Battery impedance identification method based on carrier wave of inverter double side band signal injection

Abstract

This invention belongs to the field of energy storage batteries, specifically relating to a battery impedance identification method based on inverter carrier-suppressed double-sideband signal injection. The method includes: closed-loop control of the battery-inverter-load system, using an inverter AC side reference current signal that is the sum of a fundamental reference current signal and an injected reference current signal; wherein the injected reference current signal is a carrier-suppressed double-sideband signal, and by adjusting the modulation frequency and carrier frequency of the carrier-suppressed double-sideband signal, excitation at a 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 represented by the carrier signals of each phase's carrier-suppressed double-sideband signal; anti-aliasing filtering and sampling are performed on the real-time current and voltage signals at the battery end, and the battery impedance at the target frequency is calculated based on the sampled data. 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 inverter carrier suppression double-sideband signal injection. 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, they need to be split 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 when it is working; 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 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 battery impedance. However, although this invention is an online measurement, it has the following problems: (1) This invention models the battery under test as a first-order RC equivalent circuit, which is highly subjective 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) This invention only selects three points with larger amplitudes from the above frequencies to solve the circuit equations, and the results obtained do not have universality for other points in the frequency domain; (3) This invention relies on the fundamental component and cannot be applied offline; (4) This 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) This 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 switching frequency and its multiplier ripple into the battery terminal, which can realize the online identification of the battery's high-frequency impedance, but 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 carrier suppression double-sideband 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 carrier-suppressed double-sideband 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 carrier-suppressed double-sideband (CSSB) signal. By adjusting the modulation frequency and carrier frequency of the CSSB signal, a 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 represented by the carrier signals of each phase's CSSB signal.

[0011] Anti-aliasing filtering is applied to the real-time current and voltage signals at the battery terminal, and the battery impedance at the target frequency is calculated based on the sampled data.

[0012] Furthermore, when the load is a multiphase load, the injected reference current signal is a positive-sequence carrier-suppressed double-sideband signal, a negative-sequence carrier-suppressed double-sideband signal, or the sum of a positive-sequence carrier-suppressed double-sideband signal and a negative-sequence carrier-suppressed double-sideband signal.

[0013] Furthermore, the frequency set of the response signal of the carrier-suppressed double-sideband signal on the DC side includes the target frequency, and the relationship between the target frequency and the modulation frequency and carrier frequency of the carrier-suppressed double-sideband signal is as follows:

[0014] When the load is a single-phase load, the target frequency includes 2f0, 2f1, 2f2, 2(f1±f2), and f2±f1±f0; where f1 and f2 are the modulation frequency and carrier frequency of the carrier-suppressed double-sideband signal, respectively, and f0 is the frequency of the fundamental reference current signal.

[0015] When the load is a multiphase load, and when the injected reference current signal is a positive-sequence carrier-suppressed double-sideband signal, the target frequency includes 2f. 1,p and f 2,p ±(f 1,p -f0); when the injected reference current signal is a negative-sequence carrier-suppressed double-sideband signal, the target frequency includes 2f 1,n and f 2,n ±(f 1,n +f0); when the injected reference current signal is the sum of the positive-sequence carrier-suppressed double-sideband signal and the negative-sequence carrier-suppressed double-sideband signal, the target frequency includes 2f 1,p f 2,p ±(f 1,p -f0), 2f 1,n and f 2,n ±(f 1,n +f0); where f 1,p f 2,p The modulation frequency and carrier frequency of the positive-sequence carrier-suppressed double-sideband signal are respectively, f 1,n f 2,n f0 represents the modulation frequency and carrier frequency of the negative-sequence carrier-suppressed double-sideband signal, respectively, and f0 is the frequency of the fundamental reference current signal.

[0016] Furthermore, the amplitude of the carrier-suppressed double-sideband signal satisfies the condition that the amplitude of the battery current component at the target frequency is not less than the current threshold I. th Simultaneously, the amplitude of the battery voltage component at the target frequency is not less than the voltage threshold V. th Among them, the current threshold I thand voltage threshold V th The selection of the signal-to-noise ratio (SNR) needs to meet the requirements; among them, the amplitude of the carrier-suppressed double-sideband signal is the product of the amplitude of the modulation signal and the amplitude of the carrier signal.

[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 carrier-suppressed double-sideband signal or a negative-sequence carrier-suppressed double-sideband signal, the implementation method of each control cycle in the closed-loop control is as follows:

[0018] For the n-phase current signal i on the AC side of the inverter k The inverter DC-side voltage signal u is filtered and sampled to obtain the filtered and sampled inverter AC-side n-phase current signal i. k The inverter DC-side voltage signal u′ is given by k = 1, 2, ..., n.

[0019] Based on the n-phase reference current signal i on the AC side of the inverter ref,k The fundamental reference current signal i oref,k and injected reference current signal i href,k The sum of i k ′ respectively with i href,k i oref,k The difference corresponds to the fundamental feedback current signal i in the n-phase stationary coordinate system. o,k Inject feedback current signal i h,k ;change i oref,k i href,k i o,k i h,k Transforming to a synchronous rotating coordinate system yields the fundamental reference current signal i in that coordinate system. oref,rot Inject reference current signal i href,rot Fundamental feedback current signal i o,rot Inject feedback current signal i h,rot ;

[0020] Using i oref,rot i o,rot i href,rot i h,rot And u′, execute the closed-loop decoupling control algorithm to generate duty cycle command d k 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: for i oref,rot and i o,rot The corresponding components are subtracted, and the differences between each component are processed by a PI controller to obtain the fundamental reference voltage signal v in the synchronous rotating coordinate system. o,rot The injected current closed-loop control is as follows: for i href,rot and i h,rotThe corresponding components are subtracted, and each difference is processed by a PR controller or PI controller to obtain the injected reference voltage signal v in the synchronous rotating coordinate system. h,rot ; for v o,rot and v h,rot The corresponding components are summed and transformed to the n-phase stationary coordinate system to obtain the reference voltage signal v. k Based on this, a duty cycle signal d is generated. k Based on d k 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 carrier-suppressed double-sideband signal and a negative-sequence carrier-suppressed double-sideband signal, the implementation method of each control cycle in the closed-loop control is as follows:

[0022] For the n-phase current signal i on the AC side of the inverter k The inverter DC-side voltage signal u is filtered and sampled to obtain the filtered and sampled inverter AC-side n-phase current signal i. k The inverter DC-side voltage signal u′ is given by k = 1, 2, ..., n.

[0023] Based on the n-phase reference current signal i on the AC side of the inverter ref,k The fundamental reference current signal i oref,k Positive sequence injection of reference current signal i hpref,k and negative sequence injected reference current signal i hnref,k The sum of i k ′ respectively with i hpref,k +i hnref,k i oref,k +i hnref,k i oref,k +i hpref,k The difference corresponds to the fundamental feedback current signal i in the n-phase stationary coordinate system. o,k Positive sequence injection feedback current signal i hp,k Negative sequence injection feedback current signal i hn,k ;change i oref,k i hpref,k i hnref,k i o,k i hp,k i hn,k Transforming to a synchronous rotating coordinate system yields the fundamental reference current signal i in that coordinate system. oref,rot Positive sequence injection of reference current signal i hpref,rot Negative sequence injection reference current signal i hnref,rot Fundamental feedback current signal i o,rot Positive sequence injection feedback current signal ihp,rot Negative sequence injection feedback current signal i hn,rot ;

[0024] Using i oref,rot i o,rot i hpref,rot i hp,rot i hnref,rot i hn,rot And u′, execute the closed-loop decoupling control algorithm to generate duty cycle command d k 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: for i oref,rot and i o,rot The corresponding components are subtracted, and the differences between each component are processed by a PI controller to obtain the fundamental reference voltage signal v in the synchronous rotating coordinate system. o,rot The positive sequence injection current closed-loop control is as follows: for i hpref,rot and i hp,rot The corresponding components are subtracted, and each difference is processed by a PR controller or PI controller to obtain the injected reference voltage signal v in the synchronous rotating coordinate system. hp,rot The negative sequence injection current closed-loop control is as follows: for i hnref,rot and i hn,rot The corresponding components are subtracted, and each difference is processed by a PR controller or PI controller to obtain the injected reference voltage signal v in the synchronous rotating coordinate system. hn,rot ; for v o,rot v hp,rot and v hn,rot The corresponding components are summed and transformed to the n-phase stationary coordinate system to obtain the reference voltage signal v. k Based on this, a duty cycle signal d is generated. k Based on d k A PWM pulse signal is generated and transmitted to the inverter to complete one cycle of control.

[0025] Furthermore, the method for determining the controller type used by the injection current closed-loop control for different components in the synchronous rotating coordinate system is as follows: the AC component in the synchronous rotating coordinate system uses a PR controller, and the DC component in the synchronous rotating coordinate system uses a PI controller; the coordinate axis of the AC component in the synchronous rotating coordinate system depends on the coordinate transformation matrix used to transform the signal from the stationary coordinate system to the synchronous rotating coordinate system.

[0026] Furthermore, the real-time current and voltage signals at the battery terminal are subjected to anti-aliasing filtering and sampled. The battery impedance at the target frequency is calculated based on the sampled data. This is achieved as follows:

[0027] An anti-aliasing filter is used to perform anti-aliasing filtering on the real-time current signal i(t) and the real-time voltage signal u(t) at the battery terminal, resulting in the filtered real-time current signal i at the battery terminal. f (t), Real-time voltage signal u f (t);

[0028] to i f (t), u f (t) with f s The sampling frequency is used to obtain the sampled real-time current signal i at the battery terminal. s (t), Real-time voltage signal u s (t); where f s This refers to the inverter switching frequency;

[0029] to i s (t), u s (t) Perform Fast Fourier Transform on each to obtain f = {f i ,i=1,2,...,m}, where m represents the total number of frequencies of the response signal on the DC side;

[0030] right The current and voltage components with frequencies equal to the target frequency are selected through screening to calculate the battery complex impedance at the target frequency.

[0031] This invention also provides a battery impedance spectrum identification method based on inverter carrier-suppressed double-sideband signal injection, comprising:

[0032] Based on the target frequency set, the modulation angular frequency and carrier angular frequency of the carrier-suppressed double-sideband signal are simultaneously swept multiple times. For each carrier-suppressed double-sideband signal, a battery impedance identification method based on inverter carrier-suppressed double-sideband signal injection, as described above, is executed 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 carrier suppression double-sideband signal injection as described above and / or a battery impedance spectrum identification method based on inverter carrier suppression double-sideband 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 carrier-suppressed double-sideband signal into the AC side. The modulation frequency and carrier frequency of the injected signal are both 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 without restriction on whether the battery is offline. When the present invention is applied online, 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) This 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 can 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, battery impedance information in a wider frequency range can be obtained. Generally, by reasonably setting the number of frequency sweeps and the modulation frequency, carrier frequency and amplitude of the carrier suppression double-sideband signal, 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 frequency sweeps, the carrier suppression double-sideband 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 carrier suppression double-sideband signal injection is provided for an embodiment of the present invention;

[0044] Figure 2This 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 6 A 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 carrier suppression double-sideband signal injection, provided in an embodiment of the present invention.

[0051] Figure 9 A flowchart of battery impedance identification based on inverter positive sequence carrier suppression double-sideband signal injection is provided for an embodiment of the present invention;

[0052] Figure 10 The simulation results of battery impedance spectrum identification based on inverter positive sequence carrier suppression double-sideband signal injection are provided in the embodiments of the present invention.

[0053] Figure 11 The relative error diagram for battery impedance spectrum identification based on inverter positive sequence carrier suppression double-sideband signal injection is provided for an embodiment of the present invention. Detailed Implementation

[0054] 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.

[0055] Example 1

[0056] A battery impedance identification method based on inverter carrier-suppressed double-sideband signal injection, such as... Figure 1 As shown, it includes:

[0057] 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 carrier-suppressed double-sideband signal. By adjusting the modulation frequency and carrier frequency of the carrier-suppressed double-sideband 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 represented by the carrier signal of each phase's carrier-suppressed double-sideband signal.

[0058] S2. Perform anti-aliasing filtering on the real-time current signal and real-time voltage signal at the battery terminal and sample them. Calculate the battery impedance at the target frequency based on the sampled data.

[0059] It should be noted that, as Figure 2 As 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.

[0060] In addition, to make the carrier-suppressed double-sideband signal clearer, the general formula for the carrier-suppressed double-sideband signal is given below: In the formula, n represents the number of phases, i href,2 A represents the second corresponding carrier-suppressed double-sideband signal. h ω1 represents the amplitude of the carrier-suppressed double-sideband signal, which is the product of the modulation signal amplitude and the carrier signal amplitude. ω2 represents the modulation angular frequency, and ω1 represents the carrier angular frequency. This indicates the phase of the second phase carrier-suppressed double-sideband signal in the phase sequence. In other words, when the load is a multi-phase load, the phase sequence of the carrier-suppressed double-sideband signal is represented by the carrier signal of each phase carrier-suppressed double-sideband signal.

[0061] This embodiment of the method can actively control the inverter to inject a carrier-suppressed double-sideband signal into the AC side. Both the modulation frequency and carrier frequency of this injected signal are controllable. Through the inverter's power coupling, the injected signal excites a controllable frequency disturbance on the DC side, thereby enabling battery impedance identification at different target frequencies or battery impedance spectrum identification over a wide frequency range. This method can be performed online, meaning that impedance testing of battery systems, battery modules, or individual battery cells under different operating conditions can be conducted online with minimal hardware modifications (e.g., only the battery-side sensors need adjustment). Therefore, this embodiment provides a method for battery impedance identification based on an existing battery-inverter-load topology by injecting a carrier-suppressed double-sideband signal, thereby obtaining the dynamic impedance or dynamic impedance spectrum of the battery under test under various operating conditions, meeting the needs of online or offline applications.

[0062] Optionally, when the load is a multi-phase load, the aforementioned injected reference current signal is a positive-sequence carrier-suppressed double-sideband signal, a negative-sequence carrier-suppressed double-sideband signal, or the sum of a positive-sequence carrier-suppressed double-sideband signal and a negative-sequence carrier-suppressed double-sideband signal. "Positive sequence" means that the phase sequence of each phase's carrier-suppressed double-sideband signal is consistent with the phase sequence of the load.

[0063] The following section uses a three-phase load as an example to further explain the reference current signal on the AC side of the inverter.

[0064] Inverter AC side three-phase reference current signal i abc The three-phase fundamental reference current signal i oref,abc and the three-phase injected reference current signal i href,abc The sum, its expression is:

[0065]

[0066] Among them, the fundamental reference current signal i oref,abc The expression is:

[0067]

[0068] In the above formula, ω0 is the fundamental angular frequency of the inverter under steady-state operating conditions on the AC side, and A o This represents the amplitude of the fundamental current signal.

[0069] Among them, when the three-phase injected reference current signal i href,abc For a positive-sequence carrier suppressed double-sideband signal, the injected positive-sequence carrier suppressed double-sideband signal i href,abc The expression is:

[0070]

[0071] When the three-phase injection reference current signal i href,abcThe expression for suppressing double-sideband signals with negative-sequence carriers is:

[0072]

[0073] When the three-phase injection reference current signal i href,abc The summation of the positive-sequence carrier-suppressed double-sideband (PSB) signal and the negative-sequence carrier-suppressed PSB signal is expressed as:

[0074]

[0075] In the above formula, A hp ω 1,p ω 2,p These represent the amplitude, modulation angular frequency, and carrier angular frequency of the positive-sequence carrier-suppressed double-sideband signal, respectively. hn ω 1,n ω 2,n These represent the amplitude, modulation angular frequency, and carrier angular frequency of the negative-sequence carrier-suppressed double-sideband signal, respectively. Generally, the modulation angular frequency is set to be lower than the carrier angular frequency.

[0076] Preferably, the frequency set of the response signal of the carrier-suppressed double-sideband signal on the DC side includes the target frequency, and the relationship between the target frequency and the modulation frequency and carrier frequency of the carrier-suppressed double-sideband signal is as follows:

[0077] When the load is a single-phase load, the target frequencies include 2f0, 2f1, 2f2, 2(f1±f2), and f2±f1±f0; where f1 and f2 are the modulation frequency and carrier frequency of the carrier-suppressed double-sideband signal, respectively, and f0 is the frequency of the fundamental reference current signal.

[0078] When the load is a multiphase load, and the injected reference current signal is a positive-sequence carrier-suppressed double-sideband signal, the target frequency includes 2f. 1,p and f 2,p ±(f 1,p -f0); when the injected reference current signal is a negative-sequence carrier-suppressed double-sideband signal, the target frequency includes 2f 1,n and f 2,n ±(f 1,n +f0); when the injected reference current signal is the sum of the positive-sequence carrier-suppressed double-sideband signal and the negative-sequence carrier-suppressed double-sideband signal, the target frequency includes 2f 1,p f 2,p ±(f 1,p -f0), 2f 1,n and f 2,n ±(f 1,n +f0); where f 1,p f 2,p These represent the modulation frequency and carrier frequency of the positive-sequence carrier-suppressed double-sideband signal, respectively. 1,n f2,n , respectively, are the modulation frequency and carrier frequency of the negative-sequence carrier-suppressed double-sideband signal, and f0 is the frequency of the fundamental reference current signal.

[0079] Preferably, the amplitude of the carrier-suppressed double-sideband signal satisfies the condition that the amplitude of the battery current component at the target frequency is not less than the current threshold I. th Simultaneously, the amplitude of the battery voltage component at the target frequency is not less than the voltage threshold V. th Among them, the current threshold I th and voltage threshold V th The selection of the signal-to-noise ratio (SNR) needs to meet the requirements; among them, the amplitude of the carrier-suppressed double-sideband signal is the product of the amplitude of the modulation signal and the amplitude of the carrier signal.

[0080] 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 injection of a positive-sequence carrier-suppressed double-sideband signal from the inverter is as follows: Figure 3 As 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.

[0081] The control method for each sampling period (i.e., control period) mentioned above is as follows:

[0082] (1) The filtering and sampling stage is used to sample the three-phase current i on the AC side of the inverter. abc The inverter DC-side voltage u is filtered and sampled to obtain the filtered and sampled three-phase AC-side current i of the inverter. abc And the inverter DC side voltage u′, i abc u′ is passed to the current calculation stage, and u′ is passed to the current control stage.

[0083] The above filtering uses a low-pass filter to filter out the three-phase current i on the AC side of the inverter. abc 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.

[0084] (2) The current calculation stage above receives the filtered and sampled three-phase current signal i from the inverter's AC side in the abc coordinate system. abc The fundamental reference current signal i in the abc coordinate system oref,abc Injected reference current signal i in the abc coordinate system href,abc Perform relevant current calculations to obtain the fundamental reference current signal i in the dq0 coordinate system. oref,dq0 The injected reference current signal i in the dq0 coordinate system href,dq0 The fundamental feedback current signal i in the dq0 coordinate systemo,dq0 Injected feedback current signal i in the dq0 coordinate system h,dq0 And transmit it to the current control circuit.

[0085] Specifically, the aforementioned related current calculations are based on the inverter's AC side three-phase reference current signal being the fundamental reference current signal i. oref,abc and injected reference current signal i href,abc The summation of the filtered and sampled three-phase AC current signals i of the inverter is used to... abc ′ and injected reference current signal i href,abc Fundamental reference current signal i oref,abc The difference between the two signals is taken as the fundamental feedback current signal i in the abc coordinate system. o,abc Inject feedback current signal i h,abc , change i orefa,bc i href,abc i o,abc i h,abc Transforming to the dq0 coordinate system, the corresponding fundamental reference current signal i is obtained. oref,dq0 Inject reference current signal i href,dq0 Fundamental feedback current signal i o,dq0 Inject feedback current signal i h,dq0 .

[0086] Among them, the fundamental reference current i oref,dq0 and fundamental feedback current i o,dq0 The angular frequency of the abc-dq0 coordinate transformation used is ω0; when the carrier-suppressed double-sideband signal is a positive-sequence carrier-suppressed double-sideband signal, the injected reference current i href,dq0 and injected feedback current i h,dq0 The angular frequency of the abc-dq0 coordinate transformation used is ω 2,p When the carrier-suppressed double-sideband signal is a negative-sequence carrier-suppressed double-sideband signal, the injected reference current i href,dq0 and injected feedback current i h,dq0 The angular frequency of the abc-dq0 coordinate transformation used is -ω 2,n .

[0087] Additionally, if the three-phase load is star-connected, such as Figure 4 As shown, then the aforementioned i abc ′、i o,abc i h,abc 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.

[0088] (3) The above current control circuit receives the fundamental reference current i oref,dq0 Injected reference current i href,dq0 Fundamental feedback current io,dq0 Injected feedback current i h,dq0 Based on the filtered and sampled inverter DC-side voltage u′, a dual dq0-axis closed-loop control algorithm is executed to generate the duty cycle command d. abc And transmit it to the modulation stage.

[0089] 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: for the fundamental reference current i... oref,dq0 and fundamental feedback current i o,dq0 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 v in the dq0 coordinate system. o,dq0 The injection current closed-loop control is as follows: for the injected reference current i href,dq0 and injected feedback current i h,dq0 The corresponding components are subtracted separately. The difference between the d-axis and q-axis components is calculated by a PR controller or a PI controller, and the difference between the 0-axis components is calculated by a PI controller to obtain the injected reference voltage v in the dq0 coordinate system. h,dq0 For the fundamental reference voltage v o,dq0 Injected reference voltage v h,dq0 The corresponding components are summed and transformed to the abc coordinate system to obtain the reference voltage signal v. abc Based on this, a duty cycle signal d is generated. abc The calculation formula is as follows:

[0090]

[0091] It should be noted that the type of controller (PR controller or PI controller) used for the difference between the d-axis and q-axis components in the injected current closed-loop control depends on the abc-dq0 coordinate transformation matrix used in the current calculation stage; generally, the PR controller is applied to the component with sinusoidal amplitude variation, and the PI controller is applied to the component with constant amplitude.

[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 wave, 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, such as... Figure 8 As shown, the implementation method is as follows:

[0096] An anti-aliasing filter is used to perform anti-aliasing filtering on the real-time current signal i(t) and voltage signal u(t) at the battery terminal, resulting in the filtered real-time current signal i at the battery terminal. f (t), voltage signal u f (t);

[0097] to i f (t), u f (t) with f s The sampling frequency is used to obtain the sampled real-time current signal i at the battery terminal. s (t), voltage signal u s (t); f s The value is the inverter switching frequency;

[0098] to i s (t), u s (t) Perform Fast Fourier Transform on each to obtain f = {f i ,i=1,2,...,m}, where m represents the total number of frequencies of the response signal on the DC side;

[0099] right The current and voltage components with frequencies equal to the target frequency are selected through screening to calculate the battery complex impedance at the target frequency.

[0100] This embodiment employs anti-aliasing filtering, which can filter out the switching frequency and its integer multiples of ripple and EMI signals, thereby effectively reducing the sampling frequency.

[0101] It should be noted that the real-time current signal i(t) and real-time voltage signal u(t) at the battery terminal are time-domain signals of the injected signal in a steady state; the sampling frequency f s The frequency should be set to be no less than 2.56 times the cutoff frequency of the anti-aliasing filter; the inverter switching frequency should be set to be no less than 20 times the carrier frequency f2.

[0102] Preferably, to prevent spectral leakage and spectral overlap in the aforementioned Fast Fourier Transform operation, the sampling frequency f is... s It should be set to be no less than 2.56 times the cutoff frequency of the anti-aliasing filter.

[0103] In summary, this embodiment achieves wide-frequency domain online or offline identification of battery impedance for battery systems, battery modules, or individual battery cells based on a commonly used battery-inverter-load topology, at a low cost. Furthermore, this method is data-driven, theoretically resulting in near-zero system error. Additionally, the method uses a carrier-suppressed double-sideband signal for battery impedance identification, independent of the fundamental component, and the amplitude and frequency of the response signal at the battery end are controllable.

[0104] Example 2

[0105] A battery impedance spectrum identification method based on inverter carrier-suppressed double-sideband signal injection includes:

[0106] When the load is a single-phase load, based on the target frequency set, the modulation angular frequency ω1 and carrier angular frequency ω2 of the carrier-suppressed double-sideband signal are simultaneously swept g times. During the frequency sweep, the angular frequency sets of ω1 and ω2 are respectively ω1={ω 11 ,ω 12 ,...,ω 1g}, ω2={ω 21 ,ω 22 ,...,ω 2g};

[0107] When the load is a multiphase load and the injected reference current signal is a positive-sequence carrier-suppressed double-sideband signal, the modulation angular frequency ω of the positive-sequence carrier-suppressed double-sideband signal is determined according to the target frequency set. 1,p Carrier angular frequency ω 2,p Simultaneously, g frequency sweeps are performed, during which ω... 1,p ω 2,p The sets of angular frequencies are ω 1,p ={ω 11,p ,ω 12,p ,...,ω 1g,p}, ω 2,p ={ω 21,p ,ω 22,p ,...,ω 2g,p};

[0108] When the load is a multiphase load and the injected reference current signal is a negative-sequence carrier-suppressed double-sideband signal, the modulation angular frequency ω of the negative-sequence carrier-suppressed double-sideband signal is determined according to the target frequency set. 1,n Carrier angular frequency ω 2,n Simultaneously, g frequency sweeps are performed, during which ω... 1,n ω 2,n The sets of angular frequencies are ω 1,n ={ω 11,n ,ω 12,n ,...,ω 1g,n}, ω 2,n ={ω21,n ,ω 22,n ,...,ω 2g,n};

[0109] When the load is a multiphase load and the injected reference current signal is the sum of a positive-sequence carrier-suppressed double-sideband signal and a negative-sequence carrier-suppressed double-sideband signal, the modulation angular frequency ω of the positive-sequence carrier-suppressed double-sideband signal is determined according to the target frequency set. 1,p Carrier angular frequency ω 2,p The modulation angular frequency ω of the negative-sequence carrier-suppressed double-sideband signal 1,n Carrier angular frequency ω 2,n Simultaneously, g frequency sweeps are performed, during which ω... 1,p ω 2,p ω 1,n ω 2,n The sets of angular frequencies are ω 1,p ={ω 11,p ,ω 12,p ,...,ω 1g,p}, ω 2,p ={ω 21,p ,ω 22,p ,...,ω 2g,p}, ω 1,n ={ω 11,n ,ω 12,n ,...,ω 1g,n}, ω 2,n ={ω 21,n ,ω 22,n ,...,ω 2g,n}

[0110] Generally, sweeping the modulation angular frequency can yield the complex impedance of the battery in the low-frequency region, while sweeping the carrier angular frequency can yield the complex impedance of the battery in the high-frequency region.

[0111] For each frequency sweep, a calculation is performed, that is, for each carrier-suppressed double-sideband signal, a battery impedance identification method based on inverter carrier-suppressed double-sideband signal injection as described in Example 1 is executed to obtain the impedance spectrum corresponding to the target frequency set.

[0112] The specific process is as follows:

[0113] (1) Closed-loop control is performed on the battery-inverter-load system during each frequency sweep;

[0114] (2) Anti-aliasing filtering is applied to the real-time current signal i(t) and the real-time voltage signal u(t) at the battery terminal to obtain the filtered real-time current signal i at the battery terminal. f (t), voltage signal u f (t);

[0115] (3) During each frequency sweep, the filtered real-time current signal i at the battery terminal is... f (t), Real-time voltage signal u f (t) with f s The sampling frequency is used to obtain the sampled real-time current signal i at the battery terminal. s (t), voltage signal u s (t); generally, the sampling frequency f s Set to the switching frequency, the value of which is not less than 2.56 times the cutoff frequency of the anti-aliasing filter, and not less than 20 times the carrier frequency of the carrier-suppressed double-sideband signal;

[0116] (4) During each frequency sweep, the sampled real-time current signal i at the battery terminal with a duration of t is taken. s (t), voltage signal u s (t) Perform Fast Fourier Transform on each to obtain Generally, the injected signal is in a steady state within the selected duration t, and generally, the duration t is not less than twice the period of the modulation signal;

[0117] Generally, the number of sampling points N is determined by the following formula: N = f s ·t, f should be adjusted s The values ​​of t are chosen such that N is as much as possible an integer power of 2; where f1 is the carrier-suppressed double-sideband signal modulation frequency;

[0118] (5) During each frequency sweep, Perform filtering and record the frequency points f that meet the filtering criteria. i Generally, f i Belongs to the target frequency set;

[0119] (6) During each frequency sweep, for each frequency point f in (5) above i The complex impedance of the battery is calculated using the following formula:

[0120]

[0121] After completing g frequency sweeps, the identified frequency set f = {f} is obtained. ij The set of complex impedances, j = 1, 2, ..., g} Based on this, Nyquist plots and Bode plots of battery impedance can be drawn.

[0122] Specifically, please Using the real and imaginary parts of the battery, and plotting the real part as the x-axis and the negative of the imaginary part as the y-axis, a Nyquist plot of the battery impedance can be drawn; [The remaining text appears to be incomplete and requires further context.] The magnitude (or decibel value) and principal argument value can be used to plot the amplitude-frequency response with frequency as the x-axis and the magnitude (or decibel value) as the y-axis; the phase-frequency response can be plotted with frequency as the x-axis and the principal argument value as the y-axis; the amplitude-frequency response and the phase-frequency response together form the Bode plot of the battery impedance.

[0123] To verify the feasibility of this invention, a simulation example is provided. By injecting a positive-sequence carrier suppressed double-sideband signal into a three-phase star-connected load, impedance identification is completed within a frequency range of 1Hz to 10kHz. One point is identified every 10 octaves, for a total of 36 points. The identification of the first 18 target frequencies is achieved using 2f... 1,p The identification of the last 18 frequency points is obtained by f 2,p ±(f 1,p -f0) is approximately obtained, and each pair of f 2,p ±(f 1,p -f0) approximates a target frequency. The specific process is as follows: Figure 9 As shown. The simulation results of battery impedance spectrum identification based on inverter positive-sequence carrier-suppressed double-sideband signal injection provided by this embodiment of the invention. Figure 10 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 carrier suppressed double-sideband signal injection provided in this embodiment of the invention is shown below. Figure 11 As shown. The formula for calculating the relative error is:

[0124]

[0125] In the above formula, Z true Z is the true value of the impedance. iden 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 3.5 × 10⁻⁶. -4 It has excellent battery impedance identification performance across the entire frequency band.

[0126] The relevant technical solutions are the same as those in Embodiment 1 and Embodiment 2, and will not be repeated here.

[0127] In summary, this invention proposes a method for battery impedance identification based on inverter carrier-suppressed double-sideband signal injection: reliable injection is ensured by decoupling the fundamental current signal and the injected current signal in a synchronous rotating coordinate system; a small AC signal is coupled from the AC side to the DC side through the inverter's power transfer, thereby injecting a controllable frequency excitation into the battery, creating conditions for impedance identification through the excitation-response relationship; and online identification of the battery impedance spectrum is achieved by sweeping the injected current signal. This method can accurately identify battery impedances of different scales in offline or online states in real time with minimal or no additional hardware requirements and at a low cost.

[0128] Example 3

[0129] 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 carrier suppression double-sideband signal injection as described in Embodiment 1 and / or a battery impedance spectrum identification method based on inverter carrier suppression double-sideband signal injection as described in Embodiment 2.

[0130] The relevant technical solutions are the same as those in Embodiment 1 and Embodiment 2, and will not be repeated here.

[0131] 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 carrier-suppressed double-sideband 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 carrier-suppressed double-sideband (CSSB) signal. By adjusting the modulation frequency and carrier frequency of the CSSB signal, a 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 represented by the carrier signals of each phase's CSSB signal. Anti-aliasing filtering is performed on the real-time current signal and real-time voltage signal at the battery terminal, and the battery impedance at the target frequency is calculated based on the sampled data. The frequency set of the response signal of the carrier-suppressed double-sideband signal on the DC side includes the target frequency, and the relationship between the target frequency and the modulation frequency and carrier frequency of the carrier-suppressed double-sideband signal is as follows: When the load is a single-phase load, the target frequency includes , , , ,and ;in, , These are the modulation frequency and carrier frequency of the carrier-suppressed double-sideband signal, respectively. The frequency of the fundamental reference current signal; When the load is a multiphase load, and when the injected reference current signal is a positive-sequence carrier-suppressed double-sideband signal, the target frequency includes and When the injected reference current signal is a negative-sequence carrier-suppressed double-sideband signal, the target frequency includes... and When the injected reference current signal is the sum of a positive-sequence carrier-suppressed double-sideband signal and a negative-sequence carrier-suppressed double-sideband signal, the target frequency includes... , , and ;in, , These are the modulation frequency and carrier frequency of the positive-sequence carrier-suppressed double-sideband signal, respectively. , These are the modulation frequency and carrier frequency of the negative-sequence carrier-suppressed double-sideband signal, respectively. The frequency of the fundamental reference current signal is given.

2. The battery impedance identification method according to claim 1, characterized in that, The amplitude of the carrier-suppressed double-sideband 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 of the signal-to-noise ratio (SNR) needs to meet the requirements; among them, the amplitude of the carrier-suppressed double-sideband signal is the product of the amplitude of the modulation signal and the amplitude of the carrier signal.

3. The battery impedance identification method according to claim 1 or 2, characterized in that, 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 carrier-suppressed double-sideband signal or a negative-sequence carrier-suppressed double-sideband 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 PR controller or 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.

4. The battery impedance identification method according to claim 1 or 2, characterized in that, When the load is a multiphase load and the injected reference current signal is the sum of a positive-sequence carrier-suppressed double-sideband signal and a negative-sequence carrier-suppressed double-sideband 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 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 PR controller or 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.

5. The battery impedance identification method according to claim 3 or 4, characterized in that, The method for determining the controller type used for different components in the synchronous rotating coordinate system in the closed-loop control of the injected current is as follows: the AC component in the synchronous rotating coordinate system uses a PR controller, and the DC component in the synchronous rotating coordinate system uses a PI controller; the coordinate axis of the AC component in the synchronous rotating coordinate system depends on the coordinate transformation matrix used to transform the signal from the stationary coordinate system to the synchronous rotating coordinate system.

6. The battery impedance identification method according to claim 1, characterized in that, The method of performing anti-aliasing filtering and sampling on the real-time current and voltage signals at the battery terminal, and calculating the battery impedance at the target frequency based on the sampled data, is as follows: An anti-aliasing filter is used to monitor the real-time current signal at the battery terminal. Real-time voltage signal Anti-aliasing filtering is performed to obtain the filtered real-time current signal at the battery terminal. Real-time voltage signal ; right , by The sampling frequency is used to obtain the sampled real-time current signal at the battery terminal. Real-time voltage signal ;in, This refers to the inverter switching frequency; right , Perform Fast Fourier Transform on each to obtain , , , m This indicates the total number of frequencies of the response signal on the DC side; right , The current and voltage components with frequencies equal to the target frequency are selected through screening to calculate the battery complex impedance at the target frequency.

7. A battery impedance spectrum identification method based on inverter carrier-suppressed double-sideband signal injection, characterized in that, include: Based on the target frequency set, the modulation angular frequency and carrier angular frequency of the carrier-suppressed double-sideband signal are simultaneously swept multiple times. For each carrier-suppressed double-sideband signal, the battery impedance identification method based on inverter carrier-suppressed double-sideband signal injection as described in any one of claims 1 to 6 is executed 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 carrier suppression double-sideband signal injection as described in any one of claims 1 to 6 and / or a battery impedance spectrum identification method based on inverter carrier suppression double-sideband signal injection as described in claim 7.

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