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Repeated impulses have long been considered to affect the insulation properties of electrical equipment. This interesting but rarely studied phenomenon may pose great risks to the reliable operation of power equipment. Therefore, in this work, we focus on the accumulative effect of repeated lightning impulses on the oil-impregnated paper (OIP) used in power transformers. Specifically, we study the effect of space charge on the accumulative characteristics of OIP. A repetitive impulse accumulating test platform was set up, and the tests were conducted to obtain the accumulative characteristics of OIP under repeated lightning impulses. The accumulative characteristics of OIP with various interval time were experimentally identified to study the influence of interval time on the accumulative effect. Then, space charge in OIP samples were investigated using the pulsed electro-acoustic technique. Charge behavior in OIP was analyzed under different conditions, i.e., changing the applied times, amplitude and interval time of the applied lightning impulses. Charge injection and transport occurred during lightning impulse accumulation. The increased application of lightning impulses, high applied voltage, and short interval time contributed to the accumulation and transport of space charges. At last, the possible mechanisms of the accumulative effect are discussed in this article based on the experimental results. [ABSTRACT FROM AUTHOR]

Sheet tension control is crucial in the paper winding process in order to get properly formed shipping roll(s) produced in the winder. Typically, the tension loop uses load cells as tension sensors, which are expensive and require frequent maintenance and calibration. This paper develops two new tension estimators for a two-drum electric-braking-generator production winder, based on unwinding and rewinding variables, respectively. The estimators consider all the essential dynamic, friction, and inertial variation effects. Both estimators are evaluated in typical trapezoidal winder operating cycles. Multiple sensitivity analyses show that the proposed estimators are robust to normal parameter variations, and give stable and precise sheet tension control without the use of load cell tension loops. [ABSTRACT FROM AUTHOR]

Presents a study on deterioration diagnostic techniques for applying to oil-impregnated paper film capacitors. Information on power capacitors; Methodology used in the various tests involving accelerated deterioration; Main causes of deterioration of power capacitors; Investigation of the degree of the deterioration of insulating oil power capacitors; Findings of the investigations.

The article discusses on the 32nd International Conference on Plasma Science (ICOPS) held in Monterey, California. This Special Issue focuses on Plenary and Invited Papers from ICOPS. There are invited talks included in the issue which subjects ranged from the traditional interests in basic plasma processes, microwave generation and charged particle beams, and other plasma-related topics.

Comments on a paper which suggests a ring hybrid adopting a Marchand balun. Use of the main concept that the ring hybrid consists of an in-phase divider and a balun; Comparison between measured and theoretical results of a Marchand balun without an in-phase power divider.

This paper evaluates the relationship between hazardous-rated electrical equipment, which is suitable for installation in Class I, Division 1 (Zone 1), or Division 2 (Zone 2) locations, and an arc-rated switchgear, which is designed to withstand the effects of an internal arcing fault. Using UL 1203 (Explosion-Proof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations), IEEE C37.20.7 (IEEE Guide for Testing Metal-Enclosed Switchgear Rated Up to 38 kV for Internal Arcing Faults), and the paper titled “Pressure Developed by Arcs,” this paper will explore the applicability of hazardous-rated equipment in the protection of personnel from an arc-flash hazard. [ABSTRACT FROM PUBLISHER]

This paper at first proposes a method to calculate a trigger strategy before launching in order to control the muzzle velocity of railguns. Five triggering points are set equidistantly and six pulsed forming unit (PFU) groups are triggered in total. First, given a desired muzzle velocity, the expected uniformly accelerated rectilinear motion of the armature is calculated. Second, the module number of each PFU group is obtained according to the principle of minimizing the absolute relative error between the actual and the expected velocity at each triggering point. The results show that, when the desired muzzle velocity is within [1500, 2000] m/s, the absolute muzzle velocity relative error $\delta $ is less than 0.5%. In order to achieve a better control performance, the places of the five triggering points are then optimized by a genetic algorithm (GA). The objective function is the sum of absolute $\delta $ , when the desired muzzle velocities are 1500, 1600, $\ldots $ , 2000 m/s. After the optimization, $\delta $ is reduced to less than 0.05%. At last, based on this velocity control method, the railgun system is optimized to pursue the highest system efficiency $\eta $ by GA. The independent variables are the armature mass, the precharged voltage, and the places of the five triggering points. The constraints are that the desired muzzle velocity is 1800 m/s and the absolute $\delta $ is within 1%. The results show that $\eta $ increases from 6.57% to 25.37%. [ABSTRACT FROM AUTHOR]

The significant benefits of preemptive arc-flash protection and the online condition monitoring of electrical equipment are quite well known. Our continuing research focuses on the development of new advanced sensor technologies that are cost-effective, reliable, and efficient for the early detection of faults in order to predict impending arc-flash occurrences in mediumvoltage and low-voltage switchgear and controlgear. More extensive and detailed measurements regarding significant defects that lead to an arc-flash event have been completed since the original work in Part I was completed. A more detailed analysis of the results of this additional testing is presented in this paper. It has been documented that the two major noncontact causes that lead to an arc-flash event in switchgear are insulation degradation and thermal stresses. This paper covers the detailed measurement results under both of these conditions. New sensor technologies for both the partial discharge measurement and the thermal detection are introduced and evaluated. An effective signal processing technique, which is needed for extracting the essential indication of a developing fault, is also presented. Finally, this paper outlines how a preemptive arc detection system can be connected to protection, the programmable logic controller, or the supervisory control and data acquisition. [ABSTRACT FROM PUBLISHER]

Batteries are the most commonly used electrical energy storage devices. The cost and performance of an electric vehicle (EV) are strongly affected by the proper selection of technology, number, and arrangement of the battery cells used. This paper formulates the problem of optimal sizing of the battery unit (BU) for a plug-in EV (PEV), given the specifications of the vehicle, battery cell data, and drive cycle. This paper employs a metaheuristic optimization algorithm to find the optimal size of the BU with the objective of minimizing the overall cost. Feasibility of the optimization results in terms of respecting the constraints is verified via simulation. The developed optimization platform is highly flexible and allows use of different vehicle designs, component data, and drive cycles. [ABSTRACT FROM PUBLISHER]

Magnetic shape memory (MSM) alloys are relatively new smart alloys, which have enormous potential to be used in actuators, sensors, and other electrical devices. Their large strain and considerable stress output can be controlled by magnetic fields or mechanical stresses. Maximum magnetic field-induced strain varies from 6% to 12% of the MSM element’s length depending on its microstructure. However, very low operational temperature limit is one of the main drawbacks of conventional MSM alloys. This makes their application in high-performance actuators challenging due to considerable power losses. This paper discusses different MSM actuator designs, optimized particularly for large force output for pneumatic electromagnetic valve applications. The thermal problem is addressed through analyzing the heat transfer conditions of each particular design and the effects of different cooling systems. An energy-efficient operating cycle for varying actuator loads that takes advantage of the shape memory effect is also proposed. This allows the minimization of energy losses, resulting in an acceptable increase in the temperature ensuring stable continuous actuation. [ABSTRACT FROM AUTHOR]

This paper presents a 2-D hybrid analytical modeling method for the analysis of the magnetostatic field distribution with the capability of including nonlinear materials. The model combines Fourier modeling, which is accurate and fast, with meshed magnetic equivalent circuits that have unique permeability in mesh elements and, therefore, can model local saturation. To present the diverse applicability of the proposed method, it is applied to a linear machine with permanent magnet excitation and a rotary machine with current excitation. Magnetic field calculations are compared with finite-element analysis (FEA) with good agreement. [ABSTRACT FROM AUTHOR]

This paper presents a technique for circuit breaker radiometric monitoring using broadband plana monopole antennas (PMA). Considering that this work represents the continuity of a previous research, the antenna has been miniaturized using a bioinspired geometry based on the Acer Macrophyllum leaf. The monitoring system consists in measuring the signal radiated by electric arcs in circuit breaker poles during its switching operations. By analyzing these signals, it is possible to evaluate, non-intrusively, the equipment electric and mechanical status, providing important information to maintenance crews regarding the need for interventions. By performing laboratory tests, it was confirmed that the developed bioinspired PMA has adequate gain values, radiation pattern and frequency range to circuit breaker monitoring applications. Moreover, field tests on a 230 kV SF6 circuit breaker were carried out, from which the proposed technique applicability was confirmed. The proposed monitoring technique can be considered a continuous and non-invasive solution, since the antennas can be placed at a safe distance from the equipment under analysis, without compromising the insulation. In the substation, the technique has the potential to detect problems of electrical and mechanical nature, since important operational parameters can be detected, such as opening time and pole synchronicity. [ABSTRACT FROM AUTHOR]

The efficiency of a railgun can be defined as the exchanged transferred electrical energy to the kinetic energy of the armature. According to the good relation between the applied force to the armature and the inductance gradient (L′), the importance of this parameter calculation is obviously clear. There are several researchers who calculated L′ using different numerical and analytical methods in these years. The analytical method to solve the simple problems is suitable, and numerical methods include sufficient coding time and programmer performance time. A method will be introduced in this paper to extract a formula or formulas of L′ using structural railgun parameters which can cause the results similar to the results of the numerical methods. This method has not any time problem, and so, there is a good accuracy of data analysis. In this technique, which is called intelligent estimation method, according to the behavior of the railgun magnetism and its geometrical structure, an equation with unknown multiplications for L′ formula is defined. Then, by applying the reported data in different studies for L′, these equations can be found. Finally, the proposed method introduces a closed formula for a given structure of railgun. A rectangular configuration is investigated as a case study in this paper. [ABSTRACT FROM AUTHOR]

The thrust ripple in a permanent magnet linear synchronous motor (PMLSM) is mainly generated by the detent force that is caused by the interaction between the permanent magnet (PM) and the iron core without input current in armature winding. This paper proposes two different techniques to minimize the detent force in a PMLSM. One is to choose an optimal constructive design; the other is to employ a current compensator. In this paper, we investigate the performance of detent force minimization using both of them. The effectiveness is verified by both numerical and experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a new method regarding fault distribution modeling for the stochastic prediction study of voltage sags in the distribution system. 2-D stochastic models for fault modeling make it possible to obtain the fault performance for the whole system of interest, which helps to obtain not only sag performance at individual locations but also system sag performance through system indices of voltage sag. By using the bivariate normal distribution for fault distribution modeling, this paper estimates the influence of model parameters on system voltage sag performance. The paper also develops the modified SARFIχ regarding phase loads that create better estimation for voltage sag performance for the distribution system. [ABSTRACT FROM AUTHOR]

This paper shows the generation of a local oscillator (LO) signal for cellular transceivers by means of a phase-locked loop and a phase interpolator (PI) digital-to-time converter (DTC). The PI-DTC allows arbitrary frequency shifts over a wide range. We derive a closed-form description of the spurs in the spectrum of the LO signal caused by quantization and nonlinear effects for the PI-DTC. Furthermore, we show the existence of a new class of spurs generated due to noise processes in the PI. Measurement and simulation results are in good agreement with our closed-form solution. [ABSTRACT FROM PUBLISHER]

Armature-reaction-compensated permanent-magnet synchronous generators are a particular type of hybrid excitation synchronous generators, where the main flux is created by the permanent magnets and the field winding is needed only to compensate the armature reaction. This paper studies the feasibility of an armature-reaction-compensated permanent magnet synchronous generator in island operation by comparison with a conventional electrically excited synchronous generator and permanent magnet synchronous generator. The aim of this paper is to demonstrate the performance of an armature-reaction-compensated permanent magnet synchronous generator and its operation principle in island operation. As part of the study, a 55 kW prototype was built and tested. The experimental results of the prototype are presented. [ABSTRACT FROM PUBLISHER]

This paper proposes a multidisciplinary procedure to correctly design a microgrid of all-electric nearly zero energy buildings (nZEBs) from both electrical and thermal points of view. The procedure is suitable for new buildings supplied by local renewables, without the use of fossil fuel and with zero emissions. First, the thermal demand of each single nZEB is assessed, as a function of the installation site, building layout and physics, and material composing the envelope. Thanks to heat pumps, the thermal demand is transformed in electric load. Thus, the total electric consumption profiles, which include user's appliances and heating/cooling, are studied and compared with photovoltaic (PV) generation supported by electrochemical storages. Both PV and batteries are simulated, thanks to appropriate models. Regarding the PV production assessment, this work proposes an improvement with respect to the use of traditional models, and it is based on experimental results on PV generators of recent production. The design methodology is applied to a real case of “energy community” composed of three nZEB units that will be built in the campus of Politecnico di Torino, available to students and staff. The three units share PV production and storage capacity to reach the complete grid independence. [ABSTRACT FROM AUTHOR]

This article presents the author reply to acknowledge that the paper by K. Myneni and colleagues is to the best of his knowledge, the first publication on using chaotic laser output for optical ranging. It is not his intention to neglect due credit to the authors for theft work. Indeed, he has done detailed studies on both chaotic lidar and chaotic radar. Their work is cited and discussed in this paper on chaotic radar, which is to be published in a forthcoming issue of this journal. In his opinion, it is most appropriate to cite their work in that paper be- cause their work is on optical ranging, not microwave ranging. Though they did mention radar in the introduction and conclusion, no work was done on radar. As per the author, it is not inappropriate to not keep on citing the same paper for the following reasons: it is more appropriate to cite and give due credit to in the chaotic lidar paper, which is more relevant to their work; reference does not contain any real work on radar; and aside from sharing the concept of using chaotic waveforms, chaotic lidar and chaotic radar are fundamentally different in most technical aspects.

The rapidly quenched soft magnetic materials have found many practical applications in power electronics, electric engineering, telecommunications, and other industrial sectors. The aim of this paper was to present the results of a research on fabrication technology of the amorphous and nanocrystalline cores intended for: 1) soft magnetic cores for the stators of the high-speed permanent magnet brushless direct current (PMBLDC) motors; 2) nanocrystalline soft magnetic cores for application in high-frequency power conversion; and 3) three-limb amorphous cores for the three-phase distribution transformers. The cores intended for the stator of the high-speed PMBLDC motor were made from the Metglas 2605 SA1 ribbon and then subjected to the performance tests in a model of an electric motor. The research on soft magnetic materials for high-frequency high-power conversion was concentrated on the Finemet rectangular cores with a gap and the composite ones with distributed gap, and the comodified Finemet cores with the induced transverse magnetic anisotropy. The three-limb cores for 400 kVA three-phase distribution transformer were made from the Metglas 2605 SA1 ribbon and subjected to the performance tests in electricity distribution network. It was found that all the amorphous and nanocrystalline cores fabricated under this paper enable considerable reduction in power losses. [ABSTRACT FROM PUBLISHER]

Coreless transformers are used in several applications, operating in a large range of frequencies. Their equivalent circuit model is very important to allow the proper design of any electronic circuit or load that may be electrically coupled to them. Especially, in cases where the coils of these devices are modeled with a relatively large wire gauge (when compared with the skin depth), the losses due to eddy currents must be included, otherwise their circuit simulation will be incorrect. This paper proposes a method that allows modeling the lumped parameters of coreless transformers, including the eddy currents. The method uses an optimization algorithm search through a genetic algorithm solver. Although the scope of this paper lies within coreless transformers, the whole method was designed in a generic way to model different types of electric equipment. [ABSTRACT FROM AUTHOR]

This paper presents a modulation strategy for the modular multilevel converter (MMC) which provides the voltage balancing of the capacitors of different submodules comprising the converter. Not only is this modulation applicable to MMCs constructed with classic two level (2L) submodules, but it is also effective for arrangements with different submodule concepts, for instance, topologies like neutral point clamped (NPC), flying capacitors (FCs), neutral point piloted (NPP), etc. Therefore, firstly, the general modulation philosophy is explained applied to the two level (2L) submodule concept, and secondly, the extension to 3L-NPC and 3L-FC submodule topologies is analyzed. After that, the validation of the studied modulation strategy is carried out by means of successful simulation results, at different switching frequencies and number of submodules. The corresponding experimental results are shown in Part II of this paper after having implemented the aforementioned modulation strategy in a real test bench. In addition to this, a comparison based on thermal analysis and sizing of elements among the four studied submodule topologies is also included. [ABSTRACT FROM PUBLISHER]

This paper highlights the importance of chronology on voltage protection and control apparatuses in studies of voltage security in active distribution networks with high generation capacity. This paper presents simulation results of a real-life example of a long rural distribution feeder having three voltage regulators in cascade, and a customer whose demand accounts for a large percentage of the total feeder load. The customer is also an independent power producer and its location at the far end of the feeder yields an intricate voltage protection coordination when the customer ramps up and down its own generation at the peak-demand period. [ABSTRACT FROM AUTHOR]

A novel apparatus based on variable inductors to control the insertion compensating voltage of the transmission line is proposed in this paper. The apparatus can change the alternative voltage into the desired alternative voltage directly by using the control strategy proposed in this paper and insert the voltage into the line. Since the amplitude and the phase angle of the voltage supplied by the apparatus can be adjusted continuously and independently, the apparatus can control the real- and reactive- power flow independently and realize the direct voltage regulation (DVR) and the phase angle regulation (PAR) of the transmission line. The control methods suited for the proposed apparatus about the independent control of real and reactive power flow in the transmission line and the DVR and the PAR are also proposed. The control strategy and methods are verified with experimental results and simulation results. [ABSTRACT FROM PUBLISHER]

A novel scheme is proposed to monitor the operation of capacitors scattered in MV distribution systems. It first codes each capacitor with a distinctive switching character by setting a unique combination of a three-phase switching order and time interval. As a result, the transient of the three-phase reactive power during capacitor switching will appear in a unique way. Then, the reactive power disturbances monitored in the substation are decoded to identify which capacitor is being switchedonandoff. A detailed decoding method is developed to realize this identification without being impacted by the switching interference of loads and other reactive power compensation devices. Moreover, the implementation of the proposed scheme in the field is elaborated, and the resultant three-phase voltage unbalance is analyzed in this paper. Compared with existing methods, this scheme only requires one power quality monitor located at the substation to monitor the operations (energizing or de-energizing) of downstream distribution capacitors without extra communication devices. The operation information is valuable for tackling power quality problems caused by capacitor switching and optimizing the distribution grid operation. [ABSTRACT FROM AUTHOR]

Efficiency and power loss are the necessary metrics for evaluating the performance of electrical drives. These two metrics are calculated based on the measured input and output power of the drive. Input power is calculated from the measured terminal voltages and currents, whereas output power is calculated by multiplying the measured motor speed with the measured shaft torque. Torque transducers are normally used to measure the windup shaft torque. This method is effective for steady-state speed operation. This paper proposes an observer structure that uses standard dynamometer sensors that are capable of estimating the shaft torque during both steady-state and transient speed operations. This enables the motor losses to be measured during transient speed operations (acceleration/deceleration), which is generally not feasible using standard torque sensors. [ABSTRACT FROM AUTHOR]

This paper analyzes the power-cycling capability of insulated-gate bipolar transistor (IGBT) modules in a conventional matrix converter used as a motor drive. The analysis is made under various conditions for this topology, including low-speedoperation capability, high-speed thermal and power-cycling capabilities, etc. It was found that the power-cycling mean time to failure of IGBT in a matrix converter is low when the input and output frequencies are close to each other or when the output frequency of the converter is low. As a result, the chip size of the conventional matrix converter may be larger than the other candidates. In the end of this paper, some guidance for designing a matrix converter for long-term reliabilities is also discussed. [ABSTRACT FROM AUTHOR]

Power systems with high penetration of wind power usually require long-distance transmission to export wind power to the market. Interarea oscillation is an issue faced in long-distance transmission. Can wind generation based on doubly fed induction generator (DFIG) help to damp oscillations and how? In this paper, a control scheme is developed for the DFIG with rotor-side converter to damp interarea oscillations. The DFIG is modeled in MATLAB®/Simulink utilizing its vector control scheme feature, and inner current control and outer active/reactive power control loops are modeled and designed. A two-area system that suffers from poor interarea oscillation damping along with a wind farm in the area that exports power is investigated. A damping controller is designed and time-domain simulations are used to demonstrate the effectiveness of the controller. The major contributions of the paper are as follows: 1) built a wind farm interarea oscillation study system based on the classical two-area four-machine system, 2) established that in vector control scheme, active power modulation can best help to damp oscillations, 3) successfully designed a feedback controller using remote signals with good interarea oscillation observability. [ABSTRACT FROM AUTHOR]

The direct thrust control (DTC) has been utilized as a general formalism methodology for permanent-magnet linear synchronous motors (PMLSMs). The imposition control policies did not seem to handle the inherent flux linkage problems. This paper will try to propose a solution for the problems. This paper presents a genetic P1 parameters generator and a new DTC policy for the motor control systems. Moreover, this paper also proposes a new switching table which can assist in selecting the optimum voltage vectors for the control system. The advantage of the proposed approach is that the clear presentation of the system behavior and readiness for implementation. Finally, some results of the simulation and the experiment both are met as expected. To the authors' knowledge, this is the first work that employs DTC to implement on a real-world PMLSM which is starting at arbitrary positions and can be allowed moving in the full route. [ABSTRACT FROM AUTHOR]

In a master-slave system, improving the positioning performance and the stability is needed in the case of remote control. However, if there exists time delay, the system destabilizes the performance. Furthermore, it is important to maintain the stability of not only the system but also the controlled object. This paper describes a strategy to improve these problems. This strategy enables operators to get a degree of time delay and instability by keeping the motion performance and the stability. The unstable response with a time delay is restrained by adjusting PD controller gains based on the velocity error of master-slave. Furthermore, switching bilateral control and autonomous control of slave without falling into unstable state is constructed when that cannot be restrained because of long time delay or unexpected disturbances of slave motion. The validity of the proposed strategy is confirmed by experiments stabilizing an unstable component, i.e., an inverted pendulum of slave system. [ABSTRACT FROM AUTHOR]

A 500 kJ compact pulsed power supply (PPS) system used for electromagnetic railgun (EMG) system has been developed to investigate the influence of electric parameters on muzzle velocity in the paper, from which the stability and reliability of the PPS system can be evaluated. The pulsed power supply system consists of ten modules, and each module is composed of a high energy density capacitor, a triggered vacuum switch, a pulse shaping inductor, a dump resistor and a crowbar. Influence of different parameters on the velocity was analyzed by ATP simulations in this paper. The parameters include capacitance, equivalent series resistance (ESR) of the capacitor, inductance, natural electric parameter and jitter time of the TVS. The ESR and natural electric parameters are critical influencing factors by comparing the simulation and experimental results. In the end, muzzle velocity deduced by the current, which is obtained from a new model of actual circuit, is about twenty percent lower than that in ideal condition. It is pointed out that the velocity error is mostly caused by ESR and natural electric parameter. [ABSTRACT FROM AUTHOR]

This paper presents a detailed description of design and simulation of a self-excited All-Air-Core and fabrication of a separate-excited All-Iron-Core compensated pulsed alternators (compulsator), also including the similarity and difference in configuration and principle of two prototypes. Presented are fabrication techniques, assembly processes and design methods developed specifically for pulsed power generators, including the carbon fiber rein-forced epoxy resin composite material usage of stator and rotor core in All-Air-Core compulsator, and the armature and field winding fabrication techniques and conglutination processes in All-Iron-Core compulsator. The armature winding is wound concentric winding by fiat copper bars, the end-turn superposition problem solved by heating the flat copper bar to soften them for taking shape. Designs of a lightweight self-excited All-Air-Core rotating-field passive compulsator and a separate-excited All-Iron-Core compulsator for comparison have been completed. They all have rotating-field, two-phase, four-pole, and slotless armature winding and passive compensation. The heart of the self-excited All-Air-Core passive compulsator is carbon fiber rein-forced epoxy resin composite rotor which rotates at 10000 rpm or more, and that epoxy composite resin stator reduces the saturation of the compulsator, which consequently reduces transient inductance of armature winding and increasing the magnitude of pulsed current. The usage of composite material also reduces the mass of the All-Air-Core compulsator and increases the velocity of the rotor and inertial energy storage, therefore increasing the energy density and power density. Another feature of the All-Air-Core PCPA is the use of two armature windings on the stator, which allows optimization of each armature winding to its specific duty cycle Control of self-excited process is presented as well as the synchronous control of solid-state switch in excitation circuit and discharge main circuit by the special controller. The paper presents the simulation of magnetic field at no-load and discharge instance respectively. The paper analyzes the impact of the thickness of compensation shield to the performance of compulsator. Finally, the experiment schematic of All-Air-Core compulsator system is presented. [ABSTRACT FROM AUTHOR]

The objective of this paper is to propose a new method to detect the rise of equivalent series resistor in order to realize the online failure prediction of the electrolytic capacitor for LC filter of switching-mode power converter. Characteristics of electrolytic capacitors are introduced in this paper. Different experimental measurements are conducted and shown to illustrate the properties of electrolytic capacitors. The proposed online failure prediction method has the merits of low cost and circuit simplicity. It can be integrated within the package of the electrolytic capacitor to improve its reliability. Hardware experimental results are shown to verify the performance of the proposed method. [ABSTRACT FROM AUTHOR]

A generalized approach for the assessment and description of compatibility levels between the power supply system and electrical equipment is proposed in this paper. The proposed approach is an alternative to the existing, widely used concept of electromagnetic compatibility (EMC). The existing EMC concept uses only two general stages for description and quantification of all possible interactions between power supply system and connected electrical equipment. This paper, on the other hand, discusses different types of power quality disturbances, as well as situations in which equipment has multiple malfunction criteria. The subject of the EMC is analyzed here from the equipment point of view. [ABSTRACT FROM AUTHOR]

High voltage is known to be one of the main control variables in any electrostatic-separation process. From this perspective, the aim of this paper is twofold: to develop an effective high-voltage monitoring system and to demonstrate that it can be a useful tool for controlling the overall operating conditions of an electrostatic-separator system. A custom-designed virtual instrument was employed for processing the experimental data provided by a high-voltage probe, the output of which was connected to an electrometer. In several experiments, the output of the high-voltage probe was also connected to a digital oscilloscope, in order to obtain a better understanding of the variation of the electrode potential after a spark discharge. The laps of time without corona discharge and/or with low electric field intensities could thus be accurately determined, and the impact of the spark discharges on the outcome of the separation process evaluated. The dispersion of high-voltage measured values was found to increase in the presence of the material. The statistical analysis of the data revealed a significant correlation between the standard deviation of the high-voltage and the concentration of metal in the processed material. The results of this paper could be helpful for those seeking the optimization of the operating conditions for the electrostatic separation applications, in which the metal content in the feed materials exhibits substantial fluctuation with time. [ABSTRACT FROM AUTHOR]

This paper presents a fully-digital-controlled shunt hybrid filter for damping of harmonic propagation in power distribution systems. The harmonic propagation is caused by resonance between line inductances and power capacitors installed for power factor correction. possible solution to damping out harmonic propagation is based on installation of a shunt pure active filter at the end of a feeder. This paper proposes a shunt hybrid active filter characterized by series connection of a seventh-tuned LC filter per phase and a small-rated three-phase active filter. Like the pure filter, the hybrid filter is connected to the end bus of a feeder. The capacitor of the LC filter imposes a high impedance to the fundamental frequency, so that the fundamental voltage appears across the capacitor. This unique feature allows us to directly connect the hybrid filter to the 6.6-kV power line without step-down transformers. Furthermore, the capacitor used in this hybrid filter is lighter, cheaper and smaller than the transformer used in the pure filter. Theoretical analysis, along with experimental results obtained from a 200-V, 20-kW laboratory system, verifies the viability and effectiveness of the proposed hybrid filter. [ABSTRACT FROM AUTHOR]

This paper describes an index for judging the severity of transient events in simulation. The integral square generator angle (ISGA) index strongly penalizes diverging generators but also accounts for steady-state transfer levels. This paper presents decision trees (DTs) and the ISGA index for contingency ranking and screening. Then, the ISGA is demonstrated for finding combinations of discontinuous feedforward controls to stabilize an event. [ABSTRACT FROM AUTHOR]

High-voltage, nanosecond, high-repetitive-frequency, and portable pulse generators are always required in many fields. Avalanche transistor-based Marx circuits have been widely studied to generate pulses satisfying the above requirements. However, the basic topology of an avalanche transistor-based circuit, configuration of circuit parameters, and optimal working performance (including output impedance matching) were still scarcely discussed. In this paper, the detailed process of analyzing and designing a compact Marx generator using avalanche transistors was described. Based on the conventional principles of avalanche transistors and Marx circuit, a list of useful and interesting conclusions was discovered by experiment. An example with specific parameter requirements was utilized for the clearness of illustration. The 12~cm\times 4 cm Marx circuit could finally generate pulses with a 2.5-kV amplitude, 6.0-ns width, 10-kHz repetitive frequency, lower than a 100-ps jitter and $\sim 125$ -kW maximum peak output power on a matched 50- $\Omega $ resistive load. The pulse amplitude could be adjusted from 1.5 to 2.5 kV and the pulse width could also be broadened. This paper may help to provide a reference to similar methods of producing high-voltage, nanosecond, and high-repetitive-frequency pulses. [ABSTRACT FROM PUBLISHER]

The article discusses various issues published within the issue including one by Salvador Ceballos and associates on a modified neutral-point clamped inverter with a fourth flying capacitor and another by Yun Wei Li and associates on the various space vector modulation switching sequences.

Based on understanding the characteristics of the impulse force generated by pulsed current of the armature, it is valuable to explore effective ways to improve the armature structure to enhance the stability and prevent from the transition and erosion during launching. This paper first lists a series of conversional armature and the characteristics of these armatures are illuminated. A C-shaped armature is simulated based on the electrical–magnetic–mechanical coupled analysis method. The simulation shows that the stress is mainly distributed in the area between the cross member and arm, it may lead to local deformation. A novel concave armature is proposed and the simulation results indicate that the stress is mainly distributed in the inner side of arm and the front of armature. It is beneficial to push heavy load and avoid deformation and fracture. A device is built to validate the feasibility of armature. The armature is staying still to simulate pushing the infinite heavy load. The experimental results show that the concave armature endures higher current and has the stronger capability of pushing load compared with the C-shaped armature. This type of armature provides a valuable reference for future armature design. [ABSTRACT FROM PUBLISHER]

Wireless power transfer using magnetic resonant coupling is expected to be widely used in the charging of an electric vehicle and in the use of home electric appliances. Wireless power transfer requires a high efficiency and power transfer over a long distance. However, the efficiency is reduced by the increase of the transmission distance and the change of the impedance of the receiving load. Therefore, a distance sensor using magnetic resonant coupling is proposed. In this paper, we propose a method of power transfer and distance detection using one couple of coils in real time. We also propose to use different frequencies in the power transfer and the distance detection, which are superposed and separated. Using the proposed approach, we demonstrated that the power transfer and the distance detection can be performed without relying on the change of the transmission distance. [ABSTRACT FROM AUTHOR]

In this paper, two new topologies are proposed for multilevel inverters. The proposed topologies consist of a combination of the conventional series and the switched capacitor inverter units. The proposed topologies reduce the number of switches and isolated dc voltage sources, the variety of the dc voltage source values, and the size and cost of the system in comparison with the conventional topologies. In addition, the proposed topologies can double the input voltage without a transformer. There is no need for complicated methods to balance the capacitor voltage. The simulation and experimental results of single-phase 25- and 17-level inverters are given to prove the correct operation of the proposed topologies. [ABSTRACT FROM PUBLISHER]

Heating and current drive (H&CD) systems are being investigated for a demonstration fusion power plant DEMO to deliver net electricity for the grid around 2050. Compared to ITER, which has to show the generation of 500-MW thermal power, the target of DEMO is the successful production of 300 to 500 MW electrical power to the grid and to aim for a self-sufficient tritium fuel cycle. Three H&CD systems are under development for DEMO in Europe, the electron cyclotron (EC) system, the neutral beam injection (NBI) system, and the ion cyclotron system. Based on present studies for plasma ramp-up, ramp-down, and flat top phases, to be further validated in more detailed simulations, the assumed total launched power needed from the H&CD system in DEMO is in the range of 50–100 MW, to be provided for plasma heating and control. This paper describes the design and Research and Development status of selected H&CD systems, considered for their deployment in the EU DEMO. It was always considered that different H&CD configurations and design variants will have an impact on the performances for the whole fusion plant. It shall be noted that the basis for the H&CD integrated design and system development is the actual version of the European fusion electricity roadmap. The project also elaborates on H&CD efficiency improvements which will reduce the recirculating power fraction in the future fusion power plants. Different studies under investigation will be discussed such as for NBI the photoneutralization and for EC novel concepts for gyrotron multistage-depressed collector. [ABSTRACT FROM AUTHOR]

The ground return current of a high voltage direct current system will intrude the transformers adjacent to the grounding electrode in the case of monopole operation, leading to the half-cycle saturation of transformers. To mitigate the adverse effect, placing dc blocking devices (BDs) in transformer neutrals is popularly advocated. The conventional switching method of BDs may redirect the dc flow from one transformer with a BD to neighboring transformers without BDs. In this case, the dc currents through the neutrals of those transformers may possibly exceed the threshold undesirably. This problem is due to the lack of guidance for dc current distribution from the global view by means of finite BDs. Thus, this paper presents an optimization approach for the switching of BDs based on the gravitational search algorithm. A mathematical model for investigating the dc global distribution is established with the equivalent resistive network of an ac system, the location distribution of substations and grounding electrodes. Then, an optimal switching scheme to minimize the adverse impact of dc bias is presented, and the principle and the concrete implementation process are detailed. The feasibility and the advantage of the proposed scheme are demonstrated by numerous comparative case studies. [ABSTRACT FROM AUTHOR]

In this paper, the investigation is focused on the iron loss prediction for electrical machines fed by low switching frequency inverter. An improved iron loss model is developed after reviewing various existing iron loss models considering pulse-width modulation (PWM) influence. In order to validate the improved iron loss model, iron loss tests are carried out on an electrical machine. The predicted iron loss results match well with the measured results, which shows that the improved iron loss model is able to predict iron loss in electrical machine fed by an inverter. The comparison between the predicted iron losses with and without considering the PWM influence shows that the iron loss can be significantly increased due to the influence of PWM, especially when the switching frequency is low. [ABSTRACT FROM AUTHOR]