User Manual

Control concept
Closed-loop control strategy
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temperature) or equivalent to the setpoint of the first cooling element (if the
extract air temperature is lower than the outside air temperature).
● The gain of each sequence element can be influenced individually. In this
way, e.g., the amplification factor (gain) of the energy-recovery element
varies as a function of the difference between the extract air temperature
and the outside air temperature, in order to achieve an almost constant loop
gain.
● For each element, P, PI, PID, PD or on/off control can be selected. The
control parameters for each element (controller gain, integral action time
and derivative action time) can be adjusted individually.
● If all the sequence elements have the same parameter values, the sequence
responds in exactly the same way as a single PI(D) controller whose output
variable is distributed to individual aggregates within the plant.
● The controller output and the integrator of the sequence element is limited
in the range [YctrMin] to [YctrMax]. For this purpose, the high limit of the
last enabled sequence element of the heating and cooling sequence is
limited with an anti-windup strategy (limitation of I/portion on manipulated
variable limits). All other limit values are controlled by straightforward
selection of the minimum or maximum value.
● The rate of change of the output of each sequence element is limited to the
speed of the connected actuator. This helps improve control quality.
● The type of operation of each element (heating/cooling or
humidification/dehumidification) can be selected individually for each
element.
● Only one element of the sequence can have a controlling function. When
the output of a controlling sequence element reaches [YctrMin] or
[YctrMax], control is transferred to the nearest adjacent active element
("ON").
The term higher is applied to sequence elements that correspond to higher set
points in the sequence diagram (normally cooling or dehumidification).
The term lower is applied to sequence elements that correspond to lower set
points in the sequence diagram (normally heating, energy recovery or
humidification).
Essentially, the sequence controller consists of individual PID_CTR blocks. with
each PID_CTR block acting as a sequence-controller element for an aggregate.
The PID_CTR blocks are connected (from "Low" to "High") in the same order as
the control sequences (1…n) of the sequence controller. Accordingly, the
connection of the PID_CTR blocks must take account of the intended operating
range (e.g., for heating) and the order of switching.
For example, aggregates:
1 = Re-heater, 2 = Pre-heater, 3 = Dampers, 4 = Cooling coil
Control series for heating: 3 ---> 2 ---> 1
Cooling control sequence: 4 ---> …
Naming convention
Configuration of a
sequence controller