Device integrations
Reactive power control (Data Manager)
Enabling reactive power control on an SMA Data Manager, and why the total plant power decides what every setpoint means
The EMS sends the plant a reactive power setpoint as a percentage over Modbus. The Data Manager receives it and forwards it to its inverters. Nothing happens until reactive power is enabled as a grid management service in its own right: active power and reactive power are configured separately, and enabling one does not enable the other.
A missing configuration is silent. The Data Manager accepts every write to the reactive power register without a Modbus error and simply ignores it. The only symptom is that the plant keeps delivering zero reactive power.
This also applies to the reactive operating point from the project settings: without this configuration, the plant does not take its share of it.
Use the Data Manager's own web interface
Log in to the Data Manager directly on its IP address, as Installer.
The grid management service menu does not appear in Sunny Portal. Installers who look there conclude the function is unavailable on the plant, which is not the case. Open the Data Manager on the local network instead.
Enable reactive power
Configuration > Grid management service
The overview lists the services separately. Reactive power shows Configuration & activation while it is still unconfigured, and Active once it is done.
In the Dutch interface: Configuratie > Netbeheer, row Blindvermogen, button Configuratie & activering.
Select Configuration & activation on the reactive power row and walk through the installation assistant:
Total plant power
Check this value before anything else, see the section below.
Operating mode
Choose Open-loop control. Closed-loop control needs an energy meter at the point of interconnection and stays greyed out without one.
Setpoint source
Choose Reactive power, Modbus. The cos phi options and the Q(U) curve are greyed out without a meter at the point of interconnection; a plain reactive power setpoint does not need one.
Rate of change and fallback
Leave the rate of change off unless the grid operator requires a ramp. The fallback defaults to a timeout of 600 s and a fallback value of 0 %, which is a sensible choice: the EMS refreshes the setpoint every few seconds, so the fallback only fires when the EMS is genuinely gone.
In the Dutch interface the setpoint source is called Blind vermog., modbus, and the operating mode Besturing (open-loop) versus Regeling (closed-loop).
After saving, the assistant warns that control begins once the setpoint has been transmitted at least once. That is expected: the EMS starts writing on its next control cycle.
The total plant power decides what a percentage means
Both the active and the reactive power setpoint are sent as a percentage. The Data Manager converts that percentage using Total plant power, the field in the first step of the assistant. It is a manually entered value, and nothing verifies it against the inverters that are actually connected.
If this value does not match the plant, every setpoint is wrong by the same ratio, in both directions, without any error anywhere.
On a 470 kW plant this field had been left at 220 000 W. A curtailment command of 25 % produced 55 kW instead of the expected 117.5 kW, because the Data Manager applied 25 % of 220 kW. Correcting the field to 470 000 W made the same command produce 70 kW at 15 %, exactly as expected.
Make sure the value matches the plant's installed inverter power, and that the same number is entered as the device's rated power in our platform. Registers 30233 and 31547 report the inverter power the Data Manager itself has detected, which is a useful cross-check.
Changing the total plant power recalculates every parameter derived from it, and SMA warns that user settings on those parameters can be lost. Note what is configured before changing it, and check the event monitor afterwards.
Verify on the plant
Configuration alone is not proof. Command a modest setpoint and measure what the plant does:
| Register | Meaning |
|---|---|
| 30805 | Reactive power delivered by the plant, in var |
| 32185 | Reactive power specification currently applied, in percent |
| 31239 | Active power limit received over communication, in percent |
| 32187 / 32189 | Reactive power the plant can actually deliver, under- and overexcited, in var |
| 32197 / 32199 | Those same two values as a percentage of the reference the Data Manager applies |
As long as the EMS has never written, 31239 reports the SMA "value not available" sentinel rather than zero. Once the EMS writes, both registers follow the commanded percentage within seconds. If they follow it while 30805 stays at zero, the Data Manager accepts the setpoint but the inverters do not act on it.
Read what the plant can actually deliver
An inverter rarely delivers as much reactive as active power; sixty percent is common. Under Monitoring > Instantaneous values the Data Manager shows what it has summed across its inverters. The var value is the figure that counts; the percentage beside it expresses that capacity against the nominal active power and does not change with the corrections below.
Channels Measurement.Operation.CurAvailVArOvExt and CurAvailVArOvExtNom, with UnExt for the other direction. Over Modbus: 32187 and 32189 in var, 32197 and 32199 in percent.
The plant's nominal reactive power
Under Configuration > Parameters sit Inverter.VArMaxQ1 through Q4. The Data Manager derives them from the total plant power rather than from the inverters.
Set Q1 and Q2 to the summed reactive power of the inverters, and Q3 and Q4 to the same figure with a minus sign. The Type label rows are read-only and do not follow along.
This figure governs how the Data Manager distributes a command across its inverters. Each inverter family uses its own reference and it converts the percentage per device. Get the figure wrong and the plant delivers too much or too little, without any error message.
For a command of 10 % on a 470 kW plant with 282 kvar of inverters:
| Inverter | References | Receives | Delivers |
|---|---|---|---|
| STP 125-70 | active power, 125 kW | 10.0 % | 12.5 kvar |
| Sunny Tripower CORE2 | reactive power, 66 kvar | 16.7 % | 10.6 kvar |
That 16.7 % is 10 % times 470 divided by 282.
Optimised control mode
The first step of the assistant carries a checkbox. With it enabled, every inverter receives its own setpoint instead of the command you gave.
SMA states that the mode is not possible with Sunny Tripower CORE2 inverters or with devices connected over SMA Data1. Switch the checkbox off as soon as the plant contains a CORE2. Otherwise the inverters drift apart: for the same command, two CORE2 units received 19.0 % and 24.7 %, in proportion to their output at that moment.
Check what each inverter receives
Via Select device and then Instantaneous values, Setpoint.PlantControl.Inverter.VArModCfg.VArCtlComCfg.VArNom shows the percentage sent to that unit. It is not readable on the inverter itself: the Data Manager steers over Speedwire, so 40200 and 30825 return the SMA "value not available" sentinel.
Always measure afterwards
Measure the delivered reactive power against a known command, particularly on a plant that mixes inverter families. Two or three points are enough, the response is linear. On a plant combining two Sunny Tripower CORE2 with two STP 125-70, 10 % first produced 78 kvar instead of 47; after the corrections, 46.3 kvar. If a fixed ratio remains, enter it as the device's nominal reactive power in our platform.
For inverters connected directly, without a Data Manager, see Sunny Boy / Sunny Tripower.