Abstract:
A method of operating an electric vehicle charging system utilizing a plurality of charging units and charging points is disclosed. The method includes determining a rate of charge to be delivered to each vehicle and then allocating a respective portion of the total charging capacity of the charging station to each vehicle.

Description:
FIELD OF THE INVENTION 
     The present invention relates to battery charging systems. 
     BACKGROUND 
     With the increase in popularity of electric and hybrid vehicles that utilize rechargeable battery systems for at least a portion of their power source, the need for charging stations to recharge these battery systems is increasing. Although most battery systems can be recharged from a domestic wall socket, many support faster charging at higher voltages and currents which requires more expensive dedicated equipment with specialized connectors. Some systems may use 240 Volt AC or 500 Volt DC high-current to provide greatly accelerated charging. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is illustrated by way of example, and not limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which: 
         FIG. 1  illustrates an exemplary chart showing a how charging capacity demand changes over time for a public electric vehicle charging station; 
         FIG. 2  illustrates one embodiment of an electric vehicle charging station that provides increased charging capacity utilization and increased vehicle capacity; 
         FIG. 3  shows an exemplary system diagram for a control unit; 
         FIG. 4  illustrates an exemplary sequence of operations to manage the allocation of charging capacity to vehicles requiring charge in a charging station; 
         FIG. 5  illustrates an exemplary sequence of operations to determine the allocation of charging capacity to vehicles coupled to a charging station, and 
         FIG. 6  illustrates an exemplary sequence of operations to determine the charging requirement of vehicles coupled to a charging station; and 
         FIG. 7  provides an example of a table showing the relationship between charging priority and price paid. 
     
    
    
     DETAILED DESCRIPTION 
     In various embodiments disclosed herein, an electric vehicle charging station is described that utilizes a plurality of dynamically allocated charger units and charger points to provide a number of benefits including, without limitation, a) increasing the utilization and efficiency of the available charging capacity of the charging station, b) increasing the number of vehicles that may be using the charging station at any one time, c) providing more options (including dynamically determined options) to the operators of the vehicles using the charging station regarding charging time, cost, and other factors, and d) allowing for easier maintenance of the charging station, and so forth. 
     Depending on the needs of the vehicle operator and the current state-of-charge of the battery system, the power required to charge a vehicle may vary by more than an order of magnitude. For example, a battery system requiring a 30 minute charge may require 16 times the power of a similar battery system in a similar state-of-charge requiring an 8 hour charge. An example of the charging demand profile for an electric vehicle charging station is shown in  FIG. 1 . While the charging station is easily able to accommodate the power requirements of several attached vehicles with longer required charging periods, the high power demand of 2 vehicles requiring a very short charging period during the mid-day time period causes the charging station to exceed its available charging capacity. 
       FIG. 2  illustrates one embodiment of an improved charging station  200 . A plurality of power sources  230  provide power to a plurality of charger units  210  that regulate the power and then deliver it via a power distribution network  220  to plurality of charger points  250  that are in turn coupled a plurality of vehicles requiring charge. The power source provides power to the charger units. The form of the power (e.g., AC or DC, low or high voltage, or other forms) delivered by the power source may vary depending on the specific needs of the local environment and the type and availability of external power for the system. Some charging stations may be coupled to a national or local grid. Others may be coupled to solar panels, wind turbines, self-contained generators (e.g., combustion engines), or other forms and combinations of energy supply. The power sources may be physically adjacent to the charger units, or they may be in one or more remote locations. The charger units convert energy from the power sources, using energy conversion techniques such as, but not limited to, DC to DC conversion, AC to DC conversion, DC to AC conversion, AC to AC conversion, current limiting and voltage regulation, as determined, at least in part, by the charging requirements of the vehicle that is using power from the charger unit and/or requirements of the vehicle operator (e.g., the vehicle driver, owner, custodian or other person available to specify such requirements). Power provided from the charger unit may vary over time as necessary to improve factors including, but not limited to, charger unit efficiency, charge time, battery life and charging cost to the vehicle operator. 
     One or more control units  240 , referred to collectively herein as “the control unit” manage the process of delivering power to the vehicles using the system. The control unit is coupled to the other components of the charging station using a control network  270  which may consist of a shared communication bus, point to point network, wireless network (e.g., Wi-Fi, Bluetooth, Cellular, etc.) or other form of communication mechanism or combination of communication mechanisms. The control unit may be physically co-located with the other components of the charging station, or remotely located (e.g., in a centralized data processing center that manages power delivery in multiple charging stations  200 . The control unit monitors system information from, but not limited to, the power sources, the charger units, the charger points, the vehicle and the vehicle operator to dynamically allocate charger units to charger points and to determine the various power delivery parameters for each vehicle using the system. The charger unit allocation and power delivery parameters may change over time (i.e., dynamically, during the charging interval) in response to changing system information. 
       FIG. 3  depicts an embodiment of a control unit that may be used to implement each or all of the control units of  FIG. 2 . As shown, the control unit includes a processor  310 , memory  320 , and I/O block  330  coupled together with an interconnect bus. The control unit may include numerous other functional blocks in addition to or within the functional blocks shown, including a user interface to enable control unit programming, maintenance and system-level data collection. The control unit is capable of executing programmed instructions (e.g., stored within memory  320 ) to implement various sequences of operations as described herein 
     Referring again to  FIG. 2 , the power distribution network  220  may be used to connect charger units to charger points as determined by the control unit. Depending on the charging requirements of a vehicle, more than one charger unit may be coupled to a single charger point if the power required by a vehicle exceeds the capacity of a single charger unit. Conversely, if the charging power required by multiple vehicles can be provided by a single charging unit, then multiple charger points may be coupled to a single charger unit. The mechanism for connecting a charger unit to a charger point in the power distribution network may include relays, solid state devices or any other mechanism for delivering electrical power from a power source to a load. Should one or more of the charger units become defective, the control unit may de-allocate and disconnect the charger unit(s) from any charger point(s) to allow the charger unit(s) to be safely replaced while the charging station is in operation. Although the overall capacity of the charging station is reduced by loss of a charger unit, the controller may dynamically re-allocate charger units to charger points so that the station may continue to charge all vehicles using the charging station, though at a potentially reduced rate. The charger point provides a mechanism to connect the vehicle to the charging station. The charger point may require the vehicle operator to physically plug a connector into the car, or it may automatically connect to the car using some predetermined standard mechanism. Associated with the charger point, but not necessarily physically coupled to it, is a UI device  260  that both provides information to and accepts input from the operator of the vehicle regarding the charging of the vehicle. While the UI device may be attached to the charger point, other devices, such as cell phones, operator interfaces or infotainment systems in the vehicle, or other devices, wirelessly or physically coupled to the control unit, may be used to provide information to and receive information from the control units in the charging station. 
       FIG. 4  illustrates an exemplary sequence of operations to manage the allocation of charging capacity to vehicles requiring charge in a charging station. The sequence begins at  410 , where, optionally, the available charging options are determined and presented to the operator of the vehicle. Such options include, but are not limited to, the charge time, the desired resulting state-of-charge after charging completes, and the cost options available. For example, an operator may be prompted to pay more to charge his/her vehicle in a shorter time or to ensure that the charge time is not extended if additional vehicles have coupled to the charging station and the charging demand now exceeds the available charging capacity of the station. Next, at  420 , information is optionally collected regarding operator requirements and options. One embodiment may include the storing of operator-specified preference information, either in a central location, or some other storage, possibly portable, such that the next time the operator charges the vehicle at a charging station having access to the preference information, charging options indicated by the preference information are automatically selected, thereby obviating operator entry of the same information in each charging-station visit reducing the time spent starting the charging process. At operation  430 , the charging system determines the actual charge to be delivered to each vehicle. A more detailed example of this operation is shown in  FIG. 5  and described below. At  440  the charging system allocates charging units to charge points as necessary to meet the charging requirements from operation  430 . (It should be noted that the charging requirements from  430  are maximum requirements, as the vehicle may reduce its requirements over time). Operation  440  may result in one charger unit being coupled to one charger point, multiple charger units being coupled to a single charger point, a single charger unit being coupled to multiple charger points, or any combination of the foregoing. The charger units may also be allocated in such a matter as to improve the overall electrical efficiency (and therefore cost effectiveness) of the charging station. For example, if a charger unit operates at 75% efficiency when loaded at 100% (meaning that 25% of the energy is lost during the conversion) compared to 90% efficiency when loaded at 70%, the whole charging station can operate more economically if the charger units are allocated such that they are loaded at 70%, even if this means that more charger units are in operation. Continuing at operation  450 , the charger system adjusts the charge being delivered by the charger units to the charger points to meet the specific needs of the vehicles coupled to the charger points. For example, near the end of the charging process, the power delivered to a vehicle may be reduced or tapered. At  460 , the vehicle operator is optionally provided with information, including but not limited to, the actual power being delivered to his vehicle, which may be different, more or less, from the requested power due to changes in demands from other vehicles attached to the system. At operation  470 , the system evaluates if there have been any changes in charging demand. This could occur due to various events, including but not limited to, an operator decoupling a vehicle from the charging station, a vehicle being coupled to the charging station, a change in requirements from an operator such as a need for faster charging, or a reduction in charge demand from a specific vehicle because the battery system in the vehicle is reaching a fully charged state. If demand has changed, then the system loops back to  410  and optionally presents vehicle operators with a possibly new set of charging options. If there is no change in charging demand, then the system loops back to reevaluate if any change has occurred. 
       FIG. 5  illustrates an exemplary sequence of operations that may be executed by the controller to determine the allocation of charging capacity to vehicles coupled to a charging station. The sequence begins at operation  510  where the vehicle charging demand (VCD) is determined for each vehicle. The VCD is a rate of charge that is requested for a vehicle at a particular point in time. This process is shown in  FIG. 6  and described in more detail below. Next, at  520 , the vehicle charging priority (VCP) is determined. This priority may be determined based on various factors such as the amount the operator is paying, participation in membership programs, the frequency with which the operator uses the charging station, or other factors. The control unit then uses the VCD and VCP and the system charging capacity at operation  530  to determine the vehicle charging rate (VCR) that will be delivered to the vehicle. The VCR is the actual maximum rate of charge that may be delivered to the vehicle. If the sum of all VCDs is less that the capacity of the charging station, then VCR may equal VCD. If not, then VCR may be adjusted based on VCP. Vehicles with higher VCP may receive disproportionally more power than those vehicles with lower VCP. Various techniques may be used to determine the disproportionality, such as determining the priority based on the price paid by the vehicle operator. One embodiment of the relationship between price and priority is shown in the table in  FIG. 7 . Referring to  FIG. 7 , if a vehicle operator pays $20 for a one hour 50 KW charge (as represented by  710 ), that operator&#39;s vehicle would have high priority and receive disproportionally more charge (and thus reach a charged state more quickly) than the vehicle of an operator who only pays $11 (as represented by  720 ) when the total charging demand from all vehicles exceeds the charging station capacity. Whereas if the charging demand did not exceed the charging station capacity, both of the vehicles would receive the same charging power despite the different price paid. In various other embodiments alternate or additional factors may be incorporated to determine disproportionality, including, without limitation, frequency of use of the charging station by an operator, the location, the time of day, and the time of year. 
       FIG. 6  illustrates one embodiment of a sequence of operations to determine the charging requirement of vehicles coupled to a charging station. Starting at operation  610 , it is determined if the charging station is receiving data from the vehicle (either through the charger point or via some other wireless mechanism) to allow the vehicle to request a specific VCD. If the charging station is receiving data from the vehicle, the sequence continues at  620  where it is determined if the vehicle is requesting a specific VCD. In such cases, processors or other devices in the vehicle may be self-determining the VCD based on the current battery system state-of-charge and other environmental factors (e.g., battery temperature, ambient temperature, etc.), and subsequently communicating the self-determined VCD to the charging station. If the vehicle is requesting a specific VCD (i.e., affirmative determination at  620 ), the sequence continues at operation  650 . Otherwise, if the vehicle has identified itself (decision  630 ), the sequence continues at operation  660 , if not the sequence goes to  640 . If the operator has identified the vehicle, then the sequence continues at  660 , if not the sequence proceeds to operation  670 . At operation  650  the VCD is obtained from the vehicle. At operation  660  the VCD is obtained by using stored charging reference data associated with the identified vehicle. This stored reference data, which may contain information regarding changes to the rate of charge with respect to time, battery system state-of-charge, desired charging time and other factors, may be obtained from the vehicle and/or battery system manufacturer, or accumulated from data collected while charging similar vehicles, or from some other source, or calculated based on various measured factors from the vehicle and battery system. At operation  670  the VCD is determined using charging reference data that is not associated with a specific vehicle. In such cases, as the specific vehicle is not known, the charging parameters may be more conservative, and may be based on various measured factors from the vehicle and battery system. Once the VCD has been determined, the sequence goes to  680 , where the VCD may be adjusted based on operator input, such as desired cost, charging time and other factors. Next at  690 , the electrical connection between the charger point and the vehicle is evaluated. Parameters that may be checked include, but are not limited to, the type of connection (different power levels may require different connections) and the quality of the connection (i.e. the power transfer efficiency, safety). As a result of the checks in  690 , the UI may present information to the operator such that appropriate adjustments may be made if necessary. 
     The charging station described in the foregoing increases the utilization of the available charging capacity of the charging station and the number of vehicles that may be using the charging station at any one time by dynamically allocating the charger units to charger points. Additionally, through use of a UI or similar device, it may provide more options to the operators of the vehicles using the charging station regarding charging time, cost, and other factors. The described charging station also allows for easier maintenance by, for example, permitting the replacement of portions of the charging station, such as the charger units, while the charging station is in operation as these portions may be deselected from use by the control unit. 
     In the foregoing description and in the accompanying drawings, specific terminology and drawing symbols have been set forth to provide a thorough understanding of the present invention. In some instances, the terminology and symbols may imply specific details that are not required to practice the invention. For example, the term “coupled” is used herein to express a direct connection as well as a connection through one or more intervening circuits or structures. Device or system “programming” may include, for example and without limitation, loading a control value into a register, one-time programmable-circuit (e.g., blowing fuses within a configuration circuit during device production) or other storage circuit within an integrated circuit device of the host system (or host device) and thereby control an operational aspect of the host system or establish a host system configuration. The terms “exemplary” and “embodiment” are used to express an example, not a preference or requirement. Signal paths that appear as single conductors may include multiple conductors and vice-versa, and components shown as being included within or forming part of other components may instead be disposed separately from such other components. With regard to flow diagrams and the like, the order of operations may be different from those shown and, where practical, depicted operations may be omitted and/or further operations added. 
     While the invention has been described with reference to specific embodiments thereof, it will be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope. For example, features or aspects of any of the embodiments may be applied, at least where practicable, in combination with any other of the embodiments or in place of counterpart features or aspects thereof. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.