Power Conversion Device

Abstract

A power conversion device with high conversion efficiency is provided. [Solution] A power conversion device 100 connected between a first voltage system including a first power source B1 and a second voltage system having a different voltage from the first voltage system has three or more power conversion units 110 connected in parallel between the first voltage system and the second voltage system, each of the three or more power converters 110 being connected to the first power source B1 via a first switch S1, and the maximum conversion capacity values ​​of the three or more power conversion units 110 being different from one another.

Description

[Technical Field]

[0001] The present invention relates to a power conversion device. [Background technology]

[0002] Electric vehicles are equipped with a high-voltage battery for driving an electric motor. As automobiles become more and more electrified, the power consumption of low-voltage-driven auxiliary equipment is increasing. For this reason, technology has been developed to convert the power output from the high-voltage battery into low-voltage power using a DC-DC converter and supply this power to the low-voltage-driven auxiliary equipment (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-161839 Summary of the Invention [Problem to be solved by the invention]

[0004] In low-voltage systems, power consumption can be significantly lower when the vehicle is parked than when it is driving. If a DC-DC converter with high conversion efficiency when the vehicle is driving is also used when the vehicle is parked, where power consumption is low, the conversion efficiency of the DC-DC converter will decrease.

[0005] An object of the present invention is to provide a power conversion device with high conversion efficiency. [Means for solving the problem]

[0006] In order to solve the above problem, a power conversion device according to an embodiment of the present invention is a power conversion device connected between a first voltage system including a first power source and a second voltage system having a different voltage from the first voltage system, and has three or more power conversion units connected in parallel between the first voltage system and the second voltage system, each of the three or more power converters being connected to the first power source via a first switch, and the maximum conversion capacity values ​​of the three or more power conversion units being different from one another. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a power conversion device with high conversion efficiency. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a power conversion device 100 according to an embodiment of the present invention. [Figure 2] 3 is a diagram showing the relationship between the states of the first switches S1A, S1B, and S1C and the maximum conversion capacity value of the power conversion device 100. FIG. [Figure 3] 10 is a diagram showing the relationship between power consumption in the second voltage system, the threshold value, and control of the first switch S1. FIG. [Figure 4] FIG. 10 is a diagram showing an example of a processing operation in a control unit 120. [Figure 5] FIG. 2 is a diagram illustrating another example of the power conversion device 100. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Power conversion device 100> FIG. 1 is a diagram illustrating a power conversion device 100 according to an embodiment of the present invention. The power conversion device 100 is a DC-DC converter connected between a first voltage system and a second voltage system. The voltage of the second voltage system is different from that of the first voltage system, and the power conversion device 100 converts power input from the first voltage system to a voltage of the second voltage system and outputs the converted power to the second voltage system. The voltage of the second voltage system is, for example, lower than that of the first voltage system, and the power conversion device 100 steps down the power input from the first voltage system from the voltage of the first voltage system to the voltage of the second voltage system and outputs the stepped-down power to the second voltage system.

[0010] The first voltage system includes a first power source B1 that supplies power to the first voltage system, and the power conversion device 100 converts the power supplied from the first power source B1 into a voltage for the second voltage system and outputs the converted power to the second voltage system. The first power source B1 is, for example, a storage battery. As shown in FIG. 1, the first voltage system may include one or more first loads L1 (e.g., motors) that are driven by the voltage of the first voltage system. As shown in FIG. 1, the first loads L1 may be connected to the first power source B1 via an inverter.

[0011] The second voltage system includes a plurality of second loads L2 driven by the voltage of the second voltage system. The second voltage system may also include a second power source B2 that supplies the voltage of the second voltage system. The second power source B2 is, for example, a storage battery.

[0012] The three or more power conversion devices 100 have three or more power conversion units 110 and a control unit 120. In the example shown in Fig. 1, the power conversion device 100 has, as the three or more power conversion units 110, a first power conversion unit 110A, a second power conversion unit 110B, and a third power conversion unit 110C.

[0013] Each of the three or more power conversion units 110 is connected in parallel between a first voltage system and a second voltage system. Each of the three or more power conversion units 110 is an isolated DC-DC converter that converts power input from the first voltage system from the voltage of the first voltage system to the voltage of the second voltage system and outputs the converted power to the second voltage system. Each of the three or more power conversion units 110 may be configured with one isolated DC-DC converter, or, as described in detail below, may be configured with two or more isolated DC-DC converters.

[0014] Each of the three or more power conversion units 110 is connected to a first power supply B1 via a first switch S1. That is, the power conversion device 100 has a plurality of switches S1, and each of the plurality of switches S1 corresponds one-to-one to the three or more power conversion units 110. In the example shown in FIG. 1 , the first power converter 110A corresponds to the first switch S1A and is connected to the first power supply B1 via the corresponding first switch S1A. The second power converter 110B corresponds to the first switch S1B and is connected to the first power supply B1 via the corresponding first switch S1B. The third power converter 110C corresponds to the first switch S1C and is connected to the first power supply B1 via the corresponding first switch S1C.

[0015] The three or more power conversion units 110 have different maximum conversion capacity values. In this case, it is preferable that the three or more power conversion units 110 have maximum conversion capacity values ​​that are integer multiples of a predetermined capacity value (basic capacity value). In the example shown in Fig. 1, the maximum conversion capacity value of the first power conversion unit 110A is the basic capacity value, the maximum conversion capacity value of the second power conversion unit 110B is twice the basic capacity value, and the maximum conversion capacity value of the third power conversion unit 110C is four times the basic capacity value.

[0016] The control unit 120 controls the first switch S1 based on the power consumption value in the second voltage system. In this embodiment, the power consumption value in the second voltage system changes based on which of the multiple second loads L2 included in the second voltage system is operating. That is, in this embodiment, the power consumption value in the second voltage system is determined based on, for example, the power consumption value of the operating second load L2 among the multiple second loads L2.

[0017] Therefore, the control unit 120 may, for example, acquire information relating to the start and end of operation of the second load L2, and calculate the power consumption in the second voltage system based on the acquired information relating to the start and end of operation. For example, when information relating to the start of operation of the second load L2 is acquired, the number of operating second loads L2 increases, so the power consumption in the second voltage system increases, and when information relating to the end of operation of the second load L2 is acquired, the number of operating second loads L2 decreases, so the power consumption in the second voltage system decreases.

[0018] Furthermore, the control unit 120 may measure the power consumption value in the second voltage system.

[0019] In this embodiment, the three or more power conversion units 110 have different maximum conversion capacity values. Therefore, the maximum conversion capacity value differs depending on the combination of the power conversion units 110 used. In other words, the maximum conversion capacity value of the power conversion device 100 changes depending on the state of the first switch, as shown in FIG. 2.

[0020] In the example shown in FIG. 1, there are seven combinations of power conversion units 110 that can be used: the first power conversion unit 110A only, the second power conversion unit 110B only, the second power conversion unit 110C only, a combination of the first power conversion unit 110A and the second power conversion unit 110B, a combination of the second power conversion unit 110B and the third power conversion unit 110C, a combination of the first power conversion unit 110A and the third power conversion unit 110C, and a combination of the first power conversion unit 110A, the second power conversion unit 110B and the third power conversion unit 110C.

[0021] When the first switch S1A corresponding to the first power conversion unit 110A is turned on and the first switches S1B and S1C corresponding to the second power conversion unit 110B and the third power conversion unit 110C are turned off, that is, when only the first power conversion unit 110A is used, the maximum conversion capacity value of the power conversion device 100 becomes the basic capacity value, which is the maximum conversion capacity value of the first power conversion unit 110A.

[0022] When the first switch S1B corresponding to the second power conversion unit 110B is turned on and the first switches S1A and S1C corresponding to the first power conversion unit 110A and the third power conversion unit 110C are turned off, that is, when only the second power conversion unit 110B is used, the maximum conversion capacity value of the power conversion device 100 becomes the maximum conversion capacity value of the second power conversion unit 110B (twice the basic capacity value).

[0023] When the first switches S1A and S1B corresponding to the first power conversion unit 110A and the second power conversion unit 110B are turned on and the first switch S1C corresponding to the third power conversion unit 110C is turned off, that is, when only the first power conversion unit 110A and the second power conversion unit 110B are used, the maximum conversion capacity value of the power conversion device 100 becomes the sum of the maximum conversion capacity values ​​of the first power conversion unit 110A and the second power conversion unit 110B (three times the basic capacity value).

[0024] When the first switch S1C corresponding to the third power conversion unit 110C is turned on and the first switches S1A and S1B corresponding to the first power conversion unit 110A and the second power conversion unit 110B are turned off, that is, when only the third power conversion unit 110C is used, the maximum conversion capacity value of the power conversion device 100 becomes the maximum conversion capacity value of the third power conversion unit 110C (four times the basic capacity value).

[0025] When the first switches S1A and S1C corresponding to the first power conversion unit 110A and the third power conversion unit 110C are turned on and the first switch S1B corresponding to the second power conversion unit 110B is turned off, that is, when only the first power conversion unit 110A and the third power conversion unit 110C are used, the maximum conversion capacity value of the power conversion device 100 becomes the sum of the maximum conversion capacity values ​​of the first power conversion unit 110A and the third power conversion unit 110C (five times the basic capacity value).

[0026] When the first switches S1B and S1C corresponding to the second power conversion unit 110B and the third power conversion unit 110C are turned on and the first switch S1A corresponding to the first power conversion unit 110A is turned off, that is, when only the second power conversion unit 110B and the third power conversion unit 110C are used, the maximum conversion capacity value of the power conversion device 100 becomes the sum of the maximum conversion capacity values ​​of the second power conversion unit 110B and the third power conversion unit 110C (six times the basic capacity value).

[0027] When the first switches S1A, S1B, and S1C corresponding to the first power conversion unit 110A, the second power conversion unit 110B, and the third power conversion unit 110C are turned on, that is, when all of the first switches S1A, S1B, and S1C are turned on and all of the first power conversion unit 110A, the second power conversion unit 110B, and the third power conversion unit 110C are used, the maximum conversion capacity value of the power conversion device 100 becomes the sum of the maximum conversion capacity values ​​of the first power conversion unit 110A, the second power conversion unit 110B, and the third power conversion unit 110C (7 times the basic capacity value).

[0028] That is, in this embodiment, the maximum conversion capacity value of the power conversion device 100 can be changed by the combination of first switches S1 that are turned on, that is, the combination of power conversion units 110 that are used. In the example shown in Fig. 1, three power conversion units 110A, 110B, and 110C are provided, and therefore, as shown in Fig. 2, there are seven combinations of the power conversion units 110A, 110B, and 110C, and the maximum conversion capacity value of the power conversion device 100 can take seven different values.

[0029] In this way, in this embodiment, the maximum conversion capacity value of the power conversion device 100 can take seven or more different values. Therefore, it is possible to change the maximum conversion capacity value of the power conversion device 100 so that the conversion efficiency of the power conversion device 100 is high at the power consumption value in the second voltage system. As a result, in this embodiment, it is possible to provide a power conversion device with high conversion efficiency.

[0030] Generally, for each maximum conversion capacity value, there is a power consumption value (optimum operating point) that provides the best conversion efficiency. As described above, in this embodiment, the maximum conversion capacity value differs for each combination of three or more power conversion units 110. Therefore, in this embodiment, the optimum operating point differs for each combination of power conversion units 110 used. Therefore, it is preferable that the control unit 120 controls the first switch S1 based on the power consumption in the second voltage system and the optimum operating point for each combination of power conversion units used.

[0031] In this case, a plurality of thresholds may be set, and the control unit 120 may control the first switch S1 based on the relationship between the power consumption in the second voltage system and the plurality of thresholds, as shown in Fig. 3. Fig. 3 is a diagram for the example shown in Fig. 1, showing the relationship between the power consumption P in the second voltage system, the thresholds Pt1 to Pt7, and the control of the first switch S1.

[0032] Each of the multiple thresholds corresponds to a state of the first switch S1 (i.e., each combination of the power conversion units 110 to be used), and is determined based on the maximum conversion capacity value in each state of the first switch S1 (i.e., each combination of the power conversion units 110 to be used). For example, for each combination of the power conversion units 110 to be used, the threshold corresponding to that combination (the upper limit value for that combination) is determined based on the maximum conversion capacity value or the optimal operating point for that combination.

[0033] 1, the threshold value Pt1 corresponds to a case where the first switch S1A corresponding to the first power conversion unit 110A is turned on and the first switches S1B and S1C corresponding to the second power conversion unit 110B and the third power conversion unit 110C are turned off, that is, a case where only the first power conversion unit 110A is used. Therefore, the threshold value Pt1 is determined based on a basic capacity value that is a maximum conversion capacity value of the first power conversion unit 110A or an optimal operating point of the first power conversion unit 110A.

[0034] Furthermore, the threshold value Pt2 corresponds to the case where the first switch S1B corresponding to the second power conversion unit 110B is turned on and the first switches S1A and S1C corresponding to the first power conversion unit 110A and the third power conversion unit 110C are turned off, that is, the case where only the second power conversion unit 110B is used. Therefore, the threshold value Pt2 is determined based on the maximum conversion capacity value (twice the basic capacity value) of the second power conversion unit 110B or the optimal operating point of the second power conversion unit 110B.

[0035] Furthermore, the threshold value Pt3 corresponds to the case where the first switches S1A and S1B corresponding to the first power conversion unit 110A and the second power conversion unit 110B are turned on and the first switch S1C corresponding to the third power conversion unit 110C is turned off, that is, the case where only the first power conversion unit 110A and the second power conversion unit 110B are used. Therefore, the threshold value Pt3 is determined based on the maximum conversion capacity value (three times the basic capacity value) of the combination with the second power conversion unit 110B, or the optimal operating point for the combination of the first power conversion unit 110A and the second power conversion unit 110B.

[0036] Furthermore, the threshold value Pt4 corresponds to the case where the first switch S1C corresponding to the third power conversion unit 110C is turned on and the first switches S1A and S1B corresponding to the first power conversion unit 110A and the second power conversion unit 110B are turned off, that is, the case where only the third power conversion unit 110C is used. Therefore, the threshold value Pt4 is determined based on the maximum conversion capacity value (four times the basic capacity value) of the third power conversion unit 110C or the optimal operating point of the third power conversion unit 110C.

[0037] Similarly, threshold value Pt5 is determined based on the maximum conversion capacity value (five times the basic capacity value) of the combination of the first power conversion unit 110A and the third power conversion unit 110C, or the optimal operating point of the combination of the first power conversion unit 110A and the second power conversion unit 110C. Threshold value Pt6 is determined based on the maximum conversion capacity value (six times the basic capacity value) of the combination of the second power conversion unit 110B and the third power conversion unit 110C, or the optimal operating point of the combination of the second power conversion unit 110B and the third power conversion unit 110C. Threshold value Pt7 is determined based on the maximum conversion capacity value (seven times the basic capacity value) of the combination of the first power conversion unit 110A, the second power conversion unit 110B, and the third power conversion unit 110C, or the optimal operating point of the combination of the first power conversion unit 110A, the second power conversion unit 110B, and the third power conversion unit 110C.

[0038] <Processing Operation in Control Unit 120> Fig. 4 is a diagram showing an example of the processing operation in the control unit 120. The processing operation shown in Fig. 4 is executed when information regarding the start and end of operation of the second load L2 included in the second voltage system is acquired.

[0039] The control unit 120 calculates the power consumption in the second voltage system based on the acquired information (step S401). The control unit 120 controls the first switch S1 based on the calculated power consumption and the optimal operating point of each combination of the three or more power conversion units (step S402).

[0040] <Power conversion unit 110> As described above, each of the three or more power conversion units 110 may be configured with one isolated DC-DC converter, or may be configured with two or more isolated DC-DC converters. When each of the three or more power conversion units 110 is configured with two or more isolated DC-DC converters, it is preferable that the maximum conversion capacitance values ​​of the two or more isolated DC-DC converters be the same. This makes it possible to perform noise cancellation.

[0041] In Fig. 5, each of the first power conversion unit 110A, the second power conversion unit 110B, and the third power conversion unit 110C in Fig. 1 is configured with two or more isolated DC-DC converters. In the example shown in Fig. 5, the first power conversion unit 110A is configured with two DC-DC converters whose maximum conversion capacity value is half the basic capacity value, and the second power conversion unit 110B is configured with four DC-DC converters whose maximum conversion capacity value is half the basic capacity value.

[0042] 5, in each of the three or more power conversion units 110, the two or more isolated DC-DC converters may be connected to the first switch S1 via the second switch S2. The control unit 120 may then control the first switch S1 and the second switch S2 based on the power consumption value in the second voltage system.

[0043] In this way, the maximum conversion capacity value of the power conversion device 100 can be changed by the combination of the first switch S1 and the second switch S2 to be turned on, that is, the combination of the DC-DC converters to be used. Therefore, in this way, it is possible to change the maximum conversion capacity value of the power conversion device 100 more finely so that the conversion efficiency of the power conversion device 100 becomes high at the power consumption value in the second voltage system.

[0044] For example, in the example shown in FIG. 5, if the first power conversion unit 110A is configured with two DC-DC converters whose maximum conversion capacity values ​​are half the basic capacity value, the second power conversion unit 110B is configured with four DC-DC converters whose maximum conversion capacity values ​​are half the basic capacity value, and the third power conversion unit 110C is configured with eight DC-DC converters whose maximum conversion capacity values ​​are half the basic capacity value, the maximum conversion capacity value of the power conversion device 100 can take 14 different values: half the basic capacity value, the basic capacity value, (3 / 2) times the basic capacity value, twice the basic capacity value, (5 / 2) times the basic capacity value, three times the basic capacity value, (7 / 2) times the basic capacity value, four times the basic capacity value, (9 / 2) times the basic capacity value, five times the basic capacity value, (11 / 2) times the basic capacity value, six times the basic capacity value, (13 / 2) times the basic capacity value, and seven times the basic capacity value.

[0045] The present invention has been described above in terms of preferred embodiments thereof. While the present invention has been described herein with reference to specific examples, various modifications and variations can be made to these examples without departing from the spirit and scope of the present invention as set forth in the claims. [Explanation of symbols]

[0046] 100 Power conversion device 110 Power conversion unit 110A First power conversion section 110B second power conversion unit 110C Third power conversion section 120 control section S1 First switch S2 Second switch

Claims

1. A power conversion device connected between a first voltage system including a first power supply and a second voltage system having a different voltage from that of the first voltage system, three or more power conversion units connected in parallel between the first voltage system and the second voltage system; each of the three or more power converters is connected to the first power source via a first switch; The three or more power conversion units have different maximum conversion capacity values.

2. further comprising a control unit that controls the first switch; The power conversion device according to claim 1 , wherein the control unit controls the first switch based on a power consumption value in the second voltage system.

3. 3. The power conversion device according to claim 2, wherein the control unit controls the first switch based on a power consumption value in the second voltage system and an optimal operating point for each combination of the power conversion units.

4. The power conversion device according to claim 2 , wherein a maximum conversion capacity value of the three or more power conversion units is an integer multiple of a predetermined capacity value.

5. the three or more power conversion units include a first power conversion unit, a second power conversion unit, and a third power conversion unit; a maximum conversion capacity value of the first power conversion unit is the predetermined capacity value, a maximum conversion capacity value of the second power conversion unit is twice the predetermined capacity value; The power conversion device according to claim 3 , wherein the maximum conversion capacity value of the third power conversion unit is four times the predetermined capacity value.

6. The power conversion device according to claim 1 , wherein each of the three or more power conversion units is configured by one isolated DC-DC converter.

7. The power conversion device according to claim 1 , wherein each of the three or more power conversion units is configured by two or more isolated DC-DC converters having the same maximum conversion capacity value.

8. 8. The power conversion device according to claim 7, wherein in each of the three or more power conversion units, each of the two or more isolated DC-DC converters constituting the power conversion unit is connected to the first switch via a second switch.

9. a control unit that controls the first switch and the second switch, The power conversion device according to claim 7 , wherein the control unit controls the first switch and the second switch based on a power consumption value in the second voltage system.

10. The control unit acquiring information regarding the start and end of operation of a load included in the second voltage system; The power conversion device according to claim 2 , 3 , or 8 , further comprising: a power consumption value in the second voltage system calculated based on the information relating to the start and end of operation.

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