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In this paper, a single‐phase AC‐AC converter with continuous input current and without commutation problem is proposed. The output voltage regulation achieved using a single high‐frequency switch eliminates the need for complementary switches, thereby resolving high‐frequency commutation issues and obviating the necessity for snubber circuits and a safe commutation strategy. The proposed converter operates with a continuous input current, eliminating the need for a bulky LC filter. Low‐frequency switches on the output side allow for step‐changed frequency operation without encountering commutation problems. A straightforward and adaptable switching strategy generates the step‐changed frequency at the output. The proposed converter reduces volume, weight, and cost by minimizing the total stored energy of passive components. High‐speed switching is achieved by preventing the body diode conduction of power MOSFETs, which traditionally suffer from poor reverse recovery. The operational principles of the proposed converter are delineated for various modes, and their key relationships are presented. A 110Vi(rms)/50 Hz laboratory prototype validates the performance of the proposed converter. [ABSTRACT FROM AUTHOR]

Ultrawide bandgap heterojunction p–n diodes with polarization-induced AlGaN p-type layers are demonstrated using plasma-assisted molecular beam epitaxy on bulk AlN substrates. Current–voltage characteristics show a turn-on voltage of V bi ≈ 5.5 V, a minimum room temperature ideality factor of η ≈ 1.63 , and more than 12 orders of current modulation at room temperature. A stable current operation of the ultrawide bandgap semiconductor diode is measured up to a temperature of 300 °C. The one-sided n+–p heterojunction diode design enables a direct measurement of the spatial distribution of polarization-induced mobile hole density in the graded AlGaN layer from the capacitance–voltage profile. The measured average mobile hole density is p ∼ 5.7 × 10 17 cm−3, in close agreement with what is theoretically expected from distributed polarization doping. Light emission peaked at 260 nm (4.78 eV) observed in electroluminescence corresponds to interband radiative recombination in the n+ AlGaN layer. A much weaker deep-level emission band observed at 3.4 eV is attributed to cation-vacancy and silicon complexes in the heavily Si-doped AlGaN layer. These results demonstrate that distributed polarization doping enables ultrawide bandgap semiconductor heterojunction p–n diodes that have wide applications ranging from power electronics to deep-ultraviolet photonics. These devices can operate at high temperatures and in harsh environments. [ABSTRACT FROM AUTHOR]

Commutation failure is one of the most important factors threatening the safety of multi-infeed high voltage direct current systems. To mitigate commutation failure, we have proposed a novel hybrid line-commutated converter by adding fully controlled devices to the conventional line-commutated converter. It aims to achieve auxiliary commutation and forced commutation with the help of fully controlled devices. Based on the novel hybrid line-commutated converter topology, the study investigates how to select suitable fully controlled devices and how to design the appropriate parameters of the devices. First, this article studied the general characteristics of reverse-blocking devices, including reverse-blocking integrated gate-commutated thyristor (RB-IGCT) and asymmetrical IGCT with diode (including fast recovery diode and standard recovery diode). Then, the novel commutation principle is carefully proposed and analyzed. The comprehensive simulation results and comparison study of the novel commutation principle are conducted. Then, according to the proposed commutation principle, the voltage and current working stress of devices are illustrated. According to these, vital features of devices, including recovery speed, on-state voltage, current conduction ability, surge current, maximum turn-off current, robustness, and volume of devices, are carefully analyzed and compared. Related experiments are conducted to present the vital characteristics of devices in the equivalent operating conditions in converters. Finally, the advantages and disadvantages of RB-IGCT and IGCT with fast recovery diode and standard recovery diode are comprehensively presented, which offers valuable reference considered in engineering applications. [ABSTRACT FROM AUTHOR]

It has been widely accepted to apply dc circuit breakers (DCCBs) to protect dc grids. Nevertheless, existing DCCBs have one or more following limitations: insulation recovery scheme of mechanical switch, additional precharge power supply, high conduction loss, unreliable current-breaking process, and unidirectional design. In this letter, a new DCCB with low conduction loss, simple precharging scheme, and reliable breaking ability is proposed. The proposed DCCB could break both fault and operating current actively with the same simple operation sequences. Moreover, bidirectional topology possessing all advantages mentioned previously is also presented. Topology introduction, parameters designing, and scaled-down experiment of the proposed DCCB are all presented in the letter. [ABSTRACT FROM AUTHOR]

In a hard switched mosfet based converter, turn-on energy losses is predominant in the total switching loss. At higher junction temperature the turn-on energy loss further increases due to the reverse recovery effect of the complementary mosfets body diode in a half-bridge configuration. Estimation of the switching loss under different operating conditions at an early design stage is essential for optimizing the thermal design. Analytical switching loss models available in literature are generally used for estimating the switching losses due to its accuracy and simplicity. In this article, the inaccuracy in the reported loss models due to non-inclusion of temperature-dependent reverse recovery characteristics of body diode, is investigated. A structured method to determine the temperature-dependent switching loss of a SiC mosfet in a half-bridge is presented. A simple methodology has been proposed to analyze the carrier lifetime's temperature dependencies of a SiC mosfets body diode. Device parameters from a $\text{1.2}\,\text{kV}/36\,\text{A}$ SiC mosfets datasheet are used for developing the loss model and experimental validation of the model. [ABSTRACT FROM AUTHOR]

In this letter, a high-power step-up dc/dc converter dedicated to dc offshore wind farms is proposed, with the combination of half-bridge submodules, thyristors, diodes, and transformer. Compared with the other promising dc/dc topologies, the device numbers, costs, losses, and energy storage requirement are greatly reduced. The operation principle is introduced. The effectiveness and validity are confirmed by simulation and experimental results. [ABSTRACT FROM AUTHOR]

Processing of electrical power at megawatt to gigawatt level in the industry, traction, and transmission and distribution requires high‐power devices with a blocking capability up to 10 kV. The mainstream ones require high‐purity silicon wafers with the lowest possible defect content (contamination) and maximal homogeneity of resistivity and thickness. To satisfy current ratings in a typical range of 1–6 kA, single diode or thyristor may occupy nearly the whole 100–150 mm silicon wafer. In addition to the doping profile optimization and gettering in the front‐end processes, the devices are subject to defect engineering to adjust uniformly or locally the recombination lifetime of carriers. In insulated gate bipolar transistors (IGBTs), it is also about dopant activation below 500 °C. Satisfaction of all extremal demands laid on those devices is not possible without the knowledge developed by defect engineering community in the past decades. Some relevant industrial examples of screening the contamination in typical production of silicon high‐power devices are demonstrated as well as the advanced defect engineering methods for increasing device functionality and power density. [ABSTRACT FROM AUTHOR]

This article puts forward a high repetition rate and high-voltage resonant pulse generator for plasma-assisted milling. This circuit uses only one semiconductor switch with an antiparallel diode and works in the resonant mode with the help of a resonant inductor, a resonant capacitor, and a pulse transformer to generate high-voltage pulses. An equivalent circuit of the proposed topology considering parasitic elements is established. Based on the equivalent circuit, the working principle of the pulse generator is analyzed in detail. In order to verify the theoretical analysis and circuit operation, a laboratory prototype with a 150-V dc input is implemented. The pulse repetition rate can be adjusted from 5.32 to 18.90 kHz, and the peak output voltage correspondingly varies between 8.84 and 11.7 kV. The pulse generator is used to drive a dielectric barrier discharge plasma-assisted milling chamber. Experimental results show that the pulse generator can work stably. [ABSTRACT FROM AUTHOR]

Recently, switched inductor (SI) and switched capacitor techniques in dc–dc converter are recommended to achieve high voltage by using the principle of parallel charging and series discharging of reactive elements. It is noteworthy that four diodes, one high-voltage rating switch, and two inductors are required to design classical SI boost converter (SIBC). Moreover, in classical SIBC, the switch voltage stress is equal to the output voltage. In this article, modified SIBC (mSIBC) is proposed with reduced voltage stress across active switches. The proposed mSIBC configuration in this article is transformerless and simply derived by replacing the one diode of the classical SI structure with an active switch. As a result, mSIBC required low-voltage rating active switches, since the total output voltage is shared into two active switches. Moreover, the proposed mSIBC is low in cost, provides higher efficiency, and requires the same number of components compared with the classical SIBC. The continuous conduction mode and discontinuous conduction mode analysis, the effect of nonidealities on voltage gain, design methodology, and comparison are presented in detail. The operation and performance of the designed 500-W mSIBC are experimentally validated under different perturbations. [ABSTRACT FROM AUTHOR]

Monolayer MoS2 crystals investigated in this work were grown via chemical vapor deposition on Si/SiO2 substrates. Using a wet KOH etch, these crystals were transferred onto the edge of a freshly cleaved p-Si/SiO2 wafer where they formed mechanically robust heterojunctions at the p-Si/MoS2 interface. Electrical characterization of the device across the junction yielded an asymmetric I–V response similar to that of a p-n diode. The I–V response was electrostatically tunable via an ionic liquid gel gate. This is the first report demonstrating reversible gate control of the p-Si/MoS2 diode current by several orders of magnitude while lowering its turn-on voltage. Fermi energy level shifts within the MoS2 bandgap by the gate was believed to be responsible for the observed effects. The ease of fabrication, low operating voltages (<±2 V), and moderately high throughput currents (∼1 µA) are attractive features of this diode, especially for use in sensors and power saving electronics. [ABSTRACT FROM AUTHOR]

In recent years, significant progress has been made in HVdc transmission, particularly the voltage-source-converter technology using modular multilevel converters. There is increasing demand to develop high-power dc/dc converters to interconnect HVdc systems with different voltage levels. In this paper, a novel hybrid dc/dc converter topology is proposed by the combination of a new three-switch submodule (SM) circuit and series-connected thyristors and diodes. This topology presents less amount of semiconductors, very attractive capital costs, small footprint, and low power losses. Operating principles of this new three-switch SM and the dc/dc converter are explained, while the modulation and control schemes are also developed. The validity of the proposed topology is verified by simulation results based on a 150 MW, 200 kV/300 kV dc/dc converter. Efficiency estimates indicate that this topology could have power losses as low as 0.3% rated power. A scaled-down prototype has also been built and tested to confirm its effectiveness. [ABSTRACT FROM AUTHOR]

Recently, a parametric average-value model (PAVM) has been presented for diode rectifiers with internal faults, which considers their asymmetrical operation by including the ac-side harmonics in both positive and negative sequences. In this letter, the PAVM methodology is extended and generalized for thyristor-controlled rectifiers with faults. The presented PAVM considers the firing angle of thyristors in its formulation. Using extensive computer studies, the proposed PAVM is verified to reconstruct the detailed model results even under dynamics of thyristor firing angle control under faulty conditions, while providing faster and more efficient simulations compared with the detailed model. [ABSTRACT FROM AUTHOR]

The bi-mode gate commutated thyristor (GCT) is an advanced reverse conducting device aiming high-power applications. Due to the high degree of interdigitation of diode parts and GCT parts, it is necessary to investigate how to best separate the two and at the same time, how to maximize the individual power handling capability. This work underpins the latter, for the GCT part. In achieving that, this letter details the optimization direction, identifies the design parameters that influence the maximum controllable current (MCC), and thereafter introduces a new design attribute, the “p-zone.” This new design not only improves the MCC at high temperature but also at low temperature, yielding temperature independent current handling capability and at least 1000 A, or 23.5% of improvement compared to the state-of-the-art. As a result, the proposed design constitutes an enabler for optimally designed bi-mode devices rated at least 5000 A for applications with the highest power requirement. [ABSTRACT FROM AUTHOR]

An improved lateral double-diffused MOS silicon-controlled rectifier (ILDMOS-SCR) for high-voltage electrostatic discharge (ESD) protection applications has been proposed and verified in a 0.18 µm 5 V/24 V BCD process. The proposed improved lateral double-diffused MOS silicon-controlled rectifier (LDMOS-SCR) is constructed by adding a gated P-type/intrinsic/N-type (PIN) diode into a conventional LDMOS-SCR. With part of the ESD current discharges from the surface gated PIN diode path, the proposed ILDMOS-SCR achieves a high holding voltage of 30 V as well as a high failure current of 10.04 A, which is evaluated to pass 15 KV Human Body Model (HBM) ESD stress. [ABSTRACT FROM AUTHOR]

In this Letter, an effective method for estimation of turn-off power losses of power diodes using datasheet information is proposed. An effective regression method with non-linear least-squares algorithm is used to obtain approximate representations of the reverse-recovery charge and softness factor of the diode using datasheet information. Kalman Filter (KF) algorithm is then used to accurately acquire the value of diode forward current at the turn-off instant. Finally, the obtained information is used to estimate the turn-off power losses with simple calculations, based on approximated reverse-recovery equations. Despite the simplicity of the proposed technique, the results demonstrate that the estimation error does not exceed 4% in the worst case. [ABSTRACT FROM AUTHOR]

Possible heating methods of power semiconductor devices during their testing in a high-conductivity state are discussed. It is shown that the diffusion capacitance of the p-n junction has a significant effect on measurements of device parameters. The effect of the diffusion capacitance on the results of testing of power semiconductor devices at various shapes of heating-current pulses was investigated. Conclusions on the possibility of using current pulses of various shapes for testing power semiconductor devices in the highconductivity state are drawn. [ABSTRACT FROM AUTHOR]

A positive feedback (PF) mechanism was adopted for the first time in the cell string of a 3-D NAND flash memory where n+ and p+ regions are formed on both ends of the string to implement a diode-type cell string. The body consists of a tube-type poly-Si channel. To generate the PF in the channel during a read operation, a new read operation scheme is proposed. In this paper, the simulator was calibrated in terms of trap density ( D\mathrm {it}) of a poly-Si channel extracted from fabricated 3-D NAND flash memory cells. By utilizing the PF, a NAND flash memory cell in a cell string has a steep subthreshold swing of <1 mV/decade. [ABSTRACT FROM AUTHOR]

This letter proposes a harmonic mitigation strategy to cancel out current harmonics induced by the front-end rectifiers in multidrive systems, which consist of diode rectifiers, silicon-controlled rectifiers (SCR), and boost converters in the dc-link. The proposed strategy is a combination of a new dc-link modulation scheme with a phase-shifted current control enabled by the SCR. The dc-link current modulation scheme is implemented by adding and subtracting specific modulation levels, which makes the total currents drawn from the grid “multilevel,” resulting in an improved current quality. Simulations and experiments have validated the effectiveness of the proposed harmonic mitigation solution for multidrive systems. [ABSTRACT FROM PUBLISHER]

This study presents a new resistive capacitor switching transient limiter (RCSTL) for mitigating power capacitor switching transients. The RCSTL is composed of three limiting resistors, a three‐phase full bridge diode rectifier, a thyristor and a three‐phase coupling transformer. The limiting resistors are connected in series with the capacitor bank and the thyristor is installed at the DC side of the diode rectifier. During the capacitor bank energising, the thyristor remains off and hence, the secondary side of the coupling transformer acts as open circuit. Consequently, high impedance including the transformer's magnetic reactance in parallel with the limiting resistors is inserted in series with the capacitor bank. Under such circumstance, the limiting resistors restrain the capacitor switching transients. In the steady‐state, the control system triggers the thyristor and the coupling transformer acts as short circuit. As a result, the limiting resistors are bypassed by the coupling transformer and thus, the RCSTL has no significant effect on the circuit. Analytical analysis is performed to describe different operation modes of the proposed RCSTL. A single stage of a three‐phase wye‐connected capacitor bank with 25 kVAR is energised and the performance of the proposed limiter is investigated. Both the simulation and experimental results confirm the effectiveness of the RCSTL. [ABSTRACT FROM AUTHOR]

Light-emitting diode lighting system with the proposed pseudo-sine-current controller removes most of the external passive components, which include inductor, electrolytic capacitor, freewheel diode, blocking diode, and the bleeding circuit for Triac dimming control, for low cost and small volume. Delay-lock loop control can ensure the in-phase operation of ac input voltage and current for high power factor (PF) and low total harmonic distortion (THD). In addition, redundant power loss in Triac dimming control is eliminated to get a high efficiency of 85%. Furthermore, a high PF of 0.997 and a low THD of 7.74% are also achieved owing to in-phase line voltage and current. [ABSTRACT FROM AUTHOR]

An inductor-assisted silicon-controlled rectifier (LASCR) device is proposed to protect the gigahertz ICs in nanoscale CMOS technologies from electrostatic discharge (ESD) damages. The LASCR with the assistance of inductor can provide the bidirectional ESD current paths and fine-tune the high-frequency performances. Each LASCR test device has been implemented in a compact size of \sim 100\times 100~\mu \textm^2 . The LASCR test devices have been successfully verified in a silicon chip to achieve 4–7.5 kV human-body-model ESD robustness with 1–3-dB loss in $K/Ka$ -band (18–40 GHz). With the better performances, the proposed ESD protection device is very suitable for $K/Ka$ -band applications. [ABSTRACT FROM AUTHOR]

One of the most important power quality issues is related to current harmonics generated by nonlinear loads such as diode and thyristor front-end rectifiers. Well-established solutions to overcome this problem, such as active power filters (APFs), have the required high power rating components as a major disadvantage. An alternative, called hybrid power filter (HPF), mixes low power rating active filters with passive filters. Unfortunately, many of these HPF topologies have, as a common disadvantage, a great number of passive components and/or transformers. Based on this fact, new concepts of HPFs, consisting of small-rated inverters and $LC$ filters, have been introduced with wide acceptance. The advantage comes from the fact that these HPFs are connected to the grid without any matching transformer. Recently, some topologies based on dual-converter configurations have been shown to be very attractive, where the APF (or HPF) must deal with highly nonlinear loads with high values of $di/dt$ and supplying the reactive power together with harmonic compensation. On the other hand, the drawback of dual converters is the high number of switch devices. Therefore, this paper proposes a transformerless HPF based on a new six-switch two-leg inverter with an enhanced harmonic compensation capability. Aside from presenting a reduced number of switches when compared with dual topologies, the proposed solution is capable of providing fully compensation even for loads with high harmonic content. Experimental results are presented for an HPF inverter prototype in order to demonstrate that the harmonic compensation performance meets the IEEE 519 standard. [ABSTRACT FROM PUBLISHER]

The pin-to-pin electrostatic discharge (ESD) issue for a differential low-noise amplifier (LNA) was studied in this work. A new design of ESD protection diodes with an embedded silicon-controlled rectifier (SCR) was proposed to protect the gigahertz differential LNA. The proposed ESD protection design was modified from the conventional ESD protection design without adding any extra device. The SCR path was established directly from one differential input pad to the other differential input pad so the pin-to-pin ESD robustness can be improved. This design had been verified in a 65-nm CMOS process. Besides, this design had been further applied to a 24-GHz LNA in the same 65-nm CMOS process. Experimental results had shown that the proposed ESD protection design for the differential LNA can achieve excellent ESD robustness and good RF performances. [ABSTRACT FROM AUTHOR]

Wide bandgap semiconductors show superior material properties enabling potential power device operation at higher temperatures, voltages, and switching speeds than current Si technology. As a result, a new generation of power devices is being developed for power converter applications in which traditional Si power devices show limited operation. The use of these new power semiconductor devices will allow both an important improvement in the performance of existing power converters and the development of new power converters, accounting for an increase in the efficiency of the electric energy transformations and a more rational use of the electric energy. At present, SiC and GaN are the more promising semiconductor materials for these new power devices as a consequence of their outstanding properties, commercial availability of starting material, and maturity of their technological processes. This paper presents a review of recent progresses in the development of SiC- and GaN-based power semiconductor devices together with an overall view of the state of the art of this new device generation. [ABSTRACT FROM AUTHOR]

A new silicon controlled rectifier-based power-rail electrostatic discharge (ESD) clamp circuit was proposed with a novel trigger circuit that has very low leakage current in a small layout area for implementation. This circuit was successfully verified in a 40-nm CMOS process by using only low-voltage devices. The novel trigger circuit uses a diode-string based level-sensing ESD detection circuit, but not using MOS capacitor, which has very large leakage current. Moreover, the leakage current on the ESD detection circuit is further reduced, adding a diode in series with the trigger transistor. By combining these two techniques, the total silicon area of the power-rail ESD clamp circuit can be reduced three times, whereas the leakage current is three orders of magnitude smaller than that of the traditional design. [ABSTRACT FROM AUTHOR]

Abstract: The press-pack housing was initially available only in monolithic thyristors, diodes and GTOs for high power applications with strict reliability requirements. Due the technological developments of the last years, the IGBT became a common solution for power electronics converters including the higher power range. This trend and the positive experiences on the package created a demand for press-pack IGBTs. However, since the structure of the IGBT cannot be produced on a single wafer, the press pack housing was adopted for a multi die configuration resulting in a completely new structure. The electrical, thermal and mechanical behaviour of such a package is very sensitive to the applied clamping pressure. This paper discusses this dependency for different clamping devices and their resulting pressure distributions. [Copyright &y& Elsevier]

Variable voltage and frequency are required to govern the torque-speed characteristics of many industrial drive systems. Traditionally, this is achieved with a power converting system implemented with multistage converters. This technology is based on rectifying AC power into DC and then DC into AC with an inverter circuit. The power quality concerns of both conversion stages are tackled by selecting high switching frequency PWM control and harmonics mitigation filters. Also, using a bulky DC-link capacitor is one of the big sources of low system reliability, so this approach increases the conversion losses, circuit, and control complications. The frequency step-down conversion is very attractive with direct AC-AC converters as it has a simple control and circuit structure, but these converters face poor power quality challenges once the output frequency is decreased with respect to an input. In these converters, the total harmonic distortion (THD) of the output voltage becomes very poor once the output frequency is reduced. The problem of high THD of the output is addressed in the power converting circuits implemented with line frequency multi-winding transformers. The required number of output winding and switching devices (diodes and thyristors) increases once the value of the output frequency is decreased. This will increase the overall volume, cost, and losses. The use of a bulky and costly line frequency transformer may be eliminated if AC voltage controllers have non-inverted and inverted voltage buck capabilities, such existing topologies either have complex control schemes or require a large number of operating devices. Therefore, in this research article, a new transformerless frequency step-down converter employing fewer devices is proposed. This approach is realized with a high-frequency controlled rectifier for the required voltage stabilization and a low-frequency inverter bridge for frequency control. Its validation is supported by the results attained from Simulink and practical-based prototypes. [ABSTRACT FROM AUTHOR]

Developed synthetic test circuits for thyristor valves of flexible ac transmission systems (FACTS) are established in this paper. By controlling the thyristor valves of synthetic test circuits, it can reproduce test stresses, including, but not limited to, the forward high voltage before the thyristor valve withstanding overcurrent and reverse recovery voltage after thyristor valves withstanding overcurrent, on thyristor valves in FACTS equipment equal to or greater than those that appear in commercial projects. With corresponding test circuits and control strategies, the temperature-rise test, overcurrent test, and the synthetic test for thyristor valves can be performed, respectively. Then, a protection method of synthetic test circuits is presented. Finally, a temperature-rise test platform, overcurrent test platform, and synthetic test platform for thyristor valves have been set up, respectively. The test results show that the developed circuit and proposed control and protect strategies are available to test for thyristor valves used in FACTS. [ABSTRACT FROM PUBLISHER]

Electrostatic discharge (ESD) devices based on diodes and silicon controlled rectifier for RF I/O protection are evaluated on both ESD and RF performance. Varying from the architecture, layout design and metal interconnection, candidate devices show different parasitic capacitance, ESD efficiency, and turn on speed. Potential solution for further RF I/O application is verified. [ABSTRACT FROM PUBLISHER]

The power grid, especially distribution grid, has been more complicated due to distributed generations (DGs) with renewable energy sources and the smart grid. The complexity changes two things in terms of a fault; higher prospective fault current and the temporal variation of sources and loads. To correspond to those remarkable changes, we propose a fault current controller (FCC) named “smart FCC.” The smart FCC consists of a superconducting coil with a freewheeling diode if necessary, four thyristors, and a control unit. Smart FCC can not only limit but also control the current when a fault occurs. The smart grid technology can provide so enough information that it is possible to estimate which level of limited current should be the best in the real-time situation of the grid. Based on a real-time calculation of optimal fault current using the smart grid monitoring technologies, this new device is always ready to adjust the fault current. In this paper, we introduce a concept of the smart FCC and prove the concept. Various topologies have been proposed and simulated. Finally, a case study on a distribution class of 22.9 kV smart FCC has been conducted based on a conceptional system design. [ABSTRACT FROM AUTHOR]

A 450-kJ pulsed-power supply (PPS) for electromagnetic launcher has been built up. It consists of six 75-kJ pulse forming units (PFUs). Each PFU is composed of a 75-kJ capacitor (1000 \mu \F/12.2 kV), a thyristor stack as main switch, a diode stack as crowbar, a specific pulse-shaping inductor (15\ \mu\H/18\ \m\Omega), and a coaxial cable. The peak value of the output current of one PFU is 85 kA with a peak time of 190 \mu\s. The influencing factors of overvoltages on the series thyristor valves are studied by experiments and simulations based on PSCAD/EMTDC. A proper protection is used to prevent the series thyristor valves from being damaged by overvoltage when a switch is turned on. At the end, the total discharge currents of the PPS test with a short-circuit load and a railgun load are presented, respectively. [ABSTRACT FROM AUTHOR]

pulse magnetic-field generator producing pulse amplitudes up to 50 T with base durations of unities of milliseconds is described. The pulse magnetic field is obtained during discharging a capacitive storage through a thyristor-diode switch into a nitrogen-cooled solenoid. The repetition of the pulse amplitude of the current in the solenoid is ensured with an accuracy up to tenth of shares of a percent by stabilizing the precharge voltage of the storage and thermally stabling the solenoid. Using this generator, experiments for obtaining terahertz kilowatt-power radiation from 0.9- to 1.3-THz frequencies were successfully performed. [ABSTRACT FROM AUTHOR]

Diode and thyristor rectifiers are widely used in electric motor drive systems. These nonlinear loads produce current harmonics that reduce power quality by distorting the utility voltages. One possibility to improve the power quality is to compensate the harmonics with an active power filter. The active filtering functionality can also be integrated to active rectifying mode. In this study, the Vienna rectifier operating in combined rectifying and active filtering mode is studied The paper presents an adaptive space vector modulation method that improves the harmonic compensation capabilities of the space vector controlled Vienna rectifier. The theoretical analysis is verified with simulations and measurements from laboratory prototype feeding a 5-kW load. [ABSTRACT FROM AUTHOR]

This paper describes the parallel connection of 4.5 kV integrated gate commutated thyristors (IGCTs) and diodes. The impact of varying device characteristics on the stationary current distribution of parallel connected semiconductors is investigated. Possible solutions to improve the current sharing at steady state are presented. A thermal stabilization effect of parallel connected IGCTs is discussed. Furthermore, the behavior of parallel connected devices during switching transients is investigated experimentally in a 1.5.kV, 5-kA buck converter. Especially, the impact of asymmetrical circuit layouts, magnetic couplings, different turn-ON and turn-OFF delays, and junction temperatures are considered. It is shown that a substantial current derating is necessary to enable a reliable operation of parallel IGCTs and diodes. [ABSTRACT FROM AUTHOR]

A clamp circuit using nonlinear reactors is proposed for use with high-power inverters. For stable inverter operation under all typical operation conditions, the cores have self-resetting characteristics by the introduction of an air gap. The circuit configurations are investigated using a 6-kA/6-kV gate commutated thyristor (GCT) chopper. The results are compared to those of a traditional GCT clamp-snubber circuit using a linear anode reactor. New simulation models developed for the cores and diodes are tuned by the experimental results and applied to investigate two- and three-level circuits. Using self-resetting saturable reactors, low freewheel-diode reverse-recovery stress is achieved with a very high value of di/dt. The benefits of the new circuit also are demonstrated by mixed-mode device simulation. [ABSTRACT FROM AUTHOR]

This paper describes PSpice implementation of three power electronic devices: diode, thyristor, and triac, performed to identify characteristic curve parameters. Development of these simulation models is used to support and enhance power electronics education at the undergraduate level. The proposed tests have been successfully integrated into power electronics courses. [ABSTRACT FROM AUTHOR]

In variable-speed drives systems, diode rectifiers and thyristor rectifiers are often used as the front-end circuit for ac-dc conversion. The advantages of the conventional rectifier are its simplicity and high reliability. The drawbacks include the harmonic current distortion and the lack of re-generation capability. In recent years, industries adopt the transistor-based active front-end (AFE) technologies to accomplish high power factor operation and re-generation capability. However, the cost of AFE is much higher than the conventional diode/thyristor front-end. Besides, the AFE is often less reliable than the diode/thyristor front-end under utility transients. In this paper, an IGBT-based auxiliary converter (AXC) system is proposed. The AXC operates as a shunt active filter to compensate the harmonic current of the rectifier when the load consumes power. When the dc load regenerates, the AXC system can channel the re-generation energy back into the utility system. The combination of the diode rectifier and the AXC can accomplish unity power factor operation and re-generation, but it also causes circulating current between the AXC and the rectifier, which leads to higher operational losses and higher noise level. The mechanism of the circulating current is analyzed in this paper, and solutions are also presented. Computer simulation and field test results are presented to validate the performance of the proposed AXC system. [ABSTRACT FROM AUTHOR]

There has been a rapid improvement in SiC materials and power devices during the last few years. However, the materials community has overlooked some critical issues, which may threaten the emergence of SiC power devices in the coming years. Some of these pressing materials and processing issues will be presented in this paper. The first issue deals with the possibility of process-induced bulk traps in SiC immediately under the SiC/SiO2 interface, which may be involved in the reduction of effective inversion layer electron mobility in SiC metal-oxide-semiconductor field-effect transistor (MOSFETs). The second issue addresses the effect of recombination-induced stacking faults (SFs) in majority carrier devices such as MOSFETs, Schottky diodes, and junction field-effect transistors (JFETs). In the past it was assumed that the SFs only affect the bipolar devices such as PiN diodes and thyristors. However, most majority carrier devices have built-in p-n junction diodes, which can become forward biased during operation in a circuit. Thus, all high-voltage SiC devices are susceptible to this phenomenon. [ABSTRACT FROM AUTHOR]

This paper presents an innovative method for reducing current distortion on the ac side of six-pulse parallel-connected ac/dc rectifiers. The principle of the method is to modify the current waveforms on the dc side of the rectifier by using two self-commutated switches (insulated-gate bipolar transistors). It is demonstrated that accurate shaping of currents on the dc side achieves low distortion levels in currents IA, IB, and IC on the ac side. The effectiveness of the method is confirmed by laboratory recordings, which are related to steady-state and transient studies. [ABSTRACT FROM AUTHOR]

The results of numerical modeling of the stationary nonisothermal current-voltage ( I-U) characteristics of forward-biased high-voltage diodes and thyristors in the interval of current densities J ∼ 200–500 A/cm2 revealed an N-S transition in the shape of these curves and a hysteresis in the constant current source regimes. It is established that the mechanism of these phenomena is related to a temperature-induced decrease in the coefficient of ambipolar diffusion under the conditions of enhanced recombination. Devices with such I-U characteristics can be irreversibly switched by short current pulses from stable states on the working branch to the states with high heat evolution, which leads to a risk of thermal breakdown. [ABSTRACT FROM AUTHOR]

A new type of light-emitting diodes (LEDs), a high-efficiency device based on an n-GaSb/ p-GaSb/ n-GaInAsSb/ P-AlGaAsSb thyristor heterostructure, with the maximum emission intensity at wavelength λ = 1.95 μm, has been suggested and its electrical and luminescent characteristics have been studied. It is shown that the effective radiative recombination in the thyristor structure in the n-type GaInAsSb active region is provided by double-sided injection of holes from the neighboring p-type regions. The maximum internal quantum efficiency of 77% was achieved in the structure under study in the pulsed mode. The average optical power was as high as 2.5 mW, and the peak power in the pulsed mode was 71 mW, which exceeded by a factor of 2.9 the power obtained with a standard n-GaSb/ n-GaInAsSb/ P-AlGaAsSb LED operating in the same spectral range. The approach suggested will make it possible to improve LED parameters in the entire mid-IR spectral range (2–5 μm). [ABSTRACT FROM AUTHOR]

High-voltage 4H-SiC bipolar devices, including rectifier diodes, bipolar junction transistors, and thyristors are discussed. The results of experimental and theoretical studies of the steady-state and transient characteristics of these devices are presented. Specific features of device operation, related to the specific electronic properties of silicon carbide and SiC-based p–n structures, are analyzed. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

A new control algorithm for a three-phase three-wire series active power filter is proposed. With the proposed control algorithm, the series active power filter compensates for the harmonics and reactive power that are generated by non-linear loads, such as diodes or thyristor rectifiers. The proposed control algorithm is based on the generalised p-q theory. It may be applied to both harmonic voltage sources and harmonic current sources. In this algorithm, the compensation voltage references are extracted directly. Therefore, the calculation of the compensation voltage reference will be much simpler than for other control algorithms. In addition, the difficulty of finding the voltage reference gain disappears. The compensation principle of the proposed control algorithm is presented in detail. To verify the effectiveness of the proposed algorithm, a prototype of a three-phase three-wire series active power filter has been manufactured and some experiments carried out. [ABSTRACT FROM AUTHOR]

In power stations and substations of electric power companies, power semiconductor devices such as diodes and thyristors have been used in control power supplies and emergency power supplies since the 1970s. Such equipment is designed on the assumption that power semiconductor devices are semipermanent, since their service life is much longer than that of capacitors and resistors. Therefore, it is hard to find studies that have systematically examined the long-term reliability of semiconductor devices. Such studies are very important from the viewpoint of ensuring reliability and improving the renewal period by proper equipment maintenance. This paper discusses the long-term reliability of power semiconductor devices used in power station rectifiers and substation rectifiers. © 2001 Scripta Technica, Electr Eng Jpn, 136(3): 67–75, 2001 [ABSTRACT FROM AUTHOR]

Discusses a study which fabricated light-triggered eight-kilovolts thyristors with an integrated breakover diode. Design considerations for amplifying gate structure; Experimental details of the study; Determination of the doping profiles; Values for the minimum light power necessary to turn on the thyristor.

The paper presents the effects of source inductance and discontinuous conduction in the load on the commutation, and voltage ratings of thyristors, diodes and capacitors of some commonly used chopper circuits. [ABSTRACT FROM AUTHOR]

The article presents a new method for reducing harmonics of rectifier circuits by switching taps of interphase reactor. The tap-change circuit is very simple and the addition of it only slightly increases the site and cost of the circuit. Nevertheless, it reduces the harmonic content remarkably as shown in the article. The performances of the three-tap rectifier circuit are discussed in detail in this paper. The proposed scheme is applicable not only to the thyristor rectifier but also to the diode rectifier. In the future, it would be applied further to inverters and cycloconverters.

The diode-triggered silicon-controlled rectifier (DTSCR) is frequently used for low-voltage electrostatic discharge (ESD) protection applications, but such a device can exhibit two snapbacks and consequently can possess an undesirable large trigger voltage. This letter investigates the mechanism underlying the DTSCR's multiple triggering. An improved DTSCR for reducing the second trigger voltage and increasing the ESD safe margin is proposed and verified in a 65-nm complementary metal-oxide-semiconductor process. The improved DTSCR's turn-on characteristic is also discussed. [ABSTRACT FROM PUBLISHER]