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Zhang Y.-P.,Lanzhou Jiaotong University | Du B.-X.,Dezhou Power Supply Company | Tian M.-X.,Lanzhou Jiaotong University
Gaodianya Jishu/High Voltage Engineering | Year: 2011

In the ultra-high voltage (UHV) transmission systems, controllable shunt reactor (CSR) with high-speed response can improve the transmission power and power quality by means of restricting the over-voltage and changing the power fleetly and smoothly. In order to research the compensation degree of CSR and its relation with characteristics of UHV line, on the basis of equations of uniform transmission line and ∏-type equivalent circuit of UHV line with distributed parameters considered accurately, the formula for calculating compensation degree of controllable shunt reactor which is applicable to various loads of receiving system is achieved by power flow calculation. The relationships of compensation degree, transmission power, voltage and length of the line are analyzed. For example, when transmission power of UHV transmission line is fixed and the load of receiving-end is inductive, the lower the power factor is, the lower the compensation degree is. But the situation is contrary when load of receiving-end is capacitive. The results provide a theoretical foundation for designing the control system of UHV controllable shunt reactor. Source

Jiang Y.Z.,Shandong Electric Power Research Institute | Liang Z.G.,Shandong University | Li C.,Shandong University | Du B.X.,Dezhou Power Supply Company
Advanced Materials Research | Year: 2014

This paper discusses effect of phase sequence layout on electric field under overhead lines. Charge simulation method is used. Examples of two circuit overhead lines and four circuit overhead lines show that phase arrangment of lowest height conductors has major influence and phase arrangment of middle height conductors has lesser influence on electric field under overhead lines. Interlacing placed lowest height conductors with different phase and phase arrangement of middle height conductors different from that of lowest height conductors help to reduce electric field. Source

Zhao Q.,Yanshan University | Zhang J.,Dezhou Power Supply Company
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2013

A passive lossless snubber based on magnetic coupling is proposed, which restrains the reverse recovery current and reduces the overlapping area of voltage and current during the turning-on period of switch. Therefore, the efficiency of PFC(Power Factor Correction) is enhanced and the EMI(ElectroMagnetic Interference) reduced. The energy is absorbed and transferred through the resonance of snubber inductor and capacitor. The coupled winding makes the energy of snubber inductor easy to be reset and no additional voltage stress is introduced by the snubber to the switch. The operating principle of snubber and the parameters design of key passive components are presented in detail. The experimental waveforms and efficiency comparison tests of 500 W prototype show the high efficiency of the proposed snubber. Source

Zhang F.,Shandong University | Dong X.,Shandong University | Liang J.,Shandong University | Han X.,Shandong University | And 2 more authors.
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2013

A hybrid algorithm is proposed to calculate the minimum load margin under the constraint of static voltage stability. A fast and efficient method is proposed to identify the limit induced bifurcation for the continuation power flow method, which considers the impact of reactive compensation device switching on load margin, applies the power factor of load increment to constrain the direction of load growth, and takes the generator reactive constraint into account to improve the adaptive step control strategy. A variable weight coefficient and variable learning factor strategy is adopted for the particle swarm optimization method, which applies a precocity criterion to carry out the particle variance with a certain probability and combines with the simulated annealing process to prevent local optimization. Case test verifies the effectiveness of the proposed algorithm. Source

Liu X.,Harbin Institute of Technology | Wang X.,Dezhou Power Supply Company | Huang N.,Harbin Institute of Technology | Xu D.,Harbin Institute of Technology
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2012

According to the traits of power quality data in symmetry, parity and periodicity, a data compression algorithm based on pattern similarity and LZW compressed encoding is introduced, which normalizes the distance of pattern similarity to identify the distortion for the lossy compression of undistorted data and the lossless compression of distorted data, and adopts reasonably the LZW compressed encoding to increase the compression ratio. Models are established in MATLAB7.10 environment for six kinds of typical power quality disturbance signal, simulative experiments are designed to check the distortion detection capability of normalized distance, and the comparison of compression effect between the proposed algorithm and the one-dimension discrete wavelet transform show its performance and feasibility. Source

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