Methods and systems for managing power generation and temperature control of an aerial vehicle operating in crosswind-flight mode

Patent metadata

Field	Value
Publication number	US-9422918-B2
Application number	US-201314141882-A
Country	US
Kind code	B2
Filing date	Dec 27, 2013
Priority date	Dec 27, 2013
Publication date	Aug 23, 2016
Grant date	Aug 23, 2016

Abstract

Methods and systems described herein relate to power generation control for an aerial vehicle of an air wind turbine (AWT). More specifically, the methods described herein relate to balancing power generation or preventing a component of the aerial vehicle from overheating using rotor speed control. An example method may include operating an aerial vehicle in a crosswind-flight mode to generate power. The aerial vehicle may include a rotor configured to help generate the power. While the aerial vehicle is in the crosswind-flight mode the method may include comparing a power output level of the aerial vehicle to a power threshold and, based on the comparison, adjusting operation of the rotor in a manner that generates an optimal amount of power or minimizes overheating of the aerial vehicle.

First claim

We claim:

1. A method comprising:
operating an aerial vehicle of an air wind turbine (AWT) in a crosswind-flight mode to generate power, wherein the aerial vehicle is coupled to a ground station through a tether, wherein the aerial vehicle includes at least one rotor coupled to at least one generator for power generation when the aerial vehicle operates in the crosswind-flight mode; and
while the aerial vehicle is in the crosswind-flight mode:
determining, based on sensor data, an amount of power generated by the aerial vehicle;
comparing the amount of power generated by the aerial vehicle to both a first threshold power and a second threshold power;
if the comparison indicates that the amount of power generated by the aerial vehicle is less than both the first threshold power and the second threshold power, then determining that the aerial vehicle is in a first power generation state, and operating one or more power-generation components of the aerial vehicle according to a first control scheme, wherein the first control scheme includes setting a first drag coefficient of the at least one rotor;
if the comparison indicates that the amount of power generated by the aerial vehicle is greater than or equal to the first threshold power and less than or equal to the second threshold power, then determining that the aerial vehicle is in a second power generation state, and operating the one or more power-generation components of the aerial vehicle according to a second control scheme, wherein the second control scheme includes decreasing the setting of the first drag coefficient of the at least one rotor to a second drag coefficient to control heat generation of the at least one rotor; and
if the comparison indicates that the amount of power generated by the aerial vehicle is greater than both the first threshold power and the second threshold power, then determining that the aerial vehicle is in a third power generation state, and operating the one or more power-generation components of the aerial vehicle according to a third control scheme, wherein the third control scheme includes setting a torque limit for the at least one rotor such that the at least one generator of the aerial vehicle operates at a rated power threshold.

2. The method of claim 1 , wherein each of the first control scheme, the second control scheme, and the third control scheme is selected from a plurality of control schemes comprising at least the first control scheme, the second control scheme, and the third control scheme.

3. The method of claim 1 , wherein the first control scheme maximizes power generation, wherein the second control scheme controls heat generation associated with power generation, and wherein the third control scheme controls both power generation and heat generation associated with power generation.

4. The method of claim 1 , wherein the first control scheme is selected, and wherein operating the one or more power-generation components of the aerial vehicle according to the first control scheme comprises controlling the at least one rotor via setting an advance ratio for the at least one rotor, wherein the AWT is operating below a rated power of the AWT, and wherein setting the advance ratio for the at least one rotor comprises setting a fixed advance ratio for the at least one rotor that does not equal or exceed an advance ratio resulting in rotor stall.

5. The method of claim 1 , wherein the second control scheme is selected, and wherein the at least one rotor coupled to the at least one generator comprises a first rotor coupled to a first generator and a second rotor coupled to a second generator, and wherein the first rotor is subject to a first airspeed and the second rotor is subject to a second airspeed that is greater than the first airspeed, and wherein operating the one or more power-generation components of the aerial vehicle according to the second control scheme comprises:
operating the first rotor at a first advance ratio; and
operating the second rotor at a second advance ratio that is less than the first advance ratio such that power generated by the second generator is substantially equivalent to power generated by the first generator.

6. The method of claim 1 , wherein the third control scheme is selected, and wherein operating the one or more power-generation components of the aerial vehicle according to the third control scheme further comprises:
determining a maximum current that may safely pass through the at least one generator;
for the at least one rotor coupled to the at least one generator, determining a maximum rotor torque that corresponds to the maximum current; and
setting the torque limit of the at least one rotor to the maximum rotor torque.

7. The method of claim 6 , wherein the at least one generator operates as a motor supplying torque to the at least one rotor.

8. The method of claim 1 , wherein the first threshold power corresponds to a point on a power-generation curve where an incremental increase in power generation per unit of wind speed drops due to an effect of heating in the power-generation components.

9. An airborne wind turbine (AWT) system comprising:
an aerial vehicle configured to operate in a crosswind-flight mode to generate power, wherein the aerial vehicle is coupled to a ground station through a tether, and wherein the aerial vehicle includes at least one rotor coupled to at least one generator for power generation when the aerial vehicle operates in the crosswind-flight mode; and
a control system configured to:
(i) while the aerial vehicle is in the crosswind-flight mode, receive sensor data to determine an amount of power generated by the aerial vehicle;
(ii) compare the amount of power generated by the aerial vehicle to both a first threshold power and a second threshold power;
(iii) if the comparison indicates that the amount of power generated by the aerial vehicle is less than both the first threshold power and the second threshold power, then determine that the aerial vehicle is in a first power generation state, and operate one or more power-generation components of the aerial vehicle according to a first control scheme, wherein the first control scheme includes setting a first drag coefficient of the at least one rotor;
(iv) if the comparison indicates that the amount of power generated by the aerial vehicle is greater than or equal to the first threshold power and less than or equal to the second threshold power, then determine that the aerial vehicle is in a second power generation state, and operate the one or more power-generation components of the aerial vehicle according to a second control scheme, wherein the second control scheme includes decreasing the setting of the first drag coefficient of the at least one rotor to a second drag coefficient to control heat generation of the at least one rotor; and
(v) if the comparison indicates that the amount of power generated by the aerial vehicle is greater than both the first threshold power and the second threshold power, then determine that the aerial vehicle is in a third power generation state, and operate the one or more power-generation components of the aerial vehicle according to a third control scheme, wherein the third control scheme includes setting a torque limit for the at least one rotor such that the at least one generator of the aerial vehicle operates at a rated power threshold.

10. The system of claim 9 , wherein the first control scheme maximizes power generation, wherein the second control scheme controls heat generation associated with power generation, and wherein the third control scheme controls both power generation and heat generation associated with power generation.

Assignees

• Google Inc

Inventors

• Lind Damon Vander
• Jensen Kenneth

Classifications

• F03D3/02

  having a plurality of rotors · CPC title

• F05B2240/921

  kept aloft due to aerodynamic effects · CPC title

• F03D1/02

  having a plurality of rotors · CPC title

• H02P9/04

  Control effected upon non-electric prime mover and dependent upon electric output value of the generator · CPC title

• F03D7/0204 Primary

  for orientation in relation to wind direction · CPC title