Abstract:
A system for charging an electric or hybrid-electric vehicle, the system comprising: a low power grid interface comprising an AC pole and a DC pole, the AC pole being electrically connected to an electrical power grid; a battery buffer electrically connected to the DC pole of the low power grid interface; and a DC-DC converter having an input DC pole and an output DC pole, the input DC pole being connected to the battery buffer and the output DC pole being connected to an electric vehicle, wherein the connection between the battery buffer and the DC-DC converter is a DC electrical connection.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
       [0001]    This regular U.S. patent application relies upon, claims the benefit of priority to and is a continuation-in-part of U.S. patent application Ser. No. 14/853,955, No. 15/004,980, No. 15/004,974 and No. 15/004,976, which are all incorporated by reference herein in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Field of the Invention 
         [0003]    The disclosed embodiments relate in general to the field of electric charging technology, such as electric vehicle charging, and, more specifically, to a battery-backed DC fast charging system. 
         [0004]    Description of the Related Art 
         [0005]    Wide adoption of electric vehicles by general population requires availability of substantial electrical power capacities for purposes of electric vehicle charging. Depending on the electric vehicle and the charger used, each vehicle may require 40-200 amperes of charging electric current. As would be appreciated by persons of ordinary skill in the art, simultaneous charging of a large number of electric vehicles by residents of a neighborhood may place substantial strain on the existing local power grid, which may not have been designed to accommodate such simultaneous high power loads. With the development of new electric energy storage technologies, such as graphene supercapacitors, which may be charged to full capacity in a substantially shorter times compared to conventional lithium batteries, used in most electric vehicles, this problem of handling high simultaneous charging loads will be exacerbated. In addition to electric vehicles, many houses of the future will incorporate energy storage systems, such as Tesla Powerwall battery, which may also be charged from electric grid. Charging of such energy storage systems may also put additional strain on the existing grid infrastructure. 
         [0006]    Therefore, there is an acute need for high-power DC charging stations for fast electric vehicle charging that would not put excessive strain on the existing power grid. 
       SUMMARY OF THE INVENTION 
       [0007]    The inventive methodology is directed to methods and systems that substantially obviate one or more of the above and other problems associated with conventional systems and methods for electrical vehicle charging and power grid management. 
         [0008]    In accordance with one aspect of the embodiments described herein, there is provided a system for charging an electric or hybrid-electric vehicle, the system comprising: a low power grid interface comprising an AC pole and a DC pole, the AC pole being electrically connected to an electrical power grid; a battery buffer electrically connected to the DC pole of the low power grid interface; and a DC-DC converter having an input DC pole and an output DC pole, the input DC pole being connected to the battery buffer and the output DC pole being connected to an electric vehicle, wherein the connection between the battery buffer and the DC-DC converter is a DC electrical connection. 
         [0009]    In one or more embodiments, the battery buffer comprises second life batteries. 
         [0010]    In one or more embodiments, the DC-DC converter is a buck converter. 
         [0011]    In one or more embodiments, the DC-DC converter is a CHAdeMO converter. 
         [0012]    In one or more embodiments, the battery buffer comprises a battery management system for managing the battery buffer. 
         [0013]    In one or more embodiments, the system further comprises a charge controller operatively coupled at least to the low power grid interface and the DC-DC converter for controlling the operation of the the low power grid interface and the DC-DC converter based on electrical power grid conditions. 
         [0014]    In one or more embodiments, in a first operation mode, the charge controller is configured to cause the the low power grid interface and the DC-DC converter to charge the electric vehicle. 
         [0015]    In one or more embodiments, in a second operation mode, the charge controller is configured to cause the the low power grid interface and the DC-DC converter to stop charging the electric vehicle. 
         [0016]    In one or more embodiments, in a third operation mode, the charge controller is configured to cause electrical power from the battery buffer to be supplied back to the electrical grid. 
         [0017]    In one or more embodiments, in the third operation mode, the low power grid interface operates as a grid-tie inverter. 
         [0018]    In one or more embodiments, wherein the system further comprises a low-profile mechanical assembly for housing the low power grid interface, the battery buffer and the DC-DC converter. 
         [0019]    In one or more embodiments, the low-profile mechanical assembly is adaptable for being placed on a surface of a parking lot. 
         [0020]    In one or more embodiments, the low-profile mechanical assembly comprises two ramps for vehicle wheels. 
         [0021]    In one or more embodiments, the low-profile mechanical assembly comprises a protrusion disposed between the two ramps for vehicle wheels. 
         [0022]    In one or more embodiments, the low-profile mechanical assembly is 5 inches thick 
         [0023]    In one or more embodiments, the low-profile mechanical assembly comprises attachments for loading and unloading. 
         [0024]    In accordance with another aspect of the embodiments described herein, there is provided a method for charging an electric or hybrid-electric vehicle, the method comprising: providing a low power grid interface comprising an AC pole and a DC pole, the AC pole being electrically connected to an electrical power grid; providing a battery buffer electrically connected to the DC pole of the low power grid interface; and providing a DC-DC converter having an input DC pole and an output DC pole, the input DC pole being connected to the battery buffer and the output DC pole being connected to an electric vehicle, wherein the connection between the battery buffer and the DC-DC converter is a DC electrical connection. 
         [0025]    In one or more embodiments, the battery buffer comprises second life batteries. 
         [0026]    In one or more embodiments, the DC-DC converter is a buck converter. 
         [0027]    In one or more embodiments, the DC-DC converter is a CHAdeMO converter. 
         [0028]    In one or more embodiments, the battery buffer comprises a battery management system for managing the battery buffer. 
         [0029]    In one or more embodiments, the system further comprises a charge controller operatively coupled at least to the low power grid interface and the DC-DC converter for controlling the operation of the the low power grid interface and the DC-DC converter based on electrical power grid conditions. 
         [0030]    In one or more embodiments, in a first operation mode, the charge controller is configured to cause the the low power grid interface and the DC-DC converter to charge the electric vehicle. 
         [0031]    In one or more embodiments, in a second operation mode, the charge controller is configured to cause the the low power grid interface and the DC-DC converter to stop charging the electric vehicle. 
         [0032]    In one or more embodiments, in a third operation mode, the charge controller is configured to cause electrical power from the battery buffer to be supplied back to the electrical grid. 
         [0033]    In one or more embodiments, in the third operation mode, the low power grid interface operates as a grid-tie inverter. 
         [0034]    In one or more embodiments, wherein the system further comprises a low-profile mechanical assembly for housing the low power grid interface, the battery buffer and the DC-DC converter. 
         [0035]    In one or more embodiments, the low-profile mechanical assembly is adaptable for being placed on a surface of a parking lot. 
         [0036]    In one or more embodiments, the low-profile mechanical assembly comprises two ramps for vehicle wheels. 
         [0037]    In one or more embodiments, the low-profile mechanical assembly comprises a protrusion disposed between the two ramps for vehicle wheels. 
         [0038]    In one or more embodiments, the low-profile mechanical assembly is 5 inches thick 
         [0039]    In one or more embodiments, the low-profile mechanical assembly comprises attachments for loading and unloading. 
         [0040]    Additional aspects related to the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Aspects of the invention may be realized and attained by means of the elements and combinations of various elements and aspects particularly pointed out in the following detailed description and the appended claims. 
         [0041]    It is to be understood that both the foregoing and the following descriptions are exemplary and explanatory only and are not intended to limit the claimed invention or application thereof in any manner whatsoever. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0042]    The accompanying drawings, which are incorporated in and constitute a part of this specification exemplify the embodiments of the present invention and, together with the description, serve to explain and illustrate principles of the inventive technique. Specifically: 
           [0043]      FIG. 1  illustrates a logical diagram of an exemplary embodiment of a novel high-power DC charging station for fast electric vehicle charging 
           [0044]      FIG. 2  illustrates an exemplary embodiment of a connection of the battery buffer and the DC-DC converter. 
           [0045]      FIG. 3  illustrates exemplary low profile mechanical assembly of an embodiment of the high-power DC charging station. 
       
    
    
     DETAILED DESCRIPTION 
       [0046]    In the following detailed description, reference will be made to the accompanying drawing(s), in which identical functional elements are designated with like numerals. The aforementioned accompanying drawings show by way of illustration, and not by way of limitation, specific embodiments and implementations consistent with principles of the present invention. These implementations are described in sufficient detail to enable those skilled in the art to practice the invention and it is to be understood that other implementations may be utilized and that structural changes and/or substitutions of various elements may be made without departing from the scope and spirit of present invention. The following detailed description is, therefore, not to be construed in a limited sense. 
         [0047]    In accordance with one or more embodiments described herein, there is provided a novel high-power DC charging station architecture for fast electric vehicle charging.  FIG. 1  illustrates a logical diagram of an exemplary embodiment of a novel high-power DC charging station  100  for fast electric vehicle charging. 
         [0048]    As shown in  FIG. 1 , the high-power DC charging station  100  incorporates a low power grid interface  101  coupled to the electrical grid using power feed  102 . In one or more embodiments, the grid power feed  102  may be a standard 208/240V low-power electrical connection. As would be appreciated by persons of ordinary skill in the art, the use of the low-power electrical connection allows the operator of the high-power DC charging station  100  to avoid demand charges from the utility company operating the electrical gird. 
         [0049]    In one or more embodiments, the low power grid interface  101  comprises a bidirectional AC-DC voltage/current inverter for converting the AC current supplied by the grid to DC current at a predetermined voltage for charging a battery buffer  104 . In addition, the power grid interface  101  may be used as a grid-tie inverter for converting the DC current supplied by the battery buffer  104  into grid-synchronized AC electrical power for supplying back to the grid through the grid power feed  102 . 
         [0050]    A DC output  103  of the low power grid interface  101  is electrically connected to a battery buffer  104 . In one or more embodiments, the battery buffer  104  is a 12-15 kWh second-life battery pack, which may use second life electric vehicle batteries. As would be appreciated by persons of ordinary skill in the art, second life batteries carry at least 80% of their nominal capacity and cost a fraction (e.g. $1500) of the price of a new battery. In one or more embodiments, the battery buffer  104  may be used to provide up to 50 kW power burst to the charged electric vehicle. In one or more embodiments, the battery buffer  104  may be provided with a battery management system (BMS)  108  for managing the battery of the buffer  104  by protecting the battery from operating outside its safe operating area, ensuring balanced charging and discharging of each battery cell, monitoring its state, calculating secondary data, reporting that data and controlling its environment. The aforesaid battery management system and its operation are well known to persons of ordinary skill in the art. 
         [0051]    In one or more embodiments, the battery buffer  104  is connected to a DC-DC converter  105 , which converted DC output is, in turn, is connected to an electric vehicle  106  under charge. The DC-DC converter  105  operates to convert the voltage of the battery buffer  104  into an electric vehicle charging voltage for charging the vehicle  106 . In one or more embodiments, the DC-DC converter  105  is implemented as a buck converter, well known to persons of ordinary skill in the art. In various embodiments, the buck converter may utilize high power MOSFET(s). In one or more embodiments, the DC-DC converter  105  is implemented and operates in accordance with CHAdeMO quick charging technique for battery electric vehicles delivering up to 50 kW of high-voltage direct current via a special electrical connector. The aforesaid CHAdeMO quick charging technique is well known to persons of ordinary skill in the art. In one or more embodiments, the conversion efficiency of the DC-DC converter  105  is 97% and the cost is less than $1,500. 
         [0052]    In one or more embodiments, the high-power DC charging station  100  further incorporates a networked charging controller  107 , which operates to control the high-power DC charging station  100  based on the sensed electrical grid conditions, such as grid load. In various embodiments, the networked charging controller  107  is configured to control the operating modes of the low power grid interface  101  (direct AC to DC conversion or reverse grid-tie inversion) as well as the charging of the electric vehicle through the DC-DC converter  105  (charge start or charge stop). 
         [0053]    In one or more embodiments, the networked charging controller  107  operates in conjunction with a computerized system for smart grid integrated electric vehicle charging described in co-pending U.S. patent application Ser. No. 15/004,980, incorporated herein by reference in its entirety. The networked charging controller  107  may also be connected to the electric vehicle  106  for exchanging charge-related information and commands with the vehicle. 
         [0054]    For example, when the electrical power demand in the electrical grid is low, the networked charging controller  107  may be configured to switch on the charging of the battery buffer  104  using the current supplied by the grid, thereby reducing the excess electrical power in the grid. On the other hand, when the grid under high demand, the networked charging controller  107  may be configured to switch off the charging of the battery buffer  104 . In extreme grid over-demand cases, the networked charging controller  107  may be configured to cause the electrical power stored in the battery buffer  104  to be supplied back to the power grid by means of the aforesaid low power grid interface  101  operating in the grid-tie inverter mode. 
         [0055]      FIG. 2  illustrates an exemplary embodiment of a connection of the battery buffer  104  and the DC-DC converter  105 . In the shown embodiment, the battery buffer  104  incorporates five storage batteries  201 ,  202 ,  203 ,  204  and  205  each having a nominal voltage of 100V, connected in series. Thus, the total voltage of the battery pack of the battery buffer  104  is 500V. The DC-DC converter  105  is connected between the poles of the batteries  201  and  202  and the electric vehicle. 
         [0056]    As would be appreciated by persons of ordinary skill in the art, the electrical connection technique shown in  FIG. 2  reduces the maximum voltage drop across the poles of DC-DC converter  105  to just 200V, eliminating the need for using expensive and bulky high-voltage components in its design. In addition, this type of connection arrangement ensures that the DC-DC converter  105  operates in the most efficient manner. In one or more embodiments, any imbalance in the charge/discharge state of the batteries  201 - 205  of the battery buffer  104  is corrected by the aforesaid battery management system  108 . 
         [0057]      FIG. 3  illustrates exemplary low profile mechanical assembly  300  of an embodiment of the high-power DC charging station  100 . In one embodiment, the low profile mechanical assembly  300  of the high-power DC charging station  100  is positioned on a surface of a parking lot vehicle stall. The vehicle to be charged is driven on top of the low profile mechanical assembly  300  of the high-power DC charging station  100 . As would be appreciated by persons of ordinary skill in the art, this type of mechanical configuration reduces the area of the parking lot taken by the vehicle charging equipment. 
         [0058]    The exemplary low profile mechanical assembly  300  is implemented as a low profile rigid mechanical assembly having two wheel ramps  301  and  302  for vehicle wheels as well as a protrusion  303  disposed between the two wheel ramps  301  and  302 . In one or more embodiments, the thickness of the mechanical assembly  300  is about 5 inches. For easy loading and unloading, the low profile mechanical assembly  300  may be provided with one or more attachments for lifting equipment, such as hooks, eyes or the like. In one or more embodiments, all of the components of the high-power DC charging station  100  shown in  FIG. 1  are disposed inside of the low profile mechanical assembly  300 . Power cables may be provide for connecting the the mechanical assembly  300  to the electrical grid and to the charged vehicle. In one or more embodiments, the low profile mechanical assembly  300  is further provided with WIFI or cellular connectivity for connection to data network to enable grid management. Finally, the low profile mechanical assembly  300  is provided with wire hookups for connecting the grid electrical feed and the electric vehicle charging cable. 
         [0059]    As would be appreciated by persons of ordinary skill in the art, the illustrated low profile mechanical assembly  300  is exemplary only and any other type of mechanical configuration may be used to house the components of the high-power DC charging station  100 . 
         [0060]    Finally, it should be understood that processes and techniques described herein are not inherently related to any particular apparatus and may be implemented by any suitable combination of components. Further, various types of general purpose devices may be used in accordance with the teachings described herein. It may also prove advantageous to construct specialized apparatus to perform the method steps described herein. The present invention has been described in relation to particular examples, which are intended in all respects to be illustrative rather than restrictive. 
         [0061]    Moreover, other implementations of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. Various aspects and/or components of the described embodiments may be used singly or in any combination in a high-power DC charging station. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.