JP2015080328A - Electric vehicle power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for suppressing generation of overcharging and over-discharging of each secondary battery even if any of voltage converters connected to a plurality of secondary batteries constituting a main battery of an electric vehicle stops and remaining charge capacities disperse among the plurality of secondary batteries.SOLUTION: An electric vehicle disclosed in the present specification includes: a main battery to which a plurality of secondary batteries is connected in series; a plurality of voltage converters connected to input ends of the respective secondary batteries; and a controller controlling a residual charge capacity of the main battery. Output ends of the respective voltage converters are connected in parallel and the voltage converters supply electric power to accessories connected to the output ends. The controller starts charging the main battery if the remaining charge capacity of the main battery falls below a remaining capacity lower limit, and stops charging if the remaining charge capacity exceeds a remaining capacity upper limit. If it is detected that an abnormality occurs to any of the voltage converters (S3), the controller narrows a main battery usage range from the remaining capacity lower limit to the remaining capacity upper limit (S6).

Description

  The present invention relates to a power supply system for an electric vehicle. The “electric vehicle” in this specification includes a hybrid vehicle that includes an engine together with a motor.

  An electric vehicle uses a high-power motor of several tens of kilowatts to drive the vehicle. For this reason, the capacity | capacitance of the battery which stores the electric power supplied to a motor is progressing. On the other hand, an electric vehicle is also equipped with a battery for driving a device whose operating voltage is lower than that of a motor, such as audio and lighting. In order to distinguish the two batteries, in the present specification, the former is referred to as a main battery and the latter is referred to as an auxiliary battery. In addition, a group of devices that supply power from the auxiliary battery is collectively referred to as an auxiliary machine group. Typically, the output voltage of the main battery is 100 volts or more, while the output voltage of the auxiliary battery is 12 volts or 24 volts. In addition, the main battery normally secures a high voltage output by connecting a plurality of secondary batteries (rechargeable batteries) in series.

  In a typical electric vehicle, the main battery is charged by power from a generator, a backup power source, or the like, or regenerative power from a motor, and the auxiliary battery is charged by the main battery. Such an electric vehicle includes a voltage converter that steps down the voltage of the main battery and supplies it to the auxiliary battery. Some electric vehicles include one voltage converter that steps down the output voltage of the main battery. However, a configuration in which a small voltage converter is connected to each of a plurality of secondary batteries constituting the main battery has been proposed (Patent Document 1). ). The output voltage of the voltage converter is adjusted to the output voltage of the auxiliary battery, and the outputs of the plurality of voltage converters are connected in parallel to supply power to the auxiliary battery (or auxiliary machine). According to Patent Document 1, a power supply system including a plurality of voltage converters has a plurality of types in which the voltage of the auxiliary battery is the same but the output voltage of the main battery is different by changing the number of secondary batteries connected in series. It is said that there is an advantage that it can provide a power supply system for electric vehicles.

  Moreover, the secondary battery utilized for the main battery is, for example, a lithium battery. When such a secondary battery is overcharged or overdischarged, a material such as an active material is decomposed and deterioration proceeds. Therefore, the main battery is charged such that the remaining charge (SOC: State Of Charge) is maintained within a predetermined range (SOC usage range). Here, in Patent Document 2, it is proposed to narrow the use range of the SOC as the deterioration progresses in order to suppress the progress of the deterioration.

JP 2002-10410 A JP 2008-308122 A

  As in the technique of Patent Document 1, a main battery is configured by connecting a plurality of secondary batteries in series, and a voltage converter is connected to each secondary battery, and the output of the electric vehicle is parallelized is There is also an advantage that even if the voltage converter is stopped, the power supply to the auxiliary battery can be continued with the remaining voltage converter. However, when power is supplied to the auxiliary battery through the remaining voltage converters while one (or several) voltage converters are stopped, the SOCs of the plurality of secondary batteries vary. That is, the secondary battery in which the voltage converter is stopped does not decrease the SOC as much as the secondary battery in which the voltage converter is operating. In such a situation, if charging is repeated according to the SOC of the entire main battery, overcharge or overcharge may occur in some secondary batteries, and deterioration may progress.

  The technology disclosed in this specification was created in view of the above problems. The purpose is to configure a main battery by connecting a plurality of secondary batteries in series, and in a power supply system for an electric vehicle in which a voltage converter is connected to each secondary battery, one (or several) voltage converters are provided. Even if it is a case where it stops, it is in suppressing deterioration of the secondary battery which comprises a main battery, continuing charging to an auxiliary machine battery.

  The power supply system disclosed in this specification includes a main battery, a plurality of voltage converters, and a controller. As described above, the main battery is a battery in which a plurality of secondary batteries are connected in series, and supplies power to the motor for traveling. In the plurality of voltage converters, an input end of each voltage converter is connected to each secondary battery, and an output end is connected in parallel. The parallelized output (electric power) is supplied to an auxiliary battery or an auxiliary machine group. The controller starts charging the main battery when the remaining charge amount of the main battery falls below the remaining amount lower limit value, and stops charging when the remaining charge amount exceeds the remaining amount upper limit value. Charging is typically performed by a generator in a hybrid vehicle, but an external power source (in the case of a plug-in electric vehicle) or an auxiliary power source such as a capacitor may be used. The unit of the remaining charge (SOC) is% (current electric energy / chargeable electric energy), but generally there is a unique relationship between the remaining charge and the output voltage of the battery ( When the remaining charge level decreases, the battery output voltage also decreases), and the output voltage of the battery is used as an index for measuring the remaining charge level.

  In the power supply system disclosed in this specification, when an abnormality is detected in any of the voltage converters connected to each secondary battery regardless of the progress of deterioration of the plurality of secondary batteries constituting the main battery, The voltage converter in which no abnormality is detected continues to supply power to the auxiliary battery (auxiliary machine group) and narrows the use range of the main battery from the remaining amount lower limit value to the remaining amount upper limit value. By doing so, an allowance is provided in the use range of the remaining charge, and overcharge and overdischarge are less likely to occur even if the remaining charge of each secondary battery varies.

  Note that narrowing the use range of the main battery (use range of remaining charge) is realized by increasing the remaining charge lower limit value, lowering the remaining charge upper limit value, or both. . In addition, the technology disclosed in this specification is expressed as narrowing the use range of the main battery when an abnormality is detected in any of a plurality of voltage converters, but when any of the voltage converters is stopped In addition, even when the output is small, it is preferable to perform the above-described control by regarding that the voltage converter is substantially abnormal.

  According to the technology disclosed in this specification, even if one of the voltage converters connected to the plurality of secondary batteries constituting the main battery of the power supply system stops and the remaining charge amount of each secondary battery varies, The occurrence of overcharge and overdischarge of each secondary battery can be suppressed. Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a block diagram of the electric power system of the power supply system for electric vehicles of embodiment. It is the flowchart figure which showed the process in which the power supply system for electric vehicles of embodiment determined the use range of SOC (remaining charge) of a secondary battery.

  With reference to FIG. 1, the power supply system of the electric vehicle of an Example is demonstrated. The embodiment is a power supply system 2 mounted on a hybrid vehicle including a traveling motor and an engine.

  The power supply system 2 of the embodiment includes a main battery 3 and an auxiliary battery 6 as power sources, and the remaining charge (SOC: State Of Charge) of the main battery 3 is within a predetermined use range (SOC use range). A controller 8 is provided for controlling so as to be. The main battery 3 is a battery that stores electric power for driving a traveling motor 9 (hereinafter referred to as a motor 9). The auxiliary battery 6 has an output voltage lower than that of the main battery 3 and supplies electric power to electric devices other than the motor 9.

  The main battery 3 is configured by connecting five secondary batteries 4 which are lithium batteries in series. The electric power stored in the main battery 3 is supplied to the motor 9 via the inverter 13. The inverter 13 converts the DC power of the main battery 3 into AC power suitable for driving the motor 9. The inverter 13 also includes a boost converter, which boosts the output power of the main battery 3 and converts it to alternating current.

  Voltage converters (5a, 5b) are connected to the secondary batteries 4 constituting the main battery 3, respectively. The input terminal of each voltage converter (5a, 5b) is connected to each secondary battery 4. The output terminals of the voltage converters (5a, 5b) are connected in parallel to each other and connected to the auxiliary battery 6. Thereby, the electric power stored in each secondary battery 4 is adjusted to the output voltage of the auxiliary battery 6 by each voltage converter and supplied to the auxiliary battery 6.

  An audio device 7a and a room lamp 7b are connected to the auxiliary battery 6. The controller 8 is also connected to the auxiliary battery 6. In other words, the audio device 7a, the room lamp 7b, and the controller 8 operate by receiving power from the auxiliary battery 6. A plurality of other electronic devices are connected to the auxiliary battery 6. In FIG. 1, other electronic devices are not shown for simplification. The audio equipment 7a, the room lamp 7b, the controller 8, and other electronic devices are collectively referred to as an auxiliary machine group 7.

  Here, the voltage converter 5 a is connected to the other voltage converter 5 b via the signal line 18, and the voltage converter 5 a is connected to the controller 8 via the signal line 17. The signals of each voltage converter 5b are collectively transmitted to the controller 8 by the voltage converter 5a, and conversely, the signals of the controller 8 are transmitted from the voltage converter 5a to the other voltage converter 5b. In other words, the plurality of voltage converters operate in cooperation with the voltage converter 5a serving as a master and the other converter 5b serving as a slave. The signal transmitted from the voltage converter is a signal for detecting an abnormality of the voltage converter, an output voltage of the voltage converter, an input voltage, or the like.

  The output shaft of the motor 9 and the output shaft of the engine 12 are connected to the power distribution mechanism 14. The output torque of the motor 9 and the output torque of the engine 12 are combined by the power distribution mechanism 14, and the output is transmitted to the wheels 16 via the differential gear 15. The power distribution mechanism 7 is basically a planetary gear, the output shaft of the motor 9 is connected to the sun gear, the output shaft of the engine 12 is connected to the planetary carrier, and the output shaft (the axle connected to the differential gear 15). Is connected to the ring gear. The power distribution mechanism 14 may distribute the output torque of the engine 12 between the motor 12 and the output shaft. In that case, the hybrid vehicle equipped with the power supply system 2 generates electric power with the motor 9 while traveling with the output of the engine 12. The electric power obtained by power generation is converted into DC power by the inverter 13 and charged to the main battery 3.

  The controller 8 drives the inverter 13 to charge the main battery 3 so that the SOC of the main battery 3 is within a predetermined usage range (SOC usage range). The controller 8 starts charging when the SOC of the main battery 3 falls below the lower limit value (SOC lower limit value) of the use range, and stops charging when the SOC exceeds the upper limit value (SOC upper limit value) of the use range. The drive of the inverter 13 is controlled. Note that the SOC of the main battery 3 is measured by the inverter 13 based on the output voltage of the main battery 3.

  Further, the controller 8 drives the voltage converter (5a, 5b) so as to equalize the storage capacity of the secondary battery 4, and charges the auxiliary battery 6. The voltage converter 5a receives the output voltage value of each secondary battery 4 from the other voltage converter 5b, and calculates the average value (voltage average value) of the output voltage of the secondary battery 4. The voltage average value is transmitted from the voltage converter 5a to the other voltage converter 5b together with the command value of the output current sent from the controller 8. Each voltage converter 5b adjusts the output current of each voltage converter according to the difference between the voltage average value and the output voltage of the secondary battery 4 measured by each voltage converter. For example, a voltage converter connected to the secondary battery 4 in which the output voltage of the secondary battery 4 is higher than the voltage average value corresponds to 105% of the current command value in order to increase the discharge amount more than other voltage converters. Output current. On the contrary, the voltage converter connected to the secondary battery whose output voltage is lower than the voltage average value outputs a current corresponding to 95% of the current command value.

  A process in which the controller 8 controls the SOC usage range of the main battery 3 will be described with reference to FIG. The process of FIG. 2 is started at the same time when the hybrid vehicle starts traveling, and ends when the hybrid vehicle stops traveling. First, when the hybrid vehicle starts normal running, the controller 8 determines the SOC usage range of the main battery 3 (S1). In the initial state, the SOC usage range has a lower limit of 20% and an upper limit of 80%. The controller 8 charges the main battery 3 so that the SOC is in the above-described use range until a failure running state (S6) described later is reached.

  After step S1, the controller 8 checks the degree of variation in the SOC of each secondary battery 4 (S2). Specifically, the controller 8 determines whether or not the absolute value of the difference between the average value of the output voltage of each secondary battery 4 and the output voltage of each secondary battery 4 is greater than the threshold value 0.5V. Check on all batteries. When the absolute value of the voltage difference is greater than 0.5 V in any of the secondary batteries 4 (S2: YES), the controller 8 determines that an abnormality has occurred in the secondary battery 4, and the secondary battery 4 A battery abnormality treatment state is entered (S9). At this time, the controller 8 stores in the diagnosis (not shown) that an abnormality has occurred in the secondary battery 4 and lights a caution lamp (not shown). Here, the diagnosis is a self-diagnosis device that stores information when there is an abnormality in the in-vehicle device. Thereafter, the controller 8 stops the vehicle (S10). On the other hand, when the absolute value of the voltage difference is 0.5 V or less in all the secondary batteries 4 (S2: NO), the process proceeds to step S3.

  In step S3, the controller 8 confirms whether any abnormality is detected in any of the voltage converters (5a, 5b). When abnormality is not detected (S3: NO), the controller 8 returns to the process of step S2. If an abnormality is detected (S3: YES), the controller 8 proceeds to the process of step S4. In this process, the voltage converter in which the abnormality is detected is stopped. A voltage converter in which no abnormality is detected is continuously operated. In the next processing, voltage converter abnormality treatment is performed, and the controller 8 stores in the diagnosis that abnormality has occurred in the voltage converter, and turns on the caution lamp (S5). Thereafter, the process proceeds to step S6.

  In step S6, the controller 8 narrows the SOC usage range of the main battery 3. The controller 8 lowers the upper limit value of the SOC usage range from 80% to 60%, and further increases the lower limit value of the SOC usage range from 20% to 40%. In general, failure running in a vehicle and limiting the running performance to continue running is called fail running. In the present embodiment, it is equivalent to the failure traveling that the traveling is continued with the SOC use range narrower than that in the normal traveling. Thereafter, the variation in the SOC of each secondary battery 4 is confirmed in the same manner as the process of step S2 (S7). Similarly to step S2, the controller 8 determines whether or not the absolute value of the difference between the average value of the output voltage of each secondary battery 4 and the output voltage of each secondary battery 4 is greater than a threshold value for each secondary battery. Check. Here, the threshold value is 1.0 V, and the allowable value of variation is made larger than that in step S2. In step S6, since the upper limit value of the SOC usage range has decreased from 80% to 60%, a 20% margin will be generated until overcharging occurs. For this reason, the allowable value can be increased for the variation in the output voltage of each secondary battery 4 by an amount not exceeding the margin. When the absolute value of the voltage difference between the secondary batteries 4 is 1.0 V or less (S7: NO), the controller 8 determines that there is no abnormality in each secondary battery 4, and continues the fail travel, and S7 Repeat the process. On the other hand, when the absolute value of the voltage difference is greater than 1.0 V in at least one secondary battery 4 (S7: YES), the controller 8 determines that an abnormality has occurred in the secondary battery 4 and stops the vehicle. (S8).

  Hereinafter, advantages obtained by the above-described embodiment will be described. As described above, since the voltage converter equalizes the SOC of each secondary battery, if an abnormality occurs in any of the voltage converters, the SOC of each secondary battery is not equalized. Therefore, the variation in SOC of each secondary battery 4 increases. However, in the power supply system 2 of the embodiment, when the controller 8 detects any abnormality of the voltage converter, the use range of the SOC of the main battery 3 is narrowed. Thereby, a margin arises until the secondary battery is overcharged and overdischarged. Therefore, even if the variation in the SOC of each secondary battery 4 becomes large, overcharge and overdischarge of each secondary battery 4 are prevented. For this reason, it is not necessary to stop the power supply system 2 in order to protect the main battery 3 from deterioration. Therefore, the hybrid vehicle can continue to travel.

  For repair, only the voltage converter in which an abnormality is detected needs to be replaced. Thereby, reduction of repair cost and workability | operativity can be improved. It should be noted that the variation in the SOC generated in each secondary battery 4 is automatically equalized while traveling after being replaced with a normal voltage converter.

  In addition, narrowing the SOC usage range reduces the running performance of the vehicle. It should be noted that the technology disclosed in the present specification aims to give priority to maintaining the traveling of the vehicle even when the traveling performance of the vehicle is deteriorated.

  Hereinafter, points to be noted regarding the technology shown in the embodiments will be described. The electric vehicle equipped with the power supply system 2 of the example was a hybrid vehicle including a motor and an engine for running. The technology disclosed in this specification can also be applied to a pure EV that does not include an engine and runs only by a motor. In this case, the main battery 3 is charged by regenerative power from the motor, an external power source, and an auxiliary power source.

  In the embodiment, the main battery 3 is configured by connecting five secondary batteries in series. However, the main battery 3 may be configured by connecting a plurality of secondary batteries in series.

  Also, the numerical values of the upper limit value and the lower limit value of the SOC use range shown in FIG. 2 and the threshold values for determining the variation in the SOC of each secondary battery 4 are not limited to the values shown in the embodiment. It should be noted that an appropriate value is selected depending on the type of secondary battery to be applied and the type of electric vehicle.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Power supply system 3: Main battery 4: Secondary battery 5a, 5b: Voltage converter 6: Auxiliary battery 7: Auxiliary equipment group 8: Controller 9: Motor 12: Engine 13: Inverter

Claims (1)

A main battery in which a plurality of secondary batteries are connected in series;
A plurality of voltage converters whose input ends are connected to each secondary battery and whose output ends are connected in parallel to supply power to the auxiliary machinery group;
A controller that starts charging the main battery when the remaining charge of the main battery falls below the remaining charge lower limit value, and stops charging when the remaining charge exceeds the remaining charge upper limit value;
With
The controller narrows a main battery usage range from the remaining capacity lower limit value to the remaining capacity upper limit value when an abnormality is detected in any of the plurality of voltage converters. .

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