We transform source current (Is) of Single Phase Active Front End Rectifier into Id and Iq. What should be the nature of Id and Iq? Is it possible for Id and Iq to be negative?
Id should taken along X axis and IQ should be considered along Y axis to begin with. Conventional process of resolution of vectors can be fallowed to obtain the magnitude and phase angle of resultant vector.
The Park transform is just a mathematical tool to simplify the control/calculations of AC signals. The Park transform changes an AC signal with a specific fundamental frequency to a rotating frame with that fundamental frequency. the quantities in this reference frame are dc quantities. This makes control/calculations much easier.
Since in most cases the fundamental frequency is fixed (50 or 60 Hz), the transformation from AC to 'DC' signals can be done rather easily.
For motor control the Id current is used as the magnetization current, for permanent magnet motors it shall be controlled towards zero. The Iq current is the torque related current. This current can be positive and negative (motor or generator operation).
In a rectifier this separation can also be made but than with active and reactive power.
Dear Martin Deuring and Venkataraman Chayapathy,
Generally, Id is taken as active component of current and Iq is taken as reactive component of current. For unity power factor, Iq is compared with zero and Id is compared with Iref before PI controllers.
If we interchange Id and Iq, Iq is taken as active component of current and Id is taken as reactive component of current. For unity power factor, Id is compared with zero and Iq is compared with Iref, what will be the effect? Is this conceptually correct?
Id and Iq both are DC values. Both can be used with PID controller for controlling Active and reactive current.
Please explain..............
If you momentarily forget about your rotating reference frame, you have 2 independent values (Id, Iq) that can be handled as if they were DC. From a different perspective, these 2 are the amplitides of 2 waves that are orthogonal (out of phase by 90 degrees).
When it comes to controlling you circuit, you have to do the inverse transformation. This results in values where it is difficult to discern the d resp. the q component - which is easy in the rotating reference frame system.
As already stated above: it's just a mathematical tool ('trick').
Regards
With unity power factor your reactive power shall be zero. You should control the current to the values you state.
Indeed both current values can be controlled with a PID controller since both currents behave as a DC current after applying the Park transform to Id and Iq.
Hopefully this helps. Good luck!
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