S. Daliento

A Simple Bipolar Transistor-Based Bypass Approach for Photovoltaic Modules

This paper presents a novel bypass approach for photovoltaic panels relying on a bipolar transistor operated in saturation, the activation of which is handled automatically by a circuit comprising a pair of MOS transistors only. The functioning principle of the proposed system is explained and the improvements in terms of reliability of the bypassed subpanel and power produced by the string in comparison with a traditional diode-based scheme are quantified. The analysis is corroborated by dc/transient measurements and tailored PSPICE simulations.

A novel wireless self-powered microcontroller-based monitoring circuit for photovoltaic panels in grid-connected systems

A monitoring circuit for individual photovoltaic (PV) panels in grid-connected systems is proposed, which exhibits a number of features devised to simplify and reduce cost of diagnostics and maintenance of the PV plant. In particular, the system is provided with an effective energy harvesting supply stage, which eliminates the requirement for external supply or batteries; furthermore, no cables are needed for data transfer due to the adoption of a rugged wireless connectivity.

Monitoring and Diagnostics of PV Plants by a Wireless Self-Powered Sensor for Individual Panels

In this paper, an innovative sensor suited to perform real-time measurements of operating voltage and current, open-circuit voltage, and short-circuit current of string-connected photovoltaic (PV) panels is presented. An effective disconnection system ensures that the sensor does not affect the behavior of the string during the measurement phase and offers many benefits like the automatic detection of bypass events; moreover, the sensor does not require additional cables thanks to a wireless communication and a power supply section based on energy harvesting. An extensive experimental campaign is performed to prove the reliability and usefulness of the sensor for continuous monitoring of PV plants. The capability to detect faults and accurately localize malfunctioning panels in a PV string is highlighted.

Effective real-time performance monitoring and diagnostics of individual panels in PV plants

In this paper, we present an improved version of a recently-developed monitoring circuit devised to measure the operating voltage and current, the open circuit voltage, and the short circuit current of string-connected photovoltaic (PV) panels. The system can substitute the junction box, is fully self-powered, and does not require additional cables thanks to a wireless communication. An extensive experimental campaign is performed to prove the reliability and usefulness of the system for continuous monitoring of PV plants; in particular, the capability to detect the effects of partial shading conditions on a PV string is highlighted.

Approximate Closed-Form Analytical Solution for Minority Carrier Transport in Opaque Heavily Doped Regions Under Illuminated Conditions

An approximate closed-form solution for the transport equations in heavily doped regions is proposed, leading to an expression for the minority carrier currents, in which the influence of technological parameters is easily readable. As an example, the emitter collection efficiency for a photovoltaic device is evaluated in some significant cases

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.

Accurate Maximum Power Tracking in Photovoltaic Systems Affected by Partial Shading

A maximum power tracking algorithm exploiting operating point information gained on individual solar panels is presented. The proposed algorithm recognizes the presence of multiple local maxima in the power voltage curve of a shaded solar field and evaluates the coordinated of the absolute maximum. The effectiveness of the proposed approach is evidenced by means of circuit level simulation and experimental results. Experiments evidenced that, in comparison with a standard perturb and observe algorithm, we achieve faster convergence in normal operating conditions (when the solar field is uniformly illuminated) and we accurately locate the absolute maximum power point in partial shading conditions, thus avoiding the convergence on local maxima.

An improved model for extraction of strongly spatial dependent lifetimes with the AC lifetime profiling technique

In this work, we present an improvement of the extraction method for the AC lifetime profiling technique using a more accurate evaluation of the abscissa x where the lifetime is measured. By this model, a very good extraction of strongly variable lifetime profiles is obtained.

Monitoring, Diagnosis, and Power Forecasting for Photovoltaic Fields: A Review

A wide literature review of recent advance on monitoring, diagnosis, and power forecasting for photovoltaic systems is presented in this paper. Research contributions are classified into the following five macroareas: (i) electrical methods, covering monitoring/diagnosis techniques based on the direct measurement of electrical parameters, carried out, respectively, at array level, single string level, and single panel level with special consideration to data transmission methods; (ii) data analysis based on artificial intelligence; (iii) power forecasting, intended as the ability to evaluate the producible power of solar systems, with emphasis on temporal horizons of specific applications; (iv) thermal analysis, mostly with reference to thermal images captured by means of unmanned aerial vehicles; (v) power converter reliability especially focused on residual lifetime estimation. The literature survey has been limited, with some exceptions, to papers published during the last five years to focus mainly on recent developments.

On the design and the control of a coupled-inductors boost dc-ac converter for an individual PV panel

In this paper the design and the control of an individual PV (Photovoltaic) panel dc-ac converter based on a double coupled-inductors boost topology are discussed. The operation principle of the proposed circuit is analyzed. A proper calibration of the PV panel simulation model is performed. An optimization procedure is proposed for choosing the fundamental parameters of both converter and control law based upon sliding control technique. Furthermore, a Maximum Power Point Tracking (MPPT) approach based on a Perturb & Observe (P&O) algorithm is used to track the actual maximum power point through successive approximations. Finally, the proposed inverter is employed as a grid inverter in a single PV panel application. The numerical results reported in the paper permit to confirm the feasibility of the proposed design and control strategy.