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Zhang X.,North China Electrical Power University | Wei J.,Nanjing Pengtu Power Supply Co., Ltd | Zhao D.,North China Electrical Power University | Liang W.,North China Electrical Power University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2014

Alarm information obtained under supervisory control and data acquisition systems is the basis of building a model for power grid online fault diagnosis. The main problems restricting the online application of power grid fault diagnosis are the complex modeling process and heavy maintenance requirements. Combined with the feature of alarm information acquired from the electric power dispatching automation system, this paper proposed an analytic method for power grid alarm systems using semantic analysis. The method can automatically extract the basic logic variables from alarm information by character decomposition. Based on connection analysis, the associated relation among electrical devices, circuit breakers and alarm information was built, which was corresponded to the analytical system. According to the relay protection tripping principle and the types and properties of relay protection, the associated relation between alarm information was automatically established. This relationship was coupled with the analytic rules of the model, which realized the automatic mapping from alarm information to fault diagnosis and simplified the modeling work. Finally, based on a practical fault case that occurred in a regional power grid, the validity and practicality of the proposed method for online fault diagnosis was verified. © 2014 Chinese Society for Electrical Engineering. Source

Liu B.,Nanjing Southeast University | Huang X.,Nanjing Southeast University | Li J.,Nanjing Institute of Technology | Qian X.,Nanjing Pengtu Power Supply Co., Ltd | Cheng J.,Nanjing Southeast University
Dianwang Jishu/Power System Technology | Year: 2015

Since the location and the capacity of electric vehicle (EV) charging station impact on both distribution network and transportation network, so the location and the capacity of electric vehicle charging station in distribution network should be taken into account during the planning of distributed generation (DG). For this purpose, a path selection model and an assessment model of urban traffic satisfaction are established, and the timing sequence characteristics of DG as well as the complementarity among them are researched. Considering the fact that DGs have to supply power to distribution network and EV charging stations simultaneously, a model to determine the site and capacity of DGs and EV charging stations, in which the minimum total cost, the lowest network loss and the highest traffic satisfaction are taken as the objectives, is built and solved by new multi-objective free-search algorithm, and then a Pareto solution set is achieved. Taking IEEE 33-bus distribution network as the example, the simulation is carried out and simulation results are analyzed by interactive fuzzy decision. Analysis results show that reasonable grid-connected positions of DGs and EV charging stations and their capacity configuration can be obtained by above-mentioned method, therefore, the proposed model and algorithm are feasible and effective. ©, 2015, Power System Technology Press. All right reserved. Source

Xu Q.,Nanjing Pengtu Power Supply Co., Ltd
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2011

A fast ATC(Available Transfer Capability) algorithm with steady-state voltage stability constraint for N-1 contingency is presented, which, based on the continuation power flow method and the curve fitting technique, takes the operating point of N-1 system contingency and the predicted point by sensitivity technique as the curve fitting points to find the approximate nose point for N-1 contingency and then to determine the system ATC. Simulative results of IEEE 30-bus test system validate its feasibility and correctness. Compared with the results of continuation power flow method, it has smaller error and faster speed. Source

Chen X.,Hohai University | Chen K.,Nanjing Pengtu Power Supply Co., Ltd | Liu J.,Shaanxi Electrical Power Research Institute | Ding X.,China Electric Power Research Institute | Yu K.,Hohai University
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2012

The energy balance mode in the distribution network is changed after the distributed generation, microgrid, energy storing device and charge-discharge device of electric vehicles are inserted in the grid. To promote the development of the smart grid, the objectives and devices for the intelligent dispatch of the distribution network are presented following an analysis of the characteristic of the distribution network and its dispatching and control. A multi-dimensional and multi-stage progressive intelligent dispatching mode for the distribution network based on the interaction between the network, power supply and loads are proposed to achieve the goal of efficient operation of the distribution network. And the functional structure of intelligent dispatching of the distribution network is provided. The key techniques to be solved are presented to complete the intelligent dispatching system of the distribution network. The developing tendency for the intelligent dispatching of the distribution network is explored and the research direction summed up. © 2012 State Grid Electric Power Research Institute Press. Source

Xue Y.,Zhejiang University | Xu Z.,Zhejiang University | Wang F.,Nanjing Pengtu Power Supply Co., Ltd
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2013

The topology and operation mechanism of a new alternate-arm multilevel converter (AAMC) are described. This topology has two key parts, i. e., director switches made of insulated gate bipolar transistors(IGBTs) in series and wave shaping circuits containing stacks of full bridge sub-modules(SMs). It offers some attractive features such as small amount of SMs, without circulating current, and DC blocking capacity, etc. However, voltage balancing among the SM capacitors is one of crucial problems in the AAMC. To solve it, a voltage balancing strategy based on third harmonic injection is proposed in this paper. The specific process is devided into two steps. Frstly, an energy feedback path is created between the star-point of the converter transformer and the mid-point of the DC-link spilt capacitors; then, an open-loop controller is designed to control the injection current to make sure the whole energy of the wave shaping circuits keep balance. Secondly, a modified phase-shifted carrier-based PWM is poposed to redistribute the energy within SMs. In this method, the switching amount is calculated according to the modulation wave and reference wave, and then the trigger pulses for specified modules are generated based on the polarity of the arm current and the sort results of capacitor voltages. The model of the AAMC with 10 SMs per arm is realized by PSCAD/EMTDC, and simulation results verify the effectiveness of the proposed strategy. Source

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