JP7461660B2 - Energy storage systems, new energy systems, power distribution systems, power transmission systems, transportation equipment, battery systems for electric vehicles, and battery systems for uninterruptible power supplies - Google Patents

Description

The present invention relates to an energy storage system capable of receiving and transmitting electric power between a power grid and/or a load, and new energy systems, power distribution systems, power transmission systems, and transport equipment equipped with the same, and in particular to an energy storage system suitable for performing testing or diagnosis of built-in energy storage elements, and new energy systems, power distribution systems, power transmission systems, transport equipment, battery systems for electric vehicles, and battery systems for uninterruptible power supplies equipped with the same.

In recent years, there has been an increasing demand for energy storage systems that stabilize the supply and demand of electricity by transferring power between power generation systems and loads and by connecting to the power grid. For example, there is a known energy storage system that includes a multilevel converter that combines and outputs the output voltages of the power supply circuits of the unit converters, each of which is configured by connecting a power conversion circuit and a capacitor, and is connected in series (see Patent Document 1).

To keep such a power storage system operable for a long period of time, it becomes necessary to diagnose the battery life and replace batteries with short remaining life while the system is in operation. Patent Documents 1 and 2 disclose examples of prior art for diagnosing the degradation state (degraded parts and degree of degradation) of the batteries that make up the unit converter while the system is in operation and replacing degraded batteries without stopping the operation of the power storage system. For example, Patent Document 2 discloses an inspection device that can inspect the power storage system without stopping the system.

JP 2006-174663 A JP 2012-039791 A

However, while the invention described in Patent Document 2 makes it possible to diagnose and replace the battery while the energy storage system is in operation, there is a risk that electrically diagnosing the battery's deterioration may have an adverse effect on the stability of power for external power systems and loads that are interconnected with the energy storage system. Similar problems are not limited to battery deterioration diagnosis, but also occur in situations where a current is used within the energy storage system to measure changes over time in the battery characteristics within the energy storage system and variations in the characteristics of each battery.

For example, in the power supply device disclosed in Patent Document 2, the AC waveform input to the storage element and CR circuit is controlled by gate-controlling the thyristor, and a determination process is performed to determine whether or not there is an abnormality in the rectifier circuit, capacitor, or control device based on the ratio between the DC component of the output current from the capacitor that constitutes the CR circuit and the AC component of the charging current to the storage element.

However, in this power supply device, when the deterioration of the storage element is diagnosed, current flows directly from the external power system into the thyristor to control and smooth the AC waveform. Therefore, the current flowing into the power supply device when the deterioration of the storage element is diagnosed may fluctuate the system frequency and current voltage in the power supply network and loads connected to the power supply device, temporarily impairing the stability of the system power. As a result, with the invention described in Patent Document 2, it is difficult to suppress the impact of impairing the stability of power on the power system and loads connected to the storage system during battery testing.

As mentioned above, the main cause of loss of power stability in external power systems and loads during battery testing is thought to be leakage of the current used in the battery testing from inside the energy storage system to the outside.

In view of the above problems, some embodiments of the present invention aim to provide a battery system, a new energy system, a power distribution system, a power transmission system, a battery system for transportation equipment, an electric vehicle, and a battery system for an uninterruptible power supply, which can suppress the loss of stability of the power state in external equipment when testing a battery.

The energy storage system of the present invention is characterized by comprising a main circuit section in which arms equipped with unit converters having chargeable and dischargeable energy storage elements are provided corresponding to each of the phases in a three-phase alternating current to form a ring-shaped current path, and a control means for testing the deterioration state of the energy storage element designated as the object of diagnosis by connecting the energy storage element designated as the object of diagnosis to the ring-shaped current path and passing a circulating current of any frequency through the ring-shaped current path.

The energy storage system of the present invention is characterized by comprising a main circuit section in which arms equipped with unit converters having chargeable and dischargeable energy storage elements are provided corresponding to each of the phases in a three-phase alternating current to form a circular current path, and a detection section which detects the voltage generated between the terminals of the energy storage element designated as the diagnosis target and the current flowing through the energy storage element due to circulating currents of different frequencies flowing through the circular current path.

The energy storage system of the present invention is characterized in that it comprises a transformer having a primary winding and a secondary winding corresponding to each of the interphases of a three-phase AC power source and receiving power from the three-phase AC power source via the primary winding, a unit converter having a chargeable and dischargeable energy storage element, a plurality of arms respectively connected to a plurality of the secondary windings respectively corresponding to the interphases of the three-phase AC, a plurality of circular current paths respectively corresponding to the interphases of the three-phase AC and individually formed as closed circuits formed by each of the arms and each of the secondary windings, and a control means for controlling the unit converter, passing circulating currents of different frequencies through at least one of the plurality of circular current paths, and testing the deterioration state of the energy storage element designated as the diagnosis target.

The energy storage system of the present invention is characterized in that it comprises a plurality of unit converters each having an energy storage element and capable of transmitting and receiving electric power between a connected external system, and a control means for sequentially applying AC voltages of different frequencies to the energy storage element of one of the unit converters selected from the plurality of unit converters while transmitting and receiving electric power between the plurality of unit converters and the external system, and estimating an equivalent circuit of the energy storage element.

The energy storage system of the present invention is characterized in that it is a energy storage system that is connected to an AC system and has a main circuit section provided with an arm equipped with a unit converter having a chargeable and dischargeable energy storage element, and that it is equipped with a control means that tests the deterioration state of the energy storage element designated as the diagnosis target while receiving and sending power between the AC system and the energy storage system.

The new energy system of the present invention is characterized in that it is connected to any of the storage systems described above.

The power distribution system of the present invention is characterized in that it is connected to any of the storage systems described above.

The power transmission system of the present invention is characterized in that it is connected to any of the storage systems described above.

The transportation equipment of the present invention is characterized in that it is connected to any of the storage systems described above.

The battery system of the electric vehicle of the present invention is characterized in that it is connected to any of the storage systems described above.

The battery system of the uninterruptible power supply of the present invention is characterized in that it is connected to any of the storage systems described above.

As described above, according to embodiments of the present invention, when testing a battery, the current for testing the deterioration state of the storage elements circulates inside the storage system and does not leak to the outside, thereby preventing the stability of the power state in external equipment connected to the storage system from being impaired. As a result, according to some embodiments of the present invention, it is possible to diagnose or measure the characteristics of each storage element in the storage system while continuing to operate the storage system, without affecting the external equipment connected to the storage system.

1 is a schematic diagram showing an example of a power grid system using a wind farm as an energy source, the power storage system according to a first embodiment of the present invention; 1 is a configuration diagram of a power storage system that receives and transmits power through grid interconnection with a power grid according to a first embodiment of the present invention. 2 is a diagram showing a circuit configuration of a unit converter constituting the power storage system according to the embodiment of the present invention. FIG. 1A and 1B are diagrams illustrating a voltage conversion operation of a multilevel conversion circuit that converts the voltage of storage elements connected in series in an arm into an AC waveform of a desired frequency. 13 is a diagram showing a connection state within the unit conversion circuit when diagnosing the storage element. FIG. 1 is a diagram showing an equivalent circuit representing the complex impedance of a storage element, and a locus on a complex plane that is traced by the complex impedance of the storage element in response to a change in frequency of a current flowing through the storage element; FIG. 11 is a configuration diagram of a power storage system that receives and transmits power through grid interconnection with a power grid according to a second embodiment of the present invention. FIG. 4 is a diagram showing a circuit simulation result of an example in which the power storage system according to the first embodiment of the present invention is used.

Hereinafter, several embodiments of the present invention will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. For example, expressions expressing that things are in an equal state, such as "same," "equal," and "homogeneous," not only express a strictly equal state, but also express a state in which there is a tolerance or a difference to the extent that the same function is obtained. On the other hand, expressions such as "comprise," "include," "have," "include," or "have" a component are not exclusive expressions that exclude the presence of other components.

First, the configuration and operation of the energy storage system relating to the first embodiment of the present invention will be described below with reference to Figures 1 to 6.

First Embodiment
The storage system of the first embodiment of the present invention will be described by taking as an example a case where a storage system is connected to a power grid system using a wind farm as an energy source as a new energy system. First, the configuration of a power grid system to which the storage system of the first embodiment is applied will be described with reference to FIG. 1. FIG. 1 illustrates a power grid system 1 including a power grid 5 as a relatively low-voltage power distribution system that supplies power from a power generation facility to a load, and a storage system 10 that exchanges power with the power grid 5 by system interconnection with the power grid 5. The power grid system 1 illustrated in FIG. 1 also illustrates a wind farm 92 equipped with a plurality of tower-type wind power generators that generate power by wind power according to wind conditions 91 as an example of a power generation facility. Wind-generated power 90A generated by wind power is supplied from the wind farm 92 through the power grid to a load 93 via a power conversion facility 94 to cover the power demand of the load 93.

A wind farm 92 that generates electricity using wind power, a natural energy source, is an unstable power generation facility in which the amount of electricity generated changes irregularly depending on wind conditions 91. Since the frequency of the power grid 5 changes depending on the relationship between power demand and supply, it is preferable that the output from the wind farm 92 is stable.

Therefore, in the power grid system 1, the power storage system 10 is connected to a power supply line between the power grid 5 and the load 93, and is used as a system power stabilization device that balances the relationship between power demand and supply in the power grid by transferring power to and from the power grid 5, and stabilizes the system frequency and current voltage in the power grid 5. That is, when the power output from the power generation equipment is insufficient relative to the power required by the load 93, the power storage system 10 discharges to supply the shortage to the power grid 5. Conversely, when the power output from the power generation equipment is in surplus relative to the power required by the load 93, the power storage system 10 recovers the surplus power from the power grid 5 and charges it for storage.

In the example shown in FIG. 1, when the amount of power generated by the wind farm 92, which is a power generation facility, increases with a change in wind conditions 91, and a surplus of system power occurs in the power grid 5, the power storage system 10 charges and stores a portion of the system power. Conversely, when the amount of power generated by the wind farm 92 decreases due to no wind, or when the power demand of the load 93 increases sharply, causing a shortage of system power, the power storage system 10 supplies the stored power to the power grid 5 by discharging. For example, referring to FIG. 1, when there is a shortage of system power, the power storage system 10 discharges the stored charge/discharge power 90C to the power grid 5, and a composite power 90B, which is a combination of the wind-generated power 90A generated by wind and the charge/discharge power 90C discharged from the power storage system 10, is supplied to the load 93.

In order to realize the exchange of power with the power grid 5 through the charging and discharging described above, the energy storage system 10 shown in FIG. 1 includes a circuit configuration consisting of multiple energy storage elements that can be charged and discharged, and also has a circuit configuration as a power converter that converts AC power from the power grid 5 into DC so that it can be charged into the energy storage elements, and conversely, converts the DC power discharged by the energy storage elements into AC so that it can be output to the power grid 5.

The state of the multiple storage elements that make up such a power storage system, such as their storage performance and lifespan, changes depending on the operation of the power storage system. In particular, to maintain a power storage system that receives and transmits power to and from a power grid in an operable state over the long term, it is necessary to perform a lifespan diagnosis of each storage element that makes up the power storage system while the power storage system is in operation and to identify which storage elements should be replaced with new ones. However, if a deterioration diagnosis of the storage elements is performed while a conventional power storage system is in operation, it may cause fluctuations in the system frequency and current voltage in the power grid, temporarily compromising the stability of the system power.

In contrast, the energy storage system of some embodiments of the present invention can suppress the loss of stability of power in an external power system or load when individually diagnosing a large number of energy storage elements that make up the energy storage system, as will be described in detail later with reference to Figures 2 to 5. Below, a first embodiment of the energy storage system that exchanges power by interconnecting with the power system will be described in detail with reference to Figures 2 to 5.

First, the configuration of the power grid system 1 will be described. As shown in FIG. 2, the exemplary power grid system 1 has a configuration in which a power storage system 10 is connected to a power grid 5. The power grid 5 and the power storage system 10 are connected via terminals 57u, 57v, and 57w. In the power grid 5, a power generation facility 50 that supplies three-phase AC power and a load 56 are connected via distribution lines 53u, 53v, and 53w. In FIG. 2, the wind farm 92 in FIG. 1 is shown as a schematic representation of the power generation facility 50. The load 56 is similar to the load 93 in FIG. 1, and is, for example, a consumer such as a factory or a machine or manufacturing device owned by the consumer. 2, 52u, 52v, 52w and 51u, 51v, 51w are schematic representations of the reactance and resistance components of the distribution lines 53u, 53v, 53w on the power generation facility 50 side from the terminals 57u, 57v, 57w, and 54u, 54v, 54w and 55u, 55v, 55w are schematic representations of the reactance and resistance components of the distribution lines 53u, 53v, 53w on the load 56 side from the terminals 57u, 57v, 57w. The storage system 10 of the first embodiment is used as a power system stabilizing device for stabilizing the power system 5 in the power grid system 1, which is such a three-phase AC system. Note that the storage system 10 according to some embodiments of the present invention is not limited to being connected to the power system 5 as a system power stabilizing device, and can also be used for other purposes such as an AC power source that supplies power to a load of transportation equipment such as an electric vehicle, a railroad car, a truck, or a bus as an external system.

(1-1) Overall Configuration of Energy Storage System Next, the configuration of the energy storage system 10 shown in FIG. 2 will be described according to the first embodiment of the present invention. In one example, the energy storage system 10 includes a main circuit unit 10a, an impedance characteristic measuring unit 12, and a control unit (control means) 13. The energy storage system 10 includes a main circuit unit 10a capable of power conversion of a DC voltage that can be increased or decreased in multiple stages into three inter-phase voltages in a three-phase AC voltage and outputting the voltage to the power grid system 1, an impedance characteristic measuring unit 12, and a control unit 13 that specifies a storage element 35 to be diagnosed, measures the impedance of the specified storage element 35 (FIG. 5) by the impedance characteristic measuring unit 12, and controls the connection state of the storage element to the ring-shaped current path 71. Hereinafter, the internal structure of each unit constituting the energy storage system 10 will be described in the order of the main circuit unit 10a, the impedance characteristic measuring unit 12, and the control unit 13.

(1-2) Configuration and Operation of the Main Circuit First, the configuration of the main circuit 10a will be described with reference to Fig. 2. The main circuit 10a has a so-called delta-connection MMC configuration. More specifically, the main circuit 10a includes a ring-shaped current path 71 having a delta-connection circuit topology, and is connected to the power system 5 by a three-phase AC power line. In addition, each of the three sides of the ring-shaped current path 71 having the delta-connection topology corresponds to three interphase voltages in the three-phase AC, and each of the three sides is configured as a multilevel power converter that converts and outputs the charging power as each waveform of the three-phase AC.

The detailed structure of the inside of the looped current path 71 having the Δ-connection topology in the main circuit unit 10a shown in Fig. 2 will be described below. Each side of the looped current path 71 having the Δ-connection topology is composed of three arms 11A, 11B, and 11C and reactors 14A, 14B, and 14C. The looped current path 71 is formed by connecting the reactor 14A, the arm 11A, the reactor 14B, the arm 11B, the reactor 14C, the arm 11C, and the reactor 14A in this order, forming a looped current path. Each of the three arms 11A, 11B, and 11C is configured by connecting a plurality (K units) of unit converters _Cx ⁽ⁱ⁾ (1 ≦ i ≦ K) (K is any positive integer) in cascade (series).

Further, in the example shown in Fig. 2, the main circuit section 10a includes an arm 11A that supplies an electromotive voltage between the R phase and the S phase that can be increased or decreased in multiple stages, an arm 11B that supplies an electromotive voltage between the S phase and the T phase that can be increased or decreased in multiple stages, and an arm 11C that supplies an electromotive voltage between the T phase and the R phase that can be increased or decreased in multiple stages. The arm 11A is configured by connecting multiple (K) unit converters C _A ⁽ⁱ⁾ (1 < i < K) having a chargeable and dischargeable storage element 35 in series in order to output a DC voltage that can be increased or decreased in multiple stages. Similarly, the arm 11B is configured by connecting multiple (K) unit converters C _B ⁽ⁱ⁾ (1 < i < K) in series, and the arm 11C is configured by connecting multiple (K) unit converters C _C ⁽ⁱ⁾ (1 < i < K) in series. The number of unit converters C _x ⁽ⁱ⁾ included in each of arms 11A, 11B, and 11C can be set as appropriate and may be 1. If the number of unit converters C _x ⁽ⁱ⁾ included in each of arms 11A, 11B, and 11C is large, the number of stages of the AC voltage output by power storage system 10 increases, and the waveform of the AC voltage can be made closer to a sine wave.

One end of each of the arms 11A, 11B, and 11C is connected to the terminals 57u, 57v, and 57w of the distribution lines 53u, 53v, and 53w of the power system 5 via the reactors 14A, 14B, and 14C, respectively. Specifically, the distribution line 53u has a terminal 57u, which is connected to the connection point of the arm 11A and the arm 11C of the main circuit unit 10a. The distribution line 53v has a terminal 57v, which is connected to the connection point of the arm 11B and the arm 11C of the main circuit unit 10a. The distribution line 53w has a terminal 57w, which is connected to the connection point of the arm 11C and the arm 11A of the main circuit unit 10a. In this way, the main circuit unit 10a of the storage system 10 is connected to the power system 5.

Next, the configuration of the unit converter C _x ⁽ⁱ⁾ will be described. The configuration of the unit converter C _x ⁽ⁱ⁾ is shown in Fig. 3. As shown in Fig. 3, the unit converter C _x ⁽ⁱ⁾ includes a first switch arm 33 in which a first switch 33H and a second switch 33L are connected in series, a second switch arm 34 in which a third switch 34H and a fourth switch 34L are connected in series, and a chargeable and dischargeable storage element 35. The storage element 35 is formed of a secondary battery such as a lithium ion battery, a nickel-metal hydride battery, or a nickel-cadmium battery. The unit converter C _x ⁽ⁱ⁾ is connected to a power grid system 1 as an external system, and is capable of receiving and transmitting power between the power grid system 1.

In the unit converter C _x ⁽ⁱ⁾ , the first switch 33H side end of the first switch arm 33, the third switch 34H side end of the second switch arm 34 and one terminal (positive side in this embodiment) of the storage element 35 are connected, and the second switch 33L side end of the first switch arm 33, the fourth switch 34L side end of the second switch arm 34 and the other terminal (negative side in this embodiment) of the storage element 35 are connected. In this manner, the unit converter C _x ⁽ⁱ⁾ has a full bridge circuit configuration in which the first switch arm 33, the second switch arm 34 and the storage element 35 are connected in parallel. In this embodiment, a full bridge configuration is used, but a half bridge configuration may also be used.

In the unit converter C _x ⁽ⁱ⁾ , the first switch arm 33 and the second switch arm 34 are connected in parallel, and therefore the first switch 33H and the third switch 34H are connected in series (inverse series) between the first terminal FT and the second terminal ST, and the second switch 33L and the fourth switch 34L are connected in series. Here, one of the switches connected in series between the first terminal FT and the second terminal ST (the first switch 33H and the third switch 34H) is referred to as a first switch group 36, and the other of the switches connected in series (the second switch 33L and the fourth switch 34L) is referred to as a second switch group 37.

A control unit 13 (FIG. 2), which will be described later, is connected to the unit converter C _x ⁽ⁱ⁾ , and a drive voltage (e.g., a gate voltage in the case of a switching element constituted by an FET (field effect transistor)) that controls the on/off of each switch is supplied from the control unit 13 to the first switch 33H, the second switch 33L, the third switch 34H and the fourth switch 34L.

In the unit converter C _x ⁽ⁱ⁾ , a first terminal FT is drawn from a connection point 30 between the first switch 33H and the second switch 33L of the first switch arm 33, and a second terminal ST is drawn from a connection point 32 between the third switch 34H and the fourth switch 34L of the second switch arm 34. Two adjacent unit converters C _x ⁽ⁱ⁾ are connected in series with the first terminal FT of one unit converter C _x ⁽ⁱ⁾ and the second terminal ST of the other unit converter C _x ⁽ⁱ⁾ . If the voltage of the storage element 35 is V, in the unit converter C _x ⁽ⁱ⁾ shown in Fig. 3, the voltage between the output terminals (between the first terminal FT and the second terminal ST) can be increased or decreased in three stages as follows. That is, in the unit converter C _x ⁽ⁱ⁾ , three levels of voltage, ±V and zero, can be output between the first terminal FT and the second terminal ST by switching on and off the first switch 33H, the second switch 33L, the third switch 34H and the fourth switch 34L. Note that in the first embodiment, each of the unit converters C _x ⁽ⁱ⁾ is configured to output the same voltage, but it is also possible to configure each of the unit converters C _x ^{(i) to output different voltages by appropriately changing the configuration (capacity of the storage element, etc.) of the storage element 35 included in each of the unit converters C x (i)} .

In the energy storage system 10 shown in Fig. 2, the first terminal FT of one unit converter _Cx ⁽ⁱ⁾ is connected to the second terminal ST of the adjacent unit converter _Cx ⁽ⁱ⁺¹⁾ , and a plurality (K units) of unit converters _Cx ⁽ⁱ⁾ (1 <= i <= K) are connected in series. Therefore, in the energy storage system 10, the arm 11A that applies a voltage between the R phase and the S phase, the arm 11B that applies a voltage between the S phase and the T phase, and the arm 11C that applies a voltage between the T phase and the R phase are switched to output a multi-stage voltage according to the number of unit converters _Cx ^{(i) .} In addition, in the energy storage system 10, each unit converter _Cx ⁽ⁱ⁾ is provided with a storage element ₃₅ that can charge and discharge power, so that electric energy can be stored by charging the storage element 35 from the power system 5, and the energy storage system 10 can be used as a power storage device.

(1-3) Configuration and Operation of Impedance Characteristics Measurement Unit and Control Unit First, the configuration of the impedance characteristics measurement unit 12 will be specifically described. As shown in Fig. 3, the impedance characteristics measurement unit 12 includes a voltage measurement unit 120 and a current measurement unit 121. The voltage measurement unit 120 is connected between the terminals of each storage element 35, and measures the voltage between the terminals. The current measurement unit 121 is inserted between the connection point 30 between the first switch 33H and the second switch 33L and the first terminal FT, and measures the current flowing through the annular current path 71. The current measurement unit 121 can be inserted at any position in the annular current path 71.

Next, the configuration of the control unit 13 that controls the energy storage system 10 will be described. The control unit 13 is configured to execute a control sequence that controls so that circulating currents of different frequencies flow through the annular current path 71, and to test the deterioration state of the energy storage element designated as the diagnosis target. The control unit 13 is realized, for example, by a processor, dedicated hardware designed to execute the control operation described below, or software on a general-purpose arithmetic device such as a PC. In addition, in one example, the control unit 13 may be configured as an information processing device including an arithmetic circuit and an input/output interface for electrical signals, and the arithmetic circuit may implement an arithmetic logic that executes the following controls or commands. That is, the arithmetic circuit in the control unit 13 implements (1) an operation to control the connection state of the multiple energy storage elements 35 connected along the annular current path 71, (2) output control for controlling the output of active power and reactive power to the power system 5 by the same principle and circuit operation as the conventional delta-connection MMC, (3) an operation to specify the energy storage element 35 to be diagnosed from among the multiple energy storage elements 35, and (4) an arithmetic logic that executes an operation command to the impedance characteristic measurement unit 12, etc. Furthermore, the control unit 13 can also control the active power and reactive power input and output by the power storage system 10 .

(1-3-1) Operation of outputting voltage to power system Next, a description will be given of an operation of outputting voltage to power system 5 by control unit 13. Control unit 13 sends commands to the control circuits of each unit converter to control the on/off of the switches of each unit converter C _x ⁽ⁱ⁾ , generates multi-stage three-phase AC voltages from arms 11A, 11B and 11C and outputs them between R phase and S phase, between S phase and T phase, and between T phase and R phase, respectively.

By arms 11A, 11B, and 11C outputting a voltage different from the inter-terminal voltages of terminals 57u, 57v, and 57w of distribution lines 53u, 53v, and 53w, active power and reactive power can be exchanged between the power distribution system.

In addition, since the voltage of the power distribution system and the power transmission system is a sine wave, it is preferable that each arm 11A, 11B, and 11C also outputs a voltage close to a sine wave.

Hereinafter, with reference to Fig. 4, a principle of outputting an output voltage that can be increased or decreased in multiple stages from each of the arms 11A, 11B, and 11C so as to have a waveform close to a sine wave by controlling each of the arms 11A, 11B, and 11C constituting the main circuit unit 10a shown in Fig. 2 by the control unit 13 will be described. Here, the principle will be described using an example in which each of the arms 11A, 11B, and 11C has six unit converters _Cx ⁽ⁱ⁾ (1 < i < 6, x = {A, B, C}). Specifically, a mechanism will be described in which the control unit 13 executes on/off control of the switches of the six unit converters _Cx ⁽ⁱ⁾ (1 < i < 6, x = {A, B, C}) provided in each of the arms 11A, 11B, and 11C to generate interphase voltages in three-phase AC from each of the arms 11A, 11B, and 11C, and outputting the correlation voltages from both ends of each arm 11x so as to have a waveform close to a sine wave. The mechanism is the same for each of arms 11A, 11B, and 11C, so the following description will be given taking as an example the case where the voltage output between the R phase and the S phase from arm 11A is output so as to have a waveform close to a sine wave.

4, with the vertical axis representing the voltage (positive or negative, but normalized with the maximum value of the output voltage of each unit converter set to 1) generated between the R and S phases and the horizontal axis representing time, shows the relationship between the target voltage output from arm 11A of main circuit unit 10a and the voltage generated between each output terminal (FT-ST) of each of the unit converters C _A ⁽¹⁾ to C _A ⁽⁶⁾ that make up arm 11A, over one cycle of the AC waveform. Here, the target voltage in arm 11A is the target value of the AC voltage output as the interphase voltage between the R and S phases, and is set so as to change along the AC voltage waveform that should be generated as a sine wave between the R and S phases.

4 shows, from the top, an increase/decrease voltage V _out applied in multiple stages to arm 11A between the R and S phases of power storage system 10, and V _A ⁽¹⁾ , V A (2), V _A (3 ⁾ , V _A ^{(4) ,} V _A (5), and V _A ⁽⁶⁾ applied between the output terminals (FT-ST) of each of unit converters C _A ⁽¹⁾ to C _A ^{( 6)} constituting arm _11A . Also, in Fig. 4, the intersection of the vertical and horizontal axes is set as reference potential 0, with the side above reference potential 0 being positive and the side below reference potential 0 being negative.

As shown in FIG. 4, in the main circuit section 10a, rectangular wave-shaped voltage pulses with different amplitude reference potentials and widths are generated between the output terminals (FT-ST) of the unit converters C _A ⁽¹ ) to C _A ⁽⁶⁾ constituting the arm 11A. At this time, the opening and closing of the first switch group 36 and the second switch group 37 of the unit converters C _A ⁽¹⁾ to C _A ⁽⁶⁾ is controlled so that a voltage corresponding to the target voltage is generated at both ends of the arm 11A. For example, the pulses are obtained by shifting the phase of a triangular _wave of triangular wave _PWM (Pulse-Width Modulation) control and modulating the pulse width. As a result, rectangular ^wave -shaped voltage pulses with different amplitude reference potentials and widths and the same amplitude height are generated between the output terminals (FT-ST) of the unit converters ^{C A} (1) to C A (6) constituting the arm 11A, and these voltage pulses are further synthesized. As a result, a voltage that changes stepwise in response to the target voltage expressed by a sine wave is output from arm 11A of main circuit portion 10a as a phase-to-phase voltage of the three-phase AC.

At this time, the control unit 13 included in the power storage system 10 generates a drive signal for controlling the opening and closing of the corresponding ^{first switch group 36} _and second switch group ³⁷ based on the target voltage waveform represented by a sine wave, so that the rectangular wave-like voltage _{approximating} the target voltage waveform is generated between the output terminals (FT-ST) of each of the unit converters C A (1) to C A (6). For example, the drive signal is generated by normalizing a voltage command value for the arm 11A to output a voltage and comparing the normalized voltage command value with a triangular wave. The control unit 13 outputs the generated drive signal to the gates of the semiconductor switching elements constituting the corresponding first switch group 36 and second switch group 37, and switches (ON, OFF) the corresponding switching elements. In this manner, each of the arms 11A, 11B, and 11C executes the voltage conversion operation of a multilevel conversion circuit that converts the composite voltage of the storage elements connected in series therein into an AC waveform of a desired frequency. This is an example of a control sequence for causing circulating currents of different frequencies to flow through the annular current path 71.

As described above, the opening and closing timing of the switching elements in the unit converter C _x ⁽ⁱ⁾ can be controlled by the control unit 13. This control operation by the control unit 13 makes it possible to control the current and voltage in the three arms 11A, 11B, and 11C, each of which is configured by connecting two or more chargeable and dischargeable storage elements 35 in series, so that they change with a desired AC waveform and frequency. As an example, it is possible to generate three interphase voltages in three-phase AC power to be supplied to the power system 5 at both ends of each of the three arms 11A, 11B, and 11C. At the same time, the magnitude (instantaneous value) of the current flowing through each of the three arms 11A, 11B, and 11C can be changed to have an AC waveform corresponding to each phase of the three-phase AC power. At this time, the control unit 13 can control the phase difference (power factor) between the current waveform flowing through each of the three arms 11A, 11B, and 11C and the interphase voltage waveform appearing at both ends of the arm to be a desired power factor. Therefore, by controlling the power factor of the AC power in each of the three arms 11A, 11B, and 11C, the control unit 13 is configured to perform output control to control the output of active power and reactive power to the power grid 5.

(1-3-2) Impedance characteristic measurement operation The impedance characteristic measurement operation by the impedance characteristic measurement unit 12 and the control unit 13 will be described. The control unit 13 executes a control sequence so that circulating currents of different frequencies flow through the annular current path 71. Next, the control unit 13 outputs to the impedance characteristic measurement unit 12 a signal designating the storage element 35 to be diagnosed and a signal commanding that the designated storage element 35 should be diagnosed. At that time, the control unit 13 sequentially switches the designation of the storage element 35 to be diagnosed along the annular current path 71, thereby being able to diagnose all of the storage elements 35 arranged along the annular current path 71.

On the other hand, the impedance characteristic measurement unit 12, which has received a command from the control unit 13, first identifies the storage element 35 to be diagnosed from among the multiple storage elements 35 arranged along the circular current path 71 according to the designation of the diagnosis target by the control unit 13. Next, the impedance characteristic measurement unit 12 measures the current value of the test current passed through the storage element 35 to be diagnosed by the current measurement unit 121. Next, the impedance characteristic measurement unit 12 estimates the impedance characteristic of the storage element 35 from the voltage value measured between the terminals of the storage element 35 by the voltage measurement unit 120 and the current value. Finally, the impedance characteristic measurement unit 12 outputs the impedance characteristic estimated for the storage element 35 to the control unit 13. As described above, the impedance characteristic measurement unit 12 serves as a detection unit that detects the voltage generated between the terminals of the storage element 35 designated as the diagnosis target and the current passed through the storage element due to the circulating currents of different frequencies flowing through the circular current path 71.

(1-3-3) Diagnosis of the Energy Storage Element In order to reduce the lifetime cost in the energy storage system 10 according to the embodiment of the present invention, it is important to use the energy storage element 35 in such a way that the energy storage element 35 does not deteriorate over its life. For example, it is important to check the deterioration state of the energy storage element 35, and to understand the relationship between the operation of the energy storage system 10 and the deterioration of the energy storage element 35, and to operate the energy storage system 10 based on this. It is also important not to affect the system to which the energy storage system 10 is connected when diagnosing the deterioration of the energy storage element 35. In order to diagnose the energy storage element 35 without affecting the system, in the energy storage system 10 according to the embodiment of the present invention, the control unit 13 controls the unit converter to output a positive-phase voltage or a negative-phase voltage to exchange active power and reactive power with the power grid 5. Here, if the power grid 5 is an ungrounded system, the zero-phase component does not affect the active power or reactive power. Therefore, it is preferable to use a zero-phase current or a zero-phase voltage to perform a deterioration diagnosis of the energy storage element 35. Specifically, since the energy storage system 10 has the looped current path 71 configured as a circulating path that loops between the phases, a zero-phase sequence voltage is applied to the looped current path 71 to pass a zero-phase sequence current through the looped current path 71, thereby performing deterioration diagnosis of any of the energy storage elements 35. The operation of generating a circulating current will be described below.

(1-3-4) Operation of Generating Circulating Current Next, an operation of generating a test current (hereinafter referred to as "circulating current I cir (FIG. 5)") to be passed for diagnosing the storage elements 35 in a circular current path 71 formed in the main circuit unit 10a by connecting three arms 11A, 11B, and 11C, each of which is configured by connecting two or more chargeable and dischargeable storage elements 35 in _series , will be described. In this case, the sum voltage of the positive-sequence voltage and negative-sequence voltage required for power control and the zero-sequence voltage required for passing the circulating current is output to each of the arms 11A, 11B, and 11C.

Here, the operation of the control unit 13 when testing the deterioration state of the storage element 35 designated as the diagnosis target will be described. The control unit 13 first switches the operation state of the unit converter C _x ⁽ⁱ⁾ including the storage element 35 designated as the diagnosis target from a normal operation state in which power is exchanged with the power system 5 to a test operation state in which the impedance characteristics of the storage element 35 are measured. At this time, in order to switch to the test operation state, the control unit 13 controls the switching elements in the unit converter C _x ⁽ⁱ⁾ of the full-bridge circuit configuration including the storage element 35 as follows. First, the control unit 13 controls the switching elements so that the positive and negative electrodes of the storage element 35 are connected to one and the other of the output terminal pair (pair of FT terminal and ST terminal) of the full-bridge circuit, respectively. Then, in the full-bridge circuit in which the positive and negative electrodes of the storage element 35 are connected to one and the other of the output terminal pair, respectively, a pair of switching elements that are simultaneously in a conductive state is defined as "diagonally positioned switching elements". In this way, the pair of diagonally positioned switching elements in the full bridge circuit are brought into a conductive state, thereby testing the deterioration state of the storage element 35 designated as the diagnosis target. Note that when the full bridge circuit including the storage element 35 is in a test operation state, the other switching elements, except for the shorted pair of diagonally positioned switching elements, must be brought into a non-conductive state so as not to short-circuit the terminals of the storage element 35.

For example, when the unit converter C _x ⁽ⁱ⁾ including the storage element 35 designated as the diagnosis target is configured as a full-bridge circuit as shown in Fig. 3, a pair of diagonally positioned switching elements is simultaneously brought into a conductive state as follows. For example, as a pair of switches in diagonal positions in the full-bridge circuit shown in Fig. 3, either the pair of the first switch 33H and the fourth switch 34L or the pair of the second switch 33L and the third switch 34H is selected and maintained in the on state. The other pair is brought into the off state.

Next, the control unit 13 is configured to execute a control sequence for performing the above control so that circulating currents I _cir of different frequencies flow through the annular current path 71. In this way, the arms 11A, 11B, and 11C each having a unit converter C _x ⁽ⁱ⁾ (1≦i≦K, x={A, B, C}) having a chargeable and dischargeable storage element 35 are provided corresponding to each of the phases in the three-phase AC to form the annular current path 71, so that the circulating current I _cir for testing the deterioration state of the storage element 35 can be made to flow at various different frequencies. Then, the current and voltage of the storage element 35 are measured while changing the frequency of the circulating current I _cir . At that time, it is preferable to measure the current value and voltage value at least for each frequency for a time corresponding to at least one cycle. Then, the frequency dependency of the complex impedance of the storage element 35 is calculated from the voltage value and current value of the same frequency component as the frequency of the circulating current I _cir extracted by Fourier transform or the like from the measurement results of the voltage and current described above. The impedance of each part of the storage element 35 is estimated from the complex impedance component, and the deterioration state is diagnosed. The diagnosis method will be described later.

A method for preventing a DC current from flowing out to the power system 5 in the measurement of the complex impedance will be described. When the storage element 35 of a specific cell in a specific arm is measured with a continuous sine wave current, the corresponding unit converter C _x ⁽ⁱ⁾ outputs a DC voltage. At this time, the other unit converter C _x ⁽ⁱ⁾ in the corresponding arm outputs a voltage that compensates for the DC voltage generated by the measurement, so that the arm to which the storage element 35 whose complex impedance is being measured belongs outputs a DC voltage, and it is possible to prevent a DC current from flowing out to the power system 5. As another method for preventing a DC current from flowing out to the power system 5, two arms other than the arm to which the storage element 35 whose complex impedance is being measured belongs may output a voltage that compensates for the DC voltage generated by the measurement. In this case, the DC voltage becomes zero-phase, so that the DC current does not flow out to the outside of the storage system 10. Furthermore, it is also possible to simultaneously measure the voltage and current of a specific storage element 35 in each phase (arm) by utilizing the fact that all phases (arms) output DC voltages.

As another method, it is possible to apply a voltage pulse such as a PWM pulse to pass an intermittent sine wave zero-phase current through a specific storage element 35, measure the voltage and current only when the intermittent current is passing, and obtain the complex impedance of the frequency by discrete Fourier expansion or the like. In this case, it is also possible to measure the voltage and current of a specific storage element 35 simultaneously for each phase (arm). In this way, the current for testing the deterioration state of the storage element 35 circulates inside the storage system 10 and does not leak out to the external power system 5, so that it is possible to prevent the stability of the power state in the external power system 5 and the load 56 that are interconnected with the storage system 10 from being impaired.

Next, a description will be given of a control method for passing a circulating current through the energy storage element 35. The control unit 13 performs an operation for controlling the opening and closing of the switching elements of the unit converters C _x ⁽ⁱ⁾ (1≦i≦K, x={A, B, C}) that form the ring-shaped current path 71 in accordance with a predetermined control sequence, thereby making it possible for circulating currents I _cir of different frequencies to flow through the ring-shaped current path 71.

This eliminates the need for an additional power source connectable to the main circuit unit 10a to generate the circulating current _Icir for testing the deterioration state of the storage element 35, and makes it possible to generate the circulating current _Icir for testing the deterioration state of the storage element 35 using only the voltage generated by the main circuit unit 10a itself. In one embodiment, the unit converter C _x ⁽ⁱ⁾ including the storage element 35 designated as the diagnosis target is in a test operation state in which the impedance characteristics of the storage element 35 are measured, while the other unit converters C _x ⁽ⁱ⁾ are in a normal operation state in which power is exchanged with the power system 5. Therefore, in this case, not only is power exchanged with the power system 5 by the charge/discharge operation of the other storage elements 35 excluding the storage element 35 designated as the diagnosis target, but the circulating current _Icir is also generated. In this way, the control unit 13 can sequentially apply AC voltages of different frequencies to the storage element 35 of one unit converter selected from the multiple unit converters C _x ⁽ⁱ ) while power is being exchanged between the multiple unit converters C _x ⁽ⁱ⁾ and the power grid system 1 (external system), estimate the equivalent circuit of the storage element 35, and test the deterioration state of the storage element 35 specified as the diagnosis target.

(1-3-5) Diagnosis of Energy Storage Element Using Complex Impedance Under the control of the control unit 13 on the main circuit unit 10a, the impedance characteristic measurement unit 12 measures the impedance characteristic of the energy storage element 35 while the circulating current I _cir for testing the deterioration state of the energy storage element 35 is flowing through the circular current path 71 while changing the frequency in various ways. Specifically, the impedance characteristic measurement unit 12 measures the terminal voltage of the energy storage element 35 by the voltage measurement unit 120 and measures the current flowing through the energy storage element 35 by the current measurement unit 121 in a state in which currents of various different frequencies are flowing through the energy storage element 35 designated as the diagnosis target. The impedance can be calculated from the AC voltage and AC current of the frequency component. In this way, the impedance characteristic measurement unit 12 examines how the impedance of the energy storage element 35 changes in response to changes in the frequency of the circulating current I _cir .

Next, a specific example of a method (so- _called Cole-Cole plot) in which the impedance characteristic measuring unit 12 estimates the degradation state of the diagnosis target storage element 35 from the impedance after grasping the impedance of the storage element 35 corresponding to the frequency of the circulating current I _{cir flowing through the diagnosis target storage element 35 (FIG. 5) will be described with reference to FIG. 6. In this embodiment, the degradation state of the storage element 35 is estimated based on a complex impedance characteristic described by the internal resistance and equivalent capacitance exhibited by the storage element 35 through which the circulating current I cir} flows.

In this embodiment, as shown in FIG. 6 , the above complex impedance characteristic is estimated by a locus of complex impedance drawn in accordance with the frequency change of the circulating current I _cir on a complex plane PL having a real axis R and an imaginary axis Im as coordinate axes, and the deterioration state of each part of the storage element can be estimated from the value of the equivalent circuit.

6, the semicircular locus 300a corresponds to the equivalent circuit 320a, and corresponds to the locus drawn on the complex plane PL by the complex impedance represented by the equivalent capacitance 321a and the internal resistance 322a according to each frequency of the test current flowing through the storage element 35. Similarly, the semicircular locus 300b corresponds to the equivalent circuit 320b, and the semicircular locus 300c corresponds to the equivalent circuit 320c. The semicircular locus 300b corresponds to the locus drawn on the complex plane PL by the complex impedance represented by the equivalent capacitance 321b and the internal resistance 322b according to the frequency change of the test current flowing through the storage element 35, and the semicircular locus 300c corresponds to the locus drawn on the complex plane PL by the complex impedance represented by the equivalent capacitance 321c and the internal resistance 322c according to each frequency of the test current flowing through the storage element 35.

Specifically, for example, when the impedance characteristic shown in the upper part of Fig. 6 is obtained, the equivalent circuit of the diagnosis target energy storage element 35 can usually be expressed as a series connection of a parallel connection of an equivalent capacitance 321 and an internal resistance 322, as shown in Fig. 6. Since the impedance of the energy storage element 35 is expressed as a circuit in which one or more parallel connections each formed by connecting an equivalent capacitance and an internal resistance in parallel are connected in series, it can be understood that it can be quantified as a complex impedance including a real component and an imaginary component. In order to perform such an analysis using the complex impedance, the control unit 13 may be provided with a determination means for determining the deterioration state of the energy storage element based on the complex impedance characteristic described by the internal resistance and equivalent capacitance shown by the energy storage element 35 through which the circulating current _Icir flows.

On the complex plane PL, the magnitude of the internal resistance 322a of the equivalent circuit 320a corresponds to the width of the base of the semicircular locus 300a (arrow 380a shown in FIG. 6) in the width direction along the real axis R. The magnitude of the equivalent capacitance 321a of the equivalent circuit 320a is calculated by C1 = 1/(ω1max × Rd1), where ω1max is the frequency at which the locus 300a reaches its peak (vertex 310a shown in FIG. 6) on the imaginary axis Im, and Rd1 is the magnitude of the internal resistance 322a. Similarly, the magnitude Rd2 of the internal resistance 322b of the equivalent circuit 320b is calculated from the width of the base of the semicircular locus 300b (arrow 380b shown in FIG. 6). The magnitude of the equivalent capacitance 321b of the equivalent circuit 320b is calculated from the frequency ω2max when the imaginary component of the locus 300b peaks (vertex 310b shown in FIG. 6) and the magnitude Rd2 of the internal resistance 322b by C2=1/(ω2max×Rd2). The same is true for the equivalent circuit 320c, and the magnitude Rd3 of the internal resistance 322c is calculated from the width of the base of the semicircular locus 300c (arrow 380c shown in FIG. 6). The magnitude of the equivalent capacitance 321c of the equivalent circuit 320c is calculated from the frequency ω3max when the imaginary component of the locus 300c peaks (vertex 310c shown in FIG. 6) and the magnitude Rd3 of the internal resistance 322c by C3=1/(ω3max×Rd3). The discrimination means applies equivalent circuits to each part within the storage element 35, such as the positive electrode part, the negative electrode part, the electrolyte part, etc., calculates the resistance value and capacitance value of each equivalent circuit, and judges the deterioration state of the storage element 35 from the calculated resistance value and capacitance value and their changes over time, etc.

In addition, by examining the changes in internal resistance and capacitance over time of each part, it is possible to know which parts have deteriorated to what extent. Therefore, by saving the measurement history of the impedance characteristics shown in Figure 6 in chronological order and linking and analyzing this time-series data with data that chronologically records the operating status history of the entire power grid system 1 or the storage system 10, it is possible to obtain useful information such as the time to replace the storage element 35 and the optimal method of use.

For example, in order to extend the life of the entire power grid system 1 and the energy storage system 10, (a) analysis results can be obtained that provide clues for determining what battery characteristics should be used to configure the energy storage element 35, (b) what arrangement method should be used to arrange the energy storage elements inside the energy storage system 10, and (c) what is the optimal system configuration for the entire power grid including the energy storage system 10.

More specifically, for example, by providing a data mining means in the learning section and performing data mining using time series data of active current values and reactive current values (input/output information) output by each phase of the energy storage system 10 to an external system and equivalent circuit information of each energy storage element 35, it is possible to obtain useful clues as to how the output of the energy storage system 10 is related to the deterioration of the battery. In addition, by performing data mining using time series data of input/output currents, input/output voltages, SOC (State of charge), etc. (element information) of each energy storage element 35 and equivalent circuit information of each energy storage element 35, it is possible to obtain knowledge of the state of the energy storage element 35 that is prone to deterioration. Based on the deterioration information obtained by data mining, reinforcement learning can be performed to know the conditions for extending the life of the energy storage system 10. As described above, by performing data mining and AI technology such as machine learning, it is possible to not only obtain clues to know the optimal configuration and operation method of the energy storage system 10, but also to efficiently obtain major clues to know the optimal configuration of the power grid using it.

As an example of data mining, the output voltage value and output current value (output voltage value and output current value of the unit converter) of each storage element 35 are combined with the resistance value and capacitance value (hereinafter referred to as impedance value) of each equivalent circuit. This makes it possible to know how much deterioration will progress in which part of the storage element 35 depending on how the storage element 35 is used. As another example of data mining, by combining the output voltage value and output current value or circulating current _Icir value of the storage system 10 with the impedance value of each equivalent circuit, it is possible to know which part of the storage element 35 is likely to deteriorate depending on how the storage system 10 is operated.

The change in the deterioration state of the storage element 35, i.e., the change in the impedance value of each equivalent circuit (time series data of the impedance value) can be efficiently associated with the time series data of the element information and the input/output information (deriving the correspondence relationship, deriving parameters such as the degree of contribution to the impedance value change) by implementing the above-mentioned AI technology represented by data mining and reinforcement learning. This makes it possible to operate the storage system 10 while minimizing the deterioration of the storage element 35 and to estimate the exact replacement time of the storage element 35. Furthermore, by having the control unit 13 perform this operation and having the control unit 13 automatically correct the control operation of the storage system 10 based on the estimation result, more efficient operation can be achieved.

When the control unit 13 is made to perform the association using AI, for example, the control unit 13 is provided with a learning means for associating the output voltage and output current of the storage element 35 with the deterioration state of the storage element 35, and the learning means performs the association. An example of the association by the learning means will be described. The learning means stores the element information of the storage element 35 detected by the impedance characteristic measuring unit 12, and creates time series data of the element information. In addition, the learning means stores the impedance value of the equivalent circuit estimated from the complex impedance of the storage element 35 and the deterioration state of the storage element 35, and creates time series data of the impedance value of the equivalent circuit. The learning means associates the element information of the storage element 35 with the deterioration state of the storage element 35 based on the time series data of the created element information and the time series data of the impedance value of the created equivalent circuit. At this time, teacher data of the association between the element information of the storage element 35 and the deterioration state of the storage element 35 (the impedance value of the equivalent circuit) may be given to the learning means to learn.

The learning means may also use the learning result of the association between the element information of the storage element 35 and the deterioration state of the storage element 35 as new teacher data, and again associate the element information of the storage element 35 with the deterioration state of the storage element 35. By repeating this operation, the accuracy of the association increases. Note that the learning means may associate the input/output information of the energy storage system 10 with the deterioration state of the storage element 35, instead of the element information of the storage element 35. In this case, a detector that measures active current and reactive current is provided, and the detection results of the voltage and current from the detector are stored by the learning means.

The learning means, like the control unit 13, is realized by software on a general-purpose computing device such as a processor, dedicated hardware, or a PC. In addition, the learning means may be provided in part or in whole separately from the control unit 13, or may be provided as an external device of the energy storage system 10.

Furthermore, the learning means may cause at least a part of the association work to be performed by an external device configured separately from the control unit 13 or the power storage system 10, i.e., an external device configured separately from the learning means and connected to the learning means. For example, by having computationally intensive work such as data mining performed by dedicated hardware equipped with a high-performance GPU (Graphics Processing Unit) and large-capacity memory, the calculation time can be shortened and the association work can be performed more efficiently.

In addition, by correlating the internal structure, chemical composition information, and reaction formula of the storage element 35 with the change in impedance value, it is possible to analyze what kind of battery structure is suitable for the system. In particular, when implemented using AI technology such as machine learning, the correlation can be made more efficiently.

(1-4) Advantages of the First Embodiment As described above, according to some of the above-mentioned embodiments, it is possible to perform a deterioration diagnosis of each of the storage elements 35 connected in series inside each of the arms 11A, 11B, and 11C without stopping the operation of the main circuit unit 10a that exchanges power with the power system 5. As a result, it is possible to grasp the remaining life of the storage elements 35 constituting each arm 11x in real time without stopping the operation of the storage system 10 while the storage system 10 is connected to the power system 5. Therefore, even if the characteristics of the storage elements 35 vary, it is possible to grasp in real time which storage element 35 should be replaced with a new one at a given timing while the storage system 10 is continuing to operate.

In addition, in this embodiment, the impedance of each storage element 35 connected in series inside each of the arms 11A, 11B, and 11C of the main circuit unit 10a to exchange power with the power system 5 is examined to see how it changes depending on the frequency of the current flowing through the storage element 35, and the deterioration diagnosis of the storage element 35 is performed based on this impedance change. Therefore, by recording the fluctuation history of the output frequency from the storage system 10 in chronological association with the deterioration diagnosis data of each storage element 35 as the operation history data of the storage system 10, useful information for the operation of the power grid can be obtained. In other words, information that clarifies the correlation between the operation history of the storage system 10 and the deteriorated location and degree of deterioration of the storage elements that constitute the storage element 35 can be obtained. For example, by utilizing the above operation history data, information that serves as a clue for knowing what pattern the storage system 10 in a state connected to the power system 5 should be operated according to in order to extend the life of the storage system 10 including the storage element 35 can be obtained.

In addition, information can be obtained to determine the structure of the storage element 35 that is optimal for the storage system 10 connected to the power grid.

Second Embodiment
Next, a power storage system that receives and transmits power through grid interconnection with a power grid according to a second embodiment of the present invention will be described with reference to FIG.

(2-1) Overall Configuration of the Energy Storage System The exemplary energy storage system 100 shown in FIG. 7 is a circuit system disclosed in Japanese Patent No. 6212361, and is capable of applying a zero-phase voltage to each phase to pass a zero-phase current. Therefore, as in the first embodiment, by having a circulation path that goes around between each phase, a zero-phase voltage is applied to each arm 15rs, arm 15st, and arm 15tr that has an individual circulation path and is configured as a series body of unit converters 151, and a zero-phase current is passed through, so that a deterioration diagnosis of an arbitrary energy storage element 35 can be performed. The energy storage system 100 according to this embodiment will be specifically described below. The energy storage system 100 is connected to a power system 5 that supplies three-phase AC power consisting of an R phase, an S phase, and a T phase, and is interconnected with the power system 5. The energy storage system 100 includes a transformer 110, an arm 15rs that supplies power between the R and S phases, an arm 15st that supplies power between the S and T phases, an arm 15tr that supplies power between the T and R phases, a control unit (control means) 13, and voltmeters 19rs, 19st, and 19tr.

2, the storage system 100 is an MMC for three-phase AC, but the arm 15rs, the arm 15st, and the arm 15tr are not delta-connected, but are interconnected by electromagnetic induction coupling via a magnetic circuit. In addition, according to the second embodiment, the storage system 100 shown in FIG. 7 is different from the storage system 10 shown in FIG. 2 in that the arm 15rs, the arm 15st, and the arm 15tr are electromagnetically inductively coupled to the power system 5 via a magnetic circuit formed by the iron core 113 of the transformer 110. Hereinafter, in the connection of the transformer 110, the side to which the power system 5 and the like are connected is referred to as the "primary side", and the side to which each arm 15rs, 15st, and 15tr are connected is referred to as the "secondary side". In the second embodiment, the primary side of the transformer 110 is delta-connected, forming a circulation path that circulates between each phase.

The energy storage system 100 shown in FIG. 7 is provided with a primary winding 111 (111rs, 111st, 111tr) and a secondary winding 112 (112rs, 112st, 112tr) corresponding to each of the phases of the three-phase AC, and is configured to include a transformer 110 that receives power supply from a three-phase AC power source via the primary winding 111, a unit converter 151 having a chargeable and dischargeable energy storage element, a plurality of arms 15 (15rs, 15st, 15tr) each connected to a plurality of secondary windings 112 (112rs, 112st, 112tr) respectively provided corresponding to each of the phases of the three-phase AC, and a control unit 13 that controls the connection state of the energy storage elements inside the arms 15. In the energy storage system 100 shown in FIG. 7, a plurality of annular current paths corresponding to the phases of the three-phase AC are individually formed as closed circuits 155 (155rs, 155st, 155tr) formed by each arm 15 (15rs, 15st, 15tr) and each secondary winding 112 (112rs, 112st, 112tr), and the control unit 13 is configured to execute a control sequence for performing the above control so that a zero-phase circulating current having a diagnostic frequency, i.e., a frequency different from the frequency of the power system, flows in each of the plurality of annular current paths, and to test the deterioration state of the energy storage element designated as the diagnosis target. In other words, this individual circulating path becomes a zero-phase circulating path. Furthermore, the zero-phase circulating current becomes a current circulating in the Δ connection on the primary side.

(2-2) Configuration of the transformer and peripheral circuits magnetically coupled to the system side The configuration of the transformer and peripheral circuits magnetically coupled to the power system 5 side shown in FIG. 7 will be described in detail below. As shown in FIG. 7, the transformer 110 is a three-phase transformer, and a three-legged core is used. The transformer 110 has legs 113rs, 113st, and 113tr. The primary winding 111rs and secondary winding 112rs of the R-S phase are wound around the leg 113rs and magnetically coupled. The primary winding 111st and secondary winding 112st of the S-T phase are wound around the leg 113st and magnetically coupled. The primary winding 111tr and secondary winding 112tr of the T-R phase are wound around the leg 113tr and magnetically coupled.

Six unit converters 151 are connected in series to each of arm 15rs, which supplies power between the R and S phases, arm 15st, which supplies power between the S and T phases, and arm 15tr, which supplies power between the T and R phases. Both ends of secondary winding 112rs of the R and S phases of transformer 110 are connected to both ends of arm 15rs between the U and S phases. Both ends of secondary winding 112st of the S and T phases of transformer 110 are connected to both ends of arm 15st between the S and T phases. Both ends of secondary winding 112tr of the T and R phases of transformer 110 are connected to both ends of arm 15tr between the T and R phases.

The primary winding 111rs between the R-S phases of the transformer 110 is connected between the R phase and the S phase of the power system 5. The primary winding 111st between the S-T phases of the transformer 110 is connected between the S phase and the T phase of the power system 5. The primary winding 111tr between the T-R phases of the transformer 110 is connected between the T phase and the R phase of the power system 5. That is, the primary windings 111rs, 111st, and 111tr of the transformer 110 are delta connected and connected to the power system 5.

Voltmeter 19rs is connected between the R and S phases of power system 5 and measures the line voltage Vsrs. Voltmeter 19st is connected between the S and T phases of power system 5 and measures the line voltage Vsst. Voltmeter 14tr is connected between the T and R phases of power system 5 and measures the line voltage Vstr. Each of voltmeters 19rs, 19st, and 19tr is further connected to control unit 13 by optical fiber (not shown) and transmits measured voltage information.

The control unit 13 is connected to the unit converter 151 that constitutes the voltmeters 19rs, 19st, and 19tr and each of the arms 15rs, 15st, and 15tr by optical fibers (not shown). The control unit 13 controls each of the arm voltages Vrs, Vst, and Vtr based on the line voltages Vsrs, Vsst, and Vstr measured by each of the voltmeters 19rs, 19st, and 19tr.

(2-3) Circuit Operation in the Energy Storage System Here, each voltage and current is defined as follows. The voltage across arm 15rs supplied between the R and S phases is arm voltage Vrs. The voltage across arm 15st supplied between the S and T phases is arm voltage Vst. The voltage across arm 15tr supplied between the T and R phases is arm voltage Vtr.

A secondary current Irs2 flows between the arm 15rs between the u and S phases and the secondary winding 112rs between the R and S phases of the transformer 110. A secondary current Ist2 flows between the arm 15st between the S and T phases and the secondary winding 112st of the vT phase of the transformer 110. A secondary current Itr2 flows between the arm 15tr between the w and R phases and the secondary winding 112tr of the T and R phases of the transformer 110.

A secondary voltage Vrs2 is applied across the R-S phase secondary winding 112rs of the transformer 110, and the secondary voltage Vrs2 is the same as the arm voltage Vrs. A secondary voltage Vst2 is applied across the S-T phase secondary winding 112st of the transformer 110, and the secondary voltage Vst2 is the same as the arm voltage Vst. A secondary voltage Vtr2 is applied across the T-R phase secondary winding 112tr of the transformer 110, and the secondary voltage Vtr2 is the same as the arm voltage Vtr. In addition, the voltage across the RS phase primary winding 111rs of the transformer 110 is a primary side voltage Vrs1, the voltage across the ST phase primary winding 111st of the transformer 110 is a primary side voltage Vst1, and the voltage across the TR phase primary winding 111tr of the transformer 110 is a primary side voltage Vtr1.

A system current Isr flows in the R phase of the power system 5 in the direction from the storage system 100 to the power system 5. A system current Iss flows in the S phase of the power system 5 in the direction from the storage system 100 to the power system 5. A system current Ist flows in the T phase of the power system 5 in the direction from the storage system 100 to the power system 5. The voltage between the R phase and the S phase of the power system 5 is the line voltage Vsrs. The line voltage Vsrs is measured by a voltmeter 14rs. The voltage between the S phase and the T phase of the power system 5 is the line voltage Vsst. The line voltage Vsst is measured by a voltmeter 14st. The voltage between the T phase and the R phase of the power system 5 is the line voltage Vstr. The line voltage Vstr is measured by a voltmeter 14tr.

Moreover, each of the unit converters _151rs ^(j) (1≦j≦J) constituting the arm 15rs has a circuit configuration similar to that of the full bridge circuit described above in the first embodiment with reference to FIG. 3. Moreover, each of the unit converters _151rs ^(j) (1≦j≦J) can perform the control described above in the first embodiment with reference to FIG. 4 on the switching elements in the full bridge circuit from the control unit 13. As a result, each of the unit converters _151rs ^(j) (1≦j≦J) can realize a circuit operation similar to that of the unit converter _Cx ⁽ⁱ⁾ described above in the first embodiment. The same is true for the unit converters _151st ^(j) (1≦j≦J) and the unit converters _151tr ^(j) (1≦j≦J). Furthermore, it has an impedance characteristic measuring unit (not shown), and functions as a detection unit that detects the voltage of the storage element of the unit converter 151 and the circulating current _Icir flowing through a closed circuit described later, as in the first embodiment.

(2-4) Current and voltage control operation by the control unit Next, the arm voltages Vrs, Vst, and Vtr of the arms 15rs, 15st, and 15tr will be described. For simplicity, only the arm voltage Vrs of the arm 15rs will be described below, but the same applies to the arm voltages Vst and Vtr of the arms 15st and 15tr.

The control unit 13 of the energy storage system 100 of the second embodiment performs on/off control of each switching element included in each of the unit converters _151rs ⁽¹⁾ (1≦j≦J) by carrier phase shift PWM. As a result, by controlling the opening and closing of the switching elements for each of the J unit converters _151rs ^(j) (1≦j≦J) constituting the arm 15rs, it is possible to output a voltage output between the R phase and the S phase from the arm 15rs so that the voltage has a waveform close to a sine wave. Similarly, by controlling the opening and closing of the switching elements for each of the J unit converters _151st ^(j) (1≦j≦J) constituting the arm 15st, it is possible to output a voltage output between the S phase and the T phase from the arm 15st so that the voltage has a waveform close to a sine wave. In addition, by controlling the opening and closing of the switching elements for each of the J unit converters _151tr ^(j) (1≦j≦J) that make up the arm 15tr, it is possible to output a voltage between the T phase and the R phase from the arm 15tr so that the voltage has a waveform close to a sine wave.

4, the control unit 13 controls the opening and closing of the switching elements in the unit converters constituting each of the arms 15st, 15st, and 15tr. As a result, each of the arms 15st, 15st, and 15tr performs a voltage conversion operation as a multilevel converter in order to convert the composite voltage of the storage elements connected in series inside each of the arms 15st, 15st, and 15tr into an AC waveform of a desired frequency.

Therefore, the closed circuits 155rs, 155st, and 155tr through which the test current flows correspond to the annular current path 71 formed in the main circuit section 10a shown in FIG. 5 in the first embodiment, but differ in that three closed circuits 155rs, 155st, and 155tr are formed individually corresponding to each of the three arms 15rs, 15st, and 15tr. As described above with reference to FIG. 7, in the storage system 100 according to the second embodiment, the primary side circuit of the transformer 110 is configured with a Δ connection. For this reason, even if each of the arms 15st, 15st, and 15tr outputs a zero-phase voltage and flows a zero-phase current, only a circulating current of the zero-phase current flows through the Δ connection on the primary side of the transformer 110, and does not affect the exchange of active power and reactive power between the storage system 100 and the power system 5.

Therefore, when diagnosing the deterioration of the storage element constituting the R-S phase arm 15rs, the control unit 13 controls the unit converter _151rs ^(j) (1≦j≦J) so that the circulating current 159rs of a different frequency flows through the closed circuit 155rs. Similarly, when diagnosing the deterioration of the storage element constituting the S-T phase arm 15st, the control unit 13 controls the unit converter _151st ^(j) (1≦j≦J) so that the circulating current 159st of a different frequency flows through the closed circuit 155st. Also, when diagnosing the deterioration of the storage element constituting the T-R phase arm 15tr, a control sequence is executed to control each of the unit converters _151tr ^(j) (1≦j≦J) so that the circulating current 159tr of a different frequency flows through the closed circuit 155tr. Here, the test current flowing through the closed circuits 155rs, 155st, and 155tr corresponds to the circulating current _Icir shown in FIG. 5 for the first embodiment. In this manner, the control unit 13 controls the unit converter to pass circulating currents of different frequencies through at least one of the multiple circular current paths, and tests the deterioration state of the energy storage element designated as the diagnosis target.

(2-5) Advantages of the Second Embodiment In this way, by flowing the circulating current 159rs generated by the arm 15rs including the unit converter _151rs ^(j) (1≦j≦J) having a chargeable and dischargeable storage element at various different frequencies in the closed circuit 155rs, it is possible to electrically test the deterioration state of the storage element constituting the arm 15rs. Similarly, by flowing the circulating current 159st generated by the arm 15st including the unit converter _151st ^(j) (1≦j≦J) having a storage element at various different frequencies in the closed circuit 155st, it is possible to electrically test the deterioration state of the storage element constituting the arm 15st. In addition, by flowing a circulating current 159tr generated by an arm 15tr equipped with a unit converter _151tr ^(j) (1≦j≦J) having a storage element in a closed circuit 155tr at various different frequencies, it is possible to electrically test the deterioration state of the storage element constituting the arm 15tr.

7, the arms 15rs, 15st, and 15tr, which pass currents for testing the deterioration state of the storage element during diagnosis of the storage element, are electromagnetically inductively coupled to the external power system 5 via the magnetic circuit of the transformer 110. As a result, in the second embodiment, the arms 15rs, 15st, and 15tr, which are formed by connecting the storage elements in series, can exchange power with each other without being wired to the power system 5. As a result, in the second embodiment, the current for testing the deterioration state of the storage element is prevented from flowing into the power system 5, and the stability of the power state in the power system 5 can be suppressed from being impaired.

Additional Embodiments
In both the first and second embodiments, a voltage including a plurality of different frequency components may be applied to the storage element 35 to be diagnosed at once. In this case, it is more preferable to perform Fourier analysis or the like on the impedance characteristics obtained by measuring while applying the voltage, and obtain the complex impedance for each frequency component. In this way, in the additional embodiment, the complex impedance can be measured collectively over a large number of frequency components, compared to the first and second embodiments. As a result, this embodiment has the technical advantage of being able to shorten the time required to obtain the locus of fluctuation of the complex impedance characteristic as a curve as exemplified in FIG. 7 over a certain frequency range.

In the first embodiment, as an example, the case where the storage system 10 is connected to a power distribution system (power grid 5) connected to a wind farm (wind power generation device) as a new energy system has been described, but the present invention is not limited to this. For example, it can be used by connecting it to a power distribution system to which a biomass (organic matter derived from animals and plants) power generation device, a geothermal power generation device (binary power generation), a small hydroelectric power generation device, a solar power generation device, etc. as new energy systems are connected. Furthermore, it is not limited to a relatively low-voltage power distribution system, and can be used by connecting it to, for example, a high-voltage power transmission system from a conventional high-output power plant to a substation. When connecting it to a power transmission system, a high-voltage switching element is used as a switch.

Furthermore, the storage system 10 can also be used as a battery system for an uninterruptible power supply used in a data center, etc., by connecting it to important loads such as a data center.

Furthermore, the power storage system 10 can also be connected to a motor and used as a battery system for an electric vehicle. Furthermore, when the power storage system 10 is used as a battery system for an electric vehicle, it can be connected to a power grid to charge the battery from the power grid, and can also charge and discharge the power of the battery of the electric vehicle according to the power surplus or shortage in the power grid. In addition, the voltage of the power grid can be controlled by outputting reactive power from the battery system for the electric vehicle according to the voltage of the power grid. Furthermore, an electric vehicle having this battery system for electric vehicles can be parked near an important load that is at high risk of a power outage, such as a data center, and function as an uninterruptible power supply for the important load. In this case, it is preferable to control the voltage of the power grid in cooperation with multiple electric vehicles and other uninterruptible power supplies.

<Example>
In the examples, a circuit simulation was performed on the energy storage system 10 of the first embodiment, and it was confirmed that the current required for diagnosing the deterioration of the energy storage element 35 can be passed through the energy storage system 10 without affecting the power grid 5 connected to the energy storage system 10 while continuing to operate the energy storage system 10.

The circuit simulation of this example was performed on a circuit in which the energy storage system 10 in the configuration of the first embodiment ( FIG. 2 ) was removed from the power system 5, excluding reactance components 54u, 54v, 54w and resistance components 55u, 55v, 55w of the distribution lines 53u, 53v, 53w, and a load 56. Each of the three arms 11A, 11B, 11C of the energy storage system 10 was configured to have two unit converters C _x ⁽ⁱ⁾ including energy storage elements 35 connected in series. A sum voltage of a zero-phase sequence voltage required for the flow of the circulating current I _cir and a positive-phase sequence voltage for power control of the power system 5 was output to each of the arms 11A, 11B, and 11C, and the current flowing inside the energy storage system 10 and the current supplied from the energy storage system 10 to the power system 5 were simulated.

The results of a circuit simulation performed with the above configuration will be described with reference to Fig. 8. The horizontal axis of all current waveforms shown in Fig. 8 is in seconds [sec], and the vertical axis is in amperes [A]. 8A in Fig. 8 is the current waveform of the circulating current component _Icir , and 8B is the waveform of the current component for power control of the power system 5. 8C in Fig. 8 is the waveform of the sum of the circulating current component _Icir shown in 8A and the current component for power control shown in 8B, and this sum current is the current flowing inside the power storage system 10 when the diagnosis of the storage element 35 is being performed. 8D in Fig. 8 shows the waveform of the current discharged from the storage element 35 and supplied from the storage system 10 to the power system 5.

8, when the circulating current I _cir (8 A) which is the diagnostic current was flowing, no fluctuation was observed in the current (8D) supplied from the energy storage system 10 to the power grid 5. This result shows that the energy storage system 10 can diagnose the energy storage element 35 without causing the circulating current I _cir to flow into the power grid 5, i.e., without impairing the stability of power in the external power system and load.

As described above, the control unit 13 of the energy storage system 10 can test the deterioration state of the storage element 35 designated as the diagnosis target while transferring power to and from the external power system 5, i.e., simultaneously with the transfer of power. In addition, the test of the deterioration state of the storage element 35 is not limited to when the energy storage system 10 is charging/discharging the power system 5, but can also be performed while transmitting/receiving other electrical signals, for example, signals for monitoring or managing the voltage state of the power system 5. In addition, the energy storage system 10 can test the deterioration state of the storage element 35 designated as the diagnosis target even in a state in which power and other signals are not being transferred to and from the external power system 5. For example, the energy storage system 10 may start the test of the storage element 35 in a state in which power and signals are not being transferred to and from the power system 5, and at any timing thereafter, start transferring power or signals to and from the power system 5, for example, depending on the excess or shortage of power in the power system 5.

REFERENCE SIGNS LIST 1 Power grid system 5 Power system 10 Power storage system 10a Main circuit unit 11A Arm 11B Arm 11C Arm 12 Impedance characteristic measuring unit 13 Control unit (control means)
15 (15rs, 15st, 15tr) Arm 19 (19rs, 19st, 19tr) Voltmeter 33 First switch arm 33H First switch 33L Second switch 34 Second switch arm 34H Third switch 34L Fourth switch 35 Storage element 36 First switch group 37 Second switch group 50 Power generation equipment 53u Distribution line 53v Distribution line 53w Distribution line 56 Load 57u Terminal 57v Terminal 57w Terminal 71 Circular current path 90A Wind-generated power 90B Combined power 90C Charging/discharging power 91 Wind conditions 92 Wind farm 93 Load 100 Storage system 110 Transformer 111 (111rs, 111st, 111tr) Primary winding 112 (112rs, 112st, 112tr) Secondary winding 113 Iron cores 113rs, 113st, 113tr Legs 120 Voltage measurement unit 151 Unit converter 300a Locus 300b Locus 300c Locus 310a Vertex 320a Equivalent circuit 320b Equivalent circuit 320c Equivalent circuit 321a Equivalent capacitance 321b Equivalent capacitance 321c Equivalent capacitance 322a Internal resistance 322b Internal resistance 322c Internal resistance

Claims (26)

a main circuit section in which arms each having a unit converter having a chargeable/dischargeable storage element are provided corresponding to each of the phases of a three-phase alternating current to form a ring-shaped current path;
a control means for testing a deterioration state of the storage element designated as the diagnosis target by connecting the storage element designated as the diagnosis target to the ring-shaped current path and passing a circulating current of an arbitrary frequency through the ring-shaped current path;
Equipped with
Energy storage system. a main circuit section in which arms each having a unit converter having a chargeable/dischargeable storage element are provided corresponding to each of the phases of a three-phase alternating current to form a ring-shaped current path;
and a detection unit that detects a voltage generated between the terminals of the storage element designated as a diagnosis target and a current flowing through the storage element due to circulating currents of different frequencies flowing through the ring-shaped current path.
Energy storage system. A part of the unit converter is configured as a full bridge circuit to which the storage element is connected,
a function of testing a deterioration state of the storage element designated as a diagnosis target when a pair of diagonally positioned switching elements in the unit converter configured as the full bridge circuit are in a conductive state;
The power storage system according to claim 1 or 2. a determination means for determining a deterioration state of the storage element based on an internal resistance and an equivalent capacitance of the storage element through which the circulating current flows, the internal resistance and the equivalent capacitance being obtained from a locus of the complex impedance of the storage element on a complex plane in accordance with a change in frequency of the circulating current;
The power storage system according to any one of claims 1 to 3. The circulating current is generated by charging and discharging the other storage elements except for the storage element designated as the diagnosis target.
The power storage system according to any one of claims 1 to 4. a transformer having a primary winding and a secondary winding respectively corresponding to each of the three-phase AC power phases, the transformer receiving power from a three-phase AC power source via the primary winding;
a unit converter having a chargeable/dischargeable storage element, and a plurality of arms respectively connected to the plurality of secondary windings provided correspondingly between the phases of a three-phase AC;
a plurality of circular current paths each corresponding to one of the three-phase AC phases and each formed as a closed circuit by each of the arms and each of the secondary windings;
and a control means for controlling the unit converter to pass circulating currents of different frequencies through at least one of the plurality of annular current paths, thereby testing a deterioration state of the storage element designated as a diagnosis target.
Energy storage system. The power storage system according to claim 1 or 6, wherein the control means tests a deterioration state of the power storage elements while transmitting and receiving electric power to and from a connected external power system. 7. The power storage system according to claim 1, wherein the control means exchanges power with a connected external power system by using a positive-phase current or a negative-phase current, and tests a deterioration state of the power storage elements by using a zero-phase current as the circulating current flowing through the ring-shaped current path. A plurality of unit converters each having a power storage element and capable of transferring power to and from a connected external system;
and a control means for sequentially applying AC voltages having different frequencies to the storage element of one of the unit converters selected from the plurality of unit converters while power is being exchanged between the plurality of unit converters and the external system, and estimating an equivalent circuit of the storage element.
Energy storage system. The other unit converter has a function of applying the AC voltage to one selected unit converter.
The power storage system according to claim 9 . A power storage system including a main circuit section provided with an arm including a unit converter having a chargeable and dischargeable power storage element, and connected to an AC system,
a control means for testing a deterioration state of the energy storage element designated as a diagnosis target while transferring power between the energy storage element and the AC system;
The control means has a function of diagnosing deterioration of the storage element designated as a diagnosis target by applying an AC voltage having a frequency different from a frequency of the AC system to the storage element.
Energy storage system. the AC system is a three-phase AC system;
The power storage system according to claim 11. (delete) a learning means for associating the element information of the energy storage element with a deterioration state of the energy storage element based on time series data of element information of the energy storage element and time series data of an impedance value of an equivalent circuit estimated from a complex impedance of the energy storage element,
The power storage system according to any one of claims 1 to 12. the learning means includes a data mining means for associating the element information of the energy storage element with a deterioration state of the energy storage element by data mining;
The power storage system according to claim 14. a learning means for associating the input/output information with a deterioration state of the storage element based on time series data of the input/output information and time series data of an impedance value of an equivalent circuit estimated from a complex impedance of the storage element,
The power storage system according to any one of claims 1 to 12. the learning means includes a data mining means for associating the input/output information with a deterioration state of the energy storage element by data mining;
The power storage system according to claim 16. The learning means is configured separately from the learning means and is connected to an external device that causes at least a part of the association to be performed.
The power storage system according to any one of claims 14 to 17. A power storage system including a main circuit section provided with an arm including a unit converter having a chargeable and dischargeable power storage element, and connected to an AC system,
a control means for testing a deterioration state of the energy storage element designated as a diagnosis target while transferring power between the energy storage element and the AC system;
a learning means for associating the element information of the energy storage element with a deterioration state of the energy storage element based on time series data of element information of the energy storage element and time series data of an impedance value of an equivalent circuit estimated from a complex impedance of the energy storage element,
Energy storage system. A power storage system including a main circuit section provided with an arm including a unit converter having a chargeable and dischargeable power storage element, and connected to an AC system,
a control means for testing a deterioration state of the energy storage element designated as a diagnosis target while transferring power between the energy storage element and the AC system;
a learning means for associating the input/output information with a deterioration state of the storage element based on time series data of the input/output information and time series data of an impedance value of an equivalent circuit estimated from a complex impedance of the storage element,
Energy storage system. A new energy system connected to the storage system according to any one of claims 1 to 12 and 14 to 20. A power distribution system to which the power storage system according to any one of claims 1 to 12 and 14 to 20 is connected. A power transmission system to which the power storage system according to any one of claims 1 to 12 and 14 to 20 is connected. A transport device connected to the power storage system according to any one of claims 1 to 12 and 14 to 20. A battery system for an electric vehicle to which the power storage system according to any one of claims 1 to 12 and 14 to 20 is connected. A battery system of an uninterruptible power supply connected to the power storage system according to any one of claims 1 to 12 and 14 to 20.

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