The traction network voltage low-frequency oscillation (LFO) in high-speed railways easily leads to the traction blockade of electric multiple units (EMUs), which seriously affects the normal operation of high-speed railways. A passivity-based control (PBC) strategy for single-phase EMUs rectifier is proposed in this paper. First, for the single-phase EMU rectifier, the Euler-Lagrange (EL) mathematical model in dq frame is built, which can realize the decoupling of active power and reactive power. Second, according to the unique characteristics of the rectifier, it is proven that the rectifier is strictly passive, which is the premise of PBC controller design. Third, using the deduced EL mathematical model and the passivity of rectifier, the PBC controller for the single-phase rectifier of EMUs is designed using the damping injecting method. Next, compared with dq current control and interconnection and damping assignment PBC (IDA-PBC), it can be verified that the PBC controller has better dynamic and static characteristics, and can significantly suppress the voltage LFO of traction network. In these strategies listed in this paper, using the PBC, the single-phase rectifier input current has minimal total harmonic distortion, and the dc-link voltage has minimal oscillation. Finally, the dSPACE semiphysical experiment platform of the cascade system of EMUs and traction network is built. Simulation results are validated by the dSPACE semiphysical experiments, which indicate that the PBC has the better inhibitory effect for LFO as compared with that of the IDA-PBC and dq current control in single-phase EMUs rectifier.

In this work, we extend the notion of generalized Hamming weight for classical linear block codes to linear network codes by introducing the network generalized Hamming weight (NGHW) for a given network with respect to a fixed linear network code. The basic properties of NGHW are studied. We further show that NGHW can be used as a tool to characterize the security performance of a linear network code on a wiretap network. We also introduce the notion of network maximum distance separable code (NMDS code) by extending the notion of Maximum Distance Separable code in classical algebraic coding theory. We prove that NMDS codes play an important role in minimizing the information that an eavesdropper can obtain from the network.

In this paper, we study the linear multi-source network coding security problem in, without the assumption that all source messages have positive distributions. We obtain a necessary and sufficient security condition, which can be regarded as a generalization of the one in.

With the coming competition and deregulation from marketplace, electric utilities are beginning to pay more attention on maintenance because it makes great sense in reducing operative costs and improving competition of today's utilities. In power systems there are usually millions of maintenance intensive equipments whose reliability is important to power system security and safety. In this information age, it is necessary to use computer to deal with this tremendous information and complexity related to maintenance. In this paper computerized maintenance management systems (CMMS) have been introduced and recommended to deal with this problem. This paper also discuss the general information-processing model proposed by Hassanain in order to implement the CMMS successfully. This general model consists of five sequential management processes: (1) identify asset, (2) identify performance requirements, (3) assess performance, (4) plan maintenance, (5) manage maintenance operations. Some of them has also been detailed in this paper. Successful CMMS is expected to help electric utilities manage resources effectively and improve utilities' efficiency considerably.