Inversores de tensão fonte Z: técnicas PWM.

Abstract

This work presents a hybrid pulse width modulation for Z-source converter. The technique combines the theory of space-vector PWM with the ease implementation of triangular-comparison PWM. The Z source inverter has been recently proposed and provides a unique feature of the operation buck and boost using the same circuit and performing the functions of inversion and boost input voltage in one stage. For this it employs an impedance circuit to connect the converter to a primary energy source. This characteristic is not found in any other converters, which are fed in separate by either a voltage source or a current source Usually the control of the Z source inverter is performed employing vector modulation techniques or conventional PWM strategies. Till the moment, scalar modulation has not been considered. In this type of modulation the turn-on and turn-off times of switching devices are estimated, which makes ease the use of digital signal processors, largely employed nowadays. In this work, the PWM hybrid modulation will be applied to five different inverters: two 2- level topologies with three arms or four arms; three 3-level topologies, that is, two neutral point clamped inverters using one Z network or two Z networks and a third 3-level inverter formed by two cascaded 2-level inverters. Also it is be proposed a drive system with a three-phase motor tolerant to windings open fault, from which it can be obtained the same characteristics of voltage before and after the failure. This system consists of two cascaded Z source three-arm inverters for feeding the three-phase motor with open windings. Finally, simulation and experiments results will be presented demonstrating the efficiency and quality of the proposed hybrid strategies.