International Journal of Scientific & Engineering Research, Volume 3, Issue 5, May-2012 ISSN 2229-5518 IJSER © 2012 http://www.ijser.org 1 Performance Analysis of Z-source Inverter Fed Induction Motor Drive Amol R. Sutar, Satyawan R. Jagtap, Jakirhusen Tamboli Abstract - This paper presents performance analysis and simulation of maximum constant boost-control with third harmonic injection methods for the Z-source inverter, which can obtain maximum voltage boost for a fixed modulation index. The Z-source inverter is a recently invented a new power conversion concept mainly developed for fuel cell vehicular applications. The Z-source inverter is very advantageous over traditional inverters and it can be employed in all ac and dc power conversion applications. All traditional PWM methods can be used to control Z-source inverter. Maximum constant boost control methods eliminates the low-frequency ripples in the inductor current and capacitor voltage by maintaining the shoot-through duty cycle constant, and minimize the voltage stresses of switching devices at the same time. The Maximum boost control method is suitable for relatively high output frequency only, but in the maximum constant boost control method the Z-source network design is independent of the output frequency and determined only by the switching frequency. In this paper Z-source inverter parameters such as boost factor, output dc link voltage, capacitor voltage, output ac voltage, voltage gain etc. are determined for maximum constant boost control method for a fixed modulation index and these results are verified by simulation and experiments. Index Terms- traditional inverters, Z-source inverter, voltage boost, boost factor, PWM, third harmonic injection, voltage gain. - - - - - - - - - - ♦ - - - - - - - - - - 1 INTRODUCTION Inverters are the dc to ac converters. The input dc supply is either in the form of voltage or current is converted in to variable output ac voltage. The output ac voltage can be controlled by varying input dc supply or by varying the gain of the inverter [8]. There are two types of traditional inverters based on input source used in industries for variable speed drive and many other applications; those are a) Voltage-source inverter and b) Current-source inverter. The gain of the inverter can be controlled by using pulse width modulation. Different PWM techniques are devised to control these inverters. PWM control technique also reduces harmonic distortion in the output signal and improves the performance of the inverter. PWM with third harmonic injection method eliminates third harmonic component from output waveform and also provides higher range of modulation index than regular PWM modulation technique. These PWM waveforms can be generated using analog circuits using active and passive components or it can be generated digitally using microprocessor and microcontroller [4]. Fig. 1 Traditional voltage source inverter Figure.1 shows the traditional three-phase voltage-source inverter. The dc voltage source connected at the input side across a large capacitor. DC link voltage produced across this capacitor feeds the main three-phase bridge. The input dc supply can be a battery or fuel cell stack or diode rectifier, and/or capacitor. Three phase bridge inverter circuit consists of six switches; each is composed of a power transistor and an anti-parallel diode to provide bidirectional current flow and reverse voltage blocking capability. Figure 2 shows the traditional current-source inverter (CSI). The DC current source is formed by a large dc Inductor fed by a voltage source such as a battery or fuel-cell stack or diode rectifier or converter etc. Like VSI three phase bridge inverter circuit consists of six switches; each is composed of a switching device with reverse block capability such as a gate-turn-off thyristor and SCR or a power transistor with a series diode to provide unidirectional current flow and bidirectional voltage blocking. For voltage source inverter and current source inverter the on/off time the switching devices is controlled by applying control voltage (PWM) to the control terminal i.e. gate of the device. Fig. 2 Traditional current source inverter Traditionally in most of industries these voltage-source inverter and current-source inverter are used in adjustable speed drives. But these traditional inverters have many limitations as summarized below: 1) They are either a buck or a boost converter and cannot be a buck–boost converter [1]. That is, the output voltage is either greater or smaller than the input voltage. The output