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- 저자 : ( Zhixiang Deng ) (검색결과 4 건)
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Low Frequency Current Ripple Mitigation of Two Stage Three-Phase PEMFC Generation Systems
Deng, Huiwen,Li, Qi,Liu, Zhixiang,Li, Lun,Chen, Weirong The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6
This paper presents a two stage three-phase proton exchange membrane fuel cell (PEMFC) generation system. When the system is connected to a three-phase load, it is very sensitive to the characteristics and type of the load. Especially unbalanced three-phase loads, which result in a pulsating power that is twice the output frequency at the inverter output, and cause the dc-link to generate low frequency ripples. This penetrates to the fuel cell side through the front-end dc-dc converter, which makes the fuel cell work in an unsafe condition and degrades its lifespan. In this paper, the generation and propagation mechanism of low frequency ripple is analyzed and its impact on fuel cells is presented based on the PEMFC output characteristics model. Then a novel method to evaluate low frequency current ripple control capability is investigated. Moreover, a control scheme with bandpass filter inserted into the current feed-forward path, and ripple duty ratio compensation based on current mode control with notch filter is also proposed to achieve low frequency ripple suppression and dynamic characteristics improvement during load transients. Finally, different control methods are verified and compared by simulation and experimental results.
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Low Frequency Current Ripple Mitigation of Two Stage Three-Phase PEMFC Generation Systems
Huiwen Deng,Qi Li,Zhixiang Liu,Lun Li,Weirong Chen 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6
This paper presents a two stage three-phase proton exchange membrane fuel cell (PEMFC) generation system. When the system is connected to a three-phase load, it is very sensitive to the characteristics and type of the load. Especially unbalanced three-phase loads, which result in a pulsating power that is twice the output frequency at the inverter output, and cause the dc-link to generate low frequency ripples. This penetrates to the fuel cell side through the front-end dc-dc converter, which makes the fuel cell work in an unsafe condition and degrades its lifespan. In this paper, the generation and propagation mechanism of low frequency ripple is analyzed and its impact on fuel cells is presented based on the PEMFC output characteristics model. Then a novel method to evaluate low frequency current ripple control capability is investigated. Moreover, a control scheme with bandpass filter inserted into the current feed-forward path, and ripple duty ratio compensation based on current mode control with notch filter is also proposed to achieve low frequency ripple suppression and dynamic characteristics improvement during load transients. Finally, different control methods are verified and compared by simulation and experimental results.
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Gao, Yuan,Deng, Zhixiang,Choi, Dongmin,Choi, Chang Elsevier 2018 Journal of parallel and distributed computing Vol.114 No.-
<P><B>Abstract</B></P> <P>In this paper, we propose a cooperative spectrum sensing scheme including a combined pre-detection and sleeping policy. In the scheme, the designed pre-detection sub-phase is applied at the beginning of the detection of the presence of a primary user, where all sensing nodes are involved to improve the detection performance. The sleeping policy is applied for each sensing node respectively at the end of the pre-detection sub-phase and the beginning of the transmission of the local detection results, in order to decrease sensing energy consumption. We formulate the problem of minimizing the maximum average energy consumption per sensing node in Rayleigh fading channels, considering the constraints of the required global detection and false alarm probabilities and the tolerable interference caused to the primary user. Numerical results show that the scheme achieves significant energy saving as compared to a scheme that includes only a sleeping policy and does not consider pre-detection.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We propose a combined pre-detection and sleeping scheme for spectrum sensing. </LI> <LI> The sensing performance is not affected by a high sleeping rate of secondary relays. </LI> <LI> An analytical framework is based on more practical channel conditions. </LI> <LI> A search algorithm is studied to obtain low complexity for solving the optimal problem. </LI> <LI> The proposed scheme achieves significant energy saving for spectrum sensing. </LI> </UL> </P>
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Adaptive Cooperation for Bidirectional Communication in Cognitive Radio Networks
( Yuan Gao ),( Changping Zhu ),( Zhixiang Deng ),( Yibin Tang ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.3
In the interweave cognitive networks, the interference from the primary user degrades the performance of the cognitive user transmissions. In this paper, we propose an adaptive cooperation scheme in the interweave cognitive networks to improve the performance of the cognitive user transmissions. In the proposed scheme for the bidirectional communication of two end-source cognitive users, the bidirectional communication is completed through the non-relay direct transmission, the one-way relaying cooperation transmission, and the two-way relaying cooperation transmission depending on the limited feedback from the end-sources. For the performance analysis of the proposed scheme, we derive the outage probability and the finite-SNR diversity multiplexing tradeoff (f-DMT) in a closed form, considering the imperfect spectrum sensing, the interference from the primary user, and the power allocation between the relay and the end-sources. The results show that compared with the direct transmissions (DT), the pure one-way relaying transmissions (POWRT), and the pure two-way relaying transmissions (PTWRT), the proposed scheme has better outage performance. In terms of the f-DMT, the proposed scheme outperforms the full cooperation transmissions of the POWRT and PTWRT.
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