Impact of different pulse width modulation (PWM) techniques on the performance of a three phase Z-Source inverter (ZSI).

Traditional voltage source inverters (VSIs) have recently advanced to Z-source inverters (ZSIs).A Z-source inverter is a recent topology of DC-AC inverters that was proposed in 2002 by Prof. F. Z. Peng and has taken over from its predecessors; a voltage-source inverter and a current-source inverter [1], [2], [3].There were two key modifications applied to VSIs to transform them into ZSIs, viz. the inclusion of a link Zimpedance network between a dc-source and the actual inverter stage (topological amendment); as well the inclusion of the ninth operational state, as opposed to only eight zero and active permissible operating states on VSIs, called the shoot-through state (Control scheme amendment) [2].In this dissertation, a detailed design of the ZSI is presented.LCL filter is a choice in this design because it gives superb attenuation of -60 Db/decade to switching frequency opposed to LC and L filters whose attenuation is -40 Db/decade and -20 Db/decade respectively [5].LCL filters are also light in weight, smaller in size and cheaper than LC and L filters for the same rating.Three pulse width modulation (PWM) techniques viz.simple boost control (SBC), constant boost control (CBC) as well as the maximum boost control (MBC); are developed and applied to a ZSI after-which they are compared with each other for critical performance parameters; traditional sine pulse with modulation (SPWM) is only featured as a reference for the other three PWM control techniques sine it does not boost voltage.The boost factor (B), DC-link voltage (Vdc-link) and percentage of total harmonics distortion (%THD) are exclusively dependent individuals and organisations: 