MODELING, DESIGN AND ANALYSIS OF LED LIGHTING SYSTEMS FOR APPLICATIONS IN ILLUMINATION CONTROL AND HORTICULTURE

Abstract

LED is a light emitting semiconductor device which is nowadays, swiftly replacing conventional lighting system, owing to its high intensity and low energy consumption. In this work, LED lighting Systems have been used for controlling illumination level of a given closed space and another application of LED lighting systems for horticulture has also been carried out. In order to achieve the task, the modeling of LED is required. The very basic modeling of LED can be done by considering it as a resistor. But this has some serious limitations as the non linear IV characteristics of the LED cannot be modeled using a resistor. To model the non linear IV characteristics of LED, some advanced modeling techniques viz. Piecewise Linear Approximation and Maclaurin series expansion based modeling have been taken up here. For illumination control of given closed space, LED lights have been used as controlled light source and there is some illumination due to external light sources as well. To drive the LEDs, a driver is needed which provides a DC supply to it. In this work, AC supply has been used which is fed to a rectifier coupled with a buck converter to drive the LEDs with DC. Buck converter’s switching is controlled using PWM technique. The microcontroller is given a set point which is compared to a feedback signal generated by LUX sensor. The error signal so generated is fed to a comparator unit to generate the PWM gate signal (amplified and isolated with the help of an optocoupler) which is then fed to the gate of the MOSFET switch of the buck converter. The hardware setup has been simulated first using MATLABSimulink and various important parameters such as THD have also been compared. The application of LED lighting systems for Horticulture has unconventionally been approached by using RGB LEDs as opposed to the use of hyper red or deep blue LEDs. This has been done to take care of the micronutrient requirement of the crops. The data regarding the plant (S. Platenesis), that is, the wavelength or color of light required for the optimum growth has been known beforehand and using this, light of required color is produced by applying the method of color mixing using variable duty cycles for RGB lights.