Abstract:
Integrated power conversion systems and methods for use in an electric vehicle having an electric motor, a primary high-voltage energy source, and an auxiliary energy source including a traction inverter module operable for converting a DC current generated by the high-voltage energy source into an AC current capable of powering the electric motor, and a DC/DC converter operable to step-down a voltage of the high-voltage energy source or step-up a voltage of the auxiliary energy source, wherein the traction inverter module and the DC/DC converter may share one or more common components, such as a common high-voltage DC bus capacitor, a common DC bus bar, and/or a common high-voltage transistor.

Description:
BACKGROUND OF INVENTION 
   1. Field of the Invention 
   The present invention relates generally to integrated power conversion systems and methods for use in a variety of applications, such as battery-powered (electric) vehicle applications, fuel cell vehicle applications, and hybrid electric vehicle applications. 
   2. Description of the Related Art 
   Traditionally, the power conversion system of a battery-powered electric vehicle (EV), a fuel cell vehicle, and a hybrid electric vehicle (HEV) has included a plurality of separate, discrete components and assemblies. Among these components and assemblies are a traction inverter module (TIM) and a DC/DC converter. 
   The TIM, also called the electric power inverter, is operable for converting the raw DC current generated by a high-voltage fuel cell or high-voltage storage device (e.g., battery, flywheel, or ultracapacitor) into an AC current capable of powering an electric motor, such as a traction motor or a field-oriented induction motor. This power is converted for driving and controlling the motor, i.e., for generating torque. The motor, in combination with a transaxle, converts the electrical energy into mechanical energy which turns the wheels of the vehicle. 
   The DC/DC converter utilizes pulse-width modulation (PWM) to step the voltage associated with the vehicle&#39;s high-voltage battery or fuel cell down to that which the alternator of an internal combustion engine (ICE)-powered vehicle would typically generate (13.5–14V). The DC/DC converter, which may be unidirectional or bi-directional, may be used, for example, to charge a 12V auxiliary battery, which is typically separated from the high-voltage battery or fuel cell. 
   The DC/DC converter may also be used to transfer power from the auxiliary battery to the high-voltage battery or fuel cell to, for example, start the vehicle. In general, the DC/DC converter is operable for matching a plurality of voltages. 
   Traditionally, the TIM and the DC/DC converter are separate, discrete assemblies, including a 3-phase assembly for the TIM and an H-bridge assembly for the DC/DC converter. The TIM and the DC/DC converter have typically utilized separate, discrete high-voltage DC bus capacitors, DC bus bars, and high-voltage transistors. This configuration has several important limitations. High-voltage cables must be utilized to connect the TIM and the DC/DC converter. Separate, discrete thermal management systems must be utilized to cool the TIM and the DC/DC converter. The result is a complex, bulky, costly configuration. Thus, what is needed are systems and methods for integrating the TIM and the DC/DC converter. 
   BRIEF SUMMARY OF INVENTION 
   The present invention provides systems and methods for integrating the TIM and the DC/DC converter. Specifically, the present invention provides systems and methods for integrating the high-voltage DC bus capacitors, DC bus bars, and high-voltage transistors of the TIM and the DC/DC converter. Advantageously, the systems and methods of the present invention result in a simple, compact, and inexpensive TIM DC/DC converter assembly, utilizing common high-voltage cables and a common thermal management system. 
   In one embodiment, an integrated power conversion system for use in an electric vehicle including an electric motor, a primary high-voltage energy source, and an auxiliary energy source includes a traction inverter module operable to convert a DC current generated by the primary high-voltage energy source into an AC current capable of powering the electric motor, and a DC/DC converter operable to step-down a voltage of the high-voltage energy source and/or step-up a voltage of the auxiliary energy source, wherein the traction inverter module and the DC/DC converter share one or more common components, such as a high-voltage DC bus capacitor, a common DC bus bar, and a common high-voltage transistor. 
   In another embodiment, an integrated power conversion method for use in an electric vehicle including an electric motor, a high-voltage energy source, and an auxiliary energy source includes providing a traction inverter module operable for converting a DC current generated by the high-voltage energy source into an AC current capable of powering the electric motor, providing a DC/DC converter operable for stepping-down a voltage of the high-voltage energy source or stepping-up a voltage of the auxiliary energy source, and disposing a plurality of common components within the traction inverter module and the DC/DC converter. The plurality of common components may include a common high-voltage DC bus capacitor, a common DC bus bar, and a common high-voltage transistor. 
   In a further embodiment, an integrated power conversion system for use in a power generating system including an electric motor, a high-voltage energy source, and an auxiliary energy source includes a traction inverter module operable to convert a DC current generated by the high-voltage energy source into an AC current capable of powering the electric motor, wherein the traction inverter module comprises a first circuit, and a DC/DC converter operable to step-down a voltage of the high-voltage energy source or step-up a voltage of the auxiliary energy source, wherein the traction inverter module and the DC/DC converter share a common high-voltage DC bus capacitor, a common DC bus bar, and a common high-voltage transistor. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is a circuit diagram of a system including separate, discrete TIM and DC/DC converter assemblies. 
       FIG. 2  is a circuit diagram of one embodiment of a system including integrated TIM and DC/DC converter assemblies. 
       FIG. 3  is a circuit diagram of another embodiment of a system including integrated TIM and DC/DC converter assemblies, specifically including a 55 kW TIM inverter and a 3 kW boost 2 kW buck bi-directional DC/DC converter. 
       FIG. 4  is a circuit diagram of a further embodiment of a system including integrated TIM and DC/DC converter assemblies, specifically including a 55 kW TIM inverter and a 2 kW buck converter for 12V loads. 
       FIG. 5  is a circuit diagram of a further embodiment of a system including integrated TIM and DC/DC converter assemblies, specifically including a 55 kW TIM inverter and a 45–55 kW bi-directional DC/DC converter. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , as described above, the power conversion system  10  of EVs, fuel cell vehicles, and HEVs typically includes a separate, discrete TIM assembly  12  and DC/DC converter assembly  14 . The TIM  12  inverts the high-voltage DC bus voltage to an AC voltage suitable for powering the motor  16 , such as a 3-phase AC voltage. This power is inverted for driving and controlling the motor  16 , i.e., for generating torque. The motor  16 , in combination with the transaxle, converts the electrical energy into mechanical energy which turns the wheels of the vehicle. The DC/DC converter  14  uses PWM to step the voltage associated with the vehicle&#39;s high-voltage energy source  18 , such as a battery, fuel cell, ultracapacitor, flywheel, or superconducting energy storage device down to that which the alternator of an ICE-powered vehicle would typically generate (13.5–14V). The DC/DC converter  14 , which may be unidirectional or bi-directional, may be used to charge an auxiliary energy source  20  such as a 12V auxiliary battery, which is typically separated from the high-voltage energy source  18 . The DC/DC converter  14  may also be used to transfer power from the auxiliary energy source  20  to the high-voltage energy source  18  to, for example, start the vehicle. In general, the DC/DC converter  14  is operable for matching a plurality of voltages. 
   The TIM  12  and the DC/DC converter  14  typically comprise separate, discrete assemblies, including a 3-phase assembly for the TIM  12  and an H-bridge assembly for the DC/DC converter  14 . The TIM  12  and the DC/DC converter  14  may also utilize separate, discrete high-voltage DC bus capacitors  22  and DC bus bars  24 . In this configuration, high-voltage cables must be utilized to connect the TIM  12  and the DC/DC converter  14 . Separate, discrete thermal management systems must be utilized to cool the TIM  12  and the DC/DC  14  converter. The result is a complex, bulky, costly configuration. 
   Referring to  FIG. 2 , in one embodiment, a system  30  including an integrated TIM  12  ( FIG. 1 ) and DC/DC converter  14  ( FIG. 1 ) includes two integrated assemblies: a high-voltage assembly  32 , including the TIM  12  and the high-voltage stage of the DC/DC converter  14 , and a low-voltage assembly  34 , including the low-voltage stage of the DC/DC converter  14  and a filter. The high-voltage assembly  32  is operatively connected to the low-voltage assembly  34  by a high-frequency transformer  36 . Specifically, the method may include removing the high-voltage power transistors from the DC/DC converter  14  and integrating them with the TIM&#39;s transistor module. This configuration allows the TIM  12  and the DC/DC converter  14  to share a high-voltage DC bus capacitor  38  and to utilize a simplified DC bus bar  40 . The integrated system  30  also includes the motor  16 , the high-voltage energy source  18 , and the auxiliary energy source  20 , while the high-voltage energy source  18  will typically take the form of a battery or fuel cell stack and the auxiliary energy source  20  will typically take the form of a battery, these energy sources may take the form of any or a combination of batteries, fuel cell stacks, ultracapacitors, flywheels, and/or superconducting magnetic storage devices. 
   In this configuration, high-voltage cables utilized to connect the TIM  12  and the DC/DC converter  14  may be eliminated and a common thermal management system may be utilized to cool the high-voltage power stage of the TIM  12  and the DC/DC converter  14 . The result is a simple, compact, inexpensive configuration. 
   Referring to  FIG. 3 , in another embodiment, a TIM  12 , such as a 55 kW TIM inverter, may be integrated with a DC/DC converter  14 , such as a 3 kW boost 2 kW buck bi-directional DC/DC converter. The integrated system  50  includes a high-voltage bridge module  52  for the TIM  12  and the DC/DC converter  14  and a low-voltage bridge module  54  for the DC/DC converter  14 . The high-voltage bridge module  52  is operatively connected to the low-voltage bridge module  54  by a high-frequency transformer  36 . The integrated system  50  may also include the motor  16 , a 250–420V high-voltage energy source  18 , and the auxiliary energy source  20 . The integrated system  50  may further include a plurality of switches  56 , such as insulated gate bipolar transistors (IGBTs)  58  or MOSFETs. In this configuration, high-voltage cables utilized to connect the TIM  12  and the DC/DC converter  14  may be eliminated and a common thermal management system may be utilized to cool the high-voltage power stage of the TIM  12  and the DC/DC converter  14 . Again, the result is a simple, compact, inexpensive configuration. 
   Referring to  FIG. 4 , in a further embodiment, a TIM  12 , such as a 55 kW TIM inverter, may be integrated with a DC/DC converter  14 , such as a 2 kW buck converter for 12V loads. The integrated system  60  includes a high-voltage bridge module  52  for the TIM  12  and the DC/DC converter  14  and a low-voltage rectifier  62  for the DC/DC converter  14 . The high-voltage bridge module  52  is operatively connected to the low-voltage rectifier  62  by a high-frequency transformer  36 . The integrated system  60  may also include the motor  16 , the 250–420V high-voltage energy source  18 , and the 12V auxiliary energy source  20 . The integrated system  60  may further include a plurality of switches  56  such as IGBTs  58  or MOSFETs. In this configuration, high-voltage cables utilized to connect the TIM  12  and the DC/DC converter  14  may be eliminated and a common thermal management system may be utilized to cool the TIM  12  and the DC/DC converter  14 . Again, the result is a simple, compact, inexpensive configuration. 
   Referring to  FIG. 5 , in a further embodiment, a TIM  12 , such as a 55 kW TIM inverter, may be integrated with a DC/DC converter  14 , such as a 45–55 kW bi-directional DC/DC converter. The integrated system  70  includes a high-voltage bridge module  52  for the TIM  12  and the DC/DC converter  14 . The integrated system  70  may also include the motor  16 , the 250–420V high-voltage energy source  18 , and a 150–190V auxiliary energy source  20 . The integrated system  70  may further include a plurality of IGBTs  58  or MOSFETs. In this configuration, high-voltage cables utilized to connect the TIM  12  and the DC/DC converter  14  may be eliminated and a common thermal management system may be utilized to cool the TIM  12  and the DC/DC converter  14 . Again, the result is a simple, compact, inexpensive configuration. 
   All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, including, but not limited to U.S. Serial No. 60/319,116 filed Feb. 20, 2002, are incorporated herein by reference, in their entirety. 
   From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.