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.
