Area Equalization PWM Techniques for Single-Phase Full Bridge Inverter with Fluctuating DC Input

An extension of equal sampling technique (EST) based pulse width modulation (PWM) is presented for the single-phase inverter to reduce lower order harmonics caused by the fluctuating dc input. In the EST, which has been proposed earlier for constant dc, the width of PWM pulses is determined by making the area of the PWM signal equal to the area under the sampled reference waveform. The concept of equal area criterion equally applicable for fluctuating dc input with required modifications of the governing equations. Simulation results show that EST is triumphant in reducing lower order harmonics. Potential applications of the proposed technique are in fixed and variable frequency inverters for power supplies and ac motor drives which experience voltage ripple in the dc-link either when fed from a weak ac system or when insufficient filtering is employed.