This paper studied GPS carrier phase technology for short baseline attitude determination.Aim at the measurement error generated by the noise and multi-path problem from the received signal,for existing integer ambiguity algorithm computing needs a long period of initialization time,first we established the basic model between GPS satellite differential observation equation and the geometry baseline the,then discussed the basic model combined with GPS carrier phase technology oriented principle,in the framework of short baseline attitude determination.By making full use of geometric constraints and least-squares ambiguity search algorithm,the study gave the method of selecting the master-slaves satellites used by short baseline attitude determination with single epoch data.The method avoids the carrier phase cycle slips and solves the problem which former solutions need a long time for initialization.The static experiment result shows that the method is more rapid and effective.It meets the accuracy requirement and provides reasonable scheme for the design of high accuracy GPS orientation.

This paper proposed a simple and effective method to remove haze from a single input image degraded by bad weather.First,it estimated the airlight by using dark channel prior knowledge.Then,under a mathematical model for describing the formation of a hazy image,the depth of field of each pixel was sampled to get a virtual haze-free image sequence.Finally,an exposure criterion introduced by exposure fusion algorithm was used to extract a haze-free image from the image sequence by multi-scale fashion image fusion method.The experimental results show that the proposed method can yield good results and it is appropriate for real-time applications.

Adding stabilizer to UPFC (Unified Power Flow Controller) can improve the power system dam-ping level,but its selection of installation position and feedback signal has great influence on the control effect. A 9-order mathematical model of UPFC with stabilizer is established,which considers the dynamic response of capacitor voltage,the bus voltage control,the DC voltage control and the power flow control,describing the effect of stabilizer on UPFC performance in detail. The stabilizer could be installed at parallel or serial side of UPFC. The state equations are derived based on the established model for a multi-machine power system with UPFC,and the optimal installation position and the effective feedback signal of the stabilizer are calculated with the equations. Simulation for a two-area power system with weak link is carried out using EMTDC and results show that the stabilizer designed by proposed method improves the damping level significantly.

The main function of STATCOM is voltage control. Corporated with stabilizer,STATCOM damps system power oscillation. After the dynamic function of STATCOM with stabilizer is deduced, the dynamic characteristics of STATCOM are described with 5 -order state equations. With the information of state equations,the STATCOM,which can improve the damping level of power system, is determined. The effective damping signals are further analyzed and a multi -signal stabilizer is designed. With a simulation example,the effectiveness of the designed multi -signal stabilizer is verified by the Eigenvalue analysis,as well as by the time -domain analysis of EMTDC.

为了解决局放信号自身和监测系统框架方面的诸多问题,笔者将分布式人工智能技术应用于发电机局部放电在线监测,构建了一个局部放电在线监测Multi-Agent系统.针对局放数据评估中的预处理、特征提取、趋势和指纹分析,本文分别给出了相应的处理方法及流程,基于此,给出了构建整个系统的框架及单个Agent的设计细节.分析表明,所设计的Multi-Agent系统相比其他局放在线监测系统有诸多优点.

By analyzing the state equations of unified power flow controller (UPFC) stabilizer, the influence of UPFC stabilizer on electromagnetic torque of synchronous generator is presented. Synchronizing torque and damping torque of synchronous generators are two main factors in influencing the stability of power system. In view of the possibility of worsening system synchronizing torque while improving the system damping torque by UPFC stabilizer, the parameters of UPFC stabilizer are optimized by using maximum torque area. Larger torque area could maintain enough synchronizing torque and damping torque. The optimized UPFC stabilizer can improve the synchronizing torque as well as damping torque, and therefore, improve the stability significantly. The EMTDC simulation results for an example demonstrate the efficiency of the method proposed.

Synchronizing torque and damping torque of a generator are two main factors influencing the stability of a power system,and they are organically combined with torque area.A novel method to calculate the torque area is proposed.In light of maximun torque area principle,the design of STATCOM stabilizer is optimized,and the problem of synchronizing torque being deteriorated by STATCOM is solved.When the stabilizer is put into place,it can maintain enough synchronizing torque and damping torque at the same time.This will significantly improve the stability of a system.The simulation results on EMTDC demonstrate the effectiveness of the proposed method.

Similarity rates are introduced in the interpretation of partial discharge data to analyze its stability, which is based on 26 phase distribution characteristic parameters of the fingerprint of partial discharge. With the distribution plot of similarity rates, the stability of partial discharge is analyzed. Combined with time domain signal and moment analysis, two practical cases are studied to investigate the relation between partial discharge stability and similarity rate distribution. When the similarity rate distribution plot has only one main peak or shows a tub curve, the discharge is stable, however, when two distinct main peaks occur, more attention should be paid. Results demonstrate that the similarity rate distribution plot can effectively reflect the stability of partial discharge.

For evaluating the partial discharge extent of generator,as far as the two dimensional phase resolved plots were concerned,a new type of plot,namely Sk-Ku plot,was constructed.Furthermore,the Sk-Ku plot was put into the cross analysis of partial discharge detected from two practical generators.The results analysis demonstrate that,Sk-Ku plot can effectively reflect the partial discharge extent and partial discharge derived from different generators can be compared to some extent.Sk-Ku plots of discharge magnitude and count take on the character of conic,what is more,with the increase of partial discharge,the Sk-Ku plots show the trend of shifting from 1,2 quadrants to 3,4 quadrants.In addition,the distribution range of the data decreases significantly.

Errors in IFFT(Interpolating Fast Fourier Transform) are analyzed and the signal phase is demonstrated as the main cause.It is pointed out that the algorithm applied to complex signal could not be applied to real signal.A high precision IFFT algorithm is thus presented,which corrects the spectrum of FFT to improve its precision based on FFT.Using the useful information of FFT and considering the spectrum difference between complex signal and real signal,it adopts a series of math transforms to overcome the influence of signal phase.As a result,the precision of harmonic analysis is improved without obvious increase of calculating time.Since the complex iteration and special data sampling are not necessary,the requirements for hardware are not strict in implementation.The precise magnitude,phase and frequency of harmonic components in real signal are achieved by analysis.An instance verifies its correctness and higher precision.

Influenced by factors such as different discharge mechanisms and transmitting routes, partial discharge signals can have multiple waveforms. Under such circumstances, single scaling function based wavelet cannot work. To solve the problem, in this paper a multiple scaling functions based multi-wavelet algorithm is introduced. A large number of simulations have been carried on in the paper for different forms of partial discharges. Noise-reduction performance of the proposed multi-wavelet algorithm under different PD modes is investigated by using the mean square error as the criterion to achieve optimal parameters in noise reduction. Extracting of multi-mode partial discharge signals and comparison with previously published results are also presented. The results obtained both in simulation and tests demonstrate that the multi-wavelet based algorithm with proper parameters can extract multi-mode partial discharge signals effectively, significantly improve the performance of existing optimal wavelet based and wavelet-set based algorithms.

After briefly introducing the theory of multi-wavelet based on denoising algorithm, it was applied to detect the signals of partial discharge. Partial discharges were nonstationary electric signals with various modes. In the contribution, denoising performance of multi-wavelet and wavelet under different mode of partial discharge were analyzed by Monte-Carlo simulation. Furthermore, the capability of extracting the multi-mode partial discharges was demonstrated. The results show that, compared with wavelet, multi-wavelet depends less on the prior knowledge of partial discharge, can process partial discharge with various modes, and preserves more signal features while removing noise from the measured data.

Based on a brief introduction to empirical mode decomposition (EMD), the theory is applied in analyzing the partial discharge signals. According to the statistical characteristics of intrinsic mode function (IMF) , a new denoising algorithm based on the vector threshold is proposed. Compared with the conventional wavelet based denoising algorithms, the new algorithm is simpler, more flexible, and not limited by the prerequisites of Fourier transform. The results obtained from processing and comparison with the wavelet demonstrate that the new algorithm is capable of effectively suppressing white noise and agrees fairly well with the wavelet based denoising one.

The paper puts forward a new method based on local cosine transform (LCT) to measure the time-varying harmonics in power system. Since the time-frequency window of LCT is localized well and adjustable, the method can quantify the frequency, amplitude and phase of time-varying harmonics more accurately than DFT and STFT. The time-frequency window is adjusted conveniently by using optimum base searching method. Moreover, is not necessary to have stable wave assumption in the window. The simulations and field tests show that LCT is a powerful tool and suitable for practical use.

The paper put forwards a method for selecting signal-adapted wavelet in de-noising. The method is based on constructing compacted orthogonal wavelets with Wu elimination algorithm. A threshold information cost function is used as the objective function during choosing optimal wavelet. The approach is validated by its application to de-noising for on-line PD measurement. The physical experiments and field tests show that the method improves the accuracy of the partial discharge (PD) extraction with less deformation and stronger robustness.

分析了变压器局部放电在线监测中的各种干扰,提出了分层式抑制干扰的处理模型,采用不同的数字信号处理方法分层处理各种干扰,具有结构灵活、易于扩充等特点.现场实验结果表明,该模型可有效、快速地抑制干扰,具有良好的应用前景.

There must be boundary effect when the present common wavelets, such as Symmlet wavelet, Meyer wavelet, are used in fault detection. This paper constructs several average interpolating wavelets with 2, 4, 6, 8 degrees based on Donoho's interpolating wavelet. With their advantage of boundary-correction, these new kinds of wavelet can eliminate the boundary effect significantly and have strong capability to get more concentrated information about fault position.

The effects of TCSC on the power system are discussed. The algorithm is analyzed to control the power flow with TCSC. The results of dynamic system simulation test, calculation and EMTP numerical imitation show that TCSC can effectively control the power flow of line. Through dynamic system simulation test and EMTP numerical imitation, electromagnetic transient is researched. The results show that the electromagnetic transient with TCSC is different from that with the ordinary series compensation in the same power system during fault.

Thyristor controlled series compensation (TCSC) is introduced and TCSC dynamic system simulation is designed and carried out. Based on the test results of TCSC dynamic system simulation, the steady impedance characteristics of TCSC are studied. The effects of modulation inductance and generator output on the impedance characteristics of TCSC are also analyzed. The results of calculation and EMTP simulation show the correctness of TCSC dynamic system simulation.

以补偿度取36%(其中24%不可控、12%可控)的伊敏-冯屯500 kV超高压输电系统为例,研究了以电容器电压为同步信号时可控串联补偿(TCSC)系统的内、外部故障、重合闸、电容重投时的过电压问题.提出了采用常规串补和可控串补相结合的补偿方案时TCSC装置过电压保护的参数整定原则:即以重合闸情况确定可控串补模块中氧化锌非线性电阻(MOV)的整定参数,以外部故障确定固定串补模块中MOV的整定参数,最后以内部故障较核MOV的能量容量.讨论了重合闸和电容器重投时可采取的控制策略.