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This paper proposes a diagnosis technique algorithm for a brushless dc motors under a stator inter-turn fault (ITF) condition using input impedance. The algorithm has early detection and various speed-range detection advantages. To early and accurately detect the ITF, the rotating speed, input current, voltage, resistance, and inductance must be analyzed. Therefore, we choose the input impedance as the detection factor because it includes all these factors. In this paper, the fault-detection system works without requiring a fast Fourier transform and the calculation of the negative-sequence impedance from the comparison of the measured impedance with the database impedance. The proposed technique was verified by the simulation and experiment. [ABSTRACT FROM AUTHOR]

The protection characteristics used for the detection of power systems’ oscillations are adjusted according to the recommendations of the equipment manuals and validated through transient stability studies. Once the characteristics are adjusted, the parameters do not change when topological changes occur in the system, which opens up the possibility of malfunction of the protection equipment, either by not considering special cases of failure during the study or by errors in the system. This paper describes the modeling and implementation of a virtual out-of-step protection algorithm based on traditional, unconventional methods. The proposed framework allows the user to implement a customized out-of-step protection algorithm and analyze a real fault event recorded in a COMTRADE file. Furthermore, the programming advantages include the possibility to import COMTRADE files from specific simulations and assess the adequate settings of the protective relay. The result brings a computational tool compatible with different simulation programs capable of reproducing stable and unstable power swing events through playback techniques. By assessing critical cases in which the omission of the tripping is reflected in a generator slip condition, this study proposes an alternative with the instantaneous power theory to analyze the oscillation conditions in the definite time frame. [ABSTRACT FROM AUTHOR]

Electric grid codes are expected to change in near future to accommodate an increased number of distributed generation units in the distribution power system without impairing its power quality. It is desired that the generators remain connected during voltage sags and provide ancillary services, such as voltage and reactive power control, ensuring the operational stability of the power system. This paper explores how the existing strategies for active and reactive power injection impact the operation of grid-tied inverters in terms of required power, current flowing, and reduction of active power delivery during the voltage sags. Such inputs are relevant to properly size converters for operation under fault events. In addition, this paper contributes to devise: 1) constant peak current control, 2) constant active current control, and 3) constant average active power control strategies for three-phase four-wire grid-tied inverters considering the natural (abc) reference frame. The design and implementation of the investigated power injection strategies are discussed, and their effectiveness and technical viability are analyzed through dynamic computational simulations under symmetrical/asymmetrical voltage sags, and variation of the short-circuit ratio. [ABSTRACT FROM AUTHOR]

Power generation and grid stability have become key issues in the last decade. The high penetration of large capacity wind generation into the electric power grid has led to serious concerns about its influence on the dynamic behavior of power systems. The low-voltage ride-through (LVRT) capability of wind turbines during grid faults is one of the core requirements to ensure stability in the power grid during transient conditions. The doubly-fed induction generators (DFIGs) offer several advantages when utilized in wind turbines, but discussions about their LVRT capabilities are limited. This paper presents a comprehensive study of the LVRT of grid-connected DFIG-based wind turbines. It provides a detailed investigation of the transient characteristics and the dynamic behavior of DFIGs during symmetrical and asymmetrical grid voltage sags. A detailed theoretical study supported by computer simulations is provided. This paper also provides a new rotor-side control scheme for DFIG-based wind turbines to enhance its LVRT capability during severe grid voltage sags. The proposed control strategy focuses on mitigating the rotor-side voltage and current transients during abnormal grid conditions, without any additional cost or reliability issues. As a result, the DFIG performance is improved and utility company standards are fulfilled. Computer simulations are used to verify the expanded ride-through capability of the novel strategy and its effective performance compared to the conventional control schemes. [ABSTRACT FROM AUTHOR]

This paper proposes a single-stage three-phase-to-single-phase current-fed high step-up ac–dc matrix converter. The proposed converter inserts a boost-type matrix converter, which is formed by three boost inductors and six bidirectional switches, between a three-phase ac source and a Cockcroft–Walton voltage multiplier (CWVM). By using this topology associated with power factor correction technique, the proposed converter not only achieves almost unity power factor and sinusoidal input currents with low distortion but also obtains high voltage gain at the output end. Moreover, the matrix converter generates an adjustable-frequency and adjustable-amplitude current, which injects into the CWVM to regulate the dc output voltage and smooth its ripple. With this flexible injection current, the performance of the proposed converter is superior to the conventional CWVM, which is usually energized by a single-phase ac source. The operation principle, control strategy, and design considerations of the proposed converter are detailed in this paper. Finally, simulation and experimental results demonstrate the claims and validity of the proposed converter. [ABSTRACT FROM PUBLISHER]

This paper presents a modular push–pull PWM converter (MPC) for a battery energy storage system, which is intended for grid connections to medium- or high-voltage power systems. The converter per phase consists of a center-tapped transformer and two arms based on a cascade connection of multiple bidirectional PWM chopper-cells with floating dc capacitors. This paper discusses the operating performance and control method of the MPC, focusing on voltage balancing of all the floating dc capacitors. Moreover, a comparison is made between the MPC and a modular multilevel converter (MMC), under an assumption that both are used as the same battery energy storage system. The validity of the operating performance and control method is confirmed by both computer simulation using the “PSCAD/EMTDC” software package and experiment using a three-phase, 200-V, 5-kW downscaled model. [ABSTRACT FROM PUBLISHER]

This paper presents a Scott-transformer-based power factor correction (PFC) rectifier for a three-level neutral-point-clamped (NPC) inverter-fed induction motor drive (IMD) for enhanced power quality at ac mains. Here, the Scott-transformer-based PFC rectifier is digitally controlled by a current feedforward control. The torque component of the stator current is added to the output of the dc-bus voltage proportional plus integral (PI) controller as a feedforward term, which enhances the dynamic performance of the dc-bus voltage regulation. The three-level NPC inverter is controlled by a space vector-modulated (SVM) indirect vector control scheme. The performance of the proposed dc-bus voltage loop with feedforward control is compared with the conventional one and found to offer faster response with less overshoot and undershoot. The proposed IMD system is simulated using MATLAB/Simulink and the same is validated experimentally. The proposed drive system is analyzed for a wide variation in reference speed and load torques demonstrating significant improvement in the performance indices. [ABSTRACT FROM AUTHOR]

The aim of this study is to design and implement an accurate virtual model of a basic feeder protection relay. This paper focuses on certain sets of ANSI functions and COMTRADE (Std C37.111) to interact with an online simulation subjects to different fault scenarios. The proposed methodology includes robust synchronization between power system simulations and the response of the virtual relay. The results validation integrates a distribution system simulation software running with remote control for time-based simulation, then it reproduces voltage and current signals with the virtual relay operation. The performance is assessed in three cases of study comparing real protection equipment and the operation of the virtual relay at the same fault scenarios. This paper is the next step of the attempt to reach a versatile test engine for substation automation systems, including multiple protective virtual devices, which reduces costs and allows to assess critical protection schemes. [ABSTRACT FROM AUTHOR]

This paper presents an optimal battery management algorithm for photovoltaic (PV) stations capacity firming using dynamic programming-based optimization and control architecture. The objective is to manage the output of battery energy storage system (BESS) so that PV station output swings are reduced significantly. First, BESS and PV station located in a medium-voltage distribution network on a North American power grid is modeled along with the reduced-order feeder model. Then, the proposed algorithm is designed and implemented on the power grid distribution feeder based on the feeder data streamed through utility communication infrastructure to the research laboratory. The theoretical formulation, simulation, and implementation results are discussed in detail in this paper. [ABSTRACT FROM AUTHOR]

In safety-critical systems, faults can cause life losses, environmental degradation, or significant financial losses. In this paper, a segmental stator switched reluctance machine is proposed for such applications. A short overview of its design is given. Its fault tolerance is investigated by dynamic simulations and laboratory tests. It is demonstrated via both methods that the proposed machine is able to have a continuous operation despite five severe winding fault conditions. [ABSTRACT FROM AUTHOR]

This paper proposes a space-vector dynamic model of the rotating induction motor (RIM) taking into consideration both the magnetic saturation and the iron losses expressed in a state form. Such a model tries to improve some issues of the previously developed dynamic models. The main original aspects of the proposed model are the following: the magnetic saturation of the iron core has been described on the basis of both current versus flux and flux versus current functions; the model is based on the complete T space-vector electrical scheme of the RIM; two different state formulations have been proposed; it includes the iron losses, separating them in hysteresis and eddy current ones; and it includes the effect of the load on the magnetic saturation. The proposed model has been implemented in numerical simulation in MATLAB/Simulink environment and validated experimentally on a suitably developed test set-up based on a low-power RIM. The proposed model has been exploited also to simulate the behavior of a high-power RIM. [ABSTRACT FROM AUTHOR]

This paper presents a lifetime-oriented droop control strategy for ac islanded microgrids, which is able to perform equal thermal sharing among paralleled inverters. Electro-thermal model and temperature estimation model are first established to estimate thermal characteristics of inverters, and temperature–power droop relationships are built according to the electro-thermal model. Then, a lifetime-oriented droop controller is developed to realize equal thermal stress sharing. In addition, a small-signal model of microgrid equipped with the proposed droop control is established, and the effect of electro-thermal parameters of the power devices on the closed-loop stability of a droop controller is investigated. Simulation and experimental results show that the proposed lifetime-oriented droop control is able to perform identical thermal stress sharing among paralleled inverters automatically, which mitigates the impact of thermal stresses on average lifetime of inverters and thus enhances long-term reliability of microgrids. [ABSTRACT FROM AUTHOR]

This paper focuses on a fully distributed peer-to-peer control scheme for voltage regulation and reactive power sharing of multiple inverter-based distributed energy resources (DERs) in ac microgrids. The proposed peer-to-peer control strategy is fully distributed enabled through broadcast gossip communication, where each DER unit only requires local voltage and current measurement from its own and some (but not all) nearby neighbors for the voltage and reactive power sharing control. Employing the broadcast gossip communication protocol with attractive scalability and reliability properties, the control inputs can be updated to restore the voltage magnitudes at the point of common coupling to a desired value ensuring an accurate reactive power sharing for each DER. Since the proposed distributed controllers are implemented on local DERs, the central controller and hierarchy are no longer required. Accordingly, the microgrid system stability is preserved in the peer-to-peer requirements of line switches, which in turn, enables a plug-and-play operation of DERs and their robustness against microgrid topology change scenarios. Simulation studies in a modified IEEE 34-bus test network demonstrate the effectiveness and applicability of the proposed control strategy. [ABSTRACT FROM AUTHOR]

An inter-turn fault (ITF) is conventionally analyzed by a method that uses negative-sequence components obtained by symmetrical coordinate transformations. However, this method is inefficient because it involves solving complex equations that include many parameters. This paper proposes a simplified d–q equivalent circuit model of a permanent magnet synchronous motor with an ITF. The model is developed by reflecting representative phenomena related to the negative sequence components of the fault in advance of a final model construction, such that the final model does not require the separation of positive and negative sequence components. As a result, the model can rapidly examine the influence of the fault due to the simplicity of the equations, and can help build the detection and tolerance control techniques of the fault. The model is verified by numerical analysis, simulation and experiment. [ABSTRACT FROM AUTHOR]

In this paper, a highly reliable back-to-back (BTB) power converter is proposed for doubly fed induction generator-based wind turbines (DFIG-WTs). When a power switch open-circuit fault is encountered in either the grid-side converter (GSC) or the rotor-side converter (RSC), a four-switch three-phase (FSTP) topology is formed to avoid using redundant bridge arms, which reduces the power circuit complexity and minimizes the conduction and switching losses. A simplified space vector pulsewidth modulation technique is used to eliminate sector identification and complex trigonometric calculations. In addition, the influence of dc-bus capacitor voltage unbalance on the electromagnetic torque is analyzed in detail. The offset current components are calculated, and they are deducted from the reference values in the modified control strategies to suppress the dc-bus voltage deviation. Moreover, the power loss model of a BTB converter is analyzed in detail, and the efficiency study is performed in various post-fault situations. Simulations in MATLAB/Simulink are carried out to verify the performance of a DFIG-WT based on a FSTP BTB converter. Furthermore, the control hardware-in-the-loop setup with RSC and GSC separately simulated in a digital real-time simulator is applied for experimental verification of the proposed control strategy. [ABSTRACT FROM AUTHOR]

A synchronous reluctance motor drive exhibits an inherent unlimited speed range capability; in fact, the maximum speed of this kind of machine is bounded only by mechanical limits. In order to exploit this peculiar characteristic of the drive while assuring the lowest power losses, a proper control algorithm has to be used. In particular, while the working speed is increasing, the control must be able to command the reluctance motor under the maximum torque per ampere condition at first, into the flux-weakening region, and then on the maximum torque per voltage trajectory. To this purpose, a novel voltage control loop is presented in this paper. It is combined with a field-oriented current control and profitably exploits a polar coordinate representation of the current reference to operate the reluctance machine in compliance with current and voltage rating constraints in all the different operating conditions. Additional merits of the proposed scheme are the ease of implementation and the simple design. The stability of the proposed control algorithm is proved through a small signal analysis and simulations and experimental tests confirm its effectiveness. [ABSTRACT FROM AUTHOR]

This paper analyzes the electromechanical interaction in a flywheel system with a doubly fed induction machine, used for wind farm power smoothing or grid frequency response control. The grid-connected electrical machine is subject to power control, and this can cause it to produce negative damping to the shaft torsional vibration. Resonance must be prevented, and this paper proposes a solution by coordinating the design of the electrical controller and mechanical shaft. Computer simulations are used to demonstrate the problem and the proposed solution. [ABSTRACT FROM AUTHOR]

In this paper, a sensorless controller for an interior permanent-magnet synchronous motor is presented based on well-known high-frequency signal injection techniques. The issue of the demodulation process is the key point of this paper. A novel approach based on discrete Fourier transform and nonconventional reference frame transformation is presented, allowing a simple and robust noncoherent demodulation, i.e., in which no information about the carrier phase is needed. In the classically adopted coherent approaches, in fact, uncertainty about carrier phase reflects in uncertainty in the demodulated signal amplitude, affecting observer gains and signal-to-noise ratio and definitively providing a degradation of the performance of the estimator. Analytical development of the sensorless algorithm, including the demodulation technique, is provided. A complete investigation by simulation is carried out aiming at showing the performance of the proposed method. Finally, experimental results are presented based on a prototype motor drive for city scooters. [ABSTRACT FROM AUTHOR]

This paper exploits the interaction between the low-frequency and the high-frequency fields created by signal-injection techniques during sensorless estimation of the air-gap flux position in induction machines. Such an interaction causes new phenomena that can be summarized in a modulation of the machine saturation level and creation of harmonics that contain information about the position of the flux. This paper analyzes the issues related to the presence of additional fields and predicts the resulting harmonic content using three different approaches such as analytical calculations, computer simulation, and finite element analysis. Experimental measurements confirm the conclusions of this paper. [ABSTRACT FROM AUTHOR]

This paper presents the influence of the large motor starting and the large rolling mill operation on the isolated integrated steel cogeneration facility by executing the transient stability analysis. The system configuration of the steel facility will be introduced first. Furthermore, the proper mathematical models and the accurate parameters of the cogeneration units, excitation systems, and governor systems are investigated in detail. Both the static and dynamic load models are applied in this paper. To reduce the starting current of large motors, the conventional step-down voltage method by adjusting the suitable tap position of the auto-transformer and the constant magnetic flux control method by using the variable-voltage and variable-frequency inverter are considered in the computer simulations. Also, the system voltage and frequency fluctuations due to the operation of the rolling mill will be observed and investigated carefully to verify that the isolated cogeneration can be operated well and safely. [ABSTRACT FROM AUTHOR]

This paper proposes a new vector-based dead-time compensation method for three-level T-type converters. The origins and effects of the dead-time voltage errors are analyzed in detail for different switching commutations and load conditions. In order to eliminate the dead-time distortion in each phase, a dead-time error voltage vector is introduced to adjust the reference voltage vector depending on load current polarity. The proposed vector-based dead-time compensation scheme has several advantages. First, it can be applied to multilevel converters with any number of voltage levels using any modulation schemes. Second, the pulse loss issue which is common in conventional pulse-based compensation strategies can be eliminated. In addition, the pulse saturation can be mitigated by operating the converters in overmodulation regions. All of these advantages and effectiveness of the proposed vector-based dead-time compensation method are verified through both simulation and experimental studies. [ABSTRACT FROM AUTHOR]

The arc flash hazard is related to electrical safety in work place and has gained much attention as part of the safety program for many facilities. An effective approach to reducing the arc flash hazard in existing industrial and commercial facilities is proposed in this paper. To illustrate the proposed approach and provide quantified results, computer simulation is conducted for a large oil field facility and a manufacturing facility in a commercial building as two case studies. The simulation results from the two case studies show significant reductions on the incident energy and the fault clearing time, which verifies the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper proposes a novel simple reactive power control strategy for the active load balancer (ALB) in three-phase four-wire distribution systems. The proposed reactive power control strategy may be applicable for adjustment of the source-side power factor under the balanced load condition. Only dc capacitor voltage control is used in the proposed control strategy. Therefore, the calculation blocks of the active and reactive components of the load currents are not necessary. The authors, thus, offer the simplest control strategy to control reactive power under the balanced load condition on three-phase four-wire distribution feeders. The basic principle of dc-capacitor-voltage-control-based reactive power control strategy is discussed in detail and then confirmed by digital computer simulation. A prototype experimental system was constructed and tested. Experimental results demonstrate that balanced source currents with reactive power control are achieved on three-phase four-wire distribution feeders. These experimental results also demonstrate that controlling the reactive power reduces the required power rating of the ALB compared with that of the conventional unity power factor control strategy. [ABSTRACT FROM PUBLISHER]

Electrostatic technologies have emerged as the solution of choice for the recycling of insulation contained in waste materials. The main objective of this paper is to contribute to the better understanding of the operating conditions of a new class of tribo-aero-electrostatic separators. The study of the motion of charged particles under the influence of an electric field by numerical tools facilitates the construction, implementation, and control of new electrostatic separation equipment. In effect, the trajectory of the particle can be determined precisely by the equation of forces that act on it in the electric field of the separator. COMSOL software was employed for the analysis of the electric field. A program written in MATLAB served then to simulating the trajectories of electrically charged insulating particles in the separator and enables the study of the factors that might influence the process of selective sorting of the various granular materials, i.e., geometry of the fluidized bed, velocity of the fluidization air, high-voltage applied to the electrodes, electric charge of the particles, granule size, and specific mass. Thus, an effective separation occurs in the case of particles characterized by charge/mass ratios on the order of −9 and +9\ \mu\mboxC/kg. [ABSTRACT FROM PUBLISHER]

This paper focuses on a novel modeling method for interior permanent-magnet (IPM) synchronous machines. This modeling method is based on a stator winding flux linkage table that is obtained from experimental testing. As indicated by the comparison between computer simulation and dyno testing, this modeling approach can model the nonlinear behavior of IPM synchronous machines with high fidelity without adding significant computational loads. [ABSTRACT FROM PUBLISHER]

Control structures containing cascaded loops are used in several applications for the stand-alone and parallel operation of three-phase power electronic converters. Potential interactions between these cascaded loops and the complex functional dependence between the controller parameters and the system dynamics prevent the effective application of classical tuning methods in the case of converters operating with a low switching frequency. A tuning approach guided by the eigenvalue parametric sensitivities calculated from a linearized model of the converter and its control system is proposed in this paper. The method is implemented in the form of an iterative procedure enforcing the stability of the system and ensuring that the system eigenvalues are moved away from critical locations. Numerical simulations in the time domain are presented to verify the improvement in the dynamic performance of the system when tuned with the presented algorithm compared with a conventional rule-based tuning method. [ABSTRACT FROM PUBLISHER]

An application-oriented integration concept for a half-bridge switch assembly has been developed based on the latest generation 70- \mu\m-thin insulated gate bipolar transistors and diodes, which are rated at 600 V/200 A. This paper addresses the design and reliability of the assembly, with a fully bondwireless approach using cylindrical copper bumps. Advanced numerical structural simulation techniques are also applied to assess the influence of interconnect characteristics (material, size, and shape) and try to determine an optimum solution for reducing the stress and creep strain development in the solder joint. Preliminary experimental tests of the power module are also carried out at different switching frequency and loads to prove the validity of the proposed solution in terms of electromagnetic performance. [ABSTRACT FROM AUTHOR]

Comparison and evaluation of maximum power point tracking (MPPT) algorithms for photovoltaic (PV) arrays are often carried out by computer simulation because any irradiation and temperature condition can be set up and repeated. This paper proposes a new simple calculation method for computer simulation to evaluate any MPPT algorithm. The proposed method rapidly calculates the operating point of the PV array. The 1-D Newton–Raphson method is repeated, instead of expanding this method, in multidimensional cases. The proposed method is compared with the conventional combination methods. We confirm the adequate accuracy and short calculation time of the proposed method. [ABSTRACT FROM AUTHOR]

As projects to expand the processing capacity of a gas plant located in west Texas were pursued, engineering staff observed that the planned incoming medium-voltage power feeder possessed many of the risk factors that have led to increasingly common control-power transformer (CPT) and voltage transformer (VT) failures in industry due to switching. Such failures could involve significant damage and down time. To address these concerns, a computer simulation study was undertaken. As part of initial data gathering, sweep frequency response analysis (SFRA) measurements were performed in an atypical context to establish resonant characteristics of these instrument transformers. When the remote source breaker was modeled to open, connected VTs/CPTs went into severe sub-power-frequency ferro-resonance with probable catastrophic failure. This was verified by Electromagnetic Transients Program (EMTP) simulations as well as by field measurements. The focus of this paper will be on the determination of this unique form of ferro-resonance, identification of risk factors, novel cost-effective solutions, implementation, and field measurement verification of the proposed mitigation solutions. Field measurements have shown high correlations with the EMTP simulations and have verified the effectiveness of the proposed novel mitigation solutions. [ABSTRACT FROM AUTHOR]

The installation and settings of protection devices and excitation control systems require experience since a failure can cause damage to the synchronous generator and negative impact on the power grid. A test bed implemented in a real-time digital simulator (RTDS) is presented in this paper as an alternative for the training and learning process that involves the knowledge of an effective coordination between such protection and control systems of synchronous generators. A complete generation system is implemented in a RTDS, including an excitation system model with its limiters. These limiters are coordinated with the protection functions implemented in a physical relay. The contributions of this work are the demonstration of the importance of this type of study (i.e., real-time simulations results through hardware-in-the-loop tests), the consolidation of the impedance (R-X) and admittance (G-B) planes as the more appropriate ones to analyze the coordination between the ANSI 40 function and the underexcitation limiter, and the presentation of a study focused on hydrogenerators (including novel settings for the ANSI 40 protection). [ABSTRACT FROM AUTHOR]

Nowadays, the simulation tools used to perform power system analysis are evolving into the many-core computation era; some of these techniques propose to tear the power system network into several subnetworks (islands) for its parallel processing. The island's detection is an issue considered by the power flow analysis due to management activities such as feeder reconfiguration, fault detection, and isolation, among others, that generate topological changes. These methods include graph theory, checking the circuit breaker status and on-site measurements, decision trees, frequency deviation, and pattern recognition, among other techniques, which are focused to detect topology changes that may generate islands and affect the state estimation of the system. In contrast, other techniques such as the approximate minimum degree perform a reorganization of the $Y_{{\text{BUS}}}$ matrix that describes the network components and their connectivity, looking to factorizing the $Y_{{\text{Bus}}}$ matrix to solve the power flow problem. These techniques are very functional and efficient; however, some of them require detailed information of the network, and are addressed to cover meshed and radial network configurations separately. This paper presents an iterative algorithm that uses the compressed coordinate branch-to-node matrix for detecting, classifying, and grouping islands within sparse matrixes, describing mesh or radial networks. This algorithm is a valuable tool to simplify islands location and can be implemented using any programing language due to its simplicity. This method is used in Distribution System Simulator - Real Time Version (DSSim-RT), which is a simulator based in OpenDSS, for tearing the power system network to allow the multithread power flow analysis of distribution systems in real time. [ABSTRACT FROM PUBLISHER]

This paper presents a dynamic model suitable for accurate cosimulation of fault-tolerant permanent-magnet motor drives featuring independent-phase structure. The model is developed in a circuital form where the usual inductive parameters and back electromotive force coefficient are replaced by current and rotor position dependent functions, so that the exact electromagnetic nature and geometry of the machine are accounted over the large flux-current operating range. The model functions are precomputed by a finite element method analysis of a single phase of the machine, once the magnetic independence among the phases has been verified. Then, the circuital model is solved by a dynamical simulator which implements also the drive system, converter, and control, following on the offline cosimulation approach. The proposed model is validated by experiments carried on a fault-tolerant five-phase permanent-magnet motor-drive for aeronautical application, controlled by the brushless dc technique. The results show that the modeling solution is capable to simulate the motor dynamics with a high degree of accuracy, and can be used for an effective rapid prototyping of fault-tolerant drives. [ABSTRACT FROM AUTHOR]

The paper discusses the emulation of a parallel resonant $RLC$ load by means of an electronic power converter. The main application of the analyzed approach is in the testing of grid connected resources (e.g., renewable sources), where it allows us to ease testing procedure, minimize wasted power, and reduce test-bench size. To this end, an effective control system is proposed, analyzed, and designed considering a current-controlled inverter as the basis of emulator development. The limitations of the control system are explored, highlighting the requirements of the controller in order to achieve desired emulation accuracies and avoid instability. The reported studies are verified by means of both simulations and experimental tests performed on a laboratory prototype. In particular, the proposed modeling is able to predict the presence of resonant peaks close to the current control bandwidth, giving in this way useful guidelines to minimize such an undesired effect, which is detrimental for stability when the load is connected to other systems. Finally, the experimental results from an unintentional islanding test are reported to show the equivalence of the developed active $RLC$ load with respect to a passive one. [ABSTRACT FROM AUTHOR]

The expansion of the transient operation of electrical machines as, for instance, in vehicle traction applications, demands an accurate computation of the thermal behavior under these conditions in order to enhance the economy of the design and provide a precise estimation of the overload capacity. In addition, heavy transients have been identified as specially damaging for the rotor cage of large induction motors. The aim of this paper is the development of a model able to simulate in detail the thermal and mechanical effects of a heavy transient on an induction's motor rotor featuring a damaged (with a reduced section on one of its ends) rotor bar. Some preliminary results that provide a qualitative understanding of the development of a bar breakage during a fatigue test are presented. [ABSTRACT FROM AUTHOR]

Electronically commutated motors produce a mechanical torque by switching the currents in their stator winding system according to the instantaneous rotor position during rotation. The rotor position is determined by Hall sensors capturing the magnetic field of the rotor's permanent magnets. In operation, the Hall sensors are exposed not only to the rotor field, but also to the field of stator windings. This inevitably leads to a certain commutation angle error (CA error) and a reduced motor performance. This paper presents a general 3-D magnetic field simulation approach for computing the CA error and for finding an optimal position of the Hall sensors. The obtained numerical results and their verification by measurements are presented in detail. [ABSTRACT FROM AUTHOR]

Usually, the high-gain high-efficiency dc–dc converters consist of many passive components, which increases the order of the system. As the order increases, system modeling and control become more complex. Thus, there is a need for the simplification of the small signal modeling process of such converters. This paper presents a generalized small signal model and equivalent circuit for an $n$ th-order coupled-inductor-based high-voltage gain converters (CIHVGC) that can be conveniently used for the control design. The state variable representation of a generalized coupled inductor with p windings is included. A simplified step by step procedure to obtain small signal model using visual inspection is presented. Analysis is included and verified using simulations and experiments for the output voltage regulation of high-voltage gain converters. The usefulness and versatility of the proposed model is verified with three examples of high gain converters belonging to the CIHVGC family. All the analytical, simulation, and experimental details of this paper are presented. [ABSTRACT FROM AUTHOR]

This paper proposes an identification method for induction motor parameters at standstill using integral calculations. The rotor time constant and magnetizing inductance are identified. During the identification process, the induction motor to be tested is consistently excited according to a predetermined current reference. Using the predetermined current, the induction motor emulates the rated rotor flux and the rated slip condition, even at standstill. This method is based on an integral calculation so that the results are robust to measurement noise. Based on these features, the identification result of the proposed method is quite accurate, and the method shows excellent repeatability. Due to the simplicity of the proposed technique, this method can be easily applied to commercial inverter products. Simulation and experimental results confirm the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

This paper proposes a multilevel series compensator (MSC) to deal with voltage sags/swells, harmonic compensation, or reactive power compensation. Such a device can be considered as a dynamic voltage restorer or a series active power filter (Series-APF). The MSC can improve the power quality of loads located in stiff systems. The configuration is based on three-phase bridge (TPB) converters connected by means of cascaded single-phase transformers. This arrangement permits the use of a single dc-link. A generalization for $K$ -stages in which $K$ -transformers are coupled with $K$-TPB converters is presented. The topology permits generating a high number of levels in the voltage waveforms with a low number of power switches in comparison with a classic topology. The multilevel waveforms are generated by the converters through a suitable pulsewidth modulation (PWM) strategy that takes into consideration the transformer turns ratios. Modularity and simple maintenance make the proposed MSC an attractive solution compared with some conventional configurations. Model, PWM strategy, and overall control are discussed in this paper. Simulation and experimental results are presented as well. [ABSTRACT FROM PUBLISHER]

This paper discusses the modeling and simulation of a grid-integrated photovoltaic (PV) system on a real-time digital simulator. The modeling of the PV array on the simulator, as well as, the power converter and controls for the PV system is discussed. An analysis of the real-time operation of the PV system, is presented. The benefits and considerations of power hardware in the loop simulations with a physical PV-grid converter are discussed. [ABSTRACT FROM PUBLISHER]

This paper presents a dual-electrical-port control scheme for four-quadrant operation of cascaded doubly-fed induction machine (CDFIM), which has conventionally been used as a variable-speed drive or variable-speed constant-frequency generator for limited-speed-range applications. The proposed control method enables the synchronous control of both power winding (PW) and control winding (CW) currents, and as a consequence, not only the control complexity but also the rotor slip frequency and related core losses are significantly reduced in comparison with the previously proposed single-electrical-port control scheme. It is for the first time revealed that the CDFIM drive that indirectly couples PW and CW through induction behavior can be readily controlled like a conventional induction motor to achieve the highest torque density. The torque density–speed region of the CDFIM falls within that of the power machine in singly-fed operation mode, and only a half of that of the power machine in doubly-fed operation mode, which shows the urgent need for torque density enhancement of brushless doubly-fed machines for electric vehicle/hybrid electric vehicle applications. Computer simulations and experiments are implemented to verify the dynamic performance of the proposed control method. [ABSTRACT FROM PUBLISHER]

In the case of direct or indirect contact with electrically energized parts, an electric current circulates through the body. When the magnitude and duration of the current through the heart exceed the ventricular fibrillation thresholds, the cardiac muscle starts uncoordinated contractions, greatly jeopardizing the life of the subject. Technical standards on electrical installations describe the protective measures against direct and indirect contact necessary to minimize the probability of inception of ventricular fibrillation. Safety considerations are based on experiments made in the past on animals, but the extrapolation of results to human beings is complex and rather questionable. The purpose of this study is to analyze the body factors that affect the distribution of currents passing through the human body with virtual anatomical models. A set of 16 models of individuals is used to simulate different electric contacts. The use of virtual models of a diverse population (i.e., eight males and eight females, ten adults and six children) provides a statistical support to the results. The obtained heart-current factors, are compared with values present in the literature. This paper provides a novel viewpoint on the problem, and supports the ongoing research activity and efforts to improve the electrical safety of persons. [ABSTRACT FROM PUBLISHER]

Driving is full of unpredictability and uncertainty. Standardized drive cycles, traditionally defined as velocity–time profiles, serve as test-beds for performance prediction. However, these generalized patterns do not offer real-life testing scenarios for every trip a vehicle might encounter during its life cycle. Thus, the “Journey Mapping” concept is highlighted in this paper, which redefines drive cycles more realistically as the journey of a vehicle from an origin to the destination is influenced by weather, terrain, traffic, driver behavior, road, and aerodynamic conditions. AMESim software simulations for a Ford Focus Electric 2012 were seen to predict energy consumption with about 5% error, on average, compared with the true vehicle values. [ABSTRACT FROM AUTHOR]

This paper proposes an isolated universal-link ac–ac power converter suitable for grid connection. The proposed power converter can have multiple ports to connect various loads or electric energy sources, and the configuration can be arranged according to the situation. The proposed power converter does not need to employ the large interface inductor at input side and the huge electrolytic capacitor at dc link. Moreover, it utilizes high-frequency transformers for the galvanic isolation instead of bulky line-frequency transformers. These characteristics of the proposed power converter result in the reduction of the system volume and weight remarkably. The proposed power converter is the modular structure, and an H-bridge works as a basic module of the converter. By stacking the modules, the power converter can be adapted to the high-voltage grid and the various types of loads and/or sources. This paper addresses the structure of the proposed power converter and the fundamental principle of power flow. The operation of the proposed converter is verified by both computer simulations and experimental results with a laboratory-level prototype system. [ABSTRACT FROM AUTHOR]

This paper presents an intensive discussion on an overvoltage appearing at the motor terminals of an adjustable-speed drive that consists of a voltage-source pulsewidth-modulated inverter, an induction motor, and a three-phase symmetric long cable. It describes a design procedure for a simple passive electromagnetic-interference filter based on parallel connection of an inductor and a resistor, which is intended for mitigating the overvoltage at the motor terminals. The modeling of the cable and the motor is characterized by focusing on the natural frequency or ringing frequency inherent in the cable used, which is inversely proportional to cable length. Impedance mismatch at the inverter and motor terminals causes the overvoltage that may reach double the inverter dc-link voltage. The effectiveness and validity of the simple design procedure of the filter are confirmed on the 400-V 15-kW experimental system with either a 100- or 200-m-long cable, as well as on computer simulation based on the modeling of the cable and the motor. [ABSTRACT FROM AUTHOR]

Propagating brush discharges can release large amounts of energy. From the point of view of safety, this feature makes them among the most destructive electrical discharges. This paper provides a survey of recent work in the modeling of propagating brush discharges. Experimental data from various authors are compared with a discharge model in which areas of a charged surface are modeled as capacitive cells, and bridges between cells are modeled as spark gaps driven by the tangential electric field between cells. A theory that explains the physics of this particular type of discharge is presented. Charge transfer and post-discharge charge distributions are compared between the theory and the experimental data of several authors. [ABSTRACT FROM AUTHOR]

This paper addresses the design of a new hybrid microelectromechanical systems (MEMS) micromotor. It is a small three-phase axial flux brushless dc (BLDC) motor. The stator is developed following the almost-standard CMOS technology rules used for MEMS manufacturing, and the coils have two copper layers. The rotor is made of a ring permanent magnet assembled over the stator chip. The stator design has been performed using an analytical model also presented in this paper. The microfabrication of the first prototypes is presented, followed by their characterization. With an efficiency of about 42% for an input power of 310 nW, this MEMS micromotor has very good performance and demonstrates the potential of electromagnetic systems at this scale. [ABSTRACT FROM AUTHOR]

This is an introduction to modular steel equipment shelters designed for areas with potential explosion hazards. It serves to review the chronological development of the concept of modular blast resistance, discuss processing industry events driving market demands, and catalog some typical industry responses to date. The paper also reviews levels of industry risk in the context of life safety and protection for essential/critical systems. For the purpose of this discussion, the first tier of risk (personnel protection and life safety) is briefly discussed to provide adequate background. The paper examines the second tier of risk (essential/critical equipment and electrical systems) that facility managers are becoming increasingly concerned with. The paper compares the following: 1) industry guidelines; 2) the known criterion; and 3) the available governing standards for the design and construction of modular blast-resistant structures. It presents a contemporary approach to the second tier of risk and examines the supporting data and analysis. The paper illustrates the process by discussing the following: 1) the design; 2) construction; and 3) testing of one company's blast-resistant modular systems. This includes design verification employing both Single-Degree-of-Freedom (SDOF) models and Finite Element Analysis (FEA). Further validation of the computer modeling techniques was provided by shock tube testing of the structural assemblies, under a range of peak pressures from 5.5 to 60.0 kPa (0.8-8.7 psi). Readers are able to gain knowledge and confidence in the extension of the definition of blast-resistant shelters to include electrical equipment enclosures, further reducing risk and minimizing downtime in the event of an explosive event. [ABSTRACT FROM AUTHOR]

This paper describes the dynamic overmodulation strategies for fast torque control of the high-saliency-ratio ac motor. For the high-saliency-ratio ac motor, the dynamic control of both d- and q-axes currents is required for fast torque control with optimal efficiency. However, in transient operation, the d- and q-axes current regulators are easily saturated even at low speed because the stator inductance is designed large enough to generate the desired reluctance torque. With the conventional overmodulation strategies, the current regulation performance degrades severely compared to a nonsalient motor. In this paper, the drawbacks of the conventional overmodulation strategies are investigated and a dynamic overmodulation strategy is proposed to improve the current response to fast transients. For the effective implementation of the strategy, a practical algorithm is also presented. The performance of the proposed strategy is con- firmed by computer simulation and experiment with a 3.75-kW axially laminated synchronous reluctance motor and an interior Permanent-magnet synchronous motor for 42-V integrated starter-generator applications. [ABSTRACT FROM AUTHOR]

The concept of lightly ferromagnetic rotor bars to improve the starting performance of squirrel-cage induction motors is presented in this paper. Although the induction machines are popular for their ruggedness and simplicity, their starting torque is low and the starting current is 5-8 times higher than the rated current. A simple solution to this problem is the introduction of new rotor-bar material with lightly ferromagnetic properties, which in turn improves the starting power factor due to enhanced skin effect. Relevant electromagnetic theory supporting this is e presented in this paper. A computer simulation also produced expected re sults. A 1-hp induction machine has been tested to verify the proposed methodology. [ABSTRACT FROM AUTHOR]

This paper discusses the suitability of four-phase, five-phase, and six-phase modular machines, for use in applications where servo characteristics and fault tolerance are key requirements. It is shown that an optimum slot number and pole number combination exists, for which excellent servo characteristics could be achieved, under healthy operating conditions, with minimum effects on the power density of the machine. To eliminate torque ripple due to residual cogging and various fault conditions, the paper describes a novel optimal torque control strategy for the modular permanent-magnet machines operating in both constant torque and constant power modes. The proposed control strategy enables ripple-free torque operation to be achieved, while minimizing the copper loss under voltage and current constraints. The utility of the proposed strategy is demonstrated by computer simulations on a four-phase fault-tolerant drive system. [ABSTRACT FROM AUTHOR]