Serial lithium battery pack SOC active equalization converter

Abstract

A series lithium battery pack SOC active equalization converter comprises an n-path output double-transistor forward converter, n-1 bridging capacitors and n lithium ion batteries, the n-path output double-transistor forward converter comprises power switches S1 and S2, reset diodes Dp1 and Dp2, an excitation inductor Lm, a transformer T, a first-path rectifier diode D1, a fly-wheel diode D2, an output inductor L1 and an output capacitor C1; the second path of rectifier diode D3, the fly-wheel diode D4, the output inductor L2, the output capacitor C2,..., and the like, and the nth path of rectifier diode D2n-1, the fly-wheel diode D2n, the output inductor Ln, and the output capacitor Cn. Compared with a traditional forward transformer equalization structure, the energy storage of the transformer is provided with a release loop, a reset circuit or a reset winding does not need to be additionally arranged, and the control difficulty and cost of the circuit are reduced.

Description

Technical Field

[0001] The invention relates to a lithium battery pack equalization circuit, and in particular to a series-connected lithium battery pack SOC active equalization converter. Background Art

[0002] Lithium-ion batteries are widely used as power batteries for electric vehicles due to their high energy density, long cycle life, no memory effect, high energy efficiency and no pollution. However, the voltage and capacity of a single lithium-ion battery are small, which cannot meet the capacity and power required by electric vehicles. Therefore, multiple lithium-ion batteries need to be connected in series and parallel to form a battery pack. However, differences in factors such as the environment, charge and discharge mode, and chemical properties of lithium batteries during manufacturing and use will lead to inconsistencies in the performance of single cells such as capacity, voltage, and internal resistance. These inconsistencies between single cells will cause problems such as durability, reliability, and safety of the battery pack. Therefore, in order to maintain the balance of single cells in a lithium-ion battery pack, researchers have proposed many balancing circuits, devices, and methods.

[0003] Current battery balancing technologies are mainly divided into passive balancing and active balancing. Passive balancing consumes excess energy in the form of heat through resistors, 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.

[0004] Active balancing technology is to transfer energy from a higher battery cell to a lower battery cell. For example, the patent with application publication number CN117525631A discloses an active lithium-ion battery cell balancing control method. This method groups the battery cells in the lithium-ion battery in a group of one and / or two adjacent battery cells in a group, and obtains a number of single battery cells and / or double battery cells; first balance the SOC values ​​of the two battery cells of two adjacent single battery cells, or the two battery cells in one double battery cell, and then balance the adjacent single battery cells or the balanced double battery cells until the SOC values ​​of all battery cells in the lithium-ion battery are balanced. In addition, the invention discloses a control circuit for balancing lithium-ion battery cells, which uses a logic threshold control method to adjust the size of the lithium-ion battery balancing current, reduce the balancing current and balancing time of the battery pack when charging and discharging the electrical equipment at high power, and further reduce the heat generated by the battery. Prevent excessive charging and discharging from damaging the battery cell, thereby extending the battery life. Summary of the invention

[0005] In order to solve the shortcomings of the existing lithium-ion battery pack balancing technology, the present invention proposes an active SOC balancing converter for a series lithium battery pack, which is composed of a multi-winding forward converter and multiple cross-over capacitors; the active balancing converter is based on transformer-type balancing, adopts a multi-winding transformer balancing topology, and realizes self-balancing of the series lithium battery pack by adding a cross-over capacitor between each winding. Compared with the traditional multi-winding transformer balancing structure, the transformer energy storage has a release loop, does not require a reset circuit or reset winding, and avoids the problem of terminal voltage imbalance caused by the cross-regulation rate of the transformer when the multi-winding output is in progress; effectively reduces voltage deviation and improves battery balancing accuracy.

[0006] The technical solution adopted by the invention is:

[0007] A SOC active equalization converter for a series lithium battery pack includes an n-way output dual-tube forward converter, n-1 cross-connected capacitors, and n lithium-ion batteries, wherein:

[0008] The n-way output dual-tube forward converter includes power switches S1 and S2, a reset diode D p1 and D p2 , Excitation inductance L m , transformer T and:

[0009] The first rectifier diode D1, the freewheeling diode D2, the output inductor L1, and the output capacitor C1;

[0010] The second rectifier diode D3, freewheeling diode D4, output inductor L2, output capacitor C2,

[0011] ... and so on.

[0012] The nth rectifier diode D 2n-1 , freewheeling diode D 2n , output inductor L n , output capacitor C n .

[0013] The connection form of n-channel output dual-tube forward converter is as follows:

[0014] Excitation inductance L m One end is connected to the source of power switch S1 and the primary winding L of transformer T. p Input terminal, reset diode D p1 Anode; excitation inductance L m The other end is connected to the primary winding L of transformer T p Output terminal, reset diode D p1 anode of the power switch S2; reset diode D p1 The cathode is connected to the drain of the power switch S1, and the reset diode D p2The anode is connected to the source of the power switch S2;

[0015] The secondary winding L of the transformer T s1 One end is connected to the anode of the first rectifier diode D1, the cathode of the first rectifier diode D1 is respectively connected to the cathode of the freewheeling diode D2 and one end of the first inductor L1, the other end of the first inductor L1 is connected to one end of the first output capacitor C1, and the other end of the first output capacitor C1 is respectively connected to the anode of the freewheeling diode D2 and the secondary winding L of the transformer T. s1 The other end;

[0016] The secondary winding L of the transformer T s2 One end is connected to the anode of the second rectifier diode D3, the cathode of the second rectifier diode D3 is respectively connected to the cathode of the flyback diode D4 and one end of the second inductor L2, the other end of the second inductor L2 is connected to one end of the second output capacitor C2, and the other end of the second output capacitor C2 is respectively connected to the anode of the flyback diode D4 and the secondary winding L of the transformer T. s2 The other end;

[0017] ... and so on.

[0018] The secondary winding L of the transformer T s(n-1) One end is connected to the n-1th rectifier diode D 2n-3 Anode, the n-1th rectifier diode D 2n-3 The cathode is connected to the freewheeling diode D 2n-2 Cathode, n-1th inductor L n-1 One end, the n-1th inductor L n-1 The other end is connected to the n-1 output capacitor C n-1 One end, the n-1th output capacitor C n-1 The other end is connected to the freewheeling diode D 2n-2 Anode, secondary winding L of transformer T s(n-1) The other end;

[0019] The secondary winding L of the transformer T sn One end is connected to the nth rectifier diode D 2n-1 Anode, nth rectifier diode D 2n-1 The cathode is connected to the freewheeling diode D 2n Cathode, nth inductor L n One end, the nth inductor L n The other end is connected to the nth output capacitor C n One end, the nth output capacitor C n The other end is connected to the freewheeling diode D 2n Anode, secondary winding L of transformer T sn The other end;

[0020] Among the n-1 jumper capacitors,

[0021] Cross-over capacitor C p1 One end is connected to the anode of the first rectifier diode D1, and the capacitor C p1 The other end is connected to the anode of the second rectifier diode D3;

[0022] Cross-over capacitor C p2 One end is connected to the anode of the second rectifier diode D3, and the capacitor C p2 The other end is connected to the anode of the third rectifier diode D5;

[0023] Cross-over capacitor C p(n-2) One end of the n-2 rectifier diode D 2n-5 The anode connection, across the capacitor C p(n-2) The other end is connected to the n-1th rectifier diode D 2n-3 Anode connection;

[0024] ...... and so on, the jumper capacitor C p(n-1) One end of the n-1th rectifier diode D 2n-3 The anode connection, across the capacitor C p(n-1) The other end is connected to the nth rectifier diode D 2n-1 Anode connection;

[0025] The connection form of n lithium-ion batteries is as follows:

[0026] The positive electrode of the lithium-ion battery B1 is connected to the other end of the first inductor L1 and one end of the first output capacitor C1; the negative electrode of the lithium-ion battery B1 is connected to the secondary winding L of the n-way output transformer T. s1 the other end of the first output capacitor C1;

[0027] The positive electrode of the lithium-ion battery B2 is connected to the other end of the second inductor L2 and one end of the second output capacitor C2, and the negative electrode of the lithium-ion battery B2 is connected to the secondary winding L of the n-way output transformer T. s2 the other end of the second output capacitor C2;

[0028] ... and so on.

[0029] Lithium-ion battery B n-1 The positive poles are connected to the n-1th inductor L n-1 The other end of the n-1 output capacitor C n-1 One end of battery B n-1 The negative poles are connected to the secondary windings L of the n-1 output transformers T. s(n-1) The other end of the n-1 output capacitor C n-1The other end of

[0030] Lithium-ion battery B n The positive poles are connected to the nth inductor L n The other end of the nth output capacitor C n One end of battery B n The negative poles are connected to the secondary windings L of the n-way output transformer T sn The other end of the nth output capacitor C n The other end of

[0031] The positive terminal of lithium-ion battery B1 is connected to the drain of power switch S1. n The negative electrode is connected to the source of the power switch S2.

[0032] The gates of the power switches S1 and S2 are respectively connected to controllers, and the duty ratios thereof can be varied between 0 and 0.5 and are in the same phase.

[0033] A SOC active balancing converter for a series-connected lithium battery pack containing four lithium-ion battery cells comprises a four-way output dual-tube forward converter, three cross-connected capacitors, and four lithium-ion batteries, wherein:

[0034] The 4-way output dual-tube forward converter includes power switches S1 and S2, a reset diode D p1 and D p2 , Excitation inductance L m , transformer T and:

[0035] The first rectifier diode D1, the freewheeling diode D2, the output inductor L1, and the output capacitor C1;

[0036] The second rectifier diode D3, freewheeling diode D4, output inductor L2, output capacitor C2,

[0037] The third rectifier diode D5, freewheeling diode D6, output inductor L3, output capacitor C3,

[0038] The fourth rectifier diode D7, freewheeling diode D8, output inductor L4, output capacitor C4,

[0039] The connection form of the 4-way output dual-tube forward converter is as follows:

[0040] Excitation inductance L m One end is connected to the source of power switch S1 and the primary winding L of transformer T. p Input terminal, reset diode D p1 Anode; excitation inductance L m The other end is connected to the primary winding L of transformer T p Output terminal, reset diode D p1anode of the power switch S2; reset diode D p1 The cathode is connected to the drain of the power switch S1, and the reset diode D p2 The anode is connected to the source of the power switch S2;

[0041] The secondary winding L of the transformer T s1 One end is connected to the anode of the first rectifier diode D1, the cathode of the first rectifier diode D1 is respectively connected to the cathode of the freewheeling diode D2 and one end of the first inductor L1, the other end of the first inductor L1 is connected to one end of the first output capacitor C1, and the other end of the first output capacitor C1 is respectively connected to the anode of the freewheeling diode D2 and the secondary winding L of the transformer T. s1 The other end;

[0042] The secondary winding L of the transformer T s2 One end is connected to the anode of the second rectifier diode D3, the cathode of the second rectifier diode D3 is respectively connected to the cathode of the flyback diode D4 and one end of the second inductor L2, the other end of the second inductor L2 is connected to one end of the second output capacitor C2, and the other end of the second output capacitor C2 is respectively connected to the anode of the flyback diode D4 and the secondary winding L of the transformer T. s2 The other end;

[0043] The secondary winding L of the transformer T s3 One end is connected to the anode of the third rectifier diode D5, the cathode of the third rectifier diode D5 is respectively connected to the cathode of the freewheeling diode D6 and one end of the third inductor L3, the other end of the third inductor L3 is connected to one end of the third output capacitor C3, and the other end of the third output capacitor C3 is respectively connected to the anode of the freewheeling diode D6 and the secondary winding L of the transformer T. s3 The other end;

[0044] The secondary winding L of the transformer T s4 One end is connected to the anode of the fourth rectifier diode D7, the cathode of the fourth rectifier diode D7 is respectively connected to the cathode of the freewheeling diode D8 and one end of the fourth inductor L4, the other end of the fourth inductor L4 is connected to one end of the fourth output capacitor C4, and the other end of the fourth output capacitor C4 is respectively connected to the anode of the freewheeling diode D8 and the secondary winding L of the transformer T. s4 The other end;

[0045] Among the 3 jumper capacitors,

[0046] Cross-over capacitor C p1 One end is connected to the anode of the first rectifier diode D1, and the capacitor C p1 The other end is connected to the anode of the second rectifier diode D3;

[0047] Cross-over capacitor C p2 One end is connected to the anode of the second rectifier diode D3, and the capacitor Cp2 The other end is connected to the anode of the third rectifier diode D5;

[0048] Cross-over capacitor C p3 One end is connected to the anode of the third rectifier diode D5, and the capacitor C p3 The other end is connected to the anode of the fourth rectifier diode D7;

[0049] The connection of 4 lithium-ion batteries is as follows:

[0050] The positive electrode of the lithium-ion battery B1 is connected to the other end of the first inductor L1 and one end of the first output capacitor C1; the negative electrode of the lithium-ion battery B1 is connected to the secondary winding L of the n-way output transformer T. s1 the other end of the first output capacitor C1;

[0051] The positive electrode of the lithium-ion battery B2 is connected to the other end of the second inductor L2 and one end of the second output capacitor C2, and the negative electrode of the lithium-ion battery B2 is connected to the secondary winding L of the n-way output transformer T. s2 the other end of the second output capacitor C2;

[0052] The positive electrode of the lithium-ion battery B3 is connected to the other end of the third inductor L3 and one end of the third output capacitor C3, and the negative electrode of the lithium-ion battery B3 is connected to the secondary winding L of the n-way output transformer T. s3 The other end of the third output capacitor C3;

[0053] The positive electrode of the lithium-ion battery B4 is connected to the other end of the fourth inductor L4 and one end of the fourth output capacitor C4, and the negative electrode of the lithium-ion battery B4 is connected to the secondary winding L of the n-way output transformer T. s4 the other end of the fourth output capacitor C4;

[0054] The positive electrode of the lithium-ion battery B1 is connected to the drain of the power switch S1, and the negative electrode of the battery B4 is connected to the source of the power switch S2.

[0055] When the power switches S1 and S2 are turned on at the same time, the first rectifier diode D1, the second rectifier diode D3, the third rectifier diode D5 and the fourth rectifier diode D7 are turned on, and the reset diode D p1 and D p2 , the first freewheeling diode D2, the second freewheeling diode D4, the third freewheeling diode D6 and the fourth freewheeling diode D8 are turned off; the lithium-ion battery pack adds energy to the primary winding L of the transformer T through series connection pThe energy is transferred to the secondary winding of the transformer T, the first inductor L1, the second inductor L2, the third inductor L3, the fourth inductor L4 and the cross-connected capacitor C p1 , C p2 and C p3 The output capacitors C1, C2, C3 and C4 provide energy for the lithium-ion battery pack.

[0056] When the power switches S1 and S2 are turned off at the same time, the first rectifier diode D1, the second rectifier diode D3, the third rectifier diode D5 and the fourth rectifier diode D7 are turned off, and the reset diode D p1 and D p2 , the first freewheeling diode D2, the second freewheeling diode D4, the third freewheeling diode D6 and the fourth freewheeling diode D8 are turned on; the first inductor L1 is discharged through the freewheeling diode D2, the second inductor L2 is discharged through the freewheeling diode D4, the third inductor L3 is discharged through the freewheeling diode D6, and the fourth inductor L4 is discharged through the freewheeling diode D8; the jumper capacitor C p1 , C p2 and C p3 discharge, and the output capacitors C1, C2, C3, and C4 charge.

[0057] During the entire switching cycle, the secondary winding L of the transformer T s1 , L s2 , L s3 and L s4 The average voltage is 0, and L s1 →C p1 →L s2 →C2→L s1 The KVL principle of the loop can be used to obtain the cross-connected capacitance C p1 The voltage U cp1 Equal to the lithium-ion battery B2 voltage U B2 Similarly, the cross-connect capacitor C p2 The voltage U cp2 Equal to the voltage U of the lithium-ion battery B3 B3 , the cross-capacitor C p3 The voltage U cp3 Equal to the voltage U of lithium-ion battery B4 B4 ;

[0058] During the switch on period, diodes D1, D3, D5 and D7 are turned on, and capacitor C p1 Through loop C p1 →D1→L1→C1→L2→D3→C p1 In parallel with the first output capacitor C1; during the switch off period, diodes D2, D4, D6 and D8 are turned on, and the capacitor C p1 Through loop C p1→L s1 →D2→L1→C1→L2→D4→L s2 →C p1 In parallel with the output capacitor C1, the voltage-equalizing capacitor C is connected across the entire cycle. p1 The voltage U cp1 Equal to the voltage U of the lithium-ion battery B1 B1 ;

[0059] Similarly, the cross-capacitor C in the entire cycle p2 The voltage U cp2 Equal to the lithium-ion battery B2 voltage U B2 , the capacitor C across the entire cycle p3 The voltage U cp3 Equal to the voltage U of the lithium-ion battery B3 B3 ; When the capacitor C p1 , C p2 , C p3 When it is large enough, the voltages of the lithium-ion battery cells are equal, thus achieving voltage self-balancing among the lithium-ion battery cells in the battery pack.

[0060] The present invention provides a series lithium battery pack SOC active balancing converter, the technical effects are as follows:

[0061] 1) The active balancing converter of the present invention achieves the effect of automatic voltage balancing of the output voltages of the multi-channel output forward converter by connecting a jumper capacitor between adjacent output windings of the dual-tube forward converter, thereby improving the balance of the lithium-ion battery.

[0062] 2) Compared with the traditional forward transformer balancing structure, the active balancing converter of the present invention adopts a double-tube forward transformer, and the voltage borne by the primary circuit semiconductor device is higher.

[0063] 3) The active balancing converter of the present invention avoids the problem of terminal voltage imbalance caused by the cross regulation rate when the transformer has multiple windings output, effectively reduces voltage deviation, and improves battery balancing accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0065] Figure 1 It is the circuit principle diagram of the present invention;

[0066] Figure 2 The circuit schematic diagram of the present invention is to realize SOC balancing of a battery pack of four lithium-ion batteries connected in series.

[0067] Figure 3 This is a simulation diagram of the present invention realizing the balancing of a battery pack with four lithium-ion battery cells connected in series. DETAILED DESCRIPTION

[0068] like Figure 2 As shown, a SOC active balancing converter for a series-connected lithium battery pack containing four lithium-ion battery cells includes a four-way output dual-tube forward converter, three cross-connected capacitors, and four lithium-ion batteries, wherein:

[0069] The 4-way output dual-switch forward converter includes power switches S1 and S2, a reset diode D p1 and D p2 , Excitation inductance L m , transformer T and:

[0070] The first rectifier diode D1, the freewheeling diode D2, the output inductor L1, and the output capacitor C1;

[0071] The second rectifier diode D3, freewheeling diode D4, output inductor L2, output capacitor C2,

[0072] The third rectifier diode D5, freewheeling diode D6, output inductor L3, output capacitor C3,

[0073] The fourth rectifier diode D7, freewheeling diode D8, output inductor L4, output capacitor C4,

[0074] The connection form of the 4-way output dual-tube forward converter is as follows:

[0075] Excitation inductance L m One end is connected to the source of power switch S1 and the primary winding L of transformer T. p Input terminal, reset diode D p1 Anode; excitation inductance L m The other end is connected to the primary winding L of transformer T p Output terminal, reset diode D p1 anode of the power switch S2; reset diode D p1 The cathode is connected to the drain of the power switch S1, and the reset diode D p2 The anode is connected to the source of the power switch S2;

[0076] The secondary winding L of the transformer T s1 One end is connected to the anode of the first rectifier diode D1, the cathode of the first rectifier diode D1 is respectively connected to the cathode of the freewheeling diode D2 and one end of the first inductor L1, the other end of the first inductor L1 is connected to one end of the first output capacitor C1, and the other end of the first output capacitor C1 is respectively connected to the anode of the freewheeling diode D2 and the secondary winding L of the transformer T. s1 The other end;

[0077] The secondary winding L of the transformer T s2One end is connected to the anode of the second rectifier diode D3, the cathode of the second rectifier diode D3 is respectively connected to the cathode of the flyback diode D4 and one end of the second inductor L2, the other end of the second inductor L2 is connected to one end of the second output capacitor C2, and the other end of the second output capacitor C2 is respectively connected to the anode of the flyback diode D4 and the secondary winding L of the transformer T. s2 The other end;

[0078] The secondary winding L of the transformer T s3 One end is connected to the anode of the third rectifier diode D5, the cathode of the third rectifier diode D5 is respectively connected to the cathode of the freewheeling diode D6 and one end of the third inductor L3, the other end of the third inductor L3 is connected to one end of the third output capacitor C3, and the other end of the third output capacitor C3 is respectively connected to the anode of the freewheeling diode D6 and the secondary winding L of the transformer T. s3 The other end;

[0079] The secondary winding L of the transformer T s4 One end is connected to the anode of the fourth rectifier diode D7, the cathode of the fourth rectifier diode D7 is respectively connected to the cathode of the freewheeling diode D8 and one end of the fourth inductor L4, the other end of the fourth inductor L4 is connected to one end of the fourth output capacitor C4, and the other end of the fourth output capacitor C4 is respectively connected to the anode of the freewheeling diode D8 and the secondary winding L of the transformer T. s4 The other end;

[0080] Among the 3 jumper capacitors,

[0081] Cross-over capacitor C p1 One end is connected to the anode of the first rectifier diode D1, and the capacitor C p1 The other end is connected to the anode of the second rectifier diode D3;

[0082] Cross-over capacitor C p2 One end is connected to the anode of the second rectifier diode D3, and the capacitor C p2 The other end is connected to the anode of the third rectifier diode D5;

[0083] Cross-over capacitor C p3 One end is connected to the anode of the third rectifier diode D5, and the capacitor C p3 The other end is connected to the anode of the fourth rectifier diode D7;

[0084] The connection of 4 lithium-ion batteries is as follows:

[0085] The positive electrode of the lithium-ion battery B1 is connected to the other end of the first inductor L1 and one end of the first output capacitor C1; the negative electrode of the lithium-ion battery B1 is connected to the secondary winding L of the n-way output transformer T. s1 the other end of the first output capacitor C1;

[0086] The positive electrode of the lithium-ion battery B2 is connected to the other end of the second inductor L2 and one end of the second output capacitor C2, and the negative electrode of the lithium-ion battery B2 is connected to the secondary winding L of the n-way output transformer T. s2 the other end of the second output capacitor C2;

[0087] The positive electrode of the lithium-ion battery B3 is connected to the other end of the third inductor L3 and one end of the third output capacitor C3, and the negative electrode of the lithium-ion battery B3 is connected to the secondary winding L of the n-way output transformer T. s3 The other end of the third output capacitor C3;

[0088] The positive electrode of the lithium-ion battery B4 is connected to the other end of the fourth inductor L4 and one end of the fourth output capacitor C4, and the negative electrode of the lithium-ion battery B4 is connected to the secondary winding L of the n-way output transformer T. s4 the other end of the fourth output capacitor C4;

[0089] The positive electrode of the lithium-ion battery B1 is connected to the drain of the power switch S1, and the negative electrode of the battery B4 is connected to the source of the power switch S2.

[0090] When the power switches S1 and S2 are turned on at the same time, the first rectifier diode D1, the second rectifier diode D3, the third rectifier diode D5 and the fourth rectifier diode D7 are turned on, and the reset diode D p1 and D p2 , the first freewheeling diode D2, the second freewheeling diode D4, the third freewheeling diode D6 and the fourth freewheeling diode D8 are turned off; the lithium-ion battery pack adds energy to the primary winding L of the transformer T through series connection p The energy is transferred to the secondary winding of the transformer T, the first inductor L1, the second inductor L2, the third inductor L3, the fourth inductor L4 and the cross-connected capacitor C p1 , C p2 and C p3 The output capacitors C1, C2, C3 and C4 provide energy for the lithium-ion battery pack.

[0091] When the power switches S1 and S2 are turned off at the same time, the first rectifier diode D1, the second rectifier diode D3, the third rectifier diode D5 and the fourth rectifier diode D7 are turned off, and the reset diode D p1 and D p2, the first freewheeling diode D2, the second freewheeling diode D4, the third freewheeling diode D6 and the fourth freewheeling diode D8 are turned on; the first inductor L1 is discharged through the freewheeling diode D2, the second inductor L2 is discharged through the freewheeling diode D4, the third inductor L3 is discharged through the freewheeling diode D6, and the fourth inductor L4 is discharged through the freewheeling diode D8; the jumper capacitor C p1 , C p2 and C p3 discharge, and the output capacitors C1, C2, C3, and C4 charge.

[0092] During the entire switching cycle, the secondary winding L of the transformer T s1 , L s2 , L s3 and L s4 The average voltage is 0, and L s1 →C p1 →L s2 →C2→L s1 The KVL principle of the loop can be used to obtain the cross-connected capacitance C p1 The voltage U cp1 Equal to the lithium-ion battery B2 voltage U B2 Similarly, the cross-connect capacitor C p2 The voltage U cp2 Equal to the voltage U of the lithium-ion battery B3 B3 , the cross-capacitor C p3 The voltage U cp3 Equal to the voltage U of lithium-ion battery B4 B4 ;

[0093] During the switch on period, diodes D1, D3, D5 and D7 are turned on, and capacitor C p1 Through loop C p1 →D1→L1→C1→L2→D3→C p1 In parallel with the first output capacitor C1; during the switch off period, diodes D2, D4, D6 and D8 are turned on, and the capacitor C p1 Through loop C p1 →L s1 →D2→L1→C1→L2→D4→L s2 →C p1 In parallel with the output capacitor C1, the voltage-equalizing capacitor C is connected across the entire cycle. p1 The voltage U cp1 Equal to the voltage U of the lithium-ion battery B1 B1 ;

[0094] Similarly, the capacitor C across the entire cycle p2 The voltage U cp2 Equal to the lithium-ion battery B2 voltage U B2 , the capacitor C across the entire cyclep3 The voltage U cp3 Equal to the voltage U of the lithium-ion battery B3 B3 ; When the capacitor C p1 , C p2 , C p3 When it is large enough, the voltages of the lithium-ion battery cells are equal, thus achieving voltage self-balancing among the lithium-ion battery cells in the battery pack.

[0095] Figure 3 This is a simulation diagram of the present invention realizing the balancing of a battery pack with four lithium-ion battery cells connected in series. Figure 3 It can be seen that the initial SOCs of the four battery packs are different, and the other parameters are the same, where battery B1 is 90, battery B2 is 85, battery B3 is 80, and battery B4 is 70. The converter proposed in the present invention can realize the movement of the battery cell with higher SOC to the battery cell with lower SOC, and finally the SOC of the four battery cells is balanced.

[0096] The present invention is based on transformer-type balancing and proposes a series lithium battery pack SOC active balancing converter. The circuit includes an n-winding output forward converter, n-1 cross-over capacitors and n lithium-ion batteries. The consistency of the transformer secondary side is achieved by adding a cross-over capacitor between each winding. Compared with the traditional forward transformer balancing structure, the transformer energy storage of the present invention has a release loop, and does not require a reset circuit or reset winding, which reduces the control difficulty and cost of the circuit.

Claims

1. A series lithium battery pack SOC active equalization converter, characterized in that: It includes an n-channel output dual-tube forward converter, n-1 jumper capacitors, and n lithium-ion batteries, where: The n-way output dual-tube forward converter includes power switches S1 and S2, a reset diode D p1 and D p2 , Excitation inductance L m , transformer T and: The first rectifier diode D1, the freewheeling diode D2, the output inductor L1, and the output capacitor C1; The second rectifier diode D3, freewheeling diode D4, output inductor L2, output capacitor C2, ... and so on. The nth rectifier diode D 2n-1 , freewheeling diode D 2n , output inductor L n , output capacitor C n ; The connection form of n-channel output dual-tube forward converter is as follows: Excitation inductance L m One end is connected to the source of power switch S1 and the primary winding L of transformer T. p Input terminal, reset diode D p1 Anode; Excitation inductance L m The other end is connected to the primary winding L of transformer T p Output terminal, reset diode D p1 anode of the power switch S2; reset diode D p1 The cathode is connected to the drain of the power switch S1, and the reset diode D p2 The anode is connected to the source of the power switch S2; The secondary winding L of the transformer T s1 One end is connected to the anode of the first rectifier diode D1, the cathode of the first rectifier diode D1 is respectively connected to the cathode of the freewheeling diode D2 and one end of the first inductor L1, the other end of the first inductor L1 is connected to one end of the first output capacitor C1, and the other end of the first output capacitor C1 is respectively connected to the anode of the freewheeling diode D2 and the secondary winding L of the transformer T. s1 The other end; The secondary winding L of the transformer T s2 One end is connected to the anode of the second rectifier diode D3, the cathode of the second rectifier diode D3 is respectively connected to the cathode of the flyback diode D4 and one end of the second inductor L2, the other end of the second inductor L2 is connected to one end of the second output capacitor C2, and the other end of the second output capacitor C2 is respectively connected to the anode of the flyback diode D4 and the secondary winding L of the transformer T. s2 The other end; ... and so on. The secondary winding L of the transformer T s(n-1) One end is connected to the n-1th rectifier diode D 2n-3 Anode, the n-1th rectifier diode D 2n-3 The cathode is connected to the freewheeling diode D 2n-2 Cathode, n-1th inductor L n-1 One end, the n-1th inductor L n-1 The other end is connected to the n-1 output capacitor C n-1 One end, the n-1th output capacitor C n-1 The other end is connected to the freewheeling diode D 2n-2 Anode, secondary winding L of transformer T s(n-1) The other end; The secondary winding L of the transformer T sn One end is connected to the nth rectifier diode D 2n-1 Anode, the nth rectifier diode D 2n-1 The cathode is connected to the freewheeling diode D 2n Cathode, nth inductor L n One end, the nth inductor L n The other end is connected to the nth output capacitor C n One end, the nth output capacitor C n The other end is connected to the freewheeling diode D 2n Anode, secondary winding L of transformer T sn The other end; Among the n-1 jumper capacitors, Cross-over capacitor C p1 One end is connected to the anode of the first rectifier diode D1, and the capacitor C p1 The other end is connected to the anode of the second rectifier diode D3; Cross-over capacitor C p2 One end is connected to the anode of the second rectifier diode D3, and the capacitor C p2 The other end is connected to the anode of the third rectifier diode D5; Cross-over capacitor C p(n-2) One end of the n-2 rectifier diode D 2n-5 The anode connection, across the capacitor C p(n-2) The other end is connected to the n-1th rectifier diode D 2n-3 Anode connection; ...... and so on, the jumper capacitor C p(n-1) One end of the n-1th rectifier diode D 2n-3 The anode connection, across the capacitor C p(n-1) The other end is connected to the nth rectifier diode D 2n-1 Anode connection; The connection form of n lithium-ion batteries is as follows: The positive electrode of the lithium-ion battery B1 is connected to the other end of the first inductor L1 and one end of the first output capacitor C1; the negative electrode of the lithium-ion battery B1 is connected to the secondary winding L of the n-way output transformer T. s1 the other end of the first output capacitor C1; The positive electrode of the lithium-ion battery B2 is connected to the other end of the second inductor L2 and one end of the second output capacitor C2, and the negative electrode of the lithium-ion battery B2 is connected to the secondary winding L of the n-way output transformer T. s2 the other end of the second output capacitor C2; ... and so on. Lithium-ion battery B n-1 The positive poles are connected to the n-1th inductor L n-1 The other end of the n-1 output capacitor C n-1 One end of battery B n-1 The negative poles are connected to the secondary windings L of the n-1 output transformers T. s(n-1) The other end of the n-1 output capacitor C n-1 The other end of Lithium-ion battery B n The positive poles are connected to the nth inductor L n The other end of the nth output capacitor C n One end of battery B n The negative poles are connected to the secondary windings L of the n-way output transformer T sn The other end of the nth output capacitor C n The other end of The positive terminal of lithium-ion battery B1 is connected to the drain of power switch S1. n The negative electrode is connected to the source of the power switch S2.

2. According to claim 1, a series lithium battery pack SOC active equalization converter is characterized in that: The gates of the power switches S1 and S2 are respectively connected to controllers, and the duty ratios thereof can be varied between 0 and 0.5 and are in the same phase.

3. An active SOC equalization converter for a lithium battery pack having four lithium-ion battery cells connected in series, characterized in that: It includes a 4-way output dual-switch forward converter, 3 jumper capacitors, and 4 lithium-ion batteries, including: The 4-way output dual-switch forward converter includes power switches S1 and S2, a reset diode D p1 and D p2 , Excitation inductance L m , transformer T and: The first rectifier diode D1, the freewheeling diode D2, the output inductor L1, and the output capacitor C1; The second rectifier diode D3, freewheeling diode D4, output inductor L2, output capacitor C2, The third rectifier diode D5, freewheeling diode D6, output inductor L3, output capacitor C3, The fourth rectifier diode D7, freewheeling diode D8, output inductor L4, output capacitor C4, The connection form of the 4-way output dual-tube forward converter is as follows: Excitation inductance L m One end is connected to the source of power switch S1 and the primary winding L of transformer T. p Input terminal, reset diode D p1 Anode; Excitation inductance L m The other end is connected to the primary winding L of transformer T p Output terminal, reset diode D p1 anode of the power switch S2; reset diode D p1 The cathode is connected to the drain of the power switch S1, and the reset diode D p2 The anode is connected to the source of the power switch S2; The secondary winding L of the transformer T s1 One end is connected to the anode of the first rectifier diode D1, the cathode of the first rectifier diode D1 is respectively connected to the cathode of the freewheeling diode D2 and one end of the first inductor L1, the other end of the first inductor L1 is connected to one end of the first output capacitor C1, and the other end of the first output capacitor C1 is respectively connected to the anode of the freewheeling diode D2 and the secondary winding L of the transformer T. s1 The other end; The secondary winding L of the transformer T s2 One end is connected to the anode of the second rectifier diode D3, the cathode of the second rectifier diode D3 is respectively connected to the cathode of the flyback diode D4 and one end of the second inductor L2, the other end of the second inductor L2 is connected to one end of the second output capacitor C2, and the other end of the second output capacitor C2 is respectively connected to the anode of the flyback diode D4 and the secondary winding L of the transformer T. s2 The other end; The secondary winding L of the transformer T s3 One end is connected to the anode of the third rectifier diode D5, the cathode of the third rectifier diode D5 is respectively connected to the cathode of the freewheeling diode D6 and one end of the third inductor L3, the other end of the third inductor L3 is connected to one end of the third output capacitor C3, and the other end of the third output capacitor C3 is respectively connected to the anode of the freewheeling diode D6 and the secondary winding L of the transformer T. s3 The other end; The secondary winding L of the transformer T s4 One end is connected to the anode of the fourth rectifier diode D7, the cathode of the fourth rectifier diode D7 is respectively connected to the cathode of the freewheeling diode D8 and one end of the fourth inductor L4, the other end of the fourth inductor L4 is connected to one end of the fourth output capacitor C4, and the other end of the fourth output capacitor C4 is respectively connected to the anode of the freewheeling diode D8 and the secondary winding L of the transformer T. s4 The other end; Among the 3 jumper capacitors, Cross-over capacitor C p1 One end is connected to the anode of the first rectifier diode D1, and the capacitor C p1 The other end is connected to the anode of the second rectifier diode D3; Cross-over capacitor C p2 One end is connected to the anode of the second rectifier diode D3, and the capacitor C p2 The other end is connected to the anode of the third rectifier diode D5; Cross-over capacitor C p3 One end is connected to the anode of the third rectifier diode D5, and the capacitor C p3 The other end is connected to the anode of the fourth rectifier diode D7; The connection of 4 lithium-ion batteries is as follows: The positive electrode of the lithium-ion battery B1 is connected to the other end of the first inductor L1 and one end of the first output capacitor C1; the negative electrode of the lithium-ion battery B1 is connected to the secondary winding L of the n-way output transformer T. s1 the other end of the first output capacitor C1; The positive electrode of the lithium-ion battery B2 is connected to the other end of the second inductor L2 and one end of the second output capacitor C2, and the negative electrode of the lithium-ion battery B2 is connected to the secondary winding L of the n-way output transformer T. s2 the other end of the second output capacitor C2; The positive electrode of the lithium-ion battery B3 is connected to the other end of the third inductor L3 and one end of the third output capacitor C3, and the negative electrode of the lithium-ion battery B3 is connected to the secondary winding L of the n-way output transformer T. s3 The other end of the third output capacitor C3; The positive electrode of the lithium-ion battery B4 is connected to the other end of the fourth inductor L4 and one end of the fourth output capacitor C4, and the negative electrode of the lithium-ion battery B4 is connected to the secondary winding L of the n-way output transformer T. s4 the other end of the fourth output capacitor C4; The positive electrode of the lithium-ion battery B1 is connected to the drain of the power switch S1, and the negative electrode of the battery B4 is connected to the source of the power switch S2.

4. The SOC active equalization converter for a series-connected lithium battery pack containing four lithium-ion battery cells according to claim 3, characterized in that: When the power switches S1 and S2 are turned on at the same time, the first rectifier diode D1, the second rectifier diode D3, the third rectifier diode D5 and the fourth rectifier diode D7 are turned on, and the reset diode D p1 and D p2 , the first freewheeling diode D2, the second freewheeling diode D4, the third freewheeling diode D6 and the fourth freewheeling diode D8 are turned off; the lithium ion The battery pack adds energy to the primary winding L of the transformer T through series connection. p The energy is transferred to the secondary winding of the transformer T, the first inductor L1, the second inductor L2, the third inductor L3, the fourth inductor L4 and the cross-connected capacitor C p1 , C p2 and C p3 Charging, output capacitors C1, C2, C3 and C4 provide energy for the lithium-ion battery pack; When the power switches S1 and S2 are turned off at the same time, the first rectifier diode D1, the second rectifier diode D3, the third rectifier diode D5 and the fourth rectifier diode D7 are turned off, and the reset diode D p1 and D p2 , the first freewheeling diode D2, the second freewheeling diode D4, the third freewheeling diode D6 and the fourth freewheeling diode D8 are turned on; the first inductor L1 is discharged through the freewheeling diode D2, the second inductor L2 is discharged through the freewheeling diode D4, the third inductor L3 is discharged through the freewheeling diode D6, and the fourth inductor L4 is discharged through the freewheeling diode D8; the jumper capacitor C p1 , C p2 and C p3 discharge, and the output capacitors C1, C2, C3, and C4 charge.

5. The SOC active equalization converter for a series-connected lithium battery pack containing four lithium-ion battery cells according to claim 3, characterized in that: During the entire switching cycle, the secondary winding L of the transformer T s1 , L s2 , L s3 and L s4 The average voltage is 0, and L s1 →C p1 →L s2 →C2→L s1 Loop KVL principle, jumper capacitor C p1 The voltage U cp1 Equal to the lithium-ion battery B2 voltage U B2 Similarly, the cross-connect capacitor C p2 The voltage U cp2 Equal to the voltage U of the lithium-ion battery B3 B3 , the cross-capacitor C p3 The voltage U cp3 Equal to the voltage U of lithium-ion battery B4 B4 ; During the switch on period, diodes D1, D3, D5 and D7 are turned on, and capacitor C p1 Through loop C p1 →D1→L1→C1→L2→D3→C p1 In parallel with the first output capacitor C1; during the switch off period, diodes D2, D4, D6 and D8 are turned on, and the capacitor C p1 Through loop C p1 →L s1 →D2→L1→C1→L2→D4→L s2 →C p1 In parallel with the output capacitor C1, the voltage-equalizing capacitor C is connected across the entire cycle. p1 The voltage U cp1 Equal to the voltage U of the lithium-ion battery B1 B1 ; Similarly, the capacitor C across the entire cycle p2 The voltage U cp2 Equal to the lithium-ion battery B2 voltage U B2 , the capacitor C across the entire cycle p3 The voltage U cp3 Equal to the voltage U of the lithium-ion battery B3 B3 ; When the capacitor C p1 , C p2 , C p3 When it is large enough, the voltages of the lithium-ion battery cells are equal, thus achieving voltage self-balancing among the lithium-ion battery cells in the battery pack.

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