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Tong L.,Huazhong University of Science and Technology | Zou X.,Huazhong University of Science and Technology | Zhang Y.,Hunan Electric Power Test and Research Institute | Kang Y.,Huazhong University of Science and Technology
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2011

Conventional adaptive current detection methods are always terribly disturbed by the "mutual erroneous impacts", which are due to the low SNR (signal-to-noise ratio) utility conditions, so it is difficult to make an optimal tradeoff between the speed and accuracy of those adaptive methods. This paper proposes a novel adaptive current detection method, where a sliding integration filter (SIF) is applied to eliminate the disturbances from harmonic current components and to derive the real amplitude estimation errors of fundamental active and reactive current components. Then, adaptive detection closed-loop systems are constructed based on the internal model theory so as to extract the target current components from the distorted load current rapidly and accurately. The mathematical model of the proposed adaptive method is presented, and its performances such as convergence, dynamic and steady-state responses are also illustrated by analytic methods of control theory so that theoretical instructions could be provided for designing the adaptive current detection method. Finally, simulation and experimental results of this novel detection method and previous methods are compared, which verify the correctness and effectiveness of the proposed theory and method. Source

Xu Z.,Hunan Electric Power Test and Research Institute | Zhai M.,North China Electrical Power University | Lu J.,North China Electrical Power University
IEEE Transactions on Power Delivery | Year: 2011

This paper considers the cross-layer optimization for orthogonal frequency-division multiple access-based power-line communication systems. The user scheduling in the data-link control layer selects the serving users and ascertains their optimal cross-layer parameters according to each user's quality-of-service (QoS) requirements, QoS satisfaction degree, packet traffic model, channel and queue status information, and rate of transmitted data. The resource allocation in the physical layer assigns subcarrier and power for the scheduling users according to their QoS requirements, correlative cross-layer parameters, and channel status information. Since the multiuser's subcarrier-power allocation is a layered multiobjective mixed-integer nonlinear problem with many practical restrictions, it is first transformed into the multiple simple single-objective problems by using the resource factor. After obtaining each Pareto solution of the used resources based on the resource factor for satisfying the minimal rate of each user, the remaining resources are assigned to the users with a maximal rate without considering the resource factor by using the bit-loading lookup table algorithm. Finally, the optimal solution is selected from the results of resource allocation according to the order of the partial information. Based on the typical power-line channel scenarios, the simulation results illustrate that the proposed algorithm outperforms the existing multiuser algorithms in terms of the multiple aims of resource allocation. © 2011 IEEE. Source

Long H.-G.,Hunan Electric Power Test and Research Institute
Dongli Gongcheng Xuebao/Journal of Chinese Society of Power Engineering | Year: 2010

Taking austenitic stainless steel tubes TP304H and TP347H as an example, detection tests were carried out to oxidation scales on inner surface of the tube bends using residual magnetic and lifting power method. Results show that after excitation of external magnetic field, both the density and lifting power of the scales' residual magnetism will rise with growing accumulation of scales, and once the accumulation gets to a certain amount, the variation tendency will slow down. The density and lifting power are also affected by tube size, i. e. the thicker the tube wall, or the larger the inner diameter of tube, the less they will be. For different shapes of tube bends, oxidation scales inside V type bends have the strongest magnetism and. lifting power, followed by U type, then L type. The residual magnetic and lifting power method can be taken to quickly detect the accumulation amount of oxidation scales on inner surface of austenitic stainless steel tube bends. Source

Tong L.,Huazhong University of Science and Technology | Zou X.,Huazhong University of Science and Technology | Zhang Y.,Hunan Electric Power Test and Research Institute | Kang Y.,Huazhong University of Science and Technology
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2011

With a general analysis on instantaneous power balance relationship for a single-phase unified power quality conditioner (UPQC), this paper proposed a dual current sources coordinated control strategy based on the adaptive filter current detection for UPQC. Considering that the current detection accuracy has great influences on the compensation performances of the proposed control strategy, a fixed frequency filter algorithm for improving the detection accuracy was then proposed on premise of preserving the rapidity of traditional variable-step adaptive algorithm. In view of the controller design for the UPQC in dual current sources mode, a compound controller incorporating P controller and Repetitive controller was adopted to implement the current tracking control for the series and parallel active power filters, and a small signal model of DC link voltage closed-loop control system on the whole UPQC was presented to provide theoretical indications for designing DC voltage loop controller parameters. The research results show that the UPQC based on the above-mentioned control strategy and controller design methods realizes favorable load voltage and source current compensation performances. © 2011 Chinese Society for Electrical Engineering. Source

Fang Q.,Huazhong University of Science and Technology | Wang H.,Huazhong University of Science and Technology | Wei Y.,Huazhong University of Science and Technology | Lei L.,Hunan Electric Power Test and Research Institute | And 2 more authors.
Fuel Processing Technology | Year: 2010

Numerical studies of the slagging characteristics under different operational conditions in a 300 MW down-fired boiler were carried out using slagging models coupled with gas-solid two phase flow and combustion models. Combined with the real operating conditions; comparative and detailed analysis on the slagging position, extent, and causes is presented. The results show that the serious slagging is mainly on the side walls of the lower furnace. Because of the more rapid expansion of the flue gas under the higher temperature, the flue gas in the furnace center makes the flue gas on both sides deflect and flow to the side walls; and the pulverized-coal flame impinges on the side walls. This results in the slagging on the side walls. Under off-design operating conditions, such as stopping some burners, the local flow field is asymmetric and impinges on the local arch burner, front and rear wall regions where the stopped burners are located. It leads to slight slagging on the arch burner regions and the front and rear wall regions of the lower furnace. Based on the investigation, it has been found that the serious slagging on the side walls can be effectively alleviated by cutting off the burners close to the side walls, reducing boiler load and burning low slagging-tendency coals. © 2009 Elsevier B.V. All rights reserved. Source

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