Control device and control method

Abstract

To provide a control device and a control method which can suppress an amplitude of a voltage output by a power generator.SOLUTION: A control device includes a control part. The control part controls a first DCDC converter and a second DCDC converter which are connected between a high-voltage system including a high-voltage battery and a power generator and a low-voltage system including a low-voltage battery and a load, and are connected in parallel to each other. The control part drops a generation voltage by the power generator by the first DCDC converter and supplies the generation voltage to the low-voltage system when detecting a defect of the high-voltage battery, and boosts a voltage of the low-voltage system by the second DCDC converter so as to increase a low-voltage part of the generation voltage.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a control device and a control method.

Background Art

[0002] Conventionally, in a power generation system that transmits the driving force of an engine, which is a power source of a vehicle, to a generator to generate electricity, there is a control device that controls the supply of generated power to a storage battery and various loads. Further, in this type of power generation system, a DCDC converter is connected between a high-voltage system including a high-voltage battery and a generator and a low-voltage system including a low-voltage battery and a load, and there is a technique of stepping down the voltage of the high-voltage system and supplying it to the low-voltage system.

[0003] Further, in this technique, normally, the battery voltage of the high-voltage battery is stepped down and supplied to the low-voltage system, and when a failure occurs in the high-voltage battery, the generated voltage of the generator is stepped down and supplied to the low-voltage system (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the conventional technology, due to the characteristics of the generator that repeatedly drives (generates electricity) and stops by torque to generate electricity, the fluctuation range of the generated voltage becomes large. For this reason, for example, there is a risk that the generated voltage may rise and be erroneously determined as an overvoltage abnormality, or may fall and the voltage may become lower than that of the low-voltage system. Thus, conventionally, there has been room for improvement in suppressing the fluctuation range of the voltage output by the generator.

[0006] The present invention has been made in view of the above, and an object thereof is to provide a control device and a control method capable of suppressing the amplitude of the voltage output by a generator.

Means for Solving the Problems

[0007] In order to solve the above-described problems and achieve the object, a control device according to the present invention includes a control unit. The control unit controls a first DCDC converter and a second DCDC converter that are connected between a high-voltage system including a high-voltage battery and a generator and a low-voltage system including a low-voltage battery and a load and are connected in parallel to each other. When the control unit detects a failure of the high-voltage battery, the control unit steps down the generated voltage by the generator by the first DCDC converter and supplies it to the low-voltage system, and steps up the voltage of the low-voltage system by the second DCDC converter so as to increase the low-voltage portion of the generated voltage.

Effects of the Invention

[0008] According to the present invention, the amplitude of the voltage output by the generator can be suppressed.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0010] Hereinafter, with reference to the accompanying drawings, a control device and a control method according to an embodiment will be described in detail. Note that the present invention is not limited by the embodiments shown below.

[0011] First, with reference to FIGS. 1 and 2, an outline of the control method according to the embodiment will be described. FIGS. 1 and 2 are diagrams showing an outline of the control method according to the embodiment. In FIGS. 1 and 2, a power generation system S including a control device 1 according to the embodiment is shown.

[0012] The power generation system S is, for example, a system mounted on a hybrid vehicle having an engine as a power source, and is a so-called mild hybrid system that assists the driving of the engine 10 by a motor of a motor generator (MG) 12.

[0013] In the power generation system S, the driving of the engine 10 is assisted by rotating the motor during starting or low-speed driving. Also, in the power generation system S, power is generated by regeneration from the engine 10 to the generator (MG12) during deceleration.

[0014] As shown in FIG. 1, the power generation system S includes a control device 1, an engine 10, a power transmission mechanism 11, an MG12, a transformer section 13, a load 14, a LiB (lithium ion battery) 15, and a PbB (lead battery) 16.

[0015] Also, in the present disclosure, with the transformer section 13 as a boundary, the LiB15 side, which is a high-voltage battery, is referred to as a high-voltage system 110, and the PbB16 side, which is a low-voltage battery, is referred to as a low-voltage system 120. Specifically, the high-voltage system 110 is a system including the MG12 and the LiB15, and the low-voltage system 120 is a system including the load 14 and the PbB16.

[0016] The engine 10 is a power source for traveling, and is, for example, an internal combustion engine that uses fuel such as gasoline or hydrogen. The power transmission mechanism 11 is a mechanism that transmits the driving force of the engine 10 to the MG12 or transmits the rotational force of the MG12 for assisting the driving of the engine 10 to the engine 10.

[0017] MG12 is a generator that supplies the electric power generated by the operation of engine 10 to LiB15, PbB16, and load 14, and is a generator equipped with a motor (not shown). For example, during acceleration, MG12 transmits the rotational force of the motor to power transmission mechanism 11 by rotating the motor with the electric power supplied from LiB15 to assist the driving of engine 10.

[0018] Also, during deceleration, MG12 functions as a generator. Specifically, MG12 receives the driving force of engine 10 accompanying deceleration via power transmission mechanism 11, rotates the motor with such driving force to generate electricity, and supplies the generated electric power to load 14, LiB15, and PbB16.

[0019] Transformer unit 13 is connected between high-voltage system 110 and low-voltage system 120, steps down the voltage of high-voltage system 110 and supplies it to low-voltage system 120, or steps up the voltage of low-voltage system 120 and supplies it to high-voltage system 110.

[0020] Specifically, transformer unit 13 includes a first DCDC converter 13a and a second DCDC converter 13b that are connected in parallel to each other between high-voltage system 110 and low-voltage system 120. The first DCDC converter 13a and the second DCDC converter 13b are driven according to the control of control device 1.

[0021] Note that different controls are performed for the first DCDC converter 13a and the second DCDC converter 13b during normal times (no defect in LiB15) and during a defect in LiB15, which will be described later.

[0022] The load 14 is an electrical device that consumes power, and includes, for example, devices related to comfort such as a navigation device, audio, and an air conditioner. Further, the load 14 includes, for example, devices related to vehicle driving control such as an accelerator, a brake, a power steering, headlights, a PCS (Pre-crash Safety System), an AEB (Advanced Emergency Braking System), etc., and devices related to driving safety.

[0023] Note that when a failure occurs in the LiB15, the control device 1 preferentially drives devices related to vehicle driving control and driving safety. This point will be described later.

[0024] The LiB15 is an example of a high-voltage battery, and is, for example, a 48V battery. Further, the LiB15 is connected between the MG12 and the transformer unit 13 via a relay R. The relay R is cut off when a failure occurs in the LiB15 or when the MG12 over-generates electricity.

[0025] The PbB16 is an example of a low-voltage battery, and is, for example, a 12V battery, which supplies power to the load 14 and the starter 10a, and accumulates the power supplied from the MG12 and the LiB15.

[0026] Next, an operation example of the power generation system S in normal times (when there is no failure in the LiB15) and when a failure occurs in the LiB15 will be described. First, an operation example of the power generation system S in normal times will be described with reference to FIG. 1.

[0027] As shown in FIG. 1, in normal times when no failure has occurred in the LiB15, the control device 1 steps down the battery voltage of the LiB15 with the first DCDC converter 13a and the second DCDC converter 13b respectively, and supplies it to the low-voltage system 120.

[0028] As a result, even if the amount of power required by the load 14 increases, power can be supplied from both the first DCDC converter 13a and the second DCDC converter 13b, thereby preventing a shortage of power supplied to the load 14 with high precision.

[0029] Furthermore, by operating both the first DCDC converter 13a and the second DCDC converter 13b to supply power to the load 14, the operating load of each DCDC converter can be reduced, and heat generation due to the operation of each DCDC converter can be suppressed.

[0030] In addition, the control device 1 may drive the first DC-DC converter 13a and the second DC-DC converter 13b only when the amount of power required in the low-voltage system 120, i.e., the amount of power consumed by the load 14, is large (when there are many loads 14 in operation).

[0031] In other words, when the amount of power consumed by the load 14 is small and can be met by only the first DC-DC converter 13a, the control device 1 may drive only the first DC-DC converter 13a and stop the second DC-DC converter 13b.

[0032] Next, an example of the operation of the power generation system S when the LiB 15 fails will be described with reference to Fig. 2. For example, when the battery voltage of the LiB 15 falls below a predetermined threshold, the control device 1 detects the failure of the LiB 15 and cuts off the relay R.

[0033] 2, when the LiB 15 fails, the control device 1 instructs the MG 12 to generate power, and causes the first DC-DC converter 13a to step down the voltage generated by the MG 12 and supply it to the low-voltage system 120. In addition, the control device 1 causes the second DC-DC converter 13b to step up the voltage of the low-voltage system 120 so as to increase the low-voltage portion of the generated voltage.

[0034] Here, the voltage waveforms of each part at the time of the failure of LiB15 will be described. FIG. 3 is a diagram showing the voltage waveforms of each part. In FIG. 3, from the top, the generated voltage by MG12, the output voltage of the second DCDC converter 13b when the boosting operation is performed, and the input voltage to the first DCDC converter 13a are shown respectively.

[0035] As shown in FIG. 3, due to the characteristic that the generated voltage by the power generation of MG12 repeats driving (power generation) and stopping by torque, the amplitude of the voltage value becomes large. In the example shown in FIG. 3, when the target value of the generated voltage is set near 48V, it greatly swings up or down with respect to 48V.

[0036] For this reason, for example, when the generated voltage swings up, there is a risk of being erroneously determined as an overvoltage abnormality. On the other hand, when the generated voltage swings down, there is a risk that the voltage will become lower than that of the low-voltage system 120.

[0037] Therefore, in the control method according to the embodiment, when the failure of LiB15 is detected, among the first DCDC converter 13a and the second DCDC converter 13b, for the second DCDC converter 13b, the voltage of the low-voltage system 120 is boosted and supplied to the high-voltage system 110.

[0038] In the example shown in FIG. 3, the control device 1 performs a boosting operation by the second DCDC converter 13b in the section D where the voltage value is less than the threshold value in the voltage waveform of the generated voltage. As a result, since the output voltage of the second DCDC converter 13b is added to the generated voltage, the input voltage of the first DCDC converter 13a becomes a voltage waveform in which the low-voltage part of the generated voltage has risen.

[0039] That is, in the control method according to the embodiment, the low-voltage part of the generated voltage is raised to a certain value by the output voltage of the second DCDC converter 13b. Thereby, the amplitude of the generated voltage can be suppressed. Also, since the low-voltage part of the generated voltage is raised to a certain value, it is possible to accurately avoid the generated voltage from becoming lower than the voltage of the low-voltage system 120.

[0040] Furthermore, in the control method according to the embodiment, since the low-voltage portion of the generated voltage can be boosted to a certain value, the target value of the generated voltage can be lowered.

[0041] As a result, the fluctuation range of the generated voltage can be further suppressed. Also, as the target value of the generated voltage is lowered, the voltage value when the generated voltage swings upward also becomes relatively low, so it is possible to highly accurately avoid being erroneously determined as an overvoltage abnormality.

[0042] Next, with reference to FIG. 4, the configuration of the control device 1 according to the embodiment will be described. FIG. 4 is a block diagram showing the configuration of the control device 1 according to the embodiment. As shown in FIG. 4, the control device 1 includes a control unit 2 and a storage unit 3. The control unit 2 includes a detection unit 21, a cutoff unit 22, an MG control unit 23, a converter control unit 24, and a load control unit 25. The storage unit 3 stores various information necessary for the control of the control unit 2 and information generated by the control unit 2.

[0043] Here, the control device 1 includes, for example, a computer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a data flash, input / output ports, etc., and various circuits.

[0044] The CPU of the computer functions as the detection unit 21, the cutoff unit 22, the MG control unit 23, the converter control unit 24, and the load control unit 25 of the control unit 2 by, for example, reading and executing a program stored in the ROM.

[0045] Also, at least one or all of the detection unit 21, the cutoff unit 22, the MG control unit 23, the converter control unit 24, and the load control unit 25 of the control unit 2 can be configured by hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

[0046] In addition, the memory unit 3 corresponds to, for example, a RAM or a data flash. The RAM and the data flash can store information such as various program information. Note that the control device 1 may acquire the above-described programs and various information via other computers connected by a wired or wireless network or a portable recording medium.

[0047] Next, each function of the control unit 2 (the detection unit 21, the cutoff unit 22, the MG control unit 23, the converter control unit 24, and the load control unit 25) will be described.

[0048] The detection unit 21 detects a defect in the LiB15. For example, when the detection value of the voltage sensor that detects the battery voltage of the LiB15 is less than a predetermined threshold value, the detection unit 21 detects a defect in the LiB15.

[0049] The detection unit 21 notifies the cutoff unit 22, the MG control unit 23, and the load control unit 25 that a defect in the LiB15 has been detected.

[0050] When the cutoff unit 22 detects a defect in the LiB15 by the detection unit 21, the cutoff unit 22 cuts off the relay R. Note that the cutoff unit 22 may directly perform control to cut off (or connect) the relay R, or may notify a cutoff instruction to a control device (not shown) that controls the relay R.

[0051] The MG control unit 23 controls the power generation by the MG12. For example, when the detection unit 21 detects a defect in the LiB15, the MG control unit 23 performs power generation by the MG12. The MG control unit 12 may, for example, set the set value of the power generation voltage to a voltage value lower than that in the normal state (when there is no defect in the LiB15) when the detection unit 21 detects a defect in the LiB15.

[0052] The converter control unit 24 controls the transformer unit 13. In the normal state, the converter control unit 24 steps down the battery voltage of the Li15 by the first DCDC converter 13a and the second DCDC converter 13b and supplies it to the low-voltage system 120.

[0053] Further, when the detection unit 21 detects a defect in the LiB15, the converter control unit 24 steps down the power generation voltage by the MG12 using the first DCDC converter 13a and supplies it to the low-voltage system 120.

[0054] Also, when the detection unit 21 detects a defect in the LiB15, the converter control unit 24 steps up the voltage of the low-voltage system 120 (the battery voltage of the PbB16) using the second DCDC converter 13b and supplies it to the high-voltage system 110.

[0055] Specifically, the converter control unit 24 steps up the voltage of the low-voltage system 120 so as to increase the low-voltage portion of the power generation voltage. More specifically, the converter control unit 24 monitors the voltage waveform of the power generation voltage, and in a section of the voltage waveform where the voltage value is less than a predetermined threshold value, step-up is performed by the second DCDC converter 13b.

[0056] In this way, the converter control unit 24 can increase the low-voltage portion of the power generation voltage with high precision by monitoring the voltage waveform of the power generation voltage.

[0057] The load control unit 25 controls the driving of the load 14. For example, when a defect in the LiB15 is detected, the load control unit 25 selects and drives a load 14 to be preferentially driven from among the loads 14. Specifically, the load control unit 25 selects, as the load 14 to be preferentially driven, loads related to vehicle driving such as the accelerator, brake, power steering, headlights, PCS (Pre-crash Safety System), AEB (Advanced Emergency Braking System), etc., and loads related to driving safety during driving.

[0058] For example, the load control unit 25 sets a priority for each load 14, and selects the load 14 that preferentially drives the load 14 whose priority is equal to or higher than a predetermined value. Thereby, even when a defect of the LiB 15 is detected and power is supplied only by the first DCDC converter 13a, the load 14 with a high priority can be driven. Note that a load switch (not shown) is provided for the input of each load 14, and selection can be made by turning on the load switch of the load 14 to be driven.

[0059] In this way, by selecting the load 14 that preferentially drives the load related to the running of the vehicle as the load control unit 25, the vehicle can continue to run even when a defect occurs in the LiB 15.

[0060] Next, with reference to FIG. 5, the procedure of the process executed by the control device 1 according to the embodiment will be described. FIG. 5 is a flowchart showing the procedure of the process executed by the control device 1 according to the embodiment.

[0061] As shown in FIG. 5, first, the detection unit 21 detects a defect in the LiB 15 (step S101). For example, the detection unit 21 detects a defect in the LiB 15 when the battery voltage of the LiB 15 becomes less than the threshold value.

[0062] Subsequently, when the detection unit 21 detects a defect in the LiB 15, the cutoff unit 22 cuts off the relay R (step S102).

[0063] Subsequently, the MG control unit 23 generates power by the MG 12 (step S103).

[0064] Subsequently, the converter control unit 24 monitors the voltage waveform of the generated voltage by the MG 12 (step S104).

[0065] Subsequently, the converter control unit 24 performs boosting by the second DCDC converter 13b in a section where the voltage is less than the threshold value among the monitored voltage waveforms (step S105), and ends the process.

[0066] As described above, the control device 1 according to the embodiment includes a control unit 2. The control unit 2 controls a first DCDC converter 13a and a second DCDC converter 13b that are connected between a high-voltage system 110 including a high-voltage battery (LiB15) and a generator (MG12) and a low-voltage system 120 including a low-voltage battery (PbB16) and a load 14 and are connected in parallel to each other. When the control unit 2 detects a failure of the high-voltage battery, it steps down the generated voltage by the generator using the first DCDC converter 13a and supplies it to the low-voltage system 120, and steps up the voltage of the low-voltage system 120 using the second DCDC converter 13b so as to raise the low-voltage portion of the generated voltage. Thereby, the fluctuation range of the voltage (generated voltage) output by the generator (MG12) can be suppressed.

[0067] Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the specific details and representative embodiments presented and described as above. Accordingly, various changes can be made without departing from the spirit or scope of the general inventive concept defined by the appended claims and their equivalents.

Explanation of Reference Numerals

[0068] 1 Control device 2 Control unit 3 Storage unit 10 Engine 11 Power transmission mechanism 13 Transformer unit 13a First DCDC converter 13b Second DCDC converter 14 Load 21 Detection unit 22 Shut-off unit 23 MG control unit 24 Converter control unit 25 Load control unit R Relay S Power generation system

Claims

1. A control unit is provided for controlling a first DC-DC converter and a second DC-DC converter that are connected between a high-voltage system including a high-voltage battery and a generator and a low-voltage system including a low-voltage battery and a load, and are connected in parallel with each other. The control unit When detecting a failure of the high-voltage battery, steps of stepping down the generated voltage by the generator by the first DC-DC converter and supplying it to the low-voltage system, and stepping up the voltage of the low-voltage system by the second DC-DC converter to increase a low-voltage portion of the generated voltage. A control device characterized by the above.

2. The control unit Monitors a voltage waveform of the generated voltage, and performs boosting by the second DC-DC converter in a section of the voltage waveform where a voltage value is less than a predetermined threshold value. The control device according to claim 1, characterized by the above.

3. The load Includes a plurality of loads, The control unit When detecting a failure of the high-voltage battery, selects and drives a load to be preferentially driven among the plurality of loads. The control device according to claim 1 or 2, characterized by the above.

4. The plurality of loads Include loads related to vehicle running, The control unit When detecting a failure of the high-voltage battery, selects a load related to vehicle running among the plurality of loads as the load to be preferentially driven. The control device according to claim 3, characterized by the above.

5. A control method including a control step of controlling a first DC-DC converter and a second DC-DC converter that are connected between a high-voltage system including a high-voltage battery and a generator and a low-voltage system including a low-voltage battery and a load, and are connected in parallel with each other. The control step When detecting a failure of the high-voltage battery, steps of stepping down the generated voltage by the generator by the first DC-DC converter and supplying it to the low-voltage system, and stepping up the voltage of the low-voltage system by the second DC-DC converter to increase a low-voltage portion of the generated voltage. A control method characterized by the above.

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