SMA Solar Technology AG Product Description
3 Product Description
3.1 Modbus Protocol
The Modbus Application Protocol is an industrial communication protocol that is currently used in
the solar sector mainly for system communication in PV power plants.
The Modbus protocol has been developed for reading data from or writing data to clearly defined
data areas. The Modbus specification does not prescribe what data is within which data area. The
data areas must be defined device-specifically in Modbus profiles. With knowledge of the device-
specific Modbus profile, a Modbus client (e.g. a SCADA system) can access the data of a Modbus
server (e.g. SMA devices with Modbus interface).
The Modbus profile specially developed by SunSpec is the SunSpec Modbus profile.
The mapping of the data model of the SUNNY TRIPOWER 60 inverter on the SunSpec data model
is specified in the STP60 SunSpec Modbus profile.
3.2 SunSpec Modbus Profile for SMA Devices
The SunSpec Modbus profile from the SunSpec Alliance contains a comprehensive set of measured
values and parameters for energy-generating devices in PV systems. SMA has performed a map-
ping of the special data points of the STP60 on the data points required by SunSpec. The STP60
therefore conforms with the SunSpec Modbus profile of the underlying specification version (see
Section 1 "Information on this Document", P. 5).
The SunSpec Modbus profile for the STP60 starts at the register number 40001 (see Section 3.4
"Addressing and Data Transmission in the Modbus Protocol", page 11).
3.3 PV System Topology
The Inverter Manager is connected with the SCADA system of the electric utility company or the
grid operator and can thus communicate via the IP protocol. The IP interface also enables commu-
nication via the Modbus protocol. The SUNNY TRIPOWER 60 devices that are connected to the
Inverter Manager via an SMA fieldbus are subordinate to the Inverter Manager.
From the perspective of the Modbus protocol, the Inverter Manager represents a Modbus slave
that supports the SunSpec Modbus profile and provides a gateway to the STP60 devices. The
STP60 devices can only be addressed using this gateway per unit ID.
Technical Information STP60-SunSpec_Modbus-TI-en-12 9
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