Edge gateways at each PV park, wind farm and battery site publish inverter, turbine, met station and BMS data to one broker. Your SCADA, asset management platform, O&M team and trading desk subscribe — and curtailment setpoints travel back the same way.
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PUBLISH re/solar/dallas/inv-14/telemetry
{"ts":"2026-10-22T11:30:00Z","p_ac_kw":2381.5,"p_dc_kw":2442.0,"poa_wm2":874,"t_module_c":46.2,"state":"mppt","avail":true}QoS 1 · TLS 8883 · PUBACK
A typical portfolio mixes inverter brands, turbine OEMs and battery integrators, each with its own SCADA or cloud portal. Asset managers export CSVs to compare plants, O&M contractors log into five systems to find a tripped inverter, and the direct marketer or VPP needs live output plus a dependable path for curtailment setpoints. Every new site means another VPN and another custom integration.
An edge gateway reads inverters, string boxes and trackers over Modbus TCP (SunSpec), turbine controllers and the power plant controller over Modbus or OPC UA, and the BESS through its EMS.
It publishes power, energy, availability, alarms and met data such as irradiance and wind speed to topics per technology, plant and asset — over one outbound TLS connection per site.
SCADA, the asset management platform and the historian subscribe with wildcards such as re/+/+/+/telemetry; O&M follows alarms, trading follows live plant output.
Active-power limits are published to the plant’s setpoint topic. The plant controller applies them within its own limits and confirms the applied value on a retained state topic.
Technology, plant and asset levels in the topic tree, so one wildcard covers a plant, a region or the whole portfolio. The ISA-95 workspace keeps the structure consistent as sites are added.
Only systems you authorise — your SCADA, an EMS or the VPP interface — may publish setpoints, and each gateway may publish only its own plant’s data. Per-client credentials, topic ACLs and TLS.
QoS 1 or 2 for setpoints, persistent sessions so a gateway that reconnects still receives queued commands, and Last Will to flag a plant whose link has dropped.
The live dashboard and topic monitor show values as they arrive; threshold rules alert on an inverter trip, a turbine stop or rising BESS temperature, and the 3D Digital Twin can mirror a site.
re/solar/dallas/inv-14/telemetry
re/wind/houston/wtg-07/telemetry
re/bess/dallas/state (retained)
re/solar/dallas/ppc/setpoint/set
re/solar/dallas/ppc/setpoint/state (retained)Most utility-scale inverters expose Modbus TCP, often with SunSpec models. An edge gateway — or the data logger, if it supports MQTT — polls them locally and publishes to ConnectMQ over TLS. Smaller inverters and loggers sometimes publish MQTT directly.
They do different jobs. IEC 61850 and Modbus handle substation and device communication inside the plant, and OPC UA is common between turbine controllers and plant SCADA. MQTT moves data from many plants to the many central systems that need it, with publish/subscribe and small packets for remote links. Most portfolios use several of them.
Yes, as long as the plant controller stays in charge: your control system publishes the limit to a setpoint topic with QoS 1 or 2, and the plant controller applies it within its own limits and publishes the applied value back. ConnectMQ restricts who may publish there; grid code requirements are met by your plant controls.
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