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RISS 인기검색어
- 검색키워드
- 저자 : Yunlu Li (검색결과 4 건)
- 무료
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A Hybrid Filtering Stage Based Quasi-type-1 PLL under Distorted Grid Conditions
Li, Yunlu,Wang, Dazhi,Han, Wei,Sun, Zhenao,Yuan, Tianqing The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3
For three-phase synchronization applications, the synchronous reference frame phase-locked loop (SRF-PLL) is probably the most widely used technique due to its ease of implementation and satisfactory phase tracking performance under ideal grid conditions. However, under unbalanced and distorted grid conditions, its performance tends to worsen. To deal with this problem, a variety of filtering stages have been proposed and used in SRF-PLLs for the rejection of disturbance components at the cost of degrading the dynamic performance. In this paper, to improve dynamic performance without compromising the filtering capability, an effective hybrid filtering stage is proposed and incorporated into the inner loop of a quasi-type-1 PLL (QT1-PLL). The proposed filtering stage is a combination of a moving average filter (MAF) and a modified delay signal cancellation (DSC) operator in cascade. The time delay caused by the proposed filtering stage is smaller than that in the conventional MAF-based and DSC-based PLLs. A small-signal model of the proposed PLL is derived. The stability is analyzed and parameters design guidelines are given. The effectiveness of the proposed PLL is confirmed through experimental results.
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A Hybrid Filtering Stage Based Quasi-type-1 PLL under Distorted Grid Conditions
Yunlu Li,Dazhi Wang,Wei Han,Zhenao Sun,Tianqing Yuan 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3
For three-phase synchronization applications, the synchronous reference frame phase-locked loop (SRF-PLL) is probably the most widely used technique due to its ease of implementation and satisfactory phase tracking performance under ideal grid conditions. However, under unbalanced and distorted grid conditions, its performance tends to worsen. To deal with this problem, a variety of filtering stages have been proposed and used in SRF-PLLs for the rejection of disturbance components at the cost of degrading the dynamic performance. In this paper, to improve dynamic performance without compromising the filtering capability, an effective hybrid filtering stage is proposed and incorporated into the inner loop of a quasi-type-1 PLL (QT1-PLL). The proposed filtering stage is a combination of a moving average filter (MAF) and a modified delay signal cancellation (DSC) operator in cascade. The time delay caused by the proposed filtering stage is smaller than that in the conventional MAF-based and DSC-based PLLs. A small-signal model of the proposed PLL is derived. The stability is analyzed and parameters design guidelines are given. The effectiveness of the proposed PLL is confirmed through experimental results.
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Yunlu Jiang,Hong Li 한국통계학회 2014 Journal of the Korean Statistical Society Vol.43 No.4
In this paper, a penalized weighted composite quantile regression estimation procedureis proposed to estimate unknown regression parameters and autoregression coefficientsin the linear regression model with heavy-tailed autoregressive errors. Under some conditions,we show that the proposed estimator possesses the oracle properties. In addition, weintroduce an iterative algorithm to achieve the proposed optimization problem, and usea data-driven method to choose the tuning parameters. Simulation studies demonstratethat the proposed new estimation method is robust and works much better than the leastsquares based method when there are outliers in the dataset or the autoregressive errordistribution follows heavy-tailed distributions. Moreover, the proposed estimator workscomparably to the least squares based estimator when there are no outliers and the erroris normal. Finally, we apply the proposed methodology to analyze the electricity demanddataset.
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Chemical Vapor Deposition Growth of Graphene Domains Across the Cu Grain Boundaries
Yang Wang,Yu Cheng,Yunlu Wang,Shuai Zhang,Chen Xu,Xuewei Zhang,Miao Wang,Yang Xia,Qunyang Li,Pei Zhao,Hongtao Wang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.08
Many aspects in the chemical vapor deposition (CVD) growth of graphene remain unclear such as its behavior near the catalyst grain boundaries. Here we investigate the CVD growth mechanism of graphene across the Cu grain boundaries using unidirectional aligned graphene domains, which simplifies the analysis of both graphene and Cu to a large extent. We found that for a graphene domain grown across the Cu grain boundary, the domain orientation is determined by the Cu grain where the domain nucleation center is located, and the Cu grain boundary will not change the growth behavior for this graphene domain. This growth mechanism is consistent with the Custep-attached nucleation and edge-attachment-limited growth mechanism for H-terminated graphene domains and will provide more guidance for the synthesis of high-quality graphene with less domain boundaries.
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