JP7616015B2 - Power Control Device - Google Patents

Description

The technology disclosed in this specification relates to a power control device.

Patent document 1 describes a power control device. This power control device includes a master DC-DC converter provided between a battery and a motor, and a control device that controls the operation of the master DC-DC converter. The control device controls the operation of the master DC-DC converter so that the power supplied through the master DC-DC converter is equal to or less than a stored limit value.

JP 2013-090517 A

In a DC-DC converter provided between a first circuit including a generator and a first battery, and a second circuit including a second battery and an electrical load, when the electrical load is switched on and off, there is a risk that excessive power will flow through the DC-DC converter, or that excessive input/output will occur in the generator and each battery. In order to avoid this, as in the conventional technology described above, it is possible to set a limit value for the operation of the DC-DC converter. However, simply setting such a limit value uniformly makes it difficult to appropriately suppress the above-mentioned transient phenomenon. This specification provides a technology for appropriately setting a limit value for the operation of the DC-DC converter.

This specification discloses a power control device. The power control device includes a DC-DC converter provided between a first circuit including a generator and a first battery and a second circuit including a second battery and an electric load, and a control device that controls the operation of the DC-DC converter so that the power supplied from the first circuit to the second circuit is equal to or less than a stored limit value. The control device is configured to execute a first process for determining a new target value for the power supply based on the power consumption by the electric load after the switching when the electric load is switched on and off, and a second process for changing the stored current limit value until it becomes equal to the new target value when the new target value is determined. In the second process, the speed at which the limit value is changed is changed depending on the direction in which the electric load is switched on and off and the magnitude relationship between the current limit value and the new target value.

In the power control device described above, the operation of the DC-DC converter is controlled so that the power supplied from the first circuit to the second circuit is equal to or less than the limit value stored in the control device. The limit value stored in the control device is configured to be updated when the electric load is switched on and off. First, the control device determines a new target value for the power supply based on the power consumption by the electric load after switching. Next, the control device changes the current limit value stored until it becomes equal to the new target value. At this time, the control device changes the speed at which the limit value is changed depending on the direction in which the electric load is switched on and off and the magnitude relationship of the current limit value to the new target value.

For example, when the electric load is switched from off to on and the current limit value is greater than the new target value, the control device may instantaneously change the limit value to the new target value. Suppose that in the above situation, the limit value is not instantaneously changed to the new target value (i.e., the limit value is not instantaneously lowered to the target value). In this case, when the electric load is switched from off to on, the power supplied from the first circuit to the second circuit increases, and excessive power may flow to the DC-DC converter. On the other hand, in the above configuration, in the above situation, the limit value is instantaneously changed to the new target value (i.e., the limit value is instantaneously lowered to the target value). Therefore, the power supplied from the first circuit to the second circuit is limited, and excessive power is prevented from flowing to the DC-DC converter. In this way, the control device can appropriately set the limit value for the operation of the DC-DC converter.

Alternatively, the control device may gradually change the limit value to the new target value at a predetermined rate of change when the electric load is switched from off to on and the current limit value is smaller than the new target value. Here, assume a situation in which the capacity of the first battery included in the first circuit is small, etc., and sufficient power cannot be supplied from the first battery to the DC-DC converter. In such a case, when the electric load is switched from off to on, the power generated by the generator is supplied to the second circuit via the DC-DC converter. If, in such a situation, the limit value is not gradually changed to the new target value at a predetermined rate of change (i.e., the limit value is instantly raised to the new target value), the power to be supplied from the first circuit to the second circuit will fluctuate relatively abruptly. As a result, due to the relatively abrupt change in the power to be generated by the generator, the generator may not be able to keep up with the power to be generated. On the other hand, in the above configuration, in such a situation, the limit value is gradually changed to the new target value at a predetermined rate of change, so that the power to be generated by the generator fluctuates relatively gently. As a result, the generator can appropriately generate the power it needs to generate. In this way, the control device can appropriately set limit values for the operation of the DC-DC converter.

Alternatively, the control device may gradually change the limit value to the new target value at a predetermined rate of change when the electric load is switched from on to off and the current limit value is greater than the new target value. As described above, when the electric load is on, the power generated by the generator is supplied to the second circuit via the DC-DC converter. Then, when the electric load is switched from on to off, the limit value is not gradually changed to the new target value at a predetermined rate of change (i.e., the limit value is instantly lowered to the new target value). In this case, the power to be supplied from the first circuit to the second circuit fluctuates relatively abruptly. Due to this, at least a portion of the power generated by the generator is no longer supplied to the DC-DC converter, and the power is supplied to the first battery of the first circuit. If the power is relatively large, there is a risk that the power exceeding the power permitted by the first battery is supplied to the first battery. On the other hand, in the above configuration, the limit value is gradually changed to the new target value at a predetermined rate of change, so the power supplied from the first circuit to the second circuit fluctuates relatively slowly. That is, the power supplied from the generator to the DC-DC converter also fluctuates relatively slowly. For this reason, by fluctuating the power generated by the generator while the power fluctuates relatively slowly, it is possible to prevent the generator from supplying power to the first battery that exceeds the power allowed by the first battery. In this way, the control device can appropriately set the limit value for the operation of the DC-DC converter.

As described above, by changing the speed at which the limit value is changed depending on the direction in which the electrical load is switched on and off and the magnitude relationship of the current limit value to the new target value, it is possible to appropriately set the limit value for the operation of the DC-DC converter.

1 shows a schematic circuit diagram of a power control device according to an embodiment; 4 shows a flowchart of a process executed by a control device. 1 shows a graph illustrating the relationship between limit values and target values in various situations. FIG. 13 shows a schematic circuit diagram of a modified power control device.

The power control device 2 of the embodiment will be described with reference to the drawings. As shown in FIG. 1, the power control device 2 includes a first circuit 10, a second circuit 20, a DC-DC converter 100, and a control ECU 102. The power control device 2 is mounted on a vehicle such as a hybrid vehicle. Note that the solid lines in FIG. 1 represent power lines, and the dashed lines represent signal lines.

The first circuit 10 includes a first battery 12, a first electrical load 14, and a generator 16. The first battery 12 is a secondary battery such as a lithium ion battery or a lead battery. In this embodiment, the output of the first battery 12 is greater than the output of a second battery 24 described later. The first electrical load 14 is not particularly limited, and may be one through which a large current flows when its operating state is switched from off to on. The generator 16 is, for example, a motor generator, which is a device that converts kinetic energy into electrical energy. The first battery 12 and the generator 16 are configured to be able to communicate with the control ECU 102. Although not shown, the first circuit 10 is provided with sensors (e.g., a current sensor, a voltage sensor, etc.) that can acquire information such as the current flowing through the first circuit 10, and these sensors are also configured to be able to communicate with the control ECU 102.

The second circuit 20 includes a second electric load 22 and a second battery 24. The second electric load 22 is, for example, a starter that starts an engine (not shown), and a large current flows when its operating state is switched from off to on. The second battery 24 is, for example, a secondary battery such as a lithium ion battery or a lead battery. The output of the second battery 24 is, for example, 12 volts. The second battery 24 is configured to be able to communicate with the control ECU 102. Although not shown, the second circuit 20 is provided with sensors (for example, a current sensor, a voltage sensor, etc.) that can acquire information such as the current flowing through the second circuit 20, and these sensors are also configured to be able to communicate with the control ECU 102.

The DC-DC converter 100 is provided between the first circuit 10 and the second circuit 20. The DC-DC converter 100 is a bidirectional converter capable of stepping down the power of the first circuit 10 and supplying it to the second circuit 20, and stepping up the power of the second circuit 20 and supplying it to the first circuit 10. For example, when the second battery 24 is charged, power is supplied from the first circuit 10 to the second battery 24 via the DC-DC converter 100. Also, for example, when the capacity of the second battery 24 is small when operating the second electric load 22, and sufficient power cannot be supplied from the second battery 24 to the second electric load 22, power is supplied from the first circuit 10 to the second circuit 20 via the DC-DC converter 100. The specific circuit configuration of the DC-DC converter 100 is well known, so a detailed description thereof will be omitted. The DC-DC converter 100 is configured to be able to communicate with the control ECU 102.

The control ECU 102 controls the operation of the first battery 12, the generator 16, the second battery 24, the DC-DC converter 100, etc. In particular, the control ECU 102 stores a limit value for the power supply from the first circuit 10 to the second circuit 20. The control ECU 102 controls the operation of the DC-DC converter 100 so that the power supply from the first circuit 10 to the second circuit 20 is equal to or less than the stored limit value. The control ECU 102 supplies a power generation command to the generator 16 based on the limit value, the capacity of the first battery 12, etc. As a result, power is generated in the generator 16, and the power output from the first battery 12 and the power generated by the generator 16 are supplied to the DC-DC converter 100.

Next, the process executed by the control ECU 102 will be described with reference to FIG. 2. The process in FIG. 2 is executed while the control ECU 102 is running. In the initial state in FIG. 2, the control ECU 102 stores the above-mentioned limit value.

In S10, the control ECU 102 judges whether or not an electric load off request has been acquired. The electric load off request is output from a higher-level controller (not shown) when the second electric load 22 is switched from on to off. The higher-level controller is a controller that controls the operation of the entire vehicle, and switches the second electric load 22 on and off according to the user's operation or the running state of the vehicle. When the second electric load 22 is switched from on to off, the higher-level controller transmits an electric load off request to a lower-level controller (not shown) that controls the second electric load 22. At this time, the electric load off request is also transmitted to the control ECU 102 of the power control device 2. This allows the control ECU 102 to recognize in advance that the second electric load 22 is switched from on to off. When the control ECU 102 acquires an electric load off request from the higher-level controller, it judges YES in S10 and proceeds to S40. On the other hand, if the control ECU 102 does not receive a request to turn off the electric load from the upper controller, it determines NO in S10 and proceeds to S12.

In S12, the control ECU 102 judges whether or not an electric load on request has been acquired. As with the electric load off request described above, the electric load on request is also output from the controller. That is, when the second electric load 22 is switched from off to on, the upper controller transmits an electric load on request to the lower controller that controls the second electric load 22. At this time, the electric load on request is also transmitted to the control ECU 102 of the power control device 2. This allows the control ECU 102 to recognize in advance that the second electric load 22 is switched from off to on. When the control ECU 102 acquires an electric load on request from the upper controller, it judges YES in S12 and proceeds to S20. On the other hand, when the control ECU 102 does not acquire an electric load on request from the upper controller, it judges NO in S12 and ends the processing of FIG. 2. That is, when the control ECU 102 acquires neither an electric load off request nor an electric load on request, it maintains the stored limit value.

In S20, the control ECU 102 determines a target value after the second electric load 22 is switched from off to on. Specifically, when the second electric load 22 is switched from off to on, the control ECU 102 calculates the power consumption by the second electric load 22 after the second electric load 22 is switched on, based on various information such as the current flowing through the second circuit 20. Then, the control ECU 102 determines a target value based on the calculated power consumption by the second electric load 22. In other words, the target value is the power required in the second circuit 20 after the second electric load 22 is switched from off to on. The target value is used as a target value for changing the limit value when changing the limit value of the DC-DC converter 100 described later.

In S22, the control ECU 102 determines whether the stored limit value is greater than the determined target value (see S20). If the limit value is greater than the target value, the control ECU 102 determines YES in S22 and proceeds to S30, and if the limit value is less than the target value, the control ECU 102 determines NO in S22 and proceeds to S50.

In S30, the control ECU 102 updates the stored limit value. Specifically, the control ECU 102 instantaneously changes the limit value to the target value determined in S20. In this way, when the second electric load 22 is switched from off to on and the stored limit value is greater than the target value calculated in S20, the control ECU 102 instantaneously sets the target value as a new limit value. When the processing of S30 ends, the processing of FIG. 2 ends.

In addition, in S40, the control ECU 102 determines the target value after the second electric load 22 is switched from on to off. The specific method for determining the target value is the same as the processing in S20.

In S50, the control ECU 102 sets the rate of change of the limit value. The rate of change may be, for example, a value stored in advance by the control ECU 102, or may be a value determined by the control ECU 102 based on the difference between the current limit value and the determined target value (see S20 or S40).

In S52, the control ECU 102 executes a process of changing the limit value at the change rate set in S50. Then, in S54, the control ECU 102 judges whether the changed limit value matches the determined target value (see S20 or S30). If the changed limit value matches the target value, the control ECU 102 judges YES in S54 and ends the process of FIG. 2. On the other hand, if the limit value does not match the target value, the control ECU 102 judges NO in S54 and returns to the process of S52. That is, the control ECU 102 repeatedly executes the process of changing the limit value at the set change rate until the stored limit value matches the target value.

Although not shown, as described above, the control ECU 102 controls the DC-DC converter 100 based on the new limit value set in S30 or S50 so that the power supplied from the first circuit 10 to the second circuit 20 is equal to or less than the limit value.

Next, specific cases will be described with reference to FIG. 3. First, with reference to FIG. 3(A), a case will be described in which the second electrical load 22 is switched from off to on and the current limit value is greater than the target value. In the initial state of FIG. 3(A), the second electrical load 22 is off.

As shown in FIG. 3(A), at time t1, the control ECU 102 acquires an electric load on request from a higher-level controller in response to the second electric load 22 being switched from off to on (YES in S12 in FIG. 2). In this case, the control ECU 102 determines the target value G1 after the second electric load 22 is switched from off to on (S20). In the case of FIG. 3(A), since the current limit value is greater than the target value G1 (YES in S22), the control ECU 102 instantly changes the limit value to the target value G1 (S30).

Assuming that, as shown in FIG. 3A, when the second electric load 22 is switched from off to on and the current limit value is greater than the target value G1, the limit value is not instantly changed to the target value G1 (i.e., the limit value is not instantly lowered to the target value G1). In this case, when the second electric load 22 is switched from off to on, the power supplied from the first circuit 10 to the second circuit 20 increases, and excessive power may flow to the DC-DC converter 100. On the other hand, in the configuration of this embodiment, in the above situation, the limit value is instantly changed to the target value G1 (i.e., the limit value is instantly lowered to the target value G1 (see time t1)). Therefore, the power supplied from the first circuit 10 to the second circuit 20 is limited, so that excessive power is prevented from flowing to the DC-DC converter 100. In this way, the control ECU 102 can appropriately set the limit value for the operation of the DC-DC converter 100.

Next, referring to FIG. 3(B), a case will be described in which the second electrical load 22 is switched from off to on and the current limit value is smaller than the target value. In the initial state of FIG. 3(B), the second electrical load 22 is off.

3(B), the control ECU 102 acquires an electric load on request from a higher-level controller in response to the second electric load 22 being switched from off to on at time t2 (YES in S12 in FIG. 2). In this case, the control ECU 102 determines the target value G1 (S20). In the case of FIG. 3(B), since the current limit value is smaller than the target value G1 (NO in S22), the control ECU 102 sets the change rate (i.e., the slope of the straight line between times t2 and t3 in FIG. 3(B)) (S50). The control ECU 102 changes the limit value at the set change rate (i.e., the slope) (S52). The control ECU 102 changes the limit value until it matches the target value G1 (NO in S54, S52). Then, at time t3, the limit value matches the target value G1 (YES in S54, return).

Here, assume that the capacity of the first battery 12 included in the first circuit 10 is small, and the first battery 12 cannot supply sufficient power to the DC-DC converter 100. In such a case, when the second electric load 22 is switched from off to on, the power generated by the generator 16 is supplied to the second circuit 20 via the DC-DC converter 100. If, in such a situation, the limit value is not gradually changed to the target value G1 at a predetermined change rate (i.e., the limit value is instantly increased to the target value G1), the power to be supplied from the first circuit 10 to the second circuit 20 fluctuates relatively abruptly. As a result, due to the relatively abrupt change in the power to be generated by the generator 16, the generator 16 may not be able to keep up with the power to be generated. On the other hand, in the configuration of this embodiment, in such a situation, the limit value is gradually changed to the target value G1 at a predetermined change rate (S50 to S54 in FIG. 2), so the power to be generated by the generator 16 fluctuates relatively gently. As a result, the generator 16 can appropriately generate the power that it should generate. In this way, the control ECU 102 can appropriately set limit values for the operation of the DC-DC converter 100.

Next, referring to FIG. 3(C), a case will be described in which the second electrical load 22 is switched from on to off and the current limit value is greater than the target value. In the initial state of FIG. 3(C), the second electrical load 22 is on.

3(C), the control ECU 102 acquires an electric load off request from a higher-level controller in response to the second electric load 22 being switched from on to off at time t4 (YES in S10 in FIG. 2). In this case, the control ECU 102 determines the target value G2 after the second electric load 22 is switched from on to off (S40). Then, the control ECU 102 sets the change rate (i.e., the slope of the straight line between times t4 and t5 in FIG. 3(C)) (S50). The control ECU 102 changes the limit value at the set change rate (i.e., the slope) (S52). The control ECU 102 changes the limit value until the limit value matches the target value G2 (NO in S54, S52). Then, at time t5, the limit value matches the target value G2 (YES in S54, return).

When the second electric load 22 is on, the electric power generated by the generator 16 is supplied to the second circuit 20 via the DC-DC converter 100. Then, when the second electric load 22 is switched from on to off, the limit value is not gradually changed to the target value G2 at a predetermined change rate (i.e., the limit value is instantly lowered to the target value G2). In this case, the electric power to be supplied from the first circuit 10 to the second circuit 20 fluctuates relatively abruptly. Due to this, at least a part of the electric power generated by the generator 16 is no longer supplied to the DC-DC converter 100, and the electric power is supplied to the first battery 12 of the first circuit 10. If the electric power is relatively large, there is a risk that the electric power exceeding the electric power permitted by the first battery 12 is supplied to the first battery 12. On the other hand, in the configuration of this embodiment, the limit value is gradually changed to the target value G2 at a predetermined change rate (S50 to S54 in FIG. 2), so the power supplied from the first circuit 10 to the second circuit 20 fluctuates relatively slowly. That is, the power supplied from the generator 16 to the DC-DC converter 100 also fluctuates relatively slowly. For this reason, by fluctuating the power generated by the generator 16 while the power fluctuates relatively slowly, it is possible to prevent the power supplied from the generator 16 to the first battery 12 from exceeding the power allowed by the first battery 12. In this way, the control ECU 102 can appropriately set the limit value for the operation of the DC-DC converter 100.

As described above, by changing the speed at which the limit value is changed depending on the direction in which the second electrical load 22 is switched on and off (i.e., from off to on or from on to off) and the magnitude relationship of the current limit value to the new target value, it is possible to appropriately set the limit value for the operation of the DC-DC converter 100.

Notes regarding the above embodiment are as follows. As shown in FIG. 4, the first circuit 10 does not have to be provided with the first electrical load 14. In addition, in the above embodiment, an example in which the voltages of the first circuit 10 and the second circuit 20 are different has been described, but the voltages of the first circuit 10 and the second circuit 20 may be the same.

The control ECU 102 in the embodiment is an example of a "control device" in the technology disclosed herein. The process of S20 and S40 in FIG. 2 in the embodiment is an example of a "first process" in the technology disclosed herein. The process of S30 and S50 to S54 in FIG. 2 in the embodiment is an example of a "second process" in the technology disclosed herein.

Specific examples of the technology disclosed in this specification have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of those objectives is itself technically useful.

2: Power control device 10: First circuit 12: First battery 14: First electric load 16: Generator 20: Second circuit 22: Second electric load 24: Second battery 100: DC-DC converter 102: Control ECU

Claims (4)

A power control device,
a DC-DC converter provided between a first circuit including a generator and a first battery and a second circuit including a second battery and an electrical load;
a control device that controls an operation of the DC-DC converter so that the power supplied from the first circuit to the second circuit is equal to or less than a stored limit value;
Equipped with
The control device includes:
a first process for determining, when the electric load is switched on and off, a new target value for the supply power based on power consumption by the electric load after the switching;
a second process for changing the stored current limit value until the current limit value becomes equal to the new target value when the new target value is determined;
is configured to be able to execute
In the second process, a speed at which the limit value is changed is changed depending on a direction in which the electric load is switched on and off and a magnitude relationship between the new target value and the current limit value.
Power control device. The power control device according to claim 1, wherein, when the electrical load is switched from off to on and the current limit value is greater than the new target value, the second process instantaneously changes the limit value to the new target value. The power control device according to claim 1 or 2, wherein, when the electric load is switched from off to on and the current limit value is smaller than the new target value, the second process gradually changes the limit value to the new target value at a predetermined rate of change. The power control device according to any one of claims 1 to 3, wherein, when the electric load is switched from on to off and the current limit value is greater than the new target value, the second process gradually changes the limit value to the new target value at a predetermined rate of change.

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