Oscillation frequency extraction method and system based on SOGI-FLL

Abstract

The invention discloses an oscillation frequency extraction method based on SOGI-FLL, and belongs to the technical field of power electronics, and the method comprises the steps: firstly filtering a DC component of an oscillation signal, and obtaining an AC component of the signal; real-time sampling detection is carried out according to the obtained oscillation waveform alternating current component, and the amplitude of the oscillation waveform is extracted; performing stability judgment on the system by using the alternating-current component amplitude, setting an instability threshold value and instability times of an algorithm, and when the alternating-current component amplitude of the system is continuously detected to exceed the instability threshold value for multiple times, considering that the system is unstable; starting frequency extraction after judging that the system is unstable; and after the frequency is calculated, the oscillation frequency information is output and the virtual impedance strategy design is guided. According to the method, the oscillation frequency can be rapidly extracted without obtaining system topology and device parameters in advance, the power supply stability of the system is improved by combining the virtual impedance strategy, and the method has good robustness and adaptivity.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and specifically to an oscillation frequency extraction method and system based on SOGI-FLL. Background Art

[0002] DC distribution systems are widely used in power supply systems such as communications, ships, and data centers due to their rich power supply modes, high-quality power quality, high modularity, and easy expandability. In recent years, with the rapid increase in the installed capacity of new energy power generation such as wind power and photovoltaic power, DC distribution networks have received strong attention from domestic and foreign scholars and the industrial field. Due to the access of distributed power sources and the use of a large number of power electronic components in the DC distribution network system, it generally exhibits the characteristics of low damping and weak inertia, and multi-converter group instability will occur after being disturbed, and even cause the collapse of the DC bus voltage. Solving the stability problem of the DC distribution system is of great significance for ensuring the safe operation of the system.

[0003] Impedance mismatch is the main cause of the stability problem of the DC distribution system. At the same time, in the DC distribution system, the cascade system is the most common connection form. It can be known from the Nyquist criterion that on the premise that the converter operates stably alone, if the system port loop impedance meets the Nyquist criterion, the cascade system can be considered stable. To solve the oscillation problem of the cascade system, passive or active schemes are often used to change the original input or output impedance characteristics of the system, so that impedance matching is achieved on both sides of the port to meet the criterion requirements. The more widely used passive scheme is to add passive devices such as resistors and capacitors, and the active schemes include adding auxiliary circuits and virtual impedance methods. Compared with the other two schemes, the virtual impedance strategy reshapes its impedance characteristics by changing the source-side or load-side control loop to meet the stability criterion, with lower cost and stronger applicability.

[0004] The center frequency of the band-pass filter is an important parameter affecting the oscillation suppression effect of the virtual impedance strategy. The core idea of virtual impedance is to improve the impedance characteristics of the system near the oscillation frequency to meet the stability criterion conditions. According to the impedance criterion, the potential oscillation frequency of the system is related to both the inherent parameters and the operating state of the cascaded system. The DC distribution network represented by the data center has its parameters changing with the scene transformation, resulting in a large range of oscillation frequency changes. Currently, the virtual impedance strategies are all pre-designed based on the known external system structure and parameters, and their oscillation frequencies are fixed values. When the system structure changes or the parameters of passive devices change, the oscillation frequency will change. At this time, the original virtual impedance strategy will weaken or even lose its oscillation suppression effect. If the virtual impedance algorithm is to meet the requirements in different scenarios, an algorithm for real-time monitoring of the oscillation frequency needs to be combined. Therefore, in order to enhance the stability performance of the DC distribution system and adapt to the oscillation frequency changes caused by the changes in the system architecture and parameters, an oscillation frequency extraction method based on SOGI-FLL is proposed to make the virtual impedance strategy have good robustness and universality. Summary of the Invention

[0005] To improve the stability of the DC distribution system and expand the application range of the virtual impedance strategy, the present invention proposes an oscillation frequency extraction method and system based on SOGI-FLL, which can accurately extract the current oscillation frequency of the system, has good robustness, and adapts to various working conditions.

[0006] The present invention is implemented through the following technical solutions: In a first aspect, the present application provides an oscillation frequency extraction method based on SOGI-FLL, including the following processes: Obtain the AC component of the oscillation signal and use it as the input signal of the SOGI-FLL system; Determine the orthogonal decomposition components of the AC component according to the transfer function of the SOGI-FLL system, and determine the amplitude of the AC component according to the orthogonal decomposition components and in combination with the state space equation of the SOGI-FLL system; Determine the stability of the power system according to the amplitude of the AC component and the instability threshold; When the power system is unstable, calculate the oscillation frequency according to the AC component of the oscillation signal at the current moment, and determine the virtual impedance strategy of the power system according to the oscillation frequency.

[0007] Preferably, the obtaining of the AC component of the oscillation signal includes: Obtain the oscillation signal, filter out the DC component of the oscillation signal, and obtain the AC component of the oscillation signal.

[0008] Preferably, the orthogonal decomposition amount of the AC component is determined according to the transfer function of the SOGI-FLL system, where the transfer function includes an in-phase quantity transfer function and a quadrature quantity transfer function; Determine the orthogonal decomposition amount of the AC component according to the in-phase quantity transfer function and the quadrature quantity transfer function of the SOGI-FLL system.

[0009] Preferably, the in-phase quantity transfer function of the SOGI-FLL system G d (s) is the ratio of the in-phase quantity to the input signal:

[0010] The quadrature quantity transfer function of the SOGI-FLL system G q (s) is the ratio of the quadrature quantity to the input signal:

[0011] Among them, s is the Laplace operator, k is the gain coefficient, v is the AC component, is the frequency of the AC component.

[0012] Preferably, determine the amplitude of the AC component according to the orthogonal decomposition amount and in combination with the state space equation of the SOGI-FLL system, including: Construct the state space equation of the SOGI-FLL; Rewrite the state space equation according to the stable operation regulation of the power system; Obtain the amplitude of the AC component according to the orthogonal decomposition amount.

[0013] Preferably, the state space equation of the SOGI-FLL includes the state space equation of the SOGI and the state space equation of the FLL; The state space equation of the SOGI is:

[0014]

[0015] In the formula, is , , is the state vector component, is the system matrix, is the input matrix, is the output matrix, x is the state vector of the SOGI, representing the output of the system integrator, y is the output vector; The state - space equation of the FLL is as follows:

[0016] where is the proportionality coefficient of the FLL link; The stable operation condition of the power system is and , rewrite the state vector of the SOGI to obtain the rewritten state vector of the SOGI, as follows:

[0017] When the SOGI - FLL system operates stably, x is expressed as , is expressed as ; According to the SOGI - FLL system conditions and combined with the rewritten state vector of the SOGI, determine the Jacobian matrix of the power system. The eigenvalues of the Jacobian matrix have zero real parts. Therefore, the power system is critically stable, and the steady - state response will oscillate at a frequency ; Under the condition of the critically stable power system, use the AC component of the oscillation signal as the input signal and determine the output vector. Determine the amplitude of the AC component according to the output vector; The expression of the input signal is as follows:

[0018] where V is the amplitude of the input signal, is the angular frequency, is the initial phase.

[0019] The output vector is:

[0020] Determine the amplitude of the AC component then as:

[0021] Preferably, determining the stability of the power system according to the amplitude of the AC component and the instability threshold includes: Set the instability threshold and the instability - times threshold. Compare the amplitude of the AC component with the instability threshold. When the amplitude exceeds the instability threshold, the power system is unstable. When the continuous instability times of the power system exceed the instability - times threshold, it is determined that the power system is unstable.

[0022] Preferably, calculating the oscillation frequency according to the oscillation signal at the current moment includes: The internal frequency of the SOGI-FLL system approaches the frequency of the oscillation signal at the current moment; Calculate the average value and effective value of the internal frequency of the SOGI-FLL system in real time; When the difference between the average value and the effective value is less than the threshold, the internal frequency of the SOGI-FLL system is stable, the SOGI-FLL system locks the frequency, takes the locked frequency as the oscillation frequency of the oscillation signal, and adds this frequency to the virtual impedance to suppress system oscillation.

[0023] In a second aspect, the present application provides an oscillation frequency extraction system based on SOGI-FLL, including: An acquisition module for obtaining the AC component of the oscillation signal and serving as the input signal of the SOGI-FLL system; An amplitude acquisition module for determining the orthogonal decomposition amount of the AC component according to the transfer function of the SOGI-FLL system, and determining the amplitude of the AC component according to the orthogonal decomposition amount and in combination with the state space equation of the SOGI-FLL system; A stability module for determining the stability of the power system according to the amplitude of the AC component and the instability threshold; A strategy module for calculating the oscillation frequency according to the AC component of the oscillation signal at the current moment when the power system is unstable, and determining the virtual impedance strategy of the power system according to the oscillation frequency.

[0024] In a third aspect, the present application provides an electronic device, including a memory and a processor, where a computer program is stored in the memory, and characterized in that when the processor executes the computer program, the steps of the described oscillation frequency extraction method based on SOGI-FLL are implemented.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects: The oscillation frequency extraction method based on SOGI-FLL proposed in the present application calculates the system oscillation frequency in real time under the condition of changing oscillation frequency, combines the virtual impedance strategy to improve the stability of the system, solves the oscillation problem in the DC distribution system, and can quickly extract the oscillation frequency without prior knowledge of the system architecture and external passive parameters of the converter. Combining the virtual impedance strategy improves the power supply stability of the system, and has good robustness and universality.

[0026] The present application also proposes an oscillation frequency extraction system based on SOGI-FLL, an electronic device and a computer storage medium, which have all the advantages of the above-mentioned oscillation frequency extraction method based on SOGI-FLL. Description of the Drawings

[0027] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0028] Figure 1 It is the structural block diagram of the SOGI of the present invention; Figure 2 It is the in-phase phasor transfer function G d (s), and the Bode diagram of the quadrature phasor transfer function G q (s); Figure 3 It is the structural block diagram of the SOGI-FLL of the present invention; Figure 4 It is the deviation transfer function G e (s), and the Bode diagram of the quadrature phasor transfer function G q (s); Figure 5 It is the system algorithm verification platform of the source-load cascade system with a Boost converter at the later stage of the present invention; Figure 6 It is the injection waveform of single-frequency ripple at different frequency points of the present invention; Figure 7 It is the experimental suppression effect of the adaptive anti-resonance algorithm based on SOGI-FLL under different cable lengths of the present invention; Figure 8 It is the calculation flow chart of the oscillation frequency of the present invention; Figure 9 It is the flow chart of the oscillation frequency extraction method based on SOGI-FLL of the present invention. Detailed implementation manners

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Usually, the components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the present application to be protected, but only represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0031] When the system structure changes or the parameters of passive devices change, the oscillation frequency will change. At this time, the original virtual impedance strategy weakens or even loses its suppression effect on oscillation. To improve the oscillation suppression effect, it is necessary to accurately obtain the oscillation frequency.

[0032] Based on the above problems, this application proposes an oscillation frequency extraction method based on SOGI-FLL. The core principle of this method is to judge the stability of the power system according to the amplitude of the AC component of the oscillation signal and the instability threshold. When the power system is unstable, calculate the oscillation frequency according to the AC component of the oscillation signal at the current moment, and determine the virtual impedance strategy according to the oscillation frequency.

[0033] The oscillation frequency extraction method based on SOGI-FLL can calculate the system oscillation frequency in real time when the parameters of the DC distribution network change with the scene transformation, resulting in a large change range of the oscillation frequency. Combining with the virtual impedance strategy, it improves the stability of the system, solves the oscillation problem in the DC distribution system, and can extract the frequency only according to the oscillation waveform without obtaining additional information. It has good engineering applicability and has certain operational value for improving the stability of the DC distribution system in actual engineering.

[0034] The oscillation frequency extraction method based on SOGI-FLL is introduced in detail below.

[0035] Embodiment 1 Refer to Figure 9 , an oscillation frequency extraction method based on SOGI-FLL, includes the following steps: Step 1: Filter the DC component of the oscillation signal to obtain the AC component of the oscillation signal.

[0036] As Figure 1 shown, the determination method of the AC component in this embodiment is as follows: Use a low-pass filter to perform mean filtering on the oscillation signal to obtain the AC component of the oscillation signal.

[0037] The specific process of mean filtering is: accumulate the sampling values of the oscillation signal within several cycles and calculate their average value to obtain the DC component. Let the oscillation signal subtract the obtained DC component to obtain the AC component of the oscillation signal.

[0038] Step 2: Input the AC component of the oscillation signal obtained in step S1 into the SOGI-FLL system, determine the orthogonal decomposition quantity of the AC component according to the transfer function of the SOGI-FLL system, determine the amplitude of the AC component according to the orthogonal decomposition quantity and combine with the state space equation of the SOGI-FLL system, and judge the stability according to the amplitude.

[0039] In this embodiment, the sampling frequency of real-time sampling fsample , according to the Nyquist sampling theorem, its minimum value is:

[0040] In the formula, f osc is the system oscillation frequency.

[0041] As Figure 1 shown, SOGI is a two-input and two-output system, where the input quantities are the input AC component v , and the frequency of the AC component ; the output quantities are the orthogonal decomposition quantities of the AC component, including the in-phase quantity , and the quadrature quantity .

[0042] Define the in-phase quantity transfer function of SOGI G d (s) as the ratio of the in-phase quantity to the input signal: (1.1) In the formula, s is the Laplace operator, k is the gain coefficient.

[0043] Define the quadrature quantity transfer function of SOGI G q (s) as the ratio of the quadrature quantity to the input signal: (1.2) Determine the orthogonal decomposition quantities of the AC component according to the in-phase quantity transfer function and the quadrature quantity transfer function of the SOGI model.

[0044] The state space equation of SOGI-FLL is as follows. Among them x is the state vector of SOGI, representing the output quantity of the system integrator y is the output vector:

[0045]

[0046] In the formula, is , , is the state vector component, is the system matrix, is the input matrix, is the output matrix.

[0047] The FLL state space equation is:

[0048] Among them, is the proportionality coefficient of the FLL link.

[0049] Considering that the stable operating condition of the system is and , the state vector of SOGI can be written as follows:

[0050] When considering the stable operation of the SOGI-FLL system, x is expressed as , is expressed as .

[0051] The Jacobian matrix of the system can be obtained from the above formula, and its eigenvalues have zero real parts. Therefore, it is theoretically proved that the system is critically stable, and the steady-state response will oscillate at a frequency oscillates.

[0052] Therefore, let the input signal be:

[0053] V is the amplitude of the input signal, is the angular frequency, is the initial phase.

[0054] The output vector is:

[0055] Therefore, the amplitude then of the AC component can be obtained as:

[0056] Step 3: Set the instability threshold and the number of instability times. When the amplitude of the AC component exceeds the oscillation threshold continuously for multiple times, the power system becomes unstable.

[0057] Based on the amplitude of the AC component obtained in Step 2, the stability of the power system is judged. The amplitude of the AC component is compared with the instability threshold. When it is detected that the amplitude of the AC component of the power system exceeds the instability threshold continuously for multiple times, the stable state of the power system is determined.

[0058] Specifically, when it is detected that the amplitude of the AC component exceeds the system oscillation threshold, it is considered that the system may have an instability tendency. When it is greater than the set threshold continuously for multiple times, it is determined that the system is unstable, and the oscillation frequency of the system is started to be extracted.

[0059] The instability threshold set in this embodiment is V th, the number of instability times is N, that is, the AC component amplitude of the power system is detected to exceed the threshold V for N consecutive times th When this occurs, the system is considered unstable.

[0060] Step 4: In the unstable state of the power system, calculate the oscillation frequency according to the AC component of the oscillation signal at the current moment.

[0061] In this embodiment, as Figure 2 shown, when the input signal frequency is 100 Hz, that is, the angular frequency is 200π rad / s, and the gain coefficient k is at this time, the Bode diagrams of G d ( s ) and G q ( s ) are plotted as shown in Figure 2 . For the in-phase vector transfer function G d ( s ), it is characterized by the characteristics of a band-pass filter. The center frequency is the frequency inside the SOGI, and at the center frequency, the amplitude is 0 dB and the phase is 0, indicating that when the input signal frequency exactly falls at the center frequency, after passing through the SOGI, the output signal has no change in amplitude and phase, that is, at this time the in-phase vector is exactly the same as the input signal v . When the input signal frequency is not at the center frequency, the amplitude of the output signal will be attenuated, and the phase will lead or lag.

[0062] For the quadrature vector transfer function G q ( s ), it is characterized by the characteristics of a low-pass filter. The cut-off frequency is the frequency inside the SOGI, and at the cut-off frequency, the amplitude is 0 dB and the phase is -90°, indicating that when the input signal frequency exactly falls at the center frequency, after passing through the SOGI, the output signal has no change in amplitude and phase, that is, at this time the quadrature vector has the same amplitude as the input signal v but the phase lags by 90°. When the input signal frequency is not at the cut-off frequency, the amplitude of the high-frequency component of the input signal will be attenuated, and the phase lags more and more severely as the frequency increases.

[0063] From the above analysis, it can be seen that the SOGI equivalently constructs the structures of a band-pass filter and a low-pass filter. When the center frequency of the SOGI remains the same as the input signal, the band-pass filter outputs a signal with the same amplitude and phase as the input signal, and the low-pass filter outputs a signal with the same amplitude but a quadrature phase. In addition, the output of the low-pass filter always lags behind the output of the band-pass filter by 90°. Combining the above characteristics, a frequency-locked loop (FLL) can be added on the basis of the SOGI to construct the structure of an adaptive notch filter and automatically extract the frequency of the input signal. The structural block diagram of the system after adding the FLL is as shown in Figure 3 shown.

[0064] The FLL can be regarded as a three-input single-output system. Its input signals are respectively the error between the input signal of the SOGI and the in-phase signal , the quadrature signal , the initial frequency setting value , and the output is used as the internal frequency of the SOGI . The error is multiplied by the quadrature signal to obtain an error factor , which is superimposed on the initial frequency value after inverting and scaling as the internal frequency of the SOGI.

[0065] Define the transfer function of the error with respect to the input signal v as the deviation transfer function G e ( s ). Combining Figure 3 can be deduced as:

[0066] To analyze the frequency-locking characteristics of the system after adding the FLL, the following makes a comparative analysis of the quadrature transfer function G q ( s ), and the deviation transfer function G e ( s ), as shown in Figure 4 shown.

[0067] As can be seen from the figure, when the frequency of the input signal is less than the internal frequency of the SOGI, the quadrature transfer function G q ( s ), and the deviation transfer function G e ( s) have the same phase, and the product of the two has the same sign; when the frequency is greater than the internal frequency, they have the same phase, and the product of the two has different signs. Only when the input signal frequency is exactly equal to the internal frequency, the product of the two returns to zero.

[0068] See also Figure 9 According to the above analysis, when the frequency of the input signal is less than the internal frequency of SOGI, the error factor is greater than zero, and after inverse scaling and superimposition on the internal frequency of SOGI, the internal frequency of SOGI tends to decrease; when the frequency of the input signal is greater than the internal frequency of SOGI, the error factor is less than zero, and after inverse scaling and superimposition on the internal frequency of SOGI, the internal frequency of SOGI tends to increase. Therefore, the internal frequency of SOGI can be automatically approached to the input signal frequency. The specific process of frequency locking is: the average value and effective value of the internal frequency of SOGI are calculated in real time, and when the difference between the average value and the effective value is less than the set threshold f When the frequency extraction result of the SOGI-FLL system is stable (usually 0.5 Hz), the system locks this frequency and outputs it to the virtual impedance strategy.

[0069] Step 5: Calculate the oscillation frequency according to step S4, output the oscillation frequency information and guide the design of the virtual impedance strategy to achieve system oscillation suppression.

[0070] The virtual impedance strategy used in this embodiment is the currently widely used parallel virtual impedance strategy. K In series with the bandpass filter, the bandpass filter expression is (1-6) In the formula, ω r is the center frequency of the bandpass filter, ω r It is usually close to the oscillation frequency of the system, thereby injecting damping into the system near the oscillation frequency band and suppressing the oscillation at the port.

[0071] In this embodiment, the Figure 5 The source-load cascade system verification platform with a boost converter in the rear stage is experimentally verified, and its parameters are shown in Table 1. When the system ripple is a single-frequency ripple, such as Figure 6 As shown. Where the input voltage v g The amplitude is constant at 1.5V and the frequency range is 50~300Hz. Input current i g Frequency and v g remains consistent, but the amplitude will change with the injection frequency, which depends on the magnitude of the system input impedance | Z in|=| v g / i g |. The results are shown in Table 2. At different frequencies, the proposed algorithm can accurately extract the single-frequency ripple in a short time, which proves the extraction effect of the proposed algorithm on the single-frequency ripple. To verify the verification effect of the proposed algorithm on the actual oscillation of the system, the experimental verification effect of the proposed oscillation frequency extraction method based on SOGI-FLL was tested when the front stage was respectively equipped with 1 times and 2 times of cables, resulting in impedance mismatch between the front and rear stages and causing the system to oscillate. As Figure 7 shown, and the results of extracting the frequency by the oscillation frequency extraction method based on SOGI-FLL under different cables are given. As shown in Table 3, the proposed oscillation frequency extraction method based on SOGI-FLL combined with virtual impedance can suppress the system oscillations with different frequencies caused by different cables.

[0072] In summary, the rationality of the oscillation frequency extraction method based on SOGI-FLL is verified. It can extract the oscillation frequency of the system relatively quickly and accurately when the front stage is equipped with different cables, and can suppress the oscillation frequency of the system. The adaptive anti-resonance strategy based on SOGI-FLL has a wide frequency extraction range, a fast frequency extraction response speed, and a relatively accurate frequency extraction accuracy.

[0073] Table 1

[0074] Table 2

[0075] Table 3

[0076] To sum up, the oscillation frequency extraction method based on SOGI-FLL first extracts the frequency according to the actual oscillation waveform, without the need to obtain the system architecture and specific parameters, and has universality. In addition, this method calculates the frequency based on several sampling points, requires less computing resources, and has low requirements for computing power. Secondly, considering the changes of the system structure and passive parameters in the actual system with the scenario, this method designs an oscillation frequency extraction method based on SOGI-FLL, which expands the applicable range of the virtual impedance stabilization scheme.

[0077] The above-mentioned oscillation frequency extraction method based on SOGI-FLL has the following advantages: 1. Real-time monitoring and adaptive ability Real-time monitoring of oscillation frequency: Traditional virtual impedance strategies are usually designed based on fixed system structures and parameters and cannot adapt to the changes in oscillation frequency caused by system parameter variations. This method can real-time monitor the frequency of the oscillation signal through the SOGI-FLL system, dynamically capture the changes in the system oscillation frequency, and ensure that the virtual impedance strategy always operates within the correct frequency range.

[0078] Adaptive to system changes: Since the parameters of the DC distribution network (such as cable length, load changes, etc.) will vary with the scenario, resulting in changes in the oscillation frequency. This method can adapt to these changes, adjust the virtual impedance strategy in real-time, and ensure that the system remains stable under different operating conditions.

[0079] 2. Do not need to obtain system topology and parameters in advance Do not require system topology information: Traditional virtual impedance strategies usually need to obtain the system topology structure and device parameters in advance to design an effective impedance matching scheme. This technical solution only extracts the frequency through the AC component of the oscillation signal, without the need to know the system topology structure or device parameters in advance, and has stronger universality.

[0080] Simplify the design process: Since there is no need to obtain system parameters in advance, this technical solution simplifies the design process of the virtual impedance strategy and reduces the complexity of engineering implementation.

[0081] 3. Strong robustness Strong anti-interference ability: The SOGI-FLL system has good filtering characteristics, can effectively filter out noise and interference signals, and ensure that the extracted oscillation frequency is accurate and reliable. This makes this technical solution still maintain high robustness under complex operating conditions.

[0082] Adapt to a variety of operating conditions: Since this method can adapt to the changes in system parameters, it can effectively suppress oscillations in different operating scenarios (such as data centers, ships, communication systems, etc.) and has wide applicability.

[0083] 4. Fast response and high precision Fast frequency extraction: The SOGI-FLL system can quickly lock the frequency of the input signal, with a fast response speed, and can quickly extract the oscillation frequency when the system becomes unstable, ensuring that the virtual impedance strategy is adjusted in a timely manner.

[0084] High-precision frequency extraction: Through the orthogonal decomposition and frequency-locked loop design of the SOGI-FLL system, the oscillation frequency can be extracted with high precision, ensuring that the virtual impedance strategy operates within the correct frequency range and effectively suppressing oscillations.

[0085] 5. Improve system stability Dynamic impedance matching: This method extracts the oscillation frequency in real time and dynamically adjusts the virtual impedance strategy to ensure that the system has good impedance characteristics near the oscillation frequency, thus meeting the stability criterion conditions and improving the overall stability of the system.

[0086] Suppressing the instability of multiple converters: In a DC distribution network, the instability of multiple converters is a common problem. This technical solution can effectively suppress the instability of multiple converters and prevent the DC bus voltage from collapsing by adjusting the virtual impedance strategy in real time.

[0087] 6. This method realizes the extraction of the oscillation frequency and the adjustment of the virtual impedance strategy through software algorithms, without the need for additional hardware devices, reducing the system cost.

[0088] Reducing the use of passive components: Traditional passive solutions (such as adding resistors, capacitors, etc.) require additional passive components, while this technical solution realizes impedance matching through the virtual impedance strategy, reducing the dependence on passive components and further reducing the cost.

[0089] The oscillation frequency extraction method based on SOGI-FLL effectively suppresses the oscillation problem of the DC distribution network by real-time monitoring of the oscillation frequency through the SOGI-FLL system and combining the virtual impedance strategy. Its advantages include real-time monitoring and adaptive ability, no need to pre-acquire system topology and parameters, strong robustness, fast response and high precision, improving system stability, and reducing system cost. These advantages make this method have broad application prospects in complex DC distribution network environments and can significantly improve the stability and reliability of the system.

[0090] Correspondingly, based on the above oscillation frequency extraction method based on SOGI-FLL, the present application also provides an oscillation frequency extraction system based on SOGI-FLL, which may include: An acquisition module for obtaining the AC component of the oscillation signal and using it as the input signal of the SOGI-FLL system; An amplitude acquisition module for determining the orthogonal decomposition amount of the AC component according to the transfer function of the SOGI model and determining the amplitude of the AC component according to the orthogonal decomposition amount and combining the state space equation of the SOGI-FLL system; A stability module for determining the stability of the power system according to the amplitude of the AC component and the instability threshold; A strategy module for calculating the oscillation frequency according to the oscillation signal at the current moment when the power system is unstable and determining the virtual impedance strategy of the power system according to the oscillation frequency.

[0091] It should be noted that in several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of each module is only a logical function division. In actual implementation, there may be other division methods. For example, multiple modules can be combined or integrated into another device, or some features can be ignored or not executed. The modules described as separate components may or may not be physically separated. The components shown as modules can be one physical unit or multiple physical units, that is, they can be located in one place or distributed to multiple different places. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0092] In addition, in each embodiment of the present invention, each module can be integrated in a processing unit, or each module can exist physically alone, or two or more modules can be integrated in a unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

[0093] An electronic device provided in an embodiment of the present application includes a memory and a processor. A computer program is stored in the memory. When the processor executes the computer program, the steps of the oscillation frequency extraction method based on SOGI-FLL described in any of the above embodiments are implemented.

[0094] Another electronic device provided in an embodiment of the present application may further include: an input port connected to the processor, which is used to transmit multi-modal data collected by an external acquisition device to the processor; and a display unit connected to the processor, which is used to display the processing result of the processor to the outside; a communication module connected to the processor, which is used to realize the communication between the electronic device and the outside. The display unit can be a display panel, a laser scanning display, etc.; the communication methods adopted by the communication module include but are not limited to Mobile High-Definition Link technology (HML), Universal Serial Bus (USB), High-Definition Multimedia Interface (HDMI), wireless connection (including Wireless Fidelity technology (WiFi), Bluetooth communication technology, Low-Energy Bluetooth communication technology, communication technology based on IEEE802.11s).

[0095] A computer-readable storage medium provided in an embodiment of the present application stores a computer program. When the computer program is executed by a processor, the steps of the oscillation frequency extraction method based on SOGI-FLL described in any of the above embodiments are implemented.

[0096] For the description of the relevant parts in the oscillation frequency extraction system, electronic device, and computer-readable storage medium based on SOGI-FLL provided in the embodiments of the present application, please refer to the corresponding detailed description in the oscillation frequency extraction method based on SOGI-FLL provided in the embodiments of the present application, which will not be elaborated here. In addition, the parts in the above technical solutions provided in the embodiments of the present application that are consistent with the implementation principles of the corresponding technical solutions in the prior art are not described in detail to avoid excessive elaboration.

[0097] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention fall within the protection scope of the claims of the present invention.

Claims

1. A method for extracting oscillation frequency based on SOGI-FLL, characterized in that: The process includes: Obtain the AC component of the oscillation signal and use it as the input signal of the SOGI-FLL system; Determine the orthogonal decomposition of the AC component according to the transfer function of the SOGI-FLL system, and determine the amplitude of the AC component according to the orthogonal decomposition and the state space equation of the SOGI-FLL system; Determine the stability of the power system based on the amplitude of the AC component and the instability threshold; When the power system is unstable, the oscillation frequency is calculated according to the AC component of the oscillation signal at the current moment, and the virtual impedance strategy of the power system is determined according to the oscillation frequency.

2. The oscillation frequency extraction method based on SOGI-FLL according to claim 1, characterized in that: The obtaining of the AC component of the oscillation signal comprises: An oscillation signal is obtained, a DC component of the oscillation signal is filtered out, and an AC component of the oscillation signal is obtained.

3. The oscillation frequency extraction method based on SOGI-FLL according to claim 1, characterized in that: The orthogonal decomposition of the AC component is determined according to the transfer function of the SOGI-FLL system, wherein the transfer function includes an in-phase transfer function and an orthogonal transfer function; The orthogonal decomposition of the AC component is determined according to the in-phase transfer function and the orthogonal transfer function of the SOGI-FLL system.

4. The oscillation frequency extraction method based on SOGI-FLL according to claim 3, characterized in that: The in-phase transfer function of the SOGI-FLL system G d (s) is the ratio of the in-phase quantity to the input signal: The quadrature transfer function of the SOGI-FLL system G q (s) is the ratio of the orthogonal quantity to the input signal: in, s is the Laplace operator, k is the gain coefficient, v is the AC component, is the frequency of the AC component.

5. The oscillation frequency extraction method based on SOGI-FLL according to claim 1, characterized in that: The amplitude of the AC component is determined based on the orthogonal decomposition and combined with the state space equation of the SOGI-FLL system, including: According to the state space equations of building SOGI-FLL; The state space equations are rewritten according to the stable operation regulation of the power system; The AC component amplitude is obtained according to the orthogonal decomposition.

6. The oscillation frequency extraction method based on SOGI-FLL according to claim 5, characterized in that: The state space equations of the SOGI-FLL include the state space equations of the SOGI and the state space equations of the FLL; The state space equation of the SOGI is: In the formula, for , , are the state vector components, is the system matrix, is the input matrix, is the output matrix, x is the state vector of SOGI, representing the output of the system integrator, y is the output vector; The FLL state space equation is: in, is the proportional coefficient of the FLL link; The stable operation condition of the power system is as well as , rewrite the state vector of SOGI to obtain the rewritten state vector of SOGI, as follows: When the SOGI-FLL system is running stably, x Expressed as , Expressed as ; According to the SOGI-FLL system conditions, the Jacobian matrix of the power system is determined in combination with the state vector of the rewritten SOGI. The Jacobian matrix eigenvalue has a zero real part, so the power system is critically stable, and the steady-state response will be at the frequency Oscillation Under the critical stability condition of the power system, the AC component of the oscillation signal is used as an input signal and an output vector is determined, and the amplitude of the AC component is determined according to the output vector; The expression of the input signal is as follows: in, V is the input signal amplitude, is the angular frequency, is the initial phase; Output vector for: Get the amplitude of the AC component according to the output vector den for: 。 7. The oscillation frequency extraction method based on SOGI-FLL according to claim 1, characterized in that: Determining the stability of the power system according to the amplitude of the AC component and the instability threshold comprises: An instability threshold and an instability times threshold are set, and the amplitude of the AC component is compared with the instability threshold. When the amplitude exceeds the instability threshold, the power system is unstable. When the number of consecutive instability events of the power system exceeds the instability times threshold, the power system is determined to be unstable.

8. The oscillation frequency extraction method based on SOGI-FLL according to claim 1, characterized in that: The step of calculating the oscillation frequency according to the oscillation signal at the current moment includes: The internal frequency of the SOGI-FLL system approaches the frequency of the oscillation signal at the current moment; Real-time calculation of the average and effective value of the internal frequency of the SOGI-FLL system; When the difference between the average value and the effective value is less than the threshold, the internal frequency of the SOGI-FLL system is stable, the SOGI-FLL system is frequency locked, and the locked frequency is used as the oscillation frequency of the oscillation signal, and this frequency is added to the virtual impedance to suppress system oscillation.

9. An oscillation frequency extraction system based on SOGI-FLL, characterized in that: include: The acquisition module is used to obtain the AC component of the oscillation signal and use it as the input signal of the SOGI-FLL system; An amplitude acquisition module is used to determine the orthogonal decomposition of the AC component according to the transfer function of the SOGI-FLL system, and determine the amplitude of the AC component according to the orthogonal decomposition and in combination with the state space equation of the SOGI-FLL system; A stability module for determining the stability of the power system based on the amplitude of the AC component and the instability threshold; The strategy module is used to calculate the oscillation frequency according to the AC component of the oscillation signal at the current moment when the power system is unstable, and determine the virtual impedance strategy of the power system according to the oscillation frequency.

10. An electronic device comprising a memory and a processor, wherein a computer program is stored in the memory, wherein: When the processor executes the computer program, the steps of the oscillation frequency extraction method based on SOGI-FLL as described in any one of claims 1 to 8 are implemented.

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