Output Voltage Control and Efficiency Improvement of Multistage Impulse Voltage Generator by Utilizing Inductive Energy Storage

For the conventional method of direct transfer of energy between a storage inductor and an uncoupled load inductor, the maximum energy which can be transferred to the load inductor is 25% of the initial stored energy. The Meatgrinder, a novel inductive energy storage and transfer circuit, has been shown to approach 100% energy transfer efficiency. A low-current-level experiment has been performed which has verified the predicted behavior of the inductive transfer circuit and demonstrated an energy transfer efficiency of 47.5%. In order to address the issue of the circuit operation at a higher current level, a second experiment was conducted. The peak current reached was 3.9 kA and the results verified that the current multiplication and energy transfer of the circuit does scale with current.

This paper presents the simulation and experimental analysis of an impulse voltage generator (IVG) used for atmospheric discharge voltage tests. The electrical equivalent circuit of the IVG was simulated using the electromagnetic transients program EMTP-VR. Besides the simulation of the generator operation, it was necessary to make a detailed revision of the IVG components and determine their working condition to carry the laboratory experiments. The lack of a high DC voltage source to feed the IVG led to developing a high-voltage dc supply. Although the IVG was designed and built in February 1982, this equipment was out of operation due to its DC power supply failure. Due to the interest in rehabilitating the equipment to perform high voltage experiments, and with the need to characterize insulation materials and electrical equipment subject to electrical stress, it was decided to put it back into operation. Capacitor tests were carried out for each IVG stage to determine if they fulfilled the electrical charging function. Other components were also repaired, such as damaged resistances and sphere gaps. The impulse generator was configured with a maximum of six stages which is half of the original design. Before doing an experiment with the IVG, a simulation analysis was made to study the IVG. The simulation results allow evaluating before the experimentation whether the impulse generator is working correctly; the model allows to analyze the charge and discharge of each capacitor and the electrical currents at each branch of the IVG equivalent circuit. Performance Simulation and experimental results are presented to demonstrate the IVG functionality. The IVG will be used for carrying out insulation tests made by power engineering graduate students.

Switched mode pulse power supply is a promising technique for high-power quasi-continuous laser driver. Contrast to lossy linear laser drivers, switched mode laser drivers can achieve higher efficiency. However, many challenges have been proposed, such as fast pulse edge, low current ripple. This paper proposes a multiphase interleaved pulse power supply with energy recovery and inductive storage (MIEF-PPS). The basic concept of the topology is the inclusion of a multiphase converter with pulse forming circuits to the converter system, which decouples the current slew rate and current ripple. Using an inductive storage technology and pulse forming circuits, a shorter pulse current rising time is obtained. The inductor energy is fed back to the input source not discharged to the load, resulting in a fast pulse trailing edge and energy saving. Thus the pulse current response observed when using this proposed technique is found to be much faster when compared to the conventional interleaved buck driver. Moreover, a pre-charge method is proposed to overcome the challenge of digitally controlling the inductive storage. The proposed topology was simulated in MATLAB/Simulink and validated against the experimental results of a laboratory prototype, 360 W dual-interleaved pulsed power supply.

This paper presents a simple and novel method for minimizing the performance dependence of a convection-based tilt sensor on environmental temperature fluctuation. Previously reported convective tilt sensors show considerable fluctuation in output voltage because of various external thermal effects. Therefore, it is necessary to have a complex circuit to compensate the external temperature fluctuation or an additional cautious package to reduce the thermal effect. In this paper, a convective tilt sensor that inhibits the environmental thermal effect without an additional circuit or package is discussed. An integrated thin-film-based thermoelectric device is utilized not only for heating an encapsulated air medium with a symmetric temperature profile when it is balanced, but also for minimizing external thermal effects. The hot junction of the thermoelectric device operates as a heater and the cold one keeps the temperature difference between two junctions constant regardless of the external thermal environment. The proposed tilt sensor showed a fairly linear output voltage within the inclination range of ±90° on two axes and even exhibited a consistent output voltage under various external temperature conditions. The fluctuation rate of the proposed tilt sensor was kept within less than 2% of the output voltage; this was even the case for a temperature range of 25 to 60 °C.

Boost converters are widely used in industry for many applications, such as electrical vehicles, wind energy systems, and photovoltaic energy systems, to step up the low voltages. Using the topology structure of the DC–DC boost circuit, this paper studied and designed a dual loop control method based on proportional integral controllers for improving the converter efficiency. The inner loop and outer loop controls of the traditional boost circuit are adopted in MATLAB/Simulink software to make the output of the system more stable. The input voltage is set to 24 V DC, and the desired output voltage varies from 36 to 48 V. Through simulation verification, the influence of a 1 kW sudden load connection by using a switch at a nominal output voltage of 48 V DC is studied, and the results show that it reduces the transient output voltage dips during the sudden load connection. Simulation analysis verifies the design scheme of the system, reduces the fluctuation in output voltage and power, reduces the output current ripple, minimizes the dip in voltage to a minimum possible value, and improves the dynamic characteristics and overall efficiency of the converter.

Modern societies would not survive without electricity and at the same time electrical faults could cause and have caused many catastrophes—mainly deadly fires—to our societies. There are two types of electricity sources: the voltage source such as generators, charged batteries and capacitors, and the current source such as charged inductors, current-regulated rectifiers, and superconducting magnetic energy storage. An “ideal” voltage source—that is often-sought-or-intentionally engineered—generates a constant voltage irrespective of its load current, and an “ideal” current source injects a constant current irrespective of its load voltage. However, two problems exist: (1) voltage or current sources do not represent many emerging natural/renewable energy sources such as wind turbine generators, photovoltaic cells, and fuel cells, whose output voltage and current are strongly dependent on each other, and (2) a short-circuit fault to an artificially-made and controlled “ideal” voltage source or an open-circuit fault to an “ideal” current source can cause catastrophic failures of the source itself and its surrounding circuits due to large (theoretically infinite) short-circuit current or open-circuit voltage. Here we introduce an impedance source concept to represent, characterize, and model those electricity sources whose output voltage and current are strongly dependent on each other. First, we found that many electric sources with no feedback (or active) control of their output voltage and/or current are a natural impedance source with inherent fault protection at short-circuit or open-circuit faults. Second, any electrical source can be artificially controlled to mimic a natural impedance source. Finally, we show how to apply natural impedance sources and nature-mimicking artificially-controlled sources to the electricity grid—the most complex machine ever made by human beings—to realize electricity grids that are naturally stable, self-protected against electrical faults, and resilient to natural and human-made events.

This paper presents a novel sparse matrix converter configuration that needs no bulky energy storage capacitors or inductors, and employs only unidirectional power semiconductor switches. The source side bridge is switched at the line frequency and therefore, this allows the use of the low speed high power rating switches. This feature and the use of diode-clamped multilevel topology at the output stage make this new matrix converter suitable for medium to high power applications and improves the output voltage quality. Compared to the existing multilevel matrix converter topologies, the proposed topology requires no flying or extra capacitor, a smaller number of switches and a simpler modulation strategy. Simulation results for a 220v/60Hz input source and 20KVA load show that the proposed AC/AC topology has input unity displacement power factor, high (0.95 to 0.88) input power factor for different load conditions and controllable output voltage at a desired frequency.

The four-switch buck-boost (FSBB) converter effectively reduces the average inductance current of FSBB when the input and output voltage is close to each other by using the four-mode operation, which alleviates the problem of limited duty cycle and low efficiency in the traditional control modes. However, the steady-state duty cycle mutation of FSBB with four-mode control will occur during mode switching, resulting in output voltage fluctuation. We analyzed the mechanism of duty cycle sudden change of four-mode control FSBB during mode switching, explored its influencing factors and governing laws, and proposed to use input voltage feedforward control to improve the smoothness of four-mode switching, so as to improve the response speed of output voltage when input voltage changes suddenly. The simulation results showed that after the input voltage feedforward control method was adopted, the four working modes can be switched smoothly in a wide input voltage range, the output voltage can be adjusted quickly, and the full load peak efficiency can reach 98%.

This paper presents a numerical study of transferring characteristics of momentum/energy during oxygen jetting into the slag–metal molten bath in basic oxygen furnaces by a multi-fluid volume of fluid model. The evolution of the momentum/energy and turbulence of jets along their axial travel were studied. The results were quantitatively compared within a wide range of oxygen supply pressures, at which the jets may be at under- or over-expanding state. The efficiency of the momentum/energy transfer from the jets to the molten bath was also assessed with respect to lance height and operation pressure. The numerical results show that the momentum and kinetic energy for the jets suffering from shock waves likely cause more intensive damping compared to the jets with expansion waves. The turbulence kinetic energy and turbulence dissipation rate are observed to firstly increase and then decrease. This effect is more pronounced at a lower operation pressure. Based on these results, the optimum lance height was identified for a rapid slagging operation. It is also shown that the efficiency of the energy transfer from the jets to the molten bath is very low. Decreasing lance height or increasing operation pressure promotes the efficiency of the momentum transfer from the jets to the molten bath but lowers the efficiency of the kinetic energy transfer.

This paper presents RX-Sensorless technologies required in a self-induced type of low power wireless power transfer system. Recently, apart from the fields of smartphone and electrical vehicles which have been arduously studied for application of wireless power transfer, wireless power transfer technologies are being applied to various fields. Among them, there is a very rapidly increasing demand for low power systems in displays, body implant medical devices, drones, electrical kickboards and so on. In order to acquire portability of RX side of low power systems, the most critical factors are power density and efficiency. For this purpose, there have been very much ongoing studies to improve the power density on the RX side. Among various research, most frequently used types of methods involve derivation of output voltage using the physical quantity on the TX side while removing sensors on the RX side. However, in the modeling process to derive output voltage, they fail to properly reflect the parasite components of wireless power transfer and also due to the lack of measures in case of being out of the range of resonance frequency, there tends to be a high error in the output voltage which raises an issue. Therefore, this paper aims to suggest a model which reflects the parasite resistance components and the permeability rate of medium for the TX/RX pads of wireless power transfer systems. By reflecting winding losses and eddy current losses of TX/RX pads to a model, it is possible to reflect the parasite resistance components and using the Neumann formula, it is possible to reflect it to the medium between RX/TX pads. As a result, based on the derived model, it is possible to control the output voltage. Prototypes of hardware are designed and implemented for verifications. According to the computer simulation results and test results, output voltage estimates yield an error in the range of less than or equal to 8% and model-based output voltage control also shows the control range with errors of less than or equal to 5%.

Summary form only given. Forster resonance energy transfer (FRET) is the dominant nonradiative energy transfer mechanism between a donor and acceptor fluorophore in nanometer proximity. FRET plays a pivotal role in the photosynthetic apparatus of plants and bacteria and many applications, ranging from photovoltaics and lighting, to probing molecular distances and interactions.It is an intriguing open question whether the FRET rate γFRET and the energy transfer efficiency ηFRET can also be controlled by the nanoscale optical environment, characterized by the local density of optical states (LDOS) [1]. Pioneering work suggested that the transfer rate depends linearly on the LDOS at the donor emission frequency [2], while later work suggested a dependence on the LDOS squared [3], or even a transfer rate independent of the LDOS [4]. We study the influence of the LDOS on Forster transfer, using precisely-defined, isolated, and efficient donor-acceptor pairs. The FRET pairs are dye molecules that covalently bound to the opposite ends of a 15 basepair long double-stranded with a precisely defined distance of 6.8 nm. Control over the LDOS is realized by positioning the FRET systems at well-defined distances (ranging from 60 nm to 270 nm) from a metallic mirror. The energy transfer rate γFRET and efficiency ηFRET are obtained by measuring the donor emission rate γDA in presence and the rate γD in absence of the acceptor using time-correlated single-photon counting based lifetime imaging. Our data unequivocally show that the FRET rate is independent of the LDOS at donor emission frequencies, consistent with quantum-optical theory. The FRET efficiency clearly changes with LDOS [5], since the LDOS alters the competition between the different decay processes. By controlling the radiative decay rate of the energy donor by the LDOS, the energy transfer efficiency can be enhanced or reduced. If a donor with unit quantum efficiency is placed in a 3D photonic bandgap, the energy transfer efficiency will approach 100 %, independent of the acceptor, and of the distances and orientations between the FRET partners.

We have modified a solid-state Marx generator by inserting inductors into the circuit so that the inductive energy can boost the output voltage to a level several times as high as $n \times V_{0}$ , where $n$ is the number of Marx stages and $V_{0}$ is the charging voltage of each stage. Switches in the Marx generator are properly controlled allowing certain energy transfer from the capacitors to the inductors before the output begins. As a result, when all capacitors and inductors are connected in series, the voltage generated on the load is from both capacitive energy storage and inductive energy storage. In the demonstration experiment, we have used a 4-stage Marx circuit to generate an output voltage with a peak value of ~ 9 kV on a 400- $\Omega $ load, with a charging voltage of 800 V.

This paper proposes a novel inductive contactless energy transfer system for residential distribution networks. The system is based on a resonant inverter with sliding transformers, allowing high flexibility (the connection point of the loads is movable) and high safety (electrical shocks are avoided). A new resonant topology for driving the sliding transformers is proposed which behaves as an AC high-frequency voltage source. A very interesting feature of this voltage source is that the amplitude of the output voltages is nearly constant and independent of the load consumption. The paper presents a design procedure for calculating the components and parameters of the resonant circuit. The performance of the complete contactless system is evaluated, especially the efficiency and the transient response. The reported results show good performance validating the proposed topology.

Pad misalignments are almost inevitable in most inductive power transfer (IPT) systems. It tends to cause parameter variations and, thus, significantly affects the performance of the IPT system. In this article, a hybrid IPT system with misalignment tolerance using the quadruple-D quadrature pads (QDQPs) is proposed to tolerate the x, y, z, and diagonal misalignments with load-independent output voltage, simplifying or even canceling control schemes. Besides, the proposed approach can restrict the increase of the primary current when the secondary side moves out of the operating region. Moreover, a new parametric design method is presented according to the misalignment characteristics of QDQPs. The method can limit the output voltage fluctuation to a certain range, given a predetermined misalignment distance. A 3.5-kW prototype was built to verify the proposed hybrid IPT system. The primary and secondary coil sizes are 400 mm × 400 mm, and the air gap is 150 mm. Experimental results demonstrate that the proposed hybrid system can tolerate -150 to +150 mm x-misalignment, -150 to +150 mm y-misalignment, -20 to +35 mm z-misalignment, and -100 to +100 mm diagonal misalignment with load-independent output voltage. Within the predetermined misalignment range, the output voltage fluctuation is less than 5%.

This paper proposes an open circuit fault tolerant strategy with a fault detector for the inverter stage in indirect matrix converter (IMC). When an open switch fault occurs in IMC, the location of faulty switches in the inverter stage can be exactly identified by the fault detector which compares the output voltages of the analytical model with the measured output voltages. In order to keep the continuous operation without output voltage fluctuation, the fault tolerant strategy is developed to control indirect matrix converter based on the concept of four-leg matrix converter. The proposed fault tolerant strategy can maintain the same output performance during the faulty condition as the healthy condition. Simulation results are given to verify the effectiveness of the proposed method.