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Dr. Thai-Thanh Nguyen
Clarkson University

Basic Info


Research Keywords & Expertise

0 Model Predictive Control
0 microgrid
0 power system
0 Power converter
0 Distributed control and optimization

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Career Timeline

Incheon National University

University Educator/Researcher

01 February 2020 - 01 October 2020


Incheon National University

Post Doctoral Researcher

01 February 2019 - 01 February 2020




Short Biography

Thanh Nguyen received his B.S. in Electrical Engineering from Hanoi University of Science and Technology, Vietnam, in 2013, and his Ph. D. in Electrical Engineering from Incheon National University, Korea, in 2019. From 2019 to 2020, he was a postdoctoral research associate at the Incheon National University. Since November 2020, he has been a research associate at Clarkson University, NY, USA. His research interests include power system control and stability, power converter control, and the application of power electronics to power systems.

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Journal article
Published: 28 July 2021 in Energies
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Floating offshore wind has received more attention due to its advantage of access to incredible wind resources over deep waters. Modeling of floating offshore wind farms is essential to evaluate their impacts on the electric power system, in which the floating offshore wind turbine should be adequately modeled for real-time simulation studies. This study proposes a simplified floating offshore wind turbine model, which is applicable for the real-time simulation of large-scale floating offshore wind farms. Two types of floating wind turbines are evaluated in this paper: the semi-submersible and spar-buoy floating wind turbines. The effectiveness of the simplified turbine models is shown by a comparison study with the detailed FAST (Fatigue, Aerodynamics, Structures, and Turbulence) floating turbine model. A large-scale floating offshore wind farm including eighty units of simplified turbines is tested in parallel simulation and real-time software (OPAL-RT). The wake effects among turbines and the effect of wind speeds on ocean waves are also taken into account in the modeling of offshore wind farms. Validation results show sufficient accuracy of the simplified models compared to detailed FAST models. The real-time results of offshore wind farms show the feasibility of the proposed turbine models for the real-time model of large-scale offshore wind farms.

ACS Style

Thanh-Dam Pham; Minh-Chau Dinh; Hak-Man Kim; Thai-Thanh Nguyen. Simplified Floating Wind Turbine for Real-Time Simulation of Large-Scale Floating Offshore Wind Farms. Energies 2021, 14, 4571 .

AMA Style

Thanh-Dam Pham, Minh-Chau Dinh, Hak-Man Kim, Thai-Thanh Nguyen. Simplified Floating Wind Turbine for Real-Time Simulation of Large-Scale Floating Offshore Wind Farms. Energies. 2021; 14 (15):4571.

Chicago/Turabian Style

Thanh-Dam Pham; Minh-Chau Dinh; Hak-Man Kim; Thai-Thanh Nguyen. 2021. "Simplified Floating Wind Turbine for Real-Time Simulation of Large-Scale Floating Offshore Wind Farms." Energies 14, no. 15: 4571.

Journal article
Published: 11 January 2021 in Sustainability
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Due to the uncertainty in output power of wind farm (WF) systems, a certain reserve capacity is often required in the power system to ensure service reliability and thereby increasing the operation and investment costs for the entire system. In order to reduce this uncertainty and reserve capacity, this study proposes a multi-objective stochastic optimization model to determine the set-points of the WF system. The first objective is to maximize the set-point of the WF system, while the second objective is to maximize the probability of fulfilling that set-point in the real-time operation. An increase in the probability of satisfying the set-point can reduce the uncertainty in the output power of the WF system. However, if the required probability increases, the set-point of the WF system decreases, which reduces the profitability of the WF system. Using the proposed method helps the WF operator in determining the optimal set-point for the WF system by making a trade-off between maximizing the set-point of WF and increasing the probability of fulfilling this set-point in real-time operation. This ensures that the WF system can offer an optimal set-point with a high probability of satisfying this set-point to the power system and thereby avoids a high penalty for mismatch power. In order to show the effectiveness of the proposed method, several case studies are carried out, and the effects of various parameters on the optimal set-point for the WF system are also analyzed. According to the parameters from the transmission system operator (TSO) and wind speed profile, the WF operator can easily determine the optimal set-point using the proposed strategy. A comparison of the profits that the WF system achieved with and without the proposed method is analyzed in detail, and the set-point of the WF system in different seasons is also presented.

ACS Style

Van-Hai Bui; Akhtar Hussain; Thai-Thanh Nguyen; Hak-Man Kim. Multi-Objective Stochastic Optimization for Determining Set-Point of Wind Farm System. Sustainability 2021, 13, 624 .

AMA Style

Van-Hai Bui, Akhtar Hussain, Thai-Thanh Nguyen, Hak-Man Kim. Multi-Objective Stochastic Optimization for Determining Set-Point of Wind Farm System. Sustainability. 2021; 13 (2):624.

Chicago/Turabian Style

Van-Hai Bui; Akhtar Hussain; Thai-Thanh Nguyen; Hak-Man Kim. 2021. "Multi-Objective Stochastic Optimization for Determining Set-Point of Wind Farm System." Sustainability 13, no. 2: 624.

Journal article
Published: 30 December 2020 in IEEE Access
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A large number of wind turbine generators in the large-scale offshore wind farm system poses a challenge to the wind farm control system due to the computational burden in the central control methods or the complexity of the communication network in the decentralized control strategies. A hybrid control method based on the distributed consensus control and the central model predictive control is proposed in this study to overcome the problem. Typically, the wind turbine generators in the large-scale offshore wind farm system are clustered into several groups. The consensus-based distributed reactive power coordination control is proposed to each cluster and the centralized predictive voltage control is used to manage the total reactive powers of all clusters and regulate the voltage at the point of common coupling. The gradient-descent algorithm for the optimal design of the consensus-based cluster control is presented firstly. Based on the convergence property of the consensus control, the equivalent model of the total reactive power response of each cluster is identified, which is used for the design of the centralized predictive voltage control. Eigenvalue analysis of the proposed predictive control strategy is carried out to verify the stability of the distributed and predictive control systems. The robustness of the proposed predictive controller is evaluated in the conditions of significant model errors due to the communication delay in each cluster. A comparison study with the full distributed control based on consensus algorithm is presented to demonstrate the effectiveness of the proposed control method. The feasibility of the proposed predictive controller is evaluated by the control-hardware-in-the-loop simulation using OPAL-RT Technologies. An additional comparison study in term of computation time with the central control method is also carried out. Real-time simulation results show the superior performance of the proposed hybrid method compared to the full distributed consensus controller or the central control strategies.

ACS Style

Thai-Thanh Nguyen; Hak-Man Kim. Cluster-Based Predictive PCC Voltage Control of Large-Scale Offshore Wind Farm. IEEE Access 2020, 9, 4630 -4641.

AMA Style

Thai-Thanh Nguyen, Hak-Man Kim. Cluster-Based Predictive PCC Voltage Control of Large-Scale Offshore Wind Farm. IEEE Access. 2020; 9 ():4630-4641.

Chicago/Turabian Style

Thai-Thanh Nguyen; Hak-Man Kim. 2020. "Cluster-Based Predictive PCC Voltage Control of Large-Scale Offshore Wind Farm." IEEE Access 9, no. : 4630-4641.

Journal article
Published: 09 September 2020 in IEEE Access
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In the conventional operation of a wind farm (WF) system, the operation point of each wind turbine generator (WTG) is determined to capture maximum energy individually using maximum power point tracking (MPPT) algorithm. However, this operation strategy might not ensure the maximum output power of WF due to wake effect among WTGs. Therefore, this paper develops a multi-agent-based cooperative learning strategy among WTGs using deep reinforcement learning to enhance the overall efficiency of WF by minimizing the wake effect. WTG agents are learnable units and they interact with others as an extensive-form game based on a cooperative model to achieve a common goals (i.e. maximum output power of the WF). In this game, WTG agents carry out their actions sequentially and measure a common reward which is used to update the knowledge of all agents. During the training process, WTG agents use different deep neural networks (DNNs) to improve their actions for achieving the higher reward in the long run by optimizing the weights of DNNs in each learning step. After the training process, WTG agents are able to determine optimal set-points with different input information to minimize the wake effect and to maximize the output power of the WF. Moreover, an operation strategy for the entire WF system is proposed to ensure that the WF always complies with grid-code constraints from transmission system operators, including the requirement of limited power and reserve power. In order to show the effectiveness of the proposed method, a comparison between the results using the proposed method and the conventional MPPT method is also presented in different cases, and the results show that the proposed method can increase the output power of the WF in the range of 1.99% to 4.11% with different layouts.

ACS Style

Van-Hai Bui; Thai-Thanh Nguyen; Hak-Man Kim. Distributed Operation of Wind Farm for Maximizing Output Power: A Multi-Agent Deep Reinforcement Learning Approach. IEEE Access 2020, 8, 173136 -173146.

AMA Style

Van-Hai Bui, Thai-Thanh Nguyen, Hak-Man Kim. Distributed Operation of Wind Farm for Maximizing Output Power: A Multi-Agent Deep Reinforcement Learning Approach. IEEE Access. 2020; 8 (99):173136-173146.

Chicago/Turabian Style

Van-Hai Bui; Thai-Thanh Nguyen; Hak-Man Kim. 2020. "Distributed Operation of Wind Farm for Maximizing Output Power: A Multi-Agent Deep Reinforcement Learning Approach." IEEE Access 8, no. 99: 173136-173146.

Journal article
Published: 12 August 2020 in IEEE Access
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This paper proposed a distributed reactive power coordination and voltage control of offshore wind farm based on the leader-following diffusion algorithm. Designating several wind turbine generators (WTGs) as the leaders to receive the information of voltage at point of common coupling (PCC), the reactive power generations required to minimize the voltage deviation could be computed by these leaders. The required reactive power generations are diffused throughout all WTGs by the diffusion algorithm, resulting in the coordinated operation of WTGs to regulate the PCC voltage. The proposed offshore wind farm controller is based on the hierarchical control strategy, which consists of primary and secondary layers. The primary layer is responsible for the inner current, voltage or power regulations whereas the secondary layer is based on the proposed diffusion algorithm to achieve the coordinated operation among WTGs. The proposed strategy could maintain accurate reactive power sharing among WTGs and regulate the PCC voltage. A comparison study with the conventional consensus-based control is presented to show the effectiveness of the proposed diffusion controller. The comparison results show the better performance of the proposed method in terms of dynamic responses of PCC voltage and reactive power coordination. Simulation scenarios of constant wind speed, variable wind speed, and voltage sag in the utility grid are carried out to evaluate the performance of proposed method. The proposed diffusion control is tested either in a small or large offshore wind farm systems. Effect of communication delay on the performance of proposed diffusion control is also described. An experiment of the small-scale wind farm system is conducted to show the feasibility of proposed diffusion strategy.

ACS Style

Thai-Thanh Nguyen; Hak-Man Kim. Leader-Following Diffusion-Based Reactive Power Coordination and Voltage Control of Offshore Wind Farm. IEEE Access 2020, 8, 149555 -149568.

AMA Style

Thai-Thanh Nguyen, Hak-Man Kim. Leader-Following Diffusion-Based Reactive Power Coordination and Voltage Control of Offshore Wind Farm. IEEE Access. 2020; 8 (99):149555-149568.

Chicago/Turabian Style

Thai-Thanh Nguyen; Hak-Man Kim. 2020. "Leader-Following Diffusion-Based Reactive Power Coordination and Voltage Control of Offshore Wind Farm." IEEE Access 8, no. 99: 149555-149568.

Journal article
Published: 20 June 2020 in Energies
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This paper proposes a distributed control of the microgrid (MG) system based on the diffusion algorithm. Unlike the existing decentralized strategy that focuses on the economic operation of the MG system, the proposed strategy performs secondary frequency regulation in addition to the optimization of the MG system. The hierarchical control technique is employed in this study, where the primary layer is responsible for power control and the secondary layer is responsible for the frequency control and economic operation of the MG system. A tested MG system with four distributed generations (DGs) is considered. Three types of communication topologies are evaluated in this study, which are line, ring, and full topologies. The proposed controller is compared to the conventional consensus controller to show the effectiveness of the proposed diffusion controller. Simulation results show that the proposed diffusion strategy improves the convergence speed of the distributed control, resulting in the improvement of power responses and frequency quality of the MG system. The tested system is implemented in the MATLAB/Simulink environment to show the feasibility of the proposed diffusion controller.

ACS Style

Su-Been Hong; Thai-Thanh Nguyen; Jinhong Jeon; Hak-Man Kim. Distributed Operation of Microgrids Considering Secondary Frequency Restoration Based on the Diffusion Algorithm. Energies 2020, 13, 3207 .

AMA Style

Su-Been Hong, Thai-Thanh Nguyen, Jinhong Jeon, Hak-Man Kim. Distributed Operation of Microgrids Considering Secondary Frequency Restoration Based on the Diffusion Algorithm. Energies. 2020; 13 (12):3207.

Chicago/Turabian Style

Su-Been Hong; Thai-Thanh Nguyen; Jinhong Jeon; Hak-Man Kim. 2020. "Distributed Operation of Microgrids Considering Secondary Frequency Restoration Based on the Diffusion Algorithm." Energies 13, no. 12: 3207.

Journal article
Published: 05 March 2020 in Energies
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High temperature superconducting (HTS) power cables are a potential solution for the grid integration of offshore wind farms since the HTS cable can conduct bulk wind power at low voltage levels. However, the transient current through the HTS cable in cases of low voltage ride through (LVRT) operation has a negative impact on the HTS cable operation due to the quenching phenomenon. This paper analyzes the impact of LVRT control strategies on the HTS cable operation. In addition, a coordinated control of wind turbines for LVRT improvement of an offshore wind farm is proposed. The feasibility of the HTS cable application for the grid connection of offshore wind farms is also discussed in this study. The proposed controller is designed for the wind turbine generator based on a type-4 permanent magnet synchronous generator. In the proposed controller, the transient current through the HTS cable is reduced by regulating the machine side power during fault conditions. The feasibility of the proposed controller is validated in the PSCAD/EMTDC program (Manitoba Hydro International Ltd., Winnipeg, Manitoba, Canada, version 4.2.1). The effects of transient current on the cable temperatures and resistances are analyzed in this study. Simulation results show that the proposed control strategy could reduce the transient current and temperature rise of the HTS cable.

ACS Style

Thai-Thanh Nguyen; Hak-Man Kim; Hyung Suk Yang. Impacts of a LVRT Control Strategy of Offshore Wind Farms on the HTS Power Cable. Energies 2020, 13, 1194 .

AMA Style

Thai-Thanh Nguyen, Hak-Man Kim, Hyung Suk Yang. Impacts of a LVRT Control Strategy of Offshore Wind Farms on the HTS Power Cable. Energies. 2020; 13 (5):1194.

Chicago/Turabian Style

Thai-Thanh Nguyen; Hak-Man Kim; Hyung Suk Yang. 2020. "Impacts of a LVRT Control Strategy of Offshore Wind Farms on the HTS Power Cable." Energies 13, no. 5: 1194.

Journal article
Published: 02 January 2020 in Energies
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The uses of high-temperature superconducting (HTS) cables pose a challenge of power system protection since the impedance of the HTS cable is varied during fault conditions. The protection systems should be designed properly to ensure the reliability and stability of the whole system. This paper presents a fault analysis of the co-axial HTS cable in the mesh system and proposes a coordinated protection system. In the proposed protection system, the main protection is the differential current relay whereas the backup protections are the overcurrent and directional overcurrent relays. The normal and abnormal relay operations are considered to analyze the transient fault current in the HTS cable and evaluate the performance of the proposed coordinated protection system. Characteristics of cable impedances and temperatures under various fault conditions are presented. The proposed protection scheme is validated by the simulation in the PSCAD/EMTDC program. Simulation results show that the coordinated protection scheme could successfully protect the HTS cables in both normal and abnormal relay operations.

ACS Style

Thai-Thanh Nguyen; Woon-Gyu Lee; Hak-Man Kim; Hyung Suk Yang. Fault Analysis and Design of a Protection System for a Mesh Power System with a Co-Axial HTS Power Cable. Energies 2020, 13, 220 .

AMA Style

Thai-Thanh Nguyen, Woon-Gyu Lee, Hak-Man Kim, Hyung Suk Yang. Fault Analysis and Design of a Protection System for a Mesh Power System with a Co-Axial HTS Power Cable. Energies. 2020; 13 (1):220.

Chicago/Turabian Style

Thai-Thanh Nguyen; Woon-Gyu Lee; Hak-Man Kim; Hyung Suk Yang. 2020. "Fault Analysis and Design of a Protection System for a Mesh Power System with a Co-Axial HTS Power Cable." Energies 13, no. 1: 220.

Conference paper
Published: 01 November 2019 in 2019 8th International Conference on Renewable Energy Research and Applications (ICRERA)
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A development of a simplified floating offshore wind turbine (FOWT) model for time-domain simulation was presented in this paper. We aim to develop a model that can express the most physical properties of the turbine/platform/generator & converter system of the floating offshore wind turbine, limit its complexity, and be suitable for a time-domain simulation program such as PSCAD/EMTDC, MATLAB, etc. The simplified model was developed and implemented using MATLAB, and the model was validated by using Fatigue, Aerodynamic, Structures, and Turbulence (FAST) program. Through this study, the accurate simplified FOWT model for time-domain simulation was achieved and validated.

ACS Style

Minh-Chau Dinh; Minwon Park; Thai-Thanh Nguyen. Simplified Floating Offshore Wind Turbine Model for Time-domain Simulation. 2019 8th International Conference on Renewable Energy Research and Applications (ICRERA) 2019, 270 -275.

AMA Style

Minh-Chau Dinh, Minwon Park, Thai-Thanh Nguyen. Simplified Floating Offshore Wind Turbine Model for Time-domain Simulation. 2019 8th International Conference on Renewable Energy Research and Applications (ICRERA). 2019; ():270-275.

Chicago/Turabian Style

Minh-Chau Dinh; Minwon Park; Thai-Thanh Nguyen. 2019. "Simplified Floating Offshore Wind Turbine Model for Time-domain Simulation." 2019 8th International Conference on Renewable Energy Research and Applications (ICRERA) , no. : 270-275.

Journal article
Published: 22 April 2019 in Energies
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Bypassing transient current through copper (Cu) stabilizer layers reduces heat generation and temperature rise of high-temperature superconducting (HTS) conductors, which could protect HTS cables from burning out during transient conditions. The Cu layer connected in parallel with HTS tape layers impacts current distribution among layers and variations of phase resistance in either steady-state or transient conditions. Modeling the multilayer HTS power cable is important for transient studies. However, existing models of HTS power cables have only proposed HTS cables without the use of a Cu-former layer. To overcome this problem, the authors proposed a multilayer HTS power cable model that used a Cu-former layer in each phase for transient study. It was observed that resistance of the HTS conductor increased significantly in the transient state due to a quenching phenomenon, which made the transient current mainly flow into the Cu-former layers. Since resistance of the Cu-former layer has a significant impact on the transient current, detailed modeling of the Cu-former layer is described in this study. The feasibility of the developed HTS cable model is evaluated in the PSCAD/EMTDC program.

ACS Style

Thai-Thanh Nguyen; Woon-Gyu Lee; Seok-Ju Lee; Minwon Park; Hak-Man Kim; DuYean Won; Jaeun Yoo; Hyung Suk Yang. A Simplified Model of Coaxial, Multilayer High-Temperature Superconducting Power Cables with Cu Formers for Transient Studies. Energies 2019, 12, 1514 .

AMA Style

Thai-Thanh Nguyen, Woon-Gyu Lee, Seok-Ju Lee, Minwon Park, Hak-Man Kim, DuYean Won, Jaeun Yoo, Hyung Suk Yang. A Simplified Model of Coaxial, Multilayer High-Temperature Superconducting Power Cables with Cu Formers for Transient Studies. Energies. 2019; 12 (8):1514.

Chicago/Turabian Style

Thai-Thanh Nguyen; Woon-Gyu Lee; Seok-Ju Lee; Minwon Park; Hak-Man Kim; DuYean Won; Jaeun Yoo; Hyung Suk Yang. 2019. "A Simplified Model of Coaxial, Multilayer High-Temperature Superconducting Power Cables with Cu Formers for Transient Studies." Energies 12, no. 8: 1514.

Journal article
Published: 18 April 2019 in IEEE Access
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The efficiency of the microgrid (MG) system is depended on converter and power line losses. The loss of converter relies on the load condition whereas the power line loss is affected by the line impedance. Improving the efficiency of the MG system should consider both types of losses. This paper proposed a distributed coordination control strategy of distributed generation (DGs) in the MG system for efficiency improvement considering the losses of the converter and power line. A cost function considering both types of losses is defined. The diffusion algorithm is used in the secondary control of each DG to optimize the cost function. The diffusion algorithm finds the output power of each DG that provides the highest efficiency. Considering the minimization of the converter and power line losses, the system efficiency could be improved by reducing not only converter loss but also power line loss. The proposed control method could achieve accurate power sharing at the heavy-load condition. The performance of the proposed method is similar to the conventional power-sharing control scheme at the heavy-load condition. However, at the light-load condition, the efficiency of the MG system with the proposed method could be improved. The feasibility of the proposed control strategy is validated by real-time simulation using OPAL-RT Technologies.

ACS Style

Hyeong-Jun Yoo; Thai-Thanh Nguyen; Hak-Man Kim. Diffusion-Based Distributed Coordination Control of Power Converters in MG for Efficiency Improvement. IEEE Access 2019, 7, 53347 -53357.

AMA Style

Hyeong-Jun Yoo, Thai-Thanh Nguyen, Hak-Man Kim. Diffusion-Based Distributed Coordination Control of Power Converters in MG for Efficiency Improvement. IEEE Access. 2019; 7 ():53347-53357.

Chicago/Turabian Style

Hyeong-Jun Yoo; Thai-Thanh Nguyen; Hak-Man Kim. 2019. "Diffusion-Based Distributed Coordination Control of Power Converters in MG for Efficiency Improvement." IEEE Access 7, no. : 53347-53357.

Journal article
Published: 25 March 2019 in Energies
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Variable switching frequency in the finite control set model predictive control (FCS-MPC) method causes a negative impact on the converter efficiency and the design of the output filters. Several studies have addressed the problem, but they are either complicated or require heavy computation. This study proposes a new model predictive control (MPC) method with constant switching frequency, which is simple to implement and needs only a small computation time. The proposed MPC method is based on the gradient descent (GD) method to find the optimal voltage vector. Since the cost function of the MPC method is represented in the strongly convex function, the optimal voltage vector could be found quickly by using the GD method, which reduces the computation time of the MPC method. The design of the proposed MPC method based on GD (GD-MPC) is shown in this study. The feasibility of the proposed GD-MPC is evaluated in the real-time simulation using OPAL-RT technologies. The performance of the proposed method in the case of single inverter operation or parallel inverter operation is shown. A comparison study on the proposed GD-MPC and the MPC with the concept of the virtual state vector (VSV-MPC) is presented to demonstrate the effectiveness of the proposed predictive control. Real-time simulation results show that the proposed GD-MPC method performs better with a low total harmonic distortion (THD) value of output current and short computation time, compared to the VSV-MPC method.

ACS Style

Hyeong-Jun Yoo; Thai-Thanh Nguyen; Hak-Man Kim. MPC with Constant Switching Frequency for Inverter-Based Distributed Generations in Microgrid Using Gradient Descent. Energies 2019, 12, 1156 .

AMA Style

Hyeong-Jun Yoo, Thai-Thanh Nguyen, Hak-Man Kim. MPC with Constant Switching Frequency for Inverter-Based Distributed Generations in Microgrid Using Gradient Descent. Energies. 2019; 12 (6):1156.

Chicago/Turabian Style

Hyeong-Jun Yoo; Thai-Thanh Nguyen; Hak-Man Kim. 2019. "MPC with Constant Switching Frequency for Inverter-Based Distributed Generations in Microgrid Using Gradient Descent." Energies 12, no. 6: 1156.

Journal article
Published: 13 February 2019 in IEEE Transactions on Sustainable Energy
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ACS Style

Hyeong-Jun Yoo; Thai-Thanh Nguyen; Hak-Man Kim. Consensus-Based Distributed Coordination Control of Hybrid AC/DC Microgrids. IEEE Transactions on Sustainable Energy 2019, 11, 629 -639.

AMA Style

Hyeong-Jun Yoo, Thai-Thanh Nguyen, Hak-Man Kim. Consensus-Based Distributed Coordination Control of Hybrid AC/DC Microgrids. IEEE Transactions on Sustainable Energy. 2019; 11 (2):629-639.

Chicago/Turabian Style

Hyeong-Jun Yoo; Thai-Thanh Nguyen; Hak-Man Kim. 2019. "Consensus-Based Distributed Coordination Control of Hybrid AC/DC Microgrids." IEEE Transactions on Sustainable Energy 11, no. 2: 629-639.

Journal article
Published: 06 February 2019 in IEEE Transactions on Power Electronics
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In a hybrid ac-dc microgrid, stiff voltage sources may appear in either the dc or ac subgrids which gives rise to multiple operation modes as power dispatch changes. This creates a challenge for designing the interlink converter between the ac and dc subgrids since the different modes require different interlink controls. To solve this problem, this paper proposes the concept of a transfverter inspired by how transformers link ac grids. Like a transformer, a transfverter can react to the presence of stiff voltage sources on either the dc or ac side and reflect the "stiffness" and voltage stabilizing capability to the other side. A back-to-back converter with droop control is used as the underlying technology to implement this concept. A novel optimization method called model bank synthesis is proposed to find control parameters for the interlink converter that offer the best controller performance across the different microgrid modes without requiring mode-changing of the controller. The effectiveness of the proposed solution is validated through both simulation and experiments.

ACS Style

Yunjie Gu; Yitong Li; Hyeong-Jun Yoo; Thai-Thanh Nguyen; Xin Xiang; Hak-Man Kim; Adria Junyent-Ferre; Timothy C. Green. Transfverter: Imbuing Transformer-Like Properties in an Interlink Converter for Robust Control of a Hybrid AC–DC Microgrid. IEEE Transactions on Power Electronics 2019, 34, 11332 -11341.

AMA Style

Yunjie Gu, Yitong Li, Hyeong-Jun Yoo, Thai-Thanh Nguyen, Xin Xiang, Hak-Man Kim, Adria Junyent-Ferre, Timothy C. Green. Transfverter: Imbuing Transformer-Like Properties in an Interlink Converter for Robust Control of a Hybrid AC–DC Microgrid. IEEE Transactions on Power Electronics. 2019; 34 (11):11332-11341.

Chicago/Turabian Style

Yunjie Gu; Yitong Li; Hyeong-Jun Yoo; Thai-Thanh Nguyen; Xin Xiang; Hak-Man Kim; Adria Junyent-Ferre; Timothy C. Green. 2019. "Transfverter: Imbuing Transformer-Like Properties in an Interlink Converter for Robust Control of a Hybrid AC–DC Microgrid." IEEE Transactions on Power Electronics 34, no. 11: 11332-11341.

Journal article
Published: 16 December 2018 in Energies
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Multiple battery energy storage systems (BESSs) are used to compensate for the fluctuation in wind generations effectively. The stage of charge (SOC) of BESSs might be unbalanced due to the difference of wind speed, initial SOCs, line impedances and capabilities of BESSs, which have a negative impact on the operation of the wind farm. This paper proposes a distributed control of the wind energy conversion system (WECS) based on dynamic average consensus algorithm to balance the SOC of the BESSs in a wind farm. There are three controllers in the WECS with integrated BESS, including a machine-side controller (MSC), the grid-side controller (GSC) and battery-side controller (BSC). The MSC regulates the generator speed to capture maximum wind power. Since the BSC maintains the DC link voltage of the back-to-back (BTB) converter that is used in the WECS, an improved virtual synchronous generator (VSG) based on consensus algorithm is used for the GSC to control the output power of the WECS. The functionalities of the improved VSG are designed to compensate for the wind power fluctuation and imbalance of SOC among BESSs. The average value of SOCs obtained by the dynamic consensus algorithm is used to adjust the wind power output for balancing the SOC of batteries. With the proposed controller, the fluctuation in the output power of wind generation is reduced, and the SOCs of BESSs are maintained equally. The effectiveness of the proposed control strategy is validated through the simulation by using a MATLAB/Simulink environment.

ACS Style

Cao-Khang Nguyen; Thai-Thanh Nguyen; Hyeong-Jun Yoo; Hak-Man Kim. Consensus-Based SOC Balancing of Battery Energy Storage Systems in Wind Farm. Energies 2018, 11, 3507 .

AMA Style

Cao-Khang Nguyen, Thai-Thanh Nguyen, Hyeong-Jun Yoo, Hak-Man Kim. Consensus-Based SOC Balancing of Battery Energy Storage Systems in Wind Farm. Energies. 2018; 11 (12):3507.

Chicago/Turabian Style

Cao-Khang Nguyen; Thai-Thanh Nguyen; Hyeong-Jun Yoo; Hak-Man Kim. 2018. "Consensus-Based SOC Balancing of Battery Energy Storage Systems in Wind Farm." Energies 11, no. 12: 3507.

Journal article
Published: 23 October 2018 in Energies
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Since the penetration of distributed energy resources (DERs) and energy storage systems (ESSs) into the microgrid (MG) system has increased significantly, the sudden disconnection of DERs and ESSs might affect the stability and reliability of the whole MG system. The low-voltage ride-through (LVRT) capability to maintain stable operation of the MG system should be considered. The main contribution of this study is to propose a distributed control, based on a dynamic consensus algorithm for LVRT operation of the MG system. The proposed control method is based on a hierarchical control that consists of primary and secondary layers. The primary layer is in charge of power regulation, while the secondary layer is responsible for the LVRT operation of the MG system. The droop controller is used in the primary layer to maintain power sharing among parallel-distributed generators in the MG system. The dynamic consensus algorithm is used in the secondary layer to control the accurate reactive power sharing and voltage restoration for LVRT operation. A comparison study on the proposed control method and centralized control method is presented in this study to show the effectiveness of the proposed controller. Different scenarios of communication failures are carried out to show the reliability of the proposed control method. The tested MG system and proposed controller are modeled in a MATLAB/Simulink environment to show the feasibility of the proposed control method.

ACS Style

Woon-Gyu Lee; Thai-Thanh Nguyen; Hyeong-Jun Yoo; Hak-Man Kim. Low-Voltage Ride-Through Operation of Grid-Connected Microgrid Using Consensus-Based Distributed Control. Energies 2018, 11, 2867 .

AMA Style

Woon-Gyu Lee, Thai-Thanh Nguyen, Hyeong-Jun Yoo, Hak-Man Kim. Low-Voltage Ride-Through Operation of Grid-Connected Microgrid Using Consensus-Based Distributed Control. Energies. 2018; 11 (11):2867.

Chicago/Turabian Style

Woon-Gyu Lee; Thai-Thanh Nguyen; Hyeong-Jun Yoo; Hak-Man Kim. 2018. "Low-Voltage Ride-Through Operation of Grid-Connected Microgrid Using Consensus-Based Distributed Control." Energies 11, no. 11: 2867.

Conference paper
Published: 01 October 2018 in TENCON 2018 - 2018 IEEE Region 10 Conference
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The circulating current among the parallel inverter-based distributed generations (DGs) in the microgrid (MG) system causes several negative impacts on the operation of inverters. The suppression of circulating current should be considered in the controller design of the inverter, especially in the case of using finite control set model predictive control (FCS-MPC) in which the switching frequency of the inverter is varied. This paper proposed an MPC with constant switching frequency for the inverter in the MG system. The proposed MPC is based on the use of virtual state vectors in addition to the real state vectors of the inverter. The discrete time model of inverter is used to find the optimal state vector of inverter including virtual states. The modulation voltage is calculated accordingly. The pulse width modulation is used to obtain the constant switching frequency of inverter. The MG system with three inverter-based DGs are used to show the impact of the proposed controller on the circulating current suppression. The effect of different number of virtual state vectors is presented in this study. The feasibility of the proposed controller is validated by the real time simulation using OP5600 of OPAL technologies.

ACS Style

Thai-Thanh Nguyen; Hyeong-Jun Yoo; Hak-Man Kim. Model Predictive Control of Inverters in Microgrid with Constant Switching Frequency for Circulating Current Suppression. TENCON 2018 - 2018 IEEE Region 10 Conference 2018, 1566 -1571.

AMA Style

Thai-Thanh Nguyen, Hyeong-Jun Yoo, Hak-Man Kim. Model Predictive Control of Inverters in Microgrid with Constant Switching Frequency for Circulating Current Suppression. TENCON 2018 - 2018 IEEE Region 10 Conference. 2018; ():1566-1571.

Chicago/Turabian Style

Thai-Thanh Nguyen; Hyeong-Jun Yoo; Hak-Man Kim. 2018. "Model Predictive Control of Inverters in Microgrid with Constant Switching Frequency for Circulating Current Suppression." TENCON 2018 - 2018 IEEE Region 10 Conference , no. : 1566-1571.

Journal article
Published: 27 August 2018 in Energies
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Several control strategies of the finite control set model predictive controls (FCS-MPC) have been proposed for power converters, such as predictive current control (PCC), direct predictive power control (DPPC), and predictive voltage control (PVC). However, for microgrid (MG) applications, the control strategy of the FCS-MPC for a power converter might be changed according to the operation mode of the MG system, which results in a transient response in the system voltage or current during the mode transition. This study proposes a new control strategy of FCS-MPC for use in both islanded and grid-connected operation modes of an MG system. Considering the characteristic of a synchronous generator, a direct phase angle and voltage amplitude model predictive control (PAC) of a power converter is proposed in this study for MG applications. In the islanded mode, the system frequency is directly controlled through the phase angle of the output voltage. In the grid-connected mode, a proportional-integral (PI) regulator is used to compensate for the phase angle and voltage amplitude of the power converter for constant power control. The phase angle of the system voltage can be easily adjusted for the synchronization process of an MG system. A comparison study on the proposed PAC method and existing predictive methods is carried out to show the effectiveness of the proposed method. The feasibility of the proposed PAC strategy is evaluated in a simulation-based system by using the MATLAB/Simulink environment.

ACS Style

Thai-Thanh Nguyen; Hyeong-Jun Yoo; Hak-Man Kim; Huy Nguyen-Duc. Direct Phase Angle and Voltage Amplitude Model Predictive Control of a Power Converter for Microgrid Applications. Energies 2018, 11, 2254 .

AMA Style

Thai-Thanh Nguyen, Hyeong-Jun Yoo, Hak-Man Kim, Huy Nguyen-Duc. Direct Phase Angle and Voltage Amplitude Model Predictive Control of a Power Converter for Microgrid Applications. Energies. 2018; 11 (9):2254.

Chicago/Turabian Style

Thai-Thanh Nguyen; Hyeong-Jun Yoo; Hak-Man Kim; Huy Nguyen-Duc. 2018. "Direct Phase Angle and Voltage Amplitude Model Predictive Control of a Power Converter for Microgrid Applications." Energies 11, no. 9: 2254.

Journal article
Published: 23 December 2017 in Energies
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Multiple power converters based on the droop controllers have been used widely in the microgrid (MG) system. However, owing to the different response time among several types of power converters such as grid-feeding and grid-forming converters, low frequency oscillation occurs with high overshoot in the transient state. This paper proposes a novel control strategy based on the virtual synchronous generator (VSG) for improving transient response of parallel power converters during large disturbance in the stand-alone microgrid. The proposed VSG control, which inherits the transient state characteristic of the synchronous generator, can provide inertia virtually to the system. The transient response of voltage and frequency is improved, while the total system inertia response is compensated. Thus, the system stability can be enhanced by using the proposed VSG control. Additionally, the small signal analysis of the conventional VSG controller and the proposed VSG controller are carried out to show the effectiveness of the proposed VSG controller. The derivation of frequency, which is used to evaluate the inertia support of the VSG controller to the MG system, is discussed. The simulation result demonstrates that the overshoot of the transient response can be reduced, and the system stability is improved when the proposed VSG controller is applied. The MG system based on the real-time simulator OP5600 (OPAL-RT Technologies, Montreal, QC, Canada) is carried out to verify the feasibility of the proposed VSG controller.

ACS Style

Cao-Khang Nguyen; Thai-Thanh Nguyen; Hyeong-Jun Yoo; Hak-Man Kim. Improving Transient Response of Power Converter in a Stand-Alone Microgrid Using Virtual Synchronous Generator. Energies 2017, 11, 27 .

AMA Style

Cao-Khang Nguyen, Thai-Thanh Nguyen, Hyeong-Jun Yoo, Hak-Man Kim. Improving Transient Response of Power Converter in a Stand-Alone Microgrid Using Virtual Synchronous Generator. Energies. 2017; 11 (1):27.

Chicago/Turabian Style

Cao-Khang Nguyen; Thai-Thanh Nguyen; Hyeong-Jun Yoo; Hak-Man Kim. 2017. "Improving Transient Response of Power Converter in a Stand-Alone Microgrid Using Virtual Synchronous Generator." Energies 11, no. 1: 27.

Journal article
Published: 23 October 2017 in Energies
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The use of high voltage direct current (HVDC) circuit breakers (CBs) with the capabilities of bidirectional fault interruption, reclosing, and rebreaking can improve the reliable and safe operation of HVDC grids. Although several topologies of CBs have been proposed to perform these capabilities, the limitation of these topologies is either high on-state losses or long time interruption in the case bidirectional fault current interruption. Long time interruption results in the large magnitude of the fault current in the voltage source converter based HVDC (VSC-HVDC) system due to the high rate of rise of fault current. This paper proposes a new topology of hybrid CB (HCB) with lower conduction loss and lower interruption time to solve the problems. The proposed topology is based on the inverse current injection method, which uses the capacitor to enforce the fault current to zero. In the case of the bidirectional fault current interruption, the capacitor does not change its polarity after identifying the direction of fault current, which can reduce the interruption time accordingly. A switching control algorithm for the proposed topology is presented in detail. Different operation modes of proposed HCB, such as normal current mode, breaking fault current mode, discharging, and reversing capacitor voltage modes after clearing the fault, are considered in the proposed algorithm. The proposed topology with the switching control algorithm is tested in a simulation-based system. Different simulation scenarios such as temporary and permanent faults are carried out to verify the performance of the proposed topology. The simulation is performed in the Matlab/Simulink environment.

ACS Style

Van-Vinh Nguyen; Ho-Ik Son; Thai-Thanh Nguyen; Hak-Man Kim; Chan-Ki Kim. A Novel Topology of Hybrid HVDC Circuit Breaker for VSC-HVDC Application. Energies 2017, 10, 1675 .

AMA Style

Van-Vinh Nguyen, Ho-Ik Son, Thai-Thanh Nguyen, Hak-Man Kim, Chan-Ki Kim. A Novel Topology of Hybrid HVDC Circuit Breaker for VSC-HVDC Application. Energies. 2017; 10 (10):1675.

Chicago/Turabian Style

Van-Vinh Nguyen; Ho-Ik Son; Thai-Thanh Nguyen; Hak-Man Kim; Chan-Ki Kim. 2017. "A Novel Topology of Hybrid HVDC Circuit Breaker for VSC-HVDC Application." Energies 10, no. 10: 1675.