JP2017216796A - Electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To limit variation in residual capacity among plural cell modules and suppress an over-charged state of an auxiliary equipment battery that is electrically connected to each battery module.SOLUTION: An electric vehicle 1 includes: a motor 10 being a drive source of the vehicle; a battery pack 40 for supplying the motor with power; a detection device 46 for detecting a residual capacity of each of plural battery modules 42; an auxiliary equipment battery 60 for supplying auxiliary equipment incorporated in the vehicle with power; a power line 80 electrically connected to the auxiliary equipment battery; a converter 44 for transmitting and receiving power between each of the plural battery modules and the power line; and a control device 200 for executing variation suppression control. Further, in a case where first and second battery modules, of the plural battery modules, shows a residual capacity difference being larger than a threshold, the variation suppression control is executed to minimize the residual capacity difference by transmitting and receiving power among the plural battery modules by using the converter.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for suppressing variation in remaining capacity between a plurality of battery modules mounted on an electric vehicle.

  Conventionally, an electric vehicle on which an assembled battery including a plurality of battery modules is mounted is known. In such a plurality of battery modules, the remaining capacity may vary. For example, Japanese Patent Application Laid-Open No. 2008-199789 (Patent Document 1) addresses such a problem when the remaining capacity variation between battery modules constituting the assembled battery is larger than a predetermined value. A technique for discharging a large battery module is disclosed. Patent Document 1 discloses a technique for charging an auxiliary battery using surplus power of a battery module having a large remaining capacity.

JP 2008-199789 A

  By the way, as in Patent Document 1, not only between each battery module and the auxiliary battery, but also by transferring power between each battery module, the power is transferred between each battery module, and the remaining capacity varies. It is also possible to charge the auxiliary battery while suppressing. However, when power is exchanged between each battery module in addition to between each battery module and the auxiliary battery, some power may flow to the auxiliary battery when power is exchanged between the battery modules. In this case, if the remaining capacity of the auxiliary battery is close to the fully charged state, the auxiliary battery may be in an overcharged state.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to suppress variation in remaining capacity among a plurality of battery modules and to connect auxiliary batteries electrically connected to each battery module. It is providing the electric vehicle which suppresses that it will be in an overcharge state.

  An electric vehicle according to an aspect of the present invention includes a motor that is a drive source of the vehicle, a plurality of battery modules, an assembled battery that supplies power to the motor, and detection that detects a remaining capacity of each of the plurality of battery modules. An apparatus, an auxiliary battery for supplying power to an auxiliary machine mounted on the vehicle, a power line electrically connected to the auxiliary battery, and a power line between each of the plurality of battery modules and the power line And the remaining capacity difference between the first battery module and the second battery module of the plurality of battery modules is larger than a threshold value, and the remaining capacity of the auxiliary battery is larger than the target value. If the battery capacity is high, output power from the auxiliary battery to the assembled battery until the remaining capacity of the auxiliary battery falls below the target value, and then use a converter to transfer power between multiple battery modules to determine the remaining capacity difference. If you shrink And a control unit for executing suppression control month.

  In this way, when the remaining capacity of the auxiliary battery is higher than the target value, power is output from the auxiliary battery to the assembled battery until the remaining capacity of the auxiliary battery becomes equal to or less than the target value. Therefore, after that, dispersion control is performed to reduce the remaining capacity difference by transferring power between a plurality of battery modules, and even if some power flows to the auxiliary battery, the auxiliary battery becomes overcharged. This can be suppressed. In addition, when the remaining capacity of the auxiliary battery is higher than the target value, the power of the auxiliary battery is supplied to a plurality of battery modules having a variation in the remaining capacity. Variation of the remaining capacity can be suppressed.

  According to the present invention, it is possible to provide an electric vehicle that suppresses variation in remaining capacity among a plurality of battery modules and suppresses an auxiliary battery that is electrically connected to each battery module from being overcharged. .

1 is a block diagram schematically showing an overall configuration of an electric vehicle according to an embodiment. It is a flowchart which shows the control processing performed with ECU mounted in the electric vehicle which concerns on this Embodiment. It is a figure which shows the remaining capacity of the auxiliary battery before and after execution of buffer amount ensuring control.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  In the embodiments described below, the vehicle will be described as an example of an electric vehicle equipped with a motor generator as a drive source. However, the vehicle may be an electric vehicle equipped with an assembled battery including a plurality of battery modules. That's fine. The vehicle may be, for example, a hybrid vehicle equipped with a motor generator and an engine.

  FIG. 1 is a block diagram schematically showing an overall configuration of an electric vehicle (hereinafter simply referred to as a vehicle 1) 1 according to the present embodiment. The vehicle 1 includes an MG (Motor Generator) 10, a PCU (Power Control Unit) 20, an SMR (System Main Relay) 30, an assembled battery 40, a first DC / DC converter 50, an auxiliary battery 60, an intermediate A potential bus 90 and an ECU (Electronic Control Unit) 200 are provided.

  MG10 is, for example, a three-phase AC permanent magnet motor. In response to the power supplied from the assembled battery 40 via the PCU 20, the MG 10 rotates the drive wheels of the vehicle 1. The MG 10 can also generate power by regenerative braking of the vehicle 1. In this case, the assembled battery 40 is charged by supplying the power generated in the MG 10 to the assembled battery 40 via the PCU 20.

  The PCU 20 boosts the DC power of the assembled battery 40 in accordance with a control signal from the ECU 200, converts the boosted DC power into AC power, and supplies the AC power to the MG 10. Further, during regenerative braking, the PCU 20 converts AC power generated in the MG 10 into DC power, and steps down the converted DC power to a voltage suitable for charging the battery pack 40 and supplies the voltage to the battery pack 40. The PCU 20 may convert the DC power of the assembled battery 40 into AC power without increasing the voltage and supply the AC power to the MG 10.

  The SMR 20 is electrically connected between the PCU 20 and the assembled battery 40. The SMR 20 switches the state between the PCU 20 and the assembled battery 40 to one of a conduction state (on state) and a cutoff state (off state) in accordance with a control signal from the ECU 200.

  The assembled battery 40 is a DC power source configured to be rechargeable. The assembled battery 40 typically includes a secondary battery such as a nickel metal hydride battery or a lithium ion battery. The voltage of the assembled battery 40 is, for example, a voltage of about 200V.

  The assembled battery 40 includes a plurality of battery modules 42 and a plurality of second DC / DC converters 44. The plurality of battery modules 42 are connected in series. Each of the plurality of battery modules 42 is configured by connecting a plurality of battery cells in series. The output voltage of each of the plurality of battery modules 42 is, for example, about 7-8V.

  The first DC / DC converter 50 reduces the power received from the assembled battery 40 to the auxiliary machine voltage based on a control signal from the ECU 200, and various auxiliary machines (not shown) mounted on the auxiliary battery 60 and the vehicle 1. ). The ECU 200 stops the first DC / DC converter 50 when the SOC variation control described later is executed, and operates the first DC / DC converter 50 while the vehicle 1 is traveling.

  The second DC / DC converter 44 is a converter having a smaller capacity than the first DC / DC converter 50 and capable of bidirectional power conversion. The second DC / DC converter 44 includes a terminal (hereinafter referred to as a low voltage side terminal) connected to the battery module 42 and a terminal (hereinafter referred to as a high voltage side terminal) connected to the intermediate potential bus 90. The low-voltage side terminal of the second DC / DC converter 44 is connected to a positive line connected to the positive terminal of the battery module 42 and a negative line connected to the negative terminal. A positive line and a negative line constituting the intermediate potential bus 90 are connected to the high-voltage side terminal of the second DC / DC converter 44. The intermediate potential bus 90 is used when power is exchanged between the plurality of battery modules 42 when performing SOC variation suppression control described later.

  The second DC / DC converter 44 performs voltage conversion between the battery module 42 and the intermediate potential bus 90 based on a control signal from the ECU 200. While the vehicle 1 is traveling, the ECU 200 stops the second DC / DC converter 44, and operates the second DC / DC converter 44 when executing SOC variation control described later.

  Each of the plurality of battery modules 42 of the assembled battery 40 is provided with a voltage sensor 46. The voltage sensor 46 is connected to the positive terminal and the negative terminal of the battery module 42 and detects the voltage of the battery module 42. Voltage sensor 46 outputs a signal indicating the detection result to ECU 200.

  The second DC / DC converter 44 is provided with a voltage sensor 48 that detects a voltage between the high-voltage side terminals. Voltage sensor 48 outputs a signal indicating the detection result to ECU 200.

  The auxiliary battery 60 is a secondary battery for operating various auxiliary machines. Auxiliary battery 60 is, for example, a lead storage battery. The output voltage of the auxiliary battery 60 is, for example, about 12V. The positive terminal of auxiliary battery 60 is connected to the positive output terminal of DC / DC converter 50 and also connected to the positive line of intermediate potential bus 90. The negative terminal of the auxiliary battery 60 is connected to the negative output terminal of the DC / DC converter 50 and also connected to the negative line of the intermediate potential bus 90.

  The auxiliary battery 60 is provided with a voltage sensor 62 that detects the voltage of the auxiliary battery 60. Voltage sensor 62 outputs a signal indicating the detection result to ECU 200.

  Although not particularly shown, ECU 200 includes a CPU (Central Processing Unit), a memory, an input / output buffer, and the like. ECU 200 controls various devices so that vehicle 1 is in a desired driving state based on signals from each sensor and device, and a map and program stored in memory. Various controls are not limited to processing by software, and can be processed by dedicated hardware (electronic circuit).

  In the assembled battery 40 having the above-described configuration, when charging / discharging is performed, the SOC (State Of Charge) that is the remaining capacity may vary among the plurality of battery modules 42. ECU 200 determines that SOC variation has occurred, for example, when the SOC difference between two battery modules of the plurality of battery modules is greater than a threshold value. In the present embodiment, when it is determined that such SOC variation has occurred, ECU 200 executes SOC variation suppression control while vehicle 1 is stopped, for example. The SOC variation suppression control is a control for reducing the SOC difference between the plurality of battery modules 42 by transferring power between the plurality of battery modules 42 via the second DC / DC converter 44 and the intermediate potential bus 90. .

  More specifically, the ECU 200 operates the second DC / DC converter 44 to form a current flow from the high SOC battery module 42 to the low SOC battery module 42 among the plurality of battery modules 42. Thereby, since the battery module 42 of high SOC is discharged and the battery module 42 of low SOC is charged, the dispersion | variation in SOC can be suppressed.

  At this time, the auxiliary battery 60 is also connected to the intermediate potential bus 90, so that the auxiliary battery 60 is used as a buffer for surplus energy generated when power is transferred between the battery modules 42. Therefore, a part of the power flows to the auxiliary battery 60 when power is exchanged between the plurality of battery modules 42.

  However, when power is exchanged between the plurality of battery modules 42, if the SOC of the auxiliary battery 60 is an SOC that is close to a fully charged state, the auxiliary battery 60 may be in an overcharged state.

  Therefore, in the present embodiment, ECU 200 is a case where the SOC difference between two battery modules among the plurality of battery modules 42 is larger than the threshold value, and the SOC of auxiliary battery 60 is the target value. Is higher than the target value, power is output from the auxiliary battery 60 to the assembled battery 40 until the SOC of the auxiliary battery 60 becomes equal to or lower than the target value, and then the SOC variation suppression control is performed using the plurality of second DC / DC converters 44. Shall be executed.

  In this way, since the SOC of the auxiliary battery 60 can be lowered to the target value before the SOC variation suppression control is executed, a part of the electric power is supplied to the auxiliary battery when the SOC variation suppression control is executed. Even if it flows to 60, the auxiliary battery 60 can be prevented from being overcharged.

  FIG. 2 is a flowchart showing a control process executed by ECU 200 mounted on vehicle 1 according to the present embodiment.

  In step (hereinafter, step is referred to as “S”) 100, ECU 200 determines whether or not SOC variation suppression control is necessary. The ECU 200 determines that the SOC variation suppression control is necessary when the SOC difference between the plurality of battery modules 42 is larger than the threshold value. In the present embodiment, ECU 200 determines whether or not the SOC difference is larger than the threshold, for example, by determining whether or not the voltage difference between the plurality of battery modules 42 is larger than the threshold. That is, it is determined whether or not SOC variation suppression control is necessary. For example, ECU 200 detects the voltage of each of the plurality of battery modules 42 and determines whether or not the difference between the maximum value and the minimum value is greater than a threshold value. If it is determined that SOC variation suppression control is necessary (YES in S100), the process proceeds to S102.

  In the following description, the battery module 42 having the maximum voltage is referred to as a high SOC battery module 42, and the battery module 42 having the minimum voltage is referred to as a low SOC battery module.

  In S102, ECU 200 obtains necessary buffer amount α. The necessary buffer amount α indicates an available capacity in the auxiliary battery 60 that is necessary to prevent the auxiliary battery 60 from being overcharged when the SOC variation suppression control is executed. ECU 200 calculates required buffer amount α by subtracting target SOC from SOC indicating the fully charged state of auxiliary battery 60 (hereinafter also referred to as full charged SOC). ECU 200 sets a target SOC for the temperature of auxiliary battery 60, for example.

  In S104, ECU 200 determines whether or not necessary buffer amount α is secured in auxiliary battery 60. The ECU 200 secures the necessary buffer amount α in the auxiliary battery 60 when the value obtained by subtracting the SOC of the current auxiliary battery 60 (hereinafter also referred to as current SOC) from the fully charged SOC is larger than the necessary buffer amount α. It is determined that ECU 200 calculates the current SOC based on the voltage of auxiliary battery 60 detected by voltage sensor 62, for example. When it is determined that necessary buffer amount α is secured in auxiliary battery 60 (YES in S104), the process proceeds to S106.

  In S106, ECU 200 executes SOC variation suppression control. Based on the detection result of the voltage sensor 48, the ECU 200 sets the second DC / DC converter 44 so that the voltage on the high voltage side of the second DC / DC converter 44 connected to the high SOC battery module 42 becomes the first voltage. To control. The first voltage is higher than the voltage on the high voltage side of the other second DC / DC converter 44.

  Similarly, based on the detection result of the voltage sensor 48, the ECU 200 controls the second DC / DC so that the voltage on the high voltage side of the second DC / DC converter 44 connected to the low SOC battery module 42 becomes the second voltage. The DC converter 44 is controlled.

  The second voltage is a voltage lower than the voltage on the high voltage side of the other second DC / DC converter 44 and the voltage of the auxiliary battery 60.

  In this way, a current flow from the high SOC battery module 42 to the low SOC battery module 42 can be formed. Thereby, since the battery module 42 of high SOC is discharged and the battery module 42 of low SOC is charged, the dispersion | variation in SOC can be suppressed. In addition, the object made into the battery module 42 of low SOC is not limited to one, Two or more may be sufficient.

  If it is determined that required buffer amount α is not secured in auxiliary battery 60 (NO in S104), the process proceeds to S108.

  In S108, ECU 200 executes buffer amount securing control. The buffer amount securing control discharges the auxiliary battery 60 and forms the low SOC battery module 42 by forming a current flow from the auxiliary battery 60 to the low SOC battery module 42 among the plurality of battery modules 42. It is the control which charges.

  The ECU 200 is connected to the low SOC battery module 42 such that the voltage on the high voltage side of the second DC / DC converter 44 connected to the low SOC battery module 42 is lower than the voltage of the auxiliary battery 60. The 2DC / DC converter 44 is controlled. Further, the ECU 200 connects the second DC connected to the other battery module 42 such that the voltage on the high voltage side of the second DC / DC converter 44 connected to the other battery module 42 becomes a voltage equivalent to the voltage of the auxiliary battery 60. / DC converter 44 is controlled. The ECU 200 ends the buffer amount securing control when the current SOC of the auxiliary battery 60 is equal to or less than the target SOC. ECU 200 determines whether or not the current SOC is equal to or lower than the target SOC based on the voltage of auxiliary battery 60, for example.

  The operation of ECU 200 mounted on vehicle 1 according to the present embodiment based on the above-described structure and flowchart will be described with reference to FIG. For example, it is assumed that the vehicle 1 is stopped and the SOC of the plurality of battery modules 42 of the assembled battery 40 varies. Further, it is assumed that the current SOC of auxiliary battery 60 is higher than the target SOC.

  ECU 200 acquires the voltage of each of the plurality of battery modules 42 of assembled battery 40, and determines that SOC variation suppression control is necessary when the voltage level difference is greater than the threshold value (YES in S100). ). Therefore, the ECU 200 subtracts the target SOC from the fully charged SOC to obtain the necessary buffer amount α (S102). Then, the ECU 200 determines whether or not the acquired necessary buffer amount α is secured.

  As shown in FIG. 3, if the difference between the fully charged SOC and the current SOC is smaller than the necessary buffer amount α before the execution of the buffer amount securing control, it is determined that the necessary buffer amount α is not secured in the auxiliary battery 60. (NO in S104). Therefore, buffer amount securing control is executed (S108). By executing the buffer amount securing control, the auxiliary battery 60 is discharged and the low SOC battery module 42 is charged. As a result, the SOC of the auxiliary battery 60 is lowered. The buffer amount securing control is terminated when the SOC of the auxiliary battery 60 becomes equal to or lower than the target SOC. Therefore, as shown in FIG. 3, the necessary buffer amount α is secured after execution of the buffer amount securing control. When it is determined that the necessary buffer amount α is secured (YES in S104), SOC variation suppression control is executed (S106).

  When the SOC variation suppression control is executed, the SOC is lowered by discharging the high SOC battery module 42, and the plurality of battery modules are raised by raising the SOC by charging the low SOC battery module 42. The variation in SOC between 42 is reduced. Even when a part of power flows to the auxiliary battery 60 as surplus power when the power is transferred between the battery module 42 of high SOC and the battery module 42 of low SOC at the time of execution of the SOC variation suppression control, the auxiliary battery 60 is compensated. In the machine battery 60, since the free capacity of the necessary buffer amount α is secured, it is possible to absorb surplus power that has flowed to the auxiliary battery 60 without being overcharged.

  As described above, according to the electric vehicle according to the present embodiment, when the current SOC of auxiliary battery 60 is higher than the target SOC, the auxiliary battery until the current SOC of auxiliary battery 60 becomes equal to or lower than the target SOC. Power is output from 60 to the assembled battery 40. Therefore, after that, variation control control is performed to reduce the SOC difference by transferring power between the plurality of battery modules 42, and even if a part of the power flows to the auxiliary battery, the auxiliary battery 60 is overcharged. It can be suppressed. Further, when the current SOC of the auxiliary battery 60 is higher than the target SOC, the electric power of the auxiliary battery 60 can be supplied to the battery module 42 having a low SOC. Can be suppressed. Therefore, it is possible to provide an electric vehicle that suppresses variations in remaining capacity among a plurality of battery modules and suppresses an auxiliary battery that is electrically connected to each battery module from being overcharged.

  Furthermore, since auxiliary battery 60 is suppressed from being overcharged and charged by executing the SOC variation suppression control, it is possible to maintain the SOC at a certain level or higher. Therefore, it can be suppressed that the SOC of auxiliary battery 60 is insufficient and the battery goes up.

  Furthermore, since the variation in SOC among a plurality of battery modules is suppressed by the SOC variation suppression control, the amount of charge is suppressed from being restricted due to the high or low SOC of a specific battery module. It is possible to suppress a decrease in the possible distance.

Hereinafter, modifications will be described.
In the above-described embodiment, the voltage between the high-voltage side terminals of the second DC / DC converter 44 connected to the high SOC battery module 42 becomes the first voltage, and the second DC / DC connected to the low SOC battery module 42. Although it has been described that the plurality of second DC / DC converters are controlled so that the voltage between the high-voltage side terminals of the DC converter 44 becomes the second voltage, the ECU 200 is connected to the battery module 42 having a high SOC, for example. A predetermined amount of current flows in the direction from the second DC / DC converter 44 to the intermediate potential bus 90, and a predetermined amount of current flows in the direction from the intermediate potential bus 90 to the second DC / DC converter 44 connected to the low SOC battery module 42. The plurality of second DC / DC converters 44 may be controlled so that a current flows.

  In the above-described embodiment, the electric vehicle in which only the assembled battery 40 is mounted as a DC power source has been described as an example. However, for example, the vehicle 1 may include an additional assembled battery in addition to the assembled battery 40. The additional assembled battery, like the assembled battery 40, includes a plurality of battery modules and a plurality of DC / DC converters. The plurality of battery modules are connected to the intermediate potential bus 90 via a plurality of DC / DC converters. For example, when vehicle 1 is stopped, ECU 200 determines whether or not SOC variation suppression control is necessary in assembled battery 40 and the additional assembled battery. When the ECU 200 determines that the SOC variation suppression control is necessary in the assembled battery 40, the ECU 200 reduces the variation in SOC in the assembled battery 40 by transferring power between the plurality of battery modules 42 of the assembled battery 40. When determining that the SOC variation suppression control is necessary for the additional assembled battery, the ECU 200 reduces the variation in the SOC of the additional assembled battery by transferring power between the plurality of battery modules of the additional assembled battery. When it is assumed that the remaining capacity of the assembled battery 40 and the additional assembled battery is the same (for example, immediately after charging both assembled batteries by external charging), a plurality of battery modules of the assembled battery 40 SOC variation suppression control may be executed between 42 and the plurality of battery modules of the additional assembled battery.

  In the above-described embodiment, the vehicle 1 has been described as being controlled by one ECU. However, the vehicle 1 may be controlled by a plurality of ECUs capable of bidirectional communication, for example.

In addition, you may implement the above-mentioned modification combining all or one part suitably.
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 vehicle, 10 MG, 20 PCU, 30 SMR, 40 assembled battery, 42 battery module, 44, 50 DC / DC converter, 60 auxiliary battery, 90 intermediate potential bus, 200 ECU.

Claims (1)

A motor that is a drive source of the vehicle;
An assembled battery that includes a plurality of battery modules and supplies power to the motor;
A detection device for detecting a remaining capacity of each of the plurality of battery modules;
An auxiliary battery for supplying electric power to an auxiliary machine mounted on the vehicle;
A power line electrically connected to the auxiliary battery;
A converter for transferring power between each of the plurality of battery modules and the power line;
When the remaining capacity difference between the first battery module and the second battery module of the plurality of battery modules is larger than a threshold value, and the remaining capacity of the auxiliary battery is higher than a target value. After the power is output from the auxiliary battery to the assembled battery until the remaining capacity of the auxiliary battery becomes equal to or less than the target value, power is transferred between the plurality of battery modules using the converter. An electric vehicle comprising: a control device that executes variation suppression control for reducing the remaining capacity difference.

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