JP2018042342A - Voltage equalization method of plurality of battery stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage equalization method of a plurality of battery stacks, in which executes a proper voltage equalization while maintaining durability of a SMR.SOLUTION: A voltage equalization method of a battery stack, includes: a step of determining (S16 and S20) whether a voltage difference between different battery stacks is in a predetermined range that permits an equalization processing after stopping of an operation of an electric power device (S12); a step of turning on (S30) a positive relay and a negative relay of the other side battery stacks while turning on a pre-charge relay 34 and the negative relay while setting off the positive relay of one of the battery stacks in a case where the voltage difference is within the predetermined range; and a step of maintaining (S32) a state until a predetermined time when the voltage difference between the battery stacks is reduced to a predetermined voltage difference.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a voltage equalization method for a plurality of battery stacks.

  A power supply device mounted on a vehicle or the like is configured by connecting a plurality of battery stacks in series and in parallel in order to output a predetermined high voltage and large current. For example, Patent Document 1 shows an example in which a plurality of battery stacks are connected in parallel to a motor via a power relay called SMR (System Main Relay).

  While the power supply device is in operation, each battery stack is charged and discharged, so that the open circuit voltage (OCV) of each battery stack cannot be measured. Since the SMR is cut off when the power supply device stops operating, the OCV, which is the voltage across the terminals of each battery stack, can be measured. At that time, there may be a voltage difference between the terminals of each battery stack. When the power supply is restarted in this state, the voltage difference between the battery stacks connected in parallel causes SMR. Inrush current flows, and the durability of the SMR decreases. In order to prevent this, voltage equalization between the battery stacks is performed.

JP 2010-246285 A

  In the prior art, as a voltage equalization method for a plurality of battery stacks, an equalization current of about 10 to several hundred mA is passed through the necessary battery stack. With this level of equalization current, it takes a long time to complete voltage equalization when the voltage difference between the battery stacks is large or the like, and it may not be in time for the next activation timing of the power supply device. In order to increase the equalization current, the cost of the equalization circuit and the like increases. Therefore, there is a need for a voltage equalization method for a plurality of battery stacks that can perform appropriate voltage equalization while maintaining the durability of SMR.

  A voltage equalization method for a plurality of battery stacks according to the present disclosure includes two battery stacks having a positive electrode connected to a positive electrode bus and a positive side relay, and two battery stacks having a negative electrode connected to a negative electrode bus and a negative side relay. A precharge relay with a current limiting resistor connected in series is connected in parallel only to the positive side relay of the battery stack on one side, and everything except the precharge relay is turned on to start and all relays are turned off. The battery stack voltage equalization method in the power supply apparatus that stops operation, and after the operation of the power supply apparatus stops, whether or not the voltage difference between different battery stacks is within a predetermined value range that allows the equalization processing If it is within the predetermined value range, the precharge relay and the negative side relay are turned on while the positive side relay of the battery stack on one side is off, and the other side is turned on. Together on the positive electrode side relay and the negative relay pond stack, the voltage difference between the cell stack is a predetermined time to reduce the predetermined voltage difference maintains its state.

  According to the voltage equalization method for a plurality of battery stacks according to the above configuration, voltage equalization can be achieved using a precharge relay, and therefore appropriate voltage equalization can be executed while maintaining the durability of SMR.

It is a block diagram of the vehicle drive system containing the power supply device with which the voltage equalization method of the several battery stack which concerns on embodiment is applied. It is a flowchart which shows the procedure of the voltage equalization method of the some battery stack which concerns on embodiment. In FIG. 2, it is a figure which shows ON / OFF of each relay of the power supply device in operation. In FIG. 2, it is a figure which shows ON / OFF of each relay of the power supply device which stopped operation | movement. In FIG. 2, it is a figure which shows on-off of each relay of the power supply device in process of a voltage equalization process. FIG. 6 is a diagram showing ON / OFF of each relay of the power supply device in a further voltage equalization process executed subsequently to FIG. 5. It is a flowchart which shows the procedure of the voltage equalization method using the structure of FIG.

Hereinafter, this embodiment will be described in detail with reference to the drawings. In the following, a rotating electric machine mounted on a vehicle and a drive circuit thereof are described as loads of the power supply device, but this is an example, and loads such as other auxiliary machines may be included. Although the number of rotating electrical machines is described as being one, this is an example for explanation, and there may be a plurality of rotating electrical machines, and a plurality of driving circuits may be provided in accordance therewith. The vehicle may be a hybrid vehicle in which an engine is mounted together with the rotating electrical machine.
Below, the same code | symbol is attached | subjected to the same element in all the drawings, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a configuration diagram of a vehicle drive system 10 including a power supply device 20 to which a plurality of battery stack voltage equalization methods are applied. Hereinafter, unless otherwise specified, the “voltage equalization method for a plurality of battery stacks” is referred to as a voltage equalization method. The vehicle drive system 10 is a vehicle drive system that uses a rotating electrical machine as a drive source, and includes a rotating electrical machine 12, an inverter 14, a smoothing capacitor 16, a DC / DC converter 18, and a power supply device 20. And a battery control unit 60. The rotating electrical machine 12 and its drive circuit 13 are loads that are targets for charging and discharging the power supply device 20. Since the contents of the rotating electrical machine 12 and its drive circuit 13 are well known, detailed description thereof is omitted.

  The power supply device 20 is a high-voltage high-power DC power source in which two battery stacks 22 and 24 are connected in parallel as a plurality of battery stacks. The positive electrode bus 26 of the power supply device 20 becomes the positive electrode bus of the drive circuit 13, and the negative electrode bus 28 of the power supply device 20 becomes the negative electrode bus of the drive circuit 13. Since the positive electrode bus 26 and the negative electrode bus 28 are high voltage power lines, they are insulated from the vehicle body of the vehicle and have a floating potential.

  The battery stacks 22 and 24 are rechargeable secondary batteries. As the battery stacks 22 and 24, high voltage assembled batteries in which a predetermined number of battery cells are connected in series are used. As the battery cell, a lithium ion battery or a nickel metal hydride battery is used. An example of the voltage between the terminals of the battery stacks 22 and 24 is about 200V to about 300V.

  When the two battery stacks 22 and 24 are distinguished from each other, they are referred to as a battery stack 22 on one side and a battery stack 24 on the other side. The positive electrode side relay 30 is provided between the positive electrode of the battery stack 22 on one side and the positive electrode bus 26 of the power supply device 20, and the negative electrode side relay 32 is provided between the negative electrode and the negative electrode bus 28 of the power supply device 20. . Similarly, the positive electrode side relay 36 is provided between the positive electrode of the other battery stack 24 and the positive electrode bus 26 of the power supply device 20, and the negative electrode relay 38 is provided between the negative electrode and the negative electrode bus 28 of the power supply device 20. Is provided. The difference between the battery stack 22 on one side and the battery stack 24 on the other side is that a precharge relay 34 having a current limiting resistor 35 connected in series is provided in parallel only on the positive relay 30 of the battery stack 22 on one side. Is to be.

  The positive-side relays 30 and 36 and the negative-side relays 32 and 38 include a precharge relay 34, and are power relays that block or connect high-power exchange between the drive circuit 13 and the power supply device 20. In order to facilitate understanding of the connection relationship between the five power relays and the battery stacks 22 and 24, in the following, unless otherwise specified, symbols are used instead of symbols. That is, the positive side relays 30 and 36 are indicated as SMR-B1 and SMR-B2, respectively, the negative side relays 32 and 38 are indicated as SMR-G1 and SMR-G2, respectively, and the precharge relay 34 is indicated as SMR-P. Show. SMR means a system main relay, B means that it is connected to the positive side of the battery stacks 22, 24, and G means that it is connected to the negative side of the battery stacks 22, 24. 1 and 2 after B and G mean the battery stack 22 on one side and the battery stack 24 on the other side, respectively. P means precharge.

  The SMR-P is a relay that precharges the smoothing capacitor 16 before the power supply device 20 is activated. For example, in order to start up the power supply device 20, the battery stack 22 on one side may be in any order, but when the SMR-G1 and SMR-B1 are sequentially connected, the smoothing capacitor 16 is uncharged. Because of its charging, current flows rapidly. Due to this inrush current, there is a possibility that welding will occur in the relay that is connected later in SMR-G1 and SMR-B1. To prevent this, SMR-B2 and SMR-G2 in the battery stack 24 on the other side are turned off, SMR-G1 is turned on in the battery stack 22 on one side, SMR-B1 is turned off, and SMR-P is turned off. Turn on. Since the current limiting resistor 35 is connected between the SMR-P and the positive electrode bus 26, the current from the battery stack 22 charges the smoothing capacitor 16 via the current limiting resistor 35. The resistance value of the current limiting resistor 35 is set so that the current flowing through the SMR-G1 does not become excessive. Thereby, welding of SMR-G1 can be prevented. After the smoothing capacitor 16 is appropriately precharged, SMR-P is turned off, and SMR-B1, SMR-G2, and SMR-B2 are sequentially turned on in a predetermined order. As a result, the power supply device 20 is activated while preventing relay welding.

  Note that the current from the battery stack 22 on one side limited by the current limiting resistor 35 is, for example, about one digit to several digits larger than the equalization current used in the general voltage equalization process. .

  In FIG. 1, the SMR-P is arranged in parallel with the SMR-B1 of the battery stack 22 on one side. Alternatively, the SMR-P can be arranged in parallel with the SMR-G1 of the battery stack 22 on one side. Since the battery stack 22 on one side is the battery stack on the side where the SMR-P is arranged, in FIG. 1, when the battery stack 24 is called the battery stack on one side, the SMR-P is the battery stack 24. Are arranged in parallel to the SMR-B2. Instead of this, the battery stack 24 may be arranged in parallel with the SMR-G2. Below, it is set as the arrangement | positioning relationship of FIG.

  In FIG. 1, the voltage detection unit 40 is a voltage detection unit that detects the inter-terminal voltage V <b> 1 of the battery stack 22 on one side. The current detection unit 42 is current detection means for detecting a current I1 flowing through the battery stack 22 on one side. The battery temperature detection unit 44 is a temperature detection unit that detects the battery temperature θ1 of the battery stack 22 on one side. Similarly, the battery stack 24 on the other side is provided with a voltage detector 46 that detects the inter-terminal voltage V2, a current detector 48 that detects the current I2, and a battery temperature detector 50 that detects the battery temperature θ2. These detection data are transmitted to the battery control unit 60 through appropriate signal lines.

  The start / stop command 58 is a command transmitted from a system control unit that controls the operation of the vehicle drive system 10 as a whole, and is a command for starting the power supply device 20 or a command for stopping the operation of the power supply device 20. In FIG. 1, the system controller is not shown. The start / stop command 58 is transmitted to the battery control unit 60 through an appropriate signal line.

  The battery control unit 60 controls the operations of the five relays SMR-B1, SMR-G1, SMR-P, SMR-B2, and SMR-G2 of the power supply device 20 as a whole. In particular, when a voltage difference ΔV = | V1−V2 | is generated as an absolute value between the voltage V1 between the terminals of the battery stack 22 on one side and the voltage V2 between the terminals of the battery stack 24 on the other side in the power supply device 20. , A voltage equalization process for reducing ΔV is performed. The battery control unit 60 is configured by a computer suitable for mounting on a vehicle.

  The function of the voltage equalization process of the battery control unit 60 that is a computer can be realized by the battery control unit 60 executing software. Specifically, the battery control unit 60 performs each processing procedure of the voltage equalization process program. It is realized by executing. A part of the above functions may be realized by hardware. In addition, although the battery control part 60 can also be comprised as an independent computer, it is good also as a part of function of the system control part which is not shown in figure.

  The function and effect of the above configuration, in particular, the function of voltage equalization processing of the battery control unit 60 will be described in detail with reference to FIG. FIG. 2 is a flowchart showing a procedure of voltage equalization processing. Each procedure corresponds to each processing procedure of the voltage equalization processing program.

  When the vehicle control program starts, the voltage equalization processing program also starts after initialization. When the rotating electrical machine 12 and the drive circuit 13 are operated in the vehicle, the start / stop command 58 transmits the start command for the power supply device 20 to the battery control unit 60. In response to this, the battery control unit 60 puts the power supply device 20 into an operating state (S10).

  FIG. 3 is a diagram illustrating ON / OFF of each relay of the power supply device 20 in operation. When the power supply device 20 is operating, SMR-B1, SMR-G1, SMR-B2, and SMR-G2 are turned on. The SMR-P is turned on when the smoothing capacitor 16 is charged in the precharge prior to the activation of the power supply device 20, but is turned off when the necessary charging is completed. In FIG. 1, since the state of the power supply device 20 in operation after the precharge is completed is shown, the SMR-P is in an off state.

  Since SMR-B1 and SMR-G1 are turned on, the current I1 is discharged from the battery stack 22 on one side to the positive electrode bus 26 side. Similarly, since SMR-B2 and SMR-G2 are turned on, the current I2 is discharged from the battery stack 24 on the other side to the positive electrode bus 26 side. In FIG. 3, the flowing current is indicated by a bold line, and the direction of the current is indicated by an arrow. Accordingly, the drive circuit 13 is supplied with a DC discharge current of (I1 + I2). On the contrary, when a DC charging current is supplied from the drive circuit 13 to the battery stacks 22 and 24, the direction of the current of the thick line in FIG. 3 is opposite, and the battery stacks 22 and 24 are charged.

  Note that V1 and V2 in FIG. 3 are inter-terminal voltages when current flows in the battery stacks 22 and 24, and are called CCV (Closed Circuit Voltage). The CCV is different from the open circuit voltage OCV when no current flows through the battery stacks 22 and 24.

  Returning to FIG. 2, when it becomes unnecessary to supply power to the rotating electrical machine 12 and the drive circuit 13 of the vehicle, the start / stop command 58 transmits the stop command to the battery control unit 60. In response to this, the battery control unit 60 stops the operation of the power supply device 20 (S12). FIG. 4 is a diagram illustrating on / off of each relay of the power supply device 20 whose operation has been stopped. When the power supply device 20 stops operating, all the relays SMR-B1, SMR-G1, SMR-P, SMR-B2, and SMR-G2 are turned off.

  V1 and V2 at this time are voltages between terminals when current does not flow through the battery stacks 22 and 24, and are open circuit voltages OCV. The open circuit voltage OCV can be associated with SOC (State Of Chrage) indicating the state of charge of the battery stacks 22 and 24. In the voltage equalization process, when there is a voltage difference ΔV between the open circuit voltage OCV of the battery stack 22 on one side and the open circuit voltage OCV of the battery stack 24 on the other side, the voltage difference ΔV is reduced. It is. Therefore, in the following, unless otherwise specified, the voltages, that is, the inter-terminal voltages V1 and V2, refer to the open circuit voltage OCV associated with the SOC, respectively.

Returning to FIG. 2, when the power supply device 20 stops operating, in that state, the voltage V1 between the terminals of the battery stack 22 on one side and the voltage V2 between the terminals of the battery stack 24 on the other side are acquired (S14). This procedure is executed by acquiring the detection data of the voltage detectors 40 and 46. When V1 and V2 are acquired, a voltage difference ΔV = | V1−V2 | as an absolute value between V1 and V2 is calculated, and whether or not it is equal to or _smaller than a predetermined first predetermined voltage difference ΔV _th1. It is determined (S16). The first predetermined voltage difference is set from the viewpoint of whether voltage equalization processing is possible by performing on / off control of the five relays.

If the determination in S16 is negative, ΔV> ΔV _th1 is satisfied, and the voltage difference ΔV is too large, which is not suitable for performing the voltage equalization process by the on / off control of the five relays. When the power supply device 20 is restarted in this state, a large inrush current flows between the battery stack 22 on one side and the battery stack 24 on the other side due to excessive ΔV. Since the voltage difference ΔV does not change in the precharge process performed before the restart, at least one of SMR-B1, SMR-G1, SMR-B2, and SMR-G2 is caused by the inrush current caused by the ΔV. There is a possibility of welding. Therefore, when the determination in S16 is negative, the next restart of the power supply device 20 is prohibited (S18). When the restart of the power supply device 20 is prohibited, no power is supplied to the drive circuit 13 and the rotating electrical machine 12, so that countermeasures are implemented by a predetermined diagnostic method.

If the determination in S16 is affirmative, it is next determined whether or not ΔV is equal to or greater than a predetermined second predetermined voltage difference ΔV _th2 (S18). The second predetermined voltage difference is a voltage difference that is larger than the error range, and is set from the viewpoint of whether or not it is a relatively small voltage difference that can be subjected to voltage equalization processing by performing on / off control of five relays. Is done.

  When S18 is negative, ΔV is a very small value and it is not necessary to perform the voltage equalization process, so the power sources of the voltage detectors 40 and 46 are turned off (S22). Then, after an appropriate waiting time has elapsed (S24), the power sources of the voltage detectors 40 and 46 are turned on again (S26), and the procedure returns to S14.

When S18 is positive, ΔV _th1 >ΔV> ΔV _th2 and ΔV is within a predetermined value range. In this case, the voltage equalization process of S30 or less is advanced. S30 and S32 are procedures of the first voltage equalization process. In the first voltage equalization process, the ON / OFF setting of each relay is performed as follows (S30). That is, for the battery stack 22 on one side, SMR-B1 remains off and SMR-G1 and SMR-P are turned on. For the battery stack 24 on the other side, SMR-B1 and SMR-G1 are turned on.

  FIG. 5 is a diagram illustrating ON / OFF of each relay of the power supply device 20 in the first voltage equalization process. Here, an example of V1> V2 is shown. In the first voltage equalization processing, SMR-B1 is off, but SMR-G1 and SMR-G1 are on, so that the current passing through the current limiting resistor 35 from the battery stack 22 on one side is on the positive bus 26 side. Flowing into. In the battery stack 24 on one side, SMR-B2 and SMR-G2 are on, so that the current flowing from the battery stack 22 on one side to the positive electrode bus 26 flows into the battery stack 24 on the other side. In FIG. 5, the flowing current is indicated by a thick line, and the direction of the current is indicated by an arrow. That is, a current flows from the battery stack 22 on one side in the state of the high inter-terminal voltage V1 toward the battery stack 24 on the other side of the low inter-terminal voltage V2, so that the voltage difference ΔV = | V1-V2 | Voltage equalization is performed in the direction of decreasing. When V1 <V2, the direction of the current is opposite.

  By using SMR-P in the first voltage equalization process, a current that flows due to a voltage difference ΔV between the terminal voltage V1 of the battery stack 22 on one side and the terminal voltage V2 of the battery stack 24 on the other side. I2 can be suppressed by the current limiting resistor 35. As a result, it is possible to prevent an excessive inrush current due to ΔV from flowing through SMR-G1, SMR-B2, and SMR-G2, thereby preventing relay welding and deterioration of durability.

  The use of SMR-P in the first voltage equalization process is similar to the precharge process that is performed prior to the activation of the power supply device 20, but has the following differences. In the precharge process, SMR-B2 and SMR-G2 of the other battery stack 24 are off. In the first voltage equalization process, SMR-B2 and SMR- of the other battery stack 24 are used. G2 is on. Note that the current from the battery stack 22 on one side limited by the current limiting resistor 35 is larger by about one to two digits than the equalization current used in a general voltage equalization process. Therefore, voltage equalization can be executed in a short time compared to a general voltage equalization method.

When the ON / OFF setting of each relay is performed in S30, the state is maintained for a predetermined time (S32). The predetermined time is determined as follows from the viewpoint of the durability of the relay. First, based on the voltage V1, V2 between the terminals of the battery stacks 22, 24, the internal resistance of the battery stacks 22, 24, and the battery capacity of the battery stacks 22, 24, the voltage difference ΔV = | V1-V2 | The time until the target voltage difference ΔV ₀ that is acceptable from the viewpoint of durability is obtained. And let the calculated | required time be predetermined time. The internal resistances of the battery stacks 22 and 24 can be estimated from the battery temperatures θ1 and θ2, and the battery capacities of the battery stacks 22 and 24 can use predetermined values.

One method for determining whether or not the predetermined time has been reached is that the relationship between the time integral value of the current and the amount of change in the open circuit voltage OCV is obtained in advance, and the initial voltage difference ΔV decreases to ΔV ₀ . The time integral value of the current required for. Then, the current I2 from time to time is time-integrated, and the time when the actual integrated value is equal to or greater than the time integrated value of the obtained current is set as a predetermined time. When this time is reached, the process proceeds to the next S34. Another determination method is to obtain in advance a time required to drop from the initial voltage difference ΔV to ΔV ₀ by experiment or simulation, and set this as a predetermined time. When that time is reached, the process proceeds to the next S34. .

The target voltage difference ΔV ₀ in the first voltage equalization process is determined from the viewpoint of the durability of the relay. For example, the voltage difference between the terminals of the battery stacks 22 and 24 is about several percent to 1%. . For example, set to about 200V voltages V1, V2 between the terminals of the battery stack 22 and 24, in the case where the 2% is the target voltage difference [Delta] V _0, the target voltage difference [Delta] V ₀ is about 4V or less.

If the state of S30 is maintained for a predetermined time, the voltage difference ΔV, which is the difference between the voltages of the terminals of the battery stacks 22 and 24, is reduced to the target voltage difference ΔV _0. The apparatus 20 returns to the operation stop state and all relays are turned off (S34). The voltage equalization process is terminated (S36).

  Here, in the first voltage equalization process, since the voltage difference ΔV is reduced via the current limiting resistor 35, a loss occurs in the current limiting resistor 35, and energy is wasted. This leads to a reduction in fuel consumption of the vehicle.

  FIG. 6 is a diagram showing ON / OFF of each relay of the power supply apparatus 20 that can reduce the voltage difference ΔV without energy loss due to the current limiting resistor 35. Here, an example of V1> V2 is shown. In this case, although SMR-P is off, SMR-B1 and SMR-G1 are on, so that the current from the battery stack 22 on one side flows to the positive bus 26 side without passing through the current limiting resistor 35. In the battery stack 24 on one side, SMR-B2 and SMR-G2 are on, so that the current flowing from the battery stack 22 on one side to the positive electrode bus 26 flows into the battery stack 24 on the other side. In FIG. 6, the flowing current is indicated by a thick line, and the direction of the current is indicated by an arrow. Compared with FIG. 5, since the flowing current does not pass through the current limiting resistor 35, there is no energy loss due to the current limiting resistor 35. Further, since the current flowing so as to reduce the voltage difference ΔV is larger than that in FIG. 5, the voltage difference ΔV = | V1−V2 | is faster than the reduction rate in FIG. Thus, the voltage difference ΔV can be reduced. In the following, the voltage equalization method using the on / off state of FIG. 6 is simply referred to as the method using FIG.

  However, in the method using FIG. 6, since the battery stacks 22 and 24 are energized, the amount of self-heating of the battery stacks 22 and 24 increases. Thereby, battery temperature (theta) 1 and (theta) 2 rise, and it becomes easy to produce the early deterioration of the battery stacks 22 and 24. In order to prevent this, it is conceivable to provide cooling means for the battery stacks 22 and 24 and drive them. However, if the cooling means such as a blower or a cooler is driven, the fuel consumption of the vehicle and the cruising distance are reduced. There is a risk of inviting. Therefore, in performing the voltage equalization process using the settings of each relay in FIG. 6, it is preferable to consider the increase in battery temperature θ1, θ2.

FIG. 7 is a flowchart showing the procedure of the second voltage equalization process taking into account the increase in the battery temperatures θ1 and θ2 while minimizing the loss due to the current limiting resistor 35. The second voltage equalization process is performed from a state where the voltage difference ΔV is reduced to the target voltage difference ΔV ₀ on the premise of the procedure up to S30 in the first voltage equalization process. Then, the target voltage difference ΔV ₀ is further reduced without energy loss due to the current limiting resistor 35 by the method using FIG. 6, for example, ΔV is about 1% or less of the voltage between the terminals of the battery stacks 22 and 24. And

  In FIG. 7, processing different from the flowchart of FIG. 2 is surrounded by a thick frame, and processing flow different from the flowchart of FIG. 2 is indicated by a thick line with an arrow. Since the process before S20 is the same as the content described in the flowchart of FIG. 2, a detailed description thereof will be omitted. If the determination in S20 is affirmed, the process proceeds to the first voltage equalization process in S30 in FIG. 2, but if the determination in S20 is affirmed in FIG. 7, the battery temperatures θ1 and θ2 are acquired (S40). ). Then, the first voltage equalization process of S30 and S32 is executed, and thereafter, the battery temperatures θ1 and θ2 are acquired again (S42). The reason for acquiring the battery temperatures θ1 and θ2 in two steps S42 and S44 is to carefully consider the battery temperatures θ1 and θ2. Acquisition of battery temperature (theta) 1 and (theta) 2 is performed when the battery control part 60 acquires the detection data transmitted from the battery temperature detection parts 44 and 50. FIG.

Next, it is determined whether or not the higher one of the battery temperatures θ1 and θ2 is equal to or lower than a predetermined temperature _θth . In other words, it is determined whether or not both the battery temperature θ1 and the battery temperature θ2 are equal to or lower than the predetermined temperature _θth (S44). The predetermined temperature θ _th is a temperature at which the battery temperature that rises when the method of FIG. 6 is executed is estimated in advance by experiments and simulations, and the battery cooling means does not have to be driven even if the estimated temperature rise occurs. is there.

  If the determination in S44 is affirmative, the battery cooling means is not driven even if the method using FIG. 6 is executed, and the process proceeds to S48. In S48, according to the content described in FIG. 6, the ON / OFF setting of each relay is performed as follows. That is, in the first voltage equalization process, SMR-P that was on is turned off, and SMR-B1 that was off is turned on. That is, for one battery stack 22, SMR-B1 and SMR-G1 are on and SMR-P is off. For the battery stack 24 on the other side, SMR-B1 and SMR-G1 remain on.

By executing S48, the voltage difference ΔV is further reduced. For example, if the target voltage difference ΔV ₀ is about 1% or less of the voltage between the terminals of the battery stacks 22 and 24, voltage equalization has been sufficiently performed, and the process proceeds to S34 and S36. Since the contents of S34 and S36 have been described with reference to FIG. 2, detailed description thereof will be omitted.

If the determination in S44 is negative, the method using FIG. 6 in that state is likely to drive the battery cooling means, so the state of S30 is maintained as it is (S48), and the battery temperatures θ1, θ2 are maintained. Monitor the transition. The monitoring time is about several seconds to 10 seconds. When the monitoring time has elapsed, it is determined whether or not both the battery temperature θ1 and the battery temperature θ2 are equal to or lower than the predetermined temperature _θth (S50). Since the content of S50 is the same as S44, detailed description is omitted. If the determination in S50 is affirmative, the process proceeds to S46, S34, and S36. If the determination in S50 is negative, the method using FIG. 6 cannot be executed, so that the target voltage difference ΔV ₀ is not further reduced and the power supply device 20 returns to the operation stop state, and all relays are turned off. move on. Then, the second voltage equalization process in FIG. 7 ends (S36).

  Note that the on / off setting state of each relay in the method using FIG. 6 is the same as the on / off setting state of each relay when the power supply device 20 of FIG. 3 is operating. The difference is that V1 and V2 when the power supply device 20 is operating are CCVs, and therefore, not the open circuit voltages OCV of the battery stacks 22 and 24 connected in parallel, and therefore the voltage difference ΔV between the open circuit voltages OCV. Does not appear. When the power supply device 20 executes the second voltage equalization process by the method using FIG. 6, a voltage difference ΔV of the open circuit voltage OCV appears, and between the battery stack 22 on one side and the battery stack 24 on the other side. A current for reducing ΔV flows through the voltage to equalize the voltage.

  In the battery stack voltage equalization method in the present embodiment, two battery stacks 22 and 24 having a positive electrode connected to the positive electrode bus 26 and the positive electrode side relay, and a negative electrode connected to the negative electrode bus 28 and the negative electrode side relay are provided. The power supply device 20 is connected in parallel. The power supply device 20 further includes a precharge relay 34 in which a current limiting resistor 35 is connected in series, and is connected in parallel only to the positive side relay of the battery stack on one side, and all other than the precharge relay 34 are turned on. to start. Then, all the relays are turned off to stop the operation. In the voltage equalization method for the battery stack in the power supply device 20, after the operation of the power supply device 20 is stopped (S12), the voltage difference ΔV between the different battery stacks 22 and 24 is within a predetermined value range in which the equalization processing can be permitted. Is determined (S16, S20). If within the predetermined value range, the precharge relay 34 and the negative side relay are turned on while the positive side relay of the battery stack on one side is turned off, and the positive side relay and the negative side relay of the battery stack on the other side Are turned on together (S30). Then, this state is maintained for a predetermined time until the voltage difference ΔV between the battery stacks 22 and 24 is reduced to a predetermined voltage difference (S32).

  DESCRIPTION OF SYMBOLS 10 Vehicle drive system, 12 Rotating electric machine, 13 Drive circuit, 14 Inverter, 16 Smoothing capacitor, 18 DC / DC converter, 20 Power supply device, 22, 24 Battery stack, 26 Positive bus, 28 Negative bus, 30, 36 SMR-B (Positive side relay), 32, 38 SMR-G (Negative side relay), 34 SMR-P (Precharge relay), 35 Current limiting resistor, 40, 46 Voltage detector, 42, 48 Current detector, 44, 50 Battery temperature detection unit, 58 start / stop command, 60 battery control unit.

Claims (1)

Two battery stacks having a positive electrode connected to the positive electrode bus and the positive electrode side relay and a negative electrode connected to the negative electrode bus and the negative electrode side relay are connected in parallel, and a precharge relay in which current limiting resistors are connected in series is connected to one side. The battery stack is configured to be connected in parallel only to the positive-side relay of the battery stack, and is activated by turning on all but the precharge relay, and turning off all the relays to stop the operation of the battery stack. A voltage equalization method,
After stopping the operation of the power supply device, determine whether the voltage difference between the different battery stacks is within a predetermined value range that can allow the equalization process,
If within the predetermined value range, the precharge relay and the negative relay are turned on while the positive relay of the battery stack on the one side is turned off, and the positive electrode of the battery stack on the other side is turned on. A voltage equalization method for a plurality of battery stacks, wherein both the side relay and the negative side relay are turned on, and the state is maintained for a predetermined time until the voltage difference between the battery stacks is reduced to a predetermined voltage difference.

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