Implementation of Space Vector Modulation Strategies for Voltage

Implementation of Space Vector Modulation Strategies for
Voltage Source Inverters with Induction Motor Drives
Student Krisztina Leban
“Politehnica” University of Timisoara, Bd. Vasile Parvan nr.1, Timisoara
This paper reports on a DSP implementation of a space vector pulse-width modulation
technique for three-phased voltage source inverters working with high switching frequencies in
order to generate less harmonic distortion in the output voltages or current in the motor windings.
This strategy provides more efficient use of the DC bus voltage in comparison with the direct
sinusoidal modulation technique. Also a comprehensive comparison between the implementation
of the space vector modulation and the carrier based PWM generation will be pointed out.
A standard application for this method is the speed control of induction machines. Thus
the induction machine can be smoody started with the help of the ratio voltage/frequency held
constant. The control strategy relies on a simpliļ¬ed machine model. The values of switching time
durations are obtained by real-time calculations for each period using an optimal algorithm and
the proprieties of the sinusoidal wave forms.
The TMS320F2812 DSP was used to implement this method. This DSP allows the
implementation of software written for older and slower TMS versions. It also allows flexibility
in programming giving various ways of achieving the desired results.
As the graphics show, the generated first harmonic output gets ever closer to the
sinusoidal wave when the switching frequency is raised. The maximum value of the transistor’s
switching frequency is determined in deal with the required computing time for each applied
method. The imposed frequency is around 10 kHz.