CN115494414A - Online real-time monitoring system and method for internal resistance of energy storage battery - Google Patents
Online real-time monitoring system and method for internal resistance of energy storage battery Download PDFInfo
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- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/389—Measuring internal impedance, internal conductance or related variables
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- G—PHYSICS
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- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/392—Determining battery ageing or deterioration, e.g. state of health
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
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Abstract
The invention provides an on-line real-time monitoring system and method for internal resistance of an energy storage battery, and belongs to the technical field of battery internal resistance monitoring. The bridge circuit is utilized to avoid the influence of a charger or an electric load on the battery internal resistance measuring method in the online measuring process, so that the reference condition and the withstand voltage condition of the excitation source are not influenced by the running state of the battery, the number of batteries in a battery string and the open-circuit voltage, the state adjustment of the excitation source is reduced, the closed-loop control flow of the excitation source and the battery is reduced, and the online detection of the battery internal resistance is realized under the condition that the reference condition is not changed; the problem of can't once only measure whole battery module etc is solved, realized a plurality of battery internal resistances and detected simultaneously, improved the detection efficiency of battery internal resistance parameter, reduced the required time of battery detection, reduced operating cost. The invention can be applied to the battery internal resistance detection technology and the corresponding electrical detection field, and has wide extension and wide application prospect.
Description
Technical Field
The invention belongs to the technical field of battery internal resistance monitoring, and particularly relates to an energy storage battery internal resistance online monitoring system and method based on a bridge circuit.
Background
The lithium ion batteries are used as a power source and can be used in series to meet the voltage requirement, and the whole series of batteries can be scrapped if one of the batteries fails in time. The loss is not only an expensive battery, but also system paralysis and data loss caused by uncertainty of the battery state, and the consequences are not imaginable. In order to ensure good performance and prolong the service life of the battery, the battery must be managed and controlled reasonably and effectively. The internal resistance of the battery determines the performance of the battery, so the detection of the internal resistance of the battery becomes important.
When the existing detection method is used for detecting the batteries or the battery packs, the batteries or the battery packs are mostly required to be detected off line, even the batteries are detected one by one, and the mode is not only troublesome and labor-consuming, but also low in efficiency, and seriously influences the detection efficiency of the energy storage batteries. When the existing online detection method is used for online detection of the battery or the battery pack, an excitation source needs to excite on a certain battery string voltage reference, but the open-circuit voltage of the battery string changes along with the change of the state of charge of the battery. The existing excitation source can not ensure that the on-line measurement of the internal resistance of the battery can be realized under the condition of not changing the voltage reference condition.
For example, CN 113740751A discloses a device and a method for detecting internal resistance of a battery, which improve the detection accuracy of the internal resistance of the battery by using a combination of a direct current method and an alternating current method. However, considering that the storage batteries are usually supplied in the form of battery packs, the cost problem needs to be considered when monitoring the condition of each battery. CN 216209746U discloses a portable battery internal resistance detection device. The detection of the internal resistance is realized by adopting a constant-current resistor discharge mode, but the method can only analyze the system fault off line and cannot detect the internal resistance of the battery in an on-line state. CN 1036050000A discloses an online detection mode for internal resistance of parallel storage batteries. The detection of the internal resistance is realized by adopting a mode of exciting the battery by the constant current generator, but because the excitation source of the method cannot change the voltage reference, only one excitation source can measure a single battery, and the influence of frequency on the internal resistance of the battery is ignored, so that the obtained information is not comprehensive.
Therefore, on the basis of the purposes of high efficiency, accuracy and economy, revolutionary innovative design of the problems of the monitoring methods for the internal resistance of the energy storage battery becomes a necessary research subject, and has important theoretical significance and practical application value.
Disclosure of Invention
In order to solve the problems that the battery internal resistance measuring method is influenced by loads in the online measuring process, the excitation source needs to change continuously under reference conditions and pressure-resistant conditions, the whole battery module cannot be measured at one time, and the like, the invention innovatively designs the traditional battery internal resistance measuring design idea, and provides the online real-time monitoring method for the internal resistance of the energy storage battery.
In order to achieve the purpose, the technical scheme of the invention is as follows:
an on-line real-time monitoring system for internal resistance of an energy storage battery comprises a battery string, an MCU (micro controller Unit), a response signal measuring device and an upper computer.
The MCU comprises an excitation source, a current sampling circuit, a wireless communication module and an internal resistance calculation module. The excitation source is connected to a balance position right in the middle of the two battery strings to form a Wheatstone bridge circuit; the program parameters of the MCU are modified through a serial port to change the frequency of the excitation source, and a constant alternating current excitation current signal of 0.01-10 kHz is generated. The current sampling circuit is connected with an A/D port of the MCU, and is used for sampling a current excitation signal of an excitation source and current signals of an upper half bridge and a lower half bridge (a circuit above the excitation source is taken as a boundary, a circuit above the excitation source is called the upper half bridge, and a circuit below the excitation source is called the lower half bridge) in real time by using a current continuous sampling algorithm, recording a current sampling waveform, storing the current sampling waveform in the internal resistance calculation module and providing a data source for subsequent internal resistance calculation. The wireless communication module is communicated with the wireless communication module of the response signal measuring equipment in an asynchronous communication mode, sends frequency information of the excitation source to the response signal measuring equipment, receives the voltage response signal and the phase difference information measured by the response signal measuring equipment under the frequency, stores the voltage response signal and the phase difference information in the internal resistance calculating module and provides a data source for subsequent internal resistance calculation. The internal resistance calculation module processes and calculates the stored data to obtain the internal resistance of the battery, and the internal resistance is stored in the upper computer to provide a data source for the subsequent drawing of the electrochemical impedance spectrum of the upper computer.
The response signal measuring equipment comprises a voltage sampling circuit, an alternating current transmitter and a wireless communication module. The voltage sampling circuit is connected with an A/D port of a singlechip in the response signal measuring equipment, and is used for sampling the voltage response signal of the battery in real time by using a voltage continuous sampling algorithm and recording a voltage sampling waveform. The alternating current transmitter is connected with an A/D port of a singlechip in the response signal measuring equipment, and the phase difference theta between the battery current and the battery response voltage is obtained through the battery current and the battery response voltage. The wireless communication module is used for communicating with the wireless communication module of the MCU.
The voltage sampling circuit comprises alternating current differential circuits connected in parallel at two ends of a single battery of the battery string, a secondary amplifying circuit connected with the alternating current differential circuits removes common mode noise in a noise environment, small signals needing to be detected are remained and input to a signal end of a phase-locked amplifying circuit, voltage signals at two ends of a battery current sampling resistor of the other circuit are input to a reference voltage end of the phase-locked amplifying circuit after being subjected to primary amplification, the two circuits of signals are subjected to phase-locked amplification of the phase-locked amplifying circuit to generate a circuit of voltage signals comprising direct current and multi-frequency components, the signals are subjected to low-pass filter multi-frequency components to obtain direct current voltage, the direct current voltage is converted into digital signals through AD sampling in a single chip microcomputer, and voltage amplitude values are obtained after Fourier analysis, filtering and data processing. The alternating current transmitter is connected with a secondary amplifying circuit (shared with a voltage sampling circuit) to obtain response voltage, and voltage signals at two ends of the other battery current sampling resistor are input to the alternating current transmitter after being subjected to primary amplification; the AC transducer contains a multiplier to process the two input signals, the output signal passes through a low-pass filter to filter out multi-frequency components, and the multi-frequency components are input into the single chip microcomputer to obtain the phase difference of the two signals through calculation.
The monitoring method adopting the online real-time monitoring system comprises the following steps:
step 1: connecting an excitation source to a balance position between the two battery strings to form a Wheatstone bridge circuit; the two battery strings are simultaneously excited by utilizing the current division principle.
Step 2: and modifying program parameters of the MCU through a serial port to set the excitation amplitude and frequency of the excitation source, and generating a constant alternating current excitation current signal of 0.01-10 kHz.
And step 3: a wireless communication module in the MCU sends frequency information of the excitation source to a wireless communication module in the response signal measuring equipment; and simultaneously, a current continuous sampling algorithm is utilized to sample a current excitation signal of an excitation source in real time through a current sampling circuit, a current sampling waveform is recorded, and the current sampling waveform is stored in the internal resistance calculation module.
And 4, step 4: after a wireless communication module in the response signal measuring equipment receives frequency information of an excitation source, a voltage continuous sampling algorithm is used for sampling a voltage response signal and a phase difference signal of a battery in real time through a voltage sampling circuit and an alternating current transmitter and recording a voltage sampling waveform.
And 5: and the wireless communication module in the response signal measuring equipment sends the frequency information of the excitation source, the voltage response signal of the battery and the phase difference signal to the wireless communication module in the MCU and stores the frequency information, the voltage response signal and the phase difference signal in the internal resistance calculation module of the MCU.
Step 6: and an internal resistance calculation module in the MCU performs calculation processing on the current excitation signal of the excitation source, the voltage response signal and the phase difference signal of the battery, and determines internal resistances Re (Z) and Im (Z) of the battery. The method specifically comprises the following steps:
step 6.1: and traversing the sampling point data in one period t =1/f for calculation, and defining the starting points of I, j, k, m and n by calculating a voltage effective value U [ I ], a current effective value I [ j ] and a voltage-current phase difference theta [ k ], wherein I =1, j =1, k =1, m =1 and n =1.
Step 6.2: the internal resistances Re (Z) [ m ] and Im (Z) [ n ] of the battery are determined by impedance formulae Z = U [ I ]/I [ j ] and Re (Z) = ZCos θ [ k ], im (Z) = Zsin θ [ k ].
Step 6.3: let i ' = i +1, j ' = j +1, k ' = k +1, m ' = m +1, n ' = n +1, go through all sampling points, and obtain the effective value U [ i ] of the voltage in a plurality of periods t =1/f]Effective value of current Ij]Voltage current phase difference θ k]And repeating the step 6.2 to calculate the internal resistance Re (Z) [ m ]]And Im (Z) [ n ]](ii) a Then respectively taking the average value of the internal resistances
And
to reduce errors.
And 7: and (3) changing the frequency of the excitation source by using the MCU, changing the stepping frequency when the precision requirement is not met, and repeating the step 3-6.
And 8: the MCU sends the battery internal resistance information to the upper computer by utilizing the wireless communication module.
And step 9: and drawing an electrochemical impedance spectrum by the upper computer.
Step 10: the upper computer analyzes the health degree of the battery; the method comprises the following specific steps:
step 10.1: determination of characteristic frequency point f by electrochemical impedance spectrum 1 ,f 2 And f 3 。
Step 10.2: respectively calculating ohmic internal resistances R through formulas (1) to (3) 0 Internal contact resistance R c And the internal resistance R of SEI film sei ；
R 0 ≈Real(Z(f 1 )) (1)
R c ≈Real(Z(f 2 ))-Real(Z(f 1 )) (2)
R sei ≈Real(Z(f 3 ))-Real(Z(f 2 )) (3)
Step 10.3: and respectively comparing the ohmic internal resistance, the contact internal resistance and the SEI internal resistance with set thresholds, and judging the health state of the battery.
Further, the principle of the phase difference between the response voltage and the excitation current obtained by the ac transmitter in step 4 is as follows: let f 1 (t) is a voltage input signal with noise, i.e. f 1 (t) = Vsin (ω t + α) + N (t), where Vsin (ω t + α) is a known signal, the amplitude of this voltage input signal is V, the angular frequency is ω, the phase angle is α, and N (t) is random noise; current signal of f 2 (t) = Csin (ω t + β), C is the current signal amplitude, and the phase angle is β.
Then after the multiplier there is
Due to the current signal f 2 (t) is uncorrelated with noise N (t), so that it can be filtered out by a low-pass filter
And C.n (t) sin (ω t + β), to obtain
The voltage current signal amplitude is known, then the phase difference of the two signals is θ = α - β.
Further, in the step 7, the step frequency f is changed (1) ＝0.9f (0) Calculating the internal resistance value U [ i ] in one period t =1/f]*cosθ[k]/I[j]If | U [ i-1]*cosθ[k-1]/I[j-1]-U[i]*cosθ[k]/I[j]When | > epsilon does not meet the precision requirement, the measurement stepping value is reduced to 1/10 of the original value, namely f (1) ＝0.99f (0) (ii) a If | U [ i-1]*cosθ[k-1]/I[j-1]-U[i]*cosθ[k]/I[j]When the accuracy requirement is satisfied with less than or equal to epsilon, the measured step value is kept as it is, i.e. f (1) ＝0.9f (0) (ii) a Where epsilon is the step threshold.
Further, in the step 10.1, the characteristic frequency point f 1 ,f 2 And f 3 The determination method of (2) is as follows: f. of 1 The determination is determined as any one coincident with Re (Z) axis on electrochemical impedance spectrumThe frequency value corresponding to the point; f. of 2 Determining a frequency value corresponding to the maximum value of Im (Z) on the small capacitive ring; f. of 3 The frequency value corresponding to the maximum value of Im (Z) on the large capacitive ring is determined.
The invention has the beneficial effects that: according to the online real-time monitoring method for the internal resistance of the energy storage battery, disclosed by the invention, the bridge circuit is utilized to avoid the influence of a charger or an electric load on the online measurement process of the internal resistance measurement method of the battery, so that the reference condition and the voltage withstanding condition of an excitation source are not influenced by the running state of the battery, the number of batteries in a battery string and the open-circuit voltage, the state regulation of the excitation source is reduced, the closed-loop control flow of the excitation source and the battery is reduced, and the online detection of the internal resistance of the battery is realized under the condition that the reference condition is not changed; the problem of can't once only measure whole battery module etc is solved, realized a plurality of battery internal resistances and detected simultaneously, improved the detection efficiency of battery internal resistance parameter, reduced the required time of battery detection, reduced operating cost. The invention can be applied to the battery internal resistance detection technology and the corresponding electrical detection field, and has wide extension and wide application prospect.
Drawings
Fig. 1 is a general schematic of the present invention.
FIG. 2 is a voltage sampling circuit and AC transmitter coupling circuit of the present invention.
FIG. 3 is a block diagram of a data processing communication flow according to the present invention.
Fig. 4 is a functional diagram of the MCU of the present invention.
Fig. 5 is a functional diagram of the response signal measuring apparatus of the present invention.
Fig. 6 is a flow chart of internal resistance measurement of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in FIG. 1, the invention provides an online real-time monitoring method for the internal resistance of an energy storage battery, which connects an excitation source capable of generating a constant alternating current excitation current signal of 0.01-10 kHz to a balance position between two battery strings to form a Wheatstone bridge circuit; under the condition of ignoring battery inconsistency, the voltage balance of the bridge circuit is utilized, the voltage at two ends of the middle branch circuit is 0, and the circulating current of the middle branch circuit is 0, so that the reference voltage of the excitation source is always 0, and the reference voltage of the excitation source does not need to be adjusted according to the running state of the batteries, the number of the batteries in the battery string and the open-circuit voltage. The bridge circuit has the characteristic that the circulating current of the middle branch is 0, and meanwhile, the bridge circuit can be prevented from being influenced by a charger or an electric load, so that online measurement is realized. According to the current shunting principle, two battery strings can be excited simultaneously, so that the online real-time monitoring of the internal resistances of a plurality of energy storage batteries is realized; modifying program parameters of the MCU through a serial port to set the excitation amplitude and frequency of the excitation source and generate a constant alternating current excitation current signal of 0.01-10 kHz; sending frequency information of the excitation source to a wireless communication module in response signal measuring equipment through a wireless communication module in the MCU, simultaneously sampling a current excitation signal of the excitation source in real time through a current sampling circuit by utilizing a current continuous sampling algorithm, recording a current sampling waveform, and storing the current sampling waveform in an internal resistance calculating module; after a wireless communication module in the response signal measuring equipment receives frequency information of an excitation source, a voltage continuous sampling algorithm is used for sampling a voltage response signal and a phase difference signal of a battery in real time through a voltage sampling circuit and an alternating current transmitter and recording a voltage sampling waveform; the wireless communication module in the response signal measuring equipment sends the frequency information of the excitation source, the voltage response signal of the battery and the phase difference signal to the wireless communication module in the MCU and stores the frequency information, the voltage response signal and the phase difference signal in the internal resistance calculation module of the MCU; the internal resistance calculation module in the MCU calculates and processes the current excitation signal of the excitation source, the voltage response signal and the phase difference signal of the battery, and internal resistances Re (Z) and Im (Z) of the battery are determined by an impedance formula. The process is as described above, until all the storage batteries in the whole system complete the internal resistance test, the internal resistance test process of the batteries of the whole system is finished, the obtained internal resistance information of the batteries is used for analyzing the health degree of the batteries by drawing an electrochemical impedance spectrum by an upper computer, positioning unqualified single batteries and quantifying the integrity of the battery pack.
The online real-time monitoring method for the internal resistance of the energy storage battery comprises the following specific implementation steps:
step 1: connecting an excitation source to a balance position between the two battery strings to form a Wheatstone bridge circuit; the two battery strings are simultaneously excited by utilizing the current division principle.
Step 2: and modifying program parameters of the MCU through a serial port to set the excitation amplitude and frequency of the excitation source, and generating a constant alternating current excitation current signal of 0.01-10 kHz.
And step 3: sending frequency information of an excitation source to a wireless communication module in response signal measuring equipment through a wireless communication module in the MCU; and simultaneously, a current continuous sampling algorithm is utilized to sample a current excitation signal of an excitation source in real time through a current sampling circuit, a current sampling waveform is recorded, and the current sampling waveform is stored in the internal resistance calculation module.
And 4, step 4: after a wireless communication module in the response signal measuring equipment receives frequency information of an excitation source, a voltage continuous sampling algorithm is used for sampling a voltage response signal and a phase difference signal of a battery in real time through a voltage sampling circuit and an alternating current transmitter and recording a voltage sampling waveform.
And 5: and the wireless communication module in the response signal measuring equipment sends the frequency information of the excitation source, the voltage response signal of the battery and the phase difference signal to the wireless communication module in the MCU and stores the frequency information, the voltage response signal and the phase difference signal in the internal resistance calculation module of the MCU.
Step 6: and an internal resistance calculation module in the MCU calculates and processes the current excitation signal of the excitation source, the voltage response signal of the battery and the phase difference signal, and determines internal resistances Re (Z) and Im (Z) of the battery by using an impedance formula. The method specifically comprises the following steps:
step 6.1: and calculating the voltage effective value U [ I ], the current effective value I [ j ] and the voltage-current phase difference theta [ k ] by traversing the sampling point data in one period t =1/f, and defining the starting points as I, j, k, m and n, wherein I =1, j =1, k =1, m =1 and n =1.
Step 6.2: the internal resistances Re (Z) [ m ] and Im (Z) [ n ] of the battery are determined by impedance formulae Z = U [ I ]/I [ j ] and Re (Z) = ZCos θ [ k ], im (Z) = Zsin θ [ k ].
Step 6.3: let i ' = i +1, j ' = j +1, k ' = k +1, m ' = m +1, n ' = n +1, go through all sampling points, and obtain the effective value U [ i ] of the voltage in a plurality of periods t =1/f]Effective value of current Ij]Voltage current phase difference θ k]Repeating the step 6.2 to calculate the internal resistance Re (Z) m]And Im (Z) [ n ]](ii) a Then respectively taking the average value of the internal resistances
And
to reduce the error.
And 7: the frequency of the excitation source is changed by using the MCU, and when the precision requirement is not met, the stepping frequency f is changed (1) ＝0.9f (0) Calculating an internal resistance value U [ i ] within one period t =1/f]*cosθ[k]/I[j]If | U [ i-1]*cosθ[k-1]/I[j-1]-U[i]*cosθ[k]/I[j]When epsilon does not meet the precision requirement, the measurement step value is reduced to 1/10 of the original value, namely f (1) ＝0.99f (0) (ii) a If | U [ i-1]*cosθ[k-1]/I[j-1]-U[i]*cosθ[k]/I[j]When | < epsilon meets the precision requirement, the measured step value keeps the original value, i.e. f (1) ＝0.9f (0) (ii) a And repeating the steps 3-6.
And step 8: the MCU sends the battery internal resistance information to the upper computer by utilizing the wireless communication module.
And step 9: and drawing an electrochemical impedance spectrum by the upper computer.
Step 10: the upper computer analyzes the health degree of the battery; the method comprises the following specific steps:
step 10.1: determination of characteristic frequency point f by electrochemical impedance spectroscopy 1 ,f 2 And f 3 (ii) a Characteristic frequency point f 1 ,f 2 And f 3 The determination method of (2) is as follows: f. of 1 Determining a frequency value corresponding to any point which is coincident with the Re (Z) axis on the electrochemical impedance spectrum; f. of 2 Confirmed as the Im (Z) maximum on the small capacitive ringThe corresponding frequency value; f. of 3 The frequency value corresponding to the maximum value of Im (Z) on the large capacitive ring is determined.
Step 10.2: respectively calculating ohmic internal resistances R through formulas (1) to (3) 0 Internal contact resistance R c And the internal resistance R of SEI film sei ；
R 0 ≈Real(Z(f 1 )) (1)
R c ≈Real(Z(f 2 ))-Real(Z(f 1 )) (2)
R sei ≈Real(Z(f 3 ))-Real(Z(f 2 )) (3)
Step 10.3: and respectively comparing the ohmic internal resistance, the contact internal resistance and the SEI internal resistance with set thresholds, and judging the health state of the battery.
As shown in fig. 2, the voltage sampling circuit includes an ac differential circuit connected in parallel to both ends of the single battery, a secondary amplifying circuit connected to the ac differential circuit removes common mode noise in a noise environment, leaves a small signal to be detected, and inputs the small signal to a signal end of a phase-locked amplifying circuit, and simultaneously inputs a voltage signal at both ends of another battery current sampling resistor to a reference voltage end of the phase-locked amplifying circuit after being subjected to a first-stage amplification, the two signals are subjected to a phase-locked amplification of the phase-locked amplifying circuit to generate a voltage signal including a dc component and a multi-frequency component, the voltage signal is subjected to a low-pass filter to filter the multi-frequency component to obtain a dc voltage, the dc voltage is converted into a digital signal by an AD sampling in the single chip, and a voltage amplitude is obtained after fourier analysis, filtering and data processing. The alternating current transmitter is connected with the secondary amplifying circuit to obtain the phase difference between the response voltage and the excitation current; let f 1 (t) is a voltage input signal with noise, i.e. f 1 (t) = Vsin (ω t + α) + N (t), where Vsin (ω t + α) is a known signal, the amplitude of this voltage input signal is a, the angular frequency is ω, the phase angle is α, and N (t) is random noise; current signal of f 2 (t) = Csin (ω t + β), phase angle β. Then after the multiplier there is
Due to the current signal f 2 (t) is uncorrelated with noise N (t), so that it can be filtered out by a low-pass filter
And C.n (t) sin (ω t + β), to obtain
The voltage-current signal amplitude is known, and the phase difference θ = α - β between the two signals can be easily found.
As shown in fig. 3, the response signal measuring device and the MCU adopt an asynchronous communication mode, which has low requirement on clock synchronization between the transmitter and the receiver, so that the whole apparatus is simpler and more convenient. The MCU transmits the frequency information to the response signal measuring equipment, the response signal measuring equipment measures the response signal after successfully receiving the response signal, and the measuring information and the previously received frequency information are transmitted to the MCU together, so that the frequency information and the voltage response signal measured under the frequency are corresponding to the phase difference information.
The set amplitude value, frequency value, characteristic point, set threshold value and stepping threshold value epsilon are respectively fixed reference values, and the reference values are specifically set according to the technical personnel in the field and the actual specific implementation situation, namely, the reference values need to be adjusted according to the specific type of the actual battery to be measured, for example, different reference values are set for different measuring ranges of the battery to be measured, which is realized and reasonable within the protection scope of the invention.
In conclusion, the invention solves the problems of the battery internal resistance measuring method that the measuring method is influenced by the load in the online measuring process, the reference condition and the pressure-resistant condition of the excitation source need to be changed continuously, the measuring error caused by the change of the battery electromotive force and the like, and realizes the online detection of the battery internal resistance; the problems that the whole battery module cannot be measured at one time and the like are solved, and the internal resistances of a plurality of batteries are detected simultaneously; the invention can be applied to the battery internal resistance detection technology and the corresponding electrical detection field, and has wide extension and wide application prospect.
Claims (9)
1. An on-line real-time monitoring system for the internal resistance of an energy storage battery is characterized by comprising a battery string, an MCU, a response signal measuring device and an upper computer;
the MCU comprises an excitation source, a current sampling circuit, a wireless communication module and an internal resistance calculation module; the excitation source is connected to a balance position right in the middle of the two battery strings to form a Wheatstone bridge circuit; modifying program parameters of the MCU through a serial port to change the frequency of the excitation source and generate a constant alternating current excitation current signal of 0.01-10 kHz; the current sampling circuit is connected with an A/D port of the MCU, samples a current excitation signal of an excitation source and current signals of an upper half bridge and a lower half bridge in real time by using a current continuous sampling algorithm, records a current sampling waveform, stores the current sampling waveform in the internal resistance calculation module and provides a data source for subsequent internal resistance calculation; the wireless communication module communicates with the wireless communication module of the response signal measuring equipment in an asynchronous communication mode, sends frequency information of an excitation source to the response signal measuring equipment, receives a voltage response signal and phase difference information measured by the response signal measuring equipment at the frequency, stores the voltage response signal and the phase difference information in the internal resistance calculating module, and provides a data source for subsequent internal resistance calculation; the internal resistance calculation module processes and calculates the stored data to obtain the internal resistance of the battery, stores the internal resistance in the upper computer and provides a data source for the subsequent drawing of an electromechanical impedance spectrum of the upper computer;
the response signal measuring equipment comprises a voltage sampling circuit, an alternating current transmitter and a wireless communication module; the voltage sampling circuit is connected with an A/D port of a singlechip in response signal measuring equipment, and is used for sampling a voltage response signal of the battery in real time by using a voltage continuous sampling algorithm and recording a voltage sampling waveform; the alternating current transmitter is connected with an A/D port of a singlechip in the response signal measuring equipment, and the phase difference between the alternating current transmitter and the battery is obtained through the battery current and the battery response voltage; the wireless communication module is used for communicating with the wireless communication module of the MCU.
2. The system of claim 1, wherein the voltage sampling circuit comprises ac differential circuits connected in parallel to two ends of a single battery of the battery string, a secondary amplifying circuit connected to the ac differential circuits removes common mode noise in a noise environment, leaves a small signal to be detected, and inputs the small signal to a signal end of the phase-locked amplifying circuit, and simultaneously inputs a voltage signal at two ends of a current sampling resistor of another battery to a reference voltage end of the phase-locked amplifying circuit after primary amplification, the two signals generate a voltage signal including a direct current component and a multi-frequency component after phase-locked amplification of the phase-locked amplifying circuit, the signal filters the multi-frequency component through a low-pass filter to obtain a direct current voltage, the direct current voltage is converted into a digital signal through AD sampling in the single chip microcomputer, and the voltage amplitude is obtained after fourier analysis, filtering and data processing; the alternating current transmitter is connected with the secondary amplifying circuit to obtain response voltage, and voltage signals at two ends of the other battery current sampling resistor are input to the alternating current transmitter after primary amplification; the AC transducer contains a multiplier to process the two input signals, the output signal passes through a low-pass filter to filter out the multi-frequency component, and the multi-frequency component is input into a single chip microcomputer to obtain the phase difference of the two signals through calculation.
3. A monitoring method using the on-line real-time monitoring system as claimed in claim 1 or 2, characterized in that the method comprises the steps of:
step 1: connecting an excitation source to a balance position between the two battery strings to form a Wheatstone bridge circuit; exciting the two battery strings simultaneously by utilizing a current splitting principle;
and 2, step: modifying program parameters of the MCU through a serial port to set the excitation amplitude and frequency of the excitation source and generate a constant alternating current excitation current signal of 0.01-10 kHz;
and step 3: a wireless communication module in the MCU sends frequency information of the excitation source to a wireless communication module in the response signal measuring equipment; meanwhile, a current continuous sampling algorithm is utilized to sample a current excitation signal of an excitation source in real time through a current sampling circuit, a current sampling waveform is recorded, and the current sampling waveform is stored in an internal resistance calculation module;
and 4, step 4: after a wireless communication module in the response signal measuring equipment receives frequency information of an excitation source, a voltage continuous sampling algorithm is used for sampling a voltage response signal and a phase difference signal of a battery in real time through a voltage sampling circuit and an alternating current transmitter and recording a voltage sampling waveform;
and 5: the wireless communication module in the response signal measuring equipment sends the frequency information of the excitation source, the voltage response signal of the battery and the phase difference signal to the wireless communication module in the MCU and stores the frequency information, the voltage response signal and the phase difference signal in the internal resistance calculation module of the MCU;
and 6: an internal resistance calculation module in the MCU calculates and processes a current excitation signal of an excitation source, a voltage response signal and a phase difference signal of the battery, and determines internal resistances Re (Z) and Im (Z) of the battery;
and 7: changing the frequency of the excitation source by using the MCU, changing the stepping frequency when the precision requirement is not met, and repeating the steps 3-6;
and 8: the MCU sends the battery internal resistance information to the upper computer by using the wireless communication module;
and step 9: drawing an electrochemical impedance spectrum by the upper computer;
step 10: and the upper computer analyzes the health degree of the battery.
4. The method according to claim 3, characterized in that said step 6 comprises in particular the steps of:
step 6.1: calculating the data of sampling points in one period t =1/f, and calculating a voltage effective value U [ I ], a current effective value I [ j ] and a voltage-current phase difference theta [ k ], wherein the starting points are I, j, k, m and n, and I =1, j =1, k =1, m =1 and n =1;
step 6.2: determining internal resistances Re (Z) m and Im (Z) n of the battery from impedance formulas Z = U [ I ]/I [ j ] and Re (Z) = ZCos θ [ k ], and Im (Z) = Zsin θ [ k ];
step 6.3: let i ' = i +1, j ' = j +1, k ' = k +1, m ' = m +1, n ' = n +1, go through all sampling points, and obtain the effective value U [ i ] of the voltage in a plurality of periods t =1/f]Effective value of current Ij]Voltage current phase difference θ k]And repeating the step 6.2 to calculate the internal resistance Re (Z) [ m ]]And Im (Z) [ n ]](ii) a Then respectively taking the average value of the internal resistances
And
to reduce errors.
5. Method according to claim 3 or 4, characterized in that in step 7, the step frequency f is changed (1) ＝0.9f (0) Calculating the internal resistance value U [ i ] in one period t =1/f]*cosθ[k]/I[j]If | U [ i-1]*cosθ[k-1]/I[j-1]-U[i]*cosθ[k]/I[j]When | > epsilon does not meet the precision requirement, the measurement stepping value is reduced to 1/10 of the original value, namely f (1) ＝0.99f (0) (ii) a Where epsilon is the step threshold.
6. Method according to claim 3 or 4, characterized in that said step 10 comprises in particular the steps of:
step 10.1: determination of characteristic frequency point f by electrochemical impedance spectroscopy 1 ,f 2 And f 3 ；
Step 10.2: ohmic internal resistance R is respectively calculated through formulas (1) - (3) 0 Internal contact resistance R c And resistance R in SEI film sei ；
R 0 ≈Real(Z(f 1 )) (1)
R c ≈Real(Z(f 2 ))-Real(Z(f 1 )) (2)
R sei ≈Real(Z(f 3 ))-Real(Z(f 2 )) (3)
Step 10.3: and respectively comparing the ohmic internal resistance, the contact internal resistance and the SEI internal resistance with set thresholds, and judging the health state of the battery.
7. The method according to claim 5, characterized in that said step 10 comprises in particular the steps of:
step 10.1: by electrochemical resistanceAnti-spectrum determination characteristic frequency point f 1 ,f 2 And f 3 ；
Step 10.2: respectively calculating ohmic internal resistances R through formulas (1) to (3) 0 Internal contact resistance R c And resistance R in SEI film sei ；
R 0 ≈Real(Z(f 1 )) (1)
R c ≈Real(Z(f 2 ))-Real(Z(f 1 )) (2)
R sei ≈Real(Z(f 3 ))-Real(Z(f 2 )) (3)
Step 10.3: and respectively comparing the ohmic internal resistance, the contact internal resistance and the SEI internal resistance with set thresholds, and judging the health state of the battery.
8. The method according to claim 6, characterized in that in step 10.1, the characteristic frequency point f 1 ,f 2 And f 3 The determination method of (2) is as follows: f. of 1 Determining a frequency value corresponding to any point which coincides with the Re (Z) axis on the electrochemical impedance spectrum; f. of 2 Determining a frequency value corresponding to the maximum value of Im (Z) on the small capacitive ring; f. of 3 The frequency value corresponding to the maximum value of Im (Z) on the large capacitive ring is determined.
9. The method of claim 3, 4, 7 or 8, wherein the principle of obtaining the phase difference between the response voltage and the excitation current by the ac transmitter in step 4 is as follows: let f 1 (t) is a voltage input signal with noise, i.e. f 1 (t) = Vsin (ω t + α) + N (t), where Vsin (ω t + α) is a known signal, the amplitude of the voltage input signal is V, the angular frequency is ω, the phase angle is α, and N (t) is random noise; current signal of f 2 (t) = Csin (ω t + β), C is the current signal amplitude, and the phase angle is β; then after the multiplier there is
Due to the current signal f 2 (t) is uncorrelated with noise N (t) and is therefore filtered out by a low-pass filter
And C.n (t) sin (ω t + β) to obtain
The voltage current signal amplitude is known, then the phase difference of the two signals is θ = α - β.
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