The issue of power quality in the distribution system is always in sense of the concern. With the high penetration of distributed generation (DG) currently, it tends to be more complicated. This paper presents a new a...
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The faults in electric powersystem can not be completely avoided. When powersystem operates from normal state to failure or abnormal operates, its electric quantities may change significantly. Our researches indicat...
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The faults in electric powersystem can not be completely avoided. When powersystem operates from normal state to failure or abnormal operates, its electric quantities may change significantly. Our researches indicate that the variable with the biggest coefficient in principal component usually corresponds to the fault. Therefore, utilizing real-time measurements of PMU, basing on principal components analysis technology, we have completed the fault location of electric powersystem. Of course, because of the complexity of different types of faults in powersystem, there still exists enormous problems need a close and intensive study.
Distributed generator (DG), with its flexible power generation, environment-friendly advantages has been more widely used in distribution system, which has brought some influence to the traditional distribution networ...
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ISBN:
(纸本)9781424480807
Distributed generator (DG), with its flexible power generation, environment-friendly advantages has been more widely used in distribution system, which has brought some influence to the traditional distribution network reliability evaluation. In this paper, two different models for conventional DG and wind turbine generator (WTG) are established for reliability evaluation, based on different energy sources and operation characteristics. This paper presents a technique to obtain the WTG output using statistical wind speed information, considering to the intermittent characteristics of wind power. On this basis, an improved minimal cut set algorithm is proposed to evaluate the reliability of distribution network with DG. Finally, the simulation of a typical distribution line with DG verifies the validity of this method.
This paper presents some new technologies of modular multilevel converter (MMC) for VSC-HVDC application. The origin of modular multilevel VSC and its essential working mechanism are clarified in detail. Then, the sta...
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This paper presents some new technologies of modular multilevel converter (MMC) for VSC-HVDC application. The origin of modular multilevel VSC and its essential working mechanism are clarified in detail. Then, the starting of MMC under de-energized condition is discussed and a simple but effective control scheme is proposed. Concerning the drawbacks of traditional PWM modulation technologies, i.e., SVPWM and SHPWM, an improved modulation control technology based on waveform approximation is presented. The proposed modulation technology makes the individual semiconductors have much lower switching frequency (50 Hz) resulting in lower switching losses and, consequently, lower total losses of the transmission system compared to 2 or 3-level VSC. The technologies and conclusions are validated by simulations in PSCAD/EMTDC. The theory analysis and simulation results indicate that these new technologies have great potentiality in the application of VSC-HVDC projects in future.
With the development of High Voltage Direct Current (HVDC) transmission, the impact of DC system on AC relay protection becomes more prominent. So it becomes more important to research electrical characteristics of AC...
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With the development of High Voltage Direct Current (HVDC) transmission, the impact of DC system on AC relay protection becomes more prominent. So it becomes more important to research electrical characteristics of AC system under DC faults. In PSCAD/EMTDC environment, the inverter commutation failure resulted from short circuit faults in AC line is simulated based on the electromagnetic transient model of Shandong grid containing Ningdong-Shandong DC transmission system. Prony algorithm is applied to analyze the electrical transient characteristics of AC system during commutation failure. The coincidence of fitted waveform and simulated waveform verified the validity of prony algorithm. Prony analysis results show that DC system injects a large number of inter-harmonic components into the inverter side AC system during commutation failure, and the distortion of the parallel line current is more serious than that of the fault line current, so the impact of DC system on the AC relay protection devices equipped on the parallel line is greater.
Based on the modal series method, the first-order and second-order solutions of torques were deduced. An analytical method was established for analyzing torsional dynamics. It can directly represent torsional dynamics...
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Cooperative game theory is firstly introduced into the comprehensive assessment of power quality,and a new model for combination evaluation of power quality is established based on cooperative game. The model takes in...
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ISBN:
(纸本)9781457700668
Cooperative game theory is firstly introduced into the comprehensive assessment of power quality,and a new model for combination evaluation of power quality is established based on cooperative game. The model takes into account the advantages of 4 kinds of single assessment method. By calculating the characteristic function values of various combinations to get the Shapley value of each assessment method,and then the weight value of each method in combination union can be determined,so that power quality assessment conclusion could be optimized. The conclusion also reflects the information of evaluation object from different angles. The simulation results show that the combination evaluation method with good accuracy can be effectively applied to the comprehensive assessment of power quality.
Synchronous generator excitation controlsystem is one of the most important parts of powersystemcontrol. And as PID control is one of the first developed and the most widely used control schemes in excitation syste...
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Synchronous generator excitation controlsystem is one of the most important parts of powersystemcontrol. And as PID control is one of the first developed and the most widely used control schemes in excitation system, its parameters tuning problem has been highly concerned. Since MATLAB genetic algorithm toolbox has the characteristics of strong robustness and efficient optimization, this paper first establishes a mathematical model of generator excitation system, and then uses ITSE index of terminal voltage step response curve as the optimization index, computes the fitness function based on SIMULINK platform, and uses MATLAB genetic algorithm toolbox to optimize PID parameters of synchronous generator excitation controlsystem. Applying this method to a power plant's synchronous generator excitation system, results demonstrate that dynamic characteristics are improved greatly.
Based on power electronic converting current devices which can be controlled quickly, VSC-HVDC system can regulate active power, reactive power, DC voltage, and line voltage flexibly. Different regulation strategies h...
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ISBN:
(纸本)9781424465491
Based on power electronic converting current devices which can be controlled quickly, VSC-HVDC system can regulate active power, reactive power, DC voltage, and line voltage flexibly. Different regulation strategies have different influences on the powersystem stability. A worse regulation strategiy may lead to sharp fluctuation of electrical measurements and longer regulation time, which is harmful for the system stability. It is worse when faults happen during the regulation. The traditional regulation strategy is that the reference value of regulation is set to the goal value directly, sometimes the change is very serious like the reversal of power flow, and the electrical measurements may have sharp fluctuation during the regulation. Different from the traditional regulation strategy, a new regulation strategy, called soft regulation strategy, was presented in the paper, which can minish the fluctuation of electrical measurements and shorten the regulation time. The soft regulation strategy is helpful for the system stability and the device security. The soft protection strategy for serious impact from AC faults is also presented, by which the fault terminal is softly closed and the non-fault terminal works right as before, while the DC voltage can be kept, which increases the efficiency of VSC-HVDC system and makes preparation for restoration. Simulations performed in PSCAD/EMTDC verify the proposed regulation strategy.
In practical power markets, Available Transfer Capability (ATC) is crucial for transmission customers, system operators and power marketers to make a good choice. It is an indication of the expected transfer capabilit...
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