Power grid harmonic compensation method and device for single-phase grid-connected inverter

Abstract

The invention relates to the technical field of inverter output control, in particular to a power grid harmonic compensation method and device for a single-phase grid-connected inverter. Comprising the following steps: S1, acquiring a grid-connected point voltage sampling signal from a grid-connected point, and performing harmonic extraction on the grid-connected point voltage sampling signal to obtain a harmonic signal; s2, performing phase compensation on the harmonic signal to obtain a phase compensation signal; s3, performing amplitude compensation on the phase compensation signal to obtain an amplitude compensation signal; and S4, superposing the amplitude compensation signal to a modulation instruction position controlled by the inverter. According to the method, the original control structure of the single-phase inverter is not changed, harmonic compensation is superposed at the position of the modulation instruction, and for the single-phase inverter under the background harmonic interference of the power grid, the harmonic in the output current of the single-phase inverter can be effectively inhibited, and the output electric energy quality of the single-phase inverter is improved.

Description

Technical Field

[0001] The present application relates to the technical field of inverter output control, and in particular to a grid harmonic compensation method and device for a single-phase grid-connected inverter. Background Art

[0002] With the rapid development of photovoltaic and energy storage fields, single-phase inverters have been widely used in distributed photovoltaic grid-connected and household energy storage fields. However, there are differences in the voltage quality of actual single-phase inverter installation sites. There are multiple background harmonics in the power grid at many access locations, which causes the output current of the single-phase inverter itself to be affected by the background voltage harmonics. In turn, there are a large number of harmonics in the output current, which seriously reduces the output power quality of the single-phase inverter. Effectively suppressing the influence of the background voltage harmonics of the power grid is a key means to improve the output power quality of single-phase inverters.

[0003] At present, the influence of power grid background harmonics is often suppressed from the perspective of closed-loop feedback. Traditionally, a resonant controller is often added to the current feedback closed loop. The specific control principle diagram is as follows Figure 1 As shown, Figure 1 In the figure, the single-phase inverter on the left is connected to the grid point through a filter inductor, and the voltage is sampled at the grid point to obtain the grid point voltage sampling signal v a , the single-phase inverter output end performs current sampling to obtain the output current sampling signal i a , the single-phase inverter also collects the DC voltage sampling signal v dc , voltage sampling signal v a , current sampling signal i a , DC voltage sampling signal v dc The signal inputs of the current control system, the resonant controller and the current inner loop control are modulated to perform pulse width modulation (PWM) at the command position to participate in controlling the single-phase inverter.

[0004] Generally, the center frequency of the resonant controller is set at the harmonic frequency to be compensated, and a certain bandwidth is reserved. However, due to the influence of factors such as control delay and output filter capacitance, the gain of the resonant controller under the traditional method can only be designed in a very narrow area, resulting in poor harmonic suppression effect. At present, the industry has gradually begun to pay attention to the high-frequency harmonic suppression effect, and the traditional suppression method based on harmonic controller is subject to the influence of the current closed-loop bandwidth, which is easy to cause system instability during high-frequency resonance. Summary of the invention

[0005] The purpose of this application is to provide a grid harmonic compensation method for a single-phase grid-connected inverter to solve the above technical problems;

[0006] The purpose of this application is also to provide a grid harmonic compensation device for a single-phase grid-connected inverter to solve the above technical problems;

[0007] The technical problem solved by this application can be achieved by adopting the following technical solutions:

[0008] A method for compensating harmonics of a single-phase grid-connected inverter comprises the following steps:

[0009] S1. Obtaining a grid connection point voltage sampling signal from a grid connection point, and performing harmonic extraction on the grid connection point voltage sampling signal to obtain a harmonic signal;

[0010] S2. Perform phase compensation on the harmonic signal to obtain a phase compensated signal;

[0011] S3, performing amplitude compensation on the phase compensation signal to obtain an amplitude compensation signal;

[0012] S4. Superimposing the amplitude compensation signal to the modulation instruction position of the inverter control.

[0013] Preferably, the step S1 specifically comprises the steps of:

[0014] S11, obtaining the grid connection point voltage sampling signal from the grid connection point;

[0015] S12, obtaining the fundamental angular frequency according to the grid connection point voltage sampling signal;

[0016] S13, extracting harmonics from the grid-connected point voltage sampling signal according to different multiples of the fundamental wave angular frequency to obtain the harmonic signals of multiple different angular frequencies;

[0017] In the step S2, phase compensation is performed separately on the harmonic signals of different angular frequencies to obtain a plurality of phase compensation signals. In the step S3, amplitude compensation is performed separately on the plurality of phase compensation signals to obtain a plurality of amplitude compensation signals. In the step S4, the plurality of amplitude compensation signals are superimposed together on the modulation instruction position of the inverter control.

[0018] Preferably, the harmonic signal at each angular frequency obtained in step S13 includes two mutually orthogonal orthogonal signals, and in step S2, performing phase compensation on the harmonic signal specifically includes the steps of:

[0019] Multiply one quadrature signal by cos(θ hi ), the other orthogonal signal is multiplied by -sin(θ hi ), the two products are superimposed to obtain the phase compensation signal, where θ hi Indicates the phase compensation coefficient of the harmonic corresponding to the angular frequency.

[0020] Preferably, the amplitude compensation of the phase compensation signal in step S3 is specifically performed by multiplying the phase compensation signal by the amplitude compensation coefficient k comhi , obtaining the amplitude compensation signal.

[0021] Preferably, by analyzing the transfer function of the modulation voltage signal and the capacitor voltage under the control delay and the inverter filter parameters, the theoretical amplitude attenuation and phase shift of the harmonic signal of each angular frequency are obtained, and the phase compensation coefficient θ is determined. hi and the amplitude compensation coefficient k comhi .

[0022] Preferably, the phase compensation coefficient θ hi and the amplitude compensation coefficient k comhi Obtained through actual measurement.

[0023] Preferably, the phase compensation coefficient θ is measured hi and the amplitude compensation coefficient k comhi The method is to disconnect the inverter from the power grid and disconnect the current closed-loop control, inject the voltage feedforward and harmonic disturbance signals into the voltage modulation command position, detect the harmonic voltage on the output filter capacitor, extract the amplitude and phase of the injected harmonic disturbance signal and the harmonic voltage of the output filter capacitor respectively, and convert the harmonic voltage amplitude v of the harmonic disturbance signal into disi and the harmonic voltage amplitude v of the output filter capacitor resi Divide to obtain the amplitude compensation coefficient k comhi , the harmonic voltage phase θ of the harmonic disturbance signal disi and the harmonic voltage phase θ of the output filter capacitor resi Subtract the phase compensation coefficient θ hi .

[0024] Preferably, the harmonic extraction in step S1 is implemented by a second-order generalized integrator, and the k parameter during the harmonic extraction is set to be not less than 0.1 and not more than 0.7.

[0025] Preferably, the modulation instruction of the inverter control is generated by a current inner loop control module, and the current inner loop control module is a DC voltage closed loop control module, or a power closed loop control module, or a direct current instruction given module.

[0026] A power grid harmonic compensation device for a single-phase grid-connected inverter applies the power grid harmonic compensation method for a single-phase grid-connected inverter.

[0027] Beneficial effects of the present application: Due to the adoption of the above technical solution, the present application does not change the original control structure of the single-phase inverter. By superimposing harmonic compensation at the modulation instruction position, the single-phase inverter under the background harmonic interference of the power grid can effectively suppress the harmonics in its output current and improve its output power quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A topological diagram of the prior art for suppressing background harmonics in the power grid;

[0029] Figure 2 A topological diagram of a grid harmonic compensation method for a single-phase grid-connected inverter in an embodiment of the present application;

[0030] Figure 3 This is a measured topological diagram of the compensation coefficient in the embodiment of the present application;

[0031] Figure 4a is the amplitude compensation coefficient k comhi Schematic diagram of the measured results;

[0032] Figure 4b is the phase compensation coefficient θ hi Schematic diagram of the measured results;

[0033] Figure 5a The simulation voltage result of the single-phase inverter without using the technology of the present application when the 5th and 7th harmonics exist in the power grid;

[0034] Figure 5b The simulation current result of a single-phase inverter without using the technology of the present application when the 5th and 7th harmonics exist in the power grid;

[0035] Figure 6a The simulation voltage result of the single-phase inverter using the technology of the present application when the 5th and 7th harmonics exist in the power grid;

[0036] Figure 6b The simulation current results of the single-phase inverter using the technology of the present application when the 5th and 7th harmonics exist in the power grid;

[0037] Figure 7a The simulation voltage result of the single-phase inverter without using the technology of the present application when the power grid has 11th and 13th harmonics;

[0038] Figure 7b The simulation current results of a single-phase inverter without using the technology of the present application when the 11th and 13th harmonics exist in the power grid.

[0039] Figure 8a The simulation voltage result of the single-phase inverter using the technology of the present application when the 11th and 13th harmonics exist in the power grid;

[0040] Figure 8bThe simulation current results of the single-phase inverter using the technology of the present application when the 11th and 13th harmonics exist in the power grid;

[0041] Fig. 9 A schematic diagram of the steps of a grid harmonic compensation method for a single-phase grid-connected inverter in an embodiment of the present application;

[0042] Fig.10 This is a schematic diagram of step S1 in an embodiment of the present application. DETAILED DESCRIPTION

[0043] 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 ordinary technicians in this field without creative work are within the scope of protection of this application.

[0044] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0045] The present application is further described below in conjunction with the accompanying drawings and specific embodiments, but is not intended to limit the present application.

[0046] Grid harmonic compensation method for single-phase grid-connected inverter, such as Figure 2 , Fig. 9 As shown, the steps include:

[0047] S1. Obtaining a grid connection point voltage sampling signal from a grid connection point, and performing harmonic extraction on the grid connection point voltage sampling signal to obtain a harmonic signal;

[0048] S2. Perform phase compensation on the harmonic signal to obtain a phase compensation signal;

[0049] S3, performing amplitude compensation on the phase compensation signal to obtain an amplitude compensation signal;

[0050] S4. Superimpose the amplitude compensation signal to the modulation instruction position of the inverter control.

[0051] Specifically, the present application provides a grid harmonic compensation method for a single-phase grid-connected inverter, which is used to improve the inverter output current.

[0052] The grid harmonic compensation method is a feedforward method composed of n amplitude compensation signals, where n is a positive integer. When two or more harmonics of different frequencies are extracted for compensation, for example, the 5th harmonic and the 7th harmonic are extracted, n is greater than or equal to 2. Amplitude compensation signals 1 to n are generated by the grid connection point voltage through the grid background harmonic voltage extraction module, the phase compensation module and the amplitude compensation module. In the attached figure, the grid connection point voltage is recorded as va ;

[0053] The harmonic angular frequency information required by the power grid background harmonic voltage extraction module is determined by multiplying the fundamental angular frequency obtained by the phase-locked loop by a multiple, which determines the frequency of the compensated harmonic. The harmonic angular frequency is recorded as ω in the attached figure. g , the harmonic angular frequency information of n harmonics of different frequencies to be extracted is recorded as ω h1 To hn , and record the multiples as h1 to h n It is understandable that odd harmonics are more harmful, h1 to h n The value of is generally an odd number, such as 5, 7, 9, 11, etc.

[0054] The power grid background harmonic voltage extraction module extracts two mutually orthogonal orthogonal signals from the n harmonic signals of different frequencies that need to be compensated, and outputs the 2n orthogonal signals to the phase compensation module. h1 The two orthogonal signals extracted from the harmonics of the frequency are denoted as v ah1 and v bh1 , will ω hn The two orthogonal signals extracted from the harmonics of the frequency are denoted as v ahn and v bhn ;

[0055] The phase compensation module multiplies one of the two orthogonal signals extracted from the harmonic signal of each frequency by a sine signal and the other by a cosine signal. The two products are superimposed to obtain a phase compensation signal after n phase compensation. The cosine signal is recorded as cos(θ hi ), the sinusoidal signal is recorded as -sin(θ hi ), where θ hi That is, the phase compensation coefficient;

[0056] The amplitude compensation module multiplies the input signal by the amplitude compensation coefficient to obtain the amplitude compensation signal after amplitude compensation; the grid harmonic compensation method superimposes the amplitude compensation signal 1 to the amplitude compensation signal n and injects them into the position of the single-phase inverter modulation instruction to suppress the influence of the grid background harmonic on the output power quality. The amplitude compensation coefficient in the attached figure is recorded as k comh1 to k comhn ;

[0057] The amplitude compensation coefficient of the harmonic voltage amplitude compensation module and the phase compensation parameters required for the sine signal and the cosine signal in the phase compensation module can be obtained by a method based on actual measurement or a parameter design method based on a model.

[0058] The advantage of the present application is that, for a single-phase inverter under background harmonic interference of a power grid, the harmonics in its output current can be effectively suppressed, thereby improving its output power quality.

[0059] like Figure 2 As shown, the grid harmonic compensation method for the single-phase grid-connected inverter proposed in this application is a grid-connected point measured voltage signal v a After multi-channel harmonic extraction, phase compensation and amplitude compensation, amplitude compensation signals 1 to n are obtained. Amplitude compensation signals 1 to n are superimposed on the modulation instruction position of the inverter to participate in the control of the inverter.

[0060] Figure 2 In the figure, the single-phase inverter on the left side is connected to the grid point through the filter inductor L and the filter capacitor C. The grid point voltage sampling signal v is obtained by sampling at the grid point. a , the output current sampling signal i is obtained by sampling at the inverter a And DC voltage sampling signal v dc Each sampling signal is connected to the current control system through pulse width modulation (PWM), current inner loop control and other modules. The difference between this application and the prior art is that a harmonic voltage amplitude compensation module and a harmonic voltage phase compensation module are set up, and the input of the current control system is the grid-connected point voltage sampling signal v a , and obtain the phase information and fundamental angular frequency ω through the phase-locked loop g ;

[0061] The power grid background harmonic voltage extraction module has multiple submodules, each of which corresponds to harmonic compensation of different orders. It is easy to understand that the so-called harmonics of different orders are harmonics with different multiples of angular frequency relative to the fundamental angular frequency. For each order of harmonic compensation, two orthogonal harmonic signals va are extracted. hi and vb hi Perform phase compensation (multiply by cos(θ hi ) and -sin(θ hi )), and then perform amplitude compensation (multiply by k comhi ), the present application obtains the compensation coefficient θ by parameter design based on the model and / or parameter design based on actual measurement. hi and k comhi , where i∈1 to n.

[0062] This application does not change the original current control structure of the single-phase inverter, that is, there is no need to change Figure 2The structure of the current control system only superimposes the harmonic compensation signal at the modulation command position, which is easy to implement in the existing inverter system. There is no need to carry out large-scale transformation of the entire inverter control system, which reduces the difficulty and cost of implementation. The control method proposed in this application adopts voltage feedforward control in the current control system of the single-phase inverter, and the feedforward coefficient is 1. The harmonic compensation method is only a compensation link to compensate for the difference caused by control delay. When the grid voltage drops transiently, the control method of this application will not cause inverter output current shock.

[0063] In a preferred embodiment, Fig.10 As shown, step S1 specifically includes the steps of:

[0064] S11, obtaining a grid connection point voltage sampling signal from the grid connection point;

[0065] S12, obtaining the fundamental angular frequency according to the grid connection point voltage sampling signal;

[0066] S13, extracting harmonics from the grid-connected point voltage sampling signal according to different multiples of the fundamental wave angular frequency to obtain harmonic signals of multiple different angular frequencies;

[0067] In step S2, phase compensation is performed separately on harmonic signals of different angular frequencies to obtain multiple phase compensation signals. In step S3, amplitude compensation is performed separately on the multiple phase compensation signals to obtain multiple amplitude compensation signals. In step S4, the multiple amplitude compensation signals are superimposed together on the modulation instruction position of the inverter control.

[0068] Specifically, the input of the multi-channel harmonic extraction link is the grid-connected point voltage sampling signal v a The k parameter of the harmonic extraction link can be set to 0.1~0.7, and the angular frequency of the proposed harmonic can be obtained according to the fundamental angular frequency ω obtained by the phase-locked loop. g It is obtained by multiplying by a certain multiple, for example, when compensating for the 5th harmonic, the multiple is 5, when compensating for the 7th harmonic, the coefficient is 7, and so on. The harmonic compensation link can include multiple signals that need to be compensated at the same time.

[0069] In a preferred embodiment, the harmonic signal at each angular frequency obtained in step S13 includes two mutually orthogonal orthogonal signals. In step S2, performing phase compensation on the harmonic signal specifically includes the following steps:

[0070] Multiply one quadrature signal by cos(θ hi ), the other orthogonal signal is multiplied by -sin(θ hi ), the two products are superimposed to obtain the phase compensation signal, where θ hi Indicates the phase compensation coefficient of the harmonic corresponding to the angular frequency.

[0071] Specifically, phase compensation is the harmonic extraction link to obtain two orthogonal harmonic signals v ahi and v bhi Multiply by cos(θ hi ) and sine-sin(θ hi ) and superimposed to obtain the harmonic signal after phase compensation.

[0072] When compensating multiple harmonic signals simultaneously, the orthogonal signal output by each harmonic extraction link should be phase compensated separately.

[0073] Specifically, the phase compensation of the present application is mainly orthogonal signal processing, which is for the two orthogonal harmonic signals v obtained in the harmonic extraction link. ahi and v bhi , multiplied by cos(θ hi ) and -sin(θ hi ), and then add the two multiplication results.

[0074] θ hi It is the phase compensation parameter, which is used to adjust the phase of the harmonic signal.

[0075] When compensating multiple harmonic signals simultaneously, each orthogonal signal output by the harmonic extraction link must be individually phase compensated.

[0076] The present application is based on multiplying the phase characteristics of the harmonic signal by a trigonometric function and superimposing them, which can offset and correct the phase delay caused by factors such as control delay and filter inductance / capacitance, so that the phase of the inverter output voltage can better match the phase of the background harmonics of the power grid, thereby achieving the effect of suppressing harmonics.

[0077] In a preferred embodiment, the amplitude compensation of the phase compensation signal in step S3 is specifically performed by multiplying the phase compensation signal by the amplitude compensation coefficient k comhi , and obtain the amplitude compensation signal.

[0078] Specifically, the amplitude compensation is to multiply the phase-compensated signal by the amplitude compensation coefficient k comhi , that is, the amplitude compensation signal is obtained.

[0079] When performing amplitude compensation for multiple harmonic signals at the same time, amplitude compensation should be performed separately for each phase-compensated signal.

[0080] Further specifically, each amplitude compensation module is sequentially connected to the output side of the corresponding phase compensation module. Similar to phase compensation, when amplitude compensation of multiple harmonic signals is performed simultaneously, amplitude compensation must be performed separately for each phase-compensated signal.

[0081] In a preferred embodiment, by analyzing the transfer function of the grid connection point voltage signal and the capacitor voltage under the control delay and inverter filter parameters, the theoretical amplitude attenuation and phase shift of the harmonic signal of different angular frequencies are obtained, and the phase compensation coefficient θ is determined. hi and amplitude compensation coefficient k comhi .

[0082] Specifically, the phase compensation coefficient θ in this application is hi and amplitude compensation coefficient k comhi It can be obtained through model analysis. The method is to analyze the transfer function of the modulated voltage signal and the capacitor voltage under the control delay and inverter filter parameters, obtain the amplitude attenuation and phase shift of the harmonic position of each frequency, and directly compensate for it.

[0083] In a preferred embodiment, the phase compensation coefficient θ hi and amplitude compensation coefficient k comhi Obtained through actual measurement.

[0084] In a preferred embodiment, the measured phase compensation coefficient θ hi and amplitude compensation coefficient k comhi The method is to disconnect the inverter from the grid and disconnect the current inner loop control, inject voltage feedforward and harmonic disturbance signals of various frequencies into the voltage modulation command position, detect the harmonic voltage on the output filter capacitor, extract the amplitude and phase of the injected harmonic disturbance signal and the harmonic voltage of the output filter capacitor respectively, and convert the harmonic voltage amplitude v of the harmonic disturbance signal into disi and the harmonic voltage amplitude v of the output filter capacitor resi Divide to get the amplitude compensation coefficient k comhi , the harmonic voltage phase θ of the harmonic disturbance signal disi The harmonic voltage phase of the output filter capacitor is θ resi Subtract to get the phase compensation coefficient θ hi .

[0085] In a preferred embodiment, the harmonic extraction in step S1 is implemented by a second-order generalized integrator, and the k parameter during harmonic extraction is set to be not less than 0.1 and not more than 0.7. The larger the k parameter, the slower the harmonic extraction speed, but the extraction accuracy is higher when the harmonic frequency fluctuates. In this application, 0.1-0.7 is taken to take into account both the extraction speed and the extraction accuracy.

[0086] In a preferred embodiment, the modulation command of the inverter control is generated by a current inner loop control module, which is a DC voltage closed loop control module, or a power closed loop control module, or a direct current command setting module.

[0087] Specifically, Figure 3As shown, the phase compensation coefficient θ hi and amplitude compensation coefficient k comhi It can be obtained through actual measurement. The method is to disconnect the inverter from the power grid and the closed-loop control system, inject a disturbance signal at the voltage modulation command position while retaining only the feedforward control, and detect the harmonic voltage on the output filter capacitor. A harmonic extraction algorithm, such as the Fourier algorithm, is used to extract the harmonic voltage amplitude and phase of the injected harmonic signal and the voltage on the output capacitor, respectively. The harmonic voltage amplitudes of the two are divided, and the harmonic voltage phases of the two are subtracted to obtain the required phase compensation coefficient and amplitude compensation coefficient.

[0088] Figure 4a The amplitude compensation coefficient k is given in comhi The measured results are: Figure 4b The phase compensation coefficient θ is given in hi Actual measured results.

[0089] The present application does not change the original control structure of the single-phase inverter, but only superimposes a harmonic compensation link at the modulation instruction position. It has the advantages of simple system structure and good robustness. The simulation results in Figures 5 to 8 prove that the application of the present application can make the output current sinusoidality of the single-phase inverter higher, effectively improving the output power quality of the single-phase inverter.

[0090] In FIG5 , since the technology of the present application is not adopted, when there are 5th and 7th harmonic interferences in the power grid, the output current waveform will be obviously distorted. Figure 5a is a schematic diagram of voltage distortion. Figure 5b This is a schematic diagram of current distortion. The distortion is manifested as the current waveform is no longer close to the ideal sine wave.

[0091] Compared with FIG. 5 , FIG. 6 shows that the output current and voltage waveforms of the single-phase inverter are significantly improved after adopting the technology of the present application. Figure 6a Output voltage waveform and Figure 6b The output current waveform is closer to a sine wave.

[0092] In FIG. 7 , since the technology of the present application is not adopted, when there are 11th and 13th harmonic interferences in the power grid, the output current waveform will be obviously distorted. Figure 7a is a schematic diagram of voltage distortion. Figure 7b This is a schematic diagram of current distortion. The distortion is manifested as the current waveform is no longer close to the ideal sine wave.

[0093] Compared with FIG. 7 , FIG. 8 shows that the output current and voltage waveforms of the single-phase inverter are significantly improved after adopting the technology of the present application. Figure 8a Output voltage waveform and Figure 8b The output current waveform is closer to a sine wave.

[0094] A grid harmonic compensation device for a single-phase grid-connected inverter applies the grid harmonic compensation method for a single-phase grid-connected inverter in any one of the embodiments.

[0095] The above description is only a preferred embodiment of the present application, and does not limit the implementation mode and protection scope of the present application. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present application should be included in the protection scope of the present application.

Claims

1. A method for compensating harmonics of a single-phase grid-connected inverter, characterized in that: Includes steps: S1. Obtaining a grid connection point voltage sampling signal from a grid connection point, and performing harmonic extraction on the grid connection point voltage sampling signal to obtain a harmonic signal; S2. Perform phase compensation on the harmonic signal to obtain a phase compensated signal; S3, performing amplitude compensation on the phase compensation signal to obtain an amplitude compensation signal; S4. Superimposing the amplitude compensation signal to the modulation instruction position of the inverter control.

2. The grid harmonic compensation method of the single-phase grid-connected inverter according to claim 1, characterized in that: The step S1 specifically includes the following steps: S11, obtaining the grid connection point voltage sampling signal from the grid connection point; S12, obtaining the fundamental angular frequency according to the grid connection point voltage sampling signal; S13, extracting harmonics from the grid-connected point voltage sampling signal according to different multiples of the fundamental wave angular frequency to obtain the harmonic signals of multiple different angular frequencies; In the step S2, phase compensation is performed separately on the harmonic signals of different angular frequencies to obtain a plurality of phase compensation signals. In the step S3, amplitude compensation is performed separately on the plurality of phase compensation signals to obtain a plurality of amplitude compensation signals. In the step S4, the plurality of amplitude compensation signals are superimposed together on the modulation instruction position of the inverter control.

3. The grid harmonic compensation method of the single-phase grid-connected inverter according to claim 2, characterized in that: The harmonic signals at each angular frequency obtained in step S13 respectively include two mutually orthogonal orthogonal signals. In step S2, performing phase compensation on the harmonic signals specifically includes the following steps: Multiply one quadrature signal by cos(θ hi ), the other orthogonal signal is multiplied by -sin(θ hi ), the two products are superimposed to obtain the phase compensation signal, where θ hi Indicates the phase compensation coefficient of the harmonic corresponding to the angular frequency.

4. The grid harmonic compensation method of the single-phase grid-connected inverter according to claim 3, characterized in that: In step S3, the amplitude compensation of the phase compensation signal is specifically performed by multiplying the phase compensation signal by the amplitude compensation coefficient k. comhi , obtaining the amplitude compensation signal.

5. The grid harmonic compensation method of the single-phase grid-connected inverter according to claim 4, characterized in that: By analyzing the transfer function of the modulation voltage signal and the capacitor voltage under the control delay and inverter filter parameters, the theoretical amplitude attenuation and phase shift of the harmonic signal of different angular frequencies are obtained, and the phase compensation coefficient θ is determined. hi and the amplitude compensation coefficient k comhi .

6. The grid harmonic compensation method of the single-phase grid-connected inverter according to claim 4, characterized in that: The phase compensation coefficient θ hi and the amplitude compensation coefficient k comhi Obtained through actual measurement.

7. The grid harmonic compensation method of the single-phase grid-connected inverter according to claim 6, characterized in that: The measured phase compensation coefficient θ hi and the amplitude compensation coefficient k comhi The method is to disconnect the inverter from the power grid and disconnect the current closed-loop control, inject the voltage feedforward and harmonic disturbance signals into the voltage modulation command position, detect the harmonic voltage on the output filter capacitor, extract the amplitude and phase of the injected harmonic disturbance signal and the harmonic voltage of the output filter capacitor respectively, and convert the harmonic voltage amplitude v of the harmonic disturbance signal into disi and the harmonic voltage amplitude v of the output filter capacitor resi Divide to obtain the amplitude compensation coefficient k comhi , the harmonic voltage phase θ of the harmonic disturbance signal disi and the harmonic voltage phase θ of the output filter capacitor resi Subtract the phase compensation coefficient θ hi .

8. The grid harmonic compensation method of a single-phase grid-connected inverter according to any one of claims 1 to 7, characterized in that: In step S1, the harmonic extraction is implemented by a second-order generalized integrator, and the k parameter during the harmonic extraction is set to be not less than 0.1 and not more than 0.

7.

9. The grid harmonic compensation method of a single-phase grid-connected inverter according to any one of claims 1 to 7, characterized in that: The modulation command of the inverter control is generated by a current inner loop control module, and the current inner loop control module is a DC voltage closed loop control module, or a power closed loop control module, or a direct current command given module.

10. A grid harmonic compensation device for a single-phase grid-connected inverter, characterized in that: A grid harmonic compensation method for a single-phase grid-connected inverter is applied as described in any one of claims 1 to 9.

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