Balancing circuit, controller and energy storage system

Abstract

The present application relates to a balancing circuit, a controller and an energy storage system. The balancing circuit is used to connect 2N+1 batteries connected in series, where N≥1 and is an integer; the balancing circuit includes four unidirectional Buck-Boost circuits, two of which include the same common switch tube. Compared with the traditional balancing circuit, the number of switch tubes used can be reduced, thereby reducing the circuit cost. The four unidirectional Buck-Boost circuits are used to connect the positive and negative poles of at least some of the batteries. The four unidirectional Buck-Boost circuits are used to form a first dual transmission path when the voltage of the target battery is the lowest among the 2N+1 batteries, so as to simultaneously transmit the electric energy of each battery to the target battery, and to form a second dual transmission path when the voltage of the target battery is the highest among the 2N+1 batteries, so as to simultaneously transmit the electric energy of the target battery to each battery except the target battery. The balancing circuit of the present application can transmit energy through a dual transmission path when performing energy transmission, effectively shortening the path of electric energy transmission, fast balancing speed, and improved balancing efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of balancing control, and in particular to a balancing circuit, a controller and an energy storage system. Background Art

[0002] With the massive promotion of the new energy industry, the utilization of lithium iron phosphate batteries for energy storage is also increasing, but the voltage and capacity of lithium iron phosphate batteries cannot meet the actual application. In order to obtain a high enough voltage and sufficient capacity, the batteries need to be connected in series before use. However, in reality, there are inconsistencies between each lithium iron phosphate battery, which often leads to overcharging and over-discharging of a battery when the batteries are used in series, greatly reducing the life of the lithium iron phosphate battery, and in severe cases, causing safety accidents.

[0003] For existing equalization technologies, no matter whether a common typical capacitor equalization circuit, an inductor equalization circuit, a transformer equalization circuit or a traditional converter equalization circuit is used, there is a problem of a long power transmission path. Summary of the invention

[0004] Based on this, it is necessary to provide a balancing circuit, a controller and an energy storage system to address the problem of the long power transmission path of the above-mentioned existing balancing circuit.

[0005] In a first aspect, the present application provides a balancing circuit for connecting 2N+1 batteries connected in series, where N≥1 and is an integer; the balancing circuit comprises:

[0006] Four unidirectional Buck-Boost circuits, two of which include the same common switch tube and the same coupling inductor, the four unidirectional Buck-Boost circuits are used to connect the positive and negative electrodes of at least some of the batteries, the four unidirectional Buck-Boost circuits are used to form a first dual transmission path when the voltage of the target battery is the lowest among the 2N+1 batteries, so as to simultaneously transmit the electric energy of each battery to the target battery, and are used to form a second dual transmission path when the voltage of the target battery is the highest among the 2N+1 batteries, so as to simultaneously transmit the electric energy of the target battery to each battery except the target battery; the target battery is any battery except the first battery and the 2N+1 battery among the 2N+1 batteries.

[0007] In one embodiment, the four unidirectional Buck-Boost circuits are respectively a first unidirectional Buck-Boost circuit, a second unidirectional Buck-Boost circuit, a third unidirectional Buck-Boost circuit and a fourth unidirectional Buck-Boost circuit; the first unidirectional Buck-Boost circuit and the second unidirectional Buck-Boost circuit include the same common switch tube and the same coupled inductor;

[0008] The first end of the first unidirectional Buck-Boost circuit is used to connect the positive electrode of the first battery, and the first end of the coupled inductor is used as the second end of the first unidirectional Buck-Boost circuit to connect the positive electrode of the N+1th battery; the second end of the coupled inductor is used as the first end of the second unidirectional Buck-Boost circuit to connect the negative electrode of the 2N+1th battery, and the second end of the second unidirectional Buck-Boost circuit is used to connect the negative electrode of the N+1th battery; three different ends of the third unidirectional Buck-Boost circuit are used to respectively connect the positive and negative electrodes of the Nth battery and the negative electrode of the N+1th battery; three different ends of the fourth unidirectional Buck-Boost circuit are used to respectively connect the positive and negative electrodes of the N+2th battery and the positive electrode of the N+1th battery.

[0009] In one embodiment, the first unidirectional Buck-Boost circuit includes a first diode, a common switch tube and a coupled inductor; the second unidirectional Buck-Boost circuit includes a second diode, the common switch tube and the coupled inductor; the anode of the first diode is used to connect the positive electrode of the first battery, the cathode of the first diode is connected to the first end of the common switch tube and the third end of the coupled inductor, the first end of the coupled inductor is used to connect the positive electrode of the N+1th battery, the anode of the second diode is used to connect the negative electrode of the 2N+1th battery, the cathode of the second diode is connected to the second end of the common switch tube and the fourth end of the coupled inductor, and the second end of the coupled inductor is used to connect the negative electrode of the N+1th battery;

[0010] The third unidirectional Buck-Boost circuit includes a third diode, a first switch tube and a first inductor, wherein the anode of the third diode is used to connect the negative electrode of the N+1th battery, the cathode of the third diode is connected to the first end of the first inductor and the first end of the first switch tube, the second end of the first inductor is used to connect the negative electrode of the Nth battery and the positive electrode of the N+1th battery, and the second end of the first switch tube is used to connect the positive electrode of the Nth battery;

[0011] The fourth unidirectional Buck-Boost circuit includes a fourth diode, a second switch tube and a second inductor, the cathode of the fourth diode is used to connect the positive electrode of the N+1th battery, the anode of the fourth diode is connected to the first end of the second inductor and the first end of the second switch tube, the second end of the second inductor is used to connect the positive electrode of the N+2th battery and the negative electrode of the N+1th battery, and the second end of the second switch tube is used to connect the negative electrode of the N+2th battery.

[0012] In one embodiment, N>1; the balancing circuit further includes:

[0013] The bidirectional Buck-Boost module is used to connect the positive and negative electrodes of each battery respectively.

[0014] In one embodiment, the bidirectional Buck-Boost module includes:

[0015] N bidirectional Buck-Boost circuits, each of which is used to connect the positive and negative electrodes of two batteries except the N+1th battery, and the positive electrode of one of the two batteries is connected to the negative electrode of the other battery.

[0016] In one embodiment, the two batteries are a front-stage battery and a rear-stage battery, and the negative electrode of the front-stage battery is connected to the positive electrode of the rear-stage battery; each bidirectional Buck-Boost circuit includes a third switch tube, a fourth switch tube and a third inductor;

[0017] The first end of the third switch tube is used to connect the positive electrode of the preceding battery, the second end of the third switch tube is respectively connected to the first end of the third inductor and the first end of the fourth switch tube, the second end of the third inductor is used to connect the negative electrode of the preceding battery and the subsequent battery, and the second end of the fourth switch tube is used to connect the subsequent battery.

[0018] In a second aspect, the present application provides a controller connected to the above-mentioned balancing circuit; the controller is used to enable a first control strategy to control the balancing circuit when the voltage of the target battery is the lowest among the 2N+1 batteries, so that the balancing circuit forms a first dual transmission path;

[0019] The controller is further configured to enable, when the voltage of the target battery is the highest among the 2N+1 batteries, controlling the balancing circuit under a second control strategy so that the balancing circuit forms a second dual transmission path.

[0020] In one embodiment, the balancing circuit includes a first unidirectional Buck-Boost circuit, a second unidirectional Buck-Boost circuit, a third unidirectional Buck-Boost circuit, a fourth unidirectional Buck-Boost circuit and N bidirectional Buck-Boost circuits; the first unidirectional Buck-Boost circuit and the second unidirectional Buck-Boost circuit include the same common switch tube, the third unidirectional Buck-Boost circuit includes a first switch tube, the fourth unidirectional Buck-Boost circuit includes a second switch tube, and each bidirectional Buck-Boost circuit includes a third switch tube and a fourth switch tube; the first control strategy includes:

[0021] A first control signal with a preset duty cycle is output to each controlled end of the first switch tube, the second switch tube and the third switch tube in the bidirectional Buck-Boost circuit in the first part, a second control signal with the preset duty cycle is output to each controlled end of the fourth switch tube in the bidirectional Buck-Boost circuit in the second part, and a third control signal is output to the common switch tube to control the common switch tube to be continuously disconnected; the bidirectional Buck-Boost circuit in the first part includes N / 2 bidirectional Buck-Boost circuits connected to the first battery to the Nth battery; the bidirectional Buck-Boost circuit in the second part includes N / 2 bidirectional Buck-Boost circuits connected to the N+2th battery to the 2N+1th battery; the first control signal and the second control signal have opposite levels in the same time period.

[0022] In one embodiment, the balancing circuit includes a first unidirectional Buck-Boost circuit, a second unidirectional Buck-Boost circuit, a third unidirectional Buck-Boost circuit, a fourth unidirectional Buck-Boost circuit and N bidirectional Buck-Boost circuits, wherein the first unidirectional Buck-Boost circuit and the second unidirectional Buck-Boost circuit include the same common switch tube, the third unidirectional Buck-Boost circuit includes a first switch tube, the fourth unidirectional Buck-Boost circuit includes a second switch tube, and each bidirectional Buck-Boost circuit includes a third switch tube and a fourth switch tube; the second control strategy includes:

[0023] A third control signal is output to each controlled end of the first switch tube, the second switch tube, and the fourth switch tube in each of the bidirectional Buck-Boost circuits to control each of the switch tubes to be disconnected, and a first control signal with a preset duty cycle is output to the controlled end of the common switch tube.

[0024] In a third aspect, the present application provides an energy storage system, comprising:

[0025] 2N+1 batteries connected in series; N ≥ 1 and is an integer;

[0026] The balancing circuit as described above is connected to the 2N+1 batteries connected in series;

[0027] The controller as mentioned above is connected to the balancing circuit.

[0028] The above-mentioned balancing circuit, controller and energy storage system, the balancing circuit is used to connect 2N+1 batteries connected in series, N≥1 and is an integer; the balancing circuit includes four unidirectional Buck-Boost circuits, of which two Buck-Boost circuits include the same shared switch tube and the same coupled inductor. Compared with the traditional balancing circuit, the number of switches and inductors used can be reduced, thereby reducing the circuit cost. Four unidirectional Buck-Boost circuits are used to connect the positive and negative electrodes of at least some of the batteries. The four unidirectional Buck-Boost circuits are used to form a first dual transmission path when the voltage of the target battery is the lowest among the 2N+1 batteries, so as to simultaneously transmit the electric energy of each battery to the target battery, and to form a second dual transmission path when the voltage of the target battery is the highest among the 2N+1 batteries, so as to simultaneously transmit the electric energy of the target battery to each battery except the target battery. The target battery is any battery among the 2N+1 batteries except the first battery and the 2N+1 battery. Therefore, the balancing circuit of the present application can transmit energy through the dual transmission paths when transmitting energy, effectively shortening the path of electric energy transmission, fast balancing speed, and improved balancing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic diagram of the structure of an equalization circuit in an embodiment of the present application;

[0030] Figure 2 Schematic diagram of the structure of a bidirectional Buck-Boost module when N=6 in an embodiment of the present application;

[0031] Figure 3 This is a schematic diagram of operating waveforms when the balancing circuit performs balancing work under the control of the controller in an embodiment of the present application when the voltage of the N+1th battery is the lowest among the 2N+1 batteries;

[0032] Figure 4 Schematic diagram of the structure of the equalizing circuit in one embodiment of the present application when it is acted upon by the first control signal, the second control signal and the third control signal in the time period t0-t1;

[0033] Figure 5 Schematic diagram of the structure of the equalizing circuit in one embodiment of the present application when it is acted upon by the first control signal, the second control signal and the third control signal in the time period t1-t2;

[0034] Figure 6 This is a schematic diagram of operating waveforms when the balancing circuit performs balancing work under the control of the controller in an embodiment of the present application when the voltage of the N+1th battery is the highest among the 2N+1 batteries;

[0035] Figure 7Schematic diagram of the structure of the equalizing circuit in one embodiment of the present application when the equalizing circuit is acted upon by the first control signal and the third control signal in the time period t0-t1;

[0036] Figure 8 2 is a schematic diagram of the structure of the equalizing circuit in an embodiment of the present application when the equalizing circuit is acted upon by the first control signal and the third control signal in the time period t1 - t2 .

[0037] Description of Figure Numbers:

[0038] A first unidirectional Buck-Boost circuit: 111; a second unidirectional Buck-Boost circuit: 112; a third unidirectional Buck-Boost circuit: 113; a fourth unidirectional Buck-Boost circuit: 114; a fifth unidirectional Buck-Boost circuit: 115; a first bidirectional Buck-Boost circuit: 121; a third bidirectional Buck-Boost circuit: 123; a fourth bidirectional Buck-Boost circuit: 124; and a sixth bidirectional Buck-Boost circuit: 126. DETAILED DESCRIPTION

[0039] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0040] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0041] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0042] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0043] Each PACK (battery pack) in the energy storage system is composed of several groups of battery modules connected in series with copper bars. Each battery module is composed of multiple batteries connected in series. When the battery voltage in the module is inconsistent, the use of passive balancing circuits will cause energy waste and thermal management problems, and there is a problem of long balancing time required; for capacitor-type balancing circuits, typical circuits are such as multi-switch capacitor balancing topology. This type of balancing circuit mainly utilizes the energy storage characteristics of capacitors, uses capacitors as energy transfer carriers, adjusts switches according to voltage differences, and realizes energy flow between batteries. Its advantages are good consistency, high reliability and easy implementation. Its disadvantages are that its balancing characteristics based on voltage differences also cause certain limitations, and it is only suitable for some occasions where the balancing speed and accuracy requirements are not too high. For inductive balancing circuits, typical circuits are such as traditional bidirectional Buck-Boost topology. The biggest disadvantage of this type of balancing circuit is that when the number of batteries in series is large and there is an energy imbalance between the first and last batteries in the battery pack, the energy transfer path is long and the balancing time gradually becomes longer. For transformer-type balancing circuits, typical circuits are such as balancing topologies using multiple unidirectional single-output flyback converters. Although this type of balancing circuit has good electrical isolation and high safety, the equalizer uses more transformers, making the overall system larger and more expensive. The biggest disadvantage of the traditional bidirectional Cuk converter type balancing circuit is that when there are a large number of batteries in series, the number of inductors and switch tubes used in the battery is large, the volume is large, and when there is an energy imbalance between the first and last batteries in the battery pack, the energy transfer path is longer and the balancing time gradually becomes longer.

[0044] In addition, battery balancers can be divided into two forms: passive balancers and active balancers. Passive balance, also known as energy consumption balance, refers to the consumption of all excess energy in lithium battery cells in the form of heat. This balance method has large energy loss and low balance efficiency, so the passive balance scheme is not particularly ideal in practical applications. Active balance, as a non-energy consumption balance, refers to the transfer of energy through energy storage elements, thereby reducing the inconsistency of battery packs. It can basically meet the requirements of high balance efficiency, fast balance speed, and large balance current. Therefore, active balancers have been widely used. Active balancers can usually be classified according to the energy balance transmission method, which can be divided into capacitor-based balance circuits, inductor-based balance circuits, transformer-based balance circuits, and converter-based balance circuits. Among them, converter-based balance circuits have gradually become one of the key development directions of active balancers due to their good performance and high integration. Currently, the commonly used converter-based balance circuits are mainly divided into Cuk circuits, Boost circuits, Buck-Boost circuits, etc. The typical bidirectional Buck-Boost circuit balancing topology can only realize energy transfer between adjacent batteries. When it is used in large-scale lithium battery packs, the long-distance balancing process leads to unsatisfactory balancing speed and efficiency of lithium battery packs. In addition, the typical bidirectional Buck-Boost circuit uses more components, which makes the cost high.

[0045] The balancing circuit in the present application is applied to 2N+1 batteries connected in series, where N≥1 and is an integer. The order of the batteries in the "first battery", "Nth battery", etc. described in the present application corresponds to the order of the series connection. For example, see the attached Figure 1 , the negative electrode of battery B1 is connected to the positive electrode of battery B2, the negative electrode of battery B2 is connected to the positive electrode of battery B3, and the remaining batteries are connected in series in this way. The first battery is battery B1, the second battery is battery B2, the third battery is battery B3, and so on. The target battery described in the technical solution of this application is any battery in the 2N+1 batteries except the first battery and the 2N+1th battery.

[0046] In one embodiment, see Figure 1 , attached Figure 1 FIG. 1 shows a schematic diagram of the structure of an equalization circuit in an embodiment of the present application. The equalization circuit in this embodiment includes four unidirectional Buck-Boost circuits (the four unidirectional Buck-Boost circuits are shown in FIG. Figure 1 The reference numerals in the figure are 111, 112, 113, and 114 respectively), wherein two Buck-Boost circuits (a first Buck-Boost circuit 111 and a second Buck-Boost circuit 112) include the same common switch tube S g and the same coupling inductor L m, four unidirectional Buck-Boost circuits are used to connect the positive and negative electrodes of at least some of the batteries, and the four unidirectional Buck-Boost circuits are used to form a first dual transmission path when the voltage of the target battery is the lowest among the 2N+1 batteries, so as to simultaneously transmit the electric energy of each battery to the target battery, and to form a second dual transmission path when the voltage of the target battery is the highest among the 2N+1 batteries, so as to simultaneously transmit the electric energy of the target battery to each battery except the target battery.

[0047] It can be understood that the unidirectional Buck-Boost circuit includes at least a switch tube, a diode and an inductor. The switch tube is used to control the current flow in the circuit. Under the control of the PWM (Pulse Width Modulation) signal, the switch tube is alternately turned on and off at a certain frequency (related to the duty cycle of the PWM signal), thereby realizing the up and down conversion of the input voltage; the diode is used to prevent reverse current and ensure that the current can only flow in one direction. When the switch tube is turned off, the diode allows the inductor to release energy to the output end; the inductor is used to store energy. When the switch tube is turned on, the inductor stores energy, and when the switch tube is turned off, the inductor releases energy to the output end to achieve voltage up and down. In some cases, in order to smooth the output voltage, reduce voltage fluctuations and improve the stability of the circuit, a capacitor can also be connected in parallel at the output end. The switch tube of the Buck-Boost circuit can be various types of field effect transistors, such as bipolar junction transistor (BJT), metal-oxide-semiconductor field-effect transistor (MOSFET), insulated gate bipolar transistor (IGBT), Schottky diode, etc. g The two unidirectional Buck-Boost circuits are respectively a first unidirectional Buck-Boost circuit 111 and a second unidirectional Buck-Boost circuit 112 as an example for explanation. The two unidirectional Buck-Boost circuits include the same common switch tube S g It means that the switch tube constituting the first unidirectional Buck-Boost circuit 111 and the second unidirectional Buck-Boost circuit 112 is the same. mA first winding W1 and a second winding W2 are provided. The first winding W1 is used as an operating structure in a first unidirectional Buck-Boost circuit 111, and the second winding W2 is used as an operating structure in a second unidirectional Buck-Boost circuit 112. Therefore, the first unidirectional Buck-Boost circuit 111 and the second unidirectional Buck-Boost circuit 112 are connected through the same coupling inductor L. m The energy storage function of two unidirectional Buck-Boost circuits can be realized, so the balancing circuit of the present application can reduce the number of switches and inductors and reduce circuit costs.

[0048] The above-mentioned first dual transmission path refers to two transmission paths that are conductively connected to the target battery, and the power transmission directions of these two transmission paths are respectively a first direction and a second direction. The first direction is that the battery connected in series with the positive electrode of the target battery transmits power to the target battery, and the second direction is that the battery connected in series with the negative electrode of the target battery transmits power to the target battery. Exemplarily, when the voltage of the N+1th battery is the lowest among the 2N+1 batteries, the first dual transmission path can be used to simultaneously transmit the power of the batteries on both sides of the N+1th battery to the N+1th battery, and power transmission is performed over a shorter path, which speeds up the voltage balancing speed.

[0049] The above-mentioned second dual transmission path refers to two transmission paths that are conductively connected to the target battery, and the power transmission directions of these two transmission paths are the third direction and the fourth direction respectively. The third direction is that the target battery transmits power to the battery connected in series with the positive electrode of the target battery, and the second direction is that the target battery transmits power to the battery connected in series with the negative electrode of the target battery. Exemplarily, when the voltage of the N+1th battery is the highest among the 2N+1 batteries, the second dual transmission path can be used to simultaneously transmit the power of the N+1th battery to each battery on both sides of the N+1th battery, and power transmission through a shorter path is also achieved, thereby increasing the voltage balancing speed. Specifically, the first dual transmission path and the second dual transmission path can be formed by inputting control signals of different level states to the switch tubes in the four unidirectional Buck-Boost circuits to turn on or off the corresponding switch tubes.

[0050] Compared with the traditional balancing circuit, the balancing circuit in this embodiment has two Buck-Boost circuits including the same common switch tube S. g and the same coupling inductor L m , thus reducing the number of switches and inductors used and reducing circuit costs. In addition, the balancing circuit in this embodiment can form a first dual transmission path and a second dual transmission path when transmitting power. When the battery voltage is unbalanced, there is no need to transfer power between adjacent batteries step by step as in the traditional Buck-Boost circuit, which effectively shortens the power transmission path, increases the balancing speed, reduces energy loss, and improves the balancing efficiency.

[0051] In one embodiment, continue to refer to the attached Figure 1 The four unidirectional Buck-Boost circuits are respectively a first unidirectional Buck-Boost circuit 111, a second unidirectional Buck-Boost circuit 112, a third unidirectional Buck-Boost circuit 113 and a fourth unidirectional Buck-Boost circuit 114; the first unidirectional Buck-Boost circuit 111 and the second unidirectional Buck-Boost circuit 112 include the same common switch tube S g and the same coupling inductor L m The first end of the first unidirectional Buck-Boost circuit 111 is used to connect the positive electrode of the first battery B1, and the coupling inductor L m The first end of the first unidirectional Buck-Boost circuit 111 is used as the second end of the first unidirectional Buck-Boost circuit 111 to connect the N+1th battery B N+1 The positive electrode (with Figure 1 1, where the second end of the first unidirectional Buck-Boost circuit 111 is connected to the positive electrode of the second battery B2); coupled inductor L m The second end of the second unidirectional Buck-Boost circuit 112 is used as the first end of the second unidirectional Buck-Boost circuit 112 to connect the negative electrode of the 2N+1th battery (see Figure 1 1, where N=1. In this case, the first end of the second unidirectional Buck-Boost circuit 112 is connected to the negative electrode of the third battery B3. The second end of the second unidirectional Buck-Boost circuit 112 is used to connect the negative electrode of the N+1th battery (see FIG. Figure 1 1, in which case the second end of the second unidirectional Buck-Boost circuit 112 is used to connect the negative electrode of the second battery B2); the three different ends of the third unidirectional Buck-Boost circuit 113 are used to connect the positive and negative electrodes of the Nth battery and the negative electrode of the N+1th battery respectively (see FIG. Figure 1 The third unidirectional Buck-Boost circuit 113 has three different terminals connected to the positive and negative electrodes of the first battery B1 and the positive and negative electrodes of the second battery B2 respectively; the fourth unidirectional Buck-Boost circuit 114 has three different terminals connected to the positive and negative electrodes of the N+2th battery and the positive electrode of the N+1th battery respectively (see FIG. Figure 1 The fourth unidirectional Buck-Boost circuit 114 is shown to have three different terminals connected to the positive and negative electrodes of the second battery B2 and the positive and negative electrodes of the third battery B3, respectively.

[0052] Among them, Figure 1 The first unidirectional Buck-Boost circuit 111 includes a first diode D1, a common switch tube S g and coupled inductor Lm The second unidirectional Buck-Boost circuit 112 includes a second diode D2, a common switch tube S g and coupled inductor L m The anode of the first diode D1 is used to connect the positive electrode of the first battery B1, and the cathode of the first diode D1 is connected to the common switch tube S g The first end and the coupled inductor L m The third terminal of the coupled inductor L m The first end of the first inductor L1 is used to connect the positive electrode of the N+1th battery (attached Figure 1 The figure shows the case where N=1, where the coupled inductor L m The first end of the diode D2 is connected to the positive electrode of the second battery B2), and the anode of the second diode D2 is used to connect the negative electrode of the 2N+1th battery (attached Figure 1 The figure shows the case where N=1, in which the anode of the second diode D2 is connected to the negative electrode of the third battery B3), the cathode of the second diode D2 is connected to the common switch tube S g The second end and the coupled inductor L m The fourth end of the coupled inductor L m The second end is used to connect the negative electrode of the N+1th battery (attached Figure 1 The figure shows the case where N=1, where the coupled inductor L m The second end of the coupling inductor L is connected to the positive terminal of the third battery B3). m The first end is the same name end of the first winding W1, and the coupled inductor L m The second end of the second winding W2 is the same end, and the coupling inductor L m The third end is the opposite end of the first winding W1, and the coupling inductor L m The second end of the second winding W2 is the same end, and the coupling inductor L m The fourth end is the opposite end of the second winding W2.

[0053] The third unidirectional Buck-Boost circuit 113 includes a third diode D3, a first switch tube S1 and a first inductor L1. The anode of the third diode D3 is used to connect the negative electrode of the N+1th battery. The cathode of the third diode D3 is connected to the first end of the first inductor L1 and the first end of the first switch tube S1. The second end of the first inductor L1 is used to connect the negative electrode of the Nth battery and the positive electrode of the N+1th battery (see FIG. 2 ). Figure 1 The case where N=1 is shown, in which the second end of the first inductor L1 is used to connect the negative electrode of the first battery B1 and the positive electrode of the second battery B2), and the second end of the first switch tube S1 is used to connect the positive electrode of the Nth battery (see Figure 1). Figure 1 The case where N=1 is shown, in which the second end of the first switch tube S1 is used to connect the positive electrode of the first battery B1).

[0054] The fourth unidirectional Buck-Boost circuit includes a fourth diode D4, a second switch tube S2 and a second inductor L2. The cathode of the fourth diode D4 is used to connect the positive electrode of the N+1th battery (see Figure 1 1 shows the case where N=1, in which the cathode of the fourth diode D4 is used to connect the positive electrode of the second battery B2), the anode of the fourth diode D4 is connected to the first end of the second inductor L2 and the first end of the second switch tube D2, and the second end of the second inductor L2 is used to connect the positive electrode of the N+2th battery and the negative electrode of the N+1th battery (see FIG. Figure 1 The case where N=1 is shown, at this time, the second end of the second inductor L2 is used to connect the positive electrode of the third battery B3 and the negative electrode of the N+1th battery), and the second end of the second switch tube D2 is used to connect the negative electrode of the N+2th battery (see Figure 2). Figure 1 The case where N=1 is shown, in which the second end of the second switch tube D2 is used to connect the negative electrode of the third battery B3).

[0055] For example, N=1 is used as an example for explanation. At this time, the four unidirectional Buck-Boost circuits are connected to the positive and negative electrodes of each battery. Figure 1 Taking the voltage of the middle battery as the lowest among the three batteries as an example, at this time, the first switch tube S1 and the second switch tube S2 are alternately turned on and off under the action of the first control signal with a preset duty cycle, thereby forming a first dual transmission path. Taking the voltage of the middle battery as the lowest among the three batteries as an example, at this time, the first switch tube S1 and the second switch tube S2 are continuously turned off under the action of the third control signal, and the common switch tube S g Under the action of the first control signal of the preset duty cycle, the inductor is alternately turned on and off to form a second dual transmission path. It can be understood that in order to make the charging and discharging time of the inductor the same and achieve a better balancing effect, the preset duty cycle can be 50%.

[0056] In one embodiment, N>1, in this case, the balancing circuit includes not only four unidirectional Buck-Boost circuits but also a bidirectional Buck-Boost module, and the bidirectional Buck-Boost module is used to connect the positive and negative electrodes of each battery respectively.

[0057] The bidirectional Buck-Boost module includes N bidirectional Buck-Boost circuits, each of which is used to connect the positive and negative electrodes of two batteries except the N+1th battery, and the positive electrode of one of the two batteries is connected to the negative electrode of the other battery. The bidirectional Buck-Boost circuit can be a bidirectional Buck-Boost circuit with a coupled inductor, or a bidirectional Buck-Boost balancing circuit without a coupled inductor, a bidirectional Cuk balancing circuit, etc. The structure of the bidirectional balancing circuit is not limited in this application, as long as it can achieve the same function as the bidirectional Buck-Boost circuit in this application, that is, the bidirectional Buck-Boost circuit can be replaced by other balancing circuits that have completely different balancing principles but can achieve the same voltage between batteries.

[0058] For example, see the attached Figure 2 , attached Figure 2 The schematic diagram of the structure of the bidirectional Buck-Boost module when N=6 is shown, wherein the ellipsis indicates that the third battery B3, the fourth battery B4, and the tenth battery B 10 、Battery B 11 and a second bidirectional Buck-Boost circuit connected to the third battery B3 and the fourth battery B4 and a second bidirectional Buck-Boost circuit connected to the tenth battery B 10 、Battery B 11 The fifth bidirectional Buck-Boost circuit connected is explained by taking the two batteries connected to each bidirectional Buck-Boost circuit as the front-stage battery and the rear-stage battery as an example, wherein the front-stage battery refers to the one with a smaller sequence number in the series sequence, and the rear-stage battery refers to the one with a larger sequence number in the series sequence, as shown in the attached figure. Figure 2 In the example, the first battery B1, the third battery B3, the fifth battery B5, the eighth battery B8, the tenth battery B 10 , the twelfth battery B 12 The first battery is the second battery B2, the fourth battery B4, the sixth battery B6, the ninth battery B9, the eleventh battery B 11 、Thirteenth Battery B 13 For the rear battery.

[0059] Each bidirectional Buck-Boost circuit includes a third switch tube, a fourth switch tube and a third inductor; the first end of the third switch tube is used to connect the positive electrode of the preceding battery, the second end of the third switch tube is respectively connected to the first end of the third inductor and the first end of the fourth switch tube, the second end of the third inductor is used to connect the negative electrode of the preceding battery and the negative electrode of the succeeding battery, and the second end of the fourth switch tube is used to connect the negative electrode of the succeeding battery. Figure 2The first bidirectional Buck-Boost circuit 121 connected to the first battery B1 and the second battery B2 includes a switch tube S 11 , switch tube S 12 , inductor L3, switch tube S 11 The first end is connected to the positive electrode of the first battery B1, and the switch tube S 11 The second end of the inductor L3 is connected to the first end of the switch tube S 12 The first end of the inductor L3 is connected to the negative electrode of the first battery B1 and the positive electrode of the second battery B2, and the switch tube S 12 The second end of the second battery is connected to the negative electrode of the second battery B2, and so on. The third battery and the fourth battery are connected to the second bidirectional Buck-Boost circuit. The third bidirectional Buck-Boost circuit 123 connected to the fifth battery B5 and the sixth battery B6 includes a switch tube S 15 , switch tube S 16 , an inductor L5, and a fourth bidirectional Buck-Boost circuit 124 connected to the eighth battery B8 and the ninth battery B9 includes a switch tube S 18 , switch tube S 19 , inductor L6, connected to the tenth battery and the eleventh battery is the fifth bidirectional Buck-Boost circuit, connected to the twelfth battery B 12 and the thirteenth battery B 13 The sixth bidirectional Buck-Boost circuit 126 connected includes a switch tube S 22 , switch tube S 23 , inductor L8.

[0060] If the bidirectional Buck-Boost circuit in the present application adopts a coupled inductor, the inductor L3 and the inductor L5 are respectively the first winding and the second winding of a coupled inductor, the end of the inductor L3 connected to the negative electrode of the first battery B1 is the opposite end of the first winding, the other end of the inductor L3 is the same end of the first winding, the end of the inductor L5 connected to the negative electrode of the fifth battery B5 is the opposite end of the second winding, and the other end of the inductor L5 is the same end of the second winding; the inductor L6 and the inductor L8 are respectively the first winding and the second winding of another coupled inductor, the end of the inductor L6 connected to the negative electrode of the first battery B8 is the opposite end of the first winding, the other end of the inductor L6 is the same end of the first winding, and the inductor L8 is connected to the twelfth battery B 12One end of the negative electrode is connected to the opposite end of the second winding, and the other end of the inductor L8 is the same end of the second winding. The balancing circuit in this embodiment includes a bidirectional Buck-Boost circuit and a unidirectional Buck-Boost circuit. When the battery voltage is unbalanced, it is not necessary to transfer energy between adjacent batteries step by step like the traditional Buck-Boost circuit. For example, when the voltage of the middle battery is the lowest among all batteries, the first and last batteries simultaneously transfer electric energy to the middle battery. When the voltage of the middle battery is the highest among all batteries, the middle battery simultaneously transfers electric energy to the first and last batteries, which greatly shortens the energy transfer path, reduces energy loss, and improves the balancing speed. At the same time, the balancing circuit does not require a complex control strategy in terms of control strategy. It only needs to perform open-loop control on the switch tubes in the bidirectional Buck-Boost circuit and the unidirectional Buck-Boost circuit, which reduces the occurrence of control error rate. And it can realize that two balancing circuits with different structures participate in balancing at the same time without affecting each other, which can achieve consistency between battery cells more quickly and effectively and eliminate differences.

[0061] In one embodiment, a controller is provided. The controller in this embodiment is connected to the balancing circuit in any of the above embodiments, and is used to perform the following balancing circuit control method: when the voltage of the target battery is the lowest among the 2N+1 batteries, the first control strategy is enabled to control the balancing circuit so that the balancing circuit forms a first dual transmission path; when the voltage of the target battery is the highest among the 2N+1 batteries, the second control strategy is enabled to control the balancing circuit so that the balancing circuit forms a second dual transmission path.

[0062] Wherein, the controller can be a server or a terminal. When the controller is a server, it includes a processor, a memory, an input / output interface (Input / Output, referred to as I / O) and a communication interface. Wherein, the processor, the memory and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. Wherein, the processor of the controller is used to provide computing and control capabilities. The memory of the controller includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the controller is used to store the voltage of each battery and data related to the first control strategy and the second control strategy. The input / output interface of the controller is used to exchange information between the processor and an external device. The communication interface of the controller is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, when the voltage of the target battery is the lowest among the 2N+1 batteries, the first control strategy is enabled to control the balancing circuit so that the balancing circuit forms a first dual transmission path; when the voltage of the target battery is the highest among the 2N+1 batteries, the second control strategy is enabled to control the balancing circuit so that the balancing circuit forms a second dual transmission path.

[0063] Those skilled in the art will appreciate that the above structural description of the controller does not constitute a limitation on the computer device to which the present application is applied, and a specific controller may include more or fewer components, or combine certain components, or have a different arrangement of components.

[0064] In one embodiment, the balancing circuit includes a first unidirectional Buck-Boost circuit, a second unidirectional Buck-Boost circuit, a third unidirectional Buck-Boost circuit, a fourth unidirectional Buck-Boost circuit and N bidirectional Buck-Boost circuits; the first unidirectional Buck-Boost circuit and the second unidirectional Buck-Boost circuit include the same common switch tube, the third unidirectional Buck-Boost circuit includes a first switch tube, the fourth unidirectional Buck-Boost circuit includes a second switch tube, and each bidirectional Buck-Boost circuit includes a third switch tube and a fourth switch tube; the first control strategy includes: providing a first switch tube, a second switch tube and a first part of the bidirectional Buck-Boost circuits with a first common switch tube; Each controlled end of the third switch tube in the oost circuit outputs a first control signal with a preset duty cycle, outputs a second control signal with a preset duty cycle to the common switch tube and each controlled end of the fourth switch tube in the second part of the bidirectional Buck-Boost circuit, and outputs a third control signal to the common switch tube to control the common switch tube to be continuously disconnected; the first part of the bidirectional Buck-Boost circuit includes N / 2 bidirectional Buck-Boost circuits connected to the first battery to the Nth battery; the second part of the bidirectional Buck-Boost circuit includes N / 2 bidirectional Buck-Boost circuits connected to the N+2th battery to the 2N+1th battery; the first control signal and the second control signal have opposite levels in the same time period.

[0065] See attached Figure 3 FIG. 1 is a schematic diagram of operating waveforms of the balancing circuit when performing balancing under the control of the controller when the voltage of the N+1th battery is the lowest among the 2N+1 batteries, wherein x1(t) is the waveform of the first control signal, x2(t) is the waveform of the second control signal, x3(t) is the waveform of the third control signal, and U L To remove the coupling inductance L m The voltage waveform across any inductor, i L is the current flowing through the decoupling inductor L m The current waveform of any external inductor, T is the switching period of the switch tube.

[0066] Take N=6 as an example for explanation. Figure 4 The schematic diagram of the structure of the equalizing circuit shown in FIG. 1 is a schematic diagram of the structure of the equalizing circuit when the first control signal, the second control signal and the third control signal are applied during the time period t0-t1. At this time, the first switch tube S1, the second switch tube S2 and the third switch tube (i.e., the attached) in the first part of the bidirectional Buck-Boost circuit are Figure 4 The switch tube S 11 , switch tube S 15 , switch tube S 19 And switch tube S 23The switch tube S is omitted. 13 And switch tube S 21 ) is turned on, the common switch tube S g , the fourth switch in the second part of the bidirectional Buck-Boost circuit (i.e. Figure 4 The switch tube S 12 , switch tube S 16 , switch tube S 18 And switch tube S 22 The switch tube S is omitted. 14 And switch tube S 22 ) is disconnected, where the dotted line indicates that the circuit is disconnected. At this time, the inductor L3 and the first battery B1 form a loop, the inductor L5 and the fifth battery B5 form a loop, the inductor L1 and the sixth battery B6 form a loop, the inductor L2 and the eighth battery B8 form a loop, the inductor L6 and the ninth battery B9 form a loop, and the inductor L8 and the thirteenth battery B 13 To form a circuit, there are also Figure 4 The omitted inductor L4 forms a loop with the third battery B3, and the inductor L7 forms a loop with the eleventh battery B 11 The inductors in each circuit begin to store energy, and the direction of the current flowing through each inductor is as follows: Figure 4 Indicated by the arrow.

[0067] See attached Figure 5 The structural diagram of the equalizing circuit shown in FIG. 1 is a schematic diagram of a structure when the first control signal, the second control signal and the third control signal are applied during the time period t1-t2 (t0~t2=T). At this time, the common switch tube S g , the first switch tube S1, the second switch tube S2 and the third switch tube (i.e., the attached Figure 5 The switch tube S 11 , switch tube S 15 , switch tube S 19 And switch tube S 23 The switch tube S is omitted. 13 And switch tube S 21 ) is disconnected, and the fourth switch tube (i.e., the attached Figure 5 The switch tube S 12 , switch tube S 16 , switch tube S 18 And switch tube S 22 The switch tube S is omitted. 14 And switch tube S 22) is turned on, where the dotted line indicates that the circuit is disconnected. At this time, the inductor L3 and the second battery B2 form a loop, the inductor L5 and the sixth battery B6 form a loop, the inductor L1 and the inductor L2 form a loop with the seventh battery B7, the inductor L6 and the eighth battery B8 form a loop, and the inductor L8 and the twelfth battery B 12 To form a circuit, there are also Figure 4 The omitted inductor L4 forms a loop with the fourth battery B4, and the inductor L7 forms a loop with the tenth battery B 10 The inductors in each loop begin to discharge outward, so that each battery transmits electric energy to the seventh battery B7. At this time, one of the first bidirectional transmission paths is that the inductor L3 and the second battery B2 form a loop, the inductor L4 and the fourth battery B4 form a loop, the inductor L5 and the sixth battery B6 form a loop, and the inductor L2 and the seventh battery B7 form a loop. The first direction is attached Figure 5 The i with an arrow L3 、i L5 、i L2 and omitted i L4 ,i L4 with i L3 、i L5 、i L2 The second first bidirectional transmission path is a loop formed by the inductor L1 and the seventh battery B7, a loop formed by the inductor L6 and the eighth battery B8, and a loop formed by the inductor L7 and the tenth battery B 10 The circuit is formed, the inductor L8 and the twelfth battery B 12 The second direction is attached Figure 5 The i with an arrow L1 、i L6 、i L8 and omitted i L7 ,i L7 with i L1 、i L6 、i L8 same).

[0068] In one embodiment, the balancing circuit includes a first unidirectional Buck-Boost circuit, a second unidirectional Buck-Boost circuit, a third unidirectional Buck-Boost circuit, a fourth unidirectional Buck-Boost circuit and N bidirectional Buck-Boost circuits, wherein the first unidirectional Buck-Boost circuit and the second unidirectional Buck-Boost circuit include the same common switch tube, the third unidirectional Buck-Boost circuit includes a first switch tube, the fourth unidirectional Buck-Boost circuit includes a second switch tube, and each bidirectional Buck-Boost circuit includes a third switch tube and a fourth switch tube; the second control strategy includes: outputting a third control signal to each controlled end of the first switch tube, the second switch tube, and the fourth switch tube in each bidirectional Buck-Boost circuit to control each switch tube to be disconnected, and at the same time outputting a first control signal with a preset duty cycle to the controlled end of the common switch tube.

[0069] See attached Figure 6 FIG. 1 is a schematic diagram of operating waveforms of the balancing circuit when performing balancing under the control of the controller when the voltage of the N+1th battery is the highest among the 2N+1 batteries, wherein x1(t) is a waveform diagram of the first control signal, x3(t) is a waveform diagram of the third control signal, and U L To remove the coupling inductance L m The voltage waveform across any inductor, i L is the current flowing through the decoupling inductor L m The current waveform of any external inductor, T is the switching period of the switch tube.

[0070] Take N=6 as an example for explanation. Figure 7 The structure diagram of the equalizing circuit shown in FIG. 1 is a schematic diagram of the structure of the equalizing circuit when the first control signal and the third control signal are applied during the time period t0-t1. At this time, the first switch tube S1, the second switch tube S2 and all the switch tubes in each bidirectional Buck-Boost circuit are disconnected, and the common switch tube S g The dotted line indicates that the circuit is disconnected. At this time, the coupled inductor L m The seventh battery B7 forms a loop, and the seventh battery B7 is coupled to the inductor L m Discharge, coupled inductor L m Energy storage begins, and the direction of the current flowing through each inductor is as follows Figure 7 Indicated by the arrow.

[0071] See attached Figure 8 The schematic diagram of the structure of the equalizing circuit shown in FIG. 1 is a schematic diagram of the structure of the equalizing circuit when the first control signal and the third control signal are applied during the time period t1-t2 (t0~t2=T). At this time, the common switch tube S g, the first switch tube S1, the second switch tube S2 and all the switch tubes in each bidirectional Buck-Boost circuit are disconnected, wherein the dotted line indicates that the circuit is disconnected. At this time, the coupling inductor L m The first winding W1 and the first battery B1, the second battery B2, ..., the sixth battery B6 form a loop (that is, one of the second dual transmission paths, the third direction is the additional Figure 8 The arrow i W1 ), coupled inductor L m The second winding W2 of the eighth battery B8, the ninth battery B9, ..., the thirteenth battery B 13 The loop is formed (that is, the second dual transmission path, the third direction is the additional Figure 8 The arrow i W2 ), at this time the seventh battery B7 transmits electric energy to other batteries except the seventh battery B7.

[0072] In one embodiment, an energy storage system is provided. The energy storage system in this embodiment includes 2N+1 batteries connected in series, the balancing circuit in any of the above embodiments, and the controller in any of the above embodiments; wherein N≥1 and is an integer; the balancing circuit is connected to the 2N+1 batteries connected in series, and the controller is connected to the balancing circuit.

[0073] A person of ordinary skill in the art can understand that all or part of the processes executed by the controller of the above-mentioned embodiment can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited to this. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, an artificial intelligence (AI) processor, etc., but are not limited to this.

[0074] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0075] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the application. It should be noted that, for a person of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. An equalization circuit, characterized in that: Used to connect 2N+1 batteries in series, N≥1 and is an integer; the balancing circuit includes: Four unidirectional Buck-Boost circuits, two of which are respectively a first unidirectional Buck-Boost circuit and a second unidirectional Buck-Boost circuit; the first unidirectional Buck-Boost circuit and the second unidirectional Buck-Boost circuit include a same common switch tube and a same coupled inductor; The first end of the first unidirectional Buck-Boost circuit is used to connect the positive electrode of the first battery, and the second end of the first unidirectional Buck-Boost circuit is used to connect the positive electrode of the N+1th battery; the first end of the second unidirectional Buck-Boost circuit is used to connect the negative electrode of the 2N+1th battery, and the second end of the second unidirectional Buck-Boost circuit is used to connect the negative electrode of the N+1th battery; The four unidirectional Buck-Boost circuits are used to form a first dual transmission path when the voltage of the target battery is the lowest among the 2N+1 batteries, so as to simultaneously transmit the electric energy of each battery to the target battery, and to form a second dual transmission path when the voltage of the target battery is the highest among the 2N+1 batteries, so as to simultaneously transmit the electric energy of the target battery to each battery except the target battery; the target battery is any battery among the 2N+1 batteries except the first battery and the 2N+1 battery.

2. The equalization circuit according to claim 1, characterized in that: The four unidirectional Buck-Boost circuits are respectively a first unidirectional Buck-Boost circuit, a second unidirectional Buck-Boost circuit, a third unidirectional Buck-Boost circuit and a fourth unidirectional Buck-Boost circuit; The first end of the first unidirectional Buck-Boost circuit is used to connect the positive electrode of the first battery, and the first end of the coupled inductor is used as the second end of the first unidirectional Buck-Boost circuit to connect the positive electrode of the N+1th battery; the second end of the coupled inductor is used as the first end of the second unidirectional Buck-Boost circuit to connect the negative electrode of the 2N+1th battery, and the second end of the second unidirectional Buck-Boost circuit is used to connect the negative electrode of the N+1th battery; three different ends of the third unidirectional Buck-Boost circuit are used to respectively connect the positive and negative electrodes of the Nth battery and the negative electrode of the N+1th battery; three different ends of the fourth unidirectional Buck-Boost circuit are used to respectively connect the positive and negative electrodes of the N+2th battery and the positive electrode of the N+1th battery.

3. The equalizing circuit according to claim 2, characterized in that: The first unidirectional Buck-Boost circuit includes a first diode, a common switch tube and a coupled inductor; the second unidirectional Buck-Boost circuit includes a second diode, the common switch tube and the coupled inductor; the anode of the first diode is used to connect the positive electrode of the first battery, the cathode of the first diode is connected to the first end of the common switch tube and the third end of the coupled inductor, the first end of the coupled inductor is used to connect the positive electrode of the N+1th battery, the anode of the second diode is used to connect the negative electrode of the 2N+1th battery, the cathode of the second diode is connected to the second end of the common switch tube and the fourth end of the coupled inductor, and the second end of the coupled inductor is used to connect the negative electrode of the N+1th battery; The third unidirectional Buck-Boost circuit includes a third diode, a first switch tube and a first inductor, wherein the anode of the third diode is used to connect the negative electrode of the N+1th battery, the cathode of the third diode is connected to the first end of the first inductor and the first end of the first switch tube, the second end of the first inductor is used to connect the negative electrode of the Nth battery and the positive electrode of the N+1th battery, and the second end of the first switch tube is used to connect the positive electrode of the Nth battery; The fourth unidirectional Buck-Boost circuit includes a fourth diode, a second switch tube and a second inductor, the cathode of the fourth diode is used to connect the positive electrode of the N+1th battery, the anode of the fourth diode is connected to the first end of the second inductor and the first end of the second switch tube, the second end of the second inductor is used to connect the positive electrode of the N+2th battery and the negative electrode of the N+1th battery, and the second end of the second switch tube is used to connect the negative electrode of the N+2th battery.

4. The equalization circuit according to claim 1 or 2, characterized in that: N>1; the balancing circuit further includes: The bidirectional Buck-Boost module is used to connect the positive and negative electrodes of each battery respectively.

5. The equalizing circuit according to claim 4, characterized in that: The bidirectional Buck-Boost module includes: N bidirectional Buck-Boost circuits, each of which is used to connect the positive and negative electrodes of two batteries except the N+1th battery, and the positive electrode of one of the two batteries is connected to the negative electrode of the other battery.

6. The equalizing circuit according to claim 5, characterized in that: The two batteries are a front-stage battery and a rear-stage battery, and the negative electrode of the front-stage battery is connected to the positive electrode of the rear-stage battery; each bidirectional Buck-Boost circuit includes a third switch tube, a fourth switch tube and a third inductor; The first end of the third switch tube is used to connect the positive electrode of the preceding battery, the second end of the third switch tube is respectively connected to the first end of the third inductor and the first end of the fourth switch tube, the second end of the third inductor is used to connect the negative electrode of the preceding battery and the subsequent battery, and the second end of the fourth switch tube is used to connect the subsequent battery.

7. A controller, characterized in that: Connected to the balancing circuit according to any one of claims 1 to 6; the controller is used to enable a first control strategy to control the balancing circuit when the voltage of the target battery is the lowest among the 2N+1 batteries, so that the balancing circuit forms a first dual transmission path; The controller is further configured to enable, when the voltage of the target battery is the highest among the 2N+1 batteries, controlling the balancing circuit under a second control strategy so that the balancing circuit forms a second dual transmission path.

8. The controller according to claim 7, characterized in that: The equalization circuit includes a first unidirectional Buck-Boost circuit, a second unidirectional Buck-Boost circuit, a third unidirectional Buck-Boost circuit, a fourth unidirectional Buck-Boost circuit and N bidirectional Buck-Boost circuits; the first unidirectional Buck-Boost circuit and the second unidirectional Buck-Boost circuit include the same common switch tube, the third unidirectional Buck-Boost circuit includes a first switch tube, the fourth unidirectional Buck-Boost circuit includes a second switch tube, and each bidirectional Buck-Boost circuit includes a third switch tube and a fourth switch tube; the first control strategy includes: A first control signal with a preset duty cycle is output to each controlled end of the first switch tube, the second switch tube and the third switch tube in the bidirectional Buck-Boost circuit in the first part, a second control signal with the preset duty cycle is output to each controlled end of the fourth switch tube in the bidirectional Buck-Boost circuit in the second part, and a third control signal is output to the common switch tube to control the common switch tube to be continuously disconnected; the bidirectional Buck-Boost circuit in the first part includes N / 2 bidirectional Buck-Boost circuits connected to the first battery to the Nth battery; the bidirectional Buck-Boost circuit in the second part includes N / 2 bidirectional Buck-Boost circuits connected to the N+2th battery to the 2N+1th battery; the first control signal and the second control signal have opposite levels in the same time period.

9. The controller according to claim 7, characterized in that: The equalization circuit includes a first unidirectional Buck-Boost circuit, a second unidirectional Buck-Boost circuit, a third unidirectional Buck-Boost circuit, a fourth unidirectional Buck-Boost circuit and N bidirectional Buck-Boost circuits, wherein the first unidirectional Buck-Boost circuit and the second unidirectional Buck-Boost circuit include the same common switch tube, the third unidirectional Buck-Boost circuit includes a first switch tube, the fourth unidirectional Buck-Boost circuit includes a second switch tube, and each bidirectional Buck-Boost circuit includes a third switch tube and a fourth switch tube; the second control strategy includes: A third control signal is output to each controlled end of the first switch tube, the second switch tube, and the fourth switch tube in each of the bidirectional Buck-Boost circuits to control each of the switch tubes to be disconnected, and a first control signal with a preset duty cycle is output to the controlled end of the common switch tube.

10. An energy storage system, characterized in that: include: 2N+1 batteries connected in series; N ≥ 1 and is an integer; The balancing circuit according to any one of claims 1 to 6, connected to the 2N+1 batteries connected in series; The controller according to any one of claims 7 to 9, connected to the balancing circuit.

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