Photovoltaic Evaporative Chimney I–V Measurement System

The photovoltaic evaporative chimney is a novel solar-cooling system that serves a double purpose: it increases the efficiency of the photovoltaic (PV) panels and it cools down a water stream which can be used to dissipate the heat from a refrigeration cycle. One of the major issues arising from the operation of the chimney is the temperature stratification in the panel due to the movement of the air in the chimney. This effect can trigger the activation of the bypass diodes of the module, creating local maximum power points (MPP) that can compromise the grid-tied inverter tracking. To fill this gap, this paper deals with the design and implementation of an I–V curve measurement system to be used in the performance analysis of the system. The I–V curve tracer consists of a capacitive load controlled by a single board computer. The final design includes protections, capacitor charging/discharging power electronics, remote commands inputs, and current, voltage, irradiance, and temperature sensors.The results show that the modules bypass diodes are not activated during the tests, and no local MPPs appear. Moreover, the curves measured show the benefits of the photovoltaic chimney: the cooling effect increases the power generated by the PV panels by around 10%.

Configurable IoT Open-Source Hardware and Software I-V Curve Tracer for Photovoltaic Generators

Photovoltaic (PV) energy is a renewable energy resource which is being widely integrated in intelligent power grids, smart grids, and microgrids. To characterize and monitor the behavior of PV modules, current-voltage (I-V) curves are essential. In this regard, Internet of Things (IoT) technologies provide versatile and powerful tools, constituting a modern trend in the design of sensing and data acquisition systems for I-V curve tracing. This paper presents a novel I-V curve tracer based on IoT open-source hardware and software. Namely, a Raspberry Pi microcomputer composes the hardware level, whilst the applied software comprises mariaDB, Python, and Grafana. All the tasks required for curve tracing are automated: load sweep, data acquisition, data storage, communications, and real-time visualization. Modern and legacy communication protocols are handled for seamless data exchange with a programmable logic controller and a programmable load. The development of the system is expounded, and experimental results are reported to prove the suitability and validity of the proposal. In particular, I-V curve tracing of a monocrystalline PV generator under real operating conditions is successfully conducted.

Optimization of Schottky-contact process on 4H-SiC Junction Barrier Schottky (JBS) Diodes

SiC Junction Barrier Schottky (JBS) Rectifier is a kind of unipolar power diode with low threshold voltage and high reverse blocking voltage. And the Schottky barrier Φ BN is a main technology parameter, which could greatly affect the forward conduction power and reverse leakage current in the JBS rectifiers. Therefore, it is necessary to balance the influence of Φ BN on the electrical characteristics of JBS rectifiers. In this paper, physical properties at the metal-semiconductor at the Schottky-contact could be optimized by the improvement of Schottky-contact process. And this optimization could significantly decrease Φ BN to reduce the on-state voltage drop V F and minimize negative impact on its reverse characteristics. After the completion of Silicon carbide JBS diodes, the static parameter electrical test was carried out on the wafer by using Keysight B1505A Power Device Analyzer/Curve Tracer. The test results show that the Schottky barrier height Φ BN of JBS Schottky rectifier manufactured by the modified Schottky foundation technology decreased from 1.19eV to 0.99eV and I R increased from 1.08μA to 3.73μA (reverse blocking voltage V R=1200V). It indicated that the power consumption of Schottky barrier junction in JBS rectifiers could be significantly reduced by about 25%, and I R could effectively be limited to less than 10μA.

Intermittent FOCV Using an I-V Curve Tracer for Minimizing Energy Loss

Conventional fractional open-circuit voltage (FOCV) methods in maximum power point tracking (MPPT) are widely adopted for their simple structure and low computing power requirements. However, under mismatch and environmental changing conditions, the FOCV methods introduce a large amount of energy loss due to their maximum power point being fixed at the initial setup. To reduce energy loss, the intermittent FOCV MPPT proposed in this paper regularly refreshes all the parameters for each condition in time by using an I-V curve tracer. The proposed intermittent FOCV consists of two phases: the scan and set phases. In scan phase, the I-V curve of a photovoltaic (PV) cell is scanned and its power is calculated. In set phase, the global MPP of the PV cell is extracted and set by controlling the 8-bit capacitance array. Simulation and calculation based on experimental results with a single PV cell show that the energy loss of the proposed intermittent FOCV under daily temperature and illuminance distributions decreased by up to 99.9% compared to that of the conventional FOCV.

Design and implementation of an I-V curvetracer dedicated to characterize PV panels

In recent years, solar photovoltaic energy is becoming very important in the generation of green electricity. Solar photovoltaic effect directly converts solar radiation into electricity. The output of the photovoltaic module MPV depends on several factors as solar irradiation and cell temperature. A curve tracer is a system used to acquire the PV current-voltage characteristics, in real time, in an efficient manner. The shape of the I-V curve gives useful information about the possible anomalies of a PV device. This paper describes an experimental system developed to measure the current–voltage curve of a MPV under real conditions. The measurement is performed in an automated way. This present paper presents the design, and the construction of I-V simple curve tracer for photovoltaic modules. This device is important for photovoltaic (PV) performance assessment for the measurement, extraction, elaboration and diagnose of entire current-voltage I-V curves for several photovoltaic modules. This system permits to sweep the entire I-V curve, in short time, with different climatic and loads conditions. An experimental test bench is described. This tracer is simple and the experimental results present good performance. Simulation and experimental tests have been carried out. Experimental results presented good performance.

Development Of A Device Characterization Curve Tracer for High Power Application

Due to self-heating and significant temperature rise in a power device junction, the device characterization through the DC measurement is a major issue. Short pulsed technique or Pulsed I-V (PIV) characterization is the technique which is used by commercial curve tracer and network analyzers to characterize the power devices. Although, this technique prevent excessive self-heating but doesn't guarantee that measurement will be operated in the desired accuracy range because even a moderate self heating may cause significant measurement error. In this research work, a measurement technique is introduced that results "device characterization within the desired accuracy range". The technique is based on the stimulation of the device under test (DUT) with voltage ramps that allow for "fast transient mesurement". Because, this way of stimulation excites the parasitic impedances in the DUT, a dynamic model of the DUT is presented. This model allows determining the operation conditions that "guarantee the specified measurement accuracy". The measurement procedure is described and the developed measurement algorithms are implemented in LabVIEW environment to obtain a "PC-based device characterization curve tracer for high power application". A high current power MOSFET is used as the DUT. The calibration and measurement phases are carried out by the developed curve tracer. During the calibration phase, the measurement condition including allowed junction temperature deviation, maximum ramp slope and maximum allowed drain-source voltage to "guarantee 2% measurement error" is specified. The measurement phase is carried out based on these operating conditions. The result is a family of output I-V curves for different gate voltage set. This measurement technique "validated" with that of measured based on the PIV characterization technique from the device data sheet. The discrepancy between the measurement result and datasheet curve is discussed.

Development Of A Device Characterization Curve Tracer for High Power Application

Due to self-heating and significant temperature rise in a power device junction, the device characterization through the DC measurement is a major issue. Short pulsed technique or Pulsed I-V (PIV) characterization is the technique which is used by commercial curve tracer and network analyzers to characterize the power devices. Although, this technique prevent excessive self-heating but doesn't guarantee that measurement will be operated in the desired accuracy range because even a moderate self heating may cause significant measurement error. In this research work, a measurement technique is introduced that results "device characterization within the desired accuracy range". The technique is based on the stimulation of the device under test (DUT) with voltage ramps that allow for "fast transient mesurement". Because, this way of stimulation excites the parasitic impedances in the DUT, a dynamic model of the DUT is presented. This model allows determining the operation conditions that "guarantee the specified measurement accuracy". The measurement procedure is described and the developed measurement algorithms are implemented in LabVIEW environment to obtain a "PC-based device characterization curve tracer for high power application". A high current power MOSFET is used as the DUT. The calibration and measurement phases are carried out by the developed curve tracer. During the calibration phase, the measurement condition including allowed junction temperature deviation, maximum ramp slope and maximum allowed drain-source voltage to "guarantee 2% measurement error" is specified. The measurement phase is carried out based on these operating conditions. The result is a family of output I-V curves for different gate voltage set. This measurement technique "validated" with that of measured based on the PIV characterization technique from the device data sheet. The discrepancy between the measurement result and datasheet curve is discussed.

Enhancement Mode GaN-FETs in Extreme Temperature Conditions, Part I: Static Parasitic Parameters

Smaller packaging and sizing of power electronics and higher operating temperatures of switching devices call for an analysis and verification on the impact of the parasitic components in these devices. Found drift mechanisms in an eGaN-FET are studied by literature and related to measurements performed in extreme temeprature conditions far beyond the manufacturer recommended operating range. A thermal chamber was build to precisely measure the effect of temperature in these devices using a curve tracer. It is found that the increment in RDSon, IDSS, IGSS and VSD can be justified by the theory and backed up by measurements. It is also found that the particular eGaN-FET can be suited for extreme temperature operating conditions.