Self-synchronous voltage source regulation method, system and device during off-grid switching process

Abstract

The application provides a grid-connected and off-grid switching process self-synchronous voltage source regulation method, system and device, relates to the technical field of voltage source regulation, and comprises the following steps: acquiring voltage and current instantaneous sampling quantities of a point of common coupling; constructing an equivalent impedance identification model of a power grid and outputting a time-varying equivalent impedance parameter set; constructing a phase evolution reference trajectory of a self-synchronous voltage source; when a grid-connected and off-grid switching trigger condition is met, mapping to an inner model synchronous coordinate system of the voltage source to generate a continuous phase compensation quantity; coupling and correcting the output phase and amplitude of the voltage source; and after completing the grid-connected and off-grid state migration, online reshaping the phase evolution reference trajectory. The application solves the technical problem that the prior art depends on a static or quasi-static power grid model, cannot reflect the fast time-varying characteristics of the equivalent impedance of the power grid in real time, causes a deviation accumulation between a reference phase and an actual power grid phase at the grid-connected and off-grid switching moment, and further causes a long-term stability decline of the system.

Description

Technical Field

[0001] This invention relates to the field of voltage source regulation technology, specifically to a method, system, and equipment for self-synchronizing voltage source regulation during grid-to-off-grid switching. Background Technology

[0002] With the increasing penetration rate of renewable energy, distributed power sources based on self-synchronizing voltage source converters are being used more and more widely in microgrids and weak grids. Their core requirement is to achieve seamless switching between grid-connected operation and islanded operation, and to maintain the stable consistency of voltage source phase, frequency and power output.

[0003] Existing technologies generally use PLL-based phase tracking or fixed-parameter VSG models for control. This approach can maintain synchronization when the grid impedance changes are small or the system disturbance is weak. However, since it is essentially dependent on a static or quasi-static grid model, it cannot reflect the rapid time-varying characteristics of the grid's equivalent impedance in real time. This leads to the accumulation of deviations between the reference phase and the actual grid phase at the moment of grid connection and disconnection, resulting in a gradual deterioration of control performance and a decline in long-term stability. Summary of the Invention

[0004] This application provides a self-synchronizing voltage source regulation method, system, and equipment during grid connection and off-grid switching. It aims to solve the technical problem that existing technologies rely on static or quasi-static grid models, which cannot reflect the rapid time-varying characteristics of the grid's equivalent impedance in real time. This results in the accumulation of deviations between the reference phase and the actual grid phase at the moment of grid connection and off-grid switching, leading to a decline in the long-term stability of the system.

[0005] The first aspect disclosed in this application provides a method for regulating a self-synchronizing voltage source during grid-connected / off-grid switching. The method includes: acquiring instantaneous voltage and current samples at a common coupling point to form an equivalent electrical state observation vector at the grid end; constructing a grid equivalent impedance identification model based on the electrical state observation vector and outputting a time-varying equivalent impedance parameter set; constructing a phase evolution reference trajectory of the self-synchronizing voltage source under the constraints of the time-varying equivalent impedance parameter set, and determining a reference angular frequency generation mechanism using a virtual power balance equation; mapping the phase evolution reference trajectory to the voltage source's internal model synchronization coordinate system when the grid-connected / off-grid switching trigger condition is met, generating a continuous phase compensation quantity; coupling and correcting the voltage source output phase and amplitude based on the continuous phase compensation quantity, wherein the continuous phase compensation quantity is decomposed and applied to the phase adjustment channel and amplitude adjustment channel respectively, introducing a phase continuity constraint on the voltage source output phase and a power asymptotic constraint on the voltage source output amplitude; and after completing the grid-connected / off-grid state transition, online reshaping of the phase evolution reference trajectory according to changes in grid impedance disturbance.

[0006] The second aspect of this application discloses a self-synchronizing voltage source regulation system for grid-connected and off-grid switching processes. This system is used in the aforementioned self-synchronizing voltage source regulation method for grid-connected and off-grid switching processes, applied to the dynamic switching process of a self-synchronizing voltage source converter between grid-connected and islanded operation. The system includes: an observation vector acquisition module for acquiring instantaneous voltage and current samples at the common coupling point to form an equivalent electrical state observation vector at the grid end; a parameter set acquisition module for constructing a grid equivalent impedance identification model based on the electrical state observation vector and outputting a time-varying equivalent impedance parameter set; and a reference trajectory construction module for constructing a phase evolution reference trajectory of the self-synchronizing voltage source under the constraints of the time-varying equivalent impedance parameter set. A reference angular frequency generation mechanism is determined using a virtual power balance equation; a compensation quantity generation module is used to map the phase evolution reference trajectory to the voltage source internal mode synchronization coordinate system and generate a continuous phase compensation quantity when the grid connection / disconnection switching trigger condition is met; a coupling correction module is used to perform coupling correction on the voltage source output phase and amplitude based on the continuous phase compensation quantity, wherein the continuous phase compensation quantity is decomposed and applied to the phase adjustment channel and amplitude adjustment channel respectively, introducing a phase continuity constraint on the voltage source output phase and a power asymptotic constraint on the voltage source output amplitude; an online reshaping module is used to perform online reshaping on the phase evolution reference trajectory according to the grid impedance disturbance change after the grid connection / disconnection state transition is completed.

[0007] A third aspect of this application discloses an electronic device comprising: a processor; and a memory for storing executable instructions of the processor; wherein the processor is configured to execute the aforementioned self-synchronizing voltage source regulation method during on-grid / off-grid switching.

[0008] One or more technical solutions provided in this application have at least the following beneficial effects: By collecting instantaneous values ​​of voltage and current at the common coupling point and constructing an equivalent electrical state observation vector for the power grid, the control system can acquire multi-dimensional state information, including phase shift, frequency fluctuation, and transient disturbance energy, within a unified time domain. This enables a high-precision characterization of the dynamic operation characteristics of the power grid, providing a sufficient and continuous state input foundation for subsequent impedance identification models. Based on the electrical state observation vector, an equivalent impedance identification model for the power grid is established, and a time-varying impedance parameter set is output. This expands the power grid from a static equivalent model to a dynamic parameter expression including steady-state, transient, and disturbance components, thereby enabling online tracking and separation estimation of power grid structural changes and external disturbances. This provides dynamic constraint boundaries and model basis for phase trajectory construction. Under the constraints of time-varying impedance parameters, a phase evolution reference trajectory is constructed, and a reference angular frequency generation mechanism is determined by combining the virtual power balance equation. This allows the system to form a continuous and differentiable phase evolution path during dynamic power changes, thereby achieving a self-consistent mapping relationship between power and frequency and ensuring the reference trajectory is consistent across the power grid. It maintains smoothness and stability even under impedance disturbances. During grid connection / disconnection switching, the phase evolution reference trajectory is mapped to the voltage source internal mode synchronization coordinate system to generate continuous phase compensation, unifying the alignment of the grid-connected and islanded coordinate references. This avoids phase jumps and synchronization errors caused by sudden changes in the reference system during switching, improving the transient continuity and stability of the switching process. Based on the continuous phase compensation, the output phase and amplitude are coupled and corrected. The compensation is decomposed and applied to the phase and voltage regulation channels respectively, so that the phase continuity constraint and the power asymptotic constraint work together. This ensures that the output power converges slowly while achieving a smooth phase transition, reducing switching shocks and current oscillations. After completing the grid connection / disconnection state transition, the phase evolution reference trajectory is reshaped online according to the changes in grid impedance disturbances. Through rolling updates of the trajectory structure and dynamic reparameterization mechanism, the system can continuously adapt to changes in the grid environment, thereby improving its robustness, adaptability, and rapid recovery capability from sudden disturbances during long-term operation.

[0009] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0010] Figure 1 This is a schematic flowchart of the self-synchronization voltage source adjustment method during grid-connected / off-grid switching provided in the embodiments of this application.

[0011] Figure 2 This is a schematic diagram illustrating the changing trend of time-varying equivalent impedance parameters in the self-synchronizing voltage source regulation method during grid-to-off-grid switching provided in the embodiments of this application.

[0012] Figure 3This is a schematic diagram of the self-synchronizing voltage source regulation system during grid-to-off-grid switching provided in an embodiment of this application.

[0013] Figure 4 A schematic diagram of the structure of an exemplary electronic device provided in an embodiment of this application.

[0014] Figure reference numerals: Observation vector acquisition module 10, parameter set acquisition module 20, reference trajectory construction module 30, compensation quantity generation module 40, coupling correction module 50, online reshaping module 60, processor 21, memory 22, input device 23, output device 24. Detailed Implementation

[0015] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0016] Example 1, as Figure 1 As shown in the embodiment of this application, a self-synchronizing voltage source regulation method is provided during grid-connected / off-grid switching. The method includes: The instantaneous voltage and current samples at the common coupling point are obtained to form the equivalent electrical state observation vector of the power grid.

[0017] A synchronous sampling unit is set up at the common coupling point to perform high-frequency instantaneous sampling of three-phase voltage and current, and strict synchronization of voltage and current data is achieved through timestamp alignment. After anti-aliasing filtering and scale normalization, the fundamental component and high-frequency disturbance component are extracted from the sampled data. The fundamental component is used to characterize the steady-state operation characteristics of the power grid, and the high-frequency component is used to reflect transient disturbances and harmonic distortion. The processed voltage, current, and their dq coordinate transformation results are concatenated to form a multi-dimensional feature set containing phase offset, frequency drift, and disturbance energy indicators. This set is defined as the equivalent electrical state observation vector at the power grid end, used to describe the time-varying characteristics of the electrical state at the PCC.

[0018] Based on the electrical state observation vector, a power grid equivalent impedance identification model is constructed, and a time-varying equivalent impedance parameter set is output.

[0019] Based on the electrical state observation vector, a dynamic mapping relationship between voltage and current is established, representing the equivalent impedance of the power grid as a complex parameter structure that varies with time. This structure is further decomposed into three sub-components: steady-state impedance, transient impedance, and disturbance-related impedance. The steady-state component is updated using a recursive least squares method to characterize the slowly varying network characteristics; the transient and disturbance components are estimated using Kalman filtering to describe short-term dynamic changes. Consistency constraints are introduced among the sub-models to reduce estimation bias. Finally, a time-varying equivalent impedance parameter set with time continuity is formed through weighted fusion based on signal-to-noise ratio and disturbance intensity to characterize the equivalent dynamic characteristics of the power grid.

[0020] Under the constraints of the time-varying equivalent impedance parameter set, a phase evolution reference trajectory of the self-synchronizing voltage source is constructed, and the reference angular frequency generation mechanism is determined by the virtual power balance equation.

[0021] Under the constraint of time-varying equivalent impedance parameters, the equivalent impedance of the power grid is introduced into the power balance relationship of the virtual synchronous machine, so that the active power deviation corresponds to the dynamic process of the virtual rotor. The reference angular frequency is generated from the virtual rotor acceleration integral process, where the acceleration is jointly determined by the power deviation and the impedance compensation term. Since the impedance changes with time, a piecewise integration method is introduced to discretize the acceleration, and the integration step size is adjusted according to the impedance change rate to maintain dynamic consistency. The resulting angular velocity sequence is continuously spliced ​​and smoothed by the second derivative to form a reference trajectory with continuous phase evolution characteristics, which is used to describe the phase change benchmark of the voltage source during synchronous operation.

[0022] When the grid connection switching triggering conditions are met, the phase evolution reference trajectory is mapped to the voltage source internal mode synchronization coordinate system to generate continuous phase compensation.

[0023] Under grid-connected / off-grid switching triggering conditions, a transformation relationship between the grid-connected and islanded coordinate systems is constructed based on the magnitude of grid impedance changes. This relationship is represented by a dynamic coordinate transformation matrix, which describes the differences in the coordinate representation of the reference phase under different operating modes. After inputting the phase evolution reference trajectory into this transformation relationship, the phase mapping trajectory in the internal model synchronous coordinate system is obtained. The deviation between the mapped trajectory and the actual output phase is calculated, and this deviation is processed by low-pass filtering and consistency correction to form a compensation component. This compensation component is fused with the original trajectory to obtain a continuous phase compensation amount, which characterizes the smooth transition result of the phase deviation during the switching process.

[0024] The voltage source output phase and amplitude are coupled and corrected based on the continuous phase compensation amount. The continuous phase compensation amount is decomposed and applied to the phase adjustment channel and the amplitude adjustment channel respectively. A phase continuity constraint is introduced for the voltage source output phase, and a power asymptotic constraint is introduced for the voltage source output amplitude.

[0025] The continuous phase compensation is decomposed into phase and amplitude components. The phase component describes the angle change trend, while the amplitude component describes the voltage modulation degree change. In the phase channel, a differential constraint between adjacent sampling periods is introduced to limit the phase change rate and avoid abrupt changes. Simultaneously, a recursive correction term is formed based on the prediction error, ensuring a continuous evolution of the phase change. In the amplitude channel, a mapping model is established based on the modulation ratio and power relationship, and a change rate constraint is introduced to give the voltage amplitude adjustment a gradual characteristic. The two channels are finally coupled and solved under unified constraints, ensuring that the output phase and amplitude maintain a consistent relationship and smooth transition characteristics during the dynamic process.

[0026] After completing the on-grid and off-grid state transition, the phase evolution reference trajectory is reshaped online based on the changes in grid impedance disturbance.

[0027] After completing the state transition, a phase perturbation propagation model is constructed based on the time-varying equivalent impedance parameter set to describe the impact path of impedance changes on the phase trajectory. Based on this, a rolling prediction method is used to perform multi-step estimation of the future phase trajectory and compare it with the stability constraint interval. When the prediction results deviate from the trend, the trajectory is reconstructed in segments, and the local parameter expression is redefined while maintaining the continuity constraint between segments. The reconstruction process incorporates the energy function stability condition for screening, ensuring that the adjusted trajectory satisfies the convergence characteristic. Finally, a reshaped phase reference trajectory is output, enabling the system to maintain a consistent synchronous evolution structure under impedance perturbation changes.

[0028] Furthermore, the instantaneous voltage and current samples at the common coupling point are obtained to form the equivalent electrical state observation vector at the grid end, including: Within a preset sampling period, the voltage and current of the common coupling point are sampled synchronously at multiple rates to construct a high-frequency sampling sequence and a low-frequency fundamental wave sampling sequence corresponding to the dynamic change rate of the power grid. Based on the high-frequency sampling sequence, a sliding window Fourier time-varying decomposition is performed, and phase alignment correction is performed in combination with the low-frequency fundamental wave sampling sequence to extract a unified time-frequency expression of the fundamental wave component, harmonic components, and transient disturbance components. The fundamental wave component, harmonic components, and transient disturbance components are fused and mapped with the voltage and current components in the dq rotating coordinate system through multiple channels to construct an electrical state observation vector containing phase drift characteristics, frequency offset characteristics, and disturbance energy characteristics.

[0029] A synchronous sampling mechanism is set up at the common coupling point, and three-phase voltage and current are periodically acquired according to a unified time base. The sampling process adopts a dual-rate organization method, where the high-frequency sampling sequence is used to capture rapid disturbance changes in the power grid, and the low-frequency fundamental wave sampling sequence is used to characterize periodic steady-state characteristics. The two types of sequences are synchronized and aligned on the time axis through a unified trigger signal, thereby avoiding phase misalignment problems caused by sampling drift. The high-frequency sequence corresponds to a shorter sampling interval and is used to record transient fluctuations; the low-frequency sequence corresponds to the fundamental wave periodic scale and is used to describe the steady-state operating boundary. Finally, a discrete data set of voltage and current with a time-hierarchical structure is formed, providing the basic input for subsequent time-frequency analysis. This process emphasizes the coordinated expression of power grid electrical quantities at multiple time scales.

[0030] A sliding time window structure is introduced based on the high-frequency sampling sequence. Time-varying spectral decomposition of the signal is achieved through Fourier transform within the window, mapping the voltage and current signals into fundamental, harmonic, and disturbance frequency components within a local time period. To avoid phase jumps caused by window switching, a low-frequency fundamental sampling sequence is introduced as a reference, and the phase center of each sliding window is corrected to ensure continuity and consistency of the results across windows on the time axis. The fundamental component characterizes the main energy transfer path, the harmonic components reflect the periodic distortion structure, and the transient disturbance components describe the non-steady-state impact characteristics. These three types of components are reconstructed under a unified time coordinate, forming a time-frequency expression system containing three-dimensional information of amplitude, phase, and frequency, used to describe the dynamic structural evolution of the power grid signal.

[0031] The fundamental, harmonic, and transient disturbance components obtained from time-frequency decomposition are introduced into the dq transformation framework of the synchronous rotating coordinate system, transforming the electrical quantities in the three-phase stationary coordinates into DC and AC component expressions in the rotating reference frame. In this process, the fundamental component is mainly mapped to the dq-axis DC component, used to characterize the equivalent steady-state operating state; the harmonic and disturbance components are mapped to dynamic fluctuation terms on the dq-axis, used to characterize the changes in structure deviating from the steady state. Through multi-channel feature fusion, physical quantities such as phase shift, frequency shift, and disturbance energy are uniformly encoded into a feature vector structure, where phase drift describes synchronization deviation, frequency shift reflects the degree of system operational deviation, and disturbance energy quantifies the intensity of transient effects. Finally, an electrical state observation vector is formed, providing a foundation for subsequent equivalent modeling and dynamic parameter identification.

[0032] Furthermore, a power grid equivalent impedance identification model is constructed based on the electrical state observation vector, and a time-varying equivalent impedance parameter set is output, including: A multi-scale impedance identification structure is constructed based on the electrical state observation vector, decomposing the equivalent impedance of the power grid into a parallel estimation model of steady-state impedance components, transient impedance components, and disturbance impedance components. A recursive least squares estimation and Kalman filtering fusion update mechanism is adopted to perform collaborative parameter identification on the steady-state impedance components, transient impedance components, and disturbance impedance components, and a cross-model consistency constraint term is introduced to suppress drift errors between sub-models. A model credibility evaluation function is constructed based on the voltage-current signal-to-noise ratio and transient disturbance intensity, and the estimation results of each impedance component are adaptively weighted and fused to generate a time-varying equivalent impedance parameter set with time continuity. The time-varying equivalent impedance parameter set satisfies the requirement of piecewise continuous representation of the dynamic change process of the power grid.

[0033] Based on electrical state observation vectors, the equivalent impedance of the power grid is decomposed and modeled, abstracted into three parallel substructures: steady-state impedance, transient impedance, and disturbance impedance. The steady-state impedance describes the equivalent voltage-current ratio of the power grid under slowly varying conditions; the transient impedance characterizes the short-time dynamic response of the system after a disturbance; and the disturbance impedance characterizes the impact of random shocks or aperiodic disturbances on the equivalent network parameters. These three substructures operate in parallel under the same observation input, but each corresponds to different time scales and rates of change, thus forming a multi-scale impedance identification framework to express the hierarchical dynamic structure of the power grid's equivalent parameters.

[0034] In the estimation process of each impedance sub-model, a recursive least squares method is introduced for the gradual updating of steady-state parameters to reflect slow changing trends. Simultaneously, Kalman filtering is used for recursive state estimation of transient and disturbance components to handle noisy dynamic processes. The two estimation mechanisms operate in parallel within the same time step and exchange information through a covariance propagation mechanism. To avoid parameter drift between different sub-models during evolution, a cross-model consistency constraint term is introduced to maintain the correlation between impedance components within physical constraints, thereby limiting the accumulation of estimation deviations. Essentially, this process establishes a constraint coupling structure between models at different time scales to improve the consistency and stability of parameter identification.

[0035] After obtaining the estimation results for each impedance component, an evaluation mechanism based on the voltage-current signal-to-noise ratio and transient disturbance intensity is introduced to quantify the reliability of each sub-model result. The signal-to-noise ratio reflects the reliability of the observed data, while the disturbance intensity characterizes the degree of system non-steadiness; together, they constitute the model reliability function. Based on this function, steady-state, transient, and disturbance impedance results are dynamically weighted, ensuring that high-reliability components dominate while low-reliability components automatically decay. The fused results form a unified equivalent impedance parameter expression, and a continuous update mechanism is adopted on the time axis to ensure smooth evolution of parameter changes, thereby constructing a time-varying impedance sequence with time consistency.

[0036] The resulting time-varying equivalent impedance parameter set exhibits a piecewise continuous structure in the time dimension. Specifically, the parameters change slowly during stable grid operation phases, while rapid adjustments are allowed during disturbances or switching phases. However, fusion constraints ensure that there are no abrupt jumps between segments. This characteristic is achieved through a recursive update mechanism and a weighted fusion structure, enabling the impedance parameters to reflect the differences in different grid operation phases while maintaining overall time continuity, thus meeting the requirement for a piecewise consistent description of the grid's dynamic changes.

[0037] In a specific implementation scenario, taking a 10kV distribution system switching between on-grid and off-grid operation as the object, voltage and current signals are collected at the common coupling point, with the sampling frequency set to 10kHz (high frequency) and 50Hz synchronous fundamental frequency sampling. An impedance estimation window length of 20ms is selected, forming the observation vector X(k)=[Δθ,Δf,E]. noise The equivalent impedance of the power grid is expressed in complex impedance form: Z eq (t)=R s (t)+jωL s (t)+Z p (t), where R is a t), s (t) represents the steady-state resistance component, L s (t) is the equivalent inductance, Z p (t) represents the disturbance term. In a certain switching experiment, the steady-state impedance was set to: R s =0.35Ω, L s =2.1mH; peak transient disturbance: Zp_max=0.18Ω; signal-to-noise ratio range: 18~32dB. The impedance parameters as a function of time were obtained after RLS+Kalman fusion, as shown in Table 1.

[0038] Table 1: Example Data Table

[0039] like Figure 2 As shown, the time-varying equivalent impedance parameter variation trend is given, where R... s L s Stable fluctuations, Z p The peak value appears at the moment of switching and then decays. The confidence level α is inversely correlated with the perturbation intensity.

[0040] This embodiment decomposes impedance into three parts: steady-state, transient, and disturbance, enabling continuous parameterization of the power grid at different dynamic stages. The steady-state component reflects the basic network structure, the transient component characterizes energy redistribution during switching, and the disturbance component represents the impact of nonlinear shocks. By introducing a fusion mechanism of RLS and Kalman filtering, parameter updates possess both recursiveness and state estimation capabilities, avoiding the drift problem associated with single methods. The reliability function uses signal-to-noise ratio and disturbance intensity as weights, ensuring that highly reliable observation data dominates the fusion process, thereby guaranteeing the continuity and interpretability of the time-varying impedance parameter set during switching. This parameter set serves as the input basis for subsequent phase trajectory construction and MPC optimization, ensuring physical consistency and engineering feasibility throughout the control link.

[0041] Furthermore, under the constraints of the time-varying equivalent impedance parameter set, a phase evolution reference trajectory of the self-synchronizing voltage source is constructed, and a reference angular frequency generation mechanism is determined using a virtual power balance equation, including: Based on the time-varying equivalent impedance parameter set, the voltage coupling and power damping terms in the power balance equation of the virtual synchronous machine are modified to construct a second-order nonlinear dynamic model under impedance constraints. A virtual rotor acceleration is generated based on the active power deviation, and a grid dynamic impedance compensation term is introduced according to the time-varying equivalent impedance parameter set to correct the virtual rotor acceleration online. The corrected virtual rotor acceleration is integrated piecewise, and the integration step size is adaptively adjusted based on the impedance change rate to obtain a piecewise continuous reference angular velocity constrained by impedance. The piecewise continuous reference angular velocities are then stitched together for trajectory consistency, and a second-order derivative continuity constraint is introduced for smoothing optimization to generate a phase evolution reference trajectory consistent with the time-varying equivalent impedance parameter set.

[0042] Based on a time-varying equivalent impedance parameter set, the voltage coupling and damping terms in the power balance relationship of the virtual synchronous machine are reconstructed, allowing the grid equivalent impedance to be expressed as dynamic parameters in the energy exchange representation. The voltage coupling term describes the influence path of voltage differences on power exchange, while the damping term characterizes the power oscillation attenuation mechanism. By introducing time-varying impedance characteristics, the original fixed-parameter model is transformed into a second-order nonlinear dynamic structure that changes with the network state. The state variables simultaneously include the coupled evolution relationship between angular velocity and power deviation, thus forming a dynamic synchronization model constrained by grid impedance.

[0043] Using active power deviation as the driving force, a virtual rotor acceleration expression is constructed, mapping power imbalance to equivalent mechanical acceleration changes. Based on this, a time-varying equivalent impedance parameter is introduced to compensate for and correct the grid-side dynamic response, thus correcting the impact of voltage dips and impedance changes on acceleration estimation. This compensation term essentially reflects the influence of changes in the grid's equivalent "stiffness" on the virtual rotor motion, ensuring that acceleration is not only determined by power deviation but also dynamically modulated by grid impedance, thereby forming a corrected acceleration expression that more closely reflects the actual grid interaction characteristics.

[0044] The corrected virtual rotor acceleration is integrated over time. Due to the time-varying characteristics of the grid impedance, the integration process is divided into multiple time segments, with local continuous integration used to generate the angular velocity increment within each segment. To adapt to the impedance change rate, an adaptive integration step size mechanism is introduced: the integration step size is reduced when the impedance changes rapidly to improve analytical accuracy, and increased when the change is gradual to reduce computational oscillations. Through the combination of segmented integration and step size adjustment, a reference angular velocity sequence that remains continuous under different grid conditions is obtained, thus achieving a dynamic frequency evolution expression constrained by impedance.

[0045] The segmented reference angular velocity sequences are spliced ​​along the time axis to ensure a continuous transition between segments and eliminate abrupt velocity changes between segments. Based on this, a second-order derivative continuity constraint is introduced to smooth the rate of change of angular velocity, keeping acceleration changes finite and continuous, thus avoiding high-frequency jitter in the phase trajectory. This optimization process is equivalent to adjusting the curvature constraint of the angular velocity trajectory to maintain smooth evolution characteristics in the time dimension. The final generated phase evolution reference trajectory maintains consistency with the time-varying equivalent impedance parameter set and is used to describe the synchronous phase reference under dynamic grid conditions.

[0046] Furthermore, when the grid connection / off-grid switching trigger condition is met, the phase evolution reference trajectory is mapped to the voltage source internal mode synchronization coordinate system to generate continuous phase compensation, including: An adaptive mapping relationship between the grid-connected coordinate system and the islanded coordinate system is constructed based on the time-varying equivalent impedance parameter set, forming a dynamic coordinate transformation matrix. At the moment of grid-connected / off-grid switching triggering, the dynamic coordinate transformation matrix is ​​switched online according to the abrupt change amplitude of the time-varying equivalent impedance parameter set, and the phase evolution reference trajectory is input for coordinate mapping to obtain the phase mapping trajectory in the internal model synchronous coordinate system. A compensation term is constructed based on the prediction error between the phase mapping trajectory and the actual output phase, and the compensation term is fused with the phase evolution reference trajectory to generate a continuous phase compensation amount.

[0047] Based on a time-varying equivalent impedance parameter set, a parametric model is used to model the mathematical mapping relationship between the grid-connected coordinate system and the islanded coordinate system, unifying the voltage, current, and phase expressions under both operating modes into a single transformation framework. This mapping relationship uses impedance parameters as modulation variables, enabling the coordinate transformation matrix to dynamically adjust with changes in the grid's equivalent impedance, thus forming a coordinate transformation structure that evolves with the operating state. The grid-connected coordinate system characterizes the synchronization reference under external grid constraints, while the islanded coordinate system describes the internal synchronization reference during independent operation. The two are correlated through an impedance-driven transformation matrix.

[0048] At the moment of grid-connected / off-grid switching, the dynamic coordinate transformation matrix is ​​selected and switched based on the abrupt change in the amplitude of the time-varying equivalent impedance parameter. A continuous transformation matrix is ​​used when the impedance change is small, while a modified transformation matrix is ​​used to enhance stability when the change is large. Subsequently, the phase evolution reference trajectory is input into the selected transformation structure, and phase re-expression is completed in a unified coordinate system, thus obtaining the phase mapping trajectory in the internal mode synchronous coordinate system. The core of this process lies in maintaining structural consistency in the phase description under different operating modes through impedance-driven matrix switching, avoiding phase discontinuities caused by abrupt coordinate changes.

[0049] A prediction error model is constructed based on the deviation between the phase-mapped trajectory and the actual output phase. This error reflects the degree of deviation between the mapped trajectory and the actual synchronization state. After filtering and trend extraction of the error term, a compensation component is formed. This compensation component is then superimposed and fused with the original phase evolution reference trajectory, enabling smooth correction of the trajectory along the time axis. The fusion process constrains the error change rate to avoid abrupt compensation changes, thereby generating a continuous phase compensation amount. This compensation amount essentially establishes a continuous transition relationship between coordinate transformation and the actual operating state, ensuring consistency and smoothness in phase evolution during the switching process.

[0050] Furthermore, the coupling correction of the voltage source output phase and amplitude based on the continuous phase compensation amount includes: The continuous phase compensation is decomposed into a phase correction component and an amplitude correction component, which are applied to the phase adjustment channel and the amplitude adjustment channel, respectively. In the phase adjustment channel, a phase increment differential constraint model is constructed based on adjacent sampling periods, and the phase change rate is adaptively limited by combining the time-varying equivalent impedance parameter set. At the same time, a recursive correction term is constructed based on the phase prediction error to dynamically maintain the phase continuity constraint. In the amplitude adjustment channel, an amplitude constraint model is constructed based on the dynamic mapping relationship between the voltage modulation ratio and active and reactive power, and the modulation ratio change rate is adaptively constrained by combining the time-varying equivalent impedance parameter set to form a power asymptotic adjustment boundary. The control quantity is solved based on the joint constraint relationship between the phase continuity constraint and the power asymptotic adjustment boundary to perform synchronous coupling correction control on the voltage source output phase and amplitude.

[0051] The continuous phase compensation quantity is structurally decomposed into phase correction components and amplitude correction components. The phase component describes the correction requirements for angle variation deviations, while the amplitude component reflects the adjustment requirements for voltage modulation levels. These two types of components are respectively fed into the phase adjustment channel and the amplitude adjustment channel, achieving decoupling. Based on this channel division, the phase channel handles the synchronization angle evolution problem, and the amplitude channel handles the energy output scale problem, thus forming independent adjustment paths for different physical quantities and avoiding mutual interference.

[0052] In the phase adjustment channel, a phase increment differential relationship is constructed based on adjacent sampling periods to describe the continuity constraint of phase change per unit time, ensuring that phase evolution follows a gradually smoothing change law. Based on this, a time-varying equivalent impedance parameter is introduced to adaptively limit the phase change rate, allowing the phase adjustment amplitude to adjust with changes in the dynamic characteristics of the power grid, avoiding abrupt changes. Simultaneously, a recursive correction term is constructed in conjunction with the phase prediction error, and phase deviation is gradually corrected through error feedback, maintaining the continuity and consistency of the phase trajectory, thereby achieving phase stability evolution constraint under dynamic conditions.

[0053] In the amplitude regulation channel, the voltage modulation ratio is used as the core variable. Combined with the dynamic mapping relationship between active and reactive power, a corresponding model between amplitude changes and power output is established to characterize the influence path of voltage amplitude on power distribution. Based on this, a time-varying equivalent impedance parameter is introduced to constrain the rate of change of the modulation ratio, making the amplitude adjustment process limited by the dynamic characteristics of the power grid, thereby avoiding abrupt amplitude changes. This mechanism further forms an asymptotic boundary for amplitude changes, enabling the voltage output to exhibit smooth transition characteristics during power changes.

[0054] Under the combined influence of phase continuity constraints and amplitude asymptotic boundaries, a joint constraint relationship is constructed, and a unified control quantity is solved based on this constraint system, enabling phase and amplitude adjustments to be coordinated within the same optimization framework. Essentially, this solution process involves uniformly allocating control variables while satisfying phase continuity and power asymptoticity, maintaining a coupled and coordinated relationship between the two types of regulation channels. The final output control quantity acts simultaneously on both phase and amplitude, achieving synchronous correction of the voltage source output state, ensuring the system maintains consistent overall operating characteristics under dynamic switching and disturbance conditions.

[0055] Furthermore, the phase evolution reference trajectory is reshaped online based on changes in grid impedance disturbances, including: A phase trajectory perturbation propagation model is constructed based on the time-varying equivalent impedance parameter set. A model prediction control rolling optimization structure is constructed based on the phase trajectory perturbation propagation model and the phase evolution reference trajectory to perform multi-step prediction and constraint evaluation of the future time-domain phase trajectory. When the predicted trajectory exceeds the stable operation constraint domain, a trajectory segmentation reconstruction mechanism is triggered to locally reparameterize the phase evolution reference trajectory and introduce continuity splicing constraints. The trajectory reconstruction process satisfies the stability constraint condition based on the energy function.

[0056] Based on a time-varying equivalent impedance parameter set, the equivalent dynamic characteristics of the power grid are parameterized, introducing impedance changes as a disturbance source into the phase evolution process. This allows for the construction of a phase trajectory disturbance propagation model, which describes the propagation path and impact intensity of impedance changes on phase trajectory offset over time. Furthermore, the disturbance propagation model and the phase evolution reference trajectory are integrated into a model predictive control (MPC) framework, forming a rolling optimization structure. By predicting the phase trajectory for multiple future time steps and evaluating the consistency of the prediction results in conjunction with constraints, a forward-looking adjustment mechanism for the phase trajectory in the time domain is achieved.

[0057] When the MPC prediction result exceeds the stable operation constraint domain, a trajectory segmentation reconstruction mechanism is triggered. This mechanism performs local interval reparameterization on the original phase evolution reference trajectory, enabling the trajectory to re-establish parameter description relationships within a local time period. This process adjusts the time scale and parameter distribution to allow the trajectory to readjust to the current grid impedance state within abnormal intervals. Simultaneously, continuity splicing constraints are introduced at the segment boundaries to match phase values ​​and their rates of change, preventing phase abrupt changes caused by segmentation reconstruction and ensuring the overall structural continuity and consistency of the trajectory.

[0058] In the trajectory segmentation reconstruction process, a stability constraint based on an energy function is introduced to impose energy consistency constraints on the reconstructed phase trajectory, ensuring that the trajectory evolution process meets the requirements of system energy monotonicity or boundedness. This energy function is used to characterize the stability of the system state during the phase trajectory change process. By limiting the energy increment after trajectory reconstruction, unstable divergent behavior is avoided, thereby ensuring that the trajectory maintains its overall dynamic stability characteristics during the adjustment process.

[0059] Furthermore, it also includes: A dynamic convergence function based on phase error and power deviation is constructed, and a Lyapunov candidate function is constructed based on the dynamic convergence function. The Lyapunov candidate function is evaluated in real time. When its derivative does not meet the negative definite convergence condition, an adaptive adjustment mechanism for the damping enhancement factor is triggered, and the damping coefficient is updated online in combination with the time-varying equivalent impedance parameter set. At the same time, the voltage output vector trajectory is constrained by projection correction so that it simultaneously satisfies the phase continuity constraint and the power asymptotic constraint, and outputs a synchronous control command that satisfies the grid-connected / off-grid switching stability domain constraint condition.

[0060] A dynamic convergence function is constructed based on phase error and power deviation to characterize the system's convergence trend from a deviation state to a stable state. This function comprehensively reflects the coupling degree between phase synchronization error and power balance deviation. Based on this, a Lyapunov candidate function is constructed, using the convergence function as a mapping expression in energy form to evaluate the system's stability evolution trend. This allows for a formal description of system state changes within the Lyapunov framework, providing a theoretical basis for subsequent stability assessments.

[0061] Real-time derivative calculation and evaluation of Lyapunov candidate functions are performed to determine the energy change trend of the system. When the derivative does not meet the negative definite convergence condition, it indicates that the system has a potential instability trend. At this time, a damping enhancement mechanism is triggered to adaptively adjust the damping factor. This adjustment process, combined with the time-varying equivalent impedance parameter, allows the damping coefficient to be updated with the dynamic characteristics of the power grid, thereby enhancing the system's ability to suppress disturbances and bringing the overall state back to the stable convergence range.

[0062] At the control output layer, the voltage output vector trajectory undergoes constraint projection processing to simultaneously satisfy both phase continuity and power asymptotic constraints. This projection process maps control quantities that do not meet the constraints back into the feasible region, thereby ensuring the physical realizability of the output signal. After constraint correction, synchronous control commands are generated, enabling the system to operate under stable region constraints during grid-connected / off-grid switching, achieving coordinated phase and power control output.

[0063] Example 2, based on the same inventive concept as the self-synchronization voltage source regulation method during grid-to-off-grid switching in the aforementioned examples, such as... Figure 3 As shown in the embodiment of this application, a self-synchronizing voltage source regulation system is provided during grid-connected / off-grid switching. The system includes: The observation vector acquisition module 10 is used to acquire instantaneous voltage and current samples at the common coupling point to form an equivalent electrical state observation vector at the grid end; the parameter set acquisition module 20 is used to construct a grid equivalent impedance identification model based on the electrical state observation vector and output a time-varying equivalent impedance parameter set; the reference trajectory construction module 30 is used to construct a phase evolution reference trajectory of the self-synchronizing voltage source under the constraints of the time-varying equivalent impedance parameter set, and determine the reference angular frequency generation mechanism using a virtual power balance equation; the compensation quantity generation module 40 is used to, when the grid connection / disconnection switching trigger condition is met, convert the... The phase evolution reference trajectory is mapped to the voltage source internal mode synchronization coordinate system to generate a continuous phase compensation amount; the coupling correction module 50 is used to perform coupling correction on the voltage source output phase and amplitude based on the continuous phase compensation amount, wherein the continuous phase compensation amount is decomposed and applied to the phase adjustment channel and amplitude adjustment channel respectively, introducing a phase continuity constraint on the voltage source output phase and a power asymptotic constraint on the voltage source output amplitude; the online reshaping module 60 is used to perform online reshaping on the phase evolution reference trajectory according to the grid impedance disturbance change after the completion of the grid connection and disconnection state migration.

[0064] Furthermore, the observation vector acquisition module 10 is used to perform the following operation steps: Within a preset sampling period, the voltage and current of the common coupling point are sampled synchronously at multiple rates to construct a high-frequency sampling sequence and a low-frequency fundamental wave sampling sequence corresponding to the dynamic change rate of the power grid. Based on the high-frequency sampling sequence, a sliding window Fourier time-varying decomposition is performed, and phase alignment correction is performed in combination with the low-frequency fundamental wave sampling sequence to extract a unified time-frequency expression of the fundamental wave component, harmonic components, and transient disturbance components. The fundamental wave component, harmonic components, and transient disturbance components are fused and mapped with the voltage and current components in the dq rotating coordinate system through multiple channels to construct an electrical state observation vector containing phase drift characteristics, frequency offset characteristics, and disturbance energy characteristics.

[0065] Furthermore, the parameter set acquisition module 20 is used to perform the following operation steps: A multi-scale impedance identification structure is constructed based on the electrical state observation vector, decomposing the equivalent impedance of the power grid into a parallel estimation model of steady-state impedance components, transient impedance components, and disturbance impedance components. A recursive least squares estimation and Kalman filtering fusion update mechanism is adopted to perform collaborative parameter identification on the steady-state impedance components, transient impedance components, and disturbance impedance components, and a cross-model consistency constraint term is introduced to suppress drift errors between sub-models. A model credibility evaluation function is constructed based on the voltage-current signal-to-noise ratio and transient disturbance intensity, and the estimation results of each impedance component are adaptively weighted and fused to generate a time-varying equivalent impedance parameter set with time continuity. The time-varying equivalent impedance parameter set satisfies the requirement of piecewise continuous representation of the dynamic change process of the power grid.

[0066] Furthermore, the reference trajectory construction module 30 is used to perform the following operation steps: Based on the time-varying equivalent impedance parameter set, the voltage coupling and power damping terms in the power balance equation of the virtual synchronous machine are modified to construct a second-order nonlinear dynamic model under impedance constraints. A virtual rotor acceleration is generated based on the active power deviation, and a grid dynamic impedance compensation term is introduced according to the time-varying equivalent impedance parameter set to correct the virtual rotor acceleration online. The corrected virtual rotor acceleration is integrated piecewise, and the integration step size is adaptively adjusted based on the impedance change rate to obtain a piecewise continuous reference angular velocity constrained by impedance. The piecewise continuous reference angular velocities are then stitched together for trajectory consistency, and a second-order derivative continuity constraint is introduced for smoothing optimization to generate a phase evolution reference trajectory consistent with the time-varying equivalent impedance parameter set.

[0067] Furthermore, the compensation amount generation module 40 is used to perform the following operation steps: An adaptive mapping relationship between the grid-connected coordinate system and the islanded coordinate system is constructed based on the time-varying equivalent impedance parameter set, forming a dynamic coordinate transformation matrix. At the moment of grid-connected / off-grid switching triggering, the dynamic coordinate transformation matrix is ​​switched online according to the abrupt change amplitude of the time-varying equivalent impedance parameter set, and the phase evolution reference trajectory is input for coordinate mapping to obtain the phase mapping trajectory in the internal model synchronous coordinate system. A compensation term is constructed based on the prediction error between the phase mapping trajectory and the actual output phase, and the compensation term is fused with the phase evolution reference trajectory to generate a continuous phase compensation amount.

[0068] Furthermore, the coupling correction module 50 is used to perform the following operation steps: The continuous phase compensation is decomposed into a phase correction component and an amplitude correction component, which are applied to the phase adjustment channel and the amplitude adjustment channel, respectively. In the phase adjustment channel, a phase increment differential constraint model is constructed based on adjacent sampling periods, and the phase change rate is adaptively limited by combining the time-varying equivalent impedance parameter set. At the same time, a recursive correction term is constructed based on the phase prediction error to dynamically maintain the phase continuity constraint. In the amplitude adjustment channel, an amplitude constraint model is constructed based on the dynamic mapping relationship between the voltage modulation ratio and active and reactive power, and the modulation ratio change rate is adaptively constrained by combining the time-varying equivalent impedance parameter set to form a power asymptotic adjustment boundary. The control quantity is solved based on the joint constraint relationship between the phase continuity constraint and the power asymptotic adjustment boundary to perform synchronous coupling correction control on the voltage source output phase and amplitude.

[0069] Furthermore, the online reshaping module 60 is used to perform the following operation steps: A phase trajectory perturbation propagation model is constructed based on the time-varying equivalent impedance parameter set. A model prediction control rolling optimization structure is constructed based on the phase trajectory perturbation propagation model and the phase evolution reference trajectory to perform multi-step prediction and constraint evaluation of the future time-domain phase trajectory. When the predicted trajectory exceeds the stable operation constraint domain, a trajectory segmentation reconstruction mechanism is triggered to locally reparameterize the phase evolution reference trajectory and introduce continuity splicing constraints. The trajectory reconstruction process satisfies the stability constraint condition based on the energy function.

[0070] Furthermore, the online reshaping module 60 is used to perform the following operation steps: A dynamic convergence function based on phase error and power deviation is constructed, and a Lyapunov candidate function is constructed based on the dynamic convergence function. The Lyapunov candidate function is evaluated in real time. When its derivative does not meet the negative definite convergence condition, an adaptive adjustment mechanism for the damping enhancement factor is triggered, and the damping coefficient is updated online in combination with the time-varying equivalent impedance parameter set. At the same time, the voltage output vector trajectory is constrained by projection correction so that it simultaneously satisfies the phase continuity constraint and the power asymptotic constraint, and outputs a synchronous control command that satisfies the grid-connected / off-grid switching stability domain constraint condition.

[0071] Through the foregoing detailed description of the self-synchronizing voltage source regulation method during grid-connected / off-grid switching, those skilled in the art can clearly understand the self-synchronizing voltage source regulation system during grid-connected / off-grid switching in this embodiment. Since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and relevant parts can be referred to the method section.

[0072] Example 3, Figure 4This is a schematic diagram of the electronic device provided by the self-synchronization voltage source regulation method during the grid-to-off-grid switching process of the present invention, showing an exemplary electronic device suitable for implementing the embodiments of the present invention. Figure 4 The electronic device shown is merely an example and should not be construed as limiting the functionality or scope of the embodiments of the present invention. Figure 4 As shown, the electronic device includes a processor 21, a memory 22, an input device 23, and an output device 24; the number of processors 21 in the electronic device can be one or more. Figure 3 Taking a processor 21 as an example, the processor 21, memory 22, input device 23, and output device 24 in an electronic device can be connected via a bus or other means. Figure 4 Taking the example of a connection between China and Israel via a bus.

[0073] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, the above description focuses on specific embodiments of this specification. Additionally, the processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired results. In some implementations, multitasking and parallel processing are possible or may be advantageous.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for adjusting a self-synchronizing voltage source during grid-connected / off-grid switching, characterized in that, The method is applied to the dynamic switching process of a self-synchronizing voltage source converter between grid-connected operation and islanded operation. The method includes: The instantaneous voltage and current samples at the common coupling point are obtained to form the equivalent electrical state observation vector at the power grid end; Based on the electrical state observation vector, a power grid equivalent impedance identification model is constructed, and a time-varying equivalent impedance parameter set is output. Under the constraints of the time-varying equivalent impedance parameter set, a phase evolution reference trajectory of the self-synchronizing voltage source is constructed, and the reference angular frequency generation mechanism is determined by the virtual power balance equation. When the grid connection and disconnection switching trigger conditions are met, the phase evolution reference trajectory is mapped to the voltage source internal mode synchronization coordinate system to generate continuous phase compensation amount; The voltage source output phase and amplitude are coupled and corrected based on the continuous phase compensation amount. The continuous phase compensation amount is decomposed and applied to the phase adjustment channel and the amplitude adjustment channel respectively. A phase continuity constraint is introduced to the voltage source output phase, and a power asymptotic constraint is introduced to the voltage source output amplitude. After completing the on-grid and off-grid state transition, the phase evolution reference trajectory is reshaped online based on the changes in grid impedance disturbance.

2. The self-synchronizing voltage source regulation method during grid-connected / off-grid switching as described in claim 1, characterized in that, Obtain instantaneous voltage and current samples at the common coupling point to form an equivalent electrical state observation vector at the grid end, including: Within a preset sampling period, the voltage and current of the common coupling point are sampled synchronously at multiple rates to construct a high-frequency sampling sequence and a low-frequency fundamental wave sampling sequence corresponding to the dynamic change rate of the power grid. Based on the high-frequency sampling sequence, a sliding window Fourier time-varying decomposition is performed, and phase alignment correction is performed in combination with the low-frequency fundamental sampling sequence to extract a unified time-frequency expression of the fundamental component, harmonic component and transient disturbance component. The fundamental component, harmonic components, and transient disturbance components are fused and mapped with the voltage and current components in the dq rotating coordinate system through multiple channels to construct an electrical state observation vector that includes phase drift characteristics, frequency offset characteristics, and disturbance energy characteristics.

3. The self-synchronizing voltage source adjustment method during grid-connected / off-grid switching as described in claim 2, characterized in that, Based on the electrical state observation vector, a power grid equivalent impedance identification model is constructed, and a time-varying equivalent impedance parameter set is output, including: Based on the electrical state observation vector, a multi-scale impedance identification structure is constructed, and a parallel estimation model is used to decompose the equivalent impedance of the power grid into steady-state impedance components, transient impedance components and disturbance impedance components. A recursive least squares estimation and Kalman filtering fusion update mechanism is adopted to perform collaborative parameter identification on the steady-state impedance component, transient impedance component and disturbance impedance component, and a cross-model consistency constraint term is introduced to suppress the drift error between sub-models. A model credibility evaluation function is constructed based on the voltage and current signal-to-noise ratio and transient disturbance intensity. The estimation results of each impedance component are adaptively weighted and fused to generate a time-varying equivalent impedance parameter set with time continuity. The time-varying equivalent impedance parameter set satisfies the requirement for segmented and continuous characterization of the dynamic change process of the power grid.

4. The self-synchronizing voltage source regulation method during grid-connected / off-grid switching as described in claim 1, characterized in that, Under the constraints of the time-varying equivalent impedance parameter set, a phase evolution reference trajectory of the self-synchronizing voltage source is constructed, and the reference angular frequency generation mechanism is determined by a virtual power balance equation, including: Based on the time-varying equivalent impedance parameter set, the voltage coupling term and power damping term in the power balance equation of the virtual synchronous machine are modified to construct a second-order nonlinear dynamic model under impedance constraints. The virtual rotor acceleration is generated based on the active power deviation, and the grid dynamic impedance compensation term is introduced according to the time-varying equivalent impedance parameter set to correct the virtual rotor acceleration online. The modified virtual rotor acceleration is integrated piecewise, and the integration step size is adaptively adjusted based on the impedance change rate to obtain the piecewise continuous reference angular velocity constrained by impedance. The segmented continuous reference angular velocities are stitched together for trajectory consistency, and a second-order derivative continuous constraint is introduced for smoothing optimization to generate a phase evolution reference trajectory consistent with the time-varying equivalent impedance parameter set.

5. The self-synchronizing voltage source regulation method during grid-connected / off-grid switching as described in claim 1, characterized in that, When the grid connection / off-grid switching trigger condition is met, the phase evolution reference trajectory is mapped to the voltage source internal mode synchronization coordinate system to generate continuous phase compensation quantities, including: Based on the time-varying equivalent impedance parameter set, an adaptive mapping relationship between the grid-connected coordinate system and the islanded coordinate system is constructed, and a dynamic coordinate transformation matrix is ​​formed; At the moment of grid-connected / off-grid switching, after online switching selection of the dynamic coordinate transformation matrix based on the sudden change amplitude of the time-varying equivalent impedance parameter set, the phase evolution reference trajectory is input for coordinate mapping to obtain the phase mapping trajectory in the internal mode synchronous coordinate system. A compensation term is constructed based on the prediction error between the phase mapping trajectory and the actual output phase, and the compensation term is fused with the phase evolution reference trajectory to generate a continuous phase compensation amount.

6. The self-synchronizing voltage source regulation method during grid-connected / off-grid switching as described in claim 1, characterized in that, Based on the continuous phase compensation amount, the voltage source output phase and amplitude are coupled and corrected, including: The continuous phase compensation amount is decomposed into a phase correction component and an amplitude correction component, and applied to the phase adjustment channel and the amplitude adjustment channel respectively. In the phase adjustment channel, a phase increment differential constraint model is constructed based on adjacent sampling periods, and the phase change rate is adaptively limited by combining the time-varying equivalent impedance parameter set. At the same time, a recursive correction term is constructed based on the phase prediction error to dynamically maintain the phase continuity constraint. In the amplitude adjustment channel, an amplitude constraint model is constructed based on the dynamic mapping relationship between the voltage modulation ratio and active and reactive power, and the modulation ratio change rate is adaptively constrained by the time-varying equivalent impedance parameter set to form a power asymptotic adjustment boundary. The control quantity is solved based on the joint constraint relationship between phase continuity constraint and power asymptotic adjustment boundary, and the output phase and amplitude of the voltage source are synchronously coupled and corrected.

7. The self-synchronizing voltage source regulation method during grid-connected / off-grid switching as described in claim 1, characterized in that, The phase evolution reference trajectory is reshaped online based on changes in grid impedance disturbances, including: A phase trajectory perturbation propagation model is constructed based on the time-varying equivalent impedance parameter set. A model prediction control rolling optimization structure is constructed based on the phase trajectory perturbation propagation model and the phase evolution reference trajectory to perform multi-step prediction and constraint evaluation of the future time-domain phase trajectory. When the predicted trajectory exceeds the stable operation constraint domain, the trajectory segmentation reconstruction mechanism is triggered to perform local reparameterization adjustment on the phase evolution reference trajectory and introduce continuity splicing constraints. The trajectory reconstruction process satisfies the stability constraints based on the energy function.

8. The self-synchronizing voltage source regulation method during grid-connected / off-grid switching as described in claim 7, characterized in that, Also includes: A dynamic convergence function based on phase error and power deviation is constructed, and a Lyapunov candidate function is constructed based on the dynamic convergence function. The Lyapunov candidate function is evaluated in real time. When its derivative does not meet the negative definite convergence condition, the damping enhancement factor adaptive adjustment mechanism is triggered, and the damping coefficient is updated online in combination with the time-varying equivalent impedance parameter set. Simultaneously, the voltage output vector trajectory is constrained by projection correction to ensure that it simultaneously satisfies both phase continuity constraints and power asymptotic constraints, and outputs synchronous control commands that satisfy the grid-connected / off-grid switching stability domain constraints.

9. A self-synchronizing voltage source regulation system during grid-connected / off-grid switching, characterized in that, The system is used to implement the self-synchronizing voltage source regulation method during grid-connected and islanded switching as described in any one of claims 1 to 8, and is applied to the dynamic switching process of a self-synchronizing voltage source converter between grid-connected operation and islanded operation. The system comprises: The observation vector acquisition module is used to acquire the instantaneous voltage and current samples at the common coupling point to form the equivalent electrical state observation vector of the power grid. The parameter set acquisition module is used to construct a power grid equivalent impedance identification model based on the electrical state observation vector and output a time-varying equivalent impedance parameter set. The reference trajectory construction module is used to construct the phase evolution reference trajectory of the self-synchronizing voltage source under the constraints of the time-varying equivalent impedance parameter set, and to determine the reference angular frequency generation mechanism using the virtual power balance equation. The compensation quantity generation module is used to map the phase evolution reference trajectory to the voltage source internal mode synchronization coordinate system when the grid connection and disconnection switching trigger conditions are met, and generate continuous phase compensation quantity. The coupling correction module is used to perform coupling correction on the output phase and amplitude of the voltage source based on the continuous phase compensation amount. The continuous phase compensation amount is decomposed and applied to the phase adjustment channel and the amplitude adjustment channel respectively. A phase continuity constraint is introduced on the output phase of the voltage source, and a power asymptotic constraint is introduced on the output amplitude of the voltage source. The online reshaping module is used to reshape the phase evolution reference trajectory online according to the changes in grid impedance disturbance after the completion of the on-grid and off-grid state migration.

10. An electronic device, characterized in that, The electronic device includes: processor; Memory used to store the processor's executable instructions; The processor is used to execute the self-synchronizing voltage source regulation method during grid-connected / off-grid switching as described in any one of claims 1 to 8.

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