Print ISSN: 1681-6900

Online ISSN: 2412-0758

### Keywords : Resultant Theory

##### Optimum Design of Single-Phase Cascade Multilevel Inverter Using OHESW Technique

K. S. Krikor; Khalid I. Alnaimi; Jamal A. Mohammed

Engineering and Technology Journal, 2008, Volume 26, Issue 12, Pages 1492-1507

The traditional two or three levels inverter does not completely eliminate
the unwanted harmonics in the output waveform. Therefore, using the
multilevel inverter as an alternative to traditional PWM inverters is
investigated.
This paper describes the Optimized Harmonic Elimination Stepped Waveform
OHESW technique to improve the output waveform quality of multilevel
inverter fed induction motor. A new method is presented where switching
angles are computed such that a desired fundamental sinusoidal voltage is
produced while at the same time certain higher order harmonics are eliminated.
The proposed method also is used to minimize the Total Harmonic Distortion
THD of the synthesized multilevel waveform. The THD is investigated over a
wide range of possible output control voltages and number of voltage levels
used to synthesize the output waveform.
Simulation results of a cascade multilevel inverter under OHESW technique
with 5- up to 15-levels are used to eliminate the (3rd-13th) harmonics.
induction motor is investigated.

##### Optimum Solving SHEPWM Equations for Single Phase Inverter Using Resultant Method

Jamal A. Mohammed

Engineering and Technology Journal, 2008, Volume 26, Issue 6, Pages 660-670

This paper represents new method to determine the optimum switching angles for
Selective Harmonic Eliminated PWM (SHEPWM) inverter. Such switching angles are
defined by a set of nonlinear equations to be solved using the Resultant method. This is
done by first converting these equations that specify the harmonic elimination problem into
an equivalent set of polynomial equations. Then, using the mathematical theory of
Resultants, all solutions to this equivalent problem can be found without the need for any
initial guess. The complete solutions for unipolar SHEPWM switching pattern which
produce the fundamental while not generating specifically chosen harmonics are
investigated.