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Chen G.,Southern Research Institute | Chen G.,Chongqing University | Wu X.-C.,China Southern Power Grid Dispatch and Communication Center | Liu Y.-J.,Southern Research Institute | And 4 more authors.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2011

Frequency Domain Decomposition(FDD) is introduced to identify low-frequency oscillation modes by analysis of steady-state ambient measurements in power system and some modifications to FDD are made.The relation expression between maximum singular value of PSD matrix and system eigenvalue under poorly damped mode is presented by detailed derivation of the relations among frequency response function(FRF), output power spectral density (PSD), and system eigenvalues.Modal Amplitude Coherence (MAC) is used to determine mode area size in the neighborhood of peak point on maximum SVD curve. Finally, the exact modal frequency and damping ratio can be estimated using least square method.The technique is illustrated on linear time-invariant system, WECC 9-bus system and ambient PMU measurements, to show its effectiveness.The suggested method is suitable for identification of poorly damped oscillatory modes, and is robust to noise, and has important value for real-time application.

Bi Z.-D.,NARI Group | Huang H.,China Southern Power Grid Dispatch and Communication Center | Wang X.-B.,NARI Group | Yu Q.-Y.,NARI Group | And 6 more authors.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2011

Based on online stability control decision-making technology, the on-line pre-decision system of China southern grid is developed, which is a combination of power system stability analysis, stability judging, fault pre-warning and control calculation. The system achieves the functions such as steady stability, transient stability, dynamic stability analysis and refreshing the control strategy in stability control devices. The hardware of the system is composed of database server, computation servers, Web server, monitoring and maintaining terminals, disc array, communication device, firewall, physical isolation device, communication machine, and stability control device. All analysis program is developed in C++ language, and it can support Windows and multiple types of Unix. Multi-thread algorithm, distributed computation and early termination technology are adopted to ensure the online computation speed, and the computation precision is demonstrated by comparing with the BPA transient stability computation programme.

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