Abstract:
Microprocessor technology has opened a new frontier in the automation of
industrial process controls. Interest has been growing in microprocessor based
pulse width modulator ( PWM ) schemes in recent years. Among the several
methods such as dedicated analogi digital, dedicated digital and microprocessor
method of implementation, the last one offers several advantages. PWM
inverters are used in a wide variety of industrial process such as uninterruptable
power supplies (UPS), variable speed drives etc. The popularity is mainly due to
the capability of these inverters permitting control of voltage, frequency and
harmonic content in a single power stage. These inverters employ only one dc
source with small filters at both ends of the inverter. The voltage and
frequency of these converters can be changed according to need by varying gate
or base drives of the static switches of a particular converter. The output
waveforms are nonsinusoidal in nature and the harmonic components
generated are detrimental to applications in terms of losses. These are also
detrimental to the power supply utility in terms of line harmonics injection.
Various methods have so far been used to minimize harmonics in inverters and
one of the best methods is sine pulse width modulation (SPWM). In the era of
microprocessor control and automation, there has been a constant effort by
researchers to incorporate PWM switching in various static power converter/
controller in order to obtain optimized operation. For real time implementation
of PWM waveforms using microprocessor, there are different techniques of
realization depending on the type of modulation process. The basic hard wares
and softwares get modified depending on the technique of realization and the
type of PWM waveforms. The techniques reported so far lack generality. The
purpose of this research is to investigate the possible on-line computation and
decision making for the generation of gating pulse to implement SPWM
switching of an inverter.
