Power supply system

Abstract

To perform relay abnormality diagnosis in changing a state, in which two batteries on which charging / discharging using serial connection and charging / discharging using parallel connection are possible are being charged using the parallel connection, to a state, in which a motor is driven using the serial connection.SOLUTION: Abnormal welding of a negative electrode side relay is detected on the basis of variation in voltage across terminals of a first capacitor and variation in voltage across terminals of a second capacitor when turning off the negative electrode side relay and a third parallel connection relay from a state in which a first battery and a second battery are connected in parallel by turning on a positive electrode side relay, the negative electrode side relay, a first parallel connection relay, a second parallel connection relay, the third parallel connection relay, and a charging relay, and turning off a serial connection relay and the first battery and the second battery are being charged using power from a photovoltaic power generating system.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 capable of charging and discharging by series connection and parallel connection.

Background Art

[0002] Conventionally, as this type of power supply system, one has been proposed in which a first storage battery and a second storage battery are connected in series, and an intermediate terminal between the first storage battery and the second storage battery and the neutral point of a three-phase AC motor are connected via a relay (see, for example, Patent Document 1). In this system, by performing power transfer between the storage batteries for temperature rise control, the amount of variation in the terminal voltage of the capacitor during temperature rise control is reduced compared to the case of raising the temperature by switching the upper arm and the lower arm of the inverter.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a power supply system including two batteries capable of charging and discharging by series connection and parallel connection, when charging the two batteries using the generated power from a solar panel, in order to keep the boost of the DC / DC converter low and improve efficiency, the two batteries are connected in parallel for charging. On the other hand, when driving a motor, it is preferable to connect the two batteries in series to obtain the output of the motor. When switching from a state where the two storage batteries are connected in parallel for charging to a state where the two batteries are connected in series for motor driving, an abnormality diagnosis such as a relay is required.

[0005] The main object of the power supply system of the present disclosure is to perform abnormal diagnosis of a relay when changing from a state in which two batteries capable of charging and discharging by series connection and charging and discharging by parallel connection are charged by parallel connection to a state in which the motor is driven by series connection.

Means for Solving the Problems

[0006] The power supply system of the present disclosure has adopted the following means in order to achieve the above main object.

[0007] The power supply system of the present disclosure a first battery; a second battery having the same configuration as the first battery; a series connection line connecting the negative terminal side of the first battery and the positive terminal side of the second battery; a series connection relay attached to the series connection line; a positive bus connected to the positive terminal of the first battery; a negative bus connected to the negative terminal of the second battery; an inverter connected to the positive bus and the negative bus; a three-phase AC motor driven by the inverter; a positive side relay attached to the positive bus; a negative side relay attached to the negative bus; a first capacitor connected to the inverter side from the positive side relay of the positive bus and the inverter side from the negative side relay of the negative bus; a first parallel connection line connecting the first battery side from the series connection relay of the series connection line and the negative bus; 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 the neutral point of the three-phase AC motor; a second parallel connection relay and a third parallel connection relay attached in order from the second battery side to the second parallel connection line; a second capacitor connected to the inverter side from the negative side relay of the negative bus and between the second parallel connection relay and the third parallel connection relay of the second parallel connection line; a solar power generation device connected via a power line having a charging relay from the first battery side from the positive side relay of the positive bus and from the second battery side from the negative side relay of the negative bus; a control device for controlling each relay and the inverter; a power supply system comprising The control device turns on the positive electrode side relay, the negative electrode side relay, the first parallel connection relay, the second parallel connection relay, the third parallel connection relay, and the charging relay, and turns off the series connection relay to connect the first battery and the second battery in parallel. Based on the change in the voltage across the terminals of the first capacitor and the change in the voltage across the terminals of the second capacitor when the negative electrode side relay and the third parallel connection relay are turned off from the state where the first battery and the second battery are charged in parallel using the power from the photovoltaic power generation device, it detects welding abnormalities of the negative electrode side relay. This is characterized by.

[0008] In the power supply system of the present disclosure, a first battery, a second battery having the same configuration as the first 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 connected to the positive terminal of the first battery, a negative bus connected to the negative terminal of the second battery, an inverter connected to the positive bus and the negative bus, a three-phase AC motor driven by the inverter, a positive-side relay attached to the positive bus, a negative-side relay attached to the negative bus, a first capacitor connected between the inverter side of the positive-side relay of the positive bus and the inverter side of the negative-side relay of the negative bus, a first parallel connection line connecting the first battery side from the series connection relay of the series connection line and the negative bus, 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 the neutral point of the three-phase AC motor, a second parallel connection relay and a third parallel connection relay attached in order from the second battery side to the second parallel connection line, a second capacitor connected between the inverter side of the negative-side relay of the negative bus and between the second parallel connection relay and the third parallel connection relay of the second parallel connection line, a photovoltaic power generation device connected via a power line having a charging relay between the first battery side from the positive-side relay of the positive bus and the second battery side from the negative-side relay of the negative bus, and a control device for controlling each relay and the inverter. The control device turns on the positive-side relay, the negative-side relay, the first parallel connection relay, the second parallel connection relay, the third parallel connection relay, and the charging relay, and turns off the series connection relay to connect the first battery and the second battery in parallel, and based on the change in the voltage between the terminals of the first capacitor and the change in the voltage between the terminals of the second capacitor when the negative-side relay and the third parallel connection relay are turned off, detects a welding abnormality of the negative-side relay. In a state where the first battery and the second battery are connected in parallel and the first battery and the second battery are charged in parallel using the power from the photovoltaic power generation device, the first capacitor holds the voltage of the first battery, and the second capacitor holds the voltage of the second battery.When the negative electrode side relay and the third parallel connection relay are turned off from this state, the voltages of the first capacitor and the second capacitor gradually decrease. However, if the negative electrode side relay is welded, the voltages of the first capacitor and the second capacitor are held at the voltages of the first battery and the second battery. Based on this difference, it is possible to diagnose the welding abnormality of the negative electrode side relay.

[0009] Therefore, when the negative electrode side relay and the third parallel connection relay are turned off from the state where the first battery and the second battery are being charged in parallel, if there is no change in the inter-terminal voltage of the first capacitor and the inter-terminal voltage of the second capacitor over a first predetermined time, it is determined that welding has occurred on the negative electrode side relay. If there is a change in the inter-terminal voltage of the first capacitor and the inter-terminal voltage of the second capacitor within the first predetermined time, it may be determined that no welding has occurred on the negative electrode side relay.

[0010] In the power supply system of the present disclosure, when it is determined that no welding has occurred on the negative electrode side relay, if current flows through the second parallel connection line when the upper arm of the inverter is switched over a second predetermined time, it is determined that welding has occurred on the third parallel connection relay. If no current flows through the second parallel connection line within the second predetermined time, it may be determined that no welding has occurred on the third parallel connection relay. Since the third parallel connection relay is turned off, when there is no welding abnormality in the third parallel connection relay, no current flows through the second parallel connection line even when the upper arm of the inverter is switched. On the other hand, if the upper arm of the inverter is switched when there is a welding abnormality in the third parallel connection relay, current flows through the second parallel connection line. Thereby, it is possible to diagnose the welding abnormality of the third parallel connection relay.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[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 as an embodiment of the present disclosure. The power supply system 20 of the embodiment functions as a device for exchanging power between the battery 26 and the inverter 24 that drives the 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 a battery 26, a motor 22, an inverter 24, a power supply main 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 including, for example, a rotor with permanent magnets attached to its outer surface and a stator wound with three-phase coils. The inverter 24 is composed of six transistors T1 to T6 as switching elements and six diodes D1 to D6 connected in parallel in the reverse direction to the transistors T1 to T6. The transistors T1 to T6 are arranged in pairs of two each so that the inverter 24 becomes the source side and the sink side with respect to the positive bus bar 31B and the negative bus bar 31G of the battery 26. Each of the three-phase coils (U-phase, V-phase, W-phase) of the motor 22 is connected to each of the connection points of the paired transistors. The inverter 24 forms a rotating magnetic field in the three-phase coils by controlling the ratio of the on-time of the paired transistors T1 to T6 in a state where a voltage is acting between the positive bus bar 31B and the negative bus bar 31G, and rotates the motor 22. A first capacitor 32 for smoothing is attached between the positive bus bar 31B and the negative bus bar 31G.

[0014] The battery 26 has a first battery 26a and a second battery 26b configured in the same manner as the first battery 26a. The first battery 26a and the second battery 26b are configured as, for example, lithium-ion secondary batteries or nickel-metal hydride secondary batteries. The positive terminal of the first battery 26a is connected to the positive bus bar 31B, and the negative terminal of the second battery 26b is connected to the negative bus bar 31G. The negative terminal of the first battery 26a is connected to the positive terminal of the second battery 26b by a series power line 35 to which a relay DCRNN included in the configuration of the power main circuit 30 is attached. Therefore, by turning on the relay DCRNN, the first battery 26a and the second battery 26b function as one serially connected battery.

[0015] The main power circuit 30 includes, in addition to the positive bus bar 31B, the negative bus bar 31G, and the series power line 35, a first parallel power line 36 that connects the negative terminal of the first battery 26a to the negative bus bar 31G, and a second parallel power line 37 that connects the positive terminal of the second battery 26b to the neutral point of the motor 22. A positive-side relay SMRB is attached to the positive bus bar 31B, and a negative-side relay SMRG is attached to the negative bus bar 31G. Further, a precharge circuit composed of a precharge relay SMRP and a resistor R is provided in parallel with the negative-side relay SMRG on the negative bus bar 31G. The positive-side relay SMRB, the negative-side relay SMRG, and the 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 precharge relay SMRP is turned on to charge the first capacitor 32. When the charging of the first capacitor 32 is completed, the negative-side relay SMRG is turned on and the precharge relay SMP is turned off, so that power can be supplied from the battery 26 composed of the first battery 26a and the second battery 26b connected in series to the inverter 24, or conversely, the battery 26 can be charged by the regenerative power of 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 relay DCRNB and the relay DCRN of the second parallel power line 37 and the negative bus bar 31G.

[0017] The AC charging circuit 40 includes an AC charging power line 41 connected to the positive busbar 31B and the negative busbar 31G, an on-board charger (OBC) 43 connected to the AC charging power line 41 via a filter 42, an AC charging connector 45 connected to the on-board charger 43 by a power line 44, a DC / DC converter 46 connected to the AC charging power line 41 via the filter 42 in parallel with the on-board charger 43, and an auxiliary machine 48 and a solar panel 49 connected to the DC / DC converter 46 by a power line 47. A relay SSRB is attached to the positive-side line of the 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 busbar 31B and the negative busbar 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 from various sensors are input to the electronic control unit 60. Examples of the various sensors include a voltage sensor 33 that detects the voltage VH between the terminals of the first capacitor 32, a voltage sensor 39 that detects the voltage VD between 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, a phase current sensor (not shown) that detects the phase currents Iu, Iv, Iw flowing through the three phases of the motor 22, a voltage sensor (not shown) that detects the voltage Vb1 between the terminals of the first battery 26a, and a voltage sensor (not shown) that detects the voltage Vb2 between the terminals of the second battery 26b. Since the electronic control unit 60 also functions as a control device for driving the motor 22, drive commands and the like are also input. When the power 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] Drive control signals to each relay, switching control signals to the inverter 24, etc. are output from the electronic control unit 60. Examples of each relay include a positive electrode side relay SMRB, a negative electrode 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, a relay DCRG, etc.

[0021] Figure 2 is a list showing the states of each relay in various states of the power system 20. (1) In order to drive the motor 22 as a driving motor and run, the positive electrode side relay SMRB, the negative electrode 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 connecting the connection connector from the AC charging stand to the AC charging connector 45 to charge the battery 26 with the AC power from the AC charging stand, or when connecting an external electrical load to the AC charging connector 45 and supplying power from the battery 26 to the external electrical load as AC power, the relays SSRB, SSRG, and DCRNN are turned on, and the positive-side relay SMRB, negative-side relay SMRG, relays DCRB, DCRG, DCRN, DCRB, and DCRG are turned off.

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

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

[0024] When supplying power to auxiliary equipment 48 such as a drive recorder while the vehicle is parked, turn on relays SSRB, SSRG, and DCRNN, and turn off positive-side relay SMRB, negative-side relay SMRG, relays DCRNB, DCRNG, DCRN, DCRB, and DCRG.

[0025] (6) When charging the first battery 26a and the second battery 26b in parallel using the generated power of the solar panel 49, turn on positive-side relay SMRB, negative-side relay SMRG, relays SSRB, SSRG, DCRNB, DCRNG, and DCRN, and turn off relays DCRNN, DCRB, and DCRG. FIG. 3 is an explanatory diagram showing the flow of current when charging the first battery 26a and the second battery 26b in parallel with the 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. When charging the first battery 26a and the second battery 26b in parallel with the DC power from the solar panel 49, set the on / off state of the above-described relays and turn on the upper arm of the inverter 24. As shown by the thick solid line with an arrow in FIG. 3, the first battery 26a is charged by the charging current flowing in the order of the DC / DC converter 46, filter 42, relay SSRB of the AC charging power line 41, positive bus bar 31B, first battery 26a, relay DCRNG of the first parallel power line 36, negative bus bar 31G, and relay SSRB of the AC charging power line 41 from the solar panel 49. As shown by the thick dashed line with an arrow in FIG. 3, the second battery 26b is charged by the charging current flowing in the order of the DC / DC converter 46, filter 42, relay SSRB of the AC charging power line 41, positive-side relay SMRB of the positive bus bar 31B, upper arm of the inverter 24, neutral point of the motor 22, relays DCRN and DCRNB of the second parallel power line 37, second battery 26b, negative bus bar 31G, and relay SSRB of the AC charging power line 41 from the solar panel 49. When charging by connecting the first battery 26a and the second battery 26b in series using the generated power of the solar panel 49, the relays SSRB, SSRG, and DCRNN are turned on, and the positive-side relay SMRB, negative-side relay SMRG, relays DCRNB, DCRNG, DCRN, DCRB, and DCRG are turned off.

[0026] Next, the operation of the power supply system 20 of the embodiment configured in this way, particularly the state of diagnosing the welding abnormality of the relay when shifting from the state of charging by connecting the first battery 26a and the second battery 26b in parallel using the generated power of the solar panel 49 to the state of driving and running the motor 22 as a driving motor, will be described. FIG. 4 is a flowchart showing an example of the relay welding diagnosis process executed by the electronic control unit 60.

[0027] In the relay welding diagnosis process, the electronic control unit 60 first turns off the negative-side relay SMRG and the relay DCRN from the state where the first battery 26a and the second battery 26b are connected in parallel and charged using the generated power of the solar panel 49 (step S100). Subsequently, the voltage VH across the terminals of the first capacitor 32 and the voltage VL across the terminals of the second capacitor 38 are input over a predetermined time period (step S110), and it is determined whether there is a change in the voltage VH across the terminals of the first capacitor 32 or the voltage VL across the terminals of the second capacitor 38. FIG. 5 shows a closed circuit including the first capacitor 32 and the second capacitor 38 in the state where the negative-side relay SMRG and the relay DCRN are turned off from the state where the first battery 26a and the second battery 26b are connected in parallel and charged. In the figure, the thick solid line is the closed circuit. In the state where the first battery 26a and the second battery 26b are connected in parallel and charged, as can be understood from FIG. 3, the voltage VH across the terminals of the first capacitor 32 is the voltage Vb1 of the first battery 26a, and the voltage VL across the terminals of the second capacitor 38 is the voltage Vb2 of the second battery 26b. When the negative-side relay SMRG and the relay DCRN are turned off from this state, as can be understood from the closed circuit of FIG. 5, both the voltage VH across the terminals of the first capacitor 32 and the voltage VL across the terminals of the second capacitor 38 gradually decrease over time. On the other hand, when a welding abnormality occurs in the negative-side relay SMRG, a closed circuit including the first battery 26a, the first capacitor 32, and the negative-side relay SMRG is established, and a closed circuit including the second battery 26b, the second capacitor 38, and the negative-side relay SMRG is established. As a result, the voltage VH across the terminals of the first capacitor 32 holds the voltage Vb1 of the first battery 26a, and the voltage VL across the terminals of the second capacitor 38 holds the voltage Vb2 of the second battery 26b. Therefore, the processes of steps S110 and S120 are processes for determining whether a welding abnormality has occurred in the negative-side relay SMRG. When it is determined in step S120 that there is no change in the voltage VH across the terminals of the first capacitor 32 or the voltage VL across the terminals of the second capacitor 38, it is determined that a welding abnormality has occurred in the negative-side relay SMRG (step S150), and this process is terminated.

[0028] When it is determined in step S120 that the voltage VH across the terminals of the first capacitor 32 and the voltage VL across the terminals of the second capacitor 38 are changing, it is determined that there is no welding abnormality in the negative-side relay SMRG. Then, the upper arm of the inverter 24 is switched over a predetermined time period, and the current I2 flowing through the second parallel power line 37 from the current sensor 37a is input (step S130), and it is determined whether or not a current is flowing through the second parallel power line 37 (step S140). When there is no welding abnormality in the relay DCRN, no current flows through the second parallel power line 37 even if the upper arm of the inverter 24 is switched. On the other hand, when there is a welding abnormality in the relay DCRN, a current flows through the second parallel power line 37 when the upper arm of the inverter 24 is switched. The processes of steps S130 and S140 are processes for determining whether or not there is a welding abnormality in the relay DCRN. When it is determined in step S140 that a current is flowing through the second parallel power line 37, it is determined that there is a welding abnormality in the relay DCRN (step S170), and this process is terminated.

[0029] On the other hand, when it is determined in step S140 that no current is flowing through the second parallel power line 37, it is determined that there is no welding abnormality in the negative-side relay SMRG and the relay DCRN (step S160), and this process is terminated.

[0030] In the power supply system 20 of the embodiment described above, from the state where the first battery 26a and the second battery 26b are connected in parallel and charged using the generated power of the solar panel 49, the negative-side relay SMRG and the relay DCRN are turned off, and it is determined whether or not there is a welding abnormality in the negative-side relay SMRG based on whether or not there is a change in the voltage VH across the terminals of the first capacitor 32 and the voltage VL across the terminals of the second capacitor 38 over a predetermined time period. Thereby, when switching from the state where the first battery 26a and the second battery 26b are connected in parallel and charged to the state where the motor can run, it is possible to diagnose the welding abnormality of the negative-side relay SMRG only by turning off the negative-side relay SMRG and the relay DARN.

[0031] In the power supply system 20 of the embodiment, after determining that there is no welding abnormality in the negative-side relay SMRG in a state where the negative-side relays SMRG and DARN are turned off from a state where the first battery 26a and the second battery 26b are connected in parallel and being charged, it is determined whether there is a welding abnormality in the relay DCRN based on whether current flows through the second parallel power line 37 when the upper arm of the inverter 24 is switched for a predetermined time. Thereby, when switching from a state where the first battery 26a and the second battery 26b are connected in parallel and being charged to a state where the motor can run, it is possible to diagnose a welding abnormality of the relay DCRN only by switching the upper arm of the inverter 24.

[0032] The main elements of the embodiment and the main elements of the invention described in the column of means for solving the problems will be described. 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 "solar power generation device", the negative-side relay SMRG corresponds to the "negative-side relay", the second parallel power line 37 corresponds to the "second parallel connection line", the relay DCRN corresponds to the "third parallel connection relay", the electronic control unit 60 corresponds to the "control device", and the power supply system 20 corresponds to the "power supply system". The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problems will be described. 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 "solar power generation device", the negative-side relay SMRG corresponds to the "negative-side relay", the second parallel power line 37 corresponds to the "second parallel connection line", the relay DCRN corresponds to the "third parallel connection relay", the electronic control unit 60 corresponds to the "control device", and the power supply system 20 corresponds to the "power supply system".

[0033] Note that the correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problems is an example for specifically explaining the form for implementing the invention described in the column of means for solving the problems in the embodiment, and thus does not limit the elements of the invention described in the column of means for solving the problems. That is, the interpretation of the invention described in the column of means for solving the problems should be made based on the description in that column, and the embodiment is merely a specific example of the invention described in the column of means for solving the problems.

[0034] As described above, the present disclosure has been described using embodiments. However, the present disclosure is not limited to such embodiments, and it goes without saying that the present disclosure can be implemented in various forms without departing from the gist of the present disclosure.

Industrial Applicability

[0035] The present disclosure can be used in the manufacturing industry of power systems and the like.

Explanation of Signs

[0036] 20 Power system, 22 Motor, 24 Inverter, 26 Battery, 26a First battery, 26b Second battery, 30 Main power circuit, 31a Current sensor, 31B Sapphire busbar, 31G Negative electrode busbar, 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 Onboard charger, 44 Power line, 45 AC charging connector, 46 DC / DC converter, 47 Power line, 48 Auxiliary machine, 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 having the same configuration as the first 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 connected to the positive terminal of the first battery, a negative bus connected to the negative terminal of the second battery, an inverter connected to the positive bus and the negative bus, a three-phase AC motor driven by the inverter, a positive-side relay attached to the positive bus, a negative-side relay attached to the negative bus, a first capacitor connected between the inverter side of the positive bus from the positive-side relay and the inverter side of the negative bus from the negative-side relay, a first parallel connection line connecting the first battery side from the series connection relay of the series connection line and the negative bus, 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 the neutral point of the three-phase AC motor, a second parallel connection relay and a third parallel connection relay attached in order from the second battery side to the second parallel connection line, a second capacitor connected between the inverter side of the negative bus from the negative-side relay and between the second parallel connection relay and the third parallel connection relay of the second parallel connection line, a solar power generation device connected via a power line having a charging relay between the first battery side from the positive-side relay of the positive bus and the second battery side from the negative-side relay of the negative bus, and a control device for controlling each relay and the inverter. A power supply system comprising: The control device turns on the positive-side relay, the negative-side relay, the first parallel connection relay, the second parallel connection relay, the third parallel connection relay, and the charging relay, and turns off the series connection relay to connect the first battery and the second battery in parallel, and based on the change in the voltage between the terminals of the first capacitor and the change in the voltage between the terminals of the second capacitor when the negative-side relay and the third parallel connection relay are turned off, detects the welding abnormality of the negative-side relay from a state where the first battery and the second battery are charged in parallel using the power from the solar power generation device. A power supply system characterized by the above.

2. The power supply system according to claim 1, wherein When the control device turns off the negative-side relay and the third parallel connection relay from a state where the first battery and the second battery are being charged in parallel, if there is no change in the voltage across the terminals of the first capacitor and the voltage across the terminals of the second capacitor over a first predetermined time, it determines that welding has occurred in the negative-side relay. If there is a change in the voltage across the terminals of the first capacitor and the voltage across the terminals of the second capacitor within the first predetermined time, it determines that no welding has occurred in the negative-side relay. Power supply system.

3. The power supply system according to claim 2, wherein when it is determined that no welding has occurred in the negative-side relay, if a current flows through the second parallel connection line when the upper arm of the inverter is switched over a second predetermined time, it determines that welding has occurred in the third parallel connection relay. If no current flows through the second parallel connection line within the second predetermined time, it determines that no welding has occurred in the third parallel connection relay. Power supply system.

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