User Manual

Control concept
Superposed plant controls
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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.
Power display
The block has two outputs at which it displays the current total power of the energy producers. This
consists firstly of the controlled power output [CtldPwr]. This output represents the total power switched
by the PWR_CTL block.
The other output, the present power output [PrPwr], shows the additional power output of energy
producers that are not directly switched by PWR_CTL. To do this, PWR_CTL evaluates the priority array
[PrioArr] of the MVAL blocks. In this way it can detect, e.g., that an energy producer has been switched
manually [Prio8] to a given stage.
Configuration error
The entries in the two configuration tables are checked cyclically for validity.
● A fault alarm is generated under the following circumstances:
● Aggregates no longer accessible from PWR_CTL, owing, e.g., to retrospective modifications to the
technical hierarchy, affecting the references of the energy producers
● Retrospective changes to the stage-limit value in the aggregate, making the value configured in the
profile table too high
● No multistate value object
● Reference block no longer available: e.g., deleted with delta download
● Several references to the same block
● Empty profile table
In the event of a fault alarm, all aggregates still accessible by PWR_CTL are switched OFF permanently.
Alarm management
The PWR_CTL block in the system is an alarm-generating block with a configurable alarm class [AlmCl]
and alarm function [AlmFnct].
An Offnormal process alarm is generated: