Battery system and method for diagnosing condition of link capacitor according to operation of precharge circuit

Abstract

The present invention relates to a battery system comprising: two terminals connected to an external device including a link capacitor connected in parallel to a battery pack; a precharge circuit connected between one end of the battery pack and one end of the link capacitor; a main relay connected in parallel to the precharge circuit; and a battery management system which controls a turn-on operation of a precharge relay and a main relay, calculates a reference power amount estimated to be supplied to a precharge resistor during a driving time of the precharge circuit, calculates a target power amount supplied to the precharge resistor during the driving time of the precharge circuit, and diagnoses a condition of the link capacitor as one of a plurality of failure states on the basis of a comparison result between a threshold power amount and the target power amount according to the reference power amount and a comparison result between a pack voltage of the battery pack and a link voltage between the two terminals.

Description

Method for diagnosing the status of a link capacitor according to the operation of a battery system and a precharge circuit

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0086197, filed July 1, 2024, the entire contents of which are incorporated herein by reference.

[0003] The present disclosure relates to a method for diagnosing the status of a link capacitor according to the operation of a battery system and a precharge circuit.

[0004] Secondary batteries used in electric vehicles, etc., are capable of repeated charging and discharging. In the case of a battery system including a precharge circuit including a precharge resistor and a precharge relay, the main relay may not be turned on initially during the initial stage of driving the battery, but rather the precharge relay may be turned on first while the main relay is turned off. The main relay may be configured to turn on only after a predetermined period of time has elapsed from the time the precharge relay is turned on, thereby allowing the charging and discharging path to pass through the main relay.

[0005] When the precharge relay is turned on, the link capacitor (X-cap) connected in parallel with the battery pack can be charged while the surge current is limited by the precharge resistor. In addition, when the operation of the precharge circuit is finished and the precharge relay is turned off, the link capacitor (X-cap) can be discharged.

[0006] By operating this precharge circuit, current flows through the precharge resistor, so that no rush current occurs and arcing is prevented when the main relay is turned on.

[0007] The precharge resistors provided in these precharge circuits can overheat and be damaged if excessive current flows through them, and damage to the precharge resistors can cause damage not only to the precharge circuits but also to the entire battery pack. Therefore, in order to protect the precharge resistors, it is necessary to diagnose various faults on the high-voltage lines connected to both ends of the battery pack. It is also important to identify the type of fault in the link capacitors connected to the high-voltage lines.

[0008] The present invention provides a battery system capable of diagnosing the state of a link capacitor by driving a precharge circuit including a precharge relay and a precharge resistor, and a method for diagnosing the state of a link capacitor according to the operation of the precharge circuit.

[0009] According to one aspect of the invention, a battery system comprises: a battery pack; two terminals connected to an external device including a link capacitor connected in parallel with the battery pack; a precharge circuit including a precharge resistor and a precharge relay connected in series between one end of the battery pack and one end of the link capacitor; a main relay connected in parallel with the precharge circuit; and a battery management system (BMS) that measures a pack voltage of the battery pack and a link voltage between the two terminals, controls a turn-on operation of the precharge relay and the main relay, calculates a reference power amount estimated to have been supplied to the precharge resistor during an operating time of the precharge circuit, calculates a target power amount supplied to the precharge resistor during an operating time of the precharge circuit, and diagnoses a state of the link capacitor as one of a plurality of fault states based on a comparison result of a threshold power amount according to the reference power amount and the target power amount and a comparison result of the pack voltage and the link voltage.

[0010] The BMS can calculate the reference power amount based on the capacitance of the link capacitor, the resistance value of the precharge resistor, and the pack voltage during the driving time of the precharge circuit.

[0011] The BMS further includes a current sensor connected to one end of the precharge relay to measure precharge current, and the BMS can calculate the target power amount based on the pack voltage and the precharge current flowing in the precharge relay during the driving time of the precharge circuit.

[0012] The plurality of fault states include at least one of an open fault in which at least one of the two wires between the two terminals of the link capacitor is open, a short-circuit fault in which at least one of the two terminals of the link capacitor is grounded, and a load fault in which the capacitance value of the link capacitor is smaller than or larger than a predetermined reference capacitance range, and when the state of the link capacitor is diagnosed as one of the plurality of fault states, the BMS can turn off the precharge relay and the main relay.

[0013] If the target power amount is less than a first threshold power amount that is less than the reference power amount, and the link voltage is outside a predetermined reference voltage range based on the pack voltage, the BMS can diagnose the status of the link capacitor as an open fault.

[0014] If the target power amount is less than a first threshold power amount that is less than the reference power amount, and the link voltage is within a predetermined reference voltage range based on the pack voltage, the BMS can diagnose the state of the link capacitor as the load failure and diagnose that the capacitance of the link capacitor is smaller than the lower limit of the reference capacitance range.

[0015] If the target power amount is less than the reference power amount and is within a range greater than or equal to a first threshold power amount less than the reference power amount, the BMS can diagnose the status of the link capacitor as the load failure.

[0016] If the link voltage is within a predetermined reference voltage range based on the pack voltage, the BMS can diagnose that the capacitance of the link capacitor is smaller than the lower limit of the reference capacitance range.

[0017] If the link voltage deviates from a predetermined reference voltage range based on the pack voltage, the BMS can diagnose that the capacitance of the link capacitor is greater than the upper limit of the reference capacitance range.

[0018] According to another aspect of the invention, a method for diagnosing the status of a link capacitor performed by a battery system including a battery pack, two terminals connected to an external device including a link capacitor connected in parallel with the battery pack, a precharge circuit including a precharge resistor and a precharge relay connected in series between one end of the battery pack and one of the two terminals, a main relay connected in parallel with the precharge circuit, and a battery management system (BMS) controlling a turn-on operation of the precharge relay and the main relay, the method comprising the steps of: measuring a pack voltage of the battery pack; measuring a link between the two terminals; calculating a reference power amount estimated to have been supplied to the precharge resistor during an operating time of the precharge circuit; calculating a target power amount supplied to the precharge resistor during an operating time of the precharge circuit; and diagnosing a status of the link capacitor as one of a plurality of failure states based on a comparison result between a threshold power amount according to the reference power amount and the target power amount and a comparison result between the pack voltage and the link voltage.

[0019] The method may further include calculating the reference power amount based on the capacitance of the link capacitor, the resistance value of the precharge resistor, and the pack voltage during the driving time of the precharge circuit.

[0020] The method may further include a step of measuring a precharge current by being connected to one end of the precharge relay, and a step of calculating the target power amount based on the pack voltage and the precharge current flowing in the precharge relay during the driving time of the precharge circuit.

[0021] The plurality of fault states may include at least one of an open fault in which at least one of the two wires between the two terminals of the link capacitor and the two terminals is open, a short-circuit fault in which at least one of the two terminals of the link capacitor is grounded, and a load fault in which a capacitance value of the link capacitor is smaller than or larger than a predetermined reference capacitance range, and the step of diagnosing the state of the link capacitor as one of the plurality of fault states may include a step of turning off the precharge relay and the main relay when the state of the link capacitor is diagnosed as one of the plurality of fault states.

[0022] The method may further include a step of diagnosing the status of the link capacitor as an open fault when the target power amount is less than a first threshold power amount that is less than the reference power amount and the link voltage is outside a predetermined reference voltage range based on the pack voltage.

[0023] If the target power amount is less than a first threshold power amount that is less than the reference power amount, and the link voltage is within a predetermined reference voltage range based on the pack voltage, the step of diagnosing the state of the link capacitor as the load failure and diagnosing that the capacitance of the link capacitor is smaller than the lower limit of the reference capacitance range may be further included.

[0024] If the target power amount is less than the reference power amount and is within a range greater than or equal to a first threshold power amount less than the reference power amount, the step of diagnosing the status of the link capacitor as a load failure may be further included.

[0025] If the link voltage is within a predetermined reference voltage range based on the pack voltage, a step of diagnosing that the capacitance of the link capacitor is smaller than the lower limit of the reference capacitance range may be further included.

[0026] If the link voltage is outside a predetermined reference voltage range based on the pack voltage, a step of diagnosing that the capacitance of the link capacitor is greater than the upper limit of the reference capacitance range may be further included.

[0027] According to the present invention, in order to protect the precharge resistor, the state of the link capacitor is diagnosed as one of multiple fault states, such as open fault, short-circuit fault, and load fault, by comparing the reference power amount estimated to have been supplied to the precharge resistor with the actual target power amount supplied, thereby enabling the battery system to determine the type of fault occurring in the link capacitor. In addition, the state of the link capacitor can be diagnosed more specifically based on the comparison result between the reference power amount and the target power amount and the comparison result between the link voltage and the pack voltage.

[0028] According to the present invention, by automatically detecting an open circuit fault in a high voltage line and taking countermeasures before an accident occurs to a worker, secondary safety accidents can be prevented and cause analysis can be facilitated in the event of a problem.

[0029] According to the present invention, a load failure such as vehicle misassembly is automatically detected, and a worker assembling a vehicle into a battery system is notified of the vehicle misassembly, and the link end of the vehicle can be inspected before a secondary accident occurs.

[0030] FIG. 1 is a block diagram schematically illustrating a battery system according to one embodiment.

[0031] FIG. 2 is a drawing for explaining a state in which an open circuit fault occurs in a link capacitor in the battery system illustrated in FIG. 1.

[0032] FIG. 3 is a drawing for explaining a state in which a load failure occurs in a link capacitor in the battery system illustrated in FIG. 1.

[0033] FIG. 4 is a drawing for explaining a state in which a short circuit failure occurs in a link capacitor in the battery system illustrated in FIG. 1.

[0034] FIG. 5 is a flowchart of a method for diagnosing the status of a link capacitor according to the operation of a precharge circuit according to one embodiment.

[0035] Hereinafter, the embodiments disclosed in this specification will be described in detail with reference to the attached drawings. The same or similar components will be given the same or similar drawing reference numerals, and redundant descriptions thereof will be omitted. The suffixes "module" and / or "part" used for components in the following description are given or used interchangeably only for the convenience of writing the specification, and do not in themselves have distinct meanings or roles. In addition, when describing the embodiments disclosed in this specification, if it is determined that a specific description of a related known technology may obscure the gist of the embodiments disclosed in this specification, a detailed description thereof will be omitted. In addition, the attached drawings are only intended to facilitate easy understanding of the embodiments disclosed in this specification, and the technical ideas disclosed in this specification are not limited by the attached drawings, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention.

[0036] Terms that include ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by these terms. These terms are used solely to distinguish one component from another.

[0037] In this application, terms such as “include” or “have” are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but should be understood not to exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0038] Among the configurations according to one embodiment, a configuration that controls another configuration under specific control conditions may be installed with a program implemented as a set of commands that embody the control algorithms necessary to control the other configuration. The control configuration may process input data and stored data according to the installed program to generate output data. The control configuration may include non-volatile memory for storing the program and memory for storing data.

[0039] FIG. 1 is a block diagram schematically illustrating a battery system according to one embodiment.

[0040] Referring to FIG. 1, the battery system (1) may include a battery pack (10), a current sensor (20), a battery management system (BMS) (30), a main relay (40, 41), and a precharge circuit (50).

[0041] The battery pack (10) may include two or more battery cells connected in series, two or more battery cells connected in parallel, a plurality of battery cells connected in series, or two or more battery cells connected in parallel.

[0042] The battery system (1) can be connected to an external device (2). The external device (2) can include a load and a charging device such as an inverter or a converter. If the external device (2) is a charger, the two terminals (P+, P-) of the battery system (1) can be connected to the charger and receive power from the charger to be charged. If the external device (2) is a load, the two terminals (P+, P-) of the battery system (1) can be connected to the load so that the power supplied by the battery pack (10) can be discharged through the load.

[0043] The terminal (P+) of the battery system (1) can be connected to one end of an external device (2), and the terminal (P-) of the battery system (1) can be connected to the other end of the external device (2). In the following description, the external device (2) is assumed to be a vehicle, but this is for convenience of explanation and the invention is not limited thereto.

[0044] The external device (2) may include a field load (210), a link capacitor (220), and terminals (PL+, PL-). A high voltage (HV) line of the battery pack (10) may be connected to the field load (210) and the link capacitor (220) through two terminals (P+, P-) of the battery system (1).

[0045] The link capacitor (220) may be connected in parallel with the battery pack (10) and the electric load (210), respectively. One end of the electric load (210) and the link capacitor (220) may be connected to a terminal (P+) and a terminal (PL+), and the other end of the electric load (210) and the link capacitor (220) may be connected to a terminal (P-) and a terminal (PL-). The electric load (210) may include an inverter, a converter, etc. A node (ND1) connected to one end of the link capacitor (220) may be connected to a terminal (PL+), and a node (ND2) connected to the other end of the link capacitor (220) may be connected to a terminal (PL-). The terminal (P+) and the node (ND1) may be connected by a wire (LN1), and one end of the node (ND1) and the link capacitor (220) may be connected by a wire (LN2). The other end of the node (ND2) and the link capacitor (220) can be connected by a wire (LN3), and the terminal (P-) and the node (ND2) can be connected by a wire (LN4).

[0046] A link capacitor (220) may be included in a link terminal. The link terminal may collectively refer to a plurality of wires for electrically connecting between the electric load (210) and two terminals (P+, P-) of the battery system (1). For example, the link terminal may include wires (LN1-LN4) between both ends of the link capacitor (220) and two ends (P+, P-) of the battery system (1).

[0047] The link capacitor (220) may be implemented as a single capacitor or a combination of multiple capacitors, and may also be implemented as a combination of passive and active elements. The capacitance of the link capacitor (220) is not limited and may be selected to a predetermined value according to the pack voltage of the battery pack (10).

[0048] One end of the main relay (40, 41) is connected to the battery pack (10), and the other end of the main relay (40, 41) is connected to at least one component in an external device (2). Closing and opening of the main relay (40, 41) can be controlled according to a main relay control signal (MRCS1, MRCS2) supplied from the BMS (200).

[0049] The precharge circuit (50) may include a precharge relay (501) and a precharge resistor (502). The precharge circuit (50) may be connected in parallel to the main relay (40). One end of the precharge circuit (50) may be connected to the positive electrode of the battery pack (10) and one end of the main relay (40). The other end of the precharge circuit (50) may be connected to the other end of the main relay (40) and the positive electrode (P+) of the battery system (1). Closing and opening of the precharge relay (501) may be controlled according to a precharge relay control signal (PRCS1) supplied from the BMS (200).

[0050] The precharge circuit (50) can perform precharge. Specifically, when the precharge relay (501) is turned on, the link capacitor (220) is supplied with a small current reduced by the precharge resistor (502) and is slowly precharged, so that the voltage supplied from the battery pack (10) can be charged to the link capacitor (220). In addition, when the precharge relay (501) is turned off, the link capacitor (220) can be discharged.

[0051] Therefore, when the precharge relay (501) is turned on before the main relay (40) is turned on, and the main relay (40) is turned on thereafter, the surge current due to the connection with the external device (2) is reduced, and the battery pack (10) can perform a charge / discharge operation with respect to the external device (2).

[0052] BMS (30) can control the turn-on operation of the precharge relay and the main relay according to the main relay control signal (MRCS1, MRCS2) and the precharge relay control signal (PRCS1).

[0053] The current sensor (20) is connected in series to the current path between the positive electrode of the battery pack (10) and one end of the precharge relay (501). The current sensor (20) can measure the current flowing in the precharge relay (501) (hereinafter, “precharge current”) and transmit the measurement result to the BMS (30). The BMS (30) can derive the precharge current based on the signal received from the current sensor (20).

[0054] The BMS (30) can measure the pack voltage of the battery pack (10) and the voltage (hereinafter, “link voltage”) between the two terminals (P+, P-) of the battery system (1). The BMS (30) can receive a signal indicating the positive voltage of the battery pack (10) and a signal indicating the negative voltage of the battery pack (10). The BMS (30) can measure the pack voltage of the battery pack (10) based on the signal indicating the positive voltage of the battery pack (10) and the signal indicating the negative voltage of the battery pack (10). The BMS (30) can receive a signal (VL1) indicating the voltage of the positive terminal (P+) of the battery system (1) and a signal (VL2) indicating the voltage of the negative terminal (P-) of the battery system (1). The BMS (30) can measure the link voltage based on a signal (VL1) indicating the voltage of the positive terminal (P+) of the battery system (1) and a signal (VL2) indicating the voltage of the negative terminal (P-) of the battery system (1).

[0055] The BMS (30) can repeatedly measure the pack voltage, link voltage, and precharge current of the battery pack (10) at predetermined intervals.

[0056] The time for which the precharge circuit (50) operates can be referred to as the operating time of the precharge circuit (50).

[0057] The start time of the driving time of the precharge circuit (50) may be the first time point when the BMS (30) turns on the precharge relay (501). The first time point may be the time point when the BMS (30) outputs a precharge relay control signal (PRCS1) that controls the precharge relay (501) to turn on. The BMS (30) may control the main relay (40) to turn off, control the main relay (41) to turn on, and control the precharge relay (501) to turn on to start driving the precharge circuit (50). Accordingly, the voltage of the battery pack (10) may be applied to the electric load (210) and the link capacitor (220) through the precharge circuit (50). Also, in this case, since current flows through the precharge circuit (50), current can also flow through the precharge resistor (502).

[0058] The end point of the driving time of the precharge circuit (50) may be a second point in time after the first point in time when the BMS (30) turns off the precharge relay (501). The second point in time may be a point in time when the BMS (30) outputs a precharge relay control signal (PRCS1) that controls the precharge relay (501) to turn off. The BMS (30) may end the driving of the precharge circuit (50) by controlling the precharge relay (501) to turn off at the second point in time. Accordingly, the voltage of the battery pack (10) may not be applied to the precharge circuit (50) and the link capacitor (220). In addition, in this case, since no current flows in the precharge circuit (50), no current may flow in the precharge resistor (502).

[0059] The BMS (30) can calculate the time difference between the first time point at which the precharge relay (501) is turned on and the second time point at which the precharge relay (501) is turned off as the operating time of the precharge circuit (50).

[0060] The BMS (30) can calculate the amount of power (hereinafter, “reference power”) estimated to have been supplied to the precharge resistor (502) during the operating time of the precharge circuit (50). The reference power may be an amount of power estimated in a normal state in which the link capacitor (220) does not fall under any of a plurality of fault states. The BMS (30) can calculate the amount of power (hereinafter, “target power”) supplied to the precharge resistor (502) during the operating time of the precharge circuit (50). The target power may be an actual amount of power supplied to the precharge resistor (502) during the operating time of the precharge circuit (50).

[0061] After the operating time of the precharge circuit (50) ends, the BMS (30) can diagnose the status of the link capacitor (220) as one of a plurality of failure states based on the comparison result between the critical power amount and the target power amount according to the reference power amount and the comparison result between the pack voltage and the link voltage of the battery pack (10).

[0062] The plurality of fault states may include at least one of an open fault, a short-circuit fault, and a load fault. An open fault may be a state in which at least one of the wires (LN1-LN4) between the two terminals (P+, P-) of the link capacitor (220) and the two terminals (P+, P-) of the battery system (1) is open. A short-circuit fault may be a state in which at least one of the two terminals of the link capacitor (220) is grounded. A load fault may be a state in which the capacitance value of the link capacitor (220) is smaller or larger than a predetermined reference capacitance range. Hereinafter, each of the plurality of fault states will be described as an example with reference to FIGS. 2 to 4.

[0063] FIG. 2 is a drawing for explaining a state in which an open circuit fault occurs in a link capacitor in the battery system illustrated in FIG. 1.

[0064] The external device (2_1) illustrated in Fig. 2 may represent an example of a state in which an open circuit fault has occurred in the link capacitor (220) included in the external device (2) illustrated in Fig. 1. Hereinafter, descriptions of parts of the battery system (1) and the external device (2) that overlap with the previous descriptions may be omitted.

[0065] Referring to FIG. 2, the external device (2_1) includes a full-length load (210), a link capacitor (220), and terminals (PL+, PL-), and at least one point (e.g., O1) among a plurality of points (O1-O4) connected to each of the two ends of the link capacitor (220) may be open. In one embodiment, as shown in FIG. 2, a state in which at least one of the wires (LN1-LN4) between the two ends (P+, P-) of the link capacitor (220) and the two ends (P+, P-) of the battery system (1) is disconnected and open may be referred to as an open fault.

[0066] FIG. 3 is a drawing for explaining a state in which a load failure occurs in a link capacitor in the battery system illustrated in FIG. 1.

[0067] The external device (2_2) illustrated in FIG. 3 may represent an example of a state in which a load failure occurs in the link capacitor (220) included in the external device (2) illustrated in FIG. 1. Hereinafter, descriptions of parts of the battery system (1) and the external device (2) that overlap with the previous descriptions may be omitted.

[0068] Referring to FIG. 3, the external device (2_2) includes an electric load (210), a link capacitor (221), and terminals (PL+, PL-), and the link capacitor (221) may be another example of the link capacitor (220) illustrated in FIG. 1. The capacitance value of the link capacitor (221) may be less than a lower limit of a predetermined reference capacitance range or greater than an upper limit of the reference capacitance. The predetermined reference capacitance range may be a predetermined range in which power supply from the battery pack (10) to the electric load (210) is normally performed. Here, the lower limit of the reference capacitance range may be a first level, and the upper limit of the reference capacitance range may be a second level. The capacitance value of the link capacitor (221) may be a value lower than the first level or higher than the second level.

[0069] When connecting a battery system (1) to an external device (2), a link capacitor having an appropriate capacitance is required. A load failure may include not only a case where the capacitance of the link capacitor is out of the standard capacitance range, but also a case where the battery system (1) is assembled to a wrong vehicle, a case where the link capacitor is damaged, a case where some of the multiple cables for connection between the battery system (1) and the external device (2) are not connected, and the external device (2) and the battery system (1) are incorrectly assembled. In addition, a load failure may also include a defect in setting the connection environment between the battery system (1) and the external device (2) (hereinafter, “defective pack connection environment setting”).

[0070] FIG. 4 is a drawing for explaining a state in which a short circuit failure occurs in a link capacitor in the battery system illustrated in FIG. 1.

[0071] The external device (2_3) illustrated in Fig. 4 may represent an example of a state in which a short circuit failure has occurred in the link capacitor (220) included in the external device (2) illustrated in Fig. 1. Hereinafter, descriptions of parts of the battery system (1) and the external device (2) that overlap with the previous descriptions may be omitted.

[0072] Referring to FIG. 4, the external device (2_3) includes a full-length load (210), a link capacitor (220), and terminals (PL+, PL-), and one end of the link capacitor (220) can be grounded to a ground (GND) voltage. In one embodiment, as shown in FIG. 4, a state in which at least one end of the link capacitor (220) is grounded can be referred to as a short-circuit fault.

[0073] The BMS (30) can calculate a reference power amount based on the capacitance of the link capacitor (220), the resistance value of the precharge resistor (502), and the pack voltage of the battery pack (10) during the operating time of the precharge circuit (50).

[0074] For example, BMS (30) can calculate the reference power amount according to [Mathematical Formula 1] below.

[0075]

[0076] Here, W1 is the reference power, T1 is the start time of the driving time of the precharge circuit (50), T2 is the end time of the driving time of the precharge circuit (50), Vb(T1) is the pack voltage of the battery pack (10) measured at the time point T1, R is the resistance value of the precharge resistor (502), and C is the capacitance of the link capacitor (220).

[0077] When the precharge relay (501) is turned on and the main relay (40) is turned off, an RC circuit including a precharge resistor (502) and a link capacitor (220) and using the battery pack (10) as a voltage source can be formed. The BMS (30) can estimate the reference power amount by multiplying the output value of the current calculation formula for the link capacitor corresponding to the RC circuit by the pack voltage of the battery pack (10) during the operating time of the precharge circuit (50).

[0078] Additionally, the BMS (30) can calculate the target power amount based on the pack voltage of the battery pack (10) and the precharge current flowing in the precharge relay (501) during the operating time of the precharge circuit (50).

[0079] For example, BMS (30) can calculate the reference power amount according to [Mathematical Formula 2] below.

[0080]

[0081] Here, W2 is the target power amount, T1 is the start time of the driving time of the precharge circuit (50), T2 is the end time of the driving time of the precharge circuit (50), Vb(t) is the pack voltage of the battery pack (10), and Ir(t) is the precharge current.

[0082] The BMS (30) can compare the target power amount with the threshold power amount according to the reference power amount. In addition, the BMS (30) can compare the pack voltage and link voltage of the battery pack (10).

[0083] Below, the operation of BMS (30) comparing the target power amount with the threshold power amount according to the reference power amount and comparing the pack voltage and the link voltage is described.

[0084] The threshold power amount according to the reference power amount to be compared with the target power amount may include the reference power amount, a first threshold power amount that is less than the reference power amount, a second threshold power amount that is greater than the reference power amount, etc. For example, the first threshold power amount may be 50% of the reference power amount, i.e., half of the reference power amount. Also, for example, the second threshold power amount may be 200% of the reference power amount, i.e., twice the reference power amount.

[0085] Hereinafter, for convenience of explanation, the first threshold power amount is described as 50% of the reference power amount, and the second threshold power amount is described as 200% of the reference power amount. However, this is merely an example and the invention is not limited thereto. The first threshold power amount may be a minimum standard for power amount below the reference power amount, and the second threshold power amount may be a maximum standard for power amount exceeding the reference power amount.

[0086] The BMS (30) can determine whether the target power amount is less than the first threshold power amount, within a range that is greater than or equal to the first threshold power amount and less than the reference power amount, within a range that is greater than or equal to the reference power amount and less than the second threshold power amount, or greater than or equal to the second threshold power amount.

[0087] In addition, the BMS (30) can determine whether the link voltage is within a predetermined reference voltage range based on the pack voltage of the battery pack (10). For example, the predetermined reference voltage range based on the pack voltage may be a voltage range that is 90% or more of the pack voltage of the battery pack (10). Hereinafter, for convenience of explanation, the reference voltage range is described as a voltage range that is 90% or more of the pack voltage of the battery pack (10), but this is only an example and the invention is not limited thereto. The reference voltage range may be a predetermined range based on the pack voltage.

[0088] If the target power amount is less than the first threshold power amount that is less than the reference power amount, and the link voltage is outside a predetermined reference voltage range based on the pack voltage of the battery pack (10), the BMS (30) can diagnose the status of the link capacitor (220) as an open fault.

[0089] Referring to FIG. 2, when an open circuit fault occurs, the link capacitor (220) and the battery system (1) are not connected, and both ends of the battery pack (10) are opened, so that no current may flow to the precharge resistor (502).

[0090] Accordingly, the target power amount, which is the amount of power actually supplied to the precharge resistor (502) in the battery system (1) illustrated in FIG. 2, may be less than the first threshold power amount, and the link voltage may be less than 90% of the pack voltage of the battery pack (10).

[0091] Using this, the BMS (30) can diagnose the status of the link capacitor (220) as an open fault if the target power amount is less than the first threshold power amount and the link voltage is less than 90% of the pack voltage of the battery pack (10).

[0092] In this way, if the target power amount is less than 50% of the reference power amount and the link voltage is less than 90% of the pack voltage of the battery pack (10), the BMS (30) can control the main relay (40) and the precharge relay (501) to turn off. If an open fault occurs, the current of the battery pack (10) may leak from the two terminals (P+, P-) of the battery system (1), which may cause electric shock to users such as workers. Therefore, if an open fault occurs, the BMS (30) can prevent safety accidents for users by turning off the main relay (40) and the precharge relay (501).

[0093] If the target power amount is less than the first threshold power amount and the link voltage is within a predetermined reference voltage range based on the pack voltage of the battery pack (10), the BMS (30) can diagnose the status of the link capacitor (220) as a load failure.

[0094] Referring to FIG. 3, when a load failure occurs, the capacitance value of the link capacitor (221) may be smaller than the lower limit of a predetermined reference capacitance range or larger than the upper limit of the reference capacitance range.

[0095] For example, if the target power is less than 50% of the reference power and the link voltage is more than 90% of the pack voltage of the battery pack (10), the BMS (30) can diagnose that the capacitance of the link capacitor (221) is less than a predetermined level or that the pack connection environment is faulty.

[0096] If the target power amount is within a range that is less than the reference power amount and greater than the first threshold power amount, the BMS (30) can diagnose the status of the link capacitor (221) as a load failure. In addition, if the target power amount is within a range that is less than the reference power amount and greater than the first threshold power amount, the BMS (30) can determine whether the capacitance value of the link capacitor (221) corresponding to the load failure exceeds or falls below a predetermined reference capacitance range based on the result of comparing the link voltage with the pack voltage of the battery pack (10).

[0097] If the target power is within a range that is less than the reference power and greater than the first threshold power, and the link voltage is within a predetermined reference voltage range based on the pack voltage of the battery pack (10), the BMS (30) may determine the state of the link capacitor (221) as a load failure and diagnose that the capacitance value of the link capacitor (221) is smaller than the lower limit of the predetermined reference capacitance range. For example, if the target power is within a range of 50% to 100% of the reference power, and the link voltage is 90% or more of the pack voltage of the battery pack (10), the BMS (30) may determine that the capacitance of the link capacitor (221) is smaller than a predetermined first level, or that the pack connection environment setting is faulty.

[0098] If the target power is within a range that is less than the reference power and greater than the first threshold power, and the link voltage is outside a predetermined reference voltage range based on the pack voltage of the battery pack (10), the BMS (30) may determine the status of the link capacitor (221) as a load failure and diagnose that the capacitance value of the link capacitor (221) is greater than the upper limit of the predetermined reference capacitance range. For example, if the target power is within a range of 50% to 100% of the reference power, and the link voltage is less than 90% of the pack voltage of the battery pack (10), the BMS (30) may determine that the capacitance of the link capacitor (221) is greater than a predetermined second level, or that the pack connection environment setting is faulty.

[0099] As described above, if the status of the link capacitor (221) is diagnosed as a load failure, the BMS (30) can control the main relay (40) and the precharge relay (501) to turn off. If a load failure occurs, the precharge of the precharge circuit (50) may not be performed properly. Therefore, if the BMS (30) diagnoses a load failure, the BMS (30) can prevent a risk due to the precharge not being performed properly by turning off the main relay (40) and the precharge relay (501).

[0100] Meanwhile, if the target power is greater than or equal to the reference power and less than the second threshold power, the BMS (30) can diagnose the state of the link capacitor (220, see FIG. 1) as normal. For example, if the target power is within the range of 100% to 200% of the reference power, the BMS (30) can diagnose the state of the link capacitor (220) as normal in which precharge is normally performed during the driving time of the precharge circuit (50).

[0101] If the target power amount is greater than the second threshold power amount, the BMS (30) can diagnose that a short circuit failure has occurred.

[0102] Referring to FIG. 4, when a short circuit fault occurs, at least one of the two terminals of the link capacitor (220) is connected to ground, and an amount of power greater than the amount of power allowed for the precharge resistor (502) can be supplied. In this case, the target power amount, which is the amount of power actually supplied to the precharge resistor (502), can be included in a range greater than or equal to the second threshold power amount set to twice the reference power amount.

[0103] Using this, if the target power amount is greater than the second threshold power amount, the BMS (30) can diagnose the status of the link capacitor (220) as a short-circuit failure.

[0104] In this way, if the target power amount is 200% or more of the reference power amount, the BMS (30) can control the precharge relay (501) to turn off. If a short circuit failure occurs, the precharge resistor may be damaged or the battery pack (10) may be grounded, causing the battery pack (10) to discharge. Therefore, if a short circuit failure occurs, the BMS (30) can turn off the main relay (40) and the precharge relay (501) so that no more power is supplied to the precharge resistor (502).

[0105] In another embodiment, if the target power amount is 200% or more of the reference power amount, the BMS (30) can control the main relay (40) or the precharge relay (501) to turn off.

[0106] The BMS (30) may include a notification unit (not shown) having at least one of a display device that displays a diagnosis result indicating a fault state determined as the state of the link capacitor (220) among a plurality of fault states using at least one of a symbol, a number, and a code, and a speaker device that outputs the diagnosis result as an audio signal. The BMS (30) may output the diagnosis result through the display device and / or the speaker device via the notification unit (not shown). For example, when the state of the link capacitor (220) is diagnosed as a load fault, the BMS (30) may output through the notification unit (not shown) that a load fault has occurred and whether the capacitance value of the link capacitor (220) is smaller or larger than a predetermined reference capacitance range as a diagnosis result.

[0107] When diagnostic results are output via the notification unit (not shown), users, such as operators, can inspect the vehicle's link terminals. For example, if a vehicle link terminal inspection reveals that some of the multiple cables required for connection are not connected, the missing cables can be properly connected.

[0108] Below, the trend of target power and link voltage for each of multiple failure states is described.

[0109] When the driving time of the precharge circuit (50) ends, a signal (Pre-charge process complete) indicating the end of the driving time of the precharge circuit (50) may be turned on with a True value. When the driving time of the precharge circuit (50) ends, in a normal state, the target power amount (E_PL) may be approximately equal to the reference power amount (Energy Prediction), and the link voltage (U_DC_Link) may be approximately equal to the pack voltage (U Battery Pack) of the battery pack (10).

[0110] When the operating time of the precharge circuit (50) ends and a short circuit failure occurs in the link capacitor (220), a signal indicating that a short circuit failure has occurred (Pre-charge short circuit) may be turned on with a True value. In this case, the target power amount (E(SC)) may exceed the second threshold power amount (Pre-charge Energy: Maximum Limit), and the link voltage (U_DC_Link(SC)) may be lowered to a level of 40% of the pack voltage (U Battery Pack) of the battery pack (10).

[0111] When the driving time of the precharge circuit (50) ends and a load failure (Parallel load) occurs in the link capacitor (220), a signal indicating the end of the driving time of the precharge circuit (50) (Pre-charge process complete) and a signal indicating that a load failure has occurred (Parallel load) may be turned on with a True value. In this case, the target power amount (E (Open Loop)) is less than the first threshold power amount (Pre-charge Energy: Minimum Limit), and the link voltage (U_DC_Link) may be approximately equal to the pack voltage (U Battery Pack) of the battery pack (10).

[0112] FIG. 5 is a flowchart of a method for diagnosing the status of a link capacitor according to the operation of a precharge circuit according to one embodiment.

[0113] Below, in the description of the battery system (1), any part that overlaps with the previous description may be omitted.

[0114] Referring to FIG. 5, the BMS (30) can calculate a reference power amount based on the capacitance of the link capacitor (220), the resistance value of the precharge resistor (502), and the pack voltage of the battery pack (10) during the driving time of the precharge circuit (50) (S101).

[0115] The BMS (30) can calculate the target power amount based on the pack voltage of the battery pack (10) and the precharge current flowing in the precharge relay (501) during the operation time of the precharge circuit (50) (S102).

[0116] The BMS (30) can measure the link voltage based on a signal (VL1) indicating the positive terminal (P+) voltage of the battery system (1) and a signal (VL2) indicating the negative terminal (P-) voltage of the battery system (1) (S103). In addition, the BMS (30) can measure the pack voltage of the battery pack (10) based on a signal indicating the positive voltage of the battery pack (10) and a signal indicating the negative voltage of the battery pack (10).

[0117] BMS (30) can determine whether the target power amount is less than 50% of the reference power amount (S201). Hereinafter, 50% of the reference power amount is an example of the first threshold power amount.

[0118] If the target power amount is less than 50% of the reference power amount at step S201 (e.g., in S201), the BMS (30) can determine whether the link voltage is less than 90% of the pack voltage of the battery pack (10) (S202). Hereinafter, the range of 90% or more of the pack voltage is an example of a predetermined reference voltage range.

[0119] If the link voltage is less than 90% of the pack voltage of the battery pack (10) at step S202 (e.g., at S202), the BMS (30) can diagnose the status of the link capacitor (220) as an open fault (S203).

[0120] If the link voltage is greater than 90% of the pack voltage of the battery pack (10) at step S202 (NO at S202), the BMS (30) can diagnose the status of the link capacitor (221, see FIG. 3) as a load failure (S204). The load failure at step S204 may be due to the capacitance of the link capacitor (221, see FIG. 3) being less than the lower limit of the reference capacitance range, or a fault in the pack connection environment settings.

[0121] If the target power amount is more than 50% of the reference power amount at step S201 (No at S201), the BMS (30) can determine whether the target power amount is less than the reference power amount (S205).

[0122] If the target power is less than the reference power at step S205 (yes in S205), the BMS (30) can diagnose the status of the link capacitor (221, see FIG. 3) as a load failure (S204). If the target power is within the range of 50% to 100% of the reference power and the link voltage is 90% or more of the pack voltage of the battery pack (10), the BMS (30) can determine that the capacitance of the link capacitor (221, see FIG. 3) is less than the lower limit of the reference capacitance range, or that the pack connection environment is faulty. In addition, if the target power is within the range of 50% to 100% of the reference power and the link voltage is less than 90% of the pack voltage of the battery pack (10), the BMS (30) can determine that the capacitance of the link capacitor (221, see FIG. 3) is greater than the upper limit of the reference capacitance range, or that the pack connection environment is faulty.

[0123] If the target power amount is greater than or equal to the reference power amount at step S205 (No at S205), the BMS (30) can determine whether the target power amount is less than 200% of the reference power amount (S206). Hereinafter, 200% of the reference power amount is an example of the second threshold power amount.

[0124] At step S206, if the target power amount is less than 200% of the reference power amount (in S206, yes), the BMS (30) can diagnose the link capacitor (220) as a normal state in which precharge is normally performed (S207).

[0125] At step S206, if the target power is 200% or more of the reference power (No at S206), the BMS (30) can diagnose the status of the link capacitor (220) as a short circuit failure (S208).

[0126] Following step S203, following step S204, or following step S208, the BMS (30) can turn off the main relay (40) and the precharge relay (501) (S209).

[0127] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by a person having ordinary skill in the art to which the present invention pertains also fall within the scope of the present invention.

Claims

1. Battery pack; Two terminals connected to an external device including a link capacitor connected in parallel with the above battery pack; A precharge circuit including a precharge resistor and a precharge relay connected in series between one end of the battery pack and one of the two terminals; A main relay connected in parallel to the above precharge circuit; and A battery management system (BMS) that measures the pack voltage of the battery pack and the link voltage between the two terminals, controls the turn-on operation of the precharge relay and the main relay, calculates a reference power amount estimated to have been supplied to the precharge resistor during the operating time of the precharge circuit, calculates a target power amount supplied to the precharge resistor during the operating time of the precharge circuit, and diagnoses the state of the link capacitor as one of a plurality of fault states based on a comparison result of the target power amount and a threshold power amount according to the reference power amount and a comparison result of the pack voltage and the link voltage. A battery system including:

2. In paragraph 1, The above BMS is, Calculating the reference power amount based on the capacitance of the link capacitor, the resistance value of the precharge resistor, and the pack voltage during the driving time of the precharge circuit. Battery system.

3. In paragraph 1, Further comprising a current sensor connected to one end of the above precharge relay to measure the precharge current, The above BMS is, Calculating the target power amount based on the pack voltage and the precharge current flowing in the precharge relay during the driving time of the precharge circuit. Battery system.

4. In paragraph 1, The above multiple failure states are: It includes at least one of an open fault in which at least one of the two wires between the two terminals of the link capacitor is open, a short-circuit fault in which at least one of the two terminals of the link capacitor is grounded, and a load fault in which the capacitance value of the link capacitor is less than or greater than a predetermined reference capacitance range. If the status of the above link capacitor is diagnosed as one of the above multiple fault states, The above BMS is, Turning off the above precharge relay and the above main relay, Battery system.

5. In paragraph 4, If the target power amount is less than the first threshold power amount that is less than the reference power amount, and the link voltage is outside a predetermined reference voltage range based on the pack voltage, The above BMS is, Diagnosing the status of the above link capacitor as an open fault, Battery system.

6. In paragraph 4, If the target power amount is less than the first threshold power amount that is less than the reference power amount, and the link voltage is within a predetermined reference voltage range based on the pack voltage, The above BMS is, Diagnosing the status of the link capacitor as the load failure and diagnosing that the capacitance of the link capacitor is smaller than the lower limit of the reference capacitance range, Battery system.

7. In paragraph 4, If the target power amount is less than the reference power amount and is within the range of the first threshold power amount less than the reference power amount, The above BMS is, Diagnosing the status of the above link capacitor as the above load failure, Battery system.

8. In paragraph 7, If the above link voltage is within a predetermined reference voltage range based on the above pack voltage, The above BMS is, Diagnosing that the capacitance of the above link capacitor is less than the lower limit of the above reference capacitance range, Battery system.

9. In paragraph 7, If the above link voltage is outside the predetermined reference voltage range based on the above pack voltage, The above BMS is, Diagnosing that the capacitance of the above link capacitor is greater than the upper limit of the above reference capacitance range, Battery system.

10. A method for diagnosing the status of a link capacitor performed by a battery system, comprising: a battery pack; two terminals connected to an external device including a link capacitor connected in parallel with the battery pack; a precharge circuit including a precharge resistor and a precharge relay connected in series between one end of the battery pack and one of the two terminals; a main relay connected in parallel with the precharge circuit; and a battery management system (BMS) controlling a turn-on operation of the precharge relay and the main relay. A step of measuring the pack voltage of the above battery pack; A step of measuring a link between the two terminals; A step of calculating a reference power amount estimated to have been supplied to the precharge resistor during the driving time of the precharge circuit; A step of calculating the target power amount supplied to the precharge resistor during the driving time of the precharge circuit; and A step of diagnosing the state of the link capacitor as one of a plurality of failure states based on a comparison result between the threshold power amount according to the reference power amount and the target power amount and a comparison result between the pack voltage and the link voltage, method.

11. In paragraph 10, Further comprising a step of calculating the reference power amount based on the capacitance of the link capacitor, the resistance value of the precharge resistor, and the pack voltage during the driving time of the precharge circuit. method.

12. In paragraph 10, A step of measuring precharge current by connecting to one end of the above precharge relay; and Further comprising a step of calculating the target power amount based on the pack voltage and the precharge current flowing in the precharge relay during the driving time of the precharge circuit. method.

13. In paragraph 10, The above multiple failure states are: It includes at least one of an open fault in which at least one of the two wires between the two terminals of the link capacitor is open, a short-circuit fault in which at least one of the two terminals of the link capacitor is grounded, and a load fault in which the capacitance value of the link capacitor is less than or greater than a predetermined reference capacitance range. The step of diagnosing the status of the above link capacitor as one of multiple fault states is: If the state of the link capacitor is diagnosed as one of the plurality of fault states, a step of turning off the precharge relay and the main relay is included. method.

14. In paragraph 13, If the target power amount is less than a first threshold power amount that is less than the reference power amount, and the link voltage is outside a predetermined reference voltage range based on the pack voltage, the step of diagnosing the status of the link capacitor as an open fault is further included. method.

15. In paragraph 13, If the target power amount is less than the first threshold power amount that is less than the reference power amount, and the link voltage is within a predetermined reference voltage range based on the pack voltage, the state of the link capacitor is diagnosed as the load failure, and the capacitance of the link capacitor is diagnosed as being smaller than the lower limit of the reference capacitance range, further comprising the step of: method.

16. In paragraph 13, If the target power amount is less than the reference power amount and is within a range greater than or equal to the first threshold power amount less than the reference power amount, the step of diagnosing the status of the link capacitor as the load failure is further included. method.

17. In paragraph 16, If the link voltage is within a predetermined reference voltage range based on the pack voltage, the method further includes a step of diagnosing that the capacitance of the link capacitor is smaller than the lower limit of the reference capacitance range. method.

18. In paragraph 16, If the link voltage is outside a predetermined reference voltage range based on the pack voltage, the method further includes a step of diagnosing that the capacitance of the link capacitor is greater than the upper limit of the reference capacitance range. method.

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