Fault diagnosis method for contactor, and battery system providing the same

Abstract

The present invention relates to a method for diagnosing a contactor fault and a battery system providing the method. The battery system of the present invention comprises a battery, a link capacitor connected in parallel with the battery, a precharge resistor and a precharge contactor connected in series between the battery and an external device, a main contactor connected in parallel with the precharge resistor and the precharge contactor, and a Battery Management System (BMS) that controls the switching operation of the precharge contactor and the main contactor and diagnoses a fault in the main contactor based on a battery voltage, which is a voltage across the battery measured in synchronization with the turn-on time of the main contactor, a link voltage, which is a voltage across the link capacitor, and a battery current, which is a current flowing through the battery.

Description

Technology Field

[0001] The present invention relates to a contactor fault diagnosis method for diagnosing a stuck-open fault in which the contactor is fixed in an open state, and a battery system providing the method. Background Technology

[0002] In a vehicle driven by battery power, such as an electric vehicle (EV), a battery system connecting an external device to the battery may include a battery, a contactor (or relay) section, a current sensor, a Battery Management System (BMS) that controls the battery and the contactor section, and a smoothing link capacitor (DC Link-Cap, X-cap) connected in parallel with the battery.

[0003] The contactor section may include a precharge contactor, a precharge resistor, and a main contactor. First, when the precharge contactor is turned on, the link capacitor (X-cap) is charged while the surge current is limited by the precharge resistor. Subsequently, when the main contactor is turned on and the precharge contactor is turned off, charging or discharging can be performed between the battery and an external device (motor, charger, etc.).

[0004] During the discharge process of the battery, charge is first accumulated in the link capacitor (X-cap), thereby smoothing the power from the battery, and the smoothed power is supplied to an external device (motor, etc.). As a result, the battery system can supply stable power to the external device (motor, etc.). Additionally, during the charging process of the battery, the link capacitor (X-cap) smooths the power from the external device (charger, etc.), and the smoothed power can be supplied to the battery.

[0005] Meanwhile, if the contactor fails, the electrical connection between the battery and the external device cannot be controlled normally. For example, examples of physical failures of the contactor include welding failures where the contactor is fixed in a closed state or stuck-open failures where the contactor is fixed in an open state.

[0006] Regarding the diagnosis of a stuck-open fault in a contactor, conventionally, a method was used in which the battery terminal voltage (Vb) and link voltage (Vl)(Vl) were measured during the contactor's ON operation, and the difference and error values ​​between the battery terminal voltage (Vb) and link voltage (Vl)(Vl) were compared.

[0007] However, in this case, there was a problem with misdiagnosing contactor failures when the vehicle side connected to the battery system used energy stored in the DC Link-Cap or when the debouncing time was prolonged. The problem to be solved

[0008] The present invention relates to a contactor fault diagnosis method capable of precisely diagnosing a stuck-open fault of a contactor, and a battery system providing the method. means of solving the problem

[0009] A battery system according to one feature of the present invention comprises a battery, a link capacitor connected in parallel with the battery, a precharge resistor and a precharge contactor connected in series between the battery and an external device, a main contactor connected in parallel with the precharge resistor and the precharge contactor, and a Battery Management System (BMS) that controls the turn-on operation of the precharge contactor and the main contactor, and diagnoses a fault of the main contactor based on a battery voltage, which is a voltage across the battery measured in synchronization with the turn-on time of the main contactor, a link voltage, which is a voltage across the link capacitor, and a battery current, which is a current flowing through the battery.

[0010] The above BMS can diagnose abnormal energy discharge of the link capacitor if the current value of the battery current does not correspond to zero within a predetermined error range.

[0011] The above BMS can diagnose the abnormal ON operation of the main contactor if the current value of the battery current is zero within a predetermined error range and the difference between the voltage value of the battery voltage and the voltage value of the link voltage is greater than or equal to a predetermined reference value.

[0012] The above BMS can diagnose the normal ON operation of the main contactor if the current value of the battery current is zero within a predetermined error range and the difference between the voltage value of the battery voltage and the voltage value of the link voltage is less than a predetermined reference value.

[0013] The above BMS can turn on the main contactor when the link capacitor is pre-charged with the power of the battery by turning on the pre-charge contactor, and diagnose a failure of the main contactor based on the battery voltage, the link voltage, and the battery current measured within a predetermined diagnosis time after the main contactor is turned on.

[0014] The above diagnostic time may correspond to the time from the time the main contactor turns on until the time the external device uses the energy stored in the link capacitor.

[0015] A method for diagnosing a fault in a contactor according to another feature of the present invention is a method for diagnosing a fault in a main contactor that electrically connects a battery and an external device by a Battery Management System (BMS), comprising: a step of turning on a precharge contactor connected in series with a precharge resistor between the battery and the external device; a step of turning on the main contactor when a link capacitor connected in parallel to the battery is pre-charged with the power of the battery due to the turning operation of the precharge contactor; a step of determining whether a current value of the battery current measured in synchronization with the time of turning on the main contactor corresponds to zero within a predetermined error range; a step of determining whether, if the current value corresponds to zero as a result of the determination, the difference between the voltage value of the battery voltage, which is the voltage across the battery terminals, and the voltage value of the link voltage, which is the voltage across the link capacitor terminals, is less than a predetermined reference value; and a step of diagnosing an abnormal turning operation of the main contactor if, as a result of the determination, the difference value is greater than or equal to the reference value. The battery current is, It is the current flowing through the battery.

[0016] The fault diagnosis method of the above contactor may further include a step of diagnosing the abnormal energy discharge of the link capacitor if, after the step of determining whether the current value of the battery current corresponds to zero within a predetermined error range, the current value does not correspond to zero as a result of the determination.

[0017] The fault diagnosis method of the above contactor can diagnose the normal ON operation of the main contactor after the step of determining whether the difference between the voltage value of the battery voltage and the voltage value of the link voltage is less than a predetermined reference value, if the difference value is less than the reference value as a result of the determination.

[0018] The above diagnostic time may correspond to the time from the time the main contactor turns on until the time the external device uses the energy stored in the link capacitor. Effects of the invention

[0019] The present invention can reduce the cost of replacing normal contactors due to misdiagnosis by precisely diagnosing a stuck-open fault of a contactor, and can quickly detect the cause of the defect when a defect occurs in the battery system.

[0020] The present invention can diagnose a stuck-open fault of a contactor even in the charging and discharging modes of a battery. Brief explanation of the drawing

[0021] FIG. 1 is a drawing illustrating a battery system that performs fault diagnosis of a contactor according to one embodiment. FIG. 2 is a flowchart illustrating a fault diagnosis method for a contactor according to one embodiment. Specific details for implementing the invention

[0022] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the attached drawings. Identical or similar components are assigned identical or similar reference numerals, and redundant descriptions thereof will be omitted. The suffixes "module" and / or "part" for components used in the following description are assigned or used interchangeably solely for the ease of drafting the specification and do not have distinct meanings or roles in themselves. Furthermore, in describing the embodiments disclosed in this specification, if it is determined that a detailed description of related prior art could obscure the essence of the embodiments disclosed in this specification, such detailed description will be omitted. Additionally, the attached drawings are intended only to facilitate understanding of the embodiments disclosed in this specification; the technical concept disclosed in this specification is not limited by the attached drawings, and it should be understood that they include all modifications, equivalents, and substitutions that fall within the spirit and technical scope of the invention.

[0023] Terms including ordinal numbers, such as first, second, etc., may be used to describe various components, but said components are not limited by said terms. These terms are used solely for the purpose of distinguishing one component from another.

[0024] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0025] In this application, terms such as “comprising” or “having” are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0027] FIG. 1 is a drawing illustrating a battery system that performs fault diagnosis of a contactor according to one embodiment.

[0028] Referring to FIG. 1, the battery system (1) includes a battery (10), a current sensor (20), a first voltage sensor (30), a second voltage sensor (40), a contactor part (50), and a BMS (Battery Management System) (60).

[0029] In FIG. 1, a battery (10) is connected between two output terminals (OUT1, OUT2) of a battery system (1), a contactor part (50) is connected between the positive electrode of the battery system (1) and the first output terminal (OUT1), and a current sensor (20) is connected between the negative electrode of the battery system (1) and the second output terminal (OUT2). The configurations and the connection relationships between the configurations shown in FIG. 1 are examples, but the invention is not limited thereto.

[0030] The battery (10) may include a plurality of battery cells (Cell1-Celln) electrically connected in series and parallel. In some embodiments, the battery cells may be rechargeable secondary batteries.

[0031] The current sensor (20) is connected in series to the current path between the battery (10) and an external device. The current sensor (20) can measure the battery current flowing through the battery (10), i.e., the charging current and the discharging current, and transmit the measurement results to the BMS (60).

[0032] The first voltage sensor (30) can measure the voltage across the battery (10) (hereinafter, battery voltage (Vb)) and transmit the measurement result to the BMS (60). For example, the first voltage sensor (30) can measure the battery voltage (Vb) at a predetermined period and transmit the measurement result to the BMS (60).

[0033] The second voltage sensor (40) can measure the voltage across the link capacitor (X-cap) (hereinafter, link voltage (Vl)) and transmit the measurement result to the BMS (60). For example, the first voltage sensor (30) can measure the link voltage (Vl) at a predetermined period and transmit the measurement result to the BMS (60). As shown in FIG. 1, the link capacitor (X-cap) can be connected in parallel to the battery (10).

[0034] The contactor section (50) may include a precharge resistor (Rf), a precharge contactor (SW1), and a main contactor (SW2). In FIG. 1, a main contactor (SW2) connecting the positive electrode of the battery (10) to an external device is shown, but is not limited thereto, and the contactor section (50) may further include a negative electrode main contactor (not shown) connecting the negative electrode of the battery (10) to an external device.

[0035] The precharge resistor (Rf) and the precharge contactor (SW1) can be connected in series between the positive electrode of the battery (10) and an external device. The precharge contactor (SW1) can reduce the surge current that occurs when the main contactor (SW2) is connected to the external device, thereby preventing damage to the main contactor (SW2) and the battery (10).

[0036] The pre-charge contactor (SW1) can perform pre-charging. Specifically, when the pre-charge contactor (SW1) is turned on, the link capacitor (X-cap) can slowly accumulate charge by receiving a small current reduced by the pre-charge resistor (Rf). Subsequently, the main contactor (SW2) is turned on, and after a predetermined time has elapsed with the pre-charge contactor (SW1) and the main contactor (SW2) in the ON state, the pre-charge contactor (SW1) can be turned off. Then, when the main contactor (SW2) is connected to an external device, the surge current can be reduced.

[0037] The main contactor (SW2) can be connected in series between the positive electrode of the battery (10) and an external device. Referring to FIG. 1, the main contactor (SW2) can be connected in parallel with a precharge resistor (Rf) and a precharge contactor (SW1). When the main contactor (SW2) is turned on, the battery (10) and the external device are electrically connected, and charging or discharging of the battery (10) can be performed.

[0038] The BMS (60) can control the charging or discharging of the battery (10) by controlling the switching operation of the precharge contactor (SW1) and the main contactor (SW2) included in the contactor section (50). According to one embodiment, the BMS (60) can diagnose a failure of the main contactor (SW2) based on the measurement results of the first voltage sensor (30) and the second voltage sensor (40).

[0039] For example, the BMS (60) can distinguish between the use of energy stored in the link capacitor (X-cap) of an external device (e.g., vehicle) connected to the battery system (1), abnormal ON operation of the main contactor (SW2), and normal ON operation of the main contactor (SW2).

[0040] According to one embodiment, the abnormal ON operation of the main contactor (SW2) may include a stuck open fault state in which the main contactor (SW2) is welded in an open state. A more detailed explanation is provided below in FIG. 2.

[0042] FIG. 2 is a flowchart illustrating a fault diagnosis method for a contactor according to one embodiment.

[0043] Hereinafter, with reference to FIGS. 1 and FIGS. 2, a method for diagnosing a fault in a contactor and a battery system providing the method will be described.

[0044] First, the BMS (60) controls the switching operation of the precharge contactor (SW1) to perform pre-charge logic (S100).

[0045] The BMS (60) can turn on the precharge contactor (SW1) by generating a first control signal (SC[1]) of the on level. The precharge contactor (SW1) can be connected in series with a precharge resistor (Rf) between the battery (10) and an external device.

[0046] For example, the first control signal (SC[1]) at the on level may be a signal that controls a driving power source (not shown) to generate a driving voltage supplied to the precharge contactor (SW1). When the driving power source (not shown) supplies a driving voltage to the precharge contactor (SW1) according to the first control signal (SC[1]) at the on level, the precharge contactor (SW1) can perform a turn-on operation.

[0047] Referring to FIG. 1, in a discharge mode in which power discharged from a battery (10) is supplied to an external device (e.g., a vehicle), when the pre-charge contactor (SW1) is turned on, the link capacitor (X-cap) can be pre-charged by receiving a small current reduced by the pre-charge resistor (Rf) from the battery (10). After a predetermined time has elapsed, the voltage value of the terminal voltage of the link capacitor (X-cap) (hereinafter, link voltage (Vl)) may be the same as the voltage value of the terminal voltage of the battery (10) (hereinafter, battery voltage (Vb)) within a predetermined error range.

[0048] Next, the BMS (60) generates a second control signal (SC[2]) of the ON level to control the main contactor (SW2) to turn on (S200).

[0049] The main contactor (SW2) can be turned on by generating a second control signal (SC[2]) of the ON level. The main contactor (SW2) can be connected in parallel with the precharge resistor (Rf) and the precharge contactor (SW1). Additionally, the main contactor (SW2) can electrically connect or disconnect the battery (10) and the external device through a switching operation.

[0050] For example, the second control signal (SC[2]) at the on level may be a signal that controls a driving power source (not shown) to generate a driving voltage supplied to the main contactor (SW2). When the driving power source (not shown) supplies a driving voltage to the main contactor (SW2) according to the second control signal (SC[2]) at the on level, the main contactor (SW2) can perform a turn-on operation.

[0051] According to one embodiment, after the link capacitor (X-cap) is pre-charged with the power of the battery (10) by the ON operation of the pre-charge contactor (SW1), the BMS (60) can control the main contactor (SW2) to turn on. That is, after sufficient charge is accumulated in the link capacitor (X-cap) and the voltage value of the link voltage (Vl) approaches the voltage value of the battery voltage (Vb), the BMS (60) can control the main contactor (SW2) to turn on. Then, the BMS (60) can control the pre-charge contactor (SW1) to turn off after a predetermined time has elapsed after turning on the main contactor (SW2).

[0052] For example, even if the precharge contactor (SW1) is turned off, if the main contactor (SW2) is turned on normally, the voltage value of the link voltage (Vl) can be maintained close to the voltage value of the battery voltage (Vb). However, if the main contactor (SW2) is turned on abnormally, an external device (e.g., a vehicle motor) uses the power stored in the link capacitor (X-cap) in a situation where power is not supplied normally from the battery (10) through the main contactor (SW2). Then, the voltage value of the link voltage (Vl) can become smaller than the voltage value of the battery voltage (Vb).

[0053] Next, the BMS (60) determines whether the current value of the battery current corresponds to zero within a predetermined error range (S300).

[0054] The BMS (60) can receive the battery voltage (Vb), link voltage (Vl), and battery current, respectively, measured within a predetermined diagnostic time after the main contactor (SW2) is turned on, from the first voltage sensor (30), the second voltage sensor (40), and the current sensor (20). The diagnostic time may be a time corresponding to the time from when the main contactor (SW2) is turned on until when an external device uses the energy stored in the link capacitor (X-cap). For example, the diagnostic time may be a time corresponding to 100ms or less.

[0055] According to one embodiment, before an external device (e.g., a vehicle) fully uses the power of the battery (10) smoothed through the link capacitor (X-cap), the BMS (60) can perform a fault diagnosis of the main contactor (SW2).

[0056] According to another embodiment, during the discharge of the battery (10) in which an external device (e.g., a vehicle) fully uses the power of the battery (10) smoothed through the link capacitor (X-cap), the BMS (60) can perform a fault diagnosis of the main contactor (SW2). According to yet another embodiment, during the charging of the battery (10) with the power of an external device (e.g., a charger), the BMS (60) can perform a fault diagnosis of the main contactor (SW2). For example, when the main contactor (SW2) is normally turned on and the battery (10) is in a discharged state or the battery (10) is in a charging state, the voltage value of the battery voltage (Vb) and the voltage value of the link voltage (Vl) may be the same within a predetermined error range. The following description, together with FIG. 1, is based on the premise that the BMS (60) diagnoses a fault in the contactor (SW2) before the external device (e.g., a vehicle) begins to use the power of the battery (10) smoothed through the link capacitor (X-cap).

[0057] As the first step of diagnosing a fault in the main contactor (SW2), the BMS (60) can determine whether the current value of the battery current measured within the diagnosis time corresponds to zero within a predetermined error range.

[0058] Next, if the current value of the battery current does not correspond to zero (S300, No), the BMS (60) diagnoses the abnormal energy discharge of the link capacitor (X-cap) (S400).

[0059] In the first abnormal condition, when the main contactor (SW2) is turned on, a voltage difference occurs between the battery (10) and the link capacitor (X-cap), causing current to flow in the battery (10) (e.g., current value ≠ 0A). At this time, the first abnormal condition may include a state in which (i) the voltage value of the battery voltage and the voltage value of the link voltage are different, and (ii) the main contactor (SW2) performs a normal turn-on operation.

[0060] For example, abnormal energy discharge of the link capacitor (X-cap) may include cases where an external device (e.g., a vehicle) uses the energy stored in the link capacitor (X-cap) at an abnormal time or through an abnormal path. That is, abnormal energy discharge of the link capacitor (X-cap) may refer to an abnormal energy discharge caused by the vehicle side rather than the battery system (1) side. According to one embodiment, the BMS (60) can prevent misdiagnosing the state resulting from the abnormal energy discharge of the link capacitor (X-cap) as a state resulting from a failure of the main contactor (SW2).

[0061] Next, if the current value of the battery current corresponds to zero (S300, Yes), the BMS (60) determines whether the absolute value of the difference between the voltage value of the battery voltage (Vb) and the voltage value of the link voltage (Vl) (Vb - Vl) is less than a predetermined reference value (S500).

[0062] Next, if the difference value of the judgment result is greater than or equal to the reference value (S500, No), the BMS (60) diagnoses the abnormal ON operation of the main contactor (SW2) (S600).

[0063] The second abnormal condition is a condition in which the main contactor (SW2) fails to perform a normal ON operation, so the battery system (1) and the external device are electrically incompletely connected or cannot be connected. That is, the second abnormal condition may include (i) a condition in which the link capacitor (X-cap) is not charged normally, so the voltage value of the battery voltage and the voltage value of the link voltage are different, and (ii) a condition in which the battery system (1) and the external device are not connected normally, so the battery current does not flow (e.g., current value ≈ 0A).

[0064] For example, in the case of a stuck open fault where the main contactor (SW2) is fixed in an open state (welded), the BMS (60) generates a second control signal (SC[2]) of the ON level, and even if a driving power supply (not shown) applies a driving voltage to the main contactor (SW2) according to the second control signal (SC[2]), the main contactor (SW2) may not be able to perform a normal ON operation (close).

[0065] Next, if the difference value of the judgment result is less than the reference value (S500, Yes), the BMS (60) diagnoses the normal ON operation of the main contactor (SW2) (S700).

[0066] In a normal condition, when the main contactor (SW2) is turned on, no voltage difference occurs between the battery (10) and the link capacitor (X-cap), so the battery current may not flow. That is, the current value of the battery current can correspond to zero within a predetermined error range. At this time, the normal condition may include (i) a state in which the voltage value of the battery voltage and the voltage value of the link voltage are nearly identical, and (ii) a state in which the main contactor (SW2) performs a normal turn-on operation.

[0067] Although embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modified and improved forms by those skilled in the art to which the present invention pertains also fall within the scope of the present invention.

Claims

Claim 1 The invention includes a battery, a link capacitor connected in parallel with an external device, a precharge resistor and a precharge contactor connected in series between the battery and the external device, a main contactor connected in parallel with the precharge resistor and the precharge contactor, and a Battery Management System (BMS) that controls the turn-on operation of the precharge contactor and the main contactor, and diagnoses a fault of the main contactor based on a battery voltage, which is the voltage across the battery measured in synchronization with the turn-on time of the main contactor, a link voltage, which is the voltage across the link capacitor, and a battery current, which is the current flowing through the battery. The BMS diagnoses an abnormal turn-on operation of the main contactor if the current value of the battery current is zero within a predetermined error range and the difference between the voltage value of the battery voltage and the voltage value of the link voltage is greater than or equal to a predetermined reference value. When the link capacitor is pre-charged by the power of the battery by turning on the precharge contactor, the main contactor is turned on, and the main A battery system that diagnoses a fault in the main contactor based on the battery voltage, the link voltage, and the battery current measured within a predetermined diagnostic time after the contactor is turned on, wherein the diagnostic time corresponds to the time from when the main contactor is turned on until when the external device uses the energy stored in the link capacitor. Claim 2 A battery system according to claim 1, wherein the BMS diagnoses an abnormal energy discharge of the link capacitor if the current value of the battery current does not correspond to zero within a predetermined error range. Claim 3 delete Claim 4 A battery system according to claim 1, wherein the BMS diagnoses the normal ON operation of the main contactor when the current value of the battery current is zero within a predetermined error range and the difference between the voltage value of the battery voltage and the voltage value of the link voltage is less than a predetermined reference value. Claim 5 delete Claim 6 delete Claim 7 A method for diagnosing a fault in a main contactor that electrically connects a battery and an external device by a Battery Management System (BMS), comprising: a step of turning on a precharge contactor connected in series with a precharge resistor between the battery and the external device; a step of turning on the main contactor when a link capacitor connected in parallel to the external device is pre-charged with the power of the battery due to the turning operation of the precharge contactor; a step of determining whether a current value of the battery current measured in synchronization with the time of turning on the main contactor corresponds to zero within a predetermined error range; a step of determining whether, if the current value corresponds to zero as a result of the determination, the difference between the voltage value of the battery voltage (voltage across the battery terminals) and the voltage value of the link voltage (voltage across the link capacitor terminals) is less than a predetermined reference value; and a step of diagnosing an abnormal turning operation of the main contactor if, as a result of the determination, the difference value is greater than or equal to the reference value, wherein the battery current is a current flowing through the battery, and the turning of the main contactor A method for diagnosing a fault in a contactor, wherein the battery voltage, the link voltage, and the battery current are measured within a diagnosis time from the time of on to the time when the external device uses the energy stored in the link capacitor. Claim 8 A method for diagnosing a fault in a contactor according to claim 7, further comprising, after the step of determining whether the current value of the battery current corresponds to zero within a predetermined error range, the step of diagnosing the abnormal energy discharge of the link capacitor if the current value does not correspond to zero as a result of the determination. Claim 9 A method for diagnosing a fault in a contactor according to claim 7, wherein, after the step of determining whether the difference between the voltage value of the battery voltage and the voltage value of the link voltage is less than a predetermined reference value, if the difference value is less than the reference value as a result of the determination, the main contactor is diagnosed as normal ON operation. Claim 10 delete

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