# US 10,871,145 B2 · System and method for preventing voltage collapse of wind turbine power systems connected to a power grid

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- Number: US 10,871,145 B2
- Document ID: US10871145B2
- Status: Granted
- Kind: B2
- Application number: 16/119,119
- Filed: 2018-08-31
- Published: 2019-03-07
- Granted: 2020-12-22
- Earliest claimed: 2017-09-04
- Assignees: General Electric Company
- Applicants: General Electric Company
- Inventors: Robert Gregory Wagoner; Zhuohui Tan; Weihao Zhou; Nithya Anand
- Web page: https://patentgrep.com/patent/US10871145B2

## CPC

- F03D 7/0284: {in relation to the state of the electric grid}
- F03D 9/257: {the wind motor being part of a wind farm}
- G05B 19/02: electric
- H02J 3/0014: for preventing or reducing power oscillations in networks
- H02J 3/16: by adjustment of reactive power
- H02J 3/38: Arrangements for feeding a single network from two or more generators or sources in parallel; Arrangements for feeding already energised networks from additional generators or sources in parallel
- H02J 3/381: {Dispersed generators}
- H02P 9/007: {Control circuits for doubly fed generators}
- F05B 2220/706: an electrical generator
- F05B 2270/1033: Power (if explicitly mentioned)
- F05B 2270/335: Output power or torque
- F05B 2270/337: Electrical grid status parameters, e.g. voltage, frequency or power demand
- F05B 2270/402: passive or reactive, e.g. using large wind vanes
- F05B 2270/504: electronic means, e.g. electronic tubes, transistors or IC's within an electronic circuit
- G05B 2219/2619: Wind turbines
- H02J 2101/28: Wind energy
- Y02E 10/72: Wind turbines with rotation axis in wind direction
- Y02E 10/76: Power conversion electric or electronic aspects
- Y02E 40/30: Reactive power compensation
- 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
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- 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
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A system and method for preventing voltage collapse of a wind turbine power system includes receiving a power input value and a voltage input value from a point of common coupling of the wind turbine power system. The method also includes determining a limit cycle reference point of the wind turbine power system as a function of the input values. The method further includes comparing the limit cycle reference point to at least one predetermined threshold. If the limit cycle reference point is greater than the at least one predetermined threshold, the method includes determining a delta value for the real and reactive voltage commands of the wind turbine power system. Further, the method includes determining updated real and reactive voltage commands based on the delta value. As such, the method also includes operating the wind turbine power system based on the updated real and reactive voltage commands.

## Claims

### Claim 1

A method for preventing voltage collapse of a wind turbine power system connected to a power grid, the method comprising:
receiving, via a controller of the wind turbine power system, at least one power value and at least one voltage value from a point of common coupling of the wind turbine power system;
determining, via the controller, a limit cycle reference point of the wind turbine power system as a function of a cross product of the at least one power value and the at least one voltage value, the limit cycle reference point representative of a proximity of the at least one power value or the at least one voltage value to an operational point at which voltage collapse occurs, wherein the voltage collapse occurs when the wind turbine power system serves a load that has a higher reactive power demand than the wind turbine power system can supply;
comparing the limit cycle reference point to at least one threshold;
if the limit cycle reference point is greater than the at least one threshold, determining a delta value for at least one command of the wind turbine power system;
determining at least one updated command based on the delta value and the at least one command; and,
operating the wind turbine power system based on the at least one updated command.

### Claim 2 (depends on 1)

The method of claim 1, wherein the at least one threshold comprises a first threshold, the method further comprising:
adding the delta power value to at least one of a power command or a power limiter of the wind turbine power system if the limit cycle reference point is greater than the first threshold.

### Claim 3 (depends on 2)

The method of claim 2, wherein the at least one threshold comprises a second threshold.

### Claim 4 (depends on 3)

The method of claim 3, further comprising adding the delta power value to a one or more gain coefficients of a voltage regulator of the wind turbine power system if the limit cycle reference point is less than the first threshold and greater than the second threshold.

### Claim 5 (depends on 4)

The method of claim 4, further comprising implementing a corrective action if the limit cycle reference point is greater than a damage threshold.

### Claim 6 (depends on 1)

The method of claim 1, wherein the operational point corresponds to a value on a curve of the voltage value versus the power value at which a slope of the curve is substantially vertical.

### Claim 7 (depends on 6)

The method of claim 6, wherein operating the wind turbine power system based on the at least one updated command further comprises minimizing an area of the curve representative of a limit cycle so as to maximize power while preventing voltage collapse.

### Claim 8 (depends on 1)

The method of claim 1, wherein the power grid comprises a weak grid, the weak grid characterized by short circuit currents within a predetermined range of short circuit currents of the wind turbine power system.

### Claim 9 (depends on 8)

The method of claim 8, wherein the predetermined range comprises ratios of the short circuit currents of the power grid to the short circuit currents of the wind turbine power system of from about 0.8 to about 1.2.

### Claim 10

A system for preventing voltage collapse of a wind turbine power system connected to a power grid, the system comprising:
one or more sensors for monitoring at least one power value and at least one voltage value from a point of common coupling of the wind turbine power system;
a controller communicatively coupled to the one or more sensors, the controller configured to perform one or more operations, the one or more operations comprising:
determining a limit cycle reference point of the wind turbine power system as a function of a cross product of the at least one power value and at least one voltage value, the limit cycle reference point representative of a proximity of the at least one power value and the at least one voltage value to an operational point at which voltage collapse occurs, wherein the voltage collapse occurs when the wind turbine power system serves a load that has a higher reactive power demand than the wind turbine power system can supply;
comparing the limit cycle reference point to at least one threshold;
if the limit cycle reference point is greater than the at least one threshold, determining a delta value for at least one command of the wind turbine power system;
determining at least one updated command based on the delta value and the at least one command; and,
operating the wind turbine power system based on the at least one updated command.

### Claim 11 (depends on 10)

The system of claim 10, wherein the at least one threshold comprises a first threshold and a second threshold.

### Claim 12 (depends on 11)

The system of claim 11, wherein the one or more operations further comprise:
adding the delta power value to at least one of a power command or a power limiter of the wind turbine power system if the limit cycle reference point is greater than the first threshold, and,
adding the delta power value to a one or more gain coefficients of a voltage regulator of the wind turbine power system if the limit cycle reference point is less than the first threshold and greater than the second threshold.

### Claim 13 (depends on 12)

The system of claim 12, further comprising implementing a corrective action if the limit cycle reference point is greater than a damage threshold.

### Claim 14 (depends on 10)

The system of claim 10, wherein the operational point corresponds to a value on a curve of the voltage value versus the power value at which a slope of the curve is substantially vertical, and wherein operating the wind turbine power system based on the at least one updated command further comprises minimizing an area of the curve representative of a limit cycle so as to maximize power while preventing voltage collapse.

### Claim 15 (depends on 10)

The system of claim 10, wherein the power grid comprises a weak grid, the weak grid characterized by short circuit currents within a predetermined range of short circuit currents of the wind turbine power system, wherein the predetermined range comprises ratios of the short circuit currents of the power grid to the short circuit currents of the wind turbine power system of from about 0.8 to about 1.2.

### Claim 16 (depends on 10)

The system of claim 10, wherein the wind turbine power system comprises a wind farm comprising one or more wind turbines connected to the power grid via at least one of a turbine transformer, a farm transformer, or a cluster transformer.