The reliability of conventional photovoltaic (PV) structure in shaded situations can undergo different issues related to internal and external conditions. The internal condition accounts for the ...inhomogeneity of the properties of electrothermal cells, while the external conditions connote optimal power maximum tracking techniques and protection circuit limitations. This article proposes a new technique to improve the reliability of shaded panels, considering the internal and the external issues. Our study begins with an extensive analysis to assess the vulnerability of PV cells to second-quadrant thermal stress and operational limits of bypass diode protection against hot spot. Consequently, we proposed a new system that concurrently operates with the maximum power extraction process to assist bypass diodes with hot-spot protection. This proposition results in a reconfigured panel with both a local detection circuit that defines the conduction states of bypass diodes and additional mosfet s that switch shaded subgroups. In this article, an algorithm was developed that is capable of controlling the optimal maximum operation point tracking with an on-demand deployment of the protection mosfet s, using the signals provided by the local detection circuit. A set of experiments were carried out in order to demonstrate the capability of the proposed method to prevent hot-spot damages over all shading rates and operating points. The novelty of the proposed approach is its low cost of implementation as well as its simple and efficient design. Therefore, it has the potential to be easily integrated along side existing infrastructure and maximum power point tracking algorithms.
This paper presents a new autonomous standalone circuit for HS protection. This circuit is designed to automatically detect and locate the shaded subgroup, to protect it against HS formation and ...recover its normal operating conditions. It is cost-effective and perfectly sized to embed existing conventional PV panel infrastructure since no sensors, data analysis, external sources, or heat sinks are required. This circuit includes a MOSFET to connect/disconnect the shaded subgroup. This MOSFET is controlled through digital signals provided by either an optoisolator or an oscillator. The optoisolator detects the shading occurrence while the oscillator reactivates the MOSFET and gives flexibility for global and local MPPT synchronization. Experimental results under various shading scenarios demonstrate the feasibility and the efficiency of our suggested approach.
The operating point of photovoltaic (PV) cells on the panel can shift from the first to the second quadrant (IIQ) of their current-voltage (IV) plan under certain conditions such as shading. This ...causes power losses, heat sinking, and hot spots (HS) mainly on the shadowed cell. Manufacturers match cells according to their IV measurement in the first quadrant (IQ) and add a bypass diode (DBS) to alleviate the related issues. However, these solutions cannot avoid the IIQ operation of the involved cell which results in HS. This paper presents the importance of IV electrothermal characterization of solar cells IIQ to mitigate HS. Additionally, it investigates the IIQ safe operation of different types of cells. Accordingly, we examine the power balance of a partially shaded PV panel in different operating points with individual IIQ of IV cell profiles. This work utilizes an experimental bench which has been developed to characterize the reverse behavior. An infrared thermal camera with ResearchIR software is used to evaluate temperature distributions of the cells surface and HS. Moreover, an environmental chamber is used to observe heating effects on the IV curves and breakdown (BD) mechanisms. The results demonstrate that the IV IIQ characteristics are inherently tied to the cell's thermal properties. In addition, the power losses of each type of cells with HS damage is simulated to define worst-case scenarios. As a result, the ability of high BD to survive IIQ operation excels cell with low or secondary BD. Indeed, this paper elaborates remarks to enhance shaded PV panel performance and safety regarding real implementations.
In this paper, a new strategy for maximum global operating point tracking for series-connected shaded photovoltaic (PV) panels is presented. First, we identify both possible shading profiles and ...global maximum operating point (GMOP) locations. This identification is based on the number of conducting bypass diodes that decompose the PV panel to subgroups. Afterwards, an adjusted fractional short circuit current (FSCC) is used to supply current measurements at each panel's subgroup. FSCC is provided by an electronic circuit formed by branches of MOSFET-Zener diode that is simply added between PV panels and the dc/dc converter. By exploiting the above steps, we develop a GMOP estimation algorithm. This algorithm is able to detect shading events and rates as well as their associated power modes and profiles. Subsequently, it captures the number and location of local maximum power points (LMPP) and determines the GMPP in the power vs current features of PV systems. Our proposed approach is evaluated by Simulation on Simscape MATLAB software and a set of experimental tests. The results demonstrate the capability of the proposed approach to effectively estimate GMOP under various irradiance conditions. Our method is practical since it does not require either irradiance sensors or extensive complex calculations. Therefore, it can be easily integrated with many types of maximum power point tracking control algorithms.
This paper aims at investigating the ac dynamic parameters of partially shaded solar PV cells. We employ analytical and numerical methods to extract the parameters of ac dynamic model of a PV cell. ...Particularly, the parameter identification process is based on the small signal impedance model of solar cells and its associated transfer function. This model can reflect the static and the dynamic performances of the solar cell at low and high frequencies. The analytical method utilizes mathematical equations derived from Nyquist and Bode plots, whereas the numerical method exploits Levenberg-Marquardt Least Squares (LMLS) algorithm. In this paper, we have also designed an adapted experimental laboratory circuit to measure the PV cells frequency response. The entire procedure, including the acquisition and calculation systems is completely automated using C# programming. Accordingly, we developed a low-cost setup that allows partial shading emulation as well as high power and frequency measurements. Our results demonstrate that the numerical method can achieve a better fit of data with an accuracy of 91%. Moreover, it can estimate the same parameter values in a short time with high precision.
We present in this work the study and the realization of a photovoltaic system connected to the network. This system was simulated in the Matlab/Simulink environment and a laboratory prototype was ...manufactured for various tests and measures. Results of MPPT control, PWM control of a DC/AC single-phase converter, signal filtering of harmonic of the inverter as well as synchronization with the network with a phase locked loop will be presented. It will be particularly shown how the algorithm of power tracking adjusts the point of operation for an optimal exploitation of the solar panel.
This paper describes a sensorless photovoltaic grid connected system using a MPPT technique based on optimal slope of P-I curve of power load. This system is composed of only one stage: SPWM current ...source inverter. This system operates without sensor and without tuning. Modeling is presented and a multi-objectives design is performed. The results are validated by simulation in the Matlab-Simulink environment.
