Modulation method and device of improved isolated three-level converter and related equipment

Abstract

The invention discloses a modulation method and device of an improved isolated three-level converter and related equipment. The method is applied to the technical field of modulation of a system improved isolated three-level converter, and comprises the following steps: selecting a switching sequence for outputting zero level, and determining a complementary relationship of a switching tube according to the switching sequence; according to the complementary relation of the switching tubes, primary side voltage is determined through a variable duty ratio, and secondary side voltage is determined through a fixed duty ratio; and controlling the transmission power of the system according to the phase shift angle between the primary side voltage and the secondary side voltage so as to modulate the improved isolated three-level converter. According to the scheme, level disorder can be improved, and systematicness is improved.

Description

Technical Field

[0001] This application relates to the modulation technology field of a system-improved isolated three-level converter, and specifically relates to a modulation method, device, and related equipment for an improved isolated three-level converter. Background Art

[0002] The wind energy resources on the earth are extremely rich. China has rich wind energy resources reserves. China has rich offshore wind power resources. The number of hours when the wind speed is greater than or equal to 3 m / s in the sea areas with a water depth of 2 m - 15 m along the eastern coast throughout the year is about 7000 h - 8000 h, and the exploitable wind energy resources at a height of 10 m at sea are about 750 million kW. Compared with onshore wind power, offshore wind power has a series of advantages. For example: high offshore wind speed, small eddy current intensity, low noise, etc. Therefore, vigorously developing offshore wind power is a new trend in the development of wind power.

[0003] During the process of offshore wind power generation, it is required that there is a two-way flow of energy between the offshore power generation equipment and the power grid to participate in power grid regulation. The bidirectional transformer is a key component to realize energy flow, and has advantages such as simple structure, large power density, and low loss. Studying bidirectional transformers is of great significance for the development of offshore wind power and improving the power grid quality. Compared with transformers with H-bridge and half-bridge structures, multi-level structure transformers not only have the same output characteristics and power transmission characteristics as traditional transformers, but also the voltage borne during turn-off is only 1 / (n−1) of the input or output voltage (n is the number of output levels). Therefore, multi-level transformers are widely used in high-voltage and high-power occasions to reduce switching losses, improve efficiency, and at the same time reduce costs.

[0004] However, currently, in the modulation of the existing Extended-Phase-Shift (EPS) improved isolated three-level converter, there may be potential hazards such as level disorder, poor system stability, and low efficiency when the three-level half-bridge structure outputs a zero level. Summary of the Invention

[0005] Based on this, in view of the above technical problems, it is necessary to provide a modulation method, device, and related equipment for an improved isolated three-level converter that can improve level disorder and system performance.

[0006] In a first aspect, this application provides a modulation method for an improved isolated three-level converter, and the method includes: Select a switching sequence for outputting a zero level, and determine the complementary relationship of switching tubes according to the switching sequence; According to the complementary relationship of the switching tubes, determine the primary side voltage through a variable duty cycle and determine the secondary side voltage through a fixed duty cycle; Control the transmission power of the system according to the phase shift angle between the primary side voltage and the secondary side voltage to perform modulation of the improved isolated three-level converter.

[0007] In one embodiment, select the switch sequence for outputting zero level, and determine the complementary relationship of the switching tubes according to the switch sequence, including: Select a unified switch sequence from the switch sequences for outputting zero level; Determine the complementary relationship of the switching tubes according to the unified switch sequence.

[0008] In one embodiment, according to the complementary relationship of the switching tubes, determine the primary side voltage through a variable duty cycle and determine the secondary side voltage through a fixed duty cycle, including: Determine the variable duty cycle and the fixed duty cycle according to the complementary relationship of the switching tubes; Determine the primary side voltage through a variable duty cycle and determine the secondary side voltage through a fixed duty cycle.

[0009] In one embodiment, the calculation formula for the transmission power is: ; (1) where, V in is the system input voltage; L is the sum of the equivalent inductance of the transformer leakage inductance and the externally connected inductance; T h is the half cycle; 𝜙 is the phase shift angle between the primary side voltage and the secondary side voltage; 𝜙 1 is the waveform of the three-level V AB ; m is a constant.

[0010] In a second aspect, the present application further provides a modulation device for an improved isolated three-level converter. The device includes: A selection module, configured to select a switch sequence for outputting zero level and determine the complementary relationship of the switching tubes according to the switch sequence; A determination module, configured to determine the primary side voltage through a variable duty cycle and determine the secondary side voltage through a fixed duty cycle according to the complementary relationship of the switching tubes; A control module, configured to control the transmission power of the system according to the phase shift angle between the primary side voltage and the secondary side voltage to perform modulation of the improved isolated three-level converter.

[0011] In a third aspect, the present application further provides a computer device. The computer device includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the above-mentioned modulation method of the improved isolated three-level converter are implemented.

[0012] Fourthly, the present application also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the modulation method of the improved isolated three-level converter are implemented.

[0013] Fifthly, the present application also provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the steps of the modulation method of the improved isolated three-level converter are implemented.

[0014] For the modulation method of the improved isolated three-level converter, a switching sequence with an output of zero level is selected, and the complementary relationship of the switching tubes is determined according to the switching sequence; according to the complementary relationship of the switching tubes, the primary voltage is determined by a variable duty ratio, and the secondary voltage is determined by a fixed duty ratio; according to the phase shift angle between the primary voltage and the secondary voltage, the transmission power of the system is controlled to modulate the improved isolated three-level converter. The modulation method of the improved isolated three-level converter of the present application can improve level disorder and enhance system performance. Description of the Drawings

[0015] Figure 1 It is a schematic flow chart of the modulation method of the improved isolated three-level converter in an embodiment; Figure 2 It is the main circuit topology of a three-level isolated bidirectional DC-DC transformer in an embodiment; Figure 3 It is a schematic diagram of grid connection of offshore wind power generation in an embodiment; Figure 4 It is a waveform diagram of the modulation method of the improved isolated three-level converter using the traditional EPS in an embodiment; Figure 5 It is a waveform diagram of the modulation method of the improved isolated three-level converter using the present application in an embodiment; Figure 6 It is a waveform diagram of two cases when the complementary mode of the present application uses a fixed duty ratio in an embodiment; Figure 7 For an embodiment when the switching sequence (0110) of the present application is adopted, the current i L is the current flow diagram when < 0; Figure 8 For an embodiment when the switching sequence (0110) of the present application is adopted, the current i L is the current flow diagram when > 0; Figure 9 It is a schematic flow chart of determining the complementary relationship of the switching tubes in an embodiment; Figure 10 It is a schematic flow chart of determining the primary voltage and the secondary voltage in an embodiment; Figure 11 It is a structural block diagram of a modulation device of an improved isolated three-level converter in an embodiment; Figure 12 It is an internal structure diagram of a computer device in an embodiment. Detailed implementation manners

[0016] In order to make the objectives, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0017] The wind energy resources on the earth are very rich. China has rich wind energy resource reserves. China has rich offshore wind energy resources. The number of hours when the wind speed is greater than or equal to 3 m / s in the sea areas with a water depth of 2 m - 15 m along the eastern coast of China throughout the year is about 7000 h - 8000 h, and the exploitable wind energy resources at a height of 10 m at sea are about 750 million kW. Compared with onshore wind power, offshore wind power has a series of advantages. For example, the wind speed at sea is high, the eddy current intensity is small, and the noise is small. Therefore, vigorously developing offshore wind power is a new trend in the development of wind power. Therefore, vigorously developing offshore wind power is a new trend in the development of wind power. During the process of offshore wind power generation, it is required that there is a two-way flow of energy between the offshore power generation equipment and the power grid to participate in power grid regulation. The bidirectional transformer is a key component to realize energy flow, and has the advantages of simple structure, large power density, and small loss. Studying the bidirectional transformer is of great significance for the development of offshore wind power and the improvement of power grid quality. Compared with the transformers with H-bridge and half-bridge structures, the multi-level structure transformer not only has the same output characteristics and power transmission characteristics as the traditional transformer, but also the voltage borne during turn-off is only 1 / (n−1) of the input or output voltage. Therefore, the multi-level transformer is widely used in high-voltage and high-power occasions to reduce switching losses, improve efficiency, and at the same time reduce costs. However, currently, there may be potential problems such as level disorder, poor system stability, and low efficiency when the modulation of the existing extended phase-shifted control improved isolated three-level converter outputs zero level. Based on this, the embodiments of the present application provide a modulation method for an improved isolated three-level converter to improve the above technical problems.

[0018] In one embodiment, Figure 1 It is a modulation method for an improved isolated three-level converter provided according to an embodiment of the present application, and this method is described by taking its application to a server as an example. The method includes the following steps: S101, select a switching sequence for outputting zero level, and determine the complementary relationship of switching tubes according to the switching sequence.

[0019] Optionally, the main circuit topology of the three-level isolated bidirectional transformer is as Figure 2As shown. In the figure, C d1 , C d2 and C d3 respectively represent the support capacitors on the input side and output side of the transformer. V in and V o respectively represent the input voltage and output voltage, n represents the voltage transformation ratio of the intermediate transformer, V AB and V CD respectively represent the voltages on the primary side and secondary side of the transformer, L represents the sum of the equivalent inductances of the leakage inductance of the transformer and the externally connected inductance, i L represents the equivalent inductance current, i o represents the output current. In this article, the current direction is positive as shown in the figure. The grid connection of offshore wind power equipment is as Figure 3 shown.

[0020] Screen the 16 groups of switch sequences that may exist in the main circuit topology of the three-level isolated bidirectional transformer. Among them, "0" represents the power device is turned off, and "1" represents the power device is turned on. The switch sequences that may be adopted in actual control can be obtained as shown in Table 1.

[0021] Table 1 Switch sequences that may be adopted in actual control <![CDATA[Switch sequence (S 1 / S 2 / S 3 / S4)]]> Output level Sequence 1 (1100) High level Sequence 2 (0101) Sequence 3 (0110) Sequence 4 (1010) Zero level Sequence 5 (0011) Low level According to Table 1, there is only one switch sequence for the output high level and the output low level, while there are 3 switch sequences for the output zero level. Among them, the modulation methods of the improved isolated three-level converter formed by Sequence 2 (0101) and Sequence 4 (1010) are equivalent to those of the traditional EPS improved isolated three-level converter. However, when using Sequence 2 (0101) and Sequence 4 (1010) at the output zero level, it may cause the problem of output level disorder. The level disorder caused thereby is as Figure 4 shown.

[0022] Table 2 Modulation methods of two improved isolated three-level converters formed by zero-level switch sequences <![CDATA[Existing EPS modulation method (S 1 / S 2 / S 3 / S4)]]> <![CDATA[Modulation method of the improved isolated three-level converter of the present application (S 1 / S 2 / S 3 / S4)]]> Output level Sequence 1 (1100) Sequence 1 (1100) High level Sequence 2 (0101) Sequence 4 (1010) Sequence 3 (0110) Zero level Sequence 5 (0011) Sequence 5 (0011) Low level Aiming at the level disorder caused by Switch Sequences 2 (0101) and 4 (1010) in the modulation method of the EPS improved isolated three-level converter, the modulation method of the improved isolated three-level converter in this application proposes a new switch sequence 3 (0110). The new switch sequence can not only output the zero level but also avoid the phenomenon of level disorder. There is only one new switch sequence, which is easier to implement. As Figure 5 shown, it is the waveform diagram in which the modulation method of the new improved isolated three-level converter eliminates the level disorder phenomenon.

[0023] Next, the specific implementation method of the modulation method of the newly improved isolated three-level converter will be analyzed. As can be seen from Table 2, the modulation method of the EPS improved isolated three-level converter can be regarded as a combination of two conduction modes: 1. Conversion from (1100)-(1010)-(0011). When converting from (1100) to (1010), S 2 turns off, and S 3 turns on. When converting from (1010) to (0011), S 1 turns off, and S 4 turns on. 2. Conversion from (1100)-(0101)-(0011). When converting from (1100) to (0101), S 1 turns off, and S 4 turns on. When converting from (0101) to (0011), S 2 turns off, and S 3 turns on. No matter which sequence combination, only a group of complementary switches act during each output level conversion.

[0024] In the modulation method of the new improved isolated three-level converter, (0110) is used instead of (1010) and (0101). When (1100) and (0110) are converted to each other, S 1 and S 3 act. When (0110) and (0011) are converted to each other, S 2 and S 4 act. In order not to increase the number of switching times, only a group of complementary switches can act during each output level conversion. Therefore, in the modulation of the new improved isolated three-level converter, S 1 and S 3 can be complementary, and S 2 and S 4 can be complementary.

[0025] S102. According to the complementary relationship of the switching tubes, the primary side voltage is determined by the variable duty cycle, and the secondary side voltage is determined by the fixed duty cycle.

[0026] Optionally, when S 1 and S 3 are complementary, and S 2 and S 4 are complementary, sequence 3 (0110) is used instead of sequence 4 (1010) and sequence 2 (0101). Assuming the same modulation as the EPS improved isolated three-level converter, the modulation of the fixed duty cycle improved isolated three-level converter, the waveform of the three-level V AB is controlled by ϕ1, and the phase shift angles of V AB and V CD are controlled by 𝜙. There are two cases, asFigure 6 as shown

[0027] From Figure 6 It can be seen that when a fixed duty cycle is adopted, regardless of which modulation method of the improved isolated three-level converter is used, an invalid switching combination of (1001) may occur. Therefore, when S 1 and S 3 are complementary, and S 2 and S 4 are complementary, when (0110) is used to replace (1010) and (0101), the output voltage V AB of the three-level half-bridge cannot be controlled by the phase-shifting method, and the modulation method of the PWM improved isolated three-level converter with variable duty cycle needs to be adopted.

[0028] As can be seen from Table 2, in the modulation method of the improved isolated three-level converter of the present application, S 1 is only turned on when the output is high, and S 4 is only turned on when the output is low. Therefore, the time for V 1 to be high-level output can be controlled by the on-time of S AB . Assuming this time is D 1 T h . The time for V 4 to be low-level output is controlled by the on-time of S AB . Assuming this time is D 11 T h . Usually, V AB is a three-level voltage waveform with half-wave symmetry. Therefore, the on-time of S 1 and the on-time of S 4 can be unified, that is, D 11 T h = D 1 T h , and S 1 is turned on in the first half of the modulation period of the improved isolated three-level converter, and S 4 is turned on in the second half of the modulation period of the improved isolated three-level converter. Since S1 and S3 are complementary, and S 2 and S 4 are complementary, based on the above analysis, the duty cycles of each switch tube in the three-level half-bridge structure within one carrier cycle under the new modulation method of the improved isolated three-level converter can be obtained as shown in Table 3. Where D 1 T h represents the conduction time within the half cycle T h , 0 means off, and 1 means on. The conduction signal diagram of the switch tube is as Figure 5 shown.

[0029] Table 3 and according to the duty cycle of each switching device within a carrier cycle of the three-level half-bridge structure Switching tube First half cycle (Th) Second half cycle (Th) S1 <![CDATA[D 1 T h > 0 S2 1 <![CDATA[(1−D 1 )T h > S3 <![CDATA[(1−D 1 )T h > 1 S4 0 <![CDATA[D 1 T h > According to the previous analysis, the driving signal adopts S 1 and S 3 signals are complementary, S 2 and S 4 signals are complementary, by changing the duty cycle D 1 to control the voltage waveform of V AB The secondary side uses a fixed duty cycle to control the voltage waveform of V CD voltage waveform, and then turn on to achieve the modulation of the PPS improved isolated three-level converter. The modulation of the PPS improved isolated three-level converter adopts a different switching sequence from EPS when the output is at zero level, which can eliminate the phenomenon of level disorder. At Figure 4 at t 3 ~t 4 period and t 7 ~t 8 period, it is necessary to control the three-level half-bridge structure to output zero level. At this time, the equivalent circuit of the transformer is as Figure 7 and Figure 8 shown.

[0030] The modulation of the PPS improved isolated three-level converter is controlled when the switching sequence (0110) is adopted in the three-level structure, so that S 2 and S 3 conduct simultaneously to provide a current path for i L in different directions, and finally output zero level. As Figure 7 shown, when i L <0, the current flows through S 3 and SD 6 . As Figure 8 shown, when i L >0, the current flows through SD 5 and S 2 , and in both cases, V AB can be clamped at zero level, and the phenomenon of output voltage disorder will no longer occur.

[0031] S103, according to the phase shift angle between the primary side voltage and the secondary side voltage, control the transmission power of the system to perform the modulation of the improved isolated three-level converter.

[0032] Optionally, in the control of the system transmission power, by controlling the phase shift angle 𝜙 1 between the driving signals of S 2 and S 1The T is used to adjust the three-level voltage output by the primary side of the transformer, and the phase shift angle 𝜙T between the primary and secondary side voltages is controlled to adjust the magnitude and direction of the power transmitted by the system. The power transmission calculation formula is Equation (1): ; (1) Among them, V in is the system input voltage; L is the sum of the equivalent inductances of the transformer leakage inductance and the externally connected inductance; T h is the half cycle; 𝜙 is the phase shift angle between the primary side voltage and the secondary side voltage; 𝜙 1 is the waveform of the three-level V AB ; m is a constant.

[0033] Combined with the previous analysis, it can be seen that the PPS control strategy proposed in this application can improve the power of the system and improve the efficiency of the system under the same input conditions.

[0034] For the modulation method of the above improved isolated three-level converter, the switching sequence with zero output level is selected, and the complementary relationship of the switching tubes is determined according to the switching sequence; according to the complementary relationship of the switching tubes, the primary side voltage is determined through a variable duty cycle, and the secondary side voltage is determined through a fixed duty cycle; according to the phase shift angle between the primary side voltage and the secondary side voltage, the transmission power of the system is controlled to modulate the improved isolated three-level converter. The modulation method of the improved isolated three-level converter of this application can improve the level disorder and improve the system performance.

[0035] Based on the above embodiments, the steps of determining the complementary relationship of the switching tubes are decomposed and refined by Figure 9 . As shown in Figure 9 , the implementation process is as follows: S901, select the unified switching sequence from the switching sequence with zero output level.

[0036] S902, determine the complementary relationship of the switching tubes according to the unified switching sequence.

[0037] It can be understood that a possible implementation method of determining the complementary relationship of the switching tubes is given in this embodiment, which is simple and easy to operate, and can improve the level disorder and improve the system performance.

[0038] Based on the above embodiments, the steps of determining the primary side voltage and the secondary side voltage are decomposed and refined by Figure 10 . As shown in Figure 10 , the implementation process is as follows: S1001, determine the variable duty cycle and the fixed duty cycle according to the complementary relationship of the switching tubes.

[0039] S1002, determine the primary side voltage through the variable duty cycle and determine the secondary side voltage through the fixed duty cycle.

[0040] It can be understood that in this embodiment, a possible implementation manner for determining the primary side voltage and the secondary side voltage is given. The method is simple and easy to operate, and can improve the level disorder and enhance the system performance.

[0041] It should be understood that although the steps in the flowcharts involved in the above embodiments are sequentially shown according to the indications of the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily executed at the same moment, but can be executed at different moments. The execution order of these steps or stages is not necessarily sequential, but can be executed alternately or in turn with at least a part of other steps or steps or stages in other steps.

[0042] Based on the same inventive concept, an embodiment of the present application also provides a modulation device for implementing the improved isolated three-level converter involved above. The implementation solution for solving the problem provided by this device is similar to the implementation solution described in the above method. Therefore, the specific limitations in one or more embodiments of the modulation device of the improved isolated three-level converter provided below can refer to the limitations on the modulation method of the improved isolated three-level converter in the above text, and will not be repeated here.

[0043] In one of the embodiments, through Figure 11 The structural block diagram of the modulation device of the improved isolated three-level converter in one embodiment is shown. As Figure 11 shown, a modulation device 11 of the improved isolated three-level converter is provided, where the device 11 includes a selection module 110, a determination module 111, and a control module 112, where: The selection module 110 is configured to select a switch sequence for outputting a zero level and determine the complementary relationship of the switching tubes according to the switch sequence; The determination module 111 is configured to determine the primary side voltage through a variable duty cycle and determine the secondary side voltage through a fixed duty cycle according to the complementary relationship of the switching tubes; The control module 112 is configured to control the transmission power of the system to perform modulation of the improved isolated three-level converter according to the phase shift angle between the primary side voltage and the secondary side voltage.

[0044] The modulation device of the improved isolated three-level converter selects the switch sequence with zero output level, and determines the complementary relationship of the switching tubes according to the switch sequence; according to the complementary relationship of the switching tubes, determines the primary side voltage through a variable duty cycle and determines the secondary side voltage through a fixed duty cycle; according to the phase shift angle between the primary side voltage and the secondary side voltage, controls the transmission power of the system to modulate the improved isolated three-level converter. The modulation device of the improved isolated three-level converter of the present application can improve the level disorder and enhance the system performance.

[0045] In one embodiment, the above selection module 110 is specifically configured to: Select a unified switch sequence from the switch sequences with zero output level; determine the complementary relationship of the switching tubes according to the unified switch sequence.

[0046] In one embodiment, the above determination module 111 determines the secondary side voltage by the duty cycle.

[0047] In one embodiment, the calculation formula of the transmission power is: MACROBUTTON MTPlaceRef \*MERGEFORMAT SEQ MTEqn \h \* MERGEFORMAT ( SEQ MTEqn \c \* Arabic \*MERGEFORMAT 1) Where, V in is the system input voltage; L is the sum of the equivalent inductance of the transformer leakage inductance and the externally connected inductance; T h is the half cycle; 𝜙 is the phase shift angle between the primary side voltage and the secondary side voltage; 𝜙 1 is the waveform of the three-level V AB ; m is a constant.

[0048] Each module in the modulation device of the improved isolated three-level converter can be implemented in whole or in part by software, hardware, and their combination. The above modules can be embedded in the processor of the computer device in hardware form or independent of it, or stored in the memory of the computer device in software form, so that the processor can call and execute the operations corresponding to the above modules.

[0049] In one embodiment, a computer device is provided. The computer device can be a server, and its internal structure diagram can be as Figure 12As shown. The computer device includes a processor, a memory, a network interface, and a transceiver connected by a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The transceiver of the computer device is used to perform operations of receiving data or sending data under the control of the processor. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store data such as sample data. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, it implements a modulation method for an improved isolated three-level converter.

[0050] Those skilled in the art can understand that Figure 12 the structure shown in

[0051] is only a block diagram of some structures related to the solution of this application, and does not constitute a limitation on the computer device to which the solution of this application is applied. Specifically, the computer device may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0052] In one embodiment, a computer device is provided, including a memory and a processor. A computer program is stored in the memory. The implementation of the principles and specific processes by the processor in each embodiment can be referred to the description in the embodiment of the modulation method of the improved isolated three-level converter in the foregoing embodiments, and will not be repeated here.

[0053] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by the processor, the implementation of the principles and specific processes in each embodiment can be referred to the description in the embodiment of the modulation method of the improved isolated three-level converter in the foregoing embodiments, and will not be repeated here.

[0054] It should be noted that the information involved in this application (including but not limited to the information involved in the modulation process of the improved isolated three-level converter in this application, etc.) is information or data that has been fully authorized by all parties.

[0055] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, database, or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memories. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The databases involved in the embodiments provided in the present application can include at least one of relational databases and non-relational databases. Non-relational databases can include distributed databases based on blockchain, etc., without limitation. The processors involved in the embodiments provided in the present application can be general-purpose processors, central processors, graphics processors, digital signal processors, programmable logic devices, data processing logics based on quantum computing, etc., without limitation.

[0056] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0057] The above-described embodiments merely represent several implementation manners of the present application. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A modulation method for an improved isolated three-level converter, characterized in that: The method comprises: Tie; According to the complementary relationship of the switch tubes, the primary voltage is determined by a variable duty cycle, and the secondary voltage is determined by a fixed duty cycle; According to the phase shift angle between the primary voltage and the secondary voltage, the transmission power of the system is controlled to perform modulation of the improved isolated three-level converter.

2. The method according to claim 1, characterized in that The step of selecting a switch sequence that outputs a zero level and determining a complementary relationship between switch tubes according to the switch sequence includes: Selecting a uniform switching sequence from the switching sequences outputting zero level; According to the unified switch sequence, the complementary relationship of the switch tubes is determined.

3. The method according to claim 1, characterized in that The method of determining the primary voltage by a variable duty cycle and determining the secondary voltage by a fixed duty cycle according to the complementary relationship of the switch tubes includes: Determining a variable duty cycle and a fixed duty cycle according to the complementary relationship of the switch tubes; The primary voltage is determined by the variable duty cycle, and the secondary voltage is determined by the fixed duty cycle.

4. The method according to claim 1, characterized in that The calculation formula of the transmission power is as follows: ； (1) Among them, V in is the system input voltage; L is the sum of the equivalent inductance of the transformer leakage inductance and the external series inductance; T h is a half cycle; 𝜙 is the shift angle between the primary voltage and the secondary voltage; 𝜙1 is the three-level V AB waveform; m is a constant.

5. Modulation device of improved isolated three-level converter, characterized in that: The modulation of the improved isolated three-level converter includes: A selection module, used for selecting a switch sequence that outputs a zero level, and determining a complementary relationship between switch tubes according to the switch sequence; A determination module, used to determine the primary voltage through a variable duty cycle according to the complementary relationship of the switch tubes, and to determine the secondary voltage through a fixed duty cycle; The control module is used to control the transmission power of the system according to the phase shift angle between the primary voltage and the secondary voltage to perform modulation of the improved isolated three-level converter.

6. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 4 are implemented.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 4 are implemented.

8. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 4 are implemented.

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