Modbus Gateway Voltage & PF Control

I need a substation gateway configured so it can issue real-time set-points for both voltage and power-factor on a fleet of SMA PV inverters. All messaging must follow the NIE-SSG SCADA technical guidelines and be carried over Modbus (TCP preferred, RTU acceptable if justified).
The task is purely about control: the gateway has to accept the grid operator’s Volt/Var and PF commands, translate them into the exact SMA register map, push them to each inverter, and confirm execution with the correct feedback flags.

My expectation is a turnkey configuration package that I can load into the existing gateway (Linux-based, supports DNP3 and Modbus out of the box). It should include:

• Gateway configuration files or scripts
• Register map and scaling document aligned with NIE-SSG requirements
• A brief commissioning guide and a remote test session proving dynamic voltage and PF response

Only freelancers who can point to hands-on experience doing similar Modbus control of SMA or equivalent inverters should apply—I will be looking at that first.