Power supply system and control method thereof

Abstract

The invention belongs to the technical field of converters, and particularly relates to a power supply system and a control method thereof.The power supply system comprises a direct-current input interface, a first energy storage module, a direct-current conversion module, a second energy storage module, an alternating-current conversion module, an alternating-current output interface and a control module, and the direct-current conversion module comprises N direct-current conversion units; the first energy storage module comprises N energy storage units, the second energy storage module comprises N energy storage units, the AC conversion module comprises N cascaded inversion units, and the control module is used for gradually starting the N DC conversion units according to the target position of the at least one energy storage battery, after the N direct current conversion units are all started, the N inversion units are controlled to work at the same time; according to the invention, while the problem that a cascaded H-bridge power supply system cannot realize direct current energy compensation in the prior art is solved, multiple direct current energy compensation modes also improve the application scene and stability of the power supply system.

Description

Technical Field

[0001] The present application belongs to the technical field of power electronic converters, and specifically relates to a power supply system and a control method thereof. Background Art

[0002] Current cascaded H-bridge power supply systems typically consist of multiple cascaded submodules, each containing a storage battery pack and an H-bridge power conversion circuit. Each submodule outputs a multi-level AC voltage through the series connection of the H-bridges, which is then filtered and connected to the AC grid or load. The power supply system charges the energy storage unit through the AC grid, converts the AC power into DC power, and then stores the energy in the energy storage battery. Furthermore, the DC power in the energy storage battery is converted into AC power through the H-bridge power conversion circuit and then used to power the load.

[0003] However, this cascaded H-bridge power supply system only supports energy replenishment from the AC grid and cannot directly access DC power sources such as photovoltaics and energy storage batteries, limiting its application in off-grid scenarios (such as photovoltaic power supply in remote areas) or emergency backup power supply.

[0004] Therefore, how to solve the defect that the existing cascade H-bridge power supply system cannot achieve DC energy replenishment is a problem that needs to be solved urgently. Summary of the Invention

[0005] The present application provides a power supply system and a control method thereof, which solves the problem in the related art that the power supply system cannot achieve DC energy replenishment.

[0006] In a first aspect, the present application provides a power supply system, which includes: a DC input interface; a first energy storage module, wherein the first connection end of the first energy storage module is connected to the DC input interface; a DC conversion module, wherein the DC conversion module includes N DC conversion units, and the first connection end of each DC conversion unit is connected to the second connection end of the first energy storage module; wherein N is an integer greater than or equal to 2; a second energy storage module, wherein the second energy storage module includes N energy storage units, and the first connection ends of the N energy storage units are respectively connected to the second connection ends of the N DC conversion units; the first energy storage module and the N energy storage units include at least one energy storage battery and at least one energy storage capacitor; an AC conversion module, wherein the AC conversion module The block includes N cascaded inverter units, wherein the first connection terminals of the N inverter units are respectively connected to the second connection terminals of the N energy storage units, and the third connection terminal of the nth inverter unit is connected to the second connection terminal of the n+1th inverter unit; wherein n=[1, ..., N-1]; an AC output interface, wherein the AC output interface is respectively connected to the second connection terminal of the first inverter unit and the third connection terminal of the Nth inverter unit; and a control module, wherein the control module is respectively connected to the control terminals of the N DC conversion units and the control terminals of the N inverter units, and is used to gradually start the N DC conversion units according to the target position of the at least one energy storage battery, and then control the N inverter units to work simultaneously after all the N DC conversion units are started.

[0007] In a second aspect, the present application provides a power supply system control method, which is applied to a power supply system, and the control method includes: a control module obtains at least one target position of at least one energy storage battery in the power supply system; the control module gradually starts N DC conversion units according to the at least one target position; when the N DC conversion units are started, the control module controls N inverter units to work simultaneously to generate corresponding AC power.

[0008] The technical solution provided by this application has at least the following beneficial effects:

[0009] (1) The power supply system of the present application can charge the energy storage unit in the second energy storage module or / and the first energy storage module respectively through the DC conversion module using the DC power input from the external DC power supply, the energy storage battery in the first energy storage module or / and the energy storage battery in the second energy storage module, and can invert the DC power in the second energy storage module into AC power through the cascaded N inverter units to supply power to the external load; therefore, the present application can perform DC energy replenishment through the external DC power supply, the energy storage battery in the first energy storage module or / and the energy storage battery in the second energy storage module, and solve the problem that the cascaded H-bridge power supply system in the related art cannot achieve DC energy replenishment. At the same time, multiple DC energy replenishment methods also improve the application scenarios and stability of the power supply system.

[0010] (2) The power supply system of the present application includes at least one energy storage battery and at least one energy storage capacitor. While reducing the number of BMS systems, the cost and volume of the power supply system, it is also suitable for large single-cell batteries, greatly improving the volume density or power density of the power supply system and reducing the weight of the product.

[0011] (3) The present application reduces the reliance on the BMS system for voltage balancing of the energy storage battery by including multiple energy storage capacitors in N energy storage units; then the present application can achieve voltage balancing of the energy storage unit while performing voltage conversion through the DC conversion unit, thereby improving the voltage balancing control efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification, are used to explain the principles of the present disclosure. Obviously, the drawings described below are only some embodiments of the present disclosure, and those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0013] Figure 1 Shown is a structural schematic diagram of the first power supply system provided in an embodiment of the present application.

[0014] Figure 2 Shown is a structural schematic diagram of the second power supply system provided in an embodiment of the present application.

[0015] Figure 3 Shown is a circuit diagram of the first power supply system provided in an embodiment of the present application.

[0016] Figure 4 Shown is a control flow diagram of the first power supply system provided in an embodiment of the present application.

[0017] Figure 5 Shown is a circuit diagram of a second power supply system provided in an embodiment of the present application.

[0018] Figure 6 Shown is a control flow diagram of the second power supply system provided in an embodiment of the present application.

[0019] Figure 7 Shown is a circuit diagram of a third power supply system provided in an embodiment of the present application.

[0020] Figure 8 Shown is a control flow diagram of the third power supply system provided in an embodiment of the present application.

[0021] Figure 9 The figure shows a flow chart of a power system control method provided in an embodiment of the present application.

[0022] Description of reference numerals:

[0023] 100, power supply system; 110, DC input interface; 120, first energy storage module; 130, DC conversion module; 131, first DC conversion unit; 132, second DC conversion unit; 133, third DC conversion unit; 134, fourth DC conversion unit; 140, second energy storage module; 141, first energy storage unit; 142, second energy storage unit; 143, third energy storage unit; 144, fourth energy storage unit; 150, AC conversion module; 151, first inverter unit; 152, second inverter unit; 153, third inverter unit; 154, fourth inverter unit; 160, AC output interface; 170, control module; 180, interface switching module; 190, AC input interface;

[0024] Q1, first transistor; Q2, second transistor; Q3, third transistor; Q4, fourth transistor; Q5, fifth transistor; Q6, sixth transistor; Q7, seventh transistor; Q8, eighth transistor; Q9, ninth transistor; Q10, tenth transistor; Q11, eleventh transistor; Q12, twelfth transistor; T1, transformer; U1, first triode; U2, second triode; L1, first inductor; L2, second inductor; C1, first capacitor; C2, second capacitor; R1, first resistor; R2, second resistor; K1, first relay; K2, second relay; VCC1, first power supply terminal; VCC2, second power supply terminal. DETAILED DESCRIPTION

[0025] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this application will be thorough and complete and will fully convey the concepts of the example embodiments to those skilled in the art.

[0026] In addition, described feature, structure or characteristic can be combined in one or more embodiments in any suitable manner.In the following description, many specific details are provided so as to provide a full understanding of the embodiments of the present application. However, it will be appreciated by those skilled in the art that the technical scheme of the present application can be put into practice without one or more of the specific details, or other methods, components, devices, steps etc. can be adopted. In other cases, known methods, devices, implementations or operations are not shown or described in detail to avoid blurring the various aspects of the application.

[0027] The present application is further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be understood as limiting the present application.

[0028] In a first aspect, the present application provides a power supply system, specifically including the following embodiments:

[0029] Figure 1 FIG. 1 is a schematic diagram of the structure of the first power supply system provided in an embodiment of the present application; Figure 1 As shown, the power supply system 100 includes a DC input interface 110, a first energy storage module 120, a DC conversion module 130, a second energy storage module 140, an AC conversion module 150, an AC output interface 160 and a control module 170; wherein, the DC input interface 110 is used to connect to a DC power source such as a photovoltaic input or a battery, and the AC output interface 160 is used to connect to an external AC load, so that the AC power output by the power supply system 100 provides power to the external AC load.

[0030] In this embodiment, if Figure 1 As shown, the first connection end of the first energy storage module 120 is connected to the DC input interface 110; the first energy storage module 120 can be an energy storage battery or an energy storage capacitor. The first energy storage module 120 is used to store or transfer the DC power input through the DC input interface 110.

[0031] The DC conversion module 130 of this embodiment includes N DC conversion units, and the first connection end of each DC conversion unit is connected to the second connection end of the first energy storage module 120; the second energy storage module 140 includes N energy storage units, and the first connection ends of the N energy storage units are respectively connected to the second connection ends of the N DC conversion units; wherein N is an integer greater than or equal to 2;

[0032] It should be noted that each DC conversion unit is used to boost or buck the output voltage of the first energy storage module 120 before outputting it to the corresponding energy storage unit, and is also used to boost or buck the output voltage of the energy storage unit before outputting it to the first energy storage module 120. The energy storage unit in this embodiment can be an energy storage battery or an energy storage capacitor.

[0033] Optionally, the first energy storage module 120 and the N energy storage units of this embodiment include at least one energy storage battery and at least one energy storage capacitor.

[0034] In this embodiment, the AC conversion module 150 includes N cascaded inverter units, the first connection end of each inverter unit is connected to the second connection end of each energy storage unit, and the third connection end of the nth inverter unit is connected to the second connection end of the n+1th inverter unit; wherein n is a variable, and the value range is an integer in [1,…,N]; the AC output interface 160 is respectively connected to the second connection end of the first inverter unit and the third connection end of the Nth inverter unit; it should be noted that the cascaded N inverter units are used to convert the DC power of each energy storage unit into AC power and then power the load through the AC output interface 160.

[0035] The control module 170 of this embodiment is connected to the control terminals of the N DC conversion units and the control terminals of the N inverter units, respectively, and is configured to gradually start the N DC conversion units according to the target position of at least one energy storage battery, and then control the N inverter units to operate simultaneously after all the N DC conversion units are started.

[0036] It can be seen from this that the specific working principle of the power supply system 100 provided in this embodiment is:

[0037] (1) When there is a DC input at the DC input interface 110, the control module 170 controls the N DC conversion units in the DC conversion module 130 to start up in sequence from the first DC conversion unit to the Nth DC conversion unit, so that the DC power input by the external DC power supply passes through the first energy storage module 120 and the DC conversion module 130 and is stored in the N energy storage units in the second energy storage module 140 in sequence; when all the DC conversion units are started up, the control module 170 controls the N inverter units to start up at the same time, converts the DC power in the N energy storage units into AC power, and then outputs the converted power to the external load through the AC output interface 160, thereby realizing DC energy replenishment for the power supply system 100 through the external DC power supply.

[0038] (2) When there is no DC input at the DC input interface 110, and the first energy storage module 120 is an energy storage battery and the N energy storage units are energy storage capacitors, the control module 170 controls the N DC conversion units in the DC conversion module 130 to start up in sequence from the first DC conversion unit to the Nth DC conversion unit, so that the DC power stored in the first energy storage module 120 passes through the DC conversion module 130 and charges the N energy storage units in sequence; when all the DC conversion units are started up, the control module 170 controls the N inverter units to start up at the same time, converts the DC power in the N energy storage units into AC power, and then outputs the AC power to the external load through the AC output interface 160, thereby realizing DC energy replenishment for the power supply system 100 through the energy storage battery in the first energy storage module 120.

[0039] (3) When there is no DC input at the DC input interface 110, and the first energy storage module 120 is an energy storage capacitor and the i-th energy storage unit is an energy storage battery, the control module 170 first controls the i-th DC conversion unit to start, and charges the first energy storage module 120 through the DC voltage in the i-th energy storage unit, thereby establishing the bus voltage of the first energy storage module 120; then the control module 170 controls the other DC conversion units to start in sequence, and charges the other energy storage units through the voltage on the first energy storage module 120; when all the DC conversion units are started, the control module 170 controls the N inverter units to start at the same time, converts the DC power in the N energy storage units into AC power, and then outputs it to the external load through the AC output interface 160, thereby realizing DC energy replenishment for the power supply system 100 through the energy storage battery in the second energy storage module 140.

[0040] In summary, the power supply system 100 provided in this application has at least the following beneficial effects:

[0041] (1) The power supply system 100 of the present application can charge the energy storage unit in the second energy storage module 140 or / and the first energy storage module 120 respectively through the DC conversion module 130 using the DC power input from the external DC power supply, the energy storage battery in the first energy storage module 120 or / and the energy storage battery in the second energy storage module 140, and can invert the DC power in the second energy storage module 140 into AC power through the cascaded N DC conversion units to supply power to the external load; therefore, the present application can perform DC energy replenishment through the external DC power supply, the energy storage battery in the first energy storage module 120 or / and the energy storage battery in the second energy storage module 140, and while solving the problem that the cascaded H-bridge power supply system 100 in the related art cannot achieve DC energy replenishment, the multiple DC energy replenishment methods also improve the application scenarios and stability of the power supply system 100.

[0042] (2) Since an energy storage battery needs to be independently configured with a BMS system (battery management system) for monitoring battery voltage and temperature and performing balancing control; however, the power supply system 100 of the present application includes at least one energy storage battery and at least one energy storage capacitor, especially a combination of one energy storage battery and N energy storage capacitors. While greatly reducing the number of BMS systems, the cost and volume of the power supply system 100, it is also suitable for large single-cell batteries, greatly improving the volume density or power density of the power supply system 100 and reducing the weight of the product.

[0043] (3) In order to ensure the normal operation of the N cascaded inverter units, it is necessary to balance the output voltages of the N energy storage units. The related technology usually relies on the BMS system to actively adjust the battery charging and discharging, which results in slow response speed and low balancing efficiency. However, the present application reduces the reliance on the BMS system for voltage balancing of the energy storage battery by including multiple energy storage capacitors in the N energy storage units. Then, the DC conversion unit can achieve voltage balancing of the energy storage unit while performing voltage conversion, thereby improving the voltage balancing control efficiency.

[0044] Figure 2 FIG. 1 is a schematic diagram of the structure of a second power supply system provided in an embodiment of the present application; Figure 2 As shown, the DC input interface 110 of this embodiment includes a positive terminal and a negative terminal, the first connection terminal of the first energy storage module 120 also includes a first terminal connected to the positive terminal of the DC input interface 110 and a second terminal connected to the negative terminal of the DC input interface 110, and the second connection terminal of the second energy storage module 140 includes a first terminal at the positive pole and a second terminal at the negative pole; by analogy, the first connection terminal of the energy storage unit also includes a first terminal and a second terminal, the second connection terminal of the energy storage unit also includes a first terminal and a second terminal, and the first connection terminal of the inverter unit includes a first terminal and a second terminal.

[0045] like Figure 2 As shown, the power supply system 100 of this embodiment also includes an AC input interface 190 and an interface switching module 180; the control end of the interface switching module 180 is connected to the control module 170, the first connection end of the interface switching module 180 is connected to the AC conversion module 150, the second connection end of the interface switching module 180 is connected to the AC output interface 160, and the third connection end of the interface switching module 180 is connected to the AC input interface 190, and is used to control the AC input interface 190 and / or the AC output interface 160 to be connected to the AC conversion module 150 under the action of the switching signal output by the control module 170.

[0046] It should be noted that the AC input interface 190 of this embodiment is used to connect to an external AC power source. The AC input interface 190 is connected to the AC conversion module 150 via the interface switching module 180, so that the power supply system 100 can select AC energy replenishment or DC energy replenishment according to different application scenarios, thereby improving the compatibility and flexibility of the power supply system 100. The specific working principle is as follows:

[0047] (1) When used in a DC energy replenishment scenario, the control module 170 outputs a first switching signal, and the interface switching module 180 electrically connects the AC output interface 160 to the AC conversion module 150 according to the first switching signal, and supplies power to the AC load through an external DC power supply, the energy storage battery in the first energy storage module 120, and / or the energy storage battery in the second energy storage module 140, thereby achieving DC energy replenishment.

[0048] (2) If applied in an AC energy replenishment scenario, the control module 170 outputs a second switching signal, and the interface switching module 180 electrically connects the AC input interface 190 with the AC conversion module 150 according to the second switching signal, so that the AC power output by the external AC power source is stored in the energy storage battery in the second energy storage module 140 after passing through the AC conversion module 150, or is stored in the energy storage battery in the first energy storage module 120 after passing through the DC conversion module 130, thereby realizing AC energy replenishment.

[0049] It should also be noted that Figure 2 The control module 170 is also connected to the DC conversion unit 1, DC conversion unit 2, DC conversion unit 3, inverter unit 1, inverter unit 2, inverter unit 3 and other units in the figure, which are omitted here for the simplicity of the legend lines.

[0050] Taking N=4 as an example, the circuit structure of the power supply system 100 specifically includes the following embodiments:

[0051] Figure 3 FIG. 1 is a circuit diagram of a first power supply system provided in an embodiment of the present application; FIG. Figure 3 As shown, the DC conversion unit includes a first transistor Q1, a second transistor Q2, a third transistor Q3, a fourth transistor Q4, a first inductor L1, a first capacitor C1, a transformer T1, a fifth transistor Q5, a sixth transistor Q6, a seventh transistor Q7 and an eighth transistor Q8.

[0052] Specifically, the control end of the first transistor Q1 is connected to the control module 170, and the first end of the first transistor Q1 is connected to the first end of the second connection end of the first energy storage module 120; the control end of the second transistor Q2 is connected to the control module 170, the first end of the second transistor Q2 is connected to the second end of the first transistor Q1, and the second end of the second transistor Q2 is connected to the second end of the second connection end of the first energy storage module 120; the control end of the third transistor Q3 is connected to the control module 170, and the first end of the third transistor Q3 is connected to the first end of the first transistor Q1; the control end of the fourth transistor Q4 is connected to the control module 170, the first end of the fourth transistor Q4 is connected to the second end of the third transistor Q3, and the second end of the fourth transistor Q4 is connected to the second end of the second transistor Q2; the first end of the first inductor L1 is connected to the second end of the first transistor Q1; the first end of the first capacitor C1 is connected to the second end of the third transistor Q3; the first end of the primary side of the transformer T1 is connected to the first end of the first transistor Q1; The second end of the inductor L1 is connected, and the second end of the primary side of the transformer T1 is connected to the second end of the first capacitor C1; the control end of the fifth transistor Q5 is connected to the control module 170, and the first end of the fifth transistor Q5 is connected to the first end of the first connection end of the energy storage unit; the control end of the sixth transistor Q6 is connected to the control module 170, and the first end of the sixth transistor Q6 is respectively connected to the second end of the fifth transistor Q5 and the second end of the secondary side of the transformer T1, and the second end of the sixth transistor Q6 is connected to the second end of the first connection end of the energy storage unit; the control end of the seventh transistor Q7 is connected to the control module 170, and the first end of the seventh transistor Q7 is connected to the first end of the fifth transistor Q5, and the second end of the seventh transistor Q7 is connected to the first end of the secondary side of the transformer T1; the control end of the eighth transistor Q8 is connected to the control module 170, and the first end of the eighth transistor Q8 is connected to the second end of the sixth transistor Q6.

[0053] It should be noted that the transformer T1 of this embodiment is a high-frequency transformer that provides electrical isolation and voltage conversion. The DC voltage conversion ratio is determined by setting the turns ratio of the primary winding and the secondary winding of the transformer T1. In addition, the first transistor Q1, the second transistor Q2, the third transistor Q3, and the fourth transistor Q4 form a primary bridge arm, the fifth transistor Q5, the sixth transistor Q6, the seventh transistor Q7, and the eighth transistor Q8 form a secondary bridge arm, the first inductor L1 is a resonant inductor, and the first capacitor C1 is a resonant capacitor. The specific operating principle of the DC conversion unit of this embodiment is as follows:

[0054] (1) Forward conversion mode: The control module 170 drives the primary bridge arm as an active inverter bridge arm to switch at or around the resonant frequency, and drives the secondary bridge arm as a synchronous rectifier. The specific working sequence is as follows:

[0055] ① Phase 1: The control module 170 controls the first transistor Q1 and the fourth transistor Q4 to be turned on simultaneously, and the second transistor Q2 and the third transistor Q3 to be turned off. The voltage Vin on the first energy storage module 120 is applied to the resonant cavity composed of the first inductor L1, the first capacitor C1 and the primary side of the transformer T1. Current begins to flow through the first inductor L1 and the first capacitor C1, and charges the equivalent excitation inductance in the transformer T1, thereby inducing a positive voltage on the secondary side of the transformer T1. At the same time, the control module 170 controls the fifth transistor Q5 and the eighth transistor Q8 to be turned on simultaneously, and controls the seventh transistor Q7 and the sixth transistor Q6 to be turned off. The positive voltage output by the secondary side of the transformer T1 is input into the energy storage unit.

[0056] ② Phase 2: The control module 170 controls the first transistor Q1 and the fourth transistor Q4 to be turned off at the same time, and the second transistor Q2 and the third transistor Q3 to be turned on; at this time, the voltage polarity on the resonant cavity is reversed (equivalent to applying -Vin), the resonant current flows in the opposite direction, the equivalent excitation inductance in the transformer T1 begins to discharge (the excitation current decreases), and a negative voltage is induced on the secondary side of the transformer T1; at the same time, the control module 170 controls the fifth transistor Q5 and the eighth transistor Q8 to be turned off at the same time, and controls the seventh transistor Q7 and the sixth transistor Q6 to be turned on at the same time, and the negative voltage output from the secondary side of the transformer T1 is input into the energy storage unit.

[0057] (2) Reverse conversion mode: The control module 170 drives the secondary bridge arm as an active inverter bridge arm, switching at or around the resonant frequency, and drives the primary bridge arm as a synchronous rectifier. The specific working sequence is as follows:

[0058] ① Phase 1: The control module 170 controls the seventh transistor Q7, the sixth transistor Q6, the second transistor Q2, and the third transistor Q3 to be turned on simultaneously, and the fifth transistor Q5, the eighth transistor Q8, the first transistor Q1, and the fourth transistor Q4 to be turned off. The voltage on the energy storage unit is applied to the resonant cavity after the turns ratio is converted. The current path and magnetization process are similar to those in phase ① of the forward conversion mode, but in the opposite direction. Energy is input from the secondary side, transferred to the primary side through the transformer T1, and then input into the first energy storage module 120.

[0059] ② Phase 2: The control module 170 controls the seventh transistor Q7, the sixth transistor Q6, the second transistor Q2, and the third transistor Q3 to be turned off at the same time, and the fifth transistor Q5, the eighth transistor Q8, the first transistor Q1, and the fourth transistor Q4 to be turned on. The voltage on the energy storage unit is applied to the resonant cavity after the turns ratio is converted. The current path and magnetization process are similar to those in phase ② of the forward conversion mode, but in the opposite direction. Energy is input from the secondary side, transferred to the primary side through the transformer T1, and then input into the first energy storage module 120.

[0060] In summary, the DC conversion unit of this embodiment achieves high efficiency, high power density, wide range adjustment and bidirectional energy flow DC conversion through a resonant network composed of a resonant inductor, a resonant capacitor and a high-frequency transformer, combined with a symmetrical bridge structure and synchronous rectification control.

[0061] like Figure 3 As shown, the inverter unit of this embodiment includes a ninth transistor Q9, a tenth transistor Q10, an eleventh transistor Q11, and a twelfth transistor Q12; wherein, the control end of the ninth transistor Q9 is connected to the control module 170, the first end of the ninth transistor Q9 is connected to the first end of the second connection end of the energy storage unit, and the second end of the ninth transistor Q9 serves as the second connection end of the inverter unit; the control end of the tenth transistor Q10 is connected to the control module 170, the first end of the tenth transistor Q10 is connected to the second end of the ninth transistor Q9, and the second end of the tenth transistor Q10 is connected to the second end of the second connection end of the energy storage unit; the control end of the eleventh transistor Q11 is connected to the control module 170, the first end of the eleventh transistor Q11 is connected to the first end of the ninth transistor Q9, and the second end of the eleventh transistor Q11 serves as the third connection end of the inverter unit; the control end of the twelfth transistor Q12 is connected to the control module 170, the first end of the twelfth transistor Q12 is connected to the second end of the eleventh transistor Q11, and the second end of the twelfth transistor Q12 is connected to the second end of the tenth transistor Q10.

[0062] It should be noted that the control module 170 controls the ninth transistor Q9, the tenth transistor Q10, the eleventh transistor Q11 and the twelfth transistor Q12 to be alternately turned on in a complementary pair, wherein the ninth transistor Q9 and the twelfth transistor Q12 are a pair of transistors, and the tenth transistor Q10 and the eleventh transistor Q11 are a corresponding complementary pair; and uses a high-frequency pulse signal to adjust the conduction duty cycle of each group of switching tubes to convert the DC input voltage of the energy storage unit into a high-frequency pulse square wave output; in addition, the anti-parallel diodes in the ninth transistor Q9, the tenth transistor Q10, the eleventh transistor Q11 and the twelfth transistor Q12 provide a freewheeling path for the inductive load current and realize bidirectional energy flow, and the AC power input through the AC input interface 190 is rectified and input into the energy storage unit.

[0063] like Figure 3As shown, the interface switching module 180 includes a first relay K1 and a second relay K2; the control end of the first relay K1 is connected to the control module, the first switch end of the first relay K1 serves as the first end of the first connection end of the interface switching module 180, the second switch end of the first relay K1 is connected to the first end of the AC output interface 160, the third switch end of the first relay K1 serves as the second end of the first connection end of the interface switching module 180, and the fourth switch end of the first relay K1 is connected to the second end of the AC output interface 160; the control end of the second relay K2 is connected to the control module, the first switch end of the second relay K2 is connected to the first switch end of the first relay K1, the second switch end of the second relay K2 is connected to the first end of the AC input interface 190, the third switch end of the second relay K2 is connected to the third switch end of the first relay K1, and the fourth switch end of the second relay K2 is connected to the second end of the AC input interface 190.

[0064] In another embodiment, in order to explain the control principle of the first relay and the second relay in detail, as shown in FIG. Figure 3 As shown, the interface switching module 180 of the present application also includes a first transistor U1, a first resistor R1, a second transistor U2, and a second resistor R2; specifically, the base of the first transistor U1 is connected to the control module 170, the collector of the first transistor U1 is connected to the first power supply terminal VCC1, and the emitter of the first transistor U1 is grounded through the first resistor R1; the first end of the coil of the first relay K1 is connected to the collector of the first transistor U1, the second end of the coil of the first relay K1 is connected to the second power supply terminal VCC2, the first end of the first switch K11 of the first relay K1 (that is, the first switch end of the first relay) serves as the first end of the first connection end of the interface switching module 180, and the second end of the first switch K11 of the first relay K1 (that is, the second switch end of the first relay) is connected to the first end L of the AC output interface 160. load The first end of the second switch K12 of the first relay K1 (i.e., the third end of the switch of the first relay) serves as the second end of the first connection end of the interface switching module 180, and the second end of the second switch K12 of the first relay K1 (i.e., the fourth end of the switch of the first relay) is connected to the second end N of the AC output interface 160. loadThe base of the second transistor U2 is connected to the control module 170, the collector of the second transistor U2 is connected to the first power supply terminal VCC1, and the emitter of the second transistor U2 is grounded through the second resistor R2; the first end of the coil of the second relay K2 is connected to the collector of the second transistor U2, the second end of the coil of the second relay K2 is connected to the second power supply terminal VCC2, the first end of the first switch K21 of the second relay K2 (i.e., the first end of the switch of the second relay) is connected to the first end of the first switch K11 of the first relay K1, and the second end of the first switch K21 of the second relay K2 (i.e., the second end of the switch of the second relay) is connected to the first end L of the AC input interface 190. grid The first end of the second switch K22 of the second relay K2 (i.e., the third switch end of the second relay) is connected to the first end of the second switch K12 of the first relay K1, and the second end of the second switch K22 of the second relay K2 (i.e., the fourth switch end of the second relay) is connected to the second end N of the AC input interface 190. grid connected.

[0065] It should be noted that the base of the first transistor U1 is connected to the first switching terminal of the control module 170. When the first switching terminal of the control module 170 outputs a high-level first switching signal, the first transistor U1 is turned on, energizing the ends of the coil of the first relay K1 and closing the normally-open first switch K11 and second switch K12 of the first relay K1, thereby connecting the AC output interface 160 to the AC conversion module 150. Furthermore, the base of the second transistor U2 is connected to the second switching terminal of the control module 170. When the second switching terminal of the control module 170 outputs a high-level second switching signal, the second transistor U2 is turned on, energizing the ends of the coil of the second relay K2 and closing the normally-open first switch K21 and second switch K22 of the second relay K2, thereby connecting the AC input interface 190 to the AC conversion module 150.

[0066] Optionally, the interface switching module 180 also includes a second inductor L2 and a second capacitor C2; the first end of the second inductor L2 serves as the first end of the first connection end of the interface switching module 180, and the second end of the second inductor L2 is connected to the first end of the first switch of the first relay K1; the first end of the second capacitor C2 is connected to the second end of the second inductor L2, and the second end of the second capacitor C2 serves as the second end of the first connection end of the interface switching module 180; wherein, the second inductor L2 and the second capacitor C2 have a filtering function.

[0067] Continue as Figure 3As shown, in this embodiment, the first energy storage module 120 is an energy storage battery, and the four energy storage units are energy storage capacitors, which are respectively commanded as the first energy storage unit 141, the second energy storage unit 142, the third energy storage unit 143 and the fourth energy storage unit 144; the four DC conversion units are respectively named as the first DC conversion unit 131, the second DC conversion unit 132, the third DC conversion unit 133 and the fourth DC conversion unit 134, and the four inverter units are respectively named as the first inverter unit 151, the second inverter unit 152, the third inverter unit 153 and the fourth inverter unit 154; the control method of the power supply control system is as follows Figure 4 As shown, the specific steps include:

[0068] Step S110: The control module drives the first DC conversion unit to soft-start and establish the bus voltage of the first energy storage unit;

[0069] Step S120: The control module drives the second DC conversion unit to soft start, and establishes the bus voltage of the second energy storage unit;

[0070] Step S130: The control module drives the third DC conversion unit to soft start, and establishes the bus voltage of the third energy storage unit;

[0071] Step S140: The control module drives the fourth DC conversion unit to soft-start, and establishes the bus voltage of the fourth energy storage unit;

[0072] Step S150: The control module drives all the inverter units to start simultaneously and output AC power.

[0073] It should be noted that in this embodiment, only the first energy storage module 120 is an energy storage battery. Therefore, it is necessary to start each DC conversion unit in sequence, and the energy storage capacitors in the first energy storage unit 141, the second energy storage unit 142, the third energy storage unit 143 and the fourth energy storage unit 144 are charged by the energy storage battery in the first energy storage module 120, thereby establishing the bus voltage of each energy storage capacitor in sequence; then, when the bus voltage of each energy storage capacitor is established, the control module 170 controls the cascaded four inverter units to start the inverter and output a nine-level sinusoidal AC voltage; wherein, the soft start in this embodiment is to gradually increase the output voltage or current of the DC conversion unit to avoid the surge current at the moment of system power-on causing impact on the components. In the cascaded H-bridge power supply system 100, the bus capacitor of each submodule has a zero voltage in the initial state. If all DC conversion units are started at the same time, it may cause input power overload and excessive capacitor charging current. The phased soft start breaks down the startup process of the entire system into multiple sequential steps. In each step, only part of the DC conversion unit is activated, thereby dispersing the current stress and ensuring the safe and reliable establishment of the bus voltage.

[0074] The DC conversion units in this embodiment all operate in open-loop mode, i.e., with a fixed frequency at or below the first resonant frequency. The open-loop control logic is simple. During the soft-start phase, the control module 170 only needs to activate each DC conversion unit in sequence, without the need for real-time parameter adjustment. This reduces algorithm complexity, omits voltage / current sensors and feedback circuits, and reduces hardware costs, making it suitable for cost-sensitive applications such as photovoltaic energy storage. Optionally, during the charging phase, each energy storage capacitor is charged through a DC conversion unit with the same parameters, and due to circuit symmetry, the voltage naturally tends to be consistent. Even if there are component differences, the fixed frequency of the open-loop control can still ensure that the charging rate of each path is similar, reducing the accumulation of deviations.

[0075] It should also be noted that in this embodiment, only the first energy storage module 120 is an energy storage battery, and the other energy storage units are all energy storage capacitors. While greatly reducing the number of BMS systems, the cost and volume of the power system 100, it is also suitable for large single-cell batteries, greatly improving the volume density or power density of the power system 100, and reducing the weight of the product.

[0076] Figure 5 FIG2 is a circuit diagram of a second power supply system provided in an embodiment of the present application; Figure 5 and Figure 3 The only difference is the location of the energy storage battery: Figure 3 The middle energy storage battery is located in the first energy storage module 120. Figure 5 The middle energy storage battery is located in the first energy storage unit 141 of the second energy storage module 140; Figure 5 The control method of the power control system shown is as follows Figure 6 As shown, the specific steps include:

[0077] Step S210: The control module drives the first DC conversion unit to soft-start and establish the bus voltage of the first energy storage module;

[0078] Step S220: The control module drives the second DC conversion unit to soft start, and establishes the bus voltage of the second energy storage unit;

[0079] Step S230: The control module drives the third DC conversion unit to soft-start and establish the bus voltage of the third energy storage unit;

[0080] Step S240: The control module drives the fourth DC conversion unit to soft-start, and establishes the bus voltage of the fourth energy storage unit;

[0081] Step S250: The control module drives all the inverter units to start simultaneously and output AC power.

[0082] Combine Figure 4 and Figure 6It can be seen that although the two embodiments have the same soft start sequence for the four DC conversion units, the soft start function of the first DC conversion unit 131 is different; Figure 4 In the embodiment shown, the first DC conversion unit 131 soft start establishes the bus voltage of the first energy storage unit 141, and Figure 6 In the embodiment shown, the soft start of the first DC conversion unit 131 establishes the bus voltage of the first energy storage module 120 . Other working principles are the same and will not be described in detail here.

[0083] It is worth noting that in Figure 3 In the power supply system 100 shown in FIG, the AC power output by each inverter unit needs to undergo two-stage voltage conversion, namely, the DC conversion unit and the inverter unit; Figure 5 In the power supply system 100 shown in FIG, the AC power output by the first inverter unit 151 only needs to undergo a voltage conversion from the energy storage battery to the first inverter unit 151; therefore, Figure 3 Compared to the power supply system 100 shown, Figure 5 The power supply system 100 shown also has the advantage of high voltage conversion efficiency.

[0084] Figure 7 FIG. 1 is a circuit diagram of a third power supply system provided in an embodiment of the present application; Figure 7 and Figure 5 The only difference is the number of energy storage batteries: Figure 5 The second energy storage module 140 includes only one energy storage battery, and Figure 7 The second energy storage module 140 includes two energy storage batteries, that is, the first energy storage unit 141 and the third energy storage unit 143 are both energy storage batteries; Figure 7 The control method of the power control system shown is as follows Figure 8 As shown, the specific steps include:

[0085] Step S310: The control module drives the first DC conversion unit to soft-start and establish the bus voltage of the first energy storage module;

[0086] Step S320: The control module drives the third DC conversion unit to soft start, and the first energy storage unit and the third energy storage unit enter a voltage balancing process;

[0087] Step S330: The control module drives the second DC conversion unit to soft start, and establishes the bus voltage of the second energy storage unit;

[0088] Step S340: The control module drives the fourth DC conversion unit to soft-start, and establishes the bus voltage of the fourth energy storage unit;

[0089] Step S350: The control module drives all the inverter units to start simultaneously and output AC power.

[0090] As can be seen, the control module 170 of this embodiment first drives the first DC conversion unit 131 to soft start, so that the energy storage battery in the first energy storage unit 141 charges the energy storage capacitor in the first energy storage module 120, thereby establishing the bus voltage of the first energy storage module 120; then starts the third DC conversion unit 133, so that the energy storage battery in the first energy storage unit 141 and the energy storage battery in the third energy storage unit 143 are voltage-balanced. For example, assuming that the voltage of the first energy storage unit 141 is 56V and the voltage of the third energy storage unit 143 is 55V, after both the first DC conversion unit 131 and the third DC conversion unit 133 are started, the first energy storage unit 141 and the third energy storage unit 143 will be voltage-balanced. Without considering losses, the voltage after voltage balancing is (56+55) / 2=55.5V. In addition, since the startup order of the first DC conversion unit 131 and the third DC conversion unit 133 can be interchanged, it will not be repeated here.

[0091] It is worth noting that in Figure 7 In the power supply system 100 shown, the AC power output by the first inverter unit 151 and the AC power output by the third inverter unit 153 only need to undergo one voltage conversion; therefore, Figure 7 The power system shown is 100 Figure 5 The voltage conversion efficiency of the power supply system 100 is higher.

[0092] It should be noted that this application is only Figure 3 、 Figure 5 and Figure 7 Three examples are shown in which the power supply system 100 includes at least one energy storage battery and at least one energy storage capacitor. However, there are several combinations depending on the number of energy storage batteries and energy storage capacitors, which will not be illustrated one by one here. The core control method of the present application is to treat the energy storage capacitor as an energy transfer station, and charge the energy storage unit with a high voltage to the energy storage unit with a low voltage, so that each energy storage unit in the second energy storage module 140 reaches voltage balance. Therefore, this core control method can be applied to power supply systems 100 with different combinations.

[0093] In a second aspect, the present application provides a power system control method, which specifically includes the following embodiments:

[0094] Figure 9 FIG. 1 is a flow chart of a power system control method provided by an embodiment of the present application; FIG. Figure 9 As shown, the control method specifically includes the following steps:

[0095] Step S100: The control module obtains at least one target location of at least one energy storage battery in the power supply system.

[0096] It should be noted that the above Figure 3 、 Figure 5 and Figure 7 As can be seen from the illustrated embodiment, the target location of the at least one energy storage battery in the power supply system may be any location in the first energy storage module and / or the N energy storage units.

[0097] Step S200: The control module gradually starts N DC conversion units according to at least one target position.

[0098] Optionally, when the first energy storage module is an energy storage battery and the N energy storage units are all energy storage capacitors, the control module gradually starts the N DC conversion units according to at least one target position, including: the control module drives the first DC conversion unit to the Nth DC conversion unit to start in sequence, and establishes the bus voltage from the first energy storage unit to the Nth energy storage unit in sequence.

[0099] Optionally, when the first energy storage module is an energy storage capacitor, only the i-th energy storage unit is an energy storage battery, and the other energy storage units are energy storage capacitors, the control module gradually starts N DC conversion units according to at least one target position, including: the control module drives the i-th DC conversion unit to start and establish the bus voltage of the first energy storage module; the control module drives the first DC conversion unit to the i-1th DC conversion unit to start in sequence, or / and the i+1th DC conversion unit to the Nth DC conversion unit to start in sequence; wherein i takes any value from 1 to N.

[0100] Optionally, when the first energy storage module is an energy storage capacitor, only the i-th energy storage unit and the j-th energy storage unit are energy storage batteries, and the other energy storage units are energy storage capacitors, the control module gradually starts N DC conversion units according to at least one target position, including: the control module drives the i-th DC conversion unit to start and establish the bus voltage of the first energy storage module; the control module drives the j-th DC conversion unit to start and establish a voltage equalization process for the i-th energy storage unit and the j-th energy storage unit; the control module drives the DC conversion units other than the i-th DC conversion unit and the j-th DC conversion unit to start in sequence; wherein, i and j take any values ​​from 1 to N, respectively, and i≠j.

[0101] Step S300: After the N DC conversion units are started, the control module controls the N inverter units to work simultaneously to generate corresponding AC power.

[0102] It should be noted that the working principles of step S200 and step S300 in this embodiment are the same as those in the above embodiment and will not be repeated here.

[0103] Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature specified as "first," "second," or "third" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0104] In the description of this specification, the reference terms "some embodiments", "exemplarily", etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0105] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application. Therefore, any changes or modifications made in accordance with the claims and description of the present application should fall within the scope of the patent application.

Claims

1. A power supply system, characterized in that: The power supply system comprises: DC input interface; a first energy storage module, wherein a first connection end of the first energy storage module is connected to the DC input interface; A DC conversion module, comprising N DC conversion units, wherein a first connection end of each DC conversion unit is connected to a second connection end of the first energy storage module; wherein N is an integer greater than or equal to 2; a second energy storage module, wherein the second energy storage module includes N energy storage units, wherein the first connection ends of the N energy storage units are respectively connected to the second connection ends of the N DC conversion units; the first energy storage module and the N energy storage units include at least one energy storage battery and at least one energy storage capacitor; An AC conversion module, the AC conversion module comprising N cascaded inverter units, wherein the first connection terminals of the N inverter units are respectively connected to the second connection terminals of the N energy storage units, and the third connection terminal of the nth inverter unit is connected to the second connection terminal of the (n+1)th inverter unit; wherein n = [1, ..., N-1]; an AC output interface, the AC output interface being connected to the second connection terminal of the first inverter unit and the third connection terminal of the Nth inverter unit respectively; A control module is connected to the control ends of the N DC conversion units and the control ends of the N inverter units, respectively, and is used to gradually start the N DC conversion units according to the target position of the at least one energy storage battery, and then control the N inverter units to work simultaneously after all the N DC conversion units are started.

2. The power supply system according to claim 1, wherein: The power supply system further includes: AC input interface; An interface switching module, wherein the control end of the interface switching module is connected to the control module, the first connection end of the interface switching module is connected to the AC conversion module, the second connection end of the interface switching module is connected to the AC output interface, and the third connection end of the interface switching module is connected to the AC input interface, and is used to control the AC input interface and / or the AC output interface to be connected to the AC conversion module respectively under the action of the switching signal output by the control module.

3. The power supply system according to claim 1, wherein: The DC conversion unit includes: a first transistor, wherein a control end of the first transistor is connected to the control module, and a first end of the first transistor is connected to a first end of the second connection end of the first energy storage module; a second transistor, wherein a control end of the second transistor is connected to the control module, a first end of the second transistor is connected to the second end of the first transistor, and a second end of the second transistor is connected to the second end of the second connection end of the first energy storage module; a third transistor, wherein a control terminal of the third transistor is connected to the control module, and a first terminal of the third transistor is connected to the first terminal of the first transistor; a fourth transistor, wherein a control end of the fourth transistor is connected to the control module, a first end of the fourth transistor is connected to the second end of the third transistor, and a second end of the fourth transistor is connected to the second end of the second transistor; a first inductor, wherein a first end of the first inductor is connected to the second end of the first transistor; a first capacitor, wherein a first terminal of the first capacitor is connected to the second terminal of the third transistor; a transformer, wherein a primary first end of the transformer is connected to the second end of the first inductor, and a primary second end of the transformer is connected to the second end of the first capacitor; a fifth transistor, wherein a control terminal of the fifth transistor is connected to the control module, and a first terminal of the fifth transistor is connected to a first terminal of the first connection terminal of the storage unit; a sixth transistor, wherein a control end of the sixth transistor is connected to the control module, a first end of the sixth transistor is respectively connected to the second end of the fifth transistor and the second end of the secondary side of the transformer, and a second end of the sixth transistor is connected to the second end of the first connection end of the storage unit; a seventh transistor, wherein a control end of the seventh transistor is connected to the control module, a first end of the seventh transistor is connected to the first end of the fifth transistor, and a second end of the seventh transistor is connected to the first end of the secondary side of the transformer; an eighth transistor, wherein a control end of the eighth transistor is connected to the control module, a first end of the eighth transistor is connected to the second end of the seventh transistor, and a second end of the eighth transistor is connected to the second end of the sixth transistor.

4. The power supply system according to claim 1, wherein: The inverter unit includes: a ninth transistor, wherein a control end of the ninth transistor is connected to the control module, a first end of the ninth transistor is connected to the first end of the second connection end of the storage unit, and a second end of the ninth transistor serves as the second connection end of the inverter unit; a tenth transistor, wherein a control end of the tenth transistor is connected to the control module, a first end of the tenth transistor is connected to the second end of the ninth transistor, and a second end of the tenth transistor is connected to the second end of the second connection end of the storage unit; an eleventh transistor, wherein a control end of the eleventh transistor is connected to the control module, a first end of the eleventh transistor is connected to the first end of the ninth transistor, and a second end of the eleventh transistor serves as a third connection end of the inverter unit; A twelfth transistor, wherein the control end of the twelfth transistor is connected to the control module, the first end of the twelfth transistor is connected to the second end of the eleventh transistor, and the second end of the twelfth transistor is connected to the second end of the tenth transistor.

5. The power supply system according to claim 2, wherein: The interface switching module includes: a first relay, wherein a control end of the first relay is connected to the control module, a first switch end of the first relay serves as a first end of the first connection end of the interface switching module, a second switch end of the first relay is connected to a first end of the AC output interface, a third switch end of the first relay serves as a second end of the first connection end of the interface switching module, and a fourth switch end of the first relay is connected to a second end of the AC output interface; A second relay, a control end of the second relay is connected to the control module, a first switch end of the second relay is connected to the first switch end of the first relay, a second switch end of the second relay is connected to the first end of the AC input interface, a third switch end of the second relay is connected to the third switch end of the first relay, and a fourth switch end of the second relay is connected to the second end of the AC input interface.

6. The power supply system according to claim 5, characterized in that: The interface switching module also includes: a second inductor, wherein a first end of the second inductor serves as a first end of the first connection end of the interface switching module, and a second end of the second inductor is connected to a first end of the switch of the first relay; A second capacitor, wherein a first end of the second capacitor is connected to a second end of the second inductor, and a second end of the second capacitor serves as a second end of the first connection end of the interface switching module.

7. The power supply system according to any one of claims 1 to 6, characterized in that: The first energy storage module is an energy storage battery, and the N energy storage units are energy storage capacitors; Alternatively, the first energy storage module is an energy storage capacitor, and at least one energy storage unit is an energy storage battery; Alternatively, the first energy storage module is an energy storage battery, and at least one energy storage unit is an energy storage battery.

8. A power system control method, characterized in that: Applied to the power supply system according to any one of claims 1 to 7, the control method comprises: The control module obtains at least one target location of at least one energy storage battery in the power supply system; The control module gradually starts N DC conversion units according to the at least one target position; After the N DC conversion units are started, the control module controls the N inverter units to work simultaneously to generate corresponding AC power.

9. The power system control method according to claim 8, wherein: When the first energy storage module is an energy storage battery and the N energy storage units are energy storage capacitors, the control module gradually starting the N DC conversion units according to the at least one target position includes: the control module driving the first DC conversion unit to the Nth DC conversion unit to start in sequence, and sequentially establishing the bus voltage from the first energy storage unit to the Nth energy storage unit; Alternatively, when the first energy storage module is an energy storage capacitor and only the i-th energy storage unit is an energy storage battery, the control module gradually starts the N DC conversion units according to the at least one target position, including: the control module drives the i-th DC conversion unit to start and establish the bus voltage of the first energy storage module; the control module drives the first DC conversion unit to the i-1th DC conversion unit to start in sequence, and / or the i+1th DC conversion unit to the Nth DC conversion unit to start in sequence; Here, i takes any value from 1 to N.

10. The power system control method according to claim 8, wherein: When the first energy storage module is an energy storage capacitor and only the i-th energy storage unit and the j-th energy storage unit are energy storage batteries, the control module gradually starts the N DC conversion units according to the at least one target position, including: The control module drives the i-th DC conversion unit to start and establish the bus voltage of the first energy storage module; The control module drives the jth DC conversion unit to start, and establishes a voltage balancing process between the ith energy storage unit and the jth energy storage unit; The control module drives the DC conversion units except the i-th DC conversion unit and the j-th DC conversion unit to start in sequence; Here, i and j take any value from 1 to N, and i≠j.

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