JP2018016108A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device which can adjust a transformer station transmitting voltage while suppressing an increase in discharge energy.SOLUTION: A power storage device 20, which is used at a transformer station 2 which converts incoming AC power onto DC power and supplies the same to an electric motor vehicle, comprises: a storage battery 23; a first chopper circuit part 21 which charges the storage battery by use of DC power; a second chopper circuit part 22 which converts power of the storage battery; and a charging/discharging control part 24. The transformer station comprises a rectifier 5 in which a first terminal is electrically connected to a feeder cable and a second terminal is electrically connected to a return wire via a switch 10, and a capacitor 11 which is provided in parallel with the switch and is charged with power of the storage battery converted by the second chopper circuit part. The charging/discharging control part so makes the switch as to be in conduction state or non-conduction state, and controls operation of the first chopper circuit part and the second chopper circuit part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power storage device, and more particularly to a power storage device for a DC electric vehicle.

  As a power conversion circuit of a substation for a DC electric vehicle, for example, a circuit using a transformer and a diode rectifier is known. A substation using a diode rectifier generally has a voltage-current characteristic approximated by a linear function, as the substation output current increases, the substation transmission voltage decreases. The no-load transmission voltage of the substation can be adjusted, for example, by switching the primary side tap voltage of the transformer.

  The higher the non-load transmission voltage of the substation, the shorter the power running time of the electric vehicle that receives power from the substation. That is, the higher the no-load transmission voltage of the substation, the longer the coasting time of the electric vehicle can be, and the necessary powering energy can be reduced. However, the higher the non-load transmission voltage of the substation is set, the less the regenerative current flows. For this reason, it is known that regenerative power interchange (supply of power from the regenerative vehicle to the power running vehicle) is difficult between the regenerative vehicle and the power running vehicle, and it is difficult to effectively use the regenerative power. On the other hand, the lower the unloaded transmission voltage of the substation, the easier the regenerative current flows and the more easily the regenerative power is accommodated. However, it is known that the power running energy of electric vehicles increases.

  In DC electric vehicles, a technique for installing a power storage device in parallel with a rectifier in a substation is known. The power storage device is used for the purpose of, for example, regenerative power absorption of a regenerative vehicle, peak cut of a substation output current, and suppression of voltage drop of a feeder line. Here, in Patent Document 1, a power storage device is installed along a substation or a route, the overhead voltage during power running of the electric vehicle is increased, and the coasting time is increased by reducing the power running time, thereby achieving an energy saving effect. It is exemplified to increase.

JP 2014-004914 A

  However, as shown in Patent Document 1, in the case of adopting a configuration in which a power storage device is connected between a feeder and a rail (return line), in order to boost the output voltage from a substation, the output of the power storage device The voltage had to be higher than the output voltage of the rectifier. Here, since the output voltage of the rectifier is generally high, there is a problem that the discharge energy of the power storage device increases.

  An object of the present invention made in view of such a viewpoint is to provide a power storage device capable of adjusting a substation transmission voltage while suppressing an increase in discharge energy.

  In order to solve the above-described problem, a power storage device according to an embodiment of the present invention is a power storage device used in a substation that converts received AC power into DC power and supplies the DC power to an electric vehicle, the storage battery, and the DC A first chopper circuit unit that charges the storage battery using electric power; a second chopper circuit unit that converts the electric power of the storage battery; and a charge / discharge control unit, wherein the substation includes a first terminal A rectifier that is electrically connected to the postcard wire and the second terminal is electrically connected to the return line via a switch, and is provided in parallel with the switch, and is converted by the second chopper circuit unit. And a capacitor charged by the electric power of the storage battery, wherein the charge / discharge control unit brings the switch into a conductive state or a non-conductive state, and the first chopper circuit unit and the second chopper circuit unit Control the behavior.

  Preferably, the feeder line is branched into a plurality at a branch point, and the DC power can be supplied to a plurality of electric vehicles, and the charge / discharge control unit includes a current flowing through each of the branched feeder lines. When at least one of the switches goes from the electric vehicle to the branch point, the switch is turned on.

  Preferably, the charge / discharge control unit further turns the switch on when the magnitude of the current from the electric vehicle toward the branch point is equal to or greater than a first threshold value.

  Preferably, the charge / discharge control unit sets the second chopper circuit unit to a non-conductive state when the current flowing through the branched feeders does not go from the electric vehicle to the branch point. Make it work.

  Preferably, the charge / discharge control unit operates the second chopper circuit unit by setting the switch to a non-conductive state when the magnitude of the current flowing through the feeder line is equal to or greater than a second threshold value. Let

  Preferably, the charge / discharge control unit controls the operation of the second chopper circuit unit so as to generate a predetermined voltage between the terminals of the capacitor.

  Preferably, the charge / discharge control unit controls the operation of the second chopper circuit unit so as to generate a voltage corresponding to the magnitude of the current flowing through the feeder line between the terminals of the capacitor.

  ADVANTAGE OF THE INVENTION According to this invention, the electrical storage apparatus which can adjust a substation sending voltage can be provided, suppressing the increase in discharge energy.

It is a figure which shows the structure of the electrical storage system for DC electric vehicles provided with the electrical storage apparatus which concerns on one Embodiment. It is a flowchart which shows the process of a charging / discharging control part. It is a figure explaining the pressure | voltage rise of a substation sending voltage. It is a figure which shows the structure of the electrical storage system for DC electric vehicles of a comparative example. It is a figure which shows the voltage-current characteristic of the substation of the electrical storage system for direct current electric vehicles of a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Configuration of power storage system for DC electric vehicles)
FIG. 1 shows a configuration of a power storage system 1 for a DC electric vehicle including a power storage device 20 according to an embodiment. The DC electric vehicle power storage system 1 includes a substation 2, a three-phase AC power source 3, feeders 9a, 9b, 9c, 9d, a rail 12, and electric vehicles 13a, 13b, 13c, 13d.

  The feeders 9a, 9b, 9c, 9d are wires for supplying electric power from the substation 2 to the electric cars 13a, 13b, 13c, 13d, respectively. The feeders 9a, 9b, 9c, 9d correspond to each of the branched feeders of the present invention.

  The rail 12 is a travel path for the electric cars 13a, 13b, 13c, and 13d to travel, and is grounded. The rail 12 corresponds to the return line of the present invention.

  The electric cars 13a, 13b, 13c, and 13d are electric railways in this embodiment. The electric cars 13a, 13b, 13c, and 13d are supplied with electric power from the substation 2 and run on the rails 12.

  The substation 2 includes a transformer 4, a rectifier 5, a branch point 6, feeders 7a, 7b, 7c, 7d, switches 8a, 8b, 8c, 8d, a switch 10, a capacitor 11, Voltage sensor 50, current sensors 51a, 51b, 51c, 51d, and power storage device 20 are provided. Moreover, the substation 2 is drawing in feeder 9a, 9b, 9c, 9d. Therefore, the substation 2 includes a part of feeders 9a, 9b, 9c, 9d.

  The substation 2 receives three-phase AC power (hereinafter simply referred to as AC power) from the three-phase AC power source 3 and converts it into DC voltage, and the electric vehicle 13a via the feeders 9a, 9b, 9c, 9d. , 13b, 13c, 13d. For example, a plurality of substations 2 can be arranged near the lines of the electric cars 13a, 13b, 13c, and 13d.

  The transformer 4 receives AC power from the three-phase AC power supply 3 and performs voltage conversion. More specifically, the transformer 4 steps down the AC power and outputs the stepped down AC power to the rectifier 5. The transformer 4 may be a known device such as a load tap switching transformer.

  The rectifier 5 receives AC power output from the transformer 4 and performs AC / DC conversion. The rectifier 5 may be configured by a known circuit such as a bridge rectifier using a diode. The rectifier 5 includes a first terminal and a second terminal which are output terminals for supplying a DC voltage. The first terminal feeders 9a, 9b, 9c, 9d are electrically connected, and the second terminal is electrically connected to the rail 12 (return line) via the switch 10.

  The branch point 6 connects the first terminal of the rectifier 5 and the feeders 7a, 7b, 7c, and 7d. One feeder connected to the first terminal is branched into a plurality (four) feeders 7a, 7b, 7c and 7d at a branch point 6. Here, the current flowing through the feeder is defined as a substation output current Io. The case where the current flows from the first terminal of the rectifier 5 toward the branch point 6 (from the branch point 6 toward the electric wires 7a, 7b, 7c, 7d) is defined as the positive direction of the substation output current Io. Here, in the present invention, when simply referred to as “feed wire”, it may refer to one “feed wire” before being branched into a plurality at the branch point 6. On the other hand, in the present invention, when “a plurality of feeders (branched)” is used, the feeders 7 a, 7 b, 7 c, 7 d branched at the branching point 6 or feeders 9 a, 9 b, 9 c, 9 d Correspond.

  The feeders 7a, 7b, 7c, and 7d are a plurality (four) of feeders branched at the branch point 6. The feeders 7a, 7b, 7c, and 7d are electrically connected to feeders 9a, 9b, 9c, and 9d through the switches 8a, 8b, 8c, and 8d, respectively.

  The switches 8a, 8b, 8c, 8d are switches. The switches 8a, 8b, 8c, 8d are normally in a conductive state (when the electric cars 13a, 13b, 13c, 13d are operating normally). The switches 8a, 8b, 8c, and 8d can be in a non-conductive state when, for example, an abnormality occurs and the power supply to the electric vehicles 13a, 13b, 13c, and 13d is interrupted. Note that the on / off states of the switches 8a, 8b, 8c, and 8d may be controlled by the charge / discharge control unit 24 of the power storage device 20.

  The current sensors 51a, 51b, 51c, and 51d are devices that detect currents flowing through the feeders 9a, 9b, 9c, and 9d, respectively. The currents flowing through the feeders 9a, 9b, 9c and 9d are respectively referred to as feeder currents Ia, Ib, Ic and Id. For example, when the regenerative current from the electric cars 13a, 13b, 13c, and 13d is zero, the total of the feeder currents Ia, Ib, Ic, and Id is equal to the substation output current Io.

The switch 10 is a switch. The switch 10 is provided between the second terminal of the rectifier 5 and the rail 12 (return line). The conduction state or non-conduction state of the switch 10 is controlled by an opening / closing command R ^* from the charge / discharge control unit 24 of the power storage device 20. Details of the control will be described later.

  The capacitor 11 is provided in parallel with the switch 10. The capacitor 11 is also connected to the second chopper circuit unit 22 of the power storage device 20 and is charged by the power of the storage battery 23 of the power storage device 20 converted by the second chopper circuit unit 22.

  The voltage sensor 50 is connected between the first terminal and the second terminal of the rectifier 5 and detects a rectifier output voltage Vr that is a DC output voltage of the rectifier 5. Voltage sensor 50 outputs detected rectifier output voltage Vr to charge / discharge control unit 24 of power storage device 20. Here, the voltage between the feeder and the rail 12 (return line) is defined as a substation transmission voltage Vo. The substation transmission voltage Vo is a voltage supplied to the electric cars 13a, 13b, 13c, and 13d. In the present embodiment, as described later, the substation transmission voltage Vo can be made different from the rectifier output voltage Vr.

  The power storage device 20 includes a first chopper circuit unit 21, a second chopper circuit unit 22, a storage battery 23, and a charge / discharge control unit 24.

  The first chopper circuit unit 21 is connected to the first terminal and the second terminal of the rectifier 5. The first chopper circuit unit 21 is connected to the storage battery 23. The first chopper circuit unit 21 mutually converts the DC power on the rectifier 5 side and the DC power of the storage battery 23. For example, the first chopper circuit unit 21 may charge the storage battery 23 using the DC power of the rectifier 5. For example, the 1st chopper circuit part 21 may charge storage battery 23 using regenerative electric power from a regenerative vehicle. As the first chopper circuit unit 21, for example, a known bidirectional chopper, a DC-DC converter, or the like can be used.

  The second chopper circuit unit 22 is connected to the switch 10 and the capacitor 11. The second chopper circuit unit 22 is connected to the storage battery 23. The second chopper circuit unit 22 converts the DC power of the storage battery 23 and supplies the DC power to the switch 10 side (and the capacitor 11 side). As the second chopper circuit unit 22, for example, a known bidirectional chopper, a DC-DC converter, or the like can be used.

  The storage battery 23 stores DC power. In the present embodiment, the positive electrode and the negative electrode of the storage battery 23 are respectively connected to the positive electrode and the negative electrode on the storage battery 23 side of the first chopper circuit unit 21. Further, the positive electrode and the negative electrode of the storage battery 23 are also connected to the positive electrode and the negative electrode on the storage battery 23 side of the second chopper circuit portion 22, respectively. As the storage battery 23, a well-known battery, an electric double layer capacitor, etc. can be used, for example. Moreover, the storage battery 23 may be comprised by the combination of a different kind of storage battery.

The charge / discharge control unit 24 controls the operations of the first chopper circuit unit 21 and the second chopper circuit unit 22. The charge / discharge control unit 24 controls the charge / discharge current of the storage battery 23 input / output to / from the first chopper circuit unit 21 according to the charge / discharge current command I ^* . For example, the charge / discharge control unit 24 can stop the operation of the first chopper circuit unit 21 by setting the charge / discharge current command I ^* to 0 (that is, the storage battery 23 is not charged / discharged). Further, the charge / discharge control unit 24 controls the voltage (corresponding to the voltage between the terminals of the switch 10 and the capacitor 11) output by the second chopper circuit unit 22 according to the discharge voltage command V ^* . For example, the charge / discharge control unit 24 can stop the operation of the second chopper circuit unit 22 by setting the discharge voltage command V ^* to 0 (that is, the voltage is not output to the switch 10 side). Further, the charge / discharge control unit 24 controls the open / close state (conductive state or non-conductive state) of the switch 10 according to the open / close command R ^* . Further, the charge / discharge control unit 24 detects the rectifier output voltage Vr detected by the voltage sensor 50, the feeder currents Ia, Ib, Ic, Id detected by the current sensors 51 a, 51 b, 51 c, 51 d, and the storage battery 23. A charge amount SOC indicating the charge amount is acquired. Further, the charge / discharge control unit 24 may acquire a first threshold value Ith1 and a second threshold value Ith2, which will be described later. Here, the first threshold value Ith1 and the second threshold value Ith2 may be read from, for example, a storage device included in the power storage device 20, or may be specified from the outside of the power storage device 20. The charge / discharge control unit 24 obtains the first threshold value Ith1 and the second threshold value Ith2 from the accessible storage device, but when not stored in the storage device or when the value has been updated, from other than the storage device You may make it acquire.

(Processing of charge / discharge control unit)
FIG. 2 is a flowchart showing the processing of the charge / discharge control unit 24. Hereinafter, processing of the charge / discharge control unit 24 will be described.

First, the charging / discharging control part 24 makes the switch 10 into a conduction | electrical_connection state by switching command R ^* (step S1).

  The charge / discharge control unit 24 acquires detection values and the like necessary for controlling the first chopper circuit unit 21, the second chopper circuit unit 22, and the switch 10 (step S2). In the present embodiment, the detected values are specifically the rectifier output voltage Vr, feeder currents Ia, Ib, Ic, Id, and the charge amount SOC. Further, the charge / discharge control unit 24 may further acquire the first threshold value Ith1 and the second threshold value Ith2 as detection values and the like. Here, the first threshold value Ith1 is a current threshold value used for determining whether or not a regenerative vehicle exists. The second threshold value Ith2 is a current threshold value used for determining whether or not adjustment of the substation transmission voltage Vo supplied to the power vehicle is necessary.

  Based on the feeder currents Ia, Ib, Ic, Id, the charge / discharge control unit 24 generates a negative current (electric cars 13a, 13b, 13c) in at least one of the branched feeders 9a, 9b, 9c, 9d. , 13d to determine whether or not a current from branch 13 is flowing (step S3). When it is determined that a negative current is flowing, the charge / discharge control unit 24 proceeds to step S4, and otherwise proceeds to step S5.

  When the charge / discharge control unit 24 determines in step S3 that a negative current is flowing (Yes in step S3), the charge / discharge control unit 24 determines whether the magnitude of the negative current is equal to or greater than a first threshold value Ith1 ( Step S4). The first threshold value Ith1 is set to a value large enough to avoid erroneous detection of a negative current due to detection errors of the current sensors 51a, 51b, 51c, 51d, for example. In the present embodiment, the charge / discharge control unit 24 determines that there is a regenerative vehicle capable of regenerating power with respect to the power running vehicle when the magnitude of the negative current is equal to or greater than the first threshold value Ith1 (Yes in step S4). To do. If the charge / discharge control unit 24 determines that a regenerative vehicle is present, the process proceeds to step S7; otherwise, the process proceeds to step S5.

  The charge / discharge control unit 24 determines that no negative current is flowing in Step S3 (No in Step S3), and if the magnitude of the negative current is less than the first threshold value Ith1 in Step S4 (Step S3). In S4, it is determined whether or not the magnitude of the current flowing through the feeder line is equal to or greater than the second threshold Ith2 (step S5). Here, the fact that a negative current is not flowing means that there is no current from the electric cars 13a, 13b, 13c, 13d toward the branch point 6. Further, the magnitude of the current flowing through the feeder is the magnitude of the substation output current Io from the substation 2. The charge / discharge control unit 24 can grasp the magnitude of the substation output current Io by summing the magnitudes of the feeder currents Ia, Ib, Ic, and Id. And when the magnitude | size of the electric current which flows through a feeder is more than 2nd threshold value Ith2 (Yes of step S5), the charging / discharging control part 24 determines with the power running vehicle which should supply electric power from the substation 2 existing. Here, the second threshold value Ith2 is set to a value large enough to prevent the charge / discharge control unit 24 from erroneously determining that there is a power vehicle when there is no power vehicle. For example, the second threshold value Ith2 is set to a current value that is considered to flow at least when at least one of the electric cars 13a, 13b, 13c, and 13d is powered. The charge / discharge control unit 24 proceeds to step S6 if it is determined that there is a power running vehicle, otherwise proceeds to step S7.

If the charge / discharge control unit 24 determines that there is a power running vehicle (No in step S5), the charge / discharge control unit 24 executes the control in step S6. That is, the charge / discharge control unit 24 puts the switch 10 into a non-conduction state by the switching command R ^* . In addition, the charge / discharge control unit 24 sets the charge / discharge current command I ^* to 0 and stops the operation of the first chopper circuit unit 21 (that is, does not charge / discharge the storage battery 23). Further, the charge / discharge control unit 24 sets the discharge voltage command V ^* based on the rectifier output voltage Vr and the charge amount SOC (step S6). By the control in step S6, the capacitor 11 is charged and a voltage is generated between the terminals. The substation transmission voltage Vo is a voltage between terminals of the capacitor 11 (in other words, a voltage between terminals of the switch 10 or an output voltage of the second chopper circuit unit 22) to a rectifier output voltage Vr that is a DC output voltage of the rectifier 5. Will be added. That is, the charge / discharge control unit 24 of the power storage device 20 can boost the substation transmission voltage Vo by the control in step S6. Here, the charge / discharge control unit 24 can adjust the output voltage of the second chopper circuit unit 22 by the discharge voltage command V ^* . That is, the charge / discharge control unit 24 can boost the substation transmission voltage Vo to a desired voltage value by appropriately setting the discharge voltage command V ^* .

When it is determined in step S4 that the regenerative vehicle is present (Yes in step S4), and in the case where it is not determined that the power running vehicle is present in step S5 (No in step S5), the charge / discharge controller 24 The control of S7 is executed. That is, the charge / discharge control unit 24 brings the switch 10 into a conductive state by the switching command R ^* . The charge / discharge control unit 24 sets the discharge voltage command V ^* to 0 and stops the operation of the second chopper circuit unit 22 (that is, does not output a voltage to the switch 10 side). Moreover, the charge / discharge control part 24 sets charge / discharge current instruction | command I ^* based on the rectifier output voltage Vr and charge amount SOC (step S7). At this time, the charge / discharge control unit 24 can make the regenerative current flow easily through the plurality of branched feeders. Moreover, the charge / discharge control part 24 can charge / discharge the storage battery 23 by charge / discharge current instruction | command I ^* , and can adjust the substation sending voltage Vo. That is, the charge / discharge control unit 24 of the power storage device 20 can maintain the voltage level of the substation transmission voltage Vo in which the regenerative current easily flows by the control in step S7. The charging / discharging control unit 24 of the power storage device 20 charges the storage battery 23 by charging the storage battery 23 when, for example, regenerative narrowing occurs in the electric vehicles 13a, 13b, 13c, and 13d and the substation transmission voltage Vo rises. It is possible to avoid a sudden change in Vo.

  When the power storage device 20 is stopped (Yes in step S8), the charge / discharge control unit 24 ends the series of processes. Moreover, the charge / discharge control part 24 returns to step S2 (No of step S8), when not stopping the electrical storage apparatus 20 (No of step S8).

(Boosting of substation transmission voltage)
FIG. 3 is a diagram for explaining the boosting of the substation transmission voltage Vo corresponding to the control of Step 6 of the charge / discharge control unit 24 described above.

  FIG. 3 shows the power supplied from the substation 2 to the electric cars 13a, 13b, 13c, 13d, the vertical axis shows the supply voltage, and the horizontal axis shows the supply current (substation output current Io). A voltage-current characteristic approximated by a linear function with Vo0 on the vertical axis as an initial value (hereinafter referred to as an initial voltage-current characteristic) indicates power supplied from the substation 2 when boosting is not performed. When the charge / discharge control unit 24 does not execute the control in step 6, the power supplied from the substation 2 of the DC electric vehicle power storage system 1 follows the initial voltage-current characteristics.

  On the other hand, when the charge / discharge control unit 24 executes the control of step 6, the substation transmission voltage Vo is boosted by the amount of voltage output from the second chopper circuit unit 22. In the present embodiment, the second chopper circuit unit 22 outputs a predetermined voltage regardless of the substation output current Io. Therefore, the power supplied from the substation 2 is boosted so as to follow a voltage-current characteristic approximated by a linear function with Vo on the vertical axis in FIG. 3 as an initial value. In the present embodiment, it is possible to easily switch the voltage-current characteristic that the power supplied from the substation 2 follows depending on whether or not the charge / discharge control unit 24 of the power storage device 20 executes the control of Step 6.

(Comparative example)
As described above, the power storage device 20 of the present embodiment has been described. With reference to FIGS. 4 and 5, the effect of the power storage device 20 of the present embodiment will be described while showing the power storage device 93 of the comparative example. In FIGS. 4 and 5, the same elements as those in FIGS.

  FIG. 4 shows a configuration of a power storage system 91 for a DC electric vehicle including a power storage device 93 of a comparative example. The substation 92 of the DC electric vehicle power storage system 91 does not include the switch 10, the capacitor 11, and the current sensors 51a, 51b, 51c, 51d. The power storage device 93 of the comparative example does not include the second chopper circuit unit 22. In the substation 92, the substation transmission voltage Vo and the rectifier output voltage Vr are the same unless the storage battery 23 is charged or discharged. That is, it can be considered that the power supplied from the substation 92 follows the voltage-current characteristics shown in FIG.

  In the DC electric vehicle power storage system 91 including the power storage device 93 of the comparative example, the substation transmission voltage Vo monotonously decreases as the substation output current Io increases. Assuming that the no-load transmission voltage is set low for the effective use of regenerative power, when the transmission voltage of the substation 92 needs to be boosted, the substation transmission voltage is discharged by the discharge of the storage battery 23 of the power storage device 93. It is necessary to boost Vo.

  However, when boosting the substation transmission voltage Vo, the output voltage of the power storage device 93 needs to be equal to or higher than the output voltage of the rectifier 5. Here, the DC voltage of the storage battery 23 is about 600 [V], for example, whereas the output voltage of the rectifier 5 supplied to the electric railway is generally about 1500 [V]. Therefore, the power storage device 93 needs to be greatly boosted using the first chopper circuit unit 21, which causes a problem that discharge energy increases.

  On the other hand, in the DC electric vehicle power storage system 1 including the power storage device 20 according to the present embodiment, the charging / discharging control unit 24 of the power storage device 20 can increase the substation transmission voltage Vo by performing the control in step S6. it can. The boosted substation transmission voltage Vo is obtained by adding the terminal voltage of the capacitor 11 to the rectifier output voltage Vr, which is the DC output voltage of the rectifier 5. The terminal voltage of the capacitor 11 is, for example, about 100 to 200 [V]. At this time, the power storage device 20 converts the DC voltage of about 600 [V] of the storage battery 23 by the second chopper circuit unit 22 to generate a voltage across the terminals of the capacitor 11. Therefore, the power storage device 20 according to the present embodiment can adjust (boost) the substation transmission voltage Vo to an appropriate value while suppressing an increase in discharge energy.

  Further, in the power storage device 20 according to the present embodiment, it is possible to easily increase the substation transmission voltage Vo when necessary. That is, when the charge / discharge control unit 24 determines that the magnitude of the substation output current Io is equal to or greater than the second threshold value Ith2, it is possible to immediately boost the substation transmission voltage Vo (step of FIG. 2). S5 and S6). Therefore, it is possible to set the transmission voltage of the substation 2 at no load low.

  Although the present invention has been described based on the drawings and embodiments, it should be noted that those skilled in the art can easily make various changes and modifications based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention.

  For example, in the above embodiment, currents flowing through the feeders 9a, 9b, 9c, and 9d are detected by the current sensors 51a, 51b, 51c, and 51d, respectively. However, the current flowing through the feeders 7a, 7b, 7c, 7d may be detected by the current sensors 51a, 51b, 51c, 51d.

  Further, for example, the number of feeder branches at the branch point 6 is not limited to four. In the above embodiment, the number of rectifiers 5 is one (one bank), but a plurality of rectifiers 5 may constitute a parallel bank. Further, the number of power storage devices 20 is not limited to one, and a plurality of power storage devices 20 may be connected in parallel.

  In the above embodiment, the switch 10 and the second chopper circuit unit 22 are provided between the second terminal of the rectifier 5 and the rail 12 (return line). May be provided between the terminal and the branch point 6.

Further, in the above embodiment, the magnitude of the boost of the substation transmission voltage Vo is constant regardless of the value of the substation output current Io (see FIG. 3). However, the magnitude of the boost (the voltage across the capacitor 11) may be changed according to the substation output current Io. For example, the charge / discharge control unit 24 changes the discharge voltage command V ^* according to the magnitude of the substation output current Io, so that the boosted substation transmission voltage Vo is constant regardless of the substation output current Io. The voltage may be set to (a non-load sending voltage).

  In the above embodiment, the charge / discharge control unit 24 may omit at least one of the comparison process (step S4) with the first threshold value Ith1 and the comparison process (step S5) with the second threshold value Ith2. Good. For example, when the charge / discharge control unit 24 omits steps S4 and S5, the charge / discharge control unit 24 executes the process of step S7 when it is determined that a negative current is flowing in step S3. If not, the process of step S6 is executed.

DESCRIPTION OF SYMBOLS 1 Electric power storage system for DC electric vehicles 2 Substation 3 Three-phase AC power supply 4 Transformer 5 Rectifier 6 Branch point 7a, 7b, 7c, 7d, 9a, 9b, 9c, 9d Feed wire 8a, 8b, 8c, 8d, 10 Open / close Unit 11 Capacitor 12 Rail (Return)
13a, 13b, 13c, 13d Electric vehicle 20 Power storage device 21 First chopper circuit unit 22 Second chopper circuit unit 23 Storage battery 24 Charge / discharge control unit 50 Voltage sensor 51a, 51b, 51c, 51d Current sensor

Claims (7)

A power storage device used in a substation that converts received AC power into DC power and supplies it to an electric vehicle,
A storage battery,
A first chopper circuit unit that charges the storage battery using the DC power;
A second chopper circuit for converting the power of the storage battery;
A charge / discharge control unit,
The substation is
A rectifier in which the first terminal is electrically connected to the feeder and the second terminal is electrically connected to the return line via a switch;
A capacitor provided in parallel with the switch and charged by the power of the storage battery converted by the second chopper circuit unit,
The charge / discharge control unit
A power storage device that controls the operation of the first chopper circuit unit and the second chopper circuit unit by bringing the switch into a conductive state or a non-conductive state. The feeder line can be branched into a plurality of branch points to supply the DC power to a plurality of electric vehicles,
The electricity storage according to claim 1, wherein the charge / discharge control unit sets the switch in a conductive state when at least one of currents flowing through each of a plurality of branched feeders goes from the electric vehicle to the branch point. apparatus.   3. The power storage device according to claim 2, wherein the charge / discharge control unit sets the switch to a conductive state when the magnitude of a current from the electric vehicle toward the branch point is equal to or greater than a first threshold value.   The charge / discharge control unit operates the second chopper circuit unit by setting the switch to a non-conductive state when a current flowing through a plurality of branched feeders does not go from the electric vehicle to the branch point. The power storage device according to 2 or 3.   5. The charge / discharge control unit further operates the second chopper circuit unit by setting the switch to a non-conductive state when the magnitude of the current flowing through the feeder line is equal to or greater than a second threshold value. The power storage device described in 1.   The power storage device according to claim 4 or 5, wherein the charge / discharge control unit controls an operation of the second chopper circuit unit so as to generate a predetermined voltage between terminals of the capacitor.   The charge / discharge control unit controls the operation of the second chopper circuit unit so as to generate a voltage corresponding to the magnitude of a current flowing through the feeder line between terminals of the capacitor. The power storage device described in 1.

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