Single or multi-phase cascaded hybrid H-bridge battery energy storage system, method for determining control state of its switching unit, and computer-readable storage medium

Abstract

The present application relates to a single- or multi-phase cascaded hybrid H-bridge battery energy storage system, a method for determining the control state of its switching unit, and a computer-readable storage medium. The system includes a cascaded hybrid H-bridge module and a filter circuit; the cascaded hybrid H-bridge module is connected to an external load or the power grid through the filter circuit; the cascaded hybrid H-bridge module includes m capacitor H-bridge units and n battery H-bridge units connected in cascade; wherein, m is greater than or equal to 1 and less than n, and n is greater than or equal to 2; the switching frequency of the capacitor H-bridge unit is in the high-frequency range, and the switching frequency of the battery H-bridge unit is in the low-frequency range. In a low-voltage scenario, in order to reduce the total harmonic distortion, it can be achieved by using a smaller number of capacitor H-bridge units with a higher switching frequency, without increasing the switching frequency and switching losses of each H-bridge unit, thereby reducing the overall switching frequency and switching losses of the system and improving the overall system efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage power supplies, and particularly to a single or multi-phase cascaded hybrid H-bridge battery energy storage system, a method for determining the control state of its switching unit, and a computer-readable storage medium. Background Art

[0002] With the continuous increase in the proportion of renewable energy in the power generation field, battery energy storage systems have become increasingly important. A battery energy storage (BES) system consists of a battery pack, a battery management system (BMS), a power conversion system (PCS), etc. In large-scale energy storage applications, the cascaded H-bridge (CHB) topology, as a power conversion system, has attracted much attention because of its modular design, which is convenient for voltage level expansion, can reduce the voltage stress of power devices, improve reliability and service life; can generate high-quality voltage waveforms, reduce harmonic content, and reduce the requirements for filters; and can also flexibly adjust energy and has redundancy functions.

[0003] In medium- and low-voltage scenarios, the number of H-bridge units in the cascaded H-bridge is usually limited. To reduce the total harmonic distortion (THD), the prior art needs to combine the nearest level modulation (NLM) and pulse-width modulation (PWM) for switching control in the H-bridge units. Since the number of H-bridge units in the low-voltage scenario is usually limited, it will increase the switching frequency and switching losses of power devices, inevitably reducing the overall system efficiency. Summary of the Invention

[0004] Based on this, it is necessary to provide a single or multi-phase cascaded hybrid H-bridge battery energy storage system, a method for determining the control state of its switching unit, and a computer-readable storage medium for the above technical problems.

[0005] In a first aspect, the present application provides a single-phase cascaded hybrid H-bridge battery energy storage system, including: a cascaded hybrid H-bridge module and a filter circuit; the cascaded hybrid H-bridge module is connected to an external load or the power grid through the filter circuit; the cascaded hybrid H-bridge module includes m capacitor H-bridge units and n battery H-bridge units connected in cascade; where m is greater than or equal to 1 and less than n, and n is greater than or equal to 2 and less than or equal to a first preset value; the switching frequency of the capacitor H-bridge unit is in the high-frequency range, and the switching frequency of the battery H-bridge unit is in the low-frequency range.

[0006] In a second aspect, the present application further provides a method for determining the control state of a switching unit of a single-phase or multi-phase cascaded hybrid H-bridge battery energy storage system, which is applied to the single-phase cascaded hybrid H-bridge battery energy storage system as described in the first aspect, and includes:

[0007] Determine the total output voltage level number of the cascaded hybrid H-bridge module according to the average voltage of each H-bridge unit in the cascaded hybrid H-bridge module and the arm voltage reference value of the cascaded hybrid H-bridge module;

[0008] Determine the voltage deviation between the n battery H-bridge units and the m capacitor H-bridge units;

[0009] Determine the control state of the switching unit in each H-bridge unit according to the total output voltage level number, the arm current of the cascaded hybrid H-bridge module, and the voltage deviation.

[0010] In a third aspect, the present application further provides a single-phase or multi-phase cascaded hybrid H-bridge battery energy storage system, including a plurality of the single-phase cascaded hybrid H-bridge battery energy storage systems as described in the first aspect, and the control state of the switching unit in the system is determined by the method as described in the second aspect.

[0011] In a fourth aspect, the present application further provides a computer device, including a memory and a processor, where the memory stores a computer program, and when the processor executes the computer program, the method as described in the second aspect or any of its embodiments is implemented.

[0012] In a fifth aspect, the present application further provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the method as described in the second aspect or any of its embodiments is implemented.

[0013] In a sixth aspect, the present application further provides a computer program product, including a computer program, and when the computer program is executed by a processor, the method as described in the second aspect or any of its embodiments is implemented.

[0014] In a seventh aspect, the present application further provides a multi-phase cascaded hybrid H-bridge battery energy storage system, including a plurality of the single-phase cascaded hybrid H-bridge battery energy storage systems as described in the first aspect, and the control state of the switching unit in the system is determined by the method as described in the second aspect above.

[0015] The above single-phase cascaded hybrid H-bridge module includes m cascaded capacitor H-bridge units and n battery H-bridge units, where m is greater than or equal to 1 and less than n, and n is greater than or equal to 2; the switching frequency of the capacitor H-bridge unit is in the high-frequency range, and the switching frequency of the battery H-bridge unit is in the low-frequency range. By setting a relatively large number of battery H-bridge units with a low switching frequency and a relatively small number of capacitor H-bridge units with a high switching frequency in the cascaded hybrid H-bridge module, in this way, in a low-voltage scenario, in order to reduce the total harmonic distortion, it can be achieved by using a relatively small number of capacitor H-bridge units with a high switching frequency, without increasing the switching frequency and switching losses of each H-bridge unit, thereby reducing the overall switching frequency and switching losses of the system and improving the overall system efficiency. Description of the Drawings

[0016] To more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following will briefly introduce the drawings required for use in the description of the embodiments or related technologies. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 Schematic diagram of a single-phase cascaded hybrid H-bridge battery energy storage system and its sub-module topology in an embodiment;

[0018] Figure 2 For an application in Figure 1 Flow schematic diagram of a method for determining the control state of the switching unit in a single-phase cascaded hybrid H-bridge battery energy storage system;

[0019] Figure 3 Control block diagram for calculating the reference value of the arm voltage of a cascaded hybrid H-bridge module using a dual-loop control strategy;

[0020] Figure 4 Control block diagram for determining the output voltage level number of n battery H-bridge units and the modulation ratio of pulse width modulation of the capacitor H-bridge unit;

[0021] Figure 5 Control block diagram for determining the control state of the switching unit of each battery H-bridge unit;

[0022] Figure 6 Schematic diagram of the state of a battery H-bridge unit;

[0023] Figure 7 Control block diagram for determining the control state of the switching unit of the capacitor H-bridge unit;

[0024] Figure 8Schematic diagram for comparison between the output voltage of the cascaded hybrid H-bridge module and the output voltage reference in the embodiments of the present application;

[0025] Figure 9 Schematic diagram showing the change in the connection state of the cascaded hybrid H-bridge unit module within two power frequency cycles;

[0026] Figure 10A Schematic diagram of the voltage tracking performance of a bridge arm;

[0027] Figure 10B Schematic diagram of the voltage balance of the hybrid H-bridge unit module using the method provided in the embodiments of the present application;

[0028] Figure 11 Structural block diagram of a single-phase cascaded H-bridge unit capacitor voltage strengthening and balancing device;

[0029] Figure 12 Internal structure diagram of a computer device in an embodiment;

[0030] Figure 13 Schematic diagram of a three-phase cascaded hybrid H-bridge battery energy storage system. Detailed implementation manners

[0031] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0032] In medium and low voltage scenarios, the number of H-bridge units in the cascaded H-bridge is usually limited. To reduce the Total Harmonic Distortion (THD), the prior art needs to combine the Nearest Level Modulation (NLM) and Pulse-Width Modulation (PWM) for the switching control in the H-bridge units. Since the number of H-bridge units in the low voltage scenario is usually limited, it will increase the switching frequency and switching losses of the power devices, inevitably reducing the overall system efficiency.

[0033] To solve the above problems, an embodiment of the present application provides a single / multi-phase cascaded hybrid H-bridge battery energy storage system. In this single / multi-phase cascaded hybrid H-bridge battery energy storage system, a relatively large number of battery H-bridge units with a low switching frequency are provided, and a relatively small number of capacitor H-bridge units with a high switching frequency are provided. In this way, in a low-voltage scenario, in order to reduce the total harmonic distortion, the relatively small number of capacitor H-bridge units with a high switching frequency can be utilized, without increasing the switching frequency and switching losses of each H-bridge unit. Thus, the overall switching frequency and switching losses of the system can be reduced, and the overall system efficiency can be improved.

[0034] In an embodiment of the present application, the provided single-phase cascaded hybrid H-bridge battery energy storage system includes a cascaded hybrid H-bridge module and a filtering circuit. The cascaded hybrid H-bridge module is connected to an external load or the power grid through the filtering circuit; the cascaded hybrid H-bridge module includes m capacitor H-bridge units and n battery H-bridge units connected in cascade; where m is greater than or equal to 1 and less than n; n is greater than or equal to 2 and less than or equal to a first preset value; the switching frequency of the capacitor H-bridge unit is in the high-frequency range, and the switching frequency of the battery H-bridge unit is in the low-frequency range. When constructing the cascaded hybrid H-bridge module, the connection order between the m capacitor H-bridge units and the n battery H-bridge units is flexible, and the cascading order of these units can be freely arranged according to specific application requirements and system architecture, without following a fixed sequence. As long as it is ensured that the H-bridge units are correctly cascaded with each other, the expected functions and performances can be achieved.

[0035] In some embodiments, the above first preset value can be set according to the applicable voltage scenario. For example, in a medium and low voltage scenario, the above first preset value can be greater than 2 and less than or equal to 10.

[0036] The above high-frequency range can refer to above kilohertz. Exemplarily, the switching frequency of the capacitor H-bridge unit can be on the order of kilohertz. For example, the switching frequency of the capacitor H-bridge unit can be dozens of kilohertz.

[0037] The above low-frequency range can refer to below kilohertz. Exemplarily, this low-frequency range can be greater than or equal to twice the load frequency of the load connected to the single-phase cascaded hybrid H-bridge battery energy storage system, or 2 to 8 times the traditional power frequency (50 Hz or 60 Hz).

[0038] In some preferred embodiments, the above m is 1. That is to say, 1 high-frequency capacitor H-bridge unit and multiple low-frequency capacitor H-bridge units can be provided in the cascaded hybrid H-bridge module. Only through 1 high-frequency capacitor H-bridge unit, the overall switching frequency and switching losses of the system can be reduced in a very low-cost manner, and the overall system efficiency can be improved.

[0039] In some embodiments, m is 1 and n is 8. That is to say, 1 high-frequency capacitive H-bridge unit and 8 low-frequency capacitive H-bridge units can be arranged in the cascaded hybrid H-bridge module.

[0040] Exemplarily, as Figure 1 shown in an embodiment is a single-phase cascaded hybrid H-bridge battery energy storage system, which includes a cascaded hybrid H-bridge module and a filtering circuit. The cascaded hybrid H-bridge module includes a number of cascaded capacitive H-bridge units and a number of battery H-bridge units; the filtering circuit includes an inductor L and a capacitor C1; the cascaded hybrid H-bridge module is connected to a single-phase AC load 11 (or power grid) through the filtering circuit. Among them, the topological structure of the capacitive H-bridge unit is as Figure 1 shown in (a) therein, adopting an H-bridge structure powered by a capacitor, which is used to maintain a stable DC voltage level, and its switching frequency is dozens of kilohertz. The topological structure of the battery H-bridge unit is as Figure 1 shown in (b) therein, powered by a battery pack, aiming to store and release energy as needed, and its switching frequency is twice the load frequency. Both types of H-bridge units are composed of four switching units S1, S2, S3, and S4. By precisely controlling the switching states of these switching units, the output voltage of the H-bridge unit can be managed to generate the required level. The topological structure of the single-phase system is as Figure 1 shown in (c) therein, composed of one capacitive H-bridge unit and multiple (n) battery H-bridge units in cascade. The output voltages of each H-bridge unit are combined into a stepped superimposed voltage waveform (such as Figure 1 shown in (d) therein), and a standard sine wave (such as Figure 1 shown in (e) therein) is obtained through an LC filter (i.e., composed of the inductor L and the capacitor C1 in the figure) to supply power to the single-phase AC load.

[0041] The above cascaded hybrid H-bridge module includes m cascaded capacitive H-bridge units and n battery H-bridge units, where m is greater than or equal to 1 and less than n; n is greater than or equal to 2 and less than or equal to a first preset value; the switching frequency of the capacitive H-bridge unit is in a high-frequency range, such as dozens of kilohertz; the switching frequency of the battery H-bridge unit is in a low-frequency range, such as twice the traditional power frequency (50 Hz or 60 Hz). Thus, it can be seen that a relatively large number of battery H-bridge units with a low switching frequency are arranged in the cascaded hybrid H-bridge module, and a relatively small number of capacitive H-bridge units with a high switching frequency are arranged. Thus, in a low-voltage scenario, in order to reduce the total harmonic distortion, the relatively small number of capacitive H-bridge units with a high switching frequency can be used to achieve this, without increasing the switching frequency and switching losses of each H-bridge unit, thereby reducing the overall switching frequency and switching losses of the system and improving the overall system efficiency.

[0042] The embodiment of the present application further provides a method for determining the control state of a switching unit that can be applied to the above-mentioned single-phase cascaded hybrid H-bridge battery energy storage system. This method is used to determine the switching states of the switching units in each H-bridge unit of the cascaded hybrid H-bridge module, so as to control the cascaded hybrid H-bridge module, making the total output voltage of all H-bridge units track the arm voltage reference value of the cascaded hybrid H-bridge module.

[0043] As Figure 2 shown, it is a schematic flowchart of a method for determining the control state of a switching unit applied to the above-mentioned single-phase cascaded hybrid H-bridge battery energy storage system. This method includes:

[0044] S201. Determine the total output voltage level number of the cascaded hybrid H-bridge module according to the average voltage of each H-bridge unit in the cascaded hybrid H-bridge module and the arm voltage reference value of the cascaded hybrid H-bridge module.

[0045] In some embodiments, the capacitor voltages of each capacitor H-bridge unit in m capacitor H-bridges can be obtained first, then the capacitor voltages of each battery H-bridge unit in n battery H-bridges can be obtained, and finally the average voltage of these m + n H-bridge units is calculated, that is, the average voltage of each H-bridge unit in the above-mentioned cascaded hybrid H-bridge module is obtained.

[0046] In some embodiments, the arm voltage reference value of the above-mentioned cascaded hybrid H-bridge module can be calculated by an output voltage controller. Specifically, the output voltage controller can adopt a double-loop control strategy, including an outer voltage loop and an inner current loop. Its control block diagram is as Figure 3 shown. Figure 3 It is a control block diagram for calculating the arm voltage reference value of the cascaded hybrid H-bridge module using a double-loop control strategy. As Figure 3 shown, the outer voltage loop consists of a load voltage reference value and a load voltage value, and generates an arm current reference value through a proportional-integral (PI) controller. The inner current loop is responsible for fast current regulation, inputs the error between the arm current reference value and the arm current into another PI controller, and the output is the arm voltage reference value (that is, the arm voltage reference value of the above-mentioned cascaded hybrid H-bridge module). The arm voltage reference value is used to adjust the states of the capacitor H-bridge unit and the battery H-bridge unit to ensure the efficient and reliable operation of the system.

[0047] Among them, the above PI controller is a feedback control element composed of a proportional part and an integral part, and its output is the sum of the product of the proportional gain and the error signal and the integral of the integral gain and the error signal. The proportional part enables the system to respond quickly to errors, and the integral part can eliminate the steady-state error. However, too large a proportional gain may lead to overshoot, and too strong an integral action may slow down the response or cause integral saturation. The above output voltage controller adopts a double-loop control strategy. The outer voltage loop takes the load voltage reference value and the load voltage value as inputs, and generates the arm current reference value through the PI controller, focusing on the stability of the output voltage. The inner current loop compares the arm current reference value with the actual value, and the error is output as the arm voltage reference value through the PI controller to adjust the states of the capacitor H-bridge unit and the battery H-bridge unit, ensuring the efficient and reliable operation of the system.

[0048] In the above embodiments, during the process of obtaining the arm voltage reference value, the output voltage controller adopting the double-loop control strategy plays an important role. The outer voltage loop takes the load voltage reference value and the load voltage value as inputs, and generates the arm current reference value through the proportional-integral (PI) controller. This link mainly focuses on the stability of the output voltage. By continuously comparing the desired load voltage reference value and the actual load voltage value, and using the characteristics of the PI controller (the proportional part enables the system to respond quickly to errors, and the integral part can eliminate the steady-state error) to generate an appropriate arm current reference value, it provides an accurate target value for the subsequent adjustment of the inner current loop, ensuring that the output voltage develops in a stable direction as a whole. The inner current loop is responsible for fast current regulation. The error between the arm current reference value and the arm current is input into another PI controller, and the output is the arm voltage reference value. This link plays a key role in ensuring the efficient and reliable operation of the system. By quickly responding to and adjusting the deviation of the arm current, it ensures that the current is within a reasonable range, avoiding problems such as system failures or reduced efficiency caused by abnormal currents. At the same time, through coordinated work with the outer voltage loop, the finally output arm voltage reference value can more accurately adjust the states of the capacitor H-bridge unit and the battery H-bridge unit, achieving efficient, stable and reliable control of the entire cascaded hybrid H-bridge system.

[0049] S202. Determine the voltage deviation between the n battery H-bridge units and the m capacitor H-bridge units.

[0050] In some embodiments, the average battery voltage of the n battery H-bridge units can be calculated first, then the average capacitor voltage of the m capacitor H-bridge units can be calculated, and finally the difference between the average battery voltage and the average capacitor voltage can be calculated to obtain the above voltage deviation.

[0051] In some embodiments, the total battery voltage value of n battery H-bridge units can also be calculated, the total capacitor voltage value of m capacitor H-bridge units can be calculated, and finally the difference between the total battery voltage value and the total capacitor voltage value can be calculated to obtain the above voltage deviation value.

[0052] S203. Determine the control states of the switching units in each H-bridge unit according to the total output voltage level number, the arm current of the cascaded hybrid H-bridge module, and the voltage deviation.

[0053] In medium- and low-voltage scenarios, traditional technologies need to combine nearest level modulation (NLM) and pulse width modulation (PWM) to control the switches in the H-bridge unit to reduce THD, but this will increase the switching frequency and switching losses of power devices and reduce the overall system efficiency. However, the control state determination method shown in FIG. 2 proposed in this application can achieve the goal of reducing THD by setting capacitor H-bridge units and battery H-bridge units with different switching frequencies and using fewer capacitor H-bridge units with higher switching frequencies, without increasing the switching frequency and switching losses of each H-bridge unit. Therefore, the overall switching frequency and switching losses of the system are effectively reduced, the overall system efficiency is improved, and the requirements for power quality and system performance in medium- and low-voltage scenarios are better met.

[0054] In the process shown in FIG. 2, first, the total output voltage level number is determined according to the average voltage of each H-bridge unit in the cascaded hybrid H-bridge module and the arm voltage reference value. This step lays the foundation for subsequent precise control. By obtaining the voltage information of different types of H-bridge units (capacitor H-bridge units and battery H-bridge units) and calculating the average value, the current voltage state of the system can be comprehensively understood, and then the accurate total output voltage level number can be obtained in combination with the arm voltage reference value, so that the output voltage of the system can be adjusted more precisely towards the desired level state.

[0055] In the above embodiments, in the step of determining the voltage deviation between the n battery H-bridge units and the m capacitor H-bridge units, whether the voltage deviation is obtained by calculating the difference in average values or the difference in total voltage values provides a key basis for further finely adjusting the control states of the switching units in each H-bridge unit. According to this voltage deviation, combined with factors such as the total output voltage level number and the arm current, the control state of each switching unit can be determined more precisely, so as to realize the fine adjustment of the output voltage of each H-bridge unit, ensure that the total output voltage of all H-bridge units can accurately track the arm voltage reference value of the cascaded hybrid H-bridge module, and effectively improve the stability and accuracy of the output voltage.

[0056] In summary, the control state determination method shown in Figure 2, through the above series of steps and their mutual cooperation, has demonstrated significant beneficial effects in aspects such as improving system performance, precisely controlling the output voltage, and ensuring the efficient and reliable operation of the system, providing strong support for the effective application of the cascaded hybrid H-bridge module in medium and low voltage scenarios.

[0057] In some embodiments, the output voltage levels of the n battery H-bridge units and the modulation ratio of the pulse width modulation of the m capacitor H-bridge units can be determined according to the total output voltage level number, the arm current of the cascaded hybrid H-bridge module, and the voltage deviation; based on the output voltage levels of the n battery H-bridge units, the control states of the switching units of each battery H-bridge unit are determined; based on the modulation ratio, the control states of the switching units of each capacitor H-bridge unit are determined.

[0058] In some embodiments, the process of determining the output voltage levels of the n battery H-bridge units and the modulation ratio of the pulse width modulation of the m capacitor H-bridge units according to the total output voltage level number, the arm current of the cascaded hybrid H-bridge module, and the voltage deviation may include but is not limited to the following situations:

[0059] (1) If the product of the voltage deviation and the arm current is greater than 0, the total output voltage level number is rounded down to determine the output voltage levels of the n battery H-bridge units, and the difference between the total output voltage level number and the output voltage levels of the n battery H-bridge units is used as the modulation ratio of the pulse width modulation of the m capacitor H-bridge units.

[0060] (2) If the product of the voltage deviation and the arm current is less than or equal to 0, the total output voltage level number is rounded up to determine the output voltage levels of the n battery H-bridge units, and the difference between the total output voltage level number and the output voltage levels of the n battery H-bridge units is used as the modulation ratio of the pulse width modulation of the m capacitor H-bridge units.

[0061] Figure 4 It is a control block diagram for determining the output voltage levels of the n battery H-bridge units and the modulation ratio of the pulse width modulation of the capacitor H-bridge units. As Figure 4 shown, it is illustrated by taking a cascaded hybrid H-bridge module including one capacitor H-bridge and n battery H-bridge units as an example. Figure 4 In it, If means if, Else means otherwise, and End if means end.

[0062] Figure 4 In it, the average value of the capacitor voltage Vc in the capacitor H-bridge unit and the battery voltages Vb1,..., Vbn in the n battery H-bridge units can be calculated to obtain the average voltage Vaver of each H-bridge unit in the cascaded hybrid H-bridge module, that is Figure 4The capacitance therein and the average battery voltage Vaver. Then, the reference value Vs* of the arm voltage of the cascaded hybrid H-bridge module is divided by the average of the capacitance and the battery voltage Vaver to obtain the total number of output voltage levels Nref of the cascaded hybrid H-bridge module.

[0063] As Figure 4 shown, the average battery voltage Vbat in the n battery H-bridge units can also be calculated.

[0064] As Figure 4 shown, after obtaining the total number of output voltage levels Nref and the average battery voltage Vbat, the number of output voltage levels Nbat of the n battery H-bridge units and the modulation ratio Ncap of the pulse width modulation of the capacitor H-bridge unit can be determined.

[0065] Among them, the process of determining the number of output voltage levels Nbat of the n battery H-bridge units and the modulation ratio Ncap of the pulse width modulation of the capacitor H-bridge unit can include:

[0066] If sgn(is)*sgn(Vbat - Vc) is greater than 0, then:

[0067] Nbat = floor(Nref);

[0068] Ncap = Nref - floor(Nref);

[0069] Among them, when both sgn(is) and sgn(Vbat - Vc) are positive, or both are negative, it is determined that sgn(is)*sgn(Vbat - Vc) is greater than 0.

[0070] If sgn(is)*sgn(Vbat - Vc) is less than or equal to 0, then:

[0071] Nbat = ceil(Nref);

[0072] Ncap = Nref - ceil(Nref);

[0073] Among them, when sgn(is) is positive and sgn(Vbat - Vc) is negative, or sgn(is) is negative and sgn(Vbat - Vc) is positive, it is determined that sgn(is)*sgn(Vbat - Vc) is less than 0. When one of sgn(is) or sgn(Vbat - Vc) is 0, sgn(is)*sgn(Vbat - Vc) = 0.

[0074] The above sgn() is the sign function, and is is Figure 4The arm current in it is \(i_s\), and \(V_{bat}-V_c\) represents the voltage deviation calculated from the average battery voltage \(V_{bat}\) and the capacitor voltage \(V_c\). \(N_{bat}\) is an integer. When the nearest level modulation method is applied, the state change frequency of the battery H-bridge unit is twice the grid frequency; \(N_{cap}\) is a decimal number between -1 and 1 and serves as the modulation ratio of PWM, facilitating the application of conventional PWM. The sum of \(N_{bat}\) and \(N_{cap}\) is equal to \(N_{ref}\), achieving accurate tracking of the arm voltage reference value. \(floor()\) is the floor function, and \(ceil()\) is the ceiling function.

[0075] In the above embodiments, the output voltage level of the battery H-bridge unit and the modulation ratio of the capacitor H-bridge unit can be accurately determined. By considering the key factor of the product of the voltage deviation and the arm current, it is decided whether to round up or round down the total output voltage level number, thereby determining the output voltage level number of the battery H-bridge unit and the modulation ratio of the capacitor H-bridge unit. This method makes full use of the key electrical parameter information in the system, making the determination of the output voltage level number and the modulation ratio more in line with the actual operating state of the system. Whether the product of the voltage deviation and the arm current is greater than 0 or less than or equal to 0, the level number and the modulation ratio can be accurately allocated, ensuring that the total output voltage can accurately track the arm voltage reference value, effectively reducing the error of the output voltage, and improving the power quality.

[0076] In the above embodiments, the sign function (sgn()) is used to accurately judge the positive and negative relationship between the voltage deviation and the arm current. Combining the floor function (floor()) and the ceiling function (ceil()), the accurate calculation of the output voltage level number (\(N_{bat}\)) of the battery H-bridge unit and the modulation ratio (\(N_{cap}\)) of the capacitor H-bridge unit under different conditions is realized. \(N_{bat}\) is an integer, meeting the application requirements of the nearest level modulation method, and its relationship with the arm current can further guide the control of the battery H-bridge unit. \(N_{cap}\), as a decimal number between -1 and 1, is suitable for conventional PWM applications, providing accurate parameters for the subsequent PWM-based control of the capacitor H-bridge unit. The sum of the two is equal to the total output voltage level number \(N_{ref}\), fundamentally ensuring the accurate tracking of the arm voltage reference value and improving the stability and accuracy of the output voltage of the entire cascaded hybrid H-bridge system.

[0077] In some embodiments, determining the control states of the switching units of each battery H-bridge unit based on the output voltage levels of the n battery H-bridge units may include, but is not limited to: determining the priorities of the n battery H-bridge units based on the output voltage levels and arm currents of the n battery H-bridge units; determining the connection states of the n battery H-bridge units according to the priorities of the n battery H-bridge units and the output voltage levels of the n battery H-bridge units; and determining the control states of the switching units of each battery H-bridge unit according to the connection states of each battery H-bridge unit.

[0078] Among them, the connection states include one of a forward series state, a bypass state, and a negative series state.

[0079] Among them, determining the priorities of the n battery H-bridge units based on the output voltage levels and arm currents of the n battery H-bridge units may include the following cases:

[0080] (A) If the product of the output voltage levels of the n battery H-bridge units and the arm current is greater than 0, determine the priorities of the n battery H-bridge units in descending order of battery voltage.

[0081] (B) If the product of the output voltage levels of the n battery H-bridge units and the arm current is less than or equal to 0, determine the priorities of the n battery H-bridge units in ascending order of battery voltage.

[0082] In some embodiments, the process of determining the connection states of each battery H-bridge unit according to the priorities of the n battery H-bridge units and the output voltage levels of the n battery H-bridge units may include, but is not limited to: comparing the priorities of the n battery H-bridge units with the absolute values of the output voltage levels to obtain a first comparison result; and determining the connection states of each battery H-bridge unit according to the first comparison result and the positive and negative of the output voltage levels of the n battery H-bridge units.

[0083] Exemplarily, Figure 5 is a control block diagram for determining the control states of the switching units of each battery H-bridge unit. As Figure 5As shown, the battery voltages of the n battery H-bridge units can be sorted first. When sorting, the sorting can be carried out according to the magnitude of the battery voltages, either from large to small or from small to large. And according to the output voltage level number Nbat of the above-mentioned n battery H-bridge units and the positive or negative of the arm current is, the priority of the battery H-bridge units is updated. Exemplarily, the priorities of these n battery H-bridge units can be set in turn, and the priority numbers from the highest to the lowest are 1, 2,..., n. Specifically, when Nbat * is > 0, the batteries in the battery H-bridge units connected in series to the circuit will be discharged. At this time, the battery H-bridge unit with the highest battery voltage has the highest priority (serial number 1), and the battery H-bridge unit with the lowest battery voltage has the lowest priority (serial number n); when Nbat * is <= 0, the batteries in the battery H-bridge units connected in series to the circuit will be charged. At this time, the battery H-bridge unit with the lowest battery voltage has the highest priority (serial number 1), and the battery H-bridge unit with the highest battery voltage has the lowest priority (serial number n).

[0084] Figure 5 In addition, according to the output voltage level number Nbat of the above-mentioned n battery H-bridge units and the priorities of these n battery H-bridge units, the connection states of the n battery H-bridge units can be determined.

[0085] Among them, when Nbat is positive, the sum of the voltage outputs of all battery H-bridge units is positive. Therefore, when Nbat is positive, the battery H-bridge units are either in a positive series state or in a bypass state. When Nbat is negative, the sum of the voltage outputs of all battery H-bridge units is negative. Therefore, when Nbat is negative, the battery H-bridge units are either in a negative series state or in a bypass state.

[0086] In some embodiments, the state of each battery H-bridge unit can be obtained by comparing the priority number of the battery H-bridge unit with the absolute value of Nbat. Specifically, when Nbat is greater than 0, the battery H-bridge units with priority numbers less than or equal to Nbat are in a positive series state, and the battery H-bridge units with priority numbers greater than Nbat are in a bypass state; when Nbat is less than or equal to 0, the battery H-bridge units with priority numbers less than or equal to -Nbat are in a negative series state, and the battery H-bridge units with priority numbers greater than -Nbat are in a bypass state.

[0087] After determining the connection states of the H-bridge units, according to the corresponding relationship between the connection states of the H-bridge units and the states of the switching units in the H-bridge units, the control states of each switching unit in the n battery H-bridge units can be obtained. Finally, drive signals can be generated based on the control states of each switching unit in the n battery H-bridge units, and the switching units in the battery H-bridge units can be controlled based on the generated drive signals.

[0088] Figure 6 It is a schematic diagram of the state of a battery H-bridge unit. As Figure 6 shown in Figure 6 (a) in bat , when the voltage output V of the battery H-bridge unit is positive and is is also positive, the battery in the battery H-bridge unit connected in series to the circuit will be discharged, and the control switch units S1 and S4 are closed, while the switch units S2 and S3 are open; in Figure 6 (b) in bat , when V is negative and is is positive, the battery in the battery H-bridge unit connected in series to the circuit will be charged, and the control switch units S1 and S4 are open, while the switch units S2 and S3 are closed; in Figure 6 (c) in bat , when V is positive and is is negative, the battery in the battery H-bridge unit connected in series to the circuit will be charged, and the control switch units S1 and S4 are closed, while the switch units S2 and S3 are open; in Figure 6 (d) in bat , when V is negative and is is also negative, the battery in the battery H-bridge unit connected in series to the circuit will be discharged, and the control switch units S1 and S4 are open, while the switch units S2 and S3 are closed; in Figure 6 (e) and (f) in bat , when V is 0, or when is is 0, as shown in Figure 6 (e), the control switch units S2 and S4 can be open, and the switch units S1 and S3 can be closed; or, as shown in Figure 6 (f), the control switch units S2 and S4 can be closed, and the switch units S1 and S3 can be open.

[0089] In the above embodiments, by using the product of the output voltage level number of the battery H-bridge unit and the arm current as the judgment basis, the priority sorting method of the battery H-bridge unit is determined. This method fully considers the characteristics of the battery during the charging and discharging processes, and reasonably arranges the usage order of the battery H-bridge units according to the relationship between voltage and current. When the product is greater than 0, the batteries are sorted from the highest voltage to the lowest voltage, and the batteries with higher voltage can be preferentially used for discharging; when the product is less than or equal to 0, the batteries are sorted from the lowest voltage to the highest voltage, which is beneficial to preferentially charging the batteries with lower voltage, optimizing the charging and discharging processes of the batteries, improving the usage efficiency and lifespan of the batteries, and also making the energy management of the entire system more reasonable.

[0090] In the above embodiments, based on the comparison result between the priority of the battery H-bridge unit and the absolute value of the number of output voltage levels, as well as the positive or negative of the number of output voltage levels, the connection state (forward series connection, bypass, reverse series connection) of each battery H-bridge unit can be accurately determined. This precise connection state determination method enables the battery H-bridge unit to flexibly participate in voltage output or be in a bypass state according to the system requirements, further optimizing the voltage output characteristics of the system. For example, when Nbat is greater than 0, the forward series-connected and bypass battery H-bridge units are reasonably allocated according to the priority number, ensuring the accuracy and stability of the forward voltage output; when Nbat is less than or equal to 0, the accurate control of the reverse series connection and bypass state realizes the effective management of the reverse voltage output.

[0091] In some embodiments, the process of determining the control state of the switching unit of each capacitor H-bridge unit based on the above modulation ratio may include, but is not limited to: comparing the modulation ratio with the instantaneous level of the high-frequency triangular carrier wave to obtain a second comparison result; determining the connection state of each capacitor H-bridge unit according to the second comparison result, and determining the control state of the switching unit of each capacitor H-bridge unit according to the connection state of each capacitor H-bridge unit.

[0092] Among them, the above connection state includes one of a forward series connection state, a bypass state, and a reverse series connection state.

[0093] Exemplarily, Figure 7 is a control block diagram for determining the control state of the switching unit of the capacitor H-bridge unit. As Figure 7 shown, the modulation ratio can be compared with the instantaneous level of the high-frequency triangular carrier wave. When the modulation ratio and the high-frequency triangular carrier wave are compared, when the second comparison result indicates that the capacitor needs to be charged, the capacitor H-bridge unit can enter the forward series connection state or the reverse series connection state. When the second comparison result indicates that the capacitor needs to be discharged, the connection state of the capacitor H-bridge unit can be the bypass state, and the capacitor may discharge. Because the capacitor was previously in a series connection state to participate in voltage output, when it is switched to the bypass state, the voltage difference across the capacitor will cause the capacitor to discharge through the circuit elements connected to it.

[0094] In the above embodiments, by comparing the modulation ratio with the instantaneous level of the high-frequency triangular carrier wave, the control state of the capacitive H-bridge unit is determined, providing an effective way for the precise control of the capacitive H-bridge unit. This method of determining the connection state based on the comparison result and then determining the control state of the switching unit can accurately manage the working mode of the capacitor in the circuit. When charging is required, the capacitive H-bridge unit is made to enter the forward series state or the negative series state, ensuring that the capacitor can obtain energy from the power supply and maintain an appropriate voltage level to meet the system voltage output requirements, which helps to improve the power energy storage and output capabilities of the system. When the comparison result shows that discharging is required, the capacitive H-bridge unit is switched to the bypass state, and the voltage difference across the capacitor is used to discharge through the connected circuit elements. This automatic and precise discharge control mechanism can not only reasonably release the energy stored in the capacitor but also effectively avoid problems such as overcharging of the capacitor, ensuring the safe and stable operation of the capacitor. At the same time, the clear division and flexible switching of the three connection states (forward series state, bypass state, negative series state) enable the capacitive H-bridge unit to accurately participate in or withdraw from the voltage output process according to the real-time power energy demand of the system, greatly optimizing the voltage output characteristics of the entire circuit system, improving the efficiency and reliability of the system, and reducing the power quality problems and circuit fault risks that may be caused by improper capacitor control.

[0095] Exemplarily, Figure 8 is a comparison schematic diagram between the output voltage of the cascaded hybrid H-bridge module in the embodiment of the present application and the output voltage reference. From Figure 8 it can be seen that in the embodiment of the present application, reliable operation of the system and low harmonic distortion can be ensured. Figure 8 The horizontal axis in represents time (Time), and its time unit is second (s), and the vertical axis is the voltage value (Voltage).

[0096] Among them, Figure 8 shows the waveforms of the output voltage and the output voltage reference when the system is powered on. The system output voltage shows a fast transient response when tracking the voltage reference value and can efficiently adapt to the change of the reference value. When the switching frequency of the capacitive H-bridge sub-module is 10 kHz, the total harmonic distortion (THD) is about 1.42%; when the switching frequency of the capacitive H-bridge sub-module is 20 kHz, the THD is about 0.53%.

[0097] Exemplarily, Figure 9 is a schematic diagram of the change of the connection state of the cascaded hybrid H-bridge unit module within two power frequency cycles. Figure 9 In (a) and (b) in, the horizontal axis represents time (Time), and its time unit is second (s). Figure 9 In (a) in, the stepped curve above represents the Nbat value,Figure 9 The other eight curves in (a) represent the connection states of eight battery H-bridge units. The horizontal axis represents time (Time), with the time unit being seconds (s). In the vertical axis, 1 represents the positive series state, 0 represents the bypass state, and -1 represents the negative series state. Figure 9 The curve (b) in represents the Ncap value. The horizontal axis represents time (Time), with the time unit being seconds (s). The vertical axis represents the Ncap value, and the curve represents the change of the Ncap value. By Figure 9 It can be seen that by keeping the switching frequency of the switching units in multiple battery H-bridge units at twice the load frequency, the solution in the embodiment of the present application can reduce the switching frequency to reduce switching losses and thus improve the system efficiency.

[0098] Exemplarily, Figure 10A is a schematic diagram of the arm voltage tracking performance. Figure 10A In (a), it includes the arm output voltage (Stack Voltage) and the arm voltage reference value (Stack Voltage Reference). Taking one capacitor H-bridge unit and n battery H-bridge units as an example. Figure 10A In (b), it includes the output voltage of the capacitor H-bridge unit (Cap-SM OutputVoltage), and the sum of the output voltages of n battery H-bridge units (Bat-SMs Output Voltage). By Figure 10A It can be seen that the arm voltage tracking performance is very excellent. Figure 10A In the horizontal axis represents time (Time), with the time unit being seconds (s). The vertical axis represents voltage, with the voltage unit being V.

[0099] Exemplarily, Figure 10B is a schematic diagram of the voltage balance of a hybrid H-bridge unit module using the method provided in the embodiment of the present application. Figure 10B In, a cascaded hybrid H-bridge module composed of one capacitor H-bridge unit and eight battery H-bridge units is taken as an example for illustration. Figure 10B The curve in represents the battery voltages (Capacitor Voltage) of eight battery H-bridge units, Figure 10B The straight line in represents the average battery voltage (Average Voltage) of the capacitor H-bridge unit. Figure 10B In the horizontal axis represents time (Time), with the time unit being seconds (s). The vertical axis represents voltage, with the voltage unit being V. From Figure 10B It can be seen that the method provided in the embodiment of the present application shows the voltage balance between the capacitor H-bridge unit and different battery H-bridge units, thereby extending the operating life of the system.

[0100] It should be understood that although the steps in the flowcharts involved in the above embodiments are shown in sequence according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear indication in this article, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily executed at the same moment, but can be executed at different moments. The execution order of these steps or stages is not necessarily sequential, but can be executed alternately or in turn with at least a part of other steps or steps or stages in other steps.

[0101] Based on the same inventive concept, an embodiment of the present application further provides a control state determination device for implementing the control state determination method involved above. The implementation solution provided by this device to solve the problem is similar to the implementation solution described in the above method. Therefore, the specific limitations in one or more embodiments of the control state determination device provided below can refer to the limitations on the control state determination method in the above text, and will not be repeated here.

[0102] In an exemplary embodiment, as Figure 11 shown, a structural block diagram of a control state determination device for a switching unit of a single-phase cascaded hybrid H-bridge unit battery energy storage system is provided, including:

[0103] A level number determination module 1101, configured to determine the total output voltage level number of the cascaded hybrid H-bridge module according to the average voltage of each H-bridge unit in the cascaded hybrid H-bridge module and the arm voltage reference value of the cascaded hybrid H-bridge module;

[0104] A voltage deviation determination module 1102, configured to determine the voltage deviation between the n battery H-bridge units and the m capacitor H-bridge units;

[0105] A control module 1103, configured to determine the control state of the switching unit in each H-bridge unit according to the total output voltage level number, the arm current of the cascaded hybrid H-bridge module, and the voltage deviation.

[0106] In one of the embodiments, the control module 1103 is specifically configured to: determine the output voltage level number of the n battery H-bridge units and the modulation ratio of pulse width modulation of the m capacitor H-bridge units according to the total output voltage level number, the arm current of the cascaded hybrid H-bridge module, and the voltage deviation;

[0107] Based on the output voltage level number of the n battery H-bridge units, determine the control state of the switching unit in each battery H-bridge unit;

[0108] Determine the control states of the switching units of each capacitor H-bridge unit based on the modulation ratio.

[0109] In one embodiment, the control module 1103 is specifically configured to:

[0110] If the product of the voltage deviation and the arm current is greater than 0, round down the total output voltage level number to determine the output voltage level number of the n battery H-bridge units, and use the difference between the total output voltage level number and the output voltage level number of the n battery H-bridge units as the modulation ratio of the pulse width modulation of the m capacitor H-bridge units;

[0111] If the product of the voltage deviation and the arm current is less than or equal to 0, round up the total output voltage level number to determine the output voltage level number of the n battery H-bridge units, and use the difference between the total output voltage level number and the output voltage level number of the n battery H-bridge units as the modulation ratio of the pulse width modulation of the m capacitor H-bridge units.

[0112] In one embodiment, the control module 1103 is specifically configured to:

[0113] Determine the priorities of the n battery H-bridge units based on the output voltage level numbers and the arm current of the n battery H-bridge units;

[0114] Determine the connection states of the respective battery H-bridge units according to the priorities of the n battery H-bridge units and the output voltage level numbers of the n battery H-bridge units. The connection states include one of a forward series state, a bypass state, and a negative series state;

[0115] Determine the control states of the switching units of the respective battery H-bridge units according to the connection states of the respective battery H-bridge units.

[0116] In one embodiment, the control module 1103 is specifically configured to:

[0117] Compare the priorities of the n battery H-bridge units with the absolute values of the output voltage level numbers of the n battery H-bridge units to obtain a first comparison result;

[0118] Determine the connection states of the respective battery H-bridge units according to the first comparison result and the positive or negative of the output voltage level numbers of the n battery H-bridge units.

[0119] In one embodiment, the control module 1103 is specifically configured to:

[0120] If the product of the output voltage level numbers of the n battery H-bridge units and the arm current is greater than 0, determine the priorities of the n battery H-bridge units in the order of decreasing battery voltage;

[0121] If the product of the output voltage level of n battery H-bridge units and the arm current is less than or equal to 0, then the priorities of the n battery H-bridge units are determined in ascending order of battery voltage.

[0122] In one embodiment, the control module 1103 is specifically configured to:

[0123] Compare the modulation ratio with the instantaneous level of the high-frequency triangular carrier to obtain a second comparison result;

[0124] According to the second comparison result, determine the connection states of the respective capacitor H-bridge units, where the connection states include: one of a forward series state, a bypass state, and a negative series state;

[0125] According to the connection states of the respective capacitor H-bridge units, determine the control states of the switching units of the respective capacitor H-bridge units.

[0126] Each module in the above control state determination device can be implemented in whole or in part by software, hardware, and their combination. Each of the above modules can be embedded in or independent of a processor in a computer device in hardware form, or stored in a memory in a computer device in software form, so that the processor can call and execute the operations corresponding to each of the above modules.

[0127] In an exemplary embodiment, a computer device is provided. The computer device may be a server, and its internal structure diagram may be as Figure 12 shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, abbreviated as I / O), and a communication interface. Among them, the processor, the memory, and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store data. The input / output interface of the computer device is used to exchange information between the processor and external devices. The communication interface of the computer device is used to communicate with an external terminal through a network connection. The computer program, when executed by the processor, implements a control state determination method.

[0128] Those skilled in the art can understand that Figure 12 the structure shown in merely shows a block diagram of some structures related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine some components, or have a different component layout.

[0129] In an exemplary embodiment, a computer device is provided, including a memory and a processor. A computer program is stored in the memory, and when the processor executes the computer program, each step in the above method embodiment is implemented.

[0130] Those of ordinary skill in the art can understand that all or part of the processes of implementing the methods in the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the above method embodiments. Among them, any reference to a memory, database, or other medium provided in the embodiments of the present application can include at least one of non-volatile and volatile memories. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The databases involved in the embodiments of the present application can include at least one of relational databases and non-relational databases. Non-relational databases can include distributed databases based on blockchain, etc., and are not limited thereto. The processors involved in the embodiments of the present application can be general-purpose processors, central processors, graphics processors, digital signal processors, programmable logic devices, data processing logics based on quantum computing, etc., and are not limited thereto.

[0131] In an exemplary embodiment, a multiphase cascaded hybrid H-bridge battery energy storage system is further provided, which includes a plurality of the above-mentioned single-phase cascaded hybrid H-bridge battery energy storage system switch unit control state determination methods to determine the control states of the switch units in each phase cascaded hybrid H-bridge module.

[0132] As Figure 13The three-phase cascaded hybrid H-bridge battery energy storage system shown includes 3 single-phase cascaded hybrid H-bridge battery energy storage systems. Each single-phase cascaded hybrid H-bridge battery energy storage system includes 1 single-phase cascaded hybrid H-bridge module and a filtering circuit, and is respectively connected to one phase of an external load or the power grid; the three single-phase cascaded hybrid H-bridge battery energy storage systems are connected in a star shape (such as Figure 13 in (a)) or a delta shape ( Figure 13 in (b)). The control states of the switching units in each cascaded hybrid H-bridge module in the three-phase cascaded hybrid H-bridge battery energy storage system are determined by the method for determining the control states of the switching units of the single-phase cascaded hybrid H-bridge battery energy storage system as described above.

[0133] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0134] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A method for determining the control state of a switch unit of a single-phase cascade hybrid H-bridge battery energy storage system, characterized in that: The invention is applied to a single-phase cascade hybrid H-bridge battery energy storage system, comprising: a cascade hybrid H-bridge module and a filter circuit; the cascade hybrid H-bridge module is connected to an external load or a power grid through the filter circuit; the cascade hybrid H-bridge module comprises m cascaded capacitor H-bridge units and n battery H-bridge units; wherein m is greater than or equal to 1 and less than n; n is greater than or equal to 2; the switching frequency of the capacitor H-bridge unit is in a high frequency range, and the switching frequency of the battery H-bridge unit is in a low frequency range, comprising: Determine the total output voltage level number of the cascaded hybrid H-bridge module according to the voltage average value of each H-bridge unit in the cascaded hybrid H-bridge module and the bridge arm voltage reference value of the cascaded hybrid H-bridge module; Determining a voltage deviation between the n battery H-bridge units and the m capacitor H-bridge units; If the product of the voltage deviation and the bridge arm current of the cascaded hybrid H-bridge module is greater than 0, the total output voltage level number is rounded down to determine the output voltage level number of the n battery H-bridge units, and the difference between the total output voltage level number and the output voltage level number of the n battery H-bridge units is used as the modulation ratio of the pulse width modulation of the m capacitor H-bridge units; If the product of the voltage deviation and the bridge arm current of the cascaded hybrid H-bridge module is less than or equal to 0, the total output voltage level number is rounded up to determine the output voltage level number of the n battery H-bridge units, and the difference between the total output voltage level number and the output voltage level number of the n battery H-bridge units is used as the modulation ratio of the pulse width modulation of the m capacitor H-bridge units; Determining a control state of a switch unit of each of the battery H-bridge units based on the number of output voltage levels of the n battery H-bridge units; Based on the modulation ratio, a control state of the switch unit of each of the capacitive H-bridge units is determined.

2. The method according to claim 1, characterized in that The determining the control state of the switch unit of each of the battery H-bridge units based on the number of output voltage levels of the n battery H-bridge units includes: Determining the priorities of the n battery H-bridge units based on the number of output voltage levels of the n battery H-bridge units and the bridge arm current; Determine the connection state of each of the battery H-bridge units according to the priority of the n battery H-bridge units and the number of output voltage levels of the n battery H-bridge units, wherein the connection state includes: one of a forward series state, a bypass state, and a negative series state; According to the connection state of each of the battery H-bridge units, the control state of the switch unit of each of the battery H-bridge units is determined.

3. The method according to claim 2, characterized in that The determining the connection state of each of the battery H-bridge units according to the priority of the n battery H-bridge units and the number of output voltage levels of the n battery H-bridge units includes: Comparing the priorities of the n battery H-bridge units with the absolute values ​​of the output voltage levels of the n battery H-bridge units to obtain a first comparison result; The connection state of each of the battery H-bridge units is determined according to the first comparison result and the positive and negative numbers of the output voltage levels of the n battery H-bridge units.

4. The method according to claim 2, characterized in that: The determining the priorities of the n battery H-bridge units based on the number of output voltage levels of the n battery H-bridge units and the bridge arm currents includes: If the product of the output voltage level number of the n battery H-bridge units and the bridge arm current is greater than 0, the priorities of the n battery H-bridge units are determined in descending order of battery voltage; If the product of the number of output voltage levels of the n battery H-bridge units and the bridge arm current is less than or equal to 0, the priorities of the n battery H-bridge units are determined in order of battery voltage from small to large.

5. The method according to claim 1, characterized in that The determining the control state of the switch unit of each of the capacitor H-bridge units based on the modulation ratio includes: comparing the modulation ratio and the instantaneous level of the high-frequency triangular carrier to obtain a second comparison result; Determine the connection state of each of the capacitor H-bridge units according to the second comparison result, wherein the connection state includes: a forward series state, a bypass state, and a negative series state; The control state of the switch unit of each of the capacitor H-bridge units is determined according to the connection state of each of the capacitor H-bridge units.

6. The method according to claim 1, characterized in that The m is 1.

7. A multi-phase cascade hybrid H-bridge battery energy storage system, characterized in that: It comprises a plurality of single-phase cascade hybrid H-bridge battery energy storage systems, wherein the control state of the switch unit in the single-phase cascade hybrid H-bridge battery energy storage system is determined by the method according to any one of claims 1 to 6.

8. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed by a processor, the method according to any one of claims 1 to 6 is implemented.

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