CONTACTOR COIL CURRENT REDUCTION DURING VEHICLE BATTERY CHARGING

Abstract

Vehicle (102) comprising: a traction battery (114); a circuit arrangement and a controller that is programmed to Applying a first signal to the circuit arrangement during vehicle travel to maintain an electrical connection between the traction battery (114) and an electric motor (104), and Applying a second signal to the circuitry during battery charging while the vehicle (102) is stationary to maintain an electrical connection between the traction battery (114) and a charging source, the first signal having more power than the second signal.

Description

[0001] Various embodiments relate to an electric vehicle and a method for controlling the connection to the traction battery, and more particularly to vehicles with contactors and methods and systems for reducing contactor coil current during charging.

[0002] Electric vehicles rely on batteries to provide electrical energy to propel a vehicle. Batteries are charged with electricity through circuitry from a generator or the electrical grid. The connection must be made between the battery and other circuitry in the vehicle, which can be challenging given the high power or high voltage of traction batteries.

[0003] Vehicles with a traction battery have low-voltage applications and high-voltage applications. The low voltage can be used to control a contactor that electrically connects the high voltage to high-voltage circuitry. A contactor requires a constant current to keep the contactor closed to maintain electrical connection to the battery. The present disclosure describes the use of at least two different signals to keep the contactor in the conductive state. These at least two signals can vary in electrical energy and can be selected based on the vehicle condition.

[0004] In one example, a vehicle includes a traction battery and circuitry that selectively connects the traction battery to a charging source or an electric motor. The charging circuitry includes an open state, a first closed state, and a second closed state. The open state is electrically non-conductive. The closed states are electrically conductive and have different performance associated with them.

[0005] A controller is configured to provide signals to control the circuitry state.

[0006] Other such vehicles are known from DE 10 2013 201 296 A1, DE 10 2011 101 760 A1 DE 11 2010 002 427 T5, DE 102 20 349 A1 and DE 100 60 873 A1. Fig. 1 is a hybrid electric vehicle that can be used with the described systems and methods. Fig. Figure 2 is a detailed view of a battery for a hybrid electric vehicle. Fig. 3 is a schematic view of a system including a hybrid electric vehicle. Fig. 4 is a flowchart of a method according to an example.

[0007] As an overview, the present disclosure describes systems and methods for reducing electrical power consumption while an electric vehicle is charging. Electric vehicles (EVs) may use one or more main contactors (e.g., large relays) to control the connection between the high-voltage traction battery and the rest of the vehicle. Power from the traction battery is used primarily for propulsion, but also for other uses, including providing lower voltage power, for example, 12V power, through a DC-to-DC converter. A battery control module (BCM) drives the contactor coils with lower voltage power according to a strategy implemented in embedded software. There are two setpoints for controlling power to the contactor coils.Full power is initially applied to the coils to guarantee immediate contact closure. After successful closure, the power is reduced to a lower level that guarantees closure under worst-case vibration and shock conditions, taking into account contactor mounting location, contactor orientation, etc. Plug-in hybrid electric vehicles (PHEVs) and battery electric vehicles (BEVs) both have charging modes that require the vehicle to be stationary when plugged in or otherwise connected to an electrical energy source, such as a charging source. There are conditions where lower power loads are required while the vehicle is charging, for example, to precondition the cabin.This use case results in the BCM driving the main contactors at a power level specified for worst-case road load conditions while the vehicle is stationary, i.e., not on the road. This results in wasted electrical energy.

[0008] As described herein, multiple closure setpoints are provided, with one closure setpoint using less energy than another. In one example, a three-level setpoint strategy is used for the main contactor control, that is, one closure setpoint to move the contactor to the closed position and two closure setpoints to keep the contactor closed. The third setpoint, which may be low power or lower current than the other two setpoints, is used when the electric vehicle, for example, a PHEV or a BEV, is charging. As with the existing two values, the contactor coil current value for the third setpoint may be maintained by a control loop in embedded software.It is expected that the reduction in coil current for the novel third set point to hold the contactor during vehicle charging will provide significant benefits when considering the efficiency losses of DC-DC conversion to provide the lower voltage to energize the contactor.

[0009] Fig. 1 shows an example of a hybrid electric vehicle 102, e.g., a plug-in hybrid electric vehicle. A plug-in hybrid electric vehicle 102 may include one or more electric motors 104 mechanically connected to a hybrid transmission 106. Furthermore, the hybrid transmission 106 is mechanically connected to an internal combustion engine 108. The hybrid transmission 106 may also be mechanically connected to a driveshaft 110, which is mechanically connected to the wheels 112. The electric motors 104 may provide torque to the wheels when the internal combustion engine 108 is turned on. The electric motor 104 consumes electrical energy, e.g., from a traction battery, to provide torque to propel the vehicle 102. The electric motors 104 may provide deceleration capability when the internal combustion engine 108 is turned off.The electric motors 104 may be configured as generators and may 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 because the hybrid electric vehicle 102 may operate in electric mode under certain conditions.

[0010] The traction battery 114 stores energy that can be used by the electric motors 104. The traction battery 114 typically provides a high-voltage direct current output. The battery output is in response to a battery power demand, which may be calculated from the feedforward battery power value as a function of the driver power demand and the engine power demand, which in turn may be based on speed and torque determinations. The traction battery 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 capability for the bidirectional transfer of energy between the traction battery 114 and the electric motors 104.For example, a typical traction battery 114 may provide a DC voltage, while the electric motors 104 may require three-phase current to operate. The power electronics module 116 may convert the DC voltage to the three-phase current required by the electric motors 104. In a regenerative mode, the power electronics module 116 converts the three-phase current from the electric motors 104 acting as generators to the DC voltage required by the traction battery 114. The methods described herein are equally applicable to an all-electric vehicle or any other device that uses a battery pack. The traction battery 114 may experience degradation during certain uses of the vehicle. One use where degradation occurs is storage at a high state of charge (SOC).Temperature can also be a factor in degradation. Battery degradation is unique to a specific battery type. Battery degradation may include the inability of a traction battery 114 to retain a certain amount of charge; for example, fewer kilowatt-hours or ampere-hours are stored in the traction battery 114.

[0011] In addition to providing power for propulsion, the traction battery 114 (or battery pack) may provide power for other vehicle power systems. A typical system may include a DC / DC converter module 118 that converts the high-voltage DC output of the traction battery 114 to a low-voltage DC supply compatible with other vehicle loads. Other high-voltage loads, such as compressors and electric heaters, may be connected directly from the traction battery 114 to the high-voltage bus. In a typical vehicle, the low-voltage systems are electrically connected to a 12V battery 120. A fully electric vehicle may have a similar architecture but without the internal combustion engine 108.

[0012] The traction battery 114 can be recharged by an external power source 126. The battery charge storage status can be measured as a state of charge. The external power source 126 can supply AC or DC power to the vehicle 102 by electrically connecting through a charging port 124. The charging port 124 can be any type of port configured to transfer power from the external power source 126 to the vehicle 102. The charging port 124 can be electrically connected to a power conversion module 122. The power conversion module can condition the power from the external power source 126 to supply the appropriate voltage and current levels to the traction battery 114. In some applications, the external power source 126 can be configured to supply the appropriate voltage and current levels to the traction battery 114, and the power conversion module 122 may not be required.The functions of the power conversion module 122 may be located in the external power source 126 in some applications. The vehicle's internal combustion engine, transmission, electric motors, battery, power conversion, and power electronics may be controlled by a powertrain control module (PCM) 128.

[0013] A contactor 135 is provided to electrically connect and disconnect the traction battery 114 from the other high-voltage components in the vehicle 102. The contactor 135 can receive control signals from the power electronics module 116 to change the state of the contactor from an open circuit (in its de-energized state) to a closed circuit (its energized state). The contactor 135 is operated by three signals: A high-energy signal to move the contacts in the contactor 135 to the closed position. A medium-energy signal that maintains the contactor 135 in the closed position even when the vehicle is "on" or the vehicle is moving. This medium-energy signal must ensure that the electrical connection from the battery to the rest of the vehicle, e.g., the powertrain and engine 104, is closed so that electrical energy from the traction battery 114 can power the vehicle.A low-energy signal is also applied. This signal has less power than the other two signals and can hold the contactor contacts closed when the vehicle is stationary. The low-energy signal can be used when the vehicle is charging and not moving. The contactor requires less energy to remain closed when the vehicle is off or not moving because the mechanical movements or vibrations are not generated by the vehicle and do not need to be overcome by contactor 135. Contactor 135 requires the medium-energy signal to ensure that it maintains a closed contact regardless of the vehicle's movement, vibration, shock, or other motion.

[0014] In addition to the representation of a plug-in hybrid vehicle, Fig. 1 may represent a battery electric vehicle (BEV) if component 108 is removed. Similarly, Fig. 1 may represent a traditional hybrid electric vehicle (HEV) or a power-split hybrid electric vehicle if components 122, 124, and 126 are removed. Fig. Figure 1 also illustrates the high-voltage system, which includes the electric motor(s), the power electronics module 116, the DC / DC converter module 118, the power conversion module 122, and the traction battery 114. The high-voltage system and battery pack include high-voltage components including busbars, connectors, high-voltage wires, and circuit breakers.

[0015] The individual battery cells within a battery pack can be constructed from a variety of chemical formulations. Typical battery pack chemistries include lead-acid, nickel-cadmium (NiCd), nickel-metal hydride (NiMH), lithium-ion, or lithium-ion polymer. Fig. Figure 2 shows a typical battery pack 200 in a simple series configuration of N battery cell modules 202. The battery cell modules 202 may include a single battery cell or multiple battery cells electrically connected in parallel. However, the battery pack may consist 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 important in certain arrangements to establish a reliable battery monitoring system.The accuracy of the current sensor can be useful for estimating battery state of charge and capacity. A current sensor can use a variety of methods based on physical principles to detect current, including a Hall-effect integrated circuit (IC) sensor, a transformer or current clamp, a resistor where the voltage is directly proportional to the current through it, fiber optics using an interferometer to measure the phase change in light created by a magnetic field, or a Rogowski coil. If a battery cell is charging or discharging such that the current entering or leaving the battery cell exceeds a threshold, the battery control module can disconnect the battery cell using a circuit interrupt device (CID), such as a fuse or circuit breaker.

[0016] 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 the battery cell voltage. The battery cell voltage may be the voltage of a single battery or a group of batteries electrically connected in parallel or in series. The battery pack 200 may contain up to N cSensor modules 204 may be used to measure the characteristics of all 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 include a battery distribution module (BDM) 214, which controls the flow of power into and out of the battery pack 200.

[0017] In the example of Fig. 2, the positive terminal and the negative terminal can be connected to the terminals of a contactor (in Fig. 2 not shown). The contactor can selectively connect the traction battery 114 to other circuitry and can be closed (e.g., electrically conductive) by electrically energizing a coil, moving the terminals into contact with each other, thereby electrically connecting the battery to a circuitry. When the contactor is open (e.g., not electrically conductive), the coil is not energized and does not have enough energy to move the terminals into contact and maintain contact with each other.

[0018] While the contactor 135 is shown at the top of the vehicle 102 outside the traction battery 114, the contactor 135 may also be positioned inside the traction battery 114.

[0019] Fig. 3 shows a system 300 having an electrical system 301 that electrically connects the power source 126 and the electric motor 104 to the traction battery 114. The electrical system 301 includes a contactor 311 and charging circuitry 313. The contactor 311 is configured to selectively electrically connect the traction battery 114 to circuitry connected to either the electric motor 104 or the power source 126. The contactor 311 includes four components. A housing that supports the other components and can help protect against unwanted contact with the other components. The housing can also protect against the environment. The contactor 311 includes contacts that can selectively physically move to come into mechanical and electrical contact. The contacts carry currents when closed. Examples of contacts include power contacts, auxiliary contacts, and contact springs.A coil is mounted in the housing and is an electromagnet that provides the driving force to close the contacts and electrically connect the traction battery to the electrical system 301 and thus to the electric motor 104 and the power source 126.

[0020] The charging circuitry 313 may connect the power source to the traction battery 114 to charge the traction battery 114 by forcing electrical current into the battery so that the battery stores electrical energy.

[0021] The electrical system 301 can also supply electrical power to a DC / DC converter 303. The DC / DC converter 303 steps down the voltage of the electrical system 301, and in particular the DC voltage from the traction battery 114, to a standard voltage used by vehicle systems 305, e.g., entertainment systems, cabin control systems, lighting, etc. An example of a standard vehicle voltage is 12 volts. DC-DC conversion results in electrical losses. DC / DC can schematically separate the high voltage (HV) side from the low voltage (LV) side in the vehicle's electrical systems. The high voltage side is the traction battery side. The low voltage side is opposite the high voltage and on the other side of the DC / DC converter. The low voltage side can be the 12 volt side. The DC / DC converter 303 can also supply the electrical power or signal 320 that activates the contactor 311.This electrical energy may be stored in an auxiliary battery or otherwise conditioned by other circuitry on the low-voltage side of the vehicle. As a result, the signal required to activate contactor 311 has suffered losses due to the DC / DC converter stepping down the voltage from the traction battery voltage. In a charging state, the energy converted by DC / DC converter 303 is used by electrical system 301 to close contactor 311, allowing electrical energy to flow from power source 126 to traction battery 114. A high-power signal is required to move the contacts in contactor 311 from an open, resting state to a closed, energized state.When the vehicle is moving or in the on position, a first hold signal is then applied to the contacts to keep the contacts closed under all operating conditions to supply power from the battery to the electrical system and / or electric motor 104. When the vehicle is at rest or in the "off" position, a second hold signal is then applied to the contacts to keep the contacts closed under this stable vehicle condition to supply power from power source 126 through the contactor to the traction battery 114. Because the vehicle, and thus the contactor, does not experience vibration, road effects, or other mechanical stress when it is off or plugged into a power source 126, the second hold signal has less holding power than the first hold signal. In one example, the first hold signal is approximately 200 milliamperes + / - 10 milliamperes.In one example, the first hold signal is about 150 milliamperes + / - 10 milliamperes. In one example, the high power signal is about 300 milliamperes + / - 10 milliamperes. The ranges for these signals can also be + / - 5 milliamperes or + / - 15 milliamperes. The second hold signal can be half the power of the high power signal. In one example, the second hold signal is 20-30% less than the first hold signal. In one example, the second hold signal is 25% less than the first hold signal. In one example, the second hold signal is 50% less than the first hold signal. In one example, the first hold signal is 30% greater than the second hold signal. In one example, the first hold signal is 50% greater than the second hold signal. These percentages can also be in ranges of + / - 2%, + / - 5%, or + / - 10%. In one example, the voltage for the contactor excitation signals is determined by the vehicle busbar voltage, e.g.12 volts, supplied.

[0022] Fig. Figure 4 shows a flowchart according to a method 400. At 401, it is determined whether energy should be supplied from the traction battery or from the traction battery. If not, the method then ends and the contactor remains in its open default state. If yes, the contactor is then closed at 402 with a signal at the pull-in setpoint, e.g., the high-energy signal from Fig.3. At 403, it is determined whether the vehicle is charging. For example, the vehicle is connected to an external charger. In one example, the vehicle may also be charging by an on-board electric motor. If the vehicle is not charging (i.e., step 403 is no), then the contactor is held closed with a high setpoint hold signal. If the vehicle is charging (i.e., step 403 is yes), then the contactor is held closed with a low setpoint hold signal. In one example, the low setpoint hold signal may be used when the vehicle is not "on" because the vehicle is not experiencing vibrations or mechanical shocks that could overcome the contactor closing force and open the contacts. The low setpoint hold signal has less power than the high setpoint hold signal. In one example, the low setpoint hold signal has less current than the high setpoint hold signal.

Claims

[1] Vehicle (102) comprising: a traction battery (114); a circuit arrangement and a controller that is programmed to Applying a first signal to the circuit arrangement during vehicle travel to maintain an electrical connection between the traction battery (114) and an electric motor (104), and Applying a second signal to the circuitry during battery charging while the vehicle (102) is stationary to maintain an electrical connection between the traction battery (114) and a charging source, the first signal having more power than the second signal. [2] The vehicle (102) of claim 1, wherein the controller is further programmed to apply a third signal to the circuitry to connect the traction battery (114) to the electric motor (104), the third signal having more power than the first signal. [3] The vehicle (102) of claim 2, wherein a magnitude of the power of the third signal is about 50% greater than a magnitude of the power of the first signal and about 200% greater than a magnitude of the power of the second signal. [4] The vehicle (102) of claim 1, wherein the controller is further programmed to apply a third signal to the circuitry to connect the traction battery (114) to the charging source, the third signal having more power than the first signal. [5] The vehicle (102) of claim 4, wherein a magnitude of the power of the third signal is about 50% greater than a magnitude of the power of the first signal and about 200% greater than a magnitude of the power of the second signal. [6] Traction battery control method comprising: Applying a closing signal to a contactor (135, 311) to electrically connect a traction battery (114) to a circuit arrangement to drive an electric motor (104); Applying a first hold signal (30, 50) to the contactor (135, 311) to hold the contactor (135, 311) in a closed state when the vehicle (102) is in motion, the first hold signal (30, 50) having less power than the close signal; Applying the closing signal to the contactor (135, 311) to electrically connect the traction battery (114) to the circuit arrangement to charge the battery (120); and Applying a second hold signal (20-30, 50) to the contactor (135, 311) to hold the contactor (135, 311) in a closed state during charging of the battery (120) while the vehicle (102) is stationary, wherein the second hold signal (20-30, 50) has less power than the first hold signal (30, 50). [7] The method of claim 6, wherein a magnitude of the power associated with the close signal is about 50% greater than a magnitude of the power associated with the first hold signal (30, 50) and about 200% greater than a magnitude of the power associated with the second hold signal (20-30, 50). [8] The method of claim 6, wherein a current associated with the close signal has a magnitude of about 300 milliamperes, a current associated with the first hold signal (30, 50) has a magnitude of about 200 milliamperes, and a current associated with the second hold signal (20-30, 50) has a magnitude of about 150 milliamperes. [9] The method of claim 6, wherein the second hold signal (20-30, 50) further has less voltage than the first hold signal (30, 50). [10] The method of claim 9, wherein the closing signal further has more voltage than the first holding signal (30, 50). [11] Vehicle (102) comprising: a traction battery (114); a circuit arrangement configured to selectively connect the traction battery (114) to an electric motor (104) or a charging source, the circuit arrangement having an open state in the absence of an applied voltage, a first closed state in the presence of a first applied voltage, and a second closed state in the presence of a second applied voltage that is less than the first applied voltage; and a controller programmed to deliver the applied voltages. [12] The vehicle (102) of claim 11, wherein the controller is further programmed to provide the first applied voltage while the vehicle (102) is traveling to maintain the electrical connection between the battery (120) and the electric motor (104). [13] The vehicle (102) of claim 11, wherein the controller is further programmed to provide the second voltage during charging of the battery (120) while the vehicle (102) is stationary to maintain electrical communication between the battery (120) and the charging source. [14] The vehicle (102) of claim 11, wherein a power associated with the first applied voltage is greater than a power associated with the second applied voltage. [15] The vehicle (102) of claim 11, wherein the first and second applied voltages are associated with a vehicle system bus voltage.

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