Abstract:
The preferred embodiments of the present invention utilize the internal combustion engine of a hybrid vehicle, coupled with an energy storage device and series of inverters to provide electrical power generation capability for an electric power take-off (EPTO) system. Additional embodiments of the present invention utilize an existing on-board AC induction motor to provide filtering capability for the generated AC power.

Description:
TECHNICAL FIELD 
     The present invention generally relates to vehicle on-board power generation, and more particularly relates to electric power take-off (EPTO) systems for hybrid electric vehicles. 
     BACKGROUND OF THE INVENTION 
     Traditional combustion engine power plants in cars can also be used to provide nominal amounts of alternating current (AC) electrical power through the use of an inverter circuit. In the most typical applications, the AC electrical power generated by standard combustion engines is utilized to sustain the electrical needs of the car and its accessories. This generation capability has additionally led to the widespread deployment of “convenience outlets,” which are now used to power computers, video games, cell phones, and the like. 
     While generation of AC electrical power is possible, it is difficult to obtain significant amounts of useful electrical power from standard combustion engines because the combustion engine exhibits relatively low conversion efficiency. Additionally, since most combustion engines require significant cooling during operation, extended operation of the engine to generate electricity will require the type of airflow usually generated during vehicle locomotion. Finally, environmental considerations such as air emissions and engine noise make automobiles with traditional combustion engines poor candidates for any meaningful levels of power generation, particularly to power the types of electrical loads not directly associated with the vehicle. 
     Certain new types of vehicles, known as hybrid vehicles, employ a combustion engine coupled with a combination electric motor-generator in order to provide vehicle locomotion. In some of these hybrid or mild-hybrid powertrain systems, an electric motor-generator system replaces the conventional starter motor and alternator. When the hybrid vehicle is decelerating or is stopped, the fuel flow to the engine is shut off, thereby improving fuel economy. The motor-generator system of the hybrid vehicle is implemented to enable this fuel cutoff feature while minimally affecting drivability. As with the conventional combustion engine, the power plant in hybrid vehicles can also be used to provide AC power for convenience outlets and other electrical requirements associated with the hybrid vehicle. However, as with traditional combustion engines, the present AC power generating capabilities of hybrid vehicles are limited in both scope and application. 
     In view of the foregoing, it should be appreciated that it would be desirable to provide methods for adapting the on-board components of a hybrid vehicle to generate electrical power for use in applications not directly related to the operation of the hybrid vehicle, i.e., off-vehicle loads. It is also desirable to provide electrical power for both balanced and unbalanced loads, as well as support for three-phase and single-phase voltages. Furthermore, additional desirable features will become apparent to one skilled in the art from the foregoing background of the invention and following detailed description of a preferred exemplary embodiment and appended claims. 
     SUMMARY OF THE INVENTION 
     The preferred embodiments of the present invention utilize the internal combustion engine of a hybrid vehicle, coupled with an energy storage device and a series of inverters to provide electrical power generation capability for an electric power take-off (EPTO) system. Addition embodiments of the present invention utilize an existing on-board AC induction motor to provide filtering capability for the generated AC power. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will hereinafter be described in conjunction with the appended drawing figures, wherein like numerals denote like elements, and: 
         FIG. 1  is a schematic circuit diagram depicting an EPTO system for a three-phase balanced load or two unbalanced single-phase loads in accordance with a preferred exemplary embodiment of the present invention; 
         FIG. 2  is a schematic circuit diagram depicting an EPTO system for three-phase balanced loads in accordance with an alternative preferred exemplary embodiment of the present invention; 
         FIG. 3  is a schematic circuit diagram depicting an EPTO system for single-phase unbalanced loads in accordance with a preferred exemplary embodiment of the present invention; 
         FIG. 4  is a schematic circuit diagram depicting an EPTO system for single-phase unbalanced loads in accordance with an alternative preferred exemplary embodiment of the present invention; 
         FIG. 5  is a schematic circuit diagram depicting an EPTO system for three-phase unbalanced loads in accordance with a preferred exemplary embodiment of the present invention; and 
         FIG. 6  is a schematic circuit diagram depicting an EPTO system for three-phase unbalanced loads in accordance with an alternative preferred exemplary embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following detailed description of a preferred exemplary embodiment of the invention is mainly exemplary in nature and is not intended to limit the invention or the application or use of the invention. 
     The most preferred exemplary embodiments of the present invention are described in conjunction with an Allison Transmission EV-Drive system, as provided by Allison Transmission of Indianapolis, Ind. However, it should be noted that the possible embodiments of the present invention are not limited in application to a specific transmission or to any specific electrical machines. Specifically, the present invention is capable of being used in conjunction with any transmission that employs two electrical machines with their corresponding electronics converters. Similarly, although illustrated in conjunction with induction motors, other suitable electrical machines known to those skilled in the art may be substituted. 
     Referring now to  FIG. 1 , an EPTO system  100  for powering a three-phase balanced load or two unbalanced single-phase loads in accordance with a preferred exemplary embodiment of the present invention comprises: a first AC induction motor  110 ; a second AC induction motor  120 ; a first power inverter  130 ; a second power inverter  150 ; an energy storage device  140 ; an inverter controller  160 ; a power filter  180 ; and a power distribution/protection mechanism  190 . Vehicle/transmission control bus  195 , first inverter controller bus  135 , second inverter controller bus  155 , and filter bus  165  provide communication paths between the various components. Additionally, output terminals  191  are distribution points for the power output from EPTO system  100 . In  FIG. 1 , as in all FIGs., it should be noted that the depicted connections are merely representative in nature and the actual physical connection between the various components may be accomplished in many different ways. 
     First AC induction motor  110  and second AC induction motor  120  are mechanically inter-connected through a complex planetary gear set (not shown this FIG.) and electrically coupled or connected through first power inverter  130  and second power inverter  150 . Energy storage device  140  is typically connected in parallel with first power inverter  130  and second power inverter  150 . Energy storage device  140  is any suitable type of energy storage device known to those skilled in the art such as one or more battery packs and/or ultra-capacitors. 
     First AC induction motor  110  is typically connected to an internal combustion engine prime mover (not shown this FIG.). In operation, first AC induction motor  110  acts as a generator, transforming the mechanical energy received at its input shaft, which is physically coupled to the ICE, into AC electrical energy. First power inverter  130  is electrically connected to the output of first AC induction motor  110  and operates as a boost rectifier. This allows first power inverter  130  to transform the AC electrical energy into DC electrical energy that is then stored in energy storage device  140 . 
     Second AC induction motor  120  comprises a plurality of internal windings that are interconnected by switches  121  and  122 . Switches  121  and  122  are typically located on the input terminals or the neutral connection, as shown in  FIG. 1 . Additionally, second AC induction motor  120  is typically connected to the wheels of the hybrid vehicle (not shown this FIG.) containing EPTO system  100 . Since second AC induction motor  120  is not needed for operation of EPTO system  100 , it is disconnected by opening switches  121  and  122 . 
     Second power inverter  150  is operated as an inverter, transforming DC power into AC power at a fixed frequency and voltage. The three-phase output of second power inverter  150  is filtered by power filter  180  and is then delivered to output terminals  191  through power distribution/protection mechanism  190 . In this example, output terminals  195  provide, but are not limited to, 208V 60 Hz three-phase power and can be used to supply power for a three-phase balanced load or two unbalanced single-phase loads. 
     Power filter  180  is a series of inductors and capacitors that serve to filter and smooth the AC electrical power signal delivered by second power inverter  150 . Power distribution/protection mechanism  190  provides circuit protection features and also provides for the physical distribution of the AC electrical power to an external load. Although shown as discrete components, those skilled in the art will appreciate that power filter  180  and power distribution/protection mechanism  190  may be combined into a single device. 
     Inverter controller  160  is connected to first power inverter  130  by first inverter controller bus  135  and to second power inverter  150  by second inverter controller bus  155 . Inverter controller  160  is connected to power filter  180  and power distribution/protection mechanism  190  via filter bus  165 . Inverter controller  160  is used to control the operation of first power inverter  130  and second power inverter  150  during EPTO operation. Additionally, inverter controller  160  accepts feedback from power filter  180  and power distribution/protection mechanism  190  relative to voltage and operational conditions. Finally, inverter controller  160  also communicates with the vehicle/transmission controller via bus  195  to coordinate total system management, including ICE speed control and fault handling functions. 
     Referring now to  FIG. 2 , an EPTO  200  system for powering three-phase balanced loads in accordance with an alternative preferred exemplary embodiment of the present invention comprises: a first AC induction motor  210 ; a second AC induction motor  220 ; a first power inverter  230 ; a second power inverter  250 ; an energy storage device  240 ; an inverter controller  260 ; a power filter  280 ; and a power distribution/protection mechanism  290 . Vehicle/transmission control bus  295 , first inverter controller bus  235 , second inverter controller bus  255 , and filter bus  265  provide communication paths between the various components. Additionally, output terminals  291  are distribution points for the power output from EPTO system  200 . 
     First AC induction motor  210  and second AC induction motor  220  are mechanically inter-connected through a complex planetary gear set (not shown this FIG.) and electrically coupled or connected through first power inverter  230  and second power inverter  250 . Energy storage device  240  is typically connected in parallel with first power inverter  230  and second power inverter  250 . Energy storage device  240  is any suitable type of energy storage device known to those skilled in the art such as one or more battery packs and/or ultra-capacitors. 
     First AC induction motor  210  is typically connected to an internal combustion engine prime mover (not shown this FIG.). In operation, first AC induction motor  210  acts as a generator, transforming the mechanical energy received at its input shaft, which is physically coupled to the ICE, into AC electrical energy. First power inverter  230  is electrically connected to the output of first AC induction motor  210  and operates as a boost rectifier. This allows first power inverter  230  to transform the AC electrical energy into DC electrical energy that is then stored in energy storage device  240 . 
     Second AC induction motor  220  comprises a plurality of internal windings. Additionally, second AC induction motor  220  is typically connected to the wheels of the hybrid vehicle (not shown this FIG.) containing EPTO system  200 . 
     Second power inverter  250  is operated as an inverter, transforming DC power into AC power at a fixed frequency and voltage. The three-phase output of second power inverter  250  is filtered by power filter  280  and is then delivered to output terminals  291  through power distribution/protection mechanism  290 . In this example, output terminals  295  provide, but are not limited to, 208V 60 Hz three-phase power and can be used to supply power for a three-phase balanced load or two unbalanced single-phase loads. 
     Power filter  280  is a series of inductors and capacitors that serve to filter and smooth the AC electrical power signal delivered by second power inverter  250 . In this embodiment of the present invention, the internal windings of second AC inductor motor  220  are used as part of power filter  280 . This obviates the need of the additional inductors shown in  FIG. 1 . Power distribution/protection mechanism  290  provides circuit protection features and also provides for the physical distribution of the AC electrical power to an external load. Although shown as discrete components, those skilled in the art will appreciate that power filter  280  and power distribution/protection mechanism  290  may be combined into a single device. 
     Inverter controller  260  is connected to first power inverter  230  by first inverter controller bus  235  and to second power inverter  250  by second inverter controller bus  255 . Inverter controller  260  is connected to power filter  280  and power distribution/protection mechanism  290  via filter bus  265 . Inverter controller  260  is used to control the operation of first power inverter  230  and second power inverter  250  during EPTO operation. Additionally, inverter controller  260  accepts feedback from power filter  280  and power distribution/protection mechanism  290  relative to voltage and operational conditions. Finally, inverter controller  260  also communicates with the vehicle/transmission controller via bus  295  to coordinate total system management, including ICE speed control and fault handling functions. 
     Referring now to  FIG. 3 , an EPTO system  300  for powering single-phase unbalanced loads in accordance with a preferred exemplary embodiment of the present invention comprises: a first AC induction motor  310 ; a second AC induction motor  320 ; a first power inverter  330 ; a second power inverter  350 ; an energy storage device  340 ; an inverter controller  360 ; a power filter  380 ; and a power distribution/protection mechanism  390 . Vehicle/transmission control bus  395 , first inverter controller bus  335 , second inverter controller bus  355 , and filter bus  365  provide communication paths between the various components. Additionally, output terminals  391  are distribution points for the power output from EPTO system  300 . 
     First AC induction motor  310  and second AC induction motor  320  are mechanically inter-connected through a complex planetary gear set (not shown this FIG.) and electrically coupled or connected through first power inverter  330  and second power inverter  350 . Energy storage device  340  is typically connected in parallel with first power inverter  330  and second power inverter  350 . Energy storage device  340  is any suitable type of energy storage device known to those skilled in the art such as one or more battery packs and/or ultra-capacitors. 
     First AC induction motor  310  is typically connected to an internal combustion engine prime mover (not shown this FIG.). In operation, first AC induction motor  310  acts as a generator, transforming the mechanical energy received at its input shaft, which is physically coupled to the ICE, into AC electrical energy. First power inverter  330  is electrically connected to the output of first AC induction motor  310  and operates as a boost rectifier. This allows first power inverter  330  to transform the AC electrical energy into DC electrical energy that is then stored in energy storage device  340 . 
     Second AC induction motor  320  comprises a plurality of internal windings that are interconnected by switches  321  and  322 . Switches  321  and  322  are typically located on the input terminals or the neutral connection, as shown in  FIG. 3 . Additionally, second AC induction motor  320  is typically connected to the wheels of the hybrid vehicle (not shown this FIG.) containing EPTO system  300 . Since second AC induction motor  320  is not needed for operation of EPTO system  300 , it is disconnected by opening switches  321  and  322 . 
     Second power inverter  350  is operated as an inverter, transforming DC power into AC power at a fixed frequency and voltage. The output of second power inverter  350  is filtered by power filter  380  and is then delivered to output terminals  391  through power distribution/protection mechanism  390 . In this example, output terminals  395  provide 120/240V 60 Hz single-phase power and can be used to supply power for single-phase unbalanced loads. 
     Power filter  380  is a series of inductors and capacitors that serve to filter and smooth the AC electrical power signal delivered by second power inverter  350 . Power distribution/protection mechanism  390  provides circuit protection features and also provides for the physical distribution of the AC electrical power to an external load. Although shown as discrete components, those skilled in the art will appreciate that power filter  380  and power distribution/protection mechanism  390  may be combined into a single device. 
     Inverter controller  360  is connected to first power inverter  330  by first inverter controller bus  335  and to second power inverter  350  by second inverter controller bus  355 . Inverter controller  360  is connected to power filter  380  and power distribution/protection mechanism  390  via filter bus  365 . Inverter controller  360  is used to control the operation of first power inverter  330  and second power inverter  350  during EPTO operation. Additionally, inverter controller  360  accepts feedback from power filter  380  and power distribution/protection mechanism  390  relative to voltage and operational conditions. Finally, inverter controller  360  also communicates with the vehicle/transmission controller via bus  395  to coordinate total system management, including ICE speed control and fault handling functions. 
     Referring now to  FIG. 4 , an EPTO system  400  for powering single-phase unbalanced loads in accordance with an alternative preferred exemplary embodiment of the present invention comprises: a first AC induction motor  410 ; a second AC induction motor  420 ; a first power inverter  430 ; a second power inverter  450 ; an energy storage device  440 ; an inverter controller  460 ; a power filter  480 ; and a power distribution/protection mechanism  490 . Vehicle/transmission control bus  495 , first inverter controller bus  435 , second inverter controller bus  455 , and filter bus  465  provide communication paths between the various components. Additionally, output terminals  491  are distribution points for the power output from EPTO system  400 . 
     First AC induction motor  410  and second AC induction motor  420  are mechanically inter-connected through a complex planetary gear set (not shown this FIG.) and electrically coupled or connected through first power inverter  430  and second power inverter  450 . Energy storage device  440  is typically connected in parallel with first power inverter  430  and second power inverter  450 . Energy storage device  440  is any suitable type of energy storage device known to those skilled in the art such as one or more battery packs and/or ultra-capacitors. 
     First AC induction motor  410  is typically connected to an internal combustion engine prime mover (not shown this FIG.). In operation, first AC induction motor  410  acts as a generator, transforming the mechanical energy received at its input shaft, which is physically coupled to the ICE, into AC electrical energy. First power inverter  430  is electrically connected to the output of first AC induction motor  410  and operates as a boost rectifier. This allows first power inverter  430  to transform the AC electrical energy into DC electrical energy that is then stored in energy storage device  440 . 
     Second AC induction motor  420  comprises a plurality of internal windings. Additionally, second AC induction motor  420  is typically connected to the wheels of the hybrid vehicle (not shown this FIG.) containing EPTO system  400 . 
     Second power inverter  450  is operated as an inverter, transforming DC power into AC power at a fixed frequency and voltage. The output of second power inverter  450  is filtered by power filter  480  and is then delivered to output terminals  491  through power distribution/protection mechanism  490 . In this example, output terminals  495  provide, but are not limited to, 120/240V 60 Hz supply power for unbalanced single-phase loads. 
     Power filter  480  is a series of inductors and capacitors that serve to filter and smooth the AC electrical power signal delivered by second power inverter  450 . In this embodiment of the present invention, the internal windings of second AC inductor motor  420  are used as part of power filter  480 . This obviates the need of the additional inductors shown in  FIG. 3 . Power distribution/protection mechanism  490  provides circuit protection features and also provides for the physical distribution of the AC electrical power to an external load. Although shown as discrete components, those skilled in the art will appreciate that power filter  480  and power distribution/protection mechanism  490  may be combined into a single device. 
     Inverter controller  460  is connected to first power inverter  430  by first inverter controller bus  435  and to second power inverter  450  by second inverter controller bus  455 . Inverter controller  460  is connected to power filter  480  and power distribution/protection mechanism  490  via filter bus  465 . Inverter controller  460  is used to control the operation of first power inverter  430  and second power inverter  450  during EPTO operation. Additionally, inverter controller  460  accepts feedback from power filter  480  and power distribution/protection mechanism  490  relative to voltage and operational conditions. Finally, inverter controller  460  also communicates with the vehicle/transmission controller via bus  495  to coordinate total system management, including ICE speed control and fault handling functions. 
     Referring now to  FIG. 5 , an EPTO system  500  for powering three-phase unbalanced loads in accordance with a preferred exemplary embodiment of the present invention comprises: a first AC induction motor  510 ; a second AC induction motor  520 ; a first power inverter  530 ; a second power inverter  550 ; an energy storage device  540 ; an inverter controller  560 ; a power filter  580 ; and a power distribution/protection mechanism  590 . Vehicle/transmission control bus  595 , first inverter controller bus  535 , second inverter controller bus  555 , and filter bus  565  provide communication paths between the various components. Additionally, output terminals  591  are distribution points for the power output from EPTO system  500 . 
     First AC induction motor  510  and second AC induction motor  520  are mechanically inter-connected through a complex planetary gear set (not shown this FIG.) and electrically coupled or connected through first power inverter  530  and second power inverter  550 . Energy storage device  540  is typically connected in parallel with first power inverter  530  and second power inverter  550 . Energy storage device  540  is any suitable type of energy storage device known to those skilled in the art such as one or more battery packs and/or ultra-capacitors. 
     First AC induction motor  510  is typically connected to an internal combustion engine prime mover (not shown this FIG.). In operation, first AC induction motor  510  acts as a generator, transforming the mechanical energy received at its input shaft, which is physically coupled to the ICE, into AC electrical energy. First power inverter  530  is electrically connected to the output of first AC induction motor  510  and operates as a boost rectifier. This allows first power inverter  530  to transform the AC electrical energy into DC electrical energy that is then stored in energy storage device  540 . 
     Second AC induction motor  520  comprises a plurality of internal windings that are interconnected by switches  521  and  522 . Switches  521  and  522  are typically located on the input terminals or the neutral connection, as shown in  FIG. 5 . Additionally, second AC induction motor  520  is typically connected to the wheels of the hybrid vehicle (not shown this FIG.) containing EPTO system  500 . Since second AC induction motor  520  is not needed for operation of EPTO system  500 , it is disconnected by opening switches  521  and  522 . 
     Second power inverter  550  is operated as an inverter, transforming DC power into AC power at a fixed frequency and voltage. In this embodiment of the present invention, a four-legged inverter is used to control the non-zero neutral current of the unbalanced load. During standard vehicle operation, EPTO system  500  is not used and, accordingly, the fourth leg of the inverter is disabled. Whenever EPTO system  500  is activated to deliver AC power to output terminals  591 , the fourth leg of second power inverter  550  is activated. The output of second power inverter  550  is filtered by power filter  580  and is then delivered to output terminals  591  through power distribution/protection mechanism  590 . In this example, output terminals  595  provide, but are not limited to, 120/208V 60 Hz power for three-phase unbalanced loads. 
     Power filter  580  is a series of inductors and capacitors that serve to filter and smooth the AC electrical power signal delivered by second power inverter  550 . Power distribution/protection mechanism  590  provides circuit protection features and also provides for the physical distribution of the AC electrical power to an external load. Although shown as discrete components, those skilled in the art will appreciate that power filter  580  and power distribution/protection mechanism  590  may be combined into a single device. 
     Inverter controller  560  is connected to first power inverter  530  by first inverter controller bus  535  and to second power inverter  550  by second inverter controller bus  555 . Inverter controller  560  is connected to power filter  580  and power distribution/protection mechanism  590  via filter bus  565 . Inverter controller  560  is used to control the operation of first power inverter  530  and second power inverter  550  during EPTO operation. Additionally, inverter controller  560  accepts feedback from power filter  580  and power distribution/protection mechanism  590  relative to voltage and operational conditions. Finally, inverter controller  560  also communicates with the vehicle/transmission controller via bus  595  to coordinate total system management, including ICE speed control and fault handling functions. 
     Referring now to  FIG. 6 , an EPTO system  600  for powering three-phase unbalanced loads in accordance with an alternative preferred exemplary embodiment of the present invention comprises: a first AC induction motor  610 ; a second AC induction motor  620 ; a first power inverter  630 ; a second power inverter  650 ; an energy storage device  640 ; an inverter controller  660 ; a power filter  680 ; and a power distribution/protection mechanism  690 . Vehicle/transmission control bus  695 , first inverter controller bus  635 , second inverter controller bus  655 , and filter bus  665  provide communication paths between the various components. Additionally, output terminals  691  are distribution points for the power output from EPTO system  600 . 
     First AC induction motor  610  and second AC induction motor  620  are mechanically inter-connected through a complex planetary gear set (not shown this FIG.) and electrically coupled or connected through first power inverter  630  and second power inverter  650 . Energy storage device  640  is typically connected in parallel with first power inverter  630  and second power inverter  650 . Energy storage device  640  is any suitable type of energy storage device known to those skilled in the art such as one or more battery packs and/or ultra-capacitors. 
     First AC induction motor  610  is typically connected to an internal combustion engine prime mover (not shown this FIG.). In operation, first AC induction motor  610  acts as a generator, transforming the mechanical energy received at its input shaft, which is physically coupled to the ICE, into AC electrical energy. First power inverter  630  is electrically connected to the output of first AC induction motor  610  and operates as a boost rectifier. This allows first power inverter  630  to transform the AC electrical energy into DC electrical energy that is then stored in energy storage device  640 . 
     Second AC induction motor  620  comprises a plurality of internal windings. Additionally, second AC induction motor  620  is typically connected to the wheels of the hybrid vehicle (not shown this FIG.) containing EPTO system  600 . 
     Second power inverter  650  is operated as an inverter, transforming DC power into AC power at a fixed frequency and voltage. In this embodiment of the present invention, a four-legged inverter is used to control the non-zero neutral current of the unbalanced load. During standard vehicle operation, EPTO system  600  is not used and, accordingly, the fourth leg of the inverter is disabled. Whenever EPTO system  600  is activated to deliver AC power to output terminals  691 , the fourth leg of second power inverter  650  is activated. The output of second power inverter  650  is filtered by power filter  680  and is then delivered to output terminals  691  through power distribution/protection mechanism  690 . In this example, output terminals  695  provide, but are not limited to, 120/208V 60 Hz supply power for unbalanced three-phase loads. 
     Power filter  680  is a series of inductors and capacitors that serve to filter and smooth the AC electrical power signal delivered by second power inverter  650 . In this embodiment of the present invention, the internal windings of second AC inductor motor  620  are used as part of power filter  680 . This obviates the need of the additional inductors shown in  FIG. 5 . Power distribution/protection mechanism  690  provides circuit protection features and also provides for the physical distribution of the AC electrical power to an external load. Although shown as discrete components, those skilled in the art will appreciate that power filter  680  and power distribution/protection mechanism  690  may be combined into a single device. 
     Inverter controller  660  is connected to first power inverter  630  by first inverter controller bus  635  and to second power inverter  650  by second inverter controller bus  655 . Inverter controller  660  is connected to power filter  680  and power distribution/protection mechanism  690  via filter bus  665 . Inverter controller  660  is used to control the operation of first power inverter  630  and second power inverter  650  during EPTO operation. Additionally, inverter controller  660  accepts feedback from power filter  680  and power distribution/protection mechanism  690  relative to voltage and operational conditions. Finally, inverter controller  660  also communicates with the vehicle/transmission controller via bus  695  to coordinate total system management, including ICE speed control and fault handling functions. 
     From the foregoing description, it should be appreciated that the methods described herein provide for a much-improved EPTO system for hybrid vehicles. While various preferred exemplary embodiments have been presented in the foregoing detailed description of the preferred exemplary embodiments, it should be appreciated that a vast number of variations in the embodiments exist. It should also be appreciated that the preferred exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description provides those skilled in the art with a convenient road map for implementing one or more preferred exemplary embodiments of the invention. It should also be understood that various changes may be made in the function and arrangement of elements described in the exemplary preferred embodiments without departing from the spirit and scope of the invention as set forth in the appended claims.