Development of an electricity supply system using solar energy
Ku, Daryl Dun Jie
Date of Issue2017-05-15
School of Electrical and Electronic Engineering
An efficient power conditioning system plays a significant role in the design of battery charging systems for home use. A typical battery charging system consists of two stages. The first stage is an AC-DC conversion stage which regulates the input power factor, input current total harmonic distortion and intermediate dc bus voltage. The second stage is a DC-DC conversion stage which regulates the output voltage and provides galvanic isolation. The research works presented in this report focuses on the DC-DC conversion stage of the battery charging system. Phase shift modulated (PSM) isolated full-bridge (FB) dc-dc converter topology is commonly preferred for the DC-DC stage due to its high efficiency, high power density, high reliability, and galvanic isolation capabilities. However, zero-voltage switching (ZVS) is not ensured for all switches at light load conditions resulting in poor efficiency of the converter. To meet the requirements of soft switching, Asymmetrical Pulse Width Modulation (APWM), together with auxiliary circuits ensure ZVS occurs. The aim of the auxiliary circuits is for improving the load range for ZVS. Additionally, snubber circuits can minimize the voltage spikes. In this report, two new gating techniques, namely asymmetrical pulse-width modulation and pulse width modulation are used. This report analyses a FB DC-DC converter with a capacitive output filter so that the converter is operated as a current-driven rectifier to eliminate voltage spikes. Using this topology, the converter can achieve higher efficiency with the proposed APWM technique compared to the conventional PSM technique. The operation and steady-state analysis of the converter topology will be explained in detail. Theoretical analysis is then validated with experimental data obtained from a 100 kHz, 1.2 kW converter hardware prototype.
Final Year Project (FYP)
Nanyang Technological University