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Zhou L.,Chongqing University | Chao Y.,Chongqing University | Liao B.,Sichuan Electrical Power Design and Consulting CO. | Ren W.,Chongqing University | And 2 more authors.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2014

The grid synchronization signal detection is a key to control the converter to be connected to the grid for new energy. For the weak points of the phase-lock loop, a grid synchronization signal real-time detecting method based on reference frequency is proposed in the paper. Only to detect the single-phase grid-voltage operated with sine and cosine signals of reference frequency, the grid synchronization signal can be detected in case of the three phase grid distorted and unbalanced. For the big phase deviation of the synchronization signal caused by frequency fluctuation, to improve the low-pass filtering link a negative feedback and proportional control is introduced, and the phase deviation can be corrected in satisfied index. The theoretical and experimental study results verify that the method is correct and effective. © 2014 Chin. Soc. for Elec. Eng.

Shu L.,Chongqing University | Yang Z.,Chongqing University | Jiang X.,Chongqing University | Hu Q.,Chongqing University | And 2 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2014

It is important to reveal the effect of terrestrial solar ultraviolet radiation (TSUVR) on the discharge performance of external insulation for the design and operation of power system in regions where have strong TSUVR. Consequently, we use an artificial UV lamp to imitate TSUVR in experiments to research this effect on positive DC discharge. It is found that TSUVR has no obvious effect on breakdown voltage and corona of air-gap positive DC discharge. That is because the wavelength of TSUVR is in the range of 290~400 nm, and its intensity is less than 200 W/m2, and air, Cu, and Fe can not be photoionized under TSUVR. There is no obvious effect of TSUVR on arc propagation due to energy. Although a part of the photons in TSUVR has higher energy than the work function of Al, Al could be easily oxidized, and the oxide film (Al2O3) prevents Al from being ionized by TSUVR. Therefore, TSUVR has no obvious effect on positive DC discharge performance of air gap. This research will support the design of external insulation in the regions with strong TSUVR.

Lu J.,CAS Chengdu Institute of Mountain Hazards and Environment | Liao X.,Sichuan Electrical Power Design and Consulting CO.
Advanced Materials Research | Year: 2012

According to an practical construction of an subway station, the foundation excavation three dimensional model was built by FLAC3D from the need of practical engineering. The status and variation characteristics of the displacement field, deformation field and plastic failure zone were obtained. Guiding significance was provided by the simulation. © (2012) Trans Tech Publications.

Yan W.,Chongqing University | Wang F.,Chongqing University | Tang W.-Z.,Chongqing Electric Power Research Institute | Zhao X.,Chongqing University | And 2 more authors.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

A novel partitioning method is proposed based on power sources clustering and short-circuit impedance distance, which is characterized by Mvar source nodes partitioning and load nodes mapping. The electrical distance between two Mvar source nodes is defined based on the sensitivity of voltage to reactive power injection, and the agglomerate hierarchical clustering algorithm is applied to partition the Mvar source nodes. Then the short-circuit impedance distance between multiple Mvar source nodes and a single load node is defined, and the mapping between load nodes and Mvar sources partitions is realized by minimizing the short-circuit impedance distances. With the presented method, not only the Mvar source nodes within a short electrical distance from each other, but also the load nodes and the multiple Mvar source nodes having a strong control relation can be clustered into the same partition. The other advantage with the method is that the partition is independent of the power flow state. Simulation results on IEEE39-bus system and the real Chongqing grid data demonstrate the effectiveness of the presented method.

Li G.-H.,Sichuan Electrical Power Design and Consulting CO.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010

According to the approach ability of artificial neural network, a novel transformer protection based on the artificial neural network model is proposed. Adopting artificial neural network to approach the electromagnetic relation of transformer, building artificial neural network model to substitute for transformer physical model, identifying internal parameters on line, artificial neural network model based transformer protection is realized after parameter identification. EMTP simulation results demonstrate that the proposed method can recognize internal faults within a half cycle of their occurrence, with apparent fault features and less threshold value. It can discriminate low-level internal faults, without reference to the magnetizing inrush.

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