Oscillation frequency extraction method and system based on zero crossing point detection

Abstract

The invention discloses an oscillation frequency extraction method and system based on zero crossing point detection, 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 an extreme point of the oscillation waveform and corresponding time are extracted; performing stability judgment on the system by using the alternating-current component extreme point, setting an instability threshold value and instability times of a zero crossing point algorithm, and when the alternating-current component extreme point of the system is continuously detected to exceed the instability threshold value for multiple times, considering that the system is unstable; starting zero crossing point extraction and oscillation frequency calculation after judging that the system is unstable; and outputting the oscillation frequency information and guiding the virtual impedance strategy design. According to the method, the oscillation frequency can be rapidly extracted without acquiring a system architecture and external passive parameters of the converter in advance, the power supply stability of the system is improved in combination with the virtual impedance strategy, and the method has good robustness and universality.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and in particular to an oscillation frequency extraction method and system based on zero-crossing point detection. Background Art

[0002] With the rapid growth of renewable energy distributed generation technology and electric vehicle DC loads, DC distribution systems have been widely used in many key areas such as data centers, building power supply, space stations and ships due to their high efficiency, easy maintenance and flexible controllability. However, a large number of power electronic devices are integrated into the DC distribution system. When the system impedance is mismatched, these devices may cause voltage and current oscillations at the input of the DC load, accompanied by significant noise problems. In data centers, an environment with extremely high requirements for data reliability and stability, the oscillation of the power supply not only poses a threat to the safe storage and processing of data, but may also have an adverse effect on the continuous operation of the entire system. Therefore, in-depth research and discussion on the stability of DC distribution systems, especially the challenges and solutions in impedance matching and power oscillation control, is crucial to ensure the reliability of power supply for key facilities such as data centers.

[0003] Most stability problems in DC power distribution systems are low-frequency oscillations. Low-frequency oscillations are mostly caused by the negative impedance characteristics of the converter when it is a constant power load. The fundamental reason for the oscillation of the system is that the negative damping characteristics of the system amplify small disturbances, causing the system to oscillate. In order to meet the stability criterion, the direct idea is to change the impedance characteristics of the system from a passive or active perspective. Currently, the more widely used solutions include physical damping based on adding passive devices such as capacitors, active damping by adding external active devices, and simply modifying the virtual impedance of the converter control loop. The virtual impedance method is a purely software-implemented solution with portability and scalability. It is also in line with the development trend of high-density and high-efficiency power electronic systems, which is not available in the above two methods, so it has been widely used.

[0004] However, the virtual impedance strategy still has the problem of insufficient scenario adaptability in application. The core of the virtual impedance strategy is to improve the stability near the potential oscillation frequency band of the system, so it is particularly important to obtain the potential oscillation frequency of the system. At present, the commonly used strategies are designed under the condition that the system architecture and the external passive parameters of the converter are obtained in advance, that is, the system oscillation frequency is fixed and known. However, the system structure and passive parameters of the actual DC distribution system change with the scenario, resulting in a large range of potential oscillation frequencies of the system. Therefore, the anti-resonance strategy designed under fixed parameters is difficult to apply. The virtual impedance strategy needs to be combined with a scenario adaptive algorithm to adapt to different application scenarios. Therefore, in order to enhance the stability of the DC distribution system, considering the changes in oscillation frequency caused by changes in passive parameters in the actual system, an oscillation frequency extraction method based on zero-crossing detection is proposed, which makes the virtual impedance strategy have good robustness and universality. Summary of the invention

[0005] In order to solve the problem of oscillation frequency change in DC power distribution system due to changes in system structure and passive parameters with scenes, the present invention proposes an oscillation frequency extraction method and system based on zero-crossing point detection, which can accurately extract the current oscillation frequency of the system, has good robustness, and is adaptable to various working conditions.

[0006] The present invention is achieved through the following technical solutions: In a first aspect, the present application provides an oscillation frequency extraction method based on zero-crossing point detection, comprising the following process: The stability of the power system is judged based on the extreme value points and instability threshold of the AC component of the oscillation signal; When the power system is unstable, the zero-crossing point of the oscillation signal at the current moment is obtained and the oscillation frequency is calculated, and the virtual impedance strategy is determined according to the oscillation frequency.

[0007] Preferably, the determination of the AC component includes: filtering out the DC component of the oscillation signal to obtain the AC component of the oscillation signal.

[0008] Preferably, the extreme points of the AC component include: According to the Nyquist sampling theorem, the AC component of the oscillation signal is sampled in real time to obtain the extreme value points of the AC component and their corresponding times.

[0009] Preferably, the method for determining the stability of the power system includes: When the amplitude of the extreme point of the AC component exceeds the oscillation threshold for multiple consecutive times, the power system becomes unstable.

[0010] Preferably, the method for acquiring the zero-crossing point of the oscillation signal includes: When the waveform of the oscillation signal changes from a negative extreme point to a positive extreme point, a first zero-crossing point is obtained, and when the waveform of the oscillation signal changes from a positive extreme point to a negative extreme point, a second zero-crossing point is obtained.

[0011] Preferably, the oscillation frequency of the oscillation signal is calculated as follows: The oscillation frequency of the power system is calculated according to the adjacent first zero-crossing point and the second zero-crossing point.

[0012] Preferably, the virtual impedance strategy is a parallel virtual impedance strategy, which is a proportional link and a bandpass filter in series, and the bandpass filter expression is:

[0013] Where K is the proportionality coefficient, ω r is the center frequency of the bandpass filter.

[0014] The second method, the present application provides an oscillation frequency extraction system based on zero-crossing point detection, comprising: A stability judgment module, used for judging the stability of the power system according to the extreme value point and instability threshold of the AC component of the oscillation signal; The strategy module is used to obtain the zero-crossing point of the oscillation signal at the current moment and calculate the oscillation frequency when the power system is unstable, and determine the virtual impedance strategy according to the oscillation frequency.

[0015] In a third method, the present application provides an electronic device, including: Memory for storing computer programs; A processor is used to implement the steps of the oscillation frequency extraction method based on zero-crossing point detection when executing the computer program.

[0016] A fourth method, the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the oscillation frequency extraction method based on zero-crossing point detection are implemented.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: The oscillation frequency extraction method based on zero-crossing point detection proposed in the present application calculates the system oscillation frequency in real time when the oscillation frequency changes, and improves the stability of the system in combination with the virtual impedance strategy, and solves the oscillation problem in the DC power distribution system. The method can quickly extract the oscillation frequency without obtaining the system architecture and external passive parameters of the converter in advance, and improves the power supply stability of the system in combination with the virtual impedance strategy, and has good robustness and universality.

[0018] The present application also proposes an oscillation frequency extraction system based on zero-crossing point detection, an electronic device and a computer storage medium, which have all the advantages of the above-mentioned oscillation frequency extraction method based on zero-crossing point detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 It is the principle diagram of the zero-crossing algorithm of the present invention; Figure 2 This is a schematic diagram of single-frequency oscillation of the present invention; Figure 3 This is a diagram showing the effect of single-frequency ripple extraction according to an embodiment of the present invention; Figure 4 This is a schematic diagram of multi-frequency oscillation when the frequencies of the main frequency component and the secondary frequency component are not adjacent to each other; Figure 5 This is a diagram showing the effect of frequency extraction of multi-frequency ripples by the proposed algorithm when the main frequency and the secondary frequency are not adjacent to each other in an embodiment of the present invention; Figure 6 This is a schematic diagram of multi-frequency oscillation when the frequency points of the main frequency component and the secondary frequency component of the present invention are close to each other; Figure 7 This is a diagram showing the effect of frequency extraction of multi-frequency ripples by the proposed algorithm when the main frequency and the secondary frequency are close to each other in an embodiment of the present invention.

[0021] Figure 8 The present invention is a flow chart of an oscillation frequency extraction method based on zero-crossing point detection. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. 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.

[0023] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0024] An oscillation frequency extraction method based on zero-crossing point detection includes the following processes: The stability of the power system is judged according to the extreme points and instability threshold of the AC component of the oscillation signal. When the power system is unstable, the zero-crossing point of the oscillation signal at the current moment is obtained and the oscillation frequency is calculated, and the virtual impedance strategy is determined according to the oscillation frequency.

[0025] This oscillation frequency extraction method based on zero-crossing point detection can calculate the system oscillation frequency in real time when the system structure and passive parameters of the actual DC distribution system change with the scene, resulting in changes in the system's potential oscillation frequency. Combined with the virtual impedance strategy, the stability of the system is improved, and the oscillation problem in the DC distribution system is solved. At the same time, there is no need to obtain the system architecture and external passive parameters of the converter in advance. It has high universal application and has certain operational value in improving the stability of the DC distribution system in actual projects.

[0026] Example 1 See also Figure 8 , an oscillation frequency extraction method based on zero-crossing point detection, comprising the following steps: Step 1: Filter out the DC component of the oscillation signal to obtain the AC component of the oscillation signal.

[0027] like Figure 1 As shown, the method for determining the AC component in this embodiment is as follows: The oscillation signal is filtered using a low-pass filter to obtain its DC component. The low-pass filter is specifically: (1) The cutoff frequency of the low-pass filter is .

[0028] The oscillation signal is subtracted from the DC component to obtain the AC component of the oscillation signal.

[0029] Step 2: Perform real-time sampling and detection on the AC component of the oscillation signal obtained in step S1, and extract the extreme value points of the AC component and their corresponding times.

[0030] In this embodiment, the sampling frequency of real-time sampling detection is f sample According to the Nyquist sampling theorem, its minimum value is:

[0031] In the formula, fosc is the system oscillation frequency.

[0032] Step 3: Construct the instability threshold and instability times of the zero-crossing algorithm, judge the stability of the power system according to the extreme point of the AC component obtained in step 2, compare the extreme point of the AC component with the instability threshold, and determine the stability of the power system when the amplitude of the extreme point of the AC component of the power system exceeds the instability threshold for multiple consecutive times.

[0033] Specifically, when it is detected that the amplitude of the extreme point exceeds the system oscillation threshold, it is considered that the system may have an unstable trend. When it is greater than the set threshold for multiple consecutive times, the system is judged to be unstable and the oscillation frequency of the system is extracted.

[0034] In this embodiment, the instability threshold of the zero-crossing algorithm is set to V th The number of instability is N, that is, the oscillation waveform extreme point of the power system is detected to exceed the threshold value V for N consecutive times. th , the system is considered unstable.

[0035] Step 4: When the power system is in an unstable state, obtain several zero-crossing points of the oscillation signal, and calculate the oscillation frequency of the oscillation signal according to the zero-crossing points.

[0036] In this embodiment, Figure 1 As shown, the oscillation signal is displayed as a waveform on the oscilloscope, that is, an oscillation waveform. When the oscillation waveform changes from a negative extreme-value point (NEP) to a positive extreme-value point (PEP), the waveform has a zero-crossing point (ZCP) at this time, and the zero-crossing point at this time is defined as the rising zero point (RZP); similarly, when the waveform changes from a positive extreme-value point to a negative extreme-value point, the waveform also has a zero-crossing point at this time, and the zero-crossing point at this time is defined as the descending zero point (DZP). Therefore, the oscillation frequency of the system can be calculated by detecting adjacent rising or descending points. This algorithm selects adjacent descending points to calculate the oscillation frequency.

[0037] After the system is detected to be unstable according to step 2, the oscillation frequency of the system is extracted. Since the lower jump point is actually fictitious by the algorithm and does not actually exist in the storage space of the extreme point sequence, it needs to be converted for equivalent calculation. Figure 1 , the distance between adjacent down-jump points can be approximately equivalent to the distance between adjacent negative extreme points, so the oscillation frequency of the system can be calculated by the distance between adjacent negative extreme points. The calculation formula is (1-4) 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 high-frequency oscillation suppression of the DC power distribution system based on the phase compensator.

[0038] The virtual impedance strategy used in this embodiment is the currently widely used parallel virtual impedance strategy. It is a series connection of a proportional link and a bandpass filter. The bandpass filter expression is: (1-5) Where K is the proportionality coefficient, ω r is the center frequency of the bandpass filter, ω r It is usually close to the oscillation frequency of the system, thus injecting damping into the system near the oscillation frequency band and suppressing the oscillation at the port. In this embodiment, MATLAB / simulink is used for simulation. When the system ripple is a single-frequency ripple, such as Figure 2 The single-frequency ripple tested is a single sine wave whose amplitude increases first and then decreases, which is used to simulate the divergent oscillation and convergent oscillation of the system. The results are shown in Figure 3 As shown in the figure, at different frequencies, the proposed algorithm can extract single-frequency ripples more accurately in a short time, which proves the extraction effect of the proposed algorithm on single-frequency ripples. When the system ripple is multi-frequency ripple, the multi-frequency ripple is divided into two cases: the main frequency component and the secondary frequency component are not close to each other and the main frequency component and the secondary frequency component are close to each other. First, the frequency extraction effect of the proposed algorithm when the main frequency and the secondary frequency are not close is tested, and the waveform is shown in the figure. Figure 4 The ratio of the main frequency to the secondary frequency amplitude under each working condition is 7:1:1. The test results are shown in Figure 5 As shown in the figure, when the main frequency and the secondary frequency in the system ripple are not close, the zero-crossing algorithm can still accurately extract the main frequency in the wide-band multi-frequency ripple in a short time, and accurately determine whether the system is unstable. This proves that the proposed algorithm is more ideal for extracting the frequency of multi-frequency ripple when the main frequency and the secondary frequency are not close. At the same time, the frequency extraction effect of the proposed algorithm when the main frequency and the secondary frequency are close is tested, and the waveform is shown in the figure. Figure 6 As shown in the figure, the ratio of the main frequency to the secondary frequency amplitude is 3:1 under all working conditions. Figure 7 As shown in the figure, when the main frequency and the secondary frequency in the system ripple are similar, the zero-crossing algorithm can still accurately extract the main frequency in the wide-band multi-frequency ripple in a relatively short time, and more accurately determine whether the system is unstable. This proves that when the main frequency and the secondary frequency are similar, the proposed algorithm is more ideal for frequency extraction of multi-frequency ripples.

[0039] In summary, the oscillation frequency extraction method based on zero-crossing point detection first calculates the frequency based on the actual oscillation waveform, without obtaining the system architecture and specific parameters, and is universal. In addition, this method calculates the frequency based on several extreme points, requires fewer computing resources, and does not require high computing power. Secondly, this method takes into account the changes in system structure and passive parameters in the actual system with the scene, and designs an oscillation frequency extraction method based on zero-crossing point detection, which expands the scope of application of the stabilization solution.

[0040] The present application also proposes an oscillation frequency extraction system based on zero-crossing point detection, which is characterized by comprising: A stability judgment module, used for judging the stability of the power system according to the extreme value point and instability threshold of the AC component of the oscillation signal; The strategy module is used to obtain the zero-crossing point of the oscillation signal at the current moment and calculate the oscillation frequency when the power system is unstable, and determine the virtual impedance strategy according to the oscillation frequency.

[0041] It should be noted that in the 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 only schematic. For example, the division of each module is only a logical function division. There may be other division methods in actual implementation. For example, multiple modules can be combined or integrated into another device, or some features can be ignored or not executed. The module described as a separate component may or may not be physically separated. The component displayed as a module may be a physical unit or multiple physical units, that is, it may be located in one place, or it may be distributed in multiple different places. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment.

[0042] In addition, each module in each embodiment of the present invention may be integrated into a processing unit, each module may exist physically separately, or two or more modules may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0043] 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 zero-crossing point detection described in any of the above embodiments are implemented.

[0044] Another electronic device provided in the embodiment of the present application may also include: an input port connected to the processor, used to transmit multimodal data collected by an external acquisition device to the processor; and a display unit connected to the processor, used to display the processing results of the processor to the outside world; a communication module connected to the processor, used to realize the communication between the electronic device and the outside world. The display unit can be a display panel, a laser scanning display, etc.; the communication mode adopted by the communication module includes but is 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-power Bluetooth communication technology, and communication technology based on IEEE802.11s).

[0045] An embodiment of the present application provides a computer-readable storage medium, in which a computer program is stored. When the computer program is executed by a processor, the steps of the oscillation frequency extraction method based on zero-crossing point detection described in any of the above embodiments are implemented.

[0046] For the description of the relevant parts of the oscillation frequency extraction system based on zero-crossing detection, the electronic device, and the computer-readable storage medium provided in the embodiments of the present application, please refer to the detailed description of the corresponding parts in the oscillation frequency extraction method based on zero-crossing detection provided in the embodiments of the present application, which will not be repeated here. In addition, the parts of the above-mentioned technical solutions provided in the embodiments of the present application that are consistent with the corresponding technical solutions in the prior art are not described in detail to avoid excessive elaboration.

[0047] The above contents are only for explaining 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 in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. An oscillation frequency extraction method based on zero-crossing point detection, characterized in that: The process includes: The stability of the power system is judged based on the extreme value points and instability threshold of the AC component of the oscillation signal; When the power system is unstable, the zero-crossing point of the oscillation signal at the current moment is obtained and the oscillation frequency is calculated, and the virtual impedance strategy is determined according to the oscillation frequency.

2. The oscillation frequency extraction method based on zero-crossing point detection according to claim 1, characterized in that: The determination of the AC component includes: filtering out the DC component of the oscillation signal to obtain the AC component of the oscillation signal.

3. The oscillation frequency extraction method based on zero-crossing point detection according to claim 1 is characterized in that: The extreme points of the AC component include: According to the Nyquist sampling theorem, the AC component of the oscillation signal is sampled in real time to obtain the extreme value points of the AC component and their corresponding times.

4. The oscillation frequency extraction method based on zero-crossing point detection according to claim 1 is characterized in that: The method for determining the stability of the power system comprises: When the amplitude of the extreme point of the AC component exceeds the oscillation threshold for multiple consecutive times, the power system becomes unstable.

5. The method for extracting oscillation frequency based on zero-crossing point detection according to claim 1, characterized in that: The method for obtaining the zero-crossing point of the oscillation signal comprises: When the waveform of the oscillation signal changes from a negative extreme point to a positive extreme point, a first zero-crossing point is obtained, and when the waveform of the oscillation signal changes from a positive extreme point to a negative extreme point, a second zero-crossing point is obtained.

6. The method for extracting oscillation frequency based on zero-crossing point detection according to claim 1, characterized in that: The oscillation frequency of the oscillation signal is calculated as follows: The oscillation frequency of the power system is calculated according to the adjacent first zero-crossing point and the second zero-crossing point.

7. The method for extracting oscillation frequency based on zero-crossing point detection according to claim 1, characterized in that: The virtual impedance strategy is a parallel virtual impedance strategy, which is a proportional link and a bandpass filter in series. The bandpass filter expression is: Where K is the proportionality coefficient, ω r is the center frequency of the bandpass filter.

8. An oscillation frequency extraction system based on zero-crossing detection, characterized in that: include: A stability judgment module, used for judging the stability of the power system according to the extreme value point and instability threshold of the AC component of the oscillation signal; The strategy module is used to obtain the zero-crossing point of the oscillation signal at the current moment and calculate the oscillation frequency when the power system is unstable, and determine the virtual impedance strategy according to the oscillation frequency.

9. An electronic device, characterized in that: include: Memory for storing computer programs; A processor is used to implement the steps of the oscillation frequency extraction method based on zero-crossing point detection according to claims 1-7 when executing the computer program.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the oscillation frequency extraction method based on zero-crossing point detection according to claims 1-7 are implemented.

Images