Electricity storage unit, electricity storage system, and electric energy storage and conversion system

Abstract

A power storage unit (15) for a power storage system is provided with a power storage battery pack (20) connected to a power conversion device (10), and a battery pack management device (50). The battery pack management device (50) calculates, on the basis of a target current value (Ino) and a measured current value (Int) of the storage battery pack (20), a current limit value (Ilimit) that limits the excess of a current (I) with respect to the target current value (Ino), or calculates, on the basis of a target power value (Pno) and a measured power value (Pnt) of the storage battery pack (20), a current limit value (Ilimit) that limits the excess of the current (I) with respect to the target current value (Ino). A power limit value (Plimit) exceeding the limit power with respect to the power target value (Pno) is calculated.

Description

Technical Field

[0001] The present invention relates to a technique for controlling the current and power of an energy storage bank (energy storage bank). Background Art

[0002] In recent years, in order to achieve energy conservation, energy storage systems for residential, industrial, and energy management applications have been widely popularized. As a document disclosing such a technique, there is Patent Document 1.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-205437 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] Figure 1 The energy storage system S1 includes a plurality of energy storage units 15A to 15C and an integrated battery management device 100. The plurality of energy storage units 15A to 15C include energy storage battery packs 20A to 20C and battery pack management devices (bank management devices) 50A to 50C. Each of the energy storage battery packs 20A to 20C is connected to the grid G via a power conversion device (PCS) 10. The currents I1 to I3 of the energy storage battery packs 20A to 20C preferably do not exceed the current target values of the energy storage battery packs 20A to 20C. The current target values of the energy storage battery packs 20A to 20C are limit values (upper limit values) of the current I that can safely operate the energy storage battery packs 20A to 20C.

[0008] However, in the case of a multi-bank structure, if there are temperature differences or degradation deviations among the energy storage battery packs 20A to 20C, the current may become uneven. Therefore, even if the total current IT of the energy storage system S1 is controlled to the current target value of the energy storage system S1, in some of the battery packs, the currents I1 to I3 may exceed the current target values of the energy storage battery packs 20A to 20C.

[0009] As Figure 9As shown, in the power storage system S2 with a single battery pack structure, depending on the conversion efficiency, measurement accuracy, etc. of the power conversion device 10, there are cases where the current I of the power storage battery pack 20 exceeds the current target value of the power storage battery pack 20. The conversion efficiency is the conversion efficiency from AC to DC. For example, when measuring the current at the AC terminal P1, even if the AC terminal current is maintained at the target value, after the conversion from AC to DC, due to the accuracy and deviation of the conversion efficiency, the current I of the power storage battery pack 20 may exceed the current target value of the power storage battery pack 20.

[0010] Not limited to the case of controlling the current, the same problem also exists in the case of controlling the power of the power storage battery pack.

[0011] The problem of the present invention is to suppress the excess of the current or power of the power storage battery pack.

[0012] Means for solving the problem

[0013] The power storage unit for the power storage system includes a power storage battery pack connected to the power conversion device and a battery pack management device. The battery pack management device calculates a current limit value for restricting the excess of the current relative to the current target value based on the current target value and the current measurement value of the power storage battery pack, or calculates a power limit value for restricting the excess of the power relative to the power target value based on the power target value and the power measurement value of the power storage battery pack.

[0014] The power storage system connected to the power conversion device and storing electric energy includes a plurality of power storage units and an integrated battery management device. The power storage unit includes: a power storage battery pack connected to the power conversion device; and a battery pack management device provided corresponding to the power storage battery pack. The integrated management device obtains or calculates the current limit value of each power storage battery pack from the battery pack management device, calculates the current limit value of the power storage system based on the current limit value of each power storage battery pack, or obtains or calculates the power limit value of each power storage battery pack from the battery pack management device, and calculates the power limit value of the power storage system based on the power limit value of each power storage battery pack.

[0015] The electric energy storage conversion system includes a power conversion device and the above-mentioned power storage system. The power conversion device controls the current of the power storage system to be below the current limit value of the power storage system, or controls the power of the power storage system to be below the power limit value of the power storage system.

[0016] This technology can also be applied to the control methods of power storage systems and electric energy storage conversion systems.

[0017] Advantages of the invention

[0018] This technology can suppress the excess of the current or power of the power storage battery pack. Description of the Drawings

[0019] Figure 1 is a block diagram of the system structure of the electric energy storage and conversion system.

[0020] Figure 2 is a block diagram of the electricity storage section.

[0021] Figure 3 is a diagram showing the electricity storage module and the sensor unit.

[0022] Figure 4 is a block diagram showing the electrical structure of the electricity storage system.

[0023] Figure 5 is an arithmetic block related to the current control function.

[0024] Figure 6 is a graph showing the measurement result of the current.

[0025] Figure 7A is a graph showing the measurement result of the current of the electricity storage battery pack.

[0026] Figure 7B is a graph showing the measurement result of the total current of the electricity storage system.

[0027] Figure 8A is a graph showing the current simulation result.

[0028] Figure 8B is a graph showing the current simulation result.

[0029] Figure 9 is a block diagram of the system structure of the electricity storage system. Detailed Description of the Invention

[0030] (1) The electricity storage section for the electricity storage system includes an electricity storage battery pack connected to a power conversion device and a battery pack management device. The battery pack management device calculates a current limit value for restricting an excess of the current with respect to the current target value based on the current target value and the current measurement value of the electricity storage battery pack, or calculates a power limit value for restricting an excess of the power with respect to the power target value based on the power target value and the power measurement value of the electricity storage battery pack.

[0031] According to the electricity storage section described in (1), in the case of using a multiple battery pack structure, it is possible to suppress an excess of the current of the electricity storage battery pack with respect to the current target value without depending on the temperature management of the electricity storage battery pack. In the case of using a single battery pack structure, it is possible to suppress an excess of the current of the electricity storage battery pack with respect to the current target value without depending on the conversion efficiency and measurement accuracy of the power conversion device. Therefore, the electricity storage section can be safely operated. The same applies when controlling power instead of current.

[0032] (2) Alternatively, in the power storage unit described in (1) above, the battery pack management device acquires a current measurement value at least at a prescribed period and updates the current limit value of the power storage battery pack, or acquires a power measurement value at least at a prescribed period and updates the power limit value of the power storage battery pack.

[0033] According to the power storage unit related to (2), since the current limit value is updated at a prescribed period based on the latest current measurement value, it is possible to suppress the excess of the current of the power storage battery pack with respect to the current target value without depending on the change in current. The same applies when controlling power instead of current.

[0034] (3) Alternatively, in the power storage unit described in (1) or (2) above, the battery pack management device calculates the current limit value of the power storage battery pack based on the difference between the current measurement value and the current target value of the power storage battery pack and the ratio of the current measurement value to the current target value, or calculates the power limit value of the power storage battery pack based on the difference between the power measurement value and the power target value of the power storage battery pack and the ratio of the power measurement value to the power target value.

[0035] According to the power storage unit described in (3), when limiting the excessive current to the current target value, it is possible to suppress the undershoot of the current and achieve a smooth response waveform. The same applies when controlling power instead of current.

[0036] (4) Alternatively, in the power storage unit described in any one of (1) to (3) above, the battery pack management device calculates the current limit value of the power storage battery pack or calculates the power limit value of the power storage battery pack by the following formula.

[0037] Ylimit = Yno + Ysup

[0038] Ysup = (the previous value of Ysup + Yno - Ynt) × (Yno / Ynt)

[0039] Ylimit is the current limit value or power limit value of the power storage battery pack, Yno is the current target value or power target value of the power storage battery pack, Ysup is the current suppression value or power suppression value of the power storage battery pack, and Ynt is the current measurement value or power measurement value of the power storage battery pack.

[0040] According to the power storage unit related to (4), it is possible to calculate the current suppression value and the current limit value through simple operations using the difference between the current target value and the current measurement value and the ratio of the current target value to the current measurement value. The same applies when calculating the power suppression value and the power limit value instead of the current suppression value and the current limit value.

[0041] (5) Alternatively, in the power storage unit described in any one of (1) to (4) above, the battery pack management device calculates the current limit value of the power storage battery pack or calculates the power limit value of the power storage battery pack by the following formula.

[0042] Ylimit = the previous value of Ylimit × (Yno / Ynt)

[0043] Ylimit is the current limit value or power limit value of the power storage battery pack, Yno is the current target value or power target value of the power storage battery pack, and Ynt is the current measurement value or power measurement value of each power storage battery pack.

[0044] According to the power storage unit related to (5), the current limit value can be calculated by a simple operation using the ratio of the current target value to the current measurement value. Compared with the operation method described in (4), it is not necessary to calculate the difference between the current target value and the current measurement value, and the operation load of the battery pack management device can be reduced. The same applies when calculating the power limit value instead of the current limit value.

[0045] (6) A power storage system is a system that is connected to a power conversion device and stores electrical energy, including a plurality of power storage units and an integrated battery management device. The power storage unit includes: a power storage battery pack connected to the power conversion device; and a battery pack management device provided corresponding to the power storage battery pack. The integrated management device obtains or calculates the current limit value of each power storage battery pack from the battery pack management device, calculates the current limit value of the power storage system based on the current limit value of each power storage battery pack, or obtains or calculates the power limit value of each power storage battery pack from the battery pack management device, and calculates the power limit value of the power storage system based on the power limit value of each power storage battery pack. The power storage battery pack can be the power storage battery pack described in any one of (1) to (5), or can be a power storage battery pack other than (1) to (5).

[0046] (7) An electrical energy storage conversion system includes a power conversion device and the power storage system described in (6). The power conversion device controls the current of the power storage system to be below the current limit value or controls the power of the power storage system to be below the power limit value.

[0047] According to the power system described in (6) and the electrical energy storage conversion system described in (7), it is possible to suppress the current or power of the power storage battery pack from exceeding without relying on the temperature management of the power storage battery pack. This structure is effective when the power storage system has a system structure that cannot sufficiently perform temperature management or is used in a setting environment where temperature management is difficult.

[0048] <Embodiment 1>

[0049] Figure 1 It is a block diagram of the electric energy storage conversion system M1. The electric energy storage conversion system M1 is composed of a power storage system S1 and a power conditioner 10, and is connected to the power grid G via the power conditioner 10. The power grid G has a system power supply 1, a solar power generation panel, a wind turbine and other decentralized power supplies 3, and supplies AC power at commercial frequency.

[0050] The power conditioner 10 is a bidirectional power conversion device, which has a bidirectional inverter 11, a control unit 13 and a measurement unit 15. The bidirectional inverter 11 can convert the AC power of the power grid G into DC power to charge the power storage system S1. It can convert the DC power of the power storage system S1 into AC power and output it to the power grid G. The measurement unit 15 measures the voltage and current of the AC terminal P1 or the DC terminal P2 of the power conditioner 10. In this embodiment, the voltage and current of the DC terminal P2 are measured.

[0051] The power storage system S1 can be used in various applications such as residential, industrial, and energy management. The power storage system S1 stores (charges) the surplus power of the power grid G and discharges according to the power supply and demand balance, thereby contributing to the effective and flexible use of energy.

[0052] The power storage system S1 is composed of a plurality of power storage units 15A to 15C and an integrated battery management device 100.

[0053] Each of the power storage units 15A to 15C is composed of a power storage battery pack 20A to 20C and a battery pack management device 50A to 50C.

[0054] The power storage battery packs 20A to 20C are connected in parallel with the power conditioner 10. The power storage battery packs 20A to 20C have the same structure.

[0055] As Figure 2 shown, the power storage battery packs 20A to 20C are composed of a plurality of power storage modules 30-1, power storage modules 30-2, power storage modules 30-N connected in series, a plurality of sensor units 35-1, sensor units 35-2, sensor units 35-N, and a current sensor 40. Hereinafter, the plurality of power storage modules are collectively referred to as the power storage module 30. The same applies to the sensor unit 25.

[0056] As Figure 3 shown, one power storage module 30 is composed of a plurality of power storage battery cells 31 connected in series. The power storage battery cells 31 can use lithium-ion secondary battery cells or the like.

[0057] The sensor units 35 are respectively arranged relative to the power storage module 30. The sensor units 35 detect the cell voltages Vc of the respective power storage cells 31. The sensor units 35 are provided with temperature sensors 36 and also detect the battery temperature T of the power storage module 30.

[0058] As Figure 2 shown, the sensor units 35 are communicably connected to adjacent sensor units 35. In response to an instruction from the battery pack management device 50B, the sensor units 35 sequentially transmit data from the upper-level to the lower-level sensor units 35, whereby the measurement results of the respective sensor units 25 can be collected in the lowermost sensor unit 35N and sent to the battery pack management device 50B.

[0059] The battery pack management devices 50A to 50C are provided for each power storage battery pack 20A to 20C. As Figure 4 shown, the battery pack management devices 50A to 50C include arithmetic units 51 such as CPUs and storage units 55. Data required for executing the current limiting function described later is stored in the storage unit 55.

[0060] Based on various data sent from the sensor units 35 and the current sensors 40, the battery pack management devices 50A to 50C monitor the current I of the power storage battery packs 20A to 20C, the cell voltages Vc of the respective power storage cells 31, and the battery temperature T.

[0061] The battery pack management devices 50A to 50C are communicably connected to the integrated battery management device 100. The integrated battery management device 100 includes arithmetic units 101 such as CPUs and storage units 105.

[0062] Based on the monitoring data of the power storage battery packs 20A to 20C (data of the current I of the power storage battery packs 20, the cell voltages Vc of the respective power storage cells 31, and the battery temperature T) sent from the battery pack management devices 50A to 50C, the integrated battery management device 100 monitors the state of the entire system.

[0063] 2. Current Limiting Function

[0064] Figure 5 represents an arithmetic block related to the current limiting function of the battery pack management device 50A. The arithmetic unit 51 of the battery pack management device 50A has a first arithmetic block 52 and a second arithmetic block 53. The other battery pack management devices 50B and 50C also have the same arithmetic blocks.

[0065] The first arithmetic block 52 has an internal resistance map 52A, and calculates the internal resistance R of the battery cell 31 based on the battery temperature and SOC of the battery pack 20. The SOC can be obtained by the current integration method. The SOC is the state of charge and can be expressed as the ratio of the remaining capacity [Ah] to the full charge capacity [Ah].

[0066] The first arithmetic block 52 calculates the current target value Ino of the battery pack 20 based on the data of the battery cell voltage Vc and the internal resistance R of the battery cell 31. The current target value Ino is the upper limit value of the current I that can safely operate the battery pack 20.

[0067] The current target value Ino can be obtained, for example, by a calculation formula with Vc and R as variables, or by using a reference table that determines the current target value Ino with Vc and R as input values. Generally, the lower the battery cell voltage Vc, the higher the current target value Ino, and the larger the internal resistance R, the lower the current target value Ino.

[0068] In this example, the current target value Ino during charging is calculated using the highest value of the battery cell voltage Vc, and the current target value Ino during discharging is calculated using the lowest value of the battery cell voltage Vc. The first arithmetic block 52 can also update the current target value Ino based on the data of Vc and R at each moment.

[0069] When the current target value Ino of the battery pack 20 is 50 A (Ino = 50 A), it is considered to set the current target value of the power storage system S1 to 150 A (50 A × 3). However, even if the total current IT of the power storage system S1 is controlled to 150 A by the power conditioner 10, if there are temperature differences and degradation deviations in the battery packs 20A to 20C, the currents I1 to I3 will become uneven, and in some of the battery packs 20A to 20C, the currents I1 to I3 may exceed the current target value Ino of the battery pack 20.

[0070] In Figure 1 In the example, the total current IT of the power storage system S1 is controlled to 150 A, but I1 = 45 A, I2 = 50 A, I3 = 55 A, and the current I3 of the battery pack 20C exceeds the current target value of the battery pack 20 (Ino = 50 A).

[0071] Figure 5The second arithmetic block 53 shown calculates a current suppression value Isup and a current limit value Ilimit of the storage battery pack 20 in order to suppress the excess of the current I of the storage battery pack 20 with respect to the current target value Ino. The current suppression value Isup is an adjustment amount of the current I (a decrease amplitude with respect to the current value), and the current limit value Ilimit is an upper current limit value.

[0072] Specifically, the second arithmetic block 53 includes a first arithmetic unit 53A, a second arithmetic unit 53B, a memory 53C, and an addition unit 53D.

[0073] The first arithmetic unit 53A calculates a current difference Ino - Int and a current ratio Ino / Int based on the current target value Ino and the current measurement value Int of the storage battery pack 20. When there is an overcurrent, Ino < Int, so Ino - Int < 0 and Ino / Int < 1.

[0074] The second arithmetic unit 53B calculates the current suppression value Isup based on the current difference Ino - Int, the current ratio Ino / Int, and the previous value of the current suppression value Isup stored in the memory 53C. Among them, the initial value of Isup is zero.

[0075] The addition unit 53D adds the current target value Ino and the current suppression value Isup to calculate the current limit value Ilimit. The calculation formulas for Isup and Ilimit are as follows.

[0076] Isup = (previous value of Isup + Ino - Int) × (Ino / Int) (Equation (A))

[0077] Ilimit = Ino + Isup (Equation (B))

[0078] Isup is the current suppression value of the storage battery pack 20, Ino is the current target value of the storage battery pack 20, Int is the current measurement value of the storage battery pack 20, and Ilimit is the current limit value of the storage battery pack 20. When Isup > 0 (when there is no overcurrent), it is set that Isup = 0.

[0079] The calculation example is as follows. When Ino = 50A, Int = 55A, and the previous value of Isup = 0, Ino - Int = -5A, Ino / Int = 0.9, so Isup = -4.5A and Ilimit = 45.5A.

[0080] During the operation of the energy storage system S1, the battery pack management devices 50A to 50C acquire the current measurement value Int data from the current sensor 40 at a specified period regardless of discharge and charge, and calculate the current difference Ino - Int and the current ratio Ino / Int based on the acquired latest current measurement value Int data. The current target value Ino can be calculated each time or a fixed value can be used.

[0081] Based on the current difference Ino - Int and the current ratio Ino / Int calculated at a specified period, the battery pack management devices 50A to 50C recalculate and update the current suppression value Isup and the current limit value Ilimit. The battery pack management devices 50A to 50C output the updated current limit value Ilimit to the integrated battery management device 100 each time.

[0082] The integrated battery management device 100 compares the current limit values Ilimit1 to Ilimit3 of the respective energy storage battery packs 20A to 20C sent from the battery pack management devices 50A to 50C, and determines the minimum current limit value Ilimit.

[0083] Specifically, as shown in Equation (C), it is calculated by multiplying the minimum current limit value Ilimit by the number of battery packs (parallel connection number) N of the energy storage battery pack 20.

[0084] ITL = Ilimit × N (Equation (C))

[0085] The calculation example is as follows. When Ilimit = 45.5A and N = 3, the current limit value ITL of the energy storage system S1 becomes 136.5A (45.5 × 3).

[0086] The integrated battery management device 100 calculates the current limit value ITL of the energy storage system S1 at a specified period and sends the result to the power conditioner 10.

[0087] After the control starts, the power conditioner 10 immediately controls the total current IT of the energy storage system S1 to the initial value (the current target value Ino of the energy storage battery pack 20 × the number of battery packs = 150A).

[0088] After that, the power conditioner 10 controls the total current IT of the energy storage system S1 to be equal to or less than the current limit value ITL (the minimum current limit value Ilimit of the energy storage battery pack 20 × the number of battery packs N) based on the current limit value ITL output from the integrated management device 100.

[0089] Specifically, while referring to the measurement value of the total current IT (the current at the DC terminal P2) based on the measurement unit 15, the total current IT of the energy storage system S1 is controlled to be equal to or less than the current limit value ITL via the bidirectional inverter 11.

[0090] By controlling the total current IT of the power storage system S1 to be equal to or less than the current limit value ITL, in each of the power storage battery packs 20A to 20C, it is possible to suppress the excess of the currents I1 to I3 with respect to the current target value Ino of the power storage battery pack 20.

[0091] The update period (operation period) of the current suppression value Isup and the current limit value Ilimit of the power storage battery pack 20 is preferably a period longer than the current control period of the power conditioner 10. By extending the update period, it is possible to suppress the update of the current suppression value and the current limit value in a state where the current is not adjusted. Therefore, the current suppression function can effectively function.

[0092] Figure 6 Figure 7 is a graph showing the currents I1 to I3 of the power storage battery packs 20A to 20C during discharge under the condition that there is a temperature difference between the battery packs in the power storage system S1. The power storage battery pack 20C is about 10 °C higher in temperature than the power storage battery packs 20A and 20B, creating conditions where current I easily flows (the higher the temperature, the smaller the internal resistance and the easier the current flows). The current target value Ino of the current I is 50A.

[0093] Figure 6 This is a graph in the case where the total current IT of the power storage system S1 is controlled to the initial value of 150A without the current limit function. The current I3 of the power storage battery pack 20C exceeds the current target value of 50A for the power storage battery pack 20C during the period from the start of discharge to about 30 seconds. In particular, during the period of about 10 seconds from the start of discharge, it is about 60A, exceeding 10A.

[0094] Figure 7 is a graph in the case where the current limit function is implemented and the total current IT of the power storage system S1 is limited to the current limit value ITL. Figure 7A It shows the change of the currents I1 to I3 of each power storage battery pack 20A to 20C, Figure 7B It shows the change of the total current ITL of the power storage system S1. The current I3 of the power storage battery pack 20C is larger than I1 and I2 during the period from the start of discharge to about 35 seconds. However, it is controlled to the current target value of 50A for the power storage battery pack 20C, eliminating the excess of the current I3. In the subsequent period, although the magnitude relationship of the currents I1 to I3 of the power storage battery packs 20A to 20C is reversed, the excess of the current is suppressed.

[0095] Figure 8A 、 Figure 8B It shows the result of simulating the time change of the current I of the power storage battery packs 1 to 4 in the case of implementing the current limit function during discharge for a 4-battery-pack power storage system. In Figure 8A and Figure 8BAmong them, the calculation methods of the current suppression value Isup are different. Figure 8A It is the simulation result when the current suppression value Isup based on Formula A of Embodiment 1 is used in the calculation of the current limit value Ilimit. Figure 8B It is the simulation result when the current suppression value Isup based on Formula F of Embodiment 3 is used.

[0096] Figure 8A , Figure 8B For both, the current I of the battery pack 4 exceeds the current target value of 50 A of the rechargeable battery pack about several tens of seconds after the start of the simulation, but is maintained at the current target value of 50 A of the rechargeable battery pack after about 70 seconds. When comparing Figure 8A and Figure 8B , regarding the behavior of the current I of the battery pack 4, compared with Figure 8B Figure 8A the undershoot and overshoot (part A in the figure) of the current convergence to the target value of 50 A are suppressed, and a smooth response can be achieved.

[0097] 3. Effect description

[0098] This structure can suppress the current exceeding of the currents I1 to I3 with respect to the current target value Ino of the rechargeable battery pack 20 in the rechargeable battery packs 20A to 20C, and the power storage system S1 can be safely operated.

[0099] <Embodiment 2>

[0100] In Embodiment 1, the currents I1 to I3 [A] of the rechargeable battery packs 20A to 20C are controlled, but instead of controlling the current I, the power P [W] of the rechargeable battery packs 20A to 20C can be controlled. In this case, the battery pack management device 50 can also calculate the power suppression value Psup and the power limit value Plimit by the following formulas (D) and (E).

[0101] Psup = (previous value of Psup + Pno - Pnt) × (Pno / Pnt) (Formula (D))

[0102] Plimit = Pno + Psup (Formula (E))

[0103] Psup is the power suppression value of the rechargeable battery pack 20, Pno is the power target value of the rechargeable battery pack 20, Pnt is the power measurement value of the rechargeable battery pack 20, and Plimit is the power limit value of the rechargeable battery pack 20. When Psup > 0 (when there is no power exceeding), set Psup = 0.

[0104] <Embodiment 3>

[0105] In Embodiment 3, the calculation method of the current suppression value Isup of the storage battery pack 20 is different from that in Embodiment 1. The battery pack management devices 50A to 50C calculate the current suppression value Isup of the storage battery pack 20 by the following formula (F).

[0106] Isup = previous value of Isup + (Ino - Int) × (Ino / Int) (Formula (F))

[0107] Isup is the current suppression value of the storage battery pack 20, Ino is the current target value of the storage battery pack 20, and Int is the current measured value of the storage battery pack 20.

[0108] The calculation method of Formula (F) is the same as that of Formula (A), and the current suppression value Isup of the storage battery pack 20 can be obtained.

[0109] <Other Embodiments>

[0110] The present invention is not limited to the embodiments described above and illustrated in the accompanying drawings. For example, embodiments such as the following are also included in the technical scope of the present invention.

[0111] (1) In the above embodiment, the present technology is applied to the power storage system S1 of multiple battery packs, but the present technology can also be applied to the power storage system S2 of a single battery pack (see Figure 9 ). That is, data of the current limit value Ilimit is sent from the storage battery pack 20 to the power conditioner 10, and the current I of the storage battery pack 20 is limited to be below the current limit value Ilimit by the power conditioner 10.

[0112] (2) The storage battery cells are not limited to lithium-ion secondary batteries, and other non-aqueous electrolyte secondary batteries or lead-acid batteries can also be used. A capacitor can also be used instead of the storage battery cells.

[0113] (3) In the above embodiment, the battery pack management device 50 is separately provided from the storage battery pack 20, but it can also be a part of the storage battery pack 20.

[0114] (4) In the above embodiment, as an example of the power conversion device, the power conditioner 10 is shown, but as long as it is a bidirectional power converter (a power conversion device capable of charging and discharging the power storage unit), it can also be other devices. For example, it can also be a DC / DC converter or the like.

[0115] (5) In the above embodiment, Formulas (A) and (F) are shown as the calculation formulas of the current suppression value Isup. As long as the current difference Ino - Int and the current ratio Ino / Int are used, the current suppression value Isup can also be calculated by other formulas.

[0116] In the above-described embodiment, the current suppression values Isup and current limit values Ilimit of the respective storage battery packs 20A to 20C are calculated by the respective battery pack management devices 50A to 50C. Alternatively, data of Ino and Int may be transmitted from the battery pack management devices 50A to 50C to the integrated battery management device 100, and the integrated battery management device 100 may calculate the current suppression values Isup and current limit values Ilimit of the respective storage battery packs 20A to 20C. That is, the calculation entity of the current suppression value Isup and the current limit value Ilimit may be a prescribed calculation device such as the battery pack management device 50 or the integrated battery management device 100.

[0117] In the above-described embodiment, the integrated battery management device 100 calculates the current limit value ITL of the power storage system S1 based on the current limit values Ilimit1 to Ilimit3 of the respective storage battery packs 20A to 20C. Specifically, the current limit values Ilimit1 to Ilimit3 are compared to determine the minimum current limit value Ilimit, and the current limit value ITL of the power storage system S1 is calculated based on the minimum current limit value Ilimit. As long as the method for determining the current limit value ITL of the power storage system S1 is based on the current limit values Ilimit1 to Ilimit3 of the respective storage battery packs 20A to 20C, other methods may also be used. For example, the average value of the current limit values Ilimit1 to Ilimit3 of the storage battery packs 20A to 20C may be used for determination.

[0118] In the above-described embodiment, the current target value Ino of the storage battery pack 20 is calculated based on the cell voltage Vc and the internal resistance R of the storage battery cell 31, but the current target value Ino may also be a prescribed fixed value.

[0119] In Embodiment 1, the current limit value Ilimit of the storage battery pack 20 is calculated based on the difference Ino−Int between the current measurement value Int and the current target value Ino of the storage battery pack 20 and the ratio Ino / Int of the current measurement value Int to the current target value Ino. Specifically, it is calculated by Equation A and Equation B of Embodiment 1.

[0120] Alternatively, the current limit value Ilimit of the storage battery pack 20 may be calculated based on the ratio Ino / Int of the current measurement value Int to the current target value Ino. Specifically, it may also be calculated by the following Equation (G).

[0121] Ilimit = previous value of Ilimit × (Ino / Int) (Equation (G))

[0122] Ilimit is the current limit value of each storage battery pack 20, Ino is the current target value of each storage battery pack 20, and Int is the current measurement value of each storage battery pack 20. The initial value of Ilimit is the current target value Ino. The power limit value can also be calculated by the same formula.

[0123] The current limit value Ilimit of the storage battery pack 20 can also be calculated by Formula H instead of Formula G.

[0124] Ilimit = the previous value of Ilimit × (the smallest Ino / Int) (Formula H)

[0125] The smallest Ino / Int is a value smaller than 1 and is the minimum value of Ino / Int after comparison among the storage battery packs. The power limit value can also be calculated by the same formula.

[0126] The second term on the right side of Formula G and Formula H is different. The second term of Formula G is (Ino / Int), and the second term of Formula H is (the smallest Ino / Int). Formula G is the calculation formula for the current limit value Ilimit of each storage battery pack 20, and the (Ino / Int) of the second term is the current ratio of each storage battery pack 20. Formula H is the calculation formula for the common current limit value Ilimit for each storage battery pack 20, and the (the smallest Ino / Int) of the second term is the minimum value of Ino / Int after comparison among the storage battery packs. When using Formula H, the data of Ino / Int of each storage battery pack 20A - 20C is sent from each battery pack management device 50A - 50C to the integrated battery management device 100. The integrated battery management device 100 obtains the smallest Ino / Int, and based on the obtained smallest Ino / Int, the common current limit value Ilimit for the battery pack management devices 50A - 50C can be obtained. Furthermore, the current limit value of the energy storage system S1 (ITL = Ilimit × N) can be obtained based on the obtained common current limit value Ilimit. N is the number of battery packs.

[0127] (10) In the energy storage system S1 of Embodiments 1 - 3, a selection switch may also be provided, and this selection switch selects whether to execute the current limit function in the integrated battery management device 100 (whether to output the current limit value ITL of the energy storage system S to the power conditioner 10). By providing the selection switch, the user can select whether to use the current limit function.

[0128] Description of Reference Numerals

[0129] 10 Power regulator (power conversion device); 20A~20C Battery pack; 30 Energy storage module; 35 Module sensor unit; 40 Current sensor; 50A~50C Battery pack management device; 100 Integrated battery management device; I1~I3 Currents of the battery packs; Isup Current suppression value of the battery packs; Ilimit Current limit value of the battery packs; ITL Current limit value of the energy storage system; S1, S2 Energy storage systems.

Claims

1. A power storage unit, which is a power storage unit for a power storage system, comprising: a power storage battery pack connected to a power conversion device; and a battery pack management device, wherein the battery pack management device: calculates a current limit value for limiting an excess of the current with respect to the current target value based on the current target value and the current measurement value of the power storage battery pack, or calculates a power limit value for limiting an excess of the power with respect to the power target value based on the power target value and the power measurement value of the power storage battery pack.

2. The power storage unit according to claim 1, wherein the battery pack management device acquires the current measurement value at least at a prescribed period and updates the current limit value of the power storage battery pack, or acquires the power measurement value at least at a prescribed period and updates the power limit value of the power storage battery pack.

3. The power storage unit according to claim 1 or claim 2, wherein the battery pack management device: calculates the current limit value of the power storage battery pack based on the difference between the current measurement value and the current target value of the power storage battery pack and the ratio of the current measurement value to the current target value, or calculates the power limit value of the power storage battery pack based on the difference between the power measurement value and the power target value of the power storage battery pack and the ratio of the power measurement value to the power target value.

4. The power storage unit according to claim 3, wherein the battery pack management device calculates the current limit value of the power storage battery pack or calculates the power limit value of the power storage battery pack by the following formula, Ylimit = Yno + Ysup Ysup = (the previous value of Ysup + Yno - Ynt) × (Yno / Ynt) Ylimit is the current limit value or the power limit value of the power storage battery pack, Yno is the current target value or the power target value of the power storage battery pack, Ysup is the current suppression value or the power suppression value of the power storage battery pack, and Ynt is the current measurement value or the power measurement value of the power storage battery pack.

5. The power storage unit according to claim 1 or claim 2, wherein the battery pack management device calculates the current limit value of the power storage battery pack or calculates the power limit value of the power storage battery pack by the following formula, Ylimit = the previous value of Ylimit × (Yno / Ynt) Ylimit is the current limit value or the power limit value of the power storage battery pack, Yno is the current target value or the power target value of the power storage battery pack, and Ynt is the current measurement value or the power measurement value of each power storage battery pack.

6. A power storage system, which is a power storage system connected to a power conversion device and storing electric energy, comprising: a plurality of power storage units; and an integrated battery management device, wherein the power storage unit comprises: a power storage battery pack connected to the power conversion device; and a battery pack management device provided corresponding to the power storage battery pack, wherein the integrated management device: acquires or calculates the current limit value of each power storage battery pack from the battery pack management device, calculates the current limit value of the power storage system based on the current limit values of each power storage battery pack, or acquires or calculates the power limit value of each power storage battery pack from the battery pack management device, Based on the power limit values of the respective storage battery packs, calculate the power limit value of the storage power system.

7. An electrical energy storage conversion system, comprising: a power conversion device; and the storage power system according to claim 6, the power conversion device: controls the current of the storage power system to be below the current limit value of the storage power system, or controls the power of the storage power system to be below the power limit value of the storage power system.

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