Power storage system and charging method

Abstract

This power storage system (1) includes a power storage device (100) including a battery pack (101) including a plurality of power storage cells connected in series, and a charging device (200) that supplies a charging current to the power storage device (100). The power storage system (1) comprises: an alternating current superimposing circuit (148) provided in one among the power storage device (100) and the charging device (200) and making an alternating current superimposed on the charging current; a complex impedance measuring unit (110) which is provided in the power storage device (100), measures a current value of the superimposed AC current and a voltage value of each storage cell (B0 to B5), and measures the complex impedance of each storage cell, on the basis of the measured current value and the measured voltage value; and a charging control unit which is provided in one among the power storage device (100) and the charging device (200), and controls the charging current on the basis of the complex impedance.

Description

[Technical field]

[0001] The present disclosure relates to a power storage system, a power storage device, and a charging method. [Background technology]

[0002] Automobiles that run on secondary batteries as a power source, such as hybrid electric vehicles (HEVs) or electric vehicles (EVs), are being developed. In addition, in order to safely use secondary batteries, a technology is known that estimates the remaining battery capacity and detects abnormalities using a battery management system (BMS).

[0003] For example, Patent Document 1 discloses a battery state determination device that is capable of measuring the complex impedance of a battery and diagnosing the capacity and deterioration level of the battery.

[0004] Patent Document 2 discloses a capacity maintenance rate determination device that is capable of determining the capacity maintenance rate of a battery without completely charging and discharging the battery.

[0005] Patent Document 3 discloses a vehicle controller that programs the charging and discharging of a battery using parameters of an RC circuit model that corresponds to the impedance of the battery. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2015-94726 A [Patent Document 2] JP 2011-38857 A [Patent Document 3] U.S. Patent No. 10023064 Summary of the Invention [Problem to be solved by the invention]

[0007] However, according to the conventional technology, there is a problem in that it is difficult to optimize the charging time of the power storage device. For example, when the power storage device is to be rapidly charged, it is desirable to shorten the charging time by optimizing the charging current.

[0008] The present disclosure provides a power storage system, a power storage device, and a charging method that facilitates optimization of charging time. [Means for solving the problem]

[0009] A power storage system according to one aspect of the present disclosure includes a battery pack including a plurality of power storage cells connected in series, a charging circuit that supplies a charging current to the battery pack, an AC superposition circuit that superposes an AC current on the charging current, a complex impedance measurement unit that measures a current value of the superposed AC current and a voltage value of each power storage cell, and measures a complex impedance of each power storage cell from the measured current value and the measured voltage value, and Individual storage cells Based on complex impedance Based on at least one of the estimated deterioration state and the internal temperature of each of the storage cells, and a charge control unit that controls the charging current.

[0010] Also, a power storage device according to one embodiment of the present disclosure includes a battery pack in which a plurality of power storage cells are connected in series, an AC superposition circuit that superimposes an AC current on a charging current supplied to the battery pack, and a current value of the superimposed AC current, and individual The voltage value of the storage cell is measured, and from the measured current value and the measured voltage value, The individual A complex impedance measuring unit that measures the complex impedance of the storage cell; Individual storage cells and a communication circuit that notifies the complex impedance to a charging device that supplies the charging current.

[0011] A charging method according to an embodiment of the present disclosure is a charging method for charging an energy storage device including a battery pack in which a plurality of energy storage cells are connected in series, the charging method comprising: superimposing an AC current on a charging current supplied to the battery pack; and determining a current value of the superimposed AC current and Individual Measure the voltage value of the storage cell, and from the measured current value and measured voltage value, The individualThe complex impedance of the storage cell is measured. Individual storage cells Based on complex impedance Based on at least one of the estimated deterioration state and the internal temperature of each of the storage cells, , the charging current is controlled. Effect of the Invention

[0012] According to the power storage system, the power storage device, and the charging method according to one embodiment of the present disclosure, it is possible to easily optimize the charging time. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a block diagram showing a configuration example of a power storage system according to a first embodiment. [Diagram 2] FIG. 2 is a circuit diagram showing a detailed configuration example of a measurement circuit and peripheral circuits in the power storage system of FIG. [Diagram 3] FIG. 3 is an explanatory diagram showing an example of a structure of the power storage cell according to the first embodiment and an example of an equivalent circuit model. [Figure 4] FIG. 4 is a Cole-Cole plot diagram showing an example of the complex impedance of the power storage cell according to the first embodiment. [Diagram 5] FIG. 5 is an explanatory diagram showing an example of the surface temperature and internal temperature at specific positions of the battery pack as the battery pack according to the first embodiment. [Figure 6] FIG. 6 is an explanatory diagram showing the difference in surface temperature and internal temperature of the battery pack as the battery assembly according to the first embodiment. [Figure 7] FIG. 7 is a diagram showing an example of temperature characteristics of the complex impedance of the power storage cell according to the first embodiment. [Figure 8] FIG. 8 is a block diagram showing another configuration example of the power storage system according to the first embodiment. As shown in FIG. [Figure 9] FIG. 9 is a block diagram showing a configuration example of a power storage system according to the second embodiment. As shown in FIG. [Figure 10] FIG. 10 is a circuit diagram showing a detailed configuration example of the measurement circuit and peripheral circuits in the power storage system of FIG. [Figure 11]FIG. 11 is a diagram showing a detailed configuration example of the phase synchronization unit in FIG. 10 and an example of the peripheral circuitry. [Figure 12] FIG. 12 is a diagram showing an example of an output waveform of the hysteresis circuit in FIG. [Figure 13] FIG. 13 is a block diagram showing a configuration example of a power storage system according to the third embodiment. As shown in FIG. [Figure 14] FIG. 14 is a circuit diagram showing a detailed configuration example of the measurement circuit in the power storage system of FIG. 13 and the peripheral circuits. [Figure 15] FIG. 15 is a block diagram showing in more detail the configuration related to AC frequency information in the power storage system of FIG. [Figure 16] FIG. 16 is a diagram showing an example of the transmission data in FIG. 15 and a BPSK modulated waveform. [Figure 17A] FIG. 17A is a schematic diagram showing a first application example of the power storage systems according to the first to third embodiments. [Figure 17B] FIG. 17B is a block diagram showing a first application example of FIG. 17A. [Figure 18] FIG. 18 is a schematic diagram showing a second application example of the power storage systems according to the first to third embodiments. [Figure 19A] FIG. 19A is a schematic diagram showing a third application example of the power storage systems according to the first to third embodiments. [Figure 19B] FIG. 19B is a block diagram showing a third application example of FIG. 19A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the embodiments will be described with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, the arrangement and connection forms of the components, steps, and the order of steps shown in the following embodiments are merely examples and are not intended to limit the present disclosure. In addition, the realization of the present disclosure is not limited to the current independent claims, and may be expressed by other independent claims.

[0015] In addition, each drawing is a schematic diagram and is not necessarily a precise illustration. In each drawing, the same reference numerals are used for substantially the same configurations, and duplicated explanations may be omitted or simplified.

[0016] (Embodiment 1) [1.1 Configuration of Energy Storage System 1] First, the configuration of a power storage system 1 according to the first embodiment will be described.

[0017] Fig. 1 is a block diagram showing a configuration example of a power storage system 1 according to embodiment 1. In Fig. 1, an external database 301 is also shown.

[0018] 1 includes a power storage device 100 and a charging device 200. The power storage device 100 includes a battery pack 101, a thermistor 102, a current detection resistor 103, a measuring circuit 104, a first control unit 105, a communication circuit 106, and a communication circuit 107. The charging device 200 includes a charging circuit 201, a second control unit 202, and a communication circuit 203.

[0019] The measurement circuit 104 and the part corresponding to S11 to S14 of the first control unit 105 are called a complex impedance measurement unit 110. 1 5 and second control unit 202 are referred to as a charging control unit.

[0020] The power storage device 100 includes a rechargeable secondary battery, and is mounted on, for example, a vehicle to supply electric power to a motor serving as a power source.

[0021] The battery pack 101 is a secondary battery and includes a plurality of storage cells B0 to B5 connected in series. Each storage cell is, for example, a lithium ion battery, but may be another battery such as a nickel-metal hydride battery. The storage cells may also be storage cells connected in series such as a lithium ion capacitor. The battery pack 101 is connected to a load and a charging circuit. The load is, for example, a motor of an HEV or EV, but is not limited to this. Note that, although an example of the battery pack 101 in FIG. 1 having six storage cells is shown, the number of storage cells in the battery pack 101 is not limited to six.

[0022] The thermistor 102 is a temperature sensor whose resistance value changes depending on temperature, and is attached to the surface of the battery pack 101 and used to measure the external temperature of the battery pack 101. For example, thermistor 102 is attached near the center of a side surface of the battery pack 101.

[0023] The current detection resistor 103 is a resistive element for detecting the value of an AC current superimposed on the charging current flowing through the battery pack 101 as a voltage drop.

[0024] The complex impedance measuring unit 110 measures the current value of the AC current superimposed on the charging current flowing through the battery pack 101 and the voltage values ​​of the individual storage cells B0-B5, and measures the complex impedance of each of the storage cells B0-B5 from the measured current values ​​and measured voltage values. For this reason, the complex impedance measuring unit 110 includes the measuring circuit 104 and portions equivalent to S11-S14 of the first control unit 105.

[0025] The measuring circuit 104 measures the current value of the AC current superimposed on the charging current flowing through the battery pack 101, and the voltage value of each of the power storage cells (B0 to B5). The measured current value and voltage value are complex current and complex voltage including phase information based on the superimposed AC current. Furthermore, the measuring circuit 104 measures the external temperature of the battery pack 101 using the thermistor 102.

[0026] The first control unit 105 is an MCU (Micro Controller Unit or Micro Computer Unit) including a CPU (Central Processing Unit), a memory, and an I / O (Input / Output) circuit, and performs the following processes by executing a program in the memory. The memory of the first control unit 105 stores a program that repeatedly executes the processes shown in S11 to S15 in the figure, for example. That is, the first control unit 105 acquires a complex voltage for each of the storage cells B0 to B5 from the measurement circuit 104 (S11). Furthermore, the first control unit 105 acquires a complex current as a current value of an AC current superimposed on a charging current (S12). The first control unit 105 also acquires an external temperature of the assembled battery 101 (S13). Furthermore, the first control unit 105 calculates the complex impedance of each of the storage cells B0 to B5 by dividing the acquired complex voltage by the complex current (S14). In this way, the first control unit 105 receives the measurement result of the measurement circuit 104 and is responsible for a part of the complex impedance measurement.

[0027] Furthermore, the first control unit 105 estimates the internal temperature of the battery pack 101 as a part of the charging control process (S15). That is, the first control unit 105 estimates the internal temperature of the battery pack 101 based on the acquired external temperature and the complex impedance of each of the power storage cells B0 to B5. For example, the first control unit 105 may estimate the internal temperature using temperature characteristic data indicating the correspondence between the internal temperature and the complex impedance of the battery pack 101 and temperature distribution data indicating the distribution of the external temperature and the internal temperature of the battery pack. The temperature characteristic data and the temperature distribution data may be stored in advance in the memory of the first control unit 105, or may be acquired from the database 301 via the communication circuit 107 and temporarily stored in the memory. The first control unit 105 repeatedly executes the above-mentioned S11 to S15 while the battery pack 101 is being charged by the charging device 200. This repetition is assumed to be at a cycle that can sufficiently track and detect the rate of change at which the internal temperature of the battery pack 101 rises due to heat generation caused by the charging current.

[0028] The communication circuit 106 communicates with the communication circuit 203 in the charging device 200 under the control of the first control unit 105. For example, the communication circuit 106 transmits to the charging device 200 the complex impedance of each of the power storage cells B0 to B5, the external temperature of the battery pack 101, and the estimated internal temperature.

[0029] The communication circuit 107 communicates with an external database 301. The database 301 is a database for collecting and providing battery state data of the power storage cells B0 to B5 of the battery pack 101 and battery state data related to power storage cells in other power storage devices. The battery state data includes, for example, deterioration information called SOH (State of Health).

[0030] On the other hand, the charging device 200 is a device that charges the assembled battery 101, and controls the charging current to the assembled battery 101 based on the complex impedance transmitted from the power storage device 100, the external temperature of the assembled battery 101, and the internal temperature.

[0031] The communication circuit 203 communicates with the communication circuit 106 in the power storage device 100 under the control of the second control unit 202. For example, the communication circuit 203 receives from the power storage device 100 the complex impedance of each of the power storage cells B0 to B5, the external temperature of the battery pack 101, and the estimated internal temperature.

[0032] The charging circuit 201 includes a variable current source 210. The variable current source 210 supplies a charging current to the battery pack 101 under the control of the second control unit 202.

[0033] The second control unit 202 is an MCU including a CPU, a memory, and an I / O circuit, and executes a program in the memory. The memory of the second control unit 202 stores a program for repeatedly executing the processes shown in S21 to S24 in the figure, for example. The second control unit 202 repeatedly executes the processes shown in S21 to S24 while the battery pack 101 is being charged.

[0034] First, the second control unit 202 acquires the complex impedance of each of the storage cells B0 to B5 from the power storage device 100 via the communication circuit 203 (S21), and further acquires the deterioration information (i.e., SOH) from the database 301 via the power storage device 100 and the communication circuit 203 (S22). At this time, the second control unit 202 may acquire the remaining battery capacity of each of the storage cells B0 to B5 from the first control unit 105 via the communication circuit 106 and the communication circuit 203. The remaining battery capacity may be called SOC (State of Charge). Furthermore, the second control unit 202 acquires the estimated internal temperature and the measured external temperature of each of the storage cells B0 to B5 from the power storage device 100 via the communication circuit 203 (S23). Furthermore, the communication circuit 203 determines an optimal charging current based on the complex impedance, the deterioration information, the internal temperature, and the external temperature (S24), and controls the variable current source 210 to supply the determined optimal charging current to the battery pack 101.

[0035] Regarding the optimal charging current for rapid charging, for example, the second control unit 202 determines the value of the charging current so as to shorten as much as possible the charging time until the charging level of the battery pack 101 reaches a predetermined level, within a range in which the internal temperature does not exceed a threshold value. The predetermined level may be any value, such as 80% charge, 90% charge, or full charge.

[0036] [1.2 Configuration of measuring circuit 104] Next, a detailed configuration example of the measurement circuit 104 in the complex impedance measuring section 110 will be described.

[0037] FIG. 2 is a circuit diagram showing a detailed configuration example of the measuring circuit 104 in the power storage system 1 of FIG. 1 and peripheral circuits.

[0038] The measurement circuit 104 in the figure includes a clock generation unit 140, a frequency holding unit 141, a reference signal generation unit 142, a voltage measurement unit 145, a current measurement unit 146, a temperature measurement unit 147, an AC superposition unit 148, a conversion unit 149, an integration unit 150, a holding unit 151, a temperature holding unit 152, and an IO unit 153.

[0039] The clock generating unit 140 generates a sampling clock signal. The sampling clock signal is supplied to an ADC (Analog Digital Converter) in the voltage measuring unit 145, an ADC in the current measuring unit 146, and an ADC in the temperature measuring unit 147.

[0040] The frequency holding unit 141 holds a frequency instructed from outside the power storage device 100. This frequency indicates the frequency of a reference frequency signal generated by the reference signal generating unit 142.

[0041] The reference signal generating section 142 generates a reference frequency signal having the frequency held in the frequency holding section 141 and an orthogonal reference frequency signal.

[0042] DDS143 is an abbreviation for Direct Digital Synthesizer, and includes a ROM that holds waveform data obtained by sampling a sine wave. It inputs an address that indicates the sampling point, and outputs the data of the sampling point of the sine wave (i.e., the sample value). Since the address changes continuously, the output sample value is an almost continuous sine wave.

[0043] The phase shifter 144 generates an orthogonal reference frequency signal by shifting the phase of the reference frequency signal by 90 degrees. The reference signal generating unit 142 may generate both the reference frequency signal and the orthogonal frequency signal using a single DDS 143 and may not include the phase shifter 144.

[0044] The voltage measurement unit 145 measures the voltage of the battery pack 101 by sampling the voltage of the battery pack 101 using the sampling clock signal from the clock generation unit 140. More specifically, the voltage measurement unit 145 includes the same number of analog-to-digital converters (ADC0 to ADC5) corresponding to the storage cells B0 to B5 in the battery pack 101. Each analog-to-digital converter samples the voltage of a corresponding storage cell among the plurality of storage cells B0 to B5 using the sampling clock signal from the clock generation unit 140, and converts the sampled voltage into a digital signal.

[0045] The current measurement unit 146 measures the AC current superimposed on the charging current flowing through the battery pack 101 by sampling the current of the battery pack 101 using the sampling clock signal from the clock generation unit 140. The superimposed AC current is measured as a voltage drop across the current detection resistor 103 inserted in a current loop path through which the AC current applied by the AC superimposition unit 148 flows. This voltage drop is proportional to the superimposed AC current, and therefore means an AC current value. More specifically, the current measurement unit 146 includes an analog-to-digital converter (ADC) for measuring the current of the battery pack 101, which is a secondary battery. This analog-to-digital converter samples the voltage drop across the current detection resistor 103 using the sampling clock signal from the clock generation unit 140, and converts the sampled voltage drop into a digital signal. The current measurement unit 146 and the voltage measurement unit 145 use the same sampling clock, and therefore can perform measurements with high accuracy.

[0046] The temperature measurement unit 147 measures the external temperature of the battery pack 101 using the thermistor 102 provided in the battery pack 101. The thermistor 102 may be, for example, a temperature sensor using a thermocouple or other elements. Specifically, the temperature measurement unit 147 includes an analog-to-digital converter (ADC). This analog-to-digital converter (ADC) samples the voltage of the thermistor 102 and converts the sampled voltage into a digital value.

[0047] The AC superimposing unit 148 superimposes an AC current having a frequency component of the reference frequency signal generated by the reference signal generating unit 142 on the charging current flowing through the assembled battery 101. The AC superimposing unit 148 has a differential buffer that applies the reference frequency signal to the positive and negative electrodes of the assembled battery 101 as a differential signal.

[0048] The conversion unit 149 multiplies the measurement results of the voltage measurement unit 145 and the current measurement unit 146 by the reference frequency signal and the orthogonal reference frequency signal. As a result, the conversion unit 149 converts the measurement results of the voltage measurement unit 145 and the current measurement unit 146 into real part components and imaginary part components of the complex voltage and complex current, respectively. For this reason, the conversion unit 149 includes the same number of multiplier pairs corresponding to the analog-digital converters (ADC0 to ADC5) of the voltage measurement unit 145, and a multiplier pair corresponding to the analog-digital converter of the current measurement unit 146. Each multiplier pair corresponding to the voltage measurement unit 145 is composed of a multiplier that multiplies the conversion result of the corresponding analog-digital converter (i.e., the sampled digital voltage value) by the reference frequency signal, and a multiplier that multiplies the conversion result by the orthogonal reference frequency signal. The former multiplication result indicates the real part component when the sampled voltage is expressed as a complex voltage. The latter multiplication result indicates the imaginary part component when the sampled voltage is expressed as a complex voltage. The multiplier pair corresponding to the current measurement unit 146 consists of a multiplier that multiplies the conversion result of the corresponding analog-to-digital converter (i.e., the sampled digital current value) by a reference frequency signal, and a multiplier that multiplies the conversion result by an orthogonal reference frequency signal. The former multiplication result indicates the real part component when the sampled current is expressed as a complex current. The latter multiplication result indicates the imaginary part component when the sampled current is expressed as a complex current.

[0049] Each of the analog-digital converters (ADC0 to ADC5) may be, for example, a delta-sigma type AD converter. The multiple analog-digital converters (ADC0 to ADC5) have the same AD conversion characteristics. The AD conversion characteristics are various parameters such as resolution (number of bits). Specifically, the same AD converter is used for the multiple analog-digital converters (ADC0 to ADC5). This makes it possible to reduce measurement errors caused by AD conversion between the power storage cells B0 to B5.

[0050] The integrating unit 150 averages the real and imaginary components of the complex voltage and complex current repeatedly measured by the voltage measuring unit 145 and converted by the converting unit 149. This averaging also makes it possible to improve the accuracy of the measurement. More specifically, the integrating unit 150 has the same number of averaging circuit pairs corresponding to the multiplier pairs of the converting unit 149. Each averaging circuit pair is composed of an averaging circuit that averages the real components of the complex voltage or complex current, and an averaging circuit that averages the imaginary components of the complex voltage or complex current. When the storage cell is a lithium ion battery, the internal complex impedance is, for example, several mΩ. Assuming that the superimposed AC current is 1 A, the change in output voltage is only several mV. On the other hand, since the DC output voltage of a lithium ion battery is approximately 3.4 V, a dynamic range of approximately 4 to 5 V is required to measure the voltage with an analog-to-digital converter connected to the storage cell. In this case, if the complex impedance measurement accuracy requires about 8 bits, an analog-digital converter with about 18 to 20 effective bits is required, but high-resolution AD converters consume large power and have large surface area. On the other hand, the internal complex impedance measured for electrochemical impedance analysis of lithium-ion batteries is measured in the low frequency range of 0.01 Hz to several tens of KHz, which is almost DC, so that the complex voltage cannot be measured by AC connection. In the configuration of Figure 1, it is possible to increase the resolution by integration by repeatedly applying an AC current to separate the complex voltage and complex current into real and imaginary components and averaging them. Therefore, even if an analog-digital converter has a small number of bits (for example, about 16 bits), it is possible to obtain complex impedance measurement results with 20 to 24 bits of accuracy. As a result, if the measurement accuracy of the complex voltage can be improved, the magnitude of the applied AC current can be reduced, making it easier to measure secondary batteries with large capacity and small internal complex impedance.

[0051] The holding unit 151 holds the real and imaginary components of the complex voltage and complex current after the averaging process. For this purpose, the holding unit 151 includes a number of register pairs equal to the number of storage cells of the assembled battery 101 for holding the complex voltage, and a register pair for holding the complex current. Each register pair for holding the complex voltage includes a register (Re(Vi)) for holding the real component of the complex voltage of the corresponding storage cell Bi, and a register for holding the imaginary component (Im(Vi)). Here, i is an integer from 0 to 5. The register pair for holding the complex current includes a register (Re(I0)) for holding the real component of the complex current of the corresponding assembled battery 101, and a register for holding the imaginary component (Im(I0)).

[0052] The temperature storage unit 152 stores the digital value from the temperature measurement unit 147 as temperature data.

[0053] The IO unit 153 is an input / output circuit that outputs the complex impedance held in the holding unit 151 to the first control unit 105 and receives data indicating the frequency of the reference frequency signal from the first control unit 105.

[0054] Measuring circuit 104 configured as above has almost zero phase error in voltage measurement and current measurement, and is therefore capable of performing measurements with high accuracy.

[0055] [1.3 Equivalent circuit model and complex impedance of energy storage cell] Next, an example of an equivalent circuit model of a storage cell and its element constants will be described.

[0056] FIG. 3 is an explanatory diagram showing an example of the structure of a storage cell according to an embodiment and an example of an equivalent circuit model. FIG. 3(a) shows a circuit symbol of the storage cell B0. FIG. 3(b) shows a schematic diagram of an example of the structure of the storage cell B0 when it is a lithium ion battery. The storage cell B0 has a negative electrode, a negative electrode material, an electrolyte, a separator, a positive electrode material, and a positive electrode as the premise of the equivalent circuit model. FIG. 3(c) shows an example of an equivalent circuit model of the storage cell B0. This equivalent circuit model has an inductive component L0, resistance components R0 to R2, capacitance components C1 and C2, and a lithium ion diffusion resistance component Zw. The inductive component L0 represents the impedance component of the electrode wire. The resistance component R0 represents the impedance component of the electrolyte. The parallel circuit of the resistance component R1 and the capacitance component C1 represents the impedance component of the negative electrode. The circuit portion consisting of the resistance component R2, the lithium ion diffusion resistance component Zw, and the capacitance component C2 represents the impedance component of the positive electrode. The lithium ion diffusion resistance component Zw is known as the Warburg impedance.

[0057] By calculating the element constants of each circuit element constituting such an equivalent circuit model, it is possible to estimate the state of the power storage cell B0. For example, it is possible to estimate the deterioration state of the power storage cell B0 from the change in the element constants over time.

[0058] Next, an example of the complex impedance characteristics of a battery cell will be described.

[0059] FIG. 4 is a Cole-Cole plot diagram showing an example of the complex impedance of the storage cell according to the first embodiment. The Cole-Cole plot diagram is also called a complex plane diagram or a Nyquist plot. This diagram corresponds to the equivalent circuit model of FIG. 3(c). In the method of calculating the complex impedance of a storage cell by superimposing an AC current, it is generally known that in the case of charge transfer rate limiting, it is expressed by an equivalent circuit in which a resistor and a capacitor are arranged in parallel, and in the complex plane, it becomes a semicircle. In addition, when this Warburg impedance is included, it is generally known that it becomes a straight line that rises at an angle of 45 degrees from the middle of the semicircle (near the upper right) as a slope derived from the Warburg impedance.

[0060] In calculating complex impedance, the phase error of the measurement system generally has frequency characteristics, which is a problem when measuring complex impedance at different frequencies. In particular, when plotting the complex impedance at each frequency on a Cole-Cole plot while varying the frequency, the phase error of each frequency appears as an orthogonal error between the real axis (horizontal axis) and the imaginary axis (vertical axis) on the complex plane of the Cole-Cole plot. This makes it difficult to plot an accurate Cole-Cole plot. However, in the configuration of Figure 2, the complex voltage and complex current are measured before the complex impedance is calculated, which makes it possible to extremely reduce the phase error of the voltage and current measurement system and plot an accurate Cole-Cole plot.

[0061] [1.4 External and internal temperatures] Next, the difference between the external temperature and the internal temperature of the battery pack 101 will be described. The internal temperature is an important parameter when the battery pack 101 is rapidly charged. The charging current can be set within a range that does not exceed the upper limit of the internal temperature. On the other hand, the internal temperature rises more as the charging current increases. Therefore, when the battery pack 101 is rapidly charged, the upper limit of the charging current amount differs depending on the internal temperature.

[0062] 5 is an explanatory diagram showing an example of the surface temperature and internal temperature at specific positions of a battery pack serving as the assembled battery 101 according to embodiment 1. Note that the battery pack may correspond to one storage cell instead of the assembled battery 101.

[0063] The battery pack in the figure is a schematic representation of an assembled battery 101 housed in a battery case. The internal temperature is, for example, the temperature at the three-dimensional center of gravity or center of the battery pack. The internal temperature itself cannot be directly measured by the thermistor 102. The surface temperature (also called the external temperature) is the temperature at position X near the center of the side of the battery pack. The surface temperature can be directly measured by attaching the thermistor 102.

[0064] Fig. 6 is an explanatory diagram showing the difference in surface temperature and internal temperature of a battery pack as a battery assembly according to embodiment 1. In Fig. 6(a) and (b), the horizontal axis indicates the axial direction perpendicularly passing through the side surface of Fig. 5. X indicates the intersection of the axis with the side surface on the front side of Fig. 5. Y indicates the intersection of the axis with the side surface on the rear side that is hidden and cannot be seen. The vertical axis indicates temperature.

[0065] (a) in the figure shows the temperature distribution of the battery pack when it is in thermal equilibrium. When it is in thermal equilibrium, the internal temperature is uniform when no current flows through the battery pack 101, that is, when it is in a non-charging state and no current is being supplied for a certain period of time. At this time, the internal temperature is the same as the surface temperature.

[0066] (b) in the figure shows the temperature distribution in the battery pack when it is in thermal non-equilibrium. The thermal non-equilibrium state refers to when the battery pack 101 is being charged or discharged. In the thermal non-equilibrium state, heat is generated by the current flowing inside the battery pack 101, so the internal temperature becomes higher than the surface temperature. Temperature distribution data such as (b) in the figure is useful for estimating the internal temperature from the surface temperature. However, although it is difficult to quantify the temperature distribution data, it is possible to estimate the internal temperature using the surface temperature and complex impedance.

[0067] Next, the temperature dependency of the complex impedance will be described.

[0068] FIG. 7 is a diagram showing an example of the temperature characteristic of the complex impedance of the storage cell according to the first embodiment. The diagram shows Cole-Cole plots when the temperatures of the storage cell are 20° C., 25° C., and 30° C. As described above, in order to estimate the internal temperature from the complex impedance of the storage cell, it is necessary to know the temperature dependency. use The second control unit 202 calculates the internal temperature and the complex impedance of the battery pack 101. of The temperature characteristic data showing the correspondence can be used to estimate the internal temperature.

[0069] According to the power storage system 1 of this embodiment, it is possible to optimize the charging current supplied to the power storage device 100. Since the complex impedance measured in the power storage device 100 corresponds to the internal temperature and deterioration state of the power storage cells B0 to B5, the second control unit 202 can determine a charging current suitable for the battery pack 101. For example, when the power storage device 100 is rapidly charged, the charging time can be shortened by optimizing the charging current.

[0070] [1.5 Modifications] 1 shows an example of a configuration in which the power storage system 1 is largely divided into the power storage device 100 and the charging device 200, but is not limited thereto. For example, the power storage system 1 may be an integrated system in which the power storage device 100 and the charging device 200 are integrated as shown in FIG 8. In this case, the first control unit 105 and the second control unit 202 may be integrated as a charging control unit (i.e., one MCU), and the communication circuit 106 and the communication circuit 203 may be omitted.

[0071] As described above, the energy storage system 1 according to the first embodiment includes the assembled battery 101 including a plurality of storage cells B0 to B5 connected in series, the charging circuit 201 supplying a charging current to the assembled battery 101, an AC superposition unit 148 / 204 superimposing an AC current on the charging current, a complex impedance measurement unit 110 measuring the current value of the superimposed AC current and the voltage value of each of the storage cells B0 to B5 and measuring the complex impedance of each of the storage cells from the measured current value and the measured voltage value, and a charging control unit (S15+202) controlling the charging current based on the complex impedance. Here, the charging control unit corresponds to S15 of the first control unit 105 and the second control unit 202.

[0072] This makes it easy to optimize the charging current of the power storage device. Since the complex impedance corresponds to the internal temperature and deterioration state of the power storage cell, the charging control unit can determine a charging current suitable for each power storage cell. For example, when the power storage device is rapidly charged, the charging time can be shortened by optimizing the charging current.

[0073] Here, the charge control unit may estimate the internal temperature of each of the power storage cells B0 to B5 based on the external temperature and complex impedance of the battery pack 101, and optimize the charge current according to the estimated internal temperature.

[0074] According to this, the internal temperature can be estimated from the complex impedance, and the optimum charging current can be determined under the estimated internal temperature.

[0075] Here, the charging control unit may estimate the internal temperature of each storage cell according to at least one of temperature characteristic data indicating the correspondence relationship between the internal temperature and complex impedance of the battery pack, and temperature distribution data indicating the distribution of the external and internal temperatures of the battery pack.

[0076] According to this, the internal temperature is estimated using the temperature characteristics Since at least one of the temperature distribution data and the temperature distribution data is used, the accuracy of the estimation can be improved.

[0077] Here, the charging control section may control the charging current in accordance with the deterioration state of each of the power storage cells estimated from the complex impedance.

[0078] This makes it possible to optimize the charging current depending on the deterioration state.

[0079] Here, the charging control unit may optimize the charging current in accordance with deterioration information indicating the degree of deterioration of each of the power storage cells B0 to B5, which is acquired from an external server device 302 based on the complex impedance.

[0080] According to this, the deterioration state can be estimated using an external cyber device, and the charging current can be optimized according to the estimated deterioration state.

[0081] Here, the charging control unit may determine the value of the charging current so as to shorten the charging time required for the charge level of the battery pack 101 to reach a predetermined level.

[0082] This enables rapid charging.

[0083] Here, the charge control unit may stop charging when the internal temperature reaches a threshold value.

[0084] This makes it possible to stop charging when the internal temperature exceeds the threshold value.

[0085] Here, the energy storage system includes an energy storage device 100 and a charging device 200, and the energy storage device 100 includes a battery pack 101, an AC superposition unit 148, a complex impedance measurement unit 110, and a first communication circuit 106 that transmits information regarding the complex impedance to the charging device 200, and the charging device 200 may include a charging circuit 201, a charging control unit, and a second communication circuit 203 that receives information regarding the complex impedance from the energy storage device 100.

[0086] Here, the energy storage device 100 may include a reference signal generating unit 180 that generates a reference frequency signal, the AC superposition unit 148 generates an AC current synchronized with the reference frequency signal, and the complex impedance measuring unit 110 may measure the complex impedance using the reference frequency signal.

[0087] According to this, since the same reference frequency signal is used for voltage measurement and current measurement, it is possible to improve the measurement accuracy. Also, since the reference frequency signal is used in common for the superimposed AC current and the voltage and current measurements, it is possible to improve the measurement accuracy.

[0088] Moreover, the energy storage device 100 according to the first embodiment includes an assembled battery 101 in which a plurality of energy storage cells B0 to B5 are connected in series, an AC superposition unit 148 that superimposes an AC current on a charging current supplied to the assembled battery, a complex impedance measurement unit 110 that measures a current value of the superimposed AC current and voltage values ​​of the plurality of energy storage cells B0 to B5 and measures a complex impedance of the energy storage cells from the measured current values ​​and measured voltage values, and a communication circuit 106 that notifies the complex impedance to a charging device that supplies a charging current.

[0089] This makes it easy to optimize the charging current of the power storage device. Since the complex impedance corresponds to the internal temperature and deterioration state of the power storage cell, the charging control unit can determine a charging current suitable for each power storage cell. For example, when the power storage device is rapidly charged, the charging time can be shortened by optimizing the charging current.

[0090] Moreover, the charging method according to embodiment 1 is a charging method for charging an energy storage device 100 including a battery pack 101 in which a plurality of storage cells B0 to B5 are connected in series, in which an AC current is superimposed on a charging current supplied to the battery pack 101, a current value of the superimposed AC current and voltage values ​​of the plurality of storage cells B0 to B5 are measured, a complex impedance of the storage cells is measured from the measured current value and the measured voltage value, and the charging current is controlled based on the complex impedance.

[0091] This makes it possible to easily optimize the charging current for the power storage device.

[0092] (Embodiment 2) In the first embodiment, an example has been shown in which power storage device 100 performs the superposition of an AC current for complex impedance measurement. In contrast, in the second embodiment, an example will be described in which charging device 200 performs the superposition of an AC current.

[0093] [2.1 Configuration of energy storage system 1] Fig. 9 is a block diagram showing a configuration example of a power storage system according to embodiment 2. This figure differs from Fig. 1 mainly in that a measuring circuit 104a is provided instead of the measuring circuit 104, an AC superimposing unit 204 is added to the charging device 200, and a clock circuit 205 is added. The following mainly describes the differences.

[0094] The measuring circuit 104a differs from the measuring circuit 104 in Fig. 1 mainly in that it generates a reference frequency signal synchronized with the AC current superimposed on the charging current and measures the complex voltage and complex current using this reference frequency signal. This allows the complex voltage and complex current to be measured with high accuracy, as in Fig. 1.

[0095] The clock circuit 205 generates an AC current to be superimposed and a reference frequency signal that serves as a reference for communication by the communication circuit 203 .

[0096] The communication circuit 203 has a modulation section 231 and a demodulation section 232 that perform modulation and demodulation using a reference frequency signal generated by a clock circuit 205. Furthermore, the communication circuit 106 has a modulation section 175 and a demodulation section 176 to communicate with the communication circuit 203.

[0097] The AC superimposing unit 204 superimposes an AC current synchronized with a reference frequency signal generated by a clock circuit 205 on the charging current flowing through the battery pack 101. For this purpose, the AC superimposing unit 204 has a DDS 241, a driver 242, and a transformer 243.

[0098] DDS241 is an abbreviation for Direct Digital Synthesizer, and includes a ROM that holds waveform data obtained by sampling the sine wave of the AC current to be superimposed. It inputs an address indicating the sampling point and outputs data of the sampling point of the sine wave (i.e., sample value). Since the address changes continuously, the output sample value indicates an almost continuous sine wave. Note that the waveform of the AC current to be superimposed does not have to be a sine wave, and may be a pulse waveform.

[0099] The driver 242 is a differential buffer that outputs the sine wave output from the DDS 241 to the transformer 243 as a differential signal.

[0100] The transformer 243 superimposes a differential signal indicating the AC current from the driver 242 on the charging current flowing through the battery pack 101 .

[0101] [2.2 Configuration of measuring circuit 104a] Next, the detailed configuration of the measuring circuit 104a will be described.

[0102] Fig. 10 is a circuit diagram showing a detailed configuration example of the measuring circuit 104a and the peripheral circuits in the power storage system 1 of Fig. 9. Fig. 10 differs from Fig. 2 in that the frequency holding unit 141, the reference signal generating unit 142, and the AC superimposing unit 148 are deleted, and that a phase synchronization unit 161 and a reference signal generating unit 162 are added. The following mainly describes the differences.

[0103] The phase synchronization unit 161 generates a clock signal synchronized with the AD conversion result of the current measurement unit 146, that is, the AC current superimposed on the charging current. This clock signal has a frequency indicated by the frequency data held in the frequency holding unit 141.

[0104] The reference signal generating section 162 generates a reference frequency signal and an orthogonal reference frequency signal synchronized with the clock signal from the phase synchronization section 161. For this purpose, the reference signal generating section 162 has a DDS 163 and a phase shifter 164. The DDS 163 and the phase shifter 164 may have the same configuration as the DDS 143 and the phase shifter 144 in FIG.

[0105] [2.3 Configuration of phase synchronization unit 161] Next, a more detailed configuration example of the phase synchronization unit 161 will be described.

[0106] Fig. 11 is a diagram showing a detailed configuration example of the phase synchronization unit 161 of Fig. 10 and an example of a peripheral circuit. Note that the phase synchronization unit 161 of Fig. 11 shows a configuration example that synchronously detects the input signal to the current measurement unit 146, that is, the AC current value as the voltage drop of the current detection resistor 103, rather than synchronously detecting the AD conversion result of the current measurement unit 146.

[0107] The phase synchronization unit 161 in FIG. 11 includes a hysteresis circuit 165, a comparator 166, a charge pump 167, an LPF 168, a VCO 169, and a frequency divider 170.

[0108] Hysteresis circuit 165 binarizes the AC current value detected by current detection resistor 103. FIG. 12 is a diagram showing the output waveform (A1) of hysteresis circuit 165 in FIG. 11. The horizontal axis indicates time, and the vertical axis indicates the output voltage corresponding to the current value. ITH+ and ITH- indicate examples of the upper and lower thresholds of the hysteresis characteristic. The output waveform (A1) of hysteresis circuit 165 is a pulsed rectangular wave as shown in the figure, having the same frequency 1 / T as the superimposed AC signal.

[0109] Comparator 166 compares the output signal from hysteresis circuit 165 with the frequency-divided signal from frequency divider 170 to detect the phase difference.

[0110] Charge pump 167 raises the signal indicative of the detected phase difference to the required voltage level.

[0111] The LPF 168 is called a low-pass filter or a loop filter, and smoothes the signal indicating the phase difference from the charge pump 167 .

[0112] The VCO 169 is a voltage-controlled oscillator, and outputs a signal having a frequency corresponding to the voltage of the smoothed signal.

[0113] The frequency divider 170 divides the signal from the VCO 169 and feeds it back to the comparator 166 .

[0114] With this configuration, the phase synchronization unit 161 generates a frequency signal synchronized with the AC current detected by the current detection resistor 103 .

[0115] The reference signal generating section 162 generates a reference frequency signal synchronized with the frequency signal from the phase synchronization section 161 and an orthogonal frequency signal.

[0116] According to the above configuration, even if the charging device 200 superimposes an AC current, the reference frequency signal and the orthogonal frequency signal used by the measuring circuit 104a are synchronized with the superimposed AC current, so that the complex impedance can be measured with high accuracy.

[0117] As described above, the energy storage system 1 according to the second embodiment includes the energy storage device 100 and the charging device 200. The energy storage device 100 includes the assembled battery 101, the complex impedance measuring unit 110, and the phase locked loop circuit 161 that generates a reference frequency signal synchronized with the AC current superimposed on the charging current. The charging device 200 includes the AC superimposing unit 148, the charging circuit 201, and the charging control unit. The complex impedance measuring unit 110 measures the complex impedance using the reference frequency signal.

[0118] This makes it possible to measure the complex impedance with high accuracy.

[0119] (Embodiment 3) In this embodiment, as in the second embodiment, another example will be described in which the charging device 200 superimposes an AC current for complex impedance measurement. In the second embodiment, an example has been shown in which a reference frequency signal synchronized with the AC current is generated in the power storage device 100 using a phase synchronization unit 161 that synchronously detects the AC current superimposed on the charging current. In contrast, in the third embodiment, a configuration example will be described in which a reference frequency signal is generated from AC frequency information related to the frequency of the AC current transmitted from the charging device 200 to the power storage device 100.

[0120] [3.1 Configuration of Energy Storage System 1] Fig. 13 is a block diagram showing a configuration example of a power storage system 1 according to embodiment 3. This figure differs from Fig. 9 shown in embodiment 2 mainly in that a communication clock generating unit 233 is added in a communication circuit 203, a communication clock regenerating unit 177 is added in a communication circuit 106, and a measurement circuit 104b is provided instead of the measurement circuit 104a. The following mainly describes the differences.

[0121] Similar to the second embodiment, the communication circuit 203 receives information related to the complex impedance from the communication circuit 106 of the power storage device 100. Furthermore, the communication circuit 203 transmits AC frequency information related to the frequency of the AC current superimposed on the charging current to the communication circuit 106. Note that the communication line between the communication circuit 203 and the communication circuit 106 includes a communication signal line but does not include a communication clock signal line.

[0122] The communication clock generating unit 233 generates a communication clock signal synchronized with a reference frequency signal generated by the clock circuit 205. The modulating unit 231 generates a communication signal by modulating communication data using the communication clock signal, and transmits the communication signal to the communication circuit 106.

[0123] Similar to the second embodiment, the communication circuit 106 transmits information related to the complex impedance to the charging device 200. Furthermore, the communication circuit 106 receives AC frequency information from the communication circuit 203 as a communication signal.

[0124] The communication clock regenerator 177 regenerates a communication clock signal from the communication signal received by the communication circuit 106 and supplies it to the demodulator 176. The regenerated communication clock signal is referred to as CCLK. The demodulator 176 demodulates the communication signal using the regenerated communication clock signal. Furthermore, the communication clock signal CCLK is supplied to the measurement circuit 104b. The measurement circuit 104b uses a reference frequency signal synchronized with the communication clock signal CCLK.

[0125] Here, the AC frequency information corresponds to the data timing of the communication signal and the edge timing of the communication clock signal. The AC frequency information is transmitted, for example, as a normal communication signal or a specific communication signal, constantly, occasionally, or repeatedly during the charging period.

[0126] The measurement circuit 104 b measures complex voltages and complex currents using a reference frequency signal synchronized with the communication clock signal CCLK reproduced by the communication clock reproduction unit 177 .

[0127] [3.2 Configuration of measuring circuit 104b] Next, the detailed configuration of the measuring circuit 104b will be described.

[0128] Fig. 14 is a circuit diagram showing a detailed configuration example of measuring circuit 104b and peripheral circuits in power storage system 1 of Fig. 13. Fig. 14 differs from measuring circuit 104a shown in Fig. 10 of embodiment 2 mainly in that phase synchronization unit 161 is deleted and that reference signal generating unit 180 is provided instead of reference signal generating unit 162. The following mainly describes the differences.

[0129] The reference signal generating section 180 generates a reference frequency signal synchronized with the reproduced communication clock signal CCLK. To this end, the reference signal generating section 180 includes a DDS 181 and a phase shifter 182. The DDS 181 and the phase shifter 182 may have the same configuration as the DDS 163 and the phase shifter 164.

[0130] [3.3 Communication circuit configuration] Next, among the configurations of the power storage system 1 according to this embodiment, main configurations relating to AC frequency information corresponding to the data timing of a communication signal and the edge timing of a communication clock signal will be described in more detail.

[0131] FIG. 15 is a block diagram showing in more detail the configuration related to AC frequency information in the power storage system 1 of FIG.

[0132] 15 shows an example of a configuration for performing BPSK (Binary Phase Shift Keying) modulation. To this end, the modulation unit 231 includes a transmission data buffer 245, a bipolar converter 246, a DDS 247, and a BPSK modulator 248.

[0133] The transmission data buffer 245 is a buffer register that temporarily holds the transmission data. In the figure, 100111 is shown as the transmission data S1.

[0134] The bipolar converter 246 converts the 1s and 0s of the transmitted data into +1s and -1s.

[0135] The DDS 247 generates a sine wave signal and a cosine wave signal synchronized with the communication clock signal generated by the communication clock generating unit 233 .

[0136] The BPSK modulator 248 includes two multipliers and one adder. When the bipolar-converted transmission data is −1, the BPSK modulator 248 shifts (i.e., inverts) the phases of the sine wave signal and cosine wave signal generated by the DDS 247 by 180 degrees, and when the bipolar-converted transmission data is +1, the BPSK modulator 248 does not invert the phases of the sine wave signal and cosine wave signal generated by the DDS 247. The BPSK modulator 248 generates a communication signal as the sum of a non-inverted sine wave signal and a non-inverted cosine wave signal, or the sum of an inverted sine wave signal and an inverted cosine wave signal, for each symbol of the transmission data (in this example, one symbol is one bit). FIG. 16 is a diagram showing the transmission data S1 in FIG. 15 and an example waveform D1 modulated by BPSK. For ease of understanding, the example waveform D1 shows only the non-inverted or inverted sine wave signal component.

[0137] The demodulation section 176 in FIG. 15 includes a BPSK demodulator 185 and a received data buffer 186 .

[0138] The BPSK demodulator 185 demodulates the communication data from the communication signal.

[0139] The received data buffer 186 temporarily holds the demodulated communication data.

[0140] The communication clock recovery unit 177 has a PLL 187 and recovers a communication clock signal from the communication signal.

[0141] The reference signal generating section 180 generates a reference frequency signal and an orthogonal reference frequency signal synchronized with the reproduced communication clock signal.

[0142] With such a circuit, the power storage device 100 generates a reference frequency signal synchronized with the AC current from the AC frequency information transmitted from the charging device 200. Since the measuring circuit 104b uses the reference frequency signal synchronized with the AC current, it is possible to measure the complex voltage and complex current with high accuracy.

[0143] As described above, the energy storage system 1 according to the third embodiment includes the energy storage device 100 and the charging device 200. The energy storage device 100 includes a battery pack 101, a complex impedance measuring unit 110, a first communication circuit 106 that transmits information related to complex impedance to the charging device and receives AC frequency information related to the frequency of the AC current, and a reference signal generating circuit that generates a reference frequency signal from the AC frequency information. The charging device 200 includes an AC superposition unit 148, a charging circuit 201, a charging control unit, and a second communication circuit 203 that receives information related to complex impedance from the energy storage device and transmits the AC frequency information. The complex impedance measuring unit 110 measures the complex impedance using the reference frequency signal.

[0144] According to this, since the measurement circuit 104b performs measurements using a reference frequency signal generated from AC frequency information, it is possible to measure complex voltages and complex currents with high accuracy.

[0145] Here, the second communication circuit 203 includes a communication clock generating unit 233 that generates a communication clock signal, and a modulation unit 231 that generates a communication signal by modulating communication data using the communication clock signal, the first communication circuit 106 includes a communication clock regeneration unit 177 that regenerates the communication clock signal from the communication signal, and a demodulation unit 176 that demodulates the communication signal using the regenerated communication clock signal, the AC superposition circuit 204 generates an AC current synchronized with the communication clock signal, the reference signal generating unit 180 generates a reference frequency signal synchronized with the regenerated communication clock signal, the complex impedance measuring unit 110 measures the complex impedance using the reference frequency signal, and the AC frequency information may correspond to the data timing of the communication signal and the edge timing of the communication clock signal.

[0146] This makes it possible to easily transmit the data timing of the communication signal as AC frequency information, which also corresponds to the edge timing of the regenerated communication clock signal.

[0147] In the third embodiment, the communication line connecting the communication circuit 203 and the communication circuit 106 has a communication signal line and does not have a communication clock signal line, but the present invention is not limited to this. The communication line may include both the communication signal line and the communication clock signal line. In this case, the communication clock recovery unit 177 is omitted.

[0148] In addition, to explain a case where a communication signal as AC frequency information is transmitted from the communication circuit 203 to the communication circuit 106, a configuration example has been described in which the communication circuit 203 includes the communication clock generating unit 233 and the communication circuit 106 includes the communication clock regenerating unit 177, but the present invention is not limited to this. In order to perform bidirectional communication, each of the communication circuit 203 and the communication circuit 106 may include a communication clock generating unit and a communication clock regenerating unit.

[0149] Furthermore, the communication circuit 203 and the communication circuit 106 are not limited to being connected by wire, but may be connected wirelessly.

[0150] (Examples) Next, specific application examples of the power storage system 1 according to the first to third embodiments will be described.

[0151] First, a first application example of the power storage system 1 will be described.

[0152] Fig. 17A is a schematic diagram showing a first application example of the power storage systems according to embodiments 1 to 3. Fig. 17B is a block diagram showing the first application example of Fig. 17A.

[0153] 17A, power storage device 100 is mounted on a motorcycle and supplies electric power to a motor that drives the motorcycle. When charging the power storage device 100, the power storage device 100 is connected to a charging device 200 via a charging cable P1. Also, a communication circuit 106 of the power storage device 100 and a communication circuit 203 of the charging device 200 are wirelessly connected. The communication circuit 206 of the charging device 200 is connected to a database 301 and a server device 302 via the Internet.

[0154] As shown in FIG. 17B, for example, the power storage device 100 wirelessly transmits the complex impedance and external temperature of each power storage cell to the charging device 200. The charging device 200 estimates the internal temperature of the battery pack 101 in the power storage device 100 from the complex impedance and the external temperature, and determines an optimal charging current for rapid charging according to the internal temperature. In order to determine the internal temperature, the charging device 200 accesses the server device 302 and transmits the complex impedance and charging information (e.g., SOC). The server device 302 diagnoses the deterioration state of the battery pack 101. The charging device 200 acquires deterioration information (e.g., SOH) according to the complex impedance and the charging information, and determines an optimal charging current based on the acquired deterioration information.

[0155] The connection to the Internet by the charging device 200 may be wired or wireless.

[0156] Next, a second application example of the power storage system 1 will be described.

[0157] Fig. 18 is a schematic diagram showing a second application example of the power storage system 1 according to the embodiments 1 to 3. This figure differs from Fig. 17A in that the power storage device 100, instead of the charging device 200, accesses the database 301 and the server device 302 via the Internet.

[0158] The power storage device 100 may connect to the Internet via a wired or wireless connection.

[0159] Next, a third application example of the power storage system 1 will be described.

[0160] Fig. 19A is a schematic diagram showing a third application example of the power storage systems according to embodiments 1 to 3. Fig. 19B is a block diagram showing the third application example of Fig. 19A.

[0161] 19A, the power storage device 100 and the charging device 200 are mounted on an electric vehicle. The electric vehicle includes a control device 400 as a so-called ECU (Electronic Control Unit). The control device 400 is capable of communicating with a database 301 and a server device 302, and is connected to the power storage device 100 and the charging device 200 via a communication line com. The power storage device 100 is connected to the charging device 200 via a charging cable P1 and the communication line com. The charging device 200 receives a supply of power for charging from a charging station 500 via a charging cable P2. The communication line com may be a part of a so-called wire harness.

[0162] As shown in FIG. 19B, the power storage device 100 transmits the complex impedance and the external temperature of each power storage cell to the control device 400 via the communication line com. The control device 400 estimates the internal temperature of the battery pack 101 in the power storage device 100 from the complex impedance and the external temperature, and determines an optimal charging current for rapid charging according to the internal temperature. The control device 400 transmits the complex impedance and charging information (e.g., SOC) to the server device 302 in order to determine the internal temperature. The server device 302 diagnoses the deterioration state of the battery pack 101. The control device 400 acquires deterioration information (e.g., SOH) corresponding to the complex impedance and the charging information from the server device 302, determines an optimal charging current based on the acquired deterioration information, and notifies the charging device 200 of the determined optimal charging current.

[0163] 19B, the control device 400 estimates the internal temperature, but the power storage device 100 or the charging device 200 may estimate the internal temperature. In this case, the power storage device 100 or the charging device 200 may be connected to the database 301 and the server device 302 via the control device 400 as a relay device.

[0164] Although the first to third application examples show the power storage device 100 being mounted on a vehicle, the present invention is not limited to this. For example, the power storage device 100 may be applied to a drone, an uninterruptible power supply device, a portable power supply device, and the like.

[0165] In each of the above embodiments, each component may be implemented by dedicated hardware or by executing a software program suitable for each component. Each component may be implemented by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0166] In addition, the energy storage system 1 according to one or more aspects has been described based on the embodiment, but the present disclosure is not limited to this embodiment. As long as it does not deviate from the spirit of the present disclosure, various modifications conceived by a person skilled in the art to this embodiment and forms constructed by combining components in different embodiments may also be included within the scope of one or more aspects. [Industrial Applicability]

[0167] The present disclosure is applicable to a power storage system having a secondary battery, and is applicable to, for example, an electric vehicle. [Explanation of symbols]

[0168] 1. Energy storage system 100 Electricity storage device 101 Battery pack 102 Thermistor 103 Current sensing resistor 104, 104a, 104b Measuring circuit 105 First Control Section 106, 107, 203, 206 Communication circuits 110 Complex impedance measurement unit 140 Clock Generation Unit 141 Frequency Hold Unit 142 Reference signal generator 143, 163, 181, 188, 241, 247 DDS 144, 164, 182 phase shifter 145 Voltage measurement section 146 Current measurement section 147 Temperature measurement section 148, 204 AC superposition section 149 Conversion Unit 150 Integral section 151 Holding part 152 Temperature holding part 153 IO Department 161 Phase synchronization section 162 Reference signal generator 165 Hysteresis Circuit 166 Comparator 167 Charge Pump 168 LPF 169 VCO 170 divider 171 ROM 175 Modulation section 176 Demodulation section 177 Communication Clock Recovery Unit 180 Reference signal generator 185 BPSK Demodulator 186 Receive Data Buffer 187 PLL 200 Charging device 201 Charging circuit 202 Second Control Section 205 Clock Circuit 210 Variable Current Source 231 Modulation section 232 Demodulation section 233 Communication Clock Generation Unit 242 Driver 243 Trans 245 Send Data Buffer 246 Bipolar Converter 248 BPSK Modulator 301 Database 302 Server equipment 400 Control device 500 Charging Station B0~B5 Storage cells com communication line P1, P2 charging cable

Claims

1. A power storage device having a battery pack including a plurality of power storage cells connected in series; a charging device for supplying a charging current to the battery pack; an AC superposition circuit that superimposes an AC current on the charging current, The power storage device is a complex impedance measurement unit that measures a current value of the superimposed AC current and a voltage value of each storage cell, and measures a complex impedance of each storage cell from the measured current value and the measured voltage value; a first communication circuit for communicating with the charging device; The charging device is a charging control unit that controls the charging current based on at least one of a deterioration state and an internal temperature of each of the power storage cells that are estimated based on a complex impedance of each of the power storage cells transmitted from the power storage device to the charging device via the first communication circuit; Energy storage system.

2. The power storage system according to claim 1 , The charging control unit estimates the internal temperature of each of the power storage cells according to at least one of temperature characteristic data indicating a correspondence relationship between an internal temperature of the battery pack and a complex impedance, and temperature distribution data indicating a distribution of an external temperature and an internal temperature of the battery pack. Energy storage system.

3. The power storage system according to claim 1 or 2, The charging control unit optimizes the charging current in response to deterioration information indicating a degree of deterioration of each of the power storage cells, the deterioration information being acquired from an external server device based on a complex impedance of each of the power storage cells. Energy storage system.

4. In the power storage system according to any one of claims 1 to 3, The charging control unit determines a value of the charging current so as to shorten a charging time until the charge level of the battery pack reaches a predetermined level. Energy storage system.

5. The power storage system according to claim 1 or 2, The charging control unit stops charging when the internal temperature of each of the power storage cells reaches a threshold value. Energy storage system.

6. The power storage system according to any one of claims 1 to 5, The power storage device includes the AC superposition circuit, The charging device has a second communication circuit that receives information regarding the complex impedance of each of the storage cells from the power storage device. Energy storage system.

7. The power storage system according to claim 6, the power storage device has a reference signal generating circuit that generates a reference frequency signal; the AC superposition circuit generates the AC current synchronized with the reference frequency signal; The complex impedance measuring unit measures the complex impedance of each of the power storage cells by using the reference frequency signal. Energy storage system.

8. The power storage system according to any one of claims 1 to 5, the power storage device has a phase locked loop circuit that generates a reference frequency signal synchronized with the AC current superimposed on the charging current, The charging device includes the AC superposition circuit, The complex impedance measuring unit measures the complex impedance of each of the power storage cells by using the reference frequency signal. Energy storage system.

9. The power storage system according to any one of claims 1 to 5, The first communication circuit transmits information regarding the complex impedance of each of the power storage cells to the charging device and receives AC frequency information regarding a frequency of the AC current; the power storage device has a reference signal generating circuit that generates a reference frequency signal from the AC frequency information; The charging device is The AC superposition circuit; a second communication circuit that receives information about the complex impedance of each of the power storage cells from the power storage device and transmits the AC frequency information; The complex impedance measuring unit measures the complex impedance of each of the power storage cells by using the reference frequency signal. Energy storage system.

10. A battery pack including a plurality of storage cells connected in series; a charging circuit for supplying a charging current to the battery pack; an AC superposition circuit that superposes an AC current on the charging current; a complex impedance measurement unit that measures a current value of the superimposed AC current and a voltage value of each storage cell, and measures a complex impedance of each storage cell from the measured current value and the measured voltage value; A charge control unit that controls the charging current based on at least one of a deterioration state and an internal temperature of each of the storage cells estimated based on a complex impedance of the each of the storage cells, The vehicle is provided with a power storage device and a charging device, The power storage device is The battery pack; The complex impedance measuring unit; a first communication circuit that transmits information regarding the complex impedance of each of the storage cells to the charging device and receives AC frequency information regarding a frequency of the AC current; a reference signal generating circuit that generates a reference frequency signal from the AC frequency information; The charging device is The AC superposition circuit; The charging circuit; The charging control unit; a second communication circuit that receives information about the complex impedance of each of the power storage cells from the power storage device and transmits the AC frequency information; the complex impedance measuring unit measures the complex impedance of each of the power storage cells by using the reference frequency signal; The second communication circuit is a communication clock generating unit that generates a communication clock signal; a modulation unit that generates a communication signal by modulating communication data using the communication clock signal, The first communication circuit is a communication clock regenerator that regenerates the communication clock signal from the communication signal; a demodulation unit that demodulates the communication signal using the reproduced communication clock signal, the AC superposition circuit generates the AC current synchronized with the communication clock signal; the reference signal generating circuit generates the reference frequency signal synchronized with the reproduced communication clock signal; the complex impedance measuring unit measures the complex impedance of each of the power storage cells by using the reference frequency signal; The AC frequency information corresponds to the data timing of the communication signal and the edge timing of the communication clock signal. Energy storage system.

11. A charging method for charging a power storage device including a battery pack in which a plurality of power storage cells are connected in series, comprising the steps of: superimposing an AC current on a charging current supplied to the battery pack; The power storage device measures a current value of the superimposed AC current and a voltage value of each power storage cell; The complex impedance of each of the storage cells is measured from the measured current value and the measured voltage value by the storage device; Transmitting the complex impedance of each of the power storage cells from the power storage device to a charging device via a communication circuit; The charging device controls the charging current based on at least one of a deterioration state and an internal temperature of each of the storage cells estimated based on a complex impedance of each of the storage cells. Charging method.

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