Embedded direct current subsequent commutation failure suppression method based on turn-off angle compensation

Abstract

The invention relates to the technical field of power system safety control, in particular to an embedded direct current subsequent commutation failure suppression method based on turn-off angle compensation, which comprises the following steps of: constructing an alternating current and direct current hybrid power grid simulation model; monitoring a trigger lead angle of constant turn-off angle control output and a trigger lead angle of constant current control output of the embedded direct current inverter side controller in real time; calculating a difference value between the trigger lead angle output by the constant turn-off angle control and the trigger lead angle output by the constant current control; the difference value is compared with a preset triggering threshold value, and when the difference value is larger than or equal to the preset triggering threshold value, a turn-off angle compensation mechanism is triggered; according to the alternating current and direct current hybrid power grid fault suppression method, when the alternating current and direct current hybrid power grid fault occurs, suppression of direct current follow-up commutation failure is facilitated, direct current locking is avoided, and the voltage stability of the hybrid power grid is improved.

Description

Technical Field

[0001] This application relates to the field of power system safety control technology, and in particular to an embedded DC subsequent commutation failure suppression method based on turn-off angle compensation. Background Technology

[0002] With the application of embedded DC transmission technology in regional power grids (such as the ±200kV Yangzhou-Zhenjiang DC project in Jiangsu, China), the power transmission capacity of the power grid has been improved. However, in AC / DC hybrid systems containing embedded DC, the coupling between the DC sending and receiving ends is intensified, and the response of the embedded DC during power grid faults is more complex. When a system fault occurs, it is very easy to cause DC commutation failure, and even continuous commutation failure may occur due to controller interaction. In severe cases, it can cause DC blocking and power grid voltage collapse, threatening the safe and stable operation of the power grid.

[0003] In existing technologies, suppression strategies for commutation failure mostly focus on externally fed DC systems, such as improving low-voltage current limiting circuits and optimizing controller parameters. However, these methods fail to adequately consider embedded DC systems. Embedded DC systems have tightly coupled sending and receiving ends; when a fault occurs at the sending end, it causes a voltage drop on the receiving end's AC bus, effectively resulting in a simultaneous failure at both ends. Currently, the mechanism of embedded commutation failure is unclear. Traditional methods are ill-suited to effectively address subsequent commutation failures in such complex scenarios.

[0004] Therefore, there is an urgent need for a new control method that can effectively suppress subsequent commutation failures in AC / DC hybrid power grids with embedded DC. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method that can effectively suppress subsequent commutation failures in embedded DC transmission systems during fault recovery. This method improves the transient stability of the system by detecting the switching process of the control mode and compensating the cut-off angle reference value in real time.

[0006] The technical solution adopted by this invention to solve its technical problem is: providing an embedded DC subsequent commutation failure active suppression method based on control mode switching state recognition. The core of the method lies in: capturing signals during the inverter-side control mode switching process, dynamically compensating the turn-off angle in real time to expand the commutation margin, thereby actively preventing subsequent commutation failure. The specific steps are as follows:

[0007] Step S1: Construct a simulation model of an AC / DC hybrid power grid with embedded DC, and monitor in real time the trigger lead angle of the constant current control output and the trigger lead angle of the constant turn-off angle control output of the embedded DC inverter side controller.

[0008] Step S2: Calculate the difference between the trigger lead angle of the constant turn-off angle control output and the trigger lead angle of the constant current control output;

[0009] Step S3: Compare the difference with a preset trigger threshold, and trigger the shutdown angle compensation mechanism when the difference is greater than or equal to the preset trigger threshold;

[0010] Step S4: After the shutdown angle compensation mechanism is triggered, the shutdown angle compensation amount is calculated based on the difference, and the shutdown angle compensation amount is superimposed on the shutdown angle reference value to generate the compensated shutdown angle reference value.

[0011] Further, in step S1, constructing the AC / DC hybrid power grid simulation model with embedded DC includes:

[0012] S11. Determine the topology of the embedded DC transmission system, the topology including a sending-end AC grid, a rectifier station, a DC line, an inverter station and a receiving-end AC grid, wherein the sending-end AC grid and the receiving-end AC grid are connected by at least one AC tie line to form a sending-end coupled network structure;

[0013] S12. Configure a control system for the rectifier station and the inverter station, wherein the inverter-side controller includes at least constant turn-off angle control and constant current control, and can output their respective trigger lead angle signals;

[0014] S13. Build the aforementioned topology and control system in electromagnetic transient simulation software, and set the sending-end AC bus as the fault simulation point.

[0015] Further, in step S2, the difference is the trigger lead angle of the constant turn-off angle control output minus the trigger lead angle of the constant current control output.

[0016] Furthermore, in step S3, the preset trigger threshold is determined by analyzing the dynamic curve of the trigger lead angle difference between the constant turn-off angle control and constant current control on the inverter side during the system recovery process after fault clearance, wherein the preset trigger threshold is a negative value.

[0017] Further, in step S4, calculating the shut-off angle compensation amount based on the difference includes:

[0018] Step S41: Set a compensation termination threshold;

[0019] Step S42: Compare the difference with the preset trigger threshold and the compensation end threshold;

[0020] Step S43: When the difference is less than the preset trigger threshold, the shut-off angle compensation amount is set to zero.

[0021] Step S44: When the difference is within the range formed by the preset trigger threshold and the compensation end threshold, a dynamic shut-off angle compensation amount that monotonically decreases as the difference increases is calculated according to the predefined compensation function.

[0022] Step S45: When the difference is greater than or equal to the compensation end threshold, the shut-off angle compensation amount is set to zero.

[0023] Further, in step S41, the compensation end threshold is determined by analyzing the dynamic curve of the trigger lead angle difference between the constant turn-off angle control and the constant current control on the inverter side during the system recovery process after fault clearance, wherein the compensation end threshold is a positive value.

[0024] Further, in step S44, the dynamic shut-off angle compensation amount is:

[0025] ;

[0026] in, Δβ represents the dynamic shut-off angle compensation amount, and Δβ is the difference.

[0027] Furthermore, the predefined compensation function is configured to: when the difference is equal to the preset trigger threshold, output a preset maximum shut-off angle compensation amount; when the difference increases from the preset trigger threshold to the compensation end threshold, the dynamic shut-off angle compensation amount continuously decreases from the maximum shut-off angle compensation amount to zero.

[0028] Further, in step S4, adding the shut-off angle compensation amount to the shut-off angle reference value includes:

[0029] The real-time calculated shut-off angle compensation is algebraically added to the original shut-off angle reference value in the inverter-side controller to generate a compensated shut-off angle reference value, which is then used as the new tracking target for the fixed shut-off angle control loop in the inverter-side controller.

[0030] Furthermore, the preset maximum shut-off angle compensation amount is determined through electromagnetic transient simulation.

[0031] Compared with the prior art, the beneficial effect of the present invention is that the negative threshold of the present invention can sensitively capture the critical point at which an unfavorable switch in the control mode is about to occur. At this time, the β value of the constant shut-off angle control... G The trigger lead angle β of the just-overclocked constant current control CThe system is on the verge of switching from CC mode to CEA mode, but the actual sharp deterioration of the turn-off angle has not yet occurred. By analyzing a large number of dynamic curve clusters formed by simulation, the threshold is determined so that the triggering criteria can adapt to different fault types and system operation modes, avoiding further decrease in the turn-off angle, thereby suppressing DC commutation failure and violent oscillation of DC power, making the system recovery process after the fault more stable and orderly.

[0032] Furthermore, by setting a positive compensation termination threshold, the system can automatically and accurately determine the moment when the risk is eliminated. Once Δβ reaches this threshold, the compensation amount immediately returns to zero, avoiding unnecessary compensation after the system has returned to normal. This prevents the negative impact that may occur on the steady-state operation of the system due to long-term artificial raising of the shut-off angle (such as increased reactive power consumption), ensuring the accuracy and timeliness of the suppression strategy. The dynamic compensation mechanism that decreases linearly with increasing Δβ ensures that the compensation amount of the shut-off angle reference value is a smooth transition rather than a step-like change. As the system state (Δβ) gradually improves, the compensation amount decreases synchronously and linearly, allowing the compensated shut-off angle reference value to return to the original set value without disturbance and gradually. The smooth exit process effectively prevents power or voltage oscillations that may be caused at the moment of compensation removal, greatly improving the stability of the system recovery process after a fault.

[0033] Furthermore, this invention uses a linear compensation function to ensure that the shut-off angle compensation amount... It establishes a precise mapping relationship with Δβ, providing full compensation when a control strategy switch is imminent, forcibly expanding the margin to withstand the most severe shocks; as the system recovers, the compensation amount decreases linearly, and the commutation margin smoothly reverts to the normal operating value. The linear function ensures that the compensation amount... It changes continuously and smoothly when compared with the original shut-off angle reference value γ. ref The new reference value γ' generated when performing a simple algebraic addition. ref It is also a smoothly changing signal. The inverter-side turn-off angle control loop tracks this smoothly changing reference value, so that the phase of the actual trigger pulse and the actual turn-off angle can achieve a smooth transition. This avoids secondary oscillations in DC power, voltage or current caused by step or sudden changes in compensation amount, and greatly improves the recovery quality and transient stability of the entire AC / DC system after fault clearing. Attached Figure Description

[0034] Figure 1 This is a flowchart of the embedded DC subsequent commutation failure suppression method based on turn-off angle compensation of the present invention.

[0035] Figure 2This is a flowchart illustrating the process of constructing a simulation model of an AC / DC hybrid power grid containing embedded DC in the embedded DC subsequent commutation failure suppression method based on turn-off angle compensation of this invention.

[0036] Figure 3 This is a flowchart illustrating the process of calculating the turn-off angle compensation amount based on the difference in the embedded DC subsequent commutation failure suppression method based on the turn-off angle compensation of the present invention. Detailed Implementation

[0037] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0038] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0039] Please see Figures 1-3 As shown, Figure 1 This is a flowchart of the embedded DC subsequent commutation failure suppression method based on turn-off angle compensation of the present invention. Figure 2 This is a flowchart illustrating the process of constructing a simulation model of an AC / DC hybrid power grid containing embedded DC in the embedded DC subsequent commutation failure suppression method based on turn-off angle compensation of this invention. Figure 3 This is a flowchart illustrating the process of calculating the turn-off angle compensation amount based on the difference in the embedded DC subsequent commutation failure suppression method based on the turn-off angle compensation of the present invention.

[0040] This invention relates to an embedded DC subsequent commutation failure suppression method based on turn-off angle compensation, comprising:

[0041] Step S1: Construct a simulation model of an AC / DC hybrid power grid with embedded DC, and monitor in real time the trigger lead angle of the constant current control output and the trigger lead angle of the constant turn-off angle control output of the embedded DC inverter side controller.

[0042] Step S2: Calculate the difference between the trigger lead angle of the constant turn-off angle control output and the trigger lead angle of the constant current control output;

[0043] Step S3: Compare the difference with a preset trigger threshold, and trigger the shutdown angle compensation mechanism when the difference is greater than or equal to the preset trigger threshold;

[0044] Step S4: After the shutdown angle compensation mechanism is triggered, the shutdown angle compensation amount is calculated based on the difference, and the shutdown angle compensation amount is superimposed on the shutdown angle reference value to generate the compensated shutdown angle reference value.

[0045] First, a simulation model of an AC / DC hybrid power grid with embedded DC is constructed. Simulation analysis clarifies that after a fault at the embedded DC sending end, the receiving end AC bus experiences a voltage drop, resulting in the first commutation failure. After the fault is cleared, a second commutation failure occurs due to the interaction of the controllers. Therefore, compensation is applied to the turn-off angle near the secondary switching point of the inverter-side control strategy, adjusting the trigger lead angles calculated by the two controllers (β0 and β1 respectively). G With β C The difference (denoted as Δβ) generated is used as the compensation trigger signal.

[0046] Specifically, in step S1, constructing a simulation model of an AC / DC hybrid power grid with embedded DC includes:

[0047] S11. Determine the topology of the embedded DC transmission system, the topology including a sending-end AC grid, a rectifier station, a DC line, an inverter station and a receiving-end AC grid, wherein the sending-end AC grid and the receiving-end AC grid are connected by at least one AC tie line to form a sending-end coupled network structure;

[0048] S12. Configure a control system for the rectifier station and the inverter station, wherein the inverter-side controller includes at least constant turn-off angle control and constant current control, and can output their respective trigger lead angle signals;

[0049] S13. Build the aforementioned topology and control system in electromagnetic transient simulation software, and set the sending-end AC bus as the fault simulation point.

[0050] Specifically, in step S2, the difference is the trigger lead angle of the constant turn-off angle control output minus the trigger lead angle of the constant current control output.

[0051] In this embodiment of the invention, the trigger lead angle β of the constant current control output C The trigger lead angle β of the output controlled by the fixed turn-off angle G Calculate the difference between the two, Δβ = β G -β C .

[0052] Specifically, in step S3, the preset trigger threshold is determined by analyzing the dynamic curve of the trigger lead angle difference between the constant turn-off angle control and constant current control on the inverter side during the system recovery process after fault clearance, wherein the preset trigger threshold is a negative value.

[0053] In this embodiment of the invention, a series of typical faults (such as three-phase metallic grounding and grounding through different inductive reactances) are set on the sending-end bus at 2s, and the fault duration is fixed at 0.1 seconds. Batch simulation is performed, and the system recovery process after the fault is cleared (e.g., starting from 2.1 seconds) is recorded in detail. The key acquisition variables are two trigger lead angles calculated in real time by the inverter-side controller: the fixed turn-off angle control output β. G and constant current control output β C According to the formula Δβ=β G -β C The difference is calculated in real time; the curves of Δβ changing with time obtained from multiple simulations are plotted on the same graph, forming a "dynamic curve cluster of trigger lead angle difference during fault recovery"; by analyzing the curve cluster, a common key phenomenon is found: in the initial stage after fault clearance, due to the dynamic process of the system, β G It will be temporarily less than β C (i.e., CC control is dominant, β) C (The larger the value), the negative Δβ is caused, but as the system recovers, the shut-off angle recovers, and β... G It will rapidly increase and surpass β C This causes Δβ to change from negative to positive, switching back to CEA control mode. As the CEC control output decreases and eventually exits, the risk of subsequent commutation failure increases significantly. Observations show that in simulations where subsequent commutation failure occurs, after the Δβ curve first crosses a negative critical point (preferably -0.02 radians), the system typically experiences a sharp decrease in the turn-off angle within tens of milliseconds, falling below the safety limit (e.g., 7°). Therefore, through statistical analysis, to ensure reliability and provide a certain margin, a preset trigger threshold Δβ is set. trigger It is determined to be -0.02 radians (approximately -1.15°).

[0054] The negative threshold of this invention can sensitively capture the critical point where an unfavorable switch in the control mode is about to occur. At this time, the β value of the constant off-angle control... G The trigger lead angle β of the just-overclocked constant current control C The system is on the verge of switching from CC mode to CEA mode, but the actual sharp deterioration of the turn-off angle has not yet occurred. By analyzing a large number of dynamic curve clusters formed by simulation, the threshold is determined so that the triggering criterion can adapt to different fault types and system operation modes, avoiding further reduction of the turn-off angle, thereby suppressing the failure of continuous DC commutation and the violent oscillation of DC power, making the system recovery process after the fault more stable and orderly.

[0055] Specifically, in step S4, calculating the shut-off angle compensation amount based on the difference includes:

[0056] Step S41: Set a compensation termination threshold;

[0057] Step S42: Compare the difference with the preset trigger threshold and the compensation end threshold;

[0058] Step S43: When the difference is less than the preset trigger threshold, the shut-off angle compensation amount is set to zero.

[0059] Step S44: When the difference is within the range formed by the preset trigger threshold and the compensation end threshold, a dynamic shut-off angle compensation amount that monotonically decreases as the difference increases is calculated according to the predefined compensation function.

[0060] Step S45: When the difference is greater than or equal to the compensation end threshold, the shut-off angle compensation amount is set to zero.

[0061] In this embodiment of the invention, after the compensation mechanism is triggered, the reference value γ of the shut-off angle is... ref Apply a dynamic compensation amount The compensation amount is initially a positive value (e.g., 0.174 rad) and decreases linearly as Δβ increases. A preset compensation termination threshold Δβ is defined. end (e.g., 0.05 rad), when Δβ ≥ Δβ end When the compensation amount decreases to zero, the compensation process ends. The compensation logic can be expressed by the following formula:

[0062] If Δβ ​​< Δβ trigger ,but =0;

[0063] If Δβ trigger ≤Δβ<Δβ end ,but , Decrease linearly;

[0064] If Δβ≥Δβ end ,but =0.

[0065] Specifically, in step S41, the compensation end threshold is determined by analyzing the dynamic curve of the trigger lead angle difference between the constant turn-off angle control and constant current control on the inverter side during the system recovery process after fault clearance, wherein the compensation end threshold is a positive value.

[0066] In the embodiment of this invention, under the same fault simulation case, after the compensation mechanism is triggered, the dynamic curve of Δβ is continuously observed; as the system further recovers, the AC voltage on the inverter side continues to rise, the DC current tends to stabilize, and the β output by the constant current controller... C It begins to decrease. Simultaneously, the shut-off angle begins to decrease, and the β output of the fixed shut-off angle controller... GAs the difference between the two values ​​begins to increase, the difference Δβ increases monotonically from a negative value. Analysis of the curve cluster reveals that when Δβ recovers to zero and continues to increase to a specific positive value, it can be used as a sign that the system compensation can safely exit. Statistical analysis of multiple successful recovery simulation cases shows that when Δβ reaches 0.05 radians (approximately 2.87°), the system does not experience commutation failures in the subsequent process. Therefore, the compensation termination threshold Δβ is set as... end The value is set at 0.05 radians.

[0067] This invention, by setting a positive compensation termination threshold, enables the system to automatically and accurately determine the moment when the risk is eliminated. Once Δβ reaches this threshold, the compensation amount immediately returns to zero, avoiding unnecessary compensation even after the system has returned to normal. This prevents the negative impact that could occur on the steady-state operation of the system due to long-term artificial raising of the shut-off angle (such as increased reactive power consumption), ensuring the accuracy and timeliness of the suppression strategy. The invention employs a dynamic compensation mechanism that decreases linearly with increasing Δβ, ensuring that the compensation amount of the shut-off angle reference value is a smooth transition rather than a step-like abrupt change. As the system's Δβ gradually improves, the compensation amount decreases synchronously and linearly, allowing the compensated shut-off angle reference value to return to the original set value without disturbance and gradually. The smooth exit process effectively prevents power or voltage oscillations that may occur at the moment of compensation removal, greatly improving the stability of the system recovery process after a fault.

[0068] Specifically, in step S44, the dynamic shutdown angle compensation amount is:

[0069] ;

[0070] in, Δβ represents the dynamic shut-off angle compensation amount, and Δβ is the difference.

[0071] Specifically, the predefined compensation function is configured to: output a preset maximum shut-off angle compensation amount when the difference is equal to the preset trigger threshold; and continuously decrease the dynamic shut-off angle compensation amount from the maximum shut-off angle compensation amount to zero when the difference increases from the preset trigger threshold to the compensation end threshold.

[0072] In this embodiment of the invention, the predefined compensation function is a linear compensation function. When Δβ = -0.02 rad, the initial compensation amount is... Set to 0.124 rad (the preset maximum shut-off angle compensation, which can be determined through electromagnetic transient simulation), during the process of Δβ increasing from -0.02 rad to 0.05 rad, According to the formula It decreases linearly until it reaches 0.

[0073] Specifically, in step S4, adding the shut-off angle compensation amount to the shut-off angle reference value includes:

[0074] The real-time calculated shut-off angle compensation is algebraically added to the original shut-off angle reference value in the inverter-side controller to generate a compensated shut-off angle reference value, which is then used as the new tracking target for the fixed shut-off angle control loop in the inverter-side controller.

[0075] In this embodiment of the invention, the compensated shut-off angle reference value is γ' ref =γ ref + .

[0076] This invention uses a linear compensation function to adjust the shut-off angle compensation amount. It forms a precise mapping relationship with the difference Δβ, providing full compensation when a control strategy switch is imminent, forcibly expanding the margin to withstand the most severe shocks; as the system recovers, the compensation amount decreases linearly, and the commutation margin smoothly reverts to the normal operating value. The linear function ensures that the compensation amount... It changes continuously and smoothly when compared with the original shut-off angle reference value γ. ref The new reference value γ' generated when performing a simple algebraic addition. ref It is also a smoothly changing signal. The inverter-side turn-off angle control loop tracks this smoothly changing reference value, so that the phase of the actual trigger pulse and the actual turn-off angle can achieve a smooth transition. This avoids secondary oscillations in DC power, voltage or current caused by step or sudden changes in compensation amount, and greatly improves the recovery quality and transient stability of the entire AC / DC system after fault clearing.

[0077] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. An embedded DC subsequent commutation failure suppression method based on turn-off angle compensation, characterized in that, include: Step S1: Construct a simulation model of an AC / DC hybrid power grid with embedded DC, and monitor in real time the trigger lead angle of the constant current control output and the trigger lead angle of the constant turn-off angle control output of the embedded DC inverter side controller. Step S2: Calculate the difference between the trigger lead angle of the constant turn-off angle control output and the trigger lead angle of the constant current control output; Step S3: Compare the difference with a preset trigger threshold, and trigger the shutdown angle compensation mechanism when the difference is greater than or equal to the preset trigger threshold; Step S4: After the shutdown angle compensation mechanism is triggered, the shutdown angle compensation amount is calculated based on the difference, and the shutdown angle compensation amount is superimposed on the shutdown angle reference value to generate the compensated shutdown angle reference value.

2. The embedded DC subsequent commutation failure suppression method based on turn-off angle compensation according to claim 1, characterized in that, In step S1, constructing a simulation model of an AC / DC hybrid power grid with embedded DC includes: S11. Determine the topology of the embedded DC transmission system, the topology including a sending-end AC grid, a rectifier station, a DC line, an inverter station and a receiving-end AC grid, wherein the sending-end AC grid and the receiving-end AC grid are connected by at least one AC tie line to form a sending-end coupled network structure; S12. Configure a control system for the rectifier station and the inverter station, wherein the inverter-side controller includes at least constant turn-off angle control and constant current control, and can output their respective trigger lead angle signals; S13. Build the aforementioned topology and control system in electromagnetic transient simulation software, and set the sending-end AC bus as the fault simulation point.

3. The embedded DC subsequent commutation failure suppression method based on turn-off angle compensation according to claim 1, characterized in that, In step S2, the difference is the trigger lead angle of the constant turn-off angle control output minus the trigger lead angle of the constant current control output.

4. The embedded DC subsequent commutation failure suppression method based on turn-off angle compensation according to claim 1, characterized in that, In step S3, the preset trigger threshold is determined by analyzing the dynamic curve of the trigger lead angle difference between the constant turn-off angle control and constant current control on the inverter side during the system recovery process after fault clearance, wherein the preset trigger threshold is a negative value.

5. The embedded DC subsequent commutation failure suppression method based on turn-off angle compensation according to claim 1, characterized in that, In step S4, calculating the shut-off angle compensation amount based on the difference includes: Step S41: Set a compensation termination threshold; Step S42: Compare the difference with the preset trigger threshold and the compensation end threshold; Step S43: When the difference is less than the preset trigger threshold, the shut-off angle compensation amount is set to zero. Step S44: When the difference is within the range formed by the preset trigger threshold and the compensation end threshold, a dynamic shut-off angle compensation amount that monotonically decreases as the difference increases is calculated according to the predefined compensation function. Step S45: When the difference is greater than or equal to the compensation end threshold, the shut-off angle compensation amount is set to zero.

6. The embedded DC subsequent commutation failure suppression method based on turn-off angle compensation according to claim 5, characterized in that, In step S41, the compensation end threshold is determined by analyzing the dynamic curve of the difference in trigger lead angle between the constant turn-off angle control and the constant current control on the inverter side during the system recovery process after fault clearance, wherein the compensation end threshold is a positive value.

7. The embedded DC subsequent commutation failure suppression method based on turn-off angle compensation according to claim 5, characterized in that, In step S44, the dynamic shut-off angle compensation amount is: ； in, Δβ represents the dynamic shut-off angle compensation amount, and Δβ is the difference.

8. The embedded DC subsequent commutation failure suppression method based on turn-off angle compensation according to claim 5, characterized in that, The predefined compensation function is configured to output a preset maximum shut-off angle compensation amount when the difference is equal to the preset trigger threshold. When the difference increases from the preset trigger threshold to the compensation end threshold, the dynamic shut-off angle compensation amount continuously decreases from the maximum shut-off angle compensation amount to zero.

9. The embedded DC subsequent commutation failure suppression method based on turn-off angle compensation according to claim 1, characterized in that, In step S4, adding the shut-off angle compensation amount to the shut-off angle reference value includes: The real-time calculated shut-off angle compensation is algebraically added to the original shut-off angle reference value in the inverter-side controller to generate a compensated shut-off angle reference value, which is then used as the new tracking target for the fixed shut-off angle control loop in the inverter-side controller.

10. The embedded DC subsequent commutation failure suppression method based on turn-off angle compensation according to claim 8, characterized in that, The preset maximum shut-off angle compensation amount is determined through electromagnetic transient simulation.

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