Despite the existence of accurate mathematical models facilitating the analysis of photovoltaic (PV) sources’ behaviour under diverse conditions, including normal operation and situations involving mismatch phenomena such as partial shadowing and various faults (i.e., PV cells operating in forward bias and reverse bias quadrants), an important issue still persists. Crucial parameters essential for adjusting these models, particularly those related to reverse-biased characteristics such as breakdown voltage, are often absent in manufacturers’ datasheets. This omission presents a substantial challenge, as it restricts the ability to acquire comprehensive and accurate information required for a thorough analysis of devices in the second quadrant. To address this issue, our research introduces a novel method for measuring the reverse-biased I–V characteristics of individual PV cells within a module without having to dissociate them from the PV module encapsulants. The process involves measuring the forward-bias I–V curves of both the fully illuminated PV module and a partially shaded PV module with only one completely shaded cell. This can be achieved outdoors and by utilising commercially available I–V tracers. Thus, the reverse I–V curve can easily be derived from these forward bias I–V curves. Finally, the proposed method serves as a nondestructive technique for characterising solar cells in the second quadrant. This innovative approach offers a promising solution for assessing the performance and health of PV modules without causing damage and may result in significant cost savings.
In this paper, a three-phase shunt active power filter (SAPF) controller with a fully digital implementation is presented. The main goal of this contribution is to implement a digital direct power control (DDPC) algorithm without phase-locked-loop (PLL) for SAPF. This algorithm is intended for power quality improvement and current harmonic elimination. The controller introduced in this paper is costeffective, has a fast-dynamic response, and has a simple hardware implementation. In order to comply with the above specifications, a dedicated controller has been conceived and fully implemented within a field-programmable gate array (FPGA) device. This FPGA-based controller integrates the whole signal-processing functions needed to drive the SAPF, as well as an original method for sector identification. The intended controller provides the desired power references to select the optimal switching sequences. The switching orders follow the grid reference to drive the voltage source inverter (VSI), so the SAPF achieves good performances while ensuring balanced overall supply currents, unity power factor, and reduced harmonic load currents. The proposed digital implementation achieves a valuable compromise between fast dynamic response, minimum execution time, and reduced FPGA resources, through a simple hardware design implementation. The entire system is developed and simulated using VHDL and VHDL-AMS languages.
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