Current excitation system for battery impedance spectroscopy measurement and control method thereof

Abstract

The invention provides a current excitation system for battery impedance spectroscopy measurement and a control method thereof.The current excitation system comprises a power conversion circuit and a control circuit, the power conversion circuit is connected to the two ends of a battery system in parallel, and the control circuit is connected with the power conversion circuit; the control circuit is used for acquiring a closed-loop sampling signal monitored from the power conversion circuit, and then generating a feedback control signal for controlling the power conversion circuit through a PID (Proportion Integration Differentiation) double-loop indirect control method based on the closed-loop sampling signal and the initial control signal; the power conversion circuit generates an excitation current required for battery impedance spectroscopy measurement based on the feedback control signal. The excitation current is generated by power supply of the battery system, a large amount of electric energy does not need to be consumed from the battery, and the overall implementation cost is effectively reduced through the novel circuit structure and the logic control process capable of saving computing power. According to the invention, the technical effects of simplifying the circuit topological structure and realizing low-power-consumption current excitation are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery impedance spectrum, and in particular to a current excitation system for measuring battery impedance spectrum and a control method thereof. Background Art

[0002] Electrochemical energy storage is essential for a range of applications such as electrified transportation and grid storage, so there is a need to further improve the active management and diagnostic capabilities of current battery management systems. Battery chemistries are favored for their high energy and power density, but require precise management to prevent premature degradation and failure.

[0003] Electrochemical impedance spectroscopy (EIS) is an important method for studying electrochemical interface processes. Since the measurement process does not cause damage to the battery, this method is a non-destructive measurement. It measures impedance by applying small-amplitude sinusoidal interference of different frequencies to the system. By analyzing the different frequency bands of the measured impedance spectrum, relevant information about the electrochemical reaction inside the battery can be obtained. The impedance spectrum of the battery is mainly affected by the charge state, temperature and aging state. By studying the change trend of each impedance parameter with the influencing factors, a suitable functional relationship can be established to predict the charge state, health state and remaining service life of the battery. Traditional electrochemical impedance spectroscopy measurement methods include offline measurement methods and online measurement methods. Offline measurement refers to the use of professional electrochemical impedance spectroscopy test instruments in the laboratory to measure a single battery or multiple batteries. These batteries must be removed from the actual application circuit system before testing, and these professional test instruments are expensive. Therefore, the offline measurement method can only be used for academic research and is difficult to be applied to the online monitoring of battery impedance spectra in actual battery systems. Another measurement method is online measurement, which usually adds an auxiliary circuit to the battery system. However, the existing online measurement circuit structure and measurement method are relatively complex, and there is a lack of low-cost and effective measurement methods.

[0004] That is, how to provide a current excitation system and a control method thereof for battery impedance spectrum measurement to achieve the technical effect of simplifying the circuit topology and realizing low-power current excitation is a technical problem that urgently needs to be solved in this field. Summary of the invention

[0005] In view of the above-mentioned problems, the present invention aims to provide a current excitation system and a control method thereof for battery impedance spectrum measurement, so as to solve at least one of the above-mentioned technical problems.

[0006] In a first aspect, the present invention provides a current excitation system for measuring a battery impedance spectrum, the current excitation system comprising:

[0007] A power conversion circuit and a control circuit, wherein the power conversion circuit is connected in parallel to two ends of the battery system, and the control circuit is connected to the power conversion circuit;

[0008] The control circuit is used to obtain a closed-loop sampling signal monitored from the power conversion circuit, and then generate a feedback control signal for controlling the power conversion circuit based on the closed-loop sampling signal and the initial control signal through a PID double-loop indirect control method; the power conversion circuit generates an excitation current required for battery impedance spectrum measurement based on the feedback control signal.

[0009] Preferably, the power conversion circuit comprises:

[0010] A filter circuit, wherein the positive electrode of the output end of the filter circuit is connected to the positive electrode of the battery system, and the negative electrode of the output end of the filter circuit is connected to the negative electrode of the battery system;

[0011] An inductor L1, one end of which is connected to the positive input terminal of the filter circuit;

[0012] A semiconductor switch tube Q1, wherein a current output end of the semiconductor switch tube Q1 is connected to the other end of the inductor L1;

[0013] Capacitor C d , the capacitor C d The positive electrode is connected to the current input terminal of the semiconductor switch tube Q1, and the capacitor C d The negative electrode is connected to the negative electrode of the input end of the filter circuit;

[0014] The semiconductor switch tube Q2 has a current input end connected to the other end of the inductor L1 and a current output end of the semiconductor switch tube Q1, and a current output end of the semiconductor switch tube Q2 connected to the capacitor C d The negative electrode of is connected to the negative electrode of the input end of the filter circuit;

[0015] The signal output end of the control circuit is correspondingly connected to the control end of the semiconductor switch tube Q1 and the control end of the semiconductor switch tube Q2.

[0016] Preferably, the power conversion circuit further includes:

[0017] A current sensor, the current sensor is connected in series between the negative electrode of the input end of the filter circuit and the negative electrode of the battery system;

[0018] A voltage sensor is connected in parallel to the capacitor C d at both ends;

[0019] Wherein, the signal input end of the control circuit is correspondingly connected to the current sensor and the voltage sensor.

[0020] Preferably, before acquiring the closed-loop sampling signal monitored from the power conversion circuit, the control circuit is further used to:

[0021] The initial control signal of the power conversion circuit is preset based on a setting signal of an excitation current and a capacitor voltage setting value generated by a battery impedance spectrum measurement requirement, and the initial control signal includes a control duty cycle of the semiconductor switch tube Q1 and the semiconductor switch tube Q2 to start the power conversion circuit through the initial control signal.

[0022] Preferably, the capacitor C d The actual voltage should be higher than the battery voltage of the battery system.

[0023] Preferably, the setting signal of the excitation current includes the frequency and amplitude of the excitation current.

[0024] Preferably, the acquiring of the closed-loop sampling signal monitored from the power conversion circuit comprises:

[0025] Real-time acquisition of the capacitance C monitored by the voltage sensor d A plurality of capacitor voltage sampling values ​​are obtained, and a voltage sampling average value is calculated based on the plurality of capacitor voltage sampling values; a current sampling feedback value obtained by monitoring the current sensor is obtained in real time, and the voltage sampling average value and the current sampling feedback value constitute the closed-loop sampling signal.

[0026] Preferably, the PID double-loop indirect control method comprises:

[0027] Subtract the current sampling feedback value from the AC sinusoidal waveform formed by the setting signal of the excitation current to obtain a current loop error signal;

[0028] Subtract the capacitor voltage setting value from the voltage sampling average value to obtain a voltage loop error signal;

[0029] The voltage loop error signal is superimposed on the current loop error signal to obtain a PID dual-loop indirect control signal, and then the PID dual-loop indirect control signal is converted into a modulation wave;

[0030] The modulated wave is compared with a carrier wave to obtain a feedback control signal for controlling the power conversion circuit, wherein the feedback control signal is a complementary pulse width modulation (PWM) wave for driving the semiconductor switch tube Q1 and the semiconductor switch tube Q2 respectively.

[0031] In a second aspect, the present application also provides a control method for a current excitation system for battery impedance spectrum measurement, the control method comprising:

[0032] Connecting the current excitation system described in any one of the first aspects in parallel to two ends of the battery system, and then determining the control parameters of the current excitation system according to the operating conditions of the battery system;

[0033] When the battery system is in a stationary state, disconnecting the battery system from a power grid, and then starting the current excitation system to generate an excitation current in the battery system;

[0034] When the current excitation system enters a steady-state working mode, the control parameter is modified according to the battery impedance spectrum measurement requirement to inject the excitation current corresponding to different control parameters into the battery system;

[0035] After completing the battery impedance spectrum measurement, the current excitation system is turned off, the battery system is reconnected to the power grid, and the battery system resumes normal operation.

[0036] Preferably, the control parameters include a capacitor voltage setting value and a frequency and an amplitude required for an excitation current generated according to a battery impedance spectrum measurement requirement.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] Specifically, the present invention provides a current excitation system for measuring battery impedance spectrum, including a power conversion circuit and a control circuit, wherein the power conversion circuit is connected in parallel to both ends of the battery system, and the control circuit is connected to the power conversion circuit; the control circuit is used to obtain a closed-loop sampling signal monitored from the power conversion circuit, and then generate a feedback control signal for controlling the power conversion circuit through a PID double-loop indirect control method based on the closed-loop sampling signal and the initial control signal; the power conversion circuit generates the excitation current required for battery impedance spectrum measurement based on the feedback control signal. The present application sets a power conversion circuit at both ends of the battery system, and establishes a closed-loop control of the power conversion circuit through the control circuit to generate the excitation current required for battery impedance spectrum measurement, that is, the excitation current of the present application is generated by the battery system itself, without consuming a large amount of electric energy from the battery, and the control circuit can be digitally realized by a microcontroller unit, thereby providing an AC current excitation signal with a wide frequency range, and the new circuit structure and the logic control process that saves computing power effectively reduce the overall implementation cost. The battery terminal voltage can be detected later to calculate and draw its impedance spectrum. It provides a solution basis for monitoring the health or aging of batteries through electrochemical impedance spectroscopy measurement. The present application achieves the technical effect of simplifying the circuit topology and realizing low-power current excitation.

[0039] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 This is a schematic diagram of the structure of a current excitation system for measuring battery impedance spectrum in an embodiment of the present application;

[0042] Figure 2 This is a flow chart of a control method for using a current excitation system for battery impedance spectrum measurement in an embodiment of the present application;

[0043] Figure 3 This is a waveform diagram of the excitation current generated by the current excitation system in the battery system in the embodiment of the present application. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of this specification to clearly and completely describe the technical solutions in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention; the "and / or" keyword involved in this implementation represents both and, or. In other words, A and / or B mentioned in the embodiments of this specification represent both A and B, and A or B, and describe the three states of A and B. For example, A and / or B means: only A is included but not B; only B is included but not A; A and B are included.

[0045] Meanwhile, in the embodiments of this specification, when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a central component at the same time. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be a central component at the same time.

[0046] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0047] Embodiment 1

[0048] See also Figure 1 Specifically, in the implementation manner of the current excitation system for measuring the battery impedance spectrum, the current excitation system provided in the embodiment of the present application specifically includes: a power conversion circuit and a control circuit, wherein the power conversion circuit is connected in parallel to the two ends of the battery system, and the control circuit is connected to the power conversion circuit; the control circuit is used to obtain a closed-loop sampling signal monitored from the power conversion circuit, and then generate a feedback control signal for controlling the power conversion circuit based on the closed-loop sampling signal and the initial control signal through a PID dual-loop indirect control method; the power conversion circuit generates the excitation current required for the battery impedance spectrum measurement based on the feedback control signal.

[0049] Specifically, an embodiment of the present invention provides a current excitation system for measuring battery impedance spectrum, including a power conversion circuit and a control circuit, wherein the power conversion circuit is connected in parallel to both ends of the battery system, and the control circuit is connected to the power conversion circuit; the control circuit is used to obtain a closed-loop sampling signal monitored from the power conversion circuit, and then generate a feedback control signal for controlling the power conversion circuit through a PID double-loop indirect control method based on the closed-loop sampling signal and the initial control signal; the power conversion circuit generates the excitation current required for battery impedance spectrum measurement based on the feedback control signal. The present application sets a power conversion circuit at both ends of the battery system, and establishes a closed-loop control of the power conversion circuit through the control circuit to generate the excitation current required for battery impedance spectrum measurement, that is, the excitation current of the embodiment of the present application is generated by the battery system itself, without consuming a large amount of electrical energy from the battery, and the control circuit can be digitized by a microcontroller unit to provide an AC current excitation signal with a wide frequency range. The new circuit structure and the logic control process that saves computing power effectively reduce the overall implementation cost. The battery terminal voltage can be detected later to calculate and draw its impedance spectrum. It provides a solution basis for monitoring the health or aging of batteries through electrochemical impedance spectroscopy measurement. The embodiments of the present application achieve the technical effect of simplifying the circuit topology and realizing low-power current excitation.

[0050] In a possible implementation, the power conversion circuit includes a filter circuit, an inductor L1, a semiconductor switch tube Q1, and a capacitor C dand semiconductor switch tube Q2, the positive electrode of the output end of the filter circuit is connected to the positive electrode of the battery system, and the negative electrode of the output end of the filter circuit is connected to the negative electrode of the battery system; one end of the inductor L1 is connected to the positive electrode of the input end of the filter circuit; the current output end of the semiconductor switch tube Q1 is connected to the other end of the inductor L1; the capacitor C d The positive electrode is connected to the current input terminal of the semiconductor switch tube Q1, and the capacitor C d The negative electrode of is connected to the negative electrode of the input end of the filter circuit; the current input end of the semiconductor switch tube Q2 is respectively connected to the other end of the inductor L1 and the current output end of the semiconductor switch tube Q1, and the current output end of the semiconductor switch tube Q2 is respectively connected to the capacitor C d The negative electrode of the control circuit is connected to the negative electrode of the input end of the filter circuit; wherein the signal output end of the control circuit is correspondingly connected to the control end of the semiconductor switch tube Q1 and the semiconductor switch tube Q2.

[0051] Specifically, the current excitation system of the present application is composed of a power conversion circuit and a group of control circuits. d To achieve energy exchange and buffering. Generate a setting signal for the excitation current according to the impedance spectrum measurement requirements, and the semiconductor switch tube Q1 and the semiconductor switch tube Q2 are driven by complementary pulse width modulation PWM waves.

[0052] The specific working mode of the current excitation system provided in this application is:

[0053] When the excitation current I on the battery system side is monitored by the current sensor c When the positive, the battery discharges to the capacitor C d Charging, when the excitation current I c When it is negative, the capacitance C d Discharge to charge the battery, the excitation current periodically flows to the capacitor C d The battery charges and discharges, thus generating a periodic AC excitation current. d When the voltage is lower than the set value, the excitation circuit is in the Boost working mode, and the battery supplies the capacitor C d The side discharge increases the capacitor voltage. In a semiconductor switch control timing cycle, in the positive half cycle, the semiconductor switch tube Q2 is turned on and the semiconductor switch tube Q1 is turned off. The battery, inductor L1, and semiconductor switch tube Q2 form a discharge loop. When the current flows through the inductor, the electrical energy is converted into magnetic field energy and stored in the inductor, which increases the inductor terminal voltage. In the negative half cycle, the semiconductor switch tube Q1 is turned on and Q2 is turned off. The battery and the inductor L1 terminal voltages are added together to the capacitor C. d Charge the capacitor C d The voltage increases and is greater than the battery voltage. The semiconductor switch tubes Q1 and Q2 are turned on alternately, causing the battery to continuously discharge to the capacitor, which can increase the capacitor voltage. dWhen the voltage is higher than the set value, the excitation circuit is in Buck step-down mode, and the capacitor C d The battery is charged to reduce the capacitor voltage. In a semiconductor switch control timing cycle, the semiconductor switch tube Q1 is turned on and the semiconductor switch tube Q2 is turned off in the positive half cycle. Because the capacitor voltage is higher than the battery voltage, the capacitor charges the battery. When the current flows through the inductor, the electrical energy is converted into magnetic field energy and stored in the inductor. In the negative half cycle, the semiconductor switch tube Q2 is turned on and the semiconductor switch tube Q1 is turned off. The battery, the inductor L1, and the anti-parallel diode of the semiconductor switch tube Q2 form a current loop. The inductor magnetic field energy is converted into current and continues to charge the battery. The semiconductor switch tube Q1 and the semiconductor switch tube Q2 are alternately turned on to allow the capacitor to continue to charge the battery, which can reduce the capacitor voltage. In the alternating operation of the Boost working mode and the Buck working mode, an AC excitation current is generated on the battery.

[0054] In a possible implementation, the power conversion circuit further includes a current sensor and a voltage sensor, wherein the current sensor is connected in series between the negative electrode of the input end of the filter circuit and the negative electrode of the battery system; and the voltage sensor is connected in parallel to the capacitor C d The two ends of the control circuit are connected to the current sensor and the voltage sensor. The voltage sensor can be used to monitor the capacitance C in real time. d The actual voltage is monitored in real time by the current sensor to obtain the excitation current on the battery side.

[0055] In a possible implementation manner, before acquiring the closed-loop sampling signal monitored from the power conversion circuit, the control circuit is further configured to:

[0056] The initial control signal of the power conversion circuit is preset based on the setting signal of the excitation current and the setting value of the capacitor voltage generated by the battery impedance spectrum measurement requirement. The setting signal of the excitation current and the setting value of the capacitor voltage generated based on the battery impedance spectrum measurement requirement can be control parameters of the current excitation system set in advance. The initial control signal includes a control duty cycle of the semiconductor switch tube Q1 and the semiconductor switch tube Q2 to start the power conversion circuit through the initial control signal.

[0057] Since the battery voltage is stable or changes slowly, and the AC voltage response generated by the excitation current on the battery is small, it can be approximately considered that the capacitor C d The actual voltage U c and the battery voltage U of the battery system b The following characteristics are maintained:

[0058]

[0059] Wherein d is the control duty cycle of the semiconductor switch tube in the bidirectional Buck / Boost current excitation system, that is, the control duty cycle of the semiconductor switch tube Q1 is the ratio of the conduction time of the semiconductor switch tube Q1 to the control period in one control timing cycle; the control duty cycle of the semiconductor switch tube Q2 is the ratio of the conduction time of the semiconductor switch tube Q2 to the control period in one control timing cycle.

[0060] Therefore, the control duty ratio of the semiconductor switches Q1 and Q2 can be preset according to the setting signal of the excitation current generated by the battery impedance spectrum measurement requirement and the capacitor voltage setting value B.

[0061] As an achievable method, the preset process of the initial control signal of the present application can be specifically implemented through the following process:

[0062] Since the excitation current is a sine wave, the capacitor C d The actual voltage U c (t) must present a sinusoidal wave fluctuation, and its mathematical expression is:

[0063]

[0064] Where B is the capacitor voltage setting value set in advance, which is the DC component; f sine is the frequency of the set AC excitation current; C is the DC side capacitance C d The capacitance value; Based on the above expression, the mathematical expression for controlling the duty cycle d can be obtained:

[0065]

[0066] So far, the expression of the semiconductor switch tube control signal duty cycle d(t) is obtained.

[0067] The t in the expression can be set to 0, and the finally calculated control duty cycle can be used as the initial control signal of the power conversion circuit to start the power conversion circuit, so as to generate an excitation current based on the initial control signal, and continuously correct it through the closed-loop control logic of the control circuit to obtain the excitation current required for impedance spectrum measurement.

[0068] In one possible implementation, the capacitor C d The actual voltage should be higher than the battery voltage of the battery system.

[0069] Specifically, the PID dual-loop indirect control method involved in the present application involves a voltage control loop and a current control loop, and the voltage control loop can be implemented using a PI controller, and the current control loop can be implemented using a PID controller. The output of the voltage control loop is added to the current reference signal as the input of the current control loop to generate a current DC bias, which will bias the capacitor Cd Charge / discharge to maintain the capacitor C d The actual voltage of is stable and slightly higher than the battery voltage. Therefore, the capacitor C d The actual voltage should be slightly higher than the battery voltage, so that the semiconductor switch tube can be turned on normally under the control signal and maintain the normal operation of the circuit.

[0070] In a possible implementation, the setting signal of the excitation current includes the frequency and amplitude of the excitation current. The expression and waveform of the excitation current can be determined by the frequency and amplitude of the excitation current.

[0071] In a possible implementation manner, obtaining a closed-loop sampling signal monitored from a power conversion circuit includes:

[0072] Real-time acquisition of the capacitance C monitored by the voltage sensor d A plurality of capacitor voltage sampling values ​​are obtained, and a voltage sampling average value is calculated based on the plurality of capacitor voltage sampling values; a current sampling feedback value obtained by monitoring by a current sensor is obtained in real time, and the voltage sampling average value and the current sampling feedback value constitute a closed-loop sampling signal.

[0073] The specific number of capacitor voltage sampling values ​​required to calculate the voltage sampling average value is determined by actual engineering test requirements.

[0074] In a possible implementation manner, the PID dual-loop indirect control method involved in the present application includes the following specific steps:

[0075] The current loop error signal is obtained by subtracting the current sampling feedback value from the AC sinusoidal waveform formed by the setting signal of the excitation current;

[0076] Subtract the capacitor voltage setting value from the voltage sampling average value to obtain the voltage loop error signal;

[0077] The voltage loop error signal is superimposed on the current loop error signal to obtain a PID dual-loop indirect control signal, and then the PID dual-loop indirect control signal is converted into a modulation wave;

[0078] The modulated wave is compared with the carrier wave to obtain a feedback control signal for controlling the power conversion circuit. The feedback control signal is a complementary pulse width modulation PWM wave for driving the semiconductor switch tube Q1 and the semiconductor switch tube Q2 respectively.

[0079] From the capacitor C d The voltage control loop is obtained by subtracting the capacitor voltage setting value from the voltage sampling average value. The error between the two can be calculated by the voltage loop controller of the voltage control loop to obtain the voltage loop error signal. Through this closed-loop control, it is ensured that the capacitor voltage sampling average value is approximately equal to the capacitor voltage setting value and the actual capacitor voltage Uc The average change in one cycle is zero. Since the semiconductor switching frequency of the Buck-Boost converter is much higher than the frequency of the sinusoidal excitation current, the average capacitor current in the switching cycle can be approximated as the instantaneous battery current. The AC sinusoidal waveform of the required frequency and amplitude of the excitation current is subtracted from the current sampling feedback amount, and then superimposed on the voltage loop error signal obtained from the voltage loop controller to obtain the PID dual-loop indirect control signal, thereby generating a modulation wave. The voltage control loop and the current control loop in the PID dual-loop indirect control are implemented by operational amplifiers. By comparing the modulation wave with the carrier, the drive signal of the semiconductor switch tube Q1 and Q2 can be obtained. The drive signal of the semiconductor switch tube Q1 and the drive signal of the semiconductor switch tube Q2 are opposite and complementary in positive and negative directions, and the drive signal is a complementary pulse width modulation PWM wave.

[0080] In a second aspect, the present application also provides a method for controlling a current excitation system for measuring a battery impedance spectrum, the control method specifically comprising the following steps:

[0081] The current excitation system of any one of the above-mentioned embodiments 1 is connected in parallel to both ends of the battery system, and then the control parameters of the current excitation system are determined according to the working conditions of the battery system; wherein the control parameters include the capacitor voltage setting value, the frequency and amplitude required for the excitation current generated by the battery impedance spectrum measurement requirements;

[0082] When the battery system is in a static state, the battery system is disconnected from the power grid, and then the current excitation system is started to generate an excitation current in the battery system;

[0083] When the current excitation system enters a steady-state working mode, the control parameters are modified according to the battery impedance spectrum measurement requirements to inject the excitation current corresponding to different control parameters into the battery system;

[0084] After completing the battery impedance spectrum measurement, the current excitation system is turned off, the battery system is reconnected to the power grid, and the battery system resumes normal operation.

[0085] Figure 2 The flowchart of the control method of the bidirectional Buck-Boost current excitation system for battery impedance spectrum measurement is shown. The process of using the current excitation system to assist the battery system in performing a complete impedance spectrum measurement is as follows:

[0086] (1) First, the current excitation system of any one of the above-mentioned embodiments is connected in parallel to the two ends of the battery system, and the control parameters of the current excitation system, such as the frequency and amplitude of the excitation current and the capacitor voltage setting value, are determined according to the working conditions of the battery system;

[0087] (2) When the battery system is in a static state, cut off the connection between the battery system and the power grid to prevent the power grid from interfering with the operation of the excitation system and the electrochemical impedance spectroscopy measurement; after confirming the disconnection, start the current excitation system to generate an excitation current in the battery system, and the capacitor C d Charged by battery system;

[0088] (3) At capacitor C d When the charging reaches the capacitor voltage setting value, the current excitation system enters the steady-state working mode. Then, the control parameters are modified according to the battery impedance spectrum measurement requirements to inject the excitation current corresponding to different control parameters into the battery system, so that sinusoidal currents of various frequencies can be injected into the battery system.

[0089] (4) After the battery impedance spectrum measurement is completed, the current excitation system is turned off, the battery system is reconnected to the power grid, and the battery system resumes normal operation. That is, after the impedance spectrum measurement is completed, the semiconductor switch tubes Q1 and Q2 are all turned off, and then the battery system is reconnected to the power grid, and the battery system resumes normal operation.

[0090] Since the generation of sinusoidal current requires a transient process to enter a steady state, the accuracy of the impedance spectrum test is related to the battery state. Therefore, before generating the sinusoidal excitation current of each frequency, the battery can be left to stand for a short period of time to reach a stable state so that the chemical reaction of the battery is more stable. The control parameters of the excitation current can be modified according to the actual engineering situation. After the impedance spectrum measurement is completed, the semiconductor switch tubes Q1 and Q2 are all turned off, the battery system is reconnected to the power grid, and the battery system resumes normal operation.

[0091] Figure 3 The following figure shows the excitation current waveform generated by the current excitation system on the battery system in a specific embodiment. The current waveform can quickly enter a stable state, providing excitation current conditions for impedance spectrum measurement. The specific frequency and amplitude values ​​and changes can be determined by the impedance spectrum measurement requirements and adjusted in real time.

[0092] In general, the above technical solutions proposed by the present invention can achieve the following beneficial effects:

[0093] The present invention uses AC current excitation generated by the battery itself, without consuming a large amount of electrical energy from the battery. It is implemented digitally through the control circuit, thereby providing an AC current excitation signal with a wide frequency range. The new circuit structure and the logic control process that saves computing power effectively reduce the overall implementation cost. The battery terminal voltage can be subsequently detected and its impedance spectrum can be calculated and drawn. This provides a solution basis for monitoring the health or aging of batteries through electrochemical impedance spectroscopy measurements.

[0094] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0095] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A current excitation system for battery impedance spectrum measurement, characterized in that: The current excitation system comprises: a power conversion circuit and a control circuit, wherein the power conversion circuit is connected in parallel to two ends of the battery system, and the control circuit is connected to the power conversion circuit; The control circuit is used to obtain a closed-loop sampling signal monitored from the power conversion circuit, and then generate a feedback control signal for controlling the power conversion circuit based on the closed-loop sampling signal and the initial control signal through a PID double-loop indirect control method; the power conversion circuit generates an excitation current required for battery impedance spectrum measurement based on the feedback control signal.

2. The current excitation system for battery impedance spectrum measurement according to claim 1, characterized in that: The power conversion circuit comprises: A filter circuit, wherein the positive electrode of the output end of the filter circuit is connected to the positive electrode of the battery system, and the negative electrode of the output end of the filter circuit is connected to the negative electrode of the battery system; An inductor L1, one end of which is connected to the positive input terminal of the filter circuit; A semiconductor switch tube Q1, wherein a current output end of the semiconductor switch tube Q1 is connected to the other end of the inductor L1; Capacitor C d , the capacitor C d The positive electrode is connected to the current input terminal of the semiconductor switch tube Q1, and the capacitor C d The negative electrode is connected to the negative electrode of the input end of the filter circuit; The semiconductor switch tube Q2 has a current input end connected to the other end of the inductor L1 and a current output end of the semiconductor switch tube Q1, and a current output end of the semiconductor switch tube Q2 connected to the capacitor C d The negative electrode of is connected to the negative electrode of the input end of the filter circuit; The signal output end of the control circuit is correspondingly connected to the control end of the semiconductor switch tube Q1 and the control end of the semiconductor switch tube Q2.

3. The current excitation system for battery impedance spectrum measurement according to claim 2, characterized in that: The power conversion circuit further includes: A current sensor connected in series between the negative electrode of the input end of the filter circuit and the negative electrode of the battery system; A voltage sensor is connected in parallel to the capacitor C d at both ends; Wherein, the signal input end of the control circuit is connected to the current sensor and the voltage sensor accordingly.

4. The current excitation system for battery impedance spectrum measurement according to claim 3, characterized in that: Before acquiring the closed-loop sampling signal monitored from the power conversion circuit, the control circuit is further used to: The initial control signal of the power conversion circuit is preset based on a setting signal of an excitation current and a capacitor voltage setting value generated by a battery impedance spectrum measurement requirement, and the initial control signal includes a control duty cycle of the semiconductor switch tube Q1 and the semiconductor switch tube Q2 to start the power conversion circuit through the initial control signal.

5. The current excitation system for battery impedance spectrum measurement according to claim 4, characterized in that: The capacitor C d The actual voltage should be higher than the battery voltage of the battery system.

6. The current excitation system for battery impedance spectrum measurement according to claim 5, characterized in that: The setting signal of the excitation current includes the frequency and amplitude of the excitation current.

7. The current excitation system for battery impedance spectrum measurement according to claim 6, characterized in that: The step of acquiring a closed-loop sampling signal monitored from the power conversion circuit comprises: Real-time acquisition of the capacitance C monitored by the voltage sensor d A plurality of capacitor voltage sampling values ​​are obtained, and a voltage sampling average value is calculated based on the plurality of capacitor voltage sampling values; a current sampling feedback value obtained by monitoring the current sensor is obtained in real time, and the voltage sampling average value and the current sampling feedback value constitute the closed-loop sampling signal.

8. The current excitation system for battery impedance spectrum measurement according to claim 7, characterized in that: The PID double-loop indirect control method comprises: Subtract the current sampling feedback value from the AC sinusoidal waveform formed by the setting signal of the excitation current to obtain a current loop error signal; Subtract the capacitor voltage setting value from the voltage sampling average value to obtain a voltage loop error signal; The voltage loop error signal is superimposed on the current loop error signal to obtain a PID dual-loop indirect control signal, and then the PID dual-loop indirect control signal is converted into a modulation wave; The modulated wave is compared with a carrier wave to obtain a feedback control signal for controlling the power conversion circuit, wherein the feedback control signal is a complementary pulse width modulation (PWM) wave for driving the semiconductor switch tube Q1 and the semiconductor switch tube Q2 respectively.

9. A control method for a current excitation system for battery impedance spectrum measurement, characterized in that: The control method comprises: Connecting the current excitation system described in any one of claims 1 to 8 in parallel to two ends of the battery system, and then determining the control parameters of the current excitation system according to the operating conditions of the battery system; When the battery system is in a stationary state, disconnecting the battery system from a power grid, and then starting the current excitation system to generate an excitation current in the battery system; When the current excitation system enters a steady-state working mode, the control parameter is modified according to the battery impedance spectrum measurement requirement to inject the excitation current corresponding to different control parameters into the battery system; After completing the battery impedance spectrum measurement, the current excitation system is turned off, the battery system is reconnected to the power grid, and the battery system resumes normal operation.

10. The control method of the current excitation system for battery impedance spectrum measurement according to claim 9, characterized in that: The control parameters include a capacitor voltage setting value and a frequency and an amplitude of an excitation current generated according to a battery impedance spectrum measurement requirement.

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