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Prof. Dr. Sangwook Han
Dong Seoul Univ.

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Research Keywords & Expertise

0 Power
0 Power System Analysis and Simulation
0 Power and Energy Systems
0 Power system monitoring and control
0 Power System Modelling

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Journal article
Published: 10 November 2020 in Sustainability
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This paper proposes a reinforcement learning-based approach that optimises bus and line control methods to solve the problem of short circuit currents in power systems. Expansion of power grids leads to concentrated power output and more lines for large-scale transmission, thereby increasing short circuit currents. The short circuit currents must be managed systematically by controlling the buses and lines such as separating, merging, and moving a bus, line, or transformer. However, there are countless possible control schemes in an actual grid. Moreover, to ensure compliance with power system reliability standards, no bus should exceed breaker capacity nor should lines or transformers be overloaded. For this reason, examining and selecting a plan requires extensive time and effort. To solve these problems, this paper introduces reinforcement learning to optimise control methods. By providing appropriate rewards for each control action, a policy is set, and the optimal control method is obtained through a maximising value method. In addition, a technique is presented that systematically defines the bus and line separation measures, limits the range of measures to those with actual power grid applicability, and reduces the optimisation time while increasing the convergence probability and enabling use in actual power grid operation. In the future, this technique will contribute significantly to establishing power grid operation plans based on short circuit currents.

ACS Style

Sangwook Han. Control Method of Buses and Lines Using Reinforcement Learning for Short Circuit Current Reduction. Sustainability 2020, 12, 9333 .

AMA Style

Sangwook Han. Control Method of Buses and Lines Using Reinforcement Learning for Short Circuit Current Reduction. Sustainability. 2020; 12 (22):9333.

Chicago/Turabian Style

Sangwook Han. 2020. "Control Method of Buses and Lines Using Reinforcement Learning for Short Circuit Current Reduction." Sustainability 12, no. 22: 9333.

Journal article
Published: 12 October 2020 in Sustainability
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In this paper, a method that utilizes the reinforcement learning (RL) technique is proposed to establish an optimal operation plan to obtain maximum power output from a trigen generator. Trigen is a type of combined heat and power system (CHP) that provides chilling, heating, and power generation, and the turbo expander generator (TEG) is a generator that uses the decompression energy of gas to generate electricity. If the two are combined to form a power source, a power generation system with higher efficiency can be created. However, it is very difficult to control the heat and power generation amount of TEG and trigen according to the flow rate of natural gas that changes every moment. Accordingly, a method is proposed to utilize the RL technique to determine the operation process to attain an even higher efficiency. When the TEG and trigen are configured using the RL technique, the power output can be maximized, and the power output variability can be reduced to obtain high-quality power. When using the RL technique, it was confirmed that the overall efficiency was improved by an additional 3%.

ACS Style

Hyoung Kim; Gen Song; Sangwook Han. Power Generation Optimization of the Combined Cycle Power-Plant System Comprising Turbo Expander Generator and Trigen in Conjunction with the Reinforcement Learning Technique. Sustainability 2020, 12, 8379 .

AMA Style

Hyoung Kim, Gen Song, Sangwook Han. Power Generation Optimization of the Combined Cycle Power-Plant System Comprising Turbo Expander Generator and Trigen in Conjunction with the Reinforcement Learning Technique. Sustainability. 2020; 12 (20):8379.

Chicago/Turabian Style

Hyoung Kim; Gen Song; Sangwook Han. 2020. "Power Generation Optimization of the Combined Cycle Power-Plant System Comprising Turbo Expander Generator and Trigen in Conjunction with the Reinforcement Learning Technique." Sustainability 12, no. 20: 8379.

Journal article
Published: 04 June 2020 in Energies
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Although loads are increasingly becoming concentrated in metropolitan areas, power generation has decreased in metropolitan areas and increased in nonmetropolitan areas; hence, power transmission must occur through interface lines. To achieve this, additional transmission lines must be secured because the existing interface lines have reached their large-scale power transmission limits. The Korea Electric Power Corporation has installed many high-voltage direct current lines, thereby impacting the determination of interface power flow limits. These serve as the basis for system operations. However, knowledge of operating high-voltage direct current lines as a simple transmission line in a single power system is lacking. The effects of high-voltage direct current and its related parameters for interface flow limit analysis remain unclear. Furthermore, whether high-voltage direct current should be included in the selection of the interface lines that serve as the basis for interface flow remains unclear. In addition, whether the high-voltage direct current line faults should be included in the contingency list for determining the interface flow limits has not been considered. Additionally, it has not been determined whether to operate the DC tap when performing the simulation This study addresses these issues and determines the conditions that are necessary for determining the interface flow limits when a high-voltage direct current transmission facility has been installed in a land power system. The results conclude how to reflect the above conditions reasonably when performing the interface flow limit analysis on a system that includes the HVDC lines.

ACS Style

Sangwook Han. Calculating the Interface Flow Limits for the Expanded Use of High-Voltage Direct Current in Power Systems. Energies 2020, 13, 2863 .

AMA Style

Sangwook Han. Calculating the Interface Flow Limits for the Expanded Use of High-Voltage Direct Current in Power Systems. Energies. 2020; 13 (11):2863.

Chicago/Turabian Style

Sangwook Han. 2020. "Calculating the Interface Flow Limits for the Expanded Use of High-Voltage Direct Current in Power Systems." Energies 13, no. 11: 2863.

Journal article
Published: 04 May 2020 in IEEE Access
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ACS Style

Sangwook Han. Three-Phase-Measurement-Based Load Modeling Technique Using Unbalanced Fault Data. IEEE Access 2020, 8, 83655 -83662.

AMA Style

Sangwook Han. Three-Phase-Measurement-Based Load Modeling Technique Using Unbalanced Fault Data. IEEE Access. 2020; 8 ():83655-83662.

Chicago/Turabian Style

Sangwook Han. 2020. "Three-Phase-Measurement-Based Load Modeling Technique Using Unbalanced Fault Data." IEEE Access 8, no. : 83655-83662.

Journal article
Published: 13 March 2020 in IEEE Access
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When an entire power system blacks out, the system operator uses a self-starting generator to initiate the recovery procedure that starts the priority generator using a transmission line. Because most selfstarting generators are pumped storage generators, they are located at a distance from the priority generators. This results in long transmission lines that can cause overvoltage during the recovery process through the line charging effect. Herein, the above issue is resolved by replacing the self-starting generator with an energy storage system (ESS) to reduce the possibility of overvoltage generation. The transmission line is shortened by moving the ESS closer to the priority generator, thus utilizing its flexible installation feature: an ESS has no location constraints for installation. In addition, this study determines an effective location for the ESS to minimize the reactive power requirements: moving the ESS closer to the priority generator reduces the required reactive power. Thus, the capacity of the power conditioning system can be reduced, which is advantageous in terms of cost-effectiveness.

ACS Style

Sangwook Han. Selecting an Effective ESS Installation Location From the Perspective of Reactive Power. IEEE Access 2020, 8, 51945 -51953.

AMA Style

Sangwook Han. Selecting an Effective ESS Installation Location From the Perspective of Reactive Power. IEEE Access. 2020; 8 (99):51945-51953.

Chicago/Turabian Style

Sangwook Han. 2020. "Selecting an Effective ESS Installation Location From the Perspective of Reactive Power." IEEE Access 8, no. 99: 51945-51953.

Original article
Published: 08 November 2019 in Journal of Electrical Engineering & Technology
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When supplying natural gas, KOGAS intends to utilize the new energy by installing a system that runs the generator using the energy generated when the high-pressure natural gas is reduced to low pressure, that is, TEG. In the past, the energy generated by decompressing natural gas in the supply management station was thrown into the air, but by using this to generate electricity, high-quality new energy that does not emit greenhouse gases and consumes fuel is obtained. This paper examines the characteristics of TEG power generation, examines the TEG pilot project and demonstration project conducted by Korea Gas Corporation, and discusses the voltage control scheme and grid interconnection.

ACS Style

Hyoungtae Kim; Hyunseok You; Kyoung-Shik Choi; Sangwook Han. A Study on Interconnecting to the Power Grid of New Energy Using the Natural Gas Pressure. Journal of Electrical Engineering & Technology 2019, 15, 307 -314.

AMA Style

Hyoungtae Kim, Hyunseok You, Kyoung-Shik Choi, Sangwook Han. A Study on Interconnecting to the Power Grid of New Energy Using the Natural Gas Pressure. Journal of Electrical Engineering & Technology. 2019; 15 (1):307-314.

Chicago/Turabian Style

Hyoungtae Kim; Hyunseok You; Kyoung-Shik Choi; Sangwook Han. 2019. "A Study on Interconnecting to the Power Grid of New Energy Using the Natural Gas Pressure." Journal of Electrical Engineering & Technology 15, no. 1: 307-314.

Journal article
Published: 23 April 2019 in Applied Sciences
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This study aims to develop a real-time assessing methodology for a power systems voltage stability. The proposed algorithm is based on the Thévenin equivalent (TE) impedance estimation method, which applies the phasor measurement unit technology practically. To present an accurate analysis of the real-time situations of a power system, the developed voltage stability index can be used as useful information for system operators to establish appropriate countermeasures. Moreover, by considering the results of voltage stability margin calculation within the Korean power system, the effect of voltage stability on the dynamic behavior of the system is presented. Furthermore, to increase the accuracy, load model parameter estimation is introduced in this algorithm. The load model might be used for calculating the stability margin more accurately. The power-voltage curve is drawn in theory using the TE voltages and impedances. To validate the case study of the proposed method, simulations were executed using the Matlab software. The simulations demonstrated the effectiveness of the proposed method and detected voltage stability/instability under severe contingency scenarios.

ACS Style

Yunhwan Lee; Sangwook Han. Real-Time Voltage Stability Assessment Method for the Korean Power System Based on Estimation of Thévenin Equivalent Impedance. Applied Sciences 2019, 9, 1671 .

AMA Style

Yunhwan Lee, Sangwook Han. Real-Time Voltage Stability Assessment Method for the Korean Power System Based on Estimation of Thévenin Equivalent Impedance. Applied Sciences. 2019; 9 (8):1671.

Chicago/Turabian Style

Yunhwan Lee; Sangwook Han. 2019. "Real-Time Voltage Stability Assessment Method for the Korean Power System Based on Estimation of Thévenin Equivalent Impedance." Applied Sciences 9, no. 8: 1671.

Articles
Published: 17 December 2018 in Journal of International Council on Electrical Engineering
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ESS is widely used in FR power system in Korea. In this paper, we propose a method of starting the supply generator by energizing the transmission line to the ESS instead of the self-starting generator when some area of the system is completely out of order. Simulation should be carried out to find out whether there is any problem in replacing the self-starting generator with the ESS through the calculation of the power flow and the transient stability. We used EPRI ‘s CBEST model for simulation, and utilized actual system data of KEPCO.

ACS Style

Sangwook Han. A study on alternative method of self – starting generator using ESS. Journal of International Council on Electrical Engineering 2018, 9, 1 -7.

AMA Style

Sangwook Han. A study on alternative method of self – starting generator using ESS. Journal of International Council on Electrical Engineering. 2018; 9 (1):1-7.

Chicago/Turabian Style

Sangwook Han. 2018. "A study on alternative method of self – starting generator using ESS." Journal of International Council on Electrical Engineering 9, no. 1: 1-7.