Systems and Methods for Variable Speed Drives

Patent metadata

Field	Value
Publication number	US-2016049892-A1
Application number	US-201414462384-A
Country	US
Kind code	A1
Filing date	Aug 18, 2014
Priority date	Aug 18, 2014
Publication date	Feb 18, 2016
Grant date	—

Abstract

Systems and methods for driving downhole equipment using a variable speed drive that has a switching mechanism between a first, constant-voltage capacitor bank and a second capacitor bank to control the voltage on the second capacitor bank, thereby enabling generation of a six-step output waveform while maintaining low input harmonics. In one embodiment, a variable speed drive has a converter section, an inverter section, two capacitor banks and a chopper. The converter section is controlled by a controller to convert AC power to DC power and charges the first capacitor bank to a substantially constant voltage. A chopper selectively couples the first capacitor bank to the second capacitor bank and thereby controls the voltage on the second capacitor bank. The inverter section can then produce a six-step output waveform at the voltage of the second capacitor bank. The variable speed drive can operate alternately in a pulse width modulation mode.

First claim

What is claimed is:

1 . A variable speed drive comprising:
a converter section configured to convert received AC power to DC power; a first capacitor bank coupled to the converter section, wherein the DC power produced by the converter section charges the first capacitor bank to a first voltage; a second capacitor bank coupled through a chopper to the second capacitor bank, wherein the chopper selectively enables DC power from the first capacitor bank to charge the second capacitor bank; and an inverter section coupled to the second capacitor bank and configured to invert DC power from the second capacitor bank, thereby producing an AC output waveform.

2 . The variable speed drive of claim 1 , wherein the AC output waveform comprises a six-step output waveform.

3 . The variable speed drive of claim 1 , wherein the chopper comprises a switch.

4 . The variable speed drive of claim 3 , wherein the chopper is configured to switch on and off with a duty cycle of less than 100%, and wherein the second capacitor bank is charged to a second voltage that is less than the first voltage.

5 . The variable speed drive of claim 1 , wherein the first voltage on the first capacitor bank is substantially constant.

6 . The variable speed drive of claim 1 , wherein the converter section is configured to be coupled to a three-phase external power source, wherein each phase of the three-phase external power source is selectively coupled to the first capacitor bank by a corresponding pair of switches.

7 . The variable speed drive of claim 6 , wherein the switches comprise IGBTs.

8 . The variable speed drive of claim 6 , wherein the converter section performs space vector modulation, thereby reducing input harmonics and providing a unity power factor in the variable speed drive.

9 . The variable speed drive of claim 1 , wherein the variable speed drive is configured to operate alternately in either a six-step mode or a pulse width modulation mode, wherein in the pulse width modulation mode, the chopper remains switched on and the second capacitor bank is maintained at substantially the first voltage; and wherein in the six-step mode, the chopper is alternately switched on and off, and the second capacitor bank is charged to a voltage that is determined at least in part by a duty cycle of the chopper.

10 . An artificial lift system comprising:
an electric submersible pump; and a variable speed drive coupled to the variable speed drive coupled to the electric submersible pump, wherein the variable speed drive includes
a converter section configured to convert received AC input power to DC power,
a first capacitor bank coupled to the converter section, wherein the DC power produced by the converter section charges the first capacitor bank to a first voltage,
a second capacitor bank coupled through a chopper to the second capacitor bank, wherein the chopper selectively enables DC power from the first capacitor bank to charge the second capacitor bank, and
an inverter section coupled to the second capacitor bank and configured to invert DC power from the second capacitor bank, thereby producing an AC output waveform.

11 . The artificial lift system of claim 10 , further comprising a set of boost inductors coupled to the converter section, wherein the converter section receives the AC input power through the boost inductors.

12 . The artificial lift system of claim 10 , wherein the AC output waveform comprises a six-step output waveform.

13 . The artificial lift system of claim 10 , wherein the chopper comprises a switch that is configured to switch on and off with a duty cycle of less than 100%, and wherein the second capacitor bank is charged to a second voltage that is less than the first voltage.

14 . The artificial lift system of claim 10 , wherein the first voltage on the first capacitor bank is substantially constant and is controlled by a controller coupled to the converter section, wherein the controller determines a switching algorithm used in the converter section.

15 . The artificial lift system of claim 14 , wherein the variable speed drive performs space vector modulation at the converter section, thereby reducing input harmonics and providing a unity power factor in the variable speed drive.

16 . The artificial lift system of claim 10 , wherein the variable speed drive performs space vector modulation at the converter section, thereby reducing input harmonics and providing a unity power factor in the variable speed drive.

17 . The artificial lift system of claim 10 , wherein the variable speed drive is configured to operate alternately in either a six-step mode or a pulse width modulation mode, wherein in the pulse width modulation mode, the chopper remains switched on and the second capacitor bank is maintained at substantially the first voltage; and wherein in the six-step mode, the chopper is alternately switched on and off, and the second capacitor bank is charged to a voltage that is determined at least in part by a duty cycle of the chopper.

18 . A method for producing an output waveform suitable for driving downhole equipment such as an electric submersible pump, the method comprising:
providing a variable speed drive having a converter section coupled to a first capacitor bank, a chopper coupled between the first capacitor bank and a second capacitor bank, and an inverter section coupled to the second capacitor bank; receiving AC power at the converter section from an external power source; converting the AC power to DC power; charging the first capacitor bank to a substantially constant first DC voltage; in a six-step mode, switching the chopper alternately on and off, thereby charging the second capacitor bank to a desired voltage, wherein the chopper is operable with a duty cycle of less than 100%, and wherein the second capacitor bank is chargeable to a second voltage that is less than the first voltage; and inverting the desired voltage on the second capacitor bank with the inverter section, thereby producing a six-step output waveform.

19 . The method of claim 18 , further comprising providing the output waveform to an electric submersible pump and thereby driving the electric submersible pump.

20 . The method of claim 18 , further comprising:
initially operating the variable speed drive in a pulse width modulation mode, wherein in the pulse width modulation mode, the chopper remains switched on, charging the second capacitor bank to the first DC voltage, and the inverter section inverts the voltage on the second capacitor bank, thereby producing a pulse width modulated output waveform; and thereafter discontinuing the pulse width modulation mode and operating the variable speed drive in the six-step mode.

Assignees

• Baker Hughes Inc

Inventors

• Moghadas Amin A
• Mackay Evan G
• Leuthen John M
• Pichilingue Renato L

Classifications

• E21B43/128 Primary

  Adaptation of pump systems with down-hole electric drives · CPC title

• H02P23/0081 Primary

  Electricity · mapped topic

• H02P6/14

  Electronic commutators · CPC title

• H02P21/0035

  Electricity · mapped topic

• H02M5/4585

  having a rectifier with controlled elements · CPC title