This invention disclosed is a comprehensive power quality controller for
substation in the electric power system and includes a Thyristor
Controlled Reactor (TCR), pure tuned passive filter Z.sub.f, additional
inductor L active power filter (APF), and a coupling transformer. The
Thyristor Controlled Reactor (TCR) provides inductive reactive power and
controls the active power filter (APF) as the current source, it is
connected with the additional inductor L.sub.a in parallel via the
coupling transformer, then connected to the passive filter Z.sub.f in
serial to consist a hybrid power filter system, which is connected to the
power grid via the circuit breaker or thyristor. The comprehensive filter
system provides required capacitive reactive power and filters the
harmonic produced by the load and TCR system itself. Because the capacity
of the active power filter (APF) is very small which is less than 1% of
the harmonic source capacity, so it is a solution with low cost but
simple and reliable control mode. It can suppress influence on the
passive filter by the "background harmonic" of the substation and prevent
the resonance occurred between the passive filter and power grid
impedance.