A converter-grid hybrid control method and system

Abstract

This invention discloses a hybrid control method and system for converters integrated with grids. Specifically, it analyzes the inherent structural differences between grid-connected GFL and grid-connected GFM converter controls, constructing a GFL-GFM hybrid control model based on a shared dual-inner-loop architecture. It calculates the stability intervals of GFL and GFM control under different short-circuit ratios (SCRs), and determines the switching thresholds for GFL, GFM, and hybrid control modes based on the stability boundaries. Based on the stability regions of GFL and GFM modes, it determines the upper and lower SCR thresholds, and employs a hysteresis-based adaptive hybrid control strategy to dynamically adjust the hybrid weights according to SCR changes. This invention achieves stable operation and zero-disturbance switching of the converter under three control modes: grid-connected control, grid-connected control, and hybrid control. It effectively controls the voltage amplitude near the rated value, ensuring a high-quality power supply.

Description

Technical Field

[0001] This invention relates to the field of distributed power converter control, and in particular to a hybrid control method and system for converter and grid. Background Technology

[0002] Converters are core devices connecting distributed power sources to the power grid, responsible for bidirectional conversion between direct current (DC) and alternating current (AC), ensuring stable grid operation. They play a crucial role in scenarios such as renewable energy generation, industrial and commercial energy storage, and microgrids, supporting functions such as peak shaving and valley filling, frequency and voltage regulation, and emergency power supply. They are an important supporting technology for building new power systems. The core control of converters lies in achieving efficient bidirectional conversion of electrical energy and stable system operation. Based on power electronic conversion technology and combined with advanced control algorithms, they achieve dynamic management of voltage, current, power, and other dimensions.

[0003] Converter control strategies are generally divided into two main types: "Grid Following (GFL)" and "Grid Forming (GFM)". A grid-following control system is essentially a current source and cannot provide voltage and frequency support itself, relying entirely on the grid voltage and frequency. In grid-following mode, the converter accurately captures the grid's phase information and measures the phase at the grid connection point (PCC) using a phase-locked loop (PLL) to achieve synchronization with the grid. However, this control strategy means that distributed generation cannot provide voltage and frequency support itself and must rely on the stable voltage and frequency provided by the grid to operate normally. In islanded and off-grid modes, the system will not function properly. A grid-forming control system, on the other hand, is essentially a voltage source. It can output stable voltage and frequency, improving the converter's voltage and frequency support capabilities and enhancing the stability of the power system. Regarding frequency and inertia support, grid-forming energy storage systems release DC-side stored energy through control, which is equivalent to synchronous machine inertial mechanical energy or damping energy, thereby providing inertia response and oscillation suppression.

[0004] As the proportion of renewable energy in the power grid continues to increase, the dynamic characteristics of the power system are becoming increasingly complex, and its time-varying characteristics are becoming more pronounced. Single GFL or GFM control strategies are no longer sufficient to meet the requirements of wide-condition operation of the power grid. At the same time, existing grid switching control strategies force inactive loops into an open-loop state, causing their initial values ​​to deviate from the steady-state operating point. This initialization mismatch will inevitably cause significant transient phenomena during mode switching. Summary of the Invention

[0005] The purpose of this invention is to provide a converter-grid hybrid control method and system with high power point tracking accuracy, strong stability, and good robustness, so as to achieve global stability and zero-disturbance switching of the converter under a wide range of operating conditions.

[0006] The technical solution to achieve the purpose of this invention is: a converter and grid hybrid control method, comprising the following steps:

[0007] Step 1: Analyze the inherent structural differences between grid-connected GFL and grid-connected GFM converter control. The grid-connected GFL adopts a unified voltage control framework to ensure the structural consistency between the two, and then constructs a GFL-GFM hybrid control model based on a shared dual inner loop architecture.

[0008] Step 2: Analyze the stability of the GFL-GFM hybrid control model under different short-circuit ratios (SCRs), calculate the stability intervals of the grid-following GFL and grid-forming GFM control under different SCRs, and determine the switching thresholds for the three control modes—grid-following GFL, grid-forming GFM, and GFL-GFM hybrid—based on the stability boundary.

[0009] Step 3: Based on the stable range of the grid-following GFL and grid-connecting GFM control modes, a hysteresis-based hybrid proportional adaptive control strategy is adopted. This strategy avoids fluctuations in the hybrid coefficient caused by short-circuit ratio SCR oscillations while dynamically adjusting the hybrid weight of the grid-following system, thus adaptively maintaining the stable operation of the converter under all operating conditions.

[0010] A converter and grid hybrid control system, used to implement the aforementioned converter and grid hybrid control method, specifically includes:

[0011] The GFL-GFM hybrid control model construction module analyzes the inherent structural differences between grid-connected GFL and grid-connected GFM converter control. The grid-connected GFL adopts a unified voltage control framework to ensure the structural consistency between the two, and then constructs a GFL-GFM hybrid control model based on a shared dual inner loop architecture.

[0012] The mode switching threshold generation module analyzes the stability of the GFL-GFM hybrid control model under different short-circuit ratios (SCRs), calculates the stability intervals of the following-type GFL and the network-type GFM control under different SCRs, and determines the switching thresholds of the three control modes—following-type GFL, network-type GFM, and GFL-GFM hybrid—based on the stability boundary.

[0013] The dynamic weight adjustment module, based on the stable range of the grid-following GFL and grid-connecting GFM control modes, adopts a hysteresis-based adaptive control strategy for the mixed proportional control of the grid-following and grid-connecting modes. While avoiding the fluctuation of the mixing coefficient caused by the short-circuit ratio SCR oscillation, it realizes the dynamic adjustment of the mixed weight of the grid-following and grid-connecting modes, and adaptively maintains the stable operation of the converter under all operating conditions.

[0014] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the converter-grid hybrid control method.

[0015] An electronic device includes a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the computer instructions to implement the converter-grid hybrid control method.

[0016] A computer program product includes computer instructions for causing a computer to perform steps in the aforementioned converter-grid hybrid control method.

[0017] Compared with the prior art, the significant advantages of this invention are:

[0018] (1) The method of the present invention realizes stable operation and zero-disturbance switching of the converter in three modes: grid-connected control, grid-connected control and grid-connected hybrid control. It can effectively control the voltage amplitude near the rated value and ensure high-quality power supply.

[0019] (2) A novel GFL-GFM hybrid control architecture based on a shared inner loop is adopted. By designing a voltage-controlled GFL strategy, the inherent structural differences between GFL and GFM modes are effectively eliminated, and zero-disturbance switching between GFL and GFM modes is achieved.

[0020] (3) An adaptive hybrid proportional control strategy based on short-circuit ratio (SCR) is adopted. Based on the study of the stable boundary of GFL and GFM, a hysteresis mechanism-based method is adopted to dynamically adjust the hybrid ratio according to SCR, thereby ensuring the stable operation of the system under different SCR conditions. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating a hybrid control method for converters and grids according to the present invention.

[0022] Figure 2 This is a graph showing the variation of the mixing control ratio of the method of the present invention under different SCRs in the embodiments of the present invention.

[0023] Figure 3 This is a graph showing the power output results of the method of the present invention under SCR variation in an embodiment of the present invention.

[0024] Figure 4 This is a graph showing the frequency output results of the method of the present invention under SCR variation in an embodiment of the present invention.

[0025] Figure 5 This is a graph showing the voltage output result of the method of the present invention under SCR variation in an embodiment of the present invention. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 1 As shown, this invention provides a converter-grid hybrid control method, which dynamically adjusts the mixing ratio of grid-based control and grid-connected control to eliminate transient shocks caused by sudden state changes. This method achieves stable operation and zero-disturbance switching of the converter in three modes: grid-based control, grid-connected control, and hybrid grid-connected control. Specifically, it includes the following steps:

[0028] Step 1: Analyze the inherent structural differences between grid-connected GFL and grid-connected GFM converter control. The grid-connected GFL adopts a unified voltage control framework to ensure the structural consistency between the two, and then constructs a GFL-GFM hybrid control model based on a shared dual inner loop architecture.

[0029] Step 2: Analyze the stability of the GFL-GFM hybrid control model under different short-circuit ratios (SCRs), calculate the stability intervals of the grid-following GFL and grid-forming GFM control under different SCRs, and determine the switching thresholds for the three control modes—grid-following GFL, grid-forming GFM, and GFL-GFM hybrid—based on the stability boundary.

[0030] Step 3: Based on the stable range of the grid-following GFL and grid-connecting GFM control modes, a hysteresis-based hybrid proportional adaptive control strategy is adopted. This strategy avoids fluctuations in the hybrid coefficient caused by short-circuit ratio SCR oscillations while dynamically adjusting the hybrid weight of the grid-following system, thus adaptively maintaining the stable operation of the converter under all operating conditions.

[0031] As a specific example, the grid-type GFL mentioned in step 1 adopts a unified voltage control framework, specifically including:

[0032] Step 1.1: Convert the active power tracking error into a frequency deviation and add it to the grid frequency extracted by the phase-locked loop (PLL). The frequency correction amount generated by the control branch of the mesh-type GFL is obtained. :

[0033]

[0034] in, Indicates the converter reference power. This indicates the actual output power of the converter; Indicates the power frequency coupling gain; This refers to the proportional gain of the proportional-integral regulator in the active power regulation of the grid-type GFL. This indicates the integral gain of the proportional-integral regulator in the active power regulation of the grid-type GFL; Represents the Laplace operator;

[0035] right The internal phase angle is obtained by time integration, thereby realizing dynamic active power control;

[0036] Step 1.2: In reactive power regulation, the proportional controller converts the reactive power tracking error into... Shaft voltage reference value This adjusts the voltage amplitude difference between the converter and the power grid, as shown in the following formula:

[0037]

[0038] in, express Shaft reference voltage, express Shaft reference voltage; Indicates the system's rated voltage reference value; A reference value representing reactive power. This represents the actual output value of reactive power; This represents the reactive power regulation coefficient;

[0039] Shaft voltage reference value Keep it at 0 to ensure the voltage vector direction is correct;

[0040] The above formula is used to calculate and generate frequency and voltage commands for each control mode in real time.

[0041] As a specific example, the construction of the GFL-GFM hybrid control model based on a shared dual-inner-loop architecture described in step 1 specifically includes:

[0042] Step 1.3: Construct the power angle generation loop of the GFL-GFM hybrid control model and generate the power angle:

[0043] In the power angle generation stage, a hybrid synchronization architecture with a shared integrator is adopted to eliminate phase interruption and integral saturation problems caused by inconsistent phase reference values ​​during mode switching. The hybrid synchronization architecture performs hybrid processing at the angular frequency level, as shown in the following equation:

[0044]

[0045] in, Indicates the synthesized angular frequency. Indicates the reference angular frequency; This represents the frequency correction amount generated by the control branch of the network-type GFM; This indicates the frequency correction amount generated by the control branch of the mesh-type GFL; This represents the weighting coefficient of the network-based GFM control mode in the hybrid synchronization architecture. This represents the weighting coefficient of the network-type GFL control mode in the hybrid synchronization architecture, and ;

[0046] By synthesizing angular frequency Time of progress Integrating yields the final output power angle. ;

[0047] Step 1.4: Construct the reference voltage generation loop for the GFL-GFM hybrid control model and generate the reference voltage:

[0048] To ensure a smooth transition of the outer loop voltage control characteristics between the grid-fed GFL control mode and the network-based GFM control mode, weighting coefficients are used. , The voltage reference components generated by the two control modes are weighted and mixed, and then synthesized into a unified value using the following formula. Shaft voltage reference value :

[0049]

[0050] in, This represents the reactive power regulation coefficient under the grid-type GFL control mode. This represents the reactive power regulation gain under the network-type GFM control mode. This represents the voltage compensation coefficient under the network-type GFM control mode; Indicates reactive power deviation. This indicates the voltage deviation. express Shaft voltage reference value.

[0051] As a specific example, the active power open-loop transfer function of the GFL-GFM hybrid control model in step 2 Reactive power open-loop transfer function The details are as follows:

[0052]

[0053] in, This represents the transfer function of a phase-locked loop (PLL). This represents the virtual inertia of a network-type GFM control loop. This represents the damping coefficient of the network-type GFM control loop. This represents the steady-state value of the converter port voltage. This indicates the active power regulation gain under the grid-type GFL control mode. This represents the equivalent resistance of the power grid. Represents the equivalent inductance of the power grid;

[0054] intermediate variables , and They are shown below:

[0055]

[0056] in, This represents a quadratic polynomial related to the grid impedance. This represents the coefficient related to the reactive power loop. This represents a coefficient related to the active power loop. Indicates the voltage of the power grid bus. Indicates the steady-state power angle. Indicates the power grid impedance angle. Indicates the short-circuit ratio. This indicates the rated power of the converter.

[0057] As a specific example, step 2 determines the switching thresholds for the three control modes: network-based GFL, network-based GFM, and GFL-GFM hybrid, as follows:

[0058] Step 2.2.1: Under the network-type GFM control mode, the closed-loop characteristic equation of the active power loop is:

[0059]

[0060] in, The system gain coefficient related to the active power loop is expressed as follows:

[0061]

[0062] According to the Routh-Hurwitz criterion, the critical condition for a fourth-order system to remain stable is:

[0063]

[0064] in, , , , , The coefficients of the characteristic equation are:

[0065]

[0066] in, This indicates the damping ratio under the network-type GFM control mode. This represents the natural oscillation angular frequency under the network-type GFM control mode;

[0067] By substituting the coefficients into the characteristic equation to solve for the short-circuit ratio (SCR), the upper limit of the stability of the active power loop under the network-type GFM control mode can be obtained. for:

[0068]

[0069] For reactive power loops, the characteristic equation is used. Through derivation, the upper limit of the reactive power loop in the network-type GFM control mode is obtained. for:

[0070]

[0071] in, The system gain coefficient related to the reactive power loop is expressed as follows:

[0072]

[0073] Finally, the high stability boundary of the network-based GFM control mode is defined as:

[0074]

[0075] in, This refers to the upper limit of SCR in hybrid adaptive control.

[0076] Step 2.2.2: In the grid-connected GFL control mode, the instability factor originates from the coupling effect between the phase-locked loop (PLL) and the weak power grid. The active power characteristic equation is derived as follows:

[0077]

[0078] in, The equivalent coefficients of the phase-locked loop (PLL);

[0079] If the PLL bandwidth is set much lower than the grid resonant frequency, the stability boundary of the active power loop is governed by monotonically divergent rather than oscillatory dynamics. By evaluating the characteristic equation under the static stability limit, the lower limit SCR critical value of the active power loop is obtained:

[0080]

[0081] in, The lower limit of the stability of the active power loop under the grid-type GFL control mode;

[0082] For reactive power loops, the lower limit value is obtained through a simplified stability criterion:

[0083]

[0084] in, The lower limit of the stability of the reactive power loop under the grid-type GFL control mode;

[0085] The final stability boundary of the mesh-type GFL control mode:

[0086]

[0087] in, This refers to the lower limit of SCR in hybrid adaptive control.

[0088] The derived grid stability boundary is directly assigned to the converter control mode switching threshold, i.e., set and ;

[0089] Step 2.2.3: The control mode switching threshold is represented by the following piecewise function:

[0090]

[0091] in, This indicates the switching threshold between the mesh-type GFL control mode and the GFL-GFM hybrid control mode. This indicates the switching threshold between the GFL-GFM hybrid control mode and the network-type GFM control mode.

[0092] As a specific example, the hybrid proportional adaptive control strategy based on the hysteresis mechanism in step 3 is as follows:

[0093] An improved Sigmoid function is used to dynamically adjust the weighting factor based on the SCR, determining the mixing ratio of network-following GFL and network-building GFM characteristics, as shown below:

[0094]

[0095] in, Slope factor As an upward transition center, As the descent transition center;

[0096] The improved Sigmoid function is as follows:

[0097]

[0098] in, ;

[0099] The Sigmoid function To achieve 95% transition within the input range, and to ensure full dynamic mixing within the designed SCR margin, the slope factor... The following criteria must be met:

[0100]

[0101] The present invention also provides a converter and grid hybrid control system, which is used to implement the aforementioned converter and grid hybrid control method, specifically including:

[0102] The GFL-GFM hybrid control model construction module analyzes the inherent structural differences between grid-connected GFL and grid-connected GFM converter control. The grid-connected GFL adopts a unified voltage control framework to ensure the structural consistency between the two, and then constructs a GFL-GFM hybrid control model based on a shared dual inner loop architecture.

[0103] The mode switching threshold generation module analyzes the stability of the GFL-GFM hybrid control model under different short-circuit ratios (SCRs), calculates the stability intervals of the following-type GFL and the network-type GFM control under different SCRs, and determines the switching thresholds of the three control modes—following-type GFL, network-type GFM, and GFL-GFM hybrid—based on the stability boundary.

[0104] The dynamic weight adjustment module, based on the stable range of the grid-following GFL and grid-connecting GFM control modes, adopts a hysteresis-based adaptive control strategy for the mixed proportional control of the grid-following and grid-connecting modes. While avoiding the fluctuation of the mixing coefficient caused by the short-circuit ratio SCR oscillation, it realizes the dynamic adjustment of the mixed weight of the grid-following and grid-connecting modes, and adaptively maintains the stable operation of the converter under all operating conditions.

[0105] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the converter-grid hybrid control method.

[0106] The present invention also provides an electronic device, comprising: a memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the computer instructions to realize the converter-grid hybrid control method.

[0107] The present invention also provides a computer program product, including computer instructions, which are used to cause a computer to execute the steps in the converter and grid hybrid control method.

[0108] Example

[0109] This embodiment further verifies the control effect of the proposed method through simulation examples; an electromagnetic transient model of the distributed power supply control system was established in MATLAB / SIMULINK, and a comprehensive analysis was conducted within the SCR range from 1 to 65.

[0110] Figure 2 This demonstrates the dynamic behavior of distributed resources over the entire period of grid strength variation under different SCR values. The SCR value changes from a minimum of 1 to a maximum of 65, and then returns to 1, thus covering various scenarios from ultra-weak to rigid grids. Figure 3 and Figure 4 As shown, the method of the present invention maintains accurate power point tracking throughout the entire process. Furthermore, the proposed method exhibits excellent robustness in frequency regulation. Figure 5 The voltage waveform shows that the method of the present invention effectively controls the voltage amplitude near the rated value and significantly suppresses ripple, thereby ensuring a high-quality power supply.

[0111] The above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and are not intended to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the scope of the technology disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention.

Claims

1. A converter and grid hybrid control method, characterized in that, Includes the following steps: Step 1: Analyze the inherent structural differences between grid-connected GFL and grid-connected GFM converter control. The grid-connected GFL adopts a unified voltage control framework to ensure the structural consistency between the two, and then constructs a GFL-GFM hybrid control model based on a shared dual inner loop architecture. Step 2: Analyze the stability of the GFL-GFM hybrid control model under different short-circuit ratios (SCRs), calculate the stability intervals of the grid-following GFL and grid-forming GFM control under different SCRs, and determine the switching thresholds for the three control modes—grid-following GFL, grid-forming GFM, and GFL-GFM hybrid—based on the stability boundary. Step 3: Based on the stable range of the grid-following GFL and grid-connecting GFM control modes, a hysteresis-based hybrid proportional adaptive control strategy is adopted. This strategy avoids fluctuations in the hybrid coefficient caused by short-circuit ratio SCR oscillations while dynamically adjusting the hybrid weight of the grid-following system, thus adaptively maintaining the stable operation of the converter under all operating conditions.

2. The converter and grid hybrid control method according to claim 1, characterized in that, The grid-connected GFL mentioned in step 1 adopts a unified voltage control framework, specifically including: Step 1.1: Convert the active power tracking error into a frequency deviation and add it to the grid frequency extracted by the phase-locked loop (PLL). The frequency correction amount generated by the control branch of the mesh-type GFL is obtained. : in, Indicates the converter reference power. This indicates the actual output power of the converter; Indicates the power frequency coupling gain; This refers to the proportional gain of the proportional-integral regulator in the active power regulation of the grid-type GFL. This indicates the integral gain of the proportional-integral regulator in the active power regulation of the grid-type GFL; Represents the Laplace operator; right The internal phase angle is obtained by time integration, thereby realizing dynamic active power control; Step 1.2: In reactive power regulation, the proportional controller converts the reactive power tracking error into... Shaft voltage reference value This adjusts the voltage amplitude difference between the converter and the power grid, as shown in the following formula: in, express Shaft reference voltage, express Shaft reference voltage; Indicates the system's rated voltage reference value; A reference value representing reactive power. This represents the actual output value of reactive power; This represents the reactive power voltage regulation coefficient.

3. The converter and grid hybrid control method according to claim 2, characterized in that, Step 1, which describes constructing a GFL-GFM hybrid control model based on a shared dual-inner-loop architecture, specifically includes: Step 1.3: Construct the power angle generation loop of the GFL-GFM hybrid control model and generate the power angle: In the power angle generation stage, a hybrid synchronization architecture with a shared integrator is adopted to eliminate phase interruption and integral saturation problems caused by inconsistent phase reference values ​​during mode switching. The hybrid synchronization architecture performs hybrid processing at the angular frequency level, as shown in the following equation: in, Indicates the synthesized angular frequency. Indicates the reference angular frequency; This represents the frequency correction amount generated by the control branch of the network-type GFM; This indicates the frequency correction amount generated by the control branch of the mesh-type GFL; This represents the weighting coefficient of the network-based GFM control mode in the hybrid synchronization architecture. This represents the weighting coefficient of the network-type GFL control mode in the hybrid synchronization architecture, and ; By synthesizing angular frequency Time of progress Integrating yields the final output power angle. ; Step 1.4: Construct the reference voltage generation loop for the GFL-GFM hybrid control model and generate the reference voltage: To ensure a smooth transition of the outer loop voltage control characteristics between the grid-fed GFL control mode and the network-based GFM control mode, weighting coefficients are used. , The voltage reference components generated by the two control modes are weighted and mixed, and then synthesized into a unified value using the following formula. Shaft voltage reference value : in, This represents the reactive power regulation coefficient under the grid-type GFL control mode. This represents the reactive power regulation gain under the network-type GFM control mode. This represents the voltage compensation coefficient under the network-type GFM control mode; Indicates reactive power deviation. This indicates the voltage deviation. express Shaft voltage reference value.

4. The converter and grid hybrid control method according to claim 3, characterized in that, The active power open-loop transfer function of the GFL-GFM hybrid control model in step 2 Reactive power open-loop transfer function The details are as follows: in, This represents the transfer function of a phase-locked loop (PLL). This represents the virtual inertia of a network-type GFM control loop. This represents the damping coefficient of the network-type GFM control loop. This represents the steady-state value of the converter port voltage. This indicates the active power regulation gain under the grid-type GFL control mode. This represents the equivalent resistance of the power grid. Represents the equivalent inductance of the power grid; intermediate variables , and They are shown below: in, This represents a quadratic polynomial related to the grid impedance. This represents the coefficient related to the reactive power loop. This represents a coefficient related to the active power loop. Indicates the voltage of the power grid bus. Indicates the steady-state power angle. Indicates the power grid impedance angle. Indicates the short-circuit ratio. This indicates the rated power of the converter.

5. The converter and grid hybrid control method according to claim 4, characterized in that, Step 2 determines the switching thresholds for the three control modes: GFL (Government FL), GFM (Government FL-GFM), and a hybrid GFL-GFM control mode, as follows: Step 2.2.1: Under the network-type GFM control mode, the closed-loop characteristic equation of the active power loop is: in, The system gain coefficient related to the active power loop is expressed as follows: According to the Routh-Hurwitz criterion, the critical condition for a fourth-order system to remain stable is: in, , , , , The coefficients of the characteristic equation are: in, This indicates the damping ratio under the network-type GFM control mode. This represents the natural oscillation angular frequency under the network-type GFM control mode; By substituting the coefficients into the characteristic equation to solve for the short-circuit ratio (SCR), the upper limit of the stability of the active power loop under the network-type GFM control mode can be obtained. for: For reactive power loops, the characteristic equation is used. Through derivation, the upper limit of the reactive power loop in the network-type GFM control mode is obtained. for: in, The system gain coefficient related to the reactive power loop is expressed as follows: Finally, the high stability boundary of the network-based GFM control mode is defined as: in, This refers to the upper limit of SCR in hybrid adaptive control. Step 2.2.2: In the grid-connected GFL control mode, the instability factor originates from the coupling effect between the phase-locked loop (PLL) and the weak power grid. The active power characteristic equation is derived as follows: in, The equivalent coefficients of the phase-locked loop (PLL); If the PLL bandwidth is set much lower than the grid resonant frequency, the stability boundary of the active power loop is governed by monotonically divergent rather than oscillatory dynamics. By evaluating the characteristic equation under the static stability limit, the lower limit SCR critical value of the active power loop is obtained: in, The lower limit of the stability of the active power loop under the grid-type GFL control mode; For reactive power loops, the lower limit value is obtained through a simplified stability criterion: in, The lower limit of the stability of the reactive power loop under the grid-type GFL control mode; The final stability boundary of the mesh-type GFL control mode: in, This refers to the lower limit of SCR in hybrid adaptive control. The derived grid stability boundary is directly assigned to the converter control mode switching threshold, i.e., set and ; Step 2.2.3: The control mode switching threshold is represented by the following piecewise function: in, This indicates the switching threshold between the mesh-type GFL control mode and the GFL-GFM hybrid control mode. This indicates the switching threshold between the GFL-GFM hybrid control mode and the network-type GFM control mode.

6. The converter and grid hybrid control method according to claim 5, characterized in that, The hybrid proportional adaptive control strategy based on the hysteresis mechanism in step 3 is as follows: An improved Sigmoid function is used to dynamically adjust the weighting factor based on the SCR, determining the mixing ratio of network-following GFL and network-building GFM characteristics, as shown below: in, Slope factor As an upward transition center, As the descent transition center; The improved Sigmoid function is as follows: in, ; The Sigmoid function To achieve 95% transition within the input range, and to ensure full dynamic mixing within the designed SCR margin, the slope factor... The following criteria must be met: 。 7. A converter-grid hybrid control system, characterized in that, This system is used to implement the converter and grid hybrid control method according to any one of claims 1 to 6, specifically including: The GFL-GFM hybrid control model construction module analyzes the inherent structural differences between grid-connected GFL and grid-connected GFM converter control. The grid-connected GFL adopts a unified voltage control framework to ensure the structural consistency between the two, and then constructs a GFL-GFM hybrid control model based on a shared dual inner loop architecture. The mode switching threshold generation module analyzes the stability of the GFL-GFM hybrid control model under different short-circuit ratios (SCRs), calculates the stability intervals of the following-type GFL and the network-type GFM control under different SCRs, and determines the switching thresholds of the three control modes—following-type GFL, network-type GFM, and GFL-GFM hybrid—based on the stability boundary. The dynamic weight adjustment module, based on the stable range of the grid-following GFL and grid-connecting GFM control modes, adopts a hysteresis-based adaptive control strategy for the mixed proportional control of the grid-following and grid-connecting modes. While avoiding the fluctuation of the mixing coefficient caused by the short-circuit ratio SCR oscillation, it realizes the dynamic adjustment of the mixed weight of the grid-following and grid-connecting modes, and adaptively maintains the stable operation of the converter under all operating conditions.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps in the converter and grid hybrid control method as described in any one of claims 1 to 6.

9. An electronic device, characterized in that, include: The system includes a memory and a processor, which are interconnected. The memory stores computer instructions, and the processor executes the computer instructions to implement the converter-grid hybrid control method as described in any one of claims 1 to 6.

10. A computer program product, characterized in that, Includes computer instructions, which are used to cause a computer to perform the steps in the converter and grid hybrid control method according to any one of claims 1 to 6.

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