LOW POWER PHOTO-VOLTAIC HARVESTERS AND CHARGERS WITH IMPROVED RELIABILITY, SUITABLE FOR HEAVILY OVERCAST OPERATIONS

Abstract

Photo-voltaic (PV) power harvest can have decent efficiency when working with high irradiance power. A DC-DC boost converter is a vital part of any power harvesting module. When PV operates with a DC-DC boost converter during an overcast, the module’s efficiency and output voltage is degraded due to the reduced solar power, which causes the module functionality becomes an issue.

Coupled inductors have been utilized to increase and extend the voltage gain of the boost converter. Although the duty cycle impedance matching method can accommodate the efficiency regulation in a boost converter, it suffers from voltage loss during shading.

Micro-solar energy charging systems can operate efficiently at relatively high threshold luminance, and they exhibit 0% charge efficiency below threshold luminance value. The objective of this thesis is to develop and present a systematic approach designing a low-power photo-voltaic harvester/charger with an improved efficiency, charge efficiency, functionality, sensitivity, and output voltage particularly under strong overcast, while employing minimum hardware. This will lead to the reliability improvement of this module as well, making it an ideal power source for a remote operation. The proposed topologies will introduce a matrix boost converter system and will utilize multiple techniques in a boost converter using an extra inductor in recycled, synchro-recycled, modified interleaved coupled inductors, and combined couple along with conventional boost architectures in continuous conduction mode, (CCM). By exploiting the non-linearity of the PV cell, they will also reduce the power loss and input power and will enhance the output voltage and output power simultaneously. Furthermore, the proposed topologies minimum hardware, contributes to the reliability, sensitivity, and functionality improvement particularly during an overcast. The BCM and DCM mode of the coupled inductors architecture is also dissected as well.

The proposed approaches facilitate the operating condition of the power harvester/charger. It responds to a wider range of solar irradiations and extends the solar operational range of the charger/harvester which brings multi-variables gains, including improved output current, reliability, power and voltage efficacies, and functionality. The test results of the proposed boost converters show that they achieve an efficiency of 88% and improved sensitivity of 0.17V.