Variable speed drive with topside control and subsea switching

Patent metadata

Field	Value
Publication number	US-2016248364-A1
Application number	US-201514631612-A
Country	US
Kind code	A1
Filing date	Feb 25, 2015
Priority date	Feb 25, 2015
Publication date	Aug 25, 2016
Grant date	—

Abstract

According to some embodiments, functionality of a conventional variable speed drive (VSD) for driving a subsea electric motor is “split” with the CPU with frequency converter control being located topside and the low-level switching hardware being located subsea with the subsea motor. The motor can be used, for driving a pumping or other fluid processing module in a subsea oil or gas field.

First claim

What is claimed is:

1 . A system for operating a subsea electric motor comprising:
a subsea electric motor installed in a subsea location; a surface control system configured to adjust operating speed of said subsea electric motor by outputting a series of control signals corresponding to a selected drive frequency; a communication system configured to transmit the series of control signals from the surface control system to the subsea location; a plurality of gate drivers deployed at the subsea location and configured to receive said series of control signals and output corresponding gate signals; and a plurality of semiconductor switches deployed at the subsea location and configured to receive said gate signals and convert a source power into alternating currents (AC) at said selected drive frequency thereby driving said motor at said selected drive frequency.

2 . The system according to claim 1 wherein the alternative currents are quasi-sinusoidal pulse-width modulated.

3 . The system according to claim 1 further comprising a subsea high-speed de-multiplexer deployed at the subsea location and configured to distribute the series of control signals to said plurality of gate drivers.

4 . The system according to claim 1 wherein said communication system uses one or more optical fibers to transmit said series of control signals.

5 . The system according to claim 1 wherein each of said semiconductor switches is selected from a group consisting of: a gate-controlled semiconducting switch, an insulated-gate bipolar transistor (IGBT) switching device, an integrated gate-commutated thyristor (IGCT) switching device and a gate turn-off thyristor (GTO) switch.

6 . The system according to claim 1 wherein said source power is transmitted as three-phase electric power from the surface to the subsea location and the system further comprises a rectifier system that converts the three-phase electric power into direct current (DC) electric power for use by said switches.

7 . The system according to claim 6 wherein the system further comprises a subsea transformer configured to reduce voltage levels of the transmitted three-phase electric power for use by said rectifier system.

8 . The system according to claim 1 wherein said source power is transmitted as DC electric power from the surface to the subsea location.

9 . The system according to claim 1 wherein the motor is configured to drive fluid processing equipment of a type selected from a group consisting of: subsea pump, subsea compressor, and subsea separator.

10 . The system according to claim 9 wherein the fluid processing equipment is configured for processing a fluid produced from a subterranean hydrocarbon-bearing reservoir.

11 . The system according to claim 1 wherein the surface control system is further configured to provide continuously variable control over the frequency of the motor.

12 . A system for controlling a subsea electric motor comprising:
a surface control system configured to adjust operating speed of a subsea electric motor by outputting a series of control signals corresponding to a selected drive frequency; a communication system configured to transmit the series of control signals from the surface control system to a subsea location where the subsea electric motor is deployed; a plurality of gate drivers deployed at the subsea location and configured to receive said series of control signals and output corresponding gate signals; and a plurality of semiconductor switches deployed at the subsea location and configured to receive said gate signals and convert a source power into pulse-width modulated alternating current (AC) at said selected drive frequency thereby driving said motor at said selected drive frequency.

13 . The system according to claim 12 further comprising a subsea high-speed de-multiplexer deployed at the subsea location and configured to distribute the series of control signals to said plurality of gate drivers.

14 . The system according to claim 12 wherein said communication system uses one or more optical fibers to transmit said series of control signals.

15 . The system according to claim 12 wherein each of said semiconductor active switches is an insulated-gate bipolar transistor (IGBT) switching device.

16 . A system for controlling a plurality of subsea gate-controlled semiconducting switches comprising:
a surface control system configured to output a series of control signals; a communication system configured to transmit the series of control signals from the surface control system to a subsea location; a plurality of gate drivers deployed at the subsea location and configured to receive said series of control signals and output corresponding gate voltages; and a plurality of gate-controlled semiconducting switches deployed at the subsea location and configured to open and close in a pattern that corresponds to the received gate voltages.

17 . A system according to claim 16 wherein the pattern of opening and closing of the plurality of gate-controlled semiconducting switches convert a source power into alternating currents (AC) which drives a subsea electric motor.

18 . A system according to claim 16 wherein the gate-controlled semiconducting switches are used in a system of a type selected from a group consisting of: high-voltage direct current (HVDC) electric power transmission system; subsea DC-DC converter; subsea uninterruptible power supply (UPS) system; subsea semiconducting circuit breaker; and subsea VAR compensator system.

19 . A method for controlling a subsea electric motor comprising:
at a surface location selecting a selected drive frequency; using a surface control system, generating a series of gate control signals which correspond to the selected drive frequency; transmitting the series of gate control signals to a subsea location where a subsea motor is deployed; in the subsea location, distributing the series of gate control signals to a plurality of gate drivers; using the gate drivers, converting the gate control signals into gate control voltages; and driving the electric motor by inputting said gate control voltages to a plurality of semiconductor switches deployed at the subsea location and converting a source power into modulated alternative currents at said selected drive frequency.

20 . The method according to claim 19 further comprising distributing, using a de-multiplexer deployed at the subsea location, the series of gate control signals to said plurality of gate drivers.

21 . The method according to claim 19 wherein said transmitting uses one or more optical fibers to transmit said series of gate control signals.

22 . The method according to claim 19 wherein each of said semiconductor active switches is an insulated-gate bipolar transistor (IGBT) switching device.

23 . The method according to claim 19 further comprising:
transmitting said source power as three-phase electric power from the surface to the subsea location; and
rectifying said three-phase transmitted source power using a rectifier system into direct current (DC) electric power for use by said switches.

24 . The method according to claim 23 further comprising reducing voltage levels of the transmitted three-phase electric power for use by said rectifier system using a subsea step-down transformer.

25 . The method according to claim 19 further c

Assignees

• Onesubsea Ip Uk Ltd

Inventors

• Askeland Audun Magne

Classifications

• H02J4/25

  for transfer of electric power between AC and DC networks, e.g. for supplying the DC section within a load from an AC mains system · CPC title

• F04D25/068

  Mechanical details of the pump control unit (pump control details F04D27/00) · CPC title

• F04D15/0066

  by changing the speed, e.g. of the driving engine · CPC title

• F04D27/0261

  by varying driving speed · CPC title

• F04D13/086

  the pump and drive motor are both submerged · CPC title