Partition control method for improving transient stability of GFM-VSC

Abstract

The invention discloses a partition control method for improving the transient stability of a GFM-VSC, and the method comprises the steps: continuously monitoring the voltage amplitude and phase angle of a power grid, calculating an internal state parameter through a droop control equation, and calculating the voltage drop depth, so as to start a partition control strategy; dividing a power grid voltage effective operation area by adopting voltage vector geometric analysis according to the current limitation constraint and the power grid voltage phase jump; when a power grid breaks down, a rated power angle is tracked adaptively based on an LADRC controller in a voltage phase disturbance period so as to eliminate disturbance; performing real-time state judgment according to an effective operation area of the power grid voltage, executing a virtual impedance switching strategy, and compulsorily executing steady-state fault current limitation by reconstructing a reactive power reference value in a voltage loop; based on a voltage-current double closed-loop control system, a phase-preserving amplitude limiting technology is adopted in a current inner loop to adjust the amplitude and phase of reference current so as to suppress pulse current, and a final pulse width modulation voltage instruction is obtained.

Description

Technical Field

[0001] This invention relates to the field of grid-forming voltage source converter stability control technology, and more specifically to a partitioned control method for improving the transient stability of GFM-VSC. Background Technology

[0002] In new power systems dominated by a high proportion of renewable energy, grid-forming voltage source converters (GFM-VSCs) serve as the core grid-connection interface to replace traditional synchronous generators. Their transient stability is the cornerstone of ensuring the safe operation of the system. However, the voltage source characteristics of GFM-VSCs make them highly susceptible to damage when the grid encounters extreme faults (such as deep voltage drops accompanied by phase jumps) because the feeder current far exceeds the safety limits of their semiconductor devices. To achieve self-protection, the converter usually needs to activate a fault current suppression strategy.

[0003] The most direct current-limiting control in existing research, while effectively suppressing fault current, forces the GFM-VSC to switch from the voltage source mode supporting the grid to the controlled current source mode, thereby losing its ability to support the voltage at the point of common coupling. This directly disrupts the power synchronization mechanism of the system, causing the converter power angle to oscillate violently or even lose synchronization after the fault is cleared, leading to transient instability and ultimately causing the converter to disconnect from the grid. This phenomenon is particularly severe in weak grid environments or when the fault is accompanied by a phase jump, because the phase jump will instantly change the power angle reference, further aggravating the impact on power and current.

[0004] To address this challenge, existing technical solutions include: mode switching control, but this relies on phase-locked loops and is prone to instability under weak power grids; saturation-based control, which carries the risk of resaturation after a fault and the inability to recover the mode; and voltage source fault ride-through strategies based on virtual impedance, which are computationally complex and have inherent delays, and have limited suppression effects under extreme faults. Although these strategies have achieved fault current limiting to some extent, they all come at the cost of sacrificing the transient stability of the system, or they cannot work reliably in complex phase transition scenarios.

[0005] Therefore, how to design a control strategy that does not rely on mode switching and does not require complex online calculations under extreme power grid fault conditions, so that the GFM-VSC can maintain its voltage source characteristics and power angle stability while strictly limiting the fault current, has become a core technical problem that urgently needs to be solved in the field of safe and stable operation of highly electronic power grids. This requires the control strategy to not only have fast and adaptive disturbance suppression capabilities to cope with phase jumps, but also to be able to intelligently identify the stable operating boundary of the system, and coordinate multiple current limiting methods within this boundary to achieve a unity of current suppression and transient stability.

[0006] Patent document CN116014692A discloses a grid-type VSC fault current suppression method and system based on voltage vector dynamic tracking control. This method improves dynamic response speed by eliminating the voltage-current inner loop and directly changing the modulation waveform, avoiding control bandwidth delay, while maintaining continuous operation of the power synchronization outer loop to prevent controller saturation. However, this method mainly relies on a preset feedforward compensation mechanism, and its control effect is highly dependent on accurate system models and parameter tuning. When dealing with extreme grid faults accompanied by complex phase jumps, a single feedforward compensation strategy may lack sufficient adaptive capability, making it difficult to achieve a dynamic balance between current limiting and maintaining transient stability. Furthermore, since no real-time state observation and intelligent decision-making mechanism is introduced, this method cannot adaptively adjust the control structure according to the severity of the fault, nor does it involve hierarchical coordinated suppression of steady-state fault current and inrush current.

[0007] Therefore, how to overcome the problem that existing fault current suppression methods damage the voltage source characteristics of the converter when dealing with extreme grid faults, especially voltage drops accompanied by phase jumps, leading to power angle instability and inability to maintain synchronous operation after the fault is cleared is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] In view of the above problems, the present invention provides a partition control method for improving the transient stability of GFM-VSC to overcome or at least partially solve the above problems.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A partition control method for improving the transient stability of GFM-VSC includes the following steps: S1. Continuously monitor the grid voltage amplitude and phase angle at the common coupling point of the GFM-VSC system, calculate the internal state parameters of the GFM-VSC system in real time using the droop control equation, and initiate the zone control strategy based on the real-time calculated voltage sag depth. S2. Based on the current limiting constraints and the phase jump of the grid voltage, the effective operating area of ​​the grid voltage is divided using the voltage vector geometric analytical method; S3. When a grid fault occurs, an active power-frequency loop based on a Linear Active Disturbance Rejection Control (LADRC) controller is used to adaptively track the rated power angle during voltage phase disturbances to eliminate the disturbances. S4. Based on the effective operating range of the grid voltage, perform real-time status judgment, execute virtual impedance switching strategy, and enforce steady-state fault current limitation by reconstructing the reactive power reference value in the voltage loop. S5. Based on the voltage-current dual closed-loop control system, by using phase-preserving and amplitude-limiting technology in the inner current loop, the amplitude and phase of the reference current are adjusted to suppress the pulse current, and the final pulse width modulation voltage command is obtained.

[0011] Preferably, in step S1, the internal state parameters of the GFM-VSC system include output active power, reactive power, output angular frequency, and virtual power angle. The internal state parameters of the GFM-VSC system are calculated in real time using the droop control equations as follows:

[0012]

[0013] in, This is a virtual power angle, equal to the difference between the phase of the converter output voltage and the phase of the grid voltage; The actual angular frequency of the converter output voltage. The rated angular frequency of the power grid. For rotational inertia, The active power frequency droop factor. To output active power, This is the amplitude command for the converter output voltage. This is the reference value for the rated output voltage. This refers to the reactive power voltage droop factor. Reactive power; Voltage sag depth is:

[0014] in, The rated grid voltage, For real-time measurement of fault grid voltage, when the voltage drop depth is collected... k When the value is below a preset threshold, a power grid fault is determined, and a zone control strategy is initiated.

[0015] Preferably, the specific content of step S2 is as follows: Based on real-time grid fault conditions, with the rated grid voltage direction as the reference axis, a phasor model is established based on the geometric relationship between the converter output voltage, grid fault voltage, and line voltage drop phasors. By solving the critical conditions for phasor triangle closure, the maximum and minimum boundaries of the effective operating area are calculated, and all grid voltage operating points under fault steady-state current constraints are defined.

[0016] Preferably, the phasor model established based on the geometric relationship between the converter output voltage, grid fault voltage, and line voltage drop phasors is as follows:

[0017]

[0018]

[0019]

[0020]

[0021] in, The output voltage amplitude, For the maximum boundary, For the minimum boundary, This is the normal grid voltage amplitude. This is the voltage of the power grid fault. This represents the maximum voltage drop on the line under current-limiting conditions. It is the angle between the converter output voltage and the normal grid voltage.

[0022] Preferably, step S3 includes the following: S31. Establish the controlled model, express the active power-frequency loop of GFM-VSC in the standard form of LADRC controller, and regard the unmodeled dynamics inside the system and the external phase jump disturbance as the total disturbance; The S32.LADRC controller treats the total disturbance as a new state variable, establishes an extended state-space model, and constructs a linear extended state observer (LESO) to estimate all state variables of the system in real time. S33. After estimating the total disturbance, the LADRC controller eliminates the disturbance effect through feedforward compensation.

[0023] Preferably, after estimating the total disturbance, the LADRC controller uses the following expression to eliminate the disturbance's effects through feedforward compensation:

[0024] in, For the controller's output signal, This is the gain parameter of the controller, used to adjust the strength of the control action; For controller gain, This is the rated power angle. For the virtual power angle of GFM-VSC, The deviation between the output frequency and the rated frequency of the GFM-VSC. This is a disturbance compensation term.

[0025] Preferably, the specific content of step S4 is as follows: S41. Real-time status judgment is performed based on the effective operating area of ​​the power grid voltage as defined in step S2; S42. Execute dual-path switching control based on the judgment result. When the system is judged to be within the effective operating range, the virtual impedance is not engaged; when the system is judged to be outside the effective operating range, the virtual impedance is engaged. S43. Reconstruct the reactive power reference value in the voltage loop to enforce steady-state fault current limiting.

[0026] Preferably, the virtual impedance input is:

[0027] in, The virtual inductance value that needs to be invested, This represents the voltage amplitude of the power grid during a fault. The rated angular frequency, This represents the current operating state of the system under the phase transition. This represents the voltage drop depth. This is the rated current of the converter; The specific details of reconstructing the reactive power reference value in the voltage loop are as follows:

[0028]

[0029] in, This is the converter output voltage command. This is the reference value for reactive power after reconstruction. This is the reactive voltage droop factor. This is the current measured value of the converter output voltage. This is the equivalent impedance of the line.

[0030] Preferably, step S5 includes: S51. Process the original current signal, decompose the original current reference command vector into amplitude and unit phase vectors, and set the maximum safe fault transient current to obtain the new current amplitude after limitation. S52. Recombine the limited new current amplitude with the retained phase information to reconstruct a new current reference command; S54. Input the reconstructed safety current command into the inner current loop controller to finally generate a PWM modulation signal.

[0031] Preferably, the final pulse width modulation voltage command is as follows:

[0032] in, This is the final pulse width modulation voltage command. For proportional gain, For integral gain, This is the cutoff frequency of the current controller. The rated angular frequency of the power grid. This is the reconstructed safe current command.

[0033] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a partition control method to improve the transient stability of GFM-VSC. During operation, based on the real-time monitoring of the grid voltage drop depth, phase jump situation and effective operating area determination results, a corresponding partition control strategy is formulated. The power angle stability control based on LADRC, flexible switching of virtual impedance and reactive power reference value reconstruction are organically combined to enable GFM-VSC to maintain voltage source characteristics during grid faults. Under extreme grid fault conditions, the power angle is maintained by active disturbance rejection control, while the current limiting measures are adaptively adjusted by intelligent discrimination of the effective operating area. This ensures that the fault current is quickly limited to a safe range and avoids the transient instability caused by traditional mode switching or saturation current limiting, thus significantly improving the system's fault ride-through capability. This invention achieves a balance between transient stability and current limiting through coordinated regulation of the internal state of the GFM-VSC and external grid conditions. This enhances the operational resilience of grid-forming converters in high-proportion renewable energy power systems while reducing the conservative configuration margin required to ensure transient stability. It helps improve the stable operation boundary and dispatch flexibility of power electronic power systems, providing effective technical support for the construction of new power systems and showing promising engineering application prospects. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0035] Figure 1 This is a flowchart of a partition control method for improving the transient stability of GFM-VSC provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the GFM-VSC system control architecture provided in an embodiment of the present invention; Figure 3 This is a voltage vector diagram in the coordinate system provided in the embodiments of the present invention; Figure 4 This is a schematic diagram of the virtual impedance switching strategy provided in an embodiment of the present invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] This invention discloses a partition control method for improving the transient stability of GFM-VSC, such as... Figure 1 and Figure 2 As shown, it includes the following steps: S1. Continuously monitor the grid voltage amplitude at the common coupling point of the GFM-VSC system using a voltage sensor and phase-locked loop installed at the common coupling point. and phase angle The internal state parameters of the GFM-VSC system are calculated in real time using the droop control equation, and the zonal control strategy is initiated based on the real-time calculated voltage drop depth. S2. Based on the current limiting constraints and the phase jump of the grid voltage, the effective operating area of ​​the grid voltage is divided using the voltage vector geometric analytical method; S3. When a grid fault occurs, an active power-frequency loop based on a linear self-interference control (LADRC) controller is used to adaptively track the rated power angle during voltage phase disturbances to eliminate the disturbances. S4. Based on the effective operating range of the grid voltage, perform real-time status judgment, execute virtual impedance switching strategy, and enforce steady-state fault current limitation by reconstructing the reactive power reference value in the voltage loop. S5. Based on the voltage-current dual closed-loop control system, by using phase-preserving and amplitude-limiting technology in the inner current loop, the amplitude and phase of the reference current are adjusted to suppress the pulse current, and the final pulse width modulation voltage command is obtained.

[0038] exist Figure 2 middle, and These represent the filter inductor and capacitor, respectively. It is the equivalent inductance of the line. It is the equivalent impedance of the line; and These are the mains voltage and the VSC output voltage, respectively. It is the VSC output current. and These are the reference voltage and current of VSC, respectively; and Decomposed by dq change into , , and Then the voltage-current dual closed-loop controller is fed into the voltage-current controller; after the current saturation stage, the final pulse width modulation (PWM) voltage is... u m generate; and These are the phase angles of the VSC output voltage and the mains voltage, respectively. The phase angle shift caused by the phase-locked loop (PLL) device is measured in real time to capture the voltage drop across the grid. Represents the DC power supply, and and are the droop control reference values ​​for active power and reactive power, respectively. , refers to the d-axis and q-axis reference currents after limiting. v and i These are the input reference voltage and the output reference current in the voltage control loop, respectively.

[0039] To further implement the above technical solution, in step S1, the internal state parameters of the GFM-VSC system include the output active power. reactive power Output angular frequency and virtual angle ; The internal state parameters of the GFM-VSC system are calculated in real time using the droop control equations as follows:

[0040]

[0041] in, This is a virtual power angle, equal to the converter output voltage. Phase and grid voltage Phase difference; The actual angular frequency of the converter output voltage. The rated angular frequency of the power grid. For rotational inertia, The active power frequency droop factor. To output active power, This is the amplitude command for the converter output voltage. This is the reference value for the rated output voltage. This refers to the reactive power voltage droop factor. Reactive power; Voltage sag depth is:

[0042] in, The rated grid voltage, For real-time measurement of fault grid voltage, when the voltage drop depth is collected...k When the value is below a preset threshold, a power grid fault is determined, and a zone control strategy is initiated.

[0043] In this embodiment, when the data is collected... When a power grid fault is detected, the zone control strategy is activated.

[0044] To further implement the above technical solution, the specific content of step S2 is as follows: Based on real-time grid fault conditions, with the rated grid voltage direction as the reference axis, and based on the converter output voltage... Power grid fault voltage With line voltage drop The geometric relationships of phasors are used to establish a phasor model. By solving the critical condition for the closure of the phasor triangle, the maximum boundary of the effective operating region is calculated. with minimum boundary Define the steady-state current during the fault. I = I lim All grid voltage operating points under constraints.

[0045] To further implement the above technical solutions, such as Figure 3 As shown, the phasor model established based on the geometric relationship between the converter output voltage, grid fault voltage, and line voltage drop phasors is as follows:

[0046]

[0047]

[0048]

[0049]

[0050] in, The output voltage amplitude of the converter. For the maximum boundary, For the minimum boundary, This is the normal grid voltage amplitude. This is the voltage of the power grid fault. This represents the maximum voltage drop on the line under current-limiting conditions. It is the angle between the converter output voltage and the normal grid voltage.

[0051] To further implement the above technical solution, step S3 includes the following: S31. Establish the controlled model, express the active power-frequency loop of GFM-VSC in the standard form of LADRC controller, and regard the unmodeled dynamics inside the system and the external phase jump disturbance as the total disturbance; The controlled model is:

[0052] in, Angular acceleration, representing the angle of work. This indicates the output signal of the controller. Indicates the known controller gain. Indicates the total disturbance;

[0053] in, This represents the measured active power. Indicates the droop coefficient. Indicates external disturbance; The S32.LADRC controller treats the total disturbance as a new state variable, establishes an extended state-space model, and constructs a linear extended state observer (LESO) to estimate all state variables of the system in real time. The extended state-space model is as follows:

[0054] in, This represents the virtual power angle of GFM-VSC. This indicates the deviation of the output frequency of the GFM-VSC from its rated frequency. This represents the total disturbance in the system; The Linear Extended State Observer (LESO) is specifically as follows:

[0055] in, To represent each variable in the system output Observed values ​​of the derivative Indicates the observer gain; The observer predicts the current state based on the estimated value from the previous time step and the known input through an integrator. At the same time, the observer compares the prediction with the actual output of the system, multiplies the resulting error by the gain, and then feeds it back to correct the predicted value for each state. S33. After estimating the total disturbance, the LADRC controller eliminates the disturbance effect through feedforward compensation.

[0056] To further implement the above technical solution, after estimating the total disturbance, the LADRC controller uses the following expression to eliminate the disturbance's impact through feedforward compensation:

[0057] in, For the controller's output signal, This is the gain parameter of the controller, used to adjust the strength of the control action; For controller gain, This is the rated power angle. For the virtual power angle of GFM-VSC, The deviation between the output frequency and the rated frequency of the GFM-VSC. This is a disturbance compensation term.

[0058] To further implement the above technical solution, the specific content of step S4 is as follows: S41. Real-time status judgment is performed based on the effective operating area of ​​the power grid voltage as defined in step S2; S42. Execute dual-path switching control based on the judgment result. When the system is judged to be within the effective operating range, the virtual impedance is not engaged; when the system is judged to be outside the effective operating range, the virtual impedance is engaged. S43. Reconstruct the reactive power reference value in the voltage loop to enforce steady-state fault current limiting.

[0059] In this embodiment, by determining the system operating status in real time and intelligently selecting the control path, precise current limiting is achieved while maintaining the voltage source characteristics; The discriminant for real-time status judgment based on the effective operating area of ​​the grid voltage defined in step S2 is:

[0060] When the discriminant is true, the system is in the effective operating region, and the switch is set to... In this state, without introducing virtual impedance, and after fully utilizing LADRC to establish a stable foundation, the system mainly relies on the execution capability of the underlying voltage loop; when the discriminant fails, the system exceeds the effective operating range, and the switch is activated. In this state, a virtual impedance is applied, such as Figure 4 As shown.

[0061] To further implement the above technical solution, the virtual impedance is:

[0062] in, The virtual inductance value that needs to be invested, This represents the voltage amplitude of the power grid during a fault. The rated angular frequency, This represents the current operating state of the system under the phase transition. This represents the voltage drop depth. This is the rated current of the converter; The specific details of reconstructing the reactive power reference value in the voltage loop are as follows:

[0063]

[0064] in, This is the converter output voltage command. This is the reference value for reactive power after reconstruction. This is the reactive voltage droop factor. This is the current measured value of the converter output voltage. This is the equivalent impedance of the line.

[0065] To further implement the above technical solution, step S5 includes: S51. Process the original current signal, and convert the original current reference command vector. Decomposed into amplitude and unit phase vector And set the maximum safe fault transient current. This yields a new current amplitude after limitation; S52. Recombine the limited new current amplitude with the retained phase information to reconstruct a new current reference command. ; S54. Reconstruct the safety current command The input current inner loop controller ultimately generates a PWM modulation signal.

[0066] In this embodiment, the maximum safe fault transient current is set. It is set higher than the steady-state fault current limit, allowing for brief overshoots, but must remain below the maximum rated value; if The new current amplitude after limitation ;like The new current amplitude after limitation ; The reconstructed new current reference instruction is a safe, distortion-free transient current suppression instruction, specifically:

[0067] in, This is the final synthesized reference command vector for the new current.

[0068] To further implement the above technical solution, the final pulse width modulation voltage command is as follows:

[0069] in, This is the final pulse width modulation voltage command. For proportional gain, For integral gain, This is the cutoff frequency of the current controller. The rated angular frequency of the power grid. This is the reconstructed safe current command.

[0070] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0071] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A partition control method for improving the transient stability of GFM-VSC, characterized in that, Includes the following steps: S1. Continuously monitor the grid voltage amplitude and phase angle at the common coupling point of the GFM-VSC system, calculate the internal state parameters of the GFM-VSC system in real time using the droop control equation, and initiate the zone control strategy based on the real-time calculated voltage sag depth. S2. Based on the current limiting constraints and the phase jump of the grid voltage, the effective operating area of ​​the grid voltage is divided using the voltage vector geometric analytical method; S3. When a grid fault occurs, an active power-frequency loop based on a linear self-interference control (LADRC) controller is used to adaptively track the rated power angle during voltage phase disturbances to eliminate the disturbances. S4. Based on the effective operating range of the grid voltage, perform real-time status judgment, execute virtual impedance switching strategy, and enforce steady-state fault current limitation by reconstructing the reactive power reference value in the voltage loop. S5. Based on the voltage-current dual closed-loop control system, by using phase-preserving and amplitude-limiting technology in the inner current loop, the amplitude and phase of the reference current are adjusted to suppress the pulse current, and the final pulse width modulation voltage command is obtained.

2. The partition control method for improving the transient stability of GFM-VSC as described in claim 1, characterized in that, In step S1, the internal state parameters of the GFM-VSC system include output active power, reactive power, output angular frequency, and virtual power angle. The internal state parameters of the GFM-VSC system are calculated in real time using the droop control equations as follows: in, This is a virtual power angle, equal to the difference between the phase of the converter output voltage and the phase of the grid voltage; The actual angular frequency of the converter output voltage. The rated angular frequency of the power grid. For rotational inertia, The active power frequency droop factor. To output active power, This is the amplitude command for the converter output voltage. This is the reference value for the rated output voltage. This refers to the reactive power voltage droop factor. Reactive power; Voltage sag depth is: in, The rated grid voltage, For real-time measurement of fault grid voltage, when the voltage drop depth is collected... k When the value is below a preset threshold, a power grid fault is determined, and a zone control strategy is initiated.

3. The partition control method for improving the transient stability of GFM-VSC as described in claim 1, characterized in that, The specific content of step S2 is as follows: Based on real-time grid fault conditions, with the rated grid voltage direction as the reference axis, a phasor model is established based on the geometric relationship between the converter output voltage, grid fault voltage, and line voltage drop phasors. By solving the critical conditions for phasor triangle closure, the maximum and minimum boundaries of the effective operating area are calculated, and all grid voltage operating points under fault steady-state current constraints are defined.

4. The partition control method for improving the transient stability of GFM-VSC as described in claim 3, characterized in that, The phasor model established based on the geometric relationship between the converter output voltage, grid fault voltage, and line voltage drop phasors is as follows: in, The output voltage amplitude, For the maximum boundary, For the minimum boundary, This is the normal grid voltage amplitude. This is the voltage of the power grid fault. This represents the maximum voltage drop on the line under current-limiting conditions. It is the angle between the converter output voltage and the normal grid voltage.

5. The partition control method for improving the transient stability of GFM-VSC as described in claim 1, characterized in that, The specific content of step S3 includes: S31. Establish the controlled model, express the active power-frequency loop of GFM-VSC in the standard form of LADRC controller, and regard the unmodeled dynamics inside the system and the external phase jump disturbance as the total disturbance; The S32.LADRC controller treats the total disturbance as a new state variable, establishes an extended state-space model, and constructs a linear extended state observer (LESO) to estimate all state variables of the system in real time. S33. After estimating the total disturbance, the LADRC controller eliminates the disturbance effect through feedforward compensation.

6. The partition control method for improving the transient stability of GFM-VSC as described in claim 5, characterized in that, After estimating the total disturbance, the LADRC controller uses the following expression to eliminate the disturbance's effects through feedforward compensation: in, For the controller's output signal, This is the gain parameter of the controller, used to adjust the strength of the control action; For controller gain, This is the rated power angle. For the virtual power angle of GFM-VSC, The deviation between the output frequency and the rated frequency of the GFM-VSC. This is a disturbance compensation term.

7. The partition control method for improving the transient stability of GFM-VSC as described in claim 1, characterized in that, The specific content of step S4 is as follows: S41. Real-time status judgment is performed based on the effective operating area of ​​the power grid voltage as defined in step S2; S42. Execute dual-path switching control based on the judgment result. When the system is judged to be in the effective operating area, the virtual impedance is not applied. When the system is determined to be outside the effective operating range, a virtual impedance is applied. S43. Reconstruct the reactive power reference value in the voltage loop to enforce steady-state fault current limiting.

8. The partition control method for improving the transient stability of GFM-VSC as described in claim 7, characterized in that, The virtual impedance input is: in, The virtual inductance value that needs to be invested, This represents the voltage amplitude of the power grid during a fault. The rated angular frequency, This represents the current operating state of the system under the phase transition. This represents the voltage drop depth. This is the rated current of the converter; The specific details of reconstructing the reactive power reference value in the voltage loop are as follows: in, This is the converter output voltage command. This is the reference value for reactive power after reconstruction. This is the reactive voltage droop factor. This is the current measured value of the converter output voltage. The equivalent impedance of the line. This is the rated grid voltage.

9. The partition control method for improving the transient stability of GFM-VSC as described in claim 1, characterized in that, Step S5 includes: S51. Process the original current signal, decompose the original current reference command vector into amplitude and unit phase vectors, and set the maximum safe fault transient current to obtain the new current amplitude after limitation. S52. Recombine the limited new current amplitude with the retained phase information to reconstruct a new current reference command; S54. Input the reconstructed safety current command into the inner current loop controller to finally generate a PWM modulation signal.

10. The partition control method for improving the transient stability of GFM-VSC as described in claim 1, characterized in that, The final pulse width modulation voltage command is as follows: in, This is the final pulse width modulation voltage command. For proportional gain, For integral gain, This is the cutoff frequency of the current controller. The rated angular frequency of the power grid. This is the reconstructed safe current command.

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