Study and analysis of microprocessor controlled pulse-width modulated inverter

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.