Controller, electricity storage system, and recording medium

A controller in an electricity storage system that includes a first DC/DC converter connected to a storage battery, and a bidirectional inverter connected to the first DC/DC converter. The controller includes a control circuit which changes a content to be displayed by a display, according to whether the electricity storage system is in a predetermined state in which a first PV is connected to the bidirectional inverter via a DC bus.

TECHNICAL FIELD

The present disclosure relates to a controller for controlling an electricity storage system that is connected with a storage battery, an electricity storage system that includes the controller, and a program recording medium.

BACKGROUND ART

Conventionally, there have been storage battery units which are charged with electric power supplied from a system power source, a solar cell module, and the like. For example, Patent Literature (PTL) 1 discloses a power conditioner which is capable of causing a storage battery to be charged with energy generated by a solar cell module, and supplying electric power to a load (electric power load) of electrical equipment.

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

Technical Problem

A storage battery that is connected with an electricity storage system is charged with electric power generated by a solar cell module via a DC/DC converter, for example. The electric power with which the storage battery is charged is converted from direct current (DC) electric power to alternating current (AC) electric power, and then supplied to a load used in a home, for example.

Here, for example, if the solar cell module and the DC/DC converter which the electricity storage system includes are not properly connected, the storage battery that is connected with the electricity storage system will not be charged with electric power generated by the solar cell module. However, when a user of the electricity storage system is to check whether the state of the connection is proper, the installation location of the solar module and the electricity storage system, the wiring, etc. would sometimes make it difficult for the user to check the state of the connection, and thus user convenience was poor.

In view of the above, the present disclosure provides a controller, an electricity storage system, and a recording medium with improved user convenience.

Solutions to Problem

A controller according to an aspect of the present disclosure is a controller in an electricity storage system that includes a first DC/DC converter connected to a storage battery, and a bidirectional inverter connected to the first DC/DC converter, the controller includes: a control circuit which changes a content to be displayed by a display connected with the controller, according to whether the electricity storage system is in a predetermined state in which a solar cell module is connected to the bidirectional inverter via a DC bus.

In addition, an electricity storage system according to an aspect of the present disclosure includes: the controller described above; the first DC/DC converter; the bidirectional inverter; and a second DC/DC converter connected between the solar cell module and the bidirectional inverter.

Furthermore, a recording medium according to an aspect of the present disclosure is a non-transitory computer-readable recording medium in which a program for causing a computer to execute a control method for controlling an electricity storage system that includes a first DC/DC converter connected to a storage battery, and a bidirectional inverter connected to the first DC/DC converter is recorded, the control method includes: changing a content to be displayed by a display, according to whether the electricity storage system is in a predetermined state in which a solar cell module is connected to the bidirectional inverter via a DC bus.

In addition, the present disclosure may be realized by a computer-readable recording medium, such as a CD-ROM, in which a program according to an aspect of the present disclosure is recorded. Furthermore, the present disclosure may be realized as information, data, or a signal which indicates the program. Moreover, the program, the information, the data, and the signal may be distributed via a communication network, such as the Internet.

Advantageous Effect of Invention

A controller and the like according to the present disclosure improve user convenience.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, a controller according to embodiments, an electricity storage system according to the embodiments, and a recording medium according to the embodiments will be described with reference to the drawings. The embodiments described below each show a general or a specific example. The numerical values, shapes, materials, structural elements, the arrangement and the connection of the structural elements, steps, the order of the steps, and the like described in the following embodiments are mere examples, and thus are not intended to limit the present disclosure. Furthermore, among the structural elements in the following embodiments, structural elements not recited in any of the independent claims defining the most generic part of the inventive concept are described as optional structural elements.

Note that the drawings are schematic diagrams and do not necessarily provide strictly accurate illustrations. Throughout the drawings, the same sign is given to substantially the same configuration, and redundant description is omitted or simplified.

Embodiment

[Configuration of Controller and Electricity Storage System]

A controller according to an embodiment and an electricity storage system according to the embodiment will be described with reference toFIG. 1andFIG. 2.

FIG. 1is a block diagram illustrating a system that includes a controller according to an embodiment and an electricity storage system according to the embodiment.

Controller100is a control device that controls electricity storage system200. Specifically, controller100controls first DC/DC converter210, bidirectional inverter220, and second DC/DC converter230which are included in electricity storage system200. Controller100is communicably connected with each of first DC/DC converter210, bidirectional inverter220, and second DC/DC converter230which are included in electricity storage system200. For example, controller100is communicably connected with first DC/DC converter210, bidirectional inverter220, and second DC/DC converter230which are included in electricity storage system200via respective control lines (wiring). In addition, controller100may be communicably connected with each of first DC/DC converter210, bidirectional inverter220, and second DC/DC converter230which are included in electricity storage system200in a wireless manner. In other words, controller100and the other structural elements which are included in electricity storage system200may be individually configured, or integrally configured in one housing. That is, controller100may be the so-called remote controller.

Electricity storage system200is a device for controlling the charge and the discharge of storage battery300. Storage battery300is, for example, a lithium ion battery and a lead storage battery, and is connected with first DC/DC converter210using an electric power line that is a direct current (DC) bus. For example, when storage battery300is charged with electric power from system power source600which is an external commercial power source via distribution switchboard500which is connected with bidirectional inverter220using an electric power line that is an alternating current (AC) bus, controller100controls the direction of electric power conversion performed by bidirectional inverter200. Specifically, controller100converts the alternating current (AC) electric power supplied from system power source600into direct current (DC) electric power, and outputs the DC electric power to first DC/DC converter210. Controller100controls the voltage of the DC electric power using first DC/DC100, and causes storage battery300to be charged with the DC electric power. In addition, when the electric power with which storage battery300is charged is supplied to load520, such as an electric appliance, which is connected with distribution switchboard500, controller100controls bidirectional inverter220to convert the DC electric power supplied from storage battery300to AC electric power, and outputs the AC electric power to system power source600-side.

In addition, in electricity storage system200, there may be a case in which a solar cell module (first photovoltaics (PV)400) is directly connected with second DC/DC converter230. That is, electricity storage system200is a hybrid power conditioner which is connectable with storage battery300and first PV400. Furthermore, in electricity storage system200, there may be a case in which second PV410which is a solar cell module is connected with bidirectional inverter220via power conditioning system (PCS) (power conditioner)510and distribution switchboard500. Controller100controls the charge and the discharge of storage battery300with electric power generated by first PV400and/or second PV410, according to whether first PV400and/or second PV410is connected with electricity storage system200.

Control circuit110controls the charge and the discharge of storage battery300which is connected with electricity storage system200. Control circuit110is realized by, for example, a central processing unit (CPU), and a storage device (not illustrated) in which a control program that the CPU performs is stored. The storage device can be exemplified by read-only memory (ROM), random-access memory (RAM), a hard disk drive (HDD), flash memory, and the like. Note that control circuit110may be realized as hardware by a dedicated electric circuit using a gate array and the like.

Control circuit110changes a content to be displayed by display130which is communicably connected with controller100, according to whether electricity storage system200is in a predetermined state in which first PV400is connected to bidirectional inverter220via a DC bus. Specifically, control circuit110determines whether electricity storage system200is in the predetermined state, and changes a content to be displayed by display130, according to a result of determining whether electricity storage system200is in the predetermined state. InFIG. 1, second DC/DC converter230is connected with first PV400via terminal700. That is, the state of electricity storage system200illustrated inFIG. 1satisfies the predetermined state.

In addition, control circuit110causes display130to display an indication regarding the amount of electric power generated by first PV400. For example, when first PV400generates 1.0 kW of electric power, control circuit110causes display130to display that 1.0 kW of electric power is generated, when electricity storage system200is in the predetermined state.

Here, when electricity storage system200is not in the predetermined state, control circuit110need not cause display130to display the indication regarding the amount of electric power generated by first PV400. Instead, control circuit110may cause display130to display a fixed value as the amount of electric power generated by first PV400. The fixed value is not particularly limited, but, for example, control circuit110causes display130to display 0 as the indication regarding the amount of electric power generated by first PV400.

In addition, when the state of the connection between electricity storage system200and first PV400is set by a user, control circuit110causes display130to display an indication for checking whether the state of connection between second DC/DC converter230and first PV400is normal, when electricity storage system200is in the predetermined state. On the other hand, control circuit110causes display130not to display the indication for the user to check whether the state of the connection between second DC/DC converter230and first PV400is normal, when electricity storage system200is not in the predetermined state.

In addition, when a voltage of at least a reference value is detected in terminal700which connects second DC/DC converter230and first PV400, control circuit110causes display130to display an indication showing that the voltage of at least the reference value is detected, when electricity storage system200is not in the predetermined state.

Terminal700is a terminal for electrically connecting second DC/DC converter230and first PV400.

Note that control circuit110may obtain, from current transformer (CT) sensor530which detects the direction of a current that flows through the AC bus that connects system power source600and distribution switchboard500, a signal indicating whether the current is flowing in the reverse direction, for example. Control circuit110may determine, from the signal, whether the current is flowing in the reverse direction. In this case, control circuit110may control bidirectional inverter220to convert the current from DC to AC or vice versa, according to whether electricity storage system200is in the predetermined state.

Operation unit120is an input device for obtaining an instruction from a user who operates controller100. Operation unit120is to be configured such that the user is capable of operating operation unit120. For example, operation unit120is realized by a button, a touch panel, and the like. Control circuit110determines whether electricity storage system200is in the predetermined state from the operation of operation unit120performed by the user.

Note that controller100may display an image on the display of a personal computer, a smartphone, or the like which the user possesses for the user to operate operation unit120, but may include display130.

Display130is a display device which displays the charging state and the like of storage battery300which is connected with electricity storage system200. Display130is, for example, a display.

Note that the function of operation unit120and the function of display130may be integrally formed using, for example, a touch panel display and the like. That is, the touch panel display may include the function of operation unit120and the function of display130.

FIG. 2is a diagram illustrating an example of an image that controller100according to the embodiment causes display130to display when controller100obtains, from a user, an instruction for indicating the state of connection between electricity storage system200and solar cell modules (first PV400and second PV410).

As illustrated inFIG. 2, control circuit110causes display130to display image131to obtain, from a user, whether first PV400and/or second PV410is connected to electricity storage system200. The user operates operation unit120to input whether electricity storage system200is connected with at least one of the solar cell modules. Control circuit110determines whether electricity storage system200is in the predetermined state, based on information about the state of the connection between first PV400and electricity storage system200which the user inputs.

Communication unit140is a communication interface for obtaining information which an electric power company that provides system power source600transmits. Specifically, communication unit140is a communication interface for receiving a signal which the electric power company transmits in a wired or wireless manner. Control circuit110causes display130to display an image for setting a signal (output control command) to be received via communication unit140, when electricity storage system200is in the predetermined state. The signal indicates an instruction for reducing the amount of electric power that flows in the reverse direction (reverse power flow) into system power source600. On the other hand, control circuit110causes display130not to display the image for setting the output control command to be received via communication unit140, when electricity storage system200is not in the predetermined state.

First DC/DC converter210is connected with storage battery300using a DC bus, and is a DC/DC converter for controlling the voltage of electric power with which storage battery300is charged and discharged.

Bidirectional inverter220is a bidirectional DC/AC inverter which is connected with system power source600, PCS510, load520, and the like via distribution switchboard500using an AC bus. In addition, bidirectional inverter220is connected to storage battery300via first DC/DC converter210using a DC bus, and connected with first PV400via second DC/DC converter230using a DC bus. For example, bidirectional inverter220converts AC electric power which is inputted from distribution switchboard500-side into DC electric power, then outputs the DC electric power to storage battery300-side. Furthermore, bidirectional inverter220converts DC electric power which is inputted from storage battery300-side into AC electric power, then outputs the AC electric power to distribution switchboard500-side, for example.

Second DC/DC converter230is connected with first PV400using a DC bus. Second DC/DC converter230is a DC/DC converter for controlling the voltage of electric power generated by first PV400.

[Control of Electricity Storage System]

Next, the control of display130included in electricity storage system200which control circuit110controls will be described in detail.

<Control of Display in Initialization Phase>

FIG. 3is a flowchart illustrating a procedure which controller100according to the embodiment performs for determining an image to be displayed by display130. Specifically, the flowchart illustrated inFIG. 3is a flowchart for control circuit110to determine an image to be displayed by display130, when a user is to start an operation of electricity storage system200.

First, control circuit110determines, from operation performed by a user, whether electricity storage system200is in the predetermined state in which first PV400is connected to electricity storage system200(step S101). For example, when electricity storage system200is activated, control circuit110causes display130to display image131illustrated inFIG. 2. The connection between electricity storage system200and first PV400is determined to be normal when a voltage of at least a fixed value is applied from first PV400to electricity storage system200. Control circuit110determines, from operation of operation unit120performed by the user, whether electricity storage system200is in the predetermined state.

When control circuit110determines, from operation performed by the user, that electricity storage system200is in the predetermined state in which first PV400is connected to electricity storage system200(specifically, second DC/DC converter230) (YES in step S101), control circuit110checks the state of the connection between electricity storage system200and first PV400(step S102). Control circuit110checks whether second DC/DC converter230and first PV400are electrically connected via terminal700.

Next, control circuit110checks whether the connection between second DC/DC converter230and first PV400is in a normal connection state (step S103). The normal connection state is a state in which electric power generated by first PV400flows to electricity storage system200-side via terminal700.

When control circuit110determines that the connection between second DC/DC converter230and first PV400is in the normal connection state (YES in step S103), control circuit110causes display130to display an image indicating that the connection between electricity storage system200and first PV400is in the normal connection state (step S104).

On the other hand, when control circuit110determines that the connection between second DC/DC converter230and first PV400is not in the normal connection state (NO in step S103), control circuit110causes display130to display an image indicating that the connection between electricity storage system200and first PV400is not in the normal connection state (step S105).

FIG. 4Ais a diagram illustrating an example of an image that controller100according to the embodiment causes display130to display when the state of the connection between electricity storage system200and solar cell module400is normal.

In step S104illustrated inFIG. 3, control circuit110causes display130to display image132which is illustrated inFIG. 4A, for example. Image132provides an indication, such as “PV connection: [OK]”, which can notify the user that electricity storage system200and first PV400are properly connected.

FIG. 4Bis a diagram illustrating an example of an image that controller100according to the embodiment causes display130to display when the state of the connection between electricity storage system200and solar cell module400is not normal.

In step S105illustrated inFIG. 3, control circuit110causes display130to display image133which is illustrated inFIG. 4B, for example. Image133provides an indication, such as “PV is not properly connected”, which can notify the user that electricity storage system200and first PV400are not properly connected.

As such, controller100notifies the user, via display130, whether the state of the connection between electricity storage system200and each of first PV400, storage battery300, system electricity source600, and the like which are connected with electricity storage system200is normal. Note that when second PV410is connected to electricity storage system200, control circuit110may cause display130to display the state of the connection between electricity storage system200and second PV410. In addition, when controller100and a structural element in electricity storage system200other than controller100is communicably connected in a wireless manner, control circuit110may cause display130to display the state of wireless communication between controller100and the structural element.

The following will be described with reference toFIG. 3again. When control circuit110determines, from operation performed by the user, that electricity storage system200is not in the predetermined state in which first PV400is connected to electricity storage system200(NO in step S101), control circuit110causes display130not to display an indication regarding the state of the connection between electricity storage system200and first PV400(step S106). That is, when control circuit110determines that electricity storage system200is not in the predetermined state, control circuit110does not check the state of the connection between electricity storage system200and first PV400. For example, in step S106, control circuit110causes display130not to display the indication regarding the connection between electricity storage system200and first PV400, and may cause display130to display only the state of the connection between electricity storage system200and storage battery300, or between electricity storage system200and system power source600. In addition, for example, when electricity storage system200is not in the predetermined state, control circuit110may change the indication “PV connection: [OK]” as illustrated inFIG. 4Ato an indication “PV connection: [n/a]”.

Next, the control of electricity storage system200on output control which controller100performs will be described.

In recent years, an electric power purchase scheme for an electric power company to purchase electric power (selling of electric power) generated by a solar cell module has been established. When the electric power generated by a solar cell module is sold, a user makes the electric power generated by the solar cell module to flow in the reverse direction to a system power source-side.

For example, when electricity storage system200is to function as a photovoltaic power generation system, “surplus electric power” from which electric power consumed by load520is deducted from the total electric power generated is caused to flow in the reverse direction to the system electricity source-side to be sold.

Here, the electric power company transmits, to each of photovoltaic power generation systems, an output control command for limiting the amount of electric power that flows in the reverse direction to the system power source-side using communication networks, such as the Internet, when the supply of electric power greatly exceeds demand, for example. The output control command is a signal indicating an instruction for reducing the amount of electric power that flows in the reverse direction into the system power source. In order to receive the output control command that the electric power company issues, each photovoltaic power generation system has to be connected to the electric power company via a network. For this reason, each photovoltaic power generation system needs to set up a network connection, such as setting the URL of a server of the electric power company, using a setting screen at the time of starting the operation.

FIG. 5is a flowchart illustrating an example of a procedure which controller100according to the embodiment causes display130to display an icon for setting reception of an output control command.

First, control circuit110determines, from operation performed by a user, that electricity storage system200is in the predetermined state in which first PV400is connected to electricity storage system200(step S201). For example, control circuit110causes display130to display image131illustrated inFIG. 2, when electricity storage system200is activated. Control circuit110determines, from operation of operation unit120performed by the user, whether electricity storage system200is in the predetermined state.

When control circuit110determines, from operation performed by the user, that electricity storage system200is in the predetermined state in which first PV400is connected to electricity storage system200(YES in step S201), control circuit110enables the display of an icon for activating a setting screen for the reception of an output control command (step S202). By selecting the icon for activating the setting screen at the time of starting the operation, the setting screen can be activated for setting the reception of an output control command.

On the other hand, when control circuit110determines, from operation performed by the user, that electricity storage system200is not in the predetermined state in which first PV400is connected to electricity storage system200(NO in step S201), control circuit110disables the display of the icon for activating the setting screen for the reception of an output control command (step S203). Since the icon for activating the setting screen is not displayed, and thus the icon cannot be selected at the time of starting the operation, the setting screen cannot be activated for setting the reception of an output control command.

Accordingly, controller100determines whether the reception of an output control command is needed, according to whether electricity storage system200is in the predetermined state, and causes display130to change an image that display130is caused to display, based on the result of the determination, to clarify whether the setting of the reception at the time of starting the operation is necessary.

<Control of Display in Operation Phase>

FIG. 6is a diagram illustrating an example of an image that indicates the amount of electric power generated by first PV400which controller100causes display130to display. Specifically,FIG. 6illustrates an example of an image that control circuit110causes display130to display when a user is using electricity storage system200. Note thatFIG. 6illustrates an example of an image in the case in which electricity storage system200is not in the predetermined state.

As illustrated inFIG. 6, control circuit110causes display130to display image134when the user is using electricity storage system200. For example, image134indicates the amount of electric power stored (remaining amount) in storage battery300which is connected with electricity storage system200. In addition, image134indicates the state of storage battery300whether storage battery300is charging or discharging.

In addition, image134indicates whether first PV400which is connected to electricity storage system200is generating electric power. For example, when first PV400is generating electric power, the amount of electric power which first PV400is generating will be indicated in electric power amount indicator135.

Here, when electricity storage system200and first PV400are not connected (that is, when electricity storage system200is not in the predetermined state), electric power amount indicator135need not indicate the amount of electric power which first PV400generates. Instead, electric power amount indicator135may indicate a fixed value. In other words, when control circuit110determines that electricity storage system200is not in the predetermined state, control circuit110may cause display130to display the fixed value as an indication to be indicated in electric power amount indicator135. For example, control circuit110causes 0.0 kW to be displayed as the indication to be indicated in electric power amount indicator135. Note that when electricity storage system200and first PV400are not connected, PV indicator136that indicates an indication regarding photovoltaic power generation may not be displayed.

Next, control which control circuit110performs on display130when an anomaly is detected in terminal700will be described.

FIG. 7is a block diagram illustrating a case in which electricity storage system200according to the embodiment is not in the predetermined state.

Unlike electricity storage system200illustrated inFIG. 1, first PV400and second DC/DC converter230are not connected via terminal700in electricity storage system200illustrated inFIG. 7. That is, electricity storage system200illustrated inFIG. 7is not in the predetermined state. In such a case, since first PV400is not connected to terminal700, a voltage is not normally applied to terminal700. However, for example, if wiling connected with storage battery300is accidentally connected to terminal700, a voltage is applied to terminal700. When an unexpected voltage is applied to terminal700as described, the unexpected voltage may become a cause of failure of electricity storage system200, for example. When an abnormal voltage in terminal700of at least a reference value is detected, control circuit110causes display130to display that the abnormal voltage of at least the reference value is detected, when electricity storage system200is not in the predetermined state.

FIG. 8is a flowchart illustrating an example of a procedure which controller100performs for controlling display130when a voltage of at least a reference value is detected in terminal700included in electricity storage system200according to the embodiment, when electricity storage system200is not in the predetermined state.

First, control circuit110determines, from operation performed by a user, whether electricity storage system200is in the predetermined state in which first PV400is connected to electricity storage system200(step S301). For example, control circuit110causes display130to display image131illustrated inFIG. 2, when electricity storage system200is activated. Control circuit110determines whether electricity storage system200is in the predetermined state by operation of operation unit120performed by the user.

When control circuit110determines, from operation performed by the user, that electricity storage system200is not in the predetermined state in which first PV400is connected to electricity storage system200(NO in step S301), control circuit110determines whether a voltage of at least a reference value is detected in terminal700(step S302).

Control circuit110continues to detect the voltage, when control circuit110determines that the voltage of at least the reference value is not detected in terminal700(NO is step S302).

On the other hand, when control circuit110determines that the voltage of at least the reference value is detected in terminal700(YES in step S302), control circuit110causes display130to display an image indicating that the voltage of at least the reference value is detected in terminal700(step S303).

Note that a reference value of a voltage that control circuit110determines as abnormal when the voltage is applied to terminal700is not particularly limited, when electricity storage system200is not in the predetermined state. The reference value of the voltage is to be optionally predetermined.

As has been described above, controller100according to the embodiment is a controller in electricity storage system200which includes first DC/DC converter210connected to storage battery300, and bidirectional inverter220connected to first DC/DC converter210. Controller100includes control circuit110which changes a content to be displayed by display130connected with controller100, according to whether electricity storage system200is in a predetermined state in which first PV400is connected to bidirectional inverter220via a DC bus.

With the configuration described above, control circuit110can readily notify a user of the state of the connection between bidirectional inverter220and first PV400via a DC bus by changing, according to the state of the connection, an image which control circuit110causes display130which is connected with controller100to display. Accordingly, it is possible for controller100to improve user convenience.

In addition, for example, display130may be a display included in a personal computer, a smartphone, or the like which the user possesses, but controller100may further include display130.

With the configuration described above, even when the user does not possess the display, control circuit110can readily notify the user of the state of the connection between electricity storage system200and first PV400by changing, according to the state of the connection, an image which control circuit110causes display130to display. Accordingly, it is possible for controller100to improve user convenience.

In addition, control circuit110may cause display130to display the amount of electric power generated by first PV400as an indication regarding the amount of the electric power generated by first PV400, when electricity storage system200is in the predetermined state. Furthermore, control circuit110may cause display130to display a fixed value as the indication regarding the amount of the electric power generated by first PV400, when electricity storage system200is not in the predetermined state.

With the configuration described above, even when the amount of electric power consumed by load520suddenly changes, it is possible to prevent control circuit100from controlling display130to display a value other than 0 as the amount of electric power generated due to a measurement error, although first PV400is not connected to electricity storage system200, for example.

In addition, control circuit110may cause display130to display an indication for checking whether a state of connection between first PV400and second DC/DC converter230that is connected between first PV400and bidirectional inverter220is normal, when electricity storage system200is in the predetermined state. Furthermore, control circuit110need not cause display130to display the indication for checking whether the state of the connection between first PV400and second DC/DC converter230is normal, when electricity storage system200is not in the predetermined state.

With this configuration described above, the user can readily check whether the state of the connection between electricity storage system200and first PV400is appropriate.

In addition, controller100may further include communication unit140. Control circuit110may cause display130to display an image for setting a signal to be received via communication unit140, when electricity storage system200is in the predetermined state. The signal indicates an instruction for reducing the amount of electric power that flows in a reverse direction into system power source600. Furthermore, control circuit110need not cause display130to display the image for setting the signal to be received via communication unit140, when electricity storage system200is not in the predetermined state.

With this configuration described above, the user would not have to perform unnecessary setting when setting for controlling the charge and the discharge of electricity storage system200. Accordingly, it is possible for controller100to further improve user convenience.

In addition, when a voltage of at least a reference value is detected in terminal700which connects second DC/DC converter230and first PV400, control circuit110causes display130to display an indication showing that the voltage of at least the reference value is detected, when electricity storage system200is not in the predetermined state.

With this configuration described above, it is possible for the user to readily check that an unexpected voltage is applied to terminal700. For example, when the voltage of at least the reference value is detected in terminal700, the user can immediately check whether there is any anomaly in terminal700. Accordingly, it is possible for controller100to further improve user convenience.

In addition, electricity storage system200according to an aspect of the present disclosure includes controller100, first DC/DC converter210, bidirectional inverter220, and second DC/DC converter230connected between first PV400and bidirectional inverter220.

With the configuration described above, electricity storage system200can readily notify the user whether the state of the connection between electricity storage system200and first PV400is appropriate, by changing an image which display130which is connected with electricity storage system200is caused to display, for example. Accordingly, it is possible for electricity storage system200to improve user convenience.

In addition, a recording medium according to an aspect of the present disclosure is a non-transitory computer-readable recording medium in which a program for causing a computer to execute a control method for controlling electricity storage system200that includes first DC/DC converter210connected to storage battery300, and bidirectional inverter230connected to first DC/DC converter210is recorded. The recording medium according to an aspect of the present disclosure is the non-transitory computer-readable recording medium in which the program for causing the computer to execute the control method that changes a content to be displayed by display130, according to whether electricity storage system200is in a predetermined state in which first PV400is connected to bidirectional inverter220via a DC bus.

With the configuration described above, it is possible to realize a program which can change an image to be displayed by display130, according to the state of the connection between electricity storage system200and first PV400. Accordingly, it is possible for a computer, such as controller100, which executes the program to improve user convenience.

Other Embodiment

The above has described the controller according to the embodiment, the electricity storage system according to the embodiment, and the program according to the embodiment, yet the present disclosure is not limited to the above embodiment.

For example, electricity storage system200need not include second DC/DC converter230. In this case, control circuit110determines that electricity storage system200is in the predetermined state when second DC/DC converter230and first PV400are connected to electricity storage system200.

The present disclosure also encompasses: embodiments achieved by applying various modifications conceivable to those skilled in the art to each embodiment; and embodiments achieved by optionally combining the structural elements and the functions of each embodiment without departing from the scope of the present disclosure.