Statcom Controller Operation for Automatic Voltage and Reactive Power Control

STATCOM CONTROLLER OPERATION
Automatic voltage
control.
The system consists of two
voltage governor loops
and a 3-phase PWM
rectifier inverter controller
that has two control loops
namely; active and
reactive current control
loops. Of the voltage
control loops, one loop
controls ac voltage of the
system from the ac side
of STATCOM interfaced with step-down transformer by modifying the reactive
current command Iqref of the 3-phase PWM rectifier/inverter controller. The other
voltage control dc voltage EDC of the STATCOM by adjusting active current Idref
command of the 3-phase-PWM rectifier/inverter controller.
Voltage control loop of AC bus line.
It stabilizes voltage of the STATCOM section interlinked to the 3-step-down-
transformer as described by ac bus line voltage command figure thereby
maintaining ac power line voltage. To achieve this, it follows stages described
below.
I. Vectorial addition of the active component (E¿¿ d)¿ and with reactive
component, corresponding to the line voltage of the STATCOM to the
section linked with step-down transformer, is determined using
magnitude calculator.
II. Vectorial summation is deducted from the voltage command EAC ref of the
ac bus on the STATCOM and the resultant error relayed to the PI
inverting amplifier.
III. Polarity of the error in inverted by PI inverting amplifier, then amplified
so as to acquire reactive current (Iq ¿¿ ref ) ¿ command of the PWM
rectifier/inverter controller. The reactive power is supplied by 3-phase
PWM inverter/rectifier when STATCOM’s line ac voltage is lower than ac
bus line voltage command EAC ref . Resultant effect increases line voltage
of the ac power system thus correcting the error and vice versa.
DC bus voltage control loop
Bus capacitor voltage on the DC side of the STATCOM is maintained by the following
process;
IV. DC voltage across the STATCOM is determined by the voltage sensor and
relayed to STATCOM controller.