Battery energy storage system equalization device and equalization method based on reconfigurable transformer

Abstract

The application discloses a battery energy storage system equalization device and equalization method based on a reconfigurable transformer, and belongs to the technical field of battery management. The device comprises a battery pack formed by N single batteries in series, a switch array, a reconfigurable transformer, a current monitoring circuit, an SOC monitoring circuit and a control circuit, N>=1, each single battery is connected with an input end of the SOC monitoring circuit, the switch array comprises 2N gating switches, two ends of each single battery are respectively configured with a gating switch, and the reconfigurable transformer and the input end of the current monitoring circuit are connected through the gating switches configured at the two ends, and a secondary side of the reconfigurable transformer is connected with two ends of the battery pack; the control circuit is connected with the reconfigurable transformer, the reconfigurable transformer has at least two circuit structures, and the two circuit structures correspond to different gains; and the control circuit is also connected with an output end of the SOC monitoring circuit, an output end of the current monitoring circuit and the switch array.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery management, in particular, relates to a long-series battery pack equalization device and equalization method in a battery energy storage system, and more particularly relates to a battery energy storage system equalization device and equalization method based on a reconfigurable converter. BACKGROUND

[0002] In a battery energy storage system, an electric vehicle, and other high-power application scenarios, single batteries are often constructed into a battery pack in a long-series manner to participate in energy storage and transmission. However, due to the characteristic differences between the single batteries and the unbalanced performance in the charging and discharging process, the long-series battery pack is prone to have an unbalanced problem, and this problem will further intensify as the battery energy storage system ages. This imbalance not only significantly affects the overall performance and service life of the battery pack, reduces the charging and discharging efficiency of the energy storage system, but also may cause serious safety hazards, such as fire and explosion. Therefore, it is particularly important to use a battery equalization technology to perform equalization management on the battery pack.

[0003] At present, a more common method is to use a DC / DC converter and a switch array to form an active equalization circuit to perform equalization operation on the long-series battery pack. The switch array is responsible for selecting the equalization single battery, and according to the designed equalization algorithm, different single batteries are selected to access the DC / DC converter. The primary side of the DC / DC converter accesses the switch array, and the secondary side accesses both ends of the series battery pack, and is responsible for balancing the electric quantity of each single battery. In the above scheme, the structure of the DC / DC converter is fixed, which leads to a fixed gain, and thus cannot be applied to the equalization of different numbers of single batteries, which leads to the existing equalization system having the problems of large loss, low equalization efficiency, and slow equalization speed. SUMMARY

[0004] The application provides a battery energy storage system equalization device and equalization method based on a reconfigurable converter. The equalization device adds a reconfigurable converter, and can switch the circuit structure of the reconfigurable converter according to the number of single batteries to be equalized, so as to be applicable to the equalization of different numbers of single batteries, and match appropriate conversion circuits for different numbers of single batteries, so as to improve the system equalization efficiency.

[0005] The technical solutions adopted by the application are as follows:

[0006] The first aspect of the application provides a battery energy storage system equalization device based on a reconfigurable converter. The equalization device includes a battery pack, a switch array, a reconfigurable converter, a current monitoring circuit, an SOC monitoring circuit, and a control circuit, wherein:

[0007] The battery pack is formed by N single batteries in series, N≥1, each single battery is connected with the input end of the SOC monitoring circuit, the switch array includes 2N gating switches, and one gating switch is arranged at both ends of each single battery and connects the primary side of the reconfigurable transformer and the input end of the current monitoring circuit through the gating switches arranged at both ends, and the secondary side of the reconfigurable transformer is connected with both ends of the battery pack; the control circuit is connected with the reconfigurable transformer, the reconfigurable transformer has at least two circuit structures, and the two circuit structures correspond to different gains respectively;

[0008] The control circuit is also connected with the output end of the SOC monitoring circuit, the output end of the current monitoring circuit and the switch array, and the control circuit first determines the single battery to be balanced according to the output signal of the SOC monitoring circuit, then drives the switch array to connect the corresponding single battery to the primary side of the reconfigurable transformer and the input end of the current monitoring circuit, and drives the reconfigurable transformer to switch to the circuit structure corresponding to the number of connected single batteries.

[0009] In some examples, the control circuit includes a microcontroller and a driving circuit connected with the microcontroller, and the driving circuit is connected with the reconfigurable transformer, and the driving circuit can drive the reconfigurable transformer to switch between at least two different gain circuit structures based on the instruction of the microcontroller;

[0010] The microcontroller is connected with the output end of the SOC monitoring circuit, the output end of the current monitoring circuit and the switch array, and the microcontroller first determines the single battery to be balanced according to the output signal of the SOC monitoring circuit, then drives the switch array to connect the corresponding single battery to the primary side of the reconfigurable transformer and the input end of the current monitoring circuit, and drives the reconfigurable transformer to switch to the circuit structure corresponding to the number of connected single batteries.

[0011] In some examples, the reconfigurable transformer includes:

[0012] A cascade transformer;

[0013] A primary full-bridge circuit includes a first primary half-bridge circuit formed by a first primary switch tube, a fifth primary switch tube and a second primary switch tube connected in series, and a second primary half-bridge circuit formed by a third primary switch tube and a fourth primary switch tube connected in series, and the first primary half-bridge circuit and the second primary half-bridge circuit are connected in parallel with a first capacitor, the first primary switch tube and the fifth primary switch tube are connected to both ends of the low-voltage side of the cascade transformer through a second capacitor and a third capacitor respectively, the third primary switch tube and the fourth primary switch tube are connected with the primary center tap of the cascade transformer, and

[0014] The secondary side full-bridge circuit comprises a first secondary side half-bridge circuit formed by a first secondary side switch tube and a second secondary side switch tube in series, and a second secondary side half-bridge circuit formed by a third secondary side switch tube and a fourth secondary side switch tube in series, and the first secondary side half-bridge circuit and the second secondary side half-bridge circuit are connected in parallel with a fourth capacitor and a fifth capacitor in series, the first secondary side switch tube and the second secondary side switch tube are connected to the same end of the high-voltage side of the cascade transformer through a first inductor, the third secondary side switch tube and the fourth secondary side switch tube are connected to the non-same end of the high-voltage side of the cascade transformer through a second inductor, and the fourth capacitor and the fifth capacitor are connected to the center tap of the secondary side of the cascade transformer.

[0015] In some examples, the cascade transformer is formed by cascading two transformers, and the turns ratio of each of the two transformers is 1:n.

[0016] In some examples, the first inductor and the second inductor are AC clamping inductors, and each is formed by connecting an external inductor and a leakage inductor of the cascade transformer in series.

[0017] The second aspect of the present application provides a battery energy storage system equalization method based on a reconfigurable transformer, which is based on the battery energy storage system equalization device as above, and comprises the following steps:

[0018] Determining the single battery to be equalized and the state of each single battery in the battery pack according to the output signal of the SOC monitoring circuit;

[0019] Controlling the switch array to connect the single battery to be equalized in the same state to the primary side of the reconfigurable transformer and the input end of the current monitoring circuit;

[0020] Switching the circuit structure of the reconfigurable transformer according to the number of connected single batteries, and determining the equalization working mode according to the state of the connected single batteries, wherein the equalization working mode comprises a charging equalization mode and a discharging equalization mode; and

[0021] Implementing battery equalization in the corresponding equalization working mode.

[0022] In some examples, the step of determining the single battery to be equalized and the state of each single battery in the battery pack according to the output signal of the SOC monitoring circuit comprises:

[0023] Monitoring the SOC parameters of each single battery in the battery pack in real time using the SOC monitoring circuit;

[0024] Calculating the average value of the SOC parameters of all single batteries in the battery pack;

[0025] calculating a difference between the SOC parameter of each single battery and the average value, and determining whether the difference exceeds a preset equalization threshold;

[0026] If yes, the corresponding single battery is determined as a single battery to be equalized, and whether the difference between the SOC parameter of the corresponding single battery and the average value is positive or not is determined.

[0027] If yes, the state of the corresponding single battery is determined as an overcharge state.

[0028] If no, the state of the corresponding single battery is determined as an undercharge state.

[0029] In some examples, the same state is an overcharge state or an undercharge state, and when the same state is an overcharge state, the equalization operation mode determined according to the state of the accessed single battery is a discharge equalization mode, and when the same state is an undercharge state, the equalization operation mode determined according to the state of the accessed single battery is a charge equalization mode.

[0030] In some examples, the reconfigurable transformer has a first transformation circuit structure, a second transformation circuit structure, a third transformation circuit structure, and a fourth transformation circuit structure, and the gain of the fourth transformation circuit structure is greater than the gain of the third transformation circuit structure, the gain of the third transformation circuit structure is greater than the gain of the second transformation circuit structure and the gain of the first transformation circuit structure.

[0031] In some examples, the battery pack is formed by N single batteries in series, N≥1, and when the number of single batteries to be equalized is less than 0.2N, the circuit structure of the reconfigurable transformer is switched to the fourth transformation circuit structure, when the number of single batteries to be equalized is greater than 0.8N, the circuit structure of the reconfigurable transformer is switched to the gain of the second transformation circuit structure or the first transformation circuit structure, and when the number of single batteries to be equalized is between 0.2N and 0.8N, the circuit structure of the reconfigurable transformer is switched to the third transformation circuit structure.

[0032] The reconfigurable transformer involved in the present application has a switchable circuit structure, which can be switched to different gain modes according to the number of single batteries to be equalized each time, so that the voltage gain required for matching the voltage of the equalized battery to the voltage of the battery pack can be achieved when equalizing different numbers of single batteries, thereby reducing transformer loss, improving equalization efficiency, and shortening equalization time. In addition, the reconfigurable transformer greatly improves the reliability and efficiency of the overall system compared to the fixed structure, and is particularly suitable for equalization management of long series battery packs in high-power scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1is a schematic diagram of a battery energy storage system equalization device based on a reconfigurable transformer provided by an embodiment of the present application;

[0034] Figure 2 is a first working circuit structure of a reconfigurable transformer provided by an embodiment of the present application;

[0035] Figure 3 is a second working circuit structure of a reconfigurable transformer provided by an embodiment of the present application;

[0036] Figure 4 is a third working circuit structure of a reconfigurable transformer provided by an embodiment of the present application;

[0037] Figure 5 is a fourth working circuit structure of a reconfigurable transformer provided by an embodiment of the present application;

[0038] Figure 6 is a schematic diagram of equalization for a single battery in an overcharged state provided by an embodiment of the present application;

[0039] Figure 7 is a schematic diagram of equalization for a single battery in an undercharged state provided by an embodiment of the present application;

[0040] Figure 8 is a schematic diagram of equalization for two batteries in an overcharged state provided by an embodiment of the present application;

[0041] Figure 9 is a schematic diagram of equalization for two batteries in an undercharged state provided by an embodiment of the present application;

[0042] Figure 10 is a schematic diagram of equalization for four batteries in an overcharged state provided by an embodiment of the present application;

[0043] Figure 11 is a schematic diagram of equalization for four batteries in an undercharged state provided by an embodiment of the present application;

[0044] Figure 12 is a flowchart of a battery energy storage system equalization method based on a reconfigurable transformer provided by an embodiment of the present application. DETAILED DESCRIPTION

[0045] The embodiments described below with reference to the drawings are exemplary and are only used to explain the present application, and cannot be explained as a limitation of the present application.

[0046] Figure 1 is a schematic diagram of a battery energy storage system equalization device based on a reconfigurable transformer provided by an embodiment of the present application, Figures 2 to 5are four different working circuit structures of the reconfigurable converter provided by the embodiment of the present application (see the black solid line). In each figure, B1, B2, …, B n represents a single battery, S c11 represents a single battery, S c12 represents a single battery, S c21 represents a single battery, S c22 represents a single battery, S cn1 represents a single battery, S cn2 represents a single battery, S p1 represents a single battery, S p2 represents a single battery, S p3 represents a single battery, S p4 represents a single battery, S p5 represents a primary side switch tube, S s1 represents a primary side switch tube, S s2 represents a primary side switch tube, S s3 represents a primary side switch tube, S s4 represents a secondary side switch tube, L s1 represents a secondary side switch tube, L s2 represents an inductor, T1, T2 represent a transformer, 1:n is a turns ratio of the transformer. a, b, c, d, e, f represent circuit nodes, V LV is a low voltage side voltage of the converter, used for connecting a long series battery pack; V HV is a high voltage side voltage of the converter

[0047] In combination with Figures 1 to 5 shown, the embodiment provides a battery energy storage system equalization device based on a reconfigurable converter, which comprises a battery pack, a switch array, a reconfigurable converter, a current monitoring circuit, an SOC monitoring circuit and a control circuit, wherein the SOC monitoring circuit is used to monitor the SOC parameter (State of Charge, state of charge of the battery) of each single battery in the battery pack, and the current monitoring circuit is used to monitor the current of the battery energy storage system equalization device during equalization operation. The following will introduce the battery pack, the switch array, the reconfigurable converter and the control circuit, and the connection and functions thereof with the SOC monitoring circuit and the control circuit.

[0048] Battery pack

[0049] The battery pack is formed by N single batteries in series, N≥1, as shown in Figure 1 a single battery B1, a single battery B2, …, a single battery B n a single battery B1, a single battery B2, …, a single battery B n Each of the single batteries B1, B2, …, B

[0050] Switch array

[0051] The switch array includes 2N gating switches, such as Figure 1 The indicated selector switch S c11 S-switch c12 Select switch S c21 S-switch c22 ..., Strobe switch S cn1 S-switch cn2 Furthermore, each of the aforementioned individual cells is equipped with a selector switch at each of its two ends, and each individual cell is connected to the primary side of the reconfigurable converter and the input of the current monitoring circuit via the selector switches configured at its two ends. For example, individual cell B1 is connected to the primary side of the reconfigurable converter and the input of the current monitoring circuit via the selector switches configured at its two ends. c11 and gating switch S c12 Connected to the primary side and the input of the current monitoring circuit of the reconfigurable converter, the single cell B2 is controlled by a gating switch S configured at its two ends. c21 and gating switch S c22 Connected to the primary side of the reconfigurable converter and the input of the current monitoring circuit... Single cell B n By using the gating switches S configured at both ends cn1 and gating switch S cn2 Connect to the primary side of the reconfigurable converter and the input terminal of the current monitoring circuit.

[0052] Reconfigurable transformer

[0053] The secondary side of the reconfigurable converter is connected to both ends of the battery pack. The reconfigurable converter has at least two operating circuit structures, and the reconfigurable converter has different gains when the two operating circuit structures are operating in a balanced manner. For example, Figure 1 The schematic reconfigurable converter has Figure 2 , Figure 3 , Figure 4 , Figure 5 The diagram shows four different operating circuit structures, each with a different gain.

[0054] Control circuit

[0055] The control circuit is connected with the reconfigurable converter, and the control circuit is also connected with an output end of the SOC monitoring circuit, an output end of the current monitoring circuit and the switch array. The SOC monitoring circuit collects the SOC parameters of each single battery and transmits the collected SOC parameters to the control circuit. The current monitoring circuit monitors the working current of the equalization device. The switch array is controlled by the control circuit. The control circuit first determines the single battery to be equalized according to the output signal of the SOC monitoring circuit, and then drives the switch array to make the corresponding gating switch be on or off, so as to connect the corresponding single battery to the primary side of the reconfigurable converter and the input end of the current monitoring circuit, and drive the reconfigurable converter to switch to the working circuit structure corresponding to the number of connected single batteries, and the connected single battery is equalized under the corresponding working circuit structure.

[0056] The existing equalization device generally adopts a fixed structure type converter, such as a flyback converter, a Buck-Boost converter and the like. These converters cannot switch the working structure and can only work in a fixed gain mode, that is, only when a specific number of single batteries is equalized, the equalization efficiency and speed are high, and the loss is controlled at a low level. With the use and continuous aging of the battery energy storage system, the number of single batteries that need to be equalized is not fixed. When the number of single batteries to be equalized changes, the equalization efficiency and speed of the existing equalization device become low.

[0057] Compared with the existing equalization device, the reconfigurable converter adopted in the embodiment can switch the working circuit structure according to the number of single batteries to be equalized to adapt to the needs of equalization operation of different numbers of single batteries, thereby improving the equalization efficiency. For example, when the number of single batteries to be equalized is smaller, the reconfigurable converter switches to a higher gain working circuit structure to efficiently complete the battery equalization. Moreover, the embodiment can realize simultaneous equalization of multiple single batteries, greatly accelerating the equalization speed of the battery energy storage system.

[0058] In some examples, in conjunction with Figure 1As shown, the control circuit above includes a microcontroller and a drive circuit connected to the microcontroller. The drive circuit is connected to the reconfigurable converter. The microcontroller is easy to program and design to execute the required instructions and algorithms. It can also control the drive circuit to perform corresponding actions through instructions generated by the microcontroller. Specifically, the drive circuit can drive the reconfigurable converter to switch between at least two different gain operating circuit structures based on the instructions of the microcontroller. In this way, the microcontroller can easily switch the operating circuit structure of the reconfigurable converter according to the number of individual cells to be balanced. The microcontroller is connected to the output terminal of the SOC monitoring circuit, the output terminal of the current monitoring circuit, and the switch array. The microcontroller first determines the individual cells to be balanced according to the output signal of the SOC monitoring circuit, and then drives the switch array to connect the corresponding individual cells to the primary side of the reconfigurable converter and the input terminal of the current monitoring circuit, and drives the reconfigurable converter to switch to the circuit structure corresponding to the number of individual cells connected.

[0059] Combination Figures 1 to 5 As shown, in some examples, the reconfigurable transformer includes:

[0060] A cascaded transformer, for example, is formed by cascading a first transformer T1 and a second transformer T2, with the turns ratio of the two transformers being 1:n, for example, 1≤n≤5;

[0061] The primary-side full-bridge circuit includes a first primary-side switch S. p1 Fifth primary-side switch S p5 Second primary-side switch S p2 The first primary-side half-bridge circuit connected in series, and the third primary-side switch S p3 Fourth primary-side switch S p4 The second primary-side half-bridge circuit is connected in series, and the first and second primary-side half-bridge circuits are connected in parallel with the first capacitor C1. The first primary-side switching transistor S... p1 With the fifth primary-side switch S p5 Between (point a in the diagram), the fifth primary-side switch S p5 With the second primary-side switch S p2 The points between them (point c in the diagram) are connected to the low-voltage side V of the cascaded transformer via the second capacitor C2 and the third capacitor C3, respectively. LV At both ends, the third primary-side switch S p3 Fourth primary-side switch S p4 The connection between (point b in the diagram) and the center tap of the primary side of the cascaded transformer; and,

[0062] The secondary-side full-bridge circuit includes a first secondary-side switching transistor S. s1 Second auxiliary switch S s2 The first secondary half-bridge circuit formed by series connection, and the third secondary switching transistor Ss3 , the fourth auxiliary side switch S s4 The second auxiliary side half-bridge circuit is formed in series, and the first auxiliary side half-bridge circuit and the second auxiliary side half-bridge circuit are connected in parallel with the series-connected fourth capacitor C4 and fifth capacitor C5, and the first auxiliary side switch S s1 and the second auxiliary side switch S s2 between (d point shown in the figure) through the first inductor L s1 is connected to the same end of the high-voltage side V HV of the cascade transformer, and the third auxiliary side switch S s3 and the fourth auxiliary side switch S s4 between (f point shown in the figure) through the second inductor L s2 is connected to the non-same end of the high-voltage side V HV of the cascade transformer, and the two fourth capacitors C4 are connected (e point shown in the figure) with the center tap of the auxiliary side of the cascade transformer.

[0063] And the first primary side switch S p1 , the second primary side switch S p2 , the third primary side switch S p3 , the fourth primary side switch S p4 , the fifth primary side switch S p5 , the first auxiliary side switch S s1 , the second auxiliary side switch S s2 , the third auxiliary side switch S s3 , and the fourth auxiliary side switch S s4 are connected with the driving circuit and controlled by the driving circuit to realize switching between the on and off states.

[0064] In this embodiment, the low-voltage side of the reconfigurable transformer is formed by two half-bridge circuits in parallel, the first bridge arm is composed of three power switches (the first auxiliary side switch S p1 , the fifth auxiliary side switch S p5 , and the second auxiliary side switch S p2 ) in series, and the midpoint of each two power switches is connected to the primary winding of the cascade transformer; the second bridge arm is composed of two power switches (the third auxiliary side switch S p3 , and the fourth auxiliary side switch S p4) series, two power switch midpoint connected to the center tap of the cascade transformer. The high voltage side of the reconfigurable converter is composed of two half-bridge circuits in parallel, the midpoint of each bridge arm is connected to the secondary winding of the cascade transformer. This embodiment is based on the reconfigurable converter, which can achieve multiple voltage gain while reducing the turns ratio of the transformer, helping to reduce transformer loss. In this embodiment, the PWM signal generated by the microcontroller controls the conduction of each switch tube through the drive circuit, so as to realize the switching of the working circuit structure of the reconfigurable converter. In some examples, the first inductor and the second inductor are ac clamping inductors, and are formed by the leakage inductance of the cascade transformer and an external inductor in series.

[0065] Figures 6 to 11 The number of single batteries connected to the access equalization circuit is 1, 2, and 4, respectively.

[0066] When the number of batteries that need to be balanced is 1, the reconfigurable converter switches to the high-gain working circuit structure when working in equalization (corresponding to Figure 5 ). Referring to Figure 6 , at this time, the drive signal of the secondary side of the reconfigurable converter lags behind the drive signal of the primary side of the reconfigurable converter, and the energy of the overcharged battery in the battery pack is released to the entire long series battery pack (assuming that the single battery B1 is in an overcharged state). Single battery B1 is connected to the primary side of the reconfigurable converter through gating switch S c11 , gating switch S c12 , and the SOC parameter of the single overcharged battery is balanced to the average value through the discharge of the reconfigurable converter. Referring to Figure 7 , at this time, the drive signal of the secondary side of the reconfigurable converter leads the drive signal of the primary side of the reconfigurable converter, and the energy of the battery pack is transmitted to the undercharged battery (assuming that the single battery B1 is in an undercharged state). Single battery B1 is connected to the primary side of the reconfigurable converter through gating switch S c11 , gating switch S c12 , and the SOC parameter of the single undercharged battery is balanced to the average value through the charging of the reconfigurable converter.

[0067] When the number of batteries that need to be balanced is two, the reconfigurable converter switches to the medium-gain working circuit structure when working in equalization. Referring to Figure 8 , at this time, the drive signal of the secondary side of the reconfigurable converter lags behind the drive signal of the primary side of the reconfigurable converter, and the energy of the overcharged battery in the battery pack is released to the entire long series battery pack (assuming that the single battery B1 and the single battery B2 are in an overcharged state). Single battery B1, single battery B2 are connected to the primary side of the reconfigurable converter through gating switch S c11 , gating switch S c12 , gating switch S c21 , gating switch S c22Connect to the primary side of the reconfigurable transformer, through the discharge of the reconfigurable transformer, the SOC parameters of two overcharged batteries are balanced to the average value. Referring to Figure 9 , at this time the drive signal of the secondary side of the reconfigurable transformer leads the drive signal of the primary side of the reconfigurable transformer, the energy of the battery pack is transmitted to the undercharged battery (assuming that the single battery B1 and the single battery B2 are in the undercharged state), the single battery B1 and the single battery B2 pass through the gating switch S c11 , the gating switch S c12 , the gating switch S c21 , the gating switch S c22 Connect to the primary side of the reconfigurable transformer, through the discharge of the reconfigurable transformer, the SOC parameters of two overcharged batteries are balanced to the average value. Referring to

[0068] When the number of batteries that need to be balanced is four, the reconfigurable transformer switches to the low-gain working circuit structure when balancing, referring to Figure 10 and Figure 11 . Specifically, referring to Figure 10 , at this time the drive signal of the secondary side of the reconfigurable transformer lags behind the drive signal of the primary side of the reconfigurable transformer, the energy of the overcharged battery in the battery pack is released to the entire long series battery pack (assuming that the single battery B1, the single battery B2, the single battery B3 and the single battery B4 are in the overcharged state), the single battery B1, the single battery B2, the single battery B3 and the single battery B4 pass through the gating switch S c11 , the gating switch S c12 , the gating switch S c21 , the gating switch S c22 , the gating switch S c31 , the gating switch S c32 , the gating switch S c41 , the gating switch S c42 Connect to the primary side of the reconfigurable transformer, through the discharge of the reconfigurable transformer, the SOC parameters of two overcharged batteries are balanced to the average value. Referring to Figure 11 , at this time the drive signal of the secondary side of the reconfigurable transformer leads the drive signal of the primary side of the reconfigurable transformer, the energy of the battery pack is transmitted to the undercharged battery (assuming that the single battery B1, the single battery B2, the single battery B3 and the single battery B4 are in the undercharged state) single battery B1, single battery B2, single battery B3 and single battery B4 pass through the gating switch S c11 , the gating switch S c12 , the gating switch S c21 , the gating switch S c22 , the gating switch S c31 , the gating switch S c32 , the gating switch S c41 , the gating switch S c42The primary side of the reconfigurable transformer is connected to the four undercharged batteries, and the SOC parameters of the four undercharged batteries are balanced to an average value through charging of the reconfigurable transformer.

[0069] Figure 12 FIG. 1 is a flowchart of a battery energy storage system balancing method based on a reconfigurable transformer according to an embodiment of the present application.

[0070] Referring to Figure 12 , and in combination with Figures 1 to 11 , the present application also provides a battery energy storage system balancing method based on a reconfigurable transformer. The balancing method is based on the above battery energy storage system balancing device. The balancing method comprises the following steps S10 to S40, wherein:

[0071] Step S10: determining the single battery to be balanced and the state of each single battery in the battery pack according to the output signal of the SOC monitoring circuit;

[0072] Step S20: controlling the switch array to connect the single battery to be balanced in the same state to the primary side of the reconfigurable transformer and the input end of the current monitoring circuit;

[0073] Step S30: switching the working circuit structure of the reconfigurable transformer according to the number of connected single batteries, and determining the balancing working mode according to the state of the connected single battery. The balancing working mode includes charging balancing mode and discharging balancing mode; and,

[0074] Step S40: implementing battery balancing in the corresponding balancing working mode.

[0075] The method of the present embodiment can switch the working circuit structure of the reconfigurable transformer according to the number of single batteries to be balanced connected to the balancing circuit, so that the reconfigurable transformer is always in a high-efficiency operating state, greatly improving the stability and efficiency of the battery energy storage system balancing device. Specifically, the method of the present embodiment uses the reconfigurable transformer with switchable working circuit structure to enable the reconfigurable transformer to switch different gain modes according to the number of single batteries to be balanced each time, and the fewer the number of single batteries to be balanced, the higher the gain mode in which the transformer operates, while ensuring a low transformer turns ratio, significantly reducing transformer loss, improving balancing efficiency, and shortening balancing time. In addition, the reconfigurable transformer greatly improves the reliability and efficiency of the system compared to the fixed structure transformer, and is particularly suitable for balancing management of long series battery packs in high-power scenarios.

[0076] In some examples, the step of determining the single battery to be balanced and the state of each single battery in the battery pack according to the output signal of the SOC monitoring circuit described in the above embodiment comprises:

[0077] The SOC monitoring circuit is used to monitor the SOC parameters of each single battery in the battery pack in real time, for example, the SOC parameters of each single battery are sampled to realize real-time monitoring;

[0078] The average value of the SOC parameters of all single batteries in the battery pack is calculated by using the received sampling values;

[0079] The difference between the SOC parameter of each single battery and the average value is calculated, and it is determined whether the difference exceeds a preset balancing threshold;

[0080] If yes, the corresponding single battery is determined as a single battery to be balanced, and it is also determined whether the difference between the SOC parameter of the corresponding single battery and the average value is positive, or whether the SOC parameter of the corresponding single battery is greater than the average value;

[0081] If yes, the state of the corresponding single battery is determined as an overcharged state;

[0082] If no, the state of the corresponding single battery is determined as an undercharged state.

[0083] In this example, the SOC parameters of each single battery in the battery energy storage system are monitored in real time, and the single battery to be balanced and the state are determined based on the SOC parameters, so that the number of single batteries to be balanced can be calculated, the reconfigurable converter can be switched to the corresponding working circuit structure during balancing, and the balancing mode can be determined according to the state of the single battery to be balanced, and then real-time battery balancing is realized in the corresponding balancing mode.

[0084] In some examples, the same state is an overcharged state or an undercharged state, and when the same state is an overcharged state, the balancing working mode determined according to the state of the accessed single battery is a discharging balancing mode, so that the energy of the single battery in the overcharged state is released to the long-series connected battery pack to realize discharging of the single battery, and through the discharging process, the SOC parameter of the single battery in the overcharged state is balanced to the average value; and when the same state is an undercharged state, the balancing working mode determined according to the state of the accessed single battery is a charging balancing mode, so that the energy of the long-series connected battery pack is transmitted to the single battery in the undercharged state to realize charging of the single battery, and through the charging process, the SOC parameter of the single battery in the undercharged state is balanced to the average value.

[0085] In some examples, the reconfigurable converter has a first conversion circuit structure, a second conversion circuit structure, a third conversion circuit structure, and a fourth conversion circuit structure, and the gain of the fourth conversion circuit structure is greater than the gain of the third conversion circuit structure, the gain of the third conversion circuit structure is greater than the gain of the second conversion circuit structure and the gain of the first conversion circuit structure.

[0086] In some examples, the battery pack is formed by N single batteries in series, N≥1, and when the number of single batteries to be balanced is less than 0.2N, the circuit structure of the reconfigurable transformer is switched to the fourth conversion circuit structure, when the number of single batteries to be balanced is greater than 0.8N, the circuit structure of the reconfigurable transformer is switched to the second conversion circuit structure or the first conversion circuit structure, and when the number of single batteries to be balanced is between 0.2N and 0.8N, the circuit structure of the reconfigurable transformer is switched to the third conversion circuit structure. N can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and so on. Exemplarily, N can be 10.

[0087] The reconfigurable transformer involved in the present application has a switchable circuit structure, which can be switched to different gain modes according to the number of single batteries to be balanced each time, so that high voltage gain can be achieved when balancing different numbers of single batteries, transformer loss is reduced, balancing efficiency is improved, and balancing time is shortened. In addition, the reconfigurable transformer greatly improves the reliability and efficiency of the overall system compared with the fixed structure, and is particularly suitable for balancing management of long series battery packs in high-power scenarios.

[0088] The above embodiments shown in the drawings detail the structure, features and effects of the present application. The above description is only the preferred embodiment of the present application, but the present application is not limited by the drawings. Any changes or modifications made in accordance with the concept of the present application, or equivalent embodiments with equivalent changes, are still within the scope of the present application.

Claims

1. A reconfigurable transformer based battery energy storage system equalization device, characterized in that, The battery pack, the switch array, the reconfigurable transformer, the current monitoring circuit, the SOC monitoring circuit and the control circuit, wherein: The battery pack is formed by N single batteries in series, N≥1, each single battery is connected with the input end of the SOC monitoring circuit, the switch array includes 2N gating switches, and each single battery is configured with one gating switch at both ends and connected with the primary side of the reconfigurable transformer and the input end of the current monitoring circuit through the gating switches at both ends, and the secondary side of the reconfigurable transformer is connected with both ends of the battery pack; the control circuit is connected with the reconfigurable transformer, the reconfigurable transformer has at least two circuit structures, and the two circuit structures correspond to different gains respectively; The control circuit is also connected with the output end of the SOC monitoring circuit, the output end of the current monitoring circuit and the switch array, and the control circuit first determines the single battery to be balanced according to the output signal of the SOC monitoring circuit, then drives the switch array to connect the corresponding single battery to the primary side of the reconfigurable transformer and the input end of the current monitoring circuit, and drives the reconfigurable transformer to switch to the circuit structure corresponding to the number of connected single batteries; The reconfigurable transformer includes: A cascade transformer; A primary side full bridge circuit including a first primary side half bridge circuit formed by a first primary side switch tube, a fifth primary side switch tube and a second primary side switch tube connected in series, and a second primary side half bridge circuit formed by a third primary side switch tube and a fourth primary side switch tube connected in series, and the first primary side half bridge circuit and the second primary side half bridge circuit are connected in parallel with a first capacitor, the first primary side switch tube and the fifth primary side switch tube are connected to both ends of the low voltage side of the cascade transformer through a second capacitor and a third capacitor respectively, and the third primary side switch tube and the fourth primary side switch tube are connected with the primary side center tap of the cascade transformer; and A secondary side full bridge circuit including a first secondary side half bridge circuit formed by a first secondary side switch tube and a second secondary side switch tube connected in series, and a second secondary side half bridge circuit formed by a third secondary side switch tube and a fourth secondary side switch tube connected in series, and the first secondary side half bridge circuit and the second secondary side half bridge circuit are connected in parallel with a fourth capacitor and a fifth capacitor connected in series, the first secondary side switch tube and the second secondary side switch tube are connected to the same end of the high voltage side of the cascade transformer through a first inductor, the third secondary side switch tube and the fourth secondary side switch tube are connected to the non-same end of the high voltage side of the cascade transformer through a second inductor, and the fourth capacitor and the fifth capacitor are connected with the secondary side center tap of the cascade transformer.

2. The battery energy storage system equalization apparatus of claim 1, wherein, The control circuit includes a microcontroller and a driving circuit connected with the microcontroller, and the driving circuit is connected with the reconfigurable transformer, and the driving circuit can drive the reconfigurable transformer to switch between at least two different gain circuit structures based on the instruction of the microcontroller. The microcontroller is connected with the output end of the SOC monitoring circuit, the output end of the current monitoring circuit and the switch array, and the microcontroller determines the single battery to be balanced according to the output signal of the SOC monitoring circuit, drives the switch array to connect the corresponding single battery to the primary side of the reconfigurable transformer and the input end of the current monitoring circuit, and drives the reconfigurable transformer to switch to the circuit structure corresponding to the number of connected single batteries.

3. The battery energy storage system equalization apparatus of claim 1, wherein, The cascade transformer is formed by cascading two transformers, and the turns ratio of the two transformers is 1:n.

4. The battery energy storage system equalization apparatus of claim 1, wherein, The first inductor and the second inductor are AC clamping inductors, and are formed by connecting the leakage inductance of the cascade transformer and an external inductor in series.

5. A battery energy storage system equalization method based on reconfigurable transformer, the equalization method is based on the battery energy storage system equalization device of claim 1, characterized in that, The method comprises the following steps: determining the single battery to be balanced and the state of each single battery in the battery pack according to the output signal of the SOC monitoring circuit; controlling the switch array to connect the single batteries to be balanced in the same state to the primary side of the reconfigurable transformer and the input end of the current monitoring circuit; switching the circuit structure of the reconfigurable transformer according to the number of connected single batteries, and determining the balancing mode according to the state of the connected single batteries, wherein the balancing mode comprises a charging balancing mode and a discharging balancing mode; and implementing battery balancing in the corresponding balancing mode.

6. The battery energy storage system equalization method of claim 5, wherein, The step of determining the single battery to be balanced and the state of each single battery in the battery pack according to the output signal of the SOC monitoring circuit comprises: monitoring the SOC parameter of each single battery in the battery pack in real time by using the SOC monitoring circuit; calculating the average value of the SOC parameters of all single batteries in the battery pack; calculating the difference between the SOC parameter of each single battery and the average value, and determining whether the difference exceeds a preset balancing threshold; if yes, determining the corresponding single battery as the single battery to be balanced, and determining whether the difference between the SOC parameter of the corresponding single battery and the average value is positive; if yes, determining the state of the corresponding single battery as the overcharged state; if no, determining the state of the corresponding single battery as the undercharged state.

7. The battery energy storage system equalization method of claim 6, wherein, The same state is the overcharged state or the undercharged state, and when the same state is the overcharged state, the balancing mode determined according to the state of the connected single battery is the discharging balancing mode, and when the same state is the undercharged state, the balancing mode determined according to the state of the connected single battery is the charging balancing mode.

8. The battery energy storage system equalization method of claim 6, wherein: The reconfigurable transformer has a first transformation circuit structure, a second transformation circuit structure, a third transformation circuit structure and a fourth transformation circuit structure, and the gain of the fourth transformation circuit structure is greater than the gain of the third transformation circuit structure, the gain of the third transformation circuit structure is greater than the gain of the second transformation circuit structure and the gain of the first transformation circuit structure.

9. The battery energy storage system equalization method of claim 8, wherein, The battery pack is formed by N single batteries in series, N≥1, and when the number of single batteries to be balanced is less than 0.2N, the circuit structure of the reconfigurable converter is switched to the fourth conversion circuit structure, when the number of single batteries to be balanced is greater than 0.8N, the circuit structure of the reconfigurable converter is switched to the gain of the second conversion circuit structure or the first conversion circuit structure, and when the number of single batteries to be balanced is between 0.2N and 0.8N, the circuit structure of the reconfigurable converter is switched to the third conversion circuit structure.

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