Patent Application
20130257146
1. Field
The disclosed concept pertains generally to electric vehicles and, more particularly, to electric vehicle supply equipment, such as, for example, battery charging systems.
2. Background Information
An electric vehicle (EV) charging station, also called an EV charging station, electric recharging point, charging point, and EVSE (Electric Vehicle Supply Equipment), is an element in an infrastructure that supplies electric energy for the recharging of electric vehicles, plug-in hybrid electric-gasoline vehicles, or semi-static and mobile electrical units such as exhibition stands.
Many vehicles have provisions for receiving both alternating current (AC) and direct current (DC) power. Ultimately, all vehicle batteries are charged with DC power. However, the location of the power conversion equipment varies: (1) Level 1: 120 VAC power is supplied to the vehicle through AC EVSE, and conversion to DC for charging the batteries is made on board the vehicle; (2) Level 2: 240 VAC power is supplied to the vehicle through AC EVSE, and conversion to DC for charging the batteries is made on board the vehicle; and (3) DC Charging: DC power is supplied directly to the vehicle, the supply and power conversion is made outside the vehicle.
Known DC charging equipment requires a complete AC/DC conversion within a DC charger. For example, in a typical DC charger, AC is supplied to the DC charger, is rectified to DC, and subsequently goes through a DC-DC conversion (e.g., using an inverter, a transformer and a rectifier). This functionality is all contained within the same DC charger enclosure or “box”.
Typical electric vehicle charging is currently achieved with a dedicated complete charging unit per vehicle. Due to the emerging nature of this technology, the cost of infrastructure to support conversion to electric vehicles can present a barrier for adoption.
There is room for improvement in electric vehicle supply equipment.
For fleet or commercial multi-point charging stations, an opportunity exists to reduce the cost of charging equipment by optimizing the system design. This need and others are met by embodiments of the disclosed concept where each of a plurality of direct current to direct current converters comprises an input powered by a direct current bus and an output structured to charge a corresponding one of a plurality of different electric vehicles.
In accordance with one aspect of the disclosed concept, electric vehicle supply equipment comprises: an alternating current to direct current converter comprising an alternating current input and a direct current output; a direct current bus electrically interconnected with the direct current output of the alternating current to direct current converter; and a plurality of direct current to direct current converters, each of the direct current to direct current converters comprising an input powered by the direct current bus and an output structured to charge a corresponding one of a plurality of different electric vehicles.
Each of the direct current to direct current converters may be structured to communicate with the alternating current to direct current converter.
The alternating current to direct current converter may be structured to limit power consumed by the direct current to direct current converters from the alternating current to direct current converter.
As another aspect of the disclosed concept, electric vehicle supply equipment comprises: a first processor comprising a first communication interface; an alternating current to direct current converter comprising an alternating current input and a direct current output; a direct current bus electrically interconnected with the direct current output of the alternating current to direct current converter; and a plurality of direct current to direct current converters, each of the direct current to direct current converters comprising an input powered by the direct current bus, a second processor, a second communication interface, and at least one power unit controlled by the second processor and comprising an output structured to charge the corresponding one of the different electric vehicles, wherein the first communication interface is structured to communicate with the second communication interface, and wherein the first processor is structured to communicate a power threshold from at least one of an input from a utility and an input from a user, and to communicate a number of messages to the second processor of a corresponding number of the direct current to direct current converters to limit power output by the at least one power unit of the corresponding number of the direct current to direct current converters.
A full understanding of the disclosed concept can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:
As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality).
As employed herein, the term “processor” shall mean a programmable analog and/or digital device that can store, retrieve, and process data; a computer; a workstation; a personal computer; a controller; a microprocessor; a microcontroller; a microcomputer; a central processing unit; a mainframe computer; a mini-computer; a server; a networked processor; or any suitable processing device or apparatus.
As employed herein, the statement that two or more parts are “connected” or “coupled” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts. Further, as employed herein, the statement that two or more parts are “attached” shall mean that the parts are joined together directly.
The cost (i.e., EVSE product cost and installation cost) of providing complete EVSE charging stations for each electric vehicle, such as 4,6,8,10, can be greatly reduced by consolidating the AC-DC conversion equipment (not shown) of prior electric vehicles (not shown) into the single AC-DC converter 12 supplying DC power via the distributed DC bus 18 and dispensing the DC power at the point of use with optimally sized DC-DC power converters 20. This approach differs from the known prior approach of supplying a complete AC-DC charging solution for each charging point since the initial stage of the power conversion at the AC-DC converter 12 is sized to accommodate the distributed load while the individual charging points at the DC-DC converters 20 are sized to accommodate the loading at each charging point.
The single AC-DC converter 12 creates the DC bus 18. An optional renewable energy power source 24 is electrically interconnected with and can independently power the DC bus 18. Each electric vehicle, such as 4,6,8,10, is associated with a corresponding one of the external DC-DC converters 20. The DC-DC converters 20 are not on board the electric vehicles 4,6,8,10, but rather are in a separate assembly. The electric vehicles 4,6,8,10 electrically connect to one of the DC-DC converters 20 to receive DC power. Each of the electric vehicles 4,6,8,10 is structured to receive the DC power from a corresponding one of the separate and distinct DC-DC converters 20.
As will be discussed, below, in connection with
The AC-DC converter 12 is sized and structured to power all of the plurality of different electric vehicles 4,6,8,10. Although four example electric vehicles 4,6,8,10 and four example DC-DC converters 20 are shown, the disclosed concept is applicable to any suitable count of a wide variety of different electric vehicles and DC-DC converters. Each of the DC-DC converters 20 is sized and structured to power one of the different electric vehicles 4,6,8,10.
Each of the different electric vehicles 4,6,8,10 includes an input 26 structured to receive a DC voltage 28 from the output 22 of a corresponding one of the external DC-DC converters 20.
Referring to
In
If the example master CPU 31 is at the AC-DC converter 12, then the desired power threshold can be maintained for the common DC bus 18. The individual DC-DC converters 20 can be tied together on a control and communication bus network, such as 32, in which the master CPU 31 provides the logic and associated priority for dispensing power.
The master CPU 31 can respond to an external command (e.g., without limitation, a utility company signal via, for example, cellular; power line carrier; radio). This could control or maintain the desired power level by adjusting the maximum power level on the common DC bus 18. If the preset maximum kW is 100 kW, for example and without limitation, and if the demand was 125 kW, then there would be a common reduction of 20%.
A user desire to limit peak charges can affect the single AC-DC converter 12 and the multiple DC-DC converters 20. Suppose, for example, that a user wanted to limit the amount of power in any given 15 minute period in an attempt to minimize demand charges. A similar approach as disclosed in Example 5 could be employed. The only difference would be the threshold or demand reduction signal 30 is set by the user and is not driven by an external signal from a utility.
The disclosed concept differs from the known prior proposal of supplying a complete charging solution for each charging point since the initial stage of the power conversion is sized to accommodate the distributed load with the single AC-DC converter 12, while the charging points of the individual DC-DC converters 20 are sized to accommodate the loading at each charging point and supply DC directly to the battery (not shown) of the corresponding one of the electric vehicles 4,6,8,10.
The DC-DC converters 20 are cheaper than AC-DC converters, and the cost of one relatively large AC-DC converter 12 is effectively spread over many electric vehicles, such as 4,6,8,10. Hence, the intent is to spread the one AC-DC converter 12 over relatively many electric vehicles. It is expected that: (1) consolidating the AC-DC conversion into one unit is less expensive than providing for each individual charging point; and (2) the installation cost for providing one AC supply versus relatively many is expected to reduce installation cost.
There is the one AC-DC converter 12 that creates the constant voltage common DC bus 18. Then, there are multiple isolated DC-DC converters 20 that take the constant DC voltage off of the common DC bus 18. Each of the DC-DC converters 20 generates a galvanically isolated (from the common DC bus 18) battery charging voltage 28.
As shown in
The AC-DC communication interface 40 communicates with the DC-DC communication interface 42. The AC-DC processor 34 communicates the demand reduction signal 30, which can be a power threshold from at least one of an input from a utility and an input from a user, and communicates a number of messages 44 to the DC-DC processor 36 of a corresponding number of the DC-DC converters 20 to limit power output by those converters 20.
Each of the DC-DC converters 20 is structured to reduce power output to its output 22 (
The disclosed DC-DC converters 20 are employed for battery charging. Hence, they are current controlled or current sources with a controlled output voltage, in order that the maximum battery voltage is not exceeded. Being current controlled, these DC-DC converters 20 will output only a commanded current at a given output voltage range. For a given vehicle type, the battery voltage from discharged to fully charged is not very wide, but the maximum charging power is defined at the discharged battery voltage and the maximum current that the DC-DC current source converter 20 can output. For example and without limitation, a known battery goes from about 330 VDC discharged to about 362 VDC fully charged.
When, for example, a utility company sends a demand reduction signal, such as 30, thereby providing the EVSE 2 a certain power limit, a processor (e.g., without limitation, the AC-DC converter processor 34; another suitable processor; a master CPU) receives that signal and does one of the following: (1) limits the maximum output power of each DC-DC current source converter 20 equally such that the sum of the power for all of the DC-DC converters 20 is equal to or less than the utility commanded power limit; (2) arbitrarily distributes the allowed power budget to the connected DC-DC current source converters 20 according to a suitable priority; or (3) gives the maximum power if there is only a limited number of electric vehicles, such as 4 and 6 of
Table 1, below, shows a flat demand reduction across all DC-DC converters 20 based upon an example 50% reduction. This assumes a 20 kWh battery. The initial current (62.5 A) and battery voltage (400 VDC) provide an initial energy of 6.25 kWh for the first 0.25 h (15 minutes). The total power is 6.25 kWh/0.25 h×5 units=125 kW. Similarly, the current (15 A) and battery voltage (400 VDC) for minutes 60 to 75 provide an energy of 1.5 kWh. The total power is 1.5 kWh/0.25 h×5 units=30 kW.
Table 2, below, shows that priority charging is given to units #1 and #2 in lieu of distributing power equally as in Table 1, above. The initial current (125 A) and battery voltage (400 VDC) provide an initial energy of 12.5 kWh for the first 0.25 h (15 minutes). The total power is 31 kWh/0.25 h for the first three units=124 kW. Similarly, the current (25 A total) and battery voltage (400 VDC) for minutes 60 to 75 provide an energy of 2.5 kWh total for units #4 and #5. The total power is 2.5 kWh/0.25 h for the two units=10 kW.
Preferably, the DC-DC converters 20 can input the state of battery charge for the corresponding different electric vehicles 4,6,8,10, and communicate the same to the AC-DC converter 12. In turn, the AC-DC converter 12 is further structured to input a power threshold, to input the state of battery charge of each of the different electric vehicles 4,6,8,10, and to communicate a command to a selected number of the DC-DC converters 20 to reduce power output to the output 22 for a number of the different electric vehicles 4,6,8,10 having the lowest state of battery charge until power output to the DC bus 18 is less than or equal to the power threshold.
Otherwise, if the DC-DC converters 20 cannot input the state of battery charge for the corresponding different electric vehicles 4,6,8,10, the AC-DC converter 12 is further structured to input a power threshold, to input a priority of each of the different electric vehicles 4,6,8,10, and to communicate a command to a selected number of the DC-DC converters 20 to reduce power output to the output 22 for a number of the different electric vehicles 4,6,8,10 having the lowest priority until power output to the DC bus 18 is less than or equal to the power threshold.
The AC-DC converter 12 can advantageously consider at least one of the priority and the state of battery charge for the corresponding different electric vehicles 4,6,8,10 along with the input power threshold when communicating commands to a selected number of the DC-DC converters 20 to reduce power output to the output 22.
The transformer 58 includes a primary winding 70 powered by the inverter 56 and a secondary winding 72. The rectifier 60 includes an input 74 powered by the secondary winding 72 and an output 76. The example filter 62 includes an inductor 78, a capacitor 80 and the output 22.
The controller 36 can control the inverter 56 to limit power consumed by the example DC-DC isolated converter 20 from the AC-DC converter 12, in order to provide a percentage or a priority based reduction in unit power output, as disclosed herein.
While specific embodiments of the disclosed concept have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.
