ISSN (Print) : 2320 – 3765 ISSN (Online): 2278 – 8875 International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering (An ISO 3297: 2007 Certified Organization) Vol. 2, Issue 11, November 2013 Copyright to IJAREEIE www.ijareeie.com 5442 HARMONICS REDUCTION AND RIDE- THROUGH ADJUSTABLE SPEED DRIVES DURING SYMMETRICAL VOLTAGE SAG Dr. S. S. Deswal 1 , Dr. Rajveer Mittal 2 , L. P. Singh 3 , Jitender Lather 4 Dean (Acad.) & Associate professor, Dept. of EEE, Maharaja Agrasen Institute of Technology, Rohini, Delhi, India 1 Head & Associate professor, Dept. of EEE, Maharaja Agrasen Institute of Technology, Rohini, Delhi, India 1, Assistant professor, Dept. of EEE, Maharaja Agrasen Institute of Technology, Rohini, Delhi, India 3,4 ABSTRACT: An increasing demand for high quality, reliable electrical power and increasing number of distorting loads may leads to an increased awareness of power quality both by customers and utilities. The most common power quality problems today are voltage sags, harmonic distortion and low power factor. Trading-off between the importance, the efficiency, the size, and the cost of any Voltage Sag Ride-Through system is the core of choosing the best topology. In addition, choosing the best topology for any give system depends on the interruption nature. For example, if the dominant interruption event is voltage sag; not a full outage, a ride-through system from the advanced hardware modification ASD’s category is preferred. And vice versa, if the dominant event is a full outage, an ASD with ride through mechanism from the energy storage devices category is the best in order to maintain ride-through for long durations. In this paper, a voltage sag ride-through for an ASD from the advanced hardware modification category will be investigated. The proposed system utilizes a boost converter along with supercapacitor as an energy storage device to compensate the DC-link voltage during the symmetrical voltage sag condition. The boost convert is activated to compensate the difference between the reference voltage of the DC-link and the actual voltage once it receives a signal from the voltage sag detection system. An additional advantage of using boost converter is its ability to improve the shape of the supply currents waveforms during the steady state normal operation. Thus lower total harmonic distortion (THD) can be obtained. Based on the designed topology, simulation model in MATLAB 7.5 (Sim Power Block set) has been developed for voltage unbalance conditions with supercapacitor as an energy storage device. The designed control technique is modeled, simulated and successfully implemented in the laboratory. The extensive simulation results are provided to validate the proposed system. Keywords: Electric Power Quality, Harmonics, Adjustable Speed Drives, Supercapacitor, THD. I. INTRODUCTION Power quality problem occurs as a non-standard voltage, current and frequency. The power quality has serious economic implications for customers, utilities and electrical equipment manufacturers. Modernization and automation of industry involves increasing use of computers, microprocessors and power electronic systems such as adjustable speed drives. [1-2] Integration of non-conventional generation technologies such as fuel cells, wind turbines and photovoltaic with utility grids often requires power electronic inter-faces. The power electronic systems also contribute to power quality problem (generated harmonics). The electronic devices are very sensitive to disturbances and become less tolerant to power quality problems such as voltage sags, swells and harmonics. Voltage dips are considered to be one of the most severe disturbances to the industrial equipments. Voltage support at a load can be achieved by reactive power injection at the load point of common coupling. Due to the harmonics are occurring in the system it causes losses and heating of motor. [3-5] In modern power systems, due to increase of non-linear loads, power quality has become a great concern. Nonlinear loads, which were only 15% of total loads in 1987, have increased to 50% in 2000 [6-7]. In the commercial industry,