Probing the Anti-Corrosion Behavior of X65 Steel Underwater FSW Joint in Simulated Seawater

To detect the corrosion resistance of a friction stud welding (FSW) joint in simulated seawater (a 3.5 wt% NaCl solution), the pulse electrochemical deposition method was used for electroplating Ni coating with different duty ratios (50%, 80%, and 100%) on the surface of FSW joint. The microstructure and surface structure of the coating were observed by micro-spectroscopy and other characterization methods. The corrosion behavior of the coating was analyzed by means of macroscopic electrochemical testing. The local corrosion law of joint surface and coating surface defects were innovatively explored by using micro-zone electrochemical scanning system. The coating characterization results showed that, as the duty ratio continues to increase, the coating surface becomes denser and smoother, and the corrosion products such as Fe2O3, Fe3O4, and FeOOH are generated. The results of macroscopic electrochemical experiment indicated that the coating with 100% duty ratio has the lowest corrosion current density and the maximum polarization resistance. The scanning vibrating electrode technique results showed that the corrosion current density in the defect area is higher than that in the coating area, and the maximum corrosion current density decreases with the increase of duty ratio. The localized electrochemical impedance spectroscopy results indicated that the localized impedance at the welded zone was the largest, and with the increase of the pulse duty ratio, the impedance diffusion in the defect area was decreasing.

Non-Isolated Interleaved Hybrid Boost Converter for Renewable Energy Applications

DC-DC boost converters are necessary to extract power from solar panels. The output voltage from these panels is far lower than the utility voltage levels. One of the main functions of the boost converter is to provide a considerable step-up gain to interface the panel to the utility lines. There are several techniques used to boost the low panel voltage. Some of the issues faced by these topologies are a high duty ratio operation, complex design with multiple active switches and discontinuous input current that affects the power drawn from the panel. This paper presents a boost converter topology that combines the advantages of an interleaved structure, a voltage lift capacitor and a passive voltage multiplier network. A mathematical analysis of the proposed converter during its various modes of operation is presented. A 100 W prototype of the proposed converter is designed and tested. The prototype is controlled by a PIC16F18455 microcontroller. The converter is capable of achieving a gain of 10 without operating at extremely high duty ratios. The voltage stress of the switch is far lower than the maximum output voltage.

Design and Implementation of Z-Source Inverter by Simple Boost Control Technique for Laboratory Scale Micro-Hydro Power Plant Application

In a power plant such as micro-hydropower (MHP), an induction generator (IG) is usually employed to produce electrical power. Therefore, an inverter is needed to deliver it with high efficiency. Z-source inverter (ZSI) has been introduced as a topology with many advantages over conventional inverters. This research aims to investigate the performance of ZSI based simple boost control (SBC) in laboratory-scale MHP systems using a rewinding induction generator. This research has been conducted both from simulations and experiments. Based on the result, the waveform characteristic and value of ZSI are close to the desired design. A shoot-through duty ratio of 17% can reach 60 Vrms output voltage, and this condition has a conversion ratio of about 2.05 times. Also, SBC can significantly reduce the Total Harmonic Distortion (THD). ZSI efficiency has a value of 84.78% at 50% of rating load 100 W and an average value of 80%. Compared to the previous study, the proposed design has more economical with the same component for the higher rating power. Moreover, it has a smoother and entire output waveform of the voltage.

Design of New High Step-Up DC-DC Converter Topology for Solar PV Applications

A new topology for high step-up nonisolated DC-DC converter for solar PV applications is presented in this paper. The proposed high-voltage gain converter topology has many advantages like low-voltage stress on the switches, high gain with low duty ratio, and a continuous input current. The analytical waveforms of the proposed converter are presented in continuous and discontinuous modes of operation. Voltage stress analysis is conducted. The voltage gain and efficiency of the converter in presence of parasitic elements are also derived. Performance comparison of the proposed high-gain converter topology with the recently reported high-gain converter topologies is presented. Validation of theoretical analysis is done through the test results obtained from the simulation of the proposed converter. For the maximum duty ratio of 80%, the output voltage of 670 V is observed, and the voltage gain obtained is 14. Comparison of theoretical and simulation results is presented which validates the performance of the proposed converter.

Effective elasticity and persistence of strain in active filament-motor assemblies

Cross-linked, elastic, filamentous networks that are deformed by active molecular motors feature in several natural and synthetic settings. The effective active elasticity of these composite systems determines the length scale over which active deformations persist in fluctuating environments. This fundamental quantity has been studied in passive systems; however mechanisms determining and modulating this length-scale in active systems has not been clarified. Here, focusing on active arrayed filament-motor assemblies, we propose and analyze a minimal model in order to estimate the length scale over which imposed or emergent elastic deformations or stresses persist. We combine a mean-field continuum theory valid for weakly elastic assemblies with high dimensional Multi-Particle Collision (MPC) based Brownian simulations valid for moderate to strongly elastic and noisy systems. Integrating analytical and numerical results, we show that localized strains - steady or oscillatory - persist over well-defined length scales that dependent on motor activity, effective shear elasticity and filament extensibility. Extensibility is key even in very stiff filaments, and cannot be ignored when global deformations are considered. We clarify mechanisms by which motor derived active elasticity and passive shear elasticity of the filamentous backbone combine to effectively soften filaments. Surprisingly, the predictions of the mean-field theory agree qualitatively with results from stochastic discrete filament-motor model, even for moderately strong noise. We also find that athermal motor noise impacts the overall duty ratio of the motors and thereby the persistence length in these driven assemblies. Our study demonstrates how correlated activity in natural ordered active matter possesses a finite range of influence with clear testable experimental implications.

Robust mixed H2/H∞ fuzzy tracking control of photovoltaic system subject to asymmetric actuator saturation

This paper focuses on mixed [Formula: see text] fuzzy maximum power point tracking (MPPT) of photovoltaic (PV) system under asymmetric saturation and variations in climatic conditions. To maximize the power from the PV panel array, the DC–DC boost converter is controlled by its duty ratio which is practically saturated between 0 and 1. MPPT based on conventional control presents the problems of oscillations around maximum power point (MPP) and divergence under rapid climatic changes. In order to attenuate the effect of atmospheric condition variation and take into account asymmetric saturation of the duty ratio, we propose a novel robust saturated controller based on both [Formula: see text] performances and Takagi-Sugeno (T-S) representation of PV-boost nonlinear system. Within this approach, the nonlinear PV-boost system and its reference are first described by T-S fuzzy models. Second, the saturation effect is represented by a polytopic model. Then, a fuzzy integral state feedback controller is designed to achieve stable MPPT control. Based on Lyapunov function, the mixed [Formula: see text] stabilization conditions are derived in terms of linear matrix inequalities (LMIs). The optimization of the attraction domain of closed-loop system is solved as a convex optimization problem in LMI terms. Finally, the efficiency of the proposed controller under irradiance and temperature variations is demonstrated through the simulation results. The comparison with some existing controllers shows an improvement of MPPT control performance in terms of power extraction.

Novel Interleaved High Gain Boost Converter Using Switched Capacitor

The increase in global energy demand has led to increased research in harvesting solar energy. Solar energy is widely used in homes, electric vehicles and is a great solution to power remote areas. DC–DC converters are essential in extracting power from solar panels. One of the main problems in designing converters for solar energy applications is boosting the low output voltage of the solar panel to meaningful levels. While there are several topologies to achieve high gain, some of the problems faced by them are the extreme duty ratio, complex design and discontinuous input current. This paper presents a novel topology that uses an interleaved input, a voltage lift capacitor and a hybrid switched capacitor network to achieve high gain without an extreme duty ratio or bulky magnetics. The proposed converter is controlled using a microcontroller which regulates the output voltage. The voltage lift capacitor and the switched capacitor network enhances the voltage gain over a conventional boost converter without an extreme duty ratio. The analysis and design of the proposed converter are presented and verified with a 100 W prototype. The results show that the converter provides a gain of 10, at a duty ratio of 30%, while delivering the designed output power with considerably high efficiency.

Reduced Switches Count of Five Level H-bridge Inverter with Integrated Boost Converter in Solar PV System

PV systems are becoming more popular now a days, due to increase in the energy demand and it also reduces the environment pollution around the world. This paper proposes a reduced switches count of five-level H-bridge inverter with integrated boost converter in solar PV system. The proposed 5-level reduced switches count H-bridge MLI configuration requires less no.of power semiconductor devices compared to that of conventional MLI topology. In this paper INC MPPT control technique is used, which provides a duty ratio for controlling dc-dc boost converter and allowing the PV cells to operate more efficiently and extract maximum solar energy. The phase shifted sinusoidal pulse width modulation (PSCPWM) control technique is used for controlling the gating pulse of 5-level reduced switches H-bridge inverter. To improve the quality of PV based 5-level reduced switches h-bridge inverter output parameters mainly contribute switching losses and total harmonic distortion. The proposed model is modeled and simulated in MATLAB/SIMULINK software. Keywords: PV array, H-bridge multilevel inverter, boost converter, phase shifted PWM, maximum power point tracking (MPPT), incremental conductance, total harmonic distortion (THD).