A method and system for inertia response optimization of grid-forming converters in a power system

Abstract

The application relates to a grid-forming converter inertia response optimization method and system in a power system, and the method comprises the following steps: 1. detecting the frequency of a grid-connected point in real time and calculating the frequency change rate; 2. triggering an additional fast power response control when the frequency change rate exceeds a threshold value; 3. calculating a phase angle feedforward amount according to the rated capacity and the active power instruction; 4. superimposing the phase angle feedforward amount on the phase angle generated by a rotor swing equation and synchronously applying a power instruction adjustment amount at the input end of the equation; 5. maintaining the expected output operation of the converter until a significant reverse frequency disturbance occurs or a superior power adjustment instruction is received; and 6. not triggering the additional control when the frequency change rate is lower than a preset threshold value, and keeping the original VSG steady-state operation characteristic of the grid-forming converter. The application can improve the inertia response speed of the grid-forming converter, establish short-time emergency inertia support when the power grid frequency fluctuates, effectively suppress the power grid frequency fluctuation, and guarantee the frequency stability of the whole power system.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, specifically relating to a method and system for optimizing the inertia response of a grid-type converter in a power system. Background Technology

[0002] With the accelerated pace of global energy transition, renewable energy sources, represented by wind power and solar power, have become the mainstay of new power system installations. Unlike traditional synchronous generators, wind power and solar power are connected to the grid via power electronic converters. Their core control strategy generally adopts a grid-following architecture, exhibiting controlled current source characteristics. They rely entirely on the grid to provide stable voltage and frequency references for synchronous operation, lacking their own rotational inertia and damping characteristics, and thus unable to provide the necessary voltage and frequency support to the grid. As the penetration rate of renewable energy continues to increase, the proportion of traditional synchronous generators in the power system continues to decline, resulting in a significant decrease in the overall rotational inertia level of the system. To address the inertia deficiency problem in high-proportion renewable energy power systems, grid-connected converter technology has emerged. Grid-connected converters adopt a voltage source control architecture, simulating the operating characteristics of synchronous generators to autonomously construct the grid's voltage and frequency, possessing inherent virtual inertia and damping support capabilities. Its core control element is virtual synchronous generator technology. By introducing control mechanisms such as rotor oscillation equation control, active power-frequency droop control, and reactive power-voltage droop control, the converter possesses external characteristics similar to a synchronous generator, enabling it to actively respond to grid frequency and voltage fluctuations and provide inertia support for the system. Compared to grid-connected converters, grid-connected converters do not rely on grid voltage and frequency references and can operate stably in weak grid conditions or even off-grid environments. They are core and key equipment for building all-power electronic new power systems and are widely recognized as the main power source for future high-proportion renewable energy power systems.

[0003] However, the inertial response characteristics of current grid-type converters still have significant shortcomings and cannot fully meet the grid's demand for fast frequency support. The natural inertial response of grid-type converters is realized by the rotor oscillation equation, and its active power response to grid frequency changes exhibits typical second-order system dynamic characteristics, with the response speed dependent on the inertial time constant. H Strict constraints. According to the rotor oscillation equation, the inertial time constant... H The larger the inertia, the greater the virtual inertia provided by the converter, and the stronger its ability to suppress the rate of frequency change. However, at the same time, the natural oscillation frequency of the second-order system is lower, and the active power response speed is slower. This leads to a fundamental contradiction: the grid-type converter with stronger inertia support capability has a slower inertia response speed. When the grid experiences rapid frequency fluctuations, it cannot provide sufficient power support in time and is difficult to effectively suppress frequency drops.

[0004] In addition, existing inertia testing standards for grid-connected converters are all based on the design concept of "supporting power source," assessing their inertia support capability by injecting frequency disturbances into the grid and detecting the active power response time of the converter. This testing method is inherently more suitable for grid-connected converters, which contradicts the essential characteristic of grid-connected converters as "main power sources." Under this testing standard, grid-connected converters with smaller inertia time constants obtain better test results due to their faster response speed, while converters with larger inertia time constants and stronger inertia support capabilities often fail the test.

[0005] Therefore, there is a need for a method and system that can overcome the second-order system response speed limit while preserving the true grid-connected characteristics of grid-connected converters, significantly improve the power response speed of grid-connected converters under frequency disturbances, and effectively suppress grid frequency fluctuations, so as to solve the above-mentioned technical problems. Summary of the Invention

[0006] This invention aims to optimize the inertial response speed of grid-connected converters in power systems. It addresses the problem that a larger inertial time constant leads to a slower inertial response speed due to limitations imposed by the second-order active power loop model in traditional grid-connected control. This allows grid-connected converters with large inertial time constants and strong frequency support capabilities to respond quickly to system frequency fluctuations, providing substantial active power support in a short time, thereby stabilizing the system frequency and promoting stable power system operation.

[0007] This invention provides the following technical solution: a method for optimizing the inertia response of a grid-type converter in a power system, comprising the following steps: Step S1: Real-time detection of the frequency at the grid connection point of the grid-connected converter, and calculation of the grid frequency change rate.

[0008] Step S2: If the absolute value of the frequency change rate exceeds the set threshold, trigger the additional fast power response control of the active loop of the grid-type converter VSG control system.

[0009] Step S3: Based on the rated capacity of the converter and the current active power command, solve for the phase angle feedforward based on the active power transmission principle.

[0010] Step S4: The phase angle feedforward is superimposed on the output phase angle of the rotor oscillation equation, and a matching active power command adjustment is simultaneously applied at the input of the rotor oscillation equation.

[0011] Step S5: Control the converter to maintain the desired output operation until a significant reverse frequency disturbance occurs or a power regulation command is received from the upper level.

[0012] Step S6: If the frequency change rate is lower than the preset threshold, no additional control is triggered, and the original VSG steady-state operation characteristics of the grid-type converter are maintained.

[0013] Preferably, in step S1, the grid-connected converter operates in parallel with the grid, and the frequency of the grid at the grid connection point is collected by a frequency detection module; a filter is used to filter out high-frequency noise in the grid frequency, and the grid frequency change rate is calculated by a differential algorithm.

[0014] Preferably, in step S2, a preset frequency change threshold is set, and when the frequency change rate exceeds the threshold, the additional fast power response control is enabled, and the positive and negative directions of the frequency change rate are obtained using a sign function.

[0015] More preferably, in step S2, the active power loop of the grid-type converter control system includes an active power-frequency droop element and a rotor oscillation equation element. When the grid frequency change rate is detected to exceed the threshold, additional fast power response control is activated to improve the inertia response speed of the converter under large inertia parameters. Its inertia response natural oscillation frequency is inversely proportional to the inertia time constant. A larger inertia time constant can provide stronger inertia support, but the response speed is slower.

[0016] Preferably, in step S3, the maximum active power output that the current converter can provide is obtained by the difference between the rated capacity of the converter and the current active power command. The phase angle feedforward is then obtained by dividing this difference by the synchronization coefficient according to the active power transmission principle. (2) In the formula, X * This represents the per-unit value of the converter output impedance, and Sign(RoCoF) represents the sign function of the rate of change of frequency. E * This represents the per-unit value of the internal potential generated by the converter. U * This indicates the per-unit value of the converter output voltage. This indicates the per-unit value of the active command.

[0017] Under more optimized regulation conditions, the phase angle feedforward required for fast inertia response control can be determined based on the degree of grid frequency fluctuations. The desired inertia coefficient is then set. H exp The phase angle feedforward can be obtained by multiplying the desired inertia coefficient by the grid frequency change rate. The expression for the phase angle feedforward then satisfies: (3) Preferably, in step S4, a phase angle feedforward is superimposed on the phase angle output of the rotor swing equation, and the active power output of the grid converter is rapidly increased by directly changing the phase angle; at the same time, in order to avoid the additional phase difference generated by the feedforward being eliminated by the active power loop closed-loop control, a corresponding active power command adjustment is applied to the input of the rotor swing equation.

[0018] More preferably, in step S4, low-pass filtering is performed when applying phase angle feedforward to reduce the impact of high-frequency fluctuations in the phase angle feedforward on the system phase angle stability and avoid system instability.

[0019] Preferably, in step S5, after the additional fast power response control is triggered, the converter will maintain the desired output operation to provide continuous support to the grid until the next significant reverse disturbance occurs or the power regulation command from the upper level is received before changing the power command.

[0020] Preferably, in step S6, when there are slight fluctuations in the grid frequency during normal grid operation, if the slight fluctuations do not exceed the preset frequency change rate threshold, additional fast power response control is not triggered, and the grid-connected converter maintains the native grid-connected converter control steady-state operation without disrupting the long-term synchronization stability of the system.

[0021] This invention also discloses an inertia response optimization system for grid-connected converters in power systems. This optimization system is used to implement the above-described optimization method and includes: Frequency measurement module: used to synchronously acquire the grid connection point frequency of the grid-connected converter during grid-connected operation and calculate the grid frequency change rate.

[0022] Trigger Module: Used to determine whether the current grid frequency change rate exceeds a preset threshold. When the frequency fluctuation exceeds the threshold, it enables additional power response control and obtains the positive and negative directions of the frequency fluctuation.

[0023] Calculation module: used to calculate the phase angle feedforward and the matching active power command adjustment required for additional control.

[0024] Phase angle feedforward module: used to implement phase angle feedforward, superimposing the phase angle feedforward amount onto the phase angle generated by the grid control rotor oscillation equation.

[0025] Power command module: used to synchronously apply a matching active power command adjustment at the input of the rotor oscillation equation when phase angle feedforward is applied.

[0026] The beneficial effects of this invention are: 1. This invention breaks through the speed limitation of the second-order response characteristics of traditional grid-type converters by using phase angle feedforward and power command coordinated adjustment, which greatly shortens the inertia response time. It can quickly adjust the active power output of the converter to the desired output when the grid frequency fluctuates rapidly, make up for the active power deficit of the system, and effectively suppress grid frequency drops and oscillations.

[0027] 2. This invention does not change the essence of the original grid control of the converter. Its purpose is to actively adjust the output power when the grid frequency fluctuates significantly, thereby suppressing the grid frequency change and maintaining the grid frequency stability, rather than tracking the grid frequency change. This is consistent with the characteristics of grid control to actively build voltage and frequency, and can provide effective support for the grid.

[0028] 3. This invention adds control to the original active power loop control. In a multi-machine parallel system, since the response time scale of the added fast power response control loop is significantly smaller than that of the original power loop, its adjustment process is completed before the power loop adjustment begins. Therefore, it will not have dynamic interaction with the power loop. The power distribution between different converters is controlled by the original active power loop and will not be affected by the added control loop. Attached Figure Description

[0029] Figure 1 This is a flowchart of a method and system for optimizing the inertia response of a grid-type converter in a power system according to the present invention. Figure 2 This is a schematic diagram of the active power loop additional fast power response control structure of the VSG control system according to an embodiment of the present invention; Figure 3 This is a topology diagram of the grid-type converter inertia response test system according to an embodiment of the present invention; Figure 4 The diagram shows a comparison of the optimization effects of the inertia response of the grid-type converter in an embodiment of the present invention; where (a) is the active power response with additional control, (b) is the active power response without additional control, (c) is the grid frequency with additional control, (d) is the grid frequency without additional control, (e) is the frequency change rate with additional control, and (f) is the frequency change rate without additional control. Figure 5 This is a structural diagram of a grid-type converter inertia response optimization system in a power system according to an embodiment of the present invention. Detailed Implementation

[0030] The relevant technologies of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0031] like Figures 1-5As shown, this embodiment applies to grid-connected converters in power systems. Specifically, a grid-connected converter includes: a DC energy storage unit, a converter main circuit, and a VSG control system. The DC energy storage unit includes DC battery banks for storing DC energy, or DC power generation components, such as photovoltaic arrays. The converter main circuit enables bidirectional conversion between DC power and standard AC power from the grid. The VSG control system enables the grid-connected converter to operate in grid-connected mode, ensuring that the converter meets the active / reactive power requirements of the grid, guarantees stable output voltage and current, and provides reliable voltage and frequency support to the grid by simulating the stator and rotor characteristics of a synchronous generator. This is beneficial for the stable operation of the power system when a high proportion of new energy sources are integrated into the grid.

[0032] The inertia response optimization method for grid-type converters provided in this embodiment can be executed by a grid-type converter inertia response optimization system. For example... Figure 1 As shown, the inertia response optimization method for this grid-type converter includes: S1. Real-time detection of the frequency at the grid connection point of the grid-connected converter and calculation of the grid frequency change rate; In this grid-connected converter, the DC side is connected to the DC power supply, and the AC side is connected to the power grid. Under VSG control, it operates normally in grid-connected mode, autonomously constructing its voltage frequency and maintaining synchronization with the grid. A phase-locked loop or other frequency detection module is used to synchronously acquire the real-time grid frequency at the converter's grid connection point, and a low-pass filter is used to filter the acquired frequency to remove high-frequency noise. Based on this, a differential algorithm is used to process the frequency, thereby obtaining the current grid frequency change rate.

[0033] S2. If the absolute value of the frequency change rate exceeds the set threshold, the additional fast power response control of the active loop of the grid-type converter VSG control system is triggered. The system employs a preset grid frequency change rate threshold, such as 1 Hz / s. When the absolute value of the acquired grid frequency change rate exceeds this threshold, the additional fast power response control in the active power loop of the VSG control system is enabled. Simultaneously, the positive and negative directions of the grid frequency fluctuations are obtained through a sign function and transmitted to the additional control loop. The VSG control system's active power loop includes an active power-frequency droop stage and a rotor oscillation equation stage. In the droop stage, the virtual mechanical power is obtained by superimposing the system frequency difference and the droop coefficient product with the active power command. In the rotor oscillation equation stage, the virtual mechanical power is subtracted from the mechanical power and damping power, and then integrated through an inertia simulation stage to obtain the system frequency and phase angle. Based on this, the additional fast power response control directly acts on the rotor oscillation equation stage. After the additional control is enabled, the remaining capacity of the current converter and the phase angle feedforward are calculated. The phase angle feedforward is applied to the second integral output of the rotor oscillation equation stage, and the active power command adjustment is applied to the virtual mechanical power input. Therefore, by building an additional power fast response control on the basis of the original active power control loop, the inertia response speed of the grid-type converter can be accelerated, and active power support can be provided quickly when the system frequency fluctuates greatly.

[0034] A schematic diagram of the active power loop-added fast power response control structure of the VSG control system is shown below. Figure 2 As shown, the original rotor oscillation element 210 in the active power loop operates normally. The grid frequency change rate threshold determination unit 220 detects system frequency fluctuations, obtains the sign function of the grid frequency change rate, and enables the additional control loop. After the system is enabled, the required phase angle feedforward and active power command adjustment are calculated by the feedforward calculation unit 230. Subsequently, the phase angle feedforward and active power command adjustment are applied through the phase angle feedforward channel 240 and the power command adjustment channel 250. By directly changing the phase angle, the converter output active power is quickly changed, and the phase angle feedforward adjustment is continuously effective through power command adjustment, thereby optimizing the inertia response speed of the grid converter.

[0035] S3. Based on the rated capacity of the converter and the current active power command, solve for the phase angle feedforward based on the active power transmission principle; In this system, when the grid frequency change rate exceeds a threshold, additional fast power response control will be enabled. At this point, the remaining capacity of the converter is obtained by subtracting its rated capacity from the current active power command, and this remaining capacity is used as the maximum available active power output of the converter in the additional fast power response control. According to the active power transmission principle, the converter's output active power can be expressed as the product of the synchronization coefficient and the phase angle difference between the converter and the grid. Let... E * This represents the per-unit value of the internal potential generated by the converter. U * This is the per-unit value of the converter output voltage.X * Let the output impedance of the converter be the per-unit value, then the synchronization coefficient can be defined as: (1) Based on this, to improve the inertial response speed of the grid-connected converter, the phase angle generated by the grid control can be directly changed through phase angle feedforward, thereby rapidly changing the output active power of the grid-connected converter. Therefore, in the additional fast power response control, the phase angle feedforward can be obtained by dividing the difference between the rated capacity of the phase converter and the current active power command by the converter synchronization coefficient. Here, the sign function Sign(RoCoF) of the frequency change rate obtained through the threshold detection stage represents the direction of frequency change, while the direction of converter output active power adjustment needs to be opposite to it. Therefore, the expression for the phase angle feedforward satisfies: (2) In addition, under more optimized regulation conditions, it is not necessary to adjust the converter to its maximum output; instead, the output level can be determined based on the grid fluctuation level. In this case, the degree of grid frequency fluctuation can be determined based on the grid frequency change rate, and the required phase angle feedforward for fast inertia response control can be determined according to the different fluctuation levels. The desired inertia coefficient is then set. H exp The phase angle feedforward can be obtained by multiplying the desired inertia coefficient by the grid frequency change rate. The expression for the phase angle feedforward then satisfies: (3) Meanwhile, the active power command adjustment required for the additional fast power response control will correspond to the phase angle feedforward. Under the condition of maximum output of the adjustment value, i.e. the remaining available capacity of the converter, it can be applied to the virtual mechanical power input terminal of the rotor oscillation equation to ensure that the feedforward adjustment continues to be effective.

[0036] S4. The phase angle feedforward is superimposed on the output phase angle of the rotor oscillation equation, and the matching active power command adjustment is applied synchronously at the input of the rotor oscillation equation. In the active power loop rotor oscillation equation, the power difference, after passing through the inertia simulation stage, is integrated twice and moduloed to obtain the phase angle generated by the grid-connected control. This generated phase angle is then superimposed with the feedforward phase angle through a phase angle feedforward channel to obtain the new system phase angle. By directly changing the phase angle generated by the grid-connected control, the output active power of the grid-connected converter is rapidly altered, thereby optimizing the inertia response speed of the grid-connected converter. Simultaneously, due to the presence of grid-connected active power loop closed-loop control, the additional phase difference generated by the feedforward is quickly eliminated by the closed-loop control. To ensure the continuous effectiveness of the additional fast power response control, an active power command adjustment is applied to the virtual mechanical power input terminal of the rotor oscillation equation through a power command adjustment channel. This ensures that the grid-connected converter continues to operate at the desired output, and the additional fast power response control remains effective.

[0037] S5. Control the converter to maintain the desired output operation until a significant reverse frequency disturbance occurs or a power regulation command is received from the upper level. In this system, after the additional fast power response is triggered, the converter will continuously provide inertia support to the grid at the desired output, continuously suppressing grid frequency changes. If no significant reverse frequency disturbance occurs or a higher-level regulation command is received, it indicates that the grid frequency is still fluctuating in one direction, requiring continuous inertia support; therefore, the grid converter needs to continue operating at the desired output. When a significant reverse frequency change is detected, it indicates that the previous frequency disturbance has ended, or the grid is fluctuating in the reverse direction. At this time, the additional fast power response control in the grid control will exit, phase angle feedforward and active power command regulation will be turned off, and the active power loop will return to normal operation. Then, it can be determined again whether the system's reverse frequency fluctuation exceeds the threshold, and whether to initiate a new round of additional fast power response control. In addition, when a higher-level power regulation command is received, the additional fast power response control will also exit, and the grid converter will be guided by the higher-level power regulation command.

[0038] S6. If the frequency change rate is lower than the preset threshold, no additional control is triggered, and the original VSG steady-state operation characteristics of the grid-type converter are maintained. When the grid-connected converter is operating normally, there are slight fluctuations in the grid frequency, but these fluctuations do not reach the preset frequency change threshold. At this time, the system is in normal operation, the additional fast power response control in the grid control will not be activated, and the grid-connected converter is in a native VSG control steady-state operation state.

[0039] For example, Figure 3 This embodiment provides a topology diagram of an inertial response testing system. Figure 4This section presents a comparison of the inertia response optimization effects of grid-connected converters. The left side shows the inertia response results of the grid-connected converter with the aforementioned additional fast power response control, while the right side shows the inertia response results without additional control. From top to bottom, the charts compare the power response curves, the grid frequency change curves, and the grid frequency change rate curves. After the system starts operating, the grid-connected converter initially operates under no-load conditions, with the VSG control system's active power command at 0. After 4 seconds, a large active load is applied to the grid, causing the grid frequency to drop. Analysis of the charts shows that without additional control, the grid-connected converter's active power response is naturally slower, with a response time of 48ms. The grid frequency drops to 49.35Hz, and the maximum frequency change rate reaches 3.98Hz / s, severely impacting system frequency stability. After adding the fast power response control, the active power response speed of the grid-connected converter is significantly improved, with a response time of only 15ms. Simultaneously, the increase in active power is increased. At this point, the grid-side frequency stabilizes at approximately 49.93Hz after a brief, small fluctuation, and the frequency change rate is significantly reduced compared to the state without additional control, remaining below 1Hz / s, thus ensuring system frequency stability. This result verifies the effectiveness of the proposed inertia response optimization method in improving the inertia response speed of the grid-connected converter and rapidly suppressing frequency fluctuations.

[0040] This implementation method also provides an inertia response optimization system for in-situ converters in power systems. Figure 5 This embodiment provides a structural schematic diagram of an inertia response optimization system for a grid-type converter in a power system. Figure 5 As shown, the inertia response optimization system includes: Frequency measurement module 310: used to synchronously acquire the grid connection point frequency of the grid-connected converter during grid-connected operation and calculate the grid frequency change rate; Determination trigger module 320: used to determine whether the current power grid frequency change rate exceeds a preset threshold, and to enable additional power response control and obtain the positive and negative directions of frequency fluctuation when the frequency fluctuation exceeds the threshold; Calculation module 330: used to calculate the phase angle feedforward and the matching active power command adjustment required for additional control.

[0041] Phase angle feedforward module 340: Used to implement phase angle feedforward, superimposing the phase angle feedforward amount onto the phase angle generated by the grid control rotor oscillation equation.

[0042] Power command module 350: used to synchronously apply a matching active power command adjustment at the input of the rotor oscillation equation when phase angle feedforward is applied.

[0043] The technical solution of this embodiment synchronously acquires the real-time grid frequency at the converter's grid connection point using a phase-locked loop (PLL) frequency detection module, and obtains the grid frequency change rate through a differential algorithm, providing a foundation for additional fast power response control. Based on this, the additional fast power response control is enabled by threshold judgment of the grid frequency change rate. In this additional control, the maximum active power output that the converter can currently provide is obtained based on the difference between the converter's rated capacity and the current active power command. The phase angle feedforward is obtained by dividing this by the synchronization coefficient according to the active power transmission principle, or by multiplying the desired inertia coefficient by the grid frequency change rate. Since the converter's output active power is directly related to its phase angle difference with the grid, the phase angle feedforward is applied at the output of the rotor oscillation equation to directly change the phase angle generated by the grid control, thereby rapidly adjusting the converter's output active power. Meanwhile, to prevent the additional phase difference generated by the feedforward from being eliminated by the active power loop closed-loop control, the corresponding active power command adjustment is applied synchronously at the input of the rotor swing equation. This enables a rapid change in the converter's output active power, improves the inertia response speed, provides effective inertia support for the power grid, and suppresses power grid frequency fluctuations.

[0044] In summary, this invention optimizes the inertial response of grid-connected converters, effectively solving the speed limitation of the second-order response characteristics of traditional grid-connected converters and significantly shortening the inertial response time. It allows for rapid adjustment of the converter's output active power to the desired output when the grid frequency fluctuates rapidly, compensating for system active power deficits and effectively suppressing grid frequency drops and oscillations. Furthermore, this invention does not alter the fundamental nature of grid-connected control in converters; its purpose is to actively adjust the output power when the grid frequency fluctuates significantly, thereby suppressing grid frequency changes and maintaining grid frequency stability, rather than tracking grid frequency changes. This aligns with the proactive voltage and frequency construction characteristics of grid-connected control, providing effective support for the grid and playing a crucial role in achieving a high proportion of new energy access to the grid and ensuring the stable operation of the power system.

[0045] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for optimizing the inertia response of a grid-type converter in a power system, characterized in that, Includes the following steps: Step S1: Real-time detection of the frequency at the grid connection point of the grid-connected converter, and calculation of the grid frequency change rate; Step S2: If the absolute value of the frequency change rate exceeds the set threshold, trigger the additional fast power response control of the active loop of the grid-type converter VSG control system. Step S3: Based on the rated capacity of the converter and the current active power command, solve for the phase angle feedforward based on the active power transmission principle; Step S4: The phase angle feedforward is superimposed on the output phase angle of the rotor swing equation, and a matching active power command adjustment is applied synchronously at the input of the rotor swing equation. Step S5: Control the converter to maintain the desired output operation until a significant reverse frequency disturbance occurs or a power regulation command is received from the upper level. Step S6: If the frequency change rate is lower than the preset threshold, no additional control is triggered, and the original VSG steady-state operation characteristics of the grid-type converter are maintained.

2. The method for optimizing the inertia response of a grid-type converter in a power system according to claim 1, characterized in that, In step S1, the grid-connected converter operates in parallel with the grid, and the frequency of the grid at the grid connection point is collected by a frequency detection module; a filter is used to filter out high-frequency noise in the grid frequency, and the grid frequency change rate is calculated by a differential algorithm.

3. The method for optimizing the inertia response of a grid-type converter in a power system according to claim 1, characterized in that, In step S2, a preset frequency change threshold is set. When the frequency change rate exceeds the threshold, the additional fast power response control is enabled, and the positive and negative directions of the frequency change rate are obtained using a sign function.

4. The method for optimizing the inertia response of a grid-type converter in a power system according to claim 3, characterized in that, In step S2, the active power loop of the grid-type converter control system includes an active power-frequency droop element and a rotor oscillation equation element. When the grid frequency change rate is detected to exceed the threshold, additional fast power response control is activated to improve the inertia response speed of the converter under large inertia parameters.

5. The method for optimizing the inertia response of a grid-type converter in a power system according to claim 1, characterized in that, In step S3, the maximum active power output that the converter can provide at present is obtained by the difference between the rated capacity of the converter and the current active power command. The phase angle feedforward is obtained by dividing the difference by the synchronization coefficient according to the active power transmission principle. （2） Alternatively, the phase angle feedforward required for fast inertia response control can be determined based on the degree of grid frequency fluctuation; and the desired inertia coefficient can be set. H exp The phase angle feedforward can be obtained by multiplying the desired inertia coefficient by the grid frequency change rate. The expression for the phase angle feedforward then satisfies: （3） In the formula, X * This represents the per-unit value of the converter output impedance, and Sign(RoCoF) represents the sign function of the rate of change of frequency. E * This represents the per-unit value of the internal potential generated by the converter. U * This indicates the per-unit value of the converter output voltage. Indicates the per-unit value of the active power command; H exp This represents the expected inertia coefficient.

6. The method for optimizing the inertia response of a grid-type converter in a power system according to claim 1, characterized in that, In step S4, a phase angle feedforward is superimposed on the phase angle output of the rotor swing equation, and the active power output of the grid converter is rapidly increased by directly changing the phase angle. At the same time, in order to avoid the additional phase difference generated by the feedforward being eliminated by the active power loop closed-loop control, a corresponding active power command adjustment is applied to the input of the rotor swing equation.

7. The method for optimizing the inertia response of a grid-type converter in a power system according to claim 6, characterized in that, In step S4, low-pass filtering is performed when applying phase angle feedforward to reduce the impact of high-frequency fluctuations in the phase angle feedforward on the system phase angle stability and avoid system instability.

8. The method for optimizing the inertia response of a grid-type converter in a power system according to claim 1, characterized in that, In step S5, after the additional fast power response control is triggered, the converter will maintain the desired output operation to provide continuous support to the grid until the next significant reverse disturbance occurs or the power regulation command from the upper level is received, at which point the power command will be changed.

9. The method for optimizing the inertia response of a grid-type converter in a power system according to claim 1, characterized in that, In step S6, when there are slight fluctuations in the grid frequency during normal grid operation, if the slight fluctuations do not exceed the preset frequency change rate threshold, the additional fast power response control is not triggered. The grid-connected converter maintains the native grid-connected converter control steady-state operation, and at the same time, it does not damage the long-term synchronous stability of the system.

10. A system for optimizing the inertia response of a grid-type converter in a power system, characterized in that, The optimization system is used to implement the optimization method according to any one of claims 1 to 9, and the optimization system comprises: Frequency measurement module: used to synchronously acquire the grid connection point frequency of the grid-connected converter during grid-connected operation and calculate the grid frequency change rate; Determination and triggering module: used to determine whether the current power grid frequency change rate exceeds a preset threshold, and to enable additional power response control and obtain the positive and negative directions of frequency fluctuation when the frequency fluctuation exceeds the threshold; Calculation module: used to calculate the phase angle feedforward and the matching active power command adjustment required for additional control; Phase angle feedforward module: used to implement phase angle feedforward, superimposing the phase angle feedforward amount onto the phase angle generated by the grid control rotor oscillation equation; Power command module: used to synchronously apply a matching active power command adjustment at the input of the rotor oscillation equation when phase angle feedforward is applied.

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