Supervisory Control and Data Acquisition (SCADA) systems are the underlying monitoring and control components of critical infrastructures, such as power, telecommunication, transportation, pipelines, ...chemicals and manufacturing plants. Legacy SCADA systems operated on isolated networks, that made them less exposed to Internet threats. However, the increasing connection of SCADA systems to the Internet, as well as corporate networks, introduces severe security issues. Security considerations for SCADA systems are gaining higher attention, as the number of security incidents against these critical infrastructures is increasing. In this survey, we provide an overview of the general SCADA architecture, along with a detailed description of the SCADA communication protocols. Additionally, we discuss certain high-impact security incidents, objectives, and threats. Furthermore, we carry out an extensive review of the security proposals and tactics that aim to secure SCADA systems. We also discuss the state of SCADA system security. Finally, we present the current research trends and future advancements of SCADA security.
This paper introduces an evolutionary optimization procedure for the design of permanent-magnet motors (PMMs) for electric vehicle (EV) applications, considering a specific drive cycle with multiple ...operating points. For the purposes of the analysis, the New European Drive Cycle (NEDC) has been employed with two alternative PMM configurations. Energy distribution over the NEDC for a small passenger's EV has been calculated and the equivalent multiple operating points have been extracted, using appropriate weights, in order to maintain an equal energy consumption basis, resulting in reduced computational cost. The proposed optimization technique is constituted of an adaptive differential evolution (DE) algorithm involving dynamic variation of the mutation factor, combined with finite-element (FE) and circuit models. The procedure is based on the precise calculation of the two axes input current components for each candidate solution and operating condition. The methodology introduced presents stable and fast convergence characteristics and has been applied to optimize the geometry of both surface-mounted and interior PMM configurations. The proposed motor is based on the thorough tradeoff among the two alternative optimized geometries and has been validated through measurements on a prototype.
This paper introduces a comparative study on the design of aerospace actuators concerning induction motor and permanent-magnet motor technologies. In the analysis undertaken, the two candidate ...configurations are evaluated in terms of both their electromagnetic and thermal behaviors in a combined manner. On a first step, the basic dimensioning of the actuators and their fundamental operational characteristics are determined via a time-stepping finite-element analysis. The consideration of the thermal robustness of the proposed motor configurations is integrated in the design procedure through the appropriate handling of their respective constraints. As a result, all comparisons are carried out on a common thermal evacuation basis. On a second step, a single objective optimization procedure is employed, considering several performance and efficiency indexes using appropriate weights. Manufacturing and construction-related costs for both investigated topologies are considered by employing specific penalty functions. The impact of the utilized materials is also examined. The resultant motor designs have been validated through manufactured prototypes, illustrating their suitability for aerospace actuation.
This paper investigates the harmonic losses and torque ripple of a surface permanent magnet (SPM) motor driven by pulsewidth-modulated inverter for a wide range of switching frequencies (SFs), using ...a 2-D nonlinear time stepping finite-element model, including strand conductors proximity effect, coupled with an appropriate external electric circuit. Such a method enables the estimation of torque ripple as well as the accurate prediction of the eddy current losses in the windings, lamination core, and PMs, respectively. Moreover, the total power losses of the inverter are calculated via analytical techniques. The analysis undertaken proposes an optimum SF, in terms of overall drive system efficiency and torque quality, considering multiple operating conditions. The simulated results are validated by measurements on a prototype SPM actuator, illustrating that the SF plays an important role on SPM motor drive applications.
Overall optimization of electromechanical aerospace actuators requires a multiobjective analysis to account for both performance and efficiency, while considering technical costs, due to the ...conflicting nature of the respective criteria. This paper introduces a particular multiobjective, population-based optimization methodology, using the differential evolution algorithm combined with manufacturing cost and motor-clean-interface related constraints. A magnetic equivalent circuit model is implemented and integrated in the process to account for flux leakage effects. The methodology presents stable convergence characteristics and has been applied to further extend previous work regarding the optimization of a fractional slot concentrated winding surface mounted permanent magnet motor. The resultant motor design has been validated through a prototype and experimental results illustrated its suitability for aerospace actuation.
In this paper the strategy of the extraction of an advanced simulation model of interior permanent magnet synchronous machine is suggested in order to be employed by Model Predictive Control schemes. ...The conventional dq-axis mathematical model is modified in order to include data derived from finite element analysis (FEA). Indirect interaction between FEA and circuit simulation enhances model fidelity embodying the influence of saturation and cross-coupling effects. The proposed method of developing a detailed simulation model opens new prospects on the control of electrical machines.
In this paper, a detailed analysis over a reference electric vehicle’s drive cycle of an interior Permanent Magnet Synchronous Motor (IPMSM) is implemented, in terms of motor performance, efficiency ...and field weakening capability. Initially, the electromagnetic field characteristics of a geometrically optimized IPMSM are investigated for various modes of operation by using a 2-D Finite Element (FE) model. In a next step, a robust hybrid torque control model, combining direct Maximum Torque per Ampere (MTPA) control, for constant torque operation and Voltage Constraint Tracking (VCT), for Field Weakening (FW) operation is developed. For proper IPMSM control, the proposed model considers motor magnetic saturation and cross coupling effects between direct (d) and quadrature (q) axes, including the inductance variation with both d and q axes current. Finally, the effectiveness of the control model has been validated through New European Drive Cycle (NEDC) operation for the investigated vehicle.
This paper introduces a particular permanent magnet motor (PMM) design methodology, considering advanced magnetic material characteristics, for aerospace actuator applications. In this class of ...problems, increased electromagnetic power density, fault tolerance, and high-temperature withstand properties are of major importance, and favored single-layer (SL) and double-layer (DL) fractional slot concentrated winding (FSCW) optimal topologies with different motor segmentation strategies have been compared. Under such strict nature of specifications, both operational and spatial, the implementation of advanced magnetic materials, particularly Vacoflux50 cobalt iron laminations and NMX-S43SH neodymium PMs, offer great services. The optimization methodology introduced is based on composite cost and penalty functions involving performance, efficiency, reliability, weight, and thermal criteria for multioperational behavior under normal and temporary overload conditions. An appropriate particle swarm optimization algorithm ensures fast convergence of the optimization variables. The resulting optimal SL and DL FSCW PMM configurations present certain complementary advantages, while the former one offering greater efficiency, thermal robustness, and physical segregation of the two motor parts is favored for this class of applications. Finally, the proposed motor configuration has been validated through measurements on a manufactured prototype.
This paper investigates the design and application of an improved shaft generator (SHG) system for an actual Ro-Ro ship, comprising a permanent magnet synchronous generator (PMSG) and a back-to-back ...converter. The system can operate both in generator and motoring mode, providing active power and ancillary services to the ship's grid, and driving the main shaft under emergency conditions, respectively. Although the literature in the design and optimization of the individual components is vast, the subsystems and their interactions should be studied in tandem in order to accurately evaluate the benefits of implementing such solutions in real-world applications. This paper begins by investigating and improving the design of subsystems, i.e., machine and power converter control, and then evaluates system operation under various conditions. A conventional high-speed salient-pole synchronous generator and a low-speed direct-driven PMSG are investigated. These are then geometrically optimized, based on the specified operating characteristics. Controller design is optimized, and system operation is evaluated under steady-state and transient modes. It is demonstrated that the proposed SHG can provide important grid services, act as an emergency thrust mechanism and lead to a 3% reduction in fuel consumption for a typical voyage compared with a conventional SHG system.
The Worldwide Interoperability for Microwave Access (WiMAX) family of standards have introduced a flexible, efficient, and robust wireless interface. Among other interesting features, WiMAX access ...networks bring into play a flexible determination of the ratio between the downlink and uplink directions, allowing a relation width from 3 : 1 to 1 : 1, respectively. However, this promising feature is not properly utilized, since hitherto scheduling and mapping schemes proposed neglect it. In this paper, this challenging issue is effectively addressed by proposing an adaptive model that attempts to adequately adjust the downlink-to-uplink subframe width ratio according to the current traffic conditions. In the context of a mobile WiMAX wireless access network, the base station is enhanced with an error-aware learning automaton in order to be able to identify the magnitude of the incoming and outgoing traffic flows and, in turn, to suitably define the ratio on a frame-by-frame basis. The model designed is extensively evaluated under realistic and dynamic scenarios, and the results indicate that its performance is clearly improved compared with schemes having predefined and fixed ratio values.
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