A method, device and medium for suppressing wide frequency oscillation of a three-phase grid-connected inverter

Abstract

The application provides a three-phase grid-connected inverter wide-frequency oscillation suppression method, device and medium, and belongs to the field of new energy grid-connected wide-frequency oscillation suppression. According to the impedance characteristics of the three-phase grid-connected inverter, a voltage feedback transfer function is designed, and the transfer function is equivalent, and the complex coefficient is replaced, so that the voltage feedback transfer function has clear physical meaning and realizability. Meanwhile, a digital spike filter is introduced as a frequency component selection channel, and a delay timer is introduced as a phase correction channel, to form a frequency component selection device that only allows target frequency components to pass, and in combination with the designed voltage feedback transfer function, a complete damping channel with wide-frequency oscillation suppression effect is formed. The channel can only change the impedance characteristics of the target frequency, does not affect the impedance characteristics of the non-target frequency band, and does not cause the phenomenon of borrowing damping. Meanwhile, the coefficient can be changed according to the oscillation frequency, so that the wide-frequency oscillation of the full frequency band can be suppressed.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of new energy grid-connected wide frequency oscillation suppression, and particularly relates to a three-phase grid-connected inverter wide frequency oscillation suppression method, device and medium. BACKGROUND

[0002] Wind and light, as representatives of renewable energy, have been widely used. Unlike traditional power systems, large-scale power electronic devices are constantly connected to the power grid, and the power system gradually presents the development trend of power electronics. Therefore, the wide frequency oscillation problem caused by the interaction between power electronic devices and the power grid cannot be ignored. Such oscillation may cause damage to various devices in the power system, or even lead to wide-range disconnection of new energy units, system shutdown, and even local power grid splitting, affecting the stability of the power system.

[0003] In the existing oscillation suppression technology, additional damping channels are mainly added. The additional damping control changes the original impedance characteristics by feeding the electrical quantity through the compensator to the control loop without changing the original control structure, so as to realize the function of increasing damping. However, the additional damping channels currently proposed usually have the phenomenon of "borrowing damping" (changing the impedance characteristics of non-target frequency band, and then increasing the oscillation risk of this frequency band), and are only suitable for part of the frequency band, which has certain limitations. SUMMARY

[0004] The application provides a three-phase grid-connected inverter wide frequency oscillation suppression method. The method can change the coefficient according to the oscillation frequency, and can realize the suppression of wide frequency oscillation in the full frequency band, and improve the stability of the power system.

[0005] The method comprises the following steps:

[0006] S1, based on a voltage feedback channel, a feedback value is configured to a current control inner loop of a three-phase grid-connected inverter, and a sequence impedance model of the three-phase grid-connected inverter is obtained;

[0007] S2, the sequence impedance denominator is defined as 0, and a voltage feedback channel transfer function is configured;

[0008] S3, a fast Fourier algorithm is used to detect the oscillation frequency of the grid-connected voltage of the three-phase grid-connected inverter;

[0009] S4, according to the detected oscillation frequency, an equivalent factor is calculated, and the equivalent factor is used to replace the imaginary unit in the voltage feedback channel transfer function to perform equivalent transformation, so that the voltage feedback channel before and after the equivalent has the same amplitude and phase response at the oscillation frequency;

[0010] S5, according to the detected oscillation frequency, a digital sharp peak filter corresponding to the frequency is obtained, and a delay coefficient of a delay timer is calculated based on the phase response of the digital sharp peak filter, so as to select the frequency component and correct the phase.

[0011] S6, the grid-connected voltage dq-axis signal processed by the digital spike filter for frequency component selection and the delay for phase correction is taken as the input of the voltage feedback transfer function, and the output of the voltage feedback transfer function is taken as the additional quantity added to the current inner loop, so as to reshape the impedance characteristic at the oscillation frequency and realize the oscillation suppression at the frequency.

[0012] It should be further explained that step S1 further comprises: defining the positive sequence impedance Z' of the three-phase grid-connected inverter and the negative sequence impedance Z' as follows: 11 22

[0013]

[0014] wherein, is the phase angle of the grid-connected base frequency voltage leading the grid-connected base frequency current; I1 is the amplitude of the grid-connected current base frequency component; V1 is the amplitude of the grid-connected voltage base frequency component; T p (s) is an expression related to the phase-locked loop transfer function under positive sequence disturbance, T n (s) is an expression related to the phase-locked loop transfer function under negative sequence disturbance, D0 and Q0 are constants, L f and R f are the filter inductance and the filter resistance, respectively; C dc and V dc are the inverter DC side capacitor and the DC voltage, respectively; θ PLL is the phase angle of the grid-connected voltage phase-locked loop output; H PLL (s) is the phase-locked loop transfer function; v d and v q are the d-axis and q-axis components of the grid-connected voltage obtained by park transformation; i d and i q are the d-axis and q-axis components of the grid-connected current obtained by park transformation; i dref and i qref are the reference values of the grid-connected current d-axis and q-axis components; H i (s) is the transfer function of the current inner loop; e cd and e cq are the d-axis and q-axis components of the three-phase grid-connected inverter bridge arm voltage.

[0015] It should be further explained that in the method, T p (S), T n (S), D0 and Q0 are expressed as follows:

[0016] T p (S) = 0.5H PLL (S) / (1+V1H PLL (S)) f p ​​-f1

[0017] T n (S) = 0.5H PLL (S) / (1+V1H PLL (S)) f n +f1

[0018]

[0019] Further need to explain is, in step S2, the denominator of the sequence impedance is defined as 0, and the voltage feedback channel transfer function K c (S) is configured c (S) includes: the voltage feedback channel transfer function K c (S) suitable for positive sequence disturbance and the voltage feedback channel transfer function K c (S) suitable for negative sequence disturbance;

[0020]

[0021] Further need to explain is, in step S4, the formula of the equivalent factor is:

[0022]

[0023] Further need to explain is, the transfer function after equivalent transformation is:

[0024]

[0025] Further need to explain is, the amplitude frequency response of the peak filter in S5 is:

[0026]

[0027] Wherein, A is the amplitude response of the digital peak filter, the expression is:

[0028]

[0029] Further need to explain is, in step S5, the phase correction is carried out by setting the delay time T delay of the delay timer, and the calculation formula of T delay is:

[0030]

[0031] Wherein, θ(|f p -f1|) is the phase response of the digital peak filter at |f p -f1| frequency calculated by matlab; θ(|f nf1|) is the phase response of the digital notch filter at |f n f1|) is the phase response of the digital notch filter at |f

[0032] According to another embodiment of the present application, an electronic device is provided, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor implements the steps of the three-phase grid-connected inverter wide-frequency oscillation suppression method when executing the program.

[0033] According to still another embodiment of the present application, a storage medium is also provided, having a computer program stored thereon, wherein the computer program is executable by a processor to implement the steps of the three-phase grid-connected inverter wide-frequency oscillation suppression method.

[0034] From the above technical solutions, the present application has the following advantages:

[0035] The three-phase grid-connected inverter wide-frequency oscillation suppression method provided by the present application can adjust the impedance characteristics of the inverter at the oscillation frequency by calculating the equivalent factor and replacing the imaginary unit in the transfer function, so as to make it more conducive to the suppression of oscillation. Based on the equivalent transformation, the voltage feedback channel can have the same amplitude and phase response at the oscillation frequency, thereby maintaining the stability of the power system. By using the digital notch filter, the oscillation frequency component can be accurately selected. By calculating the delay coefficient of the delay timer and performing phase correction, the phase response of the inverter at the oscillation frequency can be ensured to be consistent with the expectation. By adding the output of the voltage feedback transfer function as an additional quantity to the current inner loop, the impedance characteristics of the inverter at the oscillation frequency can be reshaped, and the oscillation suppression can be performed. The robustness of the power system is enhanced. Moreover, by suppressing the oscillation, the quality of the grid-connected voltage and current can be improved, the interference of harmonics and noise can be reduced, and the operation stability of the power system can be improved.

[0036] The three-phase grid-connected inverter wide-frequency oscillation suppression method provided by the present application is also applicable to positive and negative sequence disturbances, and the design processes of the positive and negative sequence disturbances are basically consistent. Only the coefficients of the voltage feedback channel transfer function need to be changed according to the frequency and the positive and negative sequence of the disturbance, without making great changes to the structure of the transfer function. Only the impedance characteristics at the target frequency (oscillation frequency) are changed, and the impedance characteristics at the non-target frequency band are not changed, which will not increase the oscillation risk at the non-target frequency band, avoid the phenomenon of "borrowing damping" that may occur in the traditional additional damping channel, and the key coefficients are related to the oscillation frequency. The coefficients respond to different oscillation frequencies and are suitable for wide-frequency oscillation in the full frequency band. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the present application, the drawings required to be used in the description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0038] Figure 1 Flow chart of the method for suppressing wideband oscillation of a three-phase grid-connected inverter;

[0039] Figure 2 Flow chart of an embodiment of the method for suppressing wideband oscillation of a three-phase grid-connected inverter;

[0040] Figure 3 Schematic diagram of a three-phase grid-connected inverter;

[0041] Figure 4 Current inner loop structure diagram of the three-phase grid-connected inverter with an additional voltage feedback channel;

[0042] Figure 5 Schematic diagram of an oscillation suppression damping channel;

[0043] Figure 6 Schematic diagram of a positive sequence impedance measurement value;

[0044] Figure 7 Schematic diagram of the same amplitude-frequency response and phase-frequency response;

[0045] Figure 8 Schematic diagram of an amplitude response;

[0046] Figure 9 Schematic diagram of a phase response;

[0047] Figure 10 Schematic diagram of a correction result;

[0048] Figure 11 Schematic diagram of a simulation example;

[0049] Figure 12 Time-domain simulation result diagram;

[0050] Figure 13 Electronic device example diagram. DETAILED DESCRIPTION

[0051] The three-phase grid-connected inverter wide-frequency oscillation suppression method provided in the application is based on the impedance characteristics of the three-phase grid-connected inverter, a voltage feedback transfer function is designed, and the transfer function is equivalent, the complex coefficients in the transfer function are replaced, so that the transfer function has clear physical meaning and realizability. A frequency component selection device that only allows the target frequency component to pass is formed by introducing a digital spike filter as a frequency component selection channel and a delay as a phase correction channel, and a complete damping channel with wide-frequency oscillation suppression effect is formed in combination with the designed voltage feedback transfer function. The damping channel formed in the application can only change the impedance characteristics of the target frequency, without affecting the impedance characteristics of the non-target frequency band, and the "borrowing damping" phenomenon does not occur, and the coefficients can be changed according to the oscillation frequency, so that the wide-frequency oscillation of the full frequency band can be suppressed.

[0052] The specific process of the three-phase grid-connected inverter wide-frequency oscillation suppression method will be described in detail below. In order to illustrate but not to limit, specific details such as specific system structures, technologies, etc. are proposed to thoroughly understand the embodiments of the application. However, it should be clear to those skilled in the art that the application can also be implemented in other embodiments without these specific details.

[0053] The phrase "one embodiment" or "some embodiments" described in the application means that the specific features, structures or characteristics described in the embodiment are included in one or more embodiments of the application. Therefore, the phrases "in one embodiment", "in some embodiments", "in other some embodiments", "in other some embodiments" appearing in different places in the application do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized.

[0054] The technical solutions in the embodiments of the application will be described clearly and completely in combination with the drawings in the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, not all. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0055] Please refer to Figure 1 The flowchart of the three-phase grid-connected inverter wide-frequency oscillation suppression method in a specific embodiment is shown in FIG. 1, and the method comprises the following steps.

[0056] S1, based on the voltage feedback channel, the feedback value is configured to the current control inner loop of the three-phase grid-connected inverter, and the sequence impedance model of the three-phase grid-connected inverter is obtained.

[0057] In some embodiments, a voltage feedback channel is defined to introduce a feedback voltage signal into a current control inner loop of a three-phase grid-connected inverter. A sequence impedance model is established. After the voltage feedback is introduced into the current control inner loop, a sequence impedance model of the three-phase grid-connected inverter is established.

[0058] The embodiment improves the dynamic response characteristics of the current control inner loop by introducing the voltage feedback, and improves the suppression capability of the power system to grid voltage disturbance. The oscillation characteristics of the established sequence impedance model can provide an analysis basis for an oscillation suppression strategy.

[0059] As can be seen, the embodiment optimizes the current control inner loop, reduces the influence of grid voltage fluctuation on the inverter output current, and improves grid stability.

[0060] S2, define the sequence impedance denominator as 0, and configure the voltage feedback channel transfer function.

[0061] In some embodiments, based on the sequence impedance model, the denominator is set to 0 to solve the oscillation frequency or resonance point of the system. Then, according to the solved oscillation frequency or resonance point, the transfer function of the voltage feedback channel is configured.

[0062] As can be seen, by defining the sequence impedance denominator as 0, the embodiment can identify the oscillation mode and the resonance point. Then, according to the identified oscillation mode, the transfer function of the voltage feedback channel is optimized to improve the suppression effect on the oscillation: by optimizing the voltage feedback channel, the suppression capability to the specific frequency oscillation is improved.

[0063] S3, the oscillation frequency of the grid-connected voltage of the three-phase grid-connected inverter is detected by using a fast Fourier algorithm.

[0064] In the embodiment, the waveform data of the grid-connected voltage of the three-phase grid-connected inverter is collected in real time, and the collected voltage waveform data is subjected to fast Fourier transform to convert the time domain signal into a frequency domain signal. In this way, the oscillation frequency component can be identified in the frequency domain signal.

[0065] Optionally, by monitoring the oscillation frequency component in the grid-connected voltage in real time through the FFT algorithm, the oscillation event in the grid voltage can be detected.

[0066] S4: according to the detected oscillation frequency, an equivalent factor is calculated, and the equivalent factor is replaced with an imaginary unit in the voltage feedback channel transfer function to perform equivalent transformation, so that the voltage feedback channels before and after the equivalent have the same amplitude and phase response at the oscillation frequency.

[0067] The embodiment can calculate the equivalent factor according to the detected oscillation frequency. The method based on complex operation and mathematical derivation can ensure that the voltage feedback channels before and after the equivalent transformation have the same amplitude and phase response at the oscillation frequency.

[0068] For the equivalent transformation, the calculated equivalent factor can replace the imaginary unit in the voltage feedback channel transfer function to perform the equivalent transformation. In this way, through the equivalent transformation, it is ensured that the voltage feedback channel has the same amplitude and phase response characteristics at the oscillation frequency as before the transformation.

[0069] S5: According to the detected oscillation frequency, a digital peak filter corresponding to the frequency is obtained, and the delay coefficient of the delay unit is calculated based on the phase response of the digital peak filter to perform frequency component selection and phase correction.

[0070] The embodiment can configure a digital peak filter, and design a digital peak filter corresponding to the detected oscillation frequency to ensure that the filter has the expected amplitude and phase response characteristics at a specific frequency.

[0071] The embodiment can calculate the delay coefficient of the delay unit based on the phase response characteristics of the digital peak filter to ensure that the delay unit can compensate for the phase delay introduced by the filter.

[0072] When selecting and correcting the frequency component, the component at a specific frequency can be selected through the digital peak filter, and the phase correction can be performed through the delay unit to ensure that the voltage feedback channel has accurate amplitude and phase response at the oscillation frequency.

[0073] S6: The grid-connected voltage dq-axis signal processed by the digital peak filter for frequency component selection and the delay unit for phase correction is taken as the input of the voltage feedback transfer function, and the output of the voltage feedback transfer function is taken as the additional quantity added to the current inner loop to achieve impedance characteristic remodeling at the oscillation frequency and realize oscillation suppression at the frequency.

[0074] In some embodiments, the dq-axis signal of the grid-connected voltage is processed by the digital peak filter for frequency component selection and by the delay unit for phase correction. The processed dq-axis signal is then taken as the input of the voltage feedback transfer function. By taking the processed dq-axis signal as the input of the voltage feedback transfer function, suppression of oscillation at a specific frequency is achieved.

[0075] The three-phase grid-connected inverter wide-frequency oscillation suppression method of the embodiment realizes accurate suppression of oscillation at a specific frequency by introducing voltage feedback, establishing a sequence impedance model, detecting an oscillation frequency, performing equivalent transformation, configuring a digital peak filter, and configuring a delay unit, thereby improving the stability and performance of the three-phase grid-connected inverter in a complex power grid environment.

[0076] Further, as a refinement and expansion of the specific implementation of the above embodiment, in order to completely describe the specific implementation process in the embodiment, as shown in Figure 2 , the following provides a specific implementation process of the three-phase grid-connected inverter wide-frequency oscillation suppression method.

[0077] S101, configure the feedback value to the current control inner loop of the three-phase grid-connected inverter based on the voltage feedback channel, and obtain the sequence impedance model of the three-phase grid-connected inverter.

[0078] In some embodiments, the three-phase grid-connected inverter can adopt an L-type filtering structure, as shown in Figure 3 . Figure 3 , v a , v b , v c is the grid-connected voltage, i a , i b , i c is the grid-connected current; L f , R f are the filter inductance and filter resistance, respectively; C dc , V dc are the inverter DC side capacitor and DC voltage, respectively; θ PLL is the phase angle of the grid-connected voltage output by the phase-locked loop; H PLL (s) is the transfer function of the phase-locked loop; v d , v q are the d-axis and q-axis components of the grid-connected voltage obtained by park transformation; i d , i q are the d-axis and q-axis components of the grid-connected current obtained by park transformation; i dref , i qref are the reference values of the d-axis and q-axis components of the grid-connected current; H i (s) is the transfer function of the current inner loop; e cd , e cq are the d-axis and q-axis components of the three-phase grid-connected inverter bridge arm voltage.

[0079] As shown in Figure 4 , it is the current inner loop structure of the additional voltage feedback channel of the three-phase grid-connected inverter in step S1.

[0080] As shown in Figure 4 , ω1 is the angular frequency of the fundamental voltage; K c (s) is the transfer function of the voltage feedback channel. v d , v q The output quantity of K c (s) is added to the current inner loop part, which is called an additional voltage feedback channel.

[0081] According to the harmonic linearization method, the positive sequence impedance Z′ 11 and the negative sequence impedance Z′ 22 of the three-phase grid-connected inverter after the additional voltage feedback channel are:

[0082]

[0083] wherein, is the phase angle of the grid fundamental voltage leading the grid fundamental current; I1 is the amplitude of the grid current fundamental component; V1 is the amplitude of the grid voltage fundamental component. p (S) is the expression related to the phase-locked loop transfer function under positive sequence disturbance (assuming the frequency is f p ) and T n (S) is the expression related to the phase-locked loop transfer function under negative sequence disturbance (assuming the frequency is f n ) and D0, Q0 are constants related to system parameters, and the expressions are respectively:

[0084] T p (S) = 0.5H PLL (S) / (1 + V1H PLL (S)) f p -f1

[0085] T n (S) = 0.5H PLL (S) / (1 + V1H PLL (S)) f n +f1

[0086]

[0087] This embodiment takes the positive sequence impedance as an example, Figure 6 The red solid line is the impedance theoretical value without voltage feedback channel; the blue solid line is the impedance theoretical value with voltage feedback; the red circle is the impedance measurement value without voltage feedback obtained by frequency sweeping; and the green plus sign is the impedance measurement value with voltage feedback obtained by frequency sweeping.

[0088] It can be seen that the sequence impedance model derived from the impedance theoretical value without voltage feedback and the impedance theoretical value with voltage feedback are both correct.

[0089] S102, define the sequence impedance denominator as 0, and configure the voltage feedback channel transfer function.

[0090] In this embodiment, the voltage feedback channel transfer function is:

[0091]

[0092] In order to achieve the effect of impedance remodeling, Z′ 11 and Z′ 22 denominator is 0, and the expression of K c (s) is obtained.

[0093] K cp (s) of this embodiment is the voltage feedback channel transfer function K c(s); K cn (s) is the voltage feedback channel transfer function K applicable to negative sequence disturbances. c (s).

[0094] S103. The oscillation frequency of the grid-connected voltage of the three-phase grid-connected inverter is detected using the Fast Fourier Transform algorithm.

[0095] This embodiment performs Fast Fourier Transform (FFT) analysis on a voltage signal to obtain its spectral information. FFT analysis can determine the amplitude and phase information of different frequency components in the signal. By analyzing the FFT results, the oscillation frequency components in the grid-connected voltage can be identified.

[0096] Based on the oscillation frequency detected by FFT, and combined with the control strategy of the grid-connected inverter and the characteristics of the power grid, the oscillation mechanism is analyzed. According to the oscillation mechanism, corresponding oscillation suppression is formulated. The formulated oscillation suppression can be applied to the control process of the grid-connected inverter.

[0097] S104. Calculate the equivalent factor based on the detected oscillation frequency, and replace the imaginary unit in the voltage feedback channel transfer function with the equivalent factor to perform an equivalent transformation, so that the voltage feedback channel before and after the equivalence has the same amplitude and phase response at the oscillation frequency.

[0098] In this embodiment, the formula for calculating the equivalence factor is:

[0099]

[0100] When the detected oscillation frequency is f p hour, In f p -f1 frequency is equivalent to the imaginary unit j; when the detected oscillation frequency is f n hour, In f n At frequency +f1, it is equivalent to the imaginary unit j; replace K with it. cp (s), K cn The equivalent transfer function for j in (s) is:

[0101]

[0102] After performing the equivalent substitution, Z′ 11 Z′ 22 K in cp (s-jω1) and K′ cp (s-jω1), K cn (s+jω1) and K′ cn (s+jω1) in s=j2πf p , s=j2πf nThe time domain response has the same amplitude response and phase response.

[0103] The positive sequence K cp (s-jω1) and K′ cp (s-jω1) are taken as examples, Figure 7 The equivalent K cp (s-jω1) and K′ cp (s-jω1) have the same amplitude response and phase response at the target frequency (s=j2πf p f p =200Hz).

[0104] S105, according to the detected oscillation frequency, obtaining a digital peak filter corresponding to the frequency, and calculating the delay coefficient of the delay unit based on the phase response of the digital peak filter, performing frequency component selection and phase correction.

[0105] The amplitude response of the ideal peak filter in this embodiment is:

[0106]

[0107] Wherein, A is the amplitude response of the digital peak filter, and the expression is:

[0108]

[0109] This embodiment can filter out the components of v d , v q with frequency not being f p -f1 or f n +f1.

[0110] After the processing of the digital peak filter, v d , v q only contain components of f p -f1 or f n +f1, but due to the phase response of the digital filter, f p -f1 will produce phase shift, so set T delay as the delay time of the delay unit to perform phase correction.

[0111] The calculation formula of T delay is:

[0112]

[0113] Wherein, θ(|f p -f1|) is the phase response of the digital peak filter at |f p -f1| frequency calculated by matlab; θ(|f n+f1|) is the digital spike filter calculated by MATLAB at |f n The phase response at the +f1| frequency. The above equation allows us to use a delay unit to cancel the phase shift caused by the digital spike filter, thus achieving phase-shift-free frequency component selection.

[0114] Figure 8 The peak frequency f was obtained through MATLAB calculation. p The amplitude response of the -f1=150Hz digital spike filter Figure 9 This is the phase response. It can be seen that at the target frequency f... p The filter response is 1 only at the peak frequency around -f1=150Hz, and close to 0 at other frequencies.

[0115] Based on this spike filter at f p Calculate T based on the phase response θ(150Hz) for -f1 = 150Hz. delay And set it as the coefficient of the delay to cancel out the phase response caused by the spike filter. The correction result is as follows: Figure 10 As shown.

[0116] Figure 10 The solid red line represents the original v. d The blue signal represents the signal after being filtered and phase-corrected by a spike filter. d To more clearly see the effect of phase correction, the original V signal is set. d The signal contains only f p The frequency component -f1 = 150Hz overlaps with the two signals after a period of time, indicating that the phase correction is successful and the phase shift caused by the spike filter has been eliminated.

[0117] S106. The grid-connected voltage dq-axis signal, which undergoes frequency component selection via a digital spike filter and phase correction via a delay unit, is used as the input to the voltage feedback transfer function. The output of the voltage feedback transfer function is then added to the inner current loop as an additional quantity to reshape the impedance characteristics of the oscillation frequency and suppress the oscillation at that frequency.

[0118] In this embodiment, the frequency selection module, phase correction module, and amplitude-frequency response module formed by the digital spike filter combined with the delay unit and voltage feedback channel are called a complete oscillation suppression damping channel, such as... Figure 5 As shown, Figure 5 medium signal v d The signal first enters the digital spike filter for frequency component selection, and then enters the frequency selection module, phase correction module, and amplitude-frequency response module formed by the delay and voltage feedback channel, thus realizing the signal processing of the oscillation suppression damping channel.

[0119] In this embodiment, vd v q First, frequency components are selected using a digital spike filter. After processing by the digital spike filter, v d v q Contains only f p -f1 or f n The +f1 component, but due to the phase frequency response of the digital filter, will cause f p -f1 produces a phase shift, therefore T is set delay Phase correction is performed using the delay time of the delay unit, resulting in a signal containing only frequency f. p -f1 component and no frequency shift V d (f p -f1), V q (f p -f1) or only contains frequency f n V with +f1 component and no frequency shift d (f n +f1), V q (f n +f1).

[0120] V d (f p -f1) and V q (f p -f1) Passing through K′ cp (s) can make the denominator of the positive sequence impedance Z1′1 zero, thereby suppressing the frequency f. p The oscillation. Similarly, V d (f n +f1), V q (f n +f1) Passing through K′ cn (s) can make the positive sequence impedance Z′ 22 The denominator is 0, thus the suppression frequency is f. n The oscillation.

[0121] This embodiment Figure 11 A simulation example is used to illustrate this. The positive sequence impedance of the three-phase grid-connected inverter is represented by red, and the grid impedance by black. It can be seen that both meet the oscillation condition at 474Hz, i.e., equal amplitude and 180° phase difference. The system will oscillate at a frequency of 474Hz. After the damping channel designed in this invention, the system impedance characteristic only changes at 474Hz, without affecting other impedance characteristics, as shown by the red circle in the figure. At this time, the oscillation should be suppressed. The specific time-domain simulation results are as follows. Figure 12 As shown. Figure 12 This indicates that the oscillation in the previous second was successfully suppressed after the damping channel designed in this invention was applied in the 1st second, verifying the effectiveness of this invention.

[0122] As Figure 13 shown, the present application also provides an electronic device, comprising: a display module 103, a memory 102, a processor 101 and a computer program stored in the memory 102 and executable on the processor 101, wherein the processor 101 implements the steps of the three-phase grid-connected inverter wide-frequency oscillation suppression method when executing the program.

[0123] Those skilled in the art can understand that the electronic device structure involved in the embodiments of the present application does not constitute a limitation on the electronic device, and the electronic device can include more or fewer components than the illustration, or combine certain components, or different component arrangements. In the embodiments of the present application, the electronic device includes but is not limited to a laptop computer, a desktop computer, a workstation, a personal digital assistant, a server, a blade server, a mainframe computer, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the embodiments of the present application described and / or claimed herein.

[0124] In the embodiments of the present application, the processor 101 can be implemented by using at least one of an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a processor, a controller, a microcontroller, a microprocessor, an electronic unit designed to perform the functions described herein, and in some cases, such implementation can be implemented in a controller. For software implementation, the implementation of such processes or functions can be implemented with separate software modules that allow at least one function or operation to be performed. The software code can be implemented by a software application (or program) written in any appropriate programming language, which can be stored in a memory and executed by a controller.

[0125] The display module 103 is used to display information input by a user or information provided to a user. The display module 103 can include a display panel, which can be configured in the form of a liquid crystal display (LCD), an organic light-emitting diode (OLED), etc.

[0126] The memory 102 can be used to store software programs as well as various data. The memory can include high-speed random access memory, and can also include non-volatile memory such as at least one magnetic disk storage device, flash memory device, or other volatile solid state storage device.

[0127] In addition, the electronic device includes some function modules which are not shown and will not be described here.

[0128] The application also provides a storage medium, the storage medium stores a computer program, and the computer program is executed by a processor to realize the steps of the three-phase grid-connected inverter wide-frequency oscillation suppression method.

[0129] The storage medium can adopt any combination of one or more readable media. The readable medium can be a readable signal medium or a readable storage medium. The readable storage medium may, for example, be but is not limited to an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or component, or any combination thereof. More specific examples (non-exhaustive list) of readable storage media include an electrical connection having one or more wires, a portable disc, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof.

[0130] The above description of disclosed embodiments enables one of ordinary skill in the art to make or use the application. Various modifications to these embodiments will be readily apparent to those of ordinary skill in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Accordingly, the application is not to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for suppressing wide frequency oscillations in a three-phase grid-connected inverter, the method comprising: The method comprises: S1, based on the voltage feedback channel, configuring the feedback value to the current control inner loop of the three-phase grid-connected inverter, and obtaining the sequence impedance model of the three-phase grid-connected inverter; S2, defining the sequence impedance denominator as 0, and configuring the voltage feedback channel transfer function; S3, detecting the oscillation frequency of the three-phase grid-connected inverter grid voltage by using the fast Fourier algorithm; S4, according to the detected oscillation frequency, calculating the equivalent factor, and replacing the imaginary unit in the voltage feedback channel transfer function with the equivalent factor to perform equivalent transformation, so that the voltage feedback channel before and after the equivalent transformation has the same amplitude and phase response at the oscillation frequency; S5, according to the detected oscillation frequency, obtaining the digital peak filter corresponding to the frequency, and calculating the delay coefficient of the delay device based on the phase response of the digital peak filter, and performing frequency component selection and phase correction; S6, taking the grid voltage dq axis signal processed by the digital peak filter for frequency component selection and the delay device for phase correction as the input of the voltage feedback transfer function, and taking the output of the voltage feedback transfer function as the additional quantity added to the current inner loop, to achieve impedance characteristic remodeling at the oscillation frequency and realize oscillation suppression at the frequency.

2. The method of claim 1, wherein the three-phase grid-connected inverter broadband oscillation suppression method is characterized by, Step S1 further comprises defining the positive sequence impedance Z' of the three-phase grid-connected inverter 11 and the negative sequence impedance Z' as: 22 Z' = Z - jX0 wherein, is the phase angle of the grid fundamental voltage leading the grid fundamental current; I1is the amplitude of the grid current fundamental component; V1is the amplitude of the grid voltage fundamental component; T p (s) is the expression related to the phase-locked loop transfer function under positive sequence disturbance, T n (s) is the expression related to the phase-locked loop transfer function under negative sequence disturbance, D0, Q0are constants, L f is the filter inductance; V dc is the inverter DC voltage; H i (s) is the transfer function of the current inner loop; ω1is the angular frequency of the fundamental voltage; D0, Q0are constants related to system parameters.

3. The method of claim 2, wherein the method further comprises: In the method, T p (s), T n The expressions of (s), D0, and Q0 are as follows, respectively. T p (s) = 0.5H PLL (s) / (1+V1H PLL (s)) f p -f1 T n (s) = 0.5H PLL (s) / (1+V1H PLL (s)) f n +f1 where H PLL (s) is the phase-locked loop transfer function, L f is the filter inductance.

4. The method of claim 2, wherein the method further comprises: In step S2, the sequence impedance denominator is defined as 0, and the voltage feedback channel transfer function K is configured c (s) includes: the voltage feedback channel transfer function K c (s) suitable for positive sequence disturbance and the voltage feedback channel transfer function K cp (s) suitable for negative sequence disturbance. cn (s).

5. The method of claim 4, wherein the method further comprises: In step S4, the formula for calculating the equivalent factor is:

6. The method of claim 5, wherein the method further comprises: The transfer function after equivalent transformation is:

7. The method of claim 2, wherein the method further comprises: The amplitude-frequency response of the peak filter in S5 is: Wherein, A is the amplitude response of the digital peak filter, and the expression is:

8. The method of claim 7, wherein the method further comprises: In step S5, the phase correction is performed by setting the delay time T of the delay timer delay The calculation formula of T delay is as follows: where θ(|f p -f1|) is the phase response of the digital spike filter at |f p -f1| frequency calculated by matlab; θ(|f n +f1|) is the phase response of the digital spike filter at |f n +f1| frequency calculated by matlab.

9. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor implements the steps of the three-phase grid-connected inverter wide-frequency oscillation suppression method according to any one of claims 1 to 7 when executing the program.

10. A storage medium having stored thereon a computer program, characterized in that The computer program is executed by the processor to implement the steps of the three-phase grid-connected inverter wide-frequency oscillation suppression method according to any one of claims 1 to 7.

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