Decrease In Voltage Research Articles

Dielectric and electrical properties of liquid crystals doped with ferroelectric nanoparticles

ABSTRACT The present work examines the impact of incorporating ferroelectric Ba0.85Sr0.15TiO3 nanoparticles (NPs) on the thermodynamic, dielectric, electrical, ionic, and electro-optical properties of 4-cyano-4’-octylbiphenyl (8CB) as Liquid Crystal (LC). The introduction of ferroelectric NPs results in a notable elevation of the nematic-isotropic phase transition temperature, which is consistent with theoretical models. Impedance spectroscopy was employed to investigate bulk and interfacial phenomena, revealing a low-frequency relaxation mode attributed to space charge polarisation. In comparison to the pure LC, the dielectric anisotropy and the DC conductivity were found to be increased in the doped samples. Furthermore, the reduction in the concentration of ions on the surface, their diffusion constant, and their mobility, coupled with a decrease in the threshold voltage, simultaneously indicate the trapping of ions by the ferroelectric NPs. The screening effect renders dispersed ferroelectric NPs an optimal solution for addressing the issue of ionic contamination and eliminating its deleterious effects.

Research of the distribution symmetrical components in an electrical system with a diesel generator at an unsymmetrical load

Purpose. Investigation symmetrical components of current and voltage in microgrid elements with an autonomous synchronous generator of limited power, which works in parallel with a network transformer under the condition of non-metric load. Methodology. During the research, visual programming methods were used in the Simulink/Matlab package, methods of electrical engineering theory in terms of determining symmetrical component currents and voltages in observation branches, methods of synthesizing schemes for replacing elements of electric power systems for symmetrical component currents, methods of data processing and construction diagrams using specialized software tools.. Findings. As a result the analysis known studies, it was established that under the condition of researching low-power generating systems in conditions of asymmetry, insufficient attention is paid to the nature of the asymmetric load. Using the well-known structure of a microgrid, which includes a synchronous generator, a machine load, and an external network transformer, its model was built, in which, by introducing asymmetric loads of various types, a series of experiments was implemented with the registration of voltages and currents of forward, reverse, and zero sequences in the branches of the network. The analysis of the results obtained during the research established that the positive sequence voltage in the case of a change in the active load does not change its level, under the same circumstances, in the case of an active-capacitive and active-inductive load, the voltage change has the opposite character. In the case of increasing asymmetry of an active-inductive nature, the positive sequence voltage decreases, and in the case of an active-capacitive one, it increases. The specified changes in some cases exceed 3%. Positive sequence currents in the case of active load imbalance differ slightly. In the case of a positive sequence current of the transformer, its continuous growth is observed, which in the case of active-capacitive and active-inductive loads exceeds the active one by an average of 1.5 times. Negative sequence currents in the studied model, which are formed by an asymmetrical load, are completely closed to the transformer, causing zero-sequence voltages, and the nature asymmetrical load significantly affects the value of these currents, a 61% increase was noted. Originality. It was established that in a microgrid, which includes a synchronous generator, a machine load, a symmetrical active load of comparable power to the generator, an external network transformer, in addition to the fact of asymmetry caused by an asymmetrical load, the character of an asymmetrical load (active, active-inductive or active-capacitive). Practical value. In the case of using in microgrids devices that provide an increase in the quality of electrical energy, for example, symmetrical devices, it is necessary, in addition to the asymmetry factor, to take into account the natural load that causes the latter.

The relationship of voltage variations in the third quadrant and the Schottky area ratios in a 4H-SiC SBD-embedded MOSFET

Based on the measured and the TCAD simulation results, this paper provides a detailed description of the third quadrant characteristics of the Schottky barrier diode (SBD) embedded MOSFETs with different Schottky area ratios of 2.6 %, 5.3 %, and 14.7 %. As the Schottky area ratio increases, the shift of the third quadrant turn-on voltages of the MOSFETs influenced by the gate voltage decreases. The shift rates in the conventional MOSFET and SBD-embedded MOSFETs are from 57.2 % to 0 % when Vgs changes from 0 V to −4 V. The shift rate becomes 0 % when the Schottky area ratio is larger than 5.3 %. Simultaneously, the TCAD simulation results and the measured results indicate that the SBD-embedded MOSFETs can effectively suppress the conduction of the low barrier diode and the body diode.Furthermore, the SPICE models were built to explain the physics mechanisms. The fitting error between the measured and fitting results is as low as 1.3 % among the models with the different Schottky area ratios.

The Influence of Rapid Heat Treatment During the Formation of Aluminum-Polysilicon Contacts on the Electrical Parameters of CMOS Microcircuits

The influence of rapid heat treatment (450 °C, 7 s) on the electrical parameters of CMOS integrated circuits during the formation of ohmic contact between aluminum metallization and polysilicon is considered. The following volt-ampere characteristics of the dependence of drain current on voltage were chosen as the analyzed parameters of n- and p-channel transistors: at the gate when diode-connected; on the drain at different gate voltages; on the drain in the channel breakdown mode without applying potential to the gate. A comparison of these parameters was carried out with respect to microcircuits manufactured using standard technology (450 °C, 20 min) to form these contacts. Analysis of the results showed that the use of rapid heat treatment to form an ohmic aluminum-polysilicon contact can significantly improve the above characteristics of n-MOS and p-MOS transistors. From the current-voltage characteristics of n- and p-channel transistors it follows that in the region of gate voltages greater than 0.65 V, the drain current after long-term heat treatment is higher than after quick heat treatment. Analysis of the current-voltage characteristics of the drain current versus the drain voltage showed that the drain current when using long-term heat treatment is significantly higher than after rapid heat treatment. In this case, for long-term heat treatment, there is a decrease in the channel breakdown voltage only for n-channel transistors and an increase in the drain current in the region of more than 5 V for both n- and p-channel transistors. Such improvements occur by eliminating the formation of polysilicon conglomerates in the aluminum contact, significantly reducing the epitaxial recrystallization of silicon doped with aluminum on the silicon surface, as well as reducing the microrelief of the interface of this contact and reducing the growth in the size of contact windows due to the lateral interaction of aluminum with polysilicon.

High-precision silver electrode based on PEN substrate with robust mechanical performance

Wearable electronics are becoming more and more popular, and in order to ensure the safety and accuracy of wearable electronics, the requirements for the refinement and stability of flexible electrodes are getting higher and higher. The reduction of the amount of ink jet and the reduction of surface charge density and electrostatic stress near the nozzle hole can significantly improve the jetting state of the ink. And nozzle voltage is a key factor that affects them. The spreading of ink droplets on the substrate and the formation of a specific pattern is a dynamic process, which is closely related to the properties of the substrate and the state of the ink droplets. In this paper, PEN is used as the substrate to print silver electrode, with its good thermal stability and good mechanical properties. In order to solve these problems and improve the accuracy of the electrode pattern on PEN substrate, a joint control method of ink drop spacing and nozzle voltage is proposed. It is found that the accuracy of the pattern increases with the increase of the drop spacing. At 45 μm, 90.91 % of the pattern accuracy with the ideal pattern can be achieved. As the nozzle voltage decreases, so does the satellite spot. And at 25 V, it can achieve satellite-free spot printing. Because this method avoids the adjustment of ink properties and the regulation of voltage waveform, this advancement provides a simpler solution for patterned high-precision printed silver electrodes based on flexible substrates. In addition, a silver electrode with a resistivity of 3.43 μΩ·cm was obtained at an annealing temperature of 160 °C. The resistivity change of the electrode only 7.58 % under 5000 times of bending. This is very rare in flexible electrodes.The silver film on the PEN substrate exhibited excellent adhesion under the tape test. XPS depth profiling was used to characterize the elemental states of the films at different depths. The results indicated that the coordination bond between the PEN substrate and the Ag film resulted in good bending resistance, which gives a persuasive explanation for the first time. This result is also due to the precise handling of the film, which also results in a homogeneous distribution of the film. It solves the problem of poor adhesion of silver electrodes based on other substrates or other preparation methods. Therefore, silver electrodes based on PEN substrates have a broad application prospect in the field of flexible wearable electronics.

Local calcium chloride infusion after pulsed field ablation enhances acute efficacy of cardiac electroporation.

Pulsed field ablation (PFA) has emerged as an innovative therapy for cardiac arrhythmias. Drawing parallels with PFA's application in solid tumors, calcium chloride (CaCl2) as an adjuvant therapy, known as calcium electroporation, may amplify PFA's apoptotic effects. We propose that PFA in the atrium could enhance calcium uptake through PFA-created pores, thereby increasing ablation efficacy even at reduced power levels by exploiting PFA's permeabilization effects. We conducted in vivo ablations on the atria of seven pigs using low PFA power (250 V, 20 μs for 50 pulses at 200 ms intervals). Post-PFA, we randomly administered an infusion of either 200 mg/2 ml CaCl2 (calcium group) or saline (control) directly to the ablation site via the catheter tip. We evaluated reduction in electrogram voltage amplitude, electrocardiography (ECG) parameters, ablation lesion parameters, and histology after PFA. Nineteen lesions from control and calcium groups were examined. Control lesions showed no voltage decrease post-PFA, whereas calcium-treated lesions exhibited a significant voltage reduction. Gross pathology indicated marked differences in maximum lesion surface diameter, depth, and volume between the lesion groups. Histologically, calcium group lesions were characterized by a more severe acute PFA response with contraction band necrosis, myocytolysis and nuclear pyknosis in adjacent myocardium, in addition to microhemorrhages. Infusing calcium chloride locally after PFA markedly improves the immediate efficacy of electroporation in porcine atria. This study suggests that calcium electroporation could bolster PFA outcomes without higher energy levels, potentially diminishing associated risks. These preliminary findings warrant further research into the long-term efficacy and potential clinical application of calcium electroporation in PFA.

Modelling nematic liquid crystal in fractal dimensions

In this paper we present a fractal Berreman's model which account for azimuthal surface anchoring of nematic liquid crystals which play a leading role nowadays in biomedical field and pharmaceutical controlled release dosage forms. The model is based on the concept of "product-like fractal measure" in anisotropic media which permits to describe liquid crystals formation in terms of fractal dimensions. It was observed that fractal dimensions affect both the polar azimuthal angle and the Franck excess elastic energy density of the distortion. For fractal dimensions close to unity, our analysis reveals the emergence of fluctuations and large deformations in the dynamical variables of the theory which suggest the presence of non-linear elastic instabilities or emergence of defect structures in liquid crystals. These fluctuations fade away for fractal dimensions much less than unity. We have evaluated the elastic energy per unit of area which is found to depend on the square of the fractal dimension. This leads to a decrease of the saturation voltage which is necessary to reduce the elastic energy of liquid crystals films in order to minimize the elastic energy. This reduction may describe nematic liquid crystals free from deformations, singularities or weak anchoring surfaces.

Revealing the flashover mechanism of EP/GF composite insulation under DC combined harmonic voltage

Abstract In ultra-high voltage converter stations, the phenomenon of flashover along the outer insulation of dry hollow reactors made of epoxy/glass fiber composites poses a potential threat to the stability of the power system. To enhance its flashover performance under varying complex conditions, it is necessary to conduct in-depth research on the flashover mechanism of this material under different voltage forms. This study conducted tests on the flashover voltage, surface space charge distribution, and partial discharge parameters under varying AC-DC ratios and AC frequencies, and exploring their relationships. The results show that the DC content in the AC-DC ratio decreases, the flashover voltage decreases, the apparent total discharge of partial discharges increases, and the maximum surface space charge density decreases. The main influencing factor is the increase in the number of seed charges involved in gas ionization. Increasing the AC frequency, the flashover voltage decreases, the apparent total discharge increases significantly, and the surface charge density remains basically unchanged. The main reason is that the change in the number of alternating cycles further increases the number of seed charges. This study reveals the flashover mechanism of epoxy/glass fiber composites under different voltage forms, which provides theoretical support for subsequent material modification.

Analysis and design of voltage-source parallel resonant class [formula omitted] inverter

In this paper, a detailed mathematical analysis process of the voltage-source parallel resonant (VSPR) class E/F3 inverter at 50% duty ratio is proposed. Combining the advantages of VSPR class E and F inverters, the performance of the proposed inverter can be improved greatly compared to the traditional. The transistor in the VSPR class E/F3 inverter is satisfied with zero-voltage switching(ZVS) and zero-voltage derivative switching(ZVDS) conditions. Moreover, two design freedoms can be obtained and the proposed analysis process is based on them, which can provide more flexible selections. Finally, a VSPR class E/F3 inverter is fabricated and the experiment is carried out. The measured normalized peak transistor voltage decreases by 25.6%. The output power reaches 5.06 W, and the efficiency reaches 93.75%. The measured results are well agreed with the theoretical and simulated.

One-dimensional lepidocrocite titania mesoparticles integrated with activated carbon for high-performance supercapacitor applications

Herein, we mix titania-based, TiO2, porous mesostructured, comprised of one-dimensional lepidocrocite nanofilaments, 1DLs, ≈ 5 × 7 Å2 in cross-section, with activated carbon, AC, to create unique composite structures with exceptional electrochemical properties. The synthesis method is facile, cost-effective, and scalable. While the porous mesoparticles, PMs, possess excellent protonic conductivity and exhibit enhanced faradic behavior in acidic aqueous media, their low electronic conductivity restricts their power output. The problem is solved by mixing the PMs with AC powders with various loadings. Electrolytes used were sulfuric acid, H2SO4, potassium hydroxide, KOH, lithium and Na-sulphates. The best PM loading was found to be 25 wt%. The resulting composite exhibits a specific capacitance (capacity) of 1024 Fg−1 (554 mAhg−1) at a 2 mVs−1 scan rate, with 97 % cyclic stability over 10,000 cycles when the electrolyte was 1 M H2SO4. Upon integration into a symmetrical device, the composite exhibited a specific energy of 135 Whkg−1 at 0.5 Ag−1. Further, it demonstrated a peak specific power of 18 kWkg−1, while retaining a specific energy of 54 Whkg−1 at 5 Ag−1. Notably, following 100,000 cycles at 1 Ag−1, the symmetrical cell sustained approximately 50 % of its initial specific capacitance. Subsequently, a 24 h self-discharge test revealed a decrease in cell voltage from 1.95 V to 0.48 V, thereby highlighting the potential suitability of these supercapacitors for short-term energy storage applications.

Dynamic performance analysis of proton exchange membrane fuel cell in marine applications

To investigate the dynamic characteristics of proton exchange membrane fuel cells (PEMFCs) on maritime vessels, a lumped-parameter model for the PEMFC systems was developed based on a hybrid vessel propulsion systems model. Simulations and analyses of the dynamic characteristics of PEMFCs were conducted under typical sailing conditions. The results reveal a noticeable hysteresis in the operating temperature of PEMFC stacks during vessel voyages, with a delay of about 25 s, leading to significant overvoltage in activation, ohmic, and concentration differences. Significant variations in vessel loads can cause large fluctuations in the component gas pressures in the cathode and anode flow paths within 16.6–19.8 kPa and 78.57–93.06 kPa, respectively. A comparison of different humidification levels for cathode and anode gases demonstrates that, at the same moment, as the humidification of cathode and anode gases increases from 20 % to 100 %, the water content in the proton membrane increases from 2.29 to 13.47, the ohmic impedance decreases from 1.35 mΩ/cm2 to 0.174 mΩ/cm2, and the overshoot of the fuel cell voltage decreases. The output delay decreases from 25 s to 8 s, enhancing overall fuel cell performance. These findings are significant for optimizing the design, performance, and real-time control of marine PEMFC systems.

Enhancing PEMFC performance at high current density by incorporating PTFE emulsion into catalytic layer

Mass transfer is a critical bottleneck in the development of proton exchange membrane fuel cells (PEMFCs), especially at high current densities. This study aims to enhance the power density, stability, and durability of the PEMFC by modifying the catalyst layer (CL) with polytetrafluoroethylene (PTFE). The influence of varying PTFE contents in CL was assessed through polarization curves, mass transfer resistance (Rmt), and oxygen transfer resistance (OTR) tests. The optimal performance was achieved with MEA4 (with 40 % PTFE), demonstrating a power density of 847 mW/cm2 at 1700 mA/cm2, an 8 % increase compared to MEA0 (without PTFE) at 75 °C. The Rmt of MEA4 decreased to 0.1148 Ω cm2, a 55 % reduction from MEA0 (0.2522 Ω cm2). A stability test at 1600 mA/cm for 5 h showed MEA4 maintaining a stable voltage at 0.527 V, while the MEA0 exhibited a linear voltage decrease of 0.04 mV/min with significant fluctuations over time. Accelerated stress testing (AST) is conducted under the DOE standard by 2000 voltage cycles with a triangle sweep voltage from 1.0 V to 1.5 V, which revealed that the OTR of the MEA0 increased by 37 % from 0.7198 s/m to 0.9914 s/m, whereas the MEA4 was observed to be increased from 0.74707 s/m to 0.8253 s/m with a rise of 10.5 %. In conclusion, the incorporation of PTFE into the CL enhances oxygen transfer within the CL, thus improving the power density, stability, and durability of PEMFCs at high current density.

Degradation mechanism of SiC diodes under thermal and irradiation stress

Abstract Silicon carbide (SiC)-based diodes are widely used due to their high temperature resistance. In this paper, breakdown voltage of 4H-SiC JBS diodes and capacitance-voltage of 4H-SiC MOS capacitors with identical interfacial structure were both measured at high temperature to study their interfacial properties. By analyzing the variation of interfacial properties, the correlation between thermal stress and failure mode of 4H-SiC JBS diodes was further established to reveal their degradation mechanism. During initial high temperature storage, interfacial negative effective charge density of 4H-SiC JBS diodes may increase, leading to the decrease of breakdown voltage. As storage time increases, interfacial charge density began reducing, resulting in the increase of breakdown voltage. Avalanche luminescence verifies that the variation of interfacial charge density under thermal stress led to the degradation of 4H-SiC JBS diodes and further affected their breakdown voltage. Finally, degradation mechanism of SiC-JBS, SiC-SBD and SiC-PIN diodes under irradiation stress was investigated. After irradiation, forward current of some SiC diodes increased at a small forward voltage. However, the reverse characteristics deteriorated obviously and even failed.

Полевая электронная спектроскопия молекулярно-напыленного оксидного термокатода

The results of a study of the emission characteristics of a molecular-sprayed oxide thermocathode based on triple carbonate of alkaline earth metals with an emission layer thickness of ~1 µm in the operating temperature range of 590-730 °C. are presented. The results are in good agreement with those obtained earlier for a serial oxide thermocathode with an emission layer thickness of ~100 µm applied by pulverization, and correspond to the model of a "spotted cathode" - a superposition of emission spots at different stages of activation. An idea of the activation phenomenon occurring at a given temperature in a certain range of values of the electric field strength on the surface of emission spots is detailed both with an increase and a decrease in the anode voltage. The energy spectra of the emitted electrons of a separate emission spot with a half-height width of ~100 meV have been obtained. The values of the potential change of the emitting surface of the cathode within the probed region of 0.9 V and the potential drop on the emission layer under the probed region of 4.1 V were measured.

Q-EDR Hybrid Boost Converter Operation For High Gain With Low Device Stress

Abstract: The hybrid continuous-discontinuous mode (CCM-DCM) operation of non-isolated systems is proposed in this paper. boost converter with quadratic extended duty ratio (Q-EDR) for applications with high gain and low power. The inductors at the input while the EDR was in continuous conduction mode (CCM) The mode of operation of stage inductors is discontinuous conduction. (DCM) in order to reap the advantages of CCM and DCM operation. Interleaving's ripple in the low input current and low voltage The EDR stage switches' stress remains. With what is being half and half method of activity, the inductance worth of EDR stage significant decrease in the inductor. an additional decrease in switch voltage is accomplished during turn-on progress in the proposed activity, prompting huge decrease thus on exchanging losses. This lets the converter run at higher switching speeds. frequency, thereby reducing EDR inductors' size by 45 percent in this instance an experiment confirms the proposed idea. Simulink prototype for a two-phase Q-EDR operating at 30 V-40 V to 400 V output, a gain of more than 12 at duty close to 0.54. The converter has a peak efficiency of 95.5 percent. at a switching frequency of 135 kHz and 300 W for all silicon switches.

Comparison of the effect of different external electrodes on discharge plasma-assisted diffusion flame stabilization

To optimize the design of plasma injectors, the influence of different external electrodes on plasma-assisted flame stabilization was assessed by using a nonequilibrium plasma injector flame control setup. The electrical characteristics of the injector, flame structure parameters, flame intensity, discharge power, and cost-to-effectiveness ratio under different external electrodes (four mesh electrodes and one copper foil electrode) were analyzed using electrical and optical methods. The results show that reducing the mesh size of the external electrode leads to a decrease in breakdown voltage. Compared with a ceramic dielectric barrier-based injector, an injector with a quartz dielectric barrier produces a higher breakdown voltage under the same conditions. For the same actuation voltage, the discharge current increases as the mesh size of the external electrode decreases, and combustion is enhanced by the discharge plasma; therefore, it is better to adopt a smaller mesh hole size to realize good flame stabilization under a lower actuation voltage. However, under the studied working conditions, reducing the mesh hole size of the external electrode increases the cost-to-effectiveness ratio of plasma injector-based flame stabilization. Thus, considering the cost-to-effectiveness ratio and the weight of the injector, an external electrode with a larger mesh hole size should be chosen, which contradicts the above rule.

Electrical Properties and Reliability of AlGaN/GaN High Electron Mobility Transistor under RF Overdrive Stress at High Temperature.

We have investigated the electrical properties and reliability of AlGaN/GaN high electron mobility transistors (HEMT) under high-temperature RF overdrive stress. The experimental results show that the drain current and transconductance of the device decrease at 25 °C and 55 °C but do not change significantly at 85 °C before and after the stress. The decline rate of the saturation drain current, the degradation amplitude of transconductance, and the drift amplitude of threshold voltage decrease with the increase in temperature. The results of pulse I-V and low-frequency noise tests show that the current collapse is inhibited, and the trap density is reduced at higher temperatures. The Electroluminescence (EL) test shows that the luminescence characteristics of the device after RF overdrive stress are more scattered and weaker. We believe that the degradation at lower temperatures is mainly due to the influence of the hot electron effect (HEE), while the change in electrical properties at higher temperatures is due to the weakening of HEE and the improvement of the Schottky interface.

Development of a Low-Cost Data Acquisition System for Analyzing the Health of a Photovoltaic System

In recent years, fault diagnosis has become a major concern for ensuring the sustainability of photovoltaic systems. This article aims to develop a low-cost data acquisition device based on the Arduino card to collect data using sensors on two photovoltaic modules. Four defects were intentionally created on a photovoltaic panel and analyzed individually based on the evolution of current and voltage parameters over time. The results indicate that in the event of a fault, the current drops suddenly with a slight decrease in voltage. Under normal conditions, the maximum observed current was 3.8 A for an irradiation of 904 W/m2, compared to 2.2 A for 909 W/m2 and 32.78°C in the event of partial shading. This value further decreases to a maximum of 1.8 A for 867 W/m2 in an open circuit. The observation reveals that the partial shading fault with a disconnected bypass diode and open circuit has similar characteristics to the open circuit fault. However, it is important to note that this cannot be generalized as the fault only occurs in a configuration of two PV modules in parallel.

Removal of livestock odor gas ammonia, hydrogen sulfide, methanethiol by electron beam in a continuous flow system

Odor is becoming one of the serious environmental issues as the industry develops. Electron beam technology has recently attracted attention as an AOP (Advanced Oxidation Process) for air purification, water treatment, and soil remediation. This work studied the removal of major livestock odor such as ammonia (NH3), hydrogen sulfide (H2S), and methanethiol (CH3SH) using a continuous gas flow electron beam treatment process. The effects of initial odor gas concentration, type of background gas, absorbed dose of the electron beam, voltage of the electron accelerator, and odor gas flow rate on the removal of odor gas were all studied in this continuous gas flow treatment system. As the absorbed dose of electron beam was increased, the removal efficiencies of odor gases NH3, H2S, and CH3SH all increased gradually. As the initial concentration of odor gas was decreased and as the flow rate of odor gas was increased, the removal efficiencies also increased. Regarding background gas, the odor gas removal efficiency was found to be in descending order of O2 > air > N2. The lower the voltage (MeV) of the electron beam, the higher the odor gas removal efficiency. This was attributed to the fact that, to set the same absorbed dose (kGy), as the voltage decreases, the current value (mA) increases. For the byproducts, as the absorbed dose of electron beam was increased, the concentration of byproducts increased. Regarding the gas-phase continuous electron beam treatment reactions, the optimal operating conditions must be derived by considering various operational variables, including the initial concentration, electron beam dose, background gas type, gas flow rate, and electron beam voltage. The results of this study show that, among several possibly relevant variables in removing odor gases in the continuous flow electron beam irradiation process, the current value can be considered one of the most important variables, along with the initial concentration and background gas.

An improved CB-DPWM strategy with NP voltage balance and switching loss reduction for 3-L NPC converter

Abstract The three-level (3-L) neutral-point-clamped (NPC) converter has found widespread applications in various fields, due to its simple structure, low failure rate and high efficiency. However, the 3-L NPC converter suffers the issue of unbalanced neutral-point (NP) voltage due to the divided two dc-side capacitors. The large NP voltage ripple and offset Based on the detailed analysis of the effects of vectors and clamping patterns on the NP voltage, a discontinuous optimized modulation method for NPC grid-connected inverter with both low switching loss and ability to balance NP voltage is presented. By measuring NP voltage and utilizing the property that superfluous clamping patterns have opposing effects on the NP voltage, the modulation method adjusts the NP voltage with the injection of various zero sequence voltages (ZSV) into the original sinusoidal waves. The results of this study demonstrate that the CB-DPWM can control the NP voltage balanced and decrease switching loss compared to conventional DPWM and SVPWM strategies. Moreover, the CB-DPWM strategy does not need to identify sectors and subsectors or calculate dwelling times. This modulation strategy effectively suppresses low-frequency fluctuations and deviations of the NP voltage with the injection of a simple ZSV, and improves the power quality of the output voltages and currents. Compared to the traditional SVPWM scheme, the suggested CB-DPWM has a 27 % lower overall IGBT loss. Moreover, this method is implemented through carrier waves, which is simpler than modulation schemes based on space vector, greatly shortens the program running time, and is conducive to engineering implementation.