The development of smart grid has posed a challenge to the traditional centralized dispatch mode. The basic contradiction between distributed autonomy and centralized coordination is reexamined, and an architecture of...
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The development of smart grid has posed a challenge to the traditional centralized dispatch mode. The basic contradiction between distributed autonomy and centralized coordination is reexamined, and an architecture of smart substation advanced application software system is proposed, including such advanced applications as modeling, state estimation, intelligent alarming, voltage stability assessment and control, automatic voltage control, risk assessment modeling, etc. This facilitates a change from centralized dispatch and control mode to a more reliable, agile substation-control center two-level distributed smart dispatch and control mode. The features, functions and realization of the proposed advanced application software are described, some field engineering application cases demonstrated, and certain practical aspects of implementation discussed. Finally, the prospect for future development of the smart substation advanced application software is displayed.
Voltage fluctuations occur frequently in wind farms as a result of wind power perturbation, while reactive powercontrol of various devices is always uncoordinated and often has a time lag when the system operates in ...
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The development of Smart Grid requires more accurate and fast for perception, assessment and control of powersystemstate. Widely installed phasor measurement units (PMU) and mass PMU measurements provide a good foun...
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ISBN:
(纸本)9781479917860
The development of Smart Grid requires more accurate and fast for perception, assessment and control of powersystemstate. Widely installed phasor measurement units (PMU) and mass PMU measurements provide a good foundation for this requirement, because PMU can directly measure bus voltage phasors at the rate of tens of milliseconds. Thus, the number of PMU installed in the power grid and the reliability and accuracy of PMU measurements are of great importance, which directly affect the feasibility and reliability of state perception. Actually, PMU measurements may contain bad data and the accuracy of phase measurements is not high enough. Estimation method is an effective way to deal with data contaminated by noise and bias. In this paper, we proposes the complex number weighted least squares (CWLS) estimation algorithm to process PMU measurements directly in the complex domain to obtain more accurate systemstate. Phasor error characteristics in the complex domain are analyzed depth which shows the proposed algorithm is robust to phase error. Meanwhile, an effective bad data identification method is proposed. Test results demonstrate the performance of the CWLS algorithm from the perspectives of computional efficiency, estimation quality and adaptability to inconsistent measurment errors, the robustness of the CWLS algorithm and the effectiveness of the proposed bad data identification method is also shown in the tests.
The mathematical relationship between reactive power consumed by DC system and AC voltage on inverter bus is derived under different control modes,*** on these relationships,a new definition of multi-infeed short circ...
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ISBN:
(纸本)9781510806474
The mathematical relationship between reactive power consumed by DC system and AC voltage on inverter bus is derived under different control modes,*** on these relationships,a new definition of multi-infeed short circuit ratio(MISCR) is formulated from the power-flow model of PQ decoupled *** specific influence of different control modes on voltage stability is *** the relationship between MISCR and voltage stability of AC/DC hybrid system,the characteristics of values of new MISCR are *** study of an actual regional power grid validates these characteristics.
To solve the problem of reactive power non-coordination among strongly coupled plants, a coordinating method for strongly coupled plants for automatic voltage control (AVC) is proposed. The coupling coefficient among ...
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To improve the prediction accuracy of photovoltaic (PV) power generation, the temperature of PV modules and its prediction is very important. A short-term step-wise temperature prediction model for PV module based on ...
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ISBN:
(纸本)9781510821415
To improve the prediction accuracy of photovoltaic (PV) power generation, the temperature of PV modules and its prediction is very important. A short-term step-wise temperature prediction model for PV module based on Support Vector Machine ( SVM) is proposed in this paper. Firstly, the primary impact factors of PV module temperature are determined in terms of the PV module physical characteristics and the correlation coefficient between each factor and module temperature. Secondly, two kinds of prediction models, direct and step-wise models, are built to predict module temperature respectively. For direct model, the prediction model is based on SVM using the historical data. For step-wise one, the prediction models of the primary impact factors are built at the first step and then the mapping models between module temperature and the impact factors are established. In the end, the deviations of two different kinds of prediction models are analy%ed and discussed based on actual operation data. The results indicate that the stepwise prediction model has better accuracy than the direct prediction model if other things are equal.
Powdered (below 125 μm) activated carbons made by wood (WAC) and coal (CAC) and activated coke (AC), whose BET surface areas were 551, 335 and 484 m 2 /g, respectively, were studied to adsorb organic po...
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Powdered (below 125 μm) activated carbons made by wood (WAC) and coal (CAC) and activated coke (AC), whose BET surface areas were 551, 335 and 484 m 2 /g, respectively, were studied to adsorb organic pollutants from coal gasification wastewater (CGWW). This study initially focused on the equilibrium sorption isotherms of adsorbents for the removal of chemical oxygen demand (COD) from CGWW. Molecular weight (MW) distribution and fluorescence excitation emission matrix (FEEM) were used to determine the difference of CGWW quality. Water qualities of CGWW before and after adsorption by adsorbents were also investigated. The isotherm results showed that Langmuir model fit the adsorption isotherms of activated carbons, while Freundlich model was better for that of AC. CAC and AC had a higher adsorption capacity under lower and higher COD concentration, respectively. It was also found from MW distribution and FEEM results that AC had a prior adsorption to high MW aromatic, refractory compounds in CGWW, which is good for the following biological treatment and suitable for pretreatment. This was because that the mesopores percentage of AC was 63%, which was higher than WAC and CAC.
Single Line to Ground (SLG) faults in non-effectively grounded networks are difficult to detect. Immune to neutral point grounding type, load conditions and system operation conditions, traveling-wave based method is ...
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ISBN:
(纸本)9781467380416
Single Line to Ground (SLG) faults in non-effectively grounded networks are difficult to detect. Immune to neutral point grounding type, load conditions and system operation conditions, traveling-wave based method is an effective fault line identification method. However, due to the strong coupling between the double-circuit lines, the wavefront magnitude of them are the same, and the polarity of them are opposite. Thus, the mal-identification will be resulted under such condition. This paper analyzed the traveling wave characteristics of double-circuit lines, and proposed an improved fault line identification method based on the initial process of zero sequence currents and voltage traveling waves. Tests show that, the proposed method has high effectiveness in fault line identification of double-circuit lines in distribution networks.
Similar to other major electrical apparatuses, the reliability and stability of the dc network is becoming the most important issue when using the voltage-source-converter-based multiterminal dc (VSC-MTDC) system for ...
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Electric railway brings many power quality problems to the public powersystem. In this paper, a new power quality improvement method is proposed which can alleviate the voltage unbalance and low power factor problem ...
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ISBN:
(纸本)9781467371070
Electric railway brings many power quality problems to the public powersystem. In this paper, a new power quality improvement method is proposed which can alleviate the voltage unbalance and low power factor problem of electric systems. The method is composed of a specially connected three phase to two phase transformer and a phase balancing device. The specially connected transformer has the following common characteristic: secondary voltages are equal in magnitude and differ 90 degrees in phase angle. Such transformers include Scott Transformer, Le-Blanc Transformer, and modified Wood-bridge Transformer and so on. The phase balancing device consists of two parts: one is used to regulate the power factor to unity;the other part is to transfer power flow between the two feeders, thus balancing their loads. With the proposed scheme, negative current can be eliminated and power factor can be regulated to unity. The advantage of the new method is that it is very simple and cost-effective. Validity of the proposed method is verified by simulation results. The capacity of the compensation device is also analyzed in the paper.
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