Load sharing

Synchronous is more common and the load sharing of power (watts) is a function of engine torque (fuel control) if these are for a generator set with an engine and the load sharing of amperes is a function of voltage balance between the two controlled by the voltage regulator and a cross current compensation circuit.

You can use both syncronous and asyncronous generators.

If you use a syncronous one, you can increase its load with increasing the torque of the driver engine and increasing the generator's excitation. The "load angle" ( "Beta", the angle between the axes of revolving magnetic field and the rotor) will increase with the load.

If you use asyncronous generator you only have to increase the torque. The generator will a bit speed up, its slip will grow and it will also consume more magnetizing current from the network and its share from the load will grow.

In multi engine aircraft that I worked on back in the day, the voltage regulators would keep the load fairly well balanced in the DC generators...a primitive old carbon pile would work just fine. Its an off the shelf item. AC generators..well, they were a different story! The engines had to be synchrophased in order to keep them from shaking the airplane apart, and that meant the generators were also pretty much in phase. I don't recall any ac generators doing duty as load sharing...they generally each had their own busses which could be dropped on or off as the flight engineer desired. That is to say, each generator had its own collection of loads. If one engine shut down, and a generator went off line, the FE would shed non-essential busses, and bring one of the other engine's generators over to handle the duff generator's essential loads.

Of course, now we have home power systems which produce electricity from wind, water, and whatever, and have to synchronize with the grid in order to feed power back into the grid when there is surplus available. (Some power companies don't allow this, some do.) A clever device called an "inverter" will do that for you. Don't know why they call it an inverter...it doesn't really invert! But what it does is convert your DC into AC which the grid will recognize. Again, an off the shelf item.

Hope this helps...

Honda makes portable generators (inverter-based) that will share loads automatically. The EU2000i is the model I use. The military generators used in the Army Signal Corps had synchronizing circuits where you would alter the speed slightly of one generator to change the phase and when the two alternating blinking lights were on simultaneously, you could connect them to the same bus. I believe those 60kW gensets had synchronous generators.