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In order to enable a more wide-scale utilization of PV systems, the cost of PV energy has to be comparable with other energy sources. Oversizing the PV array is one common approach to reduce the cost of PV energy, since it increases the PV energy yield during low solar irradiance conditions. However, oversizing the PV array will increase the loading of PV inverters, which may have undesired influence...
As the penetration level of grid-connected Photovoltaic (PV) systems increases, the power quality is one of the major concerns for system operators and the demands are becoming even stricter. The impact of interharmonics on the grid has been acknowledged in recent research when considering a large-scale adoption of PV inverters. However, the origins of interharmonics remain unclear. Thus, this paper...
The PV inverter lifetime is affected by the installed sites related to different solar irradiance and ambient temperature profiles. In fact, the installation site also affects the PV panel degradation rate, and thus the long-term power production. Prior-art lifetime analysis in PV inverters has not yet investigated the impact of panel degradation. This paper thus evaluates the lifetime of PV inverters...
With a still increasing penetration level of grid-connected PV systems, more advanced active power control functionalities have been introduced in certain grid regulations. A delta power constraint, where a portion of the active power from the PV panels is reserved during operation, is required for grid support (e.g., during frequency deviation). In this paper, a cost-effective solution to realize...
Performance monitoring and fault detection systems are becoming more common in large photovoltaic (PV) plants as they can contribute to decreasing operation and maintenance costs, as well as for maximizing plant yield and lifetime. However, in case of residential and smaller commercial PV system applications the cost of the performance monitoring hardware and implementation is still high. Therefore,...
Being able to monitor early signs of PV module degradation, is needed to ensure stable power production throughout the service life of a PV installation. Recently, impedance spectroscopy is proven to be a useful tool for detection of the presence and location of significant errors, and may have potential for more. In this work we describe a field test design where the modules are operating at their...
Impedance spectroscopy (IS) is an established characterization and diagnostic method for different electrical and chemical research areas such as batteries and fuel cells, but not yet widely adopted for photovoltaics (PV). This work, for the first time, investigates an IS based method for detecting potential-induced degradation (PID) in c-Si PV panels. The method has been experimentally tested on...
A method for detecting micro-cracks in solar cells using two dimensional matched filters was developed, derived from the electroluminescence intensity profile of typical micro-cracks. We describe the image processing steps to obtain a binary map with the location of the micro-cracks. Finally, we show how to automatically estimate the total length of each micro-crack from these maps, and propose a...
Pulse Width Modulated AC drives equipped with small DC-link capacitor are becoming an attractive solution for electric drive applications with moderate requirements for shaft dynamic performance. However, when these drives are fed from a weak grid a resonance between the line side impedance and the DC-link capacitor appears. Due to this resonance, the THD and the partially weighted harmonic distortion...
The photovoltaic market has been growing at a fast rate in the last two decades, and in 2014 reached a global capacity of about 180GW. Due to the increasing penetration level, large-scale energy storage systems that can compensate for its fluctuations become increasingly important. In case of off-grid systems, suitable energy storage is naturally a necessity. In areas with favorable geographical properties,...
This article proposes a method for quantifying the percentage of partially and totally disconnected solar cell cracks by analyzing electroluminescence images of the photovoltaic module taken under high- and low-current forward bias. The method is based on the analysis of the module's electroluminescence intensity distribution, applied at module and cell level. These concepts are demonstrated on a...
Grid-connected photovoltaic (PV) inverters tailored with reactive power management feature can support the grid voltage especially when the voltage fluctuates near its admissible limits. Although Q control allows reducing the grid voltage elevation along the distribution feeder, it brings extra load and power loss on the feeders and individual inverters. Simplified energy loss evaluation is carried...
In some cases it is unavoidable that part of the rooftop PV array is periodically shadowed by an adjacent object, greatly reducing yield. Usually, the time and amount of shadowing is known, and is considered as extra loss due to the location. Module Integrated Converter (MIC) systems are known to be a good solution for such cases, having the potential to increase the yield with as high as 25%, although...
This paper presents the concept and operating principles of a low-cost and flexible monitoring system for PV plants. Compared to classical solutions which can require dedicated hardware and/or specialized data logging systems, the monitoring system we propose allows parallel monitoring of PV plants with different architectures and locations by taking advantage of the intrinsic monitoring capabilities...
The accurate tracking of phase, frequency, and amplitude of different frequency components from a measured signal is an essential requirement for many digitally controlled equipment. The accurate and robust tracking of a frequency component from a complex signal was successfully applied for example in: grid connected inverters, sensorless motor control for rotor position estimation, grid voltage monitoring...
One of the main issues concerning large penetration of the renewable energy based generators on the distribution network is related to the voltage variations due to intermittent character of the solar irradiance and wind. The actual power quality standards provide only general information regarding the evaluation procedure of the voltage fluctuations and no directions regarding the sampling frequency...
Photovoltaic (PV) power among all renewable energies had the most accelerated growth rate in terms of installed capacity in recent years. Transmission System Operators (TSOs) changed their perspective about PV power and started to include it into their planning and operation, imposing PV systems to be more active in grid support. Therefore, a better understanding and detailed analysis of the PV systems...
An important and highly discussed safety issue for photovoltaic systems is that, as long as they are illuminated, a high voltage is present at the PV string terminals and cables between the string and inverters, independent of the state of the inverter's dc disconnection switch, which poses a risk for operators during maintenance or fire-fighting. One of the solutions is individual module shutdown...
The increased amount of Photovoltaic (PV) power installed into the power system every year places this renewable way of producing electricity on the third position in the renewable sources hierarchy after hydro and wind solutions. Having significant levels of renewable power penetration into the system led to stability concerns of the entire system affecting its reliability and availability. In consequence...
There are well-defined methods to measure the (increased) series resistance of PV panels in controlled laboratory conditions. However, the presence of various irradiance levels and partial shadows, in case of an outdoor installation, may affect the series resistance estimation. This paper focuses on the estimation of increased series resistance in outdoor conditions in various irradiance levels and...
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