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Superconductor–semiconductor hybrid circuits can combine the benefits of the high-speed and low-power operation of single-flux quantum circuits and high integration densities of CMOS technology such as memory. The Suzuki stack, a type of Josephson latching driver/amplifier, is a widely used interface circuit in Josephson–CMOS hybrid memories. Due to the limited cooling power at cryogenic temperatures, the power dissipation is becoming an important concern, especially in large-scale systems. An optimization technique to significantly reduce the power dissipation of Suzuki stack circuits is proposed in this article. The proposed design can reduce the power dissipation by 30–70% while causing a voltage drop of 2–9% in the output voltage depending on the circuit parameter configuration. The tradeoffs between the power dissipation and output voltage characteristics are discussed. The proposed design can operate correctly within at least $\pm$ 20% of process parameter variations as demonstrated with extensive simulations. [ABSTRACT FROM AUTHOR]

Piezoelectrically actuated fast mechanical switches provide a low-loss conduction path in hybrid circuit breakers for protecting medium-voltage direct-current systems. As the desired actuation speed approaches the driving limit of a piezoelectric actuator, excessive vibration starts to dominate its underdamped travel curves, resulting in insulation failures and delayed switching in the fast mechanical switch. To improve the underdamped travel curves into critically damped travel curves, several switching motion control schemes with active damping filters are proposed in this paper. The switching motion controllers are based on an electromechanical model of a fast mechanical switch with experimentally identified parameters. According to hardware implementation tests, the proposed closed-loop control schemes optimized the switch travel curves with a 56% reduction in the undershoot and a 75% reduction in the settling time. Equipped with the critically damped travel curves, the piezoelectrically actuated fast mechanical switch is better suited for sequential submodule operations to reduce the interruption time, the peak current and the fault energy to be absorbed in hybrid circuit breakers. [ABSTRACT FROM AUTHOR]

High-voltage direct current (HVDC) circuit breaker development and deployment strongly depend on the testing process, which ensures that the HVDC circuit breakers will satisfy design requirements. This article presents an HVDC circuit breaker test bench circuit configuration that can provide controllable large output currents to simulate different fault conditions for the current breaking test and high output voltage for the dielectric withstand test. The current breaking test circuit is based on multiple cascaded power converters connected in parallel to provide the necessary output current capability. Each cascaded power converter is composed of multiple cells that are operated by a phase-shifted pulsewidth-modulated signal for greater controllability and higher quality of the output waveform. The dielectric withstand test circuit is a simple high-voltage source with a low power rating that can also be used to charge the test bench and the internal circuitry of the circuit breaker that is to be tested. The proposed test bench ensures that fault conditions can be replicated accurately and offers greater flexibility by being able to test mechanical, semiconductor-based, or hybrid HVDC circuit breakers with different current and voltage ratings on the same hardware without any changes. The idea and the operating principle of the proposed test bench are verified experimentally on a downscaled system that consists of three cascaded power converters connected in parallel with three cells per cascaded power converter and with a total equivalent switching frequency of 92.5 kHz. [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]

Current-induced domain wall motion (CIDWM) shows promising prospects with low power, high density, high speed, and so on. Recent studies have demonstrated that magnetic tunnel junction (MTJ) based on CIDWM has great potential in mimicking a non-volatile artificial neuron and synapse. By combining the effect of the interfacial Dzyaloshinskii–Moriya interaction (DMI) to stabilize the Néel-type domain wall (DW) and the high-speed low-power advantages of spin orbit torque (SOT), the novel MTJ device is experimentally demonstrated with low threshold current and high propagation speed, which shows potential applications in the field of the artificial neuron and synapse. In this article, a compact model for CIDWM-MTJ based on SOT and DMI is presented. The model integrates the SOT mechanism for magnetization reversal and DW nucleation, CIDWM behaviors, and tunnel resistance theory of MTJ nanopillar. The micromagnetic simulation and the temporal evolution of the DW position are implemented by solving the Landau–Lifshitz–Gilbert (LLG) equation and the 1-D model. Based on the developed model, a hybrid CIDWM-MTJ/CMOS circuit is simulated for verification. The presented model combines the CIDWM dynamics and the MTJ magnetic dynamics, showing potential application for the simulation of all-spin artificial neural network (ANN). [ABSTRACT FROM AUTHOR]

This article aims to investigate the limitations on the amplitude of the conventional step recovery diode (SRD)-based Gaussian pulse transmitter and techniques to overcome the limits. The operation of the modified design is examined and compared with a conventional configuration. The results show a considerable increase in the pulse amplitude. The high pulse amplitude of the modified configuration represents an increase in the transmitter’s output power and its improved probing range. The Gaussian pulse is converted into the first derivative Gaussian pulse using a 90° broadband coupler as a differentiator and a semi-differentiator delay line circuit with balanced stubs. The output monopulse generated using the balanced stub delay line has more symmetric sidelobes with narrower pulsewidth than the 90° couplers. Experimental results have shown the high performance of the proposed transmitter over the conventional designs in terms of pulse amplitude and symmetry. [ABSTRACT FROM AUTHOR]

A new series-type hybrid circuit breaker (S-HCB) concept for dc fault protection is reported that is fundamentally different from other prior-art hybrid circuit breakers (HCB) or solid-state circuit breakers (SSCB) in the literature. The S-HCB conducts its load current through metal wires instead of power semiconductor switches and curtails its fault current to near zero throughout the entire opening process of a series mechanical switch. It offers the low on-resistance of the conventional mechanical contacts for normal operation and µs-scale fault response even faster than the fast-acting SSCBs. A proof-of-concept S-HCB prototype experimentally demonstrates the interruption of a fault current of 30 A within 10 μs at a dc voltage of 600 V. The operating principle, simulation, and experimental results are discussed in this letter. [ABSTRACT FROM AUTHOR]

The reliability of meshed DC grids mainly relies on their ability in DC fault protection and line power flow managing. Multiple DC circuit breakers (DCCB) and current flow controller (CFC) need to be installed, which significantly increases the system cost. A novel current flow controller integrated with hybrid dc circuit breaker (CFC-IHCB) is proposed to significantly reduce the loss and cost of the whole system. Only one unidirectional IGBT string based main breaker branch is needed for n lines, and the CFC function is integrated into the load communication switches (LCSs). The basic working principle of proposed topology is presented and analyzed. The functionality is verified and a comparison of the proposed solution and other DCCB/CFC solutions is given based on a multi-terminal HVDC system case study. [ABSTRACT FROM AUTHOR]

In this article, metal oxide varistor (MOV) design optimization and switching control in the main circuit breaker (MCB) branch of a progressively switched hybrid dc circuit breaker (DCCB) is presented. A progressively switched hybrid DCCB can achieve faster fault isolation with reduced peak fault current magnitude and transient recovery voltage compared with a regular hybrid DCCB due to its modified switching strategy. Consequently, thermal stress on the semiconductor devices in MCB is significantly reduced. Analytical model of the system dynamics during fault isolation with progressive switching is derived to demonstrate the switching scheme’s effect on the energy-absorbing component, MOV, during turn-off process. Derived analytical model in conjunction with the displacement curve of the fast mechanical switch of the hybrid DCCB is utilized to optimize the components of the main circuit breaker branch to reduce MOV degradation through asymmetric energy dissipation. A model of the circuit breaker is built in PSCAD to validate the performance of the proposed optimization method in a 10-kV/250-A system with four stage progressive switching. Additionally, a low voltage system model at 380 V is developed in PLECS for two stage progressive switching that works as the basis of experimental validation. This includes both lookup table-based MOV model and device thermal model for junction temperature estimation. Experimental results are provided for a 380-V system to demonstrate reduced fault current peak in a progressive switching and near uniform energy absorption in optimally selected MOVs. [ABSTRACT FROM AUTHOR]

The hybrid dc circuit breaker is one of the most promising dc circuit breakers (DCCBs). However, its cost is relatively high, and the completion of its fault isolation is significantly delayed because of the large current limiting inductors configured in the multiterminal dc grid. Besides, due to the utilization of overhead lines, the probability of temporary faults is much increased, which means there is a great possibility that the power supply can be rapidly restored by reclosing DCCBs. However, the temporary faults must be distinguished from the permanent faults before the reclosing operation to avoid damaging the fragile power electronic equipment. Therefore, considering the above issues, a novel multiport hybrid dc circuit breaker (MHCB) is proposed in this article. The MHCB mainly has three advantages: the reduced implementation cost by sharing the expensive main breaker among multiple lines, the reduced fault isolation time by bypassing the current limiting inductor during energy dissipation, and the ability to reclose softly. Extensive simulations and experiments verify the effectiveness of the device. In addition, the comparison of the new device and existed solutions is presented. [ABSTRACT FROM AUTHOR]

Long pulse gas lasers utilizing double-discharge circuits are different from the single-short pulse gas lasers in that they do not require all of the desired energy to be deposited into the peaking capacitors prior to ignition of the main gap. Instead, the majority of the energy is held in another capacitor that is then discharged in the form of a longer duration discharge pulse output compared with that of single-short pulse lasers. Extended stability of the discharge is typically achieved by igniting the main gap discharge at higher ignition voltages. Several double-discharge circuit topologies exist in the literature. However, each topology has its own disadvantages primarily centered around the components needed and the resulting complexity. In this article we introduce the application of the new hybrid circuit pulsed power topology as a double-discharge circuit with high ignition voltages. The hybrid circuit pulsed power topology was originally published by the authors of this article in their previous publication titled “A New Hybrid Pulsed Power Circuit Topology for Gas Laser Applications.” The advantage of the hybrid circuit as a double-discharge circuit is that it does not require any special device [e.g., semiconductor opening switch (SOS) diode] and can use commonly available components. [ABSTRACT FROM AUTHOR]

Nanoelectromechanical (NEM) switches offer the advantages of zero OFF-state leakage current, abrupt switching characteristics, nonvolatile (NV) operation, and relatively low ON-state resistance as compared with CMOS transistors predominantly used for digital computing today. NEM switches can be implemented using metallic interconnect layers formed in the back-end-of-line (BEOL) steps of a standard CMOS IC manufacturing process, in order to enable compact implementation of hybrid CMOS-NEM circuits. In this article, a release-etch method is developed for realizing BEOL NV-NEM switches with $\leq 100$ -nm contact gaps. A functional array of BEOL NV-NEM switches is used to implement a hybrid CMOS-NEM IC for data search applications. NV-NEM switch design optimization to minimize the programming voltage and accelerate switching speed is discussed. A scaled NV-NEM technology is projected to be advantageous for high-speed, low-power reconfigurable computing applications. This projection is validated with experimental data for a BEOL NV-NEM switch implemented with a conventional 16-nm CMOS IC manufacturing process. [ABSTRACT FROM AUTHOR]

Two key challenges in meshed multi-terminal dc (MTdc) grids are line power flow management and fault current interruption, which can be solved by current flow controllers (CFCs) and hybrid dc circuit breakers (HCBs), respectively. However, the power losses and the implementation costs of CFCs and HCBs are relatively high. In order to overcome these drawbacks, a combined HCB (CHCB) is proposed in this article by fully utilizing the core ideas of the interline dual H-bridge CFC and the HCB. The proposed device can substitute multiple HCBs at a dc bus with greatly reduced cost. In addition to the fault current interruption capability, the current flows in the adjacent lines can be controlled by the embedded multi-line CFC in the CHCB expanded from the existing interline dual H-bridge CFC. The system-level behavior of the proposed CHCB is similar to the separate solution of the typical HCB and the multi-line CFC. Extensive simulations and experiments verify the effectiveness of the proposed device. Besides, a comparison of the proposed CHCB and the separate solution is presented. [ABSTRACT FROM AUTHOR]

Medium voltage direct current (MVDC) power systems are in their early phase of development, but the lack of efficient and reliable DC circuit breakers is currently one of the most significant bottlenecks for widespread adoption of MVDC applications. Compared to protection devices in high voltage direct current (HVDC) systems, MVDC circuit breakers are expected to interrupt fault currents with higher rates of rise in more power-dense and more controllable structures. A hybrid approach with a piezoelectrically actuated fast mechanical switch in parallel to a solid-state circuit breaker is expected to meet the above requirements. A prototype of a 15 kV-class piezoelectrically actuated fast mechanical switch is presented in this paper. The prototype demonstrates an actuator opening time of 1 ms, a breakdown voltage of over 20 kV, and a continuous current rating of 500 A. After integrating the fast mechanical switch into a hybrid circuit breaker testbed, the fast mechanical switch was able to open within 1.5 ms and the fault was cleared within 5 ms. Therefore, piezoelectrically actuated fast mechanical switches can enable fast, reliable and controllable protection for various MVDC systems like electric ships, electric aircraft and microgrids that integrate distributed energy resources. [ABSTRACT FROM AUTHOR]

A mechanical switch can be used instead of a power electronic load commutation switch in orderto reduce the losses during normal power flow in standard hybrid DC circuit breakers. The success of current commutation in such hybrid breakers depends on the arc voltage formed across the contacts in the mechanical switch. The behaviour of rapidly elongated, wall constricted arcsgenerated during the opening of an ultra-fast mechanical switch in the air is studied here. The voltage-current characteristics of the generated arcs are obtained for steady state contact opening velocities of 6, 11 and 21 m/s. It is found that the arc voltage at a given current and contact separation increases with the contact opening velocity. It is shown that stationary,zero-contact-velocity characteristics can not be used to accurately quantify the voltage build-up in fast elongating arcs in hybrid breakers. A best-fitting black-box equation for the dynamic arc characteristics is presented for the tested velocities. The obtained voltage-current characteristics are used as input to simulate the current commutation process in a 12 kV hybridDC circuit breaker case-study. Different scenarios of current commutation failure related to the arc voltage build up are identified. It is shown that these failures scenarios can be avoided by increasing the contact opening velocity. [ABSTRACT FROM AUTHOR]

This article presented a new hybrid circuit breaker solution for using in dc microgrids. The proposed solution can offer a high-reliability protection feature for the dc microgrid with low conduction loss, bidirectional current flow, and galvanic isolation function. In the design, it is combined with a group of mechanical switches and semiconductors, where the mechanical switches handle the current conduction during normal operation and the semiconductors handle the breaker response during transient operation. The design fully utilizes the advantage of both types of switches and maximizes the performance and life time of the system. Throughout the design, it maintains only one mechanical switch in series with each power line; thereby, the high conductivity of the circuit breaker is maintained. At the same time, through the hybrid design, the electrical stress applied to the mechanical switch is eliminated. Thus, an effective and high-reliability solution is provided for the design of dc circuit breakers. The operation principle is explained in detail and the design guideline is provided. A 150/380 V and 15 A circuit breaker is successfully implemented, and the performance is experimentally verified, which shows good agreement with the theoretical findings. [ABSTRACT FROM AUTHOR]

Hybrid dc circuit breakers (HCBs) usually require a large number of insulated-gate bipolar transistors (IGBTs) with high turn-off capability for series and parallel connections. This requirement entails excessive cost. Compared with IGBTs, integrated gate-commutated thyristors (IGCTs) are another kind of fully controlled power device with high surge current and voltage capability but are low cost. However, the weak turn-off capability of IGCTs hinders their application to high-powered HCBs. On the basis of the complementary advantages of IGBTs and IGCTs, this paper proposes a mixture solid-state switch (MSS) for HCBs that uses the switching action of several IGBTs to create a low-current condition that favors the turning off of large-scale series-connected IGCTs. The MSS topology can significantly reduce cost while maintaining the excellent performance of traditional solid-state switches. This study also introduces two different turn-off modes for MSS, namely, single oscillation and multiple oscillations. Finally, 25 kV/20 kA prototypes in both modes are developed to verify the effectiveness of the MSS topology. [ABSTRACT FROM AUTHOR]

This paper examines two new bidirectional hybrid dc circuit breaker (CB) topologies for application in meshed dc grids. The goal is to retain performance of hybrid dc CB with bidirectional current interruption while reducing semiconductor count, dc CB size, and weight. The fault current is routed to the unidirectional internal valve using multiple additional ultrafast disconnectors. Operation of both topologies is studied using a 320-kV, 16-kA simulation model, as well as demonstrated on a 900-V, 500-A lab prototype. The control systems are presented and discussed in detail. The low-voltage hardware prototypes verify performance of several new technical and operating solutions in laboratory conditions. A comparison is made with the existing dc CB topologies and performance and reliability compromises of each topology are assessed. The conclusion is that it might be possible to halve the dc CB semiconductor count while retaining same 2 ms opening speed and bidirectional operation. [ABSTRACT FROM AUTHOR]

Adiabatic quantum-flux-parametron (AQFP) logic is a promising technology for future energy-efficient high-performance information processing systems. Its static power is zero because of ac flux bias, and its dynamic power is considerably reduced, thanks to the adiabatic switching of the junctions. The lack of high-density memories in the AQFP logic, however, makes it challenging to realize large-scale information processing systems with the use of pure AQFP circuits. We have been developing a Josephson-CMOS hybrid memory to overcome the memory bottleneck in AQFP digital systems. By utilizing the high sensitivity of the AQFP gate, the output current from CMOS memories can be significantly decreased resulting in the reduction of the power consumption. In this article, we designed and fabricated a low-power area-efficient AQFP-CMOS hybrid field-programmable gate array (FPGA), where a CMOS memory is utilized as a rewritable read-only memory to control the AQFP circuits. The AQFP circuit for the AQFP-CMOS hybrid FPGA is composed of logic blocks, switch blocks, and connection blocks, which are clocked by four-phase excitation currents. The AQFP-CMOS hybrid FPGA is fabricated by using the AIST 10 kA/cm2 Nb high-speed standard process and the Rohm 0.18 μm CMOS process. The area and power consumption of the two-by-two AQFP logic-cell system are estimated to be approximately 6.56 mm2 and 12.4 nW at 5 GHz operations, respectively. The power consumption of the CMOS memory was estimated to be 1.02 μW assuming the CMOS source voltage of 3 mV. We demonstrated the operation of the AQFP-CMOS hybrid FPGA at low speed by combining the AQFP logic and the CMOS memory. [ABSTRACT FROM AUTHOR]

The dc fault current has a high amplitude and a fast rising speed, therefore with regard to the hybrid dc circuit breaker, it is hard to meet the requirement of a high breaking capacity while maintaining economically efficient. The SI-SFCL can prevent the speed of the fault current from rising too fast, and ensure the current remains under the interrupting capability of the dc circuit breaker, so the couse of the SI-SFCL and the dc circuit breaker is an effective solution for fault clearing in dc grids. In this paper, the current-limiting requirement of the DCCB is given, and a simplified equivalent circuit of the active SI-SFCL is proposed, based on which the matching between the electrical parameters of the active SI-SFCL and the dc circuit breaker is studied. Parameter constraint and the protection voltage range of the active SI-SFCL are given. Finally, the conclusion on the matching between the electrical parameters of the active SI-SFCL and the DCCB is verified by MATLAB/Simulink. [ABSTRACT FROM AUTHOR]

This paper proposes an interleaved hybrid converter (IHC) with simultaneous dc and ac outputs for dc microgrid applications. The IHC is realized by interleaving two conventional boost converters and replacing the active switch of lower boost converter by an H-bridge voltage source inverter. This arrangement enables the proposed IHC to operate at the condition where the sum of duty ratio (\boldsymbolD ) and modulation index (\boldsymbolM ) can be more than or equal to one, i.e., \boldsymbolD + \boldsymbolM \geq 1, unlike the conventional hybrid converters. The proposed IHC is capable of giving dc with high voltage gain and improved ac with reduced harmonic distortion. Due to interleaving nature of the IHC, input current is shared between the power converters and thus enables the use of low current rated switching devices and lower values of inductors. This results in reduced power losses and increased efficiency as compared to the conventional hybrid converters. The IHC also has inherent shoot-through protection capability, better electromagnetic interference immunity, and reliability. A modified unipolar sinusoidal pulse width modulation technique is used to control the power flow of the IHC. Detailed mathematical modeling of the proposed IHC is carried out and its steady-state behavior is validated through experimental results on a 500 W laboratory prototype. [ABSTRACT FROM PUBLISHER]

An active damping method for Thomson coil actuated ultrafast mechanical switches is proposed, including its control. Ultrafast mechanical switches are crucial for both dc and ac circuit breakers that require fast-acting current-limiting capabilities. However, fast motion means high velocity at the end of travel resulting in over-travel, bounce, fatigue, and other undesirable effects. The active damping proposed in this paper not only avoids such issues but actually enables faster travel by removing limitations that would otherwise be necessary. This active damping mechanism is applicable in particular to medium- and high-voltage circuit breakers, but can be extended to actuators in general. A 15 kV/630 A/1 ms mechanical switch designed to enable the fast protection of medium voltage dc circuits is used as a testbed for the concept. The switch is based on the principle of repulsion forces (Thomson coil actuator). By energizing a second coil, higher opening speeds can be damped, resulting in limited over-travel range of the movable contact. The overall structure is simple and the size of the overall switch is minimized. To validate the concept and to study the timing control for best active damping performance, both finite element modeling and experimental studies have been carried out. [ABSTRACT FROM PUBLISHER]

This paper presents a new family of hybrid Z-source boost dc–dc converters intended for photovoltaic applications, where the high step-up dc–dc converters are demanded to boost the low-source voltages to a predefined grid voltage. Because the boost capabilities of the traditional Z-source networks are limited, the proposed converters are composed of combine traditional Z-source networks in different ways to enhance the boost abilities of the traditional Z-source networks. The new version of the proposed Z-source converters is termed as hybrid Z-source boost dc–dc converters to satisfy the traditional benefits of Z-source networks with stronger voltage boost abilities which can also be applied to dc–ac, ac–ac, and ac–dc power conversions. The performances of the proposed converters are compared with other Z-source networks behaviors. The simulation and experimental results of the proposed converters are validated at different operating conditions. [ABSTRACT FROM PUBLISHER]

This paper presents the design and experimental results of a Thomson coil-based fast mechanical switch for hybrid ac and dc circuit breakers rated at 30-kV voltage and 630-A current. The compact design with optimized circuit parameters and geometric dimensions of components targets 2-mm travel within 1 ms when driven by a 2-mF capacitor bank precharged to 500 V. The use and design of a disc spring as the damping and holding mechanism is presented. Structural design of a complete switch assembly rather than just the actuator is given. Experimental results show that the switch can travel 1.3 mm in the first 1 ms and 3.1 mm in the first 2 ms when driven by a 360-V 2-mF capacitor bank. Such fast mechanical switches facilitate hybrid circuit breaker interruptions within 2 or 3 ms for ultra-fast and highly efficient protections in 5–35 kV medium-voltage dc as well as ac systems. [ABSTRACT FROM PUBLISHER]

To open electromechanical switches within the range of tens of microseconds, we exploit repulsive electromagnetic forces between current-carrying conductor loops. For this we study the power conversion efficiency from electromagnetic to kinetic form. These studies suggest connecting moving coils in series rather than employing inductive coupling. These techniques are put into practice in two prototype switches: the first one is based on induction and the other on series connected coils. Measurements with a high-speed camera verify that both switches achieve accelerations in the magnitude of 140000 g and breaking distances of 1 mm within 50 \mus. The switch with series connected coils obtains 44% greater force than the one based on induction. [ABSTRACT FROM AUTHOR]

The current-induced perpendicular magnetic anisotropy magnetic tunnel junctions (p-MTJs) offer a number of advantages, such as high density and high speed. As p-MTJs downscale to $\sim 40$ nm, further performance enhancements can be realized thanks to high spin-torque efficiency, i.e., lower critical current density and higher thermal stability. In this paper, we investigate the origin of high spin-torque efficiency and give a phenomenological theory to describe the critical current reduction due to the subvolume activation. Based on various physical theories and structural parameters, a compact model of nanoscale MTJ is developed and demonstrates a satisfactory agreement with experimental results. Dynamic, static, and stochastic switching behaviors have been addressed and validated. Then, we perform mixed simulations for hybrid MTJ/CMOS read/write circuits, magnetic random access memory, and magnetic flip-flop to evaluate their performance. Analyses of energy consumption are given to show the prospect of MTJ technology node miniaturization. [ABSTRACT FROM AUTHOR]