A detection circuit for the impedance spectrum of an energy storage battery and its control method

Abstract

The present invention relates to a detection circuit for an energy storage battery impedance spectrum and a control method thereof, and belongs to the field of battery detection technology. The circuit includes a floating detection circuit, a microprocessor control system, a programmable electronic load, a high-precision voltage sensor, a high-precision current sensor, a charge and discharge switch, a charging power supply, and a discharge load; before applying excitation, the circuit uses a balancing capacitor as a medium, and controls the charge and discharge switch so that the balancing capacitor voltage offsets the DC voltage of the energy storage battery, thereby improving the detection accuracy of small changes in the power battery terminal voltage; in the impedance spectrum detection stage, by controlling the current flowing through the programmable electronic load, the decoupling problem of the energy storage battery charge and discharge current and the excitation current is solved; by the frequency sweeping operation of the composite excitation signal, the rapid online detection of the internal impedance spectrum of the energy storage battery is realized. The present invention can accurately detect the dynamic and static internal impedance spectra of the energy storage battery, and provide data support for the health status assessment of the energy storage battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery detection, and relates to a detection circuit for the impedance spectrum of an energy storage battery and a control method therefor. Background Art

[0002] With the rapid development of the new energy industry, the production and use scale of energy storage batteries have increased year by year, and the safety and reliability of the batteries have also attracted much attention. Electrochemical impedance spectroscopy (EIS) is a non-destructive detection technology with simple test conditions and accurate results, which can obtain various data such as the resistance and reactance of the test object, and is particularly suitable for analyzing the change of the health state of the battery.

[0003] Traditional electrochemical impedance spectrum measurement is generally based on a constant potential, applying a small-signal sinusoidal alternating current voltage signal, and analyzing the impedance characteristics of the battery at this frequency by measuring the amplitude difference and phase ratio between the alternating current voltage signal and the alternating current signal. The impedance characteristics of the battery can be characterized and evaluated by the impedance characteristics at different frequency points. However, the traditional electrochemical impedance spectrum measurement method takes a long time (usually from a few minutes to more than ten minutes), and the battery is in a dynamic process of cyclic charge and discharge during the detection process, and the internal components of the battery may have changed, resulting in the impedance characteristics obtained by the detection not being able to reflect the true performance of the battery; at the same time, from the application perspective, it is more desirable to grasp the impedance characteristics of the battery during on-line operation, so as to ensure the long-term safe and stable operation of the battery, but most of the current impedance spectrum detection technologies take the offline single battery as the research object. The dynamic impedance spectrum detection technology refers to the impedance test of the battery during operation, and by studying the dynamic performance of batteries in different health states, the relationship between the dynamic impedance spectrum and the health state of the battery is found, and then the safety monitoring of the battery is realized.

[0004] However, the dynamic impedance spectrum technology also has corresponding problems. One is that the grouped batteries have high voltage characteristics (tens to hundreds of volts) and low internal impedance characteristics (1 milliohm to 10 milliohms), which are not suitable for applying voltage excitation. In the case of applying current excitation, the extremely small change (less than 1%) of the terminal voltage is difficult to detect; the other is that the real-time change of the SOC state of the battery during operation will have a huge impact on the impedance spectrum characteristics, which places strict requirements on the detection speed of the impedance spectrum.

[0005] Therefore, it is necessary to design a new detection circuit for the impedance spectrum of an energy storage battery to address the deficiencies of the existing technology and solve or mitigate the above problems. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a detection circuit and its control method for the impedance spectrum of an energy storage battery. Aiming at the defects of the traditional impedance spectrum method, an electronic load excitation application method and a floating ground detection circuit are designed to achieve the application of excitation current with arbitrary waveforms to the energy storage battery and the detection of extremely small changes in the battery terminal voltage. By using kSa(kt) signals, sine composite signals, and Chirp signals, the detection speed of the impedance spectrum is improved, and finally, the fast and accurate detection of the static and dynamic impedance spectra of the energy storage battery is realized.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A detection circuit for the impedance spectrum of an energy storage battery includes a floating ground detection circuit, a microprocessor control system, a programmable electronic load R1, a high-precision voltage sensor U4, a high-precision current sensor U5, a charge and discharge switch S5, a charging power supply, and a discharge load; the floating ground detection circuit includes a first operational amplifier input switch S1, a charging switch S2, a discharging switch S3, a second operational amplifier input switch S4, a charging resistor R2, a discharging resistor R3, a balancing capacitor C1, a programmable instrumentation amplifier U1, a high-precision AD converter U2, and an isolation optocoupler U3.

[0009] The floating ground detection circuit, the programmable electronic load R1, the high-precision voltage sensor U4, the charging power supply, and the discharge load are respectively connected in parallel across both ends of the energy storage battery GB; the high-precision current sensor U5 is connected in series with the energy storage battery GB; the common terminal of the charge and discharge switch S5 is connected to the positive electrode of the energy storage battery GB, and the other two ends are respectively connected to the positive electrode of the charging power supply and the discharge load.

[0010] One end of the balancing capacitor C1 is connected to the common terminal of the second operational amplifier input switch S4, the discharging resistor R3, the charging resistor R2, and the isolation optocoupler U3, and the other end is connected to the ground of the discharging switch S3 and the energy storage battery; the discharging resistor R3 and the discharging switch S3 are connected in series; one end of the charging switch S2 is connected to the charging resistor R2, and the other end is connected to the first operational amplifier input switch S1 and the positive electrode of the energy storage battery GB; the positive feedback terminal of the programmable instrumentation amplifier U1 is connected to the operational amplifier input switch S1, the negative feedback terminal is connected to the operational amplifier input S4, the output terminal is connected to the data input terminal of the high-precision AD converter U2, and the control terminal is connected to the isolation optocoupler U3; the control terminal of the high-precision AD converter U2 is connected to the isolation optocoupler U3; one control terminal of the isolation optocoupler U3 is connected to the control terminals of the switches S1 to S4, and the other control terminal is connected to the microprocessor control system; the microprocessor control system is respectively connected to a wireless communication module, a programmable electronic load R1, a high-precision voltage sensor U4, and a high-precision current sensor U5.

[0011] Further, before applying the excitation current for measuring the impedance spectrum, switch S2 is in the closed state, switches S1, S3, and S4 are in the open state, and the balancing capacitor C1 is in the charging state; after the balancing capacitor reaches a steady state, switches S1 and S4 are in the closed state, switches S2 and S3 are in the open state, and the microprocessor control system controls the programmable electronic load R1 to apply a current excitation to the energy storage battery GB, and collects relevant data to calculate the internal impedance spectrum information; after the impedance spectrum measurement of the energy storage battery GB is completed, switches S1, S2, and S4 are disconnected, switch S3 is closed, and the balancing capacitor C1 discharges to zero.

[0012] Further, when the energy storage battery GB is in the offline state, the charge and discharge switch S5 is in the vacant state; when the energy storage battery GB is working, as the charge and discharge switch S5 switches, the battery is in the state of cyclic charge and discharge.

[0013] Further, when performing impedance spectrum detection, the high-precision voltage sensor U4 detects the terminal voltage of the energy storage battery GB, and the high-precision current sensor U5 detects the charge and discharge current of the energy storage battery.

[0014] Further, the control method of this circuit specifically includes the following steps:

[0015] S1: Before applying the excitation current for measuring the impedance spectrum, disconnect switches S1, S3, and S4, close the charging switch S2, and charge the balancing capacitor C1; when the terminal voltage of the balancing capacitor C1 is equal to the terminal voltage of the energy storage battery GB, disconnect the charging switch S2, and close the operational amplifier input switches S1 and S4. At this time, the differential input voltage of the programmable instrumentation amplifier U1 is close to zero;

[0016] S2: After the balancing capacitor C1 reaches a steady state, the microprocessor control system periodically collects the voltage and current data of the sensors U4 and U5. The microprocessor control system adjusts the size of the programmable electronic load R1 through the PID strategy to control the charge and discharge current waveform of the energy storage battery GB, so as to apply a current excitation to the energy storage battery GB; at the same time, the microprocessor control system controls the programmable instrumentation amplifier U1 and the high-precision AD converter U2 to collect the terminal voltage change signal of the energy storage battery GB through the isolation optocoupler U3, and transmits it to the PC through the wireless communication module;

[0017] S3: After detecting the impedance spectrum, disconnect the operational amplifier input switches S1 and S4, close the discharge switch S3, and discharge the balancing capacitor C1; when the terminal voltage of the balancing capacitor C1 drops to the safety voltage, disconnect the discharge switch S3.

[0018] Further, in step S1, charging the balancing capacitor C1 specifically includes the following steps:

[0019] S11: Before applying the excitation current for measuring the impedance spectrum, disconnect switches S1, S3, and S4, and close the charging switch S2. If the initial voltage of the balancing capacitor C1 is 0, its relevant potential is:

[0020]

[0021] where U C1+ and U C1- are the positive and negative electrode potentials of the balancing capacitor C1, U GB+ is the DC voltage of the energy storage battery GB, U GB- is the negative electrode potential of the energy storage battery GB, τ 1 is the time constant for charging the balancing capacitor C1, R 2 is the resistance value of the charging resistor R2, C 1 is the capacitance value of the balancing capacitor C1, and t is the closing time of the switch S2;

[0022] S12: After 5 - 10 τ 1 after the charging switch is closed, the balancing capacitor C1 has been fully charged, and the terminal voltage of C1 is equal to the terminal voltage of the energy storage battery GB. Disconnect the charging switch S2 and close the operational amplifier input switches S1 and S4; Connect the common terminal of the isolation optocoupler U3 to the balancing capacitor C1 and the discharge resistor R3, and at the same time connect it to the ground terminal of the high-precision AD converter U2 and the programmable instrumentation amplifier U1. The relevant potentials of the components in the floating ground detection circuit are described by the following equations:

[0023]

[0024] where U U3- is the potential of the common terminal of the isolation optocoupler U3, U in+ , U in- and U 1GND are the non-inverting input terminal potential, inverting input terminal potential, and ground terminal potential of the programmable instrumentation amplifier U1 respectively; U 2GND is the ground terminal potential of the high-precision AD converter U2.

[0025] Furthermore, the ground (common) terminal level of the components U1, U2, and U3 in the floating ground detection circuit varies with the positive electrode potential of the balancing capacitor C1. In step S1, as the balancing capacitor C1 is charged, the ground (common) terminal level of the detection circuit "rises".

[0026] Furthermore, in step S2, the impedance spectrum of the energy storage battery GB is detected, which specifically includes the following steps:

[0027] S21: When detecting the very low frequency impedance spectrum of the energy storage battery GB, select a kSa(kt) pulse signal as the excitation signal, and the preset current excitation waveform I 1 (t) is:

[0028]

[0029] Among them, A S is the amplitude of the excitation signal, k is the adjustment coefficient, which can be dynamically adjusted according to the requirements of measuring the impedance spectrum, and t is the time variable

[0030] When detecting the low-frequency impedance spectrum of the energy storage battery GB, n sine wave composite signals with different frequencies are selected as the excitation signal, and the preset current excitation waveform I 1 (t) is:

[0031]

[0032] Among them, ω i is the angular frequency of the i-th preset sine wave, A i is the amplitude of the sine wave at the angular frequency of ω i , is the phase at the angular frequency of ω i , and t is the time variable;

[0033] When detecting the high-frequency impedance spectrum of the energy storage battery GB, a Chirp signal is selected as the excitation signal, and the preset current excitation waveform I 1 (t) is:

[0034]

[0035] Among them, A C is the amplitude of the Chirp signal, f s and f e are the start frequency and end frequency of the Chirp signal respectively, t s and t e are the start time and end time of the Chirp signal respectively, and t is the time variable;

[0036] S22: Apply an excitation current to the energy storage battery GB through the programmable electronic load R1, and the specific control method is as follows:

[0037] The control system adjusts the size of the programmable electronic load R1 according to the feedback error signal I ERROR between the current value and the preset value after incremental PID operation, so that the actual charge and discharge current waveform of the energy storage battery GB approaches the preset current waveform;

[0038] The relationship expression between the output R(k) of the PID algorithm and I ERROR (k) is:

[0039] R(k) = R(k - 1) + (K i + K d ) * I ERROR(k)+(K p -2K d )I ERROR (k - 1)+K d I ERROR (k - 2)

[0040] where R(k) and R(k - 1) are the magnitudes of the programmable electronic load in the k-th and (k - 1)-th control cycles respectively, I ERROR (k) is the feedback error signal in the k-th control cycle, and K p , K i and K d are the proportional coefficient, integral coefficient, and derivative coefficient of the PID controller respectively;

[0041] S23: After applying the current excitation, the terminal voltage U 1 (t) of the energy storage battery GB is expressed as follows:

[0042]

[0043] where ω j is the angular frequency corresponding to the j-th impedance spectrum frequency point, U j is the amplitude of the AC voltage waveform at the angular frequency ω j , is the phase of the AC voltage waveform at the angular frequency ω j , t is the time variable, and m is the number of sine waves with different frequencies in the terminal voltage U 1 (t) of the energy storage battery GB;

[0044] After step S12, the potential of the non-inverting input terminal of the programmable instrumentation amplifier U1 is U 1 (t), the potential of the inverting input terminal is U GB , and the output terminal is the amplified AC signal component in U 1 (t);

[0045] The high-precision current sensor U5 collects the charge and discharge current of the energy storage battery GB The calculation formula for the electrochemical impedance spectrum is:

[0046]

[0047] where is the electrochemical impedance of the battery at the angular frequency ω j , I j is the amplitude of the current signal at the angular frequency ω j , is the phase difference of the current waveform at the angular frequency ω j ;

[0048] S24: Sequentially select the kSa(kt) pulse signal, sine wave composite signal, and Chirp signal as the current excitation signals to complete the impedance spectrum measurements of the energy storage battery for extremely low-frequency, medium-low-frequency, and high-frequency signals respectively. Then splice the impedance spectrum curves of different frequency bands to obtain the complete impedance spectrum curve of the energy storage battery.

[0049] Further, in step S3, discharging the balance capacitor C1 specifically includes the following steps:

[0050] S31: After completing the impedance spectrum detection, disconnect the operational amplifier input switches S1 and S4, close the discharge switch S3. The initial voltage of the balance capacitor C1 is U GB+ , and its related potential is:

[0051]

[0052] where τ 2 is the time constant of the discharge of the balance capacitor C1, R 3 is the resistance value of the discharge resistor R3, and t is the closing time of the switch S3;

[0053] S32: After 5 - 10 τ 2 after the discharge switch is closed, the balance capacitor C1 has been discharged completely, and the positive potential of the capacitor is close to the negative potential. Then open the discharge switch S3. As the balance capacitor C1 discharges, the ground (common) potential of U1, U2, and U3 in the floating ground detection circuit "sinks", and the related potential is described by the following equations:

[0054] U C1- = U C1+ = U U3- = U 1GND = U 2GND = 0

[0055] After the discharge is completed, the balance capacitor C1 does not store energy.

[0056] The beneficial effects of the present invention are as follows: Before applying the excitation, by using the balancing capacitor as a medium and controlling the charge and discharge switch, the voltage of the balancing capacitor is made to cancel out the DC voltage of the energy storage battery, so as to detect the minute change in the battery terminal voltage; in the impedance spectrum detection stage, by controlling the magnitude of the current flowing through the programmable electronic load, the charge and discharge current of the energy storage battery is adjusted, and after applying the excitation, the minute change in the terminal voltage of the energy storage battery is detected through an instrumentation amplifier; the excitation signal and the terminal voltage change signal are detected, and the internal impedance information of the energy storage battery is calculated; through the frequency sweep operation of the excitation signal, the internal impedance spectrum information of the energy storage battery can be obtained; by controlling the magnitude of the current flowing through the programmable electronic load, the decoupling problem of the charge and discharge current of the energy storage battery and the impedance spectrum excitation current is solved, and the on-line detection of the internal impedance spectrum of the energy storage battery is realized; by using the kSa(kt) signal, the sine wave composite signal and the Chrip signal, the detection speed of the impedance spectrum is increased, and finally the fast and accurate detection of the static and dynamic impedance spectra of the energy storage battery is realized, providing data support for the health state assessment of the energy storage battery.

[0057] Other advantages, objectives and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be learned from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification. Brief Description of the Drawings

[0058] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in preferred detail below in conjunction with the drawings, where:

[0059] Figure 1 is the detection circuit topology diagram of the impedance spectrum of the energy storage battery of the present invention;

[0060] Figure 2 is the voltage and current waveform simulation diagram of the energy storage battery under a 10 Hz sine excitation;

[0061] Figure 3 is the voltage and current waveform simulation diagram of the energy storage battery under a 1 Hz + 10 Hz composite sine excitation;

[0062] Figure 4 is the working flow chart of the impedance spectrum detection of the energy storage battery of the present invention.

[0063] Reference numerals: S1 - First operational amplifier input switch, S2 - Charging switch, S3 - Discharging switch, S4 - Second operational amplifier input switch, S5 - Charge and discharge switch, R1 - Programmable electronic load, R2 - Charging resistor, R3 - Discharging resistor, C1 - Balancing capacitor, U1 - Programmable instrumentation amplifier, U2 - High-precision AD converter, U3 - Isolation optocoupler, U4 - High-precision voltage sensor, U5 - High-precision current sensor, GB - Energy storage battery. Detailed implementation manners

[0064] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0065] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation on the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, which does not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0066] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and should not be construed as a limitation on the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0067] Please refer to Figures 1 to 4 , Figure 1It is the topology diagram of the detection circuit for the impedance spectrum of the energy storage battery provided by the present invention. This circuit includes a floating ground detection circuit, a microprocessor control system, a programmable electronic load R1, a high-precision voltage sensor U4, a high-precision current sensor U5, an energy storage battery GB, a charge and discharge switch S5, a charging power supply, and a discharge load. Among them, the floating ground detection circuit includes charge and discharge switches S1, S2, S3, S4, charge and discharge resistors R2, R3, a balancing capacitor C1, a programmable instrumentation amplifier U1, a high-precision AD converter U2, and an isolation optocoupler U3.

[0068] The floating ground detection circuit, the programmable electronic load R1, the high-precision voltage sensor U4, the charging power supply, and the discharge load are respectively connected in parallel across both ends of the energy storage battery GB; the high-precision current sensor U5 is connected in series with the energy storage battery GB; the common terminal of the charge and discharge switch S5 is connected to the positive electrode of the energy storage battery GB, and the other two ends are respectively connected to the positive electrode of the charging power supply and the discharge load.

[0069] One end of the balancing capacitor C1 is connected to the common terminal of the operational amplifier input switch S4, the discharge resistor R3, the charging resistor R2, and the isolation optocoupler U3, and the other end is connected to the discharge switch S3 and the ground of the energy storage battery. The discharge resistor R3 and the discharge switch S3 are connected in series; one end of the charging switch S2 is connected to the charging resistor R2, and the other end is connected to the operational amplifier input switch S1 and the positive electrode of the energy storage battery GB; the positive feedback terminal of the programmable instrumentation amplifier U1 is connected to the operational amplifier input switch S1, the negative feedback terminal is connected to the operational amplifier input S4, the output terminal is connected to the data input terminal of the high-precision AD converter U2, and the control terminal is connected to the isolation optocoupler U3; the high-precision AD converter U2 is connected to the isolation optocoupler U3; one control terminal of the isolation optocoupler U3 is connected to the control terminals of switches S1 to S4, and the other control terminal is connected to the microprocessor control system; the microprocessor control system is respectively connected to a wireless communication module, the programmable electronic load R1, the high-precision voltage sensor U4, and the high-precision current sensor U5.

[0070] Before applying the excitation current for measuring the impedance spectrum, the switch S2 is in the closed state, the switches S1, S3, and S4 are in the open state, and the balancing capacitor C1 is in the charging state; after the balancing capacitor reaches a steady state, the switches S1 and S4 are in the closed state, the switches S2 and S3 are in the open state, and the microprocessor control system controls the programmable electronic load R1 to apply a current excitation to the energy storage battery GB and collect relevant data to calculate the internal impedance spectrum information; after the impedance spectrum of the energy storage battery GB is measured, the switches S1, S2, and S4 are turned off, the switch S3 is closed, and the balancing capacitor C1 discharges to zero.

[0071] When the energy storage battery is in the offline state, the charge and discharge switch S5 is in the vacant state; when the energy storage battery GB is working, as the charge and discharge switch S5 is switched, the battery is in a cyclic charge and discharge state.

[0072] When performing impedance spectroscopy detection, the high-precision voltage sensor U4 detects the terminal voltage of the energy storage battery, and the high-precision current sensor U5 detects the charge and discharge current of the energy storage battery.

[0073] Figure 4 It is the working flow chart for the impedance spectroscopy detection of the energy storage battery, as Figure 4 shown. The control method of this circuit specifically includes the following steps:

[0074] S1: Before applying the excitation current for measuring the impedance spectrum, disconnect switches S1, S3, and S4, close the charging switch S2, and charge the balancing capacitor C1; when the terminal voltage of the balancing capacitor C1 is equal to the terminal voltage of the energy storage battery GB, disconnect the charging switch S2, and close the operational amplifier input switches S1 and S2. At this time, the differential input voltage of the programmable instrumentation amplifier U1 is close to zero.

[0075] Among them, charging the balancing capacitor C1 specifically includes the following steps:

[0076] S11: Before applying the excitation current for measuring the impedance spectrum, disconnect switches S1, S3, and S4, close the charging switch S2. If the initial voltage of the balancing capacitor C1 is 0, its related potentials are:

[0077]

[0078] Among them, U C1+ and U C1- are the positive and negative potentials of the balancing capacitor C1, U GB+ is the DC voltage of the energy storage battery GB, U GB- is the negative potential of the energy storage battery GB, τ 1 is the time constant for charging the balancing capacitor C1, R 2 is the resistance value of the charging resistor R2, C 1 is the capacitance value of the balancing capacitor C1, and t is the closing time of the switch S2;

[0079] S12: After 5 - 10 τ 1 after the charging switch is closed, the balancing capacitor C1 has been fully charged, and the terminal voltage of C1 is equal to the terminal voltage of the energy storage battery GB. Disconnect the charging switch S2 and close the operational amplifier input switches S1 and S4; the common terminal of the isolation optocoupler U3 is connected to the balancing capacitor C1 and the discharge resistor R3, and at the same time is connected to the ground terminal of the high-precision AD converter U2 and the programmable instrumentation amplifier U1. The related potentials of the components in the floating ground detection circuit are described by the following equations:

[0080]

[0081] Among them, U U3- is the common terminal potential of the isolation optocoupler U3, U in+ 、Uin- and U 1GND are the positive input terminal potential, the negative input terminal potential, and the ground terminal potential of the programmable instrumentation amplifier U1 respectively; U 2GND is the ground terminal potential of the high-precision AD converter U2.

[0082] In the floating ground detection circuit, the ground terminal (common terminal) levels of components U1, U2, and U3 vary with the positive terminal potential of the balancing capacitor C1. In step S1, as the balancing capacitor C1 is charged, the ground terminal (common terminal) level of the detection circuit "rises".

[0083] S2: After the balancing capacitor C1 reaches a steady state, the microprocessor control system periodically collects the voltage and current data of sensors U4 and U5, adjusts the size of the programmable electronic load R1 through the PID strategy, and controls the charge and discharge current waveform of the energy storage battery GB, thereby applying a current excitation to the energy storage battery; at the same time, the microprocessor control system controls the programmable instrumentation amplifier U1 and the AD converter to collect the terminal voltage change signal of the energy storage battery through the isolation optocoupler U3, and transmits it to the PC through wireless communication.

[0084] Among them, detecting the impedance spectrum of the energy storage battery specifically includes the following steps:

[0085] S21: When detecting the extremely low-frequency impedance spectrum of the battery, a kSa(kt) pulse signal is selected as the excitation signal, and the preset current excitation waveform I 1 (t) is:

[0086]

[0087] Among them, A S is the amplitude of the excitation signal, k is an adjustment coefficient, which can be dynamically adjusted according to the requirements of measuring the impedance spectrum, and t is a time variable;

[0088] Figure 2 、 Figure 3 are the simulation diagrams of the voltage and current waveforms of the energy storage battery under sine excitation. As shown in Figure 2 、 Figure 3 shown, when detecting the medium and low-frequency impedance spectrum of the battery, n sine wave composite signals with different frequencies are selected as the excitation signal, and the preset current excitation waveform I 1 (t) is:

[0089]

[0090] Among them, ω i is the angular frequency of the i-th preset sine wave, A i is the amplitude of the sine wave at the angular frequency of ω i , is the phase at the angular frequency of ω i , and t is a time variable;

[0091] When detecting the high-frequency impedance spectrum of a battery, a Chirp signal is selected as the excitation signal, and the preset current excitation waveform I 1 (t) is as follows:

[0092]

[0093] Among them, A C is the amplitude of the Chirp signal, f s and f e are the starting frequency and ending frequency of the Chirp signal respectively, t s and t e are the starting time and ending time of the Chirp signal respectively, and t is the time variable.

[0094] S22: Apply an excitation current to the energy storage battery GB through the programmable electronic load R1. The specific control method is as follows:

[0095] The control system adjusts the size of the programmable electronic load according to the feedback error signal I ERROR between the current value and the preset value. After incremental PID operation, the actual charge and discharge current waveform of the energy storage battery approaches the preset current waveform.

[0096] The relationship expression between the PID algorithm output R(k) and I ERROR (k) is:

[0097] R(k) = R(k - 1)+(K i +K d )*I ERROR (k)+(K p - 2K d )I ERROR (k - 1)+K d I ERROR (k - 2)

[0098] Among them, R(k) and R(k - 1) are the sizes of the programmable electronic load in the kth and (k - 1)th control cycles respectively, I ERROR (k) is the feedback error signal in the kth control cycle, and K p , K i and K d are the proportional coefficient, integral coefficient, and differential coefficient of the PID controller.

[0099] S23: After applying the current excitation, the expression of the terminal voltage U 1 (t) of the energy storage battery GB is as follows:

[0100]

[0101] Among them, ωj is the angular frequency corresponding to the j-th impedance spectrum frequency point, U j is ω j the amplitude of the AC voltage waveform at the angular frequency of ω is ω j the phase of the AC voltage waveform at the angular frequency of ω, t is the time variable, and m is the number of sine waves with different frequencies in the voltage U 1 (t) of the energy storage battery GB end.

[0102] After step S12, the potential of the non-inverting input terminal of the programmable instrumentation amplifier U1 is U 1 (t), the potential of the inverting input terminal is U GB , and the output terminal is U 1 (t) of the amplified AC signal component.

[0103] The high-precision current sensor U5 collects the charge and discharge current of the energy storage battery GB The calculation formula of the electrochemical impedance spectrum is:

[0104]

[0105] Among them, is the electrochemical impedance of the battery at the angular frequency of ω j , I j is ω j the amplitude of the current signal at the angular frequency of ω is ω j the phase difference of the current waveform at the angular frequency of ω.

[0106] S24: Sequentially select the kSa(kt) pulse signal, sine wave composite signal, and Chirp signal as the current excitation signals, respectively complete the impedance spectrum measurement of the energy storage battery for extremely low-frequency, medium-low-frequency, and high-frequency signals, and then splice the impedance spectrum curves of different frequency bands to obtain the complete impedance spectrum curve of the energy storage battery.

[0107] S3: After detecting the impedance spectrum, disconnect the op-amp input switches S1 and S4, close the discharge switch S3, and discharge the balancing capacitor C1; when the terminal voltage of the balancing capacitor C1 drops to the safe voltage, disconnect the discharge switch S3.

[0108] Among them, discharging the balancing capacitor C1 specifically includes the following steps:

[0109] S31: After completing the impedance spectrum detection, disconnect the op-amp input switches S1 and S4, close the discharge switch S3, and the initial voltage of the balancing capacitor C1 is U GB+ , then its related potential is:

[0110]

[0111] Among them, τ2 is the time constant for discharging the balancing capacitor C1, and R 3 is the resistance value of the discharge resistor R3, and t is the closing time of the switch S3;

[0112] S32: After 5 - 10 τ when the discharge switch is closed 2 later, the balancing capacitor C1 has finished discharging, the positive - terminal potential of the capacitor is close to the negative - terminal potential, and the discharge switch S3 is opened; As the balancing capacitor C1 discharges, the potential of the ground terminals (common terminals) of the instruments U1, U2, and U3 in the floating - ground detection circuit "sinks", and the relevant potentials are described by the following equations:

[0113] U C1- = U C1+ = U U3- = U 1GND = U 2GND = 0

[0114] After the discharge ends, the balancing capacitor C1 does not store energy.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A detection circuit for the impedance spectrum of an energy storage battery, characterized in that, the circuit includes a floating ground detection circuit, a microprocessor control system, a programmable electronic load R1, a high-precision voltage sensor U4, a high-precision current sensor U5, a charge and discharge switch S5, a charging power supply, and a discharge load; the floating ground detection circuit includes a first operational amplifier input switch S1, a charging switch S2, a discharging switch S3, a second operational amplifier input switch S4, a charging resistor R2, a discharging resistor R3, a balancing capacitor C1, a programmable instrumentation amplifier U1, a high-precision AD converter U2, and an isolation optocoupler U3; the floating ground detection circuit, the programmable electronic load R1, the high-precision voltage sensor U4, the charging power supply, and the discharge load are respectively connected in parallel across both ends of the energy storage battery GB; the high-precision current sensor U5 is connected in series with the energy storage battery GB; the common terminal of the charge and discharge switch S5 is connected to the positive electrode of the energy storage battery GB, and the other two ends are respectively connected to the positive electrode of the charging power supply and the discharge load; one end of the balancing capacitor C1 is connected to the common terminal of the second operational amplifier input switch S4, the discharging resistor R3, the charging resistor R2, and the isolation optocoupler U3, and the other end is connected to the ground of the discharging switch S3 and the energy storage battery; the discharging resistor R3 and the discharging switch S3 are connected in series; one end of the charging switch S2 is connected to the charging resistor R2, and the other end is connected to the first operational amplifier input switch S1 and the positive electrode of the energy storage battery GB; the positive feedback terminal of the programmable instrumentation amplifier U1 is connected to the operational amplifier input switch S1, the negative feedback terminal is connected to the operational amplifier input S4, the output terminal is connected to the data input terminal of the high-precision AD converter U2, and the control terminal is connected to the isolation optocoupler U3; the control terminal of the high-precision AD converter U2 is connected to the isolation optocoupler U3; one control terminal of the isolation optocoupler U3 is connected to the control terminals of the switches S1 to S4, and the other control terminal is connected to the microprocessor control system; the microprocessor control system is respectively connected to a wireless communication module, a programmable electronic load R1, a high-precision voltage sensor U4, and a high-precision current sensor U5.

2. The detection circuit for the impedance spectrum of an energy storage battery according to claim 1, characterized in that, before applying the excitation current for measuring the impedance spectrum, the switch S2 is in the closed state, the switches S1, S3, and S4 are in the open state, and the balancing capacitor C1 is in the charging state; after the balancing capacitor reaches a steady state, the switches S1 and S4 are in the closed state, the switches S2 and S3 are in the open state, and the microprocessor control system controls the programmable electronic load R1 to apply a current excitation to the energy storage battery GB and collect relevant data to calculate the internal impedance spectrum information; after the impedance spectrum of the energy storage battery GB is measured, the switches S1, S2, and S4 are turned off, the switch S3 is closed, and the balancing capacitor C1 discharges to zero.

3. The detection circuit for the impedance spectrum of an energy storage battery according to claim 1, characterized in that, when the energy storage battery GB is in an offline state, the charge and discharge switch S5 is in the vacant state; when the energy storage battery GB is working, as the charge and discharge switch S5 switches, the battery is in a cyclic charge and discharge state.

4. The detection circuit for the impedance spectrum of an energy storage battery according to claim 1, characterized in that, When performing impedance spectroscopy detection, the high-precision voltage sensor U4 detects the terminal voltage of the energy storage battery GB, and the high-precision current sensor U5 detects the charge and discharge current of the energy storage battery.

5. The detection circuit for the impedance spectrum of the energy storage battery according to any one of claims 1 to 4, characterized in that, the control method of this circuit specifically includes the following steps: S1: Before applying the excitation current for measuring the impedance spectrum, disconnect switches S1, S3, and S4, close the charging switch S2, and charge the balancing capacitor C1; when the terminal voltage of the balancing capacitor C1 is equal to the terminal voltage of the energy storage battery GB, disconnect the charging switch S2, and close the operational amplifier input switches S1 and S4. At this time, the differential input voltage of the programmable instrumentation amplifier U1 is close to zero; S2: After the balancing capacitor C1 reaches a steady state, the microprocessor control system periodically collects the voltage and current data of sensors U4 and U5. The microprocessor control system adjusts the size of the programmable electronic load R1 through the PID strategy to control the charge and discharge current waveform of the energy storage battery GB, thereby applying a current excitation to the energy storage battery GB; at the same time, the microprocessor control system controls the programmable instrumentation amplifier U1 and the high-precision AD converter U2 to collect the signal of the change in the terminal voltage of the energy storage battery GB through the isolation optocoupler U3, and transmits it to the PC through the wireless communication module; S3: After detecting the impedance spectrum, disconnect the operational amplifier input switches S1 and S4, close the discharge switch S3, and discharge the balancing capacitor C1; when the terminal voltage of the balancing capacitor C1 drops to a safe voltage, disconnect the discharge switch S3.

6. The detection circuit for the impedance spectrum of the energy storage battery according to claim 5, characterized in that, in step S1, charging the balancing capacitor C1 specifically includes the following steps: S11: Before applying the excitation current for measuring the impedance spectrum, disconnect switches S1, S3, and S4, close the charging switch S2. If the initial voltage of the balancing capacitor C1 is 0, then its relevant potential is: Among them, U C1+ and U C1- are the positive and negative electrode potentials of the balancing capacitor C1, U GB+ is the DC voltage of the energy storage battery GB, U GB- is the negative electrode potential of the energy storage battery GB, τ 1 is the time constant for charging the balancing capacitor C1, R 2 is the resistance value of the charging resistor R2, C 1 is the capacitance value of the balancing capacitor C1, and t is the closing time of the switch S2; S12: 5 - 10 τ after the charging switch is closed 1 After that, the balancing capacitor C1 has been fully charged, and the terminal voltage of C1 is equal to the terminal voltage of the energy storage battery GB. Disconnect the charging switch S2 and close the operational amplifier input switches S1 and S4. The common terminal of the isolation optocoupler U3 and the balancing capacitor C1 are connected to the discharge resistor R3, and at the same time are connected to the ground terminal of the high-precision AD converter U2 and the programmable instrumentation amplifier U1. The relevant potentials of the components in the floating ground detection circuit are described by the following equations: Among them, U U3- is the common terminal potential of the isolation optocoupler U3, and U in+ , U in- and U 1GND are respectively the non-inverting input terminal potential, inverting input terminal potential and ground terminal potential of the programmable instrumentation amplifier U1; U 2GND is the ground terminal potential of the high-precision AD converter U2.

7. The detection circuit for the impedance spectrum of the energy storage battery according to claim 6, characterized in that, in step S2, detecting the impedance spectrum of the energy storage battery GB specifically includes the following steps: S21: When detecting the extremely low frequency impedance spectrum of the energy storage battery GB, a kSa(kt) pulse signal is selected as the excitation signal, and the preset current excitation waveform I 1 (t) is as follows: Among them, A S is the amplitude of the excitation signal, k is the adjustment coefficient, which is dynamically adjusted according to the requirements of measuring the impedance spectrum; t is the time variable; When detecting the low-frequency impedance spectrum of the energy storage battery GB, n sine wave composite signals with different frequencies are selected as the excitation signal, and the preset current excitation waveform I 1 (t) is as follows: where ω i is the angular frequency of the i-th preset sine wave, A i is the amplitude of the sine wave at the angular frequency ω i , is the phase at the angular frequency ω i , and t is the time variable; When detecting the high-frequency impedance spectrum of the energy storage battery GB, the Chirp signal is selected as the excitation signal, and the preset current excitation waveform I 1 (t) is as follows: Among them, A C is the amplitude of the Chirp signal, f s and f e are respectively the starting frequency and the ending frequency of the Chirp signal, t s and t e are respectively the starting time and the ending time of the Chirp signal, and t is the time variable; S22: Apply an excitation current to the energy storage battery GB through the programmable electronic load R1. The specific control method is as follows: The control system adjusts the size of the programmable electronic load R1 according to the feedback error signal I between the current value and the preset value ERROR After incremental PID operation, the actual charge and discharge current waveform of the energy storage battery GB approaches the preset current waveform. The relationship expression between the PID algorithm output R(k) and I ERROR (k) is as follows: R(k) = R(k - 1)+(K i +K d )*I ERROR (k)+(K p -2K d )I ERROR (k - 1)+K d I ERROR (k - 2) where R(k) and R(k - 1) are the magnitudes of the programmable electronic load in the k-th and (k - 1)-th control cycles respectively, and I ERROR (k) is the feedback error signal in the k-th control cycle, and K p , K i and K d are the proportional coefficient, integral coefficient, and derivative coefficient of the PID controller respectively; S23: After applying the current excitation, the terminal voltage U of the energy storage battery GB 1 (t) is expressed as follows: Among them, ω j is the angular frequency corresponding to the j-th impedance spectrum frequency point, U j is the amplitude of the AC voltage waveform at the angular frequency ω j , is the phase of the AC voltage waveform at the angular frequency ω j , t is the time variable, and m is the number of sine waves with different frequencies in the voltage U 1 (t) at the GB terminal of the energy storage battery; After step S12, the potential at the non-inverting input terminal of the programmable instrumentation amplifier U1 is U 1 (t), and the potential at the inverting input terminal is U GB , and the output terminal is the amplified AC signal component in U 1 (t); The high-precision current sensor U5 collects the charging and discharging currents of the energy storage battery GB The calculation formula for the electrochemical impedance spectrum is as follows: Among them, is the electrochemical impedance of the battery at angular frequency ω j and I j is the amplitude of the current signal at angular frequency ω j , and is the phase difference of the current waveform at angular frequency ω j . S24: Sequentially select kSa(kt) pulse signals, sine wave composite signals, and Chirp signals as current excitation signals, respectively complete the impedance spectrum measurement of the extremely low frequency, medium low frequency, and high frequency signals of the energy storage battery, and then splice the impedance spectrum curves of different frequency bands to obtain the complete impedance spectrum curve of the energy storage battery.

8. The detection circuit for the impedance spectrum of the energy storage battery according to claim 7, characterized in that, in step S3, discharging the balancing capacitor C1 specifically includes the following steps: S31: After completing the impedance spectrum detection, disconnect the operational amplifier input switches S1 and S4, close the discharge switch S3. The initial voltage of the balancing capacitor C1 is U GB+ , and its related potential is as follows: Among them, τ 2 is the time constant for discharging the balancing capacitor C1, R 3 is the resistance value of the discharge resistor R3, and t is the closing time of the switch S3; S32: After 5 - 10 τ when the discharge switch is closed 2 After that, the balancing capacitor C1 has finished discharging, the positive electrode potential of the capacitor is close to the negative electrode potential, and the discharge switch S3 is opened; as the balancing capacitor C1 discharges, the ground potential of U1, U2, and U3 in the floating - ground detection circuit "sinks", and the relevant potential is described by the following equation: U C1- = U C1+ = U U3- = U 1GND = U 2GND = 0 After the discharge is completed, the balancing capacitor C1 does not store energy.

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