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The half‐bridge modular multilevel converter (HB‐MMC) is one of the most promising topologies for high‐voltage direct current (HVDC) systems. Unlike full‐bridge MMC (FB‐MMC) and clamp double sub‐module MMC (CDSM‐MMC), HB‐MMCs are defenceless against DC side faults. Different types of DC circuit breakers (DC CBs) assisted with arrester banks/damping resistors such as solid‐state CB and hybrid DC CBs can be used to interrupt the DC fault current. Arrester banks are used to protect against overvoltage after interrupting the fault current and in turn to demagnetise the circuit inductors. The main disadvantage of the arresters is that they forcibly break apart when they are overloaded. In this study, an arrester‐less fault current limiter is proposed for HB‐MMC configuration, which provides an opposing voltage during the DC side fault. This is achieved by inserting external pre‐charged capacitors in the DC current path during the fault. The selection of these external capacitors, their suitable initial voltages, and their charging stations are also presented in this study. A comparison between the proposed scheme and the CDSM‐MMC has been held as well. The proposed protection scheme is assessed using a simulation study for a point‐to‐point nine‐level HB‐MMC‐based HVDC system. [ABSTRACT FROM AUTHOR]

Repetitive Pulsed Electric Field (PEF) is a common technique for disinfecting liquids. By applying adequate PEF across germ cell membranes, an irreversible electroporation process, and cell destruction can be achieved. The PEF can be generated by applying a repetitive pulsed voltage using a high-voltage pulse generator across the cell membrane. Unipolar and bipolar high-voltage pulse generators are commonly used. Bipolar pulse generators can be implemented by employing a unipolar generator with an H-bridge output stage. The main disadvantage of this method is that the switches of the H-bridge are rated at the output high-voltage level, i.e. series-stacked semiconductor devices should be employed with static and dynamic voltage sharing to implement high-voltage switches. In this paper, a half-bridge submodule-based bipolar modular high-voltage pulse-generator fed from a relatively low-voltage dc supply is proposed. In the proposed approach, relatively low-voltage Insulated Gate Bipolar Transistors (IGBTs) are required to generate the high-voltage bipolar pulses. A detailed illustration of the proposed concept is presented. Simulation results are used to assure the viability of the proposed concept. Finally, experimental results have been obtained from a low-voltage model of the proposed generator. [ABSTRACT FROM AUTHOR]

The role of irreversible electroporation using pulsed electric field is to generate high-voltage (HV) pulses with a predefined magnitude and duration. These HV pulses are applied to the treatment chamber until decontamination of the sample is completed. In this paper, a new topology for HV rectangular pulse generation for water disinfection applications is introduced. The proposed topology has four arms comprised of series-connected half bridge modular multilevel converter cells. The rectangular pulse characteristics can be controlled via the software controller without any physical changes in power topology. The converter is capable of generating both bipolar and monopolar HV pulses with microsecond pulse durations at high a frequency rate with different characteristics. Hence, the proposed topology provides flexibility by software control, along with hardware modularity, scalability, and redundancy. Moreover, a cell’s capacitance is relatively small, which drastically reduces the converter footprint. The adopted charging and discharging process of the cell capacitors in this topology eliminate the need of any voltage measurements or complex control for cell-capacitors voltage balance. Consequently, continuity of converter operation is assured under cell malfunction. In this paper, analysis and cell-capacitor sizing of the proposed topology are detailed. Converter operation is verified using MATLAB/Simulink simulation and scaled experimentation. [ABSTRACT FROM AUTHOR]

Adjustable-speed drives based on multiphase motors are of significant interest for safety-critical applications that necessitate wide fault-tolerant capabilities and high system reliability. Although multiphase machines are based on the same conceptual theory as three-phase machines, most undergraduate electrical machines and electric drives courses do not cover this topic. Setting aside the analysis challenges addressed in state-of-the-art literature, undergraduate electrical machines and power electronics courses are a good opportunity for students to understand the main concepts underlying such electric drive systems. This paper presents an adjustable-speed multiphase drive system senior project for electrical engineering undergraduate students that addresses their attainment of the course's learning outcomes. Eight of the course's students were assigned to build the multiphase variable-speed motor drive system. From a pedagogical point of view, this paper describes the methodology of using a senior project to engage students through experiential learning of electric drive systems, which span disciplines such as electrical machines, control, power electronics, and electronics. Students acquire both technical skills and soft skills, which are evaluated through various assessment activities. A number of lessons for future work have been drawn from the experience of applying this project-based learning approach. [ABSTRACT FROM AUTHOR]

Identifying Photovoltaic (PV) array faults is crucial for improving the service life and consolidating system performance overall. The strategies based on the supervised Machine Learning (ML) approach represent an attractive solution to identify the PV array faults. However, attainable labeled data to train supervised ML algorithms present challenges in practice. Therefore, this work introduces a novel strategy that employs an ensemble learning concept in conjunction with a semi-supervised learning approach based on a self-training philosophy to realize the faults diagnosis of an arc, line-to-line, power tracker unit, open-circuit, and partial shading, under different of aspects which can directly be impacting faults behavior. The developed ensemble learning paradigm comprises multiple merged ML models, which enhances the overall diagnostics performance. Moreover, it works to alleviate the resource-intensive process, which, in turn, contributes to overcoming standard supervised ML algorithms limitations. To ensure high fault diagnostic capabilities through the proposed fault identification strategy, the principal component analysis is introduced to mitigate the correlation between variables. Moreover, the Bayesian optimization method is adopted to control the behaviors of training ML algorithms, providing models with better characterization results. The merits of the proposed strategy are corroborated through simulation and experimental case studies. [Display omitted] • A novel strategy for effective identification of faults in PV arrays. • The strategy takes into consideration of the minimum number of sensors. • The strategy works to alleviate the resource-intensive process. • The strategy can identify the faults under harsh environmental scenarios. • Strategy effectiveness has been validated by simulation and experimental results. [ABSTRACT FROM AUTHOR]

In order to generate bipolar high-voltage (HV) pulses across certain load from HV dc (HVdc) power supply, a voltage source inverter (VSI) stage should be inserted between the load and the supply. In order to meet the required HV level, series connection of semiconductor devices should be employed with dynamic voltage sharing between the involved devices. Modular multilevel converter (MMC) can be used instead of the conventional two-level VSI to alleviate the complexity introduced by the deployment of series-connected devices. The voltage level of the HVdc power supply and the voltage rating of the available semiconductor devices determine the suitable number of MMC voltage levels ( $N$ ). Capacitor voltage balancing is a vital issue for proper operation of the MMC. In general, conventional sensor-based balancing techniques require a significant amount of measurements, which increases the complexity of the system. In addition, the high dv/dt during switching times causes electromagnetic interference, which may adversely affect the accuracy of the measurements. In this paper, a sensorless voltage balancing technique is proposed for the MMC-based bipolar HV pulse generator that reduces the system sensitivity, cost, and complexity. A detailed illustration of the proposed approach is presented in this paper. The simulation and experimental results are used to validate the proposed concept. [ABSTRACT FROM AUTHOR]

Modular multilevel converters (MMCs) have become one of the most promising topologies for high-voltage dc–ac conversion. DC-side fault blocking capability of the MMC has prompted significant research in recent years. In this paper, a new switched capacitor submodule (SCSM) for MMCs is proposed which provides operation with DC fault blocking capability. In addition, successful voltage balancing is achieved with half the number of voltage sensors used with existing MMC cells. Generally, conventional sensor-based balancing techniques require a significant amount of measurements, 2m(N-1) voltage sensors, and 2m current sensors for an N-level m-phase MMC. The proposed cell will thus aid in reducing the complexity of the control system. A detailed illustration of the operational concept of the proposed architecture is presented in this paper. A comparison between the proposed SCSM and other existing MMC cells has been included to highlight the benefits of the proposed SCSM. A simulation model for an MMC-based HVDC system along with the proposed cell has been built to test its performance during normal as well as abnormal operating conditions. The simulation results show the effectiveness of the proposed architecture. [ABSTRACT FROM PUBLISHER]

One of the main merits offered by multiphase machines is their high fault-tolerant capability. Literature has demonstrated that the performance of multiphase induction machines under fault conditions is affected by the employed stator winding connection. In open-loop controlled five-phase machines, the star connection is favorable under healthy conditions while the pentagon connection is favorable and yields a lower derating factor under the open phase condition. In this paper, a new combined star/pentagon single layer winding layout that combines the advantages of both star and pentagon connections is proposed for a five-phase induction machine. Although the proposed winding is intrinsically an asymmetrical ten-phase machine, the proposed connection allows for only five-phase terminals. Moreover, the proposed winding not only yields better flux distribution compared to a conventional single layer winding, but also provides a complete cancellation of the third-order harmonic flux component caused by the induced third sequence currents due to the saturation effect and/or under unbalanced operation. Hence, the machine losses are decreased, which improves the overall machine efficiency. For the healthy case, the machine is similar to a conventional star connected five-phase machine. However, with one phase open, the proposed connection results in a lower derating factor compared to conventional connections for both open-loop and optimal current control techniques. A 1-kW prototype machine is used for experimental verification. [ABSTRACT FROM AUTHOR]

Conventional dual-active bridge topologies provide galvanic isolation and soft-switching over a reasonable operating range without dedicated resonant circuits. However, scaling the two-level dual-active bridge to higher dc voltage levels is impeded by several challenges among which the high dv/dt stress on the coupling transformer insulation. Gating and thermal characteristics of series switch arrays add to the limitations. To avoid the use of standard bulky modular multilevel bridges, this paper analyzes an alternative modulation technique, where staircase approximated trapezoidal voltage waveforms are produced; thus, alleviating developed dv/dt stresses. Modular design is realized by the utilization of half-bridge chopper cells. This way the analyzed dc-dc transformer employs modular multilevel converters operated in a new mode with minimal common-mode arm currents, as well as reduced capacitor size, hence reduced cell footprint. Suitable switching patterns are developed and various design and operation aspects are studied. Soft-switching characteristics will be shown to be comparable to those of the two-level dual-active bridge. Experimental results from a scaled test rig validate the presented concept. [ABSTRACT FROM AUTHOR]

Despite the increased interest in multiphase induction machines for safety-critical applications, machine parameter identification for the different sequence planes is still a challenging research point. In most available literature, the effect of nonfundamental sequence planes is overlooked due to the assumption of sinusoidal winding distribution and healthy operation. However, in a single layer or concentric winding layout with an odd number of phases, the effect of flux produced by nonfundamental sequence planes cannot be ignored for the open-phase case. This paper proposes a simple offline method to estimate the parameters of a five-phase induction machine corresponding to different sequence planes. The proposed technique can estimate the stator leakage inductance as well as the magnetizing inductance of both fundamental and third sequences by applying a quasi-square voltage to the stator winding while the machine is running at no-load. Consequently, the rotor circuit parameters of the fundamental sequence plane can be simply obtained by deducting the stator impedance from the blocked rotor machine impedance. For the third sequence plane, an approximate relation to estimate these parameters based on the measured fundamental sequence rotor parameters is also given. An experimental 1.5 Hp prototype machine is used to verify the proposed technique. [ABSTRACT FROM PUBLISHER]

The traditional neutral point clamped (NPC) inverter has short-circuit problem. The risk of short-circuit can be decreased by using dead-time in the switching signals. However, the dead-time decreases the achievable output voltage and causes distortion in the waveforms. To overcome the short-circuit problem, dual-buck NPC (DB-NPC) and split-inductor NPC (SI-NPC) inverters have been researched. However, the voltage stress of the two external diodes in the DB-NPC inverter is higher. On the other hand, the SI-NPC inverter has a problem of generating huge voltage spikes in the dead-time, which can destroy the semiconductor devices. In addition, the SI-NPC inverter cannot provide reactive power. This article presents a family of NPC inverters consisting of single-phase, three-phase, and cascaded inverters. The proposed inverters have no short-circuit and dead-time issues, therefore no high voltage and current spikes are caused. Also, the dead-time in the switching signals can be minimized. As a result, the magnitude of the output waveforms can be increased, and quality can be improved. Unlike the DB-NPC inverter, the voltage stress of all the semiconductor in the proposed inverter is lower, and unlike the SI-NPC inverter the proposed inverter provides reactive power. In this article, the proposed three-level NPC inverter is analyzed, designed, and tested. The voltage stress of the semiconductor devices in the proposed inverter is half of the source voltage, whereas in the conventional DB-NPC inverter the voltage stress of the two external diodes is the source voltage. In addition to the aforementioned benefits, the proposed cascaded inverter reduces the total number of inductors. To verify the analysis, detailed simulation, and experimental results of the proposed three-level inverter with input voltage 640 V, output power 1.2 kW, and output voltage 220 Vrms are provided. [ABSTRACT FROM AUTHOR]

This paper studies the effect of stator winding configuration on the performance of five-phase induction machines under healthy as well as faulty conditions. The study compares two connections, namely, star and pentagon connections. The comparison is conducted using both simulation and experimental results. The steady-state model based on symmetrical components theory is introduced for both connections with one-line open due to a converter fault, and the corresponding machine characteristic curves are estimated. During faults, two alternatives for machine operation are possible, namely, open-loop control and optimal current control. While the first alternative corresponds to higher torque ripple and unbalanced winding currents, the second option necessitates unbalanced phase voltages and typically an increased dc-link voltage to source the required optimal currents. Consequently, an increase in the employed semiconductor device rating is required, which is a critical design factor particularly in medium-voltage applications. A new V/f control technique is proposed to ensure disturbance-free operation with one-line open for both winding connections. Based on the unbalanced machine model and experimental verification, the derating factors that ensure safe machine operation for both winding connection alternatives are calculated. The comparison between the two connections shows the superiority of the pentagon connection under fault conditions in terms of efficiency, average torque, torque ripples, and derating factor. [ABSTRACT FROM PUBLISHER]

The modular multilevel converter (MMC) is a promising candidate for high-/medium-voltage high-power applications such as medium voltage ac drives due to its modularity, reliability, and scalability. The main challenge of a conventional MMC is low-frequency operation. Capacitor voltage ripple is inversely proportional to the operating frequency. Hence, operating at low frequency necessitates employing large submodule capacitances to limit voltage ripple or the utilization of energy equalization modules (EEMs). The first option negatively affects converter lifetime, and the second option requires a large number of semiconductor devices and isolating transformers. In this article, a modified MMC topology with self-energy equalization is proposed to ensure converter operation with balanced capacitor voltages with low ripple during zero-/low-frequency conditions. Operating with balanced capacitor voltages with low ripple is achieved by maintaining the same energy level in the involved upper and lower arms. A low device count alternative to the EEMs approach is proposed in this work. Detailed illustration of the operational concept and design of the associated passive components is presented. The performance of the proposed medium voltage ac drive is elucidated through simulation and experimental results. [ABSTRACT FROM AUTHOR]

Although torque enhancement in multiphase induction machines using harmonic current injection has been addressed in the literature, a detailed assessment of the effect of this enhancement on the design parameters of multiphase machines with different numbers of phases is needed. This paper addresses this topic by performing a detailed comparative study of harmonic injection torque enhancement on multiphase machines with different numbers of phases. Sets of identical dimension and volume rotors differing in their value of the bar skew angle were designed to operate with the various stator designs in order to facilitate the comparative evaluation. A mathematical approach is also introduced to enable the derivation of equivalent multiphase machine parameters based on an existing one. In addition to a detailed finite-element-analysis verification of the results, time domain MATLAB simulations are used to verify the mathematical modeling. The results provide a means to assess the extent to which such harmonic injection may be beneficial by quantifying torque enhancement as well as torque density for various multiphase machines. [ABSTRACT FROM AUTHOR]

Renewable energy sources, such as offshore wind farms, require high voltage gains in order to interface with power transmission networks. These conversions are normally made using bulky, complex, and costly transformers and high-voltage ac–dc converters with unnecessary bidirectional power flow capability. Multiple modules of single-switch single-inductor dc–dc converters can reach high gains without transformers in these applications due to low semiconductor conduction loss in high-power devices. This paper describes a new approach for high-gain high-voltage dc–dc converters using multiple modules of single-switch single-inductor transformerless converters. Results for low-voltage experimental prototypes show gains of up to 29 p.u. and demonstrate the potential of the approach as high-gain dc–dc converters for offshore wind farms. This paper then demonstrates the viability of multiple-module converters compared to a conventional high-voltage dc converter and a theoretical full-bridge converter due to fewer devices and valves, comparable isolation levels, and ease of interleaving for increased reliability. [ABSTRACT FROM AUTHOR]

Solar photovoltaic (PV) energy has witnessed double-digit growth in the past decade. The penetration of PV systems as distributed generators in low-voltage grids has also seen significant attention. In addition, the need for higher overall grid efficiency and reliability has boosted the interest in the microgrid concept. High-efficiency PV-based microgrids require maximum power point tracking (MPPT) controllers to maximize the harvested energy due to the nonlinearity in PV module characteristics. Perturb and observe (P&O) techniques, although thoroughly investigated in previous research, still suffer from several disadvantages, such as sustained oscillation around the MPP, fast tracking versus oscillation tradeoffs, and user predefined constants. In this paper, a modified P&O MPPT technique, applicable for PV systems, is presented. The proposed technique achieves: first, adaptive tracking; second, no steady-state oscillations around the MPP; and lastly, no need for predefined system-dependent constants, hence provides a generic design core. A design example is presented by experimental implementation of the proposed technique. Practical results for the implemented setup at different irradiance levels are illustrated to validate the proposed technique. [ABSTRACT FROM AUTHOR]

This article presents the operation of onboard integrated battery chargers tied to a nine-phase EV-drive train, shedding light on the charging performance during the postfault operation, when one or more faulty inverter legs are disconnected. The objective in that case is to ensure balanced grid currents, while maintaining minimum machine losses at zero average torque production. The proposed concept requires a minimalistic change from a control structure perspective to switch between the pre- and postfault cases. Limitations and fault cases are discussed and corroborated with experimental tests on a 1.5-kW prototype.The derived concept is parameter independent and applicable to nine-phase drives, irrespective of the type of rotor used. [ABSTRACT FROM AUTHOR]

Freezing desalination has gained interest due to its potential to reduce energy use. The freezing process faces challenges that limit its wide use. Washing product ice causes a large mass loss. Most freezing processes involve crushing to generate the appropriate ice form, limiting large-scale production. A vacuum pump and pressing piston are experimentally utilized to collect brine during melting to avoid washing and crushing ice. Five brine separation processes are needed to produce 2 %-salinity water. The studies used salinity-varying feed water. From the results, utilizing a vacuum pump and piston for brine separation during melting and a relatively small number of separation steps has considerably enhanced the quality of the produced water without causing significant mass loss. It is observed that 1000 ml of 15,000 ppm feed water produces freshwater with salinity and volume equal to 114 ppm and 185 ml, respectively. Results indicate that when the COP varied from 4 to 6, the system performance ratio increased from 31.74 to 47.62 and 7.94 to 11.90, with a recovery ratio equal to 0.9 and 0.6, respectively. Compared to previously described freeze desalination, MSF, MED, and MD desalination systems, the specific energy consumption increases by 71.5 %, 66.4 %, 54.5 %, and 36.1 %. • Crushing and washing free, freezing desalination technology • A technique that involves brine extraction by vacuum • Experimental investigation at different feed salinities • System performance ratio ranged from 31.74 to 47.62. [ABSTRACT FROM AUTHOR]

Interpretation of the colossal number of genetic variants identified from sequencing applications is one of the major bottlenecks in clinical genetics, with the inference of the effect of amino acidsubstituting missense variations on protein structure and function being especially challenging. Here we characterize the threedimensional (3D) amino acid positions affected in pathogenic and population variants from 1,330 disease-associated genes using over 14,000 experimentally solved human protein structures. By measuring the statistical burden of variations (i.e., point mutations) from all genes on 40 3D protein features, accounting for the structural, chemical, and functional context of the variations' positions, we identify features that are generally associated with pathogenic and population missense variants. We then perform the same amino acid-level analysis individually for 24 protein functional classes, which reveals unique characteristics of the positions of the altered amino acids: We observe up to 46% divergence of the class-specific features from the general characteristics obtained by the analysis on all genes, which is consistent with the structural diversity of essential regions across different protein classes. We demonstrate that the function-specific 3D features of the variants match the readouts of mutagenesis experiments for BRCA1 and PTEN, and positively correlate with an independent set of clinically interpreted pathogenic and benign missense variants. Finally, we make our results available through a web server to foster accessibility and downstream research. Our findings represent a crucial step toward translational genetics, from highlighting the impact of mutations on protein structure to rationalizing the variants' pathogenicity in terms of the perturbed molecular mechanisms. [ABSTRACT FROM AUTHOR]

Aim: The aim of this study was to investigate the effectiveness of using recombinant human follicle-stimulating hormone (FSH) compared with pituitary-derived porcine FSH given as one dose or multiple doses on the neonatal traits, follicular dynamics, and maternal blood biochemical constituents in Noemi ewes. Materials and Methods: A 3×2 factorial arrangement was designed utilizing 60 adults Noemi ewes to test the effects of using two sources of FSH (human vs. porcine) in addition to control, either given as a single total dose or six descending doses to provoke twinning. Six treatments (T) were tested (n=10 ewes/T). C1 and C6 served as control ewes given saline as one dose and six doses, respectively; H1 and H6 ewes were given human FSH as one and six doses; and P1 and P6 ewes were given porcine FSH similar to the above treatments. Saline and/or FSH administration were administered at days 8, 9, and 10 of the 10-day controlled internal drug release (CIDR) implant. At CIDR removal, fertile rams were used for natural mating. Blood samples for the assessment of serum metabolites were collected. Results: Twinning increased in FSH-treated ewes than control. However, giving FSH of either source as a single dose resulted in a higher incidence of stillbirths. Pregnancy rates were 30, 40, 50, 60, 70, and 80% in C1, C6, P1, P6, H1, and H6, respectively. Respective percent of ewes delivering twins/multiple birth was 0, 0, 80, 66.7, 71.4, and 87.5%. FSH of human source was more efficient for folliculogenesis than porcine FSH. Administration of FSH increased blood cholesterol, decreased high-density lipoprotein; however, low-density lipoprotein levels were not different than control. Moreover, an interaction (p<0.05) exists between source and type of FSH administration on blood glucose. Six doses of FSH elevated blood protein. Blood albumin decreased by porcine-FSH but not affected by human-FSH. Blood globulins were not different due to source of FSH, whereas giving FSH as six doses increased globulins than in single-dose protocol. Contrariwise, an interaction was found between source and type of FSH administration on elevating the activity of alanine aminotransferase and reducing the activity of aspartate aminotransferase. Conclusion: Administration of human FSH at 180 IU in six descending doses resulted in the best neonatal outcomes and maternal health in Noemi ewes. [ABSTRACT FROM AUTHOR]

Conventional modular multilevel converters (MMCs) are promising converters for high-voltage high-power applications. Unlike DC-AC conversion, DC-DC conversion of MMCs suffers from unbalanced capacitor voltages due to the energy drift problem. In this study, a new modular DC-DC converter is proposed, which consists of front-end half-bridge MMC with half-bridge submodules followed by full-bridge MMC with full-bridge submodules. The proposed modular multilevel DC-DC converter can be used effectively for connecting two different DC voltage levels in high-/medium-voltage DC grids. The proposed architecture provides successful DC-DC conversion with balanced capacitor voltages throughout the arm interchange concept. It also provides a high conversion ratio, bidirectional power flow, low losses, low current stresses, reduced number of submodules, and DC fault blocking capability. Detailed illustration, operational concept, and design of the proposed architecture with the arm interchange concept are presented. Simulation results for a high-voltage high-power DC-DC converter with the suggested approach are presented to demonstrate the system performance during different normal as well as abnormal operating conditions. Finally, a scaled-down prototype has been implemented for validation. The extracted simulation and experimental results elucidate the presented claims. [ABSTRACT FROM AUTHOR]

Conventional modular multilevel converters (MMCs) are promising converters for high‐voltage high‐power applications. Unlike DC–AC conversion, DC–DC conversion of MMCs suffers from unbalanced capacitor voltages due to the energy drift problem. In this study, a new modular DC–DC converter is proposed, which consists of front‐end half‐bridge MMC with half‐bridge submodules followed by full‐bridge MMC with full‐bridge submodules. The proposed modular multilevel DC–DC converter can be used effectively for connecting two different DC voltage levels in high‐/medium‐voltage DC grids. The proposed architecture provides successful DC–DC conversion with balanced capacitor voltages throughout the arm interchange concept. It also provides a high conversion ratio, bidirectional power flow, low losses, low current stresses, reduced number of submodules, and DC fault blocking capability. Detailed illustration, operational concept, and design of the proposed architecture with the arm interchange concept are presented. Simulation results for a high‐voltage high‐power DC–DC converter with the suggested approach are presented to demonstrate the system performance during different normal as well as abnormal operating conditions. Finally, a scaled‐down prototype has been implemented for validation. The extracted simulation and experimental results elucidate the presented claims. [ABSTRACT FROM AUTHOR]

The nine-arm modular multilevel converter (9A-MMC) has been recently proposed as a reduced MMC topology variation for six-phase drive applications, with 25% reduction in the number of employed arms and associated components, compared to a standard dual three-phase MMC, however with a limited output voltage amplitude. This paper proposes a hybrid 9A-MMC comprised of half-bridge submodules (SMs) in both the upper and lower arms, and full-bridge SMs in the middle arms. By employing the negative-voltage state of the full-bridge SMs, the hybrid 9A-MMC avoids the limitations imposed on the dc-link voltage utilization, while achieving further reduction in the component count, compared to a standard 9A-MMC with identical half-bridge SMs. The operating principles of the proposed hybrid 9A-MMC are illustrated with mathematical analysis, whereas its characteristics are verified through both simulation and experimentation. An assessment of the proposed topology quantifying its employed components is also provided, in comparison to other MMC-based six-phase machine drives. [ABSTRACT FROM AUTHOR]

This article investigates the required modifications to droop control design for optimum operation of Multi-Terminal High-Voltage Direct Current (MTHVDC) systems during line and converter outages. A typical 6-bus MTHVDC system is used in this study. Different scenarios are considered during the design process such as different outage types, violation of power ratings of system components, and variability of wind power injected into the system. A variable droop control gains technique is proposed to ensure minimum power loss and maximum annual energy collection. The study is extended to investigate the effect of employing constant droop control gains calculated during rated conditions on the system performance. Moreover, the results of the constant and the proposed variable droop gain schemes are compared. Simulation results show the effectiveness of the proposed techniques for designing optimum droop gains during abnormal conditions. Additionally, general guidelines are presented for the implementation of the proposed techniques. [ABSTRACT FROM AUTHOR]

This paper proposes a hybrid-boost Modular Multilevel Converter (MMC) for the Medium-Voltage (MV) Variable Speed Drives (VSDs) employed in subsea applications, such as oil and gas recovery. In the presented architecture, a hybrid-boost MMC with a reduced number of semiconductor devices driving a multiphase Induction Machine (IM) is investigated. The stepped output voltage generated by the MMC reduces or eliminates the filtering requirements. Moreover, the boosting capability of the proposed architecture eliminates the need for bulky low-frequency transformers at the converter output terminals. A detailed illustration of the hybrid-boost MMC operation, the expected limitations/constraints, and the voltage balancing technique are presented. A simulation model of the proposed MV hybrid-boost MMC-based five-phase IM drive has been built to investigate the system performance. Finally, a downscaled prototype has been constructed for experimental verification. [ABSTRACT FROM AUTHOR]

This paper proposes a medium-/high-voltage high-power hybrid modular dc–dc converter to interconnect two different dc-voltage levels in medium-/high-voltage dc grids. The converter consists of half-bridge submodules (SMs) rated at a moderate voltage level, i.e., series connection of semiconductor devices is avoided while connecting two high dc-voltage levels. The proposed architecture provides self-balancing operation, i.e., unlike conventional modular converters, no need for capacitor voltage measurement, which enhances the system reliability and simplicity. Sequential charging/discharging of SMs capacitors is adopted in the proposed approach to ensure a self-balanced operation. The proposed architecture can provide a high conversion ratio as well as power transfer in both directions, i.e., bidirectional dc–dc converter. Detailed illustration of the proposed approach operational concept, design, and overall control system is presented. Simulation and experimental results are presented to show the viability of the proposed configuration and validate the claims. [ABSTRACT FROM AUTHOR]

Abstract Experiments and Computational Fluid Dynamics (CFD) simulations were performed to investigate the colloidal fouling control of a vibration enhanced reverse osmosis (VERO) membrane system for up to 12 h of operation time. A porous cake mass transfer model for the reverse osmosis (RO) colloidal fouling analysis was derived by combining the cake filtration model, cake enhanced osmotic pressure (CEOP) effect, the critical flux theory, and the solute convection-diffusion model. The process of colloidal particle deposition and fouling formation on the membrane surface were visualized using this model. The permeate flux variation and cake layer distribution along the membrane were depicted. Systematic studies including different initial permeate fluxes, Reynolds numbers, particle concentrations, and vibration frequencies were carried out to investigate the system performance under different operation conditions. The results suggest that colloidal fouling induced permeate flux decline could be improved by the high-frequency vibration in the VERO module. Both simulations and experiments demonstrated that, with a fixed vibration amplitude, membrane module with higher vibration frequencies will have less NaCl accumulation and higher permeate flux under the influence of colloidal fouling. Highlights • The colloidal fouling control performance of the vibration enhanced reverse osmosis technique was investigated. • A cell-based numerical model to analyze the process of membrane colloidal fouling was developed and validated by experiments. • Axial variations of the permeate flux and fouling cake height, the CEOP effect, and critical flux theory were considered. • Membrane colloidal fouling is significantly reduced by the proposed technique based on CFD simulations and experiments. [ABSTRACT FROM AUTHOR]

Highlights • A new switching pattern is proposed for zero voltage switching of hybrid modular dc-dc converter. • The switching losses is greatly reduced by enabling operation with ZVS of the involved HV valve. • The dynamic voltage sharing of series-connected IGBTs based HV valve is simplified as the switching occurs at zero voltage. Abstract In this paper, a bidirectional non-isolated hybrid modular DC–DC converter for high-voltage (HV) applications is investigated. In this configuration, conventional Half-Bridge Sub-Modules (HB-SMs) are employed. The proposed DC–DC converter is based on connecting the SMs capacitors in series across the high DC voltage level while connecting them sequentially across the low DC voltage level. On another frontier, an HV valve, based on series-connected Insulated-Gate Bipolar Transistors (IGBTs), is required at the HV side. The main confronted challenge of the series-connected IGBTs is the voltage sharing during turn-on and turn-off periods, which necessitates the engagement of an intricate voltage sharing technique. In this work, a switching pattern is proposed to ensure zero-voltage switching (ZVS) of the involved HV valve. In order to reduce the switching losses and avoid complex active gate control recruited for dynamic voltage sharing, the zero-voltage state is extended beyond the switching time. A detailed illustration of the hybrid modular DC–DC converter is presented, elucidating the proposed switching pattern. Simulation results, using Matlab/Simulink platform, are presented to validate the contribution of the paper. Finally, a scaled-down prototype is employed for experimental verification. [ABSTRACT FROM AUTHOR]

Abstract Concentration polarization and surface fouling may be two of the most remarkable features in the pressure-driven membrane filtration process. A new numerical simulation model is proposed in this paper to study the concentration polarization (CP) and the inorganic fouling growth. The numerical study is based on the lattice Boltzmann method (LBM), which allows a simultaneous solution of the Navier–Stokes equations and the convection-diffusion equation. Simulation results are verified by comparisons with published CP and permeate flux data under the same operating conditions. Then the model is extended to predict CP in a spacer filled desalination channel. The prediction result indicates that there is a higher fouling potential near the spacer filaments due to higher CP values in that area. Coupling of the CP prediction model with gypsum growth kinetics provides an approach to study the inorganic fouling growth on the membrane surface at a single crystal level, with respect to a given solution supersaturation near the membrane surface. Predicted equivalent radius and accumulated mass of the growing gypsum crystal, under the effects of growth retardation by bicarbonate, agree with published test data and analytical results. The presented numerical model enables a direct evaluation of the impacts on the surface crystal development in the presence of antiscalants. This numerical model can be applied to identify suitable operating conditions, assist in dose selection of antiscalants when required properties are available, and predict the fouling mitigation effects in the pressure-driven membrane filtration process. Highlights • Proposed an LBM CP prediction model for membrane filtration channel with spacer filaments considered; • Proposed an LBM inorganic fouling growth model for a direct simulation of the surface fouling formation; • Formed an integrated numerical model to identify effects of operating conditions on the fouling mitigation. [ABSTRACT FROM AUTHOR]

Here, a new bi‐directional hybrid modular non‐isolated DC–DC converter is proposed where it consists of a boost converter (BC) fed from the high‐voltage (HV) side. At the BC output stage, a certain number of half bridge submodules (HB‐SMs) is connected across the BC switch. During the turn‐on period of BC switch, the HB‐SMs are connected sequentially to the low‐voltage (LV) side, which results in charging/discharging their capacitors from/into the LV side. While, during the turn‐off period, the LV side is bypassed and the HB‐SMs capacitors are connected in series across the BC output stage, which results in discharging/charging them into/from the HV side. The power flow is controlled in both directions by controlling the duty cycle. The proposed configuration provides self‐balancing operation thanks to the sequential connection of HB‐SMs capacitors, and it also provides the ability to operate with high conversion ratios. Illustration and analysis of the proposed converter and its closed‐loop controller are presented. A full design of the values and ratings of the involved components are presented. Simulation study for a 2.5 MW (25 kV/10 kV) DC–DC converter is presented. Finally, experimental results for a downscaled prototype are presented for validation. [ABSTRACT FROM AUTHOR]

Superparamagnetic iron oxide nanoparticles (SPION) Fe 3 O 4 nanoparticles were prepared using different approaches: co-precipitation and sonochemical methods. This article is a comparative study on how different synthesis techniques greatly affect the magnetic properties and heating efficiency of such nanomaterial. Another important issue addressed here is the correlation between microstructure, colloidal stability, magnetization and specific absorption rate (SAR) of the nanoparticles. The results reveal that the sonochemical method for polyethylene glycol (PEGylated) Fe 3 O 4 with size 5 nm leads to pseudo single domain with smallest loop area. Additionally, large SAR values are obtained within 10–15 min using low magnetic field. [ABSTRACT FROM AUTHOR]

The performance of a vibration enhanced reverse osmosis membrane module for desalination of artificial seawater was investigated with computational fluid dynamics (CFD) simulations and experiments. The computational model couples fluid dynamics with solutes transport inside the full length domain containing ‘zigzag’ spacers using a two dimensional, transient Large Eddy Simulation turbulence model. Both the local concentration dependent solute properties and variation of permeate flux over the membrane surface were predicted with the model. Membrane local permeate flux, concentration polarization, shear rate, and mass transfer were also calculated. The results suggest concentration polarization in the seawater desalination process could be reduced by imposing vibration on the reverse osmosis membrane. It was determined that the higher the vibration frequency the higher the membrane permeate flux while keeping the vibration amplitude constant. The CFD simulation predictions are validated against experimental data of permeate fluxes with good agreement. [ABSTRACT FROM AUTHOR]

This paper studies the postfault control of a nine-phase six-terminal induction machine (IM) during single open-line fault, which was recently proposed for high-power medium-voltage applications as a promising alternative to conventional six-phase IMs. The required optimal reference currents to provide prefault loading conditions under one-line open are derived using the two most common optimization criteria employed in multiphase drives, namely, maximum torque and minimum loss modes. A postfault controller, based on conventional decoupling Clarke's transformation, is then used to ensure the same controller structure under all conditions. Consequently, the machine characteristic curves, achievable torque, and stator copper losses under these different modes are compared. A comparison with a conventional asymmetrical six-phase winding is also given. A 1.5-Hp prototype IM is used for experimental verification. [ABSTRACT FROM PUBLISHER]

All available Pulse Width Modulation (PWM) techniques employed to different Matrix Converter (MC) topologies generally generate switching Common-Mode Voltage (CMV), which introduces numerous operational concerns in electric drives. Although a body of research for the three-phase case has been undertaken to either reduce or eliminate CMV, corresponding discussions for multiphase MC remain scarce. Interestingly enough, the three- to five-phase (3 × 5) Indirect MC (IMC) is a potential converter topology for five-phase based high power motor drives. In this paper, the different available switching states of a 3 × 5 IMC are classified based on their corresponding CMV levels. Accordingly, two different Space Vector Modulation (SVM) techniques are proposed, which can successfully reduce the peak CMV by 28% and 48%, respectively, when compared with the conventional modulation strategy, while the same maximum Voltage Transfer Ratio (VTR) is preserved. Although the 28% reduction has been alternatively achieved in literature based on carrier-based PWM, the 48% reduction attained in this study represents the maximum achievable reduction for this MC topology. The main concept is firstly introduced; then, both simulations and experiments are used to validate the proposed schemes. [ABSTRACT FROM AUTHOR]

Employing the LCL passive filter in inverter-based distributed generation to ensure high quality power delivery comes at the expense of poor performance due to the resonance phenomenon. Literature elucidated several active approaches to mitigate this phenomenon. This paper proposes a sensorless active damping technique that is able to restrain the resonant current component through the estimation of the filter capacitor current using the Kalman filter. The Kalman filter is able to improve the quality of the estimated variables in noisy environments accompanied with measurements and model uncertainties. The effect of LCL filter parameter mismatch on the performance of the Kalman filter is assessed. Stability and convergence analyses are also conducted. An effective tuning method for the grid current controller employing a proportional-resonant controller is adopted. Experimental evaluations were conducted to validate the proposed control strategy. [ABSTRACT FROM AUTHOR]

In this paper a Four-Arm Three-Phase MMC (4A-TPMMC)-based DC–AC converter is proposed. The proposed converter generates a three-phase output voltage using a lower number of components, which reduces the converter complexity and cost. The concept of the proposed approach is presented in this paper. A comparison between the conventional Six-Arm Three-Phase MMC (6A-TPMMC) and the proposed 4A-TPMMC is conducted. Two simulation models are built, one for the 6A-TPMMC, and the other for the proposed 4A-TPMMC. The simulations are carried out for the same number of submodules per arm and the same AC output voltage magnitude. Moreover, a case study using the proposed 4A-TPMMC, as a three-phase medium voltage motor drive, is considered. Finally, an experimental validation for the proposed 4A-TPMMC is presented to prove the viability of the claimed contributions. [ABSTRACT FROM PUBLISHER]

Conventional Modular Multilevel Converter (MMC) with Half-Bridge Sub-Modules (HB-SMs) can be used effectively as a solid-state high-voltage pulse generator to chop a high-voltage dc input into a bipolar pulsed output voltage without employing neither high-voltage semiconductor switches nor series-connected switches. Nonetheless, its boosting capability is constrained. In this paper, a hybrid boost MMC-based bipolar high-voltage pulse generator is proposed where each arm contains a combination of Full-Bridge SMs (FB-SMs) and HB-SMs. The HB-SMs and FB-SMs have the same rated voltage. The proposed approach is able to generate bipolar pulses, and operates with a wide range of boosting capability. Detailed illustration of the proposed configuration and its operational concept are presented. Simulation models for the proposed approach are built, for different FB-SMs to HB-SMs ratios, using Matlab/Simulink platform. Experimental results for a scaled-down prototype are presented to validate the concept. [ABSTRACT FROM PUBLISHER]

The subject of this work is the development of a novel vibration assisted seawater desalination approach which changes thermodynamic (mass transfer coefficient) and hydrodynamic (cross-flow velocity) properties to mitigate the inorganic fouling for RO membranes. A classical mass transport model and experimental measurements showed that an increased cross-flow velocity in the feed channel enhances the near membrane mass transfer coefficient, which promotes the back-diffusion of inorganic salts and reduces the concentration polarization (CP). Then a theoretical CP Finite Element Method (FEM) model incorporating increased cross-flow velocity reveals that a lower CP modulus forms near the membrane surface with a higher vibration frequency, which results in less fouling on the membrane surface. The vibration assisted desalination process was demonstrated using a linear motor driven, periodically oscillating desalination cell. A smaller flux decline was observed while using a higher vibration frequency (with a constant sinusoidal amplitude) and a higher vibration velocity (in multiple vibration forms). Process simulations and experimental observations validated that the proposed vibration assisted desalination process helps enhance the permeate flux and mitigate the formation of inorganic fouling on the RO membrane surface. [ABSTRACT FROM AUTHOR]

The conventional unipolar Marx generator can be employed for bipolar pulsed electric field by adding a high-voltage H-bridge at the load side which necessitates stacked switches. Alternatively, bipolar Marx generator with low-voltage switches can be employed. The existing bipolar Marx generators are typically fed from dc supplies, where polarized capacitors are employed. The capacitance of involved capacitors is selected such that the total energy stored in the generator's capacitors is higher than the bipolar pulse energy. As a result, polarized capacitors with relatively high capacitances are required. In addition, a high number of controlled switches per stage are required (at least four switches per stage). In this paper, a new solid-state bipolar Marx pulse generator with only three controlled switches per stage is proposed. The proposed generator is fed from sinusoidal/square ac voltage and non-polarized capacitors with low capacitance are employed. The proposed bipolar Marx-generator can be used effectively with resistive loads for exponential pulse generation. A detailed illustration of the proposed approach is presented and a discussion, to elucidate the differences between the proposed pulse generator and the other existing ones, are presented. Simulation results for the proposed pulse generator are presented to validate the concept. Finally, experimental results have been obtained from a low-voltage model of the proposed generator. [ABSTRACT FROM AUTHOR]

In this study, a new transformerless wind energy conversion system to integrate high‐power multi‐phase permanent magnet wind generators to medium‐voltage local grids is presented. The proposed converter topology consists of multi‐half‐bridge modules with a high ac–direct current (dc) boosting capability. Each phase of an open winding multi‐phase generator is connected to the ac side of a half‐bridge module, whereas the dc sides of the half‐bridge modules are connected in series forming the high‐voltage dc‐link output. The proposed architecture facilitates the employment of semiconductor switches with a relatively low‐voltage rating, which equals the dc‐link voltage divided by the number of generator phases. A detailed analysis of the proposed architecture along with the required closed‐loop control is presented. The proposed architecture is simulated under different operating conditions using a typical 2 MW system, while the experimental validation is carried out using a low‐scale prototype converter. [ABSTRACT FROM AUTHOR]

Pulsed electric field is a commonly used and effective disinfection method in drinking water treatment applications. In this paper, a transformerless unipolar/bipolar high-voltage pulse generator is presented with well-regulated pulsed output voltage for drinking water treatment via underwater pulsed corona discharge. The proposed high-voltage pulse generator is fed from a relatively low-voltage dc supply. Then, capacitor–diode voltage multiplier centrally fed from a dc–dc boost converter is used to elevate the input voltage to a proper high-voltage level. Finally, a modular multilevel converter is employed to chop the elevated voltage into unipolar or bipolar pulsed output voltage (based on the user selection). The suggested arrangement provides a high-voltage gain with relatively low-voltage components, i.e., neither high-voltage nor series-connected components are needed in the proposed approach. A comparison between the proposed approach and the other Marx-Based pulse generators has been held to show the merits of the proposed approach. A detailed design of the generator passive components and semiconductor devices has been presented. Simulation and experimental results are presented for the unipolar as well as the bipolar pulsed output to validate the proposed concept. [ABSTRACT FROM AUTHOR]

This paper introduces a non-communication based protection algorithm for Multi-Terminal High Voltage Direct Current (MTHVDC) transmission lines. The algorithm relies on using electrical current data at one end for identification of the fault zone without communication between relays. The concept is to use the fault generated transients to differentiate between internal and external faults. Shunt capacitors with predetermined values are installed at the boundary between each two HVDC line sections to assist, together with the busbar stray capacitance, in the classification of internal faults. The high frequency transients will reach the relaying point without any attenuation if the fault is internal; nevertheless, the high frequency transients will be highly attenuated if the fault is external due to the stray capacitance and the installed shunt capacitor at the connection busbar. Discrete Wavelet Transform (DWT) is used to analyze the fault current signals. MTHVDC system modeling and relay design are carried out in the MATLAB/SIMULINK environment. The results of the proposed algorithm were highly reliable regarding different types of faults with different fault resistances and at various locations. [ABSTRACT FROM AUTHOR]

Repetitive high pulsed electric field (PEF) is an effective method to kill microorganisms and bacteria in water treatment applications. The PEF can be generated by applying high-power electromagnetic pulse across the sample to be treated. There are two main types of high-voltage pulse generators, namely, unipolar and bipolar. In this paper, a full-bridge submodule-based modular high-voltage pulse generator, having the ability to generate unipolar and bipolar high-voltage pulses with different shapes from a relatively low-voltage input dc supply, is proposed. In the proposed configuration, relatively low-voltage insulated gate bipolar transistors (IGBTs) are required to generate the high-voltage bipolar pulses. A thyristor rated at the level of the pulsed output voltage is required in the proposed configuration to bypass the load during the charging process of capacitors. In the proposed approach, a thyristor is used instead of the self-commutated high-voltage switch (e.g., series-connected IGBTs), as thyristors are available with high-voltage ratings and possess inherent reverse voltage blocking capability. A detailed illustration of the proposed configuration and its operational concept are introduced in this paper. Simulation and experimental results are presented to validate the proposed approach. [ABSTRACT FROM AUTHOR]

Differential-mode buck-boost inverters have merits such as reduced switch number, ability to provide voltages higher or lower than the input voltage magnitude, improved efficiency, reduced cost and size, and increased power density, especially in low-power applications. There are five buck-boost inverters that can provide flexible output voltage without the need of a large electrolytic input side capacitor, which degrades the reliability of inverters. The continuous input current of these inverters is appropriate for maximum power point tracking operation in photovoltaic and fuel cells applications. Three of the five inverters can be isolated with high-frequency-link transformers where the common-mode leakage current can be mitigated. However, the performance and control of such converters have not been discussed in detail. In this paper, the five possible single-stage three-phase differential-mode buck-boost inverters with continuous input current are investigated and compared in terms of total losses, maximum ripple current, total harmonic distortion, and device and passive element ratings. In addition, the possible methods are presented for eliminating the input third-order harmonic current, resulting from the stored energy in the passive elements, as well as the output second-order harmonic currents. The ability for isolating the input and output sides of the inverters with a small–high frequency transformers is discussed. A changeable-terminal 2.5-kW bidirectional inverter is used to validate the design flexibility of the inverter topologies, when digital signal processor-controlled. [ABSTRACT FROM AUTHOR]

This paper presents a new configuration for integrated on-board battery chargers of electric vehicles (EVs) incorporating symmetrical six-phase machines. The configuration proposes an exclusive utilization of a nine-switch converter (NSC) along with the machine windings during both propulsion and charging of EVs. The proposed configuration has the advantage of employing a reduced number of components in both the EV (on-board) and charging station (off-board), with the privilege of avoiding machine electromagnetic torque production during charging/vehicle-to-grid (V2G) mode of operation. During charging/V2G mode, the NSC is turned into a conventional three-phase pulse width modulation rectifier and is directly connected to the three-phase mains through the machine windings. Conventional three-phase transformers can be employed for galvanic isolation. Switching between propulsion and charging modes is carried out using a simple hardware reconfiguration. Control schemes for both propulsion and charging/V2G modes are elaborated, along with the principles of operation of the NSC. Experimental results are provided to validate the theoretical deductions for the different operating modes. [ABSTRACT FROM PUBLISHER]

Voltage source converter (VSC)-based high voltage DC (HVDC) transmission is considered the future of offshore power transmission. This paper aims at providing a reliable VSC-HVDC transmission system architecture between offshore wind farms and onshore grids. In this paper, a large-capacity, low-speed flywheel energy storage system (FESS) based on a squirrel cage induction machine is applied in parallel with the VSC-HVDC at the grid side converter. The FESS is dedicated for surge power (due to power flow imbalance during fault) absorption instead of being dissipated in the form of resistive losses. Since the duration of these surges is relatively small, it has been shown that the flywheel can effectively mitigate this problem. In addition to the fault ride-through support during fault conditions, the FESS is employed for power leveling functionality during normal operation. The performance parameters of the proposed approach are investigated via both simulation and experimental results. A 132-kV, 100-MW HVDC system is simulated using MATLAB/Simulink during normal and fault conditions. The proposed architecture is substantiated experimentally through a scaled down test rig with a 2-kW FESS. [ABSTRACT FROM AUTHOR]

Converting existing ac transmission lines to an extended multiterminal three-wire bipolar HVDC system can be considered a cost-effective way to interconnect dispersed offshore wind farms to onshore ac grids instead of building new bipolar HVDC systems. To automatically coordinate between different converters in a multiterminal HVDC (MTDC) system, droop control techniques have been adopted as an effective means without the need for fast communications between units. The droop control design is mainly dependent on the line resistances. This paper shows that the equivalent resistance of a three-wire bipolar system changes based on the operational mode. The modification to droop control design of an MTDC equipped with a three-wire bipolar system is then presented to tackle this resistance variation with the operating condition. Two types of MTDC systems are considered in this work, namely, radial parallel and meshed parallel systems. Different simulation studies have been conducted to validate the results of the presented analysis. [ABSTRACT FROM PUBLISHER]

This paper presents a technique for differential protection of Multi-terminal High Voltage Direct Current (MTHVDC) transmission lines. The proposed technique depends on the electrical current data at both ends of each line section. Discrete Wavelet Transform (DWT) is used to detect DC faults as well as filter out the high frequency transients superimposed on the current signals. An operating signal and a restraining signal are used in this technique to discriminate between internal faults and external faults through their ratio in each section of the MTHVDC. The operating and restraining signals depend on energy contents of the de-noised current signals at both ends of each line section. MTHVDC modeling and relay design are carried out in the MATLAB environment. The results demonstrate the high reliability of the proposed relay in the zonal protection of MTHVDC. [ABSTRACT FROM AUTHOR]

The most recent literature on multiphase machine drives is based on voltage-source converter (VSC) systems utilizing different modulation techniques. Very little attention is given to the multiphase current-source converters (CSCs). Applying CSCs in high-power multiphase drive systems is promising and can effectively solve many technical problems associated with conventional VSC-based systems. This paper proposes a space vector pulsewidth-modulation (SVPWM) scheme suitable for a five-phase CSC. Generally, in SVPWM-CSCs, a current path should be provided for the dc-link current by ensuring that one pair of upper and lower switches is always on. Applying this constraint yields 25 different space vectors, which are mapped into two concentric decagons with ten equal sectors in the $\alpha\beta$ and $xy$ sequence planes. Each sector has two active-large vectors, two active-small vectors, and a null vector. Moreover, the active-large vectors in the $\alpha\beta$ plane are active-small vectors in the $xy$ plane, and vice versa. In the proposed scheme, the ampere-second concept is utilized to determine the ratio between the dwelling times of the large and small vectors such that the $xy$ current components are nullified, the utilization of the input dc-current is maximized, and the switching transitions are minimized, which, in turn, minimizes the CSC switching losses. The proposed scheme can effectively provide sinusoidal converter currents, which is suitable for motor drives and energy conversion applications. The proposed scheme is verified using a 1-kW prototype five-phase induction motor fed by a five-phase CSC. [ABSTRACT FROM PUBLISHER]