Measuring device, measuring method, and measuring program

Abstract

SOLUTION: To provide a measuring device which comprises an inductor, a first switch for switching between serial connection and nonconnection of the inductor and a first battery cell included in a power storage device of a measuring object, a signal control part for generating induction current according to the inductor, by switching the first switch; and a measuring unit for measuring the voltage when induction current flows, in at least one out of the first battery cell and a second battery cell included in the power storage device.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a measurement device, a measurement method, and a measurement program. [Background technology]

[0002] Patent Document 1 describes an electrochemical system comprising: "a secondary battery including a plurality of electrodes and an electrolyte; a power controller that generates a rectangular wave signal of a first frequency that does not result in zero current and applies the signal continuously to the secondary battery; a Fourier transform unit that performs a Fourier transform on a response signal of the secondary battery to the rectangular wave signal to calculate frequency characteristics including components of a plurality of second frequencies that are integer multiples of the first frequency; and a calculation unit that calculates impedance characteristics of the secondary battery at the first frequency and the plurality of second frequencies based on the frequency characteristics calculated by the Fourier transform unit, and detects changes in characteristics of the secondary battery from the impedance characteristics" (Claim 1).

[0003] Patent Document 2 states, "The current modulation circuit 56 is a circuit that uses the battery cell 42 being monitored as a power source and outputs a predetermined AC signal (sine wave signal). Specifically, the current modulation circuit 56 has a semiconductor switch element 56a (e.g., MOSFET) as a switch section, and a resistor 56b connected in series to the semiconductor switch element 56a. The drain terminal of the semiconductor switch element 56a is connected to the positive terminal of the battery cell 42, and the source terminal of the semiconductor switch element 56a is connected in series to one end of the resistor 56b. The other end of the resistor 56b is connected to the negative terminal of the battery cell 42. The semiconductor switch element 56a is configured to be able to adjust the amount of current passing between the drain terminal and the source terminal" (paragraph 0028).

[0004] Non-Patent Document 1 describes (abstract) that an active battery balancer is required in a battery management system to extend battery life and maintain high system performance. Non-Patent Document 1 also describes (abstract) a multi-way bidirectional multi-port AC-coupled (MAC) battery balancer using a multi-active bridge (MAB) converter. Non-Patent Document 1 also describes (abstract) that the converter performs online diagnostics using built-in electrochemical impedance spectroscopy (EIS) in addition to active battery balancing. [Prior art document] [Patent documents] [Patent Document 1] Patent No. 6226261 [Patent Document 2] JP 2020-180949 A [Non-patent literature] [Non-Patent Document 1] Youssef Elasser et al., "A Multiway Bidirectional Multiport-Ac-Coupled (MAC) Battery Balancer with Online Electrochemical Impedance Spectroscopy," 2020 IEEE Applied Power Electronics Conference and Exposition (APEC), IEEE, March 15-19, 2020, pp. 1475-1480 Summary of the Invention

[0005] In a first aspect of the present invention, there is provided a measuring device comprising: a first inductor; a first switch that switches whether or not the first inductor is connected in series to a first battery cell included in a storage device to be measured; a signal control unit that generates an induced current in the first inductor by switching the first switch; and a measuring unit that measures a voltage when the induced current flows in at least one of the first battery cell or a second battery cell included in the storage device.

[0006] The above-mentioned measuring device may include a second switch that switches whether or not the first inductor is connected in series to a second battery cell included in the energy storage device to be measured, and the first inductor may have a first terminal provided on the negative electrode side of the first battery cell and the positive electrode side of the second battery cell, and a second terminal provided on the positive electrode side of the first battery cell and the negative electrode side of the second battery cell, and the signal control unit may cause the first inductor to generate the induced current by switching the first switch and the second switch.

[0007] In any of the above measurement devices, the measurement section may measure voltages when the induced current flows through each of the first battery cell and the second battery cell.

[0008] With respect to any of the above-mentioned measuring devices, within the energy storage device, the negative electrode of the first battery cell may be connected to the positive electrode of the second battery cell, and the first terminal of the first inductor may be connected between the negative electrode of the first battery cell and the positive electrode of the second battery cell.

[0009] In any of the above measurement devices, the signal control unit may switch the first switch and the second switch by pulse width modulation to generate an AC induced current in the first inductor.

[0010] In any of the above measurement devices, the measurement section may further measure the induced current.

[0011] In any of the above measurement devices, the signal control unit may adjust the duty ratio of the first switch and the second switch so that a central value of the amplitude of the induced current becomes zero.

[0012] In any of the above measurement devices, the signal control unit may switch the frequency of the AC induced current to each of a plurality of set frequencies, and the measurement unit may measure the voltage waveforms of the first battery cell and the second battery cell when the frequency of the AC induced current is set to each of the plurality of set frequencies.

[0013] In any of the measurement devices described above, the measurement section may change a sampling frequency for measuring the voltage of at least one of the first battery cell or the second battery cell, depending on the frequency of the AC of the induced current.

[0014] In any of the above measurement devices, the measurement unit may set the sampling frequency so that a predetermined number of periods, equal to or greater than one period, of the AC waveform of the induced current is included within a sampling period having a predetermined number of sampling points at the sampling frequency.

[0015] In any of the above measurement devices, the signal control unit may switch the first switch and the second switch at a switching frequency at which the frequency difference between the switching frequency at which the first switch and the second switch are switched and an integer multiple of the sampling frequency is 10% or more of the sampling frequency.

[0016] In any of the above measurement devices, the signal control unit may switch the first switch and the second switch at a switching frequency such that the frequency difference between an integer multiple of the switching frequency at which the first switch and the second switch are switched and the sampling frequency is 10% or more of the switching frequency.

[0017] Any of the above measurement devices may include a calculation unit that calculates impedance characteristics of the first battery cell and the second battery cell based on voltage waveforms and current waveforms of the first battery cell and the second battery cell.

[0018] Any of the above measurement devices may include an extraction unit that extracts frequency components of each set frequency from the voltage waveforms of the first battery cell and the second battery cell measured using the AC frequency of the induced current as each set frequency.

[0019] Any of the above measurement devices may include a first filter that suppresses voltage fluctuations of the first battery cell due to switching of the first switch and the second switch, and a second filter that suppresses voltage fluctuations of the second battery cell due to switching of the first switch and the second switch.

[0020] In any of the above measurement devices, the first switch and the second switch may be connected in series between the positive electrode of the first battery cell and the negative electrode of the second battery cell, the second terminal of the first inductor may be connected to a wiring between the first switch and the second switch, the first filter may have a first capacitor having one end connected to a wiring between the positive electrode of the first battery cell and the first switch and the other end connected between the negative electrode of the first battery cell and the first terminal of the first inductor, and the second filter may have a second capacitor having one end connected to a wiring between the negative electrode of the second battery cell and the second switch and the other end connected between the positive electrode of the second battery cell and the first terminal of the first inductor.

[0021] In any of the above measurement devices, the first filter may have a second inductor provided on a wiring between the positive electrode of the first battery cell and the first switch, at a position between the positive electrode of the first battery cell and the first capacitor, and the second filter may have a third inductor provided on a wiring between the negative electrode of the second battery cell and the second switch, at a position between the negative electrode of the second battery cell and the second capacitor.

[0022] In a second aspect of the present invention, there is provided a measurement method comprising: generating an induced current by the first inductor by switching a first switch that switches whether or not the first inductor is connected in series to a first battery cell included in a storage device to be measured; and measuring a voltage when the induced current flows in at least one of the first battery cell or a second battery cell included in the storage device.

[0023] In a third aspect of the present invention, there is provided a measurement program that, when executed by a computer, causes the computer to function as a signal control unit that generates an induced current by the first inductor by switching a first switch that switches whether or not the first inductor is connected in series to a first battery cell included in a storage device to be measured, and a measurement unit that measures the voltage when the induced current flows in at least one of the first battery cell or a second battery cell included in the storage device.

[0024] The above summary of the invention does not list all of the features of the present invention, and subcombinations of these features may also be inventions. [Brief explanation of the drawings]

[0025] [Figure 1] The configuration of a measuring device 100 according to this embodiment is shown together with a power storage device 10. [Figure 2] 1 illustrates the operating principle of the measurement device 100 according to this embodiment. [Figure 3] 2 shows an operation flow of the measurement device 100 according to the present embodiment. [Figure 4] 10 shows an example of a switch control signal output by the signal control unit 120 according to the present embodiment. [Figure 5] 1 shows an example of a voltage waveform and a current waveform measured by the measurement device 100 according to the present embodiment. [Figure 6] 1 shows an example of the amplitude of a voltage waveform and a current waveform at each of a plurality of set frequencies measured by the measurement device 100 according to this embodiment. [Figure 7] 1 shows an example of a Nyquist diagram of a battery cell 20 measured by the measuring device 100 according to the present embodiment. [Figure 8] 1 shows an example of an equivalent circuit of a battery used in the measuring device 100 according to this embodiment. [Figure 9] 1 shows an enlarged view of a voltage waveform and a current waveform measured by the measurement device 100 according to the present embodiment. [Figure 10] 1 shows a portion of a measurement device 100 according to a modified example of the present embodiment. [Figure 11] 10 shows a portion of a measurement device 100 according to another modified example of the present embodiment. [Figure 12] 10 shows a current waveform according to a comparative example. [Figure 13] 4 shows a current waveform according to an example. [Figure 14] 1 shows a voltage spectrum according to an embodiment. [Figure 15] 10 shows a current spectrum according to an example. [Figure 16] 10 shows an impedance locus according to a comparative example. [Figure 17] 1 shows an impedance locus according to an example. [Figure 18] 10 shows an operational flow relating to the determination of each frequency of the measurement device 100 according to yet another modified example of the present embodiment. [Figure 19] 10 shows an example of an alias of a switching frequency that occurs in the vicinity of a frequency component of a measurement frequency during measurement. [Figure 20] The actual measurement results of aliasing are shown below. [Figure 21] An example of a frequency setting that is affected by aliasing is shown below. [Figure 22] 22 illustrates an example computer 2200 in which aspects of the present invention may be embodied, in whole or in part. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0027] 1 shows the configuration of a measuring device 100 according to this embodiment, together with a power storage device 10. The power storage device 10 is used as a power source for an electrically powered machine or a device that operates using electricity. Examples of machines or devices incorporating such a power storage device 10 include electric vehicles (hybrid vehicles, electric automobiles), electric bicycles, electric motorcycles, manned or unmanned electric aircraft, industrial machinery such as electric forklifts, or auxiliary power supplies used with power generation devices of various scales.

[0028] The energy storage device 10 incorporates one or more battery cells 20. In the example shown in the figure, the energy storage device 10 includes a plurality of battery cells 20 connected in series between a positive terminal PP and a negative terminal PN of the energy storage device 10, with the positive terminal PP side being the positive electrode and the negative terminal PN side being the negative electrode. The energy storage device 10 may be configured with a plurality of sets of two or more battery cells 20 connected in series and connected in parallel, or a plurality of sets of two or more battery cells 20 connected in parallel and connected in series. The battery cells 20 may be secondary batteries capable of storing power by charging. The battery cell 20 may be a single individual secondary battery, or may be a group of secondary batteries including two or more individual secondary batteries that is a unit of measurement by the measuring device 100.

[0029] The measuring device 100 is connected to a power storage device 10 to be measured and measures electrical parameters of at least one battery cell 20 in the power storage device 10. In this embodiment, a case will be illustrated in which the measuring device 100 measures electrical parameters of adjacent first and second battery cells 20a and 20b among a plurality of battery cells 20 connected in series. In this case, in the power storage device 10, the negative electrode of the first battery cell 20a is connected to the positive electrode of the second battery cell 20b, and no other battery cells 20 are connected between the first and second battery cells 20a and 20b. In this embodiment, the measuring device 100 can measure the impedance of the first and second battery cells 20a and 20b by electrochemical impedance spectroscopy (EIS).

[0030] The measuring device 100 may be connected to the power storage device 10 during measurement or diagnosis of the power storage device 10, measure at least one battery cell 20 in the power storage device 10, and may be removed from the power storage device 10 after the measurement. Alternatively, the measuring device 100 may be incorporated together with the power storage device 10 in a machine or device to which the power storage device 10 is to supply power, and measure at least one battery cell 20 in the power storage device 10 at a desired timing, for example, periodically.

[0031] The measurement device 100 includes an inductor 110, a first switch SW1, a second switch SW2, a signal control unit 120, a measurement unit 130, an extraction unit 140, a calculation unit 150, and an output unit 160. The inductor 110 is an example of a "first inductor." The inductor 110 may be a standalone inductor that has an inductive component but is substantially free of resistive and capacitive components, or may be an inductive circuit that has an inductive component and at least one of resistive and capacitive components.

[0032] The inductor 110 has a first terminal LP1 and a second terminal LP2. The first terminal LP1 is provided on the negative electrode side of the first battery cell 20a and the positive electrode side of the second battery cell 20b. In the example shown in the figure, the first terminal LP1 is connected to a terminal MG of the measuring device 100, which is connected between the negative electrode of the first battery cell 20a and the positive electrode of the second battery cell 20b. The second terminal LP2 is provided on the positive electrode side of the first battery cell 20a and the negative electrode side of the second battery cell 20b. In the example shown in the figure, the second terminal LP2 is connected via a first switch SW1 to a terminal MP of the measuring device 100, which is connected to the positive electrode of the first battery cell 20a. The second terminal LP2 is also connected via a second switch SW2 to a terminal MN of the measuring device 100, which is connected to the negative electrode of the second battery cell 20b.

[0033] The first switch SW1 switches whether or not the inductor 110 is connected in series to the first battery cell 20a included in the power storage device 10 under measurement. In the example shown in the figure, the first switch SW1 is connected between a terminal MP of the measuring device 100 connected to the positive electrode of the first battery cell 20a and a second terminal LP2 of the inductor 110. As a result, when the first switch SW1 is in the on state, it forms a closed loop that runs from the positive electrode of the first battery cell 20a through the first switch SW1 and the inductor 110 to the negative electrode of the first battery cell 20a, and when it is in the off state, it cuts off this closed loop.

[0034] The second switch SW2 switches whether or not the inductor 110 is connected in series to the second battery cell 20b included in the power storage device 10 under measurement. In the example shown in the figure, the second switch SW2 is connected between a terminal MN of the measuring device 100 connected to the negative electrode of the second battery cell 20b and a second terminal LP2 of the inductor 110. As a result, when the second switch SW2 is in the on state, it forms a closed loop from the positive electrode of the second battery cell 20b through the inductor 110 and the second switch SW2 to the negative electrode of the second battery cell 20b, and when it is in the off state, it cuts off this closed loop.

[0035] The first switch SW1 and the second switch SW2 may be MOSFETs (metal oxide semiconductor field effect transistors), IGBTs (insulated gate bipolar transistors), or other semiconductor switch elements. Each semiconductor switch element has a first main terminal and a second main terminal, and a control terminal that controls the connection state between the first main terminal and the second main terminal. If the semiconductor switch element is a MOSFET, the semiconductor switch element has a drain and a source as the first main terminal and a gate as the control terminal. If the semiconductor switch element is an IGBT, the semiconductor switch element has a collector and an emitter as the first main terminal and a second main terminal, and a gate as the control terminal.

[0036] The signal control unit 120 is connected to the first switch SW1 and the second switch SW2 and controls the switching of the first switch SW1 and the second switch SW2. Specifically, the signal control unit 120 supplies a switch control signal for controlling the switching of the first switch SW1 to the control terminal of the first switch SW1. The signal control unit 120 also supplies a switch control signal for controlling the switching of the second switch SW2 to the control terminal of the second switch SW2.

[0037] The signal control unit 120 switches on and off the first switch SW1 and the second switch SW2, thereby generating an induced current in the inductor 110. For example, the signal control unit 120 turns on the first switch SW1 and turns off the second switch SW2, thereby forming a closed loop (also referred to as "closed loop 1") including the first battery cell 20a, the first switch SW1, and the inductor 110, and causing a current to flow from the positive electrode of the first battery cell 20a through the first switch SW1 and the inductor 110 to the negative electrode of the first battery cell 20a. Upon receiving this current, the inductor 110 causes an induced current to flow in a direction from the second terminal LP2 to the first terminal LP1.

[0038] For example, the signal control unit 120 turns off the first switch SW1 and turns on the second switch SW2 to form a closed loop (also referred to as "closed loop 2") including the second battery cell 20b, the inductor 110, and the second switch SW2. This causes a current to flow from the positive electrode of the second battery cell 20b through the inductor 110 and the second switch SW2 to the negative electrode of the second battery cell 20b. In response to this current, the inductor 110 causes an induced current to flow from the first terminal LP1 to the second terminal LP2. In this embodiment, the measuring device 100 may realize closed loop 1 and closed loop 2, which are closed circuits that do not involve a capacitor connected in series between the inductor 110 and the corresponding battery cell 20. Furthermore, the measuring device 100 may realize closed loop 1 and closed loop 2 that do not involve a resistor component connected in series between the inductor 110 and the corresponding battery cell 20, except for resistor components required in the measuring unit 130, in order to suppress attenuation of the induced current. Alternatively, the measurement device 100 may have a resistive component connected in series between the inductor 110 and the corresponding battery cell 20 to adjust the magnitude of the induced current.

[0039] The signal control unit 120 according to this embodiment switches on and off the first switch SW1 and the second switch SW2, thereby generating an AC induced current by the inductor 110. The signal control unit 120 changes the duty ratio of the on-time of the first switch SW1 and the second switch SW2 over time, thereby approximating the waveform of the induced current to a target AC waveform.

[0040] The signal control unit 120 may be connected to the measurement unit 130. The signal control unit 120 may adjust at least one of the on time and the off time of the first switch SW1 and the second switch SW2 according to the electrical parameter measured by the measurement unit 130.

[0041] The measurement unit 130 measures electrical parameters of at least one of the first battery cell 20a or the second battery cell 20b when an induced current flows. That is, the measurement device 100 according to this embodiment measures the electrical parameters of the battery cell 20 by using the induced current generated by the inductor 110 as a measurement signal (also referred to as an "AC signal") used to measure the characteristics of the battery cell 20. The measurement unit 130 according to this embodiment includes a current measurement device 132 and a voltage measurement device 134.

[0042] The current meter 132 measures the induced current generated by the inductor 110. The current meter 132 may be provided on either the first terminal LP1 side or the second terminal LP2 side of the inductor 110 in the closed circuit including the first battery cell 20a, the first switch SW1, and the inductor 110. In the example shown in the figure, the current meter 132 is provided on a wiring portion included in common with a closed loop 1 including the first battery cell 20a, the first switch SW1, and the inductor 110, and a closed loop 2 including the second battery cell 20b, the inductor 110, and the second switch SW2. This allows the current meter 132 to measure both the induced current flowing through closed loop 1 and the induced current flowing through closed loop 2. Alternatively, a current meter 132 may be provided separately for each of closed loops 1 and 2. For example, a first current meter may measure the current flowing through the first battery cell 20a, and a second current meter may measure the current flowing through the second battery cell 20b.

[0043] The voltage meter 134 measures the voltage of at least one of the first battery cell 20a or the second battery cell 20b when an induced current flows through it. In this embodiment, the voltage meter 134 measures the voltage of each of the first battery cell 20a and the second battery cell 20b when an induced current flows through them. In the example shown in the figure, the voltage meter 134 measures the voltage at a point between the first switch SW1 and the second switch SW2 (the point connected to the second terminal LP2 of the inductor 110) using a point between the negative electrode of the first battery cell 20a and the positive electrode of the second battery cell 20b as a reference. This allows the voltage meter 134 to measure the voltage of the first battery cell 20a when the first switch SW1 is on and the second switch SW2 is off, and to measure the voltage of the second battery cell 20a when the first switch SW1 is off and the second switch SW2 is on. Alternatively, the voltage meter 134 may be provided individually for each of the first battery cell 20a and the second battery cell 20b to measure the voltage of the corresponding battery cell 20, for example, the first voltage meter may measure the voltage of the first battery cell 20a, and the second voltage meter may measure the voltage of the second battery cell 20b.

[0044] The extracting unit 140 is connected to the measuring unit 130. The extracting unit 140 extracts a frequency component corresponding to the AC frequency of the induced current generated by the inductor 110 from the voltage waveform and current waveform, which are time waveforms of the voltage and current measured by the measuring unit 130. Note that the measuring device 100 may not include the extracting unit 140, or may include only a simplified extracting unit 140. For example, if the frequency component corresponding to the AC frequency of the induced current is sufficiently large in the voltage waveform and current waveform measured by the measuring unit 130, the measuring device 100 may not include the extracting unit 140. Furthermore, for example, the extracting unit 140 may remove at least one of high-frequency components including the switching frequencies of the first switch SW1 and the second switch SW2 and DC components from the voltage waveform and the current waveform, and supply the remaining frequency components to the calculating unit 150.

[0045] The calculation unit 150 is connected to the extraction unit 140. The calculation unit 150 calculates the impedance characteristics of the first battery cell 20a and the second battery cell 20b based on the voltage waveforms and current waveforms of the first battery cell 20a and the second battery cell 20b. In this embodiment, the calculation unit 150 calculates the impedance characteristics of the first battery cell 20a and the second battery cell 20b based on the voltage waveforms and current waveforms from which the extraction unit 140 has extracted frequency components corresponding to the AC frequency of the induced current.

[0046] The output unit 160 is connected to the calculation unit 150. The output unit 160 outputs the measurement results of the first battery cell 20a and the second battery cell 20b measured by the measurement device 100. In this embodiment, the output unit 160 outputs the impedance characteristics of the first battery cell 20a and the second battery cell 20b calculated by the calculation unit 150. The output unit 160 may output the voltage and current, or the voltage waveform and the current waveform, measured by the measurement unit 130. The output unit 160 may also output the frequency components corresponding to the AC frequency of the induced current in the voltage waveform and the current waveform extracted by the extraction unit 140. The output unit 160 may also output the impedance diagram of the first battery cell 20a and the second battery cell 20b generated by the calculation unit 150. The output unit 160 may also diagnose the quality of the state of the first battery cell 20a and the second battery cell 20b based on the measurement results and output the diagnosis result.

[0047] The output unit 160 may be connected to a display device. In this case, the output unit 160 may cause the display device to display the measurement results. The output unit 160 may output the measurement results to a control device of a machine or device in which the power storage device 10 is installed. In this case, the machine or device in which the power storage device 10 is installed can perform appropriate battery management in accordance with the measurement results.

[0048] At least some of the functions of the signal control unit 120, measurement unit 130, extraction unit 140, calculation unit 150, and output unit 160 in the measurement device 100 described above may be implemented by executing a measurement program on the same or different computers, such as personal computers (PCs), tablet computers, smartphones, workstations, server computers, or general-purpose computers, or may be implemented by a computer system in which multiple computers are connected. Such computer systems are also considered computers in a broad sense. Furthermore, these functions in the measurement device 100 may be implemented by one or more virtual computer environments executable within a computer. Alternatively, each of the signal control unit 120, measurement unit 130, extraction unit 140, calculation unit 150, and output unit 160 may be a dedicated computer designed for measuring or diagnosing battery cells 20, or may be dedicated hardware implemented using dedicated circuits.

[0049] 2 illustrates the operating principle of the measuring device 100 according to this embodiment. For ease of explanation, the positive direction of the induced current I is defined as the current flowing from the positive electrode of the first battery cell 20a through the first switch SW1 and the inductor 110 to the negative electrode of the first battery cell 20a when the first switch SW1 is on and the second switch SW2 is off, and the positive direction of the induced current I is defined as the current flowing from the positive electrode of the second battery cell 20b through the inductor 110 and the second switch SW2 to the negative electrode of the second battery cell 20b when the first switch SW1 is off and the second switch SW2 is on. That is, the positive direction of the induced current I is defined as the direction from the second terminal LP2 of the inductor 110 to the first terminal LP1 when the first switch SW1 is on and the second switch SW2 is off, and the positive direction of the induced current I is defined as the direction from the first terminal LP1 to the first terminal LP2 of the inductor 110 when the first switch SW1 is off and the second switch SW2 is on. As a result, in either closed loop, when the battery cell 20 is discharging, the induced current I has a positive value, and when the battery cell 20 is charging, the induced current I has a negative value.

[0050] In the first half cycle of the current waveform of the induced current I for one AC cycle shown in the center of the figure, the signal control unit 120 controls the switching of the first switch SW1 and the second switch SW2 so that the induced current flows in a direction from the second terminal LP2 to the first terminal LP1 of the inductor 110. Specifically, the signal control unit 120 alternately repeats State 1, in which the first switch SW1 is on and the second switch SW2 is off, and State 2, in which the first switch SW1 is off and the second switch SW2 is on. The signal control unit 120 switches the first switch SW1 and the second switch SW2 at a switching frequency higher than the AC frequency of the induced current.

[0051] In State 1, the current flowing back from the positive electrode of the first battery cell 20a through the first switch SW1 and the inductor 110 to the negative electrode of the first battery cell 20a increases. In State 2, the current flowing back from the positive electrode of the second battery cell 20a through the inductor 110 and the second switch SW2 to the negative electrode of the second battery cell 20b increases. During the first half cycle of the current waveform of the induced current I, the signal control unit 120 increases the proportion of time in State 1 compared to the proportion of time in State 2. As a result, the inductor 110 flows an induced current that flows, on average, from the second terminal LP2 to the first terminal LP1. The signal control unit 120 varies the proportion of time in State 1 and the proportion of time in State 2 over time, so that the magnitude of the induced current varies sinusoidally. Alternatively, the signal control unit 120 may vary the magnitude of the induced current to, for example, a rectangular wave or various other waveforms.

[0052] In State 1, when the inductor 110 passes an induced current I from the second LP2 to the first LP1, the induced current I flows clockwise through the closed loop 1, passing from the inductor 110 through the first battery cell 20a and the first switch SW1 to the inductor 110. In this state, the first battery cell 20a is discharging. In the graph in the center of the figure, the induced current I in the direction in which the first battery cell 20a is discharging is represented by a positive sine wave in the first half cycle of the current waveform of the induced current I.

[0053] In State 2, when the inductor 110 passes an induced current I from the second LP2 to the first LP1, the induced current I flows counterclockwise through the closed loop 2, passing from the inductor 110 through the second battery cell 20b and the second switch SW2 to the negative terminal of the inductor 110. In this state, the second battery cell 20b is charged. In the graph in the center of the figure, the induced current I in the direction in which the second battery cell 20b is charged is represented by a negative sine wave in the first half cycle of the current waveform of the induced current I.

[0054] In the latter half of one AC cycle of the current waveform of the induced current I shown in the center of the figure, the signal control unit 120 controls the switching of the first switch SW1 and the second switch SW2 so that the induced current flows in a direction from the first terminal LP1 to the second terminal LP2 of the inductor 110. Specifically, the signal control unit 120 alternately repeats State 3, in which the first switch SW1 is turned off and the second switch SW2 is turned on, and State 4, in which the first switch SW1 is turned on and the second switch SW2 is turned off. The signal control unit 120 switches the first switch SW1 and the second switch SW2 at a switching frequency higher than the AC frequency of the induced current.

[0055] In State 3, the current flowing back from the positive electrode of the second battery cell 20b through the inductor 110 and the second switch SW2 to the negative electrode of the second battery cell 20b increases, while in State 4, the current flowing back from the positive electrode of the first battery cell 20a through the first switch SW1 and the inductor 110 to the negative electrode of the first battery cell 20a increases. In the last half cycle of the current waveform of the induced current I, the signal control unit 120 makes the proportion of time in State 3 greater than the proportion of time in State 4. As a result, the inductor 110 flows an induced current that flows, on average, from the first terminal LP1 to the second terminal LP2. The signal control unit 120 changes the proportion of time in State 3 and the proportion of time in State 4 over time, so that the magnitude of the induced current varies sinusoidally.

[0056] In state 3, when the inductor 110 passes an induced current I from the first LP1 to the second LP2, the induced current I flows clockwise through the closed loop 2, passing from the inductor 110 through the second switch SW2 and the second battery cell 20b to the inductor 110. In this state, the second battery cell 20b is discharged. In the graph in the center of the figure, the induced current I in the direction in which the second battery cell 20b is discharged is represented by a positive sine wave in the latter half of the current waveform of the induced current I.

[0057] In State 4, when the inductor 110 passes an induced current I from the first LP1 to the second LP2, the induced current I flows counterclockwise through the closed loop 1, passing from the inductor 110 through the first switch SW1 and the second battery cell 20a to the inductor 110. In this state, the first battery cell 20a is charging. In the graph in the center of the figure, the induced current I in the direction in which the first battery cell 20a is charging is represented by a negative sine wave in the latter half of the current waveform of the induced current I.

[0058] As described above, the signal control unit 120 switches on and off the first switch SW1 and the second switch SW2, thereby applying an AC (sine wave in the illustrated example) induced current generated by the inductor 110 to each of the first battery cell 20a and the second battery cell 20b. This allows the measurement unit 130 to measure the voltage and current of each of the first battery cell 20a and the second battery cell 20b when an AC signal is applied to each of the first battery cell 20a and the second battery cell 20b.

[0059] The measuring device 100 described above generates an AC signal for measuring the state of the battery cells 20 in the energy storage device 10 using power from the battery cells 20, eliminating the need for power supply from an external power source to generate the AC signal itself. As shown in the figure, during the first half cycle of the current waveform of the induced current I, the induced current I generated by the discharge of the first battery cell 20a charges the second battery cell 20b, and during the second half cycle of the current waveform of the induced current I, the induced current I generated by the discharge of the second battery cell 20b charges the first battery cell 20a. Since this circuit generates an AC signal by exchanging charge between the two battery cells 20 in this way, theoretically, power consumption is zero. In reality, power loss occurs due to the parasitic resistance of the first switch SW1, the second switch SW2, and the inductor 110, wiring resistance, and internal resistance of the first battery cell 20a and the second battery cell 20b. However, this circuit can measure the state of the battery cells 20 with low power consumption. In addition, for the circuits outside the closed loop for measuring the state of the battery cells 20, such as the signal control unit 120, the extraction unit 140, the calculation unit 150, and the output unit 160, either a configuration in which the battery cells 20 in the energy storage device 10 are used as the power source or a configuration in which power is supplied from an external power source can be adopted.

[0060] 3 shows the operation flow of the measuring device 100 according to this embodiment. In the process from S300 (step 300) to S350 of this operation flow, the signal control unit 120 switches the AC frequency F of the induced current to each of a plurality of set frequencies Fi (i = 1, 2, ... N, where N is a positive integer). The measurement unit 130 measures the voltage waveforms and current waveforms of the first battery cell 20a and the second battery cell 20b when the AC frequency F of the induced current is set to each of the plurality of set frequencies Fi. Then, the extraction unit 140 extracts the frequency components of each set frequency from the voltage waveforms of the first battery cell 20a and the second battery cell 20b measured using the AC frequency of the induced current as each set frequency.

[0061] Specifically, S300 and S350 are the beginning and end of the repetition for each set frequency F. Measurement apparatus 100 repeats the processes from S310 to S340 N times from i=1 to i=N.

[0062] In S310, the signal control unit 120 sets the measurement frequency F (the AC frequency F of the induced current) to the i-th set frequency Fi. In S320, the signal control unit 120 switches on and off the first switch SW1 and the second switch SW2, causing the inductor 110 to generate an AC induced current of the measurement frequency F (see the center graph in FIG. 2).

[0063] In S330, the measurement unit 130 measures the voltage and current of the first battery cell 20a and the second battery cell 20b while the inductor 110 is generating an AC induced current. Note that in this operation flow, S330 is shown as the next step after S320, but the generation of an AC induced current by the inductor 110 at each timing and the measurement of the voltage and current by the measurement unit 130 at each timing are performed in parallel.

[0064] Here, the measurement unit 130 may continuously measure the voltage and current of the first battery cell 20a and the second battery cell 20b to obtain continuous voltage and current waveforms. Alternatively, the measurement unit 130 may discretely measure the voltage and current of the first battery cell 20a and the second battery cell 20b to obtain discrete voltage and current waveforms.

[0065] When acquiring the discrete waveforms, the measurement unit 130 acquires the voltage waveform and current waveform of the first battery cell 20a, including the voltage and current measured at the timing when the first battery cell 20a passes an induced current, i.e., the timing when the first switch SW1 is turned on and the second switch SW2 is turned off. For example, the measurement unit 130 may sample the voltage and current one or more times per switching period during the period when the first switch SW1 is turned on and the second switch SW2 is turned off.

[0066] Similarly, the measurement unit 130 acquires the voltage waveform and current waveform of the second battery cell 20b, including the voltage and current measured at the timing when the second battery cell 20b passes an induced current, i.e., the timing when the first switch SW1 is off and the second switch SW2 is on. For example, the measurement unit 130 may sample the voltage and current one or more times per switching period during the period when the first switch SW1 is off and the second switch SW2 is on.

[0067] The measurement unit 130 may measure the current flowing through the inductor 110 and the voltage at the second terminal LP2 of the inductor 110 at every predetermined sampling period, outputting the voltage and current measured when the first switch SW1 is on and the second switch SW2 is off as the voltage and current of the first battery cell 20a, and outputting the voltage and current measured when the first switch SW1 is off and the second switch SW2 is on as the voltage and current of the second battery cell 20b. Such a sampling period may be the same as the switching period of the first switch SW1 and the second switch SW2, may be shorter than the switching period, or may be longer than the switching period and equal to or shorter than half the AC period.

[0068] In S340, the extraction unit 140 extracts frequency components of the measurement frequency F from the voltage waveforms and current waveforms of the first battery cell 20a and the second battery cell 20b. As an example, the extraction unit 140 may convert a target waveform in the time domain, such as a voltage waveform or a current waveform, into a waveform in the frequency domain by performing a Fourier transform. The extraction unit 140 may extract the frequency component of the measurement frequency F from the target waveform by extracting the amplitude and phase of a frequency corresponding to the measurement frequency F from the waveform in the frequency domain, i.e., the amplitude spectrum and phase spectrum.

[0069] As another example, the extraction section 140 may input the target waveform to a bandpass filter that extracts and outputs only the frequency component of the measurement frequency F or a frequency component in a predetermined frequency range including the measurement frequency F from the input signal, and extracts the frequency component of the measurement frequency F from the target waveform or a frequency component in the vicinity of the measurement frequency F. Here, the frequency range that the extraction section 140 bandpass filters may be determined appropriately depending on the accuracy required of the measurement device 100, etc.

[0070] In S350, the calculation unit 150 calculates the impedance characteristics of the first battery cell 20a and the second battery cell 20b based on the voltage waveforms and current waveforms of the first battery cell 20a and the second battery cell 20b at each of a plurality of set frequencies. In S360, the output unit 160 outputs the impedance characteristics of the first battery cell 20a and the second battery cell 20b calculated by the calculation unit 150.

[0071] FIG. 4 shows an example of a switch control signal output by the signal control unit 120 according to this embodiment. In S320 of FIG. 3, the signal control unit 120 outputs switch control signals for the first switch SW1 and the second switch SW2 to the corresponding switches, thereby causing the first switch SW1 and the second switch SW2 to perform switching. Here, the signal control unit 120 switches the first switch SW1 and the second switch SW2 at a switching frequency higher than the frequency of the AC induced current generated by the inductor 110. As an example, the measurement apparatus 100 may set the frequency of the AC induced current to a range of several mHz to several kHz, or may set the frequency to a range of several Hz to several kHz (e.g., 10 Hz to 1 kHz). The measurement apparatus 100 may set the switching frequency to several times that frequency or higher (e.g., 10 kHz or higher).

[0072] The signal control unit 120 alternately turns on the first switch SW1 and the second switch SW2. If the first switch SW1 and the second switch SW2 were turned on simultaneously, the first battery cell 20a and the second battery cell 20b, which are connected in series, would be shorted out. Therefore, the signal control unit 120 prevents the on periods of the first switch SW1 and the second switch SW2 from overlapping. Conversely, if the period during which the first switch SW1 and the second switch SW2 are simultaneously off becomes long, the induced current generated in the inductor 110 will attenuate significantly. Therefore, the signal control unit 120 may minimize the period during which the first switch SW1 and the second switch SW2 are simultaneously off.

[0073] Therefore, ideally, the signal control unit 120 switches the first switch SW1 and the second switch SW2 so that the on periods of the first switch SW1 and the second switch SW2 do not overlap and one of the switches is always on. However, in reality, since an error may occur in the switching timing, the signal control unit 120 may provide a small dead time during the on periods of the first switch SW1 and the second switch SW2, during which both the first switch SW1 and the second switch SW2 are turned off.

[0074] The signal control unit 120 may switch the first switch SW1 and the second switch SW2 by pulse width modulation to generate an AC induced current in the inductor 110. As shown in the figure, the switching period is T S , the length of the ON period of the first switch SW1 within one switching cycle is T SW1 Then, the duty ratio of the first switch SW1 in the on state is T SW1 / T S , the duty ratio of the second switch SW2 in the on state is (T S -T SW1 ) / T S This becomes:

[0075] The signal control unit 120 determines the time duration T during each switching period during which the first switch SW1 is on. SW1and the time width (T S -T SW1 ), thereby adjusting the duty ratio at which the first switch SW1 and the second switch SW2 are turned on, and thereby adjusting the magnitude of the induced current. As an example, by using a triangular wave / sine wave comparison method, the signal control unit 120 may generate, for each switching period, a first switch control signal having a pulse width corresponding to a current value corresponding to the switching period in a sine waveform corresponding to the AC induced current to be generated by the inductor 110, and output the first switch control signal to the first switch SW1, and output a second switch control signal obtained by inverting the first switch control signal to the second switch SW2. Furthermore, the signal control unit 120 may adjust the switching duty ratio in each switching period so that the magnitude of the induced current measured by the current measuring device 132 in the measuring unit 130 approaches a target current value of the target AC induced current at that timing.

[0076] The signal control unit 120 may vary the duty ratio at which each switch is turned on from 0% to 100%. Alternatively, the signal control unit 120 may vary the duty ratio within a limited range greater than 0% and less than 100%. As an example, the signal control unit 120 may vary the duty ratio within a range from 20% to 80% (maximum modulation rate of 80%). For example, the signal control unit 120 may control the duty ratio so that the maximum modulation rate is between 80% and less than 100%, or may control the duty ratio so that the maximum modulation rate is between 90% and less than 100%.

[0077] FIG. 5 shows an example of a voltage waveform and a current waveform measured by the measuring device 100 according to this embodiment (see also S330 in FIG. 3). In this figure, the horizontal axis represents time [μs], and the vertical axis represents current [mA] and voltage [V]. This figure shows the results of simulating the current waveform and current waveform of a battery cell 20 (e.g., the first battery cell 20a) when the AC period of the induced current is 1 kHz and the switching period is 100 kHz. For ease of explanation, this figure shows the current waveform and voltage waveform of the battery cell 20 in the simulation results, rather than the current and voltage measured directly by the current measuring device 132 and the voltage measuring device 134. The measurement unit 130 may acquire discrete waveforms of the current and voltage of each battery cell by outputting the current and voltage measured during the period when the first switch SW1 is on and the second switch SW2 is off as the current and voltage of the first battery cell 20a, and outputting the current and voltage measured during the period when the first switch SW1 is off and the second switch SW2 is on as the current and voltage of the second battery cell 20b.

[0078] As shown in the figure, the measuring device 100 generates an AC induced current using an inductor 110 and supplies it to a battery cell 20. In response to the AC induced current, the battery cell 20 generates a voltage having an amplitude and phase difference with respect to the induced current that depends on the characteristics and state of the battery cell 20.

[0079] The signal control unit 120 may adjust the duty ratio at which the first switch SW1 and the second switch SW2 are turned on so that the center value of the amplitude of the AC induced current is 0. In this way, the signal control unit 120 can, in principle, prevent the charge rate of the battery cell 20 being measured from changing, and can minimize loss of the charge amount of the battery cell 20 due to the measurement.

[0080] FIG. 6 shows an example of the amplitude of the voltage waveform and the current waveform at each of a plurality of set frequencies measured by the measuring device 100 according to this embodiment (see also S340 in FIG. 3). In this embodiment, the extraction unit 140 performs a Fourier transform on the voltage waveform and the current waveform of the battery cell 20 measured when each of the plurality of set frequencies is used as the measurement frequency. The upper graph in this figure shows the amplitude spectrum obtained by Fourier transforming the voltage waveform at each measurement frequency. In the upper graph in this figure, the horizontal axis is frequency [Hz], and the vertical axis is voltage amplitude [mV] at each frequency. The lower graph in this figure shows the amplitude spectrum obtained by Fourier transforming the current waveform at each measurement frequency. In the lower graph in this figure, the horizontal axis is frequency [Hz], and the vertical axis is current amplitude [mV] at each frequency.

[0081] When the extraction unit 140 performs a Fourier transform on the current waveform and voltage waveform when the AC frequency of the induced current is set to 1 kHz as shown in Fig. 5, it can obtain a Fourier spectrum including an amplitude spectrum having a peak at a frequency component corresponding to 1 kHz, as shown by the solid line in Fig. 6. Similarly, when the extraction unit 140 performs a Fourier transform on the current waveform and voltage waveform when the AC frequency of the induced current is set to other values ​​(10 values ​​less than 1 kHz in the example of this figure), it can obtain a Fourier spectrum including an amplitude spectrum having a peak at a frequency component corresponding to each AC frequency, as shown by the dashed line in Fig. 6. Note that this figure is created for the purpose of explanation, and the solid line in Fig. 6 does not represent a plot of the amplitude spectrum obtained by Fourier transforming the current waveform and voltage waveform of Fig. 5.

[0082] Furthermore, the Fourier spectrum may include phase information in addition to amplitude information, and the extraction unit 140 can obtain a Fourier spectrum including a phase spectrum. The extraction unit 140 obtains frequency components corresponding to each set frequency from the amplitude spectrum and phase spectrum when the AC frequency of the induced current is set to that set frequency, thereby extracting the frequency components (amplitude and phase in the example shown in the figure) of each set frequency from the voltage waveform and current waveform measured with the AC frequency of the induced current set to that set frequency. The amplitude and phase thus obtained represent the amplitude and phase of the sine wave of the corresponding set frequency in the voltage waveform and current waveform. Therefore, it can be considered that the extraction unit 140 extracts the sine wave waveforms of the voltage and current at the corresponding set frequency from the measured voltage waveform and current waveform through the above process.

[0083] Note that noise caused by the switching of the first switch SW1 and the second switch SW2 during measurement of the battery cell 20 appears in the amplitude spectrum as harmonics higher than the switching frequency, as shown in the figure. Therefore, the extraction unit 140 can remove noise caused by the switching of the first switch SW1 and the second switch SW2 by extracting frequency components corresponding to each set frequency from the amplitude spectrum and the phase spectrum.

[0084] FIG. 7 shows an example of a Nyquist diagram of a battery cell 20 measured by the measuring device 100 according to this embodiment. The Nyquist diagram in this figure plots the electrochemical impedance of the battery cell 20 when the AC frequency of the induced current is set to each set frequency. Here, the electrochemical impedance at each set frequency is a complex impedance having a voltage amplitude / current amplitude magnitude and a phase difference between the voltage and current. This figure plots such electrochemical impedance on a graph where the horizontal axis represents the magnitude of the real part and the vertical axis represents the magnitude of the imaginary part. Here, in this figure, the phase difference between the voltage and current is represented by a counterclockwise angle on the graph representing the phase delay of the voltage relative to the current as a complex number. In the figure, each black circle corresponds to the electrochemical impedance at each set frequency (11 in this figure).

[0085] 8 shows an example of an equivalent circuit of a battery used in the measuring device 100 according to this embodiment. The equivalent circuit in this figure models a battery cell 20 with a structure in which an internal resistance Rs is connected in series with a parallel connection of an internal resistance Rp and an internal capacitance Cp. The real part Re and imaginary part Im of the electrochemical impedance in such an equivalent circuit are expressed by the equations shown in FIG.

[0086] The calculation unit 150 can calculate the impedance characteristics of the battery cell 20 by calculating the internal parameters (internal resistance Rs, internal resistance Rp, and internal capacitance Cp in the example of this figure) of the equivalent circuit such that the electrochemical impedance of the equivalent circuit at each set frequency is closest to the measurement results of the electrochemical impedance of the battery cell 20 at each set frequency (see S350 in FIG. 3). The dashed line in FIG. 7 indicates the impedance diagram of the equivalent circuit calculated in this manner. The number of set frequencies used for measurement may be determined so that the internal parameters are uniquely determined from the measurement results of the electrochemical impedance of the battery cell 20 at each set frequency. For example, since the equivalent circuit in this figure has three internal parameters, the number of set frequencies used for measurement may be three or more. The measurement device 100 may model the battery cell 20 using an equivalent circuit different from that shown in this figure.

[0087] The measuring device 100 described above can change the switching duty ratio of the first switch SW1 and the second switch SW2 to generate induced currents having respective set frequencies using the inductor 110 and supply them to the battery cell 20 under measurement. The measuring device 100 can measure multiple battery cells 20 using a single inductor 110 by alternately supplying the induced current generated by the inductor 110 to the negative electrode of the first battery cell 20a and the positive electrode of the second battery cell 20b, which are connected to the first terminal LP1 of the inductor 110, depending on the switching state. Furthermore, in the measuring device 100, the induced current flowing in a direction discharging from one of the first battery cell 20a and the second battery cell 20b flows in a direction charging the other battery cell 20, thereby reducing power consumption of the battery cells 20 during measurement.

[0088] The measuring device 100 described above calculates each internal parameter of the equivalent circuit of the battery cell 20 from the voltage waveform and current waveform of the battery cell 20 at each set frequency. Alternatively, the measuring device 100 can have various configurations depending on the target measurement content, etc.

[0089] For example, when the voltage waveform and current waveform of the battery cell 20 are directly output, the measuring device 100 does not need to include the extracting unit 140 and the calculating unit 150. Furthermore, when the measuring device 100 does not calculate the impedance characteristics of the battery cell 20, the measuring device 100 does not need to include the calculating unit 150. In this case, the signal control unit 120 may measure the voltage waveform and current waveform of the battery cell 20 using only one set frequency as the measurement frequency.

[0090] When the measuring device 100 is used to determine the quality of the battery cell 20, the measuring device 100 may be simplified depending on the required accuracy of the quality determination. For example, the measuring unit 130 may not include the current measuring device 132, and the measuring device 100 or an external circuit may determine the quality of the battery cell 20 based on whether the voltage measured by the voltage measuring device 134 is within a predetermined range. Furthermore, instead of switching the first switch SW1 and the second switch SW2 so as to generate an AC induced current in the inductor 110, the signal control unit 120 may switch the first switch SW1 and the second switch SW2 so as to generate one or more induced currents of predetermined magnitudes in the inductor 110. The measuring device 100 or an external circuit may determine the quality of the battery cell 20 based on whether the voltage of the battery cell 20 when an induced current of a predetermined current value flows is within a predetermined range. In this case, the signal control unit 120 may control the switching of the first switch SW1 and the second switch SW2 so as to make the induced current of the inductor 110 approach a predetermined current value over a plurality of switching periods.

[0091] The connection topology of one or more battery cells 20, the inductor 110, the first switch SW1, and the second switch SW2 may be different from the above connection topology. For example, the first battery cell 20a and the second battery cell 20b may not be adjacent to each other. In this case, the measuring device 100 may include a third switch SW3 that switches whether the first terminal LP1 of the inductor 110 is connected to the negative electrode of the first battery cell 20a, and a fourth switch SW4 that switches whether the first terminal LP1 of the inductor 110 is connected to the positive electrode of the second battery cell 20b. The signal control unit 120 may turn on and off the third switch SW3 at the same timing as the first switch SW1, and may turn on and off the fourth switch SW4 at the same timing as the second switch SW2.

[0092] In this embodiment, the measuring device 100 measures both the first battery cell 20a and the second battery cell 20b using the inductor 110. Alternatively, the measuring device 100 may measure only one of the first battery cell 20a or the second battery cell 20b. For example, the measuring device 100 may use both the first battery cell 20a and the second battery cell 20b to generate an AC induced current by the inductor 110, and measure only one of the first battery cell 20a or the second battery cell 20b. Alternatively, the measuring device 100 may use either the first battery cell 20a or the second battery cell 20b to generate an induced current by the inductor 110, and measure only one or the other of the first battery cell 20a or the second battery cell 20b. For example, the signal control unit 120 may generate an induced current by the inductor 110 by switching either the first switch SW1 or the second switch SW2, and the measurement unit 130 may measure the voltage, etc., when the induced current flows in at least one of the first battery cell 20a or the second battery cell 20b.

[0093] 9 shows an enlarged view of the voltage waveforms and current waveforms measured by the measurement apparatus 100 according to this embodiment. This view is a graph showing an enlarged portion of the simulation results of the current waveforms and voltage waveforms shown in FIG. 5. In the example shown in this view, at the timing of switching the first switch SW1 and the second switch SW2, a short-circuit current flows through the first switch SW1 and the second switch SW2 due to the body diodes.

[0094] FIG. 10 shows a portion of a measuring device 100 according to a modification of this embodiment. To reduce the influence of the short-circuit current as shown in FIG. 9, the measuring device 100 according to this modification includes a first capacitor 1000a connected in parallel with the first battery cell 20a and a second capacitor 1000b connected in parallel with the second battery cell 20b in a circuit including a first switch SW1, a second switch SW2, and an inductor 110. The first capacitor 1000a is connected in parallel with the first battery cell 20a via the first switch SW1 between the first terminal LP1 and the second terminal LP2 of the inductor 110. The second capacitor 1000b is connected in parallel with the second battery cell 20b via the second switch SW2 between the first terminal LP1 and the second terminal LP2 of the inductor 110. The measuring device 100 may include only one of the first capacitor 1000a and the second capacitor 1000b.

[0095] Each of the first capacitor 1000a and the second capacitor 1000b functions as a bypass capacitor for the corresponding one of the first battery cell 20a and the second battery cell 20b. Each of the first capacitor 1000a and the second capacitor 1000b functions as a low-pass LC filter together with the inductor 110. As a result, the measuring device 100 according to this modification can reduce instantaneous fluctuations in current and voltage of the battery cell 20 due to short-circuit currents and the like that occur in high-frequency bands such as switching frequencies, as shown in FIG. 9, thereby improving measurement accuracy.

[0096] Fig. 11 shows a part of a measurement device 100 according to another modification of this embodiment. Since the measurement device 100 according to this modification is a modification of the measurement device 100 in Fig. 1 and the measurement device 100 in Fig. 10, like components are denoted by like reference numerals and descriptions thereof will be omitted.

[0097] The measurement apparatus 100 according to this modification further includes filters 1110a-b in a circuit including the first switch SW1 and second switch SW2 and the inductor 110 in the measurement apparatus 100 of Fig. 1. The measurement apparatus 100 according to this modification also has a configuration in which the capacitors 1000a-b in the measurement apparatus 100 of Fig. 10 are replaced with filters 1110a-b including the capacitors 1000a-b.

[0098] The circuit portion (the circuit portion shown in FIG. 11) that includes the battery cells 20a-b, the first switch SW1 and the second switch SW2, the inductor 110, and the filters 1110a-b and through which a current is circulated and the current and voltage are measured is also referred to as the "circuit under measurement in FIG. 11." Similarly, the circuit portion (the circuit portion corresponding to the circuit portion shown in FIG. 11) that includes the battery cells 20a-b, the first switch SW1 and the second switch SW2, and the inductor 110 in FIG. 1 and through which a current is circulated and the current and voltage are measured is also referred to as the "circuit under measurement in FIG. 1." The circuit portion shown in FIG. 10 is also referred to as the "circuit under measurement in FIG. 10."

[0099] In the measuring device 100 of this modified example, the first switch SW1 and the second switch SW2 are also connected in series between the positive electrode side of the first battery cell 20a and the negative electrode side of the second battery cell 20b, the first terminal LP1 of the first inductor is connected to the terminal MG of the measuring device 100 which is connected to the wiring between the negative electrode of the first battery cell 20a and the positive electrode of the second battery cell 20b, and the second terminal LP2 of the first inductor is connected to the wiring between the first switch SW1 and the second switch SW2.

[0100] The first filter 1110a is connected between a terminal MP of the measuring device 100 connected to the positive electrode of the battery cell 20a and a terminal MG of the measuring device 100 connected to the negative electrode of the battery cell 20a. The first filter 1110a suppresses voltage fluctuations of the first battery cell 20a caused by switching of the first switch SW1 and the second switch SW2. The first filter 1110a may also suppress current fluctuations of the first battery cell 20a caused by switching of the first switch SW1 and the second switch SW2.

[0101] The first filter 1110a shown in this figure is an LC filter and includes a capacitor 1000a and an inductor 1120a.

[0102] One end of the first capacitor 1000a is connected to the wiring between the positive electrode (or terminal MP) of the first battery cell 20a and the first switch SW1, and the other end is connected between the negative electrode (or terminal MG) of the first battery cell 20a and the first terminal LP1 of the inductor 110. As a result, the first battery cell 20a and the first capacitor 1000a are connected in parallel when viewed from the first switch SW1 and the inductor 110.

[0103] The inductor 1120a is an example of a “second inductor.” The inductor 1120a is provided on the wiring between the positive electrode of the first battery cell 20a (or the terminal MP) and the first switch SW1, at a position between the positive electrode of the first battery cell 20a and the first capacitor 1000a.

[0104] With this configuration, the first filter 1110a functions as an LC low-pass filter when viewed from the first battery cell 20a. Alternatively, the first filter 1110a may function as an RC low-pass filter when viewed from the first battery cell 20a.

[0105] The second filter 1110b is connected between a terminal MG of the measuring device 100 connected to the positive electrode of the battery cell 20b and a terminal MN of the measuring device 100 connected to the negative electrode of the battery cell 20b. The second filter 1110b suppresses voltage fluctuations in the second battery cell 20b caused by switching of the first switch SW1 and the second switch SW2. The second filter 1110b may also suppress current fluctuations in the second battery cell 20b caused by switching of the first switch SW1 and the second switch SW2.

[0106] The second filter 1110b shown in this figure is an LC filter and includes a capacitor 1000b and an inductor 1120b.

[0107] One end of the second capacitor 1000b is connected to the wiring between the negative electrode (or terminal MN) of the second battery cell 20b and the second switch SW2, and the other end is connected between the positive electrode (or terminal MG) of the second battery cell 20b and the first terminal LP1 of the inductor 110. As a result, the second battery cell 20b and the second capacitor 1000b are connected in parallel when viewed from the second switch SW2 and the inductor 110.

[0108] The inductor 1120b is an example of a “third inductor.” The inductor 1120b is provided on the wiring between the negative electrode of the second battery cell 20b (or the terminal MN) and the second switch SW2, at a position between the negative electrode of the second battery cell 20b and the second capacitor 1000b.

[0109] With this configuration, the second filter 1110b functions as an LC low-pass filter when viewed from the second battery cell 20b. Alternatively, the second filter 1110b may function as an RC low-pass filter when viewed from the second battery cell 20b.

[0110] FIG. 12 shows a current waveform according to a comparative example. The current waveform in FIG. 12 is a measured value of a current flowing through one battery cell 20 in a configuration that does not include filters 1110a-b in the circuit under test in FIG. 11 (a configuration that corresponds to the circuit under test in FIG. 1; also referred to as a "comparative example"). In contrast, FIG. 13 shows a current waveform according to an example. The current waveform in FIG. 13 is a measured value of a current flowing through one battery cell 20 in the circuit under test in FIG. 11 (a configuration that includes filters 1110a-b; also referred to as an "example").

[0111] In measuring the current values ​​in Figures 12 and 13, the DC voltage of the battery cells 20a-b was 3.7V, the inductance of the inductor 110 was 90µH, the inductance of the inductors 1120a-b was 105µH, and the capacitance of the capacitors 1000a-b was 22µF. In measuring the current values ​​in Figures 12 and 13, the switching frequency was 52kHz and the modulation rate was 85.4%. The measurement frequency (the AC frequency of the induced current) was in the range of 1kHz to 10Hz. In the current waveforms in Figures 12 and 13, the measurement frequency was 10Hz.

[0112] In a configuration without filters 1110a-b, a sinusoidal current change according to the measurement frequency is observed, as shown in Fig. 12, but the current waveform at the measurement frequency is distorted due to harmonic noise generated by the switching of the first switch SW1 and the second switch SW2. In contrast, in a configuration with filters 1110a-b, as shown in Fig. 13, the harmonic noise generated by the switching of the first switch SW1 and the second switch SW2 can be removed, making it possible to obtain a sinusoidal current waveform at the measurement frequency with less noise.

[0113] The principle of harmonic noise suppression in a configuration including the filters 1110a-b is as follows. First, as shown in FIG. 11 , when the first switch SW1 is turned on and the second switch SW2 is turned off, the current flowing through the inductor 110 circulates to the inductor 110 via the first battery cell 20a, inductor 1120a, and first switch SW1. Next, when the first switch SW1 is turned off and the second switch SW2 is turned on, the current flowing through the inductor 110 begins to circulate to the inductor 110 via the second battery cell 20b, inductor 1120b, and second switch SW2. The current flowing from the inductor 110 to the first battery cell 20a rapidly decreases to zero. Therefore, in a configuration without the first filter 1110a, the current flowing through the first battery cell 20a changes rapidly as the first switch SW1 and the second switch SW2 are switched on, and accordingly, the voltage of the first battery cell 20a also changes rapidly.

[0114] In contrast, in a configuration including the first filter 1110a, even if the first switch SW1 is turned off and the second switch SW2 is turned on, causing a rapid decrease in the current flowing from the inductor 110 to the first battery cell 20a, the induced current flowing through the inductor 1120a does not change abruptly, and the current flowing through the loop including the inductor 1120a, the first capacitor 1000a, and the first battery cell 20a changes gradually. Thus, the circuit under test in FIG. 11 is configured such that the inductor 1120a is connected in series with the first battery cell 20a, and current flows through the closed circuit including the first battery cell 20a, the inductor 1120a, and the first capacitor 1000a even when the first switch SW1 is turned off. This allows the inductor 1120a to suppress abrupt changes in the induced current. Therefore, in a configuration including the first filter 1110a, changes in the current and voltage of the first battery cell 20a due to switching of the first switch SW1 and the second switch SW2 can be suppressed. Similarly, in a configuration including the second filter 1110b, it is possible to suppress changes in the current and voltage of the second battery cell 20b that accompany the switching of the first switch SW1 and the second switch SW2.

[0115] FIG. 14 shows a voltage spectrum according to the example. FIG. 15 shows a current spectrum according to the example. The voltage spectrum in FIG. 14 and the current spectrum in FIG. 15 show the amplitude of the voltage and current flowing through the battery cell 20, measured at frequencies ranging from 1 kHz to 10 kHz in the circuit under test (configuration including filters 1110a-b) of FIG. 11. Note that in the measurements shown in these figures, the measuring unit 130 measured the current flowing through the battery cell 20 itself and the voltage between the positive and negative electrodes of the battery cell 20. The measuring unit 130 also removed harmonic components of the switching frequency using a low-pass filter.

[0116] 14 and 15, the current is almost constant regardless of the measurement frequency, while the voltage decreases as the measurement frequency increases. This characteristic matches the frequency characteristics of the impedance of a normal battery. Therefore, it can be seen that the measurement device 100 can properly measure the voltage spectrum and current spectrum of the battery cell 20.

[0117] FIG. 16 shows an impedance locus (Nyquist diagram) according to a comparative example. FIG. 17 shows an impedance locus (Nyquist diagram) according to an example. In FIGS. 16 and 17, the measurement value of "Analyzer" is the impedance of the battery cell 20 measured by an impedance analyzer, and is the target value for measurement by the measurement device 100. The measurement value of "Measurement device 100" is the impedance of the battery cell 20 measured by the measurement device 100. In the comparative example of FIG. 16, the impedance of the battery cell 20 was measured in a circuit under test that did not include the filters 1110a-b. In the example of FIG. 17, the impedance of the battery cell 20 was measured in the circuit under test of FIG. 11 (configuration that includes the filters 1110a-b).

[0118] As shown in Fig. 16, measurement apparatus 100 can measure an impedance that is somewhat close to the target even when it does not include filters 1110a-b. As shown in Fig. 17, measurement apparatus 100 can significantly improve the impedance measurement accuracy when it includes filters 1110a-b compared to when it does not include filters 1110a-b. In the examples of Figs. 16 and 17, by including filters 1110a-b, measurement apparatus 100 was able to reduce the RMSE (Root Mean Square Error) of the error from the target value by 31.1% at the sample points of the measurement frequency surrounded by the red dashed line in Fig. 17.

[0119] Fig. 18 shows an operational flow relating to the determination of each frequency in a measurement device 100 according to yet another modification of the present embodiment. This operational flow may be executed by any of the measurement device 100 of Fig. 1, the measurement device 100 of Fig. 10, and the measurement device 100 of Fig. 11. According to this operational flow, the measurement device 100 according to this modification determines the sampling frequency Fs and the switching frequency Fsw according to the measurement frequency F (the AC frequency of the induced current) used for measurement.

[0120] In S1800, the signal control unit 120 in the measurement device 100 determines a measurement frequency F. S1800 may be processing equivalent to S310 in FIG. 3. Alternatively, the signal control unit 120 may determine multiple measurement frequencies F to be measured. For example, the signal control unit 120 may acquire multiple measurement frequencies F to be measured by reading all set frequencies Fi to be measured from a storage device. Note that the measurement device 100 may receive registration of one or more measurement frequencies F (or one or more set frequencies Fi) to be measured when the measurement device 100 is manufactured or set up. The measurement device 100 may determine one or more measurement frequencies F (or one or more set frequencies Fi) to be measured in response to a specification from a user or another device when measurement is performed.

[0121] In S1810, the measurement unit 130 in the measurement device 100 determines or changes the sampling frequency Fs for measuring the voltage of at least one of the first battery cell 20a or the second battery cell 20b, depending on the measurement frequency F (the frequency of the AC induced current). S1810 may be executed before measuring the voltage waveform and the current waveform of the battery cell 20 in S330 of FIG.

[0122] For example, the measuring section 130 may change the sampling frequency Fs in proportion to the measurement frequency F. As an example, when extracting frequency components of the measurement frequency F from the voltage waveform and the current waveform, the extracting section 140 in the measuring device 100 may perform a Fourier transform on measurement data consisting of a predetermined number of sampling points. In this case, the measuring section 130 in the measuring device 100 sets the sampling frequency so that a predetermined number of periods ("wave" periods) of one or more periods of the AC waveform of the induced current are included in a sampling period of the predetermined number of sampling points at the sampling frequency. Here, wave may be an integer greater than or equal to 1, or may be a real number greater than or equal to 1.

[0123] Specifically, if the time length of one cycle (measurement cycle) of measurement frequency F is Tm, the time length of one cycle (sampling cycle) of sampling frequency Fs is Ts, and the number of sampling points is Ns, then sampling is performed at Ns sampling points over the wave cycle of measurement cycle Tm, so the sampling cycle Ts is Ts = Tm × wave / Ns. Since the sampling frequency Fs = 1 / Ts and the measurement frequency F = 1 / Tm, the sampling frequency Fs is Fs = F × Ns / wave. As a result, when changing measurement frequency F, measurement device 100 can change the sampling frequency and sample the waveform of the AC waveform of the induced current for a predetermined number of cycles (wave cycles) at a predetermined number of sampling points (Ns samples).

[0124] In S1820, the signal control unit 120 determines the switching frequency Fsw of the first switch SW1 and the second switch SW2 in accordance with the sampling frequency Fs. S1820 may be executed before switching the first switch SW1 and the second switch SW2 to measure the voltage waveform and the current waveform of the battery cell 20 in S330 of FIG.

[0125] The signal control unit 120 may determine the switching frequency Fsw individually for each sampling frequency Fs determined according to each measurement frequency F. Alternatively, the signal control unit 120 may determine a common switching frequency Fsw for multiple sampling frequencies Fs determined according to multiple measurement frequencies F.

[0126] Figure 19 shows an example of a switching frequency alias that occurs near the frequency component of the measurement frequency during measurement. In order to sample a signal waveform and reproduce the original signal waveform, it is necessary to sample at a frequency at least twice the maximum frequency of the signal waveform (sampling theorem). If there is noise at a frequency equal to or greater than half the sampling frequency, that noise will be observed as a signal that has been folded back (aliased) to a frequency equal to or less than half the sampling frequency.

[0127] 19, measurement apparatus 100 is set to a measurement frequency F of 79 Hz, a sampling frequency Fs of 20.2 kHz, and a switching frequency Fsw of 20 kHz. In this case, noise having a frequency equal to the switching frequency Fsw occurs when measurement apparatus 100 measures the current and voltage waveforms. Because the switching frequency Fsw (=20 kHz) is equal to or greater than half the sampling frequency Fs (=10.1 kHz), sampling at sampling frequency Fs does not identify the noise as being at the switching frequency Fsw. Therefore, measurement apparatus 100 observes 200 Hz noise (alias) that has been folded back into the frequency range of switching frequencies 0 to Fs / 2.

[0128] In the example shown in this figure, the switching frequency Fsw (=20 kHz) is located within the range of the sampling frequency Fs / 2 (=10.1 kHz) to the sampling frequency Fs (=20.2 kHz), so it is observed as noise (alias) at frequency Fs-Fsw (=200 Hz). Similarly, if the switching frequency Fsw is within the range of kFs to (k+1 / 2)Fs (k is an integer greater than or equal to 1), the noise of the switching frequency Fsw is observed as a signal (alias) at frequency (Fsw-kFs). If the switching frequency Fsw is within the range of (k+1 / 2)Fs to (k+1)Fs (k is an integer greater than or equal to 1), the noise of the switching frequency Fsw is observed as a signal (alias) at frequency (k+1)Fs-Fsw.

[0129] Note that the Fourier transform typically uses tens to hundreds of sample points. The Fourier transform can be performed with at least one cycle of measurement data, and the more sample points included in one cycle of measurement data, the higher the accuracy. Therefore, even in the measurement device 100, the cycle of the waveform to be measured included in the sampling period is typically close to 1 (e.g., wave=1 to 2 in this embodiment), and the number of sample points may be tens to hundreds or more (e.g., the number of sample points Ns in this embodiment ≈ tens to hundreds or more). Here, as described in relation to S1810 of FIG. 18 , since the sampling frequency Fs = measurement frequency F × Ns / wave, the measurement frequency F is sufficiently smaller than the sampling frequency Fs (approximately tens to hundreds of times smaller), and is located near frequency 0 in the frequency range from frequency 0 to the sampling frequency Fs. Therefore, in measurements using such measurement parameters, noise aliasing near frequency 0 becomes a problem.

[0130] Figure 20 shows the results of actual measurement of aliases. In the measurements shown in this figure, the measurement apparatus 100 measured the voltage and current waveforms at a measurement frequency F of 79 Hz, a sampling frequency Fs of 20.2 kHz, and a switching frequency Fsw of 20 kHz, as in Figure 19. The measurement apparatus 100 then converted the voltage and current waveforms into frequency spectra using a Fourier transform.

[0131] With this setting, as explained using Figure 19, noise near the switching frequency of 20 kHz becomes an alias near the frequency of 200 Hz (= 20.2 kHz - 20 kHz). Because this alias spreads around the frequency of 200 Hz, an error occurs in the measured values ​​of the frequency component at the measurement frequency of 79 Hz in the voltage and current waveforms measured from the circuit under test.

[0132] In order to reduce measurement errors due to aliasing caused by noise in the switching frequency Fsw that switches the first switch SW1 and the second switch SW2, in S1820 of Fig. 18, the signal control unit 120 may set the switching frequency Fsw so that the first switch SW1 and the second switch SW2 are switched at a switching frequency such that the frequency difference between the switching frequency Fsw and an integer multiple of the sampling frequency Fs is equal to or greater than a predetermined percentage of the sampling frequency. The signal control unit 120 may set this predetermined percentage to 10%, 20%, 15%, 5%, or some other value.

[0133] FIG. 21 shows an example of frequency settings affected by aliasing. As shown in the first column of the table in this figure, the measurement device 100 measured voltage and current waveforms while changing the measurement frequency by 21 points between 10 Hz and 1 kHz. At each measurement frequency, the measurement device 100 samples two periods of the AC waveform of the induced current using 512 sampling points (wave=2, Ns=512). Applying this to the equation shown in connection with S1810 in FIG. 18, sampling frequency Fs = measurement frequency F × 512 / 2 = measurement frequency F × 256. Therefore, as shown in the second column of this figure, the measurement device 100 set the sampling frequency Fs to 256 times the measurement frequency F.

[0134] In the example shown in this figure, the measurement apparatus 100 performed measurements with a switching frequency of 20 kHz. The third column of the table in this figure indicates how many times the sampling frequency Fs is relative to the switching frequency of 20 kHz. The fourth column of the table in this figure indicates how many times the sampling frequency Fs is relative to the switching frequency of 52 kHz when the switching frequency is 52 kHz.

[0135] Even in the measurement device 100 including the filters 1110a-b, the voltage and current fluctuate within a switching period Tsw in accordance with the switching of the first switch SW1 and the second switch SW2. If the sampling frequency Fs is an integer multiple of the switching frequency Fsw, the measurement section 130 performs sampling at (sampling frequency Fs / switching frequency Fsw) every switching period Tsw, with the same phase throughout the entire switching period. In this case, the measurement section 130 measures alias components of frequencies corresponding to fluctuations in the voltage and current values ​​at each phase within one switching period. Therefore, the signal control section 120 may shift the sampling frequency from an integer multiple of the switching frequency.

[0136] 18, the signal control unit 120 may set the switching frequency Fsw so that the first switch SW1 and the second switch SW2 are switched at a switching frequency such that the frequency difference between an integer multiple of the switching frequency Fsw and the sampling frequency Fs is equal to or greater than a predetermined ratio of the switching frequency. The signal control unit 120 may set this predetermined ratio to 10%, 20%, 15%, 5%, or another value.

[0137] 21, measurement errors occurred due to the influence of aliases when the measurement frequency F was 631 Hz, 398 Hz, 316 Hz, 158 Hz, and 79 Hz. These measurement results indicate that measurement errors due to the influence of aliases occurred when the measurement frequency Fs was within a range of ±0.1 times an integer multiple of the switching frequency Fsw. Based on these measurement results, the signal control unit 120 may adopt 10% as the predetermined ratio.

[0138] In S1820, the signal control unit 120 may select a switching frequency Fsw that satisfies the conditions shown in association with at least one of FIG. 20 or FIG. 21 from among multiple frequencies that can be set as the switching frequency Fsw. For example, the signal control unit 120 may select the switching frequency Fsw from among 52 kHz, 54 kHz, 55 kHz, 58 kHz, or 65 kHz. The signal control unit 120 may select a switching frequency Fsw that satisfies the conditions shown in association with at least one of FIG. 20 or FIG. 21 for each measurement frequency F to be used. Alternatively, the signal control unit 120 may select a common switching frequency Fsw that satisfies the conditions shown in association with at least one of FIG. 20 or FIG. 21 for all of the multiple measurement frequencies F.

[0139] Various embodiments of the present invention may be described with reference to flowcharts and block diagrams, where the blocks may represent (1) stages of a process in which operations are performed or (2) sections of an apparatus responsible for performing the operations. Particular stages and sections may be implemented by dedicated circuitry, programmable circuitry provided with computer-readable instructions stored on a computer-readable medium, and / or a processor provided with computer-readable instructions stored on a computer-readable medium. Dedicated circuitry may include digital and / or analog hardware circuitry, and may include integrated circuits (ICs) and / or discrete circuits. Programmable circuitry may include reconfigurable hardware circuitry, including logical AND, OR, XOR, NAND, NOR, and other logical operations, flip-flops, registers, memory elements such as field programmable gate arrays (FPGAs), programmable logic arrays (PLAs), and the like.

[0140] A computer-readable medium may include any tangible device capable of storing instructions that are executed by an appropriate device, such that the computer-readable medium having instructions stored thereon comprises an article of manufacture containing instructions that can be executed to create means for performing the operations specified in the flowcharts or block diagrams. Examples of computer-readable media may include electronic, magnetic, optical, electromagnetic, and semiconductor storage media. More specific examples of computer-readable media may include floppy disks, diskettes, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), electrically erasable programmable read-only memory (EEPROM), static random access memory (SRAM), compact disc read-only memory (CD-ROM), digital versatile disc (DVD), Blu-ray disc, memory stick, integrated circuit card, and the like.

[0141] The computer readable instructions may include either assembler instructions, Instruction Set Architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state-setting data, or source or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk®, JAVA®, C++, etc., and conventional procedural programming languages ​​such as the “C” programming language or similar programming languages.

[0142] The computer-readable instructions may be provided to a processor or programmable circuit of a programmable data processing device, such as a computer, locally or over a wide area network (WAN) such as a local area network (LAN) or the Internet, and the computer-readable instructions may be executed to create means for performing the operations specified in the flowcharts or block diagrams. Here, the computer may be a personal computer (PC), a tablet computer, a smartphone, a workstation, a server computer, a general-purpose computer, a special-purpose computer, or the like, or may be a computer system in which multiple computers are connected. Such a computer system in which multiple computers are connected is also called a distributed computing system, and is a broad definition of computer. In a distributed computing system, the multiple computers collectively execute a program by each executing a portion of the program and passing data between the computers as needed during program execution.

[0143] Examples of processors include a computer processor, a central processing unit (CPU), a processing unit, a microprocessor, a digital signal processor, a controller, a microcontroller, etc. A computer may have one or more processors. In a multiprocessor system with multiple processors, each processor executes a portion of a program and passes data between processors as needed during program execution, allowing the multiple processors to collectively execute a program. For example, in multitasking, each of the multiple processors may execute a portion of each task in small chunks by switching tasks at time slice intervals. In this case, which portion of a program each processor executes changes dynamically. Which portion of a program each of the multiple processors executes may also be statically determined by multiprocessor-aware programming.

[0144] 22 illustrates an example of a computer 2200 in which aspects of the present invention may be embodied, in whole or in part. Programs installed on the computer 2200 may cause the computer 2200 to function as or perform operations associated with an apparatus or one or more sections of the apparatus according to embodiments of the present invention, and / or to perform a process or steps of a process according to embodiments of the present invention. Such programs may be executed by the CPU 2212 to cause the computer 2200 to perform specific operations associated with some or all of the blocks of the flowcharts and block diagrams described herein.

[0145] A computer 2200 according to this embodiment includes a CPU 2212, a RAM 2214, a graphics controller 2216, and a display device 2218, which are interconnected by a host controller 2210. The computer 2200 also includes input / output units such as a communication interface 2222, a storage device 2224 such as a hard disk drive, a DVD-ROM drive 2226, and an IC card drive, which are connected to the host controller 2210 via an input / output controller 2220. The computer also includes legacy input / output units such as a ROM 2230 and a keyboard 2242, which are connected to the input / output controller 2220 via an input / output chip 2240.

[0146] The CPU 2212 operates according to programs stored in the ROM 2230 and RAM 2214, thereby controlling each unit. The graphics controller 2216 acquires image data generated by the CPU 2212 into a frame buffer or the like provided in the RAM 2214 or into the graphics controller 2216 itself, and causes the image data to be displayed on the display device 2218.

[0147] The communication interface 2222 communicates with other electronic devices via a network. The storage device 2224 stores programs and data used by the CPU 2212 in the computer 2200. The DVD-ROM drive 2226 reads programs or data from a DVD-ROM 2227 and provides the programs or data to the storage device 2224 via the RAM 2214. The IC card drive reads programs and data from an IC card and / or writes programs and data to an IC card.

[0148] The ROM 2230 stores therein a boot program or the like that is executed by the computer 2200 upon activation, and / or programs that depend on the hardware of the computer 2200. The input / output chip 2240 may also connect various input / output units to the input / output controller 2220 via a parallel port, a serial port, a keyboard port, a mouse port, etc.

[0149] The programs are provided by a computer-readable medium such as a DVD-ROM 2227 or an IC card. The programs are read from the computer-readable medium, installed in the storage device 2224, RAM 2214, or ROM 2230, which are also examples of computer-readable media, and executed by the CPU 2212. Information processing described in these programs is read by the computer 2200, and brings about cooperation between the programs and the various types of hardware resources described above. An apparatus or a method may be configured by realizing information manipulation or processing in accordance with the use of the computer 2200.

[0150] For example, when communication is performed between the computer 2200 and an external device, the CPU 2212 may execute a communication program loaded into the RAM 2214 and instruct the communication interface 2222 to perform communication processing based on the processing described in the communication program. Under the control of the CPU 2212, the communication interface 2222 reads transmission data stored in a transmission buffer processing area provided in the RAM 2214, the storage device 2224, the DVD-ROM 2227, or a recording medium such as an IC card, and transmits the read transmission data to the network, or writes reception data received from the network to a reception buffer processing area or the like provided on the recording medium.

[0151] Furthermore, the CPU 2212 may cause all or a necessary portion of a file or database stored on an external recording medium such as the storage device 2224, the DVD-ROM drive 2226 (DVD-ROM 2201), an IC card, etc. to be read into the RAM 2214, and perform various types of processing on the data on the RAM 2214. The CPU 2212 then writes back the processed data to the external recording medium.

[0152] Various types of information, such as various types of programs, data, tables, and databases, may be stored on the recording medium and may undergo information processing. The CPU 2212 may perform various types of processing on data read from the RAM 2214, including various types of operations, information processing, conditional judgment, conditional branching, unconditional branching, information search / replacement, etc., as described throughout this disclosure and specified by the instruction sequences of the programs, and write the results back to the RAM 2214. The CPU 2212 may also search for information in a file, database, etc. on the recording medium. For example, if multiple entries each having an attribute value of a first attribute associated with an attribute value of a second attribute are stored on the recording medium, the CPU 2212 may search for an entry that matches a condition specified by the attribute value of the first attribute from among the multiple entries, read the attribute value of the second attribute stored in the entry, and thereby obtain the attribute value of the second attribute associated with the first attribute that satisfies a predetermined condition.

[0153] The above-described programs or software modules may be stored in a computer-readable medium on or near the computer 2200. A recording medium such as a hard disk or RAM provided in a server system connected to a dedicated communication network or the Internet can also be used as a computer-readable medium, thereby providing the programs to the computer 2200 via the network.

[0154] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0155] It should be noted that the execution order of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before," "prior to," etc., and that the processes can be performed in any order unless the output of a previous process is used in a subsequent process. Even if the operational flow in the claims, specifications, and drawings is described using "first," "next," etc. for convenience, this does not mean that the processes must be performed in this order. [Explanation of symbols]

[0156] 10 storage device, 20 battery cell, 100 measuring device, 110 inductor, 120 signal control unit, 130 measuring unit, 132 current measuring device, 134 voltage measuring device, 140 extraction unit, 150 calculation unit, 160 output unit, 1000 capacitor, 1110a-b filter, 1120a-b inductor, 2200 computer, 2201 DVD-ROM, 2210 host controller, 2212 CPU, 2214 RAM, 2216 graphic controller, 2218 display device, 2220 input / output controller, 2222 communication interface, 2224 storage device, 2226 DVD-ROM drive, 2230 ROM, 2240 input / output chip, 2242 keyboard

Claims

1. a first inductor; a first switch that switches whether or not the first inductor is connected in series to a first battery cell included in the power storage device to be measured; a signal control unit that switches on and off the first switch to generate an induced current in the first inductor; a measurement unit that measures a voltage when the induced current flows in at least one of the first battery cell or the second battery cell included in the power storage device; and A measuring device comprising:

2. a second switch that switches whether or not the first inductor is connected in series to a second battery cell included in the power storage device to be measured; The first inductor is a first terminal provided on the negative electrode side of the first battery cell and the positive electrode side of the second battery cell; a second terminal provided on the positive electrode side of the first battery cell and the negative electrode side of the second battery cell; and The signal control unit causes the first inductor to generate the induced current by switching the first switch and the second switch. The measuring device according to claim 1 .

3. The measuring device according to claim 2 , wherein the measuring unit measures the voltage when the induced current flows through each of the first battery cell and the second battery cell.

4. In the power storage device, the negative electrode of the first battery cell is connected to the positive electrode of the second battery cell, The first terminal of the first inductor is connected between the negative terminal of the first battery cell and the positive terminal of the second battery cell. The measuring device according to claim 3 .

5. The measuring device according to claim 2 , wherein the signal control unit switches the first switch and the second switch by pulse width modulation to generate an AC induced current in the first inductor.

6. The measuring device according to claim 5 , wherein the measuring unit further measures the induced current.

7. The measuring device according to claim 6 , wherein the signal control unit adjusts the duty ratio of the first switch and the second switch so that a center value of the amplitude of the induced current becomes zero.

8. the signal control unit switches the frequency of the AC induced current to each of a plurality of set frequencies; The measurement unit measures voltage waveforms of the first battery cell and the second battery cell when the frequency of the AC induced current is set to each of the plurality of set frequencies. The measuring device according to claim 5 .

9. The measurement device according to claim 8 , wherein the measurement unit changes a sampling frequency for measuring the voltage of at least one of the first battery cell and the second battery cell in accordance with the AC frequency of the induced current.

10. 10. The measurement device according to claim 9, wherein the measurement unit sets the sampling frequency so that one or more predetermined periods of the AC waveform of the induced current are included within a sampling period having a predetermined number of sampling points at the sampling frequency.

11. 11. The measuring device according to claim 9, wherein the signal control unit switches the first switch and the second switch at a switching frequency such that a frequency difference between the switching frequency at which the first switch and the second switch are switched and an integer multiple of the sampling frequency is 10% or more of the sampling frequency.

12. 11. The measuring device according to claim 9, wherein the signal control unit switches the first switch and the second switch at a switching frequency such that a frequency difference between an integer multiple of a switching frequency at which the first switch and the second switch are switched and the sampling frequency is 10% or more of the switching frequency.

13. The measuring device according to claim 8 , further comprising a calculation unit that calculates impedance characteristics of the first battery cell and the second battery cell based on voltage waveforms and current waveforms of the first battery cell and the second battery cell.

14. 9. The measuring device according to claim 8, further comprising an extraction unit that extracts frequency components of each set frequency from the voltage waveforms of the first battery cell and the second battery cell measured using the AC frequency of the induced current as each set frequency.

15. a first filter that suppresses voltage fluctuations of the first battery cell due to switching of the first switch and the second switch; a second filter that suppresses voltage fluctuations of the second battery cell due to switching of the first switch and the second switch; The measuring device according to claim 2 , comprising:

16. the first switch and the second switch are connected in series between the positive electrode side of the first battery cell and the negative electrode side of the second battery cell; the second terminal of the first inductor is connected to a wiring between the first switch and the second switch; the first filter includes a first capacitor having one end connected to a wiring between a positive electrode of the first battery cell and the first switch and the other end connected between a negative electrode of the first battery cell and the first terminal of the first inductor; The second filter has a second capacitor, one end of which is connected to a wiring between the negative electrode of the second battery cell and the second switch, and the other end of which is connected between the positive electrode of the second battery cell and the first terminal of the first inductor.

16. The measuring device of claim 15.

17. the first filter includes a second inductor provided on a wiring between the positive electrode of the first battery cell and the first switch, at a position between the positive electrode of the first battery cell and the first capacitor; The second filter includes a third inductor provided on a wiring between the negative electrode of the second battery cell and the second switch, at a position between the negative electrode of the second battery cell and the second capacitor.

17. The measuring device of claim 16.

18. generating an induced current by a first inductor by switching a first switch that switches whether or not a first inductor is connected in series to a first battery cell included in the power storage device to be measured; measuring a voltage when the induced current flows in at least one of the first battery cell or the second battery cell included in the power storage device; A measurement method comprising:

19. When executed by a computer, the computer is a signal control unit that switches a first switch that switches whether or not a first inductor is connected in series to a first battery cell included in the power storage device to be measured, thereby generating an induced current by the first inductor; a measurement unit that measures a voltage when the induced current flows in at least one of the first battery cell or the second battery cell included in the power storage device; and A measurement program that functions as a

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