Method and device for detecting electrical leakage in a vehicle

Abstract

Vehicle comprising: a battery pack (122); an electric motor (132); a contactor (110, 112) designed to electrically connect the battery pack (122) and the electric motor (132); control circuits (106, 108) for the contactor (110, 112) including a leakage voltage sensor (104); and at least one controller programmed to output a leakage resistance value (114, 116) associated with a terminal of the battery pack (122) based on a voltage of the battery pack (122) and a leakage voltage detected by the leakage voltage sensor (104) between the battery pack (122) and a vehicle chassis when the contactor (110, 112) is closed.

Description

FIELD OF THE INVENTIONThe present disclosure relates to detection systems for electrical leakage paths in vehicles.GENERAL STATE OF THE ARTConventional electric vehicles may be equipped with a high voltage traction battery for use as a primary power source and an auxiliary battery for use in powering various electrical components. The high voltage traction battery is typically insulated from the vehicle chassis. However, it is possible that a short circuit occurs between the traction battery and the vehicle body.Some previous work to detect such resistance paths has intentionally involved providing a return path such that current flows through the resistance path into the vehicle chassis and back to the traction battery.WO 2013 / 098 876 A1 discloses an electrical leak detector for detecting an electrical leak location in an electric vehicle, which is connected to an external power line for supplying power from the outside to the battery.SUMMARY OF THE INVENTIONA vehicle includes a battery pack, an electric motor, and a contactor configured to electrically connect the battery pack and the motor. The vehicle also includes control circuits for the contactor, including a leakage voltage detection sensor, and at least one controller programmed to output a leakage resistance associated with a terminal of the battery pack based on a voltage of the battery pack and a leakage voltage detected by the sensor between the battery pack and a vehicle chassis when the contactor is closed.A leakage path detection circuit includes a first circuit configured to detect a battery voltage of a traction battery in response to closing a contactor circuit configured to electrically connect the battery and a motor. The first circuit includes an input terminal electrically connected to a first terminal of the battery and a ground connected output terminal electrically connected to a second terminal of the battery having a polarity opposite to that of the first terminal. The leakage path detection circuit also includes a second circuit configured to detect a leakage voltage associated with the battery in response to closing the contactor circuit. The second circuit includes an input terminal electrically connected to a contactor of the contactor circuit and an output terminal connected to ground. The leakage path detection circuit further includes at least one controller configured to output a leakage resistance value based on the battery voltage and the leakage voltage.A method for detecting battery leakage in a vehicle includes, responsive to closing a contactor configured to electrically connect a traction battery to a motor, outputting a resistance value of a leakage path between the battery and a vehicle chassis based on a leakage current flowing through the contactor and to the chassis.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a schematic circuit diagram of a leakage path current detection circuit that measures a battery pack voltage and a positive leakage voltage; FIG. 2 is a schematic circuit diagram of a leakage path current detection circuit that measures a battery pack voltage and a negative leakage voltage; FIG. 3 is a schematic circuit diagram of a leakage path current detection circuit that measures the positive leakage voltage and the negative leakage voltage; and FIG. 4 is a flow chart illustrating an example method for estimating leakage resistance.DETAILED DESCRIPTIONEmbodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and that other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As those of ordinary skill in the art will understand, various features illustrated and described with reference to each of the figures may be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of illustrated features provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations.The embodiments of the present disclosure generally provide multiple circuits or other electrical devices. It is intended that all references to the circuits and other electrical devices and the functionality provided by each of them are not limited to including only that illustrated and described herein. Although particular identifiers may be associated with the various circuits or other electrical devices disclosed, such identifiers are not intended to limit the scope of operation for the circuits and the other electrical devices. Such circuits and other electrical devices may be combined with one another and / or separated in any manner based on the particular type of electrical implementation desired. It will be appreciated that any circuit or other electrical device disclosed herein may include any number of microprocessors, integrated circuits, memory devices (e.g., flash, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (PROM (EEPROM), or other suitable variants thereof), and software that cooperate with one another to perform the operation(s) disclosed herein. In addition, any one or more of the electrical devices may be configured to execute a computer program embodied in a non-transitory computer readable medium programmed to perform any number of the functions as disclosed.A hybrid vehicle may include a high voltage system having a traction battery pack. The traction battery pack is in communication with an electrical load (e.g., an electric motor) via high voltage contactors. For example, at least two contactors are provided that are installed at both ends (e.g., terminals) of the traction battery pack. The positive contactor connects to a negative end of the battery pack while a negative contactor connects to a positive end of the battery pack. When the vehicle is not being used, the at least two contactors may be open and disconnect the battery system from the electrical load. When the vehicle is used, the contactors are closed and the battery system is in communication with the electrical load.This disclosure proposes a method for estimating a leak measurement (e.g., electrical isolation) between the traction battery pack and a vehicle chassis. The leak measurement method may use a monitoring circuit at the contactors and a voltage measurement algorithm. This method proposes several embodiments, as shown in the figures below, to estimate the leakage resistance value with the contactors. When using the already present monitoring circuit on the contactors, the method may not require additional circuitry (e.g., switches). The method may protect the battery from discharging when the vehicle is not being used because all contactors are open and no additional circuitry is needed, thus the leak measurement circuit is disconnected from the battery system.FIG. 1 is a schematic circuit diagram 100 of a leakage path current detection sensor that measures a battery pack voltage and a positive leakage voltage of a high voltage system according to an embodiment. The circuit diagram 100 illustrates the high voltage system, which may include a battery pack voltage sensor 102, a leakage voltage sensor 104, a positive contactor driver 106, a negative contactor driver 108, a positive contactor 110, a negative contactor 112, a positive leakage resistance estimation model 116, and a negative leakage resistance estimation model 114. A vehicle computer system (not shown) may manage the high voltage system of the hybrid vehicle. The vehicle computer system may control the contactor drivers 106, 108 and receive data from the battery pack voltage sensor 102 and the leakage path current detection sensor 104. The vehicle computer system may include one or more control modules. The one or more control modules may include a battery energy control module (BECM). The BECM may receive data from the leakage path current detection sensor 104 via an analog-to-digital converter 118. The BECM may receive data from the battery pack voltage sensor 102 via an analog-to-digital converter 120.The BECM may measure the battery pack voltage V P122 via the voltage sensor 102 and a positive leakage voltage V LP124 via the leakage voltage sensor 104. The positive leakage voltage V LP124 is measured by the leakage voltage sensor 104. The positive leakage voltage V LP124 is the voltage drop across the resistor 128a. The leakage voltage sensor 104 has a ground connection via a capacitor 130a.If the main contactors 110, 112 are closed and the battery is requested to supply the electric motor 132 to drive the hybrid vehicle, the system may estimate the leakage resistance value (i.e., the leakage level) of the high voltage system based on a current flowing through the battery 122, the leakage detection resistors R 1126 a, 126 b, and R 2128 a, 128 b, the positive leakage resistance value R LP116 and the negative leakage resistance value R LN114. The estimate of the leakage resistance value may be based on the following equation: where V P( k) 122 is the battery pack voltage at a kth sample time, V LP( k) 124 is the positive side leakage voltage at the kth sample time, R LN114 is the leakage resistance value to be estimated at the negative side, and R LP116 is the positive side leakage resistance value to be estimated. The system may include the leak detection resistors R 1126 a, 126b having the same resistance value. The leak detection resistors R 2128 a, 128 bmay have the same resistance value. In one embodiment, the resistors R 1126 a, 126 bmay have a larger resistance than the resistors R 2128 a, 128 b. The equation may be used to calculate the leakage resistance values R LN and R LP. The system may monitor whether a leakage current occurs based on the calculation in equation (1).There are several methods to calculate the leakage resistance values R LN and R LP based on the equation (1). For example, the system may implement a least mean square (LMS) filter based on equation (1) to determine the leakage resistance value. The LMS filter may define the parameter matrix A 1, the input matrix X 1 and the output matrix Y 1 as shown in the following equations: wherein A 1 is a matrix value comprising a 11, which represents a fraction of the leakage resistance R LN114 on the negative side, and a 12, which represents a fraction of the leakage resistance R LP116 on the positive side, and wherein X 1 is a matrix, the component values having known or measured values include (e.g., V P, V LP, R 1 and R 2). The input matrix X 1 is based on the LMS process framework, and where Y 1 is a matrix that includes component values with known or measured values (e.g., V P, V LP, R 1 and R 2). The output matrix Y 1 is based on the LMS process frame.In response to the following variables calculated in Equations 2, 3, and 4, the method may then reconfigure the equations based on the following equation:Based on Equation 5, using LMS, A 1 is estimated in the following equation: wherein the leakage resistance for the negative and positive sides of the high voltage system is based on the following equation:FIG. 2 is a schematic circuit diagram 200 of a leakage path current detection sensor that measures the battery pack voltage and a negative leakage voltage of the high voltage system according to an embodiment. Circuit diagram 200 illustrates the high voltage system that may include battery pack voltage sensor 102, leakage voltage sensor 105, positive contactor driver 106, negative contactor driver 108, positive contactor 110, negative contactor 112, negative leakage resistance estimation model 114, and positive leakage resistance estimation model 116. As noted above, the BECM may be in communication with and / or control the high voltage system. The BECM may receive data from the battery pack voltage sensor 102 via the analog-to-digital converter 120. The BECM may receive data from the leak path current detection sensor 105 via an analog-to-digital converter 119.The BECM may measure the battery pack voltage V P122 via the voltage sensor 102 and the negative leakage voltage V LN134 via the leakage voltage sensor 105. The negative leakage voltage V LN134 is measured by the leakage voltage sensor 105. The negative leakage voltage V LN134 is the voltage drop across the resistor 128b. The leakage voltage sensor 105 has a ground connection via a capacitor 130 b.If the main contactors 110, 112 are closed and the battery is requested to supply the electric motor 132 to drive the hybrid vehicle, the system may estimate the leakage resistance of the high voltage system based on a current flowing through the battery 122, the leakage detection resistors R 1126 a, 126 b, and R 2 128 a, 128 b, the positive leakage resistance R LP116 and the negative leakage resistance R LN114. The estimate of the leakage resistance value may be based on the following equation: where V P( k) 122 is the battery pack voltage at a kth sample time, V LN( k) 134 is the leakage voltage on the negative side at the kth sample time, R LN114 is the leakage resistance value on the negative side, R LP116 is the leakage resistance value on the positive side. The leak detection resistors are the resistors R 1126 a, 126b and the resistor R 2128 a, 128b. The equation may be used to calculate the leakage resistance values R LN and R LP. The system may monitor whether a leakage current occurs based on the calculation in equation (8).As mentioned above, several methods may be used to calculate the leakage resistance value based on equation (8), including, but not limited to, the LMS filter. The LMS filter may define the parameter matrix A 2, the input matrix X 2 and the output matrix Y 2 as shown in the following equations: wherein A 2 is a matrix value comprising a 21, which represents a fraction of the leakage resistance R LP116 on the positive side, and a 22, which represents a fraction of the leakage resistance R LN114 on the negative side, and wherein X 2 is a matrix, the component values having known or measured values include (e.g., V P, V LN, R 1 and R 2). The input matrix X 2 is based on the LMS process framework, where Y 2 is a matrix comprising component values with known or measured values (e.g., V P, V LN, R 1 and R 2). The output matrix Y 2 is based on the LMS process frame.Based on the following variables calculated in equations 9, 10, and 11, the method may define the output matrix based on the following equation:In response to Equation 12, using least mean squares (LMS), A 2 is estimated in the following equation: wherein the leakage resistance for the negative and positive sides of the high voltage system is based on the following equation:FIG. 3 is a schematic circuit diagram of a leakage path current detection circuit that measures the positive leakage voltage and the negative leakage voltage of the high voltage system according to an embodiment. The circuit diagram 300 illustrates the high voltage system, which may include two leakage voltage sensors 104, 105, the positive contactor driver 106, the negative contactor driver 108, the positive contactor 110, the negative contactor 112, the negative leakage resistance 114, and the positive leakage resistance 116. As noted above, the BECM may be in communication with and / or control the high voltage system. The BECM may receive data from the two leakage path current detection sensors 104, 105 via the analog-to-digital converters 118, 119.The BECM may measure the positive leakage voltage V LP124 and the negative leakage voltage V LN134 via the leakage voltage sensors 104, 105. The positive leakage voltage V LP124 is measured by the leakage voltage sensor 104. The positive leakage voltage V LP124 is the voltage drop across the resistor 128a. The negative leakage voltage V LN134 is measured by the leakage voltage sensor 105. The negative leakage voltage V LN134 is the voltage drop across the resistor 128b. The leakage voltage sensors 104, 105 have a ground connection via the capacitors 130 a, 130 b.In FIG. 3, the BECM measures the negative leakage voltage V LN and the positive leakage voltage V LP. If the main contactors 110, 112 are closed and the battery is requested to supply the electric motor 132 to drive the hybrid vehicle, the system may estimate the leakage resistance value of the high voltage system based on a current flowing through the battery 122, the leakage detection resistors R 1126 a, 126 b, and R 2128 a, 128 b, the positive leakage resistance value R LP116 and the negative leakage resistance value R LN114. The estimation of the leakage resistance value may be based on the following equation: where V LN134 is the leakage voltage on the negative side, V LP124 is the leakage voltage on the positive side, R LN114 is the leakage resistance value on the negative side, R LP116 is the leakage resistance value on the positive side, and the leakage detection resistances are R 1126 a, 126b, and R 2128 a, 128b. The equation may be used to calculate the leakage resistance values R LN and R LP. The system may monitor whether a leakage current occurs based on the calculation in equation (14). As stated above, the LMS filter is one of several methods for calculating the leakage resistance value based on the equation (14). The LMS filter may define the parameter matrix A 3, the input matrix X 3 and the output matrix Y 3 as shown in the following equations: wherein A 3 is a matrix value comprising a 31, which represents a fraction of the leakage resistance R LP116 on the positive side, and a 32, which represents a fraction of the leakage resistance R LN114 on the negative side, and wherein X 3 is a matrix, the component values having a measured value (e.g., V LP, V LN). The input matrix X 3 is based on the LMS process framework, where Y 3 is a matrix comprising component values with known or measured values (e.g., V LP, V LN, R 1 and R 2). The output matrix Y 3 is based on the LMS process frame.Based on the following variables calculated in equations 15, 16, and 17, the method may define the output matrix based on the following equation:In response to Equation 18, using LMS, A 3 is estimated in the following equation: wherein the leakage resistance for the negative and positive sides of the high voltage system is based on the following equation:The method and system for determining the leakage resistance value may be estimated in real time using one or more algorithms, such as a recursive least squares algorithm. For example, the recursive least squares algorithm may be used to estimate the leakage resistance in the circuitry shown in FIG. 3 based on the following equation:The recursive least squares algorithm may define the state of the output matrix as the following equation:The recursive least squares algorithm may define the state matrix as the following equation:The recursive least squares algorithm may define the output as the following equation:In response to equations 22, 23, and 24, the method may define equation 21 based on the following equation: where e(k) represents the output measurement noise. Applying the recursive least squares algorithm to equations (22)-(25), X k can be developed using the following equations: where the leakage resistance for the negative and positive sides of the high voltage system is based on the following equation:In the above recursive least squares algorithm, the initial values of P(k) and X(k) are P(0) and X(0), and the parameter R may be predetermined. The covariance of the output measurement noise is R=E(e(k) 2); the expected value of the initial state X(0) is X(O)=E(X), and the covariance of the initial state estimation value is P(0)=E[(X-X(0))(X-X(0)) T]. Normally, P(0) is related to the prior knowledge about X. If there is no knowledge about X, let P(0) = ∞×I; if there is prior knowledge about X, let P(0)=0.The estimated leakage resistance value may be very noisy, thus a moving average filter is proposed to remove the noise from the calculation of the leakage resistance value. In the filter, the parameter a may be [0, 1] as shown in the following equations:The filters in Equations (30) and (31) are low pass filters that can improve the calculation of the estimated leakage resistance estimation value for R LP and R LN by eliminating noise.FIG. 4 is a flow diagram illustrating an example method 400 for estimating the leakage resistance value in real time, according to an embodiment. The vehicle computer system may include one or more applications executing on hardware in the system. The vehicle computer system may include a processor (e.g., a BECM) in communication with the voltage system. The one or more applications executing on the processor may include instructions to monitor leak detection of the battery pack. The method 400 may be implemented using software code included in the vehicle computer system and / or the voltage system. In other embodiments, the method 400 may be implemented in other vehicle controllers (e.g., processors), divided among multiple vehicle controllers, and / or combinations thereof.Referring again to FIG. 4, the vehicle battery control system and its components illustrated in FIGS. 1, 2, and 3 will be referred to throughout the discussion of method 400 to facilitate understanding of various aspects of the present disclosure. The method 400 of monitoring leakage from the traction battery system may be implemented by: a computer algorithm, machine executable code, or software instructions programmed into one or more suitable programmable logic device(s) of the vehicle and / or charging station, such as the vehicle control module, the BECM, another controller in communication with the vehicle computer system, or a combination thereof. Although the various operations shown in the flowchart 400 appear to take place in a chronological sequence, at least some of the operations may take place in a different order, and some operations may be performed simultaneously or not at all.At operation 202, during a key-on event that allows the vehicle to be powered on, the vehicle computing system may begin powering up the one or more modules. Powering up the one or more modules may cause variables related to the high voltage system to be initialized before one or more algorithms used to monitor the battery are activated.In operation 204, the method may determine whether both contactors on the high voltage battery are closed. If the contactors are closed, the method may measure the battery pack voltage across the battery pack voltage at operation 206. If the contactors are open, the system may be in a wait state for a predefined amount of time before checking whether the high voltage battery is activated in operation 218.At operation 208, in response to the contactors being closed, the method may measure the leakage voltage via the leakage voltage sensor. The method may update the leakage resistance value on the positive side of the battery and / or on the negative side in operation 210. For example, the arrangement shown in Figure 1 and described in equations (2)-(6) allows the system to monitor the leakage resistance values using equation (7).In operation 212, the method may filter the positive and negative leakage resistance values using a filter and / or a moving average filter (e.g., a Kalman filter). For example, a low pass filter similar to equation (30) or (31) can achieve an improved overall leakage resistance by eliminating the noise from the system.In operation 214, the method may update the total leakage resistance value based on the measurement and calculation of the battery voltage of the vehicle computer system, the one or more leakage voltage sensors, or a combination thereof. For example, the total leakage resistance value R ALL may be calculated by connecting the estimated negative leakage resistance value R LN and the estimated positive leakage resistance value R LP in parallel (i.e., R ALL= R LN* R LP / ( R LN+ R LP)).In operation 216, the method may determine whether the total leakage resistance value is less than a predefined threshold. The threshold may be determined by a hazard analysis performed in the development of the battery control system. If the total leakage is less than the threshold, the vehicle computer system may report leakage and take some remedial action. For example, the vehicle computer system may activate a message (e.g., send a message to turn on a dashboard light) to inform the customer of the anomaly. In another example, if the total leakage is less than the predefined threshold, the vehicle computer system may power down the vehicle and prevent use of the vehicle. If the total leakage is greater than the threshold, the method may proceed to monitoring the system.If the method detects a key-off event in operation 222, the method may end the one or more algorithms used to manage the battery pack and / or the one or more battery cells. The vehicle computer system may have a key-off mode to allow the method in operation 224 to store one or more parameters in non-volatile memory such that these parameters may be used by the system for the next key-on event.While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The terms used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. The features of various embodiments may be combined as described above to form further embodiments of the invention that may not be explicitly described or illustrated. Although various embodiments may have been described as providing advantages over other embodiments or implementations of the prior art with respect to one or more desired characteristics, those of ordinary skill in the art will understand that compromises may be made with respect to one or more features or characteristics to achieve desired characteristics of the overall system, depending on the specific application and implementation. These features may include, but are not limited to, cost, strength, longevity, life cost, heelability, appearance, assembly, size, serviceability, weight, machability, assemblyability, etc. As such, embodiments described as less desirable than other embodiments or implementations in terms of one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.It is further described: A. Vehicle comprising:a battery pack;an electric motor;a contactor configured to electrically connect the set and the motor; control circuitry for the contactor including a leakage voltage detection sensor; andat least one controller programmed to output a leakage resistance associated with a terminal of the battery pack based on a voltage of the battery pack and a leakage voltage detected by the sensor when the contactor is closed.B. The vehicle of A, wherein the at least one controller is further programmed to issue an alert message if the leakage resistance value is less than a threshold value. C. The vehicle of A, wherein the sensor is associated with a positive terminal of the battery pack. D. The vehicle of A, wherein the sensor is associated with a negative terminal of the battery pack. E. vehicle according to A, wherein the at least one controller is further programmed to filter data from the leakage voltage detection sensor to reduce noise associated therewith. F. Leakage Path Detection Circuit Comprising:a first circuit configured to detect a battery voltage of a traction battery in response to closing of a contactor circuit,which is configured to electrically connect the battery and a motor, wherein the first circuit includes:an input terminal electrically connected to a first terminal of the battery; andan output terminal connected to ground, electrically connected to a second terminal of the battery, having a polarity opposite to that of the first terminal;a second circuit configured to detect a leakage voltage associated with the battery in response to closing the contactor circuit,wherein the second circuit includes:an input terminal electrically connected to a contactor of the contactor circuit, andan output terminal connected to ground; andat least one controller configured to output a leakage resistance value based on the battery voltage and the leakage voltage.The G. leakage path detection circuit of F, wherein the second circuit is associated with the first terminal of the battery and wherein the first terminal has a positive polarity. H. The leakage path detection circuit of F, wherein the second circuit is associated with the first terminal of the battery and wherein the first terminal has a negative polarity. I. The leakage path detection circuit of F, wherein the at least one controller is further configured to apply a filter to the leakage voltage and the battery voltage to reduce noise associated therewith. J. The leakage path detection circuit of F, wherein the at least one controller is further programmed to issue an alert message if the leakage resistance value is less than a threshold value. K. A method for detecting battery leakage in a vehicle, comprising:responsive to closing a contactor configured to electrically connect a traction battery to a motor, outputting a resistance value of a leakage path between the battery and a vehicle chassis based on a leakage current flowing through the contactor and to the chassis.L. The method of K, wherein the leakage path is defined between a positive terminal of the battery and the chassis. M. The method of K, wherein the leakage path is defined between a negative terminal of the battery and the chassis. The method of K, wherein the leakage path is defined between a positive terminal of the battery and the chassis and a negative terminal of the battery and the chassis. O. The method of K, further comprising issuing an alert message in response to the resistance value being less than a predefined threshold.

Claims

A vehicle comprising: a battery pack (122); an electric motor (132); a contactor (110, 112) configured to electrically connect the battery pack (122) and the electric motor (132); control circuitry (106, 108) for the contactor (110, 112) including a leakage voltage sensor (104); and at least one controller programmed to output a leakage resistance value (114, 116) associated with a terminal of the battery pack (122) based on a voltage of the battery pack (122) and a leakage voltage detected between the battery pack (122) and a vehicle chassis by the leakage voltage sensor (104) when the contactor (110, 112) is closed.The vehicle of claim 1, wherein the at least one controller is further programmed to issue an alert message if the leakage resistance value (114, 116) is less than a threshold value.The vehicle of claim 1, wherein the leakage voltage sensor (104) is associated with a positive terminal of the battery pack (122).The vehicle of claim 1, wherein the leakage voltage sensor (104) is associated with a negative terminal of the battery pack (122).The vehicle of claim 1, wherein the at least one controller is further programmed to filter data from the leakage voltage sensor (104) to reduce noise associated therewith.

Images