Motor vehicle

In a process of cancelling shutdown of a second converter during transmission of electric power between a first power line and a second power line with voltage conversion by a first converter in a shutdown state of the second converter, a motor vehicle performs single element switching control that switches one switching element between third and fourth switching elements of the second converter while setting the other switching element off, such as to prevent an electric current in a reverse direction to an electric current flowing in a first reactor of the first converter from flowing in a second reactor of the second converter.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2017-099757 filed on May 19, 2017, the contents of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a motor vehicle, and more specifically relates to a motor vehicle equipped with a motor, a first power storage device, a first converter, a second power storage device and a second converter.

BACKGROUND

A proposed configuration of a motor vehicle uses two converters to step up the voltage of an electric power from two batteries and supply the electric power of the stepped-up voltage to a motor (as described in, for example, JP 2011-125129A). When one converter can cover the electric power that is to be supplied to the motor, the motor vehicle of this configuration shuts down the other converter for the purpose of reducing the power consumption. In a process of cancelling this shutdown of the other converter, when the electric current flowing in the other converter exceeds a predetermined current value, a duty cycle is subjected to feedback control such that the electric current flowing in the other converter becomes equal to or less than the predetermined current value. This suppresses an excessive electric current from flowing in the converter in the process of cancelling shutdown of the converter.

Citation List

Patent Literature

SUMMARY

In the motor vehicle of the above configuration, however, an excessive electric current is likely to flow in the converter in the process of cancelling shutdown of the converter. Switching control generally provides a dead time. The presence of the dead time is likely to increase the electric current flowing in the converter. A voltage sensor and a current sensor provided in the system generally have detection errors. The electric current flowing in the converter is likely to increase by values corresponding to such detection errors. Superposition of the dead time with the detection errors of the sensors causes an excessive electric current to flow in the converter.

A motor vehicle of the present disclosure mainly aims to suppress an excessive electric current from flowing in a converter in a process of cancelling shutdown of the converter.

In order to achieve the above primary object, the motor vehicle of the disclosure is implemented by an aspect described below.

The present disclosure is directed to a motor vehicle. The motor vehicle includes a motor for driving, a power storage device, a first converter connected with a first power line which the motor is connected with, and a second power line which the power storage device is connected with, the first converter including first and second switching elements, first and second diodes and a first reactor and being configured to transmit electric power between the first power line and the second power line with voltage conversion, a second converter connected with the first power line and a third power line which the power storage device is connected with and which is different from the second power line, the second converter including third and fourth switching elements, third and fourth diodes and a second reactor and being configured to transmit electric power between the first power line and the third power line with voltage conversion, and a control device configured to perform voltage control of the first converter such that a voltage of the first power line becomes equal to a target voltage and to perform current control of the second converter such that an electric current flowing in the second reactor becomes equal to a target current. In a process of cancelling shutdown of the second converter during transmission of electric power between the first power line and the second power line with the voltage conversion by the first converter in a shutdown state of the second converter, the control device performs single element switching control that switches one switching element between the third and the fourth switching elements of the second converter while setting the other switching element off, such as to prevent an electric current in a reverse direction to an electric current flowing in the first reactor from flowing in the second reactor.

The motor vehicle of this aspect performs the voltage control of the first converter such that the voltage of the first power line becomes equal to the target voltage, and performs the current control of the second converter such that the electric current flowing in the second reactor becomes equal to the target current. In the process of cancelling shutdown of the second converter during transmission of electric power between the first power line and the second power line with voltage conversion by the first converter in the shutdown state of the second converter, the motor vehicle of this aspect performs the single element switching control that switches one switching element between the third and the fourth switching elements of the second converter while setting the other switching element off, such as to prevent the electric current in the reverse direction to the electric current flowing in the first reactor from flowing in the second reactor. Performing the single element switching control enables the electric current flowing in the second reactor to increase from the value0without causing the electric current in the reverse direction to flow in the second reactor. As a result, this suppresses an excessive electric current from flowing in the second converter.

DESCRIPTION OF EMBODIMENTS

The following describes aspects of the present disclosure with reference to some embodiments.

Embodiment

FIG. 1is a configuration diagram illustrating the schematic configuration of a hybrid vehicle20according to one embodiment of the present disclosure. As illustrated, the hybrid vehicle20of the embodiment includes an engine22, a planetary gear30, motors MG1and MG2, inverters41and42, first and second boost converters54and55, first and second batteries50and51, and a hybrid electronic control unit (hereinafter referred to as HVECU)70.

The engine22is configured as an internal combustion engine to output power using, for example, gasoline or light oil as a fuel. This engine22is operated and controlled by an engine electronic control unit (hereinafter referred to as engine ECU)24.

The engine ECU24is configured as a CPU-based microprocessor and includes a ROM configured to store processing programs, a RAM configured to temporarily store data, input/output ports and a communication port, in addition to the CPU, although not being illustrated. Signals from various sensors required for operation control of the engine22, for example, a crank angle θcr from a crank position sensor23configured to detect the rotational position of a crankshaft26, are input into the engine ECU24via the input port. Various control signals for operation control of the engine22are output from the engine ECU24via the output port. The various control signals include, for example, a driving signal to a fuel injection valve, a driving signal to a throttle motor configured to regulate the position of a throttle valve, and a control signal to an ignition coil integrated with an igniter. The engine ECU24is connected with the HVECU70via the respective communication ports. This engine ECU24operates and controls the engine22, in response to control signals from the HVECU70. The engine ECU24also outputs data regarding the operating conditions of the engine22to the HVECU70as needed basis.

The engine ECU24calculates a rotation speed of the crankshaft26, i.e., a rotation speed Ne of the engine22, based on the crank angle θcr.

The planetary gear30is configured as a single pinion-type planetary gear mechanism. The planetary gear30includes a sun gear that is connected with a rotor of the motor MG1. The planetary gear30also includes a ring gear that is connected with a driveshaft36which is coupled with drive wheels38aand38bvia a differential gear37. The planetary gear30further includes a carrier that is connected with the crankshaft26of the engine22.

The motor MG1is configured as a synchronous generator motor including a rotor with permanent magnets embedded therein and a stator with three-phase coils wound thereon. The rotor of this motor MG1is connected with the sun gear of the planetary gear30as described above. The motor MG2is also configured as a synchronous generator motor like the motor MG1. A rotor of this motor MG2is connected with the driveshaft36.

As shown inFIG. 1andFIG. 2, the inverter41is connected with first power lines46. This inverter41includes six transistors T11to T16and six diodes D11to D16. The transistors T11to T16are arranged in pairs, such that two transistors in each pair respectively serve as a source and a sink relative to a positive bus bar and a negative bus bar of the first power lines46. The six diodes D11to D16are connected in parallel to and in a reverse direction to the respective corresponding transistors T11to T16. The respective phases of the three-phase coils (U phase, V phase and W phase) of the motor MG1are connected with connection points of the respective pairs of the transistors T11to T16. When a voltage is applied to the inverter41, a motor electronic control unit (hereinafter referred to as motor ECU)40serves to regulate the rates of ON times of the respective pairs of the transistors T11to T16, such as to provide a rotating magnetic field in the three-phase coils and thereby rotate and drive the motor MG1.

Like the inverter41, the inverter42includes six transistors T21to T26and six diodes D21to D26. When a voltage is applied to the inverter42, the motor ECU40serves to regulate the rates of ON times of the respective pairs of the transistors T21to T26, such as to provide a rotating magnetic field in the three-phase coils and thereby rotate and drive the motor MG2.

The first boost converter54is connected with the first power lines46which the inverters41and42are connected with, as well as with second power lines47which the first battery50is connected with. This first boost converter54includes two transistors T31and T32, two diodes D31and D32and a reactor L1. The transistor T31is connected with the positive bus bar of the first power lines46. The transistor T32is connected with the transistor T31and with negative bus bars of the first power lines46and the second power lines47. The two diodes D31and D32are connected in parallel to and in a reverse direction to the respective corresponding transistors T31and T32. The reactor L1is connected with a connection point Cn1of the transistors T31and T32and with a positive bus bar of the second power lines47. The motor ECU40regulates the rates of ON times of the respective transistors T31and T32, so that the first boost converter54steps up the voltage of an electric power of the second power lines47and supplies the electric power of the stepped-up voltage to the first power lines46, while stepping down the voltage of an electric power of the first power lines46and supplying the electric power of the stepped-down voltage to the second power lines47.

The second boost converter55is connected with the first power lines46, as well as with third power lines48which the second battery51is connected with. Like the first boost converter54, the second boost converter55includes two transistors T41and T42, two diodes D41and D42and a reactor L2. The motor ECU40regulates the rates of ON times of the respective transistors T41and T42, so that the second boost converter55steps up the voltage of an electric power of the third power lines48and supplies the electric power of the stepped-up voltage to the first power lines46, while stepping down the voltage of the electric power of the first power lines46and supplying the electric power of the stepped-down voltage to the third power lines48.

A capacitor46afor smoothing is mounted to the positive bus bar and the negative bus bar of the first power lines46. A capacitor47afor smoothing is mounted to the positive bus bar and the negative bus bar of the second power lines47. A capacitor48afor smoothing is mounted to a positive bus bar and a negative bus bar of the third power lines48.

The motor ECU40is configured as a CPU-based microprocessor and includes a ROM configured to store processing programs, a RAM configured to temporarily store data, input/output ports and a communication port, in addition to the CPU, although not being illustrated. Signals from various sensors required for drive control of the motors MG1and MG2and the first and the second boost converters54and55are input into the motor ECU40via the input port. The signals input from the various sensors include, for example, rotational positions θm and θm2from rotational position detection sensors configured to detect the rotational positions of the respective rotors of the motors MG1and MG2and phase currents from current sensors configured to detect electric currents flowing in the respective phases of the motors MG1and MG2. The input signals also include a voltage VH of the capacitor46a(first power lines46) from a voltage sensor46bmounted between terminals of the capacitor46a,a voltage VL1of the capacitor47a(second power lines47) from a voltage sensor47bmounted between terminals of the capacitor47aand a voltage VL2of the capacitor48a(third power lines48) from a voltage sensor48bmounted between terminals of the capacitor48a.The input signals further include an electric current IL1of the reactor L1(hereinafter called first reactor current IL1) from a current sensor54amounted between the connection point Cn1of the transistors T31and T32and the reactor L1in the first boost converter54and an electric current IL2of the reactor L2(hereinafter called second reactor current IL2) from a current sensor55amounted between a connection point Cn2of the transistors T41and T42and the reactor L2in the second boost converter55. Various controls signals for drive control of the motors MG1and MG2and the first and the second boost converters54and55are output from the motor ECU40via the output port. The various control signals include, for example, switching control signals to the transistors T11to T16of the inverter41and to the transistors T21to T26of the inverter42and switching control signals to the transistors T31and T32of the first boost converter54and to the transistors T41and T42of the second boost converter55. The motor ECU40is connected with the HVECU70via the respective communication port. This motor ECU40drives and controls the motors MG1and MG2and the first and the second boost converters54and55, in response to control signals from the HVECU70. The motor ECU40also outputs data regarding the driving conditions of the motors MG1and MG2and the first and the second boost converters54and55to the HVECU70as needed basis. The motor ECU40also calculates rotation speeds Nm1and Nm2of the motors MG1and MG2, based on the rotational positions θm1and θm2of the respective rotors of the motors MG1and MG2.

The first battery50is configured as, for example, a lithium ion rechargeable battery or a nickel metal hydride battery and is connected with the second power lines47as described above. The second battery51is configured as, for example, a lithium ion rechargeable battery or a nickel metal hydride battery and is connected with the third power lines48as described above. The first and the second batteries50and51are under management of a battery electronic control unit (hereinafter referred to as battery ECU)52.

The battery ECU52is configured as a CPU-based microprocessor and includes a ROM configured to store processing programs, a RAM configured to temporarily store data, input/output ports and a communication port, in addition to the CPU, although not being illustrated. Signals from various sensors required for management of the first and the second batteries50and51are input into the battery ECU52via the input port. The signals from the various sensors include, for example, a battery voltage Vb1from a voltage sensor placed between terminals of the first battery50, a battery current Ib1from a current sensor50amounted to an output terminal of the first battery50, and a battery temperature Tb1from a temperature sensor mounted to the first battery50. The input signals also include a battery voltage Vb2from a voltage sensor placed between terminals of the second battery51, a battery current Ib2from a current sensor51amounted to an output terminal of the second battery51, and a battery temperature Tb2from a temperature sensor mounted to the second battery51. The battery ECU52is connected with the HVECU70via the respective communication ports. This battery ECU52outputs data regarding the conditions of the first and the second batteries50and51to the HVECU70as needed basis. The battery ECU52calculates states of charge SOC1and SOC2, based on integrated values of the respective battery currents Ib1and Ib2, with a view to managing the first and the second batteries50and51. The state of charge SOC1or SOC2denotes a ratio of the capacity of electric power dischargeable from the first battery50or from the second battery51at that time to the overall capacity of the first battery50or the overall capacity of the second battery51.

The HVECU70is configured as a CPU-based microprocessor and includes a ROM configured to store processing programs, a RAM configured to temporarily store data, input/output ports and a communication port, in addition to the CPU, although not being illustrated. Signals from various sensors are input into the HVECU70via the input port. The signals from the various sensors include, for example, an ignition signal from an ignition switch80, a shift position SP from a shift position sensor82configured to detect an operating position of a shift lever81, an accelerator position Acc from an accelerator pedal position sensor84configured to detect a depression amount of an accelerator pedal83, a brake pedal position BP from a brake pedal position sensor86configured to detect a depression amount of a brake pedal85, and a vehicle speed V from a vehicle speed sensor88. The HVECU70is connected with the engine ECU24, the motor ECU40and the battery ECU52via the respective communication ports as described above. This HVECU70transmits various control signals and data to and from the engine ECU24, the motor ECU40and the battery ECU52.

The hybrid vehicle20of the embodiment having the above configuration may be driven in a hybrid drive mode (HV drive mode) with operation of the engine22or in an electric drive mode (EV drive mode) with stop of operation of the engine22.

During a drive in the HV drive mode, the HVECU70first sets a required torque Tr* that is required for driving (to be output to the driveshaft36), based on the accelerator position Acc from the accelerator pedal position sensor84and the vehicle speed V from the vehicle speed sensor88. The HVECU70subsequently calculates a driving power Pdrv* that is required for driving by multiplying the set required torque Tr* by a rotation speed Nr of the driveshaft36. The rotation speed Nr of the driveshaft36may be the rotation speed Nm2of the motor MG2or a rotation speed obtained by multiplying the vehicle speed V by a conversion factor. The HVECU70then sets a required power Pe* that is required for the vehicle by subtracting a required charge-discharge power Pb* of the first battery50or the second battery51(which takes a positive value when the first battery50or the second battery51is discharged) from the calculated driving power Pdrv*. The required charge-discharge power Pb* is set based on a difference ΔSOC1or a difference ΔSOC2between the state of charge SOC1of the first battery50or the state of charge SOC2of the second battery51and a target state of charge SOC1* or a target state of charge S0C2*, such as to reduce the absolute value of the difference ΔSOC1or the absolute value of the difference ΔSOC2.

The HVECU70sets a target rotation speed Ne* and a target torque Te* of the engine22and torque commands Tm1* and Tm2* of the motors MG1and MG2, such that the required power Pe* is output from the engine22and that the required torque Tr* is output to the driveshaft36. The HVECU70subsequently sets a target voltage VH* of the first power lines46, based on a target drive point of the motor MG1(defined by the torque command Tm1* and the rotation speed Nm1) and a target drive point of the motor MG2(defined by the torque command Tm2* and the rotation speed Nm2). The HVECU70also sets a distribution ratio Dr. The distribution ratio Dr denotes a ratio of an electric power Pc1that is transmitted between the first battery50and the inverters41and42via the first boost converter54to a sum (Pc1+Pc2) of the electric power Pc1and an electric power Pc2that is transmitted between the second battery51and the inverters41and42via the second boost converter55. According to the embodiment, the distribution ratio Dr is set based on the differences ΔSOC1and ΔSOC2, such that these differences ΔSOC1and ΔSOC2are not significantly different from each other. After setting the distribution ratio Dr, the HVECU70sets a target current IL2* of the second reactor current IL2flowing in the reactor L2of the second boost converter55, based on the set distribution ratio Dr.

The HVECU70sends the target rotation speed Ne* and the target torque Te* of the engine22to the engine ECU24, while sending the torque commands Tm1* and Tm2* of the motors MG1and MG2, the target voltage VH* of the first power lines46and the target current IL2* of the second reactor current IL2to the motor ECU40. The engine ECU24performs intake air flow control, fuel injection control and ignition control of the engine22, such as to operate the engine22with the target rotation speed Ne* and the target torque Te*. The motor ECU40performs switching control of the transistors T11to T16of the inverter41and the transistors T21to T26of the inverter42, such as to drive the motors MG1and MG2with the torque commands Tm1* and Tm2*. In the case of driving the first boost converter54, the motor ECU40performs switching control of the transistors T31and T32of the first boost converter54, such that the voltage VH of the first power lines46is made equal to the target voltage VH*. This control is called voltage control. In the case of driving the second boost converter55, the motor ECU40performs switching control of the transistors T41and T42of the second boost converter55, such that the second reactor current IL2is made equal to the target current IL2*. This control is called current control.

During a drive in the EV drive mode, the HVECU70first sets the required torque Tr*, based on the accelerator position Acc from the accelerator pedal position sensor84and the vehicle speed V from the vehicle speed sensor88. The HVECU70subsequently sets a value0to the torque command Tm1* of the motor MG1and sets the torque command Tm2* of the motor MG2such that the required torque Tr* is output to the driveshaft36. Like during a drive in the HV drive mode, the HVECU70then sets the target voltage VH* of the first power lines46and the target current IL2* of the second reactor current IL2. The HVECU70subsequently sends the torque commands Tm1* and Tm2* of the motors MG1and MG2, the target voltage VH* of the first power lines46and the target current IL1* of the second reactor current IL2to the motor ECU40. The motor ECU40controls the inverters41and42and the first and the second boost converters54and55as described above.

In the hybrid vehicle20of the embodiment, in the state that the motors MG1and MG2are driven with relatively low loads, the motors MG1and MG2may be allowed to be driven with only the transmission of electric power by the first boost converter54without operation of the second boost converter55. In this case, the hybrid vehicle20of the embodiment shuts down the second boost converter55and performs only the voltage control of the first boost converter54. When the loads of the motors MG1and MG2increase and make it difficult to drive the motors MG1and MG2with only the transmission of electric power by the first boost converter54, the hybrid vehicle20of the embodiment cancels the shutdown of the second boost converter55and drives the motors MG1and MG2by ordinary control including both the voltage control of the first boost converter54and the current control of the second boost converter55. The flowchart ofFIG. 3shows one example of a second boost converter shutdown cancelling process performed in this state. This process is repeatedly performed by the motor ECU40in the state that the hybrid vehicle20shuts down the second boost converter55and performs the voltage control of the first boost converter54.

When the second boost converter shutdown cancelling process is triggered, the motor ECU40first determines whether shutdown of the second boost converter55is to be cancelled (step S100). This determination is based on determination of whether it is difficult to drive the motors MG1and MG2with only the transmission of electric power by the first boost converter54and may be, for example, based on determination of whether a drive area of the motors MG1and MG2is in a shutdown area of the second boost converter55that is determined in advance based on the rotation speed Nm1and the torque command Tm1* of the motor MG1and the rotation speed Nm2and the torque command Tm2* of the motor MG2. When it is determined that shutdown of the second boost converter55is not to be cancelled (step S110), the motor ECU40immediately terminates this process.

When it is determined that shutdown of the second boost converter55is to be cancelled (step S110), on the other hand, the motor ECU40determines whether the current control of the first boost converter54is power running control that steps up the voltage of the electric power of the second power lines47and supplies the electric power of the stepped-up voltage to the first power lines46or regenerative control that steps down the voltage of the electric power of the first power lines46and supplies the electric power of the stepped-down voltage to the second power lines47(step S120). When it is determined that the current control of the first boost converter54is the power running control, the motor ECU40performs power running-time single element switching control that switches the transistor T42forming a lower arm of the second boost converter55in the state that the transistor T41forming an upper arm of the second boost converter55is off (step S130), and sets a value1.0to a duty cycle (step S140). The motor ECU40subsequently reduces the duty cycle by a predetermined value ΔD each time until the second reactor current IL2of the reactor L2of the second boost converter55becomes equal to the target current IL2* (steps S150and S160). When the second reactor current IL2becomes equal to the target current IL2*, the motor ECU40changes over the control to the ordinary control including both the voltage control of the first boost converter54and the current control of the second boost converter55(step S210) and terminates this process. The switching of the transistor T42forming the lower arm in the state that the transistor T41forming the upper arm is off during the power running control of the first boost converter54aims to suppress electric current from flowing in the reactor L2of the second boost converter55in a direction of charging the second battery51(i.e., in the regeneration direction) by the voltage of the first power lines46when the transistor T41forming the upper arm is on. This single element switching control causes the electric current gradually increasing from the value0in the power running direction to flow in the reactor L2of the second boost converter55.

When it is determined at step5120that the control of the first boost converter54is the regenerative control, the motor ECU40performs regeneration-time single element switching control that switches the transistor T41forming the upper arm of the second boost converter55in the state that the transistor T42forming the lower arm of the second boost converter55is off (step S170), and sets a value0to the duty cycle (step S180). The motor ECU40subsequently increases the duty cycle by the predetermined value ΔD each time until the second reactor current IL2of the reactor L2of the second boost converter55becomes equal to the target current IL2* (steps S190and S200). When the second reactor current IL2becomes equal to the target current IL2*, the motor ECU40changes over the control to the ordinary control including both the voltage control of the first boost converter54and the current control of the second boost converter55(step S210) and terminates this process. The switching of the transistor T41forming the upper arm in the state that the transistor T42forming the lower arm is off during the regenerative control of the first boost converter54aims to suppress electric current from flowing in the reactor L2of the second boost converter55in a direction of discharging the second battery51(i.e., in the power running direction) by the voltage of the second battery51when the transistor T42forming the lower arm is on. This single element switching control causes the electric current gradually decreasing from the value0in the regeneration direction (i.e., the electric current having the absolute value gradually increasing) to flow in the reactor L2of the second boost converter55.

FIG. 4schematically shows time changes of the duty cycle and the second reactor current IL2of the embodiment and a comparative example when shutdown of the second converter55is cancelled during the power running control of the first boost converter54. In the comparative example, in the process of cancelling shutdown of the second converter55, the duty cycle is set to a value Duty(end) provided at the time of shutdown of the second converter55as an initial value and is subjected to feedback control such that the second reactor current IL2becomes equal to the target current IL2*. In the comparative example, at a control start time T1, the initial value of the duty cycle is set to the value Duty(end) provided at the time of shutdown of the second converter55. This causes the second reactor current IL2to once significantly increase in the negative direction (i.e., in the regeneration direction). The duty cycle is then subjected to feedback control such that the second reactor current IL2becomes equal to the target current IL2*. At a time T3, the second reactor current IL2becomes equal to the target current IL2*. In the embodiment, on the other hand, at the control start time T1, the duty cycle is set to the value1.0. The duty cycle is then reduced by the predetermined value ΔD each time until the second reactor current IL2becomes equal to the target current IL2*. This causes the second reactor current IL2to gradually increase from the value0. At a time T2, the second reactor current IL2becomes equal to the target current IL2*.

FIG. 5schematically shows time changes of the duty cycle and the second reactor current IL2of the embodiment and a comparative example when shutdown of the second converter55is cancelled during the regenerative control of the first boost converter54. The comparative example ofFIG. 5is identical with the comparative example ofFIG. 4. In the comparative example, at a control start time T4, the initial value of the duty cycle is set to the value Duty(end) provided at the time of shutdown of the second converter55. This causes the second reactor current IL2to once significantly increase in the positive direction (i.e., in the power running direction). The duty cycle is then subjected to feedback control such that the second reactor current IL2becomes equal to the target current IL2*. At a time T6, the second reactor current IL2becomes equal to the target current IL2*. In the embodiment, on the other hand, at the control start time T4, the duty cycle is set to the value0. The duty cycle is then increased by the predetermined value ΔD each time until the second reactor current IL2becomes equal to the target current IL2*. This causes the second reactor current IL2to gradually decrease (causes the absolute value of the second reactor current IL2to gradually increase) from the value0. At a time T5, the second reactor current IL2becomes equal to the target current IL2*.

As described above, in the process of cancelling shutdown of the second boost converter55under operation of the first boost converter54with the second boost converter55in the shutdown state, during the power running control of the first boost converter54, the hybrid vehicle20of the embodiment performs the power running-time single element switching control that switches the transistor T42forming the lower arm of the second boost converter55in the state that the transistor T41forming the upper arm is off. The hybrid vehicle20of the embodiment also sets the duty cycle to the value1.0and reduces the duty cycle by the predetermined value ΔD each time until the second reactor current IL2of the reactor L2of the second boost converter55becomes equal to the target current IL2*. This causes the electric current gradually increasing from the value0in the power running direction to the target current IL2* to flow in the reactor L2of the second boost converter55. During the regenerative control of the first boost converter54, on the other hand, the hybrid vehicle20of the embodiment performs the regeneration-time single element switching control that switches the transistor T41forming the upper arm of the second boost converter55in the state that the transistor T42forming the lower arm is off. The hybrid vehicle20of the embodiment also sets the duty cycle to the value0and increases the duty cycle by the predetermined value ΔD each time until the second reactor current IL2of the reactor L2of the second boost converter55becomes equal to the target current IL2*. This causes the electric current gradually decreasing from the value0in the regeneration direction to the target current IL2* (i.e., the electric current having the absolute value gradually increasing) to flow in the reactor L2of the second boost converter55. As a result, these controls suppress an excessive electric current from flowing in the second boost converter55.

The hybrid vehicle20of the embodiment includes the first boost converter54connected with the first power lines46which the inverters41and42of the motors MG1and MG2are connected with, and the second power lines47which the first battery50is connected with, and the second boost converter55connected with the first power lines46and the third power lines48which the second battery51is connected with. As shown inFIG. 6, the present disclosure may also be applied to a hybrid vehicle120of a modification that includes a first boost converter54connected with first power lines46and second power lines47which a battery150is connected with, and a second boost converter55connected with the first power lines46and third power lines48which the battery150is connected with. In other words, the first boost converter54and the second boost converter55may be configured to be connected with a single battery.

The embodiment describes the configuration of the hybrid vehicle20equipped with the engine22, the planetary gear30, the motors MG1and MG2, the first and the second batteries50and51and the first and the second boost converters54and55. The present disclosure may also be applied to a configuration of a one-motor hybrid vehicle that includes an engine, one motor, first and second batteries and first and second boost converters or to another configuration of a one-motor hybrid vehicle that includes an engine, one motor, a single battery and first and second boost converters. The present disclosure may further be applied to a configuration of an electric vehicle that includes a motor, first and second batteries and first and second boost converters without an engine or to another configuration of an electric vehicle that includes a motor, a single battery and first and second boost converters.

In the embodiment or the modification described above, a lithium ion rechargeable battery or a nickel metal hydride battery is employed as the first battery50, the second battery51or the battery150. The first battery50, the second battery51or the battery150may be any power storage device that is chargeable, for example, a capacitor.

In the motor vehicle of the above aspect, in the process of cancelling shutdown of the second converter while the first converter steps up a voltage of an electric power of the second power line and supplies the electric power of the stepped-up voltage to the first power line in the shutdown state of the second converter, the control device may perform the single element switching control to switch one switching element forming a lower arm between the third and the fourth switching elements of the second converter while setting the other switching element forming an upper arm off. This configuration does not set the switching element forming the upper arm in the on position. This suppresses electric current from flowing in the second reactor in a reverse direction (i.e., in a regeneration direction) by the voltage of the first power line and accordingly causes the electric current flowing in the second reactor to increase from the value0in the power running direction. In the motor vehicle of this configuration, the control device may perform the single element switching control to gradually reduce a duty cycle of the second converter from a value1until the electric current flowing in the second reactor becomes equal to the target current. This configuration causes the electric current flowing in the second reactor to gradually increase from the value0in the power running direction to the target current.

In the motor vehicle of the above aspect, in the process of cancelling shutdown of the second converter while the first converter steps down a voltage of an electric power of the first power line and supplies the electric power of the stepped-down voltage to the second power line in the shutdown state of the second converter, the control device may perform the single element switching control to switch one switching element forming an upper arm between the third and the fourth switching elements of the second converter while setting the other switching element forming a lower arm off. This configuration does not set the switching element forming the lower arm in the on position. This suppresses electric current from flowing in the second reactor in a reverse direction (i.e., in a power running direction) by the voltage of the third power line and accordingly causes the electric current flowing in the second reactor to increase from the value0in the regeneration direction. In the motor vehicle of this configuration, the control device may perform the single element switching control to gradually increase a duty cycle of the second converter from a value0until the electric current flowing in the second reactor becomes equal to the target current. This configuration causes the electric current flowing in the second reactor to gradually increase from the value0in the regeneration direction to the target current.

In the motor vehicle of the above aspect, the power storage device may include a first power storage device connected with the second power line, and a second power storage device connected with the third power line. In other words, the first converter and the second converter may be respectively connected with two power storage devices or may be connected with one single power storage device.

The following describes the correspondence relationship between the primary elements of the above embodiment and the primary elements of the disclosure described in Summary. The motor MG2of the embodiment corresponds to the “motor”, the first battery50and the second battery51correspond to the “power storage device”, the first boost converter54corresponds to the “first boost converter”, and the second boost converter55corresponds to the “second boost converter”.

The correspondence relationship between the primary components of the embodiment and the primary components of the present disclosure, regarding which the problem is described in Summary, should not be considered to limit the components of the present disclosure, regarding which the problem is described in Summary, since the embodiment is only illustrative to specifically describes the aspects of the present disclosure, regarding which the problem is described in Summary. In other words, the present disclosure, regarding which the problem is described in Summary, should be interpreted on the basis of the description in Summary, and the embodiment is only a specific example of the present disclosure, regarding which the problem is described in Summary.

The aspect of the present disclosure is described above with reference to the embodiment. The present 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 present disclosure.

INDUSTRIAL APPLICABILITY

The disclosure is applicable to, for example, the manufacturing industries of motor vehicles.