An advanced programmed PWM modulator for inverters which simultaneously eliminates harmonics and rejects DC link voltage ripple

A technique for generating programmed pulse width modulated (PWM) waveforms which simultaneously eliminates harmonics and rejects DC-link ripple is proposed. The technique guarantees high-quality inverter output voltage by rejecting the lower-order harmonics generated by the DC-link voltage ripple. In order to achieve this objective, the modulating function in the programmed PWM technique is suitably altered by a feedforward approach. The modulator is useful in situations where voltage ripple in the DC-link is unavoidable, such as when feeding nonlinear loads or when the front-end rectifier supplying the DC-link is fed from a weak AC system which is frequently unbalanced. A design procedure and the digital implementation of the modulator are discussed in detail.<>