Voltage Waveforms Research Articles

Targeted-Waveform Optimisation for Ozonising Dielectric Barrier DischargeReactors

ABSTRACT In this work, a method for maximizing the efficacy of ozone production by dielectric barrier discharge (DBD) is presented. By developing an optimiser-based hardware-in-the-loop system, the effects of varying input waveform parameters and the flowrate of the input gas on the reactor conditions could be explored with greater fidelity than in previous literature. The waveform used is biharmonic, consisting of the sum of two sine waves and allowing a greater number of explorable parameters. The performance of the reactor, evaluated using the parametric sweep technique, is compared to that of a hybrid optimiser combining particle swarm optimisation and pattern search. Two metrics were targeted: ozone concentration-to-power ratio (ppm/W) and ozone quantity for a given energy (g/kWh). Thus, the characteristics of the input voltage waveform and flowrate were adjusted to target high ozone generation efficacy for the reactor used in the experiment. Results show that the optimiser achieves 343 ppm/W compared to 170 ppm/W for the parametric sweep, using a similar number of measurements.

Electric field measurements in a He:N2 atmospheric pressure RF plasma jet by E-FISH

Abstract The electric field in the bulk of a self-sustained radio frequency atmospheric plasma jet (RF-APPJ) in a helium:nitrogen mixture is measured for the first time, to the best of the authors' knowledge, by electric field induced second harmonic generation (E-FISH). It is shown that the electric field in the bulk of the RF-APPJ is unexpectedly high, having an amplitude of about 1.6 kV/cm, and that it exhibits a phase shift of approximately -0.2π relative to the voltage waveform. Both findings are in contrast to low pressure capacitively coupled plasmas (CCPs), where the bulk electric field is negligible and the phase shift between the current and the voltage equals approximately to -π/2. The electron density in the bulk is estimated from the measured phase shift between the electric field, i.e. the current in the bulk, and the applied voltage by using an equivalent RC-circuit model for the discharge. The measured reduced electric field combined with the estimated electron density in the middle of the jet is used to calibrate the values of excitation rates of the N2 (C3Πu) state obtained by Phase Resolved Optical Emission Spectroscopy (PROES) in arbitrary units. The results of the electric field measurements are proposed as an input for numerical models or as a benchmark for calculations. Last but not least, special attention was paid to the calibration of the E-FISH measurement in a discharge powered by AC voltage, which includes artifacts supposedly caused by the windows of the setup.

Effects of pulse rise rate and pulse width on the dynamics of secondary streamers and radical production in atmospheric-pressure air

Abstract The role of the secondary streamer in radical production has been extensively studied, while most of studies analyzed the secondary streamer by assuming a constant electric field in the secondary streamer, thereby ignoring the dynamic nature of the secondary streamer. In this study, the dynamics of the secondary streamer and the effects of pulse rise rate and pulse width are investigated using simulations. The temporal evolution of the secondary streamer under pulsed voltage is analyzed using a novel model. The results shows that the electric field in the secondary streamer first decreases linearly with the length of the secondary streamer, and then changes with the pulsed voltage after the cessation of the secondary streamer. The decrease of the electric field in the secondary streamer is the dominant factor responsible for the cessation of the secondary streamer. As a result, radicals are predominantly produced prior to the the cessation of the secondary streamer. By understanding the dynamics of the secondary streamer, it becomes possible to control the electric field and length of the secondary streamer by adjusting the pulse rise rate and pulse width, respectively, to enhance the energy efficiency of radical production. The increase in the length of the secondary streamer is always advantageous for improving energy efficiency, as it leads to greater energy deposition within the secondary streamer. For N(4S), the optimal electric field is approximately 600 Td, which cannot be achieved in the secondary streamer. In contrast, for O(3P), the optimal electric field is around 180 Td, which can be attained by regulating the voltage waveform.

Intelligent Control of the Dynamic Voltage Restorer for Fault Ride through Capability Enhancement of a Grid-connected Photovoltaic Power Plant in accordance with Recent Moroccan Grid Code

Background: The recent development of small-scale, decentralized generation from renewable sources and the fall in the price of the equipment needed for this operation have given a new role to the distribution networks, which is to collect the energy produced by the smallest generation plants and deliver it to the end customers. However, the national Grid Codes present technical requirements in terms of FRT and particularly LVRT and HVRT which are imposed on PV plants connected to medium voltage distribution networks, to ensure the energy needed by the loads connected to the network at the time of the failure and especially sensitive ones. Methods:: In this paper, an intelligent neural network approach is applied to the DVR control circuit to enable the requirements of the sensitive load connected near the PCC, and the system is tested in the presence of a non-linear load to demonstrate its efficiency for all situations. The proposed strategy is based on the implementation of an improved ANFIS and ANN control which are compared to a tuned PI controller, the approach intends to meet the technical requirement of the recently approved Grid Code in Morocco. The simulation is performed using MATLAB Simulink. Results: The proposed approach brings great improvement to the load side voltage waveforms, and numerical experiment findings demonstrate that it can successfully guarantee the technical requirements of the electrical grid code. Conclusion: The results obtained show better behavior of the system using ANFIS and ANN control strategy in the presence of a nonlinear load and a significant improvement of the voltage THD.

Mode transition in a helium barrier discharge with oxygen admixtures: insights into a micro cavity plasma array reactor

Abstract Dielectric barrier discharges (DBDs) offer great potential for applications such as volatile organic compounds (VOCs) conversion or plasma catalysis. For many of these applications, an admixture of molecular oxygen is important, for example, to oxidize the gases to be treated. However, oxygen addition can lead to a drastic change in discharge dynamics, which may affect conversion efficiency. The discharge may transition to a filamentary mode, which could influence plasma chemical processes or in extreme cases potentially damage the reactor. This study investigates the discharge mode of a micro cavity plasma array operated at atmospheric pressure with a helium flow (1–2 slm) containing small oxygen admixtures (0%–5%). A multitude of parameters as voltage, current, power, and emission are investigated for characterization. Additionally, the electric field, mean electron energy and atomic oxygen density are examined depending on the oxygen admixture. With pure helium, a homogeneous atmospheric pressure glow discharge is observed, appearing as a quasi-continuous glow discharge. With small oxygen admixtures (0.1%–1%), individual discharge pulses become visible, though they remain separated (pseudo glow discharge). At higher oxygen admixtures ( ⩾ 1%), a mode transition to a filamentary discharge is observed. The measurements indicate that the discharge mode, especially the individual discharge pulses, has a significant impact on conversion efficiency. This knowledge can help in the future to fine-tune the discharge mode using external parameters such as voltage waveform or frequency to optimize conversion efficiency.

A dataset of voltage and current waveforms in an electric arc under low pressure for aircraft power systems

This paper presents an experimental dataset developed for the detection of parallel arc faults in aircraft electrical systems. This dataset is based on a total of 960 experiments performed in a low-pressure chamber under different conditions using two electrodes placed on the surface of an insulating material. These experiments correspond to 2 insulating materials, 12 electrode distances, and 10 pressure conditions representative of aircraft environments. Each experimental condition was repeated four times, resulting in 960 experimental recordings, each containing one million samples of time, current, and voltage signals of the electric arc induced on the surface of the insulating material. The dataset can be used to model arc behavior under different pressure conditions, to identify patterns that indicate the presence of an arc, and to accelerate the improvement of arc identification. This dataset has the potential to be used to develop arc fault detection and identification methods for more electric and all-electric aircraft and other electric vehicles.

A five‐level nested neutral point‐clamped inverter topology

AbstractClassical five‐level nested neutral point‐clamped (5L NNPC) inverter‐leg is a hybrid of the flying‐capacitor and diode‐clamped 5‐L inverter‐leg configurations. Though uniform reduced voltage stress on the constituting switches is evident in 5L NNPC inverter‐leg, trails of the drawbacks of diode‐clamping concept still exist. Compared with the classical 5L NNPC inverter, the state‐of‐the‐art diode‐free 5L NNPC inverter involves no passive power switches and has low conduction losses. However, in this 5L NNPC inverter, two of the eight active switches have blocking voltage rating of 1/2 of the input voltage. Considering this limiting topological feature, an inverter‐leg for 5L NNPC inverter is presented in this paper. In the proposed 5L NNPC inverter‐leg, only one switch has voltage stress of 1/2 of the input voltage. This reduced voltage stress has inverter cost and loss implications. The performances and competitiveness of the 5L NNPC inverter were analysed in detail and demonstrated with a prototype. The blocking voltages of all the constituting power switches; profiles of the flying‐capacitor voltages; and FFT spectrum of line voltage waveform were experimentally obtained. Experimental deactivation and activation of the inverter's capacitor voltages balancing scheme were typified for varying modulation index values.

Performance Comparison and Characterization of IPMSM Drives Fed by Symmetrical and Asymmetrical Cascaded H-Bridge Inverters

This paper presents a comparative analysis of interior permanent magnet synchronous motor (IPMSM) drives powered by symmetrical and asymmetrical cascaded H-bridge multilevel inverters. The asymmetric topology operates using multiple DC sources with different voltage values, generating a voltage waveform with more output voltage levels than its traditional counterpart, all while maintaining the same hardware configuration. The main goal is to demonstrate that asymmetrical multilevel inverters are a promising option for improving the performance of electric drives while maintaining cost-efficiency and reliability. The proposed comparison is conducted through simulations in the MATLAB/Simulink R2024a environment, which allows an in-depth analysis of the dynamic performance of the electric drive. Additionally, the variation of the DC link input power of each H-bridge and the Total Harmonic Distortion (THD) of the voltage and current of the output of the converters were studied for different operating conditions in both cases. The obtained results were confirmed through real-time validation, demonstrating the applicability of electric drives powered by asymmetric converters and the advantages, in terms of efficiency, harmonic content and dynamic performance, in certain conditions of operation in terms of speed and applied load.

Induction Motors Under Voltage Unbalance Combined with Voltage Subharmonics

In power systems, various power quality disturbances are present, including voltage deviation, voltage unbalance, and voltage waveform distortions. Voltage waveform distortions are usually identified with harmonics, but in some systems, subharmonics (subsynchronous interharmonics) and interharmonics may also occur—that is, components of frequency less than the fundamental frequency, or not an integer multiple of it. This study examines torque pulsations of an induction motor under voltage subharmonics combined with voltage unbalance. The motor and the driven DC generator vibrations were analysed under the power quality disturbances. Investigations were carried out using finite element and empirical methods. Experimental tests were performed for the maximal levels of the power quality disturbances specified or proposed in the relevant standards. For the investigated motor, under voltage subharmonics or voltage unbalance occurring as a single power quality disturbance, the vibration level was within the prescribed limit. However, under unbalance combined with subharmonics, the level could be accepted for only a limited time. Consequently, the permissible level of voltage subharmonics in non-generation installations should be interconnected with the voltage unbalance in the power system.

An arbitrary waveform neurostimulator for preclinical studies: design and verification.

Neural electrostimulation has enabled different therapies to treat a number of health problems. For example, the cochlear implant allows for recovering the hearing function and deep brain electrostimulation has been proved to reduce tremor in Parkinson's disease. Other approaches such as retinal prostheses are progressing rapidly, as researchers continue to investigate new strategies to activate targeted neurons more precisely. The use of arbitrary current waveform electrosimulation is a promising technique that allows exploiting the differences that exist among different neural types to enable preferential activation. This work presents a two-channel arbitrary waveform neurostimulator designed for visual prosthetics research. A field programmable gate array (FPGA) was employed to control and generate voltage waveforms via digital-to-analog converters. Voltage waveforms were then electrically isolated and converted to current waveforms using a modified Howland amplifier. Shorting of the electrodes was provided using multiplexers. The FPGA gateware was verified to a high level of confidence using a transaction-level modeled testbench, achieving a line coverage of 91.4%. The complete system was tested in saline using silver electrodes with diameters from 200 to 1000µm. The bandwidth obtained was 30kHz with voltage compliance ± 15V. The neurostimulator can be easily scaled up using the provided in/out trigger ports and adapted to other applications with minor modifications.

Experimental study on the influence of a PEM water electrolyzer cell's impedance on its power consumption under impaired power quality

AbstractImpaired power quality is known to increase the power consumption of water electrolysis cells without affecting the hydrogen production rate. Owing to a lack of large‐signal dynamic water electrolyzer models, simulations on the topic often consider only the static polarization curve omitting actual cell dynamics. This article aims to bridge the gap by experimentally studying the dynamic phenomena leading to additional power consumption of a polymer electrolyte membrane water electrolyzer cell using sinusoidal current ripple. The effect of ripple amplitude is analyzed with high‐speed current and voltage waveform measurements, and the frequency dependence is determined using electrochemical impedance spectroscopy. The complex cell impedance is found to be the only parameter needed for determining the additional power consumption at frequencies above . This finding enables a simple prediction of additional power consumption for arbitrary current waveforms at frequencies relevant for water electrolyzer rectifiers. At frequencies below , the static polarization curve begins to influence the voltage waveform of the specific cell, thereby reducing the predictive power of the impedance model. The results prove the use of the static polarization curve is generally inaccurate for modeling water electrolysis power consumption with ripple current.

Research on harmonic suppression method of SPWM inverter circuit for photovoltaic power generation system

To effectively reduce and suppress the harmonics generated by single-phase inverter circuits, this paper mainly investigates the harmonic characteristics of single-phase Sinusoidal Pulse Width Modulation (SPWM) inverter in the output voltage and its suppression methods. According to the SPWM principle and Fourier series theory, the mathematical model and simulation of the output voltage of the SPWM inverter are established, and the harmonic characteristics of the SPWM inverter are analyzed. Secondly, the harmonic content and distribution of the output voltage under three different carrier control methods are investigated. Then, two effective methods for suppressing the harmonics of the output voltage of single-phase SPWM inverters are investigated: selecting the appropriate carrier ratio and injecting the proper number of harmonics. Finally, the study shows that a single-phase unipolar frequency doubling SPWM inverter can effectively filter out the high harmonics, making the output voltage waveform smoother and closer to the sinusoidal waveform. This study will have a certain positive impact on the future development of energy-saving power supply, high-quality power supply, and high-performance power supply technology in China, which can realize the efficient and low-pollution use of electric energy.

A new 9-level quadruple boost inverter for grid integration

Abstract This paper presents a novel reduced switch multilevel inverter based on switched capacitor technique for grid integration. It generates nine-level output voltage waveform with only 10 switches. It is suitable for high gain applications since it has a boosting ability of four times. Another feature is that the capacitors have built-in self-voltage balancing. The level shifted pulse width modulation (LSPWM) technique is used to explore the performance of the proposed topology. To determine its optimal performance, the suggested topology is compared to the state-of-the-art topologies in the literature. Simulation of the proposed topology is done under different parameter variations. Further, the thermal design of the proposed topology is done using PLECS software to find the efficiency. Finally, the hardware prototype is implemented using dSPACE 1104 controller to verify its performance.

The effects of different pellet shapes on streamer dynamics in patterned dielectric barrier discharges

Abstract Dielectric barrier discharges (DBD) are frequently used for gas conversion for environmental protection by removing harmful components from gas streams and converting them into value added products. DBD operation is typically combined with catalysts placed on spherical dielectric beads in the plasma volume to enhance conversion rates and energy efficiency. However, the presence of such pellets blocks the gas flow and their random arrangement leads to unstable discharges. In this work, we use an advanced plasma source, the patterned DBD (p-DBD), where dielectric pellets are immersed into an electrode at fixed and controllable positions to enhance plasma stability and control. Based on experiments and simulations we study the effects of the pellet shape and the driving voltage on the spatio-temporally resolved dynamics of volume and surface streamers, that ultimately determine the generation of reactive species, plasma-catalyst coupling, and conversion rates/efficiencies via electron heating. The pellet shape is found to influence the streamer speed and the generation of energetic electrons. Via their effects on the effective capacitance of the pellet, shapes with a flatter plasma facing apex are polarized more strongly by approaching volume streamers. This results in a stronger local enhancement of the electric field at the apex, higher volume streamer speed, and more electron heating at this position. Depending on the surface topology maximum electron impact excitation of the background gas is observed at different locations along the pellet's surface. Changing the polarity of the rectangular driving voltage waveform provides control of the direction of positive/negative streamer propagation and selectivity towards anode or cathode directed streamer movement.

Dielectric Barrier Discharge Reactors for Plasma‐Assisted CO2 and CH4 Conversion: A Comprehensive Review of Reactor Design, Performance, and Future Prospects

Dielectric barrier discharge (DBD) plasma is a promising technology for catalysis due to its low‐temperature operation, cost‐effectiveness, and silent operation. This review comprehensively analyzes the design and operational parameters of DBD plasma reactors for three key catalytic applications: CH4 conversion, CO2 splitting, and dry reforming of methane (DRM). While catalyst selection is crucial for achieving desired product selectivity, reactor design and reaction parameters such as discharge power, electrode gap, reactor length, frequency, dielectric material thickness, and feed gas flow rate, significantly influence discharge characteristics and reaction mechanisms. This review also explores the influence of less prominent factors, such as electrode shape and applied voltage waveforms. Additionally, this review addresses the challenges of DBD plasma catalysis, including heat loss, temperature effects on discharge characteristics, and strategies for enhancing overall efficiency.

Comparative Analysis of Analogue and Digital Methods for Magnetic Flux Estimation in the Core of a Medium-Voltage Voltage Transformer Operating Under Ferroresonance Conditions

The main objective of the research described in the article was to determine the following: Is it possible to estimate the magnetic flux linkage in the core of a voltage transformer using analogue or digital methods? Will it be possible to estimate it approximately both in the normal state and in the state of deep core saturation (ferroresonant state)? The research aimed to identify the advantages and disadvantages of both proposed estimation methods. As part of the research described in this paper, a simulation model was developed and executed in the MATLAB/Simulink environment to generate a series of secondary voltage and flux waveforms in voltage transformers. The secondary voltage and flux waveforms were modelled under ground fault conditions, initiating ferroresonance oscillations in the medium-voltage network. To determine the associated flux from the simulated secondary voltages of the voltage transformers, an analogue integration circuit, a voltage analogue input circuit and a numerical integration algorithm with offset elimination were developed and implemented in an STM32 microcontroller. The obtained reference flux waveforms were used to verify the accuracy of the estimation of flux waveforms obtained using the analogue and digital methods. As a result, it was determined that both methods allow for a relatively accurate estimation of the periodic component of the magnetic flux. It also presented how both methods respond to the presence of slowly changing (aperiodic) components. Possible applications were proposed in order to create an innovative criterion for detecting ferroresonance oscillations.

Magnetic nanoparticle detection methods in the context of complex fluids

Foams improve mobility control in injection operations within geological settings. Nanoparticles, such as iron-oxide, have been shown to enhance the stability of foams when combined with surfactants. In this research, we leverage the magnetic properties of these nanoparticles to detect their presence as a surrogate for monitoring the geologic extent of injected fluids in the subsurface. The feasibility of using these nanoparticles for monitoring purposes stems from their detectability at low concentrations in subsurface environments. We developed two distinct methods to detect the presence of magnetite nanoparticles in complex fluids. To simulate complex subsurface fluids in a laboratory setting, we included various ions and surfactants and investigated their effects on the detection of nanoparticles. To this end, we designed an experimental setup and tested two magnetic detection methods: Induction Heating (IH) and Oscillator Frequency Shift (OFS). The IH method involves applying a high-frequency alternating magnetic field to a solution containing small amounts of magnetic nanoparticles and measuring the temperature response. We built an experimental setup to generate this magnetic field for different samples, with temperature changes recorded by an infrared camera. The results indicate that nanoparticle concentrations linearly affect the solution's temperature rise. However, the presence of ions and surfactants also influences the temperature response. The OFS method measures shifts in the resonance frequency of a circuit caused by changes in magnetic permeability inside a coil. This coil is part of a transistor oscillator circuit that produces a sinusoidal voltage waveform, with the oscillation frequency depending on the coil’s inductance. The presence of nanoparticles causes a shift in resonance frequency, which were precisely measured for various samples. The drop in resonance frequency is a linear function of nanoparticle concentration, and both methods detect concentrations as low as 150 mg/L of Fe3O4 nanoparticles.

Ar/CF4 capacitively coupled plasma generated using 40 MHz sinusoidal and 800 kHz rectangular waveform voltages

Abstract This article discusses the characteristics of an Ar/CF4 capacitively coupled plasma (CCP) excited using 40 MHz sinusoidal and 800 kHz rectangular voltage waveforms. The simulations focus on the effect of the low frequency (LF) rectangular wave duty cycle (defined as the period at negative voltage) on the plasma properties and uniformity for constant 100 W power at 40 MHz and 20 mTorr gas pressure. Given the importance of kinetic effects in low pressure CCPs, a hybrid plasma model is used. This model treats electrons as particles using the particle-in-cell formalism while ions and neutral species are represented as fluids. By incorporating electron kinetic effects, this approach allows for the accurate modeling of low-pressure CCPs with complex plasma chemistries. Results show that, at 80% duty cycle, the peak in the density of all species is near the edge of the electrodes. As the LF rectangular wave duty cycle is decreased while keeping the 40 MHz power fixed, the species’ densities increase, the 40 MHz radio-frequency voltage decreases, and the peak in species’ densities shifts towards the chamber center. These trends can be explained based on how the LF voltage modulates the coupling of 40 MHz power to the electrons. Under the conditions considered, the plasma is mostly produced through electron stochastic heating at the sheath edge by the 40 MHz voltage. The 40 MHz couples to the electrons more efficiently when the LF voltage at the powered electrode sheath is small and the sheath is thin. The plasma is produced relatively uniformly in the inter-electrode region during this phase. Therefore, at small duty cycles when the powered electrode sheath is thin for a long time, the plasma is uniform and requires a smaller 40 MHz voltage to deposit 100 W at 40 MHz in the plasma. When the LF voltage in the powered electrode sheath is large and negative, plasma production is weak and occurs at the edge of the powered electrode where the sheath is thinner. At large duty cycles, the plasma is efficiently produced for only a short period, necessitating a larger 40 MHz voltage. The plasma density also peaks near the electrode edge at large duty cycles.

Advances and Perspectives in Multilevel Converters: A Comprehensive Review

In contemporary power electronics, multilevel converters stand at the forefront of high-power, high-voltage applications, offering superior performance in terms of efficiency, reduced harmonics, and improved voltage waveform quality compared to traditional two-level converters. Their capability to synthesize waveforms with multiple voltage levels has garnered significant attention across various industrial sectors, including renewable energy systems, electric vehicles, and high-voltage power transmissions. This paper provides a comprehensive overview of multilevel converter technology, encompassing their classification, main topologies, recent advancements, and emerging trends. By exploring the evolution of multilevel converter technology and identifying future research directions, researchers and engineers can gain valuable insights into the design, optimization, and application of these advanced power electronic systems.

Insights on bacteria inactivation in water by cold plasma: Effect of water matrix and pulsed plasmas waveform on physicochemical water properties, species formation and inactivation efficiency of Escherichia coli

This study investigates the inactivation of Escherichia coli (E. coli) using pulsed dielectric barrier discharges (DBDs) powered by high-voltage nanosecond and/or microsecond pulses to establish optimal operational conditions. The effects of pulse voltage waveform and water matrix (distilled vs. tap water) were evaluated in terms of inactivation efficiency and energy consumption, along with the generation of reactive oxygen and nitrogen species (RONS). Complete E. coli inactivation (9-log CFU/ml) in distilled water was achieved within 20 min of nanopulsed-DBD treatment, coinciding with rapid acidification, while in tap water, 90 min was required for complete inactivation. Interestingly, at treatment times with similar pH levels between water types, E. coli inactivation was more effective in tap water. Ozone concentrations showed the most significant difference, being ∼6 times higher in distilled water (10.3 mg/L) than in tap water (1.7 mg/L). Although distilled and tap water had similar concentrations of short- and long-lived plasma species, the differing inactivation efficiencies indicate a synergistic effect between pH reduction and reactive species in impairing E. coli functionality. Micropulsed-DBD led to increased concentration of plasma species, faster acidification and inactivation in tap water (complete inactivation within 8 min), but at significantly higher electrical energy per order (56.9 kWh/m3 compared to 17.4 kWh/m3 for nanopulsed-DBD). The lowest energy per order was recorded for nanopulsed-DBD in distilled water, at 3.8 kWh/m³, highlighting pulsed-DBD plasma as a safe and energy-efficient method for water disinfection. This study offers valuable insights into using an innovative, sustainable plasma-based approach for bacterial inactivation.