Kian Jazayeri

A comparative study on different photovoltaic array topologies under partial shading conditions

This paper mainly analyzes the performance of different photovoltaic array configurations under various shading patterns. A Matlab/Simulink based simulation model of a PV module is utilized as the smallest building block of the mentioned topologies. The model is validated using the datasheet parameters of the ‘SOLAREX MSX-60’ PV module. The performance and output characteristics of ‘Series-Parallel’, ‘Total-Cross-Tied’ and ‘Bridge-Link’ array topologies are analyzed and compared using a 6×6 PV array under 6 different shading scenarios. The effects of bypass diodes during partial shading conditions are considered and the analysis results are presented and compared with and without bypass diodes. The mentioned shading scenarios are defined in such a way to simulate the passage of a cloud in different patterns. The results show that all the mentioned topologies have similar performances under identical illuminations while the ‘Total-Cross-Tied’ (TCT) configuration, despite the high complexity of the system, outperforms both ‘Series-Parallel’ (SP) and ‘Bridge-Link’ (BL) structures under partial shading conditions. ‘Bridge-Link’ and ‘Series-Parallel’ configurations stand on the 2nd and 3rd performance stages respectively while a Series-Parallel connection presents the least system complexity. The analyses and results provide detailed information on the characteristics of different array topologies which can be utilized by system designers to estimate the power yield and choose the most appropriate system configuration with respect to the existing environmental conditions to improve the overall efficiency.

A simple MATLAB/Simulink simulation for PV modules based on one-diode model

This paper proposes a simple and practical simulation model for solar modules using MATLAB/Simulink. The model is based on a single-diode mathematical model of a solar cell and is capable of accurate modeling of I-V and P-V characteristics of a solar module. Model parameters are obtained from manufacturers datasheets and series and shunt resistances are calculated using a simple method based on open-circuit voltage, short-circuit current and irradiance values. The model is interfaced with SimPowerSystems toolbox. This feature makes the model capable of being used with power electronic devices and elements for advance analyses. The model is validated using measured I-V characteristics of a commercially available crystalline silicon solar module and the effects of environmental conditions (temperature and irradiance) as well as the effects of cell parameters like series and shunt resistances on module characteristics are investigated. The proposed model is capable of being used by solar energy researchers, system analysts and designers as a simple and helpful tool for advance analysis requirements.

MATLAB/simulink based simulation of solar incidence angle and the sun's position in the sky with respect to observation points on the Earth

This paper proposes a simulation model for calculation of the suns position in the sky and the incidence angle of sunlight beams on the surface of solar modules with any tilt angle, located at any geographical location on the Earths surface. The electrical power generated by a solar panel directly depends on the amount of the received solar irradiance on panel surface where the received irradiance is directly proportional to the suns position in the sky. Therefore, it is of great importance for solar energy researchers and system designers to have a precise knowledge about the movement and position of the sun in the sky with respect to any specific observation point on the earth. A simple and practical simulation model of the suns position in the sky is designed using MATLAB/Simulink platform. The model simulates the suns position in the sky and solar angle of incidence based on the latitude and longitude of the observation point, solar modules azimuth and tilt angle values, the Julian day number and the local clock time. The proposed model provides the possibility of instantaneous or continuous determination and tracking of the suns position in the sky for any geographical location on earth and can be considered as a helpful tool for sun tracking and other system planning purposes.

Analysis of effects of sun's position in the sky on solar radiation and solar panel output power

It is basically approved that the output power of a solar cell/module directly depends on the amount of solar irradiance which it receives from the sun. Also it is known that the irradiance values are not constant at any specific time interval. The changes in the position of the sun with respect to earth are one of the main reasons causing the variations in the amount of incoming sunlight and its energy to the earths surface. The main focus of this paper is to analyze the effects of changes in the position of the sun in the sky on the incoming solar radiation during a whole year. Also the effects of such changes on the hourly values of solar radiation as well as the effects on the output power generated by a solar panel during a specific sample day is analyzed.

Comparative Analysis of Levenberg-Marquardt and Bayesian Regularization Backpropagation Algorithms in Photovoltaic Power Estimation Using Artificial Neural Network

This paper presents a comparative analysis of Levenberg-Marquardt (LM) and Bayesian Regularization (BR) backpropagation algorithms in development of different Artificial Neural Networks (ANNs) to estimate the output power of a Photovoltaic (PV) module. The proposed ANNs undergo training, validation and testing phases on 10000+ combinations of data including the real-time measurements of irradiance level (W/m2) and PV output power (W) as well as the calculations of the Sun’s position in the sky and the PV module surface temperature (°C). The overall performance of the LM and the BR algorithms are analyzed during the development phases of the ANNs, and also the results of implementation of each ANN in different time intervals with different input types are compared. The comparative study presents the trade-offs of utilizing LM and BR algorithms in order to develop the best ANN architecture for PV output power estimation.

Artificial neural network-based all-sky power estimation and fault detection in photovoltaic modules

Abstract. The development of a system for output power estimation and fault detection in photovoltaic (PV) modules using an artificial neural network (ANN) is presented. Over 30,000 healthy and faulty data sets containing per-minute measurements of PV module output power (W) and irradiance (W/m2) along with real-time calculations of the Sun’s position in the sky and the PV module surface temperature, collected during a three-month period, are fed to different ANNs as training paths. The first ANN being trained on healthy data is used for PV module output power estimation and the second ANN, which is trained on both healthy and faulty data, is utilized for PV module fault detection. The proposed PV module-level fault detection algorithm can expectedly be deployed in broader PV fleets by taking developmental considerations. The machine-learning-based automated system provides the possibility of all-sky real-time monitoring and fault detection of PV modules under any meteorological condition. Utilizing the proposed system, any power loss caused by damaged cells, shading conditions, accumulated dirt and dust on module surface, etc., is detected and reported immediately, potentially yielding increased reliability and efficiency of the PV systems and decreased support and maintenance costs.

A case study on solar data collection and effects of the sun's position in the sky on solar panel output characteristics in Northern Cyprus

This paper mainly focuses on methods of calculations of suns position in the sky and analyses of its effects on solar panel output characteristics collected during a case study. Methods for calculations of suns position in the sky and measurement of solar panel output characteristics are reviewed and then followed by a case study on an experimental data collection system in Northern Cyprus. During the case study, the collected ground measured data are analysed and the results are compared. The solar angle of incidence and the suns position in the sky are calculated and compared for different time intervals along with panel output characteristics. The short-term data sets belong to three sample days representing sunny, rainy and cloudy conditions in May-2012. The results highlight the effects of suns position in the sky and the incidence angles of sunlight, during different time intervals and dates, on module output characteristics. The results provide helpful information for researchers and system designers for system yield estimation purposes.

Experimental analysis of effects of connection type on PV system performance

This paper mainly focuses on experimental performance analysis of solar modules under different irradiance values. Also effects of interconnection types and bypass diode application on module output characteristics under variable shading patterns are analyzed. The mentioned analyses are based on and supported by real-time measurement data and the results confirm the direct relationship between the power generation by solar modules and the incident solar irradiance. According to the results, although higher voltage values are obtained, series strings of solar cells/modules, without bypass diodes, show a higher sensitivity to shading effects and string output power is subjected to higher amounts of reduction compared with the parallel connection conditions. On the other hand, parallel connected solar cells/modules provide higher values of generated current amounts while the output voltages are equivalent to that of each individual cell/module. Experimental results also show that application of bypass diodes in series connected module strings has a great improving effect on power production by the string. The significance of the results arises during design and planning procedures of solar energy systems, where detailed knowledge of system characteristics under different shading patterns creates the opportunity to take the required measures and obtain optimum system performance.

Experimental analysis of effects of installation alignment and solar insolation on power generation by solar panels

This paper mainly focuses on the effects of variations of solar irradiance on PV panel power outputs and considers the importance of choosing the right orientation for system installations. The analyses are based on real-time measured data collected during a 6-Month period (October/2012-March/2013) in Northern Cyprus. The mentioned data presents the months with the lowest solar insolation and the results clearly illustrate the direct relationship between the amounts of the solar irradiance and power generation by PV panels. The results can be utilized for effective use of PV systems, especially for rural areas and locations with relatively less amounts of available solar irradiance.

Determination of power losses in solar panels using artificial neural network

The main purpose of this paper is on developing an intelligent system which provides real time monitoring and fault detection for solar panels. Utilizing artificial neural network technology, the solar panel fault detection system is capable of perceiving suns position in the sky and estimating the corresponding output power of a solar panel based on the algorithms derived by the artificial neural network which has been trained on solar data at several time intervals. The system is capable of operating in any geographical location providing 24hour monitoring and fault detection as well as future power estimations for solar panels.