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The purpose of this study is to improve the control performance of grid-connected photovoltaic (PV) inverters with inductive-capacitive-inductive (LCL) filters by proposing a new robust current control based on uncertainty and disturbance estimator (UDE).

The control strategy combines the capacitor current feedback with a UDE-based control to solve robust stability issues in the presence of parametric uncertainties and disturbances.

This paper provides guidelines for tuning the controller parameters where it is shown to be easy to implement by simply selecting the appropriate feedback coefficient, the reference model and an approximate lumped disturbance bandwidth. Simulation and experimental results demonstrate the effectiveness of the proposed controller in terms of resonance damping, tracking performance and robust stability under grid uncertainties and disturbances.

This paper offers a new approach for designing implementable robust controllers for LCL-filtered grid-connected PV inverters.

A new UDE-based current control is proposed to improve the stability performance of grid-connected PV inverters. The advantages of UDE-based control are its simple structure, easy tuning and robustness under parameter uncertainties and disturbances. Simulation and experimental results support the theoretical findings.

This paper aims to investigate the common-mode voltage (CMV) issue of a three-phase four-leg voltage-source inverter. A new space vector modulation method, named as three-dimensional active zero state Pulse-width modulation (PWM) (3-D AZSPWM), is proposed to reduce the CMV level.

PWM is a general method to generate the switching signals of the power converters in order to obtain high-quality output voltages. However, the CMV produced by PWM methods has become a serious problem. 3-D AZSPWM is proposed to solve this issue. In 3-D AZSPWM, instead of using zero voltage vectors with high CMV level, appropriate complementary non-zero vectors are introduced to synthesize reference vector. The proposed method is classified into four types of AZSPWM1(a), AZSPWM1(b), AZSPWM2(a) and AZSPWM2(b) based on different complementary vectors chosen for each type. An extend software simulation using MATLAB/Simulink is performed to verify the superior performance of the proposed methods.

Compared to other reduced CMV methods, the proposed method not only reduces the CMV but also retains the positive characteristics of the three-dimensional classical space vector PWM (3-D CSVPWM).

The proposed method does not suffer from linear modulation region limitation and also does not impose additional switching loss. Furthermore, calculated output voltage harmonic distortion factor illuminates acceptable quality of output voltage produced by the proposed method.

The purpose of this paper is to describe design and development of a pole climbing robot (PCR) for inspection of industrial size pipelines. Nowadays, non‐destructive testing (NDT) methods are performed by dextrous technicians across high‐level pipes, frequently carrying dangerous chemicals. This paper reports development of a PCR that can perform in situ manipulation for NDT tests.

Introduces a PCR including a novel four‐degrees of freedom climbing serial mechanism with the nearly optimal workspace and weight, unique V‐shaped grippers and a fast rotational mechanism around the pole axis. Simplicity, safety, minimum weight, and manipulability were concerned in the design process.

The developed prototype proved possibility of application of PCRs for NDT inspection on elevated structures. Design and development of PCRs which are able to pass bends and T‐junctions faces much more difficulties than those which should climb from a straight pole.

The robot is successfully tested on an industrial size structure (exterior diameter of 219 mm) with bends and T‐junctions.

Design and development of a novel pole climbing and manipulating robot for inspection of industrial size pipelines. The robot is able to pass bends and T‐junctions. The V‐shaped grippers offer many advantages including safety and tolerance to power failure. After grasping the structure, in case of power failure in any of the grippers' motors, the robot does not slip on the structure. The Z‐axis rotational mechanism provides fast navigation around the pole which is not possible with the traditional serial articulated arms.

This paper aims to overcome the lack of methodologies for optimizing the volume of bulky low-frequency inductors that the authors came across with when working on the design of hybrid active power filters. Sound work was published concerning this well-known technology, but it became evident that the mentioned optimization topic was left unaddressed.

Using the Lagrange multipliers optimization method combined with the electromagnetic laws of inductor design, it was possible to establish a new design method to determine the optimal solutions that fulfil any given scenario of specifications. In other words, it is now possible to obtain the inductor’s geometric and electric parameters that not only satisfy the system’s electromagnetic requirements but also lead to smaller, lighter or economical solutions.

A generalized set of equations was obtained to facilitate the calculations of all the inductor-building parameters. As expected, these equations take as inputs the inductor’s required inductance, its maximum current and the desired resistance, but also a customizable cost function. The later cost function will optimize the inductor’s volumes of copper and iron and can be settled, among other purposes, for minimizing the total weight, volume or cost.

All the mathematical expressions to obtain the general optimal solutions are given as well as practical graphics for the three above-mentioned optimization criteria. Using these charts, the reader will be able to obtain by simple inspection the optimal solutions for a large, generalized universe of intended specifications.