North China Power Dispatch Center

Beijing, China

North China Power Dispatch Center

Beijing, China

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Wang M.,North China Power Dispatch Center | Bao J.,North China Power Dispatch Center | Qi X.,Beijing Electric Power Company | Zhang Z.,North China Power Dispatch Center
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2010

Accurate power system parameters are the foundation to form a reliable power system model, which is essential for state estimation, power flow and contingency analysis, network losses analysis, stability analysis and protective relay setting calculation. Based on uniform transmission line equations and ∏-type equivalent circuit equations, and on the assumption that voltage phasors and current phasors at both ends of a transmission line are known, the methods to calculate transmission line distributed parameters and accurate ∏-type equivalent circuit parameters are given. Based on phasor measurement unit (PMU) measurements and statistical theory of normal distribution, an algorithm for on-line estimation of transmission line parameters is presented. Examples based on wide area measurement system (WAMS) in North China Power Grid show that the proposed methods are accurate and reliable. ©2010 State Grid Electric Power Research Institute Press.


Huang H.,North China Electrical Power University | Song X.,China Mobile | Zhang Z.,North China Power Dispatch Center | Niu S.,North China Power Dispatch Center
Dianwang Jishu/Power System Technology | Year: 2011

Based on security isolating devices of power system a new method to implement multi-protocol information exchange and load balance is proposed. By means of setting component interface models at both ends of the security isolating device, it is just needed for the application system in security zones I or III to open appropriated application services; without any encoding and based on the service proxy the messages in the form of file can be sent to corresponding request ends in the security zone III or I. The proposed method can support concurrent access among multiple security isolating devices, thus the operating efficiency of the communication system can be improved.


Wang M.,North China Power Dispatch Center | Gao X.,North China Power Dispatch Center | Wang B.,North China Power Dispatch Center | Niu S.,North China Power Dispatch Center
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2011

Early-warning of potential sub-synchronous oscillations is essential to ensure the security of generation units and the stability of corresponding power grid. Based on the principle of phasor measurement unit (PMU), the impact of sub-synchronous oscillation on synchronous phasor measurement can be expressed as amplitude and phase angle modulation of synchronous phasor. Online monitoring and early-warning method for the sub-synchronous oscillation based on PMU measurements is given as well. Simulation and practical examples based on wide area measurement system (WAMS) at North China Power Grid show that the method proposed is feasible and reliable. © 2011 State Grid Electric Power Research Institute Press.


Wang M.,North China Power Dispatch Center | Qi X.,North China Electrical Power University | Niu S.,North China Power Dispatch Center | Han F.,North China Power Dispatch Center
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2011

Based on phasor measurement unit (PMU) measurements, an online algorithm is presented to calculate power transformer's winding reactances and transformation ratio. It is found that due to the random error of PMU measurements, the multi-period parameter calculation results comply with a normal distribution. Furthermore, based on the statistics theory of normal distribution, a robust parameter identification algorithm is proposed to give confidence interval and point estimation of transformer's parameters and transformation ratio. Considering that low voltage side of three-winding transformer is usually connected with reactive power compensation devices, the algorithm can precisely identify the tap changer position without low voltage side PMU measurements. Examples from a wide area measurement system (WAMS) in North China power grid show that the methods proposed is feasible and reliable. © 2011 State Grid Electric Power Research Institute Press.

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