Real-Time Fault Diagnosis of Sensors for Fault-Tolerant Control of Thin-Film CIGS Photovoltaics Process
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B8.12.1
Real-Time Fault Diagnosis of Sensors for Fault-Tolerant Control of Thin-Film CIGS Photovoltaics Process Bharat Joshi1, Markus E. Beck2, Jeffrey S. Britt2, Michael Chaffin1, Nicholas Gomez1, John Muha2, L.J. Simpson1, and Scott Wiedeman2 1 ITN Energy Systems Inc., 8130 Shaffer Parkway, Littleton, CO 80127 2 Global Solar Energy, Inc., 5575 S. Houghton Road, Tucson, AZ 85747
ABSTRACT ITN Energy Systems, Inc., (ITN) and Global Solar Energy, Inc., (GSE) have continued the advancement of copper indium gallium diselenide (CIGS) production technology through the development of a number of activities, including fault-tolerant control, in-situ sensors, and process improvements, with the goal of enabling uninterrupted continuous manufacturing of high quality CIGS materials that are very sensitive to processing conditions. In this paper real-time sensor fault detection and diagnosis strategies developed by ITN and GSE to enable fault-tolerant controllers for thin-film CIGS deposition process are presented. The results indicate that these strategies are very effective and they would play a major role in improving system reliability, thereby also improving yield, throughput, and efficiency. Sensing process reconfiguration methodologies that lead to fault-tolerant controllers also are briefly discussed. INTRODUCTION Today’s competitive global economy requires manufacturing industries to produce higher quality products with increased throughput and yields to achieve and maintain cost advantages. At the same time, these industries are expected to meet strict safety and environmental regulations [1]. Interest in thin film photovoltaics (PV) has expanded dramatically, but wide-scale commercial use remains limited by performance and cost. These factors are often interrelated and negatively impacted by the lack of reliable and accurate process control. ITN and GSE are using a comprehensive and systematic program to integrate intelligent process control into the manufacture of flexible, lightweight CIGS based PV with the goal of improving process throughput, yield, and module performance. Since in-situ sensors and other components are exposed to harsh environments an effective control system should also include an appropriate fault-tolerant strategy that consists of detection, location and isolation of faults followed by an adequate reconfiguration that enables the system to continue to operate within performance specifications. Critical to meeting this challenge is the quality of information that can be extracted from in-situ sensor measurements in real-time. Incorrect sensor information could force the control system to perform unsatisfactorily or even lead to instability that would adversely affect process throughput, yield, performance, and manufacturing cost. Thus faulty sensors need to be identified in real time to ensure that the manufacturing process does not continue with incorrect process settings, and if possible, the sensing process should be reconfigured so that control proceeds with accurate information.
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