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

Abstract

This invention discloses a parallel equalization system based on a bidirectional CUK converter, comprising an equalization system module and a selection switch matrix module. The selection switch matrix module includes n sets of selection switch matrices, each set containing four selection switches. The positive terminal of the first battery is connected to the drain of the first selection switch, the source of the first selection switch is connected to the drain of the third selection switch, the source of the third selection switch is connected to the negative terminal of the first battery, the drain of the second selection switch is connected to the drain of the first selection switch, the source of the second selection switch is connected to the drain of the fourth selection switch, and the source of the fourth selection switch is connected to the source of the third selection switch. The equalization system module has multiple equalizers, each connected to a corresponding selection switch matrix. Each equalizer includes two inductors, one auxiliary power switch, one control power switch, and two capacitors. This system enables equalization of multiple series-parallel battery packs during charging and discharging, offering flexible equalization methods.

Description

Technical Field

[0001] This invention relates to the field of bidirectional DC-DC CUK converters, and more specifically to a parallel equalization system based on a bidirectional CUK converter and its operating method. Background Technology

[0002] Lithium-ion batteries are used in various applications, but due to the low voltage and small capacity of a single cell, they are typically composed of multiple individual lithium-ion batteries connected in series or parallel. Because the internal resistance, total capacity, and initial capacity of each individual lithium-ion battery can vary to some extent due to manufacturing limitations, usage conditions, and environmental factors, the charge levels of each individual battery in a lithium-ion battery energy storage system will differ. This can lead to overcharging or over-discharging of some lithium-ion batteries within the battery pack. Both overcharging and over-discharging will have irreversible effects on the performance and lifespan of the individual lithium-ion batteries and the entire battery energy storage system.

[0003] A battery charge / discharge state balancing system can effectively solve the overcharging and over-discharging phenomena during the charging and discharging processes of lithium battery energy storage systems. The battery balancing system can detect and calculate the charge level of each lithium battery, and then control the current level of each battery through the balancing system, thereby achieving battery charge balance. This can effectively improve the performance of the lithium battery balancing system and extend its service life. Summary of the Invention

[0004] This invention aims to solve the technical problems existing in the prior art. In particular, it innovatively proposes a parallel equalization system based on a bidirectional CUK converter and its working method, which can realize the equalization of multiple series and parallel battery packs in the charging and discharging state, and the equalization method is flexible.

[0005] To achieve the above objectives, 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 sets of selection switch matrices, each set of selection switch matrices includes 4 selection switches. The positive terminal of the first battery is connected to the drain of the first selection switch, the source of the first selection switch is connected to the drain of the third selection switch, the gate of the first selection switch is connected to the first selection control output terminal of the control chip, the source of the third selection switch is connected to the negative terminal of the first battery, the gate of the third selection switch is connected to the third selection control output terminal of the control chip, the drain of the second selection switch is connected to the drain of the first selection switch, the source of the second selection switch is connected to the drain of the fourth selection switch, the gate of the second selection switch is connected to the second selection control output terminal of the control chip, the source of the fourth selection switch is connected to the source of the third selection switch, and the gate of the fourth selection switch is connected to the fourth selection control output terminal of the control chip.

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

[0008] The equalization system module has the same number of equalizers as the gating switch matrix, and each equalizer is associated with a corresponding gating switch matrix. Each equalizer includes two inductors, one auxiliary power switch, one control power switch, and two capacitors. One end of the first inductor is connected to the source of the first gating switch, and 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 terminal of the control chip. One end of the second inductor is connected to the source of the second gating switch, and 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 terminal of the control chip.

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

[0010] The above scheme 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)th capacitor is connected to the other end of the 2nth capacitor.

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

[0013] This invention also provides a method for operating 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 including the following steps:

[0014] S1: By controlling the chip to drive each power switch and gating switch, the output voltage and battery capacity are adjusted to select the number of equalizers connected in parallel, and to perform energy transfer from multiple batteries to one battery, from one battery to multiple batteries, and from multiple batteries to multiple batteries.

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

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

[0017] S3: The control chip drives the selection switch of the selection switch matrix to transfer energy from one battery to multiple batteries.

[0018] S4: The control chip drives the selection switch of the selection switch matrix to transfer energy between multiple batteries.

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

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

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

[0022] S2-2: The control chip drives the 4x-3, 4x, 4y-3, 4y, 4z-3, and 4z selector switches of the corresponding selector switch matrix of the discharge battery and the recharge battery to be turned on;

[0023] S2-3: The control chip drives the 2z control power switch to turn on, 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 x-th and y-th batteries, as high-energy batteries, transfer their energy to the z-th battery through this 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 based on the current required by any one of the x-th and y-th batteries, and control the 2x-th and 2y-th control power switches simultaneously through the control chip according to the drive signal with the calculated duty cycle.

[0026] S2-6: Perform asynchronous control, execute step S5, calculate the duty cycle of the PWM drive signal of the 2x control power switch and the 2y control power switch according to the required current of the xth and yth battery respectively, and control the 2x control power switch and the 2y control power switch respectively by the control chip according to the drive signal with different duty cycles.

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

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

[0029] S3-2: The control chip drives the 4x-3, 4x, 4y-3, 4y, 4z-3, and 4z selector switches of the corresponding selector switch matrix for the discharge and recharge batteries to be turned on;

[0030] S3-3: The control chip drives the 2y control power switch and the 2z control power switch to be turned on. The body diodes of the 2z-1 auxiliary power switch and the 2y-1 auxiliary power switch serve as the freewheeling diodes of the converter, forming a single-input multiple-output CUK converter. The x-th battery, as a high-energy battery, transfers its own energy to the y-th battery and the z-th battery through this 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 based on the current required by any one of the y-th and z-th batteries, and control the 2y-th and 2z-th control power switches simultaneously through the control chip according to the drive signal of the calculated duty cycle.

[0033] S3-6: Perform asynchronous control, execute step S5, calculate the duty cycle of the PWM drive signal of the 2y control power switch and the 2z control power switch according to the required current of the y-th battery and the z-th battery respectively, and control the 2y control power switch and the 2z control power switch respectively by the control chip according to the drive signal with different duty cycles.

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

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

[0036] S4-2: The control chip drives the 4x-3, 4x, 4y-3, 4y, 4z-3, 4z, 4h-3, and 4h gating switches of the corresponding gating switch matrix of the discharge battery and the recharge battery to be turned on;

[0037] S4-3: The control chip drives the 2h control power switch and the 2z control power switch to turn on. 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, forming a multiple-input multiple-output (CUK) converter. The x-th and y-th batteries, as high-energy batteries, transfer their energy to the h-th and z-th batteries through this 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 x-th and y-th batteries, and control the 2x-th and 2y-th control power switches simultaneously through the control chip according to the calculated duty cycle drive signal, and keep the 2h-th and 2z-th control power switches 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 respectively.

[0042] The control chip drives the 2x control power switch and the 2y control power switch respectively according to the drive signals with different duty cycles.

[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 and z-th batteries.

[0044] The control chip drives the 2h control power switch and the 2z control power switch respectively according to the drive signals with different duty cycles.

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

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

[0047]

[0048] Among them, L in L represents the sum of the inductance values ​​of the equalizer corresponding to the discharging battery. o This represents the sum of the inductance values ​​of the equalizers corresponding to the rechargeable batteries, where C represents the total capacitance of the equalizers corresponding to the discharging and rechargeable batteries connected in series, and u c i represents the voltage across the total capacitance of the equalizer capacitors connected in series with the capacitors corresponding to the discharging and recharging batteries. in Indicates the input current, i o U represents the output current. in U represents the input voltage. o Indicates the output voltage;

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

[0050] Solve i using the formula in step S5-1 in and i o The changes from time t0 to time t1 are as follows:

[0051]

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

[0053] S5-3: Solve the formula in step S5-2 to obtain the current i flowing through all power switches of the equalizer corresponding to the discharging 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] In the formula, C represents the total capacitance value of the equalizer capacitors corresponding to the discharging and recharging batteries connected in series, and u c This represents the voltage across the total capacitor after the equalizer capacitors corresponding to the discharge and rechargeable batteries are connected in series.

[0057] S5-4: Assume that during times t1 to t2, the control chip turns off the control power switches Qf2, Qf4, ..., Qfj of the equalizer corresponding to the discharging battery, and the inductor L... in The capacitor C discharges under the combined effect of the voltage across it and the input voltage, while the inductor L... o The capacitor C discharges under the influence of the output voltage, while it charges under the influence of the input current, as described by the following formula:

[0058]

[0059] S5-5: Calculate i in and i o The change in time t1 to t2;

[0060] Solve for i using the formula in step S5-4. in and i o The changes at times t1 to t2 are as follows:

[0061]

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

[0063]

[0064] At this stage, the input current i in and output current i o All power switches Qg1, Qg2, ..., Qgp of the equalizer corresponding to the rechargeable battery will flow through them. The current i flowing through each of these power switches can then be obtained. Qg1 i Qg2 ... Qgp The voltage u across the auxiliary power switches Qf1, Qf3, ..., Qfj-1 of the equalizer corresponding to the discharging battery and the auxiliary power switches Qg1, Qg3, ..., Qgp-1 of the equalizer corresponding to the rechargeable 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 in all of them should 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: Calculation of the duty cycle of the PWM drive signal for asynchronous control;

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

[0072]

[0073] Among them, I inWhere D is the required input current, T represents the PWM period, and D represents the PWM duty cycle.

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

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

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

[0077]

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

[0079] Combining the law of conservation of energy, i.e., U in I in =U o I o The following relationship can be obtained:

[0080]

[0081] When the state of charge (SOC) of a lithium battery is between 10% and 90%, the voltage change at the battery terminals is minimal, therefore U can be considered... o / U in If ≈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] In the formula, k1 = 2CD / [D(1-D)(2D-1)T], k2 = 2C(1-D) / [D(1-D)(2D-1)T]. Once the circuit parameters, PWM frequency, and PWM duty cycle D are determined, k1 and k2 are both constants.

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

[0085] In summary, the beneficial effects of this invention are: the system can achieve equalization of multiple series-parallel battery packs during charging and discharging, with flexible equalization methods. It can implement both synchronous and asynchronous PWM signal control. During synchronous PWM signal control, the current is automatically distributed, simplifying the control process; during asynchronous PWM signal control, the current of each battery cell is independently controlled, thereby accelerating the equalization speed; the control variable is only current, eliminating the need to control the output voltage, resulting in a simpler control method, improved equalization efficiency, and an improved equalization system structure. Attached Figure Description

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

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

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

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

[0090] Figure 5 This is a timing diagram of the parallel equalization system based on the bidirectional CUK converter of this invention.

[0091] Figure 6 This is a schematic diagram of a one-to-many equalization method connection of the parallel equalization system based on a bidirectional CUK converter according to the present invention;

[0092] Figure 7 This is a short-circuit diagram of the one-to-many equalization method of the parallel equalization system based on the bidirectional CUK converter of the present invention without the addition of pair transistors;

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

[0094] Figure 9 This is a schematic diagram of the multi-to-one equalization method of the parallel equalization system based on the bidirectional CUK converter of the present invention without the addition of transistors;

[0095] Figure 10 This is a schematic diagram of the many-to-many equalization method of the parallel equalization system based on the bidirectional CUK converter of the present invention. Detailed Implementation

[0096] The present invention will be further described below with reference to the embodiments and accompanying drawings:

[0097] like Figure 1 The parallel equalization system based on a bidirectional CUK converter is shown, including an equalization system module and a selection switch matrix module;

[0098] The selection switch matrix module includes n sets of selection switch matrices. Each set of selection switch matrices includes 4 selection switches. The positive terminal of the first battery Cell1 is connected to the drain of the first selection switch S1. The source of the first selection switch S1 is connected to the drain of the third selection switch S3. The gate of the first selection switch S1 is connected to the first selection control output terminal of the control chip. The source of the third selection switch S3 is connected to the negative terminal of the first battery Cell1. The gate of the third 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 switch S3. The gate of the fourth selection switch S4 is connected to the fourth selection control output terminal of the control chip.

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

[0100] The equalization system module has the same number of equalizers as the gating switch matrix, and each equalizer is associated with a corresponding gating switch matrix. Each equalizer 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 gating switch S1, and 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 terminal of the control chip. One end of the second inductor L2 is connected to the source of the second gating switch S2, and 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 terminal of the control chip.

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

[0102] The above scheme 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-2th capacitor C2n-2 is connected to the other end of the 2nth capacitor C2n.

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

[0105] This invention also provides a method for operating a parallel equalization system based on a bidirectional CUK converter, including one of the above-mentioned schemes based on a bidirectional CUK converter, and further comprising the following steps:

[0106] S1: By controlling the chip to drive each power switch and gating switch, the output voltage and battery capacity are adjusted to select the number of equalizers connected in parallel, and to perform energy transfer from multiple batteries to one battery, from one battery to multiple batteries, and from multiple batteries to multiple batteries.

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

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

[0109] S2-1: Select the x-th battery Cellx and the y-th battery Cellly as discharge batteries, and select the z-th battery Cellz as a rechargeable battery;

[0110] S2-2: The control chip drives the 4x-3 gating switch S4x, the 4x gating switch S4x, the 4y-3 gating switch S4y, the 4y gating switch S4y, the 4z-3 gating switch S4z-3, and the 4z gating switch S4z to be turned on.

[0111] S2-3: The control chip drives the 2z control power switch Q2z to turn on, and uses the body diode of the 2z-1 auxiliary power switch Q2z-1 as the freewheeling diode of the converter to form a multi-input single-output CUK converter. The x-th battery Cellx and the y-th battery Cellly, as high-energy batteries, transfer their own energy to the z-th battery Cellz through this 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 based on the current required by any one of the x-th cell Cellx and the y-th cell 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, execute step S5, calculate the duty cycle of the PWM drive signal of the second x control power switch Q2x and the second y control power switch Q2y according to the required current of the x-th battery Cellx and the y-th battery Celly, respectively, and control the second x control power switch Q2x and the second y control power switch Q2y respectively through the control chip according to the drive signal with different duty cycles.

[0115] S3: The control chip drives the selection switch of the selection switch matrix to transfer energy from one battery to multiple batteries.

[0116] S3-1: Select the xth battery Cellx as the discharge battery, and select the yth battery Cellly and the zth battery Cellz as the recharge batteries;

[0117] S3-2: The control chip drives the 4x-3 gating switch S4x, the 4x gating switch S4x, the 4y-3 gating switch S4y, the 4y gating switch S4y, the 4z-3 gating switch S4z-3, and the 4z gating switch S4z to be turned on.

[0118] S3-3: The control chip drives the 2y control power switch Q2y and the 2z control power switch Q2z to conduct. The body diodes of the 2z-1 auxiliary power switch Q2z-1 and the 2y-1 auxiliary power switch Q2y-1 serve as the freewheeling diodes of the converter, forming a single-input multiple-output CUK converter. The x-th battery Cellx, as a high-energy battery, transfers its own energy to the y-th battery Cellly and the z-th battery Cellz through this 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 based on the current required by any one of the y-th cell Cellly and the z-th cell Cellz, and control the 2y-th control power switch Q2y and the 2z-th control power switch Q2z simultaneously through the control chip according to the drive signal of the calculated duty cycle.

[0121] S3-6: Perform asynchronous control, execute step S5, calculate the duty cycle of the PWM drive signal of the 2y control power switch Q2y and the 2z control power switch Q2z according to the required current of the y-th cell Celly and the z-th cell Cellz, respectively, and control the 2y control power switch Q2y and the 2z control power switch Q2z respectively through the control chip according to the drive signal with different duty cycles.

[0122] S4: The control chip drives the selection switch of the selection switch matrix to transfer energy between multiple batteries.

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

[0124] S4-2: The control chip drives the following gate switches to be turned on: the 4x-3 gate switch S4x, the 4x gate switch S4x, the 4y-3 gate switch S4y, the 4y gate switch S4y, the 4z-3 gate switch S4z, the 4h-3 gate switch S4h-3, and the 4h gate switch S4h.

[0125] S4-3: The control chip drives the 2h control power switch Q2y and the 2z control power switch Q2z to conduct. 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, forming a multiple-input multiple-output CUK converter. The x-th cell Cellx and the y-th cell Cellly, as high-energy cells, transfer their energy to the h-th cell Cellly and the z-th cell Cellz through this 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 based on the current required by any one of the x-th cell Cellx and the y-th cell Cellly, 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 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 cycle of the PWM drive signal of the corresponding power switch according to the current required by the x-th cell Cellx and the y-th cell Celly respectively.

[0130] The control chip drives the second x control power switch Q2x and the second y control power switch Q2y respectively according to the drive 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 Cellly and the z-th battery Cellz.

[0132] The control chip drives the second-h control power switch Q2y and the second-z control power switch Q2z respectively according to the drive signals with different duty cycles.

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

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

[0135]

[0136] Among them, L in L represents the sum of the inductance values ​​of the equalizer corresponding to the discharging battery. o This represents the sum of the inductance values ​​of the equalizers corresponding to the rechargeable batteries, where C represents the total capacitance of the equalizers corresponding to the discharging and rechargeable batteries connected in series, and u c i represents the voltage across the total capacitance of the equalizer capacitors connected in series with the capacitors corresponding to the discharging and recharging batteries. in Indicates the input current, i o U represents the output current. in U represents the input voltage. o Indicates the output voltage;

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

[0138] Solve i using the formula in step S5-1 in and i o The changes from time t0 to time t1 are as follows:

[0139]

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

[0141] S5-3: Solve the formula in step S5-2 to obtain the current i flowing through all power switches of the equalizer corresponding to the discharging 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] In the formula, C represents the total capacitance value of the equalizer capacitors corresponding to the discharging and recharging batteries connected in series, and u c This represents the voltage across the total capacitor after the equalizer capacitors corresponding to the discharge and rechargeable batteries are connected in series.

[0145] S5-4: Assume that during times t1 to t2, the control chip turns off the control power switches Qf2, Qf4, ..., Qfj of the equalizer corresponding to the discharging battery, and the inductor L... in The capacitor C discharges under the combined effect of the voltage across it and the input voltage, while the inductor L... o The capacitor C discharges under the influence of the output voltage, while it charges under the influence of the input current. The formula is described as follows:

[0146]

[0147] S5-5: Calculate i in and i o The change in time t1 to t2;

[0148] Solve for i using the formula in step S5-4. in and i o The changes at times t1 to t2 are as follows:

[0149]

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

[0151]

[0152] At this stage, the input current i in and output current i o All power switches Qg1, Qg2, ..., Qgp of the equalizer corresponding to the rechargeable battery will flow through them. The current i flowing through each of these power switches can then be obtained. Qg1 i Qg2 ... Qgp The voltage u across the auxiliary power switches Qf1, Qf3, ..., Qfj-1 of the equalizer corresponding to the discharging battery and the auxiliary power switches Qg1, Qg3, ..., Qgp-1 of the equalizer corresponding to the rechargeable 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 in all of them should 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: Calculation of the duty cycle of the PWM drive signal for asynchronous control;

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

[0160]

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

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

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

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

[0165]

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

[0167] Combining the law of conservation of energy, i.e., U in I in =U o I o The following relationship can be obtained:

[0168]

[0169] When the state of charge (SOC) of a lithium battery is between 10% and 90%, the voltage change at the battery terminals is minimal, therefore U can be considered... o / U in If ≈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] In the formula, k1 = 2CD / [D(1-D)(2D-1)T], k2 = 2C(1-D) / [D(1-D)(2D-1)T]. Once the circuit parameters, PWM frequency, and PWM duty cycle D are determined, k1 and k2 are both constants.

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

[0173] This invention discloses a parallel equalization system based on a bidirectional CUK converter. The number of equalizers connected in parallel is selected according to the output voltage and battery capacity, allowing for equalization operations with two or more equalizers connected in parallel. This enables equalization of any number of batteries in one-to-many, many-to-one, or many-to-many configurations. The working principle of these methods is equivalent to that of one-to-one equalization, and the charging principle is equivalent to the discharging principle. The analysis focuses on the energy transfer process using a first and second equalizer connected in parallel. Since the series connection of the batteries does not affect the equalization process, the series connection is not shown for ease of analysis. The process can be roughly divided into the following two stages.

[0174] Figure 2 This is a schematic diagram of the equivalent connection in a one-to-one equilibrium mode.

[0175] Figure 3 This is the first phase (t0-t1) of the system's operation.

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

[0177]

[0178] Among them, L in L represents the sum of the inductance values ​​of L1 and L2. o This represents the sum of the inductance values ​​of L3 and L4, where C represents the capacitance of the capacitors C1, C2, C3, and C4 connected in series. c i represents the voltage across capacitor C. in Indicates the input current, i o U represents the output current. in U represents the input voltage. o This represents the output voltage. Because the output current ripple is small, it can be considered as a constant output current discharging capacitor C.

[0179] Using equation (1.1), we can solve for i. in and i o The amount of change during this stage:

[0180]

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

[0182] At this stage, the input current i in and output current i o Both currents flow through switching transistors Q1 and Q2, so the current i flowing through switching transistors 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 operation;

[0186] During this stage, power switches Q1 and Q2 are turned off, and inductor L... in The capacitor C discharges under the combined effect of the voltage across it and the input voltage, while the inductor L... o The capacitor C discharges under the influence of the output voltage, while it charges under the influence of the input current, as described by the following formula:

[0187]

[0188] In the formula, since the input current ripple is small, it can be regarded as a constant input current charging capacitor C. Using equation (1.3), i can be solved. in and i o The amount of change during this stage:

[0189]

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

[0191]

[0192] At this stage, the input current i in and output current i o Both currents flow through switching transistors Q3 and Q4, and the current i flowing through switching transistors 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 in all of them should be 0, that is:

[0197]

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

[0199]

[0200] Ignoring losses here, and combining the law of conservation of energy, i.e., U in I in =U o I o We can obtain:

[0201]

[0202] When the state of charge (SOC) of a lithium battery is between 10% and 90%, the voltage change at the battery terminals is minimal, therefore U can be considered... o / U in If ≈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] In the formula, k1 = 2CD / [D(1-D)(2D-1)T], k2 = 2C(1-D) / [D(1-D)(2D-1)T]. Once the circuit parameters, PWM frequency, and PWM duty cycle D are determined, k1 and k2 are constants. Therefore, the higher the voltage of the individual battery on the input side, the higher the corresponding equalization current; conversely, the lower the battery voltage on the output side, the higher the corresponding equalization current. Autonomous current distribution is achieved through the synchronous control of each main switch.

[0205] In particular, when multiple batteries are discharging, different duty cycles can be assigned to each equalizer to achieve independent control of the equalization current of each battery, i.e., asynchronous control, thereby improving the equalization speed of the system.

[0206] In the case of asynchronous control, taking the first battery Cell1 and the second battery Cell2 as discharging batteries, and the third battery Cell3 as a recharging battery as an example, we analyze the many-to-one energy transfer process:

[0207] Switches S1, S4, S5, S8, S9, and S12 are on, while the remaining selector switches are off. Q2 and Q4 are the main switches for the discharge-side equalizer, Q6 is always on, and the body diode of Q5 acts as the freewheeling diode for the converter, forming a dual-input single-output CUK converter. High-energy batteries Cell1 and Cell2 transfer their energy to low-energy battery Cell3 through the converter.

[0208] Asynchronous control uses drive 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 equalization current of the two channels. Combining equations (1.2), (1.4), (1.5), and (1.6), we can obtain:

[0209]

[0210] Simplifying (1.14) yields:

[0211]

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

[0213] When D1≠D2, if there are no auxiliary switches Q1 and Q3, a short circuit will occur in the equalization system, such as... Figure 7 As shown. Taking Q2 being on and Q4 being off as an example, when the body diode of Q4 experiences a forward voltage drop, i.e., U... C1 +U C2 >U C3 +U C4 U C1 It is the voltage across capacitor C1, U C2 It is the voltage across capacitor C2, U C3 It is the voltage across capacitor C3, U C4 This 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 I is the voltage across Q4. Q4 For the current of Q4, R p This is the total resistance in the circuit at this point. Since there is no resistive load in this circuit, R... p The internal resistance of the device and the wire is very small, but it will generate a very large instantaneous current I. Q4 This can lead to damage to the device.

[0217] To avoid this short circuit, auxiliary switches Q1 and Q3 are connected in series with the main switches Q2 and Q4, respectively. This pair of switches can solve the short circuit problem of the equalizer when different duty cycle signals are used to drive different equalizers, i.e., D1≠D2. This avoids the back-and-forth transmission of energy in the equalization system, thereby improving the equalization speed and efficiency of the system.

[0218] Taking the first battery Cell1 as a discharging battery and the second and third batteries Cell2 and Cell3 as rechargeable batteries as an example, the one-to-many energy transfer process is analyzed:

[0219] The total discharge current of Cell1 can be controlled by adjusting the drive signal of Q2. If a transistor pair structure is not used, the equalization structure is as follows: Figure 9 As shown, Cell2 and Cell3 can only be used as discharge batteries, and the equalization current can only be passively allocated according to the voltage, and cannot be quantitatively controlled. Figure 8 As shown, by adding transistors Q4 and Q6 and changing their on-time, the equalization current of Cell2 and Cell3 is quantitatively adjusted. This demonstrates the necessity of the MOSFET pair and the feasibility of asynchronous current control.

[0220] like Figure 5 The figure shows the circuit timing diagram of a parallel equalization system based on a bidirectional CUK converter. The equalization system can be controlled according to the timing diagram.

[0221] Taking Cell1 and Cell2 as discharging batteries, and Cell3 and Cell4 as recharging batteries as examples, this paper analyzes the many-to-many energy transfer process. Figure 10 As shown:

[0222] On the discharge side, asynchronous driving main switches Q2 and Q4 enable independent control of the two discharge currents, while on the charging side, asynchronous driving main switches Q6 and Q8 enable independent control of the two charging currents. This demonstrates that in the many-to-many balancing mode, both the input and output terminals can quantitatively control the balancing current of each path, thereby significantly improving balancing speed and efficiency.

Claims

1. A parallel equalization system based on a bidirectional CUK converter, characterized in that: Includes an equalization system module and a selection switch matrix module; The selection switch matrix module includes n sets of selection switch matrices, each set containing 4 selection switches. The positive terminal of the first battery (Cell1) is connected to the drain of the first selection switch (S1), the source of the first selection switch (S1) is connected to the drain of the third selection switch (S3), the gate of the first selection switch (S1) is connected to the first selection control output terminal of the control chip, the source of the third selection switch (S3) is connected to the negative terminal of the first battery (Cell1), and the gate of the third selection switch (S3) is connected to the third selection control output terminal of the control chip. At the gating control output terminal, the drain of the second gating switch (S2) is connected to the drain of the first gating switch (S1), the source of the second gating switch (S2) is connected to the drain of the fourth gating switch (S4), the gate of the second gating switch (S2) is connected to the second gating control output terminal of the control chip, the source of the fourth gating switch (S4) is connected to the source of the third gating switch (S3), and the gate of the fourth gating switch (S4) is connected to the fourth gating control output terminal of the control chip; and so on, the positive terminal of the nth cell (Celln) is connected to the 4nth cell. The drain of the -3 selector switch (S4n-3) is connected to the drain of the -4n-1 selector switch (S4n-1), and the gate of the -4n-3 selector switch (S4n-3) is connected to the -4n-3 selector control output terminal of the control chip. The source of the -4n-1 selector switch (S4n-1) is connected to the negative terminal of the nth cell (Celln), and the gate of the -4n-1 selector switch (S4n-1) is connected to the -4n-1 selector control output terminal of the control chip. The -4n-2 selector... The drain of switch (S4n-2) is connected to the drain of the 4n-3 selector switch (S4n-3), the gate of the 4n-2 selector switch (S4n-2) is connected to the 4n-2 selector control output terminal of the control chip, the source of the 4n-2 selector switch (S4n-2) is connected to the drain of the 4n selector switch (S4n), the source of the 4n selector switch (S4n) is connected to the source of the 4n-1 selector switch (S4n-1), and the gate of the 4n selector switch (S4n) is connected to the 4n selector control output terminal of the control chip. The equalization system module has the same number of equalizers as the gating switch matrix, and each equalizer is associated with a corresponding gating switch matrix. Each equalizer 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 gating switch (S1), and 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 terminal of the control chip. One end of the second inductor (L2) is connected to the source of the second gating switch (S2), and 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 terminal of the control chip; and so on. One end of the 2n-1 inductor (L2n-1) is connected to the source of the 4n-3 selector switch (S4n-3), and the other end of the 2n-1 inductor (L2n-1) is connected to the source of the 2n-1 auxiliary power switch (Q2n-1). The gate of the 2n-1 auxiliary power switch (Q2n-1) is connected to the 2n-1 power control output terminal of the control chip, and the source of the 2n-1 auxiliary power switch (Q2n-1) is connected to one end of the 2n-1 capacitor (C2n-1). The drain of the auxiliary power switch (Q2n-1) is connected to the drain of the 2n control power switch (Q2n); one end of the 2n inductor (L2n) is connected to the source of the 4n-2 selector switch (S4n-2), the other end of the 2n inductor is connected to the source of the 2n control power switch (Q2n), the source of the 2n control power switch (Q2n) is connected to one end of the 2n capacitor (C2n), and the gate of the 2n control power switch (Q2n) is connected to the 2n power control output terminal of the control chip. 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), and so on, the other end of the 2n-3 capacitor (C2n-3) is connected to the other end of the 2n-1 capacitor (C2n-1); 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), and so on, with the other end of the 2n-2 capacitor (C2n-2) connected to the other end of the 2n capacitor (C2n).

2. The parallel equalization system based on a bidirectional CUK converter according to claim 1, characterized in that: The negative terminal of the first battery (Cell1) is connected to the positive terminal of the second battery (Cell2), the negative terminal of the second battery (Cell2) is connected to the positive terminal of the third battery (Cell3), and so on, with the negative terminal of the (n-1)th battery (Celln-1) connected to the positive terminal of the nth battery (Celln).

3. A method for operating a parallel equalization system based on a bidirectional CUK converter, characterized in that: The parallel equalization system based on a bidirectional CUK converter, as described in any one of claims 1 to 2, further includes the following steps: S1: By controlling the chip to drive each power switch and gating switch, the output voltage and battery capacity are adjusted to select the number of equalizers connected in parallel, and to perform energy transfer from multiple batteries to one battery, from one battery to multiple batteries, and from multiple batteries to multiple batteries. When energy transfer from multiple batteries to one battery is required, execute step S2; when energy transfer from one battery to multiple batteries is required, execute step S3; when energy transfer from multiple batteries to multiple batteries is required, execute step S4. S2: The control chip drives the selection switch of the selection switch matrix to transfer energy from one battery to multiple batteries. S3: The control chip drives the selection switch of the selection switch matrix to transfer energy from one battery to multiple batteries. S4: The control chip drives the selection switch of the selection switch matrix to transfer energy between multiple batteries. S5: Calculate the duty cycle of the PWM drive signal based on the required current.

4. The operating method of a parallel equalization system based on a bidirectional CUK converter according to claim 3, characterized in that: Step S2 also includes the following steps: S2-1: Select the xth battery (Cellx) and the yth battery (Celly) as discharge batteries, and select the zth battery (Cellz) as a rechargeable battery; S2-2: The control chip drives the 4x-3 gating switch (S4x-3), 4x gating switch (S4x), 4y-3 gating switch (S4y-3), 4y gating switch (S4y), 4z-3 gating switch (S4z-3), and 4z gating switch (S4z) of the gating switch matrix corresponding to the discharge battery and the recharge battery to be turned on; S2-3: The control chip drives the 2z control power switch (Q2z) to turn on, and uses the body diode of the 2z-1 auxiliary power switch (Q2z-1) as the freewheeling diode of the converter to form a multi-input single-output CUK converter. The x-th cell (Cellx) and the y-th cell (Celly) are high-energy cells that transfer their energy to the z-th cell (Cellz) through this 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 based on the current required by any one of the x-th cell (Cellx) and y-th cell (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; S2-6: Perform asynchronous control, execute step S5, calculate the duty cycle of the PWM drive signal of the 2x control power switch (Q2x) and the 2y control power switch (Q2y) according to the required current of the xth cell (Cellx) and the yth cell (Celly), respectively, and control the 2x control power switch (Q2x) and the 2y control power switch (Q2y) respectively through the control chip according to the drive signal with different duty cycles.

5. The operating method of a parallel equalization system based on a bidirectional CUK converter according to claim 3, characterized in that: Step S3 also includes the following steps: S3-1: Select cell x (Cellx) as the discharge battery, and select cell y (Cellly) and cell z (Cellz) as the recharge batteries; S3-2: The control chip drives the 4x-3 gating switch (S4x-3), 4x gating switch (S4x), 4y-3 gating switch (S4y-3), 4y gating switch (S4y), 4z-3 gating switch (S4z-3), and 4z gating switch (S4z) of the gating switch matrix corresponding to the discharge battery and the recharge battery to be turned on; S3-3: The control chip drives the 2y control power switch (Q2y) and the 2z control power switch (Q2z) to conduct. The body diodes of the 2z-1 auxiliary power switch (Q2z-1) and the 2y-1 auxiliary power switch (Q2y-1) serve as the freewheeling diodes of the converter, forming a single-input multiple-output CUK converter. The x-th cell (Cellx) is a high-energy cell that transfers its own energy to the y-th cell (Cellly) and the z-th cell (Cellz) through this 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 based on the current required by any one of the y-th battery (Cellly) and z-th battery (Cellz), and control the 2y-th control power switch (Q2y) and the 2z-th control power switch (Q2z) simultaneously through the control chip according to the drive signal of the calculated duty cycle; S3-6: Perform asynchronous control and execute step S5. Calculate the duty cycle of the PWM drive signals of the 2y control power switch (Q2y) and the 2z control power switch (Q2z) according to the required current of the y-th cell (Cellly) and the z-th cell (Cellz). Control the 2y control power switch (Q2y) and the 2z control power switch (Q2z) respectively through the control chip according to the drive signals with different duty cycles.

6. The operating method of a parallel equalization system based on a bidirectional CUK converter according to claim 3, characterized in that: Step S4 also includes the following steps: S4-1: Select the xth battery (Cellx) and the yth battery (Celly) as discharge batteries, and select the hth battery (Celly) and the zth battery (Cellz) as recharge batteries; S4-2: The control chip drives the 4x-3 gating switch (S4x-3), 4x gating switch (S4x), 4y-3 gating switch (S4y-3), 4y gating switch (S4y), 4z-3 gating switch (S4z-3), 4z gating switch (S4z), 4h-3 gating switch (S4h-3), and 4h gating switch (S4h) of the gating switch matrix corresponding to the discharge battery and the recharge battery to be turned on; S4-3: The control chip drives the 2h control power switch (Q2y) and the 2z control power switch (Q2z) to turn on. 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, forming a multi-input multi-output CUK converter. The x-th cell (Cellx) and the y-th cell (Cellly) are high-energy cells that transfer their energy to the h-th cell (Cellly) and the z-th cell (Cellz) through this 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 based on the current required by any one of the x-th cell (Cellx) and y-th cell (Cellly), 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) 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 cell (Cellx) and the y-th cell (Celly); The control chip drives the 2x control power switch (Q2x) and the 2y control power switch (Q2y) respectively according to the drive 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 control chip drives the 2h control power switch (Q2y) and the 2z control power switch (Q2z) respectively according to the drive signals with different duty cycles.

7. The operating method of a parallel equalization system based on a bidirectional CUK converter according to claim 3, characterized in that: Step S5 also includes the following steps: S5-1: Calculated using the following formula: (1.1)； in, This represents the sum of the inductance values ​​of the equalizer corresponding to the discharging battery. This represents the sum of the inductance values ​​of the equalizers corresponding to the rechargeable batteries, and C represents the total capacitance value of the equalizers corresponding to the discharged and rechargeable batteries connected in series. This represents the voltage across the total capacitance of the equalizer capacitors connected in series, corresponding to the discharging and recharging batteries. Indicates the input current. Indicates the output current. Indicates the input voltage. Indicates the output voltage; S5-2: Calculation and exist Moment~ Change over time; Solve using the formula in step S5-1 and exist Moment~ The changes over time are as follows: (1.2)； In the formula, This indicates the stage The change This indicates the stage The change in, of which, , , Indicates the PWM period. Indicates the PWM duty cycle. for time, for time; S5-3: Solve the formula in step S5-2 to obtain the current flowing through all the power switches of the equalizer corresponding to the discharging battery. ... and all power switches of the equalizer corresponding to the rechargeable battery , ... Voltage at both ends The equation is: (1.3)； (1.4)； In the formula, C represents the total capacitance value of the equalizer capacitors corresponding to the discharge battery and the rechargeable battery connected in series. This represents the voltage across the total capacitor after the equalizer capacitors corresponding to the discharge and rechargeable batteries are connected in series. S5-4: Assuming ~ At any given time, the control chip drives the equalizer corresponding to the discharging battery to control the power switch. , ... Off, inductor The capacitor C discharges under the combined effect of the voltage across it and the input voltage, while the inductor... The capacitor C discharges under the influence of the output voltage, while it charges under the influence of the input current, as described by the following formula: (1.5)； S5-5: Calculation and exist ~ Change over time; Solve using the formula in step S5-4 to get and exist ~ The changes over time are as follows: (1.6)； In the formula, This indicates the stage The change This indicates the stage The change , and It has the following relationship: (1.7)； At this stage, the input current and output current All power switches of the equalizer corresponding to the rechargeable battery will flow through them. , ... This allows us to obtain all the power switches of the equalizer corresponding to the rechargeable battery. , ... current ... And the auxiliary power switch of the equalizer corresponding to the discharging battery. , ... Auxiliary power switch of the equalizer corresponding to the rechargeable battery , ... Voltage at both ends , ... , , ... The equation is: (1.8)； (1.9)； In one PWM cycle, and The changes should all be 0, that is: (1.10）； S5-6: When asynchronous control is required, execute S5-7; when synchronous control is required, execute S5-8. S5-7: Calculation of the duty cycle of the PWM drive signal for asynchronous control; S5-7-1: Based on formulas (1.2), (1.4), (1.5), and (1.6), the relationship between the input current and the duty cycle is as follows: (1.11）； in, For the magnitude of the input current, Indicates the PWM period. Indicates the PWM duty cycle; S5-7-2: Calculate the duty cycle corresponding to the input current magnitude according to the formula in S5-7-1; S5-8: Calculation of the duty cycle of the PWM drive signal for synchronous control; S5-8-1: According to the formula, the relationship between the input current and the duty cycle is as follows: (1.12）； in, For the magnitude of the input current, Indicates the PWM period. Indicates the PWM duty cycle; Combining the law of conservation of energy, that is The following relationship can be obtained: (1.13）； When the SOC of a lithium battery is between 10% and 90%, the change in battery terminal voltage is minimal, therefore it is considered that... Then equations (1.1) and (1.13) simplify to: (1.14）； In the formula, , Once the circuit parameters, PWM frequency, and PWM duty cycle D are determined, and Both are constants; S5-8-2: Calculate the duty cycle corresponding to the input current magnitude according to formula (1.14).

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