# US 11,898,538 B2 · Method and wind turbine for damping low frequency oscillations in an electrical supply grid

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- Number: US 11,898,538 B2
- Document ID: US11898538B2
- Status: Granted
- Kind: B2
- Application number: 17/258,113
- Filed: 2019-07-03
- Published: 2021-09-16
- Granted: 2024-02-13
- Earliest claimed: 2018-07-06
- Assignees: Wobben Properties GmbH
- Applicants: Wobben Properties GmbH
- Inventors: Johannes Brombach; Aramis Schwanka Trevisan
- Web page: https://patentgrep.com/patent/US11898538B2

## CPC

- F03D 7/0284: {in relation to the state of the electric grid}
- F03D 7/048: {controlling wind farms}
- G05B 17/02: electric
- H02J 3/00142: {Oscillations concerning frequency}
- H02J 3/381: {Dispersed generators}
- H02J 3/48: Controlling the sharing of active power
- H02J 13/12: Monitoring network conditions, e.g. electrical magnitudes or operational status
- F05B 2260/84: Modelling or simulation
- F05B 2270/337: Electrical grid status parameters, e.g. voltage, frequency or power demand
- H02J 2101/28: Wind energy
- H02J 2103/30: Simulating, planning, modelling, reliability check or computer assisted design [CAD] of electric power networks
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- F03D: WIND MOTORS
- G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G)
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- F05B: INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

Provided is a method for damping low frequency oscillations, in particular subsynchronous resonances, in an electrical supply grid by way of at least one decentralized production unit connected to the electrical supply grid, in particular a wind turbine or a wind farm, comprising the steps: feeding electrical power by way of the at least one production unit and supplementing the feeding by way of a supplementary component for damping the low frequency oscillations, wherein the supplementary component is determined depending on a simplified model of a synchronous machine.

## Claims

### Claim 1

A method for damping low frequency oscillations in an electrical supply grid using at least one wind turbine or wind farm connected to the electrical supply grid, comprising:
feeding, via a network connection point, electrical power by the at least one wind turbine or wind farm using an inverter having an inverter output;
determining a supplementary component depending on a simplified model of a synchronous machine, wherein the simplified model is limited to emulating a subset of a plurality of properties;
entering, into the simplified model, at least one instantaneous value of a voltage measurement at the inverter output, in the electrical supply grid or at a point between the inverter output and the electrical supply grid; and
supplementing the feeding of the electrical power using the supplementary component for damping the low frequency oscillations,
wherein
the simplified model of the synchronous machine reproduces an oscillation damping property of a damper cage of the synchronous machine, and
vibratory components of the synchronous machine on which the simplified model is based are not depicted or depicted having been attenuated.

### Claim 2 (depends on 1)

The method as claimed in claim 1, wherein
the supplementary component is a current that is fed in a supplementary manner, or
the supplementary component is determined from damping properties of the synchronous machine, and wherein the synchronous machine is emulated at output terminals of the at least one wind turbine or wind farm.

### Claim 3 (depends on 1)

The method as claimed in claim 1, comprising:
determining the supplementary component based on a response of the simplified model to the at least one instantaneous value of the voltage measurement.

### Claim 4 (depends on 3)

The method as claimed in claim 3, wherein:
the electrical supply grid has a line frequency, and
a generator voltage is emulated in the simplified model if the generator voltage is operated with the line frequency.

### Claim 5 (depends on 4)

The method as claimed in claim 4, wherein the generator voltage is emulated for an oscillation-free operation of the synchronous machine.

### Claim 6 (depends on 1)

The method as claimed in claim 1, comprising:
specifying an active power basic component; and
feeding the active power basic component using active power control independently of determining the supplementary component.

### Claim 7 (depends on 1)

The method as claimed in claim 1, comprising:
determining the supplementary component depending on instantaneous values of the voltage measurement such that the supplementary component only results if the voltage measurement deviates from a sinusoidal voltage without low frequency oscillation.

### Claim 8 (depends on 1)

The method as claimed in claim 1, comprising:
continually receiving a measurement voltage for three phases;
transforming the measurement voltage into d/q components for each phase;
supplying the d/q components for each phase to a d submodel and a q submodel of the simplified model, wherein the d submodel represents a behavior of a d component and the q submodel represents a behavior of a q component of the synchronous machine;
receiving or determining a d component and a q component of a current as a response of the d submodel or the q submodel to the d or q components of the measurement voltage;
transforming the d and the q components of the current into a three-phase supplementary current; and
feeding the three-phase supplementary current by the at least one wind turbine or wind farm as a supplementary component.

### Claim 9 (depends on 1)

The method as claimed in claim 1, wherein:
the simplified model for an input voltage transformed into d/q components, has a longitudinal damper resistance for a d component of the transformed input voltage and a transverse damper resistance for a q component of the transformed input voltage, wherein in the simplified model:
the d component of the transformed input voltage is applied to the longitudinal damper resistance and results in a first power loss which is received as a longitudinal power signal, and
the q component of the transformed input voltage is applied to the transverse damper resistance and results in a second power loss which is received as a transverse power signal, and
the supplementary component is generated from the longitudinal and transverse power signals by retransformation of the longitudinal and transverse power signals provided in d/q components into a three-phase power signal.

### Claim 10 (depends on 1)

The method as claimed in claim 1, wherein the low frequency oscillations are subsynchronous resonances.

### Claim 11 (depends on 1)

The method as claimed in claim 1, wherein the simplified model of the synchronous machine only reproduces one oscillation damping property of the damper cage of the synchronous machine.

### Claim 12 (depends on 1)

The method as claimed in claim 1, wherein the point between the inverter output and the electrical supply grid is the network connection point.

### Claim 13

A wind turbine or wind farm for feeding electrical power into an electrical supply grid and for damping low frequency oscillations in the electrical supply grid, comprising:
an inverter having an inverter output configured to feed electrical power into the electrical supply grid; and
a controller configured to:
determine a supplementary component for damping the low frequency oscillations;
generate a simplified model of a synchronous machine, wherein the simplified model is limited to emulating a subset of a plurality of properties;
enter, into the simplified model, at least one instantaneous value of a voltage measurement at the inverter output, in the electrical supply grid or at a point between the inverter output and the electrical supply grid; and
determine the supplementary component depending on the simplified model of the synchronous machine, and
wherein the inverter is configured to additionally feed the supplementary component into the electrical supply grid to damp the low frequency oscillations, and
wherein
the simplified model of the synchronous machine reproduces an oscillation damping property of a damper cage of the synchronous machine, and
vibratory components of the synchronous machine on which the simplified model is based are not depicted or depicted having been attenuated.

### Claim 14 (depends on 13)

The wind turbine or wind farm as claimed in claim 13, wherein:
the inverter output is configured to feed into the electrical supply grid via a network connection point, and
the wind turbine or wind farm comprises a measuring device unit configured to detect the voltage measurement at the inverter output, in the electrical supply grid, or at the point between the inverter output and the electrical supply grid.

### Claim 15 (depends on 14)

The wind turbine or wind farm as claimed in claim 14, wherein:
the supplementary component is determined based on at least one instantaneous value of the measurement voltage, wherein the measurement voltage is continually provided to the simplified model of the synchronous machine, and
a response of the simplified model to the instantaneous values of the measurement voltage is used as the supplementary component.

### Claim 16 (depends on 13)

The wind turbine or wind farm as claimed in claim 13, wherein the controller is configured to:
transform a measurement voltage that is continually received in three phases into d/q components for determining the supplementary component,
provide the d/q components of the measurement voltage for each phase to a d submodel or a q submodel of the simplified model, wherein the d submodel depicts a behavior of a d component and the q submodel depicts a behavior of a q component of the synchronous machine,
receive or determine, for each phase, a d component and a q component of a current as a response of the d submodel or the q submodel to the d component or q component of the measurement voltage,
retransform the d and the q components of the current back into a three-phase supplementary current, and
cause the supplementary current to be additionally fed as a supplementary component.