Power Management for an Airborne Wind Turbine

Abstract

Disclosed herein are systems and methods related to electric power transfer between an aerial vehicle of an airborne wind turbine and a power grid. An example power conversion system may include power converters, a DC bus connecting the power converters to the aerial vehicle, and an AC bus connecting the power converters to the power grid. The power converters may be configured to provide AC/DC power conversion between the aerial vehicle and the power grid. The power conversion system may also include switches operable to either (i) electrically connect a respective power converter to the DC bus or electrically isolate the respective power converter from the DC bus. The power conversion system may also include one or more power supplies that can be connected to the DC bus to provide backup power in the event a power converter or the power grid malfunctions.

What is claimed is: 
     
         1 . A method for operating a power conversion system, the method comprising:
 determining that a power grid electrically connected to a power conversion system is malfunctioning;   in response to determining that the power grid is malfunctioning, electrically isolating the power grid from an AC bus of the power conversion system; and   in response to determining that the power grid is malfunctioning, electrically connecting a power supply of the power conversion system to a DC bus.   
     
     
         2 . The method of  claim 1 , wherein determining that the power grid electrically connected to a power conversion system is malfunctioning comprises:
 monitoring a phase-to-phase or phase-to-ground voltage between phase terminals of an AC main of the AC bus; and   determining that the phase-to-phase or phase-to-ground voltage at phase terminals of the AC main is greater than a threshold voltage, and   wherein electrically connecting the power supply of the power conversion system to the DC bus comprises electrically connecting the power supply of the power conversion system to the DC bus in response to determining that the phase-to-phase or phase-to-ground voltage at phase terminals of the AC main is greater than the threshold voltage.   
     
     
         3 . The method of  claim 1 , wherein determining that the power grid electrically connected to a power conversion system is malfunctioning comprises:
 monitoring a phase-to-phase or phase-to-ground voltage between phase terminals of an AC main of the AC bus; and   determining that the phase-to-phase or phase-to-ground voltage at phase terminals of the AC main is less than a threshold voltage, and   wherein electrically connecting the power supply of the power conversion system to the DC bus comprises electrically connecting the power supply of the power conversion system to the DC bus in response to determining that the phase-to-phase or phase-to-ground voltage at phase terminals of the AC main is less than the threshold voltage.   
     
     
         4 . The method of  claim 1 , wherein determining that the power grid electrically connected to a power conversion system is malfunctioning comprises:
 monitoring a phase-to-phase or phase-to-ground voltage between phase terminals of an AC main of the AC bus; and   determining that a variation of the phase-to-phase or phase-to-ground voltage at phase terminals of the AC main is greater than a threshold voltage variance, and   wherein electrically connecting the power supply of the power conversion system to the DC bus comprises electrically connecting the power supply of the power conversion system to the DC bus in response to determining that the variation of the phase-to-phase or phase-to-ground voltage at phase terminals of the AC main is greater than a threshold voltage variance.   
     
     
         5 . The method of  claim 1 , wherein determining that the power grid electrically connected to a power conversion system is malfunctioning comprises:
 monitoring a phase-to-phase or phase-to-ground voltage between phase terminals of an AC main of the AC bus; and   providing signals representing the monitored voltage to a Boolean circuit configured to determine whether the power grid electrically connected to a power conversion system is malfunctioning.   
     
     
         6 . The method of  claim 5 , wherein electrically isolating the power grid from the AC bus of the power conversion system comprises using the Boolean circuit to open a switch connecting the power grid to the AC bus. 
     
     
         7 . The method of  claim 1 , wherein electrically connecting the power supply of the power conversion system to the DC bus comprises using a Boolean circuit to electrically connect one or more power supplies to the DC bus via one or more switches. 
     
     
         8 . The method of  claim 1 , wherein electrically connecting the power supply of the power conversion system to the DC bus comprises providing a nominal voltage to an aerial vehicle associated with the power conversion system via the DC bus. 
     
     
         9 . A method comprising:
 determining that a first power converter of a power conversion system is malfunctioning, wherein the power conversion system is configured to provide AC/DC power conversion between an aerial vehicle of an airborne wind turbine and a power grid; and   in response to determining that the first power converter is malfunctioning:   electrically isolating, via switching a first switch, the first power converter from a DC bus of the power conversion system such that a second power converter of the power conversion system remains connected to the DC bus; and   electrically connecting, via switching a second switch, a third power converter of the power conversion system to the DC bus.   
     
     
         10 . The method of  claim 9 , wherein the DC bus is electrically connected to the aerial vehicle via a tether. 
     
     
         11 . The method of  claim 9 ,
 wherein the first power converter comprises a positive terminal and a negative terminal, and   wherein determining that the first power converter is malfunctioning comprises at least one of (i) determining that a voltage between the positive terminal and the negative terminal is greater than a threshold voltage, (ii) determining that a voltage between the positive terminal and the negative terminal is less than a threshold voltage, or (iii) determining that a variation of voltage between the positive terminal and the negative terminal is greater than a threshold voltage variance.   
     
     
         12 . A power conversion system comprising:
 a first power converter comprising (i) a first AC port and (ii) a first DC port, wherein the first power converter is configured to provide AC/DC power conversion between the first AC port and the first DC port;   an AC bus electrically connected to (i) a power grid, and (ii) the first AC port;   a DC bus; and   a power supply,   wherein the first power converter is configured to operate in a plurality of modes, wherein operating in the plurality of modes comprises:   (i) electrically isolating the first DC port from the DC bus and electrically connecting the power supply to the first DC port, and (ii) electrically connecting the first DC port to the DC bus and electrically connecting the power supply to the first DC port.   
     
     
         13 . The power conversion system of  claim 12 , wherein operating in the plurality of modes further comprises:
 (iii) electrically isolating the first DC port from the DC bus and electrically isolating the power supply from the first DC port, and   (iv) electrically connecting the first DC port to the DC bus and electrically isolating the power supply from the first DC port.   
     
     
         14 . The power conversion system of  claim 12 , further comprising:
 a second power converter comprising (i) a second AC port and (ii) a second DC port, wherein the second power converter is configured to provide AC/DC power conversion between the second AC port and the second DC port,   wherein the AC bus is electrically connected to the second AC port.   
     
     
         15 . The power conversion system of  claim 14 , further comprising:
 a first switch operable to either (i) electrically connect the first DC port to the DC bus or (ii) electrically isolate the first DC port from the DC bus;   a second switch operable to either (i) electrically connect the second DC port to the DC bus or (ii) electrically isolate the second DC port from the DC bus; and   a third switch, wherein the switch is operable to either (i) electrically connect the power supply to the first DC port or (ii) electrically isolate the power supply from the first DC port.   
     
     
         16 . The power conversion system of  claim 12 , wherein the power supply comprises a battery. 
     
     
         16 . The power conversion system of  claim 12 , wherein electrically connecting the first DC port to the DC bus and electrically isolating the power supply from the first DC port corresponds to receiving, by the first power converter via the AC bus, AC current from the power grid and providing DC current to an aerial vehicle via the DC bus. 
     
     
         17 . The power conversion system of  claim 12 , wherein electrically isolating the first DC port from the DC bus and electrically connecting the power supply to the first DC port corresponds to the first power converter receiving DC current from the power supply and providing AC current to the AC bus. 
     
     
         18 . The power conversion system of  claim 12 , wherein electrically connecting the first DC port to the DC bus and electrically connecting the power supply to the first DC port corresponds to providing DC current to an aerial vehicle via the DC bus. 
     
     
         19 . The power conversion system of  claim 12 , wherein the first AC port comprises a 3-phase AC port. 
     
     
         20 . The power conversion system of  claim 12 , wherein the first AC port comprises a 3-phase/4-wire AC port.