A sea wind power transmission system control method, device and medium based on SLCC

Abstract

The application discloses a kind of based on SLCC's sea wind power transmission system control method, equipment, medium, it is related to offshore wind power system control technical field, method includes: constructing based on SLCC's sea wind power transmission system topology, establishes the active power balance relationship under the multi-source wind power collection scene, set maintaining near and far sea alternating current connection transformer branch of the interactive active power is zero control target, to isolate nearshore wind farm and far sea wind farm power coupling;The bottom SVG reactive power and harmonic self-control model of SLCC converter station is constructed, real-time compensation LCC conversion generated dynamic reactive power and the reactive power of far sea wind farm, and to the characteristic subharmonic current generated by LCC is self-inversion cancellation;The upper layer LCC active power follow-up control model of SLCC converter station is constructed, with the instantaneous output active power of far sea wind farm as LCC power instruction tracking value, dynamic rectification LCC rectification side trigger angle, cooperates the SVG self-compensation characteristic of bottom.

Description

Technical Field

[0001] This invention relates to the field of offshore wind power system control technology, and in particular to a control method, equipment, and medium for an offshore wind power transmission system based on SLCC. Background Technology

[0002] As the global energy structure shifts towards cleaner and lower-carbon energy, offshore wind power development is accelerating towards deep-sea and large-scale cluster development. Due to the long distances offshore and large individual installed capacities of deep-sea wind farms, high-voltage direct current (HVDC) transmission technology has become the mainstream technology for power transmission. In scenarios involving the coordinated development of near-shore and offshore wind power, the transmitting end typically uses an offshore converter platform as the power collection point. At this point, offshore space resources and load-bearing conditions face extremely stringent physical constraints.

[0003] Currently, while conventional grid-commutated converters (LCCs) are technically mature and cost-controllable for large-capacity power transmission, their operation heavily relies on AC voltage commutation at the receiving or sending end of the grid. Furthermore, they consume significant reactive power and generate predominantly secondary characteristic harmonics during both steady-state and transient processes. To meet grid connection standards for reactive power balance and harmonic filtering, LCC converter stations must be equipped with bulky AC passive filter banks and reactive power compensation devices. This significantly increases the size and structural weight of offshore converter platforms, leading to a substantial rise in engineering costs. On the other hand, while modular multilevel converters (MMCs) based on fully controlled devices can eliminate the dependence on AC passive filters and provide independent active and reactive power control capabilities, the high manufacturing cost of converter valves and switching losses during operation make them economically disadvantageous in scenarios involving massive power transmission.

[0004] Furthermore, in the operating condition where near-shore and offshore wind power share a transmission channel, near-shore AC wind power and offshore DC wind power form a strong coupling at the converter bus. The inherent random fluctuations in wind power can lead to drastic power flow shifts in the transmission channel. If the traditional LCC constant DC current or constant active power control strategy is used, sudden changes in offshore power will force active power flow to be drawn or injected through the interconnecting transformer to the near-shore AC network, which can easily cause power overload and converter bus voltage instability in the near-shore AC transmission channel. Addressing the dual technical bottlenecks of "limited space on offshore platforms" and "strong coupling of near-shore and offshore multi-source wind power," the existing technology system lacks a control strategy for offshore wind power transmission systems based on SLCC (self-adaptation statcom and line commutation converter) that can achieve both equipment compactness and decoupled collaborative control of multi-source power fluctuations. Summary of the Invention

[0005] This invention provides a control method, device, and medium for an offshore wind power transmission system based on SLCC, which solves the problem of transient steady-state control stability caused by physical space constraints and strong coupling of multiple power sources when traditional systems aggregate multi-source offshore wind power.

[0006] On one hand, the present invention provides a control method for an offshore wind power transmission system based on SLCC, the method comprising the following steps: Step S1: Construct the topology of the offshore wind power transmission system based on SLCC. The topology consists of near-shore wind farms, offshore wind farms, near-shore and offshore AC interconnection transformers, and SLCC converter stations. Step S2: Establish the active power balance relationship in the multi-source wind power aggregation scenario, and set a control target to keep the interactive active power of the branch where the near-shore and offshore AC interconnection transformer is located at zero, so as to isolate the power coupling between the near-shore wind farm and the offshore wind farm. Step S3: Construct the underlying SVG (static var generator) reactive power and harmonic self-regulating control model of the SLCC converter station, compensate the dynamic reactive power generated by the LCC converter and the reactive power of the offshore wind farm in real time, and perform self-inversion cancellation on the characteristic subharmonic current generated by the LCC. Step S4: Construct the upper-level LCC active power following control model of the SLCC converter station, using the instantaneous output active power of the offshore wind farm as the power command tracking value of the LCC, dynamically correct the rectifier side firing angle of the LCC, and coordinate with the self-compensation characteristics of the underlying SVG to realize the coordination of the physical interface and the decoupling of the control logic of near-shore and offshore wind power transmission.

[0007] In one implementation of the present invention, the active power balance relationship in step S2 satisfies the following constraint equation:

[0008] in: The active power output of the offshore wind farm; The active power transmitted from the coastal branch to the onshore power grid; The interactive active power of the near-shore and offshore AC interconnection transformer branches; when the control target is set to make When, satisfy This means that the power from offshore wind farms is transmitted only through offshore AC channels.

[0009] In one implementation of the present invention, in step S3, the underlying SVG reactive power and harmonic self-regulating control model adopts a vector control strategy based on grid voltage orientation; in the dq rotating coordinate system, the SVG reactive current command is generated through the reactive power outer loop, and its relationship is as follows:

[0010] in: This is the reactive current command value for the SVG on the q-axis. The proportional parameter of the reactive power PI controller; These are the integral parameters of the reactive PI controller; For the Laplace operator; This is a reactive power reference value, and is based on the settings. To achieve non-exchange of reactive power; This represents the actual reactive power of the system.

[0011] In one implementation of the present invention, in step S3, the LCC generated... Subharmonics are compensated using a specific subharmonic compensation strategy in SVG. A control equation incorporating a proportional resonant controller is introduced to perform zero steady-state error tracking of a specific frequency signal. The transfer function of this proportional resonant controller is as follows:

[0012] in: Let be the transfer function of the proportional resonant controller; For proportional gain; This is the resonant gain; Cutoff frequency; For the set number The resonant angular frequency controlled by a specific order harmonic; the final modulated wave output by the SVG is composed of the superposition of the fundamental component and the harmonic compensation component.

[0013] In one implementation of the present invention, in step S4, the upper-level LCC active power following control model calculates the actual active power absorbed by the SLCC using instantaneous power theory; the three-phase voltage of the converter bus and the current on the converter transformer side are converted by Clark to... After establishing a stationary coordinate system, the relationship for instantaneous active power is as follows:

[0014] in: This represents the instantaneous active power actually absorbed by the SLCC. and The converter bus voltage is respectively at shaft and Components on the axis; and The converter transformer side currents are respectively at shaft and Components on the axis.

[0015] In one implementation of the present invention, in step S4, the controller outputs the active power of the offshore wind farm instantaneously. The power command value for the LCC is used as the input to dynamically correct the rectifier-side firing angle. The correction formula is as follows:

[0016] in: The real-time rectifier-side firing angle for the LCC; This is the reference value for the firing angle under the rated operating conditions of the LCC; These are the proportional parameters of the active PI controller; These are the integral parameters of the active PI controller; This refers to the instantaneous active power output from the offshore wind farm to the converter bus. Let be the Laplace operator; through this modified relation, we can make... equal Thus maintaining interactive active power It converges to zero.

[0017] In one implementation of the present invention, in step S1, the offshore wind farm is connected to the converter bus of the SLCC converter station via a transformer, and the nearshore wind farm, after passing through the AC collection bus, has its first branch connected to the onshore power grid via a separate nearshore AC transmission channel, and its second branch connected to the converter bus of the SLCC converter station via the nearshore-offshore AC interconnection transformer; the SLCC converter station consists of a grid-commutated converter (LCC) and a static var generator (SVG), with the SVG connected in parallel to the valve side of the converter transformer of the LCC.

[0018] In one implementation of the present invention, step S4 specifically involves: using the upper-layer LCC module to implement active power following control based on instantaneous power feedback, dynamically adjusting the rectifier firing angle to match the power fluctuations of offshore wind power in real time, and ensuring that the active power interaction between near-shore and offshore systems remains at zero.

[0019] Secondly, the present invention also provides a control device for an offshore wind power transmission system based on SLCC, the device comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the aforementioned control method for an offshore wind power transmission system based on SLCC.

[0020] Finally, the present invention also provides a non-volatile computer storage medium for controlling an offshore wind power transmission system based on SLCC, which stores computer-executable instructions that are executed by a processor to implement the aforementioned control method for an offshore wind power transmission system based on SLCC.

[0021] The present invention provides a control method, equipment, and medium for an offshore wind power transmission system based on SLCC, which has the following beneficial effects: 1. Significantly reduces the footprint and investment cost of offshore converter platforms. This invention utilizes an SVG connected in parallel to the valve side of the converter transformer to implement self-regulating cancellation control of reactive power and harmonics, providing the physical basis for filterless operation of the SLCC converter station. The system eliminates the need for a large AC passive filter bank, and while retaining the low-loss characteristics of semi-controlled devices, it significantly reduces the scale of offshore platform construction.

[0022] 2. Precise logical decoupling and dynamic isolation of multi-source wind power transmission are achieved. This invention utilizes upper-level LCC active power tracking control based on instantaneous power feedback to enable real-time, adaptive tracking of transient power output fluctuations in offshore wind power. This dynamic matching mechanism strictly clamps the interactive active power of the AC interconnection line between nearshore and offshore areas near a zero reference value, effectively preventing the impact of drastic power fluctuations in offshore areas on nearshore AC transmission channels and avoiding overload risks.

[0023] 3. Improved voltage support strength and transient survivability of the sending-end weak AC system. The underlying SVG reactive power self-compensation model can locally and rapidly mitigate AC bus voltage drops induced by active power fluctuations or short-circuit faults; facing severe transient scenarios such as three-phase short circuits in offshore power grids, the system has superior transient rapid recovery capabilities compared to traditional conventional LCC transmission lines. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 A flowchart of a control method for an offshore wind power transmission system based on SLCC is provided for an embodiment of the present invention; Figure 2 A schematic diagram of the topology of a near-shore and offshore wind power co-transmission system based on SLCC is provided for an embodiment of the present invention; Figure 3 A logical architecture block diagram of the hierarchical collaborative control strategy of the SLCC system provided in an embodiment of the present invention; Figure 4The simulation waveform diagram of the active power variation characteristics of the AC tie line under the step fluctuation of wind power is provided in the embodiment of the present invention. Figure 5 This is a schematic diagram of a control device for an offshore wind power transmission system based on SLCC, provided as an embodiment of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0026] This invention provides a control method, device, and medium for an offshore wind power transmission system based on SLCC. The technical solution proposed in this invention will be described in detail below with reference to the accompanying drawings.

[0027] Figure 1 A flowchart illustrating a control method for an offshore wind power transmission system based on SLCC, provided as an embodiment of the present invention. Figure 1 As shown, the method mainly includes the following steps: Step S1: Construct the topology of the offshore wind power transmission system based on SLCC. The topology consists of near-shore wind farms, offshore wind farms, near-shore and offshore AC interconnection transformers, and SLCC converter stations. Step S2: Establish the active power balance relationship in the multi-source wind power aggregation scenario, and set a control target to keep the interactive active power of the branch where the near-shore and offshore AC interconnection transformer is located at zero, so as to isolate the power coupling between the near-shore wind farm and the offshore wind farm. Step S3: Construct the underlying SVG reactive power and harmonic self-regulating control model of the SLCC converter station, compensate the dynamic reactive power generated by the LCC converter and the reactive power of the offshore wind farm in real time, and perform self-inversion cancellation on the characteristic subharmonic current generated by the LCC. Step S4: Construct the upper-level LCC active power following control model of the SLCC converter station, using the instantaneous output active power of the offshore wind farm as the power command tracking value of the LCC, dynamically correct the rectifier side firing angle of the LCC, and coordinate with the self-compensation characteristics of the underlying SVG to realize the coordination of the physical interface and the decoupling of the control logic of near-shore and offshore wind power transmission.

[0028] Furthermore, such as Figure 2As shown, the large-scale near-shore and offshore wind power coordinated transmission system in this embodiment is physically constructed from near-shore wind farms, offshore wind farms, near-shore and offshore AC interconnection transformers, and SLCC converter stations. The offshore wind farms are connected to the converter bus of the SLCC converter station via a transformer. The near-shore wind farms, after passing through the AC collection bus, have a first branch connected to the onshore power grid via a separate near-shore AC transmission channel, and a second branch connected to the converter bus of the SLCC converter station via the near-shore and offshore AC interconnection transformer. The SLCC converter station consists of a grid-commutated converter (LCC) and a static var generator (SVG), with the SVG connected in parallel to the valve side of the LCC converter transformer.

[0029] In terms of physical connectivity, the electricity generated by the offshore wind farm is collected by the offshore booster station and then connected to the converter bus of the SLCC converter station via an AC transformer. The electricity generated by the near-shore wind farm is split through the AC collection bus (common coupling point): its first physical branch is directly connected to the onshore power grid receiving end through a separately laid near-shore AC submarine cable channel, and its second physical branch is connected to the same converter bus of the SLCC converter station through the near-shore and offshore AC interconnection transformer, providing physical support for the commutation voltage of the converter station. The hardware topology of the SLCC converter station is composed of a 12-pulse grid commutation converter (LCC) and a static var generator (SVG) connected in parallel. Its core feature is that it eliminates the AC passive filter bank required by the traditional LCC and directly connects the SVG device in parallel to the valve side of the converter transformer of the LCC device, using the controlled SVG output to offset the reactive power required by the system.

[0030] Furthermore, in step S2, a steady-state active power constraint model based on Kirchhoff's current law and the law of power conservation is established, taking into account the power aggregation characteristics at the system's converter bus. For the near-shore AC aggregation bus node, its steady-state active power balance relationship satisfies the following constraint equations:

[0031] in: The active power output of the offshore wind farm; The active power transmitted from the coastal branch to the onshore power grid; The interactive active power of the near-shore and offshore AC interconnection transformer branches; when the control target is set to make When, satisfy This forces offshore wind farms to transmit power only through a dedicated offshore AC cable channel. Logical decoupling is required for the power distribution in this physical topology: since offshore wind farms are mandated to transmit power only through a dedicated offshore AC cable channel, a control mechanism must be established to force this. This holds true consistently, such that Under these conditions, the output active power of offshore wind farms It must be strictly equal to the active power transmitted on the DC side of the LCC entity, which serves as the absolute boundary condition for isolating the power interference between near-shore and offshore wind farms.

[0032] Furthermore, in step S3, a vector control strategy based on grid voltage orientation is adopted for control. To ensure that the reactive power component interacting between the offshore wind power AC network and the near-shore wind power AC network remains constant at zero, the SVG is used to locally compensate for the lagging reactive power component consumed by the LCC due to thyristor commutation and the transient reactive power component of the offshore wind farm. Under the dq rotating coordinate frame, the reactive current command of the SVG device is generated through the reactive power outer loop regulator, and the specific relationship is as follows:

[0033] in: This is the reactive current command value for the SVG on the q-axis. The proportional parameter of the reactive power PI controller; These are the integral parameters of the reactive PI controller; For the Laplace operator; This is a reactive power reference value, and is based on the settings. To achieve non-exchange of reactive power; This represents the actual reactive power of the system.

[0034] Furthermore, regarding the characteristic subharmonics excited on the AC side by the LCC commutator operation, i.e. satisfying A specific frequency harmonic interference (k is a positive integer) drives the SVG to execute a specific subharmonic control algorithm; by introducing a specific proportional resonant (PR) controller entity algorithm into the current inner loop, zero steady-state error tracking and cancellation of the target high-frequency signal is achieved. The transfer function of the PR controller in the time-frequency domain is:

[0035] in: Let be the transfer function of the proportional resonant controller; For proportional gain; This is the resonant gain; Cutoff frequency; For the set number The resonant angular frequency controlled by a specific order harmonic; the final modulated wave output by the SVG is composed of the superposition of the fundamental component and the harmonic compensation component. The underlying modulated waveform is digitally superimposed by the generated fundamental voltage vector component and the harmonic cancellation voltage vector component calculated by the PR controller, and then outputs PWM drive signals to the thyristor valve and IGBT gate through the nearest level approximation modulation (NLM) algorithm.

[0036] Furthermore, in step S4, to achieve the goal of zero active power interaction established in step S2, the default constant DC current strategy of the LCC is abandoned, and the active power following response mechanism of the upper-level master mode is reconstructed. The active power components of the actual interaction in the SLCC system are calculated and extracted using instantaneous power theory: After the instantaneous values ​​of the three-phase voltage of the converter bus and the physical current on the grid side of the converter transformer are discretely sampled, a Clark matrix transformation is performed to transform them into a two-phase stationary coordinate system, and the active power components are calculated as follows:

[0037] in: This represents the instantaneous active power actually absorbed by the SLCC. and The converter bus voltage is respectively at shaft and Components on the axis; and The converter transformer side currents are respectively at shaft and Components on the axis.

[0038] Furthermore, in step S4, the controller outputs the active power of the offshore wind farm at an instantaneous rate. The power command value for the LCC is used as the input to dynamically correct the rectifier-side firing angle. The correction formula is as follows:

[0039] in: The real-time rectifier-side firing angle for the LCC; This is the reference value for the firing angle under the rated operating conditions of the LCC; These are the proportional parameters of the active PI controller; These are the integral parameters of the active PI controller; This refers to the instantaneous active power output from the offshore wind farm to the converter bus. Let be the Laplace operator; through this modified relation, we can make... equal Thus maintaining interactive active power Converging to zero. This automatic trigger angle adjustment logic implements forced balance: when... When the firing angle is calculated to decrease, it forces the SLCC DC voltage peak to rise and the transmission current to increase, thereby absorbing excess offshore wind power; conversely, it reduces the absorbed power, thus physically clamping the coupling power on the interconnecting transformer to zero. Combining steps S2-S4, the SLCC control block diagram is as follows: Figure 3 As shown.

[0040] Furthermore, step S4 specifically involves: utilizing the upper-layer LCC module to implement active power following control based on instantaneous power feedback, dynamically adjusting the rectifier firing angle to match the power fluctuations of offshore wind power in real time, and ensuring that the active power interaction between near-shore and offshore systems remains at zero.

[0041] Simulation verification: A verification model was built based on the quantitative topology and control equations provided in this embodiment. Its physical parameters were set as follows: near-shore wind farm rated power of 500MW and AC voltage of 500kV; offshore wind farm rated power of 2000MW and AC voltage of 66kV; near-shore / offshore AC interconnection transformer rated capacity of 300MW, transformation ratio of 500kV / 66kV, and leakage reactance of 0.08pu; SLCC converter station overall rated power of 2000MW, with DC voltage constant at... run.

[0042] Quantitative power fluctuation verification was performed within the system: Operational scenario consistency verification (wind power fluctuation verification): When the input active power of offshore wind power undergoes a step change with an amplitude difference, the LCC tracks the actual power according to the model rule in control step S4. Follow the ocean command in real time within the timing adjustment window. An equivalent change occurs, resulting in, for example Figure 4 The absolute value of the active power of the AC tie line between the near and offshore wind farms does not exceed 5% of the set wind power capacity value during this time period, and always converges to approach zero. The reactive power compensation of the SVG output by the model in step S3 is realized to cancel the reactive power missing in the system, so that the measured exchange reactive power is reset to zero after the response time difference ends.

[0043] The above describes a control system provided by an embodiment of the present invention. Based on the same inventive concept, an embodiment of the present invention also provides a control device. Figure 5 A schematic diagram of a control device provided in an embodiment of the present invention, such as... Figure 5 As shown, the device mainly includes: at least one processor 501; and a memory 502 communicatively connected to the at least one processor; wherein the memory 502 stores instructions that can be executed by the at least one processor 501, and the instructions are executed by the at least one processor 501 to enable the at least one processor 501 to perform the aforementioned control method.

[0044] In addition, embodiments of the present invention also provide a controllable non-volatile computer storage medium storing computer-executable instructions, which are executed by a processor to implement the aforementioned control method.

[0045] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of 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, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0046] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0047] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0048] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0049] The various embodiments in this invention are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the device embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0050] It should also be noted that 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 limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0051] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A control method for an offshore wind power transmission system based on SLCC, characterized in that, The method includes the following steps: Step S1: Construct the topology of the offshore wind power transmission system based on SLCC. The topology consists of near-shore wind farms, offshore wind farms, near-shore and offshore AC interconnection transformers, and SLCC converter stations. Step S2: Establish the active power balance relationship in the multi-source wind power aggregation scenario, and set a control target to keep the interactive active power of the branch where the near-shore and offshore AC interconnection transformer is located at zero, so as to isolate the power coupling between the near-shore wind farm and the offshore wind farm. Step S3: Construct the underlying SVG reactive power and harmonic self-regulating control model of the SLCC converter station, compensate the dynamic reactive power generated by the LCC converter and the reactive power of the offshore wind farm in real time, and perform self-inversion cancellation on the characteristic subharmonic current generated by the LCC. Step S4: Construct the upper-level LCC active power following control model of the SLCC converter station, using the instantaneous output active power of the offshore wind farm as the power command tracking value of the LCC, dynamically correct the rectifier side firing angle of the LCC, and coordinate with the self-compensation characteristics of the underlying SVG to realize the coordination of the physical interface and the decoupling of the control logic of near-shore and offshore wind power transmission.

2. The control method for an offshore wind power transmission system based on SLCC according to claim 1, characterized in that, The active power balance relationship in step S2 satisfies the following constraint equations: in: The active power output of the offshore wind farm; The active power transmitted from the coastal branch to the onshore power grid; The interactive active power of the near-shore and offshore AC interconnection transformer branches; when the control target is set to make When, satisfy This means that the power from offshore wind farms is transmitted only through offshore AC channels.

3. The control method for an offshore wind power transmission system based on SLCC according to claim 1, characterized in that, In step S3, the underlying SVG reactive power and harmonic self-regulating control model adopts a vector control strategy based on grid voltage orientation; in the dq rotating coordinate system, the SVG reactive current command is generated through the reactive power outer loop, and its relationship is as follows: in: This is the reactive current command value for the SVG on the q-axis. The proportional parameter of the reactive PI controller; These are the integral parameters of the reactive PI controller; For the Laplace operator; This is a reactive power reference value, and is based on the settings. To achieve non-exchange of reactive power; This represents the actual reactive power of the system.

4. The control method for an offshore wind power transmission system based on SLCC according to claim 1, characterized in that, In step S3, the LCC generated For subharmonics, the SVG employs a preset subharmonic compensation strategy; a control equation incorporating a proportional resonant controller is introduced to perform zero steady-state error tracking of the preset frequency signal. The transfer function of this proportional resonant controller is as follows: in: Let be the transfer function of the proportional resonant controller; For proportional gain; This is the resonant gain; Cutoff frequency; For the set number The resonant angular frequency is controlled by the preset subharmonic; the final modulated wave output by the SVG is composed of the superposition of the fundamental component and the harmonic compensation component.

5. The control method for an offshore wind power transmission system based on SLCC according to claim 1, characterized in that, In step S4, the upper-level LCC active power following control model calculates the actual active power absorbed by the SLCC using instantaneous power theory; the three-phase voltage of the converter bus and the current on the converter transformer side are converted by Clark to... After establishing a stationary coordinate system, the relationship for instantaneous active power is as follows: in: This represents the instantaneous active power actually absorbed by the SLCC. and The converter bus voltage is respectively at shaft and Components on the axis; and The converter transformer side currents are respectively at shaft and Components on the axis.

6. The control method for an offshore wind power transmission system based on SLCC according to claim 1, characterized in that, In step S4, the controller outputs the active power of the offshore wind farm at an instantaneous rate. The power command value for the LCC is used as the input to dynamically correct the rectifier-side firing angle. The correction formula is as follows: in: The real-time rectifier-side firing angle for the LCC; This is the reference value for the firing angle under the rated operating conditions of the LCC; These are the proportional parameters of the active PI controller; These are the integral parameters of the active PI controller; This refers to the instantaneous active power output from the offshore wind farm to the converter bus. Let be the Laplace operator; through this modified relation, we can make... equal Thus maintaining interactive active power It converges to zero.

7. The control method for an offshore wind power transmission system based on SLCC according to claim 1, characterized in that, In step S1, the offshore wind farm is connected to the converter bus of the SLCC converter station via a transformer. After the nearshore wind farm passes through the AC collection bus, the first branch is connected to the onshore power grid through a separate nearshore AC transmission channel, and the second branch is connected to the converter bus of the SLCC converter station through the nearshore-offshore AC interconnection transformer. The SLCC converter station consists of a grid-commutated converter (LCC) and a static var generator (SVG). The SVG is connected in parallel to the valve side of the converter transformer of the LCC.

8. The control method for an offshore wind power transmission system based on SLCC according to claim 1, characterized in that, Step S4 specifically involves: using the upper-level LCC module to implement active power following control based on instantaneous power feedback, dynamically adjusting the rectifier firing angle to match the power fluctuations of offshore wind power in real time, and ensuring that the active power interaction between near-shore and offshore systems remains at zero.

9. A control device for an offshore wind power transmission system based on SLCC, characterized in that, The device includes: At least one processor; and, A memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, which, when executed by the at least one processor, enables the at least one processor to perform a control method for an offshore wind power transmission system based on SLCC as described in any one of claims 1-8.

10. A non-volatile computer storage medium for controlling an offshore wind power transmission system based on SLCC, storing computer-executable instructions, characterized in that, The computer-executable instructions are executed by the processor to implement the control method for an offshore wind power transmission system based on SLCC as described in any one of claims 1-8.

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