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Wei Z.,Gansu Electric Power Research Institute | Runqing B.,Gansu Electric Power Research Institute | Ruhai H.,Gansu Electric Power Research Institute
Proceedings of 2016 IEEE Advanced Information Management, Communicates, Electronic and Automation Control Conference, IMCEC 2016 | Year: 2016

Focused on a non-electromechanical oscillation issue in Gansu province under islanding operation condition, this study investigated the possible reasons about the occurrence of oscillation by simulating the actually fault proceed and analyzing the corresponding recorded curves. It could be confirmed that unsuitable speed governor parameters of major generators were a significant reason to cause unstable swings in tested isolated system. The analyses of PSASP Small Signal Stability and PSASP-GOV were performed to investigate the possible instabilities of speed governors and exiters for Gansu province. The optimized parameters for islanding mode were generated and the feasibility was verified in field experiments. Finally, the recommended interventions were further produced for improving the stability of islanding operation conditions. © 2016 IEEE.


Liu W.,North China Electrical Power University | Liang C.,North China Electrical Power University | Xu P.,North China Electrical Power University | Dan Y.,North China Electrical Power University | And 2 more authors.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2013

Power flow betweenness and its application in vulnerable line identification in the power system are presented. Compared with (weighted) betweenness models in which power flow is supposed to be not directional and transferred only through the shortest path, the presented model bases on current operating mode and flow distribution, can effectively reflect and quantify actual effect of each line by "plant-load" pair with a more comprehensible physical background, in which maximum available transmit power between generator and load is also considered. Meanwhile, to reflect the impact of the critical line fault on the power system, analytic hierarchy process (AHP) is presented to evaluate transmission line over-load, voltage-limit, and transient stability level comprehensively. The Evaluation results are more objective and close to power system characteristics. Numeric examples of the CEPRI36 and Gansu power system show critical line identification method proposed in this paper can better reflect the degree of importance of the line in the entire power grid, and the correctness and effectiveness are verified. © 2013 Chin. Soc. for Elec. Eng.


Wen Z.,Gansu Electric Power Research Institute | He S.,Gansu Electric Power Company
APAP 2011 - Proceedings: 2011 International Conference on Advanced Power System Automation and Protection | Year: 2011

The analysis of transient stability of power system connected with large wind farm is an important issue in the planning and operation of wind farm because the reactive power variation and the real power variation of wind farm interconnected with power grid leads to voltage fluctuation and frequency fluctuation of power grid. Impact of large scale wind farm integration on electric power system, effect on electric power system produced by development of wind power in a local grid typically in China has been represented. Based on electromagnetic transient software DIgSILENT/PowerFactory, the interconnected wind farm model and VSC-HVDC model as well as HVAC and HVDC model are set up. Comparative analysis of post-fault transient performance of wind turbines with different type of tie-line has been proposed. As a character of transient stability of power system, critical clearing time of three-phase short-circuit fault is studied in this paper. The digital simulation results show that VSC-HVDC is a better measure to solve the problems of system instability due to large wind farm integration. With VSC-HVDC transmission system, the transient stability of system can be improved better by flexible operation and control. Analysis of this paper should be provided as academic reference for improving design of interconnected wind farm system. © 2011 IEEE.


Li J.,Lanzhou University of Technology | Cao J.,Lanzhou University of Technology | Jiang M.,Gansu Electric Power Research Institute
Dianwang Jishu/Power System Technology | Year: 2011

Taking the measured audible noise data of 330 kV EHV transmission lines in Gansu power grid for example, a back propagation (BP) neural network-based approach to audible noise prediction is researched. Based on the interpretation and analysis of measured audible noise data of 330 kV single-circuit transmission lines with triangle structure, the dataset sample is obtained, then 13 factors that influence audible noise are taken as input variables and the values of audible noise as output variables, and then a BP neural network prediction model with 3-layer structure is built and the proposed prediction model is trained and verified by the dataset sample. Results of simulation verification, in which partial data of some 330 kV transmission lines in the dataset sample are utilized to predict the audible noise of the rest 330 kV transmission lines, show that the predicted results of audible noise of the rest 330 kV lines by the proposed method approximately conform to the measured audible noise data of these 330 kV lines in the dataset sample, thus the proposed approach can be used as a simple and effective method for audible noise prediction of EHV transmission lines.


Yu H.,North China Electrical Power University | Liu W.,North China Electrical Power University | Wen Z.,Gansu Electric Power Research Institute | Ping D.,Gansu Electric Power Research Institute
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2010

By analyzing the mechanism of cascading failure, the topological relations of network structure, the self-critical features of lines in the transfer of system flow, combining with the probabilistic characteristics of various stages of cascading failure, a probabilistic assessment model of power system cascading failure based on line clusters is proposed. Through means of simulating cascading failure process, the indices such as overload and loss of system-load are generated to evaluate risk of cascading failure, in order to find the vulnerable spot of power system and then to generate prevention strategies to reduce the failure risk. Taking IEEE 39-bus system and Gansu power network as examples, the feasibility and effectiveness of the proposed probabilistic assessment model are validated. ©2010 State Grid Electric Power Research Institute Press.


Liu W.,North China Electrical Power University | Xie C.,North China Electrical Power University | Wen J.,North China Electrical Power University | Wang J.,North China Electrical Power University | Wang W.,Gansu Electric Power Research Institute
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2013

Taking the minimum maintenance cost and expected energy not supplied (EENS) as objective functions, this paper built a multi-objective optimization model for maintenance scheduling of transmission network and proposed an improved multi-objective particle swarm optimization algorithm based on niche technology for the built model. Through getting a set of Pareto optimal solutions, the model can coordinate the economic and reliability objectives of maintenance scheduling optimization problem. The algorithm used a niche sharing mechanism to update particle's position so as to keep the diversity of solution and the uniformity of distribution. Besides, by means of leading in chaotic mutation to part of non-dominated particles, the global searching ability of the proposed algorithm was enhanced, and local optimum was also avoided. In order to make the algorithm apply to maintenance scheduling optimization problem better, this paper processed the constraints by using a penalty function, and selected the best compromise solution from the Pareto optimal solution set according to fuzzy membership degree, and provided the scientific decision basis for maintenance plan makers. Simulation of IEEE-RTS 79 bus system testify that this algorithm can avoid the premature phenomenon and local convergence effectively in solving transmission network maintenance optimization problem, and convergence to the Pareto optimal solution set rapidly. © 2013 Chinese Society for Electrical Engineering.


Wang X.-L.,Lanzhou University of Technology | Li J.-L.,Lanzhou University of Technology | Ma C.-X.,Gansu Electric Power Research Institute
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

In order to enhance the ability of wind farm actively integrated into grid, the super short-term prediction model of wind speed and power is established. Then with the goal of the maximum wind power capture and the smooth output power and taking generator speed and pitch angle as control variables, the minimization control criterion is set out and the corresponding multi-objective optimization models are established to reduce mechanical and pitch angle stresses. The genetic algorithm is used to solve the optimal solution which is applied to wind power generation system to optimize performances. A 1.5 MW variable speed constant frequency wind power generation system is studied by the computer simulation. The results show that the output power is increased and the turbulence of power in low frequency is reduced compared with the traditional maximum power point tracking (MPPT) control strategy.


Liu W.,North China Electrical Power University | Wang J.,North China Electrical Power University | Xie C.,North China Electrical Power University | Wang W.,Gansu Electric Power Research Institute
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2012

The essence of cascading failure in complex power system, which is the main reason of large-scale blackouts, is brittleness process when the brittleness source is excited. To study how large-scale blackouts take place and the defense measures, meanwhile, find out the high-risk lines, the author proposed a brittleness source identification model for cascading failure based on brittleness theory of complex system. From the view that brittleness is the nature of power system, the model used power flow entropy to measure the condition of power grid, and analyzed the mechanism of cascading failure by brittleness relevance and entropy increase from component and macroscopic aspects respectively. Take the identifying method of brittleness sources and brittleness relevance degree of grid components into consideration, a determining process of high-risk lines was given. Through simulation of cascading failure, brittle risk entropy was applied to assess the impact of component outage from power grid operation and the load removed, and this can provide a basis for defensive strategy making. Taking Gansu power network as an example, the feasibility and effectiveness of the proposed defense model were validated. © 2012 Chinese Society for Electrical Engineering.


Liang C.,North China Electrical Power University | Liu W.-Y.,North China Electrical Power University | Wen Z.-W.,Gansu Electric Power Research Institute | Ping D.-M.,Gansu Electric Power Research Institute
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010

An original view is put forward that, under specific running state, power system self-organized criticality is related to power grid's uniform degree. The uniform degree of power network is characterized by network entropy; then a model to simulate power system self-organized criticality is proposed. Simulations in an IEEE39-bus system with the proposed model show that, under the uniform loading and flow distribution, the higher the grid's uniform degree is, the lower the probability of power cascading failure will be. Furthermore, balancing power grid's uniform degree can effectively prevent large-scale disastrous blackout and reduce the risk of entering power self-organized criticality state.


Zhou X.C.,Gansu Electric Power Research Institute | Liu F.C.,Gansu Electric Power Research Institute | Zheng J.J.,Gansu Electric Power Research Institute
Advanced Materials Research | Year: 2013

In recent years, wind power penetration into the grid has increased rapidly with abundant wind resources in Jiuquan, according to the policy of the Chinese government to "establish a 'Hexi Wind Power Corridor' and rebuild another Western 'Terrestrial Three Gorges Dam'". By the end of 2010, the total installed capacity of wind power in Jiuquan has reached 5160 MW. The wind farms are connected to 110 kV transmission network or above in Jiuquan, the studies of their impacts on the grid, in particular, the grid operation are becoming serious and urgent. Jiuquan is far away from the load center with a weak grid configuration, therefore issues such as transmission line overloading, local grid voltage fluctuation, and transient stability limitation are looming with large scale wind power integration. The power system dispatch and operation are influenced by the intermittent nature of the wind power, which should be regulated by the system reserves. This paper discusses the recent integration of wind power into the grid with a focus on the impact on the Gansu power grid operation. The paper also presents the measures to deal with these issues. © (2013) Trans Tech Publications, Switzerland.

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