Photovoltaic inverter inter-harmonic detection method based on micro-synchronous phasor sampling and CPO-ICEEMDAN

Abstract

The invention discloses a photovoltaic inverter inter-harmonic detection method based on micro-synchronous phasor sampling and CPO-ICEEMDAN, output signal data of a photovoltaic inverter is acquired by using a micro-synchronous phasor sampling device with synchronous time service, and the real-time working condition of the photovoltaic inverter is fully considered; on the basis of a CPO-ICEEMDAN algorithm, through an adaptive noise adding mechanism, the influence of noise on signal decomposition can be effectively reduced, the quality of decomposed signal components is improved, and the influence of noise in signal data on modal decomposition is effectively solved; by optimizing an internal iteration mechanism of the algorithm, the decomposition efficiency is improved, and a final result can be obtained through convergence more quickly; through more accurate noise level adjustment and an improved decomposition strategy, the modal aliasing problem existing in several traditional modal decomposition algorithms can be effectively solved, the inherent characteristics of inter-harmonic signals are accurately reserved, and the accuracy and adaptability of inter-harmonic detection of the photovoltaic inverter are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic inverter interharmonic detection, and in particular to a photovoltaic inverter interharmonic detection method based on micro-synchronous phasor sampling and CPO-ICEEMDAN. Background Art

[0002] With the continuous development of photovoltaic power generation technology, the large-scale integration of photovoltaic power generation into the power grid has become the main development trend of the world's power system today. However, the large-scale grid connection of photovoltaic power generation has caused frequent harmonic pollution, which has a serious impact on the stability of the power system and deteriorated the quality of electric energy. Among them, the photovoltaic inverter is an important part of the photovoltaic grid-connected system, and its stable and normal operation is particularly important for the overall operation of the photovoltaic grid-connected system. At present, there are many types of harmonic / interharmonic detection methods for photovoltaic grid-connected systems and photovoltaic inverters. Among them, the interharmonic detection method based on modal decomposition is more widely used, mainly including EMD (empirical mode decomposition) and its variant EEMD (ensemble empirical mode decomposition), CEEMDAN (fully adaptive noise ensemble empirical mode decomposition method), ICEEMDAN (improved fully adaptive noise ensemble empirical mode decomposition method) and other commonly used detection methods. However, the above interharmonic detection methods still have certain limitations and shortcomings:

[0003] 1. The data collection method of the output signal of the photovoltaic inverter is simple, and the real-time working conditions of the photovoltaic inverter are not considered; 2. The harmonic detection method based on empirical mode decomposition (EMD) and its improved version still has certain modal aliasing problems, low detection accuracy and poor applicability; 3. In response to the modal aliasing problem of EMD and its variants, some related studies have proposed improved interharmonic detection methods based on CEEMDAN, ICEEMDAN, etc., but the noise processing level of the above methods needs to be improved, and the modal decomposition quality of its signal is still greatly affected, which in turn affects the accuracy and adaptability of interharmonic detection. Therefore, it is particularly important to study a detection method that can solve the comprehensive problems of interharmonic detection real-time, modal aliasing, noise influence, etc. of photovoltaic inverters, and effectively improve the accuracy, real-time and adaptability of interharmonic detection methods of photovoltaic inverters. Summary of the invention

[0004] The purpose of this application is to provide a photovoltaic inverter interharmonic detection method based on micro-synchronous phasor sampling and CPO-ICEEMDAN to solve the comprehensive problems of interharmonic detection real-time, modal aliasing, noise influence, etc. of photovoltaic inverters, and effectively improve the accuracy, real-time and adaptability of the interharmonic detection method of photovoltaic inverters.

[0005] In order to solve the above technical problems, the present application provides a photovoltaic inverter interharmonic detection method based on micro-synchronous phasor sampling and CPO-ICEEMDAN, including:

[0006] S1, synchronously sampling the output signal data of the photovoltaic inverter based on a micro-synchronous phasor sampling device with synchronous timing;

[0007] S2, performing linear stabilization preprocessing on the output signal data;

[0008] S3, based on the CPO optimization algorithm, the parameters of ICEEMDAN are optimized to obtain the CPO-ICEEMDAN algorithm;

[0009] S4, using the CPO-ICEEMDAN algorithm to perform modal decomposition on the output signal data preprocessed in step S2 to obtain IMF components;

[0010] S5, performing demodulation analysis on the IMF component based on the Teager energy operator to obtain the instantaneous amplitude and frequency of the modal component IMF;

[0011] S6, accurately locate the start and end time of the transient interharmonic according to the mutation point of the instantaneous amplitude and the frequency, and use the averaging method to obtain the instantaneous amplitude and frequency of the stable transient interharmonic component in the start and end stages as the detection value of the transient interharmonic component parameter, thereby completing the interharmonic detection.

[0012] Based on the above embodiment, as a preferred implementation mode, the CPO-ICEEMDAN algorithm obtained by optimizing the parameters of ICEEMDAN based on the CPO optimization algorithm is specifically as follows:

[0013] S3-1, initializing the population of the CPO, setting the number of iterations and population size of the CPO, and setting the parameter optimization range of ICEEMDAN;

[0014] S3-2, use ICEEMDAN to decompose the signal and calculate the envelope entropy of each IMF component, and use the minimum value of the envelope entropy as the fitness function;

[0015] S3-3, determine whether the optimization reaches the termination condition of the algorithm, if so, proceed to step S3-4; if not, update the population position and return to step S3-2;

[0016] S3-4, save the optimal ICEEMDAN parameter combination (Nstd, NE), and substitute it into ICEEMDAN to construct the CPO algorithm for ICEEMDAN to obtain the CPO-ICEEMDAN algorithm.

[0017] Based on the above embodiment, as a preferred implementation mode, the instantaneous amplitude and frequency of the modal component IMF are obtained by demodulating and analyzing the IMF component based on the Teager energy operator as follows:

[0018] S5-1, square the IMF component to obtain a square signal;

[0019] S5-2, shifting the squared signal by a set time step to obtain a shifted signal;

[0020] S5-3, performing a subtraction operation on the squared signal and the shifted signal to obtain a demodulated signal;

[0021] S5-4, filtering and signal processing are performed on the demodulated signal to obtain the instantaneous amplitude and frequency of each harmonic component.

[0022] Compared with the prior art, the photovoltaic inverter interharmonic detection method based on micro-synchronous phasor sampling and CPO-ICEEMDAN provided by the present invention includes at least the following beneficial effects compared with the existing photovoltaic inverter interharmonic detection method: 1. The output signal data acquisition of the photovoltaic inverter in the present invention utilizes a micro-synchronous phasor sampling device with synchronous timing, which fully considers the real-time working conditions of the photovoltaic inverter; 2. Based on the CPO-ICEEMDAN algorithm, through the adaptive noise addition mechanism, it can effectively reduce the influence of noise on signal decomposition, improve the quality of decomposed signal components, and effectively solve the influence of noise in signal data on modal decomposition; 3. By optimizing the internal iteration mechanism of the algorithm, ICEEMDAN reduces unnecessary calculations, improves decomposition efficiency, and can converge to the final result faster; 4. This detection method can effectively solve the modal aliasing problem existing in several traditional modal decomposition algorithms through more precise noise level adjustment and improved decomposition strategy, accurately retain the inherent characteristics of interharmonic signals, and significantly improve the accuracy and adaptability of photovoltaic inverter interharmonic detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solution of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without inventiveness.

[0024] Figure 1 A flow chart of a photovoltaic inverter interharmonic detection method based on micro-synchronous phasor sampling and CPO-ICEEMDAN provided in an embodiment of the present application;

[0025] Figure 2 A flowchart of a CPO optimized ICEEMDAN algorithm provided in an embodiment of the present application;

[0026] Figure 3 A time domain waveform diagram of an original signal provided in an embodiment of the present application;

[0027] Figure 4 An ICEEMDAN decomposition result diagram provided in an embodiment of the present application;

[0028] Figure 5 A CPO-ICEEMDAN decomposition result diagram provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings.

[0030] The core of this application is to provide a photovoltaic inverter interharmonic detection method based on micro-synchronous phasor sampling and CPO-ICEEMDAN, which solves the comprehensive problems of interharmonic detection real-time, modal aliasing, noise influence, etc. of photovoltaic inverter, and effectively improves the accuracy, real-time and adaptability of the interharmonic detection method of photovoltaic inverter.

[0031] Figure 1 A flow chart of a photovoltaic inverter interharmonic detection method based on micro-synchronous phasor sampling and CPO-ICEEMDAN provided in an embodiment of the present application; Figure 2 A flowchart of a CPO optimized ICEEMDAN algorithm provided in an embodiment of the present application; Figure 3 A time domain waveform diagram of an original signal provided in an embodiment of the present application; Figure 4 An ICEEMDAN decomposition result diagram provided in an embodiment of the present application; Figure 5 A CPO-ICEEMDAN decomposition result diagram provided in an embodiment of the present application.

[0032] A photovoltaic inverter interharmonic detection method based on micro-synchronous phasor sampling and CPO-ICEEMDAN includes the following steps:

[0033] S1, synchronously sampling the output signal data of the photovoltaic inverter based on a micro-synchronous phasor sampling device with synchronous timing;

[0034] S2, preprocessing the output signal data into linear stabilization;

[0035] S3, based on the CPO optimization algorithm, the parameters of ICEEMDAN are optimized to obtain the CPO-ICEEMDAN algorithm;

[0036] S4, using the CPO-ICEEMDAN algorithm to perform modal decomposition on the output signal data preprocessed in step S2 to obtain IMF components;

[0037] S5, demodulate and analyze the IMF component based on the Teager energy operator to obtain the instantaneous amplitude and frequency of the modal component IMF;

[0038] S6, accurately locate the start and end time of the transient interharmonic according to the mutation points of the instantaneous amplitude and frequency, and use the averaging method to obtain the instantaneous amplitude and frequency of the stable transient interharmonic component in the start and end stages as the detection value of the transient interharmonic component parameters to complete the interharmonic detection.

[0039] Preferably, a photovoltaic inverter interharmonic detection method based on micro-synchronous phasor sampling and CPO-ICEEMDAN is provided. The CPO-ICEEMDAN algorithm is obtained by optimizing the parameters of the ICEEMDAN based on the CPO optimization algorithm. Specifically, the method is as follows:

[0040] S3-1, initialize the CPO population, set the number of CPO iterations and population size, and set the parameter optimization range of ICEEMDAN;

[0041] S3-2, use ICEEMDAN to decompose the signal and calculate the envelope entropy of each IMF component, and use the minimum value of the envelope entropy as the fitness function;

[0042] S3-3, determine whether the optimization reaches the termination condition of the algorithm, if so, proceed to step S3-4; if not, update the population position and return to step S3-2;

[0043] S3-4, save the optimal ICEEMDAN parameter combination (Nstd, NE), and substitute it into ICEEMDAN to construct the CPO algorithm for ICEEMDAN to obtain the CPO-ICEEMDAN algorithm.

[0044] Signal decomposition based on CPO-ICEEMDAN

[0045] See also Figure 3 , assuming that the preprocessed signal containing steady-state harmonics is y(t) = a*cos(2*pi*50*t)+0.08*a*cos(2*pi*50*3.5*t)+0.3*a*cos(2*pi*50*5*t)+0.3*a*cos(2*pi*50*5.5*t)+0.3*a*cos(2*pi*50*7*t), the signal contains fundamental wave, 5th and 7th harmonics, 3.5th and 5.5th interharmonics. Figure 2In this embodiment, the signal is decomposed by the CPO-ICEEMDAN algorithm to obtain multiple optimal component IMFs:

[0046] See also Figure 4 , Figure 5 The results of signal decomposition using ICEEMDAN and CPO-ICEEMDAN in this embodiment are shown in the figure. It can be seen from the figure that there is a large noise interference in the IMF signal component decomposed by ICEEMDAN, and the signal interference in the IMF signal component decomposed by the CPO-ICEEMDAN algorithm is less, and the decomposition accuracy of the fundamental wave, harmonics and interharmonics is higher.

[0047] Preferably, a photovoltaic inverter interharmonic detection method based on micro-synchronous phasor sampling and CPO-ICEEMDAN is specifically performed by demodulating and analyzing the IMF component based on the Teager energy operator:

[0048] S5-1, square the IMF component to obtain a square signal;

[0049] S5-2, shifting the squared signal by a set time step to obtain a shifted signal;

[0050] S5-3, performing a subtraction operation on the squared signal and the shifted signal to obtain a demodulated signal;

[0051] S5-4, filtering and signal processing are performed on the demodulated signal to obtain the instantaneous amplitude and frequency of each harmonic component.

[0052] The present invention provides a photovoltaic inverter interharmonic detection method based on micro-synchronous phasor sampling and CPO-ICEEMDAN. Compared with the existing photovoltaic inverter interharmonic detection method, 1. the output signal data of the photovoltaic inverter in the present invention is collected by using a micro-synchronous phasor sampling device with synchronous timing, which fully considers the real-time working conditions of the photovoltaic inverter; 2. based on the CPO-ICEEMDAN algorithm, through an adaptive noise addition mechanism, it can effectively reduce the influence of noise on signal decomposition, improve the quality of decomposed signal components, and effectively solve the influence of noise in signal data on modal decomposition; 3. by optimizing the internal iteration mechanism of the algorithm, ICEEMDAN reduces unnecessary calculations, improves decomposition efficiency, and can converge to the final result more quickly; 4. this detection method can effectively solve the modal aliasing problem existing in several traditional modal decomposition algorithms through more accurate noise level adjustment and improved decomposition strategy, accurately retain the inherent characteristics of interharmonic signals, and significantly improve the accuracy and adaptability of photovoltaic inverter interharmonic detection.

[0053] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the application disclosed herein. The present application is intended to cover any variations, uses or adaptations of the present application, which follow the general principles of the present application and include common knowledge or customary technical means in the art disclosed in the present application. The specification and examples are to be regarded as exemplary only, and the true scope of the present application is indicated by the claims.

[0054] It should be understood that the present application is not limited to the precise structure described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The above-described embodiments of the present application do not constitute a limitation on the scope of protection of the present application.

Claims

1. A photovoltaic inverter interharmonic detection method based on micro-synchronous phasor sampling and CPO-ICEEMDAN, characterized in that: include: S1, synchronously sampling the output signal data of the photovoltaic inverter based on a micro-synchronous phasor sampling device with synchronous timing; S2, performing linear stabilization preprocessing on the output signal data; S3, based on the CPO optimization algorithm, the parameters of ICEEMDAN are optimized to obtain the CPO-ICEEMDAN algorithm; S4, using the CPO-ICEEMDAN algorithm to perform modal decomposition on the output signal data preprocessed in step S2 to obtain IMF components; S5, performing demodulation analysis on the IMF component based on the Teager energy operator to obtain the instantaneous amplitude and frequency of the modal component IMF; S6, accurately locate the start and end time of the transient interharmonic according to the mutation point of the instantaneous amplitude and the frequency, and use the averaging method to obtain the instantaneous amplitude and frequency of the stable transient interharmonic component in the start and end stages as the detection value of the transient interharmonic component parameter, thereby completing the interharmonic detection.

2. The photovoltaic inverter interharmonic detection method based on micro-synchronous phasor sampling and CPO-ICEEMDAN according to claim 1 is characterized in that: The CPO-ICEEMDAN algorithm obtained by optimizing the parameters of ICEEMDAN based on the CPO optimization algorithm is specifically as follows: S3-1, initializing the population of the CPO, setting the number of iterations and the population size of the CPO, and setting the parameter optimization range of ICEEMDAN; S3-2, use ICEEMDAN to decompose the signal and calculate the envelope entropy of each IMF component, and use the minimum value of the envelope entropy as the fitness function; S3-3, determine whether the optimization reaches the termination condition of the algorithm, if so, proceed to step S3-4; if not, update the population position and return to step S3-2; S3-4, save the optimal ICEEMDAN parameter combination (Nstd, NE), and substitute it into ICEEMDAN to construct the CPO algorithm for ICEEMDAN to obtain the CPO-ICEEMDAN algorithm.

3. The photovoltaic inverter interharmonic detection method based on micro-synchronous phasor sampling and CPO-ICEEMDAN according to claim 1 is characterized in that: The demodulation analysis of the IMF component based on the Teager energy operator is specifically as follows: S5-1, square the IMF component to obtain a square signal; S5-2, shifting the squared signal by a set time step to obtain a shifted signal; S5-3, performing a subtraction operation on the squared signal and the shifted signal to obtain a demodulated signal; S5-4, filtering and signal processing are performed on the demodulated signal to obtain the instantaneous amplitude and frequency of each harmonic component.

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