F. Di Napoli

A PV AC-module based on coupled-inductors boost DC/AC converter

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 control strategy is based upon sliding control technique in order to exploit its well-known properties of robustness. Furthermore, a Maximum Power Point Tracking (MPPT) approach based on a Incremental Conductance (IC) algorithm is used to track the actual maximum power point. Finally, the numerical results reported in the paper permit to confirm the feasibility of the proposed design and control strategy.

Dynamic electrothermal simulation of photovoltaic plants

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 that can be solved with low CPU/memory requirements and without convergence issues by using any SPICE-like simulator. The proposed strategy can be successfully exploited for diagnostic purposes.

Single-Panel Voltage Zeroing System for Safe Access on PV Plants

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 is connected to the existing junction box and does not require additional wiring, neither for its power supply, which is always derived from the solar panel, nor for its data transmission, which is achieved through a special suited power line communication scheme exploiting the existing dc power bus. Experiments performed on a test solar field equipped with in-house made circuit prototypes evidence the reliability of the proposed approach.

Thermal feedback blocks for fast and reliable electrothermal circuit simulation of power circuits at module level

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 perform (i) an accurate and effective dynamic thermal analysis of an IGBT power module, and (ii) a fast electrothermal analysis of the aforementioned module used as a half-bridge DC-AC power converter in both normal operating mode and during a load short-circuit event.

A wireless sensor network for the monitoring of large PV plants

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 functionalities. Among them the supercapacitor based harvesting stage for self powering of the sensor network and the wireless communication which prevent additional wiring. Moreover a new performances analysis logic has been developed and implemented in a control software tool which analyzes collected data and generate graphical reports for an immediate localization of faults and yield losses.

Accurate analysis of small shadows effects on photovoltaic systems yield

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 and self-shading. The analysis is based on the interaction between highly specialized and powerful software, AUTOCAD, MATLAB and PSpice, which allow an utmost degree of accuracy.

Mixed FE–MB methodology for the evaluation of passive safety performances of aeronautical seats

ABSTRACT The certification of aircraft seats involves the investigation of the structural performance of their components under emergency landing conditions. . The paper reports the activities related to an experimental sled-test of a single row of two seats placed in front of a stiff fuselage bulkhead, by considering a single anthropomorphic dummy arranged on one of the seats. Tests have been developed at the facility equipped with a sled decelerator testing system compliant with certification requirements from FAR25 for TSO C127a regulations. Four different numerical models have been developed in order to simulate the experimental test: a full-FE modelby LSTC-LsDyna® code, a full-MB modeland a hybrid FE/MB developed using by TNO-Madymo® code and a Coupled FE/MB model. Numerical results achieved by these models have been compared with experimental ones, in order to assess their use for CBA (certification by analysis) purposeto be applied since the preliminary design phase of the seat.

A new bypass circuit for hot spot mitigation

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 performed on a commercial mono-crystalline solar panel evidenced a reduction of the reverse voltage across a shaded cell, if compared with the traditional bypass diode, of about 50%, corresponding to a temperature decease approaching 22°C.

Modulation technique for grid-tied PV multilevel inverter

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 the Phase Shifted PWM (Pulse Width Modulation) is carried out. The adopted control strategy is based upon a sorting algorithm in order to modulate only one power cell (i.e. H-bridge) per sorting cycle while the others are in fixed state. This technique allows to reduce power switching losses, thus increasing overall system efficiency. The numerical results reported in the paper permit to confirm the feasibility of the proposed modulation strategy and the better performance with respect to PS-PWM in terms of power efficiency.