State-of-charge balancing in a split-battery system

Abstract

The electric vehicle comprises: a battery system divided into first and second sectors that are substantially equal to each other; a first bidirectional DC / DC converter, the first bidirectional DC / DC converter being galvanically isolated and coupled to the first sector; and a second bidirectional DC / DC converter, the second bidirectional DC / DC converter being galvanically isolated and coupled to the second sector; wherein the first and second bidirectional DC / DC converters balance the respective states of charge of the first and second sectors before the first and second sectors are connected in parallel.

Description

[Technical Field]

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 373,934, entitled "STATE OF CHARGE BALANCING IN SPLIT BATTERY SYSTEM," filed August 30, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0002] This paper relates to state of charge (SOC) balancing in split battery systems. [Background technology]

[0003] The battery voltages of newly developed electric vehicles and plug-in hybrid electric vehicles (collectively: electric vehicles) continue to reach higher levels. For example, some electric vehicles may have battery voltages of 800 V or higher. Meanwhile, charging stations may still only support voltages below this level, such as 750 V or less than 500 V. Summary of the Invention

[0004] In one aspect, an electric vehicle comprises: a battery system divided into first and second sectors that are substantially equal to one another; a first bidirectional DC / DC converter, the first bidirectional DC / DC converter being galvanically isolated and coupled to the first sector; and a second bidirectional DC / DC converter, the second bidirectional DC / DC converter being galvanically isolated and coupled to the second sector; wherein the first and second bidirectional DC / DC converters balance the respective states of charge of the first and second sectors before the first and second sectors are connected in parallel.

[0005] Implementations may include any or all of the following features: The electric vehicle further includes an on-board charger, wherein the first and second bidirectional DC / DC converters are part of the on-board charger. The on-board charger has a multi-stage architecture further including a power factor correction stage. The power factor correction stage is common to the first and second bidirectional DC / DC converters. The electric vehicle further includes a load of the battery system, the load including a first load coupled to the first bidirectional DC / DC converter and a second load coupled to the second bidirectional DC / DC converter. The first and second sectors are connected in parallel for at least charging the battery system. The first and second sectors are connected in series for at least driving an inverter of the electric vehicle. The electric vehicle further includes a first bus bar connecting a positive terminal of the first bidirectional DC / DC converter, a positive terminal of the first sector, and a positive terminal of the second sector via a first contact between the positive terminal of the first sector and the positive terminal of the second sector. The electric vehicle further includes a second bus bar connecting the negative terminal of the second bidirectional DC / DC converter, the negative terminal of the second sector, and the negative terminal of the first sector via a second contactor between the negative terminal of the second sector and the negative terminal of the first sector. The electric vehicle further includes a third bus bar connecting the negative terminal of the first sector and the positive terminal of the second sector via a third contactor between the negative terminal of the first sector and the positive terminal of the second sector. To connect the first and second sectors in series, the first and second contactors are open and the third contactor is closed. To connect the first and second sectors in parallel, the first and second contactors are closed and the third contactor is open. [Brief explanation of the drawings]

[0006] [Figure 1] 1 illustrates an example of a system that may use a DC / DC converter to perform SOC balancing of a split battery system.

[0007] [Figure 2]2 illustrates an example of the system of FIG. 1 being charged using a native voltage DC fast charger.

[0008] [Figure 3] 2 illustrates an example of the system of FIG. 1 being charged using a legacy voltage DC fast charger.

[0009] Like reference numbers in the various drawings indicate like elements. DETAILED DESCRIPTION OF THE INVENTION

[0010] This document describes example systems and techniques that provide new power architectures and control methods for electric vehicles. The electric vehicle is provided with a battery system that is divided into at least two sectors. SOC balancing between the sectors of the battery system can be performed by a DC / DC converter in the electric vehicle. For example, this can be a galvanically isolated bidirectional DC / DC converter that is part of the electric vehicle's on-board charging system.

[0011] As mentioned, the battery system of the present disclosure is divided into sectors, which can be connected in series or parallel to each other to accommodate different voltage ranges of DC charging solutions (e.g., DC fast chargers). In some implementations, high-voltage DC fast chargers can provide voltages from about 800 V to about 1000 V. For example, these chargers can be referred to as native chargers for electric vehicles whose battery systems have a native voltage within the range of such high-voltage DC fast chargers. In contrast, in older electric vehicles, the battery systems typically have lower voltages than those of modern high-voltage DC fast chargers and are sometimes referred to as "legacy battery systems." Previous-generation DC fast chargers designed for such battery systems were then low-voltage DC fast chargers. In some implementations, low-voltage DC fast chargers can provide voltages from about 400 V to about 500 V.

[0012] A reason for using a split battery system and balancing the SOC or voltage between battery sectors may be to make the vehicle backward compatible with low-voltage DC fast chargers, sometimes referred to as legacy voltage DC fast chargers. If a vehicle with a split battery system detects that the DC fast charger supports the native battery voltage, the vehicle may connect the battery sectors in series. On the other hand, if such a vehicle detects a legacy voltage DC fast charger, the sectors may be connected in parallel. When the sectors switch between series and parallel connections, their respective voltages / SOCs should be as close to each other as possible. For example, this may avoid inrush current, energy waste, or potential overheating of the system or any of its cells.

[0013] Examples herein refer to vehicles. A vehicle is a machine that transports passengers, cargo, or both. A vehicle may have one or more motors that use at least one type of fuel or other energy source (e.g., electricity). The term electric vehicle, as used herein, includes any vehicle that has at least one electric traction motor, including, but not limited to, battery electric vehicles and plug-in hybrid electric vehicles. Examples of vehicles include, but are not limited to, cars, trucks, and buses. The number of wheels may vary among multiple types of vehicles, and one or more (e.g., all) of the wheels may be used for propulsion of the vehicle. A vehicle may include a passenger compartment that accommodates one or more people.

[0014] Examples herein refer to battery systems, which are assemblies of electrochemical cells. The battery system may be configured to power an electric motor for propulsion or to provide a stationary power source, to name just two examples. The battery system may include control circuitry for managing the charging, storage, and / or use of electrical energy in the electrochemical cells, or the battery system may be controlled by external components. For example, the battery management system can be implemented on one or more circuit boards (e.g., printed circuit boards).

[0015] Examples herein refer to electrochemical cells. Electrochemical cells can include an electrolyte and two electrodes to store energy and deliver it during use. In some implementations, the electrochemical cells can be rechargeable. For example, the electrochemical cells can be lithium-ion cells. In some implementations, the electrochemical cells can act as galvanic cells when discharged and as electrolytic cells when charged. The electrochemical cells can have at least one terminal for each electrode. The terminal, or at least a portion thereof, can be located at one end of the electrochemical cell. For example, if the electrochemical cell is cylindrical, one of the terminals can be located at the center of the end of the cell, and the can forming the cylinder can constitute the other terminal and therefore also be present at the end. Other shapes of electrochemical cells can be used, including, but not limited to, prismatic shapes.

[0016] Examples herein refer to alternating current (AC) or direct current (DC). Different voltage and current levels may be used for each of AC and DC. The example voltages mentioned herein are for illustrative purposes only. A DC / DC converter may be bidirectional, meaning it can convert from DC to DC in either direction between its respective terminals. A DC / DC converter may be galvanically isolated, meaning the input and output sides of the DC / DC converter do not share a common ground and the DC / DC converter has a transformer that eliminates any DC path between the input and output sides.

[0017] The examples described herein describe particular components of electrical circuits that are coupled or connected to one another. As used herein, coupled or connected means electrically coupled or connected, unless otherwise stated.

[0018] 1 illustrates an example of an electric vehicle 100 that includes a system 102 that can perform SOC balancing of a split-battery system using a DC / DC converter. The electric vehicle 100 and / or the system 102 can be used with one or more other examples described elsewhere herein. The electric vehicle 100 is illustrated schematically here, and many of its components are omitted for simplicity (including, but not limited to, the body, wheels, electric traction motors, power electronics, and thermal system).

[0019] The electric vehicle 100 includes a battery system 104, which may be divided into multiple sectors. Here, the battery system 104 includes a sector 104A and a sector 104B. Each of the sectors 104A-104B includes multiple electrochemical cells. The number of cells in each of the sectors 104A-104B does not necessarily have to be the same. However, if the sectors 104A-104B are to be connected in parallel with each other (e.g., as illustrated below), they should have approximately the same voltage. The sector 104A has a positive terminal 106A (i.e., a terminal having a positive potential difference compared to a reference) and a negative terminal 106B (i.e., a terminal having a negative potential difference compared to a reference). Similarly, the sector 104B has a positive terminal 108A and a negative terminal 108B.

[0020] System 102 includes a bus bar 134 that controls whether the sectors of the split battery system are connected in series or in parallel. Here, bus bar 134 connects negative terminal 106B of sector 104A and positive terminal 108A of sector 104B. Bus bar 134 may include at least one contact. For example, here, contact 136 is located between negative terminal 106B of sector 104A and positive terminal 108A of sector 104B. When contact 136 is closed and contacts 128 and 132 (described below) are open, sectors 104A-104B of battery system 104 are connected in series. When contact 136 is open and contacts 128 and 132 are closed, sectors 104A-104B are connected in parallel.

[0021] The electric vehicle 100 may have an onboard charger 110 (OBC) that can be used to charge the battery system 104 with electricity from an external power source. Here, an AC charging port 112 is shown as an example. The onboard charger 110 may have one or more power stages, such as a multi-stage architecture. In some implementations, the onboard charger 110 includes a stage that converts AC from the AC charging port 112 to DC. This may be done using a power factor correction stage 114 (PFC). For example, the power factor correction stage 114 may include a rectifier and optionally one or more filters to convert the AC power to power for a DC intermediate bus within the electric vehicle 100.

[0022] In some implementations, the onboard charger 110 has stages implemented to generate the appropriate DC for the battery system 104. This can be done using one or more DC / DC converters. Here, the system 102 has a DC / DC converter 116A for sector 104A and a DC / DC converter 116B for sector 104B. The DC / DC converter 116A has a positive terminal 118A and a negative terminal 118B. The DC / DC converter 116A also has a positive terminal 118A' and a negative terminal 118B'. Similarly, the DC / DC converter 116B has a positive terminal 120A and a negative terminal 120B, and a positive terminal 120A' and a negative terminal 120B'. Here, DC / DC converter 116A is coupled to power factor correction stage 114 by positive terminal 118A' and negative terminal 118B' and is coupled to sector 104A by positive terminal 118A' and negative terminal 118B'. Similarly, DC / DC converter 116B is coupled to power factor correction stage 114 by positive terminal 120A' and negative terminal 120B' and is coupled to sector 104B by positive terminal 120A' and negative terminal 120B'. In some implementations, the right sides of DC / DC converters 116A and 116B may be parallel to each other. Here, positive terminal 118A' is connected to positive terminal 120A', and similarly, negative terminal 118B' is connected to negative terminal 120B'. The DC / DC converters 116A and 116B may share the same bus voltage, and power may flow from one of the DC / DC converters 116A-116B to the other. For example, this may allow the DC / DC converters 116A-116B to share charging power and balance the sectors 104A-104B.

[0023] Each of the DC / DC converters 116A-116B may be bidirectional, thereby performing DC / DC conversion in either direction. For example, the DC / DC converter 116A may use the positive terminal 118A' and the negative terminal 118B' as input terminals and the positive terminal 118A and the negative terminal 118B as output terminals. As another example, the DC / DC converter 116A may use the positive terminal 118A and the negative terminal 118B as input terminals and the positive terminal 118A' and the negative terminal 118B' as output terminals. The DC / DC converter 116B may use the positive terminal 120A' and the negative terminal 120B' as input terminals and the positive terminal 120A and the negative terminal 120B as output terminals, or may use the positive terminal 120A and the negative terminal 120B as input terminals and the positive terminal 120A' and the negative terminal 120B' as output terminals.

[0024] Each of the DC / DC converters 116A-116B may be galvanically isolated. In some implementations, this may protect the battery system 104 from undesirable electrical conditions that may occur at the AC charging port 112. For example, each of the DC / DC converters 116A-116B may have a transformer that separates the side currently used as an input from the side currently used as an output.

[0025] The electric vehicle 100 may include a high-voltage load 122. Here, high voltage means that the high-voltage load 122 may be powered using a voltage on the order of the voltage across the sector 104A or sector 104B, respectively. For example, each of the sectors 104A and 104B may have a voltage on the order of half the nominal voltage of the battery system 104. Here, the high-voltage load 122A is coupled to the sector 104A, and the high-voltage load 122B is coupled to the sector 104B. When designing or configuring the electric vehicle 100, the high-voltage load 122 may be selected to operate at half the total battery voltage. By comparison, another solution is to connect the high-voltage loads 122A-122B across the positive terminal 118A and the negative terminal 120B. The input of the high-voltage loads 122A-122B may then range from the minimum voltage in parallel mode to the maximum voltage in series mode. For example, the voltage range can be from about 200V to about 925V. Alternatively, high-voltage loads 122A-122B are connected to each sector 104A-104B. The voltage range can then be between about 200V and about 463V, which is fine for the design of each load. Splitting the loads between sectors makes balancing more important because the loads may not be the same. In this way, DC / DC converters 116A-116B can be used to balance the SOC and voltage. Examples of high-voltage loads 122 include, but are not limited to, heaters, air compressors, and auxiliary power converters. These components and / or other loads can be assigned to high-voltage loads 122A-122B, respectively, so that the total load is evenly distributed within the system 102.

[0026] Electric vehicle 100 includes a DC charging port 124. In some implementations, DC charging port 124 can be used to connect to a DC fast charger to charge the vehicle. An inverter 125 of electric vehicle 100 can be coupled in parallel with DC charging port 124. For example, inverter 125 can include a switch that is operated to generate AC for at least one traction motor of electric vehicle 100.

[0027] The system 102 includes a bus bar 130 connecting the negative terminal 120B of the DC / DC converter 116B, the negative terminal 108B of the sector 104B, and the negative terminal 106B of the sector 104A. The bus bar 130 may include at least one contact. For example, here, the contact 132 is located between the negative terminal 108B of the sector 104B and the negative terminal 106B of the sector 104A.

[0028] DC / DC converters 116A-116B may perform SOC balancing in electric vehicle 100. For example, if sector 104A has a higher SOC than sector 104B, DC / DC converter 116A may transfer energy from sector 104A to the common bus at positive terminal 118A' and positive terminal 120A'. Simultaneously, DC / DC converter 116B transfers energy on the common bus to sector 104B. In this manner, energy may be shifted from sector 104A to sector 104B. Similarly, if sector 104B has a higher SOC than sector 104A, DC / DC converter 116B may transfer energy from sector 104B to the common bus at negative terminal 118B' and negative terminal 120B', and DC / DC converter 116A then transfers the energy on the common bus to sector 104A. For example, such SOC balancing can protect against surge currents and energy losses when sectors 104A-104B are connected in parallel with one another.

[0029] Electric vehicle 100 can be charged using any of several types of charging stations or charging facilities. When charging with DC, electric vehicle 100 can be connected to either a high-voltage DC fast charger (e.g., having a voltage about the native voltage of battery system 104) or a low-voltage DC fast charger (e.g., having a voltage substantially lower than the native voltage of battery system 104). Some DC charging (e.g., those mentioned below) can be performed using a DC fast charger. An example charging session is now described.

[0030] FIG. 2 illustrates an example of the system 102 of FIG. 1 being charged using a native-voltage DC fast charger. Some aspects of the system 102 are similar to or identical to the example described with reference to FIG. 1 . Only the differences are described below. Here, the DC charging port 124 is connected to a native-voltage DC fast charger that provides a relatively high voltage. Such a voltage may include, but is not limited to, a potential of approximately 800-1000 V. The voltage of the native-voltage DC fast charger may be on the order of the native voltage of the battery system 104. In a handshake procedure between the electric vehicle 100 and the charging station, the electric vehicle 100 may detect the voltage of the native-voltage DC fast charger and adjust the system 102 accordingly. In some implementations, the system 102 may then connect sectors 104A and 104B in series. For example, contacts 128 and 132 may be opened (or remain open). Busbars 126 and 130 are not shown in this example for simplicity. Contact 136 is closed to connect sectors 104A and 104B in series. Sectors 104A and 104B may also be connected in series to drive the traction motor of electric vehicle 100.

[0031] FIG. 3 illustrates an example of the system 102 of FIG. 1 being charged using a legacy voltage DC fast charger. Some aspects of the system 102 are similar or identical to the example described with reference to FIG. 1 . Only the differences are described below. Here, the DC charging port 124 is connected to a legacy voltage DC fast charger that provides a relatively low voltage. Such a voltage may include, but is not limited to, a potential of approximately 400-500 V. The voltage of the legacy voltage DC fast charger may be substantially lower than the native voltage of the battery system 104. In a handshake procedure between the electric vehicle 100 and the charging station, the electric vehicle 100 may detect the voltage of the legacy voltage DC fast charger and adjust the system 102 accordingly. In some implementations, the system 102 may then connect sectors 104A and 104B in parallel. For example, contacts 128 and 132 may be closed (or remain closed), and contact 136 may be opened (or remain open). Thus, sectors 104A and 104B are connected in parallel.

[0032] As used throughout this specification, the terms "substantially" and "about" are used to describe and take into account small variations, such as those due to processing variations. For example, they can refer to less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. Also, as used herein, indefinite articles such as "a" or "an" mean "at least one."

[0033] It should be understood that all combinations of the foregoing concepts, and additional concepts discussed in more detail below, (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein.

[0034] Although several implementations have been described, it will be understood that various modifications may be made without departing from the spirit and scope of the present specification.

[0035] Additionally, the logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. Furthermore, other processes may be provided in or deleted from the described flows, and other components may be added to or removed from the described systems. Accordingly, other implementations are within the scope of the following claims.

[0036] While certain features of the described implementations have been shown and described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and variations that fall within the scope of the implementations. They have been presented by way of example only, and not limitation, and it is to be understood that various changes in form and detail may be made. Any portions of the apparatus and / or methods described herein may be combined in any combination, except in mutually exclusive combinations. The implementations described herein may include various combinations and / or subcombinations of the functions, components, and / or features of the various implementations described.

Claims

1. a battery system divided into a first sector and a second sector that are substantially equal to one another; a first bidirectional DC / DC converter, the first bidirectional DC / DC converter being galvanically isolated and coupled to the first sector; and a second bidirectional DC / DC converter, the second bidirectional DC / DC converter being galvanically isolated and coupled to the second sector; Provided with: Here, the first bidirectional DC / DC converter and the second bidirectional DC / DC converter balance the charge states of the first sector and the second sector before the first sector and the second sector are connected in parallel. Electric car.

2. The electric vehicle of claim 1 , further comprising an on-board charger, wherein the first bidirectional DC / DC converter and the second bidirectional DC / DC converter are part of the on-board charger.

3. The electric vehicle of claim 2 , wherein the on-board charger has a multi-stage architecture further including a power factor correction stage.

4. The electric vehicle of claim 3 , wherein the power factor correction stage is common to the first bidirectional DC / DC converter and the second bidirectional DC / DC converter.

5. 2. The electric vehicle of claim 1, further comprising a load for the battery system, the load comprising a first load coupled to the first bidirectional DC / DC converter and a second load coupled to the second bidirectional DC / DC converter.

6. The electric vehicle of claim 1 , wherein the first sector and the second sector are connected in parallel for at least charging the battery system.

7. 10. The electric vehicle of claim 1, wherein the first sector and the second sector are connected in series to drive at least an inverter of the electric vehicle.

8. 2. The electric vehicle of claim 1, further comprising a first bus bar connecting a positive terminal of the first bidirectional DC / DC converter, a positive terminal of the first sector, and a positive terminal of the second sector via a first contact between the positive terminal of the first sector and the positive terminal of the second sector.

9. 9. The electric vehicle of claim 8, further comprising a second bus bar connecting a negative terminal of the second bidirectional DC / DC converter, a negative terminal of the second sector, and a negative terminal of the first sector via a second contact between the negative terminal of the second sector and the negative terminal of the first sector.

10. 10. The electric vehicle of claim 9, further comprising a third bus bar connecting the negative terminal of the first sector and the positive terminal of the second sector via a third contact between the negative terminal of the first sector and the positive terminal of the second sector.

11. 11. The electric vehicle of claim 10, wherein the first contact and the second contact are open and the third contact is closed to connect the first sector and the second sector in series.

12. 11. The electric vehicle of claim 10, wherein the first contact and the second contact are closed and the third contact is open to connect the first sector and the second sector in parallel.

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