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A three-phase converter configuration, with each phase consisting of a series chain of H-bridges has become a popular multilevel solution for STATCOM application. Such a configuration, however, is not suitable for HVDC transmission. A new concept, where the series chain of H-bridge cells is used to derive a multilevel voltage reinjection waveform, is described in a companion paper. Its application to HVDC transmission is discussed in this paper and extensive use is made of EMTDC simulation to verify its steady-state and dynamic behavior. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The proposed converter is based on the reinjection of a series of dc voltage pulses, at a frequency multiple of the fundamental, that shape the output voltage waveforms into a multilevel scheme. The reinjection ratio and frequency are chosen to convert the standard 12-pulse into 36-pulse configuration without the assistance of filters or PWM. Thus the switching losses are greatly reduced. The harmonic current injection can be kept within present standards by an appropriate choice of the interface transformer leakage reactance. [ABSTRACT FROM PUBLISHER]