Method for enhancing VSG power oscillation suppression in weak power grid and related device

Abstract

The invention belongs to the technical field of virtual synchronous generators, and discloses a method and a related device for enhancing VSG power oscillation suppression in a weak power grid, and the method comprises the steps: extracting an oscillation frequency component in an angular frequency error through a band-pass filter, and generating an active power oscillation adjustment quantity through inertia adjustment and proportional adjustment; superposing to a main power regulation branch to actively suppress active oscillation; a d-axis voltage deviation and a d-axis current deviation are respectively processed to obtain a first compensation component and a second compensation component, a third compensation component based on a d-axis voltage reference value is combined to calculate a reactive power compensation amount, and the reactive power compensation amount is input into a reactive droop control branch to enhance system damping. By adopting the method, the active and reactive power oscillation amplitudes of the VSG in the weak power grid are remarkably weakened, and the risk of electric energy quality deterioration or instability caused by continuous oscillation is avoided, so that the stable operation capability and the anti-interference performance of the system under the condition of the weak power grid are improved.

Description

Technical Field

[0001] This invention belongs to the field of virtual synchronous generator technology, and particularly relates to a method and related device for enhancing the suppression of VSG power oscillations in weak power grids. Background Technology

[0002] Currently, the global energy structure is accelerating its transition to a clean and low-carbon model, with renewable energy sources (such as wind power and photovoltaics) entering a stage of large-scale development and grid-connected application. As a key interface device between renewable energy power generation systems and the power grid, the operating characteristics of grid-connected inverters directly determine the stability and efficiency of energy transmission. However, traditional grid-connected inverters employ a phase-locked loop (PLL)-based control strategy, which inherently lacks the inertia support capabilities of synchronous generators, making it difficult to cope with dynamic scenarios such as grid frequency fluctuations and voltage disturbances. To address this, Virtual Synchronous Generator (VSG) technology has emerged. This technology simulates the rotor motion equations and excitation regulation characteristics of synchronous generators, providing necessary inertia support and damping regulation for systems operating under weak grid conditions. It also possesses independent grid-connected operation capabilities and has become one of the core development directions in the future field of grid-connected inverter control.

[0003] Although VSG technology effectively compensates for the inertia deficiency of traditional grid-connected inverters, it still faces significant challenges when applied in weak grid environments. Weak grids typically exhibit characteristics such as high line impedance, poor voltage stability, and low equivalent inertia. When the VSG interacts with a weak grid, their dynamic characteristics become coupled: on the one hand, changes in the line impedance of the weak grid alter the equivalent impedance of the VSG's output port, causing a shift in the dynamic response characteristics of its power control loop; on the other hand, the VSG's own inertia regulation process injects periodic power disturbances into the grid, and the limited damping capacity of the weak grid cannot effectively suppress these disturbances, ultimately leading to continuous oscillations in the VSG's output active or reactive power. These oscillations not only degrade the power quality of the grid-connected inverter but may also trigger system protection devices, and in severe cases, even disrupt the stable operation between the grid-connected inverter and the grid.

[0004] It is evident that in weak grid environments, existing VSG technology is prone to VSG output power oscillations due to the interaction between the characteristics of the weak grid and the dynamic characteristics of the VSG, which in turn affects the stable operation of the grid-connected inverter. Summary of the Invention

[0005] This invention provides a method and related device for enhancing VSG power oscillation suppression in weak power grids. This method can effectively suppress VSG power oscillations in weak power grid environments, thereby ensuring the stable operation of grid-connected inverters.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for enhancing VSG power oscillation suppression in weak power grids includes: Obtain the VSG output angular frequency sample value, d-axis voltage sample value, and d-axis current sample value; The VSG output angular frequency error, calculated from the VSG output angular frequency reference value and the VSG output angular frequency sample value, is input into a bandpass filter to extract the oscillation frequency. The oscillation frequency is then processed sequentially through inertial regulation and proportional regulation to output the active power oscillation regulation amount. The active power oscillation regulation amount is input into the main power regulation branch to obtain the VSG active power output amount. The voltage deviation between the d-axis voltage reference value and the d-axis voltage sample value is proportionally adjusted and filtered sequentially to obtain the first compensation component. The current deviation between the d-axis current sample value and the d-axis current reference value is proportionally adjusted and its reciprocal is taken sequentially to obtain the second compensation component. The first compensation component, the second compensation component, and the pre-calculated third compensation component are calculated to obtain the reactive power compensation amount. The reactive power compensation amount is input into the reactive power droop control branch to obtain the reactive power output of the VSG. The third compensation component is calculated based on the d-axis voltage reference value. The VSG is controlled based on its active power output and reactive power output to suppress VSG power oscillations.

[0007] Furthermore, the active power oscillation regulation amount is calculated based on the open-loop transfer function of the frequency control branch, which is specifically expressed as follows:

[0008] In the formula, This indicates the amount of active power oscillation regulation; This indicates the VSG output angular frequency error; For the proportional element of the frequency control branch; Virtual inertia coefficient for frequency control branch; Virtual damping coefficient for frequency control branch; It is a differential operator; This is the cutoff frequency of the bandpass filter; This represents the damping ratio of the bandpass filter.

[0009] Furthermore, the specific control expression for the main power regulation branch is as follows:

[0010] In the formula, The main branch power regulation amount; This is the reference value for the active power of the VSG; This refers to the active power output of the VSG. Virtual inertia coefficient of the main branch; It is a differential operator; Virtual damping coefficient of the main branch; Provides a reference value for the VSG output angular frequency; The phase angle of the grid voltage; , These are the PCC point voltage and the grid voltage, respectively.

[0011] Furthermore, the bandpass filter employs a notch filter, and the specific transfer function G1(s) of the notch filter is expressed as:

[0012] In the formula, The notch frequency, For the damping ratio, It is a differential operator.

[0013] Furthermore, the transfer function G2(s) of the notch filter is also expressed as:

[0014] In the formula, ; , ; Indicates the notch filter frequency bandwidth; Indicates the amplitude of the notch.

[0015] Furthermore, the third compensation component is calculated based on the d-axis voltage reference value after sequential filtering and proportional adjustment.

[0016] Furthermore, the calculation expression for the reactive power compensation amount is as follows:

[0017] In the formula, , These are the d-axis voltage reference value and the d-axis current reference value, respectively. , These are the d-axis voltage sampling value and the d-axis current sampling value, respectively. , These are the cutoff frequencies of the voltage feedforward filter, respectively. , , These are the proportional adjustment coefficients; For reciprocal operators; This is the reactive power compensation amount.

[0018] A system for enhancing VSG power oscillation suppression in weak power grids includes: The data acquisition module is used to acquire the VSG output angular frequency sample value, d-axis voltage sample value, and d-axis current sample value; The first adjustment module is used to input the VSG output angular frequency error, calculated from the VSG output angular frequency reference value and the VSG output angular frequency sample value, into a bandpass filter to extract the oscillation frequency; the oscillation frequency is then processed by inertial adjustment and proportional adjustment to output the active power oscillation adjustment amount; the active power oscillation adjustment amount is input to the main power adjustment branch to obtain the VSG active power output amount; The second adjustment module is used to sequentially proportionally adjust and filter the voltage deviation between the d-axis voltage reference value and the d-axis voltage sample value to obtain a first compensation component; sequentially proportionally adjust and reciprocally calculate the current deviation between the d-axis current sample value and the d-axis current reference value to obtain a second compensation component; calculate the first compensation component, the second compensation component, and a pre-calculated third compensation component to obtain the reactive power compensation amount; input the reactive power compensation amount into the reactive power droop control branch to obtain the VSG reactive power output; wherein, the third compensation component is calculated based on the d-axis voltage reference value; The control module is used to control the VSG based on its active power output and reactive power output in order to suppress VSG power oscillation.

[0019] A device for enhancing VSG power oscillation suppression in weak power grids, comprising: Memory, used to store computer programs; A processor is used to implement the steps of the above-described method for suppressing VSG power oscillations in a weak power grid when executing the computer program.

[0020] A computer-readable storage medium storing a computer program, which, when executed by a processor, is used to implement the steps of the above-described method for enhancing the suppression of VSG power oscillations in weak power grids.

[0021] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for enhancing VSG power oscillation suppression in weak power grids. It extracts the oscillation frequency component from the angular frequency error using a bandpass filter, generates an active power oscillation regulation amount through inertial and proportional regulation, and superimposes it onto the main power regulation branch to actively suppress active power oscillations. First and second compensation components are obtained by processing d-axis voltage and d-axis current deviations respectively, and then a third compensation component based on the d-axis voltage reference value is combined to calculate the reactive power compensation amount, which is input into the reactive power droop control branch to enhance system damping. The active power branch directly cancels the disturbance source by accurately extracting and reverse-compensating the oscillation frequency energy; the reactive power branch dynamically corrects the droop characteristics through multi-component collaborative compensation, enhancing the system's robustness to line impedance changes and overall damping capability. This method significantly reduces the active and reactive power oscillation amplitudes of VSGs in weak power grids, avoiding power quality deterioration or instability risks caused by continuous oscillations, thereby improving the system's stable operation and anti-interference capability under weak power grid conditions.

[0022] Preferably, in this invention, bandpass filtering, virtual inertia, and damping coefficients are integrated into a unified mathematical model. This design ensures that the compensation amount accurately matches the dynamic characteristics of the oscillation frequency, and the optimal match between compensation intensity and phase is achieved by adjusting the coefficients. This provides a quantifiable theoretical basis for oscillation suppression, making the frequency compensation process parametrically adjustable, avoiding the blindness of traditional empirical parameter tuning, and thus improving the adaptability and reliability of the oscillation suppression strategy.

[0023] Preferably, in this invention, the oscillation compensation is organically embedded into the traditional VSG active power control framework. The system's inertial support capability is maintained through a virtual inertia term, while a damping term coordinates the dynamic coupling relationship between the main power and the compensation. This achieves a seamless integration of basic power regulation and oscillation suppression functions, preserving the inertial support essence of the VSG for the power grid while ensuring the consistency of dynamic response between the main branch and the compensation branch through structured control laws, thus guaranteeing the stability of the system under all operating conditions.

[0024] Preferably, in this invention, the oscillation frequency is extracted directionally using the narrow-band impedance characteristics of a notch filter. The notch filter's transfer function is designed to selectively attenuate signals in specific frequency bands, efficiently separating background noise from the target oscillation component and avoiding phase distortion or delay problems caused by broadband filtering. This selective filtering mechanism provides a high-purity oscillation frequency input for subsequent compensation, laying the foundation for accurate suppression.

[0025] Preferably, in this invention, the bandwidth coefficient controls the frequency selection range, and the amplitude coefficient determines the suppression depth; the two work together to achieve refined capture of oscillation characteristics. This design endows the system with adaptive identification capabilities for oscillations of different intensities and frequency bands, significantly enhancing the generalization performance of the suppression strategy under complex operating conditions.

[0026] Preferably, in this invention, the voltage deviation component responds quickly to grid fluctuations, the current deviation component corrects impedance characteristics, and the reference value component provides benchmark compensation. These three components work together to reconstruct the inverter output impedance model, thus dynamically offsetting the coupling effect of line parameter changes on the reactive power loop, fundamentally enhancing the system's damping capability, and blocking the propagation path of power oscillations in the reactive power channel. Attached Figure Description

[0027] Figure 1 This is a block diagram of active power oscillation suppression control provided in an embodiment of the present invention; Figure 2 The root locus of the open-loop transfer function of the frequency control branch provided in this embodiment of the invention; wherein, (a) is the root locus varying with parameter J1; and (b) is the root locus varying with parameter D1. Figure 3 This is a block diagram of reactive power oscillation suppression control provided in an embodiment of the present invention; Figure 4 The amplitude and phase characteristic curves of the notch filter provided in the embodiments of the present invention; Figure 5 The diagram shows the separation effect of the notch filter provided in the embodiment of the present invention; wherein, (a) is the mixed signal; and (b) is the separation effect. Figure 6 A comparison diagram of different control methods for grid voltage disturbance (220V drops to 210V) provided in an embodiment of the present invention; wherein, (a) is grid voltage; (b) is output frequency; (c) is active power; and (d) is reactive power. Figure 7 The diagram shows a comparison between the oscillation suppression method under grid voltage harmonic disturbances and virtual impedance control provided in this embodiment of the invention; where (a) is the grid voltage; (b) is the output frequency; (c) is the active power; and (d) is the reactive power. Figure 8 A flowchart illustrating a method for enhancing VSG power oscillation suppression in a weak power grid, provided by an embodiment of the present invention; Figure 9 This is a schematic diagram of a structure for an enhanced VSG power oscillation suppression system in a weak power grid, provided as an embodiment of the present invention. Detailed Implementation

[0028] To further understand the content of this invention, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0029] To facilitate a better understanding of this technical solution, the technical terms involved in this invention are explained as follows: VSG (Virtual Synchronous Generator) is a technology that uses power electronics and control algorithms to simulate the operating characteristics of traditional synchronous generators, aiming to improve the stability and reliability of power systems.

[0030] PCC (Point of Common Coupling) refers to the common connection point, which is an electrical connection node shared by multiple devices or users in a power system. It usually serves as the interface between generators, loads, and the power grid.

[0031] As described in the background section, the inherent characteristics of a weak grid can interact with the VSG, causing oscillations in the VSG's output power and affecting the stable operation of the grid-connected inverter.

[0032] To address the aforementioned issues, this embodiment provides a method for enhancing VSG power oscillation suppression in weak power grids. This power oscillation suppression method can be applied indiscriminately to suppress both active and reactive power oscillations, and the frequency of oscillation suppression can be freely adjusted to effectively eliminate active and reactive power oscillations in VSGs. It features a wide range of applications and ease of implementation.

[0033] like Figure 8 As shown, this embodiment provides a method for enhancing VSG power oscillation suppression in weak power grids, including: Obtain the VSG output angular frequency sample value, d-axis voltage sample value, and d-axis current sample value; The VSG output angular frequency error, calculated from the VSG output angular frequency reference value and the VSG output angular frequency sample value, is input into a bandpass filter to extract the oscillation frequency. The oscillation frequency is then processed sequentially through inertial regulation and proportional regulation to output the active power oscillation regulation amount. The active power oscillation regulation amount is input into the main power regulation branch to obtain the VSG active power output amount. The voltage deviation between the d-axis voltage reference value and the d-axis voltage sample value is proportionally adjusted and filtered sequentially to obtain the first compensation component. The current deviation between the d-axis current sample value and the d-axis current reference value is proportionally adjusted and its reciprocal is taken sequentially to obtain the second compensation component. The first compensation component, the second compensation component, and the pre-calculated third compensation component are calculated to obtain the reactive power compensation amount. The reactive power compensation amount is input into the reactive power droop control branch to obtain the reactive power output of the VSG. The third compensation component is calculated based on the d-axis voltage reference value. The VSG is controlled based on its active power output and reactive power output to suppress VSG power oscillations.

[0034] The power oscillation suppression method provided in this embodiment will be further described below with reference to the accompanying drawings: like Figure 1 As shown, in this embodiment, the VSG output angular frequency sample value, d-axis voltage sample value, and d-axis current sample value are first acquired. Then, the VSG output angular frequency error is calculated. As input; where VSG output angular frequency error Based on VSG output angular frequency reference value With VSG output angular frequency sampling value The difference is calculated; then, the VSG output angular frequency error is used to extract different oscillation frequencies through a bandpass filter, and the adjustment amount to suppress the active power oscillation at the current frequency is calculated using the inertial element and proportional coefficient corresponding to the frequency control branch. The adjustment amount of the frequency active power oscillation Superimposed on the main power regulation branch, combined with the power regulation amount of the main branch. The final VSG active power output is generated; the control process of the main branch power regulation can be expressed as: (1) Analysis reveals the open-loop transfer function of the frequency control branch as follows: (2) in, Provides a reference value for the VSG output angular frequency; The VSG outputs the angular frequency sample value; It is a differential operator; This is the cutoff frequency of the bandpass filter; The damping ratio of the bandpass filter; Virtual inertia coefficient for frequency control branch; Virtual damping coefficient for frequency control branch; For the proportional element of the frequency control branch; This refers to the active power oscillation regulation amount; This refers to the output power of the VSG; The main branch power regulation amount; This is the reference value for the active power of the VSG; Virtual inertia coefficient of the main branch; Virtual damping coefficient of the main branch; It is the change in frequency; The phase angle of the voltage at point PCC; The phase angle of the grid voltage; For VSG's offensive angle; , These are the PCC point voltage and the mains voltage, respectively. This represents the power grid impedance.

[0035] like Figure 2 As shown, specifically as follows Figure 2 As shown in (a) and (b) in the figure, the graph is plotted according to equation (2) with respect to the parameter. and The root locus of the changing open-loop transfer function; it can be seen that, as... As the value increases, the dominant pole gets closer to the imaginary axis, meaning the stability of the frequency control branch decreases. And as... As the value of increases, the dominant pole moves further away from the imaginary axis, meaning that the stability of the frequency control branch increases. Therefore, in the method proposed in this invention, increasing It will reduce branch stability and increase It will improve the stability of the frequency control branch.

[0036] Specifically, as a preferred embodiment, the bandpass filter in this embodiment is a notch filter; notch filters are frequently used in the field of permanent magnet synchronous motor control, and can separate power oscillations and angular frequency changes caused by frequency support, and separate the angular frequency changes caused by frequency support. As the input to the feedforward path, the transfer function of the notch filter is: (3) In equation (3), It is the notch filter frequency. It is the damping ratio, which satisfies... As the damping ratio decreases, the notch filter's frequency bandwidth narrows, the attenuation amplitude increases, and the phase lag becomes larger. The core parameter of a notch filter is its notch frequency. Notch filter frequency bandwidth and notch amplitude Furthermore, the transfer function of the notch filter can also be expressed as: (4) In equation (4), let , , .

[0037] like Figure 4 As shown, the gain attenuation is significant and the phase lag is also obvious at 50Hz, but the phase lag is very small in other frequency ranges. Therefore, the notch filter has a significant separation effect on signals of specific frequencies.

[0038] like Figure 5 As shown, specifically as follows Figure 5 As shown in (a) and (b), using a mixed signal containing 50Hz and 10Hz, the notch filter can effectively separate the two signals without producing a large phase delay.

[0039] like Figure 3As shown, in the reactive power oscillation suppression process, the voltage deviation between the d-axis voltage reference value and the d-axis voltage sample value is proportionally adjusted and filtered sequentially to obtain the first compensation component. The current deviation between the d-axis current sample value and the d-axis current reference value is proportionally adjusted and its reciprocal is taken sequentially to obtain the second compensation component. The first compensation component, the second compensation component, and the pre-calculated third compensation component are calculated to obtain the reactive power compensation amount. The reactive power compensation amount is input into the reactive power droop control branch to obtain the reactive power output of the VSG. That is, based on the traditional reactive power droop control, a reactive power oscillation suppression stage is added. By collecting the d-axis voltage and d-axis current to generate the corresponding reactive power compensation amount, the feedforward compensation function of the traditional droop control is completed, improving the accuracy and speed of reactive power control. The specific expression of the reactive power oscillation stage can be expressed as follows: (5) In the formula, , These are the d-axis voltage reference value and the d-axis current reference value, respectively. , These are the d-axis voltage sampling value and the d-axis current sampling value, respectively. , These are the d-axis voltage deviation and the d-axis current deviation, respectively. , This is the cutoff frequency of the voltage feedforward filter; , , This is the proportional adjustment coefficient; For reciprocal operators; This is the reactive power compensation amount; , , These are, respectively, the reactive power reference value, the reactive power conversion quantity, and the reactive power output quantity; It is a time constant; This is the droop coefficient.

[0040] The compensation amount for reactive power droop control can be obtained through formula (5), thus completing the reactive power oscillation suppression control.

[0041] like Figure 9As shown, this embodiment also provides an enhanced VSG power oscillation suppression system in a weak grid, including: a data acquisition module for acquiring VSG output angular frequency sampling values, d-axis voltage sampling values, and d-axis current sampling values; a first adjustment module for inputting the VSG output angular frequency error calculated from the VSG output angular frequency reference value and the VSG output angular frequency sampling values ​​into a bandpass filter to extract the oscillation frequency; processing the oscillation frequency sequentially through inertial adjustment and proportional adjustment to output an active power oscillation adjustment amount; inputting the active power oscillation adjustment amount into the main power adjustment branch to obtain the VSG active power output; and a second adjustment module for inputting the d-axis voltage reference value and the d-axis voltage sampling values ​​into a bandpass filter to extract the oscillation frequency; processing the oscillation frequency sequentially through inertial adjustment and proportional adjustment to output an active power oscillation adjustment amount; and inputting the active power oscillation adjustment amount into the main power adjustment branch to obtain the VSG active power output; and a second adjustment module for inputting the d-axis voltage reference value and the d-axis voltage sampling values ​​into a bandpass filter to extract the oscillation frequency error. The voltage deviation is sequentially proportionally adjusted and filtered to obtain the first compensation component. The current deviation between the d-axis current sample value and the d-axis current reference value is sequentially proportionally adjusted and its reciprocal is calculated to obtain the second compensation component. The first compensation component, the second compensation component, and the pre-calculated third compensation component are calculated to obtain the reactive power compensation amount. The reactive power compensation amount is input into the reactive power droop control branch to obtain the VSG reactive power output. The third compensation component is calculated based on the d-axis voltage reference value. The control module is used to control the VSG based on the VSG active power output and the VSG reactive power output to suppress VSG power oscillation.

[0042] The present invention also provides a device for enhancing VSG power oscillation suppression in a weak power grid, comprising: a memory for storing a computer program; and a processor for executing the computer program to implement the steps of the method for enhancing VSG power oscillation suppression in a weak power grid.

[0043] The present invention also provides a computer program product, including a computer program / instructions that, when executed by a processor, implement the steps of the method for suppressing VSG power oscillations in a weak power grid.

[0044] When the processor executes the computer program, it implements the above-mentioned steps to enhance the suppression of VSG power oscillations in weak grids, for example: acquiring the VSG output angular frequency sample value, d-axis voltage sample value, and d-axis current sample value; The VSG output angular frequency error, calculated from the VSG output angular frequency reference value and the VSG output angular frequency sample value, is input into a bandpass filter to extract the oscillation frequency. The oscillation frequency is then processed sequentially through inertial regulation and proportional regulation to output the active power oscillation regulation amount. The active power oscillation regulation amount is input into the main power regulation branch to obtain the VSG active power output amount. The voltage deviation between the d-axis voltage reference value and the d-axis voltage sample value is proportionally adjusted and filtered sequentially to obtain the first compensation component. The current deviation between the d-axis current sample value and the d-axis current reference value is proportionally adjusted and its reciprocal is taken sequentially to obtain the second compensation component. The first compensation component, the second compensation component, and the pre-calculated third compensation component are calculated to obtain the reactive power compensation amount. The reactive power compensation amount is input into the reactive power droop control branch to obtain the reactive power output of the VSG. The third compensation component is calculated based on the d-axis voltage reference value. The VSG is controlled based on its active power output and reactive power output to suppress VSG power oscillations.

[0045] For example, the computer program can be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present invention. The one or more modules / units can be a series of computer program instruction segments capable of performing preset functions, the instruction segments describing the execution process of the computer program in the VSG power oscillation suppression device in the enhanced weak grid. For example, the computer program can be divided into a data acquisition module, a first adjustment module, a second adjustment module, and a control module; the specific functions of each module are as follows: the data acquisition module is used to acquire the VSG output angular frequency sampling value, the d-axis voltage sampling value, and the d-axis current sampling value; the first adjustment module is used to input the VSG output angular frequency error calculated from the VSG output angular frequency reference value and the VSG output angular frequency sampling value into a bandpass filter to extract the oscillation frequency; the oscillation frequency is processed sequentially through inertial adjustment and proportional adjustment to output the active power oscillation adjustment amount; the active power oscillation adjustment amount is input to the main power adjustment branch to obtain the VSG active power output amount; the second adjustment module is used to input the d-axis voltage reference value... The voltage deviation from the d-axis voltage sample value is sequentially proportionally adjusted and filtered to obtain the first compensation component. The current deviation between the d-axis current sample value and the d-axis current reference value is sequentially proportionally adjusted and its reciprocal is taken to obtain the second compensation component. The first compensation component, the second compensation component, and the pre-calculated third compensation component are calculated to obtain the reactive power compensation amount. The reactive power compensation amount is input to the reactive power droop control branch to obtain the VSG reactive power output. The third compensation component is calculated based on the d-axis voltage reference value. The control module is used to control the VSG based on the VSG active power output and the VSG reactive power output to suppress VSG power oscillation.

[0046] The VSG power oscillation suppression device for enhancing a weak grid can be a computing device such as a desktop computer, laptop, handheld computer, or cloud server. This device may include, but is not limited to, processors and memory. Those skilled in the art will understand that the above are examples of VSG power oscillation suppression devices for enhancing a weak grid and do not constitute a limitation on such devices. The device may include more components than described above, or combine certain components, or use different components. For example, the VSG power oscillation suppression device may also include input / output devices, network access devices, buses, etc.

[0047] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor, or any conventional processor. This processor is the control center for VSG power oscillation suppression in the enhanced weak grid, connecting various parts of the VSG power oscillation suppression equipment throughout the enhanced weak grid using various interfaces and lines.

[0048] The memory can be used to store the computer program and / or modules. The processor implements various functions of the enhanced VSG power oscillation suppression device by running or executing the computer program and / or modules stored in the memory and calling the data stored in the memory.

[0049] The memory may primarily include a program storage area and a data storage area. The program storage area may store the operating system and at least one application program required for a function (such as sound playback, image playback, etc.). The data storage area may store data created based on the use of the mobile phone (such as audio data, phonebook, etc.). Furthermore, the memory may include high-speed random access memory and non-volatile memory, such as hard disks, RAM, plug-in hard disks, smart media cards (SMC), secure digital cards (SD cards), flash cards, at least one disk storage device, flash memory device, or other volatile solid-state storage devices.

[0050] The present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method for enhancing VSG power oscillation suppression in a weak power grid.

[0051] If the modules / units of the enhanced weak grid power oscillation suppression system are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium.

[0052] Based on this understanding, the present invention can implement all or part of the processes in the above-described method for suppressing VSG power oscillations in enhanced weak grids, or it can be accomplished by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the above-described method for suppressing VSG power oscillations in enhanced weak grids. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or preset intermediate forms, etc.

[0053] The computer-readable storage medium may include: any entity or device capable of carrying the computer program code, recording media, USB flash drive, portable hard drive, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc.

[0054] like Figure 6 As shown, specifically as follows Figure 6 As shown in (a), (b), (d), and (d) of the diagram, the performance of the VSG power oscillation suppression method proposed in this invention is compared with that of existing virtual impedance control under grid voltage disturbances. When the grid voltage amplitude is disturbed, the output frequency of the virtual synchronous generator using the VSG power oscillation suppression method proposed in this invention shows almost no significant change, and the oscillation amplitudes of active and reactive power are also small. In contrast, the VSG output frequency oscillation amplitude using virtual impedance control is approximately 0.04 Hz, and oscillations also exist in active and reactive power. It can be seen that the transient performance of the VSG power oscillation suppression method proposed in this invention is superior to that of virtual impedance control under grid voltage disturbances.

[0055] like Figure 7 As shown, specifically as follows Figure 7As shown in (a), (b), (d), and (d) in the figure, the performance of the VSG power oscillation suppression method proposed in this invention is compared with that of the existing virtual impedance control under grid voltage harmonic disturbance. When the grid voltage is disturbed by the 5th and 7th harmonics, the output frequency of the virtual impedance control will fluctuate, and the active power and reactive power will also oscillate. However, when the VSG power oscillation suppression method proposed in this invention is used, the VSG output frequency remains basically unchanged, and the fluctuation of active power and reactive power is also small.

[0056] The comparative analysis above shows that the VSG power oscillation suppression method proposed in this invention can effectively reduce the active and reactive power oscillations of the VSG. It not only outperforms virtual impedance control in terms of power decoupling and transient stability, but also demonstrates superior robustness under grid voltage frequency, amplitude, and harmonic disturbances.

[0057] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.

[0058] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for enhancing VSG power oscillation suppression in a weak grid, characterized in that, The method comprises the following steps: obtaining a VSG output angular frequency sample value, a d-axis voltage sample value and a d-axis current sample value; inputting a VSG output angular frequency error calculated from a VSG output angular frequency reference value and the VSG output angular frequency sample value into a band-pass filter to extract an oscillation frequency; sequentially performing inertial regulation and proportional regulation on the oscillation frequency to output an active power oscillation regulation amount; inputting the active power oscillation regulation amount into a main power regulation branch to obtain a VSG active power output amount; sequentially performing proportional regulation and filtering on a voltage deviation between a d-axis voltage reference value and the d-axis voltage sample value to obtain a first compensation component; sequentially performing proportional regulation and inverse operation on a current deviation between a d-axis current sample value and a d-axis current reference value to obtain a second compensation component; calculating the first compensation component, the second compensation component and a third compensation component pre-calculated according to the d-axis voltage reference value to obtain a reactive power compensation amount; inputting the reactive power compensation amount into a reactive power droop control branch to obtain a VSG reactive power output amount; wherein the third compensation component is calculated according to the d-axis voltage reference value; controlling the VSG according to the VSG active power output amount and the VSG reactive power output amount to realize oscillation suppression of VSG power.

2. The method of claim 1, wherein the method is characterized by: The active power oscillation regulation amount is calculated based on an open-loop transfer function of the frequency control branch, and the open-loop transfer function is specifically represented as follows: wherein represents the active power oscillation regulation amount; represents the VSG output angular frequency error; is a proportional element of the frequency control branch; is a virtual inertia coefficient of the frequency control branch; is a virtual damping coefficient of the frequency control branch; is a differential operator; is a band-pass filter cutoff frequency; is a band-pass filter damping ratio.

3. The method of claim 1, wherein the method further comprises: The specific control expression of the main power regulation branch is as follows: In the formula, is the main branch power regulation amount; is the VSG active power reference value; is the VSG active power output amount; is the main branch virtual inertia coefficient; is the differential operator; is the main branch virtual damping coefficient; is the VSG output angular frequency reference value; is the grid voltage phase angle; , is the PCC point voltage and the grid voltage, respectively.

4. The method of claim 1, wherein the method is characterized by: The band-pass filter adopts a notch filter, and a specific transfer function G1(s) of the notch filter is represented as follows: wherein is a notch frequency, is a damping ratio, is a differential operator.

5. The method of claim 4, wherein the method further comprises: The transfer function G2(s) of the notch filter is also represented as follows: In the formulae, ; , ; represents a notch frequency bandwidth; represents a notch amplitude.

6. The method of claim 1, wherein the method is enhanced to suppress power oscillations of a VSG in a weak grid, and wherein the method further comprises: The third compensation component is calculated based on the d-axis voltage reference value after sequentially performing filtering and proportional regulation.

7. The method of claim 1, wherein the method is enhanced for suppressing power oscillations of VSG in a weak grid. The calculation expression of the reactive power compensation amount is as follows: In the formula, , are d-axis voltage reference value and d-axis current reference value, respectively; , are d-axis voltage sampling value and d-axis current sampling value, respectively; , are cut-off frequencies of voltage feed-forward filter, respectively; , , are proportional adjustment coefficients, respectively; is a reciprocal operator; is a reactive power compensation amount.

8. A system for enhancing VSG power oscillation suppression in a weak grid, the system comprising: a VSG power oscillation suppression system according to any one of claims 1 to 7; and a power grid according to any one of claims 1 to 7. The method comprises the following steps: a data acquisition module is configured to obtain a VSG output angular frequency sample value, a d-axis voltage sample value and a d-axis current sample value; a first regulation module is configured to input a VSG output angular frequency error calculated from a VSG output angular frequency reference value and the VSG output angular frequency sample value into a band-pass filter to extract an oscillation frequency; sequentially perform inertial regulation and proportional regulation on the oscillation frequency to output an active power oscillation regulation amount; input the active power oscillation regulation amount into a main power regulation branch to obtain a VSG active power output amount; a second regulation module is configured to sequentially perform proportional regulation and filtering on a voltage deviation between a d-axis voltage reference value and the d-axis voltage sample value to obtain a first compensation component; sequentially perform proportional regulation and inverse operation on a current deviation between a d-axis current sample value and a d-axis current reference value to obtain a second compensation component; calculate the first compensation component, the second compensation component and a third compensation component pre-calculated according to the d-axis voltage reference value to obtain a reactive power compensation amount; input the reactive power compensation amount into a reactive power droop control branch to obtain a VSG reactive power output amount; wherein the third compensation component is calculated according to the d-axis voltage reference value; A control module is configured to control the VSG according to the active power output of the VSG and the reactive power output of the VSG, so as to realize the oscillation suppression of the VSG power.

9. A device for enhancing VSG power oscillation suppression in a weak grid, characterized by, The method comprises the steps of: a memory for storing a computer program; a processor for executing the computer program to realize the steps of the method for enhancing the VSG power oscillation suppression in a weak power grid according to any one of claims 1-7.

10. A computer-readable storage medium storing a computer program, the computer program comprising instructions that, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 9. The computer program is executed by the processor to realize the steps of the method for enhancing the VSG power oscillation suppression in a weak power grid according to any one of claims 1-7.

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