An automatic equalization circuit for energy storage devices and a control method thereof

Abstract

The application provides an automatic equalization circuit of an energy storage device and a control method thereof. The automatic equalization circuit of the energy storage device comprises N energy storage modules, N-1 equalization disable switches, N LC half-bridge equalization modules and N equalization enable switches. During equalization, the state of charge equalization between the N energy storage modules is performed through the LC resonant circuit inside the N LC half-bridge equalization modules, and the state of charge equalization between the two energy storage devices inside the energy storage module is performed through the Buck-Boost converter. The circuit simultaneously realizes the state of charge equalization inside the energy storage module and between the energy storage modules, shortens the equalization time and improves the equalization efficiency. The circuit is based on a pair of complementary driving signals for autonomous equalization, has a simple circuit structure, a small number of devices, does not need a transformer and has a low cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage balancing, in particular to an automatic energy storage device balancing circuit and a control method thereof. BACKGROUND

[0002] New energy storage devices such as supercapacitors (including double-layer capacitors, lithium-ion capacitors, etc.) and batteries (including lithium-ion batteries, sodium-ion batteries, etc.) are widely used in new energy vehicles, energy storage systems, etc. due to their high power density, long service life, green environmental protection, etc.

[0003] In practical applications, multiple energy storage device monomers need to be connected in series to meet different voltage and current requirements. However, due to material, process, etc., there are differences in electrical parameters between energy storage device monomers, which may cause some monomers to be overcharged or overdischarged, thereby affecting the performance and service life of the entire system. To ensure the reliable operation of the entire energy storage system, effective means are needed to achieve the State of Charge (SOC) balancing between monomers.

[0004] Many methods have been proposed in the prior art to solve the problem of energy storage device balancing. The commonly used method in industry is the parallel absorption resistor and voltage stabilizing tube method, which also includes the introduction of active devices, the simple switching resistor method and the switching capacitor method, as well as the flyback converter method, the resonant converter method, the Buck-Boost converter method, etc. using power electronic converters. For most active balancing circuits, such circuits can achieve effective current regulation and soft switching operation, but the balancing process requires external control signals to drive, which requires a large control cost. In addition, the balancing principle process is relatively simple, the balancing rate is low, the balancing time is long, and it is not convenient for practical application.

[0005] Therefore, there is an urgent need for a self-balancing technology solution that can quickly balance, which not only improves the operational stability of the equipment and prevents accidental damage, but also helps to further improve the performance of new energy storage devices in various applications. SUMMARY

[0006] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide an automatic energy storage device balancing technology solution that can quickly balance, which balances the State of Charge between multiple energy storage modules through an LC half-bridge balancing module, and balances the State of Charge between two energy storage devices in each energy storage module through a Buck-Boost converter, thereby achieving State of Charge balancing within and between energy storage modules, shortening the balancing time and improving the balancing efficiency.

[0007] To achieve the above and other related purposes, the technical solutions provided by the present application are as follows.

[0008] An automatic equalization circuit for energy storage devices, comprising:

[0009] N energy storage modules, each of which comprises two energy storage devices and a Buck-Boost converter, the two energy storage devices being connected in series, and the Buck-Boost converter being connected to the two energy storage devices respectively to equalize the state of charge of the two energy storage devices inside the energy storage module;

[0010] N-1 equalization disable switches, which are connected in series alternately with the N energy storage modules, so that the 2N energy storage devices are connected in series through the N-1 equalization disable switches;

[0011] N LC half-bridge equalization modules, which are connected to the N energy storage modules one by one, and the first ends of the N LC half-bridge equalization modules are shorted together;

[0012] N equalization enable switches, the second ends of the N LC half-bridge equalization modules being shorted together through the N equalization enable switches connected in series one by one;

[0013] The automatic equalization circuit for energy storage devices has an equalization disable mode and an equalization enable mode; in the equalization disable mode, the N-1 equalization disable switches are closed, the N equalization enable switches are open, and the 2N energy storage devices are connected in series and charged or discharged; in the equalization enable mode, the N-1 equalization disable switches are open, the N equalization enable switches are closed, the state of charge of the N energy storage modules is equalized through the N LC half-bridge equalization modules, and the state of charge inside the energy storage module is equalized through the Buck-Boost converter; N is an integer greater than or equal to 2.

[0014] Optionally, the energy storage devices include at least supercapacitors, lithium ion batteries, and sodium ion batteries.

[0015] Optionally, the Buck-Boost converter comprises a first inductor, a first switch, and a second switch, in the energy storage module, the second end of the first energy storage device is connected to the first end of the second energy storage device, the first end of the first inductor is connected to the first end of the second energy storage device, the second end of the first inductor is connected to the first end of the first energy storage device through the connected first switch, and the second end of the first inductor is connected to the second end of the second energy storage device through the connected second switch.

[0016] Optionally, the first end of the first energy storage device in the kth energy storage module is connected to the second end of the second energy storage device in the k-1th energy storage module through the connected equalization disable switch, where k is an integer from 2 to N.

[0017] Optionally, the LC half-bridge equalization module comprises a second inductor, a first capacitor, a third switch and a fourth switch, a first end of the second inductor is a first end of the LC half-bridge equalization module, a second end of the second inductor is connected to a second end of the third switch through the first capacitor in series, a first end of the third switch is connected to a first end of a first energy storage device in the corresponding energy storage module, a second end of the third switch is connected to a first end of the fourth switch, a second end of the fourth switch is connected to a second end of a second energy storage device in the corresponding energy storage module, and a first end of the second energy storage device in the corresponding energy storage module is a second end of the LC half-bridge equalization module.

[0018] Optionally, control ends of the second switch and the third switch are connected to a first driving signal respectively to synchronously control the second switch and the third switch, control ends of the first switch and the fourth switch are connected to a second driving signal respectively to synchronously control the first switch and the fourth switch, the first driving signal and the second driving signal are complementary, and a duty cycle of the first driving signal is 50%, and when voltage equalization is performed, the first switch and the second switch are alternately turned on to work at a duty cycle of 50%.

[0019] Optionally, control ends of N-1 equalization disable switches are connected to a third driving signal respectively to synchronously control the N-1 equalization disable switches, and control ends of N equalization enable switches are connected to a fourth driving signal respectively to synchronously control the N equalization enable switches.

[0020] Optionally, on the basis of short-circuiting N LC half-bridge equalization modules, charge transfer and redistribution are realized through charging and discharging between N energy storage modules, and state of charge of the N energy storage modules is equalized.

[0021] Optionally, on the basis that the first switch and the second switch in the Buck-Boost converter are alternately turned on at a duty cycle of 50%, charge transfer and redistribution are realized through charging and discharging between two energy storage devices in each energy storage module, and state of charge of the two energy storage devices in the energy storage module is equalized.

[0022] A control method of an automatic equalization circuit of an energy storage device, applied to the automatic equalization circuit of the energy storage device in any one of the above, comprising:

[0023] N-1 equalization disable switches are closed, N equalization enable switches are opened, the equalization disable mode is entered, 2N energy storage devices are connected in series, and charging is performed through an external power supply or discharging is performed through a load.

[0024] opening N-1 of the equalization disable switches, closing N of the equalization enable switches, entering the equalization enable mode, performing state of charge equalization between N of the energy storage modules through N of the LC half-bridge equalization modules, and performing state of charge equalization between two of the energy storage devices in each of the energy storage modules through the Buck-Boost converter.

[0025] As described above, the energy storage device automatic equalization circuit and the control method thereof provided by the present application have at least the following beneficial effects:

[0026] The energy storage device automatic equalization circuit is designed in combination with N energy storage modules, N-1 equalization disable switches, N LC half-bridge equalization modules, and N equalization enable switches. In the equalization, state of charge equalization between N energy storage modules is performed through N LC half-bridge equalization modules, and state of charge equalization between two energy storage devices in an energy storage module is performed through a Buck-Boost converter. Thus, state of charge equalization in an energy storage module and between energy storage modules is simultaneously achieved, which can significantly shorten the equalization time and improve the equalization efficiency. The entire energy storage device automatic equalization circuit is based on a pair of complementary driving signals for autonomous equalization, and the corresponding circuit structure is simple and requires a small number of devices, without the need for a transformer, thereby reducing the cost. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 FIG. 1 is a structural schematic diagram of an energy storage device automatic equalization circuit in an equalization disable mode according to an embodiment of the present application.

[0028] Figure 2 FIG. 1 is a structural schematic diagram of an energy storage device automatic equalization circuit in an equalization disable mode according to an embodiment of the present application.

[0029] Figure 3 FIG. 1 is a structural schematic diagram of an energy storage device automatic equalization circuit in an equalization disable mode according to an embodiment of the present application.

[0030] Figure 4 FIG. 1 is a structural schematic diagram of an energy storage device automatic equalization circuit in an equalization disable mode according to an embodiment of the present application.

[0031] Figure 5 FIG. 1 is a structural schematic diagram of an energy storage device automatic equalization circuit in an equalization disable mode according to an embodiment of the present application.

[0032] Figure 6 FIG. 1 is a structural schematic diagram of an energy storage device automatic equalization circuit in an equalization disable mode according to an embodiment of the present application.

[0033] Figure 7 Another state structure diagram of LC half-bridge equalization module between energy storage modules in the automatic equalization circuit of energy storage device in the equalization enabled mode in embodiment one of the present application.

[0034] Figure 8 Waveform diagram of voltage change between two ends of 8 super capacitors in the automatic equalization circuit of energy storage device in the equalization enabled mode in embodiment two of the present application.

[0035] Figure 9 Waveform diagram of voltage change between two ends of 4 energy storage modules in the automatic equalization circuit of energy storage device in the equalization enabled mode in embodiment two of the present application.

[0036] Figure 10 Waveform diagram of LC resonance unit current flowing through two super capacitors in the first energy storage module in the automatic equalization circuit of energy storage device in the equalization enabled mode in embodiment two of the present application.

[0037] Figure 11 Waveform diagram of LC resonance unit current flowing through two super capacitors in the third energy storage module in the automatic equalization circuit of energy storage device in the equalization enabled mode in embodiment two of the present application.

[0038] Figure 12 Partial waveform diagram of voltage V ng between node n and g corresponding to one energy storage module in the automatic equalization circuit of energy storage device in the equalization enabled mode in embodiment two of the present application.

[0039] Figure 13 Overall waveform diagram of voltage V ng between node n and g corresponding to all energy storage modules in the automatic equalization circuit of energy storage device in the equalization enabled mode in embodiment two of the present application.

[0040] Figure 14 Circuit principle diagram corresponding to a single energy storage module in the energy storage device equalization system using only LC circuit in embodiment three of the present application.

[0041] Figure 15 Circuit principle diagram corresponding to a single energy storage module in the energy storage device equalization system using only Buck-Boost converter in embodiment three of the present application.

[0042] Figure 16 Waveform diagram of voltage change between two ends of 8 super capacitors in the energy storage device equalization system using only LC circuit based on the circuit principle diagram shown in Figure 14 .

[0043] Figure 17 Waveform diagram of voltage change between two ends of 8 super capacitors in the energy storage device equalization system using only Buck-Boost converter based on the circuit principle diagram shown in Figure 15The waveform diagram of the voltage change of the eight supercapacitors in the energy storage device equalization system using only the Buck-Boost circuit is shown. DETAILED DESCRIPTION

[0044] The advantages and effects of the present application can be easily understood by those skilled in the art from the description of the embodiments of the present application. The present application can also be implemented or applied in other different embodiments, and various modifications or changes can be made to the details in the description based on different views and applications without departing from the spirit of the present application.

[0045] Reference is made to Figures 1 to 17 It should be noted that the diagrams provided in the embodiments only schematically illustrate the basic concepts of the present application, and only the components related to the present application are shown in the diagrams, not the number, shape and size of the components when actually implemented. The shapes, number and proportions of the components when actually implemented can be arbitrarily changed, and the layout of the components can be more complex. The structures, proportions and sizes shown in the diagrams attached to the description are only used to understand and read the content disclosed in the description by those skilled in the art, and do not limit the conditions under which the present application can be implemented, so they do not have technical significance. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effects and purposes that can be achieved by the present application, should still fall within the scope of the technology disclosed by the present application.

[0046] As described in the background section, in practical applications, multiple energy storage device monomers need to be connected in series to meet different voltage and current requirements. However, due to material, process and other reasons, there are differences in electrical parameters between energy storage device monomers, which may cause some monomers to be overcharged or overdischarged, thereby affecting the performance and life of the entire system. To ensure the reliable operation of the entire energy storage system, effective means are needed to achieve the State of Charge (SOC) balance between the monomers.

[0047] Many methods have been proposed in the prior art to solve the problem of energy storage device equalization. The commonly used methods in industry are parallel absorption resistance and voltage stabilizing tube method, which also includes the introduction of active devices, simple switching resistance method and switching capacitor method, and the use of power electronic converters such as flyback converter method, resonant converter method, Buck-Boost converter method, etc.

[0048] Among them, for most active balancing circuits, the circuit can realize effective regulation of current and soft switching operation, but the balancing process needs external control signal to drive, which needs to pay a large control cost; in addition, the balancing principle process is relatively single, the balancing rate is low, the balancing time is long, and the energy storage system without balancing for a long time is not conducive to the operation stability of the equipment, which may cause accidental damage to the load, and also affects the performance and service life of the energy storage system.

[0049] Based on this, the application provides an automatic energy storage device balancing technical scheme: an automatic energy storage device balancing circuit is designed by combining N energy storage modules, N-1 balancing disable switches, N LC half-bridge balancing modules and N balancing enable switches. During balancing, the state of charge balancing between the N energy storage modules is performed by the N LC half-bridge balancing modules, and the state of charge balancing between the two energy storage devices inside the energy storage module is performed by the Buck-Boost converter, so that the state of charge balancing inside the energy storage module and between the energy storage modules is performed synchronously, so as to shorten the balancing time and improve the balancing efficiency. The entire automatic energy storage device balancing circuit is based on a pair of complementary driving signals for autonomous balancing, and the corresponding circuit structure is simple and requires fewer devices, without the need for a transformer, thereby reducing the cost.

[0050] It should be noted that the state of charge (SOC) is used to reflect the remaining capacity condition of the battery or super capacitor, and its value is defined as the ratio of the remaining capacity of the battery or super capacitor to the battery capacity, commonly expressed in percentage. Its value range is 0-1, when SOC is 0, it means that the battery is completely discharged, and when SOC is 1, it means that the battery is completely full. Therefore, in the embodiment, the SOC of the energy storage device is used to represent the electrical parameter of the energy storage device. For the energy storage device, the SOC and the voltage have a strong correlation, and the voltage of the single body is high, that is, the SOC is high. Therefore, when referring to the energy storage device, the voltage is used instead of the SOC to measure and compare the capacity condition of the energy storage device.

[0051] Embodiment one

[0052] First, as Figure 1 shown, in the embodiment of the application, an automatic energy storage device balancing circuit is provided, which comprises:

[0053] N energy storage modules, i.e. energy storage module M1, energy storage module M2, … and energy storage module MN, each energy storage module comprising two super capacitors and a Buck-Boost converter, the two super capacitors being connected in series, and the Buck-Boost converter being connected with the two super capacitors to balance the voltage (or state of charge) of the two super capacitors inside the energy storage module;

[0054] N-1 balancing disable switches, i.e. balancing disable switch SBD1 Equalization disable switch S BD2 ... and equalization disable switch S BD(N-1) , and N energy storage modules are alternately connected in series, so that 2N supercapacitors are connected in series through N-1 equalization disable switches;

[0055] N LC half-bridge equalization modules, namely LC half-bridge equalization module B1, LC half-bridge equalization module B2, ... and LC half-bridge equalization module BN, are connected one-to-one with N supercapacitor energy storage modules, and the first ends of the N LC half-bridge equalization modules are shorted together.

[0056] N equalization enable switches, i.e., equalization enable switches are off S BE1 Balanced activation switch S BE2 ... and the equalization enable switch S BEN The second ends of N LC half-bridge equalization modules are shorted together after being connected in series with N equalization enable switches.

[0057] The automatic balancing circuit for energy storage devices has a balancing disable mode and a balancing enable mode. In the balancing disable mode, N-1 balancing disable switches are closed, N balancing enable switches are open, and 2N supercapacitors are connected in series to perform charging or discharging operations. In the balancing enable mode, N-1 balancing disable switches are open, N balancing enable switches are closed, N LC half-bridge balancing modules are used to balance the voltage between the N energy storage modules, and a Buck-Boost converter is used to balance the voltage within the energy storage modules. N is an integer greater than or equal to 2.

[0058] In detail, such as Figure 1 As shown, the j-th energy storage module includes a supercapacitor SC. ja and supercapacitor SC jb Supercapacitor SC ja The second end is connected to the supercapacitor SC jb At the first end, within the j-th energy storage module, the Buck-Boost converter includes a first inductor L. dj First switch S j1 Second switch S j2 First inductor L dj The first end is connected to the supercapacitor SC jb The first terminal, the first inductor L dj The second end passes through the first switch S connected in series. j1 Supercapacitor SC connected afterward ja The first terminal, the first inductor L dj The second end also passes through a second switch S connected in series. j2 Supercapacitor SC connected afterward jbThe second end of the expression. Where j is an integer from 1 to N.

[0059] More in detail, such as Figure 1 As shown, the first energy storage module (i.e., energy storage module M1) includes a supercapacitor SC. 1a and supercapacitor SC 1b Supercapacitor SC 1a The second end is connected to the supercapacitor SC 1b At the first end, within the first energy storage module, the Buck-Boost converter includes a first inductor L. d1 First switch S 11 Second switch S 12 First inductor L d1 The first end is connected to the supercapacitor SC 1b The first terminal, the first inductor L d1 The second end passes through the first switch S connected in series. 11 Supercapacitor SC connected afterward 1a The first terminal, the first inductor L d1 The second end also passes through a second switch S connected in series. 12 Supercapacitor SC connected afterward 1b The second end.

[0060] More in detail, such as Figure 1 As shown, the second energy storage module (i.e., energy storage module M2) includes a supercapacitor SC. 2a and supercapacitor SC 2b Supercapacitor SC 2a The second end is connected to the supercapacitor SC 2b At the first end, within the second energy storage module, the Buck-Boost converter includes a first inductor L. d2 First switch S 21 Second switch S 22 First inductor L d2 The first end is connected to the supercapacitor SC 2b The first terminal, the first inductor L d2 The second end passes through the first switch S connected in series. 21 Supercapacitor SC connected afterward 2a The first terminal, the first inductor L d2 The second end also passes through a second switch S connected in series. 22 Supercapacitor SC connected afterward 2b The second end.

[0061] And so on, ..., such as Figure 1 As shown, the Nth energy storage module (i.e., energy storage module MN) includes a supercapacitor SC. Na and supercapacitor SC Nb Supercapacitor SCNa The second end is connected to the supercapacitor SC Nb At the first end, within the Nth energy storage module, the Buck-Boost converter includes a first inductor L. dN First switch S N1 Second switch S N2 First inductor L dN The first end is connected to the supercapacitor SC Nb The first terminal, the first inductor L dN The second end passes through the first switch S connected in series. N1 Supercapacitor SC connected afterward Na The first terminal, the first inductor L dN The second end also passes through a second switch S connected in series. N2 Supercapacitor SC connected afterward Nb The second end.

[0062] In detail, such as Figure 1 As shown, the supercapacitor SC in the kth energy storage module ia The first end is connected in series with a balanced disable switch S BD(i-1) Following this is the supercapacitor SC within the (k-1)th energy storage module. (i-1)b The second end of the expression, where k is an integer from 2 to N.

[0063] More in detail, such as Figure 1 As shown, the supercapacitor SC in the second energy storage module 2a The first end is connected in series with a balanced disable switch S BD1 The supercapacitor SC is then connected to the first energy storage module. 1b The second end, the supercapacitor SC in the third energy storage module 3a (Not shown in the diagram) The first terminal is connected in series with a balanced disable switch S. BD2 The supercapacitor SC in the second energy storage module is then connected. 2b The second end, and so on, ..., the supercapacitor SC in the Nth energy storage module Na The first end is connected in series with a balanced disable switch S BD(N-1) The supercapacitor SC is then connected to the (N-1)th energy storage module. (N-1)b The second end.

[0064] In detail, such as Figure 1 As shown, the j-th LC half-bridge equalization module includes a second inductor L. rj First capacitor C rj Third switch S j3 and the fourth switch S j4 Second inductor L rj The first terminal serves as the first terminal of the j-th LC half-bridge equalization module, and the second inductor Lrj The second terminal is connected in series with the first capacitor C rj Connect to the third switch S j3 The second end, the third switch S j3 The first terminal is connected to the supercapacitor SC inside the j-th energy storage module. ja The first terminal, the third switch S j3 The second terminal is connected to the fourth switch S j4 The first terminal, the fourth switch S j4 The second terminal is connected to the supercapacitor SC inside the j-th energy storage module. jb At the second end, the supercapacitor SC in the j-th energy storage module jb The first end serves as the second end of the j-th LC half-bridge equalizer module.

[0065] More in detail, such as Figure 1 As shown, the first LC half-bridge equalization module (i.e., LC half-bridge equalization module B1) includes a second inductor L. r1 First capacitor C r1 Third switch S 13 and the fourth switch S 14 Second inductor L r1 The first terminal serves as the first terminal of the first LC half-bridge equalization module, and the second inductor L r1 The second terminal is connected in series with the first capacitor C r1 Connect to the third switch S 13 The second end, the third switch S 13 The first terminal is connected to the supercapacitor SC inside the first energy storage module. 1a The first terminal, the third switch S 13 The second terminal is connected to the fourth switch S 14 The first terminal, the fourth switch S 14 The second terminal is connected to the supercapacitor SC inside the first energy storage module. 1b At the second end, the supercapacitor SC inside the first energy storage module 1b The first end serves as the second end of the first LC half-bridge equalization module.

[0066] More in detail, such as Figure 1 As shown, the second LC half-bridge equalization module (i.e., LC half-bridge equalization module B2) includes a second inductor L. r2 First capacitor C r2 Third switch S 23 and the fourth switch S 24 Second inductor L r2 The first terminal serves as the first terminal of the second LC half-bridge equalization module, and the second inductor L... r2 The second terminal is connected in series with the first capacitor C r2 Connect to the third switch S 23 The second end, the third switch S23 The first terminal is connected to the supercapacitor SC inside the second energy storage module. 2a The first terminal, the third switch S 23 The second terminal is connected to the fourth switch S 24 The first terminal, the fourth switch S 24 The second terminal is connected to the supercapacitor SC inside the second energy storage module. 2b At the second end, the supercapacitor SC in the second energy storage module 2b The first end serves as the second end of the second LC half-bridge equalization module.

[0067] And so on, ..., such as Figure 1 As shown, the Nth LC half-bridge equalization module (i.e., LC half-bridge equalization module BN) includes a second inductor L. rN First capacitor C rN Third switch S N3 and the fourth switch S N4 Second inductor L rN The first terminal serves as the first terminal of the Nth LC half-bridge equalization module, and the second inductor L rN The second terminal is connected in series with the first capacitor C rN Connect to the third switch S N3 The second end, the third switch S N3 The first terminal is connected to the supercapacitor SC inside the Nth energy storage module. Na The first terminal, the third switch S N3 The second terminal is connected to the fourth switch S N4 The first terminal, the fourth switch S N4 The second terminal is connected to the supercapacitor SC inside the Nth energy storage module. Nb At the second end, the supercapacitor SC in the Nth energy storage module Nb The first end serves as the second end of the Nth LC half-bridge equalization module.

[0068] More in detail, such as Figure 1 As shown, the second inductor L r1 First terminal, second inductor L r2 The first terminal, ... and the second inductor L rN The first ends are shorted together; the supercapacitor SC in the first energy storage module 1b First terminal equalization enable switch S BE1 At the second end, the supercapacitor SC in the second energy storage module 2b First terminal equalization enable switch S BE2 The second end, ..., the supercapacitor SC in the Nth energy storage module Nb First terminal equalization enable switch S BEN The second terminal, the equalization enable switch S BE1First terminal, equalization enable switch S BE2 The first terminal, ... and the equalization enable switch S BEN The first ends are shorted together.

[0069] In detail, such as Figure 1 As shown, each of the second switches (i.e., the second switch S) 12 Second switch S 22 ... and the second switch S N2 The control terminal of ) and each third switch (i.e., the third switch S) 13 Third switch S 23 ... and the third switch S N3 The control terminals of the first switches are connected to the first drive signal (not shown in the figure) to synchronously control the second and third switches; each of the first switches (i.e., the first switch S) 11 First switch S 21 ... and the first switch S N1 The control terminal of ) and each of the fourth switches (i.e., the fourth switch S) 14 Fourth switch S 24 ... and the fourth switch S N4 The control terminals of the switches are connected to the second drive signal (not shown in the figure) to synchronously control the first and fourth switches.

[0070] More specifically, the first drive signal and the second drive signal are complementary, and the duty cycle of the first drive signal is 50%; during voltage equalization, the first switch and the second switch are alternately turned on, operating with a 50% duty cycle.

[0071] In detail, such as Figure 1 As shown, each equalization disable switch (i.e., equalization disable switch S) BD1 Equalization disable switch S BD2 ... and equalization disable switch S BD(N-1) The control terminals of each equalization switch are connected to a third drive signal (not shown in the figure) to synchronously control each equalization disable switch; each equalization enable switch (i.e., the equalization enable switch is off) BE1 Balanced activation switch S BE2 ... and the equalization enable switch S BEN The control terminals of each switch are connected to the fourth drive signal (not shown in the figure) to synchronously control each equalization enable switch.

[0072] In detail, such as Figure 1 As shown, under the control of the third and fourth drive signals, when each equalization disable switch is closed and each equalization enable switch is open, the automatic equalization circuit of the energy storage device is in equalization disable mode. All supercapacitors are connected in series through the equalization disable switch and are charged through an external power source or discharged through a load, generating a charging and discharging current I.SC .

[0073] In detail, such as Figure 2 As shown, under the control of the third and fourth drive signals, when each equalization disable switch is open and each equalization enable switch is closed, the automatic equalization circuit of the energy storage device is in the equalization enable mode. The voltage equalization between N energy storage modules is performed through N LC half-bridge equalization modules, and the voltage equalization within the energy storage modules is performed through the Buck-Boost converter.

[0074] More in detail, such as Figure 3 and Figure 1 As shown, the LC half-bridge equalization module includes an LC resonant unit composed of a second inductor and a first capacitor, and a half-bridge composed of a third switch and a fourth switch, used for voltage equalization among the energy storage modules. During the voltage equalization process among the energy storage modules, each energy storage module exchanges energy through the LC resonant unit and the half-bridge until the voltage of each energy storage module reaches a uniform level. The half-bridge composed of the first switch and the second switch, along with the first inductor, constitutes a Buck-Boost converter, used for voltage equalization within the energy storage modules. During the voltage equalization process within the energy storage modules, the two supercapacitors in each energy storage module adjust their voltages according to the volt-second balance principle through the Buck-Boost converter, ultimately achieving voltage equalization between the two supercapacitors.

[0075] To achieve the equalization function, in equalization enabled mode, all equalization disable switches are off and all equalization enable switches are closed, such as... Figure 3 As shown.

[0076] More specifically, regarding voltage balancing within the energy storage module, inside the energy storage module Mj, the Buck-Boost converter includes an alternately conducting first switch S. j1 Second switch S j2 Each switch operates with a 50% duty cycle. During the first half of each switching cycle, the second switch S... j2 The circuit is open, and the first switch S is closed. j1 Disconnect, causing the first inductor L dj With the supercapacitor SC located low within the energy storage module jb Parallel connection, such as Figure 3 As shown; subsequently, in the latter half of the switching cycle, the first switch S... j1 The second switch S is turned on. j2 Disconnected, at this time the first inductor L dj The supercapacitor SC, which is located higher within the energy storage module ja Parallel connection, such as Figure 4 As shown. Regardless of Figure 5 and Figure 4 Which mode, the first inductor Ldj There will be a current I on it. Ldj pass.

[0077] According to the volt-second balance principle under steady-state conditions, we have the following formula:

[0078] V jb 0.5T s -V ja 0.5T s =0 (1)

[0079] Among them, V jb It is a supercapacitor SC jb The voltage value, V ja It is a supercapacitor SC ja The voltage value, T s It is the period of the first drive signal or the second drive signal.

[0080] As can be seen, under steady-state conditions, V ja =V jb Therefore, over time, the circuit gradually approaches a steady state, and the supercapacitor SC... ja The voltage on the supercapacitor SC jb The voltages on the modules will eventually reach the same level, thus achieving balance within the module.

[0081] More specifically, for voltage balancing among energy storage modules, a switch in the half-bridge circuit (i.e., the third switch S) is used. j3 and the fourth switch S j4 The third switch S is used to control the current in the LC resonant unit. j3 Accept and second switch S j2 The same drive signal, the fourth switch S j4 Accept and first switch S j1 Same drive signal, third switch S j3 and the fourth switch S j4 They operate alternately with a 50% duty cycle. During the first half of each switching cycle, the second switch S... j2 and the third switch S j3 Conductive, such as Figure 5 As shown, the current I of the LC resonant unit LCj Flowing through supercapacitor SC ja In the latter half of each switching cycle, the first switch S j1 and the fourth switch S j4 Conductive, such as Figure 6 As shown, the current I of the LC resonant unit LCj Flowing through supercapacitor SC jbThe key to this scheme lies in measuring the current passing through each energy storage module, thereby determining whether each energy storage module is in a charging or discharging state.

[0082] In more detail, using Fourier analysis, the current I in the LC resonant unit can be obtained. LCj The expression is derived, and calculations show that if the voltage of an energy storage module is higher than the average voltage of all energy storage modules, the module will discharge, and its voltage will gradually decrease; conversely, it will charge, and its voltage will gradually increase. As charging and discharging proceed, the voltage differences between the energy storage modules are gradually eliminated, ultimately achieving voltage balance among the modules.

[0083] To analyze the principle of energy balancing among the various energy storage modules, the voltage of the j-th energy storage module is denoted as V. jm It is the voltage value V corresponding to the two supercapacitors inside. ja and V jb The sum of these currents. The key to the analysis lies in the current of each energy storage module—this current is related to the current flowing through its associated LC resonant unit (by the second inductor L). rj and the first capacitor C rj The current I (composed of) LCj same.

[0084] During the first half of each switching cycle, the voltage between nodes n and g is denoted as V. nga We can obtain:

[0085]

[0086] Meanwhile, during the second half of each switching cycle, the voltage between nodes n and g is denoted as V. ngb There are also similar formulas:

[0087]

[0088] Kirchhoff's current law states that the sum of the currents in all capacitors connected to the same node n is zero, that is:

[0089]

[0090] By differentiating the above equation, we can obtain:

[0091]

[0092] Assuming all resonant capacitors (i.e. all the first capacitors) are fully discharged during circuit construction, it can be concluded that the sum of the voltages across all resonant capacitors is always zero during circuit operation.

[0093]

[0094] Based on this, equations (2) and (3) are listed for all energy storage modules (i.e., N energy storage modules), and summed to obtain:

[0095]

[0096]

[0097] Substituting equations (5) and (6), we can obtain:

[0098]

[0099]

[0100] Therefore, the voltage V between nodes n and g ng It is implemented as a square wave, with an amplitude between that of the supercapacitor modules and the supercharger cells (i.e., supercapacitors SC) in each supercapacitor energy storage module. 1a Supercapacitor SC 2a ...and supercapacitor SC Na The average voltage of the supercapacitors (SC) and the supercells (i.e., supercapacitors) in each energy storage module. 1b Supercapacitor SC 2b ...and supercapacitor SC Nb The voltage is between the negative average value of the voltage. From this square wave, the voltage of the LC resonant unit can be derived, and thus the current i through the LC resonant unit and each energy storage module can be calculated. jN Through Fourier analysis, it can be expressed as:

[0101]

[0102] The average current of each energy storage module during a complete drive cycle can be calculated and defined using the provided formula:

[0103]

[0104] The derivation of formula (12) shows that when the voltage of a certain energy storage module is higher than the average voltage of all energy storage modules, its average current is negative, that is, it is discharging to the outside; when the voltage of an energy storage module is lower than the average voltage, its average current is positive, that is, it is being charged. As the charging and discharging regulation proceeds, the voltage of each energy storage module gradually becomes consistent, and finally the voltage balance among all energy storage modules in the energy storage system is achieved.

[0105] In other words, under the equalization activation mode of the automatic equalization circuit of the aforementioned energy storage device, based on the alternating conduction of the first and second switches in the Buck-Boost converter with a 50% duty cycle, the energy stored in the inductor in the Buck-Boost converter is transferred between the two supercapacitors, realizing the relative charging and discharging between the two supercapacitors inside each energy storage module, thereby achieving charge transfer and redistribution, and equalizing the voltage (or state of charge) of the two supercapacitors inside the energy storage module; based on the short-circuited N LC half-bridge equalization modules, the relative charging and discharging between the LC resonant units in the N energy storage modules realizes charge transfer and redistribution, redistributing the charge among the N energy storage modules, and equalizing the voltage (or state of charge) of the N energy storage modules.

[0106] It should be added that the embodiments of the present invention use supercapacitors as an example to illustrate energy storage devices. However, in practical applications, energy storage devices are not limited to supercapacitors (such as double-layer capacitors and lithium-ion capacitors). The energy storage devices in the present invention can also be lithium-ion batteries or sodium-ion batteries, but are not limited to these energy storage devices. All energy storage devices currently on the market can achieve SOC balancing through the automatic balancing circuit of the energy storage device that can balance the state of charge provided by the present invention. Furthermore, it is also applicable to future energy storage devices and all fall within the protection scope of the present invention.

[0107] Secondly, based on the design concept of the automatic balancing circuit for the energy storage device described above, this invention also provides a control method for the automatic balancing circuit for the energy storage device, applied to the aforementioned automatic balancing circuit for the energy storage device, comprising the following steps:

[0108] S1: Close N-1 equalization disable switches and open N equalization enable switches to enter equalization disable mode, so that 2N supercapacitors are connected in series and charged through an external power source or discharged through a load.

[0109] S2: Disconnect N-1 equalization disable switches, close N equalization enable switches, enter equalization enable mode, perform voltage equalization between N energy storage modules through N LC half-bridge equalization modules, and perform voltage equalization between the two supercapacitors inside each energy storage module through Buck-Boost converter.

[0110] It should be noted that the detailed process of steps S1 to S2 can be referred to the relevant description of the automatic balancing circuit of the energy storage device mentioned above, and will not be repeated here.

[0111] Example 2

[0112] In this embodiment of the invention, the automatic balancing circuit of the energy storage device in Embodiment 1 is simulated and verified. The value of N is 4. The automatic balancing circuit of the energy storage device includes 4 energy storage modules, 3 balancing disable switches, 4 LC half-bridge balancing modules, and 4 balancing enable switches. The automatic balancing circuit of the energy storage device includes a total of 8 supercapacitors, which are connected in a supercapacitor string through the 3 balancing disable switches.

[0113] Specifically, each supercapacitor has a capacitance of 0.3F and an equivalent series resistance of 0.001Ω. The initial voltages of the eight supercapacitors, from top to bottom, are set as follows: 2.7V, 2.4V, 2.1V, 1.8V, 1.2V, 0.9V, 0.6V, and 0.3V, with an average voltage of 1.5V. The four energy storage modules, from top to bottom, are designated as Energy Storage Module 1, Energy Storage Module 2, Energy Storage Module 3, and Energy Storage Module 4.

[0114] In detail, in the LC resonant unit, the second inductor L rj The inductance value is set to 50μH, and the first capacitor C rj The capacitance value is set to 50.6nF; in the Buck-Boost converter, the first inductor L... dj The inductance value is set to 5μH; the equivalent series resistance of all inductors and capacitors is set to 0.01Ω; all switches (first switch S) j1 Second switch S j2 Third switch S j3 and the fourth switch S j4 The switching frequency of all components is set to 100.06kHz.

[0115] Simulation results show the voltage changes across the eight supercapacitors in the automatic balancing circuit of the energy storage device under balancing activation mode, as shown in the following waveform diagram. Figure 7 As shown, the waveforms of the voltage changes across the four energy storage modules in the automatic balancing circuit of the corresponding energy storage device under the balancing activation mode are as follows: Figure 8 As shown, the waveform of the LC resonant unit current flowing through the two supercapacitors in the first energy storage module is as follows. Figure 9 As shown, the waveform of the LC resonant unit current flowing through the two supercapacitors in the third energy storage module is as follows. Figure 10 As shown, the voltage V between nodes n and g corresponding to one energy storage module is obtained. ng The local waveform diagram is as follows Figure 11 As shown, the voltage V between nodes n and g corresponding to all energy storage modules is obtained. ng The overall waveform diagram is as follows Figure 12 As shown.

[0116] In detail, by Figure 13It can be seen that the voltage of each supercapacitor cell converges uniformly to approximately 1.5V at 0.119s. Here, voltages V1 to V8 represent the real-time voltages of the eight supercapacitors. At this point, the maximum voltage difference between the supercapacitor cells is less than 0.01V, indicating that the equalization process is complete, i.e., the equalization time is 0.119s. Furthermore, from... Figure 8 It can be seen that at 0.05s, the voltage of the first energy storage module is higher than the average voltage of the four energy storage modules, therefore the first energy storage module discharges; the voltage of the third energy storage module is lower than the average voltage, therefore the third energy storage module charges. Wherein, voltage V... M1 ~V M4 This represents the real-time voltage of the four energy storage modules, V. avg This represents the average voltage of the four energy storage modules.

[0117] In detail, by Figure 9 It can be seen that the currents on the two supercapacitors in the first energy storage module are negative pulse waveforms with alternating negative half-cycles of a sine wave. The currents flowing through the two supercapacitors are both negative, corresponding to currents i and i'. 1a and i 1b This indicates that the two supercapacitors within the first energy storage module discharge externally to reduce the voltage. Figure 10 It can be seen that the currents on the two supercapacitors in the third energy storage module are alternating positive pulse waveforms with a positive half-cycle of a sine wave. The currents flowing through both supercapacitors are positive, corresponding to currents i and i'. 3a and i 3b This indicates that the two supercapacitors in the third energy storage module are being charged to boost the voltage.

[0118] In detail, by Figure 11 It can be seen that the voltage V between nodes n and g is... ng It is indeed a square wave, with an amplitude between the average voltage (i.e., V) of the super-electrical unit above the four energy storage modules. a (e.g., 1.5V) and the negative average value of the voltage of the super-electric unit below the 4 energy storage modules (i.e., -V) b The effective voltage V between nodes n and g is between -1.5V and -1.5V. ng The waveform and amplitude were verified and are consistent with the theoretical derivation.

[0119] Therefore, the above simulation verification demonstrates the effectiveness of the modular automatic balancing circuit for energy storage devices based on LC resonant units and Buck-Boost converters proposed in Embodiment 1 of this invention.

[0120] Example 3

[0121] In this embodiment of the invention, to further verify the technical effect of the automatic balancing circuit for energy storage devices in Embodiment 1 and to evaluate the balancing time of the automatic balancing circuit for energy storage devices proposed in Embodiment 1, a comparative simulation was performed based on Embodiment 2 of the invention, comparing it with two balancing systems mentioned in the literature: one using only an LC circuit and the other using only a Buck-Boost converter. The circuit schematic diagram of a single energy storage module in the energy storage device balancing system using only an LC circuit is shown below. Figures 12-13 As shown, the circuit schematic for a single energy storage module in an energy storage device equalization system using only Buck-Boost converters is as follows: Figure 14 As shown.

[0122] In the energy storage device equalization system using only LC circuits, a single energy storage module includes supercapacitor SC1, supercapacitor SC2, and switch S. 11 Switch S 12 Switch S 13 Switch S 14 Switch S 21 Switch S 22 Switch S 23 Switch S 24 Inductor L r1 Inductor L r2 Capacitor C r1 and capacitor C r2 In an energy storage equalization system using only Buck-Boost converters, a single energy storage module corresponds to supercapacitor SC1, supercapacitor SC2, supercapacitor SC3, and switch S. 11 Switch S 12 Switch S 21 Switch S 22 Inductors L1 and L2. For detailed circuit structure, please refer to [reference needed]. Figure 15 and Figure 14 This will not be elaborated upon here.

[0123] During simulation verification, based on, for example Figure 15 The circuit shown can be expanded to include four such circuits. Figure 14 The circuit topology shown is a balancing system using only LC circuits for energy storage devices, forming a series structure of eight supercapacitors; based on... Figure 14 The circuit shown is extended to form an energy storage equalization system using only a Buck-Boost converter, comprising eight supercapacitors connected in series. Furthermore, the supercapacitor parameters and initial voltage settings are identical for all three circuits.

[0124] Through simulation verification, the results obtained under the balanced enable mode are based on, for example, Figure 15The waveform diagram shown is of the voltage changes across the eight supercapacitors in an energy storage device equalization system using only LC circuits. Figure 14 As shown, the waveforms of the voltage changes across the eight supercapacitors in the energy storage device equalization system using only the Buck-Boost converter in equalization mode are obtained. Figure 16 As shown.

[0125] In detail, by Figure 17 It can be seen that for an energy storage device equalization system using only LC circuits, the voltages of the eight supercapacitor cells reach equalization in 0.361s, i.e., the equalization time is 0.361s, where voltages V1 to V8 represent the real-time voltages of the eight supercapacitor cells; from Figure 16 It can be seen that for an energy storage device equalization system using only Buck-Boost converters, the voltages of the eight supercapacitor cells reach equalization in 1.328s, i.e., the equalization time is 1.328s, where voltages V1 to V8 represent the real-time voltages of the eight supercapacitor cells. And from... Figure 17 Figure 8 It can be seen that the equalization time of the automatic equalization circuit of the energy storage device based on LC circuit and Buck-Boost converter proposed in this invention is 0.119s.

[0126] As can be seen from the comparative simulation, the automatic equalization circuit for energy storage devices based on LC resonant circuit and Buck-Boost converter proposed in this invention can greatly shorten the equalization time, further proving the effectiveness of its performance.

[0127] In summary, the automatic balancing circuit and control method for energy storage devices provided by this invention combine N energy storage modules, N-1 balancing disable switches, N LC half-bridge balancing modules, and N balancing enable switches to design the automatic balancing circuit. During balancing, the state of charge (SOC) among the N energy storage modules is balanced through the LC resonant circuits within the N LC half-bridge balancing modules, and the SOC between two energy storage devices within each energy storage module is balanced through a Buck-Boost converter. This achieves SOC balance both within and between energy storage modules, significantly shortening the balancing time and improving balancing efficiency. The entire automatic balancing circuit is based on a pair of complementary drive signals for autonomous balancing, and the corresponding circuit structure is simple, requires fewer components, does not require a transformer, and reduces costs.

[0128] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An automatic balancing circuit for an energy storage device, characterized in that, include: N energy storage modules, each energy storage module includes two energy storage devices and a Buck-Boost converter. The two energy storage devices are connected in series, and the Buck-Boost converter is connected to the two energy storage devices respectively to balance the state of charge of the two energy storage devices inside the energy storage module. N-1 equalization disable switches are alternately connected in series with N energy storage modules, so that 2N energy storage devices are connected in series through N-1 equalization disable switches; N LC half-bridge equalization modules are connected one-to-one with N energy storage modules, and the first ends of the N LC half-bridge equalization modules are short-circuited together. N equalization enable switches, and the second ends of the N LC half-bridge equalization modules are shorted together after being connected in series with the N equalization enable switches in a one-to-one correspondence. The automatic balancing circuit for energy storage devices has a balancing disable mode and a balancing enable mode. In the balancing disable mode, N-1 balancing disable switches are closed, N balancing enable switches are open, and 2N energy storage devices are connected in series and perform charging or discharging operations. In the balancing enable mode, N-1 balancing disable switches are open, N balancing enable switches are closed, and the state of charge (SOC) among the N energy storage modules is balanced by N LC half-bridge balancing modules, and the SOC within each energy storage module is balanced by the Buck-Boost converter. N is an integer greater than or equal to 2. The Buck-Boost converter includes a first inductor, a first switch, and a second switch. Inside the energy storage module, the second end of the first energy storage device is connected to the first end of the second energy storage device, the first end of the first inductor is connected to the first end of the second energy storage device, the second end of the first inductor is connected to the first end of the first energy storage device after passing through the first switch connected in series, and the second end of the first inductor is also connected to the second end of the second energy storage device after passing through the second switch connected in series. The LC half-bridge equalization module includes a second inductor, a first capacitor, a third switch, and a fourth switch. The first end of the second inductor serves as the first end of the LC half-bridge equalization module. The second end of the second inductor is connected to the second end of the third switch via the first capacitor connected in series. The first end of the third switch is connected to the first end of the first energy storage device in the corresponding energy storage module. The second end of the third switch is connected to the first end of the fourth switch. The second end of the fourth switch is connected to the second end of the second energy storage device in the corresponding energy storage module. The first end of the second energy storage device in the corresponding energy storage module serves as the second end of the LC half-bridge equalization module. The control terminals of the second switch and the third switch are respectively connected to a first drive signal to synchronously control the second switch and the third switch; the control terminals of the first switch and the fourth switch are respectively connected to a second drive signal to synchronously control the first switch and the fourth switch; wherein, the first drive signal and the second drive signal are complementary, and the duty cycle of the first drive signal is 50%; during voltage balancing, the first switch and the second switch are alternately turned on, operating with a 50% duty cycle; The LC half-bridge equalization module includes an LC resonant unit composed of a second inductor and a first capacitor, and a half-bridge composed of a third switch and a fourth switch, used for voltage equalization between energy storage modules. During the voltage equalization process between energy storage modules, each energy storage module exchanges energy through the LC resonant unit and the half-bridge until the voltage of each energy storage module reaches the same level. The half-bridge composed of the first switch and the second switch, along with the first inductor, constitutes a Buck-Boost converter for voltage equalization within the energy storage module. During the voltage equalization process within the energy storage module, the two energy storage devices within each energy storage module adjust their voltages according to the volt-second balance principle through the Buck-Boost converter, achieving voltage equalization between the two energy storage devices.

2. The automatic balancing circuit for energy storage devices according to claim 1, characterized in that, The energy storage device includes at least a supercapacitor, a lithium-ion battery, and a sodium-ion battery.

3. The automatic balancing circuit for energy storage devices according to claim 1, characterized in that, The first terminal of the first energy storage device in the k-th energy storage module is connected to the second terminal of the second energy storage device in the (k-1)-th energy storage module after passing through a series equalization disable switch, where k is an integer from 2 to N.

4. The automatic balancing circuit for energy storage devices according to claim 1, characterized in that, The control terminals of the N-1 equalization disable switches are respectively connected to a third drive signal to synchronously control the N-1 equalization disable switches; the control terminals of the N equalization enable switches are respectively connected to a fourth drive signal to synchronously control the N equalization enable switches.

5. The automatic balancing circuit for energy storage devices according to claim 1, characterized in that, Based on the N short-circuited LC half-bridge equalization modules, charge transfer and redistribution are achieved through charging and discharging among the N energy storage modules, thereby balancing the state of charge of the N energy storage modules.

6. The automatic balancing circuit for energy storage devices according to claim 5, characterized in that, In the Buck-Boost converter, the first switch and the second switch are alternately turned on with a 50% duty cycle. Through the charging and discharging between the two energy storage devices inside each energy storage module, charge transfer and redistribution are achieved, and the state of charge of the two energy storage devices inside the energy storage module is balanced.

7. A control method for an automatic balancing circuit of an energy storage device, characterized in that, The automatic balancing circuit for energy storage devices according to any one of claims 1-6 includes: Close N-1 of the equalization disable switches and open N of the equalization enable switches to enter the equalization disable mode, so that 2N of the energy storage devices are connected in series and charged by an external power source or discharged by a load. Disconnect N-1 of the equalization disable switches, close N of the equalization enable switches, enter the equalization enable mode, perform state-of-charge equalization among N of the energy storage modules through N of the LC half-bridge equalization modules, and perform state-of-charge equalization between the two energy storage devices within each energy storage module through the Buck-Boost converter.

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