Power storage system, power storage device, and charging method

Abstract

The energy storage system (1) includes: an energy storage device (100) having a battery pack (101) comprising multiple energy storage units connected in series; and a charging device (200) supplying a charging current to the energy storage device (100). The energy storage system (1) includes: an AC superposition circuit (148) belonging to one of the energy storage device (100) and the charging device (200) for superimposing an AC current onto the charging current; a complex impedance measuring unit (110) belonging to the energy storage device (100) for measuring the current value of the superimposed AC current and the voltage value of each energy storage unit (B0 to B5), and measuring the complex impedance of each energy storage unit based on the measured current value and the measured voltage value; and a charging control unit belonging to one of the energy storage device (100) and the charging device (200) for controlling the charging current based on the complex impedance.

Description

Technical Field

[0001] This disclosure relates to energy storage systems, energy storage devices, and charging methods. Background Technology

[0002] Development is underway for vehicles powered by secondary batteries, such as HEVs (Hybrid Electric Vehicles) or EVs (Electric Vehicles). Furthermore, to ensure the safe use of secondary batteries, technologies such as battery management systems (BMS) for estimating battery capacity and detecting anomalies are known.

[0003] For example, Patent Document 1 discloses a battery state determination device that can measure the complex impedance of a battery and diagnose the battery's capacity and degradation.

[0004] Patent document 2 discloses a capacity retention determination device that can determine the capacity retention rate without performing a full charge and discharge of the battery.

[0005] Patent document 3 discloses a vehicle controller that uses parameters of an RC circuit model corresponding to the battery impedance to program the charging and discharging of the battery.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2015-94726

[0009] Patent Document 2: Japanese Patent Application Publication No. 2011-38857

[0010] Patent Document 3: US Patent No. 10023064 Summary of the Invention

[0011] The problem to be solved by the present invention

[0012] However, according to existing technology, there is a problem in optimizing the charging time of energy storage devices. For example, in the case of rapid charging of energy storage devices, it is desirable to shorten the charging time by optimizing the charging current.

[0013] This disclosure provides an energy storage system, energy storage device, and charging method that easily optimize charging time.

[0014] Problem-solving methods

[0015] One embodiment of the present invention provides an energy storage system comprising: a battery pack including a plurality of energy storage units connected in series; a charging circuit supplying a charging current to the battery pack; an AC superposition circuit superimposing an AC current onto the charging current; a complex impedance measuring unit measuring the current value of the superimposed AC current and the voltage value of each energy storage unit, and measuring the complex impedance of each energy storage unit based on the measured current value and the measured voltage value; and a charging control unit controlling the charging current based on the complex impedance.

[0016] In addition, one embodiment of the present invention provides an energy storage device comprising: a battery pack consisting of multiple energy storage units connected in series; an AC superposition circuit that superimposes an AC current onto the charging current supplied to the battery pack; a complex impedance measuring unit that measures the current value of the superimposed AC current and the voltage value of the multiple energy storage units, and measures the complex impedance of the energy storage units based on the measured current value and the measured voltage value; and a communication circuit that notifies the charging device supplying the charging current of the complex impedance.

[0017] In addition, one of the technical solutions of the present invention is a charging method for charging an energy storage device having a battery pack having multiple energy storage units connected in series. An alternating current is superimposed on the charging current supplied to the battery pack, the current value of the superimposed alternating current and the voltage value of the multiple energy storage units are measured, and the complex impedance of the energy storage units is measured based on the measured current value and the measured voltage value, and the charging current is controlled based on the complex impedance.

[0018] The effects of the invention

[0019] According to one technical solution of the present invention, the energy storage system, energy storage device and charging method can easily optimize the charging time. Attached Figure Description

[0020] Figure 1 This is a block diagram illustrating a structural example of the energy storage system according to Embodiment 1.

[0021] Figure 2 It means Figure 1 The detailed structure of the measuring circuit in the energy storage system and the circuit diagram of the surrounding circuits are shown.

[0022] Figure 3 This is an explanatory diagram showing an example of the structure and equivalent circuit model of the energy storage unit in Embodiment 1.

[0023] Figure 4 This is a Cole-cole plot showing an example of the complex impedance of the energy storage unit in Embodiment 1.

[0024] Figure 5This is an explanatory diagram showing an example of the specific locations of the surface temperature and internal temperature of the battery pack in Embodiment 1.

[0025] Figure 6 This is an explanatory diagram showing the difference between the surface temperature and the internal temperature of the battery pack, which is a battery pack in Embodiment 1.

[0026] Figure 7 This is a diagram illustrating an example of the temperature characteristics of the complex impedance of the energy storage unit in Embodiment 1.

[0027] Figure 8 This is a block diagram illustrating other structural examples of the energy storage system according to Embodiment 1.

[0028] Figure 9 This is a block diagram illustrating a structural example of the energy storage system according to Embodiment 2.

[0029] Figure 10 It means Figure 9 The detailed structure of the measuring circuit in the energy storage system and the circuit diagram of the surrounding circuits are shown.

[0030] Figure 11 It means Figure 10 A detailed structural example of the phase synchronization unit and a diagram of its surrounding circuitry are shown.

[0031] Figure 12 It means Figure 11 The output waveform of the hysteresis circuit is shown in the figure.

[0032] Figure 13 This is a block diagram illustrating a structural example of the energy storage system according to Embodiment 3.

[0033] Figure 14 It means Figure 13 The detailed structure of the measuring circuit in the energy storage system and the circuit diagram of the surrounding circuits are shown.

[0034] Figure 15 It is a more detailed expression Figure 13 A block diagram of the structure related to AC frequency information in an energy storage system.

[0035] Figure 16 It means Figure 15 The figure shows the transmitted data and the waveform after BPSK modulation.

[0036] Figure 17A This is a schematic diagram illustrating a first application example of the energy storage system according to embodiments 1 to 3.

[0037] Figure 17B It means Figure 17A The first application example is shown in the flowchart.

[0038] Figure 18This is a schematic diagram illustrating a second application example of the energy storage system according to embodiments 1 to 3.

[0039] Figure 19A This is a schematic diagram illustrating a third application example of the energy storage system according to embodiments 1 to 3.

[0040] Figure 19B It means Figure 19A The flowchart of the third application example. Detailed Implementation

[0041] The embodiments will now be described with reference to the accompanying drawings. Furthermore, the embodiments described below are general or specific examples. The numerical values, shapes, materials, constituent elements, the arrangement of constituent elements, connection methods, steps, and the order of steps shown in the following embodiments are examples and are not intended to limit this disclosure. Moreover, the implementation of this disclosure is not limited to the present independent technical solution and can be manifested by other independent technical solutions.

[0042] Furthermore, the figures are schematic diagrams and not necessarily strictly illustrated diagrams. Also, in the figures, substantially identical structures are sometimes labeled with the same reference numerals, and repeated descriptions are omitted or simplified.

[0043] (Implementation Method 1)

[0044] [1.1 Structure of Energy Storage System 1]

[0045] First, the structure of the energy storage system 1 in Embodiment 1 will be described.

[0046] Figure 1 This is a block diagram illustrating a structural example of the energy storage system 1 according to Embodiment 1. Figure 1 The diagram also shows the external database 301.

[0047] Figure 1 The energy storage system 1 includes an energy storage device 100 and a charging device 200. The energy storage device 100 includes a battery pack 101, a thermistor 102, a current detection resistor 103, a measurement 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.

[0048] Furthermore, the measuring circuit 104 and the portion corresponding to S11 to S14 of the first control unit 105 are referred to as the complex impedance measuring unit 110. The portion corresponding to S5 of the first control unit 105 and the second control unit 202 are referred to as the charging control unit.

[0049] The energy storage device 100 includes a rechargeable secondary battery, for example, mounted in a vehicle, which supplies power to an electric motor that serves as a power source.

[0050] Battery pack 101 is a secondary battery, comprising multiple energy storage units B0 to B5 connected in series. Each energy storage unit is, for example, a lithium-ion battery, but may also be other batteries such as nickel-metal hydride batteries. Alternatively, it may be an energy storage unit connected in series, such as a lithium-ion capacitor. Battery pack 101 is connected to a load and a charging circuit. The load is, for example, an electric motor of an HEV or EV, but is not limited to this. Furthermore, Figure 1 The battery pack 101 represents an example with 6 energy storage units, but the number of energy storage units in the battery pack 101 is not limited to 6.

[0051] Thermistor 102 is a temperature sensor whose resistance changes with temperature. It is attached to the surface of battery pack 101 for measuring the external temperature of battery pack 101. For example, thermistor 102 is attached near the center of the side of battery pack 101.

[0052] The current sensing resistor 103 is a resistive element used to detect the AC current value superimposed on the charging current flowing through the battery pack 101 as a voltage drop.

[0053] The complex impedance measuring unit 110 measures the current value of the alternating current superimposed on the charging current flowing through the battery pack 101 and the voltage value of each energy storage unit B0 to B5, and measures the complex impedance of each energy storage unit B0 to B5 based on the measured current value and the measured voltage value. Therefore, the complex impedance measuring unit 110 includes a measuring circuit 104 and a portion corresponding to S11 to S14 of the first control unit 105.

[0054] The measuring circuit 104 measures the current value of the alternating current superimposed on the charging current flowing through the battery pack 101, and the voltage value of each energy storage unit (B0 to B5). The measured current and voltage values ​​are complex currents and complex voltages that include phase information based on the superimposed alternating current. In addition, the measuring circuit 104 uses a thermistor 102 to measure the external temperature of the battery pack 101.

[0055] The first control unit 105 is an MCU (Micro Controller Unit or Micro Computer Unit) including a CPU (Central Processing Unit), memory, and I / O (Input / Output) circuits. It performs the following processes by executing a program stored in its memory. The memory of the first control unit 105 stores, for example, a program that repeatedly executes the processes shown in S11 to S15 of this figure. Specifically, the first control unit 105 obtains the complex voltage of each of the energy storage cells B0 to B5 from the measurement circuit 104 (S11). Furthermore, the first control unit 105 obtains the complex current as the value of an alternating current superimposed on the charging current (S12). In addition, the first control unit 105 obtains the external temperature of the battery pack 101 (S13). Then, the first control unit 105 calculates the complex impedance of each energy storage cell B0 to B5 by dividing the obtained complex voltage by the complex current (S14). Thus, the first control unit 105 receives the measurement results from the measurement circuit 104 and undertakes a part of the complex impedance measurement.

[0056] Furthermore, as part of the charging control process, the first control unit 105 estimates the internal temperature of the battery pack 101 (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 energy storage cell B0 to B5. For example, the first control unit 105 may also use temperature characteristic data showing the correspondence between the internal temperature and complex impedance of the battery pack 101, and temperature distribution data showing the distribution of the external temperature and internal temperature of the battery pack to estimate the internal temperature. The temperature characteristic data and temperature distribution data may be stored in the memory of the first control unit 105 in advance, or they may be obtained from the database 301 via the communication circuit 107 and temporarily stored in the memory. The first control unit 105 repeatedly executes the above-described S11 to S15 during the charging process of the battery pack 101 by the charging device 200. This repetition is a detection cycle that can adequately track the rate of change of the internal temperature of the battery pack 101 due to the heat generated by the charging current.

[0057] Under the control of the first control unit 105, the communication circuit 106 communicates with the communication circuit 203 within the charging device 200. For example, the communication circuit 106 sends the complex impedance of each energy storage unit B0 to B5, the external temperature of the battery pack 101, and the estimated internal temperature to the charging device 200.

[0058] The communication circuit 107 communicates with an external database 301. Database 301 is used to collect and provide battery status data for the energy storage units B0 to B5 of the battery pack 101, as well as battery status data related to energy storage units in other energy storage devices. The battery status data includes, for example, degradation information referred to as SOH (State of Health).

[0059] On the other hand, the charging device 200 is a device for charging the battery pack 101, and controls the charging current of the battery pack 101 based on the complex impedance sent from the energy storage device 100, the external temperature of the battery pack 101, and the internal temperature of the battery pack 101.

[0060] The communication circuit 203 communicates with the communication circuit 106 within the energy storage device 100 under the control of the second control unit 202. For example, the communication circuit 203 receives from the energy storage device 100 the complex impedance of each energy storage unit B0 to B5, the external temperature of the battery pack 101, and the estimated internal temperature.

[0061] The charging circuit 201 has a variable current source 210. The variable current source 210 supplies charging current to the battery pack 101 under the control of the second control unit 202.

[0062] The second control unit 202 is an MCU including a CPU, memory, and I / O circuits, and executes programs stored in the memory. The memory of the second control unit 202 stores, for example, programs that repeatedly execute the processes shown in S21 to S24 of this figure. The second control unit 202 repeatedly executes the processes shown in S21 to S24 during the charging process of the battery pack 101.

[0063] First, the second control unit 202 obtains the complex impedance of each energy storage unit B0 to B5 from the energy storage device 100 via the communication circuit 203 (S21), and obtains degradation information (i.e., SOH) from the database 301 via the energy storage device 100 and the communication circuit 203 (S22). At this time, the second control unit 202 can obtain the battery balance of each energy storage unit B0 to B5 from the first control unit 105 via the communication circuit 106 and the communication circuit 203. The battery balance is sometimes referred to as SOC: State of Charge. Furthermore, the second control unit 202 obtains the estimated internal temperature and the measured external temperature of each energy storage unit B0 to B5 from the energy storage device 100 via the communication circuit 203 (S23). Furthermore, the communication circuit 203 determines the optimal charging current based on the complex impedance, degradation information, internal temperature, and external temperature (S24), and controls the variable current source 210 to supply the determined optimal charging current to the battery pack 101.

[0064] Regarding the optimal charging current for rapid charging, for example, the second control unit 202 determines the value of the charging current in a way that minimizes the charging time until the battery pack 101 reaches a predetermined charging level, while keeping the internal temperature within a threshold range. The predetermined level can be any value, such as 80% charge, 90% charge, or fully charged.

[0065] [1.2 Structure of Measurement Circuit 104]

[0066] Next, a detailed structural example of the measurement circuit 104 within the complex impedance measurement unit 110 will be described.

[0067] Figure 2 It means Figure 1 A detailed structural example of the measuring circuit 104 in the energy storage system 1 and a circuit diagram of the surrounding circuits.

[0068] The measurement circuit 104 in this figure includes a clock generation unit 140, a frequency holding unit 141, a reference signal generation unit 142, a voltage measuring unit 145, a current measuring unit 146, a temperature measuring 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 I / O unit 153.

[0069] The clock generation unit 140 generates a sampling clock signal. The sampling clock signal is supplied to the ADC (Analog Digital Converter) in the voltage measurement unit 145, the ADC in the current measurement unit 146, and the ADC in the temperature measurement unit 147.

[0070] The frequency holding unit 141 holds the frequency indicated from outside the energy storage device 100. This frequency refers to the frequency of the reference frequency signal generated by the reference signal generating unit 142.

[0071] The reference signal generation unit 142 generates a reference frequency signal and a quadrature reference frequency signal whose frequency is held by the frequency holding unit 141. Therefore, the reference signal generation unit 142 has a DDS 143 and a phase shifter 144.

[0072] DDS143 is short for Direct Digital Synthesizer. It contains ROM that stores waveform data obtained by sampling a sine wave, inputs an address indicating the sampling point, and outputs the data of the sampling point of the sine wave (i.e., the sampled value). Because the address changes continuously, the output sampled value becomes a roughly continuous sine wave.

[0073] Phase shifter 144 generates a quadrature reference frequency signal by shifting the phase of the reference frequency signal by 90 degrees. Alternatively, the reference signal generation unit 142 may use a DDS 143 to generate both the reference frequency signal and the quadrature frequency signal, without the structure of phase shifter 144.

[0074] The voltage measuring unit 145 measures the voltage of the battery pack 101 by sampling the voltage of the battery pack 101 using a sampling clock signal from the clock generation unit 140. More specifically, the voltage measuring unit 145 includes the same number of analog-to-digital converters (ADC0 to ADC5) corresponding to the energy storage units B0 to B5 within the battery pack 101. Each analog-to-digital converter uses the sampling clock signal from the clock generation unit 140 to sample the voltage of the corresponding energy storage unit among the multiple energy storage units B0 to B5, and converts the sampled voltage into a digital signal.

[0075] The current measuring unit 146 samples the current of the battery pack 101 using a sampling clock signal from the clock generation unit 140, and measures the alternating current superimposed on the charging current flowing through the battery pack 101. The superimposed alternating current is measured as the voltage drop across the current sensing resistor 103, which is inserted into the current circulation path through which the alternating current applied by the alternating current superposition unit 148 flows. This voltage drop is proportional to the superimposed alternating current, and therefore represents the alternating current value. More specifically, the current measuring unit 146 includes an analog-to-digital converter (ADC) for measuring the current of the battery pack 101, which is a secondary battery. This ADC samples the voltage drop across the current sensing resistor 103 using a sampling clock signal from the clock generation unit 140 and converts the sampled voltage drop into a digital signal. The current measuring unit 146 and the voltage measuring unit 145 use the same sampling clock, thus enabling high-precision measurement.

[0076] The temperature measuring unit 147 uses a thermistor 102 disposed on the battery pack 101 to measure the external temperature of the battery pack 101. The thermistor 102 may be, for example, a temperature sensor using a thermocouple or other components. Specifically, the temperature measuring unit 147 includes an analog-to-digital converter (ADC). This ADC samples the voltage of the thermistor 102 and converts the sampled voltage into a digital value.

[0077] The AC superposition unit 148 superimposes an AC current having a frequency component of the reference frequency signal generated by the reference signal generation unit 142 onto the charging current flowing through the battery pack 101. The AC superposition unit 148 has a differential buffer that applies the reference frequency signal as a differential signal to the positive and negative terminals of the battery pack 101.

[0078] The conversion unit 149 multiplies the measurement results of the voltage measuring unit 145 and the current measuring unit 146 by a reference frequency signal and a quadrature reference frequency signal. Thus, the conversion unit 149 converts the measurement results of the voltage measuring unit 145 and the current measuring unit 146 into real and imaginary components of complex voltage and complex current, respectively. Therefore, the conversion unit 149 has the same number of multiplier pairs as the analog-to-digital converters (ADC0 to ADC5) of the voltage measuring unit 145, and multiplier pairs as the analog-to-digital converters of the current measuring unit 146. Each multiplier pair corresponding to the voltage measuring unit 145 consists of a multiplier that multiplies the conversion result of the corresponding analog-to-digital converter (i.e., the sampled digital voltage value) by a reference frequency signal, and a multiplier that multiplies the conversion result by a quadrature reference frequency signal. The former multiplication result represents the real component when the sampled voltage is represented as a complex voltage. The latter multiplication result represents the imaginary component when the sampled voltage is represented as a complex voltage. The multiplier pair corresponding to the current measuring 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 multiplication result of the former represents the real part of the sampled current when it is represented as a complex current. The multiplication result of the latter represents the imaginary part of the sampled current when it is represented as a complex current.

[0079] Furthermore, the analog-to-digital converters (ADC0 to ADC5) can each be, for example, delta-sigma type AD converters. Moreover, the multiple analog-to-digital converters (ADC0 to ADC5) have the same AD conversion characteristics. AD conversion characteristics are various parameters such as resolution (number of bits). Specifically, the multiple analog-to-digital converters (ADC0 to ADC5) use the same AD converter. This reduces measurement errors caused by AD conversion in the energy storage units B0 to B5.

[0080] The integrator 150 averages the real and imaginary components of the complex voltage and complex current, which are repeatedly measured by the voltage measuring unit 145 and converted by the conversion unit 149. This averaging also improves measurement accuracy. More specifically, the integrator 150 has the same number of averaging circuit pairs as the multiplier pairs of the conversion unit 149. Each averaging circuit pair consists 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. In the case of a lithium-ion battery, the internal complex impedance is, for example, a few mΩ. If the superimposed AC current is assumed to be 1A, the output voltage change is only a few mV. On the other hand, the DC output voltage of a lithium-ion battery is approximately 3.4V, so a dynamic range of approximately 4 to 5V is required to measure the voltage using an analog-to-digital converter connected to the battery. In this context, when a complex impedance measurement accuracy of approximately 8 bits is required, an analog-to-digital converter (ADC) with approximately 18 to 20 effective bits is needed. However, high-resolution ADCs have high power consumption and large area requirements. On the other hand, the internal complex impedance measured for electrochemical impedance analysis of lithium-ion batteries cannot be measured via AC connection because it is performed in a low-frequency range from approximately 0.01 Hz near DC to tens of kHz. Figure 1 In this structure, by repeatedly applying alternating current, the complex voltage or current is separated into real and imaginary components and averaged, thereby improving resolution through integration. Therefore, even analog-to-digital converters with a small bit count (e.g., around 16 bits) can obtain complex impedance measurement results with an accuracy of 20–24 bits. Thus, if the accuracy of complex voltage measurement can be improved, it is possible to reduce the magnitude of the applied alternating current, making it easier to measure secondary batteries with large capacity and low internal complex impedance.

[0081] The holding unit 151 holds the real and imaginary components of the averaged complex voltage and complex current. Therefore, the holding unit 151 has the same number of register pairs as the plurality of energy storage cells in the battery pack 101, and register pairs for holding the complex current, in order to hold the complex voltage. Each register pair for holding the complex voltage consists of a register (Re(Vi)) that holds the real component of the complex voltage of the corresponding energy storage cell Bi and a register that holds the imaginary component (Im(Vi)). Here, i is an integer from 0 to 5. Furthermore, the register pair for holding the complex current consists of a register (Re(I0)) that holds the real component of the complex current of the corresponding battery pack 101 and a register that holds the imaginary component (Im(I0)).

[0082] The temperature holding unit 152 holds the digital value from the temperature measuring unit 147 as temperature data.

[0083] 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 inputs data representing the frequency of the reference frequency signal from the first control unit 105.

[0084] The measurement circuit 104 configured as described above can perform measurements with high precision because the phase error in voltage and current measurements is approximately zero.

[0085] [1.3 Equivalent Circuit Model and Complex Impedance of the Energy Storage Unit]

[0086] Next, an example of the equivalent circuit model of the energy storage unit and its component constants will be explained.

[0087] Figure 3 These are explanatory diagrams illustrating examples of the structure and equivalent circuit model of the energy storage unit in the implementation method. Figure 3 (a) represents the circuit symbol of the energy storage unit B0. Figure 3 (b) schematically illustrates a structural example where the energy storage unit B0 is a lithium-ion battery. As a premise of the equivalent circuit model, the energy storage unit B0 has a negative electrode, a negative electrode material, an electrolyte, a separator, a positive electrode material, and a positive electrode. Figure 3 (c) represents an example of the equivalent circuit model of the energy storage unit B0. This equivalent circuit model has an inductive component L0, resistive components R0 to R2, capacitive 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 resistive component R0 represents the impedance component of the electrolyte. The parallel circuit of the resistive component R1 and the capacitive component C1 represents the impedance component of the negative electrode. The circuit consisting of the resistive component R2, the lithium-ion diffusion resistance component Zw, and the capacitive component C2 represents the impedance component of the positive electrode. The lithium-ion diffusion resistance component Zw is known as the Warburg impedance.

[0088] If the component constants of each circuit element constituting such an equivalent circuit model are calculated, the state of the energy storage unit B0 can be estimated. For example, the degradation state of the energy storage unit B0 can be estimated by the change of component constants over time.

[0089] Next, we will explain the characteristics of the complex impedance of the battery cell.

[0090] Figure 4 This is a Cole plot showing an example of the complex impedance of the energy storage unit in Embodiment 1. The Cole plot is also known as a complex plane plot or a Nyquist plot. This plot corresponds to... Figure 3(c) Equivalent circuit model. In the method of calculating the complex impedance of the energy storage unit by superimposing alternating currents, it is generally known that, in the case of charge movement speed control, the equivalent circuit is represented by a resistor and capacitor connected in parallel, which is semi-circular in the complex plane. Furthermore, in the case of including this Warburg impedance, it is generally known that, starting from the middle of the semi-circle (near the upper right), it becomes a straight line rising at an inclination of 45 degrees as caused by the Warburg impedance.

[0091] In the calculation of complex impedance, the phase error of system factors is often measured in cases where it has frequency characteristics. However, determining the complex impedance at different frequencies becomes a challenge. Specifically, when the frequency is variable and the complex impedance at each frequency is plotted on a Col plot, the phase error at each frequency is represented on the complex plane of the Col plot as an orthogonal error between the real axis (horizontal axis) and the imaginary axis (vertical axis). Therefore, it is difficult to draw an accurate Col plot. However, in... Figure 2 In this structure, the complex impedance is calculated after the complex voltage and complex current are measured, which makes the phase error of the voltage and current measurement system very small, thus making it possible to draw accurate Cole plots.

[0092] [1.4 External and Internal Temperatures]

[0093] Next, the difference between the external and internal temperatures of the battery pack 101 will be explained. The internal temperature is an important parameter when the battery pack 101 is fast-charged. The charging current can be set within the upper limit of the internal temperature. On the other hand, the higher the charging current, the higher the internal temperature rises. Therefore, when the battery pack 101 is fast-charged, the upper limit of the charging current varies depending on the internal temperature.

[0094] Figure 5 This is an explanatory diagram showing an example of the specific locations of the surface temperature and internal temperature of the battery pack in the battery pack 101 of Embodiment 1. Alternatively, the battery pack may correspond to a single energy storage unit instead of the battery pack 101.

[0095] The battery pack in the figure schematically shows a battery assembly 101 housed within a battery casing. The internal temperature is, for example, the temperature at the location of the battery pack's three-dimensional center of gravity or center. The internal temperature itself cannot be directly measured by the thermistor 102. Furthermore, the surface temperature (also called the external temperature) is the temperature at location X near the center of the side of the battery pack. The surface temperature can be directly measured by attaching the thermistor 102.

[0096] Figure 6 This is an explanatory diagram showing the difference between the surface temperature and the internal temperature of the battery pack in Embodiment 1. Figure 6 (a) and Figure 6 In (b), the horizontal axis represents the perpendicular passage. Figure 5The axial direction of the side. X indicates the axis relative to... Figure 5 The Y-axis represents the intersection of the front and back sides. The Y-axis represents the intersection of the front and back sides, which are hidden and not visible. The vertical axis represents temperature.

[0097] Figure (a) shows the temperature distribution of the battery pack at thermal equilibrium. Thermal equilibrium refers to the state where the internal temperature is the same after a period of time when no current flows through the battery pack 101, i.e., a non-charging state without current supply. At this time, the internal temperature is the same as the surface temperature.

[0098] Figure (b) shows the temperature distribution of the battery pack during thermal non-equilibrium. Thermal non-equilibrium refers to the charging or discharging of battery pack 101. During thermal non-equilibrium, the internal temperature becomes higher than the surface temperature due to the heat generated by the current flowing through battery pack 101. Temperature distribution data like that in Figure (b) helps to estimate the internal temperature based on the surface temperature. However, although temperature distribution data is difficult to quantify, the internal temperature can be estimated using surface temperature and complex impedance.

[0099] Next, the temperature dependence of complex impedance will be explained.

[0100] Figure 7 This is a graph showing an example of the temperature characteristics of the complex impedance of the energy storage unit in Embodiment 1. The graph shows Cole plots for the energy storage unit at temperatures of 20°C, 25°C, and 30°C. Thus, when estimating the internal temperature based on the complex impedance of the energy storage unit, it exhibits temperature dependence. The second control unit 202 can use this temperature characteristic data, which shows the correspondence between the internal temperature and complex impedance of the battery pack 101, to estimate the internal temperature.

[0101] According to the energy storage system 1 of this embodiment, the charging current supplied to the energy storage device 100 can be optimized. Since the complex impedance measured by the energy storage device 100 corresponds to the internal temperature and degradation state of the energy storage cells B0 to B5, the second control unit 202 can determine a suitable charging current for the battery pack 101. For example, in the case of fast charging of the energy storage device 100, the charging time can be shortened by optimizing the charging current.

[0102] [1.5 Variations]

[0103] in addition, Figure 1 The energy storage system 1 is shown as a structural example generally consisting of an energy storage device 100 and a charging device 200, but is not limited thereto. For example, the energy storage system 1 may also be as follows: Figure 8 As shown, the energy storage device 100 and the charging device 200 are integrated. In this case, the first control unit 105 and the second control unit 202 can be integrated into a charging control unit (i.e., one MCU), and the communication circuit 106 and the communication circuit 203 can be omitted.

[0104] As described above, the energy storage system 1 of Embodiment 1 includes: a battery pack 101 comprising a plurality of energy storage units B0 to B5 connected in series; a charging circuit 201 supplying a charging current to the battery pack 101; an AC superposition unit 148 / 204 superimposing an AC current onto the charging current; a complex impedance measuring unit 110 measuring the current value of the superimposed AC current and the voltage value of each energy storage unit B0 to B5, and measuring the complex impedance of each energy storage unit based on 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.

[0105] Therefore, the charging current of the energy storage device can be easily optimized. The complex impedance corresponds to the internal temperature and degradation state of the energy storage unit, allowing the charging control unit to determine the appropriate charging current for each energy storage unit. For example, in the case of rapid charging of the energy storage device, the charging time can be shortened by optimizing the charging current.

[0106] Here, the charging control unit can also estimate the internal temperature of each energy storage unit B0 to B5 based on the external temperature and complex impedance of the battery pack 101, and optimize the charging current according to the estimated internal temperature.

[0107] Therefore, the internal temperature can be estimated based on the complex impedance, and the optimal charging current can be determined at the estimated internal temperature.

[0108] Here, the charging control unit can also estimate the internal temperature of each energy storage unit based on at least one of temperature characteristic data representing the correspondence between the internal temperature and complex impedance of the battery pack, and temperature distribution data representing the distribution of the external and internal temperatures of the battery pack.

[0109] Therefore, by using at least one of the temperature characteristic data and temperature distribution data in the estimation of internal temperature, the accuracy of the estimation can be improved.

[0110] Here, the charging control unit can also control the charging current based on the degradation state of each energy storage unit estimated from the complex impedance.

[0111] Therefore, the charging current can be optimized according to the degradation state.

[0112] Here, the charging control unit can also optimize the charging current based on the degradation information obtained from the external server device 302 based on the complex impedance, which indicates the degree of degradation of each energy storage unit B0 to B5.

[0113] Therefore, it is possible to use external network devices to estimate the degradation state and optimize the charging current based on the estimated degradation state.

[0114] Here, the charging control unit can also determine the value of the charging current to shorten the charging time until the battery pack 101 reaches the specified charging level.

[0115] This enables fast charging.

[0116] Here, the charging control unit can stop charging when the internal temperature reaches a threshold.

[0117] Therefore, charging can be stopped when the internal temperature exceeds the threshold.

[0118] Here, the energy storage system may also include an energy storage device 100 and a charging device 200. The energy storage device 100 has a battery pack 101, an AC superposition unit 148, a complex impedance measuring unit 110, and a first communication circuit 106 that sends information related to complex impedance to the charging device 200. The charging device 200 has 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 100.

[0119] Here, the energy storage device 100 may also include a reference signal generating unit 180 that generates a reference frequency signal, an AC superposition unit 148 that generates an AC current synchronized with the reference frequency signal, and a complex impedance measuring unit 110 that uses the reference frequency signal to measure the complex impedance.

[0120] Therefore, since the same reference frequency signal is used in both voltage and current measurements, high-precision measurements are possible. Furthermore, because the reference frequency signal is used in all superimposed AC current, voltage, and current measurements, high-precision measurements are also possible.

[0121] Additionally, the energy storage device 100 of Embodiment 1 includes: a battery pack 101, which connects multiple energy storage units B0 to B5 in series; an AC superposition unit 148, which superimposes an AC current onto the charging current supplied to the battery pack; a complex impedance measuring unit 110, which measures the current value of the superimposed AC current and the voltage values ​​of the multiple energy storage units B0 to B5, and measures the complex impedance of the energy storage units based on the measured current value and the measured voltage value; and a communication circuit 106, which notifies the charging device that supplies the charging current of the complex impedance.

[0122] Therefore, the charging current of the energy storage device can be easily optimized. Since the complex impedance corresponds to the internal temperature and degradation state of the energy storage cell, the charging control unit can determine the appropriate charging current for each energy storage cell. For example, in the case of rapid charging of the energy storage device, the charging time can be shortened by optimizing the charging current.

[0123] In addition, the charging method of Embodiment 1 is a charging method for charging an energy storage device 100 having a battery pack 101 having multiple energy storage units B0 to B5 connected in series. An alternating current is superimposed on the charging current supplied to the battery pack 101, the current value of the superimposed alternating current and the voltage value of the multiple energy storage units B0 to B5 are measured, the complex impedance of the energy storage unit is measured based on the measured current value and the measured voltage value, and the charging current is controlled based on the complex impedance.

[0124] Therefore, it is easy to optimize the charging current of the energy storage device.

[0125] (Implementation Method 2)

[0126] In Embodiment 1, an example is shown of the energy storage device 100 performing the superposition of alternating current for complex impedance measurement. In contrast, in Embodiment 2, an example is described of the charging device 200 performing the superposition of alternating current.

[0127] [2.1 Structure of Energy Storage System 1]

[0128] Figure 9 This is a block diagram illustrating a structural example of the energy storage system according to Embodiment 2. This diagram is consistent with... Figure 1 The main differences are: a measurement circuit 104a is provided instead of a measurement circuit 104; an AC superposition section 204 is added to the charging device 200; and a clock circuit 205 is added. The following explanation focuses on these differences.

[0129] Measurement circuit 104a and Figure 1 Compared to the measurement circuit 104, the main difference lies in that it generates a reference frequency signal synchronized with the AC current superimposed on the charging current, and uses this reference frequency signal to measure the complex voltage and complex current. Therefore, it is possible to... Figure 1 As shown, the measurement of complex voltage and complex current can be performed with high precision.

[0130] The clock circuit 205 generates an AC current that should be superimposed and a reference frequency signal that serves as the communication reference for the communication circuit 203.

[0131] The communication circuit 203 includes a modulation unit 231 and a demodulation unit 232, which also use a reference frequency signal generated by the clock circuit 205 for modulation and demodulation. Furthermore, in order to communicate with the communication circuit 203, the communication circuit 106 includes a modulation unit 175 and a demodulation unit 176.

[0132] The AC superposition unit 204 superimposes the AC current synchronized with the reference frequency signal generated by the clock circuit 205 onto the charging current flowing through the battery pack 101. Therefore, the AC superposition unit 204 includes a DDS 241, a driver 242, and a transformer 243.

[0133] DDS241 is short for Direct Digital Synthesizer. It contains ROM that stores waveform data corresponding to a sine wave of superimposed AC current, takes an address indicating the sampling point as input, and outputs the data (i.e., sampled values) of the sampled sine wave. Because the address changes continuously, the output sampled values ​​represent an almost continuous sine wave. Furthermore, the waveform of the AC current to be superimposed does not have to be a sine wave; it can also be a pulsed waveform.

[0134] The driver 242 is a differential buffer that outputs the sine wave output from DDS241 as a differential signal to transformer 243.

[0135] Transformer 243 superimposes a differential signal representing the AC current from driver 242 onto the charging current flowing into battery pack 101.

[0136] [2.2 Structure of Measurement Circuit 104a]

[0137] Next, the detailed structure of the measurement circuit 104a will be explained.

[0138] Figure 10 It means Figure 9 A detailed structural example of the measuring circuit 104a in the energy storage system 1 and a circuit diagram of the surrounding circuit. Figure 10 and Figure 2 In comparison, the differences are as follows: the frequency holding unit 141, the reference signal generation unit 142, and the AC superposition unit 148 are deleted; and the phase synchronization unit 161 and the reference signal generation unit 162 are added. The following explanation focuses on the differences.

[0139] The phase synchronization unit 161 generates an AD conversion result from the current measuring unit 146, which is a clock signal synchronized with the AC current superimposed on the charging current. This clock signal has a frequency shown by the frequency data held in the frequency holding unit 141.

[0140] The reference signal generation unit 162 generates a reference frequency signal synchronized with the clock signal from the phase synchronization unit 161 and a quadrature reference frequency signal. Therefore, the reference signal generation unit 162 includes a DDS 163 and a phase shifter 164. The DDS 163 and the phase shifter 164 can have... Figure 2 The DDS143 and phase shifter 144 have the same structure.

[0141] [2.3 Structure of Phase Synchronization Unit 161]

[0142] Next, a more detailed structural example of the phase synchronization unit 161 will be described.

[0143] Figure 11 It means Figure 10 A detailed structural example of the phase synchronization unit 161 and a diagram of its surrounding circuitry are shown. Furthermore, Figure 11 The phase synchronization unit 161 is shown in the following example: instead of synchronizing the AD conversion result of the current measuring unit 146, it synchronizes the AC current value of the input signal to the current measuring unit 146, which is the voltage drop of the current sensing resistor 103.

[0144] Figure 11 The phase synchronization unit 161 includes a hysteresis circuit 165, a comparator 166, a charge pump 167, an LPF 168, a VCO 169, and a frequency divider 170.

[0145] Hysteresis circuit 165 binarizes the AC current value detected by current sensing resistor 103. Figure 12 It means Figure 11 The diagram shows the output waveform (A1) of the hysteresis circuit 165. The horizontal axis represents time, and the vertical axis represents the output voltage corresponding to the current value. ITH+ and ITH- represent examples of the upper and lower thresholds of the hysteresis characteristic. The output waveform (A1) of the hysteresis circuit 165 becomes a pulse-shaped rectangular wave with the same frequency 1 / T as the superimposed AC signal, as shown in the diagram.

[0146] Comparator 166 compares the output signal of hysteresis circuit 165 with the divided signal of frequency divider 170 to detect phase difference.

[0147] The charge pump 167 raises the signal representing the detected phase difference to the required voltage level.

[0148] The LPF168, also known as a low-pass filter or cyclic filter, smooths signals representing phase differences from the charge pump 167.

[0149] The VCO169 is a voltage-controlled oscillator that outputs a signal at a frequency corresponding to the voltage of the smoothed signal.

[0150] Frequency divider 170 divides the signal from VCO 169 and feeds the signal back to comparator 166.

[0151] With this structure, the phase synchronization unit 161 generates a frequency signal that is synchronized with the alternating current detected by the current sensing resistor 103.

[0152] The reference signal generation unit 162 generates a reference frequency signal and a quadrature frequency signal that are synchronized with the frequency signal from the phase synchronization unit 161.

[0153] Based on the above structure, even when the charging device 200 is superimposed with AC current, the reference frequency signal and quadrature frequency signal used by the measuring circuit 104a are synchronized with the superimposed AC current, thus enabling the measurement of complex impedance with high accuracy.

[0154] As described above, the energy storage system 1 of Embodiment 2 includes an energy storage device 100 and a charging device 200. The energy storage device 100 includes a battery pack 101, a complex impedance measuring unit 110, and a phase synchronization circuit 161. The phase synchronization circuit 161 generates a reference frequency signal that is synchronized with the alternating current superimposed on the charging current. The charging device 200 includes an alternating current superposition unit 148, a charging circuit 201, and a charging control unit. The complex impedance measuring unit 110 uses the reference frequency signal to measure the complex impedance.

[0155] Therefore, complex impedance can be measured with high precision.

[0156] (Implementation Method 3)

[0157] In this embodiment, similar to Embodiment 2, another example of the charging device 200 performing the superposition of alternating current for complex impedance measurement will be described. In Embodiment 2, an example was shown in which a phase synchronization unit 161, which synchronously detects the alternating current superimposed on the charging current, is used in the energy storage device 100 to generate a reference frequency signal synchronized with the alternating current. In contrast, in Embodiment 3, a structural example of generating a reference frequency signal based on alternating frequency information related to the frequency of the alternating current sent from the charging device 200 to the energy storage device 100 will be described.

[0158] [3.1 Structure of Energy Storage System 1]

[0159] Figure 13 This is a block diagram showing a structural example of the energy storage system 1 according to Embodiment 3. This diagram is different from the one shown in Embodiment 2. Figure 9 The main differences are: a communication clock generation unit 233 is added to the communication circuit 203; a communication clock regeneration unit 177 is added to the communication circuit 106; and a measurement circuit 104b is provided instead of the measurement circuit 104a. The following explanation focuses on these differences.

[0160] The communication circuit 203 receives information related to the complex impedance from the communication circuit 106 of the energy storage device 100, which is the same as in Embodiment 2. 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. Additionally, the communication line between the communication circuit 203 and the communication circuit 106 has a communication signal line but not a communication clock signal line.

[0161] The communication clock generation unit 233 generates a communication clock signal synchronized with the reference frequency signal generated by the clock circuit 205. The modulation unit 231 generates a communication signal obtained by modulating the communication data using the communication clock signal and sends it to the communication circuit 106.

[0162] The communication circuit 106 sends information related to the complex impedance to the charging device 200 in the same way as in embodiment 2. Furthermore, the communication circuit 106 receives AC frequency information from the communication circuit 203 as a communication signal.

[0163] The communication clock regeneration unit 177 regenerates a communication clock signal from the communication signal received by the communication circuit 106 and supplies this communication clock signal to the demodulation unit 176. The regenerated communication clock signal is called CCLK. The demodulation unit 176 uses the regenerated communication clock signal to demodulate the communication signal. The communication clock signal CCLK is also supplied to the measurement circuit 104b. The measurement circuit 104b uses a reference frequency signal synchronized with the communication clock signal CCLK.

[0164] Here, the AC frequency information is equivalent to the data timing of the communication signal and the edge timing of the communication clock signal. The AC frequency information, for example, as a normal communication signal or a specific communication signal, is transmitted continuously, at any time, or repeatedly during the charging period.

[0165] The measurement circuit 104b uses a reference frequency signal synchronized with the communication clock signal CCLK regenerated by the communication clock regeneration unit 177 to measure the complex voltage and complex current.

[0166] [3.2 Structure of Measurement Circuit 104b]

[0167] Next, the detailed structure of the measurement circuit 104b will be explained.

[0168] Figure 14 It means Figure 13 A detailed structural example of the measuring circuit 104b in the energy storage system 1 and a circuit diagram of the surrounding circuits. Figure 14 Compared with Implementation Method 2 Figure 10Compared to the measurement circuit 104a shown, the main differences are: the phase synchronization unit 161 is removed; and a reference signal generation unit 180 is provided instead of the reference signal generation unit 162. Hereinafter, the differences will be explained in detail.

[0169] The reference signal generation unit 180 generates a reference frequency signal synchronized with the regenerated communication clock signal CCLK. Therefore, the reference signal generation unit 180 includes a DDS 181 and a phase shifter 182. The DDS 181 and the phase shifter 182 may have the same structure as the DDS 163 and the phase shifter 164.

[0170] [3.3 Structure of Communication Circuits]

[0171] Next, the main structures related to the AC frequency information of the energy storage system 1 of this embodiment, which are equivalent to the data timing of the communication signal and the edge timing of the communication clock signal, will be described in more detail.

[0172] Figure 15 It is a more detailed expression Figure 13 A block diagram of the structure related to AC frequency information in the energy storage system 1.

[0173] Figure 15 The modulation unit 231 illustrates a structural example of performing BPSK (Binary Phase Shift Keying) modulation. Therefore, the modulation unit 231 includes a transmit data buffer 245, a bipolar converter 246, a DDS 247, and a BPSK modulator 248.

[0174] The transmit data buffer 245 is a buffer register that temporarily holds transmit data. In this figure, 100111 is exemplified as transmit data S1.

[0175] The bipolar converter 246 converts the 1 and 0 of the transmitted data into +1 and -1.

[0176] The DDS247 generates a sine wave signal and a cosine wave signal that are synchronized with the communication clock signal generated by the communication clock generation unit 233.

[0177] The BPSK modulator 248 has two multipliers and one adder. When the transmitted data after bipolar conversion is -1, the BPSK modulator 248 shifts the phase of the sine and cosine signals generated by the DDS 247 by 180 degrees (i.e., inverts them). When the transmitted data after bipolar conversion is +1, it does not invert the phase of the sine and cosine signals generated by the DDS 247. For each symbol of the transmitted data (in this example, one symbol is 1 bit), 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. Figure 16 It means Figure 15 The diagram shows the transmitted data S1 and the waveform example D1 after BPSK modulation. Furthermore, for ease of understanding, waveform example D1 only shows the non-inverted or inverted sine wave signal components.

[0178] Figure 15 The demodulation unit 176 includes a BPSK demodulator 185 and a receive data buffer 186.

[0179] The BPSK demodulator 185 demodulates communication data from communication signals.

[0180] The receive data buffer 186 temporarily holds the demodulated communication data.

[0181] The communication clock regeneration unit 177 has a PLL 187 and regenerates the communication clock signal from the communication signal.

[0182] The reference signal generation unit 180 generates a reference frequency signal and an orthogonal reference frequency signal that are synchronized with the regenerated communication clock signal.

[0183] Through this circuit, the energy storage device 100 generates a reference frequency signal synchronized with the AC current based on the AC frequency information sent from the charging device 200. The measurement circuit 104b uses the reference frequency signal synchronized with the AC current, thus enabling high-precision measurement of complex voltage and complex current.

[0184] As described above, the energy storage system 1 of Embodiment 3 includes an energy storage device 100 and a 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 sends information related to complex impedance to the charging device and receives AC frequency information related to the frequency of AC current; and a reference signal generation circuit that generates a reference frequency signal based on 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 sends AC frequency information. The complex impedance measuring unit 110 uses the reference frequency signal to measure the complex impedance.

[0185] Therefore, the measurement circuit 104b uses a reference frequency signal generated based on AC frequency information for measurement, thus enabling high-precision measurement of complex voltage and complex current.

[0186] Alternatively, the second communication circuit 203 may include: a communication clock generation unit 233 that generates a communication clock signal; and a modulation unit 231 that generates a communication signal obtained by modulating communication data using the communication clock signal. The first communication circuit 106 may include: a communication clock regeneration unit 177 that regenerates a communication clock signal based on the communication signal; and a demodulation unit 176 that demodulates the communication signal using the regenerated communication clock signal. An AC superposition circuit 204 generates an AC current synchronized with the communication clock signal. A reference signal generation unit 180 generates a reference frequency signal synchronized with the regenerated communication clock signal. A complex impedance measurement unit 110 uses the reference frequency signal to measure the complex impedance. The AC frequency information corresponds to the data timing of the communication signal and the edge timing of the communication clock signal.

[0187] Therefore, the timing of data that can be easily transmitted as communication signals is used as AC frequency information. Furthermore, the regeneration of the AC frequency information is equivalent to the edge moments of the communication clock signal.

[0188] Furthermore, while an example of a communication line connecting communication circuit 203 and communication circuit 106 in Embodiment 3 has a communication signal line but not a communication clock signal line, this is not an isolated case. The communication line may also have a structure that includes both a communication signal line and a communication clock signal line. In this case, the communication clock regeneration unit 177 is omitted.

[0189] Furthermore, to illustrate the case where a communication signal, which is AC frequency information, is sent from communication circuit 203 to communication circuit 106, a structural example is described where communication circuit 203 includes a communication clock generation unit 233 and communication circuit 106 includes a communication clock regeneration unit 177, but this is not a limitation. For bidirectional communication, communication circuit 203 and communication circuit 106 may each include a communication clock generation unit and a communication clock regeneration unit.

[0190] Furthermore, communication circuits 203 and 106 are not limited to wired connections, but can also be wirelessly connected.

[0191] (Application Example)

[0192] Next, specific application examples of the energy storage system 1 in embodiments 1 to 3 will be described.

[0193] First, the first application example of the energy storage system 1 will be explained.

[0194] Figure 17AThis is a schematic diagram illustrating a first application example of the energy storage system according to embodiments 1 to 3. Figure 17B It means Figure 17A The first application example is shown in the flowchart.

[0195] exist Figure 17A In this system, an energy storage device 100 is mounted on a two-wheeled vehicle and supplies power to the electric motor driving the vehicle. When charging the energy storage device 100, it is connected to the charging device 200 via a charging cable P1. Furthermore, the communication circuit 106 of the energy storage device 100 is wirelessly connected to the communication circuit 203 of the charging device 200. The communication circuit 206 of the charging device 200 is connected to a database 301 and a server device 302 via the Internet.

[0196] like Figure 17B As shown, for example, the energy storage device 100 wirelessly transmits the complex impedance of each energy storage cell and the external temperature to the charging device 200. The charging device 200 estimates the internal temperature of the battery pack 101 within the energy storage device 100 based on the complex impedance and external temperature, and determines the optimal charging current for fast charging based on the internal temperature. The charging device 200 accesses the server device 302 and sends complex impedance and charging information (e.g., State of Charge, SOC) to determine the internal temperature. The server device 302 diagnoses the degradation state of the battery pack 101. The charging device 200 obtains the complex impedance and degradation information (e.g., State of Health, SOH) corresponding to the charging information, and determines the optimal charging current based on the obtained degradation information.

[0197] In addition, the Internet connection of the charging device 200 can be wired or wireless.

[0198] Next, a second application example of the energy storage system 1 will be described.

[0199] Figure 18 This is a schematic diagram illustrating a second application example of the energy storage system 1 according to embodiments 1 to 3. This diagram is consistent with... Figure 17A In contrast, instead of the charging device 200, the energy storage device 100 accesses the database 301 and the server device 302 via the Internet.

[0200] In addition, the Internet connection of the energy storage device 100 can be wired or wireless.

[0201] Next, the third application example of the energy storage system 1 will be described.

[0202] Figure 19A This is a schematic diagram illustrating a third application example of the energy storage system according to embodiments 1 to 3. Figure 19B It means Figure 19A The flowchart of the third application example.

[0203] exist Figure 19A In this electric vehicle, an energy storage device 100 and a charging device 200 are mounted. The electric vehicle has a control device 400, which functions as an ECU (Electronic Control Unit). The control device 400 can communicate with a database 301 and a server device 302, and is connected to the energy storage device 100 and the charging device 200 via a communication line com. The energy 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 power from a charging station 500 via a charging cable P2. The communication line com can also be part of a wire harness.

[0204] like Figure 19B As shown, the energy storage device 100 transmits the complex impedance and external temperature of each energy storage unit to the control device 400 via the communication line com. The control device 400 estimates the internal temperature of the battery pack 101 within the energy storage device 100 based on the complex impedance and external temperature, and determines the optimal charging current for fast charging based on the internal temperature. The control device 400 may transmit the complex impedance and charging information (e.g., SOC) to the server device 302 to determine the internal temperature. The server device 302 diagnoses the degradation state of the battery pack 101. The control device 400 obtains degradation information (e.g., SOH) corresponding to the complex impedance and charging information from the server device 302, determines the optimal charging current based on the obtained degradation information, and notifies the charging device 200 of the determined optimal charging current.

[0205] In addition, Figure 19B In this case, the control device 400 estimates the internal temperature, but the energy storage device 100 or the charging device 200 can also estimate the internal temperature. In this case, the energy storage device 100 or the charging device 200 can connect to the control device 400 as a relay device, and connect to the database 301 and the server device 302.

[0206] Furthermore, examples of mounting the energy storage device 100 in a vehicle are shown in the first to third application examples, but the invention is not limited to these examples. For instance, the energy storage device 100 can also be applied to drones, uninterruptible power supplies, portable power supplies, etc.

[0207] Furthermore, in the above embodiments, each component can be constructed by dedicated hardware or implemented by executing software programs suitable for each component. Each component can also be implemented by a program execution unit such as a CPU or processor reading and executing software programs recorded on a recording medium such as a hard disk or semiconductor memory.

[0208] Furthermore, the energy storage system 1 of one or more technical solutions has been described based on the embodiments, but this disclosure is not limited to this embodiment. As long as it does not depart from the spirit of this disclosure, various modifications that can be conceived by those skilled in the art to this embodiment, and ways of constructing by combining structural elements of different embodiments, can also be included within the scope of one or more technical solutions.

[0209] Industrial applicability

[0210] This disclosure can be used in energy storage systems with secondary batteries, such as in electric vehicles.

[0211] Explanation of reference numerals in the attached figures

[0212] 1. Energy Storage System

[0213] 100 energy storage device

[0214] 101 Battery Pack

[0215] 102 Thermistor

[0216] 103 Current sensing resistor

[0217] Measurement circuits 104, 104a, and 104b

[0218] 105 First Control Department

[0219] Communication circuits 106, 107, 203, and 206

[0220] 110 Complex Impedance Measurement Section

[0221] 140 Clock Generation Unit

[0222] 141 Frequency Holding Section

[0223] 142 Reference Signal Generation Unit

[0224] 143, 163, 181, 188, 241, 247DDS

[0225] Phase shifters 144, 164, 182

[0226] 145 Voltage Measurement Section

[0227] 146 Current Measurement Section

[0228] 147 Temperature Measurement Department

[0229] 148, 204 AC Overlay Section

[0230] 149 Conversion Section

[0231] 150 points section

[0232] 151 Maintenance Department

[0233] 152 Temperature Holding Section

[0234] 153IO units

[0235] 161 Phase Synchronization Unit

[0236] 162 Reference Signal Generation Unit

[0237] 165 Hysteresis Circuit

[0238] 166 comparator

[0239] 167 Charge Pump

[0240] 168LPF

[0241] 169VCO

[0242] 170 frequency divider

[0243] 171ROM

[0244] 175 Modulation Section

[0245] 176 Mediation Department

[0246] 177 Communication Clock Regeneration Unit

[0247] 180 Reference Signal Generation Unit

[0248] 185BPSK Demodulator

[0249] 186 Receive Data Buffer

[0250] 187PLL

[0251] 200 charging device

[0252] 201 Charging Circuit

[0253] 202 Second Control Unit

[0254] 205 Clock Circuit

[0255] 210 Variable Current Source

[0256] 231 Modulation Unit

[0257] 232 De-mediation Department

[0258] 233 Communication Clock Generation Unit

[0259] 242 drive

[0260] 243 Transformer

[0261] 245 Transmit Data Buffer

[0262] 246 Bipolar Converter

[0263] 248BPSK modulator

[0264] 301 Database

[0265] 302 Server Device

[0266] 400 control device

[0267] 500 charging stations

[0268] B0~B5 energy storage units

[0269] com communication line

[0270] P1, P2 charging cables

Claims

1. An electrical storage system, wherein, have: An energy storage device having a battery pack comprising multiple energy storage units connected in series; A charging device comprising a charging circuit that supplies charging current to the battery pack; and An AC superposition circuit superimposes an AC current onto the charging current. The energy storage device has the following features: The complex impedance measuring unit measures the current value of the superimposed alternating current and the voltage value of each energy storage unit, and measures the complex impedance of each energy storage unit based on the measured current value and the measured voltage value. as well as The first communication circuit communicates with the charging device. The charging device has a charging control unit that controls the charging current based on at least one of the degradation state of each energy storage unit and the internal temperature, which is estimated from the complex impedance transmitted from the energy storage device to the charging device via the first communication circuit.

2. The energy storage system according to claim 1, wherein, The charging control unit estimates the internal temperature of each energy storage unit based on at least one of temperature characteristic data representing the correspondence between the internal temperature and complex impedance of the battery pack, and temperature distribution data representing the distribution of the external and internal temperatures of the battery pack.

3. The energy storage system according to claim 1, wherein, The charging control unit optimizes the charging current based on degradation information obtained from an external server device based on the complex impedance, which indicates the degree of degradation of each energy storage unit.

4. The energy storage system according to claim 1, wherein, The charging control unit determines the value of the charging current to shorten the charging time until the battery pack reaches a predetermined charging level.

5. The energy storage system according to claim 1, wherein, The charging control unit stops charging when the internal temperature reaches a threshold.

6. The energy storage system according to any one of claims 1 to 5, wherein, The energy storage device has the following features: The battery pack; The AC superposition circuit; The complex impedance measuring unit; and The first communication circuit, The charging device has: The charging circuit; The charging control unit; and The second communication circuit receives information related to the complex impedance from the energy storage device.

7. The energy storage system according to claim 6, wherein, The energy storage device includes a reference signal generation circuit that generates a reference frequency signal. The AC superposition circuit generates an AC current synchronized with the reference frequency signal. The complex impedance measurement unit uses the reference frequency signal to measure the complex impedance.

8. The energy storage system according to any one of claims 1 to 5, wherein, The energy storage device has the following features: The battery pack; The complex impedance measuring unit; as well as A phase synchronization circuit generates a reference frequency signal synchronized with the AC current superimposed on the charging current. The charging device has: The AC superposition circuit; The charging circuit; and The charging control unit The complex impedance measurement unit uses the reference frequency signal to measure the complex impedance.

9. The energy storage system according to any one of claims 1 to 5, wherein, The first communication circuit sends information related to the complex impedance of each energy storage unit to the charging device, and receives AC frequency information related to the frequency of the AC current. The energy storage device has the following features: The battery pack; The complex impedance measuring unit; The first communication circuit; and The reference signal generation circuit generates a reference frequency signal based on the AC frequency information. The charging device has: The AC superposition circuit; The charging circuit; The charging control unit; and The second communication circuit receives information related to the complex impedance from the energy storage device and transmits the AC frequency information. The complex impedance measurement unit uses the reference frequency signal to measure the complex impedance.

10. The energy storage system according to claim 9, wherein, The second communication circuit includes: The communication clock generation unit generates a communication clock signal; and The modulation unit generates a communication signal that modulates the communication data using the communication clock signal. The first communication circuit includes: The communication clock regeneration unit regenerates the communication clock signal from the communication signal; and The demodulation unit demodulates the communication signal using the regenerated communication clock signal. The AC superposition circuit generates the AC current synchronized with the communication clock signal. The reference signal generation circuit generates a reference frequency signal synchronized with the regenerated communication clock signal. The complex impedance measurement unit uses the reference frequency signal to measure the complex impedance of each energy storage unit. The AC frequency information is equivalent to the data timing of the communication signal and the edge timing of the communication clock signal.

11. A charging method for charging an energy storage device comprising a battery pack having multiple energy storage units connected in series, wherein, The charging current supplied to the battery pack is superimposed with the AC current. The energy storage device measures the current value of the superimposed alternating current and the voltage value of each energy storage unit. Using the energy storage device, the complex impedance of each energy storage unit is determined based on the measured current and voltage values. The complex impedance of each energy storage unit is transmitted from the energy storage device to the charging device via a communication circuit. The charging device controls the charging current based on at least one of the degradation state of each energy storage unit, which is estimated from the complex impedance of each energy storage unit, and the internal temperature.

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