Patent Publication Number: US-2019184837-A1

Title: Integrated dc vehicle charger

Description:
TECHNICAL FIELD 
     This disclosure relates to automotive electric drive and charging systems. 
     BACKGROUND 
     Hybrid-electric vehicles (HEVs) and battery electric vehicles (BEVs) may rely on a traction battery to provide power to a traction motor for propulsion, and a power inverter therebetween to convert direct current (DC) power to alternating current (AC) power. The typical AC traction motor is a three-phase motor powered by three sinusoidal signals each driven with 120 degrees phase separation but other configurations are also possible. Also, many electrified vehicles may include a DC-DC converter to convert the voltage of the traction battery to an operational voltage level of the traction motor. 
     SUMMARY 
     A vehicle has a traction battery, an electric machine having two sets of windings that share a common neutral, and first and second inverters. The inverters, during propulsion, each power a dedicated one of the sets of windings with power from the traction battery, and during charge, direct charge current from a charge port sequentially through the first inverter, the windings, and the second inverter to the traction battery. 
     A vehicle has a drive system including a battery, two inverters, an electric machine, and switches. The vehicle also has a controller that, responsive to charge mode, operates the switches to couple one of the inverters to a charge port and operates at least one of the inverters such that DC current from the charge port sequentially flows through the one of the inverters, the electric machine, and the other of the inverters to the battery. 
     A method for controlling a vehicle power system includes, by a controller, responsive to charge mode, coupling one of a pair of inverters to a charge port such that DC current from the charge port sequentially flows through the one, an electric machine, and the other of the pair to a traction battery, and responsive to propulsion mode, decoupling the one from the charge port and coupling the one to the traction battery. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a conventional off-board DC vehicle fast charge ecosystem. 
         FIG. 2  is a schematic diagram of an electrified vehicle powertrain. 
         FIG. 3  is a schematic diagram of an electrified vehicle powertrain with integrated DC charge capability. 
         FIG. 4  is a schematic diagram of an electrified vehicle. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments of the present disclosure are described herein. However, the disclosed embodiments are merely exemplary and other embodiments may take various and alternative forms that are not explicitly illustrated or described. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one of ordinary skill in the art to variously employ the present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures may be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of this disclosure may be desired for particular applications or implementations. 
     Despite differences in their architectures, electric vehicles (EVs) have similarities in their structure. For instance, a battery, inverter, and electric motor are typical building blocks for an EV. To energize the battery and provide power for the motor, two types of chargers can be employed: on-board and off-board (stand-alone) chargers. An on-board charger gives flexibility to charge anywhere there is an electric power outlet available. It may, however, add weight, volume, and cost to the vehicle. Thus, the possibility of avoiding these drawbacks by using available hardware such as the inverter and electric motor to charge the battery is desirable. 
     Considering that during charging, the vehicle is not driven, and during driving, the battery is not charged except by way of regenerative braking, integration of an on-board charger and traction system seems to be a feasible option. Additionally, DC fast chargers have gained popularity and many have focused on such designs. The significant reduction in charge time is what makes these types of chargers attractive. Here, we propose to use a vehicle&#39;s multi-phase electric machine to implement a DC charger. In certain examples, the combination of two symmetric inverters and motor windings form a full bridge DC-DC converter. Activation of some of the switches of one of the inverters and utilization of the diodes of the other of the inverters can result in a decrease in the DC power source voltage at the battery (buck mode). In this scenario, the motor windings act as a filter inductor. Activation of the switches of both of the inverters and utilization of the diodes of the other of the inverters can result in an increase in the DC power source voltage at the battery (boost mode). In this scenario, the motor windings act as a boost inductor. In both scenarios, if the switches are not operated simultaneously, an interleaved operation is possible, which may improve output voltage quality. 
     Referring to  FIG. 1 , a conventional off-board DC fast charge ecosystem  10  for a vehicle  12  includes a medium voltage utility grid  14 , conventional transformer  16 , building wire  18 , off-board DC fast charger  20 , and charge cord  22 . The off-board DC fast charger  20  includes AC/DC converter  24 , capacitor  26 , and DC/DC converter  28 . AC power from the medium voltage utility grid is transferred to the building wire  18  via the conventional transformer  16 . The AC power is then converted to DC power in the usual fashion by off-board DC fast charger  20  for delivery to the vehicle  12  via the charge cord  22 . 
     Referring to  FIG. 2 , a traction drive system  30  includes a traction battery  32 , symmetric inverters  34 ,  36 , and an electric machine  38 . Each of the inverters  34 ,  36  includes switching elements and a DC link capacitor as per usual. In other arrangements, only one of the inverters  34 ,  36  may include a DC link capacitor as known in the art. The electric machine  38  includes two-sets of three windings  40 ,  42  and a common neutral  44 . That is, the electric machine  38  is a six-phase electric machine. During propulsion, DC power from the traction battery  32  is converted by the inverters  34 ,  36  to AC power for delivery to the electric machine  38 . During regenerative braking, AC power from the electric machine  38  is converted by the inverters  34 ,  36  to DC power for delivery to the traction battery  32 . 
     Referring to  FIG. 3 , a traction drive system  46  with integrated fast charge capability includes a traction battery  48 , inverters  50 ,  52 , and an electric machine  53 . In this example, the inverter  50  includes switch-diode pairs  54 ,  56 ,  58 ,  60 ,  62 ,  64  and DC link capacitor  66 . And, the inverter  52  includes switch-diode pairs  68 ,  70 ,  72 ,  74 ,  76 ,  78  and DC link capacitor  80 . The electric machine  53  includes windings  82 ,  84 ,  86 ,  88 ,  90 ,  92  and common neutral  94 . The windings  82 ,  84 ,  86  and  88 ,  90 ,  92  are arranged in two sets of three. That is, the electric machine  53  is a six-phase electric machine. 
     In other arrangements, only one of the inverters (e.g., the inverter  52 ) may include a DC link capacitor. In such arrangements, DC link capability may need to be associated with the charging port  99 . Also, the electric machine  53  may include additional sets of windings possibly necessitating the use of additional inverters, etc. Other arrangements are also contemplated. 
     The traction drive system  46  further includes switching arrangement  96  and controller  98 . The switching arrangement  96  includes switches S 1 , S 2  that selectively electrically couple a charging port  99  therewith. The charging port  99  is arranged to receive power from a DC power source  100 . The inverters  50 ,  52 , electric machine  53 , and switching arrangement  96  are in communication with and/or under the control of the controller  98 . 
     During propulsion, the controller  98  puts switch  51  in position X and opens switch S 2  to electrically connect the traction battery  48  to inverter  50  and decouple the charging port  99  from the traction drive system  46 . DC power from the traction battery  48  may then be converted to AC power via the inverters  50 ,  52  for delivery to the electric machine  53 . 
     During charge, the controller  98  puts switch  51  in position Y and closes switch S 2  to electrically connect the inverter  50  to the charging port  99  and decouple the traction battery  48  from the inverter  50 . DC power from the charging port  99  may then flow through the inverter  50 , the electric machine  53 , the inverter  52 , and to the traction battery  48 . 
     If power from the charging port  99  is to be neither boosted or bucked, the controller  98  may turn on one or more of the switches of the switch-diode pairs  54 ,  58 ,  62  such that current flows through the corresponding windings and neutral of the electric machine  53 , and the diodes of the corresponding switch-diode pairs  68 ,  72 ,  76  to the traction battery  48 . 
     If power from the charging port  99  is to be bucked, the controller  98  may activate one or more of the switches of the switch-diode pairs  54 ,  58 ,  62  at some duty cycle such that current intermittently flows through the corresponding windings and neutral of the electric machine  53 , and the diodes of the corresponding switch-diode pairs  68 ,  72 ,  76  to the traction battery  48 . 
     If power from the charging port  99  is to be boosted, the controller  98  may activate one or more of the switches of the switch diode-pairs  54 ,  58 ,  62  and one or more of the switches of the switch-diode pairs  70 ,  74 ,  78  at some duty cycle such that current intermittently flows through the corresponding windings and neutral of the electric machine  53  and intermittently flows through the diodes of the corresponding switch-diode pairs  68 ,  72 ,  76  and the switches of the corresponding switch-diode pairs  70 ,  74 ,  78  to the traction battery  48 . 
     In this design, the switches  51 , S 2  are used to disconnect the traction battery  48  from the inverter  50 . The inverters  50 ,  52 , and the windings  82 - 92  thus can form a three-way interleaved full bridge DC-DC converter. Therefore, instead of directly connecting the traction battery  48  to the charging port  99  as with a conventional DC fast charging method, a DC-DC stage is added. Since this is a full bridge DC-DC converter, it is capable of boosting and bucking the input voltage as described above. This may make the traction drive system  46  compatible with any commercial DC fast charger regardless of its output voltage level. 
     Some arrangements may offer certain benefits. The design of the power source, for example, can be simplified since the DC-DC stage is incorporated into the charger. The systems are compatible with different DC voltage levels (different brands and products) since with a full bridge DC-DC converter, the voltage can be adjusted to any desired value. Compared with conventional DC fast charging, there are no added components except for two possible switches. Due to the full control on the output voltage level, trickle charging is feasible. This may be useful if for any reason battery voltage is low and charging at regular power could cause issues. The three-way interleaved design may reduce current ripple on the DC bus and thereby increase component life span. Due to the boosting capability, the input voltage to the charger can be lowered. 
     The architectures contemplated herein may be implemented within a variety of vehicle configurations.  FIG. 4 , for example, depicts an electrified vehicle  102  that includes one or more electric machines  104  mechanically coupled to a hybrid transmission  106 . The electric machines  104  may operate as a motor or generator. In addition, the hybrid transmission  106  is mechanically coupled to an engine  108  and a drive shaft  110  that is mechanically coupled to the wheels  112 . 
     A traction battery or battery pack  114  stores energy that can be used by the electric machines  104 . The vehicle battery pack  114  may provide a high voltage direct current (DC) output. The traction battery  114  may be electrically coupled to one or more power electronics modules  116  that implement the architectures discussed above. One or more contactors  118  may further isolate the traction battery  114  from other components when opened and connect the traction battery  114  to other components when closed. The power electronics module  116  is also electrically coupled to the electric machines  104  and provides the ability to bi-directionally transfer energy between the traction battery  114  and the electric machines  104 . For example, the traction battery  114  may provide a DC voltage while the electric machines  104  may operate with alternating current (AC) to function. The power electronics module  116  may convert the DC voltage to AC current to operate the electric machines  104 . In regenerative mode, the power electronics module  116  may convert the AC current from the electric machines  104  acting as generators to DC voltage compatible with the traction battery  114 . 
     The vehicle  102  may include a variable-voltage converter (VVC) (not shown) electrically coupled between the traction battery  114  and power electronics module  116 . The VVC may be a DC/DC boost converter configured to increase or boost the voltage provided by the traction battery  114 . By increasing the voltage, current requirements may be decreased leading to a reduction in wiring size for the power electronics module  116  and the electric machines  104 . Further, the electric machines  104  may be operated with better efficiency and lower losses. 
     In addition to providing energy for propulsion, the traction battery  114  may provide energy for other vehicle electrical systems. The vehicle  102  may include a DC/DC converter module  120  that converts the high voltage DC output of the traction battery  114  to a low voltage DC supply that is compatible with low-voltage vehicle loads  121 . An output of the DC/DC converter module  120  may be electrically coupled to an auxiliary battery  122  (e.g., 12V battery) for charging the auxiliary battery  122 . The low-voltage systems may be electrically coupled to the auxiliary battery  122 . One or more electrical loads  124  may be coupled to the high-voltage bus. The electrical loads  124  may have an associated controller that operates and controls the electrical loads  124  when appropriate. Examples of electrical loads  124  may include a fan, an electric heating element, and/or an air-conditioning compressor. 
     The electrified vehicle  102  may be configured to recharge the traction battery  114  from an external power source  126 . The external power source  126  may be a connection to an electrical outlet. The external power source  126  may be electrically coupled to a charger or electric vehicle supply equipment (EVSE)  128 . The external power source  126  may be an electrical power distribution network or grid as provided by an electric utility company. The EVSE  128  may provide circuitry and controls to regulate and manage the transfer of energy between the power source  126  and the vehicle  102 . The external power source  126  may provide DC or AC electric power to the EVSE  128 . The EVSE  128  may have a charge connector  130  for plugging into a charge port  132  of the vehicle  102 . The charge port  132  may be any type of port configured to transfer power from the EVSE  128  to the vehicle  102 . The EVSE connector  130  may have pins that mate with corresponding recesses of the charge port  132 . Alternatively, various components described as being electrically coupled or connected may transfer power using a wireless inductive coupling. 
     In some configurations, the electrified vehicle  102  may be configured to provide power to an external load. For example, the electrified vehicle may be configured to operate as a back-up generator or power outlet. In such applications, a load may be connected to the EVSE connector  130  or other outlet. The electrified vehicle  102  may be configured to return power to the power source  126 . For example, the electrified vehicle  102  may be configured to provide alternating current (AC) power to the electrical grid. The voltage supplied by the electrified vehicle may be synchronized to the power line. 
     Electronic modules in the vehicle  102  may communicate via one or more vehicle networks. The vehicle network may include a plurality of channels for communication. One channel of the vehicle network may be a serial bus such as a Controller Area Network (CAN). One of the channels of the vehicle network may include an Ethernet network defined by the Institute of Electrical and Electronics Engineers (IEEE) 802 family of standards. Additional channels of the vehicle network may include discrete connections between modules and may include power signals from the auxiliary battery  122 . Different signals may be transferred over different channels of the vehicle network. For example, video signals may be transferred over a high-speed channel (e.g., Ethernet) while control signals may be transferred over CAN or discrete signals. The vehicle network may include any hardware and software components that aid in transferring signals and data between modules. The vehicle network is not shown but it may be implied that the vehicle network may connect to any electronic module that is present in the vehicle  102 . A vehicle system controller (VSC)  134  may be present to coordinate the operation of the various components. 
     The vehicle  102  also includes the DC/DC converter module  120  for converting the voltage of the high-voltage bus to a voltage level suitable for the auxiliary battery  122  and low-voltage loads  121  (e.g., around 12 Volts). The vehicle  102  may further include additional switches, contactors, and circuitry to selectively select power flow between the traction battery  114  to the DC/DC converter  120 . 
     The processes, methods, logic, or strategies disclosed may be deliverable to and/or implemented by a processing device, controller, or computer, which may include any existing programmable electronic control unit or dedicated electronic control unit. Similarly, the processes, methods, logic, or strategies may be stored as data and instructions executable by a controller or computer in many forms including, but not limited to, information permanently stored on various types of articles of manufacture that may include persistent non-writable storage media such as ROM devices, as well as information alterably stored on writeable storage media such as floppy disks, magnetic tapes, CDs, RAM devices, and other magnetic and optical media. The processes, methods, logic, or strategies may also be implemented in a software executable object. Alternatively, they may be embodied in whole or in part using suitable hardware components, such as Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), state machines, controllers or other hardware components or devices, or a combination of hardware, software and firmware components. 
     The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure and claims. As previously described, the features of various embodiments may be combined to form further embodiments that may not be explicitly described or illustrated. While various embodiments may have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics may be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.