Output Characteristics Of Photovoltaic Array Research Articles

A multilayer integrative approach for diagnosis, classification and severity detection of electrical faults in photovoltaic arrays

Early detection of faults in photovoltaic (PV) systems is crucial for improving their lifespan and reliability. Conventional protection devices may not be able to detect electrical faults under critical conditions. This usually occurs due to (i) the current-limiting nature and non-linear output characteristics of PV arrays, (ii) the changing environmental conditions (such as irradiance and temperature variations), and (iii) the influence of the maximum power point tracker (MPPT), particularly in the presence of critical fault impedance values or mismatch levels. Therefore, modern data-driven methods are required for fault detection and classification in PV arrays. However, careful investigation in previous studies reveals the existing gaps and limitations, such as poor accuracy, and incomprehensive models which have not considered various electrical faults, low mismatch levels, and critical fault impedance values. To this end, in this study, a comprehensive multilayer model is proposed which consists of six layers for diagnosis, classification and severity identification of electrical faults in PV arrays. Each layer adopts a weighted ensemble learning (WEL) algorithm consisting of three classifiers namely Support Vector Machine (SVM), Naïve Bayes (NB) and Logistic Regression (LR). Besides, a genetic algorithm (GA) is employed in each layer to find the optimal weights for each classifier (i.e., SVM, NB and LR). The initial dataset is acquired through an investigation into the PV array current–voltage (I-V) characteristic curve and extraction of several features under various faulty and normal conditions. To reduce the dataset dimensionality thus computationally simplifying the training process, the sequential floating forward selection (SFFS) algorithm is utilized in each layer as a powerful feature selection technique. The results show a highly accurate performance in fault diagnosis, classification, and severity assessment, with an average simulation and experimental accuracies of 98.9% and 98.37%, respectively.

Research on the output characteristics of photovoltaic arrays under partial shading conditions based on peak point approximate calculation method

Research on the output characteristics of photovoltaic arrays under partial shading conditions based on peak point approximate calculation method

Application of Artificial Intelligence in PV Fault Detection

The rapid revolution in the solar industry over the last several years has increased the significance of photovoltaic (PV) systems. Power photovoltaic generation systems work in various outdoor climate conditions; therefore, faults may occur within the PV arrays in the power system. Fault detection is a fundamental task needed to improve the reliability, efficiency, and safety of PV systems, and, if not detected, the cost associated with the loss of power generated from PV modules will be quite high. Moreover, maintenance staff will take more time and effort to fix undetermined faults. Due to the current-limiting nature and nonlinear output characteristics of PV arrays, fault detection is not that easy and the application of artificial intelligence is proposed for the sake of fault detection in PV systems. The idea behind this approach is to compare the faulty PV module with its accurate model (factory fingerprint) by checking every PV array’s I–V and P–V curves using the Artificial Neural Network (ANN) logarithm as a subsection of the Artificial Intelligence’s (AI) techniques. This proposed approach achieves a high performance of fault detection and gives the advantage of determining what type of fault has occurred. The results confirm that the proposed logarithm performance becomes better as the number of distinguishing points extend, providing great value to the Solar PV industry.

Power output control method of small power photovoltaic grid connected power generation under complex illumination

Due to the irregular change of lighting conditions, there is a large error in the control of photovoltaic grid connected power output. Therefore, this paper proposes proposes a power output control method for low-power photovoltaic grid-connected power generation considering complex illumination. Based on the analysis of the basic characteristics of photovoltaic grid connected power generation, the output characteristics of photovoltaic array under complex lighting conditions are studied. Combined with its variation characteristics, based on fuzzy control strategy, the output of photovoltaic grid connected energy storage system is adjusted by filter control with variable time constant, and economic operation and stable operation are taken as constraints. The test results show that the design method has a high degree of fit between the control of photovoltaic grid connected power output and the actual results, and the error is within a reasonable range, which is obviously due to the two groups of comparison methods.

The Design and Investigation of Space Photovoltaic Array Hardware-simulator

A hardware part of space photovoltaic array simulation system is designed in this paper, to realize the actual output characteristics of photovoltaic array. In this paper, the design of a PV array emulator (PVAE) is presented. By analyzing the V-I characteristic curve of solar cell given by the previous software, the simulation scheme is developed. Secondly, the control scheme of the proposed emulator based on DC-DC converter is discussed in detail, than the transfer function of the whole system is established, at last the digital controller based on DSP is designed. A prototype 200W PVAE based on full bridge DC-DC converter has been made, the experimental results show the validity of the controller design. The application of the PVAE can greatly shorten the research and design cycle of photovoltaic array power supply system of spacecraft, improve the research efficiency and credibility of research results.

Research on Accurate Engineering Mathematical Model of PV Cells and Simulation Characteristics

It is an important basis for PV power generation and related technology research to establish an efficient and accurate photovoltaic (PV) array engineering mathematical model. For the difficult problem of traditional mathematical model of PV array to be solved, the engineering mathematical model of PV array is derived based on PV cell single diode model. The diode ideal factor, series resistance, temperature and radiation intensity of PV array on the output characteristics of PV array influences are analyzed. The model is improved and the parameters are optimized, an efficient iterative method is proposed to calculate the series resistance and parallel resistance. On Matlab platform, the comparison of 4 solar cell material property parameters is tested to verify the accuracy of the proposed solution. The results are compared with the traditional Newton iterative method and approximate fitting line method in 5 random environments, the error can be within 6%. The simulation results show that the proposed model has better versatility and sensitivity, quickly and accurately reflects the I–U and P–U output characteristics of PV arrays under variable working conditions; it meets the requirements of engineering accuracy, and provides strong support for large-scale PV power generation system and related research.

A Novel Pigeon-Inspired Optimization Based MPPT Technique for PV Systems

The conventional maximum power point tracking (MPPT) method fails in partially shaded conditions, because multiple peaks may appear on the power–voltage characteristic curve. The Pigeon-Inspired Optimization (PIO) algorithm is a new type of meta-heuristic algorithm. Aiming at this situation, this paper proposes a new type of algorithm that combines a new pigeon population algorithm named Parallel and Compact Pigeon-Inspired Optimization (PCPIO) with MPPT, which can solve the problem that MPPT cannot reach the near global maximum power point. This hybrid algorithm is fast, stable, and capable of globally optimizing the maximum power point tracking algorithm. Therefore, the purpose of this article is to study the performance of two optimization techniques. The two algorithms are Particle Swarm Algorithm (PSO) and improved pigeon algorithm. This paper first studies the mechanism of multi-peak output characteristics of photovoltaic arrays in complex environments, and then proposes a multi-peak MPPT algorithm based on a combination of an improved pigeon population algorithm and an incremental conductivity method. The improved pigeon algorithm is used to quickly locate near the maximum power point, and then the variable step size incremental method INC (incremental conductance) is used to accurately locate the maximum power point. A simulation was performed on Matlab/Simulink platform. The results prove that the method can achieve fast and accurate optimization under complex environmental conditions, effectively reduce power oscillations, enhance system stability, and achieve better control results.

Optimal Photovoltaic Array Dynamic Reconfiguration Strategy Based on Direct Power Evaluation

In actual operation, photovoltaic arrays inevitably encounter shadow problems, resulting in a power output decline and multiple peaks in the output characteristics. The effect of partial shade can be satisfactorily reduced by photovoltaic array reconfiguration. Almost all current reconfiguration techniques are based on the irradiance equalization principle. However, by analyzing the output characteristics of photovoltaic array, it is found that the irradiance equalization principle improves the output power by increasing only the minimum row current without considering the effect of the voltage, so the reconfiguration techniques based on this principle cannot obtain the global optimal configuration under some partial shading conditions. In order to maximize the output power of photovoltaic array under any partial shaded condition, this paper proposes a reconfiguration strategy based on direct power evaluation. In this approach, the reconfiguration problem is formulated as a 0-1 multi-knapsack problem, and a novel mathematical model is established to directly evaluate the maximum output power of photovoltaic array. Then, the optimal reconfiguration scheme is determined by solving the mathematical model. Finally, the effectiveness of the proposed reconfiguration strategy is proved in theory and simulations.

Quantitative estimation of mismatch losses in photovoltaic arrays under partial shading conditions

Partial shading can significantly reduce the output power of photovoltaic (PV) arrays due to mismatch losses. The mismatch losses mainly depend on the shading levels of shaded modules in the PV array. A judgment method for the states of the blocking diodes in PV modules under partial shading conditions is presented to quantify the electrical mismatch losses of PV arrays. A single diode model without any approximation is employed to find the electrical parameters of PV modules precisely from the manufacturer’s datasheet. The output characteristics of PV arrays at maximal power conditions are determined with the Lambert W function. The overall effect of the mismatch losses caused by partial shading on the output power of PV arrays with blocking diodes protection is analyzed in detail. Three types of PV arrays are utilized to quantify the mismatch losses in PV arrays under partial shading conditions. Simulation results indicate that the conventional crystalline technologies are more affected by partial shading than the thin-film technology. The PV arrays suffer from various degrees of power mismatch under partial shading conditions.

A Novel Photovoltaic Array Outlier Cleaning Algorithm Based on Sliding Standard Deviation Mutation

There is a large number of outliers in the operation data of photovoltaic (PV) array, which is caused by array abnormalities and faults, communication issues, sensor failure, and array shutdown during PV power plant operation. The outlier will reduce the accuracy of PV system performance analysis and modeling, and make it difficult for fault diagnosis of PV power plant. The conventional data cleaning method is affected by the outlier data distribution. In order to solve the above problems, this paper presents a method for identifying PV array outliers based on sliding standard deviation mutation. Considering the PV array output characteristics under actual environmental conditions, the distribution of array outliers is analyzed. Then, an outlier identification method is established based on sliding standard deviation calculation. This method can identify outliers by analyzing the degree of dispersion of the operational data. The verification part is illustrated by case study and algorithm comparison. In the case study, multiple sets of actual operating data of different inverters are cleaned, which is selected from a large grid-connected power station. The cleaning results illustrate the availability of the algorithm. Then, the comparison against the quantile-algorithm-based outlier identification method explains the effectiveness of the proposed algorithm.

Development of PV array configuration under different partial shading condition

This paper investigates the performances of different photovoltaic (PV) array under several shading condition. Four types of photovoltaic array configuration scheme which are ‘Series’ (S), Series-Parallel’ (SP), Total-Cross-Tied’ (TCT), and ‘Bridge-Link’ (BL) array topologies were tested by applying a 6x6 PV array under 6 different shading scenarios. The modeling is developed using Matlab/Simulink. The performances and output characteristics of photovoltaic array are compared and analyzed. System engineer can use the detailed characteristics of different array configuration to approximate the outcome power and pick the best configuration of the system by concerning the current natural condition to enhance the overall efficiency.

Maximum Power Point Tracking of PV Systems Based On a Novel Adaptive Variable Step Size INC MPPT Method

In the future solar energy will become a very important green energy. Maximum power point (MPP) tracking (MPPT) technology is widely used in solar photovoltaic (PV) systems to generate peak power for PV arrays that depend on solar irradiation and ambient temperature. Literature[1] shows that the maximum power point tracking (MPPT) technology can improve the efficiency of photoelectric conversion by more than 20% and the economic cost is relatively low. Based on PROTUES, the output characteristics of PV arrays under different shadow conditions are simulated and the rule between local maximum power point and open circuit voltage is obtained. Among all the MPPT strategies, the incremental conductance (INC) algorithm and perturb and observe (P&O) algorithm are widely used due to the high tracking accuracy at steady state and easy implementation.In this paper, a novel adaptive variable step size INC MPPT method is proposed according to the above rule. This algorithm not only has the advantage of INC, but also can automatically adjust the step size to track the maximum power point of PV arrays. Compared with the adaptive perturb and observe (P&O) algorithm, the proposed approach can effectively improve the MPPT steady-state response speed and accuracy simultaneously. The theoretical analysis and design principle of the proposed algorithm are presented in this paper. The simulation results show that the algorithm can accurately track the maximum power point (MPP) with shadow. The average tracking time is only 0.13 seconds, and the power tracking efficiency reaches 98%.

Analysis of Output Characteristics of Photovoltaic Array under Time-varying Shadow

The Photovoltaic (PV) array is often obscured by moving clouds, surrounding buildings, and so on. That results in the formation of partial shadow in the PV array, which leads to the multi-peak characteristics of the PV array to make the traditional maximum power point tracking (MPPT) method invalid. Therefore, it is necessary to explore and analyze the output characteristics of the PV array under partial shadows in order to improve the effectiveness and accuracy of MPPT. Partial shadow is divided into static shadow and time-varying shadow. In this paper, the output characteristics of the PV array under time-varying shadow are mainly studied. The motion of the extreme points during the process of shadow variation is obtained. These research results lay the foundation for the following MPPT algorithm.

Fault diagnosis approach for photovoltaic arrays based on unsupervised sample clustering and probabilistic neural network model

Photovoltaic power plants which work under actual conditions are composed of a large quantity of photovoltaic arrays. The complex configuration of such photovoltaic arrays frequently produces various types of fault which directly affect the safe and economic operation of the power plant. There are still some problems for fault diagnosis of photovoltaic arrays: it is difficult to precisely represent the electrical characteristics of an array under different fault conditions, fault diagnosis models require the accurate division of fault samples, but the classification of fault data depends on artificial prior knowledge. This paper proposes a fault diagnosis method wherein: (i) the photovoltaic array output characteristics and distribution of electrical eigenvectors under typical fault conditions are be effectively analyzed; (ii) the per unit method and the Gaussian kernel function are introduced into the fuzzy C means algorithm to improve the applicability and fuzzy clustering ability of the unsupervised screen for various fault samples; and (iii) a probabilistic neural network fault diagnosis model is built with clustered data as the input. Practical operation data is used to successfully validate the effectiveness and feasibility of the proposed method.

On the Output Characteristics of PV Array with Partial Shading and Different Temperature

The surface temperature of PV is different in the condition of the different shadings; the corresponding output characteristics will be different. This paper studies the influence of temperature and shading variation on the output P-V and I-V characteristics of photovoltaic array, and the effect of this difference on the global MPPT algorithm. In order to analyze the influence of temperature and shading on the output characteristics of photovoltaic array, the article assumes that a cloud drifts across the PV array, and simulates three kinds of situations. Simulation results show that, the output power decreased slightly under the different temperature and shading, but closer to the actual situation. The results will provide theoretical support for further optimization of global MPPT algorithm.

The Comprehensive Study of Electrical Faults in PV Arrays

The rapid growth of the solar industry over the past several years has expanded the significance of photovoltaic (PV) systems. Fault analysis in solar photovoltaic (PV) arrays is a fundamental task to increase reliability, efficiency, and safety in PV systems and, if not detected, may not only reduce power generation and accelerated system aging but also threaten the availability of the whole system. Due to the current-limiting nature and nonlinear output characteristics of PV arrays, faults in PV arrays may not be detected. In this paper, all possible faults that happen in the PV system have been classified and six common faults (shading condition, open-circuit fault, degradation fault, line-to-line fault, bypass diode fault, and bridging fault) have been implemented in 7.5 KW PV farm. Based on the simulation results, both normal operational curves and fault curves have been compared.

Matlab/Simulink Based Modeling to Study Effect of Partial Shadow on Solar Photovoltaic Array

Solar module is considered as fundamental power transformation unit of Photovoltaic (PV) generation system. The performance of a PV array strongly depends on operating environmental conditions such as operating temperature, solar insolation, shading array configuration. Often PV arrays get shadowed fully or partially by passing cloud, building, poles, trees, etc. Under such partial shading conditions, the operation of PV arrays get more complicated with more than one peak and it is very important to predict the characteristics to obtain possible maximum power. Furthermore, the mismatch losses and hotspot effects caused by partially shading cannot only affect the output power of solar system also can bring security and reliability problem. However, it is quite expensive and takes much time to get operating output characteristics of PV arrays under non uniform working conditions. Therefore, it is necessary to have a simulation model to study the effect of partial shading on solar PV arrays’ working characteristics. A 100 W solar panel is used as reference. The study also focuses on position of output peak power with varying location of shaded modules, different levels of solar irradiation as well as role of bypass diodes in this system. The I–V and P–V output curves of the solar PV arrays under partially shading conditions are given. The simulation results indicate that the higher number of shaded solar modules is, the lower value of power output is and the position of maximum power point does not depend on location of modules under shadow. The paper provides an easy method to study the response of solar PV arrays under non uniform working conditions: partial shadow. In addition, the following points were also investigated:

Research on the Output Characteristics of Photovoltaic Array under the Non-Uniform Light

The output characteristics of photovoltaic array was related with the topology of array, shadow distribution and illumination level. The theoretical analysis and simulation modeling of output characteristics of photovoltaic array including series array, parallel array and series-parallel array were made under the non-uniform illumination environment based on the circuit analysis. The photovoltaic cell was modeled by use of the improved two-diode model. Non uniform illumination is expanded from two illumination levels of traditional to N illumination levels and from the single series array to any number series-parallel array. The different analysis methods were adopted in different arrays for mathematical modeling and simulation. The current analysis was used in series arrays and voltage analysis used in parallel arrays. Analysis of current in branches and voltage between branches was used in series-parallel array. Then the mathematical models were established and programmed in m-file by MATLAB. The simulation models had a high computational accuracy, and were suitable for any simulation output characteristics of PV in different light environment and array topology. They could provide a theoretical basis for constructing the topological structure on the same condition and studying MPPT of PV array under non-uniform illumination.

Based on the Hybrid Energy Storage System in the Application of Stable DC Bus Voltage

Due to the large number of distributed power supply random connected to power grid, it has severely influenced on power quality of the grid. In the storage battery directly on the basis of the DC bus, adopting the method of hybrid energy storage system makes a research on the output characteristics of photovoltaic array and the charging and discharging of battery and super capacitor. Research results show that the hybrid energy storage system can take advantage of the DC/DC converter to coordinate photovoltaic array, energy storage unit and the energy flows among load, also that the stability of DC bus voltage can be ensured by the system switch from the different work patterns.

An Improved P&O MPPT Method for Photovoltaic Power System

To improve the utilization efficiency of the solar energy with certain conversion efficiency, the principle of MPPT control with Boost converter is explained according to photovoltaic array output characteristics. The disadvantage of the conventional perturbation and observation (P&O) is analyzed. A novel MPPT system based on a digital signal processor (DSP) with Boost converter and an improved P&O algorithm is proposed in this paper. The proposed MPPT system model is developed under Matlab/Simulink. At last, theory analysis indicates its feasibility while the simulation results verify its validity.