WO2012111410A1

WO2012111410A1 - Electric cell system

Info

Publication number: WO2012111410A1
Application number: PCT/JP2012/051894
Authority: WO
Inventors: 橋本　英樹; 巧大矢; 聡馬鈴木
Original assignee: 三菱重工業株式会社
Priority date: 2011-02-14
Filing date: 2012-01-27
Publication date: 2012-08-23
Also published as: JP5517965B2; JP2012170209A

Abstract

An electric cell system (100) has a power supply circuit (2) in which n series units (1), in which battery cells are connected in series, are connected in parallel;and feeds power to the load (3) side through a first protective circuit (4) and an inverter (7) in series with respect to an output terminal of the power supply circuit (2). In particular, the present invention is characterized in being provided with (n - 1) protective circuits (6) in which the resistance can be variably controlled, the protective circuits being connected in series between positive electrodes of the n series units (1) connected in parallel.

Description

Battery system

The present invention relates to a technical field of a battery system having a power supply circuit in which a plurality of series units each having a plurality of secondary battery cells connected in series are connected in parallel.

リチウム Lithium ion secondary batteries, nickel metal hydride batteries, lead batteries and the like are known as chargeable / dischargeable secondary batteries. As an application field of this type of secondary battery, for example, there is a battery system mounted on a system that requires a large amount of power, such as an electric vehicle or a hybrid electric vehicle. In particular, lithium ion secondary batteries are characterized by high energy density, high input / output density, and long cycle life. Therefore, research and development in this field are actively conducted.

Battery systems are operated by combining a plurality of secondary battery cells to form a power circuit. In particular, a power supply circuit used for supplying a large amount of power may be configured by combining series units formed by connecting a plurality of secondary battery cells in series. This configuration has an advantage that an excessive current can be prevented from flowing between battery cells when a problem such as a short circuit occurs in the power supply circuit due to some cause.

In a configuration in which series units are combined in parallel, there are individual differences in actual battery cells, so there is a considerable variation in the current value flowing through each series unit. Such a variation in current value can also occur due to variations in the environment (for example, temperature, humidity, etc.) in which each series unit is placed. If the current value flowing through each series unit varies as described above, a difference occurs in the degree of deterioration of each series unit, which is a problem.

For example, Patent Document 1 discloses a technique for suppressing variations in the current value flowing through each series unit. In Patent Document 1, state information is detected for each series unit, and the amount of current flowing through each series unit is controlled based on the detected state information, thereby suppressing variations in current value and enabling the life of the battery system. A technique for making it as long as possible is disclosed. Such adjustment of the current amount is performed by a power distribution unit inserted in series in each series unit, and the power distribution unit includes elements such as a variable resistor, a switched capacitor, a DC / DC converter, and a DC chopper, for example. Yes.

JP 2008-118790 A

However, in Patent Document 1, it is necessary to provide a power distribution unit and detection means for detecting state information for controlling the power distribution unit on a one-on-one basis with the series unit. Therefore, Patent Document 1 has a problem that the circuit configuration of the battery system is complicated, and it is difficult to realize the battery system at low cost.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a battery system capable of suppressing current value variation in each series unit at a low cost.

In order to solve the above problems, the battery system of the present invention has a power supply circuit in which n series units each having a plurality of secondary battery cells connected in series are connected in parallel to each other, and an output terminal of the power supply circuit Are connected in series with each other in a battery system that supplies power to the load side via an inverter connected to an output terminal of the first protection circuit. Further, (n-1) second protection circuits connected in series between the positive electrodes of the n series units and capable of variably controlling the resistance value are provided.

According to the present invention, it is possible to suppress variation in the current value between the series units by variably controlling the resistance value in the (n−1) second protection circuits. That is, in Patent Document 1, since it is necessary to provide the second protection circuit on a one-to-one basis with the series unit, a total of n second protection circuits are required. That's it. As described above, according to the present invention, the number of elements constituting the circuit can be reduced, so that the battery system can be downsized at the same time as the cost reduction.

The resistance value of each of the second protection circuits may be controlled so that variation in the current value flowing through each of the second protection circuits is reduced. For example, by monitoring the current value flowing through each second protection circuit, the variation in the current value is measured, and the resistance value of each second protection resistor is controlled so as to reduce the variation in the obtained current value. To adjust.

As one aspect of the present invention, the second protection circuit includes a first circuit in which a first switching unit and a fixed resistor are connected in series, and a second circuit including only the second switching unit. May be connected in parallel. In this aspect, the resistance value is variably controlled with a simpler circuit configuration by switching between the first circuit having a resistance value corresponding to the fixed resistance and the second circuit having a resistance value of substantially zero. Can do.

In this case, a capacitor may be connected in parallel to the fixed resistor. Since the battery cells constituting the battery system generate electric power mainly by a chemical reaction, it may be difficult to output sufficient electric power to meet the demand on the load side at the time of starting. In this aspect, by using the power stored in the capacitor in advance at the time of starting the battery system, it is possible to supply power quickly in response to a request from the load side.

The second protection circuit may comprise a variable resistor connected in series to the (n-1) series units. In this aspect, the variable control of the resistance value in the second circuit can be performed with finer accuracy.

In another aspect of the present invention, the n series units include at least one master unit and other slave units, and the second protection circuit in the slave unit has an output voltage of the master unit of a predetermined value. The resistance value may be variably controlled so that In this case, in particular, the second protection circuit in the slave unit may include a DC / DC converter or a chopper circuit connected in series to the slave unit.

It is a block diagram which shows the whole structure of the battery system which concerns on 1st Example. A specific circuit configuration of the protection circuit included in the battery system according to the first embodiment will be described. It is a flowchart figure which shows the control content of the 1st protection circuit by a controller. It is a flowchart figure which shows the control content of the 2nd protection circuit by a controller. It is a circuit diagram which shows one modification of the 2nd protection circuit. It is a circuit diagram which shows the other modification of a 2nd protection circuit. It is a block diagram which shows the whole structure of the battery system which concerns on 2nd Example.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

(First embodiment)
FIG. 1 is a block diagram showing the overall configuration of the battery system 100 according to the first embodiment. The electrical system 100 includes a power supply circuit 2 including a plurality of series units 1 in which a plurality of secondary battery cells are connected in series. The output terminal 2 a of the power supply circuit 2 includes a first power supply circuit 2. An electric motor 3, which is a three-phase induction motor, is connected via a protection circuit 4 (hereinafter referred to as “protection circuit 4”) and an inverter 7. The DC power output from the power supply circuit 2 is converted into AC power having a frequency and voltage value suitable for driving the electric motor 3 by the inverter 7 and supplied to the electric motor 3 as a load.

The inverter 7 is an inverter circuit of a motor control system that drives the electric motor 3 that is a three-phase induction motor and has a low driving frequency and a large current and a large power. Typically, it is a three-phase output inverter using six switching elements, and has a function of facilitating adjustment of the rotational speed and output torque of the electric motor 3 and greatly improving efficiency. The power supply motor 3 is driven by the AC power supplied through the inverter 7 as described above, and is connected to driving wheels through a power transmission mechanism connected to the output shaft thereof, so that the vehicle travels.

Here, the inverter 7 includes a smoothing capacitor or the like, and an excessive inrush current may be temporarily generated when the battery system 100 is started. The protection circuit 4 is provided to protect the electric motor 3 side from such an inrush current, and a specific circuit configuration thereof will be described later.

It should be noted that such a protection circuit 4 is also used when a power electronic component such as a DC / DC converter including a smoothing capacitor or the like is used instead of the inverter 7.

A voltmeter 8 is provided on a line connecting the protection circuit 4 and the inverter 7 so that the input voltage value to the inverter 7 can be monitored. The voltage value monitored by the voltmeter 8 is transmitted to the controller 30 that governs overall control of the battery system 100, and is used to implement control described later.

Next, the detailed configuration of the power supply circuit 2 will be described. The power supply circuit 2 includes a plurality of series units 1 connected in parallel to each other, and a second protection circuit is provided on the wiring connecting the positive electrodes of the series units 1. 6 (hereinafter referred to as “protection circuit 6”) are connected in series. Here, the secondary battery cell included in the series unit 1 is, for example, a lithium ion secondary battery cell, but various secondary battery cells such as a nickel metal hydride battery and a lead battery may be used.

Also, an ammeter 9 is connected in series to the positive electrode side of each series unit 1 so that the current value output from each series unit 1 can be monitored. The current value monitored by the ammeter 9 is transmitted to the controller 30 that controls the entire battery system 100, and is used to implement the control described later.

Here, the power supply circuit 2 includes a total of n (n is an integer of 2 or more) series units 1, and in this embodiment, n = 3 in particular. Further, (n−1) protection circuits 6 are provided for a total of n series units 1. That is, in this embodiment, two protection circuits 6 are provided for the three series units 1.

Here, since each series unit 1 connected in parallel has the same configuration and is connected to the same load (electric motor 3), the current output from each series unit 1 is ideal. The values are equal. However, in reality, the output current value varies due to the individual difference between the secondary battery cells included in each series unit 1 and the operating temperature difference of each series unit 1. Then, in the series unit 1 with a large current value to be output, the deterioration of the battery cell proceeds, and the output voltage decreases. As a result, current flows between the series units 1 due to a potential difference with the other series units 1 connected in parallel, and the battery system 100 may be in a dangerous state.

In Patent Document 1, in order to suppress such a variation in the current value output from the power supply circuit 2, it is necessary to provide the protection circuits 6 on a one-to-one basis for n series units. That is, in the prior art, when there are three series units 1, it is necessary to provide three protection circuits 6. On the other hand, in the present invention, two protection circuits 6 are sufficient for the three series units 1. Therefore, the circuitized configuration can be simplified, and a battery system adapted for cost reduction and downsizing can be realized.

Next, a specific circuit configuration of the protection circuit 6 will be described with reference to FIG. FIG. 2 is a circuit diagram illustrating a configuration of the protection circuit 6 included in the battery system 100 according to the first embodiment. In the present embodiment, the protection circuit 4 will be described below assuming that the protection circuit 4 has the same configuration as the protection circuit 6 in order to simplify the circuit configuration.

The protection circuit 6 has a configuration in which a first circuit 11 in which a switch SW1 and a load resistor 10 are connected in series and a second circuit 12 made up of only the switch SW2 are connected in parallel. The switches SW1 and SW2 are configured to be switchable on / off based on a control signal from the controller 30. Thus, by controlling the switches SW1 and SW2, the resistance value in each protection circuit 6 can be variably switched between zero and a predetermined resistance value.

Particularly in this embodiment, the load resistor 10 is a fixed resistance element having a predetermined resistance value. The predetermined resistance value is set such that when the output current value between the series units 1 varies, power is consumed by the additional resistor 10 in a line having a large current value, and the current value is reduced. Suppresses variation.

In this embodiment, a fixed resistor is used as the load resistor 10, but a variable resistor, a DC / DC converter, or the like may be used instead. In this case, since the resistance value can be variably adjusted, it is possible to suppress the variation in the current value between the series units 1 with higher accuracy.

Here, with reference to FIG. 3, the control content of the protection circuit 4 by the controller 30 will be specifically described. FIG. 3 is a flowchart showing the control contents of the protection circuit 4 by the controller 30. In the initial state, the protection circuit 4 is set so that the switch SW1 is OFF and SW2 is ON, and the output voltage from the series unit 1 side is applied to the inverter 7 side as it is.

First, the controller 30 acquires the voltage value (voltage value of the output terminal of the power supply circuit 2) V on the line connecting the protection circuit 4 and the inverter 7 from the voltmeter 8 (step S101). Then, the controller 30 determines whether or not the acquired voltage value V is greater than a preset threshold value V1 (step S102). When the voltage value V is larger than the preset threshold value V1 (step S102: YES), that is, when the voltage value V is increased due to an excessive inrush current, the controller 30 switches the switch SW1 in the protection circuit 4 to a value. By switching ON and SW2 to OFF, the output current from the series unit 1 side is consumed by the fixed resistor 10, and the inrush current is reduced. Then, the controller 30 returns the process to step S102, and when the voltage value V becomes equal to or lower than the preset threshold value V1 (step S102: NO), that is, when the excessive inrush current is settled, the switch SW1 in the protection circuit 4 Is turned OFF and SW2 is turned ON to return to the initial state.

With such control, the protection circuit 4 protects the load side from an excessive inrush current generated when the battery system 100 is started.

Subsequently, with reference to FIG. 4, the control content of the protection circuit 6 by the controller 30 will be specifically described. FIG. 4 is a flowchart showing the control contents of the protection circuit 6 by the controller 30. Similar to the protection circuit 4, in the protection circuit 6 in the initial state, the switch SW1 is set to OFF and the switch SW2 is set to ON.

First, the controller 30 acquires the current value I output from each series unit 1 from each ammeter 9 (step S201). Then, the controller 30 determines whether or not each acquired current value I is smaller than a preset threshold value I1 (step S202). Here, the threshold value I1 is a value defined in advance as the specification of the series unit 1 as a threshold value for determining that the output current value from the series unit 1 has decreased due to the progress of deterioration, and is experimental and theoretical. Alternatively, it may be set by various simulation methods.

Then, the controller 30 sets the switch SW1 of the protection circuit 6 connected to the output side of the series unit 1 whose current value I is smaller than the threshold value I1 to OFF and SW2 to ON (step S203). On the other hand, for the series unit 1 whose current value I is equal to or greater than the threshold value I1, the switch SW1 of the protection circuit 6 connected to the output side is set to ON and SW2 is set to OFF (step S204). As a result, since the current value is suppressed by the fixed resistor 10 in the series unit 1 having a large current value I to be output, variation with the series unit 1 having a small current value I can be reduced.

Such switching control of the switches SW1 and SW2 by the controller 30 may be repeated by acquiring the input current value to the protection circuit 6 periodically or irregularly.

In the present embodiment, the load resistor 8 is described as a fixed resistor. However, the variable resistor is used, and the variation in the current value is eliminated or reduced according to the current value input to each series unit 1 acquired by the controller. As described above, the resistance value may be variably controlled.

Here, a modified example of the protection circuit 6 will be described with reference to FIG. In the example of FIG. 5, a capacitor 13 is connected in parallel with the fixed resistor 10. In the battery system 100, since the battery cell mainly generates electric power by a chemical reaction, it may be difficult to output sufficient electric power necessary for the electric motor 3 that is a load at the time of starting. Even in such a case, by providing the capacitor 13, the power stored in the capacitor 13 in advance when the battery system 100 is started can be used to quickly supply power in response to a request from the load side. it can.

FIG. 6 shows another modification of the protection circuit 6. In the example of FIG. 6, in addition to the first circuit 11 and the second circuit 12 described above, a third circuit 14 in which a switch SW3 and a fixed resistor 13 are connected in series is provided. In particular, the resistance value of the fixed resistor 13 may be set to be different from that of the fixed resistor 10 in the first circuit 11. As a result, the resistance value in the protection circuit 6 can be adjusted in multiple steps by switching the switches SW1 to SW3 by the controller 30, so that the variation in the current value between the series units 1 can be performed more accurately. . Note that the switching control of the switches SW1 to SW3 may be performed following the example described above with reference to FIG.

(Second embodiment)
Next, the battery system 100 according to the second embodiment will be described with reference to FIG. FIG. 7 is a block diagram showing the overall configuration of the battery system 100 according to the second embodiment. In FIG. 7, parts common to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

In the second embodiment, one of the plurality of series units 1 included in the power supply circuit 2 is the main series unit 1a, and the other

slave series units

1b and 1c are used. In this power supply circuit 2, the output power from the main series unit 1a is basically supplied to the required power on the load side, and when the required power is insufficient, the power is supplemented from the

slave series units

1b and 1c as needed. There is a feature in the point to supply.

In this embodiment, a DC / DC converter is particularly employed as the protection circuit 6. The output voltage value of the DC / DC converter is controlled based on a control signal from the controller 30 so that the voltage value V acquired from the voltmeter 8 becomes a predetermined value V2. Unlike a fixed resistor or the like, the DC / DC converter can adjust the output voltage value more flexibly based on a control signal from the controller 30.

The present invention can be used for a battery system having a power circuit in which a plurality of series units each having a plurality of secondary battery cells connected in series are connected in parallel.

Claims

A power circuit in which n series units each having a plurality of secondary battery cells connected in series are connected in parallel to each other, and a first protection circuit is connected in series to the output terminal of the power circuit; In the battery system for supplying power to the load side via an inverter connected to the output terminal of the first protection circuit,
A battery comprising (n-1) second protection circuits connected in series between the positive electrodes of the n series units connected in parallel to each other, the resistance value of which can be variably controlled. system.
2. The battery system according to claim 1, wherein the resistance value of each second protection circuit is controlled so as to reduce variation in a current value flowing through each second protection circuit.
The second protection circuit is formed by connecting in parallel a first circuit in which a first switching unit and a fixed resistor are connected in series, and a second circuit including only the second switching unit. The battery system according to claim 1 or 2, wherein
4. The battery system according to claim 3, wherein a capacitor is connected in parallel to the fixed resistor.
The n series units include at least one master unit and other slave units,
3. The battery system according to claim 1, wherein a resistance value of the second protection circuit in the slave unit is variably controlled so that an output voltage of the master unit becomes a predetermined value.
6. The battery system according to claim 5, wherein the second protection circuit in the slave unit includes a DC / DC converter or a chopper circuit connected in series to the slave unit.