1,721,020 research outputs found
An Improved Model for AC Power from Grid Connected Photovoltaic Systems and Comparison with Large-Scale Hourly Measured Data
Get PDFThe diffusion of renewable energy sources (RES) can lead to cost reductions for the ancillary services provided to the transmission system operator, in particular, when the RES production can be estimated with appropriate accuracy. This article presents significant improvements to photovoltaic (PV) power conversion models found in the literature for grid-connected PV systems. The refinement of the conversion model is based on public hourly data of irradiance and ambient temperature, referred to the sites of three groups of PV plants, to calculate the hourly average power injected into the grid. The values obtained are compared with the hourly average power measured by the distribution system operator meters on the PV systems. A double-step optimization procedure, based on seasonal analysis, sets up the various parameters in the PV conversion model. The key result is that the deviation between the simulated and measured annual energy is reduced to less than 2%. Moreover, with the proposed model the monthly energy deviations are limited to a few percentage points. This allows for significant improvements in the estimation of the production of grid-connected PV systems
Optimisation of Generation Models for Clusters of Photovoltaic Plants
Get PDFThe present work analyses the actual production profiles of a group of tens of thousands of PV plants. Actual PV generation profiles are represented as hourly average powers gathered from the energy meters measured at the point of common coupling with the grid. After filtering, data cleaning and statistical analysis, reference PV plants are selected for the improvements of the PV generation models. Production profiles are calculated by using literature generation models, with weather data as inputs. An optimisation is performed on the parameters of the literature models to minimise the differences between the cumulative distribution functions of calculated profiles and measured data. The study compares the performance of the different models and shows how the optimisation increases the quality of the calculated profiles
Benefits of on-load tap changers coordinated operation for voltage control in low voltage grids with high photovoltaic penetration
Get PDFThe transformers that connect the Medium Voltage (MV) grid with the Low Voltage (LV) system are classically equipped with tap changers with tap positions variable only at no load. The evolution of the technologies and the increasing needs of controlling the voltage profile in the LV networks require better control capabilities. The use of MV/LV transformers with On Load Tap Changers (OLTCs) is increasing, to provide further control capabilities in LV grids with high penetration of distributed generation. In this paper, centralised voltage control is evaluated by simulating the operation of an OLTC installed inside the MV/LV transformer substation. The goal is to stabilise the voltage at the LV bus of the transformer. It is supposed that the OLTC does not communicate with other devices in the grid; thus, it does not know the voltage levels at the other nodes. At the same time, the distributed PV inverters control the voltage in their grid connection points without any information about the other nodes. The expected benefits of exploiting OLTCs in LV grids with high photovoltaic (PV) penetration are determined through indicators that assess the voltage deviations with energy flows, the global overvoltage or undervoltage persistence, and the overvoltage or undervoltage duration. The results show that the use of an OLTC can help the mitigation of voltage fluctuations, especially limiting the undervoltages. The effectiveness strongly depends on the control parameters, especially the maximum number of daily taps
Knowledge Discovery from the Statistical Analysis of On-Site Photovoltaic System Data
Get PDFThis paper presents some novel ideas and findings to assist data analysts and operators in discovering specific situations from the analysis of photovoltaic data collected in the field. The daily time series of solar irradiance and active power production are transformed into probability distribution functions (PDFs), then the skewness of the PDF is assessed as a potential indicator of orientation of the PV system in directions different from South. The relevant PDFs corresponding to bright days are identified by applying a clustering procedure. The combined calculation of skewness and correlation between solar irradiance and active power data is also used to discover specific cases in which high shadowing occurs in particular days of the year and at particular times. The analyses are carried out by using data collected on-site in PV systems installed at different locations
Comparative Analysis of Energy Yield between PERC and HJT Modules Tested in Experimental Campaigns Carried out in Northern Italy
Get PDFThe heterojunction (HJT) solar cells based on the integration of monocrystalline silicon and amorphous crystalline layers provide a remarkable improvement in terms of efficiency with respect to the Passivated Emitter and Rear Cell (PERC) modules, which are currently installed in most of plants. However, the efficiency gain in terms of energy production is not estimated by recent works in literature for the Mediterranean area: hence, this paper presents a comparative study of energy yield in Torino (latitude of 45 degrees North, Italy) between PERC and HJT modules currently available on the market for conventional PhotoVoltaic (PV) installations, having rated power higher than 400 W. The modules were tested in experimental campaigns taking place in 2023 from April to September. In particular, this work quantifies the real energy yield improvements of HJTs with respect to PERC PV modules, resulting in an energy gain of HJTs between 3% and 6%. Finally, the dependence of these energy yield gains on irradiance and modules' temperature is investigated
Statistical Validation and Power Modelling of Hourly Profiles for a Large-Scale Photovoltaic Plant Portfolio
Get PDFIn the last decades, the number of photovoltaic (PV) generators significantly increased over the world. An accurate analysis of the massive data gathered from the meters of the PV plants can improve the management of their intermittent generation. This paper presents a methodology to analyse the production profiles of a portfolio of thousands of PV plants installed in an Italian region. The procedure faces the problem of filtering poor and incomplete data, then uses a stratified sampling technique for the statistical validation of the remaining profiles. Finally, the checked production profiles are used to adjust the energy model to better match the measured data and calculate the whole PV portfolio production
Maintenance Activity, Reliability, Availability, and Related Energy Losses in Ten Operating Photovoltaic Systems up to 1.8 MW
Get PDFIn general, photovoltaic (PV) plants do not include components with moving parts and, as a consequence, they are wrongly considered maintenance-free. Thus, this article presents a maintenance, reliability, and availability analysis of ten PV systems, with different inverter configurations, in the context of the intermittent renewable energy source systems, including the wind farms. The first part of the analysis consists of the evaluation of reliability using failure rates from the literature. In the second part, these results are compared with data obtained from industrial maintenance reports in the years 2016-2018. Finally, the yearly energy losses and the availability of each PV plant are assessed
Advancements and Challenges in Photovoltaic Power Forecasting: A Comprehensive Review
Get PDFThe fast growth of photovoltaic (PV) power generation requires dependable forecasting methods to support efficient integration of solar energy into power systems. This study conducts an up-to-date, systematized analysis of different models and methods used for photovoltaic power prediction. It begins with a new taxonomy, classifying PV forecasting models according to the time horizon, architecture, and selection criteria matched to certain application areas. An overview of the most popular heterogeneous forecasting techniques, including physical models, statistical methodologies, machine learning algorithms, and hybrid approaches, is provided; their respective advantages and disadvantages are put into perspective based on different forecasting tasks. This paper also explores advanced model optimization methodologies; achieving hyperparameter tuning; feature selection, and the use of evolutionary and swarm intelligence algorithms, which have shown promise in enhancing the accuracy and efficiency of PV power forecasting models. This review includes a detailed examination of performance metrics and frameworks, as well as the consequences of different weather conditions affecting renewable energy generation and the operational and economic implications of forecasting performance. This paper also highlights recent advancements in the field, including the use of deep learning architectures, the incorporation of diverse data sources, and the development of real-time and on-demand forecasting solutions. Finally, this paper identifies key challenges and future research directions, emphasizing the need for improved model adaptability, data quality, and computational efficiency to support the large-scale integration of PV power into future energy systems. By providing a holistic and critical assessment of the PV power forecasting landscape, this review aims to serve as a valuable resource for researchers, practitioners, and decision makers working towards the sustainable and reliable deployment of solar energy worldwide
Experimental investigations to characterize power quality of AC supplied thermoelectric refrigerators
No full textRecently, thermoelectric refrigeration, using thermoelectric coolers, is gaining interest among the specialists as a green cooling technology since many advantages derive from the use of this kind of devices. Since the diffusion of thermoelectric refrigerators is likely to increase in the next future, it is important to characterize their operation when the supply is provided in alternating current (AC); in fact, in this case the refrigerators are equipped with power electronic converters supplied by the electric distribution system. In particular, power quality issues, like waveform distortion and the evaluation of electric powers, have to be considered. In this paper, the operation of a thermoelectric refrigerator connected to the low voltage AC distribution system is considered and the waveform distortion and the electric power quantities are evaluated based on experimental data
Schemes and Techniques of Synchronous Modulation of PV Inverters with High Modulation Indices: A Survey
No full textThis manuscript presents short review of schemes, techniques and algorithms of synchronous space-vector pulsewidth modulation (PWM) developed for overmodulation control of voltage source inverters of transformer-based grid-connected photovoltaic (PV) systems. These system topologies are based on dual-inverter or triple-inverter configurations supplied by the corresponding strings of PV panels, and connected specifically with inverter-side windings of power transformer. Algorithms of space-vector PWM, developed and modified for synchronous control of PV inverters with high modulation indices (operating in the zone of overmodulation) insure synchronization and symmetry of voltage waveforms, characterized by improved spectral composition, at the outputs of inverters and at the corresponding windings of multi-winding power transformer
- …
