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Zheng X.,Southwest University | Li T.,Sichuan University | Fang Y.,State Key Laboratory of Power Transmission Equipment and System Security and New Technology
Journal of Supercomputing | Year: 2012

Benign worms have been attracting wide attention in the field of worm research due to the proactive defense against the worm propagation and patch for the susceptible hosts. In this paper, two revised Worm-Anti-Worm (WAW) models are proposed for cloud-based benign worm countermeasure. These Re-WAW models are based on the law of worm propagation and the two-factor model. One is the cloudbased benign Re-WAWmodel to achieve effective worm containment. Another is the two-stage Re-WAW propagation model, which uses proactive and passive switching defending strategy based on the ratio of benign worms to malicious worms. This model intends to avoid the network congestion and other potential risks caused by the proactive scan of benign worms. Simulation results show that the cloud-based Re-WAW model significantly improves the worm propagation containment effect. The cloud computing technology enables rapid delivery of massive initial benign worms, and the two stage Re-WAW model gradually clears off the benign worms with the containment of the malicious worms. © Springer Science+Business Media, LLC 2012. Source


Zhao Y.,State Key Laboratory of Power Transmission Equipment and System Security and New Technology | Zhang X.,State Key Laboratory of Power Transmission Equipment and System Security and New Technology | Lin S.,Wenzhou Electrical Power Bureau
Chongqing Daxue Xuebao/Journal of Chongqing University | Year: 2013

Photovoltaic power generation is considered to be one of the most promising power generation forms. It is difficult to accurately assess the reliability of the photovoltaic system (PVS) for the volatility and intermittent of the light intensity. By analyzing PVS component failure modes and their impacts on PVS output power, the reliability model of PVS is built. Then the probability model of PVS output power is presented by considering both illumination uncertainty and PVS component random faults. According to the influence of components random faults outside the intentional islands on the reliability of load points inside the intentional islands, the concepts of repair zone, isolation zone and zero zone are defined. Furthermore, by considering the fail-operation of breaker and fuse, the concept for zone hierarchy is proposed, and the analytical formulas to calculate reliability indices of the load points inside the intentional islands are deduced. The application of the presented reliability evaluation model is clarified using a typical example to show the practicality and validity of the proposed approach. Source


Wu F.-F.,State Key Laboratory of Power Transmission Equipment and System Security and New Technology | Liao R.-J.,State Key Laboratory of Power Transmission Equipment and System Security and New Technology | Yang L.-J.,State Key Laboratory of Power Transmission Equipment and System Security and New Technology | Liu X.-H.,Zibo Power Supply Company | And 2 more authors.
Wuli Xuebao/Acta Physica Sinica | Year: 2013

An improved multi-component two-dimensional hybrid model is presented for the simulation of Trichel pulse corona discharge. The model is based on the plasma hydrodynamics and chemical models, including 12 species and 27 reactions. In addition, the photoionization and secondary electron emission effects are taken into account. Simulation is carried out on a bar-plate electrode configuration with an inter-electrode gap of 3.3 mm, the positive potential applied to the bar being 5.0 kV, the pressure in air discharge being fixed at 1.0 atm, and the gas temperature assumed to be a constant (300 K). In this paper, some key microscopic characteristics such as electric field distribution, net charge density distribution, electron density distribution at 5 different instants during a Trichel pulse are analyzed emphatically. Further more, the electron generation and disappearing rates, positive and negative ion distribution characteristics along the axis of symmetry are also investigated in detail in the later Trichel pulse cycle. The results can give valuable insights into the physical mechanism of negative corona discharge. © 2013 Chinese Physical Society. Source


Hu B.,State Key Laboratory of Power Transmission Equipment and System Security and New Technology | Xie K.-G.,State Key Laboratory of Power Transmission Equipment and System Security and New Technology | Li X.-L.,China Southern Power Grid Technology Research Center | Cao K.,State Key Laboratory of Power Transmission Equipment and System Security and New Technology | Liu Y.-S.,China Southern Power Grid Co.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2010

Generally, HVDC transmission system has a quite complex structure with a large number of components. As is well known, each component has a different impact on the system reliability. The technique of determining the contribution of each component to the system unreliability can be used to identify the system weak parts and provide a useful tool for the decision-making on HVDC system operation and planning processes. This paper proposes an unreliability-tracing principle based on the proportional sharing principle (PSP), and an unreliability-tracing model for HVDC transmission systems. The PSP was used in this model twice based on the sub-system division scheme. In the unreliability-tracing process of the sub-system, the contribution of each component to a sub-system unreliability index can be calculated using the PSP. In the unreliability-tracing process of the whole system, the contribution of each sub-system to the system unreliability can also be calculated using the PSP. The contribution of each component to the system unreliability can be obtained by combining the two contribution results. The case study indicated that the proposed technique can distribute the HVDC transmission system reliability index to components or sub-systems impartially and reasonably, and it can also be used to identify the system weak parts. © 2010 Chin.Soc.for Elec.Eng. Source


Yang H.,State Key Laboratory of Power Transmission Equipment and System Security and New Technology | Zhang N.,State Key Laboratory of Power Transmission Equipment and System Security and New Technology | Ye M.-J.,State Key Laboratory of Power Transmission Equipment and System Security and New Technology
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

The discrete mathematical model VSC-HVDC system in dq reference frame is derived and discrete controllers are designed for transmitting power to passive network via VSC-HVDC system. According to the discretely steady mathematical model of the converter, a constant DC voltage and constant reactive power controller is used in the rectifier-side; a constant AC voltage controller is used in the inverter-side to control the AC bus voltage. The VSC-HVDC connected to passive network digital simulation model is set up by the electromagnetic transient simulation software PACAD/EMTDC. Simulation results, in the case of various engineering, verify that the designed discrete model is correct and the control strategy is effective. Source

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