Abstract:
An automotive vehicle power system includes a battery charger having an input and output. The battery charger receives electrical energy via the input when the input is electrically connected with an electrical power source. The battery charger also alters at least one of a voltage set point and current provided at the output such that a power associated with the energy received from the power source remains approximately equal to a power target as a voltage associated with the energy received from the power source varies.

Description:
BACKGROUND 
       [0001]    The National Electric Code (NEC) requires that the AC line load for a 15 A circuit not exceed 80% of rating (12 A) for continuous loads (3 hr or longer). The NEC also requires that the AC line power not exceed 1440 W. 
       SUMMARY 
       [0002]    A vehicle may include a battery charger that has an input and output and that receives electrical energy via the input when the input is electrically connected with an electrical power source. The vehicle may also include a battery electrically connected with the output. 
         [0003]    The battery charger may control current provided to the battery via the output such that a power associated with the energy received from the power source is approximately equal to a power target. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a block diagram of an automotive vehicle electrically connected with an electrical grid. 
           [0005]      FIG. 2  is a flow chart depicting an algorithm for controlling AC line current and power while charging the batteries of  FIG. 1 . 
           [0006]      FIG. 3  is a flow chart depicting another algorithm for controlling AC line current and power while charging the batteries of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0007]    Referring to  FIG. 1 , a vehicle  10  (e.g., battery electric vehicle, plug-in hybrid electric vehicle, etc.) includes a battery charger  12 , high voltage loads  14  (e.g., a traction battery, electric machine, etc.) and low voltage loads  16  (e.g., a +12V battery, logic circuitry, etc.) The battery charger  12  is electrically connected with the high voltage loads  14  and low voltage loads  16 . The vehicle  10  also includes a controller  18 . The battery charger  12  is in communication with/under the control of the controller  18 . Other arrangements including a different number of loads, chargers, controllers, etc. are also possible. 
         [0008]    The battery charger  12  is configured to receive electrical power from an electrical grid  26  (or other electrical power source). The vehicle  10 , for example, may be plugged in to a wall outlet such that the battery charger  12  is electrically connected with the electrical grid  26  via a ground fault interrupter (GFI)  22  (or similar device) and fuse box  24 . Line and neutral wires (the AC line) and a ground wire are shown, in this example, electrically connecting the battery charger  12  and grid  26 . The ground wire is electrically connected with the neutral wire and earth ground at the fuse box  24 . Other electrical configurations, such as a 240 V arrangement with L1, L2 and ground wires, are of course also possible. 
         [0009]    The battery charger  12  may determine (e.g., measure) the voltage and current of the AC line as well as the voltage and current output to the loads  14 ,  16 . The battery charger  12 , in the embodiment of  FIG. 1 , can control the high voltage output current (the current output to the high voltage loads  14 ) and the low voltage output voltage set point (the set point of the voltage output to the low voltage loads  16 ). The battery charger  12 , however, may be configured to control any combination of the high voltage and/or low voltage output currents and/or voltage set points. 
         [0010]    The above mentioned low voltage control may allow the low voltage system to supply smooth regulated output low voltage for control electronics by supplying all required current to maintain the set point voltage up to the limit of the converter design. While the high voltage output of the battery charger  12 , in the embodiment of  FIG. 1 , has both a smooth voltage and current (power output can thus easily be maintained), the low voltage power output can fluctuate depending on loads turning on and off in the vehicle  10 . 
         [0011]    The general equation relating the input power, P acline , to the charger output power is 
         [0000]    
       
         
           
             
               
                 
                   
                     P 
                     acline 
                   
                   = 
                   
                     
                       
                         
                           V 
                           HV 
                         
                         * 
                         
                           I 
                           HV 
                         
                       
                       
                         η 
                         HV 
                       
                     
                     + 
                     
                       
                         
                           V 
                           LV 
                         
                         * 
                         
                           I 
                           LV 
                         
                       
                       
                         η 
                         LV 
                       
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where V HV  and I HV  are the charger measured high voltage output voltage and current respectively, V LV  and I LV  are the charger measured low voltage output voltage and current respectively, and η HV  and η LV  are the conversion efficiencies between the AC line and the high voltage and low voltage outputs respectively. (The efficiency of conversion varies with power output, input voltage, converter temperature, internal charger component power draw and other factors.) 
         [0012]    According to (1), one or both of the battery charger outputs (high voltage and low voltage) can be controlled to regulate the power and current on the AC line. In one example, the low voltage output is left at the demanded level and the high voltage current is reduced to control the AC line power. Other scenarios are also possible. 
         [0013]    (1) can be rewritten as 
         [0000]    
       
         
           
             
               
                 
                   
                     P 
                     acline 
                   
                   = 
                   
                     
                       
                         
                           
                             V 
                             HV 
                           
                           * 
                           
                             I 
                             HV 
                           
                         
                         + 
                         
                           
                             V 
                             LV 
                           
                           * 
                           
                             I 
                             LV 
                           
                         
                       
                       
                         η 
                         charger 
                       
                     
                      
                     
                         
                     
                      
                     where 
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
             
               
                 
                   
                     P 
                     acline 
                   
                   = 
                   
                     
                       V 
                       ac 
                     
                     * 
                     
                       I 
                       ac 
                     
                      
                     
                         
                     
                      
                     and 
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
             
               
                 
                   
                     
                       η 
                       charger 
                     
                     = 
                     
                       
                         
                           
                             V 
                             HV 
                           
                           * 
                           
                             I 
                             HV 
                           
                         
                         + 
                         
                           
                             V 
                             LV 
                           
                           * 
                           
                             I 
                             LV 
                           
                         
                       
                       
                         P 
                         acline 
                       
                     
                   
                    
                   
                       
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
         [0000]    and a new value of I VH  can be calculated from (2), (3) and (4) as follows 
         [0000]    
       
         
           
             
               
                 
                   
                     I 
                     
                       HV 
                       command 
                     
                   
                   ≅ 
                   
                     
                       
                         
                           P 
                           acline 
                         
                         * 
                         
                           η 
                           charger 
                         
                       
                       - 
                       
                         
                           V 
                           LV 
                         
                         * 
                         
                           I 
                           LV 
                         
                       
                     
                     
                       V 
                       HV 
                     
                   
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where I HVcommand  is the new charge rate command to the battery charger  12  for charging the high voltage battery  14 . 
         [0014]    The net efficiency of the battery charger  12  may first be determined from (4). With this, (5) may be used to calculate an updated high voltage charge current that would maintain the load power below the AC line limit (e.g., 1440 W). By substituting (3) into (5) and setting I ac  equal to the AC line current limit (e.g., 12 A), an updated high voltage charge current that would maintain the AC line current below its limit may also be calculated. Because the efficiencies in (1) vary with AC line conditions, (5) may result in a slight error that will be reduced each time the algorithm is performed. 
         [0015]    The above process may be repeated on a continual basis to regulate the input power or current limit, whichever is lower, as needed. An example of excessive power and excessive current draw can be shown by considering (3). Assume that the battery charger  12  is operating on a 15 A circuit. As mentioned above, the NEC limits continuous current to 12 A. Also assume that the battery charger  12  has an internal limit of 1440 W while the actual AC line voltage is 115V ac . From (3), the maximum allowed P acline  would be 1380 W and the algorithm would limit I ac  to 12 A according to (5). Now consider what happens when V ac  increases to 130V ac . From (3), I ac  must be reduced to 11 A to limit the input power to 1440 W. (5) can be used to calculate the new high voltage current command. 
         [0016]    Referring to  FIG. 2 , the AC line current may be read at operation  28 . The battery charger  12 , for example, may read (determine, measure, etc.) the AC line current in any suitable/known fashion. At operation  30 , it is determined whether the AC line current is greater than a current threshold. The battery charger  12 , for example, may determine whether the AC line current exceeds 12 A. If yes, the battery charger output current is reduced at operation  32 . For example, the battery charger  12  may reduce the high voltage (and/or low voltage) output current by 0.5 A. The algorithm then returns to operation  28 . 
         [0017]    Returning to operation  30 , if no, the AC line current and voltage is read at operation  34 . The battery charger  12 , for example, may read the AC line current and voltage in any suitable/known fashion. At operation  36 , the AC line power is determined. The battery charger  12 , for example, may determine the AC line power according to (3). At operation  38 , it is determined whether the AC line power is greater than a power threshold. For example, the battery charger  12  may determine whether the AC line power is greater than 1440 W. If no, the algorithm ends. If yes, the battery charger output current is reduced at operation  40 . The battery charger  12 , for example, may reduce the high voltage (and/or low voltage) output current by 1 A. The algorithm then returns to operation  34 . 
         [0018]    Referring to  FIG. 3 , the AC line current may be read at operation  40 . The battery charger  12 , for example, may read the AC line current in any suitable/known fashion. At operation  42 , it is determined whether the AC line current is greater than a current threshold. The battery charger  12 , for example, may determine whether the AC line current exceeds 12 A. If yes, the battery charger output current is reduced at operation  44 . For example, the battery charger  12  may reduce the high voltage (and/or low voltage) output current by 0.5 A. The algorithm then returns to operation  40 . 
         [0019]    Returning to operation  42 , if no, the AC line current and voltage is read at operation  46 . The battery charger  12 , for example, may read the AC line current and voltage in any suitable/known fashion. At operation  48 , the AC line power is determined. The battery charger  12 , for example, may determine the AC line power according to (3). At operation  50 , it is determined whether the AC line power is greater than a power threshold. For example, the battery charger  12  may determine whether the AC line power is greater than 1440 W. If no, the algorithm ends. If yes, the battery charger output voltages and currents are read at operation  52 . The battery charger  12 , for example, may read the output voltages and currents in any suitable/known fashion. At operation  54 , the battery charger efficiency is determined. The battery charger  12 , for example, may determine the battery charger efficiency according to (4). At operation  56 , the battery charger output current necessary to achieve the power threshold is determined. The battery charger  12 , for example, may determine the high voltage output current according to (5) assuming a power threshold of 1440 W. At operation  58 , the battery charger output current is set to the value determined at operation  56 . The algorithm then returns to operation  46 . (Output voltages/set points may similarly be controlled to control the AC line current and power.) 
         [0020]    In alternative embodiments, the desired charger output current required to keep the AC line current at or below its limit may be determined directly by employing operations similar to operations  52 ,  54 ,  56 . For example, after determining the AC line current and voltage and the battery charger output voltages and currents, the battery charger efficiency may be determined according to (4). The battery charger output current necessary to achieve the AC line current limit may then be determined according to (3) and (5) assuming an I ac  of, in this example, 12 A. 
         [0021]    The algorithms disclosed herein may be deliverable to/performed by a processing device, such as the battery charger  12  or controller  18 , which may include any existing electronic control unit or dedicated electronic control unit, in many forms including, but not limited to, information permanently stored on non-writable storage media such as ROM devices and information alterably stored on writeable storage media such as floppy disks, magnetic tapes, CDs, RAM devices, and other magnetic and optical media. The algorithms may also be implemented in a software executable object. Alternatively, the algorithms 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. 
         [0022]    While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. 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 invention.