ANALYSIS AND PERFORMANCE ENHANCEMENT OF SOLAR PHOTOVOLTAIC SYSTEMS UNDER SUB-OPTIMAL OPERATING CONDITIONS

Abstract

The increasing reliance on solar energy as a sustainable and renewable power source has led to significant advancements in photovoltaic (PV) technology. However, the efficiency and reliability of PV systems remain challenged by factors such as irradiance mismatch, shading, and temperature variations, which can lead to power losses, reduced system lifespan, and potential safety risks like hot spot (HS) formation. These challenges have spurred the development of innovative solutions to optimize PV array performance, particularly under sub-optimal (non-ideal) conditions. This thesis presents several novel strategies to mitigate the adverse effects of irradiance mismatch on PV systems. The key contributions include the development of the hot spot mitigation circuit (HSMC), innovative module rearrangement techniques such as the generalized module repositioning approach (GMRA), series-parallel generalized module repositioning approach (SP-GMRA), generalized panel rearrangement strategy (GPRS), series-parallel generalized panel rearrangement strategy (SP-GPRS), and the cross-diagonal module rearrangement approach (CDMRA). Additionally, advanced methods to reduce wiring complexity and minimize mismatch losses (MLs) are proposed. By addressing both performance and safety concerns in PV arrays, these techniques significantly enhance the efficiency and reliability of PV systems, contributing to more sustainable energy production. This doctoral research focuses on enhancing the performance and reliability of PV systems under irradiance mismatch conditions (IMCs), which often lead to reduced power output and potential safety concerns such as HS formation. The work introduces a variety of innovative strategies to mitigate these challenges, specifically through the development of advanced reconfiguration techniques and optimized circuit designs. A novel HSMC is proposed to effectively address HS formation and ML, improving the overall reliability of PV arrays under shaded conditions. Experimental results show that the HSMC outperforms conventional v bypass diodes (BPDs), reducing MLs by up to 89.82%, demonstrating significant improvements in power output and safety. Further, a static optimal shade dispersion (SD) strategy is introduced alongside the GMRA, designed to uniformly distribute shading across PV arrays. This method is extended to a variant called SP-GMRA, specifically tailored for series-parallel (SP) PV configurations. Both approaches are validated through simulation and hardware experiments, with the GMRA and SP-GMRA demonstrating a substantial reduction in MLs, with up to 76.3% and 27% lower ML, respectively, compared to traditional configurations. In addition to these reconfiguration techniques, a comprehensive shade-resilient approach utilizing the GPRS and SP-GPRS is proposed for enhancing the productivity of PV arrays under varying shading scenarios. Performance evaluations conducted on both simulation platforms and experimental hardware configurations show up to 75.4% reduction in MLs and up to 31% improvement in power generation for total-cross-tied (TCT) PV arrays and up to 16.1% improvement for SP arrays. The research also introduces the CDMRA, a versatile technique applicable to PV arrays of any size and structure. This approach optimizes module positioning to minimize shading impacts without disrupting the wiring system, offering a significant reduction in mismatch power loss (MPL), improved system efficiency (SE), and enhanced power boost (PB) across multiple irradiance mismatch scenarios irradiance mismatch scenarios (IMSs). To address wiring complexity in conventional TCT configurations, a modified PV arrangement (MPVA) is proposed, which reduces cross-ties by 59.37% and improves overall system performance by minimizing wiring requirements. The progressive module shift rearrangement approach (PMSRA) is introduced as a static shade mitigation technique, applicable to TCT, SP, and MPVA configurations, achieving up to 86% reduction in mismatch loss compared to conventional TCT arrays. Finally, a dual-stage three-phase grid-interfaced solar photovoltaic power generation (SPPG) system is presented, integrated with a self tuning filter (STF) to optimize the control of voltage source converters (VSCs). This system is designed to enhance power quality (PQ) by addressing issues such as harmonic rejection and power factor correction, demonstrating superior performance compared to existing classical and adaptive control techniques.