Multi-terminal isomerous new energy collection and transmission system, hierarchical control architecture and collaborative control method

Abstract

A multi-terminal heterogeneous new energy gathering and sending system, a hierarchical control architecture and a collaborative control method, the system comprising at least one first type new energy cluster and at least one second type new energy cluster; the two types of new energy clusters are connected to an AC main grid through corresponding first gathering and sending branches and second gathering and sending branches respectively; the first gathering and sending branch comprises a low-frequency AC gathering bus, a low-frequency AC transmission line and a first gathering device; the second gathering and sending branch comprises an AC gathering bus, a sending converter, a DC transmission line and a receiving converter; the DC transmission line corresponding to at least one second type new energy cluster is connected to the low-frequency AC transmission line corresponding to at least one first type new energy cluster through a mutual aid collaborative device. The application establishes a power mutual aid and collaborative control mechanism between the low-frequency AC sending branch and the DC sending branch, thereby improving the stability, economy and operation flexibility of large-scale new energy gathering and sending.

Description

Technical Field

[0001] This invention belongs to the field of new energy power system technology, and specifically relates to a multi-terminal, heterogeneous collection and transmission system and its collaborative stability control method suitable for high-proportion new energy access scenarios. It is particularly suitable for efficient collection, stable grid connection and flexible regulation of new energy in offshore, near-shore and onshore scenarios. Background Technology

[0002] With the advancement of the "dual carbon" target, the penetration rate of new energy power generation, represented by wind power and photovoltaics, continues to increase. New energy power systems are evolving from a traditional structure "primarily based on synchronous power sources" to a heterogeneous system "combining power electronic converters and synchronous power sources." The safety, stability, and economy of new energy aggregation and transmission have become core industry demands. Currently, new energy aggregation and transmission mainly adopts single-frequency AC transmission, flexible DC transmission, or low-frequency AC transmission modes, but these face many technical bottlenecks in practical applications, making it difficult to meet the high-efficiency grid connection requirements of large-scale new energy.

[0003] Among existing renewable energy aggregation and transmission schemes, industrial frequency AC transmission technology is mature and its system structure is relatively simple. However, in scenarios involving centralized aggregation and transmission of renewable energy, it is easily constrained by factors such as line charging power, reactive power balance, and voltage stability, thus limiting its transmission capacity and applicability. Low-frequency AC transmission can improve the transmission characteristics of AC transmission to some extent, but it still suffers from limited transmission capacity, high reactive power compensation requirements, and complex system configuration. Flexible DC transmission, while possessing strong long-distance and large-scale transmission capabilities and good power flow control, involves high investment in converter platforms, converter valves, and supporting offshore facilities, and its engineering implementation is complex, placing high demands on project economics and feasibility. Especially in scenarios where multiple types of renewable energy coexist and transmission demands vary significantly, a single transmission method often struggles to simultaneously achieve economic efficiency, flexibility, stable support capabilities, and fault adaptability.

[0004] New energy power generation is characterized by volatility, intermittency, and uncertainty. In scenarios involving large-scale aggregation and transmission of new energy clusters, this can easily lead to rapid fluctuations in transmitted power, disturbances in the AC bus voltage at the receiving end, and imbalances in power distribution between AC and DC branches. Especially when different new energy clusters have varying transmission distances, capacities, and transmission methods, the dynamic response capabilities of each branch to the grid are inconsistent. A single branch often struggles to independently handle multiple functions such as power smoothing, dispatch tracking, and fault support. Furthermore, most existing new energy aggregation and transmission systems rely primarily on power electronic interfaces, resulting in insufficient system inertia and short-circuit support capabilities. When the AC main grid at the receiving end is weak or experiences fault disturbances, problems such as insufficient voltage support, amplified power fluctuations, and reduced continuous grid-connected operation capabilities can easily arise.

[0005] Chinese patent application CN118232397A (published on June 21, 2024) discloses an offshore wind power transmission system with low-frequency AC and power frequency AC mutual support. In this scheme, the low-frequency wind farm in the low-frequency AC transmission unit and the power frequency wind farm in the power frequency AC transmission unit are connected or disconnected through the controlled closing or controlled closing of the source-side bidirectional interconnection switch. The AC power is frequency converted through a first frequency conversion stage or a second frequency conversion stage, thereby realizing mutual support between the low-frequency AC transmission unit and the power frequency AC transmission unit. However, the mutual assistance mechanism of this scheme mainly relies on topology switching to achieve the connection or disconnection between power frequency AC and low frequency AC units, lacking continuous and controllable power mutual assistance capability and system-level collaborative control. At the same time, this scheme is oriented towards power frequency-low frequency AC mutual assistance scenarios and has not been optimized for the mutual assistance needs between "DC transmission branches and low frequency AC branches" in large-capacity, long-distance transmission in the open sea. Under the engineering conditions of significant constraints on lightweight offshore platforms and limited equipment size and weight, its engineering adaptability and scalability for mutual assistance through multi-level frequency conversion / interconnection systems are limited, and it is difficult to provide synchronous machine-level voltage and inertia support under receiving-end fault / weak network conditions.

[0006] Chinese patent application CN120200311A (published on June 24, 2025) discloses an integrated AC / DC system with multiple sources on land and sea. This system connects offshore wind power, onshore multi-source energy, and inland receiving-end systems through an integrated switching station. The DC transmission line employs a hybrid MMC on both sides, combining uncontrolled rectifier technology with flexible DC hybrid converter technology to design a lightweight offshore wind power transmission device. This scheme uses a hybrid converter structure of uncontrolled rectifiers (DRUs) and modular multilevel converters (MMCs), with the DC side primarily using semi-controlled devices, thus limiting the freedom of DC voltage / power regulation. In high-capacity offshore operations, rapid fluctuations in wind power output or weak receiving-end grids make it difficult to achieve continuous and controllable power distribution and rapid mitigation through bidirectional mutual support. Simultaneously, the DRU introduces harmonics and reactive power requirements, typically necessitating additional filtering, compensation, and protection configurations, making it difficult to fully realize the lightweight advantages of the offshore platform.

[0007] Chinese patent application CN121150178A (published on December 16, 2025) discloses an offshore wind power collection and transmission system and method based on a multi-port, multi-frequency AC / DC hybrid integrated platform. Various wind power collection subsystems collect the output of wind turbine groups of corresponding frequencies and send them to the offshore integrated platform. The offshore integrated platform converts medium-frequency, power-frequency, and some low-frequency power into DC and transmits it to the onshore converter station through a DC transmission submarine cable. The converter station then converts it into power-frequency AC. The remaining low-frequency power is boosted and transmitted to the onshore frequency converter station through a low-frequency transmission submarine cable, where it is converted into power-frequency AC. However, this scheme involves configuring three sets of converters (medium frequency, power frequency, and low frequency) and matching transformers simultaneously within the offshore integrated platform, resulting in equipment stacking, complex interface links, and a significant increase in platform size, weight, and maintenance complexity. Its DC transmission and low frequency transmission channels are independent of each other, lacking cross-channel mutual assistance and power smoothing capabilities. At the same time, it does not introduce voltage and inertia support resources, which is not conducive to ensuring continuous grid connection and ride-through performance under weak grid or fault disturbances.

[0008] In existing technologies, relying on large-scale synchronous motors to provide inertia cannot adapt to scenarios with high penetration of new energy sources; if a pure power electronic solution is adopted, there are problems such as lack of inertia and weak fault ride-through capability. There is an urgent need for a new type of aggregation and transmission architecture, a multi-terminal heterogeneous new energy aggregation and transmission system with flexible control, fault coordination and scalability, which can improve the stability and economy of large-scale aggregation and transmission of new energy sources through the complementary advantages and coordinated control of heterogeneous branches. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing new energy collection and transmission systems, such as low inertia support capability, insufficient fault ride-through capability, high cost, and poor scalability. It provides a multi-terminal heterogeneous new energy collection and transmission system and control method. By constructing a mutual assistance and coordination mechanism between low-frequency AC transmission branches and DC transmission branches, and combining the coordinated operation of motor-generator sets and power electronic converters, it realizes flexible collection and transmission, power smoothing, scheduling support, and collaborative fault ride-through for multiple types of new energy clusters.

[0010] To achieve the above-mentioned objectives, the present invention adopts the following technical solution.

[0011] On the one hand, the present invention discloses a multi-terminal heterogeneous new energy collection and transmission system, including at least one first type and at least one second type;

[0012] Each of the first-class and second-class new energy clusters is connected to the receiving-end AC main network through the corresponding first collection and transmission branch and second collection and transmission branch, respectively.

[0013] The first collection and transmission branch includes a low-frequency AC collection bus, a low-frequency AC transmission line and a first collection device, which are connected sequentially between the first type of new energy cluster and the receiving-end AC main grid.

[0014] The second collection and transmission branch includes an AC collection bus, a sending-end converter, a DC transmission line, and a receiving-end converter, which are connected sequentially between the second type of new energy cluster and the receiving-end AC main grid.

[0015] At least one DC transmission line corresponding to a second-type new energy cluster is connected to at least one low-frequency AC transmission line corresponding to a first-type new energy cluster through a mutual assistance and coordination device.

[0016] More preferably,

[0017] The multi-terminal heterogeneous new energy collection and transmission system also includes at least one third-type new energy cluster.

[0018] Each of the third category of new energy sources is connected to the receiving end AC main network through its corresponding third collection and transmission branch.

[0019] The third collection and transmission branch includes a power frequency AC collection bus and a power frequency AC transmission line. The power frequency AC collection bus collects the third type of new energy cluster power, and the power frequency AC transmission line transmits the power to the receiving end AC main grid.

[0020] More preferably,

[0021] The first collecting device is a motor-generator set, wherein the motor is a synchronous motor, the generator is a synchronous generator, the motor and the generator have matching capacities and are coaxially connected; one side of the motor is connected to the low-frequency AC transmission line, and one side of the generator is connected to the receiving-end AC main grid.

[0022] More preferably,

[0023] The mutual assistance and coordination device enables power mutual assistance between the second and first collection and transmission branches and the first collection and transmission branch, as well as soft-start control of the first collection device.

[0024] More preferably,

[0025] The mutual assistance and coordination device is a modular commutator converter (MCC) or a modular multilevel converter (MMC).

[0026] More preferably,

[0027] When the first collection device is started, the mutual assistance and coordination device is controlled to output low-frequency, low-voltage AC power to the synchronous motor side of the first collection device to perform frequency conversion soft start on the motor-generator set; during the start-up process, the frequency and voltage of the output AC power are gradually increased so that the synchronous motor drives the synchronous generator to smoothly increase speed; when the speed of the motor-generator set meets the synchronous grid connection speed conditions, the amplitude, frequency and phase of the synchronous generator terminal voltage are adjusted so that it meets the synchronous grid connection conditions with the receiving end AC main grid; after the synchronous grid connection conditions are met, the first collection device is put into operation.

[0028] More preferably,

[0029] When the change in the output power of the first type of new energy cluster exceeds the set fluctuation threshold within a preset time interval, the difference between the target operating power and the actual operating power of the motor-generator set of the first collection device is calculated as the power tracking command of the mutual assistance and coordination device. The second type of new energy cluster is controlled to inject power or absorb power into the low-frequency AC collection bus corresponding to the first type of new energy cluster through the mutual assistance and coordination device, so as to realize the quasi-constant power operation of the motor-generator set of the first collection device.

[0030] More preferably,

[0031] When the multi-terminal heterogeneous new energy collection and transmission system is operating normally, the first collection device corresponding to each first type of new energy cluster calculates and issues unit control commands according to the dispatch control instructions and its current operating electrical parameters, so as to realize the regulation of active power output, voltage support and reactive power support of the receiving end AC main grid.

[0032] More preferably,

[0033] When a voltage drop fault is detected on the receiving end AC bus, the synchronous generator in the first collection device is controlled to enter the strong excitation operation state to provide dynamic reactive power support to the receiving end AC bus; at the same time, the mechanical inertia of the motor-generator set is used to provide frequency support; after the receiving end AC bus voltage is restored, the excitation current of the synchronous generator is gradually restored to the level before the fault according to the preset recovery rate.

[0034] More preferably,

[0035] The sending-end converter is a modular commutator (MCC), and the receiving-end converter is a modular multilevel converter (MMC) or a modular commutator (MCC).

[0036] More preferably,

[0037] In the second collection and output branch, the DC side of the sending-end modular commutator adopts dual closed-loop control. An outer loop is constructed to build the average capacitor voltage of the sub-module. A DC current reference value is generated based on the deviation between the reference value and the actual value of the average capacitor voltage of the sub-module. An inner loop is constructed to adjust the amplitude of the third harmonic component in the modulation voltage of the AC side of the sending-end MCC based on the deviation between the DC current reference value and the actual DC current. This changes the equivalent power exchange relationship between the AC and DC sides, realizes the energy balance inside the sending-end MCC, and enables the output power of the new energy source to be smoothly transmitted to the DC bus.

[0038] More preferably,

[0039] In the second collection and output branch, the DC side of the receiving-end converter adopts a topology-independent constant DC voltage control method. By constructing a DC voltage closed loop, the DC current is adjusted to stabilize the DC bus voltage at a preset reference value.

[0040] More preferably,

[0041] When the receiving-end converter is a modular commutator (MCC), it introduces a controllable third harmonic component into the AC output voltage waveform and adjusts the amplitude of the third harmonic component based on the DC bus voltage deviation to change the equivalent transformation relationship between AC voltage and DC voltage, thereby achieving regulation and stabilization of DC bus voltage.

[0042] Secondly, the present invention discloses a hierarchical control architecture based on the multi-terminal heterogeneous new energy collection and transmission system, including a scheduling control center, a local system controller, and multiple device controllers.

[0043] The dispatch control center is located at the upper layer of the control architecture and is used to issue start / stop commands, AGC active power dispatch commands, and AVC voltage / reactive power dispatch commands to the multi-terminal heterogeneous new energy aggregation and transmission system according to the operation requirements of the receiving end AC main grid.

[0044] The local system controller is located in the middle layer of the control architecture. It is used to receive instructions issued by the scheduling and control center, and, in conjunction with the real-time operating status of the first type of new energy cluster, the second type of new energy cluster, the first collection device, the mutual assistance and coordination device, and the transmitting and receiving end converters, to identify and switch the current operating mode of the multi-terminal heterogeneous new energy collection and transmission system, and to issue corresponding control settings to the controllers of each device to realize the coordinated operation between the first collection device and the second collection and transmission branch.

[0045] More preferably,

[0046] The device controller includes a mutual aid and coordination device controller, an MG controller, a sending-end converter controller, and a receiving-end converter controller.

[0047] More preferably,

[0048] When it is detected that the first collection device has not completed startup and grid connection, the local system controller enables the soft start mode and sends the soft start control setting value to the mutual assistance and coordination device controller. The mutual assistance and coordination device then performs a soft start on the first collection device. After the motor-generator speed of the first collection device meets the synchronous grid connection speed condition, the MG controller adjusts the amplitude, frequency and phase of the synchronous generator terminal voltage to control the first collection device to start operation. Then the local system controller exits the soft start mode and switches the system to normal operation mode.

[0049] More preferably,

[0050] The normal operating modes include AGC / AVC regular tracking mode, mutual power smoothing mode, and fault cooperative ride-through mode;

[0051] In the AGC / AVC normal tracking mode, the local system controller allocates targets according to the AGC active power dispatching instructions and the AVC voltage / reactive power dispatching instructions, and the MG controller performs active power and voltage / reactive power tracking control.

[0052] In the mutual assistance power smoothing mode, the local system controller sends a power tracking command to the mutual assistance and coordination device controller based on the detected output power fluctuation of the first type of new energy cluster. The mutual assistance and coordination device controller controls the second type of new energy cluster to inject power or absorb power to the low-frequency AC collection bus corresponding to the first type of new energy cluster through the mutual assistance and coordination device.

[0053] In the collaborative fault traversal mode, the local system controller sends a collaborative fault traversal operation command to the MG controller, and the MG controller switches the first collection device to the fault support operation state.

[0054] Thirdly, this invention discloses a collaborative control method for a multi-terminal heterogeneous new energy collection and transmission system based on the aforementioned hierarchical control architecture, the method comprising:

[0055] Step 1: The local system controller detects the grid connection status of the first aggregation device; if it is not connected to the grid, proceed to the soft start mode in Step 2; otherwise, proceed to Step 3.

[0056] Step 2: The local system controller controls the mutual assistance and coordination device to perform a soft start on the first collection device. After the grid connection conditions are met, the controller controls the first collection device to start operation, and then proceeds to step 3.

[0057] Step 3: Continuously monitor the system's operating status. If a system failure is detected, proceed to Step 4 to execute the collaborative fault traversal mode; otherwise, proceed to Step 5.

[0058] Step 4: The local system controller issues a collaborative fault-crossing operation command to switch the first collection device to the fault support operation state. If the fault is cleared, proceed to step 5; otherwise, maintain the collaborative fault-crossing operation mode.

[0059] Step 5: The local system controller enables the AGC / AVC normal tracking mode and monitors the output power fluctuation event of the first type of new energy cluster in real time. If a power fluctuation occurs, proceed to step 6. Otherwise, according to the AGC active power dispatching instruction and the AVC voltage / reactive power dispatching instruction, control the motor-generator set in the first collection device to track the active power setting or track the voltage / reactive power setting.

[0060] Step 6: The local system controller controls the mutual assistance and coordination device to enter the mutual assistance power stabilization mode, and controls the second type of new energy cluster to inject power or absorb power into the low-frequency AC collection bus corresponding to the first type of new energy cluster through the mutual assistance and coordination device, so that the first collection device maintains a quasi-constant power operation state.

[0061] More preferably,

[0062] In step 2, the mutual assistance and coordination device is controlled to output low-frequency, low-voltage AC power to the synchronous motor side of the first collection device to perform frequency conversion soft start on the motor-generator set; the frequency and voltage of the output AC power are gradually increased; when the speed of the motor-generator set meets the synchronous grid connection speed condition, the amplitude, frequency and phase of the voltage at the synchronous generator terminal are adjusted to make it meet the synchronous grid connection condition with the receiving end AC main grid; after meeting the synchronous grid connection condition, the first collection device is put into operation to realize the grid connection of the first collection device.

[0063] More preferably,

[0064] In step 3, when the voltage of the AC main grid bus at the receiving end drops to the set drop fault threshold and continues for a set delay, it is determined that a voltage drop fault has occurred in the system, and the local system controller enables the fault cooperative ride-through mode.

[0065] More preferably,

[0066] In step 4, the local system controller sends a coordinated fault-crossing operation command to the MG controller, controls the synchronous generator to enter the strong excitation operation state, improves the reactive power output capacity, and provides dynamic reactive power support to the receiving end AC bus; controls the first collection device to maintain continuous grid-connected operation, and uses the inherent mechanical inertia of the motor-generator set to provide frequency support to the receiving end power grid.

[0067] More preferably,

[0068] In step 5, the local system controller receives the AGC active power target value or the AVC voltage target value / reactive power target value from the dispatch control center. Based on the received target value, the local system controller sends the corresponding active power set value and voltage / reactive power adjustment set value to the MG controller, and equates the motor-generator set in the first collection device to the synchronous generator set in the receiving end AC main grid, and performs active power and voltage / reactive power tracking control.

[0069] More preferably,

[0070] In step 6, when the change in the output power of the first type of new energy cluster exceeds the set fluctuation threshold within a preset time interval, the local system controller determines that the system has entered the mutual assistance power smoothing mode. The mutual assistance and coordination device controller generates a power tracking command based on the deviation between the target operating power and the actual operating power of the first collection device. Based on the tracking command, the mutual assistance and coordination device controller controls the second type of new energy cluster to inject power or absorb power into the low-frequency AC collection bus corresponding to the first type of new energy cluster through the mutual assistance and coordination device, so as to compensate for the power fluctuation of the first type of new energy cluster and keep the first collection device in a quasi-constant power operation state.

[0071] Fourthly, the present invention discloses an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor performs the steps of the collaborative control method for the multi-terminal heterogeneous new energy collection and transmission system.

[0072] Fifthly, the present invention discloses a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the collaborative control method for the multi-terminal heterogeneous new energy collection and transmission system.

[0073] Compared with the prior art, the present invention has the following beneficial technical effects:

[0074] Compared with existing technologies, this invention addresses the demand for large-capacity new energy aggregation and transmission in deep-sea areas by proposing a multi-terminal heterogeneous aggregation and transmission topology and its collaborative control method. By classifying and configuring new energy clusters according to installed capacity and transmission distance, a hierarchical adaptation system is constructed, comprising direct grid connection to power frequency AC, grid connection to low-frequency AC via motor-generator sets, and flexible DC grid connection. This enables power sources of different scales and distances to achieve optimal transmission path matching within the same framework, thus balancing long-distance transmission capacity, engineering economy, and system scalability. Simultaneously, this invention electrically couples DC transmission lines and low-frequency AC transmission lines through a mutual assistance and coordination device, forming a controllable cross-system bidirectional power channel. Furthermore, the mutual assistance port can be expanded to connect multiple MG aggregation and transmission branches as needed, achieving power resource sharing and coordination among multiple branches and avoiding the capacity utilization limitations and redundant configurations caused by the isolated operation of each transmission channel.

[0075] Furthermore, in response to the constraints of lightweighting offshore platforms, this invention preferably adopts a modular commutator converter (MCC) at the sending end of the DC transmission system, and uses a DC-side closed-loop control strategy to achieve smooth power transmission and energy balance. While meeting control performance requirements, this reduces the size and weight of the converter equipment and maintains structural scalability, providing a more easily implemented lightweight solution for the sending end of deep-sea engineering projects.

[0076] Meanwhile, the receiving-end MG unit is directly connected to the AC main grid as a synchronous generator. It has the natural inertia and strong excitation reactive power regulation capability of a synchronous motor. It can be incorporated into the grid dispatching system to track AGC / AVC commands, and achieve active / reactive power dispatching response similar to that of a conventional synchronous generator. This improves grid friendliness and forms an effective substitute for conventional thermal power regulation resources.

[0077] Based on the above topology and device configuration, this invention further leverages the multiple collaborative control benefits of the mutual aid and coordination device: during the startup phase, the controllable frequency / voltage output of the mutual aid and coordination device is reused to achieve soft start of the MG, thereby eliminating the need for traditional dedicated startup equipment such as SFC and reducing investment costs; during the operation phase, dynamic compensation is performed on the input power of the MG motor side to achieve rapid smoothing of power fluctuations in the first type of new energy cluster, enabling the MG to operate at quasi-constant power and improving system stability; during AC faults at the receiving end, the strong reactive power regulation capability and rotational inertia of the MG unit are used to provide dynamic voltage and frequency support for the power electronic branch, achieving collaborative fault ride-through, thereby improving the overall system operation stability, grid connection continuity, and engineering adaptability. Attached Figure Description

[0078] Figure 1 A schematic diagram of a multi-terminal heterogeneous new energy collection and transmission system;

[0079] Figure 2 A schematic diagram of a scalable multi-terminal heterogeneous new energy collection and transmission system;

[0080] Figure 3 A schematic diagram of the hierarchical control architecture for a multi-terminal heterogeneous new energy collection and transmission system;

[0081] Figure 4 This is a flowchart of the soft start process for the MG unit in the collaborative control method of the present invention;

[0082] Figure 5 A schematic diagram of the collaborative control method for a multi-terminal heterogeneous new energy collection and transmission system;

[0083] Figure 6 This is the control block diagram for the DC side of the MCC at the sending end;

[0084] Figure 7 This is the control block diagram for the DC side of the receiving-end MCC. Detailed Implementation

[0085] 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 with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0086] As attached Figure 1 As shown, the multi-terminal heterogeneous new energy collection and transmission system of the present invention includes at least a first type of new energy cluster and a second type of new energy cluster, which are respectively connected to the receiving end AC power grid through a first collection and transmission branch and a second collection and transmission branch. The installed capacity of the first type of new energy cluster and its transmission distance relative to the receiving end AC main grid are both smaller than those of the second type of new energy cluster, so as to reflect the hierarchical adaptation of near-shore / small-capacity and far-shore / large-capacity scenarios.

[0087] The first type of new energy cluster may include new energy units such as wind turbines and photovoltaics. This cluster connects to the receiving-end AC main grid via a corresponding first collection and transmission branch. The first collection and transmission branch includes a low-frequency AC collection bus, a low-frequency AC transmission line, and a first collection device, sequentially connected between the first type of new energy cluster and the receiving-end AC main grid. The electrical energy output from the first type of new energy cluster is first collected to the low-frequency AC collection bus and then transmitted via the low-frequency AC transmission line to the first collection device located on the receiving end side. The first collection device is a motor-generator unit (MG unit), wherein the motor is a synchronous motor, the generator is a synchronous generator, and the motor and generator have matching capacities and are coaxially connected. The motor is connected to the low-frequency AC transmission line to absorb input power from the low-frequency AC side; its generator is connected to the receiving-end AC main grid to output power frequency AC energy to the receiving-end AC grid. This MG unit achieves energy transfer and electrical isolation between the low-frequency side and the power frequency main grid side, enabling the first type of new energy cluster to economically transmit power via low-frequency AC and achieve synchronous grid connection on the receiving end side.

[0088] The second type of new energy cluster can also include new energy units such as wind turbines and photovoltaics. This second type of new energy cluster connects to the receiving-end AC main grid via a second collection and transmission branch. The second collection and transmission branch sequentially connects the AC collection bus, the sending-end converter, the DC transmission line, and the receiving-end converter between the second type of new energy cluster and the receiving-end AC main grid. The output of the second type of new energy cluster is collected by the AC collection bus and then sequentially transmitted to the receiving-end AC grid via the second collection and transmission branch formed by the sending-end converter, the DC transmission line, and the receiving-end converter. The sending-end converter converts AC power into DC power and injects it into the DC transmission line, while the receiving-end converter converts DC power back into AC power and integrates it into the receiving-end AC grid, thus meeting the demand for large-capacity, long-distance transmission from offshore areas. The sending-end converter is a modular commutator converter (MCC), and the receiving-end converter is a modular multilevel converter (MMC) or a modular commutator converter (MCC).

[0089] Between the two types of outgoing branches mentioned above, a mutual assistance and coordination device is installed. This device is electrically connected between the DC transmission line (or its equivalent DC bus side) of the second collecting outgoing branch and the low-frequency AC transmission line of the first collecting outgoing branch, thereby establishing a controllable bidirectional power mutual assistance channel between the DC branch and the low-frequency AC branch. Through the mutual assistance and coordination device, power mutual assistance can be achieved without changing the structure of their respective main outgoing channels, and further supports functions such as soft start of MG units, smoothing of input power fluctuations on the MG side, and cooperative ride-through under fault conditions.

[0090] When the first collection device is started, the mutual assistance and coordination device is controlled to output low-frequency, low-voltage AC power to the synchronous motor side of the first collection device to perform frequency conversion soft start on the motor-generator set; during the start-up process, the frequency and voltage of the output AC power are gradually increased so that the synchronous motor drives the synchronous generator to smoothly increase speed; when the speed of the motor-generator set meets the synchronous grid connection speed conditions, the amplitude, frequency and phase of the synchronous generator terminal voltage are adjusted so that it meets the synchronous grid connection conditions with the receiving end AC main grid; after the synchronous grid connection conditions are met, the first collection device is put into operation.

[0091] When the change in the output power of the first type of new energy cluster exceeds the set fluctuation threshold within a preset time interval, the difference between the target operating power and the actual operating power of the motor-generator set of the first collection device is calculated as the power tracking command of the mutual assistance and coordination device. The second type of new energy cluster is controlled to inject power or absorb power into the low-frequency AC collection bus corresponding to the first type of new energy cluster through the mutual assistance and coordination device, so as to realize the quasi-constant power operation of the motor-generator set of the first collection device.

[0092] When the multi-terminal heterogeneous new energy collection and transmission system is operating normally, the first collection device corresponding to each first type of new energy cluster calculates and issues unit control commands according to the dispatch control instructions and its current operating electrical parameters, so as to realize the regulation of active power output, voltage support and reactive power support of the receiving end AC main grid.

[0093] The dispatch control commands include active power commands and voltage or reactive power commands issued by the dispatch control center. The operating electrical parameters include the active power output, reactive power output, generator terminal voltage, and motor-side input power of the generator in the current first collecting device motor-generator set. The unit control commands include issuing input power commands to the motor and excitation current commands to the generator. The motor absorbs active power from the low-frequency AC bus based on the input power commands, matching the mechanical power of the motor-generator set with the grid dispatch demand, and realizing the regulation of active power output to the receiving-end AC main grid. The generator adjusts its own excitation current based on the excitation current commands, controlling the generator reactive power output and generator terminal voltage, and realizing voltage and reactive power support to the receiving-end AC main grid.

[0094] When a voltage drop fault is detected on the receiving end AC bus, the synchronous generator in the first collection device is controlled to enter the strong excitation operation state to provide dynamic reactive power support to the receiving end AC bus; at the same time, the mechanical inertia of the motor-generator set is used to provide frequency support; after the receiving end AC bus voltage is restored, the excitation current of the synchronous generator is gradually restored to the level before the fault according to the preset recovery rate.

[0095] In the second collection and output branch, the DC side of the sending-end modular commutator adopts dual closed-loop control. An outer loop is constructed to measure the average capacitor voltage of the submodules, generating a DC current reference value based on the deviation between the reference and actual values ​​of the average capacitor voltage. An inner loop is constructed to adjust the amplitude of the third harmonic component introduced into the modulation voltage of the sending-end MCC AC side based on the deviation between the DC current reference value and the actual DC current. This alters the equivalent power exchange relationship between the AC and DC sides, achieving energy balance within the sending-end MCC and ensuring smooth transmission of renewable energy output power to the DC bus. The receiving-end converter in the second collection and output branch employs a topology-independent constant DC voltage control method. A DC voltage closed-loop is constructed to regulate the DC current, stabilizing the DC bus voltage at a preset reference value. When the receiving-end converter is a modular multilevel converter (MMC), its AC side uses common-mode voltage control to stabilize the DC side voltage. When the receiving-end converter is a modular commutator (MCC), it introduces a controllable third harmonic component into the AC output voltage waveform and adjusts the amplitude of the third harmonic component based on the DC bus voltage deviation to change the equivalent transformation relationship between AC voltage and DC voltage, thereby achieving regulation and stabilization of DC bus voltage.

[0096] As attached Figure 2 As shown, in the appendix Figure 1 Based on the basic structure, this invention further provides an expansion structure suitable for multi-cluster extended access, including multiple first-type new energy clusters, multiple DC ports (DC leads) are led out from the DC transmission line of the second collection and transmission branch, and are respectively connected to the low-frequency AC transmission lines of multiple first collection and transmission branches through multiple mutual assistance and coordination devices, thereby realizing the mutual assistance expansion of "DC trunk - multi-port - multi-MG circuit".

[0097] Specifically, attached Figure 2 The medium-voltage direct current (HVDC) transmission line serves as the main HVDC transmission channel. DC power is injected into it by a converter at the sending end, and then output to the receiving end AC grid by a converter at the receiving end. Several HVDC outgoing lines are installed on this main HVDC line, each corresponding to at least one mutual support and coordination device. The other side of each mutual support and coordination device is connected to different low-frequency AC transmission lines, thus establishing electrical coupling with the corresponding MG (Gas-Mount) collection and transmission circuit. Through this port-based expansion method, multiple MG grid-connected units corresponding to multiple Type I renewable energy clusters can be connected to the same HVDC transmission line as needed, achieving parallel mutual support and resource sharing across multiple branches.

[0098] With appendix Figure 1 Compared to the single-end mutual assistance structure, the attached Figure 2 The extended structure has the following engineering characteristics:

[0099] The mutual assistance port can be expanded: by setting multiple outgoing ports on the DC transmission line, the number of mutual assistance and coordination devices can be flexibly expanded, so that the DC branch can establish mutual assistance relationship with multiple MG outgoing circuits according to engineering needs;

[0100] Multi-circuit mutual assistance and coordination: Different low-frequency AC output circuits can form indirect power mutual assistance capabilities through "DC trunk + mutual assistance and coordination device". When the input power of a certain MG circuit fluctuates or needs to be started, power support / absorption can be achieved by the DC side or other circuits through the DC trunk.

[0101] The DC backbone continues to transmit power without being affected: DC transmission lines will still serve as the main transmission channels for the second type of new energy clusters. The mutual assistance port is a bypass-type controllable support interface, which can be used to smooth and optimize the distribution during normal operation, and can also provide emergency mutual assistance support during faults, so as to avoid the overall transmission capacity of the system from being reduced due to the limitation of a single branch.

[0102] Therefore, by attaching Figure 2 The DC port-based output and multi-mutual-assistance device configuration shown in this invention achieves flexibility and scalable mutual-assistance capability with multiple MG low-frequency output circuits while keeping the main output channel of the second type of new energy cluster unchanged, providing a unified topology framework for the aggregation and output of heterogeneous new energy in multiple clusters and multiple circuits.

[0103] In this invention, the extended structure of the multi-terminal heterogeneous new energy collection and transmission system can further include at least one third-type new energy cluster; each third-type new energy source is connected to the receiving-end AC main grid through a corresponding third collection and transmission branch; wherein, the third collection and transmission branch includes a power frequency AC collection bus and a power frequency AC transmission line, the power frequency AC collection bus collects the power from the third-type new energy cluster, and the power frequency AC transmission line transmits the power to the receiving-end AC main grid. The second collection and transmission branch of the second-type new energy cluster, i.e., the DC main transmission channel, can also be connected to the power frequency AC transmission line corresponding to at least one third-type new energy cluster through a mutual assistance and coordination device. The mutual assistance and coordination device achieves power mutual assistance and power fluctuation smoothing for the power frequency transmission of the third-type new energy cluster.

[0104] The first type of new energy cluster typically has an installed capacity ranging from 300MW to 4GW and a typical transmission distance ranging from 70km to 100km; it generally uses low-frequency AC power transmission to achieve grid connection, in order to balance power transmission efficiency and system stability.

[0105] The second type of new energy cluster typically has an installed capacity of more than 4GW and a typical transmission distance of more than 100km; it usually uses flexible DC transmission to connect to the grid in order to meet the low-loss transmission requirements over ultra-long distances.

[0106] The third type of new energy cluster typically has an installed capacity of less than 300MW and a typical transmission distance of less than 70km; it usually adopts power frequency AC transmission for local grid connection to simplify system structure and reduce construction and operation and maintenance costs.

[0107] It should be noted that the above typical ranges and grid connection methods are only reference classifications for engineering practice and are not absolute boundaries. In actual applications, adjustments can be made due to changes in power grid planning objectives. The capacity and distance ranges of various types of new energy clusters may overlap to some extent, and the grid connection methods can be flexibly adjusted according to engineering needs. For example, although some new energy clusters belong to the installed capacity and distance range corresponding to the first type of new energy clusters, in order to control initial construction costs, they can first be connected to the grid using power frequency AC. Subsequently, as the system expands and transmission demand increases, they can be gradually upgraded to low-frequency AC or flexible DC transmission methods. Some clusters that are close to the installed capacity and distance thresholds can also flexibly choose more suitable grid connection technologies according to the requirements of the regional power grid. Such flexible adjustments to the range and methods are only reasonable choices made based on actual conditions in engineering practice and do not affect the core design logic of this invention, which adapts to different levels of capacity and distance.

[0108] Example 1: Multi-terminal heterogeneous offshore wind power cluster collection and transmission system

[0109] When the multi-terminal heterogeneous new energy collection and transmission system of the present invention is applied to large-scale offshore wind power transmission, the multi-terminal heterogeneous offshore wind power cluster collection and transmission system includes at least one first type of offshore wind power cluster suitable for mid-to-far-sea transmission and at least one second type of offshore wind power cluster suitable for large-capacity long-distance transmission.

[0110] Each of the first-class offshore wind power clusters (applicable to offshore wind power clusters for mid-to-long-distance transmission) and the second-class offshore wind power clusters (applicable to offshore wind power clusters for large-capacity long-distance transmission) are connected to the receiving-end AC main grid through the corresponding first collection and transmission branch and second collection and transmission branch, respectively.

[0111] The first collection and transmission branch includes a low-frequency AC collection bus, a low-frequency AC transmission line, and a first collection device, which are sequentially connected between the first type of offshore wind power cluster and the receiving-end AC main grid. The first collection device is a motor-generator set, wherein the motor is a synchronous motor, the generator is a synchronous generator, and the capacity of the motor and the generator are matched and coaxially connected. One side of the motor is connected to the low-frequency AC transmission line, and the other side of the generator is connected to the receiving-end AC main grid.

[0112] The second collection and transmission branch includes an AC collection bus, a sending-end converter, a DC transmission line, and a receiving-end converter, which are connected sequentially between the second-class offshore wind power cluster and the receiving-end AC main grid.

[0113] At least one DC transmission line corresponding to a second-type offshore wind power cluster is connected to at least one low-frequency AC transmission line corresponding to a first-type offshore wind power cluster through a mutual assistance and coordination device.

[0114] In an embodiment of the present invention, the sender converter in the second collection output branch adopts a modular commutator (MCC). Since the sender converter valve is located on the offshore platform, in order to reduce the platform weight, reduce the equipment size and increase the power density, the sender converter preferably adopts an MCC topology.

[0115] To achieve smooth power delivery from new energy sources to the DC bus and maintain energy balance within the energy storage units of the sending-end MCC, the DC side of the sending-end MCC employs a control method combining outer-loop control based on the average capacitor voltage of the submodules and inner-loop control based on DC current. Specifically, the DC side of the sending-end MCC constructs an outer loop based on the average capacitor voltage of the submodules, and generates a DC current reference value from the outer loop output. Simultaneously, a DC current inner loop is constructed based on the DC current reference value. With actual DC current feedback value To adjust the deviation, the amplitude of the third harmonic component in the AC modulation voltage of the MCC at the sending end is adjusted. This is to change the equivalent power exchange relationship between the AC side and DC side of the sending-end MCC, thereby adjusting the DC side output power, realizing the internal energy balance of the sending-end MCC, and enabling the output power of new energy to be smoothly transmitted to the DC bus.

[0116] like Figure 6 As shown, This indicates a reference value for the average capacitor voltage of the MCC submodule at the sending end; The average value of the capacitor voltage of each arm or submodule of the MCC at the sending end can be expressed as:

[0117]

[0118] in, The number of submodules participating on average. For the first The capacitor voltage of each submodule.

[0119] Because there is a coupling relationship between the AC-side output voltage and the DC-side average voltage of the MCC, as shown in Equation 1; to obtain adjustable degrees of freedom on the DC side, a third harmonic component is introduced into the AC-side output voltage waveform of the sending-end converter to increase the control degrees of freedom on the DC side. The AC / DC voltage relationship at this time is shown in Equation 2. The amplitude of the third harmonic component is adjusted... By controlling the DC current, energy balance control can be achieved within the sending-end converter.

[0120] (1)

[0121] (2)

[0122] in, This refers to the amplitude of the AC side output phase voltage. The average voltage on the DC side. It is the ratio of the amplitude of the third harmonic voltage component to the amplitude of the fundamental frequency voltage.

[0123] The receiving-end converter can be either MCC or MMC. Regardless of the topology used, the DC side adopts a constant DC voltage control method. By constructing a DC voltage closed loop, the DC current is adjusted to stabilize the DC bus voltage at a preset reference value.

[0124] Taking the receiving-end converter as a modular commutator (MCC) as an example, there is a coupling relationship between its AC side output voltage and DC side average voltage. In order to achieve controllable adjustment of the DC bus voltage, the receiving-end MCC adopts a third harmonic regulation control method based on the DC bus voltage closed loop on the DC side.

[0125] Specifically, as shown in the attached document Figure 7 As shown, the DC side of the receiving end MCC uses the DC bus voltage reference value. For the target value, the actual DC bus voltage Sampling and filtering are performed to obtain a smooth DC voltage feedback value. Then, the feedback value is compared with the DC bus voltage reference value to obtain the DC voltage deviation, which is input to a PI controller to generate a voltage regulation component in the dq coordinate system. Finally, a coordinate transformation is performed, combined with a cubic angular frequency signal. Construct a third harmonic modulation signal and output the third harmonic amplitude adjustment value. By saying By introducing the received-end MCC AC modulation voltage waveform, the equivalent transformation relationship between the AC side output voltage and the DC side average voltage can be adjusted without changing the AC side fundamental output target, thereby realizing the regulation and stabilization of the received-end DC bus voltage.

[0126] A mutual assistance and coordination device is used to achieve power mutual assistance between the second and first collection and output branches and the first collection and output branch, as well as soft-start control of the first collection device. The mutual assistance and coordination device is either a modular commutator converter (MCC) or a modular multilevel converter (MMC). When the first collection device starts, the mutual assistance and coordination device outputs low-frequency, low-voltage AC power to the synchronous motor side of the first collection device for frequency conversion soft-start of the motor-generator set. During startup, the frequency and voltage of the output AC power are gradually increased, allowing the synchronous motor to drive the synchronous generator to smoothly increase speed. When the speed of the motor-generator set meets the synchronous grid connection speed conditions, the amplitude, frequency, and phase of the synchronous generator terminal voltage are adjusted to ensure synchronous grid connection with the receiving-end AC main grid. After meeting the synchronous grid connection conditions, the first collection device is put into operation. When the change in output power of the first type of new energy cluster exceeds the set fluctuation threshold within a preset time interval, the difference between the target operating power and the actual operating power of the motor-generator set of the first collection device is calculated as the power tracking command of the mutual assistance and coordination device. This commands the second type of new energy cluster to inject power or absorb power into the low-frequency AC collection bus corresponding to the first type of new energy cluster via the mutual assistance and coordination device, thereby achieving quasi-constant power operation of the motor-generator set of the first collection device. During normal operation of the multi-terminal heterogeneous new energy collection and transmission system, the first collection device corresponding to each type of new energy cluster calculates and issues motor input power commands and generator excitation current commands based on the active power commands and voltage or reactive power commands issued by the dispatch control center, combined with the current operating electrical parameters of the motor-generator set of the first collection device. This enables the regulation of active power output, voltage support, and reactive power support for the receiving end AC main grid. When a voltage drop fault is detected on the receiving end AC bus, the synchronous generator in the first collection device is controlled to enter the strong excitation operation state to provide dynamic reactive power support to the receiving end AC bus; at the same time, the mechanical inertia of the motor-generator set is used to provide frequency support; after the receiving end AC bus voltage is restored, the excitation current of the synchronous generator is gradually restored to the level before the fault according to the preset recovery rate.

[0127] Example 2: A land-based new energy cluster collection and transmission system

[0128] The multi-terminal heterogeneous new energy collection and transmission system disclosed in this invention can also be used for onshore wind power clusters and / or photovoltaic clusters. In Embodiment 2, both the sending-end converter and the receiving-end converter adopt modular multilevel converters (MMC). The AC side of the receiving-end converter uses common-mode voltage control to stabilize the DC side voltage.

[0129] The mutual aid converter can be either MCC or MMC. Regardless of the topology used, the DC side adopts a constant DC current control method. The control method can be referred to the sending-end converter, and will not be elaborated here.

[0130] like Figure 3 As shown, the present invention also discloses a hierarchical control architecture for a multi-terminal heterogeneous new energy collection and transmission system, including a scheduling control center, a local system controller, and multiple device controllers; the device controllers include a mutual aid and coordination device controller, an MG controller, a sending-end converter controller, and a receiving-end converter controller.

[0131] The dispatch control center is located at the upper layer of the control architecture and is used to issue start / stop commands, AGC active power dispatch commands, and AVC voltage / reactive power dispatch commands to the multi-terminal heterogeneous new energy aggregation and transmission system according to the operation requirements of the receiving end AC main grid.

[0132] The local system controller is located in the middle layer of the control architecture. It is used to receive instructions issued by the scheduling and control center, and, in conjunction with the real-time operating status of the first type of new energy cluster, the second type of new energy cluster, the first collection device, the mutual assistance and coordination device, and the transmitting and receiving end converters, to identify and switch the current operating mode of the multi-terminal heterogeneous new energy collection and transmission system, and to issue corresponding control settings to the controllers of each device to realize the coordinated operation between the first collection device and the second collection and transmission branch.

[0133] When it is detected that the first collection device has not completed startup and grid connection, the local system controller enables the soft start mode and sends the soft start control setting value to the mutual assistance and coordination device controller. The mutual assistance and coordination device then performs a soft start on the first collection device. After the motor-generator speed of the first collection device meets the synchronous grid connection speed condition, the MG controller adjusts the amplitude, frequency and phase of the synchronous generator terminal voltage to control the first collection device to start operation. Then the local system controller exits the soft start mode and switches the system to normal operation mode.

[0134] The normal operation modes include AGC / AVC regular tracking mode, mutual power smoothing mode, and fault cooperative ride-through mode;

[0135] In the AGC / AVC normal tracking mode, the local system controller allocates targets according to the AGC active power dispatching instructions and the AVC voltage / reactive power dispatching instructions, and the MG controller performs active power and voltage / reactive power tracking control.

[0136] In the mutual assistance power smoothing mode, the local system controller sends a power tracking command to the mutual assistance and coordination device controller based on the detected output power fluctuation of the first type of new energy cluster. The mutual assistance and coordination device controller controls the second type of new energy cluster to inject power or absorb power to the low-frequency AC collection bus corresponding to the first type of new energy cluster through the mutual assistance and coordination device.

[0137] In the collaborative fault traversal mode, the local system controller sends a collaborative fault traversal operation command to the MG controller, and the MG controller switches the first collection device to the fault support operation state.

[0138] Example 3: Multi-terminal heterogeneous new energy collection and transmission system adopts a hierarchical control architecture

[0139] The multi-terminal heterogeneous new energy collection and transmission system adopts a hierarchical control architecture, including a dispatch control center, a local system controller, and multiple device controllers; wherein, the device controllers include a mutual aid and coordination device controller, an MG controller, a sending-end converter controller, and a receiving-end converter controller.

[0140] The dispatch control center is located at the upper layer of the control architecture and is used to issue start / stop commands, AGC active power dispatch commands, and AVC voltage / reactive power dispatch commands to the system according to the operation requirements of the receiving end AC main network.

[0141] The local system controller is located in the middle layer of the control architecture. It is used to receive the upper-level operation targets issued by the scheduling and control center, and, in combination with the real-time operation status of the first type of new energy cluster, the second type of new energy cluster, the first collection device, the mutual assistance and coordination device, and the sending and receiving end converter, identify and switch the current operation mode of the system, and issue the corresponding control settings to the controllers of each device.

[0142] The mutual assistance and coordination device controller, MG controller, sending-end converter controller, and receiving-end converter controller are located in the execution layer and are respectively responsible for the fast closed-loop control of the mutual assistance and coordination device, the first collection device, the sending-end converter, and the receiving-end converter, so as to achieve the specific control objectives of each operating mode of the system.

[0143] Specifically: The dispatch control center mainly issues the following instructions to the local system controller: start and stop instructions for the first aggregation device; AGC active power target value. AVC voltage target value and / or reactive power target value .

[0144] The local system controller is used to: receive instructions from the dispatch control center; determine which operating mode the current system should enter; and send mode signals and control settings to the mutual aid and coordination device controller, MG controller, sending-end converter controller and receiving-end converter controller respectively, so as to realize the coordinated operation between the first collection device and the second collection and sending branch.

[0145] Under the hierarchical control architecture of Embodiment 3, the multi-terminal heterogeneous new energy collection and transmission system can realize the following four functional modes: mutual assistance and coordination device soft start mode, AGC / AVC normal tracking mode, mutual assistance power smoothing mode, and fault cooperative ride-through mode; among them, AGC / AVC normal tracking mode, mutual assistance power smoothing mode, and fault cooperative ride-through mode are all different typical operating modes triggered at different times in the normal operation mode.

[0146] Mode 1: Soft start mode for mutual assistance and coordination devices

[0147] Before the first collection device completes startup and grid connection, the system is in soft-start mode, and mode one is the pre-start mode;

[0148] The execution steps of this mode are as follows:

[0149] S1. When the dispatch control center sends the start command of the first collection device to the local system controller, the local system controller first checks the current status of the first collection device; if it is determined that the first collection device has not yet started and connected to the grid, the local system controller enables the soft start mode.

[0150] S2. The mutual aid and coordination device controller controls the mutual aid and coordination device to output low-frequency low-voltage AC power to the synchronous motor side of the first collection device to replace the static variable frequency starter (SFC) to realize the variable frequency start of the MG unit; subsequently, the mutual aid and coordination device controller gradually increases the frequency and voltage amplitude of the output AC power according to the preset ramp, so that the motor-generator set can smoothly increase speed.

[0151] S3. When the local system controller detects that the motor-generator speed meets the synchronous grid connection speed condition, the MG controller adjusts the amplitude, frequency and phase of the synchronous generator terminal voltage to meet the synchronous grid connection condition with the receiving end AC main grid. After the synchronous grid connection condition is met, the MG controller controls the first collection device to start operation, the local system controller exits the soft start mode and switches the system to the normal operation mode. In Example 3, the normal operation mode includes mode two, namely AGC / AVC conventional tracking mode, mode three, namely mutual power smoothing mode and mode four, namely fault cooperative ride-through mode.

[0152] Mode 2: AGC / AVC Standard Tracking Mode

[0153] After the first collection unit completes grid connection, the local system controller will use the AGC / AVC conventional tracking mode as the basic operating mode of the system and receive the AGC active power target value issued by the dispatch control center. and AVC voltage target value and / or reactive power target value The local system controller sends the corresponding active power setpoint and voltage / reactive power regulation setpoint to the MG controller based on the scheduling target.

[0154] In this mode, the MG controller equates the motor-generator set in the first collection device to a conventional synchronous generator set in the receiving-end AC main grid. Based on the set values ​​issued by the local system controller, it adjusts the input power of the synchronous motor and the excitation current of the synchronous generator, so that the first collection device has active / reactive power regulation capabilities comparable to those of a conventional synchronous generator set.

[0155] The MG controller can adjust the input power of the synchronous motor according to the deviation between the AGC active power target value and the actual active power output of the generator, so that the active power output of the first collection device tracks the active power target issued by the dispatch center. At the same time, the MG controller can adjust the excitation current of the synchronous generator according to the deviation between the AGC voltage target value or reactive power target value and the generator terminal voltage or reactive power output, so that the voltage / reactive power output of the first collection device tracks the voltage or reactive power target issued by the dispatch center.

[0156] Therefore, in Mode 2, the AGC / AVC conventional tracking mode provides the operating target by the dispatch control center, allocates the target by the local system controller, and executes active and voltage / reactive power tracking control by the MG controller, so that the first collection device can be integrated into the conventional dispatch system of the receiving end AC main grid after grid connection.

[0157] Mode 3: Mutual Power Smoothing Mode

[0158] After the first collection device has been connected to the grid, the local system controller monitors the output power changes of the first type of new energy cluster in real time. When the change in the output power of the first type of new energy cluster exceeds the set fluctuation threshold within a preset time interval, the local system controller determines that the system has entered the mutual assistance power stabilization mode and sends the power tracking set value to the mutual assistance and coordination device controller.

[0159] In this mode, the controller of the mutual aid and coordination device collects the output power of the first type of new energy cluster in real time. and at a preset time interval Internal calculation of its power change :

[0160]

[0161] The corresponding power fluctuation amplitude is:

[0162]

[0163] When the following formula is satisfied, the first type of new energy cluster is determined to have experienced a power fluctuation event exceeding the threshold:

[0164]

[0165] in, This is the rated installed capacity of the first type of new energy cluster. To set the fluctuation threshold coefficient, it can be preset by the dispatch center based on the installed capacity of the first type of new energy cluster and the allowable power fluctuation level of the first collection device. In one embodiment, the fluctuation threshold coefficient... The optimal value is 0.05. Upon detecting a fluctuation exceeding the threshold, the mutual aid and coordination device controller generates a power tracking command based on the deviation between the target operating power and the actual operating power of the first collecting device. :

[0166]

[0167] in, The target operating power of the first collecting device motor-generator set, This represents the actual operating power of the first collecting device.

[0168] Subsequently, the mutual aid and coordination device controller controls the second type of new energy cluster to inject or absorb power into the low-frequency AC collection bus corresponding to the first type of new energy cluster via the mutual aid and coordination device, in order to compensate for the power fluctuations of the first type of new energy cluster and maintain the first collection device in a quasi-constant power operation state. The quasi-constant power operation state can be expressed as:

[0169]

[0170] in, The preset allowable deviation can be pre-set by the dispatch center based on the rated capacity of the motor-generator set and system regulation requirements. In one embodiment, the allowable deviation... The preferred value is 0.01 times the target operating power.

[0171] Therefore, in Mode 3, the mutual assistance power stabilization mode is triggered by the local system controller based on the fluctuation status of new energy sources. The mutual assistance coordination device controller mainly performs fast power compensation control, while the MG controller maintains the normal grid-connected operation of the first collection device.

[0172] Mode 4: Collaborative Fault Traversal Mode

[0173] The execution steps for Mode 4 are as follows:

[0174] S1. The local system controller monitors the AC bus voltage at the receiving end in real time. When a voltage drop at the receiving end AC bus is detected, the system is determined to enter the fault cooperative ride-through state. In one embodiment, the voltage drop at the receiving end AC bus is set to be below 0.85 pu (i.e., 85% of the rated voltage) and lasts for at least 20 ms, which is determined to be a voltage drop fault.

[0175] S2. After entering the fault-cooperative ride-through state, the local system controller sends a cooperative fault-crossing operation command to the MG controller. The MG controller switches the first collection device to the fault support operation state and controls the synchronous generator to enter the strong excitation operation state to improve the reactive power output capacity and provide dynamic reactive power support to the receiving end AC bus to promote the recovery of AC voltage during the fault.

[0176] S3. During a fault, the first collection device maintains continuous grid-connected operation, utilizing the inherent mechanical inertia of the motor-generator set to form a natural buffer against the power imbalance caused by the fault, slowing down the rate of change in system frequency, and providing frequency support to the receiving-end power grid.

[0177] S4. The local system controller continuously monitors the fault recovery status. When the AC bus voltage, system frequency, and DC bus voltage at the receiving end recover to the preset normal range and remain so for a preset time, the fault is determined to be cleared. The MG controller will gradually restore the synchronous generator excitation current to the level before the fault according to the preset recovery rate and exit the fault cooperative ride-through mode. Throughout the process, the first collection device does not disconnect, and the second type of new energy cluster maintains continuous grid-connected operation.

[0178] Therefore, in Mode 4, the fault cooperative ride-through mode is triggered by the local system controller based on the system fault status, and the fault support control of the synchronous generator is mainly performed by the MG controller.

[0179] As attached Figure 5 As shown, the present invention also discloses a collaborative control method for a multi-terminal heterogeneous new energy collection and transmission system, the method comprising:

[0180] Step 1: The local system controller detects the grid connection status of the first aggregation device; if it is not connected to the grid, proceed to the soft start mode in Step 2; otherwise, proceed to Step 3.

[0181] Step 2: The local system controller controls the mutual assistance and coordination device to perform a soft start on the first collection device. After the grid connection conditions are met, the controller controls the first collection device to start operation, and then proceeds to step 3.

[0182] As attached Figure 4 As shown, the soft start procedure for the MG unit includes:

[0183] The system checks whether the MG generator unit has started. If it has not started, the mutual assistance and coordination device outputs low-frequency, low-voltage AC power and increases the amplitude of the output voltage and frequency according to a preset ramp until the frequency deviation between the synchronous motor and the voltage frequency of the new energy cluster bus is less than a preset threshold. At this time, the amplitude, frequency, and phase of the synchronous generator terminal voltage are adjusted until the synchronous grid connection conditions are met, that is, the amplitude, frequency, and phase are all less than their respective preset thresholds, and then the MG generator unit is connected to the grid.

[0184] Step 3: Continuously monitor the system's operating status. If a system failure is detected, proceed to Step 4 to execute the collaborative fault traversal mode; otherwise, proceed to Step 5.

[0185] Step 4: The local system controller issues a collaborative fault-crossing operation command to switch the first collection device to the fault support operation state. If the fault is cleared, proceed to step 5; otherwise, maintain the collaborative fault-crossing operation mode.

[0186] Step 5: The local system controller enables the AGC / AVC normal tracking mode and monitors the output power fluctuation event of the first type of new energy cluster in real time. If a power fluctuation occurs, proceed to step 6. Otherwise, according to the AGC active power dispatching instruction and the AVC voltage / reactive power dispatching instruction, control the motor-generator set in the first collection device to track the active power setting or track the voltage / reactive power setting.

[0187] Specifically, the execution steps of the AGC / AVC conventional tracking mode include:

[0188] Step 5.1: The local system controller receives the AGC active power reference value issued by the dispatch center in real time. and AVC voltage reference value or reactive power reference value And collect the current active power output of the MG unit's generator. Reactive power output Generator terminal voltage Motor side input power ;

[0189] Step 5.2: The local system controller generates the motor-side input power command based on the active power deviation. The power input command from the motor side is then sent to the MG controller.

[0190] In one embodiment, the power command is input to the motor side. It can be generated by the active power deviation via the regulator, that is:

[0191]

[0192] in, and These are the proportional coefficient and integral coefficient of the active power regulation link, respectively; The active power deviation is the difference between the AGC active power reference value and the current active power output of the MG unit's generator.

[0193] Step 5.3: The local system controller generates synchronous generator excitation current commands based on voltage deviation or reactive power deviation. The excitation current command is then sent to the MG controller; the MG controller controls the generator terminal voltage and reactive power output by adjusting the generator excitation current.

[0194] In one implementation, the excitation current command It can be generated by the regulator from voltage deviation or reactive power deviation, that is:

[0195]

[0196] or

[0197]

[0198] in, This is the initial value of the excitation current. These are the control parameters for the corresponding adjustment stage; This is the voltage deviation, which is the difference between the AVC voltage reference value and the current generator terminal voltage of the MG unit. The reactive power deviation is the difference between the reactive power reference value and the current reactive power output of the MG unit's generator.

[0199] Step 5.4: The MG controller executes the power input command from the motor. and excitation current command The input power of the synchronous motor and the excitation of the synchronous generator are controlled separately to achieve dynamic tracking of AGC / AVC scheduling commands.

[0200] Step 6: The local system controller controls the mutual assistance and coordination device to enter the mutual assistance power stabilization mode, and controls the second type of new energy cluster to inject power or absorb power into the low-frequency AC collection bus corresponding to the first type of new energy cluster through the mutual assistance and coordination device, so that the first collection device maintains a quasi-constant power operation state.

[0201] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0202] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0203] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0204] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0205] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A multi-terminal heterogeneous new energy collection and transmission system, comprising at least one type I new energy cluster and at least one type II new energy cluster; characterized in that: Each of the first-class and second-class new energy clusters is connected to the receiving-end AC main network through the corresponding first collection and transmission branch and second collection and transmission branch, respectively. The first collection and transmission branch includes a low-frequency AC collection bus, a low-frequency AC transmission line and a first collection device, which are connected sequentially between the first type of new energy cluster and the receiving-end AC main grid. The second collection and transmission branch includes an AC collection bus, a sending-end converter, a DC transmission line, and a receiving-end converter, which are connected sequentially between the second type of new energy cluster and the receiving-end AC main grid. At least one DC transmission line corresponding to a second-type new energy cluster is connected to at least one low-frequency AC transmission line corresponding to a first-type new energy cluster through a mutual assistance and coordination device. The first collection device is an electric motor-generator set; The mutual assistance and coordination device enables power mutual assistance between the second and first collection and transmission branches and the first collection and transmission branch, as well as soft-start control of the first collection device.

2. The multi-terminal heterogeneous new energy collection and transmission system according to claim 1, characterized in that: The multi-terminal heterogeneous new energy collection and transmission system also includes at least one third-type new energy cluster. Each of the third category of new energy sources is connected to the receiving end AC main network through its corresponding third collection and transmission branch. The third collection and transmission branch includes a power frequency AC collection bus and a power frequency AC transmission line. The power frequency AC collection bus collects the third type of new energy cluster power, and the power frequency AC transmission line transmits the power to the receiving end AC main grid.

3. The multi-terminal heterogeneous new energy collection and transmission system according to claim 1, characterized in that: In the motor-generator set, the motor is a synchronous motor, the generator is a synchronous generator, the motor and generator have matching capacities and are coaxially connected; one side of the motor is connected to the low-frequency AC transmission line, and one side of the generator is connected to the receiving-end AC main grid.

4. The multi-terminal heterogeneous new energy collection and transmission system according to claim 1, characterized in that: The mutual assistance and coordination device is a modular commutator converter (MCC) or a modular multilevel converter (MMC).

5. The multi-terminal heterogeneous new energy collection and transmission system according to any one of claims 2-4, characterized in that: When the first collection device is started, the mutual assistance and coordination device is controlled to output low-frequency, low-voltage AC power to the synchronous motor side of the first collection device to perform frequency conversion soft start on the motor-generator set; during the start-up process, the frequency and voltage of the output AC power are gradually increased so that the synchronous motor drives the synchronous generator to smoothly increase speed; when the speed of the motor-generator set meets the synchronous grid connection speed conditions, the amplitude, frequency and phase of the synchronous generator terminal voltage are adjusted so that it meets the synchronous grid connection conditions with the receiving end AC main grid; after the synchronous grid connection conditions are met, the first collection device is put into operation.

6. The multi-terminal heterogeneous new energy collection and transmission system according to claim 5, characterized in that: When the change in the output power of the first type of new energy cluster exceeds the set fluctuation threshold within a preset time interval, the difference between the target operating power and the actual operating power of the motor-generator set of the first collection device is calculated as the power tracking command of the mutual assistance and coordination device. The second type of new energy cluster is controlled to inject power or absorb power into the low-frequency AC collection bus corresponding to the first type of new energy cluster through the mutual assistance and coordination device, so as to realize the quasi-constant power operation of the motor-generator set of the first collection device.

7. The multi-terminal heterogeneous new energy collection and transmission system according to claim 5, characterized in that: When the multi-terminal heterogeneous new energy collection and transmission system is operating normally, the first collection device corresponding to each first type of new energy cluster calculates and issues unit control commands according to the dispatch control instructions and its current operating electrical parameters, so as to realize the regulation of active power output, voltage support and reactive power support of the receiving end AC main grid.

8. The multi-terminal heterogeneous new energy collection and transmission system according to claim 5, characterized in that: When a voltage drop fault is detected on the receiving end AC bus, the synchronous generator in the first collection device is controlled to enter the strong excitation operation state to provide dynamic reactive power support to the receiving end AC bus; at the same time, the mechanical inertia of the motor-generator set is used to provide frequency support; after the receiving end AC bus voltage is restored, the excitation current of the synchronous generator is gradually restored to the level before the fault according to the preset recovery rate.

9. The multi-terminal heterogeneous new energy collection and transmission system according to claim 1, characterized in that: The sending-end converter is a modular commutator (MCC), and the receiving-end converter is a modular multilevel converter (MMC) or a modular commutator (MCC).

10. The multi-terminal heterogeneous new energy collection and transmission system according to claim 9, characterized in that: In the second collection and output branch, the DC side of the sending end MCC adopts dual closed-loop control to construct the outer loop of the submodule average capacitor voltage and generate a DC current reference value based on the deviation between the reference value and the actual value of the submodule average capacitor voltage. A DC current inner loop is constructed. Based on the deviation between the DC current reference value and the actual DC current, the amplitude of the third harmonic component introduced in the modulation voltage of the AC side of the sending-end MCC is adjusted to change the equivalent power exchange relationship between the AC and DC sides, realize the internal energy balance of the sending-end MCC, and enable the output power of the new energy source to be smoothly transmitted to the DC bus.

11. The multi-terminal heterogeneous new energy collection and transmission system according to claim 9, characterized in that: In the second collection and output branch, the DC side of the receiving-end converter adopts a topology-independent constant DC voltage control method. By constructing a DC voltage closed loop, the DC current is adjusted to stabilize the DC bus voltage at a preset reference value.

12. The multi-terminal heterogeneous new energy collection and transmission system according to claim 11, characterized in that: When the receiving-end converter is a modular commutator (MCC), it introduces a controllable third harmonic component into the AC output voltage waveform and adjusts the amplitude of the third harmonic component based on the DC bus voltage deviation to change the equivalent transformation relationship between AC voltage and DC voltage, thereby achieving regulation and stabilization of DC bus voltage.

13. A hierarchical control architecture for the multi-terminal heterogeneous new energy collection and transmission system according to any one of claims 1-12, comprising a scheduling control center, a local system controller, and multiple device controllers; characterized in that: The dispatch control center is located at the upper layer of the control architecture and is used to issue start / stop commands, AGC active power dispatch commands, and AVC voltage / reactive power dispatch commands to the multi-terminal heterogeneous new energy aggregation and transmission system according to the operation requirements of the receiving end AC main grid. The local system controller is located in the middle layer of the control architecture. It is used to receive instructions issued by the scheduling and control center, and, in conjunction with the real-time operating status of the first type of new energy cluster, the second type of new energy cluster, the first collection device, the mutual assistance and coordination device, and the transmitting and receiving end converters, to identify and switch the current operating mode of the multi-terminal heterogeneous new energy collection and transmission system, and to issue corresponding control settings to the controllers of each device to realize the coordinated operation between the first collection device and the second collection and transmission branch.

14. The hierarchical control architecture of the multi-terminal heterogeneous new energy collection and transmission system according to claim 13, characterized in that: The device controller includes a mutual aid and coordination device controller, an MG controller, a sending-end converter controller, and a receiving-end converter controller.

15. The hierarchical control architecture of the multi-terminal heterogeneous new energy collection and transmission system according to claim 14, characterized in that: When it is detected that the first collection device has not completed startup and grid connection, the local system controller enables the soft start mode and sends the soft start control setting value to the mutual assistance and coordination device controller. The mutual assistance and coordination device then performs a soft start on the first collection device. After the motor-generator speed of the first collection device meets the synchronous grid connection speed condition, the MG controller adjusts the amplitude, frequency and phase of the synchronous generator terminal voltage to control the first collection device to start operation. Then the local system controller exits the soft start mode and switches the system to normal operation mode.

16. The hierarchical control architecture of the multi-terminal heterogeneous new energy collection and transmission system according to claim 15, characterized in that: The normal operating modes include AGC / AVC regular tracking mode, mutual power smoothing mode, and fault cooperative ride-through mode; In the AGC / AVC normal tracking mode, the local system controller allocates targets according to the AGC active power dispatching instructions and the AVC voltage / reactive power dispatching instructions, and the MG controller performs active power and voltage / reactive power tracking control. In the mutual assistance power smoothing mode, the local system controller sends a power tracking command to the mutual assistance and coordination device controller based on the detected output power fluctuation of the first type of new energy cluster. The mutual assistance and coordination device controller controls the second type of new energy cluster to inject power or absorb power to the low-frequency AC collection bus corresponding to the first type of new energy cluster through the mutual assistance and coordination device. In the collaborative fault traversal mode, the local system controller sends a collaborative fault traversal operation command to the MG controller, and the MG controller switches the first collection device to the fault support operation state.

17. A collaborative control method for a multi-terminal heterogeneous new energy collection and transmission system based on the hierarchical control architecture described in any one of claims 13-16, characterized in that, The method includes: Step 1: The local system controller detects the grid connection status of the first aggregation device; if it is not connected to the grid, proceed to the soft start mode in Step 2; otherwise, proceed to Step 3. Step 2: The local system controller controls the mutual assistance and coordination device to perform a soft start on the first collection device. After the grid connection conditions are met, the controller controls the first collection device to start operation, and then proceeds to step 3. Step 3: Continuously monitor the system's operating status. If a system failure is detected, proceed to Step 4 to execute the collaborative fault traversal mode; otherwise, proceed to Step 5. Step 4: The local system controller issues a collaborative fault-crossing operation command to switch the first collection device to the fault support operation state. If the fault is cleared, proceed to step 5; otherwise, maintain the collaborative fault-crossing operation mode. Step 5: The local system controller enables the AGC / AVC normal tracking mode and monitors the output power fluctuation event of the first type of new energy cluster in real time. If a power fluctuation occurs, proceed to step 6. Otherwise, according to the AGC active power dispatching instruction and the AVC voltage / reactive power dispatching instruction, control the motor-generator set in the first collection device to track the active power setting or track the voltage / reactive power setting. Step 6: The local system controller controls the mutual assistance and coordination device to enter the mutual assistance power stabilization mode, and controls the second type of new energy cluster to inject power or absorb power into the low-frequency AC collection bus corresponding to the first type of new energy cluster through the mutual assistance and coordination device, so that the first collection device maintains a quasi-constant power operation state.

18. The collaborative control method for a multi-terminal heterogeneous new energy collection and transmission system according to claim 17, characterized in that: In step 2, the mutual assistance and coordination device is controlled to output low-frequency, low-voltage AC power to the synchronous motor side of the first collection device to perform frequency conversion soft start on the motor-generator set; the frequency and voltage of the output AC power are gradually increased, and when the speed of the motor-generator set meets the synchronous grid connection speed conditions, the amplitude, frequency and phase of the voltage at the synchronous generator terminal are adjusted to make it meet the synchronous grid connection conditions with the receiving end AC main grid; after meeting the synchronous grid connection conditions, the first collection device is put into operation to realize the grid connection of the first collection device.

19. The collaborative control method for a multi-terminal heterogeneous new energy collection and transmission system according to claim 18, characterized in that: In step 3, when the voltage of the AC main grid bus at the receiving end drops to the set drop fault threshold and continues for a set delay, it is determined that a voltage drop fault has occurred in the system, and the local system controller enables the fault cooperative ride-through mode.

20. The collaborative control method for a multi-terminal heterogeneous new energy collection and transmission system according to claim 18 or 19, characterized in that: In step 4, the local system controller sends a coordinated fault-crossing operation command to the MG controller, controls the synchronous generator to enter the strong excitation operation state, improves the reactive power output capacity, and provides dynamic reactive power support to the receiving end AC bus; controls the first collection device to maintain continuous grid-connected operation, and uses the inherent mechanical inertia of the motor-generator set to provide frequency support to the receiving end power grid.

21. The collaborative control method for a multi-terminal heterogeneous new energy collection and transmission system according to claim 17, characterized in that: In step 5, the local system controller receives the AGC active power target value or the AVC voltage target value / reactive power target value issued by the dispatch control center; Based on the received target value, the local system controller sends the corresponding active power setpoint and voltage / reactive power regulation setpoint to the MG controller, and equates the motor-generator set in the first collection device to the synchronous generator set in the receiving end AC main grid, and performs active power and voltage / reactive power tracking control.

22. The collaborative control method for a multi-terminal heterogeneous new energy collection and transmission system according to claim 21, characterized in that: In step 6, when the change in the output power of the first type of new energy cluster exceeds the set fluctuation threshold within a preset time interval, the local system controller determines that the system has entered the mutual assistance power smoothing mode. The mutual assistance and coordination device controller generates a power tracking command based on the deviation between the target operating power and the actual operating power of the first collection device. Based on the tracking command, the mutual assistance and coordination device controller controls the second type of new energy cluster to inject power or absorb power into the low-frequency AC collection bus corresponding to the first type of new energy cluster through the mutual assistance and coordination device, so as to compensate for the power fluctuation of the first type of new energy cluster and keep the first collection device in a quasi-constant power operation state.

23. An apparatus comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, the processor executing the computer program to implement the steps of the collaborative control method for a multi-terminal heterogeneous new energy collection and transmission system according to any one of claims 17 to 22.

24. A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the collaborative control method for a multi-terminal heterogeneous new energy collection and transmission system according to any one of claims 17 to 22.

Images