Charging system

Abstract

To allow a battery to be charged by any of a power supply with a higher output voltage than the battery and a power supply with a lower output voltage than the battery, in a charging system where a battery is charged by using an inverter and a motor.SOLUTION: A charging system disclosed in the present specification includes a power reception terminal, a motor, an inverter, a plurality of neutral point switching elements, and a plurality of diodes. The power receiving terminal includes a power receiving positive end and a power receiving negative end which are connected to a power supply. The power receiving negative end is connected to a battery negative electrode. The power receiving positive end is connected to a neutral point. A capacitor is connected between the power receiving positive end and the power receiving negative end, A battery is connected to a DC end of the inverter, and one end of each of a plurality of stator coils of the motor is connected to an AC end. The neutral point switching elements each connect the other end of a corresponding one of the stator coils to the neutral point. An anode of each of the diodes is connected to the power receiving negative end, and a cathode thereof is connected to the other end of a corresponding one of the stator coils.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology disclosed in this specification relates to a charging system that includes an inverter and a motor, and can charge a battery by using the switching elements of the inverter and the stator coils of the motor as a voltage converter.

Background Art

[0002] It is known that the circuit of the stator coils of a motor and the switching elements of an inverter can be used as a boost converter. Patent Document 1 discloses an apparatus that charges a battery with a power source having an output voltage lower than that of the battery by using the stator coils of a motor and the lower switching elements of an inverter as a boost converter.

[0003] In the apparatus of Patent Document 1, when charging the battery, the other ends of a plurality of stator coils are connected to each other at the neutral point, and a power source is connected to the neutral point. The current of the power source flows through the neutral point to the stator coils. By turning on and off the lower switching elements of the first inverter, the voltage of the power source is boosted by the stator coils. The power of the power source flows to the battery through the neutral point / stator coils / upper switching elements of the first inverter. Hereinafter, for the sake of convenience of explanation, the charging method of sending power to the battery through the neutral point is referred to as neutral point charging.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the system of Patent Document 1, it is not possible to step down the power supply voltage and send power to the battery. This specification provides a charging system that uses the stator coil of a motor as a reactor and can charge the battery using either a power supply with an output voltage lower than that of the battery or a power supply with an output voltage higher than that of the battery.

Means for Solving the Problems

[0006] The charging system disclosed in this specification includes a motor, a power receiving terminal, a capacitor, an inverter, a plurality of neutral point switching elements, and a plurality of diodes. The motor includes a plurality of stator coils. The power receiving terminal includes a power receiving positive terminal and a power receiving negative terminal to which a power supply is connected. The power receiving negative terminal is connected to the negative electrode of the battery (battery negative electrode). The power receiving positive terminal is connected to the neutral point. The capacitor is connected between the power receiving positive terminal and the power receiving negative terminal. The battery is connected to the DC terminal of the inverter, and one end of the plurality of stator coils is connected to the AC terminal. Each of the plurality of neutral point switching elements connects the other end of each of the plurality of stator coils to the neutral point. The anode of each of the plurality of diodes is connected to the power receiving negative terminal, and the cathode is connected to the other end of each of the plurality of stator coils.

[0007] When the output voltage of the power supply connected to the power receiving terminal is lower than the output voltage of the battery, the controller closes the neutral point switch and turns on and off the lower switching element of the inverter. By the on-off operation of the lower switching element, the voltage of the power supply is stepped up by the stator coil. The battery can be charged with a power supply having an output voltage lower than that of the battery. On the other hand, when the output voltage of the power supply is higher than the output voltage of the battery, the controller turns on and off the neutral point switching element. By the operation of the neutral point switching element, the voltage of the power supply is stepped down by the stator coil. The battery can be charged with a power supply having an output voltage higher than that of the battery.

[0008] The details and further improvements of the technology disclosed in this specification will be described in the following "Mode for Carrying Out the Invention".

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0010] (First Embodiment) Referring to the drawings, the charging system 2 of the first embodiment will be described. FIG. 1 shows a circuit diagram of the charging system 2 of the first embodiment. The charging system 2 includes a first inverter 10, a second inverter 20, a motor 30, a plurality of neutral point switching elements 32, a plurality of diodes 33, a power receiving terminal 40, and a controller 50. In addition to the charging system 2, a battery 60 and an external power source 70 are depicted in FIG. 1. The external power source 70 is detachable from the power receiving terminal 40.

[0011] The outline of the charging system 2 will be described. The charging system 2 can charge the battery 60 with the external power source 70 connected to the power receiving terminal 40. When charging the battery 60, the lower switching element of the first inverter 10 and the stator coil 31 of the motor 30 function as a boost converter. Therefore, the battery 60 can be charged with the external power source 70 whose output voltage is lower than that of the battery 60. Also, the neutral point switching element 32, the stator coil 31, and the diode 33 function as a buck converter. Therefore, even when the output voltage of the external power source 70 is higher than the output voltage of the battery 60, the battery 60 can be charged.

[0012] The charging system 2 and the battery 60 are mounted on an electric vehicle. The motor 30 is connected to an axle (not shown) of the electric vehicle, and the charging system 2 also functions as a drive system that drives the motor 30 with the power of the battery 60 to run the electric vehicle. The motor 30 is a three-phase AC motor and has a plurality of stator coils 31. The charging system 2 can drive the motor 30 only when the external power supply 70 is not connected to the power receiving terminal 40. Next, the details of the charging system 2 will be described.

[0013] The configuration of the first inverter 10 will be described. The battery 60 is connected to the DC terminal of the first inverter 10, and one end of the stator coil 31 is connected to the AC terminal. The first inverter 10 has three sets of first series-connected bodies 11a, 11b, and 11c. The three sets of first series-connected bodies 11a, 11b, and 11c are connected in parallel between the positive electrode terminal (battery positive electrode terminal 60p) and the negative electrode terminal (battery negative electrode terminal 60n) of the battery 60. The high potential side and the low potential side of the first series-connected bodies 11a, 11b, and 11c correspond to the DC terminal of the first inverter 10.

[0014] 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 battery positive electrode terminal 60p, and the first lower switching element 13 is connected to the battery negative electrode terminal 60n. One end of each of the three stator coils 31 is connected to the midpoint (connection point of the first upper switching element 12 and the first lower switching element 13) of each of the three sets of first series-connected bodies 11a, 11b, and 11c. When the controller 50 alternately turns on and off the first upper switching element 12 and the first lower switching element 13, AC is output from the midpoint. The midpoint of the first series-connected bodies 11a, 11b, and 11c corresponds to the AC terminal of the first inverter 10.

[0015] The configuration of the second inverter 20 will be described. A battery 60 is connected to the DC terminal of the second inverter 20, and the other end of the stator coil 31 is connected to the AC terminal. The second inverter 20 has three sets of second series-connected bodies 21a, 21b, and 21c. The three sets of second series-connected bodies 21a, 21b, and 21c are connected in parallel between the battery positive terminal 60p and the battery negative terminal 60n. The high-potential side and the low-potential side of the second series-connected bodies 21a, 21b, and 21c correspond to the DC terminal of the second inverter 20.

[0016] 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 second upper switching element 22 is connected to the battery positive terminal 60p, and the second lower switching element 23 is connected to the battery negative terminal 60n. The other end of each of the three stator coils 31 is connected to the midpoint (the connection point of the second upper switching element 22 and the second lower switching element 23) of each of the three sets of second series-connected bodies 21a, 21b, and 21c. When the controller 50 alternately turns on and off the second upper switching element 22 and the second lower switching element 23, AC is output from the midpoint. The midpoint of the second series-connected bodies 21a, 21b, and 21c corresponds to the AC terminal of the second inverter 20.

[0017] Freewheeling diodes are connected in anti-parallel to the switching elements of the first inverter 10 and the second inverter 20. The freewheeling diode may be a separate element from the switching element, or may be a diode element included in the switching element.

[0018] The charging system 2 includes a plurality of neutral point switching elements 32. Each of the plurality of neutral point switching elements 32 connects the other end of each of the plurality of stator coils 31 to the neutral point 34. When the plurality of neutral point switching elements 32 are closed, the plurality of stator coils 31 are electrically connected to each other at the neutral point 34. When the plurality of neutral point switching elements 32 are opened, the plurality of stator coils 31 are electrically disconnected from the neutral point 34.

[0019] A freewheeling diode is connected in antiparallel to each of the plurality of neutral point switching elements 32. The freewheeling diode may be a separate element from the neutral point switching element 32, or may be a diode element included in the neutral point switching element 32.

[0020] The charging system 2 includes a power receiving terminal 40. The power receiving terminal 40 includes a power receiving positive terminal 40p to which the positive electrode 70p of the external power source 70 is connected, and a power receiving negative terminal 40n to which the negative electrode 70n of the external power source 70 is connected. A capacitor 41 is connected between the power receiving positive terminal 40p and the power receiving negative terminal 40n. Note that a capacitor 61 is connected between the battery positive terminal 60p and the battery negative terminal 60n.

[0021] The charging system 2 includes a pair of charging switches 35. One charging switch 35 is connected between the neutral point 34 and the power receiving positive terminal 40p, and the other charging switch 35 is connected between the anode of each of the plurality of diodes 33 and the power receiving negative terminal 40n. The charging switch 35 is provided to completely disconnect the power receiving terminal 40 from the stator coil 31.

[0022] As described above, the charging system 2 also functions as a drive system that drives the motor 30 with the power of the battery 60. The controller 50 closes the plurality of neutral point switching elements 32. When the neutral point switching elements 32 are closed, the other ends of the plurality of stator coils 31 are mutually connected at the neutral point 34.

[0023] When the neutral point switching elements 32 are closed, the motor 30 functions as a closed-type motor with the other ends Y-connected. The controller 50 stops the second inverter 20 and appropriately turns on and off the first upper switching element 12 and the first lower switching element 13 of the first inverter 10. An alternating current is supplied from the AC terminal of the first inverter 10 to the stator coil 31, and the motor 30 rotates.

[0024] When driving the motor 30 with two inverters (the first inverter 10 and the second inverter 20), the controller 50 opens a plurality of neutral point switching elements 32. One end of the stator coil 31 of the motor 30 is connected to the AC terminal of the first inverter 10, and the other end is connected to the AC terminal of the second inverter 20. The motor 30 functions as an open-type motor. When the controller 50 appropriately turns on and off the switching elements of the first inverter 10 and the second inverter 20, the motor 30 rotates. At this time, since the motor 30 is driven by the two inverters 10 and 20, it can output higher torque compared to the case of driving with only the first inverter 10.

[0025] Note that the driving of the motor 30 is limited to the case where the external power source 70 is not connected to the power receiving terminal 40. If the external power source 70 is connected when driving the motor 30, there is a risk that an inconvenient current may flow in the charging system 2. Therefore, when driving the motor 30, the pair of charging switches 35 are opened to completely disconnect the neutral point 34 and the diode 33 from the power receiving terminal 40.

[0026] The charging system 2 can charge the battery 60 whether the output voltage of the external power source 70 is higher or lower than the output voltage of the battery. Note that prior to charging the battery 60, the controller 50 closes the pair of charging switches 35.

[0027] First, the operation of the controller 50 when the output voltage of the external power source 70 connected to the power receiving terminal 40 is lower than the output voltage of the battery 60 will be described.

[0028] When an external power supply 70 with an output voltage lower than that of the battery 60 is connected to the power receiving terminal 40, the controller 50 closes a plurality of neutral point switching elements 32. Then, the controller 50 appropriately turns on and off a plurality of first lower switching elements 13 of the first inverter 10. When the controller 50 turns on the first lower switching element 13, current flows from the external power supply 70 through the neutral point switching element 32, the stator coil 31, and the first lower switching element 13 to the capacitor 61, and magnetic energy is stored in the stator coil 31. When the controller 50 switches the first lower switching element 13 from on to off, the magnetic energy of the stator coil 31 is released, and current is pushed out from the stator coil 31 toward the positive terminal 60p of the battery by the induced electromotive force. At this time, the voltage of the external power supply 70 is boosted. The current flows from the external power supply 70 to the battery 60 through the neutral point switching element 32, the stator coil 31, and the freewheeling diode of the first upper switching element 12. That is, the battery 60 is charged by the external power supply 70 having an output voltage lower than that of the battery 60.

[0029] Next, the operation of the controller 50 when the output voltage of the external power supply 70 connected to the power receiving terminal 40 is higher than the output voltage of the battery 60 will be described. In this case, the controller 50 appropriately turns on and off the neutral point switching element 32. When the controller 50 closes the neutral point switching element 32, current flows from the external power supply 70 to the battery 60 through the neutral point switching element 32, the stator coil 31, and the freewheeling diode of the first upper switching element 12. At the same time, magnetic energy is stored in the stator coil 31.

[0030] When the controller 50 switches the neutral point switching element 32 from on to off, the current from the external power supply 70 to the battery 60 stops. At the same time, the magnetic energy stored in the stator coil 31 is released. The released magnetic energy generates an induced electromotive force, and the stator coil 31 draws charge from the capacitor 41 through the diode 33 and sends it to the battery 60. That is, the neutral point switching element 32, the stator coil 31, and the capacitor 41 function as a buck converter. The battery 60 is charged by the external power supply 70 whose output voltage is higher than that of the battery 60.

[0031] The charging system 2 includes a direct charging switch 37 that connects the power receiving positive terminal 40p to the battery positive terminal 60p by bypassing the stator coil 31. When the output voltage of the external power supply 70 connected to the power receiving terminal 40 is equal to the output voltage of the battery 60, the controller 50 closes the direct charging switch 37. The external power supply 70 and the battery 60 are directly connected. In this case, current flows from the external power supply 70 to the battery 60 by bypassing the stator coil 31 and the switching element. By charging the battery 60 through the direct charging switch 37, the charging loss can be kept low.

[0032] (Second Embodiment) FIG. 2 shows a circuit diagram of the charging system 102 of the second embodiment. In the charging system 102, the diode 33 of the charging system 2 of the first embodiment is replaced with an additional switching element 133. Other configurations of the charging system 102 are the same as those of the charging system 2 of the first embodiment.

[0033] The additional switching element 133 is accompanied by a freewheeling diode 133a. The anode of each freewheeling diode 133a is connected to the power receiving negative terminal 40n, and the cathode is connected to the other end of each stator coil 31. The freewheeling diode plays the same role as the diode 33 of the charging system 2 of the first embodiment. Therefore, when the additional switching element 133 is open, the charging system 102 operates in the same way as the charging system 2 and provides the same advantages.

[0034] The advantages of having the additional switching element 133 will be described. Connect an electrical device that consumes power to the power receiving terminal 40 instead of an external power supply. When a pair of charging switches 35 are closed and the additional switching element 133 is turned on and off as appropriate, the voltage of the battery 60 is boosted and output to the power receiving terminal 40. That is, the charging system 102 including the additional switching element 133 functions as a power supply that can boost the output voltage of the battery 60 and output it externally.

[0035] Note that an electrical device that consumes power is connected to the power receiving terminal 40, and a pair of charging switches 35 and the neutral point switching element 32 are closed. When the first upper switching element 12 is turned on and off as appropriate, the voltage of the battery 60 is stepped down by the stator coil 31 and output from the power receiving terminal 40. That is, the charging system 102 can also step down the output voltage of the battery 60 and output it externally.

[0036] Some features of the charging system 2 (102) described in the embodiment will be listed. The battery 60 is connected to the DC terminal of the first inverter 10, and a plurality of stator coils 31 are connected to the AC terminal. The power receiving terminal 40 includes a power receiving positive terminal 40p and a power receiving negative terminal 40n, to which an external power supply 70 can be connected. The power receiving negative terminal 40n is connected to the battery negative terminal 60n, and the power receiving positive terminal 40p is connected to the neutral point 34 of the motor 30. A capacitor 41 is connected between the power receiving positive terminal 40p and the power receiving negative terminal 40n. Each of the plurality of neutral point switching elements 32 connects the other end of each of the plurality of stator coils 31 to the neutral point 34. The anode of each of the plurality of diodes 33 is connected to the power receiving negative terminal 40n, and the cathode is connected to the other end of each of the plurality of stator coils 31. With this configuration, the battery 60 can be charged regardless of whether the output voltage of the external power supply 70 is higher or lower than the output voltage of the battery 60. The first inverter 10 corresponds to an example of an "inverter". The external power supply 70 corresponds to an example of a "power supply".

[0037] When the output voltage of the external power supply 70 connected to the power receiving terminal 40 is lower than the output voltage of the battery 60, the controller 50 closes a plurality of neutral point switching elements 32. Then, the controller 50 turns on and off the first lower switching element 13 of the first inverter 10. As a result, the voltage of the external power supply 70 is boosted to the voltage of the battery 60. The power of the external power supply 70 is supplied to the battery 60, and the battery 60 is charged. When the output voltage of the external power supply 70 connected to the power receiving terminal 40 is higher than the output voltage of the battery 60, the controller 50 turns on and off the neutral point switching elements 32. As a result, the voltage of the external power supply 70 is bucked to the voltage of the battery 60. The power of the external power supply 70 is supplied to the battery 60, and the battery 60 is charged.

[0038] When the external power supply 70 is not connected to the power receiving terminal 40 and the battery 60 drives the motor 30, the controller 50 closes a plurality of neutral point switching elements 32. Then, the controller 50 alternately turns on and off the first upper switching element 12 and the first lower switching element 13 of the first inverter 10. The motor 30 is driven by this operation.

[0039] The charging system 2 (102) may include a direct charging switch 37 that connects the power receiving positive terminal 40p to the battery positive terminal 60p by bypassing the stator coil 31. The charging system 2 (102) may further include a second inverter 20 (sub-inverter) whose DC terminal is connected to the battery 60 and whose AC terminal is connected to the other ends of the plurality of stator coils 31.

[0040] Points to note regarding the technology described in the embodiments are described. The pair of charging switches 35 may be omitted. The pair of charging switches 35 is provided to prevent inconveniences when the motor 30 is accidentally driven while the external power supply 70 is connected.

[0041] The second inverter 20 may also be omitted. Even without the second inverter 20, the charging system 2 (102) has the advantages described above. However, by providing the second inverter 20, the motor 30 can be driven by two inverters (the first inverter 10 and the second inverter 20). That is, high torque can be output from the motor 30. The second inverter 20 corresponds to an example of a sub-inverter.

[0042] The charging system 2 (102) can drive the motor 30 with the first inverter 10 and the second inverter 20. Therefore, the charging system 2 (102) may be alternatively referred to as a "drive charging system".

[0043] The expression "the switching element is closed" means that the devices connected to both ends of the switching element are electrically connected. The expression "the switching element is opened" means that the devices connected to both ends of the switching element are electrically separated. The expression "the switching element is closed" is equivalent to the expression "the switching element is turned on". The expression "the switching element is opened" is equivalent to the expression "the switching element is turned off".

[0044] As described above, specific examples of the present invention have been described in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the 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. Also, the technology illustrated in this specification or the drawings can achieve a plurality of purposes simultaneously, and achieving one of those purposes itself has technical utility.

Explanation of Reference Numerals

[0045] 2, 102: Charging system 10, 20: Inverter 11a - 11c, 21a - 21c: Series connector 12, 22: Upper switching element 13, 23: Lower switching element 30: Motor 31: Stator coil 32: Neutral point switching element 33: Diode 34: Neutral point 35: Charging switch 37: Direct charging switch 40: Power receiving terminal 41, 61: Capacitor 50: Controller 60: Battery 70: External power source 133: Additional switching element 133a: Freewheeling diode

Claims

1. A charging system that transforms the voltage of a power source to charge a battery, a motor having a plurality of stator coils, a power receiving terminal having a power receiving positive terminal and a power receiving negative terminal to which the power source can be connected, wherein the power receiving negative terminal is connected to the battery negative terminal of the battery, and the power receiving positive terminal is connected to the neutral point of the motor, a capacitor connected between the power receiving positive terminal and the power receiving negative terminal, an inverter having a DC terminal connected to the battery and an AC terminal connected to one end of a plurality of the stator coils, a plurality of neutral point switching elements, each of the neutral point switching elements connecting the other end of each of the plurality of stator coils to the neutral point, a plurality of diodes, the anode of each of the diodes being connected to the power receiving negative terminal and the cathode being connected to the other end of each of the plurality of stator coils, A charging system comprising the above.

2. Further comprising a controller, the controller closing a plurality of the neutral point switching elements when the output voltage of the power source connected to the power receiving terminal is lower than the output voltage of the battery, turning on and off the lower switching element of the inverter to boost the voltage of the power source to charge the battery, when the output voltage of the power source connected to the power receiving terminal is higher than the output voltage of the battery, turning on and off the neutral point switching element to step down the voltage of the power source to charge the battery. The charging system according to Claim 1.

3. When the power source is not connected to the power receiving terminal and the battery is used to drive the motor, the controller closes a plurality of the neutral point switching elements and turns on and off the upper and lower switching elements of the inverter. The charging system according to Claim 1 or 2.

4. The charging system according to Claim 1, further comprising a direct charging switch that bypasses the stator coil and connects the power receiving positive terminal to the battery positive terminal.

5. The charging system according to Claim 1, further comprising a sub-inverter having a DC terminal connected to the battery and an AC terminal connected to the other end of a plurality of the stator coils.

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