
Modbus TCP
SunSpec Model 128 — Dynamic Reactive Current
SunSpec
Overview
SunSpec Model 128 is a standardised inverter control block that governs dynamic reactive current injection in grid-connected PV and storage inverters. The template reads and writes the full set of 15 registers defined by the SunSpec Alliance specification over Modbus TCP, covering reactive current gradients for voltage sag and swell, deadband boundaries, blocking-zone parameters, filter time constant, and the module enable flag. Applied through the ModbusCloud Gateway, it lets integrators monitor live configuration state and push grid-support setpoints to any SunSpec-compliant inverter from a single portal.
Use cases
- Verify that the dynamic reactive current function is enabled on each inverter after commissioning a new site.
- Monitor the sag and swell gradient setpoints across a multi-inverter fleet to confirm uniform grid-support configuration.
- Alert on unintended changes to the deadband boundaries that could cause the inverter to breach local grid-code requirements.




