Fault ride through capability

[ccdubs]

Hi all,

I am wondering for a generator of fixed rating, does an induction generator or synchronous generator have better fault ride through capability.

I imagine it would rely quite heavily on the inertia of the rotor. So which topology has a the highest inertia rotor. Also a synch genny will rotate slightly slower.

I guess this leads onto another question, for equal rating will a synch generator or induction generator be heavier/bigger. I would guess a synch generator would be smaller as I imagine the airgap flux density would be larger than that of an induction generator due to excitation rather than induction (all things being equal).

 

[jbartos]

Suggestion: Normally, it is prudent to trip a generator on the fault. Is this a theoretical question? When it comes to a heavy load transient, then it would depend on the rotating mass inertia.

 

[dpc]

I'm not clear what you mean by "fault ride-through" as applied to a generator.

 

[ccdubs]

When I say fault ride through I mean the ability of a sync generator to remain in synchronism with the grid when there is a network fault that is cleared.

Refering to the swing equations it seems that rotor inertia is the main factor. Assuming this is true which topology would have a rotor of greater inertia.

What I don't understand and have't been able to find any literature on is fault ride through (or the equivalent of) for an induction generator. I realise there isn't a syncronisation issue but there must be the concern of motoring/reverse power or large current transients or reactive power issues?

 

[dpc]

I don't think loss-of-synch is generally a problem for synch machines during a fault. The concern is heating due to high current demand.

For an induction generator, you will generally lose your excitation since the bus voltage will go near zero, so I would not expect them to help you much. If you tried to keep them on line, the speed may go high.

But I'm not burdened by a lot of actual knowledge about induction machines, so it's easy to speculate.