Method for operating doubly-fed wind turbine generator as a virtual synchronous machine to provide grid-forming control thereof

Patent metadata

Field	Value
Publication number	US-11486355-B2
Application number	US-202017139329-A
Country	US
Kind code	B2
Filing date	Dec 31, 2020
Priority date	Dec 31, 2020
Publication date	Nov 1, 2022
Grant date	Nov 1, 2022

Abstract

A method for operating an asynchronous doubly-fed wind turbine generator connected to a power grid in a grid-forming mode to emulate a virtual synchronous machine. The doubly-fed wind turbine generator includes a line-side converter coupled to a rotor-side converter via a direct current (DC) link. The method includes receiving, via a controller, at least one reference command from an external controller. The method also includes controlling rotor flux of the doubly-fed wind turbine generator using the at least one reference command. Further, the method includes providing power droop control for the doubly-fed wind turbine generator through at least one of rotor-side reference frame rotation and d-axis flux control.

First claim

What is claimed is:

1. A method for operating an asynchronous doubly-fed wind turbine generator connected to a power grid in a grid-forming mode to emulate a virtual synchronous machine, the doubly-fed wind turbine generator comprising a line-side converter coupled to a rotor-side converter via a direct current (DC) link, the method comprising:
receiving, via a controller, at least one reference command from an external controller;
controlling rotor flux of the doubly-fed wind turbine generator using the at least one reference command; and
providing power droop control for the doubly-fed wind turbine generator through at least one of rotor-side reference frame rotation and d-axis flux control.

2. The method of claim 1 , wherein the at least one reference command comprises a power reference command and a voltage reference command from the external controller, the power reference command comprising one of an active power reference command or a reactive power reference command.

3. The method of claim 2 , wherein controlling the rotor flux of the doubly-fed wind turbine generator using the at least one reference command further comprises:
receiving the voltage reference command from the external controller;
receiving a stator voltage from a stator of the doubly-fed wind turbine generator;
determining a flux command using the voltage reference command and the stator voltage; and
determining a rotor current command based on the flux command.

4. The method of claim 3 , wherein determining the rotor current command based on the flux command further comprises:
determining an air gap flux feedback signal using at least one of stator current, the stator voltage, rotor current, or rotor voltage; and
determining the rotor current command based on the flux command and the air gap flux feedback signal.

5. The method of claim 4 , further comprising determining the rotor current command based on the flux command, the air gap flux feedback signal, and the stator current.

6. The method of claim 2 , wherein providing the power droop control for the doubly-fed wind turbine generator through at least one of rotor-side reference frame rotation and d-axis flux control further comprises:
providing active power-frequency droop control for the doubly-fed wind turbine generator through rotor-side reference frame rotation; and
providing reactive power-voltage droop control for the doubly-fed wind turbine generator through d-axis flux control.

7. The method of claim 6 , wherein providing the active power-frequency droop control for the doubly-fed wind turbine generator through the rotor-side reference frame rotation further comprises:
receiving the active power reference command from the external controller;
receiving an active power feedback signal;
determining an angular frequency of the doubly-fed wind turbine generator as a function of the active power reference command and the active power feedback signal;
determining a rotor frequency using the angular frequency and a magnetizing angular frequency of the doubly-fed wind turbine generator;
determining a phase angle for a rotor-side d-q reference frame as a function of the rotor frequency; and
shifting the rotor-side d-q reference frame of the doubly-fed wind turbine generator by the phase angle to achieve the active power-frequency droop control of the doubly-fed wind turbine generator.

8. The method of claim 7 , wherein determining the phase angle for the rotor-side d-q reference frame as a function of the rotor frequency further comprises:
integrating the rotor frequency to determine the phase angle.

9. The method of claim 7 , wherein providing the power droop control for the doubly-fed wind turbine generator through at least one of rotor-side reference frame rotation and d-axis flux control further comprises:
providing a droop characteristic function relating active power values to angular frequency values; and
determining the angular frequency of the doubly-fed wind turbine generator as a function of the power reference command, the power feedback signal, and the droop characteristic function.

10. The method of claim 9 , wherein providing the reactive power-voltage droop control for the doubly-fed wind turbine generator through the d-axis flux control further comprises:
receiving the reactive power reference command from the external controller;
receiving a reactive power feedback signal;
determining a voltage command for the doubly-fed wind turbine generator as a function of one or more of the reactive power reference command, the reactive power feedback signal, and a magnetizing voltage of the doubly-fed wind turbine generator; and
controlling d-axis flux of the doubly-fed wind turbine generator using the voltage command.

11. The method of claim 10 , further comprising integrating the voltage command for the doubly-fed wind turbine generator.

12. The method of claim 10 , further comprising:
providing a droop characteristic function relating reactive power values to voltage values; and
determining the voltage command of the doubly-fed wind turbine generator as a function of the reactive power reference command, the reactive power feedback signal, and the droop characteristic function.

13. The method of claim 1 , wherein the controller comprises at least one of a turbine controller or a converter controller of the wind turbine power system.

14. A system for operating an asynchronous doubly-fed wind turbine generator connected to a power grid in a grid-forming mode to emulate a virtual synchronous machine, the doubly-fed wind turbine generator comprising a line-side converter coupled to a rotor-side converter via a direct current (DC) link, the system comprising:
a controller comprising at least one processor configured to perform a plurality of operations, the plurality of operations comprising:
receiving at least one reference command from an external controller;
controlling rotor flux of the doubly-fed wind turbine generator using the at least one reference command; and
providing power droop control for the doubly-fed wind turbine generator through at least one of rotor-side reference frame rotation and d-axis flux control.

15. The system of claim 14 , wherein the at least one reference command comprises a power reference command and a voltage reference command from the external controller, the power reference command comprising one of an active power reference command or a reactive power reference command.

16. The system of claim 15 , wherein controlling the rotor flux of the doubly-fed wind turbine generator using the at least one reference command further comprises:
receiving the voltage reference command from the external controller;
receiving a stator voltage from a stator of the doubly-fed wind turbine generator;
determining a flux command using the voltage reference command and the stator voltage; and
determining a rotor current command based on the flux command.

17. The system of claim 16 , wherein determining the rotor current command based on the flux command further comprises:
determining an air gap flux feedback signal using at least one of stator current, the stator voltage, rotor current, or rotor voltage; and
determining the rotor current command based on the flux command, the air gap flux feedback signal, and the stator current.

18. The system of claim 14 , wherein providing the power droop control for the doubly-fed wind turbine generator through at least one of rotor-side reference frame rotation and d-axis flux control further comprises:
providing acti

Assignees

• Gen Electric

Inventors

• Liu Hanchao
• Gong Maozhong
• Pan Di
• Zhang Yichao

Classifications

• H02J2101/28

  Wind energy · CPC title

• H02P2101/15

  for wind-driven turbines · CPC title

• F05B2220/70646

  Double fed induction generators (DFIGs) · CPC title

• F05B2270/342

  Wave conditions, e.g. amplitude, frequency or direction · CPC title

• H02J3/50

  Controlling the sharing of reactive power · CPC title