User Manual

Control concept
Superposed plant controls
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The operating state [OpSta] for both aggregates are formed within the
compounds as illustrated in the previous example from the AND link for [PrVal]
and [TraSta].
5.3 Superposed plant controls
Two blocks are available in Desigo for superposed plant control:
● CMD_CTL command control for sequence control
● PWR_CTL power control for stepped control
Both blocks are based on the standard BACnet Command Object. They have
both tables that define the operating modes and switching response of the
underlying aggregates. The commandable blocks in the aggregates must have a
BACnet [PrioArr] to use the following output and value blocks: AO, BO, MO,
AVAL, BVAL und MVAL.
PWR_CTL may only be communicated using the MVAL blocks based on the
specialized task – controlling steps.
Referencing
Referencing is used exclusively for communications by the superposed control
blocks with the output and value blocks in the aggregates to be commanded.
The references are derived from the Technical Designation (TD) of the block.
The reference is defined relative to the control block to the command block.
The aggregate does not have to be in the same hierarchy; cross-plant
communications is possible.
Example for a reference: B = \...\...\PreHcl’CmdVal
Where CmdVal is the designation for a BVAL object in the PreHcl aggregate.
More than one block can be referenced for each aggregate.
As the project-specific root is not part of the address, the references do not
need to be modified if the root changes. This simplifies project-specific name
changes and the copying of library solutions into a project.
The references, that is, the technical designations with relative addresses are
resolved in the controller at runtime. Any addressing errors will therefore only
be apparent during runtime. The cause of the error can largely be eliminated,
however, when parameterizing the controls blocks with the help of the Plant
Control Editors.
The figure shows that the [PrioArr] can communicate directly with the
referenced blocks. You can command switch and positioning values and enable
them. A commanded command remains valid until the priority entry is enabled
again. The control blocks automatically enables all commanded priorities, when
the block commands the aggregates to the new plant operating mode. The
entries for the [PrioArr] are deleted in the commanded blocks when restarting
the PX controller, with the exception of local, manual interventions to priority 8.
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