Power supply system

Abstract

To inhibit excessive current from flowing when charging two batteries, which are capable of performing charging / discharging using serial connection and charging / discharging using parallel connection, using the parallel connection.SOLUTION: In a power supply system comprising a first battery and a second battery capable of being charged / discharged using serial connection and being charged / discharged using parallel connection using an inverter and a three-phase coil of a motor, the second battery is charged by stepping down charge power by performing switching of the inverter when an open voltage difference obtained by subtracting an open voltage of the second battery from an open voltage of the first battery is equal to or larger than a predetermined voltage difference in starting parallel charging by turning on an upper arm of the inverter.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[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. [Background technology]

[0002] A conventional power supply system of this type has been proposed that has 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. This balances the voltages of the two batteries. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-080474 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above power supply system, if for some reason there is a difference in voltage between the two batteries and you try to charge them by connecting them in parallel, an excessive current may flow from the higher voltage battery to the lower voltage battery.

[0005] The power supply system of the present disclosure has as its main object the prevention of excessive current flow when two batteries that can be charged and discharged in series connection and in parallel connection are charged in parallel connection. [Means for solving the problem]

[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 of the present disclosure includes a first battery, a second battery, 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 of the series connection relay on the series connection line to the negative bus bar, a first parallel connection relay attached to the first parallel connection line, and a second parallel connection line connecting the positive terminal of the second battery and a neutral point of the three-phase AC motor. A power supply system comprising: a second parallel connection relay attached to the second parallel connection line in sequence from the second battery side; a DC charging connector connected via a power line having a charging relay on the inverter side from the positive side relay of the positive bus bar and on the inverter side from the negative side relay of the negative bus bar; and a control device that controls the relays and the inverter, wherein the control device is characterized in that when parallel charging of the first battery and the second battery is started with the positive side relay, the negative side relay, the first parallel connection relay, and the second parallel connection relay turned on and the series connection relay turned off, if the voltage difference obtained by subtracting the voltage of the second battery from the voltage of the first battery is equal to or greater than a predetermined voltage difference, the control device switches the inverter to reduce the charging power and charge the second battery.

[0008] In the power supply system of the present disclosure, when parallel charging of the first battery and the second battery is initiated with the positive side relay, the negative side relay, the first parallel connection relay, and the second parallel connection relay turned on and the series connection relay turned off, if the voltage difference obtained by subtracting the voltage of the second battery from the voltage of the first battery is equal to or greater than a predetermined voltage difference, the control device switches on the inverter to step down the charging power and charge the second battery. This reduces the voltage difference and prevents excessive current from flowing due to a large voltage difference when the first battery and the second battery are connected in parallel.

[0009] In such a power supply system of the present disclosure, the control device may be configured to turn on the upper arm of the inverter and start parallel charging of the first battery and the second battery when the voltage difference is less than the predetermined voltage difference.

[0010] In the power supply system of the present disclosure, the control device may be configured to turn off the upper arm of the inverter to charge only the first battery when the voltage difference is negative, i.e., when the voltage of the first battery is lower than the voltage of the second battery, and to turn on the upper arm of the inverter to start parallel charging of the first battery and the second battery when it is estimated that the voltage of the first battery is equal to or higher than the voltage of the second battery. This allows the upper arm of the inverter to turn on and start parallel charging of the first battery and the second battery when the voltage of the first battery is equal to or higher than the voltage of the second battery and the voltage difference is less than a predetermined voltage difference. In this case, when only the first battery is being charged, the control device may be configured to estimate that the open-circuit voltage of the first battery is equal to or higher than the open-circuit voltage of the second battery when the voltage of the first battery is equal to or higher than the voltage of the second battery with the charging current of the first battery limited. This is based on the fact that the voltage of the first battery with the charging current of the first battery limited is very close to the open-circuit voltage of the first battery.

[0011] In the power supply system of the present disclosure, the control device may be configured to turn off the upper arm of the inverter to charge only the first battery when the voltage of the first battery becomes lower than the voltage of the second battery while the first battery and the second battery are being charged in parallel, and then turn on the upper arm of the inverter to charge the first battery and the second battery in parallel when the voltage of the first battery is estimated to be equal to or higher than the voltage of the second battery. This allows the first battery and the second battery to be charged in parallel while ensuring that the voltage of the first battery is equal to or higher than the voltage of the second battery.

[0012] In the power supply system of the present disclosure, the control device may be configured to notify battery degradation learning when a current flows from the second battery to charge the first battery when parallel charging is terminated in a state where the open-circuit voltage of the first battery is higher than that of the second battery according to a relationship map between the battery charge state and open-circuit voltage. In this way, the relationship map between the battery charge state and open-circuit voltage can be corrected. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram showing an outline of the configuration of a power supply system 20 according to an embodiment of the present disclosure. [Figure 2] 10 is a table showing the state of each relay in various states of the power supply system 20. [Figure 3] 10 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 DC charging stand. FIG. [Figure 4] 10 is a flowchart showing an example of the first half of a parallel charging process. [Figure 5] 10 is a flowchart showing an example of a second half of the parallel charging process. DETAILED DESCRIPTION OF THE INVENTION

[0014] 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 as 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.

[0015] 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 three-phase coils (U-phase, V-phase, and W-phase) of the motor 22 are connected to the respective junctions between the paired transistors T1 to T6. 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.

[0016] 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 to which a relay DCRNN included in the main power supply circuit 30 is attached. Therefore, by turning on the relay DCRNN, the first battery 26a and the second battery 26b function as a single battery connected in series.

[0017] 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 the 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 supplying power from the battery 26 consisting of the series-connected first battery 26a and second battery 26b to the inverter 24, or conversely, charging the battery 26 using regenerative power from the motor 22.

[0018] 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.

[0019] 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.

[0020] The DC charging circuit 50 includes a DC charging power line 51 connected to the positive bus bar 31B and the negative bus bar 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.

[0021] 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 a voltage VH across the terminals of the first capacitor 32, a voltage sensor 39 that detects a voltage VD across the terminals of the second capacitor 38, a current sensor 31a that detects a current Ib1 flowing through the first battery 26a, a current sensor 37a that detects a current Id flowing through the second parallel power line 37, phase current sensors (not shown) that detect phase currents Iu, Iv, and Iw flowing through the three phases of the motor 22, a voltage sensor (not shown) that detects a voltage Vb1 across the terminals of the first battery 26a, and a voltage sensor (not shown) that detects a 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. 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.

[0022] 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.

[0023] FIG. 2 is a table showing the state of each relay when the power supply system 20 is in various states. (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 using 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.

[0024] (3) When a connector from a DC charging stand is connected to 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 DC charging connector 55 and the first battery 26a and the second battery 26b are connected in parallel and power from battery 26 is supplied to the external electrical load as DC power, positive side relay SMRB, 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.

[0025] (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 relays DCRNB, relay DCRNG, and relay DCRN are turned off.

[0026] (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, the negative side relay SMRG, DCRNB, DCRNG, DCRN, DCRB, and DCRG are turned off. (6) When the first battery 26a and the second battery 26b are connected in parallel and charged using the 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 relay DCRNN, the relay DCRB, and the relay DCRG are turned off. (7) When the first battery 26a and the second battery 26b are connected in series and charged using the 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.

[0027] Next, we will explain the operation of power supply system 20 of this embodiment configured as described above, particularly the operation when a connector from a DC charging stand is connected to DC charging connector 55 and first battery 26a and second battery 26b are connected in parallel and charged using DC power from the DC charging stand. Figure 3 is an explanatory diagram showing the current flow when first battery 26a and second battery 26b are connected in parallel and charged using DC power from the DC charging stand. In the figure, the thick solid line with an arrow indicates the charging current for first battery 26a, and the thick dashed line with an arrow indicates the charging current for second battery 26b. When a connector from a DC charging stand is connected to DC charging connector 55 and first battery 26a and second battery 26b are connected in parallel and charged using DC power from the DC charging stand, as described above, positive side relay SMRB, 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, turning on the upper arm of inverter 24. First battery 26a is charged by a charging current that flows in this order from the positive side line of DC charging power line 51 connected to DC charging connector 55, through positive side relay SMRB of positive bus 31B, first battery 26a, relay DCRNG of first parallel power line 36, negative side relay SMRG of negative bus 31G, and the negative side line of DC charging power line 51, as shown by the thick solid line with arrows in FIG. As shown by the thick dashed line with an arrow in Figure 3, the second battery 26b is charged by a charging current that flows in this order from the positive side line of the DC charging power line 51 connected to the DC charging connector 55 via the positive bus bar 31B, through 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 side relay SMRG of the negative bus bar 31G, and the negative side line of the DC charging power line 51.

[0028] In the power supply system 20 of this embodiment, parallel charging is performed using the parallel charging process illustrated in Figures 4 and 5. When the parallel charging process is executed, the electronic control unit 60 first inputs the open-circuit voltage OCV1 of the first battery 26a and the open-circuit voltage OCV2 of the second battery 26b (step S100), and determines whether the open-circuit voltage difference ΔOCV (ΔOCV = OCV1 - OCV2) obtained by subtracting the open-circuit voltage OCV2 from the open-circuit voltage OCV1 is greater than or equal to a threshold Vref1 and less than a threshold Vref2 (step S110). The open-circuit voltage OCV1 of the first battery 26a and the open-circuit voltage OCV2 of the second battery 26b may be derived by applying the power storage rate SOC to a map showing the relationship between the power storage rate SOC and the open-circuit voltage OCV of each battery. The threshold value Vref1 is a predetermined value so that the open-circuit voltage OCV1 of the first battery 26a is equal to or greater than the open-circuit voltage OCV2 of the second battery 26b even if there is a measurement error in the open-circuit voltage OCV1 of the first battery 26a or the open-circuit voltage OCV2 of the second battery 26b. The threshold value Vref2 is an allowable voltage difference between the open-circuit voltage OCV1 of the first battery 26a and the open-circuit voltage OCV2 of the second battery 26b, and is a value greater than the threshold value Vref1.

[0029] If it is determined in step S110 that the open-circuit voltage difference ΔOCV (ΔOCV = OCV1 - OCV2) is greater than or equal to the threshold value Vref1 and less than the threshold value Vref2, the upper arm of the inverter 24 is turned on to start parallel charging (step S200). As described with reference to FIG. 3, in parallel charging, the charging circuit for the second battery 26b includes the three-phase coil of the motor 22, so the impedance in the charging circuit for the second battery 26b is greater than the impedance in the charging circuit for the first battery 26a. Therefore, the charging current for the first battery 26a is slightly greater than the charging current for the second battery 26b, and the voltage Vb1 of the first battery 26a remains slightly greater than the voltage Vb2 of the second battery 26b. The reason why the voltage Vb1 of the first battery 26a is set to be slightly higher than the voltage Vb2 of the second battery 26b is to prevent current from flowing from the second battery 26b to charge the first battery 26a when parallel charging is terminated, due to the voltage Vb2 of the second battery 26b being higher than the voltage Vb1 of the first battery 26a.

[0030] If it is determined in step S110 that the open-circuit voltage difference ΔOCV (ΔOCV = OCV1 - OCV2) is less than the threshold value Vref1, only the first battery 26a is charged until a predetermined time has elapsed (steps S120, S130). The reason for charging only the first battery 26a when the open-circuit voltage difference ΔOCV is less than the threshold value Vref1 is to prevent current from flowing from the second battery 26b to charge the first battery 26a when parallel charging is initiated if the open-circuit voltage difference ΔOCV becomes a negative value. The predetermined time is a relatively short time, such as 1 second, 2 seconds, 5 seconds, or 10 seconds. After the predetermined time has elapsed, the charging current of the first battery 26a alone is limited, the voltage Vb1 (CCV1) of the first battery 26a is detected (step S140), the detected voltage Vb1 (CCV1) is regarded as the open circuit voltage OCV1 of the first battery 26a, and the open circuit voltage difference ΔOCV is calculated (step S150), and the process returns to step S110, where the open circuit voltage difference ΔOCV is within the range of equal to or greater than the threshold Vref1 and less than the threshold Vref2. As a result, charging of only the first battery 26a continues until the open circuit voltage difference ΔOCV becomes equal to or greater than the threshold Vref1.

[0031] If it is determined in step S110 that the open-circuit voltage difference ΔOCV (ΔOCV = OCV1 - OCV2) is equal to or greater than the threshold value Vref2, the upper arm of the inverter 24 is switched on and off until a predetermined time has elapsed, thereby performing parallel charging accompanied by a step-down operation of the externally charged power (steps S160 and S170). After the predetermined time has elapsed, the voltage difference ΔCCV (ΔCCV = CCV1 - CCV2) is calculated using the voltage Vb1 (CCV1) of the first battery 26a and the voltage Vb2 (CCV2) of the second battery 26b (step S180), and it is determined whether the voltage difference ΔCCV is greater than 0 and less than the threshold value Vref3 (step S190). The threshold value Vref3 may be the same as the threshold value Vref2 or a value slightly smaller than the threshold value Vref2. If it is determined that the voltage difference ΔCCV is greater than 0 and less than the threshold value Vref3, the upper arm of the inverter 24 is turned on, and parallel charging begins (step S200).

[0032] If it is determined in step S190 that the voltage difference ΔCCV is equal to or greater than the threshold value Vref3, the process returns to steps S160 and S170, where the upper arm of inverter 24 is switched to perform parallel charging accompanied by a step-down operation of the external charging power until a predetermined time has elapsed. As a result, the upper arm of inverter 24 is switched to continue parallel charging accompanied by a step-down operation of the external charging power until the voltage difference ΔCCV becomes less than the threshold value Vref3.

[0033] If it is determined in step S190 that the voltage difference ΔCCV is equal to or less than 0, the process proceeds to steps S120 and S130, where only the first battery 26a is charged for a predetermined period of time.

[0034] Once parallel charging begins, a process is performed (steps S210-S240) in which the voltage Vb1 of the first battery 26a is maintained slightly higher than the voltage Vb2 of the second battery 26b until a determination is made as to whether parallel charging is to be terminated (step S250). This process first inputs the voltage Vb1 of the first battery 26a and the voltage Vb2 of the second battery 26b (step S210), and determines whether the voltage difference ΔV (ΔV-Vb1-Vb2), obtained by subtracting the voltage Vb2 from the voltage Vb1, is a negative value (step S220). If it is determined that the voltage difference ΔV is a negative value, the upper arm of the inverter 24 is turned off and only the first battery 26a is charged (step S230), and the process returns to the process of inputting the voltage Vb1 of the first battery 26a and the voltage Vb2 of the second battery in step S210. That is, only the first battery 26a is charged until the voltage difference ΔV reaches or exceeds zero. If it is determined in step S220 that the voltage difference ΔV is equal to or greater than zero, the upper arm of the inverter 24 is turned on to perform parallel charging (step S240), and the end of parallel charging is determined (step S250). If it is not determined that parallel charging has ended, the process returns to step S210, where the voltage Vb1 of the first battery 26a and the voltage Vb2 of the second battery are input. The end of parallel charging is determined when the battery 26 is fully charged, when a predetermined charging time has elapsed, when the state of charge (SOC) of the battery 26 reaches a predetermined state indicating the end of charging, or when the user issues a command to end charging. The reason why the voltage Vb1 of the first battery 26a is maintained slightly higher than the voltage Vb2 of the second battery 26b is to prevent a current from flowing to charge the first battery 26a from the second battery 26b, which would occur if the voltage Vb2 of the second battery 26b were to exceed the voltage of the first battery 26a when parallel charging ended.

[0035] When the parallel charging is terminated, the system determines whether a charging current is flowing to the first battery 26a (step S260), and if it is determined that a charging current is flowing to the first battery 26a, it notifies the system that degradation learning of the map of the state of charge SOC and open circuit voltage OCV is necessary (step S270), and then terminates this process. On the other hand, if it is determined that a charging current is not flowing to the first battery 26a, it is determined that the map has not deteriorated, and terminates this process.

[0036] In the power supply system 20 of the embodiment described above, when parallel charging is initiated with the first battery 26a and the second battery 26b connected in parallel, if the open-circuit voltage difference ΔOCV, obtained by subtracting the open-circuit voltage OCV2 of the second battery 26b from the open-circuit voltage OCV1 of the first battery 26a, is equal to or greater than threshold Vref2, the upper arm of the inverter 24 is switched on to perform parallel charging while stepping down the external charging power until the open-circuit voltage difference ΔOCV becomes less than threshold Vref3. This prevents excessive current from flowing through the circuit due to a large open-circuit voltage difference ΔOCV when parallel charging is initiated with the upper arm of the inverter 24 turned on. Furthermore, if the open-circuit voltage difference ΔOCV is less than threshold Vref1, only the first battery 26a is charged until the open-circuit voltage difference ΔOCV becomes equal to or greater than threshold Vref1. This prevents current from flowing from the second battery 26b to charge the first battery 26a when parallel charging is initiated. In this case, the voltage Vb1 of the first battery 26a detected by limiting the charging current of the first battery 26a is regarded as the open circuit voltage OCV1 of the first battery 26a, the open circuit voltage difference ΔOCV is calculated, and only the first battery 26a is charged until the open circuit voltage difference ΔOCV becomes equal to or greater than 0, so that the true open circuit voltage difference ΔOCV can be more reliably equal to or greater than 0.

[0037] In the power supply system 20 of this embodiment, when the voltage difference ΔV obtained by subtracting the voltage Vb2 of the second battery 26b from the voltage Vb1 of the first battery 26a becomes a negative value during parallel charging, the upper arm of the inverter 24 is turned off and only the first battery 26a is charged until the voltage difference ΔV becomes equal to or greater than zero. Then, when the voltage difference ΔV becomes equal to or greater than zero, the upper arm of the inverter 24 is turned on and parallel charging is performed. This makes it possible to maintain the voltage Vb1 of the first battery 26a slightly higher than the voltage Vb2 of the second battery 26b, and prevents a current from flowing to charge the first battery 26a from the second battery 26b, which would occur if the voltage Vb2 of the second battery 26b becomes higher than the voltage of the first battery 26a when parallel charging is terminated.

[0038] In the power supply system 20 of this embodiment, when it is detected that a charging current is flowing to the first battery 26a when parallel charging is terminated, a notification is issued that degradation learning of the map of the storage ratio SOC and the open circuit voltage OCV is required. This makes it possible to notify the user that degradation learning of the map of the storage ratio SOC and the open circuit voltage OCV is required.

[0039] 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. [Industrial Applicability]

[0040] The present disclosure is applicable to the power supply system manufacturing industry and the like. [Explanation of symbols]

[0041] 20 power supply system, 22 motor, 24 inverter, 26 battery, 26a first battery, 26b second battery, 30 power supply main circuit, 31a current sensor, 31B blue bus bar, 31G negative bus bar, 32 first capacitor, 33 voltage sensor, 35 series power line, 36 first parallel power line, 37 second parallel power line, 37a current sensor, 38 second capacitor, 39 voltage sensor, 40 AC charging circuit, 41 AC charging power line, 42 filter, 43 on-board charger, 44 power line, 45 AC charging connector, 46 DC / DC converter, 47 power line, 48 auxiliary equipment, 49 solar panel, 50 DC charging circuit, 51 DC charging power line, 55 DC charging connector, 60 electronic control unit.

Claims

1. a first battery, a second battery, 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 connecting the first battery side of the series connection line to the negative bus bar. a first parallel connection line connecting a positive terminal of the second battery to a neutral point of the three-phase AC motor; 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 to a neutral point of the three-phase AC motor; second parallel connection relays attached to the second parallel connection line in this order from the second battery side; a DC charging connector connected via a power line having a charging relay on the positive side relay of the positive bus bar on the inverter side and on the negative side relay of the negative bus bar on the inverter side; and a control device that controls the relays and the inverter, When parallel charging of the first battery and the second battery is started with the positive side relay, the negative side relay, the first parallel connection relay, and the second parallel connection relay turned on and the series connection relay turned off, the control device switches on the inverter to step down the charging power and charge the second battery when a voltage difference obtained by subtracting the voltage of the second battery from the voltage of the first battery is equal to or greater than a predetermined voltage difference. A power supply system characterized by:

2. 2. The power supply system of claim 1, When the voltage difference is less than the predetermined voltage difference, the control device turns on the upper arm of the inverter to start parallel charging of the first battery and the second battery. Power supply system.

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