Vehicle power supply unit

Abstract

To make it possible to appropriately continue external charge while suppressing ripple currents, when an abnormality is detected on one of current sensors corresponding to a plurality of phases.SOLUTION: A vehicle power supply device includes an electric power converting device including switching elements and current sensors corresponding to a plurality of phases of an electric motor for running. A control device controls the electric power converting device so that electric power supplied from an external power supply through a neutral point of the electric motor is boosted and then supplied to a battery. When detecting an abnormality of one of the current sensors corresponding to a plurality of phases during charging, the control device executes ripple suppression control for continuing the charging while controlling the switching elements in normal phases so that ripple currents generated by motion of the other switching elements in the normal phases of the plurality of phases do not exceed a ripple current threshold. The ripple current threshold corresponds to an allowable value of the ripple currents generated by motion of the switching elements in a plurality of phases when no abnormality occurs on any of the current sensors corresponding to the plurality of phases.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a vehicle power supply device that is applied to an externally chargeable vehicle. [Background technology]

[0002] Patent Document 1 discloses a charging system for an electric vehicle. This charging system includes an on-board power conversion device that converts an input voltage supplied from an off-board power conversion device into a charging voltage for an on-board power storage device. To suppress current ripples occurring in the on-board power conversion device, the input voltage supplied to the on-board power conversion device is determined based on the number of operating interleaved phases and the voltage between the positive and negative terminals of the on-board power storage device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-093608 Summary of the Invention [Problem to be solved by the invention]

[0004] One method for externally charging a battery mounted on a vehicle is a neutral point charging method in which an external power source is connected to the neutral point of the electric motor used to drive the vehicle. In a vehicle power supply device that employs this method, if an abnormality is detected in one of the current sensors provided for each phase of the electric motor, external charging can be continued by controlling the switching elements of the power conversion device corresponding to the remaining normal phases. To ensure that such external charging can be continued smoothly, it is necessary to prevent external charging from being stopped due to excessive ripple current.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a vehicle power supply device that can smoothly continue external charging while suppressing ripple current when an abnormality is detected in one of the current sensors corresponding to multiple phases. [Means for solving the problem]

[0006] A vehicle power supply device according to the present disclosure is applied to a vehicle equipped with a traction electric motor having coils for multiple phases. The vehicle power supply device includes a battery, a power conversion device, and a control device. The battery supplies power to the electric motor. The power conversion device is connected in parallel with the battery and includes a switching element and a current sensor for each phase of the electric motor. The control device controls the power conversion device so that power supplied from an external power source via the neutral point of the electric motor is boosted and then supplied to the battery while the battery is being charged. When an abnormality is detected in one of the current sensors corresponding to multiple phases during charging, the control device executes ripple suppression control to continue charging while controlling the switching elements of the remaining normal phases so that ripple currents generated by operation of the switching elements of the remaining normal phases do not exceed a ripple current threshold. The ripple current threshold corresponds to the allowable value of ripple currents generated by operation of the switching elements of the multiple phases when no abnormalities occur in any of the current sensors corresponding to the multiple phases.

[0007] The plurality of phases may be three phases. In the ripple suppression control, the control device may operate the switching elements of two phases corresponding to the normal phases while maintaining a phase difference of 180° between them.

[0008] The allowable value corresponding to the ripple current threshold may be the allowable value of the ripple current generated when the three-phase switching elements are operated with a phase difference of 120° when no abnormality occurs in any of the current sensors corresponding to the three phases.

[0009] If the temperature of a component of the power conversion device exceeds a temperature threshold while ripple suppression control is being performed, the control device may limit the magnitude of the current flowing through each normal phase so that it does not exceed the magnitude of the current flowing through each phase of the multiple phases when no abnormality occurs in any of the current sensors corresponding to the multiple phases. [Effects of the Invention]

[0010] According to the vehicle power supply device according to the present disclosure, when an abnormality is detected in one of the current sensors corresponding to multiple phases, external charging can be continued smoothly while suppressing ripple current. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating an example of the configuration of a vehicle power supply device according to an embodiment; [Figure 2] FIG. 1 is a diagram for explaining a problem that occurs when external charging is performed using a neutral point charging method. [Figure 3] 5A and 5B are diagrams for specifically explaining the operation of the ripple suppression control according to the embodiment. [Figure 4] 4 is a flowchart showing a process related to control during external charging according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0013] 1. Vehicle power supply system configuration FIG. 1 is a diagram that schematically illustrates an example of the configuration of a vehicle power supply device 10 according to an embodiment. The vehicle power supply device 10 is applied to (mounted on) a vehicle 1. The vehicle 1 is a vehicle that can be charged with power from an external power source (external charging). The vehicle 1 is, for example, a battery electric vehicle (BEV). Alternatively, the vehicle 1 may be, for example, a plug-in hybrid electric vehicle (PHEV).

[0014] The vehicle 1 is equipped with a traction motor 2 having multiple phase coils 3. As an example, the motor 2 is a three-phase motor having coils 3 for each phase, i.e., a U-phase coil 3U, a V-phase coil 3V, and a W-phase coil 3W.

[0015] The vehicle power supply device 10 includes a charging inlet 12, a battery 14, a control device 16, and a power conversion device 18.

[0016] One example of the external power source is a direct current (DC) charging system 100. When external charging is performed, the charging inlet 12 is connected to a charging connector 102 of the DC charging system 100. The DC charging system 100 is a charging facility such as a charging station for supplying DC power to the vehicle 1. The battery 14 is, for example, a lithium-ion battery. The battery 14 is charged by DC power supplied from the DC charging system 100 to the charging inlet 12. The vehicle 1 is driven by an electric motor 2 that is driven by power supplied from the battery 14.

[0017] The control device 16 is an electronic control unit (ECU) including a processor and a storage device. The control device 16 executes various types of control. The various types of control include control of the power conversion device 18 for driving the electric motor 2. The various types of control also include control related to external charging, including control of the power conversion device 18. The various types of control may be realized by software processing in which a pre-stored program is executed by a processor, or may be realized by hardware processing using dedicated electronic circuits. The control device 16 is also configured to be able to communicate with the DC charging system 100 via a communication device (not shown).

[0018] The power conversion device 18 is also referred to as a PCU (power control unit) 18. The PCU 18 is connected in parallel to the battery 14. The PCU 18 has a pair of switching elements Q1 and Q2 for each phase of the electric motor 2. Each of the switching elements Q1 and Q2 is, for example, an insulated gate bipolar transistor (IGBT) with an anti-parallel diode D. Alternatively, each of the switching elements Q1 and Q2 may be, for example, a metal oxide semiconductor field effect transistor (MOSFET) made of silicon carbide (SiC). Each of the switching elements Q1 and Q2 is controlled by a gate signal from the control device 16.

[0019] The PCU 18 also has a current sensor 20 for each phase of the electric motor 2. The three current sensors 20 detect the currents Iu, Iv, and Iw flowing through the U-phase coil 3U, V-phase coil 3V, and W-phase coil 3W, respectively. The PCU 18 also has a smoothing capacitor 22. The smoothing capacitor 22 is connected in parallel with the battery 14. The PCU 18 also has a temperature sensor 24 that detects the temperatures of components. The components referred to here are, for example, switching elements Q1 and Q2.

[0020] In the U-phase, a pair of switching elements Q1 and Q2 are connected in series between a power line PL1, which is a power line on the battery 14 side, and a ground line NL. Each of the pair of switching elements Q1 (upper arm) and Q2 (lower arm) is connected in series to one end of a U-phase coil 3U. Similarly, in the V-phase, a pair of switching elements Q1 and Q2 are connected in series between a power line PL1 and a ground line NL, and each of the pair of switching elements Q1 and Q2 is connected in series to one end of a V-phase coil 3V. In the W-phase, a pair of switching elements Q1 and Q2 are connected in series between a power line PL1 and a ground line NL, and each of the pair of switching elements Q1 and Q2 is connected in series to one end of a W-phase coil 3W.

[0021] 1, the U-phase coil 3U, the V-phase coil 3V, and the W-phase coil 3W of the electric motor 2 are connected in a star configuration. That is, the electric motor 2 has a neutral point NP. The neutral point NP is connected to the charging inlet 12 via the power line PL2.

[0022] The vehicle power supply device 10 includes, as an example, five relays 26 to 34. The conduction / disconnection of each of the relays 26 to 34 is controlled by the control device 16. Specifically, the relay 26 is disposed on the power line PL2, and the relay 28 is disposed on the ground line NL between the PCU 18 and the charging inlet 12. The relays 26 and 28 are disconnected when the charging inlet 12 is not connected to the charging connector 102, and are connected when the charging inlet 12 is connected to the charging connector 102. The relay 30 is disposed on the power line PL2 between the relay 26 and a neutral point NP. The relay 32 is disposed on the ground line NL between the relay 28 and the PCU 18. The relay 30 is connected to the power line PL2 when external charging is performed using a neutral point charging method, which will be described later. The relay 32 is connected to the power line PL2 when external charging is performed using a neutral point charging method, which will be described later. The relay 32 is connected to the power line PL3 ... vehicle power supply device 10 also includes a power line PL3. One end of power line PL3 is connected to power line PL2 between relay 26 and relay 30. The other end of power line PL3 is connected to power line PL1 between the positive terminal of battery 14 and smoothing capacitor 22. Relay 34 is disposed on power line PL3. The conduction of relay 34 will be described later.

[0023] In the vehicle power supply device 10, when the electric motor 2 is driven to run the vehicle, the PCU 18 controlled by the control device 16 converts the DC power from the battery 14 into three-phase AC power and supplies it to the electric motor 2. That is, in this case, the PCU 18 functions as an inverter.

[0024] On the other hand, the combination of the coils 3 of each phase of the electric motor 2 having the neutral point NP and the PCU 18 can be used as a boost converter (boost chopper circuit) when external charging is performed.

[0025] Specifically, depending on the specifications of the DC charging system 100 connected to the vehicle power supply device 10, the supply voltage Vs from the DC charging system 100 is not necessarily the same as the voltage Vb (e.g., 800 V) of the battery 14. The supply voltage Vs is, for example, 400 V or 800 V. If the supply voltage Vs is, for example, 400 V, the vehicle power supply device 10 needs to boost the voltage for external charging. In this case, during external charging, the control device 16 controls the PCU 18 so that the power supplied from the external power source via the neutral point NP of the electric motor 2 is boosted and then supplied to the battery 14 (neutral point charging method).

[0026] To realize charging by the neutral point charging method, as described above, the combination of the coil 3 of each phase of the electric motor 2 and the PCU 18 is used as a boost converter. More specifically, in each phase, electromagnetic energy is stored in the coil 3 functioning as a reactor, and the pair of switching elements Q1 and Q2 are controlled to be turned on and off so that the stored electromagnetic energy is supplied to the power line PL1 (boost operation BO). By performing such boost operation BO, when the voltage of the battery 14 is higher than the supply voltage Vs, external charging can be performed without the need for a separate boost converter.

[0027] On the other hand, if the supply voltage Vs is 800 V, external charging can be performed without the need for voltage boosting on the vehicle power supply device 10 side. When voltage boosting is not required in this way, in the vehicle power supply device 10, during external charging, relays 26, 28, and 32 as well as relay 34 are turned on and relay 30 is turned off. This allows power to be supplied from the DC charging system 100 to the battery 14 using the power line PL3.

[0028] 2. Control during external charging External charging using the DC charging system 100 begins upon detecting that the charging connector 102 is connected to the charging inlet 12. During external charging, the control device 16 issues a current command value to the DC charging system 100 via the communication device at predetermined time intervals. The DC charging system 100 outputs a current (input current Im in FIG. 1 ) corresponding to the current command value received from the control device 16 (vehicle 1). More specifically, during external charging, the control device 16 performs feedback control of the phase currents Iu, Iv, and Iw of the electric motor 2 so that the input current Im from the DC charging system 100 (external power source) is equal to the output current Ib to the battery 14. This feedback control is achieved by controlling the operation of a pair of switching elements Q1 and Q2 for each phase so that one-third of the input current Im flows through each phase. The current values ​​shown in FIG. 1 are merely examples. If the difference between the input current Im and the output current Ib during external charging becomes large, the DC charging system 100 may stop external charging. Therefore, by performing the feedback control and keeping the difference small, external charging can be continued appropriately.

[0029] When the state of charge (SOC) of the battery 14 reaches a predetermined value during external charging, or when a preset charging time has elapsed, the control device 16 transmits a charge stop command to the DC charging system 100. As a result, external charging ends.

[0030] If an abnormality is detected in one of the current sensors 20 provided for each phase of the electric motor 2 during external charging using the neutral point charging method described above, it is possible to continue external charging by controlling the switching elements Q1 and Q2 of the PCU 18 corresponding to the remaining normal phases. To ensure smooth continuation of external charging, it is necessary to prevent external charging from being stopped due to excessive ripple current Ir. The ripple current Ir here occurs in the output current (battery current) Ib due to the on / off operation of the switching elements Q1 and Q2 of each phase performed for the boost operation BO during external charging using the neutral point charging method. More specifically, the ripple current Ir also occurs in the current flowing through the ground wire NL from the battery 14 toward the DC charging system 100.

[0031] The above-mentioned problem will be described in more detail with reference to Figures 2(A) and 2(B). First, Figure 2(A) shows the waveform of the carrier wave of each phase when no abnormality occurs in any of the current sensors 20 of each phase, and the ripple current Ir (peak-to-peak value) occurring in the output current (battery current) Ib. This carrier wave is used for switching for the boost operation BO. As a premise, in order to reduce the ripple current Ir occurring with the execution of the boost operation BO, the control device 16 performs an interleaving operation in which the three-phase carrier waves are shifted by 120° from each other, as shown in Figure 2(A). The ripple current threshold THr in Figure 2(A) will be described later.

[0032] Next, Figure 2(B) corresponds to a case where an abnormality occurs in one of the three current sensors 20 (for example, the current sensor 20 of the U phase). Figure 2(B) shows an example in which the interleaving operation using the same 120° phase difference as in the example shown in Figure 2(A) is applied to the carrier waves of normal phases (for example, the V phase and W phase), while external charging continues. In this example, as shown in Figure 2(B), the ripple current Ir cannot be reduced appropriately, and the ripple current Ir exceeds the ripple current threshold THr.

[0033] In view of the above-described problems, in this embodiment, when the control device 16 detects during external charging that an abnormality has occurred in one of the current sensors 20 corresponding to the three phases, the control device 16 executes the following "ripple suppression control." According to this ripple suppression control, the pair of switching elements Q1 and Q2 of the remaining normal phases (i.e., two phases) of the three phases is controlled so that the ripple current Ir generated by the operation of the pair of switching elements Q1 and Q2 does not exceed the ripple current threshold value THr, while the external charging continues.

[0034] The ripple current threshold THr corresponds to the allowable value of the ripple current Ir generated by the operation of the pair of three-phase switching elements Q1 and Q2 when no abnormality occurs in any of the current sensors 20 corresponding to the three phases. More specifically, this allowable value corresponds to the allowable value of the ripple current Ir generated when the pair of three-phase switching elements Q1 and Q2 are operated with a phase difference of 120° relative to each other when no abnormality occurs in any of the current sensors 20 corresponding to the three phases, as shown in FIG. 2A. Such a ripple current threshold THr (allowable value) is set in advance as the upper limit of the ripple current Ir allowed by the design of the vehicle power supply device 10 (in other words, the upper limit of the ripple current Ir during external charging).

[0035] FIG. 3 is a diagram specifically illustrating the operation of ripple suppression control according to the embodiment. In ripple suppression control, the control device 16 controls a pair of switching elements Q1 and Q2 of two phases (e.g., V and W phases) corresponding to normal phases with a phase difference of 180°. In other words, as shown in FIG. 3, an interleaving operation is performed so that the carrier waves of the two phases corresponding to normal phases are shifted by 180° from each other. As a result, the carrier waves of the two normal phases are in opposite phases. This allows external charging to continue while suppressing the ripple current Ir so that it does not exceed the ripple current threshold THr, even if an abnormality occurs in any one of the three current sensors 20. In addition, the above-mentioned feedback control is performed on the currents flowing through the two normal phases so that the input current Im and the output current Ib are equal.

[0036] 4 is a flowchart showing a process related to control during external charging according to the embodiment. The process of this flowchart is started when external charging starts, and is executed by the processor of the control device 16, for example.

[0037] In step S100, the control device 16 determines whether an abnormality has been detected in any one of the three current sensors 20. More specifically, an abnormality in the current sensor 20 here is, for example, a failure in which the output of the current sensor 20 is fixed at a certain value. Note that a known method can be used to detect an abnormality in the current sensor.

[0038] If no abnormality is detected in any of the three current sensors 20 (step S100; No), the process of this flowchart ends. On the other hand, if an abnormality is detected in any one of the three current sensors 20 (step S100; Yes), the process proceeds to step S102.

[0039] In step S102, control device 16 temporarily stops external charging and then executes a predetermined process for identifying the phase in which an abnormality has occurred in current sensor 20. Thereafter, the process proceeds to step S104.

[0040] In step S104, the control device 16 resumes external charging while executing the above-described ripple suppression control. Specifically, as already described, the control device 16 operates a pair of switching elements Q1 and Q2 for two phases corresponding to normal phases with a phase difference of 180°. That is, the phase difference of the carrier waves between the phases in the interleaved operation is changed from 120° assuming three phases to 180° targeting the two normal phases. Then, the process proceeds to step S106.

[0041] In step S106, the control device 16 uses the temperature sensor 24 to determine whether the temperature (component temperature) T of the component of the PCU 18 exceeds a predetermined temperature threshold value THt. The component temperature T is, for example, the temperature of the pair of switching elements Q1 and Q2. As a result, if the component temperature T does not exceed the temperature threshold value THt (step S106; No), the process proceeds to step S110. On the other hand, if the component temperature T exceeds the temperature threshold value THt (step S106; Yes), the process proceeds to step S108.

[0042] In step S108, the control device 16 limits the input current (charging current) Im from the DC charging system 100. Specifically, by limiting the input current Im, the control device 16 limits the magnitude of the current flowing through each normal phase so that it does not exceed (for example, is equal to) the magnitude of the current (each phase current) that flows through each of the three phases when no abnormality occurs in any of the current sensors 20 corresponding to the three phases. More specifically, the control device 16 limits the input current Im by lowering the current command value to the DC charging system 100. Then, the process proceeds to step S110.

[0043] If the input current Im is the same regardless of whether or not the current sensor 20 is abnormal, the following problem may occur when the pair of switching elements Q1 and Q2 of the normal phases (two phases) are operated with a phase difference of 180° by the process of step S104 (see FIG. 3). That is, when the pair of switching elements Q1 and Q2 are operated with a phase difference of 180° in this manner, the current of each phase (current per phase) is larger than when the pair of switching elements Q1 and Q2 are operated with a phase difference of 120° in the case where no abnormality occurs in any of the current sensors 20 corresponding to the three phases (see FIG. 2A). If there is a margin for the component temperature T, the input current Im can be the same as in the normal state even if the current of each phase increases. However, if there is not a margin for the component temperature T, it is desirable to suppress the rise in the component temperature T that accompanies the process of step S104. In this regard, the processes of steps S106 and S108 minimize the number of times the input current Im is limited, and suppress the ripple current Ir while suppressing an excessive rise in the component temperature T that accompanies the process of step S104.

[0044] In step S110, the control device 16 determines whether external charging has been completed. As a result, if external charging has not been completed (step S110; No), the process returns to step S106. On the other hand, if external charging has been completed (step S110; Yes), the process of this flowchart ends.

[0045] In the above-described embodiment, an example has been given of a vehicle power supply device 10 that is applied to a vehicle 1 that is equipped with a traction motor 2 that has a three-phase coil 3. However, the "vehicle power supply device" according to the present disclosure may also be applied to a vehicle that is equipped with a traction motor that has coils for more than three phases. [Explanation of symbols]

[0046] 1 vehicle, 2 electric motor, 3 coil of each phase, 10 vehicle power supply device, 12 charging inlet, 14 battery, 16 control device, 18 power conversion device, 20 current sensor, 22 smoothing capacitor, 24 temperature sensor, 26 to 34 relay, 100 DC charging system, 102 charging connector

Claims

1. A vehicle power supply device applied to a vehicle equipped with a driving motor having a multi-phase coil, a battery that supplies power to the electric motor; a power conversion device connected in parallel with the battery and including a switching element and a current sensor for each phase of the motor; a control device that controls the power conversion device so that power supplied from an external power supply via a neutral point of the electric motor is boosted and then supplied to the battery while the battery is being charged; Equipped with When an abnormality in one of the current sensors corresponding to the plurality of phases is detected during charging, the control device executes ripple suppression control to continue charging while controlling the switching elements of the remaining normal phases so that a ripple current generated by operation of the switching elements of the remaining normal phases among the plurality of phases does not exceed a ripple current threshold value; the ripple current threshold corresponds to an allowable value of a ripple current generated by operation of the switching elements of the plurality of phases when no abnormality occurs in any of the current sensors corresponding to the plurality of phases; The multiple phases are three phases, In the ripple suppression control, the control device operates the switching elements of two phases corresponding to the normal phases while setting a phase difference between them to 180°. A vehicle power supply device characterized by:

2. The allowable value corresponding to the ripple current threshold is an allowable value of a ripple current generated when the switching elements of the three phases are operated with a phase difference of 120° when no abnormality occurs in any of the current sensors corresponding to the three phases.

2. The vehicle power supply device according to claim 1.

3. When the temperature of a component of the power conversion device exceeds a temperature threshold value during execution of the ripple suppression control, the control device limits the magnitude of the current flowing through each of the normal phases so as not to exceed the magnitude of the current flowing through each of the multiple phases when no abnormality occurs in any of the current sensors corresponding to the multiple phases.

3. The vehicle power supply device according to claim 1 or 2.

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