Half Wave Bridge AC/DC Converters – From diode rectifiers to PWM multilevel converters

Inhalt:
In this work a particular association of AC/DC multilevel converters is proposed to update classical half wave diode or thyristor rectifiers. Nowadays, in the frame of Medium and High Power applications, new requirements on power quality lead the classical diode/thyristor rectifiers obsolete and they should be replaced. Modular multilevel structures have become very attractive for High and Medium voltages applications because they allow working at high voltage level with a high waveform quality. In this paper a new topology based on a Modular Multilevel structure, using a zigzag transformer, is proposed. After a comparison, in terms of sizing, between this new structure and the classical MMC topology, the new topology is proposed in order to upgrade the obsolete half wave rectifiers based on diodes/thyristors. The upgrading is carried out by keeping the same grid transformer and therefore the voltage and current levels. Simulations are performed in order to validate the study and evaluate the advantages.