Resonant converter and control method, device, power transmission system and storage medium

Abstract

This application provides a resonant converter, control method, device, power transmission system, and storage medium. By determining the number of series submodules K and the number of switching submodules M based on the input voltage, the series submodules control the maximum value of the fundamental inverter voltage generated by the resonant converter, thus achieving applicability to a wide range of input voltages. Then, the control parameters of the resonant converter are determined based on the number of submodules K and M and the input voltage, and the series submodules are connected to the MMC circuit according to the control parameters, while the operating state of the switching submodules is also controlled. This solves the technical problem that existing resonant converters have a limited applicable input voltage range, cannot meet the wide-range input voltage application requirements of seabed observation networks, and cause difficulties in installation and maintenance due to the coexistence of multiple resonant converters. It achieves the technical effect of uniformly applying the same set of resonant converters across a wide input voltage range, reducing installation, maintenance, and control costs, and improving the reliability and safety of the system power supply.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 2020113977458, filed with the Chinese Patent Office on December 3, 2020, entitled "Resonant Converter and Control Method, Apparatus, Transmission System and Storage Medium". Technical Field

[0002] This application relates to the field of electronic power, and in particular to a resonant converter and its control method, device, power transmission system and storage medium. Background Technology

[0003] In fields such as marine scientific research, marine resource development, and marine disaster early warning, long-term, large-scale data collection on the seabed is required. As the types of seabed data to be collected increase, the types and quantities of seabed survey equipment needed also increase, leading to ever-increasing energy consumption of seabed exploration equipment.

[0004] Seabed observation points are located far from the coast, typically tens to hundreds of kilometers away. Currently, low-voltage power transmission is used to power seabed equipment, resulting in significant energy loss. Furthermore, long-distance power transmission causes a large voltage drop at the input terminal of the seabed junction box, reducing the reliability of power supply to seabed equipment.

[0005] Traditional high-voltage transmission equipment faces the challenge of rapidly changing power supply to the same observation point in a seabed observation network. The range of transmission voltage used for seabed observation points at different locations and distances is wide, with DC high-voltage transmission ranging from several kilovolts to tens of kilovolts. In such complex scenarios, multiple different types of transmission equipment are needed for voltage reduction, or the transmission equipment needs to be frequently updated to meet the rapidly changing power supply requirements. Summary of the Invention

[0006] This application provides a resonant converter and its control method, device, transmission system, and storage medium to solve the technical problem that the resonant converters used in high-voltage direct current transmission in the prior art have a small applicable input voltage range, which cannot meet the application requirements of the wide range of input voltages of the seabed observation network, resulting in the coexistence of multiple resonant converters and causing difficulties in installation and maintenance.

[0007] In a first aspect, this application provides a resonant converter control method applied to a resonant converter, the resonant converter comprising: a modular multilevel converter (MMC) circuit, the MMC circuit comprising multiple series-connected sub-modules, the control method comprising:

[0008] The number of series submodules K and the number of switching submodules M are determined based on the obtained input voltage. The series submodules are submodules that are connected in series to the MMC circuit. The series submodules are used to control the maximum value of the fundamental frequency of the inverter voltage generated by the resonant converter.

[0009] The control parameters are determined based on the quantity K, the quantity M, and the input voltage.

[0010] The operating state of the switching submodule in the MMC circuit is controlled according to the control parameters, and the serial submodule is connected to the MMC circuit. The operating state includes the input state and the cut-off state.

[0011] In one possible design, the control parameters are determined based on the quantity K, the quantity M, and the input voltage, including:

[0012] The reference output voltage is determined based on the quantity K, the quantity M, and the input voltage.

[0013] Obtain the actual output voltage detected in real time;

[0014] The switching frequency of the switching submodule is determined based on the reference output voltage and the actual output voltage. The switching frequency is the frequency of the fundamental voltage wave generated by the resonant converter.

[0015] Control parameters include the switching frequency.

[0016] Optionally, the control parameters, determined based on the quantity K, the quantity M, and the input voltage, also include:

[0017] The maximum value of the inverter voltage fundamental frequency is determined based on the quantity K, the quantity M, and the input voltage;

[0018] Using a preset approximation model, the switching modulation code of the switching sub-module is determined based on the quantity M and the maximum value. The preset approximation model is used to make the MMC circuit generate a voltage fundamental wave of a preset shape and to equalize the voltage of each sub-module. The control parameters include the switching modulation code.

[0019] Correspondingly, the operating state of the switching submodule in the MMC circuit is controlled according to the control parameters, including:

[0020] The switching modulation coding control module alternates between the input and output states.

[0021] In one possible design, after determining the switching modulation and coding of the switching submodule based on the quantity M and the maximum value using a preset approximation model, the following is also included:

[0022] Obtain the capacitor voltage of all switching sub-modules;

[0023] Arrange all capacitor voltages in ascending or descending order to determine the switching sequence of the switching submodule;

[0024] The driving code is determined based on the switching sequence and the switching modulation code;

[0025] Control parameters include driver coding.

[0026] In one possible design, the driving code is determined based on the switching sequence and the switching modulation code, including:

[0027] The first driving code is determined based on the first switching sequence and the first modulation code in the first control cycle;

[0028] The second driving code is determined based on the second switching sequence and the first modulation code in the second control cycle, and the second control cycle is after the first control cycle.

[0029] Optionally, the second driving code is determined based on the second switching sequence and the first modulation code in the second control cycle, including:

[0030] The first modulation code is encoded in reverse order of the second cutting sequence to determine the second driving code.

[0031] Optionally, the submodule includes a bypass circuit for controlling whether the submodule is connected in series with the MMC circuit. The MMC circuit includes at least one spare submodule. The method further includes:

[0032] Obtain the fault detection results of each submodule;

[0033] The faulty submodule is determined based on the fault detection results;

[0034] The bypass circuit of the faulty submodule is controlled to disconnect the faulty submodule, and the backup submodule is controlled to connect to the MMC circuit to replace the faulty submodule.

[0035] Secondly, this application provides a resonant converter, comprising:

[0036] Voltage equalization module, upper bridge arm module, lower bridge arm module, oscillation module, centralized transformer and rectifier module;

[0037] The voltage equalization module includes a first voltage equalization capacitor and a second voltage equalization capacitor connected in series;

[0038] The upper arm module and the lower arm module are connected in series;

[0039] The first end of the oscillation module is connected between the first equalizing capacitor and the second equalizing capacitor, the second end of the oscillation module is connected between the upper bridge arm module and the lower bridge arm module, and the oscillation module is connected in series with the transformer.

[0040] The rectifier module is connected to the secondary side of the transformer;

[0041] The upper arm module and / or lower arm module include at least two sub-modules connected in series, and the sub-modules include a working sub-module and a spare sub-module.

[0042] Optionally, the upper arm module and / or lower arm module may also include: an arm inductor.

[0043] In one possible design, the oscillation module includes an LC oscillation circuit, an upper bridge arm module and / or a lower bridge arm module, the oscillation circuit and a transformer forming an LLC oscillation circuit structure.

[0044] In one possible design, the number of capacitors in the first voltage equalizing capacitor is equal to the number of sub-modules in the upper bridge arm module, and the number of capacitors in the second voltage equalizing capacitor is equal to the number of sub-modules in the lower bridge arm module.

[0045] In one possible design, the submodule includes:

[0046] The circuit consists of a first switching transistor, a second switching transistor, a capacitor, a bypass module, and a freewheeling module. The first and second switching transistors are connected in series to form a half-bridge arm structure. The positive terminal of the capacitor is connected to the input terminal of the first switching transistor, and the negative terminal of the capacitor is connected to the output terminal of the second switching transistor. The output terminal of the first switching transistor is the high potential terminal of the switching module, and the output terminal of the second switching transistor is the low potential terminal of the switching module.

[0047] The input terminal of the bypass module is connected to the high potential terminal, and the output terminal of the bypass module is connected to the low potential terminal. The bypass module is used to control the connection switch state between the switching module and the modular multilevel resonant converter.

[0048] The input terminal of the freewheeling module is connected to the high-potential terminal, and the output terminal of the freewheeling module is connected to the positive terminal of the capacitor. The freewheeling module is used to provide a freewheeling circuit for the capacitor.

[0049] Optionally, the bypass module includes a third switch, the input of which is connected to the high potential terminal and the output of which is connected to the low potential terminal.

[0050] In one possible design, the freewheeling module includes a freewheeling diode, with its input connected to a high-potential terminal and its output connected to the positive terminal of a capacitor.

[0051] Optionally, the freewheeling diode includes at least two diodes connected in parallel, with the input terminal of the diode connected to the high-potential terminal and the output terminal of the diode connected to the positive terminal of the capacitor.

[0052] Optionally, the first switching transistor may include at least two power switching transistors connected in parallel.

[0053] Optionally, the second switching transistor may include at least two power switching transistors connected in parallel.

[0054] Optionally, the third switch may include at least two power switches connected in parallel.

[0055] In one possible design, the power switching transistors include: insulated gate bipolar transistors (IGBTs) and metal-oxide-semiconductor field-effect transistors (MOSFETs).

[0056] Thirdly, this application provides a power transmission system for a submarine observation network, comprising:

[0057] Onshore power transmission terminals, submarine junction boxes, and power consumption terminals;

[0058] The submarine junction box includes any of the possible resonant converters described in the second aspect above;

[0059] The high-voltage DC power output from the shore-based power transmission terminal is stepped down by a resonant converter, and then the low-voltage DC power output from the submarine junction box supplies power to the user terminal.

[0060] Fourthly, this application provides a resonant converter control device, comprising:

[0061] The acquisition module is used to acquire the input voltage at the input terminal of the auxiliary converter;

[0062] The processing module is used to determine the number K of the series sub-modules and the number M of the switching sub-modules based on the input voltage. The series sub-modules are sub-modules that are connected in series to the MMC circuit. The series sub-modules are used to control the maximum value of the fundamental frequency of the inverter voltage generated by the resonant converter.

[0063] The processing module is also used to determine control parameters based on the quantity K, the quantity M, and the input voltage;

[0064] The processing module is also used to control the working state of the switching sub-module in the MMC circuit according to the control parameters, and to control the connection of the series sub-module in the MMC circuit. The working state includes the input state and the cut-off state.

[0065] In one possible design, the processing module is further configured to determine control parameters based on the quantity K, the quantity M, and the input voltage, including:

[0066] The processing module is also used to determine the reference output voltage based on the quantity K, the quantity M, and the input voltage;

[0067] The acquisition module is also used to acquire the actual output voltage detected in real time;

[0068] The processing module is also used to determine the switching frequency of the switching submodule based on the reference output voltage and the actual output voltage. The switching frequency is the frequency of the fundamental voltage wave generated by the resonant converter.

[0069] Control parameters include the switching frequency.

[0070] Optionally, the processing module is also used to determine control parameters based on the quantity K, the quantity M, and the input voltage, and further includes:

[0071] The processing module is also used to determine the maximum value of the inverter voltage fundamental wave based on the quantity K, the quantity M, and the input voltage;

[0072] The processing module is also used to determine the switching modulation code of the switching sub-module based on the quantity M and the maximum value using a preset approximation model. The preset approximation model is used to make the MMC circuit generate a voltage fundamental wave of a preset shape and to equalize the voltage of each sub-module.

[0073] Control parameters include switching modulation and coding;

[0074] Correspondingly, the processing module is also used to control the operating state of the switching submodule in the MMC circuit according to the control parameters, including:

[0075] The processing module is also used to control the switching submodule to alternate between the input state and the cut-off state according to the switching modulation code.

[0076] In one possible design, after the processing module determines the switching modulation and coding of the switching submodule based on the quantity M and the maximum value using a preset approximation model, it also includes:

[0077] The acquisition module is also used to acquire the capacitor voltage of all switching sub-modules;

[0078] The processing module is also used to sort all capacitor voltages in ascending or descending order to determine the switching sequence of the switching submodule;

[0079] The processing module is also used to determine the driving code based on the switching sequence and the switching modulation code;

[0080] Control parameters include driver coding.

[0081] In one possible design, the processing module is further configured to determine the driving code based on the switching sequence and the switching modulation code, including:

[0082] The processing module is also configured to determine the first driving code based on the first switching sequence and the first modulation code in the first control cycle;

[0083] The processing module is also used to determine the second driving code based on the second switching sequence and the first modulation code in the second control cycle, the second control cycle being after the first control cycle.

[0084] Optionally, the processing module is further configured to determine the second driving code based on the second switching sequence and the first modulation code in the second control cycle, including:

[0085] The processing module is also used to encode the first modulation code in reverse order of the second cutting sequence to determine the second driving code.

[0086] Optionally, the submodule includes a bypass circuit for controlling whether the submodule is connected in series with the MMC circuit. The MMC circuit includes at least one spare submodule. The control device further includes:

[0087] The acquisition module is also used to acquire the fault detection results of each sub-module;

[0088] The processing module is also used to determine the fault sub-module based on the fault detection results;

[0089] The processing module is also used to control the bypass circuit of the faulty submodule to disconnect the faulty submodule, and to control the backup submodule to connect to the MMC circuit to replace the faulty submodule.

[0090] Fifthly, this application provides an electronic device, comprising:

[0091] Memory, used to store computer programs;

[0092] The processor is used to call and execute the computer program in memory, and to execute any of the possible resonant converter control methods provided in the first aspect.

[0093] In a sixth aspect, this application provides a storage medium in which a computer program is stored, the computer program being used to execute any of the possible resonant converter control methods provided in the first aspect.

[0094] In a seventh aspect, this application also provides a computer program product, including a computer program that, when executed by a processor, implements any of the possible resonant converter control methods provided in the first aspect.

[0095] This application provides a resonant converter, control method, device, power transmission system, and storage medium. By determining the number of series submodules K and the number of switching submodules M based on the input voltage, the series submodules control the maximum value of the fundamental inverter voltage generated by the resonant converter, thus achieving applicability to a wide range of input voltages. Then, the control parameters of the resonant converter are determined based on the number of submodules K and M and the input voltage, and the series submodules are connected to the MMC circuit according to the control parameters, while the operating state of the switching submodules is also controlled. This solves the technical problem that existing resonant converters have a limited applicable input voltage range, cannot meet the wide-range input voltage application requirements of seabed observation networks, and cause difficulties in installation and maintenance due to the coexistence of multiple resonant converters. It achieves the technical effect of uniformly applying the same set of resonant converters across a wide input voltage range, reducing installation, maintenance, and control costs, and improving the reliability and safety of the system power supply. Attached Figure Description

[0096] To more clearly illustrate the technical solutions in this application 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 some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0097] Figures 1a-1b This is a schematic diagram of the power transmission system of the submarine observation network provided in this application;

[0098] Figure 2 This application provides a schematic diagram of the structure of a resonant converter;

[0099] Figure 3 A structural diagram of a submodule provided in this application;

[0100] Figure 4 A structural diagram of another submodule provided in this application;

[0101] Figures 5a-5d This is a schematic diagram of the current loop in the submodule provided in this application;

[0102] Figure 6 A schematic diagram of another resonant converter provided in this application;

[0103] Figure 7 A flowchart illustrating a resonant converter control method provided in this application;

[0104] Figures 8a-8b A schematic diagram illustrating the voltage regulation principle of submodules that are always connected in series, provided for an embodiment of this application;

[0105] Figure 9 A flowchart illustrating another resonant converter control method provided in this application;

[0106] Figure 10 This is a schematic diagram of the closed-loop control principle provided in the embodiments of this application;

[0107] Figure 11 This application provides a schematic diagram of the structure of a resonant converter control device;

[0108] Figure 12 This is a schematic diagram of the structure of an electronic device provided in this application. Detailed Implementation

[0109] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort, including but not limited to combinations of multiple embodiments, are within the scope of protection of this application.

[0110] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0111] The following explains the technical terms used in the embodiments of this application.

[0112] MMC (Modular Multilevel Converter): A new type of multilevel converter structure that inherits the advantages of cascaded multilevel structures and uses charging capacitors instead of independent power supplies. This overcomes the limitations of two-level and three-level converters in further development towards multilevel converters, while also reducing the stress on each switching module, including voltage and / or current. An MMC consists of multiple identical sub-modules (SMs) cascaded in series. The sub-module structures can be categorized into three types: half-H-bridge, full-H-bridge, and double-clamped sub-modules.

[0113] An LC resonant circuit is a circuit consisting of an inductor (represented by the letter L) and a capacitor (represented by the letter C) connected in series. This circuit can be used as an electrical resonator to store the energy of oscillations when the circuit resonates. Resonance is also called resonance.

[0114] LLC resonant circuit: This is a resonant circuit that achieves a constant output voltage by controlling the switching frequency (frequency regulation). It consists of two inductors (represented by the letters Lr and Lm) and a capacitor (represented by the letter C). Its advantages are: achieving zero-voltage turn-on (ZVS) of the two main switching transistors (such as MOSFETs) on the primary side of the transformer and zero-current turn-off (ZCS) of the rectifier diodes on the secondary side. Through soft-switching technology, it can reduce the switching losses of the power supply and improve the efficiency and power density of the power converter.

[0115] Compared to traditional AC power transmission and distribution technologies, new DC power transmission and distribution technologies (high-voltage direct current (HVDC) transmission technology) have broad application prospects in fields such as large-capacity long-distance power transmission, DC smart microgrids, high-speed rail transit, and marine observation stations due to their unique advantages. High-voltage direct current converters are one of the key technologies in the field of DC power transmission and distribution. Modular multilevel resonant converter (MMC) technology is increasingly being used in the field of HVDC transmission due to its high reliability and low loss.

[0116] The inventive concept of this application is as follows: Since there are multiple observation points in the seabed observation network, and with the continuous development of marine scientific research and marine resource development and utilization, the seabed observation network is expanding rapidly. The distance between each observation point and the coast varies greatly, generally from tens to hundreds of kilometers. If low-voltage power transmission is used to power the seabed equipment, there will be a large power loss. At the same time, long-distance power transmission will cause a large voltage drop at the input terminal of the seabed junction box, which will reduce the reliability of the power supply to the seabed equipment.

[0117] Furthermore, the types of seabed data that need to be collected at each observation point are increasing, and the energy consumption of seabed exploration equipment is being updated more frequently. This has led to different high-voltage transmission strategies being used at the shore-based high-voltage transmission ends of various observation points in the existing seabed observation network, with DC high-voltage transmission ranging from several kilovolts to tens of kilovolts. Due to the limited applicability of existing DC high-voltage transmission devices, multiple different types of DC high-voltage transmission equipment coexist in the seabed observation network. Among these, the core equipment, the high-voltage DC converter in the seabed junction box, which performs the initial voltage reduction of the shore-based high-voltage transmission, faces the most common problems.

[0118] During high-voltage power transmission, the shore-based transmission end delivers high-voltage electricity to the seabed junction box, where a resonant converter steps down the voltage to 300-400V. Then, the power system inside the junction box performs a second voltage step-down to supply power to various seabed devices.

[0119] Therefore, current staff need to install and maintain a large number of different models of resonant converters, which is inconvenient, costly, and suffers from low component interchangeability and poor scalability, leading to a decrease in the power supply reliability of the marine observation network. This prompted the inventors of this application to invent a resonant converter that can be applied to a wide input voltage range, automatically adjusts according to the input voltage without human intervention, and offers convenient power expansion, maintenance, and fault tolerance. This would allow each marine observation point's junction box to use a unified resonant converter, with good component interchangeability and standardized installation and maintenance methods, thus reducing installation and maintenance costs and improving power supply reliability. After comparing various DC high-voltage transmission topologies, the modular multilevel converter (MMC) topology, by connecting multiple sub-modules in series, significantly reduces the voltage and current withstand requirements of each component in the resonant converter, thereby reducing its size. However, how to enable it to handle a wide input voltage range remains a challenge for those skilled in the art, requiring neither technical inspiration from existing MMC technology nor simple derivation.

[0120] After extensive research, the inventors of this application discovered that the reason why the existing MMC topology cannot handle a large input voltage range is that the technical inertia of those skilled in the art is to set a fixed number of sub-modules. These sub-modules connected in series can only be controlled by two switching transistors in the sub-modules to generate a multi-level effect. The number of sub-modules determines the number of levels. The more levels there are, the fewer harmonics in the system. Therefore, those skilled in the art try to use all sub-modules for dynamic switching to generate more levels.

[0121] The inventors of this application discovered that by keeping a portion of the sub-modules continuously connected—that is, by continuously connecting the capacitors in the sub-modules to the MMC bridge arm module—the amplitude of the inverter voltage, such as a square wave voltage, generated by the resonant converter can be reduced. Based on this, the inventors of this application overcome the technical inertia of using all sub-modules for inversion, i.e., generating multi-level signals by connecting and disconnecting them. Instead, they change the approach by controlling the number of sub-modules continuously connected to the MMC bridge arm module when the input voltage changes, thereby maintaining a constant inverter voltage amplitude. This is because the higher the input voltage, the larger the inverter voltage amplitude; by increasing the number of continuously connected sub-modules, this amplitude can be reduced, thus keeping the inverter voltage amplitude constant.

[0122] The following section describes in detail the resonant converter that can realize the above-mentioned inventive concept, and its specific control method.

[0123] Figures 1a-1b Figure 1 shows a schematic diagram of the power transmission system for the submarine observation network provided in this application. As shown in Figure 1, the submarine observation network includes: a shore-based power transmission terminal and submarine observation points. Figure 1aThe diagram schematically illustrates three power transmission stations on the shore-based side: shore-based transmission terminal 101, shore-based transmission terminal 102, and shore-based transmission terminal 103; and three seabed observation points: seabed observation point A111, seabed observation point B112, and seabed observation point C113. The transmission voltage from the different power transmission stations to the seabed observation points may vary, fluctuating between several thousand volts and tens or even hundreds of kilovolts. The energy consumption of each observation point differs due to variations in the number or type of seabed equipment it possesses.

[0124] like Figure 1b As shown, the shore-based power transmission terminal 121 transmits high-voltage electricity to the junction box 122 at the seabed observation point via a submarine cable. The junction box 122 contains a resonant converter for voltage reduction. The voltage output by the resonant converter is then stepped down a second time by the power system in the junction box 122 to different electrical devices, i.e., the power consumption terminal 123, to meet the power supply needs of different electrical devices.

[0125] Figure 2 This is a schematic diagram of a resonant converter provided in this application. Figure 2 As shown, the resonant converter 200 includes:

[0126] The voltage equalization module 201, the upper bridge arm module 202, the lower bridge arm module 203, the oscillation module 204, the transformer 205, and the rectifier module 206;

[0127] The voltage equalization module includes a first voltage equalization capacitor 2011 and a second voltage equalization capacitor 2012 connected in series.

[0128] The upper arm module 202 and the lower arm module 203 are connected in series;

[0129] The first end of the oscillation module 204 is connected between the first equalizing capacitor 2011 and the second equalizing capacitor 2012, the second end of the oscillation module 204 is connected between the upper bridge arm module 202 and the lower bridge arm module 203, and the oscillation module 204 is connected in series with the transformer 205.

[0130] The rectifier module 206 is connected to the secondary side of the transformer 205;

[0131] The upper arm module 202 and / or the lower arm module 203 include at least two sub-modules connected in series, the sub-modules including a working sub-module and a spare sub-module.

[0132] The working submodule is used to dynamically engage or disengage the upper / lower bridge arm modules when the resonant converter is working normally, in order to generate the inverter voltage fundamental wave, such as a square wave or a sine wave.

[0133] The backup submodule is used in the event of irreversible damage to the working submodule. The controller directly controls the bypass module within the backup submodule to disconnect the working submodule from the bridge arm module, and the backup submodule takes over. In other words, the bypass circuit allows the submodule to be connected to or disconnected from the bridge arm module without disassembly.

[0134] Figure 3 This is a structural diagram of a submodule provided in this application. For example... Figure 3 As shown, the switching module includes: a first switching transistor 301, a second switching transistor 302, a capacitor 303, a bypass module 304, and a freewheeling module 305. The first switching transistor 301 and the second switching transistor 302 are connected in series to form a half-bridge arm structure. The positive terminal of the capacitor 303 is connected to the input terminal of the first switching transistor 301, and the negative terminal of the capacitor 303 is connected to the output terminal of the second switching transistor 302. The output terminal of the first switching transistor 301 is the high potential terminal of the switching module, and the output terminal of the second switching transistor 302 is the low potential terminal of the switching module.

[0135] The input terminal of the bypass module 304 is connected to the high potential terminal, and the output terminal of the bypass module 304 is connected to the low potential terminal. The bypass module 304 is used to control the connection switch state between the switch module and the modular multilevel resonant converter.

[0136] The input terminal of the freewheeling module 305 is connected to the high potential terminal, and the output terminal of the freewheeling module is connected to the positive terminal of the capacitor 303. The freewheeling module is used to provide a freewheeling circuit for the capacitor 303.

[0137] It should be noted that the first switching transistor 301 and the second switching transistor 302 include power switching transistors and diodes connected in anti-parallel to them. In one possible design, the power switching transistors and the diodes connected in anti-parallel to them are integrated into a single component. The capacitor 303 includes at least one separately packaged capacitor component.

[0138] Optionally, to reduce the current withstand requirement of the power switching transistors, the first switching transistor 301 and / or the second switching transistor 302 may be composed of multiple (at least two) power switching transistors connected in parallel. To reduce the voltage withstand requirement of the power switching transistors, the first switching transistor 301 and / or the second switching transistor 302 may be composed of multiple (at least two) power switching transistors connected in series. It is understood that, in order to enable the switching module to adapt to various voltage and current withstand requirements, multiple power switching transistors may also be mixed and connected, dynamically changing to a parallel or series structure by dynamically controlling some power switching transistors to be normally open or normally closed.

[0139] This embodiment provides a submodule of a resonant converter. A bypass module within the submodule controls whether the submodule is connected to the bridge arm structure of the resonant converter. This redundant installation of multiple submodules allows the resonant converter to directly switch to a backup submodule to replace the damaged one without affecting normal operation when one or more submodules fail. This solves the technical problem in existing modular multilevel converters where submodule failure leads to poor reliability and low safety in high-voltage direct current transmission systems, resulting in the inability to maintain normal operation. It achieves the technical effects of ensuring the fault tolerance rate of the resonant converter, improving its service life, and enhancing the safety of the high-voltage direct current transmission network system.

[0140] Optionally, the freewheeling module 305 includes a freewheeling diode, the input terminal of which is connected to the high-potential terminal, and the output terminal of which is connected to the positive terminal of the capacitor. Specifically, as shown... Figure 4 As shown.

[0141] Figure 4 A schematic diagram of another submodule provided in this application. For example... Figure 4 As shown, the submodule includes: a first switch 401, a second switch 402, a capacitor 403, a third switch 404, and a freewheeling diode 405. The first switch 401 and the second switch 402 are connected in series to form a half-bridge arm structure. The positive terminal of the capacitor 403 is connected to the input terminal of the first switch 401, and the negative terminal of the capacitor 403 is connected to the output terminal of the second switch 402. The output terminal of the first switch 401 is the high potential terminal of the switching module, and the output terminal of the second switch 402 is the low potential terminal of the switching module.

[0142] The input terminal of the third switch 404 is connected to the high potential terminal, and the output terminal of the third switch 404 is connected to the low potential terminal. The third switch 404 is used to control the connection switch state between the switch module and the modular multilevel resonant converter.

[0143] The input terminal of the freewheeling diode 405 is connected to the high potential terminal, and the output terminal of the freewheeling diode is connected to the positive terminal of the capacitor 403. The freewheeling diode is used to provide a freewheeling circuit for the capacitor 403.

[0144] In the above embodiment, the third switch 404 is the simplest implementation structure of the bypass module 304. Those skilled in the art can connect other components in parallel with the third switch according to the actual situation, such as a diode in reverse parallel to avoid the situation where the control of whether the bypass module is connected or not cannot be realized when the diode in the third switch is damaged.

[0145] Optionally, the first switch 401, and / or the second switch 402, and / or the third switch 404 may include at least two power switches connected in parallel.

[0146] It should be noted that power switching transistors include: Insulated Gate Bipolar Transistor (IGBT) and Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET).

[0147] Optionally, to reduce the current withstand requirement of each freewheeling diode, the freewheeling diode includes at least two diodes connected in parallel, with the input terminal of the diode connected to the high-potential terminal and the output terminal of the diode connected to the positive terminal of the capacitor. Similarly, to reduce the voltage withstand requirement, the freewheeling diode includes at least two diodes connected in series. It is understood that embodiments of this application may also include a case where at least three diodes are connected in a mixed series and parallel configuration.

[0148] During normal operation of the MMC resonant converter, submodules can only be in an on or off state; a latched state is not allowed during normal operation. However, in the event of an unrecoverable fault in a submodule due to external factors, such as damage to the second switch, the submodule can be quickly and reliably disconnected from the entire MMC resonant converter system via a bypass module. This achieves submodule redundancy and backup, eliminating the need for system shutdown for submodule replacement. Furthermore, if a submodule failure leads to damage to the first switch, the system can use a freewheeling module for current recovery, increasing the system's fault tolerance.

[0149] To illustrate the specific functions of the bypass module and the continuation module, the following will explain... Figures 5a-5d Let me explain its working principle and effects in detail.

[0150] Figures 5a-5d This is a schematic diagram of the current loop in the submodule provided in this application. Figures 5a-5b As shown, when the submodule is in the disconnected state, under normal circumstances, the capacitor 403 in the submodule is disconnected by closing the second switch 402 in the submodule. However, when the power device (IGBT or MOSFET) in the second switch 402 is damaged ( Figure 5a (Dashed-line components), the sub-module can be removed through a bypass module. When the capacitor 403 of other sub-modules of the MMC resonant converter is charging, the current flows through the power device in the third switching transistor 404. The sub-module current operating circuit is as follows: Figure 5a As shown.

[0151] When the body diode or anti-parallel diode of the power device in the second switching transistor 402 fails ( Figure 5b (Dashed-line components) When capacitor 403 of other submodules of the MMC resonant converter discharges, the current flows through the body diode or reverse parallel diode of the power device of the third switching transistor 404. The module current operating circuit is as follows: Figure 5b As shown.

[0152] When the submodule is in the active state and capacitor 403 is charging, a freewheeling circuit is needed to charge the submodule capacitor. When the body diode or reverse parallel diode of the power device in the first switching transistor 401 fails ( Figure 5c In the event of damage to the component indicated by the dashed line, current can flow through the freewheeling diode 405 to charge the capacitor 403 of the submodule. Figure 5c As shown.

[0153] When the submodule is in the active state and capacitor 403 is discharging, a freewheeling circuit is needed to discharge the submodule capacitor. When the body diode or reverse parallel diode of the power device in the first switching transistor 401 fails ( Figure 5d In the event of damage to the component indicated by the dashed line, current can flow through the power device in the first switching transistor 401 to discharge the capacitor 403 of the submodule, such as... Figure 5d As shown.

[0154] Figure 6 A schematic diagram of another resonant converter provided in this application. Figure 6 As shown, the resonant converter 600 includes:

[0155] The system includes a first equalizing capacitor 601, a second equalizing capacitor 602, an upper bridge arm module 603, a lower bridge arm module 604, an oscillation module 605, a transformer 606, and a rectifier module 607.

[0156] The number of independent capacitors 6011 included in the first voltage equalizing capacitor 601 is the same as the number of independent capacitors 6021 included in the second voltage equalizing capacitor 602, and is the same as the number of sub-modules SM in the upper bridge arm module 603 or the lower bridge arm module 604.

[0157] The upper arm module 603 and the lower arm module 604 are connected in series;

[0158] The upper arm module 603 includes: an upper arm inductor LP and multiple sub-modules SM;

[0159] The lower bridge arm module 604 includes: a lower bridge arm inductor LN and multiple sub-modules SM;

[0160] The first end of the oscillation module 605 is connected between the first equalizing capacitor 601 and the second equalizing capacitor 602, the second end of the oscillation module 605 is connected between the upper bridge arm module 603 and the lower bridge arm module 604, and the oscillation module 605 is connected in series with the transformer 606.

[0161] The rectifier module 607 is connected to the secondary stage of the transformer 606;

[0162] The rectifier module 607 is an H-bridge rectifier module;

[0163] The oscillation module 605 includes: an LC oscillation circuit, an upper bridge arm module, a lower bridge arm module, an oscillation circuit and a transformer forming an LLC oscillation circuit structure, or a bridge arm inductor, an oscillation circuit and a transformer forming an LLC oscillation circuit structure.

[0164] It should be noted that the number of cascaded submodules (SM) is greater than or equal to the number of cascaded submodules required for the MMC resonant converter to operate normally. This enables redundancy of submodules in the resonant converter. If one or more submodules fail, the redundant submodules can directly replace the failed submodules without stopping the system for replacement, thereby improving the fault tolerance and operational reliability of the resonant converter.

[0165] The following explains how to control it. Figure 2 or Figure 6 Any type of resonant converter in Figures 1a-1b The voltage reduction function is used in the power transmission system of the seabed observation network to solve the technical problem that the resonant converter of the existing high voltage direct current transmission has a small applicable input voltage range, which cannot meet the application requirements of the wide range of input voltage of the seabed observation network, resulting in the coexistence of multiple resonant converters and causing difficulties in installation and maintenance.

[0166] Figure 7 This is a flowchart illustrating a resonant converter control method provided in this application. Figure 7 As shown, the specific steps of this resonant converter control method include:

[0167] S701. Determine the number of series sub-modules K and the number of switching sub-modules M based on the obtained input voltage.

[0168] In this step, the serial submodule is continuously connected in series to... Figure 2 or Figure 6 The upper or lower bridge arm module of the resonant converter shown is a sub-module of the MMC circuit. The series sub-module is used to control the maximum value of the fundamental frequency of the inverter voltage generated by the resonant converter.

[0169] Figure 1a The voltage transmitted from the shore-based power transmission terminal of the submarine observation network power transmission system to different submarine observation point junction boxes varies between several thousand volts and tens of kilovolts. In order to unify the type of resonant converter in each junction box and reduce the installation and maintenance cost of the resonant converter, in this step, the controller of the resonant converter uses the conversion relationship between the input voltage and the required output voltage. In order to maintain the stability of the output voltage, some sub-modules need to be connected in series to the upper or lower bridge arm module.

[0170] Figures 8a-8b This is a schematic diagram illustrating the voltage regulation principle of submodules that are always connected in series, as provided in an embodiment of this application. Figure 8aAs shown, the number of sub-modules dynamically switched is M, where M is less than or equal to N. N is the maximum number of sub-modules in the resonant converter that can be switched under normal operating conditions. When the upper arm module and / or lower arm module does not have any sub-modules that are always connected in series, i.e., K=0, M=N. In this case, the sub-modules in each arm module are connected for half the time and disconnected for half the time. Then the output voltage of the MMC circuit, i.e., the upper arm module or the lower arm module, is... With input voltage Equal to the input voltage generated on the primary side of the transformer, which is also the output voltage of the fundamental frequency of the inverter voltage. As shown in formula (1):

[0171] (1)

[0172] like Figure 8b As shown, when K (K>0) sub-modules in the upper or lower arm module of the MMC circuit remain connected in series within one inverter voltage fundamental cycle, the capacitor voltage in each sub-module is... As shown in formula (2):

[0173] (2)

[0174] Because the series connection of capacitors creates a bias voltage divider, there will be a bias voltage in either the upper or lower bridge arm module. As shown in formula (3):

[0175] (3)

[0176] The input voltage generated at this time on the primary side of the transformer is the output voltage of the fundamental inverter voltage. As shown in formula (4):

[0177] (4)

[0178] like Figure 8b As shown, the amplitude of the inverter voltage fundamental frequency is compressed, while when the input voltage... When the voltage increases, in order to keep the primary input voltage of the transformer constant, the specific values ​​of M and K can be calculated using formula (4).

[0179] The embodiments of this application overcome the technical inertia of needing to use all sub-modules for dynamic switching by formula (4). By keeping some sub-modules always in operation, the primary side of the transformer of the resonant converter can obtain a relatively stable input voltage when the input voltage changes within a large range. This makes the working range of the resonant converter larger and suitable for the wide range of power transmission needs of the shore-based power transmission end of the submarine observation network power transmission system, and reduces the installation and maintenance costs of the resonant converter.

[0180] S702. Determine the control parameters based on the quantity K, quantity M, and input voltage.

[0181] In this step, the control parameters include modulation and coding for controlling the dynamic switching of each submodule, and hold-in command coding for the submodule that holds the cascaded input.

[0182] Specifically, space vector pulse width modulation (SVPWM) and its related improvements can be used to generate modulation codes that require dynamic switching.

[0183] S703. Control the working state of the switching submodule in the MMC circuit according to the control parameters, and control the series submodule to be connected in the MMC circuit.

[0184] In this step, the working status of the submodule includes the engaged state and the disengaged state.

[0185] Specifically, dynamic switching is performed based on the SVPWM modulation and coding control switching submodule.

[0186] It should be noted that when submodules are dynamically switched on and off, the timing of each submodule's on and off states can be different. The on and off times of each submodule are determined by the different step-wave approximation methods of the inverter voltage fundamental. Furthermore, the step-wave voltage generated by each submodule may not be the same. Figure 8b As shown, some steps in the stepped wave are high, while others are low, and the duration of each step can also vary. By flexibly controlling the stepped wave, different approximation forms can be obtained, generating inverter voltage fundamental waves of different shapes, such as square waves, trapezoidal waves, triangular waves, sine waves, etc., or mixed periodic waves composed of multiple waveforms. This makes the operating mode of the resonant converter more flexible and versatile, suitable for more applications, and expands the application range of the resonant converter.

[0187] This application provides a resonant converter control method. By determining the number of series submodules K and the number of switching submodules M based on the input voltage, the series submodules control the maximum value of the fundamental inverter voltage generated by the resonant converter, thus achieving applicability to a wide range of input voltages. Then, the control parameters of the resonant converter are determined based on the number of submodules K, M, and the input voltage. The series submodules are then connected to the MMC circuit according to the control parameters, while the operating state of the switching submodules is also controlled. This solves the technical problem in the prior art where the applicable input voltage range of resonant converters is relatively small, unable to meet the application requirements of the wide range of input voltages in seabed observation networks, resulting in the coexistence of multiple resonant converters and difficulties in installation and maintenance. The method achieves the technical effect of uniformly applying the same set of resonant converters across a wide input voltage range, reducing installation, maintenance, and control costs, and improving the reliability and safety of the system power supply.

[0188] Figure 9 A flowchart illustrating another resonant converter control method provided in this application. Figure 9 As shown, the specific steps of this resonant converter control method include:

[0189] S901. Determine the number of series sub-modules K and the number of switching sub-modules M based on the obtained input voltage.

[0190] In this step, the serial submodule is continuously connected in series to... Figure 2 or Figure 6 The upper or lower bridge arm module of the resonant converter shown is a sub-module of the MMC circuit. The series sub-module is used to control the maximum value of the fundamental inverter voltage generated by the resonant converter. For specific principles and terminology explanations, please refer to S701, which will not be repeated here.

[0191] S902. Determine the reference output voltage based on the quantity K, quantity M, and input voltage.

[0192] In this embodiment, the voltage ratio between the primary and secondary sides of the transformer in the resonant converter is n, and the reference output voltage is... As shown in formula (5):

[0193] (5)

[0194] S903: Obtain the actual output voltage detected in real time.

[0195] S904. Determine the switching frequency of the switching submodule based on the reference output voltage and the actual output voltage.

[0196] In this step, the switching frequency is the frequency of the fundamental voltage wave generated by the resonant converter. In this embodiment, the control parameters include the switching frequency.

[0197] S902~S904 constitute the output voltage feedback compensation control closed loop of the resonant converter control in this application. Because traditional MMC control simply controls the switching on and off of sub-modules, this method generates certain step fluctuations or harmonic interference during output voltage regulation and transformation. Therefore, considering the above, this application adopts a closed-loop control of the output voltage to adjust the switching frequency and reduce the output voltage error.

[0198] By acquiring the actual output voltage and then using a compensation network algorithm to determine the switching frequency of the submodule, the output voltage is... After compensation by the switching switch, it can be expressed by formula (6), which is shown below:

[0199] (6)

[0200] in, This is the gain corresponding to the switching frequency.

[0201] S905. Determine the maximum value of the inverter voltage fundamental frequency based on the quantity K, quantity M, and input voltage.

[0202] In this step, the calculation method for the maximum value of the inverter voltage fundamental wave is shown in formula (4), which will not be repeated here.

[0203] S906. Using a preset approximation model, determine the switching modulation coding of the switching sub-module based on the quantity M and the maximum value.

[0204] In this step, a preset approximation model is used to enable the MMC circuit to generate a voltage fundamental wave of a preset shape and to equalize the voltage of each sub-module. In this embodiment, the control parameters include switching modulation coding.

[0205] Specifically, the preset approximation model is determined based on the shape of the inverter voltage fundamental wave, such as square wave, trapezoidal wave, triangular wave, and sine wave. Each waveform corresponds to multiple stepped wave approximation methods, which can be divided into two main categories: equidistant stepped waves and non-equidistant stepped waves. An equidistant stepped wave means that the width and height of the voltage level generated by each submodule are equal, thus approximating the target voltage waveform shape linearly. In contrast, a non-equidistant stepped wave approximates the target voltage waveform non-linearly, meaning the line connecting the vertices of the square wave forms a curve.

[0206] The modulation code can be calculated based on the SVPWM algorithm. Those skilled in the art can choose the specific encoding method according to the actual situation, and this application does not limit it.

[0207] S905~S906 constitute the input voltage controlled by the resonant converter of this application. The feedback compensation control closed loop enables the resonant converter to adjust the switching status of each sub-module in a timely manner when the input voltage fluctuates, thereby improving the stability and reliability of the system.

[0208] S907, Obtain the capacitor voltage of all switching sub-modules.

[0209] In this step, to ensure that the capacitors in the resonant converter submodules are not damaged due to overcharging or over-discharging, such as... Figure 8a As shown, there is a phase difference between the voltage and current in the bridge arm module, which results in uneven charging and discharging times for each submodule. This poses a risk of overcharging or over-discharging the capacitors of the submodules. Therefore, it is necessary to detect the capacitor voltage of all submodules that need to be dynamically connected and disconnected (i.e., the connected / disconnected submodules). Real-time voltage equalization control of the submodules is also required. Steps S907 to S909 are the steps for submodule voltage equalization control.

[0210] S908. Arrange all capacitor voltages in ascending or descending order to determine the switching sequence of the switching submodule.

[0211] S909. Determine the driving code based on the switching sequence and the switching modulation code.

[0212] This step specifically includes:

[0213] First, the first driving code is determined based on the first switching sequence and the first modulation code in the first control cycle.

[0214] For example, if the first switching sequence is SM2, SM4, SM3, SM1, SM5, then the first driving code is the hexadecimal code 5EFB corresponding to 24315.

[0215] Then, the second driving code is determined based on the second switching sequence and the first modulation code in the second control cycle, which is after the first control cycle.

[0216] In one possible design, when the average difference between the capacitor voltages of all switching submodules is less than a preset threshold, the second control cycle is the second cycle after the first control cycle. That is, when the voltage difference between the capacitors is not large, voltage equalization is performed every other cycle to reduce the computational burden on the controller and reduce the controller's power consumption.

[0217] In one possible design, the second control cycle is the first cycle after the first control cycle when the average difference between the capacitor voltages of all switching submodules is greater than or equal to a preset threshold. Specifically, determining the second drive code includes: encoding the first modulation code in reverse order of the second switching sequence to determine the second drive code.

[0218] For example, the first cycle 24315 is reversed to 51342, and the hexadecimal code C88E of 51342 is generated.

[0219] S910: Control the working state of the switching submodule in the MMC circuit according to the control parameters, and control the series submodule to be connected in the MMC circuit.

[0220] In this step, the operating state of the switching submodule in the MMC circuit is controlled according to the control parameters, including:

[0221] The switching modulation coding control module alternates between the input and output states.

[0222] It should be noted that in this embodiment, dual closed-loop control and sub-module voltage equalization control are adopted to improve the stability and reliability of the resonant converter control.

[0223] Figure 10 This is a schematic diagram illustrating the closed-loop control principle provided in an embodiment of this application. Figure 10 As shown, S902~S904 constitute the output voltage feedback compensation control closed loop, and S905~S906 constitute the input voltage... The feedback compensation control closed loop, S907~S909 are sub-module voltage equalization control.

[0224] In one possible design, the resonant converter control method provided in this application further includes:

[0225] Obtain the fault detection results of each submodule;

[0226] The faulty submodule is determined based on the fault detection results;

[0227] The bypass module of the control faulty submodule disconnects the faulty submodule and controls the backup submodule to connect to the MMC circuit to replace the faulty submodule.

[0228] like Figure 3 or Figure 4 The submodules shown all have bypass circuits. If the first or second switching transistor in a submodule fails, the bypass module can disconnect the submodule and replace it with a spare. This achieves submodule redundancy, allowing the resonant converter to continue operating normally without disassembly and maintenance, thus improving the fault tolerance and reliability of the resonant converter.

[0229] This application provides a resonant converter control method. By determining the number of series submodules K and the number of switching submodules M based on the input voltage, the series submodules control the maximum value of the fundamental inverter voltage generated by the resonant converter, thus achieving applicability to a wide range of input voltages. Then, the control parameters of the resonant converter are determined based on the number of submodules K, M, and the input voltage. The series submodules are then connected to the MMC circuit according to the control parameters, while the operating state of the switching submodules is also controlled. This solves the technical problem in the prior art where the applicable input voltage range of resonant converters is relatively small, unable to meet the application requirements of the wide range of input voltages in seabed observation networks, resulting in the coexistence of multiple resonant converters and difficulties in installation and maintenance. The method achieves the technical effect of uniformly applying the same set of resonant converters across a wide input voltage range, reducing installation, maintenance, and control costs, and improving the reliability and safety of the system power supply.

[0230] Figure 11 This is a schematic diagram of a resonant converter control device provided in this application. The resonant converter control device can be implemented through software, hardware, or a combination of both.

[0231] like Figure 11 As shown, the resonant converter control device 1100 provided in this embodiment includes:

[0232] The acquisition module 1101 is used to acquire the input voltage at the input terminal of the auxiliary converter;

[0233] Processing module 1102 is used to determine the number K of series sub-modules and the number M of switching sub-modules based on the input voltage. The series sub-modules are sub-modules that are connected in series to the MMC circuit. The series sub-modules are used to control the maximum value of the fundamental frequency of the inverter voltage generated by the resonant converter.

[0234] The processing module 1102 is also used to determine control parameters based on the quantity K, the quantity M, and the input voltage;

[0235] The processing module 1102 is also used to control the working state of the switching sub-module in the MMC circuit according to the control parameters, and to control the series sub-module to be connected in the MMC circuit. The working state includes the input state and the cut-off state.

[0236] In one possible design, the processing module 1102 is further configured to determine control parameters based on the quantity K, the quantity M, and the input voltage, including:

[0237] Processing module 1102 is also used to determine the reference output voltage based on the quantity K, the quantity M and the input voltage;

[0238] The acquisition module 1101 is also used to acquire the actual output voltage detected in real time;

[0239] Processing module 1102 is also used to determine the switching frequency of the switching submodule based on the reference output voltage and the actual output voltage. The switching frequency is the frequency of the fundamental voltage wave generated by the resonant converter.

[0240] Control parameters include the switching frequency.

[0241] Optionally, the processing module 1102 is further configured to determine control parameters based on the quantity K, the quantity M, and the input voltage, and also includes:

[0242] Processing module 1102 is also used to determine the maximum value of the inverter voltage fundamental wave based on the quantity K, the quantity M and the input voltage;

[0243] The processing module 1102 is also used to determine the switching modulation code of the switching sub-module based on the quantity M and the maximum value using a preset approximation model. The preset approximation model is used to make the MMC circuit generate a voltage fundamental wave of a preset shape and to equalize the voltage of each sub-module.

[0244] Control parameters include switching modulation and coding;

[0245] Correspondingly, the processing module 1102 is also used to control the operating state of the switching submodule in the MMC circuit according to the control parameters, including:

[0246] The processing module 1102 is also used to control the switching submodule to alternate between the input state and the cut-off state according to the switching modulation code.

[0247] In one possible design, after processing module 1102 determines the switching modulation coding of the switching submodule based on the quantity M and the maximum value using a preset approximation model, it further includes:

[0248] The acquisition module 1101 is also used to acquire the capacitor voltage of all switching sub-modules;

[0249] Processing module 1102 is also used to sort all capacitor voltages in ascending or descending order to determine the switching sequence of the switching submodule;

[0250] Processing module 1102 is also used to determine the driving code based on the switching sequence and the switching modulation code;

[0251] Control parameters include driver coding.

[0252] In one possible design, the processing module 1102 is further configured to determine the driving code based on the switching sequence and the switching modulation code, including:

[0253] The processing module 1102 is further configured to determine the first driving code based on the first switching sequence and the first modulation code in the first control cycle;

[0254] Processing module 1102 is further configured to determine a second driving code based on the second switching sequence and the first modulation code in the second control cycle, wherein the second control cycle is after the first control cycle.

[0255] Optionally, the processing module 1102 is further configured to determine the second driving code based on the second switching sequence and the first modulation code in the second control cycle, including:

[0256] The processing module 1102 is further configured to encode the first modulation code in reverse order of the second switching sequence to determine the second driving code.

[0257] Optionally, the submodule includes a bypass circuit for controlling whether the submodule is connected in series with the MMC circuit. The MMC circuit includes at least one spare submodule. The control device further includes:

[0258] The acquisition module 1101 is also used to acquire the fault detection results of each sub-module;

[0259] The processing module 1102 is also used to determine the fault submodule based on the fault detection results;

[0260] The processing module 1102 is also used to control the bypass circuit of the faulty submodule to disconnect the faulty submodule, and to control the backup submodule to connect to the MMC circuit to replace the faulty submodule.

[0261] It is worth noting that, Figure 11 The resonant converter control device provided in the illustrated embodiment can execute the method provided in any of the above-described method embodiments. Their specific implementation principles, technical features, explanations of technical terms, and technical effects are similar, and will not be repeated here.

[0262] Figure 12 This is a schematic diagram of the structure of an electronic device provided in this application. Figure 12 As shown, the electronic device 1200 may include at least one processor 1201 and a memory 1202. Figure 12 The example shown is an electronic device using a processor.

[0263] The memory 1202 is used to store programs. Specifically, the program may include program code, which includes computer operation instructions.

[0264] The memory 1202 may include high-speed RAM memory, and may also include non-volatile memory, such as at least one disk storage.

[0265] The processor 1201 is used to execute computer execution instructions stored in the memory 1202 to implement the methods of the above method embodiments.

[0266] The processor 1201 may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of this application.

[0267] Optionally, the memory 1202 can be either standalone or integrated with the processor 1201. When the memory 1202 is a device independent of the processor 1201, the electronic device 1200 may further include:

[0268] Bus 1203 is used to connect processor 1201 and memory 1202. The bus can be an industry standard architecture (ISA) bus, a peripheral component (PCI) bus, or an extended industry standard architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc., but this does not mean there is only one bus or one type of bus.

[0269] Optionally, in a specific implementation, if the memory 1202 and the processor 1201 are integrated on a single chip, the memory 1202 and the processor 1201 can communicate through an internal interface.

[0270] This application also provides a computer-readable storage medium, which may include various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk. Specifically, the computer-readable storage medium stores program instructions, which are used in the methods described in the above embodiments.

[0271] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the methods described in the above embodiments.

[0272] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A control method for a resonant converter, characterized in that, The method is applied to a resonant converter, the resonant converter comprising: a modular multilevel converter (MMC) circuit, the MMC circuit comprising multiple series-connected sub-modules, and the control method comprising: The number of series submodules K and the number of switching submodules M are determined based on the obtained input voltage. The series submodules are submodules that are connected in series to the MMC circuit. The series submodules are used to control the maximum value of the fundamental inverter voltage generated by the resonant converter. The control parameters are determined based on the quantity K, the quantity M, and the input voltage; The operating state of the cutting submodule in the MMC circuit is controlled according to the control parameters, and the serial submodule is connected to the MMC circuit. The operating state includes the input state and the cut-off state.

2. The resonant converter control method according to claim 1, characterized in that, The step of determining the control parameters based on the quantity K, the quantity M, and the input voltage includes: The reference output voltage is determined based on the quantity K, the quantity M, and the input voltage; Obtain the actual output voltage detected in real time; The switching frequency of the switching submodule is determined based on the reference output voltage and the actual output voltage. The switching frequency is the frequency of the fundamental voltage wave generated by the resonant converter. The control parameters include the switching frequency.

3. The resonant converter control method according to claim 1 or 2, characterized in that, The step of determining the control parameters based on the quantity K, the quantity M, and the input voltage includes: The maximum value of the inverter voltage fundamental frequency is determined based on the quantity K, the quantity M, and the input voltage; Using a preset approximation model, the switching modulation code of the switching sub-module is determined based on the quantity M and the maximum value. The preset approximation model is used to enable the MMC circuit to generate the voltage fundamental wave of a preset shape and to equalize the voltage of each sub-module. The control parameters include the switching modulation code. Correspondingly, controlling the operating state of the switching submodule in the MMC circuit according to the control parameters includes: The switching modulation coding control controls the switching submodule to alternate between the input state and the output state.

4. The resonant converter control method according to claim 3, characterized in that, After determining the switching modulation coding of the switching submodule using a preset approximation model based on the quantity M and the maximum value, the method further includes: Obtain the capacitor voltage of all the aforementioned switching sub-modules; All the capacitor voltages are arranged in ascending or descending order to determine the switching sequence of the switching submodule; The driving code is determined based on the switching sequence and the switching modulation coding; The control parameters include the driver code.

5. The resonant converter control method according to claim 4, characterized in that, The step of determining the driving code based on the switching sequence and the switching modulation coding includes: The first driving code is determined based on the first switching sequence and the first modulation code in the first control cycle; The second driving code is determined based on the second switching sequence and the first modulation code in the second control cycle, and the second control cycle is after the first control cycle.

6. The resonant converter control method according to claim 5, characterized in that, The step of determining the second driving code based on the second switching sequence in the second control cycle and the first modulation code includes: The first modulation code is encoded in reverse order of the second switching sequence to determine the second driving code.

7. The resonant converter control method according to claim 1 or 2, characterized in that, The submodule includes a bypass circuit for controlling whether the submodule is connected in series with the MMC circuit. The MMC circuit includes at least one spare submodule. The method further includes: Obtain the fault detection results of each of the sub-modules; The faulty submodule is determined based on the fault detection results; The bypass module of the faulty submodule is controlled to disconnect the faulty submodule, and the backup submodule is controlled to connect to the MMC circuit to replace the faulty submodule.

8. A resonant converter control device, characterized in that, include: The acquisition module is used to acquire the input voltage at the input terminal of the auxiliary converter; The processing module is used to determine the number K of the series sub-modules and the number M of the switching sub-modules based on the input voltage. The series sub-modules are sub-modules that are continuously connected in series to the MMC circuit. The series sub-modules are used to control the maximum value of the fundamental inverter voltage generated by the resonant converter. The processing module is further configured to determine control parameters based on the quantity K, the quantity M, and the input voltage; The processing module is also used to control the working state of the switching submodule in the MMC circuit according to the control parameters, and to control the serial submodule to be connected in the MMC circuit. The working state includes the input state and the cut-off state.

9. An electronic device, characterized in that, include: processor; as well as, Memory for storing the computer program of the processor; The processor is configured to execute the resonant converter control method according to any one of claims 1 to 7 by executing the computer program.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the resonant converter control method according to any one of claims 1 to 7.

11. A computer program product, comprising a computer program, characterized in that, When executed by a processor, the computer program implements the resonant converter control method according to any one of claims 1 to 7.

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