Warming up methods for charge / discharge systems and secondary batteries

Abstract

The present invention provides a charge / discharge system and a secondary battery warm-up method that can safely and efficiently warm up secondary batteries without the use of auxiliary equipment. [Solution] The charge / discharge system 10 includes a bidirectional AC / DC converter 13, a first bidirectional DC / DC converter 14, and a control device 20 that controls the operation of the bidirectional AC / DC converter 13 and the operation of the first bidirectional DC / DC converter 14. The first bidirectional DC / DC converter 14 detects the battery voltage of the first secondary battery 11 and inputs the detected battery voltage to the control device 20. The charge / discharge system 10 includes a signal generator 18 that outputs an electrical signal having an amplitude indicating the magnitude of the current flowing through the first secondary battery 11 and a frequency indicating the number of times the first secondary battery 11 is switched between charging and discharging to the bidirectional DC / DC converter 15. The control device 20 performs a warm-up process that raises the temperature of the first secondary battery 11 while monitoring the battery voltage.

Description

[Technical Field]

[0001] The present disclosure relates to a charge-discharge system capable of charging and discharging a secondary battery, and a warm-up method for a secondary battery. [Background Art]

[0002] In recent years, hybrid vehicles, plug-in hybrid vehicles, and electric vehicles have become widespread. These vehicles are equipped with a charge-discharge system using a chargeable and dischargeable secondary battery.

[0003] Further, as a technology related to secondary batteries, for example, Patent Document 1 discloses a charge-discharge system that tests secondary batteries by connecting them in parallel as test batteries. The charge-discharge system tests the test battery while performing power sharing (energy sharing) between the test battery and a non-test battery, which is a secondary battery not subject to testing.

[0004] Secondary batteries have a problem that it is difficult to exhibit their original performance when the battery temperature is low. This problem is particularly prominent when the battery temperature is in an extremely low temperature state. For this reason, automotive charge-discharge systems are equipped with temperature rising heaters, heat insulating materials, and the like as auxiliary equipment capable of performing warm-up to raise the battery temperature to a practical range. Further, test charge-discharge systems are provided with a constant temperature bath in which a test battery can be placed as auxiliary equipment capable of warm-up. [Prior Art Literature] [Patent Literature]

[0005] [Patent Document 1] Japanese Unexamined Patent Publication No. 2023-10581 [Summary of the Invention] [Problem to be Solved by the Invention]

[0006] Incidentally, in recent years, as the drive batteries installed in the aforementioned vehicles have become larger, ancillary equipment such as heating elements and constant temperature chambers have also become larger. Therefore, there is a need for technology that can safely and efficiently warm up secondary batteries without using ancillary equipment. [Means for solving the problem]

[0007] A charge / discharge system that solves the above problems comprises: a bidirectional AC / DC converter having one end connected to an AC bus and the other end connected to a DC bus; a bidirectional DC / DC converter having one end connected to the DC bus and the other end connected to a secondary battery; a control device configured to control the operation of the bidirectional AC / DC converter and the bidirectional DC / DC converter according to the surplus or deficiency of power in the DC bus; a voltage detector that detects the battery voltage of the secondary battery and inputs the detected battery voltage to the control device; a signal generator that outputs an electrical signal having an amplitude indicating the magnitude of the current flowing through the secondary battery and a frequency indicating the number of times the secondary battery is switched between charging and discharging to the bidirectional DC / DC converter; and a temperature measuring device that detects the battery temperature of the secondary battery and inputs the detected battery temperature to the control device. The control device monitors the battery voltage and performs a warm-up process that controls the electrical signal according to the monitoring result of the battery voltage to raise the temperature of the secondary battery.

[0008] A secondary battery warm-up method that solves the above problems is applied to a charge / discharge system comprising: a bidirectional AC / DC converter having one end connected to an AC bus and the other end connected to a DC bus; a bidirectional DC / DC converter having one end connected to the DC bus and the other end connected to a secondary battery; and a control device configured to control the operation of the bidirectional AC / DC converter and the bidirectional DC / DC converter according to the surplus or deficiency of power in the DC bus. The secondary battery warm-up method is provided in the charge / discharge system as follows: a voltage detector that detects the battery voltage of the secondary battery and inputs the detected battery voltage to the control device; a signal generator that outputs an electrical signal having an amplitude indicating the magnitude of the current flowing through the secondary battery and a frequency indicating the number of times the secondary battery is switched between charging and discharging; and a temperature measuring device that detects the battery temperature of the secondary battery and inputs the detected battery temperature to the control device. The control device then monitors the battery voltage and performs a warm-up process that controls the electrical signal according to the monitoring result of the battery voltage to raise the temperature of the secondary battery. [Effects of the Invention]

[0009] According to this disclosure, secondary batteries can be safely and efficiently warmed up without the use of ancillary equipment. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 shows a schematic configuration of a first embodiment of the charge / discharge system. [Figure 2] Figure 2 shows an example of an electrical signal output by the signal generator in the first embodiment. [Figure 3] Figure 3 shows an example of the hardware configuration of the control device in the first embodiment. [Figure 4] Figure 4 is a flowchart showing an example of a warm-up process in the first embodiment. [Figure 5]In the first embodiment, Figure 5(a) shows an example of the change in an electrical signal based on amplitude change processing, Figure 5(b) shows an example of the change in an electrical signal based on frequency change processing, Figure 5(c) shows an example of the change in an electrical signal based on amplitude-frequency change processing, and Figure 5(d) shows an example of the change in an electrical signal based on frequency-amplitude change processing. [Figure 6] Figure 6 shows an example of the relationship between the frequency of an electrical signal and the decay of the current flowing through the first secondary battery in the first embodiment. [Figure 7] Figure 7 shows a schematic configuration of a second embodiment of the charge / discharge system. [Figure 8] In the second embodiment, Figure 8(a) schematically shows an example of power sharing, and Figure 8(b) schematically shows another example of power sharing. [Modes for carrying out the invention]

[0011] (First Embodiment) A first embodiment of the charge / discharge system and the secondary battery warm-up method will be described with reference to Figures 1 to 6.

[0012] As shown in Figure 1, the charge / discharge system 10 is configured to charge and discharge first secondary batteries 11-1, 11-2, ..., 11-m (where m is an integer of 3 or more). The charge / discharge system 10 is, for example, a system for charging or discharging first secondary batteries 11 for use in cars or homes. Alternatively, for example, the charge / discharge system 10 is a system for performing charge / discharge tests using the first secondary batteries 11 as test batteries. The first secondary batteries 11-1, 11-2, ..., 11-m are various types of secondary batteries such as lithium-ion batteries, nickel-metal hydride batteries, and all-solid-state batteries (and other power storage devices including large-capacity capacitors such as electric double-layer batteries). In the following, when the first secondary batteries 11-1, 11-2, ..., 11-m are not distinguished, they are simply referred to as first secondary batteries 11. In this embodiment, the charge / discharge system 10 is equipped with three or more first secondary batteries 11, but the charge / discharge system 10 may be equipped with fewer than three first secondary batteries 11.

[0013] The charging / discharging system 10 is connected to the AC bus 3. In addition to the AC power source 4, the AC bus 3 may also be connected to other facilities 5. The AC bus 3 supplies AC power to the charging / discharging system 10 and the other facilities 5.

[0014] The charging / discharging system 10 includes a bidirectional AC / DC converter 13, a first bidirectional DC / DC converter 14-1, 14-2, ..., 14-m, temperature measuring devices 17-1, 17-2, ..., 17-m, a signal generator 18, and a control device 20.

[0015] Note that hereinafter, the bidirectional AC / DC converter 13 is simply referred to as the AC / DC converter 13. Further, when the first bidirectional DC / DC converters 14-1, 14-2, ..., 14-m do not need to be distinguished, they are simply referred to as the DC / DC converter 14. In FIG. 1, the bidirectional AC / DC converter is simply denoted as AC / DC, and the first bidirectional DC / DC converter is simply denoted as DC / DC. Further, when the temperature measuring devices 17-1, 17-2, ..., 17-m do not need to be distinguished, they are simply referred to as the temperature measuring device 17.

[0016] (Bidirectional AC / DC Converter) The AC / DC converter 13 has one end connected to the AC bus 3 and the other end connected to the DC bus 16. The AC / DC converter 13 converts the AC power on the AC bus 3 into DC power and supplies the DC power to the DC bus 16. The AC / DC converter 13 converts the DC power on the DC bus 16 into AC power and supplies the AC power to the AC bus 3. The operation of such an AC / DC converter 13 is controlled by the control device 20.

[0017] (Bidirectional DC / DC Converter) The DC / DC converter 14 has one end connected to the AC / DC converter 13 via the DC bus 16, and the other end connected to the first secondary battery 11. The DC / DC converter 14 performs charge and discharge of the first secondary battery 11. The DC / DC converter 14 discharges the first secondary battery 11 by outputting the electric power stored in the first secondary battery 11 to the DC bus 16. The DC / DC converter 14 charges the first secondary battery 11 by supplying DC power from the DC bus 16 to the first secondary battery 11. The operation of such a DC / DC converter 14 is controlled by the control device 20. In addition, as various types of information related to the first secondary battery 11, the DC / DC converter 14 detects the voltage of the first secondary battery 11, charging power during charging, and discharging power during discharging. The DC / DC converter 14 outputs the detected various information of the first secondary battery 11 to the control device 20. The DC / DC converter 14 functions as a voltage detector.

[0018] (Temperature Measuring Device) Temperature measuring devices 17-1, 17-2, ..., 17-m are provided so as to correspond to the first secondary batteries 11-1, 11-2, ..., 11-m. The temperature measuring device 17 measures the battery temperature T, which is the temperature of the first secondary battery 11. The temperature measuring device 17 outputs the measured battery temperature T to the control device 20.

[0019] (Signal Generator) As shown in Figure 2, the signal generator 18 outputs an electrical signal S1 having an amplitude A indicating the magnitude of the energization current and a frequency f indicating the number of charge-discharge switching times of the first secondary battery 11 per unit time to the DC / DC converter 14. An example of the electrical signal S1 is a sine wave signal. The DC / DC converter 14 charges and discharges the first secondary battery 11 in accordance with the electrical signal S1. By repeating such charge and discharge, the battery temperature T of the first secondary battery 11 rises due to self-heating.

[0020] The output of the signal generator 18 is controlled by the control device 20. The amplitude A of the electrical signal S1 can be changed by the control device 20. The frequency f of the electrical signal S1 can be changed by the control device 20.

[0021] (Control device 20) Figure 3 shows an example of the hardware configuration of an information processing device H10 that functions as a control device 20. The information processing device H10 includes a communication device H11, an input device H12, a display device H13, a storage device H14, and a processor H15. Note that this hardware configuration is just one example, and other hardware may be included.

[0022] Communication device H11 is an interface that performs data transmission and reception by establishing a communication path with other devices. Communication device H11 is, for example, a network interface card or a wireless interface.

[0023] Input device H12 is a device that receives input from the user or other users. Input device H12 is, for example, a mouse or keyboard. Display device H13 is a display or touch panel that displays various information.

[0024] The storage device H14 is a storage device that stores data and various programs for executing various functions of the charge / discharge system 10. Examples of storage devices H14 include ROM (Read Only Memory), RAM (Random Access Memory), and hard disks.

[0025] The processor H15 controls each process in the information processing device H10, which functions as the control device 20, using programs and data stored in the memory device H14. Examples of processor H15 include CPUs (Central Processing Units) and MPUs (Micro Processor Units). This processor H15 executes various processes corresponding to various operations by loading programs stored in ROM, etc., into RAM. For example, when a predetermined application program is started, the processor H15 operates the processes that execute the operations described later.

[0026] The processor H15 is not limited to performing all of its operations using software. For example, the processor H15 may include dedicated hardware circuits (e.g., application-specific integrated circuits: ASICs) that perform hardware operations for at least some of the operations it performs. In other words, the processor H15 can be configured as follows:

[0027] [1] One or more processors that operate according to a computer program (software) [2] One or more dedicated hardware circuits that perform at least some of the various processes, [3] Circuits that include combinations of these. A processor includes the CPU and memory such as RAM and ROM. Memory stores program code or instructions configured to cause the CPU to perform processing. Memory, or non-temporary computer-readable media, includes any available media accessible by a general-purpose or dedicated computer.

[0028] When the control device 20 receives a start signal S through the input device H12, it performs a charge / discharge process corresponding to the start signal S. For example, if the start signal S indicates charging of the first secondary battery 11, the control device 20 performs a charging process that controls the operation of the AC / DC converter 13 and the DC / DC converter 14 so that the first secondary battery 11 is charged with a predetermined charging power.

[0029] For example, if the start signal S indicates the discharge of the first secondary battery 11, the control device 20 performs a discharge process that controls the operation of the AC / DC converter 13 and the DC / DC converter 14 so that the first secondary battery 11 is discharged with a predetermined discharge power.

[0030] For example, if the start signal S indicates a test of the first secondary battery 11, the control device 20 performs a test process that controls the operation of the AC / DC converter 13 and the DC / DC converter 14 so that the first secondary battery 11 is charged and discharged in a predetermined charge-discharge pattern.

[0031] The control device 20 performs a warm-up process prior to the charge-discharge process described above if the battery temperature T at the time the start signal S is input is less than the lower limit temperature Tmin. The lower limit temperature Tmin is the lower limit of the practical range, which is the range of battery temperatures T suitable for charging and discharging. The warm-up process is a process that raises the battery temperature T to the practical range. During the warm-up process, the control device 20 inputs an electrical signal S1 to the DC / DC converter 14 through the signal generator 18.

[0032] (Warm-up process) The warm-up process will be explained with reference to Figures 4 and 5. As shown in Figure 4, during the warm-up process, the control device 20 controls the signal generator 18 and the DC / DC converter 14 to start energizing with an initial signal (step S101). The initial signal is an electrical signal S1 having an initial amplitude A1 that is smaller than the maximum amplitude Amax and an initial frequency f1 that is smaller than the maximum frequency fmax.

[0033] Next, the control device 20 obtains the battery voltage V, which is the voltage of the first secondary battery 11, through the DC / DC converter 14, and performs a voltage determination on the obtained battery voltage V (step S102). In the voltage determination, the control device 20 determines whether the battery voltage V is within the normal range. Specifically, the control device 20 determines whether the battery voltage V is less than the determination voltage V1. The determination voltage V1 is a voltage lower than the abnormal voltage Va, which indicates that there is an abnormality in the first secondary battery 11.

[0034] Here, in the first secondary battery 11, the lower the battery temperature T is, the more easily the battery voltage V sharply rises along with charging and discharging, so the battery voltage V is more likely to reach the abnormal voltage Va. Such a sharp rise in the battery voltage V is more likely to occur as the amplitude A of the electrical signal S1 increases and as the frequency f increases. The determination voltage V1 is set to a voltage at which the possibility of the battery voltage V reaching the abnormal voltage Va is low even when charging and discharging by the electrical signal S1 are repeated. The determination voltage V1 may be a fixed value at which the battery voltage V hardly reaches the abnormal voltage Va even when the electrical signal S1 has the maximum amplitude Amax and the maximum frequency fmax, or may be a variable value selected in accordance with the amplitude A and frequency f of the electrical signal S1, the battery temperature T, and the like.

[0035] When the battery voltage V is equal to or higher than the determination voltage V1 (step S102: V≧V1), the control device 20 repeatedly performs voltage determination until the battery voltage V drops below the determination voltage V1. On the other hand, when the battery voltage V is lower than the determination voltage V1 (step S102: V<V1), the control device 20 performs temperature determination (step S103).

[0036] In the temperature determination (step S103), the control device 20 acquires the battery temperature T via the temperature measuring device 17, and determines whether or not the acquired battery temperature T has reached the target temperature T1. The target temperature T1 is a temperature included in a practical range.

[0037] When the battery temperature T has not reached the target temperature T1 (step S103: T<T1), the control device 20 executes a signal change process (step S104). In the signal change process, the control device 20 changes the electrical signal S1 such that the charge / discharge power amount of the first secondary battery 11 increases.

[0038] After executing the signal change process, the control device 20 executes voltage determination (step S102) and temperature determination (step S103) again. That is, on condition that the battery voltage V is lower than the determination voltage V1, the control device 20 repeatedly executes the signal change process until the battery temperature T reaches the target temperature T1.

[0039] As shown in Figure 5(a), one example of signal modification is amplitude modification. In amplitude modification, the control device 20 increases the amplitude A of the electrical signal S1 by a predetermined unit amplitude ΔA while maintaining the initial frequency f1. In this case, the initial frequency f1 may be the maximum frequency fmax, or a frequency smaller than the maximum frequency fmax. The unit amplitude ΔA may be a fixed value, or a variable value that increases as the battery temperature T increases.

[0040] As shown in Figure 5(b), one example of signal modification is frequency modification. In amplitude modification, the control device 20 increases the frequency f of the electrical signal S1 by a predetermined unit frequency Δf while maintaining the initial amplitude A1. In this case, the initial amplitude A1 may be the maximum amplitude Amax, or it may be an amplitude smaller than the maximum amplitude Amax. The unit frequency Δf may be a fixed value, or it may be a variable value that increases as the battery temperature T increases.

[0041] As shown in Figure 5(c), an example of signal modification processing is amplitude-frequency modification processing. In amplitude-frequency modification processing, the control device 20 increases the amplitude A of the electrical signal S1 by a unit amplitude amount ΔA and increases the frequency f of the electrical signal S1 by a unit frequency Δf. In this case, the initial amplitude A1 is smaller than the maximum amplitude Amax, and the initial frequency f1 is smaller than the maximum frequency fmax.

[0042] As shown in Figure 5(d), an example of signal modification processing is frequency-amplitude modification processing. In frequency-amplitude modification processing, the control device 20 increases the frequency f of the electrical signal S1 by a unit frequency Δf while maintaining the amplitude A of the electrical signal S1 at the initial amplitude A1. Then, when the frequency f reaches a predetermined threshold f2 at time t1, the control device 20 increases the frequency f by a unit frequency Δf and the amplitude A by a unit amplitude amount ΔA from the next frequency-amplitude modification processing.

[0043] The threshold f2 will be explained with reference to Figure 6. Figure 6 is a diagram showing an example of the relationship between the frequency f of the electrical signal S1 and the decay of the current flowing through the first secondary battery 11. In Figure 6, the first pattern shows the decay when the frequency f is increased while the amplitude A is maintained at 75% of the maximum amplitude Amax. The second pattern shows the decay when the amplitude A is increased as the frequency f increases after the frequency f exceeds 100 Hz.

[0044] As in the first pattern, when the frequency f exceeds 100 Hz, the attenuation of the current increases significantly with increasing frequency f. Therefore, even if the frequency f is increased, it is difficult to expect an increase in the amount of charge and discharge power corresponding to the increase in frequency f.

[0045] In contrast, in the second pattern, after the frequency f exceeds 100 Hz, the amplitude A is increased as the frequency f increases, thereby reducing the attenuation of the current. Therefore, it is possible to expect an increase in the amount of power charged and discharged in proportion to the increase in frequency f.

[0046] Thus, the threshold value f2 is set according to the characteristics of the first secondary battery 11. The threshold value f2 may be set after investigating the characteristics of the first secondary battery 11, or it may be set according to the type of first secondary battery 11 (such as a lithium-ion battery).

[0047] In the temperature determination step (step S103), if the battery temperature T has reached the target temperature T1 (step S103: T ≥ T1), the control device 20 terminates the warm-up process. In this warm-up process, the control device 20 monitors the battery voltage V by voltage determination (step S102) and raises the battery temperature T to the target temperature T1 by self-heating of the first secondary battery 11 using the electrical signal S1.

[0048] The effects of the first embodiment will be described. (1-1) In the charge / discharge system 10 described above, when the battery temperature T is lower than the lower limit temperature Tmin (T<Tmin), a warm-up process is executed in which charging and discharging of the first secondary battery 11 based on the electrical signal S1 generated by the signal generator 18 is repeated. This makes it possible to efficiently increase the battery temperature T without using auxiliary equipment for warming up the first secondary battery 11, such as a temperature-increasing heater, heat insulating material, or constant temperature bath. Furthermore, since the battery voltage V is monitored by voltage determination (step S102), an increase in the battery voltage V to an abnormal voltage Va is suppressed. That is, according to the charge / discharge system 10, the first secondary battery 11 can be warmed up safely and efficiently without using any auxiliary equipment.

[0049] (1-2) The control device 20 is configured to increase the amplitude A on condition that the battery voltage V is within a normal range during the warm-up process. As a result, the amount of charging / discharging power of the first secondary battery 11 per unit time increases, so the warm-up time for the first secondary battery 11 can be shortened.

[0050] (1-3) The control device 20 is configured to increase the frequency f on condition that the battery voltage V is within a normal range during the warm-up process. As a result, the amount of charging / discharging power of the first secondary battery 11 increases, so the warm-up time for the first secondary battery 11 can be shortened.

[0051] (1-4) The control device 20 may be configured such that, in the warm-up process, it starts inputting the electrical signal S1 with an initial amplitude A1 smaller than the maximum amplitude Amax, and increases the amplitude A in accordance with an increase in the frequency f on condition that the battery voltage V is within a normal range and the frequency f exceeds a threshold value f2.

[0052] With this configuration, as shown in the second pattern in Figure 6, even if the frequency f exceeds the threshold f2 (100 Hz in the case of Figure 6), the attenuation of the current can be suppressed. As a result, the amount of charge and discharge power increases in proportion to the increase in frequency f, allowing for efficient warm-up of the first secondary battery 11. It is preferable to set this initial amplitude A1 based on the characteristics of the first secondary battery 11, that is, the relationship between the frequency f of the electrical signal S1 and the attenuation of the current flowing through the first secondary battery 11. This ensures an increase in amplitude A while allowing for efficient warm-up of the first secondary battery 11 even before the frequency f reaches the threshold f2.

[0053] (Second Embodiment) A second embodiment of the charge / discharge system and secondary battery warm-up method will be described with reference to Figures 7 and 8. The main components of the charge / discharge system and secondary battery warm-up method in the second embodiment are the same as those in the first embodiment. Therefore, in the second embodiment, the differences from the first embodiment will be described in detail, while parts similar to those in the first embodiment will be denoted by the same reference numerals, and their detailed descriptions will be omitted.

[0054] As shown in Figure 7, the charge / discharge system 50 is configured to charge and discharge secondary batteries 12-1, 12-2, ..., 12-n. Secondary batteries 12-1, 12-2, ..., 12-n are various types of secondary batteries such as lithium-ion batteries, nickel-metal hydride batteries, and all-solid-state batteries (and other power storage devices including large-capacity capacitors such as electric double-layer batteries). In the following, when secondary batteries 12-1, 12-2, ..., 12-n are not distinguished, they will simply be referred to as secondary batteries 12. In this embodiment, the charge / discharge system 10 is equipped with three or more secondary batteries 12, but the charge / discharge system 10 may be equipped with fewer than three secondary batteries 12.

[0055] The charge / discharge system 50 includes second bidirectional DC / DC converters 15-1, 15-2, ..., 15-n. In the following, when the second bidirectional DC / DC converters 15-1, 15-2, ..., 14-n are not distinguished, they are simply referred to as DC / DC converter 15. In Figure 7, the second bidirectional DC / DC converter is simply referred to as DC / DC.

[0056] (Second bidirectional DC / DC converter) The DC / DC converter 15 has one end connected to the AC / DC converter 13 via a DC bus 16, and the other end connected to the secondary battery 12. The DC / DC converter 15 charges and discharges the secondary battery 12. The DC / DC converter 15 discharges the secondary battery 12 by outputting the power stored in the secondary battery 12 to the DC bus 16. The DC / DC converter 15 charges the secondary battery 12 by supplying DC power from the DC bus 16 to the secondary battery 12. The operation of the DC / DC converter 15 is controlled by the control device 20.

[0057] Furthermore, the DC / DC converter 15 detects various information about the secondary battery 12, including the voltage of the secondary battery 12, the charging power during charging, and the discharge power during discharging. The DC / DC converter 15 outputs the detected information about the secondary battery 12 to the control device 20.

[0058] (Charge / discharge mode during warm-up process) During the warm-up process, the control device 20 charges and discharges the first secondary battery 11 so that power sharing (energy sharing) occurs between the first secondary battery 11 and the second secondary battery 12.

[0059] Specifically, as shown in Fig. 8(a), when controlling the first secondary battery 11 to be in a charged state, the control device 20 controls the DC / DC converter 15 such that the electric power stored in the second secondary battery 12 is supplied to the first secondary battery 11 via the DC bus 16. Further, as shown in Fig. 8(b), when controlling the first secondary battery 11 to be in a discharged state, the control device 20 controls the DC / DC converter 15 such that the discharge power of the first secondary battery 11 is supplied to the second secondary battery 12 via the DC bus 16. The control device 20 controls the DC / DC converter 15 based on the input voltage of each second secondary battery 12 so that the voltages of the second secondary batteries 12 are uniform.

[0060] According to the charge-discharge system of the second embodiment, in addition to the effects described in (1-1) to (1-4) above, the following effects can be obtained. (2-1) The charge-discharge system 50 uses the electric power stored in the second secondary battery 12 when charging the first secondary battery 11 in the warm-up process. Further, when discharging the first secondary battery 11, the discharge power is used to charge the second secondary battery 12. As a result, the power supplied from the AC bus 3 to the DC bus 16 is reduced, so that the power consumption of the charge-discharge system 50 can be reduced.

[0061] The first and second embodiments can be modified and implemented as follows. The first and second embodiments and the following modified examples can be implemented in combination with each other within a technically consistent range.

[0062] · In the warm-up process, when the battery voltage V is equal to or higher than the determination voltage V1 (step S102: V≧V1), the control device 20 may temporarily interrupt the output of the electrical signal S1 from the signal generator 18. In such a configuration, the control device 20 temporarily interrupts the output of the electrical signal, for example, until the battery voltage V drops to a restart voltage V2 (V2<V1). In such a configuration, the determination voltage V1 may be the abnormal voltage Va.

[0063] During the warm-up process, the control device 20 may, in the signal modification process (step S104), control the electrical signal S1 based on the change in battery temperature T so that the current is maintained or reduced. For example, when the battery temperature T rises to near the target temperature T1, the control device 20 may, in the signal modification process, reduce the amplitude A by a unit amplitude amount ΔA or reduce the frequency f by a unit frequency Δf.

[0064] During the warm-up process, the control device 20 may control the electrical signal S1 output by the signal generator 18 so that power is shared among the first secondary batteries 11-1, 11-2, ..., 11-m. That is, the control device 20 controls the electrical signal S1 that the signal generator 18 outputs to the DC / DC converters 14-1, 14-2, ..., 14-m so that the discharge period of one first secondary battery 11 corresponds to the charging period of another first secondary battery 11. For example, the control device 20 controls the signal generator 18 so that it outputs the electrical signal S1 to DC / DC converter 14-1 and an inverted electrical signal of the electrical signal S1 to DC / DC converter 14-2. With this configuration, power consumption associated with the warm-up process can be reduced.

[0065] The electrical signal S1 can be any signal where the amplitude A is the magnitude of the current and the frequency f is the number of times the first secondary battery 11 is switched between charging and discharging per unit time. Therefore, the electrical signal S1 is not limited to a sine wave signal; for example, it may be a square wave signal. [Explanation of Symbols]

[0066] H10... Information processing device, H11... Communication device, H12... Input device, H13... Display device, H14... Memory device, H15... Processor, 3... AC bus, 4... AC power source, 5... Equipment, 10... Charge / discharge system, 11... Primary secondary battery, 12... Secondary secondary battery, 13... Bidirectional AC / DC converter, 14... Primary bidirectional DC / DC converter, 15... Secondary bidirectional DC / DC converter, 16... DC bus, 17... Temperature measuring instrument, 18... Signal generator, 20... Control device, 50... Charge / discharge system.

Claims

1. A bidirectional AC / DC converter having one end connected to an AC bus and the other end connected to a DC bus, A bidirectional DC / DC converter having one end connected to the DC bus and the other end connected to a secondary battery, A control device configured to control the operation of the bidirectional AC / DC converter and the operation of the bidirectional DC / DC converter in accordance with the surplus or deficiency of power in the DC bus, A voltage detector that detects the battery voltage of the secondary battery and inputs the detected battery voltage to the control device, A signal generator that outputs an electrical signal having an amplitude indicating the magnitude of the current flowing through the secondary battery and a frequency indicating the number of charge / discharge cycles of the secondary battery to the bidirectional DC / DC converter, The system includes a temperature measuring device that detects the battery temperature of the secondary battery and inputs the detected battery temperature to the control device, The control device monitors the battery voltage and performs a warm-up process that controls the electrical signal according to the battery voltage monitoring result to raise the temperature of the secondary battery. Charging and discharging system.

2. The control device is configured to increase the amplitude during the warm-up process, provided that the battery voltage is within the normal range. The charge / discharge system according to claim 1.

3. The control device is configured to increase the frequency during the warm-up process, provided that the battery voltage is within the normal range. The charge / discharge system according to claim 1.

4. The control device is configured to start inputting the electrical signal with an initial amplitude smaller than the maximum amplitude during the warm-up process, and to increase the amplitude to a size greater than the initial amplitude in response to an increase in frequency, provided that the battery voltage is within the normal range and the frequency exceeds a threshold. The charge / discharge system according to claim 3.

5. The aforementioned secondary battery is the first secondary battery, The aforementioned bidirectional DC / DC converter is the first bidirectional DC / DC converter, The system further comprises a second bidirectional DC / DC converter having one end connected to the DC bus and the other end connected to a second secondary battery. The control device is configured to supply charging power to the first secondary battery from the second secondary battery and discharge power to the second secondary battery by controlling the operation of the second bidirectional DC / DC converter in accordance with the electrical signal during the warm-up process. A charge / discharge system according to any one of claims 1 to 4.

6. A bidirectional AC / DC converter having one end connected to an AC bus and the other end connected to a DC bus, A bidirectional DC / DC converter having one end connected to the DC bus and the other end connected to a secondary battery, A method for warming up a secondary battery using a charge / discharge system comprising a control device configured to control the operation of the bidirectional AC / DC converter and the operation of the bidirectional DC / DC converter in accordance with the surplus or deficiency of power in the DC bus, A voltage detector that detects the battery voltage of the secondary battery and inputs the detected battery voltage to the control device, The charge / discharge system is provided with a signal generator that outputs an electrical signal having an amplitude indicating the magnitude of the current flowing through the secondary battery and a frequency indicating the number of charge / discharge cycles of the secondary battery to the bidirectional DC / DC converter, and a temperature measuring device that detects the battery temperature of the secondary battery and inputs the detected battery temperature to the control device. The control device monitors the battery voltage and performs a warm-up process that controls the electrical signal according to the battery voltage monitoring result to raise the temperature of the secondary battery. How to warm up a rechargeable battery.

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