Abstract:
A vehicle high voltage system may include switches (e.g., IGBTs, contactors, relays, etc.), wires, a traction battery, electrical components with electrical properties and at least one controller. The at least one controller may be programmed to modulate a switch to provide a testing voltage for the electrical components, which is less than an operating voltage of the battery, and in response to a current flow associated with the testing voltage being less than a predetermined threshold, stop current flow between the battery and electrical components.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to the control of contactors, IGBTs, relays, etc. to protect a vehicle high voltage wiring and component infrastructure. 
       BACKGROUND 
       [0002]    A hybrid-electric vehicle (HEV) or all-electric vehicle (EV) has a traction battery to store and provide energy for vehicle propulsion. The traction battery typically operates at over 100 volts, which is an increased voltage in comparison to a conventional vehicle battery voltage of 12 volts. The industry standard is that low voltage is less than 60 volts Direct Current (DC) and 30 volts Alternating Current (AC) calculated by root mean square (RMS). Voltages above this threshold are considered high voltage. The traction battery also has greater current capacity in comparison to a conventional battery, which can be in excess of 100amps·hours. This increased voltage and current is used by an electric motor(s) to convert the electrical energy stored in the battery to mechanical energy in the form of a torque which is used to provide vehicle propulsion. The battery is connected to the electric motor via wires, connectors, capacitors, and other electrical components. 
       SUMMARY 
       [0003]    A vehicle may have a high voltage system which may include a traction battery, electrical components with specific properties, a load, a power converter which is electrically connected between the battery and load, switches which may include IGBTs, MOSFETs, BJTs, relays, etc. and at least one controller. To check high voltage cable connectivity or if there is a fault with the electrical components or load, the controller may be programmed to cause the power converter to output a testing voltage to the load less than the operating voltage of the battery. If the output by the converter associated with the testing voltage indicates a fault between the battery and the load, the controller may be programmed to stop current flow between the battery and load. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is an example hybrid-electric vehicle with a battery pack; 
           [0005]      FIG. 2  is a battery pack arrangement comprised of battery cells and battery cell monitoring and controlling systems; 
           [0006]      FIG. 3  is a wiring diagram of an example hybrid electrical vehicle; 
           [0007]      FIG. 4  is a wiring diagram of a motor/generator circuit employing a boost converter; 
           [0008]      FIG. 5  is a graph that illustrates capacitor voltage with respect to time for components of a vehicle high voltage electrical system; 
           [0009]      FIG. 6  illustrates a flow diagram of an algorithm used to protect a vehicle high voltage electrical system; and 
           [0010]      FIG. 7  is a wiring diagram of a motor/generator circuit employing a buck-boost converter. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can 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 present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated 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. 
         [0012]      FIG. 1  depicts an example of a plug-in hybrid-electric vehicle  100 . The plug-in hybrid-electric vehicle  100  may comprise one or more electric motors  104  mechanically connected to a hybrid transmission  106 . In addition, the hybrid transmission  106  is mechanically connected to an engine  108 . The hybrid transmission  106  may also be mechanically connected to a drive shaft  110  that is mechanically connected to the wheels  112 . The electric motors  104  can provide propulsion when the engine  108  is turned on. The electric motors  104  can provide deceleration capability when the engine  108  is turned off. The electric motors  104  may be configured as generators and can provide fuel economy benefits by recovering energy that would normally be lost as heat in the friction braking system. The electric motors  104  may also reduce pollutant emissions since the hybrid electric vehicle  102  may be operated in electric mode under certain conditions. 
         [0013]    The fraction battery or battery pack  114  stores energy that can be used by the electric motors  104 . A vehicle battery pack  114  typically provides a high voltage DC output. The battery pack  114  is electrically connected to a power electronics module  116 . The power electronics module  116  is also electrically connected to the electric motors  104  and provides the ability to bi-directionally transfer energy between the battery pack  114  and the electric motors  104 . For example, a typical battery pack  14  may provide a DC voltage while the electric motors  104  may require a three-phase AC current to function. The power electronics module  116  may convert the DC voltage to a three-phase AC current as required by the electric motors  104 . In a regenerative mode, the power electronics module  116  will convert the three-phase AC current from the electric motors  104  acting as generators to the DC voltage required by the battery pack  114 . The methods described herein are equally applicable to a pure electric vehicle or any other device using a battery pack. 
         [0014]    In addition to providing energy for propulsion, the battery pack  114  may provide energy for other vehicle electrical systems. A typical system may include a DC/DC converter module  118  that converts the high voltage DC output of the battery pack  114  to a low voltage DC supply that is compatible with other vehicle loads. Other high voltage loads, such as compressors and electric heaters, may be connected directly to the high-voltage bus from the battery pack  114 . In a typical vehicle, the low voltage systems are electrically connected to a 12V battery  120 . An all-electric vehicle may have a similar architecture but without the engine  108 . 
         [0015]    The battery pack  114  may be recharged by an external power source  126 . The external power source  126  may provide AC or DC power to the vehicle  102  by electrically connecting through a charge port  124 . The charge port  124  may be any type of port configured to transfer power from the external power source  126  to the vehicle  102 . The charge port  124  may be electrically connected to a power conversion module  122 . The power conversion module may condition the power from the external power source  126  to provide the proper voltage and current levels to the battery pack  114 . In some applications, the external power source  126  may be configured to provide the proper voltage and current levels to the battery pack  114  and the power conversion module  122  may not be necessary. The functions of the power conversion module  122  may reside in the external power source  126  in some applications. The vehicle engine, transmission, electric motors, battery, power conversion and power electronics may be controlled by a powertrain control module (PCM)  128 . 
         [0016]    In addition to illustrating a plug-in hybrid vehicle,  FIG. 1  can illustrate a battery electric vehicle (BEV) if component  108  is removed. Likewise,  FIG. 1  can illustrate a traditional hybrid electric vehicle (HEV) or a power-split hybrid electric vehicle if components  122 ,  124 , and  126  are removed.  FIG. 1  also illustrates the high voltage vehicle system which includes the electric motor(s)  104 , the power electronics module  116 , the DC/DC converter module  118 , the power conversion module  122 , and the battery pack  114 . 
         [0017]    The individual battery cells within a battery pack may be constructed from a variety of chemical formulations. Typical battery pack chemistries may include but are not limited to lead acid, nickel cadmium (NiCd), nickel-metal hydride (NIMH), Lithium-Ion or Lithium-Ion polymer.  FIG. 2  shows a typical battery pack  200  in a simple series configuration of N battery cell modules  202 . The battery cell modules  202  may contain a single battery cell or multiple battery cells electrically connected in parallel. The battery pack, however, may be composed of any number of individual battery cells and battery cell modules connected in series or parallel or some combination thereof. A typical system may have one or more controllers, such as a Battery Control Module (BCM)  208  that monitors and controls the performance of the battery pack  200 . The BCM  208  may monitor several battery pack level characteristics such as pack current measured by a current sensor  206 , pack voltage  210  and pack temperature  212 . The performance of the current sensor  206  may be essential, in certain arrangements, to build a reliable battery monitoring system. The accuracy of the current sensor may be useful to estimate the battery state of charge and capacity. A current sensor may utilize a variety of methods based on physical principles to detect the current including a Hall effect IC sensor, a transformer or current clamp, a resistor in which the voltage is directly proportional to the current through it, fiber optics using an interferometer to measure the phase change in the light produced by a magnetic field, or a Rogowski coil. In the event a battery cell is charging or discharging such that the current entering or exiting the battery cell exceeds a threshold, the battery control module may disconnect the battery cell via the use of a circuit interrupt device (CID) such as a fuse or circuit breaker. 
         [0018]    In addition to the pack level characteristics, there may be battery cell level characteristics that need to be measured and monitored. For example, the terminal voltage, current, and temperature of each cell may be measured. A system may use a sensor module  204  to measure the characteristics of one or more battery cell modules  202 . The characteristics may include battery cell voltage, temperature, age, number of charge/discharge cycles, etc. Typically, a sensor module will measure battery cell voltage. Battery cell voltage may be voltage of a single battery or of a group of batteries electrically connected in parallel or in series. The battery pack  200  may utilize up to N c  sensor modules  204  to measure the characteristics of all the battery cells  202 . Each sensor module  204  may transfer the measurements to the BCM  208  for further processing and coordination. The sensor module  204  may transfer signals in analog or digital form to the BCM  208 . The battery pack  200  may also contain a battery distribution module (BDM)  214  which controls the flow of current into and out of the battery pack  200 . 
         [0019]      FIG. 3  is an illustration of a power electronics distribution module  214 . This battery distribution module (BDM)  214  contains the high voltage switches ( 302 ,  304 ,  306 ,  308  and  314 ) used to connect and disconnect the high voltage components. These high voltage switches ( 302 ,  304 ,  306 ,  308  and  314 ) can be relays, insulated gate bipolar junction transistors (IGBTs), metal oxide semiconductor field effect transistors (MOSFETs), bipolar junction transistors (BJTs), or other electro-mechanical or solid state switches. The battery cells  202  provide the voltage and current which flows through switches  302  and  304  to the power electronics module  116 . The current is measured in a current sensor block  310 . The current may flow as a result of switch  304  being closed and either switch  302  or  314  being closed with power moving between the battery cells  202  and the power electronics module  116 . Switch  314  in conjunction with resistor  316  is a pre-charge circuit which is used to limit the current flow into system while the system is powering up. Also, current may flow as a result of switches  308  and  306  being closed with power moving between the battery cells  202  and the power conversion module  122 . The current also may also pass through a CID  312  which can include a fuse or circuit breaker, however the CID is not required as the system may be configured to protect the circuit over the complete range of operating amp·hour time periods. The BDM  214  also may include switches  306  and  308  which alternatively connect the battery cells  202  with the power conversion module  122 . 
         [0020]      FIG. 4  is a wiring diagram of a boost converter circuit  116  that may drive one or more motor/generator  412 . The battery cells  202  having a voltage and ability to supply a current are electrically connected to the battery distribution block  214 . The battery distribution module  214  is connected to the power electronics module  116 . The power electronics module  116  may include a boost circuit with an inductor  406 , a switch  402  to charge an electric field in the inductor  406  and a switch  404  to discharge the electric field thereby changing the voltage to drive the motor/generator  412 . This DC/DC convertor circuit will convert the battery voltage to an operational voltage which may be greater than the battery cell voltage. The power converter  116  may use IGBTs, BJTs, MOSFETs, relays, or other electro-mechanical or solid state switches at location  402  and  404 . The use of IGBTs with Fast Recovery Diodes (FRDs) in this diagram is exemplary and may be accomplished using MOSFETs, BJTs, or other electro-mechanical or solid state switches. The capacitor  408  is used to filter the voltage generated by the DC/DC convertor so that the operational voltage applied to the motor control switches  410  is generally stable. This boost circuit is intended to change the voltage of the high voltage battery  202  to an operating voltage that is greater than the battery voltage. An example of this is a high voltage battery of 90-400 volts being boosted to an operating voltage of 100-1200 volts. 
         [0021]      FIG. 5  is a graph that illustrates capacitor voltage  502  with respect to time  504  for electrical components of a vehicle high voltage electrical system. As the system is powered up with the pre-charge resistor circuit  314  closed, the voltage across the capacitor  408  increases as it is charged until it reaches an upper threshold voltage level  514  at point  506 . This upper threshold voltage level  514  is chosen to be a low voltage less than 60 volts DC. Upon reaching the upper threshold voltage at  506 , the control system closes switch  402  and the charging of the capacitor  408  stops as all current is now directed through switch  402  to charge the field of the inductor  406 . The current is limited by the pre-charge resistor  316 . When the switch is closed at the point  506 , the capacitor  408  voltage may drop due to the motor or generator load demanded by the high voltage interlock HVIL test. If the voltage level drops below a lower threshold level  516  at point  508 , the control system will open the switch  402  and the capacitor  408  will begin to charge. In this example, switch  404  is a directional switch which allows current to flow in one direction, but not in the other, as such, switch  404  may be left closed through this test. If switch  404  is a bi-directional switch allowing current to flow in either direction, switch  404  will be switched complementarily to switch  402 . This feedback mechanism will maintain the voltage across the capacitor  408  between the upper threshold level  514  and lower threshold level  516 . While the voltage across the capacitor is within this voltage range, the controller may perform an interlock test to check the integrity of the high voltage system and the high voltage components. The hardware interlock test is complete at point  510 , at which point the high voltage system charging will continue as indicated by  512  if the test passes. In the event that the test does not pass, the contactors will open and the battery will be disconnected from the high voltage system and the voltage on the high voltage system will never exceed 60V, which is a low voltage. 
         [0022]      FIG. 6  is a flow diagram of a high voltage control system and interlock which may be used in a hybrid electric vehicular system or an electric vehicular system. The system initialization is in block  602  which checks to see if the contactors are closed and if the contactors are not closed. The system closes the contactors so that a current flows from the battery to the electrical components. When the contactors are closed and a current begins flowing from the battery, the high voltage system begins to charge. The pre-charging of the high voltage system is performed in block  604 . This initial pre-charging  604  is followed by a measurement of the high voltage system&#39;s voltage in block  606 . The pre-charging and voltage measurement continues until the voltage is above a lower threshold voltage level  516 , which is tested in block  608 . After the voltage increases above the lower threshold voltage level  516 , an HVIL test can be performed in block  612  while the voltage on the high voltage system is maintained between the upper threshold voltage level  514  and the lower threshold voltage level  516 , which is done in block  610 . Block  610  may include an upper voltage level test  614 , which when the voltage on the bus exceeds the upper threshold voltage level  514  a contactor is opened to stop the voltage from increasing further. Block  610  may also include a lower voltage level test  618 , which when the voltage on the bus drops below a lower threshold voltage level  512  a contactor is closed to allow the flow of current from the battery to the high voltage system. Both the HVIL testing  612  and the voltage feedback mechanism  610  will continue until the HVIL test is complete as determined in block  622 . The results of the HVIL test are evaluated in block  624 . An example HVIL test may include multiple tests in which the motor control switches  410  are selectively engaged to check conductivity of each phase of the electric machine  412  at a low voltage and not the normal operational voltage. In this example if a connector is not properly seated or connected, minimum current would flow, which would not exceed a lower predetermined threshold. This current measurement less than the lower threshold would indicate a connection fault. Likewise if there was a short circuit condition, the current flow would exceed an upper predetermined threshold. Therefore it may be desirable in this example to look for current flow to be within a predetermined range to indicate a proper connection and operational status of the components. If the results indicate that the test passed, the high voltage system is allowed to continue pre-charging over the low voltage threshold limit  514 . The continued pre-charging is performed in block  628 . If the test results indicate a fault, then the system is shut-down in block  626 . 
         [0023]      FIG. 7  is a wiring diagram of a buck-boost converter circuit  700  that may drive one or more motor/generator  412 . The battery cells  202  are electrically connected to the battery distribution block  214 . The battery distribution module  214  is connected to the power electronics module  700 . The power electronics module  700  may include a boost circuit with an inductor  406 , a switch  402  to charge an electric field in the inductor  406 , and a switch  404  to discharge the electric field thereby changing the voltage to drive the motor/generator  412 . This power electronics module  700  may also include a buck circuit using inductor  406  and switches  702  and  704 . This DC/DC convertor circuit will convert the battery voltage to an operational voltage which may be greater than the battery cell voltage. The buck-boost power converter  700  may use IGBTs, BJTs, MOSFETs, relays, or other electro-mechanical or solid state switches at locations  402  and  404 . The use of IGBTs with Fast Recovery Diodes (FRDs) in this diagram is exemplary and may be accomplished using MOSFETs, BJTs, or other electro-mechanical or solid state switches. In this example, switch  404  is a directional switch which allows current to flow in one direction, but not in the other. As such, switch  404  may be left closed through this test. If switch  404  is a bi-directional switch allowing current to flow in either direction, switch  404  will be switched complementarily to switch  402 . The capacitor  408  is used to filter the voltage generated by the DC/DC convertor so that the operational voltage applied to the motor control switches  410  is generally stable. This buck-boost circuit is intended to change the voltage of a high voltage battery  202  (having a voltage greater than 60V DC), to an operating voltage different than the battery voltage. An example of this is a high voltage battery of 90-400 volts being bucked or boosted to an operating voltage of 100-1200 volts. 
         [0024]    The processes, methods, or algorithms disclosed herein can be deliverable to/implemented by a processing device, controller, or computer, which can include any existing programmable electronic control unit or dedicated electronic control unit. Similarly, the processes, methods, or algorithms can be stored as data and instructions executable by a controller or computer in many forms including, but not limited to, information permanently stored on non-writable storage media such as ROM devices and information alterably stored on writeable storage media such as floppy disks, magnetic data tape storage, optical data tape storage, CDs, RAM devices, FLASH devices, MRAM devices and other magnetic and optical media. The processes, methods, or algorithms can also be implemented in a software executable object. Alternatively, the processes, methods, or algorithms can be embodied in whole or in part using suitable hardware components, such as Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), state machines, controllers, or any other hardware components or devices, or a combination of hardware, software and firmware components. 
         [0025]    Although exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. 
         [0026]    Although various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as 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 can be desirable for particular applications.