JP5432034B2 - Secondary battery current / voltage detector - Google Patents

Description

  The present invention relates to a current / voltage detection device for a secondary battery, and more particularly, to a detection timing of current and voltage of a battery pack.

  An electric vehicle such as an electric vehicle or a hybrid vehicle that obtains a vehicle driving force by an electric motor is equipped with a secondary battery, and the electric motor is driven by electric power stored in the secondary battery. The electric vehicle has a function of braking by causing the motor to function as a generator during regenerative braking, that is, braking the vehicle, and converting the kinetic energy of the vehicle into electric energy. The converted electric energy is returned to the secondary battery and reused when acceleration is performed.

  If the secondary battery is overdischarged or overcharged, the battery performance deteriorates. Therefore, it is necessary to grasp the state of charge (SOC) of the secondary battery and control the charging or discharging. For example, in a hybrid vehicle, the state of charge is fully charged (SOC = 100) so that the secondary battery can accept regenerative power and can supply power to the motor immediately if required. %) And the state in which no electricity is stored (SOC = 0%), and the vicinity of the middle (SOC = 50% to 60%). Therefore, it is necessary to detect the SOC of the secondary battery with high accuracy.

  The SOC of the secondary battery measures the charge / discharge current for the secondary battery, multiplies the current value by a predetermined charging efficiency η, and calculates the integrated capacity by integrating the multiplied value over a certain time interval. It can be estimated based on the accumulated capacity. At this time, the SOC estimation accuracy can be improved by correcting the charging efficiency η in accordance with the electromotive force Ve of the secondary battery. However, the electromotive force Ve of the secondary battery is within the predetermined period. Multiple pairs of terminal voltage and charge / discharge current data are acquired and stored, a linear approximation line (voltage V-current I approximation line) is obtained from these pair data by regression analysis, and the V intercept of the approximation line is unloaded. Calculate as voltage. Then, the integrated capacity is calculated by integrating the current I for a predetermined time, and the polarization voltage of the battery is obtained based on the change amount of the integrated capacity and the battery temperature in a predetermined period, and is obtained by subtracting the polarization voltage from the no-load voltage. be able to. The internal resistance of the secondary battery can also be calculated from the slope of the primary approximate line.

  Patent Document 1 below discloses a method of acquiring a pair current with respect to a voltage of a flying capacitor system, and discloses that the current of the pair current is sampled at a substantial turn-off time of the analog switch of the multiplexer. Has been.

Japanese Patent No. 3672183 JP 2008-180692 A JP 2009-52925 A

  The secondary battery's terminal voltage and charge / discharge current pair data are required to estimate the SOC of the secondary battery and the internal resistance. As in Patent Document 1, the current of the current at the time of substantial turn-off of the analog switch of the multiplexer is required. Sampling can be considered. By the way, when two different layers such as a solid electrode and an electrolyte solution are in contact with each other, a layer in which positive and negative charges are arranged at a very short distance is formed at the interface (electrical double layer). Since the voltage of the secondary battery changes due to the current flowing in the electric double layer, if the acquisition timing of the current and voltage of the secondary battery is the same timing, it becomes pair data that does not take this change into account. Therefore, an error occurs in the estimation of the SOC and internal resistance of the secondary battery.

  An object of the present invention is to improve the detection or estimation accuracy of secondary battery characteristics such as SOC and internal resistance of a secondary battery by controlling the acquisition timing of secondary battery current-voltage pair data. is there.

The present invention is an apparatus for detecting current and voltage of a secondary battery mounted on an electric vehicle and driving an electric motor as pair data, a capacitor connected to the secondary battery via a first switch group, A voltage detection unit connected to the capacitor via a second switch group; and a current detection unit that detects a current of the secondary battery, wherein the voltage detection unit is configured to turn on the first switch group and The capacitor is charged by the current from the secondary battery, and then the first switch group is turned off and the second switch group is turned on to detect the terminal voltage of the capacitor to detect the voltage of the secondary battery. And acquiring current data and voltage data by controlling the sampling timing of the current detected by the current detector and the voltage detected by the voltage detector. A is, delayed by the time of the sampling timing of the voltage from the current flows in the electric double layer of the secondary battery than the sampling timing of the current until the terminal voltage changes, the acquired current data and voltage data It is characterized by comprising acquisition means for making paired data.

  In one embodiment of the present invention, the sampling timing of the current is after the first switch group is turned on and thereafter the first switch group is turned off.

  In another embodiment of the present invention, the secondary battery is an assembled battery, and the assembled battery includes at least first and second battery blocks connected in series with each other, and the first switch group includes: A first switch connecting the positive electrode of the first battery block and one terminal of the capacitor; a second switch connecting the negative electrode of the first battery block and the positive electrode of the second battery block and the other terminal of the capacitor; And a third switch that connects the negative electrode of the second battery block and the one terminal of the capacitor, and the second switch group includes a first switch that connects the one terminal of the capacitor to the voltage detector. 4 switches and a fifth switch for connecting the other terminal of the capacitor to the voltage detection unit, and when the current voltage of the first battery block is detected, the first switch Tsu is switch and turned on and off in the interlocking manner the second switch is the at the time of current-voltage detection of the second battery block is turned on and off in the interlocking manner the second switch and the third switch.

  According to the present invention, it is possible to improve the detection or estimation accuracy of the characteristics of the secondary battery such as the SOC and the internal resistance of the secondary battery by controlling the acquisition timing of the current and voltage pair data of the secondary battery. it can.

1 is an overall configuration block diagram of an embodiment. It is a principal part circuit block diagram in FIG. It is a processing flowchart of an embodiment. It is a processing flowchart of a prior art. It is a timing chart of an embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1. Basic Configuration FIG. 1 is a configuration block diagram of a vehicle in which the secondary battery current-voltage detection device according to this embodiment is mounted. In addition, although the hybrid vehicle is illustrated as an onboard vehicle in FIG. 1, it is not limited to this, It can apply to the arbitrary vehicles provided with the motor as a drive source.

  The battery control unit (battery ECU) 20 receives information such as battery voltage and battery temperature from the secondary battery 10, estimates the SOC of the secondary battery 10 at a predetermined control timing, and estimates the estimated SOC, battery voltage, and battery. Information such as temperature is output to the hybrid control unit (HV-ECU) 40. The HV-ECU 40 controls the inverter 50, the driving force distribution mechanism 56, and the engine 60.

  The secondary battery 10 is an assembled battery, and is configured by connecting a plurality of battery blocks in series. Each battery block is configured by connecting a plurality of battery modules in series, and each battery module is configured by further connecting one or a plurality of single cells (cells) in series. The secondary battery 10 is a nickel metal hydride battery, for example.

  Secondary battery 10 is connected to motor generator (M / G) 52 via relay 38 and inverter 50. The motor generator 52 is connected to the engine 60 via a driving force distribution mechanism 56 including a planetary gear mechanism.

  The temperature sensor 32 is provided at a predetermined portion of the secondary battery 10 and detects the battery temperature of the predetermined portion of the secondary battery 10.

  The voltage detector 34 is provided for each battery block, and detects the terminal voltage of each battery block.

  The current detection unit 36 detects a charge / discharge current flowing through the secondary battery 10.

  The temperature data, the terminal voltage data, and the current data detected by the temperature sensor 32, the voltage detection unit 34, and the current detection unit 36 are supplied to the battery ECU 20 at predetermined sampling periods. The battery ECU 20 estimates the SOC and internal resistance of the secondary battery 10 based on the temperature data, terminal voltage data, and current data supplied from each sensor.

  A method for estimating the SOC in the battery ECU 20 is known, but will be briefly described below.

  The battery ECU 20 uses the terminal voltage data from the voltage detection unit 34 and the current data from the current detection unit 36 as pair data, the values of the current data in the charging direction and the discharging direction are within a predetermined range, and the pair data is being acquired. It is determined that the pair data of the terminal voltage data and the current data is valid when the amount of change in the integrated capacity is within a predetermined range. Then, a primary voltage-current approximate straight line is calculated from valid pair data by statistical processing using the least square method, and a voltage value when the current is zero is calculated as a no-load voltage.

  Further, the battery ECU 20 calculates the polarization generating component of the secondary battery 10 from the current data of the secondary battery 10, calculates the polarization decay component of the secondary battery 10, and adds these to add the secondary battery 10. Calculate the polarization voltage. The battery ECU 20 calculates a change amount of the integrated capacity in a predetermined period from the current data of the secondary battery 10, and refers to a lookup table stored in advance in a memory, thereby polarizing voltage corresponding to the change amount of the integrated capacity. You may ask for.

  Next, the battery ECU 20 calculates the electromotive force of the secondary battery 10 by subtracting the calculated polarization voltage from the calculated no-load voltage. Then, the SOC of the secondary battery 10 is estimated by correcting the charging efficiency η based on the electromotive force and integrating the current data of the secondary battery 10 for a predetermined period using the corrected charging efficiency η.

2. Configuration of Current / Voltage Detection Device FIG. 2 shows a circuit configuration diagram of the current / voltage detection device according to the present embodiment.

  The secondary battery 10 is an assembled battery, and in the figure, only three battery blocks 10-1, 10-2, 10-3 are shown for convenience of explanation, but the number is arbitrary. Battery blocks 10-1, 10-2, 10-3 are connected to each other in series.

  The positive side of the battery block 10-1 is connected to one terminal of the flying capacitor C1 via the switch S1, and the other terminal of the flying capacitor C1 is connected to one terminal of the flying capacitor C2 and connected in series. . Further, the other terminal of the flying capacitor C2 is connected to the negative electrode side of the battery block 10-1 via the switch S2.

  The other terminal of the flying capacitor C2 is connected to the positive side of the battery block 10-2 via the switch S2, and one terminal of the flying capacitor C1 is connected to the negative side of the battery block 10-2 via the switch S3. Is connected.

  One terminal of the flying capacitor C1 is connected to the positive electrode side of the battery block 10-3 via the switch S3, and the other terminal of the flying capacitor C2 is connected to the negative electrode side of the battery block 10-3 via the switch S4. Is connected.

  One terminal of the flying capacitor C1 is connected to the voltage detector 34 via the switch S5 and the resistor R1, and the other terminal of the flying capacitor C2 is connected to the voltage detector 34 via the switch S6 and the resistor R2. The

  Switches S1 to S4 that connect the battery blocks 10-1 to 10-3 of the secondary battery 10 and the flying capacitors C1 and C2 constitute a first switch group, and connect the flying capacitors C1 and C2 to the voltage detection unit 34. The switches S5 and S6 constitute a second switch group. Both the first switch group and the second switch group can be configured by analog switches.

  The voltage detector 34 detects the terminal voltage of each battery block 10-1, 10-2, 10-3 and outputs it to the battery ECU 20. That is, when the switches S1 and S2 are turned on and the other switches are turned off, only the battery block 10-1 is connected to the flying capacitors C1 and C2, and the flying capacitors C1 and C2 are charged and the terminals of the battery block 10-1 are charged. The voltage is held. Thereafter, when the switches S1 and S2 are turned off and the switches S5 and S6 are turned on, the capacitors C1 and C2 are connected to the voltage detector 34, and the terminal voltage of the capacitors C1 and C2, that is, the terminal voltage of the battery block 10-1 is changed. Detected. Next, when the switches S5 and S6 are turned off and the switches S2 and S3 are turned on, only the battery block 10-2 is connected to the flying capacitors C1 and C2, and the flying capacitors C1 and C2 are charged and the battery block 10-2 is charged. Is held. Thereafter, when the switches S5 and S6 are turned on and the other switches are turned off, the capacitors C1 and C2 are connected to the voltage detector 34, and the terminal voltages of the capacitors C1 and C2, that is, the terminal voltage of the battery block 10-2 are detected. Is done. Next, when the switches S5 and S6 are turned off and the switches S3 and S4 are turned on, only the battery block 10-3 is connected to the flying capacitors C1 and C2, the flying capacitors C1 and C2 are charged, and the battery block 10-3. Is held. Thereafter, when the switches S3 and S4 are turned off and the switches S5 and S6 are turned on, the capacitors C1 and C2 are connected to the voltage detector 34, and the terminal voltage of the capacitors C1 and C2, that is, the terminal voltage of the battery block 10-3 is changed. Detected. As described above, the terminal voltages of the battery blocks 10-1, 10-2, and 10-3 are sequentially detected by sequentially turning on and off the switches S1 to S4.

  Further, the current detection unit 36 detects the charging / discharging current of the secondary battery 10 and outputs it to the battery ECU 20. The battery ECU 20 samples and acquires current data from the current detection unit 36 at a predetermined timing, and acquires terminal voltage data and current data pair data as described above.

  However, if the current data acquisition timing is the same as the terminal voltage acquisition timing, the SOC of the secondary battery 10 cannot be estimated with high accuracy. The reason is that the voltage of the secondary battery 10 changes due to the current flowing in the electric double layer. Therefore, if the acquisition timing of the current and voltage of the secondary battery 10 is the same timing, the voltage data and current data that are not originally paired Is misrecognized as pair data. For example, assume that current data is acquired at a certain timing. However, the terminal voltage data paired with the current data is a terminal voltage after change caused by the flow of the current, not the terminal voltage caused by the flow of the current. Therefore, in the present embodiment, the current data acquisition timing is controlled in the electric double layer of the secondary battery 10 in consideration of the time from when the current flows until the terminal voltage changes. That is, current data is acquired prior to acquiring terminal voltage data, and the current data is acquired and then paired with the current data after a predetermined time, that is, the time from when the current flows until the terminal voltage changes. The terminal voltage data to be processed is acquired. The time from when the current flows until the terminal voltage changes varies depending on the type of the secondary battery 10, but in a nickel metal hydride battery, it is about 0.03 seconds.

  In FIG. 3, the detection flowchart of the terminal voltage and charging / discharging electric current of the secondary battery 10 in this embodiment is shown. The case of detecting a specific battery block of the secondary battery 10 that is an assembled battery, specifically, the terminal voltage and current of the battery block 10-1, will be described, but the same applies to other battery blocks.

  First, the battery ECU 20 supplies a control signal to the switches S1 and S2 to turn on the switches S1 and S2 (S101). As a result, current flows through the capacitors C1 and C2, and the capacitors C1 and C2 are charged. After the switches S1 and S2 are turned on, the battery ECU 20 samples the current detected by the current detection unit 36 and acquires current data (S102).

  Next, the battery ECU 20 supplies a control signal to the switches S1 and S2 to turn off the switches S1 and S2 (S103), and supplies a control signal to the switches S5 and S6 to turn on the switches S5 and S6 (S104). ). As a result, the capacitors C1 and C2 are connected to the voltage detector 34. The battery ECU 20 samples and acquires the voltage data detected by the voltage detector 34 (S105), and turns off the switches S5 and S6 (S106). The battery ECU 20 estimates the SOC of the battery block 10-1 using the current data acquired in S102 and the voltage data acquired in S105 as pair data.

  For comparison, FIG. 4 shows a detection flowchart of terminal voltage and charge / discharge current in the prior art. First, the switches S1 and S2 are turned on (S201). Then, after charging the capacitors C1 and C2, the switches S1 and S2 are turned off (S202). After the switches S1 and S2 are turned off, the current is detected (S203). At the same time, the switches S5 and S6 are turned on (S204), and the voltage is detected by the voltage detector 36 (S205). After acquiring the current and voltage data, the switches S5 and S6 are turned off (S206).

  In the process of FIG. 4, the current is detected after the switches S1 and S2 are turned off, that is, the charging of the capacitors C1 and C2 has already been completed at the time of current detection. Therefore, the change in voltage after the current flows is not reflected in the capacitors C1 and C2. On the other hand, in the present embodiment shown in FIG. 3, since the current is detected before the switches S1 and S2 are turned off, the change in voltage after the current flows is accumulated in the capacitors C1 and C2. Thus, the detected voltage data is voltage data reflecting a change after the current flows.

  FIG. 5 shows the on / off timing of each switch in the present embodiment. FIG. 5A shows the on / off timing of the switches S1 and S2. It turns on at a certain time t1, and then turns off at a time t2. On the other hand, FIG. 5B shows the current sampling timing, and the current is sampled at time t3 before the switches S1 and S2 are turned off at time t2. FIG. 5C shows the on / off timing of the switches S5 and S6, which are turned on at time t4 after time t2, and then turned off at time t5. Further, FIG. 5D shows the voltage sampling timing, and the voltage is sampled at time t6 after the switches S5 and S6 are turned on at time t4. The current data sampled at time t3 and the voltage data sampled at time t6 are pair data. In FIG. 5B, the conventional current sampling timing is indicated by a broken line for comparison. Conventionally, sampling is performed at the time t4 at the same time or after the switches S1 and S2 are turned off at the time t2. In this embodiment, as is apparent from the figure, the conventional current sampling timing is preceded in time, and is set before the timing when the switches S1 and S2 are turned off.

  As described above, in the present embodiment, when the pair data of current data and voltage data is acquired, the current data acquisition timing is temporally preceded by the voltage data acquisition timing, and the amount of change in voltage due to the current flowing is determined. Since the voltage data is acquired after reflecting the voltage on the terminal voltages of the capacitors C1 and C2, accurate pair data can be acquired, and thereby the high-accuracy SOC or internal resistance of the secondary battery 10 can be acquired. Estimation is possible.

  In the present embodiment, since the current data acquisition timing is temporally preceded by the voltage data acquisition timing, it is possible to estimate the SOC or the like with high accuracy even if there is a variation in the switch timing. Also play. That is, in the prior art, as shown in FIG. 5, the current sampling timing and the voltage sampling timing are almost the same, so that the current sampling timing is later than the voltage sampling timing due to variations in switch timing. In this case, data that is not originally paired data is handled as paired data, and high-precision estimation becomes difficult. In addition, Patent Document 1 described above describes that the switches S1 and S2 are constituted by analog switches, and that a substantial turn-off time of these analog switches is set as a current sampling timing. If there is a variation in the turn-off time, the current sampling timing varies accordingly, and it may be delayed from the voltage sampling timing. However, in this embodiment, since the current sampling timing is temporally preceded by the voltage sampling timing, there is almost no possibility of such a time reversal phenomenon, and high-precision estimation is guaranteed. Is done. The difference between the current sampling timing and the voltage sampling timing, that is, Δt = t6−t3 in FIG. 5 can be an arbitrary value within a range of 0.01 sec to 0.09 sec, for example, Δt = 0.03 sec. It can be.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment, A various deformation | transformation is possible.

  For example, although the nickel hydride battery is used as an example of the secondary battery 10 in the present embodiment, a lithium ion battery or other batteries may be used.

  In this embodiment, the difference Δt between the voltage sampling timing and the current sampling timing is set to 0.03 sec, for example, but the voltage sampling timing is synchronized with the off timing of the switches S1 and S2 and the on timing of the switches S5 and S6. The current sampling timing may be controlled to be temporally preceded by Δt from the off timing of the switches S1 and S2. In short, in consideration of the fact that the voltage changes due to the current flowing in the electric double layer, the flying capacitors C1 and C2 are charged with the changed voltage caused by the current flowing, and the flying at this time The terminal voltages of the capacitors C1 and C2 may be detected, and the current data and voltage data detected in this way may be processed as pair data. Further, in the present embodiment, two flying capacitors C1 and C2 connected in series with each other are illustrated, but a single flying capacitor may be used. Furthermore, in the present embodiment, only one set of flying capacitors C1 and C2 is provided, but a plurality of sets may be provided as necessary, and each set of flying capacitors may be one or more. A configuration in which a plurality of sets of flying capacitors is provided is described in, for example, Japanese Patent No. 3672183. A set of flying capacitors is provided by half of the number of battery blocks constituting the secondary battery 10, and one flying block is provided by two battery blocks. The voltage is detected by sharing a set of capacitors.

  10 secondary battery, S1 to S4 first switch group, S5, S6 second switch group, 20 battery ECU, 34 voltage detector, 36 current detector.

Claims (3)

A device for detecting current and voltage of a secondary battery mounted on an electric vehicle and driving an electric motor as pair data ,
A capacitor connected to the secondary battery via a first switch group;
A voltage detector connected to the capacitor via a second switch group;
A current detector for detecting the current of the secondary battery;
With
The voltage detection unit is configured such that the first switch group is turned on and the capacitor is charged by a current from the secondary battery, and then the first switch group is turned off and the second switch group is turned on and the capacitor is turned on. The voltage of the secondary battery is detected by detecting the terminal voltage of
Means for controlling the sampling timing of the current detected by the current detection unit and the voltage detected by the voltage detection unit to obtain current data and voltage data, the sampling timing of the voltage being the sampling timing of the current An acquisition means for delaying by a time from when a current flows in the electric double layer of the secondary battery until the terminal voltage changes , and using the acquired current data and voltage data as pair data;
A current-voltage detection device for a secondary battery, comprising: The apparatus of claim 1.
The current voltage detection device for a secondary battery, wherein the current sampling timing is after the first switch group is turned on and before the first switch group is turned off. The apparatus according to claim 1,
The secondary battery is an assembled battery, and the assembled battery includes at least first and second battery blocks connected in series with each other,
The first switch group includes:
A first switch connecting a positive electrode of the first battery block and one terminal of the capacitor;
A second switch connecting the negative electrode of the first battery block and the positive electrode of the second battery block and the other terminal of the capacitor;
A third switch connecting the negative electrode of the second battery block and the one terminal of the capacitor;
With
The second switch group includes:
A fourth switch for connecting the one terminal of the capacitor to the voltage detection unit;
A fifth switch for connecting the other terminal of the capacitor to the voltage detector;
With
When the current voltage of the first battery block is detected, the first switch and the second switch are turned on / off in conjunction with each other, and when the current voltage of the second battery block is detected, the second switch and the third switch are turned on / off in conjunction with each other. A current voltage detection device for a secondary battery.

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