User Manual

Control concept
Superposed plant controls
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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:
● When the step-up demand signal [StepUp] persists for longer than the
monitoring time deviation [TiMonDev], and there are no further sequence
steps to increase the power.
● When the step-up demand signal [StepUp] persists for longer than the
monitoring time deviation [TiMonDev] plus the step-up delay time of the
next sequence step, AND a step-up would cause the maximum power limit
[MaxPwr] to be exceeded.
The process alarm is reset to normal:
● When a sequence step with an increase in power becomes possible again.
Another sequence step with an increase in power becomes possible when
the [MaxPwr] limit will no longer be exceeded, or when a further sequence
step with a power increase is present.
● When there is no further [StepUp] demand signal
The text of process alarms can be defined to suit customer requirements.
Switching alternatives
Various switching alternatives can be defined by entries in the profile table.
Note that where one or more step-up sequence steps (intended to increase the
power) would, in practice, result in a drop in the power output, all steps in the
step-up sequence are enabled automatically until a sequence entry is reached,
at which the power output actually does increase as required. See also the
following example.