Solid state transformer capacitor voltage ripple self-suppression modulation method, system and device

Abstract

This invention relates to the field of power transmission engineering technology, and particularly to a method, system, and device for self-suppression modulation of capacitor voltage ripple in solid-state transformers. The method assigns triangular carrier waves of different frequencies to adjacent submodules, resulting in different initial phases of the ripple currents generated in the switching functions of adjacent submodules. The phase of the modulation wave is adjusted by precisely designed and optimized phase shift adjustments, which is equivalent to adjusting the starting time of the ripple current injection into the capacitor and the energy exchange phase. For the same bridge arm current, the amplitudes of the secondary ripple currents flowing into the capacitors of adjacent submodules are approximately equal, and the phase difference approaches 180°. Thus, in adjacent submodules, the voltage ripples generated by the integration of the secondary ripple current across their respective capacitors are correspondingly opposite in phase, thereby achieving internal ripple cancellation at the bridge arm or system level, improving the output voltage quality of the submodules, reducing capacitor stress and losses, and enhancing the efficiency, reliability, and lifespan of the entire solid-state transformer.

Description

Technical Field

[0001] This invention relates to the field of power transmission engineering technology, and in particular to a method, system and equipment for self-suppression modulation of capacitor voltage ripple in solid-state transformers. Background Technology

[0002] Modular multilevel converters (MMCs) and their derived solid-state transformer (SST) topologies have been widely used in medium- and high-voltage power conversion due to their high modularity, ease of expansion, and good output waveform quality. However, the submodule capacitor voltage in SSTs exhibits second-harmonic ripple, which is an inherent and pressing technical challenge that needs to be addressed.

[0003] Currently, the mainstream methods for suppressing capacitor voltage ripple in submodules can be divided into two categories. One is external suppression, which absorbs ripple energy by introducing ripple compensation terms into the control loop or by adding additional power buffer circuits or active filters. While effective, this method increases control complexity, reduces system reliability, and the additional hardware leads to increased costs and decreased power density. The other is internal suppression, which reduces ripple at its source by improving modulation strategies. Examples include Specific Harmonic Elimination Pulse Width Modulation (SHEPWM) or Optimized Pulse Width Modulation (OPWM), which eliminates low-order harmonics by calculating specific switching angles, indirectly affecting ripple. However, these methods are computationally complex, difficult to solve online, and have poor dynamic performance. Another example is Carrier Phase Shift Modulation (CPS), which disperses ripple energy by adjusting the carrier frequency or phase distribution, but its suppression effect is limited and usually comes at the cost of sacrificing other performance characteristics (such as switching frequency and harmonic characteristics). Yet another example is injecting common-mode voltage or circulating current, which injects specific high-frequency common-mode signals into the system or optimizes the circulating current reference value to offset ripple. This method is highly dependent on controller design, involves complex parameter design, and may introduce additional losses or electromagnetic interference. Therefore, there is an urgent need for an efficient modulation method that can achieve autonomous cancellation of submodule capacitor voltage ripple without increasing hardware or significantly increasing control complexity. Summary of the Invention

[0004] The main objective of this invention is to provide a method, system, and device for self-suppression modulation of voltage ripple in solid-state transformer capacitors. The aim is to achieve active cancellation of voltage ripple at the sub-module level through pure modulation, thereby avoiding the use of complex compensation control or additional hardware, and ultimately simplifying system design and improving power density and reliability.

[0005] To achieve the above objectives, the first aspect of this invention proposes a solid-state transformer capacitor voltage ripple self-suppression modulation method, applied to a bridge arm composed of multiple cascaded sub-modules, comprising the following steps: Acquire system operating parameters, including bridge arm modulation wave command, bridge arm current, and submodule rated capacitor voltage; A triangular carrier is generated for each submodule, and the frequency ratio of the triangular carriers between adjacent submodules is a rational number that is determined based on the number of submodules and is not equal to 1. The initial phase shift angle of each submodule is determined based on the carrier phase shift strategy; Based on the frequency ratio, the power factor angle of the bridge arm current, and the ripple frequency that needs to be canceled, the optimal phase shift adjustment amount for canceling ripple between adjacent sub-modules is determined. The optimized phase shift adjustment is applied to the initial phase shift angle of adjacent sub-module pairs, and the globally optimized set of phase shift angles is obtained through iteration or joint solution. Based on the globally optimized set of phase shift angles, the phase-shifted modulation waves of each submodule are generated. Compare the modulated wave of each submodule with the triangular carrier wave to generate the drive signal for the switching device of each submodule.

[0006] In the above-mentioned solid-state transformer capacitor voltage ripple self-suppression modulation method, the absolute value of the frequency ratio minus 1 is less than 0.5; the frequency ratio is... , , , , or any one of them; among which k For frequency ratio, N This represents the number of sub-modules in the bridge arm.

[0007] In the above-mentioned solid-state transformer capacitor voltage ripple self-suppression modulation method, the initial phase shift angle of each sub-module is calculated using the following formula: ; Let be the initial phase shift angle of the i-th submodule. i For the index of the submodule, N This represents the number of sub-modules in the bridge arm.

[0008] In the above-mentioned solid-state transformer capacitor voltage ripple self-suppression modulation method, the calculation formula for the optimized phase shift adjustment is as follows: ; in, To optimize the phase shift adjustment amount, This is a correction term related to the frequency ratio and the number of submodules. The power factor angle of the bridge arm current.

[0009] In the above-mentioned solid-state transformer capacitor voltage ripple self-suppression modulation method, the optimized phase shift adjustment is applied to the initial phase shift angle of adjacent sub-module pairs in the following way: A submodule pair is formed by two adjacent submodule pairs; For each submodule pair, keep the initial phase shift angle of the previous submodule unchanged, and increase the initial phase shift angle of the subsequent submodule by the optimized phase shift adjustment amount; Alternatively, keep the initial phase shift angle of the next submodule unchanged, and reduce the initial phase shift angle of the previous submodule by the optimized phase shift adjustment amount; Alternatively, the initial phase shift angle of the previous submodule is reduced by half of the optimized phase shift adjustment amount, and the initial phase shift angle of the next submodule is increased by half of the optimized phase shift adjustment amount.

[0010] In the above-mentioned solid-state transformer capacitor voltage ripple self-suppression modulation method, adjacent sub-modules are paired in a non-overlapping or overlapping manner to form the sub-module pair.

[0011] In the above-mentioned solid-state transformer capacitor voltage ripple self-suppression modulation method, the steps to obtain the globally optimized phase shift angle set include: Construct an optimization objective function, which is: ; in, To optimize the objective function value, i For the index of the submodule, N The number of sub-modules in the bridge arm. For the first i+ 1 The new phase shift angle after optimization of each sub-module For the first i The new phase shift angle after optimization of each submodule; For the first i+1 The initial phase shift angle of each submodule, For the first i The initial phase shift angle of each submodule, To optimize the phase shift adjustment amount, As weight; Assuming that the phase shift angle range constraint and phase order constraint are met, an optimization algorithm is used to minimize the optimization objective function to obtain the globally optimal set of phase shift angles.

[0012] In the above-mentioned solid-state transformer capacitor voltage ripple self-suppression modulation method, the calculation formula for the modulation wave after phase shifting of the submodule is as follows: ; For the first i The modulation wave signal of each submodule, where M is the modulation index. The fundamental angular frequency, For the first i The new phase shift angle after optimization of each submodule.

[0013] A second aspect of this invention provides a solid-state transformer capacitor voltage ripple self-suppression modulation system, applied to the aforementioned solid-state transformer capacitor voltage ripple self-suppression modulation method, comprising: The acquisition module is used to acquire system operating parameters, including bridge arm modulation wave commands, bridge arm currents, and submodule rated capacitor voltages. The carrier signal generation module is used to generate triangular carriers for each submodule. The frequency ratio of the triangular carriers between adjacent submodules is a rational number that is determined based on the number of submodules and is not equal to 1. The phase shift angle calculation module is used to determine the initial phase shift angle of each submodule based on the carrier phase shift strategy; determine the optimized phase shift adjustment amount to cancel the ripple between adjacent submodules based on the frequency ratio, the power factor angle of the bridge arm current and the ripple frequency to be canceled; apply the optimized phase shift adjustment amount to the initial phase shift angle of the adjacent submodule pair, and obtain the globally optimized phase shift angle set through iteration or joint solution; The modulation wave generation module is used to generate the phase-shifted modulation wave of each submodule based on the globally optimized set of phase-shift angles. The comparison module is used to compare the modulated wave of each submodule with the triangular carrier wave and generate the drive signal for the switching device of each submodule.

[0014] A third aspect of the present invention provides an electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the above-described solid-state transformer capacitor voltage ripple self-suppression modulation method.

[0015] The technical solution provided by this invention may include the following beneficial effects: In this invention, triangular carrier waves of different frequencies are assigned to adjacent submodules, resulting in different initial phases of the ripple currents generated in the switching functions of adjacent submodules. The modulation wave phase is adjusted by precisely designed optimized phase shift adjustments, which is equivalent to adjusting the starting time of the ripple current injection into the capacitor and the energy exchange phase. For the same bridge arm current, the amplitudes of the secondary ripple currents flowing into the capacitors of adjacent submodules are approximately equal, with a phase difference approaching 180°. Thus, in adjacent submodules, the voltage ripples generated by the integration of the secondary ripple current across their respective capacitors are correspondingly out of phase. When viewed from the bridge arm or system level (e.g., through voltage sequencing and equalization control), these two ripple components cancel each other out, thereby significantly reducing the overall capacitor voltage fluctuation. This achieves a solution from the source of energy interaction and signal synthesis, rather than through post-compensation.

[0016] This application improves the output voltage quality of submodules by reducing capacitor voltage ripple, thereby reducing capacitor stress and losses, and enhancing the efficiency, reliability, and lifespan of the entire solid-state transformer. Furthermore, this application achieves this through an improved modulation algorithm, eliminating the need for any additional power devices, sensors, or filtering circuits, thus reducing hardware costs and complexity. It also seamlessly integrates with existing voltage equalization control and circulating current suppression strategies. The algorithm can be embedded into existing MMC / SST modulators, requiring only updates to the carrier generation and phase shift calculation modules, making it easy to implement in engineering and flexibly expandable to pairing or grouping more submodules. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 This is a schematic flowchart of the solid-state transformer capacitor voltage ripple self-suppression modulation method of the present invention; Figure 2 This is a schematic diagram of voltage ripple according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the solid-state transformer capacitor voltage ripple self-suppression modulation system of the present invention; Figure 4 This is a schematic diagram of the electronic device of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0021] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the word "and / or" throughout the text means including three parallel solutions; taking "A and / or B" as an example, it includes solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0023] The solid-state transformer capacitor voltage ripple self-suppression modulation method of the present invention is applied to each arm of a three-phase modular multilevel solid-state transformer. Each arm is composed of multiple cascaded sub-modules, which are either half-bridges or full-bridges. The solid-state transformer capacitor voltage ripple self-suppression modulation method applies carrier waves with specific frequency relationships to adjacent sub-modules within the same arm and precisely and collaboratively adjusts the relative phase shift angle between the modulation waves of two adjacent sub-modules. This ensures that the voltage ripple formed by integrating the low-frequency (mainly second harmonic) ripple current components generated by adjacent sub-modules on the capacitor has opposite phases and equal amplitudes, thereby achieving internal ripple cancellation at the arm or system level.

[0024] The following is combined Figure 1 This invention describes a solid-state transformer capacitor voltage ripple self-suppression modulation method according to an embodiment of the present invention, taking the upper bridge arm of phase A as an example, including the following steps: Step S1: Obtain system operating parameters, including bridge arm modulation wave commands. m a (t) Bridge arm current i arm (t) and the rated capacitor voltage of the submodule Vc ref Among them, the bridge arm modulation wave command m a(t) It is generated by the output voltage control loop.

[0025] Step S2: Generate a triangular carrier wave for each submodule. The frequency ratio of the triangular carrier waves between adjacent submodules is a rational number that is not equal to 1, determined based on the number of submodules. Specifically, set the switching frequency... f sw The corresponding reference carrier frequency is f c For example, for two adjacent submodules, the first... i Each submodule generates the first triangular carrier signal. carr i (t) Its carrier frequency is f i , for the first i+1 Each submodule generates a second triangular carrier signal. carr i+1 (t) Its carrier frequency is f i+1 The frequency ratio of the triangular carrier between the two submodules k It is a simple rational number not equal to 1, and is related to the number of submodules on the bridge arm. N This correlation ensures that the fundamental and principal harmonic components of the two carriers satisfy a specific phase coupling relationship. Preferably, the absolute value of the frequency ratio minus 1 is less than 0.5; more preferably, the frequency ratio is... , , , , or any one of them; among which k For frequency ratio, N This represents the number of sub-modules in the bridge arm.

[0026] In a specific embodiment, N=4, resulting in submodules SM1, SM2, SM3, and SM4. Submodules SM1 and SM2 are paired in a non-overlapping manner to form a first submodule pair, and submodules SM3 and SM4 are paired in a second submodule pair. Within the first submodule pair, the frequency of the triangular carrier signal of submodule SM1 is set... f 1 = f c frequency ratio k = N / (N 1) The frequency of the triangular carrier signal in submodule SM2 f 2 =N·f c / (N 1) Similarly, in the second submodule pair, let the triangular carrier signal of submodule SM3... f 3 =f c The frequency of the triangular carrier signal in submodule SM4 f 4 = N·f c / (N 1) .

[0027] In another specific embodiment, N=4, resulting in submodules SM1, SM2, SM3, and SM4. Submodules SM1 and SM2 are paired in an overlapping manner to form the first submodule pair, SM2 and SM3 to form the second submodule pair, and SM3 and SM4 to form the third submodule pair. Within each submodule pair, the same frequency ratio can be set. k = N / (N 1) Alternatively, different frequency ratios with opposite numbers can be used in a cyclic process based on the pairing of odd and even numbers. Specifically, as an example of using different frequency ratios with opposite numbers in a cyclic process, in the first submodule pair, let the frequency of the triangular carrier signal of submodule SM1 be... f 1 =f c frequency ratio k = N / (N 1) The frequency of the triangular carrier signal in submodule SM2 f 2 =N·f c / (N 1) In the second submodule pair, the frequency ratio is... k = (N 1) / N The frequency of the triangular carrier signal of submodule SM2 has been determined in the first submodule pair. f 2 =N·f c / (N 1) Then the triangular carrier signal of submodule SM3 f 3 =f 2· (N 1) / N=f c In the third submodule pair, the frequency ratio is... k = N / (N 1)， The frequency of the triangular carrier signal of submodule SM3 has been determined. f 3 =f c According to frequency ratio k = N / (N 1) The triangular carrier signal of submodule SM4 f 4 =N· f c / (N 1) .

[0028] The voltage ripple of the submodule capacitor is the result of integrating the interaction between its switching function and the bridge arm current across the capacitor. The phase of the ripple is not only affected by the fundamental phase of the modulation wave, but also deeply dependent on the harmonic phase structure of the switching function, which is determined by the characteristics of the triangular carrier wave. If all submodules use the same frequency triangular carrier wave, the phase relationship of the harmonic spectrum of the submodule's switching function is fixed. Adjusting only the modulation wave phase has limited ability to regulate the ripple phase and cannot achieve precise phase cancellation.

[0029] To this end, this application assigns triangular carriers of different frequencies to adjacent sub-modules through step S2, which essentially introduces a periodically changing relative time shift into the switching function of the sub-modules, so as to work in coordination with the phase shift angle of the subsequently optimized modulation wave, thereby enabling the harmonic responses of the two sub-modules at the target ripple frequency to be precisely adjusted to a state of opposite phase.

[0030] Step S3: Determine the initial phase shift angle of each submodule based on the carrier phase shifting (CPS) strategy. Specifically, the formula for calculating the initial phase shift angle of each submodule is as follows: ; Let be the initial phase shift angle of the i-th submodule. i For the index of the submodule, N Let be the number of submodules in the bridge arm. Thus, for any pair of submodules, the initial phase angle of the i-th submodule is... The initial phase angle of the (i+1)th submodule .

[0031] Step S4: Based on the frequency ratio, the power factor angle of the bridge arm current, and the ripple frequency to be canceled, determine the optimized phase shift adjustment amount for canceling ripple between adjacent submodules; the calculation formula for the optimized phase shift adjustment amount is: ; in, To optimize the phase shift adjustment amount, This is a correction term related to the frequency ratio and the number of submodules. The power factor angle is the angle of the bridge arm current. Thus, the optimized phase shift adjustment amount for each submodule pair can be obtained through step S4.

[0032] Step S5: Apply the optimized phase shift adjustment amount to the initial phase shift angle of the adjacent sub-module pair, and obtain the globally optimized phase shift angle set through iteration or joint solution.

[0033] For example, in a pair of submodules, let the initial phase angle of the i-th submodule be... Keeping it unchanged, the optimized phase shift adjustment is fully applied to the initial phase angle of the (i+1)th submodule. Then there is Thus, based on the traditional CPS phase angle difference, an additional optimized phase shift angle is applied to cancel ripple, achieving coordinated adjustment. This paired coordinated strategy of the submodule pair is then extended to all submodule pairs. For the entire bridge arm, the set of modulation wave phase shift angles of all submodules constitutes a coordinated optimized set of traditional CPS angles. This set consists of the pairings required. The solution is obtained through iteration or joint solution.

[0034] Step S6: Based on the globally optimized phase shift angle set, generate the phase-shifted modulation wave of each submodule; specifically, the calculation formula for the phase-shifted modulation wave of the submodule is as follows: ; For the first i The modulation wave signal of each submodule, where M is the modulation index. The fundamental angular frequency, For the first i The new phase shift angle after optimization of each submodule.

[0035] Step S7: Compare the modulation wave of each submodule with the triangular carrier wave to generate the drive signal for the switching device of each submodule, that is, generate the PWM signal used to drive the power switching transistor in the submodule.

[0036] In this invention, triangular carrier waves of different frequencies are assigned to adjacent submodules, resulting in different initial phases of the ripple currents generated in the switching functions of adjacent submodules. The modulation wave phase is adjusted by precisely designed optimized phase shift adjustments, which is equivalent to adjusting the starting time of the ripple current injection into the capacitor and the energy exchange phase. For the same bridge arm current, the amplitudes of the secondary ripple currents flowing into the capacitors of adjacent submodules are approximately equal, with a phase difference approaching 180°. Thus, in adjacent submodules, the voltage ripples generated by the integration of the secondary ripple current across their respective capacitors are correspondingly out of phase. When viewed from the bridge arm or system level (e.g., through voltage sequencing and equalization control), these two ripple components cancel each other out, thereby significantly reducing the overall capacitor voltage fluctuation. This achieves a solution from the source of energy interaction and signal synthesis, rather than through post-compensation.

[0037] In one specific embodiment, the simulation is performed using the upper bridge arm of phase A of a three-phase modular multilevel solid-state transformer, with N being 4 sub-modules and a reference carrier frequency. f c The frequency is 1050Hz, the output frequency is 50Hz, the modulation ratio M is 0.9, and the power factor angle is... The angle is 30°, and the carrier frequency is higher than that. k The optimal phase shift adjustment amount is 4 / 3, calculated according to the formula. It is 52°. The result is as follows: Figure 2 The diagram shows the ripple voltage curves of the first and second submodules. Compared to traditional CPS modulation (where each submodule has the same carrier frequency and no optimized phase shift adjustment), in this specific embodiment, the voltage ripple generated by the first submodule SM1 and the voltage ripple generated by the second submodule SM2 are opposite in phase and equal in amplitude. For the total ripple of the bridge arm, it is almost zero, which can efficiently cancel the ripple.

[0038] This application improves the output voltage quality of submodules by reducing capacitor voltage ripple, thereby reducing capacitor stress and losses, and enhancing the efficiency, reliability, and lifespan of the entire solid-state transformer. Furthermore, this application achieves this through an improved modulation algorithm, eliminating the need for any additional power devices, sensors, or filtering circuits, thus reducing hardware costs and complexity. It also seamlessly integrates with existing voltage equalization control and circulating current suppression strategies. The algorithm can be embedded into existing MMC / SST modulators, requiring only updates to the carrier generation and phase shift calculation modules, making it easy to implement in engineering and flexibly expandable to pairing or grouping more submodules.

[0039] It is further worth noting that the optimized phase shift adjustment is applied to the initial phase shift angle of adjacent submodule pairs in the following manner: A submodule pair is formed by two adjacent submodule pairs; For each submodule pair, keep the initial phase shift angle of the previous submodule unchanged, and increase the initial phase shift angle of the subsequent submodule by the optimized phase shift adjustment amount, i.e. ; Alternatively, keep the initial phase shift angle of the latter submodule unchanged, and reduce the initial phase shift angle of the former submodule by the optimized phase shift adjustment amount, i.e. In this way, the optimized phase shift adjustment can be applied to adjacent submodules simply and directly.

[0040] In another embodiment, two adjacent submodules are used to form a submodule pair. The initial phase shift angle of the first submodule is reduced by half of the optimized phase shift adjustment amount, and the initial phase shift angle of the second submodule is increased by half of the optimized phase shift adjustment amount. , The optimized phase shift adjustment is evenly distributed to the initial phase shift angles of adjacent submodules. This maintains the average phase of the modulated wave from the paired submodules, minimizing the impact on the overall system fundamental voltage synthesis.

[0041] Furthermore, in step S5, the step of obtaining the globally optimized phase shift angle set includes: Construct an optimization objective function, which is: ; in, To optimize the objective function value, i For the index of the submodule, N The number of sub-modules in the bridge arm. For the first i+ 1 The new phase shift angle after optimization of each sub-module For the first i The new phase shift angle after optimization of each submodule; For the first i+1 The initial phase shift angle of each submodule, For the first i The initial phase shift angle of each submodule, To optimize the phase shift adjustment amount, For weights.

[0042] To satisfy the phase shift angle range constraint: 0 ≤ <2π Phase order constraints: ≤ As a necessary condition, an optimization algorithm is used to minimize the optimization objective function, so that the adjustment amount of the phase shift angle before and after optimization of two adjacent sub-modules is as close as possible to the optimized phase shift adjustment amount, and the adjustment amount of each phase shift angle is as small as possible, thus obtaining the globally optimal set of phase shift angles.

[0043] Another aspect of the present invention discloses a solid-state transformer capacitor voltage ripple self-suppression modulation system 300, applied to the above-mentioned solid-state transformer capacitor voltage ripple self-suppression modulation method, comprising: The acquisition module 301 is used to acquire system operating parameters, including bridge arm modulation wave command, bridge arm current and submodule rated capacitor voltage. The carrier signal generation module 302 is used to generate a triangular carrier for each submodule. The frequency ratio of the triangular carriers between adjacent submodules is a rational number that is determined based on the number of submodules and is not equal to 1. The phase shift angle calculation module 303 is used to determine the initial phase shift angle of each sub-module based on the carrier phase shift strategy; determine the optimized phase shift adjustment amount to cancel the ripple between adjacent sub-modules based on the frequency ratio, the power factor angle of the bridge arm current and the ripple frequency to be canceled; apply the optimized phase shift adjustment amount to the initial phase shift angle of the adjacent sub-module pair, and obtain the globally optimized phase shift angle set through iteration or joint solution; The modulation wave generation module 304 is used to generate the phase-shifted modulation wave of each submodule based on the globally optimized set of phase-shift angles. Comparison module 305 is used to compare the modulated wave of each submodule with the triangular carrier wave to generate the drive signal for the switching device of each submodule.

[0044] In another aspect, the present invention provides an electronic device 400, including a processor 401 and a memory 402 connected together, such as via a bus 403. Further, the electronic device 400 may also include a transceiver 404. It should be noted that in practical applications, the transceiver 404 is not limited to one, and the structure of the electronic device 400 does not constitute a limitation on the embodiments of this application. The processor 401 is used in the embodiments of this application to implement the steps of the solid-state transformer capacitor voltage ripple self-suppression modulation method. The processor 401 may be a CPU, a general-purpose processor, a DSP, an ASIC, an FPGA, or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. The processor 401 may also be a combination that implements computing functions, such as including one or more microprocessor combinations, a combination of a DSP and a microprocessor, etc. The bus 403 may include a path for transmitting information between the above components. The bus 403 may be a PCI bus or an EISA bus, etc. The bus 403 may be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 4The bus is represented by a single thick line, but this does not imply that there is only one bus or one type of bus. The memory 402 can be a ROM or other type of static storage device capable of storing static information and instructions, RAM or other type of dynamic storage device capable of storing information and instructions, or it can be an EEPROM, CD-ROM or other optical disc storage, optical disk storage (including compressed optical disks, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), magnetic disk storage medium or other magnetic storage device, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but is not limited thereto. The memory 402 is used to store application code that executes the scheme of this application, and its execution is controlled by the processor 401. The processor 401 is used to execute the application code stored in the memory 402 to implement the steps of the solid-state transformer capacitor voltage ripple self-suppression modulation method provided by this invention.

[0045] In another aspect, the present invention provides a storage medium having a computer program stored thereon, the program being executed by a processor of the steps of the solid-state transformer capacitor voltage ripple self-suppression modulation method as executed by the server described above.

[0046] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made under the concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A solid-state transformer capacitor voltage ripple self-suppression modulation method, applied to a bridge arm composed of multiple cascaded sub-modules, characterized in that: Includes the following steps: Acquire system operating parameters, including bridge arm modulation wave command, bridge arm current, and submodule rated capacitor voltage; A triangular carrier is generated for each submodule, and the frequency ratio of the triangular carriers between adjacent submodules is a rational number that is determined based on the number of submodules and is not equal to 1. The initial phase shift angle of each submodule is determined based on the carrier phase shift strategy; Based on the frequency ratio, the power factor angle of the bridge arm current, and the ripple frequency that needs to be canceled, the optimal phase shift adjustment amount for canceling ripple between adjacent sub-modules is determined. The optimized phase shift adjustment is applied to the initial phase shift angle of adjacent sub-module pairs, and the globally optimized set of phase shift angles is obtained through iteration or joint solution. Based on the globally optimized set of phase shift angles, the phase-shifted modulation waves of each submodule are generated. Compare the modulated wave of each submodule with the triangular carrier wave to generate the drive signal for the switching device of each submodule.

2. The solid-state transformer capacitor voltage ripple self-suppression modulation method according to claim 1, characterized in that: The absolute value of the frequency ratio minus 1 is less than 0.5; the frequency ratio is , , , , or any one of them; among which k For frequency ratio, N This represents the number of sub-modules in the bridge arm.

3. The solid-state transformer capacitor voltage ripple self-suppression modulation method according to claim 1, characterized in that: The formula for calculating the initial phase shift angle of each submodule is: ； Let be the initial phase shift angle of the i-th submodule. i For the index of the submodule, N This represents the number of sub-modules in the bridge arm.

4. The solid-state transformer capacitor voltage ripple self-suppression modulation method according to claim 1, characterized in that: The ripple frequency to be offset is a second harmonic ripple, and the calculation formula for the optimized phase shift adjustment is as follows: ； in, To optimize the phase shift adjustment amount, This is a correction term related to the frequency ratio and the number of submodules. The power factor angle of the bridge arm current.

5. The solid-state transformer capacitor voltage ripple self-suppression modulation method according to claim 1, characterized in that: The optimized phase shift adjustment is applied to the initial phase shift angle of adjacent submodule pairs in the following manner: A submodule pair is formed by two adjacent submodule pairs; For each submodule pair, keep the initial phase shift angle of the previous submodule unchanged, and increase the initial phase shift angle of the subsequent submodule by the optimized phase shift adjustment amount; Alternatively, keep the initial phase shift angle of the next submodule unchanged, and reduce the initial phase shift angle of the previous submodule by the optimized phase shift adjustment amount; Alternatively, the initial phase shift angle of the previous submodule is reduced by half of the optimized phase shift adjustment amount, and the initial phase shift angle of the next submodule is increased by half of the optimized phase shift adjustment amount.

6. The solid-state transformer capacitor voltage ripple self-suppression modulation method according to claim 5, characterized in that: Adjacent submodules are paired in a non-overlapping or overlapping manner to form submodule pairs.

7. The solid-state transformer capacitor voltage ripple self-suppression modulation method according to claim 1, characterized in that: The steps to obtain the globally optimized set of phase shift angles include: Construct an optimization objective function, which is: ； in, To optimize the objective function value, i For the index of the submodule, N The number of sub-modules in the bridge arm. For the first i+1 The new phase shift angle after optimization of each sub-module For the first i The new phase shift angle after optimization of each submodule; For the first i+1 The initial phase shift angle of each submodule, For the first i The initial phase shift angle of each submodule, To optimize the phase shift adjustment amount, As weight; Assuming that the phase shift angle range constraint and phase order constraint are met, an optimization algorithm is used to minimize the optimization objective function to obtain the globally optimal set of phase shift angles.

8. The solid-state transformer capacitor voltage ripple self-suppression modulation method according to claim 1, characterized in that: The formula for calculating the modulated wave after phase shifting of the submodule is: ； For the first i The modulation wave signal of each submodule, where M is the modulation index. The fundamental angular frequency, For the first i The new phase shift angle after optimization of each submodule.

9. A solid-state transformer capacitor voltage ripple self-suppression modulation system, characterized in that: The method for self-suppression modulation of capacitor voltage ripple in a solid-state transformer as described in any one of claims 1-8 includes: The acquisition module is used to acquire system operating parameters, including bridge arm modulation wave commands, bridge arm currents, and submodule rated capacitor voltages. The carrier signal generation module is used to generate triangular carriers for each submodule. The frequency ratio of the triangular carriers between adjacent submodules is a rational number that is determined based on the number of submodules and is not equal to 1. The phase shift angle calculation module is used to determine the initial phase shift angle of each submodule based on the carrier phase shift strategy; determine the optimized phase shift adjustment amount to cancel the ripple between adjacent submodules based on the frequency ratio, the power factor angle of the bridge arm current and the ripple frequency to be canceled; apply the optimized phase shift adjustment amount to the initial phase shift angle of the adjacent submodule pair, and obtain the globally optimized phase shift angle set through iteration or joint solution; The modulation wave generation module is used to generate the phase-shifted modulation wave of each submodule based on the globally optimized set of phase-shift angles. The comparison module is used to compare the modulated wave of each submodule with the triangular carrier wave and generate the drive signal for the switching device of each submodule.

10. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the solid-state transformer capacitor voltage ripple self-suppression modulation method according to any one of claims 1 to 8.

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