Failure diagnosis device and electricity storage pack

Abstract

In a failure diagnosis device (A) mounted on an electricity storage pack (1) in which a first electricity storage module (10a) and a second electricity storage module (10b) are connected in parallel, a first switch unit (30a) is connected to a power line between the first electricity storage module (10a) and a connection point (N1). A second switch unit (30b) is connected to a power line between the second electricity storage module (10b) and the connection point (N1). A management unit (20) performs failure diagnosis of the first switch unit (30a) or the second switch unit (30b) using a current flowing between the first electricity storage module (10a) and the second electricity storage module (10b).

Description

Fault diagnosis device, battery pack

[0001] The present disclosure relates to a fault diagnosis device and a battery pack that diagnose a fault of a switch connected to a power line.

[0002] Semiconductor switches are often adopted in power lines such as power supply circuits using a battery as a power source. Semiconductor switches are smaller than mechanical relays, have less wear, and have a longer lifespan. However, semiconductor switches have a relatively higher risk of malfunctioning due to electrical noise and heat compared to mechanical relays.

[0003] In recent years, there has been an increase in electrified mobility (especially air mobility such as drones). In such applications, in order to enhance safety, a fault detection function for semiconductor switches and mechanical relays connected to the power line has become important.

[0004] As a method for detecting a fault in a semiconductor switch, it is common to measure the voltage on the control / input / output side of the semiconductor switch or to measure the input / output current of the semiconductor switch. The fault detection timing is often performed before the start of power input / output, and it is difficult to detect a short circuit fault in the semiconductor switch during power input / output. In a power supply system using a battery, it is common to connect a semiconductor switch for charging and a semiconductor switch for discharging in series to the power line. When there is no load or external power source (charger) connected to the output side of the power supply system, current cannot flow through the semiconductor switch, and it is difficult to detect a fault in the semiconductor switch.

[0005] Patent Document 1 discloses a method of installing a diode in parallel with a switch inserted in the path of two power storage units, measuring the voltages at both ends of the switch, comparing the voltage difference when the switch is on with the forward voltage of the diode, and detecting an abnormality in the switch. However, the switch is limited to being between two power storage units and is not intended for switches connected to the power line to a load or a charger. Also, since there is no limit on the current flowing through the diode, detecting via the body diode of the semiconductor switch is practically difficult from the viewpoint of safety. Also, the detection direction is limited to the forward direction of the diode.

[0006] Patent No. 6215221

[0007] This disclosure is made in light of these circumstances, and its purpose is to provide a technology for performing highly accurate fault diagnosis of switches connected to a power line, regardless of whether or not a load or charging power source is connected to the outside of the energy storage pack.

[0008] To solve the above problems, a fault diagnosis device according to one aspect of the present disclosure is a fault diagnosis device mounted on a power pack in which a first power storage module and a second power storage module are connected in parallel, comprising: the first power storage module; a first switch unit connected to a power line between the connection point of the first power storage module and the second power storage module; the second power storage module; a second switch unit connected to a power line between the connection point and the second power storage module; and a management unit that performs fault diagnosis of the first switch unit or the second switch unit using the current flowing between the first power storage module and the second power storage module.

[0009] According to this disclosure, fault diagnosis of switches connected to the power line can be performed with high accuracy, regardless of whether or not a load or charging power supply is connected to the outside of the energy storage pack.

[0010] This is a diagram illustrating the configuration of a battery pack according to a comparative example. This is a diagram illustrating an example of the configuration of the switch section. Figures 3(a) and 3(b) are diagrams illustrating fault diagnosis of the charging semiconductor switch, discharging semiconductor switch, and pre-charge semiconductor switch shown in Figure 2. This is a diagram illustrating the configuration of a battery pack according to an embodiment. This is a diagram illustrating the first switching pattern in the battery pack according to the embodiment. This is a diagram illustrating the second switching pattern in the battery pack according to the embodiment. This is a diagram illustrating the third switching pattern in the battery pack according to the embodiment. This is a diagram illustrating the fourth switching pattern in the battery pack according to the embodiment. This is a diagram illustrating the fifth switching pattern in the battery pack according to the embodiment. This is a diagram illustrating the sixth switching pattern in the battery pack according to the embodiment.

[0011] Figure 1 is a diagram illustrating the configuration of a comparative example battery pack 1. The comparative example battery pack 1 includes a battery module 10, a control unit 20, and a switch unit 30. The battery module 10 includes a plurality of cells E1-En connected in series. The number of cells in series is determined by the specifications of the load 2. When the load 2 is an air mobility vehicle, the main components of the load 2 are an inverter that converts the DC power supplied from the battery pack 1 into AC power, and a motor that rotates a propeller based on the AC power supplied from the inverter.

[0012] The cells E1-En used in the battery module 10 can be lithium-ion battery cells, nickel-metal hydride battery cells, lead-acid battery cells, etc. In this specification, we will assume an example using lithium-ion battery cells (nominal voltage: 3.6-3.7V). In addition, multiple cells may be connected in parallel in the series stage of each cell in order to increase the capacity.

[0013] The switch unit 30 is connected to the power line connecting the positive terminal of the battery module 10 and the external output terminal connected to the load 2. Alternatively, the switch unit 30 may be connected to the negative power line.

[0014] Figure 2 shows an example of the configuration of the switch unit 30. The switch unit 30 includes a charging semiconductor switch Qc and a discharging semiconductor switch Qd connected in series. The switch unit 30 further includes a current limiting circuit in which a pre-charge semiconductor switch Qp and a current limiting resistor R1 are connected in series, and the current limiting circuit is connected in parallel with the discharging semiconductor switch Qd. Body diodes are formed or connected in antiparallel to the charging semiconductor switch Qc, the discharging semiconductor switch Qd, and the pre-charge semiconductor switch Qp, respectively.

[0015] For the charging semiconductor switch Qc, the discharging semiconductor switch Qd, and the pre-charge semiconductor switch Qp, for example, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors) can be used. When MOSFETs are used for the charging semiconductor switch Qc, the discharging semiconductor switch Qd, and the pre-charge semiconductor switch Qp, the parasitic diodes formed between the drain and source of each of these switches are used as body diodes, or external diode elements are connected as body diodes.

[0016] When IGBTs are used for the charging semiconductor switch Qc, the discharging semiconductor switch Qd, and the pre-charge semiconductor switch Qp, an external diode element is connected between the collector and emitter of each of these switches as a body diode.

[0017] In recent years, semiconductor switches using wide-bandgap semiconductors (e.g., silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga2O3), diamond (C)) have become popular as high-voltage, low-loss semiconductor switches. For example, SiC-MOSFETs may be used for the charging semiconductor switch Qc, the discharging semiconductor switch Qd, and the pre-charge semiconductor switch Qp.

[0018] When MOSFETs are used for the charging semiconductor switch Qc, the discharging semiconductor switch Qd, and the pre-charge semiconductor switch Qp, the source terminal of the charging semiconductor switch Qc is connected to the battery module 10, the source terminal of the discharging semiconductor switch Qd is connected to the external output terminal of the battery pack 1, and the drain terminal of the charging semiconductor switch Qc is connected to the drain terminal of the discharging semiconductor switch Qd. The pre-charge semiconductor switch Qp is connected in parallel in the same direction as the discharging semiconductor switch Qd.

[0019] Returning to Figure 1, an input voltage sensor 41 is installed on the input side (battery module 10 side) of the switch unit 30. An output voltage sensor 42 is installed on the output side of the switch unit 30. The input voltage sensor 41 and the output voltage sensor 42 each include a voltage divider resistor and a differential amplifier. The voltage divider resistor is connected between the power line and a fixed potential, and the differential amplifier amplifies the voltage divided by the voltage divider resistor and outputs it to the control unit 20.

[0020] A current sensor 43 is installed on the power line to which the switch unit 30 is connected. The current sensor 43 is installed in the section of the power line between the battery module 10 and the switch unit 30. The current sensor 43 includes a shunt resistor and a differential amplifier. The shunt resistor is connected in series with the power line. The differential amplifier amplifies the voltage across the shunt resistor and outputs it to the control unit 20. A Hall element may be used instead of the shunt resistor.

[0021] The management unit 20 manages the status of the battery module 10. The management unit 20 includes a measurement IC and a control IC. The measurement IC can be an AFE (Analog Front End) IC or an ASIC (Application Specific Integrated Circuit). The control IC can be a microcontroller.

[0022] The measurement IC acquires the input voltage value of the switch unit 30 from the input voltage sensor 41, the output voltage value of the switch unit 30 from the output voltage sensor 42, and the current value flowing through the switch unit 30 from the current sensor 43. The measurement IC transmits the acquired input voltage value, output voltage value, and current value to the control IC via the serial communication interface.

[0023] When the control IC detects overcharging, over-discharging, or overcurrent in the battery module 10, it sends a cutoff signal to the measurement IC for the switch unit 30, causing the switch unit 30 to turn off. The battery module 10 is also equipped with a temperature sensor (not shown), and the control IC also turns off the switch unit 30 if it detects a high-temperature or low-temperature abnormality in the battery module 10.

[0024] Figures 3(a) and 3(b) are diagrams illustrating the fault diagnosis of the charging semiconductor switch Qc, the discharging semiconductor switch Qd, and the pre-charge semiconductor switch Qp shown in Figure 2. In the following Figures 3(a) and 3(b) onward, the charging semiconductor switch Qc, the discharging semiconductor switch Qd, and the pre-charge semiconductor switch Qp are depicted using simple switch symbols to make their on / off states easier to understand.

[0025] Figure 3(a) shows a battery pack 1 according to a comparative example with a charger 3 connected. The charger 3 is connected to the commercial power grid and converts AC grid power to DC power. The control unit 20 controls the charging semiconductor switch Qc to the ON state, the discharging semiconductor switch Qd to the ON state, and the pre-charge semiconductor switch Qp to the OFF state. In this state, if the charging current is detected normally by the current sensor 43, the control unit 20 determines that no open fault has occurred in the charging semiconductor switch Qc.

[0026] The control unit 20 controls the charging semiconductor switch Qc to the off state, the discharging semiconductor switch Qd to the on state, and the pre-charge semiconductor switch Qp to the off state. In this state, if no current is detected by the current sensor 43, the control unit 20 determines that a short circuit failure has not occurred in the charging semiconductor switch Qc.

[0027] Figure 3(b) shows the battery pack 1 according to the comparative example with a load 2 connected. The control unit 20 controls the charging semiconductor switch Qc to the ON state, the discharging semiconductor switch Qd to the ON state, and the pre-charge semiconductor switch Qp to the OFF state. In this state, if the discharge current is detected normally by the current sensor 43, the control unit 20 determines that an open fault has not occurred in the discharging semiconductor switch Qd.

[0028] The control unit 20 controls the charging semiconductor switch Qc to the ON state, the discharging semiconductor switch Qd to the OFF state, and the pre-charge semiconductor switch Qp to the OFF state. In this state, if no discharge current is detected by the current sensor 43, the control unit 20 determines that there is no short-circuit fault in the discharging semiconductor switch Qd and no short-circuit fault in the pre-charge semiconductor switch Qp. This fault diagnosis mode is difficult to perform while the load 2 is operating because it stops the power supply to the load 2.

[0029] The control unit 20 controls the charging semiconductor switch Qc to the ON state, the discharging semiconductor switch Qd to the OFF state, and the pre-charge semiconductor switch Qp to the ON state. In this state, if the discharge current is detected normally by the current sensor 43, the control unit 20 determines that no open fault has occurred in the pre-charge semiconductor switch Qp.

[0030] In the comparative example battery pack 1, when no load 2 or charger 3 is connected to the battery pack 1, the external output terminal of the battery pack 1 becomes high impedance, making it difficult to diagnose failures of the charging semiconductor switch Qc, the discharging semiconductor switch Qd, and the pre-charge semiconductor switch Qp.

[0031] Figure 4 is a diagram illustrating the configuration of a battery pack 1 according to an embodiment. The battery pack 1 according to the embodiment includes a first battery module 10a, a first control unit 20a, a first switch unit 30a, a second battery module 10b, a second control unit 20b, and a second switch unit 30b. The configuration of the first battery module 10a, the first control unit 20a, and the first switch unit 30a is the same as the configuration of the battery module 10, control unit 20, and switch unit 30 according to the comparative example shown in Figure 1.

[0032] The configuration of the second battery module 10b, the second management unit 20b, and the second switch unit 30b is basically the same as the configuration of the first battery module 10a, the first management unit 20a, and the first switch unit 30a. Note that different types of battery cells may be used for the first battery module 10a and the second battery module 10b. For example, if the second battery module 10b is used as a spare, a less expensive type of battery cell may be used for the second battery module 10b. Also, if multiple-direction and multiple-parallel modules are used for the first battery module 10a and the second battery module 10b, the number of parallel connections may differ between the first battery module 10a and the second battery module 10b.

[0033] The first battery module 10a and the second battery module 10b are connected in parallel, and the combined power line is connected to the external output terminal of the battery pack 1. The first switch unit 30a is connected to the power line between the connection point N1 where the first battery module 10a and the second battery module 10b merge and the first battery module 10a. The second switch unit 30b is connected to the power line between the connection point N1 and the second battery module 10b.

[0034] If load 2 is an air mobility vehicle, a redundant power supply system is required. By using a battery pack 1 in which the first battery module 10a and the second battery module 10b are connected in parallel, even if one of the battery modules 10 malfunctions, flight can continue with power supplied from the other battery module 10.

[0035] The first management unit 20a and the second management unit 20b may be provided separately or integrated. If they are provided separately, the control IC of the first management unit 20a and the control IC of the second management unit 20b are connected by a communication line. Hereinafter in this embodiment, the first management unit 20a and the second management unit 20b will be collectively referred to simply as the management unit 20.

[0036] The control unit 20 uses the current (crosscurrent) flowing between the first battery module 10a and the second battery module 10b to perform fault diagnosis of the first switch unit 30a or the second switch unit 30b.

[0037] Figure 5 shows the first switching pattern in the battery pack 1 according to the embodiment. In the example shown below, it is assumed that no load 2 or charger 3 is connected to the external output terminal of the battery pack 1. Also, the voltage of the first battery module 10a at the start of diagnosis is 50V, and the voltage of the second battery module 10b is 47V. In other words, it is assumed that the voltage of the first battery module 10a is higher than the voltage of the second battery module 10b.

[0038] In the first switching pattern, the control unit 20 controls the first charging semiconductor switch Qca, the first discharging semiconductor switch Qda, the first pre-charge semiconductor switch Qpa, the second charging semiconductor switch Qcb, the second discharging semiconductor switch Qdb, and the second pre-charge semiconductor switch Qpb to the off state. In the first switching pattern, the voltages detected by the first output voltage sensor 42a and the second output voltage sensor 42b are undefined.

[0039] The control unit 20 diagnoses an abnormality if a significant current value is detected by the first current sensor 43a and the second current sensor 43b in the state of the first switching pattern. For example, if at least one of the first discharge semiconductor switch Qda and the first pre-charge semiconductor switch Qpa and the second charge semiconductor switch Qcb are short-circuited, current flows from the first battery module 10a to the second battery module 10b. Also, if the positive terminal of the first battery module 10a and the positive terminal of the second battery module 10b are short-circuited, current flows from the first battery module 10a to the second battery module 10b. If the control unit 20 diagnoses an abnormality in the first switching pattern, it prohibits the use of the battery pack 1.

[0040] If, in the state of the first switching pattern, the control unit 20 detects no significant current value in the first current sensor 43a and the second current sensor 43b (i.e., if substantially 0A is detected), it turns on the first pre-charge semiconductor switch Qpa to transition to the second switching pattern.

[0041] Figure 6 shows a second switching pattern in the battery pack 1 according to the embodiment. In the second switching pattern, the control unit 20 controls the first charging semiconductor switch Qca to the off state, the first discharging semiconductor switch Qda to the off state, the first pre-charge semiconductor switch Qpa to the on state, the second charging semiconductor switch Qcb to the off state, the second discharging semiconductor switch Qdb to the off state, and the second pre-charge semiconductor switch Qpb to the off state.

[0042] The control unit 20 checks whether the voltage value detected by the first input-side voltage sensor 41a and the voltage value detected by the first output-side voltage sensor 42a are substantially the same in the state of the second switching pattern. If they are not substantially the same, the control unit 20 diagnoses that an abnormality has occurred. For example, if at least one of the first charging semiconductor switch Qca and the first pre-charge semiconductor switch Qpa is open fault, different voltage values ​​will be detected by the first input-side voltage sensor 41a and the first output-side voltage sensor 42a. If the control unit 20 diagnoses that an abnormality has occurred in the second switching pattern, it prohibits the use of the battery pack 1.

[0043] If, in the state of the second switching pattern, the control unit 20 turns on the first charging semiconductor switch Qca, the second charging semiconductor switch Qcb, and the second discharging semiconductor switch Qdb to transition to the third switching pattern. By inserting the second switching pattern between the first and third switching patterns, the current path through the first current limiting resistor R1a can be established first, preventing inrush current from flowing from the first battery module 10a to the second battery module 10b.

[0044] FIG. 7 is a diagram showing a third switching pattern in the battery pack 1 according to the embodiment. In the third switching pattern, the management unit 20 controls the first charging semiconductor switch Qca to be in the on state, the first discharging semiconductor switch Qda to be in the off state, the first pre-charge semiconductor switch Qpa to be in the on state, the second charging semiconductor switch Qcb to be in the on state, the second discharging semiconductor switch Qdb to be in the on state, and the second pre-charge semiconductor switch Qpb to be in the off state.

[0045] In the state of the third switching pattern, the management unit 20 diagnoses the presence or absence of an open failure of the first pre-charge semiconductor switch Qpa and the presence or absence of an open failure of the second charging semiconductor switch Qcb.

[0046] In the state of the third switching pattern, when the management unit 20 does not detect a significant current value with the first current sensor 43a and the second current sensor 43b, it diagnoses that an abnormality has occurred. For example, when at least one of the first pre-charge semiconductor switch Qpa and the second charging semiconductor switch Qcb has an open failure, a significant current value is not detected by the first current sensor 43a and the second current sensor 43b. Also, when a disconnection occurs in the power line connecting the first battery module 10a and the second battery module 10b, a significant current value is not detected by the first current sensor 43a and the second current sensor 43b. When the management unit 20 diagnoses that an abnormality has occurred in the third switching pattern, it prohibits the use of the battery pack 1.

[0047] In the state of the third switching pattern, when the management unit 20 detects a significant current value with the first current sensor 43a and the second current sensor 43b, it diagnoses that no open failure has occurred in the first pre-charge semiconductor switch Qpa and no open failure has occurred in the second charging semiconductor switch Qcb. After the diagnosis, the management unit 20 turns off the first charging semiconductor switch Qca and transitions to the fourth switching pattern.

[0048] FIG. 8 is a diagram showing a fourth switching pattern in the battery pack 1 according to the embodiment. In the fourth switching pattern, the management unit 20 turns off the first charging semiconductor switch Qca, turns off the first discharging semiconductor switch Qda, turns on the first pre-charge semiconductor switch Qpa, turns on the second charging semiconductor switch Qcb, turns on the second discharging semiconductor switch Qdb, and controls the second pre-charge semiconductor switch Qpb to be in an off state.

[0049] In the state of the fourth switching pattern, the management unit 20 diagnoses whether there is a failure in the first charging semiconductor switch Qca. In the state of the fourth switching pattern, the management unit 20 determines whether the current values detected by the first current sensor 43a and the second current sensor 43b have decreased by an amount corresponding to the forward voltage Vf (usually about 0.6 to 1.0 V) of the body diode Dca of the first charging semiconductor switch Qca with respect to the current values detected by the first current sensor 43a and the second current sensor 43b in the state of the third switching pattern.

[0050] If the current value does not decrease by an amount corresponding to the forward voltage Vf of the body diode Dca, the management unit 20 diagnoses that a short circuit failure or an open circuit failure (the body diode Dca is normal) has occurred in the first charging semiconductor switch Qca. In that case, the management unit 20 prohibits the use of the battery pack 1.

[0051] If the current value decreases by an amount corresponding to the forward voltage Vf of the body diode Dca, the management unit 20 diagnoses that the first charging semiconductor switch Qca is normal. Since current flows from the first battery module 10a to the second battery module 10b and the current value changes with the on / off of the first charging semiconductor switch Qca, it can be diagnosed that the first charging semiconductor switch Qca has no open circuit failure or short circuit failure, and the body diode Dca is also normal. After the diagnosis, the management unit 20 turns on the first charging semiconductor switch Qca and turns off the second discharging semiconductor switch Qdb to transition to the fifth switching pattern.

[0052] Figure 9 shows a fifth switching pattern in the battery pack 1 according to the embodiment. In the fifth switching pattern, the control unit 20 controls the first charging semiconductor switch Qca to be ON, the first discharging semiconductor switch Qda to be OFF, the first pre-charge semiconductor switch Qpa to be ON, the second charging semiconductor switch Qcb to be ON, the second discharging semiconductor switch Qdb to be OFF, and the second pre-charge semiconductor switch Qpb to be OFF.

[0053] The control unit 20 diagnoses whether or not the second discharge semiconductor switch Qdb is faulty in the state of the fifth switching pattern. The control unit 20 determines whether the current values ​​detected by the first current sensor 43a and the second current sensor 43b in the state of the fifth switching pattern have decreased by an amount equivalent to the forward voltage Vf of the body diode Ddb of the second discharge semiconductor switch Qdb compared to the current values ​​detected by the first current sensor 43a and the second current sensor 43b in the state of the fourth switching pattern.

[0054] If the current value does not decrease by an amount equivalent to the forward voltage Vf of the body diode Ddb, the control unit 20 diagnoses that a short circuit or open circuit failure has occurred in the second discharge semiconductor switch Qdb (the body diode Ddb is normal). In that case, the control unit 20 prohibits the use of the battery pack 1.

[0055] If the current value decreases by an amount equivalent to the forward voltage Vf of the body diode Ddb, the control unit 20 diagnoses the second discharge semiconductor switch Qdb as normal. Because current flows from the first battery module 10a to the second battery module 10b, and the current value changes when the second discharge semiconductor switch Qdb is turned on or off, the control unit 20 can diagnose that the second discharge semiconductor switch Qdb is neither open-circuit nor short-circuited, and that the body diode Ddb is also normal.

[0056] After diagnosis, the control unit 20 determines whether the difference between the voltage of the first battery module 10a and the voltage of the second battery module 10b is less than a set value (for example, 1V). If the voltage difference between the two is greater than or equal to the set value, the control unit 20 waits until the voltage of the first battery module 10a is higher than the voltage of the second battery module 10b, but within a range below the set value. When the voltage of the first battery module 10a is higher than the voltage of the second battery module 10b, but within a range below the set value, the control unit 20 turns on the first discharge semiconductor switch Qda, turns off the first pre-charge semiconductor switch Qpa, and turns on the second discharge semiconductor switch Qdb to transition to the sixth switching pattern.

[0057] Figure 10 shows a sixth switching pattern in the battery pack 1 according to the embodiment. In the sixth switching pattern, the control unit 20 controls the first charging semiconductor switch Qca to be ON, the first discharging semiconductor switch Qda to be ON, the first pre-charge semiconductor switch Qpa to be OFF, the second charging semiconductor switch Qcb to be ON, the second discharging semiconductor switch Qdb to be ON, and the second pre-charge semiconductor switch Qpb to be OFF.

[0058] The control unit 20 diagnoses whether or not the first discharge semiconductor switch Qda is faulty in the state of the sixth switching pattern. The control unit 20 determines whether the current values ​​detected by the first current sensor 43a and the second current sensor 43b in the state of the sixth switching pattern have increased by an amount equivalent to the voltage drop across the first current limiting resistor R1a and an amount equivalent to the forward voltage Vf of the body diode Ddb of the second discharge semiconductor switch Qdb, compared to the current values ​​detected by the first current sensor 43a and the second current sensor 43b in the state of the fifth switching pattern.

[0059] If the current value does not rise by an amount equivalent to the voltage drop across the first current limiting resistor R1a and the forward voltage Vf of the body diode Ddb, the control unit 20 diagnoses that a short circuit or open circuit failure has occurred in the first discharge semiconductor switch Qda (the body diode Dda is normal). In that case, the control unit 20 prohibits the use of the battery pack 1.

[0060] If the current value increases by an amount equivalent to the voltage drop across the first current limiting resistor R1a and an amount equivalent to the forward voltage Vf of the body diode Ddb, the control unit 20 diagnoses the first discharge semiconductor switch Qda as normal. Since current flows from the first battery module 10a to the second battery module 10b, and the current value changes when the first discharge semiconductor switch Qda is turned on or off, the control unit 20 can diagnose that the first discharge semiconductor switch Qda is neither open-circuit nor short-circuited, and that the body diode Dda is also normal.

[0061] When the voltage of the second battery module 10b is higher than the voltage of the first battery module 10a, the control unit 20 swaps the control of the first charging semiconductor switch Qca, the first discharging semiconductor switch Qda, and the first pre-charge semiconductor switch Qpa with the control of the second charging semiconductor switch Qcb, the second discharging semiconductor switch Qdb, and the second pre-charge semiconductor switch Qpb, and performs fault diagnosis based on the first switching pattern - fourth switching pattern described above.

[0062] This allows for fault diagnosis of the second charging semiconductor switch Qcb, including whether or not there is a short circuit in the second charging semiconductor switch Qcb and whether or not there is a fault in the body diode Dcb. It also allows for diagnosis of whether or not there is an open circuit in the second pre-charging semiconductor switch Qpb.

[0063] In a system that supplies power to a load 2 using one of the first battery module 10a and one of the second battery module 10b, the management unit 20 can easily create a predetermined difference between the voltage of the first battery module 10a and the voltage of the second battery module 10b.

[0064] If the difference between the voltage of the first battery module 10a and the voltage of the second battery module 10b is greater than or equal to a set value, the management unit 20 may skip fault diagnosis of the first switch unit 30a and the second switch unit 30b.

[0065] Furthermore, if the difference between the voltage of the first battery module 10a and the voltage of the second battery module 10b is greater than or equal to a set value, the control unit 20 may control the system to the state of the fifth switching pattern described above and generate a crosscurrent with current limiting until the difference between the voltage of the first battery module 10a and the voltage of the second battery module 10b falls below the set value.

[0066] Furthermore, if the difference between the voltage of the first battery module 10a and the voltage of the second battery module 10b is greater than or equal to a set value, the management unit 20 may momentarily turn on the first switch unit 30a in a pulse-like manner to perform fault diagnosis of the second switch unit 30b.

[0067] In contrast, in a system that uses both the first battery module 10a and the second battery module 10b simultaneously to supply power to the load 2, the voltage of the first battery module 10a and the voltage of the second battery module 10b are basically the same. In this case, the management unit 20 can perform fault diagnosis of the first switch unit 30a or the second switch unit 30b after the discharge of current above a certain value from the parallel-connected first battery module 10a and the second battery module 10b to the load 2 has finished.

[0068] As the time elapsed since the start of use of battery pack 1 increases, or as the number of charge-discharge cycles increases, the difference in internal resistance between the first battery module 10a and the second battery module 10b tends to increase. When the first battery module 10a and the second battery module 10b, which are connected in parallel, are discharging a large current to load 2, the voltage of the first battery module 10a drops from the OCV (Open Circuit Voltage) by the value obtained by multiplying the internal resistance of the first battery module 10a by the discharge current of the first battery module 10a. Similarly, the voltage of the second battery module 10b drops from the OCV by the value obtained by multiplying the internal resistance of the second battery module 10b by the discharge current of the second battery module 10b. Since the first battery module 10a and the second battery module 10b are connected in parallel, their voltages become the same, and the difference in their internal resistances manifests as a difference in current.

[0069] When discharge ends in this state, the voltage in the first battery module 10a and the second battery module 10b gradually decreases toward the OCV. At this time, the rate of decrease differs depending on the difference in the internal resistance of the first battery module 10a and the second battery module 10b. Specifically, the battery module with a larger internal resistance takes longer to converge toward the OCV.

[0070] Therefore, after discharge at a current above a certain value is completed, the voltage of the battery module with the lower internal resistance rises faster than the voltage of the battery module with the higher internal resistance. In other words, a situation occurs where there is a difference between the voltage of the first battery module 10a and the voltage of the second battery module 10b. The control unit 20 can perform fault diagnosis of the first switch unit 30a or the second switch unit 30b during the period when this difference exists between the voltage of the first battery module 10a and the voltage of the second battery module 10b.

[0071] Furthermore, manufacturing variations between the first battery module 10a and the second battery module 10b, as well as environmental variations such as temperature, may cause differences in the self-discharge rates of the first battery module 10a and the second battery module 10b. If the battery pack 1 is left unattended for a long period of time without being connected to the load 2 or charger 3, a difference in the self-discharge rates of the first battery module 10a and the second battery module 10b may occur, resulting in a difference between the voltage of the first battery module 10a and the voltage of the second battery module 10b. Even when the battery pack 1 is not connected to the load 2 or charger 3, the management unit 20 can perform a fault diagnosis of the first switch unit 30a or the second switch unit 30b if a difference occurs between the voltage of the first battery module 10a and the voltage of the second battery module 10b.

[0072] As described above, according to this embodiment, by using redundant first battery module 10a and second battery module 10b, fault diagnosis of the first switch unit 30a or second switch unit 30b connected to the power line can be performed with high accuracy, regardless of whether a load 2 or charger 3 is connected to the outside of the battery pack 1. Since current can be passed bidirectionally to the first switch unit 30a or second switch unit 30b, the presence or absence of open faults and short faults of the semiconductor switches included in the first switch unit 30a or second switch unit 30b can be diagnosed with high accuracy. In addition, no additional circuit is required to perform fault diagnosis of the first switch unit 30a or second switch unit 30b, and the increase in hardware cost is suppressed.

[0073] The present disclosure has been described above based on embodiments. The embodiments are illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of their components and processing processes, and that such modifications are also within the scope of the present disclosure.

[0074] In the embodiment described above, the first switch section 30a was configured to include a current limiting circuit in which a pre-charge semiconductor switch Qpa and a current limiting resistor R1a are connected in series. However, a configuration in which the current limiting circuit is omitted is also possible. Similarly, the current limiting circuit included in the second switch section 30b can also be omitted. In this case, it is desirable to perform fault diagnosis of the first switch section 30a or the second switch section 30b only when the difference between the voltage of the first battery module 10a and the voltage of the second battery module 10b is less than a set value.

[0075] In the embodiments described above, an example was given in which a semiconductor switch is used in the first switch section 30a or the second switch section 30b. However, this disclosure does not exclude the possibility of configuring the first switch section 30a with a single mechanical relay. Similarly, it does not exclude the possibility of configuring the second switch section 30b with a single mechanical relay. When the battery pack 1 is not connected to the load 2 or the charger 3, the management unit 20 can perform fault diagnosis of the mechanical relay constituting the first switch section 30a or the mechanical relay constituting the second switch section 30b by utilizing the lateral flow between the first battery module 10a and the second battery module 10b.

[0076] In the above-described embodiment, a battery pack 1 incorporating a first battery module 10a and a second battery module 10b was explained. In this regard, at least one of the first battery module 10a or the second battery module 10b may be replaced with a capacitor module including an electric double-layer capacitor cell, a lithium-ion capacitor cell, or the like.

[0077] In the embodiment described above, the battery pack 1 is assumed to be mounted on an air mobility vehicle, but it may also be mounted on ground-based mobility vehicles such as electric motorcycles and ultra-compact EVs. Furthermore, it is not limited to mobility vehicles, but can also be applied to stationary energy storage systems, backup power supply systems installed in data centers, and the like.

[0078] The embodiments may be specified by the following items.

[0079] [Item 1] A fault diagnosis device (A) mounted on a power storage pack (1) in which a first power storage module (10a) and a second power storage module (10b) are connected in parallel, comprising: the first power storage module (10a) and a first switch unit (30a) connected to a power line between the first power storage module (10a) and the second power storage module (10b); the second power storage module (10b) and a second switch unit (30b) connected to a power line between the connection point (N1); and a management unit (20) that performs fault diagnosis of the first switch unit (30a) or the second switch unit (30b) using the current flowing between the first power storage module (10a) and the second power storage module (10b). According to this, fault diagnosis of the first switch unit (30a) or the second switch unit (30b) connected to the power line can be performed with high accuracy, regardless of whether a load (2) or charger (3) is connected to the outside of the energy storage pack (1). [Item 2] The fault diagnosis device (A) according to Item 1, wherein the first switch unit (30a) includes a first charging semiconductor switch (Qca) and a first discharging semiconductor switch (Qda) connected in series, and the second switch unit (30b) includes a second charging semiconductor switch (Qcb) and a second discharging semiconductor switch (Qdb) connected in series. According to this, fault diagnosis of the first charging semiconductor switch (Qca), the first discharging semiconductor switch (Qda), the second charging semiconductor switch (Qcb), and the second discharging semiconductor switch (Qdb) connected to the power line can be performed with high accuracy, regardless of whether a load (2) or charger (3) is connected to the outside of the energy storage pack (1).[Item 3] The fault diagnosis device (A) according to Item 2, wherein the first switch section (30a) further includes a first current limiting circuit in which a first pre-charge semiconductor switch (Qpa) and a first resistor (R1a) are connected in series in parallel with the first discharge semiconductor switch (Qda), and the second switch section (30b) further includes a second current limiting circuit in which a second pre-charge semiconductor switch (Qpb) and a second resistor (R1b) are connected in series in parallel with the second discharge semiconductor switch (Qdb), and diodes are formed or connected in antiparallel to the first charge semiconductor switch (Qca), the second charge semiconductor switch (Qcb), the first discharge semiconductor switch (Qda), the second discharge semiconductor switch (Qdb), the first pre-charge semiconductor switch (Qpa), and the second pre-charge semiconductor switch (Qpb). According to this, a limited detection current can be passed between the first energy storage module (10a) and the second energy storage module (10b). [Item 4] The control unit (20) controls the first charging semiconductor switch (Qca) to be ON, the first discharging semiconductor switch (Qda) to be OFF, the first pre-charge semiconductor switch (Qpa) to be ON, the second charging semiconductor switch (Qcb) to be ON, the second discharging semiconductor switch (Qdb) to be ON, and the second pre-charge semiconductor switch (Qpb) to be OFF when the voltage of the first energy storage module (10a) is higher than the voltage of the second energy storage module (10b), and diagnoses whether or not there is an open fault in the first pre-charge semiconductor switch (Qpa) and the second charging semiconductor switch (Qcb), as described in Item 3, Fault diagnosis device (A). According to this, it is possible to diagnose with high accuracy whether or not there is an open fault in the first pre-charge semiconductor switch (Qpa) and whether or not there is an open fault in the second charging semiconductor switch (Qcb).[Item 5] The control unit (20) controls the first charging semiconductor switch (Qca) to the off state, the first discharging semiconductor switch (Qda) to the off state, the first pre-charge semiconductor switch (Qpa) to the on state, the second charging semiconductor switch (Qcb) to the on state, the second discharging semiconductor switch (Qdb) to the on state, and the second pre-charge semiconductor switch (Qpb) to the off state when the voltage of the first charging semiconductor switch (Qca) is higher than the voltage of the second charging module (10b), thereby diagnosing whether or not there is a malfunction in the first charging semiconductor switch (Qca), as described in Item 4 (A). According to this, the presence or absence of open faults and short faults in the first charging semiconductor switch (Qca) can be diagnosed with high accuracy. [Item 6] The control unit (20) controls the first charging semiconductor switch (Qca) to be ON, the first discharging semiconductor switch (Qda) to be OFF, the first pre-charge semiconductor switch (Qpa) to be ON, the second charging semiconductor switch (Qcb) to be ON, the second discharging semiconductor switch (Qdb) to be OFF, and the second pre-charge semiconductor switch (Qpb) to be OFF when the voltage of the first energy storage module (10a) is higher than the voltage of the second energy storage module (10b), thereby diagnosing whether or not there is a malfunction in the second discharging semiconductor switch (Qdb), as described in Item 5 (A). According to this, the presence or absence of open faults and short faults in the second discharging semiconductor switch (Qdb) can be diagnosed with high accuracy. [Item 7] The control unit (20) controls the voltage of the first energy storage module (10a) to be higher than the voltage of the second energy storage module (10b) within a range below a set value, to turn on the first charging semiconductor switch (Qca), turn on the first discharging semiconductor switch (Qda), turn off the first pre-charge semiconductor switch (Qpa), turn on the second charging semiconductor switch (Qcb), turn on the second discharging semiconductor switch (Qdb), and turn off the second pre-charge semiconductor switch (Qpb), thereby diagnosing whether or not the first discharging semiconductor switch (Qda) is faulty, as described in Item 6 (A).According to this, the presence or absence of open faults and short faults in the first discharge semiconductor switch (Qda) can be diagnosed with high accuracy. [Item 8] The control unit (20) performs fault diagnosis of the first switch unit (30a) or the second switch unit (30b) according to Item 1, after the discharge of a current value of a certain value or more from the first energy storage module (10a) and the second energy storage module (10b), which are connected in parallel, to the external load (2) is completed. According to this, even when the first energy storage module (10a) and the second energy storage module (10b) are used in a state of being connected in parallel, fault diagnosis of the first switch unit (30a) or the second switch unit (30b) can be performed. [Item 9] The fault diagnosis device (A) described in Item 1, wherein the control unit (20) skips fault diagnosis of the first switch unit (30a) or the second switch unit (30b) if the difference between the voltage of the first energy storage module (10a) and the voltage of the second energy storage module (10b) is greater than or equal to a set value. This makes it possible to suppress inrush current and improve safety in fault diagnosis. [Item 10] The fault diagnosis device (A) described in Item 1, wherein the control unit (20) pulses on the first switch unit (30a) and performs fault diagnosis of the second switch unit (30b) if the voltage of the first energy storage module (10a) is greater than or equal to a set value. According to this, even when there is a large difference between the voltage of the first energy storage module (10a) and the voltage of the second energy storage module (10b), fault diagnosis of the first switch unit (30a) or the second switch unit (30b) can be performed while taking safety into consideration. [Item 11] An energy storage pack (1) comprising a first energy storage module (10a) and a second energy storage module (10b) connected in parallel, and a fault diagnosis device (A) described in any one of items 1 to 10. According to this, fault diagnosis of the first switch unit (30a) or the second switch unit (30b) connected to the power line can be performed with high accuracy, regardless of whether a load (2) or charger (3) is connected to the outside of the energy storage pack (1).

[0080] This disclosure can be used for fault diagnosis of switches connected to power lines.

[0081] 1 Battery pack, 2 Load, 3 Charger, 10a First battery module, 10b Second battery module, 20a First control unit, 20b Second control unit, 30a First switch unit, 30b Second switch unit, 41a First input voltage sensor, 42a First output voltage sensor, 43a First current sensor, 41b Second input voltage sensor, 42b Second output voltage sensor, 43b Second current sensor, Qca First charging semiconductor switch, Qda First discharging semiconductor switch, Qpa First pre-charge semiconductor switch, Qcb Second charging semiconductor switch, Qdb Second discharging semiconductor switch, Qpb Second pre-charge semiconductor switch, R1a First current limiting resistor, R1b Second current limiting resistor, E1-En Cell.

Claims

1. A fault diagnosis device mounted on a power storage pack in which a first power storage module and a second power storage module are connected in parallel, comprising: a first switch unit connected to the power line between the first power storage module and the connection point between the first power storage module and the second power storage module; a second switch unit connected to the power line between the second power storage module and the connection point; and a management unit that performs fault diagnosis of the first switch unit or the second switch unit using the current flowing between the first power storage module and the second power storage module.

2. The fault diagnosis device according to claim 1, wherein the first switch section includes a first charging semiconductor switch and a first discharging semiconductor switch connected in series, and the second switch section includes a second charging semiconductor switch and a second discharging semiconductor switch connected in series.

3. The fault diagnosis device according to claim 2, wherein the first switch section further includes a first current limiting circuit in which a first pre-charge semiconductor switch and a first resistor are connected in series in parallel with the first discharge semiconductor switch, and the second switch section further includes a second current limiting circuit in which a second pre-charge semiconductor switch and a second resistor are connected in series in parallel with the second discharge semiconductor switch, and diodes are formed or connected in antiparallel to each of the first charge semiconductor switch, the second charge semiconductor switch, the first discharge semiconductor switch, the second discharge semiconductor switch, the first pre-charge semiconductor switch, and the second pre-charge semiconductor switch.

4. The fault diagnosis device according to claim 3, wherein the control unit controls the first charging semiconductor switch to be ON, the first discharging semiconductor switch to be OFF, the first pre-charge semiconductor switch to be ON, the second charging semiconductor switch to be ON, the second discharging semiconductor switch to be ON, and the second pre-charge semiconductor switch to be OFF when the voltage of the first energy storage module is higher than the voltage of the second energy storage module, to diagnose whether or not there is an open fault in the first pre-charge semiconductor switch and whether or not there is an open fault in the second charging semiconductor switch.

5. The fault diagnosis device according to claim 4, wherein the control unit controls the first charging semiconductor switch to an off state, the first discharging semiconductor switch to an off state, the first pre-charge semiconductor switch to an on state, the second charging semiconductor switch to an on state, the second discharging semiconductor switch to an on state, and the second pre-charge semiconductor switch to an off state when the voltage of the first energy storage module is higher than the voltage of the second energy storage module, to diagnose whether or not the first charging semiconductor switch is faulty.

6. The fault diagnosis device according to claim 5, wherein the control unit controls the first charging semiconductor switch to be ON, the first discharging semiconductor switch to be OFF, the first pre-charge semiconductor switch to be ON, the second charging semiconductor switch to be ON, the second discharging semiconductor switch to be OFF, and the second pre-charge semiconductor switch to be OFF when the voltage of the first energy storage module is higher than the voltage of the second energy storage module, to diagnose whether or not the second discharging semiconductor switch is faulty.

7. The fault diagnosis device according to claim 6, wherein the control unit controls the first charging semiconductor switch to an ON state, the first discharging semiconductor switch to an ON state, the first pre-charge semiconductor switch to an OFF state, the second charging semiconductor switch to an ON state, the second discharging semiconductor switch to an ON state, and the second pre-charge semiconductor switch to an OFF state when the voltage of the first energy storage module is higher than the voltage of the second energy storage module within a range below a set value, to diagnose whether or not the first discharging semiconductor switch is faulty.

8. The fault diagnosis device according to claim 1, wherein the control unit performs fault diagnosis of the first switch unit or the second switch unit after the discharge of a current value above a certain value from the first energy storage module and the second energy storage module connected in parallel to each other to an external load has been completed.

9. The fault diagnosis device according to claim 1, wherein the control unit skips fault diagnosis of the first switch unit or the second switch unit if the difference between the voltage of the first energy storage module and the voltage of the second energy storage module is greater than or equal to a set value.

10. The fault diagnosis device according to claim 1, wherein the control unit, when the voltage of the first energy storage module is higher than the voltage of the second energy storage module by a set value or more, turns on the first switch unit in a pulsed manner to perform fault diagnosis of the second switch unit.

11. A battery pack comprising a first battery storage module and a second battery storage module connected in parallel, and a fault diagnosis device according to any one of claims 1 to 10.

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