Wind turbine for feeding electrical power into an electrical supply network

Patent metadata

Field	Value
Publication number	US-11870265-B2
Application number	US-202017422599-A
Country	US
Kind code	B2
Filing date	Jan 15, 2020
Priority date	Jan 16, 2019
Publication date	Jan 9, 2024
Grant date	Jan 9, 2024

Abstract

Provided is a method for feeding electrical power into an electrical supply network having a network voltage using a wind turbine having an inverter, which has a DC voltage intermediate circuit having an intermediate circuit voltage and a chopper circuit connected to the intermediate circuit for discharging electrical energy from the intermediate circuit. The method includes feeding electrical power into the network in a normal operation if no network fault has been detected, detecting a fault if the network voltage falls below an undervoltage value, interrupting or reducing the feed if the fault has been detected, and ending the interruption or reduction if the end of a network fault is detected. During the fault and/or from the end of the fault, the fed-in power is limited to a limit, and, to limit the power, the intermediate circuit voltage is limited using the chopper circuit depending upon the limit.

First claim

The invention claimed is:

1. A method for feeding electrical power into an electrical supply network using at least one wind turbine, comprising:
in response to determining that a network fault of the electrical supply network is not detected, feeding the electrical power into the electrical supply network using an inverter of the at least one wind turbine in a normal mode, wherein:
the electrical supply network has a network voltage, and
the inverter has a direct current (DC) voltage intermediate circuit having an intermediate circuit voltage and a chopper circuit coupled to the DC voltage intermediate circuit and configured to discharge electrical energy from the DC voltage intermediate circuit:

detecting the network fault in response to the network voltage being less than an undervoltage value associated with a nominal network voltage;
in response to detecting the network fault, interrupting the feeding of the electrical power into the electrical supply network or reducing the feeding of the electrical power into the electrical supply network;
in response to detecting an end of the network fault, terminating the interruption of the feeding of the electrical power or terminating the reduction of the feeding of the electrical power;
limiting the fed-in electrical power to a power limit during the network fault and/or after the end of the network fault; and
limiting the intermediate circuit voltage based on the power limit using the chopper circuit in order to limit the fed-in electrical power to the limit power during the network fault and/or after the end of the network fault.

2. The method as claimed in claim 1 , comprising:
limiting the fed-in electrical power to the power limit after the end of the network fault for a recovery period that is between 10 millisecond (ms) and 10 seconds, wherein the fed-in electrical power in the recovery period is the same as or lower than immediately before detecting the network fault.

3. The method as claimed in claim 1 , wherein the power limit is predefined as a time-dependent power profile in order to return the fed-in electrical power after the end of the network fault to a value of the fed-in electrical power immediately before the network fault.

4. The method as claimed in claim 1 , wherein
setting at least one cut-off voltage based on the network fault and/or the power limit, wherein the at least one cut-off voltage is used to limit the intermediate circuit voltage during the network fault and/or after the end of the network fault; and
discharging, by the chopper circuit, the electrical energy from the DC voltage intermediate circuit depending on whether the intermediate circuit voltage reaches or exceeds the cut-off voltage.

5. The method as claimed in claim 1 , comprising:
setting a lower cut-off voltage and an upper cut-off voltage based on the network fault and/or the power limit to limit the intermediate circuit voltage, wherein the upper cut-off voltage is greater than the lower cut-off voltage by a band gap that is variable;
discharging electrical energy from the DC voltage intermediate circuit using the chopper circuit in response to the intermediate circuit voltage reaching the lower cut-off voltage; or
discharging additional electrical energy from the DC voltage intermediate circuit using the chopper circuit inversely proportionally to a difference between the intermediate circuit voltage and the upper cut-off voltage.

6. The method as claimed in claim 1 , comprising:
determining an intermediate circuit operating voltage for the intermediate circuit voltage based on an operating point of the wind turbine to feed in the electrical power in the normal mode;
in response to detecting the network fault, determining an intermediate circuit fault voltage for the intermediate circuit voltage based on the determined intermediate circuit operating voltage;
in response to detecting the network fault, setting a cut-off voltage or an upper cut-off voltage to the intermediate circuit fault voltage to control the intermediate circuit voltage to the intermediate circuit fault voltage using the chopper circuit; or
after the end of the network fault, increasing the intermediate circuit fault voltage, the cut-off voltage or the upper cut-off voltage.

7. The method as claimed in claim 1 , comprising:
after the end of the network fault, returning the fed-in electrical power to a feed-in value of the normal mode.

8. The method as claimed in claim 1 , comprising:
limiting the intermediate circuit voltage based on a fed-in reactive power;
increasing the limiting of the intermediate circuit voltage with a predeterminable temporal rise after the end of the network fault; or
increasing the limiting of the intermediate circuit voltage only after a predeterminable waiting time after the end of the network fault.

9. A wind turbine for feeding electrical power into an electrical supply network having a network voltage, the wind turbine comprising:
at least one inverter configured to feed the electrical power, wherein the at least one inverter has:
a DC voltage intermediate circuit having an intermediate circuit voltage, and
a chopper circuit coupled to the DC voltage intermediate circuit and configured to discharge electrical energy from the DC voltage intermediate circuit; and

a controller configured to:
control the at least one inverter,
control the feeding of the electrical power into the electrical supply network using the at least one inverter in a normal mode in response to determining that the network fault of the electrical supply network is not detected,
detect a network fault in response to the network voltage being less than an undervoltage value associated with nominal network voltage,
in response to detecting the network fault, interrupt the feeding of the electrical power or reduce feeding of the electrical power,
in response to detecting an end of the network fault, terminate interrupting the feeding of the electrical power or terminate reducing the feeding of the electrical power,
limiting the fed-in electrical power a power limit during the network fault and/or after the end of the network fault, and
limiting the intermediate circuit voltage based on the power limit using the chopper circuit in order to limit the fed-in electrical power to the limit power during the network fault and/or after the end of the network fault.

10. A wind farm, comprising:
a plurality of wind turbines including the wind turbine as claimed in claim 9 ;
a central farm controller; and
a common inverter.

11. The method as claimed in claim 1 , the undervoltage value is less than 90% of the nominal network voltage.

12. The method as claimed in claim 11 , the undervoltage value is less than 80% of the nominal network voltage.

13. The method as claimed in claim 2 , wherein the recovery period that is between 50 ms and 2 seconds.

14. The method as claimed in claim 3 , wherein the time-dependent power profile has a rising edge.

15. The method as claimed in claim 5 , wherein
the band gap has a prefault gap before the network fault,
if the network fault is detected, the band gap is reduced in order to discharge as much electrical energy as possible from the DC voltage intermediate circuit using of the chopper circuit in response to the intermediate circuit voltage reaching the lower cut-off voltage, or
the band gap is increased after the end of the network fault in order to reduce electrical energy discharged from the DC voltage intermediate circuit.

16. The method as claimed in claim 15 , comprising:
continuously increasing the

Assignees

• Wobben Properties Gmbh

Inventors

• Beekmann Alfred
• Mackensen Ingo
• Busker Kai

Classifications

• H02J2101/28

  Wind energy · CPC title

• H02J3/381 Primary

  Dispersed generators · CPC title

• F03D7/0284

  in relation to the state of the electric grid · CPC title

• H02J3/001

  Arrangements for handling faults or abnormalities, e.g. emergencies or contingencies · CPC title

• H02J3/48

  Controlling the sharing of active power · CPC title