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Duy-Long Nguyen,Hong-Hee Lee 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.1
Accurate power sharing in a DC microgrid with a conventional distributed control scheme is impossible to achieve due to the heterogeneity of communication time delays. To address this problem, an anti-heterogeneous time delay estimator is proposed on the basis of scattering transformation and a PI consensus algorithm, and proper power allocation is achieved along with voltage compensation in a distributed fashion. In the proposed estimator, transmitted/received signals are modified via scattering transformation, and average consensus is estimated by the PI consensus algorithm. Consequently, proportional power sharing and voltage compensation are achieved concomitantly despite heterogeneous temporal delays, mismatched line resistances, and load variation. The effectiveness of the proposed method is evaluated through experiments.
TA DUY LONG,홍서기,육대식 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.12
This paper introduces a new point depletion-based source term calculation code named BESNA (Bateman Equation Solver for Nuclear Applications), which is aimed to estimate nuclide inventories and source terms from spent nuclear fuels. The BESNA code employs a new modified CE/CM (Constant Extrapolation e Constant Midpoint) predictor-corrector scheme in depletion calculations for improving computational efficiency. In this modified CE/CM scheme, the decay components leading to the large norm of the depletion matrix are excluded in the corrector, and hence the corrector calculation involves only the reaction components, which can be efficiently solved with the Talyor Expansion Method (TEM). The numerical test shows that the new scheme substantially reduces computing time without loss of accuracy in comparison with the conventional scheme using CRAM (Chebyshev Rational Approximation Method), especially when the substep calculations are applied. The depletion calculation and source term estimation capability of BESNA are verified and validated through several problems, where results from BESNA are compared with those calculated by other codes as well as measured data. The analysis results show the computational efficiency of the new modified scheme and the reliability of BESNA in both isotopic predictions and source term estimations.
Ta, Duy Long,Hong, Ser Gi,Lee, Deokjung Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.1
This paper presents the validation of the MCS code for critical safety analysis with burnup credit for the spent fuel casks. The validation process in this work considers five critical benchmark problem sets, which consist of total 80 critical experiments having MOX fuels from the International Criticality Safety Benchmark Evaluation Project (ICSBEP). The similarity analysis with the use of sensitivity and uncertainty tool TSUNAMI in SCALE was used to determine the applicable benchmark experiments corresponding to each spent fuel cask model and then the Upper Safety Limits (USLs) except for the isotopic validation were evaluated following the guidance from NUREG/CR-6698. The validation process in this work was also performed with the MCNP6 for comparison with the results using MCS calculations. The results of this work showed the consistence between MCS and MCNP6 for the MOX fueled criticality benchmarks, thus proving the reliability of the MCS calculations.
Person location estimation using an inertial sensor unit and wireless modules
Tran Duy Long,Young Soo Suh 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10
This paper is a preliminary report of location estimation combining an inertial navigation algorithm and wireless modules. Using triangulation, location can be estimated using received signal strength of wireless packets from wireless modules whose position is known. This location estimation is rather sensitive to various factors. On the other hand, an inertial navigation algorithm can provide accurate relative position estimation for a short time. Combination of these two methods is formulated as a quadratically constrained quadratic problem. Through simulation and a simple experiment, the proposed method is verified.
Cooperative control strategy for voltage restoration and power allocation in DC microgrids
Nguyen, Duy-Long,Lee, Hong-Hee The Korean Institute of Power Electronics 2020 JOURNAL OF POWER ELECTRONICS Vol.20 No.4
This paper proposes a novel cooperative control strategy for voltage restoration and power management in DC microgrids based on the DC bus signaling (DBS) method. In the conventional DBS method, the operation mode is determined according to the voltage deviation. Thus, it is difficult to achieve voltage restoration. To overcome this problem, the conventional DBS method is modified by applying the total power of dispatchable units (DUs) to identify the operation mode instead of the voltage deviation. As a result, the average output voltage of the DUs is restored to its nominal value in all of the operation modes without difficulty. In addition, accurate power sharing is achieved regardless of the line impedance or load change by regulating the voltage magnitude using a simple PI controller. Furthermore, the control performance is theoretically analyzed using a small signal analysis to evaluate the stability of system. The proposed method is validated with results from a lab scale experiment.
Distributed Interference Management in Two-Tier CDMA Femtocell Networks
Duy Trong Ngo,Long Bao Le,Le-Ngoc, T.,Hossain, E.,Dong In Kim IEEE 2012 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.11 No.3
<P>This paper proposes distributed joint power and admission control algorithms for the management of interference in two-tier femtocell networks, where the newly-deployed femtocell users (FUEs) share the same frequency band with the existing macrocell users (MUEs) using code-division multiple access (CDMA). As the owner of the licensed radio spectrum, the MUEs possess strictly higher access priority over the FUEs; thus, their quality-of-service (QoS) performance, expressed in terms of the prescribed minimum signal-to-interference-plus-noise ratio (SINR), must be maintained at all times. For the lower-tier FUEs, we explicitly consider two different design objectives, namely, throughput-power tradeoff optimization and soft QoS provisioning. With an effective dynamic pricing scheme combined with admission control to indirectly manage the cross-tier interference, the proposed schemes lend themselves to distributed algorithms that mainly require local information to offer maximized net utility of individual users. The approach employed in this work is particularly attractive, especially in view of practical implementation under the limited backhaul network capacity available for femtocells. It is shown that the proposed algorithms robustly support all the prioritized MUEs with guaranteed QoS requirements whenever feasible, while allowing the FUEs to optimally exploit the remaining network capacity. The convergence of the developed solutions is rigorously analyzed, and extensive numerical results are presented to illustrate their potential advantages.</P>
Application of ANFIS to the design of elliptical CFST columns
Ngoc-Long Tran,Trong-Cuong Vo,Duy-Duan Nguyen,Van-Quang Nguyen,Huy-Khanh Dang,Viet-Linh Tran Techno-Press 2023 Advances in computational design Vol.8 No.2
Elliptical concrete-filled steel tubular (CFST) column is widely used in modern structures for both aesthetical appeal and structural performance benefits. The ultimate axial load is a critical factor for designing the elliptical CFST short columns. However, there are complications of geometric and material interactions, which make a difficulty in determining a simple model for predicting the ultimate axial load of elliptical CFST short columns. This study aims to propose an efficient adaptive neuro-fuzzy inference system (ANFIS) model for predicting the ultimate axial load of elliptical CFST short columns. In the proposed method, the ANFIS model is used to establish a relationship between the ultimate axial load and geometric and material properties of elliptical CFST short columns. Accordingly, a total of 188 experimental and simulation datasets of elliptical CFST short columns are used to develop the ANFIS models. The performance of the proposed ANFIS model is compared with that of existing design formulas. The results show that the proposed ANFIS model is more accurate than existing empirical and theoretical formulas. Finally, an explicit formula and a Graphical User Interface (GUI) tool are developed to apply the proposed ANFIS model for practical use.