JP2020120504A - Power storage system - Google Patents

Abstract

To provide a power storage system capable of avoiding a situation where a battery becomes difficult to use, due to temperature drop of an accumulator battery after charging.SOLUTION: A power storage system for controlling charging of an accumulator battery includes a temperature sensor for measuring the temperature of the accumulator battery, a charging section for charging the accumulator battery, and a control section for controlling the charging section to start and finish charging with a prescribed charge power. When the measurement results of the temperature sensor exceeds a prescribed temperature, the control section controls the charging section to perform charging with a first charging power, and when the measurement results of the temperature sensor go below the prescribed temperature, controls the charging section to start charging with a second charging power lower than the first charging power, and finishes charging so that the temperature of the accumulator battery does not go below a temperature at which the accumulator battery becomes inoperable.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power storage system, for example, a power storage system that controls charging of a storage battery installed outdoors.

BACKGROUND ART Conventionally, there has been considered an electric power system that includes a power generation facility that uses renewable energy such as sunlight and the like, and a power storage system having a storage battery unit (see Patent Document 1).

In such an electric power system, solar power generation is performed during the daytime when solar power generation is possible, and the storage battery unit is charged by the electric power generated by the solar power generation. At night when solar power cannot be used, the storage battery unit is charged by using late-night power.

JP, 2018-6097, A

By the way, in such an electric power system, when the battery temperature of the storage battery unit is lowered to the extent that it cannot operate as a battery (for example, 0° C. or less), there is a problem that even if an attempt is made to start the discharge, the discharge becomes difficult. Particularly in a system in which a storage battery unit is installed outdoors, it is expected that the temperature will be low, and therefore low temperature measures for the battery have been required.

As described above, when it becomes difficult to start the discharge of the battery due to the temperature of the environment being lowered in the middle of the night and the like, there is a problem that it becomes difficult to use the electric power stored in the storage battery unit.

The present invention has been made in consideration of the above points, and an object of the present invention is to provide a power storage system capable of suppressing difficulty in use of the storage battery due to temperature decrease of the storage battery after completion of charging. Is.

The power storage system of the present invention is a power storage system that controls charging of a storage battery, wherein a temperature sensor that measures the temperature of the storage battery, a charging unit that charges the storage battery, and the charging unit charges with predetermined charging power. And a control unit for controlling to start and end, the control unit, when the measurement result of the temperature sensor exceeds a predetermined temperature, while charging by the charging unit with the first charging power, When the measurement result of the temperature sensor is equal to or lower than a predetermined temperature, the charging power for the storage battery is started by the charging unit with the second charging power lower than the first charging power, and the temperature of the storage battery is reached. However, the charging is terminated so as not to fall below a temperature at which the storage battery becomes inoperable.

According to this configuration, the charging power is reduced to the second charging power to start charging at a low temperature when the measurement result of the temperature sensor is equal to or lower than the predetermined temperature, and the temperature of the storage battery is set to a temperature at which the storage battery becomes inoperable. By performing the charging control that terminates the charging so as not to fall below, it is possible to prevent the storage battery from falling to a temperature at which the storage battery becomes inoperable in a standby state in which the storage battery is not charged or discharged after the completion of charging. ..

Further, the power storage system of the present invention, in the above-mentioned configuration, is provided with a battery remaining amount measuring means for measuring a battery remaining amount of the storage battery, and the control unit measures the measurement result of the temperature sensor and the battery remaining amount measuring means. The second charging power is determined based on the result.

According to this configuration, it is possible to perform the charging control such that the battery is fully charged at the target charging end time by reducing the charging power to the charging power based on the battery remaining amount and the battery temperature.

Further, in the power storage system of the present invention, in the above configuration, when the measurement result of the temperature sensor is equal to or lower than the predetermined temperature, the control unit continues charging from the start of charging to a preset target charging end time. Then, charging power at which the battery is fully charged at the charging end target time is set as the second charging power.

According to this configuration, since the charging can be continued from the start of charging to the target charging end time, it is possible to prevent the charging from ending before the target charging end time and lowering the temperature of the storage battery.

According to the present invention, it is possible to provide a power storage system capable of avoiding difficulty in using a storage battery due to a decrease in temperature of the storage battery after completion of charging.

It is a connection diagram which shows the structure of the charge control apparatus which concerns on embodiment of this invention. It is a block diagram which shows the structure of the control part of the charge control apparatus which concerns on embodiment of this invention. It is a flowchart which shows the charge control processing procedure which concerns on embodiment of this invention. It is a characteristic curve figure which shows the battery temperature and charge amount when a storage battery is charged by the charge control of the low temperature mode which concerns on embodiment of this invention. It is a characteristic curve figure which shows the battery temperature and charge amount when a storage battery is charged by the charge control of the normal mode which concerns on embodiment of this invention. It is a characteristic curve figure which shows the battery temperature and charge amount when a storage battery is charged by the charge control of the low temperature mode which concerns on other embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
As shown in FIG. 1, a power storage system 10 according to this embodiment includes a bidirectional AC/DC converter 30 connected to an AC electric circuit 20 including a commercial power system 13 and a self-sustaining output system 14, and a bidirectional DC/DC converter 40. The storage battery 50 and the control unit 70 are provided.

The AC electric circuit 20 is provided with a noise filter 21 between the commercial power system 13 and the self-sustaining output system 14 and the bidirectional AC/DC converter 30. Switch circuits S1 and S2 are provided between the bidirectional AC/DC converter 30 and the commercial power system 13, so that the bidirectional AC/DC converter 30 and the commercial power system 13 can be opened and closed. .. Further, switch circuits S5 and S6 are provided between the bidirectional AC/DC converter 30 and the self-sustaining output system 14, so that the bidirectional AC/DC converter 30 and the self-sustaining output system 14 can be opened and closed. ing. Further, switch circuits S3 and S4 are provided between the commercial power system 13 and the self-sustaining output system 14 so that the mutual systems can be opened and closed.

The bidirectional AC/DC converter 30 includes an AC side capacitor C31, AC reactors L31 and L32, an inverter 33, and an intermediate capacitor C32. The inverter 33 is a bridge connection of the switching elements Q31 to Q34. Diodes D31, D32, D33, D34 are connected in parallel in opposite directions to the switching elements Q31, Q32, Q33, Q34, respectively. The diodes D31 to D34 may be parasitic diodes. The switching elements Q31 to Q34 can be turned on/off by the control unit 70. The switching elements Q31 to Q34 can use, for example, an IGBT (Insulated Gate Bipolar Transistor) in addition to a MOSFET (metal-oxide-semiconductor field-effect transistor). The control unit 70 includes, for example, a computer, and controls the switching elements Q31 to Q34 by executing a predetermined program stored in a storage unit (not shown).

The AC side capacitor C31 and the AC reactors L31 and L32 are LC filters that smooth the waveform switched by the inverter 33.

The bidirectional DC/DC converter 40 has a high side switching element Q41 and a low side switching element Q42, a DC reactor L41, and a DC side capacitor C41, and constitutes a chopper circuit. Diodes D41 and D42 are connected in parallel in opposite directions to the switching elements Q41 and Q42, respectively. The diodes D41 and D42 may be parasitic diodes.

The switching elements Q41 and Q42 can be turned on/off by the control unit 70. In addition to MOSFETs, for example, IGBTs or the like can be used for the switching elements Q41 and Q42. The control unit 70 controls the switching elements Q41 and Q42 by executing a predetermined program stored in the storage unit.

The bidirectional DC/DC converter 40 can be used bidirectionally and functions as a step-up chopper when the storage battery 50 is discharged and a step-down chopper when the storage battery 50 is charged. Further, the inverter 33 can function as a bidirectional AC/DC converter that performs not only conversion from direct current to alternating current but also conversion from alternating current to direct current.

The DC/DC converter 40 is provided with a battery state sensor 60 for measuring the state of the storage battery 50. The battery state sensor 60 has a temperature sensor such as a thermistor provided in the vicinity of the storage battery 50, and outputs the measurement value of the temperature sensor as the temperature measurement value of the storage battery 50. Further, the battery state sensor 60 has a voltage sensor and a current sensor that measure the voltage and current of the storage battery 50, and outputs the voltage measurement value and the current measurement value of the storage battery 50. Further, the battery state sensor 60 measures and outputs the remaining battery amount (charge amount) from the terminal voltage of the storage battery 50. The temperature sensor is not limited to being provided in the vicinity of the storage battery 50, and the temperature of the storage battery 50 may be indirectly measured based on the outside air temperature or the like.

The control unit 70 is connected to the battery state sensor 60 via a sensor I/F 74 by a signal line, and measures temperature, voltage, current, and battery level (charge amount) obtained from the battery state sensor 60. ON/OFF control of the switching elements Q41 and Q42 based on Specifically, the control unit 70 controls the switching elements Q41 and Q42 so that the charging power to the storage battery 50 reaches a predetermined charging power designated value at the preset charging start time. Then, after charging is started, the amount of charge is judged based on the voltage measurement value acquired from the battery state sensor 60, and when it is detected that the amount of charge reaches a specified value or 100% (full charge), charging is terminated. Control to do.

FIG. 2 is a block diagram showing the configuration of the control unit 70. As shown in FIG. 2, the control unit 70 includes a CPU 71, a ROM 72, a RAM 73, a sensor I/F 74, a converter I/F 75, a network I/F 76, a clock 77, and an operation input unit 78 on the bus BUS.

The RAM 73 stores information necessary for controlling the charging of the storage battery 50 described later. Specifically, the start time of the midnight power time zone that is the start of charging, the end time of the midnight power time zone that is the target time of charging end, the charging power for the normal mode as the charging power (the target voltage for the normal charging) (Value and current value), charging power for low temperature mode (target voltage value and current value for charging at low temperature), and the like are stored. In the present embodiment, the charging start time is set to the start time of the midnight power time zone, but the present invention is not limited to this, and the user may manually set the charging start time via the operation input unit 78, for example. Further, the ROM 72 stores a processing program and the like for performing charge control of the storage battery 50 described later.

FIG. 3 is a flowchart showing a charging control processing procedure by the control unit 70. As shown in FIG. 3, the control unit 70 acquires current time information indicating the current time from the clock 77 (step S10), and based on the acquired current time information and the charging start time information stored in the RAM 73. Then, it is determined whether or not the current time has reached the time to start charging (step S11). The charging start time information is information indicating the start time information of the midnight power time zone or the time arbitrarily set by the user.

When the current time has not reached the charging start time at which charging should be started, the CPU 71 of the control unit 70 obtains the time information again by obtaining a negative result in step S11 (step S10). On the other hand, when the current time has reached the charging start time at which charging should be started, the CPU 71 of the control unit 70 obtains a positive result in step S11, and moves the process from step S11 to step S12 and The battery temperature measurement value is acquired from the state sensor 60, and in the subsequent step S13, information on the current remaining battery level is acquired from the battery state sensor 60.

Then, the CPU 71 shifts the processing to step S14, and selects the charging mode based on the information acquired in steps S12 to S13 described above. Specifically, if the current battery temperature of the storage battery 50 (for example, the start time of the midnight power charge) is below a predetermined reference temperature (for example, 5° C.), the charging time is thereafter. Since it is predicted that the temperature will drop below 0°C during the (midnight time zone), the charging power in the low temperature mode in which the charging power is suppressed to be lower than the charging power in the normal charging power (first charging power) Select (second charging power). When the low temperature mode is selected, the CPU 71 shifts the processing from step S15 to step S16, and based on the current battery level of the storage battery 50, until the charging end time (for example, the midnight power charge application end time). Select the charging power that will be fully charged using all of the time. That is, the charging power which is suppressed to be lower than the normal charging power and which is fully charged at the target charging end time is selected. This option is stored in the RAM 73 in advance as charging power corresponding to parameters such as the current temperature at the start of charging, the current battery level, and the charging time. Incidentally, the charging power corresponding to these parameters is set on the basis of the result of test charging according to the specifications of the storage battery 50 and the environment (temperature). For example, the result obtained by performing a trial for each condition such as how much charging power is used for charging at a certain battery temperature and remaining battery level is stored in the RAM 73. To use.

With such selection of the charging power, for example, when charging with the charging power in the normal mode, charging is performed while maintaining the charging current of 10 A (ampere), while in the low temperature mode, 5 A (ampere). The choice is made to carry out the charging while keeping the charging current suppressed to a minimum. By selecting the charging power with the charging power kept low as described above, the charging time required to reach full charge can be extended as compared with the case of charging in the normal mode. That is, it is possible to prevent the battery from becoming fully charged and ending the charging before the charging end target time, and performing control so that the battery becomes fully charged and the charging ends at the charging end target time.

On the other hand, when the current battery temperature is equal to or higher than the reference temperature described above, the CPU 71 shifts the processing from step S15 to step S17 and selects the charging power in the normal mode. As a result, the normal charging power larger than the charging power selected in the low temperature mode is selected, so that the charging is allowed to end before the charging end target time.

By performing such a charge control process, it is possible to prevent the storage battery from entering a standby state (a state in which neither charging nor discharging) occurs due to termination of charging before the target charging end time at low temperature. it can. That is, the target charging end time is set to a time that coincides with the discharging start time, and if charging is controlled so that charging ends at the target charging end time, discharging will start immediately after charging ends. .. Accordingly, it is possible to prevent the storage battery 50 from becoming inoperable temperature (for example, 0° C. or less) due to heat generation of the storage battery 50 during charging/discharging, and the storage battery 50 cannot be used due to low temperature (both charging and discharging). It is possible to prevent falling into a difficult state.

FIG. 4 is a characteristic curve diagram showing the battery temperature and the charge amount of the storage battery 50 when the storage battery 50 is charged by the charge control in the low temperature mode in the present embodiment, and FIG. 5 shows the charging in the normal mode as a comparative example. It is a characteristic curve figure which shows the battery temperature and charge amount of the storage battery 50 when the storage battery 50 was charged by control. As shown in FIG. 4, when the charging of the storage battery 50 is started with the charging power selected for the low temperature mode at the charging start time t0, the charging amount of the storage battery 50 increases as shown by the charging amount curve L11. The degree of this increase is gentler than that in the case of charging with the charging power in the normal mode (charging power larger than the charging power in the low temperature mode) (charging amount curve L1 in FIG. 5).

As a result, the charging is continued without ending until the charging end target time t3 (end time of the midnight electric power time zone), and at the charging end target time t3, the battery is fully charged (charge amount 100%) and the charging is ended. Can be controlled. In this way, by continuing the charging until the charging end target time t3, the temperature of the storage battery 50 gradually rises from the charging start time t0 as shown by the temperature curve L12 (FIG. 4), and then the charging end. Until the target time t3, a substantially constant temperature will be maintained. Then, the charging end target time t3 is set to a time that coincides with the discharging start time, so that the discharging starts immediately after the charging ends. In this case, the temperature of the storage battery 50 maintains an increased state due to heat generation during charging and discharging, and does not decrease to 0° C. at which the storage battery 50 cannot operate.

On the other hand, when the battery is charged in the normal mode (FIG. 5 ), the charging power is larger than that in the low temperature mode, so that the temperature of the storage battery 50 changes to the low temperature mode as shown by the temperature curve L2 in FIG. It rises sharply in comparison. Then, as indicated by the charging amount curve L1 in the normal mode, the storage battery 50 becomes fully charged at the time t1 before the target charging end time t3, so that the storage battery 50 starts charging at the target charging time t3 (that is, from the target time t1). Until the discharge start time), the battery is in a standby state in which neither charging nor discharging is performed. As a result, the temperature of the storage battery 50 starts to drop after the time t1 when the battery is switched to the standby state, and falls below 0° C. at the time t2, for example. That is, at the time t3 when the discharge is started, the temperature of the storage battery 50 drops to 0° C. or less, which may make it difficult to shift to the discharge.

In the present embodiment, as the charging control of the storage battery 50, the low temperature mode can be selected, so that the charging is completed and the standby state is set before the charging end target time t3, as shown in FIG. This can be avoided, and thereby, it is possible to prevent the battery temperature of the storage battery 50 from dropping to 0° C. or lower at which it cannot operate at the discharge start time (charge end target time t3).

In the above-described embodiment, when the charging mode (normal mode or low temperature mode) is selected at the start of charging, the charging is continued in the selected charging mode until the target charging end time t3. However, the charging mode may be reviewed during charging.

Specifically, as shown in FIG. 6, the control unit 70 (FIG. 1) monitors the state where the storage battery 50 acquired from the battery state sensor 60 has a charged amount (battery level) of up to 70%, At that time (time tx in FIG. 6), the charging power is reviewed. In this case, the CPU 71 of the control unit 70 acquires the current time tx from the clock 77 and calculates the remaining time based on the current time tx and the target charging end time t3. Then, charging is started from the current charging amount of 70%, and the charging power is set again so as to be fully charged when the remaining time has elapsed (charging end target time t3). This charging power can be selected from the options stored in advance in the RAM 73 as charging power corresponding to parameters such as the current temperature, the current battery level, and the charging time.

By performing such resetting of the charging power, for example, when it is predicted that the charging power set at the charging start time t0 is less than the full charge at the charging end target time t3, By resetting the charging power with a large charging power, it is possible to perform the charging control so that the battery is fully charged at the target charging end time t3. As a result, for example, the temperature of the environment in which the storage battery 50 is installed is different from the temperature assumed as the low temperature mode, and the assumed charging condition differs from the actual charging condition, resulting in a difference in the target time for full charge. If there is a possibility, the charging state can be maintained until the charging end target time t3 by resetting the charging power. This prevents the storage battery 50 from shifting to a standby state and lowering its temperature to an unusable temperature (for example, a temperature lower than 0° C.) by ending charging before the predicted time. be able to.

Contrary to the case shown in FIG. 6, when the time when the charge amount is 70% is earlier than the scheduled time, the subsequent charging power is lower than the charging power up to that point. By resetting the value, it is possible to appropriately avoid the end of charging before the target charging end time according to the actual situation such as the temperature environment.

Further, in the above-described embodiment, the case where the charging mode (either the normal mode or the low temperature mode) is selected based on the current temperature of the storage battery 50 and the remaining battery level is described, but the present invention is not limited to this. Alternatively, for example, the temperature prediction information may be acquired from outside via the network I/F 76 (FIG. 2), and the charging mode may be selected based on the acquired temperature prediction information. Specifically, when the temperature is predicted to be lower than 0° C. between the charge start time and the charge end target time as the temperature prediction information, the low temperature mode is selected to select the temperature of the environment in which the storage battery 50 is installed. The charging power can be set according to the prediction. In particular, when the storage battery 50 is installed outdoors, by considering the prediction result of the outside temperature when selecting the charging mode, the temperature of the storage battery 50 is more likely to be affected by the outside temperature (outdoors, etc.). Charge control can be effectively performed.

Further, in the above-described embodiment, the case where charging is started at a predetermined time has been described, but the present invention is not limited to this. For example, the battery temperature of the storage battery 50 can be measured by the battery state sensor 60 before the start of charging. When the battery temperature of the storage battery 50 is monitored and becomes low (for example, 0° C. or a temperature slightly higher than 0° C.), the charging start time is determined in advance (before time t0 in FIG. 4). Even at the time), charging may be started. With this configuration, even when the temperature of the storage battery 50 has already dropped to a low temperature (for example, 0° C.) at which the storage battery 50 cannot operate (charge/discharge) at the start of charging, the storage battery 50 is reliably charged. be able to. In this case, the charging control process at the start of charging can be performed by selecting the charging power by the processing procedure described above with reference to FIG.

Further, in the above-described embodiment, the case has been described in which the battery temperature serving as a reference for selecting the low temperature mode at the start of charging is set to 5° C. or lower, but the reference temperature is not limited to this, and the point is that it is midnight after starting charging. A temperature (slightly higher than 0° C.) at which the temperature of the storage battery 50 in the standby state during the power time period is predicted to be equal to or lower than the temperature (for example, 0° C.) at which the charge/discharge operation of the storage battery 50 becomes difficult. May be used as a reference temperature for mode selection at the start of charging.

10 Storage System 13 Commercial Power System 14 Independent Output System 20 AC Circuit 30 AC/DC Converter 40 DC/DC Converter 50 Storage Battery 60 Battery State Sensor 70 Control Unit

Claims (3)

A power storage system for controlling charging of a storage battery,
A temperature sensor for measuring the temperature of the storage battery,
A charging unit that charges the storage battery,
A control unit that controls the charging unit to start and end charging with predetermined charging power;
When the measurement result of the temperature sensor exceeds a predetermined temperature, the control unit performs charging by the charging unit with the first charging power, and when the measurement result of the temperature sensor is equal to or lower than the predetermined temperature. Starts charging by the charging unit with second charging power that is lower than the first charging power to charge the storage battery so that the temperature of the storage battery does not fall below a temperature at which the storage battery becomes inoperable. A power storage system characterized by terminating charging. A battery residual amount measuring means for measuring the battery residual amount of the storage battery,
The control unit is
The power storage system according to claim 1, wherein the second charging power is determined based on a measurement result of the temperature sensor and a measurement result of the battery residual amount measuring unit. The control unit is
When the measurement result of the temperature sensor is equal to or lower than the predetermined temperature, charging is continued from the start of charging to a preset charging end target time, and the charging power for fully charging at the charging end target time is the second charging power. The power storage system according to claim 1 or 2, wherein the charging power is set as the charging power of the power storage system.

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