Inverter control method and system and photovoltaic inverter

Abstract

The invention provides an inverter control method and system and a photovoltaic inverter, and belongs to the technical field of inverter control. The method comprises the following steps: firstly, analyzing a sampling signal in an inverter to obtain a plurality of frequency domain signal points; then, one or more target resonance points are determined from the multiple frequency domain signal points, filtering parameters are determined according to the frequencies of the target resonance points to obtain a band-pass filter, the sampling signals are filtered through the band-pass filter, and signal components corresponding to the target resonance points are obtained; and finally, obtaining a virtual damping output quantity according to the target resonance point and the signal component corresponding to the target resonance point, and controlling the inverter according to the virtual damping output quantity. Therefore, targeted resonance suppression is carried out on each target resonance point, so that the performance of the inverter is improved.

Description

Technical Field

[0001] The present application relates to the field of inverter control technology, and in particular to an inverter control method, system and photovoltaic inverter. Background Art

[0002] Photovoltaic inverters are grid-connected interface devices for renewable energy power generation systems. They are used to convert DC power and need to control the synchronization of the converted power with the power of the grid. In practical applications, multiple inverters are usually connected to the grid in parallel to achieve power expansion and redundant operation. Affected by the interaction between the grid and multiple inverters, each photovoltaic inverter may have multiple resonance factors during operation, thus forming different resonance points, resulting in a decrease in the performance of the inverter.

[0003] At present, in order to improve the stability of photovoltaic inverters, resistors are usually set in photovoltaic inverters to provide effective damping, so that the internal resistance of the photovoltaic inverter is greater than zero, thereby achieving the effect of suppressing resonance. However, in the use scenario of photovoltaic inverters connected to the grid, there may be multiple resonance points. If a single fixed damping is used, it is impossible to effectively suppress multiple resonance points. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present application provides an inverter control method, system and photovoltaic inverter.

[0005] In a first aspect, the present application provides an inverter control method, comprising:

[0006] Analyze the sampling signal in the inverter to obtain several frequency domain signal points;

[0007] Determine one or more target resonance points from the plurality of frequency domain signal points;

[0008] Determining filtering parameters according to the frequency of the target resonance point to obtain a bandpass filter, and filtering the sampled signal through the bandpass filter to obtain a signal component corresponding to the target resonance point;

[0009] A virtual damping output is obtained according to the target resonance point and the signal component corresponding thereto, and the inverter is controlled according to the virtual damping output.

[0010] Optionally, the sampling signal in the inverter is analyzed to obtain a number of frequency domain signal points, including:

[0011] Performing Fourier transform on the sampled signal to obtain a sampled frequency domain signal;

[0012] According to the amplitude of the sampled frequency domain signal, a plurality of the frequency domain signal points are screened out from the sampled frequency domain signal;

[0013] The sampling signal includes a voltage signal across a filter capacitor of a filter structure in the inverter or a current signal flowing through an inductor on the inverter side.

[0014] Optionally, determining one or more target resonance points from the plurality of frequency domain signal points includes:

[0015] Comparing the amplitudes of the frequency domain signal points, and determining a first resonance point from the frequency domain signal points according to the comparison result;

[0016] According to the frequency of the first resonance point, determining whether there is a second resonance point in the remaining frequency domain signal points;

[0017] If yes, taking the first resonance point and the second resonance point as the target resonance point;

[0018] If not, the first resonance point is used as the target resonance point.

[0019] Optionally, comparing the amplitudes of the frequency domain signal points and determining the first resonance point from the frequency domain signal points according to the comparison result includes:

[0020] According to the comparison result, taking the frequency domain signal point with the largest amplitude as the first signal point to be confirmed;

[0021] It is determined whether the amplitude of the first signal point to be confirmed is greater than a preset amplitude threshold; if so, the first signal point to be confirmed is used as a first resonance point.

[0022] Optionally, judging, according to the frequency of the first resonance point, whether there is a second resonance point in the remaining frequency domain signal points includes:

[0023] Determine whether there is a frequency domain signal point among the remaining frequency domain signal points whose frequency difference with the first resonance point is greater than a preset difference value;

[0024] If not, determining that the second resonance point does not exist in the remaining frequency domain signal points;

[0025] If so, taking the remaining frequency domain signal points whose frequency difference with the first resonance point is greater than a preset difference as the second signal to be confirmed;

[0026] Determining whether the amplitude of the second signal point to be confirmed is greater than a preset amplitude threshold;

[0027] If the amplitude of the second signal point to be confirmed is greater than the preset amplitude threshold, determining that the second resonance point exists in the remaining frequency domain signal points, and taking the second signal point to be confirmed as the second resonance point;

[0028] If the amplitude of the second signal point to be confirmed is less than or equal to the preset amplitude threshold, it is determined that the second resonance point does not exist in the remaining frequency domain signal points.

[0029] Optionally, the target resonance point includes a first resonance point, and obtaining a virtual damping output according to the target resonance point and the signal component corresponding thereto includes:

[0030] Inputting the frequency of the first resonance point into a preset parameter control function to obtain a damping control parameter;

[0031] transforming the signal component to obtain an equivalent current component;

[0032] The damping control parameter and the equivalent current component are multiplied to obtain the virtual damping output.

[0033] Optionally, the target resonance point includes a first resonance point and a second resonance point; and obtaining the damping control parameter according to the target resonance point and the signal component corresponding thereto includes:

[0034] Inputting the frequency of the first resonance point and the frequency of the second resonance point into a preset parameter control function respectively to obtain a first damping control parameter and a second damping control parameter;

[0035] Respectively transforming the signal component corresponding to the first resonance point and the signal component corresponding to the second resonance point to obtain a first equivalent current component and a second equivalent current component;

[0036] Obtaining a first sub-control parameter according to the first damping control parameter and the first equivalent current component;

[0037] obtaining a second sub-control parameter according to the second damping control parameter and the second equivalent current component;

[0038] The first sub-control parameter and the second sub-control parameter are superimposed to obtain the virtual damping output.

[0039] Optionally, also include:

[0040] Acquire a control transfer function of the inverter, and obtain a damping control function of the inverter according to the control transfer function;

[0041] Obtaining a resonant frequency function of a filter structure in the inverter;

[0042] According to the damping control function and the resonant frequency function, establishing a correlation function between the control parameter and the damping ratio and the resonant frequency;

[0043] The preset parameter control function is obtained according to the set target damping ratio and the correlation function.

[0044] In a second aspect, in one embodiment, the present application provides an inverter control system, including:

[0045] The frequency domain analysis module is used to analyze the sampling signal in the inverter to obtain several frequency domain signal points;

[0046] A resonance point determination module, used to determine one or more target resonance points from the plurality of frequency domain signal points;

[0047] A filtering module, configured to determine filtering parameters according to the frequency of the target resonance point to obtain a bandpass filter, and filter the sampled signal through the bandpass filter to obtain a signal component corresponding to the target resonance point;

[0048] A control module is used to obtain a virtual damping output according to the target resonance point and the signal component corresponding thereto, and control the inverter according to the virtual damping output.

[0049] In a third aspect, in one embodiment, the present application provides an electronic device, comprising a memory and a processor; the memory stores a computer program, and the processor is used to run the computer program in the memory to execute the steps in the inverter control method in any of the above embodiments.

[0050] In a fourth aspect, in one embodiment, the present application provides a storage medium, wherein the storage medium stores a computer program, and the computer program is loaded by a processor to execute the steps in the inverter control method in any of the above embodiments.

[0051] In summary, in this application, first, the sampling signal in the inverter is analyzed in the frequency domain to identify one or more target resonance points in the inverter. Secondly, the filter parameters are dynamically adjusted based on the frequency of the target resonance point and a bandpass filter is generated to more accurately extract the signal components corresponding to the target resonance point, thereby achieving separation of specific resonance frequencies. Finally, a virtual damping output is generated in combination with the target resonance point and its corresponding signal component, and the inverter is controlled using the virtual damping output, thereby achieving targeted resonance suppression for each target resonance point, thereby improving the performance of the inverter. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0053] Figure 1 This is a schematic diagram of an inverter structure in one embodiment of the present application;

[0054] Figure 2 This is a flow chart of an inverter control method in one embodiment of the present application;

[0055] Figure 3 This is a flow chart of a target resonance point identification method in one embodiment of the present application;

[0056] Figure 4 This is a flow chart of a method for determining a second resonance point in one embodiment of the present application;

[0057] Figure 5 A flow chart of a method for generating a virtual damping output in one embodiment of the present application;

[0058] Figure 6 A flow chart of a method for generating a virtual damping output in another embodiment of the present application;

[0059] Figure 7 A flow chart of a method for generating a preset parameter control function in one embodiment of the present application;

[0060] Figure 8 A block diagram of an inverter control system in one embodiment of the present application;

[0061] Fig. 9 This is a schematic diagram of a photovoltaic inverter in one embodiment of the present application. DETAILED DESCRIPTION

[0062] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0063] In the description of the present application, it should be understood that the terms "first" and "second" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. In the present application, the word "exemplary" is used to mean "used as an example, illustration or description". Any embodiment described as "exemplary" in the present application is not necessarily interpreted as being more preferred or more advantageous than other embodiments. In order to enable any technician in the field to implement and use the present application, the following description is given. In the following description, details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art can recognize that the present application can also be implemented without using these specific details. In other examples, well-known structures and processes will not be elaborated in detail to avoid unnecessary details that make the description of the present application obscure. Therefore, the present application is not intended to be limited to the embodiments shown, but is consistent with the widest range of principles and features disclosed in the present application.

[0064] As an example of an application scenario of the inverter control method, the inverter control method can be applied to a photovoltaic inverter, or the devices included in the photovoltaic inverter do not constitute a limitation on the embodiments of the present application, that is, the number of devices and types of devices included in the application scenario of the inverter control method, or the number of devices and types of devices included in each device do not affect the overall implementation of the technical solution in the embodiments of the present application, and can all be regarded as equivalent replacements or derivatives of the technical solution claimed to be protected in the embodiments of the present application.

[0065] Reference Figure 1 , Figure 1 The photovoltaic inverter includes a DC input voltage source V dc The inverter bridge VSC1 and the filter structure between the power grid interface, the structure of the inverter bridge VSC1 is not specifically limited here, and the filter structure may include an inverter side inductor L 1 、Filter inductor L 2 , grid side inductor L g and filter capacitor C 1 , as an example, the grid voltage u at the grid interface g can be 600V, the grid frequency f can be 60Hz, and the DC input voltage source V dc The output can be 1300V, and the rated power of the inverter can be 250kW; the inverter side inductor L 1 The inductance value can be 100uH, and the filter capacitor C 1 The capacitance value can be 35uF, and the filter inductor L 2The inductance value of can be 5uH. Wherein, R represents a virtual resistor realized by the steps in the inverter control method, and the virtual resistor R does not actually consume electric energy, but is used to change the dynamic characteristics of the inverter, thereby optimizing the resonance phenomenon of the inverter.

[0066] Those skilled in the art can understand that the above application scenario is merely an application scenario corresponding to the technical solution of the present application, and does not constitute a limitation on the application scenario of the technical solution of the present application. The photovoltaic inverter may also include a memory for storing information related to the inverter control method.

[0067] It should be noted that the application scenario of the above-mentioned inverter control method is merely an example. The application scenario of the inverter control method described in the embodiment of the present application is to more clearly illustrate the technical solution of the embodiment of the present application, and does not constitute a limitation on the technical solution provided in the embodiment of the present application.

[0068] Based on the application scenario of the above inverter control method, an embodiment of the inverter control method is proposed.

[0069] First, as Figure 2 As shown, in one embodiment, the present application provides an inverter control method, and the inverter control method includes steps S11 to S14, which are described in detail below.

[0070] Step S11: Analyze the sampled signal in the inverter to obtain a number of frequency domain signal points.

[0071] Step S12: determining one or more target resonance points from a plurality of frequency domain signal points.

[0072] Among them, multiple target resonance points may be resonance points generated by different reasons. For example, each inverter may have two types of resonance phenomena during operation. One is the resonance point formed by the inverter output impedance and the equivalent inductive reactance of the grid-side inductor in series, and the other is the resonance point generated by the interaction between the output impedances of multiple inverters when multiple inverters are connected in parallel.

[0073] Step S13: determining filtering parameters according to the frequency of the target resonance point to obtain a bandpass filter, and filtering the sampled signal through the bandpass filter to obtain a signal component corresponding to the target resonance point.

[0074] The bandpass filter can be expressed as Among them, ω ris the angular frequency obtained according to the frequency of the target resonance point, and Q is the quality factor of the bandpass filter. If there are multiple target resonance points, the filter parameters are determined according to the frequency of each target resonance point to obtain a bandpass filter corresponding to the target resonance frequency, so as to extract the signal component corresponding to the target resonance point. As an example, the signal component can be expressed as Among them, u c Represents the sampled signal.

[0075] Step S14: obtaining a virtual damping output according to the target resonance point and the signal component corresponding thereto, and controlling the inverter according to the virtual damping output.

[0076] In the above implementation, first, the sampling signal in the inverter is analyzed in the frequency domain to identify one or more target resonance points in the inverter. Secondly, the filter parameters are dynamically adjusted based on the frequency of the target resonance point and a bandpass filter is generated to more accurately extract the signal component corresponding to the target resonance point, thereby achieving separation of specific resonance frequencies. Finally, a virtual damping output is generated in combination with the target resonance point and its corresponding signal component, and the inverter is controlled using the virtual damping output, thereby achieving targeted resonance suppression for each target resonance point, thereby improving the performance of the inverter.

[0077] In some embodiments, step S11 may include steps S111 to S112, which are described in detail below.

[0078] Step S111: Perform Fourier transform on the sampled signal to obtain a sampled frequency domain signal.

[0079] The sampling signal includes a voltage signal at both ends of a filter capacitor of a filter structure in the inverter.

[0080] As an example, the sampled frequency domain signal is a continuous signal. The spectrum of the sampled signal is analyzed by Fourier transform. The frequency domain signal is a spectrum diagram composed of the harmonic content (amplitude) of the target signal at each frequency, thereby obtaining the sampled frequency domain signal.

[0081] Step S112: Filter out a number of frequency domain signal points from the sampled frequency domain signal according to the amplitude of the sampled frequency domain signal.

[0082] As an example, the frequency domain signal points are discrete signals, and the number of frequency domain signal points can be set according to actual conditions, for example, the number of frequency domain signal points can be 8, 10, 15 or 20, etc. Several signal points with the highest amplitude in the sampled frequency domain signal can be selected as frequency domain signal points.

[0083] Reference Figure 3In some embodiments, step S12 may include steps S121 to S124, which are described in detail below.

[0084] Step S121: comparing the amplitudes of the frequency domain signal points, and determining the first resonance point from the frequency domain signal points according to the comparison result.

[0085] As an example, the frequency domain signal point with the highest amplitude may be selected as the first resonance point to quickly identify the frequency at which the most serious resonance phenomenon occurs.

[0086] Step S122: According to the frequency of the first resonance point, determine whether there is a second resonance point in the remaining frequency domain signal points. If yes, execute step S123; if no, execute step S124.

[0087] Step S123: taking the first resonance point and the second resonance point as target resonance points.

[0088] Step S124: taking the first resonance point as the target resonance point.

[0089] As an example, each inverter may form a target resonance point due to interaction with the grid and interaction with other inverters. Depending on the actual operating conditions, the target resonance point may include only the first resonance point or the first resonance point and the second resonance point.

[0090] In the above implementation, first, by comparing the amplitudes of the frequency domain signal points, the first resonance point with the largest amplitude is determined. Secondly, based on the frequency of the first resonance point, it is further determined whether there is a second resonance point in the remaining frequency domain signal points, so as to realize the identification of multiple resonance points. Finally, the target resonance point (one or more) is dynamically determined according to the judgment result, so that not only the first resonance point with the most obvious resonance phenomenon can be identified, but also the coexistence of multiple resonance points can be identified, which helps to realize resonance suppression in the multi-machine parallel scenario.

[0091] In some embodiments, step S121 may include steps S1211 to S1214, which are described in detail below.

[0092] Step S1211: according to the comparison result, the frequency domain signal point with the largest amplitude is taken as the first signal point to be confirmed.

[0093] Step S1212: determine whether the amplitude of the first signal point to be confirmed is greater than a preset amplitude threshold, if so, execute step S1213; if not, do not execute any operation.

[0094] Step S1213: taking the first signal point to be confirmed as the first resonance point.

[0095] In the above implementation, firstly, by comparing the amplitudes of the frequency domain signal points, the frequency domain signal point with the largest amplitude can be quickly screened out as the first signal point to be confirmed. Secondly, the signal points with a small amplitude that do not require resonance suppression are effectively excluded by the preset amplitude threshold. When the amplitude of the first signal point to be confirmed meets the preset amplitude threshold, it is confirmed as the first resonance point, so that the screened out first resonance point has a significant resonance feature, avoiding additional resonance suppression at the frequency where the resonance is not obvious.

[0096] Reference Figure 4 In some embodiments, step S122 may include steps S1221 to S1225, which are described in detail below.

[0097] Step S1221: Determine whether there is a frequency domain signal point among the remaining frequency domain signal points whose frequency difference with the first resonance point is greater than a preset difference value. If not, execute step S1225; if yes, execute step S1222.

[0098] As an example, the remaining frequency domain signal points refer to frequency domain signal points other than the first resonance point. When the frequency difference between a frequency domain signal point and the first resonance point is within a preset difference range, it means that the frequency domain signal point may be a resonance caused by the same reason as the first resonance point, that is, the frequency domain signal point may be a harmonic of the first resonance point and does not need to be suppressed repeatedly. Therefore, when there is no frequency domain signal point in the remaining frequency domain signal points whose difference with the first resonance point is greater than the preset difference, it is only necessary to suppress the first resonance point and determine that there is no second resonance point. For example, the preset difference can be set to 200Hz.

[0099] Step S1222: taking the frequency domain signal points among the remaining frequency domain signal points whose frequency difference with the first resonance point is greater than a preset difference value as the second signal to be confirmed.

[0100] As an example, the second signal to be confirmed can be screened by setting a flag. In step S1221, in the order of amplitude from large to small, it is determined whether there is a frequency domain signal point whose frequency difference with the first resonance point is greater than the preset difference value among the remaining frequency domain signal points. If a frequency domain signal point whose frequency difference with the first resonance point is greater than the preset difference value appears, the flag is set to 1. If a frequency domain signal point whose frequency difference with the first resonance point is greater than the preset difference value does not appear yet, it is determined whether the frequency difference between the next frequency domain signal point and the first resonance point is greater than the preset difference value in the order of amplitude from large to small until all the remaining frequency domain signal points are traversed. If there is no frequency domain signal point whose frequency difference with the first resonance point is greater than the preset difference value among the remaining frequency domain signal points, the flag is set to 0. Thus, by identifying the state of the flag, it is determined whether there is a second identification signal to be confirmed.

[0101] Step S1223: Determine whether the amplitude of the second signal point to be confirmed is greater than the preset amplitude threshold. If the amplitude of the second signal point to be confirmed is greater than the preset amplitude threshold, execute step S1224; if the amplitude of the second signal point to be confirmed is less than or equal to the preset amplitude threshold, execute step S1225.

[0102] Step S1224: determine whether there is a second resonance point in the remaining frequency domain signal points, and use the second signal point to be confirmed as the second resonance point.

[0103] Step S1225: Determine whether there is no second resonance point in the remaining frequency domain signal points.

[0104] In the above implementation, by judging whether the frequency difference between the remaining frequency domain signal points and the first resonance point is greater than the preset difference, the signal points separated from the first resonance point frequency can be screened out more accurately, thereby avoiding repeated screening of resonance phenomena caused by the same reason, thereby determining the frequency domain range of the second resonance point. Secondly, based on the preset difference screening, the amplitude of the second signal point to be confirmed is judged by a threshold value. When the amplitude of the second signal point to be confirmed meets the preset amplitude threshold, it is confirmed as the second resonance point, so that the screened second resonance point also has a significant resonance feature, avoiding additional resonance suppression at frequencies where the resonance is not obvious.

[0105] Reference Figure 5 In some embodiments, the target resonance point includes a first resonance point, and step S14 may include steps S21 to S23, which are described in detail below.

[0106] Step S21: inputting the frequency of the first resonance point into a preset parameter control function to obtain a damping control parameter.

[0107] Among them, the preset parameter control function can be expressed as Where L1 is the inductance of the inverter side inductor. Kpwm is the setting parameter in the proportional integral controller; s is a complex variable, which represents the frequency domain characteristics of the control system. ω r1 Represents the angular frequency obtained from the frequency of the first resonance point.

[0108] Step S22: transform the signal component to obtain the equivalent current component.

[0109] As an example, the equivalent current component can be expressed as i c =Csu cr1 Among them, u cr1 Represents the signal component; since the signal component u cr1 The differential form of is equivalent to ic. Therefore, using Csu cr1 (C is the filter capacitor) indicates i c .

[0110] Step S23: multiply the damping control parameter and the equivalent current component to obtain a virtual damping output.

[0111] As an example, the virtual damping output quantity can be expressed as R vi =KCsu cr1 .

[0112] Reference Figure 6 In some embodiments, the target resonance point includes a first resonance point and a second resonance point, and step S14 may include steps S31 to S35, which are described in detail below.

[0113] Step S31: inputting the frequency of the first resonance point and the frequency of the second resonance point into a preset parameter control function respectively to obtain a first damping control parameter and a second damping control parameter.

[0114] As an example, the first damping control parameter and the second damping control parameter are generated in the same manner as the damping control parameter, which will not be described in detail herein.

[0115] Step S32: transforming the signal component corresponding to the first resonance point and the signal component corresponding to the second resonance point respectively to obtain a first equivalent current component and a second equivalent current component.

[0116] Step S33: obtaining a first sub-control parameter according to the first damping control parameter and the first equivalent current component.

[0117] Step S34: Obtain a second sub-control parameter according to the second damping control parameter and the second equivalent current component.

[0118] Step S35: superimpose the first sub-control parameter and the second sub-control parameter to obtain a virtual damping output.

[0119] As an example, since the first damping control parameter and the second damping control parameter are respectively set for the damping of different first resonance points and second resonance points, they are respectively responsible for different frequency bands. Therefore, even if the first sub-control parameter and the second sub-control parameter are superimposed to obtain a virtual damping output, the first sub-control parameter and the second sub-control parameter will not interfere with or affect each other.

[0120] As an example, the virtual damping output quantity can be expressed as R vi =K 1 Csu cr1 +K 2 Csu cr2 ; Wherein, K1 and K2 represent the first damping control parameter and the second damping control parameter respectively; u cr1 and u cr2 They represent the first equivalent current component and the second equivalent current component respectively. K1 Csu cr1 represents the first sub-control parameter; K 2 Csu cr2 The virtual damping output is added to the output terminal of the proportional-integral controller in the inverter, thereby controlling the inverter.

[0121] Reference Figure 7 In some embodiments, the inverter control method further includes steps S41 to S44, which are described in detail below.

[0122] Step S41: Acquire a control transfer function of the inverter, and obtain a damping control function of the inverter according to the control transfer function.

[0123] As an example, Figure 1 Taking the filter structure shown in the figure as an example, the transfer function can be expressed as:

[0125]

[0126] Among them, L1 is the inductance value of the inverter side inductor, L2 is the inductance value of the filter inductor; Lg is the inductance value of the grid side inductor, and its value is related to the grid inductance; C1 is the capacitance value of the filter capacitor. Kpwm, Kfi, Kpi and Kii are the setting parameters in the proportional integral controller; s is a complex variable, which represents the frequency domain characteristics of the control system.

[0127] Among them, the damping control function can be expressed as: Among them, K is an unknown control parameter, that is, it is used to obtain the damping control parameter. There is a linear relationship between K and the virtual resistance R, that is, the larger K is, the larger the resistance value of the virtual resistance R is, and the greater the damping of the inverter is.

[0128] Step S42: Obtain the resonant frequency function of the filter structure in the inverter.

[0129] As an example, Figure 1 Taking the filter structure shown in the figure as an example, the resonant frequency function can be expressed as:

[0130] Among them, ω r It represents the angular frequency obtained according to the frequency of the target resonant point. In the resonant frequency function, the inductance of the inverter side inductor, the inductance of the filter inductor and the capacitance of the filter capacitor are fixed values, while the inductance of the grid side inductor will change with the fluctuation of the grid. Therefore, the accurate target resonant frequency cannot be obtained through the resonant frequency function, and the target resonant frequency needs to be determined through frequency domain analysis.

[0131] Step S43: establishing a correlation function between the control parameter and the damping ratio and the resonant frequency according to the damping control function and the resonant frequency function.

[0132] As an example, combining the damping control function and the resonant frequency function, the correlation function can be expressed as: Among them, ε vr represents the damping ratio; Kpwm is a known value, and the correlation function is the control parameter K, the damping ratio ε vr and ω r The corresponding relationship between them.

[0133] Step S44: Obtain a preset parameter control function according to the set target damping ratio and the correlation function.

[0134] As an example, since the filter structure of the inverter is a second-order system, the target damping ratio may be in the range of 0.6-0.8, and the preferred target damping ratio is 0.707.

[0135] As an example, when the target damping ratio is 0.707, the preset parameter control function can be expressed as In the preset parameter control function, only the resonant frequency ω r is an unknown parameter. In the case of resonance suppression, the resonant frequency ω r The angular frequency of the target resonance point, that is, the resonance frequency corresponding to the maximum amplitude, is taken so that the generated damping control parameters can suppress the most obvious resonance.

[0136] In the above implementation, the damping control function is first obtained through the control transfer function of the inverter to grasp the damping characteristics of the inverter. Then, in combination with the resonant frequency function of the filter structure in the inverter, a correlation function between the control parameter and the damping ratio and the resonant frequency is established to suppress the resonance phenomenon in a targeted manner. Finally, according to the set target damping ratio and the correlation function, a preset parameter control function is obtained to obtain the damping control parameter that meets the target damping ratio under the current working condition.

[0137] Reference Figure 8 In a second aspect, in one embodiment, the present application provides an inverter control system, including a frequency domain analysis module, a resonance point determination module, a filtering module and a control module.

[0138] The frequency domain analysis module is used to analyze the sampling signal in the inverter to obtain a number of frequency domain signal points.

[0139] The resonance point determination module is used to determine one or more target resonance points from a plurality of frequency domain signal points.

[0140] The filtering module is used to determine the filtering parameters according to the frequency of the target resonance point to obtain a bandpass filter, and filter the sampled signal through the bandpass filter to obtain a signal component corresponding to the target resonance point.

[0141] The control module is used to obtain a virtual damping output according to a target resonance point and a signal component corresponding thereto, and to control the inverter according to the virtual damping output.

[0142] Among them, the above-mentioned frequency domain analysis module, resonance point determination module, filtering module and control module are respectively used to execute steps S11-S14 in the above-mentioned method embodiment. For the specific implementation methods of these functional units, please refer to the description of the above-mentioned corresponding steps, which will not be repeated here.

[0143] In a third aspect, in one embodiment, the present application provides a photovoltaic inverter, such as Fig. 9 As shown, it shows the structure of the photovoltaic inverter involved in this application, specifically:

[0144] The photovoltaic inverter may include one or more processors 401 of processing cores, one or more computer-readable storage media memories 402, a power supply 403, an input unit 404 and other components. Those skilled in the art will appreciate that Fig. 9 The structure of the photovoltaic inverter shown in the figure does not constitute a limitation on the photovoltaic inverter, and may include more or fewer components than shown in the figure, or combine certain components, or arrange the components differently. Among them:

[0145] The processor 401 is the control center of the photovoltaic inverter. It uses various interfaces and lines to connect various parts of the entire photovoltaic inverter. By running or executing software programs and / or modules stored in the memory 402, and calling data stored in the memory 402, it performs various functions of the photovoltaic inverter and processes data, thereby monitoring the photovoltaic inverter as a whole. Optionally, the processor 401 may include one or more processing cores; preferably, the processor 401 may integrate an application processor and a modem processor, wherein the application processor mainly processes the operating system, user interface and computer programs, etc., and the modem processor mainly processes wireless communications. It is understandable that the above-mentioned modem processor may not be integrated into the processor 401.

[0146] The memory 402 can be used to store software programs and modules. The processor 401 executes various functional applications and data processing by running the software programs and modules stored in the memory 402. The memory 402 may mainly include a program storage area and a data storage area, wherein the program storage area may store an operating system, a computer program required for at least one function (such as a sound playback function, an image playback function, etc.), etc.; the data storage area may store data created according to the use of the server, etc. In addition, the memory 402 may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other volatile solid-state storage devices. Accordingly, the memory 402 may also include a memory controller to provide the processor 401 with access to the memory 402.

[0147] The photovoltaic inverter also includes a power supply 403 for supplying power to each component. Preferably, the power supply 403 can be logically connected to the processor 401 through a power management system, so that the power management system can manage charging, discharging, power consumption and other functions. The power supply 403 can also include one or more DC or AC power supplies, recharging systems, power failure detection circuits, power converters or photovoltaic inverters, power status indicators and other arbitrary components.

[0148] The photovoltaic inverter may further include an input unit 404 , which may be used to receive input digital or character information.

[0149] Although not shown, the photovoltaic inverter may further include a display unit, etc., which will not be described in detail herein. Specifically in this embodiment, when the photovoltaic inverter is a model training photovoltaic inverter, the processor 401 in the photovoltaic inverter will load the executable files corresponding to the processes of one or more computer programs into the memory 402 according to the following instructions, and the processor 401 will run the computer program stored in the memory 402 to execute the steps in the inverter control method.

[0150] A person of ordinary skill in the art will appreciate that all or part of the steps in any of the methods of the above embodiments may be completed by a computer program, or by controlling related hardware through a computer program. The computer program may be stored in a computer-readable storage medium and loaded and executed by a processor.

[0151] In a fourth aspect, in one embodiment, the present application provides a storage medium storing a plurality of computer programs, which can be loaded by a processor to execute steps in an inverter control method.

[0152] It will be appreciated by those skilled in the art that any reference to memory, storage, database or other medium used in the embodiments provided herein may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in a variety of forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink), DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0153] Since the computer program stored in the storage medium can execute the steps in the inverter control method in any embodiment provided in the present application, the beneficial effects that can be achieved by the inverter control method in any embodiment provided in the present application can be achieved. Please refer to the previous embodiments for details and will not be repeated here.

[0154] The specific implementation of the above operations can be found in the previous embodiments, which will not be described in detail here.

[0155] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the detailed description of other embodiments above, and will not be repeated here.

[0156] The above is a detailed introduction to an inverter control method, system and photovoltaic inverter provided by the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

[0157] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. An inverter control method, characterized in that: include: Analyze the sampling signal in the inverter to obtain several frequency domain signal points; Determine one or more target resonance points from the plurality of frequency domain signal points; Determining filtering parameters according to the frequency of the target resonance point to obtain a bandpass filter, and filtering the sampled signal through the bandpass filter to obtain a signal component corresponding to the target resonance point; A virtual damping output is obtained according to the target resonance point and the signal component corresponding thereto, and the inverter is controlled according to the virtual damping output.

2. The inverter control method according to claim 1, characterized in that: The sampling signal in the inverter is analyzed to obtain several frequency domain signal points, including: Performing Fourier transform on the sampled signal to obtain a sampled frequency domain signal; According to the amplitude of the sampled frequency domain signal, a plurality of the frequency domain signal points are screened out from the sampled frequency domain signal; The sampling signal includes a voltage signal across a filter capacitor of a filter structure in the inverter or a current signal flowing through an inductor on the inverter side.

3. The inverter control method according to claim 2, characterized in that: The step of determining one or more target resonance points from the plurality of frequency domain signal points comprises: Comparing the amplitudes of the frequency domain signal points, and determining a first resonance point from the frequency domain signal points according to the comparison result; According to the frequency of the first resonance point, determining whether there is a second resonance point in the remaining frequency domain signal points; If yes, taking the first resonance point and the second resonance point as the target resonance point; If not, the first resonance point is used as the target resonance point.

4. The inverter control method according to claim 3, characterized in that: The comparing the amplitudes of the frequency domain signal points and determining the first resonance point from the frequency domain signal points according to the comparison result includes: According to the comparison result, taking the frequency domain signal point with the largest amplitude as the first signal point to be confirmed; It is determined whether the amplitude of the first signal point to be confirmed is greater than a preset amplitude threshold; if so, the first signal point to be confirmed is used as a first resonance point.

5. The inverter control method according to claim 3, characterized in that: The determining, according to the frequency of the first resonance point, whether there is a second resonance point in the remaining frequency domain signal points includes: Determine whether there is a frequency domain signal point among the remaining frequency domain signal points whose frequency difference with the first resonance point is greater than a preset difference value; If not, determining that the second resonance point does not exist in the remaining frequency domain signal points; If so, taking the remaining frequency domain signal points whose frequency difference with the first resonance point is greater than a preset difference as the second signal to be confirmed; Determining whether the amplitude of the second signal point to be confirmed is greater than a preset amplitude threshold; If the amplitude of the second signal point to be confirmed is greater than the preset amplitude threshold, determining that the second resonance point exists in the remaining frequency domain signal points, and taking the second signal point to be confirmed as the second resonance point; If the amplitude of the second signal point to be confirmed is less than or equal to the preset amplitude threshold, it is determined that the second resonance point does not exist in the remaining frequency domain signal points.

6. The inverter control method according to claim 1, characterized in that: The target resonance point includes a first resonance point, and obtaining a virtual damping output according to the target resonance point and the signal component corresponding thereto includes: Inputting the frequency of the first resonance point into a preset parameter control function to obtain a damping control parameter; transforming the signal component to obtain an equivalent current component; The damping control parameter and the equivalent current component are multiplied to obtain the virtual damping output.

7. The inverter control method according to claim 1, characterized in that: The target resonance point includes a first resonance point and a second resonance point; and obtaining a damping control parameter according to the target resonance point and the signal component corresponding thereto includes: Inputting the frequency of the first resonance point and the frequency of the second resonance point into a preset parameter control function respectively to obtain a first damping control parameter and a second damping control parameter; Respectively transforming the signal component corresponding to the first resonance point and the signal component corresponding to the second resonance point to obtain a first equivalent current component and a second equivalent current component; Obtaining a first sub-control parameter according to the first damping control parameter and the first equivalent current component; obtaining a second sub-control parameter according to the second damping control parameter and the second equivalent current component; The first sub-control parameter and the second sub-control parameter are superimposed to obtain the virtual damping output.

8. The inverter control method according to claim 6 or 7, characterized in that: Also includes: Acquire a control transfer function of the inverter, and obtain a damping control function of the inverter according to the control transfer function; Obtaining a resonant frequency function of a filter structure in the inverter; According to the damping control function and the resonant frequency function, establishing a correlation function between the control parameter and the damping ratio and the resonant frequency; The preset parameter control function is obtained according to the set target damping ratio and the correlation function.

9. An inverter control system, characterized in that: include: The frequency domain analysis module is used to analyze the sampling signal in the inverter to obtain several frequency domain signal points; A resonance point determination module, used to determine one or more target resonance points from the plurality of frequency domain signal points; A filtering module, configured to determine filtering parameters according to the frequency of the target resonance point to obtain a bandpass filter, and filter the sampled signal through the bandpass filter to obtain a signal component corresponding to the target resonance point; A control module is used to obtain a virtual damping output according to the target resonance point and the signal component corresponding thereto, and control the inverter according to the virtual damping output.

10. A photovoltaic inverter, characterized in that: It comprises a memory and a processor; the memory stores a computer program, and the processor is used to run the computer program in the memory to execute the steps in an inverter control method as described in any one of claims 1 to 8.

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