Method for feeding electrical power into an electrical supply network

Patent metadata

Field	Value
Publication number	US-2020366100-A1
Application number	US-201916966739-A
Country	US
Kind code	A1
Filing date	Jan 31, 2019
Priority date	Feb 1, 2018
Publication date	Nov 19, 2020
Grant date	—

Abstract

A method for exchanging or feeding electric power into an electricity supply grid that has a grid frequency using a converter-controlled generator at a grid connection point is provided. The method includes feeding in electric power depending on a control function, where the electric power may comprise active and reactive power, and the control function controls the power depending on at least one state variable of the grid. It is possible to select between a normal control function and a support control function, different from the normal control function, as the control function. The normal control function is selected when it has been detected that the grid is operating stably and the support control function is selected when a grid problem, grid fault or an end of the grid fault has been detected. The support control function controls the fed-in power to counteract an oscillation in the grid.

First claim

1 . A method for feeding electric power into an electricity supply grid that has a grid frequency by way of a converter-controlled generator at a grid connection point, comprising:
feeding in the electric power depending on a control function, wherein the electric power includes active power and reactive power, wherein the control function controls the electric power depending on at least one state variable of the electricity supply grid; and permitting selecting between a normal control function and a support control function, different from the normal control function, as the control function; determining that the electricity supply grid is operating in a stable condition; selecting the normal control function is selected when it is determined has been recognized that the electricity supply grid is operating in the stable condition; detecting a grid problem, a grid fault or an end of the grid fault; and selecting the support control function when the grid problem, the grid fault or amend of the grid fault is detected; wherein:
the support control function controls the electric in power to counteract an oscillation in the electricity supply grid, an oscillation of a synchronous generator connected to the electricity supply grid or an oscillation caused by the synchronous generator.

2 . The method as claimed in claim 1 , comprising:
counteracting an oscillation that is caused by a response of at least one synchronous generator coupled directly to the electricity supply grid to the grid problem, the grid fault or the end of the grid fault.

3 . The method as claimed in claim comprising:
recording whether at least one synchronous generator associated with oscillation to the grid connection point is coupled to the electricity supply grid, wherein the at least one synchronous generator associated with the oscillation to the grid connection point is arranged close electrically to the grid connection point or acts to an extent on the grid connection point that a generator oscillation of the at least one synchronous generator in which the at least one synchronous generator oscillates around an operating point or is measurable at the grid connection point as a frequency fluctuation or as a voltage fluctuation.

4 . The method as claimed in claim 1 , comprising:
recording a frequency gradient in the electricity supply grid and at the grid connection point, and following the grid problem, the grid fault or the end of the grid fault, resuming an active power infeed by the converter-controlled generator, and increasing in which the active power infeed with time, wherein increasing the active power infeed is performed in accordance with at least one rule from:
increasing the active power infeed depending on the recorded frequency gradient, wherein the active power infeed is increased at a slower rate in the case of a positive frequency gradient than in the case of a negative frequency gradient,
increasing the active power infeed depending on the recorded frequency gradient such that a rate of the increase is decelerated with an increasing frequency gradient, and is accelerated with a decreasing frequency gradient, and
increasing the active power infeed depending on a peak value of an oscillating frequency gradient such that, when the peak value is reduced with decelerating frequency oscillation, the rate of the increase in the active power infeed is increased.

5 . The method as claimed in claim 1 , comprising:
recording a frequency value in the electricity supply grid and at the grid connection point, and following the grid problem, grid fault or end of the grid fault, resuming an active power infeed by the converter-controlled generator, and increasing the active power infeed with time, wherein a rate of the increase is increased depending on a peak value of the grid frequency such that when the peak value decreases educed with decelerating frequency oscillation, the rate of the increase in the active power infeed is increased.

6 . The method as claimed in claim 1 , comprising:
feeding the reactive power following the grid problem, grid fault or end of the grid fault; using a reactive power function to feed in the reactive power, wherein the reactive power function specifies a relationship between a recorded voltage and the reactive power; permitting selecting between a first and a second reactive power function as the reactive power function; and selecting the first reactive power function when it is determined the electricity supply grid is operating in the stable condition, or selecting the second reactive power function if a generator oscillation of a synchronous generator, associated with oscillation to the grid connection point, has been recorded, or if the generator oscillation is expected.

7 . The method as claimed in claim 1 , wherein
the control function, in particular the support control function implements a behavior of a virtual synchronous machine with an inertia having a predefined moment of inertia, the behavior of the virtual synchronous machine is implemented at least such that:
an increase or decrease in the grid frequency leads to a decrease or increase in fed-in active power and the decrease or increase in the fed-in active power is positively correlated with the predefined moment of inertia, or
a fed-in infeed current lags or leads a grid voltage when the grid frequency increases or decreases, and the lag or lead is positively correlated with the predefined moment of inertia.

8 . The method as claimed in claim 7 , comprising:
activating the behavior of the virtual synchronous machine or increasing the moment of inertia following the grid problem, grid fault or end of the grid fault, or activating the behavior of the virtual synchronous machine or increasing the moment of inertia if oscillation of the grid frequency is detected, when the oscillating frequency passes through a pre-fault grid frequency that was recorded before the grid problem or grid fault occurred.

9 . The method as claimed in claim 1 , comprising:
implementing damping control for active oscillation damping in the support control function, or to feed in electric power, modulating a fed-in or drawn reactive power by modulating the converter-controlled generator as an admittance.

10 . The method as claimed in claim 9 , wherein the damping control includes at least one function from:
a simulation or emulation of a frequency-dependent load; and a simulation or emulation of a voltage-dependent load.

11 . The method as claimed in claim 1 , comprising:
selecting or parameterizing the support control function depending on a converter saturation, wherein the converter saturation is a measure of a proportion of power fed in by converter-controlled feeders to overall power fed into the electricity supply grid.

12 . The method as claimed in claim 1 , wherein the support control function includes a damping measure.

13 . The method as claimed in claim 1 , wherein:
when an oscillation of at least one synchronous machine is recorded in the electricity supply grid, a rapid active power recovery is performed.

14 . A converter-controlled generator for feeding electric power into an electricity supply grid that has a grid frequency, comprising:
an infeed apparatus configured to feed in the electric power depending on a control function, wherein the electric power includes active power and reactive power; and a controller configured to:
implement the control function, wherein the control function controls the electric power depending on at least one state variable of the electricity supply grid;
permit selection between

Assignees

• Wobben Properties Gmbh

Inventors

• Brombach Johannes
• Quitmann Eckard

Classifications

• H02J2101/28

  Wind energy · CPC title

• H02J2101/24

  Photovoltaics · CPC title

• H02J3/388 Primary

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• H02J3/46

  Controlling the sharing of generated power between the generators, sources or networks · CPC title

• H02J3/381 Primary

  Dispersed generators · CPC title