Patent Publication Number: US-2021164372-A1

Title: Inverter-based exhaust aftertreatment thermal management apparatuses, methods, systems, and techniques

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of International Patent Application No. PCT/US18/58319 filed on Oct. 31, 2018, the content of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     The present application relates generally to exhaust aftertreatment thermal management apparatuses, methods, systems, and techniques. Exhaust aftertreatment systems may include one or more temperature-sensitive catalysts whose temperature should be maintained at or above a desired temperature or within a desired temperature range to avoid catalyst underperformance and increased emissions or to provide regeneration of a catalyst. Examples of temperature-sensitive catalysts include selective catalytic reduction (SCR) catalysts, particulate filters such as a diesel particulate filter (DPF), selective catalytic reduction particulate filter (SCRF) catalysts, oxidation catalysts, and three-way catalysts. Under some engine operating conditions, a temperature-sensitive catalyst may not be able to achieve a desired operating temperature without being provided with additional heat beyond what is provided by engine-out exhaust temperature. A number of proposals have been made to provide augmented heating of catalysts. Some have proposed providing hydrocarbons to engine exhaust which can react with exhaust oxygen to generate additional heat, for example, by in-cylinder injection or post-cylinder injection of additional fuel. Some have proposed use of electrical heating systems to increase catalyst temperature. Heretofore, conventional approaches have suffered from a number of drawbacks, limitations, shortcomings and undesirable results including those respecting fuel economy, parasitic losses, power availability, reliability, safety, and system complexity. There remains a substantial need for the unique apparatuses, methods, systems, and techniques disclosed herein. 
     DISCLOSURE OF ILLUSTRATIVE EMBODIMENTS 
     For the purposes of clearly, concisely and exactly describing illustrative embodiments of the present disclosure, the manner, and process of making and using the same, and to enable the practice, making and use of the same, reference will now be made to certain exemplary embodiments, including those illustrated in the figures, and specific language will be used to describe the same. It shall nevertheless be understood that no limitation of the scope of the invention is thereby created and that the invention includes and protects such alterations, modifications, and further applications of the exemplary embodiments as would occur to one skilled in the art. 
     SUMMARY OF THE DISCLOSURE 
     Exemplary embodiments include unique apparatus, methods, systems and techniques for inverter-based aftertreatment thermal management. Further embodiments, forms, objects, features, advantages, aspects, and benefits shall become apparent from the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating certain aspects of an exemplary vehicle system. 
         FIG. 2  is a schematic diagram illustrating certain aspects of an exemplary inverter-based aftertreatment thermal management system which may be provided in a vehicle system such as the vehicle system illustrated in  FIG. 1   
         FIG. 3  is a flowchart illustrating an exemplary control process which may be performed in connection with an inverter-based aftertreatment thermal management system such as the exemplary system  FIG. 2 . 
         FIG. 4  is a block diagram illustrating exemplary controls which may be provided and operated in connection with an inverter-based aftertreatment thermal management system such as the exemplary system of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     With reference to  FIG. 1 , there is illustrated, a partially diagrammatic view of an exemplary vehicle  20 . In the illustrated embodiment, vehicle  20  includes hybrid powertrain system  22  which includes a driveline  27  and a hybrid power system  24 . Driveline  27  includes a torque converter or transmission clutch  25 , a transmission  26 , a differential  28 , and ground engaging wheels  29 . It should be appreciated that in this embodiment, the propulsion of the vehicle is provided by the ground engaging wheels  29  which are provided as rear wheels; however, in other applications, front-wheel drive, four-wheel drive, and all-wheel drive approaches are contemplated. In one form, vehicle  20  is a form of on-road bus, delivery truck, a service truck or the like. In other forms, vehicle  20  may be of a different type, including other types of on-road or off-road vehicles. In still other embodiments it may be a marine vehicle (boat/ship) or another type of vehicle. In yet other embodiments, rather than a vehicle, hybrid powertrain system  22 , including the hybrid power system  24  is applied to stationary applications, such as an engine-driven generator (a genset), a hybrid system-driven pump, or the like to name several possibilities. 
     Hybrid power system  24  includes internal combustion engine  32 , flywheel  33 , clutch  34 , electric machine  36 , electronic control system (ECS)  40 , air handling subsystem  50 , aftertreatment system  60 , energy storage system (ESS)  70 , power electronics system  80 , and a mechanical accessory drive (not illustrated). Air handling subsystem  50  may include one or more intake manifolds, exhaust manifolds, turbochargers, superchargers, air filters or other intake air and exhaust system components. In the illustrated embodiment, ESS  70  is configured as a high-voltage battery system. Other embodiments may include other types of battery systems or other power storage devices such as super-capacitors or ultra-capacitors. 
     In the illustrated embodiment aftertreatment system  60  includes a diesel oxidation catalyst (DOC)  62 , a diesel particulate filter (DPF)  64  and an SCR catalyst  66  which are flow coupled in series. A reductant doser (not illustrated) is provided upstream of SCR catalyst and is configured to introduce reductant, such as diesel exhaust fluid (DEF), into the exhaust flow provided to SCR catalyst  66 . One or more components of aftertreatment system  60 , such as DPF  64 , SCR catalyst  66  or both may include or may be otherwise thermally coupled with a heating element that may be selectably coupled with power electronics  80  by a switch  67  which is in operative communication with ECS  40  via CAN  99 . The heating element or elements may be resistive heating elements infrared or other types of electrical heating elements. In certain forms, switch  67  may be structured to selectably couple one or more of multiple heating elements of aftertreatment system  60  with power electronics  80 . In certain forms where only one heating element or one commonly actuated group of heating elements are utilized in aftertreatment system  60 , switch  67  may be omitted. 
     In the illustrated embodiment hybrid power system  24  is in the form of a parallel hybrid system such that engine  32  and/or electric machine  36  can provide torque for hybrid powertrain system  22  depending on whether clutch  34  is engaged or not. It should be appreciated that electric machine  36  can operate as a motor powered by electricity from ESS  70 , or as an electric power generator that captures electric energy. In other operating modes, motor/generator may be passive such that it is not providing torque to the driveline. In the depicted form, electric machine  36  has a common rotor and a common stator, and provided as an integrated single unit; however, in other embodiments, a completely or partially separate motor, generator, rotor, stator, or the like may be integrated with a diesel engine. The designated electric machine  36  is intended to encompass such variations. Furthermore, it should be appreciated that in alternative embodiments of hybrid power system  24  some of the illustrated features may be absent and/or other optional devices and subsystems may be included (not shown). 
     For the depicted embodiments, engine  32  is of a four-stroke, diesel-fueled, Compression Ignition (CI) type with multiple cylinders and corresponding reciprocating pistons coupled to a crankshaft which is coupled to a flywheel that is coupled to a controllable clutch. Engine  32  may be of a conventional type with configuration and operation modifications to complement operation in hybrid power system  24 . In other embodiments, engine  32  may be of a different type, including different fueling, different operating cycle(s), different ignition, or the like. 
     It should be appreciated that ECS  40  can be implemented in any of a number of ways which combine or distribute the control function across one or more control units in various manners. ECS  40  executes operating logic that defines various control, management, and/or regulation functions. This operating logic may be in the form of dedicated hardware, such as a hardwired state machine, analog calculating machine, programming instructions, and/or a different form as would occur to those skilled in the art. ECS  40  may be provided as a single component or a collection of operatively coupled components; and may be comprised of digital circuitry, analog circuitry, or a hybrid combination of both of these types. When of a multi-component form, ECS  40  may have one or more components remotely located relative to the others in a distributed arrangement. ECS  40  can include multiple processing units arranged to operate independently, in a pipeline processing arrangement, in a parallel processing arrangement, or the like. In one embodiment, ECS  40  includes several programmable microprocessing units of a solid-state, integrated circuit type that are disturbed throughout hybrid powertrain system  22  that each include one or more processing units and memory. For this embodiment, ECS  40  is operatively coupled with various components and systems of the vehicle  20  via a controller area network (CAN)  99 . 
     It shall be appreciated that ECS  40  may be implemented in a number of physically separate devices, such as microprocessor-based or microcontroller-based electronic control modules which are sometimes referred to as electronic control units. For example, an engine control unit (ECU) may be provided to control operation of engine  32 , air handling system  50 , and aftertreatment system  60  among other components and systems. A transmission control unit (TCU) may be provided to control operation of transmission  26 . A hybrid control unit (HCU) may be provided to control operation of electric machine  36  and/or power electronics system  80 . A battery control unit (BCU) may be provided to control operation of ESS  70  when configured as a battery. A variety of other electronic control modules or electronic control units may be provided to control operation of other actuators, components, sensors and systems of the vehicle  20 . Each of the electronic control modules or electronic control units may be operatively coupled with and may communicate with one another via CAN  99 . 
     It shall be further appreciated that ECS  40  and/or any of its constituent processors/controllers may include one or more signal conditioners, modulators, demodulators, Arithmetic Logic Units (ALUs), Central Processing Units (CPUs), limiters, oscillators, control clocks, amplifiers, signal conditioners, filters, format converters, communication ports, clamps, delay devices, memory devices, Analog to Digital (A/D) converters, Digital to Analog (D/A) converters, and/or different circuitry or functional components as would occur to those skilled in the art to perform the desired communications. 
     With reference to  FIG. 2 , there is illustrated a schematic diagram depicting certain aspects of an exemplary inverter-based aftertreatment thermal management system  200  (sometimes referred to herein as system  200 ) which may be implemented in a hybrid power system such as hybrid power system  24 . For purposes of illustration, system  200  is depicted and described in relation to certain components of hybrid power system  24 ; however, it shall be appreciated that system  200  may be implemented in a variety of other types of hybrid power systems. 
     System  200  includes an inverter module  210  which may be implemented as a part of a power electronics system such as power electronics system  80 . In the illustrated embodiment, inverter module  210  comprises a housing  270  containing electrical components of inverter module  210  which include inverter phase legs  220 ,  230  and  240 , first DC rail  215  and second DC rail  216 , a DC link capacitor  212 , and an auxiliary leg  250 . In the illustrated embodiment inverter module  210  is provided as a three-phase inverter comprising three inverter phase legs, however, it shall be appreciated that inverters with a different number of inverter phase legs may also be utilized. 
     Phase leg  220 ,  230  and  240  respectively include first switching devices  222   a ,  232   a , and  242   a  which are coupled to DC rail  215  and respective phase leg input/output nodes  224 ,  234 , and  244 , and second switching devices  222   b ,  232   b , and  242   b  which are coupled to DC rail  216  and respective phase leg input/output nodes  224 ,  234 , and  244 . First switching devices  222   a ,  232   a , and  242   a  and second switching devices  222   b ,  232   b , and  242   b  Phase legs  220 ,  230  and  240  also respectively include first antiparallel diodes  223   a ,  233   a , and  243   a  which are coupled to DC rail  215  and respective phase leg input/output nodes  224 ,  234 , and  244 , and second antiparallel diodes  223   b ,  233   b , and  243   b  which are coupled to DC rail  216  and respective phase leg input/output nodes  224 ,  234 , and  244 . First switching devices  222   a ,  232   a , and  242   a  and second switching devices  222   b ,  232   b , and  242   b  may be any of a variety of types of power electronic devices, for example, semiconductor devices such as IGBTs, MOSFETS, SiC, or other types of semiconductor devices. 
     Auxiliary leg  250  includes switching device  252   a  which is coupled with DC rail  215  and auxiliary output node  254  and switching device  252   b  which is coupled with auxiliary output node  254  and DC rail  216 . Switching devices  252   b  and  252   b  may be any of a variety of types of power electronic devices, for example, semiconductor devices such as IGBTs, MOSFETS, SiC, or other types of semiconductor devices. In certain embodiment switching device,  252   b  may be omitted and auxiliary leg  250  may operate using only switching device  252   a.    
     A number of power couplings are provided to electrically connect the electrical components of inverter module  210  contained in housing  270  with other components. Power coupling  272  provides an electrical connection between ESS  70  and DC rail  215  and DC rail  216 . Power coupling  272  provides an electrical connection between electric machine  36  and phase leg input/output nodes  224 ,  234 , and  244 . Power coupling  273  provides an electrical connection between aftertreatment system  60  and auxiliary output node  254  and DC rail  216 . In the illustrated embodiment, second power coupling  272  and third power coupling  273  are depicted at separate locations on inverter module  210 . It should be appreciated, however, that second power coupling  272  and third power coupling  273  may be provided in location as components of a multiport power coupling. 
     Inverter module  210  includes an inverter controller  204  which is in operative communication with other components of ECS  40  via CAN  99  and, for some purposes, may be considered a distributed component of ECS  40 . Inverter controller  204  is operable to control the operation of inverter module  210  in response to higher-level operation commands received from other components of ECS  40 . For example, in response to a command associated with the operation of electric machine  36  as a motor, such as a command to provide traction torque for a powertrain, inverter controller  204  operates the switching devices of phase legs  220 ,  230 , and  240  to convert DC power provided by ESS  70  to DC rails  215  and  216  to AC power output at phase leg input/output nodes  224 ,  234 , and  244  to drive electric machine  36 . 
     In another example, in response to a command associated with the operation of electric machine  36  as a generator, such as a command to provide regenerative braking, inverter controller  204  operates the switching devices of phase legs  220 ,  230 , and  240  to convert AC power received at phase leg input/output nodes  224 ,  234 , and  244  to DC power at DC rails  215  and  216 . Under some operation conditions, DC power from DC rails  215  and  216  may be utilized to charge ESS  70 . Under other operating conditions, DC power from DC rails  215  and  216  may be utilized by auxiliary leg  250  to heat one or more components of exhaust aftertreatment system  60 . In such operating conditions, DC power may be selectably supplied to DC rails  215  and  216  by ESS  70 , by the aforementioned operation of phase legs  220 ,  230 , and  240 , or by a combination of both sources. 
     As illustrated in the embodiment of  FIG. 2 , aftertreatment system  60  includes a first heating element  264  which provided in or otherwise thermally coupled with DPF  64  and a second heating element  266  which is provided in or otherwise thermally coupled with SCR catalyst  66 . Heating elements  263  and  266  are electrically connected to switch  67  which is electrically connected with inverter module  210  and is in operatively coupled with ECS  40  via CAN  99 . Switch  67  can be controlled by ECS  40  to electrically connect and disconnect one or both of heating elements  264  and  266  with inverter module  210 . As noted above, in certain forms where only one heating element or one commonly actuated group of heating elements are utilized in aftertreatment system  60 , switch  67  may be omitted. 
     Inverter controller  204  may operate switching devices  252   a  and  252   b  to provide power to one or more heating elements operatively coupled with one or more components of aftertreatment system  60  in a number of operating scenarios. For example, power generated by electric machine  36  during regenerative braking or motoring may be provided to one or more heating elements operatively coupled with a component of aftertreatment system  60  which is evaluated to be operating below a predetermined minimum operating temperature or temperature range. This may occur in combination with or instead of the use of power generated by electric machine  36  during regenerative braking or motoring to charge ESS  70 . Additionally, if ESS  70  is evaluated to have sufficient energy, power from ESS  70  may be provided to one or more heating elements operatively coupled with a component of aftertreatment system  60  which is evaluated to be operating below a predetermined maximum temperature or temperature range regardless of whether power is generated by electric machine  36 . Furthermore, power generated by electric machine  36  during regenerative braking or motoring may be provided to one or more heating elements operatively coupled with a component of aftertreatment system  60  which is evaluated to be below a predetermined maximum operating temperature when it is evaluated that ESS  70  is at a full charge capacity and cannot accept power generated by electric machine  36 . Additionally, one or more heating elements operatively coupled with a component of aftertreatment system  60  may be utilized to receive discharge current from DC link capacitor  212  in order to render inverter module  210  safe for maintenance or repair. 
     With reference to  FIG. 3 , there is illustrated a flowchart depicting certain aspects of an exemplary process  300  which may be performed in connection with an inverter-based aftertreatment thermal management system, such as system  200 , and a hybrid powertrain system, such hybrid powertrain system  22 . Process  300  is initiated at start operation  302  and proceeds to conditional  304  which determines if the hybrid powertrain system is operating in a regeneration mode. The regeneration mode may comprise a regenerative braking mode wherein an electric machine, such as electric machine  36 , is operated as a generator to slow or stop a vehicle, such as vehicle  20 , in response to an operator braking command, a motoring mode wherein an electric machine, such as electric machine  36 , is operated as a generator to slow or maintain a desired speed of a vehicle, such as vehicle  20 , for example during a hill descent, or another regeneration mode wherein an electric machine, such as electric machine  36 , is operated as a generator. 
     If conditional  304  determines that the hybrid powertrain system is not operating in a regeneration mode, process  300  proceeds to conditional  322  which determines whether one or more aftertreatment system component should be heated and whether an alternative energy source is available to heat the one or more aftertreatment system component. The determination whether one or more aftertreatment system component should be heated may be based upon an evaluation of whether a current temperature or a predicted future temperature of an aftertreatment system component, such as one or more components of aftertreatment system  60 , is below a predetermined minimum operating temperature or temperature range. The determination whether an alternative energy source is available to heat the one or more aftertreatment system component may be based upon an evaluation whether an energy storage system, such as ESS  70 , has energy available for discharge based on a desired state of charge, state of health, temperature, or other operational or state parameters of ESS  70 . If conditional  322  determines that one or more aftertreatment system component should not be heated or determines that an alternative energy source is not available, process  300  returns to conditional  304 . If conditional  322  determines that one or more aftertreatment system components should be heated and that an alternative energy source is available, process  300  proceeds to operation  324  which heats the one or more aftertreatment system component with the alternative energy source, and then returns to conditional  304 . 
     If conditional  304  determines that the hybrid powertrain system is operating in a regeneration mode, process  300  proceed to conditional  306  which determines whether an energy storage system, such as energy storage system  70 , should be charged using energy generated in the regen mode, and whether the charging need is such that the charging of the energy storage system must be given override priority to the exclusion of heating an aftertreatment system component. The determination whether an energy storage system should be charged may be based upon an evaluation of a number of operational states of parameters including, for example, state of charge, state of health, temperature, or other operational or state parameters of ESS  70 . The determination whether the charging need is such that the charging of the energy storage system must be given override priority to the exclusion of heating an aftertreatment system component may be based upon an evaluation of the energy or power that would be consumed by the heating an aftertreatment system component and an evaluation whether the remaining energy of power is sufficient to meet the changing need of the energy storage system. 
     If conditional  306  determines that an energy storage system should be charged using energy generated in the regen mode and that the charging need is such that the charging of the energy storage system must be given override priority to the exclusion of heating an aftertreatment system component, process  300  proceeds to conditional  322  and continues as described above. If conditional  306  determines that an energy storage system should not be charged using energy generated in the regen mode, or that the charging need is not such that the charging of the energy storage system must be given override priority to the exclusion of heating an aftertreatment system component, process  300  proceeds to conditional  308 . 
     Conditional  308  determines whether one or more aftertreatment system component should be heated. This determination may be based upon an evaluation of whether a current temperature or a predicted future temperature of an aftertreatment system component, such as one or more components of aftertreatment system  60 , is below a predetermined minimum operating temperature or temperature range. If conditional  308  determines that one or more aftertreatment system component should be heated, process  300  proceeds to operation  310  which operates the switches of a plurality of inverter phase legs, such as the switches of inverter phase legs  220 ,  230 , and  240 , to rectify AC power received from an electric machine, such as electric machine  36 , which is operating as a generator and to operation  312  which modulates one or more switches of an auxiliary leg, such as the switches of auxiliary leg  252 , to power one or more heating elements operatively coupled with one or more components of an exhaust aftertreatment system, such as one or more components of exhaust aftertreatment system  60 . While operations  310  and  312  are depicted sequentially for purposes of illustration and description, it shall be appreciated that they may be performed concurrently. Furthermore, in a systems which include a switch, such as switch  67 , which is structured to selectably couple one or more of multiple heating elements of aftertreatment system with power electronics, operation  312  may provide a switch actuation command effective to operate the switch to couple one or more one or more of multiple heating elements of aftertreatment system with the auxiliary leg. The selection performed by operation  312  may be based upon an indication of one or more particular components of an aftertreatment system should be heated which may be determined and provided conditional  308 . 
     If conditional  308  determines that one or more aftertreatment system components should not be heated, process  300  proceeds to conditional  316  which determines whether the power generated by the electric machine in the regeneration mode is in excess of the power that can be consumed by the energy storage system and/or other electrical loads which may receive power generated by the electric machine in the regeneration mode. If conditional  316  determines that the power generated by the electric machine in the regeneration mode is not in excess of the power that can be consumed by the energy storage system and/or other electrical loads, process  300  returns to conditional  304 . 
     If conditional  316  determines that the power generated by the electric machine in the regeneration mode is in excess of the power that can be consumed by the energy storage system and/or other electrical loads, process  300  proceeds to conditional  314  which determines whether one or more components of an exhaust aftertreatment system, such as one or more components of aftertreatment system  60 , is below a maximum temperature. This determination may be made based upon an evaluation of whether a current temperature or a predicted future temperature of an aftertreatment system component, such as one or more components of aftertreatment system  60 , is below a predetermined maximum operating temperature or temperature range. If conditional  314  determines that one or more components of an exhaust aftertreatment system is not below a maximum temperature, process  300  returns to conditional  304 . If conditional  314  determines that one or more components of an exhaust aftertreatment system is below a maximum temperature, process  300  proceeds to operation  310  and continues as described above. 
     With reference to  FIG. 4 , there is illustrated a block diagram depicting certain aspects of exemplary controls  400  which may be provided and operated in connection with an inverter-based aftertreatment thermal management system such as system  200 . Block  420  includes aftertreatment temperature predictive control logic. Block  420  receives an aftertreatment temperature input from block  412 . The temperature input may be one or more measured or estimated temperatures for one or more components of an aftertreatment system. Block  420  also receives an exhaust flow input from block  414  and an exhaust temperature input from block  416 . Block  420  may also receive other parameters pertaining to current or future exhaust or aftertreatment conditions as indicated by block  418 . Block  420  processes the inputs that it receives to determine whether one or more components of an aftertreatment system should be heated. This determination may be based upon an evaluation of whether a current temperature or a predicted future temperature of an aftertreatment system component, such as one or more components of aftertreatment system  60 , is below a predetermined minimum operating temperature or temperature range. The future operating temperature may be predicted based upon the inputs from blocks  412 ,  414 ,  416 , and  418 . 
     Block  420  provides a logical output based on the operations of its aftertreatment temperature predictive control logic to block  422  which generates an aftertreatment heat command. The aftertreatment heat command may include an identification of one or more components of an aftertreatment system that should be heated and a heating command which may be defined in terms of a heating magnitude and duration. The output of block  422  is provided to block  424  which utilizes auxiliary switch modulation logic to generate an output auxiliary switch commands  430  in response to the aftertreatment heat command received from block  422 . An enable input  428  is also provided to block  424  to selectably enable or disable the generation of auxiliary switching command  430  depending on its logical value. The enable input  428  is generated by block  426  which implements a logical AND operation for inputs  462 ,  464 , and  466 . Input  462  provides a logical value indicating whether or not a system is operating in a regeneration mode. Input  464  provides a logical value for whether or not an energy storage system requires charging. Input  466  provides value for one or more other conditions which may be established as prerequisites to enabling block  424 . 
     A number of exemplary embodiments shall now be further described. A first embodiment is a vehicle system comprising an engine configured to output torque to propel the vehicle system and to output exhaust to an exhaust aftertreatment system; an electric machine configured to selectably operate as a motor to provide torque to the vehicle system and as a generator to receive torque from the vehicle system; an inverter module including a plurality of inverter phase legs and an auxiliary leg, the plurality of inverter phase legs being operatively coupled with a first DC rail, a second DC rail, and the electric machine, the auxiliary leg being operatively coupled with the first DC rail, the second DC rail and a heating element provided in the exhaust aftertreatment system; and an electronic control system in operative communication with the inverter module and the exhaust aftertreatment system, the electronic control system being configured to: evaluate whether the electric machine is operating as a generator, selectably operate the plurality of inverter phase legs to rectify AC power received from the electric machine, evaluate whether to heat one or more components of the exhaust aftertreatment system, and selectably operate the auxiliary leg to provide rectified power from the inverter legs to one or more electrical heating elements thermally coupled with the one or more components exhaust aftertreatment system effective to heat the one or more components. 
     In certain forms of the first embodiment, the exhaust aftertreatment system comprises a selective catalytic reduction (SCR) catalyst and one or more of the electrical heating elements is thermally coupled with the SCR catalyst. In certain such forms, the exhaust aftertreatment system comprises a diesel particulate filter (DPF) and one or more of the electrical heating elements is thermally coupled with the DPF. In certain such forms, the electronic control system is configured to selectably couple neither, one, or both of the SCR catalyst and the DPF with the auxiliary leg during operation of the auxiliary leg to provide rectified power from the inverter legs. 
     In certain forms of the first embodiment, the electronic control system is configured to evaluate whether to heat one or more components of the exhaust aftertreatment system by evaluating whether the one or more components is below a predetermined temperature. In certain such forms, the electronic control system is configured to evaluate whether to heat one or more components of the exhaust aftertreatment system by evaluating whether an energy storage system can be charged and evaluating whether the one or more components is above a predetermined temperature. 
     In certain forms of the first embodiment, the electronic control system is configured to evaluate whether an energy storage system requires charging and, in response, to one of charge the energy storage system without operating the auxiliary leg to provide rectified power from the inverter legs to the one or more electrical heating elements thermally coupled with the one or more components exhaust aftertreatment system and concurrently charge the energy storage and operate the auxiliary leg to provide rectified power from the inverter legs to the one or more electrical heating elements thermally coupled with the one or more components exhaust aftertreatment system. 
     A second embodiment is a method comprising providing a vehicle system including an engine configured to output torque to propel the vehicle system and to output exhaust to an exhaust aftertreatment system, an electric machine configured to selectably operate as a motor to provide torque to the vehicle system and as a generator to receive torque from the vehicle system, an inverter module including a plurality of inverter phase legs and an auxiliary leg, the plurality of inverter phase legs being operatively coupled with a first DC rail, a second DC rail, and the electric machine, the auxiliary leg being operatively coupled with the first DC rail, the second DC rail and a heating element provided in the exhaust aftertreatment system, and an electronic control system in operative communication with the inverter module and the exhaust aftertreatment system; evaluating with the electronic control system whether the electric machine is operating as a generator, selectably controlling with the electronic control system the plurality of inverter phase legs to rectify AC power received from the electric machine, evaluating with the electronic control system whether to heat one or more components of the exhaust aftertreatment system, and selectably operate with the electronic control system the auxiliary leg to provide rectified power from the inverter legs to one or more electrical heating elements thermally coupled with the one or more components exhaust aftertreatment system effective to heat the one or more components. 
     In certain forms of the second embodiment, the exhaust aftertreatment system comprises a selective catalytic reduction (SCR) catalyst and one or more of the electrical heating elements is thermally coupled with the SCR catalyst. In certain such forms, the exhaust aftertreatment system comprises a diesel particulate filter (DPF) and one or more of the electrical heating elements is thermally coupled with the DPF. Certain such forms comprise operating the electronic control system to selectably couple neither, one, or both of the SCR catalyst and the DPF with the auxiliary leg during operation of the auxiliary leg to provide rectified power from the inverter legs. 
     In certain forms of the second embodiment, the act of evaluating with the electronic control system whether to heat one or more components of the exhaust aftertreatment comprises evaluating whether the one or more components is below a predetermined temperature. In certain such forms, the act of evaluating with the electronic control system whether to heat one or more components of the exhaust aftertreatment comprises evaluating whether an energy storage system can be charged and evaluating whether the one or more components is above a predetermined temperature. 
     Certain forms of the second embodiment comprise evaluating with the electronic control system whether an energy storage system requires charging and, in response, operating the control system to one of charge the energy storage system without operating the auxiliary leg to provide rectified power from the inverter legs to the one or more electrical heating elements thermally coupled with the one or more components exhaust aftertreatment system and concurrently charge the energy storage and operate the auxiliary leg to provide rectified power from the inverter legs to the one or more electrical heating elements thermally coupled with the one or more components exhaust aftertreatment system. 
     A third embodiment is an apparatus for selectably providing power to and receiving power from a hybrid vehicle traction motor, the apparatus comprising a DC bus including a first DC rail, a second DC rail and a capacitor operatively coupled with the first DC rail and the second DC rail; a plurality of inverter phase legs each including a respective first switch operatively coupled with the first DC rail and operatively coupled with a respective traction motor input/output node and a respective second switch operatively coupled with the respective traction motor input/output node and operatively coupled with the second DC rail; and at least one auxiliary leg including an auxiliary leg switch operatively coupled with the first DC rail and operatively coupled with a resistive heating element, the resistive heating element being operatively coupled with the auxiliary leg switch and operatively coupled with the second DC rail and being configured to thermally interface with and selectably transfer heat to an exhaust aftertreatment system component. 
     In certain forms of the third embodiment, the resistive element is thermally coupled with an SCR catalyst. In certain such forms, the resistive element dissipates heat from a regeneration energy generated by an electric machine when a high voltage battery cannot absorb the regeneration energy. In certain such forms, the resistive element is actuated by the auxiliary leg switch of the inverter based on a predetermined temperature of the exhaust aftertreatment system component. Certain such forms comprise an electronic control system configured to control operation of the plurality of inverter phase legs to convert AC power received at the respective input/output nodes to DC power provided to the DC bus and to control the auxiliary leg switch to heat the resistive heating element. Certain such forms comprise an apparatus including any of the foregoing features. 
     In certain forms of the third embodiment, the resistive element dissipates heat from a regeneration energy generated by an electric machine when a high voltage battery cannot absorb the regeneration energy. 
     In certain forms of the third embodiment, the resistive element is actuated by the auxiliary leg switch of the inverter based on a predetermined temperature of the exhaust aftertreatment system component. 
     Certain forms of the third embodiment, comprise an electronic control system configured to control operation of the plurality of inverter phase legs to convert AC power received at the respective input/output nodes to DC power provided to the DC bus and to control the auxiliary leg switch to heat the resistive heating element. 
     While illustrative embodiments of the disclosure have been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only certain exemplary embodiments have been shown and described and that all changes and modifications that come within the spirit of the claimed inventions are desired to be protected. It should be understood that while the use of words such as preferable, preferably, preferred or more preferred utilized in the description above indicates that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention, the scope being defined by the claims that follow. In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary.