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Bridge-type LC resonant lithium battery equalization circuit and SOC estimation method thereof

A resonant circuit and equalization circuit technology, applied in battery circuit devices, circuit devices, measuring electricity and other directions, can solve the problems of large switching loss, complex control, slow equalization speed, etc., to reduce switching power loss, simple control, and lower requirements. Effect

Inactive Publication Date: 2019-05-24
CHINA UNIV OF MINING & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] The purpose of the present invention is to solve the problems of traditional non-dissipative equalization, such as slow speed, complex control, large switching loss, etc., thus proposing a bridge-type LC resonant lithium battery equalization circuit, which uses the SOC estimation method of predicted current to further reduce the impact on the system hardware resource requirements, and the invention has two equalization modes

Method used

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  • Bridge-type LC resonant lithium battery equalization circuit and SOC estimation method thereof
  • Bridge-type LC resonant lithium battery equalization circuit and SOC estimation method thereof
  • Bridge-type LC resonant lithium battery equalization circuit and SOC estimation method thereof

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Embodiment 1

[0029] The embodiment of the present invention describes the implementation process of the equalization circuit working in mode 1, which is described in detail as follows:

[0030] Take 6 cells as an example, assuming that cell B 1 is the battery cell with the highest charge, B 4 It is the battery cell with the lowest charge.

[0031] The microcontroller of the equalization circuit collects the voltage of the battery cells in the battery pack, determines the SOC value of each single battery and its corresponding battery number according to the SOC estimation algorithm, and judges whether the equalization opening condition is met. If satisfied, balance is performed. At this time, the microcontroller controls the switch relay Q through the I / O port 1,1+ , Q 1,1- , Q 2,4+ and Q 2,4- , the single battery B with the highest SOC 1 and the single battery B with the lowest SOC 4 Access bridge LC resonant circuit.

[0032] Such as Figure 2~4 As shown, the controller has two ...

Embodiment 2

[0034] The embodiment of the present invention describes the implementation process of the equalization circuit working in mode 2, which is described in detail as follows:

[0035] Take 6 cells as an example, assuming that cell B 1 is the battery cell with the highest charge, B 4 It is the battery cell with the lowest charge.

[0036] The microcontroller of the equalization circuit collects the voltage of the battery cells in the battery pack, determines the SOC value of each single battery and its corresponding battery number according to the SOC estimation algorithm, and judges whether the equalization opening condition is met. If satisfied, balance is performed. At this time, the microcontroller controls the switch relay Q through the I / O port 1,1+ , Q 1,1- , Q 2,4+ and Q 2,4- , the single battery B with the highest SOC 1 and the single battery B with the lowest SOC 4 Access bridge LC resonant circuit.

[0037] Such as Figure 5-7 As shown, in this working mode, t...

Embodiment 3

[0039] Figure 8 It is an implementation flowchart of the SOC estimation method based on the predicted current provided by the embodiment of the present invention, and is described in detail as follows:

[0040] (1) Collect the initial value of battery voltage and SOC;

[0041] (2) Predicted current value

[0042] For working mode one:

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049] Among them, V 1 is the high battery voltage, V 2 is the battery voltage with low power; Δt is the duration of a state; L is the inductance of the resonant circuit, C is the capacitance of the resonant circuit; R s is the equivalent resistance of all parasitic resistances on the circuit path.

[0050] For working mode two:

[0051]

[0052]

[0053]

[0054] Among them, V 1 is the high battery voltage, V 2 is the low battery voltage; R s is the equivalent resistance of all parasitic resistances on the circuit path; V C0 is the initial value of the ...

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Abstract

The invention relates to a bridge-type LC resonant lithium battery equalization circuit and an SOC estimation method thereof, and the circuit comprises a bridge-type LC resonant circuit which consistsof two bridge-type circuits and a series LC unit and is used for the energy recovery and transfer between battery cells; a switch array which provides a path for battery energy transfer and realizesthe energy balance of the batteries in the group by adopting the SOC estimation method of the current prediction. The circuit has the following advantages of zero-current switching which reduces the switching power loss and the EMI level; two working modes which can respectively meet the requirements on the equalization speed and efficiency; simple control, wherein the control can be realized through two groups of complementary, fixed-frequency and fixed-duty-ratio PWM signals; the SOC estimation method based on the prediction current, which does not need an external current sensor, achieves the SOC estimation through the battery voltage and the circuit parameter prediction current value, solves the problem that the burden of a controller is increased due to direct current sampling, and lowers the requirement for system hardware.

Description

technical field [0001] The invention relates to a battery equalization technology and an SOC estimation method for lithium batteries. Specifically, it involves the use of a bridge-type LC series resonant circuit and a predicted current-based SOC estimation method to achieve equalization of lithium batteries. Background technique [0002] Lithium-ion batteries have the advantages of high energy density, small size, and high safety. They have become the most widely used power batteries and firmly occupy a dominant position in the market. In actual use, the operating voltage of electric vehicles is about 300V, which requires a large number of batteries to be used in series. Due to inconsistencies in production, use, and storage, individual cells behave differently, and this imbalance becomes more and more severe after several charge-discharge cycles. Due to the inconsistency between the battery cells in the battery pack, the performance of the battery pack will be reduced, th...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J7/00G01R31/382
Inventor 戴鹏常文宇李景杰郑曦公铮王江彬
Owner CHINA UNIV OF MINING & TECH