DETERIORATION DETERMINATION DEVICE, AND POWER CONVERSION DEVICE

A deterioration determination device that determines deterioration of a reactor and a smoothing capacitor included in a power conversion device, includes: a storage unit that stores a charge determination value based on a voltage change when the smoothing capacitor with no deterioration is charged by a power source electric power supplied through the reactor with no deterioration; and a calculation unit that determines at least one of the reactor and the smoothing capacitor has deteriorated when the voltage change the smoothing capacitor during charging by the power source electric power supplied through the reactor is larger than the charge determination value.

TECHNICAL FIELD

The disclosure described in this specification relates to a deterioration determination device and a power conversion device.

BACKGROUND

According to a conceivable technique, a capacitor deterioration diagnosis device is known. The capacitor deterioration diagnosis device determines the deterioration of an aluminum electrolytic capacitor based on the humidity of the ambient air around the aluminum electrolytic capacitor included in the inverter device.

SUMMARY

According to an example, a deterioration determination device that determines deterioration of a reactor and a smoothing capacitor included in a power conversion device, may include: a storage unit that stores a charge determination value based on a voltage change when the smoothing capacitor with no deterioration is charged by a power source electric power supplied through the reactor with no deterioration; and a calculation unit that determines at least one of the reactor and the smoothing capacitor has deteriorated when the voltage change the smoothing capacitor during charging by the power source electric power supplied through the reactor is larger than the charge determination value.

DETAILED DESCRIPTION

The technical content in the conceivable technique is specialized for determining the deterioration of an aluminum electrolytic capacitor. Therefore, with the technical content in the conceivable technique, it is difficult to determine the deterioration of other passive elements included in the device that performs electric power conversion.

An object of the present embodiments is to provide a deterioration determination device and a power conversion device capable of determining deterioration of different types of passive elements.

A deterioration determination device according to one aspect of the present embodiments is a deterioration determination device that determines deterioration of a reactor and a smoothing capacitor included in an electric power conversion device.

The deterioration determination device includes:a storage unit that stores a charge determination value based on a voltage change when a smoothing capacitor with no deterioration is charged by a power source electric power supplied through a reactor with no deterioration; anda calculation unit that determines that at least one of the reactor and the smoothing capacitor is deteriorated when the voltage change during charging of the smoothing capacitor by the power source electric power supplied through the reactor is greater than the charge determination value.

A deterioration determination device according to one aspect of the present embodiments is a deterioration determination device that determines deterioration of a reactor and a smoothing capacitor included in an electric power conversion device.

The deterioration determination device includes:a storage unit that stores a charge expectation time expected for completion of charging of the smoothing capacitor with no deterioration by the power source electric power supplied through the reactor with no deterioration; anda calculation unit that determines that at least one of the reactor and the smoothing capacitor is deteriorated when a charging time from a start to an end of charging the smoothing capacitor by the power source electric power supplied through the reactor is shorter than the charge expectation time.

An electric power conversion device according to one aspect of the present embodiments includes:a reactor to which a power source electric power is supplied;a smoothing capacitor charged by the power source electric power supplied through the reactor;a storage unit that stores a charge determination value based on a voltage change when a smoothing capacitor with no deterioration is charged by the power source electric power supplied through the reactor with no deterioration; anda calculation unit that determines that at least one of the reactor and the smoothing capacitor is deteriorated when a voltage change during charging of the smoothing capacitor is higher than the charge determination value.

According to this, it is possible to determine the deterioration of the reactor and the smoothing capacitor. Thus, the deterioration determination of different types of passive elements can be performed.

The reference numerals in parentheses above indicate only a correspondence relationship with the configuration described in the embodiment to be described later, and do not limit the technical range in any way.

The following describe embodiments for carrying out the present disclosure with reference to the drawings. In each embodiment, parts corresponding to the elements described in the preceding embodiments are denoted by the same reference numerals, and redundant explanation may be omitted. When only a part of the configuration is described in each embodiment, another embodiment described previously may be applied to the other parts of the configuration.

When, in each embodiment, it is specifically described that combination of parts is possible, the parts can be combined. In a case where any obstacle does not especially occur in combining the parts of the respective embodiments, it is possible to partially combine the embodiments, the embodiment and the modification, or the modifications even when it is not explicitly described that combination is possible.

First Embodiment

First, an in-vehicle system100will be described based onFIG.1. This in-vehicle system100constitutes a system of an electric vehicle such as an electric car. The in-vehicle system100has a battery200, a system switch300, a power conversion device400, and a motor500.

The in-vehicle system100includes a P bus bar610, an M bus bar620, and an N bus bar630as components for electrically connecting various electrical elements included in the above components. The in-vehicle system100also includes a U busbar641, a V busbar642, and a W busbar643.

Various electrical components included in the battery200, the system switch300, and the power conversion unit400are electrically connected via the P bus bar610, the M bus bar620, and the N bus bar630. Various electrical components included in the power converter400and the motor500are electrically connected via a U busbar641, a V busbar642and a W busbar643.

The in-vehicle system100further includes a plurality of electronic control units (ECUs). The ECUs transmit electric signals to and receive electric signals from each other via a bus wiring. A plurality of ECUs cooperate to control the electric vehicle. The ECUs control the regeneration and power running of the motor500according to a SOC of the battery200. The SOC is an abbreviation for state of charge. The ECU is an abbreviation of electronic control unit.

The battery200has a first battery210and a second battery220. Each of the first battery210and the second battery220has a plurality of battery stacks. A plurality of battery stacks are electrically connected in series or in parallel. A configuration in which at least one of the first battery210and the second battery220has one battery stack can also be adopted.

The battery stack has a plurality of secondary batteries electrically connected in series. As the secondary batteries, a lithium ion secondary battery, a nickel hydrogen secondary battery, an organic radical battery, or the like may be employed.

A P bus bar610is connected to the positive electrode of the first battery210. An M busbar620is connected to the positive electrode of the second battery220. An N busbar630is connected to the negative electrodes of the first battery210and the second battery220.

The negative electrode of the first battery210and the negative electrode of the second battery220are always electrically connected via the N bus bar630. Therefore, the potentials of the negative electrodes of the first battery210and the second battery220are the same.

The system switch300controls energization and cut off between the battery200and the electric power conversion device400. The system switch300has a first SMR310, a second SMR320and a third SMR330. The SMR is an abbreviation for System Main Relay.

Each of the first SMR310, the second SMR320, and the third SMR330is a mechanical switch. The mechanical switch is a normally closed switch that is energized when no control signal is input.

The first SMR310is provided in the P bus bar610. The second SMR320is provided in the M bus bar620. The third SMR330is provided in the N bus bar630.

The first SMR310and the third SMR330control energization and cut-off between the first battery210and the electric power conversion device400. The second SMR320and the third SMR330control energization and cut-off between the second battery220and the electric power conversion device400. The first SMR310and the second SMR320control energization and cut-off between the positive electrode of the first battery210and the positive electrode of the second battery220.

The system switch300has a precharge circuit340in addition to the above components. The precharge circuit340has a charging switch341and a charging resistor342. The charging switch341and the charging resistor342are connected in series to form a series circuit.

In this embodiment, the precharge circuit340is connected in parallel with the third SMR330. The precharge circuit340constitutes a detour path for the third SMR330.

The charge switch341is controlled to be in a cut-off state when the third SMR330is in an energization state. The charge switch341is controlled to be in the energization state when the third SMR330is in the cut-off state. The charging switch341is controlled to be in the energization state when charging the smoothing capacitor440, which will be described later.

The electric power conversion device400performs electric power conversion between the battery200and the motor500. The electric power conversion device400includes a converter401, an inverter402, a physical quantity sensor403and a control board404.

The converter401steps up (boosts) the DC power of the battery200to a voltage level suitable for the power running of the motor500. The inverter402converts the DC power into an AC power. This AC power is supplied to the motor500.

The inverter402converts an AC power generated by a power generation (i.e., regeneration) of the motor500into a DC power. The converter401steps down the DC power to a voltage level suitable for charging the battery200. This stepped-down DC power is supplied to the battery200and various electrical loads.

The physical quantity sensor403detects physical quantities of the converter401and the inverter402. The physical quantities detected by the physical quantity sensor403include, for example, temperature, current, and voltage. The physical quantity sensor403is provided in various electrical components included in the converter401and the inverter402and various busbars described above.

The control board404functions to control the switches included in the converter401and the inverter402between the energization state and the cut-off state. The control board404of this embodiment also has a function of controlling the switches included in the system switch300between the energization state and the cut-off state.

This control board404includes a gate driver405. In this embodiment, the control board404includes one EV ECU406among a plurality of ECUs. In the drawing, the gate driver405is written as GD.

A configuration in which the gate driver405and the EV ECU406are included in separate substrates can also be adopted. In the case of such a configuration, the board including the gate driver405and the board including the EVECU406are electrically connected via a wire harness, for example.

The physical quantity detected by the physical quantity sensor403is input to the control board404. Vehicle conditions are input to the control board404from other ECUs. The EV ECU406generates a control signal for controlling the switch based on various types of input information. This control signal is input to the gate driver405. In the drawing, transmission and reception of electrical signals between the EV ECU406and other ECUs are indicated by an outline white arrows.

The gate driver405amplifies the input control signal. This amplified control signal is input to the switches included in the system switch300, the converter401and the inverter402. As a result, the switch is controlled between the energization state and the cut-off state.

The motor500is connected to an output shaft of an electric vehicle (not shown). The rotation energy of the motor500is transmitted to driving wheels of the electric vehicle via the output shaft. On the contrary, the rotation energy of the driving wheels is transmitted to the motor500via the output shaft.

The motor500is power running by an AC power supplied from the electric power conversion device400. This gives the driving force to the driving wheels. Further, the motor500is regenerated by the rotation energy transmitted from the driving wheels. An AC power generated by this regeneration is converted into a DC power and is stepped down by the electric power conversion device400. This DC power is supplied to the battery200. The DC power is also supplied to various electric loads mounted on the electric vehicle.

A configuration in which the battery200includes a fuel cell may also be adopted. In this case, the AC power generated by regeneration is no longer used for charging battery200.

<Detailed Configuration of Electric Power Conversion Device>

Next, the detailed configuration of the electric power conversion device400will be described. As described above, the electric power conversion device400includes the converter401and the inverter402.

The converter401is electrically connected to the first battery210via the P bus bar610and the N bus bar630. Further, the converter401is electrically connected to the second battery220via the M bus bar620and the N bus bar630. Electrical connection between the converter401and the battery200is controlled by the system switch300.

Further, the inverter402is electrically connected to the converter401via the P bus bar610and the N bus bar630. In addition, the inverter402is electrically connected to the stator coil of the motor500via the U busbar641, the V busbar642, and the W busbar643. Electrical connection between the inverter402and the battery200is controlled by the system switch300. Specifically, the electrical connection state between the inverter402and the second battery220is also controlled by the converter401.

The converter401has a filter capacitor410, a reactor420and an A-phase switch module430. One of the two electrodes of a filter capacitor410is connected to the M bus bar620. The other of the two electrodes of the filter capacitor410is connected to the N bus bar630. The reactor420is provided in the M bus bar620. The A-phase switch module430is connected to the P bus bar610, the M bus bar620, and the N bus bar630, respectively.

The A-phase switch module430has a first switch431and a second switch432. The A-phase switch module430also has a first diode433and a second diode434. These semiconductor elements are covered with a sealing resin.

In this embodiment, n-channel IGBTs are used as the first switch431and the second switch432. As shown inFIG.1, the emitter electrode of the first switch431and the collector electrode of the second switch432are connected. Thereby, the first switch431and the second switch432are electrically connected in series.

Also, the cathode electrode of the first diode433is connected to the collector electrode of the first switch431. An anode electrode of the first diode433is connected to the emitter electrode of the first switch431. As a result, the first diode433is connected in anti-parallel to the first switch431.

Similarly, the cathode electrode of the second diode434is connected to the collector electrode of the second switch432. An anode electrode of the second diode434is connected to the emitter electrode of the second switch432. As a result, the second diode434is connected in anti-parallel to the second switch432.

Terminals are connected to collector electrodes, emitter electrodes, and gate electrodes of the first switch431and the second switch432, respectively. The tips of these terminals are exposed outside the sealing resin. Tips of these terminals are selectively connected to the P bus bar610, the M bus bar620, the N bus bar630and the control board404.

A collector electrode of the first switch431is connected to the P bus bar610. An emitter electrode of the first switch431and a collector electrode of the second switch432are connected to the M busbar620. An emitter electrode of the second switch432is connected to the N busbar630.

Thereby, the first switch431and the second switch432are connected in series in the order from the P bus bar610toward the N bus bar630. The reactor420provided in the M busbar620is connected to a midpoint between the first switch431and the second switch432.

The first SMR310is provided between the connection point of the P bus bar610with the first battery210and the connection point of first switch431with the P bus bar610. The second SMR320is provided between the reactor420and a connection point of the second battery220with the M bus bar620. The third SMR330is provided between the connection point of the N bus bar630with the first battery210and the connection point of second switch432with the N bus bar630. The third SMR330is provided between the connection point of the N bus bar630with the second battery220and the connection point of second switch432with the N bus bar630.

Therefore, when the first SMR310and the third SMR330are in the energization state while the second SMR320is in the cut off state, the electric power source voltage of the first battery210is applied to both ends of the first switch431and the second switch432connected in series. When the second SMR320and the third SMR330are in the energization state while the first SMR310is in the cut off state, the electric power source voltage of the second battery220is applied to both ends of the second switch432.

Gate electrodes of the first switch431and the second switch432are connected to the control substrate404. A control signal is input to this gate electrode. As a result, the first switch431and the second switch432are controlled to be in the energization state and the cut-off state, respectively.

Semiconductors such as Si and wide-gap semiconductors such as SiC can be used as the constituent materials of the semiconductor elements included in the converter401. The constituent material of the semiconductor element may not be particularly limited.

As the first switch431and the second switch432included in this semiconductor element, MOSFETs can be used instead of IGBTs. The type of switch element to be employed may not be particularly limited.

The inverter402has a smoothing capacitor440and a discharge resistor450. The inverter402also has a U-phase switch module461, a V-phase switch module462, and a W-phase switch module463. These various components are electrically connected in parallel between the P bus bar610and the N bus bar630.

The smoothing capacitor440has a larger capacitance than filter capacitor410. When the power conversion device400is used, the smoothing capacitor440becomes in the full charge state. When the power conversion device400is not in use, the smoothing capacitor440becomes in the discharge state.

One of the two electrodes of the smoothing capacitor440is connected to the P bus bar610. The other of the two electrodes of the smoothing capacitor440is connected to the N bus bar630.

The discharge resistor450functions to convert electric charges accumulated in the smoothing capacitor440into heat energy when the power conversion device400is not in use. One end of the discharge resistor450is connected to the P busbar610. The other end of discharge resistor450is connected to N bus bar630.

The smoothing capacitor440and the discharge resistor450are connected to each other via the P bus bar610and the N bus bar630. A closed loop including the smoothing capacitor440and the discharge resistor450is configured. When the power conversion device400is not in use, the charge accumulated in the smoothing capacitor440flows through this closed loop. The charge flowing through this closed loop is converted into heat energy by the discharge resistor450.

Each of the U-phase switch module461to W-phase switch module463has a third switch471and a fourth switch472. Also, each of the U-phase switch module461to the W-phase switch module463has a third diode473and a fourth diode474. These semiconductor elements are covered with a sealing resin.

In this embodiment, n-channel IGBTs are used as the third switch471and the fourth switch472. As shown inFIG.1, the emitter electrode of the third switch471and the collector electrode of the fourth switch472are connected. Thereby, the third switch471and the fourth switch472are electrically connected in series.

Also, the cathode electrode of the third diode473is connected to the collector electrode of the third switch471. An anode electrode of the third diode473is connected to the emitter electrode of the third switch471. As a result, the third diode473is connected in anti-parallel to the third switch471.

Similarly, the cathode electrode of the fourth diode474is connected to the collector electrode of the fourth switch472. An anode electrode of the fourth diode474is connected to the emitter electrode of the fourth switch472. As a result, the fourth diode474is connected in anti-parallel to the fourth switch472.

Terminals are connected to collector electrodes, emitter electrodes, and gate electrodes of the third switch471and the fourth switch472, respectively. The tips of these terminals are exposed outside the sealing resin. Tips of these terminals are selectively connected to the P bus bar610, the N bus bar630, the U bus bar641, the V bus bar642, the W bus bar643and the control board404.

A collector electrode of the third switch471is connected to the P bus bar610. An emitter electrode of the fourth switch472is connected to the N busbar630. Thereby, the third switch471and the fourth switch472are connected in series in the order from the P bus bar610toward the N bus bar630.

In the above described connection configuration, when the first SMR310and the third SMR330are in the energization state while the second SMR320is in the cut off state, the electric power source voltage of the first battery210is applied to both ends of the third switch471and the fourth switch472connected in series. When the second SMR320and the third SMR330are in the energization state while the first SMR310is in the cut off state, the electric power source voltage of the second battery220is applied to both ends of the third switch471and the fourth switch472connected in series.

A midpoint between the third switch471and the fourth switch472of the U-phase switch module461is connected to the U-phase stator coil of the motor500via the U busbar641. A midpoint between the third switch471and the fourth switch472of the V-phase switch module462is connected to the V-phase stator coil of the motor500via the V busbar642. A midpoint between the third switch471and the fourth switch472of the W-phase switch module463is connected to the W-phase stator coil of the motor500via the W busbar643. Thus, the U-phase switch module461to W-phase switch module463are individually connected to the U-phase stator coil to W-phase stator coil of the motor500.

Gate electrodes of the third switch471and the fourth switch472are connected to the control substrate404. Thereby, the energization state and the cut-off state of each of the third switch471and the fourth switch472can be controlled by the control board404.

Here, as the third switch471and the fourth switch472, similarly to the converter401, MOSFETs can be adopted instead of IGBTs. Similar to converter401, a semiconductor such as Si, a wide-gap semiconductor such as SiC, or the like can be used as a constituent material of the semiconductor element included in inverter402. The constituent material of the semiconductor elements included in inverter402and the constituent material of the semiconductor elements included in converter401may be the same or different.

As described above, the physical quantity sensor403detects physical quantities of the converter401and the inverter402. Specifically, physical quantity sensor403detects the voltage of the smoothing capacitor440and the temperature of the reactor420.

The physical quantity sensor403has a voltage sensor provided in the smoothing capacitor440and the P bus bar610. The voltage of the smoothing capacitor440is detected by this voltage sensor.

The physical quantity sensor403has a temperature sensor provided in the reactor420or the switch of the power conversion device400. The temperature sensor detects the temperature of the reactor420.

The physical quantity sensor403may have a current sensor that detects direct current flowing through the P bus bar610and the M bus bar620. The physical quantity sensor403may have a current sensor that detects alternating current flowing through the U busbar641the V busbar642and the W busbar643.

As noted above, the control board404includes the gate driver405and the EV ECU406The EV EU406has a storage unit407and a calculation unit408shown inFIG.1.

The storage unit407is a non-transitory tangible storage medium that non-transitory stores data and programs that can be read by a computer or a processor. The storage unit407includes a volatile memory and a nonvolatile memory. The storage unit407stores various information input to the control board404and processing results of the calculation unit408. The storage unit407stores various programs and various reference values for the calculation unit408to perform calculation process.

The calculation unit408has a processor. The calculation unit408stores various information input to the control board404in the storage unit407. The calculation unit408executes various calculation processes based on the information stored in the storage unit407.

The calculation unit408generates a control signal. This control signal is amplified by the gate driver405. With this control signal, the switches included in system switch300, the converter401, and the inverter402are controlled to be in the energization state and the cut-off state.

When charging the smoothing capacitor440, the EV ECU406controls the first SMR310in the cut-off state and the second SMR320in the energization state. At the same time, the EV ECU406controls the third SMR330in the cut-off state and the charge switch341in the energization state. Then, EV ECU406controls the switches included in the converter401and the inverter402in the cut off state.

As a result, the smoothing capacitor440is charged with the power source electric power supplied from second battery220via the reactor420. In addition to the reactor420, there are the first switch431and the first diode433in the energization path between the positive electrode of the second battery220and the smoothing capacitor440. The EV ECU406may controls the first switch431in the energization state.

For example, when the SOC of the second battery220decreases significantly, the EV ECU406may control the first SMR310in the energization state and controls the second SMR320in the cut off state. As a result, the smoothing capacitor440is charged with the power source electric power supplied from the first battery210.

After charging of the smoothing capacitor440is completed, the EV ECU406switches the third SMR330from the cut-off state to the energization state. Also, the EV ECU406switches the charging switch341from the energization state to the cut-off state. This eliminates the electric power consumption in the charging resistor342. The power source electric power from the second battery220is supplied to various electric loads.

When driving the motor500, the EV ECU406controls the first SMR310in the cut off state and controls the second SMR320in the energization state. At the same time, the EV ECU406controls the third SMR330in the energization state and the charge switch341in the cut off state. the EV ECU406controls the switches included in the converter401and the inverter402to be in the energization state and the cut-off state. Note that the EV ECU406may control the first SMR310in the energization state and control the second SMR320in the cut-off state.

the EV ECU406generates pulse signals as control signals for switches included in the converter401and the inverter402. The EV ECU406adjusts the on-duty ratio and a frequency of this pulse signal. The on-duty ratio and the frequency are determined based on the physical quantity detected by physical quantity sensor403and vehicle information input from other ECUs. This vehicle information includes the rotation angle of the motor500, the target torque of the motor500, the SOC of the battery200, and the like.

When increasing the voltage of the DC power source electric power supplied from the second battery220, the EV ECU406fixes the first switch431of the A-phase switch module430to the cut-off state. At the same time, the EV ECU406sequentially switches the second switch432of the A-phase switch module430between the energization state and the cut off state.

When decreasing the voltage of the supplied DC electric power, the EV ECU406fixes the second switch432of the A-phase switch module430to the cut-off state. At the same time, the EV ECU406sequentially switches the first switch431of the A-phase switch module430between the energization state and the cut off state.

When power running the motor500, the EV ECU406PWM-controls the third switch471and the fourth switch472provided in the U-phase switch module461to the W-phase switch module463, respectively. In this way, three-phase alternating current is generated in the inverter402.

When the motor500generates (or regenerates) the electric power, the EV ECU406stops outputting control signals to the third switch471and the fourth switch472of the U-phase switch module461to the W-phase switch module463, respectively for example. As a result, the AC electric power generated by the motor500passes through the diodes of the U-phase switch module461to the W-phase switch module463. As a result, the AC power is converted to the DC power.

When the smoothing capacitor440is to be discharged after completing the drive control of the motor500, the EV ECU406controls the switches included in the system switch300, the converter401, and the inverter402into the cut off state. As a result, the charge accumulated in the smoothing capacitor440flows through the discharge resistor450. This electric charge is actively converted into heat energy by the discharge resistor450.

When adjusting the SOCs of the first battery210and the second battery220, the EV ECU406controls the first SMR310and the second SMR320into an energization state. At the same time, the EV ECU406controls the third SMR330and the charging switch341into the cut off state. The EV ECU406controls the first switch431in the energization state. Then, the EV ECU406controls the switches included in the converter401and the inverter402in the cut off state.

Thereby, a closed loop including the first battery210and the second battery220is configured. The power source electric power is supplied via the first switch431and the reactor420to from the higher one of the output voltage of the first battery210and the second battery220to the lower one of the output voltage of the first battery210and the second battery220. Although the SOC of one of the first battery210and the second battery220is decreased, the SOC of the other is increased.

In recent years, the driving mileage tends to increase due to automatic driving of electric vehicles. As the output of the motor500mounted on an electric vehicle increases, the voltage level of the power source of the battery200tends to increase. In order to prevent failures from occurring in the power conversion device400used under such circumstances, it may be desired to detect deterioration of electrical components included in the power conversion device400.

The smoothing capacitor440has an insulating resin member including a dielectric member, a positive electrode provided on one surface of the resin member, and a negative electrode provided on the back surface thereof. For example, if a portion of the resin member deteriorates due to heat generation by the energization with a high current, it may become difficult for charges to be stored in the deteriorated portion. As a result, the capacitance of the smoothing capacitor440decreases.

When the capacitance of the smoothing capacitor440is reduced in this way, charging of the smoothing capacitor440may be completed quickly. For example, as shown inFIG.2, the voltage change becomes faster when the smoothing capacitor440is charged.

InFIG.2, the vertical axis indicates voltage and the horizontal axis indicates time. The voltage is denoted by V. The time is denoted by T. A solid line indicates the voltage change of the deteriorated smoothing capacitor440. A dashed line indicates the voltage change of the un-deteriorated smoothing capacitor440.

At time t1 and time t2 shown inFIG.2, the deteriorated smoothing capacitor440and the un-deteriorated smoothing capacitor440have different voltages and different temporal voltage changes (i.e., the voltage changes). The voltage change of the deteriorated smoothing capacitor440during the transitional period (i.e., during charging) from the start to the end of charging is larger than the voltage change of the un-deteriorated smoothing capacitor440.

Further, when the capacitance of the smoothing capacitor440decreases, the smoothing of the voltage by the smoothing capacitor440is deteriorated. For example, as shown inFIG.3, the voltage of the smoothing capacitor440in the full charge state during utilizing the capacitor440may tend to fluctuate over time. During the usage, the voltage change of the deteriorated smoothing capacitor440is greater than the voltage change of the un-deteriorated smoothing capacitor440.

InFIG.3, the vertical axis indicates voltage and the horizontal axis indicates time. The voltage is denoted by V and the time is denoted by T. A voltage change of the smoothing capacitor440that has deteriorated is indicated by a solid line, and a voltage change of the un-deteriorated smoothing capacitor440is indicated by a dashed line.

Note that a case where the smoothing capacitor440is used is a situation where the electric power conversion is performed in the electric power conversion device400by controlling the switching of a plurality of switches included in the power conversion device400between an energization state and a cut-off state. A case where the smoothing capacitor440is used is a situation where the flow direction of the current flowing through the smoothing capacitor440changes on the order of microseconds due to the electric power conversion. This is the time when the charge/discharge of the smoothing capacitor440changes on the order of microseconds due to the electric power conversion.

The reactor420has a winding core and windings. A winding wire is an insulated wire having a conductive wire and an insulating coating film covering the conductive wire. The reactor420is configured by winding this winding around a winding core. The inductance of the reactor420is proportional to the number of turns of this winding.

Due to such a configuration, for example, if the insulating properties of the insulating coating film of the winding are partially deteriorated, the wound winding may partially short-circuit. When such a short circuit occurs, the number of turns of the winding is substantially reduced. As a result, the inductance of the reactor420is reduced.

When the inductance of reactor420decreases in this way, the current flows easily through the reactor420. Therefore, the charging of the smoothing capacitor440with the power source electric power of the second battery220via the reactor420may be completed quickly. As shown inFIG.2, the voltage change becomes faster when the smoothing capacitor440is charged. In addition, due to the partial short circuit, the temperature of the reactor420is likely to increase due to energization.

The calculation unit408of the EV ECU406sequentially acquires the voltage of the smoothing capacitor440from the physical quantity sensor403in order to detect deterioration of the smoothing capacitor440and the reactor420. The calculation unit408calculates the time change (or the voltage change) of the voltage of the smoothing capacitor440.

Further, the calculation unit408sequentially acquires the temperature of the reactor420from the physical quantity sensor403. The calculation unit408calculates the time change (or the temperature change) of the temperature of the reactor420.

The storage unit407of the EV ECU406stores the charge determination value and the smoothing determination value as reference values. The charge determination value is determined based on the voltage change of the smoothing capacitor440when the smoothing capacitor440in the non-deterioration state is charged with the power source electric power of the second battery220via the reactor420in the non-deteriorated state. The smoothing determination value is determined based on the voltage change of the smoothing capacitor440in the non-deteriorated state with full charge when a plurality of switches included in the converter401and the inverter402are controlled to switch.

At least one of the first temperature determination value and the second temperature determination value is stored in the storage unit407as a reference value. The first temperature determination value is determined based on the temperature change of the reactor420in the non-deteriorated state during the energization. The second temperature determination value is determined based on the durable temperature of the reactor420. The EV ECU406corresponds to a deterioration determination device.

The calculation unit408acquires a voltage change of the smoothing capacitor440when the smoothing capacitor440is charged. Then, the calculation unit408determines whether or not the voltage change is higher (or faster) than the charge determination value. If the voltage change is higher than the charge determination value, the calculation unit408determines that at least one of the reactor420and the smoothing capacitor440has deteriorated. When the voltage change is equal to or less than the charge determination value, the calculation unit408determines that the reactor420and the smoothing capacitor440are normal.

As shown inFIG.2, regardless of the deterioration state of the smoothing capacitor440, the voltage change is sharply changed at the start of charging than at the end of charging. The voltage change at time t1 is steeper than the voltage change at time t2. The voltage change is significantly different depending on time.

For this reason, the calculation unit408may calculate, for example, a voltage change at a time when the charging of the smoothing capacitor440is expected to end (i.e., the expectation charge time), and compare the voltage change with the charge determination value.

This expectation charge time is determined based on the time required to charge the smoothing capacitor440in the non-deteriorated state. The expectation charge time is stored in the storage unit407as a reference value. The charge determination value is determined based on the voltage change during this expectation charge time.

Note that the expectation charge time may be the time itself required for charging the smoothing capacitor440in the non-deteriorated state, or may be shorter than that time. The expectation charge time may be, for example, about 9/10 or ⅞ of that time.

The calculation unit408acquires the voltage change of the fully charged smoothing capacitor440while driving the electric power conversion device400. Then, the calculation unit408determines whether or not the voltage change is higher (or faster) than the smoothing determination value. When the voltage change is higher than the smoothing determination value, the calculation unit408determines that the smoothing capacitor440has deteriorated. If the voltage change is equal to or less than the smoothing determination value, the calculation unit408determines that the smoothing capacitor440is normal.

The calculation unit408acquires the temperature change of the reactor420in the energization state. The calculation unit408determines whether the temperature change is higher (or faster) than the first temperature determination value. If the temperature change is higher than the first temperature determination value, the calculation unit408determines that the reactor420has deteriorated. When the temperature change is equal to or less than the first temperature determination value, the calculation unit408determines that the reactor420is normal.

Although not shown, it is assumed that the temperature of the reactor420may increase exponentially and rapidly when the non-energization state changes to the energization state regardless of the deterioration state of the reactor420.

Therefore, for example, when the temperature of the reactor420becomes equal to or higher than a predetermined temperature, the calculation unit408may calculate the temperature change of the reactor420and compare the temperature change with the first temperature determination value. This predetermined temperature is stored in the storage unit407as a reference value.

Note that the calculation unit408may determine whether the temperature of the reactor420is higher than the second temperature determination value. If the temperature is higher than the second temperature determination value, the calculation unit408determines that the reactor420has deteriorated. When the temperature is equal to or less than the second temperature determination value, the calculation unit408determines that the reactor420is normal. The second temperature determination value is a temperature higher than the predetermined temperature.

Next, deterioration determination processing will be described based onFIG.4. When the ignition switch of the electric vehicle is switched from the off state to the on state, the calculation unit408executes deterioration determination processing. The calculation unit408repeatedly executes the deterioration determination process as a cycle task. In addition, the start is indicated by S in the drawings. End is indicated by E.

At step S10, the calculation unit408determines whether or not the smoothing capacitor440is in a charge state. If the smoothing capacitor440is in a charge state, the calculation unit408proceeds to step S20. If the smoothing capacitor440is not in a charge state, the calculation unit408proceeds to step S30.

Note that the calculation unit408controls charging of the smoothing capacitor440When the smoothing capacitor440is being charged, the calculation unit408acquires the charging start time. This charging start time is stored in the storage unit407.

When proceeding to step S20, the calculation unit408acquires the voltage of the smoothing capacitor440from the physical quantity sensor403. At this time, the calculation unit408detects the voltage at different times. Based on these multiple voltages, the calculation unit408calculates the voltage change of the smoothing capacitor440. After this process, in the calculation unit408, the process proceeds to step S40.

Note that the calculation unit408may measure time from the charging start time of the smoothing capacitor440. Then, in step S20, the calculation unit408may calculate a voltage change after the expectation charge time has elapsed from the charging start time.

When proceeding to step S40, the calculation section408determines whether or not the voltage change is greater than the charge determination value stored in the storage unit407. If the voltage change is greater than the charge determination value, the calculation unit408proceeds to step S50. If the voltage change is equal to or less than the charge determination value, the calculation unit408proceeds to step S60.

When proceeding to step S50, the calculation unit408determines that at least one of the reactor420and the smoothing capacitor440has deteriorated. The calculation unit408then stores the deterioration determination in the storage unit407. At the same time, the calculation unit408outputs the deterioration determination to the notification device of the electric vehicle. This notifies the user of the electric vehicle of the deterioration determination. After notification of the deterioration determination, the calculation unit408ends the deterioration determination process.

When proceeding to step S60, the calculation unit408determines that the reactor420and the smoothing capacitor440are normal. The calculation unit408then stores the normal determination in the storage unit407. At the same time, the calculation unit408outputs the normal determination to the notification device. Thereby, the normal determination is notified to the user. After notification of the normal determination, the calculation unit408ends the deterioration determination process.

Retracing the flow, when it is determined in step S10that the smoothing capacitor440is not in a charged state and the process proceeds to step S30, the calculation unit408determines whether or not the power conversion device400is performing electric power conversion. That is, the calculation unit408determines whether or not the switch included in the power conversion device400is controlled to be switched. When the switching is controlled, the calculation unit408proceeds to step S70. If the switching control is not performed, the calculation unit408terminates the deterioration determination process.

When proceeding to step S70, the calculation unit408acquires the voltage of the smoothing capacitor440and the temperature of the reactor420from the physical quantity sensor403. At this time, the calculation unit408detects the voltage and the temperature at different times. Based on this, the calculation unit408calculates the voltage change and the temperature change. After this process, in the calculation unit408, the process proceeds to step S80.

The temperature change may be calculated when the temperature of the reactor420reaches or exceeds a predetermined temperature. Moreover, when the deterioration determination of the reactor420is performed based on the temperature of the reactor420, it may not be necessary to calculate the temperature change.

When proceeding to step S80, the calculation section408determines whether or not the voltage change is greater than the smoothing determination value stored in the storage unit407. If the voltage change is greater than the smoothing determination value, the calculation unit408proceeds to step S90. If the voltage change is equal to or less than the smoothing determination value, the calculation unit408proceeds to step S100.

When proceeding to step S90, the calculation unit408determines that the smoothing capacitor440has deteriorated. Then, the calculation unit408stores the deterioration determination of the smoothing capacitor440in the storage unit407. At the same time, the calculation unit408outputs the deterioration determination of the smoothing capacitor440to the notification device. Thereby, the deterioration determination of the smoothing capacitor440is notified to the user. After this process, in the calculation unit408, the process proceeds to step S110.

When proceeding to step S100, the calculation unit408determines that the smoothing capacitor440is normal. Then, the calculation unit408stores the normal determination of the smoothing capacitor440in the storage unit407. At the same time, the calculation unit408outputs the normal determination of the smoothing capacitor440to the notification device. Thereby, the normal determination of the smoothing capacitor440is notified to the user. After this process, in the calculation unit408, the process proceeds to step S110.

In step S110, the calculation unit408determines whether the temperature change or temperature is greater than the first temperature determination value or the second temperature determination value stored in the storage unit407. When performing the deterioration determination based on the temperature change, the calculation unit408determines whether the temperature change is greater than the first temperature determination value. When performing the deterioration determination based on the temperature, the calculation unit408determines whether the temperature is higher than the second temperature determination value.

When the temperature change and the temperature are collectively referred to as the temperature state, and the first temperature determination value and the second temperature determination value are collectively referred to as the temperature determination value, then in step S110, the calculation unit408determines whether the temperature state of the reactor420is greater (or higher) than the temperature determination value. When the temperature state is larger than the temperature determination value, the calculation unit408proceeds to step S120. If the temperature state is equal to or lower than the temperature determination value, the calculation unit408proceeds to step S130.

When proceeding to step S120, the calculation unit408determines that the reactor420has deteriorated. Then, the calculation unit408stores the deterioration determination of the reactor420in the storage unit407. At the same time, the calculation unit408outputs the deterioration determination of the reactor420to the notification device. Thereby, the deterioration determination of the reactor420is notified to the user. After the deterioration notification of the reactor420, the calculation unit408terminates the deterioration determination process.

Upon proceeding to step S130, the calculation unit408determines that the reactor420is normal. Then, the calculation unit408stores the normal determination of the reactor420in the storage unit407. At the same time, the calculation unit408outputs the normal determination of the reactor420to the notification device. Thereby, the normal determination of the reactor420is notified to the user. After the normal notification of the reactor420, the calculation unit408terminates the deterioration determination process.

The execution order of the state determination processing of the smoothing capacitor440in steps S80to S100and the state determination processing of the reactor420in steps S110to S130may not be particularly limited. The execution order of these two types of state determination processing may be reversed from the execution order shown inFIG.4.

As described above, the smoothing capacitor440is charged when the power conversion device400is not in use. After charging the smoothing capacitor440, the power conversion device400is used. Therefore, after the processing of steps S20and steps S40to S60shown inFIG.4, the processing of steps S30and steps S70to S130is executed. That is, after the combination of deterioration determination of the reactor420and the smoothing capacitor440, the deterioration determination of the reactor420and the deterioration determination of the smoothing capacitor440are performed individually.

Therefore, for example, when the deterioration determination of step S50is performed, it is expected that at least one of step S90and step S120is performed. If the determination of normality in step S60is performed, it is expected that steps S100and S130will each be performed.

If these expectations are not met, the calculation unit408determines that the reliability of the deterioration determination and the normality determination is low. If the reliability of the determination is low, the calculation unit408may output a determination error display to the notification device. This notifies the user of the determination error.

Note that, different from the deterioration determination process shown inFIG.4, the deterioration determination of the reactor420may be performed when the electric power conversion is not being performed in the electric power conversion device400. The deterioration determination of the reactor420can be performed when the current is flowing through the reactor420.

For example, the deterioration determination of the reactor420may be performed after step S50or step S60. The deterioration determination of the reactor420may be performed while the first SMR310and the second SMR320are controlled to be in the energization state in order to adjust the SOC of the first battery210and the SOC of the second battery220.

Then, if it is determined that at least one of the reactor420and the smoothing capacitor440has deteriorated, the calculation unit408may determine the drive restriction of the power conversion device400. The drive restriction is, for example, the limitation of the amount of current energized by the power conversion device400and the limitation of the applied voltage. Further, the calculation unit408may determine to strengthen the cooling performance of the power conversion device400by the cooler.

As described above, if the change in voltage of the smoothing capacitor440during charging is greater than the charge determination value, the calculation unit408determines that at least one of the reactor420and the smoothing capacitor440has deteriorated. Conversely, if the change in voltage of the smoothing capacitor440during charging is equal to or less than the charge determination value, the calculation unit408determines that the reactor420and the smoothing capacitor440are normal.

In this manner, the deterioration determination of the reactor420and the smoothing capacitor440can be performed together only by detecting a voltage change during charging. Thus, the deterioration determination of different types of passive elements can be performed.

When the temperature state of the reactor420in the energization state is higher than the temperature determination value, the calculation unit408determines that the reactor420has deteriorated. When the voltage change of the fully charged smoothing capacitor440during switching control is higher than the smoothing determination value, the calculation unit408determines that the smoothing capacitor440has deteriorated.

In this way, the deterioration of the reactor420and the smoothing capacitor440can be determined individually. Therefore, for example, if the reactor420and the smoothing capacitor440are individually replaceable modules from the power conversion device400, only the failure module can be replaced among these two modules.

Second Embodiment

Next, a second embodiment will be described with reference toFIG.5.

In the first embodiment, the deterioration determination of the reactor420and the smoothing capacitor440is performed based on the voltage change and the charge determination value when the smoothing capacitor440is charged. On the other hand, in the present embodiment, the deterioration determination of the reactor420and the smoothing capacitor440is performed based on the charging time of the smoothing capacitor440.

In this case, the calculation unit408executes the deterioration determination process shown inFIG.5. While the smoothing capacitor440is being charged, the calculation unit408executes steps S210to S230instead of step S40.

As described in the first embodiment, the calculation unit408acquires the voltage of the charged smoothing capacitor440at different times in step S20. Then, the calculation unit408calculates the voltage change. After this process, in the calculation unit408, the process proceeds to step S210.

When proceeding to step S210, the calculation unit408determines whether or not the voltage change has become smaller than a predetermined value. If the voltage change is not smaller than the predetermined value, the calculation unit408repeatedly executes steps S20and S210. The calculation unit408enters a standby state. When the voltage change becomes smaller than the predetermined value because the smoothing capacitor440is close to a fully charged state, the calculation unit408proceeds to step S220.

Note that the predetermined value described above is a value larger than the voltage detection error. The predetermined value is a value for determining whether the smoothing capacitor440is fully charged. The predetermined value is stored in the storage unit407as a reference value.

When proceeding to step S220, the calculation unit408calculates the charging time of the smoothing capacitor440based on the time when the voltage change becomes smaller than a predetermined value and the charging start time of the smoothing capacitor440. After this process, in the calculation unit408, the process proceeds to step S230.

When proceeding to step S230, the calculation unit408determines whether or not the charging time is shorter than the expectation charge time. If the charging time is shorter than the expectation charge time, the calculation unit408proceeds to step S50. If the charging time is equal to or longer than the expectation charge time, the calculation unit408proceeds to step S60.

The power conversion device400according to the present embodiment includes components equivalent to those of the power conversion device400according to the first embodiment. Therefore, it is expected that the power conversion device400of the present embodiment has the same effect as the power conversion device400described in the first embodiment. Therefore, the description will be omitted.

Although the present disclosure has been described in accordance with the embodiment, it is understood that the present disclosure is not limited to the embodiment and the structure. The present disclosure covers various modifications and equivalent arrangements. In addition, while the various elements are shown in various combinations and configurations, which are exemplary, other combinations and configurations, including one or more elements, or one-less element or further, are also within the spirit and scope of the present disclosure.