CN116859257A - Method and system for in-situ characterization of battery state by characteristic harmonic alternating current impedance - Google Patents
Method and system for in-situ characterization of battery state by characteristic harmonic alternating current impedance Download PDFInfo
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Abstract
The invention relates to a method and a system for characterizing the state of a battery in situ by characteristic harmonic alternating current impedance, wherein the method comprises the following steps: the specific frequency band required by battery state representation is selected through EIS test, a plurality of orders of characteristic fundamental wave frequencies are selected from the specific frequency band according to Fourier series principle and battery state representation model, current amplitude values of the characteristic fundamental waves of each order are equal or Equivalent (EAV), the characteristic fundamental waves of multiple orders are controlled to be independently generated and then are synthesized into characteristic harmonic waves, the characteristic harmonic waves are injected into a battery end, alternating voltage and current signals are collected, FFT decomposition is carried out, alternating current impedance corresponding to the characteristic fundamental waves of each order is calculated, and the current state of the battery is rapidly and accurately represented according to the state representation model of the alternating current impedance. The method provided by the invention realizes the extremely-fast measurement of the alternating-current impedance of the battery to represent the battery state under certain special scenes, such as the whole vehicle environment, in-situ charging and discharging conditions and the like, and has higher practicability.
Description
Technical Field
The invention belongs to the technical field of battery detection, and particularly relates to a method and a system for in-situ characterization of battery state by characteristic harmonic alternating current impedance.
Background
The lithium ion battery is a main energy storage form of a new energy automobile due to the advantages of high energy density, long service life, less pollution and the like. The SOC (State of Charge) of a lithium ion battery generally reflects the ratio of the remaining available capacity of the lithium ion battery after the lithium ion battery is used for a period of time or is left unused for a long period of time to the capacity in a normal full-Charge State, and is generally represented by a percentage ranging from 0 to 1, and when soc=0, the battery is completely discharged, and when soc=1, the battery is completely full-charged. Battery SOH is used to represent the state of health of a lithium battery, and typically, when the battery is used for a period of time, SOH is less than 80%, and the battery needs to be taken out of service or recycled. In addition, the lithium battery is a chemical energy storage unit with strong temperature sensitivity, and the basic electrical properties of internal resistance, discharge capacity, maximum output power, maximum input power, voltage platform and the like are greatly influenced by the change of the battery temperature T. SOC, SOH, temperature are three state variables of great concern for lithium battery state monitoring. In practical application, the EIS alternating current impedance spectrum of the lithium battery can be directly used for battery SOC estimation, SOH characterization and temperature monitoring.
However, in the traditional sense, the EIS test is carried out at a frequency range of 0.01-100 KHz, the test time is 10-100 min, and the excitation signal is of a fixed amplitude, and is generally required to be tested under static and steady-state conditions for achieving sufficient thermal balance and electric balance so as to achieve testing preconditions of linearity, causality and time invariance. The actual application conditions of the battery are generally static and dynamic and are switched rapidly and continuously, states such as SOC and temperature are changed in real time, the test frequency of 0.01-100 KHz is redundant and unnecessary, the test time of 10-100 min cannot timely and accurately reflect the continuously changed real-time state of the battery, and unnecessary trouble is caused to representing the actual state of the battery by alternating current impedance. Therefore, finding a test method capable of rapidly and accurately measuring the alternating current impedance of the battery in the dynamic in-situ change process of the lithium battery is a problem to be solved in order to represent state variables such as the SOC, SOH, temperature and the like of the lithium battery in real time.
Disclosure of Invention
In order to solve the problems, the invention aims to provide a method and a system for in-situ characterization of battery state by characteristic harmonic alternating current impedance, which can rapidly test alternating current impedance in a dynamic in-situ variation process of a lithium battery by synthesizing characteristic harmonic waves of specific significance to a plurality of orders by the in-situ harmonic waves so as to characterize state variables such as SOC, SOH, temperature and the like of the lithium battery in real time.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a method for characterizing the state of a battery in situ by using characteristic harmonic alternating current impedance, which is characterized by comprising the following steps: comprising the following steps:
step S10, performing full factor experimental design on a battery temperature T, SOC, SOH state variable phi (x), and testing full-band EIS of the battery under different state variable conditions;
step S20, according to the representation requirement of the battery state variable phi (x 1), selecting a minimum frequency band window Min, fmn (t) which is not influenced by the change of the other two state variables phi (x 2) and phi (x 3) from the full factor test results of the temperature, SOC and SOH state variables phi (x), and establishing a binary mathematical model between the characteristic alternating current impedance value and the represented state variable phi (x 1);
step S30, based on the current frequency band window, an EAV characteristic fundamental wave strategy of a plurality of orders of characteristic harmonic waves is required to be selected according to a Fourier series principle and a battery state representation model;
step S40, in the in-situ process of the direct current charging and discharging dynamics of the battery, according to the acquired EAV characteristic fundamental wave amplitude and frequency strategy, synthesizing corresponding characteristic harmonic signals in a multipath synchronization mode, and inputting the characteristic harmonic signals to a battery end;
step S50, sampling voltage and current signals of characteristic harmonic signals of a battery terminal, performing Fourier transformation, re-decomposing the voltage and current signals into a plurality of corresponding order trigonometric function characteristic fundamental waves before synthesis, and respectively calculating characteristic alternating current impedance values of each order characteristic fundamental wave lambdan;
step S60, calculating the instantaneous value of the current battery state variable phi (x 1) according to the calculated characteristic alternating current impedance value of each step of characteristic fundamental wave lambdan and the binary mathematical model between the characteristic battery state variables.
Further, the building of the binary mathematical model comprises the following steps:
step S201, defining the represented state variables as phi (x 1), and defining the other two state variables as phi (x 2) and phi (x 3); according to the full factor test result of three state variables phi (x) of the battery temperature T, SOC, SOH, selecting a frequency band fm (t) of which the alternating current impedance measurement value does not change along with the change of the state variable phi (x 2) under the condition of the same state variable phi (x 1), selecting a frequency band fn (t) of which the alternating current impedance measurement value does not change along with the change of phi (x 3), and taking the superposition frequency band of the frequency band fm and the frequency band fn as the fmn (t);
according to fmn (t) under the condition of different state variables phi (x 1), taking the minimum common frequency band in all fmn (t) as a frequency band window (Min, fmn (t)) of the characteristic harmonic wave;
in step S202, in the determined characteristic harmonic frequency band window (Min, fmn (T)), the battery temperature T is defined as Φ (x 1) as an independent variable, the ac impedance value Z corresponding to the characteristic fundamental wave λn is used as an independent variable, and a binary mathematical model between the represented state variable Φ (x 1) and the characteristic ac impedance value Z is established.
Further, in the step S30, the characteristic harmonic characteristic fundamental wave policy specifically includes:
the frequency of each order characteristic fundamental wave lambdan is selected in a frequency band window (Min, fmn (t)) of the EAV alternating current harmonic according to the Fourier series odd number principle and the battery state representation model, so that the amplitude values of the EAV characteristic fundamental waves are consistent, namely: the order characteristic fundamental wave lambdan is:
wherein b n Is the Fourier coefficient, omega 1 Is the angular frequency of the periodic signal, phi n For the initial phase of the signal, n is the characteristic fundamental wave series, n is an odd number, and nω 1 Represents n times the fundamental frequency omega of the signal 1 T is time.
Further, in the step S40, the multiple synchronous synthesized characteristic harmonic signals specifically include:
and each order of characteristic fundamental waves of lambda 1, lambda 3 and lambda 5 … … lambda n are generated by a multi-channel DDS signal source output module according to EAV characteristic fundamental wave strategies of characteristic harmonic waves corresponding to each channel of signal source subunit simultaneously, and the multi-channel EAV characteristic fundamental waves are synchronously overlapped to synthesize characteristic harmonic signals.
Further, in the step S50, the calculating the ac impedance value of each order characteristic fundamental wave λn includes the steps of:
step S501, carrying out Fourier transformation on the current sampling signal and the voltage sampling signal, and calculating to obtain the voltage amplitude and phase of each-order characteristic fundamental wave and the amplitude and phase of the current;
step S502, according to the voltage amplitude and phase, the current amplitude and phase of each-order characteristic fundamental wave lambdan, an alternating current impedance value corresponding to each-order characteristic fundamental wave of the battery is calculated.
Further, the binary mathematical model is exponential, namely:
(1) Wherein a, b and c are constants, |Z| is impedance modulus, T is battery temperature, and e is natural constant.
Further, the ac impedance values include an impedance modulus |z|, an impedance real part Z', an impedance imaginary part z″ and an impedance phase phi.
The invention also provides a system for characterizing the battery state in situ by using the characteristic harmonic alternating current impedance, which is characterized in that: the power amplifier comprises an alternating current sampling module, wherein the input end of the alternating current sampling module is connected with a battery and is used for collecting alternating current sampling signals flowing through the battery and alternating voltage sampling signals at two ends of the battery, the output end of the alternating current sampling module is connected with a DSP control module, the DSP control module is also connected with an upper computer/BMS module and a multi-channel DDS signal source module, and the multi-channel DDS signal source module is also connected with the battery through a power amplifying module;
the upper computer/BMS module is used for inputting the frequency and amplitude instructions of each order of characteristic fundamental wave current signals lambdan to the DSP control module and receiving the instantaneous calculated value of the current measured battery state variable so as to characterize the battery state;
the DSP control module is used for carrying out Fourier transformation according to the alternating current sampling signal and the alternating voltage sampling signal, decomposing the sampling signal into a plurality of orders of trigonometric function characteristic fundamental waves lambdan corresponding to the sampling signal before synthesis, and obtaining the amplitude and the phase of the voltage signal and the amplitude and the phase of the current signal of each order of characteristic fundamental waves lambdan;
the system is used for comparing the current signal frequency and amplitude instruction of each-order characteristic fundamental wave lambdan input from the upper computer/BMS module with the actual amplitude and frequency of the sampling signal obtained from the alternating current sampling module, and determining whether the frequency and amplitude instruction of each-order characteristic fundamental wave lambdan current signal is required to be subjected to closed-loop adjustment and output to the multi-channel DDS signal source module;
the characteristic alternating current impedance value corresponding to each order characteristic fundamental wave is obtained through calculation according to the voltage signal amplitude and the phase of each order characteristic fundamental wave lambdan and the current signal amplitude and the phase of each order characteristic fundamental wave lambdan obtained through Fourier decomposition;
the method is used for calculating the instantaneous calculated value of the current measured battery state variable according to the characteristic alternating current impedance value corresponding to each step of characteristic fundamental wave lambdan obtained by calculation and a preset binary mathematical model between the characteristic alternating current impedance value and the characteristic battery state variable, and outputting the instantaneous calculated value to the upper computer/BMS module;
the multi-channel DDS signal source module is used for receiving frequency and amplitude input information of each-order characteristic fundamental wave of lambda 1, lambda 3 and lambda 5 … … lambda n from the DSP control module at the kth moment; and the multi-channel DDS signal source module generates standard trigonometric function characteristic fundamental waves according to the corresponding EAV characteristic fundamental wave strategy, and the multi-channel characteristic fundamental waves are synchronously overlapped to form the characteristic harmonic signals.
Further, the DSP control module comprises a closed-loop control unit, a Fourier transform unit, an impedance calculation unit and a battery core state calculation unit, wherein the closed-loop control unit controls the multi-path DDS signal source module; meanwhile, the closed-loop control unit transmits the alternating current sampling signal and the alternating voltage sampling signal to the Fourier transform unit, the Fourier transform unit is connected with a battery core state calculation unit through an impedance calculation unit, and the output of the battery core state calculation unit is connected to the upper computer/BMS module;
the closed-loop control unit is used for comparing the frequency and amplitude instruction of each-order characteristic fundamental wave lambdan current signal with the amplitude and the actual frequency of the alternating current sampling signal, determining whether the current signal frequency and the amplitude instruction of each-order characteristic fundamental wave lambdan need to be subjected to closed-loop adjustment and selecting whether the current signal frequency and the amplitude instruction of each-order characteristic fundamental wave lambdan are output to the multi-channel DDS signal source module;
the Fourier transform unit is used for carrying out Fourier transform according to the alternating current sampling signal and the alternating voltage sampling signal to obtain the voltage signal amplitude and phase, and the current signal amplitude and phase of each-order characteristic fundamental wave lambdan; transmitting the voltage signal amplitude and phase, the current signal amplitude and phase of each-order characteristic fundamental wave lambdan to the impedance calculation unit;
the impedance calculation unit is used for calculating and obtaining a characteristic alternating current impedance value corresponding to each order characteristic fundamental wave lambdan according to the voltage signal amplitude and the phase of each order characteristic fundamental wave lambdan and the current signal amplitude and the phase; transmitting the characteristic alternating current impedance value corresponding to each order of characteristic fundamental wave lambdan to the cell state calculation unit;
the battery cell state calculating unit is used for calculating an instantaneous calculated value of the current measured battery state variable according to the characteristic alternating current impedance value corresponding to each order of characteristic fundamental wave lambdan and a preset binary mathematical model between the characteristic alternating current impedance value and the characteristic battery state variable, and outputting the instantaneous calculated value to the upper computer/BMS module.
Further, the multi-path DDS signal source module is also connected to a battery through a power amplification module; and the power amplification module is used for carrying out power amplification on the amplitude of the characteristic harmonic signal according to a preset amplification factor and outputting the amplitude to the battery to be tested.
By adopting the technical scheme, the invention has the following advantages and effects:
(1) The method and the system for characterizing the battery state in situ by the characteristic harmonic alternating current impedance can finish one alternating current impedance test within 10-100 ms at a certain moment and output the instantaneous calculated value of the current measured battery state variable in the dynamic in situ process of battery charging, discharging, continuous switching of charging and discharging and the like, and the whole test time is extremely rapid compared with 10-100 min of the traditional EIS; the frequency range of the characteristic alternating current impedance is relatively narrow and low-frequency, and the implementation difficulty and the industrial cost of the whole vehicle are low.
(2) The method and the system thereof can be used for testing in a completely steady-state condition of battery standing, can also be used for testing in a dynamic in-situ process of charging, discharging, continuous switching of charging and discharging and the like, and can completely calculate a state variable phi (x 1) on the premise of not influencing normal charging and discharging; meanwhile, through the frequency band window (Min, fmn (t)) of the designated characteristic harmonic, the influence of the other two state variables phi (x 2) and phi (x 3) on phi (x 1) is eliminated while the battery state variable phi (x 1) is represented, and the real-time state of the battery can be accurately judged.
Drawings
FIG. 1 is a flow chart of a method for characterizing the state of a battery in situ using a characteristic harmonic AC impedance in accordance with the present invention.
Fig. 2 is a schematic block diagram of a system for characterizing the state of a battery in situ using characteristic harmonic ac impedance in accordance with the present invention.
Fig. 3 is a graph of a binary mathematical model for battery temperature T calibration using characteristic ac impedance values in accordance with an embodiment of the present invention.
The reference numerals are as follows: 1-an alternating current sampling module; 2-cell; a 3-power amplification module; 4-a multi-channel DDS signal source module; a 5-DSP control module; 6-an upper computer/BMS module; 7-dc power supply/load; 051-a closed loop control unit; 052-a fourier transform unit; 053-an impedance calculation unit; 054-cell state calculation unit.
Detailed Description
The following detailed description of the embodiments of the present invention will be provided with reference to the accompanying drawings in order to more clearly understand the objects, features and advantages of the present invention. It should be understood that the embodiments shown in the drawings are not intended to limit the scope of the invention, but rather are merely illustrative of the true spirit of the invention.
The invention provides a method and a system for characterizing the state of a battery in situ by characteristic harmonic alternating current impedance, which are characterized in that the battery is injected by synthesizing specific alternating current harmonic waves, and then the alternating current harmonic waves are subjected to Fourier decomposition and reduction to be original characteristic fundamental waves of various orders, so that the alternating current impedance test can be rapidly completed within a window period of 10-100 ms in the dynamic in-situ process of direct current charging, discharging and the like of the battery, and the current state of the battery is calculated by an alternating current impedance value.
The battery to which the present invention is applied is not limited to a lithium ion secondary battery, and may be any secondary battery.
As shown in fig. 1. The invention provides a method for characterizing battery state in situ by characteristic harmonic alternating current impedance, which can be implemented by a system for characterizing battery state by testing characteristic harmonic impedance, and specifically comprises the following steps:
step S10, performing full-factor experimental design on state variables phi (x) such as battery temperature T, SOC, SOH and the like, and testing full-band EIS of the battery under different state variable conditions;
specifically, in the embodiment of the invention, alternating current of 0.1C is used as an excitation signal, the voltage of a battery terminal under the disturbance of the current excitation signal is used as a response signal, the frequency of the current excitation signal is preferably 0.01-100 KHz, and the EIS test under the condition that the battery is in a static state and a steady state is completed.
The range of the state variable value of the battery temperature T is preferably-40-60 ℃, the whole factor test design is carried out by taking 5 ℃ as the gradient, the range of the state variable value of the SOC is preferably 0-100%, the whole factor test design is carried out by taking 5% as the gradient, the range of the state variable value of the SOH is preferably 60-100%, and the whole factor test design is carried out by taking 5% as the gradient.
Step S20, selecting a minimum frequency band window (Min, fmn (t)) which is not influenced by the change of the other two state variables phi (x 2) and phi (x 3) from the full factor test results of the state variables phi (x) such as temperature, SOC, SOH and the like according to the requirement of the representation of the battery state variable phi (x 1), and establishing a binary mathematical model between the characteristic alternating current impedance value and the represented state variable phi (x 1);
specifically, in an embodiment of the present invention, battery temperature T is selected as the characterized state variable φ (x 1), SOC is the state variable φ (x 2), and SOH is the state variable φ (x 3). According to the full factor test results of the temperature, the SOC and the SOH, under the same temperature condition, selecting a frequency band fm (t) of which the alternating current impedance measurement value does not change along with the change of the SOC as more than or equal to 5Hz, selecting a frequency band fn (t) of which the alternating current impedance measurement value does not change along with the change of the SOH as less than or equal to 1000Hz, and taking the superposition frequency band of the frequency band fm and the frequency band fn as fmn (t), namely, 5-less than or equal to fmn (t) is less than or equal to 1000Hz. And taking the minimum common frequency band in all fmn (t) as a frequency band window (Min, fmn (t)) of characteristic harmonic waves according to fmn (t) under the condition of different state variables phi (x 1), namely, the frequency band window is less than or equal to 10 and less than or equal to 100Hz.
In a frequency band window (Min, fmn (T)) of the determined characteristic harmonic, the battery temperature T is defined as phi (x 1) as an independent variable, an alternating current impedance value Z (such as impedance modulus |Z|, impedance real part Z ', impedance imaginary part Z', impedance phase phi and the like) corresponding to a certain characteristic frequency lambdan (n=w0) is used as a dependent variable, and a binary mathematical model between the represented state variable phi (x 1) and the characteristic alternating current impedance value Z is tested and built at multiple points.
In the embodiment of the invention, the binary mathematical model is an exponential type, namely:
(1) Wherein a, b and c are constants, |Z| is impedance modulus, T is battery temperature, and e is natural constant.
The binary mathematical model of the invention for calibrating the battery temperature T by utilizing the characteristic alternating current impedance value is shown in figure 3.
Step S30, based on the current frequency band window, an EAV characteristic fundamental wave strategy of a plurality of orders of characteristic harmonic waves is selected according to Fourier series;
specifically, in the embodiment of the present invention, the frequency of each stage of EAV characteristic fundamental wave λn needs to be selected according to the fourier series odd-numbered principle and the battery state characterization model (n is the EAV fundamental wave series, n is 1, 3, 5, …, w, …) in the frequency band window (Min, fmn (t)) of the characteristic harmonic wave, so that the amplitudes of the EAV characteristic fundamental waves must be equal or equivalent, namely EqualAmplitudeValue, EAV;
(2) Wherein b is n Is the Fourier coefficient, omega 1 Is the angular frequency of the periodic signal, phi n For the initial phase of the signal, n is the characteristic fundamental wave series, nω 1 Represents n times the fundamental frequency omega of the signal 1 T is time.
Step S40, in the dynamic in-situ process of direct current charging, discharging and the like of the battery, according to the acquired amplitude and frequency strategies of the EAV characteristic fundamental wave, multiplexing and synchronizing corresponding characteristic harmonic signals to be input to the battery end, and adopting closed-loop control to ensure accurate input of the amplitude and frequency strategies of each-order EAV characteristic fundamental wave;
each order characteristic fundamental wave of λ1, λ3 and λ5 … … λn is generated by a multi-channel DDS signal source output module according to EAV characteristic fundamental wave strategies of corresponding characteristic harmonic waves of independent signal source subunits in the multi-channel DDS signal source module, and the multi-channel characteristic fundamental waves are synchronously overlapped to synthesize characteristic alternating current harmonic signals.
Step S50, carrying out Fourier transformation on the voltage and current signals of the characteristic alternating current harmonic signals at the battery end, re-decomposing the voltage and current signals into a plurality of corresponding order trigonometric function characteristic fundamental waves before synthesis, and respectively calculating characteristic alternating current impedance values of each order of characteristic fundamental waves lambdan, wherein the characteristic alternating current impedance values comprise impedance modulus, impedance real part, impedance imaginary part, phase difference and the like;
specifically, the method comprises the following steps:
step S501, carrying out Fourier transformation on the current sampling signal and the voltage sampling signal, and calculating to obtain the amplitude and the phase of each-order characteristic fundamental wave voltage and the amplitude and the phase of the characteristic fundamental wave current;
step S502, according to the voltage amplitude and phase, the current amplitude and phase of each-order EAV characteristic fundamental wave lambdan, calculating to obtain an alternating current impedance value corresponding to each-order EAV characteristic fundamental wave of the battery to be measured, wherein the alternating current impedance value comprises an impedance modulus |Z|, an impedance real part Z ', an impedance imaginary part Z', an impedance phase phi and the like.
Step S60, calculating the instantaneous value of the current battery state variable phi (x 1) according to the calculated characteristic alternating current impedance value of each-order EAV characteristic fundamental wave lambdan and the binary mathematical model between the represented battery state variables.
As shown in fig. 2. The invention also provides a system for characterizing the battery state in situ by the characteristic harmonic alternating current impedance, which is used in the method for characterizing the battery state in situ by the characteristic harmonic alternating current impedance, the system comprises an alternating current sampling module 1, wherein the input end of the alternating current sampling module 1 is connected with a battery 2 and is used for collecting alternating current sampling signals flowing through the battery 2 and alternating current voltage sampling signals at two ends of the battery 2, the output end of the alternating current sampling module 1 is connected with a DSP control module 5, the DSP control module 5 is also connected with an upper computer/BMS module 6 and a multi-channel DDS signal source module 4, and the multi-channel DDS signal source module 4 is also connected with the battery 2 through a power amplification module 3.
The power amplification module 3 is also connected with a direct current power supply/load 7, and the direct current power supply/load 7 provides power for the whole system.
The DSP control module 5 comprises a closed-loop control unit 051, a Fourier transform unit 052, an impedance calculation unit 053 and a battery cell state calculation unit 054, wherein the closed-loop control unit 051 controls the multipath DDS signal source module 4, the closed-loop control unit 051 transmits alternating current sampling signals and alternating voltage sampling signals to the Fourier transform unit 052, the Fourier transform unit 052 is connected with the battery cell state calculation unit 054 through the impedance calculation unit 053, and the output of the battery cell state calculation unit 054 is connected to the upper computer/BMS module 6.
In order to achieve the multiplex synchronous synthesis of each-order EAV characteristic fundamental wave of λ1, λ3, λ5 … … λn, the closed loop control of the alternating amplitude frequency of each-order characteristic fundamental wave, wherein:
the multi-path DDS signal source module 4 is used for generating standard trigonometric function characteristic fundamental waves according to each subunit and the EAV fundamental wave strategy of corresponding characteristic alternating current harmonic waves according to each independent signal source subunit in the multi-path DDS signal source module 4 and the frequency, amplitude and other input information of each order of characteristic fundamental waves of the lambda 1, lambda 3, lambda 5 … … lambda n received from the DSP control module 5 at the kth moment, and the multi-path characteristic fundamental waves are synchronously overlapped to form EAV alternating current harmonic signals;
the closed-loop control unit 051 of the DSP control module 5 is configured to compare the frequency and the amplitude command of the fundamental wave current signal of each order input from the upper computer/BMS module 6 with the amplitude and the actual magnitude of the frequency of the ac current sampling signal obtained from the ac sampling module, determine whether the frequency and the amplitude command of the fundamental wave current signal of each order need to be subjected to closed-loop adjustment, and output the closed-loop adjustment parameters to the multi-path DDS signal source module 4, if yes, output the closed-loop control adjustment parameters, and if no, perform subsequent other processing on the ac current sampling signal and the ac voltage sampling signal.
In order to realize the sampling of the characteristic alternating current harmonic signal, the Fourier transformation of the current sampling signal and the voltage sampling signal and the calculation of the characteristic alternating current impedance value of each-order characteristic fundamental wave lambdan, wherein:
the alternating current sampling module is used for collecting alternating current sampling signals flowing through the battery 2 at high frequency and alternating voltage sampling signals at two ends of the battery 2;
the fourier transform unit 052 of the DSP control module 5 is configured to perform fourier transform according to the ac current sampling signal and the ac voltage sampling signal collected by the ac sampling module, and decompose the ac current sampling signal and the ac voltage sampling signal into a plurality of order trigonometric function feature fundamental waves corresponding to each other before synthesis, so as to obtain amplitude and phase of each order feature fundamental wave voltage signal and amplitude and phase of the current signal;
the impedance calculating unit 053 of the DSP control module 5 is configured to calculate, according to the amplitude and the phase of the characteristic fundamental wave voltage signal and the amplitude and the phase of the current signal obtained by the fourier decomposition, a characteristic ac impedance value corresponding to the characteristic fundamental wave of each step, where the characteristic ac impedance value includes an impedance modulus |z|, an impedance real part Z', an impedance imaginary part z″ and an impedance phase phi.
To achieve the calculation of states of battery SOC, SOH, etc., wherein:
the electrical core state calculating unit 054 of the DSP control module 5 is configured to calculate an instantaneous calculated value of a current measured battery state variable according to the calculated characteristic ac impedance value corresponding to each order characteristic fundamental wave and a preset binary mathematical model between the characteristic ac impedance value and the characteristic battery state variable, and output the calculated value to the upper computer/BMS module 6;
the upper computer/BMS module is used for inputting frequency and amplitude commands of the characteristic fundamental wave current signals lambdan of each order to the DSP control module 5; and is adapted to receive said instantaneous calculated value of the currently measured battery state variable, thereby characterizing the battery 2 state.
Further, the various modules of the system may be selected from the following models, but are not unique. The model of the alternating current sampling module 1 is preferably LTC6813; the model of the power amplification module is preferably ATA-2022B; the model of the multi-channel DDS signal source module is preferably AD9959; the model of the DSP control module is preferably TMS320F28335.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A method for characterizing the state of a battery in situ by using characteristic harmonic alternating current impedance, which is characterized by comprising the following steps: comprising the following steps:
step S10, performing full factor experimental design on a battery temperature T, SOC, SOH state variable phi (x), and testing full-band EIS of the battery under different state variable conditions;
step S20, according to the representation requirement of the battery state variable phi (x 1), selecting a minimum frequency band window Min, fmn (t) which is not influenced by the change of the other two state variables phi (x 2) and phi (x 3) from the full factor test results of the temperature, SOC and SOH state variables phi (x), and establishing a binary mathematical model between the characteristic alternating current impedance value and the represented state variable phi (x 1);
step S30, based on the current frequency band window, an EAV characteristic fundamental wave strategy of a plurality of orders of characteristic harmonic waves is required to be selected according to a Fourier series principle and a battery state representation model;
step S40, in the in-situ process of the direct current charging and discharging dynamics of the battery, according to the acquired characteristic fundamental wave amplitude and frequency strategy, corresponding characteristic harmonic signals are synchronously synthesized in a multipath mode and input to the battery end;
step S50, sampling voltage and current signals of characteristic harmonic signals of a battery terminal, performing Fourier transformation, re-decomposing the voltage and current signals into a plurality of corresponding order trigonometric function characteristic fundamental waves before synthesis, and respectively calculating characteristic alternating current impedance values of each order characteristic fundamental wave lambdan;
step S60, calculating the instantaneous value of the current battery state variable phi (x 1) according to the calculated characteristic alternating current impedance value of each step of characteristic fundamental wave lambdan and the binary mathematical model between the characteristic battery state variables.
2. The method for characterizing a harmonic ac impedance in-situ characterization of a battery condition as defined in claim 1, wherein: the establishment of the binary mathematical model comprises the following steps:
step S201, defining the represented state variables as phi (x 1), and defining the other two state variables as phi (x 2) and phi (x 3); according to the full factor test result of three state variables phi (x) of the battery temperature T, SOC, SOH, selecting a frequency band fm (t) of which the alternating current impedance measurement value does not change along with the change of the state variable phi (x 2) under the condition of the same state variable phi (x 1), selecting a frequency band fn (t) of which the alternating current impedance measurement value does not change along with the change of phi (x 3), and taking the superposition frequency band of the frequency band fm and the frequency band fn as the fmn (t);
according to fmn (t) under the condition of different state variables phi (x 1), taking the minimum common frequency band in all fmn (t) as a frequency band window (Min, fmn (t)) of the characteristic harmonic wave;
in step S202, in the determined characteristic harmonic frequency band window (Min, fmn (T)), the battery temperature T is defined as Φ (x 1) as an independent variable, the ac impedance value Z corresponding to the characteristic fundamental wave λn is used as an independent variable, and a binary mathematical model between the represented state variable Φ (x 1) and the characteristic ac impedance value Z is established.
3. The method for characterizing a harmonic ac impedance in-situ characterization of a battery condition as defined in claim 1, wherein: in the step S30, the characteristic harmonic characteristic fundamental wave policy specifically includes:
the frequency of each order characteristic fundamental wave lambdan is selected in a frequency band window (Min, fmn (t)) of the EAV alternating current harmonic according to the Fourier series odd number principle and the battery state representation model, so that the amplitude values of the EAV characteristic fundamental waves are consistent, namely: the order characteristic fundamental wave lambdan is:
wherein b n Is the Fourier coefficient, omega 1 Is the angular frequency of the periodic signal, phi n For the initial phase of the signal, n is the characteristic fundamental wave series, n is an odd number, and nω 1 Represents n times the fundamental frequency omega of the signal 1 T is time.
4. The method for characterizing a harmonic ac impedance in-situ characterization of a battery condition as defined in claim 1, wherein: in the step S40, the multiple synchronous synthesis characteristic harmonic signals specifically include:
and each order of characteristic fundamental waves of lambda 1, lambda 3 and lambda 5 … … lambda n are generated by a multi-channel DDS signal source output module according to EAV characteristic fundamental wave strategies of characteristic harmonic waves corresponding to each channel of signal source subunit simultaneously, and the multi-channel EAV characteristic fundamental waves are synchronously overlapped to synthesize characteristic harmonic signals.
5. The method for characterizing a harmonic ac impedance in-situ characterization of a battery condition as defined in claim 1, wherein: in the step S50, the calculating the ac impedance value of each order characteristic fundamental wave λn includes the following steps:
step S501, carrying out Fourier transformation on the current sampling signal and the voltage sampling signal, and calculating to obtain the voltage amplitude and phase of each-order characteristic fundamental wave and the amplitude and phase of the current;
step S502, according to the voltage amplitude and phase, the current amplitude and phase of each-order characteristic fundamental wave lambdan, an alternating current impedance value corresponding to each-order characteristic fundamental wave of the battery is calculated.
6. A method of characterizing a harmonic ac impedance in situ characterization of a battery condition as defined in claim 1 or 2, wherein: the binary mathematical model is exponential, namely:
(1) Wherein a, b and c are constants, |Z| is impedance modulus, T is battery temperature, and e is natural constant.
7. The method for characterizing a harmonic ac impedance in-situ characterization of a battery condition as defined in claim 1, wherein: the ac impedance values include an impedance modulus |z|, an impedance real part Z', an impedance imaginary part z″ and an impedance phase phi.
8. A system for performing the method of characterizing harmonic ac impedance in-situ characterization of battery conditions as defined in any one of claims 1-7, wherein: the power amplifier comprises an alternating current sampling module, wherein the input end of the alternating current sampling module is connected with a battery and is used for collecting alternating current sampling signals flowing through the battery and alternating voltage sampling signals at two ends of the battery, the output end of the alternating current sampling module is connected with a DSP control module, the DSP control module is also connected with an upper computer/BMS module and a multi-channel DDS signal source module, and the multi-channel DDS signal source module is also connected with the battery through a power amplifying module;
the upper computer/BMS module is used for inputting the frequency and amplitude instructions of each order of characteristic fundamental wave current signals lambdan to the DSP control module and receiving the instantaneous calculated value of the current measured battery state variable so as to characterize the battery state;
the DSP control module is used for carrying out Fourier transformation according to the alternating current sampling signal and the alternating voltage sampling signal, decomposing the sampling signal into a plurality of orders of trigonometric function characteristic fundamental waves lambdan corresponding to the sampling signal before synthesis, and obtaining the amplitude and the phase of the voltage signal and the amplitude and the phase of the current signal of each order of characteristic fundamental waves lambdan;
the system is used for comparing the current signal frequency and amplitude instruction of each-order characteristic fundamental wave lambdan input from the upper computer/BMS module with the actual amplitude and frequency of the sampling signal obtained from the alternating current sampling module, and determining whether the frequency and amplitude instruction of each-order characteristic fundamental wave lambdan current signal is required to be subjected to closed-loop adjustment and output to the multi-channel DDS signal source module;
the characteristic alternating current impedance value corresponding to each order characteristic fundamental wave is obtained through calculation according to the voltage signal amplitude and the phase of each order characteristic fundamental wave lambdan and the current signal amplitude and the phase of each order characteristic fundamental wave lambdan obtained through Fourier decomposition;
the method is used for calculating the instantaneous calculated value of the current measured battery state variable according to the characteristic alternating current impedance value corresponding to each step of characteristic fundamental wave lambdan obtained by calculation and a preset binary mathematical model between the characteristic alternating current impedance value and the characteristic battery state variable, and outputting the instantaneous calculated value to the upper computer/BMS module;
the multi-channel DDS signal source module is used for receiving frequency and amplitude input information of each-order characteristic fundamental wave of lambda 1, lambda 3 and lambda 5 … … lambda n from the DSP control module at the kth moment; and the multi-channel DDS signal source module generates standard trigonometric function characteristic fundamental waves according to the corresponding EAV characteristic fundamental wave strategy, and the multi-channel characteristic fundamental waves are synchronously overlapped to form the characteristic harmonic signals.
9. The system for characterizing a harmonic ac impedance in-situ characterization of a battery condition as defined in claim 8, wherein: the DSP control module comprises a closed-loop control unit, a Fourier transform unit, an impedance calculation unit and a battery core state calculation unit, wherein the closed-loop control unit controls the multi-path DDS signal source module; meanwhile, the closed-loop control unit transmits the alternating current sampling signal and the alternating voltage sampling signal to the Fourier transform unit, the Fourier transform unit is connected with a battery core state calculation unit through an impedance calculation unit, and the output of the battery core state calculation unit is connected to the upper computer/BMS module;
the closed-loop control unit is used for comparing the frequency and amplitude instruction of each-order characteristic fundamental wave lambdan current signal with the amplitude and the actual frequency of the alternating current sampling signal, determining whether the current signal frequency and the amplitude instruction of each-order characteristic fundamental wave lambdan need to be subjected to closed-loop adjustment and selecting whether the current signal frequency and the amplitude instruction of each-order characteristic fundamental wave lambdan are output to the multi-channel DDS signal source module;
the Fourier transform unit is used for carrying out Fourier transform according to the alternating current sampling signal and the alternating voltage sampling signal to obtain the voltage signal amplitude and phase, and the current signal amplitude and phase of each-order characteristic fundamental wave lambdan; transmitting the voltage signal amplitude and phase, the current signal amplitude and phase of each-order characteristic fundamental wave lambdan to the impedance calculation unit;
the impedance calculation unit is used for calculating and obtaining a characteristic alternating current impedance value corresponding to each order characteristic fundamental wave lambdan according to the voltage signal amplitude and the phase of each order characteristic fundamental wave lambdan and the current signal amplitude and the phase; transmitting the characteristic alternating current impedance value corresponding to each order of characteristic fundamental wave lambdan to the cell state calculation unit;
the battery cell state calculating unit is used for calculating an instantaneous calculated value of the current measured battery state variable according to the characteristic alternating current impedance value corresponding to each order of characteristic fundamental wave lambdan and a preset binary mathematical model between the characteristic alternating current impedance value and the characteristic battery state variable, and outputting the instantaneous calculated value to the upper computer/BMS module.
10. The system for characterizing a harmonic ac impedance in-situ characterization of a battery condition as defined in claim 9, wherein: the multi-path DDS signal source module is also connected to a battery through a power amplification module; and the power amplification module is used for carrying out power amplification on the amplitude of the characteristic harmonic signal according to a preset amplification factor and outputting the amplitude to the battery to be tested.
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