Environmental Engineering Reference
In-Depth Information
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Figure 7.8 FOC control action in response to torque step commands.
(a) Synchronous frame response and (b) stationary frame currents
due to step torque command
currents and after a 2- to 3-phase transformation into the changes required of the
M/G phase currents. Both of these signal groups are shown in Figure 7.8. The
frequency has been scaled by a factor of 14 in these plots to better illustrate the fact
that M/G currents will have very fast transient response in relation to the requested
changes in torque.
The point to notice in Figure 7.8 is that the currents have the initial peak value
commanded. In
d-q
coordinates the synchronous frame variables are always peak
quantities rather than rms. The transformations used are power invariant, so the
'power' remains unchanged regardless of which reference frame is under
consideration.
For the next illustration the FOC controller is given a command to ramp torque
to some preset value, for example, cranking the engine, then it is given a smooth
transition from motoring into generating quadrant to simulate the transition into
generator mode after the engine has started. The magnitudes are arbitrary and used
only for illustration. The important point is to show the control actions and
responses of M/G currents. Since the 2-phase equivalent of the 3-phase stationary
