Vehicle power supply unit

Abstract

To make it possible to reduce a circulating current caused by an abnormality in a current sensor when performing external charging using a neutral point charging method.SOLUTION: A vehicle power supply apparatus includes a power conversion device that includes a switching element and a current sensor for each phase of an electric motor for driving. A control device 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 a battery during battery charging. The control device performs feedback control to control the current in each phase of the electric motor by controlling the switching element so that an input current from the external power supply and an output current to the battery are equal during charging. The control device sets the upper limit of the current in each phase on the basis of the maximum value of the input current during charging and limits the current in each phase, which is controlled by the feedback control so that the set upper limit is not exceeded.SELECTED DRAWING: Figure 3

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 battery abnormality determination device. This abnormality determination device determines whether or not a current sensor that detects the battery current has an intermediate value fixation abnormality. This determination is made based on the deviation between the integrated value of the current and the battery voltage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-069686 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. Vehicle power supply devices that use this method may perform the following feedback control of each phase current. This feedback control controls each phase current of the electric motor by controlling the switching elements of a power conversion device so that the input current from the external power source and the output current to the battery are equal.

[0005] If one of the current sensors provided for each phase of the motor experiences an abnormality (sticking abnormality) during external charging, the above feedback control will cause a circulating current to flow between the phases, resulting in a large current concentration in the phase with the abnormal current sensor, causing the temperature of the switching element to rise.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a vehicle power supply device that can reduce circulating current caused by abnormalities in the current sensor when performing external charging using a neutral point charging method. [Means for solving the problem]

[0007] 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, during charging of the battery, power supplied from an external power source via the neutral point of the electric motor is boosted and then supplied to the battery. During charging, the control device performs feedback control to control each phase current of the electric motor by controlling the switching elements so that the input current from the external power source and the output current to the battery are equal. The control device then sets an upper limit value for each phase current based on the maximum value of the input current during charging, and limits each phase current controlled by feedback control so that it does not exceed the set upper limit value.

[0008] The control device may stop charging if, while limiting each phase current by an upper limit value during charging, the absolute value of each phase current exceeds a second overcurrent threshold that is smaller than the first overcurrent threshold used while the vehicle is running.

[0009] The second overcurrent threshold may be a value smaller than the maximum value of the current supplied to each of the coils of the multiple phases to drive the electric motor while the vehicle is running. [Effects of the Invention]

[0010] According to the vehicle power supply device according to the present disclosure, when external charging is performed using the neutral point charging method, it is possible to reduce circulating current caused by an abnormality in the current sensor. [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. 10 is a diagram for explaining a problem that occurs during external charging using a neutral point charging method. [Figure 3] 4 is a flowchart showing a flow of processing during external charging according to an embodiment. [Figure 4] 10 is a diagram for explaining an overcurrent threshold TH2 during charging according to the embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiments of the present disclosure will be described with reference to the accompanying drawings. Elements common to the drawings will be designated by the same reference numerals, and redundant explanations will be omitted or simplified.

[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 respective phase currents Ii, i.e., the currents Iu, Iv, and Iw flowing through the U-phase coil 3U, the V-phase coil 3V, and the 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 the 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. Processing during external charging External charging using the DC charging system 100 starts when it is detected 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).

[0029] 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) and the output current Ib to the battery 14 are equal. This feedback control is achieved by controlling the operation of a pair of switching elements Q1 and Q2 for each phase so that a current that is 1 / 3 of the input current Im flows through each phase. The current values ​​shown in FIG. 1 are examples. If the difference between the input current Im and the output current Ib during external charging becomes large, external charging may be stopped in the DC charging system 100. Therefore, by performing this feedback control to keep this difference small, external charging can be continued appropriately.

[0030] 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.

[0031] Fig. 2 is a diagram for explaining the issues that occur during external charging using the neutral point charging method. Fig. 2 is an enlarged view of the electric motor 2 and the surrounding configuration of the PCU 18 in Fig. 1. If an abnormality occurs in one of the current sensors 20 provided for each phase of the electric motor 2 during external charging, a circulating current will occur between the phases if the above-mentioned feedback control is being performed.

[0032] More specifically, the assumed abnormality here is, for example, a failure (sticking abnormality) in which the output of the current sensor 20 is fixed at a certain value. FIG. 2 shows an example in which the U-phase current sensor 20 has a sticking abnormality. According to the feedback control described above, if the three current sensors 20 are normal, and the input current Im is, for example, 300 A, the switching elements Q1 and Q2 of each phase are controlled so that each of the phase currents Ii (i = u, v, and w) becomes 100 A in order to make the output current Ib 300 A (see FIG. 1). On the other hand, if the U-phase current sensor 20 experiencing the sticking abnormality outputs an incorrect current value that differs from the 100 A current actually flowing through the U-phase, the feedback control treats the value of the U-phase current Iu as the incorrect current value, and controls the switching elements Q1 and Q2 of each phase so that the output current Ib is maintained at a value equal to the input current Im.

[0033] As a result, as shown in Figure 2, V-phase current Iv and W-phase current Iw flow along current routes Rv and Rw. The current values ​​shown in Figure 2 are examples. When such a circulating current occurs, a large current concentrates in the U-phase, which includes the current sensor 20 with the stuck-on abnormality. As a result, the temperature of the U-phase switching elements Q1 and Q2 rises. In addition, the larger the erroneous current value output by the current sensor 20 with the stuck-on abnormality, the larger the circulating current generated as described above.

[0034] In addition, the detection range of current sensor 20 is basically set based on the phase current Ii used during normal vehicle operation. Therefore, the upper limit of the detection range is a large current value, such as 1000 A. Therefore, if a sticking abnormality occurs such that current sensor 20 erroneously outputs the upper limit of the detection range, the circulating current described above will become large.

[0035] In view of the above-mentioned problems, in this embodiment, the control device 16 executes the following process during external charging using the neutral point charging method. Fig. 3 is a flowchart showing the flow of the process during external charging according to this embodiment. The process of this flowchart is executed by, for example, the processor of the control device 16.

[0036] In step S100, control device 16 determines whether an operation to perform external charging using the neutral point charging method has been performed. Specifically, for example, the determination result is Yes when control device 16 detects connection of charging connector 102 to charging inlet 12. As a result, the process proceeds to step S102, and control device 16 sets a charging flag to ON. Note that the charging flag is set to OFF when external charging ends (including when it is completed).

[0037] In step S104 following step S102, the control device 16 sets a current upper limit guard. Specifically, the control device 16 sets an upper limit value Ilmt for each phase current Ii. Then, the control device 16 limits each of the phase currents Ii controlled by feedback control so that the currents Ii do not exceed the set upper limit values ​​Ilmt.

[0038] The upper limit value Ilmt is determined in advance as a value based on the maximum value (maximum current value Imax2) of the input current (charging current) Im. This maximum current value Imax2 is the maximum value within the range of the input current Im used during external charging, and is determined in advance. More specifically, the upper limit value Ilmt corresponds to a value obtained by adding a predetermined margin to a value obtained by dividing the maximum current value Imax2 by the number of phases of the electric motor 2 (e.g., 3). The margin is determined in consideration of various factors that cause variations in the vehicle power supply device 10, such as variations in the circuits that configure the PCU 18. As an example, if the maximum current value Imax2 is 300 A, the upper limit value Ilmt is determined to be, for example, 150 A, by adding, for example, 50 A as a margin to 100 A, which is equivalent to one-third of 300 A.

[0039] In step S106 following step S104, control device 16 selects an overcurrent threshold TH2 (second overcurrent threshold) during charging. The overcurrent threshold here is a value for determining whether an overcurrent occurs in each phase current Ii. In other words, in step S106, upon start of external charging, control device 16 changes the overcurrent threshold from overcurrent threshold TH1 (first overcurrent threshold) used while the vehicle is traveling to overcurrent threshold TH2.

[0040] FIG. 4 is a diagram illustrating the overcurrent threshold TH2 during charging according to the embodiment. The maximum current value Imax1 in FIG. 4 corresponds to the maximum value of the current supplied to each of the three-phase coils 3 to drive the electric motor 2 while the vehicle is running, in other words, the maximum value of the current used to drive the electric motor 2. The maximum current value Imax1 is, for example, 1000 A. As already explained, the maximum current value Imax2 is the maximum value of the input current (charging current) Im, for example, 300 A. In this way, the current usage range differs between when the vehicle is running and when external charging is being performed.

[0041] The overcurrent threshold TH1 used during vehicle running is determined in advance as a value greater than the maximum current value Imax1 by a predetermined amount. On the other hand, the overcurrent threshold TH2 used during charging is determined in advance as a value greater than the maximum current value Imax2 by a predetermined amount and less than the overcurrent threshold TH1. More specifically, the overcurrent threshold TH2 is determined in advance as a value less than the maximum current value Imax1. In addition, the overcurrent threshold TH2 is greater than the upper limit value Ilmt.

[0042] In step S108 following step S106, the control device 16 determines whether the absolute value of each phase current Ii is greater than the overcurrent threshold TH2. If the result of this determination is Yes, the control device 16 determines that an overcurrent is occurring in the phase for which this condition is met, and sets the charging overcurrent flag to ON (step S110). If the result of the determination in step S108 is No, the process proceeds to step S114.

[0043] In step S112 following step S110, the control device 16 stops external charging. That is, the control device 16 transmits a charge stop command to the DC charging system 100.

[0044] In step S114, the control device 16 determines whether external charging has been completed. As a result, if external charging has not been completed (step S114; No), the process returns to step S108. On the other hand, if external charging has been completed (step S114; Yes), the process of this flowchart ends.

[0045] 3.Effects As described above, according to this embodiment, during external charging using the neutral point charging method, the upper limit value Ilmt of each phase current Ii is set based on the maximum current value Imax2 of the input current Im. Then, each phase current Ii controlled by feedback control is limited so as not to exceed the set upper limit value Ilmt.

[0046] As a result, when an abnormality (fixation abnormality) occurs in one of the current sensors 20 corresponding to the three phases, the phase current Ii is prevented from being inappropriately controlled by feedback control influenced by the output of the abnormal current sensor 20. This makes it possible to reduce the circulating current caused by the abnormality of the current sensor 20. Furthermore, because the maximum current value Imax2 of the input current (charging current) Im is determined in advance, the maximum value of each phase current Ii that actually flows when external charging is being performed normally is also determined according to the maximum current value Imax2. Therefore, by determining the upper limit value Ilmt based on the maximum current value Imax2 as in this embodiment, it becomes possible to appropriately determine the upper limit value Ilmt taking into account the magnitude of each phase current Ii that can actually flow.

[0047] Furthermore, according to this embodiment, when the phase current Ii is limited by the upper limit value Ilmt during external charging, if the absolute value of the phase current Ii exceeds an overcurrent threshold TH2, which is smaller than the overcurrent threshold TH1 used during vehicle running, external charging is stopped. As shown in FIG. 4 , the current usage range differs between vehicle running and external charging. Therefore, if the same overcurrent threshold TH1 as used during vehicle running is used during external charging, it becomes difficult to detect an overcurrent because the phase current Ii is limited low by the upper limit value Ilmt. Conversely, if the same overcurrent threshold TH2 as used during external charging is used during vehicle running, an overcurrent may be erroneously determined to be occurring even when an appropriate phase current Ii is flowing. Such an erroneous determination could lead to a vehicle stop. In contrast, according to this embodiment, an overcurrent occurring during external charging can be appropriately determined by using an overcurrent threshold TH2 appropriate for use during external charging. If an overcurrent is detected, external charging is stopped, thereby appropriately protecting components of the PCU 18, such as the switching elements Q1 and Q2. In addition, as shown in Fig. 4, the overcurrent threshold TH2 is a value smaller than the maximum current value Imax1 while the vehicle is running. This also makes it possible to appropriately determine the overcurrent threshold TH2 to be used during external charging.

[0048] 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]

[0049] 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 The control device During the charging, a feedback control is performed to control each phase current of the electric motor by controlling the switching elements so that the input current from the external power supply and the output current to the battery are equal to each other. setting an upper limit value of each phase current based on a maximum value of the input current during the charging, and limiting the phase current controlled by the feedback control so as not to exceed the set upper limit value; When the phase current is limited by the upper limit value during charging, if the absolute value of the phase current exceeds a second overcurrent threshold value that is smaller than a first overcurrent threshold value used while the vehicle is running, the charging is stopped. A vehicle power supply device characterized by:

2. The second overcurrent threshold is a value smaller than a maximum value of a current supplied to each of the coils of the multiple phases to drive the electric motor while the vehicle is running.

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

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