The Mathematical Model of Pulse Width Modulation Frequency Converter

Abstract

Currently the market of three-phase standalone voltage inverters and frequency converters, which are to be used in alternating current drive and power supply, develops together with systems of control and voltage support. In connection with this, research and development of three phase stand-alone voltage inverters, that are used in control of alternating current systems, is relevant to a great degree. One of the main stages of developing the stand-alone voltage inverter is designing the control system. Any kind of control of the power converter ultimately comes down to controlling the open state time of power transistor in relation to period of its work. This method of control is referred to as the pulse width modulation. In this study the method of vector-based pulse width modulation is considered for the case of the frequency converters control system. The core of the vector pulse width modulation is about refusing from the simultaneous turning on/off all the switches during the switching period (if pulse width modulation is sine-based) in favor to switching between several pre-selected conditions of the inverter, each of which is corresponding to some spatial position of the vector. The analysis of the frequency converters operation, based on the vector pulse width modulation, is considered. The regularities describing electromagnetic transients in the frequency converters are discovered. The mathematical and computer models of the frequency converters based on the vector pulse width modulation are developed.