JP7524733B2 - Electric vehicle power supply system - Google Patents

Description

The technology disclosed herein relates to a power supply system for an electric vehicle that includes multiple battery modules.

Patent Document 1 discloses a battery control system equipped with a battery module for a vehicle that includes multiple battery cells connected in series. Some of the battery cells in the battery module are used to supply power to both the rotating electric machine for driving and the auxiliary load. The operation of the switching elements of the DC/DC converter is controlled to prevent the SOC (State Of Charge) of the cells shared with the auxiliary load from falling below the lower limit.

JP 2017-112734 A

However, in the configuration of Patent Document 1, among the battery cells of the battery module, the battery cells that are used to supply power to both the rotating electric machine for driving and the auxiliary load are predetermined. For this reason, there is a concern that variation in SOC may occur between this auxiliary shared cell and other cells dedicated to high-voltage power supply.

The technology disclosed herein aims to reduce variation in the SOC of each battery module in a power supply system for an electric vehicle equipped with multiple battery modules.

In the technology disclosed herein, a power supply system for an electric vehicle includes a plurality of battery modules, a low-voltage output terminal that outputs power of a first voltage to be supplied to an auxiliary device of the electric vehicle, a high-voltage output terminal that outputs power of a second voltage higher than the first voltage to be supplied to an electric motor of the electric vehicle, a ground terminal, a plurality of relays provided on a power supply line in the power supply system, and a control unit that controls the open/closed state of the plurality of relays, and the plurality of relays include a plurality of first relays provided on a power supply line that connects the positive electrode of each battery module to the low-voltage output terminal, a plurality of second relays provided on a power supply line that connects the negative electrode of each battery module to the ground terminal, a plurality of third relays provided between the battery modules in a circular power supply line that connects the plurality of battery modules in series and in a circular manner, and a plurality of fourth relays provided on a power supply line that connects the positive electrode of each battery module to the high-voltage output terminal.

According to this configuration, by controlling the open/close states of the multiple first relays and the multiple second relays, one of the multiple battery modules can be selected and connected between the low voltage output terminal and the ground terminal. In addition, by controlling the open/close states of the multiple third relays and the multiple fourth relays, the multiple battery modules can be connected in series between the high voltage output terminal and the ground terminal. This makes it possible to output power of the first voltage to be supplied to the auxiliary equipment while outputting power of the second voltage to be supplied to the electric motor, and to select the battery module that outputs power of the first voltage from among the multiple battery modules. Therefore, since it is possible to appropriately switch between the battery modules that output power of the first voltage while outputting power of the second voltage, it is possible to suppress variations in the SOC of each battery module.

In addition, when the control unit causes a first battery module, which is one of the plurality of battery modules, to output power of the first voltage, the control unit may: among the plurality of first relays, close a first relay corresponding to the first battery module and open other first relays; among the plurality of second relays, close a second relay corresponding to the first battery module and open other second relays; among the plurality of third relays, open a third relay between the first battery module and a battery module located on the negative electrode side of the first battery module in the annular power supply line and close other third relays; and among the plurality of fourth relays, close a fourth relay corresponding to a battery module located on the negative electrode side of the first battery module in the annular power supply line and open other fourth relays.

This allows the first battery module to output power of a first voltage to be supplied to an auxiliary device, while multiple battery modules can be connected in series to output power of a second voltage to be supplied to an electric motor.

The control unit may also be capable of acquiring the SOC (State Of Charge) of the plurality of battery modules, and when it determines that there is an imbalance in the SOC of the plurality of battery modules, it may switch the battery module that outputs the first voltage power.

This helps prevent imbalances in the SOC of each battery module.

The control unit may also execute a predetermined switching sequence when the ignition of the electric vehicle is off, and the predetermined switching sequence may include a step of opening the third relays and the fourth relays, and a step of closing the first relays and the second relays.

As a result, when the ignition is off, multiple battery modules are connected in parallel, allowing charging and discharging between each battery module, correcting any SOC imbalance.

The control unit may also execute a predetermined switching sequence when switching the battery module that outputs the first voltage from the first battery module to the second battery module, and the predetermined switching sequence may include a step of opening the plurality of third relays and the plurality of fourth relays, a step of closing a first relay corresponding to the second battery module among the plurality of first relays and closing a second relay corresponding to the second battery module among the plurality of second relays, a step of opening a first relay corresponding to the first battery module among the plurality of first relays and opening a second relay corresponding to the first battery module among the plurality of second relays, a step of closing a third relay among the plurality of third relays other than the third relay between the second battery module and the battery module located on the negative electrode side of the second battery module in the annular power supply line, and a step of closing a fourth relay among the plurality of fourth relays corresponding to the battery module located on the negative electrode side of the second battery module in the annular power supply line.

This allows the battery module that outputs the first voltage power to be supplied to the auxiliary equipment to be reliably switched.

In addition, each of the battery modules may include a plurality of cells and an output mechanism that is configured to be switchable between a first state in which the cells are connected in series to output power and a second state in which the cells are connected in parallel, and the control unit may control the state of the output mechanism of each of the battery modules, and may set the output mechanism of the battery modules that output power to the first state and set the output mechanism of the battery modules that do not output power to the second state.

This allows the charge state of the multiple cells inside a battery module that is not outputting power to be balanced.

As described above, the technology disclosed herein allows the power supply system of an electric vehicle equipped with multiple battery modules to switch between battery modules that output low-voltage power to be supplied to auxiliary equipment, thereby making it possible to suppress variation in the SOC of each battery module.

Circuit configuration example of a power supply system for an electric vehicle according to an embodiment 2A to 2B are operation examples of the power supply system shown in FIG. 1. 2 is a flowchart showing an example of control of the power supply system of FIG. 1 . Example of sequence SQ1 in FIG. Example of sequence SQ2 in FIG. 10 is a flowchart showing another example of the control of the power supply system of FIG. 1 . Example of the internal structure of a battery module Example of sequence SQ3 in FIG. Example of sequence SQ3 in FIG.

An exemplary embodiment will be described in detail below with reference to the drawings.

Figure 1 shows an example of the configuration of a power supply system for an electric vehicle according to an embodiment. The power supply system in Figure 1 includes four battery modules 10 (numbered 1 to 4 in the figure, and hereinafter referred to as modules 1 to 4 as appropriate). Each battery module 10 outputs power at a voltage of 12V. However, in this disclosure, the number of battery modules 10 included in the power supply system is not limited to four, and the output voltage of the battery modules 10 is not limited to 12V.

The power supply system of FIG. 1 includes a low voltage output terminal 21, a high voltage output terminal 22, and a ground terminal 23. The low voltage output terminal 21 is a terminal for mainly supplying power to the vehicle's auxiliary equipment, and the high voltage output terminal 22 is a terminal for mainly supplying power to the motor that drives the vehicle. In this embodiment, the low voltage output terminal 21 outputs 12V power, and the high voltage output terminal 22 outputs 48V power. However, in this disclosure, the output voltage of the power supply system is not limited to 12V or 48V.

A total of 16 relays 30 (marked with circled numbers 1 to 16 in the figure, hereinafter referred to as relays 1 to 16 as appropriate) are provided on the power lines in the power supply system of Figure 1. Each relay 30 is configured to be switchable between on (closed state) and off (open state) by a control signal sent from the control unit 15. When a relay 30 is on, the power lines on both ends are connected, and when a relay 30 is off, the power lines on both ends are disconnected.

In the power supply system of FIG. 1, relays 1, 3, 5, and 7 (multiple first relays) are provided on the power supply line connecting the positive electrode of each battery module 10 to the low-voltage output terminal 21. Relays 2, 4, 6, and 8 (multiple second relays) are provided on the power supply line connecting the negative electrode of each battery module 10 to the ground terminal 23. Relays 9, 10, 11, and 12 (multiple third relays) are provided between the battery modules 10 in the annular power supply line that connects the multiple battery modules 10 in series and in a ring shape. Relays 13, 14, 15, and 16 (multiple fourth relays) are provided on the power supply line connecting the positive electrode of each battery module 10 to the high-voltage output terminal 22. Note that one end of the relay 12 is connected to the negative electrode of module 1 (indicated by a dashed line and a thick black arrow in FIG. 1), but in the following figures, this dashed line is omitted to avoid cluttering the figures.

The power supply system in FIG. 1 can output 48V power from the high-voltage output terminal 22 by connecting four battery modules 10 in series, and in this state, can output 12V power from any one of the battery modules 10 via the low-voltage output terminal 21.

Figures 2(a)-(b) show an example of the operation of the power supply system of Figure 1. In Figures 2(a)-(b), relays 10 that are on and relays 10 that are off are distinguished from each other. In addition, the flow of electricity that outputs 12V power is shown by dashed line PL, and the flow of electricity that outputs 48V power is shown by dashed line PH. The same applies to the subsequent figures.

In FIG. 2(a), relays 1, 2, 9, 10, 11, and 16 are on, and the other relays are off. In this state, modules 4, 3, 2, and 1 are connected in series between the high-voltage output terminal 22 and the ground terminal 23, in that order. Module 1 is connected between the low-voltage output terminal 21 and the ground terminal 23. In FIG. 2(b), relays 3, 4, 10, 11, 12, and 13 are on, and the other relays are off. In this state, modules 1, 4, 3, and 2 are connected in series between the high-voltage output terminal 22 and the ground terminal 23, in that order. Module 2 is connected between the low-voltage output terminal 21 and the ground terminal 23.

In FIG. 2(c), relays 5, 6, 9, 11, 12, and 14 are on, and the other relays are off. In this state, modules 2, 1, 4, and 3 are connected in series between the high-voltage output terminal 22 and the ground terminal 23, in that order. Module 3 is connected between the low-voltage output terminal 21 and the ground terminal 23. In FIG. 2(d), relays 7, 8, 9, 10, 12, and 15 are on, and the other relays are off. In this state, modules 3, 2, 1, and 4 are connected in series between the high-voltage output terminal 22 and the ground terminal 23, in that order. Module 4 is connected between the low-voltage output terminal 21 and the ground terminal 23.

By using the power supply system of FIG. 1, 48V output and 12V output can be performed simultaneously. In addition, the battery module 10 that outputs 12V can be switched appropriately. This makes it easy to balance the SOC (State of Charge) of each battery module 10, for example.

(First control example)
FIG. 3 is a flowchart showing an example of control of the power supply system shown in FIG.

First, the control unit 15 acquires the SOC for each battery module 10 included in the power supply system (S11). Then, it is determined whether or not an SOC imbalance has occurred in each battery module 10 (S12). For example, it is determined here whether or not the difference between the maximum SOC of each battery module 10 and the SOC of the battery module 10 currently supplying 12V power exceeds a predetermined value, and if it exceeds the predetermined value, it is determined that an SOC imbalance has occurred. Note that the method of determining whether or not an SOC imbalance has occurred in each battery module 10 is not limited to this. For example, it may be determined whether or not the SOC of the battery module 10 currently supplying 12V power is below the average SOC of each battery module 10.

Then, the control unit 15 determines whether the vehicle ignition (IG) is on or off (S13). If the IG is off, sequence SQ1 is executed, and if the IG is on, sequence SQ2 is executed.

In sequence SQ1, all relays 9 to 16 provided on the high voltage line, i.e., the power supply line for implementing 48V output, are turned off (S21). Then, all relays 1 to 8 provided on the low voltage line, i.e., the power supply line for implementing 12V output, are turned on (S22).

Figure 4 shows an example of sequence SQ1. As shown in Figure 4(a), relays 1, 2, 9, 10, 11, and 16 are now on, and 48V output from modules 1 to 4 and 12V output from module 1 are being performed. As shown in Figure 4(b), in step S21, relays 9, 10, and 11 are turned off. Then, as shown in Figure 4(c), in step S22, relays 3 to 8 are turned on. As a result, the 48V output is stopped, and 12V output is performed by modules 1 to 4 connected in parallel. This prevents the SOC of only module 1 from decreasing, and eliminates the SOC imbalance of each battery module 10.

In sequence SQ2, first, it is determined whether the high voltage line is unused (S31). If the high voltage line is in use (NO in S31), sequence SQ2 is terminated. If the high voltage line is unused (YES in S31), all relays 9 to 16 installed on the high voltage line are turned off (S32). Then, the relays installed on the low voltage line of the battery module 10 (new low voltage power supply module) newly used for 12V output are turned on (S33), and the relays installed on the low voltage line of the battery module 10 (old low voltage power supply module) used for 12V output are turned off (S34). In this embodiment, the battery module 10 with the highest SOC is the new low voltage power supply module. Then, some of the relays installed on the high voltage line are turned on so that 48V output can be performed (S35).

An example of sequence SQ2 is shown in FIG. 5. As shown in FIG. 5(a), it is assumed that relays 1, 2, 9, 10, 11, and 16 are on, and 48V output from modules 1 to 4 and 12V output from module 1 are being performed. As shown in FIG. 5(b), in step S32, relays 9, 10, and 11 are turned off. Then, as shown in FIG. 5(c), in step S33, module 2 is selected as the new low-voltage power supply module, and relays 3 and 4 in its low-voltage line are turned on. As shown in FIG. 5(d), in step S34, relays 1 and 2 in the low-voltage line of module 1, which is the old low-voltage power supply module, are turned off. Then, as shown in FIG. 5(e), in step S35, relays 10 to 13 provided in the high-voltage line are turned on so that 48V output can be performed. As a result, 48V output from modules 1 to 4 and 12V output from module 2 can be performed. This makes it possible to switch battery module 10 for 12V output while maintaining 48V output.

(Second control example)
Fig. 6 is a flow chart showing another example of control of the power supply system shown in Fig. 1. In Fig. 6, steps common to Fig. 3 are given the same reference numerals, and detailed description thereof may be omitted here.

In this control example, it is assumed that each battery module 10 has an internal configuration as shown in FIG. 7. As shown in FIG. 7, each battery module 10 has four cells 40 (numbered 1 to 4 in the figure, and hereinafter referred to as cells 1 to 4 as appropriate). Each cell 40 outputs 3V power. However, the number of cells 40 included in the battery module 10 is not limited to four, and the output voltage of the cells 40 is not limited to 3V.

The battery module in FIG. 7 is provided with a total of nine internal relays 50 (numbered 1 to 9 in the figure, hereinafter referred to as internal relays 1 to 9 as appropriate). Each internal relay 50 is configured to be switchable between on (closed state) and off (open state) by a control signal sent from the control unit 15. When an internal relay 50 is on, the power lines on both ends are connected, and when an internal relay 50 is off, the power lines on both ends are disconnected.

When internal relays 2, 5, and 8 are on and internal relays 1, 3, 4, 6, 7, and 9 are off, the four cells 40 are connected in series. At this time, the battery module 10 can output 12 V (first state). On the other hand, when internal relays 1, 3, 4, 6, 7, and 9 are on and internal relays 2, 5, and 8 are off, the four cells 40 are connected in parallel. At this time, the charge states of the cells 40 can be balanced (second state). In other words, the output mechanism that is configured to be able to switch between the first state and the second state is composed of the power supply line and the internal relay 50.

As shown in FIG. 6, first, the control unit 15 acquires the SOC for each battery module 10 included in the power supply system (S11). Then, it is determined whether or not an SOC imbalance has occurred in each battery module 10 (S12). The method of determining whether or not an SOC imbalance exists is the same as in the first control example. The control unit 15 also determines whether the vehicle ignition (IG) is on or off (S13). If the IG is on, sequence SQ2 is executed. The above is the same as in the first control example.

When the IG is off, sequence SQ3 is executed between steps S21 and S22 described in the first control example. In sequence SQ3, first, the internal relays 1, 3, 4, 6, 7, and 9 of the battery modules 10 other than the old low-voltage power supply module that is outputting 12V are turned on (S41). This state is maintained until the charge state of the cells 40 is balanced (S42).

For example, in the example in Figure 8, relays 1 and 2 are on and module 1 is outputting 12V. In S41, internal relays 1, 3, 4, 6, 7, and 9 of modules 2 to 4 are turned on. As a result, in modules 2 to 4 that are not outputting 12V, internal cells 1 to 4 are connected in parallel and charge and discharge with each other, resulting in an even balance of the charge state.

Then, the relay in the low voltage line of the new low voltage power supply module is turned on, and the internal relays 2, 5, and 8 for connecting the cells in series in the new low voltage power supply module are turned on (S43). Then, the relay in the low voltage line of the old low voltage power supply module is turned off, and the internal relays 2, 5, and 8 for connecting the cells in series in the old low voltage power supply module are turned off (S44). Then, for the old low voltage power supply module, the internal relays 1, 3, 4, 6, 7, and 9 are turned on (S45). This state is maintained until the charge state balance of the cells 40 becomes uniform (S46).

For example, in the example of Figure 9, module 2 is selected as the new low-voltage power supply module that will newly output 12V. Relays 3 and 4 in the low-voltage line of module 2 are turned on, and internal relays 2, 5, and 8 for connecting cells in series within module 2 are turned on. Meanwhile, in module 1, which is the old low-voltage power supply module that no longer outputs 12V, its internal relays 1, 3, 4, 6, 7, and 9 are turned on. As a result, cells 1 to 4 are connected in parallel, and by charging and discharging each other, the charge state becomes evenly balanced.

As described above, in this embodiment, in the power supply system, the multiple relays 30 provided on the power supply lines include relays 1, 3, 5, and 7 provided on the power supply lines connecting the positive electrode of each battery module 10 to the low voltage output terminal 21, relays 2, 4, 6, and 8 provided on the power supply lines connecting the negative electrode of each battery module 10 to the ground terminal 23, relays 9-12 provided between the battery modules 10 in the annular power supply line that connects the multiple battery modules 10 in series and in a ring shape, and relays 13-16 provided on the power supply lines connecting the positive electrode of each battery module 10 to the high voltage output terminal 22.

With this configuration, by controlling the open/closed states of relays 1, 3, 5, 7 and relays 2, 4, 6, 8, one of the multiple battery modules 10 can be selected and connected between the low voltage output terminal 21 and the ground terminal 23. In addition, by controlling the open/closed states of relays 9-12 and 13-16, the multiple battery modules 10 can be connected in series between the high voltage output terminal 22 and the ground terminal 23. This makes it possible to output 48V power to be supplied to the motor while outputting 12V power to be supplied to the auxiliary equipment, and the battery module 10 that outputs 12V power can be selected from the multiple battery modules 10. Therefore, the battery module 10 that outputs 12V power while outputting 48V power can be switched appropriately.

The above-described embodiments are merely examples and should not be interpreted as limiting the scope of the present disclosure. The scope of the present disclosure is defined by the claims, and all modifications and variations that fall within the scope of equivalence of the claims are within the scope of the present disclosure.

10 Battery module 15 Control unit 21 Low voltage output terminal 22 High voltage output terminal 23 Ground terminal 30 Relay 40 Cell 50 Internal relay

Claims (6)

A power supply system for an electric vehicle,
A plurality of battery modules;
a low voltage output terminal that outputs electric power having a first voltage to be supplied to an auxiliary device of the electric vehicle;
a high voltage output terminal that outputs electric power having a second voltage higher than the first voltage to be supplied to an electric motor of the electric vehicle;
A ground terminal;
A plurality of relays provided on a power supply line in the power supply system;
a control unit for controlling an open/closed state of the plurality of relays,
The plurality of relays include
a plurality of first relays each provided in a power supply line connecting a positive electrode of each of the battery modules and the low voltage output terminal;
a plurality of second relays each provided on a power supply line connecting the negative electrode of each of the battery modules to the ground terminal;
a plurality of third relays provided between the battery modules in an annular power supply line that connects the plurality of battery modules in series and in a circular manner;
a plurality of fourth relays each provided in a power supply line connecting a positive electrode of each battery module and the high voltage output terminal. 2. The power supply system for an electric vehicle according to claim 1,
When the control unit causes a first battery module, which is one of the plurality of battery modules, to output power of the first voltage,
Among the plurality of first relays, a first relay corresponding to the first battery module is closed and other first relays are opened;
Among the plurality of second relays, a second relay corresponding to the first battery module is closed and other second relays are opened;
Among the plurality of third relays, a third relay between the first battery module and a battery module located on a negative electrode side of the first battery module in the annular power supply line is opened, and other third relays are closed;
a fourth relay corresponding to a battery module that is located on a negative electrode side of the first battery module in the annular power line is set to a closed state, and other fourth relays are set to an open state, among the plurality of fourth relays. 3. The power supply system for an electric vehicle according to claim 2,
the control unit is capable of acquiring SOC (State Of Charge) of the plurality of battery modules, and when it determines that there is an imbalance in the SOC of the plurality of battery modules, switches the battery module that is caused to output power of the first voltage. 3. The power supply system for an electric vehicle according to claim 2,
The control unit executes a predetermined switching sequence when an ignition of the electric vehicle is turned off,
The predetermined switching sequence is
placing the third relays and the fourth relays in an open state;
and closing the plurality of first relays and the plurality of second relays. 3. The power supply system for an electric vehicle according to claim 2,
the control unit executes a predetermined switching sequence when switching a battery module that outputs power of the first voltage from the first battery module to a second battery module,
The predetermined switching sequence is
placing the third relays and the fourth relays in an open state;
setting a first relay corresponding to the second battery module among the plurality of first relays in a closed state, and setting a second relay corresponding to the second battery module among the plurality of second relays in a closed state;
setting a first relay corresponding to the first battery module among the plurality of first relays in an open state and setting a second relay corresponding to the first battery module among the plurality of second relays in an open state;
closing the third relays among the plurality of third relays, other than a third relay between the second battery module and a battery module located on a negative electrode side of the second battery module in the annular power supply line;
and closing a fourth relay, among the plurality of fourth relays, that corresponds to a battery module that is located on the negative electrode side of the second battery module in the annular power line. 2. The power supply system for an electric vehicle according to claim 1,
Each of the plurality of battery modules is
A plurality of cells;
an output mechanism configured to be switchable between a first state in which the plurality of cells are connected in series to output electric power and a second state in which the plurality of cells are connected in parallel,
The control unit controls a state of the output mechanism of each of the battery modules; and
setting the output mechanism of the battery module that outputs electric power to the first state;
a power supply system for an electric vehicle, the power supply system being characterized in that the output mechanism is set to the second state for the battery module that is not causing the battery module to output electric power.

Images