Development of a Sensorless Buck Converter for Electro-Chemical Applications

Abstract

The study of DC-DC converters have attracted much attention due to their extensive application in power electronics, controls and renewable energy. The power from the photovoltaic sources is unregulated and to put it in use, it needs to be regulated. The DC-DC converter provides regulated output voltage that can be greater than or less than the input voltage. Some of the applications in electro-chemical field requires a stable input for their proper working and as the conventional PID (Proportional Integral Derivative) controllers do not work efficiently under varying conditions, different control algorithm has been studied to make the converters robust. The Sliding Mode Control (SMC) is robust to the input and the load variations. However, due to the discontinuous control in SMC chattering occurs ,which causes high heat loss in the system. The Sliding Mode Observer reduces the chattering phenomenon and provides a stable output necessary for the electro-chemical applications. In this thesis a buck converter is designed and fabricated for the use in electro-refining industries, which provides constant voltage and constant current. As the input power, from the photovoltaic, and the load parameters keep on changing the SMC is executed using real time NI FPGA 9683 board. In order to reduce the cost of the system, a sensor less system is designed. The role of the current sensor is played by the Sliding Mode Observer (SMO) and hence the current sensor could be removed. The results of hardware implementation had a close resemblance with the simulation results. The advantage of using Sliding Mode Observer resulted in the increase in the stability of the output and decrease in the cost, as the current sensor is no more required.