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Li H.,Shanghai University of Electric Power | Jin Y.,Shanghai University of Electric Power | You D.,Shandong Power Dispatching Center | Zhu Z.,Shandong Electric Power Research Institute
Advanced Materials Research | Year: 2012

Hopf bifurcation is regarded as one of the three kinds of bifurcations which can cause voltage instability. The Hopf bifurcation was obtained if a pair of complex conjugate eigenvalues of Jacobian matrix crossing the imaginary axis. To calculate the critical eigenvalues of bulk power system, a restarted-refined Arnoldi method is introduced. The refined Ritz vectors are used as the approximations based on the refined projection theory in order to enrich the information of the eigenvectors in the projective subspace. Two examples indicate that the method can work out a set of conjugate eigenvalues which will show whether the Hopf bifurcation appears and provide the datum for the dynamic voltage stability analysis ulteriorly. © (2012) Trans Tech Publications, Switzerland. Source


Li H.,Shanghai University of Electric Power | You D.,Shandong Power Dispatching Center | Gao Y.,Qinhuangdao Power Supply Company | Shen L.,Qinhuangdao Power Supply Company | Wang Z.,Qinhuangdao Power Supply Company
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2013

A continuous method to calculate the Hopf bifurcation in small disturbance is presented. The second-order sensitivities of the selected eigenvalues with respect to loads variation which have more perfect linear behavior are computed and used to determine the step size of the continuation method. For lightly loaded conditions, it is expected that a small variation in the load would result in a small variation in the operation point which is far away from the HB point. Therefore, the step size could be larger. On the other hand, when the operation point is close to the HB point, a smaller step should be defined otherwise the HB point may be overleaped. Source


Wang H.,Shandong University | He C.,Shandong University | Fu L.,Shandong Power Dispatching Center
DRPT 2011 - 2011 4th International Conference on Electric Utility Deregulation and Restructuring and Power Technologies | Year: 2011

This paper study the power system restoration procedure with external power supplies through HVDC transmission channel. The simplified models of the transmission system under different control modes are established and their stability margin are analyzed by root locus diagram. In consideration of the influence of the short circuit capacity and rotating inertia of power grid at sending end on the stability of HVDC control system, selection and coordinated strategies of HVDC control modes are given during different stages of system restoration. The procedure of power system restoration with HVDC supporting include two phases, phase I is DC line connecting to weak AC system in the receiving end and phase II is load picking up with HVDC power supporting. In phase I, the adaptability of general HVDC control modes are analyzed, and the appropriate control modes are given. In phase II, the control modes transfer strategies are given under large voltage declining during the receiving end AC system is weak. In both of the two phases, detailed stability analysis are carried out for checking the key controller parameters setting. For accelerating load restoration, the amount of load that can be restored once a time for different short circuit capacity of power grid at sending end and receiving end is analyzed. Last, the effectiveness of HVDC stability mechanism analysis is validated by the simulation of Ningdong-Shandong HVDC system using PSCAD/EMTDC. © 2011 IEEE. Source


Liu X.,Shandong University | Liu Y.,Shandong University | Qiu X.,Shandong Power Dispatching Center
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2012

The influence of Yindong 660 kV DC block fault on power system stability in the initial stage of UHV AC project is analyzed. It is proposed to shed part of Shandong Power Grid loads after the DC bi-polar block to reduce the power transmission from Central China Power Grid to North China Power Grid for system instability prevention. The corresponding load shedding control system is designed, which computes the loads to be shed in real time according to the operating condition of power grid and selects the proper substations for load shedding based on the nature of loads. Compared with the bisection method, the critical shedding load search based on the string cut method more rapidly determines the loads to be shed in Shandong Power Grid after DC block fault. Source


Wang H.,Shandong University | Liu X.,Shandong University | Chen Z.,North China Grid Company | Fang G.,Shandong Power Dispatching Center | Fu L.,Shandong Power Dispatching Center
Dianwang Jishu/Power System Technology | Year: 2013

To utilize the advantage of traditional universal generating function (UGF) method in fast and simple calculation and remedy the defect of dissatisfied accuracy of evaluation results by this method due to neglecting the influence of time-sequence in the application, based on improved traditional UGF method a probabilistic production simulation algorithm is proposed and applied in probabilistic production simulation of power system connecting with wind farm. Firstly, a method combining principal component analysis (PCA) with hierarchical cluster analysis is adopted to obtain typical time-sequential samples of wind power output; then a UGF model for wind power output is established by apportionment in average. During the establishment of the UGF model, by means of choosing proper common factor the state values are turned into integral multiples of common factor to effectively restrain the exponential growth of state number and alleviate the explosion of state number. Secondly, the UGF modeling of post-clustering time-sequential wind power output mode is performed to obtain time-sequential UGF model of wind power output, which can incarnate both fluctuation and uncertainty of wind power output, thus the insufficient representativeness of wind power features based on traditional UGF method due to neglecting time-sequence characteristic is overcome. Finally, the effectiveness of the proposed algorithm is verified by modified IEEE-RTS 79 system. Source

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