JP2017077073A - Power storage system and power storage method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage system and a power storage method which can restore an operation of a load device in a short time when a power-generation element performs power generation.SOLUTION: A power storage system comprises: a solar battery operable to perform an environmental power generation; a first storage battery which is charged with a power generated by a power-generation element, and supplies a power to a load device; a second storage battery smaller than the first storage battery in capacity; first and second switch parts operable to selectively set a parallel connection state in which the first and second storage batteries are connected in parallel between a feeder line and a ground, and a series connection state in which the first and second storage batteries are connected in series between the feeder line and the ground; a voltage detector part operable to detect a voltage when the first storage battery is overdischarged; and a changeover part operable to control the switch parts according to the voltage detected by the voltage detector part.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a power storage system and a power storage method for storing power generated by a power generation element that performs environmental power generation in a storage battery and supplying power to a load device.

  In recent years, energy harvesting devices (energy harvesting elements) such as wireless sensors and remote control switches that operate without wiring or battery replacement by obtaining electrical energy from the surrounding environment due to low power consumption of electronic circuits and wireless technologies. Attention has been paid. For this reason, for example, development of a low illuminance dye-sensitized solar cell for energy harvesting that is supposed to be used in indoor light such as a fluorescent lamp or LED lighting is being promoted.

  Patent Document 1 describes a method for obtaining an appropriate power generation amount required for a solar cell based on the amount of power demand and adjusting the power generation amount of the solar cell in accordance with the required power generation amount. .

JP 2013-78235 A

  Attempts have been made to generate power in a solar cell under a low illuminance environment such as room light, store the generated power in a storage battery, and drive the load device with the stored power. In this case, it is desirable to use a lithium ion capacitor as the storage battery because of its large capacity and low leakage current.

  Commercially available lithium ion capacitors are mainly 40F (Farad), 100F or more. Moreover, it is preferable to use a lithium ion capacitor by the voltage more than a lower limit voltage (for example, about 2V) from a viewpoint of preventing deterioration of a cell. For this reason, in the power supply device, when the charging voltage of the lithium ion capacitor drops below, for example, 2.5 V, the operation of the load device is temporarily stopped to stop the supply of power, and then the power generation element When power generation starts, the power supply device starts recharging of the lithium ion capacitor by the power generation element.

  Here, it is desired that the time from when the power supply device stops the operation of the load device to stop the supply of power until the operation of the system is restored by restarting the power generation is desired. However, in the conventional power supply device, since a large-capacity lithium ion capacitor is used as a storage battery, it takes a very long time from restarting power generation to charging the storage battery and returning the system.

  In order to shorten the time for returning the operation of the system, it is conceivable to reduce the hysteresis voltage of the threshold voltage when detecting the charging voltage of the lithium ion capacitor used as the storage battery. However, if the hysteresis voltage of the threshold voltage is reduced, the operation of the load device is stopped by a slight voltage change after the system operation is resumed, and the operation becomes unstable.

  The present invention has been made in view of the above problems, and provides a power storage system and a power storage method capable of returning the operation of a load device in a short time when a power generation element generates power. For the purpose.

In order to achieve the above object, a power storage system according to one embodiment of the present invention includes a power generation element that performs environmental power generation, a power supply line that supplies power to a load device, and power generated by the power generation element via the power supply line. A first storage battery that is charged and supplies power to the load device; a second storage battery having a smaller capacity than the first storage battery; and the first storage battery and the second storage battery between the power supply line and the ground. A switch unit that selectively sets a parallel connection state in which the first storage battery and the second storage battery are connected in series between the power supply line and the ground; A voltage detection unit that detects a voltage at which the first storage battery is over-discharged, and a switching unit that controls the switch unit in accordance with a detection voltage of the voltage detection unit, wherein the switching unit includes: The detection voltage drops A first threshold voltage to be compared with the voltage at the time and a second threshold voltage to be compared with a voltage when the detection voltage of the voltage detection unit is increased, and the switch unit is set in the parallel connection state Sometimes, the switching unit compares the detection voltage of the voltage detection unit with the first threshold voltage, and when the detection voltage of the voltage detection unit becomes equal to or lower than the first threshold voltage, the switching unit is When the switch unit is set in the series connection state, the switching unit compares the detection voltage of the voltage detection unit with the second threshold voltage and sets the voltage detection unit. When the detected voltage becomes equal to or higher than the second threshold voltage, the switch unit is set to the parallel connection state.
Thus, in the power storage system according to one embodiment of the present invention, when the power generation element generates power, the operation of the load device can be restored in a short time.

Moreover, the electrical storage system which concerns on 1 aspect of this invention WHEREIN: The said switch part opens and closes the 1st switch part which opens and closes between the said feeder and the said 1st storage battery, the said 2nd storage battery and the said 1st. A second switch part selectively connected to the storage battery side, the first switch part is set so that the power supply line and the first storage battery are electrically connected, and the second switch part is By setting the ground side to be selected, the parallel connection state is established, and the first switch unit is set so as to cut off between the power supply line and the first storage battery, and the second switch unit is You may make it set it as the said serial connection state by setting to select the said 1st storage battery side.
Thereby, in the power storage system according to one aspect of the present invention, the first switch unit and the second switch unit connect the first storage battery and the second storage battery in parallel between the power supply line and the ground, It can selectively set to the state which connects a 1st storage battery and a 2nd storage battery in series between a feeder and a ground. When the system is restarted, the restart time can be shortened by connecting the first storage battery and the second storage battery in series between the power supply line and the ground.

Further, in the power storage system according to one aspect of the present invention, the capacity of the first storage battery is a power generation amount of the power generation element, an average value of power consumption of the load device that supplies power from the first storage battery, and A time for continuously driving the load device with the power stored in the first storage battery, and the capacity of the second storage battery is an average value of the power generation amount of the power generation element and the power consumption of the load device. And the time from when the operation of the load device stops due to a decrease in the charging voltage of the first storage battery until the power generation element generates power and restores the operation of the load device. It may be.
Thereby, in an electrical storage system, a load apparatus can be continuously driven for desired time with the electric power accumulate | stored in the 1st storage battery. Further, in the power storage system, when the power generation is performed by the power generation element, the operation of the load device can be restored in a desired time.

Further, in the power storage system according to one aspect of the present invention, the voltage detection unit detects a voltage of the power supply line, the first threshold voltage is set according to a lower limit voltage of the first storage battery, and the first The two threshold values may be set to a voltage obtained by adding a hysteresis voltage to the first threshold voltage.
By setting the first threshold voltage according to the lower limit voltage of the first storage battery, deterioration of the cells of the first storage battery can be prevented. The second threshold voltage can be stabilized by setting the first threshold voltage to a voltage obtained by adding a hysteresis voltage.

Further, in the power storage system according to one aspect of the present invention, the voltage detection unit detects a voltage of the first storage battery, and the first threshold voltage is set according to a lower limit voltage of the first storage battery, The second threshold value may be set to a voltage obtained by adding a corrected hysteresis voltage corrected according to the capacity of the first storage battery and the capacity of the second storage battery to the first threshold voltage.
By setting the first threshold voltage according to the lower limit voltage of the first storage battery, deterioration of the cells of the first storage battery can be prevented. In addition, the second threshold voltage is a voltage obtained by adding a corrected hysteresis voltage corrected according to the capacity of the first storage battery and the capacity of the second storage battery, so that the operation can be stabilized.

Moreover, the electrical storage system which concerns on 1 aspect of this invention WHEREIN: You may make it a said 1st storage battery be a capacitor of a kind with a smaller leakage current than a said 2nd storage battery.
In the power storage system having such a configuration, the large-capacity first storage battery needs to retain electric charge for a long time. For this reason, a capacitor with a small leakage current is used for the first storage battery.

The power storage system according to one aspect of the present invention includes a DC / DC converter that converts an output voltage of the power generation element into a predetermined voltage and supplies power to the first storage battery and the second storage battery, and the DC The / DC converter may control the output voltage so that the charging voltage of the first storage battery does not exceed a predetermined upper limit voltage.
Accordingly, the power storage system can convert the output voltage of the power generation element into a voltage that can operate the load device. Further, the DC / DC converter can prevent the first storage battery from being overcharged.

In the power storage system according to one aspect of the present invention, the first storage battery may be a lithium ion capacitor.
In the power storage system having such a configuration, the large-capacity first storage battery needs to retain electric charge for a long time. For this reason, a lithium ion capacitor with a small leakage current is used for the first storage battery.

In order to achieve the above object, a power storage method according to an aspect of the present invention includes a power generation element that performs environmental power generation, a power supply line that supplies power to a load device, and power generated by the power generation element via the power supply line. A first storage battery that is charged and supplies power to the load device; a second storage battery having a smaller capacity than the first storage battery; and the first storage battery and the second storage battery between the power supply line and the ground. A switch unit that selectively sets a parallel connection state in which the first storage battery and the second storage battery are connected in series between the power supply line and the ground; A power storage method in a power storage system comprising: a voltage detection unit that detects a voltage at which the first storage battery is overdischarged; and a switching unit that controls the switch unit according to a detection voltage of the voltage detection unit, wherein the switching Part is A first threshold voltage to be compared with a voltage when the detection voltage of the voltage detection unit is decreased, and a second threshold voltage to be compared with a voltage when the detection voltage of the voltage detection unit is increased, and When the switch unit is set in the parallel connection state, the switching unit compares the detection voltage of the voltage detection unit with the first threshold voltage, and the detection voltage of the voltage detection unit is the first threshold voltage. And when the switch unit is set in the series connection state, the switching unit sets the detection voltage of the voltage detection unit when the switch unit is set in the series connection state. Comparing with the second threshold voltage, and setting the switch unit in the parallel connection state when the detection voltage of the voltage detection unit is equal to or higher than the second threshold voltage.
Thus, in the power storage system, when the power generation element generates power, the operation of the load device can be restored in a short time.

  According to the power storage system of the present invention, when the power generation element generates power, the operation of the load device can be restored in a short time.

It is a block diagram which shows the structural example of the electrical storage system which concerns on 1st Embodiment. It is explanatory drawing which shows the electric power feeding state in each switch state in the electrical storage system which concerns on 1st Embodiment. It is explanatory drawing of switch control in an electrical storage system in 1st Embodiment. It is a flowchart which shows the process sequence in the electrical storage system which concerns on 1st Embodiment. It is a block diagram which shows the structural example of the electrical storage system which concerns on 2nd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a configuration diagram illustrating a configuration example of a power storage system 100 according to the present embodiment. The power storage system 100 supplies power to the load device 200 and operates the load device 200. The load device 200 is, for example, an environment monitoring device that functions as a wireless sensor that operates without wiring or battery replacement. This environmental monitoring device includes a temperature sensor that measures the temperature in a room such as an office, and a humidity sensor that measures the humidity in the room. The load device 200 operates in response to power supply from the power storage system 100. The load device 200 starts operating when the power supply voltage supplied from the power storage system 100 is, for example, 5.2 V or more, and is supplied from the power storage system 100. The operation is stopped when the power supply voltage becomes 2.5 V or less. Each voltage value mentioned above is an example, and is not limited to this. The voltage value according to the storage battery used for the electrical storage system 100 and the voltage value according to the use of the electrical storage system 100 may be sufficient.

  As shown in FIG. 1, a power storage system 100 includes a solar battery 110 using an energy harvesting element, a DC / DC converter 120 (DC voltage-DC voltage converter), a first storage battery 130, and a second storage battery 140. , A switching unit 150, a first switch unit 160, a voltage detection unit 170, and a second switch unit 180.

  The solar cell 110 is a low-illuminance solar cell, for example, a solar cell that is used at an illuminance of 10,000 (Lux) or less. The solar battery 110 is configured to connect a plurality of solar battery cells arranged on the light receiving surface side in series to obtain a predetermined output voltage Vs. The input side of the DC / DC converter 120 is connected to the output side of the solar cell 110.

  The DC / DC converter 120 converts the voltage Vs input from the solar battery 110 into a voltage corresponding to the power supply voltage to the load device 200. The output side of the DC / DC converter 120 is connected to the power supply line DCL1. Electric power is supplied to the load device 200 through the feeder line DCL1. For example, when the output voltage Vs of the solar cell 110 is lower than the voltage required by the load device 200, the DC / DC converter 120 is configured by a boost converter device or the like. Further, the DC / DC converter 120 controls the output voltage so that the charging voltage of the first storage battery 130 does not exceed a predetermined upper limit voltage.

  The first switch unit 160 turns ON or OFF between the positive electrode (+) terminal of the first storage battery 130 and the power supply line DCL1. The terminal a of the first switch unit 160 is connected to the power supply line DCL1 through the voltage detection unit 170, and is connected to the positive electrode (+) terminal of the second storage battery 140. The terminal b of the first switch unit 160 is connected to the positive electrode (+) terminal of the first storage battery 130 and to the terminal f of the second switch unit 180.

  The first storage battery 130 is charged by the generated power of the solar battery 110 and supplies power to the load device 200. The first storage battery 130 is a large-capacity capacitor, for example, a 40 F (Farad) lithium ion capacitor (LIC). The negative electrode (−) terminal of the first storage battery 130 is connected to the ground GND. The positive (+) terminal of the first storage battery 130 is connected to the terminal b of the first switch unit 160 and to the terminal f of the second switch unit 180. Note that the first storage battery 130 needs to store charges for a long time, and thus a lithium ion capacitor with a small leakage current is used. The capacity | capacitance of the 1st storage battery 130 is not limited to 40F, A suitable capacity | capacitance is based on the electric power generation amount of the solar cell 110, the average value of the power consumption of the load apparatus 200, and the time to drive the load apparatus 200 continuously. Can be selected. The first storage battery 130 is charged to a voltage of, for example, about 2.5V to 3.7V at the time of shipment.

  The second storage battery 140 is a capacitor having a smaller capacity than that of the first storage battery 130, and is, for example, a 1F (Farad) electric double layer capacitor (EDLC). The positive electrode (+) terminal of the second storage battery 140 is connected to the power supply line DCL <b> 1 via the voltage detection unit 170 and to the terminal a of the first switch unit 160. The negative electrode (−) terminal of the second storage battery 140 is connected to the common terminal d of the second switch unit 180. In addition, the capacity | capacitance of the 2nd storage battery 140 is not limited to 1F, suitably based on the electric power generation amount of the solar cell 110, the average value of the power consumption of the load apparatus 200, and the time which the load apparatus 200 wants to return. Capacitors with a large capacity can be selected.

  The second switch unit 180 selectively connects the negative electrode (−) terminal of the second storage battery 140 to the ground GND side and the positive electrode (+) terminal side of the first storage battery 130. The common terminal d of the second switch unit 180 is connected to the negative (−) terminal of the second storage battery 140. The terminal e of the second switch unit 180 is connected to the ground GND. The terminal f of the second switch unit 180 is connected to the positive (+) terminal of the first storage battery 130 and to the terminal b of the first switch unit 160. Hereinafter, a state in which the common terminal d and the terminal e of the second switch unit 180 are connected is referred to as a state in which the second switch unit 180 selects the ground GND side. The state where the common terminal d and the terminal f of the second switch unit 180 are connected is referred to as a state where the second switch unit 180 selects the first storage battery 130 side.

  The voltage detector 170 is provided to detect the overdischarge voltage of the first storage battery 130. In other words, the lithium ion capacitor constituting the first storage battery 130 has a lower limit voltage, and when the battery is overdischarged to this lower limit voltage, the cell is deteriorated. The voltage detector 170 detects a voltage corresponding to the charging voltage of the first storage battery 130 so that the lithium ion capacitor constituting the first storage battery 130 is not overdischarged to the lower limit voltage. Here, the voltage detection unit 170 detects the voltage corresponding to the overdischarge voltage of the first storage battery 130 by detecting the voltage Vout of the feeder line DCL1 and outputting this voltage detection signal Vf to the switching unit 150. Yes. The voltage detection unit 170 is configured using, for example, a resistance voltage dividing circuit.

  The switching unit 150 controls the first switch unit 160 and the second switch unit 180 according to the detection voltage of the voltage detection unit 170. The switching unit 150 includes a comparison unit 151. The comparison unit 151 compares the voltage detection signal Vf from the power supply line DCL1 input from the voltage detection unit 170 with a predetermined first threshold voltage Ref1 and second threshold voltage Ref2 included in the comparison unit 151. The first threshold voltage Ref1 is a threshold voltage at which the voltage Vout of the feeder line DCL1 drops from the normal state and the load device 200 stops operating. The first threshold voltage Ref1 is set according to the lower limit voltage of the lithium ion capacitor constituting the first storage battery 130. The lower limit voltage of the lithium ion capacitor is, for example, about 2V, and the first threshold voltage Ref1 is, for example, 2.5V. The second threshold voltage Ref2 is a threshold voltage when the voltage Vout of the feeder line DCL1 rises from the state where the load device 200 stops operating and returns to the normal state. The second threshold voltage Ref2 is a voltage higher than the first threshold voltage Ref1 by a voltage corresponding to the hysteresis voltage. The hysteresis voltage is, for example, 2.7V, and the second threshold voltage Ref2 is (2.5V + 2.7V = 5.2V).

  In the normal state, the switching unit 150 outputs a control signal CNT1 that turns on the first switch unit 160, and outputs a control signal CNT2 that causes the second switch unit 180 to select the ground GND side. The normal state is a state in which the first storage battery 130 and the second storage battery 140 are charged by the generated power of the solar battery 110 and power is mainly supplied from the first storage battery 130 to the load device.

  In the normal state, when the power generation of the solar cell 110 is stopped, the voltage Vout of the power supply line DCL1 is changed from the voltage in the normal state (for example, 3 V) to the first threshold voltage Ref1 (for example, based on the voltage detection signal Vf input from the voltage detection unit 170 The switching unit 150 determines that the voltage has dropped to 2.5 V) or less. When determining in this way, the switching unit 150 outputs the control signal CNT1 for turning the first switch unit 160 to the OFF state, and outputs the control signal CNT2 for selecting the second switch unit 180 to the first storage battery 130 side. To do. As a result, the first storage battery 130 and the second storage battery 140 are switched from parallel connection to series connection, and the voltage Vout of the feeder line DCL1 is added to the charge voltage of the second storage battery 140 and the charge voltage of the first storage battery 130. Become a voltage. Further, the load device 200 stops operating.

  The first storage battery 130 and the second storage battery 140 are connected in parallel immediately after the first switch section 160 is in the OFF state and the second switch section 180 is selected on the first storage battery 130 side (also referred to as a fast startup state). Therefore, the voltage Vout of the feeder line DCL1 is about twice the first threshold voltage Ref1. The voltage Vout of the feeder line DCL1 increases due to the subsequent restart of power generation of the solar battery 110. When the voltage Vout of the feeder line DCL1 rises to the second threshold voltage Ref2 (5.2V), the operation of the load device 200 is first restored. Further, the switching unit 150 determines that the voltage Vout of the power supply line DCL1 has increased to the second threshold voltage Ref2, outputs a control signal CNT1 for turning on the first switch unit 160, and sets the second switch unit 180 to ground. A control signal CNT2 to be selected on the GND side is output. Thereby, the 1st storage battery 130 and the 2nd storage battery 140 switch from a serial connection to a parallel connection. Thus, the switching unit 150 has a hysteresis characteristic with a width of 2.7 V between the first threshold voltage Ref1 (2.5 V) and the second threshold voltage Ref2 (5.2 V), and the first switch unit 160 The second switch unit 180 is controlled.

  In FIG. 1, the example comprised with the switch using a mechanical contact as the 1st switch part 160 and the 2nd switch part 180 is shown. The switch may include a semiconductor switch using a semiconductor switching element such as a MOSFET (Metal Oxide Field Effect Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor).

  Next, the operation of the power storage system 100 will be described. FIG. 2 is an explanatory diagram illustrating a power supply state in each switch state in the power storage system according to the present embodiment. FIG. 2A is an explanatory diagram when the first switch unit 160 is in the ON state and the second switch unit 180 is in the state of selecting the ground GND side. In this state, the terminal a and the terminal b of the first switch unit 160 are connected, and the common terminal d and the terminal e of the second switch unit 180 are connected. In this case, the positive electrode (+) terminal of the first storage battery 130 is connected to the power supply line DCL1 via the first switch unit 160, and the negative electrode (−) terminal of the first storage battery 130 is connected to the ground GND. The positive electrode (+) terminal of the second storage battery 140 is connected to the power supply line DCL1, and the negative electrode (−) terminal of the second storage battery 140 is connected to the ground GND through the second switch unit 180. Therefore, the first storage battery 130 and the second storage battery 140 are connected in parallel between the feeder line DCL1 and the ground GND.

  In the normal state, the first storage battery 130 and the second storage battery 140 are charged by the generated power of the solar battery 110, and the discharge currents Ia3 and Ia4 are supplied from the first storage battery 130 and the second storage battery 140 to the load device 200. Supply power. As described above, in the normal state, the first storage battery 130 and the second storage battery 140 are connected in parallel between the feeder line DCL1 and the ground GND, depending on the generated power from the solar battery 110 and the operating state of the load device 200. Thus, the first storage battery 130 and the second storage battery 140 are charged and discharged. In addition, since the capacity | capacitance of the 1st storage battery 130 is larger than the capacity | capacitance of the 2nd storage battery 140, it is the 1st storage battery 130 that mainly charges / discharges the electric power generated from the solar cell 110.

  When the power generation of the solar battery 110 is stopped, the discharge of the first storage battery 130 and the second storage battery 140 proceeds, and the voltage Vout of the feeder line DCL1 decreases. When the voltage Vout of the power supply line DCL1 drops below the first threshold voltage Ref1 (2.5 V), the load device 200 stops operating, and the switching unit 150 turns off the first switch unit 160 and The 2 switch unit 180 is in a state of selecting the first storage battery 130 side.

  FIG. 2B is an explanatory diagram when the first switch unit 160 is in an OFF state and the second switch unit 180 is in a state where the first storage battery 130 side is selected. In this state (high-speed startup state), the terminal a and the terminal b of the first switch unit 160 are cut off, and the common terminal d and the terminal f of the second switch unit 180 are connected. In this case, the positive electrode (+) terminal of the first storage battery 130 is connected to the negative electrode (−) terminal of the second storage battery 140 via the second switch unit 180. Therefore, the first storage battery 130 and the second storage battery 140 are switched from the parallel connection to the series connection between the power supply line DCL1 and the ground GND, and the voltage Vout of the power supply line DCL1 is about the first threshold voltage Ref1 (2.5V). Doubled.

  Thereafter, when the power generation of the solar battery 110 is resumed, the current Ib flows from the solar battery 110 to the series circuit of the first storage battery 130 and the second storage battery 140, and charging to the first storage battery 130 and the second storage battery 140 is performed. Be started. As a result, the voltage Vout of the feeder line DCL1 further increases.

Here, the capacity (for example, 1F) of the second storage battery 140 is smaller than the capacity (for example, 40F) of the first storage battery 130. For this reason, when the charging from the solar battery 110 to the second storage battery 140 is started, the charging voltage of the second storage battery 140 rapidly increases. Since the voltage Vout of the power supply line DCL1 is an added value of the charging voltage of the first storage battery 130 and the charging voltage of the second storage battery 140, the voltage Vout of the power supply line DCL1 is rapidly increased by the increase of the charging voltage of the second storage battery 140. To rise.
When the voltage Vout of the feeder line DCL1 rises to the second threshold voltage Ref2 (5.2 V) or higher, the operation of the load device 200 is restored, and the switching unit 150 is configured as shown in FIG. The first switch unit 160 is turned on, and the second switch unit 180 is selected to select the ground GND side. As a result, the first storage battery 130 and the second storage battery 140 are switched from the serial connection to the parallel connection, and power is mainly supplied again from the first storage battery 130 to the load device 200. The power storage system 100 is in a normal state. Return to the operation.

  In the present embodiment, the switching unit 150 has a hysteresis characteristic having a width of 2.7 V between the first threshold voltage Ref1 (2.5 V) and the second threshold voltage Ref2 (5.2 V). The switch unit 160 and the second switch unit 180 are controlled. For this reason, stable operation can be maintained.

  FIG. 3 is an explanatory diagram of switch control in the power storage system 100 according to the present embodiment. In FIG. 3, the horizontal axis indicates time, and the vertical axis indicates the detection voltage of the voltage detection unit 170.

  It is assumed that the power generation operation of the solar cell 110 is stopped in a normal state at time t0. At this time, it is assumed that the first switch unit 160 is in an ON state and the second switch unit 180 is in a state of selecting the ground GND side. When the power generation operation of the solar battery 110 is stopped, the first storage battery 130 and the second storage battery 140 are discharged, and the detection voltage of the voltage detection unit 170 decreases as shown in FIG.

  When the detection voltage of the voltage detection unit 170 decreases to the first threshold voltage Ref1 (2.5 V) or less at time t1, the load device 200 stops operating. And the 1st switch part 160 will be in an OFF state, the 2nd switch part 180 will be in the state which selects the 1st storage battery 130 side, and the 1st storage battery 130 and the 2nd storage battery 140 are between the feeder line DCL1 and the ground GND. Are connected in series, and the voltage Vout of the feeder line DCL1 is approximately twice the first threshold voltage Ref1 (2.5 V).

  Thereafter, it is assumed that the power generation operation of the solar cell 110 is resumed at time t2. When the power generation of the solar battery 110 is resumed, a charging current flows from the solar battery 110 to the series circuit of the first storage battery 130 and the second storage battery 140. Thereby, the detection voltage of the voltage detection part 170 rises. Since the second storage battery 140 having a small capacity is connected in series to the first storage battery 130, the voltage Vout of the feeder line DCL1 rises rapidly. For this reason, as shown in FIG. 3, the detection voltage of the voltage detection part 170 is rising rapidly after the time t2.

  At time t3, when the detection voltage of the voltage detection unit 170 rises to the second threshold voltage Ref2 (5.2V) or higher, the operation of the load device 200 is restored, the first switch unit 160 is turned on, The 2 switch unit 180 enters a state of selecting the ground GND side and returns to the normal operation. In the normal state, since the first storage battery 130 and the second storage battery 140 are connected in parallel between the power supply line DCL1 and the ground GND, the detection voltage of the voltage detection unit 170 gradually increases after time t3. To go.

  As described above, in the power storage system 100 according to the present embodiment, the first storage battery 130 and the small-capacity second storage battery 140 are arranged in series between the power supply line DCL1 and the ground GND in the high-speed startup state. Is done. Thereby, the electrical storage system 100 can return operation | movement of the load apparatus 200 which operation | movement stopped once because the voltage value of the 1st storage battery 130 fell, after the electric power generation of the solar cell 110 was restarted.

  In the normal state, since the first storage battery 130 and the second storage battery 140 are connected in parallel between the power supply line DCL1 and the ground GND, the second storage battery 140 is also charged. Therefore, when the first storage battery 130 and the second storage battery 140 are connected in series between the power supply line DCL1 and the ground GND, electric charge remains in the second storage battery 140. Thereby, compared with the case where the 2nd storage battery 140 is returned from the state discharged completely, the return time can be shortened.

FIG. 4 is a flowchart showing a processing procedure in the power storage system 100 according to the present embodiment.
First, it is assumed that the power storage system 100 is operating in a normal state (parallel connection) (step S101). That is, in the power storage system 100, the first switch unit 160 is in the ON state, the second switch unit is in the state of selecting the ground GND side, the voltage Vout of the power supply line DCL1 exceeds 2.5V, and the load device Assume that 200 is operating.

  Subsequently, the voltage detection unit 170 detects the voltage Vout of the feeder line DCL1, and outputs the voltage detection signal Vf to the switching unit 150 (step S102). Subsequently, the switching unit 150 determines whether or not the detection voltage of the voltage detection unit 170 is equal to or lower than the first threshold voltage Ref1 (2.5 V) (step S103). In step S103, when it is determined that the detection voltage of the voltage detection unit 170 is not less than or equal to the first threshold voltage Ref1 (2.5V) (step S103: No), the load device 200 continues to operate (step S104). The power storage system 100 returns to the process of step S102. Subsequently, the power storage system 100 executes the processing from step S102 onward again.

  On the other hand, when it is determined in step S103 that the voltage Vout of the feeder line DCL1 is equal to or lower than the first threshold voltage Ref1 (2.5 V) (step S103: Yes), the load device 200 stops operating (step S105). Then, the power storage system 100 proceeds to the process of step S106.

  In step S106, the switching unit 150 switches the first switch unit 160 from the ON state to the OFF state, and switches the second switch unit 180 to a state of selecting the first storage battery 130 side. Thereby, the 1st storage battery 130 and the 2nd storage battery 140 are connected in series between electric power feeding line DCL1 and ground GND. Then, when the solar battery 110 is generating power, the solar battery 110 is charged into the series circuit of the first storage battery 130 and the second storage battery 140 (step S107).

  Subsequently, the voltage detection unit 170 detects the voltage Vout of the feeder line DCL1, and outputs the voltage detection signal Vf to the switching unit 150 (step S108). The switching unit 150 determines whether or not the detection voltage of the voltage detection unit 170 is equal to or higher than the second threshold voltage Ref2 (5.2V) (step S109). When it is determined in step S109 that the detection voltage of the voltage detection unit 170 is not equal to or higher than the second threshold voltage Ref2 (5.2V) (step S109: No), the process returns to step S106, and the switching unit 150 The first switch unit 160 is maintained in the OFF state, and the second switch unit 180 is maintained in the state in which the first storage battery 130 side is selected (step S106). Subsequently, the power storage system 100 repeatedly executes the processes after step S106.

  In the power storage system 100, when the solar battery 110 does not generate power and the solar battery 110 does not charge the series circuit of the first storage battery 130 and the second storage battery 140, the voltage Vout of the feeder line DCL1 does not increase. The processing from step S106 to step S109 is repeatedly executed. When power generation from the solar battery 110 resumes, a charging current flows through the series connection of the first storage battery 130 and the second storage battery 140, and the voltage Vout of the feeder line DCL1 increases.

  When it is determined that the voltage Vout of the feeder line DCL1 has risen to the second threshold voltage Ref2 (5.2 V) or higher (step S109: Yes), the operation of the load device 200 is restored (step S110), and the switching unit 150 Switches the first switch unit 160 from the OFF state to the ON state, and switches the second switch unit 180 to the state of selecting the ground GND side (step S111). Thereby, the electrical storage system 100 returns to a normal state (parallel connection). Subsequently, the power storage system 100 returns to the process of step S102 and executes the processes after step S102 again.

  As described above, the power storage system 100 of the present embodiment includes a power generation element (for example, the solar battery 110) that performs environmental power generation, the power supply line DCL1 that supplies power to the load device 200, and power generation of the power generation element via the power supply line. The first storage battery 130 that is charged with power and supplies power to the load device, the second storage battery 140 that has a smaller capacity than the first storage battery, and the first storage battery and the second between the power supply line and the ground (GND) A parallel connection state in which the storage batteries are connected in parallel (FIG. 2A) and a serial connection state in which the first storage battery and the second storage battery are connected in series between the power supply line and the ground (FIG. 2B). Switch units (first switch unit 160, second switch unit 180) that are selectively set, voltage detection unit 170 that detects a voltage at which the first storage battery is overdischarged, and a detection voltage of the voltage detection unit Switch A switching unit 150 that controls the first threshold voltage Ref1 to be compared with the voltage when the detection voltage of the voltage detection unit is decreased, and the voltage when the detection voltage of the voltage detection unit is increased. When the switch unit is set in a parallel connection state, the switching unit compares the detection voltage of the voltage detection unit with the first threshold voltage and detects the detection voltage of the voltage detection unit. Is set to a series connection state when the voltage becomes equal to or lower than the first threshold voltage, and when the switch unit is set to the series connection state, the switching unit sets the detection voltage of the voltage detection unit to the second threshold value. When the detection voltage of the voltage detection unit becomes equal to or higher than the second threshold voltage as compared with the voltage, the switch unit is set in a parallel connection state.

  With this configuration, in this embodiment, when the power generation element generates power, the operation of the load device can be restored in a short time.

[Second Embodiment]
FIG. 5 is a configuration diagram illustrating a configuration example of the power storage system 100A according to the present embodiment. The position of the voltage detector 170A is different from the position of the voltage detector 170 of the first embodiment. Other configurations are the same as those in the first embodiment, and the same components are denoted by the same reference numerals, and redundant description is omitted.

  In the first embodiment, the voltage detection unit 170 detects a voltage between the ground GND and the power supply line DCL1 and outputs the voltage to the switching unit 150. On the other hand, in the second embodiment, the voltage detection unit 170A detects a voltage between the ground GND and the positive electrode (+) terminal of the first storage battery 130 and outputs the voltage to the switching unit 150.

  In the first embodiment, the first threshold voltage Ref1 is set according to the lower limit voltage of the lithium ion capacitor that constitutes the first storage battery 130. The first threshold voltage Ref1 is a threshold voltage when the first switch unit 160 is in an ON state and the second switch unit 180 is in a state of selecting the ground GND side. At this time, since the first switch unit 160 is in the ON state, the voltage between the ground GND and the power supply line DCL1 is equal to the voltage between the ground GND and the positive electrode (+) terminal of the first storage battery 130. Accordingly, the first threshold voltage Ref1A in the case of the second embodiment is, for example, in accordance with the lower limit voltage of the lithium ion capacitor constituting the first storage battery 130, similarly to the first threshold voltage Ref1 in the case of the first embodiment. Set to 2.5V.

  In the first embodiment, the second threshold voltage Ref2 is set to a voltage that is higher than the first threshold voltage Ref1 by a voltage corresponding to the hysteresis voltage. The second threshold voltage Ref2 is a threshold voltage when the first switch unit 160 is in an OFF state and the second switch unit 180 is in a state of selecting the first storage battery 130 side. In this case, the voltage detection unit 170 in the case of the first embodiment detects the voltage between the ground GND and the power supply line DCL1, and this voltage is the charge voltage of the first storage battery 130 and that of the second storage battery 140. Addition value with charging voltage. On the other hand, in the voltage detection unit 170A in the case of the second embodiment, the voltage between the ground GND and the first storage battery 130 (charge voltage of the first storage battery 130) is detected. It becomes a different value by the charge voltage. Therefore, in the second embodiment, the second threshold voltage Ref2A is added to the first threshold voltage Ref1A by adding a corrected hysteresis voltage corrected according to the capacity of the first storage battery 130 and the capacity of the second storage battery 140. It is set.

That is, in the first embodiment, the second threshold voltage Ref2 (5.2V) is higher than the first threshold voltage Ref1 (2.5V) by a voltage 2.7V corresponding to the hysteresis voltage (2.5V + 2.7V = 5.2V). Here, the hysteresis voltage of 2.7 V is a rise in the charging voltage (2.5 V) of the second storage battery 140 immediately after being connected in series and the charging voltage of the second storage battery 140 mainly due to the subsequent power generation of the solar battery 110. Minutes (0.2V).
In the present embodiment, when the capacity of the first storage battery 130 is 40F and the capacity of the second storage battery 140 is 1F, the voltage change of 0.2V in the second storage battery 140 is (0.2V in the first storage battery 130). This corresponds to a voltage change of × (1F / 40F)) V. Therefore, the second threshold voltage Ref2A in the present embodiment is expressed by the following equation (1).

Ref2A = 2.5V + (0.2V × (1F / 40F)) (1)

Set as That is, when the second threshold voltage Ref2A is the capacity C1 of the first storage battery 130 and the capacity C2 of the second storage battery 140, the second threshold voltage Ref2A is represented by Ref2A = 2.5V + (0.2V × (C2 / C1)). Note that the values of 2.5 V and 0.2 V in the formula (1) are merely examples, and the present invention is not limited thereto.

  As described above, in the power storage system 100A of the present embodiment, the voltage detection unit 170A detects the voltage of the first storage battery 130, the first threshold voltage Ref1A is set according to the lower limit voltage of the first storage battery, The second threshold voltage Ref2A is set to a voltage obtained by adding a corrected hysteresis voltage corrected according to the capacity of the first storage battery and the capacity of the second storage battery 140 to the first threshold voltage.

  With this configuration, in this embodiment, the first threshold voltage is set according to the lower limit voltage of the first storage battery, thereby preventing the deterioration of the cells of the first storage battery. Moreover, in this embodiment, operation | movement can be stabilized by making the 2nd threshold voltage into the voltage which added the correction | amendment hysteresis voltage corrected according to the capacity | capacitance of a 1st storage battery, and the capacity | capacitance of a 2nd storage battery.

As mentioned above, although this invention was demonstrated, the electrical storage system of this invention is not limited only to the above-mentioned illustration example, Of course, in the range which does not deviate from the summary of this invention, a various change can be added.
For example, in the above-described example, the example of the solar cell 110 using the environmental power generation element as the power generation element is shown, but the present invention is not limited thereto. The power generation element may be any power generation element that can perform environmental power generation. Here, energy harvesting other than light is, for example, power generation by heat, vibration, wind power, radio waves, and the like.

  The power storage systems 100 and 100A can be used as a power source for opening and closing a door and a power source for an electrical switch. When the power storage system is used as a power source for opening and closing a door, the power consumption of the power source for opening and closing the door and the power source of the electric switch varies depending on the installation environment and usage conditions. Even if it hits, the balance of power generation and power consumption may be negative. In such a case, the power storage systems 100 and 100A can be suitably used.

DESCRIPTION OF SYMBOLS 100,100A ... Power storage system, 110 ... Solar cell, 120 ... Converter, 130 ... First storage battery, 140 ... Second storage battery, 150 ... Switching part, 151 ... Comparison part, 160 ... First switch part, 170, 170A ... Voltage Detection unit, 180 ... second switch unit

Claims (9)

A power generation element that performs energy harvesting,
A power supply line for supplying power to the load device;
A first storage battery that is charged with the generated power of the power generation element via the feeder and that supplies power to the load device;
A second storage battery having a smaller capacity than the first storage battery;
A parallel connection state in which the first storage battery and the second storage battery are connected in parallel between the power supply line and the ground, and the first storage battery and the second storage battery between the power supply line and the ground. A switch part that is selectively set to a serial connection state connected in series;
A voltage detector for detecting a voltage at which the first storage battery is overdischarged;
A switching unit that controls the switch unit according to a detection voltage of the voltage detection unit;
With
The switching unit has a first threshold voltage to be compared with a voltage when the detection voltage of the voltage detection unit is decreased, and a second threshold voltage to be compared with a voltage when the detection voltage of the voltage detection unit is increased. And
When the switch unit is set in the parallel connection state, the switching unit compares the detection voltage of the voltage detection unit with the first threshold voltage, and the detection voltage of the voltage detection unit is the first threshold value. When the voltage falls below the voltage, the switch unit is set in the series connection state,
When the switch unit is set in the series connection state, the switching unit compares the detection voltage of the voltage detection unit with the second threshold voltage, and the detection voltage of the voltage detection unit is the second threshold value. A power storage system that sets the switch unit to the parallel connection state when the voltage exceeds a voltage. The switch unit includes a first switch unit that opens and closes between the power supply line and the first storage battery, and a second switch unit that selectively connects the second storage battery to the ground side and the first storage battery side. And consist of
The first switch unit is set to conduct between the power supply line and the first storage battery, and the second switch unit is set to select the ground side, thereby setting the parallel connection state. ,
By setting the first switch part so as to cut off between the power supply line and the first storage battery, and setting the second switch part to select the first storage battery side, the series connection The power storage system according to claim 1 in a state. The capacity of the first storage battery is determined based on the amount of power generated by the power generation element, the average value of power consumption of the load device that supplies power from the first storage battery, and the power stored in the first storage battery. Set based on the continuous driving time,
The capacity of the second storage battery is the power generation amount after the operation of the load device is stopped due to a decrease in the power generation amount of the power generation element, the average power consumption of the load device, and the charge voltage of the first storage battery. The power storage system according to claim 1, wherein the power storage system is set based on a time until the element generates power and returns the operation of the load device.   The voltage detection unit detects a voltage of the feeder line, the first threshold voltage is set according to a lower limit voltage of the first storage battery, and the second threshold voltage is a hysteresis voltage to the first threshold voltage. The power storage system according to any one of claims 1 to 3, wherein the power storage system is set to a voltage obtained by adding a voltage.   The voltage detection unit detects a voltage of the first storage battery, the first threshold voltage is set according to a lower limit voltage of the first storage battery, and the second threshold voltage is set to the first threshold voltage. The power storage system according to any one of claims 1 to 3, wherein the power storage system is set to a voltage obtained by adding a corrected hysteresis voltage corrected according to the capacity of the first storage battery and the capacity of the second storage battery.   The power storage system according to any one of claims 1 to 5, wherein the first storage battery is a capacitor of a type having a smaller leakage current than the second storage battery. A DC / DC converter that converts the output voltage of the power generation element into a predetermined voltage and supplies power to the first storage battery and the second storage battery;
The power storage system according to claim 1, wherein the DC / DC converter controls an output voltage so that a charging voltage of the first storage battery does not exceed a predetermined upper limit voltage.   The power storage system according to claim 1, wherein the first storage battery is a lithium ion capacitor. A power generation element that performs environmental power generation, a power supply line that supplies power to the load device, a first storage battery that is charged by the generated power of the power generation element via the power supply line and supplies power to the load device, and A second storage battery having a smaller capacity than the first storage battery, a parallel connection state in which the first storage battery and the second storage battery are connected in parallel between the power supply line and the ground, and the power supply line and the ground. A switch unit that selectively sets the first storage battery and the second storage battery in series to each other in series, a voltage detection unit that detects a voltage at which the first storage battery is overdischarged, and A power storage method in a power storage system comprising: a switching unit that controls the switch unit according to a detection voltage of a voltage detection unit,
The switching unit has a first threshold voltage to be compared with a voltage when the detection voltage of the voltage detection unit is decreased, and a second threshold voltage to be compared with a voltage when the detection voltage of the voltage detection unit is increased. And
When the switch unit is set in the parallel connection state, the switching unit compares the detection voltage of the voltage detection unit with the first threshold voltage, and the detection voltage of the voltage detection unit is the first threshold value. When the voltage is equal to or lower than the voltage, the step of setting the switch unit in the series connection state;
When the switch unit is set in the series connection state, the switching unit compares the detection voltage of the voltage detection unit with the second threshold voltage, and the detection voltage of the voltage detection unit is the second threshold value. A step of setting the switch unit to the parallel connection state when the voltage exceeds a voltage;
A power storage method comprising:

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