Cascaded H-bridge voltage reinjection - Part I: A new concept in multilevel voltage-source conversion

A new multilevel configuration is proposed for use in voltage source conversion of large power and voltage ratings; it consists of the standard double bridge converter and a series chain of H-bridges, each connected to a capacitor. The H-bridge chain is connected between the middle node of the dc capacitors and the neutral point of the two main bridges. The new reinjection configuration provides all the features of the previously proposed multilevel reinjection schemes with a considerably reduced number of switches (that only increases in direct proportion to the converter dc voltage rating) and acts as a dynamic voltage balancer for the main bridge switches. Extensive simulation is carried out to verify the steady state waveforms and the dynamic behavior with reference to the STATCOM application.