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LVRT and Power Smoothening of DFIG-based Wind Turbine Systems using Energy Storage Devices
Thanh Hai Nguyen,Dong-Choon Lee 제어로봇시스템학회 2010 제어로봇시스템학회 국제학술대회 논문집 Vol.2010 No.10
This paper proposes a ride-through technique of doubly-fed induction generator (DFIG) wind turbine systems. The control technique uses energy storage devices (ESD) which are controlled with current and power control loops. During grid faults, the generator output power can be reduced by increasing the generator speed, resulting in increased inertial energy of the rotational body. Also, the output power fluctuation of the generator due to wind speed variation is smoothened by controlling the ESD appropriately. The PSCAD/EMTDC simulation results have proved the effectiveness of the proposed algorithm.
Ride-through of DFIG Wind Turbine Systems Using Energy Storage Unit
Thanh Hai Nguyen(뉴옌탄하이),Dong-Choon Lee(이동춘) 전력전자학회 2010 전력전자학술대회 논문집 Vol.2010 No.7
This paper deals with a ride-through technique of doubly-fed induction generator (DFIG) wind turbine systems using energy storage unit (ESU). By increasing the machine speed, some portion of the turbine power can be stored in the system inertia during grid faults. Also keeping the operation of rotor-side converter (RSC) and grid-side converter (GSC), the rotor current and DC-link voltage can be limited. The effectiveness of the proposed method is verified by simulation results for 2[MW] DFIG wind turbine system.
Low Voltage Ride-Through of DFIG Wind Turbine Systems Using Crowbar
Thanh Hai Nguyen,Kyung-Hyun Kim,Dong-Choon Lee 전력전자학회 2009 전력전자학술대회 논문집 Vol.2009 No.1
This paper deals with the operation of doubly-fed induction generator(DFIG) for wind turbine systems under the grid fault conditions using crowbar. The crowbar protection is able to prevent the high fault rotor currents which flow into the rotor-side converter and a fast DC voltage increasing. Only one crowbar resistor through diode rectifier connected to the rotor side of DFIG is considered. The paper provides a design for selecting the crowbar resistance, and describes the control strategy for crowbar when the grid fault occurs and is cleared. Simulation results are shown for a 2MW DFIG system using PSCAD.
A D2D communication architecture under full control using SDN
( Thanh-hai Ngo ),( Younghan Kim ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.8
Device-to-device (D2D) communication is a potential solution to the incessant increase in data traffic on cellular networks. The greatest problem is how to control the interference between D2D users and cellular mobile users, and between D2D users themselves. This paper proposes a solution for this issue by putting the full control privilege in cellular network using the software-defined networking (SDN) concept. A software virtual switch called Open vSwitch and several components are integrated into mobile devices for data forwarding and radio resource mapping, whereas the control functions are executed in the cellular network via a SDN controller. This allows the network to assign radio resources for D2D communication directly, thus reducing interference. This solution also brings out many benefits, including resource efficiency, energy saving, topology flexibility, etc. The advantages and disadvantages of this architecture are analyzed by both a mathematical method and a simple implementation. The result shows that implementation of this solution in the next generation of cellular networks is feasible.
Power Smoothening Control of Wind Farms Based on Inertial Effect of Wind Turbine Systems
Thanh Hai Nguyen,Dong-Choon Lee,Jong-Ho Kang 대한전기학회 2014 Journal of Electrical Engineering & Technology Vol.9 No.3
This paper proposes a novel strategy for attenuating the output power fluctuation of the wind farm (WF) in a range of tens of seconds delivered to the grid, where the kinetic energy caused by the large inertia of the wind turbine systems is utilized. A control scheme of the two-level structure is applied to control the wind farm, which consists of a supervisory control of the wind farm and individual wind turbine controls. The supervisory control generates the output power reference of the wind farm, which is filtered out from the available power extracted from the wind by a low-pass filter (LPF). A lead-lag compensator is used for compensating for the phase delay of the output power reference compared with the available power. By this control strategy, when the reference power is lower than the maximum available power, some of individual wind turbines are operated in the storing mode of the kinetic energy by increasing the turbine speeds. Then, these individual wind turbines release the kinetic power by reducing the turbine speed, when the power command is higher than the available power. In addition, the pitch angle control systems of the wind turbines are also employed to limit the turbine speed not higher than the limitation value during the storing mode of kinetic energy. For coordinating the de-rated operation of the WT and the storing or releasing modes of the kinetic energy, the output power fluctuations are reduced by about 20%. The PSCAD/EMTDC simulations have been carried out for a 10-MW wind farm equipped with the permanent-magnet synchronous generator (PMSG) to verify the validity of the proposed method.
A Novel Submodule Topology of MMC for Blocking DC-Fault Currents in HVDC Transmission Systems
Thanh Hai Nguyen,Dong-Choon Lee 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
This paper proposes a novel topology of submodule (SM) for the modular multilevel converters (MMC) applying to the high-voltage DC (HVDC) transmission systems, where the DC-fault current due to the freewheeling effect of the diode rectifier is blocked during a short-circuit fault in the DC cables. An additional insulated-gate bipolar translator (IGBT) with a low voltage rating is required to be connected in series at the output terminal of a conventional half-bridge SM, where the anti-parallel diode of the additional IGBT is used to block the current from the grid to the DC-link side. Moreover, the additional switching loss of the embedded switch is negligible since the switch is turned on all the time. Therefore, compared with the MMC based on the full-bridge (FB) SM or the hybrid topology of half-bridge (HB) and FBSM, the proposed topology not only provides the DC-fault current blocking capability but also has a lower cost and power loss. The validity of the proposed scheme is verified by the simulation results of 300- MW HVDC transmission system.
Hai Thanh Nguyen,Cham Ngoc Thi Nguyen,Thao Minh Nguyen Phan,Tinh Cong Dao 대한전자공학회 2021 IEIE Transactions on Smart Processing & Computing Vol.10 No.2
The application of Artificial Intelligence (AI) in medicine has been a leading concern worldwide. Artificial intelligence-based systems not only support storing a large amount of data but also assist doctors in making a diagnosis. In addition, deep learning has obtained numerous achievements that greatly supported the development of image-based diagnostic methods. On the other hand, deep learning models still work as a black box that makes interpreting the output a challenge. Diagnosis based on images is currently a trend that plays a key role in clinical treatment by discovering abnormal regions for disease diagnosis. This paper proposes a computer-aid diagnosis system to support a pleural effusion diagnosis based on Chest X-ray (CXR) images. This study investigated several shallow convolutional neural network architectures that classify CXR images as well as the technique for processing imbalanced data using oversampling technology. The best model in the experiments was chosen to generate explanations using the Local Interpretable Model-agnostic Explanations (LIME) to support providing signals for pleural effusion diagnosis. The proposed method is expected to provide more informative CXR images of the pleural effusion diagnosis process.
Thanh Hai Nguyen,Dong-Choon Lee 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
This paper proposes a new control scheme of a vector-controlled induction machine (IM) drives in overmodulation range to maximize the voltage utilization of the voltage-source inverter. For an operation in overmodulation region, a modified voltage reference is generated for the space-vector pulsewidth modulation (SVPWM). The harmonic current components in the feedback currents needs to be eliminated before feeding to the PI current controllers to improve the control performance. The response of PI current controllers in overmodulation range has been analyzed. A composite observer is applied to estimate the harmonic components of the currents, which is good performance without delay compared with the measured currents. The proposed method has been verified by simulation results.