Power control method and device suitable for conventional direct current networking transformation

Abstract

The invention discloses a power control method and device suitable for conventional direct current networking transformation, which are applied to the technical field of power control, and the method comprises the steps: obtaining output current data and direct current side voltage data, and obtaining grid-connected voltage data and grid-connected phase angle data; extracting a frequency oscillation component from the instantaneous power data; performing adaptive frequency tracking processing on the frequency oscillation component by using a fast Fourier analysis technology to obtain dominant oscillation frequency data; inputting the direct current side voltage data into a cross coupling damping matrix for processing to obtain gain compensation data; acquiring impedance data of the target power grid in real time, and generating an anti-oscillation power signal based on the gain compensation data and the impedance data; and performing power control on the target power grid by using the anti-oscillation power signal. According to the method provided by the invention, the problem of broadband oscillation generated in the process of replacing the reactive power compensation equipment of the direct current application with the network construction type SVG can be solved, so that the safe operation of the power grid is ensured.

Description

Technical Field

[0001] This invention relates to the field of power control technology, and in particular to a power control method and apparatus suitable for the retrofitting of conventional DC grids. Background Technology

[0002] High-voltage direct current (HVDC) transmission technology using grid-commutated converters (LCCs) has advantages such as long transmission distance, large transmission capacity, flexible control, and no synchronization problems when interconnecting power grids. It is suitable for network interconnection between power systems and the transmission of power from giant energy bases, and has been widely used.

[0003] Currently, most of the ±500kV conventional DC transmission projects in operation use passive filters and capacitors as reactive power compensation equipment. However, when DC power fluctuates drastically, the reactive power of the DC system becomes unbalanced, leading to AC voltage overvoltage problems. In severe cases, this can cause a large number of new energy units to disconnect from the grid, affecting the safe operation of the system.

[0004] Therefore, grid-forming static var generators (SVG) can inject reactive power into the connection point in a timely manner when DC power fluctuates drastically. They can not only dynamically compensate reactive power, but also actively establish voltage and frequency support in weak grid or islanded modes. However, when using grid-forming SVG to replace conventional DC engineering reactive power compensation equipment, although it can significantly improve the system's dynamic reactive power support and voltage construction capabilities, it also introduces significant broadband oscillation risks. This may lead to large-scale grid disconnection of new energy units, overstress damage to key electrical equipment, and serious deterioration of power quality, ultimately threatening the safe and stable operation of the DC transmission and receiving system and causing serious power supply accidents.

[0005] Therefore, how to solve the wideband oscillation problem that occurs when using grid-type SVG to replace conventional DC application reactive power compensation equipment has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] This invention provides a power control method and apparatus suitable for conventional DC grid-based retrofitting, in order to solve the wideband oscillation problem generated during the process of replacing reactive power compensation equipment in conventional DC applications with grid-based SVG, thereby ensuring the safe operation of the power grid.

[0007] To address the aforementioned technical problems, this invention provides a power control method applicable to conventional DC grid-based retrofitting, applied during the process of connecting a grid-type reactive power generator to the target power grid. The method includes:

[0008] The output current data and DC side voltage data of the grid-type reactive power generator are obtained, and the grid connection voltage data and grid connection phase angle data of the grid connection point between the grid-type reactive power generator and the target power grid are obtained.

[0009] Frequency oscillation components are extracted from the instantaneous power data of the grid-type reactive power generator, wherein the frequency oscillation components are determined by the output current data, the grid-connected voltage data, and the grid-connected phase angle data;

[0010] The frequency oscillation components are subjected to adaptive frequency tracking processing using fast Fourier analysis technology to obtain the dominant oscillation frequency data of the target power grid.

[0011] The DC-side voltage data is input into the constructed cross-coupling damping matrix for processing to obtain gain compensation data. The construction process includes processing the dominant oscillation frequency data using phase lead compensation technology to obtain the same-channel damping coefficient, performing mode decoupling processing on the dominant oscillation frequency data to obtain the cross-channel damping coefficient, and constructing the cross-coupling damping matrix based on the same-channel damping coefficient and the cross-channel damping coefficient.

[0012] The impedance data of the target power grid is acquired in real time, and an anti-oscillation power signal is generated based on the gain compensation data and the impedance data.

[0013] The target power grid is controlled using the anti-oscillation power signal.

[0014] As one preferred embodiment, the extraction of frequency oscillation components from the instantaneous power data of the grid-type reactive power generator includes:

[0015] Based on the orthogonal signal generation method, the output current data, the grid-connected voltage data, and the grid-connected phase angle data are processed to obtain the instantaneous power data of the grid-type reactive power generator;

[0016] The instantaneous power data and the DC-side voltage data are filtered and extracted to obtain the frequency oscillation component.

[0017] As one preferred embodiment, the adaptive frequency tracking processing of the frequency oscillation components using Fast Fourier Analysis to obtain the dominant oscillation frequency data of the target power grid includes:

[0018] The frequency oscillation component is processed by a sliding time window to obtain the oscillation time-domain data;

[0019] The power spectrum of the oscillation time-domain data was estimated using fast Fourier analysis to obtain a power spectral density map.

[0020] Peak search is performed on the power spectral density map to obtain the dominant oscillation frequency data of the target power grid.

[0021] As one preferred embodiment, the process of using phase lead compensation technology to process the dominant oscillation frequency data to obtain the same-channel damping coefficient includes:

[0022] The dominant oscillation frequency data is converted to obtain the target angular frequency;

[0023] The target angular frequency is processed using phase lead compensator technology to obtain the compensation coefficient;

[0024] Based on the compensation coefficient, the damping coefficient of the same channel is determined.

[0025] As one preferred embodiment, the modal decoupling processing of the dominant oscillation frequency data to obtain the cross-channel damping coefficient includes:

[0026] The dominant oscillation frequency data is linearized to obtain the Jacobian matrix of the target power grid;

[0027] The Jacobian matrix is ​​subjected to eigenvalue decomposition and mode identification to obtain several eigenvectors and several oscillation modes that match the eigenvectors;

[0028] Factor analysis was performed on each of the oscillation modes to obtain the modal factor matrix;

[0029] The modal factor matrix is ​​processed using a decoupling controller to obtain the cross-channel damping coefficient.

[0030] As one preferred embodiment, constructing the cross-coupled damping matrix based on the same-channel damping coefficient and the cross-channel damping coefficient includes:

[0031] The initial damping matrix is ​​obtained by configuring the matrix elements of the same-channel damping coefficient and the cross-channel damping coefficient using matrix synthesis technology.

[0032] The initial damping matrix is ​​subjected to gain adjustment to obtain the cross-coupling damping matrix.

[0033] As one preferred embodiment, the generation of the anti-oscillation power signal based on the gain compensation data and the impedance data includes:

[0034] The impedance data is processed by power sensitivity calculation using the impedance-power mapping relationship to obtain the reference anti-oscillation power;

[0035] The gain compensation data and the reference anti-oscillation power are subjected to amplitude-phase adjustment processing using gain weighted synthesis technology to obtain the anti-oscillation power signal.

[0036] The present invention also provides a power control device suitable for conventional DC grid transformation, comprising:

[0037] The acquisition module is used to acquire the output current data and DC side voltage data of the grid-type reactive power generator, and to acquire the grid connection voltage data and grid connection phase angle data of the grid connection point between the grid-type reactive power generator and the target power grid.

[0038] An extraction module is used to extract frequency oscillation components from the instantaneous power data of the grid-type reactive power generator, wherein the frequency oscillation components are determined by the output current data, the grid-connected voltage data, and the grid-connected phase angle data;

[0039] An adaptive module is used to perform adaptive frequency tracking processing on the frequency oscillation components using fast Fourier analysis technology to obtain the dominant oscillation frequency data of the target power grid.

[0040] The processing module is used to input the DC-side voltage data into the constructed cross-coupling damping matrix for processing to obtain gain compensation data. The construction process includes processing the dominant oscillation frequency data using phase lead compensation technology to obtain the same-channel damping coefficient, performing mode decoupling processing on the dominant oscillation frequency data to obtain the cross-channel damping coefficient, and constructing the cross-coupling damping matrix based on the same-channel damping coefficient and the cross-channel damping coefficient.

[0041] The generation module is used to acquire the impedance data of the target power grid in real time, and generate an anti-oscillation power signal based on the gain compensation data and the impedance data;

[0042] A control module is used to perform power control on the target power grid using the anti-oscillation power signal.

[0043] The present invention also provides a power control device suitable for conventional DC grid-based retrofitting, comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the power control method for conventional DC grid-based retrofitting as described above.

[0044] The present invention further provides a computer-readable storage medium storing a computer program, wherein when the device containing the computer-readable storage medium executes the computer program, it implements the power control method applicable to conventional DC grid transformation as described above.

[0045] Compared with the prior art, the beneficial effects of the present invention are at least one of the following:

[0046] Compared with existing technologies, this invention extracts frequency oscillation components from instantaneous power by real-time acquisition of output current, DC-side voltage, grid connection point voltage, and phase angle data of the grid-type reactive power generator. It then uses Fast Fourier Analysis for adaptive frequency tracking to determine the dominant oscillation frequency. Based on this frequency, it obtains the same-channel damping coefficient through phase lead compensation and the cross-channel damping coefficient through mode decoupling, constructing a cross-coupling damping matrix. The DC-side voltage is then input into the matrix to calculate gain compensation data. Finally, it combines real-time grid impedance to generate an anti-oscillation power signal, injecting positive damping power in the opposite direction to the oscillation into the grid. This dynamically and accurately suppresses broadband oscillations, solving the oscillation problem caused by multi-band coupling and time-varying grid impedance when grid-type equipment replaces traditional reactive power compensation devices. Attached Figure Description

[0047] Figure 1 This is a flowchart illustrating a power control method applicable to conventional DC grid transformation in one embodiment of the present invention.

[0048] Figure 2 This is a schematic diagram of the structure of a power control device suitable for conventional DC grid transformation in one embodiment of the present invention;

[0049] Figure 3 This is a schematic diagram of the structure of a power control device suitable for conventional DC grid transformation in one embodiment of the present invention;

[0050] Figure label:

[0051] Among them, 11 is the acquisition module; 12 is the extraction module; 13 is the adaptive module; 14 is the processing module; 15 is the generation module; 16 is the control module; 21 is the processor; and 22 is the memory. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0053] In the description of this invention, it should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the invention. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0054] One embodiment of the present invention provides a power control method applicable to conventional DC grid transformation. For details, please refer to [link to relevant documentation]. Figure 1 , Figure 1 The diagram shown is a flowchart illustrating a power control method applicable to conventional DC grid transformation in one embodiment of the present invention. The method includes:

[0055] S1: Obtain the output current data and DC side voltage data of the grid-type reactive power generator, and obtain the grid connection voltage data and grid connection phase angle data of the grid connection point between the grid-type reactive power generator and the target power grid;

[0056] S2: Extract the frequency oscillation component from the instantaneous power data of the grid-type reactive power generator, wherein the frequency oscillation component is determined by the output current data, the grid-connected voltage data and the grid-connected phase angle data;

[0057] S3: Adaptive frequency tracking processing is performed on the frequency oscillation components using fast Fourier analysis technology to obtain the dominant oscillation frequency data of the target power grid;

[0058] S4: Input the DC-side voltage data into the constructed cross-coupling damping matrix for processing to obtain gain compensation data. The construction process includes processing the dominant oscillation frequency data using phase lead compensation technology to obtain the same-channel damping coefficient, performing mode decoupling processing on the dominant oscillation frequency data to obtain the cross-channel damping coefficient, and constructing the cross-coupling damping matrix based on the same-channel damping coefficient and the cross-channel damping coefficient.

[0059] S5: Acquire the impedance data of the target power grid in real time, and generate an anti-oscillation power signal based on the gain compensation data and the impedance data;

[0060] S6: Perform power control on the target power grid using the anti-oscillation power signal.

[0061] Specifically, the application background of this invention is that during the process of connecting a grid-type reactive power generator to the target power grid, when the fast control loop of the grid-type reactive power generator and the inductive impedance presented by the power grid system have an unfavorable dynamic interaction, this interaction causes the system to exhibit negative damping characteristics in a specific frequency band, resulting in the amplification of small disturbances and thus triggering continuous broadband oscillations.

[0062] The key to suppressing broadband oscillations lies in: real-time identification of oscillation characteristics, injection of positive damping in the opposite direction to the oscillation, and dynamic adaptation to changes in the power grid.

[0063] The system acquires the output current and DC side voltage data of the grid-connected reactive power generator, as well as the grid connection voltage and phase angle data of the grid connection point between the grid-connected reactive power generator and the target power grid.

[0064] Among them, the grid connection point voltage and grid connection phase angle directly reflect the oscillation state of the grid side, the output current data reflects the interactive response between the equipment's own output and the grid oscillation, and the DC side voltage data indirectly affects the AC side output characteristics, which is an important data for damping compensation.

[0065] In step S2, the frequency oscillation component is extracted from the instantaneous power data of the grid-type reactive power generator. Specifically, this includes: processing the output current data, the grid-connected voltage data, and the grid-connected phase angle data based on the orthogonal signal generation method to obtain the instantaneous power data of the grid-type reactive power generator; and filtering and extracting the instantaneous power data and the DC-side voltage data to obtain the frequency oscillation component.

[0066] Specifically, by using a synchronous rotating coordinate system transformation, also known as the Park transformation, the collected three-phase output current, grid-connected voltage, and grid-connected phase angle are transformed from the stationary ABC coordinate system to a dq coordinate system that rotates synchronously with the grid fundamental frequency. In this rotating coordinate system, the original AC voltage and current components are decoupled into two DC components, namely the d-axis component and the q-axis component. Using the voltage and current components on these two axes, the instantaneous active power and instantaneous reactive power output of the grid-type reactive power generator are calculated in real time according to the instantaneous power theory.

[0067] The instantaneous active power, instantaneous reactive power, and the directly acquired DC-side voltage signal are fed into a filter, which is usually a high-pass filter or a band-pass filter. After filtering, the output is the AC pulsating part of the instantaneous power and the AC pulsating part of the DC-side voltage.

[0068] It should be noted that a high-pass filter sets a very low cutoff frequency to completely filter out the DC component and slowly changing trend components in the signal; a band-pass filter is more precise and can only allow signals within a preset frequency range that may oscillate to pass through.

[0069] By filtering, the average power representing the normal operating state of the device is removed, leaving only the oscillating power component representing the abnormal state.

[0070] Next, in step S3, the frequency oscillation component is subjected to adaptive frequency tracking processing using Fast Fourier Analysis (FFT) to obtain the dominant oscillation frequency data of the target power grid. Specifically, this includes: performing sliding time window processing on the frequency oscillation component to obtain oscillation time-domain data; performing power spectrum estimation processing on the oscillation time-domain data using FFT to obtain a power spectrum density map; and performing peak search on the power spectrum density map to obtain the dominant oscillation frequency data of the target power grid.

[0071] The core of sliding time window processing is to dynamically capture real-time and effective time-domain signals. Specifically, a fixed-length time window is determined, and this length needs to match the frequency resolution requirements of subsequent Fast Fourier Transform (FFT) analysis.

[0072] The continuously acquired frequency oscillation components are filled into the time window in chronological order. As new oscillation signal data is continuously input, the time window will slide synchronously, that is, discarding the oldest data acquired in the window and incorporating the latest acquired data, always keeping the data in the window as a time domain signal of a fixed length near the current time. The final output is the continuously updated oscillation time domain data.

[0073] The sliding time window processing technique is used because Fast Fourier Analysis requires a fixed length of time-domain data for frequency domain conversion. On the other hand, the frequency of the broadband oscillation of the power grid drifts in real time with load changes and equipment status adjustments. If a fixed time window is used, the analysis results will be lagging and unable to track frequency changes in a timely manner. The sliding window ensures that the latest oscillation signal is analyzed each time by updating the data in real time, laying the foundation for subsequent adaptive tracking.

[0074] A Fast Fourier Transform (FFT) is performed on the windowed oscillation time-domain data to transform it from the time domain to the frequency domain. The output of the FFT is a complex number that contains the amplitude and phase information of each frequency component.

[0075] Next, the square of the complex modulus of each frequency point in the FFT transform result is taken to obtain the power of that frequency component. Plotting the power of all these frequency points together gives us the power spectral density map.

[0076] By displaying the power at each frequency, the power spectral density plot can clearly identify which frequency has the strongest and most significant oscillation energy. The vertical axis of the power spectral density plot directly reflects the intensity of the oscillation, providing a quantitative basis for identifying the dominant oscillation frequency.

[0077] The scanning algorithm automatically scans the entire power spectral density map to find all local maxima, i.e., peak points. However, not all peaks are oscillation modes of interest. Specific analysis modes include: setting a minimum power threshold to filter out weak energy or false peaks that may be caused by noise; focusing the search range on frequency bands prone to oscillation, such as subsynchronous and supersynchronous frequency bands, and ignoring normal components such as power frequency, based on the characteristics of the power grid system; and selecting the frequency corresponding to the peak with the highest power among all peaks that pass the threshold as the dominant oscillation frequency.

[0078] In step S4, the DC-side voltage data is input into the constructed cross-coupling damping matrix for processing to obtain gain compensation data. The construction process includes processing the dominant oscillation frequency data using phase lead compensation technology to obtain the same-channel damping coefficient, performing mode decoupling processing on the dominant oscillation frequency data to obtain the cross-channel damping coefficient, and constructing the cross-coupling damping matrix based on the same-channel damping coefficient and the cross-channel damping coefficient.

[0079] Specifically, the dominant oscillation frequency data is processed using phase lead compensation technology to obtain the co-channel damping coefficient, including: converting the dominant oscillation frequency data to obtain a target angular frequency; processing the target angular frequency using phase lead compensator technology to obtain a compensation coefficient; and determining the co-channel damping coefficient based on the compensation coefficient.

[0080] The dominant oscillation frequency data is converted using the following formula:

[0081] ω=2π×f

[0082] Where ω is the target angular frequency and f is the dominant oscillation frequency data.

[0083] The reason for the conversion is that it facilitates the subsequent design and calculation of the compensator. Since the transfer function of the phase lead compensator is usually defined based on the angular frequency, this step ensures that the frequency data is compatible with the control system model, providing a basis for parameter calculation.

[0084] Next, we analyze the inherent phase characteristics of the co-channel control loop of the grid-type reactive power generator at the target angular frequency. Due to the presence of energy storage components such as inductors and capacitors in the control loop, as well as the controller's operational delay, the control output will inevitably experience phase lag when the signal is transmitted at the target angular frequency. If the lagging signal is directly used as the damping signal, it will lead to asynchrony between the damping signal and the oscillation signal, or even inject negative damping, thereby exacerbating the oscillation. Therefore, a phase lead compensator needs to be introduced. The key parameters of the compensator—time constant and attenuation coefficient—can be calculated based on the target angular frequency.

[0085] The specific calculation process includes: calculating the phase to be compensated based on the inherent phase lag of the circuit. For example, if the lag is 60°, a compensator needs to be designed to provide a 30°-60° lead phase to ensure that the total phase deviation is controlled near 0° and that the damping signal and the oscillation signal are in phase.

[0086] Based on the target angular frequency and the required lead phase, the time constant and attenuation coefficient of the compensator are derived by using the phase compensation formula. These two parameters together determine the lead capability and amplitude characteristics of the compensator at the target angular frequency, and are collectively referred to as the compensation coefficient.

[0087] The compensation coefficient in this process directly defines the operating characteristics of the phase lead compensator, ensuring that the compensator can accurately provide the required lead phase at the target angular frequency of the current dominant oscillation, offsetting the inherent lag of the control loop, and making the subsequently generated damping signal in phase with the oscillation signal, thus laying the foundation for injecting positive damping. Without this step, even if the damping coefficient is calculated later, the damping effect will fail due to phase lag.

[0088] Based on the compensation coefficient, the damping coefficient of the same channel is determined as follows: The time constant determines the response speed of the compensator to signal changes. The smaller the time constant, the faster the response and the faster it can follow the oscillation changes. The attenuation coefficient determines the adjustment of the signal amplitude by the compensator. The smaller the attenuation coefficient, the stronger the amplitude amplification capability of the compensator for the target angular frequency signal. Then, combining the amplitude of the power oscillation in the channel, the deviation of the current fluctuation, and the maximum output current / voltage limit of the grid-type reactive power generator in the channel, the correlation between the compensation coefficient and the damping force is established.

[0089] Specifically, if the time constant and attenuation coefficient in the compensation coefficient are small, and the current oscillation intensity is large, then a large damping coefficient needs to be designed to ensure that sufficient damping force can be provided to suppress strong oscillations.

[0090] If the time constant or attenuation coefficient in the compensation coefficient is large, or the output capacity of the equipment is close to the upper limit, a smaller damping coefficient needs to be designed to avoid overloading the equipment or causing new disturbances due to overcompensation.

[0091] Finally, through simulation verification or experimental calibration, such as testing the damping effect under different compensation coefficients and different oscillation scenarios, the optimal damping force is recorded, and the co-channel damping coefficient that can both ensure phase in-phase and effectively suppress oscillation under the current compensation coefficient is finally determined.

[0092] The process of obtaining the cross-channel damping coefficient is as follows: the dominant oscillation frequency data is linearized to obtain the Jacobian matrix of the target power grid; the Jacobian matrix is ​​decomposed into eigenvalues ​​and modal identification to obtain several eigenvectors and several oscillation modes that match the eigenvectors; factor analysis is performed on each oscillation mode to obtain a modal factor matrix; the modal factor matrix is ​​processed using a decoupling controller to obtain the cross-channel damping coefficient.

[0093] Specifically, firstly, the steady-state equilibrium point of the target power grid under its current operating state is determined, i.e., the normal operating point without oscillations. Then, based on the dynamic equations describing the interaction between the power grid and the grid-type reactive power generator, a Taylor expansion is performed at the steady-state equilibrium point. During the expansion, higher-order nonlinear terms in the expansion are ignored, and only first-order linear terms are retained, approximating the originally complex nonlinear system as a linear system. The core coefficient matrix of this linear system is the Jacobian matrix. Each element in the matrix represents the degree of influence of the change of one state variable on another state variable, and the matrix dimension is consistent with the number of system state variables, i.e., the number of control channels.

[0094] In actual power grid operation, the interaction between voltage and current is nonlinear, making it difficult to separate the coupling relationship between channels through direct analysis. However, the linearized Jacobian matrix can approximate this nonlinear coupling as a linear correlation, making subsequent mathematical analysis operable and providing a prerequisite for identifying independent oscillation modes.

[0095] Next, the Jacobian matrix is ​​decomposed into eigenvalues ​​and eigenvectors. Each eigenvalue consists of a real part and an imaginary part. The real part reflects the stability of the mode, while the size of the imaginary part corresponds to the oscillation frequency; the larger the imaginary part, the higher the oscillation frequency. The eigenvectors corresponding to the eigenvalues ​​reflect the degree of participation of the oscillation mode in various state variables. For example, in a certain eigenvector, the element corresponding to the d-axis current has the largest absolute value, followed by the element corresponding to the q-axis voltage, indicating that the oscillation mode is mainly participated in by both the d-axis current and the q-axis voltage. Then, the imaginary part of the eigenvalues ​​is converted into the actual frequency, and the eigenvalues ​​and corresponding eigenvectors that match the dominant oscillation frequency are found. The dynamic characteristics represented by this set of eigenvalues ​​and eigenvectors are the dominant oscillation mode, and other secondary oscillation modes will also be identified.

[0096] For each oscillation mode, factor analysis is performed on its corresponding eigenvector. First, the absolute values ​​of each element in the eigenvector are normalized. The normalized element values ​​are the participation factors of the channel to the current oscillation mode: the larger the participation factor, the stronger the contribution of the channel's fluctuations to the oscillation mode. Second, the signs of the elements in the eigenvector are retained. Same signs indicate that the fluctuations of the two channels are in phase, and opposite signs indicate that they are out of phase. Finally, the participation factors and phase signs of all oscillation modes are organized into a matrix according to the mode-channel dimension, i.e., the mode factor matrix. The rows of the matrix correspond to the oscillation modes, the columns correspond to the control channels, and the element values ​​are participation factors × phase signs, which directly reflect the direction and strength of the coupling influence of a certain channel on a certain mode.

[0097] Based on the coupling relationship reflected in the modal factor matrix, the design goal of the decoupling controller is determined. For the control channels involved in the dominant oscillation mode, it is ensured that the damping adjustment of one channel after decoupling will not interfere with the other channel. Then, a decoupling algorithm is designed based on the inverse compensation principle. Finally, the stability of these compensation coefficients is verified, and the coefficients are adjusted in combination with the actual output capacity of the equipment. The compensation coefficients used to cancel the coupling between channels are the cross-channel damping coefficients.

[0098] The preferred method for stability verification is to substitute the values ​​into a linear system to verify whether the real part of the eigenvalues ​​becomes more negative after compensation, thereby ensuring that the system is more stable.

[0099] The matrix element configuration of the co-channel damping coefficient and the cross-channel damping coefficient is performed using matrix synthesis technology to obtain an initial damping matrix; the gain of the initial damping matrix is ​​then adjusted to obtain the cross-coupling damping matrix.

[0100] In this process, firstly, the dimensions of the initial damping matrix are determined, and the previously obtained damping coefficients for the same channel are filled into the diagonal positions of the matrix. The diagonal elements represent the damping effect of a certain channel on itself, which is the basis for single-channel oscillation suppression. Then, the damping coefficients for the cross channels are filled into the off-diagonal positions of the matrix. The off-diagonal elements represent the coupling cancellation effect of a certain channel on another channel, corresponding to the interference compensation between channels.

[0101] The obtained initial damping matrix is ​​optimized to ensure that it matches the actual equipment capacity and grid oscillation requirements, avoiding undercompensation or overcompensation.

[0102] Next, the DC-side voltage data is preprocessed, such as filtering out steady-state components and retaining fluctuation components related to oscillations, to ensure that the input signal only reflects the influence of oscillations. Then, the preprocessed DC-side voltage data is converted into a vector signal that conforms to the input format of the cross-coupling damping matrix. Then, through matrix multiplication, the voltage signal vector is multiplied by the cross-coupling damping matrix, so that the voltage fluctuation signal and the damping coefficients of the same channel and cross channel in the matrix act respectively. Finally, the result of the calculation is the gain compensation data corresponding to each control channel.

[0103] This step links the equipment status with damping compensation to generate precise control data. The DC side voltage is the core supporting parameter of the grid-type reactive power generator. Its fluctuations directly reflect the interaction between the equipment and the grid oscillations. Inputting it into the cross-coupled damping matrix allows the gain compensation data to adapt to the current oscillation intensity and channel coupling in real time, avoiding undercompensation or overcompensation caused by using fixed gain. This provides quantitative and dynamic compensation instructions for the subsequent generation of anti-oscillation power signals.

[0104] The impedance data of the target power grid is acquired in real time, and an anti-oscillation power signal is generated based on the gain compensation data and the impedance data; the anti-oscillation power signal is used to control the power of the target power grid.

[0105] The process of generating an anti-oscillation power signal based on the gain compensation data and the impedance data includes: performing power sensitivity calculation on the impedance data using the impedance-power mapping relationship to obtain a reference anti-oscillation power; and performing amplitude-phase adjustment processing on the gain compensation data and the reference anti-oscillation power using gain weighted synthesis technology to obtain the anti-oscillation power signal.

[0106] Specifically, a mathematical model is established to describe the relationship between the device's output power and the grid impedance, i.e., the impedance-power mapping relationship. Then, real-time acquired grid impedance data is substituted into this mapping model to perform power sensitivity calculations. The essence of sensitivity calculation is to analyze how the required compensation power should change for each point change in impedance. Finally, considering the severity of the current oscillation, a preliminary reference anti-oscillation power is calculated to counteract the oscillation. This reference power includes not only amplitude information but also phase information to ensure that it is opposite to the oscillation power component, thereby injecting positive damping.

[0107] The impedance-power mapping relationship is usually derived from the basic theory of power systems. It means that under a specific grid impedance, how much active or reactive power should be injected to most effectively change the voltage and current at the grid connection point, thereby achieving the purpose of suppressing oscillations.

[0108] The reference anti-oscillation power is used as the basic signal, and gain compensation data calculated from the cross-coupling damping matrix is ​​introduced.

[0109] Gain compensation data contains two layers of information: first, amplitude weight, which determines how much the reference power needs to be amplified or reduced to adapt to the device's own control capabilities and the current oscillation intensity of each channel; second, phase weight, which determines how much the phase of the reference power needs to be fine-tuned to accurately compensate for the phase deviation caused by the device's internal control delay and inter-channel coupling.

[0110] Gain-weighted synthesis technology combines these two methods. It scales the reference anti-oscillation power based on the amplitude weights in the gain compensation data, and simultaneously performs fine-tuning of the phase lead or lag based on the phase weights. After dual adjustment of amplitude and phase, the output is an anti-oscillation power signal that can be directly used to control the grid-type reactive power generator.

[0111] Another embodiment of the present invention provides a power control device suitable for conventional DC grid transformation. For details, please refer to [link to relevant documentation]. Figure 2 , Figure 2 The diagram shown is a structural schematic of a power control device suitable for conventional DC grid transformation in one embodiment of the present invention. The device includes:

[0112] The acquisition module 11 is used to acquire the output current data and DC side voltage data of the grid-type reactive power generator, and to acquire the grid connection voltage data and grid connection phase angle data of the grid connection point of the grid-type reactive power generator and the target power grid.

[0113] Extraction module 12 is used to extract frequency oscillation components from the instantaneous power data of the grid-type reactive power generator, wherein the frequency oscillation components are determined by the output current data, the grid-connected voltage data and the grid-connected phase angle data;

[0114] The adaptive module 13 is used to perform adaptive frequency tracking processing on the frequency oscillation components using fast Fourier analysis technology to obtain the dominant oscillation frequency data of the target power grid.

[0115] Processing module 14 is used to input the DC-side voltage data into the constructed cross-coupling damping matrix for processing to obtain gain compensation data. The construction process includes processing the dominant oscillation frequency data using phase lead compensation technology to obtain the same-channel damping coefficient, performing mode decoupling processing on the dominant oscillation frequency data to obtain the cross-channel damping coefficient, and constructing the cross-coupling damping matrix based on the same-channel damping coefficient and the cross-channel damping coefficient.

[0116] The generation module 15 is used to acquire the impedance data of the target power grid in real time, and generate an anti-oscillation power signal based on the gain compensation data and the impedance data;

[0117] The control module 16 is used to perform power control on the target power grid using the anti-oscillation power signal.

[0118] See Figure 3 This is a schematic diagram of the structure of a power control device suitable for conventional DC grid-based retrofitting provided in an embodiment of the present invention. The power control device for conventional DC grid-based retrofitting provided in this embodiment includes a processor 21, a memory 22, and a computer program stored in the memory 22 and configured to be executed by the processor 21. When the processor 21 executes the computer program, it implements the steps as described in the power control method embodiment above, for example... Figure 1 The steps S1 to S6 described above; or, when the processor 21 executes the computer program, it implements the functions of each module in the above-described device embodiments, such as the acquisition module 11.

[0119] For example, the computer program can be divided into one or more modules, which are stored in the memory 22 and executed by the processor 21 to complete the present invention. The one or more modules can be a series of computer program instruction segments capable of performing specific functions, which describe the execution process of the computer program in a power control device suitable for conventional DC grid transformation. For example, the computer program can be divided into an acquisition module 11, an extraction module 12, an adaptive module 13, etc., with the specific functions of each module as follows:

[0120] The acquisition module 11 is used to acquire the output current data and DC side voltage data of the grid-type reactive power generator, and to acquire the grid connection voltage data and grid connection phase angle data of the grid connection point of the grid-type reactive power generator and the target power grid.

[0121] Extraction module 12 is used to extract frequency oscillation components from the instantaneous power data of the grid-type reactive power generator, wherein the frequency oscillation components are determined by the output current data, the grid-connected voltage data and the grid-connected phase angle data;

[0122] The adaptive module 13 is used to perform adaptive frequency tracking processing on the frequency oscillation components using fast Fourier analysis technology to obtain the dominant oscillation frequency data of the target power grid.

[0123] Processing module 14 is used to input the DC-side voltage data into the constructed cross-coupling damping matrix for processing to obtain gain compensation data. The construction process includes processing the dominant oscillation frequency data using phase lead compensation technology to obtain the same-channel damping coefficient, performing mode decoupling processing on the dominant oscillation frequency data to obtain the cross-channel damping coefficient, and constructing the cross-coupling damping matrix based on the same-channel damping coefficient and the cross-channel damping coefficient.

[0124] The generation module 15 is used to acquire the impedance data of the target power grid in real time, and generate an anti-oscillation power signal based on the gain compensation data and the impedance data;

[0125] The control module 16 is used to perform power control on the target power grid using the anti-oscillation power signal.

[0126] Power control devices suitable for conventional DC grid-based retrofitting may include, but are not limited to, processor 21 and memory 22. Those skilled in the art will understand that the schematic diagram is merely an example of a power control device and does not constitute a limitation on the power control device. It may include more or fewer components than illustrated, or combine certain components, or use different components. For example, the power control device may also include input / output devices, network access devices, buses, etc.

[0127] The processor 21 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. The processor 21 is the control center of the power control device, connecting all parts of the power control device through various interfaces and lines.

[0128] The memory 22 can be used to store the computer program and / or modules. The processor 21 implements various functions of the power control device by running or executing the computer program and / or modules stored in the memory 22 and calling the data stored in the memory 22. The memory 22 may mainly include a program storage area and a data storage area. The program storage area may store the operating system, at least one application program required for a function (such as sound playback function, image playback function, etc.), etc.; the data storage area may store data created according to the use of the mobile phone (such as audio data, phonebook, etc.). In addition, the memory 22 may include high-speed random access memory, and may also include non-volatile memory, such as hard disk, memory, plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, at least one disk storage device, flash memory device, or other volatile solid-state storage device.

[0129] If the power control device integrated module is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented 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 various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0130] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0131] Accordingly, embodiments of the present invention provide a computer-readable storage medium, the computer-readable storage medium including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to perform steps in the power control method of the above embodiments, for example... Figure 1 Steps S1 to S6 as described above.

[0132] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A power control method applicable to conventional DC grid transformation, characterized in that, The method, applied to the process of connecting a grid-type reactive power generator to a target power grid, includes: The output current data and DC side voltage data of the grid-type reactive power generator are obtained, and the grid connection voltage data and grid connection phase angle data of the grid connection point between the grid-type reactive power generator and the target power grid are obtained. Frequency oscillation components are extracted from the instantaneous power data of the grid-type reactive power generator, wherein the frequency oscillation components are determined by the output current data, the grid-connected voltage data, and the grid-connected phase angle data; The frequency oscillation components are subjected to adaptive frequency tracking processing using fast Fourier analysis technology to obtain the dominant oscillation frequency data of the target power grid. The DC-side voltage data is input into the constructed cross-coupling damping matrix for processing to obtain gain compensation data. The construction process includes processing the dominant oscillation frequency data using phase lead compensation technology to obtain the same-channel damping coefficient, performing mode decoupling processing on the dominant oscillation frequency data to obtain the cross-channel damping coefficient, and constructing the cross-coupling damping matrix based on the same-channel damping coefficient and the cross-channel damping coefficient. The impedance data of the target power grid is acquired in real time, and an anti-oscillation power signal is generated based on the gain compensation data and the impedance data. The target power grid is controlled using the anti-oscillation power signal.

2. The power control method applicable to conventional DC grid transformation as described in claim 1, characterized in that, The extraction of frequency oscillation components from the instantaneous power data of the grid-type reactive power generator includes: Based on the orthogonal signal generation method, the output current data, the grid-connected voltage data, and the grid-connected phase angle data are processed to obtain the instantaneous power data of the grid-type reactive power generator; The instantaneous power data and the DC-side voltage data are filtered and extracted to obtain the frequency oscillation component.

3. The power control method applicable to conventional DC grid transformation as described in claim 1, characterized in that, The adaptive frequency tracking processing of the frequency oscillation components using Fast Fourier Analysis (FFT) to obtain the dominant oscillation frequency data of the target power grid includes: The frequency oscillation component is processed by a sliding time window to obtain the oscillation time-domain data; The power spectrum of the oscillation time-domain data was estimated using fast Fourier analysis to obtain a power spectral density map. Peak search is performed on the power spectral density map to obtain the dominant oscillation frequency data of the target power grid.

4. The power control method applicable to conventional DC grid transformation as described in claim 1, characterized in that, The process of using phase lead compensation technology to process the dominant oscillation frequency data to obtain the same-channel damping coefficient includes: The dominant oscillation frequency data is converted to obtain the target angular frequency; The target angular frequency is processed using phase lead compensator technology to obtain the compensation coefficient; Based on the compensation coefficient, the damping coefficient of the same channel is determined.

5. The power control method applicable to conventional DC grid transformation as described in claim 1, characterized in that, The modal decoupling processing of the dominant oscillation frequency data to obtain the cross-channel damping coefficient includes: The dominant oscillation frequency data is linearized to obtain the Jacobian matrix of the target power grid; The Jacobian matrix is ​​subjected to eigenvalue decomposition and mode identification to obtain several eigenvectors and several oscillation modes that match the eigenvectors; Factor analysis was performed on each of the oscillation modes to obtain the modal factor matrix; The modal factor matrix is ​​processed using a decoupling controller to obtain the cross-channel damping coefficient.

6. The power control method applicable to conventional DC grid transformation as described in claim 1, characterized in that, The construction of the cross-coupled damping matrix based on the same-channel damping coefficient and the cross-channel damping coefficient includes: The initial damping matrix is ​​obtained by configuring the matrix elements of the same-channel damping coefficient and the cross-channel damping coefficient using matrix synthesis technology. The initial damping matrix is ​​subjected to gain adjustment to obtain the cross-coupling damping matrix.

7. The power control method applicable to conventional DC grid transformation as described in claim 1, characterized in that, The generation of the anti-oscillation power signal based on the gain compensation data and the impedance data includes: The impedance data is processed by power sensitivity calculation using the impedance-power mapping relationship to obtain the reference anti-oscillation power; The gain compensation data and the reference anti-oscillation power are subjected to amplitude-phase adjustment processing using gain weighted synthesis technology to obtain the anti-oscillation power signal.

8. A power control device suitable for the retrofitting of conventional DC grids, characterized in that, include: The acquisition module is used to acquire the output current data and DC side voltage data of the grid-type reactive power generator, and to acquire the grid connection voltage data and grid connection phase angle data of the grid connection point between the grid-type reactive power generator and the target power grid. An extraction module is used to extract frequency oscillation components from the instantaneous power data of the grid-type reactive power generator, wherein the frequency oscillation components are determined by the output current data, the grid-connected voltage data, and the grid-connected phase angle data; An adaptive module is used to perform adaptive frequency tracking processing on the frequency oscillation components using fast Fourier analysis technology to obtain the dominant oscillation frequency data of the target power grid. The processing module is used to input the DC-side voltage data into the constructed cross-coupling damping matrix for processing to obtain gain compensation data. The construction process includes processing the dominant oscillation frequency data using phase lead compensation technology to obtain the same-channel damping coefficient, performing mode decoupling processing on the dominant oscillation frequency data to obtain the cross-channel damping coefficient, and constructing the cross-coupling damping matrix based on the same-channel damping coefficient and the cross-channel damping coefficient. The generation module is used to acquire the impedance data of the target power grid in real time, and generate an anti-oscillation power signal based on the gain compensation data and the impedance data; A control module is used to perform power control on the target power grid using the anti-oscillation power signal.

9. A power control device suitable for the retrofitting of conventional DC grids, characterized in that, It includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor, when executing the computer program, implements the power control method applicable to conventional DC grid transformation as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, wherein when the device containing the computer-readable storage medium executes the computer program, it implements the power control method applicable to conventional DC grid transformation as described in any one of claims 1 to 7.

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