A Novel Control Method for Transformerless H-Bridge Cascaded STATCOM With Star Configuration

Abstract

This paper presents a transformerless static synchronous
compensator (STATCOM) system based on multilevel
H-bridge converter with star configuration. This proposed control
methods devote themselves not only to the current loop control but
also to the dc capacitor voltage control.With regards to the current
loop control, a nonlinear controller based on the passivity-based
control (PBC) theory is used in this cascaded structure STATCOM
for the first time. As to the dc capacitor voltage control, overall
voltage control is realized by adopting a proportional resonant
controller. Clustered balancing control is obtained by using an active
disturbances rejection controller. Individual balancing control
is achieved by shifting the modulation wave vertically which can
be easily implemented in a field-programmable gate array. Two
actual H-bridge cascaded STATCOMs rated at 10 kV 2 MVA are
constructed and a series of verification tests are executed. The experimental
results prove that H-bridge cascaded STATCOM with
the proposed control methods has excellent dynamic performance
and strong robustness. The dc capacitor voltage can be maintained
at the given value effectively.