The term regenerate is sometimes used rather loosely. All types of electrical braking convert kinetic energy to electrical energy. The differences are in the details of operation and the ultimate handling of the braking energy.
With the most strict definition of regeneration, the braking energy is returned to a source that can use the recovered energy rather than dissipated it as heat.
With plugging, the kinetic braking energy is converted to electrical energy in the motor rotor where is is dissipated as heat.
I believe that one form of dynamic braking involves shorting the motor leads of connecting a resistor across them. With those methods, the braking energy is dissipated in the rotor or in the rotor plus the external resistors.
DC braking involves connecting the motor to a DC power supply. I believe that is sometimes called DC dynamic braking and works similarly to other methods of dynamic braking.
When a motor is coasting at a speed higher than the synchronous speed for utility power operation, connecting the motor to the utility will result in the motor be braked to near utility synchronous speed with some of the braking energy being returned to the utility source and the remainder dissipated in the rotor.
Operating the motor using a variable frequency drive (VFD) provides similar braking methods with better performance and a higher rate a energy recovery in regeneration.
Re Comment:
In a VFD, the motor will regenrate braking energy to the VFD any time the output waveform frequency is below the frequency corresponding to the operating speed of the motor. A regenerative front end can return that energy to the connected utility source.
Conventional plug reversing is not an acceptable mode of operation for a VFD. However it is possible for a VFD to determine the speed and direction of a spinning motor and take control of it.
