28 System description
Converter control
General
The WTC operates as the overriding controller of the converter. It is connected to the
NDCU control unit of the rotor-side converter via fieldbus. The rotor-side converter control
program controls the rotor-side power modules according to the references and
commands sent by the overriding controller.
PLC interface
The converter can be connected to an external control system – usually a PLC controller –
via a fieldbus adapter connected to channel CH0 of the NDCU control unit.
The following diagram shows the PLC interface:
The converter can be set to receive all of its control information through the fieldbus
interface, or the control can be distributed between the fieldbus interface and other
available sources, eg, digital and analog inputs.
Fieldbus
Other
devices
PLC
Control Word (CW)
References
Data Flow
Status Word (SW)
Actual values
Parameter R/W requests/responses
Fieldbus adapter
Process I/O (cyclic)
Service messages (acyclic)
Nxxx
RDCU
Grid-side converter
NDCU
Rotor-side converter
CH0
CH0 CH2
CH3 CH4
NETA-01 (optional)
Turbine intranet (Ethernet)
Other
devices
WTC
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