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For forest-products-based industries, the significant benefits of preemptive arc-flash protection and online condition monitoring of electrical equipment are not well known. This paper provides a summary of the research surrounding the development and testing of new advanced sensor technologies for this purpose. This paper builds on the authors' initial research and their supporting publications providing more extensive and detailed field measurements supporting the preemptive detection of significant defects that can lead to an arc-flash event. The early detection of impending faults and the prediction of future arc-flash occurrences in medium voltage (MV) switchgears and motor control centers (MCCs) can be very beneficial. The development of new sensor technologies both for partial discharge measurement and thermal detection are discussed and evaluated. The two most common noncontact causes leading to an arc-flash event in MV switchgears and MCCs are insulation degradation and thermal stresses. This paper will highlight very detailed results measured under both of these conditions in laboratory and actual installed conditions. An effective signal processing method, which is used for extracting the essential indication data and for the integration of this system into existing protection programmable logic control or supervisory control and data acquisition (SCADA) systems, is outlined. [ABSTRACT FROM AUTHOR]

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 proposes a vector control strategy for independent control of two permanent-magnet synchronous motors (PMSMs) using a single four-leg inverter (4LI). An expanded two-arm modulation to obtain a balanced three-phase output voltage is described. This paper also proposes a method to compensate for the fluctuations in the neutral point voltage of two split capacitors in the dc link. The experimental results show that independent speed and position control of two PMSMs can be achieved using a single 4LI with the proposed vector control method. [ABSTRACT FROM AUTHOR]

This paper will present a new approach that is advantageous to medium-voltage (MV) distribution design configurations for large industrial and power distribution system configurations [specifically main-tie-main (MTM)] for large industrial and power station installations. Sixty years of traditional low-cost design approaches (typical MTM and operated with open tiebreaker) are re-evaluated to demonstrate that traditional low capital cost design may miss improvement opportunities. Those opportunities can be major capital expenditure reduction, power quality improvement, MV motor soft starter deletion, and improved system stability to name a few. Many designers may not have considered the component interrelationships and/or their tradeoffs when in an integrated system. The designer and/or user should consider the advantages of higher short-circuit capacity (SCC) systems by integrating fault current limiters and MV switchgear. Utilizing higher SCC systems permits power system designer optimization opportunities not possible before using conventional design methods. This paper will provide documentation of substantial savings of capital investment and energy under higher SCC conditions. The savings in one system component will offset another's increased cost. An obvious benefit of stiffer systems is ease of direct-on-line starting of large motor-driven compressor trains. The future need for motor soft starters minimizing system impact will be challenged. This paper may change fundamental system design methodology for system designers by removing several performance tradeoffs. This paper, in its original version, was previously presented at the 2010 IEEE/IAS/Petroleum Chemical Industry Conference. It was expanded with new sections for the 2017 IEEE/Industry Applications Society (IAS)/Pulp, Paper Forestry Industries Conference to include pre-emptive prefault adjustable power quality and multisourced networked power systems. [ABSTRACT FROM PUBLISHER]

The major types of slowly developing faults, which can lead to arc faults in switchgear and controlgear, such as partial discharge, arcing, and heating due to poor connections, can now be successfully detected and monitored. In parts I and II of this paper series, a detailed review of the immediate causes of arc faults, along with an overview of preignition and postignition methods for its mitigation, was presented. Various hybrid nonintrusive sensors were developed in the laboratory to implement preignition detection techniques. The major types of slowly developing electrical faults were created in the laboratory, and the sensors were employed to evaluate their performance along with an effective signal processing technique. Part III of the work is based on the successful performance of the sensors outside of laboratory conditions. Hybrid sensors have been installed in a real-world application, i.e., switchgear located in substations. This paper presents interesting results about this practical application and includes valuable discussion on the performance evaluation of different sensors, which further justifies the usefulness of the new sensors for online condition monitoring of switchgear, controlgear, and cable termination boxes. The implementation of this technology in industry may provide promising results in avoiding major accidents such as arc-flash in the switchgear and controlgear. [ABSTRACT FROM AUTHOR]

Multioutput converters with single input source are currently studied as an alternative to conventional dc–dc topologies in order to improve power density in low-power multiload applications. This paper reviews three different ways in which a boost topology can be customized to supply multiple outputs. The first way uses a charge-sharing approach using individual switches to distribute inductor energy to different capacitors. The second method of creating a multiport converter (MPC) combines two converters with similar front end to generate two outputs using only one controlled switch. Using this method, a boost converter can be combined with single–ended primary–inductor converter (SEPIC), Cuk, and current source converter topologies. The third method uses time multiplexing of switches to produce two regulated ports and is referred to as switched-boost action. This method uses relatively less number of switches and allows regulation and control of all the outputs. Practical utility of switched-boost action based MPC is reported in this paper. This switched-boost MPC is applied to a renewable power converter system to interface a solar panel, a battery, and home loads to produce a 12-V and a 48-V bus. The 12-V bus is interfaced to battery and capable of optimally charging the battery in constant current–constant voltage (CC-CV) mode. The converter is demonstrated to operate with solar panel as it supplies a 12-V battery and a 48-V load bus. When the solar power is not available, the converter automatically goes into a mode in which the 12-V battery supplies the loads on the 48-V bus. [ABSTRACT FROM AUTHOR]

In this paper, an overview of the main motor features influencing the protection devices settings is presented, pointing out key differences between three-phase direct-on-line (DOL) motors of different efficiency classes. The results of experimental tests and simulations are presented and discussed in the scope of the motor protection against overload, short-circuit, current unbalance, and locked-rotor conditions, for 7.5-kW, four-pole, IE2- and IE3-class squirrel-cage induction motors (SCIMs) and for IE4-class line-start permanent-magnet motors (LSPMs), offering important data related to their electrical and thermal behaviors. Two commercial digital thermal-magnetic motor protection devices, whose thermal models were designed for IE1- and IE2-class motors, are evaluated in terms of operation effectiveness in the tested motors. This paper is important for industry due to the significant penetration of IE3-class induction motors, as well as to the recent introduction into the market of IE4-class induction motors and LSPMs. [ABSTRACT FROM PUBLISHER]

Oversizing electrical distribution equipment is a concern in industrial facilities. It adds cost and can increase fault levels. IEEE Std 141-1993 provides guidelines on how to size electrical equipment, but at the early stage of the project, when the equipment is being purchased, much of the process information necessary to properly size the equipment is preliminary at best. In addition, much is left to the discretion of the individual design engineer, who is often not an employee of the facility's eventual owner and, therefore, may have no incentive to reduce equipment size. In fact, depending upon the contractual relationship and due to the preliminary data, compressed schedule, and long delivery, design engineers tend to oversize the equipment. This paper describes an approach for establishing a load-based upper size limit to control oversizing of electrical equipment. This paper will demonstrate that establishing this upper limit can effectively control oversizing of the electrical equipment with information available at the early stage of the project. The resulting safety and economic benefits of the properly sized electrical equipment cascade throughout the power system. [ABSTRACT FROM AUTHOR]

This paper proposes an adaptive power management strategy for photovoltaic (PV) generation units in a standalone microgrid. In existing microgrid configurations, the PV units are controlled using droop control technique, which ensures load sharing among the distributed generation (DG) inverters. However, the intermittency in power generation of PV-based DG poses many challenges to the standalone operation of a microgrid, the ineffective volt-ampere (VA) utilization being one among them. This paper proposes an adaptive droop control, which enables the maximum utilization of the VA rating of the interfacing inverter in a PV/battery hybrid system. With the proposed technique, as the generation goes down, the DG inverter is controlled to support the reactive power demand of the load, thereby utilizing the rating of the inverter switches effectively. The applicability of the proposed adaptive control method is analyzed using detailed simulation and real-time hardware-in-loop studies. [ABSTRACT FROM AUTHOR]

Finite state model predictive control (MPC) has been recently applied to several converter topologies, as it can provide many advantages over other MPC techniques. The advantages of MPC include fast dynamics, multitarget control capability, and relatively easy implementation on digital control platforms. However, its inherent variable switching frequency and lower steady-state waveform quality with respect to standard control, which includes an appropriate modulation technique, represent a limitation to its applicability. Modulated model predictive control (M2 PC) combines all the advantages of MPC with the fixed switching frequency characteristic of pulse-width modulation algorithms. The work presented in this paper focuses on the indirect matrix converter (IMC), where the tight coupling between rectifier stage and inverter stage has to be taken into account in the M2PC design. This paper proposes an M2PC solution, suitable for IMC, with a switching pattern that emulates the desired waveform quality features of space vector modulation for matrix converters. The switching sequences of the rectifier stage and inverter stage are rearranged in order to always achieve zero-current switching on the rectifier stage, thus simplifying the current commutation strategy. [ABSTRACT FROM AUTHOR]

Power quality metering is a situation that often does not afford the safety of deenergizing equipment before connecting probes; this is especially true for continuous processes such as those found in refineries. In this situation, a connection to energized equipment may be more common. When potential and current transformers are present in switchgear, it is usually desirable to make the probe connections to the secondary of these transformers. Generally, these connections are made in switchgear metering compartments, which are presumed to have low arc-flash risk due to the limited exposure to energized power conductors. Often in these situations only shock hazard is considered and arc-flash hazard is not, but is it safe to assume there is no arc-flash hazard? The NFPA 70E-2015 Standard states that opening doors to expose bare energized parts requires arc-flash personal protective equipment (PPE). The standard also states that work on control circuits with exposed energized parts greater than 120 V requires arc-flash PPE. Therefore, according to the NFPA 70E, in a control cabinet containing, for example, voltage transformers with exposed primary terminals above 120 V, an arc-flash hazard exists and arc-flash PPE is required. However, the question remains, what level is the hazard and how should it be assessed? This paper will evaluate arc-flash energy in metering compartments, determine if arc-flash hazard should be a legitimate concern when working in energized metering compartments, and improve overall awareness when working in these situations. [ABSTRACT FROM PUBLISHER]

The switched shunting resistor circuit is a classical and practical passive equalization scheme that nevertheless suffers from the voltage imbalance after the charging process. It results from the discrepancy of the shunting resistor and the physical characteristics of supercapacitor (SC) cells. In this paper, the distributed voltage equalization control strategies with the proportional-integral (PI) observer for the switched shunting resistor circuit are analyzed and compared. First, the charging and equalizing system is modeled as the switched system and the system observability is proved. The decentralized control and consensus control are analyzed and their shortages are presented. Then, the leader–follower cooperative control is proposed to improve the charging time while keeping the equalization performance. Meanwhile, the PI observer is designed to estimate the internal capacitance voltage of an SC precisely to avoid the effect of equal series resistance. The control convergence is proved by using the Lyapunov stability and switched system theory. The experimental results show that the proposed method has much superiority and wide applicability than the existing methods for equalizing voltages of SCs. [ABSTRACT FROM AUTHOR]

Renforth et al. in 2017 present a novel online partial discharge (OLPD) high-voltage (HV) insulation condition monitoring (CM) solution to monitor complete HV networks in petrochemical and other critical industry facilities. Continuous, 24/7 OLPD insulation monitoring of in-service cables, switchgear, transformers, and rotating machines operating at 3000 V and above provides operators with an early warning against incipient HV insulation faults that manifest themselves through high PD activity. Knowledge of the type, severity, and source of any site(s) of PD across the HV network (including remotely connected plant such as Ex/ATEX HV motors located in hazardous gas zones) enables pinpointed preventative maintenance interventions to be made to the HV insulation system during planned maintenance turnarounds to avoid unplanned outages. To monitor a complete HV network, OLPD sensors and monitoring nodes are distributed at strategic locations across the network. The CM data from the distributed nodes are passed via Ethernet/LAN to a partial discharge monitoring server (PDMS) located at the control center of the facility with a secure internet connection. The PDMS operates an advanced OLPD monitoring database for the logging, display, benchmarking, trending, and visualization of the PD monitoring data on a graphical user interface. The insulation condition criticality (from 0% to 100%) of each phase of all of the individual HV plant items monitored is presented on a series of mimic screens of the HV network single-line diagram. This paper concludes with a case study of a complete HV network OLPD monitoring design solution implemented at a large, crude-oil processing facility in Eurasia. [ABSTRACT FROM AUTHOR]

DC microgrid systems with hybrid energy resources are of significant interest in shipboard and spacecraft applications. In such a system, coordinated operation of circuit breakers (CBs) and disconnecting switches (DSs) can rapidly isolate short-circuit faults and restore the system very fast. In this paper, we investigate a new protection scheme for a Multi-Bus dc systems based on an event classification approach. The proposed protection scheme transfers less data when compared with commonly used data-based protection methods and does not require high-speed communication and synchronization. The results show that the developed protection scheme is able to identify the type of fault accurately, isolate the faulted area, and restore the system very quickly while maintaining continuous power to the loads. [ABSTRACT FROM PUBLISHER]

Parallel ac-link universal power converters are a relatively new class of power converters that can be configured as dc–dc, dc–ac, ac–dc, and ac–ac. These converters are extensions of a buck–boost converter in which the current of the inductor is alternating and the input and output can have any number of phases with any forms, voltage amplitude, or frequency. By placing a small capacitor in parallel with the link inductor, all the switches can benefit from soft switching. The main limitation of the parallel ac-link universal power converter is its large number of switches. A three-phase ac–ac configuration requires 24 unidirectional switches. This paper proposes two topologies based on the parallel ac-link universal power converters that significantly reduce the number of switches. One of the proposed topologies reduces the number of switches in a three-phase ac–ac configuration to 16. The other topology reduces the number of switches to 10. The latter can offer galvanic isolation with only a single-phase high-frequency transformer. This paper presents the principles of the operation of the proposed topologies and evaluates them through simulation and experiments. [ABSTRACT FROM AUTHOR]

This paper presents two power-generation systems with a two-phase permanent-magnet (PM) synchronous machine associated with a rectifier with small number of controlled switches. The topologies are conceived with the purpose of converting wind energy into electrical energy for low-power applications, providing an enormous potential to be used in urban areas. They can be used in applications connected to the grid or in the stand-alone mode or feeding a microgrid. Compared with some three-phase generation systems with reduced number of controlled switches, the proposed topologies permit obtaining sinusoidal controlled machine currents, reducing dc-link voltage and providing $dq$ currents with low harmonic distortion. [ABSTRACT FROM AUTHOR]

A digital dead-beat current controller for voltage source converters is presented in this paper. The control structure is specified in a digital hardware description language, synthesized, and deployed on a field-programmable gate array chip. By updating, with negligible computation delay, the duty cycle twice in a switching period, the reference current error is nulled in half a modulation period, so that the controller's small-signal bandwidth is maximized. In addition, due to a simple transient detection circuit, the large-signal response delay is reduced to a small fraction of the modulation period, which is determined by the chosen current signal oversampling rate. The controller can effectively support different voltage-source inverter applications, such as active filters, uninterruptible power supplies, microgrid distributed energy resource controllers, and dc–dc converter applications, including interface converters for renewable energy sources, laboratory battery chargers, and electronic welding machines. [ABSTRACT FROM AUTHOR]

The architecture of a mission critical power system has to be designed with structures that allow the simultaneous operation of multiple sources (architecture efficiency). Opportunely organized, the business continuity management will project its program and take actions on the sources. Complete control of the system is necessary for all operating occurrences in an electrical power system. Complexity requires that “safe sets” of operating procedures have to be identified, selected, and authorized, as adopting the Parise program. A Human Competent Reaction has to guarantee the operation efficiency as providing decision-making in emergency statuses. The paper deals with a sample case of a system with multiple sources applying the micro approach of the “flock” logic that consists in managing exclusively the adjacencies of each node. The adoption of mechanical locking tools assists the switching procedures. [ABSTRACT FROM AUTHOR]

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]

This paper proposes an offline single-stage light-emitting diode (LED) driver based on a novel approach to reduce low-frequency ripple in LED arrays supplied from mains, while assuring high input power factor (PF). The proposal employs a series resonant dc–dc converter integrated into a bridgeless boost power factor correction (PFC) stage. The resonant stage works to reduce the low-frequency ripple transmitted from the output of the PFC stage to the LEDs with only small power losses. This solution achieves three main goals: 1) reduction of the bulk capacitance used at the dc bus, allowing for the use of long-life film capacitors; 2) increase in the overall efficiency of the LED driver owing to the low switching and conduction losses in the shared switching network; and 3) assuring high input PF. Experimental results of a driver without electrolytic capacitors for a 100-W street lighting LED luminaire are presented, showing overall efficiency in excess of 92%, input PF greater than 0.97, and line current harmonic content in compliance with the IEC 61000-3-2 standard. [ABSTRACT FROM AUTHOR]

An open-winding permanent-magnet synchronous generator (PMSG) system with the integration of fully controlled and uncontrolled converter is investigated in this paper, in which half the amount of controllable power switches are needed compared with the conventional open winding system fed by two voltage source converters. The voltage space vector of open winding PMSG is modulated by controlled converter, which will be integrated with the voltage vector by uncontrolled converter to implement the operation of open winding PMSG. In order to analyze and compare the operation capability on the different dc voltage ratios, the available modulation range of the open winding PMSG is analyzed in detail. Moreover, unity power factor control is proposed as the optimized control method to achieve the maximum modulation index. Finally, a 1-kW experimental setup is built to validate the theoretical investigation on the open winding PMSG system. [ABSTRACT FROM AUTHOR]

In this paper, a switched reluctance motor (SRM) with phase windings similar to an autotransformer is presented. The new winding structure allows for fast demagnetization. This enhances the machine performance at high speeds. During demagnetization, the dc bus voltage is applied to a portion of the phase winding, and accordingly a higher negative demagnetization voltage/turn is applied. This results in the faster discharge of the phase excitation currents. The power electronic converter configuration is modified to facilitate the new winding topology. However, the number of switches is the same as a conventional half-bridge converter used in SRMs. The proposed SRM drive with the modified winding configuration is verified through finite element analysis based circuit simulations and experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a single-stage light-emitting diode (LED) driver based on a bridgeless power factor correction (PFC) converter and a half-bridge CLCL resonant converter for street lighting applications. The proposed single-stage topology integrates the PFC converter and the CLCL resonant converter by sharing active power switches. The bridgeless PFC converter adopts two buck–boost circuits operating in discontinuous-conduction mode to achieve input-current shaping. It uses two diodes instead of a rectifier bridge to reduce the power loss caused by the diodes. Owing to its superior soft-switching characteristics, the CLCL resonant converter is used. The proposed LED driver has superior features, such as high efficiency, near unity power factor, low total harmonic distortion, and relatively few diodes. A 100-W lab prototype is successfully implemented, and the experimental results verify the effectiveness and feasibility of the proposed LED driver. [ABSTRACT FROM AUTHOR]

This paper proposes and investigates a multilevel ac six-phase motor drive. The system is composed of five isolated three-leg voltage source inverters feeding the open-end windings of an asymmetrical six-phase induction motor (SPIM), which is adequate to generate multilevel voltages for high-power systems with voltage rating restrictions. A simple space vector pulse-width modulation (PWM) based on three similar individual planes and its implementation by means of equivalent level-shifted PWM are presented. A space vector pattern with a high number of voltage vectors redundancies is obtained. These redundancies and the application sequence of the voltage vectors are selected to minimize the amount of changes in the switching states and to decrease the harmonic distortion of the generated voltages. The vector pattern of this optimal modulation is obtained by analyzing only one plane and applied in the same way to the three planes as if they were independent. The developed PWM techniques have low computational complexity and are suitable for low-cost hardware implementations. Simulation results are used to compare the proposed topology with a conventional configuration in terms of harmonic distortion and semiconductor losses. Experimental results demonstrate the feasibility of the proposed drive system. [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]

A zero-current switching full-bridge isolated dc/dc converter based on a semiresonant L-C cell has been developed in this paper. With respect to the classical full-bridge configuration, no additional switches are required, thus by preserving its simplicity and robustness. The proposed architecture allows achieving zero-current switching at both primary and secondary sides. A 50-kW prototype has been developed and tested in different operating conditions. The experimental results are in agreement with the simulations by confirming the goodness of the proposed solution. Efficiency up to 97% at full load operating condition has been reached in the laboratory prototype. [ABSTRACT FROM PUBLISHER]

This paper presents a case study of a medium-voltage three-phase capacitor bank (CB) energization, based on an unsynchronized switching scheme using three independent pole vacuum switches simultaneously commanded. The motivations are cost reduction and simplification of the switching scheme. The maximum current and voltage peaks during transients caused by connection of CB with three independent pole switches or a three-phase mechanically coupled switch are compared. A probabilistic assessment for the overcurrents and overvoltages based on Monte Carlo simulation is also performed. The obtained results show that three single-phase unsynchronized switches could be used in a CB, with good transitory response. [ABSTRACT FROM PUBLISHER]

A modular quasi-resonant bidirectional dc–dc converter composed of half-bridge gallium nitride modules (HBGM) with reduced switch voltage stress is proposed in this paper. By using an auxiliary capacitor, a resonant circuit is formed to shape the current and voltage so that zero-voltage switching at turn-on instant is achieved. Since the switching loss dominates the power losses in a high-frequency dc–dc converter, the soft-switching performance leads to a noticeable reduction in the total loss; so, the operating temperature will decrease, and consequently, size of the heatsink will be reduced. The proposed circuit takes advantage of enhancement-mode gallium nitride (eGaN) switches regarding their small on-resistance RDS(on), low gate charge, and fast switching speed to improve both efficiency and power density. The main performance issue of adopting GaN switches in a bidirectional dc–dc converter is the high voltage stress of GaN devices, which is handled by connecting the HBGM in the active-clamped stacked configuration, as well as optimizing printed circuit board layout design. Finally, a 1 kW, 600 V laboratory prototype operating at 100 kHz is implemented to validate the proposed concept. [ABSTRACT FROM AUTHOR]

The paper focuses on the active balance of modular hybrid asymmetrical cascade multilevel drives. It investigates special configurations where the high-voltage cell can be operated at low-switching frequency, while correcting the energy imbalances of the low-voltage cells. Among these, it proposes to use configurations with no more than two types of cells and switching devices for modularity. It proposes a high-dynamic performance active balance scheme that decouples the correction of the different imbalances. This allows fast control of the load, while maximizing the inverter voltage use, which results in a higher energy efficiency. An optimal feedback is proposed to correct phase imbalances through the control of the common mode of the low-voltage cells. The effectiveness of the proposed concepts is validated experimentally on a multilevel drive. [ABSTRACT FROM AUTHOR]

This paper presents a new nonisolated buck/boost-type multilevel dc–dc converter suitable for high-power and medium/high-voltage application. The main features of the proposed topology are as follows: low voltage across the semiconductors, low switching losses, and reduced volume of the output filter. The theoretical analysis is carried out for a five-level bidirectional structure of the proposed converter, operating in Buck mode. The proposed topology presents some capacitors, and their voltage must be balanced for proper operation of the converter. Thus, a capacitor voltage balancing active control using a feedforward technique is proposed and analyzed in detail. In order to validate the theoretical analysis, a prototype with 10 kW output power capability, 1.3 kV to 800 V input-to-output voltage, and 20 kHz of switching frequency was built and experimented. The results attest the advantages of the new dc–dc topology, as well as the new capacitor voltage control technique. [ABSTRACT FROM AUTHOR]

This paper presents a novel perspective to understand different winding configurations of flux-switching permanent magnet (FSPM) machines. A simple analytical method is used for the calculation of total offset angle of flux linkages by taking into account an offset angle of stator slot and rotor poles. The closed-form solution is presented to find the sequence of phase windings. The 12-slot/10-pole and 12-slot/13-pole FSPM machines are conceptually segregated into two sets of 6-slot/10-pole and 6-slot/13-pole machines, respectively. This is used to address even harmonic elimination and winding configuration properties in even and odd number of rotor pole configurations. Finite element analysis and experimental results verify the concept. [ABSTRACT FROM AUTHOR]

The European approach underlines the equipment integrity for the safety against electrical hazards “giving collective protective measures priority over individual protective measures” and promotes passive measures against the electric shock that assists to prevent the arc flash hazard. The International Electrotechnical Commission/European Standards (IEC-EN) passive measures are based on the international protection (IP) code, safety procedures, medium voltage (MV) isolator switches with three statuses, MV switchboards tested against internal arcs, and forms of separation for MV-low voltage switchgears. This paper suggests a tentative criterion prospecting a reference value of the arc current to adopt in the protection coordination design. [ABSTRACT FROM AUTHOR]

In recent years, a three-level T-type inverter has attracted considerable attention due to its advantages, such as simple structure and higher efficiency. However, the reliability of a three-level T-type inverter is particularly important as increased power switches are used. Therefore, a fault-tolerant three-level T-type inverter is proposed in this paper. Fault diagnosis and fault-tolerant control strategies for power switches both in half-bridge and neutral-point bridge are investigated. Under fault-tolerant operation, redundant fourth-leg is used to balance neutral-point voltage and the low-frequency voltage oscillation is eliminated completely. The fault ride-through capability and high-quality output waveforms can be obtained. The effectiveness of the proposed inverter topology and control methods is validated by the simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper presents multilevel ac–dc single-phase power conversion cells for applications in which the regenerative operation is either not required or prohibited. The ac primary power source is a single phase from a permanent magnet generator or from an electrical grid. The cells are composed of two h-bridges in cascade: 1) an unidirectional high-voltage h-bridge with two controlled switches; and 2) two power diodes, processing the active power, and a low-voltage h-bridge with four controlled switches and a floating capacitor. These cells can be part of multiphase systems, in which it is required one cell for each phase. Some examples of application for three-phase systems are given, exploring different ways of connection between the single-phase cells. Simulation and experimental results regarding the proposed cells and conventional h-bridge based ac–dc converters are shown for validation and comparison purposes. [ABSTRACT FROM PUBLISHER]

In order to solve the problems caused by the pulsating current ripple of switching-mode power converters, a passive pulsating ripple canceling circuit (PPRCC) is proposed in this paper. The features of the proposed PPRCC include simple, modular structure, and high degree of design flexibility. By integrating the proposed PPRCC, an input current ripple-free flyback-type converter is adopted and analyzed as an example because of its comprehensive utilization in small power rating commercial products. In addition, the switch voltage spike of flyback converter can be suppressed by integrating the proposed PPRCC without using snubbers, it turns out that the efficiency can be further improved. The corresponding operating principle, steady-state analysis, and zero ripple design criteria of the proposed PPRCC are provided. Finally, a 100 W laboratory prototype is constructed to verify the effectiveness of the proposed principle. Experimental results show that the resulting peak-to-peak input current ripple is reduced by 96% and nearly 0.5% and 1.7% improvement in efficiency can be achieved by the proposed PPRCC, at 80 W and 100 W load conditions, respectively. [ABSTRACT FROM PUBLISHER]

Arc flash on distribution circuits is a safety issue that can impact work practices for line and substation workers. This paper shows test results for arc flash events in medium-voltage switchgear cubicles and live-front transformer enclosures. Both scenarios can result in more incident energy than the prediction of the IEEE 1584-2002. Much higher than expected energies were measured from rack-in style switchgear breaker cubicles due to the orientation of the electrodes. Live-front transformer cubicles showed wide variability that was not directly related to the enclosure size or arc directionality. Unexpectedly high energies were measured in multiple configurations. For selection of the appropriate clothing systems, incident energy multipliers are suggested based on the IEEE 1584-2002. [ABSTRACT FROM AUTHOR]

Starting of an induction motor is a process that creates many challenging problems for the motor and operations of the power system. The induction motor can be damaged, characteristics can be changed, and performances of the motor can be worsened. Having a significantly higher starting current than the rated current can produce mechanical and thermal stress on the motor and the loads. High-voltage fluctuations, dips, and sags can occur in electrical power systems associated with the motor. Many different methods have been developed to address particular induction motor starting problems associated with motor size and the stability of the connected network. A soft starter is a relatively new device and is used for smooth start of induction motors, particularly medium voltage motors, and adds flexibility in the operation and the interoperability. It is an integration of complex power control apparatus for reducing starting current in a medium voltage solid state soft starter. Electrical transients during switching ON and OFF processes are a major concern for the silicon controlled rectifiers (SCRs), current rise rate during switching ON—di/dt, and over voltages during switching OFF—dv/dt. During the transient process, the currents rise and di/dt passing through the SCRs can damage them. This paper is focused on identification of parameters of the transient process, protection, and limitation of di/dt by inserting an inductor in the soft starter circuit to limit di/dt to a safe level. Mathematical analyses for the purposes of the SCR protection and measurements are presented. [ABSTRACT FROM AUTHOR]

In this paper, current collapse phenomena and thermal effects in normally-off and normally-on GaN HEMTs are investigated. The experimental results show that a high-off-state voltage and high-switched drain current at high junction temperature cause an increase of the on-state resistance ${{\rm{R}}_{{\rm{DSON}}}}$. Varying the switching frequency from 50 to 400 kHz, an increase of the on-state resistance is further observed for both types of GaN devices. It is evident from these experiments that the number of switching transients significantly influences the increase of the RDSON, suggesting that this increase is due to a current collapse in GaN HEMTs. A detailed comparison of the evaluated R DSON between GaN transistors and the high-speed CoolMOS-C7 transistor is presented. [ABSTRACT FROM AUTHOR]

A near-miss shock incident occurred on a heated air blower control panel during construction activities. This paper describes the investigation and findings of the team, with follow-up items to ensure that future equipment brought to the site will be properly inspected for safe design. [ABSTRACT FROM AUTHOR]

The phase modulated full bridge resonant transition converter (PMRTC) is commonly used for high-gain, high-power applications, as PMRTC converters retain the qualitative nature of hard switched pulse-width modulation counterparts with additional damping ($R_d$), where R_d$ is load, transformer turns ratio and frequency dependent. The PMRTC converter enables operation at a higher switching frequency due to the soft-switching nature, thereby achieving better power density. For battery fed high-power, high-gain applications, PMRTC exhibits a significant drop in the dc gain due to R_d$ and other nonidealities, limiting the maximum frequency of operation. Thus, computing this drop and analyzing the effects of switching frequency becomes necessary in achieving the required steady-state dc gain. From the analysis, it is observed that, for a choice of switching frequency above , the required steady-state dc gain is not achieved for any turns ratio. Hence, to increase the switching frequency of operation of a PMRTC converter, a two-transformer configuration is adapted and with this configuration, the dc gain loss model, power loss, and efficiency model and small-signal model are established. The design guidelines on the choice of switching frequency and transformer turns ratio based on the proposed models is described. The proposed models with the presented design guidelines are validated in simulations and hardware prototype for a 1 kW PMRTC converter. [ABSTRACT FROM AUTHOR]

Characteristics of an electric arc in industrial and utility electrical equipment is dependent on many factors such as fault-current level, duration of the arc, geometry of feeding conductors and electrodes, proximity of panels, and other items affecting the direction or focus of the arc energy. The voltage rating of the system will affect the overall dimensions of conductor spacing, which will result in higher released energy for the same fault conditions. Another factor of importance is the type of heat energy (predominately radiant or predominately convective). This can be generalized into four types: 1) moving high-heat flux arc in open air of overhead lines or substation buswork; 2) stationary directional high-heat flux arc in open air at the end of overhead line or substation buswork or transformer bushing; 3) ejected directional high-heat flux arc in enclosed medium-voltage switchgear or cable-splice failure; and d) directional hot air exhaust from low heat-flux arc in low-voltage switchboards’ cabinets and motor control centers. The results of experimental testing for type 1 arc behavior and incident heat energy measurements of a moving and stationary open-air arc are presented and discussed. Work practices for mitigating the effect of electric arc are recommended for overhead lines. [ABSTRACT FROM PUBLISHER]

An improved topology for dc–dc converters used in hybrid power source systems, which consist of a fuel cell (FC) and electric double-layer capacitors (EDLCs), is proposed. The new topology has three transistors, and switch timing for this topology and a control method for power management between the FC and EDLCs are discussed. This new topology overcomes the two drawbacks of the previous topology with two transistors and a diode: the slightly higher load voltage and insufficient EDLC charging under low-load conditions. The introduction of two switching modes allows for the bidirectional current of the EDLCs and enables power distribution between the FC and EDLCs. A pseudo FC and bipolar power supply that imitate the EDLCs and load are used to measure the static characteristics and show that the proposed topology with switch timing operates as designed. In addition, the dynamic characteristics are measured for actual EDLCs and a bipolar power supply into which waveforms are programmed as selected functions when an actual smartphone is operated to verify that the proposed control method can distribute power to both the FC and EDLCs and manage the state of charge of the EDLCs. [ABSTRACT FROM AUTHOR]

A response by A.C. Binojkumar et al. to a letter to the editor about their article "A variable switching frequency PWM technique for induction motor drive to spread acoustic noise spectrum with reduced current ripple," published in a previous issue of the journal is presented.

Impedance source inverters (ISIs) are gaining attention due to features such as single-stage conversion, buck-boost capability, and inherent shoot-through protection. To maintain the required ac output voltage, typically ISIs are operated at a higher dc-link voltage due to constrained modulation index. This also increases voltage stress across capacitors and switches of the converter. This voltage stress is approximately double compared to that of voltage source inverter with preboost stage (Boost-VSI). To mitigate this problem, a new pulsewidth modulation (PWM) scheme for the active-front-end based ISIs (AFE-ISIs) is proposed. The proposed scheme enables the ISIs to produce high ac gain with lower voltage stress across the capacitor and switches. In other words, the proposed scheme blends the advantages of Boost-VSI into ISIs. With the new PWM scheme, there are also reductions in output voltage total harmonic distortion, switching frequency ripple in the inductor current, and power loss in the converter. A prototype of the current-fed switched inverter, an AFE-ISI, is designed, and the proposed PWM scheme is implemented. Experimental results obtained are in accordance with the proposed theory and show that the voltage stress has reduced from 325 V to 203 V for an ac output of 110 V. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "A variable switching frequency PWM technique for induction motor drive to spread acoustic noise spectrum with reduced current ripple," by A.C. Binojkumar et al., published in a previous issue of the journal.

A new computationally efficient paradigm for the design and analysis of switched reluctance machines is proposed. At the heart of the rapid analysis and design methodology is the reduced-order computational method based on a flux-tube model, which has been refined and extended. It is demonstrated how the improved model enables consistent and accurate analysis and design optimization. Instead of an analytical derivation, an automatic generation of cubic splines is introduced to model the magnetic flux. The flux-linkage functions obtained from the improved flux-tube method indicate that the method offers good accuracy compared with the finite-element-based analysis, but with significantly improved computational efficiency. The approach is applicable to translating and rotating switched reluctance machines of various topologies, and therefore, enables rapid design search and optimization of novel topologies. [ABSTRACT FROM AUTHOR]

Design rules of multiple multiphase winding configurations are investigated from the perspective of phase shift between adjacent winding sets in flux-switching permanent magnet (FSPM) machines. The relations between torque/rectified voltage and phase shift for any multiple multiphase winding topology are theoretically derived, directly showing the influence of phase shift on torque/rectified voltage harmonic components. It can be learned that the optimal phase shift for the lowest torque ripple and dc voltage oscillation depends on the winding types. Symmetrical winding is not always appropriate for any occasion. To verify the analytical results, the static characteristics of the dual three-phase, four three-phase, triplex three-phase, dual six-phase, and triplex four-phase FSPM machines with specific stator/rotor-pole combinations are studied by finite-element (FE) analysis. The FE-predicted dominant torque ripple and rectified voltage pulsation components for symmetrical and asymmetric phase shifts are in good agreement with the theoretical derivation. Prototypes are built and tested to verify the analytical and FE results. [ABSTRACT FROM AUTHOR]

A hybrid resonant pulse-width modulation (PWM) bridgeless ac–dc power factor correction (PFC) boost converter is proposed for application in power supplies and battery chargers. The bridgeless operation of the proposed converter eliminates the need for the front-end diode bridge rectifier. The PWM switches share the same gating signal, so the converter does not need extra circuitry to sense the positive or negative ac input line-cycle operation. The resonant tank components are relatively small in size and, unlike a totem-pole PFC converter, the hybrid-resonant mode of operation alleviates the reverse-recovery losses for the body diodes of the PWM switches. The inherent inrush current-limiting capabilities improve the system reliability. Moreover, the converter architecture enables simple implementation of lightning and surge protection systems. To verify the proof of concept, experimental results are presented for a 650-W prototype at 70-kHz switching frequency, universal ac input, and 400-V dc output. [ABSTRACT FROM PUBLISHER]

Impulse commutation obtains zero current commutation of devices in a circuit with a short resonance impulse using a simple resonant tank. This concept has been studied, extended, and implemented for a three-phase push–pull current-fed single-inductor topology to achieve soft commutation and device voltage clamping solving the traditional issue of device turn-off voltage overshoot. The push–pull topology is attractive owing to single inductor, all common source devices connected to common supply ground, and reduced gate driving requirements. Detailed operation, analysis, and design of this topology have been reported with impulse commutation. With a small resonant tank and partial resonance, impulse commutation procures merits of voltage clamping, low circulating current, and load adaptive zero-current switching of the devices. Variable-frequency modulation regulates load voltage and maintains the impulse commutation with source voltage variation. Experimental results on a 1-kW proof-of-concept hardware prototype are demonstrated to observe the operation, performance, and verify the proposed concept and claims. [ABSTRACT FROM PUBLISHER]

Power distribution equipment is the backbone of any Industrial process infrastructure. Safety and reliability are the two most important criteria in the proper functioning of the power distribution system. Low-voltage switchgear (LVS) is an important part of power distribution. Minimizing arcing faults in the switchgear is of utmost importance to enable a safe environment. Arcing faults increase the temperatures inside the equipment beyond 20,000 K, rapidly heating air and vaporizing metal parts. This expanding plasma creates severe mechanical and thermal stress in the equipment which can blow open doors and fragment/burn through the enclosure. Arc-resistant LVS is designed to provide an additional degree of protection for operating personnel performing normal operating duties in close proximity to the equipment. A series of arc flash simulations were performed on arc-resistant LVS in both bare bus (noninsulated) and insulated/isolated bus configurations. In all simulations, insulated/isolated bus had significantly shorter arcing duration and lower energy emitted. [ABSTRACT FROM AUTHOR]