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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.


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.


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.


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.


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.


Xu X.,Central China Electrical Power Dispatching and Communication Center | Lin T.,Wuhan University | Gao Y.,Wuhan University | Zhang F.,Wuhan University
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2013

A method of inter-area mode oscillation prediction based on CBR (Case-Based Reasoning) theory and OAPID (Oscillatory Active Power Increment Distribution) theory is proposed for interconnected power grids, which, based on the measurements of WAMS (Wide Area Measurement System), issues the warning of inter-area mode oscillation before low-frequency system oscillation occurs and provides the advice of system operating mode adjustment during system oscillation to improve system damping. Results of a test for a regional power grid according to its actual WAMS data demonstrate the feasibility and effectiveness of the proposed method.


Yu G.,Hubei Engineering University | Lin T.,Hubei Engineering University | Xu X.,Central China Electrical Power Dispatching and Communication Center | Ye J.,Hubei Engineering University | And 2 more authors.
Dianwang Jishu/Power System Technology | Year: 2015

Probabilistic harmonic power flow (PHPF) is basis of evaluating impact of wind power integration on grid. A PHPF scheme based on 2 m+1 point estimate is proposed on account of uncertainties of injected harmonic current amplitudes and phases caused by intermittent and volatile new energy power generation device connected to electricity grid. This method eliminates establishment of analytic relationship between input and output random variables, dispenses with probability density function of input random variables. According to higher moment of sample data for making up estimation point, expectation, variance and other statistical parameters of branches can be calculated. Actual example is adopted to validate the proposed method and results show that accuracy of this method is similar to that of the Monte Carlo simulation with less calculation time. In comparison with interval analysis method, the proposed method is more scientific and reasonable. Moreover, results considering double uncertainty amplitude and phase of harmonic injection source conform practical situation better. ©, 2015, Power System Technology Press. All right reserved.


Yu G.,Wuhan University | Yu G.,China University of Technology | Lin T.,Wuhan University | Lin T.,China University of Technology | And 3 more authors.
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2016

The operations of smart distribution grid, such as the staged grid-connection of DGs(Distributed Generators), may change the eigenvalues of grid node admittance matrix, resulting in the harmonic resonance mode change and the harmonic resonance frequency shift, which could not be effectively dealt with by the modal analysis method or traditional suppression measures. A strategy of passive filter optimization is proposed, which builds an optimization model with the minimum modal impedance amplitude of target mode as its objective and applies the improved PGSA(Plant Growth Simulation Algorithm) to solve it. With the standard IEEE 14-bus system as a test example, the proposed method is verified and compared with the traditional method, showing its effectiveness and superiority. © 2016, Electric Power Automation Equipment Press. All right reserved.


Bi R.,Wuhan University | Lin T.,Wuhan University | Chen R.,Wuhan University | Xu X.,Central China Electrical Power Dispatching and Communication Center | Ye J.,Wuhan University
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2016

With the rapid development of AC-DC hybrid power system, the risk of cascading failures caused by DC block or line tripping is also increasing. Relevant control measures should be taken to avoid further overload according to the operation status of power grid. In smart grid, HVDC and thyristor controlled series capacitor (TCSC) can also be taken as control measures to further reduce the amount of load shedding. The sensitivity and optimization based methods are often utilized to formulate the security correction strategies. The sensitivity based method functions well in online generation rescheduling and load shedding. However, the power flow sensitivities of DC power and TCSC reactance are discovered to vary according to control variable rather than being constant. So it's difficult for the sensitivity based method to be applied to security correction strategy of AC/DC hybrid power system. A modified optimization method, which uses heuristic search principle, is proposed against the defects of excessive optimization variables and heavy computational burden, which results in the limitation for online application. Based on load shift factor(LSF), few generator and load nodes are rapidly selected to control overload effectively. Aiming at the minimum amount of load shedding, an optimization model is proposed, in which HVDC power and reactance of TCSC, in addition to the power of the selected nodes are taken as optimization variables. Intelligent optimization algorithm is adopted to obtain security correction scheme. Based on modified IEEE 30-node benchmark, the validity and superiority of the proposed method is verified by comparing the result obtained by the proposed method with those without utility of heuristic search or without taking DC power and TCSC reactance into consideration. © 2016, The editorial office of Transaction of China Electrotechnical Society. All right reserved.


Xu X.,Central China Electrical Power Dispatching and Communication Center | Lin T.,Hubei Engineering University | Zhang F.,Hubei Engineering University | Li Q.,Hubei Engineering University
Dianwang Jishu/Power System Technology | Year: 2012

To research low-frequency oscillation caused by load, the quantitative analysis and calculation of participating degree of load in low-frequency oscillation are performed, and by means of introducing load sensitivity as quantization index the way by which the load sensitivity influences on oscillation mode is analyzed. To avoid too heavy calculation burden during the online eigenvalue computation of large-scale power grid, the total least squares-estimation of signal parameters via rotational invariance techniques (TLS-ESPRIT) is utilized to identify the oscillatory active power increment distribution (OAPID) of load to indirectly reflect load sensitivity and participating degree of load in the oscillation. The availability of the proposed method is verified by simulation results of a 4-machine 2-area system and actual power grid.

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