CiA® 437 series of documents: CANopen application profile for grid-based photovoltaic
The CiA 437 application profile defines a virtual control network for photovoltaic systems feeding its current into the power supply grid. The CANopen interfaces for all connected devices are defined. This includes interfaces to photovoltaic controller, photovoltaic inverters, solar panel tracking systems, sensors for wind speed and direction, radiation sensors, energy sensors, etc. Photovoltaic modules combined to a string may be diagnosed and tracked. Information about power supply grid may be collected.
Because of large amount of possible devices in photovoltaic systems, the devices may be connected within several cascaded CANopen networks. The network architecture is described by means of virtual devices (indivisible logical function of a device) thus allowing physical location of devices anywhere in the network(s). Each virtual device (e.g. inverter, solar panel tracker) is defined by means of its application and configuration parameter. Assignment of node-IDs for CANopen devices may be fulfilled automatically via Layer Setting Services, as specified in CiA 305. Additionally a mechanism for automatic addressing of physical devices is specified. Thus plug-and-play behavior of the system is achievable. The CiA 437 comprises three parts:
- Part 1 specifies general definitions
- Part 2 specifies pre-defined communication objects (PDOs and MPDOs)
- Part 3 specifies process data and configuration parameters
Respectively up to 254 inverters, panel tracking devices, string diagnostic devices and grid diagnostic devices are possible in the specified network. Each string diagnostic device may provide up to 16 channels. Also the maximal number of certain sensors is fixed to 254. Connection of generic I/O modules is possible. The profile is suitable for networking of small photovoltaic systems in private households as well as of large-scale photovoltaic plants.
The total output energy of an inverter (64-bit value) is transmitted via TPDOs, whose number depends on the inverter number. Because more than 3 000 process and configuration parameters are specified MPDOs are used for transmission of the application objects, thus allowing mapping of several parameters in the same MPDO.
For more detailed information CiA members may download the CiA 437 specifications from CiA’s members-only website.
