electric vehicles

Abstract

This specification provides a method for equalizing the current supplied to two batteries when charging them in an electric vehicle in which the two batteries are connected in parallel to a power receiving terminal. [Solution] A controller sets the average value of the current supplied to the first battery (first measured current) and the current supplied to the second battery (second measured current) as a target current for the current to be supplied to the second battery. If the second measured current is higher than the target current, the controller fixes the first and second lower switching elements to off and repeatedly turns on and off the first upper switching element to reduce the power supply voltage and output it to the second battery. If the second measured current is lower than the target current, the controller fixes the first upper switching element to on and fixes the first lower switching element to off and repeatedly turns on and off the second lower switching element to increase the power supply voltage and output it to the second battery. If the second measured current is equal to the target current, the controller fixes the first and second lower switching elements to off and fixes the first upper switching element to on.

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to an electric vehicle, and more particularly to an electric vehicle that has a power receiving terminal and can charge a battery from a power source connected to the power receiving terminal. [Background technology]

[0002] An electric vehicle includes a battery, an inverter, and an electric motor. The inverter includes two switching elements connected in series, with the midpoint of the series connection connected to the stator coil of the electric motor. It is known that a circuit consisting of the stator coil of the electric motor and the switching elements of the inverter can be used as a voltage converter. Patent Document 1 discloses a technology in which a power supply is connected to the neutral point of the stator coil, and the stator coil and the switching elements of the inverter are used as a boost circuit to boost the voltage of the power supply and charge the battery. For ease of explanation, hereinafter, "electric motor" will be simply referred to as "motor."

[0003] Furthermore, Patent Document 2 discloses an electric vehicle having a first battery and a second battery. When driving the motor, the first battery and the second battery are connected in series. When charging the battery with a power source external to the electric vehicle, the first battery and the second battery are connected in parallel. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-184947 [Patent Document 2] Japanese Patent Application Publication No. 2019-118221 Summary of the Invention [Problem to be solved by the invention]

[0005] When two batteries are connected in parallel and charged, even slight differences in the battery characteristics can cause the current to flow unevenly. This specification provides an electric vehicle that uses the motor's stator coil and the inverter's switching elements as voltage converters to ensure that current flows evenly to the two batteries connected in parallel during charging. [Means for solving the problem]

[0006] The electric vehicle disclosed in this specification includes first and second batteries, a motor, first and second inverters, first and second current sensors, a power receiving terminal, a circuit selector, and a controller. The motor includes a stator coil. The positive and negative terminals of the first battery are referred to as the first positive terminal and the first negative terminal, respectively, and the positive and negative terminals of the second battery are referred to as the second positive terminal and the second negative terminal, respectively. The first current sensor measures the current flowing in and out of the first battery, and the second current sensor measures the current flowing in and out of the second battery.

[0007] The power receiving terminal has a power receiving positive terminal and a power receiving negative terminal to which an external power source of the electric vehicle can be connected. The power receiving positive terminal is connected to the first positive terminal, and the power receiving negative terminal is connected to ground.

[0008] The first inverter includes a first DC terminal, a first upper switching element, and a first lower switching element. The first DC terminal is connected to the first positive terminal (and the power receiving positive terminal). The first upper switching element and the first lower switching element are connected in series between the first DC terminal and ground. The midpoint of the series connection of the first upper switching element and the first lower switching element is connected to one end of the stator coil. In the following, for ease of explanation, the "switching element" may be referred to as the "SW element."

[0009] The second inverter includes a second DC terminal, a second upper switching element, and a second lower switching element. The second upper switching element and the second lower switching element are connected in series between the second DC terminal and ground. The midpoint of the series connection of the second upper switching element and the second lower switching element is connected to the other end of the stator coil.

[0010] The circuit selector can select either a series mode or a parallel mode. In the series mode, the circuit selector connects the first negative terminal to the second positive terminal and connects the first DC terminal to the second DC terminal. In the parallel mode, the circuit selector connects the first negative terminal to ground and connects the second positive terminal to the second DC terminal and disconnects the first DC terminal from the second DC terminal.

[0011] The controller sets the circuit selector to series mode when driving the motor with high torque. The controller sets the circuit selector to parallel mode when a power supply is connected to the power receiving terminal. When a power supply is connected to the power receiving terminal, the controller sets the circuit selector to parallel mode and executes the following process: (1) The controller sets the average value of the first measured current measured by the first current sensor and the second measured current measured by the second current sensor as the target current for the current to be supplied to the second battery.

[0012] (2) If the second measured current is higher than the target current, the controller fixes the first lower switching element and the second lower switching element to OFF, and repeatedly turns the first upper switching element on and off to step down the power supply voltage and output it to the second battery. Note that the second upper switching element may be on or off. This is because current is always allowed to flow from the stator coil to the second DC terminal (second battery) through the diode associated with the second upper switching element.

[0013] (3) When the second measured current is lower than the target current, the controller fixes the first upper switching element to ON and fixes the first lower switching element to OFF, and repeatedly turns the second lower switching element on and off to boost the power supply voltage and output it to the second battery. At this time, the second upper switching element may be either ON or OFF.

[0014] (4) When the second measured current is equal to the target current, the controller fixes the first lower switching element and the second lower switching element to OFF and fixes the first upper switching element to ON. At this time, the second upper switching element may be either ON or OFF.

[0015] By the above process, the second measured current (i.e., the current supplied to the second battery) becomes equal to the first measured current (i.e., the current supplied to the first battery). Details and further improvements of the technology disclosed in this specification will be described in the following "Description of Embodiments of the Invention." [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a circuit diagram of an electric vehicle according to an embodiment of the present invention, showing the flow of current when driving a motor. [Figure 2] 2 is a circuit diagram of an electric vehicle according to an embodiment. FIG. 2 shows the current flow when two batteries are charged by a power source. [Figure 3] 10 is a flowchart of the process of the controller during charging. DETAILED DESCRIPTION OF THE INVENTION

[0017] An electric vehicle 2 according to an embodiment will be described with reference to the drawings. FIG. 1 shows a circuit diagram of the electric vehicle 2. The electric vehicle 2 includes a first battery 3, a second battery 4, a first inverter 10, a second inverter 20, a motor 30, a circuit selector 40, a power receiving terminal 50, and a controller 7. FIG. 1 also shows a power source 70 connected to the power receiving terminal 50, but the power source 70 is not actually connected to the power receiving terminal 50 in FIG. In the following, to simplify the description, a "switching element" will be referred to as an "SW element."

[0018] An axle (not shown) is connected to the output shaft of the motor 30. The motor 30 is driven by power from the first battery 3 and the second battery 4, which drives the electric vehicle 2. The motor 30 is a three-phase AC motor and has multiple stator coils 31. The thick arrows in FIG. 1 indicate the flow of current when the motor 30 is driven. The first DC terminal 10p of the first inverter 10 is connected to the second DC terminal 20p of the second inverter 20 by the circuit selector 40, and the first battery 3 and the second battery 4 are connected in series. The configurations of the circuit selector 40, the first inverter 10, and the second inverter 20 will be described later. Power from the first battery 3 and the second battery 4, which are connected in series, is supplied to the first inverter 10 and the second inverter 20. The DC power of the batteries is converted by the first inverter 10 and the second inverter 20 into AC power suitable for driving the motor 30, and is supplied to the motor 30 (stator coil 31).

[0019] The configuration of the first inverter 10 will be described. The first inverter 10 has a first DC terminal 10p, three sets of first series-connected bodies 11a, 11b, and 11c, and a capacitor 15. The three sets of first series-connected bodies 11a, 11b, and 11c are connected in parallel between the first DC terminal 10p and ground 9. The ground 9 is common to the first inverter 10 and the second inverter 20.

[0020] Each of the three sets of first series-connected bodies 11a, 11b, and 11c includes a first upper switching element 12 and a first lower switching element 13 connected in series. The first upper switching element 12 is connected to the first DC end 10p, and the first lower switching element 13 is connected to the ground 9. One end of each of the three stator coils 31 is connected to the midpoint of each of the three sets of first series-connected bodies 11a, 11b, and 11c (the connection point between the first upper switching element 12 and the first lower switching element 13).

[0021] A free wheel diode is connected in anti-parallel to each of the first upper switching elements 12 and each of the first lower switching elements 13. The free wheel diode always passes a current from the ground 9 side to the first DC end 10p side. The free wheel diode may be an element separate from the first upper switching element 12 (first lower switching element 13), or may be a diode function included in the element of the first upper switching element 12 (first lower switching element 13).

[0022] A capacitor 15 is connected between the first DC terminal 10p and the ground 9. The capacitor 15 suppresses fluctuations in current / voltage caused by the on / off of the switching element.

[0023] The configuration of the second inverter 20 will be described. The second inverter 20 has a second DC terminal 20p, three sets of second series-connected bodies 21a, 21b, and 21c, and a capacitor 25. Each of the three sets of second series-connected bodies 21a, 21b, and 21c includes a second upper switching element 22 and a second lower switching element 23 connected in series. The other ends of the three stator coils 31 are connected to the midpoints of the three sets of second series-connected bodies 21a, 21b, and 21c (the connection points of the second upper switching element 22 and the second lower switching element 23). The configuration of the second inverter 20 is the same as that of the first inverter 10, so a detailed description will be omitted.

[0024] A first current sensor 5 is connected in series to the first battery 3, and a second current sensor 6 is connected in series to the second battery 4. The first current sensor 5 (second current sensor 6) measures the current flowing in and out of the first battery 3 (second battery 4). The measured currents of the current sensors 5 and 6 are sent to a controller 7. As will be described in more detail later, when charging the two batteries, the controller 7 controls each of the switching elements so that the measured currents of the current sensors 5 and 6 are equal.

[0025] The positive electrode of the first battery 3 (first battery positive terminal 3p) is connected to the first DC terminal 10p, and the negative electrode of the second battery 4 (second battery negative terminal 4n) is connected to the ground 9. The connection relationship between the negative electrode of the first battery 3 (first battery negative terminal 3n) and the positive electrode of the second battery 4 (second battery positive terminal 4p) is determined by the circuit selector 40. Next, the circuit selector 40 will be described.

[0026] The circuit selector 40 includes a first switch 41, a second switch 42, a third switch 43, and a fourth switch 44. The first switch 41 is connected between the first battery negative terminal 3n and the second battery positive terminal 4p. The second switch 42 is connected between the first battery negative terminal 3n and ground 9. The third switch 43 is connected between the second battery positive terminal 4p and the second DC terminal 20p. The fourth switch 44 is connected between the first DC terminal 10p and the second DC terminal 20p.

[0027] The circuit selector 40 is controlled by the controller 7. The controller 7 sets the circuit selector 40 to either the series mode or the parallel mode. In the series mode, the controller 7 closes the first switch 41 and the fourth switch 44 and opens the second switch 42 and the third switch 43. In FIG. 1, the circuit selector 40 is set to the series mode. In the series mode, the first battery negative terminal 3n and the second battery positive terminal 4p are connected, and the first DC terminal 10p and the second DC terminal 20p are connected. Note that the first battery negative terminal 3n is disconnected from the ground 9, and the second battery positive terminal 4p is disconnected from the second DC terminal 20p.

[0028] In the parallel mode, the controller 7 opens the first switch 41 and the fourth switch 44 and closes the second switch 42 and the third switch 43. This causes the first battery negative terminal 3n to be connected to the ground 9, and the second battery positive terminal 4p to be connected to the second DC terminal 20p. The first battery negative terminal 3n is disconnected from the second battery positive terminal 4p, and the first DC terminal 10p is disconnected from the second DC terminal 20p.

[0029] When the motor 30 is to output high torque, the controller 7 sets the circuit selector 40 to series mode. AC power is supplied to the first inverter 10 and the second inverter 20 from the series-connected first battery 3 and second battery 4. The thick arrows in FIG. 1 indicate the current flow at this time. The controller 7 supplies a PWM signal (basic PWM signal) identical to the PWM signal supplied to the first upper switching element 12 to the second lower switching element 23, and supplies an inverted signal of the basic PWM signal to the first lower switching element 13 and the second upper switching element 22, thereby driving these switching elements on and off. This allows approximately twice as much current to flow through the motor 30 as when the motor 30 is driven by the first inverter 10 alone, thereby generating high torque. The configuration shown in FIG. 1, in which an inverter is connected to each end of the stator coil 31, is sometimes called a dual-inverter system.

[0030] When the motor 30 is to output medium or low torque, the controller 7 sets the circuit selector 40 to series mode and opens the fourth switch 44. The controller 7 fixes the second upper switching element 22 to on and fixes the second lower switching element 23 to off. Fixing all second upper switching elements 22 to on connects the other ends of the stator coils 31 to each other. In a motor, the point where the other ends of multiple stator coils are connected is called the neutral point. A configuration in which one end of a stator coil is connected to an inverter and the other end is connected to the neutral point is the well-known one-inverter-one-motor configuration. A predetermined basic PWM signal drives the first upper switching element 12 on and off, and a signal obtained by inverting the basic PWM signal drives the first lower switching element 13 on and off. This causes an alternating current to flow through the stator coil 31, causing the motor 30 to output torque.

[0031] The electric vehicle 2 can connect a power source to the power receiving terminal 50 to charge the first battery 3 and the second battery 4. Next, the processing of the controller 7 when the power receiving terminal 50 and the power source 70 are connected will be described.

[0032] The power receiving terminal 50 has a power receiving positive terminal 50p and a power receiving negative terminal 50n. The positive terminal 70p of the power source 70 is connected to the power receiving positive terminal 50p, and the negative terminal 70n of the power source 70 is connected to the power receiving negative terminal 50n. The power receiving negative terminal 50n is connected to the ground 9, and the power receiving positive terminal 50p is connected to the first battery positive terminal 3p and the first DC terminal 10p.

[0033] When the power supply 70 is connected to the power receiving terminal 50, the controller 7 sets the circuit selector 40 to parallel mode. The first battery 3 and the second battery 4 are connected in parallel to the power supply 70. However, the first inverter 10, the motor 30 (stator coil 31), and the second inverter 20 are connected between the power supply 70 and the second battery 4. The controller 7 fixes the first lower switching element 13 and the second lower switching element 23 to OFF, and fixes the first upper switching element 12 and the second upper switching element 22 to ON. In this way, the power supply 70 and the second battery 4 are directly connected. The first battery 3 is always directly connected to the power supply 70.

[0034] When the power supply 70 is connected to the power receiving terminal 50, current flows from the power supply 70 to the first battery 3 and the second battery 4 through the power receiving terminal 50. The current flow at this time is indicated by the thick arrows in FIG. 2. The current supplied from the power supply 70 branches at point A in FIG. 2 and flows to the first battery 3 and the second battery 4. However, the current flows from point A through the first inverter 10, the motor 30, and the second inverter 20 to the second battery 4.

[0035] When two batteries are connected in parallel and charged, it is desirable that the current supplied to each battery be equal. However, even a slight difference in the characteristics of the first battery 3 and the second battery 4 will result in more current flowing to one battery and less current flowing to the other battery.

[0036] 2, the voltage ratio between the first DC terminal 10p and the second DC terminal 20p can be adjusted as desired. By adjusting the voltage ratio between the first DC terminal 10p and the second DC terminal 20p, it is possible to equalize the current supplied to the first battery 3 and the second battery 4, even if the batteries have different characteristics. Below, we will explain the charging process performed by the controller 7 when the power source 70 is connected, as well as the mechanism for equalizing the current flowing through the first battery 3 and the second battery 4 using two inverters and a stator coil.

[0037] The current supplied to the first battery 3 is measured by a first current sensor 5. The current supplied to the second battery 4 is measured by a second current sensor 6. Now, the current measured by the first current sensor 5 (i.e., the current supplied to the first battery 3) is referred to as the first measured current, and the current measured by the second current sensor 6 (i.e., the current supplied to the second battery 4) is referred to as the second measured current.

[0038] Fig. 3 shows a flowchart of the charging process executed by the controller 7. The process in Fig. 3 starts when an external power supply 70 is connected to the power receiving terminal 50. Although not shown in Fig. 3, when the power supply 70 is connected to the power receiving terminal 50, the controller 7 first sets the circuit selector 40 to the parallel mode (Fig. 2). Then, the controller 7 executes the following processes (1) to (4).

[0039] (1) The controller 7 sets the average value of the first measured current and the second measured current as a target current (step S2). Here, the target current is a target value of the current to be supplied to the second battery 4. Next, the controller 7 compares the second measured current with the target current (steps S3 and S5).

[0040] The process when the second measured current is equal to the target current (steps S3: YES, S4) will be described later. More precisely, "when the second measured current is equal to the target current" means that the second measured current is equal to the target current within a predetermined tolerance range. In other words, the equation "second measured current = target current" more precisely means "|second measured current - target current| ≦ tolerance."

[0041] (2) If the second measured current is higher than the target current (step S5, YES), the controller 7 fixes the first lower switching element 13 and the second lower switching element 23 to OFF, and repeatedly turns the first upper switching element 12 ON and OFF (step S6). The "ON / OFF control" described in step S6 of FIG. 3 means repeatedly turning the switching elements ON and OFF. Note that the second upper switching element 22 may be ON or OFF. This is because a current can always flow from the stator coil 31 to the second DC terminal 20p (i.e., the second battery 4) due to the free wheel diode connected in antiparallel to the second upper switching element 22.

[0042] By controlling the on / off of the first upper switching element 12, the current flowing from the first DC terminal 10p to the stator coil 31 is reduced. Furthermore, when the first upper switching element 12 is switched from on to off, the self-induction of the stator coil 31 causes the charge of the capacitor 15 to be drawn up through the freewheeling diode associated with the first lower switching element 13 and flow to the stator coil 31 and the second DC terminal 20p, so the voltage at the second DC terminal 20p does not drop to zero. By controlling the on / off of the first upper switching element 12, the voltage applied to the first DC terminal 10p (i.e., the voltage of the power source 70) is stepped down and output from the second DC terminal 20p (i.e., output to the second battery 4). Because the voltage applied to the second battery 4 (the voltage at the second DC terminal 20p) is lower than the voltage applied to the first battery 3 (the voltage at the first DC terminal 10p), the current flowing to the second battery 4 decreases and the current flowing to the first battery 3 increases. The second measured current decreases and the first measured current increases. In this way, both the first measured current and the second measured current converge to the target current. That is, the currents flowing through the first battery 3 and the second battery 4 become equal.

[0043] Strictly speaking, "the second measured current is higher than the target current" means "the second measured current>(the target current+the tolerance)".

[0044] (3) If the second measured current is lower than the target current (step S5, NO), the controller 7 fixes the first upper switching element 12 to ON, fixes the first lower switching element 13 to OFF, and repeatedly turns the second lower switching element 23 ON and OFF (step S7). The "ON / OFF control" described in step S7 of FIG. 3 also means repeatedly turning the switching elements ON and OFF. Note that in this case, the second upper switching element 22 may be ON or OFF. This is because a current can always flow from the stator coil 31 to the second DC terminal 20p (i.e., the second battery 4) due to the free wheel diode connected in antiparallel to the second upper switching element 22.

[0045] When the second lower switching element 23 is off, a current flows from the first DC terminal 10p to the second DC terminal 20p, so that the first DC terminal 10p and the second DC terminal 20p are at the same potential. When the second lower switching element 23 is switched from off to on, the first DC terminal 10p is electrically connected to the ground 9 through the stator coil 31 and the second lower switching element 23, so that a large current flows through the stator coil 31. At this time, magnetic energy is accumulated in the stator coil 31. When the second lower switching element 23 is switched from on to off, the flow of current from the stator coil 31 to the ground 9 is interrupted. Due to the self-induction of the stator coil 31, the charge of the capacitor 15 is drawn up through the freewheeling diode associated with the first lower switching element 13 and flows to the stator coil 31 and the second DC terminal 20p, thereby increasing the voltage of the second DC terminal 20p. That is, the voltage applied to the first DC terminal 10p is boosted and appears at the second DC terminal 20p. Because the voltage applied to the second battery 4 (the voltage at the second DC terminal 20p) is higher than the voltage applied to the first battery 3 (the voltage at the first DC terminal 10p), the current flowing to the second battery 4 increases and the current flowing to the first battery 3 decreases. The second measured current increases and the first measured current decreases. In this way, both the first measured current and the second measured current converge to the target current. That is, the currents flowing to the first battery 3 and the second battery 4 become equal.

[0046] Strictly speaking, "the second measured current is lower than the target current" means "the second measured current<(target current-tolerance)".

[0047] (4) If the second measurement current is equal to the target current (step S3: YES), the controller 7 fixes the first lower switching element 13 and the second lower switching element 23 to OFF and fixes the first upper switching element 12 to ON (step S4). At this time, the second upper switching element 22 may be either ON or OFF. The voltage at the second DC terminal 20p becomes equal to the voltage at the first DC terminal 10p. The state in which the second measurement current is equal to the target current is maintained.

[0048] The controller 7 repeats the above-described processes (1) to (4) (processing from steps S2 to S7) until the first battery 3 and the second battery 4 are fully charged (or reach a specified charge amount) (step S8: NO, S2). If the second measured current becomes equal to the target current and then, after a while, the second measured current becomes greater than the target current (or the second measured current < the target current), the process of step S6 (processing of step S7) is executed again.

[0049] 3, the second measured current is maintained equal to the first measured current, that is, the currents supplied to the first battery 3 and the second battery 4 are maintained equal to each other.

[0050] As described above, the electric vehicle 2 can supply current equally to the first battery 3 and the second battery 4 by utilizing the dual inverter configuration.

[0051] Some of the structural features of the electric vehicle 2 are listed below. The electric vehicle 2 includes a first inverter 10, a second inverter 20, and a motor 30. The motor 30 includes a plurality of stator coils 31. The first inverter 10 includes a plurality of first series-connected bodies 11a, 11b, and 11c, each of which is a series-connected body of a first upper switching element 12 and a first lower switching element 13. In each series-connected body, the first upper switching element 12 is located closer to the first DC end 10p, and the first lower switching element 13 is located closer to ground 9. The midpoint of each of the plurality of first series-connected bodies 11a, 11b, and 11c is connected to one end of the corresponding stator coil 31.

[0052] The second inverter 20 includes a plurality of second series-connected bodies 21a, 21b, and 21c, each of which is a series-connected body of a second upper SW element 22 and a second lower SW element 23. In each series-connected body, the second upper SW element 22 is located closer to the second DC end 20p, and the second lower SW element 23 is located closer to the ground 9. The midpoint of each of the plurality of second series-connected bodies 21a, 21b, and 21c is connected to the other end of the corresponding stator coil 31.

[0053] Here are some points to note regarding the technology described in the examples. The technology disclosed in this specification can be applied not only to electric vehicles that do not have engines, but also to hybrid vehicles that have a battery, a motor, and an engine. In other words, the term "electric vehicle" in this specification refers to any vehicle that has a motor and a battery for driving, and can also include hybrid vehicles.

[0054] In the embodiment, the controller 7 simultaneously controls the on / off of all the first upper switching elements 12. Alternatively, the controller 7 simultaneously controls the on / off of all the second lower switching elements 23. The controller 7 may also control the on / off of one or two switching elements and keep the remaining switching elements connected in parallel off.

[0055] The tolerance is set to a current width in which the first measured current and the second measured current can be considered to be substantially equal.

[0056] The first battery 3 and the second battery 4 basically have the same performance (same output voltage). However, there are slight differences in their characteristics due to manufacturing errors, differences in the degree of deterioration, and so on. Therefore, when the first battery 3 and the second battery 4 are connected in parallel to a power supply, the currents that flow may differ. Furthermore, because the difference in characteristics between the first battery 3 and the second battery 4 is slight, the currents that flow to each battery can be adjusted by providing a slight voltage difference between the first DC terminal 10p and the second DC terminal 20p. Furthermore, the voltage of the power supply 70 is the same as that of the first and second batteries.

[0057] The expression "fixing an SW element on" is equivalent to the expression "closing an SW element," which means electrically connecting a device connected to each end of the SW element. The expression "fixing an SW element off" is equivalent to the expression "opening an SW element," which means electrically disconnecting a device connected to each end of the SW element.

[0058] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives alone is technically useful. [Explanation of symbols]

[0059] 2: Electric vehicle 3, 4: Battery 5, 6: Switch 7: Controller 9: Ground 10: First inverter 12, 13, 22, 23: Switching elements (SW elements) 15, 25: Capacitor 20: Second inverter 30: Motor 31: Stator coil 40: Circuit selector 50: Power receiving terminal 70: Power supply

Claims

[Claim 1] a motor having a stator coil; a first battery having a first positive terminal and a first negative terminal; Grand and a second battery having a second positive terminal and a second negative terminal connected to the ground; a first current sensor that measures current flowing into and out of the first battery; a second current sensor that measures current flowing into and out of the second battery; a power receiving terminal including a power receiving positive terminal and a power receiving negative terminal to which a power source can be connected, the power receiving positive terminal being connected to the first positive terminal and the power receiving negative terminal being connected to the ground; a first inverter including a first DC terminal connected to the first positive terminal, and including a first upper switching element and a first lower switching element connected in series between the first DC terminal and the ground, wherein a midpoint of a series connection of the first upper switching element and the first lower switching element is connected to one end of the stator coil; a second inverter including a second DC terminal and a second upper switching element and a second lower switching element connected in series between the second DC terminal and the ground, the midpoint of the series connection of the second upper switching element and the second lower switching element being connected to the other end of the stator coil; a circuit selector for selecting either a series mode in which the first negative terminal is connected to the second positive terminal and the first DC terminal is connected to the second DC terminal, or a parallel mode in which the first negative terminal is connected to the ground and the second positive terminal is connected to the second DC terminal and the first DC terminal is disconnected from the second DC terminal; A controller; It is equipped with the controller sets the circuit selector to the parallel mode when the power supply is connected to the power receiving terminal; (1) setting an average value of a first measured current measured by the first current sensor and a second measured current measured by the second current sensor as a target current of a current to be supplied to the second battery; (2) when the second measured current is higher than the target current, the first lower switching element and the second lower switching element are fixed to be off, and the first upper switching element is repeatedly turned on and off to reduce the voltage of the power supply and output it to the second battery; (3) when the second measured current is lower than the target current, the first upper switching element is fixed on, the first lower switching element is fixed off, and the second lower switching element is repeatedly turned on and off to boost the voltage of the power supply and output it to the second battery; (4) when the second measured current is equal to the target current, the first lower switching element and the second lower switching element are fixed to OFF, and the first upper switching element is fixed to ON; Electric car.

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