Software and Hardware Implementation of Quasi z Source Inverter in DC-DC Converter with DC Motor as Load

Abstract

DC/DC power converters are employed in applications like telecom, industrial, automotive, military, aerospace and motor drives. The dc/dc converter market is forecast to grow at a strong rate to $ 4.3 billion by 2016. The primary factor limiting the widespread application of low voltage producing renewable energy sources to motor load is interfacing of converter system. The traditional voltage source inverter (VSI) cannot be dealt without overrating of inverter because VSI is a buck converter. Because of this, VSI with transformer and additional converter is usually used to produce desired voltage for connecting the utility. This leads to a higher component count and low efficiency which defeats the goal of cost reduction. Z-source inverter (ZSI) has been suitable for the low input and high output dc drive application because of the capability of voltage buck, boost and inversion in a single stage using shoot-through operating mode. By using the quasi-z-source-inverter (qzsi) a new topology derived by ZSI, draws a constant current from input and capable of handling a wide input voltage range. It also features lower component rating and reduced impact on input source, efficient, compared to traditional ZSI. For high power applications, bridge-type qzsi-based dc/dc converters are used for applications where output needs to be completely isolated from input; isolating converters are implemented to meet the safety standards. This project involves design; simulation and hardware implementation of a step-up dc/dc converter topology connected with the chopper circuit intended for dc motor drive application. In the present project a voltage fed quazi z source inverter is used to convert dc into ac. A special strategy called as shoot through state is employed for qzsi which is based on pulse width modulation technique. Shoot through state increases the voltage gain of qzsi as compared to traditional VSI with PWM techniques. The present project is simulated in MATLAB/Simulink for three phase ac link and three phase VDR with dc motor as inductive load. The motor characteristics were observed in Simulink for input voltage of 40 V. A laboratory prototype for single phase with input voltage of 12 V (dc) from battery operating at 25 kHz switching frequency has been built for the dc motor of specifications as 1/12 HP, 220 V, 0.8 A, 9500 rpm drives and tested to verify the effectiveness of the proposed project. The experimental results from the prototype under different operating conditions are also presented.

Keywords: DC to DC converter (DC-DC), voltage doubler rectifier (VDR), isolation transformer, pulse width modulation (PWM), Quasi z source inverter (qZSI)