JP2018026927A - Power storage system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress in-rush current occurring between power storage sections while a relay is closing, without performing voltage adjustment between power storage sections by a cyclic current, in a power storage system including first and second power storage sections.SOLUTION: A controller 100 controls system main relays 24, 34, 44 so that a battery stack having the highest voltage, out of the battery stacks 20, 30, 40, is electrically connected with a capacitor 52 at first. When the difference of the voltage of other battery stack and the voltage of the capacitor 52 goes below a specified value, the controller 100 controls the system main relays 24, 34, 44 so that both other battery stack and the battery stack having the highest voltage are electrically connected with the capacitor 52.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power storage system, and particularly to a power storage system including first and second power storage units connected in parallel.

  Japanese Patent No. 5682708 (Patent Document 1) discloses a power storage system including first and second power storage devices connected in parallel. First and second relays are connected in series to the first and second power storage devices, respectively. Between the first and second power storage devices, a circulating current is allowed to flow from the power storage device having a high electromotive voltage to the power storage device having a low electromotive voltage. The first and second relays are opened after the voltage difference between the first and second power storage devices becomes a predetermined value or less due to the circulating current.

  Therefore, according to this power storage system, when the first and second relays are closed next time, the voltage difference between the first and second power storage devices is equal to or less than a predetermined value. Inrush current generated between the devices can be suppressed (see Patent Document 1).

Japanese Patent No. 5682708

  In the power storage system disclosed in Patent Document 1, a part of electric energy is consumed by heat or the like when a circulating current is generated for voltage adjustment between the first and second power storage devices. As a result, for example, the distance that a vehicle equipped with this power storage system can travel using the electric power stored in the first and second power storage devices is shortened.

  The present invention has been made to solve such a problem, and an object of the present invention is to perform voltage adjustment between power storage units by circulating current in a power storage system including first and second power storage units. Rather, the inrush current generated between the power storage units when the relay is closed is suppressed.

  A power storage system according to an aspect of the present invention supplies power to a load device. The load device includes a capacitor connected between the power line pair. The power storage system includes first and second power storage units, first and second relays, and a control device. The first and second power storage units are connected in parallel between the power line pair. The first and second relays are connected in series to the first and second power storage units between the power line pairs, respectively. The control device controls the first and second relays. The control device controls the first and second relays such that the power storage unit having the higher voltage among the first and second power storage units is first electrically connected to the capacitor. When the difference between the voltage of the lower power storage unit and the voltage of the capacitor of the first and second power storage units is equal to or less than a predetermined value, the control device is configured to both the first and second power storage units. Controls the first and second relays to be electrically connected to the capacitor.

  In this power storage system, the power storage unit (high voltage power storage unit) having the higher voltage among the first and second power storage units is first connected to the capacitor. Thereafter, when the difference between the voltage of the other power storage unit (low voltage power storage unit) and the voltage of the capacitor becomes equal to or less than a predetermined value, the low voltage power storage unit is connected to the capacitor. Since the impedance of the low voltage storage unit is higher than that of the capacitor when viewed from the high voltage storage unit, the current flowing from the high voltage storage unit to the low voltage storage unit when the low voltage storage unit and the capacitor are connected is limited. . In addition, since the voltage difference between the low voltage power storage unit and the capacitor is less than a predetermined value, and the current flowing from the low voltage power storage unit to the capacitor is limited when the low voltage power storage unit and the capacitor are connected, Closing of the relay for connecting the capacitor is performed substantially without arc. Therefore, according to this power storage system, inrush current generated between the power storage units when the relay is closed can be suppressed without causing any new problem even if the voltage between the power storage units is not adjusted by the circulating current. it can.

  According to the present invention, in a power storage system including the first and second power storage units, the inrush current generated between the power storage units when the relay is closed can be suppressed without adjusting the voltage between the power storage units using the circulating current. Can do.

It is a block diagram of the electrical storage system mounted in the vehicle according to this Embodiment. It is a figure for demonstrating an example of the closing timing of the system main relay in a vehicle. It is a flowchart which shows the process sequence regarding closure of a system main relay.

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

[Vehicle configuration]
FIG. 1 is a configuration diagram of a power storage system mounted on a vehicle according to the present embodiment. Referring to FIG. 1, vehicle 1 includes a battery pack 10, a PCU 50, and a control device 100. The battery pack 10 supplies power to the PCU 50. The PCU 50 uses a power supplied from the battery pack 10 to drive a motor generator (not shown), for example. Thereby, the driving force of the vehicle 1 is generated.

  Further, the PCU 50 supplies, for example, to the battery pack 10 the electric power generated by the motor generator during the braking operation of the vehicle 1 or when the acceleration is reduced. The battery pack 10 stores electric power supplied from the PCU 50.

  The PCU 50 includes a converter and an inverter (not shown), and further includes a capacitor 52 and a voltage sensor 54. The capacitor 52 is a smoothing capacitor. Capacitor 52 is connected between power lines PL and NL. The voltage sensor 54 detects the voltage VL of the capacitor 52. The voltage sensor 54 outputs a signal indicating the detection result to the control device 100.

  The battery pack 10 includes battery stacks 20, 30, 40, voltage sensors 22, 32, 42, system main relays 24, 34, 44, 62, a precharge relay 64, a limiting resistor 66, and power lines PL, NL. Including.

  Battery stacks 20, 30, and 40 are connected in parallel to each other between power lines PL and NL. Each of the battery stacks 20, 30, 40 includes a plurality of single cells connected in series. The single battery is, for example, a nickel metal hydride battery or a lithium ion battery.

  The voltage sensors 22, 32, and 42 are connected in parallel to the battery stacks 20, 30, and 40, respectively. The voltage sensors 22, 32, and 42 detect the voltage between the terminals of the battery stacks 20, 30, and 40, respectively. The voltage sensors 22, 32 and 42 output a signal indicating the detection result to the control device 100.

  System main relays 24, 34, 44 are connected in series to the positive electrodes of battery stacks 20, 30, 40 between power lines PL, NL, respectively. The system main relay 62 is connected between the node 68 (the negative side of the battery stack 20, 30, 40) and the PCU 50 on the power line NL.

  The precharge relay 64 is connected to the system main relay 62 in parallel. A limiting resistor 66 is connected to the precharge relay 64 in series.

  When at least one of system main relays 24, 34, 44 is closed, and further, any of system main relay 62 and precharge relay 64 is closed, battery pack 10 and PCU 50 are electrically connected. The In the vehicle 1, when any of the system main relays 24, 34, 44 is closed (when the capacitor 52 is precharged), the system main relay 62 is initially kept open and the precharge relay 64 is closed. Made. Since the limiting resistor 66 is connected in series to the precharge relay 64, the inrush current from the battery pack 10 to the capacitor 52 is suppressed.

  The control device 100 includes a CPU (Central Processing Unit), a storage device, and an input / output buffer (all not shown). The control device 100 controls the operation of the vehicle 1 according to input signals from each sensor or the like. Note that the control by the control device 100 may be realized by software, or may be realized by dedicated hardware (electronic circuit).

[Reduction of circulating current that can occur between battery stacks]
As described above, in the vehicle 1, the battery stacks 20, 30, and 40 are connected in parallel. A voltage difference may occur between the battery stacks 20, 30, and 40. If there is a difference in voltage between the battery stacks 20, 30, and 40 and the system main relays 24, 34, and 44 are simultaneously closed when the vehicle system is started, an inrush current is generated between the battery stacks 20, 30, and 40. It can happen.

  In order to suppress the inrush current between the battery stacks 20, 30, and 40 at the time of starting the vehicle system, for example, a method of allowing a circulating current between the battery stacks 20, 30, 40 before the vehicle system is stopped can be considered. According to this method, when the vehicle system is stopped, the voltage between the battery stacks 20, 30, and 40 is substantially the same. Therefore, even if the system main relays 24, 34, and 44 are simultaneously closed when the vehicle system is started next time, No inrush current occurs between the battery stacks 20, 30, and 40.

  However, according to this method, a part of the electric power stored in the battery stacks 20, 30, 40 is consumed by heat or the like due to the circulating current generated before the vehicle system is stopped. As a result, the distance that the vehicle 1 can travel is shortened by the electric power stored in the battery stacks 20, 30, and 40.

  The inrush current generated between the battery stacks 20, 30, 40 when the system main relays 24, 34, 44 are closed is suppressed without adjusting the voltage between the battery stacks 20, 30, 40 by allowing the circulating current. Therefore, control device 100 included in vehicle 1 according to the present embodiment executes the following control.

  Control device 100 controls system main relays 24, 34, and 44 so that the battery stack having the highest voltage (for example, battery stack 20) is first electrically connected to capacitor 52. Then, when the difference between the voltage of the battery stack having the lowest voltage (for example, battery stack 40) and the voltage of capacitor 52 is equal to or less than a predetermined value, control device 100 The system main relays 24, 34 and 44 are controlled so that both the low battery stack and the capacitor 52 are electrically connected. For example, when the battery stack having the lowest voltage is connected to the capacitor 52, the predetermined value is determined in advance so that the current generated between the battery stack having the lowest voltage and the capacitor 52 is within a range that does not cause a problem. ing. For example, the predetermined value may be 0 (zero).

  In addition, when the difference between the voltage of the battery stack having the second lowest voltage (for example, battery stack 30) and the voltage of capacitor 52 is equal to or less than a predetermined value, control device 100 determines whether battery stacks 20, 30, and 40 The system main relays 24, 34 and 44 are controlled so that all are electrically connected to the capacitor 52.

  Since the impedance of the battery stack having the lowest voltage is higher than that of the capacitor 52 when viewed from the battery stack having the highest voltage, the voltage from the battery stack having the highest voltage is connected when the battery stack having the lowest voltage is connected to the capacitor 52. The current flowing through the lowest battery stack is limited. In addition, since the difference between the voltage of the battery stack having the lowest voltage and the voltage of the capacitor 52 is equal to or less than a predetermined value and the current flowing from the battery stack having the lowest voltage to the capacitor 52 is limited, the battery stack having the lowest voltage is used. The relay for electrically connecting the capacitor 52 and the capacitor 52 is substantially arc-free. The same applies to the case where the battery stack having the second lowest voltage and the capacitor 52 are connected. Therefore, according to the vehicle 1, even if the voltage between the battery stacks 20, 30, and 40 is not adjusted by the circulating current, the battery is not closed when the system main relays 24, 34, and 44 are closed without causing any new problem. Inrush current generated between the stacks 20, 30, 40 can be suppressed.

  FIG. 2 is a diagram for explaining an example of closing timing of the system main relays 24, 34, 44 in the vehicle 1. With reference to FIG. 2, the horizontal axis represents time, and the vertical axis represents the detection result of the voltage sensor 54. In this example, it is assumed that the voltage of the battery stack 20 is the highest among the battery stacks 20, 30, and 40, the voltage of the battery stack 30 is the next highest, and the voltage of the battery stack 40 is the lowest.

  Since the voltage of the battery stack 20 is the highest among the battery stacks 20, 30, and 40, the control device 100 closes the system main relay 24 (corresponding to the battery stack 20) at time t0. At this time, since neither the system main relay 62 nor the precharge relay 64 is closed, the voltage sensor 54 indicates 0V. That is, the system main relay 24 is closed with no electric arc.

  At time t1, control device 100 closes precharge relay 64. Thereby, the battery stack 20 and the capacitor 52 are electrically connected. As described above, since the limiting resistor 66 is connected in series to the precharge relay 64, the inrush current from the battery stack 20 to the capacitor 52 is suppressed.

  Thereafter, the voltage VL of the capacitor 52 rises, and at time t2, the detection result of the voltage sensor 54 reaches VB3 which is the same as the voltage of the battery stack 40 having the lowest voltage. At this timing, control device 100 executes control for closing system main relay 44 (corresponding to battery stack 40). Even when the system main relay 44 is closed, since the impedance of the battery stack 40 is higher than that of the capacitor 52 when viewed from the battery stack 20, the current flowing from the battery stack 20 to the battery stack 40 is limited. That is, the inrush current flowing from the battery stack 20 to the battery stack 40 is suppressed. Further, since the voltages of the battery stack 40 and the capacitor 52 are the same, the current flowing from the battery stack 40 to the capacitor 52 is limited. That is, the system main relay 44 is closed with substantially no arc.

  Thereafter, it is assumed that the voltage VL of the capacitor 52 further increases, and at time t3, the detection result of the voltage sensor 54 reaches VB2 that is the same as the voltage of the battery stack 30 having the second lowest voltage. At this timing, the control device 100 executes control for closing the system main relay 34 (corresponding to the battery stack 30). Even in this case, the current flowing from the battery stack 20 to the battery stack 30 and the current flowing from the battery stack 30 to the capacitor 52 are limited.

  After that, after the voltage of the capacitor 52 reaches a predetermined voltage (for example, near the voltage VB1 of the battery stack 20), the control device 100 executes control for closing the system main relay 62, and turns off the precharge relay 64. Control for opening is executed (not shown). Thus, according to the vehicle 1, the voltage between the battery stacks 20, 30, 40 is not adjusted by the circulating current, and the battery stacks 20, 30, 40 are connected when the system main relays 24, 34, 44 are closed. The generated inrush current can be suppressed.

  Next, a specific processing procedure for closing the system main relays 24, 34, 44 in the vehicle 1 will be described.

[Relay closing procedure]
FIG. 3 is a flowchart showing a processing procedure related to closing of the system main relays 24, 34, 44. Referring to FIG. 3, the process shown in this flowchart is executed by control device 100 after receiving a vehicle system activation instruction from the user.

  The control device 100 executes control for closing the system main relay (system main relay 24, 34 or 44) corresponding to the battery stack having the highest voltage among the battery stacks 20, 30, and 40 (step S100). . Thereafter, control device 100 executes control for closing precharge relay 64 (step S110).

  As described above, in the vehicle 1, after the system main relay corresponding to the battery stack having the highest voltage is closed, the system main relay corresponding to the battery stack having the lowest voltage is sequentially closed. The control device 100 stores in the internal memory a variable n indicating what number (nth) voltage of the battery stack corresponding to the system main relay to be closed next is the lowest. When precharge relay 64 is closed in step S110, control device 100 substitutes 1 as the initial value of variable n (step S120).

  Thereafter, the control device 100 determines the voltage of the battery stack having the nth lowest voltage (the detection result of the voltage sensor corresponding to the battery stack having the nth lowest voltage) and the voltage of the capacitor 52 (the detection result of the voltage sensor 54). It is determined whether or not the difference is equal to or less than a predetermined value (step S130). When it is determined that the difference between the voltage of the battery stack having the nth lowest voltage and the voltage of capacitor 52 is greater than the predetermined value (NO in step S130), control device 100 waits until the difference becomes equal to or smaller than the predetermined value. .

  If it is determined that the difference between the voltage of the battery stack having the nth lowest voltage and the voltage of capacitor 52 is equal to or less than a predetermined value (YES in step S130), control device 100 sets the battery stack having the nth lowest voltage. The corresponding system main relay is closed (step S140). Thereafter, control device 100 determines whether or not all system main relays 24, 34, and 44 corresponding to battery stacks 20, 30, and 40 are closed (step S150).

  If it is determined that some of system main relays 24, 34, 44 are not closed (NO in step S150), control device 100 adds 1 to variable n (step S160). Thereafter, the process proceeds to step S130. The processes of steps S130 to S160 are repeatedly executed until all the system main relays 24, 34, 44 are closed.

  If it is determined that all of system main relays 24, 34, 44 are closed (YES in step S150), control device 100 determines whether the voltage of capacitor 52 has reached a predetermined voltage (step S170). ). If it is determined that the voltage of capacitor 52 has not reached the predetermined voltage (NO in step S170), control device 100 waits until the voltage of capacitor 52 reaches the predetermined voltage.

  If it is determined that the voltage of capacitor 52 has reached the predetermined voltage (YES in step S170), control device 100 executes control for closing system main relay 62 (step S180). Thereafter, the control device 100 executes control for opening the precharge relay 64 (step S190). Thereby, the processing shown in this flowchart is completed.

  As described above, in vehicle 1 according to the present embodiment, control device 100 includes system main relay 24 such that the battery stack having the highest voltage (for example, battery stack 20) is electrically connected to capacitor 52 first. , 34, 44 are controlled. Then, when the difference between the voltage of another battery stack (for example, battery stack 40) and the voltage of capacitor 52 is equal to or less than a predetermined value, control device 100 determines the battery stack having the highest voltage as compared with the other battery stack. The system main relays 24, 34 and 44 are controlled so that both of them are electrically connected to the capacitor 52.

  Thus, according to the vehicle 1, the voltage is generated between the battery stacks 20, 30, 40 when the system main relays 24, 34, 44 are closed without adjusting the voltage between the battery stacks 20, 30, 40 by circulating current. Inrush current can be suppressed.

  In the above embodiment, the closing order of the system main relays 24, 34, 44 is adjusted in order to suppress the inrush current between the battery stacks 20, 30, 40. However, the scope of application of the present technology is not limited to this. For example, even in a vehicle in which a plurality of battery packs are connected in parallel, the present technology can be applied to suppress an inrush current between the plurality of battery packs. In this case, for example, a system main relay is provided in each of the plurality of battery packs, and the system main relay corresponding to the battery pack having the highest voltage among the plurality of battery packs is closed first, and then the voltage is You may close in order from the system main relay corresponding to a low battery pack.

  In the above embodiment, three battery stacks (battery stacks 20, 30, 40) are connected in parallel. However, the number of battery stacks (power storage units) connected in parallel is not limited to this. For example, two may be sufficient and four or more may be sufficient.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 vehicle, 10 battery pack, 20, 30, 40 battery stack, 22, 32, 42, 54 voltage sensor, 24, 34, 44, 62 system main relay, 50 PCU, 52 capacitor, 64 precharge relay, 66 limiting resistance , 68 nodes, 100 control devices, PL, NL power lines.

Claims (1)

A power storage system for supplying power to a load device, wherein the load device includes a capacitor connected between a pair of power lines,
First and second power storage units connected in parallel between the power line pair;
A first relay and a second relay connected in series to the first and second power storage units between the power line pair;
A control device configured to control the first and second relays,
The controller is
Controlling the first and second relays such that the higher voltage storage unit of the first and second storage units is first electrically connected to the capacitor;
When the difference between the voltage of the lower power storage unit of the first and second power storage units and the voltage of the capacitor is equal to or less than a predetermined value, both the first and second power storage units A power storage system that controls the first and second relays to be electrically connected to the capacitor.

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