High-voltage direct-hanging energy storage system and control method

Abstract

The invention discloses a high-voltage direct-hanging energy storage system and a control method, and relates to the technical field of power systems. The high-voltage direct-hanging energy storage system comprises at least one single-phase energy storage circuit, in the single-phase energy storage circuit, a direct-current energy storage module is formed by connecting N energy storage sub-modules in series, each energy storage sub-module comprises a half-bridge unit and an energy storage element, and the energy storage sub-modules are used for achieving switching of working states of input, switching-out or locking through the half-bridge units; the current conversion module comprises a first bridge arm branch and a second bridge arm branch; the first bridge arm branch and the second bridge arm branch are used for being connected to the two ends of a direct-current energy storage module in parallel, and the midpoint of the first bridge arm branch and the midpoint of the second bridge arm branch are used for being electrically connected with an alternating-current interface of one phase of an alternating-current power grid. The direct current energy storage module is used for generating a multi-level voltage equivalent to a half sine wave, and the current conversion module is used for performing forward output or reverse output on the multi-level voltage. According to the embodiment of the invention, the overall performance of the energy storage system can be effectively improved.

Description

Technical Field

[0001] This application belongs to the technical field of power systems, and particularly relates to a high-voltage direct-connected energy storage system and a control method therefor. Background Art

[0002] At present, energy storage devices can store and release electrical energy, and play an important role in scenarios such as peak shaving and frequency modulation, new energy consumption, and large-scale new energy transmission. They are one of the indispensable important devices for building a new power system. However, at the present stage, the energy storage devices in traditional technologies directly connect the batteries in parallel to the DC-side bus, and then convert them into alternating current through a centralized converter, and then step up the voltage through a transformer and connect to the power grid. This method requires a large number of DC cables, DC busbars, and transformers, resulting in an obvious increase in the structure load and energy storage cost, and increasing the complexity and cost of the system. In addition, the control of such centralized converters is relatively complex, and it is difficult to achieve precise voltage and power control. Based on this, the industry still urgently needs a high-voltage direct-connected energy storage solution to fully reduce the system cost and complexity, and improve the flexibility and reliability of the operation of the energy storage system. Summary of the Invention

[0003] The embodiments of this application provide a high-voltage direct-connected energy storage system and a control method therefor, which can fully reduce the cost and complexity of the energy storage system, improve the flexibility and reliability of the operation of the energy storage system, and thus effectively improve the overall performance of the energy storage system.

[0004] In a first aspect, the embodiments of this application provide a high-voltage direct-connected energy storage system, which includes at least one single-phase energy storage circuit. The single-phase energy storage circuit includes:

[0005] A DC energy storage module, which is formed by connecting N energy storage sub-modules in series. Each energy storage sub-module includes a half-bridge unit and an energy storage element. The energy storage sub-module is used to switch the working state of input, cut-out, or locking through the half-bridge unit, where N is a positive integer;

[0006] A commutation module, which includes a first bridge arm branch and a second bridge arm branch; the first bridge arm branch and the second bridge arm branch are used to be connected in parallel at both ends of the DC energy storage module, and the midpoints of the first bridge arm branch and the second bridge arm branch are used to be electrically connected to the AC interface of one phase of the AC power grid;

[0007] Among them, the DC energy storage module is used to generate a multi-level voltage equivalent to a sine half-wave, and the commutation module is used to output the multi-level voltage forward or backward to obtain a single-phase AC voltage of one phase of the AC power grid.

[0008] In some possible implementation manners, the half-bridge unit includes a first bridge arm unit and a second bridge arm unit;

[0009] The first end of the first arm unit is electrically connected to the positive electrode of the corresponding energy storage element. The second end of the first arm unit is electrically connected to the first end of the second arm unit, and the second end of the second arm unit is electrically connected to the negative electrode of the corresponding energy storage element;

[0010] Set the second end of the first arm unit as the first node and the second end of the second arm unit as the second node;

[0011] The second node in the i-th energy storage sub-unit is electrically connected to the first node in the (i + 1)-th energy storage sub-unit. The first ends of the first arm branch and the second arm branch are respectively electrically connected to the first node in the first energy storage sub-unit. The first ends of the first arm branch and the second arm branch, and the second ends of the first arm branch and the second arm branch are respectively electrically connected to the second node in the N-th energy storage sub-unit, where 1 ≤ i ≤ N;

[0012] Wherein, both the first arm unit and the second arm unit include a switching tube and an anti-parallel diode arranged at both ends of the switching tube.

[0013] In some possible implementation manners, the energy storage sub-module further includes an interface unit; the interface unit includes a support capacitor and a filtering unit, and the filtering unit includes a filtering inductor;

[0014] The positive electrode of the energy storage element is electrically connected to the first end of the first arm unit through the filtering inductor;

[0015] The first end of the support capacitor is electrically connected to the first end of the first arm unit, and the second end of the support capacitor is electrically connected to the negative electrode of the energy storage element.

[0016] In some possible implementation manners, the first arm branch includes two groups of valve strings connected in series, and the second arm branch includes two groups of valve strings connected in series;

[0017] Any group of valve strings includes a plurality of switching units connected in series, and the switching unit includes an IGCT and an anti-parallel diode arranged at both ends of the IGCT.

[0018] In some possible implementation manners, set the valve string corresponding to the upper arm of the first arm branch as the first valve string, the valve string corresponding to the upper arm of the second arm branch as the second valve string, the valve string corresponding to the lower arm of the first arm branch as the third valve string, and the valve string corresponding to the lower arm of the second arm branch as the fourth valve string;

[0019] At least one of the first valve string and the fourth valve string, and at least one of the second valve string and the third valve string further includes: at least one hybrid switching unit;

[0020] The hybrid switching unit is connected in series with a plurality of switching units in the corresponding valve string, and the hybrid switching unit includes an IGCT, an IGBT and an anti-parallel diode connected in parallel.

[0021] In some possible embodiments, a valve string including a hybrid switch unit is set as a target valve string;

[0022] When the target valve string is in the stage of waiting to be turned on, the IGBT in the corresponding hybrid switch unit is turned on first, the IGCT in the corresponding hybrid switch unit is turned on, and the IGBT in the corresponding hybrid switch unit is turned off at zero voltage;

[0023] And / or, when the target valve string is in the stage of waiting to be turned off, the IGBT in the corresponding hybrid switch unit is turned on first, the IGCT in the corresponding hybrid switch unit is turned off at zero voltage, and the IGBT in the corresponding hybrid switch unit is turned off later.

[0024] In some possible embodiments, the switch unit further includes: a diode, a capacitor and a resistor;

[0025] The anode of the diode is electrically connected to the cathode of the anti-parallel diode in the switch unit, the cathode of the diode is electrically connected to the anode of the anti-parallel diode through the capacitor, and the resistor is connected in parallel with the capacitor.

[0026] Based on the same inventive concept, in a second aspect, an embodiment of the present application provides a control method for a high-voltage direct-connected energy storage system, which is applied to the high-voltage direct-connected energy storage system according to any one of the foregoing embodiments of the present application; the control method for the high-voltage direct-connected energy storage system includes:

[0027] Controlling the half-bridge units in N energy storage sub-modules in the DC energy storage module to realize the switching of the working states of the corresponding energy storage sub-modules for input, cut-out or locking, so that the DC energy storage module generates a multi-level voltage equivalent to a sine half-wave;

[0028] Controlling the first bridge arm branch and the second bridge arm branch in the commutation module so that the commutation module outputs the multi-level voltage in the forward or reverse direction to obtain a single-phase AC voltage of one phase of the AC power grid.

[0029] In some possible embodiments, the half-bridge unit includes a first bridge arm unit and a second bridge arm unit, and both the first bridge arm unit and the second bridge arm unit include a switching tube and an anti-parallel diode arranged at both ends of the switching tube;

[0030] Controlling the half-bridge units in N energy storage sub-modules in the DC energy storage module to realize the switching of the working states of the corresponding energy storage sub-modules for input, cut-out or locking, includes:

[0031] Controlling the switching tube in the corresponding first bridge arm unit to be turned on and the switching tube in the second bridge arm unit to be turned off to realize the input of the corresponding energy storage sub-module;

[0032] Control the switch tube in the corresponding first arm unit to turn off and the switch tube in the second arm unit to turn on, so as to realize the cut-out of the corresponding energy storage sub-module;

[0033] Control the switch tube in the corresponding first arm unit to turn off and the switch tube in the second arm unit to turn off, so as to realize the locking of the corresponding energy storage sub-module.

[0034] In some possible implementation manners, set the valve string corresponding to the upper arm of the first arm branch as the first valve string, the valve string corresponding to the upper arm of the second arm branch as the second valve string, the valve string corresponding to the lower arm of the first arm branch as the third valve string, and the valve string corresponding to the lower arm of the second arm branch as the fourth valve string;

[0035] Control the first arm branch and the second arm branch in the commutation module, so that the commutation module outputs the multi-level voltage in the forward direction or the reverse direction, including:

[0036] Control the first valve string and the fourth valve string to turn on, and control the second valve string and the third valve string to turn off, so that the commutation module outputs the multi-level voltage in the forward direction;

[0037] Control the first valve string and the fourth valve string to turn off, and control the second valve string and the third valve string to turn on, so that the commutation module outputs the multi-level voltage in the reverse direction.

[0038] In some possible implementation manners, at least one of the first valve string and the fourth valve string, and at least one of the second valve string and the third valve string further include: at least one hybrid switch unit;

[0039] The hybrid switch unit is connected in series with multiple switch units in the corresponding valve string, and the hybrid switch unit includes an IGCT, an IGBT and an antiparallel diode connected in parallel;

[0040] Set the valve string including the hybrid switch unit as the target valve string;

[0041] When the target valve string is in the to-be-opened stage, control the IGBT in the corresponding hybrid switch unit to turn on first, the IGCT in the corresponding hybrid switch unit to turn on, and the IGBT in the corresponding hybrid switch unit to turn off at zero voltage;

[0042] And / or, when the target valve string is in the to-be-shut-off stage, control the IGBT in the corresponding hybrid switch unit to turn on first, the IGCT in the corresponding hybrid switch unit to turn off at zero voltage, and the IGBT in the corresponding hybrid switch unit to turn off later.

[0043] In some possible implementation manners, the control method of the high-voltage direct-connected energy storage system further includes:

[0044] Compare the current voltage of the DC energy storage module with the target voltage of the modulation wave to obtain the absolute value of the voltage difference between the current voltage and the target voltage;

[0045] When the absolute value of the voltage difference reaches the preset voltage value and the target voltage is higher than the current voltage, control one of the N energy storage sub-modules to be put into operation;

[0046] When the absolute value of the voltage difference reaches the preset voltage value and the target voltage is lower than the current voltage, control one of the N energy storage sub-modules to be cut out;

[0047] Wherein, the preset voltage value is half of the voltage of the energy storage element.

[0048] In some possible implementation manners, the control method of the high-voltage directly-connected energy storage system further includes: sorting the state of charge of the energy storage elements in the energy storage sub-modules among the N energy storage sub-modules;

[0049] Controlling one of the N energy storage sub-modules to be put into operation includes:

[0050] When the DC energy storage module is in the charging state, control the energy storage sub-module with the lowest state of charge among the N energy storage sub-modules that have not been put into operation to be put into operation;

[0051] When the DC energy storage module is in the discharging state, control the energy storage sub-module with the highest state of charge among the N energy storage sub-modules that have not been put into operation to be put into operation;

[0052] Controlling one of the N energy storage sub-modules to be cut out includes:

[0053] When the DC energy storage module is in the charging state, control the energy storage sub-module with the highest state of charge among the N energy storage sub-modules that have not been cut out to be cut out;

[0054] When the DC energy storage module is in the discharging state, control the energy storage sub-module with the lowest state of charge among the N energy storage sub-modules that have not been cut out to be cut out.

[0055] In some possible implementation manners, when the absolute value of the voltage difference does not reach the preset voltage value, the control method of the high-voltage directly-connected energy storage system further includes:

[0056] When the DC energy storage module is in the charging state, control the energy storage sub-module with the lowest state of charge among the N energy storage sub-modules that have not been put into operation to be put into operation, and control the energy storage sub-module with the highest state of charge among the N energy storage sub-modules that have not been cut out to be cut out;

[0057] When the DC energy storage module is in the discharging state, control the energy storage sub-module with the highest state of charge among the N energy storage sub-modules that are not put into operation to be put into operation, and control the energy storage sub-module with the lowest state of charge among the N energy storage sub-modules that are not cut out to be cut out.

[0058] In some possible implementation manners, the control method of the high-voltage directly-connected energy storage system further includes:

[0059] Adopt N sets of triangular waves with an amplitude of 1 and a frequency of f c as the carrier wave, and the phase difference between adjacent triangular waves is Use a sine half-wave with an amplitude of and a frequency of 100 Hz as the modulation wave, and generate a PWM signal through the modulation of the triangular wave and the modulation wave;

[0060] The PWM signal is used to control the half-bridge units in the N energy storage sub-modules of the DC energy storage module to realize the switching of the working states of the corresponding energy storage sub-modules, such as being put into operation, cut out, or locked;

[0061] wherein, f c > 500 Hz and is an integer multiple of 100 Hz, U bat is the voltage of the energy storage element, and U peak is the peak value of the output AC phase voltage.

[0062] In a third aspect, an embodiment of the present application provides a control device for a high-voltage directly-connected energy storage system. The control device for the high-voltage directly-connected energy storage system includes:

[0063] A processor and a memory storing computer program instructions;

[0064] When the processor executes the computer program instructions, it implements the control method of the high-voltage directly-connected energy storage system provided in any one of the above embodiments of the present application.

[0065] In a fourth aspect, an embodiment of the present application provides a computer storage medium. Computer program instructions are stored on the computer-readable storage medium. When the computer program instructions are executed by a processor, they implement the control method of the high-voltage directly-connected energy storage system provided in any one of the above embodiments of the present application.

[0066] In a fifth aspect, an embodiment of the present application provides a computer program product. When the instructions in the computer program product are executed by the processor of an electronic device, the electronic device is caused to execute the control method of the high-voltage directly-connected energy storage system provided in any one of the above embodiments of the present application.

[0067] As can be seen from the above description, a high-voltage direct-connected energy storage system and control method provided by an embodiment of the present application arrange the energy storage of each phase in three-phase respectively, and each phase uses a corresponding single-phase energy storage circuit to access the AC power grid. The single-phase energy storage circuit includes two parts: a DC energy storage module and a commutation module. The DC energy storage module is composed of N energy storage sub-modules connected in series. The energy storage sub-module includes a half-bridge unit and an energy storage element. The energy storage sub-module is used to realize the switching of the working states of input, cut-off or locking through the half-bridge unit, so as to generate a multi-level voltage equivalent to a sine half-wave. The commutation module can realize the forward output or reverse output of the multi-level voltage by the conduction of the devices in the first bridge arm branch and the second bridge arm branch, so as to finally obtain the single-phase AC voltage required for one phase of the AC power grid.

[0068] Compared with the related technology, a high-voltage direct-connected energy storage system and control method provided by an embodiment of the present application directly realizes the output of a single-phase AC voltage by adopting a single-phase energy storage circuit including the above-mentioned DC energy storage module and commutation module, reduces the dependence on a large number of DC cables and transformers, etc., and thus fully reduces the complexity and cost of the energy storage system. Moreover, the independent control and energy storage management of each phase in the three-phase in the present application also improve the flexibility and reliability of the energy storage system, and thus can effectively improve the overall performance of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0070] Figure 1 is a schematic structural diagram of a high-voltage direct-connected energy storage system provided by an embodiment of the present application;

[0071] Figure 2 is a schematic structural diagram of another high-voltage direct-connected energy storage system provided by an embodiment of the present application;

[0072] Figure 3 is a schematic working principle diagram of a high-voltage direct-connected energy storage system provided by an embodiment of the present application;

[0073] Figure 4 is a schematic structural diagram of a DC energy storage module provided by an embodiment of the present application;

[0074] Figure 5 is a schematic diagram of the working state of a DC energy storage module provided by an embodiment of the present application;

[0075] Figure 6 is a schematic structural diagram of an interface unit in a DC energy storage module provided by an embodiment of the present application;

[0076] Figure 7 It is a schematic structural diagram of another high-voltage direct-connected energy storage system provided by an embodiment of the present application;

[0077] Figure 8 It is a schematic structural diagram of a valve string provided by an embodiment of the present application;

[0078] Figure 9 It is a schematic diagram of the working state of a commutation module provided by an embodiment of the present application;

[0079] Figure 10 It is a schematic diagram of the working state of another commutation module provided by an embodiment of the present application;

[0080] Figure 11 It is a schematic diagram of the high-load operation of a commutation module provided by an embodiment of the present application;

[0081] Figure 12 It is a schematic structural diagram of a switch unit in a valve string provided by an embodiment of the present application;

[0082] Figure 13 It is provided by an embodiment of the present application Figure 12 A schematic diagram of the working state of the shown switch unit;

[0083] Figure 14 It is a schematic structural diagram of a valve string including a hybrid switch unit provided by an embodiment of the present application;

[0084] Figure 15 It is a schematic diagram of the principle of single-phase energy storage circuit output power control provided by an embodiment of the present application;

[0085] Figure 16 It is a schematic flowchart of a control method for a high-voltage direct-connected energy storage system provided by an embodiment of the present application;

[0086] Figure 17 It is a schematic structural diagram of a control device for a high-voltage direct-connected energy storage system provided by an embodiment of the present application. Detailed Embodiments

[0087] The features and exemplary embodiments of various aspects of the present application will be described in detail below. 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 specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than limiting the present application. For those skilled in the art, the present application can be implemented without some of these specific details. The following description of the embodiments is only intended to provide a better understanding of the present application by showing examples of the present application.

[0088] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the said element.

[0089] It should be understood that the term "and / or" used in this text is only an associative relationship describing associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. Additionally, the character " / " in this text generally indicates that the associated objects before and after are in an "or" relationship.

[0090] In the embodiments of the present application, the term "electrically connected" can refer to two components being directly electrically connected, or can also refer to two components being electrically connected via one or more other components.

[0091] In the embodiments of the present application, the first node, the second node, and the third node are only defined for the convenience of describing the circuit structure, and the first node, the second node, and the third node are not an actual circuit unit.

[0092] Without departing from the spirit or scope of the present application, various modifications and variations can be made to the present application, which are obvious to those skilled in the art. Therefore, the present application is intended to cover modifications and variations of the present application that fall within the scope of the corresponding claims (the claimed technical solutions) and their equivalents. It should be noted that the embodiments provided in the embodiments of the present application can be combined with each other without contradiction.

[0093] Before elaborating on the technical solutions provided in the embodiments of the present application, for the convenience of understanding the embodiments of the present application, the present application first specifically describes the problems existing in the related art:

[0094] In view of the above, in order to solve the problems of the prior art, the embodiments of the present application provide a high-voltage direct-connected energy storage system 1000 and a control method. It should be noted that the embodiments provided by the present application are not used to limit the scope of the present disclosure.

[0095] First, a high-voltage direct-connected energy storage system 1000 provided by the embodiments of the present application will be introduced below. Please refer to Figure 1, Figure 1 It is a schematic structural diagram of a high-voltage direct-connected energy storage system 1000 provided by an embodiment of the present application.

[0096] As Figure 1 shown, an embodiment of the present application provides a high-voltage direct-connected energy storage system 1000. The high-voltage direct-connected energy storage system 1000 includes at least one single-phase energy storage circuit, and the single-phase energy storage circuit includes a DC energy storage module 100 and a commutation module 200.

[0097] More specifically, please refer to Figure 2 , Figure 2 It is a schematic structural diagram of another high-voltage direct-connected energy storage system provided by an embodiment of the present application. In Figure 2 , the DC energy storage module 100 is formed by connecting N energy storage sub-modules 10 in series. The energy storage sub-module 10 includes a half-bridge unit and an energy storage element. The energy storage sub-module 10 is used to realize the switching of the working states of input, cut-out or locking through the half-bridge unit, and N is a positive integer.

[0098] The above commutation module 200 includes a first bridge arm branch and a second bridge arm branch; the first bridge arm branch and the second bridge arm branch are used to be connected in parallel at both ends of the DC energy storage module 100, and the midpoints of the first bridge arm branch and the second bridge arm branch are used to be electrically connected to an AC interface of one phase of the AC power grid 300.

[0099] Among them, the DC energy storage module 100 is used to generate a multi-level voltage equivalent to a sine half-wave, and the commutation module 200 is used to output the multi-level voltage forward or backward to obtain a single-phase AC voltage of one phase of the AC power grid 300.

[0100] Specifically, the high-voltage direct-connected energy storage system 1000 includes at least one single-phase energy storage circuit. For example, for a three-phase AC power grid 300, one single-phase energy storage circuit is provided for each of the a, b, and c phases. It should be understood that Figure 1 , Figure 2 the scheme in uses a star connection method, but the high-voltage direct-connected energy storage system 1000 of the present application can also be applied to a delta connection method, and the present application does not make strict restrictions here.

[0101] The above DC energy storage module 100 is formed by connecting N energy storage sub-modules 10 in series. The DC energy storage module 100 adopts a multi-level technology and uses a half-bridge unit to realize the switching of the working states of input, cut-out or locking, so as to control the input and cut-out of the energy storage element.

[0102] In this way, by controlling the switching of the energy storage sub-module 10, the DC energy storage module 100 can flexibly output N + 1 levels between 0 and NUbat, and thus can periodically generate a multi-level voltage equivalent to the sine half-wave |sinωt| by controlling the change of the level output over time. Wherein, Ubat is the voltage of a single energy storage element.

[0103] For the multi-level voltage output generated by the DC energy storage module 100 in two consecutive cycles, the above commutation module 200 controls the conduction of the devices in the first bridge arm branch and the second bridge arm branch, so as to be in the forward output state and the reverse output state respectively in two consecutive cycles.

[0104] For example, please refer to Figure 3 , Figure 3 which is the working principle diagram of a high-voltage direct-connected energy storage system provided by an embodiment of the present application. As Figure 3 shown, the commutation module 200 outputs the multi-level voltage generated by the DC energy storage module 100 in the forward direction in the first cycle, and outputs the output voltage of the DC energy storage module 100 in the reverse direction in the second cycle, so as to finally generate a voltage output close to sinωt at the corresponding single-phase AC outgoing line terminal.

[0105] It should be noted that the energy storage element can be a super capacitor or an electrochemical battery. Select the corresponding scheme according to the different application scenarios of the energy storage system. If it is mainly used in scenarios such as peak shaving and new energy consumption, a battery with a higher energy density can be selected; if it is mainly used in scenarios such as reactive power compensation, frequency and voltage support, a super capacitor with a higher power density can be selected. In the following of this application, the working state of the DC energy storage module 100 will be mainly described by taking the battery as an example.

[0106] From the above description, it can be seen that a high-voltage direct-connected energy storage system 1000 provided by an embodiment of the present application arranges the energy storage of each phase in three phases, and each phase uses the corresponding single-phase energy storage circuit to access the AC power grid 300. The single-phase energy storage circuit includes two parts: a DC energy storage module 100 and a commutation module 200. The DC energy storage module 100 is composed of N energy storage sub-modules 10 connected in series. The energy storage sub-module 10 includes a half-bridge unit and an energy storage element. The energy storage sub-module 10 is used to realize the switching of the working states of input, cut-out or locking through the half-bridge unit, so as to generate a multi-level voltage equivalent to the sine half-wave. The commutation module 200 can realize the forward output or reverse output of the multi-level voltage by the conduction of the devices in the first bridge arm branch and the second bridge arm branch, so as to finally obtain the single-phase AC voltage required for one phase of the AC power grid 300.

[0107] Compared with the related art, a high-voltage direct-connected energy storage system 1000 provided by an embodiment of the present application directly realizes the output of single-phase AC voltage by adopting a single-phase energy storage circuit including the above-mentioned DC energy storage module 100 and commutation module 200, reducing the dependence on a large number of DC cables and transformers, etc., thereby fully reducing the complexity and cost of the energy storage system. Moreover, in the present application, independent control and energy storage management are performed on each phase of the three-phase, improving the flexibility and reliability of the energy storage system, and also being able to better achieve voltage balance and power control, thereby effectively improving the overall performance of the energy storage system.

[0108] Please refer to the following Figure 4 , Figure 4 which is a schematic structural diagram of a DC energy storage module provided by an embodiment of the present application. According to some embodiments of the present application, optionally, the half-bridge unit includes a first bridge arm unit 11 and a second bridge arm unit 12;

[0109] The first end of the first bridge arm unit 11 is electrically connected to the positive electrode of the corresponding energy storage element, the second end of the first bridge arm unit 11 is electrically connected to the first end of the second bridge arm unit 12, and the second end of the second bridge arm unit 12 is electrically connected to the negative electrode of the corresponding energy storage element;

[0110] Set the second end of the first bridge arm unit 11 as the first node N1, and the second end of the second bridge arm unit 12 as the second node N2;

[0111] The second node N2 in the i-th energy storage sub-unit is electrically connected to the first node N1 in the i + 1-th energy storage sub-unit. The first end of the first bridge arm branch and the first end of the second bridge arm branch are respectively electrically connected to the first node N1 in the first energy storage sub-unit. The first end of the first bridge arm branch, the first end of the second bridge arm branch, the second end of the first bridge arm branch, and the second end of the second bridge arm branch are respectively electrically connected to the second node N2 in the N-th energy storage sub-unit, 1 ≤ i ≤ N;

[0112] Among them, both the first bridge arm unit 11 and the second bridge arm unit 12 include a switching tube and an anti-parallel diode arranged at both ends of the switching tube.

[0113] In this embodiment, as Figure 4 shown, it specifically shows the series connection mode of N energy storage sub-modules 10, and the specific structures of the first bridge arm unit 11 and the second bridge arm unit 12 in the half-bridge unit. Both the first bridge arm unit 11 and the second bridge arm unit 12 include a switching tube and an anti-parallel diode arranged at both ends of the switching tube.

[0114] During specific operation, the half-bridge unit in the energy storage sub-module 10 can be specifically divided into three working states: input, cut-out, and lock according to different switching tubes being turned on, as Figure 5 (a), 5(b), and 5(c) shown.

[0115] In Fig. 5(a), taking the switching device in the first bridge arm unit 11 as the upper switch, the switching device in the second bridge arm unit 12 as the lower switch, and the energy storage element as the battery as an example: when the upper switch is turned on and the lower switch is turned off, the energy storage sub-module 10 is in the working state of being put into operation, the battery is connected to the circuit, and it can be charged or discharged. The energy storage sub-module 10 outputs the battery voltage.

[0116] In Fig. 5(b), when the lower switch is turned on and the upper switch is turned off, the energy storage sub-module 10 is in the state of being cut out of operation, the battery is cut out of the circuit, and it will not be charged or discharged. The voltage output by the energy storage sub-module 10 to the outside is 0 (ignoring the conduction voltage of the device).

[0117] In Fig. 5(c), when both the upper and lower switches are turned off, the energy storage sub-module 10 is in the locked state of operation. The battery can only be uncontrollably charged through the anti-parallel diode of the device. The module voltage is related to the external circuit and will not exceed the battery voltage.

[0118] It should be understood that the above-mentioned switching device is, for example, an IGBT (Insulated Gate Bipolar Transistor). The switching speed of the IGBT is relatively fast. Therefore, it can fully meet the strong current interruption requirements of the energy storage sub-module 10 when it is put into operation and cut out, so as to ensure the output reliability of the multi-level voltage.

[0119] Please refer to the following Figure 6 , Figure 6 which is a schematic structural diagram of an interface unit in a DC energy storage module provided by an embodiment of the present application. According to some embodiments of the present application, optionally, the energy storage sub-module 10 further includes an interface unit 13; the interface unit 13 includes a support capacitor C1 and a filtering unit, and the filtering unit includes a filtering inductor L1;

[0120] The positive electrode of the energy storage element is electrically connected to the first end of the first bridge arm unit 11 through the filtering inductor L1;

[0121] The first end of the support capacitor C1 is electrically connected to the first end of the first bridge arm unit 11, and the second end of the support capacitor C1 is electrically connected to the negative electrode of the energy storage element.

[0122] In this embodiment, as shown in Figure 6 (a), the energy storage sub-module 10 is further provided with an interface unit 13. The left side of the interface unit 13 is connected to the energy storage element, and the right side of the interface unit 13 is connected to the half-bridge unit. The interface unit 13 includes a support capacitor C1 and a filtering unit. The interface unit 13 can effectively absorb harmonic current, keep the current of the energy storage element constant, and avoid the reduction of the service life of the energy storage element caused by the ripple current.

[0123] The support capacitor C1 can maintain the voltage stability of the energy storage elements in the energy storage sub-module 10. For example, during the battery discharge process, especially during high-rate discharge, the battery voltage may drop rapidly. The support capacitor C1 in this embodiment can provide additional electrical energy to maintain the battery voltage at a certain level, thereby improving the stability of the system. Moreover, the support capacitor C1 can also absorb part of the current harmonics, thereby smoothing the voltage fluctuations.

[0124] The above-mentioned setting of the filter inductor L1 can effectively remove current filtering, thereby improving the stability of the energy storage elements. It should be added that in this embodiment, the filter inductor L1 is taken as an example to illustrate the filter unit. However, in some other possible embodiments, for example Figure 6 the LC network shown in (b) can be used to form a filter circuit to achieve the function of the filter unit, or other filter structures can be used to achieve the function of the filter unit, which is not strictly limited here. Figure 6 In (b), adding the capacitor C2 and the inductor L2 can more effectively filter the harmonics of the energy storage elements.

[0125] Please refer to the following Figure 7 , Figure 7 which is a schematic structural diagram of another high-voltage direct-connected energy storage system provided by the embodiment of the present application. According to some embodiments of the present application, optionally, the first bridge arm branch includes two groups of valve strings T1 and T2 connected in series, and the second bridge arm branch includes two groups of valve strings T3 and T4 connected in series;

[0126] Any group of valve strings includes a plurality of switch units 20 connected in series. The switch unit 20 includes an IGCT and an antiparallel diode arranged at both ends of the IGCT. As Figure 7 shown, four groups of valve strings are used in the above commutation module 200 to implement the first bridge arm branch and the second bridge arm branch.

[0127] Please refer to the following Figure 8 , Figure 8 which is a schematic structural diagram of a valve string provided by the embodiment of the present application. As Figure 8 shown, taking the valve string T1 as an example, each group of valve strings includes a plurality of switch units 20 connected in series.

[0128] The switch unit 20 includes an IGCT (Integrated Gate-Commutated Thyristor) and an antiparallel diode arranged at both ends of the IGCT. That is to say, each group of valve strings uses multiple IGCTs connected in series, and each IGCT is shunted by an antiparallel diode, and the antiparallel diode can realize reverse current conduction.

[0129] During specific operation, by controlling the conduction and cutoff of each valve string in the first bridge arm branch and the second bridge arm branch, the three operating states of forward output, reverse output, and blocking of the commutation module 200 can be achieved. For ease of description, hereinafter, the valve string corresponding to the upper bridge arm of the first bridge arm branch is set as the first valve string T1, the valve string corresponding to the upper bridge arm of the second bridge arm branch is set as the second valve string T2, the valve string corresponding to the lower bridge arm of the first bridge arm branch is set as the third valve string T3, and the valve string corresponding to the lower bridge arm of the second bridge arm branch is set as the fourth valve string T4.

[0130] Please refer to Figure 9 , Figure 9 which is a schematic diagram of the operating states of a commutation module provided by an embodiment of the present application. When the first valve string T1 and the fourth valve string T4 are conducting, as Figure 9 (a) shows, during charging on the DC side, the charging current flows into the DC energy storage module 100 on the DC side through the antiparallel diodes in the first valve string T1 and the fourth valve string T4 to charge the energy storage elements in the DC energy storage module 100.

[0131] Or, as Figure 9 (b) shows, during discharging on the DC side, the multi-level voltage generated by the commutation module 200 for the DC energy storage module 100 is in the forward output state, and the DC voltage generated by the DC energy storage module 100 is directly output to the AC outgoing line through the IGCTs in the first valve string T1 and the fourth valve string T4.

[0132] Please refer to Figure 10 , Figure 10 which is another schematic diagram of the operating states of a commutation module provided by an embodiment of the present application. When the second valve string T2 and the third valve string T3 are conducting, as Figure 10 (a) shows, during charging on the DC side, the charging current flows reversely into the DC energy storage module 100 on the DC side through the antiparallel diodes in the second valve string T2 and the third valve string T3 to charge the energy storage elements in the DC energy storage module 100.

[0133] Or, as Figure 10 (b) shows, during discharging on the DC side, the multi-level voltage generated by the commutation module 200 for the DC energy storage module 100 is in the reverse output state, and the DC voltage generated by the DC energy storage module 100 is reversely output to the AC outgoing line through the IGCTs in the second valve string T2 and the third valve string T3.

[0134] When the IGCTs in all four groups of valve strings are cutoff, the H-bridge is in the blocking state, and the DC energy storage module 100 performs uncontrolled charging. This uncontrolled charging process is similar to Figure 9 (a), Figure 10 (a), and will not be elaborated here.

[0135] As shown above, the commutation module 200 can achieve high overload operation by utilizing the high current-carrying capacity of the IGCT device.

[0136] Specifically, please refer to Figure 11 , Figure 11 which is a schematic diagram of the high overload operation of a commutation module provided by an embodiment of the present application. As Figure 11 shown, the energy storage system usually operates under the rated condition of active power P = 1 and reactive power Q ≈ 0, and the AC voltage and current are basically in phase. The commutation action of the commutation module 200 occurs at the moment when the output voltage of the DC energy storage module 100 on the DC side returns to zero. At this time, since the phase angle between the AC voltage and current is close to zero, the AC voltage crosses zero, and the current is also close to the zero-crossing point. The IGCT device is in the zero-voltage turn-off condition, and the turn-off current is also very small.

[0137] Please continue to refer to Figure 11 , when the energy storage system operates under the high overload condition of active power P = 3 and reactive power Q ≈ 0, the AC current is 3 times the rated current. However, since the IGCT has a high current-carrying capacity and can withstand large currents, the IGCT can conduct current safely at 3 times the AC current without damage. When the commutation module 200 commutes, the AC voltage crosses zero, and the current is also close to the zero-crossing point, and the IGCT can be reliably turned off.

[0138] In this way, high overload operation can be achieved by utilizing the high current-carrying capacity of the IGCT device. Moreover, when the commutation module 200 performs zero-voltage commutation, the IGCT can also be reliably turned off at zero current.

[0139] It should be added that in some other embodiments, the above-mentioned switching unit 20 may also include an IGBT and an antiparallel diode arranged at both ends of the IGBT, or include other types of switching tubes and antiparallel diodes arranged at both ends of the switching tube, which are not strictly limited herein.

[0140] Next, please refer to Figure 12 , Figure 12 which is a schematic structural diagram of a switching unit in a valve string provided by an embodiment of the present application. According to some embodiments of the present application, optionally, the switching unit 20 further includes: diode D f , capacitor C s and resistor R s ;

[0141] The anode of diode D f is electrically connected to the cathode of the antiparallel diode D r in the switching unit 20. The cathode of diode D f is electrically connected to the anode of the antiparallel diode D r through a capacitor. Resistor R s is connected to capacitor Cs Parallel connection.

[0142] In this embodiment, by further arranging an RCD branch including a diode D f , a capacitor C s and a resistor R s in the switching unit 20, the voltage balance can be effectively maintained during the valve string turn-off process.

[0143] Combined with Figure 12 the structure, please refer to Figure 13 , Figure 13 which is a schematic diagram of the working state of the switching unit provided by the embodiment of the present application. In Figure 12 shown, when the corresponding valve string (such as the first valve string T1) is conducting normally in Figure 13 (a), the IGCT ( Figure 12 the T m switching tube) in the switching unit is conducting; in Figure 13 (b), when the corresponding valve string (such as the first valve string T1) is turned off, in the switching unit 20 thereof, the voltage of the T m device rises rapidly first. When the voltage exceeds the voltage of the capacitor C s , the diode D f conducts, and the arm current flows through the capacitor C s and charges the capacitor C s . The voltage of the T m device is clamped by the capacitor and the balance is achieved; in Figure 13 (c), the capacitor voltage promotes the commutation of the current at the same time; in Figure 13 (d), when the commutation process is completed, the diode D f turns off, and the capacitor C s slowly discharges through the resistor R s to prepare for the next turn-off.

[0144] Among them, an energy extraction power supply can be connected in parallel across the capacitor C s so as to supply power to other electrical devices by using the energy in the capacitor C s to improve the energy utilization rate.

[0145] According to some embodiments of the present application, optionally, the valve string corresponding to the upper arm of the first arm branch is set as the first valve string T1, the valve string corresponding to the upper arm of the second arm branch is set as the second valve string T2, the valve string corresponding to the lower arm of the first arm branch is set as the third valve string T3, and the valve string corresponding to the lower arm of the second arm branch is set as the fourth valve string T4.

[0146] As Figure 14As shown, at least one of the first valve string T1 and the fourth valve string T4, and at least one of the second valve string T2 and the third valve string T3 further includes: at least one hybrid switch unit 30;

[0147] The hybrid switch unit 30 is connected in series with a plurality of switch units 20 in the corresponding valve string. The hybrid switch unit 30 includes an IGCT, an IGBT, and an antiparallel diode connected in parallel.

[0148] The high-voltage direct-connected energy storage system 1000 proposed in this embodiment is also applicable to a four-quadrant power regulation system. For such a system, when the system operates under the rated reactive power condition of P = 0 and Q = 1, there is a 90° phase difference between the AC voltage and the current. When the AC voltage returns to zero and the commutation module 200 performs a commutation action, the arm current in the commutation module 200 just reaches the peak value, and the IGCT needs to turn off the rated current under the zero-voltage turn-off condition. Under the high-multiple load condition, it is necessary to turn off 3 times the rated current, exceeding the maximum turn-off current of the IGCT, and it is difficult to use the IGCT for turning off.

[0149] Considering the above situation, this embodiment proposes to add a set of hybrid switch units 30 that cooperate with IGBTs and IGCTs in the valve string. As Figure 14 shown, an IGBT, an IGCT, and an antiparallel diode are connected in parallel to form the hybrid switch unit 30, and then a hybrid switch unit 30 is used to be connected in series with a plurality of switch units 20 in the valve string to form a hybrid arm.

[0150] More specifically, the valve string including the hybrid switch unit 30 is set as the target valve string;

[0151] When the target valve string is in the stage to be turned on, the IGBT in the corresponding hybrid switch unit 30 is turned on first, the IGCT in the corresponding hybrid switch unit 30 is turned on, and the IGBT in the corresponding hybrid switch unit 30 is turned off under zero voltage;

[0152] And / or, when the target valve string is in the stage to be turned off, the IGBT in the corresponding hybrid switch unit 30 is turned on first, the IGCT in the corresponding hybrid switch unit 30 is turned off under zero voltage, and the IGBT in the corresponding hybrid switch unit 30 is turned off later.

[0153] In this embodiment, the working principle of the hybrid switch unit 30 is specifically described. When the target valve string is in the stage of waiting to be turned on, the di / dt control during the IGBT turn-on is more flexible. Therefore, the IGBT in the corresponding hybrid switch unit 30 turns on first, the IGCT in the corresponding hybrid switch unit 30 turns on, and then the IGBT in the corresponding hybrid switch unit 30 turns off at zero voltage. In this way, during the subsequent valve string operation stage, the current conduction mainly relies on the IGCT. Therefore, the valve string has high surge capacity and low conduction loss during operation. In this way, the advantages of high surge capacity and low conduction loss of the IGCT and the advantages of large turn-off current and controllable di / dt during turn-on and turn-off of the IGBT can be exerted. The hybrid bridge arm can utilize the strong turn-off ability of the hybrid switch unit to turn off the overload current, which is more flexible than the single IGCT control.

[0154] When the target valve string is in the stage of waiting to be turned off, the IGBT in the corresponding hybrid switch unit 30 turns on first, the IGCT in the corresponding hybrid switch unit 30 turns off at zero voltage, and all the current is transferred to the corresponding IGBT. Finally, by utilizing the characteristic that the IGBT has a large turn-off current and can achieve strong turn-off, the IGBT in the corresponding hybrid switch unit 30 is turned off later. In this way, the hybrid switch unit 30 is completely turned off.

[0155] Therefore, by using the hybrid switch unit provided in this embodiment, even when there is a large phase difference between the AC voltage and current, the valve string in the commutation module can achieve reliable turn-off under high-magnitude overload current, thus fully improving the reliability and safety of the energy storage system operation.

[0156] Generally speaking, the high-voltage direct-connected energy storage system 1000 proposed in the embodiment of this application has the ability of four-quadrant operation and can send or absorb active power and reactive power to the AC power grid 300. Its power exchange situation is as Figure 15 shown, Figure 15 which is a schematic diagram of the principle of single-phase energy storage circuit output power control provided in the embodiment of this application. Figure 15 Phase a is selected for illustration, and the principles of the other two phases are the same.

[0157] Set the effective value of the AC phase voltage generated by the energy storage system to be U c , the phase is δ, the effective value of the AC phase current is I c , the power factor angle is , the bridge arm reactance value is L s , then the active power and reactive power output by phase a of the energy storage system can be calculated according to the following formulas (1) and (2) respectively:

[0158]

[0159] The above active power and reactive power can also be estimated according to the following formulas (3) and (4):

[0160]

[0161] In a three-phase symmetrical operation scenario, the output power of each phase is the same. Then, the total active power output and reactive power output of the energy storage device can be calculated according to the following formulas (5) and (6):

[0162] P t = 3P(5)

[0163] Q t = 3Q(6)

[0164] In summary, by controlling the amplitude and phase of the AC phase voltage generated by the energy storage system, the output power of the energy storage system can be controlled. In actual operation, a certain control strategy is usually adopted, with the output current or the grid connection point voltage as the control target, rather than directly controlling the output voltage of the commutation module 200. The high-voltage direct-connected energy storage system 1000 proposed in the embodiments of the present application can adopt grid-following control or grid-forming control, which are respectively applicable to strong power grids with a large short-circuit ratio and weak power grids with a small short-circuit ratio, and the strategy can be flexibly switched according to the operating conditions.

[0165] It should also be added that in order to fully ensure the practicability of the high-voltage direct-connected energy storage system 1000, the present application also provides some electrical design and selection schemes for components next:

[0166] (1) For the scheme of using supercapacitors as energy storage elements, for an energy storage system with an AC voltage level of U N and a capacity of S N , its rated current can be calculated according to . Given the required discharge time t o of the energy storage system, the total energy storage E s that the supercapacitor needs to have is E N t o .

[0167] Considering that the capacitance value of a single DC supercapacitor module is C s , the upper limit of the operating voltage is U max , and the lower limit of the operating voltage is U min , then the available energy of the supercapacitor The effective energy storage of the energy storage system is E total = 3NE c , where N is the number of series-connected single-phase DC modules. During design, it should be ensured that E total ≥ S N t o .

[0168] In addition, to ensure that the energy storage system can output AC voltage normally, it is necessary to ensure that the supercapacitor can also output the required level when operating at the lower limit of the voltage. Denote the peak value of the phase voltage on the AC side as U a , then the device should also satisfy NU min ≥U a .

[0169] (2) For the energy storage element using the battery solution, an energy storage system with an AC voltage level of U N and a capacity of S N , its rated current can be calculated according to . The output voltage of the energy storage battery is relatively stable when the SOC changes. Denote its output voltage as U bat . The battery energy storage system usually requires a discharge time of 2h. Then the total energy storage of this energy storage system E s = 2h·S N .

[0170] The energy that can be stored in a single battery module is the energy released when the battery discharges from the upper limit of SOC to the lower limit of SOC. Taking a lithium battery as an example, its upper limit of SOC is 0.9 and its lower limit of SOC is 0.2. Then its available energy E bat is the difference in the energy storage of the battery when the SOC is 0.9 and when the SOC is 0.2. Consistent with the supercapacitor solution, the effective energy storage of the energy storage system is E total = 3NE bat , where N is the number of series-connected single-phase DC modules.

[0171] Therefore, during design, it should be ensured that E total ≥2h·S N , and NU bat ≥U a .

[0172] (3) This embodiment also gives a selection principle for switching devices for design reference. For the fully controlled devices in the DC module, IGBT devices are usually selected. Its withstand voltage level should be higher than the highest operating voltage U dc of the energy storage element. The current-carrying capacity should meet the average value of the sine half-wave current with the peak value of the maximum phase current peak on the AC side as the peak value where is the power frequency period.

[0173] The commutation module is selected with IGCT devices in series. Its total withstand voltage level should meet the peak value of the highest phase voltage on the AC side The current-carrying capacity should meet half of the average value of the sine half-wave current with the peak value of the maximum phase current peak on the AC side as the peak value The turn-off ability should be able to turn off a current with a magnitude of the peak value of the maximum phase current on the AC side .

[0174] Based on the high-voltage direct-connected energy storage system provided in the foregoing embodiments, for the same inventive concept, the embodiments of the present application provide a control method for a high-voltage direct-connected energy storage system, which is applied to the high-voltage direct-connected energy storage system according to any one of the foregoing embodiments of the present application. Please refer to the following Figure 16 , Figure 16 which is a schematic flow chart of a control method for a high-voltage direct-connected energy storage system provided by an embodiment of the present application. As Figure 16 shown, the control method for the high-voltage direct-connected energy storage system includes the following steps:

[0175] S1610, controlling the half-bridge units in N energy storage sub-modules in the DC energy storage module to realize the switching of the working states of the corresponding energy storage sub-modules, such as being put into operation, cut out, or locked, so that the DC energy storage module generates a multi-level voltage equivalent to a sine half-wave;

[0176] S1620, controlling the first bridge arm branch and the second bridge arm branch in the commutation module so that the commutation module outputs the multi-level voltage in the forward or reverse direction to obtain a single-phase AC voltage of one phase of the AC power grid.

[0177] Compared with the related art, the control method for a high-voltage direct-connected energy storage system provided by the embodiments of the present application controls the half-bridge units in N energy storage sub-modules in the DC energy storage module to realize the switching of the working states of the corresponding energy storage sub-modules, such as being put into operation, cut out, or locked, so that the DC energy storage module generates a multi-level voltage equivalent to a sine half-wave, and controls the first bridge arm branch and the second bridge arm branch in the commutation module so that the commutation module outputs the multi-level voltage in the forward or reverse direction to obtain a single-phase AC voltage of one phase of the AC power grid. The embodiments of the present application directly realize the output of a single-phase AC voltage based on the above-mentioned DC energy storage module and commutation module including single-phase settings, reducing the dependence on a large number of DC cables and transformers, etc., thereby fully reducing the complexity and cost of the energy storage system. Moreover, the independent control and energy storage management of each phase in the three phases in the present application also improve the flexibility and reliability of the energy storage system, thereby effectively improving the overall performance of the energy storage system.

[0178] According to some embodiments of the present application, optionally, the half-bridge unit includes a first bridge arm unit and a second bridge arm unit, and both the first bridge arm unit and the second bridge arm unit include a switching tube and an anti-parallel diode arranged at both ends of the switching tube;

[0179] Controlling the half-bridge units in N energy storage sub-modules in the DC energy storage module to realize the switching of the working states of the corresponding energy storage sub-modules, including:

[0180] Control the switch tube in the corresponding first arm unit to conduct and the switch tube in the second arm unit to turn off, so as to realize the input of the corresponding energy storage sub-module;

[0181] Control the switch tube in the corresponding first arm unit to turn off and the switch tube in the second arm unit to conduct, so as to realize the cut-out of the corresponding energy storage sub-module;

[0182] Control the switch tube in the corresponding first arm unit to turn off and the switch tube in the second arm unit to turn off, so as to realize the locking of the corresponding energy storage sub-module.

[0183] According to some embodiments of the present application, optionally, set the valve string corresponding to the upper arm of the first arm branch as the first valve string, the valve string corresponding to the upper arm of the second arm branch as the second valve string, the valve string corresponding to the lower arm of the first arm branch as the third valve string, and the valve string corresponding to the lower arm of the second arm branch as the fourth valve string;

[0184] Control the first arm branch and the second arm branch in the commutation module, so that the commutation module outputs the multi-level voltage in the forward or reverse direction, including:

[0185] Control the first valve string and the fourth valve string to conduct, and control the second valve string and the third valve string to turn off, so that the commutation module outputs the multi-level voltage in the forward direction;

[0186] Control the first valve string and the fourth valve string to turn off, and control the second valve string and the third valve string to conduct, so that the commutation module outputs the multi-level voltage in the reverse direction.

[0187] According to some embodiments of the present application, optionally, at least one of the first valve string and the fourth valve string, and at least one of the second valve string and the third valve string further include: at least one hybrid switch unit;

[0188] The hybrid switch unit is connected in series with a plurality of switch units in the corresponding valve string, and the hybrid switch unit includes an IGCT, an IGBT and an antiparallel diode connected in parallel;

[0189] Set the valve string including the hybrid switch unit as the target valve string;

[0190] When the target valve string is in the to-be-opened stage, control the IGBT in the corresponding hybrid switch unit to conduct first, the IGCT in the corresponding hybrid switch unit to conduct, and the IGBT in the corresponding hybrid switch unit to turn off at zero voltage;

[0191] And / or, when the target valve string is in the to-be-turned-off stage, control the IGBT in the corresponding hybrid switch unit to conduct first, the IGCT in the corresponding hybrid switch unit to turn off at zero voltage, and the IGBT in the corresponding hybrid switch unit to turn off later.

[0192] It should be understood that, for the sake of brevity, the specific control methods of the above DC energy storage module and converter module can be referred to the corresponding description part of the working principle in the aforementioned high-voltage direct-connected energy storage system, and will not be elaborated here.

[0193] According to some embodiments of the present application, optionally, the control method of the high-voltage direct-connected energy storage system further includes:

[0194] Comparing the current voltage of the DC energy storage module with the target voltage of the modulation wave to obtain the absolute value of the voltage difference between the current voltage and the target voltage;

[0195] When the absolute value of the voltage difference reaches the preset voltage value and the target voltage is higher than the current voltage, controlling one of the N energy storage sub-modules to be put into operation;

[0196] When the absolute value of the voltage difference reaches the preset voltage value and the target voltage is lower than the current voltage, controlling one of the N energy storage sub-modules to be cut out; wherein, the preset voltage value is half of the voltage of the energy storage element.

[0197] In this embodiment, the control of the DC energy storage module adopts multi-level technology, for example, the nearest level approximation modulation method can be selected. If the nearest level approximation modulation is adopted, taking the fundamental frequency of 50Hz as an example, the modulation wave is: a sine half-wave with an amplitude equal to the peak value of the AC phase voltage and a frequency of 100Hz. The current voltage of the DC energy storage module can be obtained by multiplying the number of energy storage sub-modules put into operation by the voltage of the energy storage element in the energy storage sub-module, or can be measured by an on-line measurement method, which is not strictly limited here.

[0198] According to the change of time, comparing the current voltage of the DC energy storage module with the target voltage at the current moment indicated by the modulation wave waveform. When the voltage difference between the two reaches half of the voltage of a single energy storage element, if the target voltage indicated by the modulation wave is higher, one energy storage sub-module is put into operation; if the current voltage of the DC energy storage module is higher, one energy storage sub-module is cut out, so that the voltage change of the DC energy storage module is basically consistent with the modulation wave.

[0199] According to some embodiments of the present application, optionally, the control method of the high-voltage direct-connected energy storage system further includes: sorting the state of charge of the energy storage elements in the N energy storage sub-modules;

[0200] Controlling the energy storage sub-module among the N energy storage sub-modules to be put into operation includes:

[0201] When the DC energy storage module is in a charging state, controlling the energy storage sub-module that is not put into operation and has the lowest state of charge among the N energy storage sub-modules to be put into operation;

[0202] When the DC energy storage module is in the discharging state, control the energy storage sub-module with the highest state of charge among the N non-activated energy storage sub-modules to be activated;

[0203] Control one of the N energy storage sub-modules to be cut out, including:

[0204] When the DC energy storage module is in the charging state, control the energy storage sub-module with the highest state of charge among the N non-cut-out energy storage sub-modules to be cut out;

[0205] When the DC energy storage module is in the discharging state, control the energy storage sub-module with the lowest state of charge among the N non-cut-out energy storage sub-modules to be cut out.

[0206] Taking the energy storage element as a battery as an example, in order to maintain the balance of the battery's SOC (State of Charge), the SOC states of the batteries in the N energy storage sub-modules can be sorted regularly.

[0207] When the DC energy storage module is in the charging state, if an energy storage sub-module needs to be activated, the energy storage sub-module with the lowest SOC among the N non-activated energy storage sub-modules can be selected to ensure that the battery can be fully charged in time and avoid undercharging, thus affecting the overall performance of the DC energy storage module. If an energy storage sub-module needs to be cut out, the module with the highest SOC among the N non-cut-out energy storage sub-modules can be selected to avoid overcharging of the battery caused by continuous charging of the battery with a higher SOC, thus triggering battery safety problems.

[0208] Similarly, when the DC energy storage module is in the discharging state, if an energy storage sub-module needs to be activated, the energy storage sub-module with the highest SOC among the N non-activated energy storage sub-modules can be selected to fully undertake the discharging responsibility. If an energy storage sub-module needs to be cut out, the module with the lowest SOC among the N non-cut-out energy storage sub-modules can be selected to avoid the battery with a lower SOC being in a state of power loss for a long time, thus affecting the battery life.

[0209] In this way, this embodiment can better cope with the inconsistency of the batteries, fully maintain the battery balance of each energy storage element during the charging and discharging processes, thereby ensuring the safety and efficiency during the charging and discharging processes, and further helping to effectively extend the battery life and optimize the battery performance.

[0210] According to some embodiments of the present application, optionally, when the absolute value of the voltage difference does not reach the preset voltage value, the control method of the high-voltage direct-connected energy storage system further includes:

[0211] When the DC energy storage module is in the charging state, control the energy storage sub-module with the lowest state of charge (SOC) among the N energy storage sub-modules that are not put into operation to be put into operation, and control the energy storage sub-module with the highest SOC among the N energy storage sub-modules that are not cut out to be cut out;

[0212] When the DC energy storage module is in the discharging state, control the energy storage sub-module with the highest SOC among the N energy storage sub-modules that are not put into operation to be put into operation, and control the energy storage sub-module with the lowest SOC among the N energy storage sub-modules that are not cut out to be cut out.

[0213] In this embodiment, in order to achieve a better SOC balancing effect during the charging and discharging process of the battery, when the absolute value of the voltage difference does not reach the preset voltage value, even if it is not necessary to put into operation or cut out the energy storage sub-module, it is also possible to simultaneously put into operation and cut out an energy storage sub-module according to the SOC state sorting of the battery, so as to swap the put-in energy storage sub-module with the non-put-in energy storage sub-module.

[0214] When the DC energy storage module is in the charging state, control the energy storage sub-module with the lowest SOC among the N energy storage sub-modules that are not put into operation to be put into operation, and control the energy storage sub-module with the highest SOC among the N energy storage sub-modules that are not cut out to be cut out. In this way, overcharging and undercharging problems can be effectively avoided, the consistency and energy utilization rate of multiple batteries can be improved, and battery balancing can be better achieved.

[0215] When the DC energy storage module is in the discharging state, control the energy storage sub-module with the highest SOC among the N energy storage sub-modules that are not put into operation to be put into operation, and control the energy storage sub-module with the lowest SOC among the N energy storage sub-modules that are not cut out to be cut out. In this way, the energy of the high-SOC battery can be fully utilized, while protecting the low-SOC battery, and the problem of deep discharge can be effectively avoided, so as to better achieve battery balancing.

[0216] According to some embodiments of the present application, optionally, the control method of the high-voltage direct-connected energy storage system further includes:

[0217] Use N sets of triangular waves with an amplitude of 1 and a frequency of f c as the carrier wave, and the phase difference between adjacent triangular waves is Use a sine half-wave with an amplitude of and a frequency of 100 Hz as the modulation wave, and generate a PWM signal through the modulation of the triangular wave and the modulation wave;

[0218] The PWM signal is used to control the half-bridge units in the N energy storage sub-modules of the DC energy storage module to realize the switching of the working states of the corresponding energy storage sub-modules, such as being put into operation, cut out, or locked;

[0219] wherein, f c> 500 Hz and is an integer multiple of 100 Hz, U bat is the voltage of the energy storage element, U peak is the peak value of the output AC phase voltage.

[0220] In this embodiment, the control of the DC energy storage module adopts multi-level technology. For example, the above-mentioned carrier phase-shifted modulation method can be selected. If carrier phase-shifted modulation is adopted, N sets of triangular waves with an amplitude of 1 and a frequency of f c are used as carriers, and the phase difference between the triangular waves is With an amplitude of (where U peak is the peak value of the output AC phase voltage, U bat is the module battery voltage), a sine half-wave with a frequency of 100 Hz is used as the modulation wave.

[0221] Thus, based on the above triangular wave and modulation wave, a PWM (Pulse Width Modulation) signal is generated through modulation as the switching signal of each energy storage sub-module in the DC energy storage module, which is beneficial to realizing high-quality multi-level output of the DC energy storage sub-module.

[0222] It should be noted that f c > 500 Hz and is an integer multiple of 100 Hz. By setting the frequency of the triangular wave higher than the frequency of the modulation wave, the quality of the output waveform can be effectively improved, the harmonic content can be reduced, and the output waveform can be made smoother.

[0223] Based on the control method of the high-voltage directly-connected energy storage system provided in the above embodiment, for the same inventive concept, the present application also provides a high-voltage directly-connected energy storage device corresponding to the control method of the above high-voltage directly-connected energy storage system. The following is through Figure 17 to introduce the control device of the high-voltage directly-connected energy storage system in detail.

[0224] The following please refer to Figure 17 , Figure 17 which is a schematic structural diagram of the control device of the high-voltage directly-connected energy storage system provided in an embodiment of the present application.

[0225] The control device of the high-voltage directly-connected energy storage system may include a processor 1701 and a memory 1702 storing computer program instructions.

[0226] Specifically, the above-mentioned processor 1701 may include a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application.

[0227] The memory 1702 may include a mass storage for data or instructions. By way of example and not limitation, the memory 1702 may include a hard disk drive (HDD), a floppy disk drive, a flash memory, an optical disk, a magneto-optical disk, a magnetic tape, or a universal serial bus (USB) drive, or a combination of two or more of these. Where appropriate, the memory 1702 may include removable or non-removable (or fixed) media. Where appropriate, the memory 1702 may be internal or external to the integrated gateway disaster recovery device. In a particular embodiment, the memory 1702 is a non-volatile solid-state memory.

[0228] The memory may include a read-only memory (ROM), a random access memory (RAM), a magnetic disk storage media device, an optical storage media device, a flash memory device, an electrical, optical, or other physical / tangible memory storage device. Thus, in general, the memory includes one or more tangible (non-transitory) computer-readable storage media (e.g., memory devices) encoded with software including computer-executable instructions, and when the software is executed (e.g., by one or more processors), it is operable to perform the operations described with reference to the method according to an aspect of the present disclosure.

[0229] The processor 1701 reads and executes the computer program instructions stored in the memory 1702 to implement the control method of any one of the high-voltage direct-connected energy storage systems in the above embodiments.

[0230] In one example, the control device of the data high-voltage direct-connected energy storage system may further include a communication interface 1703 and a bus 1710. Among them, as Figure 17 shown, the processor 1701, the memory 1702, and the communication interface 1703 are connected through the bus 1710 and complete communication with each other. The communication interface 1703 is mainly used to implement communication between the modules, devices, units, and / or devices in the embodiments of the present application.

[0231] The bus 1710 includes hardware, software, or both, and couples components of the control device of the high-voltage direct-connected energy storage system to each other. By way of example and not limitation, the bus may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a Front-Side Bus (FSB), a HyperTransport (HT) interconnect, an Industry Standard Architecture (ISA) bus, an InfiniBand interconnect, a Low Pin Count (LPC) bus, a memory bus, a MicroChannel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCI-X) bus, a Serial Advanced Technology Attachment (SATA) bus, a Video Electronics Standards Association Local (VLB) bus, or other suitable buses or a combination of two or more of these. Where appropriate, the bus 1710 may include one or more buses. Although the embodiments of the present application describe and illustrate specific buses, the present application contemplates any suitable bus or interconnect.

[0232] The control device of the high-voltage direct-connected energy storage system executes the control method of the high-voltage direct-connected energy storage system in the embodiments of the present application, thereby implementing the control method of the high-voltage direct-connected energy storage system described in the embodiments of the present application.

[0233] In addition, in combination with the control method of the high-voltage direct-connected energy storage system in the above embodiments, the embodiments of the present application can be implemented by providing a computer storage medium. Computer program instructions are stored on the computer storage medium; when the computer program instructions are executed by a processor, any one of the control methods of the high-voltage direct-connected energy storage system in the above embodiments is implemented.

[0234] Based on the control method of the high-voltage direct-connected energy storage system in the above embodiments, the embodiments of the present application provide a computer program product. When the instructions in the computer program product are executed by the processor of an electronic device, the electronic device is caused to execute the control method of the high-voltage direct-connected energy storage system provided in any one of the above embodiments of the present application.

[0235] It should be clear that the present application is not limited to the specific configurations and processes described above and illustrated in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and illustrated as examples. However, the method process of the present application is not limited to the specific steps described and illustrated, and those skilled in the art can make various changes, modifications, and additions, or change the order between steps after understanding the spirit of the present application.

[0236] The functional blocks shown in the above-described structural block diagrams can be implemented as hardware, software, firmware, or a combination thereof. When implemented in hardware, it can be, for example, an electronic circuit, an application-specific integrated circuit (ASIC), appropriate firmware, a plug-in, a functional card, and so on. When implemented in software, the elements of the present application are programs or code segments used to perform the required tasks. The program or code segment can be stored in a machine-readable medium or transmitted via a data signal carried in a carrier wave over a transmission medium or a communication link. A "machine-readable medium" can include any medium that can store or transmit information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical discs, hard disks, fiber optic media, radio frequency (RF) links, and so on. The code segment can be downloaded via a computer network such as the Internet, an intranet, and so on.

[0237] It should also be noted that the exemplary embodiments mentioned in the present application describe some methods or systems based on a series of steps or devices. However, the present application is not limited to the order of the above steps, that is, the steps can be executed in the order mentioned in the embodiments, or different from the order in the embodiments, or several steps can be executed simultaneously.

[0238] Aspects of the present disclosure have been described above with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present disclosure. It should be understood that each block in the flowcharts and / or block diagrams, and the combinations of blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device to produce a machine, such that the instructions executed by the processor of the computer or other programmable data processing device enable the implementation of the functions / actions specified in one or more blocks of the flowcharts and / or block diagrams. Such a processor can be, but is not limited to, a general-purpose processor, a special-purpose processor, a special application processor, or a field-programmable logic circuit. It is also understood that each block in the block diagrams and / or flowcharts, and the combinations of blocks in the block diagrams and / or flowcharts, can also be implemented by dedicated hardware that performs the specified functions or actions, or by a combination of dedicated hardware and computer instructions.

[0239] As described above, this is only the specific implementation manner of the present application. Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the systems, modules, and units described above can refer to the corresponding processes in the foregoing method embodiments, and will not be elaborated herein. It should be understood that the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present application.

[0240] Those skilled in the art should understand that the above embodiments are all exemplary rather than restrictive. Different technical features appearing in different embodiments can be combined to achieve beneficial effects. Based on the study of the drawings, the specification, and the claims, those skilled in the art should be able to understand and implement other variations of the disclosed embodiments. In the claims, the term "comprising" does not exclude other structures; the quantity refers to "one" but does not exclude a plurality; the terms "first" and "second" are used to label names rather than to indicate any specific order. Any reference signs in the claims should not be construed as limiting the scope of protection. The fact that certain technical features appear in different dependent claims does not mean that these technical features cannot be combined to achieve beneficial effects.

Claims

1. A high-voltage direct-connected energy storage system, characterized in that The system includes at least one single-phase energy storage circuit, and the single-phase energy storage circuit includes: A DC energy storage module, which is composed of N energy storage sub-modules connected in series. Each energy storage sub-module includes a half-bridge unit and an energy storage element. The energy storage sub-module is used to realize the switching of the working states of input, cut-out or locking through the half-bridge unit, where N is a positive integer; A commutation module, which includes a first bridge arm branch and a second bridge arm branch. The first bridge arm branch and the second bridge arm branch are used to be connected in parallel at both ends of the DC energy storage module. The midpoints of the first bridge arm branch and the second bridge arm branch are used to be electrically connected to the AC interface of one phase of the AC power grid; Wherein, the DC energy storage module is used to generate a multi-level voltage equivalent to a sine half-wave, and the commutation module is used to output the multi-level voltage forward or backward to obtain a single-phase AC voltage of one phase of the AC power grid.

2. The system according to claim 1, wherein The half-bridge unit includes a first bridge arm unit and a second bridge arm unit; The first end of the first bridge arm unit is electrically connected to the positive electrode of the corresponding energy storage element. The second end of the first bridge arm unit is electrically connected to the first end of the second bridge arm unit. The second end of the second bridge arm unit is electrically connected to the negative electrode of the corresponding energy storage element; The second end of the first bridge arm unit is set as the first node, and the second end of the second bridge arm unit is set as the second node; The second node in the i-th energy storage sub-unit is electrically connected to the first node in the (i + 1)-th energy storage sub-unit. The first ends of the first bridge arm branch and the second bridge arm branch are respectively electrically connected to the first node in the first energy storage sub-unit. The first ends of the first bridge arm branch and the second bridge arm branch, and the second ends of the first bridge arm branch and the second bridge arm branch are respectively electrically connected to the second node in the N-th energy storage sub-unit, where 1 ≤ i ≤ N; Wherein, both the first bridge arm unit and the second bridge arm unit include a switching tube and an anti-parallel diode arranged at both ends of the switching tube.

3. The system according to claim 2, wherein The energy storage sub-module further includes an interface unit. The interface unit includes a support capacitor and a filtering unit, and the filtering unit includes a filtering inductor; The positive electrode of the energy storage element is electrically connected to the first end of the first bridge arm unit through the filtering inductor; The first end of the support capacitor is electrically connected to the first end of the first bridge arm unit, and the second end of the support capacitor is electrically connected to the negative electrode of the energy storage element.

4. The system according to claim 1, wherein The first bridge arm branch includes two groups of valve strings connected in series, and the second bridge arm branch includes two groups of valve strings connected in series; Any one group of the valve strings includes a plurality of switching units connected in series, and each switching unit includes an IGCT and an anti-parallel diode arranged at both ends of the IGCT.

5. The system according to claim 4, wherein The valve string corresponding to the upper bridge arm of the first bridge arm branch is set as the first valve string, the valve string corresponding to the upper bridge arm of the second bridge arm branch is set as the second valve string, the valve string corresponding to the lower bridge arm of the first bridge arm branch is set as the third valve string, and the valve string corresponding to the lower bridge arm of the second bridge arm branch is set as the fourth valve string; At least one of the first valve string and the fourth valve string, and at least one of the second valve string and the third valve string further includes: at least one hybrid switch unit; The hybrid switch unit is connected in series with a plurality of the switch units in the corresponding valve string, and the hybrid switch unit includes an IGCT, an IGBT, and an antiparallel diode connected in parallel.

6. The system according to claim 5, wherein Set the valve string including the hybrid switch unit as the target valve string; When the target valve string is in the stage to be turned on, the IGBT in the corresponding hybrid switch unit is turned on first, the IGCT in the corresponding hybrid switch unit is turned on, and the IGBT in the corresponding hybrid switch unit is turned off at zero voltage; And / or, when the target valve string is in the stage to be turned off, the IGBT in the corresponding hybrid switch unit is turned on first, the IGCT in the corresponding hybrid switch unit is turned off at zero voltage, and the IGBT in the corresponding hybrid switch unit is turned off later.

7. The system according to claim 5, wherein The switch unit further includes: a diode, a capacitor, and a resistor; The anode of the diode is electrically connected to the cathode of the antiparallel diode in the switch unit, the cathode of the diode is electrically connected to the anode of the antiparallel diode through the capacitor, and the resistor is connected in parallel with the capacitor.

8. A control method for a high-voltage directly-connected energy storage system, characterized in that, Applied to the high-voltage direct-connected energy storage system according to any one of claims 1-7; the method includes: Controlling the half-bridge units in N energy storage sub-modules in the DC energy storage module to realize the switching of the working states of the corresponding energy storage sub-modules to be put in, cut out, or locked, so that the DC energy storage module generates a multi-level voltage equivalent to a sine half-wave; Controlling the first bridge arm branch and the second bridge arm branch in the commutation module to make the commutation module output the multi-level voltage forward or backward to obtain a single-phase AC voltage of one phase of the AC power grid.

9. The method according to claim 8, wherein The half-bridge unit includes a first bridge arm unit and a second bridge arm unit, and both the first bridge arm unit and the second bridge arm unit include a switching tube and an antiparallel diode arranged at both ends of the switching tube; The controlling the half-bridge units in N energy storage sub-modules in the DC energy storage module to realize the switching of the working states of the corresponding energy storage sub-modules to be put in, cut out, or locked includes: Controlling the switching tube in the corresponding first bridge arm unit to conduct and the switching tube in the second bridge arm unit to turn off to realize the putting in of the corresponding energy storage sub-module; Controlling the switching tube in the corresponding first bridge arm unit to turn off and the switching tube in the second bridge arm unit to conduct to realize the cutting out of the corresponding energy storage sub-module; Controlling the switching tube in the corresponding first bridge arm unit to turn off and the switching tube in the second bridge arm unit to turn off to realize the locking of the corresponding energy storage sub-module.

10. The method according to claim 8, wherein Set the valve string corresponding to the upper bridge arm of the first bridge arm branch as the first valve string, the valve string corresponding to the upper bridge arm of the second bridge arm branch as the second valve string, the valve string corresponding to the lower bridge arm of the first bridge arm branch as the third valve string, and the valve string corresponding to the lower bridge arm of the second bridge arm branch as the fourth valve string; Controlling the first arm branch and the second arm branch in the commutation module to enable the commutation module to output the multi-level voltage in the forward or reverse direction, including: Controlling the first valve string and the fourth valve string to conduct, and controlling the second valve string and the third valve string to turn off, so that the commutation module outputs the multi-level voltage in the forward direction; Controlling the first valve string and the fourth valve string to turn off, and controlling the second valve string and the third valve string to conduct, so that the commutation module outputs the multi-level voltage in the reverse direction.

11. The method according to claim 10, wherein At least one of the first valve string and the fourth valve string, and at least one of the second valve string and the third valve string further includes: at least one hybrid switch unit; The hybrid switch unit is connected in series with a plurality of switch units in the corresponding valve string, and the hybrid switch unit includes an IGCT, an IGBT, and an antiparallel diode connected in parallel; Setting the valve string including the hybrid switch unit as the target valve string; When the target valve string is in the to-be-conducted stage, controlling the IGBT in the corresponding hybrid switch unit to conduct first, the IGCT in the corresponding hybrid switch unit to conduct, and the IGBT in the corresponding hybrid switch unit to turn off at zero voltage; And / or, when the target valve string is in the to-be-cut-off stage, controlling the IGBT in the corresponding hybrid switch unit to conduct first, the IGCT in the corresponding hybrid switch unit to turn off at zero voltage, and the IGBT in the corresponding hybrid switch unit to turn off later.

12. The method according to claim 8, characterized in that The method further includes: Comparing the current voltage of the DC energy storage module with the target voltage of the modulation wave to obtain the absolute value of the voltage difference between the current voltage and the target voltage; When the absolute value of the voltage difference reaches the preset voltage value and the target voltage is higher than the current voltage, controlling one of the N energy storage sub-modules to be put into operation; When the absolute value of the voltage difference reaches the preset voltage value and the target voltage is lower than the current voltage, controlling one of the N energy storage sub-modules to be cut out; Wherein, the preset voltage value is half of the voltage of the energy storage element.

13. The method according to claim 12, wherein The method further includes: sorting the state of charge of the energy storage elements in the energy storage sub-modules among the N energy storage sub-modules; The controlling one of the N energy storage sub-modules to be put into operation includes: When the DC energy storage module is in the charging state, controlling the energy storage sub-module that is not put into operation and has the lowest state of charge among the N energy storage sub-modules to be put into operation; When the DC energy storage module is in the discharging state, controlling the energy storage sub-module that is not put into operation and has the highest state of charge among the N energy storage sub-modules to be put into operation; The controlling one of the N energy storage sub-modules to be cut out includes: When the DC energy storage module is in the charging state, controlling the energy storage sub-module that is not cut out and has the highest state of charge among the N energy storage sub-modules to be cut out; When the DC energy storage module is in the discharging state, control the energy storage sub-module with the lowest state of charge among the N energy storage sub-modules that have not been cut out to be cut out.

14. The method according to claim 13, wherein When the absolute value of the voltage difference does not reach the preset voltage value, the method further includes: When the DC energy storage module is in the charging state, control the energy storage sub-module with the lowest state of charge among the N energy storage sub-modules that have not been put into operation to be put into operation, and control the energy storage sub-module with the highest state of charge among the N energy storage sub-modules that have not been cut out to be cut out; When the DC energy storage module is in the discharging state, control the energy storage sub-module with the highest state of charge among the N energy storage sub-modules that have not been put into operation to be put into operation, and control the energy storage sub-module with the lowest state of charge among the N energy storage sub-modules that have not been cut out to be cut out.

15. The method according to claim 8, characterized in that The method further includes: Use N triangular waves with an amplitude of 1 and a frequency of f c as the carrier wave, and the phase difference between adjacent triangular waves is Taking a sine half-wave with an amplitude of and a frequency of 100 Hz as the modulation wave, through the triangular wave and the modulation Generate a PWM signal through wave-making modulation; The PWM signal is used to control the half-bridge units in the N energy storage sub-modules of the DC energy storage module to realize the switching of the working states of corresponding energy storage sub-modules, such as being put into operation, cut out, or locked. Among them, f c > 500 Hz and is an integer multiple of 100 Hz, U bat is the voltage of the energy storage element, U peak is the peak value of the output AC phase voltage.

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