Comparative study on photovoltaic tracer between capacitive load and converter approaches under partial shading

Abstract

Generation of electrical energy through the photovoltaic (PV) conversion of incoming sunlight represents a significant alternative. Shading and PV material degradation are examples of aspects that affects the quality of PV system. The output power of PV decreases is a lot worse than it initially seems. To quickly identify the losses affecting the PV system, PV tracers are introduced. PV tracers are commonly used to determine the health of the PV module during commissioning and annual maintenance of a plant. The plant is taken offline during this operation and the I-V curve is then shows by an impedance sweep. There are many PV tracers on the market. They are primarily focused on fault detection and performance assessment of PV plants. The acquisition of this equipment is limited to specific tasks because of its high cost. Because of lower price, higher sampling rate and portability, the I-V curve tracers with a capacitive load are more desirable. However, the device design and operation entail higher complexity and requires the scale of the capacitor. This project report presents the comparative study between capacitor load method and Cuk converter approaches under partial shading condition. The capacitor sizing solve the issue of acquiring appropriate capacitor for the system. It was properly sized by taking into account the various configurations of PV modules and the charge time required for service at different irradiance levels. These optimal sampling rate for the recording of I-V data is decided. A high sample rate requires a lot of memory, especially for long tracking periods of the I-V curve. In comparison, during the short I-V tracking period, the low sampling rate can yield to missing data. The problem lies in designing an online PV tracer that enables the I-V curve to be registered on request from an online PV device without interrupting the power flow. In strategic plant maintenance, this approach of I-V curve-based plant surveillance can be efficient in reducing downtime and optimizing production. The Cuk converter known as having optimum performance under DC-DC converter was analyzed. Obtaining the appropriate duty ratio to achieve fine result was studied to prove the performance of Cuk converter. Simulations under partial shading condition was generated to verify this study. With preliminary results, details on the analysis and design process for the developed PV tracer are presented.