JP3794224B2 - Vehicle power supply - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicular power supply device suitable for application to a drive module such as an electric vehicle.
[0002]
[Prior art]
Conventionally, a drive module of a vehicle such as an electric vehicle has a battery and a power supply capacitor (hereinafter referred to as a PC) that supplements the battery power as a power supply device that supplies power to an inverter that drives a three-phase AC motor. The technology which improves the acceleration performance of an electric vehicle by this is adopted.
[0003]
FIG. 7 is a diagram showing general output characteristics of a battery and a power supply capacitor that are employed in the vehicle power supply device. The state of charge (SOC) is sufficiently charged to about 100% of the rating. In this state, since the terminal voltage of the PC is higher than the terminal voltage of the battery, the power of the battery can be supplemented and the acceleration performance can be improved at the beginning of the discharge.
[0004]
However, since the charge capacity of the PC is small compared to the charge capacity of the battery, the terminal voltage of the PC quickly decreases as soon as discharging (motor driving) continues, and becomes lower than the terminal voltage of the battery. Therefore, the energy in the PC cannot be used up efficiently.
[0005]
[Problems to be solved by the invention]
Therefore, for example, in Japanese Patent Application Laid-Open No. 9-322314, as shown in FIG. 8, a battery 104 and a PC 105 are connected in parallel to a control inverter 102 of a motor 103, and a PC voltage is changed by a converter (boost circuit) 101. A technique for preventing the voltage from becoming smaller than the voltage has been proposed. This boosting technique is a technique in which energization of the PC 105 is interrupted by a switching element QS such as a thyristor, thereby boosting the output terminal voltage of the converter 101 by using a transient current generated in a coil (DCL), and the discharge is continued. By switching the switching element QS according to the decrease in the PC terminal voltage, the energy charged in the PC 105 can be used up efficiently. However, in order to realize this function by the converter 101, it is necessary to increase the capacity of the DCL considerably, which contributes to an increase in weight. Therefore, it is not realistic to employ it in an electric vehicle that is a moving body.
[0006]
In addition, as shown in FIG. 9, by switching on and off the switching elements QA and QB provided in the switching box 201 as appropriate, the battery 204 and the PC 205 are discharged in series connection during power running, and the output voltage of the PC 205 is 0V. When only the battery 204 is selected, and only the PC 205 is connected to the inverter 202 during power regeneration, and only the battery 204 is selected when the output voltage of the PC 205 approaches a predetermined upper limit value. According to the technology, it is possible to use up the energy of the PC 205 without mounting a DCL that causes an increase in weight, but since a current always flows through the PC 205, there is a bypass circuit for preventing inversion and overcurrent. It is necessary separately and there are many restrictions when charging.
[0007]
Accordingly, an object of the present invention is to provide a vehicle power supply device that efficiently uses the power of a capacitor.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a vehicle power supply device according to the present invention is characterized by the following configuration.
[0009]
That is, for example, a vehicle power supply device including a battery capable of charging / discharging high power using a chemical reaction and a capacitor capable of charging / discharging small power in a short time compared to the battery, The detection means for detecting the terminal voltage and the electrical connection state between the battery and the capacitor are switched to parallel connection when the terminal voltage at the time of discharging the capacitor is greater than a predetermined value, and in series when the terminal voltage is smaller than the predetermined value. Switching means for switching to connection, and the predetermined value is set to be larger than the terminal voltage of the battery .
[0014]
【The invention's effect】
According to the present invention, it is possible to provide a vehicle power supply device that efficiently uses the power of the capacitor.
[0015]
That is, according to the invention of claim 1, the electrical connection between the battery and the capacitor, because it is switched to the parallel connection or serial connection in accordance with the terminal voltage during discharge of the capacitor, the power of the capacitor Can be used efficiently. In particular, the connection state is switched to parallel connection when the terminal voltage at the time of discharging the capacitor is greater than a predetermined value, and is switched to series connection when the terminal voltage is smaller than the predetermined value, and the predetermined value is greater than the terminal voltage of the battery. By setting, the energy charged in the capacitor can be efficiently discharged in any connection state.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, a vehicle power supply device according to the present invention will be described in detail with reference to the drawings as an embodiment in which the vehicle power supply device is applied to a drive module of an electric vehicle.
[0020]
FIG. 1 is a diagram illustrating a system configuration of a vehicle power supply device according to the present embodiment.
[0021]
In the figure, an inverter 2 controls the rotation of a three-phase AC motor 3. The battery 4 is a main power source capable of charging and discharging high power using a chemical reaction, and is connected to the input terminal of the inverter 2 and also connected to the terminals T3 and T4 of the switching unit 1. The PC 5 is an auxiliary power source using an electric double layer capacitor or the like that can charge and discharge a small amount of electric power in a short time compared to the battery 4, and is connected to the terminals T 1 and T 2 of the switching unit 1. The switching unit 1 can switch the electrical connection state between the battery 4 and the PC 5 to a series connection or a parallel connection according to the control of the electronic control unit (ECU) 10.
[0022]
That is, the switching unit 1 includes switching elements Qs1 and Qs2 such as thyristors for intermittently energizing the PC5, a coil (DCL) for generating a transient current by the intermittent current, and the battery 4 and the PC5 connected in series or in parallel. Switching elements Q1 to Q4 for switching to connection are provided. These switching elements are appropriately turned on and off as will be described later by a microcomputer (not shown) provided in the ECU 1, thereby boosting the terminal voltage of the PC 5 and switching the connection between the battery 4 and the PC 5. Is realized.
[0023]
Next, the timing for switching between parallel connection and series connection will be described.
[0024]
FIG. 4 is a diagram for explaining the relationship between the circuit switching operation of the vehicle power supply device and the terminal voltage of the PC in the present embodiment, and the negative slope straight line shown in FIG. 4 corresponds to the continuous discharge. The output characteristic of a general power supply capacitor in which the terminal voltage decreases is shown.
[0025]
In this embodiment, the terminal voltage of the PC 5 having such output characteristics is discharged from the charged state (that is, the state where the SOC is sufficiently charged to about 100% of the rated value) at the predetermined upper limit value (drive of the motor 3). Until the terminal voltage of the PC 5 drops to the predetermined threshold value V1, the battery 4 and the PC 5 are connected in parallel. When the terminal voltage becomes smaller than the threshold value V1, the battery 4 and PC5 is used by switching to serial connection. In this case, if the threshold value V1 is set larger than the terminal voltage of the battery 4, the terminal voltage of the PC5 is higher than the terminal voltage of the battery 4 when connected in parallel, and the terminal voltage of the battery 4 and the terminal voltage of the PC5 when connected in series. Since the terminal voltage is added, the energy charged in the PC 5 can be efficiently discharged in any connection state.
[0026]
Further, as the threshold value V1 is set to a larger value, the capacity and physical size of the DCL can be reduced. Therefore, the threshold value V1 is desirable as a power supply device for a mobile body that is required to be reduced in weight. However, when switching from the parallel connection to the serial connection, the input voltage applied to the inverter 2 is determined from the combined voltage in the parallel state between the terminal voltage of the battery 4 and the terminal voltage of the PC 5 (= threshold value V1). Since the voltage suddenly changes to the added voltage, the larger the threshold value V1 is set, the larger the potential difference is applied to the inverter 2, which adversely affects the inverter 2 and affects the riding comfort of the vehicle. It also becomes a factor of torque fluctuation of the motor 3 that gives Therefore, the threshold value V1 is preferably set to a voltage value as large as possible within the range allowed by the rating (performance) of the inverter 2 and within the range of torque fluctuations that are perceptible.
[0027]
Next, the operation state at the time of parallel connection and series connection will be described.
[0028]
FIG. 2 is a diagram illustrating the flow of current when the vehicle power supply device according to the present embodiment is connected in parallel, and the flow of the discharge current at this time is indicated by an arrow in FIG.
[0029]
In the figure, the switching element Q1 is turned off, the switching element Q2 is turned on, the switching element Q3 is turned off, and the switching element Q4 is turned on, so that the battery 4 and the PC 5 are electrically connected. It is in the state of parallel connection.
[0030]
In this parallel connection state, the switching elements Qs1 and Qs2 repeat switching as the terminal voltage of the PC 5 decreases. As a result, the energization of the PC 5 is interrupted in the DCL according to the switching operation, and a transient current is generated in the DCL. Therefore, the terminal voltage of the PC 5 is boosted, and the switching element Q2 is Since the conductive state is set, the terminal voltage at the terminal T3 of the switching unit 1 is always maintained at a higher level than the terminal voltage of the battery 4.
[0031]
FIG. 3 is a diagram for explaining the flow of current when the vehicle power supply device according to this embodiment is connected in series. The flow of the discharge current at this time is indicated by an arrow in FIG.
[0032]
In the figure, the switching element Q1 is turned off, the switching element Q2 is turned off, the switching element Q3 is turned on, and the switching element Q4 is turned off, and the switching elements Qs1 and Qs2 are both turned off. Thus, the battery 4 and the PC 5 are electrically connected in series.
[0033]
Thus, if the electrical connection state of the battery 4 and the PC 5 is switched to the serial connection or the parallel connection by the switching unit 1 according to the charge amount of the PC 5, the electric energy of the PC 5 is used efficiently (use up). )be able to.
[0034]
Next, the case where the power supply switching control by the switching unit 1 described above is applied when the electric vehicle is traveling uphill will be described.
[0035]
FIG. 5 is a diagram for explaining power supply switching control when the electric vehicle equipped with the vehicle power supply device according to the present embodiment travels uphill.
[0036]
First, in steady running where the amount of change in the accelerator opening α is substantially zero, parallel connection is selected, and generally in the initial stage of starting uphill driving, the accelerator opening by the occupant is generally shown in FIG. Since the amount of change of α becomes large, the connection is switched from the parallel connection to the series connection in order to achieve the required traveling output (climbing ability).
[0037]
In the later stage when the climbing is finished, the occupant suppresses the accelerator opening α to the accelerator opening at the time of steady traveling before starting the climbing or to an accelerator opening smaller than the opening. Therefore, switching from series connection to parallel connection is performed at this timing.
[0038]
FIG. 6 is a flowchart showing a power supply switching process for an electric vehicle equipped with the vehicle power supply device in the present embodiment, and shows a control procedure executed by a CPU (not shown) of the ECU 10.
[0039]
In the figure, Steps S1 to S3: Obtain navigation information (or information on roads from the road side infrastructure) from a navigation unit (not shown) (Step S1), and based on the obtained information. Then, it is determined whether or not the host vehicle is traveling uphill (step S2). When the determination is NO (when the vehicle is not traveling uphill), the process proceeds to step S10, and when the vehicle is YES (uphill traveling). Based on the obtained information, the length of the uphill currently traveling is determined (step S3).
[0040]
In step S3, the climbing length is determined by calculating the moving average value of the accelerator opening α in a predetermined period until the present time for each control cycle, and increasing the accelerator when traveling on an uphill exceeding a certain length. By using the general driving characteristic of the driver to depress, when the calculated moving average value exceeds a predetermined value, it may be determined that the climb is long.
[0041]
Step S4, Step S5: It is determined whether or not the length of the uphill determined in Step S3 is longer than a predetermined distance (Step S4). If this determination is NO (when the uphill is shorter than the predetermined distance), a step is performed. Proceeding to S10, if YES (when the uphill is longer than the predetermined distance), it is determined whether or not the change amount of the accelerator opening α in the predetermined period is larger than a predetermined value Δα (step S5).
[0042]
Step S6: Since it is determined in step S5 that the change amount of the accelerator opening α is smaller than the predetermined value Δα, it is determined in this step whether the internal flag FL is 1, and this determination is NO (FL = 0) ), The process proceeds to step S10, and if YES (FL = 1), the process proceeds to step S7. The internal flag FL is a processing flag for storing that the amount of change in the accelerator opening α exceeds the predetermined value Δα in the determination of step S5 in the previous control cycle, as indicated by a period P in FIG. In addition, there is a general driving characteristic of the driver that the accelerator is greatly depressed in the initial stage of climbing, and then the accelerator is depressed slightly. This is used to prevent switching to parallel connection again at the timing when is returned.
[0043]
Steps S7 and S8: Since it is determined that the change amount of the accelerator opening α is larger than the predetermined value Δα in step S5 or FL = 1 in step S5, the battery 4 and the PC 5 are determined in this step. Are connected in series (or maintained in series) (step S7), and the internal flag FL is set to 1 (step S8).
[0044]
Steps S9 and S12: It is determined whether or not the current charge amount (storage amount) of the PC 5 is smaller than a predetermined value PCo (step S9). If YES (charge amount <PCo) in this determination, the current serial amount is already in series. In the case of connection, if the serial connection is maintained more than this, the PC 5 may be recharged, so the process proceeds to step S10 to set the parallel connection. When NO (charge amount ≧ PCo), the accelerator opening α is In order to determine whether or not it is in a so-called substantially fully closed state (depression amount is substantially zero), it is determined whether the accelerator opening α is smaller than a predetermined value α1 (step S12).
[0045]
When the determination in step S12 is YES (α <α1), the process proceeds to step S10. When NO (α ≧ α1), it is determined that the vehicle is continuing to climb up, the process proceeds to step S13.
[0046]
Here, if it is determined in step S12 that the accelerator opening α is smaller than the predetermined value α1, the reason for proceeding to step S10 to perform parallel connection setting will be described. The accelerator opening α is substantially fully closed. The situation is that the climbing of the vehicle is almost finished, and the driver slows down the accelerator and starts adjusting the speed for traveling on flat ground, causing deceleration and the like, and the power regeneration operation by the inverter 2 and the motor 3 starts. In order to charge the regenerative power output from the inverter 2 to the PC 5 that can be charged in a short time compared to the battery 4 with high efficiency, the state of the series connection This is because parallel connection is desirable.
[0047]
Step S10, Step S11: It is determined that the battery 4 and the PC 5 are connected in parallel (or maintained in parallel) (Step S10), the internal flag FL is set to 0 (Step S11), and the process proceeds to Step S15. In step S10, charging of the PC 5 by the battery 4 may be started.
[0048]
Step S13: It is determined whether or not the current charge amount of PC5 is larger than the predetermined value PCo and smaller than the predetermined value PC1, and if this determination is YES (PCo <charge amount <PC1), the process proceeds to step S14, and NO ( When the charge amount> PC1), it can be determined that the current charge amount of the PC5 is sufficient, so the process proceeds to step S15 to execute (or maintain) the series connection determined in step S7. Here, the predetermined value PC1 may be set to a value of about 25% of the rated full charge amount of PC5.
[0049]
Step S14: It is determined whether or not the vehicle speed V of the host vehicle is greater than a predetermined value V1, and when this determination is YES (V> V1), the torque shock that occurs even when switching from the serial connection state to the parallel connection is small. Since it can be determined that the occupant does not feel uncomfortable, the process proceeds to step S10 to perform parallel connection setting. When NO (V ≦ V1), step S15 is performed to execute (or maintain) the serial connection determined in step S7. Proceed to
[0050]
Step S15: Depending on the state of the internal flag FL set in Step S8 or Step S11, the operation states of the switching elements Q1 to Q4 of the switching unit 1 are set in series as described above with reference to FIGS. Control connection or parallel connection and return. Further, when switching to parallel connection in this step, the step-up operation at the terminal T3 of the switching unit 1 is also executed by controlling the switching frequency of the switching elements Qs1 and Qs2 according to the drop in the terminal voltage of the PC5.
[0051]
In the switching control process described above, the timing for switching from parallel connection to serial connection is not set at the start position of the uphill that can be detected in advance by navigation information or the position near it, and the accelerator is greatly depressed. The reason for setting after starting high acceleration (high output) is that, as a general occupant characteristic, the tolerance range for occupant torque shock is greater in the acceleration state than in steady driving. It is.
[0052]
Further, the determinations in step S9 and step S13 described above may be made by comparing the terminal voltage of the PC 5 with a predetermined voltage instead of performing the determination based on the charge amount.
[0053]
Thus, according to the switching control process described above, the electrical connection between the battery 4 and the PC 5 is appropriately switched by the switching unit 1 in accordance with the traveling state of the vehicle, so that the electrical energy of the PC 5 can be used efficiently. Can do.
[Brief description of the drawings]
FIG. 1 is a diagram showing a system configuration of a vehicle power supply device according to an embodiment.
FIG. 2 is a diagram for explaining a current flow when the vehicle power supply device according to the present embodiment is connected in parallel.
FIG. 3 is a diagram illustrating a current flow when the vehicle power supply device according to the present embodiment is connected in series.
FIG. 4 is a diagram illustrating the relationship between the circuit switching operation of the vehicle power supply device and the terminal voltage of the PC in the present embodiment.
FIG. 5 is a diagram for explaining power supply switching control during uphill running of an electric vehicle equipped with a vehicle power supply device according to the present embodiment.
FIG. 6 is a flowchart showing power source switching processing of an electric vehicle equipped with the vehicle power source device in the present embodiment.
FIG. 7 is a diagram showing general output characteristics of a battery and a power supply capacitor employed in the vehicle power supply device.
FIG. 8 is a diagram showing a system configuration of a conventional vehicle power supply device (example of parallel connection).
FIG. 9 is a diagram showing a system configuration of a vehicle power supply device as a conventional example (example of series connection).
[Explanation of symbols]
1: Switching unit,
2, 102, 202: inverter,
3, 103, 203: motor,
4, 104, 204: battery,
5, 105, 205: Power supply capacitor (PC),
10: Electronic control unit (ECU),
201: switching box,

Claims (1)

A power supply device for a vehicle comprising a battery capable of charging and discharging high power and a capacitor capable of charging and discharging small power in a short time compared to the battery,
Detecting means for detecting a terminal voltage of the capacitor;
Switching means for switching an electrical connection state between the battery and the capacitor to a parallel connection when a terminal voltage at the time of discharging of the capacitor is larger than a predetermined value, and to switch to a serial connection when smaller than the predetermined value ;
Equipped with a,
The vehicle power supply device , wherein the predetermined value is set to be larger than a terminal voltage of the battery .

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