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CN114814367B - A method for testing AC internal resistance and power factor of lithium batteries based on FFT - Google Patents

A method for testing AC internal resistance and power factor of lithium batteries based on FFT Download PDF

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Publication number
CN114814367B
CN114814367B CN202210329091.8A CN202210329091A CN114814367B CN 114814367 B CN114814367 B CN 114814367B CN 202210329091 A CN202210329091 A CN 202210329091A CN 114814367 B CN114814367 B CN 114814367B
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sinusoidal
lithium battery
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internal resistance
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CN114814367A (en
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李有财
李东平
朱哲浩
熊刚
邓秉杰
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Fujian Nebula Electronics Co Ltd
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Fujian Nebula Electronics Co Ltd
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/08Measuring resistance by measuring both voltage and current
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R21/00Arrangements for measuring electric power or power factor
    • G01R21/006Measuring power factor
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/36Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/389Measuring internal impedance, internal conductance or related variables

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  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Measurement Of Resistance Or Impedance (AREA)
  • Tests Of Electric Status Of Batteries (AREA)
  • Secondary Cells (AREA)

Abstract

The invention provides a lithium battery alternating-current internal resistance and power factor testing method based on FFT, which belongs to the technical field of lithium battery testing and comprises the steps of S10, sequentially adjusting gears of reference resistors of an access device interface module, S20, outputting sinusoidal voltage signals to a sinusoidal current generating module by a control module, sampling the sinusoidal voltage signals and sinusoidal current signals flowing through the reference resistors through a high-speed sampling module to calculate reference resistance parameters, S30, accessing the lithium battery into the device interface module, S40, sampling sinusoidal current signals flowing through the lithium battery through the high-speed sampling module to calculate lithium battery parameters, and S50, calculating the alternating-current internal resistance, power factor and alternating-current internal resistance components of the lithium battery by the control module based on the reference resistance parameters and the lithium battery parameters. The invention has the advantages of greatly reducing the test cost of the alternating current internal resistance and the power factor of the lithium battery and greatly improving the test precision.

Description

FFT-based lithium battery alternating-current internal resistance and power factor testing method
Technical Field
The invention relates to the technical field of lithium battery testing, in particular to a method for testing alternating current internal resistance and power factors of a lithium battery based on FFT.
Background
With the rising and development of new energy, the lithium battery is used as a green high-energy chemical power supply, has the advantages of high energy, high power, low cost and the like, and is widely applied to the new energy industry. In order to ensure the use safety of the lithium battery, a series of tests are required to be carried out on the lithium battery before leaving the factory, and the AC internal resistance and the power factor are important indexes to be tested.
For the test of the alternating current internal resistance, the internal reference resistance and the external equipment are switched to each other in a hardware mode in the prior art so as to test a conversion level signal of a signal effective value generated when the sinusoidal current flows, the conversion level signal is used for sampling by a sampling module, and the impedance value of the external equipment is converted in a proportional operation mode. However, in the conventional method, an effective value conversion module needs to be additionally provided, and the effective value conversion module can only obtain an effective value of the sinusoidal current signal, but cannot obtain a frequency spectrum and a phase of each component, and the effective value conversion module needs to be provided, so that the test cost is high, and the test precision is still to be improved.
For testing of power factors, conventionally, a method of capturing edges generated when 2 paths of signals cross zero points to obtain time differences of the edges and further converting corresponding phase angles is adopted. However, in the conventional method, a phase detection module is required to be additionally provided, the calculated phase angle precision is limited by the timing resolution of the timer, when the waveform is disturbed, the test result can jump, the test cost is high due to the need of providing the phase detection module, and the test precision and stability are still to be improved.
Conventionally, for testing ac internal resistance and power factor, reference resistors are configured on the original circuit, and a corresponding number of four-wire resistors are required to be provided according to the gear of hardware, so that if the yield is improved, the production cost is greatly improved.
Therefore, how to provide a method for testing the alternating current internal resistance and the power factor of the lithium battery based on the FFT, so as to reduce the testing cost of the alternating current internal resistance and the power factor of the lithium battery and improve the testing precision, and the method becomes a technical problem to be solved urgently.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for testing the alternating current internal resistance and the power factor of a lithium battery based on FFT, which can reduce the testing cost of the alternating current internal resistance and the power factor of the lithium battery and improve the testing precision.
The invention discloses a method for testing the alternating-current internal resistance and the power factor of a lithium battery based on FFT, which comprises the following steps:
step S10, the upper computer sets a control module to enter a debugging mode, and gears of reference resistors of the interface module of the access equipment are sequentially adjusted;
Step S20, a control module outputs a sinusoidal voltage signal to a sinusoidal current generation module, the sinusoidal voltage signal and a sinusoidal current signal flowing through a reference resistor are sampled by a high-speed sampling module, and further reference resistance parameters under the reference resistor of each gear are respectively calculated by fast Fourier transformation;
Step S30, the upper computer sets a control module to enter a use mode, and the lithium battery is connected into the equipment interface module;
Step S40, the control module continuously outputs a sinusoidal voltage signal to the sinusoidal current generating module, the sinusoidal current signal flowing through the lithium battery is sampled through the high-speed sampling module, and then the lithium battery parameters of the lithium battery are calculated through fast Fourier transform;
and S50, the control module calculates the alternating current internal resistance, the power factor and the alternating current internal resistance component of the lithium battery based on the reference resistance parameter and the lithium battery parameter, and sends the calculation result to the upper computer.
Further, the step S20 specifically includes:
s21, the control module outputs a sinusoidal voltage signal to the sinusoidal current generating module;
s22, a sinusoidal current generating module generates a sinusoidal current signal based on the sinusoidal voltage signal and inputs the sinusoidal current signal into a reference resistor;
S23, the signal amplifying module amplifies and filters a sinusoidal current signal flowing through the reference resistor through the equipment interface module and inputs the sinusoidal current signal into the high-speed sampling module, and the sinusoidal voltage signal received by the sinusoidal current generating module is amplified and filtered and then inputs the sinusoidal voltage signal into the high-speed sampling module;
step S24, the high-speed sampling module samples the sinusoidal current signal and the sinusoidal voltage signal and then inputs the sinusoidal current signal and the sinusoidal voltage signal into the control module;
And S25, the control module calculates reference resistance parameters including a first alternating current signal amplitude value, a first phase angle sine value, a first phase angle cosine value and a reference resistance value under each gear reference resistance through fast Fourier transformation based on the received sinusoidal current signal and sinusoidal voltage signal, and stores the reference resistance parameters.
Further, the step S22 specifically includes:
The sinusoidal current generating module rectifies and filters the input sinusoidal voltage signal to generate a sinusoidal current signal, and the sinusoidal current signal is input into a reference resistor through the equipment interface module.
Further, the step S24 specifically includes:
the high-speed sampling module samples the sinusoidal current signal and the sinusoidal voltage signal at a preset sampling frequency and then inputs the sinusoidal current signal and the sinusoidal voltage signal into the control module, wherein the sampling frequency is at least 2 times of the frequency of the sinusoidal voltage signal.
Further, the step S25 specifically includes:
step S251, a control module calculates a real component Rex and an imaginary component Imx of the sinusoidal current signal under each gear reference resistance through fast Fourier transformation, and calculates a real component Remcu and an imaginary component Immcu of the sinusoidal voltage signal;
step S252, calculating ac signal amplitudes Ax and Amcu based on the Rex, im x, remcu, and Im mcu, and taking the Ax as a first ac signal amplitude:
step S253, calculating a first phase angle sine value sin delta and a first phase angle cosine value cos delta based on the Rex, im x, remcu, im mcu, ax and Amcu:
sin delta=sin x*cos mcu-cos x*sin mcu;
cos delta=cos x*cos mcu+sin x*sin mcu;
sin x=Re x/Ax;
sin mcu=Re mcu/Amcu;
cos x=Im x/Ax;
cos mcu=Im mcu/Amcu;
And step S254, recording the reference resistance value of the reference resistor of each gear, and storing the reference resistance parameters including the first alternating current signal amplitude, the first phase angle sine value, the first phase angle cosine value and the reference resistance value.
Further, the step S40 specifically includes:
step S41, the control module continuously outputs a sinusoidal voltage signal to the sinusoidal current generating module;
Step S42, a sinusoidal current generating module generates a sinusoidal current signal based on the sinusoidal voltage signal and inputs the sinusoidal current signal into a lithium battery;
s43, the signal amplifying module amplifies and filters sinusoidal current signals flowing through the lithium battery through the equipment interface module and inputs the sinusoidal current signals into the high-speed sampling module;
step S44, after the high-speed sampling module samples the sinusoidal current signal, the sinusoidal current signal is input into the control module;
And step S45, the control module calculates lithium battery parameters including a second alternating current signal amplitude, a second phase angle sine value and a second phase angle cosine value of the sinusoidal current signal flowing through the lithium battery through fast Fourier transformation.
Further, in the step S50, the calculation step of the ac internal resistance is as follows:
the control module obtains a first alternating current signal amplitude and a reference resistance value of a reference resistance gear corresponding to the lithium battery, and calculates alternating current internal resistance based on the first alternating current signal amplitude, the reference resistance value and the second alternating current signal amplitude:
ac internal resistance=second ac signal amplitude/first ac signal amplitude;
The calculation formula of the power factor is as follows:
cosα=cos delta*cos L+sin delta*sin L;
Wherein cos alpha represents a power factor, cos L represents a second phase angle cosine value, sin L represents a second phase angle sine value;
the calculation formula of the alternating current internal resistance component is as follows:
ac internal resistance component = ac internal resistance x cos α.
The invention has the advantages that:
The method has the advantages that the external reference resistor is used for replacing the traditional reference resistor configured on the original circuit, the hardware cost is greatly reduced, the testing flexibility is improved, the sine voltage signal and the sine current signal are sampled, the alternating-current internal resistance, the power factor and the alternating-current internal resistance component of the lithium battery are calculated by utilizing the fast Fourier transformation, the circuit which is provided with an effective value conversion module and a phase detection module in addition is not needed, the hardware cost is further reduced, the later maintenance is convenient, errors caused by the direct-current component and other frequency components in the sine current signal on the calculation result are eliminated through the fast Fourier transformation, the calculation result of the alternating-current internal resistance is more accurate, the resolution and the accuracy of the calculation result of the power factor are higher, the calculation result of the alternating-current internal resistance component is more stable, the testing cost of the alternating-current internal resistance and the power factor of the lithium battery is finally realized, and the testing precision is greatly improved.
Drawings
The invention will be further described with reference to examples of embodiments with reference to the accompanying drawings.
Fig. 1 is a flowchart of a method for testing the alternating current internal resistance and the power factor of a lithium battery based on FFT.
Fig. 2 is a hardware architecture diagram of the present invention.
Detailed Description
The technical scheme of the embodiment of the application has the general idea that the external reference resistor is used for replacing the traditional reference resistor configured on the original circuit, the AC internal resistance, the power factor and the AC internal resistance component of the lithium battery are calculated by utilizing the fast Fourier transform, the traditional effective value conversion module and the phase detection module are omitted, so that the test cost of the AC internal resistance and the power factor of the lithium battery is reduced, and the error of the DC component and other frequency components in the sinusoidal current signal to the calculation result is eliminated by the fast Fourier transform, so that the test precision is improved.
Referring to fig. 1 to 2, the test system of the present invention includes an upper computer, a control module, a sinusoidal current generating module, an equipment interface module, a signal amplifying module, a high-speed sampling module, a reference resistor and a lithium battery;
The input end of the control module is connected with the upper computer and the high-speed sampling module, the output end of the control module is connected with the sinusoidal current generating module and the reference resistor, the equipment interface module is respectively connected with the sinusoidal current generating module, the signal amplifying module, the reference resistor and the lithium battery, and the output end of the signal amplifying module is connected with the high-speed sampling module.
The system comprises a high-speed sampling module, a control module, a device interface module, a standard resistor, a lithium battery, a high-speed sampling module, a power factor and an alternating current internal resistance component, wherein the high-speed sampling module is used for outputting a sinusoidal voltage signal with fixed frequency to the sinusoidal current generating module, acquiring sampling data from the high-speed sampling module, performing fast Fourier transformation on the sampling data to calculate the alternating current internal resistance, the power factor and the alternating current internal resistance component of the lithium battery, the sinusoidal current generating module is used for converting the sinusoidal voltage signal into a sinusoidal current signal and outputting the sinusoidal current signal to the standard resistor and the lithium battery, the device interface module is used for connecting the standard resistor or the lithium battery, the signal amplifying module is used for filtering and amplifying the signal, the high-speed sampling module is used for sampling the signal output by the signal amplifying module, the standard resistor is used for providing a standard for related calculation, and the lithium battery is a four-wire standard resistor, and the lithium battery is the alternating current internal resistance, the power factor and the alternating current internal resistance component to be tested.
The invention relates to a preferred embodiment of a method for testing alternating current internal resistance and power factors of a lithium battery based on FFT, which comprises the following steps:
step S10, the upper computer sets a control module to enter a debugging mode, and gears of reference resistors of the interface module of the access equipment are sequentially adjusted;
Step S20, a control module outputs a sinusoidal voltage signal to a sinusoidal current generating module, the sinusoidal voltage signal and a sinusoidal current signal flowing through a reference resistor are sampled by a high-speed sampling module, and further reference resistance parameters under each gear reference resistor are calculated by Fast Fourier Transform (FFT) respectively;
step S30, the upper computer sets a control module to enter a use mode, and the lithium battery is connected with the equipment interface module;
step S40, the control module continuously outputs sinusoidal voltage signals to the sinusoidal current generating module through an internal DAC unit, the sinusoidal current signals flowing through the lithium battery are sampled through the high-speed sampling module, and then lithium battery parameters of the lithium battery are calculated through fast Fourier transform;
and S50, the control module calculates the alternating current internal resistance, the power factor and the alternating current internal resistance component of the lithium battery based on the reference resistance parameter and the lithium battery parameter, and sends the calculation result to the upper computer.
The step S20 specifically includes:
s21, the control module outputs a sinusoidal voltage signal to the sinusoidal current generating module;
s22, a sinusoidal current generating module generates a sinusoidal current signal based on the sinusoidal voltage signal and inputs the sinusoidal current signal into a reference resistor;
S23, the signal amplifying module amplifies and filters a sinusoidal current signal flowing through the reference resistor through the equipment interface module and inputs the sinusoidal current signal into the high-speed sampling module, and the sinusoidal voltage signal received by the sinusoidal current generating module is amplified and filtered and then inputs the sinusoidal voltage signal into the high-speed sampling module;
step S24, the high-speed sampling module samples the sinusoidal current signal and the sinusoidal voltage signal in real time and then inputs the sinusoidal current signal and the sinusoidal voltage signal into the control module through the communication interface;
And S25, the control module calculates reference resistance parameters including a first alternating current signal amplitude value, a first phase angle sine value, a first phase angle cosine value and a reference resistance value under each gear reference resistance through fast Fourier transformation based on the received sinusoidal current signal and sinusoidal voltage signal, and stores the reference resistance parameters.
The step S22 specifically includes:
The sinusoidal current generating module rectifies and filters the input sinusoidal voltage signal to generate a sinusoidal current signal, and the sinusoidal current signal is input into a reference resistor through the equipment interface module.
The step S24 specifically includes:
the high-speed sampling module samples the sinusoidal current signal and the sinusoidal voltage signal at a preset sampling frequency and then inputs the sinusoidal current signal and the sinusoidal voltage signal into the control module, wherein the sampling frequency is at least 2 times of the frequency of the sinusoidal voltage signal.
The step S25 specifically includes:
step S251, a control module calculates a real component Rex and an imaginary component Imx of the sinusoidal current signal under each gear reference resistance through fast Fourier transformation, and calculates a real component Remcu and an imaginary component Immcu of the sinusoidal voltage signal;
step S252, calculating ac signal amplitudes Ax and Amcu based on the Rex, im x, remcu, and Im mcu, and taking the Ax as a first ac signal amplitude:
Step S253, calculating a first phase angle sine value sin delta and a first phase angle cosine value cos delta based on the Rex, im x, remcu, immcu, ax, and Amcu:
sin delta=sin x*cos mcu-cos x*sin mcu;
cos delta=cos x*cos mcu+sin x*sin mcu;
sin x=Re x/Ax;
sin mcu=Re mcu/Amcu;
cos x=Im x/Ax;
cos mcu=Im mcu/Amcu;
And step S254, recording the reference resistance value of the reference resistance of each gear, and storing the reference resistance parameters comprising the first alternating current signal amplitude, the first phase angle sine value, the first phase angle cosine value and the reference resistance value into the EEPROM. Namely, each reference resistance value corresponds to a first alternating current signal amplitude value, a first phase angle sine value and a first phase angle cosine value respectively.
The step S40 specifically includes:
step S41, the control module continuously outputs a sinusoidal voltage signal to the sinusoidal current generating module;
Step S42, a sinusoidal current generating module generates a sinusoidal current signal based on the sinusoidal voltage signal and inputs the sinusoidal current signal into a lithium battery;
s43, the signal amplifying module amplifies and filters sinusoidal current signals flowing through the lithium battery through the equipment interface module and inputs the sinusoidal current signals into the high-speed sampling module;
step S44, after the high-speed sampling module samples the sinusoidal current signal, the sinusoidal current signal is input into the control module;
and step S45, the control module calculates lithium battery parameters including a second alternating current signal amplitude, a second phase angle sine value and a second phase angle cosine value of the sinusoidal current signal flowing through the lithium battery through fast Fourier transformation. The calculation formulas of the second alternating current signal amplitude, the second phase angle sine value and the second phase angle cosine value are respectively the same as the calculation formulas of the first alternating current signal amplitude, the first phase angle sine value and the first phase angle cosine value.
In the step S50, the calculation step of the ac internal resistance is as follows:
the control module obtains a first alternating current signal amplitude and a reference resistance value of a reference resistance gear corresponding to the lithium battery from the EEPROM, and calculates alternating current internal resistance based on the first alternating current signal amplitude, the reference resistance value and the second alternating current signal amplitude:
ac internal resistance=second ac signal amplitude/first ac signal amplitude;
The calculation formula of the power factor is as follows:
cosα=cos delta*cos L+sin delta*sin L;
Wherein cos alpha represents a power factor, cos L represents a second phase angle cosine value, sin L represents a second phase angle sine value;
since the sinusoidal voltage signal formed on the reference resistor and the sinusoidal current signal flowing through the reference resistor are in phase, it can be approximately considered that the phase angle α between the signal of the lithium battery and the signal of the reference resistor of the present gear is approximately equal to the impedance angle of the lithium battery;
the calculation formula of the alternating current internal resistance component is as follows:
ac internal resistance component = ac internal resistance x cos α.
In summary, the invention has the advantages that:
The method has the advantages that the external reference resistor is used for replacing the traditional reference resistor configured on the original circuit, the hardware cost is greatly reduced, the testing flexibility is improved, the sine voltage signal and the sine current signal are sampled, the alternating-current internal resistance, the power factor and the alternating-current internal resistance component of the lithium battery are calculated by utilizing the fast Fourier transformation, the circuit which is provided with an effective value conversion module and a phase detection module in addition is not needed, the hardware cost is further reduced, the later maintenance is convenient, errors caused by the direct-current component and other frequency components in the sine current signal on the calculation result are eliminated through the fast Fourier transformation, the calculation result of the alternating-current internal resistance is more accurate, the resolution and the accuracy of the calculation result of the power factor are higher, the calculation result of the alternating-current internal resistance component is more stable, the testing cost of the alternating-current internal resistance and the power factor of the lithium battery is finally realized, and the testing precision is greatly improved.
While specific embodiments of the invention have been described above, it will be appreciated by those skilled in the art that the specific embodiments described are illustrative only and not intended to limit the scope of the invention, and that equivalent modifications and variations of the invention in light of the spirit of the invention will be covered by the claims of the present invention.

Claims (3)

1. A lithium battery alternating current internal resistance and power factor testing method based on FFT is characterized by comprising the following steps:
step S10, the upper computer sets a control module to enter a debugging mode, and gears of reference resistors of the interface module of the access equipment are sequentially adjusted;
Step S20, a control module outputs a sinusoidal voltage signal to a sinusoidal current generation module, the sinusoidal voltage signal and a sinusoidal current signal flowing through a reference resistor are sampled by a high-speed sampling module, and further reference resistance parameters under the reference resistor of each gear are respectively calculated by fast Fourier transformation;
Step S30, the upper computer sets a control module to enter a use mode, and the lithium battery is connected into the equipment interface module;
Step S40, the control module continuously outputs a sinusoidal voltage signal to the sinusoidal current generating module, the sinusoidal current signal flowing through the lithium battery is sampled through the high-speed sampling module, and then the lithium battery parameters of the lithium battery are calculated through fast Fourier transform;
Step S50, the control module calculates the alternating current internal resistance, the power factor and the alternating current internal resistance component of the lithium battery based on the reference resistance parameter and the lithium battery parameter, and sends the calculation result to the upper computer;
the step S20 specifically includes:
s21, the control module outputs a sinusoidal voltage signal to the sinusoidal current generating module;
s22, rectifying and filtering the input sinusoidal voltage signal by a sinusoidal current generating module to generate a sinusoidal current signal, and inputting the sinusoidal current signal into a reference resistor through an equipment interface module;
S23, the signal amplifying module amplifies and filters a sinusoidal current signal flowing through the reference resistor through the equipment interface module and inputs the sinusoidal current signal into the high-speed sampling module, and the sinusoidal voltage signal received by the sinusoidal current generating module is amplified and filtered and then inputs the sinusoidal voltage signal into the high-speed sampling module;
Step S24, the high-speed sampling module samples the sinusoidal current signal and the sinusoidal voltage signal at a preset sampling frequency and then inputs the sinusoidal current signal and the sinusoidal voltage signal into the control module, wherein the sampling frequency is at least 2 times of the frequency of the sinusoidal voltage signal;
Step S25, the control module calculates reference resistance parameters including a first alternating current signal amplitude value, a first phase angle sine value, a first phase angle cosine value and a reference resistance value under each gear reference resistance through fast Fourier transformation based on the received sinusoidal current signals and sinusoidal voltage signals, and stores the reference resistance parameters;
the step S25 specifically includes:
step S251, the control module calculates a real component Rex and an imaginary component Imx of the sinusoidal current signal under each gear reference resistance through fast Fourier transformation, and calculates a real component Remcu and an imaginary component Immcu of the sinusoidal voltage signal;
Step S252, calculating ac signal amplitudes Ax and Amcu based on the Rex, imx, remcu and Immcu, and taking the Ax as a first ac signal amplitude:
Step S253, calculating a first phase angle sine value sindelta and a first phase angle cosine value cosdelta based on the Rex, imx, remcu, immcu, ax and Amcu:
sindelta=sinx*cosmcu-cosx*sinmcu;
cosdelta=cosx*cosmcu+sinx*sinmcu;
sinx=Rex/Ax;
sinmcu=Remcu/Amcu;
cosx=Imx/Ax;
cosmcu=Immcu/Amcu;
And step S254, recording the reference resistance value of the reference resistor of each gear, and storing the reference resistance parameters including the first alternating current signal amplitude, the first phase angle sine value, the first phase angle cosine value and the reference resistance value.
2. The method for testing the internal AC resistance and the power factor of the lithium battery based on the FFT of claim 1, wherein the step S40 specifically comprises the following steps:
step S41, the control module continuously outputs a sinusoidal voltage signal to the sinusoidal current generating module;
Step S42, a sinusoidal current generating module generates a sinusoidal current signal based on the sinusoidal voltage signal and inputs the sinusoidal current signal into a lithium battery;
s43, the signal amplifying module amplifies and filters sinusoidal current signals flowing through the lithium battery through the equipment interface module and inputs the sinusoidal current signals into the high-speed sampling module;
step S44, after the high-speed sampling module samples the sinusoidal current signal, the sinusoidal current signal is input into the control module;
And step S45, the control module calculates lithium battery parameters including a second alternating current signal amplitude, a second phase angle sine value and a second phase angle cosine value of the sinusoidal current signal flowing through the lithium battery through fast Fourier transformation.
3. The method for testing the alternating current internal resistance and the power factor of the lithium battery based on the FFT of claim 2, wherein in the step S50, the alternating current internal resistance is calculated as follows:
the control module obtains a first alternating current signal amplitude and a reference resistance value of a reference resistance gear corresponding to the lithium battery, and calculates alternating current internal resistance based on the first alternating current signal amplitude, the reference resistance value and the second alternating current signal amplitude:
ac internal resistance=second ac signal amplitude/first ac signal amplitude;
The calculation formula of the power factor is as follows:
cosα=cosdelta*cosL+sindelta*sinL;
wherein cos alpha represents a power factor, cosL represents a second phase angle cosine value, sinL represents a second phase angle sine value;
the calculation formula of the alternating current internal resistance component is as follows:
ac internal resistance component = ac internal resistance x cos α.
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