User Manual

Control concept
Superposed plant controls
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output [PrPwr] is switched in accordance with the power profile in the new
profile table.
The profile definition determines the order in which individual aggregates are to
be switched on or off. The following information must be entered for every
sequence entry:
● Object: Selected from the previously referenced aggregates.
● Stage limitation: Limit up to which the aggregate may be enabled.
● Control type: Specifies whether the enabled stages are to be switched
permanently or released to the control system.
– Fixed: The total power provided by a given switch stage is switched on
or off permanently. This option can be used, e.g., for a specific base
load which is required to be present at all times. The command is
implemented with Priority 14.
– Enable: The power actually required from the released switch stage is
determined by local control of the aggregates. The command is
implemented with Priority 16.
For each sequence step, the function block only ever releases the last
aggregate marked Release to the control system. It displays this released
object [RlsObj], with the released object stage [RlsObjSt], at the output. All
other aggregates are fixed at the released stage value. If none of the
aggregates is marked Release, the aggregate of the current sequence step is
released to the control system.
On/Off switching of PWR_CTL
When PWR_CTL is switched on [ValPgm = On], the first step in the sequence
of the current profile is executed immediately. In this case, the switch-on delay
is not valid. If the trigger for default power is on [PwrTrg = On], the aggregate
is switched directly to the default power level [DefPwr].
A switch-off command [ValPgm = Off], disables all the energy producers
defined in the profile table with Priority 14.
Out of service
If the PWR_CTL function is taken out of service [OoServ = On], then all
referenced aggregates are switched OFF with Priority 14, without taking
account of delay times. The monitoring of the aggregates is disabled.
Demand signals
The current power demand is determined locally in the energy producers. In the
event of a power deficit or surplus, the aggregate will send the appropriate
demand signal to the PWR_CTL block. The demand signal from the aggregate
can be generated, e.g., on the basis of the boiler setpoint deviation and the
primary flow. The demand signals of the separate aggregates are combined and
transmitted to the [StepUp] or [StepDn] input of the PWR_CTL block. After
expiry of the relevant delay times, the block executes the appropriate sequence
step to increase or reduce the power, as necessary.
When both [StepUp] and [StepDn] demand signals are present simultaneously,
[StepDn] takes priority.
Direct switching of a load
In cases where the power is to be increased or decreased without observing the
delay times, the default-power trigger input [PwrTrg] can be used to switch to a
defined default power level [DefPwr]. From the current profile, and taking
account of the current power output, the PWR_CTL block determines the
sequence steps required to cover the power demand and implements them
directly.