Patent Publication Number: US-10778100-B2

Title: Power supply device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present disclosure claims priority to Japanese Patent Application No. 2017-204395 filed Oct. 23, 2017, which is incorporated herein by reference in its entirety including specification, drawings and claims. 
     TECHNICAL FIELD 
     The present disclosure relates to a power supply device and more specifically relates to a power supply device including a plurality of boost converters that are connected in parallel to each other and that are configured to transmit electric power with conversion of a voltage between a power storage device side and an electric load side. 
     BACKGROUND 
     A proposed configuration of a power supply device mounted on a vehicle includes two boost converters that are connected in parallel to each other and that are placed between a battery and a motor for driving (as described in, for example, JP 2010-104139A). This device uses the two boost converters with switching over the drive mode between a mode in which only one boost converter is driven and a mode in which two boost converters are driven. 
     SUMMARY 
     In the power supply device of the above configuration, however, when the two boost converters have identical characteristics or more specifically when reactors respectively included in the two boost converters have identical inductances, the two boost converters have identical resonance frequencies. In the case where a load variable frequency of the motor is equal to the resonance frequencies of the two boost converters, in the drive mode that drives only one boost converter, resonance occurs whether only the first boost converter is driven or only the second boost converter is driven. 
     A power supply device of the present disclosure mainly aims to suppress the occurrence of resonance with a load variable frequency of an electric load. 
     In order to achieve the above primary object, the power supply device of the present disclosure employs the following configuration. 
     The present disclosure is directed to a power supply device. The power supply device includes a power storage device, a first boost converter provided to include a first reactor of a first inductance and configured to transmit electric power with conversion of voltage between the power storage device side and an electric load side, a second boost converter provided to include a second reactor of a second inductance, connected in parallel to the first boost converter relative to the electric load, and configured to transmit electric power with conversion of voltage between the power storage device side and the electric load side, a capacitor mounted on the electric load side of the first boost converter and the second boost converter and a control device configured to control the first boost converter and the second boost converter. The second inductance is different from the first inductance. 
     The power supply device of this aspect is equipped with the first boost converter configured to transmit power with conversion of voltage between the power storage device side and the electric load side and with the second boost converter connected in parallel to the first boost converter relative to the electric load. The second inductance of the second reactor included in the second boost converter is different from the first inductance of the first reactor included in the first boost converter. The first boost converter and the second boost converter accordingly have different resonance frequencies. This configuration can use the boost converter that does not cause resonance with the load variable frequency of the electric load. As a result, this suppresses the occurrence of resonance with the load variable frequency of the electric load. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a configuration diagram illustrating the schematic configuration of an electric vehicle with a power supply device according to one embodiment of the present disclosure mounted thereon; 
         FIG. 2  is a configuration diagram illustrating the schematic configuration of an electric drive system including a motor; 
         FIG. 3  is a flowchart showing one example of a drive mode permission/prohibition routine performed by an electronic control unit; and 
         FIG. 4  is a diagram illustrating one example of a relationship of an electric sixth-order variable frequency to a motor rotation speed when the motor is a 4 pole-pair motor. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The following describes some aspects of the present disclosure with referring to an embodiment.  FIG. 1  is a configuration diagram illustrating the schematic configuration of an electric vehicle  20  with a power supply device according to one embodiment of the present disclosure mounted thereon.  FIG. 2  is a configuration diagram illustrating the schematic configuration of an electric drive system including a motor  32 . As shown in  FIG. 1 , the electric vehicle  20  of the embodiment includes a motor  32 , an inverter  34 , a battery  36  as a power storage device, first and second boost converters  40  and  41 , and an electronic control unit  70 . The battery  36 , the first and second boost converters  40  and  41  and the electronic control unit  70  correspond to the power supply device according to the embodiment. 
     The motor  32  is configured as, for example, a synchronous generator motor and includes a rotor connected with a driveshaft  26  that is coupled with drive wheels  22   a  and  22   b  via a differential gear  24 . The inverter  34  is connected with the motor  32  and with high voltage-side power lines  42 . The electronic control unit  70  performs switching control of a plurality of switching elements (not shown) included in the inverter  34 , so as to rotate and drive the motor  32 . A capacitor  46  for smoothing is mounted to a positive electrode line and a negative electrode line of the high voltage-side power lines  42 . 
     The battery  36  is configured as, for example, a lithium ion rechargeable battery or a nickel metal hydride battery and is connected with low voltage-side power lines  44  as second power lines. A system main relay  38  configured to connect and disconnect the battery  36  and a capacitor  48  for smoothing are mounted in this sequence from the battery  36 -side to a positive electrode line and a negative electrode line of the low voltage-side power lines  44 . 
     As shown in  FIG. 2 , the first boost converter  40  is connected with the high voltage-side power lines  42  and with the low voltage-side power lines  44  and is configured as a known step-up/down converter including two transistors T 11  and T 12 , two diodes D 11  and D 12  and a reactor L 1 . The transistor T 11  is connected with the positive electrode line of the high voltage-side power lines  42 . The transistor T 12  is connected with the transistor T 11  and with the negative electrode lines of the high voltage-side power lines  42  and of the low voltage-side power lines  44 . The reactor L 1  is connected with a connection point between the transistors T 11  and T 12  and with the positive electrode line of the low voltage-side power lines  44 . The electronic control unit  70  regulates the rate of ON time of the transistors T 11  and T 12  of the first boost converter  40 , so that the first boost converter  40  supplies the power of the low voltage-side power lines  44  to the high voltage-side power lines  42  with stepping up the voltage of the power, while supplying the power of the high voltage-side power lines  42  to the low voltage-side power lines  44  with stepping down the voltage of the power. A resonance frequency fc 1  of the first boost converter  40  may be calculated by using an inductance L 1  of the reactor L 1  of the first boost converter  40  and an electrostatic capacitance C of the capacitor  46  mounted to the high voltage-side power lines  42  according to Expression (1) given below: 
     
       
         
           
             
               
                 
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     The second boost converter  41  is configured as a boost converter having the same performance as that of the first boost converter  40  within a manufacturing error and the like. More specifically, like the first boost converter  40 , the second boost converter  41  is connected with the high voltage-side power lines  42  and with the low voltage-side power lines  44  and is configured as a known step-up/down converter including two transistors T 21  and T 22 , two diodes D 21  and D 22  and a reactor L 2 . The electronic control unit  70  regulates the rate of ON time of the transistors T 21  and T 22  of the second boost converter  41 , so that the second boost converter  41  supplies the power of the low voltage-side power lines  44  to the high voltage-side power lines  42  with stepping up the voltage of the power, while supplying the power of the high voltage-side power lines  42  to the low voltage-side power lines  44  with stepping down the voltage of the power. A resonance frequency fc 2  of the second boost converter  41  may be calculated according to Expression (2) given below, and a resonance frequency fc 3  in the case where both the first boost converter  40  and the second boost converter  41  are driven may be calculated according to Expression (3) given below: 
     
       
         
           
             
               
                 
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     The electronic control unit  70  is configured as a CPU-based microprocessor and includes a ROM configured to store processing programs, a RAM configured to temporarily store data, a non-volatile flash memory and input/output ports, in addition to the CPU, although not being illustrated. 
     As shown in  FIG. 1 , signals from various sensors are input into the electronic control unit  70  via the input port. The signals input into the electronic control unit  70  include, for example, a rotational position θm from a rotational position detection sensor  32   a  configured to detect the rotational position of the rotor of the motor  32  and phase currents Iu and Iv from current sensors configured to detect electric currents flowing in the respective phases of the motor  32 . The input signals also include a voltage Vb from a voltage sensor  36   a  mounted between terminals of the battery  36 , an electric current Ib from a current sensor  36   b  mounted to an output terminal of the battery  36 , and a battery temperature Tb from a temperature sensor  36   c  mounted to the battery  36 . The input signals additionally include a voltage VH of the high voltage-side power lines  42  (capacitor  46 ) from a voltage sensor  46   a  mounted between terminals of the capacitor  46  and a voltage VL of the low voltage-side power lines  44  (capacitor  48 ) from a voltage sensor  48   a  mounted between terminals of the capacitor  48 . The input signals further include electric currents IL 1  and IL 2  of the reactors L 1  and L 2  from current sensors  40   a  and  40   b  configured to detect electric currents flowing in the reactors L 1  and L 2  of the first and the second boost converters  40  and  41  and temperatures tc 1  and tc 2  of the first and the second boost converters  40  and  41  from temperature sensors  40   b  and  41   b  mounted to the first and the second boost converters  40  and  41 . The input signals also include an ignition signal from an ignition switch  80  and a shift position SP from a shift position sensor  82  configured to detect an operating position of a shift lever  81 . The input signals further include an accelerator position Acc from an accelerator pedal position sensor  84  configured to detect a depression amount of an accelerator pedal  83 , a brake pedal position BP from a brake pedal position sensor  86  configured to detect a depression amount of a brake pedal  85 , and a vehicle speed V from a vehicle speed sensor  88 . 
     As shown in  FIG. 1 , various control signals are output from the electronic control unit  70  via the output port. The signals output from the electronic control unit  70  include, for example, switching control signals to the plurality of switching elements included in the inverter  34 , switching control signals to the transistors T 11  and T 12  of the first boost converter  40 , switching control signals to the transistors T 21  and T 22  of the second boost converter  41 , and a drive control signal to the system main relay  38 . The electronic control unit  70  calculates an electrical angle θe and a rotation speed Nm of the motor  32 , based on the rotational position θm of the rotor of the motor  32  from the rotational position detection sensor  32   a.    
     The electronic control unit  70  calculates a state of charge SOC of the battery  36 , based on an integrated value of the electric current Ib of the battery  36  from the current sensor  36   b . The electronic control unit  70  also calculates input and output limits Win and Wout that denote maximum allowable powers to be charged into and discharged from the battery  36 , based on the calculated state of charge SOC and the battery temperature Tb from the temperature sensor  36   c  mounted to the battery  36 . The state of charge SOC herein denotes a ratio of the capacity of electric power dischargeable from the battery  36  to the overall capacity of the battery  36 . 
     In the electric vehicle  20  of the embodiment having the above configuration, the electronic control unit  70  first sets a required torque Td* that is required for driving (required for the driveshaft  26 ), based on the accelerator position Acc and the vehicle speed V, and multiplies the required torque Td* by a rotation speed of the driveshaft  26  to set a load power Pm which the motor  32  is required to output for driving. The electronic control unit  70  subsequently sets a torque command Tm* such that the load power Pm is output from the motor  32 . The electronic control unit  70  then performs switching control of the switching elements included in the inverter  34 , such as to output the torque command Tm*. The electronic control unit  70  also sets a target voltage VH* of the high voltage-side power lines  42 , based on the torque command Tm*, and controls the first boost converter  40  and the second boost converter  41  to supply the load power Pm to the inverter  34  with stepping up the voltage of the power from the battery  36  to the target voltage VH*. The first boost converter  40  and the second boost converter  41  are controlled in a range of an allowed drive mode. When the load power Pm has a small value, only one boost converter is driven out of the first boost converter  40  and the second boost converter  41 . When the load power Pm has a large value, on the other hand, both the first boost converter  40  and the second boost converter  41  are driven. According to the embodiment, a mode in which only the first boost converter  40  is driven is specified as first drive mode. A mode in which only the second boost converter  41  is driven is specified as second drive mode. A mode in which both the first boost converter  40  and the second boost converter  41  are driven is specified as third drive mode. 
     The following describes operations of the power supply device mounted on the electric vehicle  20  of the embodiment having the above configuration or more specifically a series of operations to suppress resonance based on a rotational frequency of the motor  32 .  FIG. 3  is a flowchart showing one example of a drive mode permission/prohibition routine performed by the electronic control unit  70 . This routine is performed repeatedly at every predetermined time interval (for example, at every several tens msec). 
     When the drive mode permission/prohibition routine is triggered, the electronic control unit  70  first calculates a load variable frequency fm of the motor  32  (step S 100 ). According to the embodiment, a procedure of calculating the load variable frequency fm of the motor  32  specifies in advance a relationship between the rotation speed Nm and the load variable frequency fm of the motor  32 , stores the specified relationship as a load variable frequency setting map, and reads a value of the load variable frequency fm corresponding to a given rotation speed Nm of the motor  32  from the map.  FIG. 4  shows one example of a relationship of an electric sixth-order variable frequency to the motor rotation speed Nm when the motor  32  is a 4 pole-pair motor. When the motor  32  is a 4 pole-pair motor, the load variable frequency fm of the motor  32  is the electric sixth-order variable frequency. As shown in  FIG. 4 , the electric sixth-order variable frequency linearly changes against the rotation speed Nm of the motor  32 . Accordingly, the load variable frequency fm is unequivocally determined against the rotation speed Nm of the motor  32 . 
     The electronic control unit  70  subsequently calculates the resonance frequencies fc 1 , fc 2  and fc 3  in the respective drive modes of the first boost converter  40  and the second boost converter  41  (step S 110 ). The resonance frequency fc 1  in the first drive mode (i.e., mode in which only the first boost converter  40  is driven) is calculated according to Expression (1) given above. The resonance frequency fc 2  in the second drive mode (i.e., mode in which only the second boost converter  41  is driven) is calculated according to Expression (2) given above. The resonance frequency fc 3  in the third drive mode (i.e., mode in which both the first boost converter  40  and the second boost converter  41  are driven) is calculated according to Expression (3) given above. 
     The electronic control unit  70  subsequently determines whether a difference between the load variable frequency fm and the resonance frequency fc 1  in the first drive mode (i.e., an absolute value of a difference by subtracting the resonance frequency fc 1  from the load variable frequency fm) is less than a threshold value α (step S 120 ). The threshold value α herein denotes a criterion value used to determine whether the load variable frequency fm is coincident with the resonance frequency fc 1  and is set to a small positive value. More specifically, when the difference between the load variable frequency fm and the resonance frequency fc 1  in the first drive mode is less than the threshold value α, employing the first drive mode to control the first boost converter  40  and the second boost converter  41  causes resonance. When it is determined that the difference between the load variable frequency fm and the resonance frequency fc 1  in the first drive mode is less than the threshold value α, the electronic control unit  70  determines that driving the first boost converter  40  and the second boost converter  41  in the first drive mode causes resonance and thereby prohibits the first drive mode while permitting the second drive mode and the third drive mode (step S 130 ), before terminating this routine. Accordingly, when the load power Pm has a small value, the control of the first boost converter  40  and the second boost converter  41  drives only the second boost converter  41 . When the load power Pm has a large value, on the other hand, the control of the first boost converter  40  and the second boost converter  41  drives both the first boost converter  40  and the second boost converter  41 . This configuration suppresses resonance caused by driving the first boost converter  40  and the second boost converter  41  in the first drive mode. 
     When it is determined at step S 120  that the difference between the load variable frequency fm and the resonance frequency fc 1  in the first drive mode is equal to or greater than the threshold value α, the electronic control unit  70  subsequently determines whether a difference between the load variable frequency fm and the resonance frequency fc 2  in the second drive mode (i.e., an absolute value of a difference by subtracting the resonance frequency fc 2  from the load variable frequency fm) is less than the threshold value α (step S 140 ). When it is determined that the difference between the load variable frequency fm and the resonance frequency fc 2  in the second drive mode is less than the threshold value α, the electronic control unit  70  determines that driving the first boost converter  40  and the second boost converter  41  in the second drive mode causes resonance and thereby prohibits the second drive mode while permitting the first drive mode and the third drive mode (step S 150 ), before terminating this routine. Accordingly, when the load power Pm has a small value, the control of the first boost converter  40  and the second boost converter  41  drives only the first boost converter  40 . When the load power Pm has a large value, on the other hand, the control of the first boost converter  40  and the second boost converter  41  drives both the first boost converter  40  and the second boost converter  41 . This configuration suppresses resonance caused by driving the first boost converter  40  and the second boost converter  41  in the second drive mode. 
     When it is determined at step S 140  that the difference between the load variable frequency fm and the resonance frequency fc 2  in the second drive mode is equal to or greater than the threshold value α, the electronic control unit  70  subsequently determines whether a difference between the load variable frequency fm and the resonance frequency fc 3  in the third drive mode (i.e., an absolute value of a difference by subtracting the resonance frequency fc 3  from the load variable frequency fm) is less than the threshold value α (step S 160 ). When it is determined that the difference between the load variable frequency fm and the resonance frequency fc 3  in the third drive mode is less than the threshold value α, the electronic control unit  70  determines that driving the first boost converter  40  and the second boost converter  41  in the third drive mode causes resonance and thereby prohibits the third drive mode while permitting the first drive mode and the second drive mode (step S 170 ), before terminating this routine. Accordingly, the control of the first boost converter  40  and the second boost converter  41  drives only one of the first boost converter  40  and the second boost converter  41 , irrespective of the magnitude of the load power Pm. This configuration suppresses resonance caused by driving the first boost converter  40  and the second boost converter  41  in the third drive mode. 
     When it is determined at step S 160  that the difference between the load variable frequency fm and the resonance frequency fc 3  in the third drive mode is equal to or greater than the threshold value α, the electronic control unit  70  determines that no resonance occurs and permits all the drive modes (step S 180 ), before terminating this routine. Accordingly, when the load power Pm has a small value, the control of the first boost converter  40  and the second boost converter  41  drives only one of the first boost converter  40  and the second boost converter  41 . When the load power Pm has a large value, on the other hand, the control of the first boost converter  40  and the second boost converter  41  drives both the first boost converter  40  and the second boost converter  41 . 
     The power supply device mounted on the electric vehicle  20  of the embodiment described above employs different settings for the inductance L 1  of the reactor L 1  of the first boost converter  40  and for the inductance L 2  of the reactor L 2  of the second boost converter  41 . This configuration enables the boost converters to be driven without causing resonance with the load variable frequency fm of the motor  32 . More specifically, the power supply device calculates the load variable frequency fm and the resonance frequencies fc 1 , fc 2  and fc 3  in the respective drive modes. When the difference between the load variable frequency fm and the resonance frequency fc 1  in the first drive mode is less than the threshold value α, the power supply device prohibits the first drive mode, while permitting the second drive mode and the third drive mode. When the difference between the load variable frequency fm and the resonance frequency fc 2  in the second drive mode is less than the threshold value α, the power supply device prohibits the second drive mode, while permitting the first drive mode and the third drive mode. When the difference between the load variable frequency fm and the resonance frequency fc 3  in the third drive mode is less than the threshold value α, the power supply device prohibits the third drive mode, while permitting the first drive mode and the second drive mode. When all the differences between the load variable frequency fm and the resonance frequencies fc 1 , fc 2  and fc 3  in the respective drive modes are equal to or greater than the threshold value α, the power supply device permits all the drive modes. As a result, this configuration suppresses resonance with the load variable frequency fm of the motor  32 . 
     The power supply device mounted on the electric vehicle  20  of the embodiment determines whether the difference between the load variable frequency fm and the resonance frequency fc 1  in the first drive mode is less than the threshold value α. When the difference between the load variable frequency fm and the resonance frequency fc 1  in the first drive mode is equal to or greater than the threshold value α, the power supply device subsequently determines whether the difference between the load variable frequency fm and the resonance frequency fc 2  in the second drive mode is less than the threshold value α. When the difference between the load variable frequency fm and the resonance frequency fc 2  in the second drive mode is equal to or greater than the threshold value α, the power supply device subsequently determines whether the difference between the load variable frequency fm and the resonance frequency fc 3  in the third drive mode is less than the threshold value α. The sequence of the determinations of whether the differences between the load variable frequency fm and the respective resonance frequencies fc 1 , fc 2  and fc 3  in the respective drive modes are equal to or greater than the threshold value α is, however, not limited to the sequence of the first drive mode, the second drive mode and the third drive mode but may be any sequence. 
     The power supply device mounted on the electric vehicle  20  of the embodiment employs the identical value α for the respective drive modes as the threshold value used to determine whether the load variable frequency fm is coincident with the resonance frequency fc 1 , fc 2  or fc 3  in each of the drive modes. According to a modification, different values α 1 , α 2  and α 3  (where α 1 ≠α 2 , α 1 ≠α 3 , and α 2 ≠α 3 ) may be employed as threshold values for the respective drive modes. 
     The power supply device mounted on the electric vehicle  20  of the embodiment is equipped with two boost converters having different characteristics (different inductances of reactors), i.e., the first boost converter  40  and the second boost converter  41 . The power supply device may be equipped with three or more boost converters having different characteristics. 
     The power supply device mounted on the electric vehicle  20  of the embodiment uses one battery  36  as a power storage device. The power storage device may be a capacitor used in place of the battery  36 . 
     The embodiment describes the configuration of the power supply device mounted on the electric vehicle  20  that is driven with power from the motor  32 . The present disclosure may also be implemented by the configuration of a power supply device mounted on a hybrid vehicle that is driven with the power from a motor and the power from an engine or by the configuration of a power supply device built in stationary equipment such as construction equipment. 
     In the power supply device of this aspect, the control device may control the first boost converter and the second boost converter by employing one drive mode among a plurality of drive modes including a first drive mode in which only the first boost converter is driven, a second drive mode in which only the second boost converter is driven and a third drive mode in which both the first boost converter and the second boost converter are driven. The first inductance of the first reactor included in the first boost converter is different from the second inductance of the second reactor included in the second boost converter. This provides different resonance frequencies in the first drive mode, in the second drive mode and in the third drive mode. In this case, a load variable frequency may denote a drive frequency of the electric load, a first resonance frequency may denote a resonance frequency in the first drive mode, a second resonance frequency may denote a resonance frequency in the second drive mode, and a third resonance frequency may denote a resonance frequency in the third drive mode. (1) When a difference between the load variable frequency and the first resonance frequency is less than a first threshold value, the control device may prohibit the first drive mode, while permitting the second drive mode and the third drive mode, (2) when a difference between the load variable frequency and the second resonance frequency is less than a second threshold value, the control device may prohibit the second drive mode, while permitting the first drive mode and the third drive mode, (3) when a difference between the load variable frequency and the third resonance frequency is less than a third threshold value, the control device may prohibit the third drive mode, while permitting the first drive mode and the second drive mode, and (4) when the difference between the load variable frequency and the first resonance frequency is equal to or greater than the first threshold value, the difference between the load variable frequency and the second resonance frequency is equal to or greater than the second threshold value, and the difference between the load variable frequency and the third resonance frequency is equal to or greater than the third threshold value, the control device may permit the first drive mode, the second drive mode and the third drive mode. This configuration enables the first boost converter and the second boost converter to be driven in the drive mode that does not cause resonance with the load variable frequency of the electric load. The first threshold value, the second threshold value and the third threshold value may be all different values or may be all an identical value, or any two of the threshold values may be an identical value. 
     The following describes the correspondence relationship between the primary components of the embodiment and the primary components of the disclosure described in Summary. The battery  36  of the embodiment corresponds to the “power storage device”, the first boost converter  40  corresponds to the “first boost converter”, the second boost converter  41  corresponds to the “second boost converter”, the capacitor  46  corresponds to the “capacitor”, and the electronic control unit  70  corresponds to the “control device”. Further, the motor  32  and inverter  34  of the embodiment correspond to the “electric load”. 
     The correspondence relationship between the primary components of the embodiment and the primary components of the disclosure, regarding which the problem is described in Summary, should not be considered to limit the components of the disclosure, regarding which the problem is described in Summary, since the embodiment is only illustrative to specifically describes the aspects of the disclosure, regarding which the problem is described in Summary. In other words, the disclosure, regarding which the problem is described in Summary, should be interpreted on the basis of the description in the Summary, and the embodiment is only a specific example of the disclosure, regarding which the problem is described in Summary. 
     The aspect of the disclosure is described above with reference to the embodiment. The disclosure is, however, not limited to the above embodiment but various modifications and variations may be made to the embodiment without departing from the scope of the disclosure. 
     INDUSTRIAL APPLICABILITY 
     The technique of the disclosure is preferably applicable to the manufacturing industries of the power supply device and so on.