Controller for a permanent magnet generator and a generator in combination with such a controller
View Patent ↗A generator controller for controlling a permanent magnet generator where each phase of the generator is connectable to a DC link via electrically controllable switches, the controller characterised by a data processor adapted to receive a measurement of generator current output and a demand current, and to form a current error between the demanded value and the measured generator current; derive a target voltage as a function of the current error; and form control signals for the electrically controllable switches as a function of the target voltage.
1. A generator controller for controlling a permanent magnet generator where each phase of the generator is connectable to a DC link via electrically controllable switches, the controller characterised by a data processor adapted to
1) receive a measurement of generator current output and a demand current, and to form a current error between the demand current and the measured generator current; to form a target voltage phase angle as a function of a demanded power factor angle and a calculated current phase shift relative to a frame of reference, and to form control signals for controlling the electrically controllable switches as a function of the target voltage and the voltage phase angle,
2) derive a target voltage as a function of the current error; and
3) form control signals for the electrically controllable switches as a function of the target voltage.
2. A generator controller as claimed in claim 1 , in which the controller comprises a transform device for receiving measurements of phase current and converting them into a current vector having a magnitude and a phase with respect to the frame of reference.
3. A generator controller as claimed in claim 2 , in which the transform device performs a Clark's transform.
4. A generator controller as claimed in claim 3 , in which the transform device or the data processor takes the results of the Clark's transform and performs a conversion to polar values such that the generator output current is represented by a magnitude and a phase angle.
5. A generator controller as claimed in claim 1 , in which the current error is multiplied by a coefficient to produce a target voltage magnitude.
6. A generator controller as claimed in claim 1 , in which one of the demanded current and the current error is used in the calculation of the voltage phase angle.
7. A generator controller as claimed in claim 6 , in which one of the demanded current and the current error is used to calculate a compensating phase angle, which is combine with a demanded power factor angle and a current phase angle to produce the voltage phase angle.
8. A generator controller as claimed in claim 7 , in which current error is used to produce a target voltage magnitude, and that the target voltage magnitude and the voltage phase angle are transformed into target phase voltages.
9. A generator controller as claimed in claim 8 , in which the target voltage magnitude and the voltage phase angle are operated on using a polar to Cartesian co-ordinate conversion and an inverse Clark's transform.
10. A power generator system comprising a permanent magnet generator and a generator controller as claimed in claim 1 .