VSG control-based high-voltage direct-current transmission low-frequency oscillation suppression method

Abstract

The invention provides a VSG control-based high-voltage direct-current power transmission low-frequency oscillation suppression method, which is applied to a VSG control-based high-voltage direct-current power transmission inverter, and the high-voltage direct-current power transmission inverter at least comprises a direct-current voltage control loop and an active power control loop. The method comprises the following steps of: before a reference power signal generated by a direct-current voltage control loop is input into an active power control loop, executing lead-lag correction on the reference power signal; through lead-lag correction and reconstruction of a transfer function between a direct-current voltage control loop and an active power control loop, a phase margin at a low frequency band is increased to suppress low-frequency oscillation caused by coupling of the direct-current voltage control loop and the active power control loop, so that the stability and the anti-interference capability of the system are improved, and the reliability of the system is improved. And the adaptability and robustness of the control strategy are enhanced, no extra hardware device needs to be introduced, and the cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of power system control technology, and in particular to a method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control. Background Technology

[0002] Against the backdrop of traditional fossil fuels facing depletion and environmental pollution, new energy sources have experienced rapid development. Wind power, photovoltaics, and other new energy sources are gradually becoming key components in replacing traditional fossil fuels, achieving dual-carbon goals, and building new power systems. However, my country's clean energy sources, such as wind and solar power, are mainly distributed in the northwest region, while the electricity load centers are primarily located in the eastern coastal areas, resulting in significant geographical disparities between energy and load. In this context, long-distance, high-capacity power transmission has become an inevitable choice, and high-voltage direct current (HVDC) transmission technology is widely used due to its advantages of large transmission capacity, low loss, and low line construction costs.

[0003] With the advancement of dual-carbon goals, the high proportion of photovoltaic power integrated into the grid, while reducing environmental pollution and improving the energy supply structure, also brings new challenges to the frequency security operation of the power system. One key to solving these problems is to introduce grid-connected devices with inertia support capabilities, but the additional introduction of energy storage equipment leads to significant investment. Therefore, virtual synchronous generator based high voltage direct current (VSG-HVDC) transmission technology has become an economical solution; however, while providing inertia, this strategy also introduces the risk of low-frequency oscillations.

[0004] However, existing technologies have many shortcomings in suppressing low-frequency oscillations. For example, based on small-signal model eigenvalue analysis and particle swarm optimization algorithms, an additional damping controller with the goal of providing maximum positive damping has been designed for matched-control wind farms via LCC-HVDC systems. However, this strategy is highly dependent on accurate system models, has insufficient parameter robustness, and its control effect may degrade when the system operating point or parameters change over a wide range. Based on wideband impedance modeling and active impedance shaping techniques, two high-frequency oscillation suppression methods, voltage band-stop and virtual admittance band-pass filtering, have been proposed for grid-type MMCs. However, their drawback is that the research focuses on the high-frequency band of the converter itself and lacks applicability to the more common subsynchronous oscillation problem in large-scale hybrid energy transmission systems. Based on FSSO mechanism analysis and a multi-objective optimization framework, a passive defense strategy has been proposed to simultaneously improve damping, avoid interharmonic frequencies, and take into account fault ride-through performance by optimizing wind farm control parameters. However, its drawback is that the optimization process is complex and is a post-event mitigation, failing to actively eliminate the interharmonic excitation sources generated by the LCC-HVDC itself. In summary, existing oscillation suppression methods have significant shortcomings in terms of adaptability, synergy, and engineering feasibility. Summary of the Invention

[0005] This invention provides a method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control, in order to solve the technical problem of poor low-frequency oscillation suppression in the prior art.

[0006] On one hand, this invention provides a method for suppressing low-frequency oscillations in high-voltage direct current (HVDC) transmission based on VSG control. The method is applied to a HVDC inverter employing VSG control, wherein the HVDC inverter includes at least a DC voltage control loop and an active power control loop. The method includes: Before the reference power signal generated by the DC voltage control loop is input to the active power control loop, a lead-lag correction is performed on the reference power signal; By using the lead-lag correction, the transfer function between the DC voltage control loop and the active power control loop is reconstructed, increasing the phase margin in the low-frequency band to suppress low-frequency oscillations caused by the coupling between the DC voltage control loop and the active power control loop.

[0007] According to the present invention, a method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control reconstructs the transfer function between the DC voltage control loop and the active power control loop through the lead-lag correction, including: Determine the target zero frequency and the target pole frequency; wherein the target pole frequency is less than the target zero frequency; The attenuation factor is obtained based on the target zero frequency and the target pole frequency; The time constant is obtained based on the target zero-point frequency; Based on the time constant and the attenuation factor, the transfer function between the DC voltage control loop and the active power control loop is reconstructed.

[0008] According to the present invention, a method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control is provided, and the reconstructed transfer function is expressed by the following formula: ; in, For the refactored transfer function; DC gain; It is a time constant; It is the attenuation factor, and ; It is a complex frequency variable.

[0009] According to the present invention, a method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control is provided, which obtains the time constant according to the target zero-point frequency, including: Convert the target zero-point frequency to the target zero-angular frequency; The time constant is obtained based on the target zero-point angular frequency.

[0010] The present invention provides a method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control, which obtains a time constant based on a target zero-point angular frequency, including: Determine the reciprocal of the target's zero-point angular frequency to obtain the time constant; The time constant is expressed by the following formula: T = 1 / (2πfz), where fz is the target zero-point frequency and T is the time constant.

[0011] The present invention provides a method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control, which obtains an attenuation factor according to the target zero-point frequency and the target pole frequency, including: Calculate the ratio of the target zero frequency to the target pole frequency to obtain the attenuation factor; The attenuation factor is expressed by the following formula: =fz / fp; Where α is the attenuation factor, fz is the target zero frequency, and fp is the target pole frequency.

[0012] According to the present invention, a method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control is provided, wherein the range of DC gain is determined in the following manner: When only the phase margin needs to be improved without changing the low-frequency gain, the DC gain is set to 1. When it is necessary to improve the phase margin and change the low-frequency gain, the DC gain should be greater than 1.

[0013] According to the present invention, a method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control is provided, wherein the target zero-point frequency ranges from 0.5 Hz to 1 Hz. The target pole frequency ranges from 0.1 Hz to 0.4 Hz.

[0014] According to the present invention, a method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control is provided, wherein the target zero-point frequency is 1Hz; The target pole frequency is 0.1 Hz.

[0015] According to the present invention, a method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control is provided, wherein the frequency band of the low-frequency oscillation is from 0.1 Hz to 1 Hz.

[0016] The low-frequency oscillation suppression method for high-voltage direct current transmission based on VSG control provided by this invention performs lead-lag correction on the reference power signal generated by the DC voltage control loop before it is input to the active power control loop, reconstructs the transfer function between the DC voltage control loop and the active power control loop, increases the phase margin in the low-frequency band, and effectively suppresses the low-frequency oscillations caused by the coupling between the DC voltage control loop and the active power control loop. This not only improves the stability and anti-interference capability of the system, but also enhances the adaptability and robustness of the control strategy. At the same time, it does not require the introduction of additional hardware devices, reducing costs and significantly improving the low-frequency oscillation suppression effect and overall performance of the high-voltage direct current transmission system. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating the low-frequency oscillation suppression method for high-voltage direct current transmission based on VSG control provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the improved VSG-HVDC active power control topology with hysteresis correction provided in the embodiments of the present invention. Figure 3 This is a schematic diagram of the VSG-HVDC output power curve under a reference DC jump before the hysteresis improvement provided in the embodiment of the present invention; Figure 4This is a schematic diagram of the VSG-HVDC output frequency curve under a reference DC jump before the hysteresis improvement provided in the embodiment of the present invention; Figure 5 This is a schematic diagram of the VSG-HVDC output power curve under grid frequency jumps before the hysteresis improvement provided in the embodiment of the present invention; Figure 6 This is a schematic diagram of the VSG-HVDC output frequency curve under grid frequency jump before the hysteresis improvement provided in the embodiment of the present invention; Figure 7 This is a schematic diagram of the VSG-HVDC output power curve under a reference DC jump after the hysteresis improvement provided in the embodiment of the present invention; Figure 8 This is a schematic diagram of the VSG-HVDC output frequency curve under a reference DC jump after the hysteresis improvement provided in the embodiment of the present invention; Figure 9 This is a schematic diagram of the VSG-HVDC output power curve under grid frequency jump after the hysteresis improvement provided in the embodiment of the present invention; Figure 10 This is a schematic diagram of the VSG-HVDC output frequency curve under grid frequency jump after the hysteresis improvement provided in the embodiment of the present invention; Figure 11 This is a schematic diagram of the structure of the electronic device provided in an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0020] Figure 1 This is a schematic flowchart of the low-frequency oscillation suppression method for high-voltage direct current transmission based on VSG control provided in an embodiment of the present invention.

[0021] See Figure 1 The method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control is applied to high-voltage direct current transmission inverters using VSG control. The high-voltage direct current transmission inverter includes at least a DC voltage control circuit and an active power control circuit.

[0022] The method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control includes the following steps.

[0023] Step 101: Before the reference power signal generated by the DC voltage control loop is input to the active power control loop, perform lead-lag correction on the reference power signal; Step 102: By using lead-lag correction, reconstruct the transfer function between the DC voltage control loop and the active power control loop to increase the phase margin in the low-frequency band, thereby suppressing the low-frequency oscillations caused by the coupling between the DC voltage control loop and the active power control loop.

[0024] In this embodiment, by performing lead-lag correction on the reference power signal generated by the DC voltage control loop before it is input to the active power control loop, the transfer function between the DC voltage control loop and the active power control loop is reconstructed, increasing the phase margin in the low-frequency band. This effectively suppresses low-frequency oscillations caused by the coupling between the DC voltage control loop and the active power control loop, improving the system's stability and anti-interference capability, enhancing the adaptability and robustness of the control strategy, and eliminating the need for additional hardware devices, thus reducing costs and significantly improving the low-frequency oscillation suppression effect and overall performance of the high-voltage direct current transmission system.

[0025] In one embodiment of this specification, the transfer function between the DC voltage control loop and the active power control loop is reconstructed through lead-lag correction, including: Determine the target zero frequency fz and the target pole frequency fp; wherein the target pole frequency fp is less than the target zero frequency fz; The attenuation factor α is obtained based on the target zero frequency fz and the target pole frequency fp. The time constant is obtained based on the target zero-point frequency fz. ; Based on the time constant and attenuation factor, the transfer function between the DC voltage control loop and the active power control loop is reconstructed.

[0026] In this embodiment, by determining the target zero-point frequency and pole frequency, and calculating the attenuation factor and time constant based on these frequency parameters, the transfer function between the DC voltage control loop and the active power control loop is reconstructed. This method provides the system with flexible parameter adjustment capabilities, enabling precise optimization of the system's phase margin and dynamic performance, thereby effectively suppressing low-frequency oscillations and enhancing the system's stability and adaptability.

[0027] In one embodiment of this specification, the reconstructed transfer function is represented by the following formula (1): (1); in, For the refactored transfer function; DC gain; It is a time constant; It is the attenuation factor, and ; It is a complex frequency variable.

[0028] In this embodiment, the mathematical model of the lead-lag compensation stage is clarified through a specific transfer function formula. This formula further refines the reconstruction of the system transfer function by introducing DC gain, time constant, and attenuation factor. This not only provides a clear theoretical basis for the design but also enables the system to achieve better phase compensation and dynamic response characteristics in the low-frequency range, significantly improving the system's stability and performance.

[0029] In one embodiment of this specification, the time constant is obtained based on the target zero-point frequency fz. ,include: Convert the target zero frequency fz into the target zero angular frequency; The time constant is obtained based on the target zero-point angular frequency. .

[0030] In this embodiment, by converting the target zero-point frequency into the target zero-point angular frequency and calculating the time constant based on this, a simple and accurate method is provided to determine the key parameters of the correction stage. This method makes the design process more intuitive and controllable, ensuring that the correction stage can accurately provide the required phase compensation within the target frequency band, thereby effectively suppressing low-frequency oscillations and improving system stability.

[0031] In one embodiment of this specification, the time constant is obtained based on the target zero-point angular frequency. ,include: Determine the reciprocal of the target zero-point angular frequency to obtain the time constant. ; time constant This can be expressed by the following formula: T = 1 / (2πfz), where fz is the target zero frequency.

[0032] In this embodiment, the calculation method for the time constant is further clarified, namely, it is determined by the reciprocal of the target zero-point angular frequency. This direct calculation method not only simplifies the design process but also ensures the accuracy of the time constant, enabling the correction stage to function precisely within the target frequency band, thereby effectively improving the system's phase margin and dynamic performance.

[0033] In one embodiment of this specification, the attenuation factor α is obtained based on the target zero frequency fz and the target pole frequency fp, including: Calculate the ratio of the target zero frequency fz to the target pole frequency fp to obtain the attenuation factor α; The attenuation factor α is expressed by the following formula: =fz / fp.

[0034] In this embodiment, the attenuation factor is determined by calculating the ratio of the target zero-frequency to the pole-frequency, providing a clear parameter basis for the design of the correction stage. This method allows designers to flexibly adjust the characteristics of the correction stage to ensure that it provides appropriate phase compensation within the target frequency band, thereby effectively suppressing low-frequency oscillations and improving the system's stability and dynamic response capability.

[0035] In one embodiment of this specification, the DC gain The scope is determined in the following way: When only phase margin needs to be improved without changing the low-frequency gain The value is 1; When it is necessary to improve the phase margin and change the low-frequency gain, The value is greater than 1.

[0036] In this embodiment, the range of DC gain values ​​and their corresponding design objectives are clearly defined. When only the phase margin needs improvement without changing the low-frequency gain, the value is set to 1; when both phase margin and low-frequency gain need improvement, the value is greater than 1. This flexible gain adjustment method allows the system to optimize performance under different design requirements, further enhancing the system's stability and adaptability.

[0037] In one embodiment of this specification, the target zero-point frequency fz ranges from 0.5 Hz to 1 Hz; The target pole frequency fp ranges from 0.1 Hz to 0.4 Hz.

[0038] In this embodiment, by defining the range of target zero-point and pole frequencies, a specific frequency range is provided for the design of the correction stage. This range ensures that the correction stage can effectively cover the low-frequency oscillation band while avoiding adverse effects on other frequency bands of the system. This precise frequency range setting makes the system perform better in suppressing low-frequency oscillations, thus improving the overall system performance.

[0039] In one embodiment of this specification, the target zero-point frequency fz is 1Hz; The target pole frequency fp is 0.1Hz.

[0040] In this embodiment, the specific values ​​of the target zero-point frequency and pole frequency are further clarified, namely, the target zero-point frequency is 1Hz and the pole frequency is 0.1Hz. These specific design parameters enable the correction stage to accurately provide the required phase compensation within the critical frequency band, thereby effectively suppressing low-frequency oscillations and improving the system's stability and dynamic response capability.

[0041] In one embodiment of this specification, the frequency band of the low-frequency oscillation is from 0.1 Hz to 1 Hz.

[0042] In this embodiment, the frequency range of the low-frequency oscillation is defined as 0.1Hz to 1Hz. This definition provides a clear frequency range for the system design, enabling the correction stage to specifically optimize system performance within this frequency range. By matching the frequency characteristics of the correction stage with the frequency range of the low-frequency oscillation, the system can more effectively suppress low-frequency oscillations and improve overall stability.

[0043] Figure 2 This is a schematic diagram of the improved VSG-HVDC active power control topology with hysteresis correction provided in an embodiment of the present invention. (See also...) Figure 2 , Figure 2 The left half of the diagram can be considered as a DC voltage control loop, and the right half as an active power control loop. The DC side of the converter is connected to a long-distance high-voltage DC transmission line, while the AC side is linked to the point of common coupling (PCC) via a filter. When the converter uses a virtual synchronous machine control with DC voltage series connection, it mainly includes a DC voltage control loop, an active power control loop, a reactive power control loop, and a voltage-current dual closed-loop control loop. Since the analysis of this scheme focuses on the low-frequency band, and the bandwidth of the voltage-current dual closed-loop is usually in the hundreds to thousands of hertz range, the small-signal modeling of VSG-HVDC only needs to consider the DC loop and the active power outer loop. The simplified control topology is as follows: Figure 2 As shown.

[0044] The transfer function from the new DC reference voltage to the DC output voltage of the system with hysteresis correction is shown in Equation (2) below: (2); in, V dcref Indicates the DC reference voltage. V dc Indicates the DC output voltage. This represents the transfer function. Wherein, ; ; ; .

[0045] Represents the transfer function of a PI (proportional-integral) controller; This represents the transfer function of a virtual synchronous generator (VSG), simulating the dynamic behavior of a synchronous generator; The transfer function of the DC voltage control loop is represented by the following formula (3): Before introducing hysteresis compensation, the transfer function can be represented by the following formula (3): (3).

[0046] The above formula (2) can be simplified, as shown in the following formula (4): (4); in, Indicates DC gain; This represents the proportional coefficient of the PI process; It is a complex frequency variable; Indicates the integral coefficient of the PI link; V is the time constant; dc0 Indicates the steady-state value of DC voltage; C dc Indicates DC capacitor; J represents the damping factor; J represents the moment of inertia of the VSG; D represents the damping coefficient. This represents the synchronization coefficient. Additionally... Figure 2 In this context, P0 represents the system's reference power; P represents the system's actual output power; and PI represents the proportional-integral controller, which converts the DC voltage error (…). V dcref - V dc The output frequency is converted into an active power command P0 to achieve DC voltage stabilization; Δω represents the output frequency change; ωg represents the grid frequency; and δ represents the phase angle.

[0047] For this scheme, the bandwidth of the PI element in the DC loop is 10. -3 The frequency range is around Hz, while the bandwidth of the VSG control loop is several hertz. Therefore, the cutoff frequency limits of the hysteresis element introduced in this scheme are selected as 0.1Hz and 1Hz, respectively. The specific parameter design idea is as follows: The mathematical description of the lag compensator is in the form of a first-order zero pole, and the standard transfer function is as shown in the above formula (1).

[0048] In the above formula (1), the parameter It is the time constant that determines the zero-point position. And... It is an attenuation factor greater than 1, which determines the frequency spacing between poles and zeros. DC gain This is used to independently adjust the low-frequency gain level of the system. From the perspective of the pole-zero distribution, the zero-point frequency is... The pole frequency is There is a clear relationship between the two, because The poles are always located before the zeros, meaning the pole frequency is less than the zero frequency. This is the fundamental reason for its unique frequency response characteristics.

[0049] The frequency characteristics of the hysteresis compensator determine its final control effect. In terms of amplitude-frequency characteristics, when the frequency is much lower than the pole frequency, its gain is approximately constant. This allows it to maintain or increase the system's low-frequency gain, helping to improve steady-state error. In the mid-frequency range between the pole and zero frequencies, the amplitude curve steadily decreases with a slope of -20dB / dec. This attenuation characteristic is used to suppress the system's open-loop amplitude-frequency curve, thereby reducing the system's crossover frequency. When the frequency is far above the zero frequency, the gain will stabilize at a lower level. In terms of phase frequency characteristics, the hysteresis corrector introduces negative phase (i.e., phase lag) over a wide bandwidth, with the maximum hysteresis phase occurring at the geometric center between the zero and pole frequencies. Place, This represents the geometric center frequency. Therefore, during the design process, the maximum hysteresis phase point must be carefully placed in a region far below the system's new crossover frequency to avoid substantial damage to the phase margin. This is crucial for the successful design of the hysteresis compensator.

[0050] The design process of a hysteresis compensator is a systematic parameter determination process. First, the zero-point frequency needs to be determined based on the requirements for the system's crossover frequency and stability margin. and pole frequency And convert them into their respective angular frequencies. and And must meet The relationship. Then, the time constant is calculated using the definition. and attenuation factor Next, the DC gain needs to be determined. If the goal is merely to reshape the frequency response curve without altering the steady-state performance, then typically... If it is necessary to further improve the steady-state accuracy of the system, then a value greater than 1 needs to be calculated based on the requirements of the static error coefficient. Finally, by substituting all the determined parameters into the standard transfer function form, the complete corrector model can be constructed. .

[0051] For example, regarding zero frequency and pole frequency The design requirements allow for the calculation of the angular frequency. , This leads to the time constant. and attenuation factor If DC gain is taken The final hysteresis compensator transfer function is shown in formula (5) below: (5).

[0052] The hysteresis corrector will to It provides a continuous -20dB / dec attenuation band within the frequency range, which can effectively help the system suppress mid-frequency resonance peaks or combat model uncertainties, thereby robustly improving the system's phase margin.

[0053] The output response of the VSG-HVDC based on hysteresis compensation under reference DC power jumps and grid frequency jumps is shown below: Will Figure 3 and Figure 4 respectively with Figure 7 and Figure 8 By comparison, it can be seen that the improved system exhibits superior transient performance when the DC voltage reference value undergoes a step change. Figure 7 and Figure 3 As can be seen from the comparison, the overshoot of the output power is significantly reduced, and the power curve is smooth and converges quickly to the new steady-state value, avoiding the large fluctuations and continuous oscillations in the original system's power response. Figure 8 and Figure 4 The frequency curves show that the improved system has a smaller frequency deviation and recovers to the rated value faster, indicating that the system can better maintain frequency stability when dealing with sudden changes in internal commands, thus reducing the impact on the system itself.

[0054] Will Figure 5 and Figure 6 respectively with Figure 9 and Figure 10 By comparison, it can be seen that when the grid frequency experiences frequency drops, the improved system exhibits stronger robustness and more effective frequency support capabilities. Figure 9 and Figure 5 As can be seen from the output power curve, the improved system exhibits a significantly reduced power fluctuation amplitude under disturbances and is able to calm oscillations more quickly, smoothly transitioning to a new power equilibrium point. Correspondingly, the frequency response curve... Figure 10 and Figure 6 The improved system has a higher minimum frequency (i.e., a smaller frequency deviation) and a faster and smoother frequency recovery process, indicating that it has better inertia and damping characteristics, which can more effectively suppress frequency fluctuations caused by grid disturbances and improve grid-connected operation stability.

[0055] In summary, the improved VSG-HVDC control system effectively enhances its dynamic response quality under two typical disturbance conditions through optimization of control strategies and parameters. Specifically, this manifests as smaller overshoot, faster response and recovery speeds, and a smoother convergence process. This demonstrates that the improvements effectively enhance system damping and optimize the closed-loop pole configuration, thereby simultaneously balancing response speed and stability, and significantly improving the overall dynamic performance and anti-interference capability of the system.

[0056] In terms of control system performance, the DC voltage transfer function after introducing a lead-lag compensation element shows significant improvements in several aspects compared to the original system. Frequency domain analysis reveals that the original system, due to the strong coupling between the virtual synchronous machine rotor dynamics and the DC voltage control outer loop, suffers from insufficient phase margin, making it prone to weakly damped low-frequency oscillations and extremely sensitive to parameter changes. The new system, by introducing… This correction stage, thanks to the positive phase compensation provided by its advanced network near the crossover frequency, effectively offsets the phase lag accumulated by multiple stages, raising the system phase margin to a safe level. This improvement fundamentally enhances the system's relative stability and significantly suppresses the risk of low-frequency oscillations in power and DC voltage. Simultaneously, the newly added closed-loop zero accelerates the system response, while adjusting... and The parameters can be flexibly configured to position the zero and poles, causing the dominant poles to move further away from the imaginary axis and closer to the real axis. This increases the system damping ratio, reduces overshoot, and shortens the settling time, achieving synergistic optimization of response speed and stability.

[0057] From the perspective of overall system performance, this improvement also significantly enhances the robustness and adjustability of the control system. The original system could only be improved by adjusting the PI controller... and Balancing dynamic performance and stability using two parameters limits design freedom and often makes it difficult to simultaneously achieve all performance metrics. The new system, however, addresses this by... , , The three additional parameters provide richer adjustment dimensions, enabling the controller to maintain excellent performance over a wider range of operating conditions. This enhanced adjustment capability makes the system more adaptable to external disturbances such as grid impedance changes and operating point fluctuations, effectively reducing parameter sensitivity. Furthermore, the introduction of the correction stage not only does not increase the system order, but also optimizes pole placement by reshaping the root locus. While maintaining the original DC voltage regulation accuracy, it comprehensively improves the system's dynamic response quality, stability boundary, and anti-interference capability, providing a more reliable control scheme for the stable operation of the virtual synchronous generator under weak grid conditions.

[0058] Figure 11 This is a schematic diagram of the structure of the electronic device provided in an embodiment of the present invention.

[0059] like Figure 11As shown, the electronic device may include a processor 1110, a communications interface 1120, a memory 1130, and a communication bus 1140. The processor 1110, communications interface 1120, and memory 1130 communicate with each other via the communication bus 1140. The processor 1110 can call logic instructions from the memory 1130 to execute a VSG-based low-frequency oscillation suppression method for high-voltage direct current transmission.

[0060] Furthermore, the logical instructions in the aforementioned memory 1130 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, essentially, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0061] On the other hand, the present invention also provides a computer program product, which includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer is able to execute the VSG-based low-frequency oscillation suppression method for high-voltage direct current transmission provided by the above methods.

[0062] In another aspect, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to perform the VSG-based low-frequency oscillation suppression method for high-voltage direct current transmission provided by the above methods.

[0063] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0064] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications 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.

Claims

1. A method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control, characterized in that, The method is applied to a high-voltage direct current (HVDC) transmission inverter using VSG control, wherein the HVDC transmission inverter includes at least a DC voltage control circuit and an active power control circuit, and the method includes: Before the reference power signal generated by the DC voltage control loop is input to the active power control loop, a lead-lag correction is performed on the reference power signal; By using the lead-lag correction, the transfer function between the DC voltage control loop and the active power control loop is reconstructed, increasing the phase margin in the low-frequency band to suppress low-frequency oscillations caused by the coupling between the DC voltage control loop and the active power control loop.

2. The method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control according to claim 1, characterized in that, The transfer function between the DC voltage control loop and the active power control loop is reconstructed through the aforementioned lead-lag correction, including: Determine the target zero frequency and the target pole frequency; wherein the target pole frequency is less than the target zero frequency; The attenuation factor is obtained based on the target zero frequency and the target pole frequency; The time constant is obtained based on the target zero-point frequency; Based on the time constant and the attenuation factor, the transfer function between the DC voltage control loop and the active power control loop is reconstructed.

3. The method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control according to claim 2, characterized in that, The reconfigured transfer function is expressed by the following formula: ； in, For the refactored transfer function; DC gain; It is a time constant; It is the attenuation factor, and ; It is a complex frequency variable.

4. The method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control according to claim 2, characterized in that, Based on the target zero-point frequency, the time constant is obtained, including: Convert the target zero-point frequency to the target zero-angular frequency; The time constant is obtained based on the target zero-point angular frequency.

5. The method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control according to claim 4, characterized in that, Based on the target zero-point angular frequency, the time constant is obtained, including: Determine the reciprocal of the target's zero-point angular frequency to obtain the time constant; The time constant is expressed by the following formula: T = 1 / (2πfz), where fz is the target zero-point frequency and T is the time constant.

6. The method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control according to claim 2, characterized in that, Based on the target zero-point frequency and the target pole frequency, the attenuation factor is obtained, including: Calculate the ratio of the target zero frequency to the target pole frequency to obtain the attenuation factor; The attenuation factor is expressed by the following formula: =fz / fp; Where α is the attenuation factor, fz is the target zero frequency, and fp is the target pole frequency.

7. The method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control according to claim 3, characterized in that, The range of DC gain is determined in the following way: When only the phase margin needs to be improved without changing the low-frequency gain, the DC gain is set to 1. When it is necessary to improve the phase margin and change the low-frequency gain, the DC gain should be greater than 1.

8. The method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control according to claim 2, characterized in that, The target zero-point frequency ranges from 0.5Hz to 1Hz; The target pole frequency ranges from 0.1 Hz to 0.4 Hz.

9. The method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control according to claim 8, characterized in that, The target zero-point frequency is 1Hz; The target pole frequency is 0.1 Hz.

10. The method for suppressing low-frequency oscillations in high-voltage direct current transmission based on VSG control according to claim 1, characterized in that, The frequency range of the low-frequency oscillation is from 0.1 Hz to 1 Hz.

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