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Liu L.,Hubei Engineering University | Lin T.,Hubei Engineering University | Xu X.,Central China Electrical Power Dispatching and Communication Center
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2012

In order to make synchronized phasor measurement meet the accuracy requirements under dynamic conditions, a complex bandpass-filtering algorithm was proposed. Its measurement bandwidth and group delay corresponding to various phasor-uploading rates were provided to make the method be able to output amplitude modulated components without distortion, restrain the out-of-band interference and have short dynamic response time. Based on acquired phase angles, the weighted least squares (WLS) was applied, instead of traditional derivation operation, to improve frequency measurement robustness. Simulation and field test results show that the proposed method complies with the level 1 of IEEE Standard C37.118-2005 under steady state, and has high accuracy under dynamic conditions. In addition, the method has small amount of computation and is fast enough for online application. © 2012 Chin. Soc. for Elec. Eng. Source

Yu G.,Hubei Engineering University | Yu G.,Hubei Collaborative Innovation Center for High Efficient of Solar Energy | Lin T.,Hubei Engineering University | Lin T.,Hubei Collaborative Innovation Center for High Efficient of Solar Energy | Xu X.,Central China Electrical Power Dispatching and Communication Center
IET Conference Publications | Year: 2015

Probabilistic harmonic power flow (PHPF) is the basis of evaluating the impact of new energy integration to the grid. A PHPF scheme based on 2m+1 point estimate method (2m+1 PEM) was proposed in this paper on account that the uncertainties of injected harmonic current amplitudes and phases caused by intermittent and volatile new energy power generation device connected to the electricity grid. This method avoids the establishment analytic form relationship between input random variables and output random variables. According to the high order moment of sample data to makeup estimation point, the expectation, variance and other statistical information of branches could be calculated. Actual example is adopted to validate the method described in this article and result show that the accuracy of this method is similar to the ratio of the Monte Carlo simulation method in the case of less calculated amounts. As a comparison of interval analysis method (IAM), the results are more scientific and reasonable. Moreover, considering double uncertainties including amplitude and phase of harmonic injection source matches the practice better. Source

Liu L.,Hubei Engineering University | Lin T.,Hubei Engineering University | Xu X.,Central China Electrical Power Dispatching and Communication Center | Yu G.,Hubei Engineering University | Chen R.,Hubei Engineering University
International Transactions on Electrical Energy Systems | Year: 2015

A novel scheme based on the complex atom transform (CAT) for detection of subsynchronous oscillations (SSO) is proposed in this paper. SSO components and the fundamental are closely spaced in frequency domain causing the possibility of aliasing. Some conventional SSO detection methods share the problems of low mode resolution and slow dynamic response. The CAT has flexible window in time-frequency domain. By adjusting the window of the CAT, the scheme can achieve high multi-mode resolution, desirable accuracy and fast dynamic response when analyzing multi-mode SSO waveforms to facilitate multi-mode SSO suppression. First step of the scheme is to use the CAT to obtain oscillation frequencies and envelope curves of SSO waveforms. The least squares (LS) method is then deployed to measure initial oscillation amplitude and damping ratio from the envelope curve. The effectiveness and correctness of the proposed scheme are verified with simulations using both an artificially generated signal and the IEEE First Benchmark Model. Compared with the conventional methods, such as the continuous wavelet transform (CWT), the scheme has higher mode resolution, more desirable accuracy and faster dynamic response. In addition, the scheme is simple and the computation burden is low; thus, it is easy to be implemented for online application. Moreover, the CAT-based scheme can also be used for synchrophasor measurements; hence, the scheme can be integrated into phasor measurement units (PMU), which are installed in generator terminals. Copyright © 2013 John Wiley & Sons, Ltd. Source

Ding S.,Wuhan University | Lin T.,Wuhan University | Zhai X.,Wuhan University | Xu X.,Central China Electrical Power Dispatching and Communication Center | And 2 more authors.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2016

In order to accurately analyze the running features of load nodes with large-scale new energy sources access to the grid, according to the Thevenin equivalent theory, the electric network system including large-scale new energy sources can be equivalent to 3 nodes. On the basis of the equivalent system, the state vulnerability assessment method and index based on short-circuit capability for load nodes are built up, which makes the system of state vulnerability assessment more perfect. Based on the results of state vulnerability index, the PAM clustering algorithm and Homogeneity-Separation (HS) index are used to find out the nodes which need more attention. In addition, the improved IEEE-39 node system is simulated and analyzed. The result is compared with that of traditional voltage margin index assessment, simulation shows the effectiveness of this state vulnerability assessment method based on short-circuit capability and the rationality of using the PAM clustering algorithm to identify weak nodes, which have the application of on-line prospect. © 2016, Power System Protection and Control Press. All right reserved. Source

Zhang J.,Hubei Engineering University | Lin T.,Hubei Engineering University | Yu G.,Hubei Engineering University | Chen R.,Hubei Engineering University | And 2 more authors.
Dianwang Jishu/Power System Technology | Year: 2014

To improve small signal stability of power system the coordinated optimization strategy among damping controllers is researched. A mode, which is selected and to be improved, is taken as the target mode and taking the maximized damping ratio under the target mode as the optimization objective an optimization model is established, and the coordinated optimization of damping controller parameters is performed by a cloud model theory based improved plant growth simulation algorithm (PGSA). Through improving search step-length and adding cloud model theory into the iterations both search efficiency and convergence speed of the improved PGSA are increased, meanwhile the defect that conventional PGSA is not suitable to the optimization of continuous functions is remedied. Farther, based on the calculation case of large-scale power grid and taking the local and interregional low-frequency oscillation modes as objectives respectively the parameters of damping controllers are optimized, and simulation results show that the proposed method is valid. Source

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