Patent Application
20240359572
The present application generally relates to electrified vehicle charging and, more particularly, to DC-DC boost systems and methods for recharging higher voltage battery packs with lesser rated charging stations.
An electrified vehicle includes one or more electric motors that generate propulsive drive torque using electrical energy (e.g., current) provided by one or more high voltage battery packs. There are two primary ways to charge a high voltage battery pack of an electrified vehicle: (1) alternating current (AC) on-board charging and (2) direct current (DC) fast charging (also known as “Mode 4”). There are dedicated vehicle components for supporting each charging technique. In the DC fast charging mode, the charging station is connected directly to the high voltage battery pack. Most installed DC charging stations are rated for 400 volts (400V), excluding specific highway DC charging stations. In order to charge higher voltage battery systems (e.g., 800V battery systems), electrified vehicles often include a DC boost charging module (DCBCM), which adds significant cost/space/weight and integration complexity to the electrified vehicle. Accordingly, while such conventional electrified vehicle charging systems and methods do work well for their intended purpose, there exists an opportunity for improvement in the relevant art.
According to one example aspect of the invention, a direct current to direct current (DC-DC) boosting and fast charging system for an electrified vehicle is presented. In one exemplary implementation, the DC-DC boosting and fast charging system comprises an inverter electrically connected to a direct current (DC) power source and to an electric motor, configured to receive and DC power source into three phase alternating current (AC) power, and comprising three inductor phase legs configured to generate and output three AC phase currents, respectively, a plurality of relay switches electrically connected between the DC power source, the inverter, and a high voltage (HV) battery system rated at a first voltage, wherein at least one of the plurality of relay switches is connected to a midpoint of one of the three inductor phase legs of the inverter, and a controller configured to control a boosted fast charging mode wherein the DC power source is a DC charging station rated at a second voltage that is less than the first voltage and the plurality of relay switches are opened/closed such that the second voltage is provided to the inverter and to the HV battery system for recharging, wherein providing the second voltage to the inverter via the plurality of relay switches causes the inverter to generate and output one AC phase current that causes the electric motor to inductively generate and provide two AC phase currents back to the inverter, which are converted to a third DC voltage for further boosted recharging of the HV battery system.
In some implementations, the inverter includes an additional capacitor associated with the at least one relay switch of the plurality of relay switches connected to the midpoint of the one of the three inductor phase legs of the inverter. In some implementations, the plurality of relay switches includes five relay switches with one relay switch for each of positive voltage and ground and three relay switches connected to three midpoints of the three inductor phase legs of the inverter, respectively. In some implementations, the plurality of relay switches further includes one or more bypass relay switches for bypassing the inverter and electrically connecting the DC power source to the HV battery system. In some implementations, the controller is configured to control a normal operating mode wherein the DC power source is the HV battery system, the plurality of relay switches are open, and the inverter is configured to generate and output three AC phase currents that cause the electric motor to rotate and generate propulsive drive torque for the electrified vehicle.
In some implementations, the first voltage is approximately 800 volts and the second and third voltages are each approximately 400 to 500 volts. In some implementations, the controller is configured to control a non-boosted fast charging where wherein the DC power source is a DC charging station rated at a fourth voltage that is approximately equal to the first voltage and positive and negative relay switches of the plurality of relay switches are closed such that the fourth voltage is provided to the HV battery system for recharging. In some implementations, the first and fourth voltages are approximately 400 volts or 800 volts.
According to another example aspect of the invention, a DC-DC boosting and fast charging method for an electrified vehicle is presented. In one exemplary implementation, the method comprises providing an inverter electrically connected to a DC power source and to an electric motor, configured to receive and DC power source into three phase AC power, and comprising three inductor phase legs configured to generate and output three AC phase currents, respectively, providing a plurality of relay switches electrically connected between the DC power source, the inverter, and an HV battery system rated at a first voltage, wherein at least one of the plurality of relay switches is connected to a midpoint of one of the three inductor phase legs of the inverter, and controlling, by a controller of the electrified vehicle, a boosted fast charging mode wherein the DC power source is a DC charging station rated at a second voltage that is less than the first voltage and the plurality of relay switches are opened/closed such that the second voltage is provided to the inverter and to the HV battery system for recharging, wherein providing the second voltage to the inverter via the plurality of relay switches causes the inverter to generate and output one AC phase current that causes the electric motor to inductively generate and provide two AC phase currents back to the inverter, which are converted to a third DC voltage for further boosted recharging of the HV battery system.
In some implementations, the inverter includes an additional capacitor associated with the at least one relay switch of the plurality of relay switches connected to the midpoint of the one of the three inductor phase legs of the inverter. In some implementations, the plurality of relay switches includes five relay switches with one relay switch for each of positive voltage and ground and three relay switches connected to three midpoints of the three inductor phase legs of the inverter, respectively. In some implementations, the plurality of relay switches further includes one or more bypass relay switches for bypassing the inverter and electrically connecting the DC power source to the HV battery system. In some implementations, the method further comprises controlling, by the controller, a normal operating mode wherein the DC power source is the HV battery system, the plurality of relay switches are open, and the inverter is configured to generate and output three AC phase currents that cause the electric motor to rotate and generate propulsive drive torque for the electrified vehicle.
In some implementations, the first voltage is approximately 800 volts and the second and third voltages are each approximately 400 to 500 volts. In some implementations, the method further comprises controlling, by the controller, a non-boosted fast charging where wherein the DC power source is a DC charging station rated at a fourth voltage that is approximately equal to the first voltage and positive and negative relay switches of the plurality of relay switches are closed such that the fourth voltage is provided to the HV battery system for recharging. In some implementations, the first and fourth voltages are approximately 400 volts or 800 volts.
Further areas of applicability of the teachings of the present application will become apparent from the detailed description, claims and the drawings provided hereinafter, wherein like reference numerals refer to like features throughout the several views of the drawings. It should be understood that the detailed description, including disclosed embodiments and drawings referenced therein, are merely exemplary in nature intended for purposes of illustration only and are not intended to limit the scope of the present disclosure, its application or uses. Thus, variations that do not depart from the gist of the present application are intended to be within the scope of the present application.
As previously discussed, most installed direct current (DC) electrified vehicle charging stations are rated for 400 volts (400V), excluding specific highway DC charging stations. In order to charge higher voltage battery systems (e.g., 800V battery systems), electrified vehicles often include a DC boost charging module (DCBCM), which adds significant cost/space/weight and integration complexity to the electrified vehicle. As a result, the present application is directed to improved systems and methods for recharging higher voltage battery systems (e.g., 800V battery systems) with lower rated DC charging stations (e.g., 400V charging stations) and without the need for the large and expensive DCBCM. These systems and methods utilize the electrified vehicle's existing inverter and electric motor(s)—the components typically generating propulsive drive torque—to perform the 400V-800V boost function. While 400V-800V is a common example in today's vehicles, the techniques could be applicable to other boost configurations (400V-1200V, 800V-1200V, etc.). The only additional componentry needed is a few switches/relays and a small DC capacitor. In some implementations, more switches/relays could also be added for balancing the boost current among the three phases for even further improved performance.
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The electrified powertrain 108 could optionally include an internal combustion engine 136 configured to combust a mixture of air and fuel (gasoline, diesel, etc.) to generate mechanical energy (drive torque) that could be utilized for vehicle propulsion and/or for recharging the battery systems 128, 132. A controller 140 controls operation of the electrified vehicle 100 and, more particularly, the electrified powertrain 108 (e.g., to meet or satisfy a driver or operator torque request), including specific components for recharging control as described in greater detail below. The electrified powertrain 108 also includes a plurality of relay switches 144 as part of the DC-DC boosting and fast charging system 104 according to the principles of the present application. In one configuration (also referred to herein as “a non-boosted fast charging mode”), the relay switches 144 are configured to bypass the inverter 124 such that an external DC charging station 148 is directly connected to the HV battery system 128. In another configuration (also referred to herein as “a boosted fast charging mode”), some of the relay switches 144 are configured to connect the external DC charging station 148 to a midpoint of one inductor phase leg (not shown) of the inverter 124, which causes the powered inductor phase leg to generate AC phase currents in the other two inductor phase legs (not shown) and output a DC voltage for further (boosted) recharging of the HV battery system 128.
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It will be appreciated that the term “controller” as used herein refers to any suitable control device or set of multiple control devices that is/are configured to perform at least a portion of the techniques of the present application. Non-limiting examples include an application-specific integrated circuit (ASIC), one or more processors and a non-transitory memory having instructions stored thereon that, when executed by the one or more processors, cause the controller to perform a set of operations corresponding to at least a portion of the techniques of the present application. The one or more processors could be either a single processor or two or more processors operating in a parallel or distributed architecture.
It should also be understood that the mixing and matching of features, elements, methodologies and/or functions between various examples may be expressly contemplated herein so that one skilled in the art would appreciate from the present teachings that features, elements and/or functions of one example may be incorporated into another example as appropriate, unless described otherwise above.
