JP2014011875A - Power storage system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage system for suppressing interruption of power supply from an inverter device to a load while the inverter device is in autonomous operation.SOLUTION: A power storage system 3 having a storage battery 30 connected to a power transmission line 7 for connecting a DC power supply 1 for outputting DC power and an inverter device 2 for converting the DC power to AC power and superimposing the AC power on a system 5 has: a first mode in which charging the storage battery 30 through the power transmission line 7 is possible when the DC power is output from the DC power supply 1, while the inverter device 2 is superimposing the AC power on the system 5; and a second mode in which charging the storage battery 30 is inhibited, while the inverter device 2 does not superimpose the AC power on the system 5 and is supplying the AC power to a load 6.

Description

The present invention relates to a power storage system connected to a power transmission line that connects a solar cell and an inverter device.

2. Description of the Related Art In recent years, a solar power generation system having a solar cell and an inverter device (system interconnection device) that performs an interconnection operation in which DC power output from the solar cell is converted into AC power and superimposed on a commercial power system is provided. Has been. An inverter device of such a photovoltaic power generation system is a load that disconnects the solar cell from the commercial power system and does not superimpose the power output from the solar cell on the commercial power system when a power failure occurs in the commercial power system. The self-sustaining operation is performed.

In addition, a storage battery is connected to a power transmission line connecting the solar battery and the inverter device via a charge / discharge circuit, so that power can be supplied from the storage battery to the inverter device, or the power of the power transmission line (from the power of the solar cell or the system) A photovoltaic power generation system that makes it possible to charge a storage battery with electric power rectified via an inverter device has been proposed (Patent Document 1).
JP 2008-54473 A

In the solar power generation system described in Patent Document 1, since the power that can be output from the solar battery varies according to the variation in the amount of solar radiation, the storage battery is switched between discharging and charging according to the variation. For example, the storage battery is switched from charging to discharging at night when the solar battery cannot output DC power, or during low solar radiation where the output is significantly suppressed. Moreover, when the solar power generation system described in Patent Literature 1 can sufficiently cover the load from the solar battery, the storage battery is switched from discharging to charging and the storage battery is charged with DC power output from the solar battery. be able to. This operation can be performed in the same way during the interconnecting operation and the independent operation.

However, when switching between charging and discharging, for example, an operation to gradually increase the discharge voltage or the charge voltage to prevent inrush current at the start of discharge or at the start of charge is sufficient. A period during which a large amount of power cannot be output is provided.

For this reason, during the self-sustaining operation, the output of the solar cell can be sufficiently obtained, and the electric power output by the solar cell with respect to the load is changed due to the sudden change in the amount of solar radiation while switching from discharging to charging. When the solar power generation system cannot be obtained sufficiently, the conventional photovoltaic power generation system performs an operation of switching from charging to discharging. In this case, during the switching period, power cannot be sufficiently output from the solar battery or the storage battery to the load, the power supply from the inverter device to the load is interrupted, and the load must be stopped. There was a problem of disappearing.

The present invention has been made in view of such a point, and provides a power storage system that suppresses interruption of power supply from an inverter device to a load when the inverter device is operating independently. Objective.

In order to achieve the above object, a power storage system according to the present invention is a storage battery connected to a power transmission line that connects a DC power source that outputs DC power and an inverter device that converts the DC power to AC power and superimposes it on the grid. In the power storage system, the storage battery can be charged via the power transmission line when DC power is output from the DC power supply while the inverter device superimposes the AC power on the grid. And a second mode in which charging of the storage battery is prohibited when the inverter device supplies AC power to a load without superimposing the AC power on the grid. .

In this way, when the inverter device supplies the AC power to the load without performing superimposition on the AC power system converted by the inverter device (independent operation), from the solar cell to the storage battery. Charging is prohibited and the period for switching between discharging and charging is eliminated. For this reason, since the output of a solar cell is small and the period when electric power cannot be obtained also from a storage battery is lost, it can suppress that the electric power supply from an inverter apparatus to load is interrupted.

In the above-described invention, in the second mode, the discharge amount of the storage battery is controlled so that the sum of the discharge power and the DC power output from the DC power supply corresponds to the load.

Further, in the above-described invention, when the second mode is selected, when the capacity of the storage battery becomes equal to or less than a first predetermined amount, the mode is switched to the third mode in which only the storage battery is charged.

Moreover, in the above-mentioned invention, it notifies, when it switches from 2nd mode to 3rd mode.

In the above-described invention, when the second mode is selected and the capacity of the storage battery is equal to or less than a second predetermined amount, charging is performed when the DC power output from the DC power source is larger than the load. And switching to the fourth mode for discharging when the DC power output from the DC power supply is smaller than the load.

In the above-described invention, when the fourth mode is selected, when the capacity of the storage battery becomes equal to or smaller than the first predetermined amount smaller than the second predetermined amount, the mode is switched to the third mode in which only the storage battery is charged. It is characterized by that.

Moreover, in the above-mentioned invention, it notifies, when it switches from 2nd mode to 4th mode.

ADVANTAGE OF THE INVENTION According to this invention, when the inverter apparatus is carrying out the self-sustained operation, the electrical storage system which suppresses that the electric power supply to a load from an inverter apparatus is interrupted can be provided.

1 is a configuration diagram showing a solar power generation system 100. FIG. 2 is a configuration diagram of an inverter device 2. FIG. 1 is a configuration diagram of a power storage system 3. FIG. It is a flowchart of operation | movement of the electrical storage system in 1st Embodiment. It is a flowchart of operation | movement of the electrical storage system in 2nd Embodiment.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram illustrating a photovoltaic power generation system 100 according to the first embodiment.

The solar power generation system 100 includes a solar cell 1, a grid interconnection device 2 (inverter device 2), and a power storage system 3.

In the solar cell 1, the amount of power generation changes according to the amount of solar radiation. The solar cell 1 includes a plurality of single cell solar cells, and is configured by connecting a plurality of single cell solar cells in series and / or in parallel. For example, rated voltage is 250V, 300V, output 2.4Kw, output 4.
8Kw.

The inverter device 2 is connected to the solar cell by the power transmission line 7. The inverter device 2 inputs the DC power output from the solar cell 1 through the power transmission line 7, converts the input DC power into AC power, and the inverter device 2 converts the AC power into the grid connection. It superimposes on the commercial power system 5 via the relay 21 (interconnection operation).

Further, when the commercial power system 5 is out of power, the DC power output from the solar cell 1 and / or the power storage system 3 is input via the power transmission line 7 and the input DC power is converted into AC power.
Then, the inverter device does not superimpose the AC power on the commercial power system 5 and supplies the AC power to the load 6 via the autonomous operation relay 22 (independent operation). The inverter device 2 has a function of detecting a power failure in the commercial power system 5 and automatically switching between the grid operation and the independent operation. In addition, you may comprise so that switching between interconnection operation and independent operation can be performed manually after the inverter apparatus 2 detects a power failure and stops. FIG. 2 shows a configuration diagram of the inverter device 2.

The inverter device 2 includes a booster circuit 23, an inverter circuit 24, an inverter control circuit 26,
A grid interconnection relay 21 and a self-sustaining operation relay 22 are provided.

As shown in FIG. 2, the booster circuit 23 includes a boost chopper circuit having a reactor, a switch element, and a diode. Further, the booster circuit 23 is connected to the power transmission line 7 on the input side, and controls the duty ratio of the switch element to boost the DC power inputted from the power transmission line 7 to the inverter device 2 (boost circuit 23) to a desired voltage. To do.

The inverter circuit 24 is configured by a bridge circuit configured by a plurality of switch elements connected in a full bridge and a filter circuit provided at a subsequent stage (AC side) of the bridge circuit. By performing PWM control of this switch element, the DC power output from the booster circuit 23 is converted into AC power. The bridge circuit outputs the converted AC power to the filter circuit.

The filter circuit is composed of two reactors and a capacitor, and removes the high-frequency component of the AC power output from the bridge circuit. The AC power from which the high frequency component has been removed is output to the commercial power system via the grid interconnection relay 21 or to the load 6 via the autonomous operation relay 22.

The inverter control circuit 26 includes a booster circuit 23, an inverter circuit 24, and a grid interconnection relay 2.
1. Control the operation of the independent operation relay 22. The inverter control circuit 26 determines whether or not the commercial power system 5 has a power failure at the time of startup. When the commercial power system 5 has a power failure, the inverter control circuit 26 opens the grid connection relay 21 and closes the independent operation relay 22 to perform independent operation. Further, when the commercial power system 5 is supplying power, the inverter control circuit 26 closes the grid connection relay 21 and opens the independent operation relay 22 to perform the linked operation.

The power storage system 3 will be described with reference to the drawings. FIG. 3 shows a configuration diagram of the power storage system 3. The power storage system 3 includes a storage battery 30, a charge / discharge circuit 31, and a power storage system control circuit 32. In addition, the power storage system 3 can be retrofitted to a consumer who already uses the solar cell 1 and the inverter device 2.

The power storage system 3 includes a charge main control (first mode or third mode) that enables charging of the storage battery 30 via the power transmission line 7 when DC power is output from the solar battery 1, and charging of the storage battery. And a discharge main control (second mode) that enables discharge from the storage battery 30 to the inverter circuit. The user can select which of the main charging control and the main discharging control to operate the power storage system 3. This choice is
This can be done by operating an input unit (not shown) provided on the remote control 9 or the housing of the power storage system 3.

Since the power storage system 3 of the first embodiment assumes an emergency auxiliary power supply when a power failure occurs, the discharge main control can be selected only during the independent operation. Further, the main charging control can be selected during the interconnecting operation or the independent operation.

Since the storage battery 30 is used as an auxiliary power source, for example, an inexpensive product such as a lead storage battery is used, and the cells are connected in series and / or in parallel so that the rated voltage is 12 [V] to 240 [V]. Connected to and configured. In addition, you may utilize other batteries, such as a lithium ion battery and a nickel metal hydride battery.

The charge / discharge circuit 31 charges and discharges the storage battery 30 via the transformer 40. The transformer 40 has a power supply side winding 41 connected to the power transmission line and a storage battery side winding 51 connected to the storage battery 30. The two windings 41 and 51 are wound around a common core 50. The charging / discharging circuit 31 is configured to discharge the storage battery 30 when the turns ratio of the power supply side winding 41 and the storage battery side winding 51 is the number of turns of the power supply side winding 41 / the number of turns of the storage battery side winding 51. Than the turns ratio,
It is comprised so that the turns ratio when charging a storage battery can be enlarged.

In the charging / discharging circuit 31, one end of the charging switch element 42 is connected in series with the winding 41, and the winding 41 is connected to the positive electrode side of the power transmission line 7 via the reactor 44. The other end of the charging switch element 42 is connected to the negative electrode side of the power transmission line 7. The charging circuit 31 includes a diode 43 that bypasses the other end side of the charging switch element 42 and a part of the winding 41 and is connected in parallel with the charging switch 42. The charge / discharge circuit 31 includes a capacitor 45 that connects between the winding 41 and the reactor 44 and the negative side of the transmission line 7.

In the charge / discharge circuit 31, one end of the discharge switch element 52 is connected in series with the winding 51, and the winding 51 is connected to the positive electrode side of the storage battery 30 via the reactor 54. Further, the other end of the discharging switch element 52 is connected to the negative electrode side of the storage battery 30. The charge / discharge circuit 31 includes a diode 53 that bypasses the other end of the discharge switch element 52 and is connected in parallel with the discharge switch 52. The charge / discharge circuit 31 has a capacitor 55 that connects between the winding 51 and the reactor 54 and the negative electrode side of the storage battery 30.

When charging the storage battery 30, the charging / discharging circuit 31 charges using all the windings 41. Specifically, when charging the storage battery 30, the discharging switch element 52 is cut off, and the charging switch element 42 is periodically turned on or off to periodically turn the two windings 41 a and 41 b. Conduct. At this time, a signal having a duty ratio such that the output voltage from the solar battery 1 is stepped down to a voltage slightly higher than the voltage of the storage battery 30 is created by the power storage system control circuit 32 and input to the charging switch element 42. In addition, the charging / discharging circuit 31 starts a target voltage (
The duty ratio of the charging switch element 42 is gradually increased until it reaches (duty ratio).
In addition, the charging / discharging circuit 31 gradually reduces the current duty ratio to turn off the charging switch element 42 when the charging is finished.

In this way, when a current flows through the winding 41 and the charging switch element 42, a current in a direction in which the storage battery 30 is charged flows through the diode 53, bypassing the discharging switch element 52, and the storage battery 30 Charged. Charging is performed by constant current charging in which the current flowing through the storage battery 30 is constant until the voltage of the storage battery 30 reaches a predetermined voltage value. When the voltage is greater than the predetermined voltage value, the voltage applied to the storage battery 30 is constant. Perform constant voltage charging.

When the storage battery 30 is discharged, a part of the winding 41 is discharged. When discharging the storage battery 30, the charging switch element 42 is cut off, and the discharging switch element 52 is periodically turned on or off, and the storage battery 30 side winding 51 is turned on periodically. At this time, a signal having a constant duty ratio is input so that the output voltage from the storage battery 30 is constant. Similarly to the charging, the charging / discharging circuit 31 gradually increases the duty ratio of the discharging switch element 52 until the target voltage (duty ratio) is reached at the start of discharging. The discharge switch element 52 is turned off by gradually decreasing the duty ratio.

In this way, when a current flows through the winding 51 and the discharging switch element 52, a current flows from the negative electrode side to the positive electrode side of the power transmission line, bypassing the charging switch element 42, and the inverter device. 2 is supplied with the output power of the storage battery. In addition, since the discharge control is performed so that the output voltage becomes the constant voltage V1, when the output voltage (output power) of the solar battery is smaller than the constant voltage V1, it is stored in the storage battery 30 so as to supplement the power. Electric power is output to the inverter device 2. When the output voltage (output power) of the solar cell 1 is larger than the constant voltage V1, the voltage discharged by the charge / discharge circuit 31 is smaller than the output voltage of the solar cell 1, so that the discharge switch 52 operates. However, the discharge of the storage battery 30 is stopped. Thus, in the main discharge control, the discharge amount of the storage battery 30 is controlled so that the sum of the amount of DC power output from the solar battery 1 corresponds to the power consumption of the load.

The power storage system control circuit 32 controls the operation of the charge / discharge circuit 31. The operation of the charging / discharging circuit 31 varies depending on whether the charging main control is selected by the user or the discharging main control is selected.

For the charge main control and the discharge main control, the user may simply switch (so as not to be automatically switched by the power storage system 3), but in the first embodiment,
As shown below, the power storage system 3 determines and switches these.

FIG. 4 is a flowchart of the operation of the power storage system in the first embodiment. When the operation starts, the power storage system control circuit 32 determines whether or not the charging main operation is selected (step S11). When the main charging operation is selected, the power storage system control circuit 32 proceeds to step S12 in order to perform the main charging control of block A shown in FIG.

In step S <b> 12, it is determined whether or not the solar battery 1 can output DC power of a predetermined amount or more that can charge the storage battery 30. The determination can be made by detecting the output voltage of the solar cell 1. The output voltage of the solar cell 1 can be detected by detecting the voltage of the capacitor 45. When the determination in step S12 is YES, the power storage system control circuit 32
It is determined that charging is possible, the charging / discharging circuit 32 is charged, and the process returns to step S11. If the determination in step S12 is NO, the power storage system control circuit 32 determines that charging is impossible, causes the charge / discharge circuit 32 to stop charging, and returns to step S11.

Next, when it is determined in step S11 that the main charging operation is not selected, the power storage system control circuit 32 determines that the main discharging operation is selected, and the main discharging control of block B shown in FIG. Therefore, the power storage system control circuit 32 proceeds to step S21.

In step S21, it is determined whether the commercial power system 5 has a power failure. If the power storage system control circuit 32 determines that the commercial power system 5 has not failed, it switches from the discharge main control to the charge main control (step S22) and proceeds to step S12. As a result, when the commercial power system 5 is supplying power, the storage battery 30 is not discharged (discharge main control is not performed). The power failure detection by the power storage system control circuit 32 can be performed by monitoring the voltage of the commercial power system 5. That is, commercial power system 5
Can be determined that the power failure has not occurred, and can be determined to be a power failure if the voltage of the commercial power system 5 is not as specified.

When the storage system control circuit 32 determines in step S21 that the commercial power system 5 has a power failure, the storage system control circuit 32 determines whether or not the capacity SOC of the storage battery 30 is larger than the first predetermined amount th1 (step S23). Here, the first predetermined amount th1 is set to a value in a state where the capacity of the storage battery 30 is almost empty. For example, when the capacity SOC at the time of full charge is set to 100%, the first predetermined amount th1 is set to about 0 to 20%. The capacity SOC of the storage battery 30 can be obtained, for example, by providing a current sensor between the storage battery 30 and the reactor 54 and monitoring the current charged to the storage battery and the current discharged from the storage battery. Further, the capacity SOC of the storage battery 30 can be obtained by detecting the open voltage of the storage battery 30. This method requires a device for detecting the open circuit voltage.

In step S23, the power storage system control circuit 32 determines that the capacity SOC is the first predetermined amount th.
If it is determined that it is smaller than 1, the discharging is stopped (step S25), and the user is informed of switching from the main discharging control (second mode) to the main charging control (third mode) that only charges the storage battery (step 3). S26) and the process proceeds to step S22.

In step S23, the power storage system control circuit 32 determines that the capacity SOC is the first predetermined amount th.
When it is determined that it is not smaller than 1, the power storage system control circuit 32 determines that the storage battery 30 can be discharged, causes the charge / discharge circuit 32 to discharge (step S24), and returns to step S11. In this manner, in the first embodiment, the charging and discharging operations of the storage battery 30 of the power storage system 3 are controlled.

It should be noted that the charging main control and the discharging main control can be appropriately switched by the user during the operation according to this flowchart. In addition, when the switching is performed by the user, the power storage system control circuit 32 performs the current operation (charging or
Stop discharging and return to the start.

As described above, according to the first embodiment, the inverter device 2 supplies the AC power to the load 6 without superimposing the AC power converted by the inverter device 2 on the commercial power system 5 (independent operation). In other words, charging from the solar cell 1 to the storage battery 30 is prohibited and the period for switching between discharging and charging is eliminated. For this reason, there is no period when the output of the solar cell 1 is small and no power can be obtained from the storage battery 30. For this reason, it can suppress that the electric power supply from the inverter apparatus 2 to the load 6 is interrupted.

In addition, according to the first embodiment, since the power storage system 3 can detect a power failure, the inverter control circuit 26 and the power storage system control circuit 32 do not particularly perform communication or the like even if they are retrofitted. It is possible to operate.

In addition, the inverter device 2 often stops its operation for safety when the input is lost during the autonomous operation. In such a state, the user must operate the inverter device 2 so that the inverter device 2 operates again and supplies power to the load. However, according to the first embodiment, the period for switching between discharging and charging, that is, the solar cell 1
Therefore, it is possible to eliminate a period in which no power is obtained from the storage battery 30 and there is no input to the inverter device 2. For this reason, it is possible to save the user from having to restart the inverter device 2 until the storage battery 30 becomes empty.

In the first embodiment, charging / discharging is gradually started or charging / discharging is gradually ended at the start or end of discharging or charging (charging / discharging). By doing so, it is possible to prevent an unexpectedly large current (inrush current) from flowing due to a sudden voltage applied to the power transmission line 7 or the power storage system 3.

In addition, gradually charging / discharging leads to a longer period for switching between discharging and charging, but discharge main control (first mode, which prohibits charging when discharging from the storage battery 30)
(Third mode). For this reason, the period which switches discharge and discharge automatically can be eliminated. Thereby, even if charging / discharging is started gradually or charging / discharging is ended gradually, it is possible to prevent the power supply from the inverter device 2 to the load 6 from being interrupted by switching between charging and discharging.

Further, according to the first embodiment, when the discharge main control is selected, the storage battery 30
Is switched to the main charging control for charging only the storage battery 30 when the capacity SOC of the battery becomes equal to or less than the first predetermined amount th1. Thereby, it can switch to the control which can charge automatically, when the storage battery 30 becomes empty in discharge main control.

Further, according to the first embodiment, in order to notify the user that the main discharge control has been switched to the main charge control, the user is prohibited from discharging from the storage battery 30 and the storage battery 30 is empty. You can know quickly.

(Second Embodiment)
In the second embodiment, when the discharge main control is performed, the storage battery 3 as in the first embodiment.
The charging prohibit mode (second mode) in which charging to 0 can be prohibited and discharging can be selected, and the charging permission mode (fourth mode) in which both charging and discharging of the storage battery 3 can be performed are selected. Can be switched.

The selection of the charge prohibition mode and the charge permission mode can be performed by operating an input unit provided on the remote controller 9 or the housing of the power storage system 3. Moreover, it is preferable that the switching between the charging main control and the discharging main control and the switching between the charging prohibition mode and the charging permission mode can be performed more easily.

Specifically, switching between the charge main control and the discharge main control can be performed with fewer button presses than when switching between the charge inhibition mode and the charge permission mode. Further, switching between the charge main control and the discharge main control can be performed using either the operation of the input unit provided in the housing of the power storage system 3 or the remote controller 9 to switch between the charge prohibition mode and the charge permission mode. May not be performed unless the operation of the input unit provided in the housing of the power storage system 3 is performed.

There are the following reasons for this. In the charge permission mode, charging / discharging of the power storage system 3 is switched. Therefore, when the output of the solar cell 1 suddenly decreases, there is a possibility that charging / discharging cannot be switched in time and power supply to the load 6 cannot be performed. Switching to the charge prohibition mode The charge permission mode is to select whether or not the user accepts this possibility. For this reason, it is preferable not to easily switch between the charge prohibition mode and the charge permission mode. The switching between the main charging control and the main discharging control is not limited to such selection, but is performed by selecting charging / discharging, and may be easily switched.

For charge main control, discharge main control, charge prohibition mode, and charge permission mode,
In this case, in the second embodiment, the power storage system 3 determines and switches them as described below, although it may be merely switched by the user (not to be automatically switched by the power storage system 3).

FIG. 5 is a flowchart of the operation of the power storage system in the second embodiment. In the second embodiment, the block B of the first embodiment is changed to the block C and used. Block A
Since this is the same as in the first embodiment, description thereof is omitted.

When it is determined in step S11 that the charging main operation is not selected, the power storage system control circuit 32 determines that the discharging main operation is selected and performs the discharging main control of the block C shown in FIG. The power storage system control circuit 32 proceeds to Step S31.

In step S31, it is determined whether the commercial power system 5 has a power failure. If the power storage system control circuit 32 determines that the commercial power system 5 has not failed, it switches from the discharge main control to the charge main control (step S32) and proceeds to step S12. As a result, when the commercial power system 5 is supplying power, the storage battery 30 is not discharged (discharge main control is not performed). Since the detection of the power failure by the power storage system control circuit 32 can be performed in the same manner as in step S21, the description thereof is omitted.

Moreover, in step S31, the electrical storage system control circuit 32 determines whether it is a charge prohibition mode, when it determines with the commercial power grid 5 having failed (step S33).
In the charge inhibition mode, the power storage system control circuit 32 determines whether or not the capacity SOC of the storage battery 30 is larger than the second predetermined amount th2 (step S34). Step S
In 33, when the power storage system control circuit 32 determines that the charging prohibit mode is not set,
The power storage permission mode is determined and the process proceeds to step S38.

If it is determined in step S34 that the capacity SOC of the storage battery 30 is greater than the second predetermined value th2, the power storage system control circuit 32 determines that the storage battery 30 can be discharged and causes the charge / discharge circuit 32 to discharge. (Step S35) Return to step S11. Where the second predetermined amount t
h2 is set to a value larger than the first predetermined value th1. For example, the capacity SOC when fully charged is 10
When it is set to 0%, it is preferable to set it at about 20 to 50%.

When it is determined in step S34 that the capacity SOC of the storage battery 30 is smaller than the second predetermined value th2, the power storage system control circuit 32 switches from the charge prohibition mode to the charge permission mode (step S36), This is notified (step S37), and the process proceeds to step S38.

In step S38, the power storage system control circuit 32 determines whether or not the capacity SOC of the storage battery 30 is larger than the first threshold value. When it determines with the capacity | capacitance SOC of the storage battery 30 being larger than a 1st threshold value by step S38, the electrical storage system control circuit 32 transfers to step S39. Further, when it is determined in step S38 that the capacity SOC of the storage battery 30 is smaller than the first threshold, the power storage system control circuit 32 determines that the capacity SOC of the storage battery 30 is almost empty, and proceeds to step S40.

In step S39, the electrical storage system control circuit 32 determines whether the output voltage Vs of the solar cell 1 is larger than the voltage threshold value Vth. Here, the voltage threshold Vth is a solar cell that can be sufficiently output from the solar cell 1 by adding the maximum power that can be supplied to the storage battery 30 to the maximum power that can be output when the inverter device performs self-sustaining operation. A voltage value of 1 should be set.

If it is determined in step S39 that the output voltage Vs of the solar cell 1 is greater than the voltage threshold Vth, the power storage system control circuit 32 determines that the storage battery 30 can be charged, and step S
14 to cause the charge / discharge circuit 32 to discharge. If it is determined in step S39 that the output voltage Vs of the solar cell 1 is smaller than the voltage threshold Vth, the power storage system control circuit 32 proceeds to step S35 and causes the charging / discharging circuit 31 to perform a discharging operation.

In step S40, the power storage system control device 32 stops discharging the storage battery 30, switches from the main discharge control to the main power storage control (step S41), and allows the user to charge only the storage battery from the main discharge control (second mode). The switch to the main charging control (third mode) to be performed is notified (step S42), and the process returns to step S11. In this manner, in the second embodiment, the charging and discharging operations of the storage battery 30 of the power storage system 3 are controlled.

It should be noted that the charge main control and the discharge main control can be appropriately switched by the user during the operation according to this flowchart, or the charge prohibition mode and the charge permission mode can be switched. Further, when switching is performed by the user, the power storage system control circuit 32 may stop the current operation (charging or discharging) and return to the start.

As described above, according to the second embodiment, when the charge prohibition mode is selected, the inverter device 2 does not superimpose the AC power converted by the inverter device 2 on the commercial power system 5 and loads the load 6. When the AC power is supplied (independent operation), charging from the solar cell 1 to the storage battery 30 is prohibited, and the period for switching between discharging and charging is eliminated. For this reason,
The output of the solar cell 1 is small, and there is no period during which no power can be obtained from the storage battery 30. Thereby, it can suppress that the electric power supply from the inverter apparatus 2 to the load 6 stops.

In addition, according to the second embodiment, when the charge prohibition mode is selected, the storage battery 30
Is less than the second predetermined amount th2, the DC power output from the solar cell 1 is larger than the load 6 (determined by Vs> Vth), and the DC power output from the solar cell 1 from the load 6 is charged. Is switched to the charge permission mode for discharging when V is smaller (determined by Vs <Vth). By doing in this way, when the battery decreases, the storage battery 30 can be charged, and the storage battery 30 can be used for a longer period than in the first embodiment.

When the charge permission mode (fourth mode) is selected and the capacity SOC of the storage battery 30 becomes equal to or less than the first predetermined amount th1 which is smaller than the second predetermined amount th2, the main charging control (first control) that only charges the storage battery 30 is performed. 3 mode). Thereby, in charge permission mode, when the storage battery 30 becomes empty, it can switch to the control which can be charged automatically.

When switching from the charge prohibition mode to the charge permission mode, the user is notified. Thereby, when the output of the solar cell 1 suddenly decreases, it is possible to notify the user that there is a possibility that charging / discharging cannot be switched in time and power supply to the load 6 may not be possible.

As mentioned above, although one Embodiment of this invention was described, the above description is for making an understanding of this invention easy, and does not limit this invention. It goes without saying that the present invention can be changed and improved without departing from the gist thereof, and that the present invention includes equivalents thereof.

For example, the solar cell 1 is used as a DC power source, but the DC power source whose output fluctuates due to an external factor (unexpectedly), for example, a generator using renewable energy, such as a wind power generator, etc. This power storage system 3 can also be used.

Further, for example, the user is notified that the main discharge control has been switched to the main charge control, but the capacity SOC of the storage battery 30 is determined by using the third predetermined value th3 that is slightly larger than the first predetermined value th1. When it becomes smaller than the predetermined value th3, the user may be notified that the main discharge control will soon be switched to the main charge control. By doing in this way, the user can detect that the capacity SOC of the storage battery 30 is likely to be empty and adjust the load and the like.

Further, for example, the user is informed that the mode is switched from the charge prohibition mode to the discharge prohibition mode. However, the capacity SOC of the storage battery 30 is the fourth predetermined value th4 that is slightly larger than the second predetermined value th2. When the value is smaller than the predetermined value th4, the user may be notified that the charging prohibition mode will soon be switched to the discharge prohibition mode. By doing so, the user can detect the possibility that charging / discharging cannot be switched in time and cannot supply power to the load 6, and can adjust the load and the like.

In the second embodiment, when the user has selected the charge prohibition mode and the capacity SOC of the storage battery 30 decreases, the charge prohibition mode is automatically switched to the charge permission mode. And in that case, it was made to remain in charge permission mode, but storage battery 30
If the capacity SOC is sufficient, the charging permission mode may be automatically returned to the charging prohibition mode. Further, at that time, even when the capacity SOC of the storage battery 30 is further reduced and the main control is switched to the charge main control, the charge prohibition mode may be automatically returned to the charge permission mode. By doing so, it is possible to suppress the possibility of lingering indefinitely even though the possibility that the switching of charging and discharging is not in time and the power supply to the load 6 cannot be performed is eliminated.

1 Solar cell 2 Inverter device (Inverter device)
DESCRIPTION OF SYMBOLS 3 Power storage system 5 Commercial power system 6 Load 7 Power transmission line 8 Load 21 Grid connection relay 22 Self-sustained operation relay 23 Inverter control circuit 24 Inverter circuit 26 Inverter control circuit 30 Storage battery 31 Charge / discharge circuit 32 Power storage system control circuit

Claims (7)

In a power storage system having a storage battery connected to a power transmission line that connects a DC power source that outputs DC power and an inverter device that converts the DC power to AC power and superimposes it on the system,
A first mode enabling charging of the storage battery via the power transmission line when DC power is output from the DC power supply while the inverter device superimposes the AC power on the grid; and the inverter A power storage system comprising: a second mode in which charging of the storage battery is prohibited when the apparatus supplies AC power to a load without superimposing the AC power on the grid. 2. The power storage system according to claim 1, wherein in the second mode, the discharge amount of the storage battery is controlled such that the sum of the discharge power and the DC power output from the DC power supply corresponds to the load. 3. When the second mode is selected, the mode is switched to the third mode in which only the storage battery is charged when the capacity of the storage battery becomes equal to or less than a first predetermined amount.
The power storage system described in 1. The power storage system according to claim 3, wherein a notification is given when the mode is switched from the second mode to the third mode. When the second mode is selected and the capacity of the storage battery is equal to or less than a second predetermined amount, charging is performed when the DC power output from the DC power supply is greater than the load, and the DC is more than the load. The power storage system according to claim 1 or 2, wherein the power storage system is switched to a fourth mode in which discharge is performed when the DC power output from the power source is small. When the fourth mode is selected, when the capacity of the storage battery becomes equal to or less than a first predetermined amount smaller than the second predetermined amount, the mode is switched to a third mode in which only the storage battery is charged. 5. The power storage system according to 5. The power storage system according to claim 5 or 6, wherein notification is given when the mode is switched from the second mode to the fourth mode.

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