# US 11,114,839 B2 · System and method for mitigating overvoltage on a DC link of a power converter

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- Number: US 11,114,839 B2
- Document ID: US11114839B2
- Status: Granted
- Kind: B2
- Application number: 16/192,913
- Filed: 2018-11-16
- Published: 2020-05-21
- Granted: 2021-09-07
- Earliest claimed: 2018-11-16
- Assignees: General Electric Company
- Applicants: General Electric Company
- Inventors: Dustin Howard; Einar Vaughn Larsen
- Web page: https://patentgrep.com/patent/US11114839B2

## CPC

- H02H 3/44: responsive to the rate of change of electrical quantities
- H02P 9/102: {for limiting effects of transients}
- H02H 7/1216: {for AC-AC converters}
- H02H 7/1222: {responsive to abnormalities in the input circuit, e.g. transients in the DC input}
- H02P 29/0241: {the fault being an overvoltage}
- F03D 7/042: {by means of an electrical or electronic controller}
- F03D 9/255: {connected to electrical distribution networks; Arrangements therefor}
- F03D 17/00: Monitoring or testing of wind motors, e.g. diagnostics (testing during commissioning of wind motors F03D13/30)
- F05B 2220/30: in turbines
- F05B 2270/337: Electrical grid status parameters, e.g. voltage, frequency or power demand
- H02K 7/183: {wherein the turbine is a wind turbine (adaptation of a wind turbine to an electric generator F03D9/25)}
- H02M 1/32: Means for protecting converters other than automatic disconnection
- H02M 5/4585: {having a rectifier with controlled elements}
- H02P 9/006: {Means for protecting the generator by using control (control effected upon generator excitation circuit to reduce harmful effects of overloads or transients H02P9/10)}
- H02P 9/007: {Control circuits for doubly fed generators}
- Y02E 10/72: Wind turbines with rotation axis in wind direction
- Y02E 10/76: Power conversion electric or electronic aspects
- H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H)
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- F03D: WIND MOTORS
- 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
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A system and method for mitigating overvoltage on a DC link of a power converter of an electrical power system connected to a power grid includes receiving a voltage feedback signal from the DC link for a predetermined time period. The method also includes determining a rate of change of the voltage feedback signal during the predetermined time period. Further, the method includes predicting a future voltage value on the DC link as a function of the voltage feedback signal and the rate of change of the voltage feedback signal. Moreover, the method includes controlling the electrical power system based on the future voltage value.

## Claims

### Claim 1

A method for mitigating overvoltage on a DC link of a power converter of an electrical power system connected to a power grid caused by transients on the power grid, the method comprising:
receiving a voltage feedback signal from the DC link;
determining a rate of change of the voltage feedback signal during the predetermined time period by processing the voltage feedback signal via a differential element, the differential element comprising a washout filter and a low-pass filter;
predicting a future voltage value on the DC link by summing the voltage feedback signal and the rate of change of the voltage feedback signal; and,
controlling the electrical power system based on the future voltage value.

### Claim 2 (depends on 1)

The method of claim 1 wherein the low-pass filter comprises a frequency range of from about 500 radians/second (rad/s) to about 1500 rad/s.

### Claim 3 (depends on 1)

The method of claim 1, further comprising restricting, via at least one of an offset or a limiter, the rate of change of the voltage feedback signal to positive changes of a certain magnitude.

### Claim 4 (depends on 3)

The method of claim 3, further comprising restricting, via the offset and the limiter, the rate of change of the voltage feedback signal to positive changes of the certain magnitude.

### Claim 5 (depends on 1)

The method of claim 1, further comprising applying a gain to the rate of change of the voltage feedback signal.

### Claim 6 (depends on 5)

The method of claim 5, further comprising tuning the gain so as to accurately predict the future voltage value on the DC link, the gain being greater than about 2.

### Claim 7 (depends on 1)

The method of claim 1, wherein controlling the electrical power system based on the future voltage value further comprises implementing a corrective action when the future value exceeds a predetermined threshold.

### Claim 8 (depends on 7)

The method of claim 7, wherein the corrective action comprises at least one of turning on a crowbar circuit on a rotor-side converter of the power converter or shutting down the electrical power system.

### Claim 9 (depends on 1)

The method of claim 1, wherein the generator comprises a doubly-fed asynchronous generator (DFAG).

### Claim 10 (depends on 1)

The method of claim 1, wherein the electrical power system comprises at least one of a wind turbine power system, a solar power system, an energy storage power system, or combinations thereof.

### Claim 11

A method for mitigating overvoltage on a DC link of a power converter of an electrical power system connected to a power grid caused by transients on the power grid, the method comprising:
receiving a voltage feedback signal from the DC link;
determining a power going into the DC link of the power converter;
receiving an active power feedback from a rotor-side converter of the power converter;
receiving an active power feedback from a line-side converter of the power converter;
determining a difference between the active power feedback from the rotor-side converter and the active power feedback from the line-side converter, the difference representing the power going into the DC link;
receiving a DC capacitance from the DC link;
predicting a future voltage value on the DC link as a function of the difference between the active power feedback from the rotor-side converter and the active power feedback from the line-side converter, the voltage feedback signal, and the DC capacitance; and,
controlling the electrical power system based on the future voltage value.

### Claim 12

A wind turbine power system connected to a power grid, the wind turbine power system comprising:
a doubly-fed asynchronous generator (DFAG) comprising a rotor and a stator, the DFAG connected to the power grid;
a power converter comprising a rotor-side converter electrically coupled to a line-side converter via a DC link; and,
a controller communicatively coupled to the DFAG and the power converter, the controller configured to perform a plurality of operations, the plurality of operations comprising:
receiving a voltage feedback signal from the DC link for a predetermined time period;
determining a rate of change of the voltage feedback signal during the predetermined time period by processing the voltage feedback signal via a differential element, the differential element comprising a washout filter and a low-pass filter; and,
predicting a future voltage value on the DC link by summing the voltage feedback signal and the rate of change of the voltage feedback signal; and,
controlling the electrical power system based on the future voltage value.

### Claim 13 (depends on 12)

The wind turbine power system of claim 12, wherein determining the rate of change of the voltage feedback signal during the predetermined time period further comprises processing, via a differential element, the voltage feedback signal.

### Claim 14 (depends on 12)

The wind turbine power system of claim 12, wherein the one or more operations further comprise restricting, via at least one of an offset or a limiter, the rate of change of the voltage feedback signal to positive changes of a certain magnitude.

### Claim 15 (depends on 12)

The wind turbine power system of claim 12, further comprising applying a gain to the rate of change of the voltage feedback signal.