No they can't.
The power supply, in this case the generator, must be able to supply enough power for it to work.
The transformer is not able to magically increase the power output of the original power source. Instead it will waste some in the process of transforming the voltage, so you get even less power out of it.
You need a bigger generator for this task.
The problem you are facing is the conservation of energy. And energy is power over time. So if you have a power supply with
200 W, it will give you
200 J per second of energy.
If you have a device using
700 W, it will need
700 J every second. No transformer in the world is able to give you
700 J of energy every second when it is supplied only with
200 J per second.
You could do an
interleaved mode, so you could store energy for
4 seconds, then you have
800 J, then you can power your device for one second. That is the was those ultra high power lasers work - they would need more power than the grid is able to supply, so they are driven pulsed so there is time to charge.
In your case that is not possible.
As for your comment, please do not mix up the units. What is shown in that video is a step up from
3 V to
500 V. Only the voltage is increased. The product of voltage and current is the same (well minus losses).
So if that guy takes
500 W from the
500 V (1 A), he needs to have
3 V and
166 A (500 W) at the input.
There is no way around energy conservation.