Energy storage device, method for controlling an energy storage device, and power control device.

Abstract

To provide a power storage device capable of reducing a loss of power outputted by a power generation device, a control method for the power storage device, and a power control device.SOLUTION: A power storage device 10 comprises: a storage battery 14; an input terminal 18 which is configured connectable to a power generation device 40; a power conversion section 153 by which a current is pulled in from the power generation device 40 through the input terminal 18 and power is stored in the storage battery 14; a measurement section 12 which measures the pulled-in current; and a control section 11 which controls the power conversion section 153. As a procedure for setting a target current, the control section 11 executes the steps of: controlling the power conversion section 153 so as to increase the pulled-in current; acquiring a measurement of the pulled-in current; and setting the target current on the basis of a measurement just before the measurement of the pulled-in current falls in a case where the measurement of the pulled-in current falls. The control section controls the power conversion section 153 in such a manner that the pulled-in current becomes the set value of the target current.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a power storage device, a control method for the power storage device, and a power control device.

Background Art

[0002] There is known a system that improves the charging efficiency of a storage battery by adjusting the charging power output from an AC / DC converter that converts the power generated by a solar panel from AC to DC and charges the storage battery (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the power storage device draws current from the power generation device, the drawn current is limited so that the power generation device does not fall into an overload state. If the drawn current is excessively limited, the power that is not stored in the power storage device among the output of the power generation device is lost. It is required to reduce the loss of the power output by the power generation device.

[0005] An object of the present disclosure is to provide a power storage device, a control method for the power storage device, and a power control device that can reduce the loss of the power output by the power generation device.

Means for Solving the Problems

[0006] An energy storage device according to one embodiment of the present disclosure comprises a battery, an input terminal configured to be connectable to a power generation device, a power conversion unit, a measurement unit, and a control unit. The power conversion unit draws current from the power generation device through the input terminal and stores it in the battery. The measurement unit measures the current drawn in from the power generation device through the input terminal. The control unit controls the power conversion unit. The control unit performs a procedure to set a target current, which is a target value of the current to be drawn from the power generation device to the power conversion unit. The procedure to set the target current includes controlling the power conversion unit so that the drawn current increases. The procedure to set the target current includes obtaining a measurement of the drawn current while the power conversion unit is being controlled to increase the drawn current. The procedure to set the target current includes setting the target current based on the measurement immediately before the measurement of the drawn current drops if the measurement of the drawn current drops while the power conversion unit is being controlled to increase the drawn current. The control unit controls the power conversion unit so that the drawn current reaches the set value of the target current.

[0007] A method for controlling an energy storage device according to one embodiment of the present disclosure is a method for controlling an energy storage device comprising a battery, an input terminal configured to be connectable to a power generation device, a power conversion unit, a measuring unit, and a control unit. The power conversion unit draws current from the power generation device through the input terminal and stores it in the battery. The measuring unit measures the current drawn in from the power generation device through the input terminal. The control unit controls the power conversion unit. The method for controlling the energy storage device includes the control unit setting a target current, which is a target value of the current to be drawn in from the power generation device to the power conversion unit. The method for controlling the energy storage device includes the control unit controlling the power conversion unit so that the drawn current becomes the set value of the target current. The control unit setting the target current includes controlling the power conversion unit so that the drawn current increases. The control unit setting the target current includes obtaining a measurement of the drawn current while controlling the power conversion unit so that the drawn current increases. Setting the target current by the control unit includes setting the target current based on the measurement value immediately before the drop in the measured value of the incoming current, if the measured value of the incoming current drops while the control unit is controlling the power conversion unit to increase the incoming current. In this disclosure, "a drop in the measured value of the incoming current" refers to a situation where, while the system is being controlled to increase the incoming current, the current value rapidly decreases to below the stop threshold or to zero.

[0008] A power control device according to one embodiment of the present disclosure controls an energy storage device having a battery, an input terminal configured to be connectable to a power generation device, and a power conversion unit that draws current from the power generation device through the input terminal and stores it in the battery. The power control device comprises a control unit that controls the power conversion unit and a measuring unit that measures the incoming current drawn from the power generation device through the input terminal. The control unit performs a procedure to set a target current, which is a target value of the current to be drawn from the power generation device to the power conversion unit. The procedure to set the target current includes controlling the power conversion unit so that the incoming current increases. The procedure to set the target current includes obtaining a measurement of the incoming current while the power conversion unit is being controlled to increase the incoming current. The procedure to set the target current includes setting the target current based on the measurement immediately before the measurement of the incoming current drops if the measurement of the incoming current drops while the power conversion unit is being controlled to increase the incoming current. The control unit controls the power conversion unit so that the incoming current reaches the set value of the target current. [Effects of the Invention]

[0009] According to an embodiment of the energy storage device, a control method for the energy storage device, and a power control device of this disclosure, the loss of power output by the power generation device is reduced compared to the case where the components of this disclosure are not present. [Brief explanation of the drawing]

[0010] [Figure 1] This block diagram shows an example configuration of a power control system according to one embodiment. [Figure 2] This diagram illustrates the potential surplus output current that may arise when setting the incoming current of a power storage device while considering the error range of the output current of the power generation device. [Figure 3] This diagram illustrates the increase or decrease in the set value of the incoming current for a power storage device. [Figure 4] This graph shows an example of the time variation of measured current when the current is controlled to increase. [Figure 5]This flowchart shows an example of a procedure for controlling an energy storage device according to one embodiment. [Modes for carrying out the invention]

[0011] For example, when a storage device draws in and stores the output current from an external power generation device such as a solar power generation device, the storage device prevents the external power generation device from overloading and shutting down by reducing the incoming current when it determines that the output current from the external power generation device is insufficient.

[0012] However, underestimating the output current from the external power generator can cause the energy storage device to reduce the incoming current too much. Specifically, when the energy storage device sets the incoming current based on the current measurement value of the external power generator, if the current measurement value of the external power generator includes an error that results in a small measurement, the energy storage device may reduce the set value of the incoming current too much. When the energy storage device reduces the incoming current too much, the current from the external power generator that is not drawn into the energy storage device becomes a loss. To minimize this loss, the energy storage device is required to set the incoming current appropriately. When the external power generator is a stable power source, the energy storage device can set the incoming current according to the capacity of the external power generator so as to minimize the loss of output current from the external power generator. In this disclosure, a stable power source is defined as an external generator that has the capacity to output current without overloading the incoming current required by the energy storage device, within a current range that takes into account the rated error relative to the rated current.

[0013] Hereinafter, as one embodiment of the present disclosure, a power control system 1 (see Figure 1) and an energy storage device 10 (see Figure 1) that can reduce the power loss output by an external generator, which is a power generation device 40 (see Figure 1), will be described.

[0014] (Example configuration of power control system 1) As shown in Figure 1, a power control system 1 according to one embodiment includes a power storage device 10, a load 30 and a specific load 32, and a power generation device 40.

[0015] The power control system 1 is connected to the power grid 80. The power grid 80 supplies alternating current power to the load 30 and the energy storage device 10. The power generation device 40 supplies alternating current power to the energy storage device 10.

[0016] The energy storage device 10 draws current from the power generation device 40 and charges the storage battery 14. The energy storage device 10 supplies the discharge current of the storage battery 14 or the current drawn from the power generation device 40 to the load 30 or a specific load 32. The energy storage device 10 may feed the discharge current of the storage battery 14 or the current drawn from the power generation device 40 back to the power grid 80 in reverse power flow.

[0017] The load 30 operates by receiving power supply from the power grid 80. The load 30 may become inoperable when a power outage occurs in the power grid 80. The energy storage device 10 may operate to supply power to the load 30 when a power outage occurs in the power grid 80. The load 30 may resume operation by receiving power supply from the energy storage device 10. The specific load 32 operates by continuously receiving power supply from the energy storage device 10 regardless of whether a power outage occurs in the power grid 80.

[0018] <Energy storage device 10> The energy storage device 10 includes a control unit 11, a storage unit 12, a measurement unit 13, a storage battery 14, power conversion units 151 to 153, CTs (Current Transformers) 161 to 162, switches 171 to 174, and an input terminal 18. The energy storage device 10 is connected to the power generation device 40 at the input terminal 18. In other words, the input terminal 18 is configured to be connectable to the power generation device 40.

[0019] The storage battery 14 may be configured to include a secondary battery such as a lithium-ion battery.

[0020] It is assumed that the power conversion unit 151 is a DC-DC converter. It is assumed that the power conversion unit 152 is a bidirectional inverter that converts DC and AC bidirectionally. When the power generation device 40 supplies alternating current power, it is assumed that the power conversion unit 153 is an AC-DC converter that converts AC to DC. When the power generation device 40 supplies direct current power, it is assumed that the power conversion unit 153 is a DC-DC converter.

[0021] The power conversion unit 152 is connected to the power grid 80, the load 30, and the specific load 32 on the AC side. When the power generation device 40 supplies AC power, the power conversion unit 153 is connected to the power generation device 40 on the AC side. When the power generation device 40 supplies DC power, the power conversion unit 153, which is a DC-DC converter, is connected to the power generation device 40 at one end on the DC side. When the power generation device 40 supplies AC power, the power conversion unit 152 and the power conversion unit 153 are connected to each other on the DC side. When the power generation device 40 supplies DC power, the power conversion unit 153, which is a DC-DC converter, is connected to the DC side of the power conversion unit 152 at the other end on the DC side. Also, one end of the DC side of the power conversion unit 151 is connected to the storage battery 14. The other end of the DC side of the power conversion unit 151 is connected to the wiring where the DC sides of the power conversion units 152 and 153 are connected to each other.

[0022] The power conversion units 151 and 153 draw current from the power generation device 40 through the input terminal 18 and store it in the storage battery 14.

[0023] CT161 is a sensor for measuring the current flowing through the storage battery 14 or the current output from the storage battery 14. CT162 is a sensor for measuring the drawn current from the power generation device 40. The drawn current is the current drawn by the power storage device 10 from the power generation device 40. Hereinafter, acquiring the measured value of the CT means measuring the current value using the CT.

[0024] Switches 171 to 174 are controlled to either a closed state, which allows conductivity between the two terminals, or an open state, which insulates the two terminals. The control unit 11 may control the open / closed state of switches 171 to 174. Switch 171 is connected between the power conversion unit 151 and the storage battery 14. Switch 172 is connected between the power conversion unit 153 and the input terminal 18. In other words, switch 172 is connected between the power conversion unit 153 and the power generator 40. Switch 173 is connected between the power conversion unit 152 and the power grid 80 and the load 30. Switch 174 is connected between the power conversion unit 152 and the specific load 32. The power control system 1 does not necessarily have to include switches 174 and the specific load 32.

[0025] The measurement unit 13 acquires the measured value of the incoming current of the CT 162. The control unit 11 acquires the measured value of the incoming current from the measurement unit 13 and stores the acquired measured value in the storage unit 12. The control unit 11 may also control the incoming current from the power generator 40 by controlling the power conversion units 151 to 153. The control unit 11 may also control the open / closed state of switches 171 to 174.

[0026] The control unit 11 may include at least one processor to provide control and processing capabilities for performing various functions of the energy storage device 10. The processor may include a CPU (Central Processing Unit). The processor can execute programs that realize various functions of the energy storage device 10. The processor may be implemented as a single integrated circuit. An integrated circuit is also called an IC (Integrated Circuit). The processor may be implemented as a plurality of communicably connected integrated circuits and discrete circuits. The processor may be implemented based on various other known technologies.

[0027] The storage unit 12 may store various information, or programs for operating each component of the energy storage device 10. The storage unit 12 may be composed of, for example, a semiconductor memory. The storage unit 12 may function as the work memory of the control unit 11. The storage unit 12 may be included in the control unit 11.

[0028] The measurement unit 13 acquires the measurement value of the CT 162. The measurement value of the CT 162 is the measurement value of the incoming current drawn in from the power generation device 40 through the input terminal 18. In other words, the measurement unit 13 measures the incoming current drawn in from the power generation device 40 through the input terminal 18. The measurement unit 13 may be equipped with a communication interface to acquire measurement value information from the CT 162. The measurement unit 13 may be connected to the CT 162 via wired or wireless communication.

[0029] The control unit 11, the storage unit 12, and the measurement unit 13 may be configured as an integrated device such as a server. The control unit 11, the storage unit 12, and the measurement unit 13 may be configured as a separate power control device from the energy storage device 10.

[0030] <Power generator 40> The power generation device 40 may include, for example, a power generation device such as a fuel cell. The power generation device 40 may also include a power conditioner (PCS: Power Conditioning System) that adjusts the current or voltage of the generated power so that the power generated by the power generation device is drawn into the energy storage device 10. Devices that generate power using devices such as fuel cells, energy storage devices, or engine generators may be included in the stable power supply described above. The power generation device may also include devices that are not stable power supplies and generate power using renewable energy sources such as solar power or wind power.

[0031] The power conditioner may include a power conversion device such as a converter or inverter. The power conditioner may convert the DC power output by the power generation device into AC power. The power conditioner may convert the DC power output by the power generation device into DC power of a different voltage. The power conditioner outputs the converted power to the energy storage device 10.

[0032] The power generator 40 is equipped with a current transformer (CT) 41 for measuring the current output to the energy storage device 10. The CT 41 is connected between the power generator 40 and the input terminal 18 of the energy storage device 10. The power generator 40 also has an overload protection function that stops the output if the current value measured using the CT 41 exceeds the maximum rated output.

[0033] The number of power generation devices 40 is not limited to one, but may be two or more. The number of power generation devices included in one power generation device 40 is not limited to one, but may be two or more.

[0034] (Example of operation of power control system 1) The control unit 11 of the energy storage device 10 may control the current drawn by the power conversion unit 153 from the power generation device 40. Specifically, the control unit 11 sets a target current, which is a target value for the current drawn by the power conversion unit 153 from the power generation device 40. Based on the measured value of the drawn current, the control unit 11 controls the power conversion unit 153 so that the drawn current becomes the target current.

[0035] The actual current that can be output from the power generator 40 is within the rated error range relative to the rated current of the power generator 40. If the current that the energy storage device 10 requests to draw from the power generator 40 is greater than the current that the power generator 40 can actually output, the power generator 40 will be overloaded and shut down. In other words, if the current that the energy storage device 10 requests from the power generator 40 exceeds the current capacity that the power generator 40 can actually output, the power generator 40 will be overloaded and shut down. Therefore, the control unit 11 of the energy storage device 10 controls the power conversion unit 153 so that the current it requests from the power generator 40 does not exceed the current capacity that the power generator 40 can actually output.

[0036] For example, as shown in Figure 2, if the output current rating of the power generator 40 is 7.00A, and the actual error range of the current that can be output is ±2%, then the actual current output capacity of the power generator 40 is in the range of 6.86A to 7.14A. In this case, in order for the current that the energy storage device 10 requests from the power generator 40 not to exceed the actual current output capacity of the power generator 40, the energy storage device 10 needs to control the power conversion unit 153 so that the incoming current that the energy storage device 10 actually draws in is 6.86A or less.

[0037] Here, the incoming current of the energy storage device 10 is controlled based on the measurement of the incoming current by the CT 162. For example, let's assume that the measurement error of the CT 162 is ±2%. In this case, when the energy storage device 10 sets a target current and controls the power conversion unit 153, the range of current that the power conversion unit 153 may actually draw in is within an error range of ±2% of the target current. In order to ensure that the current requested by the energy storage device 10 from the power generator 40 does not exceed the current output capacity of the power generator 40, the upper limit of the error range of the target current needs to be 6.86A or less. Therefore, the energy storage device 10 needs to set the target current to 6.72A so that +2% of the target current is 6.86A.

[0038] In the example described above, if the energy storage device 10 is set to a target current of 6.72A and the measurement error of the CT162 is -2%, the actual incoming current may only be 6.58A. On the other hand, if the current that the power generator 40 actually outputs is +2% of the rated current, the actual output current may be 7.14A. In this case, since the output current of the power generator 40 is 7.14A and the incoming current of the energy storage device 10 is only 6.58A, there is a surplus current of 0.56A that is not drawn in. This surplus current of 0.56A can be a loss. In other words, the loss can be the sum of the error in the rated output current of the power generator 40 and the error in the measurement of the CT162.

[0039] As a control method for the comparative example, one could set the target current to a larger value, and if the overload protection function of the power generator 40 is activated, it could be determined that the actual output current of the power generator 40 is below the rated value, and the target current could be lowered. However, with this method, losses continue to occur by the amount of the lowered target current.

[0040] Therefore, the control unit 11 of the energy storage device 10 according to one embodiment of this disclosure sets a target current to minimize the loss of output current from the power generator 40 that occurs when the design takes into account the error of the CT 162 that measures the incoming current. For example, as shown in Figure 3, suppose the error range of the output current of the power generator 40 is in the range of 6.86A to 7.14A. On the other hand, suppose the initial setting value of the incoming current of the energy storage device 10 is 7.00A. The initial setting value is the target current set when the energy storage device 10 is shipped from the factory. The control unit 11 raises the set value of the incoming current as the target current when the actual output current of the power generator 40 is greater than 7.00A. The control unit 11 lowers the set value of the incoming current as the target current when the actual output current of the power generator 40 is less than 7.00A. The control unit 11 controls the incoming current so that it approaches the target current. By raising or lowering the set value of the incoming current according to the actual output current of the power generation device 40, the difference between the output current from the power generation device 40 and the incoming current of the energy storage device 10 is reduced. As a result, the loss of output current from the power generation device 40 is reduced.

[0041] Specifically, the control unit 11 performs the following procedure to set a target current, which is the target value of the current to be drawn from the power generator 40 to the power conversion unit 153. The control unit 11 controls the power conversion unit 153 to increase the incoming current and obtains a measurement of the incoming current while the power conversion unit 153 is being controlled to increase the incoming current. The control unit 11 may store the measurement of the incoming current in the storage unit 12.

[0042] The control unit 11 can obtain a relationship that can be represented by a graph showing that the value of the current drawn from the power generator 40 increases as time progresses, for example, as shown in Figure 4. In the graph in Figure 4, the horizontal axis represents time, and the vertical axis represents the value of the current drawn from the power generator 40. The control unit 11 controls the power conversion unit 153 to increase the value of the current drawn from the power generator 40 to 6.72A, 6.79A, 6.86A, and 6.93A when the time reaches T1, T2, T3, and T4, respectively.

[0043] The times T1 to T4 correspond to the times when the measurement unit 13 samples the measured value of CT162. The interval between times T1 to T4 is assumed to be the sampling period of the measurement unit 13. The sampling period of the measurement unit 13 may be set to, for example, 1 second or 0.1 seconds. The sampling period of the measurement unit 13 is not limited to these examples and may be set to various values.

[0044] In the graph of Figure 4, the increase in current value per unit time is constant. However, the increase in current value does not have to be constant. In other words, the relationship between time and current value may be represented by a straight line graph, or by a broken line or curved line graph.

[0045] The control unit 11 increases the current value to 6.93A at time T4, and then controls the power conversion unit 153 to further increase the current value. However, as shown in the graph in Figure 4, at time TS after time T4, the current value decreases sharply and falls below the stop judgment value or to zero. This phenomenon of the current value dropping is caused by an overload stop of the power generator 40. The control unit 11 sets the target current based on the measured value of the incoming current immediately before the incoming current drops while the power conversion unit 153 is being controlled to increase the incoming current. The measured value of the incoming current immediately before the incoming current drops while the power conversion unit 153 is being controlled to increase the incoming current is also called the immediate prior measurement value. For example, if the control unit 11 has acquired the measurement value as shown in the graph in Figure 4, it may acquire the current value of 6.93A at time T4 as the immediate prior measurement value and set the target current to 6.93A. If the control unit 11 has stored the measured value of the incoming current in the storage unit 12, it may acquire the immediate prior measurement value from the storage unit 12. In this disclosure, "the measured value of the incoming current drops" refers to a situation where, while the system is being controlled to increase the incoming current, the current value rapidly decreases to below the stop threshold or to zero.

[0046] The stop judgment value is a threshold value compared with the measured value of the incoming current in order to determine that the power generator 40 has stopped due to overload. The stop judgment value may be determined based on the characteristics of the output current when the power generator 40 stops due to overload. The stop judgment value may be set in the storage unit 12 at the time of factory shipment. The stop judgment value may be determined based on noise or offset of the measured value output by the CT 162 when the incoming current becomes zero. The control unit 11 may determine that the incoming current has dropped when the measured value of the incoming current falls below the stop judgment value, or it may determine that the incoming current has dropped when the measured value of the incoming current becomes zero.

[0047] The most recent measurement may be a measurement taken at a time determined based on the time when the measured value of the incoming current dropped. For example, the measured value of the incoming current at a time a grace period before the time when the measured value of the incoming current dropped may be adopted as the most recent measurement. The grace period may be determined, for example, based on the sampling period in which the measurement unit 13 samples the measured value of the incoming current by the CT162. If the grace period is set to the time of one sampling period, the measurement obtained in the sampling one sampling period before the sampling when the measured value of the incoming current dropped will be adopted as the most recent measurement.

[0048] If the power generator 40 is set to shut down under overload conditions that the incoming current continues for at least one hour, the grace period may be determined based on the first hour. For example, if the first hour is set to 0.5 seconds, the grace period may be set to 1 second or more. If one sampling period is 1 second, in the graph of Figure 4, the target current may be set to 6.86A, which is the measured value of the incoming current at time T3, at least 1 second before time TS.

[0049] The control unit 11 may set the target current to the immediately preceding measurement value. The control unit 11 may also set the target current to a value obtained by multiplying the immediately preceding measurement value by an attenuation coefficient. The attenuation coefficient may be, for example, 0.99. In other words, the control unit 11 may set the target current to a value obtained by subtracting 1% from the immediately preceding measurement value.

[0050] The control unit 11 controls the power conversion unit 153 so that the incoming current becomes the target current. By controlling the power conversion unit 153 using the measured value when the incoming current is not dropping as the target current, the control unit 11 can draw in a current close to the upper limit that the power generator 40 can output.

[0051] The control unit 11 may control the power conversion unit 153 so that the current value of the incoming current increases until it reaches an upper limit, as long as the current value of the incoming current does not decrease rapidly. The upper limit may be set based on the power conversion unit 153's ability to draw in current, i.e., the power that the power conversion unit 153 can receive. The upper limit may also be set based on the measurement error of the CT 162. If the current value does not decrease rapidly while the control unit 11 is controlling the power conversion unit 153 to increase the current value until it reaches an upper limit, the control unit 11 may determine that the power generator 40 can output a current greater than or equal to the upper limit and set the target current to the upper limit.

[0052] The control unit 11 may calculate the target current by the product of the initial current and the target setting coefficient. The initial current is the initial value set in the energy storage device 10, for example, the value set at the time of factory shipment. The target setting coefficient is assumed to be set to 1 at the time of factory shipment. The control unit 11 may set the target current by setting the target setting coefficient based on the immediately preceding measurement value. Specifically, when the control unit 11 controls the current value of the incoming current to increase until it reaches the upper limit, for example, let's assume that the set value of the incoming current increases or decreases as shown in Figure 3. Under this assumption, if the initial current is 7.0[A] and the target setting coefficient is 2%, then the target current is 7.14[A]. Now, let's assume that when the incoming current is increased to 7.1[A], the current value decreases sharply. If the measurement value of the incoming current just before the measurement value drops was 7.07[A], the control unit 11 may set the target setting coefficient to 1%((7.07-7)÷7×100). Furthermore, in the above example, if the current value decreases sharply when the incoming current is increased to 7.0[A], the control unit 11 may set the target setting coefficient to -2% and temporarily set the initial current to 6.86[A]. If the current value does not decrease sharply thereafter, the control unit 11 may determine that it is possible to continue the incoming power supply and increase the incoming power current value by increasing the target setting coefficient by +0.3% increments. Also, if the current value decreases sharply when the incoming power supply is increased to 6.95[A], and the measured value just before the measured value of the incoming power supply drops was 6.93[A], the control unit 11 may set the target setting coefficient to -1%((6.93-7)÷7×100).

[0053] If no initial current is set for the energy storage device 10, the control unit 11 may perform a procedure to set a target current at startup. If an initial current is set for the energy storage device 10, the control unit 11 may control the power conversion unit 153 using the initial current as the target current, or it may perform a procedure to set a target current at startup.

[0054] <Example of a procedure for controlling the energy storage device 10> The control unit 11 of the energy storage device 10 may execute a control method for the energy storage device 10, which includes, as an example, the procedure shown in the flowchart of Figure 5. The control method for the energy storage device 10 may be executed by a processor in the control unit 11 as a control program for the energy storage device 10. The control program may be stored in a non-temporary computer-readable medium.

[0055] The control unit 11 controls the power conversion unit 153 so that the incoming current from the power generator 40 increases (step S1). The control unit 11 acquires the measured value of the incoming current by the CT 162 using the measurement unit 13 (step S2). The control unit 11 may store the acquired measured value in the storage unit 12.

[0056] The control unit 11 determines whether the measured value of the incoming current has dropped (step S3). The control unit 11 may determine that the measured value of the incoming current has dropped, for example, if the measured value of the incoming current falls below the stop judgment value. The control unit 11 may determine that the measured value of the incoming current has dropped if the measured value of the incoming current becomes zero. If the measured value of the incoming current has not dropped (step S3: NO), the control unit 11 determines whether the incoming current has increased to the upper limit (step S4). If the incoming current has not increased to the upper limit (step S4: NO), the control unit 11 returns to the procedure in step S1 and further increases the incoming current. If the incoming current has increased to the upper limit (step S4: YES), the control unit 11 sets the upper limit to the target current (step S5).

[0057] If the measured value of the incoming current drops (step S3: YES), the control unit 11 acquires the measured value of the incoming current immediately before the drop, i.e., the most recent measured value (step S6). If the control unit 11 has stored the measured value of the incoming current in the storage unit 12, it may acquire the most recent measured value from the storage unit 12. The control unit 11 sets the target current based on the most recent measured value (step S7).

[0058] After setting the target current in step S5 or S7, the control unit 11 controls the power conversion unit 153 so that the incoming current becomes the target current (step S8). After executing the procedure in step S8, the control unit 11 terminates the execution of the procedure in the flowchart of Figure 5.

[0059] (Small summary) As described above, the energy storage device 10 according to this embodiment can set the measured value of the incoming current just before the power generator 40 overloads and shuts down as the target current by increasing the incoming current and obtaining the measured value just before it drops. In this way, the energy storage device 10 can draw in a current close to the upper limit that the power generator 40 can output, regardless of the measurement error of the CT 162. As a result, the amount of power from the output of the power generator 40 that is not stored in the energy storage device 10 and is lost is reduced.

[0060] (Other embodiments) The following describes an example of the configuration of the energy storage device 10 according to another embodiment.

[0061] <Operation after setting the target current> The control unit 11 of the energy storage device 10 controls the power conversion unit 153 so that the incoming current becomes the set value of the target current after setting the target current. However, while the power conversion unit 153 is being controlled so that the incoming current becomes the set value of the target current, the measured value of the incoming current may drop, for example, due to the power generator 40 being shut down due to an overload, or due to the power generator 40 being shut down arbitrarily. If the power generator 40 has stopped and the measured value of the incoming current has dropped, the control unit 11 may restart the procedure for setting the target current after the power generator 40 has restarted.

[0062] The power generator 40 may be modified by replacement or repair. The control unit 11 may re-execute the procedure for setting the target current if the power generator 40 is modified.

[0063] The control unit 11 may terminate the current draw from the power generator 40. If the control unit 11 terminates the current draw from the power generator 40, it may re-execute the procedure for setting the target current after the power generator 40 has restarted. The control unit 11 may also re-execute the procedure for setting the target current if a waiting time or longer elapses between the termination of the current draw from the power generator 40 and the restart of the power generator 40. The waiting time may be set to the time during which the power generator 40 can be modified. In other words, if the time elapsed before the power generator 40 restarts is longer than the time during which the power generator 40 can be modified, the control unit 11 may determine that the power generator 40 may have been modified and re-execute the procedure for setting the target current. The control unit 11 may also re-execute the procedure for setting the target current if the number of times the waiting time or longer elapses between the termination of the current draw from the power generator 40 and the restart of the power generator 40 reaches the number of standby determinations. The number of standby determinations is set to one or more as appropriate. Furthermore, the control unit 11 may re-execute the procedure for setting the target current when the number of times the power supply from the power generator 40 has been terminated reaches the termination determination count.

[0064] <Determining a stable power supply> As described above, in this disclosure, the stable power supply is a power generator 40 that has the capability to continuously output current without overloading the incoming current required by the energy storage device 10. The control unit 11 of the energy storage device 10 may control the incoming current with a target current set by the control method described above, regardless of whether the power generator 40 is a stable power supply. By controlling the incoming current with a target current set by the control method described above, a current close to the upper limit that the power generator 40 can output is drawn into the energy storage device 10, taking into account the measurement error of the CT 162.

[0065] Here, the frequency of overload shutdowns of the power generator 40 may decrease when the power generator 40 is a stable power source compared to when the power generator 40 is not a stable power source. The control unit 11 may determine whether the power generator 40 is a stable power source, and if the power generator 40 is a stable power source, it may execute the control method described above to set the target current and control the incoming current. On the other hand, if the power generator 40 is not a stable power source, the control unit 11 may avoid overload shutdowns of the power generator 40 by setting the incoming current according to the voltage value of the input terminal 18 that receives power from the power generator 40. In this way, the control unit 11 of the energy storage device 10 can perform appropriate coordinated operations in both cases, whether the power generator 40 is a stable power source or not. As a result, the energy storage device 10 can draw in a current close to the upper limit that the power generator 40 can output, while reducing the frequency of overload shutdowns of the power generator 40.

[0066] The control unit 11 may determine if the power generator 40 is a stable power source by performing the procedure for setting the target current two or more times, and if the phenomenon of the measured value of the incoming current dropping occurs two or more times while the power conversion unit 153 is being controlled to increase the incoming current, the control unit 11 may set the target current based on the most recent measured value. For example, the control unit 11 may determine that the power generator 40 is a stable power source if the procedure for setting the target current is performed two or more times and the most recent measured value each time is the same. Alternatively, the control unit 11 may determine that the power generator 40 is a stable power source if the difference between the most recent measured values ​​each time the procedure for setting the target current is performed two or more times is less than the difference determination value. The difference determination value is a threshold value compared with the difference between the most recent measured values ​​each time the procedure for setting the target current is performed two or more times in order to determine if the power generator 40 is a stable power source. The difference determination value may be set based on the measurement error of the CT 162.

[0067] When the control unit 11 determines that the power generator 40 is a stable power source, it may set the measured value of the incoming current just before the measured value drops as the target current. In other words, the control unit 11 may set the incoming current that matches the actual capacity of the power generator 40 as the target current.

[0068] Conversely, the control unit 11 may determine that the power generator 40 is not a stable power source if the measured value of the incoming current immediately before the drop was a different value. The control unit 11 may also display this determination that the power source is not stable using a display device or the like.

[0069] The diagrams illustrating the embodiments described herein are schematic. Dimensions and proportions shown in the drawings do not necessarily correspond to actual dimensions.

[0070] While embodiments relating to this disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art can make various modifications or alterations based on this disclosure. Therefore, it should be noted that these modifications or alterations are within the scope of this disclosure. For example, the functions included in each component can be rearranged in a logically consistent manner, and multiple components can be combined into one or separated.

[0071] In the embodiments described herein, an example is shown in which the energy storage device 10 draws in and stores the output current from an external power generator. In other embodiments, as described above, the power control device may be configured to include a control unit 11, a storage unit 12, and a measurement unit 13 as separate components from the energy storage device 10. The power control device may also reverse the flow of output current from the external power source to the power grid. The power control device may also supply the output current from the external power source to a load 30 that consumes forward power flow from the power grid, thereby reducing the forward power flow.

[0072] In one embodiment, (1) the energy storage device comprises a battery, an input terminal configured to be connectable to a power generation device, a power conversion unit that draws current from the power generation device through the input terminal and stores it in the battery, a measuring unit that measures the current drawn in from the power generation device through the input terminal, and a control unit that controls the power conversion unit. The control unit performs the following steps as a procedure for setting a target current, which is a target value of the current to be drawn in from the power generation device to the power conversion unit: control the power conversion unit so that the drawn current increases, acquire a measurement value of the drawn current while the power conversion unit is being controlled to increase the drawn current, and if the measurement value of the drawn current drops while the power conversion unit is being controlled to increase the drawn current, set the target current based on the measurement value immediately before the measurement value of the drawn current drops, and control the power conversion unit so that the drawn current becomes the set value of the target current.

[0073] (2) In the energy storage device described in (1) above, the control unit may control the power conversion unit so that the incoming current increases up to the upper limit that the power conversion unit or the storage battery can receive.

[0074] (3) In the energy storage device described in (1) or (2) above, the target current may be calculated by the product of the initial current and the target setting coefficient. The control unit may set the target setting coefficient based on the measurement value of the incoming current immediately before the measurement value drops.

[0075] (4) In any one of the energy storage devices described in (1) to (3) above, if the measured value of the incoming current drops due to the shutdown of the power generator while the control unit is controlling the power conversion unit so that the incoming current becomes the set value of the target current, the control unit may perform the procedure to set the target current after the power generator has been restarted.

[0076] (5) In any one of the energy storage devices described in (1) to (4) above, the control unit may perform the procedure for setting the target current when the power generation device is changed.

[0077] (6) In any one of the energy storage devices described in (1) to (5) above, the control unit may, after terminating the power supply from the power generator, perform the procedure for setting the target current after the power generator has restarted.

[0078] (7) In the energy storage device described in (6) above, the control unit may perform the procedure for setting the target current if a waiting period or longer has elapsed between the termination of the power supply from the power generation device and the restart of the power generation device.

[0079] (8) In the energy storage device described in (7) above, the control unit may perform the procedure for setting the target current when the number of times the waiting period or longer elapses between the termination of the power supply from the power generation device and the restart of the power generation device reaches the number of standby determinations.

[0080] (9) In any one of the energy storage devices described in (6) to (8) above, the control unit may perform the procedure for setting the target current when the number of times the power supply from the power generator has been terminated reaches the termination determination count.

[0081] (10) In any one of the energy storage devices described in (1) to (9) above, if the control unit performs the procedure for setting the target current two or more times and controls the power conversion unit to increase the incoming current, and the phenomenon of the measured value of the incoming current dropping occurs two or more times, the control unit may set the target current based on the measured value immediately before the drop in the incoming current.

[0082] (11) In the energy storage device described in (10) above, if the control unit controls the power conversion unit to increase the incoming current and the measured value of the incoming current drops two or more times, the control unit may set the target current based on the measured value immediately before the incoming current drops, provided that the difference between the measured values ​​immediately before the incoming current drops in each instance is less than the difference determination value.

[0083] In one embodiment, (12) a method for controlling an energy storage device is a method for controlling an energy storage device comprising: a storage battery; an input terminal configured to be connectable to a power generation device; a power conversion unit that draws current from the power generation device through the input terminal and stores it in the storage battery; a measuring unit that measures the current drawn in from the power generation device through the input terminal; and a control unit that controls the power conversion unit. The method for controlling the energy storage device includes the control unit setting a target current, which is a target value of the current to be drawn in by the power conversion unit from the power generation device; and the control unit controlling the power conversion unit so that the drawn current becomes the set value of the target current. The control unit setting the target current includes controlling the power conversion unit so that the drawn current increases; obtaining a measurement value of the drawn current while the power conversion unit is being controlled to increase the drawn current; and, if the measurement value of the drawn current drops while the power conversion unit is being controlled to increase the drawn current, setting the target current based on the measurement value immediately before the measurement value of the drawn current drops.

[0084] In one embodiment, (13) the power control device controls an energy storage device having a battery, an input terminal configured to be connectable to a power generation device, and a power conversion unit that draws current from the power generation device through the input terminal and stores it in the battery. The power control device includes a control unit that controls the power conversion unit and a measuring unit that measures the incoming current drawn in from the power generation device through the input terminal. The control unit performs the following steps as a procedure for setting a target current, which is a target value of the current to be drawn in from the power generation device to the power conversion unit: control the power conversion unit so that the incoming current increases; obtain a measurement value of the incoming current while the power conversion unit is being controlled so that the incoming current increases; and if the measurement value of the incoming current drops while the power conversion unit is being controlled so that the incoming current increases, set the target current based on the measurement value immediately before the drop in the measurement value of the incoming current, and then controls the power conversion unit so that the incoming current reaches the set value of the target current. [Explanation of Symbols]

[0085] 1. Power control system 10. Energy storage device (11: control unit, 12: memory unit, 13: measurement unit, 14: battery, 151-153: power conversion unit, 161-162: CT, 171-174: switch, 18: input terminal) 30 load 32 Specific load 40 Power generation equipment (41:CT) 80 Power grid

Claims

1. Storage batteries and An input terminal configured to be connectable to a power generation device, A power conversion unit that draws current from the power generation device through the input terminal and stores it in the battery, A measuring unit for measuring the incoming current drawn in from the power generation device through the input terminal, A control unit that controls the power conversion unit and Equipped with, The control unit, As a procedure for setting a target current, which is the target value of the current to be drawn from the power generator to the power conversion unit, the power conversion unit is controlled to increase the incoming current; a measurement of the incoming current is obtained while the power conversion unit is being controlled to increase the incoming current; and if the measurement of the incoming current drops while the power conversion unit is being controlled to increase the incoming current, the target current is set based on the measurement immediately before the drop in the measurement of the incoming current. The power conversion unit is controlled so that the incoming current reaches the set value of the target current. Energy storage device.

2. The power storage device according to claim 1, wherein the control unit controls the power conversion unit or the storage battery so that the incoming current increases to an upper limit that the power conversion unit or the storage battery can receive.

3. The aforementioned target current is calculated by the product of the initial current and the target setting coefficient. The energy storage device according to claim 1, wherein the control unit sets the target setting coefficient based on the measurement value of the incoming current immediately before the measurement value of the incoming current drops.

4. The energy storage device according to any one of claims 1 to 3, wherein if the measured value of the incoming current drops due to the shutdown of the power generation device while the control unit is controlling the power conversion unit so that the incoming current becomes the set value of the target current, the control unit executes a procedure to set the target current after the power generation device has been restarted.

5. The energy storage device according to any one of claims 1 to 3, wherein the control unit performs a procedure for setting the target current when the power generation device is changed.

6. The energy storage device according to any one of claims 1 to 3, wherein the control unit, when it has finished drawing power from the power generation device, executes a procedure to set the target current after the power generation device has restarted.

7. The energy storage device according to claim 6, wherein the control unit performs a procedure to set the target current when a waiting period or longer elapses between the termination of power supply from the power generation device and the restart of the power generation device.

8. The energy storage device according to claim 7, wherein the control unit executes a procedure to set the target current when the number of times the waiting period or longer elapses between the termination of power supply from the power generation device and the restart of the power generation device reaches the number of waiting determination counts.

9. The energy storage device according to claim 6, wherein the control unit executes a procedure to set the target current when the number of times the power supply from the power generator has been terminated reaches the termination determination count.

10. The energy storage device according to any one of claims 1 to 3, wherein the control unit performs the procedure for setting the target current two or more times, and if the phenomenon of the measured value of the incoming current dropping occurs two or more times while the control unit is controlling the power conversion unit to increase the incoming current, the control unit sets the target current based on the measured value immediately before the measured value of the incoming current drops.

11. The energy storage device according to claim 10, wherein the control unit, while controlling the power conversion unit to increase the incoming current, if the phenomenon of the measured value of the incoming current dropping occurs two or more times, and in each instance the difference between the measured values ​​immediately before the drop in the incoming current is less than the difference determination value, sets the target current based on the measured value immediately before the drop in the incoming current.

12. Storage batteries and An input terminal configured to be connectable to a power generation device, A power conversion unit that draws current from the power generation device through the input terminal and stores it in the battery, A measuring unit for measuring the incoming current drawn in from the power generation device through the input terminal, A control unit that controls the power conversion unit and A control method for an energy storage device comprising: The control unit sets a target current, which is the target value of the current to be drawn from the power generation device to the power conversion unit, The control unit controls the power conversion unit so that the incoming current becomes the set value of the target current. Includes, The control unit sets the target current, Controlling the power conversion unit so that the incoming current increases, Obtaining a measured value of the incoming current while the power conversion unit is controlled to increase the incoming current, If the measured value of the incoming current drops while the power conversion unit is being controlled to increase the incoming current, the target current is set based on the measured value immediately before the drop in the incoming current. A method for controlling an energy storage device, including the control of an energy storage device.

13. A power control device for controlling an energy storage device having a battery, an input terminal configured to be connectable to a power generation device, and a power conversion unit that draws current from the power generation device through the input terminal and stores it in the battery, The system comprises a control unit for controlling the power conversion unit and a measuring unit for measuring the incoming current drawn in from the power generation device through the input terminal, The control unit, As a procedure for setting a target current, which is the target value of the current to be drawn from the power generator to the power conversion unit, the power conversion unit is controlled to increase the incoming current; a measurement of the incoming current is obtained while the power conversion unit is being controlled to increase the incoming current; and if the measurement of the incoming current drops while the power conversion unit is being controlled to increase the incoming current, the target current is set based on the measurement immediately before the drop in the measurement of the incoming current. The power conversion unit is controlled so that the incoming current reaches the set value of the target current. Power control device.

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