Pt. Cheng et al., CONTROL OF SQUARE-WAVE INVERTERS IN HIGH-POWER HYBRID ACTIVE-FILTER SYSTEMS, IEEE transactions on industry applications, 34(3), 1998, pp. 458-472
This paper presents a new control scheme for a hybrid parallel active
filter (HPAF) system intended for high-power applications-up to 100-MW
nonlinear loads-to meet IEEE 519 recommended harmonic standards. The
active filter inverter is realized with small-rated (1%-2% of the load
rating) square-wave inverters operating at the dominant harmonic freq
uencies. The proposed system achieves harmonic isolation at desired do
minant harmonic frequencies, such as the fifth and seventh, even in th
e presence of supply voltage harmonic distortions. A novel method of a
ctive filter inverter de-bus control, as proposed here, achieves power
balancing by exchanging energy at the fundamental frequency and at th
e dominant harmonic frequency (such as the fifth). The proposed square
-wave inverter-based HPAF system provides improved filtering character
istics as compared to the conventional passive filter and is expected
to be cost effective for high-power nonlinear loads compared to the co
nventional passive filter or other active filtering solutions. The con
cept of harmonic isolation at dominant harmonic frequencies by square-
wave inverters with the proposed control scheme is validated by simula
tion results.