Design of Robust Feedback Controller for a UPS System in Industrial Application

This paper presents a novel Sliding Mode Control (SMC) approach for a three phase AC/DC/AC Voltage source UPS used in Industrial applications. The proposed controller is robust for sudden change in loads and more efficient. Most of the industries run with critical loads, so there is always a need to supply better quality of inverter output voltage waveform. A mathematical model of the system is derived using state space modeling. Using the model, a design procedure of controller implementation using the state variables necessary to obtain a stable system is developed. It can be operated for both linear and non-linear load conditions very effectively. It reduces steady state error and is easy to implement. Load voltage regulation is also found to be within the standards. The dynamic nature of the controller is verified. A phase trajectory is plotted to show the nature of the SMC characteristic in reaching the origin. Frequency response characteristics are plotted to realize the state variables to obtain stability. The simulation work is performed in PSCAD/EMTDC version 4.6. and the system stability condition is analyzed from frequency response plots obtained in MATLAB R2012b platform. The proposed controller can be effectively used in all high power industrial applications.