Method for the voltage-impressing feed of electrical power into an electrical supply grid by means of a wind power installation

Patent metadata

Field	Value
Publication number	US-11258262-B2
Application number	US-202017066078-A
Country	US
Kind code	B2
Filing date	Oct 8, 2020
Priority date	Oct 11, 2019
Publication date	Feb 22, 2022
Grant date	Feb 22, 2022

Abstract

Provided is a method for feeding electrical power into an electrical supply grid having a grid voltage by a wind power installation. The installation comprises a generator for generating a generator current, an active rectifier for rectifying the generator current into a rectified current, a direct voltage intermediate circuit having an intermediate circuit voltage for receiving the rectified current, a chopper circuit for diverting excess energy out of the direct voltage intermediate circuit, and an inverter for generating an infeed current for feeding into the electrical supply grid. The feed takes place in a voltage-impressing manner, so that the inverter counteracts a deviation of the grid voltage from a voltage setpoint value through an adjustment of the fed current. The active rectifier has a lower current limit to limit a fall of the rectified current to protect the generator during a change of the grid voltage amplitude or phase.

First claim

The invention claimed is:

1. A method for feeding electrical power into an electrical supply grid having a grid voltage by a wind power installation, comprising:
generating, by a generator, a generator current;
rectifying, by an active rectifier coupled to the generator, the generator current into a rectified current;
receiving, by a direct voltage intermediate circuit coupled to the active rectifier and having an intermediate circuit voltage, the rectified current;
diverting, by a chopper circuit coupled to the direct voltage intermediate circuit, excess energy out of the direct voltage intermediate circuit;
generating, by an inverter coupled to the direct voltage intermediate circuit, an infeed current; and
feeding the infeed current into the electrical supply grid in a voltage-impressing manner, wherein the inverter is configured to adjust the infeed current to counteract a deviation of the grid voltage from a voltage setpoint value, wherein:
the active rectifier has a lower current limit operative to, in response to a change in an amplitude or phase of the grid voltage, limit a drop in the rectified current to protect the generator,
the lower current limit is set and changed based on an operating point of the wind power installation, and
the chopper circuit is controlled to divert the excess energy arising in the direct voltage intermediate circuit or a portion of the excess energy arising in the direct voltage intermediate circuit in response to current limiting of the active rectifier.

2. The method as claimed in claim 1 , wherein the operating point of the wind power installation is an operating point of the active rectifier.

3. The method as claimed in claim 1 , wherein:
the chopper circuit is configured to divert the excess energy from the direct voltage intermediate circuit in response to the intermediate circuit voltage reaching a threshold voltage,
the active rectifier is controlled by the rectified current and the active rectifier regulates the intermediate circuit voltage, and
in response to the rectified current reaching the lower current limit, the rectified current is limited, the intermediate circuit voltage rises and reaches the threshold voltage, and the chopper circuit responds and diverts the excess energy away from the direct voltage intermediate circuit.

4. The method as claimed in claim 3 , wherein the active rectifier regulates the intermediate circuit voltage to a voltage value or a range of voltage values below the threshold voltage based on a rectifier droop function.

5. The method as claimed in claim 1 , wherein the chopper circuit diverts the excess energy based on a chopper droop function that specifies a relationship between a chopper power to be diverted from the direct voltage intermediate circuit and a difference between the intermediate circuit voltage and a threshold voltage.

6. The method as claimed in claim 5 , wherein the chopper droop function specifies a linear relationship.

7. The method as claimed in claim 1 , wherein:
using a regulation specification to regulate the intermediate circuit voltage, wherein the regulation specification includes a rectifier regulation and a chopper regulation, wherein:
the rectifier regulation specifies a relationship between the intermediate circuit voltage and the rectified current, wherein the rectified current is set by the active rectifier such that:
the rectified current falls with a rising intermediate circuit voltage until the rectified current reaches the lower current limit, and
the rectified current is held at the lower current limit as the intermediate circuit voltage continues to rise, and

the chopper regulation specifies a relationship between the intermediate circuit voltage and chopper power to be diverted from the direct voltage intermediate circuit by the chopper circuit such that:
in response to the intermediate circuit voltage exceeding a threshold voltage, the chopper power increases with the rising intermediate circuit voltage, wherein the lower current limit is changed depending on the threshold voltage or the threshold voltage is changed depending on the lower current limit.

8. The method as claimed in claim 7 , wherein the regulation specification is a regulation droop function, the rectifier regulation is a rectifier droop function and the chopper regulation is a chopper droop function.

9. The method as claimed in claim 7 , wherein the rectified current falls linearly with the rising intermediate circuit voltage.

10. The method as claimed in claim 7 , wherein the threshold voltage is changeable based on the operating point of the wind power installation, and wherein:
the threshold voltage is set depending on the lower current limit and is changed in response to a change in the lower current limit,
the threshold voltage is set to an intermediate circuit reference value that the intermediate circuit voltage reaches when the rectified current has fallen to the lower current limit, or
the threshold voltage is set depending on the intermediate circuit reference value and to a value that differs from the intermediate circuit reference value by less than 5%.

11. The method as claimed in claim 1 , wherein:
the lower current limit of the active rectifier is a dynamic function that depends on an instantaneous rectified current.

12. The method as claimed in claim 11 , wherein:
in a stationary case, the lower current limit is less than the rectified current by an undershoot difference, and
in an event of a fall in the rectified current, the lower current limit tracks, using the dynamic function, the rectified current less the undershoot difference, wherein the dynamic function has a low-pass behavior.

13. The method as claimed in claim 1 , wherein:
the inverter has an upper inverter current limit, and
in response to a voltage drop in the grid voltage, the upper inverter current limit is operative to place an upper limit on a rise of the infeed current to protect the generator.

14. The method as claimed in claim 13 , wherein the upper inverter current limit is set and changed depending on the operating point of the wind power installation.

15. The method as claimed in claim 14 , wherein the operating point of the wind power installation is an operating point of the inverter or an operating point of the intermediate circuit voltage.

16. The method as claimed in claim 13 , wherein:
the upper inverter current limit is a dynamic function that depends on an instantaneous infeed current,
in a stationary case, the upper inverter current limit is above the instantaneous infeed current by an overshoot difference, and
in an event of a rise in the infeed current, the upper inverter current limit tracks a sum of the instantaneous infeed current and the overshoot difference, wherein the dynamic function has a low-pass behavior.

17. The method as claimed in claim 16 , wherein the overshoot difference is based on an overshoot value by which the intermediate circuit voltage exceeds a threshold voltage.

18. The method as claimed in claim 1 , wherein:
an increase in a real power fed in is limited to 5% to 20% above the real power fed in or in relation to a rated power of the wind power installation, and
a reduction of the real power fed in of up to a value of −100% in relation to the real power fed in or in relation to the rated power of the wind power installation is permitted.

19. A wind power installation for feeding electrical power into an electrical supply grid having a grid voltage, the wind power installation compr

Assignees

• Wobben Properties Gmbh

Inventors

• Brombach Johannes
• Quitmann Eckard
• Emanuel Hanna

Classifications

• H02J2101/28

  Wind energy · CPC title

• H02J3/381 Primary

  Dispersed generators · CPC title

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title

• H02M7/44

  by static converters · CPC title

• G01R19/16538

  in AC or DC supplies (G01R19/16519 and G01R19/16528 take precedence) · CPC title