Method for feeding electrical power into an electric supply network

Patent metadata

Field	Value
Publication number	US-10794364-B2
Application number	US-201816046636-A
Country	US
Kind code	B2
Filing date	Jul 26, 2018
Priority date	Jan 27, 2016
Publication date	Oct 6, 2020
Grant date	Oct 6, 2020

Abstract

A method for feeding electrical power, by a one wind power installation, a power plant or a generation plant, into an electrical supply grid is provided. The grid has a grid voltage having a grid frequency at a grid connection point. In the method a reference system having a reference frequency, a reference phasor having a reference angle, and a reference amplitude of an output voltage are specified. The reference angle revolves at the reference frequency and the reference frequency substantially corresponds to the grid frequency. A phase angle between the output voltage and the grid voltage is specified and an infeed angle is determined. The output voltage is generated having a voltage amplitude depending on the reference amplitude, a frequency depending on the reference frequency and the infeed angle. Tracking of the behavior of the grid voltage is delayed by the reference system.

First claim

The invention claimed is:

1. A method for feeding electrical power, by at least one wind power installation or a power plant, into an electrical supply grid having a grid voltage and an associated grid frequency at a grid connection point, the method comprising:
specifying a reference system including a reference frequency, a reference phasor having a reference angle, and a reference amplitude of an output voltage to be generated, wherein the reference angle revolves at the reference frequency and the reference frequency substantially corresponds to the grid frequency,
specifying a phase angle between the output voltage and the grid voltage,
determining a feed-in angle, which revolves with the reference angle, from the specified phase angle, wherein when the reference frequency corresponds to the grid frequency, the specified phase angle becomes a phase angle between the output voltage generated at the feed-in angle and the grid voltage,
generating the output voltage having a voltage amplitude that depends on the reference amplitude, a frequency that depends on the reference frequency, and the feed-in angle, and
performing delay tracking of the reference system by at least causing the reference system to track a behavior of the grid voltage in a delayed manner, wherein causing the reference system to track the behavior of the grid voltage in the delayed manner includes:
causing the reference amplitude to track the grid voltage in a delayed manner, or
causing the reference frequency to track the grid frequency in a delayed manner, wherein causing the reference frequency to track the grid frequency in the delayed manner includes:
detecting a phase angle between the generated output voltage and the grid voltage,
determining a difference between the specified phase angle and the detected phase angle,
changing the reference angle to reduce the difference according to a magnitude using a delay function, and
adjusting the reference frequency to the changed reference angle.

2. The method as claimed in claim 1 , comprising:
causing the reference system to track the behavior of the grid voltage using predetermined delay dynamics.

3. The method as claimed in claim 2 , wherein:
the predetermined delay dynamics or the delay tracking are set based on the grid connection point, or
additional power or resulting excess power from rotation energy required for delayed tracking is offset or stored as rotation energy or is taken from an energy store or is stored in the energy store.

4. The method as claimed in claim 2 , wherein the predetermined delay dynamics include a delay function, and wherein the delay function is a pt1 function or a pt2 function having a non-overshooting step response.

5. The method as claimed in claim 4 , comprising:
generating an output voltage that produces a current fed-in to the electrical supply grid, and
selecting the delay function or delay dynamics such that when at least one state in the electrical supply grid changes:
a generation of the output voltage initially remains substantially unchanged, and
a resulting change of the fed-in current is initially not substantially counteracted, and according to the selecting of the delay function or delay dynamics, the method reacts to the change in the at least one state in the electrical supply grid immediately with a changed fed-in current.

6. The method as claimed in claim 1 , comprising:
before performing delay tracking of the reference system, setting the reference frequency to the grid frequency.

7. The method as claimed in claim 1 , wherein:
performing delay tracking of the reference system includes making the reference system track the grid voltage and deviate from the grid voltage in at least one variable at least by a predetermined minimum deviation, and
performing normal operations when the reference system does not track the grid voltage or does not deviate from the grid voltage in the at least one variable at least by the predetermined minimum deviation,
wherein a limit value specified for the normal operations may be exceeded by a predetermined tolerance value in a tracking operation.

8. The method as claimed in claim 7 , wherein at least one overshoot is permitted during normal operations from a list including:
the specified limit value is a maximum feed-in current and the predetermined minimum deviation is at least 10% of the maximum feed-in current,
the specified limit value is a maximum power to be fed in and the predetermined minimum deviation is at least 10% of the maximum power to be fed in,
the specified limit value is a maximum permissible temperature in an inverter that generates the output voltage and the predetermined minimum deviation is at least 10 kelvin,
the specified limit value is a maximum permissible value of an integral of the temperature over a predetermined time and the predetermined minimum deviation is at least 10 kelvin*second, and
the specified limit value is a maximum change in frequency and the predetermined minimum deviation is at least 0.5 Hz/s.

9. The method as claimed in claim 1 , wherein:
the electrical supply grid is associated with a nominal frequency,
the reference frequency is made to track the grid frequency independently of whether the grid frequency approaches or diverges from the nominal frequency, wherein
tracking the reference frequency is delayed to a greater extent when the grid frequency diverges from the nominal frequency than when the grid frequency approaches the nominal frequency.

10. The method as claimed in claim 1 , comprising:
setting the reference frequency to a value between the grid frequency and a nominal frequency of the electrical supply grid, and
compensating for a deviation between the reference system and the grid voltage by changing a feed-in current to the electrical supply grid.

11. The method as claimed in claim 1 , comprising:
controlling a plurality of wind power installations connected to the electrical supply grid at a plurality of grid connection points for feeding in electrical power at at least the grid connection point of the plurality of grid connection points.

12. The method as claimed in claim 11 , comprising:
determining, for each of the plurality of grid connection points, a location property, the location property being a measure of a functional position of the grid connection point in relation to a coupling strength of the respective grid connection point for the electrical supply grid, wherein the location property is indicative of a strength of a coupling between the grid connection point and the electrical supply grid,
specifying at least one operating setting of a wind power installation of the plurality of wind power installations based on the location property of the grid connection point using which the one wind power installation feeds in electrical power.

13. The method as claimed in claim 12 , wherein specifying the at least one operating setting includes at least one of:
specifying a rotational speed characteristic curve based on the location property, wherein a higher rotational speed is higher corresponds to stronger coupling between the grid connection point and the electrical supply grid,
specifying a permissible rotational speed band in which the rotational speed is varied to provide or deliver rotation energy, wherein a wider rotational speed band corresponds to stronger coupling between the grid connection point and the electrical supply grid,
selecting delay dynamics for performing delay tracking based on the location property, wherein the greater the delay, the more strongly the grid connection point is coupled to the electrical supp

Assignees

• Wobben Properties Gmbh

Inventors

• Brombach Johannes

Classifications

• H02J2101/28

  Wind energy · CPC title

• F03D9/257 Primary

  the wind motor being part of a wind farm · CPC title

• H02J3/40

  Synchronisation of generators for connection to a network or to another generator · CPC title

• H02J3/381 Primary

  Dispersed generators · CPC title

• F03D9/11

  storing electrical energy · CPC title