficiency. In this paper, a novel coordinated control algorithm is proposed for distributed battery ESSs (BESSs). The neighboring BESSs of a simulation system are grouped and controlled by a main control center. The main control center sends charging or discharging operation signals to each BESS. The primary objective of the proposed coordinated control scheme is to mitigate voltage and frequency deviations. In order to verify the proposed algorithm, the BESSs are connected to a distribution system of the Korea Electric Power Corporation. The results are compared with those obtained using uncoordinated control scheme with on-load tap changer considering aspects of power quality (voltage and frequency variation). The simulation results show that the voltage and frequency deviations are reduced with the proposed coordinated control algorithm.
Journal of Electrical Engineering and Technology, Mar 1, 2014
Due to increased concerns for rising oil prices and environmental problems, various solutions hav... more Due to increased concerns for rising oil prices and environmental problems, various solutions have been proposed for solving energy problems through tightening environmental regulations such as those regarding CO 2 reduction. Among them, Electrical Vehicles (EVs) are evaluated to be the most realistic and effective approach. Accordingly, research and development on EVs and charging infrastructures are mainly proceeding in developed countries. Since EVs operate using electric energy form a battery, they must be connected to the power system to charge the battery. If many EVs are connected during a short time, power quality problems can occur such as voltage sag, voltage unbalance and harmonics which are generated from power electronics devices. Therefore, when EVs are charged, it is necessary to analyze the effect of power quality on the distribution system, because EVs will gradually replace gasoline vehicles, and the number of EVs will be increased. In this paper, a battery for EVs and a PWM converter are modeled using an ElectroMagnetic Transient Program (EMTP). The voltage sag and unbalance are evaluated when EVs are connected to the distribution system of the Korea Electric Power Corporation (KEPCO). The simulation results are compared with IEEE standards.
Journal of Electrical Engineering and Technology, 2014
As environmentally friendly energy takes center stage, interests for Electric Vehicles/Plug in Hy... more As environmentally friendly energy takes center stage, interests for Electric Vehicles/Plug in Hybrid Electric Vehicles (EVs/PHEVs) are getting increase. With this trend, there is no doubt EVs will take large portion to penetrations of total cars. Therefore, accurate EV modeling is required. Battery is one of the main components with the power system view of aspect. Hence, in this paper, reviews and discussions of some types of batteries for EV are contained by considering energy density and weight of the batteries. In addition, simulations of Li-Ion battery are accomplished with various variables such as temperature, capacity fading and charge/discharge current. It is confirmed that temperature is the main factor of capacity fading. Validation of the modeled battery is also conducted by comparing it with commercialized battery.
It is well known that the Low-Voltage DC (LVDC) distribution system is a promising topology as a ... more It is well known that the Low-Voltage DC (LVDC) distribution system is a promising topology as a future smart distribution system due to its high efficiency and reliability. However, there are still some challenges in the construction and implementation of an LVDC system. For practical application of the LVDC system, therefore, it is necessary to perform any simulation in advance by considering various conditions that can occur in an LVDC system. In order to provide a foundation for analyzing a DC system, this paper presents an LVDC distribution system model including essential components such as power electronic devices, Distributed Energy Resource (DER), and Energy Storage System (ESS), which can be considered for implementation in an LVDC system using ElectroMagnetic Transient Program (EMTP) software. Moreover, an analysis of the characteristic in both the steady state and the transient state is conducted in an LVDC distribution system.
Journal of Electrical Engineering and Technology, Jul 1, 2015
This paper analyzes the effect of voltage sag on distribution systems due to the connection of El... more This paper analyzes the effect of voltage sag on distribution systems due to the connection of Electric Vehicles (EVs). In order to study the impact of the voltage sag on the power system, two scenarios have been selected in this paper. The distribution system and EVs are modeled using the Electro Magnetic Transients Program (EMTP). The numbers of EVs are predicted based on the number of vehicles in distribution system of Seoul. In addition, the number of EVs is set up using realtime traffic in Seoul to simulate Scenario I and II. The simulation results show that voltage sag can occur if the distribution system has more than 30% of the total number of vehicles.
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Papers by Soon-Jeong Lee