Along with the enhancement of voltage level, harmful affect of the secondary arc current to the system becomes more and more serious. The transmission power of the lines is one of factors that influence the secondary ...
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Along with the enhancement of voltage level, harmful affect of the secondary arc current to the system becomes more and more serious. The transmission power of the lines is one of factors that influence the secondary arc current obviously. The voltage distribution along the transmission line will changes according to the different transmission power, which will lead to the variation of the induction component from the sound phases when the fault occurs. In this paper, the quadric-mode transformation is adopted to establish the mathematic model of secondary arc current in the double-circuit transmission line. According to the variation of power transmission, the secondary arc current of different fault point is calculated. The results indicate that secondary arc current is influenced much by the line transmission power, and the variation trend changes along with the fault point. When the fault occurs in head or terminal of the line, the secondary arc current may becomes larger along with the increasing of the transmission power, thus effective suppress measurements must be taken.
The linearization equations of load models including fifth-order motor, constant impedance (Z), constant current (I) and constant power (P) are derived, which can interface with the network equations for the analysis ...
The linearization equations of load models including fifth-order motor, constant impedance (Z), constant current (I) and constant power (P) are derived, which can interface with the network equations for the analysis of subsynchronous resonance (SSR). The IEEE First Benchmark Model is adopted to analyze the effect of the above load models on the damping characteristics of torsional modes. It is observed that the analysis result can be optimistic without inclusion of load models and there is no any load model which ensures that the results are always conservative.
This paper proposed a novel dynamic reactive power compensation circuit topology which is applicable to low voltage distribution system. It described the composition, features, and working principle of dynamic reactiv...
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This paper proposed a novel dynamic reactive power compensation circuit topology which is applicable to low voltage distribution system. It described the composition, features, and working principle of dynamic reactive power compensation system. Open-loop SPWM control strategy is applied for the inverter, by adjusting the inverter output voltage to dynamically regulate the absorption or emission of reactive power by SVC, zero reactive power compensation of the system can be achieved. With the combination of fixed compensation capacitor the capacity of the inverter can be smaller when it compensates the reactive powerdynamically, it can improve the power factor and voltage level fast, efficiently and reliably. It overcomes the switching oscillation and the shortcomings of inadequate compensation, at the same time, reduce power loss and improve the voltage quality.
A novel dynamic reactive power compensation circuit topology suitable for low voltage distribution system was proposed. The efficient compensation of unbalanced load could be realized by the structure of three-phase f...
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A novel dynamic reactive power compensation circuit topology suitable for low voltage distribution system was proposed. The efficient compensation of unbalanced load could be realized by the structure of three-phase four-leg inverter circuit. The sinusoidal pulse width modulation (SPWM) control of inverter could ensure the low distortion of voltage and current. Besides, by the regulation of the inverter's output voltage, the compensation reactive power could be dynamically regulated and the aim of system's zero reactive power compensation could be realized. Combined with fixed capacitor compensator, small capacity of inverter is required to compensate dynamic reactive power. The novel dynamic static var compensator (SVC) could improve the system's power factor and voltage stability. Finally, simulations are carried on the platform of PSCAD/EMTDC. The results show that the proposed control strategy is feasible and efficient.
In accordance with the familiar power quality problem, such as voltage sag, flicker, harmonic suppression and short circuit fault, this paper designed a novel series voltage quality regulator in medium voltage for the...
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In accordance with the familiar power quality problem, such as voltage sag, flicker, harmonic suppression and short circuit fault, this paper designed a novel series voltage quality regulator in medium voltage for the multiple objective control basing on the cascaded multilevel H-bridge method, and analysis its working principle in detail. A Short-circuit current limiter is designed in this paper, the control strategy multiple objective control is proposed as well. The simulation model is established by PSCAD/EMTDC. Finally, the rationality of the main circuit topology design is tested through low-voltage experiment. The simulation result and the text show that the design of voltage regulator and the control strategy this paper proposed can compensate the voltage feasibly and efficiently.
Dissolved gas-in-oil analysis (DGA) is an important method to find the hidden or incipient insulation faults of oil-immersed power transformer. Matter element theory was employed to research the fault diagnosis of tra...
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ISBN:
(纸本)9781424443673
Dissolved gas-in-oil analysis (DGA) is an important method to find the hidden or incipient insulation faults of oil-immersed power transformer. Matter element theory was employed to research the fault diagnosis of transformer with qualitative and quantity advantages. However, the method did not consider the uncertain essence of the fault diagnosis of transformer. And in the fact, there were two uncertain characteristic in it, random and fuzzy. Hence a new fault diagnosis method is presented in this paper. The method has two advantages of considering two uncertain characteristic and realizing fault diagnosis qualitatively and quantitatively based on cloud model and matter element theory. By building the cloud matter element models of transformer fault diagnosis and calculating the correlation function of feature matter element models and standard ones, fault modes of transformer are identified effectively. Then, the results of examples research indicate the method is effective.
With rapid development of wind power generation, large capacity wind farms are connected into the transmission system. Comparing with traditional power plant, the transient characteristics of transmission grid includi...
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With rapid development of wind power generation, large capacity wind farms are connected into the transmission system. Comparing with traditional power plant, the transient characteristics of transmission grid including wind farm are worthy investigating. The wind farm based-on wound rotor induction generators (WRIGs) shares high market occupancy in China, but academic researches on this grid-connected wind generation are few. So in this paper, the transient characteristics of the powersystem, adding a WRIGs wind farm and adding a traditional power plant, are compared. Effect of a WRIGs wind farm on transient performances of transmission grid is discussed. And the control effect on transient stability, when the WRIGs wind farm participating in systemcontrol during system fault, is investigated. Finally, simulation results are validated by using CIGREB4-39 grid. It is concluded that the transient performance of WRIGs wind farm is better than that of traditional power plant.
controllable reactor is an important voltage control and reactive power compensation device in powersystem which is wide range voltage application, high reliability, low harmonic and simple maintenance, etc. The reac...
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ISBN:
(纸本)9781424427994
controllable reactor is an important voltage control and reactive power compensation device in powersystem which is wide range voltage application, high reliability, low harmonic and simple maintenance, etc. The reactor iron core magnetic field distribution directly affects the reactor's loss and other properties. In this paper, aiming at six kinds of typical controllable reactor core structure, magnetic field is analyzed in theory and then the core magnetic field distribution analysis are compared for the first time by model building in the finite element analysis software ANSYS and imposing different exciting currents. Moreover, six kinds of core structure's loss are compared by the use of the ANSYS inner set loss algorithm and the influence of excitation on the loss for a particular core is verified. The analysis results indicate that finite element analysis software can effectively analyze and compare the magnetic field distribution and the loss for different kinds of reactor core structure.
A good Black-Start scheme is important and necessary to resume power supply fast and efficiently after black out, and how to choose black-start power is the first thing to consider in the scheme. In this paper, the ad...
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A good Black-Start scheme is important and necessary to resume power supply fast and efficiently after black out, and how to choose black-start power is the first thing to consider in the scheme. In this paper, the advantages of VSC-HVDC as black start power are analyzed. The ability of VSC-HVDC to soft energize major powersystem equipment is proved through simulation by software PSCAD/EMTDC. Simulation waveforms during soft energization are illustrated. These plots have described the good voltage and frequency characteristics of VSC-HVDC. Furthermore, the transition from black start control to normal power flow control is discussed. Simulation results indicate that by using soft energization, VSC-HVDC is an ideal black start power.
Wide area measurement system (WAMS) has been widely used in powersystemdynamicmonitoring and control, such as low frequency identification and control, stability assessment and preventive control, etc. However, as ...
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Wide area measurement system (WAMS) has been widely used in powersystemdynamicmonitoring and control, such as low frequency identification and control, stability assessment and preventive control, etc. However, as a measurement tool, phasor measurement unit (PMU) has the measurement error and bad data unavoidably. If the raw measurements are applied in powersystem analysis and control directly, the unexpected consequence might be resulted in. Aiming at this problem, a novel dynamic state estimator for generator state variables is proposed in this paper. The corresponding mathematical model is given in detail. Bad data detection and elimination approach is presented as well. The simulation results show that the proposed method can provide the estimated trajectories of the generators in real-time, which eliminates the impact of measurement error and bad data and could give the backbone for WAMS based dynamic applications and real-time control.
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