JP2015012711A - Battery system and current regulation method of battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery system capable of making power consumption of battery modules uniform while using the battery modules which are connected in parallel, without incurring instantaneous interruption or the like in a current path, and a current regulation method of the battery module.SOLUTION: In a battery system 100 comprising a plurality of battery modules 1a, 1b and 1c, an electronic control unit 5 detects current values of the battery modules, calculates remaining capacitances of the battery modules and calculates an average value of the remaining capacitances of all the battery modules. The electronic control unit 5 outputs a pulse width modulation signal to electrification/cutoff means 4a, 4b and 4c while enlarging an on/off duty ratio for a battery module of which the remaining capacitance is higher than the average value, in comparison with the other battery modules and reducing an on/off duty ratio for a battery module of which the remaining capacitance is lower than the average value, in comparison with the other battery modules. In accordance with the pulse width modulation signal, the electrification/cutoff means 4a, 4b and 4c are electrified and cut off.

Description

  The present invention relates to a battery system having a plurality of rechargeable battery modules connected in parallel, and a current adjustment method for the battery modules.

  In electric vehicles for work such as forklifts, and vehicles such as EV, HV, and PHV, a battery system that has a large capacity by connecting a plurality of rechargeable battery modules in parallel so that a large current can be supplied to the load. Used.

  In such a battery system, even when a plurality of battery modules are simply connected in parallel and fed to a load, the power of each battery module is evenly consumed due to variations in the internal resistance of each battery module. Therefore, the state of charge of each battery module becomes uneven. As a result, the deterioration rate of each battery module varies, and the life of each battery module becomes non-uniform. For this reason, the method of equalizing the lifetime of each battery module is strongly desired.

  Since the remaining life of a battery module becomes shorter as the amount of power used is larger, when using a battery system having a plurality of battery modules, each battery module is switched according to the amount of electricity stored and connected to a load. It has been proposed that the amount of power used is made uniform and the remaining life is made uniform (see, for example, Patent Document 1).

  FIG. 5 shows a configuration example of a conventional battery system having a plurality of battery modules. As shown in FIG. 5, in a battery system 100 having a plurality of battery modules 1a, 1b, 1c, each battery module 1a, 1b, 1c is selectively switched by the switching means 11 according to the amount of stored electricity. Connect to load 14.

  The switching means 11 has a larger amount of power stored in the battery modules 1a, 1b, 1c under the control of the control means 13 based on the detected voltage values of the battery modules 1a, 1b, 1c detected by the voltage detection means 12. The battery modules 1a, 1b, 1c are selectively connected to the load 14. By doing so, the power consumption of each battery module 1a, 1b, 1c is made uniform, and the remaining life of the battery module is made uniform.

JP 2012-120403 A

  In a battery system having a plurality of battery modules, the power of each battery module is not evenly consumed due to variations in the internal resistance of each battery module, etc., and the charging state of each battery module becomes uneven, and the life of each battery module Becomes uneven.

  Therefore, in order to make the charging state of each battery module uniform, for example, as shown in FIG. 5, each battery module 1 a, 1 b, 1 c is switched by the switching means 11 according to the amount of stored electricity and connected to the load 14. In the configuration, when the switching means 11 switches the battery modules 1a, 1b, and 1c, an instantaneous interruption occurs in the current path to the load 14.

  When an instantaneous interruption of the current path occurs with respect to a load 14 through which a large current flows like an electric vehicle such as a forklift, a sudden change in voltage and current occurs in the load 14 and causes various adverse effects.

  In view of the above problems, the present invention does not change the battery modules 1a, 1b, and 1c, and therefore, even during power feeding from the battery modules 1a, 1b, and 1c to the load 14, an instantaneous interruption or the like occurs in the current path. A battery system capable of preventing the difference in the charging state of each battery module 1a, 1b, 1c while using the battery modules 1a, 1b, 1c connected in parallel, and a current adjustment method for the battery module The purpose is to provide.

  A battery system according to one aspect of the present invention is a battery system having a plurality of battery modules connected in parallel, and is connected to each of the battery modules, and energizes and shuts off the current flowing through each battery module. An on / off duty ratio, which is a ratio of energization time to on / off time, is output to the energization interruption means and the energization interruption means according to the state of charge of each battery module, and the pulse width modulation is output. And a pulse width modulation signal output means for energizing and interrupting the energization interruption means by a signal. Thereby, while using each battery module connected in parallel, it becomes possible to adjust the charge condition of each battery module, and to prevent the expansion of the difference in charge condition.

  The battery module further comprises a remaining capacity calculating means for calculating a remaining capacity of each battery module, wherein the pulse width modulation signal output means changes the on / off duty ratio with respect to the battery module having the remaining capacity larger than the other battery modules. A pulse width modulation signal having a larger on-off duty ratio than other battery modules is output to a battery module that is larger than the other battery modules and has a smaller remaining capacity than the other battery modules. To do. As a result, when the full charge capacities of the battery modules are the same, it is possible to adjust the charge state of each battery module while using the battery modules connected in parallel, and to prevent an increase in the difference in the charge state. .

  The battery module further comprises a charge rate calculation means for calculating a charge rate that is a ratio of a remaining capacity to a full charge capacity of each of the battery modules, and the pulse width modulation signal output means has a higher charge rate than the other battery modules. For the module, the on / off duty ratio is increased compared to other battery modules, and for the battery module whose charge rate is smaller than other battery modules, the on / off duty ratio is decreased compared to other battery modules. The pulse width modulation signal thus output is output. Thereby, when the full charge capacity of each battery module differs, it becomes possible to adjust the charge state of each battery module, using each battery module connected in parallel, and to prevent the expansion of the difference in charge state.

  According to the present invention, the state of charge of each battery module is adjusted while using the battery modules connected in parallel without causing an instantaneous interruption or the like in the current path even during power feeding from each battery module of the battery system to the load. Thus, it is possible to prevent an increase in the difference between the charged states, and to uniformize the deterioration rate of each battery module.

It is a figure which shows the structural example of embodiment of the battery system of this invention. It is a figure which shows the 1st operation example of embodiment of the battery system of this invention. It is a figure which shows the 2nd operation example of embodiment of the battery system of this invention. It is a figure which shows the example of a PWM signal. It is a figure which shows the structural example of the conventional battery system.

  The structural example of embodiment of the battery system of this invention is demonstrated with reference to FIGS. In FIG. 1, 100 is a battery system. 1a, 1b, and 1c are battery modules, 2a, 2b, and 2c are rechargeable storage batteries in the battery modules 1a, 1b, and 1c, and 3a, 3b, and 3c are current values flowing through the battery modules 1a, 1b, and 1c. Detecting current sensors 4a, 4b, 4c are energization interrupting means for opening and closing the current paths of the battery modules 1a, 1b, 1c, and 5 is an electronic control unit for controlling energization / interruption of the energization interrupting means 4a, 4b, 4c. , 6 are main switches.

  In a battery system 100 in which battery modules 1a, 1b, and 1c having a plurality of rechargeable storage batteries 2a, 2b, and 2c as shown in FIG. 1 are connected in parallel to increase the capacity, a load (not shown) is provided from the battery system 100. In addition to the main switch 6 that controls energization / interruption of the current path to (), a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), mechanical relay, etc. are provided for each current path of each battery module 1a, 1b, 1c. The energization interruption means 4a, 4b, 4c used are provided.

  FIG. 1 shows a configuration example in which MOSFETs and diodes are used as the current cutoff means 4a, 4b, 4c. This configuration example will be described with respect to the energization cut-off means 4a. When the power is supplied (discharged) from the battery module 1a to the load (not shown), the MOSFET 41 and the MOSFET 43 are brought into conduction, whereby the storage battery 2a → main switch 6 → load. (Illustration omitted) → The power is supplied to the load through the current path of MOSFET 43 → MOSFET 41, and the power supply to the load is stopped by turning off the MOSFET 41 and the MOSFET 43.

  Further, when charging by a regenerative current from a load (not shown), the MOSFET 41 and the MOSFET 43 are brought into a conducting state, whereby the storage battery 2a is connected by a current path of the load (not shown) → the main switch 6 → the storage battery 2a → the MOSFET 41 → the MOSFET 43. Is charged and the MOSFET 41 and the MOSFET 43 are cut off to stop charging.

  In this way, by controlling the conduction and interruption of the MOSFETs 41 and 43 of the energization interruption means 4a, the discharging and charging of the battery module 1a can be controlled. Energization / interruption of the energization / interruption means 4a, 4b, 4c of the battery modules 1a, 1b, 1c is controlled by the electronic control unit 5.

  The electronic control unit 5 monitors the state of each of the battery modules 1a, 1b, 1c, and when the battery modules 1a, 1b, 1c are overcharged or overdischarged, the energization cutoff means 4a, 4b, 4c The battery module 1a, 1b, 1c can be prevented from being overcharged or overdischarged.

  In such a battery system 100, the current adjustment method according to the charge state of each battery module by the electronic control unit 5 will be described. Here, as the state of charge of the battery module, a charge rate (SOC: Charge Of State) which is a ratio of the remaining capacity of the battery module or the remaining capacity to the full charge capacity can be used.

  The electronic control unit 5 reads the current values of the battery modules 1a, 1b, 1c from the current sensors 3a, 3b, 3c, for example, as in the flow of the first operation example shown in FIG. 2 (step S21). At this time, the electronic control unit 5 functions as the current detection means 51.

  The electronic control unit 5 calculates the accumulated current value from the read current value, calculates the remaining capacity of each battery module 1a, 1b, 1c from the initial remaining capacity and the accumulated current value (step S22), and all the battery modules. The average value of the remaining capacity of 1a, 1b, 1c is calculated (step S23). At this time, the electronic control unit 5 functions as the remaining capacity calculation means 52.

  In addition to the above calculation method, the remaining capacity is obtained by reading a voltage value from a voltage sensor (not shown) that measures the voltage value of each battery and using the SOC-CCV characteristic curve from the voltage value. X full charge capacity) can also be calculated. Here, the SOC-CCV characteristic curve is a characteristic curve showing a correlation between the charging rate (SOC) and the closed circuit voltage (CCV) of the battery. In addition to the SOC-CCV characteristic curve, a model or the like is used, or the open circuit voltage (OCV) is estimated from the closed circuit voltage (CCV) of the battery, and the remaining capacity is calculated using the open circuit voltage (OCV). Can also be calculated.

  Based on the difference between the remaining capacity of each battery module 1a, 1b, 1c and the average value of the whole, the electronic control unit 5 applies to each energization cutoff means 4a, 4b, 4c of each battery module 1a, 1b, 1c. Control as follows.

  The electronic control unit 5 controls the energization interruption means 4a, 4b, 4c of the battery modules 1a, 1b, 1c by a pulse width modulation (PWM) signal that repeats energization and interruption at a predetermined cycle. The on / off duty ratio, which is the ratio between the energization time and the cutoff time within the predetermined period, is determined as follows (step S24).

  (1) The on / off duty ratio is increased and the energization time ratio is increased with respect to the energization cutoff means 4a, 4b, 4c of the battery modules whose remaining capacity is larger than the average value of all the battery modules 1a, 1b, 1c.

  (2) The on / off duty ratio is reduced and the energization time ratio is reduced with respect to the energization cutoff means 4a, 4b, 4c of the battery modules whose remaining capacity is smaller than the average value of all the battery modules 1a, 1b, 1c.

  In addition, when determining the on / off duty ratio, for example, the remaining capacity of each of the battery modules 1a, 1b, and 1c is compared with each other in addition to the method of determining based on the difference from the overall average value as described above. It is also possible to increase / decrease the on / off duty ratio of a module having a large / small remaining capacity.

  The electronic control unit 5 sends out the PWM signal having the on / off duty ratio determined in the above-described step 24 to the energization cutoff means 4a, 4b, 4c of the battery modules 1a, 1b, 1c (step S25). At this time, the electronic control unit 5 functions as pulse width modulation (PWM) signal output means 53.

  Each energization shut-off means 4a, 4b, 4c drives an open / close switch such as MOSFET 43 according to the PWM signal to open / close the current path of each battery module 1a, 1b, 1c (step S26). Then, it returns to step S21 and repeats the same operation.

  Note that, as in the first operation example of FIG. 2, based on the remaining capacity of each battery module 1a, 1b, 1c, the power consumption of each battery module 1a, 1b, 1c is made uniform, and each battery module 1a, The lifetimes of 1b and 1c can be made uniform when the full charge capacities of the battery modules 1a, 1b and 1c are the same.

  When the full charge capacities of the battery modules 1a, 1b, and 1c are different, based on the remaining capacities of the battery modules 1a, 1b, and 1c, the power consumption of the battery modules 1a, 1b, and 1c is equalized. A battery module with a small full charge capacity is likely to be used in an overdischarge region, and a battery module with a small full charge capacity has a short life.

  Therefore, instead of determining the on / off duty ratios of the energization cutoff means 4a, 4b, 4c of the battery modules 1a, 1b, 1c based on the remaining capacity as in the first operation example shown in FIG. Based on the charging rates of the modules 1a, 1b, and 1c, the on / off duty ratios of the energization cutoff means 4a, 4b, and 4c are determined.

  FIG. 3 shows a flow of a second operation example in which the on / off duty ratio of the energization cutoff means 4a, 4b, 4c is determined based on the charging rates of the battery modules 1a, 1b, 1c. In the flow of the second operation example in FIG. 3, the same steps as those in the flow of the first operation example in FIG.

  In the flow of the second operation example of FIG. 3, the electronic control unit 5 reads the current values of the battery modules 1a, 1b, and 1c in step S21, as in the first operation example of FIG. From the initial charging rate and the integrated current value, the charging rate (SOC) of each battery module 1a, 1b, 1c is calculated (step S31), and the charging rate of all the battery modules 1a, 1b, 1c is calculated. An average value is calculated (step S32). At this time, the electronic control unit 5 functions as a charging rate calculation means. The charging rate calculation means is obtained by replacing the remaining capacity calculation means 52 in FIG. 1 with a charging rate calculation means.

  In addition to the above-described calculation method, the charging rate (SOC) is calculated by reading a voltage value from a voltage sensor (not shown) that measures the voltage value of each battery and using the SOC-CCV characteristic curve from the voltage value. You can also. In addition to the SOC-CCV characteristic curve, a model or the like is used, or the open circuit voltage (OCV) is estimated from the closed circuit voltage (CCV) of the battery, and the charging rate is calculated using the open circuit voltage (OCV). Can also be calculated.

  Based on the difference between the charging rate of each of the battery modules 1a, 1b, and 1c and the overall average value, the electronic control unit 5 applies the current-carrying-off means 4a, 4b, and 4c of each of the battery modules 1a, 1b, and 1c. The on / off duty ratio is determined as follows (step S33).

  (1) The on / off duty ratio is increased and the ratio of energization time is increased with respect to the energization cutoff means 4a, 4b, 4c of the battery modules whose charging rate is larger than the average value of all the battery modules 1a, 1b, 1c.

  (2) The on / off duty ratio is reduced and the energization time ratio is reduced with respect to the current-carrying-off means 4a, 4b, 4c of the battery modules whose charging rate is smaller than the average value of all the battery modules 1a, 1b, 1c.

  Also in this embodiment, when determining the on / off duty ratio, for example, the charging rate of each of the battery modules 1a, 1b, and 1c other than the method of determining based on the difference from the overall average value as described above. (SOC) may be compared with each other to increase / decrease the on / off duty ratio of modules having a large / small charging rate (SOC).

  The electronic control unit 5 sends the on / off duty ratio PWM signal determined as described in (1) and (2) above to the energization cutoff means 4a, 4b, 4c of the battery modules 1a, 1b, 1c. Since this operation is the same as or after step S25 in the operation example of FIG.

  FIG. 4 shows an example of the on / off duty ratio of the PWM signal sent from the electronic control unit 5 in step 25 of the operation example of FIG. 2 or FIG. In FIG. 4, the horizontal axis indicates time, the vertical axis indicates the amplitude voltage of the PWM signal, and the pulse waveform of the PWM signal is indicated by a rectangle.

  FIG. 4A shows an example of an on / off duty ratio for a battery module in which the remaining capacity or the charging rate is in a range that is about the same as the average value. In the case of this example, the pulse width with an on / off duty ratio of 50% is substantially equal to the energization time and the cutoff time.

  FIG. 4B shows an example of an on / off duty ratio for a battery module having a remaining capacity or a charging rate smaller than an average value. In this example, the on / off duty ratio is set to a pulse width of 50% or less. FIG. 4C shows an example of an on / off duty ratio for a battery module having a remaining capacity or a charging rate larger than an average value. In this example, the on / off duty ratio is set to a pulse width of 50% or more.

  In FIG. 4, the remaining capacity or the charging rate of each battery module 1a, 1b, 1c is divided into three stages, which are less than, equal to, or more than the overall average value, and the remaining capacity or the charging rate increases. As shown, an example of generating a PWM signal whose on / off duty ratio increases is shown.

  However, the on / off duty ratio continuously increases as the remaining capacity or the charging rate increases according to the difference or ratio between the remaining capacity or the charging rate of each battery module 1a, 1b, 1c and the overall average value. Or it is good also as a structure which produces | generates the PWM signal which increases in steps by arbitrary appropriate steps.

  In addition, by appropriately adjusting the phase of the PWM signal sent to each energization interruption means 4a, 4b, 4c of each battery module 1a, 1b, 1c, each energization interruption means 4a, 4b, 4c does not become an interruption state all at once. As described above, by sending a PWM signal so that at least one of the battery modules 1a, 1b, and 1c is alternately energized, no instantaneous interruption occurs in power supply from the battery system 100. be able to.

  As described above, according to the present invention, the battery modules 1a, 1b, and 1c are connected in parallel, and power is supplied from the battery modules 1a, 1b, and 1c to the load. While using the battery modules 1a, 1b, and 1c without causing an instantaneous interruption or the like in the current from the battery system 100, the remaining capacity or the charging rate of each of the battery modules 1a, 1b, and 1c is adjusted, and each battery module 1a is adjusted. , 1b, 1c can be made uniform.

  As a result, it is possible to prevent the difference between the remaining capacity or the charging rate of each battery module 1a, 1b, 1c, and to make the deterioration rate of each battery module uniform. Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various configurations or embodiments can be taken without departing from the scope of the present invention. Can do.

DESCRIPTION OF SYMBOLS 100 Battery system 1a, 1b, 1c Battery module 2a, 2b, 2c Storage battery 3a, 3b, 3c Current sensor 4a, 4b, 4c Current interruption means 41, 43 MOSFET
42,44 Diode 5 Electronic control unit 6 Main switch

Claims (6)

In a battery system having a plurality of battery modules connected in parallel,
Energization cutoff means connected to each of the battery modules and energizing and shutting off current flowing in each battery module;
The on / off duty ratio, which is the ratio between the energization time and the on-off time, is output to the energization cut-off means according to the charge state of each battery module, and the energization is performed according to the pulse width modulation signal. Pulse width modulation signal output means for energizing and shutting off the shut-off means;
A battery system comprising: A remaining capacity calculating means for calculating the remaining capacity of each battery module;
The pulse width modulation signal output means makes the on / off duty ratio larger than that of the other battery modules, and the remaining capacity is smaller than that of the other battery modules, with respect to the battery module having the remaining capacity larger than that of the other battery modules. The battery system according to claim 1, wherein a pulse width modulation signal in which the on / off duty ratio is smaller than that of other battery modules is output to the battery module. Charge rate calculation means for calculating a charge rate that is a ratio of the remaining capacity to the full charge capacity of each battery module,
The pulse width modulation signal output means makes the on / off duty ratio larger than that of the other battery modules, and the charging rate is smaller than that of the other battery modules, for the battery module having the charging rate larger than that of the other battery modules. The battery system according to claim 1, wherein a pulse width modulation signal in which the on / off duty ratio is smaller than that of other battery modules is output to the battery module. A method for adjusting the current of each battery module in a battery system having a plurality of battery modules connected in parallel,
A pulse width modulation signal output step for outputting a pulse width modulation signal in which an on / off duty ratio, which is a ratio between an energization time and an interruption time of the current flowing through each battery module, varies depending on a charge state of each battery module;
Energization interruption step of energizing and interrupting each battery module by the pulse width modulation signal;
For adjusting the current of a battery module. A remaining capacity calculating step of calculating a remaining capacity of each battery module;
In the pulse width modulation signal output step, for the battery module having the remaining capacity larger than the other battery modules, the on / off duty ratio is made larger than that of the other battery modules, and the remaining capacity is smaller than the other battery modules. The battery module current adjustment method according to claim 4, wherein a pulse width modulation signal in which the on / off duty ratio is smaller than that of other battery modules is output to the battery module. A charge rate calculating step of calculating a charge rate that is a ratio of a remaining capacity to a full charge capacity of each battery module;
In the pulse width modulation output step, for the battery module having the charging rate larger than that of the other battery module, the on / off duty ratio is made larger than that of the other battery module, and the charging rate is smaller than that of the other battery module. The battery module current adjustment method according to claim 4, wherein a pulse width modulation signal in which the on / off duty ratio is smaller than that of other battery modules is output to the battery module.

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