Lithium battery fast charging converter based on EIS measurement control and adjustment method

Abstract

The present invention provides a lithium battery fast charging converter based on electrochemical impedance spectroscopy (EIS) measurement control and an adjustment method. Before charging, the initial voltage, current and temperature of a lithium battery are measured, and the lithium battery is charged on the basis of an initial state of the lithium battery; and during charging, a perturbation electrical signal formed by superimposing a direct current on a weak sine wave that does not affect the operation of the battery is sent to the lithium battery, EIS measurement and analysis of the lithium battery are performed by means of the EIS technology to obtain state information of the lithium battery, and charging parameters of the charging converter are adjusted on the basis of the state information of the lithium battery. By means of the solution provided by the present invention, the state of a lithium battery is monitored in real time by means of the EIS technology, and charging parameters are dynamically adjusted, so as to implement an efficient, fast and safe charging process.

Description

A lithium battery fast charging converter and adjustment method based on EIS detection control Technical Field

[0001] The present invention relates to the technical field of lithium battery charging, and in particular to a lithium battery fast charging converter based on EIS detection control and an adjustment method. Background Art

[0002] Traditional fast charging strategies for high-energy-density lithium batteries usually use high current for fast charging. The high current density and high temperature during fast charging may cause lithium plating, which can lead to reduced electrochemical reactions, uneven electrodes and other problems. At the same time, fast charging under complex working conditions will aggravate the degradation of battery life, resulting in dynamic inactivation, electrolyte degradation, electrode expansion, thermal runaway and other problems.

[0003] Due to the above-mentioned shortcomings of the fast charging strategy of high-energy-density lithium batteries, it is necessary to improve the fast charging strategy of lithium batteries to achieve high-efficiency charging of high-energy-density lithium batteries and extend the life of lithium batteries. At present, the commonly used fast charging strategy for lithium batteries is through constant voltage or constant current charging. However, constant voltage or constant current charging will cause the internal temperature of the battery to rise as the charging time increases, and the charging efficiency will decrease accordingly. Moreover, long-term use of constant voltage or constant current charging will lead to a reduction in battery life. Therefore, the fast charging strategy can be improved by changing the charging current waveform or the charging voltage waveform. However, changing the charging current waveform or the charging voltage waveform to quickly charge high-energy-density lithium batteries also faces some problems that need to be solved, such as long charging time and inability to operate at maximum efficiency in real time.

[0004] Therefore, it is necessary to further improve the fast charging method of high-energy-density lithium batteries to overcome the shortcomings of the above-mentioned lithium battery fast charging strategy and further improve the charging efficiency. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a lithium battery fast charging converter and adjustment method based on EIS detection control, which uses EIS technology to monitor the status of the lithium battery in real time and dynamically adjust the charging parameters to achieve an efficient, fast and safe charging process.

[0006] In a first aspect, the present invention provides a lithium battery fast charging converter based on EIS detection control, comprising: a front-stage AC / DC conversion unit, a rear-stage DC / DC conversion unit, a ripple generation unit, and an EIS detection unit;

[0007] The input end of the front-stage AC / DC conversion unit is connected to the AC power supply, and the output end is connected to the rear-stage DC / DC conversion unit, which is used to convert the AC power of the AC charging source into the DC power required by the lithium battery;

[0008] The input end of the rear-stage DC / DC conversion unit is connected to the output end of the front-stage AC / DC conversion unit, and the output end is connected to the lithium battery, and is used to convert the DC voltage from the front-stage AC / DC conversion unit into the voltage required by the lithium battery under the control of the ripple generation unit and the EIS detection unit;

[0009] The ripple generating unit is connected to the subsequent DC / DC conversion unit and is used to output a disturbance electrical signal composed of a superposition of a direct current and a weak sine wave that does not affect the operation of the battery to the subsequent DC / DC conversion unit;

[0010] The EIS detection unit is connected to the subsequent DC / DC conversion unit and is used to measure the equivalent circuit parameters of the lithium battery through EIS technology and adjust the charging current and charging time of the charging converter according to the equivalent circuit parameters.

[0011] Optionally, the subsequent DC / DC conversion unit adopts an LLC converter topology.

[0012] Optionally, the EIS detection unit includes a sampling module, a fast Fourier transform module, an EIS generation module, a fitting module, and a control module.

[0013] In a second aspect, the present invention provides a method for adjusting a lithium battery fast charging converter based on the EIS detection control described in claims 1-3, comprising:

[0014] Before charging, measure the initial voltage, current, and temperature of the lithium battery, and charge the lithium battery according to the initial state of the lithium battery;

[0015] During the charging process, a disturbance electrical signal consisting of a superposition of DC current and a weak sine wave that does not affect the battery's operation is sent to the lithium battery. The AC impedance spectrum of the lithium battery is measured and analyzed using EIS technology to obtain the lithium battery status information, and the charging parameters of the charging converter are adjusted according to the lithium battery status information.

[0016] Optionally, the step of measuring and analyzing the AC impedance spectrum of the lithium battery using EIS technology to obtain the status information of the lithium battery includes:

[0017] A sinusoidal wave disturbance signal with a continuously increasing frequency from 0.1Hz to 100kHz is used for frequency sweeping. The voltage and current of the lithium battery response at a series of different frequencies are collected for spectrum analysis, and the EIS data of the lithium battery is plotted.

[0018] An equivalent circuit model of the lithium battery is obtained and fitted with the alternating current impedance spectrum (EIS) data of the lithium battery to obtain the equivalent circuit parameters of the lithium battery.

[0019] Optionally, adjusting the charging parameters of the charging converter according to the status information of the lithium battery includes:

[0020] According to the principle of maximum power output under the critical state of lithium battery, the charging current information and charging time of lithium battery are determined according to the equivalent circuit parameters of lithium battery;

[0021] The charging current and charging time output by the subsequent DC / DC conversion unit are adjusted according to the charging current information and charging time of the lithium battery. When the lithium battery reaches the required charging state or the charging time reaches the preset value, the charging process is ended.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] Compared with traditional lithium battery fast charging strategies, online EIS technology can monitor the status of lithium batteries in real time, determine the equivalent circuit parameters of lithium batteries, and more accurately understand the health and performance of lithium batteries; based on the real-time detected EIS data, the charging parameters can be adjusted in time to maximize the charging efficiency and speed; through real-time monitoring and feedback control, the current in the charging process can be better controlled, which can effectively prevent the lithium battery from overloading or overheating during the charging process, reduce the heat generation of the lithium battery, improve the safety of charging, and thus help extend the life of the lithium battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0025] FIG1 is a schematic structural diagram of a lithium battery fast charging converter based on EIS detection control provided in a first embodiment of the present disclosure;

[0026] FIG2 is a flow chart of an adjustment method for a lithium battery fast charging converter based on EIS detection control provided in a second embodiment of the present disclosure. DETAILED DESCRIPTION

[0027] Embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0028] The technical solution of the present invention is described in detail below with reference to specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0029] 1 , a first embodiment of the present disclosure provides a lithium battery fast charging converter based on EIS detection control, comprising: a front-stage AC / DC conversion unit, a rear-stage DC / DC conversion unit, a ripple generation unit, and an EIS detection unit;

[0030] The input end of the front-stage AC / DC conversion unit is connected to the AC power supply, and the output end is connected to the rear-stage DC / DC conversion unit, which is used to convert the AC power of the AC charging source into the DC power required by the lithium battery;

[0031] The input end of the rear-stage DC / DC conversion unit is connected to the output end of the front-stage AC / DC conversion unit, and the output end is connected to the lithium battery, and is used to convert the DC voltage from the front-stage AC / DC conversion unit into the voltage required by the lithium battery under the control of the ripple generation unit and the EIS detection unit;

[0032] In this embodiment, the post-stage DC / DC conversion unit adopts an LLC converter topology structure, which has the characteristics of good isolation, lower loss, and a wide output range.

[0033] The ripple generating unit is connected to the subsequent DC / DC conversion unit and is used to output a disturbance electrical signal composed of a superposition of a direct current and a weak sine wave that does not affect the operation of the battery to the subsequent DC / DC conversion unit;

[0034] The EIS detection unit is connected to the subsequent DC / DC conversion unit and is used to measure the equivalent circuit parameters of the lithium battery through EIS technology and adjust the charging current and charging time of the charging converter according to the equivalent circuit parameters;

[0035] In this embodiment, it includes a sampling module, a fast Fourier transform module, an EIS generation module, a fitting module, and a control module.

[0036] Compared with traditional converters, the charging converter provided in this embodiment emits a disturbance point signal that gradually increases from low frequency to high frequency through a ripple generation unit. The EIS detection unit collects the voltage and current of the lithium battery for spectrum analysis, plots the AC impedance spectrum EIS data of the lithium battery, and then fits it with the equivalent circuit model of the lithium battery. The control module then controls the lithium battery fast charging process in real time, thereby achieving a fast and efficient lithium battery charging process.

[0037] 2 , a second embodiment of the present disclosure provides an adjustment method for a lithium battery fast charging converter based on EIS detection control, comprising:

[0038] Before charging, measure the initial voltage, current, and temperature of the lithium battery, and charge the lithium battery according to the initial state of the lithium battery;

[0039] Among them, the measured initial voltage, current, and temperature of the lithium battery are used to analyze the health status of the lithium battery and provide a basis and reference for subsequent fast charging adjustments.

[0040] During the charging process, a disturbance electrical signal consisting of a superposition of DC current and a weak sine wave that does not affect the battery's operation is sent to the lithium battery. The AC impedance spectrum of the lithium battery is measured and analyzed using EIS technology to obtain the lithium battery status information, and the charging parameters of the charging converter are adjusted according to the lithium battery status information.

[0041] In this embodiment, the AC impedance spectrum measurement and analysis of the lithium battery using the EIS technology to obtain the status information of the lithium battery includes:

[0042] A sinusoidal wave disturbance signal with a continuously increasing frequency from 0.1Hz to 100kHz is used for frequency sweeping. The voltage and current of the lithium battery response at a series of different frequencies are collected for spectrum analysis, and the EIS data of the lithium battery is plotted.

[0043] An equivalent circuit model of the lithium battery is obtained and fitted with the alternating current impedance spectrum (EIS) data of the lithium battery to obtain the equivalent circuit parameters of the lithium battery.

[0044] Among them, the equivalent circuit parameters can reflect the electrochemical characteristics of lithium batteries, such as resistance, capacitance and inductance.

[0045] In this embodiment, adjusting the charging parameters of the charging converter according to the status information of the lithium battery includes:

[0046] According to the principle of maximum power output under the critical state of lithium battery, the charging current information and charging time of lithium battery are determined according to the equivalent circuit parameters of lithium battery;

[0047] The charging current information may include the waveform and amplitude of the charging current.

[0048] The charging current and charging time output by the subsequent DC / DC conversion unit are adjusted according to the charging current information and charging time of the lithium battery. When the lithium battery reaches the required charging state or the charging time reaches the preset value, the charging process is ended.

[0049] The adjustment method of the lithium battery fast charging converter based on EIS detection control provided in this embodiment introduces an online EIS detection method, which accurately analyzes the lithium battery status through the AC impedance spectrum EIS data of the lithium battery to adjust the charging parameters of the charging converter in real time to achieve optimal charging efficiency and speed. In addition, based on the online EIS detection, the temperature and current of the lithium battery can be monitored in real time to prevent dangerous situations such as overcharging and overheating.

Claims

1. A lithium battery fast charging converter based on EIS detection control, characterized in that: include: Front-stage AC / DC conversion unit, rear-stage DC / DC conversion unit, ripple generation unit and EIS detection unit; The input end of the front-stage AC / DC conversion unit is connected to the AC power supply, and the output end is connected to the rear-stage DC / DC conversion unit, which is used to convert the AC power of the AC charging source into the DC power required by the lithium battery; The input end of the rear-stage DC / DC conversion unit is connected to the output end of the front-stage AC / DC conversion unit, and the output end is connected to the lithium battery, and is used to convert the DC voltage from the front-stage AC / DC conversion unit into the voltage required by the lithium battery under the control of the ripple generation unit and the EIS detection unit; The ripple generating unit is connected to the subsequent DC / DC conversion unit and is used to output a disturbance electrical signal composed of a superposition of a direct current and a weak sine wave that does not affect the operation of the battery to the subsequent DC / DC conversion unit; The EIS detection unit is connected to the subsequent DC / DC conversion unit and is used to measure the equivalent circuit parameters of the lithium battery through EIS technology and adjust the charging current and charging time of the charging converter according to the equivalent circuit parameters.

2. The lithium battery fast charging converter based on EIS detection control according to claim 1, characterized in that: The post-stage DC / DC conversion unit adopts an LLC converter topology structure.

3. The lithium battery fast charging converter based on EIS detection control according to claim 1, characterized in that: The EIS detection unit includes a sampling module, a fast Fourier transform module, an EIS generation module, a fitting module, and a control module.

4. A method for adjusting a lithium battery fast charging converter based on the EIS detection control according to claims 1-3, characterized in that: include: Before charging, measure the initial voltage, current, and temperature of the lithium battery, and charge the lithium battery according to the initial state of the lithium battery; During the charging process, a disturbance electrical signal consisting of a superposition of DC current and a weak sine wave that does not affect the battery's operation is sent to the lithium battery. The AC impedance spectrum of the lithium battery is measured and analyzed using EIS technology to obtain the lithium battery status information, and the charging parameters of the charging converter are adjusted according to the lithium battery status information.

5. The adjustment method of the lithium battery fast charging converter based on EIS detection control according to claim 4, characterized in that: The method of measuring and analyzing the AC impedance spectrum of the lithium battery using the EIS technology to obtain the status information of the lithium battery includes: A sinusoidal wave disturbance signal with a continuously increasing frequency from 0.1Hz to 100kHz is used for frequency sweeping. The voltage and current of a series of lithium battery responses at different frequencies are collected for spectrum analysis, and the EIS data of the lithium battery is plotted. An equivalent circuit model of the lithium battery is obtained and fitted with the alternating current impedance spectrum (EIS) data of the lithium battery to obtain the equivalent circuit parameters of the lithium battery.

6. The adjustment method of the lithium battery fast charging converter based on EIS detection control according to claim 5, characterized in that: The step of adjusting the charging parameters of the charging converter according to the status information of the lithium battery includes: According to the principle of maximum power output under the critical state of lithium battery, the charging current information and charging time of lithium battery are determined according to the equivalent circuit parameters of lithium battery; The charging current and charging time output by the subsequent DC / DC conversion unit are adjusted according to the charging current information and charging time of the lithium battery. When the lithium battery reaches the required charging state or the charging time reaches the preset value, the charging process is ended.

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