Parallel equalization system based on bidirectional CUK converter and working method thereof

Abstract

The invention discloses a parallel equalization system based on a bidirectional CUK converter. The parallel equalization system comprises an equalization system module and a selective switch matrix module, the selection switch matrix module comprises n groups of gating switch matrixes, each group of gating switch matrix comprises four gating switches, the positive electrode of the first battery is connected with the drain electrode of the first gating switch, the source electrode of the first gating switch is connected with the drain electrode of the third gating switch, and the source electrode of the third gating switch is connected with the negative electrode of the first battery; the drain electrode of the second gating switch is connected with the drain electrode of the first gating switch, the source electrode of the second gating switch is connected with the drain electrode of the fourth gating switch, and the source electrode of the fourth gating switch is connected with the source electrode of the third gating switch; the equalization system module is provided with a plurality of equalizers, and each equalizer is connected with a corresponding gating switch matrix; each equalizer comprises two inductors, one auxiliary power switch, one control power switch and two capacitors. Balancing of a plurality of series-parallel battery packs in charging and discharging states can be realized, and the balancing mode is flexible.

Description

Technical Field

[0001] The invention relates to the field of bidirectional DC-DC CUK converters, and in particular to a parallel balancing system based on a bidirectional CUK converter and a working method thereof. Background Art

[0002] Lithium-ion batteries are used in many occasions, but due to the low voltage and small battery capacity of a single cell, they are usually composed of multiple single lithium batteries connected in series or in parallel in practical applications. The internal resistance, total capacity, initial capacity and other performance of each single lithium battery may vary slightly due to manufacturing process limitations, usage conditions and environment, resulting in differences in the power of each single lithium battery in the lithium-ion battery energy storage system, which may cause some lithium batteries in the lithium battery pack to be overcharged or over-discharged. Whether it is overcharging or over-discharging, it will have an irreversible impact on the performance and life of the single lithium battery and the entire battery energy storage system.

[0003] The battery charge and discharge status balancing system can effectively solve the overcharge and overdischarge phenomenon of the lithium battery energy storage system during the charging and discharging process. The battery balancing system can detect and calculate the power of each lithium battery, and then control the current size of each lithium battery through the balancing system, so as to achieve battery power balancing, which can effectively improve the performance of the lithium battery balancing system and extend its service life. Summary of the invention

[0004] The present invention aims to solve the technical problems existing in the prior art, and particularly innovatively proposes a parallel balancing system based on a bidirectional CUK converter and a working method thereof, which can achieve balancing of a multi-cell series-parallel battery pack in a charging and discharging state, and the balancing method is flexible.

[0005] In order to achieve the above object, the present invention provides a parallel equalization system based on a bidirectional CUK converter, including an equalization system module and a selection switch matrix module;

[0006] The selection switch matrix module includes n groups of gate switch matrices, each group of gate switch matrices includes 4 gate switches, the positive electrode of the first battery is connected to the drain of the first gate switch, the source of the first gate switch is connected to the drain of the third gate switch, the gate of the first gate switch is connected to the first gate control output terminal of the control chip, the source of the third gate switch is connected to the negative electrode of the first battery, the gate of the third gate switch is connected to the third gate control output terminal of the control chip, the drain of the second gate switch is connected to the drain of the first gate switch, the source of the second gate switch is connected to the drain of the fourth gate switch, the gate of the second gate switch is connected to the second gate control output terminal of the control chip, the source of the fourth gate switch is connected to the source of the third gate switch, and the gate of the fourth gate switch is connected to the fourth gate control output terminal of the control chip;

[0007] ..., the positive electrode of the nth battery is connected to the drain of the 4n-3th gate switch (S4n-3), the source of the 4n-3th gate switch is connected to the drain of the 4n-1th gate switch, the gate of the 4n-3th gate switch (S4n-3) is connected to the 4n-3th gate control output terminal of the control chip, the source of the 4n-1th gate switch is connected to the negative electrode of the nth battery, the gate of the 4n-1th gate switch is connected to the 4n-1th gate control output terminal of the control chip, the drain of the 4n-2th gate switch is connected to the drain of the 4n-3th gate switch, the gate of the 4n-2th gate switch is connected to the 4n-2th gate control output terminal of the control chip, the source of the 4n-2th gate switch is connected to the drain of the 4nth gate switch, the source of the 4nth gate switch is connected to the source of the 4n-1th gate switch, and the gate of the 4nth gate switch is connected to the 4nth gate control output terminal of the control chip;

[0008] The balancing system module is provided with the same number of equalizers as the gate switch matrix, and each equalizer is connected to the corresponding gate switch matrix; each equalizer includes 2 inductors, 1 auxiliary power switch, 1 control power switch and 2 capacitors, one end of the first inductor is connected to the source of the first gate switch, the other end of the first inductor is connected to the source of the first auxiliary power switch and one end of the first capacitor, the drain of the first auxiliary power switch is connected to the drain of the second control power switch, and the gate of the first auxiliary power switch is connected to the first power control output of the control chip; one end of the second inductor is connected to the source of the second gate switch, the other end of the second inductor is connected to the source of the second control power switch, the source of the second control power switch is connected to one end of the second capacitor, and the gate of the second control power switch is connected to the second power control output of the control chip;

[0009] ..., one end of the 2n-1th inductor is connected to the source of the 4n-3th selection switch, the other end of the 2n-1th inductor is connected to the source of the 2n-1th auxiliary power switch, the gate of the 2n-1th auxiliary power switch is connected to the 2n-1th power control output terminal of the control chip, the source of the 2n-1th auxiliary power switch is connected to one end of the 2n-1th capacitor, and the drain of the 2n-1 power switch is connected to the drain of the 2n control power switch; one end of the 2nth inductor is connected to the source of the 4n-2th selection switch, the other end of the 2nth inductor is connected to the source of the 2nth control power switch, the source of the 2nth control power switch is connected to one end of the 2nth capacitor, and the gate of the 2nth control power switch is connected to the 2nth power control output terminal of the control chip.

[0010] In the above scheme: it also includes: the other end of the first capacitor is connected to the other end of the third capacitor, the other end of the third capacitor is connected to the other end of the fifth capacitor, ..., the other end of the 2n-3 capacitor is connected to the other end of the 2n-1 capacitor.

[0011] In the above scheme: the other end of the second capacitor is connected to the other end of the fourth capacitor, the other end of the fourth capacitor is connected to the other end of the sixth capacitor, ..., the other end of the 2n-2 capacitor is connected to the other end of the 2n capacitor.

[0012] In the above scheme: the negative end of the first battery is connected to the positive end of the second battery, the negative end of the second battery is connected to the positive end of the third battery, ..., the negative end of the nth battery is connected to the positive end of the nth battery.

[0013] The present invention also provides a working method of a parallel equalization system based on a bidirectional CUK converter, including the parallel equalization system based on a bidirectional CUK converter described in the above scheme, and further comprising the following steps:

[0014] S1: The control chip drives each power switch and the gate switch, adjusts the output voltage and the battery capacity to select the number of equalizers in parallel, and performs energy transmission from multiple batteries to one battery, from one battery to multiple batteries, and from multiple batteries to multiple batteries;

[0015] When energy transmission from multiple batteries to one battery is required, step S2 is executed; when energy transmission from one battery to multiple batteries is required, step S3 is executed; when energy transmission from multiple batteries to multiple batteries is required, step S4 is executed;

[0016] S2: The control chip drives the gate switch of the selection switch matrix to transfer energy from one battery to another through multiple batteries;

[0017] S3: The control chip drives the gate switch of the selection switch matrix to transmit energy to multiple batteries through one battery;

[0018] S4: The control chip drives the gate switch of the selection switch matrix to transmit energy from multiple batteries to multiple batteries;

[0019] S5: Calculate the duty cycle of the PWM drive signal according to the required current.

[0020] In the above scheme: step S2 also includes the following steps:

[0021] S2-1: select the xth battery and the yth battery as discharge batteries, and select the zth battery as charge battery;

[0022] S2-2: driving the 4x-3th gate switch, 4xth gate switch, 4y-3th gate switch, 4yth gate switch, 4z-3th gate switch, and 4zth gate switch of the gate switch matrix corresponding to the discharge battery and the charge battery through the control chip to turn on;

[0023] S2-3: The control chip drives the 2z control power switch to conduct, and uses the body diode of the 2z-1 auxiliary power switch as the freewheeling diode of the converter to form a multi-input single-output CUK converter. The xth battery and the yth battery are high-energy batteries and transmit their own energy to the zth battery through the CUK converter;

[0024] S2-4: When synchronous control is required, execute S2-5; when asynchronous control is required, execute S2-6;

[0025] S2-5: Perform synchronous control, execute step S5, calculate the duty cycle of the PWM drive signal according to the current required by any one of the x-th battery and the y-th battery, and control the 2x-th control power switch and the 2y-th control power switch simultaneously according to the calculated duty cycle drive signal through the control chip;

[0026] S2-6: Perform asynchronous control and execute step S5. Calculate the duty ratio of the PWM drive signal of the 2xth control power switch and the 2yth control power switch according to the required current of the xth battery and the yth battery, and control the 2xth control power switch and the 2yth control power switch according to the drive signals with different duty ratios through the control chip.

[0027] In the above scheme: step S3 also includes the following steps:

[0028] S3-1: Select the xth battery as the discharge battery, and select the yth battery and the zth battery as the charge battery;

[0029] S3-2: driving the 4x-3th gate switch, 4xth gate switch, 4y-3th gate switch, 4yth gate switch, 4z-3th gate switch, and 4zth gate switch of the gate switch matrix corresponding to the discharge battery and the charge battery to turn on through the control chip;

[0030] S3-3: The control chip drives the 2yth control power switch and the 2zth control power switch to turn on, and the body diodes of the 2z-1th auxiliary power switch and the 2y-1th auxiliary power switch serve as the freewheeling diodes of the converter to form a single-input multi-output CUK converter. The xth battery, as a high-energy battery, transmits its own energy to the yth battery and the zth battery through the CUK converter;

[0031] S3-4: When synchronous control is required, execute S3-5; when asynchronous control is required, execute S3-6;

[0032] S3-5: Perform synchronous control, execute step S5, calculate the duty cycle of the PWM drive signal according to the current required by any one of the yth battery and the zth battery, and control the 2yth control power switch and the 2zth control power switch simultaneously according to the calculated duty cycle drive signal through the control chip;

[0033] S3-6: Perform asynchronous control and execute step S5. According to the required currents of the yth battery and the zth battery, the duty cycles of the PWM drive signals of the 2y-controlled power switch and the 2z-controlled power switch are calculated respectively. The 2y-controlled power switch and the 2z-controlled power switch are controlled respectively by the control chip according to the drive signals with different duty cycles.

[0034] In the above scheme: step S4 also includes the following steps:

[0035] S4-1: Select the xth battery and the yth battery as discharge batteries, and select the hth battery and the zth battery as charge batteries;

[0036] S4-2: driving the 4x-3 gate switch, 4x gate switch, 4y-3 gate switch, 4y gate switch, 4z-3 gate switch, 4z gate switch, 4h-3 gate switch, and 4h gate switch of the gate switch matrix corresponding to the discharge battery and the charge battery through the control chip to turn on;

[0037] S4-3: The control chip drives the 2h control power switch and the 2z control power switch to turn on, and the body diodes of the 2z-1 auxiliary power switch and the 2h-1 auxiliary power switch serve as the freewheeling diodes of the converter to form a multi-input multi-output CUK converter. The xth battery and the yth battery serve as high-energy batteries and transmit their own energy to the hth battery and the zth battery through the CUK converter;

[0038] S4-4: When synchronous control is required, execute S4-5; when asynchronous control is required, execute S4-6;

[0039] S4-5: Perform synchronous control, execute step S5, calculate the duty cycle of the PWM drive signal according to the current required by any one of the xth battery and the yth battery, and control the 2xth control power switch and the 2yth control power switch at the same time according to the calculated duty cycle drive signal through the control chip, and keep the 2hth control power switch and the 2zth control power switch turned on;

[0040] S4-6: perform asynchronous control;

[0041] S4-6-1: Control the current on the discharge side, execute step S5, and calculate the duty cycle of the PWM drive signal of the corresponding power switch according to the current required by the x-th battery and the y-th battery;

[0042] The 2xth controlled power switch and the 2yth controlled power switch are driven respectively according to driving signals with different duty cycles through the control chip.

[0043] S4-6-2: Control the current on the charging side, execute step S5, and calculate the duty cycle of the PWM drive signal of the corresponding power switch according to the current required by each battery in the h-th battery section and the z-th battery section;

[0044] The 2h-th control power switch and the 2z-th control power switch are driven respectively according to driving signals with different duty cycles through the control chip.

[0045] In the above scheme: step S5 also includes the following steps:

[0046] S5-1: Calculate using the following formula:

[0047]

[0048] Among them, L in Represents the sum of the inductance values ​​of the discharge battery and the inductance of the balancer, L o represents the sum of the inductance values ​​of the inductors of the equalizers corresponding to the rechargeable battery, C represents the capacitance value of the total capacitance of the capacitors of the discharge battery and the equalizers corresponding to the rechargeable battery connected in series, u c Represents the voltage value across the total capacitor after the capacitors of the equalizer corresponding to the discharge battery and the charge battery are connected in series, i in Indicates the input current, i o Indicates the output current, U in Indicates the input voltage, U o Indicates the output voltage;

[0049] S5-2: Calculation i in and i o The amount of change from time t0 to time t1;

[0050] Solve i by the formula in step S5-1 in and i o The change from t0 to t1 is as follows:

[0051]

[0052] In the formula, Δi in1 Indicates that this stage i in The change in Δi o Indicates that this stage i oThe change in U c0 =u(t0), DT=t1-t0, T represents the PWM period, D represents the PWM duty cycle, t1 is the time t1, and t0 is the time t0;

[0053] S5-3: Solve the formula of step S5-2 to obtain the current i flowing through all power switches of the equalizer corresponding to the discharge battery. Qf1 、i Qf2 ,……i Qfj And the voltage u across all power switches Qg1, Qg2, ..., Qgp of the equalizer corresponding to the rechargeable battery Qgz The equation is:

[0054] i Qf1 =i Qf2 =…=i Qfj =i in +i o (1.3)

[0055]

[0056] Where C represents the capacitance of the total capacitance of the capacitors of the discharge battery and the equalizer corresponding to the charge battery connected in series, u c It represents the voltage value across the total capacitance of the equalizer corresponding to the discharge battery and the charge battery after the capacitance is connected in series;

[0057] S5-4: Assume that at time t1-t2, the control chip drives the control power switches Qf2, Qf4, ..., Qfj of the equalizer corresponding to the discharge battery to be turned off, and the inductor L in The capacitor C discharges under the combined action of the voltage and the input voltage, while the inductor L o The capacitor C is discharged under the action of the output voltage, and charged under the action of the input current. The formula is described as follows:

[0058]

[0059] S5-5: Calculation i in and i o The amount of change between t1 and t2;

[0060] By using the formula in step S5-4, we can solve i in and i o The change from t1 to t2 is as follows:

[0061]

[0062] In the formula, Δi in2 Indicates that this stage i in The change in Δi o2 Indicates that this stage io The change in U c0 =u(t1),U C1 and U C0 Has the following relationship:

[0063]

[0064] During this phase, the input current i in and the output current i o will flow through all power switches Qg1, Qg2, ..., Qgp of the equalizer corresponding to the rechargeable battery, and the current i flowing through all power switches Qg1, Qg2, ..., Qgp of the equalizer corresponding to the rechargeable battery can be obtained respectively. Qg1 、i Qg2 、……、i Qgp The voltage u across the auxiliary power switches Qf1, Qf3, ..., Qfj-1 of the equalizer corresponding to the discharge battery and the auxiliary power switches Qg1, Qg3, ..., Qgp-1 of the equalizer corresponding to the charging battery Qf1 、u Qf3 、……、u Qfj-1 、u Qg1 、u Qg3 、……、u Qgp-1 The equation is:

[0065] i Q3 =i Q4 =i in +i o (1.8)

[0066]

[0067] In one PWM cycle, i in and i o The changes should all be 0, that is:

[0068]

[0069] S5-6: When asynchronous control is required, execute S5-7; when synchronous control is required, execute S5-8;

[0070] S5-7: Calculate the duty cycle of the asynchronously controlled PWM drive signal;

[0071] S5-7-1: According to formulas (1.2), (1.4), (1.5) and (1.6), the relationship between input current and duty cycle is as follows:

[0072]

[0073] Among them, I inis the required input current, D is the duty cycle, T is the PWM period, and D is the PWM duty cycle;

[0074] S5-7-2: Calculate the duty cycle corresponding to the input current according to the formula in S5-7-1.

[0075] S5-8: Calculate the duty cycle of the PWM drive signal for synchronous control;

[0076] S5-8-1: According to the formula, the relationship between input current and duty cycle is as follows:

[0077]

[0078] Among them, I in is the required input current, D is the duty cycle, T is the PWM period, and D is the PWM duty cycle;

[0079] Combined with the law of conservation of energy, that is, U in I in =U o I o , the relationship is as follows:

[0080]

[0081] When the lithium battery SOC is between 10% and 90%, the battery terminal voltage changes slightly, so it can be considered that U o / U in ≈1, then equations (1.1) and (1.12) can be simplified to:

[0082] I o ≈I in =k in U in -k2U o ; (1.13);

[0083] Where, k1 = 2CD / [D(1-D)(2D-1)T], k2 = 2C(1-D) / [D(1-D)(2D-1)T]. When the circuit parameters, PWM frequency and PWM duty cycle D are determined, k1 and k2 are constants;

[0084] S5-8-2: Calculate the duty cycle corresponding to the input current according to formula (1.13).

[0085] In summary, the beneficial effects of the present invention are as follows: the system can realize the balancing of multiple series-parallel battery packs in the charging and discharging state, and the balancing method is flexible. It can realize PWM signal synchronous control and PWM signal asynchronous control. When the PWM signal synchronous control is performed, the current will be distributed automatically, simplifying the control process; when the PWM signal asynchronous control is performed, the current of each battery is independently controlled to speed up the balancing speed; the control variable is only the current, and the output voltage does not need to be controlled. The control method is simple, the balancing efficiency is improved, and the balancing system structure is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 It is a circuit diagram of a parallel equalization system based on a bidirectional CUK converter of the present invention;

[0087] Figure 2 It is a schematic diagram of equivalent connection of a one-to-one balancing mode of a parallel balancing system based on a bidirectional CUK converter of the present invention;

[0088] Figure 3 This is the first stage of the parallel equalization system based on the bidirectional CUK converter of the present invention;

[0089] Figure 4 This is the second stage of the parallel equalization system based on the bidirectional CUK converter of the present invention;

[0090] Figure 5 It is a timing diagram of the operation of the parallel equalization system based on the bidirectional CUK converter of the present invention;

[0091] Figure 6 It is a schematic diagram of a one-to-many balancing mode connection of a parallel balancing system based on a bidirectional CUK converter of the present invention;

[0092] Figure 7 It is a short-circuit schematic diagram of a one-to-many balancing mode of a parallel balancing system based on a bidirectional CUK converter of the present invention without adding a pair of tubes;

[0093] Figure 8 It is a schematic diagram of the many-to-one balancing mode connection of the parallel balancing system based on the bidirectional CUK converter of the present invention;

[0094] Fig. 9 It is a connection schematic diagram of a many-to-one balancing mode without adding a pair of tubes of a parallel balancing system based on a bidirectional CUK converter of the present invention;

[0095] Fig.10 It is a schematic diagram of the connection of a many-to-many balancing mode of a parallel balancing system based on a bidirectional CUK converter of the present invention. DETAILED DESCRIPTION

[0096] The present invention will be further described below by way of embodiments and in conjunction with the accompanying drawings:

[0097] like Figure 1 A parallel balancing system based on a bidirectional CUK converter is shown, comprising a balancing system module and a selection switch matrix module;

[0098] The selection switch matrix module includes n groups of gate switch matrices, each group of gate switch matrices includes 4 gate switches, the positive electrode of the first battery Cell1 is connected to the drain of the first gate switch S1, the source of the first gate switch S1 is connected to the drain of the third gate switch S3, the gate of the first gate switch S1 is connected to the first gate control output terminal of the control chip, the source of the third gate switch S3 is connected to the negative electrode of the first battery Cell1, the gate of the third gate switch S3 is connected to the third gate control output terminal of the control chip, the drain of the second gate switch S2 is connected to the drain of the first gate switch S1, the source of the second gate switch S2 is connected to the drain of the fourth gate switch S4, the gate of the second gate switch S2 is connected to the second gate control output terminal of the control chip, the source of the fourth gate switch S4 is connected to the source of the third gate switch S3, and the gate of the fourth gate switch S4 is connected to the fourth gate control output terminal of the control chip;

[0099] ..., the positive electrode of the nth battery Celln is connected to the drain of the 4n-3th gate switch (S4n-3), the source of the 4n-3th gate switch S4n-3 is connected to the drain of the 4n-1th gate switch S4n-1, the gate of the 4n-3th gate switch S4n-3 is connected to the 4n-3th gate control output terminal of the control chip, the source of the 4n-1th gate switch S4n-1 is connected to the negative electrode of the nth battery Celln, and the gate of the 4n-1th gate switch S4n-1 is connected to the 4n-1th gate control output terminal of the control chip control output end, the drain of the 4n-2th gate switch S4n-2 is connected to the drain of the 4n-3th gate switch S4n-3, the gate of the 4n-2th gate switch S4n-2 is connected to the 4n-2th gate control output end of the control chip, the source of the 4n-2th gate switch S4n-2 is connected to the drain of the 4nth gate switch S4n, the source of the 4nth gate switch S4n is connected to the source of the 4n-1th gate switch S4n-1, and the gate of the 4nth gate switch S4n is connected to the 4nth gate control output end of the control chip;

[0100] The balancing system module is provided with the same number of equalizers as the gate switch matrix, and each equalizer is connected to the corresponding gate switch matrix; each equalizer includes 2 inductors, 1 auxiliary power switch, 1 control power switch and 2 capacitors, one end of the first inductor L1 is connected to the source of the first gate switch S1, the other end of the first inductor L1 is connected to the source of the first auxiliary power switch Q1 and one end of the first capacitor C1, the drain of the first auxiliary power switch Q1 is connected to the drain of the second control power switch Q2, and the gate of the first auxiliary power switch Q1 is connected to the first power control output end of the control chip; one end of the second inductor L2 is connected to the source of the second gate switch S2, the other end of the second inductor L2 is connected to the source of the second control power switch Q2, the source of the second control power switch Q2 is connected to one end of the second capacitor C2, and the gate of the second control power switch Q2 is connected to the second power control output end of the control chip;

[0101] ..., one end of the 2n-1th inductor L2n-1 is connected to the source of the 4n-3th selection switch Q4n-3, the other end of the 2n-1th inductor L2n-1 is connected to the source of the 2n-1th auxiliary power switch Q2n-1, the gate of the 2n-1th auxiliary power switch Q2n-1 is connected to the 2n-1th power control output terminal of the control chip, the source of the 2n-1th auxiliary power switch Q2n-1 is connected to one end of the 2n-1th capacitor C2n-1, and the The drain of the 2n-1 power switch Q2n-1 is connected to the drain of the 2n-th control power switch S2n; one end of the 2n-th inductor L2n is connected to the source of the 4n-2-th selection switch S4n-2, the other end of the 2n-th inductor is connected to the source of the 2n-th control power switch Q2n, the source of the 2n-th control power switch Q2n is connected to one end of the 2n-th capacitor C2n, and the gate of the 2n-th control power switch Q2n is connected to the 2n-th power control output terminal of the control chip.

[0102] In the above scheme: it also includes: the other end of the first capacitor C1 is connected to the other end of the third capacitor C3, the other end of the third capacitor C3 is connected to the other end of the fifth capacitor C5, ..., the other end of the 2n-3 capacitor C2n-3 is connected to the other end of the 2n-1 capacitor C2n-1.

[0103] In the above scheme: the other end of the second capacitor C2 is connected to the other end of the fourth capacitor C4, the other end of the fourth capacitor C4 is connected to the other end of the sixth capacitor C6, ..., the other end of the 2n-2 capacitor C2n-2 is connected to the other end of the 2nth capacitor C2n.

[0104] In the above scheme: the negative end of the first battery Cell1 is connected to the positive end of the second battery Cell2, the negative end of the second battery Cell2 is connected to the positive end of the third battery Cell3, ..., the negative end of the n-1th battery Celln-1 is connected to the positive end of the nth battery Celln.

[0105] The present invention also provides a working method of a parallel equalization system based on a bidirectional CUK converter, including a parallel equalization system based on a bidirectional CUK converter in the above scheme, and further comprising the following steps:

[0106] S1: The control chip drives each power switch and the gate switch, adjusts the output voltage and the battery capacity to select the number of equalizers in parallel, and performs energy transmission from multiple batteries to one battery, from one battery to multiple batteries, and from multiple batteries to multiple batteries;

[0107] When energy transmission from multiple batteries to one battery is required, step S2 is executed; when energy transmission from one battery to multiple batteries is required, step S3 is executed; when energy transmission from multiple batteries to multiple batteries is required, step S4 is executed;

[0108] S2: The control chip drives the gate switch of the selection switch matrix to transfer energy from one battery to another through multiple batteries;

[0109] S2-1: select the x-th battery Cellx and the y-th battery Celly as discharge batteries, and select the z-th battery Cellz as charge battery;

[0110] S2-2: driving the 4x-3th gate switch S4x-3, 4xth gate switch S4x, 4y-3th gate switch S4y-3, 4yth gate switch S4y, 4z-3th gate switch S4z-3, and 4zth gate switch S4z of the gate switch matrix corresponding to the discharge battery and the charge battery through the control chip;

[0111] S2-3: The control chip drives the 2zth control power switch Q2z to turn on, and uses the body diode of the 2z-1th auxiliary power switch Q2z-1 as the freewheeling diode of the converter to form a multi-input single-output CUK converter. The xth battery Cellx and the yth battery Celly, as high-energy batteries, transfer their own energy to the zth battery Cellz through the CUK converter;

[0112] S2-4: When synchronous control is required, execute S2-5; when asynchronous control is required, execute S2-6;

[0113] S2-5: Perform synchronous control, execute step S5, calculate the duty cycle of the PWM drive signal according to the current required by any one of the x-th battery Cellx and the y-th battery Celly, and control the 2x-th control power switch Q2x and the 2y-th control power switch Q2y simultaneously through the control chip according to the drive signal of the calculated duty cycle;

[0114] S2-6: Perform asynchronous control and execute step S5. According to the required currents of the xth battery Cellx and the yth battery Celly, the duty cycles of the PWM drive signals of the 2xth controlled power switch Q2x and the 2yth controlled power switch Q2y are calculated respectively. The 2xth controlled power switch Q2x and the 2yth controlled power switch Q2y are controlled respectively by the control chip according to the drive signals with different duty cycles.

[0115] S3: The control chip drives the gate switch of the selection switch matrix to transmit energy to multiple batteries through one battery;

[0116] S3-1: Select the x-th battery Cellx as the discharge battery, and select the y-th battery Celly and the z-th battery Cellz as the charge batteries;

[0117] S3-2: driving the 4x-3th gate switch S4x-3, 4xth gate switch S4x, 4y-3th gate switch S4y-3, 4yth gate switch S4y, 4z-3th gate switch S4z-3, and 4zth gate switch S4z of the gate switch matrix corresponding to the discharge battery and the charge battery through the control chip;

[0118] S3-3: The control chip drives the 2yth control power switch Q2y and the 2zth control power switch Q2z to turn on, and the body diodes of the 2z-1th auxiliary power switch Q2z-1 and the 2y-1th auxiliary power switch Q2y-1 serve as the freewheeling diodes of the converter to form a single-input multi-output CUK converter. The xth battery Cellx, as a high-energy battery, transmits its own energy to the yth battery Celly and the zth battery Cellz through the CUK converter;

[0119] S3-4: When synchronous control is required, execute S3-5; when asynchronous control is required, execute S3-6;

[0120] S3-5: Perform synchronous control, execute step S5, calculate the duty cycle of the PWM drive signal according to the current required by any one of the yth battery Celly and the zth battery Cellz, and control the 2yth control power switch Q2y and the 2zth control power switch Q2z simultaneously through the control chip according to the calculated duty cycle drive signal;

[0121] S3-6: Perform asynchronous control and execute step S5. According to the required currents of the yth battery Celly and the zth battery Cellz, the duty cycles of the PWM drive signals of the 2y-controlled power switch Q2y and the 2z-controlled power switch Q2z are calculated respectively. The 2y-controlled power switch Q2y and the 2z-controlled power switch Q2z are controlled respectively by the control chip according to the drive signals with different duty cycles.

[0122] S4: The control chip drives the gate switch of the selection switch matrix to transmit energy from multiple batteries to multiple batteries;

[0123] S4-1: Select the x-th battery Cellx and the y-th battery Celly as discharge batteries, and select the h-th battery Celly and the z-th battery Cellz as charge batteries;

[0124] S4-2: driving the 4x-3th gate switch S4x-3, 4xth gate switch S4x, 4y-3th gate switch S4y-3, 4yth gate switch S4y, 4z-3th gate switch S4z-3, 4zth gate switch S4z, 4h-3th gate switch S4h-3, and 4hth gate switch S4h of the gate switch matrix corresponding to the discharge battery and the charge battery through the control chip;

[0125] S4-3: The control chip drives the 2h control power switch Q2y and the 2z control power switch Q2z to turn on, and the body diodes of the 2z-1 auxiliary power switch Q2z-1 and the 2h-1 auxiliary power switch Q2y-1 serve as the freewheeling diodes of the converter to form a multi-input and multi-output CUK converter. The xth battery Cellx and the yth battery Celly, as high-energy batteries, transfer their own energy to the hth battery Celly and the zth battery Cellz through the CUK converter;

[0126] S4-4: When synchronous control is required, execute S4-5; when asynchronous control is required, execute S4-6;

[0127] S4-5: Perform synchronous control, execute step S5, calculate the duty cycle of the PWM drive signal according to the current required by any one of the x-th battery Cellx and the y-th battery Celly, and control the 2x-th control power switch Q2x and the 2y-th control power switch Q2y at the same time through the control chip according to the drive signal of the calculated duty cycle, and keep the 2h-th control power switch Q2y and the 2z-th control power switch Q2z turned on;

[0128] S4-6: perform asynchronous control;

[0129] S4-6-1: Control the current on the discharge side, execute step S5, and calculate the duty ratio of the PWM drive signal of the corresponding power switch according to the current required by the x-th battery Cellx and the y-th battery Celly;

[0130] The 2xth controlled power switch Q2x and the 2yth controlled power switch Q2y are driven respectively by the control chip according to driving signals with different duty cycles.

[0131] S4-6-2: Control the current on the charging side, execute step S5, and calculate the duty cycle of the PWM drive signal of the corresponding power switch according to the current required by each battery in the h-th battery Celly and the z-th battery Cellz;

[0132] The 2h-th controlled power switch Q2y and the 2z-th controlled power switch Q2z are driven respectively by the control chip according to driving signals with different duty cycles.

[0133] S5: Calculate the duty cycle of the PWM drive signal according to the required current.

[0134] S5-1: Calculate using the following formula:

[0135]

[0136] Among them, L in Represents the sum of the inductance values ​​of the discharge battery and the inductance of the balancer, L o represents the sum of the inductance values ​​of the inductors of the equalizers corresponding to the rechargeable battery, C represents the capacitance value of the total capacitance of the capacitors of the discharge battery and the equalizers corresponding to the rechargeable battery connected in series, u c Represents the voltage value across the total capacitor after the capacitors of the equalizer corresponding to the discharge battery and the charge battery are connected in series, i in Indicates the input current, i o Indicates the output current, U in Indicates the input voltage, U o Indicates the output voltage;

[0137] S5-2: Calculation i in and i o The amount of change from time t0 to time t1;

[0138] Solve i by the formula in step S5-1 in and i o The change from t0 to t1 is as follows:

[0139]

[0140] In the formula, Δi in1 Indicates that this stage i in The change in Δi o Indicates that this stage i o The change in U c0 =u(t0), DT=t1-t0, T represents the PWM period, D represents the PWM duty cycle, t1 is the time t1, and t0 is the time t0;

[0141] S5-3: Solve the formula of step S5-2 to obtain the current i flowing through all power switches of the equalizer corresponding to the discharge battery.Qf1 、i Qf2 ,……i Qfj And the voltage u across all power switches Qg1, Qg2, ..., Qgp of the equalizer corresponding to the rechargeable battery Qgz The equation is:

[0142] i Qf1 =i Qf2 =…=i Qfj =i in +i o (1.3)

[0143]

[0144] Where C represents the capacitance of the total capacitance of the capacitors of the discharge battery and the equalizer corresponding to the charge battery connected in series, u c It represents the voltage value across the total capacitance of the equalizer corresponding to the discharge battery and the charge battery after the capacitance is connected in series;

[0145] S5-4: Assume that at time t1-t2, the control chip drives the control power switches Qf2, Qf4, ..., Qfj of the equalizer corresponding to the discharge battery to be turned off, and the inductor L in The capacitor C discharges under the combined action of the voltage and the input voltage, while the inductor L o The capacitor C is discharged under the action of the output voltage, and charged under the action of the input current. The formula is as follows:

[0146]

[0147] S5-5: Calculation i in and i o The amount of change between t1 and t2;

[0148] By using the formula in step S5-4, we can solve i in and i o The change from t1 to t2 is as follows:

[0149]

[0150] In the formula, Δi in2 Indicates that this stage i in The change in Δi o2 Indicates that this stage i o The change in U c0 =u(t1),U C1 and U C0 Has the following relationship:

[0151]

[0152] During this phase, the input current i in and the output current i o will flow through all power switches Qg1, Qg2, ..., Qgp of the equalizer corresponding to the rechargeable battery, and the current i flowing through all power switches Qg1, Qg2, ..., Qgp of the equalizer corresponding to the rechargeable battery can be obtained respectively. Qg1 、i Qg2 、……、i Qgp The voltage u across the auxiliary power switches Qf1, Qf3, ..., Qfj-1 of the equalizer corresponding to the discharge battery and the auxiliary power switches Qg1, Qg3, ..., Qgp-1 of the equalizer corresponding to the charging battery Qf1 、u Qf3 、……、u Qfj-1 、u Qg1 、u Qg3 、……、u Qgp-1 The equation is:

[0153] i Q3 =i Q4 =i in +i o (1.8)

[0154]

[0155] In one PWM cycle, i in and i o The changes should all be 0, that is:

[0156]

[0157] S5-6: When asynchronous control is required, execute S5-7; when synchronous control is required, execute S5-8;

[0158] S5-7: Calculate the duty cycle of the asynchronously controlled PWM drive signal;

[0159] S5-7-1: According to formulas (1.2), (1.4), (1.5) and (1.6), the relationship between input current and duty cycle is as follows:

[0160]

[0161] Among them, I in is the required input current, D is the duty cycle, T is the PWM period, and D is the PWM duty cycle;

[0162] S5-7-2: Calculate the duty cycle corresponding to the input current according to the formula in S5-7-1.

[0163] S5-8: Calculate the duty cycle of the PWM drive signal for synchronous control;

[0164] S5-8-1: According to the formula, the relationship between input current and duty cycle is as follows:

[0165]

[0166] Among them, I in is the required input current, D is the duty cycle, T is the PWM period, and D is the PWM duty cycle;

[0167] Combined with the law of conservation of energy, that is, U in I in =U o I o , the relationship is as follows:

[0168]

[0169] When the lithium battery SOC is between 10% and 90%, the battery terminal voltage changes slightly, so it can be considered that U o / U in ≈1, then equations 1.1 and 1.12 can be simplified to:

[0170] I o ≈I in =k in U in -k2U o ; (1.13);

[0171] Where, k1 = 2CD / [D(1-D)(2D-1)T], k2 = 2C(1-D) / [D(1-D)(2D-1)T]. When the circuit parameters, PWM frequency and PWM duty cycle D are determined, k1 and k2 are constants;

[0172] S5-8-2: Calculate the duty cycle corresponding to the input current according to formula (1.13).

[0173] The parallel balancing system based on the bidirectional CUK converter of the present invention selects the number of parallel equalizers according to the output voltage and battery capacity as needed, and can perform balancing operations by connecting two equalizers in parallel or multiple equalizers in parallel, so as to realize the balancing mode of any battery section to any battery section, such as one-to-many, many-to-one, and many-to-many. The working principle of these modes is equivalent to the working principle of one-to-one balancing, and the charging principle is equivalent to the discharging principle. The first equalizer is selected to be connected in parallel with the second equalizer, and the one-to-one energy transmission process is analyzed. Because the structural battery series relationship does not affect the balancing process, the series relationship is not marked for the convenience of analysis. The general process is divided into the following two stages.

[0174] Figure 2 This is a schematic diagram of equivalent connection in a one-to-one balanced manner.

[0175] Figure 3 The first phase (t0-t1) of the system's operation;

[0176] In this stage, the power switches Q1 and Q2 are turned on, the inductors L1 and L2 are charged under the action of the input voltage, the second battery Cell2 is charged under the joint action of the capacitors C1, C2, C3 and C4, and the capacitors C1, C2, C3 and C4 are discharged under the action of the output current. The formula is described as follows:

[0177]

[0178] Among them, L in It represents the sum of the inductance of L1 and L2. o represents the sum of the inductance of L3 and the inductance of L4, C represents the capacitance of capacitors C1, C2, C3 and C4 in series, u c Represents the voltage value across the capacitor C, i in Indicates the input current, i o Indicates the output current, U in Indicates the input voltage, U o Represents the output voltage. Since the output current ripple is small, it can be regarded as a constant output current to discharge the capacitor C.

[0179] Using formula (1.1), we can solve for i in and i o Amount of change at this stage:

[0180]

[0181] In the formula, Δi in1 Indicates that this stage i in The change in Δi o Indicates that this stage i o The change in U c0 =u(t0), DT=t1-t0, T represents a PWM control cycle, and D represents the PWM duty cycle.

[0182] During this phase, the input current i in and the output current i o will flow through the switch tubes Q1 and Q2, so the current i flowing through the switch tubes Q1 and Q2 can be obtained respectively. Q1 、i Q2 And the voltage u across Q3 and Q4 Q3 The equation is:

[0183] iQ1 =i Q2 =i in +i o (1.3)

[0184]

[0185] Figure 4 The second phase (t1-t2) of the system's work;

[0186] In this stage, the power switches Q1 and Q2 are turned off and the inductor L in The capacitor C discharges under the combined action of the voltage and the input voltage, while the inductor L o The capacitor C is discharged under the action of the output voltage, and charged under the action of the input current. The formula is described as follows:

[0187]

[0188] In the formula, since the input current ripple is small, it can be regarded as a constant input current to charge the capacitor C. Using formula (1.3), we can solve i in and i o Amount of change at this stage:

[0189]

[0190] In the formula, Δi in2 Indicates that this stage i in The change in Δi o2 Indicates that this stage i o The change in U c0 =u(t1),U C1 and U C0 Has the following relationship:

[0191]

[0192] During this phase, the input current i in and the output current i o will flow through the switch tubes Q3 and Q4, and the current i flowing through the switch tubes Q3 and Q4 can be obtained respectively. Q3 、i Q4 And the voltage u across Q1 and Q3 Q1 ,u Q3 The equation is:

[0193] i Q3 =i Q4 =i in +i o (1.8)

[0194]

[0195] It can be concluded that the sum of the voltages of Q1 and Q3 is always equal to the voltage across capacitor C.

[0196] In one PWM cycle, i in and i o The changes should all be 0, that is:

[0197]

[0198] Combining equations (1.2), (1.6), (1.7) and (1.10), we can obtain:

[0199]

[0200] Ignoring the loss here, combined with the law of conservation of energy, that is, U in I in =U o I o , we can get:

[0201]

[0202] When the lithium battery SOC is between 10% and 90%, the battery terminal voltage changes slightly, so it can be considered that U o / U in ≈1, then equations (1.1) and (1.12) can be simplified to:

[0203] I o ≈I in =k in U in -k2U o (1.13)

[0204] Where, k1=2CD / [D(1-D)(2D-1)T], k2=2C(1-D) / [D(1-D)(2D-1)T]. When the circuit parameters, PWM frequency and PWM duty cycle D are determined, k1 and k2 are constants. Therefore, the higher the voltage of the single battery on the input side, the higher the corresponding balancing current, and the lower the voltage of the battery on the output side, the higher the corresponding balancing current. The autonomous current distribution is achieved through the synchronous control of each main switch.

[0205] In particular, when multiple batteries are discharged, different duty cycles can be given to each balancer to achieve independent control of the balancing current of each battery, that is, asynchronous control, thereby improving the balancing speed of the system.

[0206] In the case of asynchronous control, taking the first battery Cell1 and the second battery Cell2 as discharge batteries and the third battery Cell3 as a charging battery as an example, the many-to-one energy transmission process is analyzed:

[0207] S1, S4, S5, S8, S9, and S12 are turned on, and the other selection switches are turned off. Q2 and Q4 are the main switches of the discharge side equalizer, Q6 is always turned on, and the body diode of Q5 is used as the freewheeling diode of the converter to form a dual-input single-output CUK converter. The high-energy batteries Cell1 and Cell2 transfer their own energy to the low-energy battery Cell3 through the converter.

[0208] The asynchronous control method uses driving signals with different duty cycles to control the main switches Q2 and Q4 of the equalizers connected to Cell1 and Cell2 respectively, which can achieve quantitative control of the two-way balancing current. Combining equations (1.2), (1.4), (1.5) and (1.6), we can get:

[0209]

[0210] Simplifying (1.14) we can obtain:

[0211]

[0212] In the formula, k = 2CU0 / T. When the load of the converter is connected to the battery, the voltage across the battery changes slowly, so it can be considered that U o is a constant, and C is also a constant when the circuit structure is fixed. By using formula (1.15), we can get that when the duty cycle D∈(0.5,1), the input current I in It is positively correlated with the duty cycle D. Therefore, when the output voltage is fixed and the control period is fixed, quantitative control of the balanced current can be achieved by simply adjusting the PWM duty cycle.

[0213] When D1≠D2, if there are no auxiliary switches Q1 and Q3, the balancing system will be short-circuited, such as Figure 7 As shown. Taking Q2 as an example, when Q4's body diode is subjected to a forward voltage drop, that is, U C1 +U C2 >U C3 +U C4 , where U C1 is the voltage across capacitor C1, U C2 is the voltage across capacitor C2, U C3 is the voltage across capacitor C3, U C4 is the voltage across capacitor C4. At this time, the body diode of Q4 will conduct.

[0214] U Q4 =U C1 +U C2 -U C3 +U C4 (1.16)

[0215]

[0216] U Q4 is the voltage across Q4, I Q4 is the current of Q4, R p This is the total resistance of the loop. Since there is no resistive load in this loop, R p It is only the internal resistance of the device and the wire, which is very small and will generate a huge instantaneous current I Q4 Cause damage to the device.

[0217] To avoid this short-circuit situation, auxiliary switches Q1 and Q3 are added in series with the main switches Q2 and Q4 respectively. This pair of tubes structure can solve the short-circuit problem of the equalizer when different duty cycle signals are used to drive it, that is, D1≠D2, and avoid the back and forth transmission of energy in the balancing system, thereby improving the balancing speed and balancing efficiency of the system.

[0218] Take the first battery Cell1 as a discharge battery, the second battery Cell2 and the third battery Cell3 as charging batteries as an example to analyze the one-to-many energy transmission process:

[0219] The total discharge current of Cell1 can be controlled by adjusting the drive signal of Q2. If the pair structure is not used, the balanced structure is as follows Fig. 9 As shown, Cell2 and Cell3 can only be used as discharge batteries, and the balancing current can only be passively distributed according to the voltage, and quantitative control cannot be achieved. Figure 8 As shown, adding pairs of tubes Q4 and Q6 and changing the conduction time of Q4 and Q6 can quantitatively adjust the balanced current of Cell2 and Cell3. This proves the necessity of MOS pairs of tubes and the feasibility of current asynchronous control.

[0220] like Figure 5 As shown, it is a circuit timing diagram of the parallel balancing system based on the bidirectional CUK converter when it is working, and the timing control of the balancing system can be performed according to the timing diagram.

[0221] Taking the first battery Cell1 and the second battery Cell2 as discharge batteries, and the third battery Cell3 and the fourth battery Cell4 as rechargeable batteries as examples, the many-to-many energy transmission process is analyzed. Fig.10 As shown:

[0222] The discharge side drives the main switches Q2 and Q4 asynchronously to achieve independent control of the two discharge currents, and the charging side drives the main switches Q6 and Q8 asynchronously to achieve independent control of the two charging currents. It can be seen that in the many-to-many balancing mode, both the input and output ends can quantitatively control the balancing current of each path, thereby greatly improving the balancing speed and balancing efficiency.

Claims

1. A parallel equalization system based on a bidirectional CUK converter, characterized in that: Including a balance system module and a selection switch matrix module; The selection switch matrix module includes n groups of gate switch matrices, each group of gate switch matrices includes 4 gate switches, the positive electrode of the first battery (Cell1) is connected to the drain of the first gate switch (S1), the source of the first gate switch (S1) is connected to the drain of the third gate switch (S3), the gate of the first gate switch (S1) is connected to the first gate control output terminal of the control chip, the source of the third gate switch (S3) is connected to the negative electrode of the first battery (Cell1), and the third gate switch (S3) is connected to the negative electrode of the first battery (Cell1). The gate of the second selection switch (S3) is connected to the third selection control output terminal of the control chip, the drain of the second selection switch (S2) is connected to the drain of the first selection switch (S1), the source of the second selection switch (S2) is connected to the drain of the fourth selection switch (S4), the gate of the second selection switch (S2) is connected to the second selection control output terminal of the control chip, the source of the fourth selection switch (S4) is connected to the source of the third selection (S3) switch, and the gate of the fourth selection switch (S4) is connected to the fourth selection control output terminal of the control chip; ..., the positive electrode of the nth battery (Celln) is connected to the drain of the 4n-3th gate switch (S4n-3), the source of the 4n-3th gate switch (S4n-3) is connected to the drain of the 4n-1th gate switch (S4n-1), the gate of the 4n-3th gate switch (S4n-3) is connected to the 4n-3th gate control output terminal of the control chip, the source of the 4n-1th gate switch (S4n-1) is connected to the negative electrode of the nth battery (Celln), and the gate of the 4n-1th gate switch (S4n-1) is connected to the 4n-1th gate control output terminal of the control chip. The drain of the 4n-2th gate switch (S4n-2) is connected to the drain of the 4n-3th gate switch (S4n-3), the gate of the 4n-2th gate switch (S4n-2) is connected to the 4n-2th gate control output terminal of the control chip, the source of the 4n-2th gate switch (S4n-2) is connected to the drain of the 4nth gate switch (S4n), the source of the 4nth gate switch (S4n) is connected to the source of the 4n-1th gate switch (S4n-1), and the gate of the 4nth gate switch (S4n) is connected to the 4nth gate control output terminal of the control chip; The balancing system module is provided with the same number of balancers as the gate switch matrix, and each balancer is connected to the corresponding gate switch matrix; each balancer includes two inductors, one auxiliary power switch, one control power switch and two capacitors, one end of the first inductor (L1) is connected to the source of the first gate switch (S1), the other end of the first inductor (L1) is connected to the source of the first auxiliary power switch (Q1) and one end of the first capacitor (C1), the drain of the first auxiliary power switch (Q1) is connected to the drain of the second control power switch (Q2), and the gate of the first auxiliary power switch (Q1) is connected to the first power control output end of the control chip; one end of the second inductor (L2) is connected to the source of the second gate switch (S2), the other end of the second inductor (L2) is connected to the source of the second control power switch (Q2), the source of the second control power switch (Q2) is connected to one end of the second capacitor (C2), and the gate of the second control power switch (Q2) is connected to the second power control output end of the control chip; ..., one end of the 2n-1th inductor (L2n-1) is connected to the source of the 4n-3th selection switch (Q4n-3), the other end of the 2n-1th inductor (L2n-1) is connected to the source of the 2n-1th auxiliary power switch (Q2n-1), the gate of the 2n-1th auxiliary power switch (Q2n-1) is connected to the 2n-1th power control output terminal of the control chip, the source of the 2n-1th auxiliary power switch (Q2n-1) is connected to one end of the 2n-1th capacitor (C2n-1), and the The drain of the 2n-1 power switch (Q2n-1) is connected to the drain of the 2n-th control power switch (S2n); one end of the 2n-th inductor (L2n) is connected to the source of the 4n-2-th selection switch (S4n-2); the other end of the 2n-th inductor is connected to the source of the 2n-th control power switch (Q2n); the source of the 2n-th control power switch (Q2n) is connected to one end of the 2n-th capacitor (C2n); and the gate of the 2n-th control power switch (Q2n) is connected to the 2n-th power control output end of the control chip.

2. A parallel equalization system based on bidirectional CUK converter according to claim 1, characterized in that: Also includes: The other end of the first capacitor (C1) is connected to the other end of the third capacitor (C3), the other end of the third capacitor (C3) is connected to the other end of the fifth capacitor (C5), ..., the other end of the 2n-3 capacitor (C2n-3) is connected to the other end of the 2n-1 capacitor (C2n-1).

3. A parallel equalization system based on bidirectional CUK converter according to claim 2, characterized in that: The other end of the second capacitor (C2) is connected to the other end of the fourth capacitor (C4), the other end of the fourth capacitor (C4) is connected to the other end of the sixth capacitor (C6), ..., the other end of the 2n-2 capacitor (C2n-2) is connected to the other end of the 2n capacitor (C2n).

4. A parallel equalization system based on bidirectional CUK converter according to claim 3, characterized in that: The negative end of the first battery (Cell1) is connected to the positive end of the second battery (Cell2), the negative end of the second battery (Cell2) is connected to the positive end of the third battery (Cell3), ..., the negative end of the (n-1)th battery (Celln-1) is connected to the positive end of the nth battery (Celln).

5. A working method of a parallel equalization system based on a bidirectional CUK converter, characterized in that: A parallel equalization system based on a bidirectional CUK converter according to any one of claims 1 to 4, further comprising the following steps: S1: The control chip drives each power switch and the gate switch, adjusts the output voltage and the battery capacity to select the number of equalizers in parallel, and performs energy transmission from multiple batteries to one battery, from one battery to multiple batteries, and from multiple batteries to multiple batteries; When energy transmission from multiple batteries to one battery is required, step S2 is executed; when energy transmission from one battery to multiple batteries is required, step S3 is executed; when energy transmission from multiple batteries to multiple batteries is required, step S4 is executed; S2: The control chip drives the gate switch of the selection switch matrix to transfer energy from one battery to another through multiple batteries; S3: The control chip drives the gate switch of the selection switch matrix to transmit energy to multiple batteries through one battery; S4: The control chip drives the gate switch of the selection switch matrix to transmit energy from multiple batteries to multiple batteries; S5: Calculate the duty cycle of the PWM drive signal according to the required current.

6. The working method of a parallel equalization system based on a bidirectional CUK converter according to claim 5, characterized in that: Step S2 also includes the following steps: S2-1: select the x-th battery (Cellx) and the y-th battery (Celly) as discharge batteries, and select the z-th battery (Cellz) as charge battery; S2-2: The 4x-3th gate switch (S4x-3), 4xth gate switch (S4x), 4y-3th gate switch (S4y-3), 4yth gate switch (S4y), 4z-3th gate switch (S4z-3), and 4zth gate switch (S4z) of the gate switch matrix corresponding to the discharge battery and the charge battery are driven to turn on by the control chip; S2-3: The control chip drives the 2zth control power switch (Q2z) to turn on, and uses the body diode of the 2z-1th auxiliary power switch (Q2z-1) as the freewheeling diode of the converter to form a multi-input single-output CUK converter. The xth battery (Cellx) and the yth battery (Celly) are high-energy batteries that transfer their own energy to the zth battery (Cellz) through the CUK converter; S2-4: When synchronous control is required, execute S2-5; when asynchronous control is required, execute S2-6; S2-5: Perform synchronous control, execute step S5, calculate the duty cycle of the PWM drive signal according to the current required by any one of the x-th battery (Cellx) and the y-th battery (Celly), and control the 2x-th control power switch (Q2x) and the 2y-th control power switch (Q2y) simultaneously through the control chip according to the calculated duty cycle drive signal; S2-6: Perform asynchronous control and execute step S5. According to the required currents of the xth battery (Cellx) and the yth battery (Celly), the duty cycles of the PWM drive signals of the 2xth controlled power switch (Q2x) and the 2yth controlled power switch (Q2y) are calculated respectively. The 2xth controlled power switch (Q2x) and the 2yth controlled power switch (Q2y) are controlled respectively by the control chip according to the drive signals with different duty cycles.

7. The working method of a parallel equalization system based on a bidirectional CUK converter according to claim 5, characterized in that: Step S3 also includes the following steps: S3-1: select the x-th battery (Cellx) as the discharge battery, and select the y-th battery (Celly) and the z-th battery (Cellz) as the rechargeable batteries; S3-2: The 4x-3th gate switch (S4x-3), 4xth gate switch (S4x), 4y-3th gate switch (S4y-3), 4yth gate switch (S4y), 4z-3th gate switch (S4z-3), and 4zth gate switch (S4z) of the gate switch matrix corresponding to the discharge battery and the charge battery are driven by the control chip to turn on; S3-3: The control chip drives the 2yth control power switch (Q2y) and the 2zth control power switch (Q2z) to turn on, and the body diodes of the 2z-1th auxiliary power switch (Q2z-1) and the 2y-1th auxiliary power switch (Q2y-1) serve as the freewheeling diodes of the converter to form a single-input multi-output CUK converter. The xth battery (Cellx) serves as a high-energy battery and transmits its own energy to the yth battery (Celly) and the zth battery (Cellz) through the CUK converter; S3-4: When synchronous control is required, execute S3-5; when asynchronous control is required, execute S3-6; S3-5: Perform synchronous control, execute step S5, calculate the duty cycle of the PWM drive signal according to the current required by any one of the yth battery (Celly) and the zth battery (Cellz), and control the 2yth control power switch (Q2y) and the 2zth control power switch (Q2z) simultaneously through the control chip according to the calculated duty cycle drive signal; S3-6: Perform asynchronous control and execute step S5. According to the required currents of the yth battery (Celly) and the zth battery (Cellz), the duty cycles of the PWM drive signals of the 2y-controlled power switch (Q2y) and the 2z-controlled power switch (Q2z) are calculated respectively. The 2y-controlled power switch (Q2y) and the 2z-controlled power switch (Q2z) are controlled respectively by the control chip according to the drive signals with different duty cycles.

8. The working method of a parallel equalization system based on a bidirectional CUK converter according to claim 5, characterized in that: Step S4 also includes the following steps: S4-1: select the x-th battery (Cellx) and the y-th battery (Celly) as discharge batteries, and select the h-th battery (Celly) and the z-th battery (Cellz) as charge batteries; S4-2: The 4x-3 selection switch (S4x-3), 4x selection switch (S4x), 4y-3 selection switch (S4y-3), 4y selection switch (S4y), 4z-3 selection switch (S4z-3), 4z selection switch (S4z), 4h-3 selection switch (S4h-3), and 4h selection switch (S4h) of the selection switch matrix corresponding to the discharge battery and the charge battery are driven by the control chip to turn on; S4-3: The control chip drives the 2h control power switch (Q2y) and the 2z control power switch (Q2z) to turn on, and the body diodes of the 2z-1 auxiliary power switch (Q2z-1) and the 2h-1 auxiliary power switch (Q2y-1) serve as the freewheeling diodes of the converter to form a multi-input and multi-output CUK converter. The x-th battery (Cellx) and the y-th battery (Celly) serve as high-energy batteries and transmit their own energy to the h-th battery (Celly) and the z-th battery (Cellz) through the CUK converter; S4-4: When synchronous control is required, execute S4-5; when asynchronous control is required, execute S4-6; S4-5: Perform synchronous control, execute step S5, calculate the duty cycle of the PWM drive signal according to the current required by any one of the x-th battery (Cellx) and the y-th battery (Celly), and control the 2x-th control power switch (Q2x) and the 2y-th control power switch (Q2y) simultaneously through the control chip according to the calculated duty cycle drive signal, and keep the 2h-th control power switch (Q2y) and the 2z-th control power switch (Q2z) turned on; S4-6: perform asynchronous control; S4-6-1: Control the current on the discharge side, execute step S5, and calculate the duty cycle of the PWM drive signal of the corresponding power switch according to the current required by the x-th battery (Cellx) and the y-th battery (Celly); The 2xth controlled power switch (Q2x) and the 2yth controlled power switch (Q2y) are driven respectively by the control chip according to driving signals with different duty cycles. S4-6-2: Control the current on the charging side, execute step S5, and calculate the duty cycle of the PWM drive signal of the corresponding power switch according to the current required by each battery in the h-th battery (Celly) and the z-th battery (Cellz); The 2h-th controlled power switch (Q2y) and the 2z-th controlled power switch (Q2z) are driven respectively according to driving signals with different duty cycles through the control chip.

9. The working method of a parallel equalization system based on a bidirectional CUK converter according to claim 5, characterized in that: Step S5 also includes the following steps: S5-1: Calculate using the following formula: Among them, L in Represents the sum of the inductance values ​​of the discharge battery and the inductance of the balancer, L o represents the sum of the inductance values ​​of the inductors of the equalizers corresponding to the rechargeable battery, C represents the capacitance value of the total capacitance of the capacitors of the discharge battery and the equalizers corresponding to the rechargeable battery connected in series, u c Represents the voltage value across the total capacitor after the capacitors of the equalizer corresponding to the discharge battery and the charge battery are connected in series, i in Indicates the input current, i o Indicates the output current, U in Indicates the input voltage, U o Indicates the output voltage; S5-2: Calculation i in and i o The amount of change from time t0 to time t1; Solve i by the formula in step S5-1 in and i o The change from t0 to t1 is as follows: In the formula, Δi in1 Indicates that this stage i in The change in Δi o Indicates that this stage i o The change in U c0 =u(t0), DT=t1-t0, T represents the PWM period, D represents the PWM duty cycle, t1 is the time t1, and t0 is the time t0; S5-3: Solve the formula of step S5-2 to obtain the current i flowing through all power switches of the equalizer corresponding to the discharge battery. Qf1 、i Qf2 ,……i Qfj And the voltage u across all power switches Qg1, Qg2, ..., Qgp of the equalizer corresponding to the rechargeable battery Qgz The equation is: i Qf1 =i Qf2 =…=i Qfj =i in +i o (1.3) Where C represents the capacitance of the total capacitance of the capacitors of the discharge battery and the equalizer corresponding to the charge battery connected in series, u c It represents the voltage value across the total capacitance of the equalizer corresponding to the discharge battery and the charge battery after the capacitance is connected in series; S5-4: Assume that at time t1-t2, the control chip drives the control power switches Qf2, Qf4, ..., Qfj of the equalizer corresponding to the discharge battery to be turned off, and the inductor L in The capacitor C discharges under the combined action of the voltage and the input voltage, while the inductor L o The capacitor C is discharged under the action of the output voltage, and charged under the action of the input current. The formula is as follows: S5-5: Calculation i in and i o The amount of change between t1 and t2; By using the formula in step S5-4, we can solve i in and i o The change from t1 to t2 is as follows: In the formula, Δi in2 Indicates that this stage i in The change in Δi o2 Indicates that this stage i o The change in U c0 =u(t1),U C1 and U C0 Has the following relationship: During this phase, the input current i in and the output current i o will flow through all power switches Qg1, Qg2, ..., Qgp of the equalizer corresponding to the rechargeable battery, and the current i flowing through all power switches Qg1, Qg2, ..., Qgp of the equalizer corresponding to the rechargeable battery can be obtained respectively. Qg1 、i Qg2 、……、i Qgp The voltage u across the auxiliary power switches Qf1, Qf3, ..., Qfj-1 of the equalizer corresponding to the discharge battery and the auxiliary power switches Qg1, Qg3, ..., Qgp-1 of the equalizer corresponding to the charging battery Qf1 、u Qf3 、……、u Qfj-1 、u Qg1 、u Qg3 、……、u Qgp-1 The equation is: i Q3 =i Q4 =i in +i o (1.8) In one PWM cycle, i in and i o The changes should all be 0, that is: S5-6: When asynchronous control is required, execute S5-7; when synchronous control is required, execute S5-8; S5-7: Calculate the duty cycle of the asynchronously controlled PWM drive signal; S5-7-1: According to formulas (1.2), (1.4), (1.5) and (1.6), the relationship between input current and duty cycle is as follows: Among them, I in is the required input current, D is the duty cycle, T is the PWM period, and D is the PWM duty cycle; S5-7-2: Calculate the duty cycle corresponding to the input current according to the formula in S5-7-1. S5-8: Calculate the duty cycle of the PWM drive signal for synchronous control; S5-8-1: According to the formula, the relationship between input current and duty cycle is as follows: Among them, I in is the required input current, D is the duty cycle, T is the PWM period, and D is the PWM duty cycle; Combined with the law of conservation of energy, that is, U in I in =U o I o , the relationship is as follows: When the lithium battery SOC is between 10% and 90%, the battery terminal voltage changes slightly, so it can be considered that U o / U in ≈1, then equations (1.1) and (1.12) can be simplified to: I o ≈I in =k in U in -k2U o ; (1.13); Where, k1 = 2CD / [D(1-D)(2D-1)T], k2 = 2C(1-D) / [D(1-D)(2D-1)T]. When the circuit parameters, PWM frequency and PWM duty cycle D are determined, k1 and k2 are constants; S5-8-2: Calculate the duty cycle corresponding to the input current according to formula (1.13).

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