Power transmission systems, control methods, equipment and media

Abstract

This application discloses a power transmission system, control method, equipment, and medium. The power transmission system includes: a DC bus, comprising a first DC bus, a second DC bus, and a medium-voltage DC bus, the medium-voltage DC bus being electrically connected to a reference voltage terminal; a first grid-commutated converter and a second grid-commutated converter, the first grid-commutated converter and the second grid-commutated converter being connected in series between the first DC bus and the second DC bus; both the first grid-commutated converter and the second grid-commutated converter are used to transmit power to a first AC grid; a first DC transformer and a second DC transformer, the first DC transformer and the second DC transformer being connected in series between the first DC bus and the second DC bus; the nodes between the medium-voltage DC bus and the first grid-commutated converter and the second grid-commutated converter, as well as the nodes between the first DC transformer and the second DC transformer, are electrically connected. This method can reduce power loss.

Description

Technical Field

[0001] This application belongs to the field of power transmission technology, and in particular relates to a power transmission system, control method, equipment and medium. Background Technology

[0002] High Voltage Direct Current (HVDC) transmission technology has become one of the important transmission methods in modern power systems due to its low loss, high stability, and flexible current control capabilities. To utilize HVDC-enabled DC grids, they need to be integrated into AC grids. Traditionally, integrating a DC grid into an AC grid requires building an AC substation and using a Modular Multilevel Converter (MMC) as the converter to achieve this integration.

[0003] However, MMC and its supporting equipment require a large amount of land, making them difficult to deploy in areas with scarce land resources, such as cities. At the same time, the above solutions require the connection of DC power grid, AC substation, multi-stage transformers, and AC power grid, resulting in significant energy loss during multiple conversion processes. Summary of the Invention

[0004] This application provides a power transmission system, control method, equipment, and medium that can improve power utilization.

[0005] In a first aspect, embodiments of this application provide a power transmission system, including: The DC bus includes a first DC bus, a second DC bus, and a medium-voltage DC bus. The medium-voltage DC bus is electrically connected to the reference voltage terminal. One of the first DC bus and the second DC bus is a positive DC bus, and the other is a negative DC bus. The first grid phase-commutation converter and the second grid phase-commutation converter are connected in series between the first DC bus and the second DC bus; both the first grid phase-commutation converter and the second grid phase-commutation converter are used to transmit power to the first AC grid. The first DC transformer and the second DC transformer are connected in series between the first DC bus and the second DC bus. Both the first DC transformer and the second DC transformer are used to output DC power to the load. Among them, the nodes between the medium-voltage DC bus and the first grid phase converter and the second grid phase converter, as well as the nodes between the first DC transformer and the second DC transformer, are electrically connected.

[0006] Secondly, embodiments of this application provide a control method for a power transmission system, including: When the power transmission system is in operation, the first current on the DC side of the first grid commutator and the second current on the DC side of the second grid commutator are obtained. If the target current in the first current and the second current is greater than or equal to a preset value, the target grid commutator corresponding to the target current is determined to be in the target state, and the parameters of the non-target grid commutator are adjusted to reduce the DC current of the non-target grid commutator to the reference current, and to control the output power of the non-target grid commutator to the preset power; the non-target grid commutator is the grid commutator other than the target grid commutator in the first grid commutator and the second grid commutator. Simultaneously reduce the internal potential of the target DC transformer corresponding to the target grid commutator to increase the output power of the target DC transformer.

[0007] Thirdly, embodiments of this application provide a control device for a power transmission system, comprising: Control unit, used for: When the power transmission system is in operation, the first current on the DC side of the first grid commutator and the second current on the DC side of the second grid commutator are obtained. If the target current in the first current and the second current is greater than or equal to a preset value, the target grid commutator corresponding to the target current is determined to be in the target state, and the parameters of the non-target grid commutator are adjusted to reduce the DC current of the non-target grid commutator to the reference current, and to control the output power of the non-target grid commutator to the preset power; the non-target grid commutator is the grid commutator other than the target grid commutator in the first grid commutator and the second grid commutator. Simultaneously reduce the internal potential of the target DC transformer corresponding to the target grid commutator to increase the output power of the target DC transformer.

[0008] Fourthly, embodiments of this application provide an electronic device, the device comprising: Processor and memory storing computer program instructions; The processor executes computer program instructions to perform the control method of the power transmission system described in the second aspect above.

[0009] Fifthly, embodiments of this application provide a computer storage medium storing computer program instructions, which, when executed by a processor, implement the control method for the power transmission system described in the second aspect.

[0010] In a sixth aspect, embodiments of this application provide a computer program product, including a computer program that, when processed by a processor, implements the control method for the power transmission system described in the second aspect.

[0011] The power transmission system, control method, equipment, medium, and products provided in this application can achieve direct grid connection between high-voltage DC power grids and AC power grids, reducing multi-stage energy conversion and improving energy utilization. Simultaneously, it can directly output usable DC power to users, providing better power supply. Furthermore, this power transmission system decouples the DC power supply system from the AC power supply system, preventing them from interfering with each other and improving power supply stability. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of a power transmission system provided for some embodiments of this application.

[0014] Figure 2 This is a schematic diagram of another power transmission system provided for some embodiments of this application.

[0015] Figure 3 This is a flowchart illustrating a control method for a power transmission system provided in some embodiments of this application.

[0016] Figure 4 This is a schematic diagram of a control device for a power transmission system provided in some embodiments of this application.

[0017] Figure 5 This is a schematic diagram of the hardware structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0018] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.

[0019] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0020] Before describing the technical solutions provided in the embodiments of this application, in order to facilitate understanding of the embodiments of this application, this application first specifically explains the problems existing in the related technologies: In the process of connecting high-voltage direct current (HVDC) transmission systems to urban AC or DC power grids, traditional AC grid connection technologies rely on a complex energy conversion path involving HVDC, high-voltage AC, multi-stage transformers, and medium-voltage AC; while traditional DC grid connection relies on an energy conversion path involving HVDC, high-voltage AC, medium-voltage AC, and medium-voltage DC. Both conversion paths suffer from significant energy losses due to their multi-stage transformation architecture.

[0021] At the same time, the two conversion paths affect each other, resulting in low power transmission stability.

[0022] Based on this, embodiments of this application provide a power transmission system, control method, device, medium, and product that can solve the above-mentioned problems. The power transmission system provided in this application embodiment will be described in detail below.

[0023] In some embodiments, such as Figure 1 As shown, this application provides a power transmission system, including: The DC bus includes a first DC bus 101, a second DC bus 102 and a medium-voltage DC bus 103. The medium-voltage DC bus 103 is electrically connected to the reference voltage terminal GND. One of the first DC bus 101 and the second DC bus 102 is a positive DC bus and the other is a negative DC bus. The first grid phase-commutation converter 10 and the second grid phase-commutation converter 20 are connected in series between the first DC bus 101 and the second DC bus 102; both the first grid phase-commutation converter 10 and the second grid phase-commutation converter 20 are used to transmit power to the first AC grid. The first DC transformer 30 and the second DC transformer 40 are connected in series between the first DC bus 101 and the second DC bus 102. Both the first DC transformer 30 and the second DC transformer 40 are used to output DC power to the load. The nodes between the medium-voltage DC bus 103 and the first grid phase converter 10 and the second grid phase converter 20, as well as the nodes between the first DC transformer 30 and the second DC transformer 40, are electrically connected.

[0024] The aforementioned line commutated converter (LCC) is a device capable of converting DC power into high-voltage AC power. It can stably clamp the voltage of the high-voltage DC bus to its rated value, thereby enabling power transmission to the first AC power grid. It is conceivable that the first line commutated converter 10 and the second line commutated converter 20 can be connected to the same first AC power grid, or they can be connected to first AC power grids with different voltages.

[0025] The aforementioned Direct Current Transformer (DCT) is capable of providing a stable DC power to the load. Its output power, which directly supplies DC power to the load, can be adjusted by modifying parameters such as the voltage turns ratio. This DC transformer is an isolation transformer and can specifically include dual active bridge DC transformers, resonant modular multilevel converters (MMC), face-to-face MMC, flexible converters, etc.

[0026] In some examples, the aforementioned DC transformer can be a dual active bridge DC transformer, which enables millisecond-level fast response. That is, when a power transmission system including this DC transformer determines that the grid commutation converter has failed, it can quickly redistribute the output power by controlling parameters such as the switching frequency and phase shift angle range of the dual active bridge DC transformer.

[0027] In some examples, the aforementioned load may include devices that can start and output DC power based on a medium-voltage AC power grid, such as charging piles in the city or solid-state transformers (SSTs); at the same time, the aforementioned load may be devices that output AC power based on DC power, such as direct current / alternating current converters (DC / AC).

[0028] It is conceivable that, when the aforementioned DC transmission system is in operation, to prevent excessive current from being generated on the medium-voltage DC bus 103 and causing system failure, the output power of the first grid-commutated converter 10 and the second grid-commutated converter 20 can be controlled to be the same. Similarly, the output power of the first DC transformer 30 and the second DC transformer 40 can be the same. That is, when the DC transmission system is in operation, the output power of the first grid-commutated converter 10 and the second grid-commutated converter 20 can be monitored in real time, and their parameters, such as adjusting their firing angle parameters, can be adjusted to make their output power the same. Similarly, the output power of the first DC transformer 30 and the second DC transformer 40 can be monitored in real time, and their parameters, such as adjusting their switching frequency and phase shift angle range, can be adjusted to make their output power the same.

[0029] In some embodiments, the aforementioned DC transformer can be installed in cities, for example, to provide stable DC or AC power to urban users, while the grid-commutated converter, due to the large size of its related equipment, can be installed in suburban areas with abundant land resources.

[0030] The first DC bus 101 and the second DC bus 102 mentioned above are either positive DC buses or negative DC buses. For example, if the first DC bus 101 is a positive DC bus, then the second DC bus 102 is a negative DC bus; or if the first DC bus 101 is a negative DC bus, then the second DC bus 102 is a positive DC bus.

[0031] This embodiment of the application, by setting up the aforementioned power transmission system, enables direct grid connection between the high-voltage DC power grid and the AC power grid, reducing multi-stage energy conversion and improving energy utilization. Simultaneously, it can output usable DC power to users, providing better power supply. Furthermore, this power transmission system decouples the DC power supply system from the AC power supply system, preventing them from interfering with each other and improving power supply stability.

[0032] It is conceivable that in existing technologies, high-voltage direct current (HVDC) grids need to output DC power to users through transmission paths of high-voltage DC, high-voltage AC, medium-voltage AC, and medium-voltage DC, resulting in multi-stage energy conversion and significant losses. Therefore, embodiments of this application provide, as follows: Figure 2 Another power transmission system shown, such as Figure 2 As shown, the load includes a DC-AC converter 50 and a solid-state transformer 60. The DC-AC converter 50 is electrically connected to the first DC transformer 30, and the solid-state transformer 60 is electrically connected to the second DC transformer 40. The DC-AC converter 50 is used to convert the DC power output from the first DC transformer 30 into AC power and input AC power into the second AC power grid.

[0033] Here, based on the different loads mentioned above, the power transmission system includes two power transmission paths: the first is a DC-to-AC transmission path via the first DC transformer 30, the DC-AC converter 50, and the second AC power grid; the second is a DC transmission path via the second DC transformer 40 and the solid-state transformer 60. This is to meet the differentiated power needs of different users.

[0034] In some examples, when the aforementioned power transmission system is in operation, the parameters of the DC-AC converter 50 and the solid-state transformer 60 can be controlled separately to make their output power the same.

[0035] This application embodiment, by setting the load to include a DC-AC converter and a solid-state transformer, avoids the energy loss caused by the need for multi-stage energy conversion in the prior art, thereby improving energy utilization. Simultaneously, it enables the output of usable AC power from the DC-AC converter and usable DC power from the solid-state transformer, meeting the differentiated electricity needs of different users.

[0036] In some embodiments, such as Figure 2 As shown, the DC-AC converter 50 includes at least two DC-AC converters 50, which are connected in parallel between the first DC transformer 30 and the second AC power grid.

[0037] like Figure 2 In this configuration, at least two DC-AC converters 50 can be electrically connected to the same second AC power grid and supply power to the same AC power grid; or, at least two DC-AC converters 50 can be connected to different second AC power grids and can supply power to different second AC power grids respectively.

[0038] This application embodiment, by setting a DC-AC converter including at least two DC-AC converters, can adapt to the diverse output of the power system. At the same time, in the event of a failure of any one DC-AC converter, the stable operation of the entire power transmission system can be achieved by adjusting the output power of the other DC-AC converters.

[0039] In some embodiments, the DC transformer is a dual active bridge DC transformer.

[0040] The output power of the dual active bridge DC transformer can be controlled by adjusting the phase shift angle. Furthermore, this dual active bridge DC transformer has a fast response speed, which can suppress power fluctuations in the grid commutation converter and improve the power supply stability of the transmission system.

[0041] In some embodiments, such as Figure 3 As shown in the figure, this application provides a control method for a power transmission system, which may include: S310: When the power transmission system is in operation, obtain the first current on the DC side of the first grid phase converter and the second current on the DC side of the second grid phase converter.

[0042] The first and second currents can be collected in real time using sensors.

[0043] S320: If the target current in the first current and the second current is determined to be greater than or equal to a preset value, the target grid phase-commutation converter corresponding to the target current is determined to be in the target state, and the parameters of the non-target grid phase-commutation converter are adjusted to reduce the DC side current of the non-target grid phase-commutation converter to the reference current, and the output power of the non-target grid phase-commutation converter is controlled to the preset power; the non-target grid phase-commutation converter is the grid phase-commutation converter other than the target grid phase-commutation converter in the first grid phase-commutation converter and the second grid phase-commutation converter.

[0044] If the target current is determined to be greater than or equal to a preset value, it can be determined that the target grid commutator corresponding to the target current is in a commutation failure fault state. In this case, the parameters of the non-target grid commutator can be adjusted with the goal of reducing the DC-side current of the non-target grid commutator to the reference current and the output power of the non-target grid commutator. For example, as shown in... Figure 1 Taking the power transmission system shown as an example, if it is determined that the first current is greater than or equal to the preset value, it can be determined that the first grid commutation converter is in a commutation failure fault state. The parameters of the second grid commutation converter, such as the firing angle, can be adjusted to reduce the DC side current to the reference current and reduce its output power to the reference power.

[0045] As can be expected, all output power discussed in this article refers to active power.

[0046] S330: Synchronously reduce the internal potential of the target DC transformer corresponding to the target grid commutator to increase the output power of the target DC transformer.

[0047] It is conceivable that when the DC current of the target grid commutator corresponding to the aforementioned target current surges, the voltage of the DC bus electrically connected to it will drop sharply, thereby reducing the internal potential of the target DC transformer corresponding to the target grid commutator. Here, the internal potential can be reduced by adjusting parameters such as the modulation ratio, phase offset, and virtual impedance in the target grid commutator. In some examples, continuing with the example of the first current being greater than or equal to a preset value, the internal potential of the first DC transformer can be reduced simultaneously. Furthermore, the current absorbed by the first DC transformer can be discharged by increasing the output power of the load electrically connected to the first DC transformer.

[0048] This embodiment of the application monitors the first current on the DC side of the first grid-commutated converter and the second current on the DC side of the second grid-commutated converter in real time when the power transmission system is in operation. When the target current is determined to be greater than or equal to a preset value, the parameters of the non-target grid-commutated converter are adjusted to reduce its DC-side current and output power, thereby protecting the non-target grid-commutated converter. Simultaneously, the internal potential of the target DC transformer is reduced, allowing some current to be discharged to the DC transformer, preventing power transmission system current overload.

[0049] In some embodiments, after simultaneously reducing the internal potential of the target DC transformer corresponding to the target grid commutator to increase the output power of the target DC transformer, the control method further includes: The output power of the target DC transformer is determined as the output power reference value, and the parameters of the non-target DC transformer are adjusted to increase the output power of the target DC transformer to the output power reference value. The non-target DC transformer is the DC transformer other than the target DC transformer among the first DC transformer and the second DC transformer.

[0050] It is conceivable that while reducing the internal potential of the target DC transformer, its output power will increase. To ensure the current stability of the medium-voltage DC bus, the parameters of the non-target DC transformer are further improved to increase the output power of the target DC transformer to the reference value of the target DC transformer's output power. In some examples, continuing to take the target DC transformer as the first DC transformer, the output power of the first DC transformer can be determined as the output power reference value, and the parameters of the second DC transformer are adjusted to increase the output power of the second DC transformer to the aforementioned output power reference value.

[0051] This application embodiment increases the output power of the non-target DC transformer by synchronously adjusting its parameters, so that its output power is balanced with that of the target DC transformer. This can minimize the current value of the medium-voltage DC bus and maintain the stability of the power transmission system.

[0052] In some embodiments, the control method described above may further include: Adjust the output power of the load electrically connected to the target DC transformer to the output power reference value.

[0053] It is conceivable that as the output power of the target DC transformer increases, the output power of the load electrically connected to the target DC transformer can be adjusted to the reference value of the output power, so that the target DC transformer and the load can cooperate synchronously to discharge power.

[0054] In some embodiments, the load includes a DC-AC converter and a solid-state transformer. The DC-AC converter is electrically connected to a first DC transformer, and the solid-state transformer is electrically connected to a second DC transformer. The DC-AC converter is used to convert the DC power output from the first DC transformer into AC power and input AC power into a second AC power grid. The control method further includes: Obtain the voltage value of the medium-voltage DC bus when the power transmission system is in operation; When the voltage value is less than or equal to the preset voltage value, it indicates that the output power of the solid-state transformer increases. The parameters of the DC-AC converter are adjusted to control the voltage of the medium-voltage DC bus to the rated voltage value.

[0055] When the power transmission system is in operation, the voltage value of the medium-voltage DC bus can be monitored in real time. If the voltage value is less than or equal to the preset voltage value, it indicates a sudden increase in the output power of the solid-state transformer, meaning that the power of the medium-voltage DC bus is insufficient. The power of the medium-voltage DC bus can be compensated by adjusting the parameters of the DC-AC converter. For example, the parameters of the DC-AC converter can be adjusted to reduce the output power fed into the second AC grid. Furthermore, the parameters of the DC-AC converter can be adjusted to reverse the power flow and draw power from the second AC grid to feed into the medium-voltage DC bus.

[0056] This application embodiment achieves stable voltage control of the medium-voltage DC bus by adjusting the parameters of the DC-AC converter when the voltage of the medium-voltage DC bus is determined to be less than or equal to a preset voltage value, thereby controlling the voltage of the medium-voltage DC bus to the rated voltage value, which is beneficial to the stable operation of the power transmission system.

[0057] Based on the same inventive concept, embodiments of this application also provide a control device for a power transmission system.

[0058] In some embodiments, such as Figure 4 As shown in the figure, this application provides a control device for a power transmission system, which may include: Control unit, used for: When the power transmission system is in operation, the first current on the DC side of the first grid commutator and the second current on the DC side of the second grid commutator are obtained. If the target current in the first current and the second current is greater than or equal to a preset value, the target grid commutator corresponding to the target current is determined to be in the target state, and the parameters of the non-target grid commutator are adjusted to reduce the DC current of the non-target grid commutator to the reference current, and to control the output power of the non-target grid commutator to the preset power; the non-target grid commutator is the grid commutator other than the target grid commutator in the first grid commutator and the second grid commutator. Simultaneously reduce the internal potential of the target DC transformer corresponding to the target grid commutator to increase the output power of the target DC transformer.

[0059] This embodiment of the application, through a control unit, monitors in real time the first current on the DC side of the first grid-commutated converter and the second current on the DC side of the second grid-commutated converter when the power transmission system is in operation. When the target current is determined to be greater than or equal to a preset value, the parameters of the non-target grid-commutated converter are adjusted to reduce its DC-side current and output power, thus protecting the non-target grid-commutated converter. Simultaneously, the internal potential of the target DC transformer is reduced, allowing some current to be discharged to the DC transformer, preventing power transmission system current overload.

[0060] In some embodiments, the control unit is further configured to: The output power of the target DC transformer is determined as the output power reference value, and the parameters of the non-target DC transformer are adjusted to increase the output power of the target DC transformer to the output power reference value. The non-target DC transformer is the DC transformer other than the target DC transformer among the first DC transformer and the second DC transformer.

[0061] In some embodiments, the control unit is further configured to: Adjust the output power of the load electrically connected to the target DC transformer to the output power reference value.

[0062] In some embodiments, the load includes a DC-AC converter and a solid-state transformer, the DC-AC converter being electrically connected to a first DC transformer, and the solid-state transformer being electrically connected to a second DC transformer. The DC-AC converter is used to convert the DC power output from the first DC transformer into AC power and input AC power into a second AC power grid; the control unit is further used to: Obtain the voltage value of the medium-voltage DC bus when the power transmission system is in operation; When the voltage value is less than or equal to the preset voltage value, it indicates that the output power of the solid-state transformer increases. The parameters of the DC-AC converter are adjusted to control the voltage of the medium-voltage DC bus to the rated voltage value.

[0063] The apparatus of the above embodiments is used to implement the control method of the corresponding power transmission system in any of the foregoing embodiments, and has the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0064] Figure 5 A schematic diagram of the hardware structure of an electronic device is provided in the application embodiment.

[0065] The electronic device 500 may include a processor 501 and a memory 502 storing computer program instructions.

[0066] Specifically, the processor 501 may include a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits that can be configured to implement the embodiments of this application.

[0067] Memory 502 may include mass storage for data or instructions. For example, and not limitingly, memory 502 may include a hard disk drive (HDD), floppy disk drive, flash memory, optical disk, magneto-optical disk, magnetic tape, or Universal Serial Bus (USB) drive, or a combination of two or more of these. Where appropriate, memory 502 may include removable or non-removable (or fixed) media. Where appropriate, memory 502 may be internal or external to the integrated gateway disaster recovery device. In a particular embodiment, memory 502 is non-volatile solid-state memory.

[0068] In a particular embodiment, memory 502 includes read-only memory (ROM). Where appropriate, the ROM may be a mask-programmed ROM, a programmable ROM (PROM), an erasable PROM (EPROM), an electrically erasable PROM (EEPROM), an electrically rewritable ROM (EAROM), or flash memory, or a combination of two or more of these.

[0069] Memory may include read-only memory (ROM), random access memory (RAM), disk storage media devices, optical storage media devices, flash memory devices, and electrical, optical, or other physical / tangible memory storage devices. Therefore, typically, memory includes one or more tangible (non-transitory) computer-readable storage media (e.g., memory devices) encoded with software including computer-executable instructions, and when the software is executed (e.g., by one or more processors), it is operable to perform the operations described with reference to the method according to the first aspect of this application.

[0070] The processor 501 reads and executes computer program instructions stored in the memory 502 to implement any of the power transmission system control methods in the above embodiments.

[0071] In one example, the electronic device may also include a communication interface 503 and a bus 504. Wherein, as... Figure 5 The processor 501, memory 502, and communication interface 503 are connected through bus 504 and complete communication with each other.

[0072] The communication interface 503 is mainly used to realize communication between various modules, devices, units and / or equipment in the embodiments of this application.

[0073] Bus 504 includes hardware, software, or both, that couples components of an online data traffic metering device together. For example, and not limitingly, the bus may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a Front Side Bus (FSB), HyperTransport (HT) interconnect, an Industry Standard Architecture (ISA) bus, an Infinite Bandwidth Interconnect, a Low Pin Count (LPC) bus, a memory bus, a Microchannel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCI-X) bus, a Serial Advanced Technology Attachment (SATA) bus, a Video Electronics Standards Association Local (VLB) bus, or other suitable buses, or combinations of two or more of these. Where appropriate, bus 504 may include one or more buses. Although specific buses are described and illustrated in embodiments of this application, any suitable bus or interconnect is contemplated herein.

[0074] The electronic devices described above are used to implement the control methods of the corresponding power transmission systems in any of the foregoing embodiments, and have the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0075] Furthermore, in conjunction with the power transmission system control methods in the above embodiments, this application embodiment can provide a computer storage medium for implementation. This computer storage medium stores computer program instructions; when these computer program instructions are executed by a processor, they implement any of the power transmission system control methods in the above embodiments.

[0076] Furthermore, in conjunction with the power transmission system control methods described in the above embodiments, this application can provide a computer program product for implementation. When the instructions of this computer program product are executed by the processor of an electronic device, they implement any of the power transmission system control methods described in the above embodiments.

[0077] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of this application (including the claims) is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the embodiments of this application as described above, which are not provided in the details for the sake of brevity.

[0078] The functional blocks shown in the above-described structural diagram can be implemented as hardware, software, firmware, or a combination thereof. When implemented in hardware, they can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this application are programs or code segments used to perform the required tasks. Programs or code segments can be stored on a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried on a carrier wave. "Machine-readable medium" can include any medium capable of storing or transmitting information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, radio frequency (RF) links, etc. Code segments can be downloaded via computer networks such as the Internet, intranets, etc.

[0079] It should also be noted that the exemplary embodiments mentioned in this application describe methods or apparatuses based on a series of steps or devices. However, this application is not limited to the order of the above steps; that is, the steps can be performed in the order mentioned in the embodiments, or in a different order, or several steps can be performed simultaneously.

[0080] The aspects of this application have been described above with reference to flowchart illustrations and / or block diagrams of methods, apparatus (devices), and computer program products according to embodiments of this application. It should be understood that each block in the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine such that these instructions, executable via the processor of the computer or other programmable data processing apparatus, enable the implementation of the functions / actions specified in one or more blocks of the flowchart illustrations and / or block diagrams. Such a processor can be, but is not limited to, a general-purpose processor, a special-purpose processor, a special application processor, or a field-programmable logic circuit. It is also understood that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can also be implemented by dedicated hardware performing the specified functions or actions, or can be implemented by a combination of dedicated hardware and computer instructions.

[0081] The above description is merely a specific embodiment of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the devices, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A power transmission system, characterized in that, include: The DC bus includes a first DC bus, a second DC bus, and a medium-voltage DC bus. The medium-voltage DC bus is electrically connected to the reference voltage terminal. One of the first DC bus and the second DC bus is a positive DC bus, and the other is a negative DC bus. A first grid-commutated converter and a second grid-commutated converter are connected in series between the first DC bus and the second DC bus; both the first grid-commutated converter and the second grid-commutated converter are used to transmit power to the first AC grid. A first DC transformer and a second DC transformer are connected in series between the first DC bus and the second DC bus. Both the first DC transformer and the second DC transformer are used to output DC power to the load. The medium-voltage DC bus is electrically connected to the nodes between the first grid phase converter and the second grid phase converter, as well as to the nodes between the first DC transformer and the second DC transformer.

2. The power transmission system according to claim 1, characterized in that, The load includes a DC-AC converter and a solid-state transformer. The DC-AC converter is electrically connected to the first DC transformer, and the solid-state transformer is electrically connected to the second DC transformer. The DC-AC converter is used to convert the DC power output from the first DC transformer into AC power and input the AC power into the second AC power grid.

3. The power transmission system according to claim 2, characterized in that, The DC-AC converter includes at least two DC-AC converters, which are connected in parallel between the first DC transformer and the second AC power grid.

4. The power transmission system according to any one of claims 1-3, characterized in that, The DC transformer is a dual active bridge DC transformer.

5. A control method for a power transmission system, characterized in that, The control method, applied to the power transmission system according to any one of claims 1-4, comprises: When the power transmission system is in operation, the first current on the DC side of the first grid commutator and the second current on the DC side of the second grid commutator are obtained. If the target current in the first current and the second current is determined to be greater than or equal to a preset value, the target grid phase-commutation converter corresponding to the target current is determined to be in the target state, and the parameters of the non-target grid phase-commutation converter are adjusted to reduce the DC-side current of the non-target grid phase-commutation converter to a reference current, and to control the output power of the non-target grid phase-commutation converter to a preset power; the non-target grid phase-commutation converter is the grid phase-commutation converter other than the target grid phase-commutation converter in the first grid phase-commutation converter and the second grid phase-commutation converter. The internal potential of the target DC transformer corresponding to the target grid phase converter is reduced simultaneously to increase the output power of the target DC transformer.

6. The control method for a power transmission system according to claim 5, characterized in that, After simultaneously reducing the internal potential of the target DC transformer corresponding to the target grid commutator to increase the output power of the target DC transformer, the control method further includes: The output power of the target DC transformer is determined as the output power reference value, and the parameters of the non-target DC transformer are adjusted to increase the output power of the target DC transformer to the output power reference value. The non-target DC transformer is the DC transformer other than the target DC transformer among the first DC transformer and the second DC transformer.

7. The control method for a power transmission system according to claim 6, characterized in that, Also includes: Adjust the output power of the load electrically connected to the target DC transformer to the output power reference value.

8. The control method for a power transmission system according to any one of claims 5-7, characterized in that, The load includes a DC-AC converter and a solid-state transformer. The DC-AC converter is electrically connected to the first DC transformer, and the solid-state transformer is electrically connected to the second DC transformer. The DC-AC converter is used to convert the DC power output from the first DC transformer into AC power and input the AC power into a second AC power grid. The control method further includes: When the power transmission system is in operation, the voltage value of the medium-voltage DC bus is obtained; When the voltage value is less than or equal to the preset voltage value, it indicates that the output power of the solid-state transformer has increased. The parameters of the DC-AC converter are adjusted to control the voltage of the medium-voltage DC bus to the rated voltage value.

9. An electronic device, characterized in that, The device includes: a processor, and a memory storing computer program instructions; The processor reads and executes the computer program instructions to implement the control method of the power transmission system as described in any one of claims 5 to 8.

10. A readable storage medium, characterized in that, The readable storage medium stores computer program instructions, which, when executed by a processor, implement the control method for the power transmission system as described in any one of claims 5 to 8.

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