JP2014064357A - Power storage device and dc system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the voltage of a DC bus while securing autonomous control of a power converter connected to the DC bus in a DC system supplying DC power.SOLUTION: A DC system includes a power system 50, a photovoltaic power generation system 60 as a DC power source, and a power storage device 100 coupled between the power system 50 and the photovoltaic power generation system 60. The power storage device 100 includes a DC bus 30 for transmitting DC power, a connection terminal 40 for electrically connecting the photovoltaic power generation system 60 to the DC bus 30, a bidirectional DC/AC converter 10 for bidirectionally converting power between the DC bus 30 and the power system 50, and a storage battery 20 which is directly connected to the DC bus 30 and outputs a power supply voltage to the DC bus 30.

Description

  The present invention relates to a power storage device, and more particularly to a power storage device applied to a DC system that supplies DC power.

  As a DC system for supplying power by converting AC power from commercial power into DC power, for example, in Japanese Patent Application Laid-Open No. 2011-101523 (Patent Document 1), by using a secondary battery, a solar battery, or the like as a distributed power supply, A power distribution system has been proposed in which not only DC power obtained by converting power from a commercial power supply but also DC power obtained from these distributed power supplies can be used.

  The power distribution system described in Patent Document 1 includes a storage battery and a solar battery as a distributed power supply, and a power supply device that converts power from the storage battery, the solar battery, and a commercial power supply into desired power and outputs the power. The power supply output from the power supply device is configured to be supplied to a plurality of loads via the power supply line. In the above configuration, the power supply device has a plurality of module devices including power converters that convert input power into desired output power, and the bus line provided in the panel device is connected to the power supply device. Each module device is connected.

  By adopting such a configuration, in Patent Document 1, a power converter having a function of autonomously controlling each output power so that power corresponding to power requested from the load is supplied to the load is provided as a module device. As a module, it is possible to add or replace power converters according to the load.

JP 2011-101523 A

  The power distribution system described in Patent Document 1 is provided between a commercial power supply and a power supply line as a power converter that constitutes a power supply device, and is capable of mutually converting AC power and DC power. A module device comprising a directional AC / DC converter is provided. This AC / DC converter performs bidirectional power conversion between the commercial power supply and the bus line so that the DC voltage on the bus line is maintained at 350V. For example, when the voltage on the bus line is less than 350V, the AC / DC converter converts AC power from the commercial power source into DC power and outputs it.

  However, as described above, when AC power is converted to DC power and output to the bus line, it is necessary to arrange a large number of capacitors (for example, electrolytic capacitors) for smoothing the converted DC voltage. Therefore, an increase in the size and cost of the module device becomes a problem.

  In addition, since the AC side of the AC / DC converter is required to transfer a system frequency sine wave current to and from the commercial power source, the commercial power is supplied only at the timing of the zero cross point of the AC power supplied from the commercial power source. The amount of power exchanged with the power supply can be adjusted. For this reason, as described above, in the configuration in which the DC voltage on the bus line is controlled using the AC / DC converter, there is a limit in increasing the response speed of the control, and the bus line is affected by disturbance such as load fluctuation. It becomes difficult to suppress voltage pulsation. It is necessary to design other module devices (power converters) connected to the bus line so as to allow the pulsation of the DC voltage. Further, since the pulsation of the DC voltage may increase as the number of module devices connected to the bus line increases, the voltage on the bus line tends to become unstable.

  Furthermore, when the voltage on the bus line decreases instantaneously due to disturbance due to load fluctuations, the peak voltage of the voltage output to the AC side of the AC / DC converter falls below the normal voltage level, causing AC There is a risk of distorting the current waveform. If this happens, it will affect the quality of AC power.

  Therefore, in a configuration in which a plurality of module devices (power converters) are connected to the bus line, control for stabilizing the DC voltage on the bus line can be performed in cooperation between the plurality of module devices. Desired. However, in such cooperative control, since the overall operation is controlled based on the output voltage of each module device, there is a possibility that the module device cannot be easily added or replaced.

  Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to ensure the autonomous control of the power converter connected to the DC bus in the DC system, while maintaining the voltage of the DC bus. It is to stabilize.

  In one aspect of the present invention, the power storage device transfers power between the power system and the DC power source. The power storage device includes a first DC bus for transmitting DC power, a first connection for electrically connecting a DC power source to the first DC bus, a first DC bus, and a power system. And a power conversion unit that bi-directionally converts power and a power storage unit that outputs a power supply voltage to the first DC bus.

  According to this invention, since the storage battery directly connected to the DC bus stabilizes the voltage of the DC bus, each power converter connected to the DC bus can perform autonomous control. Thereby, it is possible to realize a DC system that can easily supply DC power stably even when the specification of the DC system is changed by modularizing the power converter.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows schematically the whole structure of the direct current | flow system to which the electrical storage apparatus by Embodiment 1 of this invention is applied. It is a figure which shows the remaining capacity-voltage curve of a storage battery. It is a circuit diagram which shows the detailed structure of the bidirectional | two-way DC / AC converter in FIG. It is a figure which shows an example of the target value setting table | surface used by a bidirectional | two-way DC / AC converter. 3 is a flowchart showing a control processing procedure for realizing self-path current control in the power storage device according to the first embodiment. 5 is a flowchart showing a control processing procedure for realizing battery current control in the power storage device according to the first embodiment. It is a figure which shows roughly the structure of the whole DC system with which the electrical storage apparatus by Embodiment 2 of this invention is applied. It is a figure explaining the interchange of the electric power in the direct current | flow system by this Embodiment 2. FIG. It is a figure which shows roughly the structure of the whole DC system with which the electrical storage apparatus by Embodiment 3 of this invention is applied. 12 is a flowchart illustrating an operation for determining whether or not power can be interchanged in the power storage device according to the third embodiment. 10 is a flowchart for explaining a modification example of the operation for determining whether or not to allow power interchange in the power storage device according to the third embodiment. It is a figure which shows roughly the structure of the whole DC system with which the electrical storage apparatus by Embodiment 4 of this invention is applied. 10 is a flowchart illustrating an operation for determining whether or not power can be interchanged in the power storage device according to the fourth embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Embodiment 1]
FIG. 1 is a diagram schematically showing an overall configuration of a direct current system to which a power storage device according to Embodiment 1 of the present invention is applied.

  Referring to FIG. 1, the DC system includes a power system 50, a solar power generation system 60 that is a DC power source, and a power storage device 100 coupled between the power system 50 and the solar power generation system 60. In the DC system according to the present embodiment, a case will be described in which one power system 50, one photovoltaic power generation system 60, and one power storage device 100 are provided. It may be individual.

  The power system 50 is typically a single-phase three-wire commercial AC power system. In the single-phase three-wire commercial AC power system, the neutral wire is grounded via a resistor, and AC200V is supplied using two wires other than the neutral wire (R-phase wire RL and T-phase wire TL). To do.

  The solar power generation system 60 includes a solar battery 62 and a DC / DC converter 64. The solar cell 62 is composed of a crystalline solar cell, a polycrystalline solar cell, a thin film solar cell, or the like. DC / DC converter 64 is connected between solar cell 62 and power storage device 100, converts the DC power received from solar cell 62 into a voltage, and supplies it to power storage device 100. The DC / DC converter 64 performs control (so-called maximum power point tracking control) such that maximum power can be acquired from the solar cell 62.

(Configuration of power storage device)
The power storage device 100 includes a direct current bus 30, a storage battery 20, a monitoring unit 22, a bidirectional DC / AC converter 10, and connection terminals 40 and 42.

  The DC bus 30 is a power line for transmitting DC power, and includes a positive bus PL and a negative bus NL that are power line pairs. Bidirectional DC / AC converter 10, storage battery 20, and connection terminals 40 and 42 are connected to DC bus 30.

  Connection terminals 40 and 42 constitute a “connection unit” for electrically connecting a DC power source provided outside power storage device 100 to DC bus 30. In the DC system according to the first embodiment, connection terminal 40 electrically connects photovoltaic power generation system 60 to DC bus 30. By connecting the photovoltaic power generation system 60 to the connection terminal 40, the power generated by the solar battery 62 is supplied to the DC bus 30.

  The storage battery 20 is a rechargeable power storage element, and typically includes a secondary battery such as a lithium ion battery or a nickel metal hydride battery. The storage battery 20 is configured by connecting a plurality of battery cells in series, and has a rated voltage of 380 V as an example. FIG. 2 is a diagram showing a remaining capacity-voltage curve of the storage battery 20. In FIG. 2, the horizontal axis indicates the remaining capacity (SOC: State of Charge) (%) of the storage battery 20, and the vertical axis indicates the voltage (V) of the storage battery 20. The SOC is a percentage (0 to 100%) of the current remaining capacity with respect to the full charge capacity. Referring to FIG. 2, storage battery 20 is 340 V when empty (SOC is 0%), 360 V when SOC is 20%, 380 V (rated voltage) when SOC is 50%, and SOC. When it is 80%, it becomes 400V, and when fully charged (SOC is 100%), it becomes 420V.

  In power storage device 100 according to the first embodiment, storage battery 20 is “directly connected” to DC bus 30, and exchanges DC power with DC bus 30. Here, “directly connected” means that a power converter such as a DC / DC converter is not interposed between the DC bus 30 and the storage battery 20. Accordingly, the voltage of the DC bus 30 is substantially equal to the power supply voltage of the storage battery 20.

  In the characteristics shown in FIG. 2, the voltage of the storage battery 20 has a wide SOC range from 20% to 80%, and the fluctuation range of 380 ± 20 V is suppressed. Thus, since the voltage change is relatively stable with respect to the SOC change, the storage battery 20 has a high voltage stabilization capability. Therefore, by controlling the charging / discharging of the storage battery 20 so that the SOC is maintained within the SOC range (for example, 20% to 80%) in which the voltage can be stabilized, the storage battery 20 provides a stable voltage with respect to the DC bus 30. Can be supplied.

  The monitoring unit 22 detects the state value of the storage battery 20 based on the outputs of the current sensor 15, the voltage sensor 16 and the temperature sensor 17 provided in the storage battery 20. Specifically, the current sensor 15 detects a charge / discharge current (battery current) Ib input / output to / from the storage battery 20 and outputs the detected value to the monitoring unit 22. The voltage sensor 16 detects the charge / discharge voltage (battery voltage) Vb of the storage battery 20 and outputs the detected value to the monitoring unit 22. The temperature sensor 17 detects the temperature (battery temperature) Tb of the storage battery 20 and outputs the detected value to the monitoring unit 22.

  The current sensor 15 detects the charging current Ich to the storage battery 20 as a positive battery current Ib, and detects the discharge current Idc from the storage battery 20 as a negative battery current Ib. The current sensor 15 corresponds to a “charge / discharge current detector”.

  Monitoring unit 22 estimates the SOC of storage battery 20 based on the detected value of battery current Ib from current sensor 15, the detected value of battery voltage Vb from voltage sensor 16, and the detected value of battery temperature Tb from temperature sensor 17. To do. For example, the monitoring unit 22 calculates the estimated SOC value based on the relationship between the open circuit voltage of the storage battery 20 and the SOC. Alternatively, the estimated SOC value may be calculated sequentially based on the integrated value of the charge / discharge amount of the storage battery 20. The integrated value of the charge / discharge amount can be obtained by temporally integrating the product (electric power) of the battery current Ib and the battery voltage Vb. As a method for estimating the SOC, other known general techniques can be used. Hereinafter, the battery current Ib, the battery voltage Vb, the battery temperature Tb, and the estimated SOC value are collectively referred to as “battery data”.

  Bidirectional DC / AC converter 10 is connected between DC bus 30 and power system 50. Bidirectional DC / AC converter 10 converts the DC power received from DC bus 30 into AC power and supplies it to power system 50. The bidirectional DC / AC converter 10 converts AC power received from the power system 50 into DC power and supplies it to the DC bus 30. As described above, power storage device 100 according to the first embodiment is configured to be able to buy grid power from a power company or the like (power purchase) and to sell surplus power to the power company or the like (power sale). .

  In FIG. 1, for current flowing in bidirectional DC / AC converter 10 (hereinafter also referred to as “self-path current”) Iinv, the self-path current during power purchase is Ibuy, and the self-path current during power sale is Icell. Is written. As will be described later, the values of the currents Isel and Ibuy can be freely set by the user of the direct current system or the electric power company.

  Here, in power storage device 100 according to the first embodiment, as described above, the voltage of DC bus 30 can be stabilized by utilizing the high voltage stabilization capability of storage battery 20. Therefore, in the photovoltaic power generation system 60 and the bidirectional DC / AC converter 10 connected to the DC bus 30, there is no need to coordinately perform control for suppressing voltage fluctuation of the DC bus 30. Thereby, the solar power generation system 60 and the bidirectional DC / AC converter 10 can autonomously control the power input / output to / from the DC bus 30.

  Specifically, in the solar power generation system 60, the DC / DC converter 64 is configured such that the solar battery 62 when the voltage of the DC bus 30 is lower than 420 V (corresponding to the voltage of the storage battery 20 in the fully charged state). The maximum power point tracking control. When the voltage of DC bus 30 reaches 420 V, DC / DC converter 64 switches solar power 62 from the maximum power point tracking control to control for maintaining the voltage of DC bus 30 at 420 V.

  Further, in the bidirectional DC / AC converter 10, electric power exchanged between the DC bus 30 and the electric power system 50 in response to a request for electric power sold or purchased from an electric power company or the SOC of the storage battery 20. To control.

(Configuration of bidirectional DC / AC converter)
Next, with reference to the drawings, the configuration of bidirectional DC / AC converter 10 that is one form of the “power converter” according to the first embodiment of the present invention will be described.

FIG. 3 is a circuit diagram showing a detailed configuration of the bidirectional DC / AC converter 10 in FIG.
Referring to FIG. 3, bidirectional DC / AC converter 10 includes a bidirectional inverter 200, interconnection reactors 210 and 220, a current sensor 230, a voltage sensor 240, and a control unit 250.

  The bidirectional inverter 200 converts DC power received from the DC bus 30 into AC power and outputs the AC power to the power system 50 in accordance with switching control signals S1 to S4 from the control unit 250 when selling power. Bidirectional inverter 200 converts AC power received from power system 50 into DC power and outputs it to DC bus 30 in accordance with switching control signals S1 to S4 from control unit 250 during power purchase.

  Specifically, bidirectional inverter 200 includes transistors Q1 to Q4, which are switching elements, and diodes D1 to D4. Transistors Q1 and Q2 are connected in series between positive bus PL and negative bus NL constituting DC bus 30. An intermediate point between transistors Q1 and Q2 is connected to R-phase line RL. Interconnection reactor 210 is connected to R-phase line RL.

  Transistors Q3 and Q4 are connected in series between positive bus PL and negative bus NL. An intermediate point between transistors Q3 and Q4 is connected to T-phase line TL. Interconnection reactor 220 is connected to T-phase line TL. Between the collectors and emitters of the transistors Q1 to Q4, diodes D1 to D4 that flow current from the emitter side to the collector side are respectively connected. Transistors Q1-Q4 and diodes D1-D4 constitute a full bridge circuit.

  As the transistors Q1 to Q4, for example, IGBTs (Insulated Gate Bipolar Transistors) can be used. Alternatively, a power switching element such as a power MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) may be used.

  Current sensor 230 is inserted in T-phase line TL, detects a current value (own path current) Iinv of power exchanged between bidirectional inverter 200 and power system 50, and the detection result is sent to control unit 250. Output. The current sensor 230 corresponds to a “own path current detection unit”.

  Voltage sensor 240 is connected between positive bus PL and negative bus SL, detects voltage value Vdc of DC power exchanged between DC bus 30 and bidirectional inverter 200, and the detection result is a control unit 250. Output to. Since the storage battery 20 is “directly connected” to the DC bus 30 as described above, the voltage Vdc of the DC bus 30 is equal to the battery voltage Vb. In reality, a slight voltage difference is generated between the voltage value Vdc and the battery voltage Vb due to the wiring impedance, but it is assumed to be negligibly small in the present embodiment.

  The control unit 250 includes the own path current Iinv received from the current sensor 230, the voltage Vdc received from the voltage sensor 240, the battery current Ib received from the current sensor 15, and the battery data (battery voltage Vb, Based on the battery temperature Tb and the remaining battery charge SOC), switching control signals S1 to S4 for controlling on / off of the transistors Q1 to Q4 are generated according to a control structure described later, and the bidirectional inverter 200 is controlled. .

  Specifically, control unit 250 sets a control target value in bidirectional inverter 200. This control target value includes a current target value Inv * of the own path current Iinv and a current target value Ib * of the battery current Ib. In the following description, the current target value Iinv * of the own path current Iinv is also referred to as “own path current target value”, and the current target value Ib * of the battery current Ib is also referred to as “battery current target value”.

  The control target values (the self-path current target value Iinv * and the battery current target value Ib *) are determined in advance so as to become different values according to the date and time or the SOC of the storage battery 20, and stored in a memory (not shown). be able to. FIG. 4 is a diagram illustrating an example of a target value setting table used by the bidirectional DC / AC converter 10. In the figure, as described above, the battery current is represented with the charging direction of the storage battery 20 as a positive direction and the discharge direction of the storage battery 20 as a negative direction. The self-path current Iinv is described with the power selling direction as the positive direction and the power purchase direction as the negative direction. Battery current target value Ib * includes current target value Ich * of charging current Ich and current target value Idc * of discharge current Idc. The own path current target value Iinv * includes a current target value Isel * of the own path current Isel at the time of power sale and a current target value Ibuy * of the own path current Ibuy at the time of power purchase.

  Control unit 250 sets own path current target value Iinv * or battery current target value Ib * according to the date and time and SOC of storage battery 20 in accordance with the target value setting table shown in FIG. Or you may make it acquire the control target value set according to the target value setting table | surface of FIG. 4 by communicating between the control part 250 and the exterior of a DC system.

  Referring to FIG. 4, for example, when the SOC of storage battery 20 is not less than 20% and less than 80% in the time zone from 7:00 to 17:00, the power generated by photovoltaic power generation system 60 is actively sold. The self-path current target value Iinv * is set to 10A so as to be charged. That is, the self-path current target value Isell * at the time of power sale is set to 10A. In this case, the control unit 250 controls the bidirectional inverter 200 by generating the switching control signals S1 to S4 such that the own path current Iinv becomes the own path current target value Iinv *.

  On the other hand, when the SOC of the storage battery 20 is less than 20% in the time zone from 7:00 to 17:00, the battery current target value is set so that the storage battery 20 is charged with the power generated by the solar power generation system 60. Set Ib * to 8A. That is, the target current value Ich * of the charging current Ich of the storage battery 20 is set to 8A. In this case, the control unit 250 controls the bidirectional inverter 200 by generating the switching control signals S1 to S4 so that the battery current Ib becomes the battery current target value Ib *.

  In addition, the control part 250 is with respect to the alternating current power (alternating current voltage, alternating current (self-path current) Iinv) exchanged between the electric power grid | system 50 and the bidirectional | two-way inverter 200 in the production | generation of switching control signal S1-S4. Execute power factor correction control. Specifically, control unit 250 improves the power factor by correcting the waveform of the alternating current so as to match the phase of the alternating current with the phase of the alternating voltage.

In the following description, in order to distinguish each current control, the current control based on the own path current target value Iinv * is also referred to as “own path current control”, and the current control based on the battery current target value Ib * is “ Also referred to as “battery current control”.
(1) Self-path current control When controlling power exchanged with the power system 50 by self-path current control, in response to fluctuations in power supplied from the solar power generation system 60 to the DC bus 30, The power charged / discharged in the storage battery 20 varies. Therefore, during the execution of the self-path current control, there is a possibility that the current range in which the battery current Ib can flow through the storage battery 20 may be out of range. In order to suppress the performance deterioration of the storage battery 20 due to such excess of current, it is necessary to keep the battery current Ib within the current range during the execution of the self-path current control.

  Therefore, when the battery current Ib is out of the predetermined current range during execution of the self-path current control, the control unit 250 causes the self-path current target value Iinv * so that the battery current Ib falls within the current range. Adjust.

  FIG. 5 is a flowchart showing a control processing procedure for realizing self-path current control in the power storage device according to the first embodiment. The control process according to the flowchart shown in FIG. 5 is executed by the control unit 250 at regular control cycles. Each step shown in FIG. 5 is realized by software processing and / or hardware processing by the control unit 250.

  Referring to FIG. 5, control unit 250 sets current target value Iinv ** of self-path current Iinv at step S01. Specifically, control unit 250 sets self-path current target value Iinv * according to the date and time and SOC of storage battery 20 by referring to a target value setting table (FIG. 4) stored in a memory (not shown). . The control unit 250 sets the self-path current target value Iinv * determined according to the target value setting table as an initial value of the self-path current target value Iinv **. That is, the initial value Iinv * is a variable value that changes according to the date and time and the SOC of the storage battery 20.

  Next, the control unit 250 generates the switching control signals S1 to S4 so that the own path current Iinv becomes the own path current target value Iinv **, and controls the bidirectional inverter 200 (current control). Specifically, in step S02, control unit 250 compares self-path current Iinv detected by current sensor 230 with self-path current target value Iinv **. When the self-path current Iinv is smaller than the self-path current target value Iinv ** (when YES is determined in step S02), the control unit 250 sets the self-path current Iinv and the self-path current target value Iinv ** in step S02. The switching control signals S1 to S4 based on the current deviation are generated. By performing such control, the own path current Iinv changes in the positive direction (the power selling direction) (that is, the own path current Iinv increases).

  On the other hand, when the self-path current Iinv is equal to or greater than the self-path current target value Iinv ** (when NO is determined in step S02), the control unit 250 performs the self-path current Iinv and the self-path current target value Iinv in step S04. Switching control signals S1 to S4 based on the current deviation from ** are generated. By performing such control, the own path current Iinv changes in the negative direction (the power purchase direction) (that is, the own path current Iinv decreases).

  The control unit 250 acquires the battery current Ib from the current sensor 15 during the execution of the current control shown in steps S02 to S04. Then, control unit 250 determines whether or not battery current Ib is within a predetermined current range. Specifically, in step S05, control unit 250 determines whether or not battery current Ib is greater than or equal to lower limit value Ibmin of the current range. When battery current Ib is smaller than lower limit value Ibmin (when NO is determined in step S05), control unit 250 decreases own path current target value Iinv ** by a predetermined amount ΔI1 in step S06.

  That is, when the discharge current Idc of the storage battery 20 is out of the current range (when NO is determined in step S05), the control unit 250 reduces the own path current target value Iinv ** so as to decrease the own path current target value Iinv **. Adjust *. In the bidirectional DC / AC converter 10, the power conversion operation is executed in accordance with the adjusted self-path current target value Iinv **, thereby reducing the self-path current Isel at the time of power sale, while at the time of power purchase. The self-path current Ibuy at increases. In this way, by adjusting the self-path current target value Iinv ** so that the power supplied from the storage battery 20 to the DC bus 30 is reduced at the time of selling and buying power, the discharge current Idc of the storage battery 20 is adjusted. Falls within the current range.

  On the other hand, when battery current Ib is equal to or greater than lower limit value Ibmin of the current range (when YES is determined in step S05), control unit 250 further determines that battery current Ib is upper limit value Ibmax of the current range in step S07. It is determined whether or not: When battery current Ib is larger than upper limit value Ibmax (NO in step S07), control unit 250 decreases own path current target value Iinv ** by predetermined amount ΔI1 in step S08.

  That is, when the charging current Ich of the storage battery 20 is out of the current range (NO determination in step S07), the control unit 250 increases the own path current target value Iinv ** so as to increase the own path current target value Iinv **. Adjust *. In the bidirectional DC / AC converter 10, the power conversion operation is executed in accordance with the adjusted self-path current target value Iinv **, thereby increasing the self-path current Isel at the time of power sale while purchasing power. The self-path current Ibuy at is reduced. In this way, the charging current Ich of the storage battery 20 is adjusted by adjusting the self-path current target value Iinv ** so that the power supplied from the storage battery 20 to the DC bus 30 increases at the time of power sale and purchase. Falls within the current range.

  Thus, when the battery current Ib deviates from the current range of the storage battery 20, the own path current target value Iinv ** is increased or decreased by a predetermined amount ΔI1 so that the battery current Ib falls within the current range. The predetermined amount ΔI1 is determined in consideration of the control speed of current control in the bidirectional AC / DC converter 10.

  On the other hand, in step S07, when battery current Ib is equal to or lower than upper limit value Ibmax (when YES is determined in step S07), that is, when battery current Ib is within the current range, control unit 250 performs step S09. Through S12, a return process for returning the own path current target value Iinv ** to the initial value Iinv * is executed.

  Specifically, in step S09, control unit 250 determines whether own path current target value Iinv ** is greater than initial value Iinv *. When own path current target value Iinv ** is larger than initial value Iinv * (when YES is determined in step S09), control unit 250 decreases own path current target value Iinv ** by a predetermined amount ΔI2 in step S10. Let

  On the other hand, when the own path current target value Iinv ** is equal to or smaller than the initial value Iinv * (when NO is determined in step S09), the control unit 250 further performs the own path current target value Iinv ** as the initial value in step S11. It is determined whether it is smaller than Iinv *. When own path current target value Iinv ** is smaller than initial value Iinv * (when YES is determined in step S11), control unit 250 increases own path current target value Iinv ** by a predetermined amount ΔI2 in step S12. Let The predetermined amount ΔI2 is determined in consideration of the control speed of current control in the bidirectional AC / DC converter 10. On the other hand, when the own path current target value Iinv ** is equal to the initial value Iinv * (when NO is determined in step S11), the return processing of the above-described own path current target value Iinv ** is not performed.

As described above, the control unit 250 adjusts the self-path current target value Iinv ** so that the battery current Ib is within the current range of the storage battery 20 during the self-path current control. Thereby, the power storage device 100 can exchange power with the power system 50 while observing the current limitation of the storage battery 20.
(2) Battery current control On the other hand, when the electric power charged / discharged to / from the storage battery 20 by the battery current control is controlled from the electric power system 50, the electric power is supplied from the solar power generation system 60 to the DC bus 30. In response to the fluctuation of the electric power, the electric power inputted to and outputted from the bidirectional DC / AC converter 10 fluctuates. Therefore, there is a possibility that the current range in which the self-path current Iinv can flow to the bidirectional DC / AC converter 10 may be out of the battery current control. This current range is determined based on the rated output of the bidirectional DC / AC converter 10, for example.

  When executing the battery current control, the control unit 250 adjusts the battery current target value Ib * so that the own path current Iinv falls within the current range when the own path current Iinv is out of the predetermined current range. To do.

  FIG. 6 is a flowchart showing a control processing procedure for realizing battery current control in the power storage device according to the first embodiment. The control process according to the flowchart shown in FIG. 6 is executed by the control unit 250 at regular control cycles. Each step illustrated in FIG. 6 is realized by software processing and / or hardware processing by the control unit 250.

  Referring to FIG. 6, control unit 250 sets current target value Ib ** of battery current Ib in step S21. Specifically, control unit 250 sets battery current target value Ib * according to the date and time and the SOC of storage battery 20 by referring to a target value setting table (FIG. 4) stored in a memory (not shown). Control unit 250 sets battery current target value Iib * determined according to the target value setting table as an initial value of battery current target value Ib **. That is, the initial value Ib * is a variable value that changes according to the date and time and the SOC of the storage battery 20.

  Next, the control unit 250 generates the switching control signals S1 to S4 so that the battery current Ib becomes the battery current target value Ib **, and controls the bidirectional inverter 200 (current control). Specifically, control unit 250 compares battery current Ib detected by current sensor 15 with battery current target value Ib ** in step S22. When the battery current Ib is smaller than the battery current target value Ib ** (when YES is determined in step S22), the control unit 250 sets the current deviation between the battery current Ib and the battery current target value Ib ** in step S23. Based on the switching control signals S1 to S4 are generated. By performing such control, the battery current Iib changes in the positive direction (charging direction) (that is, the battery current Ib increases).

  On the other hand, when battery path current Ib is equal to or greater than battery current target value Ib ** (when NO is determined in step 22), control unit 250 determines battery current Ib and battery current target value Ib ** in step S24. The switching control signals S1 to S4 based on the current deviation are generated. By performing such control, the battery current Ib changes in the negative direction (discharge direction) (that is, the battery current Ib decreases).

  The control unit 250 acquires the self-path current Iinv from the current sensor 230 during the execution of the current control shown in steps S22 to S24. Then, the control unit 250 determines whether or not the own path current Iinv is within a predetermined current range. Specifically, in step S25, control unit 250 determines whether or not own path current Iinv is equal to or greater than lower limit value Iinvmin of the current range. When own path current Iinv is smaller than lower limit value Iinvmin (when NO is determined in step S25), control unit 250 decreases battery current target value Ib ** by predetermined amount ΔI3 in step S26.

  That is, when own path current Ibuy at the time of power purchase is out of the current range (NO determination in step S25), control unit 250 causes battery current target value Ib * to decrease battery current target value Ib **. Adjust *. Then, by executing the power conversion operation according to the adjusted battery current target value Ib **, the battery current (charge current) Ich at the time of charging is reduced in the storage battery 20, while the battery current (at the time of discharging) ( Discharge current) Idc increases. In this way, the battery current target value Ib ** is adjusted so that the power supplied from the DC bus 30 to the storage battery 20 during charging decreases while the power supplied from the storage battery 20 to the DC bus 30 increases during discharging. By doing so, the own path current Iinv at the time of power purchase falls within the current range.

  On the other hand, when the own path current Iinv is equal to or greater than the lower limit value Iinvmin of the current range (when YES is determined in step S25), the control unit 250 further causes the own path current Iinv to exceed the upper limit of the current range in step S27. It is determined whether or not the value is less than or equal to Iinvmax. When own path current Iinv is larger than upper limit value Iinvmax (NO in step S27), control unit 250 decreases battery current target value Ib ** by a predetermined amount ΔI3 in step S28.

  That is, when self-path current Isel at the time of power sale is out of the current range (NO determination in step S27), control unit 250 increases battery current target value Ib ** so as to increase battery current target value Ib **. Adjust *. By executing the power conversion operation according to the adjusted battery current target value Ib **, the battery current (charge current) Ich at the time of charging increases in the storage battery 20, while the battery current (discharge current) at the time of discharge increases. ) Idc decreases. In this way, the battery current target value Ib ** is adjusted so that the power supplied from the DC bus 30 to the storage battery 20 during charging increases while the power supplied from the storage battery 20 to the DC bus 30 decreases during discharging. By doing so, the self-path current Iinv at the time of power sale falls within the current range.

  Thus, when the self-path current Iinv is out of the current range of the bidirectional DC / AC converter 10, the battery current target value Ib ** is set to a predetermined amount so that the self-path current Iinv is within the current range. Increase or decrease by ΔI3. This predetermined amount ΔI3 is determined in consideration of the control speed of current control in the bidirectional AC / DC converter 10.

  On the other hand, when the own path current Iinv is equal to or lower than the upper limit value Iinvmax in step S27 (when YES is determined in step S27), that is, when the own path current Iinv is within the current range, the control unit 250 By steps S29 to S32, a return process for returning the battery current target value Ib ** to the initial value Ib * is executed.

  Specifically, control unit 250 determines whether or not battery current target value Ib ** is larger than initial value Ib * in step S29. When battery current target value Ib ** is larger than initial value Ib * (when YES is determined in step S29), control unit 250 decreases battery current target value Ib ** by a predetermined amount ΔI4 in step S30.

  On the other hand, when battery current target value Ib ** is equal to or smaller than initial value Ib * (when NO is determined in step S29), control unit 250 further performs battery current target value Ib ** to initial value Ib * in step S31. It is determined whether it is smaller. When battery current target value Ib ** is smaller than initial value Ib * (when YES is determined in step S31), control unit 250 increases battery current target value Ib ** by a predetermined amount ΔI4 in step S32. This predetermined amount ΔI4 is determined in consideration of the control speed of current control in the bidirectional AC / DC converter 10. On the other hand, when the battery current target value Ib ** is equal to the initial value Ib * (when NO is determined in step S31), the above-described return processing of the battery current target value Ib ** is not performed.

  As described above, control unit 250 adjusts battery current target value Ib ** so that self-path current Iinv is within the current range of bidirectional DC / AC converter 10 during execution of battery current control. . Thereby, the power storage device 100 can charge and discharge the storage battery 20 while observing the current limitation of the bidirectional DC / AC converter 10.

  Thus, according to the power storage device according to the first embodiment, since the storage battery directly connected to the DC bus stabilizes the voltage of the DC bus, in the plurality of power converters connected to the DC bus, There is no need to coordinately perform control for suppressing voltage fluctuations. Thereby, the several power converter can control the electric power input / output with respect to a DC bus autonomously. As a result, since it is easy to add and change an external DC power source connected to the DC bus, it is possible to easily change the specifications of the DC system.

[Embodiment 2]
FIG. 7 is a diagram schematically showing an overall configuration of a DC system to which the power storage device according to Embodiment 2 of the present invention is applied.

  Referring to FIG. 7, power storage device 110 according to the second embodiment includes a storage battery (hereinafter also referred to as “external storage battery”) 25 provided outside power storage device in direct-current bus in power storage device 100 shown in FIG. 1. 30 is further provided with a connection terminal 44 for electrical connection to 30 and a direct current bus 34 for transmitting direct current power exchanged between the external storage battery 25 and the direct current bus 30.

  The external storage battery 25 is configured by a secondary battery such as a lithium ion battery or a nickel metal hydride battery, similarly to the storage battery 20. The external storage battery 25 is configured by connecting a plurality of battery cells in series, and has the same rated voltage (380 V) as the storage battery 20.

  In the second embodiment, the monitoring unit 22 is configured to output battery data (battery current, battery temperature) of the external storage battery 25 based on outputs of a current sensor, a voltage sensor, and a temperature sensor (not shown) provided in the external storage battery 25. And SOC). As an example, the monitoring unit 22 can acquire battery data of the external storage battery 25 by performing power line communication or wireless communication using the DC bus 34 with the external storage battery 25.

  Or it is good also as a structure which acquires the charging / discharging electric current of the external storage battery 25 which the said current sensor detected by inserting and connecting the current sensor to DC bus 34. In this case, the monitoring unit 22 estimates the SOC of the external storage battery 25 based on the detected value of the battery current from the current sensor. Therefore, the battery current and the SOC are omitted from the battery data of the external storage battery 25 acquired by the monitoring unit 22.

  The DC bus 30 is provided with a current sensor 18 for detecting the total value of the charging / discharging current Ib of the storage battery 20 and the charging / discharging current Ibext of the external storage battery 25. Current sensor 18 detects a total value Ib # (Ib # = Ib + Ibext) of charge / discharge currents Ib and Ibext, and outputs the detected value to bidirectional DC / AC converter 10.

  In power storage device 100 according to Embodiment 1 described above, the configuration in which storage battery 20 inside the device is directly connected to DC bus 30 has been described. However, in Embodiment 2 of the present invention, external storage battery 25 is further directly connected to DC bus 30. . Thereby, since the capacity | capacitance of a storage battery increases substantially, the electric power which a storage battery can input / output with respect to the DC bus 30 can be increased. As a result, more power can be accommodated between the power system 50 and the external DC power source or DC load, so that the number of external DC power sources or DC loads can be increased or higher. Electric power specifications can be applied.

  In the DC system shown in FIG. 7, power storage device 110 is coupled among power system 50, solar power generation system 60, and power storage system 70. By connecting power storage system 70 to connection terminal 42, power is exchanged between DC bus 30 and power storage system 70. Power storage system 70 includes a storage battery 74 and a DC / DC converter 72 that performs bidirectional voltage conversion between storage battery 74 and DC bus 30. The voltage conversion operation in the DC / DC converter 72 is controlled according to a switching command from a control unit (not shown) according to the voltage of the storage battery 74 and the voltage of the DC bus 30.

FIG. 8 is a diagram for explaining power interchange in the DC system according to the second embodiment.
Referring to FIG. 8, bidirectional DC / AC converter 10, storage battery 20, solar power generation system 60, and power storage system 70 are connected to DC bus 30. An external storage battery 25 is further connected to the DC bus 30 via a DC bus 34.

  In the above DC system, it is assumed that the rated power indicating the maximum input / output power of the bidirectional DC / AC converter 10 is 4 kW, and the rated charge / discharge power indicating the maximum charge / discharge power of the storage battery 20 is 2 kW. Further, it is assumed that the rated generated power indicating the maximum generated power of the solar power generation system 60 is 3 kW, and the rated charge / discharge power of the power storage system 70 is 5 kW.

  In this case, in the power storage device 110, the maximum value of the power input from the bidirectional DC / AC converter 10 and the storage battery 20 to the DC bus 30 is 6 kW (= 4 kW + 2 kW). It can be supplied to an external DC power source. Further, since the maximum value of the power output from the DC bus 30 to the bidirectional DC / AC converter 10 and the storage battery 20 is 6 kW (= 4 kW + 2 kW), the DC bus 30 accepts 6 kW of power from an external DC power source. be able to. That is, the DC bus 30 has a 6 kW power supply capability and a 6 kW power acceptance capability with an external DC power source.

  On the other hand, the maximum value of power input from the external DC power source (solar power generation system 60 and power storage system 70) to the DC bus 30 is 8 kW (= 3 kW + 5 kW). Further, the maximum value of the power output from the DC bus 30 to the external DC power source is 5 kW. Therefore, when the power input to the DC bus 30 from the DC power source reaches the maximum value of 8 kW, the power receiving capacity (6 kW) of the DC bus 30 is exceeded. In such a situation, there is a possibility that the storage battery 20 is charged with power exceeding the rated charging power.

  Therefore, in the second embodiment, the external storage battery 25 is further connected to the DC bus 30 to cause the external storage battery 25 to recover the excess power. In the example of FIG. 8, by using a storage battery having a rated charge / discharge power of 2 kW as the external storage battery 25, the DC bus 30 can receive all the power (8 kW) supplied from an external DC power source.

  In power storage device 110 according to the second embodiment, bidirectional DC / AC converter 10 performs the above-described self-path current control and battery current control with the total value Ib # of the charge / discharge current detected by current sensor 18. Run based on. Specifically, in the self-path current control, control unit 250 sets a current range of charge / discharge current total value Ib # based on the current ranges for storage battery 20 and external storage battery 25. Then, control unit 250 adjusts self-path current target value Iinv * such that total value Ib # of the charge / discharge current is within the current range.

  In the battery current control, instead of the battery current target value Ib * of the storage battery 20, the battery current target value Ib ## of the storage batteries 20 and 25 as a whole is set, and the total value Ib # of the charge / discharge current is set to this battery. Bidirectional inverter 200 is controlled to have current target value Ib ##. Battery current target value Ib ## can be set according to the SOC of storage battery 20 and external storage battery 25.

  As described above, according to the power storage device according to the second embodiment, the external storage battery is configured to be directly connected to the DC bus, so that the storage battery and the external storage battery can stabilize the voltage of the DC bus, More power can be accommodated between the grid and the external DC power source or DC load. As a result, further enrichment of the specifications of the DC system can be realized.

[Embodiment 3]
FIG. 9 schematically shows an overall configuration of a DC system to which the power storage device according to Embodiment 3 of the present invention is applied.

  Referring to FIG. 9, power storage device 120 according to the third embodiment further includes information acquisition unit 80 for acquiring information related to an external DC power source in power storage device 100 shown in FIG. 1. .

  The information acquisition unit 80 acquires information related to power input / output from / to the DC bus 30 by the external DC power source (solar power generation system 60 and power storage system 70). The information related to the power includes, for example, rated power indicating the maximum input / output power of the DC power source. Alternatively, instantaneous power supplied from the DC power source to the DC bus 30 may be included.

  The information acquisition unit 80 is configured to be capable of power line communication using the DC bus 30 with an external DC power source. When a DC power source is connected to the connection terminals 40 and 42, the information acquisition unit 80 acquires information on the power described above by performing communication with the DC power source.

  Information acquisition unit 80 may be configured to communicate with a DC power source wirelessly. Alternatively, each of the connection terminals 40 and 42 is configured with a dedicated connector corresponding to the type of DC power source to be connected, and a sensor for detecting that the DC power source is connected to the connector is provided. It is good also as a structure. In said structure, the information acquisition part 80 acquires the information regarding the electric power of a corresponding DC power source by discriminating the kind of connector from the detection signal output from the said sensor.

  In bidirectional DC / AC converter 10, control unit 250 determines whether or not power can be interchanged between power system 50, DC power source, and power storage device 120 based on the power information acquired by information acquisition unit 80. Determine whether.

  Specifically, as described in FIG. 7, the control unit 250 is based on the power that can be input to and output from the DC bus 30 of the bidirectional DC / AC converter 10 and the power that can be charged and discharged by the storage battery 20. The power supply capability and power acceptance capability of the DC bus 30 are calculated. For example, the control unit 250 calculates a value obtained by summing the rated output power of the bidirectional DC / AC converter 10 and the rated discharge power of the storage battery 20 as the power supply capability of the DC bus 30. Further, the control unit 250 calculates a value obtained by summing the rated input power of the bidirectional DC / AC converter 10 and the rated charging power of the storage battery 20 as the power receiving capability of the DC bus 30.

  The controller 250 further calculates input / output power required for the DC bus 30. For example, the control unit 250 calculates a value obtained by summing the rated generated power of the solar power generation system 60 and the rated discharge power of the power storage system 70 as requested input power that is power that requests the DC bus 30 to be accepted. In addition, the control unit 250 calculates the rated charging power of the power storage system 70 as required output power that is power that requests the DC bus 30 to supply.

  Then, the control unit 250 compares the calculated required input power of the DC bus 30 with the power acceptance capability of the DC bus 30, and compares the calculated required output power of the DC bus 30 with the power supply capability of the DC bus 30. To do. When at least one of the power reception capability and the power supply capability is less than the required power, control unit 250 determines that the interchange of power among power system 50, the DC power source, and power storage device 120 is impossible.

  FIG. 10 is a flowchart illustrating an operation for determining whether or not to allow power interchange in the power storage device according to the third embodiment. Note that the flowchart shown in FIG. 10 can be realized by executing a program stored in advance in the control unit 250.

  Referring to FIG. 10, when power storage device 120 is activated in step S41, in step S42, information acquisition unit 80 communicates with an external DC power source so that the direct power source is DC. Information on power input / output to / from the bus 30 is acquired. The information acquisition unit 80 sends the acquired power information of the DC power source to the control unit 250 of the bidirectional DC / AC converter 10.

  In step S <b> 43, control unit 250 determines whether or not power interchange is possible among power system 50, DC power source, and power storage device 120 based on the acquired power information. Specifically, the control unit 250 calculates the power supply capability and power reception capability of the DC bus 30 by the method described above. Further, the control unit 250 calculates the required input power and the required output power for the DC bus 30 by the method described above. The control unit 250 compares the calculated required input power of the DC bus 30 with the power receiving capability of the DC bus 30, and compares the calculated required output power of the DC bus 30 with the power supply capability of the DC bus 30.

  When the required input power is smaller than the power acceptance capability of DC bus 30 and the required output power is smaller than the power supply capability of DC bus 30, control unit 250 controls power system 50, DC power source, and power storage device 120. It is determined that power can be interchanged between them (YES determination in step S43). Therefore, the control unit 250 proceeds to step S44 and controls the power conversion operation in the bidirectional inverter 200 by executing the above-described current control.

  On the other hand, when the power receiving capability of the DC bus 30 is smaller than the required input power, or when the power supply capability of the DC bus 30 is smaller than the required output power, the control unit 250 includes the power system 50, the DC power source. Then, it is determined that power cannot be interchanged between power storage devices 120 (NO determination in step S43). In this case, in step S45, the control unit 250 outputs a warning to the user of the DC system that power cannot be accommodated. The warning may be displayed or may be performed by voice.

  In addition, although the structure which outputs the warning to the effect that the interchange of electric power is impossible was demonstrated in FIG. 10, the interchange of electric power is carried out by restrict | limiting the input-output power with respect to the DC bus 30 of an external DC power source. You may make it possible.

  FIG. 11 is a flowchart for explaining a modification example of the operation for determining whether or not to allow power interchange in the power storage device according to the third embodiment. The flowchart shown in FIG. 11 is different from the flowchart shown in FIG. 10 in that step S46 is provided instead of step S45.

  Referring to FIG. 11, control unit 250 performs steps S <b> 41 to S <b> 43 similar to FIG. 10, based on the power information of the external DC power source, between power system 50, DC power source, and power storage device 120. It is determined whether or not power can be accommodated. If it is determined that power can be interchanged, the control unit 250 controls the power conversion operation in the bidirectional inverter 200 in step S44.

  On the other hand, when it is determined that power interchange is impossible, the control unit 250 limits input / output power to the DC bus 30 of the external DC power source in step S46. Specifically, when the required input power to the DC bus 30 exceeds the power receiving capability of the DC bus 30, the control unit 250 determines the required input power for the power receiving capability from the rated generated power of the solar power generation system 60. The power obtained by subtracting the excess amount is set as the power generation allowable power of the solar power generation system 60. Alternatively, the power obtained by subtracting the excess from the rated discharge power of the power storage system 70 is set as the discharge allowable power of the power storage system 70. Alternatively, both the generated power of the solar power generation system 60 and the discharge power of the power storage system 70 may be reduced.

  On the other hand, when the required output power of the DC bus 30 exceeds the power supply capability of the DC bus 30, the control unit 250 subtracts the excess of the required output power with respect to the power supply capability from the rated charging power of the power storage system 70. Let the electric power be the chargeable electric power of the power storage system 70.

  As described above, according to the power storage device according to the third embodiment, the power information of the external DC power source can be acquired when the power storage device is started, so that power interchange between the power system, the DC power source, and the power storage device is possible. Whether it is possible or not can be determined. Thereby, it is possible to notify the user of the direct current system in advance whether or not the power can be accommodated. Alternatively, when it is determined that power interchange is impossible, power interchange can be realized by limiting the input / output power of the external DC power source.

[Embodiment 4]
FIG. 12 is a diagram schematically showing an overall configuration of a direct current system to which the power storage device according to the fourth embodiment of the present invention is applied.

  Referring to FIG. 12, power storage device 130 according to the fourth embodiment includes a connection terminal 44 for electrically connecting external storage battery 25 to DC bus 30 and external storage battery 25 in power storage device 120 shown in FIG. 9. DC bus 34 for transmitting DC power transmitted / received to / from DC bus 30, and a total value Ib # for detecting charging / discharging current Ib of storage battery 20 and charging / discharging current Ibext of external storage battery 25. A current sensor 18 is further provided. Since the configuration for directly connecting external storage battery 25 to DC bus 30 is the same as that in FIG. 7, detailed description thereof will not be repeated. The configuration of current sensor 18 is also the same as that in FIG. 7, and thus detailed description will not be repeated.

  In the power storage device 130 according to the fourth embodiment, the information acquisition unit 80 acquires information related to power input / output from / to the DC bus 30 by the external DC power source (solar power generation system 60 and power storage system 70). In addition, it is configured to be able to acquire information on charge / discharge power of the external storage battery 25. The information related to the charge / discharge power includes the rated charge / discharge power of the external storage battery 25.

  In bidirectional DC / AC converter 10, control unit 250 calculates the power reception capability and power supply capability of DC bus 30 based on the power information from information acquisition unit 80. The power receiving capacity of the DC bus 30 is calculated by adding the rated charging power of the external storage battery 25 to the total value of the rated input power of the bidirectional DC / AC converter 10 and the rated charging power of the storage battery 20. Similarly, the power supply capability of the DC bus 30 is calculated by adding the rated discharge power of the external storage battery 25 to the total value of the rated output power of the bidirectional DC / AC converter 10 and the rated discharge power of the storage battery 20. The

  When controller 250 further calculates the required input power and the required output power for DC bus 30, based on these calculated results, the above-described method is used to connect power system 50, DC power source, and power storage device 130. It is determined whether or not power can be accommodated.

  In the fourth embodiment, the external storage battery 25 is directly connected to the DC bus 30, thereby increasing the power receiving capability and the power supply capability of the DC bus 30. Therefore, when at least one of the increased power acceptance capability and power supply capability is less than the required power, control unit 250 cannot exchange power among power system 50, DC power source, and power storage device 120. Judge that there is.

  FIG. 13 is a flowchart illustrating an operation for determining whether or not power can be interchanged in the power storage device according to the fourth embodiment. The flowchart shown in FIG. 13 further includes step S47 in the flowchart shown in FIG.

  Referring to FIG. 13, control unit 250 acquires power information of an external DC power source in step S42 similar to that in FIG. 10, and acquires information related to charge / discharge power of external storage battery 25 in step S47. Then, in step S43 similar to FIG. 10, the control unit 250 determines the power system 50, the DC power source, and the power storage device 120 based on the power information of the external DC power source and the charge / discharge power information of the external storage battery 25. It is determined whether power can be interchanged between the two. If it is determined that power can be interchanged, the control unit 250 controls the power conversion operation in the bidirectional inverter 200 in step S44.

  On the other hand, when it is determined that power interchange is impossible, the control unit 250 outputs a warning to that effect to the user of the DC system in step S45 similar to FIG.

  Instead of the warning in step S45, power interchange may be realized by limiting input / output power to / from the DC bus 30 of the external DC power source in step S46 of FIG.

(DC system configuration example)
In the above-described first to fourth embodiments, the configuration in which the photovoltaic power generation system 60, the power storage system 70, and the power system 50 are connected to the power storage devices 100 to 130 as an example of the DC system has been described. However, the application of the present invention is not limited to such a DC system. Specifically, the present invention can be applied if a power storage device is connected between the power system and the DC power source. Therefore, for example, the solar power generation system 60 and the power storage system 70 are illustrated as the DC power source, but a wind power generation device, a fuel cell, and the like may be used. Further, a DC load may be connected to the power storage device together with the DC power source.

  In the first to fourth embodiments described above, the bidirectional DC / AC converter 10 that performs bidirectional power conversion between the DC bus 30 and the power system 5 has been described as the power converter. DC / AC converter for converting the DC power received from AC to AC power and supplying it to the power system 50, and AC / AC for converting AC power received from the power system 50 to DC power and supplying it to the DC bus 30 It is good also as a structure provided with a DC converter.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  10 Bidirectional DC / AC converter, 15, 18, 230 Current sensor, 16, 240 Voltage sensor, 17 Temperature sensor, 20 Storage battery, 22 Monitoring unit, 25 External storage battery, 30, 34 DC bus, 40, 42, 44 Connection Terminal, 50 Power system, 60 Solar power generation system, 62 Solar battery, 64 DC / DC converter, 70 Power storage system, 72 DC / DC converter, 74 Storage battery, 100, 110, 120, 130 Power storage device, 200 Bidirectional Inverter, 210, 220 interconnected reactor, 250 control unit.

Claims (11)

A power storage device that transfers power between a power system and a DC power source,
A first DC bus for transmitting DC power;
A first connection for electrically connecting the DC power source to the first DC bus;
A power converter that performs bidirectional power conversion between the first DC bus and the power system;
A power storage device comprising: a power storage unit that outputs a power supply voltage to the first DC bus. A self-path current detection unit for detecting a self-path current flowing through the power conversion unit;
The power storage device according to claim 1, further comprising self-path current control means for controlling power conversion in the power conversion unit so that the self-path current becomes a control target value. A charge / discharge current detection unit for detecting a charge / discharge current of the power storage unit;
The apparatus further comprises first adjusting means for adjusting the control target value so that the detected value of the charge / discharge current falls within a predetermined current range during execution of the self-path current control means. The power storage device described. A second DC bus connected to the first DC bus;
A second connection part for electrically connecting an external power storage unit provided outside the power storage device to the second DC bus;
The charge / discharge current detection unit is configured to detect a total value of charge / discharge currents of the power storage unit and the external power storage unit,
The power storage device according to claim 3, wherein the first adjustment unit changes the predetermined current range according to a current range of the external power storage unit. A charge / discharge current detection unit for detecting a charge / discharge current of the power storage unit;
The power storage device according to claim 1, further comprising charge / discharge current control means for controlling power conversion in the power conversion unit such that the charge / discharge current becomes a control target value. A self-path current detection unit for detecting a self-path current flowing through the power conversion unit;
6. The apparatus according to claim 5, further comprising second adjusting means for adjusting the control target value so that a detected value of the self-path current falls within a predetermined current range during execution of the charge / discharge current control means. The power storage device described.   The power storage device according to claim 1, further comprising: an information acquisition unit configured to acquire information related to electric power that the DC power source inputs and outputs to and from the first DC bus. A second DC bus connected to the first DC bus;
A second connection unit for electrically connecting an external power storage unit provided outside the power storage device to the second DC bus;
2. The power storage device according to claim 1, further comprising an information acquisition unit configured to acquire information related to power input / output to / from the first DC bus by the DC power source and the external power storage unit. Determination means for determining whether or not power interchange is possible among the power system, the DC power source, and the power storage device based on the information about the power;
The power storage device according to claim 7 or 8, further comprising notification means for notifying the determination result when the determination means determines that power accommodation is impossible. Determination means for determining whether or not power interchange is possible among the power system, the DC power source, and the power storage device based on the information about the power;
8. The apparatus further comprises a limiting unit configured to limit the power that the DC power source inputs and outputs to the first DC bus when it is determined by the determination unit that the interchange of power is impossible. Or the electrical storage apparatus of 8. A DC power source;
A power storage device for transferring power between a power system and the DC power source,
The power storage device
A first DC bus for transmitting DC power;
A first connection for electrically connecting the DC power source to the first DC bus;
A power converter that performs bidirectional power conversion between the first DC bus and the power system;
And a power storage unit that outputs a power supply voltage to the first DC bus.

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