A Battery Impedance Identification Method Based on Inverter Constant Amplitude AC Small Signal Injection

Abstract

This invention belongs to the field of energy storage batteries, specifically relating to a battery impedance identification method based on inverter constant-amplitude AC small-signal injection. The method includes: closed-loop control of the battery-inverter-load system; the inverter AC side reference current signal used is the sum of the fundamental reference current signal and the injected reference current signal; wherein the injected reference current signal is a constant-amplitude AC small signal, and by adjusting the frequency of the constant-amplitude AC small signal, excitation at the target frequency can be injected into the battery; when the load is a multi-phase load, the phase sequence of the injected reference current signal is reflected by the phase of each phase's constant-amplitude AC small signal; based on the real-time current signal and real-time voltage signal at the battery terminal, the battery impedance at the target frequency is calculated. This invention can perform wide-frequency range battery impedance spectrum identification on battery systems, battery modules, or battery cells under different operating conditions online.

Description

Technical Field

[0001] This invention belongs to the field of energy storage batteries, and more specifically, relates to a battery impedance identification method based on constant amplitude AC small signal injection from an inverter. Background Technology

[0002] Electrochemical impedance spectroscopy (EIS), as a non-destructive parametric measurement technique, can effectively determine battery kinetic behavior and is widely used to assess battery state of charge, state of health, and state of energy. Simultaneously, battery impedance spectroscopy can be used to estimate the internal temperature and dendrite growth state of a battery, thus providing support for addressing safety issues such as battery thermal runaway, short circuits, and abuse.

[0003] The current battery electrochemical impedance measurement process has four main characteristics: (1) it adopts an offline measurement method, that is, the battery needs to be separated from its application scenario and measured separately; (2) there are certain requirements for the scale of the object to be measured, even the more advanced measurement equipment can only directly measure small and medium-sized battery systems; (3) it is carried out under static conditions, that is, only the impedance data of the battery in a static state can be obtained; (4) it has high requirements for measurement equipment, mainly using electrochemical workstations, frequency response analyzers, impedance analyzers, precision LCR instruments, etc.

[0004] Analysis revealed the following problems with the above features: Regarding feature (1), offline measurement would hinder the normal operation of the device under test; Regarding feature (2), existing measurement equipment is difficult to directly measure the impedance of large battery systems. For large-scale batteries under test, it is necessary to split them up for measurement; Regarding feature (3), the impedance performance of batteries varies under different operating conditions. Only the dynamic impedance spectrum measured during the actual use of the battery can effectively characterize the true characteristics of the battery under the current operating conditions. Therefore, the results measured under the current static operating conditions cannot effectively reflect the true impedance of the battery; Regarding feature (4), the high cost of professional testing equipment is one of the main bottlenecks in the promotion and popularization of battery impedance measurement.

[0005] Based on the battery-inverter topology, due to the influence of factors such as inverter dead time and load imbalance, the voltage and current flowing through the battery contain the fundamental frequency and its even multiples. Patent CN102768304A uses the voltage and current components with larger amplitudes in these frequency components to identify the battery impedance. However, although this scheme is an online measurement, it has the following problems: (1) The invention models the battery under test as a first-order RC equivalent circuit, which has a strong subjectivity in the selection of the battery model and cannot fully reflect the various polarization characteristics of the battery, that is, there is an inherent error in the modeling stage; (2) The invention only selects three points with larger amplitudes from the above frequencies to solve the circuit equation, and the results obtained do not have universality for other points in the frequency domain; (3) The invention relies on the fundamental component and cannot be applied offline; (4) The invention is based on the ripple component generated on the DC side by factors such as inverter dead time and load imbalance, and its magnitude and frequency are to some extent uncontrollable; (5) The invention cannot analyze the battery impedance below the fundamental frequency.

[0006] Based on the same battery-inverter topology, another patent, CN113281668B, uses the inverter to inject the excitation of the switch and its multiple ripples into the battery terminal, thereby realizing the identification of the battery's high-frequency impedance, but it cannot obtain the battery impedance information in the mid-to-low frequency range.

[0007] In summary, developing a method for online impedance testing of battery systems, battery modules, or individual battery cells under different operating conditions is an urgent problem to be solved in this field. Summary of the Invention

[0008] To address the shortcomings and improvement needs of existing technologies, this invention provides a battery impedance identification method based on inverter constant amplitude AC small signal injection. The purpose is to provide a method for online impedance testing of battery systems, battery modules, or battery cells under different operating conditions.

[0009] To achieve the above objectives, according to one aspect of the present invention, a battery impedance identification method based on inverter constant-amplitude AC small-signal injection is provided, comprising:

[0010] A closed-loop control is performed on the battery-inverter-load system. The inverter AC side reference current signal used in the control process is the sum of the fundamental reference current signal and the injected reference current signal. The injected reference current signal is a constant amplitude AC small signal. By adjusting the frequency of the constant amplitude AC small signal, the target frequency excitation can be injected into the battery. When the load is a multi-phase load, the phase sequence of the injected reference current signal is reflected by the phase of each phase constant amplitude AC small signal.

[0011] Based on the real-time current and voltage signals at the battery terminal, the battery impedance at the target frequency is calculated.

[0012] Furthermore, when the load is a multiphase load, the constant amplitude AC small signal is the sum of a positive sequence constant amplitude AC small signal, a negative sequence constant amplitude AC small signal, or a positive sequence constant amplitude AC small signal and a negative sequence constant amplitude AC small signal.

[0013] Furthermore, the frequency set of the response signal of the constant amplitude AC small signal on the DC side includes the target frequency, and the relationship between the target frequency and the frequency of the constant amplitude AC small signal is as follows:

[0014] When the load is a single-phase load, the target frequency is: , , ;in, The frequency of the constant amplitude AC small signal is... The fundamental reference signal frequency;

[0015] When the load is a multiphase load, and the injected reference current signal is a positive-sequence constant-amplitude AC small signal, then the target frequency is: When the injected reference current signal is a negative-sequence constant-amplitude AC small signal, the target frequency is: When the injected reference current signal is the sum of a positive-sequence constant-amplitude AC small signal and a negative-sequence constant-amplitude AC small signal, then the target frequency is... , , ;in, , These are the frequencies of the positive and negative sequence constant amplitude AC small signals, respectively. The fundamental reference signal frequency is denoted as .

[0016] Furthermore, the amplitude of the constant amplitude AC small signal satisfies the condition that the amplitude of the battery current component at the target frequency is not less than the current threshold. Meanwhile, the amplitude of the battery voltage component at the target frequency is not less than the voltage threshold. Among them, the current threshold and voltage threshold The selection needs to meet the signal-to-noise ratio requirements.

[0017] Furthermore, when the load is a single-phase load, or when the load is a multi-phase load and the injected reference current signal is a positive-sequence constant-amplitude AC small signal or a negative-sequence constant-amplitude AC small signal, the implementation method of each control cycle in the closed-loop control is as follows:

[0018] AC side of the inverter n Phase current signal and inverter DC side voltage signal Filtering and sampling are performed to obtain the AC side of the inverter after filtering and sampling. n Phase current signal and inverter DC side voltage signal ;in, ;

[0019] Based on the AC side of the inverter n Phase reference current signal The fundamental reference current signal and injected reference current signal The sum of will respectively with , Doing the difference corresponds to... n Fundamental feedback current signal in phase stationary coordinate system Inject feedback current signal ;Will , , , Transforming to a synchronous rotating coordinate system yields the fundamental reference current signal in that coordinate system. Inject reference current signal Fundamental feedback current signal Inject feedback current signal ;

[0020] use , , , and Execute the closed-loop decoupling control algorithm to generate duty cycle commands. The closed-loop decoupling control algorithm includes fundamental current closed-loop control and injected current closed-loop control. The fundamental current closed-loop control is as follows: [The text abruptly ends here, so the translation stops as well.] and The corresponding components are subtracted, and the differences between each component are processed by a PI controller to obtain the fundamental reference voltage signal in the synchronous rotating coordinate system. The injected current closed-loop control is as follows: for and The corresponding components are subtracted, and each difference is processed by a PI controller to obtain the injected reference voltage signal in the synchronous rotating coordinate system. ;right and Sum the corresponding components respectively, and transform to n In the stationary coordinate system, the reference voltage signal is obtained. Based on this, a duty cycle signal is generated. ,based on A PWM pulse signal is generated and transmitted to the inverter to complete one cycle of control.

[0021] Furthermore, when the load is a multiphase load, and the injected reference current signal is the sum of a positive-sequence constant-amplitude AC small signal and a negative-sequence constant-amplitude AC small signal, the implementation method of each control cycle in the closed-loop control is as follows:

[0022] AC side of the inverter n Phase current signal and inverter DC side voltage signal Filtering and sampling are performed to obtain the AC side of the inverter after filtering and sampling. n Phase current signal and inverter DC side voltage signal ;in, ;

[0023] Based on the AC side of the inverter n Phase reference current signal The fundamental reference current signal Positive sequence injection of reference current signal and negative sequence injected reference current signal The sum of will respectively with , , Doing the difference corresponds to... n Fundamental feedback current signal in phase stationary coordinate system Positive sequence injection feedback current signal Negative sequence injection feedback current signal ;Will , , , , , Transforming to a synchronous rotating coordinate system yields the fundamental reference current signal in that coordinate system. Positive sequence injection of reference current signal Negative sequence injection reference current signal Fundamental feedback current signal Positive sequence injection feedback current signal Negative sequence injection feedback current signal ;

[0024] use , , , , , and Execute the closed-loop decoupling control algorithm to generate duty cycle commands. The closed-loop decoupling control algorithm includes fundamental current closed-loop control, positive-sequence injection current closed-loop control, and negative-sequence injection closed-loop control. The fundamental current closed-loop control is as follows: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] and The corresponding components are subtracted, and the differences between each component are processed by a PI controller to obtain the fundamental reference voltage signal in the synchronous rotating coordinate system. The positive sequence injection current closed-loop control is as follows: for and The corresponding components are subtracted, and each difference is processed by a PR controller or PI controller to obtain the injected reference voltage signal in the synchronous rotating coordinate system. The negative sequence injection current closed-loop control is as follows: for and The corresponding components are subtracted, and each difference is processed by a PI controller to obtain the injected reference voltage signal in the synchronous rotating coordinate system. ;right , and Sum the corresponding components respectively, and transform to n In the stationary coordinate system, the reference voltage signal is obtained. Based on this, a duty cycle signal is generated. ,based on A PWM pulse signal is generated and transmitted to the inverter to complete one cycle of control.

[0025] Furthermore, the angular frequencies of the coordinate transformation matrices for the positive-sequence constant-amplitude AC small signal and the negative-sequence constant-amplitude AC small signal, when transformed from the stationary coordinate system to the synchronously rotating coordinate system, are respectively... , .

[0026] Furthermore, based on the real-time current and voltage signals at the battery terminal, the battery impedance at the target frequency is calculated, as follows:

[0027] Real-time current signal at the battery terminal or real-time voltage signal To determine whether a steady state has been reached: or If, using a bandpass filter, the peak-to-peak difference of the current signal over Y consecutive disturbance periods is less than TH1, or the peak-to-peak difference of the voltage signal over Y consecutive disturbance periods is less than TH2, then... or Entering steady state; the center frequency of the bandpass filter is the maximum target frequency, the disturbance period is the period corresponding to the maximum target frequency, and TH1 and TH2 are both thresholds;

[0028] like or If it has not reached a steady state, then wait. Z Repeat the previous step after each of the aforementioned disturbance cycles; if or If a steady state has been reached, proceed to the next step;

[0029] Calculate the peak-to-peak value of the battery current for each target frequency. M Average value of each period Battery voltage peak value at M Average value of each period ,in, For the target frequency, N The total number of target frequencies;

[0030] based on , Calculate the complex impedance of the battery at each target frequency.

[0031] This invention also provides a battery impedance spectrum identification method based on inverter constant-amplitude AC small-signal injection, comprising:

[0032] Based on the target frequency set, the angular frequency of the constant amplitude AC small signal is swept multiple times; for each constant amplitude AC small signal, the battery impedance identification method based on the inverter constant amplitude AC small signal injection is performed as described above to obtain the impedance spectrum corresponding to the target frequency set.

[0033] The present invention also provides a computer-readable storage medium comprising a stored computer program, wherein, when the computer program is executed by a processor, it controls the device where the storage medium is located to execute a battery impedance identification method based on inverter constant amplitude AC small signal injection as described above and / or a battery impedance spectrum identification method based on inverter constant amplitude AC small signal injection as described above.

[0034] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0035] (1) The present invention proposes to actively control the inverter to inject a constant amplitude AC small signal into the AC side. The modulation frequency and carrier frequency of the injected signal are controllable. Through the power coupling of the inverter, a controllable frequency disturbance is excited on the DC side, thereby enabling battery impedance identification at different target frequencies. This method can be performed online. When the present invention is applied, there is no need to separate the battery from its application scenario and measure it separately. Therefore, the impedance test method will not affect the normal operation of the device under test.

[0036] (2) The present invention has no requirements on the size of the object being tested and can complete the online impedance identification of battery systems, battery modules or battery cells.

[0037] (3) Since the present invention needs to be executed online, the impedance performance of the battery under different operating conditions can be measured, thereby obtaining the dynamic impedance spectrum of the battery during actual use, reflecting the battery impedance change in real time, effectively characterizing the true characteristics of the battery, and providing an effective reference for the battery management system.

[0038] (4) Based on the existing battery-inverter-load topology, the present invention requires almost no additional hardware and can accurately identify battery impedance under various operating conditions in real time with low measurement cost.

[0039] (5) Based on the existing battery-inverter-load topology, this invention has no requirement for the number of load phases, has a wide range of applications, and is conducive to the promotion and popularization of battery impedance measurement.

[0040] (6) Since the modulation frequency and carrier frequency of the injected signal are both controllable, the controllable frequency disturbance is excited on the DC side through the power coupling of the inverter. Therefore, the battery impedance information in a wider frequency range can be obtained. Generally, by reasonably setting the number of frequency sweeps and the constant amplitude AC small signal modulation frequency, carrier frequency and modulation amplitude, the lower limit of the frequency to be measured can reach mHz and the upper limit of the frequency to be measured can reach kHz.

[0041] (7) The present invention takes less time. Generally, the battery impedance identification time can be optimized by reasonably setting the number of sweeps, the constant amplitude AC small signal modulation frequency and the carrier frequency.

[0042] (8) The calculation of this invention is relatively simple, the software implementation is relatively easy, and it is easy to implement, and it has certain industrial application prospects. Attached Figure Description

[0043] Figure 1 A flowchart of a battery impedance identification method based on inverter constant amplitude AC small signal injection is provided for an embodiment of the present invention.

[0044] Figure 2 This is a schematic diagram of a battery-inverter-load system provided in an embodiment of the present invention;

[0045] Figure 3 This is a block diagram of a control method for battery impedance identification based on a battery-inverter-three-phase load system provided in an embodiment of the present invention.

[0046] Figure 4 This is a schematic diagram of a battery-inverter-three-phase star-connected load system provided in an embodiment of the present invention;

[0047] Figure 5 This is a control block diagram of the current calculation stage of a battery-inverter-three-phase star-connected load system provided in an embodiment of the present invention.

[0048] Figure 6A reference voltage generation block diagram for the current control loop of a battery-inverter-three-phase star-connected load system provided in an embodiment of the present invention;

[0049] Figure 7 This is a block diagram for generating the duty cycle of the current control loop in a battery-inverter-three-phase star-connected load system provided in an embodiment of the present invention.

[0050] Figure 8 This is a flowchart of battery-side data processing based on inverter constant amplitude AC small signal injection, provided in an embodiment of the present invention.

[0051] Figure 9 The simulation results of battery impedance spectrum identification based on inverter positive-sequence constant-amplitude AC small-signal injection are provided in the embodiments of the present invention.

[0052] Figure 10 The relative error diagram for battery impedance spectrum identification based on inverter positive-sequence constant-amplitude AC small-signal injection is provided for an embodiment of the present invention. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0054] Example 1

[0055] A battery impedance identification method based on inverter constant amplitude AC small-signal injection, such as... Figure 1 As shown, it includes:

[0056] S1. Closed-loop control is performed on the battery-inverter-load system. The inverter AC side reference current signal used in the control process is the sum of the fundamental reference current signal and the injected reference current signal. The injected reference current signal is a constant amplitude AC small signal. By adjusting the frequency of the constant amplitude AC small signal, the target frequency excitation can be injected into the battery. When the load is a multi-phase load, the phase sequence of the injected reference current signal is reflected by the phase of the constant amplitude AC small signal of each phase.

[0057] S2. Based on the real-time current and voltage signals at the battery terminal, the battery impedance at the target frequency is calculated.

[0058] It should be noted that, as Figure 2As shown, the battery-inverter-load system topology targeted by the method in this embodiment is as follows: the battery is connected to the inverter, and the inverter supplies power to the load. This embodiment's method is based on an existing battery-inverter-load topology and does not limit the load connection method, the number of load phases, or the number of inverter arms.

[0059] In addition, to make the constant amplitude AC small signal clearer, the general formula for the constant amplitude AC small signal is given below: In the formula, n Indicates the number of phases. This represents the second corresponding constant amplitude AC small signal. This represents the amplitude of a constant-amplitude AC small signal. Represents the angular frequency of a constant-amplitude AC small signal. This indicates the phase of the second phase constant amplitude AC small signal in the phase sequence. In other words, when the load is a multi-phase load, the phase sequence of the injected reference signal is reflected by the phase of each phase constant amplitude AC small signal.

[0060] This embodiment of the method can actively control the inverter to inject a constant-amplitude AC small signal with appropriate amplitude and controllable frequency into the AC side. Through the power coupling of the inverter, a controllable frequency disturbance is excited on the DC side, thereby achieving battery impedance identification at the target frequency or battery impedance spectrum identification over a wide frequency range. This method can be performed online, meaning that impedance identification can be performed online for battery systems, battery modules, or individual battery cells under different operating conditions with minimal hardware changes (e.g., only the battery-side sensors need to be adjusted). Therefore, this embodiment provides a method for battery impedance identification based on an existing battery-inverter-load topology by injecting a constant-amplitude AC small signal, thereby obtaining the dynamic impedance or dynamic impedance spectrum of the battery under test under various operating conditions, meeting the requirements of online applications.

[0061] Optionally, the aforementioned constant-amplitude AC small signals can be positive-sequence constant-amplitude AC small signals, negative-sequence constant-amplitude AC small signals, or the sum of positive-sequence constant-amplitude AC small signals and negative-sequence constant-amplitude AC small signals. Positive sequence means that the phase sequence of each phase's constant-amplitude AC small signals is consistent with the load phase sequence.

[0062] The following explanation uses a three-phase load as an example to further illustrate the reference current signal on the AC side of the inverter.

[0063] Inverter AC side three-phase reference current Three-phase fundamental reference current signal and three-phase injected reference current signal The sum, its expression is:

[0064]

[0065] Among them, the fundamental reference current signal The expression is:

[0066]

[0067] In the above formula, The fundamental angular frequency of the inverter under steady-state operating conditions on the AC side. This represents the amplitude of the fundamental current signal.

[0068] Among them, when the reference current signal is injected For a positive-sequence constant-amplitude AC small signal, its expression is:

[0069] ;

[0070] When the reference current signal is injected For a negative-order, constant-amplitude AC small signal, its expression is:

[0071] ;

[0072] When the reference current signal is injected The summation of the positive-sequence constant-amplitude AC small-signal and the negative-sequence constant-amplitude AC small-signal is expressed as:

[0073] ;

[0074] In the above formula, , These are the positive and negative sequence constant amplitude AC small signal angular frequencies, respectively. , The amplitudes of positive and negative sequence constant amplitude AC small signals are given.

[0075] Preferably, the frequency set of the response signal of the constant amplitude AC small signal on the DC side includes the target frequency, and the relationship between the target frequency and the frequency of the constant amplitude AC small signal is as follows:

[0076] When the load is a single-phase load, the target frequency is , , ;in, The frequency of a constant amplitude AC small signal, The fundamental reference signal frequency;

[0077] When the load is a multiphase load, and the injected reference current signal is a positive-sequence constant-amplitude AC small signal, the target frequency is: When the injected reference current signal is a negative-sequence constant-amplitude AC small signal, the target frequency is: When the injected reference current signal is the sum of a positive-sequence constant-amplitude AC small signal and a negative-sequence constant-amplitude AC small signal, the target frequency is: , , ;in, , These are the frequencies of positive and negative sequence constant amplitude AC small signals, respectively. The fundamental reference signal frequency is denoted as .

[0078] In addition, the amplitude of the constant amplitude AC small signal satisfies the requirement that the amplitude of the battery current component at the target frequency is not less than the current threshold. Meanwhile, the amplitude of the battery voltage component at the target frequency is not less than the voltage threshold. Among them, the current threshold and voltage threshold The selection needs to meet the signal-to-noise ratio requirements.

[0079] That is, when the load is a single-phase load, the amplitude of the constant amplitude AC small signal satisfies the frequency requirement of... Battery current component amplitude at the location Not less than the current threshold At the same time, the frequency is Battery voltage component amplitude at the location Not less than the voltage threshold ;in, The frequency of a constant amplitude AC small signal;

[0080] When the load is a multiphase load, and the injected reference current signal is a positive-sequence constant-amplitude AC small signal, the amplitude of the constant-amplitude AC small signal satisfies the following frequency requirement: Battery current component amplitude at the location Not less than the current threshold At the same time, the frequency is Battery voltage component amplitude at the location Not less than the voltage threshold When the injected reference current signal is a negative-sequence constant-amplitude AC small signal, the amplitude of the constant-amplitude AC small signal satisfies the following frequency: Battery current component amplitude at the location Not less than the current threshold At the same time, the frequency is Battery voltage component amplitude at the location Not less than the voltage threshold When the injected reference current signal is the sum of a positive-sequence constant-amplitude AC small signal and a negative-sequence constant-amplitude AC small signal, the amplitudes of the positive and negative-sequence constant-amplitude AC small signals respectively meet the above requirements; among which, , These are the frequencies of positive and negative sequence constant amplitude AC small signals, respectively.

[0081] Preferably, taking a three-phase load and an injected reference current signal as an example, the above-mentioned closed-loop control method for battery impedance identification based on the positive-sequence constant-amplitude AC small-signal injection from the inverter, such as... Figure 3As shown, it includes: a filtering and sampling stage, a current calculation stage, a current control stage, and a modulation stage. In each sampling cycle, these four stages are executed sequentially to complete the control of the battery-inverter-load system.

[0082] The control method for each sampling period (i.e., control period) mentioned above is as follows:

[0083] (1) The filtering and sampling stage is used to sample the three-phase current on the AC side of the inverter. and inverter DC side voltage Filtering and sampling are performed to obtain the filtered and sampled three-phase AC currents of the inverter. and inverter DC side voltage ,Will The data is passed to the current calculation stage. It is transmitted to the current control circuit.

[0084] The above filtering uses a low-pass filter to filter out the three-phase current on the AC side of the inverter. The switching frequency and its multiplier ripple are measured. The sampling period can be the inverter switching period or 0.5 times the inverter switching period.

[0085] (2) The above current calculation stage receives the filtered and sampled three-phase current signal of the inverter AC side in the abc coordinate system. Fundamental reference current signal in the abc coordinate system Injected reference current signal in the abc coordinate system Perform relevant current calculations to obtain the fundamental reference current signal in the dq0 coordinate system. Injected reference current signal in the dq0 coordinate system Fundamental feedback current signal in the dq0 coordinate system Injected feedback current signal in the dq0 coordinate system And transmit it to the current control circuit.

[0086] Specifically, the aforementioned relevant current calculations are based on the inverter's AC side three-phase reference current signal being the fundamental reference current signal. and injected reference current signal The summation of the filtered and sampled three-phase AC current signals of the inverter is used to obtain the final signal. With the injected reference current signal Fundamental reference current signal The difference between the two signals is taken separately, and the result is used as the fundamental feedback current signal in the abc coordinate system. Inject feedback current signal ,Will , , , Transforming to the dq0 coordinate system yields the fundamental reference current signal. Inject reference current signal Fundamental feedback current signal Inject feedback current signal .

[0087] Among them, the fundamental reference current and fundamental feedback current The angular frequency of the abc-dq0 coordinate transformation used is When the injected current signal is a positive-sequence constant-amplitude AC small signal, the injected reference current... and injected feedback current The angular frequency of the abc-dq0 coordinate transformation used is When the injected current signal is a negative-sequence constant-amplitude AC small signal, the injected reference current... and injected feedback current The angular frequency of the abc-dq0 coordinate transformation used is .

[0088] Additionally, if the three-phase load is star-connected, such as Figure 4 As shown, the aforementioned , , The zero-axis component after transforming from the abc coordinate system to the dq0 coordinate system is 0. The current calculation process is as follows: Figure 5 As shown.

[0089] (3) The above current control circuit receives the fundamental reference current. Inject reference current Fundamental feedback current Injecting feedback current and the DC-side voltage of the inverter after filtering and sampling Execute the dual dq0 axis closed-loop control algorithm to generate duty cycle commands. And transmit it to the modulation stage.

[0090] The aforementioned dual dq0-axis closed-loop control algorithm comprises two parts: fundamental current closed-loop control and injected current closed-loop control. The fundamental current closed-loop control is as follows: [The text abruptly shifts to a different topic] ...fundamental reference current... and fundamental feedback current The corresponding components are subtracted, and the differences between the d-axis, q-axis, and 0-axis components are calculated by a PI controller to obtain the fundamental reference voltage in the dq0 coordinate system. The injection current closed-loop control is as follows: The injection reference current... and injected feedback current The corresponding components are subtracted, and the differences between the d-axis, q-axis, and 0-axis components are calculated by a PI controller to obtain the injected reference voltage in the dq0 coordinate system. ; for the fundamental reference voltage Injected reference voltage The corresponding components are summed and transformed to the abc coordinate system to obtain the reference voltage signal. Based on this, a duty cycle signal is generated. The calculation formula is as follows:

[0091] .

[0092] Additionally, if the three-phase load is star-connected, such as Figure 4 Given the aforementioned topology, the aforementioned dual dq0-axis closed-loop control algorithm does not require control of the 0-axis component, and the current control loop is as follows: Figure 6 and Figure 7 As shown.

[0093] (4) The modulation stage is used to receive the duty cycle command, compare it with the carrier, generate PWM pulses, and transmit them to the three-phase inverter.

[0094] The above modulation stage includes three-channel PWM modulation. The three channels use a unified carrier wave and are compared with the corresponding duty cycle commands to generate six PWM pulses.

[0095] Preferably, the battery impedance at the target frequency is calculated based on the real-time current and voltage signals at the battery terminal, as shown above. Figure 8 As shown, the implementation method is as follows:

[0096] Real-time current signal at the battery terminal or real-time voltage signal To determine whether a steady state has been reached: or If, using a bandpass filter, the peak-to-peak difference of the current signal over Y consecutive disturbance periods is less than TH1, or the peak-to-peak difference of the voltage signal over Y consecutive disturbance periods is less than TH2, then... or Entering steady state; the center frequency of the bandpass filter is the maximum target frequency, the disturbance period is the period corresponding to the maximum target frequency, and TH1 and TH2 are both thresholds;

[0097] like or If it has not reached a steady state, then wait. Z Repeat the previous step after one disturbance cycle; if or If a steady state has been reached, proceed to the next step;

[0098] Calculate the peak-to-peak value of the battery current for each target frequency. M Average value of each period Battery voltage peak value at M Average value of each period ,in, For the target frequency, N The total number of target frequencies;

[0099] based on , Calculate the complex impedance of the battery at each target frequency.

[0100] Example 2

[0101] A battery impedance spectrum identification method based on inverter constant-amplitude AC small-signal injection includes:

[0102] Based on the target frequency set, the angular frequency of the constant amplitude AC small signal is swept multiple times; for each sweep, calculation is performed, that is, for each constant amplitude AC small signal, a battery impedance identification method based on inverter constant amplitude AC small signal injection as described in Example 1 is executed to obtain the impedance spectrum corresponding to the target frequency set.

[0103] The specific process is as follows:

[0104] (1) To or real-time voltage signal To determine whether a steady state has been reached: or If, using a bandpass filter, the peak-to-peak difference of the current signal over Y consecutive disturbance periods is less than TH1, or the peak-to-peak difference of the voltage signal over Y consecutive disturbance periods is less than TH2, then... or Entering steady state; the center frequency of the bandpass filter is the maximum target frequency, the disturbance period is the period corresponding to the maximum target frequency, and TH1 and TH2 are both thresholds.

[0105] (2) If or If it has not reached a steady state, then wait. Z Repeat the previous step after one disturbance cycle; if or If a steady state has been reached, proceed to the next step;

[0106] (3) Calculate the peak-to-peak value of the battery current at each target frequency. M Average value of each period Battery voltage peak value at M Average value of each period ,in, For the target frequency, N The total number of target frequencies; , The calculation formulas are as follows:

[0107] ;

[0108] ;

[0109] (4) Based on , The complex impedance of the battery at each target frequency is calculated using the following formula:

[0110] .

[0111] To verify the feasibility of this invention, a simulation example is provided. Impedance identification is performed within a frequency range of 1Hz to 10kHz by injecting a positive-sequence constant-amplitude AC small signal into a three-phase star-connected load. One point is identified every ten octaves, for a total of 36 points. The injected positive-sequence constant-amplitude AC small signal has an amplitude of 0.2A. An inductive load is used on the AC side, with a fundamental current amplitude of 3A. Using the decoupling control method in the synchronous coordinate system described above, the total harmonic distortion (THD) on the AC side in steady state is 7.07% (calculated up to 20kHz), which meets the requirements of the national standard GB 12668—1990 "Inverter Standards and Product Test Requirements". The simulation results of battery impedance spectrum identification based on positive-sequence constant-amplitude AC small signal injection from the inverter provided by this embodiment of the invention are presented below. Figure 9 As shown in the figure, within the frequency range of 1Hz to 10kHz, the identified value tracks the changes in the true value very well. The relative error diagram of battery impedance spectrum identification based on inverter positive-sequence constant-amplitude AC small-signal injection provided in this embodiment of the invention is shown below. Figure 10 As shown. The formula for calculating the relative error is:

[0112]

[0113] In the above formula, This is the true value of the impedance. This represents the impedance identification value. As can be seen from the figure, using the method provided in this patent, the relative error of impedance identification across the entire frequency band is less than [value missing]. It has excellent battery impedance identification performance across the entire frequency band.

[0114] The relevant technical solutions are the same as in Embodiment 1, and will not be repeated here.

[0115] In summary, this invention proposes a method for battery impedance identification based on inverter constant-amplitude AC small-signal injection. By decoupling the fundamental current signal and the injected current signal in a synchronous rotating coordinate system, reliable injection performance is ensured. The AC small signal is coupled from the AC side to the DC side through the inverter's power transfer, thereby injecting controllable frequency excitation into the battery, creating conditions for impedance identification through the excitation-response relationship. Online identification of the battery impedance spectrum is achieved by sweeping the injected current signal. This method can identify battery impedances of different scales in real-time and at low cost, without requiring almost any additional hardware.

[0116] Example 3

[0117] A computer-readable storage medium includes a stored computer program, wherein, when the computer program is executed by a processor, it controls the device where the storage medium is located to perform a battery impedance identification method based on inverter constant amplitude AC small signal injection as described in Embodiment 1 and / or a battery impedance spectrum identification method based on inverter constant amplitude AC small signal injection as described in Embodiment 2 above.

[0118] The relevant technical solutions are the same as those in Embodiment 1 and Embodiment 2, and will not be repeated here.

[0119] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A battery impedance identification method based on inverter constant amplitude AC small signal injection, characterized in that, include: A closed-loop control is performed on the battery-inverter-load system. The inverter AC side reference current signal used in the control process is the sum of the fundamental reference current signal and the injected reference current signal. The injected reference current signal is a constant amplitude AC small signal. By adjusting the frequency of the constant amplitude AC small signal, the target frequency excitation can be injected into the battery. When the load is a multi-phase load, the phase sequence of the injected reference current signal is reflected by the phase of each phase constant amplitude AC small signal. Based on the real-time current and voltage signals at the battery terminal, the battery impedance at the target frequency is calculated. Wherein, when the load is a single-phase load, or when the load is a multi-phase load and the injected reference current signal is a positive-sequence constant-amplitude AC small signal or a negative-sequence constant-amplitude AC small signal, the implementation method of each control cycle in the closed-loop control is as follows: AC side of the inverter n Phase current signal and inverter DC side voltage signal Filtering and sampling are performed to obtain the AC side of the inverter after filtering and sampling. n Phase current signal and inverter DC side voltage signal ;in, ; Based on the AC side of the inverter n Phase reference current signal The fundamental reference current signal and injected reference current signal The sum of will respectively with , Doing the difference corresponds to... n Fundamental feedback current signal in phase stationary coordinate system Inject feedback current signal ;Will , , , Transforming to a synchronous rotating coordinate system yields the fundamental reference current signal in that coordinate system. Inject reference current signal Fundamental feedback current signal Inject feedback current signal ; use , , , and Execute the closed-loop decoupling control algorithm to generate duty cycle commands. The closed-loop decoupling control algorithm includes fundamental current closed-loop control and injected current closed-loop control. The fundamental current closed-loop control is as follows: [The text abruptly ends here, so the translation stops as well.] and The corresponding components are subtracted, and the differences between each component are processed by a PI controller to obtain the fundamental reference voltage signal in the synchronous rotating coordinate system. The injected current closed-loop control is as follows: for and The corresponding components are subtracted, and each difference is processed by a PI controller to obtain the injected reference voltage signal in the synchronous rotating coordinate system. ;right and Sum the corresponding components respectively, and transform to n In the stationary coordinate system, the reference voltage signal is obtained. Based on this, a duty cycle signal is generated. ,based on A PWM pulse signal is generated and transmitted to the inverter to complete one cycle of control. The battery impedance at the target frequency is calculated based on the real-time current and voltage signals from the battery terminal. This is achieved as follows: Real-time current signal at the battery terminal or real-time voltage signal To determine whether a steady state has been reached: or If, using a bandpass filter, the peak-to-peak difference of the current signal over Y consecutive disturbance periods is less than TH1, or the peak-to-peak difference of the voltage signal over Y consecutive disturbance periods is less than TH2, then... or Entering steady state; the center frequency of the bandpass filter is the maximum target frequency, the disturbance period is the period corresponding to the maximum target frequency, and TH1 and TH2 are both thresholds; like or If it has not reached a steady state, then wait. Z Repeat the previous step after each of the aforementioned disturbance cycles; if or If a steady state has been reached, proceed to the next step; Calculate the peak-to-peak value of the battery current for each target frequency. M Average value of each period Battery voltage peak value at M Average value of each period ,in, For the target frequency, N The total number of target frequencies; based on , Calculate the complex impedance of the battery at each target frequency.

2. The battery impedance identification method according to claim 1, characterized in that, When the load is a multiphase load, the constant amplitude AC small signal is the sum of a positive sequence constant amplitude AC small signal, a negative sequence constant amplitude AC small signal, or a positive sequence constant amplitude AC small signal and a negative sequence constant amplitude AC small signal.

3. The battery impedance identification method according to claim 1, characterized in that, The frequency set of the response signal of the constant amplitude AC small signal on the DC side includes the target frequency, and the relationship between the target frequency and the frequency of the constant amplitude AC small signal is as follows: When the load is a single-phase load, the target frequency is: , , ;in, The frequency of the constant amplitude AC small signal is... The fundamental reference current signal frequency; When the load is a multiphase load, and the injected reference current signal is a positive-sequence constant-amplitude AC small signal, then the target frequency is: When the injected reference current signal is a negative-sequence constant-amplitude AC small signal, the target frequency is: When the injected reference current signal is the sum of a positive-sequence constant-amplitude AC small signal and a negative-sequence constant-amplitude AC small signal, then the target frequency is... , , ;in, , These are the frequencies of the positive and negative sequence constant amplitude AC small signals, respectively. The frequency of the fundamental reference current signal is denoted as .

4. The battery impedance identification method according to claim 1, characterized in that, The amplitude of the constant amplitude AC small signal satisfies the requirement that the amplitude of the battery current component at the target frequency is not less than the current threshold. Meanwhile, the amplitude of the battery voltage component at the target frequency is not less than the voltage threshold. Among them, the current threshold and voltage threshold The selection needs to meet the signal-to-noise ratio requirements.

5. The battery impedance identification method according to any one of claims 1 to 4, characterized in that, When the load is a multiphase load, and the injected reference current signal is the sum of a positive-sequence constant-amplitude AC small signal and a negative-sequence constant-amplitude AC small signal, the implementation method of each control cycle in the closed-loop control is as follows: AC side of the inverter n Phase current signal and inverter DC side voltage signal Filtering and sampling are performed to obtain the AC side of the inverter after filtering and sampling. n Phase current signal and inverter DC side voltage signal ;in, ; Based on the AC side of the inverter n Phase reference current signal The fundamental reference current signal Positive sequence injection of reference current signal and negative sequence injected reference current signal The sum of will respectively with , , Doing the difference corresponds to... n Fundamental feedback current signal in phase stationary coordinate system Positive sequence injection feedback current signal Negative sequence injection feedback current signal ;Will , , , , , Transforming to a synchronous rotating coordinate system yields the fundamental reference current signal in that coordinate system. Positive sequence injection of reference current signal Negative sequence injection reference current signal Fundamental feedback current signal Positive sequence injection feedback current signal Negative sequence injection feedback current signal ; use , , , , , and Execute the closed-loop decoupling control algorithm to generate duty cycle commands. The closed-loop decoupling control algorithm includes fundamental current closed-loop control, positive-sequence injection current closed-loop control, and negative-sequence injection current closed-loop control. The fundamental current closed-loop control is as follows: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] and The corresponding components are subtracted, and the differences between each component are processed by a PI controller to obtain the fundamental reference voltage signal in the synchronous rotating coordinate system. The positive sequence injection current closed-loop control is as follows: for and The corresponding components are subtracted, and each difference is processed by a PR controller or PI controller to obtain the injected reference voltage signal in the synchronous rotating coordinate system. The negative sequence injection current closed-loop control is as follows: for and The corresponding components are subtracted, and each difference is processed by a PI controller to obtain the injected reference voltage signal in the synchronous rotating coordinate system. ;right , and Sum the corresponding components respectively, and transform to n In the stationary coordinate system, the reference voltage signal is obtained. Based on this, a duty cycle signal is generated. ,based on A PWM pulse signal is generated and transmitted to the inverter to complete one cycle of control.

6. The battery impedance identification method according to claim 1, characterized in that, The angular frequencies of the coordinate transformation matrices for the positive-sequence constant-amplitude AC small signal and the negative-sequence constant-amplitude AC small signal from the stationary coordinate system to the synchronously rotating coordinate system are respectively... , .

7. A method for battery impedance spectrum identification based on inverter constant-amplitude AC small-signal injection, characterized in that, include: Based on the target frequency set, the angular frequency of the constant amplitude AC small signal is swept multiple times; For each constant amplitude AC small signal, perform the battery impedance identification method based on inverter constant amplitude AC small signal injection as described in any one of claims 1 to 6 to obtain the impedance spectrum corresponding to the target frequency set.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored computer program, wherein, when the computer program is executed by a processor, it controls the device where the storage medium is located to perform a battery impedance identification method based on inverter constant amplitude AC small signal injection as described in any one of claims 1 to 6, or a battery impedance spectrum identification method based on inverter constant amplitude AC small signal injection as described in claim 7.

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