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Synchronised Pulsewidth Modulation Strategies Based On Space Vector Approach For Induction Motor Drives

Electronic Theses of Indian Institute of Science

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Title Synchronised Pulsewidth Modulation Strategies Based On Space Vector Approach For Induction Motor Drives
 
Creator Narayanan, G
 
Subject Electrical Engineering
Power Electronics
Pulsewidth Modulation (PWM)
PWM Inverter
AC Drives
Variable Speed Drives
High Power Drives
Induction Motor Drives
Synchronised Powerwidth Modulation
Space Vector
Electrical Motors Induction
Overmodulation
Switching Sequences
Harmonic Distortion
Stator Flux Ripple
PWM Strategies
Voltage-frequency Converters
Harmonic analysis
Real time PWM
Electric Inverters
Synchorised PWM
PWM Waveform
Pulsewidth Modulated Inverter
Per-phase Approach
 
Description In high power induction motor drives, the switching frequency of the inverter is quite low due to the high losses in the power devices. Real-time PWM strategies, which result in reduced harmonic distortion under low switching frequencies and have maximum possible DC bus utilisation, are developed for such drives in the present work.

The space vector approach is taken up for the generation of synchronised PWM waveforms with 3-Phase Symmetry, Half Wave Symmetry and Quarter Wave Symmetry, required for high-power drives. Rules for synchronisation and the waveform symmetries are brought out. These rules are applied to the conventional and modified forms of space vector modulation, leading to the synchronised conventional space vector strategy and the Basic Bus Clamping Strategy-I, respectively. Further, four new synchronised, bus-clamping PWM strategies, namely Asymmetric Zero-Changing Strategy, Boundary Sampling Strategy-I, Basic Bus Clamping Strategy-II and Boundary Sampling Strategy-II, are proposed. These strategies exploit the flexibilities offered by the space vector approach like double-switching of a phase within a subcycle, clamping of two phases within a subcycle etc. It is shown that the PWM waveforms generated by these strategies cannot be generated by comparing suitable 3-phase modulating waves with a triangular carrier wave.

A modified two-zone approach to overmodulation is proposed. This is applied to the six synchronised PWM strategies, dealt with in the present work, to extend the operation of these strategies upto the six-step mode. Linearity is ensured between the magnitude of the reference and the fundamental voltage generated in the whole range of modulation upto the six-step mode. This is verified experimentally.

A suitable combination of these strategies leads to a significant reduction in the harmonic distortion of the drive at medium and high speed ranges over the conventional space vector strategy. This reduction in harmonic distortion is demonstrated, theoretically as well as experimentally, on a constant V/F drive of base frequency 50Hz for three values of maximum switching frequency of the inverter, namely 450Hz, 350Hz and 250Hz.

Based on the notion of stator flux ripple, analytical closed-form expressions are derived for the harmonic distortion due to the different PWM strategies. The values of harmonic distortion, computed based on these analytical expressions, compare well with those calculated based on Fourier analysis and those measured experimentally.
 
Publisher Indian Institute of Science
 
Contributor Ranganathan, V T
 
Date 2005-08-30T10:36:18Z
2005-08-30T10:36:18Z
2005-08-30T10:36:18Z
1999-08
 
Type Electronic Thesis and Dissertation
 
Format 406092 bytes
265191 bytes
380589 bytes
523049 bytes
application/pdf
application/pdf
application/pdf
application/pdf
 
Identifier http://etd.iisc.ernet.in/handle/2005/139
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Language en
 
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