Control method and device for offshore low-frequency alternating current system

Abstract

The invention provides a control method of an offshore low-frequency alternating current system, a control device of the offshore low-frequency alternating current system and a storage medium. The method comprises the steps that the output power of an offshore wind plant, the rated power of a DRU-MMC module and the actual output power are acquired; calculating a power deviation value, and adjusting and controlling the parallel auxiliary converter through PID based on the deviation value so as to adjust the power output of the wind power plant; and under the condition that the second target power is greater than the first target power, if the onshore station fails, the submarine cable interconnection switch is switched off, the voltage of the offshore station is maintained to be stable through reactive power control, and meanwhile, the DRU-MMC module outputs the target power. The method improves system automation and fault recovery capability, ensures safe and stable operation of the wind power plant, and solves the problems of low automation level, poor fault recovery capability and power grid stability and the like caused by dependence on manual operation or relatively complex manual operation of the offshore wind power plant in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a control method for an offshore low-frequency alternating current system, a control device for an offshore low-frequency alternating current system, and a computer-readable storage medium. Background Art

[0002] As an important development direction of renewable energy, offshore wind farms have received extensive attention and rapid development. Compared with onshore wind farms, the advantages of offshore wind farms are obvious. First, offshore wind resources are abundant and stable, and the number of hours of power generation is high; second, offshore wind farms are almost not restricted by terrain and landforms, and have greater development potential; third, offshore wind farms can achieve large-scale centralized power generation to meet the needs of future energy transformation. In addition, during the construction and operation of offshore wind power, its environmental impact is relatively small, especially in the mid-sea area, where wind farms have more abundant wind resources and are suitable for large-scale layout.

[0003] In the power transmission system of COSCO wind farms, DC transmission technology has become the mainstream technical solution due to its low loss, high efficiency and adaptability to large-capacity and long-distance power transmission. The DC transmission system composed of modular multilevel converters (MMC) and diode rectifier units (DRU) can significantly reduce system losses during power transmission, has a small footprint and weight, and its control method is relatively simple and economical. This makes this technology have a good application prospect in the DC transmission solution of offshore wind farms, especially in the power output problem of COSCO wind farms. The combination of MMC and DRU can effectively improve the transmission efficiency and reduce the construction and operation costs of wind farms.

[0004] However, in practical applications, the particularity of offshore wind farms makes the stability and security of the power system face some technical challenges. For example, since offshore wind farms are far away from land, it is difficult to quickly repair them when a fault occurs, and the ability of the power grid to start and maintain the system voltage becomes a key issue. In order to ensure that offshore wind farms can achieve self-recovery startup and stable operation of the system in the event of sudden outages or failures, the design of auxiliary converters has become the core of solving this problem. In the prior art, the role of auxiliary converters is to provide a "black start" function for offshore wind farms and maintain the stability of the system AC voltage.

[0005] Although the existing DC transmission system can provide good power transmission performance, the black start process in the existing technology usually requires relatively complex manual intervention and operation, which not only increases the difficulty of operation, but also may cause the system to be unable to achieve rapid self-recovery in an emergency. Especially for offshore wind farms far away from land, the lack of effective automated control means will prolong the fault recovery time and affect the operational stability of the wind farm and the security of the power grid. Summary of the invention

[0006] The main purpose of the present application is to provide a control method for an offshore low-frequency AC system, a control device for an offshore low-frequency AC system and a computer-readable storage medium, so as to at least solve the problems in the prior art that offshore wind farms rely on manual or relatively complex manual operations, resulting in low automation levels, poor fault recovery capabilities and grid stability.

[0007] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a control method for an offshore low-frequency AC system is provided, wherein the offshore low-frequency AC system includes an offshore wind farm, a DRU-MMC module and a parallel auxiliary converter, the DRU-MMC module includes an offshore station DRU and an onshore station MMC, the parallel auxiliary converter includes an offshore station and an onshore station, and the control method includes: obtaining the output power of the offshore wind farm to obtain a first target power, obtaining the rated output power of the DRU-MMC module to obtain a second target power, obtaining the output power of the DRU-MMC module to obtain a third target power; in the case where the second target power is greater than the first target power, if the first target power is greater than the third target power, If a preset power or the MMC power of the land station is limited, the difference between the first target power and the third target power is calculated to obtain a first power deviation value, and the parallel auxiliary converter is controlled to perform PID adjustment on the offshore wind farm based on the first power deviation value, and the adjusted first target power is output by the DRU-MMC module; when the second target power is greater than the first target power, if the land station fails, the submarine cable connecting switch of the parallel auxiliary converter is disconnected to disconnect the land station, and the parallel auxiliary converter is controlled to perform reactive control to maintain the AC voltage fluctuation of the offshore station less than the first threshold, and the DRU-MMC module is used to output the first target power.

[0008] Optionally, after obtaining the output power of the offshore wind farm, obtaining the first target power, obtaining the rated output power of the DRU-MMC module, obtaining the second target power, obtaining the output power of the DRU-MMC module, and obtaining the third target power, the method further includes: when the second target power is less than or equal to the first target power, calculating the difference between the first target power and the second target power to obtain a second power deviation value; outputting the portion of the second power deviation value in the first target power with the parallel auxiliary converter; and outputting the portion of the second target power in the first target power with the DRU-MMC module.

[0009] Optionally, after obtaining the output power of the offshore wind farm, obtaining the first target power, obtaining the rated output power of the DRU-MMC module, obtaining the second target power, obtaining the output power of the DRU-MMC module, and obtaining the third target power, the method further includes: when the second target power is less than or equal to the first target power, if the onshore station fails, controlling the parallel auxiliary converter to limit the power of the offshore wind farm to control the first target power to be less than the second target power.

[0010] Optionally, the offshore station also includes an energy storage / AC energy consumption device. After controlling the parallel auxiliary converter to limit the power of the offshore wind farm to control the first target power to be less than the second target power, the method also includes: if the parallel auxiliary converter fails to limit the power of the offshore wind farm, controlling the energy storage / AC energy consumption device to absorb the part of the second power deviation in the first target power, and outputting the part of the second target power in the first target power with the DRU-MMC module.

[0011] Optionally, the offshore low-frequency AC system also includes a low-frequency AC circuit breaker. After controlling the parallel auxiliary converter to limit the power of the offshore wind farm to control the first target power to be less than the second target power, the method also includes: if the parallel auxiliary converter fails to limit the power of the offshore wind farm and the energy storage / AC energy consumption device fails, controlling the DRU-MMC module and the parallel auxiliary converter to trip.

[0012] Optionally, the offshore low-frequency AC system further includes a low-frequency AC circuit breaker, and the method further includes: in the event of a fault in the offshore station, controlling the DRU-MMC module and the parallel auxiliary converter to trip.

[0013] Optionally, the offshore station also includes an energy storage / AC energy consumption device. After controlling the parallel auxiliary converter to perform PID adjustment on the offshore wind farm based on the first power deviation value, and outputting the adjusted first target power with the DRU-MMC module, the method also includes: in the event that the DRU-MMC module fails and trips, obtaining the rated output power of the parallel auxiliary converter to obtain a fourth target power; controlling the parallel auxiliary converter to limit the power of the offshore wind farm to control the first target power to be less than the fourth target power; if the parallel auxiliary converter fails to limit the power of the offshore wind farm, controlling the energy storage / AC energy consumption device to absorb the part of the first target power that exceeds the fourth target power; if the parallel auxiliary converter fails to limit the power of the offshore wind farm and the energy storage / AC energy consumption device fails, controlling the parallel auxiliary converter to trip, and controlling the wind turbine of the offshore wind farm to stop running.

[0014] Optionally, after controlling the parallel auxiliary converter to perform reactive control to maintain the AC voltage fluctuation of the offshore station less than a first threshold, and using the DRU-MMC module to output the first target power, the method further includes: in the event that the DRU-MMC module fails and trips, controlling the parallel auxiliary converter to trip, and controlling the wind turbines of the offshore wind farm to stop running.

[0015] According to another aspect of the present application, a control device for an offshore low-frequency AC system is provided, wherein the offshore low-frequency AC system includes an offshore wind farm, a DRU-MMC module and a parallel auxiliary converter, wherein the DRU-MMC module includes an offshore station DRU and an onshore station MMC, wherein the parallel auxiliary converter includes an offshore station and an onshore station, and wherein the control device includes: a first acquisition unit, configured to acquire the output power of the offshore wind farm to obtain a first target power, acquire the rated output power of the DRU-MMC module to obtain a second target power, acquire the output power of the DRU-MMC module to obtain a third target power; and a first control unit, configured to, when the second target power is greater than the first target power, acquire the output power of the DRU-MMC module to obtain a third target power. If a preset power or the MMC power of the land station is limited, the difference between the first target power and the third target power is calculated to obtain a first power deviation value, and the parallel auxiliary converter is controlled to perform PID adjustment on the offshore wind farm based on the first power deviation value, and the adjusted first target power is output by the DRU-MMC module; a second control unit is used to disconnect the submarine cable connecting switch of the parallel auxiliary converter to disconnect the land station when the second target power is greater than the first target power and if the land station fails, and control the parallel auxiliary converter to perform reactive power control to maintain the AC voltage fluctuation of the offshore station less than a first threshold, and output the first target power by the DRU-MMC module.

[0016] According to another aspect of the present application, a computer-readable storage medium is provided, wherein the computer-readable storage medium includes a stored program, wherein when the program is executed, the device where the computer-readable storage medium is located is controlled to execute any one of the methods described.

[0017] By applying the technical solution of this application, this application obtains the output power of the offshore wind farm, the rated and actual output power of the DRU-MMC module, and performs PID adjustment based on the power deviation value to control the parallel auxiliary converter to accurately adjust the offshore wind farm, thereby realizing automatic optimization and adjustment of the system power. At the same time, when a failure occurs in the onshore station, this application effectively maintains the voltage stability of the offshore station by disconnecting the submarine cable contact switch and performing reactive power control, thereby ensuring the safe operation of the system in the event of a failure. This solves the problems in the prior art that offshore wind farms rely on manual or relatively complex manual operations, resulting in low automation levels, poor fault recovery capabilities, and poor grid stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A DRU-MMC system diagram provided in an embodiment of the present application is shown;

[0019] Figure 2A schematic flow chart of a control method for a marine low-frequency AC system provided according to an embodiment of the present application is shown;

[0020] Figure 3 A structural block diagram of a control device for a marine low-frequency AC system provided according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0021] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0022] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0023] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0024] For the convenience of description, some nouns or terms involved in the embodiments of the present application are explained below:

[0025] DRU (Diode Rectifier Unit): A diode-based rectifier used to convert AC power into DC power. The main feature of DRU is that it does not have the ability to output AC voltage, so it cannot directly provide AC voltage support. In offshore low-frequency transmission systems, DRU is usually connected in parallel with a small modular multilevel converter (MMC) to establish the AC voltage of the offshore station.

[0026] MMC (Modular Multilevel Converter): It is an efficient and flexible power electronic device used to convert direct current into alternating current. The working principle of MMC is to gradually increase the output voltage through multiple power modules, which can achieve a smoother waveform output and reduce system losses. In offshore low-frequency power transmission systems, MMC is usually used for power conversion between offshore stations and onshore stations to ensure that the direct current generated by wind farms can be efficiently and stably converted into alternating current output.

[0027] As introduced in the background technology, offshore wind farms in the prior art require relatively complex manual intervention and operation, which not only increases the difficulty of operation, but may also cause the system to be unable to quickly self-recover in an emergency. In order to solve the problems of offshore wind farms in the prior art relying on manual or relatively complex manual operations, resulting in low automation levels, poor fault recovery capabilities and grid stability, the embodiments of the present application provide a control method for an offshore low-frequency AC system, a control device for an offshore low-frequency AC system and a computer-readable storage medium.

[0028] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0029] In this embodiment, a control method for operating an offshore low-frequency AC system is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0030] The embodiment of the present application provides a control method for an offshore low-frequency AC system, wherein the offshore low-frequency AC system includes an offshore wind farm, a DRU-MMC module, and a parallel auxiliary converter. Figure 1 A DRU-MMC system diagram provided in an embodiment of the present application is shown, as shown in FIG. Figure 1 As shown, the DRU-MMC module includes an offshore station DRU and a land station MMC, the parallel auxiliary converter includes an offshore station and a land station, and the land station MMC includes a flow A circuit breaker 2, a charging resistor and a bypass switch 2, and the land station includes a flow A circuit breaker 1, a charging resistor and a bypass switch 1.

[0031] Among them, the DRU-MMC onshore station MMC is a half-bridge submodule or a full half-bridge submodule, the offshore station DRU is an uncontrolled rectifier diode, and the parallel auxiliary converters are both MMC half-bridge submodules at the offshore station and the onshore station. At the same time, an AC energy consumption device or energy storage device is configured at the offshore station. Among them, the full-bridge submodule has the ability to output the opposite DC voltage, and the half-bridge submodule only has the ability to output the forward voltage. In actual applications, it is configured according to the ratio of one top. The offshore wind farm is responsible for collecting offshore wind energy and converting it into electrical energy. Wind turbines are usually used to achieve this function. The electrical energy is output in the form of direct current for subsequent power transmission and conversion. The DRU-MMC module consists of the offshore station DRU and the onshore station MMC, and is mainly used to realize the conversion and transmission of electrical energy. The parallel auxiliary converter includes converters of the offshore station and the onshore station, which are used to provide additional power regulation and support during system operation. Specifically, the electricity generated by the wind farm is processed by the DRU-MMC module (composed of a DRU and a small MMC in parallel) at the offshore station, and the electricity is transmitted to the onshore station using a DC cable. The onshore station uses a large MMC for power conversion to ensure that the power can be stably and efficiently transmitted to the grid. Since the DRU module at the offshore station does not have the ability to output AC voltage, the parallel small MMC is relied on to achieve AC voltage generation at the offshore station, thereby ensuring the stable operation of the entire system.

[0032] Figure 2 FIG. 1 is a flow chart of a control method for a marine low-frequency AC system according to an embodiment of the present application. Figure 2 As shown, the method comprises the following steps:

[0033] Step S201, obtaining the output power of the offshore wind farm to obtain a first target power, obtaining the rated output power of the DRU-MMC module to obtain a second target power, obtaining the output power of the DRU-MMC module to obtain a third target power;

[0034] Specifically, the output power of the offshore wind farm, the rated output power of the DRU-MMC module and the output power of the DRU-MMC module are obtained. Through these data, the power generation capacity of the wind farm and the power output of the DRU-MMC module can be understood in real time, providing a basis for subsequent control decisions.

[0035] Step S202, when the second target power is greater than the first target power, if the first target power is greater than the first preset power or the land station MMC power is limited, the difference between the first target power and the third target power is calculated to obtain a first power deviation value, and the parallel auxiliary converter is controlled based on the first power deviation value to perform PID regulation on the offshore wind farm, and the adjusted first target power is output by the DRU-MMC module;

[0036] Specifically, by calculating the power deviation in real time and making precise adjustments based on the PID control method, the power coordination between the offshore wind farm and the DRU-MMC module is ensured, thereby optimizing power output, reducing losses, and improving the overall efficiency of the system. PID regulation can accurately control the system power, ensure the safe and stable operation of the power grid, and improve the power generation efficiency of the wind farm.

[0037] Step S203, when the second target power is greater than the first target power, if the land station fails, the submarine cable connecting switch of the parallel auxiliary converter is disconnected to disconnect the land station, and the parallel auxiliary converter is controlled to perform reactive power control to maintain the AC voltage fluctuation of the offshore station less than the first threshold, and the DRU-MMC module outputs the first target power.

[0038] Specifically, when a failure occurs at the land station, the system can automatically disconnect the submarine cable interconnection switch of the parallel auxiliary converter and control the parallel auxiliary converter to enter the reactive control mode to maintain the AC voltage fluctuation of the offshore station less than the preset first threshold. At this time, the DRU-MMC module will continue to output the first target power to the system to ensure the normal operation of the system. It ensures that even if a failure occurs at the land station, the offshore low-frequency AC system can still operate stably, avoiding system crashes or voltage instability caused by failures at the land station. Through the reactive control mode, the system can stabilize the voltage, ensure the safe operation of the offshore station, and avoid problems such as unstable power grids or excessive voltage fluctuations.

[0039] Through this embodiment, an efficient and stable offshore low-frequency AC system control method is provided. First, the system accurately obtains the output power of the wind farm and the power data of the DRU-MMC module to ensure that the power status of the system can be mastered in real time under any operating conditions. By calculating the power deviation and using PID regulation for precise control, the power coordination between the wind farm and the DRU-MMC module is guaranteed, thereby minimizing power loss and improving system efficiency. When a failure occurs in the onshore station, the system can automatically disconnect the contact switch and switch to reactive control mode, effectively maintaining the voltage stability of the offshore station, and ensuring the normal power output of the DRU-MMC module to avoid system failure or instability. While reducing human intervention, the entire method optimizes power output and power distribution, helps to achieve more efficient wind power generation and more stable grid operation, and ensures a safe, reliable and stable connection between the offshore wind farm and the grid. It solves the problems of low automation level, poor fault recovery capability and grid stability caused by the reliance on manual or more complex manual operations in the prior art.

[0040] As a possible implementation manner, after obtaining the output power of the offshore wind farm, obtaining the first target power, obtaining the rated output power of the DRU-MMC module, obtaining the second target power, obtaining the output power of the DRU-MMC module, and obtaining the third target power, the method further includes:

[0041] Step S301, when the second target power is less than or equal to the first target power, calculating the difference between the first target power and the second target power to obtain a second power deviation value;

[0042] Specifically, by calculating the power deviation value in real time, the system can accurately determine the power gap and ensure that the subsequent adjustment process is more efficient and accurate. This provides a reliable basis for subsequent power allocation and control, ensuring that the system's power transmission meets the predetermined goals and avoiding grid instability caused by insufficient or excessive power.

[0043] Step S302, outputting a portion of the first target power corresponding to the second power deviation value by using a parallel auxiliary converter;

[0044] Specifically, according to the second power deviation value, the parallel auxiliary converter outputs part of the power to the system according to the control requirements to make up for the power shortage. This process allows the parallel auxiliary converter to respond to power demand changes in real time and quickly adjust the output to help the system maintain balance.

[0045] Step S303: outputting the portion of the second target power in the first target power by using the DRU-MMC module.

[0046] Specifically, the DRU-MMC module is responsible for outputting the remaining power according to the calculation results. Specifically, the second target power will continue to be output by the DRU-MMC module, so that the DRU-MMC module can ensure the stable output power of the system while minimizing the power fluctuation of the system, further improving the stability and efficiency of the entire offshore low-frequency AC system.

[0047] This embodiment improves the power regulation and stability of the offshore low-frequency AC system through an accurate power calculation and allocation method. First, by calculating the power difference (the second power deviation value), the system can quickly respond to the power difference between the wind farm and the DRU-MMC module, and adjust the power output according to actual needs. The flexible adjustment capability of the parallel auxiliary converter enables rapid replenishment when power is insufficient, avoiding the impact of power fluctuations on the system. At the same time, the DRU-MMC module continues to output the remaining power to ensure the smooth operation of the system and avoid the risks caused by excessive load of a single device. Ultimately, through this precise power allocation and control strategy, the entire system can not only improve operating efficiency, but also maintain good dynamic response capabilities when power differences occur, ensuring long-term stable operation of the system. This method not only reduces dependence on human intervention, but also makes the power regulation of wind farms and offshore low-frequency AC systems more automated and intelligent, ensuring the safety and stable operation of the power grid.

[0048] As a possible implementation manner, after obtaining the output power of the offshore wind farm, obtaining the first target power, obtaining the rated output power of the DRU-MMC module, obtaining the second target power, obtaining the output power of the DRU-MMC module, and obtaining the third target power, the method further includes:

[0049] When the second target power is less than or equal to the first target power, if the onshore station fails, the parallel auxiliary converter is controlled to limit the power of the offshore wind farm to control the first target power to be less than the second target power.

[0050] Specifically, when the second target power is less than or equal to the first target power, if a failure of the onshore station is detected (for example, the MMC of the onshore station cannot work properly, or other system failures cause the onshore station to be unable to output power), the system will limit the power of the offshore wind farm by connecting the auxiliary converter in parallel. The purpose of this control is to ensure that the first target power does not exceed the second target power, and to prevent excess or imbalanced power due to failure of the onshore station.

[0051] It can be seen that when a fault occurs in the onshore station, power limitation of the offshore wind farm by parallel auxiliary converters can effectively prevent power overload and avoid system failure or damage caused by unstable power transmission. At the same time, this measure can ensure that even when a fault occurs in the onshore station, the offshore wind farm and system can still operate safely and stably, reduce the need for human intervention, and improve the automation and reliability of the system. By controlling the power flow, the safety of power distribution is ensured, thereby protecting the wind farm and grid equipment from the risk of overload.

[0052] As a possible implementation, the offshore station further includes an energy storage / AC energy consumption device. After controlling the parallel auxiliary converter to limit the power of the offshore wind farm so as to control the first target power to be less than the second target power, the method further includes:

[0053] If the parallel auxiliary converter fails to limit the power of the offshore wind farm, the energy storage / AC energy consumption device is controlled to absorb the second power deviation in the first target power, and the DRU-MMC module outputs the second target power in the first target power.

[0054] Specifically, if it is found that the power limit of the parallel auxiliary converter on the offshore wind farm fails, that is, when the parallel auxiliary converter cannot effectively limit the power, resulting in power imbalance or system instability, the system will automatically start the energy storage device or AC energy consumption device to intervene. Specifically, the system absorbs the power deviation part through the energy storage device or AC energy consumption device to ensure that the output power of the offshore wind farm does not exceed the maximum range that the system can carry. At the same time, the DRU-MMC module will continue to output the second target power on demand to ensure that the power distribution of the system is balanced and minimize possible overload or loss.

[0055] This implementation method introduces energy storage devices and AC energy consumption devices to automatically absorb power deviations when the parallel auxiliary converter fails, effectively ensuring the stable operation of the system. This measure enhances the emergency response capability and flexibility of the system, not only improves the accuracy of power distribution, but also ensures the power matching between the wind farm and the power grid, avoiding the risks of power overload. The coordinated work of energy storage and energy consumption devices improves the stability of the system in the event of faults or load fluctuations, ensuring a continuous and stable supply of electricity.

[0056] As a possible implementation, the offshore low-frequency AC system further includes a low-frequency AC circuit breaker. After controlling the parallel auxiliary converter to limit the power of the offshore wind farm so as to control the first target power to be less than the second target power, the method further includes:

[0057] If the parallel auxiliary converter fails to limit the power of the offshore wind farm and the energy storage / AC energy consumption device fails, the DRU-MMC module and the parallel auxiliary converter are controlled to trip.

[0058] Specifically, if the parallel auxiliary converter cannot effectively limit the power and the energy storage device / AC energy consumption device fails (for example, it cannot absorb the power deviation), the system will initiate emergency protection measures. Specifically, the low-frequency AC circuit breaker will be triggered, and the DRU-MMC module and the parallel auxiliary converter will trip together, cutting off the power transmission of the offshore low-frequency AC system. This measure is intended to prevent further system damage or grid instability caused by power imbalance or equipment failure.

[0059] It can be seen that by introducing low-frequency AC circuit breakers, the system can quickly cut off power transmission when the parallel auxiliary converter fails and the energy storage device cannot work properly, avoiding possible grid instability or equipment damage. This design improves the emergency response capabilities of wind farms and offshore low-frequency AC systems in the face of sudden failures, ensuring the safety of equipment and systems. At the same time, the tripping protection mechanism can minimize the impact of system failures on grid stability, reducing potential maintenance costs and grid recovery time.

[0060] As a possible implementation manner, the offshore low-frequency AC system further includes a low-frequency AC circuit breaker, and the method further includes:

[0061] In case of offshore station failure, the DRU-MMC module and parallel auxiliary converter are controlled to trip.

[0062] Specifically, if a fault occurs in the offshore station (for example, the offshore station loses the ability to control the AC voltage or other key equipment fails), the DRU-MMC module and the parallel auxiliary converter will be controlled to trip. This means that the power transmission of the entire offshore low-frequency AC system will be quickly cut off. The tripping operation is achieved by triggering the low-frequency AC circuit breaker, thereby preventing the fault from spreading and ensuring the safety of other parts of the system.

[0063] It can be seen that when a fault occurs at an offshore station, timely tripping can effectively prevent the fault from propagating to the onshore station or other system parts, ensuring the stability of the entire power grid. By automatically controlling the tripping, the system can quickly respond to the fault without manual intervention, reducing further damage to the equipment. Especially in the case of loss of voltage control or other faults at the offshore station, the tripping mechanism can cut off the source of the fault, prevent it from affecting the operation of the entire system, and ensure the reliability and safety of the power grid.

[0064] As a possible implementation, the offshore station further includes an energy storage / AC energy consumption device. After the parallel auxiliary converter is controlled based on the first power deviation value to perform PID regulation on the offshore wind farm and the DRU-MMC module outputs the regulated first target power, the method further includes:

[0065] Step S401, when a fault occurs and the DRU-MMC module trips, the rated output power of the parallel auxiliary converter is obtained to obtain a fourth target power;

[0066] Specifically, when the DRU-MMC module fails and trips, the system first obtains the rated output power of the parallel auxiliary converter to obtain a fourth target power, which is used to evaluate the maximum power output capability of the parallel auxiliary converter when the DRU-MMC fails.

[0067] Step S402, controlling the parallel auxiliary converter to limit the power of the offshore wind farm, so as to control the first target power to be less than the fourth target power;

[0068] Specifically, the system controls the parallel auxiliary converter to limit the power of the offshore wind farm to ensure that the first target power is less than or equal to the fourth target power. This process limits the upper limit of the wind farm's transmission power by adjusting the parallel auxiliary converter to avoid power overload caused by DRU-MMC failure.

[0069] Step S403: if the parallel auxiliary converter fails to limit the power of the offshore wind farm, the energy storage / AC energy consumption device is controlled to absorb the portion of the first target power that exceeds the fourth target power;

[0070] Specifically, if the parallel auxiliary converter cannot effectively control the power limit, the system will control the energy storage / AC energy consumption device to absorb the power exceeding the fourth target power. This can effectively avoid the occurrence of overload and ensure the safe operation of the power system.

[0071] Step S404: if the parallel auxiliary converter fails to limit the power of the offshore wind farm and the energy storage / AC energy consumption device fails, the parallel auxiliary converter is controlled to trip, and the wind turbines of the offshore wind farm are controlled to stop running.

[0072] Specifically, if the parallel auxiliary converter continues to be unable to effectively limit power and the energy storage / AC energy consumption device fails, the system will trigger the parallel auxiliary converter to trip and control the wind turbines in the offshore wind farm to stop operating. This measure can quickly disconnect the faulty part, prevent system overload, and ensure the safety of equipment and power grid.

[0073] Through this implementation, in the event of a DRU-MMC module failure, multiple protection measures are combined with the parallel auxiliary converter, energy storage / AC energy consumption device, and wind turbine shutdown to ensure that the system can respond quickly in the event of a failure and avoid system crashes due to power mismatch or equipment failure. This control method can effectively control the upper limit of wind farm power, avoid power overload, reduce system losses, and protect equipment from further damage. By sequentially triggering power limitation, energy storage device absorption, and trip protection, the system can provide layered protection to ensure the long-term stable operation of wind farms, parallel auxiliary converters, and power grids.

[0074] As a possible implementation manner, after controlling the parallel auxiliary converter to perform reactive power control to maintain the AC voltage fluctuation of the offshore station less than the first threshold, and outputting the first target power with the DRU-MMC module, the method further includes:

[0075] In the event of a fault and tripping of the DRU-MMC module, the parallel auxiliary converter is controlled to trip, and the wind turbines of the offshore wind farm are controlled to stop running.

[0076] Specifically, when the DRU-MMC module fails and trips, the system responds immediately and triggers the parallel auxiliary converter to trip. This operation can quickly cut off the faulty part and prevent the fault from spreading to other parts, thereby avoiding wider equipment damage or system collapse. At the same time, the system controls the wind turbines in the offshore wind farm to stop operating. Since DRU-MMC failure may cause unstable power transmission, stopping the operation of the wind turbines can help reduce power fluctuations and prevent the system from being affected by overload or unstable power input. Stopping the wind turbines will effectively prevent equipment damage and ensure system recovery.

[0077] This implementation ensures the system's fault response capability by quickly taking two key measures: tripping the parallel auxiliary converter and stopping the wind turbine when the DRU-MMC module fails. This can effectively cut off the source of the fault, prevent unstable power from being transmitted to the power grid or other equipment, and protect the safety of the system. At the same time, by stopping the operation of the wind turbine, the negative impact of unstable power on the wind farm is prevented, and system overload and equipment damage are effectively avoided, ensuring rapid system recovery and minimizing downtime. This solution enhances the system's tolerance to faults and self-healing capabilities, and improves the stability and reliability of offshore wind farms.

[0078] The embodiment of the present application also provides a control device for an offshore low-frequency AC system. It should be noted that the control device for an offshore low-frequency AC system of the embodiment of the present application can be used to execute the control method for an offshore low-frequency AC system provided by the embodiment of the present application. The device is used to implement the above-mentioned embodiments and preferred implementation modes, and those that have been described will not be repeated. As used below, the term "module" can implement a combination of software and / or hardware for a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

[0079] The following is an introduction to the control device of the marine low-frequency AC system provided in the embodiment of the present application.

[0080] The offshore low-frequency AC system includes an offshore wind farm, a DRU-MMC module and a parallel auxiliary converter. The DRU-MMC module includes an offshore station DRU and an onshore station MMC. The parallel auxiliary converter includes an offshore station and an onshore station. Figure 3 1 is a structural block diagram of a control device for a marine low-frequency AC system according to an embodiment of the present application. Figure 3 As shown, the control device includes: a first acquisition unit 10 , a first control unit 20 and a second control unit 30 .

[0081] The first acquisition unit 10 is used to acquire the output power of the offshore wind farm, obtain the first target power, acquire the rated output power of the DRU-MMC module, obtain the second target power, acquire the output power of the DRU-MMC module, and obtain the third target power;

[0082] Specifically, the output power of the offshore wind farm, the rated output power of the DRU-MMC module and the output power of the DRU-MMC module are obtained. Through these data, the power generation capacity of the wind farm and the power output of the DRU-MMC module can be understood in real time, providing a basis for subsequent control decisions.

[0083] The first control unit 20 is used for calculating the difference between the first target power and the third target power to obtain a first power deviation value when the second target power is greater than the first target power, if the first target power is greater than the first preset power or the land station MMC power is limited, and controlling the parallel auxiliary converter to perform PID regulation on the offshore wind farm based on the first power deviation value, and outputting the adjusted first target power with the DRU-MMC module;

[0084] Specifically, by calculating the power deviation in real time and making precise adjustments based on the PID control method, the power coordination between the offshore wind farm and the DRU-MMC module is ensured, thereby optimizing power output, reducing losses, and improving the overall efficiency of the system. PID regulation can accurately control the system power, ensure the safe and stable operation of the power grid, and improve the power generation efficiency of the wind farm.

[0085] The second control unit 30 is used to disconnect the submarine cable connecting switch of the parallel auxiliary converter to disconnect the land station if the land station fails when the second target power is greater than the first target power, and control the parallel auxiliary converter to perform reactive power control to maintain the AC voltage fluctuation of the offshore station less than the first threshold, so as to output the first target power with the DRU-MMC module.

[0086] Specifically, when a failure occurs at the land station, the system can automatically disconnect the submarine cable interconnection switch of the parallel auxiliary converter and control the parallel auxiliary converter to enter the reactive control mode to maintain the AC voltage fluctuation of the offshore station less than the preset first threshold. At this time, the DRU-MMC module will continue to output the first target power to the system to ensure the normal operation of the system. It ensures that even if a failure occurs at the land station, the offshore low-frequency AC system can still operate stably, avoiding system crashes or voltage instability caused by failures at the land station. Through the reactive control mode, the system can stabilize the voltage, ensure the safe operation of the offshore station, and avoid problems such as unstable power grids or excessive voltage fluctuations.

[0087] Through this embodiment, a control device for an offshore low-frequency AC system is provided, and the device includes: a first acquisition unit, a first control unit, and a second control unit. The first acquisition unit is used to acquire the output power of the offshore wind farm to obtain the first target power, acquire the rated output power of the DRU-MMC module to obtain the second target power, acquire the output power of the DRU-MMC module to obtain the third target power; the first control unit is used to calculate the difference between the first target power and the third target power to obtain the first power deviation value when the second target power is greater than the first target power, if the first target power is greater than the first preset power or the MMC power of the land station is limited, and control the parallel auxiliary converter to perform PID regulation on the offshore wind farm based on the first power deviation value, and output the adjusted first target power with the DRU-MMC module; the second control unit is used to disconnect the submarine cable contact switch of the parallel auxiliary converter to disconnect the land station if the land station fails when the second target power is greater than the first target power, and control the parallel auxiliary converter to perform reactive control to maintain the AC voltage fluctuation of the offshore station less than the first threshold, and output the first target power with the DRU-MMC module. The device reduces human intervention while optimizing power output and power distribution, helping to achieve more efficient wind power generation and more stable grid operation, ensuring a safe, reliable and stable connection between offshore wind farms and the grid. It solves the problems of low automation level, poor fault recovery capability and grid stability caused by the reliance on manual or complex manual operations in existing technologies.

[0088] As a possible implementation manner, the device further includes: a calculation unit, a first output unit, and a second output unit.

[0089] a calculation unit, configured to calculate a difference between the first target power and the second target power to obtain a second power deviation value when the second target power is less than or equal to the first target power;

[0090] Specifically, by calculating the power deviation value in real time, the system can accurately determine the power gap and ensure that the subsequent adjustment process is more efficient and accurate. This provides a reliable basis for subsequent power allocation and control, ensuring that the system's power transmission meets the predetermined goals and avoiding grid instability caused by insufficient or excessive power.

[0091] A first output unit, configured to output a portion of the first target power having a second power deviation value by means of a parallel auxiliary converter;

[0092] Specifically, according to the second power deviation value, the parallel auxiliary converter outputs part of the power to the system according to the control requirements to make up for the power shortage. This process allows the parallel auxiliary converter to respond to power demand changes in real time and quickly adjust the output to help the system maintain balance.

[0093] The second output unit is used to output the second target power portion of the first target power by using the DRU-MMC module.

[0094] Specifically, the DRU-MMC module is responsible for outputting the remaining power according to the calculation results. Specifically, the second target power will continue to be output by the DRU-MMC module, so that the DRU-MMC module can ensure the stable output power of the system while minimizing the power fluctuation of the system, further improving the stability and efficiency of the entire offshore low-frequency AC system.

[0095] As a possible implementation manner, the device further includes: a limiting unit.

[0096] The limiting unit is used to control the parallel auxiliary converter to limit the power of the offshore wind farm when the second target power is less than or equal to the first target power and if the onshore station fails, so as to control the first target power to be less than the second target power.

[0097] Specifically, when the second target power is less than or equal to the first target power, if a failure of the onshore station is detected (for example, the MMC of the onshore station cannot work properly, or other system failures cause the onshore station to be unable to output power), the system will limit the power of the offshore wind farm by connecting the auxiliary converter in parallel. The purpose of this control is to ensure that the first target power does not exceed the second target power, and to prevent excess or imbalanced power due to failure of the onshore station.

[0098] As a possible implementation, the offshore station also includes an energy storage / AC energy consumption device, and the device also includes: an absorption unit.

[0099] The absorption unit is used to control the energy storage / AC energy consumption device to absorb the second power deviation in the first target power if the parallel auxiliary converter fails to limit the power of the offshore wind farm, and output the second target power in the first target power with the DRU-MMC module.

[0100] Specifically, if it is found that the power limit of the parallel auxiliary converter on the offshore wind farm fails, that is, when the parallel auxiliary converter cannot effectively limit the power, resulting in power imbalance or system instability, the system will automatically start the energy storage device or AC energy consumption device to intervene. Specifically, the system absorbs the power deviation part through the energy storage device or AC energy consumption device to ensure that the output power of the offshore wind farm does not exceed the maximum range that the system can carry. At the same time, the DRU-MMC module will continue to output the second target power on demand to ensure that the power distribution of the system is balanced and minimize possible overload or loss.

[0101] As a possible implementation manner, the offshore low-frequency AC system further includes a low-frequency AC circuit breaker, and the device further includes: a first tripping unit.

[0102] The first tripping unit is used to control the DRU-MMC module and the parallel auxiliary converter to trip if the parallel auxiliary converter fails to limit the power of the offshore wind farm and the energy storage / AC energy consumption device fails.

[0103] Specifically, if the parallel auxiliary converter cannot effectively limit the power and the energy storage device / AC energy consumption device fails (for example, it cannot absorb the power deviation), the system will initiate emergency protection measures. Specifically, the low-frequency AC circuit breaker will be triggered, and the DRU-MMC module and the parallel auxiliary converter will trip together, cutting off the power transmission of the offshore low-frequency AC system. This measure is intended to prevent further system damage or grid instability caused by power imbalance or equipment failure.

[0104] As a possible implementation manner, the offshore low-frequency AC system further includes a low-frequency AC circuit breaker, and the device further includes: a second tripping unit.

[0105] The second trip unit is used to control the tripping of the DRU-MMC module and the parallel auxiliary converter in the event of an offshore station failure.

[0106] Specifically, if a fault occurs in the offshore station (for example, the offshore station loses the ability to control the AC voltage or other key equipment fails), the DRU-MMC module and the parallel auxiliary converter will be controlled to trip. This means that the power transmission of the entire offshore low-frequency AC system will be quickly cut off. The tripping operation is achieved by triggering the low-frequency AC circuit breaker, thereby preventing the fault from spreading and ensuring the safety of other parts of the system.

[0107] As a possible implementation, the offshore station further includes an energy storage / AC energy consumption device, and the device further includes: an acquisition unit, a power limiting unit, a power absorbing unit and a third tripping unit.

[0108] An acquisition unit, configured to acquire the rated output power of the parallel auxiliary converter to obtain a fourth target power when the DRU-MMC module fails and trips;

[0109] Specifically, when the DRU-MMC module fails and trips, the system first obtains the rated output power of the parallel auxiliary converter to obtain a fourth target power, which is used to evaluate the maximum power output capability of the parallel auxiliary converter when the DRU-MMC fails.

[0110] A power limiting unit, used for controlling the parallel auxiliary converter to limit the power of the offshore wind farm, so as to control the first target power to be less than the fourth target power;

[0111] Specifically, the system controls the parallel auxiliary converter to limit the power of the offshore wind farm to ensure that the first target power is less than or equal to the fourth target power. This process limits the upper limit of the wind farm's transmission power by adjusting the parallel auxiliary converter to avoid power overload caused by DRU-MMC failure.

[0112] A power absorption unit, used for controlling the energy storage / AC energy consumption device to absorb a portion of the first target power that exceeds the fourth target power if the parallel auxiliary converter fails to limit the power of the offshore wind farm;

[0113] Specifically, if the parallel auxiliary converter cannot effectively control the power limit, the system will control the energy storage / AC energy consumption device to absorb the power exceeding the fourth target power. This can effectively avoid the occurrence of overload and ensure the safe operation of the power system.

[0114] The third tripping unit is used to control the parallel auxiliary converter to trip and control the wind turbines of the offshore wind farm to stop running if the parallel auxiliary converter fails to limit the power of the offshore wind farm and the energy storage / AC energy consumption device fails.

[0115] Specifically, if the parallel auxiliary converter continues to be unable to effectively limit power and the energy storage / AC energy consumption device fails, the system will trigger the parallel auxiliary converter to trip and control the wind turbines in the offshore wind farm to stop operating. This measure can quickly disconnect the faulty part, prevent system overload, and ensure the safety of equipment and power grid.

[0116] As a possible implementation manner, the device further includes: a fourth tripping unit.

[0117] The fourth trip unit is used to control the parallel auxiliary converter to trip and control the wind turbines of the offshore wind farm to stop running when the DRU-MMC module fails and trips.

[0118] Specifically, when the DRU-MMC module fails and trips, the system responds immediately and triggers the parallel auxiliary converter to trip. This operation can quickly cut off the faulty part and prevent the fault from spreading to other parts, thereby avoiding wider equipment damage or system collapse. At the same time, the system controls the wind turbines in the offshore wind farm to stop operating. Since DRU-MMC failure may cause unstable power transmission, stopping the operation of the wind turbines can help reduce power fluctuations and prevent the system from being affected by overload or unstable power input. Stopping the wind turbines will effectively prevent equipment damage and ensure system recovery.

[0119] The control device of the marine low-frequency AC system includes a processor and a memory. The first acquisition unit, the first control unit, the second control unit, etc. are all stored in the memory as program units, and the processor executes the program units stored in the memory to implement corresponding functions. The modules are all located in the same processor; or, the modules are located in different processors in any combination.

[0120] The processor includes a kernel, which calls the corresponding program unit from the memory. One or more kernels can be set, and the communication efficiency can be improved by adjusting the kernel parameters.

[0121] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM, and the memory includes at least one memory chip.

[0122] An embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium includes a stored program, wherein when the program is executed, the device where the computer-readable storage medium is located is controlled to execute the control method of the marine low-frequency AC system.

[0123] Specifically, the control method of the offshore low-frequency AC system includes:

[0124] Step S201, obtaining the output power of the offshore wind farm to obtain a first target power, obtaining the rated output power of the DRU-MMC module to obtain a second target power, obtaining the output power of the DRU-MMC module to obtain a third target power;

[0125] Specifically, the output power of the offshore wind farm, the rated output power of the DRU-MMC module and the output power of the DRU-MMC module are obtained. Through these data, the power generation capacity of the wind farm and the power output of the DRU-MMC module can be understood in real time, providing a basis for subsequent control decisions.

[0126] Step S202, when the second target power is greater than the first target power, if the first target power is greater than the first preset power or the land station MMC power is limited, the difference between the first target power and the third target power is calculated to obtain a first power deviation value, and the parallel auxiliary converter is controlled based on the first power deviation value to perform PID regulation on the offshore wind farm, and the adjusted first target power is output by the DRU-MMC module;

[0127] Specifically, by calculating the power deviation in real time and making precise adjustments based on the PID control method, the power coordination between the offshore wind farm and the DRU-MMC module is ensured, thereby optimizing power output, reducing losses, and improving the overall efficiency of the system. PID regulation can accurately control the system power, ensure the safe and stable operation of the power grid, and improve the power generation efficiency of the wind farm.

[0128] Step S203, when the second target power is greater than the first target power, if the land station fails, the submarine cable connecting switch of the parallel auxiliary converter is disconnected to disconnect the land station, and the parallel auxiliary converter is controlled to perform reactive power control to maintain the AC voltage fluctuation of the offshore station less than the first threshold, and the DRU-MMC module outputs the first target power.

[0129] Specifically, when a failure occurs at the land station, the system can automatically disconnect the submarine cable interconnection switch of the parallel auxiliary converter and control the parallel auxiliary converter to enter the reactive control mode to maintain the AC voltage fluctuation of the offshore station less than the preset first threshold. At this time, the DRU-MMC module will continue to output the first target power to the system to ensure the normal operation of the system. It ensures that even if a failure occurs at the land station, the offshore low-frequency AC system can still operate stably, avoiding system crashes or voltage instability caused by failures at the land station. Through the reactive control mode, the system can stabilize the voltage, ensure the safe operation of the offshore station, and avoid problems such as unstable power grids or excessive voltage fluctuations.

[0130] Optionally, after obtaining the output power of the offshore wind farm, obtaining the first target power, obtaining the rated output power of the DRU-MMC module, obtaining the second target power, obtaining the output power of the DRU-MMC module, and obtaining the third target power, the method also includes: when the second target power is less than or equal to the first target power, calculating the difference between the first target power and the second target power to obtain a second power deviation value; outputting the portion of the second power deviation value in the first target power with a parallel auxiliary converter; and outputting the portion of the second target power in the first target power with the DRU-MMC module.

[0131] Optionally, after obtaining the output power of the offshore wind farm, obtaining the first target power, obtaining the rated output power of the DRU-MMC module, obtaining the second target power, obtaining the output power of the DRU-MMC module, and obtaining the third target power, the method also includes: when the second target power is less than or equal to the first target power, if the onshore station fails, controlling the parallel auxiliary converter to limit the power of the offshore wind farm to control the first target power to be less than the second target power.

[0132] Optionally, the offshore station also includes an energy storage / AC energy consumption device. After controlling the parallel auxiliary converter to limit the power of the offshore wind farm to control the first target power to be less than the second target power, the method also includes: if the parallel auxiliary converter fails to limit the power of the offshore wind farm, then controlling the energy storage / AC energy consumption device to absorb the part of the second power deviation in the first target power, and outputting the part of the second target power in the first target power with the DRU-MMC module.

[0133] Optionally, the offshore low-frequency AC system also includes a low-frequency AC circuit breaker. After controlling the parallel auxiliary converter to limit the power of the offshore wind farm to control the first target power to be less than the second target power, the method also includes: if the parallel auxiliary converter fails to limit the power of the offshore wind farm and the energy storage / AC energy consumption device fails, controlling the DRU-MMC module and the parallel auxiliary converter to trip.

[0134] Optionally, the offshore low-frequency AC system further comprises a low-frequency AC circuit breaker, and the method further comprises: in case of an offshore station failure, controlling the DRU-MMC module and the parallel auxiliary converter to trip.

[0135] Optionally, the offshore station also includes an energy storage / AC energy consumption device. After controlling the parallel auxiliary converter to perform PID adjustment on the offshore wind farm based on the first power deviation value, and outputting the adjusted first target power with the DRU-MMC module, the method also includes: in the event that the DRU-MMC module fails and trips, obtaining the rated output power of the parallel auxiliary converter to obtain a fourth target power; controlling the parallel auxiliary converter to limit the power of the offshore wind farm to control the first target power to be less than the fourth target power; if the parallel auxiliary converter fails to limit the power of the offshore wind farm, controlling the energy storage / AC energy consumption device to absorb the part of the first target power that exceeds the fourth target power; if the parallel auxiliary converter fails to limit the power of the offshore wind farm and the energy storage / AC energy consumption device fails, controlling the parallel auxiliary converter to trip, and controlling the wind turbines of the offshore wind farm to stop running.

[0136] Optionally, after controlling the parallel auxiliary converter to perform reactive power control to maintain the AC voltage fluctuation of the offshore station less than a first threshold value and outputting the first target power with the DRU-MMC module, the method also includes: in the event that the DRU-MMC module fails and trips, controlling the parallel auxiliary converter to trip and controlling the wind turbines of the offshore wind farm to stop running.

[0137] An embodiment of the present invention provides a processor, and the processor is used to run a program, wherein the control method of the marine low-frequency AC system is executed when the program is run.

[0138] An embodiment of the present invention provides a communication system, which includes a primary communication domain, a secondary communication domain processor, a memory, and a program stored in the memory and executable on the processor. When the processor executes the program, at least the control method steps of the above-mentioned marine low-frequency AC system are implemented.

[0139] The present application also provides a computer program product, which, when executed on a data processing device, is suitable for executing a program for initializing at least the steps of the control method for the marine low-frequency alternating current system.

[0140] Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order than here, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0141] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0142] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0143] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0144] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0145] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0146] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0147] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0148] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0149] From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:

[0150] 1) The control method of the offshore low-frequency AC system of the present application, first, the system accurately obtains the output power of the wind farm and the power data of the DRU-MMC module to ensure that the power status of the system can be mastered in real time under any operating conditions. By calculating the power deviation and using PID regulation for precise control, the power coordination between the wind farm and the DRU-MMC module is guaranteed, thereby minimizing power loss and improving system efficiency. When a failure occurs in the onshore station, the system can automatically disconnect the contact switch and switch to reactive control mode, effectively maintaining the voltage stability of the offshore station, and ensuring the normal power output of the DRU-MMC module to avoid system failure or instability. While reducing human intervention, the entire method optimizes power output and power distribution, helps to achieve more efficient wind power generation and more stable power grid operation, and ensures a safe, reliable and stable connection between the offshore wind farm and the power grid. It solves the problems of low automation level, poor fault recovery capability and power grid stability caused by the reliance on manual or more complex manual operations in the prior art.

[0151] 2) The control device of the offshore low-frequency AC system of the present application comprises: a first acquisition unit, a first control unit and a second control unit. The first acquisition unit is used to acquire the output power of the offshore wind farm, obtain the first target power, acquire the rated output power of the DRU-MMC module, obtain the second target power, acquire the output power of the DRU-MMC module, and obtain the third target power; the first control unit is used to calculate the difference between the first target power and the third target power to obtain the first power deviation value when the second target power is greater than the first target power, if the first target power is greater than the first preset power or the MMC power of the land station is limited, and control the parallel auxiliary converter to perform PID adjustment on the offshore wind farm based on the first power deviation value, and output the adjusted first target power with the DRU-MMC module; the second control unit is used to disconnect the submarine cable connecting switch of the parallel auxiliary converter to disconnect the land station if the land station fails when the second target power is greater than the first target power, and control the parallel auxiliary converter to perform reactive power control to maintain the AC voltage fluctuation of the offshore station less than the first threshold, and output the first target power with the DRU-MMC module. The device reduces human intervention while optimizing power output and power distribution, helping to achieve more efficient wind power generation and more stable grid operation, ensuring a safe, reliable and stable connection between offshore wind farms and the grid. It solves the problems of low automation level, poor fault recovery capability and grid stability caused by the reliance on manual or complex manual operations in existing technologies.

[0152] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A control method for a marine low-frequency AC system, characterized in that: The offshore low-frequency AC system includes an offshore wind farm, a DRU-MMC module and a parallel auxiliary converter, the DRU-MMC module includes an offshore station DRU and an onshore station MMC, the parallel auxiliary converter includes an offshore station and an onshore station, and the control method includes: Obtaining the output power of the offshore wind farm to obtain a first target power, obtaining the rated output power of the DRU-MMC module to obtain a second target power, and obtaining the output power of the DRU-MMC module to obtain a third target power; In the case where the second target power is greater than the first target power, if the first target power is greater than the first preset power or the land station MMC power is limited, the difference between the first target power and the third target power is calculated to obtain a first power deviation value, and the parallel auxiliary converter is controlled to perform PID regulation on the offshore wind farm based on the first power deviation value, and the adjusted first target power is output by the DRU-MMC module; When the second target power is greater than the first target power, if the land station fails, the submarine cable connecting switch of the parallel auxiliary converter is disconnected to disconnect the land station, and the parallel auxiliary converter is controlled to perform reactive power control to maintain the AC voltage fluctuation of the offshore station less than the first threshold, and the DRU-MMC module outputs the first target power.

2. The method according to claim 1, characterized in that After obtaining the output power of the offshore wind farm, obtaining the first target power, obtaining the rated output power of the DRU-MMC module, obtaining the second target power, obtaining the output power of the DRU-MMC module, and obtaining the third target power, the method further includes: When the second target power is less than or equal to the first target power, calculating the difference between the first target power and the second target power to obtain a second power deviation value; outputting a portion of the first target power having the second power deviation value by the parallel auxiliary converter; The DRU-MMC module outputs a portion of the first target power that is the second target power.

3. The method according to claim 2, characterized in that After obtaining the output power of the offshore wind farm, obtaining the first target power, obtaining the rated output power of the DRU-MMC module, obtaining the second target power, obtaining the output power of the DRU-MMC module, and obtaining the third target power, the method further includes: In the case that the second target power is less than or equal to the first target power, if the onshore station fails, the parallel auxiliary converter is controlled to limit the power of the offshore wind farm, so as to control the first target power to be less than the second target power.

4. The method according to claim 3, characterized in that The offshore station further includes an energy storage / AC energy consumption device. After controlling the parallel auxiliary converter to limit the power of the offshore wind farm so as to control the first target power to be less than the second target power, the method further includes: If the parallel auxiliary converter fails to limit the power of the offshore wind farm, the energy storage / AC energy consumption device is controlled to absorb the second power deviation in the first target power, and the DRU-MMC module outputs the second target power in the first target power.

5. The method according to claim 4, characterized in that The offshore low-frequency AC system further includes a low-frequency AC circuit breaker. After controlling the parallel auxiliary converter to limit the power of the offshore wind farm so as to control the first target power to be less than the second target power, the method further includes: If the parallel auxiliary converter fails to limit the power of the offshore wind farm and the energy storage / AC energy consumption device fails, the DRU-MMC module and the parallel auxiliary converter are controlled to trip.

6. The method according to claim 1, characterized in that The offshore low-frequency AC system further includes a low-frequency AC circuit breaker, and the method further includes: In the event of a failure of the offshore station, the DRU-MMC module and the parallel auxiliary converter are controlled to trip.

7. The method according to claim 1, characterized in that The offshore station further includes an energy storage / AC energy consumption device. After controlling the parallel auxiliary converter to perform PID regulation on the offshore wind farm based on the first power deviation value and outputting the adjusted first target power with a DRU-MMC module, the method further includes: In the case where the DRU-MMC module fails and trips, obtaining the rated output power of the parallel auxiliary converter to obtain a fourth target power; controlling the parallel auxiliary converter to limit the power of the offshore wind farm, so as to control the first target power to be less than the fourth target power; If the parallel auxiliary converter fails to limit the power of the offshore wind farm, controlling the energy storage / AC energy consumption device to absorb the portion of the first target power that exceeds the fourth target power; If the parallel auxiliary converter fails to limit the power of the offshore wind farm and the energy storage / AC energy consumption device fails, the parallel auxiliary converter is controlled to trip and the wind turbines of the offshore wind farm are controlled to stop running.

8. The method according to claim 1, characterized in that After controlling the parallel auxiliary converter to perform reactive power control to maintain the AC voltage fluctuation of the offshore station less than a first threshold, and outputting the first target power with the DRU-MMC module, the method further includes: In the case that the DRU-MMC module fails and trips, the parallel auxiliary converter is controlled to trip, and the wind turbines of the offshore wind farm are controlled to stop running.

9. A control device for a marine low-frequency AC system, characterized in that: The offshore low-frequency AC system includes an offshore wind farm, a DRU-MMC module and a parallel auxiliary converter, the DRU-MMC module includes an offshore station DRU and an onshore station MMC, the parallel auxiliary converter includes an offshore station and an onshore station, and the control device includes: A first acquisition unit is used to acquire the output power of the offshore wind farm to obtain a first target power, acquire the rated output power of the DRU-MMC module to obtain a second target power, and acquire the output power of the DRU-MMC module to obtain a third target power; a first control unit, configured to calculate the difference between the first target power and the third target power to obtain a first power deviation value when the second target power is greater than the first target power, if the first target power is greater than a first preset power or the land station MMC power is limited, control the parallel auxiliary converter to perform PID regulation on the offshore wind farm based on the first power deviation value, and output the adjusted first target power with a DRU-MMC module; A second control unit is used for disconnecting the submarine cable connecting switch of the parallel auxiliary converter to disconnect the land station when the second target power is greater than the first target power and if the land station fails, and controlling the parallel auxiliary converter to perform reactive power control to maintain the AC voltage fluctuation of the offshore station less than a first threshold, so as to output the first target power with the DRU-MMC module.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored program, wherein when the program is executed, the device where the computer-readable storage medium is located is controlled to execute the method according to any one of claims 1 to 8.

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