Energy storage system and control method

Abstract

This invention provides an energy storage system and control method that can control charging and discharging in a way that maximizes economic efficiency, in accordance with the electricity rate plans of power companies. [Solution] The energy storage system includes a battery and a control unit that controls the charging and discharging of the battery. The control unit discharges the battery during the discharge period of the day and charges the battery with grid power during the charging period of the day. The discharge period includes the maximum unit price period in an electricity rate plan where the unit price of electricity is set for each period of the day, and the charging period includes the minimum unit price period in an electricity rate plan where the unit price is set to the minimum, with the minimum unit price period being daytime.

Description

Technical Field

[0001] The present disclosure relates to a power storage system and a control method.

Background Art

[0002] The following Patent Document 1 discloses a power storage system that can efficiently utilize a storage battery when multi-stage electricity rates are set for each time zone. This power storage system predicts the transition of the power consumption amount of a load, generates a remaining amount value function at time t based on the predicted transition and the electricity rates for each time zone, and calculates the value when charging based on the remaining amount of the storage battery. If the value when charging is higher than the electricity rate in the current time zone, charging is performed; if it is lower, discharging is performed; and if they are equal, charging and discharging are not performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, with the spread of solar power generation systems, the amount of electricity sold to power companies has increased, leading to an increase in the daytime electricity supply. If power companies implement output curtailment to maintain the balance of electricity supply and demand, the electricity generated by solar power generation systems will be wasted due to the curtailment. Since energy storage systems can function as a means of adjusting electricity supply and demand, it is expected that output curtailment can be avoided by effectively utilizing energy storage systems. On the other hand, for users who have installed energy storage systems, it is preferable that the energy storage system is controlled in a way that increases economic benefits (reduces the amount of electricity bill paid). However, in Patent Document 1, complex calculations are required to control the charging and discharging of the storage battery, and depending on the electricity rate plan provided by the power company (hereinafter also simply referred to as the rate plan), the economic benefits for users who have installed energy storage systems may not increase (the amount of electricity bill paid may not decrease).

[0005] Therefore, this disclosure aims to provide an energy storage system and control method that can control charging and discharging in a way that maximizes economic efficiency in accordance with the electricity rate plans of power companies. [Means for solving the problem]

[0006] A certain aspect of the present disclosure relates to an energy storage system which includes a battery and a control unit which controls the charging and discharging of the battery, wherein the control unit discharges the battery during the discharge period of the day and charges the battery with grid power during the charging period of the day, the discharge period which includes the maximum unit price period in an electricity rate plan in which the unit price of electricity is set for each period of the day, and the charging period which includes the minimum unit price period in an electricity rate plan in which the unit price is set lowest, the minimum unit price period which is included in the daytime. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide an energy storage system and control method that can control charging and discharging in a way that maximizes economic efficiency in accordance with the electricity rate plans of power companies. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a block diagram showing the configuration of an energy storage system according to an embodiment of this disclosure. [Figure 2] Figure 2 is a flowchart showing the operation of determining the charge and discharge schedule by the energy storage system shown in Figure 1. [Figure 3] Figure 3 shows the screen for selecting a pricing plan. [Figure 4] Figure 4 is a table showing the pricing plans. [Figure 5] Figure 5 is a graph showing an example of a pricing plan. [Figure 6] Figure 6 is a graph showing an example of a pricing plan different from that shown in Figure 5. [Figure 7] Figure 7 is a flowchart showing the charging and discharging operation of the energy storage system shown in Figure 1. [Figure 8] Figure 8 is a graph showing the control based on the charge / discharge schedule determined according to the pricing plan shown in Figure 5. [Figure 9] Figure 9 is a graph showing the control based on the charge / discharge schedule determined according to the pricing plan shown in Figure 6. [Figure 10] Figure 10 is a flowchart showing the operation of determining the charge and discharge schedule by the modified energy storage system. [Figure 11] Figure 11 shows a screen for entering information regarding electricity charges. [Modes for carrying out the invention]

[0009] [Description of Embodiments in this Disclosure] The embodiments of this disclosure are listed and described below. At least some of the embodiments described below may be combined in any way.

[0010] (1) The energy storage system relating to the first aspect of this disclosure includes a battery and a control unit that controls the charging and discharging of the battery, wherein the control unit discharges the battery during the discharge period of the day and charges the battery with grid power during the charging period of the day, the discharge period includes the maximum unit price period in an electricity rate plan where the unit price of electricity is set for each period of the day, and the charging period includes the minimum unit price period in an electricity rate plan where the unit price is set for the lowest unit price, the minimum unit price period is included in the daytime. This makes it possible to reduce the cost of using grid power in buildings such as houses where the energy storage system is installed, in line with the electricity rate plan of the power company, thereby increasing the economic effect. In addition, during the daytime when the amount of grid power supply increases due to the sale of electricity generated by solar power generation systems, the battery will be charged with grid power, which will increase daytime electricity consumption and contribute to maintaining the balance of power supply and demand in the grid.Therefore, it is possible to avoid the implementation of output curtailment by power companies.

[0011] (2) In (1) above, the electricity rate plan may include a period of time with a higher unit price than a predetermined value, which is different from the period of time with the highest unit price, and the control unit may set the period of time with a higher unit price as the discharge period, and the predetermined value may be greater than the minimum unit price and less than the maximum unit price. This makes it possible to extend the discharge time of the storage battery and further reduce the cost of using grid electricity.

[0012] (3) In (1) or (2) above, the control unit may charge the battery so that it is fully charged at the end of the charging period. This reduces the time the battery remains in a fully charged state and suppresses power loss.

[0013] (4) In any one of (1) to (3) above, the control unit may put the battery into a standby state until the end of the charging period after the battery has reached a fully charged state through charging during the charging period. This makes it easy to set the start time of charging during the charging period.

[0014] (5) In any one of (1) to (4) above, the power storage system may further include a display unit and an operation unit. The display unit may display a plurality of electricity rate plans for each power company. The control unit may, upon receiving that one electricity rate plan has been selected from the plurality of electricity rate plans by the operation unit, identify the maximum unit price time zone and the minimum unit price time zone in the electricity rate plan. Thereby, the user can easily set the contracted rate plan in the power storage system.

[0015] (6) In any one of (1) to (4) above, the power storage system may further include an operation unit. The control unit may obtain, via the operation unit, information specifying a time zone and a unit price corresponding to the time zone as an electricity rate plan. Thereby, the power storage system can accurately set the rate plan.

[0016] (7) In any one of (1) to (4) above, the power storage system may further include an operation unit. The minimum unit price time zone and the maximum unit price time zone may be set as the charging time zone and the discharging time zone, respectively, by the operation unit. Thereby, the user can set the charging time zone and the discharging time zone so that the usage fee of the grid power is reduced in accordance with the electricity rate plan.

[0017] (8) In any one of (1) to (7) above, the electricity rate plan may include a plurality of maximum unit price time zones. The control unit may further charge the storage battery with grid power in a time zone having the same end time as the end time of a period between adjacent maximum unit price time zones and not including the minimum unit price time zone. Thereby, it is possible to avoid the situation where the storage battery cannot be discharged during the maximum unit price time zone because the storage battery is fully charged before the maximum unit price time zone. Therefore, the usage fee of the grid power can be further reduced and the economic effect can be higher.

[0018] (9) In any one of (1) to (8) above, the energy storage system may further include a power conversion unit that generates a DC voltage for charging the battery from grid power, and the charging power for charging the battery may be determined such that the power loss of the power conversion unit is minimized during the continuous period from the start of charging the battery until the battery is fully charged. This makes it possible to efficiently reduce the cost of using grid power and increases the economic effect.

[0019] (10) In any one of (1) to (9) above, the control unit may calculate the cumulative discharge power by accumulating the discharge power of the storage battery over a day, or may stop the discharge of the storage battery when the cumulative discharge power exceeds the upper limit discharge power, and the upper limit discharge power may be calculated based on the warranty period of the energy storage system and the maximum charging capacity of the storage battery. This makes it possible to reduce the cost of using grid electricity over the entire warranty period and increases the economic effect.

[0020] (11) The control method relating to the second aspect of this disclosure is a control method for an energy storage system having a battery, comprising the steps of discharging the battery during a discharge period of the day and charging the battery with grid power during a charging period of the day, wherein the discharge period includes the maximum unit price period in an electricity rate plan where the unit price of electricity is set for each period of the day, and the charging period includes the minimum unit price period in an electricity rate plan where the unit price is set to the minimum, with the minimum unit price period being daytime. This makes it possible to reduce the cost of using grid power in buildings such as houses where the energy storage system is installed, in line with the electricity rate plan of the power company, thereby increasing the economic effect. In addition, during the daytime when the amount of grid power supply increases due to the sale of electricity generated by solar power generation systems, the battery will be charged with grid power, which will increase daytime electricity consumption and contribute to maintaining the balance of power supply and demand in the grid. Therefore, it is possible to avoid the implementation of output curtailment by power companies.

[0021] [Details of the embodiments of this disclosure] In the following embodiments, identical parts are assigned the same reference numeral. Their names and functions are also identical. Therefore, detailed descriptions of them will not be repeated.

[0022] (System Configuration) Referring to Figure 1, the energy storage system 100 according to the embodiment of this disclosure includes a battery 102, a DC / AC converter 104, a control unit 106, and a timer 108. The energy storage system 100 is installed in a house or the like. The energy storage system 100 is connected to a grid 190.

[0023] The storage battery 102 is a rechargeable battery such as a lithium-ion secondary battery. The storage battery 102 functions as a DC power source. The DC power output from the storage battery 102 is converted to AC power by the DC / AC converter 104 and supplied to loads 192 such as household appliances located indoors.

[0024] The DC / AC converter 104 is connected to the grid 190 and receives power from the grid 190. The DC / AC converter 104 is capable of bidirectional power conversion, converting the AC power supplied from the grid 190 into DC power to charge the battery 102. The energy storage system 100 may also be interconnected with the grid 190.

[0025] The control unit 106 includes, for example, a CPU (Central Processing Unit) and memory (neither of which are shown). The functions of the control unit 106 are realized by the CPU reading and executing a program stored in memory. The control unit 106 controls the DC / AC converter 104. The control unit 106 controls the power conversion function, i.e., the input and output voltages and currents, by outputting control signals for the switching elements that make up the DC / AC converter 104. The control unit 106 monitors the power supply status (purchased power) from the grid 190 using a current sensor (not shown) or the like. The control unit 106 obtains the State of Charge (SOC) representing the remaining battery charge of the battery 102 from the battery 102, and controls the DC / AC converter 104 according to the SOC to supply the discharge power of the battery 102 to the load 192. The timer 108 receives a request from the control unit 106 and outputs information representing the current time (hereinafter simply referred to as the current time) to the control unit 106.

[0026] The energy storage system 100 is connected to a remote control 120 and a communication device 122 located indoors. The remote control 120 includes a display unit, an operating unit, a CPU, and memory (none of which are shown). The functions of the remote control 120 are realized by the CPU reading and executing a program stored in memory. The remote control 120 is connected to the control unit 106 and exchanges information with the control unit 106. The display unit and operating unit of the remote control 120 may be, for example, an integrated device in which a touch panel is superimposed on a liquid crystal panel. The communication device 122 communicates with external devices via a network 194 such as the Internet, upon receiving instructions from the control unit 106.

[0027] Figure 1 shows a server 130, which is a computer configured for a power company or similar entity. The server 130 receives requests from external sources (such as a battery storage system 100) via the network 194 and transmits information regarding electricity charges (such as information regarding rate plans).

[0028] (Operation of the energy storage system) (Determining the charge / discharge schedule) Referring to Figure 2, the operation of determining the charge and discharge schedule by the energy storage system 100 will be explained. The process shown in Figure 2 is started, for example, when the CPU inside the control unit 106 receives a notification from the remote control 120, reads a program stored in the memory inside the control unit 106, and executes it. When the remote control 120 detects an operation by the user to set an electricity rate plan, it notifies the control unit 106 of this. As will be described later, the control unit 106 executes a program for controlling the charging and discharging of the battery 102 (hereinafter referred to as the charge and discharge control program) in parallel with this program.

[0029] In step 200, the control unit 106 causes the remote control 120 to display a screen for selecting a power company and rate plan. After that, control proceeds to step 202. For example, the control unit 106 sends a screen display instruction to the remote control 120, and the remote control 120, upon receiving the instruction, reads image data from its internal memory and displays a screen as shown in Figure 3. The screen 300 displays a list of multiple power company names. When the remote control 120 detects an operation on the displayed screen, it changes the screen according to that operation. For example, when the scroll bar 302 is operated, the remote control 120 scrolls the list display, erases some of the displayed power company names, and displays new power company names. When the user selects one of the power company names displayed in the list, the remote control 120 displays the selected power company name in a way that indicates it has been selected (for example, by inverting the brightness or changing the color), and displays the rate plan name offered by the selected power company in the display area 304. When one of the displayed rate plans is selected and the confirmation button 306 is pressed, the remote control 120 transmits information identifying the selected rate plan to the control unit 106. The name of the power company and the name of the rate plan for each power company may be stored in the internal memory of the remote control 120 as text data beforehand. The control unit 106 may also transmit the name of the power company and the name of the rate plan for each power company (text data) to the remote control 120 along with the instructions for the screen display.

[0030] In step 202, the control unit 106 determines whether a rate plan has been determined. If it is determined that a rate plan has been determined, control proceeds to step 204. Otherwise, step 202 is repeated. Specifically, the control unit 106 determines that a rate plan has been determined when it receives information identifying the rate plan from the remote control 120. The control unit 106 receives text data from the remote control 120, for example, representing the name of the power company and the rate plan name.

[0031] In step 204, the control unit 106 obtains information regarding the rate plan determined in step 202. The control then proceeds to step 206. For example, the control unit 106 controls the communication device 122 to obtain rate plan information from the server 130 via the network 194. The control unit 106 obtains information such as that shown in Figure 4. In Figure 4, T1 to T5 represent information for distinguishing time zones. The start and end times represent the earliest and last times in each time zone, respectively. The unit price represents the usage fee (electricity charge) per kWh of grid power in each time zone. That is, a "time zone" means a continuous period with two different start and end times, where the same unit price is set. In Figure 4, if y1=y5, the time zone T5 on the current day and the time zone T1 on the following day may be treated as one time zone. The control unit 106 may also access each power company in advance to obtain information on each rate plan and store it in its internal memory. In that case, the control unit 106 can use the name of the power company and the rate plan name received from the remote control 120 to search its internal memory and identify the information for the corresponding rate plan.

[0032] In step 206, the control unit 106 determines the time period with the lowest unit price (hereinafter referred to as the minimum unit price time period) as the charging time period based on the pricing plan information obtained in step 204. After that, the control proceeds to step 208. In the case of the pricing plan shown in Figure 4, the minimum value (minimum unit price) among y1 to y5 is identified, and the time period corresponding to it is identified. For example, if y3 is the minimum value, time period T3 is determined as the charging time period. If there are multiple minimum unit prices, each minimum unit price time period is determined as a charging time period. For example, in Figure 4, if y3 and y5 are both the minimum values, time periods T3 and T5 are determined as charging time periods.

[0033] In step 208, the control unit 106 determines from the rate plan information obtained in step 204 whether there are multiple time periods with the highest unit price (hereinafter referred to as the "maximum unit price time period"). If it is determined that there are multiple, the control proceeds to step 210. Otherwise (there is only one maximum unit price time period), the control proceeds to step 212.

[0034] In step 210, the control unit 106 determines, based on the rate plan information obtained in step 204, that the period between adjacent maximum rate time zones, which does not include the minimum rate time zone, has the same end date as the period between adjacent maximum rate time zones, and is designated as the charging time zone. The control then proceeds to step 212. This determines that the time zone immediately preceding a specific maximum rate time zone is designated as the charging time zone. The immediately preceding time zone refers to the time zone that is adjacent to the maximum rate time zone and precedes the maximum rate time zone. Multiple time zones may be included between two adjacent maximum rate time zones. Of these time zones, the time zone immediately preceding the maximum rate time zone is designated as the charging time zone. However, if the minimum rate time zone is included between adjacent maximum rate time zones, the time zone immediately preceding the maximum rate time zone is not designated as the charging time zone. Since the minimum rate time zone is designated as the charging time zone and the battery 102 is fully charged, there is no need to charge the battery 102 during other time zones included between adjacent maximum rate time zones.

[0035] In step 212, the control unit 106 determines the charging start time and stores it in internal memory. Then, the control proceeds to step 214. The control unit 106 determines the charging start time by subtracting a predetermined charging time from the end of each charging time period determined in steps 206 and 210. The charging time can be predetermined. For example, the charging power of the battery 102 can be set to a predetermined value, and the time required to fully charge the battery 102 from a state of charge (SOC) of the battery 102 that is at its lower limit (a predetermined value greater than 0) can be determined as the charging time. The battery 102 can be fully charged at the end of the charging time period or just before it. If the SOC of the battery 102 is not at the lower limit when charging of the battery 102 begins, the battery 102 will be fully charged in a shorter time than the charging time, and then enter a standby state. Standby state means a state in which neither charging nor discharging of the battery 102 is performed. Even in the standby state, the SOC of the battery 102 decreases. The shorter the period during which the battery 102 is in standby mode, the more power loss can be suppressed.

[0036] In step 214, the control unit 106 determines the discharge start time and discharge end time and stores them in its internal memory. Then, the control proceeds to step 216. Specifically, the control unit 106 determines the maximum unit price time period as the discharge time period from the price plan information obtained in step 204, and determines its start and end times as the discharge start time and discharge end time, respectively.

[0037] In step 216, the control unit 106 modifies the current charge / discharge schedule using the charge start time, discharge start time, and discharge end time determined in steps 212 and 214, notifies the charge / discharge control program (described later) of the modification, and then terminates this program.

[0038] For example, suppose the pricing plan identified in step 204 is as shown in Figure 5. In Figure 5, the horizontal axis represents the time of day (i.e., from 0:00 to 24:00 (0:00 the next day)), and the vertical axis represents the unit price of electricity. In the pricing plan shown in Figure 5, the time period with the lowest unit price is time period T3 (10:00 to 16:00), and the time periods with the highest unit price are time period T2 (8:00 to 10:00) and time period T4 (16:00 to 18:00). Time periods T1 (0:00 to 8:00) and T5 (18:00 to 24:00) are time periods where the unit price is between the maximum and minimum unit prices. Time period T3 is determined as the charging time period by step 206 shown in Figure 2. Time period T1, which is immediately preceding the time period T2 with the highest unit price, is determined as the charging time period by step 210. In the pricing plan shown in Figure 5, there are two periods between two adjacent highest-priced time zones (time zone T2 and time zone T4). One period is formed by time zone T3, and the other is formed by time zones T5 and T1. Time zone T3 has already been determined as a charging time zone. Since the period formed by time zones T5 and T1 does not include a lowest-priced time zone, time zone T1, which is immediately preceding time zone T2, is determined as a charging time zone.

[0039] In step 212 described above, 4 hours are subtracted from 16:00, the end of time zone T3 (charging time zone), to determine 12:00 as the charging start time Cs1. Similarly, 4 hours are subtracted from 8:00, the end of time zone T1 (charging time zone), to determine 4:00 as the charging start time Cs2. In step 214, the start and end times of time zones T2 and T4, which are the highest-priced time zones, are determined as the discharge start time and discharge end time, respectively. That is, the start time (8:00) and end time (10:00) of time zone T2 are determined as the discharge start time Ds1 and discharge end time De1, respectively. Also, the start time (16:00) and end time (18:00) of time zone T4 are determined as the discharge start time Ds2 and discharge end time De2, respectively. This determines a new charge / discharge schedule for controlling the battery 102.

[0040] Let's further explain using a different pricing plan than Figure 5. Referring to Figure 6, this pricing plan divides the day into six time zones (time zones T1 to T6). The pricing plan in Figure 6 is the same as the pricing plan shown in Figure 5, but with the start and end times of time zone T4 delayed by two hours, and the period during which the original time zone T4 existed is designated as time zone T6 with the same unit price as time zones T1 and T5. The process shown in Figure 2 is executed for this pricing plan. In step 206, time zone T3 is determined as the charging time zone. In step 210, as in Figure 5, time zone T1 is determined as the charging time zone. However, time zone T6, which is immediately preceding time zone T4, the highest-priced time zone, is not determined as the charging time zone. Of the period between two adjacent highest-priced time zones (time zones T2 and T4), the period formed by time zones T3 and T6 includes time zone 3, which has the lowest unit price, so time zone T6 is not set as the charging time zone.

[0041] Step 212, described above, determines the charging start times Cs1 and Cs2. Step 214 determines the start time (8am) and end time (10am) of time period T2 as the discharge start time Ds1 and discharge end time De1, respectively, and the start time (6pm) and end time (8pm) of time period T4 as the discharge start time Ds2 and discharge end time De2, respectively. This determines a new charge-discharge schedule for controlling the battery 102.

[0042] (Charge / Discharge Control) Referring to Figure 7, the operation of the energy storage system 100 in controlling the charging and discharging of the battery 102 will be explained. The process shown in Figure 7 is started when the CPU inside the control unit 106 reads and executes a program (charging and discharging control program) stored in the memory inside the control unit 106. Information necessary for controlling the charging and discharging of the battery 102, such as the initial charging and discharging schedule and charging power, is assumed to be stored in the memory inside the control unit 106 in advance.

[0043] In step 400, the control unit 106 determines whether the charge / discharge schedule has been updated. Specifically, the control unit 106 determines whether it has received the notification in step 216 shown in Figure 2, and if it has received it, it determines that the schedule has been updated. If it is determined that the schedule has been updated, the control proceeds to step 402. Otherwise, the control proceeds to step 404.

[0044] In step 402, the control unit 106 obtains the updated charge / discharge schedule. Specifically, the control unit 106 identifies the charge start time, discharge start time, and discharge end time determined in steps 212 and 214 of Figure 2. The control then proceeds to step 404. For the rate plan shown in Figure 5, the charge start times Cs1 and Cs2, a pair of discharge start times Ds1 and discharge end times De1, and a pair of discharge start times Ds2 and discharge end times De2 are identified and used in subsequent processing.

[0045] In step 404, the control unit 106 obtains the current time from the timer 108 and determines whether the charging start time has elapsed. If it is determined that the time has elapsed, the control proceeds to step 406. Otherwise, the control proceeds to step 412. For the rate plan shown in Figure 5, the control unit 106 determines whether either the charging start time Cs1 or the charging start time Cs2 has elapsed.

[0046] In step 406, the control unit 106 performs charging of the battery 102. The charging power used is a value stored in the internal memory of the control unit 106. After that, the control proceeds to step 408.

[0047] In step 408, the control unit 106 obtains the State of Charge (SOC) from the battery 102 and determines whether the battery 102 is fully charged. If it is determined that the battery is fully charged, the control proceeds to step 412. Otherwise, the control proceeds to step 410.

[0048] In step 410, the control unit 106 obtains the current time from the timer 108 and determines whether the current time falls within the discharge period. Specifically, the control unit 106 determines whether the current time falls within the period defined by a pair of discharge start and end times. If it is determined that the battery is within the discharge period, the control proceeds to step 414. Otherwise, the control returns to step 406. This maintains the charging process described in step 406 until the battery 102 is fully charged. As described above, the charging power of the battery 102 is set to be fully charged during the charging period. However, it is possible that the discharge period, which is the period with the highest unit price, may occur before the battery 102 is fully charged. Step 410 is provided to ensure that the battery 102 is not charged by grid power with the highest unit price.

[0049] In step 412, the control unit 106 obtains the current time from the timer 108, similar to step 410, and determines whether the current time falls within the discharge period. If it is determined that the discharge period is in effect, the control proceeds to step 414. Otherwise, the control proceeds to step 418.

[0050] In step 414, the control unit 106 discharges the battery 102. That is, the control unit 106 discharges the battery 102 in accordance with the power consumption of the load 192. After that, the control proceeds to step 416.

[0051] In step 416, the control unit 106 obtains the State of Charge (SOC) from the battery 102 and determines whether the SOC is below the lower limit of discharge. If it is determined to be below the lower limit, the control proceeds to step 418. Otherwise, the control returns to step 412. As a result, the battery 102 is discharged by step 414 until the discharge time period has passed or the SOC is below the lower limit of discharge.

[0052] In step 418, the control unit 106 stops discharging the battery 102. The control then proceeds to step 420.

[0053] In step 420, the control unit 106 determines whether or not it has received a termination instruction. If it determines that it has received a termination instruction, it terminates the program. Otherwise, control returns to step 400, and the above-described process is executed. The termination instruction is given, for example, by operating the remote control 120.

[0054] As described above, the control unit 106 can control the charging and discharging of the battery 102 according to a predetermined charge and discharge schedule. If the rate plan is changed and the program shown in Figure 2 is executed, changing the charge and discharge schedule, the control unit 106 can control the charging and discharging of the battery 102 according to the changed charge and discharge schedule in step 402.

[0055] Figure 8 shows the change in the State of Charge (SOC) of the battery 102 due to the charge / discharge control described above, under the pricing plan shown in Figure 5. In Figure 8, a solid line graph representing the change in SOC (see the vertical axis on the right) is shown below the graph representing the pricing plan. MAX represents the maximum value of SOC (corresponding to a full charge), and MIN represents the lower limit of SOC. The SOC graph shows the change from point P1, which represents the state in which the battery 102 is fully charged, to just before 8:00 the next day. Discharge is performed from point P1 (discharge start time Ds1 (8:00)) to time period T2 (discharge time period with the highest unit price), and the SOC of the battery 102 decreases. Discharge stops at discharge end time De1 (10:00), and the battery 102 enters a standby state. In the standby state, the SOC is maintained at a value greater than the lower limit MIN. At the charging start time Cs1 (12:00), charging of battery 102 is performed using grid power with the lowest unit price, and the SOC reaches MAX before the discharge start time Ds2 (16:00), and battery 102 is fully charged. Discharge is performed during time period T4 (discharge time period with the highest unit price), and the SOC of battery 102 decreases. Discharge stops at the discharge end time De2 (18:00), and battery 102 enters a standby state. The next day, at the charging start time Cs2 (4:00), charging of battery 102 is performed using grid power that is not the lowest unit price but is cheaper than the highest unit price, and the SOC reaches MAX before the discharge start time Ds1 (8:00), and battery 102 is fully charged. It enters a standby state until the discharge start time Ds1 (8:00). After that, the same control is repeated.

[0056] Similarly, Figure 9 shows the change in the State of Charge (SOC) of the battery 102 due to the charge / discharge control described above, in the case of the rate plan shown in Figure 6. In Figure 9, the SOC graph, as in Figure 8, starts from point P1, which represents the state in which the battery 102 is fully charged, and shows the change until just before 8:00 the next day. Similar to Figure 8, discharge is performed from point P1 (discharge start time Ds1 (8:00)) during time period T2 (discharge time period with the highest unit price), the SOC of the battery 102 decreases, and discharge stops at discharge end time De1 (10:00), and the battery 102 enters a standby state. At charge start time Cs1 (12:00), charging of the battery 102 is performed using grid power with the lowest unit price, and the SOC reaches MAX (battery 102 is fully charged) before the end of time period T3 (16:00), and the battery 102 enters a standby state. Unlike Figure 8, in Figure 9, the battery 102 remains in a standby state during the following time period T6. From the following time period T4 until the next day's time period T1, the charging and discharging of the battery 102 is controlled as shown in Figure 8, and the SOC changes.

[0057] As described above, the energy storage system 100 includes a battery 102 and a control unit 106 that controls the charging and discharging of the battery 102. The control unit 106 discharges the battery 102 during the discharge period of the day and charges the battery 102 with power from the grid 190 during the charging period of the day. The discharge period includes the maximum unit price period, in which the unit price of electricity is highest in an electricity rate plan where the unit price of electricity is set for each time period of the day. The charging period includes the minimum unit price period, in which the unit price is lowest in an electricity rate plan. Therefore, the cost of using grid electricity in buildings such as houses where the energy storage system is installed can be reduced in accordance with the electricity company's rate plan, resulting in a high economic effect.

[0058] If the minimum rate period in the pricing plan is set to daytime, when the supply of grid power increases due to the sale of electricity generated by the solar power generation system, then by determining the charging and discharging periods as described above, the battery 102 will be charged by grid power during the daytime. This will increase daytime electricity consumption and contribute to maintaining the balance of electricity supply and demand in the grid. Therefore, it is possible to avoid the power company implementing output curtailment. Daytime refers to the longest period from sunrise to sunset. Daytime can be any period during which electricity can be generated by the solar power generation system, and the start and end times of daytime are arbitrary. For example, daytime is from 10:00 to 16:00. Daytime could also be from 11:00 to 16:00, from 12:00 to 16:00, from 10:00 to 15:00, or from 10:00 to 14:00.

[0059] As described above, the control unit 106 displays multiple rate plans for each power company on the remote control 120, allowing the user to select one. This makes it easy for the user to set their contracted rate plan in the energy storage system 100.

[0060] As described above, the control unit 106 charges the battery 102 so that it is fully charged at the end of the charging period. This reduces the time that the battery 102 remains in a fully charged state, thereby suppressing power loss.

[0061] As described above, the control unit 106 puts the battery 102 into a standby state until the end of the charging period, after the battery 102 has reached a fully charged state through charging during the charging period. This makes it easy to set the charging start time during the charging period.

[0062] As described above, if the pricing plan includes multiple maximum-price time zones, the control unit 106 further charges the battery 102 with power from grid 190 during a time zone (time zone T1) that has the same end date as the period between adjacent maximum-price time zones (time zones T2 and T4) and does not include the minimum-price time zone (time zone T3), specifically during the period (time zones T5 and T1). This allows the battery to be fully charged before the maximum-price time zone, preventing it from becoming unable to discharge during the maximum-price time zone. Consequently, the cost of using grid electricity can be further reduced, resulting in greater economic benefits.

[0063] The above example shows a pricing plan with multiple time periods with the highest unit price (time periods T2 and T4), but it is not limited to this. There may also be pricing plans with only one time period with the highest unit price. For example, in the pricing plan shown in Figure 5, there may be a pricing plan where the unit price in time period T2 is the highest, and the unit price in time period T4 is slightly lower. In that case, the control unit 106 may set the time period with a unit price greater than a predetermined value (high-unit-price time period) as the discharge time period. This allows for a longer discharge time for the storage battery, further reducing the cost of using grid power. The predetermined value should be greater than the minimum unit price and less than the maximum unit price.

[0064] The example described above involves charging the battery 102 so that it is fully charged at the end of the minimum price period and so that it is fully charged immediately before the discharge period, but the explanation is not limited to this. Charging start times can be arbitrarily set in the minimum price period and the period immediately preceding the discharge period. For example, in Figure 8, the charging start time Cs1 may be set to the start of period T3 (10:00). Charging start time Cs2 may be set to the start of period T1 (0:00).

[0065] (modified version) The above describes a case where the user specifies a rate plan for the energy storage system 100 and the energy storage system 100 acquires the rate plan information, but it is not limited to this. The user may also input the rate plan information into the energy storage system 100. In that case, the program executed by the control unit 106 of the energy storage system 100 shown in Figure 1 (see Figure 2) is modified as shown in Figure 10. The flowchart shown in Figure 10 is the same as the flowchart shown in Figure 2, with steps 200 and 202 replaced by steps 240 and 242, respectively. In Figure 10, steps with the same reference numerals as in Figure 2 are the same as in Figure 2. Therefore, in the following, we will mainly explain the differences without repeating redundant explanations.

[0066] Referring to Figure 10, in step 240, the control unit 106 causes the remote control 120 to display a screen for inputting the time period and the unit price of electricity for the day. Then, control proceeds to step 242. For example, the control unit 106 sends a screen display instruction to the remote control 120, and the remote control 120, upon receiving the instruction, reads the corresponding image data from its internal memory and displays a screen as shown in Figure 11. In the screen 310, each row includes a cell 312 for inputting the start date, a cell 314 for inputting the end date, and a cell 316 for inputting the unit price. The three cells in each row identify one time period and the unit price for that time period. For example, the user refers to the rate plan of their contracted electricity company and inputs the start date, end date, and unit price in one or more rows. After input, when the confirmation button 318 is operated, the remote control 120 transmits the input information to the control unit 106.

[0067] In step 242, the control unit 106 determines whether the input of the rate plan has been completed. If it is determined that it has been completed, control proceeds to step 204. Otherwise, step 242 is repeated. Specifically, the control unit 106 determines that the input has been completed when it receives information (start date, end date, and unit price) entered on the screen 310 from the remote control 120. The control unit 106 stores the data received from the remote control 120 as a rate plan in its internal memory.

[0068] The control unit 106 processes the rate plan received from the remote control 120 in step 242 and stored in its internal memory, and executes steps 204 onward as described above. As a result, a new charge / discharge schedule is determined according to the rate plan input via the remote control 120.

[0069] As described above, the control unit 106 acquires information identifying the time period (start and end dates) and the unit price corresponding to the time period, which are input via the operation unit of the remote control 120, as a rate plan. This allows the rate plan to be accurately set in the energy storage system 100.

[0070] In the above, we described a case where the energy storage system 100 (control unit 106) determines the charging and discharging time zones from the rate plan, but the user may also set the charging and discharging time zones. For example, the control unit 106 may display a rate plan as shown in Figure 4 on the display unit of the remote control 120, and the user may operate the control unit to set the time zones to be used for charging and the time zones to be used for discharging. As described above, the user can set the time zone with the highest unit price as the discharging time zone and the time zone with the lowest unit price as the charging time zone. Alternatively, the user may set the time zone with the lowest unit price and the time zone with the second lowest unit price as the charging time zone, and set the other time zones as the discharging time zone. When the remote control 120 transmits the set charging and discharging time zone information to the control unit 106, the control unit 106 can identify the charging start time, discharging start time, and discharging end time based on the received information and create a charge / discharge schedule for the battery 102. This allows the user to set the charging and discharging time zones in accordance with the power company's electricity rate plan so as to reduce the cost of using grid electricity.

[0071] The above describes a case where the charging power and charging time are predetermined, but is not limited to this. The charging power and charging time may be set so as to minimize the power loss of the energy storage system 100 (mainly power loss due to the DC / AC converter 104) during charging of the battery 102. For example, in an energy storage system, there is a negative correlation between charging power and charging time; charging with a large charging power results in a shorter charging time to full charge, while charging with a small charging power results in a longer charging time to full charge. Power loss associated with charging tends to increase regardless of whether the charging power is small or large, and a charging power at which power loss is minimized (minimal) is observed. Therefore, by charging the battery 102 with varying charging power and measuring the charging time to full charge and power loss, the charging power and charging time at which power loss is minimized can be identified. The identified charging time can be subtracted from the time when the battery 102 is fully charged (e.g., the end of the charging period) to determine the charging start time. By using a specific charging power source and performing charging and discharging from the start time, it is possible to efficiently reduce the cost of using grid electricity, resulting in greater economic benefits.

[0072] In the above, the case in which the battery 102 is discharged according to the power consumption of the load during the discharge period was described, but discharge may be restricted considering the warranty period of the energy storage system 100. For example, the discharge power of the battery 102 is accumulated over the course of a day, and if the accumulated value (hereinafter referred to as the accumulated discharge power amount) reaches a preset upper limit, the discharge of the battery 102 is stopped even during the discharge period of that day. The accumulated discharge power amount is reset every day. The upper limit (hereinafter referred to as the upper limit discharge power amount) can be calculated from the warranty period and the rated power of the energy storage system 100. For example, the upper limit discharge power amount is calculated by multiplying the total accumulated power of charging and discharging the battery 102 during the warranty period of the energy storage system 100 by the ratio of one day to the warranty period. The upper limit discharge power amount may be set in advance in the internal memory of the control unit 106. For example, if the maximum charging capacity of the battery 102 is 10kWh and the warranty period for the energy storage system 100 is set to 15 years, assuming that it is charged and discharged once a day, then the total cumulative amount of electricity discharged from the battery during the warranty period is: 10 (kWh / day) × 365 (days / year) × 15 (years) = 54,750 (kWh) Therefore, the ratio of one day to the 15-year warranty period is 1 (day) / (15 × 365 (days)), Upper limit discharge energy = 54,750 (kWh) × 1 / (15 × 365) = 10 (kWh) This means that, based on the calculated upper limit of discharge power, the battery 102 is permitted to be charged and discharged once a day. If the warranty period for the energy storage system 100 is set to the same 15 years, assuming two charges and discharges per day, the total accumulated power will double, so the upper limit of discharge power will be 20 (kWh). This will reduce electricity costs over the entire warranty period of the energy storage system 100, resulting in greater economic benefits.

[0073] Furthermore, the warranty period is not limited to a standard period (e.g., 15 years); a longer period can be set when installing the energy storage system. In that case, the upper limit of discharge power can be calculated in the same manner. Using the calculated upper limit of discharge power, discharge should be limited so that the cumulative amount of discharge power per day does not exceed the upper limit.

[0074] The above describes a case where rate plan information is input from the remote control 120 via the screens shown in Figures 3 and 11, but is not limited to this. If the control unit 106 has a wireless communication function that can access a WiFi router or the like, it may display the screen shown in Figure 3 or Figure 11 on the user's mobile terminal device (such as a smartphone) and input rate plan information from the mobile terminal device.

[0075] The present disclosure has been described above by describing embodiments, but the embodiments described above are illustrative and the present disclosure is not limited to the embodiments described above. The scope of the present disclosure is given by the claims, with reference to the detailed description of the invention, and includes all modifications within the meaning and scope equivalent to the wording contained herein. [Explanation of Symbols]

[0076] 100 Energy Storage Systems 102 Storage Battery 104 DC / AC Converter 106 Control Unit 108 timers 120 Remote Controls 122 Communication equipment 130 servers 190 strains 192 load 194 Network 300, 310 screens 302 Scroll bar 304 Display area 306, 318 Confirm button Cells 312, 314, and 316 Cs1, Cs2 Charging start time Ds1, Ds2 discharge start time De1, De2 discharge end time P1 point T1, T2, T3, T4, T5, T6 time zones

Claims

1. Storage batteries and The set includes a control unit that controls the charging and discharging of the battery, The control unit, The storage battery is discharged during the discharge period of the day. During the charging period of the aforementioned day, the storage battery is charged using grid power. The aforementioned discharge period includes the maximum unit price period in an electricity rate plan where the unit price of electricity is set for each time period of the day, The charging time period includes the minimum unit price time period in the electricity rate plan where the unit price is the lowest. The aforementioned minimum price period is included in the daytime for energy storage systems.

2. The aforementioned electricity rate plan includes a period of time with a higher unit price than a predetermined value, which is different from the period of time with the maximum unit price. The control unit sets the high-price time period as the discharge time period, The energy storage system according to claim 1, wherein the predetermined value is greater than the minimum unit price and less than the maximum unit price.

3. The energy storage system according to claim 1 or 2, wherein the control unit charges the storage battery so that the storage battery is fully charged at the end of the charging period.

4. The energy storage system according to claim 1 or 2, wherein the control unit, after the battery has reached a fully charged state due to charging during the charging period, keeps the battery in a standby state until the end of the charging period.

5. It further includes a display unit and an operating unit, The display unit displays multiple electricity rate plans for each power company. The energy storage system according to claim 1 or 2, wherein the control unit, upon receiving that one electricity rate plan has been selected from among a plurality of electricity rate plans by the operation unit, identifies the maximum unit price time period and the minimum unit price time period for that electricity rate plan.

6. Further including the control section, The energy storage system according to claim 1 or 2, wherein the control unit acquires information specifying the time period and the unit price corresponding to the time period as the electricity rate plan via the operation unit.

7. Further including the control section, The energy storage system according to claim 1 or 2, wherein the operating unit sets the minimum unit price time period and the maximum unit price time period as the charging time period and the discharge time period, respectively.

8. The aforementioned electricity rate plan includes multiple periods with the highest unit price, The energy storage system according to claim 1 or 2, wherein the control unit further charges the battery with grid power during the time period which has the same end date as the end date of the period between adjacent maximum-price time periods and which does not include the minimum-price time period.

9. The system further includes a power conversion unit that generates a DC voltage for charging the battery from the grid power, The energy storage system according to claim 1 or claim 2, wherein the charging power for charging the storage battery is determined such that the power loss of the power conversion unit is minimized during the continuous period from the start of charging the storage battery until the storage battery is fully charged.

10. The control unit, The discharge power of the aforementioned battery over one day is accumulated to calculate the accumulated discharge power, In response to the cumulative discharge amount exceeding the upper limit discharge amount, the discharge of the storage battery is stopped. The energy storage system according to claim 1 or claim 2, wherein the upper limit discharge amount is calculated based on the warranty period of the energy storage system and the maximum charging capacity of the battery.

11. A method for controlling an energy storage system having a battery, The steps include discharging the battery during the discharge period of the day, The step includes charging the storage battery with grid power during the charging period in the aforementioned day, The aforementioned discharge period includes the maximum unit price period in an electricity rate plan where the unit price of electricity is set for each time period of the day, The charging time period includes the minimum unit price time period in the electricity rate plan where the unit price is the lowest. The control method wherein the aforementioned minimum unit price time period is included in the daytime.

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