I would like to understand if it is possible to use a circuit to regulate the countertorque provided by a permanent magnet synchronous generator (PMSG) all the way from zero torque to a maximum torque. I am thinking mostly about PMSGs like those used in wind turbines.
There are several papers online that discuss "direct torque control" (DTC) of a PMSG. E.g.:
I am trying to understand how this works in detail and what range of torque values is available (as a % of the generator's maximum countertorque).
How does DTC work, in layman's terms, when applied to a generator? Are these methods effectively decreasing the load felt by the generator? Or, are they putting a current into the generator to drive it like a motor and compensate for the inherent electromagnetic torque? Or some other explanation?
What is the range of torque values that such methods enable? How rapidly and reliably can the torque be controlled? In particular, can these methods enable the PMSG to have zero countertorque at one moment and a maximum countertorque a few moments later?
I have read about both "field-oriented control" (FOC) and "direct torque control" (DTC). Can both of these methods be used to adjust the countertorque provided by a PMSG?
Finally, in an electrically excited synchronous generator (EESG), it seems intuitive that you could reduce the countertorque provided the generator all the way to zero by simply decreasing the DC current in the field coils, without a complicated control circuit. Is this correct? How does this torque-control approach compare to using DTC?