Energy storage system

Abstract

To provide a power storage system that allows captive consumption of generated electric power without involving an increase in cost.SOLUTION: A power storage system according to the present invention is a system that is provided in parallel with general loads and a photovoltaic power generation system in a power line with a reverse power relay connected to a commercial power system, and can perform negative power supply for storing power supplied from the power line and positive power supply for supplying the stored power to the power line. When an inverse load flow to the commercial power system is detected by the reverse power relay (S1 is 0→1) while positive or negative power supply (S3) is being performed, the power storage system reduces the power supply (S3) at a predetermined gradient, and when the inverse load flow is no longer detected (S1 is 1→0) as a result of this, increases the power supply (S3) at the predetermined gradient.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a power storage system provided in parallel with a general load and a solar power generation system on a power line with a reverse power relay connected to a commercial power system.

Background Art

[0002] FIG. 5 shows a general power storage system 100. As shown in the figure, the power storage system 100 is provided in parallel with a general load 101 and a solar power generation system 102 on a power line 21 connected to a commercial power system (hereinafter also simply referred to as "system") 20. The power storage system 100 includes a storage battery (not shown), and supplies the generated power of the solar cell 104 to at least one of the general load 101, the specific load 103, the system 20, and the storage battery, or supplies the generated power of the solar power generation system 102 and the power from the system 20 to at least one of the storage battery and the specific load 103.

[0003] By the way, with the recent decrease in the power purchase price, there has been a growing movement to consume as much as possible the generated power of the solar power generation system 102 and the solar cell 104 for self-consumption. Self-consumption means consuming the generated power not by supplying it to the system 20 (selling electricity), but by supplying it to the general load 101, the specific load 103, and the storage battery. When taking such a movement, usually, in order to monitor the power transfer with the system 20, a wattmeter 105 is newly installed on the power line 21. However, the installation of the wattmeter 105 may cost more than the economic merit of self-consumption, and in that case, the installation of the wattmeter 105 is not suitable as a means to achieve self-consumption.

[0004] Note that controlling the output for self-consumption using the measurement result of the wattmeter is described in, for example, Non-Patent Document 1.

Prior Art Documents

Non-Patent Documents

[0005] [Non-Patent Document 1] Field Logic Co., Ltd. Web page, System configuration example for output control for self-consumption, [online], Solutions / Output control for self-consumption, [Accessed September 27, 2022], Internet<URL:https: / / www.f-logic.jp / solution / control_consumption.html> [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] This invention has been made in view of the above circumstances, and aims to provide an energy storage system that enables the self-consumption of generated electricity without increasing costs. [Means for solving the problem]

[0007] To solve the above problems, the energy storage system according to the present invention is installed in parallel with general loads and a solar power generation system on a power line equipped with a reverse power relay connected to a commercial power grid, and is a system capable of negative power supply, which stores the power supplied from the power line, and positive power supply, which supplies the stored power to the power line, and has the following configuration: when a reverse power flow to the commercial power grid is detected by the reverse power relay while positive or negative power supply is being performed, the power supply is reduced by a preset slope, and when the reverse power flow is no longer detected, the power supply is increased by a preset slope.

[0008] In this configuration, self-consumption is achieved using reverse power relays, which are often pre-installed in various facilities, rather than power meters. Therefore, this configuration can save on the cost of installing power meters.

[0009] Furthermore, in this configuration, when a reverse power relay detects a reverse power flow to the commercial power grid while a positive or negative power supply is being provided, the power supply decreases at a predetermined rate, and when the reverse power flow is no longer detected, the power supply increases at a predetermined rate. In other words, in this configuration, the power supply begins to change slowly rather than in a step-like manner, triggered by the detection or discontinuation of reverse power flow. Therefore, this configuration prevents sudden increases or decreases in power supply. Consequently, this configuration prevents unnecessary increases in the amount of electricity sold or purchased, similar to the case where precise control is performed using high-cost power meters.

[0010] The above energy storage system may include a bidirectional DC / AC converter connected to a power line, a battery connected to the bidirectional DC / AC converter, a DC / DC converter connected to the bidirectional DC / AC converter and also connected to a solar cell, and a control unit that controls the bidirectional DC / AC converter and the DC / DC converter based on whether or not reverse power flow is detected.

[0011] Furthermore, the energy storage system may include a bidirectional DC / AC converter connected to a power line, a battery connected to the bidirectional DC / AC converter, and a control unit that controls the bidirectional DC / AC converter based on whether or not reverse power flow is detected. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide an energy storage system that enables the self-consumption of generated electricity without increasing costs. [Brief explanation of the drawing]

[0013] [Figure 1] This is a block diagram showing an energy storage system and its surroundings according to a first embodiment of the present invention. [Figure 2] This is a block diagram showing the configuration of the control unit as shown in Figure 1. [Figure 3] Figure 2 is a graph showing the relationship between the detection signal S1, the intermediate signal S2, and the command signal S3. [Figure 4] This is a block diagram showing a power storage system and its surroundings according to a second embodiment of the present invention. [Figure 5] This block diagram shows a conventional energy storage system and its surrounding components. [Modes for carrying out the invention]

[0014] Hereinafter, an embodiment of the energy storage system according to the present invention will be described with reference to the attached drawings.

[0015] [First Embodiment] Figure 1 shows a first embodiment of the energy storage system 1A according to the present invention. As shown in the figure, the energy storage system 1A is used by being installed in parallel with a general load 22 and a solar power generation system (solar cell 25 and power conditioner 26) on a power line 21 connected to a commercial power grid 20, and comprises a bidirectional DC / AC converter 3 connected to the power line 21 via a switch 2, a storage battery 5 and a DC / DC converter 4 connected to the bidirectional DC / AC converter 3, and a control unit 10 that controls the bidirectional DC / AC converter 3 and the DC / DC converter 4. The DC / DC converter 4 is connected to a solar cell 24.

[0016] The solar power generation system (25,26) supplies generated power P3 to power line 21 independently of the energy storage system 1A.

[0017] The energy storage system 1A primarily performs the following operations (1), (2), and (3) under the control of the control unit 10, by operating the bidirectional DC / AC converter 3 and the DC / DC converter 4. (1) The power generated by the solar cell 24 is supplied to at least one of the following: the storage battery 5, the specific load 23, and the power line 21 (including the general load 22). (2) The stored power of the battery 5 is supplied to at least one of the specific load 23 and the power line 21 (including the general load 22). (3) Supply the power supplied from the power line 21 to at least one of the specific load 23 and the storage battery 5. The power from the power line 21 includes the generated power of the photovoltaic power generation systems (25, 26) and the power supplied from the grid 20.

[0018] In this specification, the fact that the power storage system 1A is supplying power by the above operations (1) and (2) (that is, the power P1 is positive) may be expressed as "the power storage system 1A is performing positive power supply", "the power supply by the power storage system 1A is positive", etc. Also, in this specification, the fact that power is being supplied to the power storage system 1A by the above operation (3) (that is, the power P1 is negative) may be expressed as "the power storage system 1A is performing negative power supply", "the power supply by the power storage system 1A is negative", etc.

[0019] The switch 2 is configured to switch from the closed state, which is the normal state, to the open state when a power outage occurs in the grid 20. When the switch 2 switches to the open state, it means that the power storage system 1A is disconnected from the power line 21. After being disconnected, the driving of the specific load 23 is continued by the stored power of the storage battery 5 or the generated power of the solar cell 24.

[0020] As shown in FIG. 1, a reverse power relay 27 is provided on the power line 21. And the control unit 10 can also control the bidirectional DC / AC conversion unit 3 and the DC / DC conversion unit 4 based on a detection signal S1 indicating whether a reverse power flow is detected by this reverse power relay 27 (that is, whether the remaining power P4 obtained by subtracting the power P2 flowing toward the general load 22 from the sum of the power P1 and the generated power P3 is positive). The detection signal S1 is "1" when a reverse power flow is detected, and "0" otherwise.

[0021] As shown in Figure 2, the control unit 10 includes a lamp processing unit 11 and a command signal generation unit 12. The lamp processing unit 11 performs lamp limitation processing on the detection signal S1 based on a preset lamp setting value (slope), thereby generating an intermediate signal S2. The command signal generation unit 12 generates a command signal S3 related to power P1 using the following equation with the intermediate signal S2 as a variable. S3 = (0.5 - S2) × 2 × Po Po is the rated power of the energy storage system 1A (more precisely, the bidirectional DC / AC converter 3). In this embodiment, the rated power Po is set to 10 kW.

[0022] Figure 3 shows an example of the relationship between the detection signal S1, the intermediate signal S2, and the command signal S3.

[0023] When the reverse power relay 27 detects a reverse power flow at time t1, when the power supply from the energy storage system 1A is positive (more specifically, power P1(S3) is +4[kW]), the detection signal S1 changes from 0 to 1, and the intermediate signal S2 begins to increase at a preset slope. Consequently, the command signal S3 begins to decrease.

[0024] Even if the power supply from the energy storage system 1A stops at time t2 (more specifically, even if the power P1 (S3) becomes ±0 [kW]), the reverse power relay 27 still detects reverse power flow, and therefore the command signal S3 continues to decrease. At this time, power P4, which is the remaining power after subtracting power P2 from the generated power P3, is flowing into the grid 20 in reverse.

[0025] When the power supply from the energy storage system 1A is negative (more specifically, when the power P1(S3) is -6.8[kW]) at time t3, the reverse power relay 27 stops detecting reverse power flow, the detection signal S1 changes from 1 to 0, and the intermediate signal S2 begins to decrease at a preset slope. Consequently, the command signal S3 begins to increase.

[0026] When the reverse power relay 27 detects a reverse power flow at time t4, when the power supply from the energy storage system 1A is negative (more specifically, when the power P1(S3) is -1[kW]), the detection signal S1 changes from 0 to 1, and the intermediate signal S2 begins to increase at a preset slope. Consequently, the command signal S3 begins to decrease. After that, when the reverse power relay 27 no longer detects a reverse power flow, the detection signal S1 changes from 1 to 0, and the intermediate signal S2 begins to decrease at a preset slope. Consequently, the command signal S3 begins to increase.

[0027] Even if the power supply from the energy storage system 1A is stopped at time t5 (more specifically, even if the power P1(S3) becomes ±0[kW]), the command signal S3 continues to increase because the reverse power relay 27 still has not detected the reverse power flow. Subsequently, when the reverse power relay 27 detects the reverse power flow, the detection signal S1 changes from 0 to 1, and the intermediate signal S2 begins to increase at a preset slope. Along with this, the command signal S3 begins to decrease.

[0028] When the power supply from the energy storage system 1A is positive (more specifically, power P1(S3) is +1[kW]) at time t6, and the reverse power relay 27 stops detecting reverse power flow, the detection signal S1 changes from 1 to 0, and the intermediate signal S2 begins to decrease at a preset slope. Consequently, the command signal S3 begins to increase.

[0029] Thus, the control unit 10 of the energy storage system 1A according to this embodiment achieves self-consumption using a reverse power relay 27, which is often pre-installed in various facilities, rather than a power meter. Therefore, this configuration makes it possible to save on the cost of installing a power meter.

[0030] Furthermore, when the energy storage system 1A is supplying positive or negative power, the control unit 10 detects a reverse power flow to the grid 20 by the reverse power relay 27 and reduces the power supply at a preset rate. When the reverse power flow is no longer detected, it increases the power supply at a preset rate. According to the energy storage system 1A of this embodiment, by slowly changing the operating state of the bidirectional DC / AC converter 3 and the DC / DC converter 4 through this control of the control unit 10, it is possible to prevent abrupt increases or decreases in positive or negative power supply, and consequently, to prevent an increase in the amount of electricity sold or purchased unnecessarily.

[0031] [Second Example] Figure 4 shows a second embodiment of the present invention, specifically a power storage system 1B. As shown in the figure, the power storage system 1B is installed in parallel with a general load 22 and a solar power generation system (25, 26) on a power line 21 connected to a grid 20. It comprises a bidirectional DC / AC converter 3 connected to the power line 21 via a switch 2, a battery 5 connected to the bidirectional DC / AC converter 3, and a control unit 10 that controls the bidirectional DC / AC converter 3. The power storage system 1B differs from the power storage system 1A in that it does not have a DC / DC converter 4 connected to a solar cell 24 (see Figure 1), but is otherwise similar to the power storage system 1A.

[0032] The energy storage system 1B primarily performs the following operations (1) and (2) when the bidirectional DC / AC converter 3 operates under the control of the control unit 10. (1) The stored power of the battery 5 is supplied to at least one of the specific load 23 and the power line 21 (including the general load 22). (2) Power from the power line 21 is supplied to at least one of the specific load 23 and the storage battery 5.

[0033] According to the energy storage system 1B of this embodiment, the same effects as in the first embodiment can be obtained by slowly changing the operating state of the bidirectional DC / AC converter 3 by the same control of the control unit 10 as in the first embodiment.

[0034] [Differentiation] Although the first and second embodiments of the energy storage system according to the present invention have been described above, the configuration of the present invention is not limited to these.

[0035] For example, the energy storage system 1A may omit switch 2, or may have an additional switch, or may have a large-capacity capacitor to stabilize the voltage at the connection point between the bidirectional DC / AC converter 3, the DC / DC converter 4, and the battery 5, or may have a noise filter at any location. The same applies to the energy storage system 1B.

[0036] Furthermore, energy storage systems 1A and 1B do not need to be connected to the specific load 23.

[0037] The fact that the control unit 10 is composed of a lamp processing unit 11 and a command signal generation unit 12, and that the command signal generation unit 12 determines the command signal S3 according to the formula "S3 = (0.5 - S2) × 2 × Po", is merely one example. [Explanation of Symbols]

[0038] 1A, 1B Energy Storage System 2 Switch 3. Bidirectional DC / AC Conversion Section 4 DC / DC conversion section 5. Storage Battery 10 Control Unit 11 Lamp Processing Unit 12 Command signal generation section 20 Commercial power system 21 Power lines 22 General load 23 Specific load 24 Solar Cells 25 Solar Cells 26 Power Conditioner 27 Reverse power relay

Claims

1. A power storage system is installed in parallel with a general load and a solar power generation system on a power line equipped with a reverse power relay connected to a commercial power grid, and is capable of performing a first operation of storing power supplied from the power line and a second operation of supplying the stored power to the power line, When the first operation described above is being performed and the reverse power relay is detecting a reverse power flow to the commercial power system, the power supplied from the power line is increased at a predetermined gradient. When the first operation is being performed and no reverse power flow is detected, the power supplied from the power line is reduced by a predetermined slope, and when the power reaches zero as a result, the second operation is started. When the second operation described above is being performed and a forward reverse power flow is detected, the power supplied to the power line is reduced by a predetermined slope, and when the power reaches zero as a result, the first operation described above is started. When the second operation described above is being performed and no reverse power flow is detected, the power supplied to the power line is increased at a predetermined rate. A power storage system characterized by the following features.

2. A bidirectional DC / AC converter connected to the aforementioned power line, A storage battery connected to the aforementioned bidirectional DC / AC converter, A DC / DC converter connected to the aforementioned bidirectional DC / AC converter and also connected to a solar cell, Based on whether or not the aforementioned reverse power flow is detected, the control unit controls the bidirectional DC / AC converter and the DC / DC converter. The energy storage system according to claim 1, characterized by comprising:

3. A bidirectional DC / AC converter connected to the aforementioned power line, A storage battery connected to the aforementioned bidirectional DC / AC converter, A control unit that controls the bidirectional DC / AC converter based on whether or not the aforementioned reverse power flow is detected. The energy storage system according to claim 1, characterized by comprising:

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