The Internet of Things (IoT) provides a salient communication environment to facilitate the coordinated charging of electric vehicle (EV) load. However, as IoT is connected with the public network, the coordinated charging system is in a low-level cyber security and greatly vulnerable to malicious attacks. This paper investigates the malicious mode attack (MMA), which is a new cyberattack pattern that simultaneously attacks massive EV charging piles to generate continuous sinusoidal power disturbance with the same frequency as the poorly-damped wide-area electromechanical mode. Thereby, high amplitude forced oscillations could be stimulated by MMA, which seriously threats the power system stability. First, the potential threat of MMA is clarified by investigating the vulnerability of the IoT-based coordinated charging load control system, and an MMA process like Mirai is pointed out as an example. And then, based on the attack process, an MMA model is established for impact analysis where expressions of the mean and stochastic responses of the MMA forced oscillation are derived to discover main impact factors. Further, to mitigate the impact of MMA, a defense strategy based on multi-index information active disturbance rejection control is proposed to improve the stability and anti-disturbance ability of the power system, which considers the impact factors of both mode damping and disturbance compensation. Simulations are conducted to verify the existence and characteristics of MMA threats, and the efficiency of the proposed defense strategy is also validated.
In this paper, we adopt a novel topological approach to fault diagnosis. In our researches, global information will be introduced into electric power system, we are using mainly BFS of graph theory algorithms to resolve fast and exact discrimination of faulty components and faulty sections, and finally accomplish fault diagnosis. Graph theory algorithms can be used to model many different physical and abstract systems such as transportation and communication networks, models for business administration, political science, and psychology and so on. In the study of fault diagnosis in electric power system, especially the fault diagnosis for mechanically-driven sections of equipments in power plant, graph theory algorithms must also have a good prospect of application.
The local renewable energy protection is of great theoretical value and practical significance in ensuring the safe and reliable operation of power grids with large-scale renewable sources. In order to solve the problems of the protection of renewable energy integrated in the grid, this chapter analyses in depth the fault characteristics of renewable energy sources, centralized renewable energy protection and distributed renewable energy protection. It proposes a current differential protection scheme for the outgoing transmission line based on fault steady-state components, which is not affected by fault resistance or load current, and is highly reliable and sensitive in fault identification. The chapter further introduces an adaptive protection approach for distribution networks containing distributed generation, which can eliminate the influence of distributed generation (DG) on the branch current and increase the protection range of the main protection and backup protection.
Concerning subsynchronous oscillation caused by the integration of doubly-fed induction generator (DFIG) to power grid via series compensation line, an active damping control strategy based on remodeling of multiple energy branches in DFIG is proposed. First, according to the flow path of oscillation components, energy branches in DFIG are divided. Second, potential energy and dissipation energy are defined characterizing accumulation and consumption of energy during oscillation. Then, by analyzing the contribution of energy branches to potential energy and dissipation energy, key energy branches affecting the stability of system are screened. On this basis, the relations among stator voltage, potential energy, and dissipation energy are established, and frequency-dependent energy compensation functions in key branches are derived. By assessing their impact on low voltage ride through (LVRT) performance of DFIG, the compensation branch compatible with DFIG fundamental frequency characteristics are screened. Then, take sub/supersynchronous frequency stability coefficient ratio as the objective function, and the requirement on stability in sub/supersynchronous frequency band as the constraints. The compensation branch parameter optimization scheme is established. Finally, a test system is built in RT-LAB for verification. Simulation results demonstrate that, the proposed strategy can realize active damping control in multiple oscillation cases, and guarantee the stability of system in full frequency band. Besides, the strategy does not affect LVRT performance of DFIG and is well compatible with DFIG fundamental frequency characteristics.
In view of the jump characteristic of power system, a time-delay stability control strategy that avoids the effect of jump progress is proposed in this study. First, the Newton–Leibniz formula based on the free weighting matrix and the time-delay system model considering Markov jump are introduced to the differential equation of Lyapunov–Krasovskii functional, and a non-linear minimising time-delay controller considering the jump characteristic of power system is designed. Then, the Schur complement is used to decouple the non-linear items in the control algorithm, so that the matrix inequalities containing the non-linear items are transformed to standard linear matrix inequalities. Thus, low solving efficiency due to iteration could be avoided. Time-domain simulation tests on the IEEE 16-machine 68-bus system verify that the proposed controller could effectively damp the inter-area oscillations before and after the system jump, and the system after jump will not go unstable due to the time-delay control measures before the jump. Compared with traditional time-delay control methods, the proposed method is suitable for power system with jump characteristic and has better computational efficiency.
As an important component, Super Luminescent Diode (SLD) is the most crucial factor that affects life and reliability of Interferotic Fiber Opitc Gyroscope(IFOG). Therefore, research on the reliability of SLD is the base of research on the reliability of IFOG. Research on the reliability of SLD was processed through accelerated life test (ALT). Based on related theoretic analysis, the sensitive stress was thus decided. By analyzing the failure mechanism and the configuration of SLD, an Arrhenius life-stress relationship was obtained, i.e. the accelerated model. Using Weibull distribution as its life distribution function, reliability assessment was achieved applying MLE data assessment method. And reliability assessment results of SLD at 25degC was gained. By analyzing the reliability assessment results, conclusion can be made that ALT on SLD is feasible.
Based on grille fractal and self-adaptive morphological filter, a novel approach to identify inrush current and internal fault current is presented. Side by side with analyzing differential current by grille fractal, the proposed method can filtrate noises and interference signals of grille curves by means of generalized morphological filter combining with self-adaptive algorithm. On the basis of comparing the feature of inrush current’s grille curve with that of fault current, a novel transformer protection scheme is proposed, which is not affected by add-assist circulation current at delta side on Y/D connection transformer. Results of dynamic tests show that the proposed method is sensitive to slight internal fault and the transformer can be switched off quickly and reliably by protection device based on the proposed method while internal fault of transformer occurs.
Concerning the stochastic excitation caused by wind power fluctuation and the stochastic parameter of virtual inertia caused by wind speed uncertainty, a power system stability analysis method considering the Wiener noise is proposed in this paper. First, based on the reduced-order model of DFIG retaining virtual inertia control and phase-locked loop (phase-locked loop) dynamics, the analytic function relationship between stochastic parameters and elements in the state matrix is derived using the sensitivity analysis method; thus, the model of interconnected system with stochastic parameters considering the Wiener noise is established. And by constructing the Lyapunov functional containing the model of stochastic parameters, the linear matrix inequality (LMI) that satisfies the robust stochastic stability criterion is derived. Furthermore, by transforming the solving of LMI to a feasibility problem, the stability of system is identified. And then, by calculating online system instability probability under the current operating condition, the probability stability analysis method is proposed. On this basis, a system stochastic stability degree index is defined in this paper, which quantifies the effect of stochastic parameters on system small-signal stability, and could provide more effective information for the safe and stable operation of power system. Simulation tests on the IEEE four-generator two-area system and the New England 10-machine 39-bus system verify that the proposed method could effectively identify the small-signal stability of power system under the joint influence of stochastic parameter and stochastic external excitation, and is applicable to complex system with multiple generators.
The management of distributed energy resources using standard Information and Communication Technology (ICT) has attracted a lot of attentions recently. With high integration of ICT infrastructure, security has gained tremendous importance for energy distribution and energy automation systems. The cryptographic techniques play critical roles in achieving the information security goals. This paper focuses on the issues of cyber attacks to the wind farm communication network. Based on the key agreement protocol in secure group communication, and considering the characteristics of the wind farm, this paper presents a security communication framework to guarantee the reliable information exchange for the wind farm communication network. The analysis results are also given in the paper.
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