Online partial discharge monitoring for power equipments is useful to improve the capacity of the power supply. Main technology for PD testing is introduced in this paper. Advantages and disadvantages of pulse current...
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ISBN:
(纸本)9789881532329
Online partial discharge monitoring for power equipments is useful to improve the capacity of the power supply. Main technology for PD testing is introduced in this paper. Advantages and disadvantages of pulse current, UHF, ultrasonic and TEV method are present. The status quo of online PD monitoring is analyzed, and the detection effect of online PD monitoring is not good. Opinions to improve the effect are given. They include built-in sensors, increasing sensitivity and sample rate. Analysis of the state quo indicates that the relevant technical standards and specifications must be revised to improve the normalization and standardization.
A broadband RF energy harvesting system over a frequency range of 900MHz-3GHz has been designed and tested. Some detailed issues of RF design have been studied and tested to improve the efficiency of the rectifier. Te...
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A broadband RF energy harvesting system over a frequency range of 900MHz-3GHz has been designed and tested. Some detailed issues of RF design have been studied and tested to improve the efficiency of the rectifier. Test results show that as low as -20dBm RF power can be harvested by this system. The series and parallel connections of two RF energy harvesting systems have also been studied, compared with the single system.
Based on summarizing the features of selecting critical flowgates in actual power grid, an automatic discovery method of powersystem critical flowgates considering multiple security themes in power grid is proposed. ...
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Based on summarizing the features of selecting critical flowgates in actual power grid, an automatic discovery method of powersystem critical flowgates considering multiple security themes in power grid is proposed. Based on topological structure of power grid and online power flow, the electric partitioning of power grid is performed and different types of critical flowgates are selected according to different security theme: according to the demand on transient security theme the long-distance transmission channel composed by tie line between electric partitionings is chosen as critical flowgate;according to the demand on thermal stability theme, the transmission channel composed of high voltage transmission lines with high transmission capacity, which interact each other obviously, is chosen as critical flowgate;according to the thermal stability at load side the transmission channel composed of low voltage transmission lines with higher transmission capacity, which interact each other obviously, is chosen as critical flowgate. Taking Guangdong power Grid in China as testing example, test results show that the proposed method considers common security themes in power grid accurately and different kinds of critical flowgates can be attained;the obtained critical flowgates not only conform to a posteriori critical flowgate given by experts in the field of power grid operation, and new critical flowgates can be discovered, besides, the discovery results are reasonable and creditable.
This paper presents a kind of HVIGBT transient mixture model and corresponding parameter extraction method. The HVIGBT model can divide into MOSFET and BJT two parts. The two models are formed respectively according t...
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This paper presents a kind of HVIGBT transient mixture model and corresponding parameter extraction method. The HVIGBT model can divide into MOSFET and BJT two parts. The two models are formed respectively according to HVIGBT work principle, in addition, the carrier transport equations have been simplified for avoiding Kirk effect in BJT model. The transient model is realized in PSIM software in the paper. Extraction methods, which include estimation by empirical values, calculation by testing waveforms and comparison with same type models, are adopted in extracting model parameters. Through comparing testing and simulation waveforms, the model's simulation accuracy is proved.
The random and intermittent nature of wind power (WP) makes the integration of large-scale wind farms into powersystem problematic. The energy storage system (ESS) is an effective means to smooth the WP. This paper p...
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The random and intermittent nature of wind power (WP) makes the integration of large-scale wind farms into powersystem problematic. The energy storage system (ESS) is an effective means to smooth the WP. This paper presents a novel Kalman filter (KF) based adaptive wind power smoothing method to determine the power output of an ESS. ESS capacity can be significantly reduced by adjusting the parameters of KF adaptively according to the WP fluctuation. Meanwhile, a fuzzy logic controller is introduced to manage the remained energy level (REL) of the ESS. By considering the current WP fluctuation, the REL and the power output of the ESS together in the controller, the REL can be successfully managed to a reasonable range without deteriorating the WP fluctuation. A test case based on data from an actual wind farm validated the effectiveness of the proposed method.
With the rapid growth of grid-connected wind power penetration level,it is necessary to study the impacts of wind power on powersystem *** small-signal stability of powersystems with large-scale wind power is explor...
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With the rapid growth of grid-connected wind power penetration level,it is necessary to study the impacts of wind power on powersystem *** small-signal stability of powersystems with large-scale wind power is explored using the eigenvalue analysis method.A prototype sample system,the two-synchronous-generator system with a wind farm,is proposed for theoretical ***,simplified models of wind turbines(WTs)and the corresponding equivalent models of wind farms are *** kinds of typical WT models,i.e.,squirrel cage induction generator,doubly-fed induction generator,and permanent magnet synchronous generator are ***,based on the simplified equivalent models,effects of large-scale wind farms on the electromechanical oscillation modes(EOMs)of synchronous systems are *** results indicate that wind farms of the three kinds of WTs have positive effects on ***,long transmission lines connecting wind farmto the systemmay produce negative effects on the small-signal stability of the system.
Due to the energy crisis of the next fifty years, an increasing number of large-scale wind farms are integrating into powersystems. Parallel simulation platforms are indispensable to evaluate the effects of wind farm...
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ISBN:
(纸本)9781479936571
Due to the energy crisis of the next fifty years, an increasing number of large-scale wind farms are integrating into powersystems. Parallel simulation platforms are indispensable to evaluate the effects of wind farm integration. A GPU-based parallel simulation platform is constructed in this paper to test the feasibility of simulating integration systems on GPU. By adopting previous research work such as averaged model and improved EMTP algorithm, models and algorithm of the platform are firstly introduced. Then the hardware and software architecture of the platform are put forward, which combine CPU configuration and GPU computing. Finally, a wind farm with different numbers of DFIGs are used to test the performance of the platform. Results show that the platform has excellent accuracy, efficiency and scalability. The work of this paper proves the feasibility to simulate wind farm integrating dynamics adopting GPU and its potential to reach tremendous efficiency and scalability.
In the conventional phase-shift control of isolated bidirectional DC-DC converters, the phenomenon of power backflow is quite obvious. General improved phase-shift control methods can reduce the power backflow of the ...
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ISBN:
(纸本)9781479957774
In the conventional phase-shift control of isolated bidirectional DC-DC converters, the phenomenon of power backflow is quite obvious. General improved phase-shift control methods can reduce the power backflow of the input. However, they do not take the power backflow of the output into consideration. In this paper, a novel phase-shift control of isolated bidirectional DC-DC converters for unidirectional power flow is proposed. It can eliminate the power backflows of both the input and the output at the same time. Furthermore, the converters in the proposed phase-shift control can achieve the zero-current switching in the whole power rang. Experimental results from a prototype verify the feasibility and validity of the proposed control method, and show superior performance.
Low voltage distribution network usually operates under three-phase unbalanced conditions. And the distributed generators (DGs), integrated with distribution network, show different behaviors under different control s...
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This paper describes several methods for condition-based maintenance,introduced CBM,RCM development process,the main theoretical logic,techniques and *** on the health index based on equipment maintenance strategies,n...
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This paper describes several methods for condition-based maintenance,introduced CBM,RCM development process,the main theoretical logic,techniques and *** on the health index based on equipment maintenance strategies,namely *** on the development of narrative context,theoretical foundation,model healthy *** for its application in power transformers were introduced.
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