Voltage mode control of single phase DC-AC boost inverter

Abstract

This thesis proposes, analyzes and verifies a voltage mode controller usmg feedforward pulse width modulation to control the output voltage of a boost inverter. At first a conventional voltage mode controller is designed using the transfer function of the boost inverter. The transfer function is derived using simple phase leg averaging technique. Then a feedback loop is designed using proportional plus integral compensator. The controller provided good performance with resistive loads and certain range oflagging loads. The output voltage crosses IEEE Std 519 Voltage Harmonic Limits slightly for highly inductive loads. Regulation is well for certain load range. In case of. supply voltage variations the regulation degrades. This conventional controller has the advantage of simplicity. Only one controller is required to control both dc-dc-boost converters. A better voltage mode controller is sought to drive the inductive load as well as reduce source disturbances. After reviewing various literatures feedforward compensation of input voltage variation seemed to be better option to simplifY the feedback loop and improve the performance of the converter. The limitations of conventional voltage mode controller are eliminated with the use of feedforward pulse width modulation technique along with simple voltage feedback loop using proportional plus integral compensator. The simulated output waveforms of the boost inverter using proposed control scheme confirmed good performance of this controller. It is found that each the output voltage waveform is almost purely Sinusoidal in nature which is very mUch desired. The waveforms also have shown good transient response with less overshoot and less ringing. The THD is always within IEEE Std 519 Voltage Harmonic Limits under wide range of both resistive loads and lagging loads. The regulation is good under similar load variations. With the variation of source 'this controller kept THD of output voltage within limit and regulated the output voltage very well. So the proposed controller has the ability to reduce THD and regulate the output voltage in case of both load and source variations.