Rear Side Research Articles

Energy Flow during Baseball Machine Hitting.

The primary aims of the study were to perform a descriptive analysis of hitting energetics off a pitching machine and to compare between the rear- and lead-side lower and upper extremities. Eighty-five high school to minor league baseball athletes participated. Five full-effort swings off a pitching machine with the fastest exit velocity were used for analysis. Energy flow was quantified using a segment power analysis. Wilcoxon signed-rank test revealed significant differences between rear- and lead-side energetics during both swing phases. During the stride, the rear knee and shoulder generated more energy than the lead side. Throughout the swing phase the lead knee, hip, and elbow generated more energy than the rear side, but at the shoulder the rear side generated significantly more energy than the lead. Most intriguing, differing energy transfer directions between the rear and lead knee and shoulder joints were reported. Furthermore, descriptive results revealed energy is predominantly transferred across the knee, shoulder, and elbow joints, while the hips primarily display energy generation. The descriptive nature of the study provides a foundation for future research and can be used as a resource for training personnel to design effective training protocols aimed at maximizing performance.

The change of the absorptance at the transition from partial- to full-penetration laser welding

Full-penetration laser welding processes are necessarily associated with significant changes of the geometrical properties of the keyhole at the beginning of the process when the keyhole expands all the way through the workpiece and finally pierces the bottom of the sheet. The impact that this transition has on the absorptance was investigated by means of X-ray imaging to determine the geometry of the keyhole and subsequent raytracing to calculate the distribution of the absorbed irradiance. The results show a significant drop of the overall absorptance when the bottom of the capillary opens through the rear side of the workpiece which in practice is noticed by an unstable behavior of the keyhole. Since the drop of the absorptance is less pronounced for smaller diameters of the keyhole, one may recommend the application of laser beams with small diameters at least during the initial phase until the keyhole is fully developed and reliably reaches through the bottom surface of the welded sheet.

TCAD simulation of germanium-based heterostructure solar cell employing molybdenum oxide as a hole-selective layer

Molybdenum Oxide (MoO x ) has been used as a hole-extraction film for photovoltaic (PV) applications; however, its interaction with Germanium (Ge)-based solar cells is less understood. For the first time, this paper aims to physically model the Ge solar cell that incorporates MoO x for hole transportation at the front side of the PV device facing the sunlight. However, the charge transportation process within the PV device is influenced by several design parameters that need optimization. A higher work function of MoO x increases the barrier height against minority carriers of electrons which is beneficial for extricating holes at the front interface of MoO x /Ge. A progressive reduction in the recombination of charge carriers has been observed by including a passivation layer of amorphous silicon (i-a-Si:H). Similarly, inserting a passivation and back surface field (BSF) stack of i-a-Si:H strengthens the electric field and likewise reduces the recombination at the rear side of the device. An enhanced doping concentration of BSF assists in the favorable alignment of energy bands for improved charge transportation within the solar cell as the rear passivation maintains the field strength for accelerated movement of charge carriers. However, optimizing the thickness of the front-passivation film is challenging due to the parasitic absorption of light at larger thicknesses. A comparative study with the reference device revealed that the proposed device exhibited a step-increase in the conversion efficiency (η) from 4.23% to 13.10%, with a higher J sc of 46.4 mA cm−2, V oc of 383 mV, and FF of 74%. The proposed study is anticipated to meet the research gap in the physical device modelling of Ge-based solar cells employing high work function MoO x as a carrier-selective layer that could be conducive to the development of highly efficient multijunction solar cells.

Mechanism of temporal interface evolution and internal circulations during the droplet formation in a planar slit T-microchannel

The present study has numerically explored the mechanism of interface evolution and internal flow circulations during the droplet formation in two-phase flow through a planar T-microchannel. The two-dimensional unsteady form of the conservative level set equation coupled with Navier–Stokes equations has been solved using the finite element method. The range of parameters include the contact angle (θ) from 120° to 180°, and the flow rate ratio (Qr) from 0.1 to 10 for the low capillary number (Cac≤10−2). The present study indicates that surface wettability plays a crucial role in influencing the temporal evolution of the interface. The internal flow circulation in the droplet is controlled by the axial and radial velocities primarily influenced by shear stress. The newly introduced novel “interface-to-neck ratio” parameter has provided another platform to investigate the pinch-off dynamics of droplets. Moreover, the phenomenon of droplet pinch-off is primarily initiated and driven by the Laplace pressure, defined by three distinct approaches: the pressure difference method, the determination of the minimum local radius of curvature on the rear side, and a calculation of the neck width. The predictive correlations have been established to estimate the droplet characteristics as a function of the flow rate ratio and contact angle. The findings reported have significant implications for the design of droplet dispensing systems that depend on surface wettability as a critical regulating parameter.

Electrical and thermal performance of bifacial photovoltaics under varying albedo conditions at temperate climate (UK)

Bifacial photovoltaics (bPV) provide an advantage over their traditional monofacial counterparts as they can utilise solar radiation incident on both the front and rear side of the module, allowing for increased energy production. While this is an advantage on the side of bPV, the amount of energy produced by the rear side of the bPV panel can vary greatly depending on the inclination and azimuth of the panel as well as external climatic and ground albedo conditions. This paper aims to analyse the electrical and thermal performance of bPV under varying albedo conditions, using two different materials: grass, and a reflective material. It also contains an example of bifaciality testing under real-world conditions. Several experiments were conducted to evaluate the electrical performance and the temperature distribution of the bPV panel under different weather conditions at the UK location and then the results were compared with the single diode model of bPV. Furthermore, a bPV panel temperature model has been developed for the temperate climate condition of UK. The results show that the open circuit voltage of the system increases with irradiance up to around 800 W/m2, at which point it decreased due to the increased PV system temperature. The normalised efficiency for the PV system under different conditions were also evaluated, which showed that the bPV module was most efficient under diffuse irradiance conditions, encouraging the use of the bPV technology in the UK.

Bearing capacity of modified suction caissons in clay overlying sand under monotonic horizontal loading

The modified suction caisson (MSC) is an innovative foundation for fixing offshore wind turbines, consisting of an internal caisson (IC) and an external skirt (ES). In this study, the Plaxis3D is conducted on the bearing capacity of the MSC in clay overlying sand under monotonic horizontal loading. The parameters of the aspect ratio of the IC, the size of the ES, the clay thickness, and the soil strength are considered. Results show that the horizontal ultimate bearing capacity of the MSC decreases as the length ratio of the ES to IC decreases. Moreover, the width of the ES enhances the horizontal bearing capacity of the MSC higher than the length of the ES. With the increase of the clay thickness, the rotation center of the TSC and MSC exhibits two and three stage change patterns, respectively. When the clay and sand are the inhomogeneous soils, the horizontal ultimate bearing capacity of the MSC is enhanced by 8.96% compared to the homogeneous soils. Additionally, the passive and active earth pressures around the MSC are mainly generated at the front and rear side of the loading direction, respectively. This study will provide theoretical guidance for the design of the MSC.

High energy neutral atom emission from rear side of foils

Intense laser pulses focused onto a solid micron foil target are best known for generation of large electrostatic sheath fields at the target rear and acceleration of protons to MeV energies. The fact that such acceleration schemes also generate fast neutral atoms has received comparatively less attention. A quantitative assessment of the neutralization fraction reveals novel and often unexpected aspects of electron-ion interaction in regions far from dense plasmas. At the rear side of laser irradiated foil, a few hundred keV accelerated neutral Hydrogen atoms are observed. Neutralisation fraction is much larger than that anticipated from the collisional charge transfer and is about 300% larger for ions of ⩽ 100 keV energy. Corroborated by particle-in-cell simulations, the larger neutralisation fraction is attributed to electron-recombination as the protons co-propagate with the low energy electrons.

Novel cooling system for free-standing photovoltaic panels

ABSTRACT Although photovoltaic (PV) technologies enjoy tremendous benefits and hold the huge potential to lower building overall energy consumption, there is a major drawback. PV efficiency is extremely sensitive to heat and significantly reduced by increasing setting temperature and solar irradiance; thereby, thermal management in PV collectors plays a significant role in generating electrical energy. Using oscillating heat pipes attached to the rear side of PV panels is considered a novel and useful approach to dissipating heat. In this study, a novel cooling system that consists of a newly designed spiral oscillating heat pipe is introduced, while DI water and 0.2 g/l graphene are used as working fluid and PV panels are located at tilt angles of 30° and 60°. The OHP efficiency is higher at 60°; however, the efficiency of PV is maximized at 30° since the panel is exposed to maximum solar irradiance. The research demonstrates that the cooling method proves highly effective, especially in the hottest time of the day and the power output improves considerably from 38 W to more than 42 W at 30°, while the value is about 39.7 W when water is used as a coolant.

Scour at the rear side of rubble mound revetments due to random wave overtopping: Laboratory experiments

This study presents the physical model experiments on the wave overtopping induced bed level changes at an unprotected rear side of a rubble mound revetment with a crown wall. In the experiments, the wave conditions, the backfill material size, and the backfill depth (vertical distance from the crest level to the rear side bed level) are varied. Two mobility parameters, namely the densimetric overtopping discharge and the relative fall velocity, are introduced to represent the initiation of motion and suspension of the backfill material, respectively. The temporal evolution of scour depth at the rear side is related to the mobility parameter, the number of waves and the backfill depth utilizing regression analyses. The effect of the backfill depth on the scour is found very limited for the available data set. However, the time scale of the scour is found to be related with the backfill depth only. For the present data set, it varied within a range of 1500–16000 number of waves approximately, with an average of 5600 waves. An equilibrium scour profile is reached 3 to 4 times the time scale. The geometry of the scour profile is expressed in terms of the scour depth, based on the equilibrium scour profile data.

How will the combining of the elevation of rail lines with urban redevelopment reduce the north–south (east–west) disparity in the city? A case study of Kyoto-Osaka-Kobe conurbation, Japan

Railroads are generally the primary public transportation system connecting the region. However, when a railway crosses a city, it divides it into north-south (east-west), creating the front and rear sides of the city. In Japan, grade separation projects elevate the existing railway lines. The primary purpose is to relieve traffic congestion caused by railroad crossings. However, integrating the north–south axis has also been highlighted. In addition, creating a new centrality to station spheres in mature cities will be an essential guideline for the future formation of an urban structure centered on station spheres by transit-oriented development. This study focused on 12 cases in which an elevated railway line in the Kyoto-Osaka-Kobe conurbation of Japan was combined with an urban redevelopment project. We investigated changes in land use and land prices in the surrounding area. The study results confirmed that the disparity between the front and rear sides tended to shrink. In addition, based on the station's characteristics and area to be redeveloped, a policy for more effective integrated redevelopment and elevation projects was identified. The findings of this study will assist in reorganizing cities into a more sustainable urban structure by eliminating urban fragmentation centered on railway stations.

Design and Optimization of Heat Dissipation for a High-Voltage Control Box in Energy Storage Systems

Abstract To address the issue of excessive temperature rises within the field of electronic device cooling, this study adopts a multi-parameter optimization method. The primary objective is to explore and realize the design optimization of the shell structure of the high-voltage control box, aiming to effectively mitigate the temperature rise in internal components and enhance their thermal management efficacy without altering the fan performance, environmental conditions, or spatial layout. Initially, the study employs computational fluid dynamics methods to investigate the heat dissipation characteristics of the high-voltage control box, subsequently verifying the simulation parameters' accuracy through temperature rise tests. Building upon this foundation, the article conducts a thorough analysis of how the position and shape of the box's openings impact the device's temperature rise. The findings suggest that configuring circular openings on the front and rear sides can optimize the heat dissipation effect. Moreover, the SHERPA algorithm was employed to refine the size and distribution of the openings on the outer shell of the high-voltage control box through multi-parameter optimization, yielding locally optimal structural parameters. Post-optimization, the temperature measurement points within the high-voltage control box exhibited a maximum reduction in temperature rise of 27.16%. The pivotal contribution of this methodology is the application of a data-driven decision-making process for the enhancement of conventional heat dissipation designs. This research offers invaluable practical insights and novel perspectives on the optimization of thermal management designs for box-type electronic devices, significantly advancing the field of thermal management technology in electronic devices.

Passive Control Measures of Wind Flow around Tall Buildings

The growth and diversification of tall buildings demands higher performance standards that encompass serviceability and resilience. In this respect, the control of air flow around tall buildings poses challenges to minimising the energy that could induce large vibrations or forces. The present investigation scrutinises the flow around a tall structure with variations on its surface roughness by adding balconies to the facade, as a form of passive control of the flow loads. This is conducted through flow simulations across optimised computational arrays that capture 3D effects. To illustrate the applicability of the proposed approach, two types of facades rotated 0∘, 90∘ and 180∘ are considered while focusing on pressure and vorticity fields. It was found that the presence of balconies produces zig-zag patterns on the face where they are located, whereas balconies on the front facade reduce drag with respect to the smooth case. Furthermore, buildings with balconies on their lateral faces experience some increase in drag force and the improvement of the aerodynamics around the lateral pedestrian zones. No qualitative variations between triangular and rectangular balconies were found, excepting some changes in pressure magnitude on the rear side induced by balconies placed on the front and rear facades. Through the comparison of results, it was confirmed that the findings align with previous studies undertaken for medium and low-rise buildings. This reinforces the proposal of using such passive control measures to improve the aerodynamic performance of tall buildings. The study enables the quantification of flow configurations and forces on the building’s faces. Some of the proposed passive control measures effectively mitigate pressure levels while causing large local disturbs on pressure and vorticity that should be attended to by designers of this type of facades.

Development of high conducting phosphorous doped nanocrystalline thin silicon films for silicon heterojunction solar cells application

We have investigated the plasma-enhanced chemical vapor deposition growth of the phosphorus-doped hydrogenated nanocrystalline silicon (n-nc-Si:H) film as an electron-selective layer in silicon heterojunction (SHJ) solar cells. The effect of power densities on the precursor gas dissociation are investigated using optical emission spectra and the crystalline fraction in n-nc-Si:H films are correlated with the dark conductivity. With the P d of 122 mW cm−2 and ∼2% phosphorus doping, we observed Raman crystallinity of 53%, high dark conductivity of 43 S cm−1, and activation energy of ∼23 meV from the ∼30 nm n-nc-Si:H film. The n-nc-Si:H layer improves the textured c-Si surface passivation by two-fold to ∼2 ms compared to the phosphorus-doped hydrogenated amorphous silicon (n-a-Si:H) layers. An enhancement in the open-circuit voltage and external quantum efficiency (from >650 nm) due to the better passivation at the rear side of the cell after integrating the n-nc-Si:H layer compared to its n-a-Si:H counterpart. An improvement in the charge carrier transport is also observed with an increase in fill factor from ∼71% to ∼75%, mainly due to a reduction in electron-selective contact resistivity from ∼271 to ∼61 mΩ-cm2. Finally, with the relatively better c-Si surface passivation and carrier selectivity, a power conversion efficiency of ∼19.90% and pseudo-efficiency of ∼21.90% have been realized from the SHJ cells.

Effect of boundary conditions on the low‐velocity impact damage mechanism of fiber metal laminate

AbstractThe boundary condition is a very important factor when characterizing the impact performance of a material or a structure. However, its effect on fiber metal laminate (FML) has been rarely mentioned. In the present investigation, three levels of low‐velocity impact tests were conducted on the glass fiber reinforced aluminum laminate (Glare) under two different boundary conditions, one was that defined in ASTM D7136 and another one was self‐designed that has the same constraint area but different constraint degree. One basis of the experiments, finite element analyses were performed to gain a deeper understanding of the different damage mechanisms. With which another three boundary conditions were investigated for further considering the effect of constraint areas on both the impact and non‐impact sides, including that defined in another commonly used standard ASTM D5628 and two self‐designed cases. It was indicated that the boundary conditions influenced less the force and energy responses of Glare laminate, regardless of the impact damage levels, and hardly on the damage behavior as well when perforation was encountered. However, influences were obtained under lower and intermediate damage levels, and it was the constraint area on the rear side and constraint degree that played the dominant roles, respectively. The results achieved can provide suggestions for reasonably evaluating the low‐velocity impact performance of FML.Highlights Comparisons were made between the low‐velocity impact behavior of Glare laminates under five different boundary conditions. Boundary conditions influenced hardly on maximum impact force and energy absorbed ratio, but evidently on damage behavior. Constraint area and constraint degree governed damage mechanism under lower and intermediate impact energies, respectively. Influence of boundary conditions on damage behavior disappeared when the impact energy was enough to perforate Glare laminate.

Experimental and numerical investigations of tube inserted with novel perforated rectangular V-shape vortex generators

The utilization of punched vortex generators has been established as an effective means to enhance heat transfer in heat exchangers. However, there are few studies on the use of perforated rectangular winglet pairs in heat exchange tubes and the study of perforation parameters based on this approach in the existing literature. In this paper, three parameters, including three height ratios, four perforation indices, and three pitch ratios, are considered experimentally and numerically. In the Reynolds number range of 7454–13,664, the effects of perforated rectangular vortex generator pairs on fluid flow and heat transfer are obtained by scaling parameters such as Nusselt number ratio, friction factor ratio, thermal enhancement factor, field synergy number, entropy generation, and exergy efficiency. The numerical results indicate that the perforation will lead to a reduction in turbulent kinetic energy in the local multi-longitudinal vortices on the rear side of the vortex generator, resulting in a decrease in local heat transfer as well as friction loss. Meanwhile, the pitch of perforated rectangular vortex generator pairs plays a crucial role in heat transfer and friction loss, enabling an increase in the Nusselt number of smooth tubes by 68–257%. Furthermore, the results are proved using the principle of entropy generation and exergy efficiency analysis. As Reynolds number increases, the thermal enhancement factor gradually decreases. Notably, the maximum thermal enhancement factor of 1.43 is achieved when the Reynolds number is equal to 7454, the height ratio is 0.08, the perforation index is 0.18, and the pitch ratio is 1.04.

Optimization of BLDC-based electric vehicles: Vehicle dynamics modelling through dual-motor approach and designing a novel augmented TLBO algorithm for PID control

The work primarily focuses on increasing the efficiency of EV drive in electric two-wheeler by working on several aspects, such as modulating the vehicle’s design, optimizing the control strategy, and increasing the speed range using a dual-motor approach. The dynamics of electric two-wheeler have been discussed with a mathematical vehicle model and further tuning of several aspects. Besides, this paper also introduces a novel Augmented Teaching and Learning based Optimization (ATLBO) technique designed exclusively to control BLDC motors for the electric two-wheeler vehicle. Besides, the designed technique has been implemented for the widely used commercial e-bike of Hero Company. Most two-wheeler electric motors are mounted on the rear side of the wheel, which has a limited speed range. Therefore, an analysis has been performed to increase the vehicle’s speed range using a dual motor, from 45 km hr−1 to 62 km hr−1, proving to be a viable alternative to a single motor generally used in an electric bike. ATLBO technique has been designed against a conventional TLBO to optimize the proportional-integral-derivative (PID) controller for the speed control of a linear brushless DC (BLDC) motor. The proposed method has several advantages, including ease of implementation, a consistent convergence characteristic, and high computational efficiency. Furthermore, the literature has validated the merits of the presented novel control technique. The only disadvantage of using a dual motor is the initial cost, but the overall cost is moderated in the long-term usage for its augmented performance parameters. The performance parameters of the above technique are analyzed against other optimization techniques like conventional Teaching and Learning based optimization (TLBO), Particle Swarm Optimization (PSO). MATLAB/Simulink models the brushless DC motor and implements ATLBO, TLBO, and PSO algorithms. It has been found that the response obtained from ATLBO is comparatively much faster than other optimization techniques, which supports the motor for quick acceleration as well as more efficient in improving the step response characteristics such as rise time, settling time, and steady-state error in the speed control of a linear BLDC motor.

Novel adjustable backflow structure in electric coolant pump for balancing hydraulic performance and reducing temperature rise

An electric coolant pump serves as the source for coolant circulation in the thermal management of electric vehicles. To address the thermal issues for the printed circuit board integrated within the electric coolant pump, a novel backflow structure with an adjustable orifice diameter is designed from the impeller outlet to the printed circuit board to promote convective heat dissipation. Eventually, this flow returns to the impeller inlet, thereby altering the hydraulic performance of pump. The balance between hydraulic performance and temperature rise is achieved by adjusting the orifice diameter. Considering the variations in coolant properties with respect to temperature, numerical simulations of the electric coolant pump are performed using the unsteady compressible Reynolds-Averaged Navier-Stokes Equations. There is good agreement between experimental and numerical simulations results in both cases with and without an orifice. On an average, by increasing the orifice diameter by 1.5 mm which results in a 1.11 % decrease in efficiency, a 0.008 decrease in pressure coefficient, and a reduction of temperature by 2.98 K on printed circuit board. As the orifice diameter increases, leakage losses in the rear side chamber increases with the improvement of heat dissipation. The clash between the backflow jet and the inflow from the suction pipe results in significant entropy generation, forming jet vortices and increasing in pressure fluctuation. However, when the orifice diameter exceeds 3 mm, the cooling advantages no longer justify the trade-off in hydraulic performance. Thus, 3 mm orifice diameter is an optimal compromise between hydraulic performance and temperature control.

CIGS bifacial solar cells with novel rear architectures: Simulation point of view and the creation of a digital twin

The performance of bifacial Cu(In,Ga)Se2 (CIGS) cells does not yet reach the one of monofacial cells, with standard Mo rear contacts. By exploring optoelectronic simulations, this study addresses the impact of a transparent conducting oxide layer used as rear contact in CIGS solar cells. These simulations, which aim to create a digital twin of bifacial CIGS solar cells, offer insight into the impact of novel rear contact architectures. It was observed that with an indium tin oxide (ITO) rear contact the CIGS cell performance lacks in comparison to a Mo one due to an electrical barrier, under rear side illumination these devices may only reach 3.9 % in conversion efficiency. The implementation of dielectric rear passivation schemes have great performance benefits in cells with Mo rear contacts. Therefore, the same passivation strategy in ITO contacts is discussed and additional novel architectures are proposed, from which a design of alternated lines between dielectric and 15 nm Mo layers on ITO showed promising results. Such rear architectures aim to achieve i) a highly transparent rear contact, ii) an ohmic-like behaviour with CIGS, and iii) a low defective interface with rear passivation. The selenization of the complete 15 nm Mo in the proposed novel architecture during the CIGS growth was considered, resulting in transmittance values above 70 % and, notably, reaching the transparency of bare ITO in the infrared range. Such rear architecture may provide for bifacial CIGS solar cells with conversion efficiency values surpassing 20 and 15 % for front and rear side illumination, respectively, allowing to fully exploit bifaciality.

The design of a novel two-dimensional deployable mechanism for large-aperture planar antennas

Large-aperture planar antennas are essential in applications like satellite communication and Earth observation. In order to accommodate them within the constrained storage space of rockets during launch, the development of high-folding-ratio mechanisms becomes imperative. However, most of the existing planar antennas rely on one-dimensional deployable mechanisms, limiting their width and impeding the development of planar antennas with larger apertures. The lack of two-dimensional deployable planar antennas is primarily due to their stringent requirements, including the need for flat reflecting surfaces, regular panel shapes to accommodate electronic devices on the panels’ rear sides and minimal inter-panel gaps. In this paper, we introduce a novel two-dimensional deployable mechanism for the development of large-aperture planar antennas, capable of simultaneously meeting these requirements. Firstly, the architecture of the proposed mechanism and its two-step deployment procedure are described; next, the kinematics on the displacement level are conducted; moreover, a case study is presented to demonstrate its folding performance and frequency response. These studies indicate that the antenna thus obtained can achieve efficient two-dimensional folding while offering a reasonable frequency response, which can be a practical solution for the development of large-aperture planar antennas.

Reliability Improvement of Grid Connected PV Inverter Considering Monofacial and Bifacial Panels Using Hybrid IGBT

The development of bifacial photovoltaics has led to significant advancements in solar energy. Unlike traditional solar panels, which only generate electricity from the front side, these panels capture the energy from the rear and front surfaces. Bifacial photovoltaics utilize a dual-sided absorption to capture the sunlight that falls on nearby structures and the ground. This technology helps boost their efficiency and makes them an economical and sustainable choice. Furthermore, the increased energy production from the rear side of bifacial panels may lead to higher voltage fluctuations, which affects the thermal stability of PV inverter. Nevertheless, PV inverter is regarded as critical component which affects the reliability performance. Hence in this paper reliability improvement methodology with hybrid IGBT is proposed for the PV inverter. The hybrid IGBT consists of Silicon (Si) IGBT and Silicon Carbide (SiC) Schottky diode. A test case of 3-kW Monofacial and Bifacial grid connected PV inverter system with various albedos is considered. Mission profile for one year at Hyderabad, India location is logged for the assessment. B10 lifetime is calculated for the proposed hybrid IGBT. The effectiveness of the proposed hybrid IGBT is evaluated in comparison with conventional IGBT. The proposed hybrid IGBT significantly improves the reliability performance of the PV inverter.