Island detection and self-synchronization grid-connection method for offshore floating power generation device

Abstract

The present application relates to the technical fields of power system grid-connected control, and discloses an offshore floating power generation device island detection and self-synchronization grid-connected method, which is used to solve the problem that transient oscillation is difficult to effectively suppress in the self-synchronization grid-connected process after island detection in the traditional method; the method first realizes accurate island identification by collecting voltage and frequency signals at the grid-connected interface in combination with multi-cycle deviation determination and adaptive threshold; after island confirmation, the virtual synchronous machine mode is switched, transient power fluctuation and phase difference are used to set damping and perform voltage closed-loop calibration, so that the device converges to the phase and voltage alignment with the power grid; after the alignment condition is met, gradual power injection is used to complete grid connection, and the voltage, frequency and power balance are monitored through parameter cycle verification; if necessary, hierarchical adjustment or rollback is performed, so that transient oscillation and power impact are suppressed in the whole process from island detection to re-grid connection and stable operation, and the grid connection stability and adaptability are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power system grid-connected control, in particular to an island detection and self-synchronization grid-connected method for offshore floating power generation devices. BACKGROUND

[0002] As a new renewable energy device, offshore floating power generation devices are often deployed in marine environments and transmit power to the grid through grid-connected mode. However, when the grid fails or is disconnected, an island operation state may be formed, which needs to be detected and self-synchronized to ensure system stability and power continuity. In the prior art, island detection usually uses power disturbance or frequency offset methods, and self-synchronization grid connection relies on virtual synchronous machine (VSG) control, which can simulate the inertia and damping characteristics of traditional generators to automatically adjust power and phase. However, these methods often face transient oscillation problems during re-griding after island detection, i.e. voltage and frequency instability caused by power fluctuations and phase differences, which easily leads to grid impact or equipment damage, limiting the reliable application of offshore floating devices.

[0003] For example, patent CN116933497A discloses a photovoltaic virtual synchronous generator power station grid-connected island detection method, which changes the reference power periodically and judges the island state according to the power-frequency characteristic coefficient to achieve fast detection. This patent emphasizes the real-time and accuracy of detection, but it relies on simple power adjustment for self-synchronization grid connection after island confirmation, without introducing a dedicated damping mechanism for the transient process, resulting in difficulty in effectively suppressing oscillation caused by power mismatch or wave disturbance in the dynamic environment of offshore floating devices, which easily produces sustained oscillation during re-griding, affecting system recovery efficiency. Patent CN101944746A discloses an island detection method, device and system for a photovoltaic grid-connected power generation system, which monitors the matching of load power and inverter output and selects an active detection mode (such as frequency offset) to identify the island. This patent provides a device-level implementation scheme for easy integration, but its self-synchronization grid connection part only relies on basic phase shift control and does not fully consider the suppression of transient oscillation after islanding, resulting in amplification of oscillation amplitude when the platform moves or wind waves cause additional disturbances in offshore floating power generation devices, making it difficult to stabilize quickly and increasing the risk of grid instability.

[0004] In summary, although the prior art has made progress in island detection, the defect of ineffective suppression of transient oscillation during self-synchronization grid connection after island detection has not been solved. Specifically, these methods lack adaptive damping algorithms for offshore floating environments and cannot suppress power-angle oscillation in real time, resulting in low grid connection efficiency and increased safety hazards, and a new method is urgently needed to overcome this technical problem. SUMMARY

[0005] In view of the deficiencies of the prior art, the offshore floating power generation device island detection and self-synchronization grid connection method is provided to solve the problem of difficulty in effectively inhibiting transient oscillation in the self-synchronization grid connection process after island detection in the traditional method.

[0006] To achieve the purpose of inhibiting the difficulty in transient oscillation in the grid connection process mentioned in the background art, the present application provides the following technical solutions:

[0007] The offshore floating power generation device island detection and self-synchronization grid connection method comprises:

[0008] S1: Monitor the offshore floating power generation device grid connection state, identify the island by collecting voltage and frequency signals, and confirm and start synchronization preparation when the deviation exceeds the threshold value;

[0009] S2: After confirming the island formation, switch the device to the virtual synchronous machine mode, adjust the reference phase to match the grid, and collect transient power fluctuation data;

[0010] S3: Dynamically set the damping parameters based on the transient power fluctuation data, continuously monitor the phase difference between the device and the grid, and optimize the control response of the virtual synchronous machine;

[0011] S4: During the dynamic setting of the damping parameters, introduce a voltage feedback loop to real-time calibrate the output voltage amplitude;

[0012] S5: When the phase deviation and amplitude deviation are within the preset alignment range, issue a grid connection instruction to complete the physical connection with the grid in a gradual power injection manner, and maintain the damping parameter adjustment;

[0013] S6: After the grid connection is completed, continue to monitor the overall system stability, maintain the synchronization state through periodic parameter verification, and enter the normal operation mode of the offshore floating power generation device.

[0014] In a preferred embodiment, monitoring the offshore floating power generation device grid connection state, identifying the island by collecting voltage and frequency signals, and confirming and starting synchronization preparation when the deviation exceeds the threshold value, comprises:

[0015] A voltage sensor and a frequency sensor are arranged at the grid connection interface to collect grid side signals and monitor the grid connection state;

[0016] The voltage sensor is connected to the three-phase alternating current output end to collect phase voltage amplitude and phase sequence information;

[0017] The frequency sensor is connected in parallel to the bus to obtain the voltage period through zero-crossing detection, and calculate the current grid frequency accordingly;

[0018] The sampling results are refreshed and cache updated, and the deviation threshold is set. After multiple cycles of review, the island formation is confirmed;

[0019] After confirmation, the multi-dimensional operating state parameters are recorded and a synchronization token is generated. The synchronization token is used to preload the virtual synchronous machine parameters, and the device is switched to a synchronization preparation state.

[0020] In a preferred embodiment, after confirming the island formation, the device is switched to a virtual synchronous machine mode, the reference phase matching the grid is adjusted, and transient power fluctuation data is collected, including:

[0021] The device is switched to a virtual synchronous machine mode, receives a synchronization token and issues a mode switching instruction, activates the power electronic controller to load the parameter set and initializes the related state variables;

[0022] The conventional power output loop is disconnected, the virtual synchronous machine control loop is enabled, and the phase and frequency of the output voltage are associated through a phase-locked loop, gradually increasing or decreasing the internal reference phase;

[0023] During the adjustment process, the attitude data is filtered, and the phase difference is continuously monitored until the phase difference converges to generate an adjustment token;

[0024] Transient power fluctuations are collected in parallel, active and reactive components are measured through power sensors, results are organized into time series and peak and valley events are marked, and data is stored in a structured manner.

[0025] In a preferred embodiment, the damping parameters are dynamically set based on transient power fluctuation data, and the phase difference between the device and the grid is continuously monitored, including:

[0026] After the control system receives the adjustment token, the transient power fluctuation data in it is input into the control module, and is written into the calculation buffer in chronological order;

[0027] The buffer data is classified, peak and valley events are extracted, and the damping coefficient is adjusted based on the fluctuation amplitude;

[0028] Environmental compensation logic is introduced to separate low-frequency mechanical components from the power sequence, calculate the net fluctuation amplitude and set the damping accordingly;

[0029] The phase difference is continuously monitored, and the damping and step size are adaptively adjusted according to the difference sign and amplitude, and a state token is generated.

[0030] In a preferred embodiment, the control response of the virtual synchronous machine is optimized, including:

[0031] The net fluctuation amplitude and the change in phase difference are integrated to optimize the virtual synchronous machine response, and within the limited damping adjustment range, the control parameters are constantly refreshed through iteration.

[0032] The main processor is responsible for data input and fluctuation analysis, and the auxiliary processor is responsible for phase measurement and filtering, both of which share key variables to share the computing load;

[0033] The execution cycle matches the grid frequency, and the key intermediate quantity is reported to the upper system every cycle;

[0034] The updated damping parameters and residual error in the setting output are packaged to generate a token.

[0035] In a preferred embodiment, during the dynamic setting of the damping parameters, a voltage feedback loop is introduced to calibrate the output voltage amplitude in real time, including:

[0036] Read the state token, write the damping coefficient in it to the voltage control unit, and configure the closed-loop feedback structure;

[0037] Calculate the deviation and issue the calibration instruction in each control cycle, inject the damping as a gain weight, and adjust the step size adaptively according to the deviation;

[0038] Collect the output voltage amplitude, send it to the sampling module after amplification and filtering, compare the deviation sign and size of the measured value and the standard value by the main controller, and adjust the reference voltage or modulation depth accordingly;

[0039] Continuously monitor the phase difference and check the threshold range, when the deviation is out of limit, fall back to phase tracking or reduce the step size, generate and transmit the grid-ready signal after convergence, and package the state quantity for transmission.

[0040] In a preferred embodiment, when the phase deviation and amplitude deviation are both within the preset alignment range, issue the grid connection instruction to complete the physical connection with the grid in a gradual power injection mode, including:

[0041] After receiving the ready token, latch the parameters in it and mark the current state as valid, then start the grid connection control sequence, and trigger the subsequent action when the preset alignment range is met;

[0042] Activate the grid connection switch, first drive the auxiliary contact to complete pre-charging and detect voltage and current, close the main contact when normal, and cancel the closing command and fall back to the calibration process when abnormal;

[0043] Start with low power, incrementally adjust the inverter reference value, dynamically correct the step size by measuring the deviation, and judge the oscillation by combining power fluctuation and attitude data while fine-tuning the damping;

[0044] Set the monitoring rollback condition during power injection, freeze the power increment when the deviation is out of limit, trigger power reduction or split, mark the state as abnormal, and fall back to the calibration step.

[0045] In a preferred embodiment, the damping parameter adjustment is maintained, including:

[0046] The operating parameters are recorded and uploaded to the upper system through the interface; when the injection power reaches the target and the indicators in the continuous period are stable, it is marked as a stable state, the increment is stopped, and only small adjustments are retained;

[0047] A grid-connected completion token is generated, and parameters such as damping coefficient, power and deviation statistics, and protection statistics are encapsulated and recorded, and transmitted through the internal bus.

[0048] In a preferred embodiment, after grid connection is completed, the overall system stability is continuously monitored, and the synchronization state is maintained through periodic parameter verification until the offshore floating power generation device enters the normal operation mode, including:

[0049] After receiving the grid-connected completion token, the parameters are latched and written into the register, and the grid-connected stable initial state is marked;

[0050] Start the monitoring sequence to collect voltage, frequency and power data at a unified timestamp, and align and filter noise from the collected results;

[0051] Deploy sensor nodes to arrange phase voltage, frequency and power measurement points downstream of the grid connection switch, and access a unified time synchronization source and an internal data bus;

[0052] Periodically verify the deviation, perform hierarchical early warning and adjustment damping, power reduction or rollback;

[0053] After cumulative statistics, mark normal and appropriately extend the period, while retaining collection, out-of-limit detection, and log record uploading and result feedback.

[0054] Compared with the prior art, the offshore floating power generation device island detection and self-synchronization grid connection method provided by the present application has the following beneficial effects:

[0055] 1.The method of island detection and self-synchronization grid-connection for offshore floating power generation device, which introduces voltage and frequency deviation multi-cycle review and adaptive threshold setting in island detection stage, combines historical stable working conditions and offshore measured data to improve the reliability of island detection, and uses virtual synchronous machine mode to take over device operation after confirming island, dynamically sets damping parameters based on transient power peak-valley characteristics and net fluctuation amplitude, and superimposes voltage amplitude closed-loop feedback and phase difference constraint, so that the synchronization process of the device under complex sea conditions can be adaptively adjusted according to disturbance intensity; in the grid-connection stage, gradual power injection and multi-condition rollback strategy are used, and after grid-connection, voltage, frequency and power balance state are continuously evaluated through multi-point measurement and periodic parameter verification, and necessary adjustment or rollback decision is fed back to the previous control link, finally a whole-process closed-loop vibration suppression control framework from island detection, self-synchronization grid-connection to stable operation is constructed in offshore floating environment, which effectively reduces the risk of transient oscillation and grid impact in re-griding and improves long-term operation stability and safety, thereby solving the problem that transient oscillation in the process of self-synchronization grid-connection after island detection in the traditional method is difficult to effectively suppress.

[0056] 2.The method of island detection and self-synchronization grid-connection for offshore floating power generation device, which expands the whole process from island detection to re-griding from single-link control to multi-stage collaborative control framework, no longer relies on fixed parameter virtual synchronous machine or simple voltage and frequency threshold, but takes island confirmation as the starting point, introduces synchronization token, adjustment token and completion token state carriers in turn, and makes transient power peak-valley characteristics, phase difference evolution, voltage amplitude deviation and platform attitude and other multi-source information run through key links such as damping setting, voltage calibration and power injection, so that the control decisions of each stage are based on the convergence results and operation records of the previous stage; at the same time, after grid-connection, voltage, frequency and power balance state are continuously evaluated through multi-point sensors and periodic parameter verification, and hierarchical adjustment or rollback is performed according to the deviation degree, instead of one-time large correction when disturbance occurs, so that the control law can still maintain smooth transition and gradual adjustment of parameters under the condition of significant offshore wind and platform sway, the re-griding stable time is shortened, the grid-connection impact and misoperation protection risk are reduced, and the controllability and engineering applicability of offshore floating power generation device under complex sea conditions are improved under the premise of ensuring device safety. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 The flow chart of island detection and self-synchronization grid-connection method for offshore floating power generation device. DETAILED DESCRIPTION

[0058] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those ordinarily skilled in the art without creative effort belong to the scope of the present application.

[0059] Embodiment 1 Figure 1 The island detection and self-synchronization grid-connection method of the offshore floating power generation device is given, including:

[0060] S1: Monitor the connection state of the offshore floating power generation device power grid, identify the island by collecting voltage and frequency signals, and confirm and start synchronization preparation when the deviation exceeds the threshold value;

[0061] S2: After confirming the island formation, switch the device to the virtual synchronous machine mode, adjust the reference phase to match the power grid, and collect transient power fluctuation data;

[0062] S3: Dynamically set the damping parameters based on the transient power fluctuation data, continuously monitor the phase difference between the device and the power grid, and optimize the control response of the virtual synchronous machine;

[0063] S4: During the dynamic setting of the damping parameters, introduce a voltage feedback loop to real-time calibrate the output voltage amplitude;

[0064] S5: When the phase deviation and amplitude deviation are both within the preset alignment range, issue a grid-connection instruction to complete the physical connection with the power grid in a gradual power injection manner, and keep the damping parameter adjustment;

[0065] S6: After the grid-connection is completed, continue to monitor the overall system stability, maintain the synchronization state through periodic parameter verification, and enter the normal operation mode of the offshore floating power generation device.

[0066] S1: Monitor the connection state of the offshore floating power generation device power grid, identify the island by collecting voltage and frequency signals, and confirm and start synchronization preparation when the deviation exceeds the threshold value, which is specifically implemented as:

[0067] First, a voltage sensor and a frequency sensor are arranged at the grid-connection interface of the power generation device installed on a semi-submersible or tension leg floating platform for real-time monitoring of electrical parameters on the grid side; the voltage sensor uses a Hall effect AC voltage sensor with electrical isolation function, connected to the three-phase AC output of the device, for collecting the phase voltage amplitude and phase sequence information of phases A, B and C; the frequency sensor uses a crystal oscillator frequency measurement unit, connected in parallel to the grid-side bus, to obtain the period of the grid voltage through zero-crossing detection, thereby calculating the current grid frequency; the housings of the two types of sensors meet the IP67 protection level and have salt mist, corrosion and vibration resistant structures to adapt to the high humidity, surge impact and platform sway of the offshore environment; the sensor output is sent to the analog-to-digital converter inside the device through an isolation and conditioning circuit, and the converter continuously collects voltage and frequency related signals at a sampling frequency of not less than 1 kHz;

[0068] To ensure real-time performance and load balancing, the control module refreshes and updates the sampling results based on a timing interrupt with a period of 10 ms, and performs digital low-pass filtering on multiple sampling points within each refresh period to suppress transient disturbances caused by high-frequency noise and mechanical vibrations; the control module reads the latest batch of valid sampling data from the temporary buffer, calculates the effective value and representative peak value of the three-phase voltage, and calculates the current grid frequency based on the voltage zero-crossing interval; the rated grid voltage and frequency parameters are stored in advance, with the rated voltage set to 220V or 380V three-phase system according to the type of connected grid, and the rated frequency set to 50Hz or 60Hz; based on this, the control module calculates the relative deviation of the measured voltage from the rated voltage and the absolute deviation of the measured frequency from the rated frequency, and uses the resulting voltage deviation and frequency deviation as indicators for subsequent island detection;

[0069] Default thresholds are set for the above deviations, with the voltage deviation threshold set to ±5% of the rated voltage and the frequency deviation threshold set to ±0.5Hz, and an automatic calibration mechanism is used to adapt to different device capacities and grid characteristics; during automatic calibration, the system selects a time window during which the device is in a normal grid-connected stable operation stage, statistically analyzes the voltage deviation and frequency deviation in this window, and calculates the mean and standard deviation of the deviations respectively; the candidate threshold interval is determined by adding or subtracting several times the standard deviation from the mean mentioned above; then, the pre-stored standard parameters are called, the candidate threshold interval is compared with the allowed deviation range specified in the relevant standards for grid connection and island detection such as IEC62116 and GB / T19964, and the candidate threshold is trimmed within the standard allowed range; based on this, the threshold is fine-tuned in combination with the measured data on the sea and the upper limit of the device capacity to avoid false positives caused by a too low threshold or missed detection caused by a too high threshold; the calibrated voltage deviation threshold and frequency deviation threshold are written to the non-volatile memory and used as effective determination thresholds in subsequent operation;

[0070] In the daily monitoring process, when any phase voltage deviation exceeds the voltage threshold value, or the frequency deviation exceeds the frequency threshold value, the control module first marks the current time as the starting point of the suspected islanding event, and continuously monitors the voltage and frequency of the same measurement point for at least three subsequent grid cycles; if the related deviation value always exceeds the corresponding threshold value within the continuous three cycles, it is determined that the abnormality is not a transient disturbance, but a state of losing support power on the grid side, and the system confirms the event as island formation accordingly; otherwise, if the voltage deviation and frequency deviation recover within the threshold range within the review period, it is considered that the event is caused by a short-time disturbance, the island confirmation is abandoned, and the device running state is restored to normal monitoring;

[0071] Upon confirmation of island formation, the control module reads multi-dimensional operating state parameters from the voltage and frequency acquisition channels and the internal measurement unit of the device, including three-phase voltage deviation values, current frequency deviation values, active power and reactive power output by the power generation device, time stamps, floating platform attitude angles, longitudinal and lateral accelerations, environmental wind speed, rotational speeds of key rotating components, and power module temperature, etc., and arranges the above data into a structured record and writes it into a non-volatile memory, where the record is used for subsequent fault tracing and optimized adjustment of threshold parameters, and also serves as a historical operating reference for self-synchronous grid-connected control;

[0072] After completing the state recording, the control module generates a synchronization token for the subsequent control flow, where the synchronization token contains deviation information at the island confirmation time, voltage phase reference in the recent stable operating phase, power setting reference, frequency adjustment suggestion, and corresponding time marker, and is transmitted to the synchronization controller through the internal bus of the device; the synchronization controller preloads the initial parameter set of the virtual synchronous machine mode after receiving the synchronization token, which is used for subsequent phase tracking, damping setting and grid-connected sequence planning, to achieve smooth transition from island operation to re-grid process; At the same time, the control module interrupts the current normal grid-connected output according to the event-driven logic, switches the power generation device to the synchronization preparation state, and sends a notification to the platform attitude control unit, so that the platform reduces the influence of large-scale swinging on the electrical synchronization process by adjusting the anchoring, ballast or control fins in the island state;

[0073] To improve the reliability of the monitoring link under offshore working conditions, two independent voltage acquisition channels and frequency acquisition channels can be configured at the key grid-connected position when the sensors are arranged, and consistency check is performed on the two-way data in the control module; when single-way data anomaly or loss is detected, automatically switch to the standby channel to ensure the continuous effectiveness of the island detection criterion;

[0074] The control module also compensates for periodic shifts of the platform according to the output of the attitude sensor when calculating the voltage deviation and the frequency deviation, separates the low-frequency swing component from the voltage signal and the frequency signal, makes the deviation determination mainly reflect the electrical side changes rather than mechanical movements, and monitors the data and the determination results are periodically uploaded to the upper computer or the centralized monitoring system through the embedded communication interface according to the standard protocol such as Modbus, so as to realize remote monitoring, historical data analysis and parameter maintenance.

[0075] S2: After confirming the island formation, the switching device is switched to the virtual synchronous machine mode, the reference phase is matched to the power grid, and the transient power fluctuation data are collected, which are specifically implemented as follows:

[0076] After confirming the island formation in the foregoing, the control system receives the synchronization token generated by the monitoring module, and according to the synchronization token, issues a mode switching instruction to the power electronic controller inside the device, so as to switch the offshore floating power generation device from the conventional power output mode to the virtual synchronous machine control mode; the power electronic controller adopts an embedded processor structure based on a DSP (Digital Signal Processor) or an FPGA (Field Programmable Gate Array), which is used to execute a high-frequency control algorithm; after receiving the switching instruction, the control unit first completes the switching of the running mode flag bit, loads a preset virtual synchronous machine parameter set, and initializes the internal state variables according to the phase reference and the power reference in the synchronization token, so that the initial state of the virtual synchronous machine is basically consistent with the stable running state before the island.

[0077] In the conventional power output mode, the device usually adopts a maximum power point tracking logic to control the output power; after the mode switching, the control unit disconnects the power reference loop in the conventional mode and enables the virtual synchronous machine control loop; the control loop is based on the equivalent rotor dynamics of the synchronous generator, and associates the output voltage phase and frequency of the device with the grid reference phase, and realizes frequency tracking and phase synchronization through a phase-locked loop; the control unit calculates the initial phase difference based on the synchronization token and the current measurement value, obtains the latest phase difference in each grid cycle, determines the adjustment direction and amplitude according to the sign and size of the phase difference, and adjusts the internal reference phase in a step-by-step incremental or decremental manner, for example, with a step size of about 0.1° per cycle; when the phase difference decreases after the adjustment in the last cycle, the current adjustment direction is maintained, and when the phase difference increases, the adjustment direction is automatically reversed, so that the phase difference gradually converges in multiple cycles.

[0078] During the phase adjustment process, the control unit continuously considers the influence of the offshore floating platform attitude change on the phase measurement; the attitude data from the attitude sensor and gyroscope are filtered and modeled in the control unit to estimate the phase drift component caused by platform pitch and roll, and to compensate in the phase lock loop, so that the adjustment of the internal reference phase is mainly aimed at the electrical side difference, rather than the measurement deviation caused by mechanical motion; when a large wind speed or attitude change amplitude exceeding the preset threshold is monitored, the control unit automatically reduces the single-cycle phase adjustment step size to reduce the risk of over-regulation and improve the convergence stability in complex sea conditions;

[0079] At the same time of mode switching and phase adjustment starting, the control unit performs acquisition and recording of transient power fluctuation data in parallel; the power sensor is arranged in the three-phase line at the output side of the inverter to measure the three-phase active and reactive power components output by the device, and the sampling rate is set to at least 10 kHz to capture the high-frequency power peak and valley changes occurring during the phase adjustment process; the acquired power data is processed by a front-end filter circuit to suppress high-frequency noise and obvious mechanical vibration interference; the filtered data is organized by the control unit into a time-stamped time series written to the buffer, and a transient power fluctuation segment is generated for each power grid cycle, and the corresponding phase difference and control state for the cycle are recorded at the same time;

[0080] For subsequent damping parameter optimization and dynamic adjustment, the control unit preliminarily classifies and labels the transient power fluctuation data in the buffer; power peaks exceeding a certain proportion of the rated power are marked as high-amplitude peak events, and power valleys below the set reference are marked as low-amplitude valley events, and the active and reactive components are distinguished at the time of marking; the proportion threshold and reference value are pre-calibrated according to the device capacity and allowed fluctuation range, for example, the high-amplitude peak determination threshold can be set to 1.1 times the rated power, and the valley reference can be set to 0.9 times the rated power, wherein the threshold can also be adjusted in combination with grid connection technical specifications and offshore measured operation data. Various events are stored in a structured form, using a floating-point array to save fluctuation amplitude, duration, and occurrence time information, and the internal reference phase, phase difference, and mode state at the time of triggering the event are recorded simultaneously;

[0081] During the operation in the virtual synchronous machine mode, the control unit continuously monitors the difference between the internal reference phase and the grid reference phase; when the output of the phase-locked loop indicates that the phase difference is reduced to a preset threshold and remains stable for a plurality of consecutive grid cycles, it is determined that the phase synchronization is completed; wherein the phase difference threshold can be determined according to the grid connection technical specification and simulation and test results, and a compromise value is usually selected in the range of 3° to 10°, and in the embodiment, the preset threshold is set to 5°, and it is required that the phase difference does not exceed the value in a plurality of consecutive cycles; when the above conditions are met, the control unit marks the current operating state as the phase synchronization completion state, generates an adjustment token for the next step of adjustment, packs the transient power fluctuation data in the buffer area in the recent period of time and the corresponding mark, and transmits them to the damping parameter adjustment module or the upper control module together with the phase synchronization completion flag, for the optimization and setting of the subsequent damping coefficient and power distribution strategy;

[0082] In order to ensure the safety and reliability of the mode switching and phase adjustment process, the control unit performs self-checking before executing mode switching, and the self-checking content includes checking the configuration integrity of the virtual synchronous machine control loop, the connectivity of the voltage, frequency and power sensor channels, whether the power supply voltage is in the allowed range and the internal communication link state. When the self-checking is passed, the mode switching is allowed to be executed and the virtual synchronous machine operation is entered; if the self-checking is not passed, the safe shutdown state is maintained or returned, and the fault flag is reported to the upper monitoring system, so as to avoid misentry into the synchronous control state in the case of abnormal key components; in S2, the island confirmation signal, the synchronization token, the mode switching instruction, the phase-locked loop output and the transient power fluctuation data are transmitted and buffered through the internal bus in the predetermined format, to provide continuous and traceable input data for the subsequent damping adjustment and grid recovery steps.

[0083] S3: dynamically setting the damping parameters based on the transient power fluctuation data, continuously monitoring the phase difference between the device and the grid, and optimizing the control response of the virtual synchronous machine, which is specifically implemented as:

[0084] After completing the virtual synchronous machine mode switching and generating the adjustment token, the control system receives the adjustment token through the internal data bus, and inputs the transient power fluctuation data carried in the adjustment token into the control module; the adjustment token includes the power time sequence in the recent period of time and the corresponding event mark and state information, and the control module writes the related data into the local calculation buffer area in time sequence after receiving, to ensure the continuity and integrity of the data used for subsequent analysis, so that the transient response just collected can be directly used as the input basis for damping setting in the transition stage after mode switching;

[0085] After obtaining the transient power fluctuation data, the control module first quantitatively analyzes the power fluctuation amplitude and adjusts the damping coefficient of the virtual synchronous machine accordingly; the control module classifies the peak events and valley events recorded in the buffer, classifies the power peaks exceeding a certain proportion of the rated power as high-amplitude peaks, and classifies the power valleys below the preset reference as low-amplitude valleys; the proportion threshold and the reference value are pre-calibrated in the parameter configuration stage, for example, the high-amplitude peak determination threshold can be set to 1.1 times the rated power, and the valley reference can be set to 0.9 times the rated power, and can be corrected in combination with the device capacity, grid connection technical specifications and offshore measured operation data; the control module counts the occurrence frequency and amplitude distribution of high-amplitude peaks and low-amplitude valleys within a preset analysis window, when the proportion of high-amplitude peaks is high or the amplitude is large, the damping coefficient is increased in the preset direction to enhance the damping ability of the oscillation; when the fluctuation is in the low-amplitude interval, the damping coefficient is appropriately reduced to maintain the response sensitivity of the virtual synchronous machine. The update of the damping coefficient is iterated in units of control periods, and the parameters are refreshed once according to the latest fluctuation statistics in each iteration period, so that the damping setting can continuously track the transient changes;

[0086] In order to distinguish between electrical disturbances and mechanical disturbances caused by the offshore environment, the control module introduces an environmental compensation logic when analyzing power fluctuations; the accelerometer and attitude sensor configured by the device output real-time platform acceleration and attitude change data, the control module establishes a compensation model based on these data, corrects the periodic components in the power time series, separates the low-frequency components related to platform pitch and roll height from the power fluctuations, and obtains the net fluctuation amplitude mainly caused by electrical transients; The increase and decrease of the damping coefficient is mainly determined by the net fluctuation after compensation, so as to avoid the mechanical swing caused by the sea wave from misleading the damping adjustment;

[0087] During the damping setting process, the control module continuously monitors the phase difference between the internal reference phase and the grid reference phase of the device at the same time, and the phase difference is used as an auxiliary index to participate in the damping parameter setting; among them, the phase measurement is completed through the voltage sampling and phase calculation module in the virtual synchronous machine control loop, to obtain the current internal reference phase in milliseconds, and compare it with the grid reference phase to form a sequence of phase difference changes over time; the control module dynamically adjusts the step size of the damping coefficient update according to the absolute value of the phase difference, when the phase difference is in a large interval, the damping update speed is appropriately increased, so that the system can suppress large amplitude oscillation faster; when the phase difference is close to the phase synchronization threshold set in the foregoing, the damping update step is reduced, so that the damping setting process is smoother, and a new oscillation is avoided due to excessive adjustment when approaching the synchronization state; Before participating in the damping setting, the phase difference data is filtered by digital filtering to remove the slow drift component corresponding to the low-frequency platform swing, so that the offset reflected by it is mainly caused by electrical disturbances;

[0088] On the basis of the comprehensive power fluctuation analysis result and the phase difference auxiliary information, the control module optimizes the control response of the virtual synchronous machine; the adjustment range of the damping coefficient is limited to a certain multiple interval of the standard damping value in the parameter configuration stage, for example, set to 0.5 times to 2.0 times, so as to ensure that the adjustment range of the damping coefficient is always within the safe range allowed by the device and grid connection specification when the fluctuation strength changes; the specific upper and lower limits can be iteratively set within the above interval through simulation calculation and offshore test, so that the voltage and frequency recovery time of the device under typical fault and disturbance working conditions meets the relevant grid connection requirements; in each damping update period, the control module comprehensively considers the occurrence frequency of high amplitude peaks, the valley depth, the net fluctuation amplitude and the current phase difference, and calculates the update direction and increment of the damping coefficient: for the case that the net fluctuation amplitude is large and the phase difference deviates obviously, a larger damping increment is selected to suppress the oscillation faster; for the case that the fluctuation is small and the phase difference is close to the synchronization threshold, a smaller damping increment is used for fine tuning, so that the output of the virtual synchronous machine gradually transitions to the stable state, thereby balancing the oscillation suppression capability and dynamic tracking performance in the offshore floating environment.

[0089] The entire dynamic damping setting process is continuously connected with the foregoing; the transient power fluctuation data and phase difference state at the time of completing the mode switching are recorded in the adjustment token output in the foregoing, which are used as the initial input of the damping setting in this step, so as to avoid the cold start delay caused by reacquiring data after switching; the updated damping coefficient, the net power fluctuation statistical result and the residual phase difference and other state quantities obtained in the damping setting process are encapsulated as a new state token, which is transmitted to the subsequent voltage amplitude calibration or grid recovery step through the internal bus, so that the subsequent link can complete the voltage amplitude calibration and grid operation on the basis of stable damping and phase;

[0090] At the control implementation level, the control module can be configured in a distributed structure, the main processor is responsible for data input, fluctuation analysis and damping calculation, the auxiliary processor is responsible for phase difference measurement and filtering processing, and the two share key variables through a high-speed internal bus to share the calculation load and improve the response speed; the execution period of the damping setting algorithm can be set to about 50 ms, which is matched with the control period of the virtual synchronous machine and the grid frequency, so as to guarantee the real-time performance while taking into account the calculation complexity; the damping setting result and key intermediate quantities can be reported to the upper computer or centralized monitoring system through the CAN bus (Controller Area Network) or other industrial field buses every period, for operation recording and parameter backtracking.

[0091] S4: In the process of dynamic setting of damping parameters, a voltage feedback loop is introduced to calibrate the output voltage amplitude in real time, which is specifically implemented as:

[0092] After the dynamic setting of the virtual synchronous machine damping parameter is completed and the state token is generated in the foregoing, the control system reads the updated damping coefficient and related operating state information from the state token, writes the damping coefficient into the voltage control unit of the main controller through an internal data bus, and configures a closed-loop feedback structure between the main controller and the voltage sensor, so that the deviation of the device output voltage amplitude from the standard voltage of the power grid can be measured and corrected in real time in the closed loop; wherein the main controller is the core node of the feedback loop, one side receives the parameter input from the damping setting module, and the other side receives the real-time feedback quantity of the voltage sensor, and completes the deviation calculation and the issuance of the calibration instruction in the same control period, so that the voltage calibration phase is directly entered after the damping setting is completed;

[0093] The specific operation of injecting the damping parameter into the feedback loop is as follows: at the end of the damping setting step, the parameter update is triggered by the setting completion flag output in the foregoing, the original fixed damping coefficient setting is interrupted, and the latest damping coefficient is written into the input buffer area of the voltage control unit; the writing process is completed in digital form through the internal signal bus on the control board, including the current value of the damping coefficient and the corresponding fluctuation characteristic index, to avoid delay and distortion caused by analog transmission; the main controller reads the damping coefficient from the input buffer area at the beginning of each control period, and uses the damping coefficient as the gain weight in the voltage calibration algorithm, so that the correction step of the voltage amplitude changes adaptively with the damping level; when the damping is small and the system needs to improve the response speed, the single-period voltage adjustment amplitude is appropriately increased; when the damping is large and the system is close to the stable state, the single-period adjustment amplitude is reduced, so as to keep the voltage calibration consistent with the damping characteristics;

[0094] After the feedback loop is established and the damping parameter injection is completed, the output voltage amplitude of the device is continuously collected and iteratively calibrated through the voltage sensor; wherein the voltage sensor is installed in the three-phase line downstream of the inverter, and is used to measure the effective value of the three-phase voltage; the sampling signal is input into the sampling module of the main controller after being amplified and anti-aliasing filtered in the front end; the control system pre-stores the standard line voltage or phase voltage reference value according to the grid access conditions, for example, the rated line voltage of a 380V three-phase system, and calculates the deviation between the measured voltage effective value and the standard value in each iteration period; according to the sign and size of the deviation, the main controller adjusts the reference voltage or the modulation depth in the voltage control unit, reduces the reference quantity when the feedback voltage is higher than the standard, increases the reference quantity when the feedback voltage is lower than the standard, and uses the current damping coefficient as a weight factor to determine the single-period adjustment amplitude; and through multi-period iteration, the deviation of the output voltage amplitude from the standard value is gradually converged; and the voltage sensor housing adopts a waterproof and corrosion-resistant structure, and the control system executes a self-checking program at a preset period to ensure the accuracy and reliability of the feedback measurement in the marine environment;

[0095] In the voltage amplitude calibration process, the control system continuously monitors the phase difference between the internal reference phase and the grid reference phase to ensure that the phase synchronization state established in the foregoing is still maintained when adjusting the voltage amplitude; wherein the phase difference is provided by the phase measurement module in the virtual synchronous machine control loop, and the main controller reads the current phase difference at each iteration period and checks whether it remains within the phase synchronization threshold range set in the foregoing, for example, no more than 5°; when it is detected that the phase difference is always within the threshold range and only small fluctuations occur, the voltage calibration can be normally executed according to the intended step size; when the phase difference deviates from the synchronization threshold range, the main controller triggers a rollback process to call the virtual synchronous machine phase tracking logic to re-converge, or temporarily reduces the voltage calibration step size, to avoid continuing to increase the voltage output in the case of phase desynchronization, thereby ensuring that the voltage calibration process does not destroy the existing phase synchronization relationship;

[0096] To realize automatic determination of grid-connected conditions, the control system sets up amplitude and phase double-threshold judgment logic in the voltage feedback loop; when the relative deviation absolute value of the output voltage amplitude and the standard voltage is less than the preset amplitude threshold value, and the absolute value of the phase difference is less than the preset phase threshold value for a plurality of consecutive iteration periods, a grid-connected readiness signal is generated; wherein the amplitude threshold value can be set to about 1% of the rated voltage according to the grid-connected technical specifications and simulation and test results, and the phase threshold value can be set to no more than 0.5°, and the above threshold values can be fine-tuned in engineering applications in combination with device capacity and offshore working conditions; the number of consecutive iteration periods can be set to an integer value in the range of 3 to 10 periods according to the signal noise level and grid disturbance characteristics, and is optimized and selected through simulation and offshore test; after meeting the double-threshold conditions and remaining stable for a set iteration period, the main controller packages the state quantities such as the current damping coefficient, the voltage reference quantity, the residual deviation and the phase difference into a readiness token, which is transmitted to the grid-connected control module through the internal bus, for guiding subsequent grid-connected switch actions and selection of power gradual injection strategies;

[0097] In terms of control implementation, the voltage feedback calibration algorithm is executed in a fixed cycle iteration, and the iteration period can be set to about 20 ms, which can be coordinated with the voltage waveform period of a 50 Hz grid, ensuring real-time while controlling the calculation load; a multi-stage amplification and filtering circuit is used to improve the signal-to-noise ratio of the voltage feedback signal, and the main controller and the sampling module exchange sampling data and calibration results through a high-speed internal bus; wherein the voltage calibration results and key intermediate quantities can be periodically uploaded to the upper computer or centralized monitoring system through RS-485, CAN bus (Controller Area Network) or other industrial field buses, for operation recording and parameter tracing.

[0098] S5: When the phase deviation and amplitude deviation are both within the preset alignment range, issue a grid-connection instruction to complete physical connection with the power grid in a gradual power injection manner, and maintain damping parameter adjustment, which is implemented as follows:

[0099] After outputting the grid-connection readiness signal, the control system receives a readiness token generated by the voltage feedback calibration module, which carries the current damping coefficient, the operation state information related to phase and voltage alignment, and the double-threshold judgment result. The control system first latches the above parameters in the internal state register, marks the readiness state as valid, and starts the grid-connection control sequence. The trigger condition of the grid-connection control sequence completely depends on the double-threshold judgment result of the previous step, and the phase difference and amplitude difference are no longer calculated separately, thereby ensuring that the grid-connection command is only triggered when the phase difference, amplitude deviation, and their stable duration all meet the preset requirements.

[0100] After the grid-connection control sequence is started, the control system first controls the grid-connection switch of the device to complete physical connection with the grid side. The grid-connection switch is arranged between the AC output end of the device and the grid interface, and can use a high-capacity contactor or circuit breaker structure with a closing coil and have wet and salt mist resistance. The main controller outputs a closing control signal to preferentially drive the pre-charge or auxiliary contact to close, and pre-charge and continuity detection are performed on the connection circuit through a current-limiting resistor or soft-start circuit. When the voltage difference and current impulse are both within the safe range, the main contact is then driven to close to achieve formal grid connection. During the closing process, the current sensor and voltage sensor collect the impulse current and voltage change at the moment of closing in real time. Once the current exceeds the preset overcurrent threshold or the voltage deviation exceeds the allowed range, the control system immediately cancels the closing command, quickly opens the switch, and returns the state to the S4 calibration stage for realignment. The overcurrent threshold, voltage deviation allowed range, and frequency deviation bandwidth can be set according to the rated parameters of the device and related grid-connection technical specifications, and adjusted based on simulation and type test results.

[0101] After the grid-connected switch is safely closed and no protection action is triggered, the control system starts a gradual power injection process, starting from low power and gradually increasing the output power to the grid side; the initial injection power can be set to 5% to 10% of the rated power, and the specific proportion is adjusted according to the signal device capacity, the grid short-circuit capacity and the field test results; the main controller controls the output power slope by adjusting the pulse width modulation signal or the active power reference value of the inverter, and increases the injection power by a preset step at each injection stage, for example, it can increase by 5% or 10% of the rated power within a time interval of 200ms to 500ms, until the target operating power is reached; wherein the power sensor is arranged at the AC output side, and real-time measurement of three-phase active power and reactive power is performed, and the control system dynamically adjusts the next incremental step according to the deviation between the measured power and the target injection curve: in the case of weak grid or large disturbance, the step size is appropriately reduced, and when the grid condition is stable, a larger step size can be used to shorten the grid-connected time, so as to balance the grid-connected stability and efficiency under the premise of meeting the grid-connected specification;

[0102] During the gradual power injection process, the control system keeps the damping parameter adjustment logic formed in the foregoing effective, so that the damping coefficient is fine-tuned around the aforementioned set value within a preset range to cope with possible transient disturbances in the offshore environment; wherein the main controller collects power fluctuation data and auxiliary information such as platform attitude and acceleration at each injection stage, and judges the oscillation degree in the injection process according to the change of the net power fluctuation amplitude; when the fluctuation amplitude is detected to increase, the damping coefficient is temporarily increased to enhance the damping capacity, and when the fluctuation is weakened and the system approaches stability, the damping coefficient is appropriately reduced to improve the dynamic response; the above adjustment is always within the upper and lower limits of the damping coefficient set in the foregoing, avoiding excessive damping changes affecting the output capacity; the phase measurement module continuously monitors the difference between the internal reference phase and the grid phase, and once the phase difference deviates from the synchronization threshold, the control system can slow down the power increment speed or temporarily stay at the current power level, and if necessary, call the virtual synchronous machine phase tracking logic for correction, so as to ensure that the synchronization state is always maintained during the power increasing process;

[0103] To ensure the safety and controllability of the grid-connection process, the control system sets multiple monitoring and fallback conditions during the power injection stage, including but not limited to: voltage deviation exceeding amplitude threshold, current or power surge exceeding protection threshold, phase difference exceeding synchronization threshold range, frequency deviation exceeding allowed bandwidth, etc.; once any of the indicators exceeds the pre-set limit for consecutive injection cycles, the control system freezes the power increment, and triggers a rapid power reduction or split action according to the degree of abnormality, reduces the output power to a lower level according to the predetermined slope, disconnects the grid connection switch if necessary, and marks the current state as an abnormal grid-connection event, and re-executes the calibration and condition judgment in S4; the pre-set limit value can be adjusted by referring to the grid access specification, device rated parameters, and simulation and offshore test results, so that the protection action can respond to abnormalities in a timely manner, and is not overly sensitive to normal short-term disturbances;

[0104] During the power injection stage, the current power level, damping coefficient, phase difference, voltage deviation, and protection state, etc. are recorded periodically by the main controller, and can be uploaded to the upper monitoring system through the field bus or Ethernet interface for real-time monitoring and post-analysis; when the gradual power injection reaches the predetermined target power and the monitoring indicators remain within the allowed range for consecutive injection cycles, the control system marks the current grid-connection state as a stable grid-connection state, stops increasing the power, and only makes small adjustments according to the system operation demand; the number of consecutive injection cycles can be set to an integer value within the range of 3 to 10 injection cycles in combination with the grid disturbance characteristics and control cycle, and can be optimized by simulation and offshore test; after meeting the above conditions, the control system generates a grid-connection completion token, packages and records the final damping coefficient, steady-state output power, voltage and phase deviation statistics, and protection action statistics, and transmits them to the subsequent stability monitoring and operation optimization module through the internal bus, providing initial reference for state evaluation and parameter adjustment in the long-term operation stage.

[0105] S6: After grid-connection, continue to monitor the overall system stability, maintain synchronization state through periodic parameter verification, until the offshore floating power generation device enters normal operation mode, the specific implementation is:

[0106] After completing the gradual power injection and marking the device as a stable grid-connection state, the control system receives the grid-connection completion token, reads and latches the steady-state damping coefficient, output power, and voltage and phase deviation, etc. from it, and writes the above parameters into the monitoring initialization register, marks the current working condition as the initial state of stable grid-connection, and starts the stability monitoring sequence at the same time; the stability monitoring sequence takes the steady-state parameters in the grid-connection completion token as the reference benchmark, avoiding premature entry into long-term monitoring when the power injection has not fully converged, so that the subsequent judgment is based on a relatively stable starting point;

[0107] After the start of the monitoring sequence, the control system collects key electrical quantities in the grid-connected operation stage in a multi-point manner based on the aforementioned sensor configuration; the sensor nodes include at least three phase voltage measurement points, one system frequency measurement point, and one power summary measurement point, wherein the phase voltage sensors are arranged in the three-phase line downstream of the grid-connected switch, the frequency sensor is connected to the grid-side bus, and the power sensor is arranged on the AC output bus to measure the summary values of three-phase active power and reactive power; each sensor adopts a waterproof and corrosion-resistant structure and is connected to a unified time synchronization source to form a multi-point collection and centralized processing monitoring structure through the internal data bus of the device; when a single sensor node is abnormal, other nodes can continue to provide key electrical quantities, thereby achieving a certain degree of redundancy and fault tolerance;

[0108] During the stability monitoring process, the control system collects voltage, frequency, and power data in real time at a fixed sampling period; the sampling period can be set to about 100 ms, which can balance the time resolution and processor computing load under the premise of meeting the dynamic response requirements of the power grid. The sampling period can be set after simulation and test verification in combination with the device control bandwidth and processor performance; voltage sampling includes three-phase voltage effective value and waveform distortion index, frequency sampling records the current system frequency and its short-term change rate, and power sampling records active power, reactive power, and power factor; the collected analog signals are digitized by the front-end conditioning circuit and high-precision analog-to-digital converter and written into the sampling buffer, the control system aligns the data of different sensors according to the unified time stamp, and combines the output of auxiliary sensors such as platform attitude and acceleration to filter out low-frequency noise components caused by platform shaking, so that the data entering the subsequent verification link mainly reflects the electrical side working conditions;

[0109] Based on real-time collection, the control system performs periodic verification of key parameters according to a preset verification period to determine whether the grid-connected operation remains within the allowed range; the verification period can be set to about 5 s, which can be shortened to about 3 s under conditions of strong wind and waves or frequent power grid disturbances. The specific value can be set according to the signal noise level, power grid disturbance characteristics, and simulation and offshore test results; at the beginning of each verification period, the control system extracts the statistical results of a recent period from the sampling buffer, compares the three-phase voltage effective value with the rated voltage (e.g., 220 V or 380 V), compares the frequency with the 50 Hz or 60 Hz standard value, compares the output power with the target steady-state power, and calculates power balance rate and power factor; the allowed range of voltage deviation can be set to ±2% of the rated value, the allowed range of frequency deviation can be set to ±0.1 Hz, and the power balance rate can be set to no less than 95%; the above threshold values can be set in reference to the grid-connected technical specifications and device rated parameters, and combined with simulation and offshore test data;

[0110] When the periodic verification results show that all parameters are within the allowed range, the control system maintains the current operating condition, only makes small adjustments to the output power and power factor according to load changes or scheduling instructions, and continuously records relevant operating data; when the deviation of a parameter exceeds the corresponding threshold in a single verification but the duration is short, the control system can first issue a warning mark and enter an observation state, and judge whether the deviation is caused by a transient disturbance by shortening the verification period and enhancing filtering; when it is found that one or more parameters exceed the threshold in consecutive multiple verification periods, the control system marks this state as a stability anomaly, and triggers the corresponding processing strategy according to the anomaly type, such as moderately adjusting the damping coefficient within the set range, reducing the output power, or re-executing the voltage amplitude calibration, and if necessary, falling back to the S4 or S5 step to realign or restore the gradual power injection; during the above processing process, the control system preferentially uses hierarchical adjustment and step-by-step rollback, and handles the anomaly in stages under the premise of not complete splitting;

[0111] To determine whether the device enters the normal operation mode, the control system accumulates and counts the periodic verification results during the monitoring process; when the voltage deviation, frequency deviation, power balance rate and other key indicators remain within the preset threshold range for consecutive verification periods, and no overcurrent, overvoltage, step loss and other protection events are triggered, the current operating state is marked as a normal operation mode; the number of consecutive verification periods can be set to an integer value within the range of 10 to 30 periods, and the specific value can be optimized and selected through simulation and field test according to signal fluctuation characteristics, verification period and offshore operation experience; after confirming the entry into the normal operation mode, the control system can appropriately lengthen the verification period to reduce the calculation load, while retaining the basic acquisition and out-of-limit detection functions, so as to still discover abnormalities and take measures in time when the environment or load changes suddenly;

[0112] During the entire stability monitoring process, the control system writes the key monitoring data and periodic verification results in chronological order into the operation log, including the statistical parameters of each verification period, whether the warning or rollback is triggered, the environmental parameter summary, and the normal operation confirmation time point, etc.; according to the communication conditions, these logs can be uploaded to the upper monitoring system or cloud platform through the field bus, Ethernet or satellite communication link, for remote operation and maintenance, fault tracing and control strategy optimization; at the same time, the monitoring module feeds back the stability evaluation results and recommended adjustment amount to the upstream control module through the internal bus, for subsequent scheduling strategy and maintenance plan calling; through the above data recording and feedback mechanism, the stability monitoring step can not only support real-time control, but also continuously provide data support for long-term operation analysis and maintenance decision.

[0113] The scheme of the embodiment first monitors the grid connection state of the device in real time, arranges voltage sensors and frequency sensors at the grid interface, continuously collects grid-side voltage and frequency signals, and compares them with standard values. When the deviation exceeds the preset threshold, such as voltage ± 5% or frequency ± 0.5 Hz and lasts for several cycles, island formation is confirmed, the deviation and environmental state data are recorded, and subsequent synchronization preparation is triggered. Subsequently, the device is switched to a virtual synchronous machine control mode, the internal control unit is activated, the operation is converted from conventional power output to simulated synchronous generator mode, the internal reference phase is gradually adjusted to track the grid phase, and transient power peak and valley fluctuation data are collected. Then, the fluctuation data is used to dynamically set the damping parameters, and the control response is optimized based on continuous monitoring of the phase difference, so that the device gradually approaches the grid synchronization condition. On this basis, a voltage feedback loop is introduced, the set damping parameters are used as input, combined with voltage amplitude feedback iterative calibration, the phase difference and amplitude difference are gradually reduced, and when the alignment meets the preset range, such as phase difference not greater than 0.5° and voltage deviation not greater than 1%, the grid connection instruction is issued, the grid connection switch is closed, the output is smoothly increased from low power through gradual power injection, and the damping fine-tuning is maintained to suppress wind and wave disturbance. Finally, in the grid-connected state, the voltage, frequency and power data are continuously collected by the multi-point sensor, the actual value is compared with the standard value according to the periodic parameter verification strategy, and the rollback or recalibration is triggered when the limit is exceeded. Until all indicators are stable within the allowed range for continuous multiple cycles, it is confirmed that the normal operation mode is entered, and a complete closed-loop process from island detection, self-synchronization and grid connection to stable operation is formed.

[0114] It should be noted that the application can be deployed in the device itself to realize embedded application, or run on PC terminal or other terminal with user interface, so as to meet various hardware environments and use requirements.

[0115] The above-described embodiments can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented by software, the above-described embodiments can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, the processes or functions described in the embodiments of the present application are wholly or partially generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium or transferred from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions can be transferred from one website, computer, server, or data center to another website, computer, server, or data center through wireless or wired transmission. The wired transmission includes optical fiber, twisted pair, coaxial cable, etc. The wireless transmission includes infrared, microwave, etc. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server, data center, etc. containing one or more available medium collections. The available medium can be a magnetic medium (for example, a floppy disk, a hard disk, a magnetic tape), an optical medium (for example, a DVD), or a semiconductor medium. The semiconductor medium can be a solid-state disk.

[0116] Those skilled in the art can clearly understand that, for the convenience and brevity of the description, the specific working processes of the above-described system, device and module can refer to the corresponding processes in the foregoing method embodiments, which will not be described here.

[0117] In the embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the modules is only a logical function division. In actual implementation, another division mode can be used. For example, a plurality of modules or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the shown or discussed modules can be indirect coupling or communication connection through some interfaces, devices or modules, which can be electrical, mechanical or other forms.

[0118] The modules described as separate components can or can not be physically separated, and the components shown as modules can or can not be physical modules, which can be located in one place or distributed on a plurality of network modules. Some or all of the modules can be selected according to actual needs to achieve the purpose of the embodiments.

[0119] In addition, each functional module in the embodiments of the present application can be integrated in one processing module, or each module can exist physically separately, or two or more modules can be integrated in one module.

[0120] If the functions are implemented in the form of software functional modules and sold or used as independent products, they can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application can be embodied in the form of a software product in essence or in the form of a part or the technical solutions of the present application that make contributions to the prior art. The computer software product is stored in a storage medium and includes a number of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the embodiments of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various media that can store program codes.

[0121] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0122] Finally: the above is only the preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for island detection and self-synchronization grid-connection of offshore floating power generation units, characterized in that, Comprise: S1: Monitor the grid connection state of the offshore floating power generation device, identify the island by collecting voltage and frequency signals, confirm and start synchronization preparation when the deviation exceeds the threshold, arrange voltage sensors and frequency sensors at the grid-connected interface to collect grid-side signals, monitor the grid connection state, the voltage sensor accesses the three-phase AC output end to collect phase voltage amplitude and phase sequence information, the frequency sensor is connected in parallel to the bus to obtain the voltage period through zero-crossing detection, and the current grid frequency is calculated accordingly, the sampling results are refreshed and cached, and the deviation threshold is set, the island formation is confirmed after multiple period reviews, after confirmation, record the multi-dimensional operating state parameters and generate a synchronization token, use the synchronization token to preload the virtual synchronous machine parameters, and switch the device to the synchronization preparation state; S2: After confirming the island formation, switch the device to the virtual synchronous machine mode, adjust the reference phase to match the grid, and collect transient power fluctuation data, switch the device to the virtual synchronous machine mode, receive the synchronization token and issue the mode switching instruction, activate the power electronic controller to load the parameter set and initialize the related state variables, disconnect the regular power output loop, enable the virtual synchronous machine control loop, and associate the phase and frequency of the output voltage through the phase-locked loop, gradually increase or decrease the internal reference phase, filter the attitude data during the adjustment process, and continuously monitor the phase difference, generate an adjustment token after the phase difference converges, and collect transient power fluctuations in parallel, measure the active and reactive components through the power sensor, organize the results into a time series and mark the peak and valley events, and structure the data for storage; S3: Dynamically set the damping parameters based on the transient power fluctuation data, continuously monitor the phase difference between the device and the grid, input the transient power fluctuation data in the adjustment token into the control module after the control system receives it, and write it into the calculation buffer in chronological order, classify the buffer data, extract the peak and valley events, and adjust the damping coefficient increment or decrement based on the fluctuation amplitude, introduce environmental compensation logic, separate the low-frequency mechanical component from the power sequence, calculate the net fluctuation amplitude and set the damping accordingly, continuously monitor the phase difference, and adaptively adjust the damping and step size according to the difference sign and amplitude, and generate a state token to optimize the control response of the virtual synchronous machine, optimize the virtual synchronous machine response based on the net fluctuation amplitude and phase difference change, continuously refresh the control parameters within the limited damping adjustment range, the main processor is responsible for data input and fluctuation analysis, the auxiliary processor is responsible for phase measurement and filtering, and the two share the calculation load through shared key variables, the execution period matches the grid frequency, and the key intermediate quantities are reported to the upper system at each period, the updated damping parameters and residual difference in the setting output are packaged to generate a state token; S4: During the dynamic setting of the damping parameters, introduce a voltage feedback loop to calibrate the output voltage amplitude in real time; S5: When the phase deviation and amplitude deviation fall within the preset alignment range, issue a grid connection instruction to complete the physical connection with the grid in a gradual power injection manner, and maintain the damping parameter adjustment; S6: After grid connection is completed, the overall system stability is continuously monitored, and the synchronous state is maintained through periodic parameter verification until the offshore floating power generation device enters a normal operation mode.

2. The island detection and self-synchronization grid-connection method for offshore floating power generation device according to claim 1, characterized in that, In the process of dynamic setting of damping parameters, a voltage feedback loop is introduced to calibrate the output voltage amplitude in real time, including: Read the state token, write the damping coefficient in it to the voltage control unit, and configure the closed-loop feedback structure; Calculate the deviation in each control period and issue a calibration instruction to inject damping as a gain weight, and adjust the step size adaptively according to the deviation; Collect the output voltage amplitude, send it to the sampling module after amplification and filtering, and compare the measured value with the standard value by the main controller, and adjust the reference voltage or modulation depth according to the deviation sign and size; Continuously monitor the phase difference and check the threshold range, and when the deviation is out of limit, fall back to phase tracking or reduce the step size, and generate a grid connection ready token after convergence, and encapsulate and transmit the state quantity.

3. The island detection and self-synchronization grid-connection method for offshore floating power generation device according to claim 2, characterized in that, When the phase deviation and amplitude deviation are both within the preset alignment range, issue a grid connection instruction to complete the physical connection with the power grid in a gradual power injection mode, including: After receiving the ready token, latch the parameters in it and mark the current state as valid, then start the grid connection control sequence, and trigger the subsequent action when the preset alignment range is met; Activate the grid connection switch, first drive the auxiliary contact to complete the pre-charge and detect the voltage and current, close the main contact in normal condition, and cancel the closing command and fall back to the calibration process in abnormal condition; Start with low power, incrementally adjust the inverter reference value, dynamically correct the step size by measuring the deviation, and judge the oscillation by combining power fluctuation and attitude data while fine-tuning the damping; Set the monitoring rollback condition during power injection, freeze the power increment when the deviation is out of limit, and trigger power reduction or splitting, mark the state as abnormal and fall back to the calibration step.

4. The island detection and self-synchronization grid-connection method for offshore floating power generation device according to claim 1, characterized in that, Maintain damping parameter adjustment, including: Record the operating parameters and upload them to the upper system through the interface; when the injected power reaches the target and the indicators are stable in consecutive periods, mark it as stable state, stop incrementing, and only keep small adjustments; Generate a grid connection completion token, encapsulate and record the damping coefficient, power and deviation statistics and protection statistics, and transmit them through the internal bus.

5. The island detection and self-synchronization grid-connection method for offshore floating power generation device according to claim 4, characterized in that, After grid connection is completed, the overall system stability is continuously monitored, and the synchronous state is maintained through periodic parameter verification until the offshore floating power generation device enters a normal operation mode, including: After receiving the grid connection completion token, write the parameters to the register and mark the initial state of stable grid connection; Start the monitoring sequence to collect voltage, frequency and power data at a unified timestamp, and align and filter the collected results; Deploy sensor nodes to measure the phase voltage, frequency and power downstream of the grid connection switch, and connect to a unified time synchronization source and internal data bus; Periodically verify the deviation, perform hierarchical early warning and adjust the damping, reduce the power or fall back; Mark it as normal after cumulative statistics, and appropriately extend the period, while retaining collection, out-of-limit detection and log record uploading and result feedback.

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