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This paper presents a single-phase ac power supply circuit that based on modified voltage-fed quasi-Z-source inverter topology; it suits to the light or the heavy load and is fit for the resistive, inductive, or capacitive load. The topology, operating principle, voltage gain, control method, and its realization by DSP are described in this paper. The feasibility and rationality of the system is verified by the simulation and experimental results. [ABSTRACT FROM PUBLISHER]

Nowadays, the proliferation of photovoltaic (PV) generators and plug-in hybrid electric vehicles (PHEVs) into power distribution systems highly escalates. The variable PV power and the abrupt power charging of PHEVs result in system power and voltage fluctuations. This paper presents the new application of the superconducting coil (SC), which is connected between the dc link of PV generators to solve this problem. Using the dc-to-dc converter as an interfaced circuit, the SC can share the inverters with the PV generators. In addition, the PV generators with the common SC are able to provide the smooth power output and regulate the system voltage. The PV inverters and the dc-to-dc converter are controlled by the proportional–integral (PI) controllers. The optimization of the PI parameters and SC inductance is performed, so that the power and voltage fluctuations are minimized. Simulation results indicate that the PV generators with the common SC, which has a lower SC inductance, provide the same smoothing effect on the PV power fluctuation as the superconducting magnetic energy storage (SMES) installed at the PV terminal. In addition, they give the superior voltage regulation effect to the SMES. [ABSTRACT FROM AUTHOR]

The superconducting magnetic energy storage (SMES) device has been known as one of the most promising energy storage device as the superconducting coil shows almost zero electrical resistance. With a proper power conditioning circuit, it can have a super-fast unlimited charging/discharging cycle and handle a high pulse power. This feature becomes very attractive for power system applications as it can be utilized to solve the problems of voltage fluctuation, frequency deviation, and power supply disruption. This paper presents a novel concept for the integration of a low-cost micro-SMES (μ-SMES) unit with a residential photovoltaic (RPV) system to mitigate the solar photovoltaic output power intermittency. The low-cost magnesium di-boride (MgB2) superconductor wire is used to design the μ-SMES unit. The performance of a 10-kW RPV-SMES is evaluated in the PSIM software environment. [ABSTRACT FROM AUTHOR]

Rooftop transformer-less photovoltaic inverters (TLPVIs) have the potential to inject a very small dc current into the distribution network. The dc current quantity can be very high in a residential power distribution system where several TLPVIs are installed. Distribution transformers (DTs) supplying power to the customers in the networks can be adversely saturated with this high dc current accumulated from the small dc current injected by individual TLPVI. In this paper, a systematic investigation is carried out on the dc current injection potential of commercially available TLPVIs. Furthermore, the influence of this aggregated dc current on the DTs are analyzed through modelling, simulation, and laboratory testing. A three-phase three-leg transformer is used to analyze the effects of the high dc injection from the TLPVIs. A finite element analysis is carried out in COMSOL Multiphysics environment to explore the dc current injection effect. The results show that the injected dc current from TLPVIs highly affect the DTs and a solution is needed to overcome this challenge before the problem spreads widely and causes a barrier to the growth of the integration of renewable resources to the power grids. [ABSTRACT FROM AUTHOR]

This paper systematically elaborates the mechanism and experimental verification of bidirectional wireless power transfer (WPT) technology. The mathematic model of bidirectional power flow is presented and a phase-angle control method is introduced to effectively regulate the direction and magnitude of power flow in one WPT device. Simulation and experiments are carried out to verify the effectiveness of bidirectional WPT and its control algorithm. The measured results match well with the bidirectional power flow mechanism, and thus lay some bases for implementing large-scale bidirectional WPT device developments. [ABSTRACT FROM AUTHOR]

As compute demands and their large energy costs continue to rise in the datacenter, it is imperative to identify low energy compute solutions. One approach is to investigate device schemes based on collective mode phenomena arising at low temperatures where power dissipation and switching voltage can be extremely low. Additionally, such devices could also have applications in quantum computing where such a low power logic/memory scheme could possibly be integrated onto the qubit plane, which is typically at ∼10 mK temperature. Josephson Junction Field Effect Transistor (JJFET) is a promising candidate for low power operation with zero voltage drop across its drain-source terminals while operating in the superconducting regime. JJFET logic gate is typically realized as a n-type JJFET connected in a common-source configuration with a current source load. This results in high noise margin for logic-1 input but not for both logic-1 and 0. In this paper, we propose an overdamped region, n-type JJFET based digital logic using a cascaded common-source configuration-based design yielding high noise margin for both the logic inputs. DC noise margin sensitivity analysis is performed for the bias current and threshold voltage modulation. The noise margin can be further improved (approaches ideal inverter case) by cascading multiple common source stages yielding higher inverter gain. [ABSTRACT FROM AUTHOR]

This paper describes the test facility and load test program for a 3-MW high-temperature superconducting (HTS) motor for ship propulsion. The test facility was used to conduct a constant-load test and a variable-load test. The program consisted of the constant-load test, the variable-load test, and the inspection after tests. During the constant-load test, the motor efficiency was measured at various rotor speeds and torques, and the 100-h cumulative endurance test at 3 MW was completed successful. The variable-load test is composed of three different modes that simulated an emergency maneuver of full astern to stop the ship and avoid a collision, and they have been verified. After the series of tests, the HTS motor was taken apart and an inspection confirmed that there was no problem with the HTS field coils or other main parts. This program demonstrated the reliability of the 3-MW HTS motor for ship propulsion. [ABSTRACT FROM AUTHOR]

Current-fed quasi-Z-source inverters (qZSIs) have many advantages over traditional current source inverters and current-fed Z-source inverters. This paper presents and analyzes novel adjustable speed drive systems based on the current-fed qZSI that could provide bidirectional power flow, including their topologies, operating principle, and voltage gain. The simulation results are given to verify the rationality and feasibility of the proposed topologies. [ABSTRACT FROM PUBLISHER]

MgB2 material operating at moderate field can conveniently be considered for short-term cost-effective implementation of superconducting magnetic energy storage (SMES). Due to the intrinsic performance of this material, moderate field operation and cryogen free cooling in the range 10–20 K need to be considered. For investigating the feasibility of MgB2 based SMES technology a 10 kW—2 s system is under development. A small MgB2 coil was developed and tested as the first step of this study. The cooling was obtained by means of a cryogen-free test facility based on a two-stages Gifford–McMahon regenerative heat exchanger. A power conditioning system (PCS) was also developed in order to connect the coil with the power grid. The PCS is based on power mosfet components and consists of two parallel dc/dc boost converters and an inverter connected to a common dc bus at 100 V. Continuous operation of the coil at a charge/discharge rate up to 24 kW can be achieved by means of the PCS. Details of the layout of the coil and the thermal connection with the cryocooler are discussed in this paper. Results of cooling test are reported. Possible SMES operation is also discussed. [ABSTRACT FROM PUBLISHER]

The zero resistance of superconducting material is observed only with a DC current, while transmission loss occurs with an AC current. Power converters use electronic devices which generate harmonic currents due to their high switching frequency. The authors expect that harmonic currents also influence the losses in the superconducting DC power cables of a DC transmission system. [ABSTRACT FROM PUBLISHER]

Thyristor converters are used as power conditioning systems for superconducting coils. The objective of this work is to discuss the series compensation of thyristor converters using variable series capacitors. Traditional thyristor converters operate with lagging power factor requiring large reactive compensation efforts. Similarly, the series capacitor can control the coil voltage through a unity power factor thyristor converter with a resulting leading power factor seen from the grid. Therefore, by combining the two, both leading and lagging reactive power control, and also the active power control of the superconducting coils can be achieved. In order to demonstrate the feasibility of the series compensation of the thyristor converter, a prototype converter using a gate-commuted series capacitor (GCSC) is developed. From the experimental results using a superconducting coil, the authors demonstrated the leading current control capability of the series compensated thyristor converter, and verified the leading, lagging, and unity power factor control capability based on thyristor converter systems. This feature leads to a potential reduction in reactive power compensation need of 50 percent of the conventional thyristor converter system. [ABSTRACT FROM PUBLISHER]

A 0.5 MVA/1 MJ superconducting magnetic energy storage system (SMES) has been installed in a superconducting power substation. The SMES is designed to compensate active power fluctuations, current harmonics and reactive power of the downstream load. The system configurations and control strategies are described. Experimental and field test results show that the proposed SMES can effectively improve the power quality of the power system. [ABSTRACT FROM PUBLISHER]

Low-pass filters are implemented as impedance inverters for a bandstop filter design. The choice of the order of the low-pass filter impacts the usable passband bandwidth of the bandstop filter. A great savings in size occurs when implemented with highly miniaturized low temperature superconducting lumped elements. A standard multilayer niobium based fabrication process is used to fabricate the lumped element bandstop filter. The filter is tested and suggestions are made to further improve the return loss outside of the rejection band. [ABSTRACT FROM AUTHOR]

We present simple Complementary Josephson Junction circuits using 1 kA/cm/sup 2/ Nb junctions. We use long, sine-shaped junctions in order to achieve gain and suppressed side lobes. We have simulated layout-extracted simple inverter and ring oscillator circuits to evaluate the performance of these circuits in 1 kA/cm/sup 2/ technology. Projected gate delays with possible higher critical current density technologies are also simulated. We have experimentally tested the operation of inverter circuits. [ABSTRACT FROM PUBLISHER]