Unstable Parallel Generators

This is called alternator synchronization, and all power companies do this. Usually one generator is the master and the other tracks it very closely with a controller.

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alternator synchronization

Let's reason together. Two generators in parallel can work together:

IF the resistance to the common node is high enough, AND the load change is much slower, than either controller + excitation can handle. Every generator responds properly to slowly changing load. The resistance requirement frequently met by the internal resistance of the generators. The manufacturer can answer that, and adding external power resistors to mend that problem is a simple solution. But, I do not think your problem is such.

But, there is a second, independent problem you can take care with some help. Every regulator has a time constant, with which it follows sudden load change, like you switching on big lights or a baking oven, or some such. In a parallel arrangement BOTH regulators respond to the load change, and tries to regulate it out, as if the other does not exist.

The solution is straightforward. With ALL modern regulators, you must have an interconnect, in which one is the master, and the rest are slaves. Since one regulates all, all behave as dictated.

If different generations of generators and controllers are mixed, that option is normally not available, nor would I trust it without thorough testing. But, you always can count on, or make one controller markedly slower, than the other. In this case, two quite dissimilar generators can coexists allright.

For starter, I would like to see the slower generator regulate at least 2x, preferably 3x slower. You cannot see, and do that without measurements using an oscilloscope, or a PC application doing the same. Any good geek knowing what I am talking about can do that for you. After that, yo have to pore thru the Maintenance Manuals, and if all fails, contact the manufacturers with a very specific question: " What do I do to SLOW down the regulator by the x factor". I am willing to bet, that you will solve it on your own, but if not, the manufacturers tech will answer your specific question in a very short order, and exactly.

Now - obviously - there is a small price for such a loose arrangement. The regulation is 30% or 50% slower, than the fast regulating generator. I believe you can live with that.

And when we meet, you owe me a drink.