system, the slow transient characteristic may result in the uncontrollability
of the dc-link voltage in the transient region. If
the transient state occurs, above all, the currents should follow
the reference currents as soon as possible. The synchronous
regulator gives the desirable performance in the steady state,
but cannot guarantee the fast tracking to the reference current
in the transient region. In this scheme, because the and
axes are separately controlled, only one-dimensional (1-D)
analysis is possible, and, as a result, this scheme fails to the
fast tracking to the reference current. Recently, the minimumtime
current controller, which guarantees the fastest transient
response, has been reported [7], [14]. The basic concept of
this current controller is to find the optimal control voltage
for tracking the reference current with minimum time based
on optimal control theory. But the minimum-time current
controller suffers from the large computation burden, so it has
the difficulty in applying to the industrial fields.
In this paper, a new simple current controller with both
the satisfactory steady-state characteristics and fast transient
response is proposed. In this scheme, a reference modification
part is incorporated with the generally used synchronous-frame
PI controller for the fast transient response. The proposed current
controller has a similar characteristic as the synchronousframe
PI controller in the steady state and as the minimumtime
current controller in the transient state. Simulation and
experimental results are presented and show the effectiveness
of the proposed current controller. In the simulation and
experimental results, both the current controller and dc-link
regulator show the conspicuous performance improvement.