JP2019022302A - Power storage device and electrical power system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a storage battery for electric power to be used as long as possible by devising its usage. SOLUTION: This is a power storage device which is connected to a load in a consumer and an AC power line to which a commercial power system is connected, and which is grid-connected, and a storage battery, a storage battery management unit that manages the state of charge of the storage battery, and AC A power conversion unit having a function of converting to AC to charge the storage battery, and a function of discharging the storage battery to convert DC to AC and supplying power to the AC circuit, and a control unit for controlling the power conversion unit to charge and discharge the storage battery. And the control unit discharges the storage battery when the discharge standby time reaches a predetermined time after the storage battery is charged to a state corresponding to full charge, and also discharges the storage battery and corresponds to complete discharge. The battery is charged when the charging standby time after reaching the predetermined state reaches a predetermined time. [Selection diagram] Fig. 5

Description

  The present invention relates to a power storage device and a power supply system.

  Many power supply systems that use a power generation facility such as solar power generation and a storage battery have already been proposed (see, for example, Patent Documents 1 to 4). For example, even for small-scale customers such as ordinary households, it is considered that power supply should be as independent of the commercial power system as possible by providing not only solar power generation equipment but also storage batteries. Moreover, even if it does not install a solar power generation facility, it can respond to a peak shift by installing a storage battery, and can use the electric power of the night time cheaply of the unit price of electric energy. As such a power storage battery, a lithium ion battery is generally used.

JP 2004-180467 A JP 2012-139019 A JP 2013-5584 A JP 2013-172495 A

  The power storage battery as described above is still an expensive product for home use, and becomes more expensive as the storage capacity is increased. Therefore, once installed, we want to be able to use it for as long as possible. The life of a storage battery is greatly influenced not only by aging but also by how it is used.

  In view of such a problem, an object of the present invention is to make it possible to use a power storage battery for as long as possible by means of how to use it.

  A power storage device according to an expression of the present invention is a power storage device connected to a grid connected to a load and a commercial power system connected to a consumer, and manages a storage battery and a charge state of the storage battery. A storage battery management unit; a power conversion unit having a function of converting alternating current into direct current to charge the storage battery; and a function of discharging the storage battery to convert direct current into alternating current to supply power to the alternating current circuit; and the power conversion And a controller that charges and discharges the storage battery by controlling the storage unit, and the control unit charges the storage battery and reaches a state corresponding to full charge when the standby time reaches a predetermined time. The storage battery is discharged when the storage battery is discharged, and the storage battery is discharged and the charging standby time after reaching a state corresponding to complete discharge reaches a predetermined time.

  In addition, a power supply system according to an expression of the present invention includes an AC electric circuit to which a commercial power system is connected, a load in a consumer connected to the AC electric circuit, and a power storage device that is connected to the AC electric circuit and connected to the system A power storage system comprising: a storage battery; a storage battery management unit that manages a charge state of the storage battery; a function of charging the storage battery by converting alternating current into direct current; and the storage battery. A power conversion unit having a function of discharging and converting direct current to alternating current and supplying power to the alternating current circuit; and a control unit that controls the power conversion unit to charge and discharge the storage battery, and the control unit includes: When the discharge standby time after the storage battery is charged and becomes a state corresponding to full charge reaches a predetermined time, the storage battery is discharged, and after the storage battery is discharged and becomes a state corresponding to complete discharge Electrostatic waiting time is a power supply system for charging reaches a predetermined time.

  According to the present invention, it is possible to extend the life of a storage battery.

It is a single line connection figure which shows the circuit structure of a power supply system. It is a graph which shows an example of a 1-day SOC change in case a storage battery waits for a long time with a full charge. It is a graph which shows an example of a 1-day SOC change when a storage battery waits for a long time by complete discharge. It is a graph which shows aged deterioration of two samples of a storage battery. It is a flowchart which shows an example of the charging / discharging control which a control part performs. It is a graph which shows an example of a 1-day SOC change in the case of performing charging / discharging control of FIG. It is a graph which shows the other example of a 1-day SOC change in the case of performing charging / discharging control of FIG. It is a single line connection figure which shows the other circuit structure of a power supply system.

[Summary of Embodiment]
The gist of the embodiment of the present invention includes at least the following.

  (1) This is a power storage device connected to a grid connected to a load and a commercial power system in a consumer, and a storage battery, a storage battery management unit for managing the state of charge of the storage battery, A function of charging the storage battery by converting alternating current to direct current; and a power converter having a function of discharging the storage battery to convert direct current to alternating current and feeding the alternating current circuit; and controlling the power converter A control unit that charges and discharges the storage battery, and the control unit discharges the storage battery when the discharge standby time after reaching the state corresponding to full charge by charging the storage battery reaches a predetermined time, Further, the battery is charged when the charging standby time after the storage battery is discharged to reach a state corresponding to complete discharge reaches a predetermined time.

  In the power storage device configured as described above, the standby time after the state corresponding to full charge and the standby time after the state corresponding to complete discharge are always within a predetermined time. Thereby, it can suppress that a storage battery deteriorates early, and can implement | achieve the lifetime improvement of a storage battery.

(2) In the power storage device of (1), when the discharge standby time reaches a predetermined time, the control unit may output an alarm to discharge the storage battery.
In this case, when the user of the power storage device receives an alarm and actively consumes necessary power, the storage battery can be discharged.

  (3) Moreover, from another viewpoint, this is an AC power circuit to which a commercial power system is connected, a load in a customer connected to the AC power circuit, and a power storage system connected to the AC power circuit and connected to the system. A power storage system comprising: a storage battery; a storage battery; a storage battery management unit that manages a charge state of the storage battery; a function of charging alternating current into direct current and charging the storage battery; and the storage battery A power conversion unit having a function of converting DC to AC and supplying power to the AC circuit, and a control unit that controls the power conversion unit to charge and discharge the storage battery, and the control unit includes: When the discharge standby time after the storage battery is charged and becomes a state corresponding to full charge reaches a predetermined time, the storage battery is discharged, and after the storage battery is discharged and becomes a state corresponding to complete discharge Waiting for charging Charging the time reaches the predetermined time.

  In the power storage device of the power supply system configured as described above, the standby time after the state corresponding to full charge and the standby time after the state corresponding to complete discharge are always within a predetermined time. Become. Thereby, it can suppress that a storage battery deteriorates early, and can implement | achieve the lifetime improvement of a storage battery. Further, when the discharge standby time after reaching a state corresponding to full charge reaches a predetermined time, the storage battery can be discharged by supplying power to the load. If the load is, for example, a hot water storage type electric water heater, the discharge power is stored instead of the heat energy. If the load is another storage battery, it can be stored in another storage battery without consuming energy wastefully by charging the other storage battery. Moreover, when it is possible to sell the power of the storage battery, the discharged power can be sold.

[Details of the embodiment]
Hereinafter, a power storage device and a power supply system according to an embodiment of the present invention will be described with reference to the drawings.

<< Circuit Configuration and Operation of Power Supply System and Power Storage Device >>
FIG. 1 is a single-line connection diagram illustrating a circuit configuration of the power supply system 100. In the figure, a commercial power system 3 is connected to an AC circuit 2 in a distribution board 1 of a consumer. Further, a power conditioner 5 is connected to the photovoltaic power generation panel 4. The power conditioner 5 is connected to the AC electric circuit 2. The fuel cell 17 is also connected to the AC circuit 2 via the power conditioner 18. The solar power generation panel 4 and the power conditioner 5 constitute a solar power generation device 21. The fuel cell 17 and the power conditioner 18 constitute a fuel cell power generator 22.

  A customer load 7 is connected to the AC circuit 2 in the distribution board 1 via a circuit breaker 6. The circuit breaker 6 is normally closed. Here, for simplification of illustration, only one circuit breaker and one load are shown, but actually, the circuit breaker and the load are connected to the AC circuit 2 over a plurality of systems.

  In addition, a grid-connected power storage device 8 is connected to the AC electric circuit 2. In the power storage device 8, a bidirectional inverter 9 as a “power conversion unit” is connected to the AC electric circuit 2 via an interconnection relay (opening / closing unit) 10. The storage battery 11 is connected to the bidirectional inverter 9 via the opening / closing part 12. The storage battery 11 is a lithium ion battery, for example. The storage battery 11 is provided with a BMS (Battery Management System) 13 as a “storage battery management unit”. The BMS 13 can be integrated with the control unit 14. The voltage sensor 16 that detects the voltage of the AC circuit 2 is provided in the power storage device 8, for example.

  The BMS 13 acquires various information related to the storage battery 11 such as a state of charge (SOC), a terminal voltage, a cell voltage, and a temperature of the storage battery 11. The information is sent to the control unit 14. The control unit 14 controls the switching operation of the bidirectional inverter 9 and the opening / closing operations of the interconnection relay 10 and the opening / closing unit 12. Usually, both the interconnection relay 10 and the opening / closing part 12 are closed.

In addition, a current sensor 15 is provided on the electric circuit connecting the commercial power system 3 and the AC electric circuit 2 in the distribution board 1. Each measurement output of the current sensor 15 and the voltage sensor 16 is sent to the control unit 14, and based on these, the control unit 14 detects the power delivered between the commercial power system 3 and the distribution board 1. Can do.
The control unit 14 includes, for example, a computer, and realizes necessary control functions by causing the computer to execute software (computer program). The software is stored in a storage device (not shown) of the control unit 14.

  Moreover, the control part 14 is connected so that communication with the two power conditioners 5 and 18 is possible, and can acquire the information of generated electric power from these. The control unit 14 determines charging / discharging / standby of the storage battery 11 based on the information on the generated power and the information on the power transferred between the commercial power system 3 and the distribution board 1.

  In FIG. 1, during the photovoltaic power generation by the photovoltaic power generation panel 4, the power conditioner 5 is performing grid-connected operation, and the output (direct current) of the photovoltaic power generation panel 4 is converted into alternating current generated power. It is sent to electric circuit 2. The generated power can be consumed by the customer's load 7, and if there is surplus power, the reverse power (sold power) to the commercial power system 3 and the storage battery 11 can be charged. The bidirectional inverter 9 when charging the storage battery 11 performs conversion from alternating current to direct current based on the control of the control unit 14.

  During operation of the fuel cell 17, the power conditioner 18 is performing grid connection operation (but not selling power), and the output (DC) of the fuel cell 17 is converted into AC generated power. It is sent to electric circuit 2. The generated power can be consumed by the customer's load 7 or can be used for charging the storage battery 11 as necessary. The bidirectional inverter 9 when charging the storage battery 11 performs conversion from alternating current to direct current based on the control of the control unit 14.

  Power can be supplied from the fuel cell 17 or the commercial power system 3 to the load 7 during a time period (mainly at night) when solar power generation is not performed. Further, the storage battery 11 can be discharged to supply the power consumption of the load 7 from the power storage device 8. The bidirectional inverter 9 when discharging the storage battery 11 performs conversion from direct current to alternating current based on the control of the control unit 14. In addition, the storage battery 11 at night can be charged with the electric power of the commercial power system 3.

  1 is merely an example, and one or both of the solar power generation device 21 and the fuel cell power generation device 22 may not be provided.

<< Example of charge / discharge for 1 day >>
As for the state of charge (SOC) of the storage battery 11, for example, 90% or more is “full charge” and 10% or less is “complete discharge”. In addition, since these numerical values differ also with the capacity | capacitance and kind of storage battery, they are not absolute numbers but an example.

  FIG. 2 is a graph showing an example of a change in the SOC of the day when the storage battery is fully charged and waits for a long time. The vertical axis represents SOC [%], and the horizontal axis represents time [hour] of the day. In the graph, for the sake of simplification, the full charge is described as a state where the SOC is 100%, and the complete discharge is described as a state where the SOC is 0% (the same applies to FIG. 3). For example, the storage battery capacity is 3 kWh and the maximum output is 1.5 kW. In this example, in this example, discharge starts at 1.5 kW from a fully charged state at 7 am, and complete discharge at 9 am. Charging starts at 1.5 kW from 9 o'clock and fully charged at 11:00. If it is used in this way, 20 hours from 11:00 am to 7:00 am the next morning will be a long standby time with a full charge.

  FIG. 3 is a graph showing an example of a change in the SOC of the day when the storage battery waits for a long time with complete discharge. The vertical axis represents SOC [%], and the horizontal axis represents time [hour] of the day. For example, the storage battery capacity is 3 kWh and the maximum output is 1.5 kW. In the figure, in this example, charging starts at 1.5 kW from a fully discharged state at 7 am and becomes fully charged at 9 am. From 9 o'clock, discharge starts at 1.5 kW and complete discharge at 11:00. If it is used in this way, 20 hours from 11:00 am to 7:00 am the next morning will be a long standby time with complete discharge.

The above two examples are the examples with the longest standby time, and it is expected that the deterioration of the storage battery will be accelerated if actually used in this way.
Here, it was investigated by simulation how the difference in standby time affects the life of the storage battery. As a sample, a case where the standby time at full charge was 11 hours per day and a case where the standby time at full charge was 0 hours per day (no standby time) were compared under the following conditions.

《Relationship between standby time and service life》
Storage battery capacity: 3.2 kWh
Charging conditions: constant current / constant voltage system, 18.9A, 116.2V
Discharge condition: constant power method, 1500W
Number of cycles per day: 2 cycles Further, the temperature conditions were the following temperatures as the average indoor temperatures for January to December.

FIG. 4 is a graph showing the aging of two samples of storage batteries.
The horizontal axis represents the number of years, and the vertical axis represents the capacity maintenance rate [%]. Here, there is a slight difference even when there is no daily standby time at full charge and when the standby time is 11 hours every day, even after one year from the start of use. The difference opens. Comparing the years when the capacity maintenance rate becomes 50%, 13.7 years when there is no standby time at full charge, and 11.7 years when the standby time at full charge is 11 hours every day I got the result. In other words, it can be seen that usage with a long standby time greatly affects the life as the years pass.
Therefore, charge / discharge control for shortening the standby time will be described.

<Example of charge / discharge control>
FIG. 5 is a flowchart showing an example of charge / discharge control performed by the control unit 14 (FIG. 1).
When charging / discharging control is started, the control unit 14 determines whether to perform charging, discharging, or standby (step S1). When charging is performed, the process proceeds from step S2 to step S3, and if not fully charged, charging is performed (step S4). When charging is continued, steps S1, S2, S3, and S4 are repeated. When full charging is reached, charging is stopped and standby is performed (step S9).

  After the start of standby, the control unit 14 determines whether or not a predetermined time has elapsed (step S10), and repeats steps S1, S2, S7, S9, and S10 until the predetermined time has elapsed. And when predetermined time passes, the control part 14 will perform forced discharge (step S11). Forced discharge is performed by supplying electric power to the load 7 or other consumer's load. If the SOC is within a predetermined range (for example, less than 90%) due to the forced discharge (Yes in Step S12), the control unit 14 returns to Steps S1 and S2, and repeats Steps S1, S2, S5, and S6 to continue discharging. . When stopping the discharge, steps S1, S2, S7, and S8 are repeated.

  Moreover, when discharging in step S1, S2, the control part 14 progresses to step S5 from step S2, and it discharges if it is not complete discharge (step S6). When the discharge is continued, the steps S1, S2, S5, and S6 are repeated, and when the complete discharge is reached, the discharge is stopped and waited (step S13).

  After the standby is started, the control unit 14 determines whether or not a predetermined time has elapsed (step S14), and repeats steps S1, S2, S7, S8, S13, and S14 until the predetermined time has elapsed. And when predetermined time passes, the control part 14 will perform forced charge (step S15). If the SOC is within a predetermined range (for example, higher than 10%) due to forced charging (Yes in Step S16), the control unit 14 returns to Steps S1 and S2, and if charging continues, Steps S1, S2, S3, and S4 are performed. repeat. When charging is stopped, steps S1, S2, S7, and S8 are repeated.

  FIG. 6 is a graph showing an example of a daily SOC change when the charge / discharge control of FIG. 5 is performed. The vertical axis represents SOC [%], and the horizontal axis represents time [hour] of the day. In the graph, for the sake of simplification, the full charge is described as a state where the SOC is 100%, and the complete discharge is described as a state where the SOC is 0% (the same applies to FIG. 7). For example, the storage battery capacity is 3 kWh and the maximum output is 1.5 kW. The predetermined waiting time is 5 hours in this example.

  In FIG. 6, in this example, discharge starts at 1.5 kW from a fully charged state at 1 o'clock and complete discharge at 3 o'clock. After waiting for 1 hour from 3 o'clock, charging starts at 1.5 o'clock at 4 o'clock and fully charged at 6 o'clock. At 7 o'clock after waiting for 1 hour from 6 o'clock, discharge starts at 1.5 kW from the fully charged state, and complete discharge at 9 o'clock. Charging starts at 1.5 kW at 9 o'clock and becomes fully charged at 11 o'clock. Thereafter, when 5 hours elapse without a discharge command (16:00), the discharge is forcibly started, and when it is performed until 20:00, the SOC becomes a predetermined range (below 90%), and there is no further discharge command. If it becomes, it becomes standby.

  In the case of FIG. 6, the continuous standby time at full charge is 5 hours. Even if 1 hour from 0 o'clock to 1 o'clock is added, the standby time of 1 day at full charge is 6 hours. Obviously, the waiting time at full charge is reduced compared to FIG. If the “predetermined time” in step S10 in FIG. 5 is further shortened, the standby time can be further shortened. However, it is necessary to appropriately determine the predetermined time in consideration of the number of cycles.

  In addition, in order to perform forced discharge, the demand which uses discharge electric power is needed. When the load 7 (FIG. 1) receives power supply from the commercial power system 3, the power to be purchased can be reduced by sending forced discharge power into the AC circuit 2. However, the load 7 may be a minute electric power depending on the time zone or season. In such a case, it is conceivable that there is no demand for (or poor) discharge power even if forced discharge is desired.

Thus, for example, securing power demand in the following form is conceivable.
(A) If it is a consumer in which HEMS (Home Energy Management System) is introduced, a load can be easily secured before forced discharge is performed. As the load, a device that stores energy, such as another power storage device (including a battery such as an electric vehicle) or a hot water storage type electric water heater, is more preferable.
(B) Although it is not possible at this time to reversely tide the power of the storage battery via the grid connection, the discharge power can be used for selling power if it becomes possible in the future.
(C) When forced discharge is required, the control unit 14 outputs an alarm together in, for example, step S11 (FIG. 5) to prompt the user to use power. In response to this, the user can ensure power demand if he / she actively uses necessary home appliances.
(D) It is conceivable that a VPP (Virtual Power Plant) is configured in the region and discharge power is provided to other consumers.

  FIG. 7 is a graph showing another example of the daily SOC change when the charge / discharge control of FIG. 5 is performed. The vertical axis represents SOC [%], and the horizontal axis represents time [hour] of the day. For example, the storage battery capacity is 3 kWh and the maximum output is 1.5 kW. The predetermined waiting time is 5 hours in this example.

  In FIG. 7, in this example, charging starts at 1.5 kW from the state of complete discharge at 1 o'clock and becomes fully charged at 3 o'clock. After waiting for 1 hour from 3 o'clock, discharge starts at 1.5 kW at 4 o'clock and complete discharge at 6 o'clock. At 7:00 after waiting for 1 hour from 6 o'clock, charging starts at 1.5 kW from the state of complete discharge and becomes fully charged at 9 o'clock. At 9 o'clock, discharge starts at 1.5 kW, and at 11:00, complete discharge occurs. Thereafter, when 5 hours have passed without a charge command (16:00), charging is forcibly started, and when it is performed until 20:00, the SOC becomes a predetermined range (above 10%), and there is no further charge command. If it becomes, it becomes standby.

  In the case of FIG. 7, the continuous standby time in complete discharge is 5 hours. Even if 1 hour from 0 o'clock to 1 o'clock is added, the standby time of 1 day in complete discharge is 6 hours. Obviously, the waiting time for complete discharge is reduced when compared with FIG. If the “predetermined time” in step S14 in FIG. 5 is further shortened, the standby time can be further shortened. However, it is necessary to appropriately determine the predetermined time in consideration of the number of cycles.

<Summary>
As described above, the control unit 14 of the power storage device 8 charges the storage battery 11 when the discharge standby time (discharge standby time) after the storage battery 11 is charged and becomes in a state corresponding to full charge reaches a predetermined time. Force to discharge. In addition, the control unit 14 forcibly charges the battery 11 when the storage battery 11 is discharged and the charging standby time (waiting time for charging) after reaching the state corresponding to complete discharge reaches a predetermined time.
In the power storage device 8 that performs such charge / discharge control, the standby time after the state corresponding to full charge and the standby time after the state corresponding to complete discharge are always within a predetermined time. . Thereby, it can suppress that a storage battery deteriorates early, and can implement | achieve the lifetime improvement of a storage battery.

<Other configuration examples>
FIG. 8 is a single-line connection diagram illustrating another circuit configuration of the power supply system 100. The difference from FIG. 1 is that an information processing device 19 is provided above the power storage device 8, the solar power generation device 21, and the fuel cell power generation device 22 and is connected to the Internet 20. In this case, for example, the aforementioned alarm (c) in the case of forced discharge can be transmitted to the user's mobile device. A user who has received an alarm can send a signal to operate a specific electrical device. Therefore, even if the user is not necessarily at home, the user can assist the forced discharge in response to the alarm.

《Supplementary Note》
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Distribution board 2 AC circuit 3 Commercial electric power system 4 Solar power generation panel 5 Power conditioner 6 Circuit breaker 7 Load 8 Power storage device 9 Bidirectional inverter 10 Interconnection relay 11 Storage battery 12 Opening and closing part 13 BMS
DESCRIPTION OF SYMBOLS 14 Control part 15 Current sensor 16 Voltage sensor 17 Fuel cell 18 Power conditioner 19 Information processing apparatus 20 Internet 21 Solar power generation apparatus 22 Fuel cell power generation apparatus 100 Power supply system

Claims (3)

A power storage device connected to a grid connected to a load in a consumer and an AC power line to which a commercial power system is connected,
A storage battery,
A storage battery management unit for managing the state of charge of the storage battery;
A function of converting alternating current to direct current to charge the storage battery, and a power converter having a function of discharging the storage battery and converting direct current to alternating current to feed the alternating current circuit,
A control unit that controls the power conversion unit to charge and discharge the storage battery,
The control unit discharges the storage battery when the discharge standby time after reaching a state corresponding to full charge by charging the storage battery reaches a predetermined time, and corresponds to complete discharge by discharging the storage battery. A power storage device that is charged when a charging standby time after a state reaches a predetermined time.   The power storage device according to claim 1, wherein when the discharge standby time reaches a predetermined time, the control unit outputs an alarm to discharge the storage battery. An AC power circuit to which a commercial power system is connected;
A load on a consumer connected to the AC circuit;
A power storage system connected to the AC electrical path and interconnected with the grid, the power storage device comprising:
A storage battery,
A storage battery management unit for managing the state of charge of the storage battery;
A function of converting alternating current to direct current to charge the storage battery, and a power converter having a function of discharging the storage battery and converting direct current to alternating current to feed the alternating current circuit,
A control unit that controls the power conversion unit to charge and discharge the storage battery,
The control unit discharges the storage battery when the discharge standby time after reaching a state corresponding to full charge by charging the storage battery reaches a predetermined time, and corresponds to complete discharge by discharging the storage battery. A power supply system that charges when the charging standby time after reaching the state reaches a predetermined time.