IJSTE - International Journal of Science Technology & Engineering | Volume 1 | Issue 11 | May 2015 ISSN (online): 2349-784X All rights reserved by www.ijste.org 505 Analysis of Sliding Mode Observer Based SVPWM Inverter Fed BLDC Motor M. Rameshkanna Mrs. S. Sivaranjani PG Scholar Assistant Professor Department of M.E. Power Systems Engineering Department of Electrical Electronics Engineering V.S.B Engineering College, Karur-639111 V.S.B Engineering College, Karur-639111 Abstract This paper proposes a sliding mode control scheme for effective speed tracking by obtaining ripple free torque through the inner loop current control for a BLDC motor. Sliding mode observer is a parameter for estimating the phase to phase trapezoidal back- EMF in sensor less mode. BLDC motor drive uses one or more sensors giving positional information to keep synchronization. Such implementation results in a higher drive cost due to sensor wiring and implementation in the motor. This project shows that the torque and speed control of three phase BLDC motors. Using sliding mode observer it is used to estimate the back EMF for sensorless operation. This project proposes, a space vector pulse width modulation(SVPWM) technique is employed to obtain the required output voltage in the line side of the inverter to control the BLDC motor speed and the same was simulated using MATLAB software. Keywords: BLDC Motor, Voltage Source Inverter, Sliding Mode Observer, Direct Torque Control ________________________________________________________________________________________________________ I. INTRODUCTION BLDC motors are becoming so popular in industrial applications. Because of its High efficiency, High torque, Low acoustic noise, Less maintenance, longer life time and large inertia ratio when compared to brushless AC motors. BLDC motor is also known as electronically commutated motors are synchronous motors. A BLDC motor is an inside out DC commutator motor with mechanical commutator replaced by an electronic switching converters. The existing converter are current source inverter. In current source inverter the reliability is low, complexity is high and the power factor is low with decreasing speed. To overcome these limitations Voltage source inverter is used. II. VOLTAGE SOURCE INVERTER Voltage source inverter, is an electronic device or circuitry that changes direct current (DC) to alternating current (AC). The input voltage, output voltage, frequency, and overall power handling depends on the design of specific device or circuitry. The inverter does not produce any power; the power is provided by the DC source. A power inverter can be entirely electronic or may be a combination of mechanical effects and electronic circuitry. Static inverters do not use moving parts in the conversion process. Input voltage typical power inverter device or circuit requires a relatively stable DC power source capable of supplying enough current for the intended power demands of the system. The input voltage depends on the design and purpose of the inverter. Examples include: 1) 12 VDC, for smaller consumer and commercial inverters that typically run from a rechargeable 12V lead acid battery. 2) 24 and 48 VDC, which are common standards for home energy systems. Operation of Voltage Source Inverter: A. Single-phase VSIs are used primarily for low power range applications, while three-phase VSIs cover both medium and high power range applications. Figure 1 shows the circuit schematic for a three-phase VSI. Switches in any of the three legs of the inverter cannot be switched off simultaneously due to this resulting in the voltages being dependent on the respective line current's polarity. States 7 and 8 produce zero AC line voltages, which result in AC line currents freewheeling through either the upper or the lower components. For three-phase PWM, three modulating signals that are 120 degrees out of phase with one another are used in order to produce out of phase load voltages. In order to preserve the SVPWM features with a single carrier signal, the normalized carrier frequency, mf, needs to be a multiple of three. This keeps the magnitude of the phase voltages identical, but out of phase with each other by 120 degrees. The only way to control the load voltage is by changing the input DC voltage.