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What is the difference between "emergency power" and "off-grid operation"?

Emergency power
If the AC grid fails, the battery storage continues to supply power. In the case of a salidomo©, the switchover to emergency power happens in less than 20 milliseconds, so you don't notice anything about the switchover.

Off-grid operation
If the AC grid fails, all producers (PV inverters or solar charge controllers) and the consumers continue to function. The producers are controlled via a variable frequency of the AC current (frequency up -> PV production throttled, frequency down -> PV production increased). Off-grid operation is thus an extended emergency power supply - also called "AC microgrid" in technical jargon.

A salidomo© can do both. If the PV inverter is connected to the AC input of the salidomo© (between mains and salidomo©), then the PV inverter will also switch off in the event of mains failure. If the PV inverter is connected to the AC output of the salidomo© (between salidomo© and the "critical" loads, which are also supplied without mains), then the PV inverters continue to function and are controlled by the salidomo© by raising and lowering the frequency. (In this case, the 1:1 rule must be observed).

If DC/DC converters (called "solar charge controllers") are attached to the salidomo© to convert the DC solar power into DC battery power, then the PV system will function independently of the AC grid anyway. DC connections for solar charge controllers are provided in the salidomo©.


1:1 rule or how much photovoltaic power can I use in stand-alone operation

If PV inverters are connected to the AC output of the salidomo© with the aim of ensuring that solar power continues to be available in stand-alone operation even in the event of a grid failure, then the following must be observed:

  1. The PV inverter power (kVA) connected to the AC output of the salidomo© must not exceed the battery inverter power of the salidomo©. For the salidomo© 9 and 18 this is a maximum of 9 kVA PV inverter power and for the salidomo© EXT 27 and 36 it is a maximum of 15 kVA PV inverter power.
  2. Attention technology nerds: It is possible to throttle the power of a PV inverter below the power of the battery inverters in the event of a mains failure with a reliable mains monitoring relay and appropriate configuration of the PV inverter. However, Victron expressly warns against this power throttling. If the inverters or household appliances break down due to high voltage peaks**, no guarantee is given.

** The voltage peaks occur when there are large load fluctuations in the stand-alone grid and at the same time too much PV power, which cannot be throttled quickly enough by the frequency regulation of the Victron inverters. (The production cannot be adapted quickly enough to the consumption).