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This paper presents a method for determining the complex refractive index of a Transparent and Conductive Oxide that is embedded in a multilayer structure. The procedure assumes that the optical properties of others materials forming the structure are known and only the real and the imaginary part of the refractive index are unknowns. The refractive index is determined by exploiting the matrix model...
This paper proposes a segmentation method to analyze thermographic images of large solar fields with the aim to identify the borders of photovoltaic modules. This kind of analysis allows to correctly attribute possible faults, revealed by thermography, to a well specified solar panel. Moreover, the knowledge of the specific model of solar panel allows to bring the analysis to the single solar cell...
Over-temperature occurring in silicon solar panels, subject to partial shadowing, are reduced by means of a series connected voltage divider which sustains part of the reverse voltage developing across the shaded solar cells. The circuit is based on a power MOSFET which is driven by the output voltage of the solar panel. When the solar panel is uniformly illuminated the MOSFET is in the ON state and...
In this paper the hardware implementation of a PV microinverter based on dual coupled-inductors dc-dc converters is presented. Coupled-inductors were sized to ensure a high coupling factor, as well as to reach the desiderate voltage gain. Moreover, wide Band-Gap devices allowed to reduce weight and volume of the overall system. The control technique was optimized by adding a PI regulator to a sliding...
In this paper the control of a grid-tied PV (Photovoltaic) Cascaded H-bridge inverter is discussed. The operation principle of the considered circuit is analyzed and a particular attention is paid to the different modulation techniques well-suited for this configuration. Moreover, some critical implementation issues are addressed, while a fair comparison between the proposed modulation scheme and...
Thermal Feedback Blocks are a viable approach to perform thermal and electrothermal simulations of electronics systems with very fast-switching inputs, for which the coupling of a finite-element method thermal solver with a physics-based or a circuit simulator cannot be used. In this work, we describe a RC-based thermal network improving the conventional Foster and Cauer solutions, which is used to...
Overtemperature occurring in silicon solar panels subject to partial shadowing are reduced by means of a new bypass circuit. The circuit exploits a series connected power MOSFET which sustains part of the reverse voltage developing across the shaded solar cell. Neither power supply nor control logic are required, resulting in an appealing advantage with respect the other active bypass circuits. Experiments...
The lifetime estimation of power converters is a crucial issue for the reliability of electrical generators with renewable sources. During normal operations, the switching devices show junction temperature cycles that are widely recognized as the main cause of their failures. Although in-line junction temperature monitoring is extremely difficult, its knowledge is essential in order to achieve a reliable...
In this paper, an effective circuit for both voltage and current zeroing of single solar panels embedded in a solar field is presented. The circuit interrupts the panel current by means of a solid-state power switch and zeros the panel voltage by means of an electromechanical relay. Each solar panel can be either connected or disconnected from the string independently from each other. The circuit...
This paper presents a fast and accurate approach for the dynamic electrothermal analysis of photovoltaic (PV) plants with a cell-level discretization. A circuit model is developed for the elementary cell, and an equivalent electrical network is automatically built in a preprocessing stage to account for the power-temperature feedback. The PV plant under analysis is represented as an electrical macrocircuit...
Small shadows are often neglected in the prediction of energy producible by photovoltaic systems. This is mostly due to the lack of specific tools available in commercial design software packages, which neither allow realistic drawings nor can account for individual solar cells currents. In this paper the effects of small shadows are accurately analyzed with reference to two special cases, a TV antenna...
This paper propose a new system to short circuit a photovoltaic panel, embedded in a photovoltaic string, with the aim to ensure safe operation of firemen in case of fire. The circuit is activated by a wireless command and doesn't require additional wiring. Moreover it is self powered by the solar panel itself and can be either turned on or turned off in a fully reversible way.
In this paper a new monitoring system, suitable for large photovoltaic fields, is presented. Differently from others available monitoring systems the new approach is based on a sensor network which collects detailed information about the electrical performances of each string forming a photovoltaic plant. A devised electronic board has been specifically developed and prototyped which embeds innovative...
In this paper the design and the control of a PV (Photovoltaic) AC-module based on a double coupled-inductors boost topology are discussed. This circuital configuration allows obtaining of the high voltage amplification needed in individual panel applications. The operation principle of the proposed circuit is analyzed and a proper calibration of the PV panel simulation model is performed. The adopted...
TCO (Transparent Conductive Oxides) layers often exhibit very rough surfaces and their optical properties, can not be described by one dimensional analytical models and numerical approaches must be adopted. However, computational time becomes, often, too large. In this paper we propose an automated procedure, based on the interaction between MATLAB and the Sentaurus TCAD environment which finds, in...
The operation of micro-optoelectronic devices relies on optical properties of materials, first of all the wavelength dependent refractive index. Standard measurement techniques are often prone to significant ambiguities caused by the periodic nature of the optical response. In this paper we propose a procedure which exploits transmittance measurements, performed at variable light incidence angle,...
Electronic switching devices often requires some form of post processing to adjust, with high spatial resolution, the value of the recombination lifetime. The most selective killing technique used so far exploits high energy helium implantation. The main obstacle to the proper modeling of implantation effects comes from the unavailability of reliable measurement techniques able to “look” into the...
In this paper, a novel circuit model of photovoltaic (PV) cells is presented, which exploits the thermal equivalent of the Ohm's law and the macromodeling technique to describe the temperature dependence of all key parameters and allow a specific temperature for each cell. The model is compatible with commercial SPICE-like simulation tools, and suitable to be employed for dynamic electrothermal (ET)...
In this paper, an innovative topology performing a Power Line Communication on DC bus, with series connected photovoltaic modules, is presented. The circuit ensures the transmission on the DC bus even if the transceivers cannot share the same reference voltage. Moreover, a circuit solution avoiding that the operating point of the photovoltaic string can be affected is proposed. The circuit is provided...
This paper focuses on the performance evaluation of grid-connected photovoltaic (PV) inverters in terms of static maximum power point tracking (MPPT) efficiency. A simple test-bench set-up is proposed to accurately analyze the behavior of commercial inverters applied to PV plants under partial shading conditions. The system performs a real-time monitoring of the operating point of the PV plant during...
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