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Controlling output

Write methods raise ErrorLimitingDVInterface (or ErrorTurnOnDVInterface / ErrorTurnOffDVInterface) if the Modbus write fails. Unsupported operations raise ErrorUnsupportedOperationDVInterface. See Exceptions.

turn_on()

Set the plant to maximum output — removes any active Direktvermarkter limitation:

iface.turn_on()

Internally this writes the driver's "no limitation / 100%" command to the device.

turn_off()

Set the plant to minimum output:

iface.turn_off()

Equivalent to sending a 0% setpoint. The exact effect depends on the device — most inverters ramp to near-zero rather than hard-stopping.

limit_plant(percent)

Convenience method with built-in range validation:

iface.limit_plant(80)    # 80% of rated output
iface.limit_plant(0)     # minimum
iface.limit_plant(100)   # full power

Raises ValueError for values outside [0, 100]. Use this in production code to catch programming errors early.

set_limitation_dv_percent(percent)

Same as limit_plant but without the range check. Accepts any float:

iface.set_limitation_dv_percent(80.0)

Use when the setpoint comes from a validated external source (e.g. a polling task that already validated the market signal).

set_limitation_dv_w(watts)

Limit by absolute watt value instead of percentage:

iface.set_limitation_dv_w(50000.0)  # cap at 50 kW

Not supported by all drivers

SolarLog and SMA do not support watt-based Direktvermarkter limits — these drivers set supports_dv_watt_limit = False and raise ErrorUnsupportedOperationDVInterface. Check iface.supports_dv_watt_limit or use set_limitation_dv_percent for portable code.

Meteocontrol and Smartdog support watt-based limits.

Watchdog behaviour (Smartdog)

The Smartdog's setpoint registers have a 5-minute timeout — if no Modbus communication arrives within 5 minutes, the device resets to unrestricted output. For continuous curtailment, repeat the set_limitation_dv_percent call at least once every 4 minutes:

from dv_interfaces import get_interface, stream
from itertools import islice

with get_interface('smartdog', '10.8.0.42') as iface:
    iface.set_limitation_dv_percent(70.0)

    # Refresh setpoint every 240 s to stay inside the 300 s watchdog window
    for result in stream(iface, interval_s=240):
        iface.set_limitation_dv_percent(70.0)

Watchdog behaviour (SolarLog)

SolarLog similarly requires the Direktvermarkter to write a WatchDog_Tag (a 32-bit counter) along with each setpoint update. The driver handles this automatically — each call to set_limitation_dv_percent or turn_on/turn_off writes the full 3-register control block (watchdog tag + mode + value).