An Australian analysis group has used an SMA inverter to shift the working level of a PV array and demonstrated its potential to provide photoluminescence photos for rooftop and large-scale photo voltaic installations.
A staff of scientists from the University of New South Wales (UNSW), SMA Australia, and Gentari Solar Australia have demonstrated a brand new methodology for daylight photoluminescence (DPL) imaging utilizing a commercially out there inverter to shift the working level of a PV array.
“The methodology permits quick and high-quality luminescence picture acquisition in the course of the day, enabling environment friendly efficiency and high quality monitoring with out the necessity to join particular electrical {hardware} or to make any adjustments to system wiring,” the analysis group stated, noting it may very well be utilized to rooftop and huge scale PV programs.
The proposed methodology relies on a method the place the emitted luminescence is different by manipulating {the electrical} working level of the modules, and a photoluminescence (PL) is obtained because the distinction between the 2 photos. This is achieved by taking PL photos of an open circuit (OC) and the utmost energy level (MPP).
Before this work, this method was solely demonstrated in personalized gear on a big scale, whereas the usage of commercially out there inverters for switching was solely completed on a small scale. In this research, business inverters had been used with none {hardware} or firmware modifications.
The demonstration of a roof system happened round midday on an April day within the suburbs of Sydney with an irradiance of 770 W/m2. The roof system is a 12 kW array counting on 35 bifacial 350 W glass-glass modules. Each module comprises 120 half-cell PERC cells with a nominal open circuit voltage of 682 mV per cell. The system is related, and its switching is managed, by a 10-kW SMA Sunnyboy Tripower inverter.
“The SMA inverters used on this research permit manipulation of energy setpoint settings utilizing a parameter referred to as ‘Active energy, guide setpoint,'” the group defined. “The transition of the ability output from 100% to zero takes place in lower than 150 ms, however as a result of lengthy dwell time of about 1.5 s, the overall cycle time is about 3 s. The particular person digital camera photos had been obtained with publicity occasions between 15 and 20 ms.
The utility-scale demonstration happened on a sunny day in October, in a 149 MW farm, with an irradiance of 950 W/m2. The farm has 400 W monofacial half-cell modules on a single-axis tracker. The modules are product of PERC photo voltaic cells with a nominal open-circuit voltage of 690 mV. The operation makes use of 2.75 MW SMA central inverters of the Sunny Central 2750-EV mannequin. Each inverter is related to roughly 9,000 modules.
“For the proof of idea of large-scale DPL picture acquisition utilizing inverter-based switching reported right here, just one 2.75 MW inverter was switched,” defined the lecturers. “As a precaution, solely <60% of the inverter's rated DC energy is transferred at any time (ie, between 90% and 30% of most energy) to keep away from the potential threat of thermal biking in energy electronics. In the identical context, we all know that as a substitute of automated switching."
The pictures, on this case, had been taken from a remotely piloted plane (RPA). In the RPA, an Indium Gallium Arsenide (InGaAs) digital camera (1,280 by 1,024-pixel decision) is mounted. The similar digital camera was additionally used within the roof demonstration. Each picture was captured with an publicity time of 15 ms.
“It has been proven that close-up high-resolution and high-quality photos of particular person modules of a roof system can establish microcracks and particular person defects on the cell stage,” stated scientists. “In distinction, RPA-based overview photos of huge sections of farms permit the identification of coarse module and system-level defects whereas close-up photos allow the detection of even cell-level defects.”
In addition, the researchers emphasised that quantitative evaluation can precisely assess voltage variations inside and between modules. “The capabilities demonstrated right here, and in future work, might drive inverter producers to make the mandatory switching capabilities extra accessible (for instance, via firmware updates) for much less distant future,” they stated.
The novel method is introduced within the paper “Daylight photoluminescence imaging of photovoltaic programs utilizing inverter-based switching,” revealed in Advances in Photovoltaics.
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