Motor torque ripple reduction using DC bus harmonics

Patent metadata

Field	Value
Publication number	US-9912266-B2
Application number	US-201615226220-A
Country	US
Kind code	B2
Filing date	Aug 2, 2016
Priority date	Aug 2, 2016
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

Abstract

A method and system of reducing/eliminating ripple in an electric motor. An electric parameter, such as current is sensed in an input electric signal. Ripple is detected in the signal using one or more current sensors and a discrete Fourier transform calculation. Ripple is reduced by adjusting the electric signal being sent from a drive control to an electric motor, using a closed-loop configuration. The electric motor might be a regenerative electric motor that is configured to sink or supply electricity to a power grid.

First claim

What is claimed is:

1. A method comprising:
sensing an electric parameter of an input electric signal;
detecting a ripple in an AC component of the electric parameter;
determining a correction to reduce the ripple in the AC component; and
applying the correction to an electric signal supplied to an energy sink to reduce torque ripple; wherein:
detecting the ripple comprises using a discrete Fourier transform on the input electric signal to detect a non-zero result.

2. The method of claim 1 wherein the energy sink is chosen from an electric motor or a power grid.

3. The method of claim 1 wherein:
the electric parameter is chosen from current, voltage, or power.

4. The method of claim 1 further comprising:
analyzing the electric signal supplied to the energy sink to create a closed-loop control that reduces the ripple to zero.

5. The method of claim 4 wherein:
the electric signal supplied to the energy sink comprises a three-phase AC signal; and
analyzing the electric signal supplied to the energy motor comprises measuring current in at least two of the three-phases of the three-phase AC signal.

6. The method of claim 1 wherein:
the input electric signal is a DC electric signal; and
sensing the electric parameter comprises sensing an AC component in the DC electric signal.

7. The method of claim 6 wherein:
sensing the AC component in the DC signal comprises using a current sensor optimized to detect a non-zero AC component in the DC signal.

8. A system comprising:
a DC power input;
an inverter arranged to convert the DC power input to a three-phase AC power;
a drive control coupled to the inverter; and
an energy sink electric motor coupled to the drive control; wherein:
the drive control is arranged to perform:
sensing an electric parameter of the DC power input;
detecting a ripple in an AC component of the electric parameter;
determining a correction to reduce the ripple in the AC component; and
applying the correction to an electric signal supplied to the energy sink to reduce torque ripple; wherein:
detecting the ripple comprises using a discrete Fourier transform on the input electric signal to detect a non-zero result.

9. The system of claim 8 wherein:
the electric parameter is chosen from current, voltage, or power.

10. The system of claim 8 wherein the drive control is further arranged to perform:
analyzing the electric signal supplied to the energy sink electric motor to create a closed-loop control that reduces the ripple to zero.

11. The system of claim 10 wherein:
the electric signal supplied to the energy sink comprises a three-phase AC signal; and
the analyzing the electric signal supplied to the energy sink comprises measuring current in at least two of the three-phases of the three-phase AC signal.

12. The system of claim 8 wherein:
the input electric signal is a DC electric signal;
the sensing the electric parameter comprises sensing an AC component in the DC electric signal.

13. The system of claim 12 wherein:
the sensing the AC component in the DC signal comprises using a current sensor optimized to detect a non-zero AC component in the DC signal.

14. The system of claim 12 wherein the current sensor comprises:
a core with at least one air gap arranged to prevent saturation of the core; and
a wire arranged around the core, wherein the wire has a resistance of 20 to 30 ohms.

15. The system of claim 14 wherein:
the wire is located on a printed circuit board (PCB).

16. The system of claim 14 wherein:
the core is selected from a ferrite, solid steel, or a laminated steel.

17. The system of claim 8 further comprising:
an AC power input; and
a converter arranged to convert the AC power input to a DC power input.

18. The system of claim 8 wherein:
the energy sink is chosen from an electric motor or a power grid.

Assignees

• Otis Elevator Co

Inventors

• Marvin Daryl J
• Li Zhenhong

Classifications

• H02P6/14

  Electronic commutators · CPC title

• H02P6/10 Primary

  Arrangements for controlling torque ripple, e.g. providing reduced torque ripple · CPC title

• H02P6/34

  Modelling or simulation for control purposes · CPC title

• H02P27/06

  using DC to AC converters or inverters (H02P27/05 takes precedence) · CPC title

• H02P29/50

  Reduction of harmonics · CPC title