Space Vector Model for Nine Switch Inverter

Topics: Direct current, Alternating current, Switched-mode power supply Pages: 23 (4159 words) Published: July 9, 2012
CHAPTER 1

INTRODUCTION

1.1 GENERAL
Nowadays, there is a demand of power supply. As an electrical engineer, it is necessary to design system with low cost, reduced losses and higher efficiency. This paper proposes nine-switch converter with single controller, rather than using 12 switches for operation of drives separately. In electrical vehicle drives mostly AC motors are used. It is because of its well known advantages like simplicity, reliability, lack of mechanical commutator and brushes, ability to work under unfriendly conditions (dust, humidity, etc.) and low cost. The most popular AC machines are induction motors - IM and permanent magnet synchronous motors - PMSM. These motors can be supplied from power electronics converters (like VSI inverters). Therefore, are used in various applications like hybrid electric vehicles HEV, public transport, machine tools drives, etc. Some of these applications have to work above nominal speed. This is essential in EV and public transport drives. High-speed operation can be achieved either by increasing supply voltage (not always possible) or by field weakening. In the IM field-weakening operation can be easily performed.

The above requirements are not fulfilled in scalar control, where only angular speed (frequency) and magnitudes of flux, current and voltage vectors are adjusted. Instantaneous positions of these vectors are not controlled. Therefore, space vector control methods have been strongly developed. In this case, not only angular speed (frequency) and magnitudes of flux, current and voltage vectors, but also instantaneous position of these vectors is controlled. This ensures excellent dynamic and stable steady state operation of space vector control methods.

1.2 OBJECTIVE

The aim of this project is to develop the space vector modulation (SVM) of nine-switch inverter and nine-switch-z-source inverter. Develop a method to increases the sum of modulation indices up to 15% in contrast with the conventional scheme in which the sum of modulation indices is less than the one by using Z source dc/dc inverter.

Also, in order to further reduce the cost of power devices and also thermal heat effect and to reduce the number of semiconductor switching, specific SVM switching pattern is presented. This feature will be advantageous for high-power inverter applications where cost and efficiency are key decision factors.

1.3 ORGANISATION OF THE REPORT

This report has been organized into the following chapters.

Chapter 1: Gives the introduction and objective of the project and the way the various chapters are organized.

Chapter 2: Focuses on the basic principle of PWM based inverters and operation of nine-switch inverter and implementation of space vector modulation in it.

Chapter 3: Explains the impedance source inverter and its advantages over the conventional inverters

Chapter 4: Describes the simulation model and results.

Chapter 5: Describes the hardware implementation of the project.

Chapter 6: Concludes the project with the scope for improvement.

CHAPTER 2

PULSE WIDTH MODULATION

2.1 GENERAL:

The advent of the transformerless multilevel inverter topology has brought forth various pulse width modulation (PWM) schemes as a means to control the switching of the active devices in each of the multiple voltage levels in the inverter. The most efficient method of controlling the output voltage is to incorporate pulse width modulation control (PWM control) within the inverters.

In this method, a fixed dc input voltage is supplied to the inverter and a controlled ac output voltage is obtained by adjusting the on and off periods of the inverter devices. Voltage-type...

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