Control method of modularized multi-level battery energy storage system, medium and device

Abstract

The invention discloses a control method of a modular multilevel battery energy storage system, a medium and a device, the system comprises X phases, each phase comprises Y bridge arms, the bridge arms in each phase are connected in parallel, each bridge arm is formed by series connection of sub-module battery units with the same number, and when the voltages between the bridge arms are not equal, the sub-module battery units are connected in parallel. The method comprises the steps that the actual value of the X-th phase circulation is obtained, and the actual value of the circulation is used for representing the size of the circulation flowing through the X-th phase; obtaining a direct current component of the X-th phase to obtain a circulating current direct current quantity reference value, and obtaining a reference component of the X-th phase to obtain a circulating current base frequency reference value; subtracting a ring current reference value from the ring current actual value to obtain a ring current difference value, the ring current reference value being the sum of the direct current component of the Xth phase and the reference component of the Xth phase; a correction signal is obtained at least based on the circulating current difference value, and the correction signal is used for correcting the output voltage of the sub-module battery unit, so that the circulating current difference value approaches zero.

Description

Technical Field

[0001] The present application relates to the field of energy storage, and in particular to a control method, medium and device for a modular multi-level battery energy storage system. Background Art

[0002] In existing energy storage systems, since there are often differences in voltage levels between phases and bridge arms within the system, these imbalances will lead to circulating currents. Circulating currents will not only increase system losses and reduce energy efficiency, but may also have an adverse effect on system stability, leading to unbalanced charging and discharging of battery cells and shortening their service life.

[0003] Traditional voltage balancing control methods are difficult to accurately adjust these voltage deviations, resulting in difficulty in effectively suppressing circulating currents, further increasing the complexity of system design and maintenance.

[0004] Accordingly, the art needs a new control solution for energy storage systems to solve the above problems. Summary of the invention

[0005] In order to overcome the above-mentioned defects, the present invention is proposed to provide a solution or at least partially solve the technical problem that the circulating current is difficult to effectively suppress in the prior art.

[0006] In a first aspect, the present invention provides a control method for a modular multi-level battery energy storage system, wherein the system comprises X phases, wherein each phase comprises Y bridge arms, the bridge arms in each phase are connected in parallel, and each bridge arm is composed of the same number of submodule battery units connected in series, and when the voltages between the bridge arms are unequal, a circulating current is induced in the system, and the method comprises: obtaining an actual value of the circulating current of the Xth phase, wherein the actual value of the circulating current is used to characterize the magnitude of the circulating current flowing through the Xth phase; obtaining a DC component of the Xth phase to obtain a DC reference value of the circulating current, and obtaining a reference component of the Xth phase to obtain a base frequency reference value of the circulating current, wherein the DC component of the Xth phase is used to characterize the magnitude of the circulating current flowing through the Xth phase; obtaining a DC component of the Xth phase to obtain a DC reference value of the circulating current, and obtaining ... The value is used to characterize the deviation between the voltage level of the Xth phase and the voltage level of the overall system, and the circulating current base frequency reference value is used to characterize the voltage deviation between different bridge arms in the same phase; the circulating current actual value is subtracted from the circulating current reference value to obtain a circulating current difference value, the circulating current reference value is the sum of the DC component of the Xth phase and the reference component of the Xth phase, and the circulating current reference value is used to characterize the value of the circulating current caused by the voltage deviation between the phase and the system and between different bridge arms in the same phase; at least based on the circulating current difference value, a correction signal is obtained, wherein the correction signal is used to correct the output voltage of the submodule battery unit so that the circulating current difference value approaches 0.

[0007] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the correction signal is obtained at least based on the circulating current difference, including: obtaining a first voltage value Uxyz and a first average voltage value Uxy, wherein the first voltage value is used to characterize the voltage value of the first sub-module battery cell located in the X-th phase and the Y-th bridge arm, and the first average voltage value Uxy is used to characterize the average value of the voltages of each sub-module battery cell on the X-th phase and the Y-th bridge arm; based on the first average voltage value Uxy and the first voltage value, obtaining a sub-module correction reference value, and the sub-module correction reference value is used to adjust the input or output power of the first sub-module battery cell; based on the circulating current difference and the sub-module correction reference value, obtaining a correction signal.

[0008] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the DC component of the Xth phase is calculated to obtain a circulating DC reference value, including: obtaining a second average voltage value Ubess and a third average voltage value Ux, wherein the second average voltage value Ubess is obtained by averaging the voltages Uxyz of each sub-module battery cell and is used to characterize the average value of the voltages of all sub-module battery cells, and the third average voltage value Ux is used to characterize the average value of the voltages of each sub-module battery cell on the Xth phase; at least the second average voltage value and the third average voltage value are subtracted, and the obtained difference is adjusted by a first proportional regulator to obtain a circulating DC reference value.

[0009] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, each phase is composed of two upper and lower bridge arms, and the reference component of the Xth phase is calculated to obtain the circulating current base frequency reference value, including: obtaining a fourth average voltage Uxp and a fifth average voltage Uxn, wherein the fourth average voltage Uxp is used to characterize the average voltage of each sub-module battery unit in the upper bridge arm, and the fifth average voltage Uxn is used to characterize the average voltage of each sub-module battery unit in the lower bridge arm; subtracting the fourth average voltage Uxp from the fifth average voltage Uxn to obtain a voltage difference between the bridge arms, processing the voltage difference between the bridge arms by a proportional regulator, and performing a phase synchronization operation with the Xth phase to obtain the circulating current base frequency reference value.

[0010] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the submodule correction reference value is obtained based on the first average voltage value Uxy and the first voltage value, including: subtracting the first average voltage value Uxy from the first voltage value Uxyz to obtain the voltage difference in the bridge arm, wherein the voltage difference in the bridge arm is used to characterize the deviation between the first submodule battery cell and the average voltage of each submodule battery cell in the bridge arm; for the voltage difference in the bridge arm, after passing it through a proportional regulator, a submodule correction reference value is obtained, wherein the voltage difference in the bridge arm has a positive and negative sign, and the positive and negative signs are used to characterize the charge and discharge state of the first submodule battery cell under the control of the correction signal.

[0011] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the correction signal is obtained based on the circulating current difference and the submodule correction reference value, including: obtaining the original control signal of the first submodule battery cell; superimposing the original control signal, the circulating current difference and the submodule correction reference value to obtain the correction signal, wherein the correction signal is used to control the first submodule battery cell.

[0012] As an alternative or supplement to the above scheme, in a method according to one embodiment of the present invention, the sub-module battery unit includes a battery unit and a control unit, wherein the control unit is used to control the duty cycle of the bridge arm to which the battery unit is connected; the two bridge arms of each phase are connected in parallel, and one end of each of the bridge arms is connected to the power grid via an inductor.

[0013] As an alternative or supplement to the above scheme, in a method according to one embodiment of the present invention, the actual value of the X-phase circulating current is obtained by the following steps: obtaining the upper bridge arm current and the lower bridge arm current of the X-phase, wherein the upper bridge arm current and the lower bridge arm current are both signed currents; adding the upper bridge arm current and the lower bridge arm current and averaging them to obtain the actual value of the X-phase circulating current.

[0014] In a second aspect, a control device is provided, the control device comprising a processor and a storage device, the storage device being suitable for storing a plurality of computer programs, the computer programs being suitable for being loaded and run by the processor to execute the control method for a modular multi-level battery energy storage system described in any one of the technical solutions of the control method for the modular multi-level battery energy storage system.

[0015] In a third aspect, a computer-readable storage medium is provided, wherein a plurality of computer programs are stored in the computer-readable storage medium, wherein the computer programs are suitable for being loaded and run by a processor to execute the control method of the modular multi-level battery energy storage system described in any one of the technical solutions of the control method of the modular multi-level battery energy storage system.

[0016] The above one or more technical solutions of the present invention have at least one or more of the following beneficial effects:

[0017] In the technical solution of the present invention, the actual value of the circulating current is obtained and an accurate reference value of the circulating current DC and the base frequency reference value are generated, which can effectively characterize the voltage deviation inside the system. By calculating the circulating current difference and generating a correction signal to dynamically adjust the output voltage of the submodule battery unit, accurate voltage balance is achieved. This method significantly reduces the energy loss inside the system, improves the overall energy efficiency and stability of the energy storage system, prolongs the service life of the battery unit, and simplifies the design and maintenance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0020] Figure 1 is a flowchart of main steps of a control method for a modular multi-level battery energy storage system according to an embodiment of the present invention;

[0021] Figure 2 is a schematic diagram of a circuit structure of a modular multi-level battery energy storage system according to an embodiment of the present invention;

[0022] Figure 3 is a schematic structural diagram of a submodule battery unit according to an embodiment of the present invention;

[0023] Figure 4 is a schematic diagram of a main method flow according to an embodiment of the present invention;

[0024] Figure 5 is a grid-connected power given simulation waveform diagram according to an embodiment of the present invention;

[0025] Figure 6 is based on Figure 5 And the experimental effect diagram obtained using the control method of the modular multi-level battery energy storage system. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0027] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0028] See attached Figure 1 , Figure 1 1 is a flow chart of the main steps of a control method for a modular multi-level battery energy storage system according to an embodiment of the present invention. Figure 1 and Figure 4 As shown, the control method of the modular multi-level battery energy storage system in the embodiment of the present invention mainly includes the following steps S10 to S40.

[0029] Step S10: Obtain the actual value of the X-th phase circulating current.

[0030] In this embodiment, the actual value of the circulating current is used to characterize the size of the circulating current flowing through the Xth phase.

[0031] In one embodiment, the upper bridge arm current and the lower bridge arm current of the Xth phase are detected by a current sensor, which are marked as ixp and ixn respectively, wherein the upper bridge arm current and the lower bridge arm current are signed currents, and the sign indicates the direction of the two currents, wherein the sign is positive or negative. Wherein "x" represents the phase, "p" represents the upper rocker arm, and "n" represents the lower rocker arm. Then, ixp and ixn are added and divided by two to obtain the actual value of the circulating current icx. The formula is expressed as:

[0032]

[0033] For example, ixp = 2.0 A, ixn = -2.2 A. Then the calculated icx is 0.1 A. In addition, ixp and ixn can also be expressed in the form of trigonometric functions or phasors, which will not be repeated here.

[0034] The actual value icx of the circulating current obtained by the above formula can accurately reflect the circulating current passing through the current phase.

[0035] like Figure 2 As shown, Figure 2 It is a schematic diagram of the circuit structure of a modular multi-level battery energy storage system. Figure 2 The energy storage system in adopts a three-phase configuration, and each phase includes an upper bridge arm and a lower bridge arm. Each bridge arm is composed of multiple submodule battery cells Uxyz (SM) connected in series, and the number of submodule battery cells on each bridge arm is the same. When the voltages at both ends of each bridge arm are consistent, no circulating current will be generated. When the voltages at both ends of each bridge arm are inconsistent, the bridge arms with different voltages form a loop with a voltage difference, thereby causing a circulating current. It is precisely because the outputs of each submodule battery cell in the bridge arm are inconsistent that the voltages between the bridge arms are inconsistent.

[0036] In the configuration of each phase, the upper bridge arm and the lower bridge arm are respectively composed of multiple sub-module battery cells connected in series. The sub-module battery cells generate the output voltage of each phase through precise regulation. Specifically, the upper bridge arms of phase a, phase b and phase c generate voltage signals Uap, Ubp and Ucp respectively, while the lower bridge arms generate voltage signals Uam, Ubm and Ucm.

[0037] like Figure 3 As shown, Figure 3 It is a schematic diagram of the structure of a submodule battery unit. The internal structure of the submodule battery unit includes a control unit (two switch units S1 and S2) and a battery unit (capacitor C0 and battery Bat). Furthermore, the source of the switch unit S1 is connected to the drain of the switch unit S2; the drain of the switch unit S1 is respectively connected to the anode of the capacitor C0 and the anode of the battery Bat; the source of the switch unit S2 is respectively connected to the cathode of the capacitor C0 and the cathode of the battery Bat. The control unit is used to control the ratio (duty cycle) of the access time of the battery unit in the bridge arm in the cycle, and the average voltage of the submodule battery unit output to the outside and the average voltage of the internal charging can be further adjusted by the ratio of the access time in the cycle. The battery unit can be a battery pack, a battery module, a battery cell, etc., which are energy storage units based on the battery cell structure, and the factory voltage of each submodule battery cell is consistent.

[0038] In order to limit the fluctuation of circulating current and improve the stability of the system, an inductor element L0 is set between the upper and lower bridge arms of each phase. The function of the inductor element is to smooth the current fluctuation and reduce the impact of circulating current on the system, thereby ensuring the smooth operation of the system under dynamic conditions.

[0039] The final output of the system is composed of three-phase voltages Usa, Usb and Usc after passing through the inductor. By adjusting the output of each submodule battery unit, the voltage signal of each phase can be synchronized with the grid frequency, thereby achieving a stable three-phase output. These voltage signals pass through the inductor L s It is transmitted to the output end of the system to generate currents isa, isb and isc, thus reflecting the overall power output of the system.

[0040] Step S20: acquiring the DC component of the Xth phase to obtain a reference value of the circulating DC amount, and acquiring the reference component of the Xth phase to obtain a reference value of the circulating current base frequency.

[0041] In this embodiment, the circulating DC value is used to characterize the deviation between the voltage level of the Xth phase and the voltage level of the overall system, and the circulating base frequency reference value is used to characterize the voltage deviation between different bridge arms in the same phase.

[0042] The generation of circulating current DC quantity reference value and circulating current base frequency reference value will be introduced in detail later.

[0043] 1) Reference value of circulating DC

[0044] First, the voltage Uxyz of each submodule battery cell in the system is obtained.

[0045] In this embodiment, the voltage of each submodule battery unit in the energy storage system is measured to ensure that accurate voltage data is obtained.

[0046] First, the system monitors the voltage of each submodule battery cell in real time through a voltage sensor. In one embodiment, the voltage value of the submodule battery cell is marked as Uxyz, where "x" represents the number of the phase to which it belongs, "y" represents the position of the bridge arm (upper bridge arm or lower bridge arm), and "z" represents the number of the specific submodule in the bridge arm. This naming rule ensures that each submodule battery cell can be accurately located in the system to avoid data confusion.

[0047] by Figure 2 For example, Uap1 represents the voltage across the submodule battery cell (SM1) numbered 1 in the a phase, p bridge arm (upper bridge arm).

[0048] This step achieves comprehensive perception of the system voltage state by accurately acquiring the voltage Uxyz of each sub-module battery cell, providing a reliable data basis for subsequent circulating current control and modulation signal generation.

[0049] Afterwards, the second average voltage value Ubess and the third average voltage value Ux are obtained, wherein the second average voltage value Ubess is obtained by averaging the voltage Uxyz of each submodule battery cell, and is used to characterize the average value of the voltage of all submodule battery cells. Specifically, the second average voltage value Ubess is obtained by summing the voltage data of all submodules in the system and then dividing it by the total number of submodules. The third average voltage value Ux is used to characterize the average voltage of each submodule battery cell on the Xth phase.

[0050] The reference value of the circulating DC amount is obtained by subtracting the second average voltage value Ubess from the third average voltage value Ux and adjusting the value after the subtraction through a proportional regulator.

[0051] The second average voltage value Ubess is subtracted from the third average voltage value Ux, and the difference obtained is used to measure the voltage deviation between the Xth phase and the system as a whole. The difference is adjusted by the proportional regulator and used to generate a reference value of the circulating DC. The proportional regulator amplifies the voltage difference to a suitable adjustment range by setting a suitable gain parameter so as to accurately control the DC component of the circulating current. The proportional regulator is used in this technology to map one value to another value through a mapping relationship.

[0052] 2) Reference value of circulating base frequency

[0053] After the DC component is obtained, a reference component of the Xth phase is further obtained to generate a circulating current base frequency reference value.

[0054] Obtain a fourth average voltage Uxp and a fifth average voltage Uxn, wherein the fourth average voltage Uxp is used to characterize the average voltage of each submodule battery cell in the upper bridge arm of the Xth phase, and the fifth average voltage Uxn is used to characterize the average voltage of each submodule battery cell in the lower bridge arm of the Xth phase.

[0055] At least the fourth average voltage Uxp is subtracted from the fifth average voltage Uxn to obtain a voltage difference between the bridge arms, which is used to describe the voltage imbalance between the upper and lower bridge arms. The voltage difference between the bridge arms is then adjusted by a proportional regulator, and then phase synchronization is performed with the phase to obtain a circulating current base frequency reference value.

[0056] Specifically, the voltage difference between the bridge arms is processed by a proportional regulator, and then the processed signal is phase-synchronized with the grid synchronization signal cos(ωt+θx) to make the generated circulating base frequency reference value consistent with the grid frequency. Among them, θx is the phase of the Xth phase. The phase synchronization operation ensures that the generated circulating base frequency reference value can accurately reflect the changes in the grid frequency and avoid inaccurate adjustments caused by phase misalignment. This step realizes the detection and correction of the voltage imbalance of the upper and lower bridge arms in the same phase by generating the circulating base frequency reference value, providing an accurate reference for the realization of voltage balance within the system.

[0057] In the whole process of generating the circulating current reference value, the calculation results of the DC quantity and the base frequency quantity will be processed comprehensively. Specifically, the circulating current DC quantity reference value and the circulating current base frequency reference value are added to obtain the final circulating current reference value. The circulating current reference value is used to characterize the value of the circulating current caused by the imbalance between the phase and the system and the imbalance between different bridge arms in the same phase.

[0058] The circulating current is caused by the voltage difference, so different voltage differences constitute different components of the circulating current. Therefore, the actual value of the previous circulating current should be composed of at least the following parts: 1) The voltage difference caused by the voltage difference between the phase and other phases. Each phase can be regarded as a large energy storage unit, so that the original system becomes a parallel connection of three energy storage units. If there is a voltage difference between different phases, the energy storage unit with a higher voltage will charge the energy storage unit with a lower voltage. This part corresponds to the reference value of the circulating current DC quantity, in which the reference value of the circulating current DC quantity uses the second average voltage value Ubess to represent the voltage of other submodule batteries in the system. 2) The voltage difference caused between different bridge arms in the same phase, the bridge arms are connected to the phase line, and the different bridge arms in the same phase are also in parallel. So similar to the above, the voltage difference between different bridge arms will also generate circulating current. This part corresponds to the reference value of the circulating current base frequency.

[0059] Then, the circulating current reference value is subtracted from the actual circulating current value to obtain the abnormal current, that is, the circulating current difference value.

[0060] Step S30: subtract the circulating current reference value from the circulating current actual value to obtain a circulating current difference value.

[0061] In this embodiment, the circulating current difference represents the difference between the actual circulating current value and the circulating current reference value. Since the circulating current reference value is the desired circulating current value, the circulating current difference reflects the difference between the two. Due to its inherent properties, there must be a difference between the actual circulating current value and the circulating current reference value. As the circulating current difference decreases, the actual circulating current value and the circulating current reference value will continue to decrease until the actual circulating current value and the circulating current reference value completely disappear, and the voltages between the battery cells of each submodule in the system are the same.

[0062] Further, the circulating current actual value is subtracted from the circulating current reference value and passed through a proportional regulator to obtain a circulating current difference value. In one embodiment, the proportional regulator may be a given coefficient product, PID, PIR, etc. After being processed by a limiter, the circulating current difference value removes the extreme waveform and serves as one of the bases for subsequent correction signals.

[0063] Step S40: obtaining a correction signal based at least on the circulating current difference.

[0064] In this embodiment, the correction signal is used to correct the output voltage of the battery unit of the submodule so that the circulating current difference approaches zero.

[0065] In one implementation, in addition to the circulating current difference, in order to more accurately control each submodule battery cell, a submodule correction reference value is also required. The details are as follows:

[0066] First, a first average voltage value Uxy is obtained, wherein the first average voltage value Uxy is used to characterize the average value of the battery cell voltages of each submodule on the Yth bridge arm of the Xth phase, and is used to reflect the average voltage of each submodule on the current bridge arm.

[0067] Then, based on the first average voltage value Uxy and the first voltage value Uxyz, a submodule correction reference value is obtained. The first voltage value is used to characterize the voltage value of the first submodule battery unit located in the Yth bridge arm of the Xth phase, and the submodule correction reference value is used to adjust the input or output power of the first submodule battery unit.

[0068] Further, the first average voltage value Uxy and the first voltage value Uxyz are subtracted to obtain the voltage difference in the bridge arm. The voltage difference in the bridge arm is used to characterize the deviation between the average voltage of the first submodule battery cell and the average voltage of each submodule battery cell in the bridge arm. In other words, the voltage difference in the bridge arm is used to describe the voltage deviation between a specific submodule battery cell and the bridge arm. Specifically, a positive voltage difference indicates that the submodule voltage is higher than the average level of the bridge arm, and a negative voltage difference indicates that the voltage is lower than the average level of the bridge arm.

[0069] The voltage difference in the bridge arm is input to the proportional regulator. Through the gain setting of the proportional regulator, the voltage difference can be mapped to a suitable control range to generate a submodule correction reference value. The submodule correction reference value contains positive and negative signs, which are used to determine the charge and discharge state of the first submodule battery cell during the adjustment process. The positive sign indicates that the discharge is carried out under the control of the correction signal, and the negative sign indicates charging. This step achieves an accurate description of the voltage deviation of each submodule by generating a submodule correction reference value, and provides a quantitative reference for the control system during the adjustment process.

[0070] After the submodule correction reference value is generated, it is combined with the circulating current difference to further generate a correction signal.

[0071] Furthermore, the original control signal, the circulating current difference and the submodule correction reference value are superimposed to obtain the correction signal.

[0072] By comprehensively considering the voltage difference information of each part, the voltage of a single submodule can be accurately corrected to achieve overall balance of the system voltage.

[0073] First, the original control signal is the basic working state signal set by the control system for each submodule when there is no voltage deviation. This signal reflects the submodule switching mode and power output level of the system under ideal conditions. However, due to various deviations in the system, such as voltage inconsistency between submodules or fluctuation of each phase voltage, high-precision voltage balancing control cannot be achieved by relying solely on the original control signal. Therefore, the original control signal needs to be corrected to better adapt to actual operating conditions.

[0074] Next, by superimposing the circulating current difference with the original control signal, the information of the voltage imbalance in the system can be directly introduced into the control logic of the submodule. Combining the circulating current difference with the original control signal can ensure that the output of the submodule can reflect the voltage deviation in the current system, thereby having a positive adjustment effect on the voltage balance of the overall system.

[0075] At the same time, the submodule correction reference value is also superimposed on the above signal as a key adjustment amount. The submodule correction reference value mainly focuses on the local voltage deviation between each submodule and its bridge arm. By adding this reference value to the control signal, the voltage of a specific submodule can be finely adjusted to ensure voltage consistency within a local range. In this way, the system can effectively regulate global and local voltage imbalances at the same time, making the adjustment more targeted and accurate.

[0076] By superimposing the original control signal, the circulating current difference and the submodule correction reference value, the final correction signal contains the information of the overall system voltage deviation and the voltage deviation of each submodule. This comprehensive signal will be used as the final input of the controller and directly used to adjust the power output of each submodule. The correction signal can gradually adjust the voltage state of the submodule to be consistent with the system voltage requirement by changing the switching frequency, working time and power output level of the submodule in real time.

[0077] like Figure 5 and 6 As shown, Figure 5 It is a grid-connected power given simulation waveform diagram according to an embodiment of the present invention. Figure 6It is the simulation waveform obtained by the MATLAB / Simulink model established according to the present invention. Figure 5 It can be seen that the grid-connected power command jumps from 10kW to -5kW at the 4th second. Figure 6 It can be seen that after using this method, the voltages of the battery cells of each submodule finally tend to be consistent when connected to the grid.

[0078] The core idea of ​​this technology is to precisely adjust the voltage of each submodule battery cell by utilizing the characteristics of circulating current. Circulating current is a direct reflection of the voltage difference between each submodule in the system. By regulating the circulating current, the voltage deviation information can be effectively transmitted to the control logic of each submodule. The ultimate goal is to make all submodule battery cells in the system tend to be consistent in voltage level through circulating current adjustment, so as to achieve the balance and stability of the entire energy storage system. This can not only extend the battery life, but also improve the overall work efficiency of the system, and ensure the stable operation of the energy storage system under different loads and working conditions.

[0079] It should be pointed out that although the various steps in the above embodiments are described in a specific order, those skilled in the art can understand that in order to achieve the effects of the present invention, different steps do not have to be performed in such an order. They can be performed simultaneously (in parallel) or in other orders. These changes are within the scope of protection of the present invention.

[0080] It is understood by those skilled in the art that the present invention implements all or part of the processes in the method of the above embodiment, and can also be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes a computer program, and the computer program can be in source code form, object code form, executable file or some intermediate form. The computer-readable storage medium may include: any entity or device, medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electric carrier signal, telecommunication signal and software distribution medium that can carry the computer program. It should be noted that the content contained in the computer-readable storage medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable storage media do not include electric carrier signals and telecommunication signals.

[0081] Furthermore, the present invention also provides a control device. In an embodiment of a control device according to the present invention, the control device includes a processor and a storage device. The storage device can be configured to store a program for executing a control method for a modular multi-level battery energy storage system of the above method embodiment. The processor can be configured to execute the program in the storage device, which includes but is not limited to a program for executing a control method for a modular multi-level battery energy storage system of the above method embodiment. For ease of explanation, only the parts related to the embodiment of the present invention are shown. For specific technical details not disclosed, please refer to the method part of the embodiment of the present invention. The control device can be a control device device formed by various electronic devices.

[0082] Furthermore, the present invention also provides a computer-readable storage medium. In a computer-readable storage medium embodiment according to the present invention, the computer-readable storage medium can be configured to store a program for executing the control method of the modular multi-level battery energy storage system of the above-mentioned method embodiment, and the program can be loaded and run by the processor to implement the control method of the above-mentioned modular multi-level battery energy storage system. For ease of explanation, only the parts related to the embodiment of the present invention are shown. For specific technical details not disclosed, please refer to the method part of the embodiment of the present invention. The computer-readable storage medium can be a storage device formed by various electronic devices. Optionally, the computer-readable storage medium in the embodiment of the present invention is a non-temporary computer-readable storage medium.

[0083] Further, it should be understood that since the setting of each module is only for illustrating the functional units of the device of the present invention, the physical devices corresponding to these modules may be the processor itself, or a part of the software in the processor, a part of the hardware, or a part of the combination of software and hardware. Therefore, the number of each module in the figure is only schematic.

[0084] Those skilled in the art will appreciate that the modules in the device can be adaptively split or merged. Such splitting or merging of specific modules will not cause the technical solution to deviate from the principle of the present invention, and therefore, the technical solutions after splitting or merging will fall within the protection scope of the present invention.

[0085] It should be noted that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of this application, and these improvements and modifications should also be regarded as the scope of protection of this application.

Claims

1. A control method for a modular multi-level battery energy storage system, characterized in that: The system includes X phases, each phase includes Y bridge arms, the bridge arms in each phase are connected in parallel, each bridge arm is formed by connecting the same number of submodule battery cells in series, and when the voltages between the bridge arms are unequal, a circulating current is caused in the system, and the method includes: Acquire an actual value of a circulating current of the Xth phase, wherein the actual value of the circulating current is used to characterize the magnitude of the circulating current flowing through the Xth phase; Obtaining a DC component of the Xth phase to obtain a reference value of a circulating DC amount, and obtaining a reference component of the Xth phase to obtain a reference value of a circulating current base frequency, wherein the circulating DC amount is used to characterize a deviation between a voltage level of the Xth phase and a voltage level of the overall system, and the circulating current base frequency reference value is used to characterize a voltage deviation between different bridge arms in the same phase; Subtracting a circulating current reference value from the circulating current actual value to obtain a circulating current difference value, wherein the circulating current reference value is the sum of the DC component of the X-th phase and the reference component of the X-th phase, and the circulating current reference value is used to characterize the value of the circulating current caused by the voltage deviation between the phase and the system and between different bridge arms in the same phase; At least based on the circulating current difference, a correction signal is obtained, wherein the correction signal is used to correct the output voltage of the submodule battery unit so that the circulating current difference approaches zero.

2. The method according to claim 1, characterized in that The obtaining of a correction signal based at least on the circulating current difference comprises: Obtaining a first voltage value and a first average voltage value, wherein the first voltage value is used to represent the voltage value of the first submodule battery unit located in the Yth bridge arm of the Xth phase, and the first average voltage value is used to represent the average value of the voltages of the submodule battery units on the Yth bridge arm of the Xth phase; Based on the first average voltage value and the first voltage value, obtaining a submodule correction reference value, wherein the submodule correction reference value is used to adjust the input or output power of the battery unit of the first submodule; A correction signal is obtained based on the circulating current difference and the submodule correction reference value.

3. The method according to claim 1, characterized in that The step of calculating the DC component of the X-th phase to obtain a reference value of the circulating DC amount includes: Obtaining a second average voltage value and a third average voltage value, wherein the second average voltage value is obtained by averaging the voltages of the battery cells of each submodule and is used to represent the average voltage of all the battery cells of the submodules, and the third average voltage value is used to represent the average voltage of each battery cell of the submodule on the Xth phase; At least the second average voltage value is subtracted from the third average voltage value, and the obtained difference is adjusted by a first proportional regulator to obtain a circulating DC reference value.

4. The method according to claim 2, characterized in that: Each phase is composed of two upper and lower bridge arms. The reference component of the Xth phase is obtained to obtain the reference value of the circulating current base frequency, including: Obtaining a fourth average voltage and a fifth average voltage, wherein the fourth average voltage is used to characterize the average voltage of each submodule battery cell in the upper bridge arm, and the fifth average voltage is used to characterize the average voltage of each submodule battery cell in the lower bridge arm; The fourth average voltage is subtracted from the fifth average voltage to obtain a voltage difference between the bridge arms, the voltage difference between the bridge arms is processed by a proportional regulator, and a phase synchronization operation is performed with the Xth phase to obtain the circulating current base frequency reference value.

5. The method according to any one of claims 2 to 4, characterized in that: The obtaining of the submodule correction reference value based on the first average voltage value and the first voltage value includes: Subtracting the first average voltage value from the first voltage value to obtain a voltage difference value within the bridge arm, wherein the voltage difference value within the bridge arm is used to characterize a deviation between the first submodule battery cell and the average voltage of each submodule battery cell in the bridge arm; For the voltage difference in the bridge arm, after passing it through a proportional regulator, a submodule correction reference value is obtained, wherein the voltage difference in the bridge arm has a positive and negative sign, and the positive and negative signs are used to characterize the charging and discharging state of the first submodule battery unit under the control of the correction signal.

6. The method according to any one of claims 2 to 4, characterized in that: The obtaining of a correction signal based on the circulating current difference and the submodule correction reference value comprises: Acquire the original control signal of the battery unit of the first submodule; The original control signal, the circulating current difference and the submodule correction reference value are superimposed to obtain the correction signal, wherein the correction signal is used to control the first submodule battery unit.

7. The method according to claim 4, characterized in that The submodule battery unit includes a battery unit and a control unit, wherein the control unit is used to control the duty cycle of the bridge arm to which the battery unit is connected; the two bridge arms of each phase are connected in parallel, and one end of each bridge arm is connected to the power grid through an inductor.

8. The method according to claim 7, characterized in that The actual value of the X-th phase circulating current is obtained by the following steps: Obtaining an upper bridge arm current and a lower bridge arm current of an X-th phase, wherein the upper bridge arm current and the lower bridge arm current are both signed currents; The upper bridge arm current and the lower bridge arm current are added and averaged to obtain the actual value of the X-phase circulating current.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored program, wherein the program executes the method according to any one of claims 1 to 8 when executed.

10. An electronic device comprising a memory and a processor, characterized in that: A computer program is stored in the memory, and the processor is configured to execute the method according to any one of claims 1 to 8 through the computer program.

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