Power source system

Abstract

This power source system comprises: a first battery; a second battery having the same configuration as the first battery; a voltage converter connected to an on-board power generation device; a series / parallel switching circuit capable of switching between series connection of the first battery and the second battery and parallel connection thereof, by turning on and off a plurality of relays; and a control device for controlling driving of the plurality of relays of the series / parallel switching circuit. When the first battery and the second battery are charged using electric power from the power generation device, the control device controls the plurality of relays so that the first battery and the second battery are charged in parallel connection.

Description

Power System

[0001] The present disclosure relates to a power supply system, and more particularly to a power supply system including two batteries that can be charged and discharged by series connection and by parallel connection.

[0002] A conventional power supply system of this type has been proposed that includes two batteries that can be charged and discharged in series or in parallel (see, for example, Patent Document 1). In this system, the batteries are charged and discharged so that the potential difference between the two batteries is equal to or less than a predetermined threshold, thereby balancing the voltages of the two batteries.

[0003] Japanese Patent Application Laid-Open No. 2019-080474

[0004] However, in the above-mentioned power supply system, when the motor is driven, the two batteries are connected in series and discharged, and when charging from an external power source, the two batteries are connected in parallel and charged, or the two batteries are connected in series and charged.However, when charging the two batteries using power generated by an on-board solar panel, it is necessary to consider whether to charge the two batteries in series or in parallel.

[0005] The power supply system of the present disclosure has as its main object to improve the efficiency when charging two batteries that can be connected in series or in parallel using power from an on-board power generation device.

[0006] The power supply system of the present disclosure employs the following measures to achieve the above-mentioned main object.

[0007] The power supply system disclosed herein is an on-board power supply system comprising: a first battery; a second battery having the same configuration as the first battery; a voltage converter connected to an on-board power generation device; a series-parallel switching circuit having a plurality of relays that can switch between a series connection of the first battery and the second battery and a parallel connection of the first battery and the second battery by turning the plurality of relays on and off; and a control device that drives and controls the plurality of relays of the series-parallel switching circuit, wherein the control device controls the plurality of relays so that the first battery and the second battery are charged in a parallel connection when charging the first battery and the second battery with power from the power generation device.

[0008] The power supply system disclosed herein is mounted on a vehicle and includes a first battery, a second battery having the same configuration as the first battery, a connector for connecting to a power generation device, a series-parallel switching circuit that switches between a series connection of the first battery and the second battery and a parallel connection of the first battery and the second battery by turning on and off multiple relays, and a control device that drives and controls the multiple relays of the series-parallel switching circuit. The power generation device is mounted on the vehicle. The control device controls the multiple relays to charge the first battery and the second battery in a parallel connection when charging the first battery and the second battery with power from the power generation device. When charging the first battery and the second battery in a parallel connection, the charging voltage needs to be slightly higher than the voltage of the first battery or the second battery, and when charging the first battery and the second battery in a series connection, the charging voltage needs to be slightly higher than the sum of the voltages of the first battery and the second battery. Therefore, when charging the first battery and the second battery in a parallel connection, the voltage converter only needs to boost the voltage to a lower level than when charging the first battery and the second battery in a series connection. This reduces loss during voltage step-up in the voltage converter, improving charging efficiency. Here, the power generation device also includes a solar power generation device.

[0009] In the power supply system of the present disclosure, the relays that are frequently in the on state among the plurality of relays may be configured as normally-on relays or semiconductor switches, thereby improving the durability of the relays that are frequently in the on state.

[0010] In the power supply system of the present disclosure, the series-parallel switching circuit includes a series connection line connecting the negative terminal of the first battery and the positive terminal of the second battery, a series connection relay attached to the series connection line, a positive bus bar connected to the positive terminal of the first battery, a negative bus bar connected to the negative terminal of the second battery, an inverter connected to the positive bus bar and the negative bus bar, a three-phase AC motor driven by the inverter, a positive side relay attached to the positive bus bar, a negative side relay attached to the negative bus bar, and a series connection relay connected to the series connection line by the series connection relay. The three-phase AC motor may include a first parallel connection line connecting a first battery side and the negative bus bar, a first parallel connection relay attached to the first parallel connection line, a second parallel connection line connecting a positive terminal of the second battery and a neutral point of the three-phase AC motor, and a second parallel connection relay and a third parallel connection relay attached to the second parallel connection line in this order from the second battery side, wherein the connection connector is connected from the positive side relay of the positive bus bar to the first battery side and from the negative side relay of the negative bus bar to the second battery side via a power line having a charging relay. In this case, the series connection relay and the charging relay may be configured as a normally-on relay or a semiconductor switch.

[0011] 1 is a configuration diagram showing an outline of the configuration of a power supply system 20 according to an embodiment of the present disclosure. 2 is a table showing the states of each relay in various states of the power supply system 20. 3 is an explanatory diagram showing the flow of current when a first battery 26a and a second battery 26b are connected in parallel and charged with DC power from a solar panel 49. 4 is an explanatory diagram showing the flow of current when a first battery 26a and a second battery 26b are connected in series and charged with DC power from a solar panel 49.

[0012] Next, a mode (embodiment) for carrying out the present disclosure will be described. Fig. 1 is a configuration diagram showing an outline of the configuration of a power supply system 20 according to one embodiment of the present disclosure. The power supply system 20 of the embodiment functions as a device for exchanging power between a battery 26 and an inverter 24 that drives a motor 22, and also functions as a device for charging and discharging the battery 26 using the motor 22 and the inverter 24 as needed. The power supply system 20 includes the battery 26, the motor 22, the inverter 24, a main power supply circuit 30, an AC charging circuit 40, a DC charging circuit 50, and an electronic control unit 60.

[0013] The motor 22 is configured as a well-known three-phase AC motor, for example, including a rotor with a permanent magnet attached to its outer surface and a stator around which three-phase coils are wound. The inverter 24 is configured with six transistors T1 to T6 as switching elements and six diodes D1 to D6 connected in parallel in reverse to the transistors T1 to T6. The transistors T1 to T6 are arranged in pairs, two at a time, so that the inverter 24 is on the source side and the other on the sink side of the positive bus 31B and negative bus 31G of the battery 26. The transistors T1 to T6 are connected to the three-phase coils (U-phase, V-phase, and W-phase) of the motor 22 at their respective junctions. The inverter 24 generates a rotating magnetic field in the three-phase coils and drives the motor 22 to rotate by controlling the proportion of the on-time of the paired transistors T1 to T6 while a voltage is applied between the positive bus 31B and negative bus 31G. A first smoothing capacitor 32 is attached between the positive bus bar 31B and the negative bus bar 31G.

[0014] The battery 26 includes a first battery 26a and a second battery 26b configured similarly to the first battery 26a. The first battery 26a and the second battery 26b are configured, for example, as lithium-ion secondary batteries or nickel-metal hydride secondary batteries. The positive terminal of the first battery 26a is connected to a positive bus 31B, and the negative terminal of the second battery 26b is connected to a negative bus 31G. The negative terminal of the first battery 26a is connected to the positive terminal of the second battery 26b via a series power line 35 equipped with a relay DCRNN included in the main power supply circuit 30. Therefore, by turning on the relay DCRNN, the first battery 26a and the second battery 26b function as a single battery connected in series.

[0015] In addition to the positive bus 31B, negative bus 31G, and series power line 35, the power supply main circuit 30 also includes a first parallel power line 36 connecting the negative terminal of the first battery 26a to the negative bus 31G, and a second parallel power line 37 connecting the positive terminal of the second battery 26b to the neutral point of the motor 22. A positive relay SMRB is attached to the positive bus 31B, and a negative relay SMRG is attached to the negative bus 31G. A precharge circuit consisting of a precharge relay SMRP and a resistor R is also provided in parallel with the negative relay SMRG on the negative bus 31G. The positive relay SMRB, negative relay SMRG, and precharge circuit constitute a system main relay. That is, when the first battery 26a and the second battery 26b are connected in series, the positive side relay SMRB is turned on and the pre-charge relay SMRP is turned on to charge the first capacitor 32, and when charging of the first capacitor 32 is completed, the negative side relay SMRG is turned on and the pre-charge relay SMP is turned off, thereby enabling power from the battery 26 consisting of the first battery 26a and the second battery 26b connected in series to be supplied to the inverter 24, or conversely, the battery 26 to be charged using regenerative power from the motor 22.

[0016] A relay DCRNG is attached to the first parallel power line 36. A relay DCRNB is attached to the second parallel power line 37 on the side of the second battery 26b, and a relay DCRN is attached to the neutral point side of the motor 22. A second capacitor 38 is attached between the relays DCRNB and DCRN on the second parallel power line 37 and the negative bus 31G.

[0017] AC charging circuit 40 includes an AC charging power line 41 connected to positive bus 31B and negative bus 31G, an on-board charger (OBC) 43 connected to AC charging power line 41 via filter 42, an AC charging connector 45 connected to on-board charger 43 via power line 44, a DC / DC converter 46 connected to AC charging power line 41 via filter 42 so as to be in parallel with on-board charger 43, and auxiliary equipment 48 and a solar panel 49 connected to DC / DC converter 46 via power line 47. A relay SSRB is attached to the positive side line of AC charging power line 41, and a relay SSRG is attached to the negative side line.

[0018] The DC charging circuit 50 includes a DC charging power line 51 connected to the positive bus 31B and the negative bus 31G, and a DC charging connector 55 connected to the DC charging power line 51. A relay DCRB is attached to the positive side line of the DC charging power line 51, and a relay DCRG is attached to the negative side line.

[0019] The electronic control unit 60 is configured as a microcomputer centered around a CPU (not shown). Signals are input to the electronic control unit 60 from various sensors. Examples of the various sensors include a voltage sensor 33 that detects the voltage VH across the terminals of the first capacitor 32, a voltage sensor 39 that detects the voltage VD across the terminals of the second capacitor 38, a current sensor 31a that detects the current Ib1 flowing through the first battery 26a, a current sensor 37a that detects the current Id flowing through the second parallel power line 37, phase current sensors (not shown) that detect the phase currents Iu, Iv, and Iw flowing through the three phases of the motor 22, a voltage sensor (not shown) that detects the voltage Vb1 across the terminals of the first battery 26a, and a voltage sensor (not shown) that detects the voltage Vb2 across the terminals of the second battery 26b. The electronic control unit 60 also functions as a control device for driving the motor 22, and therefore receives drive commands and other inputs. In addition, when the power supply system 20 is mounted on a vehicle and the motor 22 is used as a driving motor, the accelerator opening and vehicle speed may be input to the electronic control unit 60, and the electronic control unit 60 may generate a torque command for the motor 22.

[0020] The electronic control unit 60 outputs drive control signals to the respective relays and switching control signals to the inverter 24. Examples of the respective relays include a positive side relay SMRB, a negative side relay SMRG, a precharge relay SMRP, a relay DCRNN, a relay DCRNG, a relay DCRNB, a relay DCRN, a relay SSRB, a relay SSRB, a relay DCRB, and a relay DCRG.

[0021] 2 is a table showing the states of the relays in various states of the power supply system 20. (1) When the motor 22 is driven as a traction motor to travel, the positive side relay SMRB, the negative side relay SMRG, the relay SSRB, the relay SSRG, and the relay DCRNN are turned on, and the relays DCRB, DCRG, DCRN, DCRB, and DCRG are turned off. (2) When a connector from an AC charging stand is connected to AC charging connector 45 and battery 26 is charged with AC power from the AC charging stand, or when an external electrical load is connected to AC charging connector 45 and power from battery 26 is supplied to the external electrical load as AC power, relays SSRB, SSRG, and DCRNN are turned on, and positive side relay SMRB, negative side relay SMRG, relay DCRB, relay DCRG, relay DCRN, relay DCRB, and relay DCRG are turned off.

[0022] (3) When a connector from a DC charging stand is connected to the DC charging connector 55 and the first battery 26a and the second battery 26b are connected in parallel and charged using DC power from the DC charging stand, or when an external electrical load is connected to the DC charging connector 55 and the first battery 26a and the second battery 26b are connected in parallel and power from the battery 26 is supplied to the external electrical load as DC power, the positive side relay SMRB, the negative side relay SMRG, relay SSRB, relay SSRG, relay DCRB, relay DCRG, relay DCRN, relay DCRB, and relay DCRG are turned on, and relay DCRNN is turned off.

[0023] (4) When a connector from a DC charging stand is connected to the DC charging connector 55 and the first battery 26a and the second battery 26b are connected in series and charged using DC power from the DC charging stand, or when an external electrical load is connected to the DC charging connector 55 and the first battery 26a and the second battery 26b are connected in series and power from the battery 26 is supplied to the external electrical load as DC power, the positive side relay SMRB, the negative side relay SMRG, relay SSRB, relay SSRG, relay DCRNN, relay DCRB, and relay DCRG are turned on, and the relays DCRNB, DCRNG, and DCRN are turned off.

[0024] (5) When power is supplied to an auxiliary device 48 such as a drive recorder while the vehicle is parked, the relays SSRB, SSRG, and DCRNN are turned on, and the positive side relay SMRB, negative side relay SMRG, relay DCRNB, relay DCRNG, relay DCRN, relay DCRB, and relay DCRG are turned off.

[0025] (6) When the first battery 26a and the second battery 26b are connected in parallel and charged using power generated by the solar panel 49, the positive side relay SMRB, the negative side relay SMRG, the relay SSRB, the relay SSRG, the relay DCRNB, the relay DCRNG, and the relay DCRN are turned on, and the relays DCRNN, DCRB, and DCRG are turned off. Figure 3 is an explanatory diagram showing the current flow when the first battery 26a and the second battery 26b are connected in parallel and charged using DC power from the solar panel 49. In the figure, the thick solid line with an arrow indicates the charging current of the first battery 26a, and the thick dashed line with an arrow indicates the charging current of the second battery 26b. Note that when the first battery 26a and the second battery 26b are connected in parallel and charged using DC power from the solar panel 49, the above-mentioned relays are turned on and off, and the upper arm of the inverter 24 is turned on. As shown by the thick solid line with an arrow in Fig. 3, the first battery 26a is charged by a charging current that flows in this order from the solar panel 49 to the DC / DC converter 46, the filter 42, the relay SSRB of the AC charging power line 41, the positive electrode bus 31B, the first battery 26a, the relay DCRNG of the first parallel power line 36, the negative electrode bus 31G, and the relay SSRB of the AC charging power line 41. The second battery 26b is charged by a charging current that flows in this order from the solar panel 49 to the DC / DC converter 46, the filter 42, the relay SSRB of the AC charging power line 41, the positive electrode relay SMRB of the positive electrode bus 31B, the upper arm of the inverter 24, the neutral point of the motor 22, the relay DCRN and relay DCRNB of the second parallel power line 37, the second battery 26b, the negative electrode bus 31G, and the relay SSRB of the AC charging power line 41. In this case, the boosted voltage of the DC / DC converter 46 is slightly higher than the voltage of the first battery 26a and the second battery 26b.

[0026] (7) When the first battery 26a and the second battery 26b are connected in series and charged using power generated by the solar panel 49, the relays SSRB, SSRG, and DCRNN are turned on, and the positive-side relay SMRB, the negative-side relay SMRG, relay DCRNB, relay DCRNG, relay DCRN, relay DCRB, and relay DCRG are turned off. Figure 4 is an explanatory diagram showing the current flow when the first battery 26a and the second battery 26b are connected in series and charged using DC power from the solar panel 49. In the figure, the thick solid line with an arrow indicates the charging current for charging the first battery 26a and the second battery 26b. 4, the first battery 26a and the second battery 26b are charged by a charging current that flows in this order from the solar panel 49 through the DC / DC converter 46, the filter 42, the relay SSRB of the AC charging power line 41, the positive electrode bus 31B, the first battery 26a, the relay DCRNN of the series connection power line 35, the second battery 26b, the negative electrode bus 31G, and the relay SSRB of the AC charging power line 41. In this case, the boosted voltage of the DC / DC converter 46 is slightly higher than the sum of the voltages of the first battery 26a and the second battery 26b, and is higher than when the first battery 26a and the second battery 26b are connected in parallel and charged.

[0027] In the power supply system 20 of this embodiment, when the first battery 26a and the second battery 26b are charged using power generated by the solar panel 49, the first battery 26a and the second battery 26b are connected in parallel. By connecting the first battery 26a and the second battery 26b in parallel in this manner, the boost voltage of the DC / DC converter 46 can be lowered compared to when the first battery 26a and the second battery 26b are connected in series, thereby reducing loss in the DC / DC converter 46 and improving charging efficiency. Note that instead of the solar panel 49, another power generation device, such as a fuel cell, may be installed.

[0028] In the power supply system 20 of the embodiment, as shown in Fig. 2, the relays SSRB, SSRG, and DCRNN are frequently turned on. For this reason, in the power supply system 20 of the embodiment, the relays SSRB, SSRG, and DCRNN are normally on relays or semiconductor switches. This makes it possible to improve the durability of these relays, which are frequently turned on.

[0029] The correspondence between the main elements of the embodiment and the main elements of the invention described in the "Means for Solving the Problem" section will be described below. In the embodiment, the first battery 26a corresponds to the "first battery," the second battery 26b corresponds to the "second battery," the solar panel 49 corresponds to the "power generation device," the DC / DC converter 46 corresponds to the "voltage converter," the main power supply circuit 30 corresponds to the "series-parallel switching circuit," the electronic control unit 60 corresponds to the "control device," and the power supply system 20 corresponds to the "power supply system."

[0030] The correspondence between the main elements of the embodiments and the main elements of the invention described in the "Means for Solving the Problem" section does not limit the elements of the invention described in the "Means for Solving the Problem" section, since the embodiments are examples for specifically explaining the mode for implementing the invention described in the "Means for Solving the Problem" section. In other words, the interpretation of the invention described in the "Means for Solving the Problem" section should be based on the description in that section, and the embodiments are merely specific examples of the invention described in the "Means for Solving the Problem" section.

[0031] The present disclosure has been described above using embodiments, but the present disclosure is not limited to these embodiments in any way, and it goes without saying that the present disclosure can be embodied in various forms within the scope that does not deviate from the gist of the present disclosure.

[0032] The present disclosure is applicable to the power supply system manufacturing industry and the like.

Claims

1. A power supply system for a vehicle comprising: a first battery; a second battery having the same configuration as the first battery; a voltage converter connected to an on-board power generation device; a series-parallel switching circuit having a plurality of relays that can switch between a series connection of the first battery and the second battery and a parallel connection of the first battery and the second battery by turning the plurality of relays on and off; and a control device that drives and controls the plurality of relays of the series-parallel switching circuit, wherein the control device controls the plurality of relays so that the first battery and the second battery are charged in parallel when charging the first battery and the second battery with power from the power generation device.

2. A power supply system according to claim 1, wherein the relays which are frequently in an on state among said plurality of relays are configured as normally-on relays or semiconductor switches.

3. A power supply system according to claim 1 or 2, the series-parallel switching circuit comprises: a series connection line connecting the negative terminal of the first battery and the positive terminal of the second battery; a series connection relay attached to the series connection line; a positive bus bar connected to the positive terminal of the first battery; a negative bus bar connected to the negative terminal of the second battery; an inverter connected to the positive bus bar and the negative bus bar; a three-phase AC motor driven by the inverter; a positive side relay attached to the positive bus bar; a negative side relay attached to the negative bus bar; a first parallel connection line connecting the first battery side and the negative bus bar via the series connection relay on the series connection line; a first parallel connection relay attached to the first parallel connection line; a second parallel connection line connecting the positive terminal of the second battery and a neutral point of the three-phase AC motor; the connector is connected to the first battery side of the positive electrode side relay of the positive electrode bus bar and to the second battery side of the negative electrode side relay of the negative electrode bus bar via a power line having a charging relay.

4. A power supply system according to claim 3, wherein the series connection relay and the charging relay are configured as normally-on relays or semiconductor switches.

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