JP2012253849A - Power storage system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage system for easy suppression of frequent switching of charging/discharging in each battery element.SOLUTION: The power storage system includes a battery part containing a plurality of battery elements for charging/discharging. It includes an operation mode setting part which sets an operation mode, in other words a charge operation for charging the battery part or a discharge operation for discharging, being switchable to be one of a first mode and a second mode. In the first mode, the entire or a part of a plurality of battery elements is used for charge operation while other battery elements are not used for the discharge operation, otherwise, the entire or a part of the plurality of battery elements is used for discharge operation while other battery elements are not used for the charge operation. In the second mode, the plurality of battery elements are classified into charging elements and discharging elements, and the charging elements are used for the charge operation while the discharging elements are used for the discharge operation.

Description

  The present invention relates to a power storage system that performs power storage.

  2. Description of the Related Art Conventionally, a power storage system has been proposed in which generated power such as a solar battery is stored in a storage battery, and the stored power is supplied to consumers. Generally, in a power storage system, when the generated power exceeds the power demand, the storage battery is charged to store the surplus power, and in the reverse situation, the storage battery is discharged to supply power to the consumer. Is called.

  Thus, for example, it is possible to store the generated power of the solar cell during the day and supply the stored power at night. In general, a storage battery is a battery element (for example, a battery cell or a battery in which a plurality of battery cells are connected) that can be charged / discharged due to an increase in charge / discharge capacity or the like. Are provided). Each of the battery elements is integrally used. When the storage battery is charged, the entire battery element is used for charging, and when the storage battery is discharged, the entire battery element is used for discharging.

  Patent Document 1 discloses a conventional example related to a power storage system. In this conventional example, the charging / discharging operation of the charging / discharging element is switched based on a comparison between the output of a DC power source such as a solar battery and its target value. As a result, it is possible to absorb fluctuations in the generated power of the DC power source due to fluctuations in solar radiation, etc., and suppress fluctuations in the reverse power flow to the system.

Japanese Patent Laid-Open No. 2001-5543

  When the power storage system is used, for example, under a situation where the generated power and the power demand are antagonized, charging / discharging of the storage battery is frequently switched, and charging / discharging is frequently switched in each battery element. This may lead to a reduction in the life of the storage battery, complication of control associated with charge / discharge switching, and power loss.

  In view of the above-described problems, an object of the present invention is to provide a power storage system that can easily suppress frequent switching between charging and discharging in each battery element.

  In order to achieve the above object, a power storage system according to the present invention includes a battery unit having a plurality of battery elements that can be charged and discharged, and charging operation for charging and storing input power in the battery unit, and the battery A power storage system that performs a discharge operation of discharging and outputting electric power stored in the unit, wherein the operation mode of the power storage system is set to be switchable between the first mode and the second mode. In the first mode, all or a part of the plurality of battery elements are used for the charging operation, and other battery elements are not used for the discharging operation, or the plurality of battery elements Are used for the discharging operation, and other battery elements are not used for the charging operation. Tteri element is separated to the discharging element and the charging element, the charging element is used in the charging operation, and a form in which discharge elements are used configuration in the discharge operation.

  According to this configuration, for example, the operation mode is set to the second mode in a period (for example, an antagonistic period referred to in the description of the present embodiment) in which charging / discharging of the battery unit is frequently switched. In this way, it is possible to suppress frequent switching between charging and discharging in each battery element.

  In the above configuration, the operation mode setting unit may switch the operation mode according to the magnitude of the input power. More specifically, as the configuration, surplus power out of the power generated by the distributed power supply is input, and the operation mode setting unit switches the operation mode according to the magnitude of the surplus power. It is good also as a structure. More specifically, the operation mode setting unit may be configured to switch the operation mode according to the current time.

  More specifically, in the situation where the operation mode is the second mode, the battery is separated into the charging elements using the electric power stored in the battery elements separated into the discharging elements. It may be configured to increase the charging current of the battery element.

  More specifically, in the situation where the operation mode is the first mode, the electric power stored in the battery element that is separated into the charging element when the second mode is entered next is Alternatively, the battery may be moved to the battery element that is sorted into the discharging element when the second mode is set.

  More specifically as the above configuration, as a first mode, a charging mode in which all or a part of the plurality of battery elements are used for the charging operation and other battery elements are not used for the discharging operation, and In addition, all or a part of the plurality of battery elements are used for the discharge operation, and other battery elements are provided with both discharge modes that are not used for the charge operation. The operation mode may be configured to be switchable to any one of the charge mode, the discharge mode, and the second mode.

  More specifically, as the above configuration, the battery element and the discharge element that are separated into the charging elements between when the charge mode is switched to the second mode and when the discharge mode is switched to the second mode are used. It is good also as a structure which reverses the battery element sorted into an element.

  As described above, according to the power storage system of the present invention, it is possible to suppress frequent switching between charging and discharging in each battery element.

It is a lineblock diagram of an electric power system which has an electrical storage system concerning a 1st embodiment of the present invention. It is a flowchart regarding the operation | movement in charge / discharge combined mode. It is a flowchart regarding the operation | movement in charge mode. It is a flowchart regarding the operation | movement in discharge mode. It is explanatory drawing regarding the operation | movement form of the said electrical storage system. It is a block diagram of an electric power system which has an electrical storage system which concerns on 2nd Embodiment of this invention.

  A power storage system according to an embodiment of the present invention will be described below with reference to the drawings, taking the first embodiment and the second embodiment as examples.

1. First Embodiment [Configuration of power system including power storage system]
First, the first embodiment will be described. FIG. 1 illustrates a configuration example of a power system including the power storage system according to the present embodiment. As shown in the figure, the power system 9 includes a power storage system 1 according to the present embodiment, a solar cell (PV) 2, a power conditioner (power conditioner) 3, a distribution board 4, a load 5 at a consumer, and a power system. 6 etc.

  The power storage system 1 stores externally supplied power (surplus power of the generated power of the solar battery 2) in the battery unit 11, and the stored power is externally supplied to the load 5 via the power conditioner 3 or the like. ) A system configured to discharge. The configuration and operation of the power storage system 1 will be described in detail again.

  The solar cell 2 is formed from a solar cell panel or the like, and is a device that generates electric power by photoelectrically converting received sunlight. The solar cell 2 is connected to the power storage system 1 and the power conditioner 3, and can generate generated power (DC power). It can be said that the solar cell 2 is one form of a distributed power source.

  The power conditioner 3 is connected to the solar cell 2 and the distribution board 4, and has a function of converting the DC power received from the solar cell 2 to AC and sending it to the distribution board 4. The power conditioner 3 is also connected to the power storage system 1 and has a function of converting the DC power received from the power storage system 1 into AC and sending it to the distribution board 4. In addition, a load 5 and a power system 6 are connected to the distribution board 4, and power obtained from the power conditioner 3 and the power system 6 can be supplied to the load 5. The load 5 corresponds to various electric devices (such as lighting devices) that consume power. Further, as shown in FIG. 1, the distribution board 4 is connected to an outlet of a commercial power source, and an electric device connected to the outlet is also included in the load 5.

  The power system 9 generally operates as follows according to the control mainly performed by the power conditioner 3. In a situation where the amount of power generated by the solar cell 2 (hereinafter referred to as “power generation amount”) does not exceed the amount of power consumed by the load 5 (hereinafter referred to as “demand amount”), the generated power of the solar cell 2 Almost all of these are sent to the load 5.

  At this time, the shortage of power in the load 5 (difference between the demand amount and the power generation amount) is compensated by the power stored in the power storage system 1 being sent to the load 5 through the power conditioner 3. At this time, the power storage system 1 discharges the electric power stored in the battery unit 11 and outputs it to the power conditioner 3. If the shortage is still not resolved, the shortage can be resolved by supplying power from the power system 6.

  On the other hand, in a situation where the power generation amount exceeds the demand amount, surplus power (the difference between the power generation amount and the demand amount) of the generated power of the solar cell 2 is sent to the load 5 in accordance with the demand amount. And may be simply referred to as “surplus power” hereinafter). At this time, the power storage system 1 charges the battery unit 11 to store the input surplus power. For example, when the battery unit 11 is fully charged, the surplus power may flow backward to the power system 6 (power is sold).

[Detailed configuration of power storage system]
Next, the detailed configuration of the power storage system 1 will be described with reference to FIG. As shown in the figure, the power storage system 1 includes a battery unit 11, a DC-DC converter 12, a control unit 13, current measuring units (15a, 15b), and switches (SW1 to SW4).

  The battery unit 11 includes a first battery BAT1, a second battery BAT2, and a battery converter (having a DC-DC converter function) 11a. Each battery (BAT1, BAT2) has a form in which a plurality of battery cells BS are connected in series, and can be charged and discharged.

  The battery converter 11a is connected to each battery (BAT1, BAT2), and can move the power stored in one battery to the other battery. Moreover, the converter 11a for batteries has a connection line for every battery cell BS in each battery (BAT1, BAT2), and can control the storage amount for each battery cell BS. Thereby, the battery converter 11a can perform an initial operation described later.

  The DC-DC converter 12 has an input side connected to a line connecting the solar cell 2 and the power conditioner 3, and an output side wired to the first battery BAT1 and the second battery BAT2. The wiring connecting the DC-DC converter 12 and the first battery BAT1 is a charging wiring corresponding to the first battery BAT1, and the wiring connecting the DC-DC converter 12 and the second battery BAT2 corresponds to the second battery BAT2. This is a wiring for charging. Surplus power is input to the DC-DC converter 12, and this surplus power is sent to each battery (BAT1, BAT2) as charging power via each charging wire.

  The first battery BAT1 and the second battery BAT2 are also connected to the power conditioner 3 by wiring. The wiring connecting the first battery BAT1 and the power conditioner 3 is a discharging wiring corresponding to the first battery BAT1, and the wiring connecting the second battery BAT2 and the power conditioner 3 is a discharging wiring corresponding to the second battery BAT2. The electric power discharged from each battery (BAT1, BAT2) is output to the power conditioner 3 via each discharge wiring.

  Here, the DC-DC converter 12 shown in FIG. 1 has a terminal that is connected to the first battery BAT1 and a terminal that is connected to the second battery BAT2, but these terminals are made common to be the same. May be. Similarly, the power conditioner 3 shown in FIG. 1 has a terminal that is connected to the first battery BAT1 and a terminal that is connected to the second battery BAT2, but these terminals are shared and are the same. May be.

  Each switch (SW1 to SW4) plays a role of switching between conduction (ON) and non-conduction (OFF) of the charging wiring or discharging wiring. More specifically, the switch SW1 switches ON / OFF of the charging wiring corresponding to the first battery BAT1. The switch SW2 switches ON / OFF the discharge wiring corresponding to the first battery BAT1. The switch SW3 switches on / off the charging wiring corresponding to the second battery BAT2. The switch SW4 switches ON / OFF the discharge wiring corresponding to the second battery BAT2.

  When the switch SW1 is ON and the switch SW2 is OFF, the first battery BAT1 is used for charging surplus power, but is not used for discharging to the power conditioner 3. On the other hand, when the switch SW1 is OFF and the switch SW2 is ON, the first battery BAT1 is used for discharging to the power conditioner 3, but is not used for charging surplus power.

  When the switch SW3 is ON and the switch SW4 is OFF, the second battery BAT2 is used for charging surplus power, but is not used for discharging to the power conditioner 3. On the other hand, when the switch SW3 is OFF and the switch SW4 is ON, the second battery BAT2 is used for discharging to the power conditioner 3, but is not used for charging surplus power.

  The control unit 13 has a function of determining which period of the “power generation amount advantage period”, “demand amount advantage period”, and “antagonism period” belongs to. The “power generation advantage period” is a period in which the power generation amount stably exceeds the demand amount, and the magnitude relationship between the power generation amount and the demand amount is expected to hardly change. The “demand amount dominant period” is a period in which the demand amount exceeds the power generation amount relatively stably and the magnitude relationship between the power generation amount and the demand amount is expected to hardly change.

  In addition, the “competition period” is a period in which the demand amount and the power generation amount are relatively antagonistic, and the magnitude relationship between the power generation amount and the demand amount is likely to change frequently. That is, the “antagonizing period” is a period in which the power generation amount is likely to be less than the demand amount compared to the “power generation amount advantage period”, and the demand amount is likely to be less than the power generation amount compared to the “demand amount advantage period”.

  From the viewpoint of the power storage system 1, the “power generation amount advantage period” is a period in which power that can be used for charging the battery unit 11 is stably input and power output by discharging the battery unit 11 is almost unnecessary. It can be said that. Similarly, it can be said that the “demand amount dominant period” is a period in which almost no electric power that can be used for charging the battery unit 11 is input and output of electric power by discharging the battery unit 11 is particularly required. Similarly, the “competitive period” includes a situation in which a relatively small amount of power that can be used for charging the battery unit 11 is input and a situation in which a relatively small amount of power output from the discharge of the battery unit 11 is required. It can be said that this is a period that changes at short intervals.

  In addition, various forms may be adopted for the procedure for determining which of the “power generation advantage period”, “demand amount advantage period”, and “antagonism period” the current time belongs to. Is possible. Specific examples of the form include the following first and second examples.

  The first example is an example in which information on the amount of surplus power is used. When this example is adopted, the control unit 13 monitors the amount of surplus power input from the solar cell 2. When the surplus power exceeds a predetermined threshold, it is determined that the current time belongs to the “power generation advantage period”. On the other hand, when the state where the surplus power is zero continues for a predetermined time or more, it is determined that the current time belongs to the “demand amount dominant period”. If none of these applies, it is determined that the current time belongs to the “competition period”.

  The second example is an example using information on the current time. When this example is adopted, the control unit 13 indicates the time zone correspondence information indicating which time zone each of the “power generation advantage period”, the “demand amount advantage period”, and the “competition period” corresponds to. have. The time zone correspondence information is, for example, “power generation advantage period” is “time zone from 9 am to 3 pm”, and “demand amount advantage period” is “time zone from 6 pm to 6 am The “competitive period” is a time zone that does not correspond to any of these. Generally, with regard to power generation and demand, the tendency of how to change during the day is empirically known, so it is possible to provide such time zone correspondence information in advance. .

  Then, the control unit 13 monitors the current time using the clock function, and determines which period the current time belongs to based on the current time and the above-described time zone correspondence information. The amount of power generation may change depending on the season and weather. For example, the amount of solar radiation increases because the amount of solar radiation increases near the summer, and the amount of solar power decreases because the amount of solar radiation decreases as the day is cloudy. Therefore, it is desirable that the time zone correspondence information is appropriately corrected in accordance with information such as the season and weather at that time.

  Moreover, the control part 13 transmits the result of discrimination | determination to which period the present time belongs to the battery converter 11a. Thereby, the battery converter 11a can perform an operation according to the result of the determination. The control unit 13 controls ON / OFF switching of each switch (SW1 to SW4) according to the determination result. How each switch (SW1 to SW4) is switched will be apparent from the following description.

  The current measuring unit 15a is provided at a common portion of the charging wiring and the discharging wiring corresponding to the first battery BAT1, and measures the charging / discharging current of the first battery BAT1. The current measuring unit 15b is provided in a common portion of the charging wiring and the discharging wiring corresponding to the second battery BAT2, and measures the charging / discharging current of the second battery BAT2. Information on measurement results of the respective current measurement units (15a, 15b) is transmitted to the battery converter 11a. Each current measuring part (15a, 15b) is formed using, for example, a shunt resistor or a hall sensor.

  Further, the battery converter 11 a has a function of restricting charging / discharging of the battery unit 11 according to the amount of power stored in the battery unit 11 in order to prevent overcharge and overdischarge of the battery unit 11. More specifically, the battery converter 11a determines the latest SOC of the battery unit 11 based on the measurement result of each current measurement unit (15a, 15b) (for example, using the integrated value of the current charge / discharge current). [State Of Charge: battery remaining amount] is continuously estimated.

  When this SOC reaches a predetermined upper limit value Emax, the battery converter 11a notifies the DC-DC converter 12 via the control unit 13 so that the battery unit 11 is no longer charged. To be notified. As a result, the DC-DC converter 12 operates so as not to flow a charging current to the battery unit 11. When the SOC reaches a predetermined lower limit value Emin, the battery converter 11a notifies the power conditioner 3 via the control unit 13 so that the battery unit 11 is no longer discharged. . As a result, the power conditioner 3 operates so that a discharge current does not flow from the battery unit 11. Thereby, the overcharge and overdischarge of the battery part 11 are prevented. In the present embodiment, as described above, the battery converter 11a has a function of preventing overcharge and overdischarge, but other devices may have the function.

  The battery converter 11a has a function of performing a cell balance operation. The cell balance operation is an operation for moving the electric power for each battery cell BS to equalize the storage amount of the battery cells BS in the same battery. By performing the cell balance operation, the state of charge of each battery (BAT1, BAT2) is optimized, and the function of each battery can be fully exhibited.

[Operation of power storage system]
Next, the operation of the power storage system 1 will be described. As a basic operation, the power storage system 1 performs a charging operation in which surplus power is charged and stored in the battery unit 11, and a discharging operation in which the power stored in the battery unit 11 is discharged and output to the power conditioner 3 side.

  As the operation mode of the power storage system 1, “charge mode”, “discharge mode”, and “charge / discharge combined mode” are prepared, and any one of these is set to be switchable. Yes. The power storage system 1 operates according to the currently set operation mode. The main operation flow for each of these operation modes will be described below.

  First, the flow of operation in the charge / discharge mode will be described with reference to the flowchart shown in FIG. When the operation mode is switched from the charging mode to the charge / discharge combined mode (“charging mode” in step S11), the control unit 13 turns on the switches SW2 and SW3 and turns off the switches SW1 and SW4 (step S11). S12).

  When the switch SW2 is turned on, the first battery BAT1 is wired to the power conditioner 3. As a result, the discharge toward the power conditioner 3 can be performed using the first battery BAT1. Further, when the switch SW3 is turned ON, the second battery BAT2 is wired to the DC-DC converter 12. As a result, surplus power can be charged using the second battery BAT2.

  In addition, it is avoided that the surplus electric power is charged using the first battery BAT1 by turning off the switch SW1. That is, the first battery BAT1 is used as a “discharge battery” used exclusively for discharging. Further, when the switch SW4 is turned off, the discharge toward the power conditioner 3 using the second battery BAT2 is avoided. That is, the second battery BAT2 is used as a “charging battery” used exclusively for charging.

  On the other hand, when the operation mode is switched from the discharge mode to the charge / discharge combined mode (“discharge mode” in step S11), the control unit 13 turns on the switches SW1 and SW4 and turns off the switches SW2 and SW3. (Step S13).

  When the switch SW1 is turned on, the first battery BAT1 is wired to the DC-DC converter 12. As a result, surplus power can be charged using the first battery BAT1. Further, when the switch SW4 is turned on, the second battery BAT2 is connected to the power conditioner 3 by wiring. As a result, the discharge toward the power conditioner 3 can be performed using the second battery BAT2.

  Note that the discharge toward the power conditioner 3 using the first battery BAT1 due to the switch SW2 being turned off is avoided. That is, the first battery BAT1 is used as a “charging battery” used exclusively for charging. Further, the charging of surplus power using the second battery BAT2 is avoided by turning off the switch SW3. That is, the second battery BAT2 is used as a “discharge battery” exclusively used for discharging.

  By the operation in step S12 or S13, the first battery BAT1 and the second battery BAT2 are separated into a charging battery and a discharging battery. A charging battery is used for the operation (charging operation) for charging the surplus power to the battery unit 11, and the discharging battery is used for the operation (discharging operation) for discharging the electric power stored in the battery unit 11 to the power conditioner 3 side. Will be used.

  Therefore, even if the magnitude relationship between the power generation amount and the demand amount changes frequently, a situation where charging / discharging is switched in each battery (used alternately for charging and discharging) is avoided. Thus, the charge / discharge combined mode is an operation mode particularly suitable for an antagonistic period in which the magnitude relationship between the power generation amount and the demand amount is likely to change frequently.

  Further, after performing the operation of step S12 or S13, the control unit 13 monitors whether or not the power generation advantage period has arrived (step S14) and whether the demand amount advantage period has arrived (step S15). When the power generation amount advantage period has arrived (Y in step S14), the operation mode of the power storage system 1 is switched to the charging mode, and when the demand amount advantage period has come (Y in step S15), the power storage system. The operation mode 1 is switched to the discharge mode.

  Next, the flow of operation in the charging mode will be described with reference to the flowchart shown in FIG. When the operation mode is switched from the charge / discharge mode to the charge mode, the control unit 13 turns on at least one of the switches SW1 and SW3 and turns off the switches SW2 and SW4 (step S21).

  When at least one of the switches SW1 and SW3 is turned on, at least one of the first battery BAT1 and the second battery BAT2 is wired to the DC-DC converter 12. As a result, at least one of the first battery BAT1 and the second battery BAT2 is used for charging the surplus power. That is, the charging mode is an operation mode in which the whole or a part of the plurality of batteries (BAT1, BAT2) included in the battery unit 11 is used for the charging operation.

  For example, in a situation where the charging state of each battery is to be adjusted, the control unit 13 turns on one of the switches SW1 and SW3 (only one battery is used for the charging operation). Both SW3 are set to ON (both batteries are used for the charging operation). As a form of charge state adjustment, both batteries (BAT1, BAT2) are adjusted to a state where they can be used for charging at the same time when the supply power peak is reached. Adjust the charge amount of the battery on the discharge side for the next charge / discharge mode (adjust the charge amount so that one can maintain discharge during the charge / discharge mode) The form etc. are mentioned.

  Note that when both batteries are used, it is possible to charge large power more efficiently than when only one of the batteries is used. Thus, the operation mode in which both batteries are used is an operation mode particularly suitable for a situation where the battery unit 11 should be charged with high power as efficiently as possible (for example, at the time of supply power peak). In addition, it is avoided that surplus electric power flows toward the power conditioner 3 by turning off the switches SW2 and SW4. Accordingly, a reduction in charging efficiency can be suppressed, and unnecessary power consumption can be suppressed by completely stopping the function of supplying the battery power to the load in the power conditioner 3.

  Further, after performing the operation of step S21, the control unit 13 monitors whether or not the above-described antagonistic period has arrived (step S22). When the antagonistic period has arrived, after the initial operation is executed by the battery converter 11a (step S23), the operation mode of the power storage system 1 is switched to the charge / discharge mode.

  In the initial operation, the electric power stored in the battery (one of the first battery BAT1 and the second battery BAT2) that is sorted into the charging battery when the charge / discharge combined mode is entered next is charged next. This is an operation of moving to a battery (the other of the first battery BAT1 and the second battery BAT2) that is sorted into a discharge battery when the discharge combined mode is set. In the initial operation in step S23, since the second battery BAT2 is then separated into charging batteries (see steps S11 and S12), the electric power stored in the second battery BAT2 is stored in the first battery BAT1. Will be moved to.

  According to the initial operation, the electric power in the battery unit 11 is biased toward the discharging battery so that the amount of charge stored in the discharging battery is more sufficient, and the discharging operation in the next charge / discharge mode is more stable. It becomes possible to make it. Note that the amount of power transfer in the initial operation and the state of charge (SOC) of the battery unit 11 can be appropriately set in advance.

  Next, the flow of operation in the discharge mode will be described with reference to the flowchart shown in FIG. When the operation mode is switched from the charge / discharge combined mode to the discharge mode, the control unit 13 turns on at least one of the switches SW2 and SW4 and turns off the switches SW1 and SW3 (step S31).

  When at least one of the switches SW2 and SW4 is turned on, at least one of the first battery BAT1 and the second battery BAT2 is wired to the power conditioner 3. As a result, at least one of the first battery BAT1 and the second battery BAT2 is used for discharging toward the power conditioner 3. That is, the discharge mode is an operation mode in which the whole or a part of the plurality of batteries (BAT1, BAT2) included in the battery unit 11 is used for the discharge operation.

  For example, in a situation where the state of charge of each battery is to be adjusted, the control unit 13 turns on one of the switches SW2 and SW4 (only one battery is used for the discharge operation), and in the other situation, the switch SW2 and the switch SW2 Both SW4 are set to ON (both batteries are used for discharging operation). As a form of charge state adjustment, adjust the charge amount of the battery on the discharge side for the next charge / discharge mode (adjust the charge amount so that one can maintain discharge during the charge / discharge mode) And a mode in which the amount of charge is adjusted in order to maintain a state in which both batteries (BAT1, BAT2) can be discharged at the same time when a high power discharge power peak occurs.

  When both batteries are used, it is possible to discharge large power more efficiently than when only one of the batteries is used. Thus, the operation mode in which both batteries are used is an operation mode particularly suitable for a situation where the battery unit 11 should discharge a large amount of power as efficiently as possible (for example, at the time of peak discharge power). It is to be noted that the discharge power does not flow toward the DC-DC converter 12 by turning off the switches SW1 and SW3. As a result, a reduction in discharge efficiency is suppressed, and unnecessary power consumption is suppressed by completely stopping the operation of the DC-DC converter 12.

  Moreover, after performing the operation | movement of step S31, the control part 13 monitors whether the antagonistic period mentioned above has arrived (step S32). When the antagonistic period has arrived, after the initial operation described above is executed by the battery converter 11a (step S33), the operation mode of the power storage system 1 is switched to the charge / discharge mode.

  In the initial operation in step S33, the first battery BAT1 is then separated into charging batteries (see steps S11 and S13), so that the electric power stored in the first battery BAT1 is stored in the second battery. It will be moved to BAT2.

  In this embodiment, the initial operation is executed in both the charge mode and the discharge mode, but may be executed only in one of them. The timing at which the initial operation is performed is not limited to just before switching to the charge / discharge mode, but can be any time in the charge mode or the discharge mode.

  How the operation mode of the power storage system 1 changes during the day by performing the series of operations described above (steps S11 to S33) will be described with reference to FIG. The upper side of FIG. 5 shows an example of a graph showing the transition of the power generation amount (shown by a solid line) and the demand amount (shown by a broken line) during the day. The lower side of FIG. Correspondingly, the operation mode of the power storage system 1 changes. Further, the portion surrounded by the broken line on the upper side of FIG. 5 represents a more detailed state of a part of the graph.

  As shown on the upper side of FIG. 5, the amount of power generation is almost zero at night when the sun does not appear, which is the demand amount dominant period. And when the sun rises and the amount of power generation gradually increases, it will eventually become an antagonistic period. After that, if the amount of power generation exceeds the amount of demand, and the amount of power generation further increases, the power generation amount dominant period will eventually come. And after noon, when the amount of power generation gradually decreases, it will eventually become an antagonistic period. After that, if the power generation amount falls below the demand amount, and the power generation amount further decreases, it will eventually become a demand amount dominant period.

  As shown in the lower part of FIG. 5, as shown in the lower side of FIG. 5, the power storage system 1 changes as “(demand amount advantage period) → competition period → power generation amount advantage period → antagonism period → demand amount advantage period”. The operation mode changes as follows: “(discharge mode) → charge / discharge combined mode → charge mode → charge / discharge combined mode → discharge mode”. In other words, the power storage system 1 takes an appropriate operation mode according to which period the current time belongs.

  Further, when switching from the charging mode to the charge / discharge mode, the power storage system 1 separates the first battery BAT1 into a discharging battery and the second battery BAT2 into a charging battery. In addition, when the storage system 1 is switched from the discharge mode to the charge / discharge combined mode, the first battery BAT1 is sorted into a charging battery, and the second battery BAT2 is sorted into a discharging battery.

  In other words, the power storage system 1 separates the battery into the charge battery and the discharge battery between when the charge mode is switched to the charge / discharge combined mode and when the discharge mode is switched to the charge / discharge combined mode. The battery to be turned is reversed. Thereby, it becomes easy to stabilize the discharge operation by biasing the power in the battery unit 11 toward the discharge battery. In the power storage system 1, ON / OFF control of each switch (SW 1 to SW 4) is performed by adjusting the power distribution of the charging power and discharging power to each battery (BAT 1, BAT 2) in the charge / discharge combined mode. Is realized.

2. Second Embodiment Next, a second embodiment will be described. Note that the second embodiment is provided with a function of reducing an error in estimating the state of charge (SOC) of the battery unit 11 in order to perform charge / discharge control while preventing overcharge and overdischarge of the battery unit 11. Except for this point and the points related thereto, this is basically the same as the first embodiment. In the following description, emphasis is placed on the description of parts different from the first embodiment, and description of the same parts as in the first embodiment may be omitted.

  FIG. 6 illustrates a configuration example of a power system including the power storage system according to the present embodiment. As shown in the figure, the power storage system 1 includes a battery unit 11, a DC-DC converter 12, a control unit 13, current measurement units (15a, 15b), and switches (SW1 to SW4). The battery converter 11a is provided with a current adjusting unit 17.

  Here, the error rate of the measurement result of each current measurement unit (15a, 15b) increases as the current to be measured decreases. Therefore, if the measurement target current continues to be small, the SOC estimation error increases, and a large deviation may occur between the estimated SOC value and the actual value.

  When such a shift cannot be prevented, it is necessary to excessively increase the control margin in order to ensure proper charge / discharge (avoidance of overcharge and overdischarge) according to the SOC. . As a result, the allowable range of SOC becomes narrow, and it becomes difficult to make full use of the battery performance.

  In particular, during the antagonism period, surplus power is reduced because the power generation amount and the demand amount are antagonizing, and the charging current of the charging battery (which can be said to be a measurement target of the current measuring unit on the charging battery side) tends to be minute. . Therefore, in the present embodiment, the current adjustment unit 17 is provided so that the charging current of the charging battery is increased during the antagonistic period so that the estimation error of the SOC is suppressed as much as possible.

  The current adjustment unit 17 has one end on the middle of the charging wiring corresponding to the first battery BAT1 (point A shown in FIG. 6) and the other end on the middle of the charging wiring corresponding to the second battery BAT2 (see FIG. 6). Are connected to point B) shown in FIG. The point A is set closer to the DC-DC converter 12 than the current measuring unit 15a. The point B is set closer to the DC-DC converter 12 than the current measuring unit 15b.

  When the current time belongs to the antagonistic period, the current adjustment unit 17 connects the wiring on the charging battery side (one of the points A and B) to the wiring on the charging battery side (of the points A and B). A predetermined amount of current is supplied to the other side. For example, when the second battery BAT2 is sorted into a discharging battery and the first battery BAT1 is sorted into a charging battery, a predetermined amount of current flows from point B to point A. Become.

  Thereby, a part or all of the discharge current of the discharging battery is added to the charging current for charging the charging battery (current of surplus power). That is, the charging current of the charging battery is increased using the electric power stored in the discharging battery. As a result, a state in which the charging current is very small is avoided, and the above-described SOC estimation error is suppressed as much as possible.

  Further, during the antagonistic period, the discharge current of the discharge battery (which can also be said to be a measurement target of the current measurement unit on the discharge battery side) tends to be minute. Therefore, the current adjusting unit 17 increases the charging current as described above when the charging current is very small. On the other hand, when the discharging current is very small, the current adjusting unit 17 increases the discharging current of the discharging battery (the increased amount is the discharging current). After passing through the current measuring unit on the battery side, the battery flows from the wiring on the discharging battery side to the wiring on the charging battery side and is charged to the charging battery).

  In addition, when the charging current or the discharging current is small even during the non-competitive period (simply when the amount of power generation is small or the power demand is small), the direct battery (BAT1, BAT2) is operated in the same manner as described above. ), And the SOC estimation error may be reduced.

  Further, in the power storage system 1, it is necessary for stable operation to perform charging and discharging so as not to make the overcharge and overdischarge prevention protection circuits work as much as possible. For that purpose, it is necessary to correctly estimate the SOC. is there. As described above, in the second embodiment, by increasing the charging current or discharging current, the SOC estimation error is suppressed as much as possible, and charging / discharging is performed so that the overcharge and overdischarge prevention protection circuits are not used as much as possible. It is possible to do.

3. Third Embodiment Next, a third embodiment will be described. In the description of the third embodiment, emphasis is placed on the description of parts different from the first embodiment, and the description of the same parts as in the first embodiment may be omitted.

  As in the case of the first embodiment (see FIG. 1), the power storage system 1 according to the present embodiment includes a battery unit 11, a DC-DC converter 12, a control unit 13, a current measurement unit (15a, 15b), and Each switch (SW1 to SW4) is provided.

  In the present embodiment, the cell balance operation is performed so that the above-described initial operation (with power transfer between the batteries) is performed efficiently. That is, in the present embodiment, the cell balance operation of the following form is performed.

  One battery is configured to achieve cell balance in the battery by discharging each cell. Then, the discharge power in this cell balance is added to the power transferred to the other battery and used for charging the other battery. At that time, in the battery to be charged (the other battery), charging is performed for each cell, whereby cell balancing is also performed at the same time in the battery to be charged.

  In this way, it is possible to realize a cell balance operation that matches the power transfer between batteries, which is an initial operation. Therefore, it becomes possible to effectively use the cell balance power of charging and discharging for the charging state in the charging / discharging mode.

4). Others As described above, the power storage system 1 according to the present embodiment includes the battery unit 11 including the first battery BAT1 and the second battery BAT2 (one form of a plurality of battery elements) that can be charged and discharged, and the surplus A charging operation for charging and storing electric power (one form of input electric power) in the battery unit 11 and a discharging operation for discharging and outputting the electric power stored in the battery unit 11 are performed. The power storage system 1 is configured to switch the operation mode between the first mode (a combination of the charging mode and the discharging mode) and the second mode (a charge / discharge combined mode) ( Operation form setting unit).

  In the first mode, all or part of the batteries (BAT1, BAT2) are used for the charging operation, and other batteries are not used for the discharging operation (charging mode), or the batteries (BAT1, BAT2). Are used for the discharge operation, and other batteries are in an operation mode (discharge mode) not used for the charge operation. In the second mode, a plurality of batteries (BAT1, BAT2) are separated into a charging battery (charging element) and a discharging battery (discharging element), the charging battery is used for the charging operation, and the discharging operation is discharged. This is an operation mode in which a battery is used. Therefore, it is possible to suppress frequent switching of charging / discharging in each battery (BAT1, BAT2).

  As a more specific configuration of the present embodiment, both the charging mode and the discharging mode are provided as the first mode, and the operation mode of the power storage system 1 is the charging mode, the discharging mode, and the second mode. It is set to be switchable to either one. As a modification of the present embodiment, neither the switch SW1 nor SW3 is turned off in the charge mode, and neither of the switches SW2 and SW4 is turned off in the discharge mode. In this case, the charging mode is an operation mode in which the entire battery (BAT1, BAT2) is used for the charging operation, and the discharging mode is an operation mode in which the entire battery (BAT1, BAT2) is used for the discharging operation.

  In addition, as an operation mode (operation mode) related to charging or discharging of the power storage system, there may be an operation mode other than the first mode and the second mode described above. For example, depending on whether it is an emergency stop mode (an operation mode that stops all charging / discharging in preparation for an unexpected situation) or a cell balance operation mode (either charging or discharging all battery cells BS) (Operation mode for performing equalization of the storage amount of the battery cells BS in the same battery) may be provided as the operation mode of the storage system.

  In these operation modes, for example, when the first mode or the second mode is set, the first mode or the second mode is interrupted urgently (or if necessary or according to a predetermined sequence). (Or by switching the operation mode).

  Note that the first example described above is adopted as a procedure for determining which of the “power generation advantage period”, “demand quantity advantage period”, and “antagonism period” the current time belongs to. If it is, the operation mode of the power storage system 1 is switched according to the amount of surplus power (the amount of input power). When the second example described above is adopted, the operation mode of the power storage system 1 is switched according to the current time. The “competition period” is a period in which charging and discharging of the battery unit is expected to switch relatively frequently. The “power generation advantage period” and the “demand amount advantage period” are compared with the “competition period”. It can be said that this is a period in which charging / discharging of the part is expected not to be frequently switched.

  Moreover, although the electrical storage system 1 of this embodiment is utilized for the use which outputs the stored surplus electric power to the load 5 according to a demand, the electrical storage system which concerns on this invention can be utilized for various other uses. . The power storage system exhibits a particularly remarkable effect under various environments in which a period during which charging / discharging of the battery unit is expected to be switched relatively frequently may occur.

  Further, the battery element that can be charged and discharged is not limited to the battery (BAT1, BAT2), and may be, for example, a battery cell. Further, the number of battery elements is not limited to two and may be three or more. In addition, the power storage system 1 may charge the battery unit 11 with power supplied from the power system 6 during, for example, a demand-dominant period (particularly at night).

  The configuration of the present invention can be variously modified in addition to the above embodiment without departing from the spirit of the invention. That is, the above-described embodiment is an example in all respects, and should be considered not restrictive. The technical scope of the present invention is shown not by the above description of the embodiment but by the scope of the claims, and is understood to include all modifications within the meaning and scope equivalent to the scope of the claims. Should.

  The present invention can be used for a power storage system for storing surplus power.

1 Power Storage System 2 Solar Cell (Distributed Power Supply)
DESCRIPTION OF SYMBOLS 3 Power conditioner 4 Distribution board 5 Load 6 Electric power system 9 Electric power system 11 Battery part 11a Converter for battery 12 DC-DC converter 13 Control part 15a, 15b Current measurement part 17 Current adjustment part BAT1 1st battery (one of battery elements)
BAT2 Second battery (one of the battery elements)
BS battery cell SW1-SW4 switch

Claims (8)

A battery unit having a plurality of battery elements that can be charged and discharged;
A power storage system that performs a charging operation of charging and storing input power in the battery unit, and a discharging operation of discharging and outputting the power stored in the battery unit,
An operation mode setting unit that sets the operation mode of the power storage system to be switchable to either the first mode or the second mode;
The first mode is
All or some of the plurality of battery elements are used for the charging operation, and other battery elements are not used for the discharging operation, or all or some of the plurality of battery elements are used for the discharging operation. Used, other battery elements are in a form not used for the charging operation,
The second mode is
The power storage system, wherein the plurality of battery elements are classified into a charging element and a discharging element, the charging element is used for the charging operation, and the discharging element is used for the discharging operation. The operation mode setting unit
The power storage system according to claim 1, wherein the operation mode is switched according to the magnitude of the input electric power. The power storage system according to claim 2, wherein surplus power out of the power generated by the distributed power supply is input.
The operation mode setting unit
The power storage system, wherein the operation mode is switched according to the amount of the surplus power. The operation mode setting unit
The power storage system according to claim 1, wherein the operation mode is switched according to a current time. In the situation where the operation mode is the second mode,
The charge current of the battery element sorted by the charging element is increased by using the electric power stored in the battery element sorted by the discharging element. The electrical storage system in any one. In the situation where the operation mode is the first mode,
Next, the electric power stored in the battery element that is sorted into the charging element when the second mode is entered is moved to the battery element that is sorted into the discharging element when the second mode is entered next. The power storage system according to any one of claims 1 to 5, wherein As the first mode,
A charging mode in which all or a part of the plurality of battery elements are used for the charging operation, and no other battery element is used for the discharging operation, and all or a part of the plurality of battery elements is the discharging operation. Other battery elements are provided with both discharge modes not used for the charging operation,
The operation mode setting unit
The power storage system according to any one of claims 1 to 6, wherein an operation mode of the power storage system is set to be switchable to any one of a charge mode, a discharge mode, and a second mode. Between when switching from the charging mode to the second mode and when switching from the discharging mode to the second mode,
The power storage system according to claim 7, wherein the battery element sorted into the charging element and the battery element sorted into the discharging element are reversed.

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