An offshore wind turbine electromechanical transient data processing method and device

Abstract

The application discloses a kind of offshore wind turbine electromechanical transient data processing method and device, belong to wind power generation technical field, solve large-scale offshore wind power grid connection full power network type transient control difficult, control strategy independent cause data fragmentation, the problem of high operation and maintenance cost.This application is less than or equal to 1 microsecond synchronous precision acquisition grid voltage, current, frequency, phase angle parameter, through positive and negative sequence component separation algorithm to build the network type electromechanical transient model containing generator, converter and grid interaction;Design symmetrical / unsymmetrical short-circuit fault control, dynamic energy interaction and active power support strategy, integrated into hybrid synchronization control system and establish multi-module collaborative logic.The application realizes full power network type transient control, completes multi-dimensional transient data unified processing, improves wind power grid connection stability and operation and maintenance efficiency.

Description

Technical Field

[0001] This invention relates to the field of wind power generation technology, and in particular to a method and apparatus for processing electromechanical transient data of offshore wind turbines. Background Technology

[0002] A wind turbine is a system that converts the kinetic energy of wind into electrical energy. It consists of a wind turbine, a generator, a support tower, and a control system. Maintaining a constant output frequency is crucial for wind turbines to be connected to the grid. Traditional wind power systems primarily employ constant speed and frequency or variable speed and constant frequency operation, achieving frequency stability through mechanical or power electronic means.

[0003] With the rapid growth of offshore wind power installed capacity, the impact of large-scale wind power grid connection on the safe and stable operation of the power system is becoming increasingly significant. Currently, offshore wind turbines mainly adopt a grid-following control method, which tracks the grid voltage phase through a phase-locked loop and relies on the grid to provide voltage and frequency support. Under this control method, wind turbines lack inertial response and damping regulation capabilities, and cannot actively participate in grid frequency and voltage regulation. When grid faults or disturbances occur, the system stability is poor.

[0004] In existing grid-connected wind power control technologies, control strategies for symmetrical short-circuit faults, voltage support technologies for asymmetrical short-circuit faults, and active power support strategies under frequency disturbances are often implemented independently. These individual control strategies are independent of each other and lack a unified coordination mechanism, resulting in fragmented system data. This makes it impossible to achieve unified acquisition and processing of transient data across all dimensions, such as voltage, current, frequency, phase angle, and junction temperature, hindering system data integration and comprehensive analysis of transient characteristics. Furthermore, staff need to analyze isolated control schemes under different fault scenarios separately, leading to a large workload, low operation and maintenance efficiency, and high on-site commissioning costs.

[0005] Furthermore, existing electromechanical transient modeling methods typically focus on a single time scale, failing to adequately consider the coupling characteristics of multiple physical processes such as electromagnetic transients, electromechanical transients, and energy interactions. This results in an inability to accurately capture transient processes at different time scales, including microsecond-level switching dynamics, millisecond-level inertial responses, and second-level pitch control, leading to limited model accuracy. Existing overcurrent protection methods are primarily passive, initiating protection only after a fault occurs. This makes it difficult to balance the grid's transient support capabilities during the initial fault phase with the safety protection of power devices, thus requiring improvements in converter reliability and fault tolerance.

[0006] Therefore, a new technical solution is needed to achieve full-power grid-connected transient control of offshore wind turbines, integrate multi-scenario transient control strategies into a unified system, establish multi-module collaborative logic, realize unified processing of all-dimensional transient data, and improve modeling accuracy and the initiative of overcurrent protection to meet the requirements of large-scale offshore wind power grid connection for the safe and stable operation of the power system. Summary of the Invention

[0007] The purpose of this invention is to provide a method and apparatus for processing electromechanical transient data of offshore wind turbines, in order to solve the problems in the prior art, such as the inability to achieve full-power grid-type transient control at sea, data fragmentation caused by the independence of individual control strategies, large workload for staff analysis, the inability of traditional single-timescale focusing modeling to accurately capture multi-timescale transient processes, and the passive response of overcurrent protection.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A method for processing electromechanical transient data of offshore wind turbines includes the following steps: real-time acquisition of grid voltage, current, frequency, and phase angle parameters, wherein the time synchronization accuracy of the acquisition is less than or equal to 1 microsecond; employing a positive / negative sequence component separation algorithm to establish a grid-based electromechanical transient model including the interaction of generators, converters, and the grid; establishing a symmetrical short-circuit fault control strategy based on the grid-based electromechanical transient model, wherein the symmetrical short-circuit fault control strategy includes adjusting active power commands, monitoring power device junction temperature, dynamically adjusting switching frequency, and modulation strategy; and establishing an asymmetrical short-circuit fault control strategy. The asymmetric short-circuit fault control strategy includes calculating the peak transient current, using virtual impedance control or current compensation strategies to reduce the impact of negative sequence components, and optimizing the output voltage waveform; establishing a dynamic energy interaction and active power support strategy, which includes quantifying the equivalent inertia time constant and damping coefficient, designing an active power droop control module, and coordinating power output adjustment under grid frequency disturbances; integrating the symmetric short-circuit fault control strategy, the asymmetric short-circuit fault control strategy, and the dynamic energy interaction and active power support strategy into a hybrid synchronous control system to establish multi-module collaborative logic.

[0009] Preferably, the grid-type electromechanical transient model includes an equivalent circuit model of a permanent magnet synchronous generator, a switching function model of a grid-side converter, and a positive / negative sequence equivalent impedance model of the power grid.

[0010] Preferably, the positive / negative sequence component separation algorithm includes an improved instantaneous symmetrical component method, positive sequence virtual impedance control, and negative sequence virtual impedance control. The positive sequence virtual impedance includes a proportional term, an integral term, and a differential term. The negative sequence virtual impedance contains a negative sequence virtual resistance that is greater than or equal to three times the negative sequence virtual reactance.

[0011] Preferably, the network-type electromechanical transient model further includes a multi-coordinate system coupling model, a virtual synchronous machine control, a dynamic current limiting model, and an interactive model under asymmetric faults. The virtual synchronous machine control includes an active-frequency loop and a reactive-voltage loop.

[0012] Preferably, the monitoring of the junction temperature of the power device includes acquiring the case temperature of the converter module through a thermistor or temperature diode, and calculating the junction temperature using a transient thermal impedance model in combination with real-time current and switching frequency; when the junction temperature is greater than or equal to 120 degrees Celsius, the switching frequency is linearly reduced by 5% for every 1 degree Celsius increase, and is reduced to a minimum of 40% of the rated frequency; when the junction temperature is greater than or equal to 140 degrees Celsius, the drive pulse is immediately blocked; space vector pulse width modulation is used under normal operating conditions, and discontinuous pulse width modulation is switched when the junction temperature is greater than or equal to 110 degrees Celsius or the short-circuit current exceeds 1.5 times the rated current.

[0013] Preferably, the monitoring of the junction temperature of the power device also includes overcurrent prediction-correction, establishing a junction temperature prediction model based on a first-order thermal network model, and introducing wind speed feedforward compensation in the junction temperature prediction model; when the predicted junction temperature exceeds 125 degrees Celsius, the current slope limit is activated 10 milliseconds in advance to limit the rate of change of current with respect to time to within 50 amperes per microsecond, while the current reference value is linearly reduced to 0.8 times the rated current.

[0014] Preferably, the multi-module collaborative logic includes setting the collaborative module body, setting collaborative triggering conditions, setting priorities, and setting interaction logic. The collaborative module body includes a symmetrical short-circuit fault control module, an asymmetrical short-circuit fault voltage support module, an active power frequency support module, and a dynamic current limiting module. The symmetrical short-circuit fault control module is triggered when a symmetrical drop in three-phase voltage is detected and the positive sequence voltage is below 0.9 per unit value; the asymmetrical short-circuit fault voltage support module is triggered when a negative sequence voltage component is detected above 0.05 per unit value; and the active power frequency support module is triggered when the grid frequency deviation is greater than 0.1 Hz for 20 milliseconds. When the current command calculated by any module exceeds the time-varying maximum allowable current, the dynamic current limiting module is forcibly intervened. The priority of the dynamic current limiting module is higher than that of the symmetrical short-circuit fault control module and the asymmetrical short-circuit fault voltage support module. The priority of the symmetrical short-circuit fault control module and the asymmetrical short-circuit fault voltage support module is higher than that of the active frequency support module. Each module outputs active current command and reactive current command, which are aggregated to the unified limiting and arbitration unit through the real-time data bus. The arbitration unit selects the command according to priority and records the currently active module number through the state machine to achieve bumpless switching.

[0015] Preferably, the establishment of the grid-type electromechanical transient model further includes establishing a three-layer nested solver. The first layer is an electromagnetic transient layer with a time step of 1 microsecond, solving the switching function model and positive / negative sequence instantaneous value equations of the grid-side converter, discretized using the implicit trapezoidal integral method and iterating 3 times per step. The second layer is an electromechanical transient layer with a time step of 1 millisecond, solving the generator mechanical equations, the active-frequency loop and reactive-voltage loop of the virtual synchronous machine, using the fourth-order Runge-Kutta method. The second layer receives the average power calculated by the first layer at each step and provides the voltage reference value to the first layer. The third layer is an energy interaction layer with a time step of 100 milliseconds, solving the pitch angle control, wind speed-power curve and long-term heat accumulation model, using the forward Euler method. The third layer updates the mechanical torque and rated power limit to the second layer at each step. The first layer and the second layer exchange power and voltage through a 1-millisecond sliding average window, and the second layer and the third layer exchange torque and power limit through a zero-order hold. The calculations of each layer are performed in parallel and synchronized by a global clock.

[0016] An electromechanical transient data processing device for offshore wind turbines includes a data acquisition unit, a main control processing unit, a storage unit, and a communication unit. The data acquisition unit, storage unit, and communication unit are all electrically connected to the main control processing unit. The main control processing unit integrates an electromechanical transient modeling module, a symmetrical fault control module, an asymmetrical fault control module, an active power frequency support module, and a hybrid synchronous control core module. The electromechanical transient modeling module is used to construct a grid-type electromechanical transient model incorporating the interaction between the generator, converter, and power grid, using a positive / negative sequence component separation algorithm. The symmetrical fault control module is used to adjust active power commands and monitor the grid-type electromechanical transient model according to the active power command. The system measures the junction temperature of power devices and generates symmetrical short-circuit fault control commands. The asymmetrical fault control module calculates transient current peak values, uses virtual impedance control or current compensation strategies to reduce the impact of negative sequence components, optimizes the output voltage waveform, and generates asymmetrical short-circuit fault control commands. The active power frequency support module quantifies the equivalent inertia time constant and damping coefficient, generates active power droop control signals, and adjusts power output under grid frequency disturbances. The hybrid synchronous control core module integrates the control commands of the symmetrical fault control module, the asymmetrical fault control module, and the active power frequency support module, establishes multi-module collaborative logic, and outputs unified grid-connected transient control commands.

[0017] Preferably, the data acquisition unit is a synchronous phasor acquisition module based on synchronous phasor measurement unit technology, used to acquire grid voltage, current, frequency, and phase angle parameters in real time, and the time synchronization accuracy of the acquisition is less than or equal to 1 microsecond.

[0018] Preferably, the electromechanical transient modeling module includes a generator modeling submodule, a converter modeling submodule, a power grid interaction modeling submodule, a sequence component separation submodule, and a virtual synchronous machine control submodule.

[0019] Preferably, the sequence component separation submodule is based on the improved instantaneous symmetrical component method to realize the sequence component decomposition under asymmetrical faults. The sequence component separation submodule has built-in positive sequence virtual impedance control unit and negative sequence virtual impedance control unit. The positive sequence virtual impedance control unit is used to support the stability of grid voltage and frequency, and the negative sequence virtual impedance control unit is used for grid asymmetrical fault management. The negative sequence virtual resistance in the negative sequence virtual impedance control unit is greater than or equal to three times the negative sequence virtual reactance.

[0020] Preferably, the electromechanical transient modeling module also includes a coordinate transformation submodule, a virtual synchronous machine control submodule, a dynamic current limiting submodule, and an asymmetrical fault interaction submodule. The coordinate transformation submodule is used to realize the transformation and decoupling from the three-phase stationary coordinate system to the synchronous rotating coordinate system. The virtual synchronous machine control submodule includes an active-frequency control loop and a reactive-voltage control loop to give the inverter the inertial response and damping regulation characteristics of a synchronous generator. The dynamic current limiting submodule is used to generate a time-varying maximum allowable current threshold based on the thermal characteristics of the power devices. The asymmetrical fault interaction submodule is used to construct positive and negative sequence power coupling equations to achieve decoupling control of positive sequence active power and negative sequence reactive power.

[0021] Preferably, the symmetrical fault control module has a built-in junction temperature prediction-correction unit, which is used to predict the junction temperature of the power device in advance, and to start the current slope limit in advance when the predicted junction temperature exceeds a preset threshold.

[0022] Preferably, the active frequency support module has a built-in active droop control unit, which is used to coordinate with the grid-type electromechanical transient model to complete the dynamic adjustment of power output under the scenario of grid frequency disturbance, and establish a dynamic energy interaction mechanism between the wind turbine and the grid.

[0023] Preferably, the hybrid synchronous control core module has a built-in scenario priority judgment unit and an instruction fusion unit. The scenario priority judgment unit is used to identify the power grid operating conditions and match the priority of the corresponding control module. The instruction fusion unit is used to coordinate and integrate multiple sets of control instructions to generate a conflict-free unified control signal.

[0024] Preferably, the main control processing unit is also communicatively connected to a simulation verification module. The simulation verification module is built on a real-time simulation platform or a hardware-in-the-loop platform and is used to test the system response under different short-circuit ratio scenarios to verify the minimum retrofit capacity and economic optimization target of the wind turbine.

[0025] Preferably, it further includes a touch display unit, a mounting support unit, a transparent protective unit, and a dustproof and heat dissipation unit. The touch display unit is communicatively connected to the main control processing unit for real-time data display and operation interaction. The mounting support unit provides a fixed mounting base for the touch display unit and has a built-in height adjustment structure. The transparent protective unit covers the operating surface of the touch display unit for physical protection and to prevent accidental touches. The dustproof and heat dissipation unit provides dust protection and heat dissipation for the main body of the device.

[0026] The beneficial effects of this invention are: (1) By constructing a full-link grid-type electromechanical transient model that includes permanent magnet synchronous generators, grid-side converters, and grid interaction, and combining virtual synchronous machine control embedding, the inverter-like synchronous generator is endowed with inertial response, damping regulation and voltage / frequency support capabilities. This breaks through the technical bottleneck that traditional offshore wind power cannot achieve full-power grid-type transient control, and can actively participate in grid frequency / voltage regulation, effectively supporting the safe and stable operation of the system after large-scale offshore wind power grid connection. (2) By integrating multiple transient control strategies such as symmetrical short-circuit fault control, asymmetrical short-circuit fault voltage support, and frequency disturbance active power support into a unified hybrid synchronous control system, a multi-module collaborative logic is established, realizing the unified acquisition, processing and analysis of transient data in all dimensions such as voltage, current, frequency, phase angle, and junction temperature, avoiding data silos and providing a complete data foundation for the analysis of system transient characteristics; (3) Through a unified hybrid synchronous control system and multi-module collaborative logic, staff can complete the collaborative processing of multiple types of transient problems such as symmetrical / asymmetrical faults, frequency disturbances, and overcurrent constraints through a single system, which significantly reduces the workload of analysis. At the same time, based on the multi-scenario simulation verification of the real-time simulation platform, system performance testing and parameter tuning can be completed in advance, reducing on-site debugging costs and greatly improving the efficiency and convenience of offshore wind power operation and maintenance analysis. (4) By dynamically adjusting the phase angle of the positive sequence virtual impedance and the ratio of the negative sequence resistance, a composite sequence impedance reshaping technology is constructed, which realizes the decoupled control of active power support and negative sequence suppression under asymmetrical faults. It optimizes the grid frequency / voltage support capability through positive sequence virtual impedance and accurately suppresses the impact of negative sequence components on the converter through negative sequence virtual impedance, effectively improving the system stability and voltage balance capability under asymmetrical faults. (5) By establishing a three-layer nested solver that includes microsecond-level switching dynamics of electromagnetic transients, millisecond-level inertial response of electromechanical transients, and second-level pitch control of energy interaction, transient processes at different time scales are accurately captured. This breaks through the limitations of traditional modeling, which focuses on a single time scale and separates multiple physical processes. It achieves a full-dimensional and high-precision characterization of the transient characteristics of offshore wind turbines, providing more accurate model support for control strategy design. (6) By introducing wind speed feedforward compensation into the converter junction temperature prediction model, an overcurrent prediction-correction algorithm is designed to predict the junction temperature of power devices in advance. When the predicted junction temperature exceeds 125 degrees Celsius, the current slope limit is activated 10 milliseconds in advance, realizing active prediction and early correction overcurrent protection. This not only ensures the transient support capability of the power grid in the early stage of the fault, but also effectively avoids the overheating damage of the devices, thereby improving the reliability and fault tolerance of the converter. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the electromechanical transient data processing method for offshore wind turbines according to the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] Example 1: Please see Figure 1 As shown, the present invention provides a method for processing electromechanical transient data of offshore wind turbines, including the following steps: Step S01: Establishment of the network-type electromechanical transient model Based on synchronous phasor measurement unit (PMU) technology, multiple parameters, including grid voltage, current, frequency, and phase angle, are acquired in real time. The PMU acquisition system uses GPS timing to ensure that the time synchronization accuracy of data from distributed measurement points is less than or equal to 1 microsecond. The acquired three-phase voltage and three-phase current signals are converted from analog to digital and then enter the digital signal processing unit.

[0030] By combining a positive / negative sequence component separation algorithm, an electromechanical transient model of a grid-connected wind turbine generator, including the interaction between the generator, converter, and power grid, is established. This model comprises the following three core sub-models: (1) Equivalent circuit model of permanent magnet synchronous generator In the synchronously rotating dq coordinate system, the voltage equation of the permanent magnet synchronous generator is:

[0031] in, It is the direct-axis voltage. It is the quadrature axis voltage. Stator phase resistance, For direct-axis current, For quadrature axis current, The rate of change of the direct-axis current with respect to time. Let be the rate of change of the quadrature-axis current with respect to time. It is a direct-axis inductor. It is a quadrature axis inductor. Electric angular velocity, It is a permanent magnet flux linkage.

[0032] The mechanical motion equation of the generator rotor is:

[0033] in, The moment of inertia of the rotor. For mechanical angular velocity, For mechanical angular acceleration, For mechanical torque, For electromagnetic torque, This is the damping coefficient. Electromagnetic torque. The relationship with current is: ,in It is an extreme logarithm.

[0034] (2) Switching function model of grid-side converter The grid-side converter adopts a three-phase full-bridge topology, with each phase arm consisting of two switching transistors (upper and lower). (Definition) , , These are the switching functions for the three-phase bridge arms. When the upper bridge arm is on, the switching function is 1; when the lower bridge arm is on, the switching function is 0. The relationship between the three-phase output voltage and the switching function is as follows:

[0035] in, , , These are the three-phase output voltages. This is the DC bus voltage. This is the voltage scaling factor. This represents the zero-sequence component of the switching function. This model accurately characterizes the impact of converter switching actions on the output voltage, providing a mathematical foundation for subsequent control strategy design.

[0036] (3) Positive / negative sequence equivalent impedance model of power grid Voltage fluctuations at the grid connection point can be decomposed into positive-sequence and negative-sequence components. The equivalent impedance model of the power grid is as follows:

[0037] in, This is the positive sequence voltage deviation. This is a negative sequence voltage deviation. For positive sequence equivalent impedance, It is the negative sequence equivalent impedance. This is the positive sequence current on the grid side. This is the negative sequence current on the grid side. This represents the positive sequence current component output by the converter. This represents the negative-sequence current component of the converter output. This model reveals the mechanism by which the converter output current affects the grid voltage, providing a theoretical basis for control strategies under asymmetrical faults.

[0038] In some embodiments, the separation of positive / negative sequence components is achieved using an improved instantaneous symmetrical component method. This method converts the instantaneous voltage samples in the three-phase stationary coordinate system into positive-sequence fundamental, negative-sequence fundamental, positive-sequence second harmonic, and negative-sequence second harmonic voltage components using a rotation factor transformation matrix.

[0039] in, , , These are the sampled values ​​of the three-phase instantaneous voltage. The positive-sequence fundamental voltage component. It is the negative sequence fundamental voltage component. This is the positive-sequence second harmonic voltage component. It is the negative-sequence second harmonic voltage component. For the symmetric component method, the normalized coefficients are... Let be the rotation factor, defined as .

[0040] To support the stability of the power grid voltage and frequency, a positive-sequence virtual impedance is set. :

[0041] in, This is the proportionality coefficient. The integral coefficient is... These are the differential coefficients. For complex frequency variables, The cutoff angular frequency, It is a first-order low-pass filter used to suppress high-frequency noise.

[0042] To mitigate asymmetrical faults in the power grid, a negative-sequence virtual impedance is set. :

[0043] in, For negative sequence virtual resistance, It is a negative-sequence virtual reactance and satisfies the constraint conditions. This constraint ensures that the negative-sequence virtual impedance exhibits resistive characteristics, effectively suppressing the impact of negative-sequence current on the converter.

[0044] In some embodiments, the network-type electromechanical transient model further includes multi-coordinate system coupling modeling, virtual synchronous machine control embedding, dynamic current limiting model, and interaction model under asymmetric faults.

[0045] Multi-coordinate system coupled modeling is used to decouple and simplify three-phase physical quantities, providing an accurate mathematical model for subsequent control. A synchronous rotating coordinate system is established, including the positive-sequence component. Coordinate system and negative order components Coordinate system. The coordinate transformation matrix is:

[0046] in, The transformation matrix from the three-phase stationary abc coordinate system to the synchronously rotating dq coordinate system is a core mathematical tool for converting three-phase AC quantities into DC quantities in the dq coordinate system. This is the amplitude normalization coefficient. To synchronize the rotation angle, Let be the cosine projection coefficient of the phase a charge onto the d-axis. Let be the cosine projection coefficient of the phase b charge onto the d-axis. Let be the cosine projection coefficient of the c-phase charge onto the d-axis. Let be the sinusoidal projection coefficient of phase a charge onto the q-axis. Let be the sinusoidal projection coefficient of the b-phase charge onto the q-axis. The sinusoidal projection coefficient of the c-phase charge onto the q-axis is given.

[0047] Virtual synchronous machine control is embedded to endow inverters with the external characteristics of synchronous machines, solving the technical problems of lack of inertia and damping in traditional inverters. Virtual synchronous machine control includes an active-frequency loop and a reactive-voltage loop.

[0048] The rotor motion equations of a synchronous generator simulated by the active-frequency loop are as follows:

[0049] in, For electrical angular velocity deviation, For virtual inertia constant, This is a reference value for active power. Electromagnetic active power, This represents the damping power. The equation shows that when the electromagnetic active power... Less than the reference value At that time, electric angular velocity Increase the frequency and decrease it, thus achieving frequency regulation.

[0050] The reactive-voltage loop simulates the excitation characteristics of a synchronous generator:

[0051] in, This is the voltage reference value. The rated voltage reference value, This is the reactive power-voltage regulation coefficient. This is a reference value for reactive power. This represents electromagnetic reactive power. The equation shows that when electromagnetic reactive power... Less than the reference value At that time, voltage reference value Increase the voltage and decrease it, thus achieving voltage regulation.

[0052] The dynamic current limiting model is used to impose hardware limits on virtual synchronous machine control commands, preventing overheating and damage to converter power devices during transient processes. (Time-varying maximum allowable current) for:

[0053] in, Rated current, This is the short-time overload factor. The thermal time constant, For time, This is an exponentially decaying term. The model shows that, in the initial stage of a fault, the converter can experience short-term overload output. The rated current is doubled, and as time increases, the current is allowed to gradually decay to the rated value, achieving a balance between transient support capability and device safety.

[0054] The interaction model under asymmetric faults is used for mathematical modeling of asymmetric faults in power grids and to optimize transient control performance. The positive and negative sequence power coupling equations are as follows:

[0055] in, This refers to the total active power of the three phases. This refers to the total reactive power of the three phases. This is the normalization coefficient for three-phase power. This represents the positive sequence voltage-current phase difference. This represents the negative sequence voltage-current phase difference. Through sequence decoupling control, the positive sequence active and negative sequence reactive components can be independently adjusted, achieving precise control under asymmetrical fault conditions.

[0056] Step S02: Establishment of Symmetrical Short-Circuit Fault Control Strategy Based on the transient model established in step S01, the active power command is adjusted to match the active power feedback after the fault, thus preventing system synchronism loss. When a symmetrical voltage dip in the grid is detected, the symmetrical fault control module immediately activates. First, it reads the steady-state value of active power before the fault. Then, based on the magnitude of the grid voltage after the fault Calculate the reference value of active power during the fault period. :

[0057] in, This is the rated voltage. This adjustment strategy ensures that the active power command matches the degree of grid voltage drop, avoiding system insynchrony caused by excessive power command.

[0058] Meanwhile, the junction temperature and losses of power devices are monitored in real time, and the switching frequency and modulation strategy are dynamically adjusted to limit the short-circuit current amplitude and improve the withstand capability.

[0059] In some embodiments, real-time monitoring of the junction temperature of power devices is achieved by acquiring the case temperature of the converter module through a thermistor NTC or a temperature diode. Combined with real-time current With switching frequency Using the transient thermal impedance model Calculate junction temperature :

[0060] in, It is the sum of conduction loss and switching loss. This is the junction-to-case thermal impedance characteristic curve. Conduction loss. The switching loss is proportional to the square of the effective value of the current. It is proportional to the switching frequency.

[0061] The rules for dynamically adjusting the switching frequency and modulation strategy are as follows: when At that time, each rise The switching frequency decreases linearly. The minimum frequency is reduced to the rated frequency. This rule reduces switching losses and slows down the rate of junction temperature rise by lowering the switching frequency.

[0062] when If this occurs, the drive pulse is immediately blocked, triggering over-temperature protection. This threshold is set based on the maximum junction temperature limit of the IGBT module to ensure device safety.

[0063] Modulation strategy optimization rule: Under normal operating conditions, Space Vector Pulse Width Modulation (SVPWM) is adopted. This modulation method has the advantages of high DC voltage utilization and low output voltage harmonic content. When Or the short-circuit current exceeds When the fault is cleared, it switches to discontinuous pulse width modulation (DPWM), which reduces switching losses by decreasing the number of switching actions. After the fault is cleared, it resumes SVPWM after a 100-millisecond delay, which ensures that the device junction temperature drops sufficiently.

[0064] In some embodiments, an overcurrent prediction-correction algorithm is also employed to achieve overcurrent protection with active prediction and early correction.

[0065] The junction temperature prediction model is based on a first-order thermal network model and incorporates wind speed feedforward compensation.

[0066] in, To predict the junction temperature, For thermal resistance, For heat capacity, For ambient temperature, The current wind speed, As the reference wind speed, This represents the wind speed feedforward coefficient. This model considers the impact of air cooling on junction temperature, improving prediction accuracy.

[0067] The basis for determining the 10-millisecond lead time is based on the short-circuit withstand time of the IGBT module. Experimental data on the relationship between junction temperature and temperature, when hour, To ensure a 5-millisecond safety margin after the current slope limiting is activated and before the device actually turns off due to overcurrent, a prediction lead of 10 milliseconds is selected. This value is obtained through joint calibration using RT-LAB hardware-in-the-loop simulation and power cycling experiments.

[0068] Correction action: when Immediately activate the current slope limit to... Limited to Within this range, the current reference value is linearly reduced to... If the predicted junction temperature continues to rise to... If the fault occurs, a protective blockade will be implemented. This correction strategy achieves a balance between the power grid's transient support capability in the early stages of a fault and the safety protection of the devices.

[0069] Step S03: Establishment of Asymmetric Short-Circuit Fault Control Strategy Based on the grid voltage sag depth and converter output capacity, the peak transient current is calculated, and the positive / negative sequence current distribution characteristics during the fault are derived. Those skilled in the art can determine the peak current during the fault using known methods for calculating peak transient current, such as formulas based on voltage sag amplitude and short-circuit impedance, according to the grid voltage sag depth and converter output capacity.

[0070] Virtual impedance control or current compensation strategies are employed to reduce the impact of negative sequence components on the converter. Virtual impedance control introduces a virtual impedance into the control loop. This alters the external characteristics of the converter, making it suppress negative-sequence current. The current compensation strategy counteracts the influence of the negative-sequence component by injecting a compensation current that is in the opposite phase to the negative-sequence current.

[0071] The output voltage waveform is optimized by incorporating an overmodulation strategy. The overmodulation strategy allows the modulation amplitude to exceed the carrier amplitude, improving DC voltage utilization and ensuring sufficient output voltage amplitude to support grid voltage recovery even when the grid voltage drops.

[0072] Step S04: Establishment of Dynamic Energy Interaction and Active Power Support Strategy The interaction between the wind turbine's mechanical torque and the power grid frequency is analyzed, and the equivalent inertial time constant and damping coefficient are quantified. The moment of inertia of the wind turbine rotor is also analyzed. With virtual inertia constant The relationship is:

[0073] in, For mechanical angular velocity, Rated capacity. Damping coefficient. The effect of system frequency deviation on active power output is characterized by its numerical value, which is obtained through identification of the system frequency response characteristics.

[0074] Design an active power droop control module. The mathematical expression for active power droop control is:

[0075] in, This is the active power reference value. The droop coefficient is... This is the actual angular frequency. This is the rated angular frequency. This control strategy simulates the frequency regulation characteristics of a synchronous generator, automatically increasing active power output to support grid frequency recovery when the grid frequency drops.

[0076] Under grid frequency disturbances, power output is adjusted collaboratively by a transient model and a droop control module to balance the system's power angle stability. The transient model provides accurate predictions of the system's dynamic response, while the droop control module adjusts the active power reference value based on the frequency deviation. Together, they achieve rapid and accurate frequency support.

[0077] Step S05: Establishing Multi-Module Collaboration Logic The symmetrical short-circuit fault control strategy, the asymmetrical short-circuit fault control strategy, and the dynamic energy interaction and active power support strategy are integrated into the hybrid synchronous control system to establish multi-module collaborative logic.

[0078] In some embodiments, the multi-module collaboration logic is specifically defined as follows: The main components of the collaborative module include a symmetrical short-circuit fault control module, an asymmetrical short-circuit fault voltage support module, an active frequency support module, and a dynamic current limiting module.

[0079] Collaborative triggering conditions: When a symmetrical voltage drop in the three phases is detected and the positive sequence voltage is below 0.9 per unit, the symmetrical fault control module is triggered; when a negative sequence voltage component is detected... When the grid frequency deviation occurs, the asymmetric fault support module is triggered; The active power frequency support module is triggered after 20 milliseconds; when the current command calculated by any module exceeds... At that time, the dynamic current limiting module will be forcibly intervened.

[0080] The priorities, from highest to lowest, are: dynamic current limiting module, symmetrical / asymmetrical fault support module, and active frequency support module. Higher priority modules can override the power commands of lower priority modules, ensuring device safety and system stability.

[0081] Interaction logic: Each module outputs active current commands. and reactive current command The data is aggregated to a unified limiting and arbitration unit via a real-time data bus. The arbitration unit selects instructions according to priority and records the currently active module number through a state machine to achieve seamless switching. The state machine adopts a finite state machine (FSM) architecture, defining multiple states such as normal operation, symmetrical fault, asymmetrical fault, frequency disturbance, and overcurrent protection, as well as the transition conditions and actions between states.

[0082] In some embodiments, the establishment of a network-type electromechanical transient model also includes establishing a three-layer nested solver to accurately capture transient processes at different time scales.

[0083] The first layer is the electromagnetic transient layer, with a time step of [time step size missing]. This paper proposes a method to solve the switching function model and positive / negative sequence instantaneous value equations of the grid-side converter. Implicit trapezoidal integration is used for discretization, with three iterations per step. Implicit trapezoidal integration offers advantages such as good numerical stability and high accuracy, making it suitable for solving rigid differential equations.

[0084] The second layer is the electromechanical transient layer, with a time step of [time step]. This method solves the generator mechanical equations, the active-frequency loop of the virtual synchronous machine, and the reactive-voltage loop. A fourth-order Runge-Kutta method is employed, which offers advantages such as high computational accuracy and fast convergence. The second layer receives the average power calculated in the first layer at each step. and provide voltage reference values ​​to the first layer. .

[0085] The third layer is the energy interaction layer, with a time step. The problem involves solving for pitch angle control, wind speed-power curves, and a long-term heat accumulation model. The forward Euler method is employed, as it is computationally simple and suitable for slowly varying processes with large time constants. The mechanical torque is updated from the third layer to the second layer in each step. and rated power limits.

[0086] Inter-layer data exchange mechanism: The first and second layers exchange power and voltage through a 1-millisecond moving average window. The moving average window averages the instantaneous power values ​​of the first layer over 1000 time steps to obtain the average power required by the second layer. The second and third layers exchange torque and power limits through a zero-order hold, which maintains a constant value within the sampling interval. Parallel computation of each layer is synchronized by a global clock, which uses GPS timing to ensure the consistency of the time base of each layer and achieve multi-timescale joint simulation.

[0087] Through the above methods, this invention achieves full-power grid-connected transient control of offshore wind turbines. By constructing a full-link transient model including permanent magnet synchronous generators, grid-side converters, and grid interaction, and combining it with virtual synchronous machine control embedding, the inverter is endowed with the inertial response, damping regulation, and voltage / frequency support capabilities of a synchronous generator. This overcomes the technical bottleneck of traditional offshore wind power's inability to achieve full-power grid-connected transient control, enabling it to actively participate in grid frequency / voltage regulation and effectively support the safe and stable operation of the system after large-scale offshore wind power grid connection. By integrating multiple scenario transient control strategies, such as symmetrical short-circuit fault control, asymmetrical short-circuit fault voltage support, and frequency disturbance active power support, into a unified hybrid synchronous control system, and establishing multi-module collaborative logic, the invention achieves unified acquisition, processing, and analysis of all-dimensional transient data, including voltage, current, frequency, phase angle, and junction temperature, avoiding data silos and providing a complete data foundation for system transient characteristic analysis. Through the unified hybrid synchronous control system and multi-module collaborative logic, staff can complete the collaborative processing of multiple types of transient problems, such as symmetrical / asymmetrical faults, frequency disturbances, and overcurrent constraints, through a single system, significantly reducing the workload of analysis. By dynamically adjusting the phase angle of the positive-sequence virtual impedance and the ratio of the negative-sequence resistance, a composite-sequence impedance reshaping technique is constructed, achieving decoupled control of active power support and negative-sequence suppression under asymmetrical faults. This technique optimizes the grid frequency / voltage support capability through positive-sequence virtual impedance and precisely suppresses the impact of negative-sequence components on the converter through negative-sequence virtual impedance, effectively improving system stability and voltage balance under asymmetrical faults. Furthermore, by establishing a three-layer nested solver encompassing microsecond-level switching dynamics of electromagnetic transients, millisecond-level inertial response of electromechanical transients, and second-level pitch control of energy interaction, transient processes at different time scales are accurately captured. This overcomes the limitations of traditional modeling, which focuses on a single time scale and fragments multiple physical processes, achieving a full-dimensional, high-precision characterization of the transient characteristics of offshore wind turbines, providing more accurate model support for control strategy design. By introducing wind speed feedforward compensation into the converter junction temperature prediction model, an overcurrent prediction-correction algorithm is designed to predict the junction temperature of power devices in advance. When the predicted junction temperature exceeds 125 degrees Celsius, the current slope limit is activated 10 milliseconds in advance, realizing active prediction and early correction overcurrent protection. This not only ensures the grid transient support capability in the early stage of a fault, but also effectively avoids device overheating damage, thereby improving the reliability and fault tolerance of the converter.

[0088] Example 2: In some embodiments, an electromechanical transient data processing device for offshore wind turbines is also provided for executing the method described in Embodiment 1. The device includes a data acquisition unit, a main control processing unit, a storage unit, and a communication unit, all of which are electrically connected to the main control processing unit.

[0089] The data acquisition unit is a synchronous phasor acquisition module based on synchronous phasor measurement unit (PMU) technology, used to acquire grid voltage, current, frequency, and phase angle parameters in real time, with a time synchronization accuracy of less than or equal to 1 microsecond. The data acquisition unit includes a voltage transformer, a current transformer, an analog-to-digital converter (ADC), a GPS timing module, and a digital signal processor (DSP). The voltage and current transformers convert the high-voltage, high-current signals of the grid into low-voltage, low-current signals. The ADC converts analog signals into digital signals. The GPS timing module provides a high-precision time reference, and the DSP performs phasor calculations and data packaging.

[0090] The main control processing unit has built-in electromechanical transient modeling module, symmetrical fault control module, asymmetrical fault control module, active frequency support module and hybrid synchronous control core module.

[0091] The electromechanical transient modeling module is connected to the data acquisition unit to receive the power grid operating parameters collected by the data acquisition unit. Combined with the positive / negative sequence component separation algorithm, it constructs a grid-type electromechanical transient model that includes the interaction between generators, converters and the power grid.

[0092] In some embodiments, the electromechanical transient modeling module includes a generator modeling submodule, a converter modeling submodule, a power grid interaction modeling submodule, a sequence component separation submodule, and a virtual synchronous machine control submodule.

[0093] The generator modeling submodule is used to construct the equivalent circuit model and rotor mechanical equation model of the permanent magnet synchronous generator, and to calculate the electromagnetic torque and mechanical angular velocity of the generator based on the real-time collected voltage and current data.

[0094] The converter modeling submodule is used to construct the switching function model of the grid-side converter and calculate the three-phase output voltage of the converter based on the switching function state.

[0095] The power grid interactive modeling submodule is used to construct the positive / negative sequence equivalent impedance model of the power grid and calculate the power grid impedance parameters based on the power grid voltage and the converter output current.

[0096] The sequence component separation submodule uses an improved instantaneous symmetrical component method to decompose sequence components under asymmetrical faults. It incorporates a positive-sequence virtual impedance control unit and a negative-sequence virtual impedance control unit. The positive-sequence virtual impedance control unit is used to support the stability of the power grid voltage and frequency, while the negative-sequence virtual impedance control unit is used for asymmetrical fault management in the power grid. In the negative-sequence virtual impedance control unit, the negative-sequence virtual resistance is greater than or equal to three times the negative-sequence virtual reactance.

[0097] The virtual synchronous machine control submodule has built-in active-frequency control loop and reactive-voltage control loop, which are used to give the inverter the inertial response and damping regulation characteristics of a synchronous generator.

[0098] In some embodiments, the electromechanical transient modeling module also includes a coordinate transformation submodule, a dynamic current limiting submodule, and an asymmetric fault interaction submodule.

[0099] The coordinate transformation submodule is used to realize the transformation and decoupling from the three-phase stationary coordinate system to the synchronous rotating coordinate system, converting the three-phase AC quantities into DC quantities in the dq coordinate system, thus simplifying the design of the control algorithm.

[0100] The dynamic current limiting submodule is used to generate a time-varying maximum allowable current threshold based on the thermal characteristics of the power devices, and to impose hardware limits on control commands to prevent the power devices of the converter from overheating and being damaged during transient processes.

[0101] The asymmetric fault interaction submodule is used to construct positive and negative sequence power coupling equations, realize the sequence decoupling control of positive sequence active power and negative sequence reactive power, and optimize the control performance under asymmetric faults.

[0102] The symmetrical fault control module is connected to the electromechanical transient modeling module. It is used to adjust the active power command according to the network-type electromechanical transient model so that the active power command matches the active power feedback after the fault. At the same time, it monitors the junction temperature of the power devices in real time and generates control commands under symmetrical short-circuit faults.

[0103] In some embodiments, the symmetrical fault control module incorporates a junction temperature prediction-correction unit to predict the junction temperature of power devices in advance. When the predicted junction temperature exceeds a preset threshold, the current slope limiting is activated in advance to achieve active overcurrent protection. The junction temperature prediction-correction unit is based on a first-order thermal network model and incorporates wind speed feedforward compensation to improve the accuracy of junction temperature prediction.

[0104] The asymmetric fault control module is connected to the electromechanical transient modeling module. It is used to calculate the peak transient current based on the grid voltage drop depth and the converter output capacity, derive the positive / negative sequence current distribution characteristics during the fault, adopt virtual impedance control or current compensation strategy to reduce the impact of negative sequence components on the converter, optimize the output voltage waveform by combining overmodulation strategy, and generate control commands under asymmetric short-circuit fault.

[0105] The active frequency support module is connected to the electromechanical transient modeling module to analyze the interaction between the wind turbine's mechanical torque and the grid frequency, quantify the equivalent inertial time constant and damping coefficient, generate active droop control signals, coordinate with the electromechanical transient model to adjust power output under grid frequency disturbances, balance the system's power angle stability, and generate control commands under frequency disturbance scenarios.

[0106] In some embodiments, the active frequency support module has a built-in active droop control unit, which is used to coordinate with the grid-type electromechanical transient model to complete the dynamic adjustment of power output under grid frequency disturbance scenarios, and establish a dynamic energy interaction mechanism between the wind turbine and the grid.

[0107] The hybrid synchronous control core module is communicatively connected to the symmetrical fault control module, the asymmetrical fault control module, and the active frequency support module, respectively. It is used to integrate and receive symmetrical short-circuit fault control commands, asymmetrical short-circuit fault control commands, and frequency disturbance scenario control commands, establish multi-module collaborative control logic, generate unified wind turbine grid-connected transient control commands, and send them to the wind turbine converter execution unit through the communication unit.

[0108] In some embodiments, the hybrid synchronous control core module incorporates a scenario priority judgment unit and an instruction fusion unit. The scenario priority judgment unit identifies the power grid operating conditions and matches the priorities of corresponding control modules. Based on parameters such as power grid voltage, frequency, and negative sequence components, it determines whether the current scenario is normal operation, symmetrical fault, asymmetrical fault, or frequency disturbance, and determines the activation state and priority of each control module. The instruction fusion unit coordinates and integrates multiple sets of control instructions to generate conflict-free unified control signals, selects valid instructions according to priority, and achieves seamless switching between different control modes through a state machine.

[0109] The storage unit is used to store program code, model parameters, historical data, and other information required for the main control processing unit to run. The storage unit can use storage media such as flash memory, hard disk, or solid-state drive.

[0110] The communication unit is used to enable data interaction between the main control processing unit and external devices, including issuing control commands to the wind turbine converter actuator, uploading data to the host computer monitoring system, and coordinating communication with other wind turbines. The communication unit can use communication protocols such as Ethernet, CAN bus, and Modbus.

[0111] In some embodiments, the main control processing unit is also communicatively connected to a simulation verification module. This module, built on an RT-LAB or HIL (Hardware-in-the-Loop) platform, is used to test the system response under different short-circuit ratio (SCR) scenarios, verifying the minimum retrofit capacity and economic optimization targets for wind turbines. The RT-LAB platform is a high-performance real-time simulation and testing platform that enables offline verification and parameter tuning of control algorithms, reducing on-site debugging costs. The HIL platform connects the actual controller to the simulation system, allowing verification of the actual performance of the control algorithm on the real controller.

[0112] In some embodiments, the device further includes a touch display unit, a mounting support unit, a transparent protective unit, and a dustproof and heat dissipation unit.

[0113] The touch display unit communicates with the main control processing unit for real-time data display and operation interaction. The touch display unit can display operating parameters such as grid voltage, current, frequency, active power, reactive power, and junction temperature, as well as status information such as control mode, fault status, and alarm information. Operators can perform parameter settings, mode switching, and fault reset via the touch screen.

[0114] The mounting support unit provides a fixed mounting base for the touch display unit and has a built-in height adjustment structure, allowing operators to adjust the display height according to actual needs and improve operational convenience.

[0115] A transparent protective unit covers the operating surface of the touch display unit for physical protection and to prevent accidental touches, avoiding dust, water droplets, and foreign objects from contacting the display screen and extending the service life of the equipment.

[0116] The dustproof and heat dissipation unit is used to provide dust protection and heat dissipation for the main body of the device. The dustproof unit adopts a sealed structure and dust filter to prevent dust from entering the device. The heat dissipation unit adopts heat dissipation methods such as fans, heat sinks, and heat pipes to ensure that the main control processing unit operates stably within the rated temperature range.

[0117] Through the above-mentioned device, the present invention realizes the hardware implementation of the electromechanical transient data processing method for offshore wind turbines, providing a complete technical solution for the engineering application of grid-type wind turbines.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for processing electromechanical transient data of offshore wind turbines, characterized in that, Includes the following steps: S01: Real-time acquisition of grid voltage, current, frequency, and phase angle parameters, with the time synchronization accuracy of the acquisition being less than or equal to 1 microsecond. A positive / negative sequence component separation algorithm is used to establish a grid-type electromechanical transient model that includes the interaction between generators, converters, and the grid. S02: Based on the aforementioned network-type electromechanical transient model, a symmetrical short-circuit fault control strategy is established, which includes adjusting the active power command, monitoring the junction temperature of power devices, dynamically adjusting the switching frequency, and the modulation strategy. S03: Establish an asymmetric short-circuit fault control strategy, which includes calculating the peak value of transient current, using virtual impedance control or current compensation strategy to reduce the influence of negative sequence components, and optimizing the output voltage waveform. S04: Establish a dynamic energy interaction and active power support strategy, which includes quantifying the equivalent inertial time constant and damping coefficient, designing an active power droop control module, and coordinating power output adjustment under grid frequency disturbances. S05: Integrate the symmetrical short-circuit fault control strategy, the asymmetrical short-circuit fault control strategy, and the dynamic energy interaction and active power support strategy into the hybrid synchronous control system to establish multi-module collaborative logic.

2. The method for processing electromechanical transient data of offshore wind turbines according to claim 1, characterized in that, The establishment of the grid-type electromechanical transient model of the generator in step S01 includes: An equivalent circuit for a permanent magnet synchronous generator is established, comprising a direct-axis voltage equation and a quadrature-axis voltage equation. The direct-axis voltage is equal to the sum of the products of the stator phase resistance and the direct-axis current, and the direct-axis inductance and the rate of change of the direct-axis current with respect to time, minus the product of the electric angular velocity, the quadrature-axis inductance, and the quadrature-axis current. The quadrature-axis voltage is equal to the sum of the products of the stator phase resistance and the quadrature-axis current, and the quadrature-axis inductance and the rate of change of the quadrature-axis current with respect to time, plus the product of the electric angular velocity and the sum of the direct-axis inductance, the direct-axis current, and the permanent magnet flux linkage. Establish a mechanical equation, which states that the product of the rotor's moment of inertia and the mechanical angular acceleration is equal to the mechanical torque minus the electromagnetic torque minus the product of the damping coefficient and the mechanical angular velocity. The step S01 of establishing the grid-type electromechanical transient model of the converter includes: A grid-side converter switching function model is established, wherein the three-phase output voltages are each equal to half of the DC bus voltage multiplied by the corresponding phase switching function minus one-third of the sum of the three-phase switching functions. The step S01 of establishing a grid-based electromechanical transient model for power grid interaction includes: A power grid equivalent impedance model is established, wherein the positive sequence voltage deviation is equal to the positive sequence equivalent impedance multiplied by the sum of the positive sequence current on the power grid side and the positive sequence current component output by the converter, and the negative sequence voltage deviation is equal to the negative sequence equivalent impedance multiplied by the sum of the negative sequence current on the power grid side and the negative sequence current component output by the converter.

3. The method for processing electromechanical transient data of offshore wind turbines according to claim 1, characterized in that, The positive / negative order component separation algorithm used in step S01 includes: An improved instantaneous symmetrical component method is used to decompose the sequence components under asymmetrical faults. The improved instantaneous symmetrical component method converts the three-phase instantaneous voltage sample values ​​into positive-sequence fundamental voltage components, negative-sequence fundamental voltage components, positive-sequence second harmonic voltage components, and negative-sequence second harmonic voltage components through a rotation factor transformation matrix. A positive-sequence virtual impedance is set to support the stability of the mains voltage and frequency. The positive-sequence virtual impedance includes a proportional term, an integral term, and a derivative term. The derivative term includes a first-order low-pass filter. A negative-sequence virtual impedance is set up for the management of power grid asymmetric faults. The negative-sequence virtual impedance includes a negative-sequence virtual resistance and a negative-sequence virtual reactance. The negative-sequence virtual resistance is greater than or equal to three times the negative-sequence virtual reactance.

4. The method for processing electromechanical transient data of offshore wind turbines according to claim 1, characterized in that, The step S01 of establishing the network-type electromechanical transient model also includes: A multi-coordinate system coupling model is established, which includes a positive-sequence component synchronous rotating coordinate system and a negative-sequence component synchronous rotating coordinate system. The AC quantity in the three-phase stationary coordinate system is converted into the DC quantity in the synchronous rotating coordinate system through a coordinate transformation matrix. The system incorporates a virtual synchronous machine control, which includes an active-frequency loop and a reactive-voltage loop. In the active-frequency loop, the electrical angular velocity deviation is equal to half of the virtual inertia constant multiplied by the active power reference value minus the electromagnetic active power and then minus the damping power. In the reactive-voltage loop, the voltage reference value is equal to the rated voltage base value plus the reactive-voltage regulation coefficient multiplied by the difference between the reactive power reference value and the electromagnetic reactive power. A dynamic current limiting model is established, in which the time-varying maximum allowable current is equal to the rated current multiplied by a factor plus a short-time overload factor and a factor minus the natural exponent, which is the exponent of negative time divided by the thermal time constant. An interaction model under asymmetric faults is established, which includes positive and negative sequence power coupling equations. These equations enable the decoupling control of positive sequence active and negative sequence reactive components.

5. The method for processing electromechanical transient data of offshore wind turbines according to claim 4, characterized in that, Monitoring the junction temperature of the power device in step S02 includes: The case temperature of the converter module is collected by a thermistor or temperature diode. Combined with the real-time current and switching frequency, the junction temperature is calculated using a transient thermal impedance model. The junction temperature is equal to the case temperature plus the product of power loss and transient thermal impedance. The power loss is the sum of conduction loss and switching loss. When the junction temperature is greater than or equal to 120 degrees Celsius, the switching frequency decreases linearly by 5% for every 1 degree Celsius increase, and drops to a minimum of 40% of the rated frequency. When the junction temperature is greater than or equal to 140 degrees Celsius, the drive pulse is immediately blocked. Under normal operating conditions, space vector pulse width modulation is used. When the junction temperature is greater than or equal to 110 degrees Celsius or the short-circuit current exceeds 1.5 times the rated current, it switches to discontinuous pulse width modulation. After the fault is cleared, space vector pulse width modulation is restored after a delay of 100 milliseconds. The monitoring of the power device junction temperature in step S02 also includes overcurrent prediction-correction: A junction temperature prediction model is established based on a first-order thermal network model. The junction temperature prediction model introduces wind speed feedforward compensation. The predicted junction temperature is equal to the current junction temperature plus the power loss minus the difference between the current junction temperature and the ambient temperature divided by the thermal resistance, multiplied by the time step, divided by the heat capacity, plus the wind speed feedforward coefficient multiplied by the difference between the current wind speed and the reference wind speed. When the predicted junction temperature exceeds 125 degrees Celsius, the current slope limit is activated 10 milliseconds in advance to limit the rate of change of current with respect to time to within 50 amperes per microsecond, while the current reference value is linearly reduced to 0.8 times the rated current.

6. The method for processing electromechanical transient data of offshore wind turbines according to claim 5, characterized in that, The establishment of multi-module collaborative logic in step S05 includes: The main body of the collaborative module is defined, which includes a symmetrical short-circuit fault control module, an asymmetrical short-circuit fault voltage support module, an active frequency support module, and a dynamic current limiting module. The system sets coordinated triggering conditions. When a symmetrical drop in three-phase voltage is detected and the positive sequence voltage is lower than 0.9 per unit, the symmetrical short-circuit fault control module is triggered. When a negative sequence voltage component is detected to be greater than 0.05 per unit, the asymmetrical short-circuit fault voltage support module is triggered. When the grid frequency deviation is greater than 0.1 Hz for 20 milliseconds, the active frequency support module is triggered. When the current command calculated by any module exceeds the time-varying maximum allowable current, the dynamic current limiting module is forcibly intervened. Priorities are set such that the dynamic current limiting module has a higher priority than the symmetrical short-circuit fault control module and the asymmetrical short-circuit fault voltage support module, and the symmetrical short-circuit fault control module and the asymmetrical short-circuit fault voltage support module have a higher priority than the active frequency support module. The interaction logic is set up so that each module outputs active current command and reactive current command, which are aggregated to a unified limiting and arbitration unit through a real-time data bus. The arbitration unit selects commands according to priority and records the currently active module number through a state machine to achieve seamless switching.

7. The method for processing electromechanical transient data of offshore wind turbines according to claim 6, characterized in that, The step S01 of establishing the network-type electromechanical transient model also includes establishing a three-layer nested solver: The first layer is the electromagnetic transient layer with a time step of 1 microsecond. The switching function model and positive / negative sequence instantaneous value equations of the grid-side converter are solved. The implicit trapezoidal integration method is used for discretization and each step is iterated 3 times. The second layer is the electromechanical transient layer with a time step of 1 millisecond. It solves the generator mechanical equations, the active-frequency loop and the reactive-voltage loop of the virtual synchronous machine, and adopts the fourth-order Runge-Kutta method. At each step, the second layer receives the average power calculated by the first layer and provides the first layer with the voltage reference value. The third layer is the energy interaction layer with a time step of 100 milliseconds. It solves the pitch angle control, wind speed-power curve and long-term heat accumulation model using the forward Euler method. The third layer updates the mechanical torque and rated power limit to the second layer in each step. The first layer and the second layer exchange power and voltage through a sliding average window with a length of 1 millisecond, and the second layer and the third layer exchange torque and power limits through a zero-order hold. The parallel calculations of each layer are synchronized by a global clock.

8. A device for processing electromechanical transient data of an offshore wind turbine, comprising a data acquisition unit, a main control processing unit, a storage unit, and a communication unit, wherein the data acquisition unit, the storage unit, and the communication unit are all electrically connected to the main control processing unit, characterized in that, The main control processing unit has the following built-in features: The electromechanical transient modeling module is used to construct a network-type electromechanical transient model that includes the interaction between generators, converters and the power grid by combining the positive / negative sequence component separation algorithm; The symmetrical fault control module is used to adjust the active power command, monitor the junction temperature of power devices, and generate symmetrical short-circuit fault control commands according to the network electromechanical transient model. The asymmetric fault control module is used to calculate the peak value of transient current, reduce the influence of negative sequence components by adopting virtual impedance control or current compensation strategies, optimize the output voltage waveform, and generate asymmetric short-circuit fault control commands. The active frequency support module is used to quantify the equivalent inertial time constant and damping coefficient, generate active droop control signals, and adjust power output under grid frequency disturbances. The hybrid synchronous control core module is used to integrate the control commands of the symmetrical fault control module, the asymmetrical fault control module, and the active frequency support module, establish multi-module collaborative logic, and output unified grid-connected transient control commands.

9. The offshore wind turbine electromechanical transient data processing device according to claim 8, characterized in that, The data acquisition unit is a synchronous phasor acquisition module based on synchronous phasor measurement unit technology, used to acquire grid voltage, current, frequency, and phase angle parameters in real time. The time synchronization accuracy of the acquisition is less than or equal to 1 microsecond.

10. The offshore wind turbine electromechanical transient data processing device according to claim 8, characterized in that, The electromechanical transient modeling module includes a generator modeling submodule, a converter modeling submodule, a power grid interaction modeling submodule, a sequence component separation submodule, and a virtual synchronous machine control submodule. The sequence component separation submodule is based on the improved instantaneous symmetrical component method to realize the sequence component decomposition under asymmetrical faults. The sequence component separation submodule has built-in positive sequence virtual impedance control unit and negative sequence virtual impedance control unit. The positive sequence virtual impedance control unit is used to support the stability of grid voltage and frequency. The negative sequence virtual impedance control unit is used for grid asymmetrical fault management. The negative sequence virtual resistance in the negative sequence virtual impedance control unit is greater than or equal to three times the negative sequence virtual reactance. The electromechanical transient modeling module also includes a coordinate transformation submodule, a virtual synchronous machine control submodule, a dynamic current limiting submodule, and an asymmetrical fault interaction submodule. The coordinate transformation submodule is used to realize the transformation and decoupling from the three-phase stationary coordinate system to the synchronous rotating coordinate system. The virtual synchronous machine control submodule has built-in active-frequency control loop and reactive-voltage control loop to give the inverter the inertial response and damping regulation characteristics of a synchronous generator. The dynamic current limiting submodule is used to generate the time-varying maximum allowable current threshold based on the thermal characteristics of the power devices. The asymmetrical fault interaction submodule is used to construct positive and negative sequence power coupling equations to realize the decoupling control of positive sequence active power and negative sequence reactive power.

11. The offshore wind turbine electromechanical transient data processing device according to claim 8, characterized in that, The symmetrical fault control module has a built-in junction temperature prediction-correction unit, which is used to predict the junction temperature of the power device in advance. When the predicted junction temperature exceeds a preset threshold, the current slope limit is activated in advance.

12. The offshore wind turbine electromechanical transient data processing device according to claim 8, characterized in that, The active frequency support module has a built-in active droop control unit, which is used to work with the grid-type electromechanical transient model to dynamically adjust the power output under grid frequency disturbance scenarios, and establish a dynamic energy interaction mechanism between the wind turbine and the grid.

13. The offshore wind turbine electromechanical transient data processing device according to claim 8, characterized in that, The hybrid synchronous control core module has a built-in scenario priority judgment unit and an instruction fusion unit. The scenario priority judgment unit is used to identify the power grid operating conditions and match the priority of the corresponding control module. The instruction fusion unit is used to coordinate and integrate multiple sets of control instructions to generate a conflict-free unified control signal.

14. The offshore wind turbine electromechanical transient data processing device according to claim 8, characterized in that, The main control processing unit is also communicatively connected to a simulation verification module. The simulation verification module is built on a real-time simulation platform or a hardware-in-the-loop platform and is used to test the system response under different short-circuit ratio scenarios to verify the minimum retrofit capacity and economic optimization target of the wind turbine.

15. The offshore wind turbine electromechanical transient data processing device according to claim 8, characterized in that, It also includes a touch display unit, a mounting support unit, a transparent protective unit, and a dustproof and heat dissipation unit. The touch display unit is communicatively connected to the main control processing unit for real-time data display and operation interaction. The mounting support unit provides a fixed mounting base for the touch display unit and has a built-in height adjustment structure. The transparent protective unit covers the operating surface of the touch display unit for physical protection and to prevent accidental touches. The dustproof and heat dissipation unit provides dust protection and heat dissipation for the main body of the device.

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