Battery charge system

Abstract

To charge a battery without generating a torque of a motor.SOLUTION: A battery charge system 1 includes: a motor 3 having plural-phase windings 3u to 3w, the motor driving a vehicle; an inverter 4 for converting power distributed between a battery 2 and the motor 3; and a controller 5 for controlling the inverter 4. The system boosts a charger voltage output from a charging stand 16 for charging the battery 2, by using the windings 3u to 3w and the inverter 4, to charge the battery 2 having a voltage higher than the charger voltage. The battery charging system 1 includes a lock mechanism for preventing the rotation shaft of the motor 3 from being fixed while the vehicle is parking-locked.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a battery charging system for charging a battery. [Background technology]

[0002] Currently, while 800V charging stations are beginning to be installed, their adoption rate is low, with 400V charging stations still the norm. BEV is an abbreviation for Battery Electric Vehicle. To charge a BEV equipped with an 800V battery at a 400V charging station, a voltage regulator such as a charging-specific boost converter that converts 400V to 800V is required.

[0003] Patent Document 1 discloses a technology for boosting a charger voltage output from a charging stand using a motor winding and an inverter to charge a battery with a voltage higher than the charger voltage. Hereinafter, the technology disclosed in Patent Document 1 will be simply referred to as the prior art. According to the prior art, it is possible to charge a battery by boosting the voltage of the charging stand (charger) without providing a separate voltage adjustment device such as a boost converter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-51850 Summary of the Invention [Problem to be solved by the invention]

[0005] In the prior art, when charging the battery, the parking brake is applied and the parking lock is released to move the motor rotor to a target position, but depending on the amount of movement, the vehicle may move. Furthermore, in the prior art, the target position is defined as 0 degrees and 180 degrees at the angle θ between the stator and rotor. Note that θ is defined as the electrical angle of the rotor N pole relative to the stator U phase. Therefore, the prior art has the following problems:

[0006] In other words, when the target position is 180 degrees, the torque increases in response to the positional deviation, causing the rotor to move on its own and generating a locking torque. Therefore, even if feedback control is attempted, since the vehicle does not have a torque sensor and torque is estimated from a current sensor and a position sensor, errors in the position sensor will generate torque, and the rotor will continue to rotate, preventing the locking torque from becoming zero. Also, when the target position is 0 degrees, the above problem does not occur while the charging current is small, but a similar problem occurs when the charging current increases.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a battery charging system that can charge a battery without generating torque from a motor. [Means for solving the problem]

[0008] The battery charging system described in claim 1 comprises a motor for driving a vehicle and having multi-phase windings, an inverter for converting the power flowing between a battery and the motor, and a control device for controlling the inverter, and is a system that uses the windings and the inverter to boost a charger voltage output from a charger for charging the battery, thereby charging the battery at a voltage higher than the charger voltage.

[0009] The battery charging system of the above configuration includes a locking mechanism that prevents the motor's rotating shaft from being fixed while the vehicle is in parking lock. This prevents the vehicle from moving while the motor's rotor is rotating, allowing the motor's rotor to move freely and preventing the generation of torque due to misalignment. Therefore, the above configuration allows the battery to be charged without generating torque from the motor. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a battery charging system according to a first embodiment. [Figure 2] FIG. 1 is a diagram illustrating a configuration of a reduction gear that constitutes a locking mechanism according to a first embodiment. [Figure 3] FIG. 1 is a diagram illustrating a schematic configuration of a motor according to a first embodiment. [Figure 4] FIG. 10 is a diagram schematically illustrating an example of waveforms of torques of the motor according to the first embodiment; [Figure 5] FIG. 10 is a diagram showing an example of the relationship between torque and charger current generated when the current vector electrical angle α is 3 degrees according to the first embodiment; [Figure 6] FIG. 10 is a diagram for explaining the charge current dependency of the torque zero stable point according to the first embodiment; [Figure 7] FIG. 1 is a diagram showing an example of a method for determining an input phase and an output phase according to the first embodiment; [Figure 8] FIG. 10 is a diagram illustrating an example of control for rotating the rotor position of the motor to a desired position before starting charging according to the first embodiment. [Figure 9] FIG. 10 is a diagram showing an example of a rotor target electrical angle according to the first embodiment; [Figure 10] FIG. 1 is a diagram showing an example of current distribution of three-phase currents when the q-axis current is zero according to the first embodiment; [Figure 11] FIG. 1 is a diagram illustrating a manner in which the rotor moves to maintain the zero torque stable point in response to the charging current according to the first embodiment. [Figure 12]FIG. 2 is a diagram illustrating a manner in which the rotor moves to maintain the zero torque stable point in response to the charging current according to the first embodiment. [Figure 13] FIG. 1 is a diagram schematically illustrating a flow of processing for preparing for charging according to a first embodiment; [Figure 14] FIG. 10 is a diagram for explaining an example of a method for moving the rotor position according to the first embodiment; [Figure 15] FIG. 1 is a diagram showing an example of waveforms of the charging current, the electrical angle θe, and the torque according to a comparative example. [Figure 16] FIG. 1 is a diagram showing an example of waveforms of a charging current, an electrical angle θe, and a torque according to the first embodiment; [Figure 17] FIG. 2 is a diagram illustrating an example of waveforms of the charging current, the electrical angle θe, and the torque according to a comparative example. [Figure 18] FIG. 2 is a diagram illustrating an example of waveforms of the charging current, the electrical angle θe, and the torque according to the first embodiment. [Figure 19] FIG. 10 is a diagram illustrating a configuration of a battery charging system according to a second embodiment. [Figure 20] FIG. 10 is a diagram showing an example of a specific configuration of a control device according to a second embodiment. [Figure 21] FIG. 10 is a diagram schematically illustrating a flow of processing during charging when current ratio correction is performed according to the second embodiment. [Figure 22] FIG. 1 is a diagram showing a flow of processing during charging when phase switching is performed according to the second embodiment. [Figure 23] FIG. 2 is a diagram illustrating a flow of processing during charging when phase switching is performed according to the second embodiment. [Figure 24] FIG. 10 is a diagram illustrating a configuration of a battery charging system according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, several embodiments will be described with reference to the drawings. Note that substantially the same components in the respective embodiments will be denoted by the same reference numerals, and the description thereof will be omitted. (First embodiment) The first embodiment will be described below with reference to FIGS.

[0012] <Overall structure> As shown in Fig. 1, the battery charging system 1 of this embodiment is a system for charging a battery 2 mounted on a vehicle such as a BEV, and includes a motor 3, an inverter 4, and a control device 5 that controls the inverter 4. The battery 2 supplies DC voltage to the inverter 4 and can be configured as a battery pack in which secondary batteries such as lithium-ion batteries are connected in series in multiple stages. The terminals of the battery 2 are connected to a pair of DC power supply lines 6 and 7. Specifically, the positive electrode of the battery 2 is connected to the DC power supply line 6, and the negative electrode is connected to the DC power supply line 7.

[0013] The motor 3 has multiple phases, specifically three-phase windings 3u, 3v, and 3w, and a neutral point 8 to which one terminal of the windings 3u, 3v, and 3w is connected. In other words, the motor 3 is a star-connected three-phase AC motor. The motor 3 drives the vehicle, that is, it is the driving source for running the vehicle. The inverter 4 is a power conversion device that converts the power flowing between the battery 2 and the motor 3.

[0014] The inverter 4 includes a plurality of capacitors 10a, 10b, an inverter main circuit 11, current sensors 12a, 12b, voltage sensors 13a, 13b, a rotor position sensor 14, a charging relay 15, etc. The positive terminal of capacitor 10a is connected to the DC power supply line 6, and the negative terminal thereof is connected to a node Nm. The positive terminal of capacitor 10b is connected to the node Nm, and the negative terminal thereof is connected to the DC power supply line 7. In other words, the plurality of capacitors 10a, 10b are connected in series between the positive electrode of battery 2 and the negative electrode of battery 2. Node Nm is a node where the plurality of capacitors 10a, 10b are connected to each other, and functions as an intermediate terminal.

[0015] The inverter 4 is a T-type NPC three-level inverter and includes an inverter main circuit 11 made up of switch elements Q1 to Q12. Each of the switch elements Q1 to Q12 is configured using an N-channel MOSFET. Each of the switch elements Q1 to Q12 includes a body diode connected between the drain and source with the source side serving as the anode. Note that the switch elements Q1 to Q12 may also be configured using other semiconductor switching elements, such as IGBTs. The switch elements Q1 to Q6 are connected between DC power supply lines 6 and 7 to form a three-phase full-bridge circuit.

[0016] That is, the drains of the switching elements Q1, Q3, and Q5 are connected to a DC power supply line 6, and the sources of the switching elements Q2, Q4, and Q6 are connected to a DC power supply line 7. The source of the switching element Q1 and the drain of the switching element Q2 are connected to a node Nu. The source of the switching element Q3 and the drain of the switching element Q4 are connected to a node Nv. The source of the switching element Q5 and the drain of the switching element Q6 are connected to a node Nw.

[0017] Node Nu functions as a U-phase output terminal of inverter 4 and is connected to the other terminal of U-phase winding 3u of motor 3. Node Nv functions as a V-phase output terminal of inverter 4 and is connected to the other terminal of V-phase winding 3v of motor 3. Node Nw functions as a W-phase output terminal of inverter 4 and is connected to the other terminal of W-phase winding 3w of motor 3.

[0018] In the above configuration, switch elements Q1, Q3, and Q5 are provided between each of the three-phase windings 3u, 3v, and 3w of the motor 3 and the positive electrode of the battery 2, and correspond to multiple positive-side switch elements. Also, in the above configuration, switch elements Q2, Q4, and Q6 are provided between each of the three-phase windings 3u, 3v, and 3w of the motor 3 and the negative electrode of the battery 2, and correspond to multiple negative-side switch elements. In the following description, switch elements Q1, Q3, and Q5 may be collectively referred to as positive-side switch elements, and switch elements Q2, Q4, and Q6 may be collectively referred to as negative-side switch elements.

[0019] The switch elements Q7 and Q8 are provided so as to be able to open and close between the node Nm and the node Nu. Specifically, the sources of the switch elements Q7 and Q8 are connected together. The drain of the switch element Q7 is connected to the node Nm, and the drain of the switch element Q8 is connected to the node Nu. The switch elements Q9 and Q10 are provided so as to be able to open and close between the node Nm and the node Nv. Specifically, the sources of the switch elements Q9 and Q10 are connected together. The drain of the switch element Q9 is connected to the node Nm, and the drain of the switch element Q10 is connected to the node Nv.

[0020] Switching elements Q11 and Q12 are provided so as to be able to open and close between node Nm and node Nw. Specifically, the sources of switching elements Q11 and Q12 are connected together. The drain of switching element Q11 is connected to node Nm, and the drain of switching element Q12 is connected to node Nw. In the above configuration, switching elements Q7 to Q12 are provided between node Nm and the three-phase windings 3u, 3v, and 3w of motor 3, respectively, and correspond to a plurality of intermediate switching elements. In the following description, switching elements Q7 to Q12 may be collectively referred to as intermediate switching elements.

[0021] The control device 5 is equipped with various functional blocks, and controls the intermediate switch elements, positive side switch elements, and negative side switch elements through the operation of these functional blocks. The control device 5 performs PWM control on the drive of the positive side switch elements and negative side switch elements. PWM is an abbreviation for Pulse Width Modulation. The control device 5 generates switch signals that drive each of the switch elements Q1 to Q12. The switch signals generated by the control device 5 are provided to the gates of the switch elements Q1 to Q12. In this way, the control device 5 controls the on / off of the switch elements Q1 to Q12.

[0022] Current sensor 12a detects the U-phase current of motor 3 and outputs a detection signal corresponding to the detected value Iu to control device 5. Note that in FIG. 1 and other figures, each signal may be indicated by a symbol corresponding to the value represented by the signal. Current sensor 12b detects the V-phase current of motor 3 and outputs a detection signal corresponding to the detected value Iv to control device 5. In this embodiment, the U-phase current and V-phase current of the three-phase current of motor 3 are detected, but it is sufficient to detect the currents of any two of the three phases. Alternatively, a configuration in which all three phase currents are detected may be used.

[0023] Voltage sensor 13a detects the battery voltage, which is the voltage of battery 2. Voltage sensor 13a outputs a detection signal corresponding to the detected value VH of the battery voltage to control device 5. Voltage sensor 13b detects the voltage between node Nm and the negative electrode of battery 2, that is, the intermediate terminal voltage, which is the voltage across capacitor 10b. Voltage sensor 13b outputs a detection signal corresponding to the detected value VL of the intermediate terminal voltage to control device 5.

[0024] Rotor position sensor 14 detects the rotation angle of motor 3, specifically the mechanical angle, and outputs a detection signal corresponding to the detected value θm to control device 5. Control device 5 can detect the electrical angle θe based on the detected value θm of rotor position sensor 14. Battery charging system 1 is configured such that inverter 4 is connected to current-output charging stand 16, which is equipment provided outside the vehicle, and that windings 3u, 3v, 3w of motor 3 and inverter 4 are used to boost the charger voltage output from charging stand 16 and charge battery 2, which has a voltage higher than the charger voltage.

[0025] Charging relay 15 is provided to connect charging stand 16 to inverter 4. Contact 15a of charging relay 15 is provided so as to be able to open and close between one output terminal of charging stand 16 and node Nm. Contact 15b of charging relay 15 is provided so as to be able to open and close between the other output terminal of charging stand 16 and DC power line 7.

[0026] In the above configuration, charging stand 16 functions as a charger for charging battery 2. Also, in the above configuration, charging relay 15 functions as a connection part that can connect charging stand 16 for charging battery 2 to node Nm. In inverter 4 configured as above, contacts 15a and 15b of charging relay 15 are closed when charging stand 16 is connected.

[0027] <Lock mechanism configuration> The battery charging system 1 is provided with a locking mechanism that prevents the rotation shaft of the motor 3 from being fixed while the vehicle is in a parking lock state. As shown in Fig. 2, the locking mechanism 21 is configured with a reduction gear 22 including a planetary gear 22b. The reduction gear 22 includes a sun gear 22a connected to a motor shaft that is the shaft of the motor 3, a planetary gear 22b connected to the drive system of the vehicle, i.e., an axle that is the shaft of the vehicle, and a ring gear 22c. In this embodiment, the battery 2 is charged when the vehicle is in a parking range for parking.

[0028] The reduction gear 22 configured as described above has a configuration in which the ring gear 22c is fixed when in the drive range in which the vehicle is driven. Furthermore, the reduction gear 22 configured as described above has a fixed planetary gear 22b when in the parking range, that is, when the vehicle is parked and the battery 2 is being charged. Note that in FIG. 2, the parking range is abbreviated as P range, and the drive range is abbreviated as D range. That is, when the vehicle is parked and the battery 2 is being charged, the reduction gear 22 configured as described above has a locked position for the planetary gear 22b and a free position for the sun gear 22a. With this configuration, the rotor of the motor 3 is free while the battery 2 is being charged.

[0029] <Controller function> The control device 5 includes, as part of its functional blocks, a voltage control unit 17 and a phase current control unit 18. The voltage control unit 17 controls the voltage of the node Nm to be within the range of the output voltage of the charging stand 16 by stepping down the voltage of the battery 2. The control device 5 receives an intermediate terminal voltage command representing a command value VL* of the intermediate terminal voltage transmitted from a higher-level ECU (not shown).

[0030] Voltage control unit 17 controls the voltage of node Nm, i.e., the intermediate terminal voltage, based on the intermediate terminal voltage command. Phase current control unit 18 determines one input phase and two output phases from the three phases through which the current from charging stand 16 is passed to motor 3. Phase current control unit 18 can also control the current ratio, which is the ratio of currents flowing through the two output phases other than the input phase out of the three phases.

[0031] The voltage control unit 17 performs calculations to control the voltage of the node Nm within the output voltage range of the charging stand 16. When controlling the current ratio, the phase current control unit 18 executes the following control. That is, the phase current control unit 18 calculates three-phase currents by performing coordinate transformation using the electrical angle when the rotation of the motor 3 stops and the d-axis current value and the q-axis current value at which the torque of the motor 3 is equal to or less than a predetermined threshold torque. The phase current control unit 18 determines, as the input phase, the phase corresponding to the maximum current value, which is the maximum absolute value among the calculated current values, which are the values ​​of the currents of the three phases calculated. In the following description, the phase corresponding to the maximum current value among the calculated current values ​​may be referred to as the maximum absolute value phase.

[0032] The phase current control unit 18 calculates the current ratio of the output phases (the two phases other than the input phase) by dividing each of the calculated current values ​​of the three phases by the maximum current value, and sets the result of multiplying the current ratio by the calculation result of the voltage control unit 17 as the current command for the three phases. In this case, the threshold torque is set to a value lower than the holding force of the parking brake provided on the vehicle. In this case, the phase current control unit 18 performs coordinate transformation with the value of the q-axis current set to 0.

[0033] When charging the battery 2 by boosting the charger voltage, the control device 5 controls the switch elements of the input phase, which is one of the three phases, and the output phase, which is one of the two phases other than the input phase, as follows: The control device 5 fixes the middle switch element corresponding to the input phase to on, fixes the positive and negative switch elements corresponding to the input phase and the middle switch element corresponding to the output phase to off, and then controls the on / off of the positive and negative switch elements corresponding to the output phase, thereby charging the battery 2.

[0034] For example, when the input phase is the W phase and the output phases are the U phase and the V phase, the switch elements Q11 and Q12 are fixed on, and the switch elements Q5 to Q10 are fixed off, and the on / off of the switch elements Q1 to Q4 is PWM controlled to charge the battery 2.

[0035] In order to solve the problems in the conventional technology, the control device 5 is configured to execute a unique control described below. Prior to describing the various controls by the control device 5, the problems in the conventional technology will be described in detail with reference to Figures 3 to 6. However, as shown in Figure 3 etc., the electrical angle of the N pole in the magnet that constitutes the rotor 31 relative to the U phase of the stator of the motor 3, that is, the position of the d-axis in the magnet 32 ​​that constitutes the rotor 31 of the motor 3 relative to the U phase, is defined as θe, and the current phase, which is the position of the current vector relative to the d-axis, is defined as α.

[0036] Furthermore, in this specification, the position of the d-axis may be referred to as the rotor electrical angle, and the current phase may be referred to as the current vector electrical angle or simply as the electrical angle. Furthermore, in Figure 4 and other figures, the vertical axis represents torque, and the horizontal axis represents the current vector electrical angle α. Also, in Figure 4 and other figures, the dotted line represents magnet torque Ta, the dashed-dotted line represents reluctance torque Tb, and the solid line represents torque Tc, which is the sum of Ta and Tb. As shown in Figure 4, if the q-axis current Iq is zero, that is, if α = 0 degrees or α = 180 degrees, then torque Tc is zero.

[0037] However, if the detected value of rotor electrical angle θe deviates by 3 degrees from the actual true value due to position sensor error, i.e., error in rotor position sensor 14, mechanical play, etc., the d-axis will deviate by 3 degrees. Therefore, even if the current vector electrical angle α is set to zero (α=0 degrees) for the detected value of rotor electrical angle θe, the electrical angle α with respect to the actual d-axis will be 3 degrees. The torque generated when "α=3 degrees" increases in accordance with the current of charging stand 16, which is a charger, i.e., the charger current, as shown in FIG. 5, for example. Note that in this specification, the charger current may be referred to as the charging current.

[0038] Furthermore, the zero-torque stable point, which is the rotor position where torque is stable at zero, depends on the charging current. When the electrical angle α is 180 degrees, as shown in Figure 6, torque increases with position misalignment regardless of whether the charging current is 50 A, 100 A, or 400 A. In other words, since the torque / electrical angle slopes downward to the right in this case, if the actual rotor position advances due to a position sensor error, the current phase lags more than expected, generating positive torque. As a result, the rotor advances, further increasing the positive torque. Note that in Figure 6 and other figures, this rotor position where torque increases with position misalignment is referred to as the zero-torque unstable point. In other words, regardless of the magnitude of the charging current, the zero-torque unstable point occurs when the electrical angle α is 180 degrees.

[0039] On the other hand, when the electrical angle α is 0 degrees and the charging current is a relatively small value such as 50 A, as shown in the left diagram of Fig. 6, the torque / electrical angle slopes upward to the right, meaning that if the actual rotor position is leading due to a position sensor error, the current phase lags behind more than expected, generating negative torque, which in turn causes the rotor to move in the direction of decreasing torque and reducing the error torque. In other words, when the charging current is a relatively small value, the zero torque stable point occurs when the electrical angle α is 0 degrees.

[0040] However, even when the electrical angle α is 0 degrees, as shown in the center and right diagrams of Figure 6, when the charging current becomes relatively large, such as 100 A or 400 A, the effect of reluctance torque causes the torque / electrical angle curve to reverse and slope downward to the right, resulting in a state in which the torque increases in the direction of rotor displacement as the rotor position shifts. In other words, when the charging current is relatively large, the zero torque unstable point occurs when the electrical angle α is 0 degrees. Note that when the charging current is 100 A, the zero torque stable point occurs when the electrical angle α is 60 degrees or -55 degrees. Also, when the charging current is 400 A, the zero torque stable point occurs when the electrical angle α is 80 degrees or -80 degrees.

[0041] Next, the content of control specific to the control device 5 of this embodiment will be described. The control device 5 detects the rotor position of the motor 3 while the vehicle is stopped, and determines the input phase and output phase based on the detection result. Specifically, the control device 5 determines the input phase and output phase so that the current phase α during charging of the battery 2 falls within a range in which it can assume a value of 0 degrees. More specifically, the control device 5 determines the input phase and output phase as shown in FIG. 7.

[0042] That is, when the rotor electrical angle θe is between 0 degrees and 60 degrees or between 300 degrees and 360 degrees, the control device 5 sets the input phase to the U phase and the output phases to the V phase and W phase. When the rotor electrical angle θe is between 60 degrees and 180 degrees, the control device 5 sets the input phase to the U phase and the output phases to the W phase and U phase. When the rotor electrical angle θe is between 180 degrees and 300 degrees, the control device 5 sets the input phase to the W phase and the output phases to the U phase and V phase.

[0043] Before charging of the battery 2 begins, the control device 5 executes control to align the d-axis of the magnet 32 ​​constituting the rotor 31 of the motor 3 with the input phase based on the results of determining the input phase and output phase. In other words, the control device 5 executes control to rotate the rotor position, which is the position of the rotor 31 of the motor 3, to a desired position before charging begins. The desired position, i.e., the target electrical angle of the rotor 31, is the position where the rotor electrical angle θe is 0 degrees as shown in the left diagram of FIG. 8, the position where the rotor electrical angle θe is 120 degrees as shown in the center diagram of FIG. 8, and the position where the rotor electrical angle θe is 240 degrees as shown in the right diagram of FIG. 8, etc. Note that in FIG. 8 and other figures, the electromagnet generated by the motor current is indicated by the reference numeral 33.

[0044] Specifically, the control device 5 determines the target electrical angle α of the rotor 31, i.e., the best initial position of the rotor 31, based on the detected rotor electrical angle θe, which is the detected value of the rotor electrical angle θe, as shown in Fig. 9. That is, the control device 5 sets the target electrical angle α to 0 degrees when the detected rotor electrical angle θe is between 0 degrees and 60 degrees or between 300 degrees and 360 degrees. Furthermore, the control device 5 sets the target electrical angle α to 120 degrees when the detected rotor electrical angle θe is between 60 degrees and 180 degrees. Furthermore, the control device 5 sets the target electrical angle α to 240 degrees when the rotor electrical angle θe is between 180 degrees and 300 degrees.

[0045] 10 shows the current distribution of the three-phase currents Iu, Iv, and Iw when the q-axis current Iq=0, that is, when only the d-axis current Id>0 exists. As is clear from FIGS. 8 and 10, when the rotor electrical angle θe is 0, 120, or 240 degrees, the current vector electrical angle α=0, and the currents of the two output phases are equalized, enabling increased output. For this reason, the control device 5 may perform feedback control of the current ratio so that the current ratio, which is the ratio of the currents of the two output phases while the battery 2 is being charged, is equalized.

[0046] In this embodiment, the control device 5 increases the charging current, which is the current that flows during charging, through feedback control with a fixed output charge ratio, without feedback of the output current ratio relative to the rotor position. In this manner, the rotor 31 of the motor 3 moves automatically to maintain the zero torque stable point, as shown in Figures 11 and 12. The upper diagrams in Figures 11 and 12 are diagrams that schematically show examples of motor torque waveforms, and the upward arrows in Figures 11 and 12 represent the current vector electrical angle α corresponding to the rotor position at that time. The lower diagrams in Figures 11 and 12 are diagrams that schematically show the motor configuration.

[0047] As shown in the left diagrams of Figures 11 and 12, when the charging current is 50 A, the current vector electrical angle α is 0 degrees, and the rotor 31 moves to the zero torque stable point. As shown in the center diagrams of Figures 11 and 12, when the charging current is 100 A, the current vector electrical angle α is 60 degrees or -55 degrees, and the rotor 31 moves to the zero torque stable point. As shown in the right diagrams of Figures 11 and 12, when the charging current is 400 A, the current vector electrical angle α is 80 degrees or -80 degrees, and the rotor 31 moves to the zero torque stable point.

[0048] Next, the operation of the above configuration will be described. The processing performed by control device 5 before starting charging of battery 2, that is, the flow of the charging preparation processing, is shown in a flowchart in Figure 13. As shown in Figure 13, in step S101, the rotor position is detected based on the detection value θm of rotor position sensor 14. In step S102, the input phase and output phase are determined based on the rotor position detection result. In step S103, control is executed to rotate rotor 31 so that the rotor position becomes the target electrical angle. After step S103 is executed, the charging preparation processing performed before starting charging is completed.

[0049] As the specific content of the process of step S103, that is, the control for rotating the rotor 31 so that the rotor position becomes the target electrical angle, for example, one of the following two control examples can be adopted: In the first control example, the output voltage pulse is gradually changed from the duty ratio of the detected electrical angle to the duty ratio of the nearest target electrical angle, thereby making the rotor position become the target electrical angle.

[0050] The nearest target electrical angle is the electrical angle that has the smallest difference from the detected electrical angle among multiple target electrical angles, i.e., target electrical angles of 0, 120, and 240 degrees. For example, as shown in FIG. 14, when the detected electrical angle is 165 degrees, the target electrical angle of 120 degrees is the nearest target electrical angle. In the second control example, the duty ratio of the nearest target electrical angle is output as an output voltage pulse for a short period of time, thereby setting the rotor position to the target electrical angle. In both of these control examples, it is desirable to set the duty ratio sufficiently small, that is, to avoid excessive current flow.

[0051] According to the present embodiment described above, the following effects can be obtained. The battery charging system 1 of this embodiment includes a locking mechanism 21 that prevents the rotating shaft of the motor 3 from being fixed while the vehicle is in parking lock. As a result, in the configuration of this embodiment, the vehicle does not move when the rotor 31 of the motor 3 rotates, so the position of the rotor 31 of the motor 3 can be freely moved and no positional deviation torque is generated. Therefore, with the configuration of this embodiment, the battery 2 can be charged without generating torque from the motor 3.

[0052] The effects obtained by this embodiment become clearer when compared with a comparative example corresponding to the prior art. Figures 15 and 16 show the results of a simulation under the following conditions. <Condition> Input phase → U phase Output phase → V phase and W phase (current ratio is "1:1") Initial electrical angle α → 0 degrees When the angle is off by 3 degrees (initial position θe = 3 degrees)

[0053] As shown in Figure 15, in the comparative example, the rotor is fixed in the initial position, so rotor 31 does not move in response to changes in the charging current, but torque is generated. In contrast, as shown in Figure 16, in the present embodiment, rotor 31 is free, so rotor 31 moves freely in response to changes in the charging current, and as a result, torque is suppressed.

[0054] 17 and 18 show the simulation results under the following conditions. <Condition> Input phase → U phase Output phase → V phase and W phase (current ratio is "1:1") Initial electrical angle α → 180 degrees When the angle is off by 3 degrees (initial position θe = 177 degrees)

[0055] As shown in Figure 17, in the comparative example, the rotor is fixed in the initial position, so rotor 31 does not move in response to changes in the charging current, but torque is generated. In contrast, as shown in Figure 18, in the present embodiment, rotor 31 is free, so rotor 31 moves freely in response to changes in the charging current, and as a result, torque is suppressed.

[0056] In this embodiment, the control device 5 detects the position of the rotor 31 of the motor 3 while the vehicle is stopped and determines the input phase and output phase based on the detection result. In this way, movement toward the optimal rotor position can be reduced. Furthermore, before starting charging of the battery 2, the control device 5 executes control to align the d-axis of the magnet 32 ​​constituting the rotor 31 of the motor 3 with the input phase based on the result of determining the input phase and output phase. In this way, the current vector electrical angle α becomes 0 degrees, the currents of the two output phases become equal, and output can be increased while movement toward the optimal rotor position can be reduced.

[0057] Furthermore, the control device 5 increases the charging current, which is the current that flows during charging, through feedback control with the output charge ratio fixed, without feedback of the output current ratio relative to the rotor position. In this way, the motor 3 operates to automatically maintain the zero torque stable point, which eliminates the influence of position errors and makes it possible to adjust the current balance.

[0058] (Second embodiment) The second embodiment will be described below with reference to FIGS. 19, a battery charging system 41 of the present embodiment differs from the battery charging system 1 of the first embodiment shown in FIG. 1 in that a control device 42 is provided instead of the control device 5. The control device 42 differs from the control device 5 in that a phase current control device 43 is provided instead of the phase current control device 18.

[0059] The battery charging system 41 includes a temperature sensor for detecting the element temperature, which is the temperature of the switch elements Q1 to Q12 that constitute the inverter 4, and a temperature sensor for detecting the winding temperature, which is the temperature of the windings 3u to 3w of the motor 3. The control device 42 can detect the element temperature and the winding temperature based on a detection signal corresponding to a detection value T1 of the element temperature and a detection signal corresponding to a detection value T2 of the winding temperature that are output from the temperature sensors.

[0060] If the phase current control unit 43 determines, based on the element temperature detection results, that the difference between the element temperatures of the two output phases is equal to or greater than a predetermined threshold value during charging of the battery 2, that is, if it determines that a temperature imbalance has occurred, the phase current control unit 43 can perform current ratio correction to change the current ratio so that the current of the output phase having the higher element temperature is reduced. Also, if the phase current control unit 43 determines, based on the winding temperature detection results, that a temperature imbalance has occurred during charging of the battery 2, the phase current control unit 43 can perform current ratio correction to change the current ratio so that the current of the output phase having the higher winding temperature is reduced.

[0061] The current ratio correction may be performed based on a map prepared in advance or on feedback. Since it takes a relatively long time for the temperature to change after the current has changed, the time constant of the correction, i.e., the gradient of the change in the current ratio, should be sufficiently large compared to the gradient of the change in the current.

[0062] The phase current control unit 43 can perform phase switching to switch the input phase to another phase when the element temperature of the input phase is higher than the element temperature of the output phase based on the detection result of the element temperature while the battery 2 is being charged. Furthermore, the phase current control unit 43 can perform phase switching to switch the input phase to another phase when the winding temperature of the input phase is higher than the winding temperature of the output phase based on the detection result of the winding temperature while the battery 2 is being charged. Furthermore, the phase current control unit 43 can perform phase switching to switch the input phase to another phase after an arbitrary period has elapsed while the battery 2 is being charged, that is, to periodically interchange the input phase and the output phase.

[0063] A specific configuration of the control device 42 is shown in Fig. 20, for example. The voltage control unit 17 includes a subtractor 47 that subtracts the detection value VL of the voltage sensor 13b from the command value VL* of the intermediate terminal voltage, and a PI controller 48 that outputs a signal corresponding to the current command IL* by performing PI control on the output signal of the subtractor 47. In this way, the voltage control unit 17 performs PI control based on the command value VL* of the intermediate terminal voltage and the detection value VL of the voltage sensor 13b, and calculates the current command IL*.

[0064] The electrical angle calculation unit 49 converts the detection value θm of the rotor position sensor 14 into an electrical angle θe. This conversion can be performed using the formula "electrical angle θe = detection value θm of the mechanical angle × number of pole pairs of the motor 3." The phase current control unit 43 includes an input phase determination unit 50, a current ratio calculation unit 51, a phase current command calculation unit 52, a W-phase current calculation unit 53, and a PI control unit 54.

[0065] The input phase determination unit 50 determines the input phase and the output phase based on the electrical angle θe. Based on the results of determining the input phase and the output phase, the input phase determination unit 50 outputs positive and negative switch signals Su2, Sv2, and Sw2, which are switch signals corresponding to the positive and negative switch elements, and intermediate switch signals Snu, Snv, and Snw, which are switch signals corresponding to the intermediate switch elements. The input phase determination unit 50 can perform the above-mentioned phase switching based on the detected values ​​T1 and T2 while the battery 2 is being charged. Furthermore, the input phase determination unit 50 can perform the above-mentioned phase switching at a timing when an arbitrary period has elapsed while the battery 2 is being charged.

[0066] The current ratio calculation unit 51 calculates current ratios Ru, Rv, and Rw representing the respective ratios of the U-phase current, V-phase current, and W-phase current of the motor 3 from the electrical angle θe. The current ratio calculation unit 51 can perform the current ratio correction described above based on the detected values ​​T1 and T2. The phase current command calculation unit 52 includes a multiplier 52u that multiplies the current command IL* by the current ratio Ru to output a signal corresponding to the U-phase phase current command Iu*, a multiplier 52v that multiplies the current command IL* by the current ratio Rv to output a signal corresponding to the V-phase phase current command Iv*, and a multiplier 52w that multiplies the current command IL* by the current ratio Rw to output a signal corresponding to the W-phase phase current command Iw*. In this way, the phase current command calculation unit 52 multiplies the current command IL* by the current ratios Ru, Rv, and Rw to calculate the phase current commands Iu*, Iv*, and Iw*.

[0067] The W-phase current calculation unit 53 is configured with a subtractor that subtracts the detection value Iv of the current sensor 12b from a value obtained by inverting the sign of the detection value Iu of the current sensor 12a and outputs a signal corresponding to the calculated value Iw of the W-phase current. In this way, the W-phase current calculation unit 53 calculates the W-phase current from the U-phase current and the V-phase current. Specifically, the W-phase current calculation unit 53 calculates the W-phase current as "Iw = -Iu - Iv."

[0068] The PI control unit 54 includes a subtractor 55u that subtracts the detected value Iu from the phase current command Iu*, and a PI controller 56u that outputs a signal corresponding to a phase voltage command Vu* of the U phase by performing PI control on the output signal of the subtractor 55u. The PI control unit 54 also includes a subtractor 55v that subtracts the detected value Iv from the phase current command Iv*, and a PI controller 56v that outputs a signal corresponding to a phase voltage command Vv* of the V phase by performing PI control on the output signal of the subtractor 55v.

[0069] Furthermore, the PI control unit 54 includes a subtractor 55w that subtracts the calculated value Iw from the phase current command Iw*, and a PI controller 56w that outputs a signal corresponding to the W-phase phase voltage command Vw* by performing PI control on the output signal of the subtractor 55w. In this way, the PI control unit 54 performs PI control using the phase current commands Iu*, Iv*, Iw*, the detection values ​​Iu, Iv of the current sensors 12a, 12b, and the calculated value Iw obtained as a result of calculation by the W-phase current calculation unit 53, thereby calculating the phase voltage commands Vu*, Vv*, Vw*.

[0070] The PWM modulation units 57u, 57v, and 57w calculate duties from the phase voltage commands Vu*, Vv*, and Vw* and the detection value VH of the voltage sensor 13a. The PWM modulation units 57u, 57v, and 57w PWM-modulate the calculated duties to calculate positive and negative switch signals Su1, Sv1, and Sw1, which are switch signals corresponding to the positive and negative switch elements.

[0071] The switch signal selection unit 58 transmits to the inverter 4 a signal obtained by calculating the logical product, i.e., AND, of the positive and negative switch signals Su1, Sv1, and Sw1 transmitted from the PWM modulation units 57u, 57v, and 57w and the positive and negative switch signals Su2, Sv2, and Sw2 transmitted from the input phase determination unit 50. The switch signal selection unit 58 also transmits the intermediate switch signals Snu, Snv, and Snw transmitted from the input phase determination unit 50 to the inverter 4 as they are.

[0072] Next, the operation of the above configuration will be described. The processing performed by the control device 42 while the battery 2 is being charged, that is, the flow of the charging processing, can be represented as a flowchart as shown in Figures 21 to 23. Note that Figure 21 corresponds to the charging processing when the phase current control unit 43 performs current ratio correction, and Figures 22 and 23 correspond to the charging processing when the phase current control unit 43 performs phase switching.

[0073] [1] Charging process when current ratio correction is performed 21, in step S201, it is determined whether or not a temperature imbalance has occurred based on the detection results of the element temperature or winding temperature. If it is determined that no temperature imbalance has occurred, step S201 results in "NO" and the process proceeds to step S203. On the other hand, if it is determined that a temperature imbalance has occurred, step S201 results in "YES" and the process proceeds to step S202.

[0074] In step S202, the current ratio of the two output phases is corrected based on the detection result of the element temperature or winding temperature. After step S202 is executed, the process proceeds to step S203. In step S203, it is determined whether charging has finished. If it is determined that charging has not finished, the result in step S203 is "NO" and the process returns to step S201. On the other hand, if it is determined that charging has finished, the result in step S203 is "YES" and the charging process ends.

[0075] [2] Charging process when switching phases (1) 22, in step S301, it is determined based on the detection result of the element temperature or winding temperature whether the temperature of the input phase is high, specifically whether the element temperature or winding temperature of the input phase is higher than the element temperature or winding temperature of at least one of the two output phases. If it is determined that the temperature of the input phase is lower than the temperatures of both of the two output phases, the result in step S301 is "NO" and the process proceeds to step S303. On the other hand, if it is determined that the temperature of the input phase is higher than the temperature of at least one of the two output phases, the result in step S301 is "YES" and the process proceeds to step S302.

[0076] In step S302, phase switching is performed to switch the input phase to another phase, specifically, one of the two output phases that has a lower temperature than the input phase, based on the detection results of the element temperature or winding temperature. After step S302 is performed, the process proceeds to step S303. In step S303, it is determined whether charging has ended. If it is determined that charging has not ended, step S303 returns to "NO" and the process returns to step S301. On the other hand, if it is determined that charging has ended, step S303 returns to "YES" and the charging process ends.

[0077] [3] Charging process when switching phases (2) 23, in step S401, it is determined whether or not a given period has elapsed, that is, whether or not it is time to switch, which is the time to execute phase switching. If it is determined that it is not time to switch, the result in step S401 is "NO" and the process proceeds to step S403. On the other hand, if it is determined that it is time to switch, the result in step S401 is "YES" and the process proceeds to step S402.

[0078] In step S402, phase switching is performed to switch the input phase to another phase, specifically, one of the two output phases that has a lower temperature than the input phase, based on the detection results of the element temperature or winding temperature. After step S402 is performed, the process proceeds to step S403. In step S403, it is determined whether charging has ended. If it is determined that charging has not ended, step S403 returns to "NO" and the process returns to step S401. On the other hand, if it is determined that charging has ended, step S403 returns to "YES" and the charging process ends.

[0079] According to the present embodiment described above, the phase current control unit 43 of the control device 42 can correct the current ratio or perform phase switching based on the detection results of the element temperature or winding temperature, or can perform phase switching to periodically interchange the input and output phases. This makes it possible to balance the temperatures of the elements and windings corresponding to each of the three phases, and uniformly distributes heat therefrom, thereby improving charging power.

[0080] (Third embodiment) The third embodiment will be described below with reference to FIG. As shown in Fig. 24, a battery charging system 61 of this embodiment has a modified inverter configuration compared to the battery charging system 1 of the first embodiment shown in Fig. 1. Specifically, an inverter 62 of the battery charging system 61 is configured as a normal inverter, unlike the inverter 4 of the first embodiment which is a three-level inverter. An inverter main circuit 63 of the inverter 62 differs from the inverter main circuit 11 of the first embodiment in that it includes relays 64-66 instead of the switch elements Q7-Q12.

[0081] Relay 64 is provided so as to be able to open and close between node Nm and node Nu. Relay 65 is provided so as to be able to open and close between node Nm and node Nv. Relay 66 is provided so as to be able to open and close between node Nm and node Nw. The opening and closing of relays 64 to 66 is controlled by a control device 67. During normal motor driving, the control device 67 controls all of the relays 64 to 66 to be open, i.e., to be open. During charging, the control device 67 controls only the relays 64 to 66 that correspond to the input phase to be closed, i.e., to be turned on.

[0082] As described above, even in the present embodiment in which the inverter configuration has been modified compared to the first embodiment, the control device 67 performs control similar to that of the control device 5 of the first embodiment, thereby achieving the same functions and effects as the first embodiment.

[0083] (Other embodiments) The present invention is not limited to the embodiments described above and illustrated in the drawings, but can be modified, combined, or expanded as desired without departing from the spirit of the invention. The various characteristics, values, etc. shown in the above embodiments are merely examples and are not intended to be limiting.

[0084] The positive-side capacitor, which is a capacitor connected between the positive electrode of the battery 2 and the node Nm, is not limited to being constituted by one capacitor 10a, but may be constituted by, for example, two or more capacitors connected in parallel.Furthermore, the negative-side capacitor, which is a capacitor connected between the node Nm and the negative electrode of the battery 2, is not limited to being constituted by one capacitor 10b, but may be constituted by, for example, two or more capacitors connected in parallel.

[0085] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure. [Explanation of symbols]

[0086] 1, 41, 61...battery charging system, 2...battery, 3...motor, 3u, 3v, 3w...winding, 4, 62...inverter, 5, 42, 67...control device, 8...neutral point, 10a, 10b...capacitor, 15...charging relay, 16...charging stand, Nm...node, Q1, Q3, Q5...positive side switching element, Q2, Q4, Q6...negative side switching element, Q7 to Q12...intermediate switching element

Claims

1. A battery charging system comprising: a motor (3) for driving a vehicle and having multi-phase windings (3u, 3v, 3w); an inverter (4, 62) for converting power flowing between a battery (2) and the motor; and a control device (5, 42, 67) for controlling the inverter, wherein the battery charging system uses the windings and the inverter to boost a charger voltage output from a charger (16) for charging the battery, thereby charging the battery at a voltage higher than the charger voltage, A battery charging system comprising a locking mechanism (21) that prevents the rotation shaft of the motor from being fixed while the vehicle is in parking lock.

2. The motor has a neutral point (8) to which one terminal of each of the multiple phase windings is connected, The inverter is a plurality of capacitors (10a, 10b) connected in series between the positive terminal of the battery and the negative terminal of the battery; a plurality of intermediate switch elements (Q7 to Q12) provided between an intermediate terminal (Nm) to which the plurality of capacitors are connected and each of the plurality of phase windings; a plurality of positive-side switch elements (Q1, Q3, Q5) provided between each of the plurality of phase windings and the positive electrode of the battery; a plurality of negative-side switch elements (Q2, Q4, Q6) provided between each of the plurality of phase windings and the negative electrode of the battery; a connection portion (15) capable of connecting the charger to the intermediate terminal; Equipped with 2. The battery charging system according to claim 1, wherein the control device determines one input phase and multiple output phases from among the multiple phases, fixes the intermediate switch element corresponding to the input phase to on, fixes the positive side switch element and the negative side switch element corresponding to the input phase and the intermediate switch element corresponding to the output phase to off, and then controls on / off of the positive side switch element and the negative side switch element corresponding to the output phase, thereby boosting the charger voltage and charging the battery.

3. 3. The battery charging system according to claim 2, wherein the control device detects a rotor position of the motor while the vehicle is stopped, and determines the input phase and the output phase based on the detection result.

4. 4. The battery charging system according to claim 3, wherein the control device executes control to align the d-axis of a magnet constituting the rotor of the motor with the input phase based on the results of determining the input phase and the output phase before starting charging of the battery.

5. 3. The battery charging system according to claim 2, wherein the control device controls the current ratio, which is the ratio of the currents of the two output phases during charging of the battery, to be equal to each other.

6. 3. The battery charging system according to claim 2, wherein the control device (42) detects an element temperature, which is the temperature of an element constituting the inverter, while the battery is being charged, and based on the detection result, changes the current ratio so that the current of the output phase having the higher element temperature is reduced.

7. 3. The battery charging system according to claim 2, wherein the control device detects a winding temperature that is a temperature of the winding during charging of the battery, and changes the current ratio based on the detection result so that a current of one of the two output phases having a higher winding temperature is reduced.

8. 3. The battery charging system of claim 2, wherein the control device (42) detects an element temperature, which is the temperature of an element constituting the inverter, while the battery is being charged, and switches the input phase to another phase if the element temperature of the input phase is higher than the element temperature of the output phase based on the detection result.

9. 3. The battery charging system according to claim 2, wherein the control device detects a winding temperature that is a temperature of the winding during charging of the battery, and switches the input phase to another phase when the winding temperature of the input phase is higher than the winding temperature of the output phase based on the detection result.

10. 3. The battery charging system according to claim 2, wherein the control device (42) switches the input phase to another phase at a timing when an arbitrary period has elapsed while the battery is being charged.

11. 3. The battery charging system according to claim 1, wherein the locking mechanism is configured by a reduction gear (22) including a planetary gear (22b).

12. The reduction gear is a sun gear (22a) connected to a motor shaft, which is the shaft of the motor; The planetary gear is connected to an axle that is an axle of the vehicle; a ring gear (22c), 12. The battery charging system according to claim 11, wherein the planetary gear is fixed while the battery is being charged, and the ring gear is fixed when the vehicle is in a drive range in which the vehicle is traveling.

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