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A novel hybrid 18-level inverter topology for open-end winding induction motor (OWIM) is presented in this paper. In the proposed topology one end of the open-end winding IM is fed by a conventional two-level inverter, while other end is connected to a nine-level cascade H-bridge (CHB) inverter. The combined effect of these two inverters generates 18 levels in the phase voltage of open-end winding IM. The two-level inverter with higher DC link voltage has lower switching frequency and thereby reduces the switching losses. In addition to that, the proposed topology requires less number of components as compared to conventional multilevel inverter (MLI) topologies. An interesting feature of the proposed topology is that, it can operate in nine-level mode by connecting the motor winding in star in case of failure of the two-level inverter. Similarly, if the fault occurs in CHB inverter the proposed inverter can operate in two-level mode. Thus, the reliability of the system is improved. The proposed topology is experimentally verified on 1.5 kW OWIM. The experimental results have proven an excellent steady-state as well as transient-state performance of the proposed inverter in the entire range of linear modulation. [ABSTRACT FROM AUTHOR]

In this study, a new multi-point clamped (MPC), three-phase two-leg, five-level unidirectional front end high-powerfactor converter is proposed for directly connected wind energy conversion system with a permanent magnet synchronous generator. The proposed topology can be modelled and modulated similarly to other existing MPC structured converters with the omission of clamping diodes and bidirectional switches. The proposed converter has an advantage of reduced power semiconductor device count and maximum device stress. A factor (normalised index) is introduced and comprehensive comparative analysis with N level existing topologies is carried out. The minimum value of the normalised index makes the proposed topology as a suitable option for medium-voltage and high-power applications. Also, the fault ride through capability is one of the key performance indicators is also investigated on proposed topology under voltage sag condition. Further, steady state and transient performance of topology during load as well as dc-link voltage change are presented. Minimum distorted and balanced line currents with unity power factor are drawn from supply by implementing negative sequence elimination control algorithm. The validation of proposed topology is verified with simulation and a down-scaled experimental setup. [ABSTRACT FROM AUTHOR]

Highlights • Demands minimum PSD count because, the absence of clamping devices. • The number of maximum voltage rating of PSDs are minimum. • Minimum total blocking voltage. • The efficiency of overall converter system is high. • More reliable and the overall performance is good. Abstract In this paper, a new multi-point clamped (MPC), three phase two leg, five level front end high power factor converter (TP-TL-5LHPFC) for direct connected wind energy conversion system with permanent magnet synchronous generator (PMSG) is proposed. The converter can be modeled and modulated similar to other existing MPC structured converters with omission of clamping diodes and bi directional switches. The proposed converter has an advantage of reduced power semi conductor device (PSD) count along with reduced maximum device stress. The concept can be extended to increase the converter voltage levels by adding extra half bridges at the top and bottom of the converter. A factor (normalized index) is introduced and comprehensive comparative analysis with N level existing topologies is carried out. The minimum value of normalized index makes the proposed topology is suitable option for medium voltage and high power applications. In addition, the fault ride through capability is one of the key performance indicator for large motor drive systems is investigated on proposed topology under various unbalanced input conditions i.e. voltage sag and line to ground fault. Further, steady state and transient performance of topology during load as well as dc link voltage variation is presented. Minimum distorted and balanced line currents with nearly unity power factor (UPF) are drawn from supply by implementing negative sequence elimination control algorithm. The validation of proposed topology is verified with simulation and a down scaled experimental setup. [ABSTRACT FROM AUTHOR]

Space vector modulation (SVM) is a widely used method for multilevel inverters. Most of the SVM methods are nearest three vector (N3V) based schemes. Therefore, several researchers have proposed advanced implementation algorithms with reduced complexity for N3V methods. However, topologies like neutral point (NP) clamped inverter (NPCI) require some distinctive methods (called as non-N3V methods) to balance NP voltage for high modulation index and low power factor operations. Currently, the existing non-N3V methods exercise highly complex algorithms for duty ratio calculation and subtriangle identification. This paper presents a new approach, suitable for both N3V and non-N3V methods, with reduced implementation complexity. The proposed algorithm is based on an equivalent two-level space vector diagram and does not require any trigonometry, coordinate transformation, or volt-second balance solution. Unlike other carrier-based methods, it can change the switching sequence as well as the duration of redundant vectors. Moreover, the proposed approach does not require extra steps for implementing hybrid modulation and it can also be extended to multilevel topologies. One N3V, two non-N3V, and hybrid methods are developed using the proposed modulation algorithm, and are compared in detail. Simulation and experimentation on a three-level NPCI verify the validity of the proposed algorithm. [ABSTRACT FROM PUBLISHER]

In this article, a new hybrid nine-level inverter topology for an induction motor with an open-end stator winding is proposed. In the proposed topology, one end of the open-end winding is fed by a three-phase five-level inverter, and the other end is connected to a conventional three-phase two-level inverter. The three-phase five-level structure is realized by cascading a three-level flying capacitor inverter with capacitor-fed H-bridge in each phase. In the proposed topology, a total of 17,576 space vector combinations are available; hence, the capacitor voltages can be maintained at desired levels using switching redundancies. As compared to conventional topologies that require 48 switches, the proposed topology requires only 30 switches and completely eliminates the requirement of clamping diodes, which are required in a neutral point clamped inverter. Also, it requires only two capacitors per phase, whereas the nine-level flying capacitor inverter requires 28 capacitors per phase. In case of fault in any H-bridge, the system can be operated as a five-level inverter at its full power rating and improves the reliability of the inverter. The performance of the proposed system has been experimentally investigated on a 1.5-kW open-end stator winding induction motor, and results are presented. [ABSTRACT FROM AUTHOR]

In this paper, a novel nine-level inverter topology for open-end winding induction motor is proposed. This topology requires less number of components as compared to conventional topologies. The proposed inverter uses two three-phase three-level cascade inverters to generate nine-level in the phase voltage of open-end winding induction motor. An interesting feature of this topology is that in case of failure of any three-level inverter, it can be bypassed and the proposed topology can operate in three-level mode hence reliability of the circuit is improved. Out of two three-level inverters, the inverter which operates at higher DC link voltage switches less as compared to the inverter which operates at a lower DC link voltage, thus switching losses are reduced. A 1.5-kW induction motor is run with the proposed inverter at different modulation indices, and the performance of the drive is evaluated under steady and transient states. [ABSTRACT FROM AUTHOR]

This paper proposes a mathematical model for three-phase multilevel diode clamped ac/dc converter (DCC) in abc-reference frame, in order to study dynamic responses and stability of the system, where multilevel converters are employed. An attempt is made to model the converter adopting 5-level DCC and can be easily extended to DCC with any number of levels. The converter output and dc capacitor voltages are expressed in terms of input source currents and switching functions; which are basic inputs provided to a converter. Connection and capacitor currents of the converter have been analyzed. The effectiveness of the proposed mathematical model is verified by the computer simulations and experimental results. The obtained mathematical model has been validated with the physical converter model in MATLAB/Simulink environment and the prototype model using dSPACE DS under closed loop control system. The developed mathematical model equations are able to represent the physical converter with similar characteristics. [ABSTRACT FROM AUTHOR]

In this paper, the multilevel inverter (MLI) harmonic filter with modified modulation and advanced intelligent control scheme is described and implemented. The proposed scheme has three artificial intelligence-based controllers that are used for harmonic excerption, ripple reduction in dc capacitor voltage, and modulation, respectively. The artificial neural network (ANN) is applied for separating harmonic constituents from load, and fuzzy logic concept is utilized for dc capacitor voltage ripple minimization and current error adaptation for modulation. Further, the level-shifted multicarrier modulation is modified for balanced switching by rotating carriers for generating gate pulses for devices of inverter. The cascaded H-bridge topology of MLI is selected as filter due to its modular and compact structure. The instantaneous power theory is altered by using neural network for obtaining corrupted portion from load current and calculating reference values for compensation. The simulation model is developed by using MATLAB/SIMULINK, and hardware module is executed using dSPACE DS1103. The simulation performance is analyzed for various load conditions including transient states. The proposed topology performance is justified for its efficiency and viability through exhaustive simulation and experimentation. The total harmonic distortion in source current (THD), power factor, and voltage ripples is being used as evaluation criteria to quantify the results. [ABSTRACT FROM AUTHOR]

Highlights: [•] 5-Level, CHB MLI harmonic filter using artificial intelligence is proposed. [•] Neural network based controller for modified p–q theory is designed. [•] Fuzzy logic controllers for dc voltage regulation and MLI modulation are designed. [•] The simulation performance comparison with PI and AI controllers is demonstrated. [•] Experimentation proves the efficiency of proposed controller. [ABSTRACT FROM AUTHOR]

Abstract: Custom power devices (CPDs) have been developed to solve the power quality problems of the distribution systems. Among these CPDs, distribution static synchronous compensator (D-STATCOM) attained a great interest to the researchers and practising engineers. In this paper, the performance of a reduced rating D-STATCOM has been thoroughly investigated for power quality improvement in three-phase, four-wire distribution systems. The complete arrangement considered in this work comprises of a three-phase, three-wire (3P3W) D-STATCOM, zigzag-delta transformer and a single-phase active power filter (APF). This hybrid approach significantly reduces the rating of the overall compensator and improves the performance under non-ideal utility voltage conditions. To show the efficacy of the compensator, extensive simulation studies have been carried out for both normal an unbalanced/distorted utility voltage conditions in MATLAB/SIMULINK® environment using power system blockset toolboxes. Moreover, experimental results obtained from the laboratory system further verify the viability and effectiveness of the compensator. [Copyright &y& Elsevier]

Abstract: In this paper, a reduced rating T-connected transformer based D-STATCOM has been proposed for power quality improvement in three-phase, four-wire (3P4W) distribution systems. The complete arrangement considered in this work comprises of a three-phase, three-wire (3P3W) D-STATCOM, a T-connected transformer and a single-phase active power filter (APF). This hybrid approach significantly improves the performance of the D-STATCOM under distorted/unbalance source voltage conditions. To show the efficacy of the proposed compensator, extensive simulation studies have been carried out in MATLAB/Simulink™ environment using power system blockset toolboxes. [Copyright &y& Elsevier]

This paper presents the development and implementation of multilevel inverter (MLI)-based active power filter (APF) using DSP of dSPACE. Implementation of MLI for APF in high-voltage system eliminates use of bulky and high-cost transformer to connect APF. This algorithm, to generate switching signal of devices, is developed in MATLAB SIMULINK. The reference signals of APF are generated by using instantaneous reactive power (p-q) theory. Carrier phase-shifted pulse width modulation (CPS-PWM) scheme is implemented to generate switching signals which reduces the individual device switching frequency. Experimental results of prototype model are presented under different loading conditions to investigate the steady-state and transient performance of the APF. [ABSTRACT FROM AUTHOR]

Abstract: In many residential and office buildings, power is distributed through a three-phase, four-wire (3P4W) systems. The non-linear and unbalanced loads in these systems may result in excessive neutral currents, which may potentially damage the neutral conductor and distribution transformer while affecting the safety of the consumers. Several techniques have been reported in literature to overcome this problem. This paper presents a comprehensive review of neutral current compensation methods, their topologies, and their technical and economical limitations. Simulations are also carried out in MATLAB/SIMULINK environment for comparing the existing methods. [Copyright &y& Elsevier]

Many proteinuric renal conditions are accompanied by renal inflammation. Nicotine is known to have anti-inflammatory properties and is used in oral form to help subjects quit smoking. A potential anti-inflammatory role of nicotine in proteinuric renal diseases has not been investigated to date. We therefore evaluated the effects of oral nicotine in a rat model of proteinuria-induced renal inflammation. We used a well-established model of adult (24 wk of age) male Munich-Wistar-Frömter rats. Animals were given three different physiological doses of nicotine in drinking water for 28 wk until 52 wk of age (long term). A group without nicotine served as a parallel control. At 52 wk of age, the control group had a 2.1 times reduction in creatinine clearance, 3.2 times increase in urinary protein excretion, an increased focal glomerulosclerosis (FGS) score, increased glomerular desmin deposition, decreased glomerular podocin, and a higher accumulation of macrophages and myofibroblasts compared with 24-wk-old animals. Oral treatment with nicotine dose dependently preserved renal function and halted proteinuria progression, which were independent of blood pressure reduction. It also reduced FGS, desmin deposition, podocin loss, and density of renal macrophages and myofibroblasts. Nicotine also reduced the level of gene expression of the renal inflammatory markers monocyte chemoattractant protein and vascular cell adhesion molecule-1. In conclusion, long-term oral nicotine preserved kidney function, reduced proteinuria, reduced renal inflammation, and protected progression of renal structural damage in a rat model of proteinuria. We further suggest evaluating nicotine as a potential additional therapeutic option for treating proteinuric kidney diseases. [ABSTRACT FROM AUTHOR]

This paper deals with the real time implementation of 11-level cascade multilevel inverter-based STATCOM using personal computer (PC) and ADD-ON cards for power system voltage control at the point of common coupling. Complete hardware and software development procedures have been explained in depth for direct as well as indirect control schemes. Experimental results are presented and it is shown that voltage control is achieved using cascade multilevel inverter based STATCOM, thus verifying the very basic purpose of STATCOM. Real time implementation using PC-based control technique has certain merits over digital signal processor based implementation, and some of these merits are high processing speed and low cost of implementation; therefore, PC-based implementation can be used in industry as well as for utility applications. [ABSTRACT FROM AUTHOR]

In this article, an artificial neural-network-based implementation of space-vector pulse-width modulation of a three-phase neutral-point clamped bidirectional converter with improved power quality is proposed. The neural-network-based controller offers the advantage of very fast implementation of the space-vector pulse-width modulation algorithm. This makes it possible to use an application-specific integrated circuit chip in place of a digital signal processor. The proposed scheme employs a three-layer feed-forward neural network, which receives the command voltage and angle information at the input and generates symmetrical pulse-width modulation waves for three phases of the converter with the help of a single timer and some simple logic circuits. The neural-network-based modulator distributes the switching states in such a way so as to balance the neutral-point voltage. The data to be used to train the network by a back-propagation algorithm are generated by simulating the conventional space-vector modulation-based converter for simulation and by experimentally running the space-vector modulation-based converter using a digital signal processor for experimentation. The performance of a neutral-point clamped bidirectional rectifier has been evaluated with the artificial neural-network-based modulator. The simulation results obtained are validated experimentally using a digital signal processor (DS1104) of dSPACE (dSpace, Germany). The results obtained show an excellent performance of the neural-network-based modulator. [ABSTRACT FROM AUTHOR]

Abstract: The generation of harmonics and reactive power flow in a power system is greatly influenced by the widespread use of power electronic converters in addition to other sources of harmonics and reactive power. The design, development and successful application of single-phase, power quality improvement converters in domestic, commercial and industrial environment has made possible the design and development of three-phase, power quality improvement converters and their widespread use in different applications. This paper deals with a comprehensive review of three-phase, power quality improvement converter configurations, control approaches, performance on supply and load sides in terms of input power factor, THD and well-regulated, reduced-rippled dc output, power rating, cost and selection for specific applications. It also provides state-of-the-art of power quality improvement converter technology to researchers, designers and engineers working on three-phase, switched-mode ac–dc converters. [Copyright &y& Elsevier]

Programmable logic devices (PLDs) are increasing their presence in power electronics and motion control applications. With rising gate densities of PLDs, larger functionality is being incorporated. This paper looks at certain areas of motion control that are making use of PLD for faster control and in taking the processing load off the system microprocessor. [ABSTRACT FROM AUTHOR]

Response to Discussion on "Nearest and Non-Nearest Three Vector Modulations of NPCI Using Two-Level Space Vector Diagram - A Novel Approach". Frequency modulation, Reactive power, Switching frequency, Harmonic analysis, Oscillators, Switches. [Extracted from the article]

This paper presents a new control algorithm for a shunt active power filter to compensate harmonics and reactive power required by nonlinear loads. If the utility voltage is distorted, active power filter (APF) allows similar level of distortion in the compensated source current. Therefore, the resultant source currents have the same waveform as that of the supply voltage, thereby attributing the responsibility of utility and customer at the point of common coupling (PCC). Due to similar shape of the source voltage and currents, reactive power is compensated completely. The proposed scheme provides an additional feature of compensation of either only harmonics, or both harmonics and reactive power simultaneously, based on the desired capacity of the APE Various simulation results are presented with ideal and distorted mains voltage and compared with other algorithms. Proposed algorithm is implemented as a prototype to verify the simulation results. [ABSTRACT FROM AUTHOR]

This paper presents complete design, simulation, and experimental investigations on a 3-phase shunt active power filter to compensate harmonics and the reactive power requirement of nonlinear loads. The paper describes the complete design aspects of power circuit elements and control circuit parameters. The compensation process is based on sensing line currents only, an approach different from conventional methods that require the harmonics and reactive volt-ampere requirement of the load. Various simulation results are presented to study the performance during steady-state and transient conditions to validate the design. A laboratory prototype has been developed to verify the simulation results. The control scheme is realized on a dedicated micro-controller-based system. PWM pattern generation is based on carrierless hysteresis-based current control to obtain the switching signals. Based on simulation and experimental results it can be concluded that the compensation process is simple and easy to implement. The spectral performance shows that the active filter brings the THD of the system well below 5%, the limit imposed by the IEEE-519 standard. [ABSTRACT FROM AUTHOR]

• This paper presents a novel technique which will significantly reduce the operating time of the distance relay for second zone internal faults over the conventional schemes. • The proposed method is capable of selecting single pole as well as three-pole breaker operation according to the faulted phases. • The proposed method has the capability to sense RCBO even during occurrence of a pole jam situation in case of three-pole breaker operation. • The technique is validated by performing Hardware-in-Loop using real time digital simulator and real time automatic controller (RTAC). The proposed algorithm is programmed in RTAC using IEC 61,131–3 industrial automation programming language. An algorithm for second zone acceleration of the distance relay utilising the sequence voltages along with healthy phases impedances is presented in this paper. Specifically, the algorithm employs variation in sequence voltage ratio indices to sense the single-pole remote circuit breaker operation (RCBO), while utilising both magnitude and angle of the healthy phase impedance for sensing three-pole RCBO operation. Additionally, the developed algorithm can also identify the faulty phases based on variations in impedance magnitude. To avoid false-trip during transient faults, impedance of the faulted phase before RCBO is compared with its value after RCBO. Performance of the proposed approach is validated for various internal and external faults covering addition of parallel link, presence of noise, different load angle, fault location, fault inception angle, fault impedance, source impedance and errors in measurement/transmission line parameters on an existing 230 kV transmission line modelled in PSCAD/EMTDC software. The results, obtained from both simulation as well as Hardware in Loop (HIL) simulation through laboratory prototype, designate that the proposed approach performs appropriately regardless of power flow direction, fault resistance magnitude, and light load conditions. The results also reveal that the suggested approach is able to accelerate trip within a cycle after RCBO event, which is comparable to or faster than many existing methods. Compared to several existing approaches in the literature, it also outperforms in terms of sensitivity, reliability and selectivity. [ABSTRACT FROM AUTHOR]

Standalone DC microgrids (SDCMGs) are emerging as prominent solutions to remote customers. As these SDCMGs mainly depend on renewable energy sources to curb carbon emission, reliability of the system is lessened due to their intermittent nature. The battery could offer a solution to this problem as it is inherently enclosed by DC grid for power balancing, but the purpose may not be served completely due to high capital cost and maintenance. Thus, the diesel generator (DG) becomes a major alternative to overcome this issue because of low investment, high compatibility, and flexibility. However, DG inhibits with cranking delay, sluggish response and low fuel efficiency under frequent switching and variable loading scenarios. To suppress the issues, a new power management strategy (PMS) is developed to ensure proper coordination between different sources, storage devices and loads in SDCMG. In addition to this, an effective control scheme is also proposed to achieve seamless regulation of DC bus voltage even under extreme conditions. In this study, different SDCMG configuration is considered for testing and simulation of system is carried out in real‐time digital simulator to prove their viability. A scaled prototype is developed to validate simulation results and authenticate proposed PMS and control scheme. [ABSTRACT FROM AUTHOR]

The tradeoff between advantages and the overall part count of classical multilevel converters are leading to an active interest on introducing a new topology with reduced power semiconductor device (PSD) count. In this paper, a new multipoint clamped three-phase five-level high-power-factor converter (5L-HPFC) is proposed. The converter can be modeled as a diode-clamped converter with omission of clamping diodes. The impact of voltage stress on PSDs with two pulsewidth modulation strategies is studied, and a methodology for reducing switch stress per each leg is presented. Comprehensive comparative analysis is carried out with existing topologies. The minimum value of normalized index makes the proposed topology suitable for medium-voltage and high-power applications. In addition, a new single-band hysteresis current controller (SBHC) is proposed and compared with conventional single-band and multiband current control techniques for ac–dc power conversion applications. Furthermore, the proposed topology with the SBHC is investigated under the following conditions: bidirectional power flow capability, supply unbalance, harmonics elimination, and power factor correction. The validation of a new 5L-HPFC with the proposed controlling scheme is verified with simulation and a downscaled experimental setup. [ABSTRACT FROM AUTHOR]

This paper presents a capacitor voltage balancing topology using a three-level boost converter (TLBC) for a neutral point clamped (NPC) three-level inverter fed surface permanent magnet synchronous motor drive (SPMSM). It enhanced the performance of the drive in terms of its voltage THD and torque pulsation. The main attracting feature of the proposed control is the boosting of the input voltage and at the same time the balancing of the capacitor voltages. This control also reduces the computational complexity. For the purpose of close loop vector control, a software based cost effective resolver to digital converter RDC-less estimation is implemented to calculate the speed and position. The proposed drive is simulated in the MATLAB/SIMULINK environment and an experimental investigation using dSPACE DS1104 validates the proposed drive system at different operating condition. [ABSTRACT FROM AUTHOR]

Abstract—The most commonly employed DC power supply in industrial processes, such as chemical electrolysis, aluminum potlines, DC arc furnaces, graphitizing furnaces, copper refining, plasma torches, the starting process of aircraft, the large Hadron collider, and nuclear fusion, is a magnetic confinement approach based on a line frequency isolated transformer with a phase-controlled rectifier. These power supplies suffer from high conduction losses, low efficiency, large size, and heavy weight. In this article, a high-frequency isolated three-phase resonant DC-DC converter is proposed for high power applications that demand low voltage, isolation, good regulation against load and line disturbances, and fast dynamic response. The modeling, control, and design of the proposed converter are carried out under symmetrical control with fixed frequency operation, and its steady-state analysis has been presented according to the description of the operational stages of the converter. Mathematical modeling of the LLC resonant tank network is presented, and its design curves are plotted against a variation of normalized frequency for different values of load. Based on mathematical analysis, a 5-V/150-A prototype model has been built and tested under various operating conditions, and the obtained experimental results are presented. [ABSTRACT FROM PUBLISHER]

Abstract: Hydropower is a major energy source among the renewable energy sources. According to “BP Statistical Review of World Energy, June 2013”, 16.34 percentage of global power generation acquire from hydropower. To attain efficient generation in hydro plant, extensive design with the up to date technology is mandatory. To make the generation more effective various technologies are adopted, among these the very effective one is power electronics (PE) technology. The paper has reviewed the challenges in how PE technology fits in as the solution for various hydroelectric energy systems (HEES). The PE technology is adapted efficiently in various parts of HEES like, grid integration, machine control, switching (pumping mode to generating mode and vice versa), power control, voltage and frequency control, power factor correction, etc., The advancement of PE technology diminishes the cost and space of the plant and enhances the power handling capability. The paper emergence the outstanding features of power electronics in various aspects that will extensively contribute to the development of HEES around the world. In addition, PE contribution satisfies the need of reliability, dynamic response, efficiency, protection, etc., in HEES. [Copyright &y& Elsevier]

This paper presents a modulation strategy for self-balancing of capacitor voltages of three-phase neutral-point clamped bi-directional rectifier (without feedback controller and sensors). It is identified that regions within a sector are divided into two categories: (a) One small vector among three selected vectors and (b) Two small vectors among three selected vectors. For category (a) positive and negative commutation state of small vector is implemented for equal duty cycle but for category (b) positive and negative commutation state of small vectors is implemented for unequal duty cycle. Based on this observation, an innovative idea is executed to remove these discrepancies. The innovative optimized space vector switching sequences negative and positive commutation state of both the small vectors are implemented for equal duty cycle during each sampling period resulting in self-balancing of DC-bus capacitors with much reduced ripples under steady-state and dynamic load conditions for both rectification and inversion mode of operation. The converter exhibits excellent performance in terms of other critical parameters like unity input power factor, low input current THD, minimum possible switching losses, reduced-rippled and well-regulated DC voltage. The proposed control algorithm is tested through exhaustive simulation of converter using MATLAB Simulink software. [ABSTRACT FROM AUTHOR]

Industrial applications such as welding, plasma cutting, and surface hardening require a large DC current at low voltage. In such applications, the rating of power supply varies from few kilowatts to hundreds of kilowatts. The power supply employs in such applications particularly in arc welding process is expected to operate from open-circuit (no-load) to short-circuit (when the electrode sticks to the workpiece for a short span of time) quickly. In this paper, high-frequency isolated multiphase DC-DC converter is proposed which is well suited for aforementioned applications. Based on mathematical analysis, a simulation study with 5 kW, 5 V/1,000 A proposed model is carried out using Simulink block set and Sim Power System tool box and its performances are evaluated under symmetrical control methods. To verify the simulation results, scaled prototype model of rating 1.5 V/100 A is developed and tested with aforementioned control method under different operating conditions. In comparison with conventional welding power supply employed in many industries, the performance of proposed converter is improved significantly in terms of size and weight, efficiency and dynamic response. [ABSTRACT FROM AUTHOR]

This paper presents the design and implementation of a simple neutral point potential (NPP) regulator for a three-level diode-clamped inverter employing a sine-triangle regulator in conjunction with a closed-loop controller with reduced switching losses. The regulator principle is based on adding a continuous variable offset voltage which regulates the midpoint potential of the dc bus. The novelty of the proposed NPP regulator is in the determination of the magnitude of variable offset voltage based upon the average value, peak-to-peak amplitude, total harmonic distortions, and third harmonic content in NPP. Aside from maintaining dc-bus voltage balance, the proposed regulator leads to a significant reduction in the voltage distortion at the NP, resulting in the reduction of the required dc-bus capacitance. It also reduces the switching losses of the inverter by inserting the “no-switching” zone within each half cycle of the fundamental voltage wave. Analytical, computer simulation, and experimental results verifying the approach are presented in this paper for various load power factor angles. [ABSTRACT FROM AUTHOR]

Highlights: [•] Interleaved control methods consist of symmetrical and asymmetrical are proposed. [•] Proposed converter with aforesaid control enables smaller size of passive elements. [•] A 5V/150A prototype model is built and tested under various operating conditions. [•] The proposed converter with symmetrical control assures better heat distribution. [Copyright &y& Elsevier]

In this article, phase disposition pulse width modulation based reduced switching state multipoint clamped (MPC)-five level unidirectional rectifier has been proposed. The converter has been modeled and modulated similar to conventional MPC structured converter topologies without additional clamping diodes and flying capacitors. Besides that, the proposed topology has minimum total blocking voltage, thereby reducing losses and improved efficiency. Moreover, it enhances the system reliability, minimizes the cost, and weight of the converter system. The principle of operation, mathematical formulation, and control implementation of the proposed topology has been presented in this article. A relative comparison with existing unidirectional topologies has also been addressed. Moreover, the validated experimental results of the proposed topology have been presented along with the prototype hardware setup. [ABSTRACT FROM AUTHOR]

Background: The prevalence of dermatophytes varies with season, geographical area, socio-economic factors and effective management strategies.Aims: The aim of the study was to assess the prevalence of pathogenic dermatophytes, clinical types of dermatophyte fungal infection, and in vitro antifungal drug susceptibility testing against dermatophytes.Methods: Three hundred and ninety five patients with dermatophytosis were enrolled from five cities (Mumbai, Delhi, Lucknow, Kolkata and Hyderabad) across India. All patients were subjected to clinical examination and investigations, including potassium hydroxide microscopy, fungal culture and antifungal drug susceptibility testing.Results: Trichophyton rubrum was the most common species identified (68.4%), followed by T. mentagrophytes (29.3%). Within species, T. mentagrophytes was prevalent in humid environmental conditions (Mumbai and Kolkata), whereas T. rubrum was prevalent in noncoastal areas (Delhi, Lucknow and Hyderabad). Tinea corporis (71.4%) and tinea cruris (62.0%) were the common clinical types observed. antifungal drug susceptibility testing data indicated that minimum inhibitory concentration required to inhibit the growth of 90% of organisms (MIC-90) was lowest for griseofulvin (0.25-3.0 μg/mL). Among oral antifungals, the mean MIC of itraconazole was within the range (0.84 [0.252] μg/ mL), whereas high mean MIC values were reported for terbinafine (0.05 [0.043] μg/mL). Among topical agents, lowest mean MIC values were reported for luliconazole (0.29 [0.286] μg/mL), eberconazole (0.32 [0.251]) μg/mL and amorolfine (0.60 [0.306]) μg/mL.Limitations: Lack of correlation between in vitro antifungal susceptibility and clinical outcome and absence of defined MIC breakpoints.Conclusion: T. rubrum was the most common, followed by T. mentagrophytes as an emerging/codominant fungal isolate in India. Tinea corporis was the most common clinical type of dermatophytosis. Mean MIC of terbinafine was above the reference range, while it was within the range for itraconazole; griseofulvin had the lowest mean MIC. Luliconazole presented the lowest mean MIC values across cities. [ABSTRACT FROM AUTHOR]

In this article, an optimization procedure for calculating the switching angles of a cascade multi-level inverter is presented. Specifically, the objective is to calculate the switching angles for a fundamental frequency switching scheme such that the individual harmonic components, as well as the total harmonic distortion in the inverter output voltage, satisfy the limit set by various standards. The feasibility of the proposed methodology has been validated through computational, simulation, and experimental studies on an 11-level cascade multi-level inverter, where close agreement among the results obtained by these three studies (computational, simulation, and experimental) have been observed. [ABSTRACT FROM AUTHOR]

This paper presents an optimal design and its realization of poly-phase induction motor using Quadratic Interpolation based Particle Swarm Optimization (QI-PSO). The optimization algorithm considers the efficiency, starting torque and temperature rise as objective function (which are considered separately) and nine performance related items as constraints. The QI-PSO algorithm was implemented on a test motor and the results are compared with the Simulated Annealing (SA) technique, Standard Particle Swarm Optimization (SPSO), and normal design. Some benchmark problems are used for validating QI-PSO. From the test results QI-PSO gave better results and more suitable to motor's design optimization. Optimized variables are realized by PC-IMD (Induction Motor Drives) of SPEED (Scottish Power Electronics and Electric Drives) software. C++ code is used for implementing entire algorithms. [ABSTRACT FROM AUTHOR]

A new technique for power transformer protection, that depends on the calculation of fault detection ratio (FDR) based on quartile of superimposed differential currents is presented. Internal faults are detected by comparing FDR with the predetermined threshold derived through analytical analysis and verified based on simulation results. The performance of the presented scheme is tested by modeling an existing Indian power transmission network using PSCAD/EMTDC software. Various types of abnormal conditions such as magnetizing inrush (including sympathetic and recovery) and over-excitation along with several types of internal (winding, inter-winding and turn-to-turn) faults have been investigated. Its validity has also been checked on the data of magnetizing inrush and simultaneous inrush with the internal fault in the transformer, which was obtained from the real network. The results reveal the effectiveness of the suggested technique in differentiating internal faults from other abnormal conditions. Further, it remains stable during heavy through fault with current transformer saturation. It is equally applicable for different ratings and winding connections of power transformers. Finally, comparative evaluation of the proposed scheme with the conventional and several existing techniques shows its superiority in terms of higher sensitivity during internal faults and improved stability in case of non-internal faults. [ABSTRACT FROM AUTHOR]