Multi-layer equalization circuit for battery pack

Abstract

The utility model discloses a multi-layer equalization circuit for a battery pack, which comprises n batteries connected in series, and every two adjacent batteries are connected with an equalization module to form a first-layer equalization unit; every two adjacent first-layer balancing units are connected with one balancing module to form a second-layer balancing unit, and every two adjacent (k-1) th-layer balancing units are connected with one balancing module to form a kth-layer balancing unit; when the number n of the batteries is an odd number larger than 1, the remaining single batteries are virtualized as the last equalization unit of the first layer, and the last equalization unit and the adjacent first layer equalization unit are connected with an equalization module to form a first second layer equalization unit; and when the number of the (k-1) th layer of balancing units is an odd number greater than 1, virtualizing the remaining single balancing units in the (k-1) th layer as the last balancing unit in the kth layer, and connecting the last balancing unit and the adjacent balancing unit in the kth layer with a balancing module to form a first (k + 1) th layer of balancing unit. According to the utility model, the equalization time is shortened, and the equalization efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technology of battery management systems, and particularly to a multi-layer equalization circuit for a battery pack. Background Art

[0002] Lithium batteries are widely used in energy storage power stations, new energy vehicles and other fields due to their high reliability, no memory effect, low self-discharge rate and other advantages. To meet the voltage and capacity requirements, multiple lithium batteries need to be connected in series to form a battery pack. When the battery is repeatedly charged and discharged, due to the initial capacity differences, asymmetric attenuation characteristics, uneven temperature distribution and other phenomena of each battery, there are inevitable differences in the chemical and electrical characteristics of the batteries, resulting in uneven charge and discharge. Without any control, when the battery works in this unbalanced state for a long time, its energy storage capacity will seriously decline. In the worst case, there may even be a fire or explosion, causing serious losses.

[0003] Existing battery equalization technologies are divided into active equalization and passive equalization. Passive equalization has a large energy loss during the equalization process and is accompanied by serious heating phenomena. Existing active equalization generally only sets a single layer of equalization energy, which can only be transferred between adjacent batteries, with a long equalization time and low equalization efficiency. When the number of batteries is large, large-scale equalization cannot be achieved. Utility Model Content

[0004] Aiming at the problems of high energy consumption, long time and low energy utilization rate in the existing reconfigurable battery equalization technology, the present utility model proposes a multi-layer equalization circuit for a battery pack.

[0005] To achieve the above object, the present utility model adopts the following technical solutions:

[0006] A multi-layer equalization circuit for a battery pack includes n batteries, the n batteries are connected in series, and an equalization module is connected between every two adjacent batteries to form a first-layer equalization unit; an equalization module is connected between every two adjacent first-layer equalization units to form a second-layer equalization unit, and an equalization module is connected between two adjacent (k - 1)-th layer equalization units to form a k-th layer equalization unit;

[0007] When the number of batteries n is an odd number greater than 1, the remaining single battery is virtualized as the last equalization unit of the first layer, and an equalization module is connected between it and the adjacent first-layer equalization unit to form the first second-layer equalization unit;

[0008] When the number of (k - 1)-th layer equalization units is an odd number greater than 1, the remaining single equalization unit of the (k - 1)-th layer is virtualized as the last equalization unit of the k-th layer, and an equalization module is connected between it and the adjacent k-th layer equalization unit to form the first (k + 1)-th layer equalization unit;

[0009] When the number of the last - layer balancing units is 1, a multi - layer balancing circuit of n batteries is formed.

[0010] Further, the balancing module includes a first MOSFET, a second MOSFET, and an inductor. The first MOSFET and the second MOSFET are connected in series. One end of the inductor is connected to the series connection point of the first MOSFET and the second MOSFET. The source electrode of the first MOSFET, the drain electrode of the second MOSFET, and the other end of the inductor are respectively the first end, the second end, and the third end of the balancing module.

[0011] Still further, the first MOSFET and the second MOSFET are matched and are MOSFETs of the same model.

[0012] Even further, two adjacent batteries are connected to a balancing module to form a first - layer balancing unit. Specifically: the positive electrode of the previous battery among two adjacent batteries, the negative electrode of the subsequent battery, and the series connection point of the two batteries are respectively connected to the first end, the second end, and the third end of the balancing module.

[0013] Two adjacent first - layer balancing units are connected to a balancing module to form a second - layer balancing unit. Specifically: after the two adjacent first - layer balancing units are connected in series, they are connected in parallel with the balancing module, and the series connection point of the two adjacent first - layer balancing units is connected to the third end of the balancing module.

[0014] Two adjacent (k - 1) - layer balancing units are connected to a balancing module to form a k - layer balancing unit. Specifically: after the two adjacent (k - 1) - layer balancing units are connected in series, they are connected in parallel with the balancing module, and the series connection point of the two adjacent (k - 1) - layer balancing units is connected to the third end of the balancing module.

[0015] Even further, when the number of batteries n is an odd number greater than 1, the remaining single battery is virtualized as the last balancing unit of the first layer, and a balancing module is connected to the adjacent first - layer balancing unit to form the first second - layer balancing unit. Specifically: the second end and the third end of the balancing module are respectively connected to the negative electrode and the positive electrode of the remaining single battery, and the first end of the balancing module is connected to the first end of the adjacent first - layer balancing unit;

[0016] When the number of (k - 1) - layer balancing units is an odd number greater than 1, the remaining single balancing unit of the (k - 1) - layer is virtualized as the last balancing unit of the k - layer, and a balancing module is connected to the adjacent k - layer balancing unit to form the first (k + 1) - layer balancing unit. Specifically: the second end and the third end of the balancing module are respectively connected to the second end and the first end of the remaining single balancing unit of the (k - 1) - layer, and the first end of the balancing module is connected to the first end of the adjacent (k - 1) - layer balancing unit.

[0017] Furthermore, it further includes a control circuit, which is connected to the gates of the first MOSFET and the second MOSFET in each equalization module for controlling the conduction and cutoff of the first MOSFET and the second MOSFET.

[0018] Furthermore, it further includes a voltage measurement element for measuring the voltage of each battery. The voltage measurement element can be a voltage sensor. A voltage sensor is connected in parallel to each battery, and the output of the voltage sensor is electrically connected to the control circuit to transmit the measured battery voltage data to the control circuit.

[0019] Compared with the prior art, the utility model has the following beneficial effects:

[0020] 1. Without adding equalization modules, the utility model can greatly reduce the equalization time and greatly improve the equalization efficiency only by changing the connection method, and without increasing the cost;

[0021] 2. The utility model realizes modularization and can be extended to multiple batteries for use, making it more suitable for actual application scenarios;

[0022] 3. The utility model uses fewer components, has a lower cost, and higher stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of the equalization module in the utility model.

[0024] Figure 2 It is a schematic overall structural diagram of the utility model.

[0025] Figure 3 It is a schematic structural diagram of a multi-layer equalization circuit composed of 15 batteries in an embodiment of the utility model.

[0026] Figure 4 It is a schematic structural diagram of the first stage of the charging equalization process in the utility model.

[0027] Figure 5 It is a schematic structural diagram of the second stage of the charging equalization process in the utility model.

[0028] Figure 6 It is a schematic structural diagram of the traditional equalization circuit adopted in an embodiment of the utility model.

[0029] In the figure: the equalization module 1-i represents the i-th equalization module in the first layer, the equalization module 2-i represents the i-th equalization module in the second layer, the equalization module 3-i represents the i-th equalization module in the third layer, the equalization module k-i represents the i-th equalization module in the k-th layer, and Bi represents the i-th battery, where i is a natural number;

[0030] 1 - The first MOSFET, 2 - The second MOSFET, 3 - Inductor. Detailed implementation manners

[0031] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and through specific embodiments. Those skilled in the art should understand that the specific implementation manners are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0032] As Figures 1-3 shown, a multi - layer equalization circuit for a battery pack includes n batteries, and the n batteries are connected in series. An equalization module is connected between every two adjacent batteries to form a first - layer equalization unit; an equalization module is connected between every two adjacent first - layer equalization units to form a second - layer equalization unit, and an equalization module is connected between two adjacent k - 1 - layer equalization units to form a k - layer equalization unit;

[0033] When the number of batteries n is an odd number greater than 1, the remaining single battery is virtualized as the last equalization unit of the first layer, and an equalization module is connected between it and the adjacent first - layer equalization unit to form the first second - layer equalization unit;

[0034] When the number of k - 1 - layer equalization units is an odd number greater than 1, the remaining single equalization unit of the k - 1 layer is virtualized as the last equalization unit of the k layer, and an equalization module is connected between it and the adjacent k - layer equalization unit to form the first k + 1 - layer equalization unit;

[0035] When the number of the last - layer equalization units is 1, a multi - layer equalization circuit for n batteries is formed.

[0036] Among them, the equalization module includes a first MOSFET 1, a second MOSFET 2, and an inductor 3. The first MOSFET 1 and the second MOSFET 2 are connected in series. One end of the inductor 3 is connected to the series connection point of the first MOSFET 1 and the second MOSFET 2. The source electrode of the first MOSFET 1, the drain electrode of the second MOSFET 2, and the other end of the inductor 3 are respectively the first end, the second end, and the third end of the equalization module.

[0037] The first MOSFET 1 and the second MOSFET 2 are matched and are MOSFETs of the same model.

[0038] Specifically, an equalization module is connected between two adjacent batteries to form a first - layer equalization unit, specifically: the positive electrode of the previous battery, the negative electrode of the subsequent battery, and the series connection point of the two batteries among two adjacent batteries are respectively connected to the first end, the second end, and the third end of the equalization module;

[0039] Two adjacent first-layer equalization units are connected to an equalization module to form a second-layer equalization unit. Specifically: the two adjacent first-layer equalization units are connected in series and then connected in parallel with the equalization module, and the series connection point of the two adjacent first-layer equalization units is connected to the third terminal of the equalization module;

[0040] Two adjacent (k - 1)-layer equalization units are connected to an equalization module to form an i-layer equalization unit. Specifically: the two adjacent (k - 1)-layer equalization units are connected in series and then connected in parallel with the equalization module, and the series connection point of the two adjacent (k - 1)-layer equalization units is connected to the third terminal of the equalization module.

[0041] When the number of batteries n is an odd number greater than 1, the remaining single battery is virtualized as the last equalization unit of the first layer, and is connected to an adjacent first-layer equalization unit with an equalization module to form the first second-layer equalization unit; specifically: the second terminal and the third terminal of the equalization module are respectively connected to the negative electrode and the positive electrode of the remaining single battery, and the first terminal of the equalization module is connected to the first terminal of the adjacent first-layer equalization unit;

[0042] When the number of (k - 1)-layer equalization units is an odd number greater than 1, the remaining single equalization unit of the (k - 1) layer is virtualized as the last equalization unit of the k layer, and is connected to an adjacent k-layer equalization unit with an equalization module to form the first (k + 1)-layer equalization unit; specifically: the second terminal and the third terminal of the equalization module are respectively connected to the second terminal and the first terminal of the remaining single equalization unit of the (k - 1) layer, and the first terminal of the equalization module is connected to the first terminal of the adjacent (k - 1)-layer equalization unit.

[0043] Further, the present invention further includes a control circuit, the control circuit is connected to the gates of the first MOSFET and the second MOSFET in each equalization module, and is used to control the conduction and cut-off of the first MOSFET and the second MOSFET. It also includes a voltage measurement element, and the voltage measurement element is used to measure the voltage of each battery. Specifically, it is a voltage sensor, and each battery is connected in parallel with a voltage sensor, and the output of the voltage sensor is electrically connected to the control circuit to transmit the measured battery voltage data to the control circuit.

[0044] This embodiment specifically gives a multi-layer equalization circuit constructed with 15 batteries B1 - B15, as Figure 3 shown. 15 batteries form a four-layer equalization circuit. The first layer includes 7 equalization units and 1 virtual equalization unit, the second layer includes 4 equalization units, the third layer includes 2 equalization units, and the fourth layer has only one equalization unit. When the number of batteries n is an even number, such as n is 16, that is, the multi-layer equalization circuit constructed with 16 batteries B1 - B16 is as Figure 1As shown, 16 batteries form a four-layer balancing circuit. The first layer includes 8 balancing units, the second layer includes 4 balancing units, the third layer includes 2 balancing units, and the fourth layer has only 1 balancing unit.

[0045] It should be particularly noted that in Figures 2-6 the attached drawings, for the purpose of reducing the circuit complexity, the schematic diagrams of the microprocessor and voltage measuring elements are omitted.

[0046] The working principle of the present utility model is as follows:

[0047] As Figures 4-5 shown, taking 4 batteries B1 - B4 as an example, a two-layer balancing circuit is constructed. The first-layer balancing units include two, namely battery B1, B2 and the connected balancing module 1-1, battery B3, B4 and the connected balancing module 1-2. The balancing module 1-1 includes a first MOSFET tube composed of a field-effect transistor Q1 and a diode D1, a second MOSFET tube composed of a field-effect transistor Q2 and a diode D2, and an inductor L1. The balancing module 1-2 includes a first MOSFET tube composed of a field-effect transistor Q3 and a diode D3, a second MOSFET tube composed of a field-effect transistor Q4 and a diode D4, and an inductor L2; the second-layer balancing unit is one, and the second-layer balancing unit includes a first MOSFET tube composed of a field-effect transistor Q5 and a diode D5, a second MOSFET opinion inductor L3.

[0048] During the charging process of the battery pack, if the voltage of battery B1 is higher than that of battery B2, and the average voltage of battery B1 and battery B2 is greater than the average voltage of battery B3 and battery B4, and both reach the balancing threshold, at this time the multi-layer balancing circuit starts to balance, and the balancing process is mainly reflected in two stages.

[0049] The first stage: At this time, the control circuit sends out a PWM signal to control the conduction of the field-effect transistor Q1. The field-effect transistor Q1, inductor L1 and battery B1 form an energy storage loop, constituting the first-layer balancing unit. Inductor L1 is charged by battery B1, and the charging stops at t = DT. At this time, the current of inductor L1 reaches the peak value; at the same time, the field-effect transistor Q5 is also controlled to conduct by the signal sent out by the control circuit. The field-effect transistor Q5, inductor L3, and batteries B1 and B2 form a loop, constituting the second-layer balancing unit. Inductor L3 is charged by batteries B1 and B2, and the charging stops at t = DT. At this time, the current of inductor L3 reaches the peak value.

[0050] In the second stage, the diode D2 conducts for freewheeling. Then, the diode D2, the inductor L1, and the battery B2 form an energy storage loop, constituting the first-layer equalization unit. The inductor L1 discharges to the battery B2 until the current of the inductor L1 becomes zero. At the same time, the diode D6 also conducts for freewheeling. Then, the diode D6, the inductor L3, and the batteries B3 and B4 form an energy storage loop, constituting the second-layer equalization group. The inductor L3 discharges to the batteries B3 and B4 until the current of the inductor L3 becomes zero.

[0051] To verify the equalization time and efficiency of the present invention, 16 identical batteries are connected in series, and a traditional equalization circuit is used for equalization, as Figure 6 shown. The experimental data of the present invention and the traditional equalization circuit are as follows in the table:

[0052] Experimental data of the present invention and the traditional equalization circuit

[0053]

[0054] It can be seen from the data in the above table that by using the equalization circuit of the present invention, the charging equalization time is shortened by 40.8%, the static equalization efficiency is increased by 2 times, and the discharging equalization time is shortened by 34.5%.

Claims

1. A multi-layer equalization circuit for a battery pack, characterized in that: The invention comprises n batteries, wherein the n batteries are connected in series, and each two adjacent batteries are connected to a balancing module to form a first-layer balancing unit; each two adjacent first-layer balancing units are connected to a balancing module to form a second-layer balancing unit, and each two adjacent k-1-th layer balancing units are connected to a balancing module to form a k-th layer balancing unit; When the number of batteries n is an odd number greater than 1, the remaining single battery is virtualized as the last balancing unit of the first layer, and connected to the adjacent first-layer balancing unit by a balancing module to form the first second-layer balancing unit; When the number of balancing units in the k-1th layer is an odd number greater than 1, the remaining single balancing unit in the k-1th layer is virtualized as the last balancing unit in the kth layer, and connected to the adjacent kth layer balancing unit by a balancing module to form the first k+1th layer balancing unit; When the number of balancing units in the last layer is 1, a multi-layer balancing circuit for n batteries is formed.

2. A multi-layer equalization circuit for a battery pack according to claim 1, characterized in that: The balancing module includes a first MOSFET tube, a second MOSFET tube and an inductor, the first MOSFET tube and the second MOSFET tube are connected in series, one end of the inductor is connected to the series point of the first MOSFET tube and the second MOSFET tube, the source of the first MOSFET tube, the drain of the second MOSFET tube, and the other end of the inductor are respectively the first end, the second end and the third end of the balancing module.

3. The multi-layer equalization circuit for a battery pack according to claim 2, characterized in that: The first MOSFET tube matches the second MOSFET tube and are MOSFET tubes of the same model.

4. The multi-layer equalization circuit for a battery pack according to claim 2, characterized in that: The two adjacent batteries are connected to a balancing module to form a first-layer balancing unit, specifically: the positive electrode of the first battery, the negative electrode of the second battery, and the series connection point of the two batteries are respectively connected to the first end, the second end, and the third end of the balancing module; The two adjacent first-layer balancing units are connected to a balancing module to form a second-layer balancing unit, specifically: the two adjacent first-layer balancing units are connected in series and then connected in parallel with the balancing module, and the series connection point of the two adjacent first-layer balancing units is connected to the third end of the balancing module; The two adjacent k-1th layer balancing units are connected to a balancing module to form an i-th layer balancing unit, specifically: the two adjacent k-1th layer balancing units are connected in series and then connected in parallel with the balancing module, and the series connection point of the two adjacent k-1th layer balancing units is connected to the third end of the balancing module.

5. The multi-layer equalization circuit for a battery pack according to claim 2, characterized in that: When the number of batteries n is an odd number greater than 1, the remaining single battery is virtualized as the last balancing unit of the first layer, and a balancing module is connected to the adjacent first-layer balancing unit to form the first second-layer balancing unit; specifically: the second end and the third end of the balancing module are respectively connected to the negative electrode and the positive electrode of the remaining single battery, and the first end of the balancing module is connected to the first end of the adjacent first-layer balancing unit; When the number of balancing units in the k-1th layer is an odd number greater than 1, the remaining single balancing unit in the k-1th layer is virtualized as the last balancing unit in the kth layer, and connected to an adjacent kth layer balancing unit by a balancing module to form the first k+1th layer balancing unit; specifically: the second end and the third end of the balancing module are respectively connected to the second end and the first end of the remaining single balancing unit in the k-1th layer, and the first end of the balancing module is connected to the first end of the adjacent k-1th layer balancing unit.

6. The multi-layer equalization circuit for a battery pack according to claim 2, characterized in that: It also includes a control circuit, which is connected to the gates of the first MOSFET tube and the second MOSFET tube in each equalizing module and is used to control the conduction and cutoff of the first MOSFET tube and the second MOSFET tube.

7. The multi-layer equalization circuit for a battery pack according to claim 1, characterized in that: A voltage measuring element is also included, and the voltage measuring element is used to measure the voltage of each battery.

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