The distribution network structure planning can enhance the reliability and the efficiency of the grid. An adaptive ant colony algorithm based on cloud model was proposed and applied in distribution network structure ...
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The distribution network structure planning can enhance the reliability and the efficiency of the grid. An adaptive ant colony algorithm based on cloud model was proposed and applied in distribution network structure planning in this paper. In view of the main disadvantage of being inclined to local convergence and slow convergence speed of traditional ant colony algorithm, the parameter ρ and Q were qualitatively controlled and dynamically selected in this paper by employing the uncertain qualitative association rule inference based on cloud model, which is one indefinite model for transformation between qualitative and quantitative knowledge. The algorithm overcomes the shortcoming of traditional ant colony algorithm, and the simulation results of power distribution network planning demonstrated the efficiency of the algorithm.
In the extra high voltage (EHV) transmission system, the transient single-phase to ground faults are the most frequent to occur. Even after the opening of breakers in the two sides of the fault line, an induced curren...
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In the extra high voltage (EHV) transmission system, the transient single-phase to ground faults are the most frequent to occur. Even after the opening of breakers in the two sides of the fault line, an induced current still exists in the arc because of the electrostatic and the electromagnetic coupling from the other two sound phases. Along with the enhancement of the voltage grade, the influence of the secondary arc becomes more and more, and may probably lead to the failure of the reclosing if the secondary arc is not extinguished promptly. In this paper, the dynamic secondary arc model (including recovery voltage and the secondary arc current) in single-phase asymmetric breaking is established based on the distribution parameters of EHV long-line. The method of twice-mode transformation is adopted to calculate the steady-state value of the secondary arc current and recovery voltage. Furthermore, the affects of different overhead line models on the secondary arc current are also analyzed through the real time digital simulation.
With the rapid development of electric electronic technology, non-linear loads, large capacity converters, etc. increase mostly, which brings about the serious problems such as harmonics. Thus, the traditional power t...
With the rapid development of electric electronic technology, non-linear loads, large capacity converters, etc. increase mostly, which brings about the serious problems such as harmonics. Thus, the traditional power theory based on the average is unable to meet with the practical require. In this paper, the power definition in the sinusoidal and non-sinusoidal circuit is discussed and the waveform similarity between voltage and current is analyzed due to the criterion of minimum mean square deviation. Furthermore, the relationships among the waveform similarity factor, displacement power factor and real power factor are also discussed. The results show that power components are well analyzed in use of waveform similarity under the conditions of non-sinusoidal. At the same time, waveform similarity provides a simple but effective method for the calculation of power factor.
The radiation and propagation of electromagnetic (EM) waves generated from PD caused by the obstruction of main transformer components are studied by FDTD simulation in order to get more information for PD location an...
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The radiation and propagation of electromagnetic (EM) waves generated from PD caused by the obstruction of main transformer components are studied by FDTD simulation in order to get more information for PD location an...
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The radiation and propagation of electromagnetic (EM) waves generated from PD caused by the obstruction of main transformer components are studied by FDTD simulation in order to get more information for PD location and diagnosis. Current filament, perfect conductive cylinder and perfect conductive spiral coil models are used to simulate the radiation and the influences of iron-core and transformer coil to the propagation of EM waves. The results demonstrate dynamic propagation process of EM waves in time order, and prove the correctness of the shortest optical path principle. But the attenuation and distortion of EM waves-especially the first peak amplitude-caused by the obstruction of large solid conductive obstacle like iron-core are quite intensive that it may cause great difficulties to identify exact arriving time position of incident waves coming along the shortest optical path. While the influences of the coil to the propagation of EM waves are so little that HF EM waves can penetrate it in almost linear path.
HVDC transmission lines system has some advantages, but it can generate an effect on the environment nearby due to the corona, especially the ionized field. Based on the electromagnetic field theory, a simple method t...
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ISBN:
(纸本)3952299049
HVDC transmission lines system has some advantages, but it can generate an effect on the environment nearby due to the corona, especially the ionized field. Based on the electromagnetic field theory, a simple method to analyze the ionized field generated from the bundled conductors of bipolar lines is proposed. And then, after the validity of the method is testified, some examples are analyzed and some conclusions are drawn finally. The results have been used in the design of ±800kV HVDC transmission lines system in China.
Traditional voltage injection methods for DVR are in-phase strategy which injects voltage in phase with the sag voltage and missing voltage technique which compensates for the difference between the sag and pre-sag vo...
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Traditional voltage injection methods for DVR are in-phase strategy which injects voltage in phase with the sag voltage and missing voltage technique which compensates for the difference between the sag and pre-sag voltages. Since a certain component of injected voltage is in-phase with the load current, DVR has to provide some amount of energy to the grid. This paper use DQ analyzing method based on instantaneous reactive power theories to detect and obtain the parameters of source side voltage for balanced faults of three-phase three-wire system. Through circumgyrating the phasor and injecting voltage with an appropriate advance phase relative to source side voltage, the minimum energy injection can be achieved. For unbalanced faults, fictitious three-phase voltages which come from a single- phase source can be constructed mathematically, so unbalanced faults can be dealt with easily in a balanced way. Simulation results are presented to demonstrate the validity of the proposed method.
Nowadays worldwide, distributed generation plays a more and more important role in world's energy supply system. But distributed resources' innate weaknesses cause some problems such as wavy output power and i...
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Nowadays worldwide, distributed generation plays a more and more important role in world's energy supply system. But distributed resources' innate weaknesses cause some problems such as wavy output power and instability of power generation. These innate weaknesses are hard to overcome only through improving one single distributed generation plant or adding energy storage equipment etc. In this article, a new concept of connecting several AC distributed generation plants (such as wind farm) via VSC-converter, and DC distributed generation plants (such as solar cell) via DC/DC converter and forming a low voltage DC network is given. This low DC network will be integrated into AC grid in some proper way. Namely equalize these small distributed generation plants to a big power generation farm to improve stability of electricity generation. Some simulations based on PSCAD/EMTDC are also given.
HVDC transmission lines system has some advantages, but it can generate an effect on the environment nearby due to the corona, especially the ionized field. Based on the electromagnetic field theory, a simple method t...
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HVDC transmission lines system has some advantages, but it can generate an effect on the environment nearby due to the corona, especially the ionized field. Based on the electromagnetic field theory, a simple method to analyze the ionized field generated from the bundled conductors of bipolar lines is proposed. And then, after the validity of the method is testified, some examples are analyzed and some conclusions are drawn finally. The results have been used in the design of plusmn800 kV HVDC transmission lines system in China
Voltage fluctuation and flicker are mainly caused by surge load with large capacity, which may lead to the unstable operation of the motor, the poor characteristics of electrical equipments and the mis-operation of th...
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Voltage fluctuation and flicker are mainly caused by surge load with large capacity, which may lead to the unstable operation of the motor, the poor characteristics of electrical equipments and the mis-operation of the electronic device even damage etc. Traditional SVC can adjust the reactive power ideally to maintain the system voltage of the connection point and play an excellent role in suppressing the voltage fluctuation and flicker. The minor defect is that it can not be directly applied to the ultrahigh or extra-high voltage system. This paper puts forward a topology of SVC based on the controllable reactor. It can be made into voltage at any level to connect to the ultra-high or extra-high voltage network directly, and can dynamically adjust the saturation degree of the controllable reactor according to the fluctuation of the reactive power of the system, smoothly change the reactive power it sends out, effectively suppress the voltage fluctuation and flicker. Meanwhile, H alpha control is taker as the main control strategy. The validity of proposed approach is verified by calculation and simulation.
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