The present document relates to charging of electric vehicles.
In order to reduce the charging time for electric vehicles, DC fast charge stations have been created with capabilities for currents up to 500 amps and increasing to over 2,000 amps in the future. With these very high charging currents, electric vehicle systems may demand methods and systems to efficiently transfer the energy from the charging station to the high voltage batteries of the electric vehicles without degrading the vehicle or the charging station. To charge smoothly, protection systems may be included that mitigate transmission of current spikes to the electric vehicle in the event of a short circuit. Due to the large stored energy and low resistance wiring and connections in the vehicle, short circuit currents can reach 200,000 amps with voltages at 1,000 volts. When subject to such large short circuit currents, vehicle components, including charging infrastructure, may become degraded due to generation of large quantities of heat that may exceed a heat tolerance of the components. Thus, development of a strategy to provide efficient charging as well as short circuit circumvention may be desirable.
In one example, the issues described above may be addressed by a system for controlling charging of a vehicle, including a charge coupler and a control box electrically coupled to the charge coupler. The control box may include a fuse device, at least one temperature sensor for monitoring a temperature of the fuse device, a cooling system for cooling the fuse device based on a signal from the temperature sensor, and a charging interface communicatively coupled to the temperature sensor, wherein the fuse device is configured to be current limiting under a short circuit condition to mitigate an overcurrent event. In this way, protection of the vehicle against large short circuit currents may be provided at the point of connection to the DC charging current input and the protection may be adjusted based on the type of charging provided to the vehicle.
As one example, temperature sensing of the fuse device may allow for detection and control of charging current based on the fuse device temperature. A control box [herein referred to as an integrated protection control box (IPCB)] may mitigate transmission of short circuit currents to a vehicle with low power loss and allow for bi-directional current transfer. Coordination between the fuse device, active cooling, and temperature detection may allow for both reliable operation with low power loss as well as protection of fault conditions. Further, the IPCB may protect against short-circuits without inhibiting vehicle-to-grid energy transfer.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
The following description relates to systems and methods for short circuit protection of a charge coupler for an electric vehicle such as the charge coupler of
Turning now to
Vehicle charging station 130 electrically couples energy from energy grid 103 to electric vehicle 110 through a first wire 107a and high voltage charge coupler (HV CCS) 104 and/or through a second wire 107b and a high voltage megawatt charge coupler (HV MCS) 106. In one example, HV CCS 104 may be selected when electric vehicle 110 is a personal electric vehicle while HV MCS 106 may be selected when electric vehicle 110 is a commercial sized electric vehicle such as a large truck or bus. HV CCS 104 and/or HV MCS 106 may be electrically coupled to the DC output 116 via a charge coupler 102. Charge coupler 102 may connect to an IPCB 114.
IPCB 114 may be configured to prevent short circuit current spikes from reaching DC output 116. IPCB 114 may include a fuse device 118, a cooling system 120 and a charging interface connector 122. Short circuit current spikes can be caused by degradation of AC to DC converters 131 internal to the vehicle charging station 130 or may also be caused by a break in first wire 107a or second wire 107b. Further, IPCB 114 may be configured to allow current to flow from energy grid 103 to DC output 116 or from DC output 116 back to energy grid 103. Criteria for selection of the fuse device for IPCB 114 are discussed below with respect to
A high speed fuse may act as a current limiting device and may be used as a fuse device for an IPCB, such as IPCB 114 of
Turning now to
The current-limiting effect of the high speed fuse may be from a fuse element of the high speed fuse configured to heat or melt when an overcurrent is passing through the high speed fuse causing the resistance of the fuse to increase. In this way, the high speed fuse prevents the current spike from being transmitted through the high speed fuse. Graph 200 shows a threshold magnitude of prospective current (IP) relative to a fuse's peak let through current is demanded before the current-limiting effect may be realized for a fuse with a specific normal current rating (IN). The fuse device may be current limiting for the current input range expected for a short circuit condition.
A high speed fuse may be selected to protect HV CCS type 1 and type 2 connections (e.g., a connection between HV CCS 104 and DC output 116 via charge coupler 102 as shown in
Table 1 below shows I2T rating for fuses having a voltage rating of 1000 Vdc and in a range of current ratings from 250 A to 800 A. Each fuse may correspond to plots shown in
In addition to a maximum peak current and I2T, a fuse device in an IPCB may operate in an environment where an environmental temperature may reach 85° C. Environmental temperatures and other factors may affect a permissible current load for a fuse. The permissible current load may correspond to an amount of current which may pass through the fuse before it becomes current limiting. Further, the permissible current load may be less than a rated current of the fuse device. Equation 1 below may be used to calculate a maximum permissible continuous RMS load current (e.g., permissible current load, Irms) for a fuse. In one example, an Irms of at least 500 A may be desired to meet the current demand of a charging device such as charge coupler 102 of
I
rms
=I
n
×K
t
×K
e
×K
v
×K
a
×K
x (1)
Normal current rating (IN or In) is the rated current of a given fuse link, Kt is an ambient temperature correction factor (as discussed below with respect to
An Irms for a 630 A fuse operating at 85° C. may be calculated using equation 1. In may be 630 A, Ke may be assumed based on the required bus bar size, Ka may be 0.9 at 4000 m, and Kx may be assumed to be 0.8 for an uncooled box. Kv may be determined by plot 600 of
Kt may be determined by plot 500 of
Turning now to
Temperature sensors 708a and 708b may be thermally coupled to bus bar 714 at opposite sides of fuse device 702 along the x-axis. Temperature sensor 708a may be positioned at charger side 703 of fuse device 702 and temperature sensor 708b may positioned at a vehicle side 705 of fuse device 702. Bus bar 714 may be thermally coupled to fuse device 702. In this way, temperature sensors 708a and 708b may be used in combination or separately to monitor a temperature of fuse device 702. Temperature sensors 708a and 708b may enable a charging current to be adjusted based a monitored temperature of fuse device 702. Temperature sensors 708a and 708b may be communicatively coupled to a charging interface connector 720, and the charging interface may be included in IPCB 700 but spaced away from fuse device 702 bus bar 714. Further, charging interface connector 720 may include a processor and non-volatile memory, configured to store instructions. Charging interface connector 720 may be configured to receive a temperature input from temperature sensors 708a and 708b and in response, modify a charging or discharging current input to IPCB 700 in response to the temperature input. For example, temperature sensor 708a may send a temperature reading above a temperature threshold. In response, the charging interface may decrease the charging current input.
IPCB 700 may further include a cooling system 722 for moderating a temperature of fuse device 702. Fuse device 702 may be cooled by cooling system 722 which may include a thermal pad 716, a cold plate 706, and a cooling chamber 704. In one example cooling chamber 704 may include a coolant tube routed in an area of fuse device 702. In an alternate example, the cooling chamber 704 may be formed as a coolant path between the cold plate 706 and a lower plate of the cooling system 722. Fuse device 702 may sit on thermal pad 716 (e.g., fuse device 702 may be above thermal pad 716 on a y-axis). Further, a surface of thermal pad 716 may be in face sharing contact with fuse device 702. Thermal pad 716 may be positioned between fuse device 702 and cold plate 706 along a y-axis. A lower surface (e.g., with respect to the y-axis) of thermal pad 716 may be in face sharing contact with an upper (e.g., with respect to the y-axis) surface of cold plate 706. Thermal pad 716 may be a compressible pad configured to transfer thermal energy from fuse device 702 to cold plate 706. Thermal pad 716 may also provide electrical isolation between fuse device 702 and the cold plate 706. Coolant may flow through cooling chamber 704 following arrow 718. The coolant may be fluidically coupled to a liquid coolant circuit of a vehicle. In this way, a component which decreases a temperature of the coolant (e.g., a heat exchanger) of cooling system 722 may be positioned external to enclosure 724. In an alternate embodiment, a finned metal heatsink (not shown) may be coupled to thermal pad 716 and may conductively draw power (e.g., thermal energy) away from the fusing element. Cooling system 722 may operate independent of a temperature of fuse device 702 or alternatively, cooling system 722 may be partially controlled by charging interface connector 720.
Turning now to
At 302, method 300 includes determining if charging is demanded. If charging is demanded, method 300 proceeds to 304 and includes flowing current from an energy grid (e.g., energy grid 103 to the DC output. If charging is not demanded, then discharging is demanded and method 300 proceeds to 306 and includes flowing current from the DC output to the energy grid. Following step 304 or step 306, method 300 proceeds to 308. Additionally, a third state of no charging and no discharging may be provided.
At 308, method 300 includes receiving a temperature reading from a temperature sensor. The temperature sensor may be temperature sensor 708a and/or temperature sensor 708b as described above with respect to
At 310, method 300 includes determining if the received temperature is above a threshold temperature. The threshold temperature may be a temperature above which the expected life of the fuse at a specific demanded charging current may be reduced. As one example, the demanded charging current may be 500 A which may correspond to a temperature threshold equal to 60° C. when the fuse device is a high speed fuse rated at 630 A. The temperature threshold may be determined based on equation (1) and a temperature correction factor as described in
If, at 310, the received temperature is not above the threshold temperature (e.g., at or below the threshold temperature), method 300 proceeds to 312 includes maintaining or increasing the charging current or discharging current. Maintaining or increasing the charging or discharging current may include maintaining or increasing a magnitude of current flowing through the fuse device, either to or from the DC output. If the temperature is at or close to (e.g., within 5% of) the threshold temperature, the charging or discharging current may be maintained. In this way, the charging or discharging current may be maximized based on the temperature of fuse device and an overall charging time may be decreased. If, at 310, the received temperature is above the threshold temperature, method 300 proceeds to 314 to decrease the charging current or discharging current. Decreasing the charging or discharging current includes decreasing a magnitude of current flowing through the fuse device, either to or from the DC output.
Optionally, at 316, method 300 includes adjusting a cooling system of the IPCB (e.g., cooling system 722). The cooling system may be adjusted enhance cooling of the fuse device, thereby decreasing a temperature of the fuse device and allowing an increase in charging or discharging current. In one example, the cooling system may be adjusted by adjusting a flow rate of coolant through a coolant tube. As another example, adjusting the cooling system may include altering a path of the coolant such that the coolant cools only to the fuse device and not to other components of the vehicle, thereby decreasing an overall heat load on the cooling system. In this way, a temperature of the fuse device may be decreased and a current passing through the fuse device may be maintained below the threshold current. Method 300 returns to the start.
The technical effect of method 300 is that an amount of current flowing through a fuse device of an IPCB may be optimized. In this way, a charging or discharging current may be more sensitive to operating conditions of the fuse device, thereby realizing both fast charging/discharging times while also mitigating transmission of short circuit currents to a DC output. The IPCB box may protect a DC output (e.g., a vehicle) from degradation due to short-circuit currents while still allowing bi-directional current flow, both to and from the DC output. Further, the charging current may be efficiently transferred through the IPCB with low power loss.
The disclosure also provides support for a system for controlling charging of a vehicle, comprising: a charge coupler, an integrated protection control box (IPCB) electrically coupled to the charge coupler, the IPCB including, a fuse device, at least one temperature sensor for monitoring a temperature of the fuse device, a cooling system for cooling the fuse device, and a charging interface connector communicatively coupled to the at least one temperature sensor, wherein the fuse device is configured to be current limiting under a short circuit condition to mitigate an overcurrent event. In a first example of the system, the fuse device is opened when a charging current increases above a threshold current to prevent transmission of the charging current to the vehicle. In a second example of the system, optionally including the first example, a permissible current of the fuse device is increased when the fuse device is cooled by the cooling system. In a third example of the system, optionally including one or both of the first and second examples, the IPCB further includes a bus bar and the at least one temperature sensor is coupled to the bus bar. In a fourth example of the system, optionally including one or more or each of the first through third examples, the cooling system is coupled to a coolant circuit of the vehicle. In a fifth example of the system, optionally including one or more or each of the first through fourth examples, the cooling system is coupled to a finned metal heatsink. In a sixth example of the system, optionally including one or more or each of the first through fifth examples, the IPCB allows bi-directional current flow.
The disclosure also provides support for a method for controlling overcurrent events during vehicle charging, comprising: determining if charging is demanded, receiving a temperature reading from a temperature sensor coupled to a fuse device of a control box, the control box coupled to a charging device of a vehicle to mitigate transmission of a short-circuit from the charging device to the vehicle and including a charging interface connector configured to control a charging current and a discharging current, responsive to the received temperature being above a threshold temperature and demanded charging, decreasing the charging current, and in response to the received temperature being below the threshold temperature and demanded charging increasing the charging current. In a first example of the method, the temperature sensor is positioned on a charger side of the fuse device and/or a vehicle side of the fuse device. In a second example of the method, optionally including the first example, the method further comprises: in response to the received temperature being above the threshold temperature and demanded discharging, decreasing the discharging current, and in response to the received temperature being below the threshold temperature and demanded discharging, increasing the discharging current. In a third example of the method, optionally including one or both of the first and second examples, the threshold temperature is set based on an ambient temperature correction for a permissible current of the fuse device. In a fourth example of the method, optionally including one or more or each of the first through third examples, the permissible current is less than a rated current of the fuse device. In a fifth example of the method, optionally including one or more or each of the first through fourth examples, the method further comprises: in response to the received temperature being equal to the threshold temperature, maintaining the charging current. In a sixth example of the method, optionally including one or more or each of the first through fifth examples, the temperature sensor is coupled to the fuse device via a bus bar.
The disclosure also provides support for an integrated protection control box of a vehicle, comprising: a fuse device with fuse elements configured to open based on a current at a charging device coupled to the integrated protection control box, a cooling system for maintaining a temperature of the fuse device below a threshold temperature, and a charging interface connector configured to control the current at the charging device based on the temperature of the fuse device. In a first example of the system, the integrated protection control box is configured with software configured to estimate the temperature of the fuse device based on one or more operating parameters. In a second example of the system, optionally including the first example, a surface of the fuse device is in face sharing contact with a thermal pad of the cooling system. In a third example of the system, optionally including one or both of the first and second examples, a surface of the thermal pad is in face sharing contact with a cold plate of the cooling system. In a fourth example of the system, optionally including one or more or each of the first through third examples, the integrated protection control box is positioned inside an enclosure. In a fifth example of the system, optionally including one or more or each of the first through fourth examples, the cooling system includes a cooler positioned external to the enclosure.
The present application claims priority to U.S. Provisional Application No. 63/268,257, entitled “SYSTEMS AND METHODS FOR VEHICLE CHARGING”, and filed on Feb. 18, 2022. The entire contents of the above-identified application are hereby incorporated by reference for all purposes.
Number | Date | Country | |
---|---|---|---|
63268257 | Feb 2022 | US |