SunSpec Model 64414 — DER Simulation Controls
SunSpec Model 64414 is a vendor-extension Modbus TCP model that provides DER simulation controls, used in hardware-in-the-loop test environments, software simulators, and conformance test rigs for distributed energy resources. The template reads the model identifier, block length, and simulation timestamp, and exposes writable registers for temperature, irradiance, irradiance model source, grid model source, per-phase grid voltage (phases A, B, and C), and grid frequency. Importing this template into the ModbusCloud portal lets you monitor and inject simulation inputs over Modbus TCP without opening a separate test tool.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 11, read and write
- Brand
- SunSpec
- Last updated
Registers (11)
11 read, 8 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| id | Read | ||||
| l | Read | ||||
| time | Read | ||||
| temperature | °C | Read and write | |||
| gridmodelsource | Read and write | ||||
| irradiancemodelsource | Read and write | ||||
| irradiance | Read and write | ||||
| gridvoltagea | V | Read and write | |||
| gridvoltageb | V | Read and write | |||
| gridvoltagec | V | Read and write | |||
| gridfrequency | Hz | Read and write |
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If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Monitor the active irradiance model source string to verify which simulation profile a DER test rig is currently applying.
- Track per-phase grid voltage registers (phases A, B, C) to confirm that voltage injection sequences are executed as scripted.
- Alert on unexpected changes to the gridfrequency register during automated conformance test runs to detect test-script errors.
- Record simulation timestamp values alongside irradiance and temperature to correlate test conditions with DER response data.
- Compare grid voltage and frequency register values against expected test vectors to validate DER behavior under off-nominal grid conditions.
Installation
Enable Modbus TCP on the DER simulator or test platform under the communication or Modbus section, noting the IP address and port (typically 502).
Connect the ModbusCloud Gateway to the same Ethernet network as the simulator host, ensuring no firewall blocks TCP port 502 between them.
In your ModbusCloud portal, add the Gateway, then import the SunSpec Model 64414 template and set the Modbus unit ID to match the simulator's configured slave address.
Verify the connection by reading the id register (address 0): a value of 64414 confirms the correct model is addressed and data is flowing.
Things to watch for
Why do id and l registers return 0xFFFF instead of expected values?
0xFFFF is the SunSpec unimplemented-register sentinel. If the simulator has not fully initialised the model block, or the Modbus map start address does not align with where the Gateway is reading, the id and l registers appear as 0xFFFF. Confirm that the SunSpec map starts at address 0 and that the simulator is fully running before polling.
The gateway connects but gridvoltagea, gridvoltageb, and gridvoltagec all read zero.
Float32 registers occupy two consecutive 16-bit Modbus registers and are stored in big-endian word order per the SunSpec specification. If the Gateway byte-order setting does not match, both words decode to zero. Verify that the Modbus TCP bridge is set to big-endian word order and that function code 3 is used on the correct pair of addresses.
Timestamp string register reads garbled characters. What is wrong?
SunSpec string registers store ASCII characters packed two per 16-bit register, big-endian. If your Modbus client swaps byte order within each register, each pair of characters appears reversed. Ensure the TCP client uses big-endian byte order as defined in the SunSpec Device Information Model Specification.
Is it safe to write temperature, irradiance, and grid voltage registers during a live conformance test?
Writing these RW registers injects conditions directly into the DER simulation engine. Incorrect values, especially extreme voltage or frequency figures, can trigger protective responses in the simulated or physically connected DER, invalidate test sequences, or in hybrid setups affect real inverter behavior. Always verify the target unit ID and register address before writing, and coordinate writes with the test script operator.
Knowledge base articles for this device
SunSpec Modbus: one register map for many inverters
SunSpec Modbus is the open register map SMA, Fronius, SolarEdge and Kostal share. The layout, int+SF vs float, the TCP port per brand and reading a mixed fleet.
Fronius Modbus: read a Symo GEN24 over Modbus TCP
Fronius Modbus explained: enable Modbus TCP on the Symo GEN24 on port 502, choose between int+SF and float, read the right SunSpec registers and scale them correctly. Practical guide for solar installers.
SMA Modbus: reading a Sunny Boy over Modbus TCP (installers)
SMA Modbus explained: enable the Modbus TCP server on port 502, choose between the SMA profile (unit ID 3) and SunSpec (unit ID 126), read the right registers, and handle the NaN values at night. Practical guide for installers.
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