Input / output upper and lower limit value determination method, power supply control device, and power storage system

Abstract

To provide a determination method for upper / lower limit values of input / output, and a power supply control device and a power storage system that are capable of suppressing fluctuations in SOC of a second power supply.SOLUTION: A determination method for upper / lower limit values of input / output is to set upper / lower values of input / output of an output type battery 12 of a power storage system, including a capacity type battery 11 and the output type battery 12, which has a smaller capacity but a higher output than the capacity type battery 11. The determination method for the upper / lower limit values of input / output includes: a maximum input / output value acquiring step for acquiring the maximum input / output value at each continuous input / output time in a SOC of the output type battery 12; an input / output request value acquiring step for of acquiring an input / output request value of the output type battery 12 at each continuous input / output time; and a determining step for determining the upper / lower values of the input / output of the output type battery 12 from an intersection of the maximum input / output value and the input / output request value having the same continuous input / output time in a graph where a horizontal axis is the SOC and a vertical axis is the maximum input / output value for each continuous input / output time, and a graph where the horizontal axis is the SOC and the vertical axis is the input / output request value for each continuous input / output time.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for determining upper and lower input / output limits, a power supply control device, and a power storage system. [Background technology]

[0002] In the power supply system described in Patent Document 1, due to the demand for high capacity and high output, a high-capacity power supply and a high-output power supply are connected in parallel via a power conversion circuit, etc. This power supply system is installed in a vehicle, and the method of distributing power between the two types of power supplies is changed depending on the driving mode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-187756 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the power supply system described in Patent Document 1 is installed in a vehicle, but there is also a power storage system that charges and discharges to and from a power grid. In such a power storage system, the SOC, which indicates the state of charge of a high-power power supply, can fluctuate significantly when power is distributed by the power company depending on its purpose. For this reason, there is a need to suppress the SOC fluctuations of high-power power supplies. [Means for solving the problem]

[0005] A method for determining upper and lower input / output limits that solves the above-mentioned problem is a method for determining upper and lower input / output limit values of a second power source of a power storage system including a first power source and a second power source that has a smaller capacity but a larger output than the first power source, and includes: a maximum input / output value acquisition step of acquiring a maximum input / output value that can be input / output for each continuous input / output time in an SOC that indicates the state of charge of the second power source; an input / output requirement value acquisition step of acquiring an input / output requirement value that is an input / output value required to return the SOC to a center SOC that serves as the control center when the second power source performs input / output control for each of the continuous input / output times; and a determination step of determining the upper and lower input / output limit values of the second power source from the intersection of the maximum input / output value and the input / output requirement value for the same continuous input / output time on a graph whose first axis is the SOC and whose second axis is the SOC and whose first axis is the input / output requirement value for each of the continuous input / output times.

[0006] According to the above method, the upper and lower limits of input and output at the SOC of the second power source are determined from the intersection of the maximum input and output values and the input and output requirement values for the same continuous input and output time in a graph showing the maximum input and output values for each continuous input and output time at the SOC of the second power source and a graph showing the input and output requirement values for each continuous input and output time at the SOC of the second power source. This allows the upper and lower limits of input and output to be determined taking the maximum input and output values into consideration, and allows the input and output to be set large within a range that does not cause battery degradation. This makes it possible to suppress fluctuations in the SOC of the second power source.

[0007] In the above-described method for determining the upper and lower input / output limits, the absolute values of the determined upper and lower input / output limits have a peak near the SOC at which the maximum input / output value is maximized, and decrease as they move away from the peak.

[0008] Regarding the above-mentioned method for determining input / output upper and lower limit values, it is preferable that the second power source functions to back up the first power source, and when there is no external output request, the second power source inputs the SOC from the first power source so that the SOC returns to the center SOC, and then waits while the SOC is returned to the center SOC.

[0009] According to the above method, the second power supply inputs power from the first power supply to back up the first power supply by outputting a high power when an external output request is received. Therefore, upper and lower limits of the power input and output can be determined taking into account the maximum input and output values, allowing the input and output to be set at a large value. Therefore, fluctuations in the SOC of the second power supply can be suppressed.

[0010] A power supply control device that solves the above problem is a power supply control device that controls a power storage system including a first power supply and a second power supply that has a smaller capacity but a larger output than the first power supply, and obtains the maximum input / output value that can be input / output for each continuous input / output time in the SOC that indicates the state of charge of the second power supply, and obtains an input / output requirement value that is the input / output value required to return the SOC to a center SOC that serves as the control center when the second power supply performs input / output control for each continuous input / output time, and controls the input / output using upper and lower limit values of the input / output of the second power supply determined from the intersection of the maximum input / output value and the input / output requirement value for the same continuous input / output time on a graph whose first axis is the SOC and whose second axis is perpendicular to the first axis is the maximum input / output value for each continuous input / output time, and a graph whose first axis is the SOC and whose second axis is the input / output requirement value for each continuous input / output time.

[0011] According to the above configuration, upper and lower limits of input / output at the SOC of the second power source are controlled from the intersection of the maximum input / output value and the input / output requirement value for the same continuous input / output time in a graph showing the maximum input / output value for each continuous input / output time at the SOC of the second power source and a graph showing the input / output requirement value for each continuous input / output time at the SOC of the second power source. This allows the upper and lower limits of input / output to be determined taking the maximum input / output value into consideration, and allows the input / output to be set large within a range that does not cause battery degradation. This makes it possible to suppress fluctuations in the SOC of the second power source.

[0012] In the above power supply control device, the absolute values of the determined upper and lower limit values of the input and output have a peak near the SOC where the maximum input and output value is maximized, and decrease as they move away from the peak. In the above power supply control device, it is preferable that the second power supply inputs the SOC from the first power supply so as to return the SOC to the central SOC when there is no external output request.

[0013] According to the above configuration, the second power supply provides high output when there is an external output request, and receives input from the first power supply when there is no external output request. Therefore, upper and lower limits of the input and output can be determined taking into account the maximum input and output values, allowing the input and output to be set at a large value. Therefore, fluctuations in the SOC of the second power supply can be suppressed.

[0014] The power storage system that solves the above problem includes a first power source, a second power source that has a smaller capacity but a larger output than the first power source, and the above power source control device. According to the above configuration, the upper and lower limits of the input / output for the SOC of the second power source are controlled from the intersection of the maximum input / output value and the input / output requirement value for the same continuous input / output time in a graph showing the maximum input / output value for each continuous input / output time at the SOC of the second power source and a graph showing the input / output requirement value for each continuous input / output time at the SOC of the second power source. This allows the upper and lower limits of the input / output to be determined taking the maximum input / output value into consideration, allowing the input / output to be set at a large value. This makes it possible to suppress fluctuations in the SOC of the second power source. [Effects of the Invention]

[0015] According to the present invention, fluctuations in the SOC of a high-output power supply can be suppressed. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a power storage system. [Figure 2] 3 is a diagram showing a calculation process of an output value performed by the power supply control device of the embodiment. [Figure 3] 6 is a graph showing maximum input / output values and input / output requirement values of a second power source of the power supply control device of the embodiment. [Figure 4] 6 is a graph showing upper and lower limit values of input and output of a second power source of the power storage system of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] An embodiment of a power supply control device and a power storage system will be described below with reference to Figures 1 to 4. In the power storage system, the power supply control device controls the output from and input to the power supply.

[0018] (Energy Storage System 10) As shown in FIG. 1, a power storage system 10 is connected to a commercial power grid 1 and inputs and outputs power to and from the commercial power grid 1. The power storage system 10 includes a capacity battery 11, an output battery 12, and a power supply control device 20. The capacity battery 11 corresponds to a first power source and has a larger capacity than the output battery 12. The capacity battery 11 is, for example, a lithium-ion secondary battery. The output battery 12 corresponds to a second power source and has a larger output than the capacity battery 11. The output battery 12 is, for example, a nickel-metal hydride secondary battery. The output battery 12 functions to back up the capacity battery 11 when output is required. For this reason, the power supply control device 20 waits, returning the SOC indicating the state of charge to a central SOC, in order to respond to sudden requests. When there is no output request from the external commercial power grid 1, the power supply control device 20 inputs power from the capacity battery 11 to the output battery 12. For this reason, the output battery 12 inputs and outputs power so as to return its SOC to the central SOC. The central SOC is the SOC that serves as the control center when controlling input and output. The central SOC can be set arbitrarily.

[0019] A first measuring instrument 11A that measures the voltage, current, etc. of the capacitive battery 11 is provided on the connection line between the capacitive battery 11 and the commercial power grid 1. The first measuring instrument 11A outputs the measurement results to the power supply control device 20. A second measuring instrument 12A that measures the voltage, current, etc. of the output-type battery 12 is provided on the connection line between the output-type battery 12 and the commercial power grid 1. The second measuring instrument 12A outputs the measurement results to the power supply control device 20. The power supply control device 20 calculates the SOC of the capacitive battery 11 from the measurement results of the first measuring instrument 11A. The power supply control device 20 also calculates the SOC of the output-type battery 12 from the measurement results of the second measuring instrument 12A.

[0020] (Power supply control device 20) The Power Control Device 20 may be configured as one or more processors that execute various processes according to a computer program (software). The processes executed by the Power Control Device 20, i.e., the processor, include a method for determining upper and lower input / output limits. The method for determining upper and lower input / output limits includes a maximum input / output value acquisition step, an input / output demand value acquisition step, and a determination step, as described below. The Power Control Device 20 may also be configured as a circuit including one or more dedicated hardware circuits, such as an application-specific integrated circuit (ASIC), or a combination thereof, that execute at least some of the various processes. The processor includes a CPU and memory, such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to execute the processes. The memory, i.e., computer-readable medium, includes any available medium accessible by a general-purpose or special-purpose computer. The programs stored on the computer-readable medium include an input / output determination program. The input / output determination program causes the Power Control Device 20 to execute the maximum input / output value acquisition step, the input / output demand value acquisition step, and the determination step.

[0021] The power supply control device 20 includes an acquisition unit 21 and a determination unit 22. The acquisition unit 21 acquires the maximum input / output values that can be input / output during each continuous input / output time period at the SOC of the output-type battery 12. The acquisition unit 21 corresponds to a maximum input / output value acquisition unit. The acquisition unit 21 also acquires input / output requirement values, which are input / output values required for the output-type battery 12 to return its SOC to the center SOC during each continuous input / output time period. The acquisition unit 21 corresponds to an input / output requirement value acquisition unit. The determination unit 22 determines the upper and lower limit values of the input / output of the output-type battery 12 based on the maximum input / output value and the input / output requirement value during each continuous input / output time period.

[0022] (Output value calculation process) Next, the calculation process of the output value of the power supply control device 20 will be described with reference to Fig. 2. When there is an output request from the commercial power grid 1, the power supply control device 20 calculates the output value according to the requested power.

[0023] First, the power supply control device 20 acquires the SOC of the output-type battery 12 and calculates the input / output instruction values of the output-type battery 12 (step S1). That is, the power supply control device 20 calculates the input / output instruction values of the output-type battery 12 so that the SOC of the output-type battery 12 returns to the center SOC. The power supply control device 20 calculates the input / output instruction values based on upper and lower limit values of input / output for the output request.

[0024] Next, the power supply control device 20 calculates the power required by the capacity battery 11 (step S2). That is, the power required by the capacity battery 11 is calculated by subtracting the input / output instruction value of the output battery 12 calculated in step S1 from the output request of the commercial power grid 1.

[0025] Next, the power supply control device 20 calculates the power requirement of the output-type battery 12 (step S3). That is, the power requirement of the output-type battery 12 is calculated by subtracting the power requirement of the capacity-type battery 11 calculated in step S2 from the output requirement of the commercial power grid 1.

[0026] Next, the power supply control device 20 can obtain the output of the capacity type battery 11 calculated in step S1 and the output of the output type battery 12 calculated in step S2 as output values.

[0027] (Calculation of upper and lower limits of input and output) Next, with reference to Figures 3 and 4, the calculation of the upper and lower limit values of the input and output of the output type battery 12 by the power supply control device 20 will be described. The upper and lower limit values of the input and output are calculated and set in advance. The power supply control device 20 may calculate and update the upper and lower limit values of the input and output at any timing. In this embodiment, the center SOC of the output type battery 12 is set to 60%. In Figures 3 and 4, the horizontal axis, which is the first axis, represents the SOC, and the vertical axis, which is the second axis perpendicular to the first axis, represents the input and output value.

[0028] The power supply control device 20 acquires the maximum input / output value graphs A1, A2, A3, ... and the input / output demand value graphs B1, B2, B3, ... in advance when the output-type battery 12 is installed in the power storage system 10. This process corresponds to a maximum input / output value acquisition step and an input / output demand value acquisition step.

[0029] As shown in FIG. 3 , the mountain-shaped graphs A1, A2, A3, etc. show the maximum input / output values that can be input / output at each continuous input / output time at the SOC of the power-generating battery 12, with the peak at the SOC at which the maximum input / output value is greatest. The graphs A1, A2, A3, etc. show that the maximum input / output value decreases as the continuous input / output time increases. While the graphs show continuous input / output times up to 3 seconds, the graphs remain similar even after 4 seconds. Furthermore, graphs B1, B2, B3, etc., where the input / output value passes through zero at a center SOC of 60%, show the input / output demand value, which is the input / output value required for the power-generating battery 12 to return its SOC to the center SOC during each continuous input / output time. The maximum input / output value decreases and the slope becomes shallower as the continuous input / output time increases. While the graphs show continuous input / output times up to 3 seconds, the graphs remain similar even after 4 seconds.

[0030] Note that Figure 3 only shows the maximum input / output values and input / output demand values on the discharge side where the SOC is 60% or higher. Maximum input / output values and input / output demand values also exist on the charge side where the SOC is below 60%, and the graph is point-symmetrical with respect to the discharge side and the center SOC, but these are omitted here. The graph of maximum input / output values on the charge side is a downward-convex mountain shape. The graph of input / output demand values on the charge side shows that the input demand value increases as the SOC decreases from the center SOC. Therefore, on the discharge side as well, the upper and lower input / output limit values can be obtained by connecting the intersections of the maximum input / output values and input / output demand values for each continuous input / output time.

[0031] In FIG. 3, the SOC at which the maximum input / output values are maximized and the center SOC are the same, but they do not have to be the same. In other words, the SOC at which the maximum input / output values are maximized is determined by the battery, and the center SOC is set by the user. In particular, graphs A1, A2, A3, ... have a peak near the SOC at which the maximum input / output values are maximized, and decrease as they move away from the peak. The graph in FIG. 4 is an example, and the shape of the graph changes when the center SOC setting is changed.

[0032] The determination unit 22 calculates the intersections between the graphs A1, A2, A3, ... of maximum input / output values and the graphs B1, B2, B3, ... of input / output request values, which have the same continuous input / output time. The determination unit 22 can then determine the upper and lower limit values of the input / output by connecting the calculated intersections. This process corresponds to the determination step.

[0033] As shown in FIG. 4, the absolute values of the determined upper and lower limit values of input and output have peaks on both the charge and discharge sides near the SOC where the maximum input and output values are greatest, and decrease as they move away from the peaks.

[0034] The power supply control device 20 determines input / output instruction values based on the determined upper and lower limit values of input / output and the output request. If the input / output value of the output request is smaller than the upper or lower limit values, the power supply control device 20 sets the output request as the input / output instruction value, and if the input / output value of the output request is larger than the upper or lower limit values, the power supply control device 20 sets the upper or lower limit values as the input / output instruction value.

[0035] According to the above, the upper and lower limit values of the input and output can be determined taking into consideration the maximum input and output values, and the input and output can be set to large values. Next, the effects of this embodiment will be described.

[0036] (1) The upper and lower limits of input and output at the SOC of the output-type battery 12 are determined from the intersection of the maximum input and output values and the required input and output values for the same continuous input and output time between graphs A1, A2, A3, ... showing the maximum input and output values for each continuous input and output time at the SOC of the output-type battery 12 and graphs B1, B2, B3, ... showing the required input and output values for each continuous input and output time at the SOC of the output-type battery 12. This allows the upper and lower limits of input and output to be determined taking the maximum input and output values into consideration, and allows the input and output to be set large within a range that does not cause battery degradation. This makes it possible to suppress fluctuations in the SOC of the output-type battery 12.

[0037] (2) When there is an external output request, the output-type battery 12 backs up the capacity-type battery 11 by providing high output, so when there is no external output request, power is input from the capacity-type battery 11. Therefore, the upper and lower limits of the input and output of this power can be determined taking into account the maximum input and output values, and the input and output can be set to be large. This makes it possible to suppress fluctuations in the SOC of the output-type battery 12.

[0038] (Other embodiments) The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0039] In the above embodiment, the absolute values of the determined upper and lower input / output limits peak near the center SOC and decrease as the SOC becomes larger because the SOC at which the maximum input / output values are maximized coincides with the center SOC. However, if the SOC at which the maximum input / output values are maximized does not coincide with the center SOC, the absolute values of the determined upper and lower input / output limits become zero at the center SOC, peak near the center SOC, and do not decrease as the SOC becomes larger. Such upper and lower input / output limits are also acceptable. Even with such upper and lower input / output limits, the input / output can be set large, thereby suppressing fluctuations in the SOC of the output-type battery 12.

[0040] In the above embodiment, the first axis of SOC is the horizontal axis and the second axis of input / output values is the vertical axis. However, the first axis of SOC may be the vertical axis and the second axis of input / output values may be the horizontal axis. In the above embodiment, the power supply control device 20 determines the upper and lower limit values of the input and output. However, the power supply control device 20 may not include the acquisition unit 21 and the determination unit 22, and may control the input and output using upper and lower limit values that have been similarly determined in advance by another device.

[0041] In the above embodiment, the capacity battery 11, which is the first power source, is a lithium ion secondary battery, and the output battery 12, which is the second power source, is a nickel-metal hydride secondary battery. However, the first power source and the second power source may be combined in other ways as long as the second power source has a smaller capacity but a larger output than the first power source.

[0042] In the above embodiment, the power storage system 10 is connected to the commercial power grid 1. However, the power storage system 10 is not limited to being connected to the commercial power grid 1, and may be connected to other devices that require a power source. [Explanation of symbols]

[0043] 1…Commercial power grid 10...Energy storage system 11...Capacitive battery, the first power source 11A...First measuring instrument 12...Output battery as second power source 12A...Second measuring instrument 20...Power supply control device 21…Acquisition part 22...Decision Section

Claims

1. 1. A method for determining upper and lower input / output limit values for a power storage system including a first power source and a second power source having a smaller capacity but a larger output than the first power source, the method comprising: a maximum input / output value acquisition step of acquiring a maximum input / output value that can be input / output during each continuous input / output time in an SOC that indicates a state of charge of the second power source; an input / output requirement value acquisition step of acquiring an input / output requirement value that is an input / output value required to return the SOC to a center SOC that serves as a control center when the second power source performs input / output control during each of the continuous input / output times; a determination step of determining upper and lower limit values of input / output of the second power source from an intersection of the maximum input / output value and the input / output required value for the same continuous input / output time between a graph having a first axis representing the SOC and a second axis perpendicular to the first axis representing the maximum input / output value for each continuous input / output time, and a graph having the first axis representing the SOC and the second axis representing the input / output required value for each continuous input / output time. How to determine upper and lower input / output limits.

2. The absolute values of the determined upper and lower limit values of the input and output have a peak near the SOC at which the maximum input and output value is maximized, and decrease as they move away from the peak. The method for determining upper and lower input / output limits according to claim 1.

3. The second power supply functions to back up the first power supply, and when there is no external output request, the second power supply inputs the SOC from the first power supply so as to return the SOC to the central SOC, and waits while returning the SOC to the central SOC.

3. The method for determining upper and lower input / output limits according to claim 1 or 2.

4. A power supply control device that controls a power storage system including a first power supply and a second power supply that has a smaller capacity but a larger output than the first power supply, obtaining a maximum input / output value that can be input / output during each continuous input / output time in an SOC that indicates the state of charge of the second power source; acquire an input / output requirement value that is an input / output value required to return the SOC to a center SOC that serves as a control center when the second power source performs input / output control during each of the continuous input / output times; Control is performed using upper and lower limit values of the input / output of the second power source determined from the intersection of the maximum input / output value and the input / output required value for the same continuous input / output time in a graph in which a first axis is the SOC and a second axis perpendicular to the first axis is the maximum input / output value for each continuous input / output time, and a graph in which the first axis is the SOC and the second axis is the input / output required value for each continuous input / output time. Power control device.

5. The absolute values of the determined upper and lower limit values of the input and output have a peak near the SOC at which the maximum input and output value is maximized, and decrease as the value moves away from the peak. The power supply control device according to claim 4 .

6. The second power supply receives an input from the first power supply so that the SOC returns to the center SOC when there is no external output request. The power supply control device according to claim 4 .

7. a first power source; a second power source having a smaller capacity but a larger output than the first power source; The power supply control device according to any one of claims 4 to 6, Energy storage system.

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