Basler Electric DGC-2020HD - Manual (Page 123)

9469300990 Rev B 113
Bias Control
Settings are provided for AVR Bias Control and Governor Bias Control. Refer to the Tuning PID Settings
chapter for instructions on Tuning Speed PID Settings and Load Control PID Settings.
AVR Bias Control Settings
BESTCOMSPlus Navigation Path: Settings Explorer, Bias Control Settings, AVR Bias Control Settings
Front Panel Navigation Path: Settings > Bias Control > AVR Bias Control
When using the contact output type, the DGC-2020HD adjusts the generator voltage and frequency by
issuing voltage correction signals to the generator AVR (automatic voltage regulator). Correction signals
are issued in the form of DGC-2020HD output contact closures. These correction signals can be either
continuous or proportional. Proportional correction uses control pulses of varying widths and intervals.
Initially, long pulses are issued when the voltage and frequency differences are large. As the correction
pulses take effect and the voltage and frequency differences become smaller, the correction pulse widths
are proportionally decreased. Proportional correction pulses are beneficial in applications where fixed
correction pulses can result in overshooting the slip frequency and regulation offset targets.
When using the analog output type, a PID controller controls the voltage bias from the DGC-2020HD to
the voltage regulator. The controller adjusts the bias output to drive the error between desired generator
voltage and measured generator voltage to zero. Settings are provided for proportional gain, integral gain,
derivative gain, derivative filter constant, and loop gain of the PID controller.
var/PF Control
The var/PF controller is used to implement var and Power Factor control of the generator when it is
paralleled to the utility as indicated by the Parallel to Mains logic element in BESTlogic™Plus. If var/PF
control is enabled, the generator breaker is closed, the generator is stable, and the Parallel to Mains logic
element is true, the var/PF controller will become active. Whenever these conditions are not true, the
var/PF controller is disabled, and the machine will operate in voltage droop.
When control is enabled and the control mode is set to var, the var setpoint can be derived from either a
user setting or an analog input. The DGC-2020HD calculates an operating kvar setpoint based on the
kvar setpoint source setting. When this is set to User Setting, the operating kvar setpoint is equal to the
configured kvar setpoint. When the kvar setpoint source setting is set to a DGC-2020HD analog input or
an AEM-2020 input, the operating kvar setpoint is equal to the value calculated from the analog input.
Parameters are available for kvar analog max and kvar analog min.
When the bias control output type is set to analog, a PID controller controls the var/PF bias from the
DGC-2020HD to the voltage regulator. The controller adjusts the bias output to drive the error between
desired generator var/PF and measured generator var/PF to zero. Settings are provided for proportional
gain, integral gain, derivative gain, derivative filter constant, and loop gain of the PID controller.
The percent voltage droop to be used when the unit is in droop mode is determined by the droop
percentage setting. Voltage droop mode is entered any time the generator breaker is open. Voltage droop
is also the mode when the generator breaker is closed and var/PF control is disabled, or the Parallel to
Mains logic element is not true since var/PF control is not enabled until the Parallel to Mains logic element
is true. If it is desired to disable voltage droop, set the droop percentage to 0. The voltage droop gain
setting determines the gain factor applied to the voltage droop percentage to compensate for governor
differences and achieve desired droop performance. In order to test the operation of droop, the unit must
be loaded to full load and the resulting generator voltage should be compared to the desired droop. If it is
not possible to load the unit to full load, the droop test can be performed at partial load. The expected
voltage is determined by the following equation.
Expected voltage reduction in droop - (actual load/machine capacity)
∗ (droop percentage/100) ∗ rated
voltage
If the actual voltage drop does not match the expected value, calculate the error by dividing the expected
drop by the actual drop, and putting the result in as the droop gain.
DGC-2020HD Bias Control