Power storage system, power storage device, method of controlling power storage device, and control program for power storage device

Abstract

To provide a power storage system that enables intake of electric power to a power storage device without relying on an instruction from the outside of the power storage system, and enables power supply to the outside of the power storage device.SOLUTION: A power storage system 1 comprises: a power storage device 2; and a control device 3. The power storage device 2 includes: a power storage unit 14 that stores electricity; and a main circuit unit 13 that receives and supplies power between a wiring 7 and each of external devices 6 connected to the power storage system 1, and the power storage unit 14. The control device 3 includes: a data acquisition unit 11 that acquires wiring voltage data that indicates a voltage of the wiring 7 and power demand data that indicates a demand for power of each external device 6; and a control unit 12 that makes the main circuit unit 13 take in power to the power storage unit 14 from the wiring 7 or supply power to the wiring 7 from the power storage unit 14 on the basis of the wiring voltage data, and performs diagnosis of the power demand data, and makes the main circuit unit 13 supply power to the external device 6 from the power storage unit 14 on the basis of a diagnosis result.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a power storage system for storing power, a power storage device, a control method for the power storage device, and a control program for the power storage device.

Background Art

[0002] Conventionally, a power storage device that stores power taken in from a railway overhead wire has been known. Patent Document 1 discloses a power storage device including a power storage unit electrically connected to a vehicle and a power load other than the vehicle in a railway, and supplying the power stored in the power storage unit to at least one of the vehicle and the power load. The power storage device according to Patent Document 1 supplies power to at least one of the vehicle and the power load when the power consumption of the power-using facility including the vehicle and the power load becomes equal to or higher than a threshold value. The power storage device according to Patent Document 1 receives a signal indicating that the power consumption of the power-using facility has become equal to or higher than the threshold value from a substation that supplies power to the power-using facility or an operation command station that monitors the operation of the vehicle or the like, and supplies power according to the signal. Thus, the power storage device according to Patent Document 1 takes in power into the power storage device and supplies power outside the power storage device according to a command from outside the system having the power storage device. Hereinafter, a system having a power storage device is referred to as a power storage system.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] It has been desired that the power storage system takes in power into the power storage device and supplies power outside the power storage device without depending on a command from outside the power storage system.

[0005] The present disclosure has been made in view of the above, and an object thereof is to obtain a power storage system that enables power to be taken into a power storage device and power to be supplied from the power storage device to the outside without a command from outside the power storage system.

Means for Solving the Problems

[0006] In order to solve the above-described problems and achieve the object, a power storage system according to the present disclosure is a power storage system that stores power taken from a railway overhead line. The power storage system according to the present disclosure includes a power storage device and a control device. The power storage device has a power storage unit that stores electricity, and a main circuit unit that transfers power between the overhead line and each of the external devices connected to the power storage system and the power storage unit. The control device has a data acquisition unit that acquires overhead line voltage data indicating the voltage of the overhead line and power demand data indicating the power demand by the external device, and based on the overhead line voltage data, causes the main circuit unit to take in power from the overhead line into the power storage unit or supply power from the power storage unit to the overhead line, and based on the power demand data, causes the main circuit unit to supply power from the power storage unit to the external device.

Advantages of the Invention

[0007] The power storage system according to the present disclosure has an effect that power can be taken into the power storage device and power can be supplied from the power storage device to the outside without a command from outside the power storage system.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0009] Hereinafter, a power storage system, a power storage device, a control method for the power storage device, and a control program for the power storage device according to the embodiments will be described in detail with reference to the drawings.

[0010] Embodiment 1. FIG. 1 is a diagram showing a configuration example of a power storage system 1 according to Embodiment 1. The power storage system 1 stores the power taken in from the overhead line 7 of the railway. The power storage system 1 is installed, for example, in a station building.

[0011] Power is supplied to the overhead line 7 from a plurality of substations 5. A train running on the rails is connected to the overhead line 7 when the pantograph of the train contacts the overhead line 7. FIG. 1 shows the power storage system 1, two of the plurality of substations 5 connected to the overhead line 7, and an external device 6 connected to the power storage system 1. The illustration of the rails and the train is omitted. The number of substations 5 connected to the overhead line 7 is assumed to be arbitrary.

[0012] The power storage system 1 includes a power storage device 2 that stores the power taken in from the overhead line 7 of the railway, a control device 3 that controls the power storage device 2, a charging interface 4, and a circuit breaker 10. The external device 6 is a device that can be charged by the power supply from the power storage system 1. The external device 6 is charged by being connected to the charging interface 4. In Embodiment 1, the external device 6 is assumed to be an electric vehicle (EV: Electric Vehicle). Note that the external device 6 may be any device that can be charged and is not limited to an electric vehicle.

[0013] The power storage device 2 includes a main circuit unit 13 and a power storage unit 14. The main circuit unit 13 transfers electric power between each of the overhead line 7 and the external device 6 and the power storage unit 14. The power storage unit 14 stores electricity.

[0014] The main circuit unit 13 includes a power conversion unit 15 and an input / output switching circuit 16. The power conversion unit 15 converts the voltage of the electric power taken in from the overhead line 7 into the same voltage as the voltage used by the external device 6. In the following description, it is assumed that the voltage of the overhead line 7 is DC (Direct Current) 1500V and the voltage of the external device 6 is DC500V.

[0015] When electric power is taken into the main circuit unit 13 from the overhead line 7, the power conversion unit 15 converts DC1500V system DC power into DC500V system DC power. The main circuit unit 13 outputs the power whose voltage has been converted by the power conversion unit 15 to the power storage unit 14. The power storage unit 14 stores and discharges electricity at DC500V. Also, when electric power is supplied from the power storage unit 14 to the overhead line 7, the power conversion unit 15 converts DC500V system DC power into DC1500V system DC power. The power conversion unit 15 is, for example, a bidirectional DC / DC converter. Note that the voltage of the overhead line 7 may be a voltage other than the DC1500V system, and the voltage of the external device 6 may be a voltage other than the DC500V system.

[0016] A voltage sensor for detecting the overhead line voltage, which is the voltage of the overhead line 7, is attached to the power conversion unit 15. Illustration of the voltage sensor is omitted. The voltage sensor detects the overhead line voltage at the measurement point on the overhead line 7. The voltage sensor outputs overhead line voltage data indicating the overhead line voltage to the control device 3.

[0017] The input / output switching circuit 16 switches between turning on and off the power supply from the overhead line 7 to the power storage unit 14, turning on and off the power supply from the power storage unit 14 to the overhead line 7, and turning on and off the power supply from the power storage unit 14 to the external device 6. The main circuit unit 13 performs the power transfer between the overhead line 7 and the power storage unit 14 and the power transfer between the power storage unit 14 and the external device 6 by such input / output switching in the input / output switching circuit 16. The input / output switching circuit 16 may further be able to switch between turning on and off the power supply from the overhead line 7 to the external device 6. In this case, the main circuit unit 13 performs the power transfer between the overhead line 7 and the external device 6.

[0018] The control device 3 includes a data acquisition unit 11 and a control unit 12. The data acquisition unit 11 acquires overhead line voltage data indicating the voltage of the overhead line 7 and power demand data indicating the power demand by the external device 6. The data acquisition unit 11 acquires the overhead line voltage data output from the above voltage sensor. The data acquisition unit 11 acquires the power demand data output from the charging interface 4. In FIG. 1, the arrow from the power conversion unit 15 to the data acquisition unit 11 represents that the overhead line voltage data is sent from the voltage sensor to the data acquisition unit 11. The arrow from the charging interface 4 to the data acquisition unit 11 represents that the power demand data is sent from the charging interface 4 to the data acquisition unit 11.

[0019] The power demand data includes, for example, information indicating the presence or absence of connection of the external device 6 to the charging interface 4. Further, the power demand data may include information indicating the charging rate of the external device 6 connected to the charging interface 4, or information on the amount of power required for charging the external device 6 connected to the charging interface 4. Note that the power demand data may include information other than the information described here.

[0020] The data acquisition unit 11 outputs the acquired overhead line voltage data and the acquired power demand data to the control unit 12. In FIG. 1, the arrow from the data acquisition unit 11 to the control unit 12 indicates that the overhead line voltage data and the power demand data are sent from the data acquisition unit 11 to the control unit 12.

[0021] The control unit 12 controls the main circuit unit 13 and the power storage unit 14 based on the overhead line voltage data and the power demand data. The control unit 12 causes the main circuit unit 13 to perform power intake from the overhead line 7 to the power storage unit 14 or power supply from the power storage unit 14 to the overhead line 7 based on the overhead line voltage data. Further, the control unit 12 diagnoses the power demand data and causes the main circuit unit 13 to supply power from the power storage unit 14 to the external device 6 based on the diagnosis result. That is, the control unit 12 causes the main circuit unit 13 to supply power from the power storage unit 14 to the external device 6 based on the power demand data. The control unit 12 may further cause the main circuit unit 13 to supply power from the overhead line 7 to the external device 6 based on the power demand data. In this case, the main circuit unit 13 performs power transfer between the overhead line 7 and the external device 6.

[0022] The control unit 12 controls each of the power storage unit 14, the power conversion unit 15, and the input / output switching circuit 16 by outputting control signals to each of them. The power storage unit 14 performs power intake and discharge according to the control signal. The power conversion unit 15 converts the DC power taken in from the overhead line 7 and the DC power supplied to the overhead line 7 according to the control signal. The input / output switching circuit 16 switches the input / output according to the control signal. In FIG. 1, the arrow from the control unit 12 to the power storage unit 14 indicates that a control signal is sent from the control unit 12 to the power storage unit 14. The arrow from the control unit 12 to the power conversion unit 15 indicates that a control signal is sent from the control unit 12 to the power conversion unit 15. The arrow from the control unit 12 to the input / output switching circuit 16 indicates that a control signal is sent from the control unit 12 to the input / output switching circuit 16. Note that in FIG. 1, the control device 3 is shown as a device outside the power storage device 2, but the control device 3 may be a device inside the power storage device 2.

[0023] One example of the charging interface 4 is an EV charging stand installed around a railway station building. The external device 6 is connected to the power storage device 2 via the charging interface 4 by being connected to the charging interface 4.

[0024] The circuit breaker 10 is connected between the power storage device 2 and the overhead line 7. The circuit breaker 10 opens and closes an electric circuit including the power storage device 2 and the overhead line 7 by switching between energization and current interruption.

[0025] For example, assume that the external device 6 is capable of rapid charging and normal charging, which is slower than rapid charging. A first voltage that is the voltage of the external device 6 during rapid charging and a second voltage that is the voltage of the external device 6 during normal charging are different from each other. In this case, the power conversion unit 15 may convert the voltage of the power taken in from the overhead line 7 to the same voltage as either the first voltage or the second voltage.

[0026] Due to the regenerative operation of the train connected to the overhead line 7, regenerative power is generated in the overhead line 7. The power storage system 1 takes in power from the overhead line 7 to the power storage unit 14 when regenerative power is generated. The power storage system 1 supplies the power stored in the power storage unit 14 to the overhead line 7 when a voltage drop occurs in the overhead line 7. By such an operation of the power storage system 1, effective utilization of regenerative power becomes possible.

[0027] FIG. 2 is a diagram showing an example of power supply to the overhead line 7 by the power storage system 1 according to Embodiment 1. The graph at the upper part of FIG. 2 shows the relationship between the position on the overhead line 7 and the overhead line voltage before power is supplied to the overhead line 7. The graph at the lower part of FIG. 2 shows the relationship between the position on the overhead line 7 and the overhead line voltage when power is supplied to the overhead line 7. In FIG. 2, P1 is the position to which one of two adjacent substations 5 is connected. P2 is the position to which the other of the two substations 5 is connected. The measurement point on the overhead line 7 to which the power storage system 1 is connected exists between P1 and P2.

[0028] In the overhead line 7, voltage drops due to power transmission losses in the overhead line 7 may occur. Also, in the overhead line 7, voltage drops due to the tractive effort of the train may occur. In the graph at the upper part of FIG. 2, a voltage drop where the overhead line voltage becomes lower than each of the voltage value at P1 and the voltage value at P2 occurs at a position between P1 and P2. In FIG. 2, V A is the voltage value at P2. V B1 is the voltage value at the position where the overhead line voltage becomes minimum between P1 and P2 before power is supplied to the overhead line 7. The arrow shown in the graph at the upper part of FIG. 2 indicates that a voltage drop from V A to V B1 has occurred.

[0029] In the graph at the lower part of FIG. 2, by supplying power to the overhead line 7, the voltage drop is improved compared to the graph at the upper part of FIG. 2. In FIG. 2, V B2 is the voltage value at the position where the overhead line voltage becomes minimum between P1 and P2 when power is being supplied to the overhead line 7. The arrow shown in the graph at the lower part of FIG. 2 indicates that, by supplying power to the overhead line 7, a voltage boost from V B1 to V B2 has occurred at the position between P1 and P2.

[0030] In this way, by compensating the overhead line voltage by supplying power to the overhead line 7, it becomes possible to improve the voltage drop. By improving the voltage drop, stable running of the train can be continued. Also, when regenerative power is generated, the power taken from the overhead line 7 to the power storage unit 14 is used for boosting the overhead line voltage, making it possible to effectively utilize the regenerative power.

[0031] Next, a specific example of the control of the power storage device 2 by the control device 3 will be described. The control device 3 selects a control mode from among the first to fifth control modes, which are five control modes, based on the overhead line voltage data and the power demand data. The control device 3 executes control in the selected control mode.

[0032] The first control mode is a control mode in which power is not taken in from the overhead line 7 to the power storage unit 14, and power is not supplied from the power storage unit 14 to each of the overhead line 7 and the external device 6.

[0033] The second control mode is a control mode in which power is taken in from the overhead line 7 to the power storage unit 14 when the charge rate of the power storage unit 14 is smaller than a preset target value. The target value is the value of the target charge rate when taking in power to the power storage unit 14. The power storage system 1 takes in power from the overhead line 7 to the power storage unit 14 in the second control mode when power supply from the power storage unit 14 to the overhead line 7 or the external device 6 is not being performed. When the charge rate of the power storage unit 14 reaches the target value, the power storage system 1 stops taking in power to the power storage unit 14 and switches the control mode to the first control mode.

[0034] The third control mode is a control mode in which power is taken in from the overhead line 7 to the power storage unit 14 when regenerative power is generated by the regenerative operation of a train connected to the overhead line 7. The third control mode is a control mode for taking in the surplus of power when regenerative power is generated into the power storage unit 14. The power storage system 1 performs power intake in the third control mode when it is determined based on the generated regenerative power and the overhead line voltage data.

[0035] The fourth control mode is a control mode in which power is supplied from the power storage unit 14 to the overhead line 7. The power storage system 1 supplies power to the overhead line 7 in the fourth control mode when the overhead line voltage indicated in the overhead line voltage data is lower than a preset reference voltage. The reference voltage is the voltage serving as a reference for whether the overhead line voltage is stable or not. When the overhead line voltage becomes lower than the reference voltage due to the train's power running or the like, the power storage system 1 supplies power to the overhead line 7 in the fourth control mode to stabilize the overhead line voltage.

[0036] The fifth control mode is a control mode for supplying power from the power storage unit 14 to the external device 6 for charging the external device 6. The power storage system 1 supplies power to the external device 6 in the fifth control mode when the charging rate of the power storage unit 14 is equal to or higher than a first threshold value during the business hours, which is the time period when the train is in commercial operation on the railway. The first threshold value is set as the lower limit of the charging rate of the power storage unit 14 when it is possible to supply power for stabilizing the overhead line voltage. If the charging rate of the power storage unit 14 is lower than the first threshold value, it becomes difficult to supply the power necessary for stabilizing the overhead line voltage to the overhead line 7 in a situation where power supply to the train is required. When the charging rate of the power storage unit 14 drops to the first threshold value during the business hours, the power storage system 1 does not supply power to the external device 6 and takes in power to the power storage unit 14 in the second control mode or the third control mode.

[0037] The power storage system 1 supplies power to the external device 6 in the fifth control mode when the charging rate of the power storage unit 14 is equal to or higher than a second threshold value during the late night hours, which is a time period other than the business hours. The second threshold value is set as the lower limit of the charging rate of the power storage unit 14 when power supply to the overhead line 7 is not required and charging of the external device 6 is possible. In the late night hours when power supply to the overhead line 7 is not required because the train is not in commercial operation, if the charging rate of the power storage unit 14 is lower than the second threshold value, it becomes difficult to supply the power necessary for charging the external device 6 to the external device 6. When the charging rate of the power storage unit 14 drops to the second threshold value during the late night hours, the power storage system 1 does not supply power to the external device 6 and takes in power to the power storage unit 14 in the second control mode.

[0038] The control device 3 stores parameter values that are referred to in selecting the control mode. The parameter values are the value of the reference voltage, the target value of the charging rate, the first threshold value, and the second threshold value. The control device 3 reads out these parameter values and selects the control mode based on the result of comparing the overhead line voltage data or the power demand data with the parameter values.

[0039] Here, the relationship between the charging rate of the power storage unit 14 and the control mode will be described. FIG. 3 is a diagram showing an example of changes in the charging rate of the power storage unit 14 in the power storage system 1 according to the first embodiment. In the graph shown in FIG. 3, the vertical axis represents the charging rate of the power storage unit 14, and the horizontal axis represents time. In FIG. 3, C1 is the second threshold value, C2 is the first threshold value, and C3 is the target value of the charging rate of the power storage unit 14. Each of t0 - t14 represents time.

[0040] Assume that at t0, the external device 6 is not connected to the charging interface 4. As shown in FIG. 3, the charging rate at t0 is smaller than C3. Since the charging rate of the power storage unit 14 is smaller than C3, the control unit 12 selects the second control mode. When the charging rate of the power storage unit 14 is smaller than C3, the control unit 12 selects the second control mode and causes the main circuit unit 13 to take in power from the overhead line 7 to the power storage unit 14. That is, the control unit 12 causes the power conversion unit 15 to perform conversion from DC1500V - system DC power to DC500V - system DC power, and causes the input / output switching circuit 16 to supply power from the overhead line 7 to the power storage unit 14. The power storage system 1 continues to take in power to the power storage unit 14 in the second control mode from t0 until t1 when the charging rate reaches C3. At t1, the control unit 12 switches the control mode from the second control mode to the first control mode. From t1 to t2, the first control mode is maintained, and the charging rate becomes constant at C3.

[0041] At time t2, assume that the overhead line voltage becomes lower than the reference voltage due to the train's power running or the like. The control unit 12 compares the value of the overhead line voltage indicated in the overhead line voltage data with the value of the read reference voltage, and determines that the overhead line voltage is lower than the reference voltage. Since the overhead line voltage is lower than the reference voltage, the control unit 12 selects the fourth control mode. At time t2, the control unit 12 switches the control mode from the first control mode to the fourth control mode. When the overhead line voltage indicated in the overhead line voltage data is lower than the reference voltage, the control unit 12 causes the main circuit unit 13 to supply power from the power storage unit 14 to the overhead line 7. That is, the control unit 12 causes the power conversion unit 15 to perform conversion from DC 500V system DC power to DC 1500V system DC power, and causes the input / output switching circuit 16 to supply power from the power storage unit 14 to the overhead line 7. Due to the discharge of the power storage unit 14, the charge rate of the power storage unit 14 decreases from C3.

[0042] At time t3, assume that the overhead line voltage becomes equal to or higher than the reference voltage. At time t3, the control unit 12 stops the power supply from the power storage unit 14 to the overhead line 7. Since the charge rate of the power storage unit 14 is smaller than C3, the control unit 12 selects the second control mode. From time t4, the control unit 12 causes the main circuit unit 13 to take in power from the overhead line 7 into the power storage unit 14. The power storage system 1 continues to take in power into the power storage unit 14 in the second control mode from time t4 until time t5 when the charge rate reaches C3. At time t5, the control unit 12 switches the control mode from the second control mode to the first control mode.

[0043] Assume that regenerative power is generated by the regenerative operation of the train from t6 to t7. The control unit 12 determines that regenerative power has been generated based on the overhead line voltage data. For example, the control unit 12 determines whether regenerative power has been generated by comparing the threshold value of whether the train is performing a regenerative operation with the value of the overhead line voltage. When the control unit 12 determines based on the overhead line voltage data that regenerative power has been generated by the regenerative operation of the train connected to the overhead line 7, the control unit 12 selects the third control mode and causes the main circuit unit 13 to take in power from the overhead line 7 to the power storage unit 14. That is, the control unit 12 causes the power conversion unit 15 to perform conversion from DC 1500V system DC power to DC 500V system DC power, and causes the input / output switching circuit 16 to supply power from the overhead line 7 to the power storage unit 14. The power storage system 1 continues to take in power to the power storage unit 14 in the third control mode from t6 to t7 when regenerative power is being generated. Due to the power intake to the power storage unit 14, the charging rate of the power storage unit 14 becomes greater than C3. At t7, the control unit 12 switches the control mode from the third control mode to the first control mode.

[0044] Assume that an external device 6 is connected to the charging interface 4 at t8, which is a time included in the business hours. The control unit 12 determines that the external device 6 is connected to the charging interface 4 based on the power demand data. The charging rate at t8 is greater than C2. Since the control unit 12 satisfies the condition that the charging rate of the power storage unit 14 is C2 or more during the business hours, the control unit 12 selects the fifth control mode. At t8, the control unit 12 switches the control mode from the first control mode to the fifth control mode. The control unit 12 causes the main circuit unit 13 to supply power from the power storage unit 14 to the external device 6. That is, the control unit 12 causes the input / output switching circuit 16 to supply power from the power storage unit 14 to the external device 6.

[0045] Assume that the charge rate of the power storage unit 14 reaches C2 at t9. The control unit 12 stops the power supply from the power storage unit 14 to the external device 6 at t9. As a result, the power storage system 1 restricts the discharge of the power storage unit 14 so that the charge rate of the power storage unit 14 does not become smaller than C2 in order to maintain a state where power supply for stabilizing the overhead line voltage is possible during business hours. If charging of the external device 6 is required even after t9, the power storage system 1 resumes the power supply from the power storage unit 14 to the external device 6 after the charge rate of the power storage unit 14 has recovered.

[0046] The charge rate of the power storage unit 14 at t9 is smaller than C3. Since the charge rate of the power storage unit 14 is smaller than C3, the power storage system 1 takes in power from the overhead line 7 to the power storage unit 14 in the second control mode or the third control mode. Here, assume that regenerative power is generated by the regenerative operation of the train from t9 to t10. At t9, the control unit 12 selects the third control mode based on the determination that regenerative power has been generated, and switches the control mode from the fifth control mode to the third control mode. The control unit 12 causes the main circuit unit 13 to take in power from the overhead line 7 to the power storage unit 14 in the third control mode.

[0047] At t10 when the generation of regenerative power has ceased, the control unit 12 stops the intake of power from the overhead line 7 to the power storage unit 14 in the third control mode. Assume that at t10, the charge rate of the power storage unit 14 is still smaller than C3. Since the charge rate of the power storage unit 14 is smaller than C3, the control unit 12 selects the second control mode. The control unit 12 switches the control mode from the third control mode to the second control mode. The control unit 12 causes the main circuit unit 13 to take in power from the overhead line 7 to the power storage unit 14 in the second control mode. When the charge rate of the power storage unit 14 reaches C3 at t11, the control unit 12 switches the control mode from the second control mode to the first control mode at t11.

[0048] In addition, when charging of the external device 6 is required even after t9, the power storage system 1 may supply power from the overhead line 7 to the external device 6 after t9. That is, the power storage system 1 may directly supply power from the overhead line 7 to the external device 6 without passing through the power storage unit 14. The control unit 12 determines that charging of the external device 6 is required based on power demand data indicating that the connection of the external device 6 to the charging interface 4 continues. The power storage system 1 supplies power from the overhead line 7 to the external device 6 in parallel with taking in power from the overhead line 7 to the power storage unit 14 in the second control mode or the third control mode. The control unit 12 causes the main circuit unit 13 to take in power from the overhead line 7 to the power storage unit 14 and supply power from the overhead line 7 to the external device 6 in the second control mode or the third control mode. In this example, the control unit 12 causes the main circuit unit 13 to supply power from the overhead line 7 to the power storage unit 14 and supply power from the overhead line 7 to the external device 6 based on the power demand data.

[0049] The power storage system 1 may supply power from the overhead line 7 to the external device 6 in parallel with supplying power from the power storage unit 14 to the external device 6 in the fifth control mode. In this case, the control unit 12 causes the main circuit unit 13 to supply power from the power storage unit 14 to the external device 6 and supply power from the overhead line 7 to the external device 6 in the fifth control mode.

[0050] Suppose that the external device 6 is connected to the charging interface 4 at t12 which is a time included in the late-night time zone. The charging rate at t12 is greater than C1. Since the control unit 12 satisfies the condition that the charging rate of the power storage unit 14 is C1 or more in the late-night time zone, the fifth control mode is selected. At t12, the control unit 12 switches the control mode from the first control mode to the fifth control mode. The control unit 12 causes the main circuit unit 13 to supply power from the power storage unit 14 to the external device 6.

[0051] Assume that the charging rate of the power storage unit 14 reaches C1 at t13. The control unit 12 stops the power supply from the power storage unit 14 to the external device 6 at t13. Thereby, in order for the power storage system 1 to avoid a situation where it cannot supply the power required for charging the external device 6 during the late-night time zone, the power storage system 1 restricts the discharge of the power storage unit 14 before the charging rate of the power storage unit 14 becomes smaller than C1. If the charging of the external device 6 is requested even after t13, the power storage system 1 resumes the power supply from the power storage unit 14 to the external device 6 after the charging rate of the power storage unit 14 has recovered.

[0052] Thereafter, at t14, since the charging rate of the power storage unit 14 of the power storage system 1 is smaller than C3, the power storage system 1 starts taking in power from the overhead line 7 to the power storage unit 14 in the second control mode. The control unit 12 causes the main circuit unit 13 to take in power from the overhead line 7 to the power storage unit 14 until the charging rate of the power storage unit 14 reaches C3.

[0053] Note that if the charging of the external device 6 is requested even after t12, the power storage system 1 may supply power from the overhead line 7 to the external device 6 after t12. That is, the power storage system 1 may directly supply power from the overhead line 7 to the external device 6 without passing through the power storage unit 14. The control unit 12 determines that the charging of the external device 6 is requested from the power demand data indicating that the connection of the external device 6 to the charging interface 4 continues. The power storage system 1 supplies power from the overhead line 7 to the external device 6 in parallel with taking in power from the overhead line 7 to the power storage unit 14 in the second control mode. The control unit 12 causes the main circuit unit 13 to perform taking in power from the overhead line 7 to the power storage unit 14 in the second control mode and supplying power from the overhead line 7 to the external device 6. In this example, the control unit 12 causes the main circuit unit 13 to perform supplying power from the overhead line 7 to the power storage unit 14 and supplying power from the overhead line 7 to the external device 6 based on the power demand data.

[0054] The power storage system 1 may also supply power from the overhead line 7 to the external device 6 in parallel with the power supply from the power storage unit 14 to the external device 6 in the fifth control mode. In this case, the control unit 12 causes the main circuit unit 13 to supply power from the power storage unit 14 to the external device 6 and from the overhead line 7 to the external device 6 in the fifth control mode.

[0055] Note that the control unit 12 may obtain the time period during which power is supplied to the external device 6 based on the power demand data, and cause the main circuit unit 13 to supply power from the power storage unit 14 to the external device 6 during the obtained time period. For example, the control unit 12 estimates the time period during which charging of the external device 6 is required based on past power demand data, and causes the main circuit unit 13 to supply power to the external device 6 during the estimated time period. Thereby, when charging of the external device 6 is regularly required, the power storage system 1 can supply power to the external device 6 according to the charging demand.

[0056] The control device 3 may obtain a demand plan, which is a schedule for charging the external device 6, as power demand data, and cause the main circuit unit 13 to supply power to the external device 6 according to the demand plan. For example, for the power supply to the external device 6 during the late-night time period when power supply from the power storage unit 14 to the overhead line 7 is unnecessary, the control device 3 may follow the demand plan during the late-night time period. Thereby, the power storage system 1 can supply power to the external device 6 according to the demand plan.

[0057] FIG. 4 is a flowchart showing the procedure of processing by the control device 3 included in the power storage system 1 according to Embodiment 1. Prior to the processing according to the procedure shown in FIG. 4, the control unit 12 reads parameter values such as the value of the reference voltage, the target value of the charge rate, the first threshold value, and the second threshold value.

[0058] In step S1, the data acquisition unit 11 acquires overhead line voltage data and power demand data. The data acquisition unit 11 outputs the acquired overhead line voltage data and the acquired power demand data to the control unit 12.

[0059] In step S2, the control unit 12 determines whether the overhead line voltage is lower than the reference voltage. The control unit 12 determines whether the overhead line voltage is lower than the reference voltage by comparing the value of the overhead line voltage indicated in the overhead line voltage data with the value of the reference voltage.

[0060] When the overhead line voltage is lower than the reference voltage (step S2, Yes), in step S3, the control unit 12 causes the main circuit unit 13 to supply power from the power storage unit 14 to the overhead line 7 in the fourth control mode.

[0061] On the other hand, when the overhead line voltage is equal to or higher than the reference voltage (step S2, No), in step S4, the control unit 12 determines whether regenerative power has been generated by the regenerative operation of the train. The control unit 12 determines whether regenerative power has been generated, for example, by comparing the value of the overhead line voltage indicated in the overhead line voltage data with a threshold value for determining regenerative power.

[0062] When it is determined that regenerative power has been generated (step S4, Yes), in step S5, the control unit 12 causes the main circuit unit 13 to take in power from the overhead line 7 to the power storage unit 14 in the third control mode. Thereby, the power storage system 1 takes in the regenerative power generated by the regenerative operation of the train into the power storage unit 14.

[0063] On the other hand, when it is determined that no regenerative power has been generated (step S4, No), in step S6, the control unit 12 determines whether the current time is a late-night time zone when the train is not in commercial operation.

[0064] When it is a time period during which the commercial operation of the train is not being carried out (step S6, Yes), in step S7, the control unit 12 causes the main circuit unit 13 to supply power to the external device 6 in accordance with the fifth control mode. Here, it is assumed that the external device 6 is connected to the charging interface 4. That is, it is assumed that the charging of the external device 6 is requested. The control unit 12 causes the main circuit unit 13 to supply power from the power storage unit 14 to the external device 6 when the charging rate of the power storage unit 14 is equal to or higher than the second threshold value. The external device 6 is charged by the power supply from the power storage unit 14. When the charging rate of the power storage unit 14 drops to the second threshold value due to the power supply from the power storage unit 14 to the external device 6, the control unit 12 stops the power supply from the power storage unit 14 to the external device 6. The control unit 12 takes in power from the overhead line 7 to the power storage unit 14 in accordance with the second control mode, and after the charging rate of the power storage unit 14 has recovered, resumes the power supply from the power storage unit 14 to the external device 6 in accordance with the fifth control mode. The control unit 12 may cause the main circuit unit 13 to supply power from the overhead line 7 to the external device 6 in parallel with the taking in of power from the overhead line 7 to the power storage unit 14 in accordance with the second control mode.

[0065] On the other hand, when it is a time period during which the commercial operation of the train is being carried out (step S6, No), in step S8, the control unit 12 determines whether the charging rate of the power storage unit 14 is smaller than the target value.

[0066] When the charging rate of the power storage unit 14 is smaller than the target value (step S8, Yes), in step S9, the control unit 12 causes the main circuit unit 13 to take in power from the overhead line 7 to the power storage unit 14 in accordance with the second control mode.

[0067] On the other hand, when the charging rate of the power storage unit 14 is equal to or higher than the target value (step S8, No), in step S10, the control unit 12 determines whether the external device 6 is connected to the charging interface 4. That is, the control unit 12 determines whether the charging of the external device 6 is requested.

[0068] When an external device 6 is connected to the charging interface 4 (step S10, Yes), in step S11, the control unit 12 causes the main circuit unit 13 to supply power to the external device 6 in the fifth control mode. The control unit 12 causes the main circuit unit 13 to supply power from the power storage unit 14 to the external device 6 when the charging rate of the power storage unit 14 is equal to or higher than the first threshold value. The external device 6 is charged by the power supply from the power storage unit 14. When the charging rate of the power storage unit 14 drops to the first threshold value due to the power supply from the power storage unit 14 to the external device 6, the control unit 12 stops the power supply from the power storage unit 14 to the external device 6. The control unit 12 takes in power from the overhead line 7 to the power storage unit 14 in the second control mode or the third control mode, and after the charging rate of the power storage unit 14 recovers, resumes the power supply from the power storage unit 14 to the external device 6 in the fifth control mode. The control unit 12 may cause the main circuit unit 13 to supply power from the overhead line 7 to the external device 6 in parallel with taking in power from the overhead line 7 to the power storage unit 14 in the second control mode or the third control mode.

[0069] On the other hand, when the external device 6 is not connected to the charging interface 4 (step S10, No), the control unit 12 does not take in power from the overhead line 7 to the power storage unit 14, and also does not supply power from the power storage unit 14 to each of the overhead line 7 and the external device 6. That is, the first control mode is selected as the control mode.

[0070] As described above, the control device 3 ends the processing according to the procedure shown in FIG. 4. The control device 3 controls the power storage device 2 while switching the control mode according to the overhead line voltage data and the power demand data by repeating the processing according to the procedure shown in FIG. 4.

[0071] According to Embodiment 1, the power storage system 1 includes a power storage device 2 and a control device 3. The power storage device 2 has a main circuit unit 13 and a power storage unit 14, and the main circuit unit 13 transfers power between each of the overhead line 7 and the external device 6 and the power storage unit 14. The control device 3 includes a data acquisition unit 11 that acquires overhead line voltage data and power demand data, and based on the overhead line voltage data, causes the main circuit unit 13 to take in power from the overhead line 7 to the power storage unit 14 or supply power from the power storage unit 14 to the overhead line 7, and based on the power demand data, causes the main circuit unit 13 to supply power from the power storage unit 14 to the external device 6. The power storage system 1 can control the power transfer between each of the overhead line 7 and the external device 6 and the power storage unit 14 based on the overhead line voltage data and the power demand data acquired by the data acquisition unit 11. Thereby, the power storage system 1 and the power storage device 2 can take in power into the power storage device 2 and supply power to the outside of the power storage device 2 without being based on a command from outside the power storage system 1.

[0072] Further, the main circuit unit 13 includes a power conversion unit 15 that converts the voltage of the power taken in from the overhead line 7 to the same voltage as the voltage used by the external device 6, and outputs the power whose voltage has been converted by the power conversion unit 15 to the power storage unit 14. The power storage device 2 can supply power at the same voltage as the voltage used by the external device 6 to the external device 6 even if it does not include a load-side converter that is a converter for converting the voltage of the power output from the power storage device 2 to the external device 6. Thereby, the power storage system 1 can simplify the configuration of the power storage device 2 because the load-side converter is unnecessary.

[0073] Also, the control unit 12 causes the main circuit unit 13 to supply power from the overhead line 7 to the external device 6 based on the power demand data. Thereby, the power storage system 1 can directly supply power from the overhead line 7 to the external device 6 when power supply to the external device 6 is required.

[0074] Further, when the charging rate of the power storage unit 14 is lower than a preset target value, the control unit 12 causes the main circuit unit 13 to take in power from the overhead line 7 into the power storage unit 14. Thereby, the power storage system 1 can automatically take in power from the overhead line 7 into the power storage unit 14 until the charging rate of the power storage unit 14 reaches the target value.

[0075] Further, when the charging rate of the power storage unit 14 drops to a first threshold value during a time period when train commercial operation is being carried out on the railway, the control unit 12 causes the main circuit unit 13 to take in power from the overhead line 7 into the power storage unit 14. Thereby, the power storage system 1 can maintain a state in which it can supply power necessary for stabilizing the overhead line voltage to the overhead line 7 during a time period when train commercial operation is being carried out.

[0076] Further, when the charging rate of the power storage unit 14 drops to a second threshold value during a time period when train commercial operation is not being carried out on the railway, the control unit 12 causes the main circuit unit 13 to take in power from the overhead line 7 into the power storage unit 14. Thereby, the power storage system 1 can maintain a state in which it can supply power necessary for charging the external device 6 to the external device 6 during a time period when train commercial operation is not being carried out.

[0077] Further, the control unit 12 obtains a time period during which power supply to the external device 6 is performed based on power demand data, and causes the main circuit unit 13 to supply power from the power storage unit 14 to the external device 6 during the obtained time period. Thereby, the power storage system 1 can supply power to the external device 6 in accordance with the demand for power supply.

[0078] Further, when it is determined based on the regenerative power generated by the regenerative operation of the train connected to the overhead line 7 and the overhead line voltage data, the control unit 12 causes the main circuit unit 13 to take in power from the overhead line 7 into the power storage unit 14. The power storage system 1 takes in the surplus of the power when the regenerative power is generated into the power storage unit 14, and supplies the power taken into the power storage unit 14 to the overhead line 7 or the external device 6. Thereby, the power storage system 1 can effectively utilize the regenerative power.

[0079] Embodiment 2. FIG. 5 is a diagram showing a configuration example of the power storage system 1A according to Embodiment 2. The power storage system 1A according to Embodiment 2 is different from the power storage system 1 according to Embodiment 1 in that power can be supplied from the external power source 20 to the external device 6. In Embodiment 2, the same components as those in Embodiment 1 described above are denoted by the same reference numerals, and the configuration different from that in Embodiment 1 will be mainly described.

[0080] The external power source 20 is a power source outside the power storage system 1A and is, for example, a commercial power source. The voltage conversion device 21 converts the voltage of the external power source 20 into the same voltage as the voltage used by the external device 6. The voltage conversion device 21 outputs power of the same voltage as the voltage used by the external device 6 to the charging interface 4. The voltage conversion device 21 outputs, for example, power of DC500V to the charging interface 4. The voltage conversion device 21 supplies power to the external device 6 via the charging interface 4. In FIG. 5, the voltage conversion device 21 is shown as a device outside the power storage system 1A, but the voltage conversion device 21 may be a device inside the power storage system 1A.

[0081] The power storage system 1A includes a power storage device 2, a control device 3A, a charging interface 4, and a circuit breaker 10. The control device 3A includes a data acquisition unit 11 and a control unit 12A. Similar to the control unit 12 shown in FIG. 1, the control unit 12A outputs control signals to each of the power storage unit 14, the power conversion unit 15, and the input / output switching circuit 16. Further, the control unit 12A outputs a control signal to the voltage conversion device 21. In FIG. 5, the arrow from the control unit 12A to the voltage conversion device 21 indicates that a control signal is sent from the control unit 12A to the voltage conversion device 21. The voltage conversion device 21 performs voltage conversion and power supply to the external device 6 according to the control signal.

[0082] When the control unit 12A determines that it is difficult to supply power from the power storage unit 14 to the external device 6 and from the overhead line 7 to the external device 6, the main circuit unit 13 is not made to supply power to the external device 6, and the voltage conversion device 21 is made to perform voltage conversion and supply power to the external device 6. Thereby, power is supplied from the external power source 20 to the external device 6. For example, when the charge rate of the power storage unit 14 has dropped to the first threshold value during business hours or when the charge rate of the power storage unit 14 has dropped to the second threshold value during late-night hours, the control unit 12A determines that it is difficult to supply power from the power storage unit 14 to the external device 6. Also, for example, when the overhead line voltage is equal to or lower than the reference voltage, the control unit 12A determines that it is difficult to supply power from the overhead line 7 to the external device 6.

[0083] When the control unit 12A determines that at least one of the power supply from the power storage unit 14 to the external device 6 and the power supply from the overhead line 7 to the external device 6 is possible, the voltage conversion device 21 is not made to perform voltage conversion and supply power to the external device 6, and the main circuit unit 13 is made to supply power to the external device 6. In this way, the control unit 12A switches the power supply from the power storage device 2 to the external device 6 and the power supply from the external power source 20 to the external device 6.

[0084] According to the second embodiment, since the control unit 12A can switch the power supply from the power storage device 2 to the external device 6 and the power supply from the external power source 20 to the external device 6, the power storage system 1A can supply the power of the external power source 20 to the external device 6 when it is difficult to supply power from the power storage unit 14 to the external device 6 and from the overhead line 7 to the external device 6.

[0085] In the first and second embodiments, the power storage systems 1 and 1A are assumed to supply power to the external device 6 which is a device capable of being charged, but it is not limited to this. The power storage systems 1 and 1A may supply power to an external device which is a device other than a device capable of being charged. For example, the power storage systems 1 and 1A may supply power to the electrical equipment installed in the station building.

[0086] Next, the hardware configuration for realizing the control devices 3 and 3A according to Embodiment 1 or 2 will be described. The control devices 3 and 3A are realized by a processing circuit. The processing circuit may be a circuit in which a processor executes software, or may be a dedicated circuit.

[0087] When the processing circuit is realized by software, the processing circuit is, for example, the control circuit 30 shown in FIG. 6. FIG. 6 is a diagram showing a configuration example of the control circuit 30 according to Embodiment 1 or 2. The control circuit 30 includes an input unit 31, a processor 32, a memory 33, and an output unit 34. The input unit 31 is an interface circuit that receives data input from outside the control circuit 30 and supplies it to the processor 32. The output unit 34 is an interface circuit that sends data from the processor 32 or the memory 33 to the outside of the control circuit 30.

[0088] The control devices 3 and 3A are realized by software, firmware, or a combination of software and firmware. The software or firmware is described as a program and stored in the memory 33. In the control circuit 30, the processor 32 reads and executes the program stored in the memory 33, thereby realizing each function of the control devices 3 and 3A. That is, the control circuit 30 includes a memory 33 for storing a program in which the processing of the control devices 3 and 3A is ultimately executed. Also, this program can be said to cause a computer to execute the procedures and methods of the control devices 3 and 3A. The memory 33 is also used as a temporary memory when the processor 32 executes various processes.

[0089] Processor 32 is a CPU (Central Processing Unit). Processor 32 may also be a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, or a DSP (Digital Signal Processor). Memory 33 may be, for example, a non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (registered trademark) (Electrically Erasable Programmable Read Only Memory), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile Disc), etc.

[0090] FIG. 6 is an example of hardware when the functions of control devices 3 and 3A are realized by a general-purpose processor 32 and a memory 33. However, the functions of control devices 3 and 3A may be realized by a dedicated hardware circuit. FIG. 7 is a diagram showing a configuration example of a dedicated hardware circuit 35 according to Embodiment 1 or 2.

[0091] The dedicated hardware circuit 35 includes an input unit 31, an output unit 34, and a processing circuit 36. The processing circuit 36 is a single circuit, a composite circuit, a programmed processor, a parallel-programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a circuit combining these. The control devices 3 and 3A may be realized by the processing circuit 36 according to function, or the functions of the control devices 3 and 3A may be realized by the processing circuit 36 as a whole. Note that the control devices 3 and 3A may be realized by combining the control circuit 30 and the hardware circuit 35.

[0092] The configurations shown in the above embodiments are examples of the content of the present disclosure. The configurations of each embodiment can be combined with other known technologies. The configurations of each embodiment may be appropriately combined with each other. It is possible to omit or change a part of the configuration of each embodiment without departing from the gist of the present disclosure.

[0093] Hereinafter, various aspects of the present disclosure will be collectively described as appendices.

[0094] (Appendix 1) A power storage system that stores power taken from a railway overhead wire, a power storage unit that stores electricity, a main circuit unit that transfers power between the overhead wire and each of the external devices connected to the power storage system and the power storage unit, a power storage device having the above, a data acquisition unit that acquires overhead wire voltage data indicating the voltage of the overhead wire and power demand data indicating the power demand by the external device, a control unit that causes the main circuit unit to take in power from the overhead wire to the power storage unit or supply power from the power storage unit to the overhead wire based on the overhead wire voltage data, and causes the main circuit unit to supply power from the power storage unit to the external device based on the power demand data, a control device having the above, and is provided with A power storage system characterized by the above. (Appendix 2) The main circuit unit includes a power conversion unit that converts the voltage of the power taken from the overhead wire into the same voltage as the voltage used by the external device, and outputs the power whose voltage has been converted by the power conversion unit to the power storage unit. The power storage system according to Appendix 1, characterized by the above. (Appendix 3) The control unit causes the main circuit unit to supply power from the overhead wire to the external device based on the power demand data. The power storage system according to Appendix 1 or 2, characterized by the above. (Appendix 4) When the charging rate of the power storage unit is lower than a preset target value, the control unit causes the main circuit unit to take in power from the overhead line to the power storage unit. The power storage system according to any one of Appendices 1 to 3, characterized by the above. (Appendix 5) When the charging rate of the power storage unit drops to a first preset threshold value during the time period when train commercial operation is being carried out on the railway, the control unit causes the main circuit unit to take in power from the overhead line to the power storage unit. The power storage system according to any one of Appendices 1 to 3, characterized by the above. (Appendix 6) When the charging rate of the power storage unit drops to a second preset threshold value that is lower than the first threshold value during the time period when train commercial operation is not being carried out on the railway, the control unit causes the main circuit unit to take in power from the overhead line to the power storage unit. The power storage system according to Appendix 4, characterized by the above. (Appendix 7) The control unit obtains the time period during which power is supplied to the external device based on the power demand data, and causes the main circuit unit to supply power from the power storage unit to the external device during the obtained time period. The power storage system according to any one of Appendices 1 to 6, characterized by the above. (Appendix 8) When the voltage shown in the overhead line voltage data is lower than a preset reference voltage, the control unit causes the main circuit unit to supply power from the power storage unit to the overhead line. The power storage system according to any one of Appendices 1 to 7, characterized by the above. (Appendix 9) When it is determined based on the regenerative power generated by the regenerative operation of the train connected to the overhead line and the overhead line voltage data, the control unit causes the main circuit unit to take in power from the overhead line to the power storage unit. The power storage system according to any one of Appendices 1 to 8, characterized by the above. (Supplementary Note 10) The control unit switches between power supply from the power storage device to the external device and power supply from a power source outside the power storage device to the external device. The power storage system according to any one of Supplementary Notes 1 to 9, characterized by the above. (Supplementary Note 11) A power storage device that stores power taken from a railway overhead line, a power storage unit that stores electricity, and a main circuit unit that transfers power between each of the overhead line and an external device connected to the power storage device and the power storage unit. The main circuit unit takes in power from the overhead line to the power storage unit or supplies power from the power storage unit to the overhead line based on overhead line voltage data indicating the voltage of the overhead line, and supplies power from the power storage unit to the external device based on power demand data indicating the power demand by the external device. The power storage device is characterized by the above. (Supplementary Note 12) A method for controlling a power storage device that stores power taken from a railway overhead line, the method being controlled by a computer, the steps of obtaining overhead line voltage data indicating the voltage of the overhead line and power demand data indicating the power demand by an external device connected to the power storage device, causing the power storage device to take in power from the overhead line to the power storage device or supply power from the power storage device to the overhead line based on the overhead line voltage data, and causing the power storage device to supply power from the power storage device to the external device based on the power demand data. The method for controlling a power storage device is characterized by the above. (Supplementary Note 13) The steps of obtaining overhead line voltage data indicating the voltage of a railway overhead line and power demand data indicating the power demand by an external device connected to a power storage device that stores power taken from the overhead line, Based on the overhead line voltage data, causing the power storage device to take in power from the overhead line or supply power from the power storage device to the overhead line; Based on the power demand data, causing the power storage device to supply power from the power storage device to the external device, and causing a computer to execute the steps. A control program for a power storage device, characterized by the above.

Explanation of Signs

[0095] 1,1A Power storage system, 2 Power storage device, 3,3A Control device, 4 Charging interface, 5 Substation, 6 External device, 7 Overhead line, 10 Circuit breaker, 11 Data acquisition unit, 12,12A Control unit, 13 Main circuit unit, 14 Power storage unit, 15 Power conversion unit, 16 Input / output switching circuit, 20 External power source, 21 Voltage conversion device, 30 Control circuit, 31 Input unit, 32 Processor, 33 Memory, 34 Output unit, 35 Hardware circuit, 36 Processing circuit.

Claims

1. A power storage system for storing power taken in from an overhead line of a railway, comprising: a power storage unit for storing electricity; a main circuit unit that transfers power between the overhead line and each of external devices connected to the power storage system and the power storage unit; a power storage device having the above; a data acquisition unit that acquires overhead line voltage data indicating the voltage of the overhead line and power demand data indicating the power demand by the external devices; a control unit that causes the main circuit unit to take in power from the overhead line to the power storage unit or supply power from the power storage unit to the overhead line based on the overhead line voltage data, and causes the main circuit unit to supply power from the power storage unit to the external devices based on the power demand data; a control device having the above, and A power storage system characterized by the above.

2. The main circuit unit includes a power conversion unit that converts the voltage of the power taken in from the overhead line into the same voltage as the voltage used by the external devices, and outputs the power whose voltage has been converted by the power conversion unit to the power storage unit. The power storage system according to claim 1, characterized by the above.

3. The control unit causes the main circuit unit to supply power from the overhead line to the external devices based on the power demand data. The power storage system according to claim 1 or 2, characterized by the above.

4. When the charging rate of the power storage unit is smaller than a preset target value, the control unit causes the main circuit unit to take in power from the overhead line to the power storage unit. The power storage system according to claim 1 or 2, characterized by the above.

5. When the charging rate of the power storage unit drops to a first threshold value set in advance during the time period when train commercial operation is carried out on the railway, the control unit causes the main circuit unit to take in power from the overhead line to the power storage unit. The power storage system according to claim 1 or 2, characterized in that.

6. When the charging rate of the power storage unit drops to a second threshold value that is smaller than the first threshold value and is set in advance during the time period when train commercial operation is not carried out on the railway, the control unit causes the main circuit unit to take in power from the overhead line to the power storage unit. The power storage system according to claim 5, characterized in that.

7. The control unit obtains the time period during which power is supplied to the external device based on the power demand data, and causes the main circuit unit to supply power from the power storage unit to the external device during the obtained time period. The power storage system according to claim 1 or 2, characterized in that.

8. When the voltage shown in the overhead line voltage data is lower than a reference voltage set in advance, the control unit causes the main circuit unit to supply power from the power storage unit to the overhead line. The power storage system according to claim 1 or 2, characterized in that.

9. When the control unit determines based on the regenerative power generated by the regenerative operation of the train connected to the overhead line and the overhead line voltage data, the control unit causes the main circuit unit to take in power from the overhead line to the power storage unit. The power storage system according to claim 1 or 2, characterized in that.

10. The control unit switches between power supply from the power storage device to the external device and power supply from a power source outside the power storage device to the external device. The power storage system according to claim 1 or 2, characterized in that.

11. A power storage device that stores electric power taken in from a railway overhead line, comprising: a power storage unit that stores electricity; a main circuit unit that transfers electric power between each of the overhead line and external devices connected to the power storage device and the power storage unit, wherein the main circuit unit takes in electric power from the overhead line to the power storage unit or supplies electric power from the power storage unit to the overhead line based on overhead line voltage data indicating the voltage of the overhead line, and supplies electric power from the power storage unit to the external devices based on power demand data indicating the power demand by the external devices. A power storage device characterized by the above.

12. A method for controlling a power storage device that stores electric power taken in from a railway overhead line, the method comprising: obtaining overhead line voltage data indicating the voltage of the overhead line and power demand data indicating the power demand by external devices connected to the power storage device; causing the power storage device to take in electric power from the overhead line to the power storage device or supply electric power from the power storage device to the overhead line based on the overhead line voltage data; and causing the power storage device to supply electric power from the power storage device to the external devices based on the power demand data. A method for controlling a power storage device, characterized by the above.

13. obtaining overhead line voltage data indicating the voltage of a railway overhead line and power demand data indicating the power demand by external devices connected to a power storage device that stores electric power taken in from the overhead line; causing the power storage device to take in electric power from the overhead line to the power storage device or supply electric power from the power storage device to the overhead line based on the overhead line voltage data; Causing a computer to execute a step of causing the power storage device to supply power from the power storage device to the external device based on the power demand data A control program for a power storage device, characterized by the above

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