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The photovoltaic literature contains a wide range of methods for translating the I–V curves of a solar device to other conditions of irradiance and cell temperature, different from those under which the measurements were performed. Some of these translation methods are included as part of the International Standard IEC 60891. In this paper, these techniques are classified, reviewed, and implemented to perform a deep comparative analysis between them and to discuss their suitability for converting the I–V curves of photovoltaic modules under different scenarios of irradiance and temperature. From the analysis conducted, it can be seen that the interpolation method proposed in IEC 60891 achieves accurate results when it is applied to correct small and medium irradiance and temperature gaps. If no interpolation is possible and for large irradiance corrections, other procedures described in IEC 60891 can be applied. However, certain explicit methods based on the single-diode model or on the double-diode model can overcome the most well-known approaches proposed by the standard. [ABSTRACT FROM AUTHOR]

This paper proposes an energy management system (EMS) for a photovoltaic (PV) grid-connected charging station with a battery energy storage system (BESS). The main objective of this EMS is to manage the energy delivered to the electric vehicle (EV), considering the price and C O 2 emissions due to the grid's connection. Thus, we present a multi-objective two-stage optimization to reduce the impact of the charging station on the environment, as well as the costs. The first stage of the optimization provides an energy schedule, taking into account the PV forecast, the hourly grid's C O 2 emissions factor, the electricity price, and the initial state of charge of the BESS. The output from this first stage corresponds to the maximum power permitted to be delivered to the EV by the grid. Then, the second stage of the optimization is based on model predictive control that looks to manage the energy flow from the grid, the PV, and the BESS. The proposed EMS is validated using an actual PV/BESS charging station located at the University of Trieste, Italy. Then, this paper presents an analysis of the performance of the charging station under the new EMS considering three main aspects, economic, environmental, and energy, for one month of data. The results show that due to the proposed optimization, the new energy profile guarantees a reduction of 32% in emissions and 29% in energy costs. [ABSTRACT FROM AUTHOR]

This paper reviews the current techniques used in energy management systems to optimize energy schedules into microgrids, accounting for uncertainties for various time frames (day-ahead and real-time operations). The current uncertainties affecting applications, including residential, commercial, virtual power plants, electric mobility, and multi-carrier microgrids, are the main subjects of this article. We outline the most recent modeling approaches to describe the uncertainties associated with various microgrid applications, such as prediction errors, load consumption, degradation, and state of health. The modeling approaches discussed in this article are probabilistic, possibilistic, information gap theory, and deterministic. Then, the paper presents and compares the current optimization techniques, considering the uncertainties in their problem formulations, such as stochastic, robust, fuzzy optimization, information gap theory, model predictive control, multiparametric programming, and machine learning techniques. The optimization techniques depend on the model used, the data available, the specific application, the real-time platform, and the optimization time. We hope to guide researchers to identify the best optimization technique for energy scheduling, considering the specific uncertainty and application. Finally, the most challenging issues to enhance microgrid operations, despite uncertainties by considering new trends, are discussed. [ABSTRACT FROM AUTHOR]

The degradation of two amorphous silicon‐based photovoltaic (PV) modules, namely, of single junction amorphous silicon (a‐Si) and of micromorph tandem (a‐Si/ μ‐Si), after 11 years of exposure in the south of Spain is analyzed. Their I‐V curves were measured outdoors to study the changes of the electrical parameters in the course of three different periods: during the initial days of exposure, during the first year, and in the subsequent 10‐year period. The translation of the curves to an identical set of operating conditions, which enables a meaningful comparison, was done by the different correction procedures described in the standard IEC60891:2021, including the procedure 3, which does not require the knowledge of module parameters, whose values are typically not available. The annual power degradation rates over the entire 11‐year period are 1.12% for the a‐Si module, which is 3.02% for the first year, and 0.98% for the a‐Si/ μ‐Si, which is 2.29% for the initial year. [ABSTRACT FROM AUTHOR]

Digital electronics has become a standard for controlling electrical systems. This is due to the constant improvement of the digital devices, whether in terms of density, performance, flexibility of use, or cost reduction. This article looks into system-on-chip (SoC) field-programmable gate array (FPGA) for controlling complex electrical energy systems. These devices encompass multicore floating-point microprocessors embedded with standard peripherals and an FPGA fabric that allows the design of custom peripherals and specific hardware (HW) accelerators. Thus, SoC FPGA devices can be regarded as a good compromise between “super” microcontrollers (very fast in terms of computation but with a fixed microarchitecture) and pure FPGAs (ideal for specific concurrent microarchitectures but limited in terms of density). [ABSTRACT FROM AUTHOR]

In this paper, the results of the analysis of the degradation of a set of single‐crystalline silicon modules after 21 years are presented. The comparison of the main electrical parameters and the series and of the shunt resistances measured in 1996 and 2017 is performed, so that the annual degradation rate is evaluated. In addition, a detailed analysis of the parameter uncertainties has been performed in order to determine its impact on the results. A visual inspection of the modules has also been carried out in order to show the correlation with the variation of the electrical performance. Finally, the temperature coefficients of the degraded modules have been estimated and compared with the nominal ones. The results shown in the paper reveal that the mean annual degradation rate in terms of power is close to 0.9%. [ABSTRACT FROM AUTHOR]

Presents information on the 22nd IEEE International Conference on Industrial Technology. [ABSTRACT FROM AUTHOR]

The nine papers in this special section focus on photovoltaic module and sub-module level power electronics. Grid connected photovoltaic energy systems have experienced an explosive growth over the last decade, with a cumulative installed capacity surpassing the 400 GW milestone as of 2017. Among PV system configurations, distributed module-level converter architectures can lead to a higher energy yield by mitigating partial shading, persistent shading (soiling, snow, bird droppings, and fallen leaves), mismatch, and aging, through a higher maximum power point tracking (MPPT) efficiency. Also, distributed electronics might be the key for implementing diagnostic and prognostic actions at a module level. Among these configurations, microinverters (also known as ac-module inverter), which connect a single PV module to the grid, and PV power optimizers, which are dc–dc converters performing the MPPT function at a module level, have attracted the academic and industrial interest in the last decade. So much so, that both microinverters and dc–dc power optimizers are commercialized by tens of companies around the world, with a great variety of circuit topologies, which comprise combinations of one or more power stages, interleaved converters, resonant converters, topologies with and without isolation, etc. [ABSTRACT FROM AUTHOR]

In this paper, an efficient method for the online identification of the photovoltaic single-diode model parameters is proposed. The combination of a genetic algorithm with explicit equations allows obtaining precise results without the direct measurement of short circuit current and open circuit voltage that is typically used in offline identification methods. Since the proposed method requires only voltage and current values close to the maximum power point, it can be easily integrated into any photovoltaic system, and it operates online without compromising the power production. The proposed approach has been implemented and tested on an embedded system, and it exhibits a good performance for monitoring/diagnosis applications. [ABSTRACT FROM AUTHOR]

A zero-current switching full-bridge isolated dc/dc converter based on a semiresonant L-C cell has been developed in this paper. With respect to the classical full-bridge configuration, no additional switches are required, thus by preserving its simplicity and robustness. The proposed architecture allows achieving zero-current switching at both primary and secondary sides. A 50-kW prototype has been developed and tested in different operating conditions. The experimental results are in agreement with the simulations by confirming the goodness of the proposed solution. Efficiency up to 97% at full load operating condition has been reached in the laboratory prototype. [ABSTRACT FROM PUBLISHER]

The way of implementing an adaptive maximum power point tracking algorithm for photovoltaic (PV) applications in a field programmable gate array (FPGA) is described in this paper. A dual Kalman filter allows estimating the settling time of the whole system, including the PV source and the dc/dc converter controlling the operating point thereof, so that the tracking algorithm self adapts its parameters to the actual weather conditions. The real-time identification need of this application requires an FPGA platform, so that the intrinsic algorithm parallelism is exploited and the execution time is reduced. The tradeoff solutions proposed in this paper, accounting for the algorithm complexity and the limited FPGA hardware, as well as some solutions for optimizing the implementation are described. The proposed adaptive algorithm is implemented in a low-cost Xilinx Spartan-6 FPGA and it is validated through experimental tests. [ABSTRACT FROM PUBLISHER]

Vanadium redox flow battery (VRFB) systems complemented with dedicated power electronic interfaces are a promising technology for storing energy in smart-grid applications in which the intermittent power produced by renewable sources must face the dynamics of requests and economical parameters. In this article, we review the vanadium-based technology for redox flow batteries (RFBs) and highlight its strengths and weaknesses, outlining the research that aims to make it a commercial success. [ABSTRACT FROM PUBLISHER]

In this paper, the use of the Dual Kalman Filter for the identification of photovoltaic system parameters is presented. The system includes the photovoltaic source, the dc/dc converter and the battery/dc bus and both its states and parameters in the actual operating conditions are identified. In particular, the proposed approach gives the confidence interval for the system settling time, which is used for the real-time optimization of the perturbative maximum power point tracking algorithm. The proposed technique is implemented by using a Field-Programmable Gate Array and it is validated by means of both simulation and experimental results. [ABSTRACT FROM PUBLISHER]

The long power production warranties guaranteed by the manufacturers of photovoltaic (PV) modules (25 years) are a vital factor for the economical viability of PV systems. Nevertheless, recent studies have demonstrated that the modules may experience an early degradation, which turns into the reduction of the power production or even the damage of the entire PV module. In this paper, a method aimed at detecting the module degradation is introduced. It detects and quantifies the degradation by means of two indicators, which are aimed at estimating the increment of the modules series resistance, this parameter being one of the most affected by some degradation mechanisms. The increase of the series resistance value is estimated through the evaluation of the error in predicting the position of the maximum power point, which is obtained by comparing the experimental measurements with the single-diode model. The proposed method is experimentally validated, and it is compared with other methods reported in the literature. The results show that the proposed indicators are able to accurately estimate the increments of the series resistance with a low sensitivity to the irradiance and temperature values. This feature improves the accuracy and the reliability of the diagnosis processes and monitoring systems. [ABSTRACT FROM PUBLISHER]

In the last five years, the desire to improve the control of photovoltaic (PV) arrays working in mismatched conditions has stimulated substantial research and development. Recent research has revived the previously discounted idea of changing the electrical connection between the PV modules according to their operating conditions and load requests. The switching matrix is reliable and allows the additional cost of module-level switching converters to be avoided and also maintains high efficiency under infrequent mismatched conditions. The PV array electrical reconfiguration also enables the best load matching between the PV source and its varying load. Such issues are discussed in this article with an overview of the main aspects introduced in the technical literature. [ABSTRACT FROM PUBLISHER]

Photovoltaic (PV) systems are one of the main actors in distributed power generation. In particular, in urban contexts, the PV generators can be subjected to mismatching phenomena due to the different orientation of the modules with respect to the sun rays or due to shadowing. In these cases, the maximum power point tracking (MPPT) function must be designed carefully. In this paper, architecture, including one dc/dc converter for each PV generator, is considered. The converters' output terminals are series connected to a high-voltage dc bus, where also a bidirectional dc/dc converter managing the power from/to a storage device is plugged. The functional constraints deriving from the dc/dc converters' connection, the mismatching phenomena, the MPPT capabilities of the inverter, connected with its input terminals at the dc bus, are taken into account in order to determine the best operating point of the system as a whole. The real-time constrained optimization problem is solved by using the particle swarm optimization method, which needs the knowledge of the actual current versus voltage curve of each PV generator. The practical impact of this need is also discussed in the paper. The feasibility and the performances of the proposed approach are experimentally validated by using a laboratory prototype. [ABSTRACT FROM PUBLISHER]

The maximum power point (MPP) tracking function allows one to extract the maximum power from the photovoltaic (PV) system in any operating condition. The perturb and observe technique is one of the mainly used algorithms aimed at this function. Its performances depend on the values of the two design parameters, which are the amplitude and the frequency of the perturbations that it applies in identifying the position of the MPP. In this paper, a method for the online optimization of the perturbation period is presented. It is based on the identification of the whole system, including the PV source and the dc/dc converter controlling it. The system impulse and frequency responses are evaluated by using the cross-correlation method. Such a technique, as well as the tracking algorithm, is effectively implemented by using a field-programmable gate array, and it is validated by means of simulation and experimental results. [ABSTRACT FROM PUBLISHER]

In this paper, the procedure for designing a sliding-mode controller for maximum power point tracking photovoltaic (PV) applications is proposed. It is applied to a single-ended primary inductor converter, thus to a fourth-order topology, but it can be extended to a wide class of converters suitable for PV applications. The reachability and existence conditions give rise to a number of design inequalities that add to the classical steady-state conditions in order to have the desired closed-loop converter's performances. The superiority of the control technique over the classical tracking methods is analytically demonstrated through the procedure proposed in this paper. The analytical results have been validated by means of both simulations and experiments. [ABSTRACT FROM PUBLISHER]

In practical photovoltaic (PV) installations the operating conditions of the panels the PV array is made of are different owing to different factors. Such irregular conditions are known as 'mismatching conditions' and produce multiple maxima in the power-voltage curves of any PV array. The traditional maximum power point tracking (MPPT) techniques are able to track one of those maxima, but they cannot guarantee the extraction of the maximum power the PV array would be able to deliver. To overcome this problem, many techniques have been presented in the literature: they use one converter for the entire array (centralised MPPT), one converter for each part of the array (distributed MPPT) or they reconfigure the PV array (RMPPT). This paper presents the general architectures used by 61 different MPPT techniques, by discussing their main advantages and disadvantages, in order to give to the reader a comprehensive view of both the control strategies and the architectures for extracting the maximum power from a mismatched PV field. Moreover, the widely adopted techniques for each hardware structure are presented in a structured and compact way, thus providing to the reader some guidelines regarding the technique's operation principle and hardware requirements. [ABSTRACT FROM AUTHOR]

In practical photovoltaic (PV) installations the operating conditions of the panels the PV array is made of are different owing to different factors. Such irregular conditions are known as 'mismatching conditions' and produce multiple maxima in the power-voltage curves of any PV array. The traditional maximum power point tracking (MPPT) techniques are able to track one of those maxima, but they cannot guarantee the extraction of the maximum power the PV array would be able to deliver. To overcome this problem, many techniques have been presented in the literature: they use one converter for the entire array (centralised MPPT), one converter for each part of the array (distributed MPPT) or they reconfigure the PV array (RMPPT). This paper presents the general architectures used by 61 different MPPT techniques, by discussing their main advantages and disadvantages, in order to give to the reader a comprehensive view of both the control strategies and the architectures for extracting the maximum power from a mismatched PV field. Moreover, the widely adopted techniques for each hardware structure are presented in a structured and compact way, thus providing to the reader some guidelines regarding the technique's operation principle and hardware requirements. [ABSTRACT FROM AUTHOR]

The main design objective of photovoltaic (PV) systems has been, for a long time, to extract the maximum power from the PV array and inject it into the ac grid. Therefore, the maximum power point tracking (MPPT) of a uniformly irradiated PV array and the maximization of the conversion efficiency have been the main design issues. However, when the PV plant is connected to the grid, special attention has to be paid to the reliability of the system, the power quality, and the implementation of protection and grid synchronization functions. Modern power plants are required to maximize their energy production, requiring suitable control strategies to solve the problems related to the partial shading phenomena and different orientation of the PV modules toward the sun. Moreover, the new policy concerning the injection of reactive power into the grid makes the development of suitable topologies and control algorithms mandatory. A general view of actual solutions for applications of the PV energy systems is presented. This article covers several important issues, including the most reliable models used for simulation, which are useful in the design of control systems, and the MPPT function, particularly in distributed ?applications. The main topologies used in the PV power processing system and, finally, grid connection aspects are discussed, with emphasis on synchronization, protections, and integration. [ABSTRACT FROM PUBLISHER]

ABSTRACT In this paper, a Distributed Maximum Power Point Tracking (D-MPPT) approach in photovoltaic (PV) applications is discussed. The proposed control method is suitable for the granular control of the PV generator at a module level or even at a sub-module level. D-MPPT is usually implemented by means of independent converters, each one of them running its own MPPT algorithm. Instead, the architecture proposed in this paper consists of only one digital controller, implementing a multivariable MPPT algorithm based on the Perturb and Observe approach, acting on a number of dc/dc converters, each one of them dedicated to a single PV module. The proposed control strategy reduces the number of current sensors with respect to the classical D-MPPT architecture and tracks the maximum power evaluated at the dc/dc converters' output. Planar solid immersion mirror simulations and experimental results confirm the validity of the approach and of the design guidelines proposed in the paper. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Sliding mode is a control technique that is widely employed in switching converter applications. Such a nonlinear control technique, which is commonly implemented by means of analog circuitry only, forces the switches commutations by comparing a reference signal with a combination of signals acquired on the converter itself. In this way, the control action and the switching modulation are integrated in a single functional block. In this paper the implementation of the sliding mode controller in a low cost digital device is discussed. The proposed approach profits from features offered by some digital devices, e.g., the dsPic33FJ16GS502 family from Microchip Technology Inc., in order to make the implementation simple. In the paper, the aspects related to the accuracy of the comparison between the signals required by the sliding mode controller are discussed. Moreover, the elaboration time needed to calculate the signals that drive the converter's switching devices is the subject of an in-depth analysis. The techniques proposed in the paper have been validated by means of simulations and through experimental results performed on a switching dc/dc converter for photovoltaic applications. [ABSTRACT FROM PUBLISHER]

This paper introduces a novel maximum power point tracking (MPPT) technique aimed at maximizing the power produced by photovoltaic (PV) systems. The largest part of the MPPT approaches presented in the literature are based on the sensing of the PV generator voltage. On the contrary, in this paper, a current-based technique is proposed: the sensing of the current in the capacitor placed in parallel with the PV source is one of the innovative aspects of the proposal. A dual control technique based on an inner current loop plus an outer voltage loop allows to take profit of the fast current tracking capability of the inner current loop while the voltage loop benefits from the logarithmic dependency of the PV voltage on the irradiation level. The features of the proposed algorithm, particularly in terms of tracking of irradiation variations and disturbance rejection, are supported by theoretical analysis, simulations, and experimental results. The technique described in this paper is patent pending. [ABSTRACT FROM PUBLISHER]

TEODI is the acronym of a maximum power point tracking (MPPT) technique which has been recently presented in the literature. Such a technique is particularly suitable in distributed MPPT photovoltaic (PV) applications, and it is based on the equalization of the output operating points, of the dc/dc converters dedicated to each subsection of the PV array, in correspondence of the forced displacement of their input operating points. The main advantages of TEODI, its performances in terms of MPPT efficiency and speed of tracking, and the intrinsic capability to attenuate the effect, on the voltages of the PV modules, of the 100/120 Hz disturbances coming from the grid are shown by means of simulation results and experimental findings obtained by using a laboratory prototype developed by means of analog circuitry only. [ABSTRACT FROM PUBLISHER]

The high design complexity of photovoltaic plants is due to several variables which sometimes affect relevantly its efficiency. The evaluation of all technical and economic aspects of design is therefore essential to establish the actual sustainability of the system. Furthermore, the expansion of the PV market, due to the growing interest in the environmental problems and to the introduction of an articulated policy of incentives, has led to a strong supply growth in the sector, with a great variability of available products; so, the evaluation of the optimal plant configuration according to specific needs is often difficult. This paper describes a methodology, based on a complex plant simulator, which processes available data for every component of the system and allows making a reasoned choice of the best suited system configuration. This simulator evaluates, under various loading conditions, the behaviour of each photovoltaic architecture, obtained from the combination of the components to be assessed. Finally, an optimization model which analyzes the mutual interactions between technical and economic parameters, helping to choose the best compromise between energetic and economic performances is proposed. [ABSTRACT FROM AUTHOR]

In this paper, a novel maximum power point tracking algorithm based on the perturb-and-observe (P&O) technique is introduced. The novelty of the approach is represented by the perturbation of more control variables, rather than just one. This allows the increase of the power extracted from the photovoltaic (PV) field as compared to the case of perturbation of a single control variable. The proposed technique overcomes the limitations of any existing tracking technique dedicated to PV arrays exhibiting a unique maximum power point, thus not only of the P&O approach, whenever dynamic constraints ensuring the correct system behavior must be fulfilled too. The proposed multivariable approach is described by means of its application to a single-stage one-cycle controlled PV inverter. [ABSTRACT FROM AUTHOR]

The study of a double-stage single-phase inverter for fuel-cell-based applications is proposed in this paper. A novel control strategy aimed at reducing the low-frequency oscillations of the fuel-cell (FC) current in order to guarantee the FC safety operating conditions is proposed. The reduction of such oscillations increases the FC lifetime and avoids high mechanical stress of the membrane and unnecessary consumption of reactants. Furthermore, it allows one to design a strategy for extracting the maximum power from the FC stack with a total control of the concentration losses. Simulation and experimental results confirm the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

In this paper, a polymer-electrolyte-membrane fuel-cell (FC) model that is useful for simulation and control purposes is presented. The model uses both electrical-circuit components and functional blocks to reproduce both static and dynamic FC behaviors. Its main feature is in the reproduction of the oxygen-excess-ratio behavior, but it is also able to interact with any electrical device connected at the FC terminals, e.g., a load or a switching converter. Consequently, the proposed model can be used to develop new control strategies aimed at avoiding the oxygen-starvation effect and/or minimizing the fuel consumption. The model has been customized for a Ballard Nexa 1.2-kW power system, and this has allowed an experimental validation by means of measurements performed on a real FC device. [ABSTRACT FROM AUTHOR]

This paper presents a novel method to design the output filter of low-voltage/high-current buck dc-dc switching regulators. The method is based on the concept of acceptability boundary curves (ABCs). ABCs are the curves bounding the regions in the space of parameters, including commercial components which ensure an acceptable output voltage ripple and a load-transient surge based on design specifications. ABCs help in quickly finding tradeoff design solutions, as well as in a better understanding of the functional correlations among power components. Examples regarding buck converters for point-of-load applications are discussed to highlight the flexibility and reliability of the ABC-based design method. Experimental measurements confirm the analytical results and numerical predictions. [ABSTRACT FROM AUTHOR]

In double-stage grid-connected photovoltaic (PV) in. verters, the dynamic interactions among the dc/dc and dc/ac stages and the maximum power point tracking (MPPT) controller may reduce the system performances. In this paper, the detrimental effects, particularly in terms of system efficiency and MPPT performances, of the oscillations of the PV array voltage, taking place at the second harmonic of the grid frequency are evidenced. The use of a proper compensation network acting on the error signal between a reference signal provided by the MPPT controller and a signal that is proportional to the PV array voltage is proposed. The guidelines for the proper joint design of the compensation network (which is able to cancel out the PV voltage oscillations) and of the main MPPT parameters are provided in this paper. Simulation results and experimental measurements confirm the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

The article discusses various reports published within the issue, including one by Maffezzoni and colleagues on an electrothermal macromodel for photovoltaic (PV) module, one by Velasco-Quesada and colleagues on an electrical array configuration approach on the PV plant and another by Romero-Cadaval and colleagues on a grid-connected PV system which employs two parallel-connected inverters.