Lithium ion battery SOC active equalization circuit based on Zeta converter

Abstract

A Zeta converter-based lithium ion battery SOC active equalization circuit comprises an n-path output Zeta converter, n-1 bridging capacitors and n lithium ion batteries, and the n-path output Zeta converter comprises a direct current input source uin, a power switch S1, an input inductor Lm, an input capacitor Cm, a first-path output diode D1, an output inductor L1 and an output capacitor C1; the first path of output diode D1, the second path of output diode D2, the output inductor L2 and the output capacitor C2, the third path of output diode D3, the output inductor L3, the output capacitor C3,..., and the like, and the nth path of output diode Dn, the output inductor Ln and the output capacitor Cn. The equalization circuit comprises an n-path output Zeta converter, n-1 bridging capacitors and n lithium ion batteries, and output consistency is realized by adding one bridging capacitor between each path. Compared with a traditional multi-path series equalization structure, automatic voltage equalization between the battery units is achieved through the bridging capacitors, complex sampling and control algorithms are not needed, voltage deviation is effectively reduced, and the battery equalization precision is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery equalization, and in particular to a lithium-ion battery SOC active equalization circuit based on a Zeta converter. Background Art

[0002] Lithium-ion batteries occupy a core position in the electric vehicle power battery market due to their outstanding energy density, long-term cycle stability, no memory effect, and high efficiency and environmentally friendly characteristics. However, the voltage and capacity limitations of single cells make it difficult to directly meet the high performance requirements of electric vehicles. Therefore, building a battery pack composed of multiple batteries in series and parallel has become an inevitable choice. However, this combination strategy also raises new problems: manufacturing differences, operating environment differences, and different charging and discharging strategies lead to mismatches in capacity, voltage, internal resistance, etc. among the single cells in the battery pack, which not only weakens the overall durability and reliability of the battery pack, but also poses a severe challenge to the safety of the system. Therefore, in order to maintain the balance of single cells in lithium-ion battery packs, researchers have proposed many balancing circuits, devices, and methods. Current battery balancing technologies are mainly divided into passive balancing and active balancing. Passive balancing consumes excess energy in the form of heat through resistance, but this method will cause energy loss in the battery pack, and the high temperature environment caused by improper heat dissipation will damage the performance of the battery pack.

[0003] Active balancing technology is to transfer energy from a higher battery cell to a lower battery cell. For example, the patent document with application publication number CN113489083A discloses a hierarchical balancing control method for lithium-ion battery packs based on a buck-boost converter. This method adds multiple energy storage inductance elements, diodes, and balancing control switches to the lithium-ion battery pack. By controlling the switch to close, the single battery with higher energy storage stores excess energy in the corresponding inductance, and then controls the switch to close to transfer the energy in the inductance to the single battery with lower energy storage, forming a balancing control of the series lithium-ion battery pack. In addition, two adjacent single batteries are formed into a small module, and then the adjacent small modules are formed into a large module. Through logical control, each level is balanced to achieve three-level balancing control. The balancing control method proposed in this patent can not only achieve balancing between two adjacent single batteries, but also indirectly achieve balancing between two non-adjacent single batteries through balancing control between adjacent modules, shortening the energy transmission path and improving the efficiency of the battery pack balancing system. However, the balancing circuit used in this control method includes multiple control switches, and the logical control is very complex. Summary of the invention

[0004] In order to solve the shortcomings of the existing lithium-ion battery pack balancing technology, the present invention proposes a lithium-ion battery SOC active balancing circuit based on a Zeta converter, and the balancing circuit is composed of multiple Zeta converters and multiple cross-over capacitors. The balancing circuit is based on the Zeta circuit and proposes a new type of battery SOC active balancing circuit, which includes an n-way output Zeta converter, n-1 cross-over capacitors and n lithium-ion batteries. The output consistency is achieved by adding a cross-over capacitor between each path. Compared with the traditional multi-series Zeta circuit balancing structure, the present invention realizes automatic voltage balancing between battery cells through cross-over capacitors, does not require complex sampling and control algorithms, and avoids the terminal voltage imbalance problem caused by the cross-regulation rate when the multi-series Zeta circuit outputs; effectively reduces voltage deviation and improves battery balancing accuracy.

[0005] The technical solution adopted by the present invention is:

[0006] The active SOC balancing circuit of a lithium-ion battery based on a Zeta converter comprises an n-way output Zeta converter, n-1 cross-connected capacitors and n lithium-ion batteries, wherein: an n-way output Zeta converter comprises a DC input source u in , a power switch S1, an input inductor L m , an input capacitor C m as well as:

[0007] The first output diode D1, output inductor L1, output capacitor C1;

[0008] The second output diode D2, output inductor L2, output capacitor C2,

[0009] The third output diode D3, output inductor L3, output capacitor C3,

[0010] ... and so on.

[0011] The nth output diode D n , output inductor L n , output capacitor C n ;

[0012] The connection form of n-way output Zeta converter is as follows:

[0013] DC input source u in The positive electrode is connected to the drain of the power switch S1, and the input inductor L m One end of the capacitor C m One end is connected to the source of the power switch S1, and the input inductor L m The other end is connected to the anode of diode D1 and the DC input source u inThe negative pole of the power switch S1 is connected to the controller.

[0014] The cathode of the first output diode D1 is connected to one end of the output inductor L1 and the input capacitor C m At the other end, one end of the output capacitor C1 is connected to the other end of the output inductor L1, and the other end of the output capacitor C1 is connected to the anode of the first output diode D1;

[0015] The cathode of the second output diode D2 is connected to one end of the output inductor L2, one end of the output capacitor C2 is connected to the other end of the output inductor L2, and the other end of the output capacitor C2 is connected to the anode of the second output diode D2;

[0016] The cathode of the third output diode D3 is connected to one end of the output inductor L3, one end of the output capacitor C3 is connected to the other end of the output inductor L3, and the other end of the output capacitor C3 is connected to the anode of the third output diode D3;

[0017] ... and so on.

[0018] The nth output diode D n The cathode of the connected output inductor L n One end of the output capacitor C n One end of the output inductor L n The other end of the output capacitor C n The other end is connected to the nth output diode D n anode.

[0019] The connection between n-1 jumper capacitors and each output is as follows:

[0020] Capacitor C m1 One end of the diode D1 is connected to the cathode, and the capacitor C m1 The other end is connected to the cathode of diode D2;

[0021] Capacitor C m2 One end of the diode D2 is connected to the cathode, and the capacitor C m2 The other end is connected to the cathode of diode D3.

[0022] ... and so on.

[0023] Capacitor C m(n-1) One end of the diode D n-1 The cathode connection of capacitor C m(n-1) The other end of the diode D n cathode connection.

[0024] The connection form of n lithium-ion batteries and n-output Zeta converters is as follows:

[0025] One end of the lithium-ion battery B1 is connected to the intersection where the other end of the output inductor L1 is connected to one end of the capacitor C1, and the other end of the lithium-ion battery B1 is connected to the intersection where the anode of the diode D1 is connected to the other end of the capacitor C1;

[0026] One end of the lithium-ion battery B2 is connected to the intersection where the other end of the output inductor L2 is connected to one end of the capacitor C2, and the other end of the lithium-ion battery B2 is connected to the intersection where the anode of the diode D2 is connected to the other end of the capacitor C2;

[0027] ... and so on.

[0028] Lithium-ion battery B n One end of the output inductor L n The other end of the capacitor C n One end of the lithium-ion battery B is connected to the intersection of n The other end of the diode D n The anode and capacitor C n The other end is connected to the intersection point.

[0029] The connection between n lithium-ion batteries is as follows:

[0030] The other end of the lithium-ion battery B1 is connected to one end of the lithium-ion battery B2.

[0031] The other end of the lithium-ion battery B2 is connected to one end of the lithium-ion battery B3.

[0032] ... and so on.

[0033] Lithium-ion battery B n-1 The other end of the lithium-ion battery B n one end of the .

[0034] The gate of the power switch S1 is connected to a controller, and its duty cycle can be changed between 0 and 1.

[0035] Take four single lithium-ion batteries B1, B2, B3, and B4 connected in series to form a battery pack as an example: the lithium-ion battery SOC active balancing circuit based on the Zeta converter includes a 4-way output Zeta converter, 3 cross-connected capacitors and 4 lithium-ion batteries, wherein: a 4-way output Zeta converter includes a DC input source u in , a power switch S1, an input inductor L m , an input capacitor C m as well as:

[0036] The first output diode D1, output inductor L1, output capacitor C1;

[0037] The second output diode D2, output inductor L2, output capacitor C2,

[0038] The third output diode D3, output inductor L3, output capacitor C3,

[0039] The fourth output diode D4, output inductor L4, output capacitor C4;

[0040] The connection form of the 4-way output Zeta converter is as follows:

[0041] DC input source u in The positive electrode is connected to the drain of the power switch S1, and the input inductor L m One end of the capacitor C m One end is connected to the source of the power switch S1, and the input inductor L m The other end is connected to the anode of diode D1 and the DC input source u in The negative pole of the power switch S1 is connected to the controller.

[0042] The cathode of the first output diode D1 is connected to one end of the output inductor L1 and the input capacitor C m At the other end, one end of the output capacitor C1 is connected to the other end of the output inductor L1, and the other end of the output capacitor C1 is connected to the anode of the first output diode D1;

[0043] The cathode of the second output diode D2 is connected to one end of the output inductor L2, one end of the output capacitor C2 is connected to the other end of the output inductor L2, and the other end of the output capacitor C2 is connected to the anode of the second output diode D2;

[0044] The cathode of the third output diode D3 is connected to one end of the output inductor L3, one end of the output capacitor C3 is connected to the other end of the output inductor L3, and the other end of the output capacitor C3 is connected to the anode of the third output diode D3;

[0045] The cathode of the fourth output diode D4 is connected to one end of the output inductor L4, one end of the output capacitor C4 is connected to the other end of the output inductor L4, and the other end of the output capacitor C4 is connected to the anode of the nth output diode D4.

[0046] The connection between the three jumper capacitors and each output is as follows:

[0047] Capacitor C m1 One end of the diode D1 is connected to the cathode, and the capacitor C m1 The other end is connected to the cathode of diode D2;

[0048] Capacitor C m2 One end of the diode D2 is connected to the cathode, and the capacitor C m2 The other end is connected to the cathode of diode D3.

[0049] Capacitor C m3 One end of the diode D3 is connected to the cathode, and the capacitor C m3 The other end is connected to the cathode of diode D4.

[0050] The connection between 4 lithium-ion batteries and 4-way output Zeta converter is as follows:

[0051] One end of the lithium-ion battery B1 is connected to the intersection where the other end of the output inductor L1 is connected to one end of the capacitor C1, and the other end of the lithium-ion battery B1 is connected to the intersection where the anode of the diode D1 is connected to the other end of the capacitor C1;

[0052] One end of the lithium-ion battery B2 is connected to the intersection where the other end of the output inductor L2 is connected to one end of the capacitor C2, and the other end of the lithium-ion battery B2 is connected to the intersection where the anode of the diode D2 is connected to the other end of the capacitor C2;

[0053] One end of the lithium-ion battery B3 is connected to the intersection where the other end of the output inductor L3 and one end of the capacitor C3 are connected, and the other end of the lithium-ion battery B3 is connected to the intersection where the anode of the diode D3 and the other end of the capacitor C3 are connected;

[0054] The connection between the 4 lithium-ion batteries is as follows:

[0055] The other end of the lithium-ion battery B1 is connected to one end of the lithium-ion battery B2.

[0056] The other end of the lithium-ion battery B2 is connected to one end of the lithium-ion battery B3.

[0057] The other end of the lithium ion battery B3 is connected to one end of the lithium ion battery B4.

[0058] When the power switch S1 is turned on, the first output diode D1, the second output diode D2, the third output diode D3 and the fourth output diode D4 are turned off. m , output inductor L1, input capacitor C m The output capacitor C1 charges the lithium-ion battery B1, and the cross-connect capacitor C m1 Charge the output inductor L2, output capacitor C2 and lithium-ion battery B2, and cross-connect capacitor C m2 Charge the output inductor L3, output capacitor C3 and lithium-ion battery B3, and connect the capacitor C m3 Charge the output inductor L4, the output capacitor C4 and the lithium-ion battery B4;

[0059] When the power switch S1 is turned off, the first output diode D1, the second output diode D2, the third output diode D3 are turned off, and the fourth output diode D4 is turned on.m To capacitor C m , cross-capacitor C m1 , cross-capacitor C m2 , cross-capacitor C m3 The output capacitor C1 charges the lithium-ion battery B1, and the cross-capacitor C m1 Charge the output inductor L2, output capacitor C2 and lithium-ion battery B2, and cross-connect capacitor C m2 Charge the output inductor L3, output capacitor C3 and lithium-ion battery B3, and connect the capacitor C m3 Charge the output inductor L4, output capacitor C4 and lithium-ion battery B4.

[0060] The principle of lithium-ion battery balancing is to maintain the lithium-ion battery cells in a series-connected battery pack in a balanced state. Currently, the balance of the entire lithium-ion battery pack is mainly determined by whether the terminal voltage of the lithium-ion battery cells is balanced.

[0061] When the power switch S1 is turned on, there is a loop C m1 →L1→C1→L2→C m1 According to the inductor volt-second balance principle, the average voltage of the inductor is 0, and the KVL theorem shows that u Cm1 =u C1 , there exists a loop C1→B1→C1, and from the KVL theorem we know that u C1 =u B1 ; Similarly, there is a loop C m2 →L2→C2→L3→C m2 According to the inductor volt-second balance principle, the average voltage of the inductor is 0, and the KVL theorem shows that u Cm2 =u C2 , there exists a loop C2→B2→C2, and from the KVL theorem we know that u C2 =u B2 ; There is a loop C m3 →L3→C3→L4→C m3 According to the inductor volt-second balance principle, the average voltage of the inductor is 0, and the KVL theorem shows that u Cm3 =u C3 , there is a loop C3→B3→C3, and from the KVL theorem we know that u C3 =u B3 .

[0062] When the power switch S1 is turned off, there is a loop C m1 →D1→C2→D2→C m1 According to the KVL theorem, we know that u Cm1 =u C2 , there exists a loop C2→B2→C2, and from the KVL theorem we know that u C2 =uB2 ; Similarly, there is a loop C m2 →D2→C3→D3→C m2 According to the KVL theorem, we know that u Cm2 =u C3 , there is a loop C3→B3→C3, and from the KVL theorem we know that u C3 =u B3 ; There is a loop C m3 →D3→C4→D4→C m3 According to the KVL theorem, we know that u Cm3 =u C4 , there is a loop C4→B4→C4, and from the KVL theorem we know that u C4 =u B4 .

[0063] During the entire switching cycle, according to the capacitance ampere-second balance principle and the above analysis, we can know that: Cm1 =u C1 and u Cm1 =u C2 ,u C1 =u B1 and u C2 =u B2 , then u C1 =u C2 =u B1 =u B2 , similarly there is u C2 =u C3 ,u C3 =u C4 ,u C3 =u B3 and u C4 =u B4 , then u C1 =u C2 =u C3 =u C4 ,u B1 =u B2 =u B3 =u B4 , that is, the voltage of each lithium-ion battery cell is equal, achieving the balance of the lithium-ion battery pack.

[0064] The present invention provides a lithium-ion battery SOC active equalization circuit based on Zeta converter, and the technical effects are as follows:

[0065] 1) The balancing circuit of the present invention achieves the effect of automatic voltage balancing of the output voltages of the multi-output Zeta converters by connecting a jumper capacitor between adjacent outputs of the Zeta converters, thereby improving the battery balancing degree.

[0066] 2) The balancing circuit of the present invention has a simple circuit topology and uses only one switch, which reduces the difficulty of control system design. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0068] Figure 1 It is the circuit principle diagram of the present invention;

[0069] Figure 2 The circuit schematic diagram of the present invention is to realize SOC balancing of a battery pack with four single cells connected in series.

[0070] Figure 3 This is a simulation diagram of the present invention realizing balancing of a battery pack with four battery cells connected in series. DETAILED DESCRIPTION

[0071] like Figure 2 As shown, a lithium-ion battery SOC active balancing circuit based on a Zeta converter includes a 4-way output Zeta converter, 3 cross-connected capacitors and 4 lithium-ion batteries, wherein:

[0072] A 4-way output Zeta converter includes a DC input source u in , a power switch S1, an input inductor L m , an input capacitor C m , the first output diode D1, output inductor L1, output capacitor C1, the second output diode D2, output inductor L2, output capacitor C2, the third output diode D3, output inductor L3, output capacitor C3, the fourth output diode D4, output inductor L4, output capacitor C4.

[0073] The basic 4-way output Zeta converter connection is as follows:

[0074] DC input source u in The positive electrode is connected to the drain of S1, and the input inductor L m One end of the capacitor C m One end is connected to the source of the power switch S1, and the input inductor L m The other end is connected to the anode of diode D1 and the DC input source u in The negative pole of S1 is connected to the controller, and the cathode of diode D1 is connected to one end of the output inductor L1 and the capacitor C mAt the other end, one end of the output capacitor C1 is connected to the other end of the output inductor L1, and the other end of the capacitor C1 is connected to the anode of the diode D1. The cathode of the diode D2 is connected to one end of the output inductor L2, one end of the output capacitor C2 is connected to the other end of the output inductor L2, and the other end of the capacitor C2 is connected to the anode of the diode D1. The cathode of the diode D3 is connected to one end of the output inductor L3, one end of the output capacitor C3 is connected to the other end of the output inductor L3, and the other end of the capacitor C3 is connected to the anode of the diode D3. The cathode of the diode D4 is connected to one end of the output inductor L4, one end of the output capacitor C4 is connected to the other end of the output inductor L4, and the other end of the capacitor C4 is connected to the anode of the diode D4.

[0075] The connection between the jumper capacitor and each output is as follows:

[0076] Capacitor C m1 One end of the diode D1 is connected to the cathode, and the capacitor C m1 The other end of the capacitor is connected to the cathode of the diode D2. m2 One end of the diode D2 is connected to the cathode, and the capacitor C m2 The other end of is connected to the cathode of diode D3. m3 One end of the diode D3 is connected to the cathode, and the capacitor C m3 The other end is connected to the cathode of diode D4.

[0077] The connection form of multi-output battery unit is as follows:

[0078] One end of the lithium ion battery B1 is connected to the intersection where the other end of the output inductor L1 and one end of the capacitor C1 are connected, and the other end of the lithium ion battery B1 is connected to the intersection where the anode of the diode D1 and the other end of the capacitor C1 are connected; one end of the lithium ion battery B2 is connected to the intersection where the other end of the output inductor L2 and one end of the capacitor C2 are connected, and the other end of the lithium ion battery B2 is connected to the intersection where the anode of the diode D2 and the other end of the capacitor C2 are connected; one end of the lithium ion battery B3 is connected to the intersection where the other end of the output inductor L3 and one end of the capacitor C3 are connected, and the other end of the lithium ion battery B3 is connected to the intersection where the anode of the diode D3 and the other end of the capacitor C3 are connected; one end of the lithium ion battery B4 is connected to the intersection where the other end of the output inductor L4 and one end of the capacitor C4 are connected, and the other end of the lithium ion battery B4 is connected to the intersection where the anode of the diode D4 and the other end of the capacitor C4 are connected. The other end of lithium ion battery B1 is connected to one end of lithium ion battery B2, the other end of lithium ion battery B2 is connected to one end of lithium ion battery B3, and the other end of lithium ion battery B3 is connected to one end of lithium ion battery B4.

[0079] The gate of the power switch S1 is connected to a controller, and its duty cycle can be changed between 0 and 1. When the power switch S1 is turned on, the first output diode D1, the second output diode D2, the third output diode D3 and the fourth output diode D4 are turned off. m , output inductor L1, input capacitor C m The output capacitor C1 charges the lithium-ion battery B1, and the cross-connect capacitor C m1 Charge the output inductor L2, output capacitor C2 and lithium-ion battery B2, and cross-connect capacitor C m2 Charge the output inductor L3, output capacitor C3 and lithium-ion battery B3, and connect the capacitor C m3 Charge the output inductor L4, output capacitor C4 and lithium-ion battery B4.

[0080] When the power switch S1 is turned off, the first output diode D1, the second output diode D2, the third output diode D3 are turned off, and the fourth output diode D4 is turned on. m To capacitor C m , cross-capacitor C m1 , cross-capacitor C m2 , cross-capacitor C m3 The output capacitor C1 charges the lithium-ion battery B1, and the cross-capacitor C m1 Charge the output inductor L2, output capacitor C2 and lithium-ion battery B2, and cross-connect capacitor C m2 Charge the output inductor L3, output capacitor C3 and lithium-ion battery B3, and connect the capacitor C m3 Charge the output inductor L4, output capacitor C4 and lithium-ion battery B4.

[0081] The principle of lithium-ion battery balancing is to maintain the lithium-ion battery cells in a series-connected battery pack in a balanced state. Currently, the balance of the entire battery pack is mainly determined by whether the terminal voltage of the lithium-ion battery cells is balanced.

[0082] When switch S1 is turned on, there is a loop C m1 →L1→C1→L2→C m1 According to the inductor volt-second balance principle, the average voltage of the inductor is 0, and the KVL theorem shows that u Cm1 =u C1 , there exists a loop C1→B1→C1, and from the KVL theorem we know that u C1 =u B1 ; Similarly, there is a loop C m2 →L2→C2→L3→C m2 According to the inductor volt-second balance principle, the average voltage of the inductor is 0, and the KVL theorem shows that u Cm2=u C2 , there exists a loop C2→B2→C2, and from the KVL theorem we know that u C2 =u B2 ; There is a loop C m3 →L3→C3→L4→C m3 According to the inductor volt-second balance principle, the average voltage of the inductor is 0, and the KVL theorem shows that u Cm3 =u C3 , there is a loop C3→B3→C3, and from the KVL theorem we know that u C3 =u B3 .

[0083] When switch S1 is turned off, there is a loop C m1 →D1→C2→D2→C m1 According to the KVL theorem, we know that u Cm1 =u C2 , there exists a loop C2→B2→C2, and from the KVL theorem we know that u C2 =u B2 ; Similarly, there is a loop C m2 →D2→C3→D3→C m2 According to the KVL theorem, we know that u Cm2 =u C3 , there is a loop C3→B3→C3, and from the KVL theorem we know that u C3 =u B3 ; There is a loop C m3 →D3→C4→D4→C m3 According to the KVL theorem, we know that u Cm3 =u C4 , there is a loop C4→B4→C4, and from the KVL theorem we know that u C4 =u B4 .

[0084] During the entire switching cycle, according to the capacitance ampere-second balance principle and the above analysis, it can be known that u Cm1 =u C1 and u Cm1 =u C2 ,u C1 =u B1 and u C2 =u B2 , then u C1 =u C2 =u B1 =u B2 , similarly there is u C2 =u C3 ,u C3 =u C4 ,u C3 =u B3 and u C4=u B4 , then u C1 =u C2 =u C3 =u C4 ,u B1 =u B2 =u B3 =u B4 , that is, the voltage of each lithium-ion battery cell is equal, achieving the balance of the battery pack.

[0085] Figure 3 This is a simulation diagram of the present invention realizing the balancing of a battery pack with four battery cells in series. Figure 3 It can be seen that when charging multiple groups of batteries with different initial SOCs (State of Charge), different battery SOCs are constantly balanced and charged toward the same SOC, and quickly reach a relatively stable and close SOC value, indicating that the topology has a good balanced charging effect and a fast speed.

[0086] Compared with the traditional multi-channel series equalization structure, the present invention realizes automatic voltage equalization between battery cells through jumper capacitors, does not require complex sampling and control algorithms, effectively reduces voltage deviation, and improves the equalization accuracy of lithium-ion batteries.

Claims

1. A lithium-ion battery SOC active equalization circuit based on a Zeta converter, characterized in that: It includes an n-way output Zeta converter, n-1 cross-connected capacitors and n lithium-ion batteries, wherein: an n-way output Zeta converter includes a DC input source u in , a power switch S1, an input inductor L m , an input capacitor C m as well as: The first output diode D1, output inductor L1, output capacitor C1; The second output diode D2, output inductor L2, output capacitor C2, The third output diode D3, output inductor L3, output capacitor C3, ... and so on. The nth output diode D n , output inductor L n , output capacitor C n ; The connection form of n-way output Zeta converter is as follows: DC input source u in The positive electrode is connected to the drain of the power switch S1, and the input inductor L m One end of the capacitor C m One end is connected to the source of the power switch S1, and the input inductor L m The other end is connected to the anode of diode D1 and the DC input source u in The negative pole of the power switch S1 is connected to the controller. The cathode of the first output diode D1 is connected to one end of the output inductor L1 and the input capacitor C m At the other end, one end of the output capacitor C1 is connected to the other end of the output inductor L1, and the other end of the output capacitor C1 is connected to the anode of the first output diode D1; The cathode of the second output diode D2 is connected to one end of the output inductor L2, one end of the output capacitor C2 is connected to the other end of the output inductor L2, and the other end of the output capacitor C2 is connected to the anode of the second output diode D2; The cathode of the third output diode D3 is connected to one end of the output inductor L3, one end of the output capacitor C3 is connected to the other end of the output inductor L3, and the other end of the output capacitor C3 is connected to the anode of the third output diode D3; ... and so on. The nth output diode D n The cathode of the output inductor L n One end of the output capacitor C n One end of the output inductor L n The other end of the output capacitor C n The other end is connected to the nth output diode D n Anode; The connection between n-1 jumper capacitors and each output is as follows: Capacitor C m1 One end of the diode D1 is connected to the cathode, and the capacitor C m1 The other end is connected to the cathode of diode D2; Capacitor C m2 One end of the diode D2 is connected to the cathode, and the capacitor C m2 The other end is connected to the cathode of diode D3; ... and so on. Capacitor C m(n-1) One end of the diode D n-1 The cathode connection of capacitor C m(n-1) The other end of the diode D n The cathode connection of The connection form of n lithium-ion batteries and n-output Zeta converters is as follows: One end of the lithium-ion battery B1 is connected to the intersection where the other end of the output inductor L1 is connected to one end of the capacitor C1, and the other end of the lithium-ion battery B1 is connected to the intersection where the anode of the diode D1 is connected to the other end of the capacitor C1; One end of the lithium-ion battery B2 is connected to the intersection where the other end of the output inductor L2 is connected to one end of the capacitor C2, and the other end of the lithium-ion battery B2 is connected to the intersection where the anode of the diode D2 is connected to the other end of the capacitor C2; ... and so on. Lithium-ion battery B n One end of the output inductor L n The other end of the capacitor C n One end of the lithium-ion battery B is connected to the intersection of n The other end of the diode D n The anode and capacitor C n The other end of the intersection is connected; The connection between n lithium-ion batteries is as follows: The other end of the lithium-ion battery B1 is connected to one end of the lithium-ion battery B2. The other end of the lithium-ion battery B2 is connected to one end of the lithium-ion battery B3. ... and so on. Lithium-ion battery B n-1 The other end of the lithium-ion battery B n one end of the .

2. The lithium-ion battery SOC active equalization circuit based on Zeta converter according to claim 1, characterized in that: The gate of the power switch S1 is connected to a controller, and its duty cycle can be changed between 0 and 1.

3. Zeta converter-based lithium-ion battery SOC active equalization circuit, characterized by: It includes a 4-way output Zeta converter, 3 cross-connected capacitors and 4 lithium-ion batteries, wherein: a 4-way output Zeta converter includes a DC input source u in , a power switch S1, an input inductor L m , an input capacitor C m as well as: The first output diode D1, output inductor L1, output capacitor C1; The second output diode D2, output inductor L2, output capacitor C2, The third output diode D3, output inductor L3, output capacitor C3, The fourth output diode D4, output inductor L4, output capacitor C4; The connection form of the 4-way output Zeta converter is as follows: DC input source u in The positive electrode is connected to the drain of the power switch S1, and the input inductor L m One end of the capacitor C m One end is connected to the source of the power switch S1, and the input inductor L m The other end is connected to the anode of diode D1 and the DC input source u in The negative pole of the power switch S1 is connected to the controller. The cathode of the first output diode D1 is connected to one end of the output inductor L1 and the input capacitor C m At the other end, one end of the output capacitor C1 is connected to the other end of the output inductor L1, and the other end of the output capacitor C1 is connected to the anode of the first output diode D1; The cathode of the second output diode D2 is connected to one end of the output inductor L2, one end of the output capacitor C2 is connected to the other end of the output inductor L2, and the other end of the output capacitor C2 is connected to the anode of the second output diode D2; The cathode of the third output diode D3 is connected to one end of the output inductor L3, one end of the output capacitor C3 is connected to the other end of the output inductor L3, and the other end of the output capacitor C3 is connected to the anode of the third output diode D3; The cathode of the fourth output diode D4 is connected to one end of the output inductor L4, one end of the output capacitor C4 is connected to the other end of the output inductor L4, and the other end of the output capacitor C4 is connected to the anode of the nth output diode D4; The connection between the three jumper capacitors and each output is as follows: Capacitor C m1 One end of the diode D1 is connected to the cathode, and the capacitor C m1 The other end is connected to the cathode of diode D2; Capacitor C m2 One end of the diode D2 is connected to the cathode, and the capacitor C m2 The other end is connected to the cathode of diode D3; Capacitor C m3 One end of the diode D3 is connected to the cathode, and the capacitor C m3 The other end is connected to the cathode of diode D4; The connection between 4 lithium-ion batteries and 4-way output Zeta converter is as follows: One end of the lithium-ion battery B1 is connected to the intersection where the other end of the output inductor L1 is connected to one end of the capacitor C1, and the other end of the lithium-ion battery B1 is connected to the intersection where the anode of the diode D1 is connected to the other end of the capacitor C1; One end of the lithium-ion battery B2 is connected to the intersection where the other end of the output inductor L2 is connected to one end of the capacitor C2, and the other end of the lithium-ion battery B2 is connected to the intersection where the anode of the diode D2 is connected to the other end of the capacitor C2; One end of the lithium-ion battery B3 is connected to the intersection where the other end of the output inductor L3 and one end of the capacitor C3 are connected, and the other end of the lithium-ion battery B3 is connected to the intersection where the anode of the diode D3 and the other end of the capacitor C3 are connected; The connection between the 4 lithium-ion batteries is as follows: The other end of the lithium-ion battery B1 is connected to one end of the lithium-ion battery B2. The other end of the lithium-ion battery B2 is connected to one end of the lithium-ion battery B3. The other end of the lithium ion battery B3 is connected to one end of the lithium ion battery B4.

4. The lithium-ion battery SOC active equalization circuit based on Zeta converter according to claim 3 is characterized in that: When the power switch S1 is turned on, the first output diode D1, the second output diode D2, the third output diode D3 and the fourth output diode D4 are turned off; the power supply to the input inductor L m , output inductor L1, input capacitor C m and output capacitor C1; output capacitor C1 charges lithium-ion battery B1, and the cross-connect capacitor C m1 Charge the output inductor L2, output capacitor C2 and lithium-ion battery B2, and connect the capacitor C m2 Charge the output inductor L3, output capacitor C3 and lithium-ion battery B3, and connect capacitor C m3 Charge the output inductor L4, output capacitor C4 and lithium-ion battery B4; When the power switch S1 is turned off, the first output diode D1, the second output diode D2, the third output diode D3 are turned off, and the fourth output diode D4 is turned on; the input inductor L m To capacitor C m , cross-capacitor C m1 , cross-capacitor C m2 , cross-capacitor C m3 Charging; output capacitor C1 charges the lithium-ion battery B1, and the cross-connect capacitor C m1 Charge the output inductor L2, output capacitor C2 and lithium-ion battery B2, and connect the capacitor C m2 Charge the output inductor L3, output capacitor C3 and lithium-ion battery B3, and connect capacitor C m3 Charge the output inductor L4, output capacitor C4 and lithium-ion battery B4.

5. The lithium-ion battery SOC active equalization circuit based on Zeta converter according to claim 3, characterized in that: When the power switch S1 is turned on, there is a loop C m1 →L1→C1→L2→C m1 , according to the inductor volt-second balance principle, The average voltage of the inductor is 0, so from the KVL theorem we know that u Cm1 =u C1 , there exists a loop C1→B1→C1, and from the KVL theorem we know that u C1 =u B1 ; Similarly, there is a loop C m2 →L2→C2→L3→C m2 According to the inductor volt-second balance principle, the average voltage of the inductor is 0, and the KVL theorem shows that u Cm2 =u C2 , there exists a loop C2→B2→C2, and from the KVL theorem we know that u C2 =u B2 ; There is a loop C m3 →L3→C3→L4→C m3 According to the inductor volt-second balance principle, the average voltage of the inductor is 0, and the KVL theorem shows that u Cm3 =u C3 , there is a loop C3→B3→C3, and from the KVL theorem we know that u C3 =u B3 ; When the power switch S1 is turned off, there is a loop C m1 →D1→C2→D2→C m1 According to the KVL theorem, we know that u Cm1 =u C2 , there exists a loop C2→B2→C2, and from the KVL theorem we know that u C2 =u B2 ; Similarly, there is a loop C m2 →D2→C3→D3→C m2 According to the KVL theorem, we know that u Cm2 =u C3 , there is a loop C3→B3→C3, and from the KVL theorem we know that u C3 =u B3 ; There is a loop C m3 →D3→C4→D4→C m3 According to the KVL theorem, we know that u Cm3 =u C4 , there is a loop C4→B4→C4, and from the KVL theorem we know that u C4 =u B4 ; During the entire switching cycle, according to the capacitance ampere-second balance principle and the above analysis, we can know that: Cm1 =u C1 and u Cm1 =u C2 ,u C1 =u B1 and u C2 =u B2 , then u C1 =u C2 =u B1 =u B2 , similarly there is u C2 =u C3 ,u C3 =u C4 ,u C3 =u B3 and u C4 =u B4 , then u C1 =u C2 =u C3 =u C4 ,u B1 =u B2 =u B3 =u B4 , that is, the voltage of each lithium-ion battery cell is equal, achieving the balance of the lithium-ion battery pack.

Images