Selective harmonics elimination in multilevel inverter by a derivative-free iterative method under varying voltage...

Area of Science:

• Electrical Engineering
• Power Electronics
• Control Systems

Background:

• Selective Harmonics Elimination Pulse Width Modulation (SHE PWM) is crucial for reducing switching losses in medium and high power converters.
• Multilevel converters benefit from SHE PWM, improving output waveforms, reducing switching losses, and lowering dv/dt.
• Asymmetrical cascaded H-bridge multilevel inverters are employed for high-power applications.

Purpose of the Study:

• To investigate SHE PWM for asymmetrical cascaded H-bridge multilevel inverters under unequal DC voltage conditions.
• To explore both fundamental and multiple switching cases for enhanced harmonic elimination.
• To present an advanced derivative-free numerical technique for solving SHE equations.

Main Methods:

• Utilizing an advanced derivative-free numerical technique to solve nonlinear transcendental SHE equations.
• Implementing a method that avoids Jacobian evaluation for faster calculations.
• Employing an identity matrix as an initial guess, removing the need for precise proximity.
• Investigating unequal DC voltage conditions to eliminate lower-order harmonics.

Main Results:

• Achieved elimination of targeted lower-order harmonics by adjusting DC voltage inequalities.
• Obtained exact solutions for switching angles ensuring complete harmonic elimination.
• Validated the proposed technique through simulation and hardware results.

Conclusions:

• The proposed derivative-free numerical technique is effective for SHE PWM in asymmetrical cascaded H-bridge multilevel inverters.
• The method simplifies implementation and offers fast convergence without requiring precise initial guesses.
• The study confirms the viability of SHE PWM for high-quality output waveforms and reduced switching losses in power converters.