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Read operation induced disturbance in SET-state in a tungsten oxide resistive switching memory is investigated. We observe that the reduction of oxygen vacancy density during read-disturb follows power-law dependence on cumulative read-disturb time. Our study shows that the SET-state readdisturb immunity progressively degrades by orders of magnitude as SET/RESET cycle number increases. To explore the cause of the read-disturb degradation, we perform a constant voltage stress to emulate high-field stress effects in SET/RESET cycling. We find that the read-disturb failure time degradation is attributed to high-field stress-generated oxide traps. Since the stressgenerated traps may substitute for some of oxygen vacancies in forming conductive percolation paths in a switching dielectric, a stressed cell has a reduced oxygen vacancy density in SET-state, which in turn results in a shorter read-disturb failure time. We develop an analytical read-disturb degradation model including both cycling induced oxide trap creation and read-disturb induced oxygen vacancy reduction. Our model can well reproduce the measured read-disturb failure time degradation in a cycled cell without using fitting parameters. [ABSTRACT FROM AUTHOR]

The paper presents the first results of an exploratory research work, aiming the experimental evaluation of the mechanical contact between conforming surfaces of metallic bodies. The proposed procedure—that is based on the measurement of electric potentials—is able to determine the actual contact pattern and estimate the force distribution on the opposing surfaces. In the present paper, the contact properties along a curve are evaluated, but the basic principles supporting the solution of the more general surface contact problem are also laid down. The goal of this research work is to provide a reliable basis for the investigation of contact-related effects on the modal properties of structures and machines. The distribution of electric contact resistivity can also be assessed using this method, opening the way to the refined characterization of electric switches and connectors. During the application of the method, measured electric voltage values are processed by a neural network trained on a data set generated by finite element software. The resulting electric contact conductivity distribution is used to determine the contact force distribution, taking into account the equilibrium of forces and moments. The results are also checked by available alternative experimental methods. [ABSTRACT FROM AUTHOR]

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In this paper, a single-inductor dual-output (SIDO) dc–dc converter is proposed. The significant feature of the proposed converter is feeding a constant power load in low-voltage side (LVS) port, where even feeding a variable load at LVS does not have any cross regulation to high-voltage side port with the desired approximation. Magnificently, both merits are obtained in open-loop manner, which is an outstanding characteristic in comparison with that of the existed converters. In this paper, soft commutation and soft switching of switches and diodes are investigated along with the aforementioned main novelty. Moreover, detailed theoretical analyses of the proposed SIDO dc–dc converter in continuous conduction mode are presented besides the comparisons with some other structures. Finally, theoretical analyses are verified through a 1500 W experimental prototype results. [ABSTRACT FROM AUTHOR]

Thanks to the favorable advantage of low cost, integrated three-port dc–dc converters with reduced switches have attracted extensive attention. In order to provide more new topologies, this paper aims to propose a programmable topology derivation method, which effectively simplifies the cumbersome process of the conventional combination method. Instead of the manual connection and examination, the proposed alternative can quickly and rigorously derive multiple viable integrated three-port dc–dc topologies from a great number of possible connections with the aid of computer program. Besides, generalized analysis is also accomplished, with which performance characteristics of all derived converters are simultaneously obtained and then a comprehensive comparison can be easily conducted to select a preferred one for the practical application. Finally, an example-specific application with one input and two outputs is given, with topology selection, design, and experimental results demonstrated in detail. [ABSTRACT FROM AUTHOR]

The non-inverting buck boost (NIBB) converter has attracted significant attention in recent years, as it shares ground between input and output, and the voltage stress of switches is lower. In order to investigate the differences between NIBB and conventional buck boost converters, a comprehensive comparison and analysis of these two converters were conducted in terms of their operation principles, which includes multi-mode control strategy and dual-edge modulation here, and also the characteristics of switches and passive components in the two converters were analysed. The results show that NIBB is better than conventional buck boost circuit in these aspects of electrical stress, power loss, cost, passive component volume, and so on. Two prototypes for the two converters with 10 kW/20 kHz were designed and simulated, respectively, for verifying the results. Analytical and simulated results confirmed the conclusions. [ABSTRACT FROM AUTHOR]

Summary: This work proposes the conception of a nonisolated direct current (DC)‐DC buck‐boost converter employing the three‐state switching cell. Similarly to interleaving, it is possible to achieve higher power levels than that regarding the classical buck‐boost converter, but prominent advantages over the interleaved approach result, ie, the input current is continuous for duty ratios higher than 0.5; good current sharing is achieved without the need of special control schemes; and the active switches are connected to the same reference node as the input voltage source, as there is no need to use isolated drive circuitry. A thorough quantitative and qualitative analysis is carried for the entire range of the duty cycle D, considering that the proposed converter presents distinct behaviors for D < 0.5 and D > 0.5. An experimental prototype is developed and evaluated, while the results are discussed in detail. A direct current (DC) to direct current buck‐boost converter based on the three‐state switching cell is presented. The topology is adequate for high‐power, high‐current applications, with significant advantages if compared with similar approaches, eg, nonpulsating input current and good current sharing without the need of dedicated control techniques. [ABSTRACT FROM AUTHOR]

This paper presents a multiphysics analysis of thermally actuated RF MEMS switches for use in power limiter applications. RF MEMS switches can self-actuate when operating under high RF power levels. The level of power at which the switch actuates, can be varied by controlling the applied dc actuation voltage. MEMS switches are, therefore, proposed for use in power limiter applications. The objective of the multiphysics analysis presented in this paper is to combine thermal analysis, with mechanical analysis and RF analysis to derive a relationship between the RF power needed for self-actuation and the dc voltage applied to the thermal actuator. A thermally actuated MEMS switch is fabricated and tested. It is used as a test bed for demonstrating the proposed multiphysics analysis. The experimental results obtained for this switch confirm the approach used to construct a multiphysics analysis for thermally actuated MEMS switches. The results obtained also demonstrate that thermally actuated MEMS switches offer improved device sensitivity, when used in power limiter applications, in comparison with their counterparts electrostatically actuated MEMS switches. [2018-0106] [ABSTRACT FROM AUTHOR]

The aim of this study is to present a new cost effective topology for Symmetric multilevel inverters (SMLIs) configurations, which can generate a great number of output voltage levels with a least of switching devices. The proposed structure contains a novel switched-dc-source (SDCS) sub-module that can produce three positive output voltage levels with a contribution of four equal dc voltage sources, two unidirectional, and one bi-directional power switches. Accordingly, to create a uniform staircase output voltage with multiple levels, the proposed SDCS sub-module is integrated into a new design. Therefore, a new family of reduced switch-count (RSC)-SMLIs is derived, which is capable of generating at least 13- and 15-level output voltages using only ten power switches and nine gate drivers. Furthermore, when employing several of the proposed SDCS sub-modules in series, a new generalised RSC-SMLI topology is obtained. Comparisons with prior-art SMLIs structures are done, which also highlights the beneficial potential of the proposed topology. To demonstrate the superior performance of the proposed topology, several simulation and experimental results have been provided. [ABSTRACT FROM AUTHOR]

This studies a parallel current-fed resonant converter with the advantages of the balance current sharing and no input ripple current. The basic structure of the developed circuit includes a boost converter and half-bridge resonant converter with the same power switches to reduce switch counts. Two boost-type converters with an interleaved pulse with modulation are used in the front stage to eliminate input ripple current and reduce the size of boost inductor. Parallel resonant converter with magnetic coupling current balancing cell is adopted in the rear stage to automatically balance two resonant circuits and realise the zero-voltage turn-on switching for power devices. The voltage doubler circuit is employed on the secondary-side to achieve high-voltage output. The developed converter can be used for current-type input source and voltage-type output. Finally, experiments with 1 kW laboratory prototype are provided to confirm the feasibility of the proposed converter. [ABSTRACT FROM AUTHOR]

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

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

Z-source inverter has recently been introduced to overcome the limitations of conventional voltage source inverter. This paper deals with a novel topology of single-phase Z-source inverter (ZSI). This topology reduced the number of passive elements and active switches in order to make the inverter cheaper and smaller in size compared to traditional ZSI. Detailed analysis of the proposed topology is presented in this paper which includes calculations of boost factor, total harmonic disorder, magnitude of output voltage etc. Modulation technique used to control the switching of the proposed inverter is explained in detail. This paper also compares the proposed topology with conventional topologies of Z-source inverter. Simulation results of MATLAB and real-time simulators are shown to explain the working of the proposed topology. [ABSTRACT FROM AUTHOR]

In this paper, a high-voltage unipolar pulse power generator is introduced for electroporation applications. Operating principle of the proposed structure is based on the buck–boost (BB) converter. The generator is comprised of parallel modules connected to the converter through an SCR and is supplied by a low-voltage dc source. Each module consists of an insulated gate bipolar transistor (IGBT), two diodes, and a capacitor. In fact, the proposed topology is a combination of the Marx generator and BB (MG-BB) converter. In comparison with other modular MG-BB structures, the proposed topology achieves interesting advantages including simpler structure, reduction of IGBTs voltage rating, and reducing number of components (inductors and switches). In order to clarify the features of the proposed structure, it has been compared with other unipolar MGs considering different aspects including the number of circuit components, number of required input supplies, amplitude of the output pulse, and the maximum voltage across switches and diodes. To validate the effectiveness of the structure, simulation and experimental results are presented. The results confirm that the proposed topology is capable of generating unipolar pulses with desirable amplitude and repetition frequency using a low-voltage dc supply. [ABSTRACT FROM AUTHOR]

In this paper, performances on two kinds of aggregated flyback microinverters are compared in aspect of harmonic resonances, which are controlled by current feedback control and peak current control. Based on the Norton models of flyback microinverters obtained by a small-signal modeling approach, potential harmonic resonances with the grid are analyzed. Following that, an impedance-based stability criterion is proposed, where the resonance frequency can be calculated and predicted based on the derived Norton models and the system admittance matrix of aggregated microinverters. After comprehensive analysis and comparisons, it is found that the peak-current-control-based flyback microinverters has better performance on damping the harmonic resonances than the current feedback controlled one. Simulations and experiments are carried out for verifying the effectiveness of the presented models and the correctness of the analysis results. [ABSTRACT FROM AUTHOR]

For a current-fed dual-active-bridge bidirectional dc–dc converter, an extended duty cycle control is proposed. The low-voltage-side (LVS) bottom switch duty cycle can operate lower than 50%. The conduction loss of switches can be reduced by using low-voltage-ratingmosfets for the LVS. Meanwhile, a voltage mismatching control with adaptive clamp voltage regulation is proposed to achieve zero-voltage switching for all switches throughout full load range. Besides, for LVS dc inductors, a magnetic-integrated technique is used to reduce core loss, and power density can be improved by the use of only one core. The effectiveness of the proposed control is verified by the experimental results of a 1-kW laboratory prototype. [ABSTRACT FROM AUTHOR]

This paper proposes a Class-DEMtuned power amplifier. The proposed amplifier achieves zero-voltage switching (ZVS), zero-voltage derivative switching (ZVDS), and zero-current switching (ZCS) at turning-on, and ZVS, ZVDS, ZCS, and zero-current derivative switching at turning-off. Therefore, the switching losses are extremely low, which is suitable for high-frequency operation. Moreover, the switch voltage stress is low, which is no more than its input voltage. A proposed amplifier was designed, built, and tested. The measured power conversion efficiency was 93.2% under the condition of the main input voltage of 46.8 V, the operating frequency of 1 MHz, and the output power of 4.87 W. [ABSTRACT FROM AUTHOR]

The multilevel inverter (MLI) has ascertained its gravity in high-power applications for the past three decades through perennial topological modifications from the pristine structure and development of apposite modulation strategies. The benefits, including subtle switch voltage stress, reduced output voltage total harmonic distortion (THD), tolerable electromagnetic compatibility (EMC), minimal switching losses and d v / d t stress, have prepared it as a very promising candidate in high-power drives and electric utility applications. Meanwhile, MLI has few drawbacks such as higher number of switches with associated peripherals (gate driver circuits, protection circuits and heat sinks) which makes the overall system complex, bulky and costly. There have been many attempts to curb the component count in MLI structure. In this paper, a new topology is developed with a perspective to wane the switch count, which also has the ability of working in both symmetrical and asymmetrical modes. The performance of the proposed segmented ladder-structured MLI (SLSMLI) topology is substantiated with simulation study and experimentation. [ABSTRACT FROM AUTHOR]

Prefire is the unexpected breakdown of gas switch at triggered mode and have to be limited at extremely low level in fast linear transformer driver (FLTD). In this paper, the dispersion of breakdown voltage as well as prefire characteristics of high pressure gas spark switches under typical working conditions of FLTD was investigated and reported. Tested switches included a three-electrode field-distortion gas switch (TFGS) and a six-stage multichannel gas switch (SMGS), which had compact structure and low inductance. The results showed that the self-breakdown voltage of both TFGS and SMGS obeyed three parameter well-bull distribution and the dispersion of Ub at ±90 kV could reach 4% of TFGS and 14% of SMGS, respectively. The dispersion of Ub was remarkably influenced by the floating potential of middle electrode. By grounding the triggering electrode via a kilohm resistor, the dispersion of Ub decreased to 2% in TFGS and 6.5% in SMGS, respectively. When a voltage equalization method by cascade resistors was introduced, the dispersion of Ub in SMGS dramatically decreased to 4.4%. In repetitive operation at triggered mode, the prefire rate of TFGS reached 0.9% at $\gamma = 80{\%}$ working coefficient and decreases with the decrease of $\gamma $ , being 0.3% at $\gamma = 72{\%}$ and 0.2% at $\gamma = 65{\%}$ , respectively. The prefire rate of SMGS was much higher, reaching 1.7% at $\gamma = 72{\%}$ and 0.7% at $\gamma = 65{\%}$ , and decreased to 0.6% and 0.3%, respectively, after applying the equalizing resistors. Generally, the prefire rate of SMGS was somewhat higher than that of TFGS with the same working coefficient and the floating potential limiting was imperative for prefire inhibition. [ABSTRACT FROM AUTHOR]

Failure progression of metal oxide-based surge arresters in response to exposure to harmonics is modeled using the accelerated failure time model. Multistress accelerated ageing tests, with and without ac distorted voltage stress, are conducted on arrester samples sourced from different suppliers to obtain baseline and harmonic-factor logarithmic life and reliability functions. A maximum likelihood approach is taken to estimate the accelerated failure time model parameters based on the failure time data. The modeled harmonic-factor reliabilities prove metal oxide varistors life acceleration and show multiplicative failure progression of up to 41 times faster for a total harmonic distortion (THD) content of 8.52% in the applied voltage stress. [ABSTRACT FROM AUTHOR]

This letter proposes a switching controller (SC) for the grid-side converter (GSC) of doubly-fed induction generator-based wind turbines (DFIGWTs) to improve the disturbance rejection capability of the GSC based on bang–bang funnel control. A bang–bang funnel controller (BBFC) is designed and activated in the cases where the dc-link voltage of a DFIGWT is disturbed far away from its nominal value. A conventional vector controller (VC) is switchedonoperation when the tracking error of dc-link voltage converges within a prespecified error funnel. The BBFC and the VC constitute a SC. The disturbance rejection performance of the SC was tested through hardware-in-the-loop experiments. [ABSTRACT FROM AUTHOR]

Internal dielectric strength of vacuum interrupters (VIs) is primarily determined by the macroscopic electric field strength and effective area on the electrode surfaces. While internal dielectric strength is usually not an issue for medium-voltage VIs ($U_{m}$ ≤ 52 kV), it requires special consideration when going to higher voltage levels. Generally, the vacuum breakdown is initiated by field emissions from critical enhancement points with higher electric field on a cathode. The most critical point of the macroscopic electric field in a VI is present at the front contact edge between the main contacts. A vapor shield of a VI is one component that determines the electric field strength and distribution. Its floating electrical potential can basically be determined by the geometry of the VI and its surroundings. Since the shield potential can change the maximum electric field strength at the front contact edge in the VI, it seems possible to increase the internal dielectric strength of the VI by giving the vapor shield a well-defined electric potential. The present study focuses on the possibility of electrical potential control of the vapor shield for increasing the internal withstand voltage of the VI. Basically, the potential control of the vapor shield can be realized by connecting a parallel capacitor network. This allows controlling the shield potential arbitrarily between H.V. potential and zero by changing the voltage division ratio. From the field calculation results for a 72.5 kV VI model, the maximum electric field strength can be reduced by up to 23.3% compared to a floating vapor shield. Dielectric withstand tests for the 72.5 kV VI with potential control to determine the internal breakdown voltage with positive impulse voltage were carried out. The experimental results show that the breakdown voltage can be increased by 11.2%, by setting the vapor shield potential to one-third of the applied voltage. The increase in the breakdown voltage of the VI can be explained by the relaxation of the electric field on the critical point as a result of the decrease in the potential difference between cathode and vapor shield. [ABSTRACT FROM AUTHOR]

Controlled switching technology operates circuit breakers at the minimum arcing time for short-circuit current interruption. However, there is no report to reveal a relationship between the short-circuit current interrupting capability with the minimum arcing time and the opening velocities of vacuum interrupters. The objective of this paper is to reveal a relationship between the short-circuit current interrupting capability with the minimum arcing time and the opening velocities of vacuum interrupters. A 40.5-kV fast vacuum circuit breaker prototype was built up which was equipped with a commercial 40.5 kV–31.5 kA vacuum interrupter and it was driven by an electromagnetic repulsion mechanism. It provided an average velocities ranging from 2.5 to 5.5 m/s. A total of 50 times of 40-kA short-circuit current interrupting tests were carried out in a synthetic circuit. Test results showed that the minimum arcing time of successful interruption decreased with the increasing of the average opening velocity. The minimum arcing gap was determined as 1.8 mm and it kept as a constant as the average opening velocity increased. The experimental results also showed a relationship between the arc energy density and the arc extinguishing gap, which acted a linear boundary between the successful and failure short-current interruptions. [ABSTRACT FROM AUTHOR]

On transmission lines where switching surges are not mitigated with closing resistors and/or surge arresters, high-speed reclosing on a line with trapped charge will produce high overvoltages that have been measured above 3 p.u. Careful simulations of these switching events using available electromagnetic transient (EMT) programs consistently produce significantly higher voltages than the measurements. This indicates a phenomenon present on the line that acts to reduce the switching surge magnitudes but is not typically modeled. This paper aims to identify the required simulation practices in reproducing the field measured overvoltages in EMT simulations and investigates the sensitivity of results to modeling approaches and electrical parameters. Field measurements from a switching surge test of a 230-kV line without surge mitigation have been used for model comparisons. Variations in frequency-dependent line modeling, ground resistivity, skin effect, shunt conductance, parallel lines, and source-side detail have been tested in an unsuccessful attempt to decrease the difference between the field measurements and the higher simulation overvoltages. It is demonstrated that even though the pattern of the transient voltage waveforms can be reproduced very well using frequency-dependent line models, the magnitude of the maximum overvoltage is significantly overestimated unless the effect of corona is considered. Two types of corona models are tested, and both demonstrate that corona is the primary factor that allows the simulations to correctly reproduce high peak overvoltage measurements. [ABSTRACT FROM AUTHOR]

This study introduces a new single-phase Z-source T-type inverter (SPZT2I) with five-level voltage at the output. The proposed inverter allows the power switches in a phase leg conducting simultaneously without any problems. Moreover, the proposed inverter can produce the buck-boost output voltage with a single-stage power conversion. Two shoot-through control strategies are presented to create a five-level voltage at the output. Operating principles, theoretical analysis, and comparison of the proposed SPZT2I with the conventional five-level inverters are illustrated. Also, the simulation results using PSIM software are provided. Finally, a 400 W prototype is constructed to confirm properties of the proposed concepts. [ABSTRACT FROM AUTHOR]

A new 11-level inverter using a coupled inductor and a transformer is proposed. The proposed inverter increases maximum output voltage and decreases current stress on switches. A comprehensive comparison is conducted among the proposed inverter and some of the recent presented inverters in terms of number of components, maximum output voltage, and voltage and current stresses on the switches. Moreover, the design calculations of a single-phase inverter in addition to the transformer and coupled inductor design are given. In order to verify the performance of the proposed topologies, the experimental results are presented. [ABSTRACT FROM AUTHOR]

The high-power switch plays an important part in a pulse power system. With the trend of pulse power technology toward modularization, miniaturization, and accuracy control, higher requirements on electrical trigger and jitter of the switch have been put forward. A high-power low-jitter corona-stabilized triggered switch (CSTS) is designed in this paper. This kind of CSTS is based on corona stabilized mechanism, and it can be used as a main switch of an intense electron-beam accelerator (IEBA). Its main feature was the use of an annular trigger electrode instead of a traditional needle-like trigger electrode, taking main and side trigger rings to fix the discharging channels and using SF6/N2 gas mixture as its operation gas. In this paper, the strength of the local field enhancement was changed by a trigger electrode protrusion length Dp. The differences of self-breakdown voltage and its stability, delay time jitter, trigger requirements, and operation range of the switch were compared. Then the effect of different SF6/N2 mixture ratio on switch performance was explored. The experimental results show that when the SF6 is 15% with the pressure of 0.2 MPa, the hold-off voltage of the switch is 551 kV, the operating range is 46.4%–93.5% of the self-breakdown voltage, the jitter is 0.57 ns, and the minimum trigger voltage requirement is 55.8% of the peak. At present, the CSTS has been successfully applied to an IEBA for long time operation. [ABSTRACT FROM AUTHOR]

This paper presents a new concept and approach for topology control and switching in distribution systems by extending the traditional circuit switching to laterals and single-phase loads. Voltage unbalance and other key performance indicators including voltage magnitudes, line loading, and energy losses are used to characterize and demonstrate the technical value of optimizing system topology on a per-phase basis in response to feeder conditions. The near-optimal per-phase topology control is defined as a series of hierarchical optimization problems. The proposed approach is applied to IEEE 13-bus and 123-bus test systems for demonstration, which included the impact of integrating electric vehicles (EVs) in the test circuit. It is concluded that the proposed approach can be effectively leveraged to improve voltage profiles with electric vehicles, the extent of which depends on the performance of the base case without EVs. [ABSTRACT FROM AUTHOR]

A multiperiod network reconfiguration to meet the requirement of hourly hosting capacity under a minimal required number of switching operations, taking into consideration the uncertainty of renewable generation, is formulated as a nonlinear, nondifferentiable integer optimization problem with nonlinear equality and inequality constraints. A four-stage solution methodology, including an assessment stage, a time-partitioning stage, an optimization stage, and an evaluation stage, is developed to solve the constrained large-scale nonlinear integer optimization problem. A fuzzy C-means clustering algorithm is applied to partition the time period to facilitate the design of a minimum-number switching solution. A hybrid particle swarm optimization algorithm is developed to find an optimal network topology for each partitioned time period. The IEEE 123-bus case and a 1001-node system, three-phase and unbalanced, are used to evaluate the proposed method with promising results. [ABSTRACT FROM AUTHOR]

The expected abolishment of SF6-gas in medium-voltage switchgear has prompted a search for replacements for the switch types that depend on SF6 to obtain the required capability, reliability, compactness, and cost. Ablation of polymers can enhance the arc-quenching capabilities in certain electrical switch designs. Several aspects, like electric arc plasma composition, gas flow, and wall stabilization, must play together to obtain successful interruption. In this paper, open and closed switch geometries and two nozzle materials [polypropylene (PP) and polytetrafluoroethylene (PTFE)] are studied in medium-voltage interruption experiments. Fundamental differences in the arc-quenching process for PP and PTFE are shown. In the case of PTFE, the current interruption performance depends on gas flow resulting from the pressure built up under the high-current period. In the case of PP, the gas flow plays a lesser role for the arc-quenching capability as the interruption capability is large even in an open design with no forced gas flow around current zero. Current chopping happens a few tens of microseconds before voltage zero crossing; thereafter, a remnant conductance in the contact gap is observed, lasting for up to several milliseconds. This can be explained by an arc-to-glow transition in the presence of hydrogen. [ABSTRACT FROM AUTHOR]

This letter presents an inductive power transfer system based on a new variable coil structure to achieve load-independent constant current (CC) and constant voltage (CV) outputs for charging electric bicycles (EBs), without involving complex control strategies. The new variable coil structure consists of three-layer coils, i.e., two bipolar coils and one unipolar coil, on the transmitter side and one unipolar coil on the receiver side. The compact and portable receiver with series compensation is installed in the EB, while two switches on the transmitter side at the power charging station are utilized to reconfigure the transmitter coil structure to select the charging mode, i.e., CC mode or CV mode. The proposed system can achieve zero phase angle operation, fixed operating frequency, and zero-voltage switching, which will lower the power rating of power switches and improve the efficiency. A laboratory prototype is built to verify the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

Inductive power transfer (IPT) for battery charging applications has significant advantages over the traditional plug-in system. Since misalignment between the primary and secondary windings is inevitable, it is of significance to improve the misalignment tolerance of IPT systems with constant-current (CC) and constant-voltage (CV) outputs for battery charging. In this paper, the load-independent output characteristic of the hybrid topology and the function switching between CC and CV of the reconfigurable topology are analyzed. Besides, a hybrid and reconfigurable IPT system with 3-D misalignment tolerance for CC and CV outputs is proposed, simplifying or even canceling control schemes. Moreover, a novel parametric design method is given for the IPT system, which can suppress the fluctuation of the output voltage/current within a certain range of misalignment. In order to validate the performance of the proposed topology, a 1-kW prototype is built, and the corresponding experiments are carried out. In the CC/CV mode, the system can operate with the longitudinal misalignment to 50% when the load varies from 36 to 480 Ω, and the fluctuation of the output current/voltage is within 5%. Similarly, the misalignment in Y- and Z-axis is 12.5% and 33.3%, respectively. [ABSTRACT FROM AUTHOR]

This letter presents a single-phase cascaded transformer based multilevel inverter with a modified carrier-based level shift sinusoidal pulse width modulation (LS-SPWM) technique. The developed topology has two bridges with individual low frequency transformers. The bridges can generate quasi-square waveform and pulse width modulated waveform independently and energized the two transformers whose secondary terminals are cascaded to attain 19-level output voltage waveform across the load. The anticipated configuration has the least number of components to reduce the cost and enhance the reliability of the converter for medium power applications with inbuilt isolation. Furthermore, this letter presents the most common LS-SPWM technique with a new carrier to enhance the fundamental magnitude and shifts the dominant harmonics into three times of the traditional strategy for the same modulation indices. The performance of the proposed topology is validated with experimental results. [ABSTRACT FROM AUTHOR]

The five-level modular neutral-point-clamped (5L-MNPC) converter is realized by connecting two three-level neutral-point-clamped modules in series. For five-level operation, each dc-bus capacitor voltage of the modular neutral-point-clamped topology should be regulated at one-fourth of the net dc-bus voltage. In this letter, a simple voltage-balancing approach based on the carrier-based modulation scheme is proposed to achieve the above objectives. The proposed approach uses the redundancy switching states along with the current direction and the instantaneous value of the dc-bus capacitor voltage to achieve the voltage balancing in the 5L-MNPC topology. The dynamic performance of the 5L-MNPC topology with the proposed voltage-balancing approach is verified experimentally. [ABSTRACT FROM AUTHOR]

A two-stage switched-capacitor based multilevel inverter possesses a drawback such that switches in the second stage (i.e., H-bridge) endure higher voltage stress. To resolve this problem, this letter proposes a single-stage switched-capacitor module (S3CM) topology for cascaded multilevel inverter, which ensures the peak inverse voltage across all the switches within the dc source voltage. A total of nine voltage levels can be generated with only one dc source and two incorporated capacitors. Hence, the number of isolated dc sources is significantly reduced compared to a cascaded H-bridge. In addition, voltage boosting gain of two is achieved. A comparative analysis of the recent topology reveals that the proposed S3CM topology achieves switch count reduction. The operation of the proposed topology is validated through circuit analysis followed by simulation and experimental results of a single-module (9-level) prototype. [ABSTRACT FROM AUTHOR]

Detection and analysis of series arc in low-voltage switchboards have significant meaning for preventing the electrical fires. However, the conventional current and voltage methods have low a sensitivity to sense the minute arc discharge, leading to the fail operation of arc fault circuit interrupter. Therefore, this paper dealt with the application of non-conventional methods, including the ultra-violet (UV), acoustic emission (AE), and transient earth voltage (TEV) sensor in arc detection, for the purpose of improving the detection sensitivity and reducing the potential electric fires. Three types of typical arc faults in low-voltage switchboards were simulated and the actual detection environment was configured. From the results, the wavelength of UV light emitted from arc was 200-400 nm and the arc-induced AE signal had a frequency range of 40-600 kHz. The TEV signals generated from three types of arc faults presented different frequency spectrums, based on which the time-frequency map was used to classify the fault type. [ABSTRACT FROM AUTHOR]

This paper proposes a new single-phase single-stage switched-boost inverter with four switches. Like the quasi-Z-source inverter and quasi-switched boost inverter (qSBI), the proposed inverter has the main features as continuous input current, buck/boost voltage with single-stage conversion, and shoot-through immunity. Compared to the qSBI, the proposed inverter uses one more capacitor and one less switch. This paper presents the operating principles, pulse-width modulation control strategy, parameter design guidelines, and simulation results for the proposed inverter. To verify the performance of the proposed inverter, an 800-W prototype was built with an 110 V/50 Hz output voltage in stand-alone and grid-connected modes. The simulation and experimental results matched those of the theoretical analysis. [ABSTRACT FROM AUTHOR]

This article presents a model to simulate disconnecting switches in transient studies. The distance between contacts of a disconnecting switch does not change instantaneously; it takes several seconds to complete the full movement from closed to open, or vice-versa. The disconnecting switches are able to operate with lower current amplitudes, so a disconnecting switch is operated only when the circuit breaker is in open position. However, even with the circuit breaker open, there is a current flowing through the grading capacitors. The grading capacitors in conjunction with the busbar capacitance form a capacitive divider, and there is a floating voltage in the busbar. When the contacts of the disconnecting switch move, the withstand voltage varies and an electric arc appears. This arc is unstable and is interrupted and reignited several times. Each arc reignition causes a sudden voltage change that propagates through the busbar and impacts any connected equipment. The developed model, with the withstand voltage variation and the electric arc behaviour taken into account, calculates the fast transient overvoltages originated during a disconnecting switch operation. The amplitude and waveform of these overvoltages may then be used to evaluate the impact on insulation ageing. [ABSTRACT FROM AUTHOR]

This paper deals with implementation of a single-phase three level converter system under low voltage condition. The frequency of the switches is made constant and involves change in ${t_{on}}$ t o n and ${t_{off}}$ t o f f duration. For this condition the pulse width modulation control scheme for a single phase three level rectifier is developed to improve the power quality. The hysteresis current control technique is adopted to bring forth three-level PWM on the dc side of the bridge rectifier and to achieve high power factor and low harmonic distortion. Based on the proposed control scheme, the line current is driven to follow the sinusoidal current command which is in phase with the supply voltage. By using three-level voltage pattern the blocking voltage of each power device is clamped to half of the dc link voltage. The simulation and experimental results of 20W converter under low input voltage condition are shown to verify the circuit performance. Open loop simulation and hardware tests are implemented by applying a low voltage of 15 V(rms) on the input side. [ABSTRACT FROM AUTHOR]

In this paper, the remedial operation of switch faults will be investigated comprehensively for T-type-three-level-inverter-fed dual three-phase motor drives. The open-circuit switch faults in multiple phase legs are discussed at first. The faulty conditions are classified into five categories. Different remedial strategies, namely Type-I to Type-V schemes, are proposed for different faulty conditions. In particular, three kinds of Type-III fault-tolerant control schemes are proposed by using medium-voltage vectors to synthesize small-voltage vectors, in such a way that the mid-point voltage in a dc link can be stabilized well. Then, the short-circuit faults in both clamping switches and half-bridge switches are investigated. By analysis, their operation conditions are equivalent to conditions loss of both P and N voltage levels and open-phase faults, respectively. Thus, the corresponding remedial strategies can be applied accordingly. Particularly, a voltage compensation control method is proposed for conditions, where open-switch faults coexist with open-phase operation induced by short-circuit faults in half-bridge switches. The validity of all of theoretical analysis and the proposed remedial strategies has been verified by experiments. [ABSTRACT FROM PUBLISHER]

The alternate arm converter (AAC) is an emerging fault-tolerant multilevel converter topology from the same family of multilevel converters as the modular multilevel converter (MMC). Due to the alternate operation of the converter arms, energy balancing in the AAC is not continuous, but restricted to small time intervals. This paper develops a gradient-based current control and energy-balancing method for the AAC. The proposed strategy enforces the dynamic limits on the redundant submodules (SMs) during the overlap period and allocates effectively the maximum available number of redundant SMs to control the circulating current. The choice of the gradient as the circulating current control parameter improves the energy regulation capability of the AAC, and the enforcement of dynamic limitations avoids distortions of the output voltage. Results from an AAC-based HVDC converter model derived from the CIGRE benchmark MMC system demonstrate that the proposed strategy delivers improved energy control and balancing with good harmonic performance compared to existing current control methods for the AAC while also maintaining zero-current switching of the director switches of the AAC arms. [ABSTRACT FROM AUTHOR]

Power losses in a distribution system are commonly minimised via optimal network reconfiguration (NR). Previously, research on NR was focused on planning, where the final configuration reporting the lowest power losses being the main goal. However, power losses during switching operations from the original state to the optimal state of configuration were not considered. This study discusses the optimal switching path for minimising power losses when reconfiguring a network. The simultaneous optimal NR and distributed generation (DG) output was also proposed. The proposed methodology involves: (i) optimal NR and DG output simultaneously and (ii) optimal switching path to convert the network from the initial configuration to the final configuration obtained from (i). The selected optimisation technique in this study is the firefly algorithm. The proposed method was tested using IEEE 33-bus, 69-bus, and 118-bus radial distribution networks, while also accounting for static and dynamic loads. The results confirmed the effectiveness of the proposed method in determining the optimal path of switching operations, as well as the optimal network configuration and optimal output of DG units. [ABSTRACT FROM AUTHOR]

Nowadays, low power factor (PF) is a serious problem that has gained more importance in power electronics area. In this study, a unity PF control (UPC) strategy for boundary conduction mode (BCM) buck-buck/boost PF correction converter is proposed. The proposed control strategy can achieve high PF and low total harmonic distortion by utilising the input and output voltages to modulate the on-time of both buck and buck/boost switches. The operating principles and comparative analysis of BCM buck-buck/boost converter with conventional non-UPC and UPC are analysed. For verifying the effectiveness of the proposed control strategy, the experimental verifications are carried out from a 100 W universal input prototype. [ABSTRACT FROM AUTHOR]

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

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

A novel active controlled primary current cutting-off zero-voltage and zero-current switching (ZVZCS) PWM three-level dc-dc converter (TLC) is proposed in this paper. The proposed converter has some attractive advantages. The OFF voltage on the primary switches is only Vin/2 due to the series connected structure. The leading-leg switches can obtain zero-voltage switching (ZVS), and the lagging-leg switches can achieve zero-current switching (ZCS) in a wide load range. Two MOSFETs, referred to as cutting-off MOSFETs, with an ultra-low on-state resistance are used as active controlled primary current cutting-off components, and the added conduction loss can be neglected. The added MOSFETs are switched ON and OFF with ZCS that is irrelevant to the load current. Thus, the auxiliary switching loss can be significantly minimized. In addition, these MOSFETs are not series connected in the circuit loop of the dc input bus bar and the primary switches, which results in a low parasitic inductance. The operation principle and some relevant analyses are provided, and a 6-kW laboratory prototype is built to verify the proposed converter. [ABSTRACT FROM AUTHOR]

In this paper, a single-phase multilevel ac/ac converter with reduced number of power semiconductor devices is proposed. For the simple case of a three-level converter, only three bidirectional switches and two capacitors are required. The proposed converter provides a highly sinusoidal and regulated output voltage with a simple topology. The efficiency is high because in each state of operation only one semiconductor conducts. The converter can be easily extended to any desired levels in the output voltage to even more reduce the output total harmonics distortion. Another advantage of the proposed converter is that by increasing the voltage levels, the stress on the switches will decrease. The proper performance of the proposed converter is confirmed through extensive simulation and experimental tests. [ABSTRACT FROM PUBLISHER]

This paper presents design and simulation of uniform structured RF MEMS capacitive shunt switch using FEM tool and HFSS software. The switches with different shaped meanders and perforations which result in less spring constant, less pull-in voltage, high isolation loss, high switching speed and low insertion loss have been designed. From the simulated results it is observed that the rectangular perforations gives the better results, when compared with square and cylindrical shaped perforations. Comparative study is done for zigzag, plus and three square shaped meander along with rectangular perforations on each structure. When the gap between the dielectric and the movable beam is 0.8 µm, the up state capacitance for HfO2 is 4.06fF and for Si3N4 is 3.80fF. The downstate capacitance for HfO2, Si3N4 is 49fF, 26.9fF respectively. The capacitance ratio is 120.6. Poly-tetra-fluoro-ethylene material is given for the movable beam whose young’s modulus is 0.4 GPa and the spring constant is calculated theoretically for each structure; by using this the pull in voltage and the settling time are calculated. Step switch with three square Meander has switching time 10.25 µs, pull in voltage as 2.45 V. By using HFSS 3-D electromagnetic model we observed the return loss (S11) is less than −60 dB, the insertion loss is less than −0.07 dB in the range of 1–40 GHz frequency and switch isolation (S21) is −61 dB at 28 GHz frequency. [ABSTRACT FROM AUTHOR]