Power supply system

Abstract

To increase a power-saving effect of a user.SOLUTION: A power supply system PCS includes: a power conversion unit 2 provided between a system power supply Q and a storage battery B; and a control unit 4. The control unit 4 calculates a break-even efficiency ηd due to charging / discharging of the storage battery B from a price ratio between a daytime power purchase price C1 and a nighttime power purchase price C2. When an overall efficiency η0, which is a product of a charge efficiency η1 and a discharge efficiency η2 of the power conversion unit, is less than or equal to the break-even efficiency ηd, the control unit stops an operation of charging the storage battery B from the system power supply Q and calculates a cumulative value of a charge power amount required during a stop period of the charging operation. When the accumulated requested charge power amount is more than or equal to a predetermined specified value, the control unit starts the operation of charging the storage battery B from the system power supply Q.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a power supply system that charges a storage battery with grid power and supplies either the discharged power of the storage battery or the grid power to a load. [Background technology]

[0002] Due to the liberalization of the electric power market, electricity prices are no longer uniform, and the selling and purchasing of electricity has become more diverse, creating a need for electricity buying and selling methods and power supply systems that can achieve energy conservation. Against this background, a patent application has been filed with the aim of enabling users to enjoy the price benefits of selling and purchasing electricity.

[0003] For example, Patent Document 1 discloses a technology in which the cost of power supply calculated from the expected power supply efficiency during the time period when daytime electricity rates apply and the nighttime electricity rate is compared with the daytime electricity rate, and if the cost of power supply is cheaper than the daytime electricity rate, the discharged power of a storage battery is supplied to a load. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-50783 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in Patent Document 1, when there is a load fluctuation, the expected effect of reducing the amount of purchased power (power saving effect) may not be sufficiently obtained. Specifically, even if charging is performed at night when cheaper nighttime power rates apply and discharging is performed during the day when daytime power rates apply, the power conversion efficiency decreases during both charging and discharging when the load is low, so the expected effect of reducing the amount of purchased power may not be obtained.

[0006] Figure 7 shows an example of profit and loss fluctuations due to the time of day when electricity is purchased and charging / discharging efficiency. In the example of Figure 7, the price setting is set at 21.94 yen / kWh during the day and 15.12 yen / kWh during the night, and the profit and loss is shown for the cases where 8 kWh of electricity is purchased during each time period and consumed within the home without charging or discharging (shown as "in-home consumption 1" in Figure 7), where it is charged into a storage battery (shown as "storage battery storage" in Figure 7), and where the electricity charged into the storage battery is discharged (shown as "in-home consumption 2" in Figure 7).

[0007] "In-home consumption 1" and "In-home consumption 2" in Figure 7(a) show the profit and loss for each charge / discharge efficiency when electricity is purchased during the day and consumed within the home during the day, "In-home consumption 1" in Figure 7(b) shows the case when electricity is purchased at night and consumed within the home during the night, and "In-home consumption 2" in Figure 7(b) shows the case when electricity is purchased at night and consumed within the home during the day.For ease of explanation, the power conversion efficiency from purchased electricity to direct consumption by in-home loads without charging / discharging by the power conditioner is set to 100%.

[0008] From Figure 7(a), even if the charging efficiency and discharging efficiency are both 90%, when the storage battery is charged and then discharged, the amount of electricity available for domestic consumption is 6.5 kWh, resulting in a power loss of 1.52 kWh, which is equivalent to a loss of -33.3 yen in value. From this point on, it can be seen that the lower the charging and discharging efficiency, the greater the loss.

[0009] As shown in Figure 7(b), when the charging efficiency and discharging efficiency are both 90%, the amount of electricity available for "in-home consumption 2" is the same, 6.5 kWh. However, in the case of nighttime power purchases, because the rate is set low, even if a power loss of 1.52 kWh occurs, the profit is 21.2 yen. However, the lower the efficiency, the lower the profit, and in this example, when the charging efficiency and discharging efficiency are both 80%, it turns into a loss.

[0010] In this way, the power conversion efficiency of charging and discharging has a significant impact on the savings in purchased electricity charges.

[0011] Furthermore, in Patent Document 1, when the discharged power of a storage battery is supplied to a load, the power supply cost calculated from the expected power supply efficiency and the nighttime power rate is compared with the daytime power rate, and if the power supply cost is cheaper than the daytime power rate, the power cut-off unit is controlled; however, the criteria for determining whether the cost is cheaper are not clearly stated.

[0012] In view of the above-mentioned problems, an object of the present invention is to provide a power supply system that further enhances the energy saving effect for users. [Means for solving the problem]

[0013] A power supply system according to a first aspect of the present invention is configured to charge a storage battery with grid power supplied from a grid, and to supply at least one of the grid power and the discharged power of the storage battery to a load. The power supply system includes: a power conversion unit provided between the grid and the storage battery; and a control unit that calculates a break-even efficiency for charging and discharging the storage battery based on a set price ratio between a daytime power purchase price and a nighttime power purchase price, stops charging the storage battery from the grid when an overall efficiency, which is the product of the charging efficiency and the discharging efficiency of the power conversion unit, is equal to or less than the break-even efficiency, calculates a cumulative value of the amount of charging power requested during the suspension of the charging operation, and starts charging the storage battery when the cumulative amount of requested charging power reaches or exceeds a predetermined value.

[0014] According to the above aspect, the break-even efficiency for charging and discharging the storage battery is calculated based on the set daytime power purchase price and nighttime power purchase price. If the overall efficiency, which is the product of the charging efficiency and discharging efficiency of the power conversion unit, is equal to or less than the break-even efficiency, the charging operation from the grid power source to the storage battery is stopped. This prevents unnecessary power purchase losses for the user. Furthermore, by focusing on the fact that high power conversion efficiency can be achieved when the charging power exceeds a certain level, the accumulated amount of charging power requested during the period when the charging operation is stopped is calculated. If the accumulated amount of requested charging power exceeds a predetermined value, the charging operation to the storage battery is started. This makes it possible to minimize power purchase losses for the user. In other words, it is possible to increase the user's energy savings.

[0015] In the power supply system according to the first aspect, the control unit may be configured to update the charging efficiency and the discharging efficiency as needed in response to a change in charging power and / or discharging power of the storage battery.

[0016] This enables the control unit to perform control in accordance with fluctuations in charging efficiency and discharging efficiency caused by changes in charging power and / or discharging power, thereby further increasing the power saving effect for the user. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a power supply system that increases the saving effect of the user. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a block diagram showing the overall configuration of a power supply system according to a first embodiment. [Figure 2] Flowchart showing an example of operation of a power supply system [Figure 3] A diagram showing the relationship between the charge / discharge power of the storage battery and the power conversion efficiency of the power conversion unit. [Figure 4] Timing chart for explaining the charging and discharging operation of the power supply system [Figure 5] A diagram showing an example of power flow during user-set operation (nighttime) [Figure 6] A diagram to explain the break-even point when purchasing electricity at nighttime electricity rates and consuming it at daytime electricity rates. [Figure 7] Diagram to explain fluctuations in profit and loss due to power purchase time periods and charging / discharging efficiency [Figure 8] FIG. 10 is a block diagram showing the overall configuration of a power supply system according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present invention, its scope of application, or its uses.

[0020] First Embodiment FIG. 1 is a block diagram showing an example of the configuration of a power supply system PCS according to the first embodiment.

[0021] The power supply system PCS includes a power conversion unit 2, a power measurement unit 3, a control unit 4, and a storage unit 5, which are provided between a power system Q and a storage battery B. A part or all of the power supply system PCS is implemented in a power conditioner 1. In this embodiment (FIG. 1), an example is shown in which the power conversion unit 2, the power measurement unit 3, the control unit 4, and the storage unit 5 are implemented in the power conditioner 1.

[0022] The power conversion unit 2 includes, as a component, an inverter (not shown) provided between the system power supply Q and the storage battery B. In a "charge mode" in which the storage battery B is charged from the system power supply Q, the power conversion unit 2 converts AC input from the system power supply Q into DC and outputs the DC to the DC bus. In a "discharge mode" in which the storage battery B is discharged, the power conversion unit 2 converts the bus voltage of the DC bus into AC and outputs the AC to the household load Z. The DC bus may be connected directly to the storage battery B, or may be connected to the storage battery B via a DC / DC converter (not shown) included in the power conversion unit 2.

[0023] The overall efficiency η0 of the power conversion unit 2 is expressed by the following formula.

[0024] η0=η1×η2 (1)

[0025] Here, η1 is the power conversion efficiency of the power conversion unit 2 when charging the storage battery B from the system power supply Q. η2 is the power conversion efficiency of the power conversion unit 2 when discharging from the storage battery B to the system power supply Q or the household load Z. In the following description, η1 may be referred to as the "charging efficiency" and η2 may be referred to as the "discharging efficiency." The charging efficiency η1 and the discharging efficiency η2 may be updated as needed in response to changes in the charging power and / or discharging power of the storage battery B.

[0026] The power measurement unit 3 has a configuration that measures the charging power (hereinafter simply referred to as "charging power") from the system power supply Q to the storage battery B and the discharging power (hereinafter simply referred to as "discharging power") from the storage battery B to the domestic load Z. Note that the specific configuration of the power measurement unit 3 is not particularly limited as long as it can measure the charging power and discharging power. For example, the power measurement unit 3 has a current sensor, a voltage sensor, etc. as its configuration.

[0027] The control unit 4 has a function of controlling the charging and discharging operations of the power conversion unit 2. The operation of the control unit 4 is mainly realized by a computer (including an MCU (Micro Controller Unit)) executing a program. In other words, the computer has, as its main hardware configuration, a processor that executes a program stored in an internal or external storage unit 5.

[0028] There is no restriction on the type of processor as long as it can realize functions by executing a program. For example, a processor may be composed of multiple electronic circuits such as a semiconductor integrated circuit (LSI (Large Scale Integrated Circuit), PLD (Programmable Logic Device), etc.). The processor may be integrated on a single chip or may be separated into multiple chips. In the case of multiple chips, they may be integrated into a single device or may be provided in separate devices.

[0029] The storage unit 5 includes a non-temporary storage area such as a computer-readable read-only memory (ROM), and specifically is a storage device such as a semiconductor memory, a hard disk drive (HDD), a solid state drive (SSD), an optical disk, etc. The program may be stored in the storage unit 5 in advance, or may be supplied to the storage unit 5 via the Internet, etc.

[0030] Specifically, the control unit 4 calculates the break-even efficiency ηd for charging and discharging the storage battery B based on the price ratio between the daytime electricity purchasing price C1 and the nighttime electricity purchasing price C2 set by the user and stored in the memory unit 5, based on the following equation (2):

[0031] ηd=C1 / C2 (2)

[0032] Figure 6 shows the relationship between the price advantage (price difference) between the daytime power purchase price C1 and the nighttime power purchase price C2 and the amount of power conversion loss. For example, in Figure 6, if 8 kWh is purchased at the nighttime power rate, the break-even point for daytime discharge is 5.5 kWh. In this case, the power conversion efficiency at the break-even point is 68.9%.

[0033] The daytime electricity purchase price C1 and the nighttime electricity purchase price C2 are not limited to being set by user input, but may be provided to the memory unit 5 via the Internet, for example, from a terminal device or server owned by an electric power company or other service provider.

[0034] The control unit 4 stops the charging operation from the system power source Q to the storage battery B when the overall efficiency η0, which is the product of the charging efficiency η1 and the discharging efficiency η2 of the power conversion unit 2, becomes equal to or less than the break-even efficiency ηd. The control unit 4 is also configured to calculate a cumulative value of the amount of charging energy requested during the period when the charging operation is stopped, and start the charging operation to the storage battery when the cumulative requested amount of charging energy (hereinafter also referred to as "requested charging amount") becomes equal to or greater than a predetermined specified value. There is no particular limitation on the method for calculating the cumulative value of the amount of charging energy, but for example, time integration can be suitably used. An example of the operation of the control unit 4 will be described below with reference to a specific example.

[0035] - Example of power supply system operation - Next, an example of the operation of the power management and supply system PCS will be described with reference to FIGS.

[0036] (Charging operation) FIG. 2 is a flowchart showing an example of the charging operation.

[0037] In S11, the control unit 4 sets a threshold value for the charge start power (hereinafter simply referred to as "charge start power Tb1") and a threshold value for the charge stop power (hereinafter simply referred to as "charge stop power Tb2"). Since the charge efficiency η1 and the discharge efficiency η2 are updated as needed in accordance with changes in the charge power and / or discharge power of the storage battery B, the charge start power Tb1 and the charge stop power Tb2 are also updated accordingly.

[0038] Specifically, the control unit 4 calculates the break-even efficiency ηd from the set daytime power purchasing price C1 and nighttime power purchasing price C2 using the above-mentioned formula (2). Next, it calculates the charging efficiency η1 and discharging efficiency η2 at which the overall efficiency η0 is higher than the break-even efficiency ηd.

[0039] For example, if the daytime power purchasing price C1 is 21.94 yen and the nighttime power purchasing price C2 is 15.21 yen, the break-even efficiency ηd is 15.21 / 21.94=69.3%. Here, the overall efficiency η0 is set to be higher than the break-even efficiency ηd, so if the charging efficiency η1 and discharging efficiency η2 are calculated as being equal, for example, the charging efficiency η1 and discharging efficiency η2 are each required to be 83.2% or higher.

[0040] Fig. 3 shows the relationship between the charge / discharge power and the power conversion efficiency of the power conversion unit 2. As shown in Fig. 3, the power conversion efficiency tends to increase as the charge / discharge power increases.

[0041] The storage unit 5 stores the power conversion efficiency (hereinafter referred to as the "power conversion efficiency characteristic") corresponding to the charge / discharge power of the power conversion unit 2 applied to the power supply system PCS. The control unit 4 calculates the charge start power Tb1 based on the set charging efficiency η1 and the power conversion efficiency characteristic. In the example of FIG. 3, 180 W corresponding to the charging efficiency η1 (83.2%) is set as the charge start power Tb1. The charge stop power Tb2 is set to a value obtained by adding a predetermined hysteresis to the charge start power Tb1. The predetermined hysteresis can be set arbitrarily. In the example of FIG. 3, 71.8% is set as the minimum operating efficiency, and 160 W corresponding to this is set as the charge stop power Tb2. The charge start power Tb1 may also be set based on the loss power. In the example of FIG. 3, the charge start power Tb1 (referred to as the operation start power in FIG. 3) is set to be the minimum loss power.

[0042] In S12, the control unit 4 determines whether the cumulative value of the requested charge amount exceeds the charge start power Tb1. If the cumulative value of the requested charge amount exceeds the charge start power Tb1 (Yes in S12), the control unit 4 executes a charging operation in which the power conversion unit 2 charges the storage battery B with power supplied from the system power source Q. On the other hand, if the cumulative value of the requested charge amount is equal to or less than the charge start power Tb1, the control unit 4 does not start the charging operation even if the charging request is accepted, and the flow returns to S11. In S11, the charge start power Tb1 and the charge stop power Tb2 are set.

[0043] Generally, the operation of a power conditioner is performed by controlling the charging and discharging power. In contrast, the power conditioner 1 of the present disclosure is characterized in that it controls the charging and discharging power based on the amount of power that takes into account the electricity rate. More specifically, it is characterized in that the amount of charging and discharging power is calculated using the concept of "time x (required charging power / required discharging power)."

[0044] 4, the required charge amount during the charge standby period is the charge standby period Tc (Tc=t1-t0) and the cumulative value of the required power during that period, i.e., the area of ​​region R1 (the region with downward slanting lines in FIG. 4). The control unit 4 determines the charge start timing and the charge start power based on the size of the area of ​​region R1.

[0045] Similarly, the required discharge amount during the discharge standby period is the discharge standby period Td (Td=t6-t5) and the cumulative value of the required power E3 during that period, i.e., the area of ​​region R2 (the region with upward slanting lines in Figure 4). The control unit 4 determines the discharge start timing and discharge start power based on the size of the area of ​​region R2.

[0046] The operation of S12 will be described in more detail with reference to FIG.

[0047] At time t0 in Fig. 4, a charge request is received by the control unit 4. Then, from time t0 to time t3, a constant requested charge amount is maintained, and the cumulative value of the requested charge amount increases linearly (see E1 in Fig. 4).

[0048] At time t0, since the cumulative value of the required charge amount is 0 [Wh], the determination in S12 is NO, and the flow returns to S11. In S11, it is assumed that there is no change in the charging start power Tb1 and the charging stop power Tb2.

[0049] At time t1 (t1 < t3), the control unit 4 waits for charging even if the cumulative value of the required charge amount reaches the charging start power Tb1 (see D1 in FIG. 4). Since the discharge power is determined by the state of the in-house load Z, if the charging to the storage battery B is started immediately after the cumulative value of the required charge amount reaches the charging start power Tb1, the cumulative value of the required charge amount will decrease, and there is a possibility that the charging power will fall below the charging stop power Tb2 at an early stage after the start of charging, resulting in unstable control operation. Therefore, in this embodiment, the charging operation is started from time t2 (t2 = t1 + tw1) when the charging start standby time tw1 has elapsed from time t1 (see D2 in FIG. 4). The charging start standby time tw1 is an arbitrarily set value and is determined based on, for example, the change in the cumulative value of the required charge amount (the slope of E1 in FIG. 4). For example, the charging start standby time tw1 is set to be shorter as the slope of E1 becomes steeper and longer as the slope of E1 becomes gentler. By adopting such a configuration, the stability of control can be enhanced.

[0050] In S14, the control unit 4 determines whether the cumulative value of the required charge amount has become less than or equal to the charging stop power Tb2. Then, when the cumulative value of the required charge amount becomes less than or equal to the charging stop power Tb2 (YES in S14), the control unit 4 executes control to stop the charging operation from the utility power source Q to the storage battery B for the power conversion unit 2.

[0051] The operation of S14 will be described in more detail with reference to Fig. 4. In Fig. 4, at time t3, the requested charging power starts to decrease and the charging operation continues, so the cumulative value of the requested charging amount drops linearly (see E2 in Fig. 4). Even after the cumulative value of the requested charging amount starts to decrease at time t3, the control unit 4 continues the charging operation until the cumulative value of the requested charging amount becomes equal to or less than the charging stop power Tb2 (see D4 in Fig. 4). Then, at time t4 (t4>t3), when the cumulative value of the requested charging amount becomes equal to or less than the charging stop power Tb2 (YES in S14), the control unit 4 controls the power conversion unit 2 to stop the charging operation from the system power source Q to the storage battery B (see D5 in Fig. 4).

[0052] (Discharge operation) Next, the discharging operation will be explained. This can be explained by replacing "charge" with "discharge" in Figure 2.

[0053] In S11 of FIG. 2, the control unit 4 sets a threshold value for discharge start power (hereinafter simply referred to as "discharge start power Td1") and a threshold value for discharge stop power (hereinafter simply referred to as "discharge stop power Td2"). The charging efficiency η1 and the discharging efficiency η2 are updated as needed in response to changes in the charging power and / or discharging power of the storage battery B, and the discharge start power Td1 and the discharge stop power Td2 are also updated accordingly. A specific setting example of the discharge start power Td1 is the same as the charging start power Tb1 in the charging operation described above, and is set based on the daytime power purchasing price C1, the nighttime power purchasing price C2, and the break-even efficiency ηd. The discharge stop power Td2 is set to a value obtained by adding a predetermined hysteresis to the discharge start power Td1. The predetermined hysteresis can be set arbitrarily.

[0054] In S12, the control unit 4 determines whether the cumulative value of the requested discharge power amount (hereinafter also referred to as "requested discharge amount") exceeds the discharge start power Td1. If the cumulative value of the requested discharge amount exceeds the discharge start power Td1 (Yes in S12), the control unit 4 executes a discharge operation to cause the power conversion unit 2 to discharge the power charged in the storage battery B. On the other hand, if the cumulative value of the requested discharge amount is equal to or less than the discharge start power Td1, the control unit 4 does not start the discharge operation even if the discharge request is accepted, and the flow returns to S11. In S11, the discharge start power Td1 and the discharge stop power Td2 are set.

[0055] The operation of S12 will be described in more detail with reference to FIG.

[0056] At time t5 in Fig. 4, a discharge request is received by the control unit 4. Then, from time t5 to time t8, a constant requested discharge amount is maintained, and the cumulative value of the requested discharge amount increases linearly (see E3 in Fig. 4).

[0057] At time t5, the cumulative value of the required discharge amount is 0 [Wh], so the determination in S12 is NO and the flow returns to S11. In S11, it is assumed that there is no change in the discharge start power Td1 and the discharge stop power Td2.

[0058] At time t6 (t5 < t6), even if the cumulative value of the required discharge amount reaches the discharge start power Td1, the control unit 4 waits for discharge (see D6 in FIG. 4). Since the discharge power is determined by the state of the in-house load Z, if the discharge of the storage battery B is started immediately after reaching the discharge start power Td1, the cumulative value of the required discharge amount decreases, and there is a possibility that the control operation becomes unstable because the discharge power falls below the discharge stop power Td2 at an early stage after the start of discharge. Therefore, in the present embodiment, the discharge operation is started from time t7 (t7 = t6 + tw2) when the discharge start standby time tw2 has elapsed from time t6 (see D7 in FIG. 4). The discharge start standby time tw2 is an arbitrarily set value, and is determined based on, for example, the change amount (the slope of E3 in FIG. 4) of the cumulative value of the required discharge amount. For example, the discharge start standby time tw2 is set to be shorter as the slope of E3 becomes steeper, and longer as the slope of E3 becomes gentler.

[0059] In S14, the control unit 4 determines whether the cumulative value of the required discharge amount has become less than or equal to the discharge stop power Td2. Then, when the cumulative value of the required discharge amount becomes less than or equal to the discharge stop power Td2 (YES in S14), the control unit 4 executes control to stop the discharge operation of the storage battery B for the power conversion unit 2.

[0060] The operation of S14 will be described more specifically with reference to FIG. 4. In FIG. 4, at time t8, the required discharge amount starts to decrease, but since the discharge operation continues, the cumulative value of the required discharge amount decreases linearly (see E4 in FIG. 4). Even after the cumulative value of the required discharge amount starts to decrease at time t8, the control unit 4 continues the discharge operation until the cumulative value of the required discharge amount becomes less than or equal to the discharge stop power Td2 (see D9 in FIG. 4). Then, at time t9 (t9 > t8), when the cumulative value of the required discharge amount becomes less than or equal to the discharge stop power Td2 (YES in S14), the control unit 4 executes control to stop the discharge operation of the storage battery B for the power conversion unit 2 (see D10 in FIG. 4).

[0061] As described above, according to this embodiment, the break-even efficiency ηd for charging and discharging the storage battery B is calculated based on the power purchase prices (daytime power purchase price C1 and nighttime power purchase price C2) set by the user. When the overall efficiency η0, which is the product of the charging efficiency η1 and the discharging efficiency η2 of the power conversion unit 2, is equal to or less than the break-even efficiency ηd, the charging operation from the grid power source Q to the storage battery B is stopped. This prevents the user from incurring unnecessary losses in purchasing power. Furthermore, by focusing on the fact that high power conversion efficiency can be achieved when the charging power exceeds a certain level, the accumulated amount of charging power requested during the suspension period of the charging operation is calculated. When the accumulated amount of requested charging power exceeds the predetermined value, i.e., the charging start power Tb1, the charging operation to the storage battery B is started. This prevents the user from incurring unnecessary losses in purchasing power. In other words, the user's energy saving effect can be further enhanced. The same applies to the discharging operation. Specifically, the break-even efficiency ηd for charging and discharging storage battery B is calculated, and when the overall efficiency η0, which is the product of the charging efficiency η1 and the discharging efficiency η2 of the power conversion unit 2, is equal to or less than the break-even efficiency ηd, the discharging operation of storage battery B is stopped. Furthermore, focusing on the fact that high power conversion efficiency can be obtained when the discharge power exceeds a certain level, the accumulated value of the amount of discharge power requested during the period when the discharging operation is stopped is calculated, and when the accumulated amount of requested discharge power exceeds a predetermined specified value, the discharge start power Td1, the discharging operation of storage battery B is started.

[0062] Second Embodiment Fig. 8 is a block diagram showing a configuration example of a power supply system PCS according to the second embodiment. In Fig. 8, the same components as those in Fig. 1 are denoted by the same reference numerals. In the following explanation, differences from the first embodiment will be mainly described, and explanations of overlapping components and functions may be omitted.

[0063] The power supply system PCS of FIG. 8 includes a V2H unit 7 and a storage battery unit 9 in addition to the configuration of FIG. 1. Compared with the configuration of FIG. 1, the power supply system PCS of FIG. 8 includes an in-vehicle storage battery B1 and a stationary storage battery B2 as the storage battery B. The power supply system PCS of FIG. 8 also includes an inverter 11 provided in the power conditioner 1 and a DC / DC converter 71 provided in the V2H unit 7 as the power conversion unit 2. In other words, the power conditioner 1 includes the control unit 4 and the inverter 11, and the V2H unit 7 includes the DC / DC converter 71 and a V2H controller 72. The power conditioner 1 is an example of a power conditioner device. The V2H unit 7 is an example of a charge / discharge unit device. The V2H controller 72 is an example of a second control unit.

[0064] The operation of the power conditioner 1 is the same as that of the first embodiment described above. For example, in a charging mode, the inverter 11 converts AC input from the system power supply Q into DC and outputs the DC to the DC bus DB. In addition, in a discharging mode, the inverter 11 converts the bus voltage of the DC bus DB into AC and outputs the AC to the household load Z. The control unit 4 has a function of controlling the charging and discharging operation of the power conversion unit 2. A specific example of the operation of the control unit 4 is the same as that of the first embodiment described above, and a detailed description thereof will be omitted here.

[0065] The vehicle 8 includes an on-board storage battery B1, an on-board communication unit 81, and an ECU (Electronic Control Unit) 82. Although a detailed description thereof will be omitted as it is not related to the subject matter of the disclosed technology, the vehicle 8 is equipped with a plurality of ECUs 82. The ECUs 82 control various operations of the vehicle 8, including running, braking, and steering. The on-board communication unit 81 is configured to be able to communicate with the communication unit 73 of the V2H unit 7 based on a predetermined communication protocol (for example, the CAN protocol). The on-board storage battery B1 is mounted on the vehicle 8, such as an electric vehicle, and is used as a power source for the vehicle 8. The on-board storage battery B1 is connected to a DC bus DB via the V2H unit 7.

[0066] The V2H (Vehicle to Home) unit 7 includes a DC / DC converter 71, a V2H controller 72, and a communication unit 73 that communicates with an in-vehicle communication unit 81. The V2H unit 7 is configured to be capable of operating in a discharge mode (hereinafter simply referred to as the "discharge mode") in which the in-vehicle storage battery B1 is discharged, and a charge mode (hereinafter simply referred to as the "charge mode") in which the in-vehicle storage battery B1 is charged. In the discharge mode, the V2H unit 7 converts the discharge power output from the in-vehicle storage battery B1 to a predetermined voltage and outputs it to the DC bus DB. In the charge mode, the V2H unit 7 converts the bus voltage of the DC bus DB and supplies it to the in-vehicle storage battery B1 as charging power.

[0067] In the charging mode, the DC / DC converter 71 converts the bus voltage of the DC bus DB to a predetermined voltage and outputs charging power to the vehicle storage battery 51, while in the discharging mode, it converts the output voltage of the vehicle storage battery B1 to a predetermined voltage and outputs it to the DC bus DB.

[0068] The V2H controller 72 receives an operation command for charging or discharging the in-vehicle storage battery B1 from the control unit 4, and controls the DC / DC converter 71 based on the operation command, thereby controlling the charging and discharging of the in-vehicle storage battery B1. The V2H controller 72 can be realized, for example, by a so-called microcomputer. Specifically, the function of the V2H controller 72 is realized, for example, by a control unit such as a processor or a controller executing a program stored in a memory or the like. Furthermore, the function of the V2H controller 72 may be realized by an FPGA or a logic circuit such as a sequencer.

[0069] As in the first embodiment, the control unit 4 stops the charging operation from the grid power source Q to the in-vehicle storage battery B1 when the overall efficiency η0, which is the product of the charging efficiency η1 and the discharging efficiency η2 of the power conversion unit 2, is equal to or less than the break-even efficiency ηd. In the example of FIG. 4 , the control unit 4 stops the charging operation from the grid power source Q to the in-vehicle storage battery B1 during a charging standby period Tc. The V2H controller 72 may stop communication with the vehicle 8 during the charging standby period in which the control unit 4 stops the charging operation of the in-vehicle storage battery B1. Specifically, under the control of the V2H controller 72, communication between the communication unit 73 and the in-vehicle communication unit 81 is stopped. Then, the V2H controller 72 may start communication with the vehicle 8 before the cumulative value of the requested charging energy becomes equal to or greater than a predetermined value and the control unit 4 starts the charging operation of the in-vehicle communication unit 81. Specifically, under the control of the V2H controller 72, communication between the communication unit 73 and the in-vehicle communication unit 81 is started. Note that the charging standby period Tc is an example of a stop period in which the charging operation is stopped.

[0070] Furthermore, for example, the control unit 4 stops the discharging operation of the in-vehicle storage battery B1 when the overall efficiency η0, which is the product of the charging efficiency η1 and the discharging efficiency η2 of the power conversion unit 2, is equal to or less than the break-even efficiency ηd. In the example of FIG. 4 , the control unit 4 stops the discharging operation of the in-vehicle storage battery B1 during a discharge standby period Td. The V2H controller 72 may stop communication with the vehicle 8 during the discharge standby period in which the control unit 4 stops the discharging operation of the in-vehicle storage battery B1. Specifically, under the control of the V2H controller 72, communication between the communication unit 73 and the in-vehicle communication unit 81 is stopped. Then, the V2H controller 72 may start communication with the vehicle 8 before the cumulative value of the requested discharge energy becomes equal to or greater than a predetermined value and the control unit 4 starts the discharging operation of the in-vehicle communication unit 81. Specifically, under the control of the V2H controller 72, communication between the communication unit 73 and the in-vehicle communication unit 81 is started. Note that the discharge standby period Td is an example of a stop period in which the charging operation is stopped.

[0071] As described above, during the charging standby period Tc, it is possible to reduce power consumption by stopping communication between the V2H unit 7 and the vehicle 8. Similarly, during the discharging standby period Td, it is possible to reduce power consumption by stopping communication between the V2H unit 7 and the vehicle 8.

[0072] In the above embodiment, the control unit 4 of the power conditioner 1 controls the charging standby and discharging standby of the in-vehicle storage battery B1, but this is not limiting. For example, some or all of the functions of the control unit 4 described in the first and second embodiments may be provided in the V2H controller 72.

[0073] <Other embodiments> As described above, the embodiments have been described as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited to these, and can be applied to embodiments in which appropriate modifications, substitutions, additions, omissions, etc. are made. Furthermore, it is also possible to combine the components described in the above embodiments to create new embodiments.

[0074] In the above embodiment, an example was shown in which the charging efficiency η1 and the discharging efficiency η2 were assumed to be equal in the process of calculating the overall efficiency η0 to be higher than the break-even efficiency ηd. However, in an actual product, the charging efficiency η1 and the discharging efficiency η2 are not necessarily equal, so the optimal power may be set for each of the charging start power Tb1 and the discharging start power Td1.

[0075] For example, FIG. 5 shows the relationship between the charging efficiency η1 and the discharging efficiency η2 when the overall efficiency is 68.9%. At point P1, the charging efficiency η1 is 95% and the discharging efficiency η2 is 73%. At point P2, the charging efficiency η1 is 73% and the discharging efficiency η2 is 95%. The area between points P1 and P2 is a controllable charging / discharging efficiency region (referred to as a "controlled charging / discharging efficiency region" in the drawing). As can be seen from FIG. 5, the charging efficiency η1 or the discharging efficiency η2 may be calculated based on the other. When the intersection of the charging efficiency η1 and the discharging efficiency η2 is within the hatched region in FIG. 5, this can be considered to be the region where the overall efficiency η0 is greater than the break-even efficiency ηd, i.e., the region where charging / discharging is performed.

[0076] In the above embodiment, the control unit 4 starts charging the storage battery B after the accumulated requested amount of charging energy reaches the charging start power Tb1 and the charging start wait time tw1 corresponding to the gradient E1 (see FIG. 4 ), which is the gradient of change in the accumulated value of the requested amount of charging energy, has elapsed. However, this is not limited to this. For example, the charging start wait time tw1 may be omitted and the set value of the charging start power Tb1 may be set to a value with a predetermined margin. The same applies to discharging the storage battery B; the discharge start power Td1 may be set to a value with a predetermined margin and the discharge start wait time tw2 may not be omitted.

[0077] In the second embodiment, the V2H controller 72 may include a mode selection function for selecting, for example, which mode to operate in among a charge mode, a discharge mode, and an autonomous driving mode. In the autonomous driving mode, artificial intelligence (AI) may be used to perform automatic control to reduce electricity charges. Specifically, for example, in the autonomous driving mode, the amount of power consumption in the household load Z may be predicted based on data accumulated in the past, and charging and discharging of the in-vehicle storage battery 51 may be controlled according to the prediction result so as to optimize electricity charges. In the configuration of the second embodiment, the charging start waiting time tw1 may be set based on capacity information of the in-vehicle storage battery B1 acquired from the vehicle 8. Similarly, the discharging start waiting time tw2 may be set based on capacity information of the in-vehicle storage battery B1 acquired from the vehicle 8.

[0078] In the above embodiment, the timing to start charging during a charge standby period is determined based on the requested charge amount, i.e., the amount of power, during the charge standby period. However, this is not a limitation. For example, the timing to start charging during a charge standby period may be determined based on the power value during the charge standby period. More specifically, the control unit 4 may start charging when the requested charge power value during the charge standby period, i.e., the period during which the charging operation is stopped, exceeds a predetermined value. The predetermined value of the requested charge power value is not particularly limited, but may be set to, for example, a power value at which the conversion efficiency changes significantly. In the example of FIG. 3 described above, the predetermined value of the requested charge power value is set to, for example, 300 W. Similarly, the timing to start discharging during a discharge standby period is determined based on the requested discharge amount, i.e., the amount of power, during the discharge standby period. However, this is not a limitation. For example, the timing to start discharging during a discharge standby period may be determined based on the power value during the discharge standby period. More specifically, the control unit 4 may start discharging when the required discharge power value requested during the discharge standby period, i.e., the period during which the discharging operation is stopped, exceeds a predetermined value. The predetermined value of the required discharge power value is not particularly limited, but is set to a power value at which the conversion efficiency changes significantly, similar to the starting power of the charging operation. In the example of FIG. 3 described above, the predetermined value of the required discharge power value is set to, for example, 300 W. Note that the configuration and operation are similar to those of the above-described embodiment, except that the power value is used as the reference instead of the amount of power, and similar effects are obtained. Specifically, even when the power value is used as the reference, it is possible to minimize the power purchase loss for the user. Furthermore, using the power value as the reference has the effect of improving the responsiveness of the start of charging and discharging. [Industrial Applicability]

[0079] According to the present invention, in a power supply system in which system power supplied from a system is charged into a storage battery and either the discharged power of the storage battery or the system power is supplied to a load, the present invention is extremely useful because it can increase the power saving effect of the user. [Explanation of symbols]

[0080] PCS power supply system 1 Power conditioner (power conditioner device) 2 Power conversion section 4. Control section 7 V2H unit (charging and discharging unit device) 71 DC / DC converter (converter) 72 V2H controller (second control section) 8 vehicles B. Storage battery B1 On-board storage battery

Claims

1. A power supply system configured to be able to charge a storage battery with system power supplied from a system, and to be able to supply discharge power of the storage battery and the system power to a load, a power conversion unit provided between the grid and the storage battery; a control unit that calculates a break-even efficiency for charging and discharging the storage battery based on a set price ratio between a daytime power purchase price and a nighttime power purchase price, stops a charging operation for charging the storage battery with the grid power when an overall efficiency, which is the product of the charging efficiency and the discharging efficiency of the power conversion unit, becomes equal to or less than the break-even efficiency, calculates a cumulative value of a requested amount of charging energy requested during a period when the charging operation is stopped, and starts the charging operation when the cumulative value of the requested amount of charging energy becomes equal to or greater than a predetermined value. A power supply system characterized by:

2. A power supply system configured to be able to charge a storage battery with system power supplied from a system, and to be able to supply discharge power of the storage battery and the system power to a load, a power conversion unit provided between the grid and the storage battery; a control unit that calculates a break-even efficiency for charging and discharging the storage battery based on a set price ratio between a daytime power purchase price and a nighttime power purchase price, stops the discharging operation of the storage battery when an overall efficiency, which is the product of the charging efficiency and the discharging efficiency of the power conversion unit, becomes equal to or less than the break-even efficiency, calculates a cumulative value of a requested discharged power amount requested during a period when the discharging operation is stopped, and starts the discharging operation when the cumulative value of the requested discharged power amount becomes equal to or greater than a predetermined value. A power supply system characterized by:

3. 3. The power supply system according to claim 1, The control unit updates the charging efficiency and the discharging efficiency as needed in response to changes in charging power and / or discharging power of the storage battery. A power supply system characterized by:

4. The power supply system according to claim 1, The control unit starts the charging operation after a waiting time corresponding to a gradient of change in the accumulated value of the requested amount of charging energy has elapsed after the accumulated value of the requested amount of charging energy has reached a predetermined specified value or more. A power supply system characterized by:

5. The power supply system according to claim 2, The control unit starts the discharge operation after a waiting time corresponding to a gradient of change in the cumulative value of the required discharge power amount has elapsed after the cumulative value of the required discharge power amount has reached a predetermined specified value or more. A power supply system characterized by:

6. The power supply system according to claim 1, The storage battery is an on-board storage battery mounted on a vehicle, The power supply system includes: a second control unit that stops communication with the vehicle during a stop period in which the control unit stops the charging operation of the in-vehicle storage battery, and starts communication with the vehicle before the cumulative value of the requested charging energy amount becomes equal to or exceeds a predetermined specified value and the charging operation is started; A power supply system characterized by:

7. The power supply system according to claim 2, The storage battery is an on-board storage battery mounted on a vehicle, The power supply system includes: a second control unit that stops communication with the vehicle during a stop period in which the control unit stops the discharging operation of the vehicle-mounted storage battery, and starts communication with the vehicle before the cumulative value of the required discharge power amount becomes equal to or greater than a predetermined specified value and the discharging operation is started; A power supply system characterized by:

8. The power supply system according to claim 6 or 7, the power conversion unit includes an inverter connected to a grid and a converter provided between the inverter and the on-board storage battery; a power conditioner device having the inverter and the control unit; a charge / discharge unit device having the converter and the second control unit; A power supply system characterized by:

9. The power supply system according to claim 6 or 7, the power conversion unit includes an inverter connected to a grid and a converter provided between the inverter and the on-board storage battery; a power conditioner device having the inverter; a charge / discharge unit device having the converter, the control unit, and the second control unit; A power supply system characterized by:

10. a charging / discharging unit device configured to be able to communicate with an on-board storage battery of a vehicle; and a power conditioner device connected to the charging / discharging unit device, for supplying charging power to the on-board storage battery via the charging / discharging unit device or receiving discharged power from the on-board storage battery via the charging / discharging unit device, The power conditioner device is a power conversion unit provided between the grid and the on-board storage battery; a control unit that stops a charging operation for charging the on-board storage battery with grid power supplied from the grid when an overall efficiency, which is the product of the charging efficiency and the discharging efficiency of the power conversion unit, becomes equal to or lower than a break-even efficiency for charging and discharging the on-board storage battery calculated from a daytime power purchase price and a nighttime power purchase price, calculates a cumulative value of a requested amount of charging power requested during a period when the charging operation is stopped, and starts the charging operation when the cumulative value of the requested amount of charging power becomes equal to or higher than a predetermined specified value; The charge / discharge unit device includes a second control unit that stops communication with the vehicle while the charging operation by the control unit is stopped, and starts communication with the vehicle before the cumulative value of the requested charging energy amount becomes equal to or exceeds a predetermined value and the charging operation is started. A power supply system characterized by:

11. a charging / discharging unit device configured to be able to communicate with an on-board storage battery of a vehicle; and a power conditioner device connected to the charging / discharging unit device, for supplying charging power to the on-board storage battery via the charging / discharging unit device or receiving discharged power from the on-board storage battery via the charging / discharging unit device, The power conditioner device is a power conversion unit provided between the grid and the on-board storage battery; a control unit that stops a discharging operation of discharging the on-board storage battery when an overall efficiency, which is the product of the charging efficiency and discharging efficiency of the power conversion unit, becomes equal to or less than a break-even efficiency for charging and discharging the on-board storage battery calculated from a daytime power purchase price and a nighttime power purchase price, calculates a cumulative value of a requested discharge amount of power requested during a period when the discharging operation is stopped, and starts the discharging operation when the cumulative value of the requested discharge amount of power becomes equal to or greater than a predetermined specified value; The charge / discharge unit device includes a second control unit that stops communication with the vehicle while the control unit stops the discharging operation and starts communication with the vehicle before the cumulative value of the required discharge power amount becomes equal to or exceeds a predetermined value and the discharging operation is started. A power supply system characterized by:

12. A power supply system configured to be able to charge a storage battery with system power supplied from a system, and to be able to supply discharge power of the storage battery and the system power to a load, a power conversion unit provided between the grid and the storage battery; and a control unit that calculates a break-even efficiency for charging and discharging the storage battery based on a set price ratio between a daytime power purchase price and a nighttime power purchase price, stops a charging operation for charging the storage battery with the grid power when an overall efficiency, which is the product of the charging efficiency and the discharging efficiency of the power conversion unit, becomes equal to or less than the break-even efficiency, and starts the charging operation when a requested charging power value requested during a period when the charging operation is stopped becomes equal to or greater than a predetermined value. A power supply system characterized by:

13. A power supply system configured to be able to charge a storage battery with system power supplied from a system, and to be able to supply discharge power of the storage battery and the system power to a load, a power conversion unit provided between the grid and the storage battery; and a control unit that calculates a break-even efficiency for charging and discharging the storage battery based on a set price ratio between a daytime power purchase price and a nighttime power purchase price, stops the discharging operation of the storage battery when an overall efficiency, which is the product of the charging efficiency and the discharging efficiency of the power conversion unit, is equal to or less than the break-even efficiency, and starts the discharging operation when a required discharge power value requested during a period in which the discharging operation is stopped is equal to or greater than a predetermined value. A power supply system characterized by:

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