Method and system for charging and heating a traction battery

Abstract

The present disclosure provides methods and systems for charging and heating a traction battery. Systems and methods for operating a vehicle powertrain system are described. The vehicle power system includes an inverter and an electric machine. The switch and the diode are arranged in a manner that allows the traction battery to be charged by either the lower voltage charger or the higher voltage charger. Additionally, the switch and the diode allow the vehicle powertrain to heat the traction battery such that the traction battery may operate within a desired temperature range.

Description

Technical Field

[0001] The present description relates to methods and systems for charging and heating a traction battery of an electric or hybrid vehicle. The methods and systems may be particularly useful for vehicles including a higher voltage traction battery. Background Art

[0002] An electric or hybrid vehicle may include a traction battery that provides power to and receives power from an electric motor. The electric motor may be operated as a motor to provide propulsion to the wheels, and the electric motor may be operated as a generator or alternator to convert the kinetic energy of the vehicle into electrical energy. The traction battery may be configured as a four hundred volt battery. However, a recent trend includes replacing the four hundred volt battery with an eight hundred volt battery to reduce vehicle weight and improve vehicle efficiency. However, many fast direct current (DC) chargers are configured as four hundred volt chargers, not eight hundred volt chargers. For this reason, there may be compatibility issues between existing chargers and the proposed traction battery. Summary of the invention

[0003] Recently, eight-hundred-volt vehicle electrical systems have been proposed to improve system efficiency and reduce vehicle weight. By powering an electric motor that supplies propulsion via an eight-hundred-volt battery, the weight of the electric motor can be reduced. However, because eight-hundred-volt motors and traction batteries are relatively new, few eight-hundred-volt chargers are constructed and can be used to charge these traction batteries. On the other hand, four-hundred-volt chargers are relatively more common, but connecting them to an eight-hundred-volt vehicle electrical system may not be as effective as desired. For example, a four-hundred-volt charger can be connected to an eight-hundred-volt traction battery by operating the vehicle's inverter in boost mode, thereby boosting the four-hundred-volt to eight-hundred-volt. However, operating the inverter in boost mode may reduce charging efficiency due to higher losses from the inverter, motor windings, and motor core. Therefore, it may be desirable to provide a way to more efficiently charge a vehicle's higher voltage electrical system via a lower voltage vehicle charger.

[0004] The inventors herein have recognized the above-mentioned problems and have developed a vehicle power system comprising: a traction battery including a first group of battery cells arranged in series and a second group of battery cells arranged in series, the first group of battery cells being arranged in series with the second group of battery cells; a high voltage terminal directly electrically coupled to the first group of battery cells; a low voltage terminal directly electrically coupled to the second group of battery cells; a medium voltage terminal directly electrically coupled to the first group of battery cells and the second group of battery cells; a motor for providing propulsion for the vehicle; and an inverter coupled to the traction battery and the motor.

[0005] By including a three-terminal battery in the vehicle electrical system, the three-terminal battery can be charged via a low voltage charger (e.g., a four hundred volt charger) that outputs a low voltage. Specifically, the low voltage charger can be coupled to a first group of battery cells via high voltage terminals of the traction battery and medium voltage terminals of the traction battery, such that half of the battery cells of the traction battery can be charged via the low voltage charger during a first time period. The low voltage charger can be coupled to a second group of battery cells via medium voltage terminals of the traction battery and low voltage terminals of the traction battery, such that the other half of the battery cells of the traction battery can be charged via the low voltage charger during a second time period.

[0006] The present description may provide several advantages. Specifically, the method may improve the charging efficiency of the traction battery. Furthermore, the method allows the traction battery to be charged via a lower voltage charger (e.g., a four hundred volt charger) and a higher voltage charger (e.g., an eight hundred volt charger). Additionally, the method allows the battery to be heated to a desired operating temperature range with less loss than other methods.

[0007] The above advantages and other advantages and features of the present specification will be readily apparent from the following detailed description when taken alone or in conjunction with the accompanying drawings.

[0008] It will be appreciated that the above summary is provided to introduce in simplified form a series of concepts further described in the detailed description. This is not meant to identify the key features of the claimed subject matter, the scope of which is uniquely defined by the claims attached to the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address any disadvantages mentioned above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Advantages described herein will be more fully understood by reading examples of embodiments referred to herein as detailed descriptions when read alone or with reference to the accompanying drawings, in which:

[0010] Figure 1 is a schematic view of an example electric vehicle.

[0011] Figure 2 is a schematic diagram of an improved traction battery charging system.

[0012] Figure 3 and Figure 4 The charging system operating sequence is shown.

[0013] Figure 5 An example charging system circuit is shown.

[0014] Figures 6 to 8 An additional charging system operating sequence is shown.

[0015] Fig. 9 A flow chart of a method for operating a vehicle charging and heating system is shown. DETAILED DESCRIPTION

[0016] The present specification relates to operating a charging and heating system for a traction battery. The charging and heating system can improve charging efficiency when charging a higher voltage battery via a battery charger that outputs a lower voltage. Specifically, according to the systems and methods described herein, a four hundred volt charger can charge an eight hundred volt battery. The charging and heating system can be included in an electric vehicle, such as Figure 1 The charging and heating system can be as shown in Figure 2 The charging and heating system can be constructed as shown in Figure 3 , Figure 4 and Figures 6 to 8 The charging and heating system may include Figure 5 The control circuit shown in Fig. 9 Method to operate the charging and heating system.

[0017] Figure 1 1 is a block diagram of a vehicle 121 including a powertrain or driveline 100. The front of the vehicle 121 is indicated at 110, and the rear of the vehicle 121 is indicated at 111. The driveline 100 includes an electric machine 126. The electric machine 126 may consume or generate electric power depending on its operating mode. Figure 1 , the mechanical connections between the various components are shown as solid lines, while the electrical connections between the various components are shown as dashed lines.

[0018] The transmission system 100 has a rear axle 122. In some examples, the rear axle 122 may include two half shafts, such as a first half shaft 122a and a second half shaft 122b. The transmission system 100 also includes front wheels 130 and rear wheels 131. The rear wheels 131 may be driven via the motor 126.

[0019] The rear axle 122 is coupled to the motor 126. The rear drive unit 136 can transfer power from the motor 126 to the axle 122, thereby rotating the rear wheels 131. The rear drive unit 136 can include a low gear 175 and a high gear 177 coupled to the motor 126 via an output shaft 126o of the motor 126. The low gear 175 can be engaged via a fully closed low gear clutch 176. The high gear 177 can be engaged via a fully closed high gear clutch 178. The high gear clutch 178 and the low gear clutch 176 can be opened and closed via commands received by the rear drive unit 136 via a controller area network (CAN) 199. Alternatively, the high gear clutch 178 and the low gear clutch 176 can be opened and closed via a digital output or pulse width provided by the control system 114. The rear drive unit 136 can include a differential 128 so that torque can be provided to the first half shaft 122a and the second half shaft 122b. In some examples, an electronically controlled differential clutch (not shown) may be included in rear drive unit 136 .

[0020] The motor 126 may receive power from an onboard electrical energy storage device 132. In addition, the motor 126 may provide a generator function to convert the kinetic energy of the vehicle into electrical energy, which may be stored at the electrical energy storage device 132 for later use by the motor 126. The inverter 134 may convert the alternating current generated by the motor 126 into direct current for storage at the electrical energy storage device 132, and vice versa. The electric drive system 135 includes the motor 126 and the inverter 134. The electrical energy storage device 132 may be a traction battery (e.g., a battery that supplies power to propel the vehicle), a capacitor, an inductor, or other electrical energy storage device. The power flowing into the electric drive system 135 may be monitored via a current sensor 145 and a voltage sensor 146. The position and speed of the motor 126 may be monitored via a position sensor 147. The torque generated by the motor 126 may be monitored via a torque sensor 148.

[0021] In some examples, electrical energy storage device 132 can be configured to store electrical energy that can be provided to other electrical loads resident on the vehicle (in addition to the motor), including cabin heating and air conditioning systems, engine starting systems, headlight systems, cabin audio and video systems, etc.

[0022] The control system 114 may communicate with the motor 126, the electrical energy storage device 132, etc. The control system 114 may receive sensory feedback information from the electric drive system 135, the electrical energy storage device 132, etc. In addition, the control system 114 may send control signals to the electric drive system 135, the electrical energy storage device 132, etc. in response to the sensory feedback. The control system 114 may receive an indication of an operator-requested output of the vehicle propulsion system from the human operator 102 or the autonomous controller. For example, the control system 114 may receive sensory feedback from a pedal position sensor 194 in communication with a pedal 192. The pedal 192 may schematically refer to a driver demand pedal. Similarly, the control system 114 may receive an indication of an operator-requested vehicle deceleration via the human operator 102 or the autonomous controller. For example, the control system 114 may receive sensory feedback from a pedal position sensor 157 in communication with a vehicle deceleration pedal 156.

[0023] The electrical energy storage device 132 may periodically receive electrical energy from a power source residing external to the vehicle (e.g., not part of the vehicle), such as a stationary power grid (not shown). As a non-limiting example, the powertrain 100 may be configured as a plug-in electric vehicle (EV), whereby electrical energy may be supplied to the electrical energy storage device 132 via a power grid (not shown).

[0024] The energy storage device 132 includes an energy storage device controller 139 and a power distribution module 138. The energy storage device controller 139 can provide charge balancing between energy storage elements (e.g., battery cells) and communication with other vehicle controllers (e.g., controller 112). The power distribution module 138 controls the flow of power into and out of the energy storage device 132.

[0025] One or more wheel speed sensors (WSS) 195 may be coupled to one or more wheels of the powertrain 100. The wheel speed sensors may detect the rotational speed of each wheel. Such an example of a WSS may include a permanent magnet type sensor.

[0026] The controller 112 may include a portion of a control system 114. In some examples, the controller 112 may be a single controller for the vehicle. The control system 114 is shown as receiving information from a plurality of sensors 116 (various examples of which are described herein) and sending control signals to a plurality of actuators 181 (various examples of which are described herein). As an example, the sensors 116 may include tire pressure sensors (not shown), wheel speed sensors 195, etc. In some examples, sensors associated with the motor 126, the wheel speed sensors 195, etc. may transmit information about various states of motor operation to the controller 112. The controller 112 includes a non-transitory (e.g., read-only memory) 165, a random access memory 166, a digital input / output 168, and a microcontroller 167. The controller 112 may receive input data via a CAN 199 and provide the data to a human / machine interface 140.

[0027] Reference now Figure 2 , inverter 134 is shown electrically coupled to electrical energy storage device 132 (eg, traction battery), inverter 134 is directly electrically coupled to motor 126, and external DC charger 260 is shown directly coupled to motor 126 and third transistor 224. Figure 2 , "direct electrical coupling" refers to a first electrical component being electrically coupled to a second electrical component without intermediate electrical components other than electrical conductors. Figure 2 Nodes 250 show connections between various conductors, but not every node is labeled.

[0028] In this example, the energy storage device 132 includes a plurality of battery cells connected in series to increase the voltage of the energy storage device 132. The energy storage device 132 is shown as having a first group of battery cells 234 and a second group of battery cells 233. The first group of battery cells is configured to have a first output voltage (e.g., 400 volts) when fully charged, and the second group of battery cells is configured to have the same output voltage as the first group of battery cells. Thus, when the first group and the second group are connected as shown in FIG. Figure 2 When the battery pack is connected in series as shown in , the total voltage of the battery pack is the voltage of the first battery group plus the voltage of the second battery group. The energy storage device 132 includes a higher voltage battery terminal 132a, a lower voltage battery terminal 132b and a medium voltage terminal 132c. The higher voltage battery terminal 132a is directly electrically connected to the first group of battery cells 234. The medium voltage terminal 132c is directly electrically connected to the first group of battery cells 234 and the second group of battery cells 233. The lower voltage battery terminal 132b is directly electrically connected to the second group of battery cells 233. The voltage of the lower voltage battery terminal is less than the voltage of the medium voltage terminal, and the voltage of the medium voltage battery terminal is less than the voltage of the higher voltage terminal.

[0029] The inverter 134 includes a controller 202 that can communicate with the inverter via a controller area network (not shown). Figure 1 134. The controller 202 is electrically coupled to the bases of the transistors 210 to 215 of the inverter 134. The controller 202 may also be electrically coupled to the bases of the transistors 220 to 224. The transistors 210 to 215 and the transistors 220 to 224 operate in a switching mode, and these transistors may be referred to as switches. The controller 202 may supply control signals to independently activate and deactivate the transistors 210 to 215 and the transistors 220 to 224. The controller 202 includes inputs and outputs 202a (e.g., digital inputs, digital outputs, analog inputs, analog outputs), a memory 202b (e.g., a non-transitory memory, a random access memory, and a read-only memory), and a processor 202c.

[0030] Transistors 210 to 215 and transistors 220 to 224 are shown as insulated gate bipolar transistors (IGBTs), but in alternative configurations, these transistors may be metal oxide field effect transistors (MOSFETs), field effect transistors (FETs), or other known types of transistors. The controller 202 may start the IGBT via supplying a higher potential voltage to the gates of transistors 210 to 215 and the gates of transistors 220 to 224. The controller 202 may deactivate the IGBT via supplying a lower potential voltage to the gates of transistors 210 to 215 and the gates of transistors 220 to 224. The gate of the transistor is indicated by the letter "B". The collector of the transistor is indicated by the letter "C". The emitter of the transistor is indicated by the letter "E". Each transistor includes a diode, and the diode is biased to allow current to flow from the emitter lead of the transistor to the collector lead of the transistor. The anode of the diode is marked A, and the cathode of the diode is marked Ct. The inverter 134 also includes a filter capacitor 231.

[0031] The inverter 134 is also shown as being directly electrically coupled to the coils 126a, 126b, and 126c of the motor 126 (e.g., a three-phase motor that can operate as a motor or a generator). The motor 126 is constructed with coils 126a to 126c in a Y-shaped configuration, wherein the coils are tied together at a node 250. A first conductor 251 electrically connects the node 250, the emitter of the first transistor 220, and the DC charger 260. A second conductor 253 electrically couples the medium voltage terminal 132c to the emitter of the second transistor 222 and the collector of the third transistor 224. The third conductor 252 is electrically coupled to the lower voltage battery terminal 132b of the energy storage device 132 and the anode of the diode 230. The first transistor 220 is shown in parallel with the diode 220a. The second transistor 222 is shown in parallel with the diode 222a. The third transistor 224 is shown in parallel with the diode 224a. Fourth conductor 254 is shown electrically coupling the emitter of third transistor 224 to the cathode of diode 230 and DC charger 260. First transistor 220 is electrically connected in series to second transistor 222 via conductor 221. Third transistor 224 may selectively couple second conductor 253 to DC charger 260.

[0032] therefore, Figure 1 and Figure 2A system provides a vehicle power system, which includes: a traction battery, the traction battery including a first group of cells arranged in series and a second group of cells arranged in series, the first group of cells being arranged in series with the second group of cells; a high voltage terminal, the high voltage terminal being directly electrically connected to the first group of cells; a low voltage terminal, the low voltage terminal being directly electrically connected to the second group of cells; a medium voltage terminal, the medium voltage terminal being directly electrically connected to the first group of cells and the second group of cells; a motor, the motor being used to provide propulsion for the vehicle; and an inverter, the inverter being connected to the traction battery and the motor. In a first example, the vehicle power system further includes: a first conductor, the first conductor being connected to a node where three coils of the motor are directly electrically connected; a second conductor, the second conductor being directly electrically connected to the medium voltage terminal; and a third conductor, the third conductor being directly electrically connected to the low voltage terminal. In a second example that may include the first example, the vehicle power system further includes a first transistor that is directly electrically connected to a second transistor in series, the first transistor being directly connected to the first conductor, and the second transistor being directly connected to the second conductor. In a third example, which may include one or both of the first and second examples, the vehicle power system further includes a third transistor, which is arranged along the second conductor and is directly electrically coupled to the second transistor. In a fourth example, which may include one or more of the first to third examples, the vehicle power system further includes a first diode arranged in parallel with the first transistor, a second diode arranged in parallel with the second transistor, and a third diode arranged in parallel with the third transistor. In a fifth example, which may include one or more of the first to fourth examples, the vehicle power system further includes a fourth diode arranged along the third conductor. In a sixth example, which may include one or more of the first to fifth examples, the vehicle power system further includes six transistors forming an inverter, which are electrically coupled to the high voltage terminal and the low voltage terminal.

[0033] Figure 1 and Figure 2The system also provides a vehicle power system, which includes: a first group of battery cells; a second group of battery cells, the second group of battery cells being arranged in series with the first group of battery cells; an inverter, the inverter being electrically connected to the first group of battery cells and the second group of battery cells; and a controller, the controller including executable instructions stored in a non-transitory memory, the executable instructions causing the controller to operate the vehicle power system in a first mode, a second mode, a third mode, and a fourth mode, the first mode being a vehicle driving mode, the second mode being a four-hundred-volt charging mode, the third mode being an eight-hundred-volt charging mode, and the fourth mode being a battery heating mode. In a first example, the vehicle power system includes: wherein the four-hundred-volt charging mode includes charging the first group of battery cells at a different time than charging the second group of battery cells. In a second example that may include the first example, the vehicle power system includes: wherein the eight-hundred-volt charging mode includes charging the first group of battery cells and the second group of battery cells simultaneously. In a third example, which may include one or both of the first and second examples, the vehicle power system includes: wherein the battery heating mode includes charging and discharging the first group of battery cells out of phase with charging and discharging the second group of battery cells. In a fourth example, which may include one or more of the first to third examples, the vehicle power system includes: wherein the heating mode includes activating and deactivating a plurality of switches of the inverter.

[0034] Reference now Figure 3 , the prophetic graphs show how the second transistor 222 and the third transistor 224 operate when charging an eight hundred volt battery via a four hundred volt charger (eg, four hundred volt charging mode). The graphs are aligned in time.

[0035] from Figure 3 The first graph from the top of is a graph of the signal driving the second transistor 222 with respect to time. The vertical axis represents volts and the horizontal axis represents time. The second transistor 222 is turned on, so that current is allowed to flow through the second transistor 222 when the trace 302 is at a higher level (e.g., 1). The second transistor 222 is turned off so that current does not flow through the second transistor 222.

[0036] from Figure 3 The second graph from the top of is a graph of the signal driving the third transistor 224 with respect to time. The vertical axis represents volts and the horizontal axis represents time. The third transistor 224 is turned on, so that when the trace 304 is at a higher level (e.g., 1), current is allowed to flow through the third transistor 224. The third transistor 224 is turned off so that current does not flow through the third transistor 224.

[0037] When the second transistor is enabled and the third transistor is disabled, current may flow from the DC charger to the second battery cell 233 without causing current to flow to the first battery cell 234. Specifically, current from the DC charger may flow through the diode 220a, the second transistor 222, and through the medium voltage terminal 132c to charge the second battery cell 233. Because the third transistor 224 is turned off when the second transistor 222 is turned on, the DC charger is not short-circuited.

[0038] When the third transistor is enabled and the second transistor is disabled, current can flow from the DC charger to the first group of battery cells 234 without causing current to flow to the second group of battery cells 233. Specifically, current from the DC charger can flow through coils 126a to 126c and through diodes in parallel with transistors 210, 212, and 214, through higher voltage battery terminal 132a to charge the first group of battery cells 234. Because the second transistor 222 is turned off when the third transistor 224 is turned on, the DC charger is not short-circuited.

[0039] Reference now Figure 4 , a prophetic graph shows how current from a DC charger is distributed to a first group of battery cells and a second group of battery cells of a traction battery when charging an eight-hundred-volt battery via a four-hundred-volt charger (eg, a four-hundred-volt charging mode). The graphs are aligned in time.

[0040] from Figure 4 The first graph from the top of is a graph of a 400 volt DC fast charger current output versus time. The vertical axis represents current in amperes, while the horizontal line represents time. Trace 402 represents the DC fast charger current output.

[0041] from Figure 4 The second graph from the top of FIG. 4 is a graph of the amount of current supplied to the first group of battery cells 234 during the four hundred volt fast charge mode. The vertical axis represents the amount of current supplied to the first group of battery cells 234 of the electrical energy storage device 132, and the horizontal line represents time. Trace 404 represents the amount of current delivered to the first group of battery cells.

[0042] from Figure 4 The third graph from the top of FIG. 4 is a graph of the amount of current supplied to the second group of battery cells 233 during the four hundred volt fast charge mode. The vertical axis represents the amount of current supplied to the second group of battery cells 233 of the electrical energy storage device 132, and the horizontal line represents time. Trace 406 represents the amount of current delivered to the second group of battery cells.

[0043] It can be observed that the DC fast charger current is constant, while the amount of current supplied to the first group of battery cells and the amount of current supplied to the second group of battery cells vary. The current delivered to the first group of battery cells is 180 degrees out of phase with the amount of current delivered to the second group of battery cells. This is due to the manner in which the second transistor and the third transistor operate. Furthermore, this allows the first group of battery cells to charge when the second group of battery cells are not charging, and vice versa. Furthermore, the amount of time that the first group of battery cells is charged is equal to the amount of time that the second group of battery cells is charged, so that the two groups of battery cells are charged evenly.

[0044] Reference now Figure 5 , an example circuit 500 for heating an eight hundred volt battery or an AC voltage battery including a medium voltage terminal is shown. The circuit 500 can be operated when the vehicle is stationary and not moving. In addition, the example circuit 500 can be activated when the vehicle including the circuit is not electrically connected to an external charger. The circuit 500 can be activated when the first switch or transistor 220 and the second transistor or switch 224 are turned on and when the third transistor or switch 224 is turned off.

[0045] Circuit 500 includes a duty cycle voltage source 504, a comparator 502, a carrier voltage source 506, a square wave voltage source 510, two AND gates 512 / 514, and an AND gate 508. The two AND gate outputs drive or are input to the bases of transistors 210 to 215. The duty cycle voltage source output is input to the + terminal of comparator 502, and the carrier power supply output is input to the - terminal of comparator 502. The output of comparator 502 and the output of the AND gate 508 are input to separate inputs of the AND gate 512. The bases of transistors 210, 212, and 214 are driven by the output of the AND gate 512. The square wave voltage source output is delivered to the NOT gate 508 and the AND gate 514. The output of the comparator 502 is also delivered to the input of the AND gate 514. The AND gate 514 drives the bases of transistors 211, 213, and 215.

[0046] Reference now Figure 6 , shows the output voltage of square wave voltage source 510. Trace 602 represents the Figure 5 The voltage at the output of the square wave voltage source 510 is shown in FIG. 5. In this example, the square wave varies between zero volts and 1 volt. The square wave can cause the NOT gate 508, the AND gate 512, and the AND gate 514 to change operating states. In this example, the duty cycle of the square wave is 50%, and the frequency of the square wave is f0.

[0047] Reference now Figure 7 , shows the output voltage of duty cycle voltage source 504 and the output of carrier voltage source 506. Trace 702 represents the Figure 5The voltage at the output of the carrier voltage source 506 is represented by trace 704 as Figure 5 The duty cycle voltage source 504 has a voltage at its output. In this example, the carrier varies between zero volts and 1 volt. Whenever the carrier voltage is above or below the duty cycle voltage, the comparator output can change state. In this example, the frequency of the carrier is f sw .

[0048] Reference now Figure 8 , showing indicative current flow during heating of a battery comprising medium voltage terminals. Figure 8 The graphs are aligned in time.

[0049] from Figure 8 The first graph from the top is the flow into (-) and out of (+) the first set of battery cells of the traction battery (e.g., Figure 2 234). The vertical axis represents the current flowing into and out of the first group of battery cells, and the horizontal axis represents time. Trace 802 represents the amount of current flowing into and out of the first group of battery cells.

[0050] from Figure 8 The second graph from the top is the flow into (-) and out of (+) the second set of battery cells of the traction battery (e.g., Figure 2 233). The vertical axis represents the current flowing into and out of the second group of battery cells, and the horizontal axis represents time. Trace 804 represents the amount of current flowing into and out of the second group of battery cells.

[0051] from Figure 8 The third graph from the top is the current flowing into (-) and out of (+) the motor windings of the battery cells of the traction battery (e.g., Figure 2 806 represents the amount of current flowing into and out of the windings of the motor.

[0052] During the battery heating mode, the first group of battery cells is supplied with current, and the supply current is opposite to the second group of battery cells. Driving current into and out of the battery cells to the motor windings causes the traction battery to generate heat, and the heat warms the traction battery. The traction motor does not generate torque in this mode.

[0053] Reference now Fig. 9 , a method for charging and heating a traction battery is shown. Fig. 9 The method may include storing Figure 1 and Figure 2 In addition, Fig. 9 The method can be used with Figure 1 and Figure 2 The system works cooperatively to selectively charge the traction battery using chargers that output different voltage levels. Fig. 9 The method may provide an efficient way to heat a traction battery when a vehicle including the traction battery is not moving.

[0054] At 902, method 900 determines a vehicle operating mode. The vehicle operating mode may include, but is not limited to, a driving mode in which the traction battery can supply power to propel the vehicle when the traction battery is not being charged. The vehicle operating mode may also include a four hundred volt charging mode for an eight hundred volt traction battery, which may also be referred to as a switching charging mode. The vehicle operating mode may also include an eight hundred volt charging mode or a switchless charging mode. In addition, the vehicle mode may include a traction battery heating mode. Method 900 may determine the operating mode of the vehicle based on inputs to the vehicle. For example, if the propulsion source of the vehicle is commanded based on a driver demand pedal position and a vehicle deceleration pedal position, method 900 may determine that the vehicle is in a driving mode. If the vehicle is stopped and plugged into a DC charger that outputs 400 volts, method 900 may determine that the vehicle is in a switching charging mode. When the vehicle is stopped and plugged into an eight hundred volt charger, method 900 may determine that the vehicle is in a switchless charging mode. When the vehicle is stopped, the ambient temperature is below a threshold temperature, and the traction battery temperature is below a threshold temperature, method 900 may determine that the vehicle is in a traction battery heating mode. After determining the vehicle operating mode, method 900 proceeds to 904.

[0055] At 904 , method 900 determines whether the vehicle is in driving mode. If so, the answer is yes and method 900 proceeds to 920 . Otherwise, the answer is no and method 900 proceeds to 906 .

[0056] At 920, the method 900 turns off the first switch 220, turns off the second switch 222, and turns off the third switch 224. The method 900 also operates the switches or transistors 210 to 215 so that the motor 126 propels the vehicle 121. Alternatively, the method 900 may operate the transistors 210 to 215 to convert the kinetic energy of the vehicle into electrical energy, which is stored in the electrical energy storage device 132. The method 900 may operate the motor 126 via the switching transistors 210 to 215 according to space vector pulse width modulation. The method 900 proceeds to exit.

[0057] At 906, method 900 determines whether the vehicle is in a four-hundred-volt charging or switching charging mode. If so, the answer is yes, and method 900 proceeds to 922. Otherwise, the answer is no, and method 900 proceeds to 908.

[0058] At 922, the method 900 begins switching the second transistor 222 and the third transistor 224, as shown in FIG. Figure 3 In addition, the first transistor 220 is commanded to be turned off (disconnected), and the transistors 210 to 215 are commanded to be turned off. The switching of the second transistor is opposite to the switching of the third transistor, as shown in FIG. Figure 3 This allows a first group of battery cells (e.g., 234) having a voltage of four hundred volts or less to be charged via a four hundred volt charger. In addition, it allows a second group of battery cells (e.g., 233) having a voltage of four hundred volts or less to be charged via the same four hundred volt charger. The switch and Figure 2 The circuit arrangement shown in allows both the first group of battery cells and the second group of battery cells to be charged during one charging cycle (e.g., Figure 3 The method 900 may charge the first group of battery cells during a first portion of the charging cycle and the second portion of the charging cycle. The first group of battery cells may be charged during a first portion of the period when the second group of battery cells are not charged, and the second group of battery cells may be charged during a second portion of the period when the first group of battery cells are not charged. Thus, the method 900 charges half of the battery cells during the first portion of the charging cycle and charges the other half of the battery cells during the second portion of the charging cycle.

[0059] During a first portion of the charge cycle when the first transistor 220 is off and the third transistor 224 is on, current flows from the DC charger through coils 126a to 126c; through a diode in parallel with transistors 210, 212, and 214; to the battery cell 234; the current returns via the second conductor 253 and the third transistor 224. During a second portion of the charge cycle when the first transistor 220 is on and the third transistor 224 is off, current flows from the DC charger through diode 220a; through the second transistor 222, through the second conductor 253, to the battery cell 233; the current returns via the third conductor 252 and diode 230. The method 900 charges the battery and exits.

[0060] At 908, method 900 determines whether the vehicle is in eight hundred volt charging or unswitched charging mode. If so, the answer is yes and method 900 proceeds to 924. Otherwise, the answer is no and method 900 proceeds to 910.

[0061] At 924, method 900 turns off first transistor 220, second transistor 222, third transistor 224, and transistors 210 to 215. The external DC charger is electrically coupled to motor 126, and the voltage from the DC charger is passed to node 250, which then continues through the diode in parallel with transistors 210, 212, and 214 before reaching higher voltage battery terminal 132a. Lower voltage battery terminal 132b is connected via Figure 2 The third conductor 252 and the diode 230 are electrically coupled to the lower voltage side of the DC charger 260. Thus, the eight hundred volts output by the DC charger is applied across both of the first group of battery cells 234 and the second group of battery cells 233 between the higher voltage battery terminal 132a and the lower voltage battery terminal 132b. Thus, the method 900 charges all battery cells simultaneously. The method 900 charges the battery and exits.

[0062] At 910, method 900 judges whether the vehicle is in a battery heating mode. If so, the answer is yes and method 900 proceeds to 926. Otherwise, the answer is no and method 900 proceeds to 912. Battery heating mode may be entered when the vehicle is not being driven, the battery is not in a four hundred volt or eight hundred volt charging mode, and when the traction battery temperature is below a threshold temperature.

[0063] At 926, the method turns on the first switch 220 and the second switch 222. The method 900 also turns off the third switch 224. The method 900 performs Figure 5 The circuit shown in drives transistors 210 to 215. Transistors 210 to 215 are driven via a square wave and a carrier. In one example, the square wave has a frequency of 50 Hertz (Hz) and the carrier frequency is 10000 Hz. After charging the traction battery, method 900 proceeds to exit.

[0064] At 912, method 900 turns off the first switch, the second switch, and the third switch and turns off transistors 210 to 215. The vehicle and motor 126 may be disabled at this time. Method 900 proceeds to exit.

[0065] therefore, Fig. 9A method for a vehicle power system is provided, comprising: in a first mode, alternating between delivering power from a first charger to a first group of battery cells of a traction battery and delivering power from the first charger to a second group of battery cells of the traction battery; and in a second mode, simultaneously delivering power from the second charger to the first group of battery cells and the second group of battery cells. In a first example, the method further comprises: in a third mode, alternating between supplying current and receiving current via the first group of battery cells; and alternating between supplying current and receiving current via the second group of battery cells, the first group of battery cells supplying current when the second group of battery cells receive current, and the first group of battery cells receiving current when the second group of battery cells supply current. In a second example that may include the first example, the method comprises: wherein the first charger outputs a first voltage to the first group of battery cells and the second group of battery cells, and the second charger outputs a second voltage, the second voltage being greater than the first voltage. In a third example that may include one or both of the first example and the second example, the method further comprises an inverter, the inverter comprising a plurality of switches, and the plurality of switches are driven during the third mode via a circuit comprising a comparator, two AND gates, and a NOT gate. In a fourth example, the method includes: wherein the first mode includes switching a second transistor in the vehicle power system opposite to switching of a third transistor in the vehicle power system. In a fifth mode that may include one or more of the first to fourth modes, the method includes: wherein: the first mode includes applying a higher voltage to a second conductor during a first portion of a traction battery charge cycle, the second conductor being directly electrically coupled to a medium voltage terminal of the second group of battery cells, and applying a lower voltage to the second conductor during a second portion of the traction battery charge cycle. In a sixth mode that may include one or more of the first to fifth modes, the method includes: wherein the traction battery charge cycle includes charging the first group of battery cells during a first fifty percent of the traction battery charge cycle, and charging the second group of battery cells during a second fifty percent of the traction battery charge cycle. In a seventh mode that may include one or more of the first to sixth modes, the method includes: wherein the first group of battery cells is arranged in series with the second group of battery cells.

[0066] It should be noted that the example control and estimation routines included herein can be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in a non-transitory memory and can be executed by a control system including a controller in combination with various sensors, actuators and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies (such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc.). Therefore, the various actions, operations and / or functions shown may be executed in the sequence shown, executed in parallel, or omitted in some cases. Similarly, the processing order is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the actions, operations and / or functions shown may be repeatedly executed according to the specific strategy used. In addition, at least a portion of the described actions, operations and / or functions may graphically represent the code in the non-transitory memory of a computer-readable storage medium to be programmed into the control system. When the described actions are performed by executing instructions in combination with one or more controllers in a system including various engine hardware components, the control action may also transform the operating state of one or more sensors or actuators in the physical world.

[0067] This specification ends here. Without departing from the spirit and scope of this specification, those skilled in the art will think of many variations and modifications after reading this specification. For example, this specification can be advantageously applied to electric vehicles and hybrid vehicles.

[0068] According to the present invention, a vehicle power system is provided, which has: a traction battery, the traction battery including a first group of battery cells arranged in series and a second group of battery cells arranged in series, the first group of battery cells and the second group of battery cells being arranged in series; a high voltage terminal, the high voltage terminal being directly electrically coupled to the first group of battery cells; a low voltage terminal, the low voltage terminal being directly electrically coupled to the second group of battery cells; a medium voltage terminal, the medium voltage terminal being directly electrically coupled to the first group of battery cells and the second group of battery cells; a motor, the motor being used to provide propulsion for the vehicle; and an inverter, the inverter being coupled to the traction battery and the motor.

[0069] According to an embodiment, the present invention is also characterized by: a first conductor, which is connected to a node where the three coils of the motor are directly electrically connected; a second conductor, which is directly electrically connected to the medium voltage terminal; and a third conductor, which is directly electrically connected to the low voltage terminal.

[0070] According to an embodiment, the invention is also characterized by a first transistor being directly electrically coupled in series to a second transistor, the first transistor being directly coupled to the first conductor, the second transistor being directly coupled to the second conductor.

[0071] According to an embodiment, the invention is also characterized by a third transistor arranged along the second conductor and directly electrically coupled to the second transistor.

[0072] According to an embodiment, the present invention is also characterized by a first diode arranged in parallel with the first transistor, a second diode arranged in parallel with the second transistor, and a third diode arranged in parallel with the third transistor.

[0073] According to an embodiment, the invention also features a fourth diode arranged along the third conductor.

[0074] According to an embodiment, the present invention is also characterized by six transistors included in the inverter, the six transistors being electrically coupled to the high voltage terminal and the low voltage terminal.

[0075] According to the present invention, a method for a vehicle powertrain system includes: in a first mode, alternating between delivering power from a first charger to a first group of battery cells of a traction battery and delivering power from the first charger to a second group of battery cells of the traction battery; and in a second mode, simultaneously delivering power from a second charger to the first group of battery cells and the second group of battery cells.

[0076] In one aspect of the invention, the method comprises: in a third mode, alternating between supplying current and receiving current via the first group of battery cells; and alternating between supplying current and receiving current via the second group of battery cells, the first group of battery cells supplying current when the second group of battery cells receives current, and the first group of battery cells receiving current when the second group of battery cells supplies current.

[0077] In one aspect of the present invention, the first charger outputs a first voltage to the first group of battery cells and the second group of battery cells, and the second charger outputs a second voltage, the second voltage being greater than the first voltage.

[0078] In one aspect of the invention, the method includes an inverter, the inverter includes a plurality of switches, and the plurality of switches are driven during the third mode via a circuit including a comparator, two AND gates and a NOT gate.

[0079] In one aspect of the invention, the first mode comprises switching a second transistor in the vehicle powertrain opposite to switching of a third transistor in the vehicle powertrain.

[0080] In one aspect of the invention, the first mode includes applying a higher voltage to a second conductor during a first portion of a traction battery charging cycle, the second conductor being directly electrically coupled to a medium voltage terminal of the second group of battery cells, and applying a lower voltage to the second conductor during a second portion of the traction battery charging cycle.

[0081] In one aspect of the invention, the traction battery charging cycle includes charging the first group of battery cells during a first fifty percent of the traction battery charging cycle and charging the second group of battery cells during a second fifty percent of the traction battery charging cycle.

[0082] In one aspect of the invention, the first group of battery cells and the second group of battery cells are arranged in series.

[0083] According to the present invention, a vehicle power system is provided, which has: a first group of battery cells; a second group of battery cells, which are arranged in series with the first group of battery cells; an inverter, which is electrically connected to the first group of battery cells and the second group of battery cells; and a controller, which includes executable instructions stored in a non-volatile memory, and the executable instructions cause the controller to operate the vehicle power system in a first mode, a second mode, a third mode and a fourth mode, the first mode being a vehicle driving mode, the second mode being a four-hundred-volt charging mode, the third mode being an eight-hundred-volt charging mode, and the fourth mode being a battery heating mode.

[0084] According to an embodiment, the four hundred volt charging mode includes charging the first group of battery cells at a different time than charging the second group of battery cells.

[0085] According to an embodiment, the eight hundred volt charging mode includes charging the first group of battery cells and the second group of battery cells simultaneously.

[0086] According to an embodiment, the battery heating mode comprises charging and discharging the first group of battery cells out of phase with charging and discharging the second group of battery cells.

[0087] According to an embodiment, the battery heating mode includes activating and deactivating a plurality of switches of the inverter.

Claims

1. A vehicle power system, comprising: a traction battery, the traction battery comprising a first group of battery cells arranged in series and a second group of battery cells arranged in series, the first group of battery cells being arranged in series with the second group of battery cells; a high voltage terminal, the high voltage terminal being directly electrically coupled to the first group of battery cells; a low voltage terminal, the low voltage terminal being directly electrically coupled to the second group of battery cells; and a medium voltage terminal, the medium voltage terminal being directly electrically coupled to the first group of battery cells and the second group of battery cells; A motor, the motor being used to provide propulsion for the vehicle; as well as An inverter is coupled to the traction battery and the electric machine.

2. The vehicle power system of claim 1, further comprising: a first conductor coupled to a node where three coils of the motor are directly electrically coupled; a second conductor electrically coupled directly to the medium voltage terminal; and a third conductor electrically coupled directly to the low voltage terminal.

3. The vehicle power system of claim 2 further comprising a first transistor electrically coupled directly to a second transistor in series, the first transistor being directly coupled to the first conductor and the second transistor being directly coupled to the second conductor. 4 . The vehicle power system of claim 3 , further comprising a third transistor disposed along the second conductor and directly electrically coupled to the second transistor. 5 . The vehicle power system of claim 4 , further comprising a first diode arranged in parallel with the first transistor, a second diode arranged in parallel with the second transistor, and a third diode arranged in parallel with the third transistor.

6. The vehicle power system of claim 5, further comprising a fourth diode disposed along the third conductor. 7 . The vehicle power system of claim 6 , further comprising six transistors included in the inverter, the six transistors being electrically coupled to the high voltage terminal and the low voltage terminal.

8. A method for a vehicle power system, comprising: in a first mode, alternating between delivering power from a first charger to a first group of battery cells of a traction battery and delivering power from the first charger to a second group of battery cells of the traction battery; In a second mode, power is delivered simultaneously from a second charger to the first group of battery cells and the second group of battery cells.

9. The method of claim 8, further comprising: in a third mode, alternating between supplying current and receiving current via the first group of battery cells; and alternating between supplying current and receiving current via the second group of battery cells, the first group of battery cells supplying current when the second group of battery cells receives current, and the first group of battery cells receiving current when the second group of battery cells supplies current.

10. The method of claim 9, wherein the first charger outputs a first voltage to the first group of battery cells and the second group of battery cells, and the second charger outputs a second voltage, the second voltage being greater than the first voltage.

11. The method of claim 10, further comprising an inverter, the inverter comprising a plurality of switches, and driving the plurality of switches during the third mode via a circuit comprising a comparator, two AND gates, and a NOT gate.

12. The method of claim 8, wherein the first mode includes switching a second transistor in the vehicle powertrain opposite to switching of a third transistor in the vehicle powertrain.

13. The method of claim 8, wherein the first mode comprises: applying a higher voltage to a second conductor during a first portion of a traction battery charging cycle, the second conductor being directly electrically coupled to a medium voltage terminal of the second group of battery cells; and applying a lower voltage to the second conductor during a second portion of the traction battery charging cycle.

14. The method of claim 13, wherein the traction battery charging cycle comprises: The first group of battery cells is charged during a first fifty percent of the traction battery charging cycle; and the second group of battery cells is charged during a second fifty percent of the traction battery charging cycle.

15. The method of claim 8, wherein the first group of battery cells and the second group of battery cells are arranged in series.

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