Voltage Superposition Research Articles

A Compact Gigawatt Pulsed Power Generator for High-Power Microwave Application

Nanosecond square voltage pulse is of wide interest because of its potential military and industrial applications, such as high-power microwave (HPM). In this article, a gigawatt pulsed power generator (PPG) for HPM based on the multistage pulse forming networks (PFNs) with a voltage superposition using the Marx scheme, i.e., PFN-Marx generator, is proposed through the theory analysis, numerical simulation, processing manufacturing, and performance experiment. The PPG consists of the main subsystems of the primary power and pulse modulation subsystems. The primary power subsystem is a modular bipolar dc high-voltage generator based on the ac–dc–ac, high-frequency transformer, and voltage multipliers by using the power electronics switches. It can generate bipolar dc high voltage of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 42 kV to charge the PFN-Marx generator. As for the pulse modulation subsystem, the PFN-Marx technique is preferred, which consists of 24-stage and six <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{L}$</tex-math> </inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{C}$</tex-math> </inline-formula> sections. To verify the PPG, an experimental prototype is fabricated and tested. It has a characteristic impedance of about 40 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol\Omega$</tex-math> </inline-formula> and can deliver square voltage wave with an output voltage pulse of about 500 kV, full-width at half-maximum (FWHM) of 94 ns, and 10%–90% rise time of fewer than 35 ns, indicating its ability to deliver peak power beyond 6.25 GW. In addition, a transit-time oscillator was connected and can radiate microwave power of 0.8 GW at 12.89 GHz for the cathode voltage of 372 kV and the beam current of 9.3 kA.

Study on Space Charge Characteristics in XLPE Under DC Voltage Superimposed by Impulse Voltage

In direct current (dc) transmission lines, power cables are susceptible to the invasion of switching overvoltage or lightning overvoltage. This causes the accumulation of space charge in the insulation due to the higher transient composite electric stress. Space charge is an important factor in dielectric breakdown, especially under high electric stress. However, until now, there are few reports on space charge characteristics under the composite stresses of dc voltage and impulse voltage. In this article, a modified pulsed electroacoustic space charge measurement system used for dc voltage superimposed by impulse voltage is developed by reasonably choosing resistor and capacitor elements in the measuring system. Then, space charge characteristics in cross-linked polyethylene (XLPE) are measured under dc voltage, impulse voltage, and dc voltage superimposed by impulse voltage. The test results show that hetero-charges dominated in the XLPE bulk under a positive dc voltage, whereas homo-charge injection occurred from the semiconductor (SC) electrode under a negative dc voltage. However, a continuous impulse voltage with high amplitude can cause a large degree of homo-charge injection from both electrodes. Moreover, greater homo-charge injection appeared under the negative impulse voltage than that under the positive impulse voltage. Under a dc voltage superimposed by an impulse voltage, the superposition of voltages with the same polarities facilitated homo-charges injection from both electrodes to a greater extent than did the superposition of voltages with opposite polarities. Furthermore, regardless of the polarity of the applied dc voltage, greater space charge accumulation appeared in XLPE when a negative impulse voltage is superimposed.

A Novel Direct‐Current Piezoelectric Energy Harvester with Sustainable Output

The crest factor is an important indicator to measure the performance of the load. To reduce the crest factor of the system and improve the internal stability of the circuit, this article proposes a novel direct‐current piezoelectric energy harvester with sustainable output (S‐PEH). Voltage superposition with phase coupling could significantly improve the stability of the circuit system and reduce the interference and damage of transient pulses to the system. Here, the influence of angle size and phase number on the output performance of S‐PEH is studied. S‐PEH could produce a more stable voltage output with a low crest factor through phase coupling. At 3 P 120°, the optimum MAX voltage and root mean square (RMS) voltage are 29.06 and 16.55 V. The maximum RMS power is 1.38 mW. When the rotating speed is 550 r min−1, the lowest crest factor is 1.35. The charging rate is four times higher than a single‐group piezoelectric patch. Experiments show that S‐PEH can make light‐emitting diodes (LEDs) and calculators work stably. These results show that S‐PEH has great prospects in the power supply of wireless sensor networks and microelectronic devices.

Harmonic Contribution Assessment Based on the Random Sample Consensus and Recursive Least Square Methods

This paper deals with a method of quantifying the harmonic contribution of each harmonic source to system voltage distortion. Assessing the harmonic contribution of individual harmonic sources is essential for mitigating and managing system harmonic levels. Harmonic contributions can be evaluated using the principle of voltage superposition with equivalent voltage models for harmonic sources. In general, the parameters of equivalent voltage models are estimated numerically because it is difficult to measure them directly. In this paper, we present an effective method for estimating equivalent model parameters based on the random sample consensus (RANSAC) and recursive least square (RLS) with a variable forgetting factor. The procedure for quantifying harmonic contributions using equivalent models is also introduced. Additionally, we propose a network diagram of harmonic contributions that makes it easy to understand the harmonic distortion contributions of all harmonic sources.

High voltage nanosecond pulse generator based on avalanche transistor Marx bank circuit and linear transformer driver.

Avalanche transistor Marx bank circuits (MBCs) are widely used in high voltage repetitive nanosecond pulse generators, but problems exist with respect to increasing the output voltage due to the limited pulsed current. Accordingly, a novel topology based on an avalanche transistor MBC combined with a linear transformer driver is proposed, the latter of which exhibits advantageous stress distribution and modular structure. A four-module prototype with four units in each module is developed in the laboratory. The output characteristics are investigated by varying important parameters such as the main capacitance, the number of conducting units, the number of cascaded modules, and the trigger signal time delay. The test results verify the validity of the proposed topology. For a 50 Ω resistive load, the prototype can generate pulses with an amplitude of 10.9 kV, a rise time of 3.3ns, and a voltage superposition efficiency of 89%. The topology proposed in this paper may help to provide a method to further improve the output performance of avalanche transistor MBCs.

Effects of Spike Voltages Coupling With High dV/dt Square Wave on Dielectric Loss and Electric-Thermal Field of High-Frequency Transformer

The insulation of high-frequency transformers (HFTs) has a significant impact on the safety and reliability of high voltage power electronic transformers (PETs). The transient voltages from the rapid turn-off and turn-on of the high voltage power semiconducting device increase the insulation stress and loss, resulting in thermal stress distortion. However, few studies have presented an accurate evaluation of the dielectric loss, especially under high dV / dt square waves. This paper focuses on the dielectric loss calculation in HFT insulation by analyzing the loss from a high-frequency square wave with spike voltages. A step function that is equivalent to spike voltage superposition is proposed for the quantitative calculation of the dielectric loss of epoxy resin. A cutoff frequency ( $f_{\mathrm {c}}$ ) is defined to indicate high dV/dt characteristics. A similar narrow step function is used for simulating spike voltage at the rising/falling edge. The additional dielectric loss increases with the spike voltage and the duration. The electric field and temperature distributions are simulated in a 10 kW, 10 kHz HFT by considering the calculation of dielectric loss. The spike voltages enhance the electric field and temperature in the insulation. The increase in the external temperature (close to the glass transition temperature ( $T_{\mathrm {g}}$ ) of epoxy resin) causes a significant increase in the insulation temperature. This paper is of great importance to the design and application of HFT insulation.

PFC Converter with Improved Input Current Zero-crossing Distortion

In this study, a voltage superposition concept is used without phase adjustment of the input current command and without enlarging the turn-on period of the switch in the vicinity of the zero input voltage, but only with a few components added to the PFC converter, so as to improve the zero-crossing distortion of the input current, thereby further reducing the total harmonic distortion. Eventually, the mathematical deductions and experimental results are provided to verify the effectiveness of the proposed circuit.

Theoretical Optimization of Stimulation Strategies for a Directionally Segmented Deep Brain Stimulation Electrode Array.

Programming deep brain stimulation (DBS) systems currently involves a clinician manually sweeping through a range of stimulus parameter settings to identify the setting that delivers the most robust therapy for a patient. With the advent of DBS arrays with a higher number and density of electrodes, this trial and error process becomes unmanageable in a clinical setting. This study developed a computationally efficient, model-based algorithm to estimate an electrode configuration that will most strongly activate tissue within a volume of interest. The cerebellar-receiving area of motor thalamus, the target for treating essential tremor with DBS, was rendered from imaging data and discretized into grid points aligned in approximate afferent and efferent axonal pathway orientations. A finite-element model (FEM) was constructed to simulate the volumetric tissue voltage during DBS. We leveraged the principle of voltage superposition to formulate a convex optimization-based approach to maximize activating function (AF) values at each grid point (via three different criteria), hence increasing the overall probability of action potential initiation and neuronal entrainment within the target volume. For both efferent and afferent pathways, this approach achieved global optima within several seconds. The optimal electrode configuration and resulting AF values differed across each optimization criteria and between axonal orientations. This approach only required a set of FEM simulations equal to the number of DBS array electrodes, and could readily accommodate anisotropic-inhomogeneous tissue conductances or other axonal orientations. The algorithm provides an efficient, flexible determination of optimal electrode configurations for programming DBS arrays.

A novel particle swarm optimization maximum power point tracking control method based on the direct current voltage superposition principle under partially shaded conditions

In this paper, a novel particle swarm optimization maximum power point tracking (MPPT) control method is presented to gain the maximum power point of photovoltaic (PV) power, which is based on the direct current voltage superposition principle to predict the output characteristic of a PV array at partial shading. The proposed control method conveniently can be used in the real-time MPPT control strategy for large-scale PV systems, and with the implementation of the collect circuit it is easy to gain the global peak of multiple PV arrays, thereby resulting in lower cost and higher overall efficiency. The proposed method is proved by using simulation results.

高重复频率脉冲功率技术及其应用:(4)半导体开关的特长与局限性

Power semiconductor devices have been used for repetitive pulsed power generation, due to their advantages in stability, reliability, and lifetime. On the other hand, their limitations in power capability and noise vulnerability are expected to be overcome by using various techniques in gate control and circuit configuration. In this paper, some pulse circuit methods to improve the working ability of semiconductor switches are introduced, including using a number of devices in series and parallel, voltage superposition, combination and complementation of switching devices.

Critical Analysis of the Current and Voltage Superposition Approaches at Sharing Harmonic Distortion Responsibility

Faced with the guidelines contained in documents approved by the National Electric Power Agency PRODIST - Module 8, amongst other indicators of electric power supply quality, the harmonic distortions appear as an important issue. The mentioned regulation takes into account specific matters such as definitions, measurement procedures, benchmarks, etc. Focusing the subject of voltage distortions and the establishment of approaches to determine the responsibility for possible violations of given limits emerges as an important task. This research topic has been taken into account by the literature and a few procedures to characterize the responsibility of a given distortion level due to supplier and consumer has been proposed. The most widespread solutions are based on frequency domain superposition principles. Having this in mind, the current paper conducts a critical analysis performance of the superposition methodology throughout two possible ways of dealing with the subject. The first uses the current contributions and the other by focusing the voltage harmonic found at a given busbar. The studies highlight that the current procedure do not lead to consistent results whereas the voltage method seems to provide a promising manner of dealing with the identification of the harmonic distortion responsibility.

Research on the Voltage Regulation of in Interconnected Distributed Network - Distributed Generation

Voltage regulation can be control after distributed generation (DG) into the distribution network. This paper deals with a voltage regulation algorithm for a grid-connected DG, based on active and reactive power control. It also proposes the algorithm of the simplified voltage—superposition theorem. The proposed method is applied to the power distribution system model, and its effectiveness is verified through simulation results. At in the end of the paper, we make a conclusion.

A Pulsed Power Supply Based on Power Semiconductor Switches and Transmission Line Transformer

Transmission line transformers (TLT's) as pulse transformers have received increasingly more attention due to their excellent frequency response characteristics over conventional wound transformers. This transformer basically consists of equal lengths of transmission line (normally coaxial cables are used) connected in parallel at the input side of the transformer, and in series at the output side so that the output voltage can be boosted in proportion. Because the reactance of the outer conductor increases with the rise of the frequency of the input voltage, the output voltage of each transmission line can be isolated mutually when the frequency is high enough. Then, the output voltage will be amplified through the voltage superposition. To minimize the substantial loss of voltage gain and obtain a low pulse droop rate, one stage transformer is entwined together as a unit, the number of stages of the transformer can increase easily by piling units one by one. This spiral construction makes the transmission line transformers much more compact. On the other hand, with the development of modern semiconductor technology, high voltage, fast rise time power semiconductor devices have been produced, the collector emitter breakdown voltage of one IGBT is to 1.7 kV and the rise time is 100 ns. This paper describes a kind of compact pulse power supply constructed by combining transmission line transformer and modern power semiconductor devices-IGBTs. High voltage IGBTs (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CES</sub> =1.7 kV) have been used as charge switches, short pulses can be obtained at the input port of the transformer, then the output pulse amplitude is 10 kV through a 10-stage transmission line transformer. Finally, the output voltage pulse waveforms are given in the paper.

Control of the charge and the nonlinear oscillation of dust particles by alternating current voltage superposition on the cathode in a direct current discharge

Experimental and theoretical studies were conducted to investigate the control of charge and modification of nonlinear oscillations of externally injected dust particles in a dc discharge. The superposition of ac voltage on a dc cathode led to plasma density modulation, which brought about a drastic change of particle oscillation characteristics. Examples of the changes include disappearance of the subharmonic resonance peak and hysteresis as the ac superposition voltage was increased, which is attributed to the fact that the ac superposition made sheath structure less nonlinear and less parametrically resonant. In addition, as the ac frequency decreased from 5kHzto1kHz at the same ac voltage (15V), the subharmonic peak became weakened along with its frequency. This result demonstrates that the dust charge is the main parameter in determining occurrence of the subharmonic resonance peak. We consequently expect that modification of the oscillation dynamics of dust particles and furthermore the separate control of the charge may be possible by the ac modulation of the dc biased cathode.

Flattop acceleration system in the RIKEN AVF cyclotron

A flattop acceleration system has been developed and installed in the RIKEN Azimuthally Varying Field (AVF) cyclotron in order to improve the transmission efficiency and energy spread of beams. The flattop accelerating voltage is generated by a superposition of voltages of the fundamental and third harmonics on the dee, by attaching an additional resonator capacitively coupled to the main resonator. The flattop voltage could be generated from 36 to 63 MHz corresponding to the third harmonic of the operating frequency range of 12–21 MHz. A beam acceleration test was carried out and beam emittance in the longitudinal phase space was measured using a spectrometer. With this flattop system, the single-turn extraction was achieved more easily and the momentum spread was reduced to one-third. The beam transmission efficiency through the AVF cyclotron as well as the RIKEN Ring Cyclotron (RRC) has also been improved.

A computer simulation to help in teaching inductionphenomena

The motion of a magnet through a coil is analysedthrough a model of magnetic monopoles. The magnetic flux of amonopole passing through a loop is explained and also its rate ofchange. By a superposition of voltages produced by the monopoleson the coils the shape of the voltage versus time graph is explained.Also examined is the interaction of a magnet moving through aloop and the fall of a magnet through a solenoid, or independentloops and the fall of the magnet in a metal pipe. This software can help thestudent to apply principles of mechanics and improveunderstanding of graphs.

PD characteristics in an air-filled void at room temperature under superimposed sinusoidal voltages

Partial discharge in an artificial air-filled void under superimposed sinusoidal voltages is investigated at room temperature in order to clarify the effect of voltage superposition. The applied voltage waveform is composed of a 60 Hz fundamental sinusoidal wave and a high frequency sinusoidal wave of 300 Hz to 1.2 kHz. It was found that PD started when the peak value of the superimposed voltage reached the PD inception voltage under 60 Hz sinusoidal voltage. Also, PD occurrence frequency increased remarkably when the peak value of the high frequency component exceeded a critical value, which is smaller than the PD inception voltage under 60 Hz sinusoidal voltage. PD characteristics under such conditions were discussed as the effect of the residual voltage, caused by the surface charge deposited in the void by the preceding PD. The obtained experimental results suggest that the superposition of high frequency component accelerates the degradation of the solid insulator containing void defects.

The ac superposition method, a new hot-line diagnostic method for 6-kV XLPE power cables

Water trees are the most hazardous factor affecting the life of XLPE distribution cables and the major cause of insulation failure. It is well known that insulation failure causes stoppages in electrical service and requires extensive repair work. Up to now, deterioration of cable insulation has been diagnosed mainly by the dc leakage current method. However, application of this method for diagnostic measurements requires interruption of electrical service. Several types of hot-line diagnostic methods (including the dc component current and dc superposition methods) were developed to detect water tree deterioration. However, these methods have some shortcomings, such as being subject to effects of stray currents and the accuracy of measurements not being sufficiently high. Therefore, we have attempted to develop a new hot-line diagnostic method. We investigated whether the signals produced by superposition of voltages of various frequencies to the cover layer of energized cables were correlated with deterioration by the water treeing. As a result, we found that a deterioration signal of 1 Hz was observed when we superposed an ac voltage (commercial frequency × 2 +1 Hz) on the cover layer of cable where the water tree had occurred in the insulation. © 1999 Scripta Technica, Electr Eng Jpn, 130(2): 49–58, 2000

A test method for 50 Hz capability of vacuum interrupter materials

This investigation method allows an excellent comparison of the interruption behavior of contact materials in real vacuum tubes by using small cylindrical contact samples (12 mm diameter) in a special experimental setup. The described investigations were carried out with different CuCr materials in an ultrahigh vacuum test vessel. For the test an apparent current density similar to the stress in real switches is applied to the contact materials of reduced size. A high current circuit with a current of 10.7 kA peak is used for the interruption check. After current zero a Weil-Dobke voltage superposition circuit applies a transient recovery voltage (36 kV, 41 kHz) to the open gap to test the restrike behavior. From the measured data the percentage of successful interruptions of the total number of tests and the re-ignition times were taken as quality criteria. Compared to interruption capacity, measurements with real breakers the results of the developed test method show very similar rankings for different contact materials.

Effect of superposition of sinusoidal voltages on the electroluminescence of (Zn, Cd, Hg) S: Cu, In phosphor

The electroluminescence due to the superposition of sinusoidal voltages of two different or two equal frequencies has been investigated. The superposition of the lower-frequency voltage on the high-frequency voltage causes reduction in the electroluminescent output and a shift in electroluminescent spectra is noticed towards shorter wavelengths. The superposition of voltages of equal frequencies leads to reinforcement in the electroluminescent output with respect to that of the separately applied voltages. The superposition of a higher-frequency voltage upon the lower-frequency one causes a reinforcement but the shift of spectra towards the shorter-wavelength side is again noticed. The voltage dependence of the light output shows deviation from the standard equation, B = B 0 exp(- b/ V 1 2 ), at lower voltages. These phenomena have been discussed in the light of existing theories.