JP2016004680A - Battery system and method of controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an occurrence probability of failures of a switch provided between a heater and a power source thereof, in a battery system that comprises a battery heated by the heater for use.SOLUTION: A battery system 200 comprises: a battery B heated for use; a heater 14 for heating the battery B; a plurality of switches SW1 and SW2 provided in series between a power source 4 for supplying power to the heater 14 and the heater 14; and a controller 20 that performs switching control for on/off-switching the switches SW1 and SW2 to adjust the supply of power to the heater 14, and that performs shift control for switching the switch to be switch-controlled between the plurality of switches SW1 and SW2.

Description

  The present invention relates to a battery system including a battery to be used by heating, and a control method for the battery system.

  In recent years, there has been an increasing market need for a system including a battery (secondary battery) that can be used as an emergency power source in the event of a power failure, for example. As a battery of the system, a molten salt battery, a sodium sulfur battery, a lithium ion battery, a lead battery, and the like are known. Among these, a molten salt battery (see, for example, Patent Document 1) has a high energy density. In addition, it has the advantage of being non-flammable and has attracted attention.

  Although the molten salt battery can be operated at room temperature, it is preferable to raise the temperature to about 60 ° C. to 90 ° C. in order to fully exhibit the performance. In the case of a sodium-sulfur battery, the operating temperature is, for example, about 300 ° C. Further, in the case of a lithium ion battery or a lead battery, the operating temperature does not need to be higher than room temperature (20 ° C.), but for example, when used in a cold region where the ambient temperature is 0 ° C. or lower, the operating temperature is 0 ° C. or higher. It is preferable to use the product after the temperature has been raised.

JP 2009-066764 A

  In a battery system equipped with a battery used by heating such as a molten salt battery, it is necessary to raise the temperature of the battery. For this purpose, the battery system includes a heater and a control unit (microcomputer) that controls the heat generated by the heater. And. In this battery system, a switch is provided between the heater and its power source. In order to bring the battery to a desired temperature, the control unit may perform on / off switching control of the switch. The controller can finely adjust the power supply to the heater by performing, for example, PWM control on the switch.

  As the switch, for example, a field effect transistor (FET) can be used. However, frequent on / off switching may cause a short circuit failure. If a short circuit failure occurs in the switch, control becomes impossible, electric power continues to be supplied to the heater, the heater temperature rises, and the battery temperature may greatly exceed a desired value.

  Therefore, the present invention provides a battery system that can reduce the probability of failure of a switch provided between the heater and its power source (probability of failure of the switch per unit time), and An object of the present invention is to provide a method for controlling such a battery system.

  A battery system according to one embodiment of the present invention is provided in series between a battery to be used by heating, a heater for heating the battery, a power source for supplying power to the heater, and the heater. A plurality of switches, and a control unit that performs switching control for adjusting the power supply to the heater by performing on / off switching of the switches, and that performs switching control for switching a switch that performs the switching control among the plurality of switches. It has.

  The battery system control method according to one aspect of the present invention includes a battery used by heating, a heater for heating the battery, a power source for supplying power to the heater, and the heater. A battery system including a plurality of switches provided in series with each other, wherein the switches are turned on / off to adjust power supply to the heater, and the plurality of switches to be turned on / off are switched. Switch between the switches.

  According to the present invention, it is possible to reduce the probability of failure of a switch provided between a heater and its power source.

1 is a schematic diagram showing in principle the basic structure of a power generation element in a molten salt battery. It is a perspective view which shows simply the laminated structure of a molten salt battery main body. It is a cross-sectional view of a molten salt battery main body. It is a perspective view which shows the outline of the external appearance of the molten salt battery comprised by accommodating the molten salt battery main body in the battery container. It is a perspective view (a partial cross section is included) which shows an example of the state which arranged the plurality of molten salt batteries in the outer case, and comprised the assembled battery. It is a block diagram which shows the circuit structure of the molten salt battery system which concerns on one form of this invention. It is a flowchart which shows a control method. It is a time chart which shows the on-off switching operation | movement of a switch. It is a block diagram which shows the circuit structure of a molten salt battery system. It is a time chart which shows the on-off switching operation | movement of the switch in the molten salt battery system shown in FIG.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described.
(1) A battery system according to an aspect of the present invention includes a battery used by heating, a heater for heating the battery, a power source for supplying power to the heater, and the heater in series. And switching control for adjusting the power supply to the heater by switching the switch on and off, and switching control for switching the switch for performing the switching control among the plurality of switches. And a control unit.

According to the battery system configured as described above, a plurality of switches are provided in series between the power source for supplying power to the heater and the heater. The power supply to the heater is adjusted by on / off switching, and the remaining switches may be maintained in the on state. In another period, the power supply to the heater may be adjusted by maintaining the one switch in the on state and switching one of the other switches on and off. In this manner, the heater can be controlled by switching the switch for performing the switching control between the plurality of switches.
Here, a switch maintained in an on state has a lower probability of occurrence of a failure (such as a short circuit failure) than a switch that is switched on and off. For this reason, it is possible to reduce the probability of occurrence of a failure in each of the plurality of switches by switching the switch that performs the switching control as described above between the plurality of switches.

(2) Further, even if any one of the plurality of switches is short-circuited, the control unit is configured to adjust the power supply to the heater by switching on and off the remaining switches. Is preferred.
In this case, even if one of the switches is short-circuited, the power supply to the heater is adjusted by switching the remaining switches on and off to prevent the heater from being disabled. it can. As a result, it is possible to suppress the occurrence of a problem that the battery temperature greatly exceeds a desired value.

(3) The battery system according to (1) or (2) further includes a detection unit that detects an abnormality in the heater, and when the detection unit detects an abnormality, the control unit includes a plurality of control units. It is preferable to perform control to turn off all the switches.
In this case, the power supply to the heater can be stopped regardless of which of the switches is short-circuited, and the occurrence of problems that cause the battery temperature to greatly exceed the desired value is suppressed. It becomes possible to do.

(4) In the battery system according to (3), the detection unit includes a sensor that detects the temperature of the heater, and detects that the temperature is abnormal when the temperature detected by the sensor is equal to or higher than a threshold value. It can be set as the structure to do. In this case, until the heater temperature reaches the threshold, the control unit can adjust the power supply of the heater using a switch that is not short-circuited.
(5) Or, in the battery system according to (3), the detection unit includes a timer that measures a continuous energization time to the heater, and is abnormal when the continuous energization time is equal to or greater than a threshold value. It can be set as the structure detected. When the switch is short-circuited, on / off switching is not performed, and power is continuously supplied to the heater. Therefore, an abnormality is detected by measuring the continuous energization time of the heater with a timer. Is possible.

(6) Moreover, it is preferable that each said battery system is further provided with the fuse which is connected in series with the said heater, and fuse | melts by overheating and interrupts | blocks the electric power supply to the said heater.
In this case, even if all the switches are short-circuited and the power supply to the heater is excessive, the power supply is forcibly cut off by the fuse being blown, and the heat generation by the heater can be stopped. It becomes.

  (7) Moreover, the control method of the battery system concerning 1 aspect of this invention is the battery used by heating, the heater for heating the said battery, the electric power source for supplying electric power to the said heater, and the said heater A plurality of switches provided in series with each other, and a method of controlling a battery system, wherein the switches are turned on and off to adjust power supply to the heater, and the on and off switching is performed. The switch to be switched is switched among the plurality of switches.

According to this control method, since a plurality of switches are provided in series between a power source for supplying power to the heater and the heater in the battery system, one switch is turned on / off for a certain period. Then, the power supply to the heater may be adjusted and the remaining switches may be kept on. In another period, the power supply to the heater may be adjusted by maintaining the one switch in the on state and switching one of the other switches on and off. In this way, the heater can be controlled by switching the switch to be turned on / off between a plurality of switches.
Here, a switch maintained in an on state has a lower probability of occurrence of a failure (such as a short circuit failure) than a switch that is switched on and off. For this reason, it becomes possible to reduce the occurrence probability of failure in each of the plurality of switches by switching the switches to be switched between the plurality of switches as described above.

[Details of the embodiment of the present invention]
Hereinafter, preferred embodiments will be described with reference to the drawings. The battery system described below is a molten salt battery system including a molten salt battery.

<Basic structure of molten salt battery>
First, the molten salt battery provided in the battery system will be described.
FIG. 1 is a schematic diagram showing in principle the basic structure of a power generation element in a molten salt battery. The molten salt battery includes a positive electrode 1, a negative electrode 2, and a separator 3 interposed therebetween as power generation elements. The positive electrode 1 is composed of a positive electrode current collector 1a and a positive electrode material 1b. The negative electrode 2 includes a negative electrode current collector 2a and a negative electrode material 2b.

The material of the positive electrode current collector 1a is, for example, an aluminum nonwoven fabric (wire diameter: 100 μm, porosity: 80%). The positive electrode material 1b is a mixture of, for example, NaCrO ₂ as a positive electrode active material, acetylene black, PVDF (polyvinylidene fluoride), and N-methyl-2-pyrrolidone at a mass ratio of 85: 10: 5: 100. It is a thing. And what was kneaded in this way is filled in the positive electrode collector 1a of an aluminum nonwoven fabric, and it presses after drying. Thereby, the plate-shaped positive electrode 1 is obtained.
On the other hand, the negative electrode 2 is formed by plating an Sn-Na alloy containing, for example, tin as a negative electrode active material on an aluminum negative electrode current collector 2a.

The separator 3 interposed between the positive electrode 1 and the negative electrode 2 is obtained by impregnating a glass non-woven fabric (thickness 200 μm) or a polyolefin sheet (thickness 50 μm) with a molten salt as an electrolyte. This molten salt is, for example, a mixture of NaFSA (sodium bisfluorosulfonylamide) 56 mol% and KFSA (potassium bisfluorosulfonylamide) 44 mol%, and has a melting point of 57 ° C. At a temperature equal to or higher than the melting point, the molten salt melts and becomes an electrolytic solution in which high-concentration ions are dissolved, and touches the positive electrode 1 and the negative electrode 2. Moreover, this molten salt is nonflammable. The operating temperature range of this molten salt battery is higher than normal temperature (20 ° C.) and is 57 ° C. to 190 ° C.
In addition, although the material, component, and numerical value of each part mentioned above are suitable examples, it is not limited to these.

<Specific structure of molten salt battery>
Next, a more specific configuration of the power generation element of the molten salt battery will be described. FIG. 2 is a perspective view schematically showing a laminated structure of a molten salt battery main body (main body portion as a battery) 10, and FIG. 3 is a cross-sectional view of the molten salt battery main body 10.
2 and 3, the rectangular flat plate-like negative electrode 2 and the rectangular flat plate-like positive electrode 1 accommodated in the bag-like separator 3 are opposed to each other and are stacked in the vertical direction in FIG. It has a laminated structure. The separator 3 is interposed between the adjacent positive electrode 1 and negative electrode 2. In other words, the positive electrode 1 and the negative electrode 2 are alternately stacked via the separator 3.

  In FIG. 3, six negative electrodes 2 and five positive electrodes 1 are superimposed, but the actual number of layers is, for example, 20 positive electrodes 1 and 21 negative electrodes 2. The separator 3 has 20 bags as “bags”, but the number interposed between the positive electrode 1 and the negative electrode 2 is 40. The separator 3 is not limited to a bag shape, and may be 40 separated sheets. In FIG. 3, the separator 3 and the negative electrode 2 are drawn so as to be separated from each other, but they are in close contact with each other when the molten salt battery is completed. The positive electrode 1 is also in close contact with the separator 3.

<One form of practical unit cell>
The molten salt battery main body 10 configured as described above is accommodated in a rectangular parallelepiped battery container made of, for example, an aluminum alloy, and forms a unit cell, that is, a physical individual as a battery.
FIG. 4 is a perspective view showing an outline of the appearance of a molten salt battery B configured by accommodating the molten salt battery main body 10 in the battery container 11. 2 and 3, terminals (only the terminal 1t of the positive electrode 1 is shown) are drawn out of the battery case 11 from the positive electrode 1 and the negative electrode 2, respectively. In FIG. 4, a safety valve 12 for releasing the pressure when the internal atmospheric pressure rises excessively is provided at the top of the battery container 11. The inner surface of the battery container 11 is insulated. The battery container 11 is heated by, for example, a heater to be described later that is in close contact with the front and back surfaces, and as a result, the electrolyte salt becomes a molten salt electrolyte.

<One form of practical assembled battery>
FIG. 5 is a perspective view (including a partial cross-section) illustrating an example of a state in which the assembled battery 100 is configured by arranging a plurality of molten salt batteries B as unit cells configured as described above in the outer box 13. It is. However, illustration of details, such as a terminal of molten salt battery B, is omitted. If necessary, the battery pack 100 can be configured by a large number of molten salt batteries by arranging the molten salt batteries in a plurality of rows in a direction (depth direction) orthogonal to the direction of the arrangement.

A plurality of molten salt batteries B are connected in series or in series-parallel according to the required output (voltage, current). Thereby, the assembled battery 100 is used with a desired voltage / current rating. Between each battery container 11, a planar heater 14 is provided. Due to the heat generated by the heater 14, the molten salt battery B is heated to a temperature equal to or higher than the melting point of the molten salt and kept warm. In order to obtain a stable molten state, the entire assembled battery 100 is heated to 90 ° C. to 95 ° C. Thereby, molten salt will melt | dissolve and it will be in the state which can be charged and discharged. That is, the molten salt battery B is a battery (secondary battery) used by heating.
The method of providing the heater 14 is merely an example, and various changes such as a configuration in which one heater 14 is provided for each fixed number (plurality) of molten salt batteries B and a configuration in which the heater 14 is brought into contact with the bottom surface or the side surface. Is possible.

In this way, by configuring the assembled battery 100 accommodated in the outer box 13, it is difficult for heat generated from the heater 14 to escape to the outside of the outer box 13, and the heat retaining effect of the assembled battery 100 by the outer box 13 is obtained. It is done. Therefore, the thermal efficiency is improved, and the molten salt can be maintained at a temperature higher than the melting point, particularly at a suitable 90 ° C. to 95 ° C. with less power.
In addition, the assembled battery 100 does not necessarily have to be accommodated in the outer box 13, and can be used in a state in which the assembled battery 100 is simply assembled without the outer box.

<Molten salt battery system>
FIG. 6 is a block diagram illustrating a circuit configuration of a molten salt battery system 200 according to an embodiment of the present invention. In this embodiment, an AC load 7a is connected to the main power line L0 connected to the normal power source (commercial power source) 4 via the inverter 6, and a DC load 7b is also connected to the main power line L0. Has been. A molten salt battery system 200 (hereinafter also referred to as a battery system 200) is connected to the main power line L0.
The loads 7 a and 7 b are normally connected to the normal power source 4, but are electrically connected to the battery system 200 only when the normal power source 4 fails or when the normal power source 4 is not used. The If a switching device is provided so as to automatically perform such switching, the battery system 200 can also be used as an uninterruptible power supply.

  The battery system 200 includes a first power line L1 and a second power line L2 connected to the main power line L0. The battery system 200 includes a battery that operates by heating. The battery is a molten salt battery B. In particular, in the present embodiment, in order to secure a voltage / current necessary as an output to the load 7, the assembled battery 100 (FIG. 4) in which a plurality of molten salt batteries B shown in FIG. 5).

  The battery system 200 further includes a heater 14 for heating the molten salt battery B (the assembled battery 100) and switches SW1, SW2, and SW3. In FIG. 6, only one heater 14 is shown for ease of explanation, but actually, a plurality of heaters 14 are provided as shown in FIG. These heaters 14 are branched from the first power line L1 and connected. That is, each heater 14 is configured to receive power from the normal power source 4. Further, the battery system 200 includes a fuse 30.

  A first switch SW1, a second switch SW2, a fuse 30, and a heater 14 are connected to the first power line L1. The first switch SW1 and the second switch SW2 are configured in series between the heater 14 and the normal power source 4 for supplying power to the heater 14. The third switch SW3 and the molten salt battery B (the assembled battery 100) are connected to the second power line L2.

  Each of the switches SW1, SW2, and SW3 is configured to perform on / off switching (switching). Various types of switches SW1, SW2, and SW3 can be adopted. However, the switches SW1, SW2, and SW3 of this embodiment are semiconductor switching elements, and in particular, FET (Field Effect Transistor). It is. These switches SW1, SW2, and SW3 are switched from on to off and from off to on in response to a control signal (drive signal) output from the control unit 20 described later.

  The functions of the switches SW1, SW2, and SW3 will be described. The first and second switches SW1 and SW2 are turned on to electrically connect the normal power source 4 and the heater 14. The third switch SW3 is a switch that enables the molten salt battery B to be electrically connected to the main power line L0. The third switch SW3 can be charged with power from the normal power source 4 in the on state, or the normal power source 4 is stopped ( When a power failure occurs, power can be supplied to the loads 7a and 7b (discharge is possible).

  The fuse 30 is connected in series with the heater 14, and is blown by overheating to cut off the power supply to the heater 14. More specifically, the fuse 30 has a small amount of self-heating due to electric current, but the temperature rises due to the heat of the heater 14 installed in the vicinity, and the fuse element (fusible body) is blown to supply power to the heater 14. It is a thermal fuse that shuts off

The battery system 200 includes a control unit 20, a first temperature sensor 21 for the heater 14, and a second temperature sensor 22 for the battery B.
The control unit 20 includes a microcomputer mounted on a substrate, and executes control of the battery system 200 described later according to a predetermined control program.
The first temperature sensor 21 is made of, for example, a thermocouple, and measures the temperature (ambient temperature) of the heater 14. The second temperature sensor 22 is made of, for example, a thermocouple, and measures, for example, the temperature of the battery container 11 as the temperature of the molten salt battery B. The measured values of these sensors 21 and 22 are input to the control unit 20. The first temperature sensor 21 is mainly used for detecting an abnormality in the heater 14, and the second temperature sensor 22 is mainly for the control unit 20 to determine whether the molten salt battery B can be charged or discharged. Used for.

  Furthermore, the battery system 200 further includes a detection unit 25 that detects an abnormality in the heater 14. The detection unit 25 of the present embodiment includes the first temperature sensor 21 and the function of the control unit 20. When the measurement value of the first temperature sensor 21 is input to the control unit 20, the control unit 20 compares the measurement value with a preset threshold value, and when the measurement value is equal to or greater than the threshold value, the heater 14. Detects overheating abnormalities. Thus, when the temperature of the heater 14 exceeds the threshold value, it is detected as abnormal.

  The control unit 20 has a function of controlling the battery system 200 in addition to the function as (a part of) the detection unit 25. Specifically, as the control of the battery system 200, the control unit 20 performs switching control that is first control and alternate control that is second control.

The switching control is control for adjusting the power supply to the heater 14 by switching on / off any one of the plurality of switches SW1, SW2. At this time, the remaining switches that are not switched on and off are maintained in the on state. That is, only one switch is switched on and off, and the remaining switches are always in the on state.
In the present embodiment, the on / off switching is performed by PWM (Pulse Width Modulation) control, whereby the power supply to the heater 14 can be adjusted (finely adjusted), and the temperature of the heater 14 is set to a desired temperature. be able to.

  The alternation control is control for switching a switch for performing the switching control between the plurality of switches SW1 and SW2. That is, it is control which switches the switch which carries out on-off switching in order (alternately). In this alternation control, the switch for performing the switching control is switched at a required time interval. This time interval is equal to a “feedback period” described later in a specific example of the control method.

<Regarding Control Method of Battery System 200>
A control method of the battery system 200 having the above configuration will be described with reference to FIGS. FIG. 7 is a flowchart showing this control method.
The second temperature sensor 22 measures the temperature of the molten salt battery B (step St1 in FIG. 7), and the control unit 20 determines whether the molten salt battery B can be charged or discharged based on the measured value. That is, the measured value is compared with the operating temperature (for example, 57 ° C.) of the molten salt battery B (step St2 in FIG. 7). When the measured value is lower than the operating temperature (in the case of “Yes” in step St2), charging or discharging is impossible, and control of power supply from the normal power source 4 to the heater 14 is started (step of FIG. 7). St3), the molten salt battery B is heated (step St4 in FIG. 7).

  In FIG. 8, in this power supply control (step St <b> 3), the control unit 20 performs feedback control based on the measured value of the first temperature sensor 21 using the two switches SW <b> 1 and SW <b> 2. FIG. 8 is a time chart showing the on / off switching operation of the switches SW1 and SW2. The subject of the processing described below is the control unit 20 unless otherwise specified. Each of the periods T1, T2, T3... Shown in FIG. 8 corresponds to a feedback cycle.

  In the first period T1, PWM control is performed using the first switch SW1, and the first switch SW1 is switched on and off. On the other hand, in this period T1, the second switch SW2 maintains the “on” state. That is, the first switch SW1 is switched on and off in one PWM cycle (on / off switching cycle), and this switching is continued during the feedback cycle (period T1), whereas the second switch SW2 is switched on. Regardless of the PWM period, it is continuously on during the feedback period (period T1).

In the next second period T2, PWM control is performed using the second switch SW2, and the second switch SW2 is switched on and off. On the other hand, in this period T2, the first switch SW1 maintains the “on” state. That is, the second switch SW2 is switched on and off in one PWM cycle (on / off switching cycle), and this switching is continued during the feedback cycle (period T2), whereas the first switch SW1 is switched on. Regardless of the PWM period, it is continuously on during the feedback period (period T2).
Thereafter, the operation in the period T1 and the operation in the period T2 are alternately repeated. That is, in the next period T3, the same operation as in the period T1 is performed.

Then, the measured value of the first temperature sensor 21 and the target temperature are compared for each feedback cycle, and the ON time (on duty) in the PWM cycle is adjusted for each feedback cycle according to the result.
Such control of power supply to the heater 14 (step St3) is continued until operation is stopped (charging or discharging is stopped) (step St5 in FIG. 7). As a result, the molten salt battery B is heated to the target temperature and kept at the target temperature.

As described above, in the battery system 200 of the present embodiment, the switches (SW1, SW2) for adjusting the power supply to the heater 14 are doubled. In the control method of the present embodiment, the molten salt battery B is Along with control (switching control) for adjusting the power supply to the heater 14 by switching on and off one switch SW1 (or SW2) in order to increase the temperature and to keep the temperature of the molten salt battery B whose temperature has been increased. Then, a control (alternating control) for switching the switch to be switched on and off between the two switches SW1 and SW2 is performed.
That is, in the case of the battery system 200 shown in FIG. 6, since two switches SW1 and SW2 for adjusting the power supply to the heater 14 are provided in series, a certain period (period T1 shown in FIG. 8). Then, while the power supply to the heater 14 is adjusted by switching on / off one switch SW1, the remaining switch SW2 may be maintained in the on state. In another period (period T2 shown in FIG. 8), the power supply to the heater 14 may be adjusted by maintaining the one switch SW1 in the on state and switching the other switch SW2 on and off. In this way, the heater 14 can be controlled by switching the switch to be turned on / off between the two switches SW1 and SW2.

  Here, in the switches SW1 and SW2 such as the FETs of the present embodiment, when the switches SW1 and SW2 are kept in the on state, the probability of occurrence of a short fault is lower than when the on / off switching is performed. Therefore, by switching the switch to be switched between the two switches SW1 and SW2 as in the present embodiment, it is possible to reduce the probability of occurrence of a short fault in each of the switches SW1 and SW2. As a result, it is possible to reduce the probability that a failure will occur as a whole battery system 200 including such switches SW1 and SW2.

  A case where either one of the two switches SW1 and SW2 has a short circuit will be described. Note that the control unit 20 is unclear (which cannot be detected) as to which of the switches SW1 and SW2 is short-circuited, but here, for the sake of explanation, it is assumed that the second switch SW2 is short-circuited. . Since the second switch SW2 has a short circuit failure, it is always on.

  In this case, with reference to FIG. 8, PWM control using the first switch SW1 that is not short-circuited is performed in the period T1. Thereby, the power supply to the heater 14 is adjusted. However, in the next period T2, the second switch SW2, which is to be PWM-controlled, has a short circuit failure, so that a control signal (drive signal) for PWM control is transmitted from the control unit 20 to the second switch SW2. On / off switching is not performed. For this reason, in the period T2, electric power is continuously supplied to the heater 14, and the temperature of the heater 14 greatly increases as compared with the case where the PWM control is executed. However, in the next period T3, similarly to the period T1, PWM control by the first switch SW1 that is not short-circuited is executed, and the power supply to the heater 14 is adjusted.

  As described above, in this embodiment, even if any one of the two switches SW1 and SW2 (SW2 in this embodiment) is short-circuited, the control unit 20 controls the remaining switches (in this embodiment). SW1) is switched on and off to adjust the power supply to the heater 14. That is, according to the present embodiment, it is possible to prevent the heater 14 from being completely disabled. As a result, it is possible to suppress the occurrence of a problem that the temperature of the molten salt battery B greatly exceeds a desired value.

When the heater 14 is controlled by the remaining switch SW2 that is not short-circuited, the feedback cycle, that is, the alternation cycle of the switch that performs on / off switching is preferably set to be relatively short. This is because if the alternation period (feedback period) is too long, the duration of power supply to the heater 14 becomes long and the molten salt battery B may exceed the desired temperature.
Therefore, it is preferable to set this alternation cycle as “a time during which the temperature rise of the heater 14 is less than 5 ° C. when power is continuously supplied”. For example, although it varies depending on the capacity of the heater 14, the alternation period (feedback period) is preferably about 5 to 15 seconds, and is set to 10 seconds in this embodiment. Note that the PWM period can be several milliseconds to 1 second, and is set to 100 milliseconds in this embodiment.

  Moreover, the battery system 200 of this embodiment is provided with the detection part 25 which detects abnormality in the heater 14 as above-mentioned. Here, the detection unit 25 includes a first temperature sensor 21 that detects the temperature of the heater 14. When the temperature detected by the first temperature sensor 21 is equal to or higher than a threshold value, the control unit 20 is “abnormal”. Is detected. The threshold is a temperature when the temperature of the molten salt battery B heated by the heater 14 is higher as the temperature of the molten salt battery B exceeds the specified temperature. For example, when the temperature of the molten salt battery B is controlled to be 90 ° C. to 95 ° C. (control temperature range), the threshold value related to the temperature of the heater 14 may be set to 95 ° C. which is the upper limit value of the control temperature range. it can. According to the configuration of the detection unit 25, until the temperature of the heater 14 reaches a threshold value, the control unit 20 can adjust the power supply of the heater 14 using a switch that is not short-circuited.

  When the “abnormality” is detected by the detection unit 25, the control unit 20 performs control to turn off all the two switches SW1 and SW2. In this case, since the two switches SW1 and SW2 are connected in series, the power supply to the heater 14 can be stopped regardless of which of the two switches SW1 and SW2 is short-circuited. Become. As a result, it is possible to suppress the occurrence of a problem that the temperature of the molten salt battery B greatly exceeds a desired value. Further, when an abnormality is detected, all the switches SW1 and SW2 are turned off, so that the power supply to the heater 14 can be surely stopped without knowing which switch has a short circuit failure.

  As another control when “abnormality” is detected by the detection unit 25, the control unit 20 may perform control for notifying the owner or the administrator of the battery system 200 of information indicating abnormality. . For this purpose, the battery system 200 includes an output unit 26 (see FIG. 6) that outputs information indicating abnormality. Examples of the output unit 26 include a monitor and a speaker. In the case of a monitor, characters or the like can be displayed as information indicating abnormality. In the case of a speaker, sound can be output as information indicating abnormality. In addition to the control for turning off all the switches SW1 and SW2, the control by the output unit 26 may be executed.

Further, although the possibility is low, a case where both the switches SW1 and SW2 are short-circuited will be described. As described above, in this embodiment, the fuse 30 is connected in series with the heater 14, and the fuse 30 is installed in the vicinity of the heater 14. Therefore, if both the switches SW1 and SW2 are short-circuited and the heater 14 is overheated, the fuse element (the fusible element) of the fuse 30 is melted by this overheat, and the power supply to the heater 14 is cut off. can do.
Therefore, even if all the switches SW1 and SW2 included in the first power line L1 are short-circuited and the power supply to the heater 14 is excessive, the power supply is forcibly cut off by the fuse 30 being blown. The heat generation by the heater 14 can be stopped.

In the above description, the switch failure is a short failure, but the switch can also be an open failure. In this case, even if the control unit 20 transmits a control signal (drive signal) to the switches SW1 and SW2, power is not supplied to the heater 14, and the temperature of the heater 14 and the molten salt battery B does not increase. Therefore, when the temperature rise is not detected in at least one of the first temperature sensor 21 and the second temperature sensor 22, the control unit 20 (detection unit 25) uses the measured values from the sensors 21 and 22. Based on this, it is possible to detect an abnormality caused by an open failure of the switch.
In this case, the control unit 20 can perform control for notifying the owner or manager of the battery system 200 of information indicating abnormality. This control is the control using the output unit 26 and is the same as that in the case of a short circuit failure, and the description thereof is omitted here.

[Another example of the detection unit 25]
In the above-described embodiment, the detection unit 25 has been described with respect to the configuration that detects the abnormality in the heater 14 using the first temperature sensor 21 that detects the temperature of the heater 14, but the second temperature sensor 22 may be used. That is, since the abnormality due to the temperature rise of the molten salt battery B is caused by the overheating of the heater 14, the detection unit 25 includes a second temperature sensor 22 that detects the temperature of the molten salt battery B. When the measured temperature is equal to or higher than the threshold value, it may be detected as abnormal.
As described above, even when the second temperature sensor 22 is used or the first temperature sensor 21 is used as in the embodiment, the temperature of the heater 14 or the molten salt battery B reaches the threshold value. The control unit 20 can adjust the power supply of the heater 14 using a switch that is not short-circuited.

Moreover, the detection part 25 can be set as the structure which monitors values other than temperature and detects abnormality. That is, as shown in FIG. 6, the ammeter 27 is provided on the first power line L <b> 1, and the measured value of the ammeter 27 is transmitted to the control unit 20. The control unit 20 has a function as a timer 28 for measuring time. In addition to acquiring data of a current value flowing through the heater 14, the control unit 20 can continuously acquire current through the heater 14 by the timer 28. Can be measured.
As described above (see FIG. 8), in the control of power supply to the heater 14, alternation control for switching the switch to be turned on / off is performed for each feedback cycle (periods T1, T2,...). For this reason, in each period T1, T2,..., The power supplied to the heater 14 should be intermittent, and a current sufficient to cause the heater 14 to generate heat does not continuously flow for the feedback period. Therefore, the timer 28 measures the time during which a current sufficient to cause the heater 14 to generate heat (this time is referred to as continuous energization time) is measured, and the measured time is equal to or exceeds the time of the feedback cycle. If it is, it can be estimated that one of the switches SW1 and SW2 is short-circuited.
As described above, as another example of the detection unit 25, the detection unit 25 includes the timer 28 that measures the continuous energization time to the heater 14, and the measured continuous energization time is a threshold value (in this embodiment, the time of the feedback cycle). ) It is configured to detect that there is an abnormality when it is above.

Furthermore, it is possible to estimate a switch having a short circuit failure. For example, when the continuous energization time in one feedback cycle (for example, period T1) for switching on / off the switch SW1 is equal to the time of the feedback cycle, the control unit 20 can estimate that the switch SW1 has a short circuit failure. . Further, when the continuous energization time in one feedback cycle (for example, the period T2) for switching the switch SW2 on and off is equal to the time of the feedback cycle, the control unit 20 can estimate that the switch SW2 is short-circuited. .
When it is estimated that the switch SW1 is short-circuited, the control unit 20 may always switch the switch SW2 on and off during the heating process of the molten salt battery B (step St4 in FIG. 7). Similarly, when it is estimated that the switch SW2 is short-circuited, the control unit 20 may always switch the switch SW1 on and off during the heating process of the molten salt battery B (step St4 in FIG. 7). . In this way, even if one of the switches is short-circuited, only the other normal switch is switched on and off, thereby suppressing the occurrence of a problem that the temperature of the molten salt battery B greatly exceeds a desired value. It becomes possible.

[Appendix 1]
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 meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

For example, although a battery that operates by heating, that is, a battery that requires temperature adjustment has been described as the molten salt battery B in the above embodiment, other batteries may be used. For example, a sodium sulfur battery, a lithium ion battery, and a lead battery may be used.
In the case of a sodium-sulfur battery, the operating temperature is, for example, about 300 ° C., and the temperature is raised to this operating temperature by the heater 14. Further, in the case of a lithium ion battery or a lead battery, the operating temperature does not need to be higher than room temperature (20 ° C.), but when used in a cold district where the ambient temperature is 0 ° C. or less, for example, the heater 14 It is preferable to use after raising the temperature to 0 ° C. or higher.

  Further, in the above embodiment, the case where PWM control is executed as control of power supply to the heater 14 has been described. However, other on / off switching control may be used, and PFM (Pulse Frequency Modulation) control may be used. Good.

  Further, the number of switches for adjusting the power supplied to the heater 14 may be plural, and in the above-described embodiment, the number is two, but may be three or more. In this case as well, these switches are connected in series, and there is only one switch that performs on / off switching (switching control), and the rest are always in the on state. Then, alternation control for sequentially switching on / off switching is performed. Thereby, the probability of occurrence of a short circuit failure in each switch can be reduced.

  Moreover, in the said embodiment, although the power source which can supply electric power to the battery system 200 was only the normal power source (1st power source) 4 which is a commercial power source, it was installed separately from the normal power source 4 Or a second power source that operates independently. In this case, power is supplied to the heater 14 by the second power source. That is, the first power line L1 shown in FIG. 6 may be configured to be connected to the second power source installed in parallel with the normal power source 4 instead of the main power line L0. Thereby, it is possible to reduce the power burden required for heating the molten salt battery B for the normal power source 4. The second power source is a power source different from the normal power source 4, and is based on, for example, a power source provided from a power conditioner for solar power generation or wind power generation, an engine generator, a fuel cell, a storage battery, or the like. It can be a power source.

[Appendix 2]
Further, similarly to the above-described embodiment, as a battery system that can reduce the probability of failure of a switch provided between the heater and its power source, and a control method for such a battery system The following technical means exist.

(1. Battery system)
A battery to be used by heating;
A heater for heating the battery;
A plurality of switches provided in parallel between a power source for supplying power to the heater and the heater;
A control unit that performs switching control that switches on and off the switch to adjust power supply to the heater, and performs switching control that switches a switch that performs the switching control between the plurality of switches;
Battery system.

According to the battery system configured as described above, a plurality of switches are provided in parallel between the power source for supplying power to the heater and the heater. The power supply to the heater may be adjusted by on / off switching, and the remaining switches may be maintained in the off state. In another period, the power supply to the heater may be adjusted by maintaining the one switch in the off state and switching on / off one of the other switches.
Here, a switch maintained in an off state has a lower probability of occurrence of a failure (such as a short failure) than a switch that is switched on and off. For this reason, it is possible to reduce the probability of occurrence of a failure in each of the plurality of switches by switching the switch that performs the switching control as described above between the plurality of switches.

(2. Battery system control method)
A battery used for heating; a heater for heating the battery; a power source for supplying power to the heater; and a plurality of switches provided in parallel between the heaters. A method for controlling a battery system, comprising:
A control method of a battery system, wherein the switch is turned on / off to adjust power supply to the heater and the switch to be turned on / off is switched between the plurality of switches.

According to this control method, since a plurality of switches are provided in a double row between the power source for supplying power to the heater and the heater in the battery system, one switch is turned on / off for a certain period. Switching may be performed to adjust the power supply to the heater, and the remaining switches may be kept off. In another period, the power supply to the heater may be adjusted by maintaining the one switch in the off state and switching on / off one of the other switches. That is, the heater can be controlled by switching the switch to be turned on / off between a plurality of switches.
Here, a switch maintained in an off state has a lower probability of occurrence of a failure (such as a short failure) than a switch that is switched on and off. For this reason, it becomes possible to reduce the occurrence probability of failure in each of the plurality of switches by switching the switches to be switched between the plurality of switches as described above.

This will be specifically described. FIG. 9 is a block diagram showing a circuit configuration of (1. Battery system). The battery system shown in FIG. 9 is a molten salt battery system 200.
In the molten salt battery system 200, two switches SW 1 and SW 2 are provided in parallel between the normal power source 4 for supplying power to the heater 14 and the heater 14.
Also in this battery system 200, in order to raise the temperature of the molten salt battery B and to keep the temperature of the heated molten salt battery B, the control unit 20 sets one switch SW1 (or SW2). On / off switching is performed to perform switching control for adjusting the power supply to the heater 14, and alternate control is performed to switch the switch for performing the switching control between the two switches SW1 and SW2.
The circuit configuration of the battery system 200 shown in FIG. 9 is different from the circuit configuration shown in FIG. 6 in the connection form of the switches SW1 and SW2, but is otherwise the same, and the description of the same points is omitted. .

Further, the control (control method) performed by the control unit 20 is partially different. That is, in the case of the battery system 200 shown in FIG. 9, as shown in the time chart of FIG. 10, in a certain period T <b> 1, while the one switch SW <b> 1 is switched on and off to adjust the power supply to the heater 14, The switch SW2 may be kept off. In the next period T2, the power supply to the heater 14 may be adjusted by maintaining the one switch SW1 in the off state and switching the other switch SW2 on and off. In this way, the heater 14 can be controlled by switching the switch for performing the switching control between the two switches SW1 and SW2.
By switching the switch for performing the switching control between the two switches SW1 and SW2, it is possible to reduce the probability of failure in each of the switches SW1 and SW2.

  Further, the number of switches for adjusting the power supplied to the heater 14 may be plural, and in the above-described embodiment, the number is two, but may be three or more. Also in this case, these switches are connected in parallel, and there is only one switch that performs on / off switching (switching control), and the rest are always in the off state. Then, alternation control for sequentially switching on / off switching is performed.

DESCRIPTION OF SYMBOLS 1 Positive electrode 1a Positive electrode collector 1b Positive electrode material 1t Terminal 2 Negative electrode 2a Negative electrode collector 2b Negative electrode material 3 Separator 4 Normal power source (power source)
6 Inverter 7a AC load 7b DC load 10 Molten salt battery main body 11 Battery container 12 Safety valve 13 Outer box 14 Heater 20 Control unit 21 First temperature sensor 22 Second temperature sensor 25 Detection unit 26 Output unit 27 Ammeter 28 Timer 30 Fuse 100 Battery pack 200 Molten salt battery system L1 1st power line L2 2nd power line SW1 1st switch SW2 2nd switch SW3 3rd switch T1 period T2 period T3 period

Claims (7)

A battery to be used by heating;
A heater for heating the battery;
A plurality of switches provided in series between a power source for supplying power to the heater and the heater;
A control unit that performs switching control that switches on and off the switch to adjust power supply to the heater, and performs switching control that switches a switch that performs the switching control between the plurality of switches;
Battery system.   2. The battery system according to claim 1, wherein even if any one of the plurality of switches is short-circuited, the control unit performs on / off switching of the remaining switches to adjust power supply to the heater. A detector for detecting an abnormality in the heater;
The battery system according to claim 1, wherein when an abnormality is detected by the detection unit, the control unit performs control to turn off all of the plurality of switches.   The battery system according to claim 3, wherein the detection unit includes a sensor that detects a temperature of the heater, and detects that the temperature is abnormal when the temperature detected by the sensor is equal to or higher than a threshold value.   The battery system according to claim 3, wherein the detection unit includes a timer that measures a continuous energization time to the heater, and detects an abnormality when the continuous energization time is equal to or greater than a threshold value.   The battery system according to any one of claims 1 to 5, further comprising a fuse connected in series with the heater and fused by overheating to cut off power supply to the heater. A battery used by heating, a heater for heating the battery, a power source for supplying power to the heater, and a plurality of switches provided in series between the heaters A method for controlling a battery system, comprising:
A control method of a battery system, wherein the switch is turned on / off to adjust power supply to the heater and the switch to be turned on / off is switched between the plurality of switches.

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