Method and apparatus for pulse-width modulation of a variable-frequency drive

Patent metadata

Field	Value
Publication number	US-2017272017-A1
Application number	US-201414900033-A
Country	US
Kind code	A1
Filing date	Jun 27, 2014
Priority date	Jun 28, 2013
Publication date	Sep 21, 2017
Grant date	—

Abstract

The present invention disclose a method and apparatus for pulse-width modulation (PWM) of a variable-frequency drive (VFD), the method comprising: for each sector of a space vector graph for PWM of the VFD, identifying at least two possible clamping phases in switching between the vectors in the sector; comparing currents in multiple phases in at least one PWM cycle; in the sector of the space vector graph corresponding to the PWM cycle, determining the possible clamping phase with the maximum current in the at least two possible clamping phases; and clamping the determined possible clamping phase with the maximum current.

First claim

1 . A method for pulse-width modulation PWM of a variable-frequency drive VFD, comprising:
for each sector of a space vector graph for PWM of the VFD, identifying at least two possible clamping phases in switching between the vectors in the sector; comparing currents in multiple phases in at least one PWM cycle; in the sector of the space vector graph corresponding to the PWM cycle, determining the possible clamping phase with the maximum current in the at least two possible clamping phases; and clamping the determined possible clamping phase with the maximum current.

2 . The method according to claim 1 , wherein the at least two possible clamping phases are two possible clamping phases, the multiple phases are three phases, and in the sector of the space vector graph corresponding to the PWM cycle, determining the possible clamping phase with the maximum current in the at least two possible clamping phases comprises:
determining the phase with the largest current and the phase with the second largest current in the three phases; determining whether the phase with the largest current is a possible clamping phase in the sector of space vector graph corresponding to the PWM cycle; in response to the determination being positive, determining that the phase with the largest current is the possible clamping phase with the maximum current to be clamped; and in response to the determination being negative, determining that the phase with the second largest current is the possible clamping phase with the maximum current to be clamped.

3 . The method according to claim 1 , further comprising:
obtaining a real-time current magnitude, wherein the steps of comparison, determination and clamping in the method are performed only when the real-time current magnitude is larger than a threshold.

4 . The method according to claim 1 , wherein the VFD is used in an electro-hydraulic pump system.

5 . The method according to claim 1 , wherein the space vector graph is a space voltage vector graph, and the vectors are voltage vectors.

6 . The method according to claim 1 , further comprising:
in the PWM cycle, switching between the vectors while the possible clamping phase with the maximum current in the sector of the space vector graph corresponding to the PWM cycle is clamped.

7 . An apparatus for pulse-width modulation PWM of a VFD, comprising:
an identifying module configured to, for each sector of a space vector graph for PWM of the VFD, identify at least two possible clamping phases in switching between the vectors in the sector; a comparison module configured to compare currents in multiple phases in at least one PWM cycle; a determination module configured to, in the sector of the space vector graph corresponding to the PWM cycle, determine the possible clamping phase with the maximum current in the at least two possible clamping phases; and a clamping module configured to clamp the determined possible clamping phase with the maximum current.

8 . The apparatus according to claim 7 , wherein the at least two possible clamping phases are two possible clamping phases, the multiple phases are three phases, and in the sector of space vector graph corresponding to the PWM cycle, the determination module comprises:
a first determination sub-module configured to determine the phase with the largest current and the phase with the second largest current in the three phases; a second determination sub-module configured to determine whether the phase with the largest current is a possible clamping phase in the sector of space vector graph corresponding to the PWM cycle; a third determination sub-module configured to, in response to the determination being positive, determine that the phase with the largest current is the possible clamping phase with the maximum current to be clamped; and a fourth determination sub-module configured to, in response to the determination being negative, determine that the phase with the second largest current is the possible clamping phase with the maximum current to be clamped.

9 . The apparatus according to claim 7 , further comprising:
an obtaining module configured to obtain a real-time current magnitude, wherein the comparison module, the determination module and the clamping module in the apparatus perform the operations only when the real-time current magnitude is larger than a threshold.

10 . The apparatus according to claim 7 , wherein the VFD is used in an electric motor-driven hydraulic pump system.

11 . The apparatus according to claim 7 , wherein the space vector graph is a space voltage vector graph, and the vectors are voltage vectors.

12 . The apparatus according to claim 7 , further comprising:
a switch module configured to, in the PWM cycle, switch between the vectors while the possible clamping phase with the maximum current in the sector of the space vector graph corresponding to the PWM cycle is clamped.

Assignees

• Eaton Corp

Inventors

• Chen Yilun
• Cheng Xiaomeng

Classifications

• H02P27/08

  with pulse width modulation · CPC title

• F04B49/06

  Control using electricity (regulating by means of floats actuating electric switches F04B49/04) · CPC title

• H02P23/0077

  Characterised by the use of a particular software algorithm · CPC title

• H02M7/53875 Primary

  with analogue control of three-phase output · CPC title

• F04B49/065

  and making use of computers · CPC title