DE102016106776A1 - Vehicle high voltage system insulation test - Google Patents

Abstract

An insulation testing system for a vehicle includes a communication interface, a current sensor, multiple impedances, and a controller. The controller is programmed to electrically connect a selected one of the impedances between a traction battery of the vehicle and a low voltage subsystem of the vehicle. The connection creates a leakage path between the traction battery and the subsystem. The controller is further programmed to output a diagnostic status based on a current associated with the leakage path and a signal received via a communication interface indicative of an isolation fault between the battery and the subsystem.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of Application No. 14 / 264,342, filed April 29, 2014, which claims the benefit of US Provisional Application No. 61 / 872,709 filed on Aug. 31, 2013, the disclosures of which are hereby incorporated by reference in their entirety are.

FIELD OF THE INVENTION

The present application relates to testing the performance of hybrid and electric vehicle electrical components with respect to isolation between high and low voltage electrical systems.

GENERAL PRIOR ART

A high voltage traction battery can be used for hybrid and electric vehicle applications. Vehicles with a traction battery may include a battery management system (BMS) with a battery electronic control module (BECM) that monitors the insulation between the high voltage system and the vehicle's low voltage system. The BECM may provide a diagnostic indicator and / or shut down various systems or subsystems if isolation between the high and low voltage systems is compromised.

It may be advantageous to evaluate the performance of the isolation monitoring feature as early as possible in the development cycle of the BECM hardware and software. However, a suitable test environment may not be available until prototype battery packs or prototype vehicles are available. In addition, changes in hardware or software during vehicle development may impact isolation monitoring, and on battery pack and vehicle levels, with limited resource availability, immediate validation and immediate testing may be difficult.

BRIEF SUMMARY OF THE INVENTION

An insulation tester for a vehicle includes a communication interface, multiple impedances, and a controller. The controller is programmed to electrically connect a selected one of the impedances between a traction battery of the vehicle and a subsystem of the vehicle. The connection creates a leakage path between the traction battery and the subsystem. The controller is further programmed to output a diagnostic status based on a current associated with the leakage path and a signal from the communication interface.

A test system for a vehicle includes a current sensor, multiple impedances, a communication interface, and a controller. The controller is programmed to respond to isolation fault feedback from the communication interface. The controller is further programmed to connect a selected one of the impedances in series with the current sensor, a battery, and a subsystem of the vehicle to produce a leakage path bridging an isolation barrier between a high voltage bus of the vehicle and the subsystem.

A method of vehicle isolation testing by a controller includes electrically coupling a selected impedance between a traction battery and a subsystem of a vehicle. The method further includes the controller enabling the traction battery to energize the impedance via a high voltage interlock circuit that transmits a leakage current from the battery through a sensor and the impedance to the subsystem. In addition, the method includes the controller outputting a diagnostic status based on the leakage current and a signal received via a communications interface indicative of an isolation fault between the battery and the subsystem.

BRIEF DESCRIPTION OF THE DRAWINGS

1 FIG. 10 is a diagram of a representative vehicle having a traction battery and associated controller with an isolation monitor for monitoring isolation between a high voltage and a low voltage electrical system according to various embodiments of the disclosure; FIG.

2 FIG. 12 is a diagram of a representative traction battery pack including a controller and circuitry for monitoring isolation; FIG.

3 FIG. 12 is a diagram illustrating a representative embodiment of an isolation monitor tester with a leak bus connecting a high voltage cell string to a leak array and a leak target or sink; FIG. and

4 FIG. 10 is a diagram illustrating the operation of a power tool for evaluating an isolation monitor according to embodiments of the disclosure. FIG.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described herein. It should be understood, however, that the disclosed embodiments are merely examples and other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features may 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 how to use the present invention differently. As one of ordinary skill in the art appreciates, various features illustrated and described with reference to any 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. However, various combinations and modifications of features consistent with the teachings of this disclosure may be desired for particular applications or implementations.

1 shows a representative vehicle with a traction battery. While the illustrated representative embodiment shows a plug-in hybrid electric vehicle, one of ordinary skill in the art will recognize that various embodiments may be utilized with other types of electric and hybrid vehicles having a traction battery. For example, systems and methods described herein may equally apply to an electric vehicle without an internal combustion engine or any other device using a traction battery or battery pack and associated high voltage electrical system that is electrically isolated from a low voltage electrical system, typically 12V or 24V.

A typical plug-in hybrid electric vehicle 2 may include one or more electrical machines acting as motors 4 can be operated mechanically with a hybrid transmission 6 are connected. In addition, the hybrid transmission 6 mechanically with an internal combustion engine 8th connected. The hybrid transmission 6 can also be mechanical with a drive shaft 10 connected mechanically with the wheels 12 connected is. The electric motors 4 may provide propulsion and deceleration capability when the internal combustion engine 8th is switched on or off. The electric motors 4 may also act as generators and provide fuel economy benefits by recovering energy that would normally be lost as heat in the friction braking system. The electric motors 4 can also reduce pollutant emissions since the hybrid electric vehicle 2 under certain conditions in an electric mode can be operated.

The traction battery pack 14 stores energy from the electric motors 4 can be used. A vehicle battery pack 14 typically provides a high voltage DC output. The battery pack or the traction battery 14 is electric with a power electronics module 16 connected. The power electronics module 16 is also electric with the electric motors 4 and provides the ability to bi-directionally transfer energy between the battery pack 14 and the electric motors 4 , For example, a typical traction battery 14 deliver a DC voltage while the electric motors 4 may require a three-phase AC power to function. The power electronics module 16 can convert the DC voltage into a three-phase AC current, as done by the electric motors 4 is needed. The power electronics module 16 can also change the battery voltage when driving the electric motors 4 to convert high voltage used, this conversion being accomplished by a variable voltage DC / DC converter, also referred to as a high voltage converter. In a regenerative mode, the power electronics module becomes 16 the three-phase AC current from the acting as generators electric motors 4 in through the battery pack 14 convert required DC voltage. In addition, in a regenerative mode, the power electronics module can supply the high voltage from the electric motors 4 convert to a battery voltage. A high voltage lock can be used on both the traction battery 14 as well as high voltage components on a high voltage bus. The high voltage components include the electric motors 4 , the power electronics module 16 , the battery pack 14 , the DC / DC converter module 18 and associated components operated by battery voltage or high voltage from the variable voltage converter. A high voltage interlock can be used to provide a current flow and a high voltage potential at the terminals of the battery pack 14 to block. To the current flow and the high voltage potential at the terminals of the battery pack 14 To enable both electrical and mechanical coupling of the high voltage interlock must be made. The high voltage interlock is often built into the battery and high voltage systems, but an external high voltage interlock bypass circuit may be used in conjunction with the high voltage interlock to allow the high voltage system to start up during testing and evaluation. In addition, the high voltage latch may be used to remove high voltage components from the traction battery pack 14 to disconnect or disable by electrically opening a connection therebetween.

In addition to providing power to the drive, the battery pack may 14 Provide power for other vehicle power systems. A typical system may be a DC / DC converter module 18 included the high voltage DC output of the battery pack 14 converts to a low voltage DC supply that is compatible with other vehicle loads. The low voltage DC supply has a positive terminal and a negative terminal, also referred to as ground. The negative terminal or the ground may be electrically connected to the vehicle chassis, in which the chassis, a negative terminal and ground, though electrically connected, may have different electrical characteristics. Other high voltage loads, such as compressors and electric heaters, can go directly to the high voltage bus from the battery pack 14 be connected. In a typical vehicle, the low voltage systems are electrically powered by a 12V battery 20 connected and electrically isolated from the high voltage electrical system. A fully electric vehicle may have a similar architecture, but without the internal combustion engine 8th ,

The battery pack 14 can by an external power source 26 be recharged. The external power source 26 can by electrically connecting to a charging port 24 AC or DC power to the vehicle 2 deliver. The loading port 24 can be any type of port that is configured to transfer power from the external power source 26 to the vehicle 2 , The loading port 24 can be electric with a power conversion module 22 be connected. The power conversion module can measure the power from the external power source 26 condition to the correct voltage and current levels to the battery pack 14 to deliver. For some applications, the external power source may be 26 be configured to supply the correct voltage and current levels to the battery pack 14 to deliver, and the power conversion module 22 may not be required. The functions of the power conversion module 22 may be in some applications in the external power source 26 are located.

Battery packs can be constructed from a variety of chemical formulations. Typical battery packs are lead acid, nickel metal hydride (NiMH) or lithium ion. 2 shows a typical battery pack 30 in a simple series configuration of N battery cells 32 , However, other battery packs may consist of a different number of individual battery cells connected in series or in parallel or some combination thereof. A typical system may have one or more controllers, such as a battery energy control module (BECM). 36 that the performance of the battery pack 30 monitor and control. The BECM 36 may have several battery pack level characteristics, such as packet current 38 , Package voltage 42 and package temperature 40 monitor. The BECM 36 may have nonvolatile memory so that data can be stored when the BECM is in an off state. Stored data may be available on the next key cycle.

The BECM 36 may include hardware and / or software to perform an isolation monitor function. The isolation monitor function monitors the electrical isolation of the high voltage electrical system from the vehicle's low voltage electrical system by detecting leakage currents. Upon detecting a leakage current exceeding a predetermined level, the isolation monitor may set a diagnostic code and / or perform various control functions to disable or disable one or more vehicle systems or subsystems to reduce continued exposure of vehicle components, maintenance techniques, or occupants to high voltage or to prevent. An isolation monitor performance tool according to embodiments of the present disclosure may be used to package hardware and associated software of the BECM 36 outside the vehicle so that an actual vehicle or traction battery pack is not needed.

In addition to the battery pack level characteristics, there may be battery cell level characteristics provided by the BECM 36 be measured and monitored, and proper operation, which is evaluated by an isolation monitor tool according to embodiments of the present disclosure. For example, the terminal voltage, current and temperature of each cell can be measured. A battery controller 36 can voltage monitoring circuits 34 for measuring the voltage at the terminals of each of the N cells 32 of the battery pack 30 contain. The voltage monitoring circuits 34 may be a network of resistors and capacitors configured to provide proper scaling and filtering of the cell voltage signals. The voltage monitoring circuits 34 Other components may also be used to properly sense the cell voltages and convert the voltages to digital values for use in a microprocessor contain. The voltage monitoring circuits 34 can also provide isolation so that high voltages can affect other circuitry within the BECM 36 do not damage. An isolation monitor performance tool according to embodiments of the present disclosure may be used to evaluate the operation of these components and circuitry, as well as the ability of the BECM isolation monitor software to detect leakage through one or more of these components and circuitry. The performance of the BECM isolation monitor software can be tested using an isolation monitor performance tool.

As generally in the representative embodiment of 3 can be an isolation monitor performance tool 100 a leak bus 106 , a leak array 102 and a leak target 104 contain. In one embodiment, the leak target is 104 in a battery simulator 98 Hardware interface layer integrated or built-in. During operation becomes a connection of a cell 108 within the high voltage cell chain 110 which simulates a multicellular high voltage vehicle traction battery under the control of the microprocessor 114 via one or more associated source switches 122 selectively with the leak bus 106 connected. The leak array 102 consists of a number of components 116 . 118 to provide a desired real or complex impedance. In the illustrated embodiment, an array of parallel resistors 116 and capacitors 118 each with other values of resistance or capacitance selectively through one or more level switches 112 via the microprocessor 114 switched to the desired real or complex impedance in the leakage circuit 106 or to provide the leak path. Other embodiments may also include inductive loads. The microprocessor 114 selectively activates a destination switch 120 to close the leak path or leakage circuit. In the illustrated embodiment, a target is a second voltage source that represents a typical vehicle low voltage system, which may be 12V, for example. Another destination may be grounded to simulate a vehicle chassis. Other embodiments may include multiple targets of varying voltage levels.

The isolation monitor performance tool 100 may include a wiring harness for connection to a battery controller. The voltage sources 108 inside the battery simulator 98 may be connected to the battery controller in the same manner as actual cells within the traction battery pack. The high voltage cell chain 110 can simulate the actual battery cells ( 2 . 32 ). For the battery controller, the high-voltage cell chain 110 appear as a normal battery pack when the switches are not activated. When various combinations of switches are activated, the battery controller may detect a leakage current using an internal isolation monitor.

The microprocessor 114 can use various combinations of switches to test the response of the insulation monitor being tested. The microprocessor 114 can determine the response of the insulation monitor to be tested via the external communication link 124 monitor. The isolation monitor to be tested can display one or more diagnostic codes indicating isolation detection via the external communication link 124 send. The microprocessor 114 can correlate the diagnostic code with the switch settings to determine if the isolation monitor has taken the correct action. The microprocessor may operate in a control loop mode in which various impedances are selectively coupled and decoupled based on time in which the correlation of the faults and impedances is manually performed. Alternatively, the microprocessor may operate on the basis of a feedback loop in which the microprocessor selectively couples and decouples impedances in response to signals received from the BECM. For example, the examiner 100 couple a very low impedance between the traction battery and the target (low voltage positive, negative, ground or chassis), after which the BECM will detect the isolation fault and signal the status of the fault via the communication interface (CAN or Ethernet). Based on the status signal from the BECM, the examiner may 100 decouple the impedance and select a second impedance to couple to test the sensitivity of the BECM isolation test. To improve performance, it is desirable to have a current sensor in the tester 100 either on the leak bus 106 or the leak destination bus 104 to have placed. Here, the current sensor is implemented independently of the impedances and provides a more accurate leakage current reading.

The switches can be implemented with a variety of components. The switches or switching elements can be implemented as relays. The microprocessor can energize a coil associated with the relay to move a contact. The switches may also be implemented as solid-state devices, such as transistors. The microprocessor may have associated circuitry for driving a gate of a transistor device to activate the switching device.

4 illustrates the generation of a leak path from the top of the high voltage cell string 110 through a resistor R1 150 to the 12V supply 158 in the low voltage range. This is achieved by using the microprocessor 114 the switches identified by ellipses 152 . 154 . 156 closes. The microprocessor 114 can also have an external communication interface 124 , such as Ethernet or CAN, to allow external control of the system and provide status and feedback to external controllers.

Referring again to 3 can be in the microprocessor 114 Implemented strategy to ensure that at all times only one source switch 122 is closed to protect against shorting cell outputs. The strategy can also ensure that at any one time only a destination switch 120 is closed in the 3 configuration prevents a direct short circuit of the low voltage source from 12V to ground.

The isolation monitor performance tool 100 The present disclosure may be used in a laboratory testing environment during all phases of battery system and vehicle development. The power tool may also be used by service engineers to test operation of a battery electronic control module (BECM) and associated circuitry during vehicle servicing.

The use of the isolation monitor performance tool 100 may provide useful information for battery controller design and implementation at an early stage of vehicle development when a prototype high voltage traction battery or other system components may not be available. An isolation monitor performance tool 100 of various embodiments may be incorporated into existing battery simulator devices 98 which may allow the introduction of a variable leak into a high voltage system without manual contact of components to high voltage potentials or allow the introduction of complex impedances into a high voltage system. Additional advantages of an isolation monitor evaluation tool according to embodiments of the disclosure may include providing automated control of the leak source, a variable real or complex impedance, and a selectable target or selectable sink. In addition, various embodiments allow the automated introduction of a leak to any point along the cell string.

The processes, methods, or algorithms disclosed herein may be provided to or implemented by a processing device, controller, or computer, which may include any existing programmable electronics controller or dedicated electronics controller. Similarly, the processes, methods, or algorithms may be stored as data and instructions that may be executed by a controller or computer in many forms, including, but not limited to, information stored permanently on nonwritable storage media, such as ROM devices, and information that may be stored be stored changeable on recordable storage media such as floppy disks, magnetic tapes, CDs, RAM devices and other magnetic and optical media. The processes, methods or algorithms may be implemented in a software executable object. Alternatively, the processes, methods, or algorithms may be wholly or partially embodied using appropriate hardware components, such as application specific integrated circuits (ASIC), field programmable gate arrays (FPGAs), state machines, controllers, or other hardware components or devices or a combination of hardware, software and firmware components.

Although embodiments are described above, these embodiments are not intended to describe all possible forms included in the claims. The words 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. As described above, the features of various embodiments may be combined to form further embodiments of the invention, which may not be explicitly described or illustrated. While various embodiments may be described as providing or preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, one of ordinary skill in the art will recognize that one or more features or characteristics may be adversely affected Achieve overall system attributes that depend on the specific application and implementation. These attributes may include cost, strength, durability, life-cycle cost, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, among others. As such, embodiments that are described as being less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.

Claims (18)

 Insulation tester for a vehicle, comprising: a communication interface; several impedances; and a controller programmed to electrically connect a selected one of the impedances between a traction battery and a subsystem of the vehicle to create a leakage path therebetween and to output a diagnostic status based on a current associated with the leakage path and a signal received via the communication interface indicating an insulation fault between the battery and the subsystem.  Insulation tester according to claim 1, wherein the communication interface is a CAN interface (CAN - Controller Area Network) or Ethernet.  The isolation tester of claim 2, wherein the controller is further programmed to select a different one of the impedances in response to a different signal received via the communication interface to disconnect the selected one of the impedances to connect the various ones of the impedances to the traction battery and another Issue diagnostic status.  The insulation tester of claim 1, wherein electrically connecting a selected one of the impedances between a traction battery and a subsystem of the vehicle includes electrically connecting the selected ones of the impedances to less than all battery cells of the traction battery to provide a voltage potential between the traction battery and the subsystem to create.  An insulation tester according to any one of claims 1 to 4, further comprising a current sensor electrically disposed between the selected one of the impedances and the traction battery, wherein a magnitude of the current is based on an output of the sensor.  An insulation tester according to any one of claims 1 to 5, further comprising a high voltage lock bypass circuit configured to pass the current when the high voltage lock bypass circuit is activated.  Insulation tester according to one of claims 1 to 6, further comprising a current sensor, which is arranged electrically in series with the traction battery and the subsystem.  Insulation tester according to one of claims 1 to 7, wherein the subsystem is a positive low-voltage terminal, a low-voltage ground or a chassis.  A method of vehicle isolation testing comprising: through a controller, electrically coupling a selected impedance between a traction battery and a subsystem of a vehicle; Allowing the traction battery to energize the impedance via a high voltage latch circuit that passes a leakage current from the battery through a sensor and the impedance to the subsystem; and Outputting a diagnostic status based on the leakage current and a signal received via a communications interface indicative of an insulation fault between the battery and the subsystem.  The method of claim 9, wherein the subsystem is a positive low voltage terminal, a low voltage ground, or a chassis.  The method of claim 9 or claim 10, wherein the sensor is electrically disposed between the impedance and the traction battery.  The method of claim 9, wherein allowing the traction battery to energize the impedance includes electrically coupling less than all cells of the traction battery to create a voltage potential between the traction battery and the subsystem.  Method according to one of claims 9 to 12, wherein the communication interface is a CAN interface (CAN - Controller Area Network) or Ethernet.  Test system for a vehicle, comprising: a current sensor; several impedances; a communication interface; and a controller programmed to, in response to an isolation fault feedback from the communication interface, connect a selected one of the impedances in series with the current sensor, a battery, and a subsystem of the vehicle to produce a leakage path that provides an isolation barrier between a high voltage bus of the vehicle and the subsystem bridged.  The test system of claim 14, wherein the subsystem is a positive low voltage terminal, a low voltage ground, or a chassis. The test system of claim 14 or claim 15, wherein the controller is further programmed to select a different one of the impedances, disconnect the selected ones of the impedances, connect the other one of the impedances to the battery, and one in response to another isolation fault feedback from the communication interface other diagnostic status.  Test system according to one of claims 14 to 16, wherein the communication interface is a CAN interface (CAN - Controller Area Network) or Ethernet.  The test system of claim 14, further comprising a high voltage lock bypass circuit configured to pass a current associated with the leakage path when the high voltage lock bypass circuit is activated.

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