Originally posted by lamagra
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A standalone inverter or standalone generator will supply a constant (within reason) voltage and will supply current when there is a load to consume it.
A generator connected in parallel with the grid will behave differently to some extent. The control system will apply some logic to decide how much load the generator will carry but typically the generator will be running at the full power output of its prime mover (engine) and will supply power to local loads and possibly feed power back to the grid. In that mode is it also acting more as a current source than a voltage source.
If it is configured to not feed power back into the grid, then as the local loads decrease the controls will throttle back the prime mover to reduce the generator output.
A pure grid tie inverter will always deliver its maximum power output based on the available DC input. It counts on the grid being a infinite current sink and is acting as a pure current source.
A hybrid inverter will also be acting as a current source when paralleled to the grid, with the option of reducing its output to prevent back feed to the grid. In that case the excess PV power is either left unused or is diverted to battery charging.
When the hybrid inverter is in off grid mode it supplies its own AC reference voltage waveform and it is acting as a voltage source.
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