Electric automobile

Abstract

The invention relates to an electric automobile. When two batteries of an electric vehicle are charged by an external power supply, current flows through the two batteries equally. When the output power of the power supply is too low, the charging time is prevented from being prolonged. The controller sets an average value of a first current supplied to the first battery and a second current supplied to the second battery as a target current of a current supplied to the second battery. When the second current is higher than the target current, the controller fixes the first / second lower SW element to be off, turns the first upper SW element on and off, reduces the voltage of the power supply, and outputs the voltage to the second battery. When the second current is lower than the target current, the controller fixes the first upper SW element to be turned on and fixes the first lower SW element to be turned off, and turns the second lower SW element on and off to boost the voltage of the power supply and output the voltage to the second battery. When the power supplied from the power source is lower than the minimum power, the controller fixes the first / second lower SW element to be off and fixes the first / second upper SW element to be on.

Description

Technical Field

[0001] The technology disclosed in this specification relates to an electric vehicle. In particular, it relates to an electric vehicle having power receiving terminals and capable of charging a battery using a power source connected to the power receiving terminals. Background Technology

[0002] Electric vehicles include a battery, an inverter, and an electric motor. The inverter has a series connection of two switching elements, the midpoint of which is 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 technique 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 to charge the battery. Hereinafter, for simplicity, "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. In the case of a drive motor, the first battery and the second battery are connected in series. In the case of charging the batteries using an external power source for the electric vehicle, the first battery and the second battery are connected in parallel.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2005-184947

[0007] Patent Document 2: Japanese Patent Application Publication No. 2019-118221 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] When charging two batteries connected in parallel, slight differences in battery characteristics can lead to uneven current flow. When charging two batteries connected in parallel to an external power source, it is desirable for the current flowing through each battery to be equal. By effectively utilizing the motor's stator coils and the inverter's switching elements as voltage converters, the current can flow equally through the two parallel-connected batteries during charging. However, if the output power of the external power source is too low, the charging time will increase due to power losses in the switching element's on / off control. Alternatively, the charging time may further increase because the power source voltage cannot be sufficiently boosted due to power losses in the switching element's on / off control. This specification provides an electric vehicle that, when the power source's output power is sufficiently high, ensures that the current flows equally through the two batteries during charging, and prevents prolonged charging time when the power source's output power is too low.

[0010] Solution for solving the problem

[0011] The electric vehicle disclosed in this specification includes a first / second battery, a motor, a first / second inverter, a first / second current sensor, power receiving terminals, a circuit selector, and a controller. The motor includes stator coils. 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 into and out of the first battery, and the second current sensor measures the current flowing into and out of the second battery.

[0012] The power receiving terminal has a positive terminal and a negative terminal that can be connected to an external power source of the electric vehicle. The positive terminal is connected to the first positive terminal, and the negative terminal is connected to the ground wire.

[0013] The first inverter has 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 receiving positive terminal). The first upper switching element and the first lower switching element are connected in series between the first DC terminal and the ground wire. 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. It should be noted that, for the sake of simplicity, the "switching element" will sometimes be referred to as the "SW element".

[0014] The second inverter has a second DC terminal, a second upper SW element, and a second lower SW element. The second upper SW element and the second lower SW element are connected in series between the second DC terminal and the ground wire. The midpoint of the series connection of the second upper SW element and the second lower SW element is connected to the other end of the stator coil.

[0015] The circuit selector can select either series or parallel mode. In series mode, the circuit selector connects the first negative terminal to the second positive terminal and the first DC terminal to the second DC terminal. In parallel mode, the circuit selector connects the first negative terminal to ground and the second positive terminal to the second DC terminal, separating the first DC terminal from the second DC terminal.

[0016] When the motor is driven with high torque, the controller sets the circuit selector to series mode. When the power supply is connected to the receiving terminal, the controller sets the circuit selector to parallel mode. When the power supply is connected to the receiving terminal, the controller sets the circuit selector to parallel mode. Moreover, when the power supplied from the power source is higher than a predetermined minimum power in (1), the controller performs the following (1A)-(1D) processes to make the current flow equally through both batteries.

[0017] (1A) 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 supplied to the second battery.

[0018] (1B) If the second measured current is higher than the target current, the controller will keep the first lower SW element and the second lower SW element in the off position, and repeatedly turn the first upper SW element on and off to reduce the voltage of the power supply and output it to the second battery. It should be noted that the second upper SW element can be turned on or off. This is because the allowable current always flows from the stator coil to the second DC terminal (second battery) through the diode attached to the second upper SW element.

[0019] (1C) When the second measured current is lower than the target current, the controller fixes the first upper SW element to be on and the first lower SW element to be off, and repeatedly switches the second lower SW element on and off to boost the voltage of the power supply and output it to the second battery. At this time, the second upper SW element can also be either on or off.

[0020] (1D) When the second measured current is equal to the target current, the controller fixes the first lower SW element and the second lower SW element to be disconnected, and fixes the first upper SW element to be connected. At this time, the second upper SW element can also be either connected or disconnected.

[0021] Through the above processing, the second measured current (i.e., the current supplied to the second battery) is equal to the first measured current (i.e., the current supplied to the first battery).

[0022] On the other hand, (2) when the power supplied from the power source is lower than the minimum power, the controller fixes the first lower SW element and the second lower SW element to be disconnected, and fixes the first upper SW element and the second upper SW element to be connected. Since the on / off control of the SW elements is not performed, by fixing the SW elements to be connected or disconnected, the power loss in the inverter is suppressed, and the charging time can be prevented from becoming longer.

[0023] The details of the technology disclosed in this specification and further improvements are described in the following "Detailed Description". Attached Figure Description

[0024] Figure 1 This is a circuit diagram of an electric vehicle according to an embodiment. Figure 1 This indicates the flow of current when driving a motor.

[0025] Figure 2 This is a circuit diagram of an electric vehicle according to an embodiment. Figure 2 This indicates the flow of current when two batteries are charged by a power source.

[0026] Figure 3 This is a flowchart of the controller's processing during charging.

[0027] Figure 4 This is a flowchart of the controller's processing during charging (continued). Figure 3 ).

[0028] Explanation of reference numerals in the attached figures

[0029] 2: Electric vehicle; 3, 4: Battery; 5, 6: Switch; 7: Controller; 9: Ground wire; 10: First inverter; 12, 13, 22, 23: Switching elements (SW elements); 15, 25: Capacitors; 20: Second inverter; 30: Motor; 31: Stator coil; 40: Circuit selector; 50: Power receiving terminal; 70: Power supply. Detailed Implementation

[0030] The electric vehicle 2 of the embodiment will be described with reference to the accompanying drawings. Figure 1 The diagram shows the circuit of electric vehicle 2. 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, power receiving terminals 50, and a controller 7. Figure 1 The document also depicts a power supply 70 connected to the power receiving terminal 50, but... Figure 1 In this case, the power supply 70 is not connected to the power receiving terminal 50. Hereinafter, for the sake of simplicity, the "switching element" will be referred to as the "SW element".

[0031] An axle (not shown) is connected to the output shaft of motor 30. Motor 30 is powered by electricity from first battery 3 and second battery 4, thereby propelling electric vehicle 2. Motor 30 is a three-phase AC motor with multiple stator coils 31. Figure 1 The thick arrow indicates the current flow when driving the motor 30. The first DC terminal 10p of the first inverter 10 is connected to the second DC terminal 20p of the second inverter 20 via a circuit selector 40, and the first battery 3 and the second battery 4 are connected in series. It should be noted that the structure of the circuit selector 40, the first inverter 10, and the second inverter 20 will be described later. The power from the series-connected first battery 3 and second battery 4 is supplied to the first inverter 10 and the second inverter 20. The DC power from 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).

[0032] The structure of the first inverter 10 is described below. The first inverter 10 has a first DC terminal 10p, three sets of first series connectors 11a, 11b, and 11c, and a capacitor 15. The three sets of first series connectors 11a, 11b, and 11c are connected in parallel between the first DC terminal 10p and the ground wire 9. It should be noted that the ground wire 9 is shared by the first inverter 10 and the second inverter 20.

[0033] The three sets of first series connectors 11a, 11b, and 11c each have a first upper SW element 12 and a first lower SW element 13 connected in series. The first upper SW element 12 is connected to the first DC terminal 10p, and the first lower SW element 13 is connected to the ground wire 9. At the midpoint of each of the three sets of first series connectors 11a, 11b, and 11c (the connection point of the first upper SW element 12 and the first lower SW element 13), one end of each of the three stator coils 31 is connected.

[0034] A freewheeling diode is connected in reverse parallel to each of the first upper SW elements 12 and each of the first lower SW elements 13. The freewheeling diode always allows current to flow from the ground line 9 side to the first DC terminal 10p side. The freewheeling diode can be a different element from the first upper SW element 12 (first lower SW element 13), or it can be a diode function embedded in the element of the first upper SW element 12 (first lower SW element 13).

[0035] A capacitor 15 is connected between the first DC terminal 10p and the ground wire 9. The capacitor 15 suppresses the current / voltage fluctuations caused by the switching of the SW component.

[0036] The structure of the second inverter 20 will be described. The second inverter 20 has a second DC terminal 20p, three sets of second series connectors 21a, 21b, and 21c, and a capacitor 25. Each of the three sets of second series connectors 21a, 21b, and 21c has a second upper SW element 22 and a second lower SW element 23 connected in series. The other ends of three stator coils 31 are connected to the midpoint of each of the three sets of second series connectors 21a, 21b, and 21c (the connection point between the second upper SW element 22 and the second lower SW element 23). The structure of the second inverter 20 is the same as that of the first inverter 10, therefore detailed description is omitted.

[0037] A first current sensor 5 is connected in series with the first battery 3, and a second current sensor 6 is connected in series with the second battery 4. The first current sensor 5 (and the second current sensor 6) measures the current flowing into and out of the first battery 3 (and the second battery 4). The measured currents from current sensors 5 and 6 are sent to the controller 7. As detailed later, the controller 7 controls each SW component to ensure that the measured currents from current sensors 5 and 6 are equal when charging the two batteries.

[0038] The positive terminal of the first battery 3 (positive terminal 3p) is connected to the first DC terminal 10p, and the negative terminal of the second battery 4 (negative terminal 4n) is connected to the ground wire 9. The connection relationship between the negative terminal of the first battery 3 (negative terminal 3n) and the positive terminal of the second battery 4 (positive terminal 4p) is determined by the circuit selector 40. Next, the circuit selector 40 will be explained.

[0039] 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 negative terminal 3n of the first battery and the positive terminal 4p of the second battery. The second switch 42 is connected between the negative terminal 3n of the first battery and ground 9. The third switch 43 is connected between the positive terminal 4p of the second battery and the second DC terminal 20p. The fourth switch 44 is connected between the first DC terminal 10p and the second DC terminal 20p.

[0040] The circuit selector 40 is controlled by the controller 7. The controller 7 sets the circuit selector 40 to either a series mode or a parallel mode. In 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. Figure 1 In this circuit, the circuit selector 40 is set to series mode. In series mode, the negative terminal 3n of the first battery is connected to the positive terminal 4p of the second battery, and the first DC terminal 10p is connected to the second DC terminal 20p. It should be noted that the negative terminal 3n of the first battery is disconnected from the ground wire 9, and the positive terminal 4p of the second battery is disconnected from the second DC terminal 20p.

[0041] In parallel mode, controller 7 opens switch 41 and switch 44, and closes switch 42 and switch 43. Therefore, the negative terminal 3n of the first battery is connected to ground 9, and the positive terminal 4p of the second battery is connected to the second DC terminal 20p. It should be noted that the negative terminal 3n of the first battery is disconnected from the positive terminal 4p of the second battery, and the first DC terminal 10p is disconnected from the second DC terminal 20p.

[0042] When the motor 30 outputs high torque, the controller 7 sets the circuit selector 40 to series mode. Alternating current is supplied from the series connection of the first battery 3 and the second battery 4 to the first inverter 10 and the second inverter 20. Figure 1The thick arrow indicates the current flow at this time. Controller 7 provides the same PWM signal (basic PWM signal) provided to the first upper SW element 12 to the second lower SW element 23, and supplies the signal that inverts the basic PWM signal to the first lower SW element 13 and the second upper SW element 22, driving these SW elements to switch on and off. Thus, approximately twice the current flows through the motor 30 compared to the case where the motor 30 is driven only by the first inverter 10, resulting in high torque in the motor 30. Inverters are connected to each end of the stator coil 31. Figure 1 The structure is sometimes referred to as a dual inverter system.

[0043] It should be noted that when the motor 30 outputs 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 SW element 22 to be on and the second lower SW element 23 to be off. By fixing all the second upper SW elements 22 to be on, the other ends of the stator coils 31 are interconnected. In a motor, the point where the other ends of multiple stator coils are connected is called the neutral point. The structure where one end of the stator coil is connected to the inverter and the other end is connected to the neutral point is a well-known single-inverter single-motor structure. The first upper SW element 12 is driven to switch on and off using a predetermined basic PWM signal, and the first lower SW element 13 is driven to switch on and off using a signal that inverts the basic PWM signal. Thus, alternating current flows through the stator coils 31, and the motor 30 outputs torque.

[0044] Electric vehicle 2 connects to a power source at power receiving terminal 50, enabling it to charge the first battery 3 and the second battery 4. Next, the processing of controller 7 when power receiving terminal 50 and power source 70 are connected will be explained.

[0045] The power receiving terminal 50 has a positive power receiving terminal 50p and a negative power receiving terminal 50n. The positive terminal 70p of the power supply 70 is connected to the positive power receiving terminal 50p, and the negative terminal 70n of the power supply 70 is connected to the negative power receiving terminal 50n. The negative power receiving terminal 50n is connected to the ground wire 9, and the positive power receiving terminal 50p is connected to the positive terminal 3p of the first battery and the first DC terminal 10p.

[0046] When power supply 70 is connected to power receiving terminal 50, controller 7 sets circuit selector 40 to parallel mode. First battery 3 and second battery 4 are connected in parallel with power supply 70. First inverter 10, motor 30 (stator coil 31), and second inverter 20 are connected between power supply 70 and second battery 4. Controller 7 keeps first lower SW element 13 and second lower SW element 23 disconnected, and keeps first upper SW element 12 and second upper SW element 22 connected. Thus, power supply 70 is directly connected to second battery 4. First battery 3 is always directly connected to power supply 70.

[0047] When the power supply 70 is connected to the receiving terminal 50, current flows from the power supply 70 to the first battery 3 and the second battery 4 via the receiving terminal 50. Figure 2 The thick arrow indicates the current flow at this moment. The current supplied from power source 70 is... Figure 2 The current flows from point A to the first battery 3 and the second battery 4. Specifically, the current flows from point A through the first inverter 10, the motor 30, and the second inverter 20 to the second battery 4.

[0048] When charging two batteries connected in parallel, it is desirable to supply equal current to each battery. However, if the characteristics of the first battery 3 and the second battery 4 are slightly different, excessive current will flow through one battery and less current will flow through the other.

[0049] In Adoption Figure 2 In this structure, the voltage ratio between the first DC terminal 10p and the second DC terminal 20p can be arbitrarily adjusted. By adjusting the voltage ratio between the first DC terminal 10p and the second DC terminal 20p, even if the characteristics of the first battery 3 and the second battery 4 are different, the current supplied to both batteries can be made equal. When adjusting the voltage ratio between the first DC terminal 10p and the second DC terminal 20p, the on / off control of any SW element is performed. When the on / off control of the SW element is performed, a power loss occurs in that SW element. When the power supplied from the power source is low, the charging time may increase due to the power loss. Furthermore, the voltage at the first DC terminal 10p may not be sufficiently boosted due to the power loss, further increasing the charging time.

[0050] In this embodiment, the electric vehicle 2 ensures that the current flowing in the first battery 3 and the second battery 4 is equal when the output power of the power source 70 is sufficiently high (the output power is higher than a predetermined minimum power). On the other hand, it avoids prolonged charging time when the output power of the power source 70 is insufficient (the output power is lower than the minimum power). The charging process performed by the controller 7 when the power source 70 is connected, and the mechanism by which the current flowing in the first battery 3 and the second battery 4 is equalized using two inverters and stator coils, will be explained below.

[0051] The current supplied to the first battery 3 is measured by the first current sensor 5. The current supplied to the second battery 4 is measured by the 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 called 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 called the second measured current.

[0052] exist Figure 3 and Figure 4 The flowchart shows the charging process performed by controller 7. Figure 3 , Figure 4 The processing begins when the external power supply 70 is connected to the power receiving terminal 50. It should be noted that... Figure 3 Not shown in the diagram, but when power supply 70 is connected to power receiving terminal 50, controller 7 first sets circuit selector 40 to parallel mode ( Figure 2 ).

[0053] First, the controller 7 determines the power supplied from the power source 70 (the output power of the power source 70). When communication with the power source 70 is possible, the controller 7 obtains the output power of the power source 70 through communication. When communication with the power source 70 is not possible, the controller 7 obtains the output power of the power source 70 based on its output voltage and output current. Specifically, the controller 7 keeps the first lower SW element 13 and the second lower SW element 23 disconnected, and keeps the first upper SW element 12 and the second upper SW element 22 connected. Thus, the power source 70 is directly connected to the second battery 4. The controller 7 adds the first measured current and the second measured current to obtain the output current of the power source 70. Furthermore, the controller 7 obtains the output voltage of the power source 70 through a voltage sensor (not shown).

[0054] The controller 7 compares the output power of the power supply with a predetermined minimum power (step S2). The value of the minimum power is pre-stored in the controller 7. The minimum power is predetermined based on the condition that the battery charging time does not exceed a predetermined upper limit time.

[0055] If the output power of power supply 70 is higher than the minimum power (step S2: YES), controller 7 performs the following processes (1A) to (1D). If the output power of power supply 70 is lower than the minimum power (step S2: NO), controller 7 performs process (2). Figure 4 (The processing).

[0056] The handling of the case where the output power of power supply 70 is higher than the minimum power (step S2: YES) will be explained.

[0057] (1A) The controller 7 sets the average value of the first measured current and the second measured current as the target current (step S3). Here, the target current refers to the target value of the current supplied by the second battery 4. Next, the controller 7 compares the second measured current with the target current (steps S4, S6).

[0058] The handling of the case where the second measured current is equal to the target current (steps S4: YES, S5) will be described later. It should be noted that "the case where the second measured current is equal to the target current" more strictly means that the second measured current and the target current are equal within a predetermined tolerance range. In other words, the equation "second measured current = target current" more strictly means that "|second measured current - target current| ≤ tolerance".

[0059] (1B) If the second measured current is higher than the target current (step S6: YES), the controller 7 keeps the first lower SW element 13 and the second lower SW element 23 disconnected, and repeatedly switches the first upper SW element 12 on and off (step S7). Figure 3 The "on / off control" described in step S7 refers to repeatedly switching the SW element on and off. It should be noted that the second upper SW element 22 can be both on and off. This is because, by using the freewheeling diode connected in reverse parallel with the second upper SW element 22, the current can always flow from the stator coil 31 to the second DC terminal 20p (i.e., the second battery 4).

[0060] By controlling the on / off state of the first upper SW element 12, the current flowing from the first DC terminal 10p to the stator coil 31 is reduced. Furthermore, when the first upper SW element 12 switches from on to off, due to the self-induction of the stator coil 31, the charge of the capacitor 15 is drawn up through the freewheeling diode attached to the first lower SW element 13 and flows to the stator coil 31 and the second DC terminal 20p, thus preventing the voltage at the second DC terminal 20p from dropping to zero. By controlling the on / off state of the first upper SW element 12, the voltage applied to the first DC terminal 10p (i.e., the voltage of the power supply 70) is reduced and output from the second DC terminal 20p (i.e., output to the second battery 4). Since 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 through the second battery 4 decreases, and the current flowing through the first battery 3 increases. The second measured current decreases, and the first measured current increases. In this way, both the first and second measured currents converge to the target current. That is, the currents flowing in the first cell 3 and the second cell 4 become equal.

[0061] It should be noted that "the second measured current is higher than the target current" strictly refers to "the second measured current > (target current + tolerance)".

[0062] (1C) If the second measured current is lower than the target current (step S6: NO), the controller 7 fixes the first upper SW element 12 to be on and the first lower SW element 13 to be off, repeatedly switching the second lower SW element 23 on and off (step S8). Figure 3The "on / off control" described in step S8 also refers to repeatedly switching the SW element on and off. It should be noted that in this case, the second upper SW element 22 can also be turned on or off. This is because, by using the freewheeling diode connected in reverse parallel with the second upper SW element 22, the current can always flow from the stator coil 31 to the second DC terminal 20p (i.e., the second battery 4).

[0063] When the second lower SW element 23 is disconnected, current flows from the first DC terminal 10p to the second DC terminal 20p, thus the first DC terminal 10p and the second DC terminal 20p become equipotential. When the second lower SW element 23 switches from disconnected to connected, the first DC terminal 10p is connected to the ground wire 9 via the stator coil 31 and the second lower SW element 23, thus a large current flows through the stator coil 31. At this time, magnetic energy is stored in the stator coil 31. When the second lower SW element 23 switches from connected to disconnected, the current flow from the stator coil 31 to the ground wire 9 is cut off. Through the self-induction of the stator coil 31, the charge of the capacitor 15 is attracted up through the freewheeling diode attached to the first lower SW element 13 and flows to the stator coil 31 and the second DC terminal 20p, thus pushing up the voltage at 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 through the second battery 4 increases, while the current flowing through the first battery 3 decreases. The second measured current rises, and the first measured current falls. Thus, both the first and second measured currents converge to the target current. That is, the currents flowing in the first battery 3 and the second battery 4 become equal.

[0064] It should be noted that "the second measured current is lower than the target current" strictly refers to "the second measured current < (target current - tolerance)".

[0065] (1D) When the second measured current is equal to the target current (step S4: YES), the controller 7 fixes the first lower SW element 13 and the second lower SW element 23 to be disconnected, and fixes the first upper SW element 12 to be connected (step S5). At this time, the second upper SW element 22 can also be either connected or disconnected. The voltage at the second DC terminal 20p is equal to the voltage at the first DC terminal 10p. The state in which the second measured current is equal to the target current is maintained.

[0066] The controller 7 repeatedly performs the above-described processes (1A) to (1D) (processes in steps S3 to S8) until the first battery 3 and the second battery 4 are fully charged (or reach the specified charge amount) (step S9: NO, S3). Shortly after the second measured current equals the target current, the second measured current becomes greater than the target current (or the second measured current is less than the target current), and then the process in step S7 is executed again (processes in step S8).

[0067] Through repeated practice Figure 3 The processing (the processing in (1A) to (1D) above) maintains the state in which the second measuring current is equal to the first measuring current. That is, the current supplied to the first battery 3 and the second battery is maintained to be equal.

[0068] If the first battery 3 and the second battery 4 reach full charge (or reach the specified charge level), then the controller 7 ends the process (step S9: YES, end). Although in Figure 3 Not shown in the diagram, but as a termination process, controller 7 instructs power supply 70 to stop output.

[0069] On the other hand, in step S2, if the output power of power supply 70 is less than the minimum power (step S2: NO), controller 7 executes... Figure 4 The processing. It should be noted that in the branch judgment of step S2, the case of "the output power of power supply 70 is equal to the minimum power" can be included in "YES" or "NO".

[0070] If the power supplied from the power source 70 is lower than the minimum power (step S2: NO), the controller 7 fixes the first lower SW element 13 and the second lower SW element 23 to be disconnected, and fixes the first upper SW element 12 and the second upper SW element 22 to be connected (step S12).

[0071] Controller 7 maintains the state of step S12 until the first battery 3 and the second battery 4 are fully charged (or reach a specified charge level) (step S13: NO). If the first battery 3 and the second battery 4 are fully charged (or reach a specified charge level), controller 7 ends the process (step S13: YES, end). Figure 4 Not shown in the diagram, but as a termination process, controller 7 instructs power supply 70 to stop output.

[0072] Through the process in step S12, the second battery 4 is also directly connected to the power supply 70 in the same way as the first battery 3. Current from the power supply 70 flows through both the first battery 3 and the second battery 4. If the characteristics of the first battery 3 and the second battery 4 are slightly different, the current flowing in the first battery 3 and the second battery 4 will be of different magnitudes.

[0073] When the output power of power supply 70 is lower than the minimum power, the current supplied to the two batteries is uneven, but because there is no on / off control by the SW component, the power loss is reduced. Figure 4 This process enables the output power of the power supply 70 to be effectively used for battery charging. It prevents a reduction in the power supplied to the battery due to power loss, thus preventing prolonged charging time.

[0074] As described above, the electric vehicle 2 can supply current equally to the first battery 3 and the second battery 4 using a dual-inverter structure. Furthermore, when the output power of the external power source 70 is low, the electric vehicle 2 abandons the practice of supplying current equally to the two batteries, thus suppressing the extension of charging time.

[0075] Here are some structural features of the electric vehicle 2. The electric vehicle 2 includes a first inverter 10, a second inverter 20, and a motor 30. The motor 30 has multiple stator coils 31. The first inverter 10 is a series connection of a first upper SW element 12 and a first lower SW element 13, and has multiple first series connectors 11a, 11b, and 11c. In each series connector, the first upper SW element 12 is located closer to the first DC terminal 10p, and the first lower SW element 13 is located closer to the ground wire 9. The midpoint of each of the multiple first series connectors 11a, 11b, and 11c is connected to one end of each stator coil 31.

[0076] The second inverter 20 is a series connection of the second upper SW element 22 and the second lower SW element 23, and has multiple second series connections 21a, 21b, and 21c. In each series connection, the second upper SW element 22 is located on the side closer to the second DC terminal 20p, and the second lower SW element 23 is located on the side closer to the ground wire 9. The midpoint of each of the multiple second series connections 21a, 21b, and 21c is connected to the other end of each stator coil 31.

[0077] This document describes important considerations related to the techniques illustrated in the embodiments. The techniques disclosed herein can be applied not only to electric vehicles without an engine, but also to hybrid vehicles equipped with a battery, motor, and engine. That is, the term "electric vehicle" in this specification only needs to include a motor and battery for driving, and may also include hybrid vehicles.

[0078] In this embodiment, the controller 7 simultaneously controls the on / off state of all the first upper SW elements 12. Alternatively, the controller 7 simultaneously controls the on / off state of all the second lower SW elements 23. The controller 7 may also control the on / off state of one or two SW elements, keeping the remaining SW elements connected in parallel disconnected.

[0079] The tolerance is set to a current amplitude that can be considered substantially equal to the first and second measured currents.

[0080] Battery 3 (first battery) and battery 4 (second battery) have essentially the same performance (same output voltage). However, due to manufacturing errors and differences in the degree of degradation, their characteristics differ slightly. Therefore, sometimes the current flowing through batteries 3 and 4 differs when they are connected in parallel with the power supply. Furthermore, since the difference in characteristics between batteries 3 and 4 is very small, a small voltage difference between the first DC terminal 10p and the second DC terminal 20p can be used to adjust the current flowing through each battery. Additionally, the voltage of the power supply 70 is the same as the voltage of the first and second batteries.

[0081] The statement "fixing the SW component to the ON position" is equivalent to the statement "closing the SW component," which means electrically connecting the devices connected to each terminal of the SW component. The statement "fixing the SW component to the OFF position" is equivalent to the statement "opening the SW component," which means electrically disconnecting the devices connected to each terminal of the SW component.

[0082] The specific examples of the present invention have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations to the specific examples described above. The technical elements illustrated in this specification or drawings exert their technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of application. Furthermore, the technology illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful.

Claims

1. An electric vehicle, wherein, This electric vehicle has the following features: A motor, equipped with stator coils; The first battery has a first positive terminal and a first negative terminal; Ground wire; The second battery has a second positive terminal and a second negative terminal connected to the ground wire; The first current sensor measures the current flowing into and out of the first battery; The second current sensor measures the current entering and exiting the second battery; The power receiving terminal has a positive power receiving terminal and a negative power receiving terminal that can be connected to a power source. The positive power receiving terminal is connected to the first positive terminal, and the negative power receiving terminal is connected to the ground wire. The first inverter has a first DC terminal connected to the first positive terminal, and has a first upper switching element and a first lower switching element connected in series between the first DC terminal and the ground wire, wherein 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. The second inverter has 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 wire. 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. The circuit selector selects either a series mode or a parallel mode. In the series mode, the first negative terminal is connected to the second positive terminal, and the first DC terminal is connected to the second DC terminal. In the parallel mode, the first negative terminal is connected to the ground wire, and the second positive terminal is connected to the second DC terminal, while the first DC terminal is disconnected from the second DC terminal. as well as Controller When the power supply is connected to the power receiving terminal, the controller sets the circuit selector to the parallel mode. (1) When the power supplied from the power source is higher than the predetermined minimum power, (1A) 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 is set as the target current for the current supplied to the second battery. (1B) When the second measured current is higher than the target current, the first lower switch element and the second lower switch element are fixed to be open, and the first upper switch element is repeatedly switched on and off to reduce the voltage of the power supply and output it to the second battery. (1C) When the second measured current is lower than the target current, the first upper switch element is fixed to be turned on, and the first lower switch element is fixed to be turned off. The second lower switch element is repeatedly turned on and off to boost the voltage of the power supply and output it to the second battery. (1D) When the second measured current is equal to the target current, the first lower switch element and the second lower switch element are fixed to be open, and the first upper switch element is fixed to be closed. (2) When the power supplied from the power source is lower than the minimum power, the first lower switch element and the second lower switch element are fixed to be disconnected, and the first upper switch element and the second upper switch element are fixed to be connected.

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