Method and apparatus for control of electrical machines
View Patent ↗A method for finding an operating point of an electric motor which includes the steps of generating a perturbation signal, combining the perturbation signal with a current magnitude related to a drive system of the motor or combining the perturbation signal with a power magnitude related to the motor, yielding a combined signal, and sending, based on the combined signal, a flux adjustment signal to adjust a flux of the motor. An apparatus for finding an operating point of an electric motor comprising is also presented.
1. A method for finding an operating point of an electric motor comprising the steps of:
generating a perturbation signal using a pseudo random signal generator;
combining said generated perturbation signal with a current magnitude related to said motor or combining said perturbation signal with a power magnitude related to a drive system of said motor, yielding a combined signal, wherein said power magnitude is obtained at least partly using measurements of current or voltage, and wherein said power magnitude is obtained as a minimum input volt amperes power; and
sending, based on said combined signal, a flux adjustment signal to adjust a flux of said motor.
2. The method of claim 1 , wherein said steps of generating, combining and sending are repeated.
3. The method of claim 2 , wherein said method ends when said current magnitude or said power magnitude is stable.
4. The method of claim 1 , wherein said method ends when a reference signal for a torque of said motor changes more than a threshold amount.
5. The method of claim 1 , wherein said method is started when an operating point of said motor changes, due to an external factor to said motor, and a reference signal related to said operating point change is stable.
6. The method of claim 5 , wherein said external factor is selected from the group consisting of a torque reference change, a speed reference change or a combination of these.
7. The method of claim 1 , wherein said method occurs periodically in an electric motor.
8. The method of claim 1 , wherein said combining involves multiplying said perturbation signal with said current magnitude or said power magnitude.
9. The method of claim 1 , wherein said power magnitude is obtained as a power input of said motor.
10. The method of claim 1 , wherein said power magnitude is obtained as a power input of a motor system including a motor, an inverter and a rectifier.
11. The method of claim 1 , wherein said power magnitude is a power factor.
12. The method of claim 1 , wherein said current magnitude related to said motor is obtained by measuring currents of said motor.
13. The method of claim 1 , wherein said current magnitude or said power magnitude signal is passed through a high pass filter and a low pass filter before being combined with said perturbation signal.
14. The method of claim 1 , wherein said perturbation signal is passed through a high pass filter and a low pass filter before combining said perturbation signal with said current magnitude signal or said power magnitude signal.
15. The method of claim 1 , wherein said adjustment signal is output from a proportional integral controller.
16. An apparatus for finding an operating point of an electric motor comprising:
a pseudo random perturbation signal generator for generating a perturbation signal;
a combiner for combining perturbation signals generated by said pseudo random perturbation signal generator with a current magnitude related to said motor or combining said perturbation signal with a power magnitude related to a drive system of said motor, yielding a combined signal wherein said power magnitude is obtained at least partly using measurements of current or voltage and wherein said power magnitude is obtained as a minimum input volt amperes power; and
an adjuster for sending, based on said combined signal, a flux adjustment signal to adjust a flux of said motor.
17. The apparatus of claim 16 , further comprising a direct torque control module.
18. The apparatus of claim 16 , further comprising a vector control module.
19. A system comprising:
a pseudo random perturbation signal generator for generating a perturbation signal;
a combiner for combining perturbation signals generated by said pseudo random perturbation signal generator with a current magnitude related to a motor or combining said perturbation signal with a power magnitude related to a drive system of said motor, yielding a combined signal wherein said power magnitude is obtained at least partly using measurements of current or voltage and wherein said power magnitude is obtained as a minimum input volt amperes power;
an adjuster for sending, based on said combined signal, a flux adjustment signal to adjust a flux of said motor to approach an optimum operating point.