Zeng L.,Hebei Electric Power Research Institute |
Wang F.,Hohai University |
Liu D.,Hohai University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2011
The optimal layouts of wind turbine-generator (WTG) in wind farm are influenced by WTG wake when the site of wind farm is selected. At present, the research achievements in China and abroad on WTG wake and overlay model in actual wind farm mainly focus on one-dimension linear model. Aiming to improve the situation, more complete reasonable WTG wake model was constructed and its boundary in wake was nonlinear with the distance. In addition, according to actual circumstance in WTG wake, different fuller WTG overlay models were built to adapt to the situation of existing wind farm. The comparison results of engineering examples with 3-dimension numerical simulation show that the wake and overlay model in WTG proposed in this paper are more reasonable and it can effectively improve the generation benefit of wind farm. © 2011 Chin. Soc. for Elec. Eng.
State Grid Corporation of China, Hebei Electric Power Research Institute and Hebei Electrical Power Commissioning Institute | Date: 2014-06-24
A system for staring a large-scale power load in a micro grid comprises a PCC grid connection switch, a micro grid alternating-current bus, an active power filter (APF), an energy storage inverter, an energy storage battery, a current-limiting resistor R, contactors K1-K3, a time relay KT, a power supply relay board, a micro grid maser control system, a frequency converter rectifying circuit, a frequency converter filter circuit, and a frequency converter inverter circuit. There are the advantages: an output torque of a power load can be effectively improved by using a variable frequency starting apparatus, and a starting current is also small; the provided method can effectively reduce a harmonic current when a variable frequency starting apparatus starts a power load, the phenomenon that two power sources supply power on a direct-current side of the variable frequency starting apparatus at the same time is avoided, thereby improving the stability and the economy of a micro grid.
Ma L.,Ordnance Engineering College |
Kang J.,Ordnance Engineering College |
Meng Y.,Hebei Electric Power Research Institute |
Lv L.,62191 Troops of PLA
Yi Qi Yi Biao Xue Bao/Chinese Journal of Scientific Instrument | Year: 2013
Aiming at the problem that at early stage of bearing fault, the feature components of the original vibration data are easy to be submerged in noise signal and can not be detected in time. According to the de-noising principle of Morlet wavelet transform, a method is presented, which determines the optimal scale parameter based on scale related power distribution, so that the signal is filtered under this scale and the impact feature components are extracted. The main filtering procedures include: the minimum Shannon entropy is used to optimize the Morlet wave shape factor, the best match between mother wavelet and signal fault feature is realized; the scale-power spectrum is plotted with the wavelet transform coefficients of the best Morlet continuous wavelet under different transform scales; and according to the accumulative characteristic of the fault feature power in specific scale range, the scale parameter with best filtering effect is selected from the extreme points in the scale power spectrum. The actual processing result for bearing full lifetime vibration datasets shows that the proposed method can extract the weak feature components and detect the existence of related outer-race fault in advance compared with root-mean-square trend. So this method can be regarded as an effective approach for diagnosing bearing incipient fault.
Zhao Z.-B.,North China Electrical Power University |
Suo Z.-G.,Hebei Electric Power Research Institute
Gaodianya Jishu/High Voltage Engineering | Year: 2011
In accordance with the arbitrarily disposed grounding electrodes, taking the effect of grounding grid into account, we put forward a new method to inverse the parameters of horizontally stratified soil model on the basis of the Green function of horizontal multiple-layer soil and the calculation model of grounding grid with unequal spacing. The proposed method can be used in later expansion of station to select measurement electrode and the minimum distance of grounding grid in soil parameter measurement. In the validation of the method, the effectiveness of the equal-spacing four-electrode method, straight four-electrode method, and arbitrary four-electrode method is evaluated. By taking a simple grounding grid as example, the inversed soil model and grounding resistivity are compared for the cases with and without consideration of grounding grid. The effective range of the grounding grid is defined. It is required that, on the premise of measurement standard, the space between the connection line of measurement electrodes and the grounding gird edge is not less than 0.618 times that of the diagonal the grounding gird.
Ma W.,Chongqing University |
Wang M.,Chongqing University |
Li C.,Hebei Electric Power Research Institute
Nonlinear Dynamics | Year: 2012
One-cycle controlled Cuk converter is a piecewise smooth nonlinear system. In this paper, sampled-data model is applied to analyze the dynamics of this converter. The results show that the four eigenvalues of the converter can be two pairs of complex conjugates, and that one pair may move out of the unit circle as some parameters are varied. This causes occurrence of slow-scale oscillation as a result of the Neimark-Sacker bifurcation in the input stage of the converter. Bifurcation may jeopardize the performance of the converter by decreasing the efficiency. A washout filter is used to control the bifurcation so as to stabilize the converter, and the effects of parameters of the filter on the stability of the converter are analyzed. Experimental measurements are provided to verify the analytical results. © 2011 Springer Science+Business Media B.V.
Chunxi L.,North China Electrical Power University |
Ling W.S.,North China Electrical Power University |
Yakui J.,Hebei Electric Power Research Institute
Energy Conversion and Management | Year: 2011
The influence of enlarged impeller in unchanged volute on G4-73 type centrifugal fan performance is investigated in this paper. Comparisons are conducted between the fan with original impeller and two larger impellers with the increments in impeller outlet diameter of 5% and 10% respectively in the numerical and experimental investigations. The internal characteristics are obtained by the numerical simulation, which indicate there is more volute loss in the fan with larger impeller. Experiment results show that the flow rate, total pressure rise, shaft power and sound pressure level have increased, while the efficiency have decreased when the fan operates with larger impeller. Variation equations on the performance of the operation points for the fan with enlarged impellers are suggested. Comparisons between experiment results and the trimming laws show that the trimming laws for usual situation can predict the performance of the enlarged fan impeller with less error for higher flow rate, although the situation of application is not in agreement. The noise frequency analysis shows that higher noise level with the larger impeller fan is caused by the reduced impeller-volute gap. © 2011 Elsevier Ltd. All rights reserved.
He L.,Hebei Electric Power Research Institute |
Hao X.-G.,Hebei Electric Power Research Institute
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010
The necessity of communication network testing in digitalized substation is analyzed. By referring to the acceptance test specification for LAN systems GB/T 21671-2008, communication network testing items and testing methods in digital substation are proposed. Two testing examples are given, including optical power testing and the switch latency and frame lost testing. The testing results are analyzed too. At last the prospect of test technology of communication network is analyzed.
Hebei Electric Power Research Institute and Hebei Electrical Power Commissioning Institute | Date: 2015-09-27
Provided are an anti-islanding method for a distributed generator in a direct current distribution grid and an anti-islanding device therefor. The method includes: feeding an alternating voltage component into an output end of the AC/DC interface transverter, a frequency of the alternating voltage component being less than the power frequency; sampling a first voltage signal of an output end of the DC/DC transverter; extracting a first effective value of an alternating signal included in the first voltage signal; comparing the first effective value with a first preset voltage; and controlling the distributed generator to stop operation, in a case that it is determined that the first effective value is less than the first preset voltage, which indicates that islanding occurs for the distributed generator.
Hebei Electric Power Research Institute | Date: 2011-09-16
A method for calculating a primary time constant of a power grid. It comprises the steps of: establishing an electromechanical transient model of the power grid using the widely used power system analysis software package (PSASP) according to the actual power grid parameters and network topology; establishing an electromagnetic transient model under PASAP using the actual power grid parameters for a site which requires the calculation of the primary time constant of the power grid, and setting a ground short circuit fault at the site; obtaining a transient short circuit current of the short circuit point of the power grid using a hybrid simulation method of the electromechanical and electromagnetic transient models; filtering out a periodic component in the transient short circuit current to obtain a non-periodic component attenuated with time, and finding the attenuation time constant of the non-periodic component which is the primary time constant of the power grid.
Jia B.,Hebei Electric Power Research Institute
Gaodianya Jishu/High Voltage Engineering | Year: 2012
To obtain ageing conditions of composite insulators after being operated, six composite insulators of three manufacturers are selected to perform hydrophobicity test, Fourier infrared spectroscopic analysis, thermoanalysis, and scanning electron microscope (SEM) detection. The results indicate that, hydrophobic groups, Si-CH 3 and -CH 3, of silicone rubber surface are less than those of inner part. -OH group has not obvious rule between surface and inner. Hydrophobic groups, Si-CH 3 and -CH 3, can be used as indicator of hydrophobicity variation, but -OH can not be used for this purpose. The composition of surface and inner layers of new composite insulator is similar. The inorganic compound of surface and inner layers of operated insulator has not obvious rule. The high polymer of surface and inner decreases with time, and the mass of inner is more than that of surface layer. For low molecular weight compound, the mass of surface layer is more than that of inner layer. Operation time affects SEM result to some extent. The hydrophobic level of new composite insulators belongs to HC1, and the hydrophobic level of operated composite insulators belongs to HC2~HC3. Different sheds or different positions of composite insulator may have different hydrophobicity.