This paper puts forward an auxiliary fuzzy logic controller for the Voltage Source Converter based HVDC transmission system, VSC-HVDC, to improve the stability of the AC/ DC system by damping the oscillation effective...
详细信息
This paper puts forward an auxiliary fuzzy logic controller for the Voltage Source Converter based HVDC transmission system, VSC-HVDC, to improve the stability of the AC/ DC system by damping the oscillation effectively after disturbance. The fast control capability of the VSC-HVDC and the process of area mode oscillations are analyzed. No detailed model of the system is required for the design of the proposed control scheme. The controller judges the operation states and the control effect and accordingly adjusts its active power order in an adaptive way by using fuzzy rules, so as to damp out the area mode oscillation. Simulation results on the IEEE 4-generator AC/DC powersystems have shown that the controller can enhance the dynamic stability of interconnected powersystems effectively and is robust to the variation of system operating conditions and oscillation modes.
Thyristor controlled series capacitor (TCSC) used in power transmission line can increase the transportability and the stability of system, and decrease the system loss significantly. At the same time, TCSC brings man...
详细信息
Thyristor controlled series capacitor (TCSC) used in power transmission line can increase the transportability and the stability of system, and decrease the system loss significantly. At the same time, TCSC brings many serious problems to transmission lines fault location and protective relaying. This paper analyzes the influence of TCSC to EHV transmission line protection, especially to the high-frequency directional protection. It can be obtained from the analyzing that the addition of TCSC to EHV transmission line would make the high-frequency directional protection unwanted operation or failure to operate. In order to solute the problems TCSC caused, this paper presents a novel transient protection scheme based on wavelet transform (WT). The simulation tests have proved that the analyzing and solution of the appearance of TCSC in EHV transmission line are correct.
Energy storage system is an all-important part in photovoltaic. A new bidirectional DC-AC-DC converter for supercapacitor energy storage system in photovoltaic generation is put forward. In the beginning, some experim...
详细信息
Energy storage system is an all-important part in photovoltaic. A new bidirectional DC-AC-DC converter for supercapacitor energy storage system in photovoltaic generation is put forward. In the beginning, some experiments on super capacitor have been performed, which shows super capacitor has good performance in quick charge and discharge. And mathematical model of the dual full-bridge bidirectional DC-AC-DC converter circuits with a transformer and its simplified model are derived. In the end, A phase current in the transformer primary side (ia) can be investigated with mathematical calculation simulation and detailed circuit simulation. The comparative result shows the mathematical model rationality. Through deduction, unified model of SESS also can be gotten.
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 ...
详细信息
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.
Concrete-polluted silicone rubber (SIR) insulators are common nature-polluted insulators. A type of concrete-polluted SIR insulators with different content of concrete was evaluated. The flashover voltage of concrete-...
详细信息
ISBN:
(纸本)9781424416219
Concrete-polluted silicone rubber (SIR) insulators are common nature-polluted insulators. A type of concrete-polluted SIR insulators with different content of concrete was evaluated. The flashover voltage of concrete-polluted insulators was tested after placing in artificial climatic chamber for 6 hours with ultrasonic fog device continual working. The incepted discharge area always occurs at the umbrella edge and the connected area of the hardware fittings and core rod for light concrete-polluted SIR insulators. However, the incepted discharge area always occurs at connected place of core rod and hardware fitting for heavy concrete-polluted one. The flashover voltage decreases with the increase of concrete content by a power function and the influence factor of the concrete deposit density b is 0.194. Even though after a long time transfer, the hydrophobicity of heavy concrete-polluted SIR insulators also decrease with the increase of concrete-polluted content.
The fast control capability of the VSC-HVDC and the process of area mode oscillations are analyzed. An auxiliary fuzzy logic controller designed in Matlab for the voltage source converter based HVDC transmission syste...
详细信息
The fast control capability of the VSC-HVDC and the process of area mode oscillations are analyzed. An auxiliary fuzzy logic controller designed in Matlab for the voltage source converter based HVDC transmission system, VSC-HVDC, to improve the stability of the AC/DC system is designed to enhance stability by increasing the deceleration energy of oscillation. Simulation results on the IEEE 4-generator AC/DC powersystems have shown that the controller can enhance the dynamic stability of interconnected powersystems effectively and is robust to the variation of system operating conditions and oscillation modes.
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...
详细信息
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.
Zero-sequence harmonics caused by nonlinear loads usually result in high voltage distortion levels throughout the facility, neutral conductor overloading, motor heating, transformer heating, increased losses, and exce...
详细信息
Zero-sequence harmonics caused by nonlinear loads usually result in high voltage distortion levels throughout the facility, neutral conductor overloading, motor heating, transformer heating, increased losses, and excessive harmonic injection onto the utility supply system. This paper presents a novel method to eliminate zero-sequence harmonics by using Zero-sequence Resister Block (ZRB) and Zig-Zag transformer. Zig-Zag transformer is a special connection of three-phase transformerpsilas windings. The ZRB is also a special connected transformer, whose three windings are wounded in the same core. The ZRB has zero reactance for positive and negative-sequence components but giving three times of self-reactance for zero-sequence reactance. In this paper, an analysis is carried out; simulations and laboratory tests are used to evaluate the performance of the Zig-Zag transformer and ZRB under various system conditions. The simulation and laboratory test results indicate that the combination of ZRB and Zig-Zag transformer as filter is a better and effective way to attenuate the neutral current, which also provides an innovational way to improve power quality.
Based on the experiment carried out in the lab on several cables in which there are some typical PD models, the relationship between the single acoustic signal generated by the partial discharge and the apparent disch...
详细信息
ISBN:
(纸本)9781424416219
Based on the experiment carried out in the lab on several cables in which there are some typical PD models, the relationship between the single acoustic signal generated by the partial discharge and the apparent discharge magnitude in a line frequency cycle are researched. Further more, through the detection system which is combined of the VHF PD detection method and the acoustic emission detection method, the expressions of the relationship between the voltage value, which is gotten directly from the detection system and the apparent discharge magnitude are gotten by the curve fitting method. At the same time, the method of locating the defect manually with the acoustic sensor is introduced simply in the paper.
暂无评论