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Ou Z.,University of Jinan | Cheng X.,University of Jinan | Zong X.,University of Jinan | Zhang J.,University of Jinan | Hou G.,Heze Power Supply Company
Dianli Xitong Zidonghua/Automation of Electric Power Systems

The number of measurements is often smaller than that of states in harmonic state estimation (HSE). This is a difficulty in HSE, which makes the measurement-state equation underdetermined, and the system incompletely observable. In light of the problem, three aspects are studied in this paper. Firstly, the equation is turned from underdetermined to determined or even overdetermined by combining mathematical analysis and power system analysis, and proceeding from reducing the quantity of states. On the premise that system complete observability, is ensured, the number of measurement will be greatly reduced. Secondly, singular value decomposition (SVD) is applied to finding the observable islands and their calculation. Thirdly, by referring to the matrix condition number, a practical linearly independent ranking method is proposed. The method is applied to guiding the adjustment and increase of equipment to realize fine observability. Finally, the Heze-Fangshan 220 kV-110 kV-35 kV distribution system is presented to illustrate the application of SVD and the proposed method. ©, 2015, State Grid Electric Power Research Institute Press. All right reserved. Source

Cheng X.-G.,University of Jinan | Zhang M.-H.,University of Jinan | Zong X.-J.,University of Jinan | Ren H.-W.,University of Jinan | And 2 more authors.
Dianji yu Kongzhi Xuebao/Electric Machines and Control

The three-phase APF was modeled as a switched affine system. Then, based on the space voltage vector diagram and waveform of three phase supply voltage, three phase supply voltage was divided into six sectors. In each sector, according to convex combination stability condition, a switching subsystem combination which met secondary stability condition was set up. Meanwhile, a common Lyapunov function was selected. From the stability theory of switched systems, the subsystem of the combination, which has minimum derivative of Lyapunov function, was selected. Finally, the validity of proposed control method was confirmed by Simulink and experimental results. ©, 2014, Editorial Department of Electric Machines and Control. All right reserved. Source

Zhao Z.-T.,Shandong University | Zhang D.-H.,Shandong University | Li Y.-S.,Heze Power Supply Company | Liu Y.,Shandong University | Sun D.-D.,Shandong University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control

System parameters such as the inter-harmonic impedance are crucial to the identification of inter-harmonics sources. To suppress the effects of colored noise in the voltage and current signals, a method based on generalized least squares is proposed to estimate system parameters for the first time. This method eliminates the effect of the correlation between variables by converting the colored noise to the white noise firstly, and then carrying out parameters estimation with the converted data, which reduces inter-harmonic impedance estimation error compared with the conventional regression method. In addition, this paper introduces quantitative index to quantify the responsibilities at both sides combined with the national standard. Simulation analysis and practical testing data prove the method effective and feasible. Source

Duan D.-P.,Beijing Electrical Power Research Institute | Zhao C.-N.,Heze Power Supply Company | Zhan H.-M.,North China Electrical Power University | Zheng S.-S.,North China Electrical Power University
Gaoya Dianqi/High Voltage Apparatus

In order to detect the UHF signal of GIS inner partial discharge, it's necessary to install partial discharge sensor on the metal flange pouring hole of basin-type insulator, which will produce influences on the electric field of basin-type insulator surface. To study the effect of the dimension and structure of pouring hole of metal flange to the electric field of basin-type insulator surface, ANSYS is adopted to calculate the electric field of basin-type insulator of 252 kV three phase in three tank type GIS. The simulation results show that the structure of pouring hole has a significant effect on the electric field of basin-type insulator surface. The dimension of pouring hole of metal flange has few influence on the electric field of basin-type insulator surface. Compared with no pouring hole, the maximum electric field of basin-type insulator surface increases by 3.21%, which achieved the anticipated target. Source

Zhang Y.-F.,University of Jinan | Cheng X.-G.,University of Jinan | Zong X.-J.,University of Jinan | Guo B.-Z.,CAS Academy of Mathematics and Systems Science | And 2 more authors.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control

In view of the compensation error of Active Power Filter(APF) due to the traditional linear control strategy, a novel control approach of APF is proposed by using the switched system theory of nonlinear dynamics. Firstly, the accurate model of switched system of APF is established. On this basis, a switched system error model is established using APF balance state. After that, a reasonable switched path is designed as the system control input. The proposed approach ensures the error converges to zero and the compensation current tracks the reference accurately. Finally, by comparing with the traditional control strategy, the effectiveness and rationality of the approach proposed are shown by the simulation and comparison. Source

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