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This paper proposes a novel droop control strategy for addressing the voltage problem against disturbance in a transmission system connected with a utility-scale photovoltaic. Typically, a voltage control at the renewable energy sources (RESs) connected to the transmission grid uses a reactive power–voltage control scheme with a fixed dead band. However, this may cause some problems; thus, this paper proposes a method for setting a dead band value that varies with time. Here, a method for calculating an appropriate dead band that satisfies the voltage maintenance standard for two disturbances is described using voltage sensitivity analysis and the equation of existing droop control. Simulation studies are conducted using the PSS® E program to analyze the short term voltage stability and display the results for various dead bands. The proposed modeling and operational strategy are validated in simulation using a modified IEEE 39 bus system. The results provide useful information, indicating that the control scheme through an adaptive dead band enables more stable system operation than that through a fixed dead band.
Woosung Kim; Sungyoon Song; Gilsoo Jang. Droop Control Strategy of Utility-Scale Photovoltaic Systems Using Adaptive Dead Band. Applied Sciences 2020, 10, 8032 .
AMA StyleWoosung Kim, Sungyoon Song, Gilsoo Jang. Droop Control Strategy of Utility-Scale Photovoltaic Systems Using Adaptive Dead Band. Applied Sciences. 2020; 10 (22):8032.
Chicago/Turabian StyleWoosung Kim; Sungyoon Song; Gilsoo Jang. 2020. "Droop Control Strategy of Utility-Scale Photovoltaic Systems Using Adaptive Dead Band." Applied Sciences 10, no. 22: 8032.
Renewable generation in power systems has proved to be challenging for system operators owing to the increasing levels of penetration. The operation of power systems currently requires additional flexibility and reserves due to the intermittency and unpredictability of renewable generators. However, it is difficult to precisely predict and control the stochastic nature of renewable sources; nevertheless, its capacity continues to increase. To monitor and control renewable generators efficiently, the entire system needs to be established in a hierarchical order. This study proposed the concept of a substation that is uniquely designed for renewable interconnection. The purpose of this substation is simple: to make the renewable generators dispatchable to operators such that each group of renewable generators is sufficiently stable to be considered as conventional generators. For this purpose, methods for sizing and controlling energy storage system are proposed based on forecasts and error distributions.
Yeuntae Yoo; Seungmin Jung; Sungwoo Kang; Sungyoon Song; Jaehyeong Lee; Changhee Han; Gilsoo Jang. Dispatchable Substation for Operation and Control of Renewable Energy Resources. Applied Sciences 2020, 10, 7938 .
AMA StyleYeuntae Yoo, Seungmin Jung, Sungwoo Kang, Sungyoon Song, Jaehyeong Lee, Changhee Han, Gilsoo Jang. Dispatchable Substation for Operation and Control of Renewable Energy Resources. Applied Sciences. 2020; 10 (21):7938.
Chicago/Turabian StyleYeuntae Yoo; Seungmin Jung; Sungwoo Kang; Sungyoon Song; Jaehyeong Lee; Changhee Han; Gilsoo Jang. 2020. "Dispatchable Substation for Operation and Control of Renewable Energy Resources." Applied Sciences 10, no. 21: 7938.
This paper proposes a recurrent neural network (RNN)-based maximum frequency deviation forecasting model for power systems with high photovoltaic power (PV) penetration. The proposed RNN model extracts the nonlinear features and invariant structures exhibited in regional PV power output data and time-variable frequency data in case of contingency. To capture the regularity and random characteristics of PV power output, a probability power flow-dynamic tool (PPDT) for uncertain power system modeling has been developed. This tool considers all possible combinations of PV power generation patterns, even those with low probability, such as those caused by passing clouds. The results are verified by a comparison of various artificial intelligence methods using case studies from the South Korean power system. An online dispatch algorithm that considers the frequency constraints for a designated contingency can be implemented by using the proposed model.
Sungyoon Song; Yoongun Jung; Changhee Han; Seungmin Jung; MinHan Yoon; Gilsoo Jang. Recurrent Neural-Network-Based Maximum Frequency Deviation Prediction Using Probability Power Flow Dynamic Tool. IEEE Access 2020, 8, 182054 -182064.
AMA StyleSungyoon Song, Yoongun Jung, Changhee Han, Seungmin Jung, MinHan Yoon, Gilsoo Jang. Recurrent Neural-Network-Based Maximum Frequency Deviation Prediction Using Probability Power Flow Dynamic Tool. IEEE Access. 2020; 8 (99):182054-182064.
Chicago/Turabian StyleSungyoon Song; Yoongun Jung; Changhee Han; Seungmin Jung; MinHan Yoon; Gilsoo Jang. 2020. "Recurrent Neural-Network-Based Maximum Frequency Deviation Prediction Using Probability Power Flow Dynamic Tool." IEEE Access 8, no. 99: 182054-182064.
Recent research on wind-farm control methods has focused until now on maximising the efficiency and durability of farm operations, as verified for a normalised electrical layout. However, with the increase of turbine size and capacity, it is necessary to develop modifications of the farm management plan that can support the increasing demands of the wind-turbine industry. Here the authors propose a modification that focuses on a proportional reactive power-dispatch method that is applied to radial offshore farm networks. They improve a previously developed method of proportionally distributing reactive power commands by considering the actual configuration of an offshore platform. To confirm the applicability of this method in transient state, they examine case studies using a time-varying signal for a reactive power reference under fluctuating wind. Electromagnetic transients using DC software tools are used to estimate the electrical loss and verify the efficiency of this strategy.
Yeuntae Yoo; Seungmin Jung; Jae‐Hyeong Lee; Sungyoon Song; Gilsoo Jang. Modified reactive power allocation strategy for large‐scale offshore wind turbine considering subsystem configuration. IET Generation, Transmission & Distribution 2020, 14, 5135 -5142.
AMA StyleYeuntae Yoo, Seungmin Jung, Jae‐Hyeong Lee, Sungyoon Song, Gilsoo Jang. Modified reactive power allocation strategy for large‐scale offshore wind turbine considering subsystem configuration. IET Generation, Transmission & Distribution. 2020; 14 (22):5135-5142.
Chicago/Turabian StyleYeuntae Yoo; Seungmin Jung; Jae‐Hyeong Lee; Sungyoon Song; Gilsoo Jang. 2020. "Modified reactive power allocation strategy for large‐scale offshore wind turbine considering subsystem configuration." IET Generation, Transmission & Distribution 14, no. 22: 5135-5142.
This study proposes an adaptive droop control strategy to be used in hybrid static synchronous compensator (STATCOM) systems. The proposed voltage-sensitivity-based adaptive droop control scheme using a hybrid STATCOM system is introduced to eliminate the possibility of interference with the other voltage regulation devices while achieving better voltage regulation without having to implement a full observation of the corresponding network. The sensitivity-analysis is performed by the voltage control of STATCOM system and the sliding-mode-control is included for control system robustness. A comparison between fixed and adaptive control methods is made through case studies of the IEEE 39-bus test system. The results were further verified through a transient simulation of the hybrid STATCOM system that considers both low and high penetration levels of inverter-based reactive power resources.
Sungyoon Song; Changhee Han; Gyu-Sub Lee; Roy A. McCann; Gilsoo Jang. Voltage-Sensitivity-Approach-Based Adaptive Droop Control Strategy of Hybrid STATCOM. IEEE Transactions on Power Systems 2020, 36, 389 -401.
AMA StyleSungyoon Song, Changhee Han, Gyu-Sub Lee, Roy A. McCann, Gilsoo Jang. Voltage-Sensitivity-Approach-Based Adaptive Droop Control Strategy of Hybrid STATCOM. IEEE Transactions on Power Systems. 2020; 36 (1):389-401.
Chicago/Turabian StyleSungyoon Song; Changhee Han; Gyu-Sub Lee; Roy A. McCann; Gilsoo Jang. 2020. "Voltage-Sensitivity-Approach-Based Adaptive Droop Control Strategy of Hybrid STATCOM." IEEE Transactions on Power Systems 36, no. 1: 389-401.
This study proposes a cost-based adaptive (CBA) droop control strategy for use in a voltage source converter (VSC)-based multi-terminal high voltage direct current (MTDC) system. Rather than using a fixed droop gain, we suggest the CBA droop control scheme, which reduces the total incremental generation cost of ac systems, while sharing the burden based on the available capacity of VSCs at the postcontingency- steady-state operating point. Following a certain VSC outage in the MTDC system, unbalanced power is allocated based on the equal incremental cost principle to reduce the total active power generation cost. The results were verified through a transient simulation on an MTDC system with four monopole VSCs, and outage contingency scenarios were presented with three groups of generation cost curves. The results indicate that the CBA droop control strategy can provide greater contributions to the economic operation of the MTDC system, while achieving robust control.
Sungyoon Song; Roy A. McCann; Gilsoo Jang. Cost-Based Adaptive Droop Control Strategy for VSC-MTDC system. IEEE Transactions on Power Systems 2020, 36, 659 -669.
AMA StyleSungyoon Song, Roy A. McCann, Gilsoo Jang. Cost-Based Adaptive Droop Control Strategy for VSC-MTDC system. IEEE Transactions on Power Systems. 2020; 36 (1):659-669.
Chicago/Turabian StyleSungyoon Song; Roy A. McCann; Gilsoo Jang. 2020. "Cost-Based Adaptive Droop Control Strategy for VSC-MTDC system." IEEE Transactions on Power Systems 36, no. 1: 659-669.
As the penetration rate of renewable enery resources (RES) in the power system increases, uncertainty and variability in system operation increase. The application of energy storage systems (ESS) in the power system has been increased to compensate for the characteristics of renewable energy resources. Since ESS is a controllable and highly responsive power resource, primary frequency response and inertia response are possible in case of system contingency, so it can be utilized for frequency regulation (FR) purposes. In frequency regulation, reduction of the Rate of Change of Frequency (RoCoF) and increase the frequency nadir by improving the response characteristics are important factors to secure frequency stability. Therefore, it is important to control ESS with proper parameters according to changing system situation. In this paper, we propose a method to calculate and apply a frequency droop, which is basically required according to the power system condition based on swing equation and effective inertia assessment. In addition, a method to estimate RoCoF droop according to the correlation with frequency by estimating the systematic inertia in the current situation is proposed. The case study for verification of the proposed method was performed through dynamic simulation using actual Korean power system data. The results show that the proposed method is more effective than the governor-free of the conventional thermal generator and conventional droop control-based FR-ESS.
MinHan Yoon; Jaehyeong Lee; Sungyoon Song; Yeontae Yoo; Gilsoo Jang; Seungmin Jung; Sungchul Hwang. Utilization of Energy Storage System for Frequency Regulation in Large-Scale Transmission System. Energies 2019, 12, 3898 .
AMA StyleMinHan Yoon, Jaehyeong Lee, Sungyoon Song, Yeontae Yoo, Gilsoo Jang, Seungmin Jung, Sungchul Hwang. Utilization of Energy Storage System for Frequency Regulation in Large-Scale Transmission System. Energies. 2019; 12 (20):3898.
Chicago/Turabian StyleMinHan Yoon; Jaehyeong Lee; Sungyoon Song; Yeontae Yoo; Gilsoo Jang; Seungmin Jung; Sungchul Hwang. 2019. "Utilization of Energy Storage System for Frequency Regulation in Large-Scale Transmission System." Energies 12, no. 20: 3898.
The penetration level of renewable energy resources has grown in such a way that their effects on the power system can no longer be neglected. In order to cope with these problems, grid operators are forced to improve the stability of grid connection point, and the static synchronous compensator (STATCOM), which has a fast dynamic response is emerging as an alternative. Due to the prohibitive cost of STATCOM, however, grid operators have begun applying a new concept of Hybrid STATCOM, which is a combination of Mechanically Switched Capacitors (MSCs) and STATCOM. Thus, this paper investigates the use of new coordinated control between STATCOM and MSCs, and the solution relies on the required reactive power estimation method using Online Grid Strength Level (OGSL) index, which is newly proposed in this paper, and the optimal MSCs allocation algorithm. Following the proposed procedure, an improved coordinated control scheme is obtained whose objective is to reduce the switching times of MSCs while maximizing the reserve reactive power margin of STATCOM in transient state. This proposal is analyzed on the Jeju island power system in Korea with the developed Hybrid STATCOM model.
Sungyoon Song; Sungchul Hwang; Gilsoo Jang; MinHan Yoon. Improved Coordinated Control Strategy for Hybrid STATCOM Using Required Reactive Power Estimation Method. IEEE Access 2019, 7, 84506 -84515.
AMA StyleSungyoon Song, Sungchul Hwang, Gilsoo Jang, MinHan Yoon. Improved Coordinated Control Strategy for Hybrid STATCOM Using Required Reactive Power Estimation Method. IEEE Access. 2019; 7 (99):84506-84515.
Chicago/Turabian StyleSungyoon Song; Sungchul Hwang; Gilsoo Jang; MinHan Yoon. 2019. "Improved Coordinated Control Strategy for Hybrid STATCOM Using Required Reactive Power Estimation Method." IEEE Access 7, no. 99: 84506-84515.
The application of the direct current (DC) transmission is increasing through the interconnection between grids or the renewable energy resource integration. Various types of DC transmission topology are researched, and the hybrid multi-terminal high voltage DC (HVDC), called the “MTDC”, is one of the research subjects. The hybrid multi-terminal HVDC is the MTDC system that is composed with the Line Commutated Converter (LCC) and Voltage Source Converter (VSC). Most hybrid MTDC research has been focused on the connection of the renewable energy generation sources, especially offshore wind farms. However, the DC grid built with a hybrid MTDC was recently proposed due to the development of the converter technology. Therefore, the DC grid is expected to be able to substitute some parts of the transmission grid instead of the alternating current (AC) system, and the operation strategies of the DC grid are still being researched. The DC grid has the advantage of being able to control the power flow, which can even improve the stability of the connected AC system. The dynamic model is required to analyze the improvement of the AC system by the operation strategy of the hybrid MTDC, however, there is no generic model for the system. In this paper, an operation strategy of the hybrid MTDC is proposed to improve the stability of the AC power system by increasing the utilization of parallel AC transmission lines under the contingency condition. Furthermore, studies on the modeling method for a hybrid MTDC analysis were performed. The proposed modeling method and operation strategy were verified in simulations for which a modified IEEE 39 bus test system was used. The improvement of transient stability by the proposed hybrid MTDC system was shown in the simulation results.
Sungchul Hwang; Sungyoon Song; Gilsoo Jang; MinHan Yoon. An Operation Strategy of the Hybrid Multi-Terminal HVDC for Contingency. Energies 2019, 12, 2042 .
AMA StyleSungchul Hwang, Sungyoon Song, Gilsoo Jang, MinHan Yoon. An Operation Strategy of the Hybrid Multi-Terminal HVDC for Contingency. Energies. 2019; 12 (11):2042.
Chicago/Turabian StyleSungchul Hwang; Sungyoon Song; Gilsoo Jang; MinHan Yoon. 2019. "An Operation Strategy of the Hybrid Multi-Terminal HVDC for Contingency." Energies 12, no. 11: 2042.
As a proportion of generation using renewable energy increases in a power system, the need for facility investment is increasing in not only the distribution system but also the transmission system. However, it is inefficient to invest in new equipment to deal with the short peak output of renewable energy generation. For this reason, this paper proposes a method for operating the grid more flexibly, through an optimal operating strategy of the direct current (DC) line at medium-voltage (MV) level, thereby delaying the facility investment in the transmission line. In order to determine the optimal operating point of the converter connected with a DC line, the swarm intelligence-based optimization technique, which can minimize multi-objective function, is used. In addition, in order to overcome the communication dependency of the centralized control, which needs to receive information about the optimal operating point computed by the system operator, this paper proposes a decentralized emergency control (DEC) method in case of a communication fault.
Changhee Han; Sungyoon Song; Juyong Kim; Gilsoo Jang. Enhancing Line Capacity Utilization in Power Transmission System Using Active MVDC Link. Energies 2019, 12, 1589 .
AMA StyleChanghee Han, Sungyoon Song, Juyong Kim, Gilsoo Jang. Enhancing Line Capacity Utilization in Power Transmission System Using Active MVDC Link. Energies. 2019; 12 (9):1589.
Chicago/Turabian StyleChanghee Han; Sungyoon Song; Juyong Kim; Gilsoo Jang. 2019. "Enhancing Line Capacity Utilization in Power Transmission System Using Active MVDC Link." Energies 12, no. 9: 1589.
The sizes of PV power plants have grown in such a way that their effects on the power system can no longer be neglected. In order to address these issues, grid operators are forced to expand grid connection points, and a power flow analysis considering uncertain renewable generation is required. Thus, a modified probabilistic power flow (PPF) analysis for practical grid planning is suggested in this paper. The regularity and randomness of PV power are modeled by a Monte Carlo-based probabilistic model combining both k-means clustering and the kernel density estimation method. The certain cluster group is selected so as to reflect the severe PV generation scenario, and the chi-square test to represent the $n$ th conservative network planning was suggested. In order to provide the power flow result more effectively, a mapping function of graphic representation based on a significant grid code violation is provided in an automatic PPF tool written by Python scripts. Following this procedure yields a reasonable network design for various renewable energy penetration levels.
Sungyoon Song; Changhee Han; Seungmin Jung; MinHan Yoon; Gilsoo Jang. Probabilistic Power Flow Analysis of Bulk Power System for Practical Grid Planning Application. IEEE Access 2019, 7, 45494 -45503.
AMA StyleSungyoon Song, Changhee Han, Seungmin Jung, MinHan Yoon, Gilsoo Jang. Probabilistic Power Flow Analysis of Bulk Power System for Practical Grid Planning Application. IEEE Access. 2019; 7 ():45494-45503.
Chicago/Turabian StyleSungyoon Song; Changhee Han; Seungmin Jung; MinHan Yoon; Gilsoo Jang. 2019. "Probabilistic Power Flow Analysis of Bulk Power System for Practical Grid Planning Application." IEEE Access 7, no. : 45494-45503.
In this paper, the generator angle stability of several active power control schemes of a voltage-source converter (VSC)-based high-voltage DC (HVDC) is evaluated for two interconnected AC systems. Excluding frequency control, there has been no detailed analysis of interconnected grids depending upon the converter power control, so six different types of active power control of the VSC-HVDC are defined and analyzed in this paper. For each TSO (transmission system operator), the applicable schemes of two kinds of step control and four kinds of ramp-rate control with a droop characteristic are included in this research. Furthermore, in order to effectively evaluate the angle stability, the Generators-VSC Interaction Factor (GVIF) index is newly implemented to distinguish the participating generators (PGs) group which reacts to the converter power change. As a result, the transient stabilities of the two power systems are evaluated and the suitable active power control strategies are determined for two TSOs. Simulation studies are performed using the PSS®E program to analyze the power system transient stability and various active power control schemes of the VSC-HVDC. The results provide useful information indicating that the ramp-rate control shows a more stable characteristic than the step-control for interconnected grids; thus, a converter having a certain ramp-rate slope similar to that of the other generator shows more stable results in several cases.
Sungyoon Song; MinHan Yoon; Gilsoo Jang. Analysis of Six Active Power Control Strategies of Interconnected Grids with VSC-HVDC. Applied Sciences 2019, 9, 183 .
AMA StyleSungyoon Song, MinHan Yoon, Gilsoo Jang. Analysis of Six Active Power Control Strategies of Interconnected Grids with VSC-HVDC. Applied Sciences. 2019; 9 (1):183.
Chicago/Turabian StyleSungyoon Song; MinHan Yoon; Gilsoo Jang. 2019. "Analysis of Six Active Power Control Strategies of Interconnected Grids with VSC-HVDC." Applied Sciences 9, no. 1: 183.
This paper proposes two novel power control strategies to improve the angle stability of generators using a Back-to-Back (BTB) system-based voltage source converter (VSC). The proposed power control strategies have two communication systems: a bus angle monitoring system and a special protection system (SPS), respectively. The first power control strategy can emulate the behaviour of the ac transmission to improve the angle stability while supporting the ac voltage at the primary level of the control structure. The second power control scheme uses an SPS signal to contribute stability to the power system under severe contingencies involving the other generators. The results for the proposed control scheme were validated using the PSS/E software package with a sub-module written in the Python language, and the simple assistant power control with two communication systems is shown to improve the angle stability. In conclusion, BTB VSCs can contribute their power control strategies to ac grid in addition to offering several existing advantages, which makes them applicable for use in the commensurate protection of large ac grid.
Sungyoon Song; Sungchul Hwang; Baekkyeong Ko; Seungtae Cha; Gilsoo Jang. Novel Transient Power Control Schemes for BTB VSCs to Improve Angle Stability. Applied Sciences 2018, 8, 1350 .
AMA StyleSungyoon Song, Sungchul Hwang, Baekkyeong Ko, Seungtae Cha, Gilsoo Jang. Novel Transient Power Control Schemes for BTB VSCs to Improve Angle Stability. Applied Sciences. 2018; 8 (8):1350.
Chicago/Turabian StyleSungyoon Song; Sungchul Hwang; Baekkyeong Ko; Seungtae Cha; Gilsoo Jang. 2018. "Novel Transient Power Control Schemes for BTB VSCs to Improve Angle Stability." Applied Sciences 8, no. 8: 1350.
In the Korean power system, growing power loads have recently created the problems of voltage instability and fault current in the Seoul Capital Area (SCA). Accordingly, the back-to-back (BTB) voltage source converter (VSC) high-voltage direct-current (HVDC) system is emerging to resolve such problems with grid segmentation. However, non-convergence problems occur in this metropolitan area, due to the large change of power flow in some contingencies. Therefore, this paper proposes two kinds of AC transmission emulation control (ATEC) strategies to improve the metropolitan transient stability, and to resolve the non-convergence problem. The proposed ATEC strategies are able to mitigate possible overloading of adjacent AC transmission, and maintain power balance between metropolitan regions. The first ATEC strategy uses a monitoring system that permits the reverse power flow of AC transmission, and thus effectively improves the grid stability based on the power transfer equation. The second ATEC strategy emulates AC transmission with DC link capacitors in a permissible DC-link voltage range according to angle difference, and securely improves the gird stability, without requiring grid operator schedule decisions. This paper compares two kinds of ATEC schemes: it demonstrates the first ATEC strategy with specific fault scenario with PSS/E (Power Transmission System Planning Software), and evaluates the second ATEC strategy with internal controller performance with PSCAD/EMTDC (Power System Electromagnetic Transients Simulation Software).
Sungyoon Song; Jongin Kim; Junghun Lee; Gilsoo Jang. AC Transmission Emulation Control Strategies for the BTB VSC HVDC System in the Metropolitan Area of Seoul. Energies 2017, 10, 1143 .
AMA StyleSungyoon Song, Jongin Kim, Junghun Lee, Gilsoo Jang. AC Transmission Emulation Control Strategies for the BTB VSC HVDC System in the Metropolitan Area of Seoul. Energies. 2017; 10 (8):1143.
Chicago/Turabian StyleSungyoon Song; Jongin Kim; Junghun Lee; Gilsoo Jang. 2017. "AC Transmission Emulation Control Strategies for the BTB VSC HVDC System in the Metropolitan Area of Seoul." Energies 10, no. 8: 1143.
Sungyoon Song; Bokyung Ko; JaeWan Suh; Changhee Han; Gilsoo Jang. Operation algorithm of PV/BESS application considering demand response uncertainty in an independent microgrid system. Journal of International Council on Electrical Engineering 2017, 7, 242 -248.
AMA StyleSungyoon Song, Bokyung Ko, JaeWan Suh, Changhee Han, Gilsoo Jang. Operation algorithm of PV/BESS application considering demand response uncertainty in an independent microgrid system. Journal of International Council on Electrical Engineering. 2017; 7 (1):242-248.
Chicago/Turabian StyleSungyoon Song; Bokyung Ko; JaeWan Suh; Changhee Han; Gilsoo Jang. 2017. "Operation algorithm of PV/BESS application considering demand response uncertainty in an independent microgrid system." Journal of International Council on Electrical Engineering 7, no. 1: 242-248.