Efficiency Improvement of Nonuniformly Aged PV Arrays

Abstract

Abstract-The utilization of solar energy by photovoltaic (PV) systems have received much research and development (R&D) attention across the globe. In the past decades, a large number of PV array have been installed. Since the installed PV arrays often operate in harsh environments, non-uniform aging can occur and impact adversely on the performance of PV systems, especially in the middle and late periods of their service life. Due to the high cost of replacing aged PV modules by new modules, it is appealing to improve energy efficiency of aged PV systems. For this purpose, this paper presents a PV module reconfiguration strategy to achieve the maximum power generation from non-uniformly aged PV arrays without significant investment. The proposed reconfiguration strategy is based on the cell-unit structure of PV modules, the operating voltage limit of gird-connected converter, and the resulted bucket-effect of the maximum short circuit current. The objectives are to analyze all the potential reorganization options of the PV modules, find the maximum power point and express it in a proposition. This proposition is further developed into a novel implementable algorithm to calculate the maximum power generation and the corresponding reconfiguration of the PV modules. The immediate benefits from this reconfiguration are the increased total power output and maximum power point voltage information for global maximum power point tracking (MPPT). A PV array simulation model is used to illustrate the proposed method under three different cases. Furthermore, an experimental rig is built to verify the effectiveness of the proposed method. The proposed method will open an effective approach for condition-based maintenance of emerging aging PV arrays. Index Terms-Maximum power tracking, non-uniform aging,Manuscript received May 13, 2015; revised October 11, 2015 and January 31, 2016; accepted August 24, 2015. Copyright © 2010 IEEE. Personal use of this material is permitted. However, permission to use this material for any other purposes must be obtained from the IEEE by sending a request to pubs-permissions@ieee.org.Y I. INTRODUCTIONSolar energy utilization has received much attention across the globe over the last decades [1]- [6]. Currently, photovoltaic (PV) power devices are gaining in popularity in the global renewable energy market, primarily owing to the reducing manufacture costs of PV panels and continuous improvement in power conversion technologies [7]- [8]. In practice, high energy conversion efficiency and long effective service time can help reducing capital and operating costs and thus are highly desired.With the improvement of materials technologies, monocrystalline silicon and multicrystalline silicon now can be economically produced in large quantities. However, their energy conversion efficiency from solar to electricity is still low. Typical efficiency for monocrystalline silicon solar cells is around 20% while it is 18% for multicrystalline silicon solar cells [9]. On the power electronics side, hig...

Gene Evaluation Algorithm for Reconfiguration of Medium and Large Size Photovoltaic Arrays Exhibiting Non-Uniform Aging

“…Alternatively, the genetic algorithm approach used to identify the optimised maximum power output from non-uniformly aged PV modules in an array. Other strategies have demonstrated effectiveness in addressing module rearrangement problems for both small-and large-scale PV arrays, but these required searching all potential combinations of PV rearrangements, resulting in excessive computational complexity and time requirements [3,7]. Another benefit is that only the affected PV modules require repositioning, whereas the others can remain in their original positions.…”

“…The most effective solution to this is the replacement of the affected modules with new equivalents, but this is expensive and may introduce a disparity between the characteristics of the existing and newly introduced modules. This can have a 'bucket effect' that prevents the array from producing its optimum power [3,4].The power of a PV cell is reduced relative to its rated power as it ages. As this can cause a decrease in the cell's short-circuit current to have a much higher effect than a reduction in its open-circuit voltage, typically the short-circuit current measurement is an indicator of the condition of the cell [5,6].…”

“…Examples of online approaches to reconfiguring the mismatched PV array to enhance its power efficiency are given in [9,10], but these involve drawbacks such as costly switch and relay requirements and complex calculations. The series-parallel array featured in [3] has just a single short-circuit current per module to indicate its condition, despite the non-uniformly aging process across the modules. This means the calculation requirements are considerably diminished.…”

“…The most effective solution to this is the replacement of the affected modules with new equivalents, but this is expensive and may introduce a disparity between the characteristics of the existing and newly introduced modules. This can have a 'bucket effect' that prevents the array from producing its optimum power [3,4].…”

A Photovoltaic Array Fault Diagnosis Method Considering the Photovoltaic Output Deviation Characteristics

“…Through the above analysis, the methods using operational data of PV array are the most potential fault diagnosis method. But the operational data of the PV array will change with the external environment [28,29], and the output characteristics of the array are easily covered by a large number of data. The author of this paper studied the spatial-temporal distribution characteristics of PV array under different faults [30] and the statistical characteristics of PV array output under different conditions [31].…”