1,720,976 research outputs found
A Wireless Self-Powered I-V Curve Tracer for On-Line Characterization of Individual PV Panels
No full textThe behavior of a photovoltaic (PV) generator under specific irradiance and temperature conditions is mainly described by its current-voltage (I-V) characteristic. Therefore, the I-V curve tracing has to be considered the most accurate and effective diagnostic tool for the proper identification of PV panels' failures. In this article, an innovative I-V curve tracer for individual PV panels is presented. It ensures the following advantages. 1) An optimized I-V curve measurement due to an innovative tracing algorithm. 2) In-situ characterization during normal operation owing to a proper disconnection circuit. 3) Full portability thanks to a Li-ion battery power supply and a Bluetooth communication. The proposed tool has been designed and realized. The resulting prototype has been used to measure the I-V curve of a PV panel both in uniform and partial shading conditions
A tool providing I-V curve and IS analysis of a PV module embedded in a string
No full textTo sustain the green transition, the Photovoltaic (PV) source is called to play a relevant role. To this aim the optimal energy yield of PV plants must be ensured by smart monitoring and diagnostics tools based on module-level characterization devices declined as IoT (Internet of Things) sensors. In this paper, the authors discuss the applicability of a I-V (current-voltage) tracer conceived to perform online electrical characterization of individual PV modules, to be adopted also for impedance spectroscopy analysis. Numerical simulation performed in Spice environment proves the applicability of the proposed approach. Nevertheless, challenging design aspects are also highlighted
A GaN based bidirectional switch for matrix converter applications
No full textThe operation of bidirectional switches, based on normally OFF GaN devices and suitable for matrix converter applications, is investigated in terms of static power dissipation. To this end, nine homemade prototypes, suited for the nine legs of a three-phase/three-phase converter, have been specifically designed and fabricated. A typical four steps switching sequence, for exchanging the current from one leg to another, has been implemented. Results show that "diode mode"operation, exhibited by the GaN device in the OFF state, strongly affects power dissipation
Impedance Spectroscopy as On-Field Monitoring Technique for PV Modules
No full textDetecting degradation phenomena on photovoltaic (PV) module working under real operating conditions is challenging. In recent years, impedance spectroscopy (IS) has been explored as a promising technique for the detection of faults in PV systems. The adoption of IS in on-field monitoring and diagnostic tools requires a reliable and straightforward ac model of the device under test. To this aim, the authors analyze the frequency response of standard crystalline silicon (c-Si) based PV module working under real operating conditions by means of technology computer aided design (TCAD) simulations in Sentaurus environment. The simulated experiments emulate the behavior of the PV module both in healthy and faulted conditions. Finally, the considerations arising from this analysis help to define practical guidelines as well as highlighting limitations of the adopted technique
Merged Photovoltaic/Wave System for the Power Supply of a Marine Buoy for Harbour Monitoring
No full textDynamic Modeling of Si-based Photovoltaic Modules using Impedance Spectroscopy Technique
No full textIn a scenario where the deployment of photovoltaic (PV) systems is increasing, the characterization and the monitoring of the state of health are pivotal. To this aim, Impedance Spectroscopy (IS) provides useful information about the dynamics of PV generators. In this work, an equivalent electric ac model for the characterization of PV modules is discussed. The model is applied to experimental spectra measured on a 52Wp c-Si based PV module in outdoor conditions. The fitting problem is solved by means of two different approaches, one based on the analytic solution of the model equations which employs few points of the experimental spectrum and the other based on an optimization algorithm, requiring the whole set of frequency points. The parameters' values obtained from both approaches are commented, providing useful information on the behavior of the PV module under test
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
SiC MOSFET C-V Characteristics with Positive Biased Drain
No full textEven if SiC MOSFETs technology has undergone huge progress in last years, there are some issues still open, such as high traps density at the SiO2/SiC interface. This work focuses on the measurement of the Gate capacitance when a DC bias is applied between Drain and Source to characterize the SiO2/SiC interface. The experimental curves, performed on a commercial SiC power MOSFET, exhibit a peak when the Gate voltage approaches the threshold voltage. Such peak is analyzed through TCAD simulations and its origin is addressed. Numerical analysis shows that this peak is associated to the displacement current, with a strong dependence on the traps concentration at the SiO2/SiC interface
A voltage divider strategy for reducing the hot spot temperature in partially shaded solar panels
No full textOver-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 does not affect the operation of the module, while, when the solar panel is partially shaded, and the output voltage decreases, the MOSFET enters in the pinch-off operation mode, thus subtracting its voltage from the reverse voltage across the shaded cell. Experiments performed on a commercial solar panel showed one third of reduction of the reverse voltage across shaded solar cells, with a reduction of the hot spot temperature of about 25°C
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